Water R718 as refrigerant (Turbo water vapor compression chiller, Absorbtion chiller, Adsorption chiller)
Updated articles of Water R718 as refrigerant (Turbo water vapor compression chiller, Absorbtion chiller, Adsorption chiller)
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30 November 2012
The Danish Technological Institute (DTI) is one of the world's largest private institutes within research and technology and is now the new Bronze Partner on R718.com. DTI has contributed to the development of a completely new type of axial compressor for chillers that uses water as refrigerant. The new compressor reduces the amount of greenhouse gases which are currently being emitted when synthetic refrigerants are used. Additionally the new compressor also solves flammability and toxicity concerns.
Estimations show that systems using the newly developed compressor could save between 10-30% energy, while greenhouse gas emissions can be reduced by 15-40% compared to HFCs based systems. According to DTI, the market potential of large-scale water refrigeration and air conditioning systems is EUR 1.3-2.0 billion a year.
Future applications of the project are not only refrigeration and air conditioning systems for office buildings, large shops, hospitals and other substantial buildings, but also other areas and industries like drying processes and distillation or high temperature heat pumps as well as ice production and storage.
Project developments
Other parties to this innovative project were the Japanese company Kobe Steel, Ltd. and the Danish arm of the US company Johnson Controls Inc, supported by the Danish Energy Agency,. and the three Japanese power companies, Tokyo Electric Power Company, Chubu Electric Power Company and Kansai Electric Power Company. DTI has produced the initial compressor design and has invested 700,000€ in advanced testing facilities.
Kobe Steel, Ltd. and the Japanese power companies have manufactured a prototype for a future commercial system to be used in the Japanese market based on the development work performed by DTI. The long-term testing of the prototype will continue over the next couple of years, during which the product will also be improved. Johnson Controls Inc. plans to set up a demonstration system in Denmark in cooperation with Kobe Steel, Ltd., DTI and a large Danish Company. The system is to be used for long-term testing, product maturing and as a showcase.
DTI and R718.com
The Institute has decided to become a Bronze partner of R718.com in order to share its long expertise in the management of innovative and complex international research and development projects. Also the presence of DTI will promote and support a faster introduction of new technologies using water as refrigerant in cooling, refrigeration and heating.
"DTI appreciates the efforts done by the team behind R718.com in disseminating sustainable and efficient refrigeration technologies like R718 worldwide. R718.com offers an excellent platform for all players in this field working with the process of development, commercialization and implementation of the Water vapor refrigeration technology. DTI strongly encourages the players to use R718.com to exchange information, share experience, bring news and promote the technology in general to support water as one of the important refrigerants of the future," explained Hans Madsbøll, DTI Refrigeration and Heat Pump Technology expert.
About DTI
"The Danish Technological Institute is a self-owned and not-for-profit institution with 850 employees, founded in 1906 and occupies the crucial position where research, business and community converge. We develop, apply and disseminate research- and technologically-based knowledge for the Danish and International business sectors. As such, we participate in development projects, which are of use to society in close collaboration with leading research and educational institutions both in Denmark and abroad."
"Our most important task is to ensure that new knowledge and technology quickly can be converted into value for our customers in the form of new or improved products, materials, processes, methods and organisational structures" concludes Hans Madsbøll.
Useful contacts
Claus S. Poulsen
Centre Manager at DTI
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The Basics of R718: Water vapour compression
16 August 2012
The fourth article in "The Basics of R718" series focuses on the water vapour compression and the hurdles that need to be overcome for wider deployment of this technology. Examples of related research and design suggestions are presented together with a summary of the findings.
Related articles
The Basics of R718: Technology Fundamentals
06 August 2012
The Basics of R718: the Absorption cycle
09 August 2012
The Basics of R718: the Adsorption cycle
10 August 2012
Challenges of R718
A very high latent heat of evaporation (2,270kJ/kg) and a high critical temperature (380°C – 386°C) makes water a potentially very efficient refrigerant. According to researchers from University of Wisconsin the theoretical COP is 8.39, only slightly lower than the theoretical COP of R134a (8.47). However, despite the fact that water vapour compression systems work on the Rankine cycle, components and materials differ largely from conventional refrigeration equipment.
Special components are required because of extremely high specific volume (the density of water vapour is extremely low), around two orders of magnitude greater than a typical HFC refrigerant. This makes the process of compressing low pressure, high specific volume vapour to a pressure (and therefore temperature) that is high enough to allow heat rejection from the system challenging.
Water vapour compressor
Out of all system components, the most challenging requirements are on the compressor side. According to J. Kühnl-Kinel the swept volume of a water vapour compressor has to be some 500 times higher than for a conventional refrigerant. Furthermore, water yields only 340 kW of refrigeration for a swept volume of 100,000 m3/h.
Wight et al. (2000) carried out a scoping analysis of turbo-compressor technology applied to steam compression. The authors concluded that a single-stage compressor was not feasible (extremely high capital cost, technically challenging design) for several reasons:
The two-stage configuration was able to achieve predicted efficiencies of 80% with large impeller diameters but with somewhat lower tip velocities (nominally 1600 ft/sec) implying a more technically achievable compressor.
The most promising compressor technology identified by Wight et al., in terms of total geometric size and performance, was a multistage axial compressor configuration consisting of between 6 & 7 stages. The efficiency of this type of compressor was estimated at 82% and the size and tip speeds required were reasonable, 4.5 ft and 1400 ft/sec, respectively. The disadvantage is that axial compressors are sophisticated and expensive devices when compared to centrifugal compressors.
R718 Turbo chiller
Norbert Müller from Michigan State University researching an R718 turbo chiller design estimates the volume flow requirement for water as a refrigerant to be 200 times higher and about double the pressure ratio for some applications compared with classical refrigerants like R134a or R12. The high pressure ratio requires a two to four times higher compressor tip speed depending on the impeller design.
According to Müller some design challenges are successfully solved in commercial industrial plants mainly installed in Europe using unique high-performance mixed-flow turbo compressors with or without stationary guide vanes. Concepts such as flow compressors with inducer or pre-runner or axial multistage compressors, promising a higher pressure ratio or a more compact design are under investigation.
To achieve high pressure ratios a large diameter impeller is combined with high rotations. The lightweight impellers with extremely thin, mostly straight blades, made from special materials like titanium or composites represents a major challenge for manufacturing. The R718 turbo chiller uses direct heat exchangers allowing for a higher overall COP.
Economic feasibility
Special requirements regarding components result in expensive systems with long delivery times. A team of researchers from University of Wisconsin performed simulations using component level models and investigated the economic feasibility of a water-based vapor compression chiller with a nominal capacity of 1000 tons. After comparing several configurations, a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers was found the most attractive system.
The authors of the study compared the life-cycle costs of both an R134a and R718 refrigeration cycle and found that the initial system cost associated with using water as a refrigerant in the vapour compression cycle greatly exceeded the savings in operating costs associated with its somewhat higher COP.
From an environmental point of view, R718 is the ideal refrigerant. It has been deployed in systems based on adsorption and absorption refrigeration cycle with success. Efforts have been made to overcome R718 disadvantages in water vapour compression, but further research and development is required to introduce a commercially viable solution.
Whilst achieving a high COP is still the primary target for a refrigeration system, environmental parameters like Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) are becoming more and more restrictive. With regards to these aspects water is the most environmentally benign refrigerant and is thus one of the most promising natural refrigerants.
Water as refrigerant - series of articles explains the fundamentals on R718.com
A first series of articles on R718.com explains the fundamentals of water refrigeration technologies, shedding light on the differences between absorption and adsorption cycles as well as water vapour compression. Recent papers look at solar heating and cooling whilst the events section indicates where the experts will meet over the coming months.
The recentely launched R718.com is dedicated to bring water refrigeration faster to market by offering latest news, cutting edge products and a global expert community to our readers, members and visitors. As water refrigeration is a fairly young technololgy with many challanges ahead, R718.com kicked off with an article series explaining the fundamentals:
The Basics of R718: Technology Fundamentals
The newly launched industry platform R718.com brings a series of articles covering topics such as the characteristics of water as a refrigerant, available R718 technology, latest research and market trends. In this first article R718.com provides an overview of fundamentals of this natural refrigerant.
The Basics of R718: the Absorption cycle
Following the “Technology Fundamentals”, the second "The Basics of R718" article focuses on the principles of absorption technology. R718.com designed an easy to understand absorption cycle chart to graphically demonstrate processes that occur during the operation of absorption chillers.
The Basics of R718: the Adsorption cycle
Following the “the Absorption cycle”, the third "The Basics of R718" article focuses on the principles of adsorption technology. To graphically demonstrate processes that occur during the operation of adsorption chillers R718.com has designed two easy to understand adsorption cycle diagrams.
The Basics of R718: Water vapour compression
The fourth article in "The Basics of R718" series focuses on the water vapour compression and the hurdles that need to be overcome for wider deployment of this technology. Examples of related research and design suggestions are presented together with a summary of the findings.
Products and community
The products section will soon list innovative products using water as refrigerant. Whether you want to display your product to an expert readership or you are looking for products to purchase, this will be the right section for you.
As mentioned above the community gives you access to over 10,000 experts around the world specialised in natural refrigerants. Via a file sharing function, you can showcase your activities by uploading videos, brochures, presentations, picture galleries, articles.... and get peer review.
Papers and events
The knowledge section lists presentations and reports relevant for natural refrigerants in general and technical information on R718 technologies in particular. Two of the latest papers are:
A River of Energy Solutions – Solar Heating & Cooling
According to the presentation, building heat loads are 60% made up of space cooling and heating and water heating; and solar thermal heating and cooling has begun taking up more of this market share in recent years. The presentation looks at a number of commercial and residential examples that have successfully applied solar thermal to their building’s energy mix. Flat plate collectors and evacuated tube collectors are diagrammed by the presentation and offered as successful examples of widely used solar thermal technology.
Solar Cooling and Process Heat for Emerging Markets and Developing Countries
This presentation outlines the benefits of solar cooling and process heat for emerging markets and developing countries, and charts the work of Solar Installation Design (S.O.L.I.D) to increase its market penetration. S.O.L.I.D works to deliver fixed price turnkey installations for cash, with case studies included of existing projects such as the EA Tower in Pristina and the Olympic Sailing Village in China.
The events listing gives you an overview of where the international natural refrigerant community is gathering. The "attending" function is particularly convenient as you can see which of the community members is attending, allowing you to set up meetings in the run-up to the event.
Activate your account on R718.com
To activate your account on R718.com, simply go to “my profile” (top-right corner) and you will see “connect to R718.com”. Click on it and voilà , your account is activated on R718.com. From there on, you can log in on all platforms with the same email address and password and conveniently switch between the communities by clicking on the little icon in the top-right corner.
If you have any questions or remarks, please don't hesitate to let us know!
