Thermodynamic assessment of a modified ejector-assisted heat pump cycle with dual-evaporator for cold climates

As an expansion work recovery device, ejector could be used for heat pump performance improvement. Therefore, a modified ejector-assisted heat pump cycle with dual-evaporator is proposed. On the basis of traditional ejector-assisted heat pump cycle, an additional vapor–liquid separator and evaporator are introduced to decrease the refrigerant's vapor quality entering the evaporator and lift the average evaporating temperature, which can improve the thermodynamic and economic performance of the heat pump when operating at extremely low ambient temperature. Then, the performance comparisons of basic vapor compression heat pump cycle, traditional cycle and modified cycle are presented by theoretical analysis. Under given operating conditions, the results illustrate that the volumetric heating capacity of the modified cycle shows an improvement of 72.4 % and 20.4 %, and the heating coefficient of performance indicates an improvement of 40.7 % and 13.4 % compared to the basic cycle and traditional cycle. Due to the expansion work recovery of the ejector, the exergy destruction is significantly reduced. Therefore, the total exergy destruction of modified cycle is 51.4 % and 16.4 % lower than that of basic cycle and traditional cycle. Furthermore, the cost per unit of exergy production of MEHPC is 27.0 % and 2.2 % lower than that of BHPC and EHPC, respectively. The modified cycle exhibits better performance than that of basic cycle and traditional cycle. This paper aims to provide theoretical guidance for the development of high-performance heat pump cycle in cold climate applications.