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Resulting design criteria The system technology can be based on the experience with R22 and R502 over a wide area. On the thermodynamic side, a heat ex- changer between the suction and liquid line is recommended as this will improve the refrigerating capacity and COP. BITZER offers the whole program of reciprocating, scroll and screw com- pressors for R404A and R507A. Supplementary BITZER information con- cerning the use of HFC blends (see also https://www.bitzer.de) o Technical Information A-540 „Retrofit R22 or R404A/R507A – Step by step” R407A/407B/407F/407H as substitutes for R22 and R502 As an alternative to the earlier described substitutes, additional mixtures have been developed based on R32 which is chlorine free (ODP = 0) and flammable like R143a. The refrigerant R32 is also of the HFC type and initially was regarded as a main candi- date for R22 alternatives (page 20). How- ever, due to extent of blend variations com- parable thermodynamic characteristics to R404A/R507A can also be obtained. These kind of refrigerants were marketed at first under the trade name KLEA® 60/61 (ICI) and are listed as R407A/R407B* in the ASHRAE nomenclature. Honeywell has developed another blend with the trade name Performax® LT (R407F according to ASHRAE nomenclature) and introduced it into the market, similar Daikin Chemical with R407H. For both blends, the R32 proportion is higher than for R407A, while the R125 proportion is lower. With R407H, this results in certain restrictions for low temperature applications. However, the necessary conditions for alter- natives containing R32 are not quite as favourable compared to the R143a based substitutes discussed earlier. The boiling point of R32 is very low at -52°C, in addition the isentropic compression exponent is even higher than with R22. Rather high pro- portions of R125 and R134a are necessary to match the characteristics at the level of R404A and R507A. The flammability of R32 is thus effectively suppressed, but the large differences in boiling points with a high pro- portion of R134a lead to a larger tempera- ture glide. The main advantage of R32 is the relatively low global warming potential (GWP = 675), so that even in combination with R125 and R134a it is significantly lower than with the R143a based alternatives mentioned above (R407A: GWP = 2107, R407F: GWP = 1825, R407H: GWP = 1490). Thus, they also comply with the require- ment of the new EU F-Gas Regulation which from 2020 will only allow refrigerants of GWP < 2500. Measurements made with R32 containing blends do show certain capacity reductions compared to R404A and R507A, with low evaporating temperatures. The COP how- ever shows less deviation and is even higher in medium temperature applications (Fig. 18). * Meanwhile, R407B is no longer available in the mar- ket. Due to the historical development of HFC blends this refrigerant will, however, still be considered in this Report. o Technical Information KT-500 „BITZER refrigeration compressor oils for reciprocating compressors“ Substitutes for R22 in refrigeration systems Fig. 17 18 R407A, R407F/R404A – comparison of discharge gas temperature of a Fig. 18 Comparison of performance data of a semi-hermetic semi-hermetic compressor compressorPDF Image | REFRIGERANT REPORT 21
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