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HFC refrigerants R134a as substitute for R12 and R22 R134a was the first chlorine free (ODP = 0) HFC refrigerant that was tested comprehen- sively. It is now used world-wide in many refrigeration and air conditioning units with good results. As well as being used as a pure substance, R134a is also applied as a component of a variety of blends. R134a has similar thermodynamic properties to R12: Refrigerating capacity, energy demand, temperature properties and pressure levels are comparable, at least in air conditioning and medium temperature refrigeration plants. This refrigerant can therefore be used as an alternative for most former R12 applications. For some applications R134a is even pre- ferred as a substitute for R22, an impor- tant reason being the limitations to the use of R22 in new plants and for service. How- ever, the lower volumetric refrigerating capacity of R134a (Fig. 9) requires a larger compressor displacement than with R22. There are also limitations in the application with low evaporating temperatures to be considered. Comprehensive tests have demonstrated that the performance of R134a exceeds the- oretical predictions over a wide range of compressor operating conditions. Tempera- ture levels (discharge gas, oil) are even lower than with R12 and, therefore, sub- stantially lower than R22 values. There are thus many potential applications in air con- ditioning and medium temperature refriger- ation plants as well as in heat pumps. Good heat transfer characteristics in evaporators and condensers (unlike zeotropic blends) favour an economical use. R134a is also characterized by a compar- ably low GWP (1430). Therefore, in view of future restrictions (for example EU F-Gas Regulation), the use of this refrigerant will still be possible for quite some time. If required, systems can later be converted relatively easily to non-flammable (A1) HFO/HFC alternatives with a GWP of approx. 600 (Tab. 5). Lubricants for R134a and other HFCs The traditional mineral and synthetic oils are not miscible (soluble) with R134a and other HFCs described in the following and are therefore only insufficiently transported around the refrigeration circuit. Immiscible oil can settle out in the heat exchangers and prevent heat transfer to such an extent that the plant can no longer be operated. New lubricants were developed with the appropriate solubility and have been in use for many years. These lubricants are based on Polyol Ester (POE) and Polyalkylene Glycol (PAG). For further explanations on lubricants see chapter “Lubricants for compressors”, page 41. Fig. 8 R134a/R12 – comparison of performance data of a semi-hermetic compressor Fig. 9 R134a/R22 – comparison of performance data of a semi-hermetic compressor 9 t CPDF Image | REFRIGERANT REPORT 21
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