The experimental system of household air-source heat pump water heater with flash tank was set up

and its operation perform- ance at different temperatures was studied in the environmental control room

and compared with the single-stage compression system. The results show that the heating capacity and heating COP of the household air-source heat pump water heater with flash tank are greater than that of the single-stage compression system

and the heating capacity increases 21. 3% when the ambient temperature is -15 ℃ . The heat- ing time of air-source heat pump water heater with flash tank system is shortened by 20. 1% compared with that of single-stage system un- der the same water volume and initial and ending temperatures. The discharge temperature of the compressor is reduced by 11. 3 ℃

which ensures the operation safety of the unit. The calculation of APF shows that the system of flash tank replenishment is better in the ar- ea with lower ambient temperature.