Energy, exergy, and exergoeconomic analyses of an air source transcritical CO2 heat pump for simultaneous domestic hot water and space heating.

The transcritical CO 2 heat pump system experiences significant throttling losses in space heating operation due to the higher temperature of returning water. This paper presents an energy, exergy, and exergoeconomic analyses of an air source transcritical CO 2 heat pump integrating a tri-partite gas cooler, which is an effective method to match CO 2 temperature glide with water for simultaneous domestic hot water and space heating (DHW+SH) production. A pinch point-based numerical model is developed to find the optimal discharge pressure. This validated model is then utilized to investigate the impacts of water inlet temperature and ambient temperature. Two configurations are examined: one with only DHW supply and the other with DHW+SH supply. The results indicate that combining SH with DHW enhances COP by 7.5% with a 7.9% reduction in discharge pressure at 10 °C ambient temperature and 10 °C water inlet temperature. At a water temperature of 10 °C, exergy efficiency improves by 4%. The compressor accounts for 54%–60% of the total exergy loss. The DHW+SH system exhibits an average exergy destruction reduction of 7.6%. With each 5 °C rise in ambient temperature, the DHW+SH system's total exergy destruction cost rate decreases on average 7.7% compared to the DHW system. Furthermore, the combined exergy destruction cost rate of GC2 and GC3 in DHW+SH is significantly lower (by 48.2%) than only GC3 in DHW. The exergoeconomic factors of the compressor, gas cooler 2, and gas cooler 3 emphasize the need to decrease their costs to enhance cost-effectiveness. • Transcritical CO 2 heat pump with tri-partite gas cooler is studied for simultaneous domestic hot water and space heating (DHW+SH). • Energy, exergy, and exergoeconomic comparative analyses between only DHW supply and DHW+SH supply are investigated. • Combining SH with DHW improves COP by 7.5% with a 7.9% reduction in discharge pressure compared to DHW. • The exergy destruction of DHW+SH is lower due to the improvement in temperature matching. • DHW+SH system's total exergy destruction cost rate drops on average 7.7% per 5 °C ambient temperature increase compared to DHW. [ABSTRACT FROM AUTHOR]