Also, if you would like some more explanations on the different features and how to best use them for finding the information you are looking for or increasing the visibility of your company, let us know - we are happy to call you and explain more in detail.
Kind regards,
Sabine
Community Coordinator
s.lobnig@R718.com
+32 2 230 3700
System manufacturer | Combined heating & cooling
Ohmstrasse 3,
D-85716 Unterschleissheim, Germany
t | +49 89 310 44 84
f | +49 89 310 44 85
ZEO-TECH GmbH has developed a novel energy conversion process for the efficient generation and storage of heating and cooling power. This process is based on natural ingredients, zeolite and water, and is therefore compatible with the most stringent environment protection rules. Heat is the sole driving force needed. Application areas are for example:
In the course of 20 years since Zeo-Tech was founded, the underlying technology was continuously tested, modified, re-tested and optimised. A large number of devices had to be developed from scratch in order to make a low cost mass production vacuum system possible. Patents and protected base technologies plus the know-how, the craftsmanship and the patience of the Zeo-Tech team members are the business foundation of Zeo-Tech.
No other energy conversion process offers similar benefits as the zeolite/water sorption technology. The choice of zeolite, a solid, crystalline adsorbent and water as working-fluid was considered exotic during the start-up years of Zeo-Tech. In the meantime, the crucial technological advancements have been made by the Zeo-Tech team and this choice has turned out to be a real winner.
Coming soon: Water axial compressor prototype for commercial chillers by Johnson Controls
13 September 2012
R718.com interviewed Alexander Cohr Pachai, Johnson Controls industrial refrigeration technology manager, at the Sabroe Factory. Our new Silver Partner presents the results of 15 years research into a new water compressor type. Developed and tested in Denmark thanks to a public grant, the prototype has been installed in a water vapour process cooling plant and aims at replacing refrigeration plants that use traditional HFCs refrigerants.
R718.com: Water seems to be the perfect refrigerant: cheap, readily available, zero GWP, non-flammable and non-toxic. Why has water as a refrigerant not taken off yet?
Alexander Cohr Pachai: Water is the oldest refrigerant. It has been used in a variety of systems and in many different ways. In 1995, Sabroe and the Danish Technological Institute installed a water vapour system for trial operation in Lego, Denmark.
After 10 years of operation, we could see that we needed to improve a number of things before the system could become a commercially viable solution. The efficiency of the first compressor was not good enough and some other small technicalities needed further improvement. Intense research and development work and further testing lead us to the design of a new type of compressor, more compact, more efficient and more cost effective.
R718.com: What are the technologies in water refrigeration that seem the most promising and why?
Alexander Cohr Pachai: Vapour compression has always had a better efficiency than absorption/adsorption systems. Absorption systems are mainly used where heating costs are very cheap or free of charge to make it feasible. With the new vapour compression system, we will be closer to what other refrigeration systems can provide in terms of efficiency. We are also working hard to make it competitive in terms of first costs so that we can provide the market with cost effective chillers.
R718.com: Which is the most important technical issue to be solved before R718 can become a mainstream solution?
Alexander Cohr Pachai: Production volume. With volume comes the necessary economy scale so that we can reach the cost level the market is looking for. Over the years, a number of challenges have been solved. Now we stand with a product that just needs the final touch to reach the level we can be satisfied with. Saying this, I also know that the first product we put out now will be different than the product we will sell in ten years time. But the same goes for cars, motorbikes and many other things on the market. Development never stops.
R718.com: How do you evaluate the market potential for R718 and which region or market is likely to take off first?
Alexander Cohr Pachai: I believe that R718 will become popular in warm climates and in production environments. The advantage of water is that, unless special care is required for the cooling process, it is not necessary to use other heat exchangers. The refrigerant is cheap and you can release it without any special precautions.
R718.com: What will be the main applications?
Alexander Cohr Pachai: R718 systems can be used everywhere. As water is neither toxic nor flammable and since it does not break down to toxic or acid break down products, it can be used everywhere. It is, therefore, the perfect media for process engineering and air conditioning. When an application requires temperatures lower than 0°C, we will select either ammonia or hydrocarbons chillers.
R718.com: Can R718 technologies compete with conventional systems?
Alexander Cohr Pachai: The good news is yes. There is more to this story. At low evaporation temperatures water vapour systems can have slightly poorer efficiency, but since there is no heat exchanger in the cycle, the evaporation temperature will also be about 5K higher than conventional systems. The efficiency for water vapour systems increases by about 10%/K higher evaporation temperature compared to 2% for conventional system. It is clear that water vapour systems will benefit more from the new trends in many applications, where we see that the required water temperature is about 18°C.
When it comes to price comparisons, it is the old story about comparing apples with apples. If we compare the turnkey project, the benefit of using a cheap refrigerant will be a game changer. Also, if you get a leak, water is cheap to top up. Water goes in the drain and nobody will be in danger.
The refrigeration system using water vapour compression is also working at negative pressure and, therefore, there is no risk of explosion or fire when air gets in the system. Only for heat pumps using R718 you will have above atmospheric pressure, but again, at very moderate pressures, so there is no problem. Water is a very promising alternative here, but we still have to investigate further for this application.
R718.com: Can you tell us already a bit more about the prototype JCI is working on?
Alexander Cohr Pachai: The system built for the field test at Lego in Billund, Denmark, is based on a multi stage axial compressor. For those who are not familiar with this type of compressor, you can compare it with the first part of a jet engine that you find on most airplanes.
The condenser, heat exchangers here, releases directly the heat in the ambient air, which means that the condensing temperature will only be about 1K over the wet bulb temperature. Since the ground water in the area is full of different minerals, the heat exchanger must be located between the loop going to the molding machines to avoid clogging up the cooling channels in the molding head. Our challenge is then to figure out a way to change the water in the evaporator on regular basis.
R718.com: How did you tackle the R718's problem of extremely high specific volume?
Alexander Cohr Pachai: We evaluated different compressor technologies and axial compressor appeared to be the solution involving the least possible compromises. We also decided to use water as a lubricant for the bearings. We did not go for the easiest solution but for the right solution. Then, we dedicated a lot of time finding the right shape of impellers and how operate the compressor.
R718.com: How challenging was it to find a suitable design and material for the rotor?
Alexander Cohr Pachai: It has been a challenge to find the right design but also to find the right materials. We had to remember that the first impellers can be affected by water droplets. When the compressor is rotating at high speed, droplets hit the surface and erode the material. We had to take this into consideration when designing the new compressor.
R718.com: What is the size of the impellers and tip velocities of the tested system?
Alexander Cohr Pachai: The impellers have different diameters exactly like the compressor in the jet engine. At this stage, we prefer to keep the exact dimensions of the impellers confidential. We may also in the future develop a variety of diameters for different capacities and for different operational conditions.
R718.com: Could you tell us more about the overall parameters of the system that will be tested?
Alexander Cohr Pachai: The field test unit will be installed in parallel with existing ammonia chillers that operate at normal process temperatures. The capacity is about 750 kW and the efficiency is expected to be almost the same or slightly lower than the one of the ammonia systems at the current running conditions.
Useful contacts
Alexander Cohr Pachai
Technology Manager at Johnson Controls
Send Message
The Basics of R718: Technology Fundamentals
06 August 2012
The newly launched industry platform R718.com brings a series of articles covering topics such as the characteristics of water as a refrigerant, available R718 technology, latest research and market trends. In this first article R718.com provides an overview of fundamentals of this natural refrigerant.
Related articles
R718.com joins the ranks of the leading natural refrigerant platforms
02 August 2012
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
Advantages of R718
Abundance & Safety: The natural refrigerant R718, also known as dihydrogen monoxide, H20, water or water vapour is one of the Earth’s most abundant elements. From an environmental point of view, water is probably the ideal refrigerant for applications above 0°C. On the list of R718’s favourable characteristics are non-toxicity, non-flammability, 0 Ozone Depletion Potential (ODP), 0 (very low) Global Warming Potential (GWP), low cost and nearly unlimited availability.
Regulatory Relief: In this respect, R718 even exceeds other natural refrigerants like hydrocarbons or ammonia whose use is, in some countries, restricted due to flammability and toxicity related concerns. Being subject to no present or future environmental or safety regulations, investments in development of technology using water as a refrigerant are considered a low risk.
Efficiency: Also from a thermodynamic point of view, water has several specific characteristics that make it potentially a very efficient refrigerant (COP). R718 has a very high latent heat of evaporation (2,270kJ/kg), approximately five times higher than hydrocarbon R290 (428kJ/kg), four times higher than R744 (574kJ/kg) or slightly less than double the latent heat of evaporation of R717 (1,369kJ/kg). In other words, R718 absorbs significantly larger amounts of energy in the form of heat during a change of phase from liquid to gas without a change in temperature. The critical temperature of water is 380°C - 386°C, which is nearly triple the critical temperature of ammonia (132°C).
Main applications
Water has been extensively used as a process fluid (distillation, drying processes), as a heat transfer or energy storage medium (central heating, system cooling, ice storage systems) and as a working fluid in Rankine power generation cycle.
In refrigeration applications, the use of water as a refrigerant has been mostly limited to absorption systems built around a binary fluid comprised of lithium bromide and water and adsorption systems, using water as refrigerant and the mineral zeolite as adsorber. Systems using these two technologies can be driven by heat sources such as solar thermal, biomass or industrial waste heat and therefore possess additional environmental and economic benefits over purely electric driven machines. Because adsorption and absorption systems are the most important of the R718 applications, R718.com will dedicate individual articles to these technologies in the following issues of this launch series.
Limitations and research challenges
An obvious limitation is the low freezing point at atmospheric pressure. Water leads to corrosion and oxidation of many metals. Water is more reactive than other refrigerants and requires special attention on choosing the right materials used in the R718 systems during the design phase.
A number of factors limit the attractiveness of water-based vapour compression refrigeration cycles. Water vapour has very high specific volume (the density of water vapour is extremely low), around two orders of magnitude greater than a typical HFC refrigerant. That makes the process of compressing low pressure, high specific volume vapour to a pressure (and therefore temperature) that is high enough to allow heat rejection from the system challenging.
Large compressors with specially designed components, using materials such as titanium are required. Such compressors are more expensive and have long delivery times. Water based refrigeration systems operate in very low pressure environment that makes their continued operation free of contaminants (air) difficult.
Research in these areas (e.g. high speed, multi-stage, axial compressors are tested; turbo chillers with specially designed turbines and alternative steam ejector systems are in the development phase) points to a promising future for water being a viable alternative to HFC refrigerants. Details on R718 technology progress will be presented also in the separate article focused on latest research and development.
Thermal properties of water (source here) are:
R718.com joins the ranks of the leading natural refrigerant platforms
02 August 2012
Latest news on developments in water refrigeration technologies, reports on important players in the sector, technical details on state-of-the art products, updates on relevant policies and access to THE global natural refrigerants community uniting over 10,000 experts - this is R718.com, the new platform focusing on everything regarding water as a refrigerant. Sign up and help to bring water as refrigerant faster to market!
