Comparison of the refrigerants HFC 134a and CFC 12

A comparison of the refrigerants HFC 134a and CFC 12 has been carried out and the results from a theoretical analysis and from tests with an open piston compressor are reported in this paper. The results indicate that the tested compressor will give a greater refrigerating capacity with HFC 134a than with CFC 12 for certain operating conditions. However, the results also indicate an increased operating power for the compressor over the entire temperature range. As a result the coefficient of performance is decreased. Another noticeable result is dependency of the compressor's isentropic efficiency on temperature when using HFC 134a. This might be explained by the properties of the polyalkene glycol oil which is used with HFC 134a. The increased cost of using HFC 134a is justified if the environmental aspects are considered and the practical problems, such as the influence on the material in the refrigeration cycle, can be solved.     

HFC 134a as a substitute refrigerant for CFC 12

In response to international protocol agreements and national regulatory actions promoted by the increasing concern for ozone depletion and the greenhouse effect, HFC 134a has emerged as a leading candidate for CFC 12 substitution in automotive air conditioners, centrifugal chillers and residential refrigerators and freezers. This Paper discusses compressor and refrigeration system requirements and information gaps for HFC 134a application as a CFC 12 substitute.     

A simple experimental investigation of saturated vapour pressure for HFC134a-oil mixtures

A new refrigerant , HFC134a, seems to be the most promising substitute for CFC12. The vapour pressure of HFC134a-oil mixtures is one parameter that is important for a proper analysis of the operation of refrigeration systems. This paper presents vapour pressure curves for HFC134a and three kinds of representative oil for different oil percentages, and for the temperature range from -20 to +40°C (253.15–313.15 K).     

Evaluation of supplementary/retrofit refrigerants for automobile air-conditioners charged with CFC12Evaluation des frigorigènes supplémentaires / de remplacement pour des systèmes de conditionnement d''air automobiles utilisant du CFC12

In this study, thermodynamic performance of supplementary/retrofit refrigerant mixtures for CFC12 used in existing automobile air-conditioners was examined. A thermodynamic computer analysis of an automobile air-conditioner was carried out for the initial screening of possible mixture candidates, and refrigerant mixtures composed of HCFC22, HFC134a, HCFC142b, RE170 (dimethylether), HC290 (propane), and HC600a (iso-butane) were proposed to supplement CFC12. Also a breadboard type refrigeration test facility was manufactured to verify the performance of the alternative refrigerant mixtures proposed through the computer analysis. Test results showed that HFC134a/RE170 mixture with zero ozone depletion potential is the best long term candidate to supplement CFC12. On the other hand, HCFC22/HFC134a/RE170 and HCFC22/HFC134a/HCFC142b mixtures are good only as short term supplementary/retrofit alternatives since they contain HCFC22. A hydrocarbon mixture of HC290/HC600a showed a good performance but its use in existing automobile air-conditioners should be carefully considered due to its flammability.     

Performance evaluation of environmentally benign refrigerants in heat pumps 2: An experimental study with HFC134a

The performance characteristics of HFC134a in an industrial (water to water) heat-pump test facility at Electricité de France with a twin-screw compressor are presented. The performance of HFC134a has been studied in terms of performance parameters of the compressor (e.g. its volumetric and isentropic efficiencies) and of the heat-pump system (e.g. coefficient of performance and volumetric heating capacity) with a view to using it in new installations for low to medium temperature (< 70°C) applications as well as to replacing CFC12 in existing installations. The influence of degree of superheat on the miscibility of HFC134a with ester oil and on the viscosity of the oil-refrigerant mixture has also been studied for various discharge pressures.     

Refrigerant 134a: The first step into a new age of refrigerants

Many papers have been published on R134a within the last four years, beginning from the point when it became apparent that R134a would be the favourite for replacing the most important fully halogenated refrigerant worldwide, R12. This paper summerizes the requirements for a suitable replacement for R12, the criteria leading to the selection of R134a, the developmental efforts that have been made and the results of this process. In particular, chemical properties, material compatibility and thermodynamic properties of R134a are described. Because of the different chemistry in comparison with CFC refrigerants, special requirements for suitable compressor lubricants and system cleanliness are mentioned. Finally, some explanations of installing closed pruduct cycles for CFCs and their substitutes are given.     

