A study on the cycle variations of reversed Brayton cycle heat pumps for high-temperature heat supply to improve performance

초록

This study developed cycle configurations to improve the performance of a high-temperature heat pump based on a reversed Brayton cycle. Various configurations, including the heat recovery, cascade, and stepwise expansion cycles, were evaluated alongside the simple cycle to enhance the turbine inlet temperature and maximize the coefficient of performance (COP) Theoretical analysis under ideal conditions confirmed the improvements in COP in all proposed configurations. Actual cycle analysis, accounting for efficiency and component losses, identified the optimal pressure ratios for each cycle. The heat recovery and cascade cycles achieved COP improvements of 5.37 %, while the stepwise expansion cycle showed the greatest improvement at 7.38 %. An economic evaluation, assuming 5110 annual operating hours, showed that the simple cycle had a payback period (PBP) of 4.7 years. The heat recovery and stepwise expansion cycles showed greater economic feasibility, with PBPs of 4.2 and 4.5 years, respectively. The cascade cycle, however, showed minimal COP improvement and a longer PBP of 6.9 years, reflecting the limited benefit of adding excessive components. These findings provide valuable guidelines for cycle optimization, showing that well-balanced cycle designs can significantly enhance efficiency and economic performance, highlighting their potential as sustainable alternatives to fossil fuel boilers in industrial applications.

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