| Summary: | To solve the problem of poor heat transfer effect in the subcooled region of integrated condenser, a combined condenser for instant heat pump water heater (IHPWH) was proposed and designed based on the condenser design model, aiming at obtaining an optimal design method of condenser. The off-design performances of heat pump water heater (HPWH) with a combined condenser (HPWHCC) and HPWH with an integrated condenser (HPWHIC) were investigated and compared based on the Mopt IHPWH test unit, aiming at verifying the feasibility of using a combined condenser replacement of an integrated condenser in the IHPWH. The results show that the heat transfer area of combined condenser is only 83.33 % of that of integrated condenser. Compared with the HPWHIC, the HPWHCC achieves basically equivalent COP and heating capacities and slightly higher discharge temperatures under variable heat sink outlet temperature (HSOT) condition and variable heat sink inlet temperature (HSIT) condition. Therefore, the combined condenser has the obvious potential to replace the integrated condenser in the IHPWH. The HSOT has a remarkable influence on the COP of HPWHIC and HPWHCC but a small influence on their heat capacities, while the HSIT has a small influence on their COP and heat capacities.
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