Measurement of the viscosity of HFC 134a in the temperature range 213–423 K and at pressures up to 30 MPa

The viscosity of HFC 134a was measured over the range of temperatures from 213 to 423 K and pressures up to 30 MPa. The experimental method was that of the capillary flow and a closed-circuit high-pressure viscometer was used. The sample fluid was circulated through a stainless-steel capillary from a highpressure plunger system. The constant of the capillary was calibrated against the reference standard, pure water. The viscosity of the sample was calculated from the flow rate, the pressure drop at the capillary, and the capillary constant using the Hagen-Poiseuille equation. Measurements were made at a total of 39 points on eight isotherms. The measurement uncertainty of the viscosities was estimated as ±1.3%. Based on the present results, an empirical equation for the viscosity of HFC 134a has been correlated. The viscosity on the saturation line calculated by the equation compares with experimental viscosity data in other previous studies. There are rather considerable differences among these measurements. Comparisons of the data for HFC 134a with those for CFC 12 show that the viscosity of HFC 134a is similar in magnitude to that of CFC 12 at temperatures around 300 K but is higher at lower temperatures and lower at higher temperatures. The pressure gradients for these two corresponding substances are similar over the entire temperature range.     

冰淇淋机制冷系统性能及新型环保制冷剂热力学分析

针对软冰淇淋机首先确定了其计算工况，在分析冰淇淋机制冷循环的基础上，应用NIST的REFPROPV6.0软件编写了通用的计算程序，对不同工质的冰淇淋机循环过程进行了计算。经过计算可以发现，纯质HFC134a,HFC125,HFC143a,HFC32和HFC152a等中没有一种工质的热工性能，安全性能和环境性能可以完全满足替代要求，根据蒸气压相似原则，考虑各纯质的优缺点及混合制冷剂配对原则，确定了混合工质HFC134a/HFC32(70/30mass%)作为冰淇淋机的替代制冷剂。     

Degradation of polyethylene terephthalate films in the presence of lubricants for HFC 134a: a critical issue for hermetic motor insulation systems

Earlier studies conducted in the use of sealed tubes with polyalkylene glycol lubricants and polyethylene terephthalete (PET) films revealed that the PET films exhibited embrittlement and (visual) degradation. This led to an investigation of PET embrittlement mechanisms with the new lubricants used with HFC 134a. The lubricants studied were three polypropylene glycols (the monol, the diol and the completely end-capped glycols), pentaerythritol ester and a blend of monol and ester. The effects of moisture content, temperature and lubricant structure were studied. All lubricants in this study were of viscosity grade ISO-32 (150 SUS). The results were compared to PET film embrittlement in the presence of CFC 12 and mineral oil. This study reconfirmed the earlier findings that the PET films must be dried to lower than 0.1 wt.% moisture content for use in hermetic systems. This paper discusses the effect of the moisture content of the lubricant and the effect of the lubricant structure on PET films. The dependence of the various mechanisms on temperature is shown. Esters and end-capped polyalkylene glycols are recommended for use with HFC 134a.     

Comparative assessment of HFC134a and some refrigerants as alternatives to CFC12

A composite plot relating evaporating temperature T_EV, condensing temperature T_CO, pressure ratio (PR) and theoretical Rankine coefficient of performance (COP)_RR is presented for HFC134a. The theoretical performance of HFC134a has been comparatively assessed along with HCFC22, HFC134, HFC152a, HCFC124 and HCFC142b as alternatives to CFC12 by using the standard refrigeration parameters including pressure ratio, specific compressor displacement, theoretical Rankine coefficient of performance, shaft power per ton of refrigeration. A discussion of the practical implications of the choice of the alternatives to CFC12 is also presented.     

