Experimental study of air source heat pump water heater: Energy, exergy, and entransy analysis

With the continuous progress of urbanization, building energy consumption is increasing dramatically. At present, energy consumption caused by air conditioning accounts for a half in typical building energy consumption in China. Using exergy and entransy analysis, this paper experimentally studies the thermal performance of an air source heat pump water heater and its components under different meteorological conditions. This paper, for the first time, introduces the dimensionless number of entransy dissipation ratio (EDR), namely the percentage of a component's entransy dissipation into the entire system. The findings indicate that with the increase in air temperature, the heat production, the EDR of condenser and evaporator, and the exergy efficiency of condenser and compressor increase while the exergic efficiency of evaporator and throttle valve decrease. In the case of increased air flow rate, the heat production and exergy destruction of water heater as well as the EDR of evaporator are enhanced, while the exergy efficiency of evaporator, compressor and throttle and the EDR of condenser decrease, with the exergy efficiency of the throttle remaining the highest. The irreversibility rates of components are affected by change in the relative humidity of air, which is specified as follows: The percentage range of irreversibility rates for compressor, condenser, throttle and evaporator is 11.5–16 %, 37–45 %, 6.8–11.5 % and 32–41 %, respectively.