Abstract
Due to the relatively high global warming potential value of R410A, a lot of effort has been devoted to the exploration of potential refrigerants to replace R410A in heat pump applications. Natural refrigerants with single-digit global warming potential values have not yet shown readiness. Therefore, some synthetic refrigerants with global warming potential values significantly lower than R410A, such as R32 and the R32-based blend D2Y60, are getting more attention. To evaluate the transient performance of these two drop-in low-global warming potential refrigerants, two dynamic heat pump models, based on different platforms, have been developed to simulate a heat pump cycle during both steady state and transient operations. Both models include an efficiency-based compressor model, two control volume-based heat exchanger models, a control volume-based valve model, a segmented pipe model and a lumped-capacitance accumulator model. In order to speed up the simulations, accelerated refrigerant property routines were developed for R32 and D2Y60 based on National Institute of Standards and Technology's (NIST's) REFPROP database (2013). The simulation results have been compared with the published experimental data. The data includes steady-state operation data based on ASHRAE steady-state tests, and transient data from ASHRAE's cyclic operation D-test. The validation of R410A, R32 and D2Y60 cycles under steady-state operating conditions (ASRHAE A and B tests and one in-house 'extended' condition) shows that most of the simulations are within 5% measured values. The transient simulation results demonstrate that both models capture the dynamic performance of vapor compression cycle during start-up and shut-down.