Related articles
R718 water as refrigerant 3rd generation
05 October 2011
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
In July 2012, shecco launched R718.com - a platform dedicated to water as refrigerant. R718.com joins the ranks of the foremost global natural refrigerant platforms that have so far focused on CO2 (R744), hydrocarbons and ammonia. The aim: bringing natural refrigerants faster to market.
"After the success of R744.com, ammonia21.com, and hydrocarbons21.com, which was successfully launched in 2009, we are proud to bring a fourth natural refrigerant platform online: R718.com, which will focus exclusively on water as refrigerant and with this, present another technology that is apt to help us fight climate change,” says Marc Chasserot, founder and editor-in-chief of R718.com. “Furthermore, R718.com fits in seamlessly with the other three natural refrigerant platforms and serves as a gateway to THE global online community uniting experts in natural refrigerants from all over the world.”
news - products - community
Three pillars ensure that R718.com caters to the needs of an international expert community:
R718.com community members have access to many new features, amongst which:
Join in the global community on natural refrigerant fluids
The R718.com community is a gateway to the first global platform uniting over 10,000 experts in the field of natural refrigerants. Being a member of R718.com also allows you to log into R744.com, hydrocarbons21.com and ammonia21.com once your account has been activated. Consequently, you can choose whether the information and content that you want to share should appear on one, two, three or all four platforms.
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
R718.com provides an overview of three papers presented in the Absorption Prototype session at the GL 2012 conference in Delft, the Netherlands. Advances in absorption technology and its design are discussed. Promising results of simulations and experimental studies point to increased efficiency and extended range of operations.
Related articles
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
Development of double-output absorption heat pump chiller with improved heating efficiency - T. Fujii, Y. Sakano, et al
A prototype of a double-output absorption heat pump chiller (AHPC) with combined COP 3.3 was presented by researchers from Hitachi. Steam consumption of the double-output AHPC is reduced by 34% in comparison with conventional systems (absorption chiller and boiler). This lithium bromide/water system provides hot and chilled water simultaneously with heating and cooling capacities 296kW and 158kW, respectively. From the simulation and experimental results, heating COP improved from 1.0 to 2.15 by recovering heat from chilled water as the additional heat source. The initial construction difficulty was higher pressure than in conventional systems caused by hot water. To reduce working pressure and solution concentration a two-stage evaporation and absorption was applied. Energy savings are expected from installation of this heat source machine, especially in facilities with year-round cooling and heating demands.
First operation experiences with novel resorption chillers to generate cooling from waste heat and biomass – K. Helle, T. Weimer at al
Authors of this paper introduce resorption cooling technology and point out promising experimental results for a thermal driven ammonia water system with plate heat exchangers as absorbers and desorbers. Resorption chillers consist of two solvent loops which are coupled by an exchange of gaseous refrigerant medium. A first test was conducted on a small resorption plant with a maximum cooling capacity of 2kW and a resorption chiller in combination with a FLOX burner for bio-fuels. Resorption chillers can achieve a COP > 0.4.
Advantages of resorption system:
Disadvantages of resorption system:
Self adaptive refrigerant flow low temperature driven dual lift absorption cycle – M. Guerra
In his presentation, Guerra introduced an air- cooled absorption system in which the refrigerant flow self adapts to the evaporator and absorber loads to improve efficiency, stability and to extend the range of operations. The system using ammonia and water as working fluids was developed to allow operation with low generator temperature input. This prototype system was run with hot water at inlet temperatures from 70°C to 95°C and with air temperatures ranging from 25°C to 40°C. With 92°C driving hot water, 7°C outlet chilled water and at 35°C outdoor ambient temperature the prototype chiller has a cooling capacity of 3.4kW with COP 0.29 and 360 W power consumption for the solution pump and the fan. Inlet temperature 79°C results in a cooling capacity of 2.5kW with COP 0.28 and 285 W power consumption. Author concludes that the operation of the prototype has proven to be stable and repeatable.
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
The 10th IIR Gustav Lorentzen Conference on Natural Refrigerants, a key event covering the latest research results and advances in water, air, CO2, ammonia and hydrocarbon HVAC&R technologies is being held on 25 - 27 June 2012 in Delft, Netherlands. Keep abreast of progress and trends with R718.com, which is reporting live from Delft.
Related articles
Water as refrigerant can enable an end to EU f-gas reliance
01 June 2012
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
More than 230 participants are attending the three-day Gustav Lorentzen conference organised by the International Institute of Refrigeration (IIR), the Royal Dutch Association of Refrigeration and the Delft University of Technology. Attracting a wide range of international specialists from science and industry sectors, the conference will facilitate an effective exchange of experience and knowledge on the latest research relating into R718, including:
The keynote speakers will include:
Some more details can be found in the follow up article(s):
34% performance improvement - novel absorption systems discussed at GL 2012
About Gustav Lorentzen
The conference is named in honour of Norwegian Scientist and engineer Gustav Lorentzen who rediscovered how CO2 could be used as a refrigerant in a simple and efficient way in heating and cooling applications.
Water as refrigerant can enable an end to EU f-gas reliance
01 June 2012
Already the most commonly used liquid as a heat transfer fluid in secondary refrigeration and air-conditioning, water (R718) is also part of the basket of identified HFC replacement primary refrigerants that could enable an end to EU’s reliance on f-gases, according to a recent report.
As the EU is considering revisions to the F-Gas Regulation, a new report titled ‘Availability of Low-GWP Alternatives to HFCs: Feasibility of an Early Phase-Out of HFCs by 2020’ outlines a clear timetable, setting out the dates by which the use of HFCs can be banned in new equipment, with a complete phase-out possible by 2020 in 20 sub-sectors. The report also outlines and provides case studies on the various available HFC alternative technologies, including water as refrigerant.
5-10% better energy efficiency for large centrifugal chillers with water refrigerant
The thermophysical properties of water as refrigerant makes it suitable for applications above 0°C, where it can be used in larger chillers with good energy efficiency. “For large centrifugal chillers, water as refrigerant is an environmentally benign solution, with 5-10% better energy efficiency” reads the report.
Examples of available water refrigerant based vapour compression products
The report points out that water as refrigerant has since many years been marketed by a manufacturer of centrifugal compressor desalination equipment in Israel, with installations of the technology that can be found in South Africa, Denmark and Japan.
More recently, a group of Japanese and American companies along with a Danish research institute have developed two water vapour compressors of 0.8 and 1.8 MW under a project funded by the Danish Energy Agency.
Finally, the report makes a reference to a German company that has developed a centrifugal chiller/ heat pump with water as refrigerant of about 5 to 15 kW capacity. The company declares energy efficiencies much higher than HFC systems.
Absorption systems with water refrigerant could become more attractive where solar collectors supply heat
Besides vapour compression cycle technology, the report also considers not in kind alternatives such as absorption air-conditioning systems typically found in large buildings in big cities with electrical grid limitations in the summer.
Using the principle that some gases are absorbed by certain liquids, absorption air conditioning systems typically use water as the refrigerant and lithium bromide as the absorbent, with the other typical pairs being ammonia (refrigerant) and water (absorbent).
“The energy efficiency of a gas fired absorption chiller is usually only 25% of that of a comparable compressor system. Based on the typical efficiency for converting fossil fuel into electricity (25-30%) and the energy mix of Europe, the CO2 balance is about equal for compression and gas fired absorption systems. Absorption systems could become more attractive where heat is supplied by solar collectors. On the other hand, if electricity production is mostly from renewable energy, as for example in Norway, electrically driven vapor compression systems will also have lower CO2 emissions due to energy use”.
Water as one of many refrigerants in basket of low-GWP technologies
The report asserts that no single low-GWP technology could replace HFCs in all applications: “Crucially, there is no single alternative that will replace HFCs in all applications, just as there is no single fluorinated greenhouse gas that can be used in all applications. The low-GWP technology that is most appropriate will depend on a number of factors including the local economic and regulatory situation, as well as climatic and other factors.”
Other natural refrigerants discussed in the report include hydrocarbon isobutene, hydrocarbon propane, hydrocarbon pentane, hydrocarbon propylene, various hydrocarbon blends such as the butane-isobutane-propane-ethane blend (R441A), ammonia, carbon dioxide (CO2), and the combination of different natural refrigerants in cascade systems.
The Basics of R718: the Absorption cycle
09 August 2012
Following the “Technology Fundamentals”, the second "The Basics of R718" article focuses on the principles of absorption technology. R718.com designed an easy to understand absorption cycle chart to graphically demonstrate processes that occur during the operation of absorption chillers.
Related articles
The Basics of R718: Technology Fundamentals
06 August 2012
Eco-School project: adsorption chiller reduces energy consumption by 42%
07 August 2012
R718.com joins the ranks of the leading natural refrigerant platforms
02 August 2012
Absorption is defined as the penetration of one substance into the bulk of another substance. It is the phenomenon in which atoms, molecules, or ions of one material enter a bulk phase – gas, liquid or solid of another material with uniform distribution throughout the bulk.
The absorption thermodynamic cycle generates refrigeration effect through the use of two fluids – an absorbent (lithium bromide) and a refrigerant (water) and a heat source substituting the electrical input in the vapour compression cycle. The compressor is replaced by an absorber, a solution pump and a generator. The thermal energy from a heat source is transferred to a heat sink (chilled water) through the absorbent fluid and the refrigerant.
The absorption chiller is based on absorbing and then releasing water vapour into and out of a lithium bromide solution. Since no chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) are used the cooling process is environment friendly. Furthermore, industrial waste heat, solar thermal, biomass or another renewable source of energy can be used to drive the absorption cycle.
Principle of adsorption chillers
The basic property of an absorption chiller is that one specific pressure and temperature corresponds to one solubility value of a solution. The single-effect absorption chiller operates in 4 key steps, resembling the functions of the 4 chambers, as demonstrated in the absorption cycle graph below:
1. Generator
The lithium-bromide solution (pink colour) is pumped into the generator and is heated by a heat source, raising the lithium bromide solution to a temperature where the liquid refrigerant (blue colour) vaporizes and flows to the condenser. The concentrated lithium bromide solution (brown colour) flows down to the absorber chamber.
2. Condenser
In the condenser, the cooling water absorbs the heat of condensation from the vaporized refrigerant, changing the refrigerant into a liquid. The liquid refrigerant travels from the condenser through expansion piping to the evaporator during which the liquid refrigerant experiences a drop in pressure and temperature.
3. Evaporator
The liquid refrigerant is pumped to the evaporator and sprayed on the top of the chilled water tube bundle. At low evaporator pressures, the liquid refrigerant vaporizes, removing energy from the chilled water. The liquid refrigerant that is vaporized then travels from the evaporator to the absorber.
