Thermodynamic Performance of a High‐Temperature Steam Heat Pump with Multistage Evaporation Using Water as Refrigerant

To improve energy efficiency and reduce environmental impact, a multistage evaporation high‐temperature steam heat pump system using water as the working fluid is proposed. EBSILON software is employed to evaluate the thermodynamic performance of single‐stage, two‐stage, and multistage configurations by analyzing temperature matching between the heat source and refrigerant, t–s diagrams, and intermediate pressures. Results indicate that at heat source temperatures of 50/70°C and heat sink temperatures of 90/140°C, the two‐stage evaporator configuration (TSEC) exhibits 8.43% higher thermal efficiency and 6.10% higher exergy efficiency, respectively, compared to the single‐stage evaporation configuration (SSEC). The multistage evaporation configuration (MSEC) further improves these two efficiencies by 2.96% and 3.45%, respectively, relative to TSEC. Moreover, when the heat sink temperature decreases from 180°C to 140°C, the coefficient of performance (COP) of the MSEC rises from 2.21 to 2.77. Similarly, when the heat source temperature increases from 40/60°C to 70/90°C, it boosts its COP from 2.40 to 3.84. Specifically, within the studied temperature range, every 10°C reduction in heat sink temperature increases the COP by 5.81%, while every 10°C increase in heat source temperature raises the COP by 16.97%. These findings confirm the universal applicability of the multistage evaporation high‐temperature steam heat pump with water as the refrigerant, laying a theoretical foundation for its engineering applications.