复叠式高温热泵低温级工质最小熵增法筛选  

Screening of Low-temperature Stage Working Fluid by Minimum Entropy Increase Method for Cascade High-temperature Heat Pump

作　　者：董胜明 张蓓 胡晓微[1] 王佳文 朱婷婷 DONG Shengming;ZHANG Bei;HU Xiaowei;WANG Jiawen;ZHU Tingting

机构地区：[1]天津商业大学天津市制冷技术重点实验室,天津300134

出　　处：《煤气与热力》2022年第6期5-10,共6页Gas & Heat

基　　金：天津市自然科学基金“太阳能高温热泵供暖及有机朗肯循环低温发电复合系统关键技术研究”(18JCYBJC90500);天津市技术创新引导专项基金“集成发电热泵一体化机组的研制”(20YDTPJC01150);天津市自然科学基金“农村用高效低成本太阳能空气采暖节能技术研究”(18JCQNJC77400)。

摘　　要：设定3种工况,选择R245fa作为复叠式高温热泵系统的高温级工质,将R134a、R245fa按不同质量比(9:1、8:2、7:3、6:4)混合后的非共沸混合工质(以下简称混合工质)作为低温级工质。基于最小熵增法计算蒸发器中混合工质的相对额外熵增。以相对额外熵增最小作为目标,筛选混合工质的最优质量比。采用实验方法验证最小熵增法筛选混合工质最优质量比的可行性。由理论计算结果可知:3种工况最小理论相对额外熵增对应的混合工质质量比分别为9:1、8:2、8:2。当工况1-3的混合工质质量比分别为9:1、8:2、8:2时,混合工质与热源水的换热温差在蒸发器沿程的波动最小。由实验结果可知:3种工况最高系统制热性能系数对应的混合工质质量比分别为9:1、8:2、8:2。根据系统制热性能系数实验结果筛选出的最优混合工质质量比,与采用最小熵增法的理论筛选结果一致。3种工况最小实验相对额外熵增对应的混合工质质量比分别为9:1、8:2、8:2。实验获得的各工况的最优混合工质质量比与理论分析结果一致,验证了理论方法的正确性。Three working conditions are set, R245 fa is selected as the high-temperature working fluid of the cascade high-temperature heat pump system, and the non-azeotropic mixed working fluid(hereinafter referred to as the mixed working fluid) is used as the low-temperature working fluid, after mixing R134 a and R245 fa according to different mass ratios(9∶1,8∶2,7∶3 and 6∶4). The relative additional entropy increase of mixed working fluid in evaporator is calculated based on the minimum entropy increase method. The optimal mass ratio of mixed working fluid is selected with the minimum increase in relative additional entropy as the goal. The feasibility of screening the optimal mass ratio of mixed working fluid by minimum entropy increase method is verified by the experimental method. The theoretical calculation results show that the mass ratios of the mixed working fluids corresponding to the minimum theoretical relative additional entropy increase under the three working conditions are 9∶1,8∶2 and 8∶2 respectively. When the mass ratios of the mixed working fluids under working conditions 1-3 are 9∶1,8∶2 and 8∶2 respectively, the heat exchange temperature difference between the mixed working fluid and the heat source water has the least fluctuation along the evaporator. It can be seen from the experimental results that the mass ratios of the mixed working fluids corresponding to the highest heating performance coefficients of the system under the three working conditions are 9∶1,8∶2 and 8∶2 respectively. The optimal mass ratios of the mixed working fluids are screened out according to the experimental results of the heating performance coefficient of the system, which are consistent with the theoretical screening results using the minimum entropy increase method. The mass ratios of the mixed working fluids corresponding to the minimum experimental relative additional entropy increase under the three working conditions are 9∶1,8∶2 and 8∶2 respectively. The optimal mass ratios of the mixed

关 键 词：非共沸混合工质 复叠式高温热泵 最小熵增法 相对额外熵增 

分 类 号：TU995.7[建筑科学—供热、供燃气、通风及空调工程]