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Refrigerants for special applications R124 and R142b as substitutes for R114 and R12B1 In place of R114 and R12B1 previously used in high-temperature heat pumps and crane air conditioning systems, HCFCs R124 and R142b can still be used as alter- natives in most regions outside of the EU. With these gases it is also possible to use long proven lubricants, preferably mineral oils and alkyl benzenes with high viscosity. Because of their ozone depleting potential, these refrigerants will only be an interim solution. In the EU member states as well as in some other regions, the application of HCFCs is no longer allowed. For R124 and R142b the same restrictions are valid as for R22 (page 8). The flammability of R142b and the resulting safety implications should also be considered (safety group A2). Resulting design criteria/ Converting existing plants Compared to R114, the alternatives have lower boiling temperatures (approx. -10°C), which results in larger differences in the pressure levels and volumetric refrigerating capacities. This leads to stronger limitations in the application range at high evaporating and condensing temperatures. Converting an existing installation will in most cases necessitate the exchange of the compressor and control devices. Owing to the lower volume flow (higher volumetric refrigerating capacity), adjustments to the evaporator and the suction line may be required. Over the previous years BITZER com- pressors have been found to be well suited with R124 and R142b in actual installations. Depending on the applica- tion range and compressor type modifi- cations are necessary, however. Perfor- mance data including further design instructions are available on request. Chlorine free substitutes for special applications Due to the limited market for systems with extra high and low temperature applica- tions, the development of alternative refrige- rants and system components for these has been pursued less intensely. In the meantime, a group of alternatives for the CFC R114 and Halon R12B1 (high tem- perature), R13B1, R13 and R503 (extra low temperature) have been offered as replace- ments. On closer examination, however, the thermodynamic properties of the alterna- tives differ considerably from the previously used substances. This can cause costly changes especially with the conversion of existing systems. Alternatives for R114 and R12B1 R227ea and R236fa are considered suitable substitutes even though they may no longer be used in new installations in the EU from 2020, due to their high GWP. R227ea cannot be seen as a full replace- ment. Although tests and experience in real plants show favorable results, a critical tem- perature of 102°C limits the condensing temperature to 85..90°C with conventional plant technology. R236fa provides the more favourable condi- tions at least in this regard – the critical temperature is above 120°C. A disadvan- tage, however, is the lower volumetric re- frigerating capacity. It is similar to R114 and 40% below the performance of R124, which is still widely used for extra high tempera- ture applications. R600a (Isobutane) will be an interesting alternative where safety regulations allow the use of hydrocarbons (safety group A3). With a critical temperature of 135°C, con- densing temperatures of 100°C and more are within reach. The volumetric refriger- ating capacity is almost identical to R124. The "Low GWP" refrigerant R1234ze(E) (page 24) can also be regarded as a poten- tial candidate for extra high temperature applications. Compared to R124, its refrige- rating capacity is 10 to 20% higher, its pres- sure level about 25% higher. At identical refrigerating capacities, the mass flow dif- fers only slightly. Its critical temperature is 109°C, which would enable an economical operation up to a condensing temperature of about 90°C. However, like R1234yf, R1234ze(E) shows low flammability and therefore classified into the new safety group A2L. The corresponding safety regu- lations must be observed. As no sufficient operating experience is available so far, the suitability of this refrige- rant for long-term use cannot be assessed yet. 37PDF Image | REFRIGERANT REPORT 21
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