Performance evaluation of a novel mixed-refrigerant recuperative heat pump with a large temperature lift for space heating

Abstract

The conventional techniques for space heating consume great energy and cause great CO2 emissions, which is not meet the requirement of sustainable development. Heat pumps are regarded as suitable for space heat because of their high performance. However, conventional heat pumps cannot realize efficient heating with large temperature lifts, which limits their application for space heating. Mixed-refrigerant recuperative heat pumps (MRHP) show high performance for hot water making with large temperature lifts, which are a potential and efficient technique for space heating. Hence, this work aims to investigate whether the MRHP is a high-performance technique for space heating and provides a novel high-performance MRHP for space heating. The performance of a conventional MRHP system is firstly investigated to validate its feasibility in space heating applications. The results reveal that the conventional MRHP system performs poorly in large temperature lift scenarios. Then, based on this analysis, a novel MRHP is proposed, which exhibits better performance in space heating scenarios with a large temperature lift. Moreover, the novel system is compared with the cascade heat pump and trans-critical CO2 heat pump, another space heating technique, to show its advantage. The COP of the novel system is 4.7% higher than that of a cascade heat pump. In addition, the novel system shows a lower pressure ratio than the conventional cascade heat pump and lower operating pressure than the trans-critical CO2 heat pump. Therefore, the novel MRHP system exhibits immense application potential in space heating and is a commercially affordable solution for the next-generation heat pumps.