4. Absorber
In the absorber, the concentrated liquid lithium bromide solution absorbs the vaporized refrigerant and the cooling water absorbs the vapour absorption heat. As the refrigerant vapour is absorbed the concentrated solution returns to a diluted state. After the absorption, the diluted liquid lithium-bromide solution is pumped to the generator, completing the refrigerant cycle.
Characteristics of absorption chillers
There are a number of absorption chillers commercially available, ranging from single-effect indirect-fired (steam, hot water) chillers with a COP<1, originating in 1950s, to double-effect direct-fired (gas, oil burner) chillers, and novel triple-effect absorption chillers with a COP reaching 1.8.
Single-effect absorption chillers have a single generator and condense all vaporized refrigerant in a single condenser. Double-effect absorption chillers have two generators and the vaporized refrigerant from the high temperature generator is the thermal source for the low temperature generator, reducing the cooling requirement for the vaporized refrigerant. Triple-effect chillers operate with three generators (low, medium and high temperature).
The cooling capacity of absorption chillers ranges from 5kW up to 12 MW. Lithium bromide – water is the most commonly used pair of working fluids, followed by water – ammonia. The heat source can be any suitable industrial waste stream (exhaust, steam, hot water, etc.) or any suitable combustible (natural gas, biogas, diesel, waste oil, wood pellets, etc.) higher than 80°C. Using abundant solar thermal energy as a heat source to power the absorption cycle is a particularly environmentally friendly solution.
Advantages of absorption chillers
The Basics of R718: the Adsorption cycle
10 August 2012
Following the “the Absorption cycle”, the third "The Basics of R718" article focuses on the principles of adsorption technology. To graphically demonstrate processes that occur during the operation of adsorption chillers R718.com has designed two easy to understand adsorption cycle diagrams.
Related articles
The Basics of R718: the Absorption cycle
09 August 2012
Eco-School project: adsorption chiller reduces energy consumption by 42%
07 August 2012
The Basics of R718: Technology Fundamentals
06 August 2012
Adsorption is defined as a process that occurs when a gas or liquid accumulates on the surface of a solid (more rarely a liquid) forming a molecular or atomic film. Adsorption is useful for separating certain molecules from one another.
Adsorbents are most commonly found as carbon or oxygen compounds. Oxygen compound adsorbents are used to manufacture silica gel and zeolite, two major materials used in adsorption chillers operating with water as a refrigerant. Ammonia is an alternative to R718 as a refrigerant.
Adsorption is typically an exothermic process, as gases are adsorbed on a substrate, heat is released. Heat is required to release the accumulated gas once again. It is the reversibility of this process that laid the foundation for the refrigeration effect used in adsorption chillers.
An adsorption cycle for refrigeration does not use any mechanical energy, but only heat energy. Renewable sources of energy like solar thermal or waste heat from industrial processes can provide hot water to drive the adsorption cycle.
Principle of adsorption chillers
The adsorption chiller consists of an evaporator, a condenser and two adsorption chambers (1&2). All four chambers are operated at nearly a full vacuum. The adsorption chambers alternate in their adsorbing and desorbing functions. The two-phase chamber alternation principle will be explained in the graphics below, designed by R718.com.
Phase One. The sorbent in chamber 1 is regenerated using hot water from the external heat source. Hot water enters chamber 1 to desorb the silica gel/zeolite. The water vapour is driven from the sorbent and rises to the condenser where it is then condensed to a liquid state. The condensed water is recycled in a closed-loop to the bottom of the system where it is available for re-use.
At the same time the sorbent in chamber 2 adsorbs the water vapour entering from the evaporator through the open ports at the bottom of the chamber. Chamber 2 has to be cooled in order to remove the heat deposited by the adsorption process and to enable a continuous adsorption. Due to the low pressure conditions in the evaporator, the refrigerant injected into the evaporator is transferred into the gas phase by the evaporation heat from the chilled water – the useful product of adsorption cycle. If the sorption material in the adsorption chamber is saturated with water vapour to a certain degree, the chambers switch over in their function.
Phase Two. When the adsorbant in chamber 1 is dry and the adsorbant in chamber 2 is saturated with water, the process in the adsorption chiller reverses. Several valves are used to equalize the pressure among the chambers. Cool water is run through chamber 1 to transfer any residual heat to chamber 2, which begins the heating process marking the end of the reversal process. In Phase Two dry chamber 1 begins to adsorb water vapour entering the chamber from the evaporator while chamber 2 releases, or desorbs, water into the condenser. The rest of the cycle is analogous to the process explained in Phase One above.
Characteristics of adsorption chillers
Adsorption chillers are a unique approach to achieving air conditioning and process cooling. Hot water is used to drive the chiller rather than from large amounts of electricity, as happens in conventional air conditioners.
Adsorption chillers use solid sorption materials instead of liquid solutions. Market available systems use water as refrigerant and silica gel and zeolite as the adsorbent.
The cooling capacity of adsorption chillers ranges from 5kW up to 500kW. Under typical operation conditions with a driving temperature of 80°C, the systems achieve a coefficient of performance (COP) of about 0.6, but operation is possible even with temperatures of approximately 50°C.
The adsorption chillers are based on adsorbing and then releasing water vapour onto and out of a silica gel or zeolite. Since no chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) are used the cooling process is environment friendly. The whole system uses only fraction of the electricity of conventional chillers.
The heat source to provide hot water can be any suitable industrial waste heat or any suitable combustible (natural gas, biogas, diesel, waste oil, wood pellets, etc.) higher than 50°C. Using abundant solar thermal energy as a heat source to power the adsorption cycle is a particularly environmentally friendly solution and its deployment is increasing.
Advantages of adsorption chillers
R718 water as refrigerant 3rd generation
05 October 2011 | ILK
Since 2000, numerous installations for different customers have demonstrated the technical feasibility and the capability of water as refrigerant. Based on the high performance axial compressor, developed by the ILK, water chillers with a performance of 400 kW to 1000 kW were produced and applied.
With the introduced concept of the R718 Turbo Chiller 3rd generation an important step has been taken from technical feasibility to economical equality. By improving primary components such as turbo compressor and heat exchanger, the compressor efficiency and the coefficient of performance of the chiller has been immensely increased compared to the first and second generation. New procedural and design engineering solutions, general improvements and simplifications enormously reduce the expenditure in manufacturing
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R718 water as refrigerant 3rd
R718 water as refrigerant 3rd generation
Since 2000, numerous installations for different customers have demonstrated the technical feasibility and the capability of water as refrigerant. Based on the high performance axial compressor, developed by the ILK, water chillers with a performance of 400 kW to 1000 kW were produced and applied.
With the introduced concept of the R718 Turbo Chiller 3rd generation an important step has been taken from technical feasibility to economical equality. By improving primary components such as turbo compressor and heat exchanger, the compressor efficiency and the coefficient of performance of the chiller has been immensely increased compared to the first and second generation. New procedural and design engineering solutions, general improvements and simplifications enormously reduce the expenditure in manufacturing.
Since over 8 years R718 Turbo Water Chillers are operating with water as refrigerant in Germany and Luxemburg. In the last years the new refrigerant technology has demonstrated its technical feasibility and reliability under challenging operating conditions.
ILK Dresden and Axima Refrigeration GmbH work togehter on a joint projekt. The aim is to launch sucessfully the 3rd Generation of R718 Turbo Water Chillers at the market.
Design conditions for R718 chiller Water R718 is no refrigerant like others, which are usually used in water chillers. The special characteristics of water R718 have consequences for compressor and equipment layouts. Pressure ratio and specific volume of water vapor differ immensely from those of usual refrigerants.
For an operating temperature range of 32 K and a condensing temperature of 4 °C there is, for common refrigerants like R134a, a pressure ratio of approx. 2.8 necessary, whereas it is for R718 approx. 7.2. The intake volume for R134a is 0,3 m3/s and for R718 60 m3/s for a cooling capacity of 1000 kW and a condensing temperature of 4 °C.
Process configuration with water vapor turbo compressor. The vapor high-performance axial compressor can be applied in different processes.
For instance in
The term direct evaporation refers to the process when some water, as the energy transfer medium, evaporates in the evaporator due to relaxation and becomes in this way to refrigerant water.Direct condensation exists when the refrigerant condenses directly in the cooling water.
R718 Turbo Chiller 3rd Generation
Conclusion
The undisputed advantages of water as refrigerant are environmental compatibility, cleanliness, plant safety, reliability, maintainability and energy efficiency. So far, they could be realized only in a small number of implemented plants. The manufacture expenditures of the first and second generation were too high.
With the presented concept of a 3rd generation of R718 Turbo Chillers an important step was taken from the technical to the economic feasibility of R718 chiller sets. Improved main components, such as turbo compressor and heat exchanger, noticeably increase the efficiency and performance of the water chiller. New procedural and constructional solutions, improvements and simplifications reduce the manufacture expenditures.
With the realization of this concept in a serial production water as refrigerant changes the status of an exotic cooling procedure to an economic alternative of cold water production.
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Post by Arda Rahardja Lukitobudi @ Grup FB IKARA
New large scale water vapor compressor in RAC systems by DTI30 November 2012
The Danish Technological Institute (DTI) is one of the world's largest private institutes within research and technology and is now the new Bronze Partner on R718.com. DTI has contributed to the development of a completely new type of axial compressor for chillers that uses water as refrigerant. The new compressor reduces the amount of greenhouse gases which are currently being emitted when synthetic refrigerants are used. Additionally the new compressor also solves flammability and toxicity concerns.
Estimations show that systems using the newly developed compressor could save between 10-30% energy, while greenhouse gas emissions can be reduced by 15-40% compared to HFCs based systems. According to DTI, the market potential of large-scale water refrigeration and air conditioning systems is EUR 1.3-2.0 billion a year.
Future applications of the project are not only refrigeration and air conditioning systems for office buildings, large shops, hospitals and other substantial buildings, but also other areas and industries like drying processes and distillation or high temperature heat pumps as well as ice production and storage.
Project developments
Other parties to this innovative project were the Japanese company Kobe Steel, Ltd. and the Danish arm of the US company Johnson Controls Inc, supported by the Danish Energy Agency,. and the three Japanese power companies, Tokyo Electric Power Company, Chubu Electric Power Company and Kansai Electric Power Company. DTI has produced the initial compressor design and has invested 700,000€ in advanced testing facilities.
Kobe Steel, Ltd. and the Japanese power companies have manufactured a prototype for a future commercial system to be used in the Japanese market based on the development work performed by DTI. The long-term testing of the prototype will continue over the next couple of years, during which the product will also be improved. Johnson Controls Inc. plans to set up a demonstration system in Denmark in cooperation with Kobe Steel, Ltd., DTI and a large Danish Company. The system is to be used for long-term testing, product maturing and as a showcase.