The halocarbon contamination problem. Part II: Chlorofluorocarbons in the environmentProblémes de la contamination pas les hydrocarbures halogéné. 2e partie: les hydrocarbure chlorofluorés dans l'environnement

Chlorofluorocarbons (CFCs) have a number of uses in several major industries, including refrigeration. The theory that CFCs deplete stratospheric ozone has attracted considerable concern and major research programmes are in hand to assess the net effect of CFCs in conjunction with the many other reactions which occur in the stratosphere.Despite the considerable uncertainties which exist and the need for an explanation of various discrepancies in the science, action has been taken in some countries to control or prohibit the use of CFCs in aerosols. Some consideration is also being given to control of other uses, including refrigeration.The two most important CFCs, 11 and 12, widely used as aerosol propellants, are also of importance to the refrigeration industry; CFC 11 as a blowing agent for insulating polyurethane foam, and CFC 12 as a primary refrigerant. These compounds are those most seriously affected by the ozone problem although they are not the only ones.Regulation of CFC 11 and 12 in any sector of use has a direct or indirect effect on the refrigeration industry, the magnitude depending on the patterns of use which vary from country to country. It is intended to review the overall situation from a regulatory and political standpoint, the industrial actions undertaken and intended, and where possible to make predictions for the future.     

The halocarbon contamination problem. Part II: Chlorofluorocarbons in the environment

Chlorofluorocarbons (CFCs) have a number of uses in several major industries, including refrigeration. The theory that CFCs deplete stratospheric ozone has attracted considerable concern and major research programmes are in hand to assess the net effect of CFCs in conjunction with the many other reactions which occur in the stratosphere.Despite the considerable uncertainties which exist and the need for an explanation of various discrepancies in the science, action has been taken in some countries to control or prohibit the use of CFCs in aerosols. Some consideration is also being given to control of other uses, including refrigeration.The two most important CFCs, 11 and 12, widely used as aerosol propellants, are also of importance to the refrigeration industry; CFC 11 as a blowing agent for insulating polyurethane foam, and CFC 12 as a primary refrigerant. These compounds are those most seriously affected by the ozone problem although they are not the only ones.Regulation of CFC 11 and 12 in any sector of use has a direct or indirect effect on the refrigeration industry, the magnitude depending on the patterns of use which vary from country to country. It is intended to review the overall situation from a regulatory and political standpoint, the industrial actions undertaken and intended, and where possible to make predictions for the future.     

HFC134a/HC600a/HC290 mixture a retrofit for CFC12 systems

The environmental concerns with the impact of refrigerant emissions lead to the importance in identifying a long-term alternative to meet all requirements in respect of system performance and service. Even though HFC134a and HC blend (containing 55.2% HC600a and 44.8% HC290 by weight) have been reported to be substitutes for CFC12, they have their own drawbacks in respect of energy efficiency/flammability/serviceability aspects of the system. In this present work, experimental investigation has been carried out on the performance of an ozone friendly refrigerant mixture (containing HFC134a/HC blend) in two low temperature systems (a 165 l domestic refrigerator and a 400 l deep freezer) and two medium temperature systems [a 165 l vending machine (visi cooler) and a 3.5 kW walk-in cooler]. The oil miscibility of the new mixture with mineral oil was also studied and found to be good. The HFC134a/HC blend mixture that contains 9% HC blend (by weight) has better performance resulting in 10–30% and 5–15% less energy consumption (than CFC12) in medium and low temperature system, respectively.     

Condensation heat transfer coefficients of enhanced tubes with alternative refrigerants for CFC11 and CFC12Coefficients de transfert de chaleur de condensation de tubes à surface augmentée fonctionnant avec des frigorigènes de remplacement de CFC11 et de CFC12

In this study, condensation heat transfer coefficients (HTCs) of a plain tube, low fin tube, and Turbo-C tube were measured for the low pressure refrigerants CFC11 and HCFC123 and for the medium pressure refrigerants CFC12 and HFC134a. All data were taken at the vapor temperature of 39°C with a wall subcooling of 3–8°C. Test results showed that the HTCs of HFC123, an alternative for CFC11, were 8.2–19.2% lower than those of CFC11 for all the tubes tested. On the other hand, the HTCs of HFC134a, an alternative for CFC12, were 0.0–31.8% higher than those of CFC12 for all the tubes tested. For all refrigerants tested, the Turbo-C tube showed the highest HTCs among the tubes tested showing almost an 8 times increase in HTCs as compared to the plain tube. Nusselt's prediction equation yielded a 12% deviation for the plain tube data while Beatty and Katz's prediction equation yielded a 20.0% deviation for the low fin tube data.     

