基于减小中间换热器㶲损的自复叠热泵系统最佳工质循环配比分析及实验研究
Analysis and experimental study on optimal working fluid mixture ratio of auto-cascade heat pump systems based on reducing intermediate heat exchanger exergy loss
摘要：
从自复叠热泵系统的循环㶲损出发进行分析,发现中间换热器㶲损最大,进而对减小㶲损的方法进行了理论分析,并以R290/R170、R600a/R1150两种不同沸点差的二元混合工质组合为例,深入研究了混合工质循环配比对中间换热器㶲损的影响。通过实验测试,验证了不同循环配比下整机性能的变化。结果表明:中间换热器㶲损大小取决于换热过程高压侧及低压侧的温度匹配程度,可通过热当量比来体现,热当量比越接近1,㶲损越小;不同混合工质组合,存在各自的最佳循环配比,使得整机性能最佳,该最佳循环配比与理论分析得到的使中间换热器㶲损最小的循环配比接近。
Abstract：
Starting from the exergy loss of the auto-cascade heat pump system cycle, this paper analyses and finds that the intermediate heat exchanger has the largest exergy loss. Then, a theoretical analysis is conducted on the methods to reduce the exergy loss. Taking two binary mixed working fluid combinations of R290/R170 and R600a/R1150 with different boiling point differences as examples, the influence of the mixture ratio of the mixed working fluid on the exergy loss of the intermediate heat exchanger is studied in depth. Through experimental testing, the changes in the overall performance under different mixture ratios are verified. The results show that the exergy loss of the intermediate heat exchanger depends on the temperature matching degree of the high-pressure side and the low-pressure side during the heat exchange process, and can be reflected by the thermal equivalent ratio. The closer the thermal equivalent ratio is to 1, the smaller the exergy loss is. For different mixed working fluid combinations, there is an optimal mixture ratio that makes the overall performance the best. The optimal mixture ratio is close to the mixture ratio with the smallest exergy loss in the intermediate heat exchanger as analysed theoretically.
Keywords:auto-cascade heat pump; intermediate heat exchanger; exergy loss; mixed working fluid; mixture ratio; thermal equivalent ratio; performance improvement