DTI and R718.com
The Institute has decided to become a Bronze partner of R718.com in order to share its long expertise in the management of innovative and complex international research and development projects. Also the presence of DTI will promote and support a faster introduction of new technologies using water as refrigerant in cooling, refrigeration and heating.
"DTI appreciates the efforts done by the team behind R718.com in disseminating sustainable and efficient refrigeration technologies like R718 worldwide. R718.com offers an excellent platform for all players in this field working with the process of development, commercialization and implementation of the Water vapor refrigeration technology. DTI strongly encourages the players to use R718.com to exchange information, share experience, bring news and promote the technology in general to support water as one of the important refrigerants of the future," explained Hans Madsbøll, DTI Refrigeration and Heat Pump Technology expert.
About DTI
"The Danish Technological Institute is a self-owned and not-for-profit institution with 850 employees, founded in 1906 and occupies the crucial position where research, business and community converge. We develop, apply and disseminate research- and technologically-based knowledge for the Danish and International business sectors. As such, we participate in development projects, which are of use to society in close collaboration with leading research and educational institutions both in Denmark and abroad."
"Our most important task is to ensure that new knowledge and technology quickly can be converted into value for our customers in the form of new or improved products, materials, processes, methods and organisational structures" concludes Hans Madsbøll.
Useful contacts
Claus S. Poulsen
Centre Manager at DTI
Send Message
The Basics of R718: Water vapour compression
16 August 2012
The fourth article in "The Basics of R718" series focuses on the water vapour compression and the hurdles that need to be overcome for wider deployment of this technology. Examples of related research and design suggestions are presented together with a summary of the findings.
Related articles
The Basics of R718: Technology Fundamentals
06 August 2012
The Basics of R718: the Absorption cycle
09 August 2012
The Basics of R718: the Adsorption cycle
10 August 2012
Challenges of R718
A very high latent heat of evaporation (2,270kJ/kg) and a high critical temperature (380°C – 386°C) makes water a potentially very efficient refrigerant. According to researchers from University of Wisconsin the theoretical COP is 8.39, only slightly lower than the theoretical COP of R134a (8.47). However, despite the fact that water vapour compression systems work on the Rankine cycle, components and materials differ largely from conventional refrigeration equipment.
Special components are required because of extremely high specific volume (the density of water vapour is extremely low), around two orders of magnitude greater than a typical HFC refrigerant. This makes the process of compressing low pressure, high specific volume vapour to a pressure (and therefore temperature) that is high enough to allow heat rejection from the system challenging.
Water vapour compressor
Out of all system components, the most challenging requirements are on the compressor side. According to J. Kühnl-Kinel the swept volume of a water vapour compressor has to be some 500 times higher than for a conventional refrigerant. Furthermore, water yields only 340 kW of refrigeration for a swept volume of 100,000 m3/h.
Wight et al. (2000) carried out a scoping analysis of turbo-compressor technology applied to steam compression. The authors concluded that a single-stage compressor was not feasible (extremely high capital cost, technically challenging design) for several reasons:
- low efficiency (less than 75% for the radial bladed unit)
- very large impellers (20 ft in diameter)
- very high tip velocities (2200 ft/sec) leading to large stresses and high Mach numbers
The two-stage configuration was able to achieve predicted efficiencies of 80% with large impeller diameters but with somewhat lower tip velocities (nominally 1600 ft/sec) implying a more technically achievable compressor.
The most promising compressor technology identified by Wight et al., in terms of total geometric size and performance, was a multistage axial compressor configuration consisting of between 6 & 7 stages. The efficiency of this type of compressor was estimated at 82% and the size and tip speeds required were reasonable, 4.5 ft and 1400 ft/sec, respectively. The disadvantage is that axial compressors are sophisticated and expensive devices when compared to centrifugal compressors.
R718 Turbo chiller
Norbert Müller from Michigan State University researching an R718 turbo chiller design estimates the volume flow requirement for water as a refrigerant to be 200 times higher and about double the pressure ratio for some applications compared with classical refrigerants like R134a or R12. The high pressure ratio requires a two to four times higher compressor tip speed depending on the impeller design.
According to Müller some design challenges are successfully solved in commercial industrial plants mainly installed in Europe using unique high-performance mixed-flow turbo compressors with or without stationary guide vanes. Concepts such as flow compressors with inducer or pre-runner or axial multistage compressors, promising a higher pressure ratio or a more compact design are under investigation.
To achieve high pressure ratios a large diameter impeller is combined with high rotations. The lightweight impellers with extremely thin, mostly straight blades, made from special materials like titanium or composites represents a major challenge for manufacturing. The R718 turbo chiller uses direct heat exchangers allowing for a higher overall COP.
Economic feasibility
Special requirements regarding components result in expensive systems with long delivery times. A team of researchers from University of Wisconsin performed simulations using component level models and investigated the economic feasibility of a water-based vapor compression chiller with a nominal capacity of 1000 tons. After comparing several configurations, a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers was found the most attractive system.
The authors of the study compared the life-cycle costs of both an R134a and R718 refrigeration cycle and found that the initial system cost associated with using water as a refrigerant in the vapour compression cycle greatly exceeded the savings in operating costs associated with its somewhat higher COP.
From an environmental point of view, R718 is the ideal refrigerant. It has been deployed in systems based on adsorption and absorption refrigeration cycle with success. Efforts have been made to overcome R718 disadvantages in water vapour compression, but further research and development is required to introduce a commercially viable solution.
Whilst achieving a high COP is still the primary target for a refrigeration system, environmental parameters like Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) are becoming more and more restrictive. With regards to these aspects water is the most environmentally benign refrigerant and is thus one of the most promising natural refrigerants.
Water as refrigerant - series of articles explains the fundamentals on R718.com
A first series of articles on R718.com explains the fundamentals of water refrigeration technologies, shedding light on the differences between absorption and adsorption cycles as well as water vapour compression. Recent papers look at solar heating and cooling whilst the events section indicates where the experts will meet over the coming months.
The recentely launched R718.com is dedicated to bring water refrigeration faster to market by offering latest news, cutting edge products and a global expert community to our readers, members and visitors. As water refrigeration is a fairly young technololgy with many challanges ahead, R718.com kicked off with an article series explaining the fundamentals:
The Basics of R718: Technology Fundamentals
The newly launched industry platform R718.com brings a series of articles covering topics such as the characteristics of water as a refrigerant, available R718 technology, latest research and market trends. In this first article R718.com provides an overview of fundamentals of this natural refrigerant.
The Basics of R718: the Absorption cycle
Following the “Technology Fundamentals”, the second "The Basics of R718" article focuses on the principles of absorption technology. R718.com designed an easy to understand absorption cycle chart to graphically demonstrate processes that occur during the operation of absorption chillers.
The Basics of R718: the Adsorption cycle
Following the “the Absorption cycle”, the third "The Basics of R718" article focuses on the principles of adsorption technology. To graphically demonstrate processes that occur during the operation of adsorption chillers R718.com has designed two easy to understand adsorption cycle diagrams.
The Basics of R718: Water vapour compression
The fourth article in "The Basics of R718" series focuses on the water vapour compression and the hurdles that need to be overcome for wider deployment of this technology. Examples of related research and design suggestions are presented together with a summary of the findings.
Products and community
The products section will soon list innovative products using water as refrigerant. Whether you want to display your product to an expert readership or you are looking for products to purchase, this will be the right section for you.
As mentioned above the community gives you access to over 10,000 experts around the world specialised in natural refrigerants. Via a file sharing function, you can showcase your activities by uploading videos, brochures, presentations, picture galleries, articles.... and get peer review.
Papers and events
The knowledge section lists presentations and reports relevant for natural refrigerants in general and technical information on R718 technologies in particular. Two of the latest papers are:
A River of Energy Solutions – Solar Heating & Cooling
According to the presentation, building heat loads are 60% made up of space cooling and heating and water heating; and solar thermal heating and cooling has begun taking up more of this market share in recent years. The presentation looks at a number of commercial and residential examples that have successfully applied solar thermal to their building’s energy mix. Flat plate collectors and evacuated tube collectors are diagrammed by the presentation and offered as successful examples of widely used solar thermal technology.
Solar Cooling and Process Heat for Emerging Markets and Developing Countries
This presentation outlines the benefits of solar cooling and process heat for emerging markets and developing countries, and charts the work of Solar Installation Design (S.O.L.I.D) to increase its market penetration. S.O.L.I.D works to deliver fixed price turnkey installations for cash, with case studies included of existing projects such as the EA Tower in Pristina and the Olympic Sailing Village in China.
The events listing gives you an overview of where the international natural refrigerant community is gathering. The "attending" function is particularly convenient as you can see which of the community members is attending, allowing you to set up meetings in the run-up to the event.
Activate your account on R718.com
To activate your account on R718.com, simply go to “my profile” (top-right corner) and you will see “connect to R718.com”. Click on it and voilà , your account is activated on R718.com. From there on, you can log in on all platforms with the same email address and password and conveniently switch between the communities by clicking on the little icon in the top-right corner.
If you have any questions or remarks, please don't hesitate to let us know!
Also, if you would like some more explanations on the different features and how to best use them for finding the information you are looking for or increasing the visibility of your company, let us know - we are happy to call you and explain more in detail.
Kind regards,
Sabine
Community Coordinator
s.lobnig@R718.com
+32 2 230 3700
Zeo-Tech GmbH
System manufacturer | Combined heating & cooling
Ohmstrasse 3,
D-85716 Unterschleissheim, Germany
t | +49 89 310 44 84
f | +49 89 310 44 85
ZEO-TECH GmbH has developed a novel energy conversion process for the efficient generation and storage of heating and cooling power. This process is based on natural ingredients, zeolite and water, and is therefore compatible with the most stringent environment protection rules. Heat is the sole driving force needed. Application areas are for example:
- domestic heating and hot water boilers,
- food and beverage cooling,
- domestic, office and vehicle airconditioning.
In the course of 20 years since Zeo-Tech was founded, the underlying technology was continuously tested, modified, re-tested and optimised. A large number of devices had to be developed from scratch in order to make a low cost mass production vacuum system possible. Patents and protected base technologies plus the know-how, the craftsmanship and the patience of the Zeo-Tech team members are the business foundation of Zeo-Tech.
No other energy conversion process offers similar benefits as the zeolite/water sorption technology. The choice of zeolite, a solid, crystalline adsorbent and water as working-fluid was considered exotic during the start-up years of Zeo-Tech. In the meantime, the crucial technological advancements have been made by the Zeo-Tech team and this choice has turned out to be a real winner.
Coming soon: Water axial compressor prototype for commercial chillers by Johnson Controls
13 September 2012
R718.com interviewed Alexander Cohr Pachai, Johnson Controls industrial refrigeration technology manager, at the Sabroe Factory. Our new Silver Partner presents the results of 15 years research into a new water compressor type. Developed and tested in Denmark thanks to a public grant, the prototype has been installed in a water vapour process cooling plant and aims at replacing refrigeration plants that use traditional HFCs refrigerants.
