HFO Refrigerants in Heat Pumps and their role in cost-effectively reducing GHG emissions and reliance on natural gas [6]

The electrification of residential heating is crucial to the reduction of greenhouse gases emissions and reliance on natural gas. R-410A, and lately R-32, are widely used in residential and light commercial air-conditioning, Heat Pump and chiller systems. Increasing concerns about climate change have resulted in the proposal of various environmental regulations to phase out R-410A, R-32 and other hydrofluorocarbons. This presentation focuses on R-410A replacement refrigerants with GWP lower than 150 for residential air-to-water Heat Pump applications. HFO blends, such as R-455A and R-454C, can have comparable efficiency of R-410A while displaying reduced flammability compared to hydrocarbons. R-1234yf, which has been used in mobile air conditioning systems, is another alternative with GWP of <4 (AR4).

Thermodynamic properties for these refrigerants show a need to increase compressor displacement to match R-410A capacity and increased surface area of heat exchangers to match or surpass R-410A efficiency. To this end various evaporator and condenser geometries were modelled to determine the optimal design that could match or surpass the R-410A baseline. System enhancements such as heat exchanger circuitry optimization, use of high side liquid receiver and use of suction liquid line heat exchanger allow the R-455A and R-454C systems to surpass R-410A performance. Through optimal design it’s possible to match or surpass the performance of R-410A with these low GWP refrigerants while providing greater charge limits compared to hydrocarbons, safer operation, and maintenance due to their lower flammability. The performance of the R-455A and R-454C system with all cycle enhancements allows them to provide higher COP than R-290, which when considered for the entire residential market could lead to a significant reduction in total power consumption and strain on the grid.