Environmentally Friendly Refrigerants Now Become Just a Matter of Course.
It's all over but the shouting as far as alternative refrigerants are concerned. What used to be called the International Conference on Ozone Protection Technologies has been merged with the International Climate Change Conference to form the Earth Technologies Forum.
Per Rosenqvist of the European Commission delivered an update on European Union policy, which is proposing to advance elimination of hydrochlorofluorocarbons (HCFCs) to 2008 instead of 2015, which later date had been well ahead of the world deadline set by the Montreal Protocol.
New refrigeration and air conditioning systems, except for reversible air conditioning, would have to eliminate use of HCFCs after next year (2001), under the current draft. New reversible air conditioning systems would face a 2004 deadline, and all existing systems would have to switch by 2008.
When it comes to alternative refrigerants themselves, however, the encyclopedists have arrived. James M. Calm, an engineering consultant based in Great Falls, Virginia, USA, presented a data base running to more than 10 pages that offered comprehensive information on several hundred refrigerants and blends.
Calm's table gives the chemical formula of each refrigerant, or the percentage breakdown of refrigerants for blends, the molecular mass and other physical data, safety data (ASHRAE code citations), atmospheric life (how many years it takes each to break down), and - last but far from least - ozone depletion potential (ODP) and global warning potential (GWP).
European regulations against chlorofluorocarbons (CFCs) and HCFCs -"more stringent than any others" - were the keynote of a presentation by Marc Barreau of Elf Atochem S.A., Levallois-Perret, France, on the state of HCFC substitutes for air conditioning applications.
ODP-free hydrofluorocarbons (HFCs) are already widely used in Europe, Barreau noted, whether in pure form or blends. The most accepted are HFC-32 (CH2F2, methylene fluoride), HFC-125 (CHF2CF3), HFC 134a (CH2CF3) and HFC-143a (CH3CF3). R-407C, a widely used blend, is 23% HFC-32, 25% HFC-125 and 52% HFC-134a. These all work in existing equipment at minimal cost or system redesign, he added.
A number of major OEMs (original equipment manufacturers) have already specified HFC-134a and R-407C for their new systems, Barreau said. Moreover, a survey a year ago of 50 refrigeration and air conditioning companies by the International Institute of Refrigeration showed strong support for the same two refrigerants, which don't have the pressure and compatibility problems associated with other alternatives.
"Beyond 1998, it seems very possible that HFC-134a will be used more and more in low-input power systems, but at the same time be the key choice for industrial applications," Barreau ventured. "HFC-134a should coexist with R-407C in the light and heavy commercial segment. R-407C is associated with semi-hermetic reciprocating compressors and HFC-134a with semihermetic screw compressors."
Related to Barreau's paper was one by Horst Kruse and Holger Konig of the German Institute of Refrigeration on the comparative performance of R-407C and R-410A, the latter a 50-50 blend of HFC-32 and HFC-125 marketed by DuPont as Suva 9100.
"The comparison of R-22 substitutes has shown that R-410A as a near azeotropic refrigerant mixture shows a very advantageous energetic behavior but needs adjustment of compressor size and pressure design regulations," the pair concluded. "The zeotropic mixture R-407C has disadvantages concerning demixing behavior in the two phase regions of the system, leading to changed refrigerant composition."
R-407C's problems with lower heat transfer coefficients can be overcome by adaptation of temperature profiles of internal and external fluids in heat exchangers, they added. "But with this measure, the behavior of R-407C is still inferior from an energetic point of view as compared with R-410A. Propane is in this respect similar to R-410A, but its flammability requires further safety measures that may increase overall plant costs."
Subcooling of liquid refrigerant as it leaves the condenser could reduce the inefficiency of supermarket freezer cycles, according to a paper by Boris Yudin, Mikhail Boiarski and Oleg Podcherniaev of InterCool Energy Corp., Latham, New York.
An advanced subcooler could increase efficiency of a freezer using R-507 by 40%, the trio reported, compared to 20% for conventional mechanical subcooling, 10% each for a screw compressor economizer or a liquid suction heat exchanger, and a mere 5% for natural subcooling.
The advanced system they recommend uses a two-circuit heat exchanger that effectively combines the liquid-section heat exchanger and the evaporator. Using a zeotropic refrigerant with a significant temperature glide, it is designed to provide temperature-distributed refrigeration in order to minimize subcooler power consumption.
RELATED ARTICLE: Hydrocarbons: Are They Safe? IIR Considers New Standards
Hydrocarbons (HCs) as refrigerants have long been a no-no to the refrigeration industry: too much danger of fire or explosions. But now they're coming back into favor, and the International Institute of Refrigeration (IIR) has looked into potential changes in safety standards.
Several European countries have already done so, and are allowing HC systems for home freezers and refrigerators and even for refrigerated cabinets at supermarkets. But the limits are strict in the United States and elsewhere, with agencies like Underwriters Laboratories and the International Electrotechnical Commission as gatekeepers.
Instead of prohibiting HCs outright for household appliances and supermarket systems, the relaxed regulations is Germany, Sweden and the UK simply set stricter conditions for HCs than for non-flammable refrigerants. Charge size limitations, also known as "practical limits" or "refrigerant quantity limits" figure in the codes. So do minimum space requirements for units using HCs, and the proximity to them of' potential ignition sources.
But there can be pitfalls in such codes, the IIR advised, because operators of HC systems may place them in too small a space to be safe in case of a refrigerant leakage. Moreover, because HCs are denser than ordinary air, they can initially "pool" on the floor even if the amounts aren't that great. Furthermore, how are manufacturers Supposed to know about potential "ignition sources: in homes and public areas, as opposed to controlled facilities?
"Expanding the use of Class 3 flammable refrigerants in home appliances and publicly occupied spaces has been presented as a solution to global warming problems," the IIR paper concluded. "But this changes past safety practices, and should be done with great care to ensure that the safety of the public is maintained."
RELATED ARTICLE: DuPont Redesigns Packaging For Suva Refrigerant Line
Packaging for Suvar refrigerants from DuPont, Wilmington, Delaware, USA, has been redesigned to make usage simpler and provide more useful information.
The biggest change is removal of the dip tube. With the new container, retrieving the liquid is accomplished by inverting the cylinder. The change is indicated by a bright green "Alert to Invert" icon.
The bottom flap of the container features pressure and temperature information, making it convenient for the user.
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|Title Annotation:||includes related articles on hydrocarbons and Du Pont's new packaging for Suva refrigerant line|
|Publication:||Quick Frozen Foods International|
|Date:||Apr 1, 1999|
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