New year rings in countdown to find HCFC replacements.
The countdown used to be to the year 1995, for getting rid of CFCs (chlorofluorocarbons). Now the commercial refrigeration industry is targeting 2030 (global deadline to stop using HCFCs (hydrofluorocarbons), or even 2015 (proposed European Union deadline for the phaseout).
Papers at the 1994 International CFC and Halon Alternatives Conference in Washington, DC, reflected the shift in concern - and the fact that the action has moved from the theoretical to the commercial stage, with rival suppliers using papers to promote their companies' products.
One paper by researchers for Elf Atochem, for example, heralded that firm's new ternary mixture, Forane FX-220, as a substitute for HCFC-22 in refrigeration and air-conditioning, while another reported field trials of other Forane refrigerants as replacements for R-12 and R-502.
Sylvie Macaudiere and G.D. Rolotti, in their study on behalf of Elf Atochem, reported on the performance of Forane FX-220, in terms of thermodynamic properties - close to those for HCFC-22. But their parameters were for household air conditioning rather than industrial refrigeration.
In collaboration with P. Weiss and M. Barreau, two other Elf researchers, Rolotti presented results of field trials of several Forane refrigerants in supermarket refrigeration systems. It turns out, they said, that the replacements not only work as well or better, but don't even require field assistance from the company to install.
Forane 134a or Forane FX56 (for retrofit) are Elf's alternatives to CFC-12, while Forane FX70 or Forane FX10 (retrofit) can replace R-502. Forane R404A, a 44-52-4 ratio near azeotropic blend of HFCs-125, 134a and 143a, had already been recommended as a replacement for HCFC-22 in low-temperature refrigeration systems, and new equipment is even being custom designed for it.
Forane FX10, also known as R408A, is another near azeotropic blend, offering a 90% reduction in ODP (ozone depletion potential) and an 80% reduction in HGWP (global warming potential) versus R-502. It also offers better cooling capacity in hermetic compressors, the Elf researchers said. French supermarket chain Casino is among those having already retrofitted R-502 systems with R408A.
The only problem with R408A is that it contains HCFC-22 as well as HFCs 125 and 143a; that makes it compatible with existing lubricants, but it will have to be replaced eventually - and perhaps sooner than expected if deadlines for HCFC phase-out are moved up again. Forane FX56 (R409A), another Elf blend recommended as a replacement for R-12 in both display cabinets and transport refrigeration systems, is a blend of HCFCs 22, 124 and 142b: same problem, but more so.
Three researchers for ICI Klea introduced TEWI (Total Equivalent Warming Impact) as a new criterion for alternative refrigerants. T.W. Dekleva, G.H. Haines and R.E. Low argued that their company's refrigerants offer both greater energy efficiency in new and existing equipment and "a coherent and logical strategy for management of a smooth transition from R-502 to a zero ODP refrigerant with minimal environmental impact."
Field tests for KLEA 407A (a 20-40-40 blend of HFCs-32, 125 and 134a), the trio said, indicate that it "can outperform R-502 and R404A in many existing evaporator designs." A supermarket chain in Texas, meanwhile, has switched to KLEA 407B (a 10-70-20 blend of HFCs 32, 125 and 134a) for low-temperature equipment, with no loss of efficiency; while Kirby's Refrigeration is getting higher efficiency with 407B. Not only that, the paper reported, but both blends offer HGWP ratings well below those for R-507 and R-404A.
Another corporate entry, from Mark L. Robin of the Fluorine Chemicals Department of Great Lakes Chemical Corp., focused on the thermophysical properties of HFC-227ea. It can be used as a refrigerant although it has broader applications as a fire-suppression agent and as a propellant.
Some research papers still came from universities. S.M. Sami of the University of Moncton, Moncton, New Brunswick, Canada, evaluated a blend called NARM III (a blend of HFCs 32, 125, 143a and 134a) as an alternative to both HCFC-22 and CFC-502, finding that it actually enhanced the efficiency of equipment by 9.5% and 8.9%, respectively, over the old refrigerants.
Sami's set-up was a vapor compression heat pump, with compressor, oil separator, condenser, pre-condenser, pre-evaporator, adjustable expansion device, capillary tubes and evaporator. It was connected to various types of heat pumps and a domestic refrigerator for the experiments, which concluded that NARM III "could be used as a long term viable replacement for CFCs and HCFCs."
Three researchers from Keio University, Yokohama, Japan (Akihiro Osajima, Haruki Sato and Koichi Watanabe) presented a new model for thermodynamic study of two binary refrigerant mixtures, R32-134a and R32-125.
"The proposed model consists of the PR equation for the VLE behavior, which has to be combined with the truncated virial equation of state for the vapor phase of these mixtures with different compositions," they explained. "The compared results clearly show a satisfactory agreement in general between the present results with the REFPROP, but the difference between them becomes larger for both mixtures at higher temperatures."
