Performance analysis of a novel multi-heat sinks heat pump based on two-stage ejector-compression cycle

This study proposes a multi-heat sinks heat pump based on a two-stage ejector-compression cycle. The system produces two kinds of heat sink, e.g., the hot water of high temperature ranging from 60 to 90 °C, which shows high applied potential in hot water production or wall radiator heating, and of low temperature ranging from 30 to 40 °C, which can be applied in space heating. A validated theoretical model was constructed to compare and analyze the performance between the two-stage compression two heat sinks heat pump cycle (TSC) and ejector two-stage compression multi-heat sinks heat pump cycle (ETSC) under various operated conditions. The sensitive analysis of four operative parameters, evaporation temperature (T₁), condensation temperature (T₄, T₇), and load ratio (LR), on system performance has been conducted, which provides the direction of system performance optimization. The results show that the heating coefficient of performance (COP_h), volumetric heating capacity (q_v) and entrainment ratio (µ) are more sensitive to the variation of T₁. The exergy loss per kilowatt heating capacity is more sensitive to T₄ variation. Besides, more air source energy is absorbed in the evaporator by the ejector, and then ETSC performance outperforms the TSC, especially under the high demand of high-temperature heat sink conditions. Lastly, the ecofriendly refrigerants R290 and R1234yf show good potential as the alternative for the R134a in the ETSC. The results hope to promote the further improvement and application of two stage compression cycle.