Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Abstract

This study reports the numerical analyses of a CO 2 transcritical cycle on solar assisted heat pump water heating system in which evacuated tube U-pipe solar collector is utilized as an evaporator. This simulation model can predict operating characteristics for moderate meteorological conditions of North Dakota. The main purpose of this work is to simulate the overall performance of the heat pump cycle by varying compressor speed. From the analysis the coefficient of performance (COP) value is predicted from 1.5 -2.8 with three different average solar insolation. The results showed that the performance of the system significantly influenced by the compressor speed and solar irradiation. This study also calculated the instantaneous collector efficiency and found in the range of 50 -55%.

Recent Advances in Transcritical CO2 (R744) Heat Pump System: A Review

“…They recommended that, for a CO 2 driven HP with a solar evaporator, the use of an EEV is essential to continuously adjust the CO 2 flow to the evaporator in order to maximize the system's performance. Unlike Faria et al's design [122], a U-pipe solar collector was utilized as the evaporator in Islam et al's work [133], which showed that the system COP could be improved by an average of 57% with a compressor speed decrease from 1500 to 900 rpm. They found that the collector efficiency was in the range of 50% to 55%.…”