Lower-GWP Refrigerants, Heat Pump, Transient, Simulation, Validation
The need for making a shift from refrigerants with high Global Warming Potential (GWP) to those with lower GWP is becoming increasingly important. A broad spectrum of alternative refrigerants have been proposed and their performance needs to be investigated through simulation and testing. To evaluate the performance of these candidates, the Air Conditioning, Heating and Refrigeration Institute (AHRI) has announced an industry-wide research program for studying the performance of low GWP refrigerants for major product categories such as air conditioners, heat pumps, chillers and refrigerators. One such study investigated alternatives to R410A, namely R32, D2Y60 and L41a. The investigation was conducted using a 3-ton residential split heat pump unit. This paper presents Simulink®-based steady state and transient analysis of the heat pump unit using two of the alternative refrigerants, R32 and D2Y60. A simplified, finite control volume approach is used to model the heat exchangers, while the expansion valve and compressor are treated as quasi-steady state components. The steady state and transient results compare well with measured data and the transient trends of the model are reproduced as expected, although with faster system response due to the exclusion of a TXV and accumulator. The proposed model can reasonably predict both steady state and transient performance of the heat pump for all the refrigerants analyzed under the operating conditions simulated. The results show that comparable capacities to the R410A baseline can be obtained using R32, although with a lower COP due to degradations in compressor efficiencies. For D2Y60 cycles, the capacities and COP are generally lower than the baseline cycle.
Steady State and Transient Validation of Heat Pumps Using Alternative Lower-GWP Refrigerants