A curved baffle-type inlet structure was designed for a water storage tank to improve the performance of an air-source heat pump water heater system. A heat pump water heater test bench was set up to compare the extraction efficiency and COP of the curved baffle inlet structure to the direct-entrance and side-entrance inlet structures. The experimental results showed that the thermal stratification of water along the height direction was effectively released by the curved baffle-type inlet structure. Compared to the direct-entrance inlet structure water heater

the extraction efficiency increased from 52.87% to 96.60% with a curved baffle-type inlet heat pump water heater when the inlet flow rate ranged from 5 L/min to 10 L/min

and the COP improved from 7.14% to 7.40%. Contrary to the side-entrance inlet structure water heater

the extraction efficiency increased from 38.37% to 76.99% with a curved baffle-type inlet heat pump water heater when the inlet flow rate ranged from 5 to 10 L/min

and the COP improved from 3.22% to 5.53%. The performance improvement increased as the inlet flow rate increased. The curved baffle-type inlet structure of the heat pump water heater simultaneously increased the extraction efficiency and the system’s COP.