Experimental investigation on the influence of internal heat exchanger in a transcritical CO2 heat pump water heater

Abstract This paper presents a numerical study on the influence of internal heat exchanger (IHX) exchanging surface in the performance of a transcritical CO2 heat pump water heater at different operating conditions. Five different IHX geometries and four different evaporation temperatures have been studied with water temperature ranging from 10 °C to 60 °C at the gas cooler inlet. The results show a strong influence of IHX characteristics on system’s performance.

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Optimal discharge pressure in transcritical CO2 heat pump water heater with internal heat exchanger based on pinch point analysis

International Journal of Refrigeration ◽

10.1016/j.ijrefrig.2020.06.003 ◽

2020 ◽

Vol 118 ◽

pp. 12-20

Author(s):

Zuliang Ye ◽

Yikai Wang ◽

Yulong Song ◽

Xiang Yin ◽

Feng Cao

Keyword(s):

Heat Exchanger ◽

Heat Pump ◽

Internal Heat ◽

Water Heater ◽

Pinch Point ◽

Internal Heat Exchanger ◽

Heat Pump Water Heater ◽

Point Analysis ◽

Discharge Pressure

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The Influence of Internal Heat Exchanger on the Performance of Transcritical CO2 Water Source Heat Pump Water Heater

Energies ◽

10.3390/en13071787 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1787

Author(s):

Fan Feng ◽

Ze Zhang ◽

Xiufang Liu ◽

Changhai Liu ◽

Yu Hou

Keyword(s):

Heat Exchanger ◽

Heat Pump ◽

Internal Heat ◽

Water Source ◽

Hot Water ◽

Operational Performance ◽

Water Heater ◽

Source Temperature ◽

Internal Heat Exchanger ◽

Heat Pump Water Heater

The characteristics of the transcritical CO2 heat pump water heater (HPWH) system are; a lower inlet hot water temperature (Ti-hw) (sometimes this is lower than the water source temperature), and an outlet gas cooler temperature (To-gc) which is affected by the Ti-hw and often lower than the critical temperature. In order to study the effects of the internal heat exchanger (IHX) on the operational performance of the transcritical CO2 HPWH when To-gc is low, a transcritical CO2 water source HPWH experiment platform is established to conduct experimental research and comparative analysis on the operational performance of the transcritical CO2 water source HPWH, with or without IHX. It is found that, if only the coefficient of performance (COP) and heating at the optimal exhaust pressure of the transcritical CO2 water source HPWH were considered, COP and the heating of the non-IHX system would be slightly higher than those of the IHX system at the lower hot water flow and water source temperature, and this increase was not obvious. At the higher hot water flow rate and water source temperature, COP and the heating of the non-IHX system were also higher than those of the IHX system, and the increase was obvious. The experiment results showed that, near the optimal exhaust pressure, the variation range of COP and heating of the IHX system is relatively small, and the system has a relatively high stability.

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