三氟碘甲烷作为冰箱制冷剂的理论循环分析

通过对环保工质三氟碘甲烷(CF3I)的饱和蒸汽压曲线、冰箱名义工况和变工况下循环性能等三方面的理论分析,发现CF3I和CF3I的摩尔组成在50%-65%范围的CF3I/HC290混合工质,理论循环性能与CFC12接近,具有作为冰箱中CFC12灌注式替代物的潜力.     

CFC research programmes in Western Europe

The structure of CFC use in Western Europe is different from that in the USA and Japan, with the highest percentage use of CFCs in Europe in aerosols. The use of CFCs in automotive air conditioning in the EEC is much less than elsewhere and this, together with the fact that R-12 and R-22 already have similar market shares, means that the refrigeration industry in Western Europe will not be as greatly affected by CFC reduction as elsewhere. More stringent reduction programmes than those imposed by the Montreal Protocol are in force in most Western European countries, to some extent due to consumer and environmental pressure group influences. Some countries, especially in Scandinavia, are introducing additional legislation to restrict CFC use. The strongest stand has been taken by the Federal Republic of Germany, which requires a 95% reduction in CFC use by 1995, with a voluntary ban from 1992. This paper discusses in detail European research programmes into CFC replacements. Many projects have been proposed, including work on refrigerants [fundamentals (four projects), thermophysical properties (18 projects) and lubricants and materials (five projects)] and cycles and components (17 projects).     

Condensation heat transfer coefficients of R1234yf on plain, low fin, and Turbo-C tubes

In this study, external condensation heat transfer coefficients (HTCs) of HFC134a and R1234yf are measured on a plain, low fin, and Turbo-C tubes at the saturated vapor temperature of 39 °C with the wall subcooling of 3-8 °C. R1234yf is a new alternative refrigerant of low greenhouse warming potential for replacing HFC134a, one of the greenhouse gases in Kyoto protocol, used extensively in automobile air conditioners and other refrigeration systems. Test results show that the condensation HTCs of R1234yf are very similar to those of HFC134a for all three surfaces tested. For the development of heat transfer correlations, thorough property measurements are needed for R1234yf in the near future.     

二甲醚作为汽车空调制冷剂的性能研究

本文对二甲醚（DME）用作汽车空调制冷剂的性能与现有汽车空调制冷剂R134a进行了对比。首先比较了二甲醚和R134a的基础热力性质，然后对二甲醚和R134a的汽车空调标准工况和变工况下制冷循环性能进行了详细的理论计算及分析。分析表明：二甲醚的制冷性能与R134a基本相似，而性能系数（COP）却优于R134a。因此，更具环保优势的二甲醚是一种理想的潜在的汽车空调制冷剂。     

The need to curb CFC emissions

The need to be careful with CFC emissions is acknowledged, due to the possible influence on the ozone layer around the globe and the greenhouse effect. A brief overview of the scientific and political conferences on this problem is given with the resulting conclusions and resolutions. Activities of the IIR on the subject of using CFCs in refrigeration technology are described. The possibilities of decreasing CFC emission and eventual substitution of these media are also discussed. The application of alternative systems and media creates many problems. The consequences of restrictions on the use of CFCs in refrigeration must be considered very seriously to obtain optimal solutions from both the ecological and economical point of view. This is very important for the well-being of mankind.

Résumé

The need to be careful with CFC emissions is acknowledged, due to the possible influence on the ozone layer around the globe and the greenhouse effect. A brief overview of the scientific and political conferences on this problem is given with the resulting conclusions and resolutions. Activities of the IIR on the subject of using CFCs in refrigeration technology are described. The possibilities of decreasing CFC emission and eventual substitution of these media are also discussed. The application of alternative systems and media creates many problems. The consequences of restrictions on the use of CFCs in refrigeration must be considered very seriously to obtain optimal solutions from both the ecological and economical point of view. This is very important for the well-being of mankind.     

Chlorofluorocarbons and the environment

Stricter regulations of the manufacture of chlorofluorocarbons (CFCs) will have important effects on the refrigeration industry. These are discussed and possible substitutes for the CFCs considered.