Another trio from Jiaotong University, Xi'an, China (Hong-wei Xiang, Lian-cheng Tan and Zhong-qi Chen) offered a "crossover model" for the thermodynamic properties of HFC-134a. The point of their paper was the "crossover equation," which can be used for a comprehensive analysis of "all the thermodynamic properties in every region," and is thus superior to traditional approaches. Figures for isochoric heat capacity against temperature obtained with the new equation, for example, differed sharply with those from previous models.
Susumu Misaki of the Research Institute of Innovative Technology for the Earth, and Akira Sekiya of the National Institute of Materials and Chemicals Research in Ibaraki (also Japan) were the only ones this time around to look into more exotic potential substitutes for CFCs.
Instead of HFCs, their project is looking into fluorinated alcohol, fluorinated ether, fluorinated amine and fluorinated alkyl or alkoxyl silane. Except for the fluorinated ethers, they said, none of these had been seriously investigated before. Nearly all of them have extremely low HGWP ratings - 0.01 to 0.15 on a scale with CFCs as base 1.00. Toxicity is also low for most of them. Actual performance evaluations as refrigerants were still under way, however, at the time they wrote their paper.
Four researchers at Arizona State University (K.L. Whitfield, D.S.C. Chau, B.D. Wood and Warren Rice), went off the beaten track with a proposal for a hydraulic refrigeration system using n-butane as the refrigerant. It may show "unique promise as part of ice or clathrate energy storage systems," they concluded, but it has "not yet been possible to confidently determine several economic matters."
Besides the refrigerants themselves, lubricants to use with them are a growing concern. V.Z. Geller and M.E. Paulaitis of the University of Delaware, in collaboration with D.B. Bivens and A. Yokozeki of DuPont, offered a study on viscosities of alternative refrigerant/lubricant oil mixtures.
The researchers paid particular attention to R134a with various polyolester (POE) mole concentrations and temperatures, results of which were presented in tables accompanying their paper; but they also tested HFCs 32, 125, 143a, and blends of 32125, 32-125-134a and 125-134a-143a; along with HCFC22 and CFC115. From all those tests, they developed a general model that "requires limited information for parameter determinations, and can be applied to reliably estimate the viscosity and density of refrigerant/lubricant oil mixture."
R.W. Yost and C.L. Jarrell of ICI Klea weighed in with their own study on the solubility of HFC refrigerants in synthetic lubricants and its effect on viscosity. They too focused on POE lubricants, obtained from commercial sources.
Although POE's have previously been shown to work well with HFC134a (and are already being used with HCFC-22 in commercial installations), there is still "limited published data on the physical characteristics of these refrigerant-lubricant mixtures," they complained. In their paper, they offered data on the solubility of HFCs 32, 125 and 134a in RL32S, one of ten POEs evaluated for viscosity and miscibility.
None of the HFCs proved as soluble as HCFC-22, although HFC-134a came closer than the others whether based on weight or molar concentration. Tests with other POE lubricants showed little difference in solubility or resulting viscosity.
Kenneth C. Lilje and Mahmood Sabahi of Albemarle Corp. came up with a "novel class" of synthetic lubricants for use with HFCs in compressors. The company produces malonate-acrylate esters, which it says can be tailor-made to meet the viscosity requirements of any application.
Malonate-acrylate esters, they argued, are miscible with HFC134a but also "exhibit outstanding thermal and hydrolytic stability and show outstanding compressor results without the use of performance-enhancing additives." Such additives, they noted, are required with both POEs and polyalkylene glycols (PAGs), another popular class of synthetic lubricants, because of problems with hydrolytic instability, poor lubricity, and potentially promoting copper plating in wet systems.
Practical experiences with CFC replacements were the subject of some papers. One team from ICI Klea, for example, reported on use of its KLEA 66, a HFC blend tentatively designated R-407C by ASHRAE) as a replacement for R-22 in European installations. Another ICI Klea team studied the use of molecular sieve dessicants with HFCs, while a team from Lubrizol Corp. outlined its stationary retrofit procedure for converting refrigeration systems to HFCs. And H. Gwinn Henry of H.G. Henry & Associates reviewed the phase-out of CFCs at GM Hughes Electronics.
For further information, contact the Alliance for Responsible Atmospheric Policy, P.O. Box 236, Frederick, Maryland 21701, USA; telephone 301-695-3762. fax 301-695-0175.
Industry Unit Hails Crackdown On Black Market CFC Imports
A US government crackdown on illegal imports of chlorofluorocarbons (CFCs) has won praise from the Alliance for Responsible Atmospheric Policy.
Dave Stirpe, president of the Alliance, said black marketeers are trying to circumvent the ban on new production and trade of new CFCs by labeling them as recycled. Currently, there isn't a ban on recycled or reclaimed CFCs, but the Environmental Protection Agency (EPA) is considering imposition of permits.
Freshly-manufactured CFCs may be imported only in specified amounts for specified companies under special allowances. Unlimited amounts of contaminated, recycled and reclaimed CFCs may be imported, however, and illegal importers are thus mislabeling new CFCs as old CFCs, or even as propane, to get around restrictions. In some cases, the illegal CFCs have turned out to be substandard, and could thus damage refrigeration systems.
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|Publication:||Quick Frozen Foods International|
|Date:||Apr 1, 1995|
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