R718.com: Water seems to be the perfect refrigerant: cheap, readily available, zero GWP, non-flammable and non-toxic. Why has water as a refrigerant not taken off yet?
Alexander Cohr Pachai: Water is the oldest refrigerant. It has been used in a variety of systems and in many different ways. In 1995, Sabroe and the Danish Technological Institute installed a water vapour system for trial operation in Lego, Denmark.
After 10 years of operation, we could see that we needed to improve a number of things before the system could become a commercially viable solution. The efficiency of the first compressor was not good enough and some other small technicalities needed further improvement. Intense research and development work and further testing lead us to the design of a new type of compressor, more compact, more efficient and more cost effective.
R718.com: What are the technologies in water refrigeration that seem the most promising and why?
Alexander Cohr Pachai: Vapour compression has always had a better efficiency than absorption/adsorption systems. Absorption systems are mainly used where heating costs are very cheap or free of charge to make it feasible. With the new vapour compression system, we will be closer to what other refrigeration systems can provide in terms of efficiency. We are also working hard to make it competitive in terms of first costs so that we can provide the market with cost effective chillers.
R718.com: Which is the most important technical issue to be solved before R718 can become a mainstream solution?
Alexander Cohr Pachai: Production volume. With volume comes the necessary economy scale so that we can reach the cost level the market is looking for. Over the years, a number of challenges have been solved. Now we stand with a product that just needs the final touch to reach the level we can be satisfied with. Saying this, I also know that the first product we put out now will be different than the product we will sell in ten years time. But the same goes for cars, motorbikes and many other things on the market. Development never stops.
R718.com: How do you evaluate the market potential for R718 and which region or market is likely to take off first?
Alexander Cohr Pachai: I believe that R718 will become popular in warm climates and in production environments. The advantage of water is that, unless special care is required for the cooling process, it is not necessary to use other heat exchangers. The refrigerant is cheap and you can release it without any special precautions.
R718.com: What will be the main applications?
Alexander Cohr Pachai: R718 systems can be used everywhere. As water is neither toxic nor flammable and since it does not break down to toxic or acid break down products, it can be used everywhere. It is, therefore, the perfect media for process engineering and air conditioning. When an application requires temperatures lower than 0°C, we will select either ammonia or hydrocarbons chillers.
R718.com: Can R718 technologies compete with conventional systems?
Alexander Cohr Pachai: The good news is yes. There is more to this story. At low evaporation temperatures water vapour systems can have slightly poorer efficiency, but since there is no heat exchanger in the cycle, the evaporation temperature will also be about 5K higher than conventional systems. The efficiency for water vapour systems increases by about 10%/K higher evaporation temperature compared to 2% for conventional system. It is clear that water vapour systems will benefit more from the new trends in many applications, where we see that the required water temperature is about 18°C.
When it comes to price comparisons, it is the old story about comparing apples with apples. If we compare the turnkey project, the benefit of using a cheap refrigerant will be a game changer. Also, if you get a leak, water is cheap to top up. Water goes in the drain and nobody will be in danger.
The refrigeration system using water vapour compression is also working at negative pressure and, therefore, there is no risk of explosion or fire when air gets in the system. Only for heat pumps using R718 you will have above atmospheric pressure, but again, at very moderate pressures, so there is no problem. Water is a very promising alternative here, but we still have to investigate further for this application.
R718.com: Can you tell us already a bit more about the prototype JCI is working on?
Alexander Cohr Pachai: The system built for the field test at Lego in Billund, Denmark, is based on a multi stage axial compressor. For those who are not familiar with this type of compressor, you can compare it with the first part of a jet engine that you find on most airplanes.
The condenser, heat exchangers here, releases directly the heat in the ambient air, which means that the condensing temperature will only be about 1K over the wet bulb temperature. Since the ground water in the area is full of different minerals, the heat exchanger must be located between the loop going to the molding machines to avoid clogging up the cooling channels in the molding head. Our challenge is then to figure out a way to change the water in the evaporator on regular basis.
R718.com: How did you tackle the R718's problem of extremely high specific volume?
Alexander Cohr Pachai: We evaluated different compressor technologies and axial compressor appeared to be the solution involving the least possible compromises. We also decided to use water as a lubricant for the bearings. We did not go for the easiest solution but for the right solution. Then, we dedicated a lot of time finding the right shape of impellers and how operate the compressor.
R718.com: How challenging was it to find a suitable design and material for the rotor?
Alexander Cohr Pachai: It has been a challenge to find the right design but also to find the right materials. We had to remember that the first impellers can be affected by water droplets. When the compressor is rotating at high speed, droplets hit the surface and erode the material. We had to take this into consideration when designing the new compressor.
R718.com: What is the size of the impellers and tip velocities of the tested system?
Alexander Cohr Pachai: The impellers have different diameters exactly like the compressor in the jet engine. At this stage, we prefer to keep the exact dimensions of the impellers confidential. We may also in the future develop a variety of diameters for different capacities and for different operational conditions.
R718.com: Could you tell us more about the overall parameters of the system that will be tested?
Alexander Cohr Pachai: The field test unit will be installed in parallel with existing ammonia chillers that operate at normal process temperatures. The capacity is about 750 kW and the efficiency is expected to be almost the same or slightly lower than the one of the ammonia systems at the current running conditions.
Useful contacts
Alexander Cohr Pachai
Technology Manager at Johnson Controls
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The Basics of R718: Technology Fundamentals
06 August 2012
The newly launched industry platform R718.com brings a series of articles covering topics such as the characteristics of water as a refrigerant, available R718 technology, latest research and market trends. In this first article R718.com provides an overview of fundamentals of this natural refrigerant.
Related articles
R718.com joins the ranks of the leading natural refrigerant platforms
02 August 2012
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
Advantages of R718
Abundance & Safety: The natural refrigerant R718, also known as dihydrogen monoxide, H20, water or water vapour is one of the Earth’s most abundant elements. From an environmental point of view, water is probably the ideal refrigerant for applications above 0°C. On the list of R718’s favourable characteristics are non-toxicity, non-flammability, 0 Ozone Depletion Potential (ODP), 0 (very low) Global Warming Potential (GWP), low cost and nearly unlimited availability.
Regulatory Relief: In this respect, R718 even exceeds other natural refrigerants like hydrocarbons or ammonia whose use is, in some countries, restricted due to flammability and toxicity related concerns. Being subject to no present or future environmental or safety regulations, investments in development of technology using water as a refrigerant are considered a low risk.
Efficiency: Also from a thermodynamic point of view, water has several specific characteristics that make it potentially a very efficient refrigerant (COP). R718 has a very high latent heat of evaporation (2,270kJ/kg), approximately five times higher than hydrocarbon R290 (428kJ/kg), four times higher than R744 (574kJ/kg) or slightly less than double the latent heat of evaporation of R717 (1,369kJ/kg). In other words, R718 absorbs significantly larger amounts of energy in the form of heat during a change of phase from liquid to gas without a change in temperature. The critical temperature of water is 380°C - 386°C, which is nearly triple the critical temperature of ammonia (132°C).
Main applications
Water has been extensively used as a process fluid (distillation, drying processes), as a heat transfer or energy storage medium (central heating, system cooling, ice storage systems) and as a working fluid in Rankine power generation cycle.
In refrigeration applications, the use of water as a refrigerant has been mostly limited to absorption systems built around a binary fluid comprised of lithium bromide and water and adsorption systems, using water as refrigerant and the mineral zeolite as adsorber. Systems using these two technologies can be driven by heat sources such as solar thermal, biomass or industrial waste heat and therefore possess additional environmental and economic benefits over purely electric driven machines. Because adsorption and absorption systems are the most important of the R718 applications, R718.com will dedicate individual articles to these technologies in the following issues of this launch series.
Limitations and research challenges
An obvious limitation is the low freezing point at atmospheric pressure. Water leads to corrosion and oxidation of many metals. Water is more reactive than other refrigerants and requires special attention on choosing the right materials used in the R718 systems during the design phase.
A number of factors limit the attractiveness of water-based vapour compression refrigeration cycles. Water vapour has very high specific volume (the density of water vapour is extremely low), around two orders of magnitude greater than a typical HFC refrigerant. That makes the process of compressing low pressure, high specific volume vapour to a pressure (and therefore temperature) that is high enough to allow heat rejection from the system challenging.
Large compressors with specially designed components, using materials such as titanium are required. Such compressors are more expensive and have long delivery times. Water based refrigeration systems operate in very low pressure environment that makes their continued operation free of contaminants (air) difficult.
Research in these areas (e.g. high speed, multi-stage, axial compressors are tested; turbo chillers with specially designed turbines and alternative steam ejector systems are in the development phase) points to a promising future for water being a viable alternative to HFC refrigerants. Details on R718 technology progress will be presented also in the separate article focused on latest research and development.
Thermal properties of water (source here) are:
- Maximum density at 4°C - 1,000 kg/m3, 1.940 slugs/ft3
- Specific Weight at 4°C - 9.807 kN/m3, 62.43 Lbs./Cu.Ft, 8.33 Lbs./Gal., 0.1337 Cu.Ft./Gal.
- Freezing temperature - 0°C
- Boiling temperature - 100°C
- Latent heat of melting - 334 kJ/kg
- Latent heat of evaporation - 2,270 kJ/kg
- Critical temperature - 380°C - 386°C
- Critical pressure - 221.2 bar, 22.1 MPa (MN/m2)
- Specific heat water - 4.187 kJ/kgK
- Specific heat ice - 2.108 kJ/kgK
- Specific heat water vapour - 1.996 kJ/kgK
- Thermal expansion from 4°C to 100°C - 4.2x10-2
- Bulk modulus elasticity - 2.15 x 109(Pa, N/m2)
R718.com joins the ranks of the leading natural refrigerant platforms
02 August 2012
Latest news on developments in water refrigeration technologies, reports on important players in the sector, technical details on state-of-the art products, updates on relevant policies and access to THE global natural refrigerants community uniting over 10,000 experts - this is R718.com, the new platform focusing on everything regarding water as a refrigerant. Sign up and help to bring water as refrigerant faster to market!
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R718 water as refrigerant 3rd generation
05 October 2011
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
In July 2012, shecco launched R718.com - a platform dedicated to water as refrigerant. R718.com joins the ranks of the foremost global natural refrigerant platforms that have so far focused on CO2 (R744), hydrocarbons and ammonia. The aim: bringing natural refrigerants faster to market.
