For finned-tube heat exchangers

owing to the extremely different refrigerant pressure drop characteristics between evaporation and condensation modes

the optimum refrigerant channel number of the evaporation mode is larger than that of the condensation mode. However

the conventional heat exchanger cannot achieve better matching characteristics between the refrigerant circuit and variations in operating conditions. To solve this problem

a vapor-bypassed evaporation technique is applied in a residential air conditioner

and experimental studies have been conducted to investigate the corresponding system performance under various operating conditions. Experimental results show the following: under heating mode

as the heating capacity ranges 2~5 kW

the vapor-bypassed evaporation system yields 2.5%~7.2% higher COP over baseline; under cooling mode

when the cooling capacity increases from 1.5 kW to 4.5 kW

the COP of vapor-bypassed evaporation system is improved by 8.6%~3.5% in comparison with the baseline; finally

according to the GB 21455—2019 Standard[1]

the APF (annual performance factor) of vapor-bypassed evaporation system is improved by 6.4%.