In this paper, the effect of intermediate water temperature on the performance of a combined R134a and transcritical CO₂ heat pump was studied theoretically and experimentally. The mathematical model was first validated using experimental data and then applied to analyze the performance of the combined system. The results show that there exists an optimal intermediate water temperature (water inlet temperature at the gas cooler) at which the combined system has the highest COP. This optimal intermediate water temperature varies with the ambient air temperature. Furthermore, the effect of intermediate water temperature on individual R134a and transcritical CO₂ subsystems was investigated.The results show that both heating capacity and power consumption in the R134a subsystem increase as the intermediate water temperature increases. However, power consumption in the CO₂ system drops slightly, and heating capacity reaches an optimal value as the intermediate water temperature increases from 15 to 32 °C under ambient air temperatures ranging from −20 to 7 °C.

Item Type:	Refereed Article
Keywords:	transcritical CO2 heat pump, R134a heat pump, space heating, coefficient of performance
Research Division:	Engineering
Research Group:	Mechanical engineering
Research Field:	Energy generation, conversion and storage (excl. chemical and electrical)
Objective Division:	Energy
Objective Group:	Energy efficiency
Objective Field:	Residential energy efficiency
UTAS Author:	Wang, X (Professor Xiaolin Wang)
ID Code:	118728
Year Published:	2017
Web of Science® Times Cited:	18
Deposited By:	Engineering
Deposited On:	2017-07-18
Last Modified:	2018-06-18
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