Effect of heat transfer area and refrigerant mass flux in a gas cooler on heating performance of air-source transcritical CO2 heat pump water heater system.

Highlights: [•] A prototype of transcritical CO2 heat pump water heater was introduced. [•] Experiment was conducted for a prototype of transcritical CO2 heat pump water heater. [•] Simulation was conducted for two categories of gas coolers. [•] Variation of the optimal pressure with heat transfer area was illustrated. [•] Variation of the optimal pressure with CO2 mass flux was illustrated. [ABSTRACT FROM AUTHOR]