"After the success of R744.com, ammonia21.com, and hydrocarbons21.com, which was successfully launched in 2009, we are proud to bring a fourth natural refrigerant platform online: R718.com, which will focus exclusively on water as refrigerant and with this, present another technology that is apt to help us fight climate change,” says Marc Chasserot, founder and editor-in-chief of R718.com. “Furthermore, R718.com fits in seamlessly with the other three natural refrigerant platforms and serves as a gateway to THE global online community uniting experts in natural refrigerants from all over the world.”
news - products - community
Three pillars ensure that R718.com caters to the needs of an international expert community:
- news: updates on latest developments in industry, policy, technology and research
- products:a list of state-of-the-art products with technical descriptions and a competent contact person for more information
- community:a common space for international experts to exchange information, best practice, business opportunities....
R718.com community members have access to many new features, amongst which:
- Community activities:a page summarising the on-going activity of community members, where they can share thoughts, links, and news on natural refrigerants in general and R718 in particular;
- File sharing:attach your presentation, press release, product brochure, picture galleries.... for all members to see in the timeline
- Inbox: the R718.com messaging system makes it easy to connect with members and exchange information, set up meetings, get to know each other;
- Forum: a place to discuss amongst experts pending issues, technological developments, new regulations.... related to water as refrigerant;
- Noticeboard: a section to post and view opportunities related to water refrigeration, such as career prospects, training, partner search, funding, call for papers...
Join in the global community on natural refrigerant fluids
The R718.com community is a gateway to the first global platform uniting over 10,000 experts in the field of natural refrigerants. Being a member of R718.com also allows you to log into R744.com, hydrocarbons21.com and ammonia21.com once your account has been activated. Consequently, you can choose whether the information and content that you want to share should appear on one, two, three or all four platforms.
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
R718.com provides an overview of three papers presented in the Absorption Prototype session at the GL 2012 conference in Delft, the Netherlands. Advances in absorption technology and its design are discussed. Promising results of simulations and experimental studies point to increased efficiency and extended range of operations.
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Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
Development of double-output absorption heat pump chiller with improved heating efficiency - T. Fujii, Y. Sakano, et al
A prototype of a double-output absorption heat pump chiller (AHPC) with combined COP 3.3 was presented by researchers from Hitachi. Steam consumption of the double-output AHPC is reduced by 34% in comparison with conventional systems (absorption chiller and boiler). This lithium bromide/water system provides hot and chilled water simultaneously with heating and cooling capacities 296kW and 158kW, respectively. From the simulation and experimental results, heating COP improved from 1.0 to 2.15 by recovering heat from chilled water as the additional heat source. The initial construction difficulty was higher pressure than in conventional systems caused by hot water. To reduce working pressure and solution concentration a two-stage evaporation and absorption was applied. Energy savings are expected from installation of this heat source machine, especially in facilities with year-round cooling and heating demands.
First operation experiences with novel resorption chillers to generate cooling from waste heat and biomass – K. Helle, T. Weimer at al
Authors of this paper introduce resorption cooling technology and point out promising experimental results for a thermal driven ammonia water system with plate heat exchangers as absorbers and desorbers. Resorption chillers consist of two solvent loops which are coupled by an exchange of gaseous refrigerant medium. A first test was conducted on a small resorption plant with a maximum cooling capacity of 2kW and a resorption chiller in combination with a FLOX burner for bio-fuels. Resorption chillers can achieve a COP > 0.4.
Advantages of resorption system:
- No purification of gas necessary
- Only small amount of ammonia gas used
- Reduced maximum pressure
- Adjustable pressure – depending on the solution concentration
Disadvantages of resorption system:
- More complexity – additional solvent loop with pump, valve and heat exchanger
- Additional fluid flow between the cold and hot solvent cycle needed
- Slightly reduced COP compared to conventional ammonia systems
Self adaptive refrigerant flow low temperature driven dual lift absorption cycle – M. Guerra
In his presentation, Guerra introduced an air- cooled absorption system in which the refrigerant flow self adapts to the evaporator and absorber loads to improve efficiency, stability and to extend the range of operations. The system using ammonia and water as working fluids was developed to allow operation with low generator temperature input. This prototype system was run with hot water at inlet temperatures from 70°C to 95°C and with air temperatures ranging from 25°C to 40°C. With 92°C driving hot water, 7°C outlet chilled water and at 35°C outdoor ambient temperature the prototype chiller has a cooling capacity of 3.4kW with COP 0.29 and 360 W power consumption for the solution pump and the fan. Inlet temperature 79°C results in a cooling capacity of 2.5kW with COP 0.28 and 285 W power consumption. Author concludes that the operation of the prototype has proven to be stable and repeatable.
Spotlight on cutting edge R718 technologies at 10th Gustav Lorentzen
25 June 2012
The 10th IIR Gustav Lorentzen Conference on Natural Refrigerants, a key event covering the latest research results and advances in water, air, CO2, ammonia and hydrocarbon HVAC&R technologies is being held on 25 - 27 June 2012 in Delft, Netherlands. Keep abreast of progress and trends with R718.com, which is reporting live from Delft.
Related articles
Water as refrigerant can enable an end to EU f-gas reliance
01 June 2012
34% performance improvement - novel absorption systems discussed at GL 2012
03 July 2012
More than 230 participants are attending the three-day Gustav Lorentzen conference organised by the International Institute of Refrigeration (IIR), the Royal Dutch Association of Refrigeration and the Delft University of Technology. Attracting a wide range of international specialists from science and industry sectors, the conference will facilitate an effective exchange of experience and knowledge on the latest research relating into R718, including:
- Absorption solar: LiBr/H20 absorption chillers,
- Absorption fundamentals: CO2absorption enhancement by natural refrigerant with Al2O3 nanoparticles
- Absorption prototypes: First operating experiences with novel resorption chillers to generate cooling from waste heat and biomass
The keynote speakers will include:
- Predag Hrnjak (USA, University of Illinois) – “Research advances related to Natural Refrigerants”
- Andy Pearson (UK, Star Refrigeration Ltd) – “Market success of Natural Refrigerants”
- Alberto Cavallini (Italy, University of Padua) – “Heat transfer and pressure drop of Natural Refrigerants in mini-channels”
- Ekkes Bruck (NL, Delft University of Technology) – “Magnetic refrigeration for industrial applications”
Some more details can be found in the follow up article(s):
34% performance improvement - novel absorption systems discussed at GL 2012
About Gustav Lorentzen
The conference is named in honour of Norwegian Scientist and engineer Gustav Lorentzen who rediscovered how CO2 could be used as a refrigerant in a simple and efficient way in heating and cooling applications.
Water as refrigerant can enable an end to EU f-gas reliance
01 June 2012
Already the most commonly used liquid as a heat transfer fluid in secondary refrigeration and air-conditioning, water (R718) is also part of the basket of identified HFC replacement primary refrigerants that could enable an end to EU’s reliance on f-gases, according to a recent report.
As the EU is considering revisions to the F-Gas Regulation, a new report titled ‘Availability of Low-GWP Alternatives to HFCs: Feasibility of an Early Phase-Out of HFCs by 2020’ outlines a clear timetable, setting out the dates by which the use of HFCs can be banned in new equipment, with a complete phase-out possible by 2020 in 20 sub-sectors. The report also outlines and provides case studies on the various available HFC alternative technologies, including water as refrigerant.
5-10% better energy efficiency for large centrifugal chillers with water refrigerant
The thermophysical properties of water as refrigerant makes it suitable for applications above 0°C, where it can be used in larger chillers with good energy efficiency. “For large centrifugal chillers, water as refrigerant is an environmentally benign solution, with 5-10% better energy efficiency” reads the report.
Examples of available water refrigerant based vapour compression products
The report points out that water as refrigerant has since many years been marketed by a manufacturer of centrifugal compressor desalination equipment in Israel, with installations of the technology that can be found in South Africa, Denmark and Japan.
More recently, a group of Japanese and American companies along with a Danish research institute have developed two water vapour compressors of 0.8 and 1.8 MW under a project funded by the Danish Energy Agency.
Finally, the report makes a reference to a German company that has developed a centrifugal chiller/ heat pump with water as refrigerant of about 5 to 15 kW capacity. The company declares energy efficiencies much higher than HFC systems.
Absorption systems with water refrigerant could become more attractive where solar collectors supply heat
Besides vapour compression cycle technology, the report also considers not in kind alternatives such as absorption air-conditioning systems typically found in large buildings in big cities with electrical grid limitations in the summer.
Using the principle that some gases are absorbed by certain liquids, absorption air conditioning systems typically use water as the refrigerant and lithium bromide as the absorbent, with the other typical pairs being ammonia (refrigerant) and water (absorbent).
“The energy efficiency of a gas fired absorption chiller is usually only 25% of that of a comparable compressor system. Based on the typical efficiency for converting fossil fuel into electricity (25-30%) and the energy mix of Europe, the CO2 balance is about equal for compression and gas fired absorption systems. Absorption systems could become more attractive where heat is supplied by solar collectors. On the other hand, if electricity production is mostly from renewable energy, as for example in Norway, electrically driven vapor compression systems will also have lower CO2 emissions due to energy use”.
Water as one of many refrigerants in basket of low-GWP technologies
The report asserts that no single low-GWP technology could replace HFCs in all applications: “Crucially, there is no single alternative that will replace HFCs in all applications, just as there is no single fluorinated greenhouse gas that can be used in all applications. The low-GWP technology that is most appropriate will depend on a number of factors including the local economic and regulatory situation, as well as climatic and other factors.”
Other natural refrigerants discussed in the report include hydrocarbon isobutene, hydrocarbon propane, hydrocarbon pentane, hydrocarbon propylene, various hydrocarbon blends such as the butane-isobutane-propane-ethane blend (R441A), ammonia, carbon dioxide (CO2), and the combination of different natural refrigerants in cascade systems.
The Basics of R718: the Absorption cycle
09 August 2012
Following the “Technology Fundamentals”, the second "The Basics of R718" article focuses on the principles of absorption technology. R718.com designed an easy to understand absorption cycle chart to graphically demonstrate processes that occur during the operation of absorption chillers.
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Absorption is defined as the penetration of one substance into the bulk of another substance. It is the phenomenon in which atoms, molecules, or ions of one material enter a bulk phase – gas, liquid or solid of another material with uniform distribution throughout the bulk.
The absorption thermodynamic cycle generates refrigeration effect through the use of two fluids – an absorbent (lithium bromide) and a refrigerant (water) and a heat source substituting the electrical input in the vapour compression cycle. The compressor is replaced by an absorber, a solution pump and a generator. The thermal energy from a heat source is transferred to a heat sink (chilled water) through the absorbent fluid and the refrigerant.
The absorption chiller is based on absorbing and then releasing water vapour into and out of a lithium bromide solution. Since no chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) are used the cooling process is environment friendly. Furthermore, industrial waste heat, solar thermal, biomass or another renewable source of energy can be used to drive the absorption cycle.
