Characteristics and optimization of a direct boiling hightemperature steam heat pump
As a conventional steam generation approach in high-temperature steam heat pumps, flash evaporation suffers from several drawbacks, including a complex system configuration, substantial space requirements, and relatively low efficiency. In contrast, direct boiling steam generation offers a more streamlined system architecture and significantly reduces the physical footprint of the installation. It can also narrow the operating condition of the system, thereby enhancing the cycle performance. This study investigates the influence of critical parameters, such as temperature difference and recompression ratio, on the performance of a directboiling high-temperature steam heat pump. A mathematical model was developed to investigate the impact of variations in condensing temperature differences and compression ratios on heat capacity and power consumption. The analysis revealed that increasing the condenser temperature difference enhances heat absorption but also raises compressor power consumption, thereby reducing COP. The recompression ratio significantly impacts the temperature distribution within the cycle, with higher ratios increasing superheat and initially improving system COP, which can reach up to a 31.3% enhancement. Optimal recompression ratios are context-dependent, balancing performance, stability, and investment, and are influenced by operating conditions such as saturation steam and environmental heat source temperatures. Within the studied parameters, a recompression ratio of 2.0 to 2.6 is deemed optimal for system efficiency.