oil return, R22 replacement, drop-in refrigerant R438
The aim of the study presented in this paper is an experimental investigation of the oil return characteristics of alternative refrigerants for residential air conditioning systems using R22. Due to the phase-out of HCFC refrigerants, the production of R22 will be stopped by the year 2020. In some cases of vapor compression systems installed in the field, it will be necessary to replace the R22 with alternative drop-in refrigerants as a part of maintenance procedures. Since R22 system typically use mineral oils and HFC replacement refrigerants use POE or PAG oils. It may be necessary to change the type of oil used inside the system when retrofitting an existing R22 system with an alternative drop-in refrigerant. Changing the oil in a vapor compression system is an expensive proposition due to the required flushing and cleaning of the system before the new oil can be installed. Therefore, refrigerant manufacturers are searching for alternative refrigerants, which are compatible with mineral oils and have similar working performance and conditions as R22. The measurement of the oil return in the suction line helps to draw conclusions about the ability of the oil circulating back to the compressor. In this study, a unitary spilt-system air conditioner with a cooling capacity of 7 kW was equipped with an oil separator and oil measuring cylinder in the suction line. The experimental test setup was designed and built to measure the mass of oil returned to the compressor. Â The weight of the oil collected in the suction line using three different compositions of the alternative drop-in refrigerant R438 are compared to the mass of oil returned when using R22.