Principle of adsorption chillers
The basic property of an absorption chiller is that one specific pressure and temperature corresponds to one solubility value of a solution. The single-effect absorption chiller operates in 4 key steps, resembling the functions of the 4 chambers, as demonstrated in the absorption cycle graph below:
1. Generator
The lithium-bromide solution (pink colour) is pumped into the generator and is heated by a heat source, raising the lithium bromide solution to a temperature where the liquid refrigerant (blue colour) vaporizes and flows to the condenser. The concentrated lithium bromide solution (brown colour) flows down to the absorber chamber.
2. Condenser
In the condenser, the cooling water absorbs the heat of condensation from the vaporized refrigerant, changing the refrigerant into a liquid. The liquid refrigerant travels from the condenser through expansion piping to the evaporator during which the liquid refrigerant experiences a drop in pressure and temperature.
3. Evaporator
The liquid refrigerant is pumped to the evaporator and sprayed on the top of the chilled water tube bundle. At low evaporator pressures, the liquid refrigerant vaporizes, removing energy from the chilled water. The liquid refrigerant that is vaporized then travels from the evaporator to the absorber.
4. Absorber
In the absorber, the concentrated liquid lithium bromide solution absorbs the vaporized refrigerant and the cooling water absorbs the vapour absorption heat. As the refrigerant vapour is absorbed the concentrated solution returns to a diluted state. After the absorption, the diluted liquid lithium-bromide solution is pumped to the generator, completing the refrigerant cycle.
Characteristics of absorption chillers
There are a number of absorption chillers commercially available, ranging from single-effect indirect-fired (steam, hot water) chillers with a COP<1, originating in 1950s, to double-effect direct-fired (gas, oil burner) chillers, and novel triple-effect absorption chillers with a COP reaching 1.8.
Single-effect absorption chillers have a single generator and condense all vaporized refrigerant in a single condenser. Double-effect absorption chillers have two generators and the vaporized refrigerant from the high temperature generator is the thermal source for the low temperature generator, reducing the cooling requirement for the vaporized refrigerant. Triple-effect chillers operate with three generators (low, medium and high temperature).
The cooling capacity of absorption chillers ranges from 5kW up to 12 MW. Lithium bromide – water is the most commonly used pair of working fluids, followed by water – ammonia. The heat source can be any suitable industrial waste stream (exhaust, steam, hot water, etc.) or any suitable combustible (natural gas, biogas, diesel, waste oil, wood pellets, etc.) higher than 80°C. Using abundant solar thermal energy as a heat source to power the absorption cycle is a particularly environmentally friendly solution.
Advantages of absorption chillers
- The working fluids are natural refrigerants water and ammonia with no Global Warming Potential (GWP) and no Ozone Depletion Potential (ODP)
- Electric power consumption is only 1/20 - 1/10 of a vapour compression type chiller
- Chills water down to 9°C
- High reliability and low maintenance
- No compressors results in less noise and vibration free operation
- Can be powered by renewable heat sources
- Low pressure operation system considered safe
- Excellent operating characteristics under a partial load
The Basics of R718: the Adsorption cycle
10 August 2012
Following the “the Absorption cycle”, the third "The Basics of R718" article focuses on the principles of adsorption technology. To graphically demonstrate processes that occur during the operation of adsorption chillers R718.com has designed two easy to understand adsorption cycle diagrams.
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09 August 2012
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06 August 2012
Adsorption is defined as a process that occurs when a gas or liquid accumulates on the surface of a solid (more rarely a liquid) forming a molecular or atomic film. Adsorption is useful for separating certain molecules from one another.
Adsorbents are most commonly found as carbon or oxygen compounds. Oxygen compound adsorbents are used to manufacture silica gel and zeolite, two major materials used in adsorption chillers operating with water as a refrigerant. Ammonia is an alternative to R718 as a refrigerant.
Adsorption is typically an exothermic process, as gases are adsorbed on a substrate, heat is released. Heat is required to release the accumulated gas once again. It is the reversibility of this process that laid the foundation for the refrigeration effect used in adsorption chillers.
An adsorption cycle for refrigeration does not use any mechanical energy, but only heat energy. Renewable sources of energy like solar thermal or waste heat from industrial processes can provide hot water to drive the adsorption cycle.
Principle of adsorption chillers
The adsorption chiller consists of an evaporator, a condenser and two adsorption chambers (1&2). All four chambers are operated at nearly a full vacuum. The adsorption chambers alternate in their adsorbing and desorbing functions. The two-phase chamber alternation principle will be explained in the graphics below, designed by R718.com.
Phase One. The sorbent in chamber 1 is regenerated using hot water from the external heat source. Hot water enters chamber 1 to desorb the silica gel/zeolite. The water vapour is driven from the sorbent and rises to the condenser where it is then condensed to a liquid state. The condensed water is recycled in a closed-loop to the bottom of the system where it is available for re-use.
At the same time the sorbent in chamber 2 adsorbs the water vapour entering from the evaporator through the open ports at the bottom of the chamber. Chamber 2 has to be cooled in order to remove the heat deposited by the adsorption process and to enable a continuous adsorption. Due to the low pressure conditions in the evaporator, the refrigerant injected into the evaporator is transferred into the gas phase by the evaporation heat from the chilled water – the useful product of adsorption cycle. If the sorption material in the adsorption chamber is saturated with water vapour to a certain degree, the chambers switch over in their function.
Phase Two. When the adsorbant in chamber 1 is dry and the adsorbant in chamber 2 is saturated with water, the process in the adsorption chiller reverses. Several valves are used to equalize the pressure among the chambers. Cool water is run through chamber 1 to transfer any residual heat to chamber 2, which begins the heating process marking the end of the reversal process. In Phase Two dry chamber 1 begins to adsorb water vapour entering the chamber from the evaporator while chamber 2 releases, or desorbs, water into the condenser. The rest of the cycle is analogous to the process explained in Phase One above.
Characteristics of adsorption chillers
Adsorption chillers are a unique approach to achieving air conditioning and process cooling. Hot water is used to drive the chiller rather than from large amounts of electricity, as happens in conventional air conditioners.
Adsorption chillers use solid sorption materials instead of liquid solutions. Market available systems use water as refrigerant and silica gel and zeolite as the adsorbent.
The cooling capacity of adsorption chillers ranges from 5kW up to 500kW. Under typical operation conditions with a driving temperature of 80°C, the systems achieve a coefficient of performance (COP) of about 0.6, but operation is possible even with temperatures of approximately 50°C.
The adsorption chillers are based on adsorbing and then releasing water vapour onto and out of a silica gel or zeolite. Since no chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) are used the cooling process is environment friendly. The whole system uses only fraction of the electricity of conventional chillers.
The heat source to provide hot water can be any suitable industrial waste heat or any suitable combustible (natural gas, biogas, diesel, waste oil, wood pellets, etc.) higher than 50°C. Using abundant solar thermal energy as a heat source to power the adsorption cycle is a particularly environmentally friendly solution and its deployment is increasing.
Advantages of adsorption chillers
- The working fluid is natural refrigerant water (or ammonia) with no Global Warming Potential (GWP) and no Ozone Depletion Potential (ODP)
- No internal solution pump and electricity consumption is reduced to a minimum
- Heat source temperatures as low as 50°C
- Chilled water output as low as 3-5°C
- Very long continuous operation possible
- High reliability and even less maintenance than absorption chillers
- Simple mechanical construction, robustness
- No danger of crystallization and thus no limitation in temperatures
- Long operating life (silica gel lasts 30 years)
- Can be powered by renewable heat sources
- Very low sound pressure level <50dB
R718 water as refrigerant 3rd generation
05 October 2011 | ILK
Since 2000, numerous installations for different customers have demonstrated the technical feasibility and the capability of water as refrigerant. Based on the high performance axial compressor, developed by the ILK, water chillers with a performance of 400 kW to 1000 kW were produced and applied.
With the introduced concept of the R718 Turbo Chiller 3rd generation an important step has been taken from technical feasibility to economical equality. By improving primary components such as turbo compressor and heat exchanger, the compressor efficiency and the coefficient of performance of the chiller has been immensely increased compared to the first and second generation. New procedural and design engineering solutions, general improvements and simplifications enormously reduce the expenditure in manufacturing
Article continues:
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R718 water as refrigerant 3rd
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R718 water as refrigerant 3rd generation
Since 2000, numerous installations for different customers have demonstrated the technical feasibility and the capability of water as refrigerant. Based on the high performance axial compressor, developed by the ILK, water chillers with a performance of 400 kW to 1000 kW were produced and applied.
With the introduced concept of the R718 Turbo Chiller 3rd generation an important step has been taken from technical feasibility to economical equality. By improving primary components such as turbo compressor and heat exchanger, the compressor efficiency and the coefficient of performance of the chiller has been immensely increased compared to the first and second generation. New procedural and design engineering solutions, general improvements and simplifications enormously reduce the expenditure in manufacturing.
Since over 8 years R718 Turbo Water Chillers are operating with water as refrigerant in Germany and Luxemburg. In the last years the new refrigerant technology has demonstrated its technical feasibility and reliability under challenging operating conditions.
ILK Dresden and Axima Refrigeration GmbH work togehter on a joint projekt. The aim is to launch sucessfully the 3rd Generation of R718 Turbo Water Chillers at the market.
Design conditions for R718 chiller Water R718 is no refrigerant like others, which are usually used in water chillers. The special characteristics of water R718 have consequences for compressor and equipment layouts. Pressure ratio and specific volume of water vapor differ immensely from those of usual refrigerants.
For an operating temperature range of 32 K and a condensing temperature of 4 °C there is, for common refrigerants like R134a, a pressure ratio of approx. 2.8 necessary, whereas it is for R718 approx. 7.2. The intake volume for R134a is 0,3 m3/s and for R718 60 m3/s for a cooling capacity of 1000 kW and a condensing temperature of 4 °C.
Process configuration with water vapor turbo compressor. The vapor high-performance axial compressor can be applied in different processes.
For instance in
- cleaning and concentration processes,
- for ice production with direct evaporation,
- for water desalination,
- and in chillers and/or heat pumps.
The term direct evaporation refers to the process when some water, as the energy transfer medium, evaporates in the evaporator due to relaxation and becomes in this way to refrigerant water.Direct condensation exists when the refrigerant condenses directly in the cooling water.
R718 Turbo Chiller 3rd Generation
Conclusion
The undisputed advantages of water as refrigerant are environmental compatibility, cleanliness, plant safety, reliability, maintainability and energy efficiency. So far, they could be realized only in a small number of implemented plants. The manufacture expenditures of the first and second generation were too high.
With the presented concept of a 3rd generation of R718 Turbo Chillers an important step was taken from the technical to the economic feasibility of R718 chiller sets. Improved main components, such as turbo compressor and heat exchanger, noticeably increase the efficiency and performance of the water chiller. New procedural and constructional solutions, improvements and simplifications reduce the manufacture expenditures.
With the realization of this concept in a serial production water as refrigerant changes the status of an exotic cooling procedure to an economic alternative of cold water production.
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