Research on the optimized design of air-water source coupling heat pump system

Abstract This study focuses on the “temperature slip” problem in air-water source coupled heat pump (A-WSCHP) system caused by capacity mismatch between water source heat pump (WSHP) and air source heat pump (ASHP). The capacity ratio Ruc (ratio of the maximum heating capacity of ASHP to that of WSHP) is established as a key parameter. Its impact on the “temperature slip” phenomenon and dynamic performance of the system during coupled operation is thoroughly analyzed. Based on the TRNSYS platform, a dynamic model of the heating system in a cold area (Taiyuan, Shanxi Province, 780 m2 building) is constructed, the water supply temperature in the middle loop is set at 25°C, and the water supply temperature at the end is set at 50 °C, with the focus on comparing and analyzing the effect of the Ruc in the 0.6–1.2 range. It is found that Ruc is the root cause of the phenomenon of “temperature slippage”, and its effect makes the middle tank temperature TINT significantly disturbed. In contrast, the hot water temperature TH has less impact. When the Ruc = 1.0 “temperature slip” phenomenon disappeared, but TINT fluctuation time needs to be further shortened. When designing the A-WSCHP system to select Ruc, the typical ambient temperature and the lowest ambient temperature during the heating period should be considered comprehensively, with priority given to the reference to the typical ambient temperature and focusing on considering the differences in the system under the low-temperature condition.