R236fa/R32 mixed refrigerant of large glide temperature selection and experimental verification

doi:10.16085/j.issn.1000-6613.2018-0827

Abstract

Abstract: For the diversified selection of the composition and components of the mixed refrigerant under different refrigeration conditions, the optimal selection method of R236fa/R32 components with large glide temperature mixed refrigerant for two evaporation temperature refrigeration unit was proposed, which has the condensation temperature range of 311-333K and the evaporation temperature range of 269-290K. The nonlinear change of temperature with enthalpy of R236fa/R32 was studied theoretically. The entropy increase calculation model of mixed refrigerant evaporation heat transfer process was established based on the nonlinear change characteristics of temperature and enthalpy. The optimum composition of the mixed refrigerant was determined by the change of entropy of the high and low temperature evaporator with different components. The temperature distribution in the heat exchanger, the coefficient of performance (COP) value and the power consumption of the compressor were obtained by the experimental study. The results of the optimized method were verified. The results showed that the entropy increase model could better reflect the COP characteristics of the refrigerant and the power consumption of the compressor with different components. The entropy of the evaporator increased first then decreased with the increase of R32mass fraction. When the refrigerant mixture was R236fa/R32(4:6), both the entropy increase of low temperature evaporator and high temperature evaporator were the smallest due to the nonlinear variation of temperature with enthalpy value. Therefore, 4:6 was the best component of 236fa/R32 in the two evaporation temperature refrigeration system. The experimental results were highly consistent with the theoretical analysis. This method can provide reference for the selection of refrigerant mixtures under different refrigeration conditions.

Key words: R236fa/R32, analysis of temperature and enthalpy, temperature glide, pinch point, entropy increase

摘要： 针对适用不同制冷工况下混合工质组成及组分的多样化选择问题，提出了对应用于双温制冷机组的大滑移温度混合工质R236fa/R32组分在冷凝温度范围为311～333K、蒸发温度范围为269～290K的优选方法。对R236fa/R32的温度随焓值非线性变化特性进行了理论研究；建立了混合制冷剂蒸发换热过程由于温度随焓值非线性变化特性产生的熵增模型，通过对混合工质不同组分高、低温蒸发器的熵增变化情况确定最佳组分。并搭建了试验台，通过实验研究得到了该混合工质不同组分下在换热器中的温度分布情况、制冷效率（COP）及压缩机功耗情况验证该优选方法的结果。研究结果表明：该熵增模型能够较好地反映该混合制冷剂不同组分的COP特性及压缩机功耗，随着R32质量分数的增加，蒸发器的熵增先增大、后减小，在R236fa/R32为4∶6时，低温蒸发段和高温蒸发段由于温度随焓值非线性变化特性产生的熵增都最小，因此为该机组的最佳组分，验证了理论分析的正确性。该方法可以为不同工况下混合工质的优选提供参考。

关键词: R236fa/R32, 温焓分析, 滑移温度, 传热窄点, 熵增

CLC Number:

TK123

YU Pengfei, ZHANG Xiaosong, WEN Xiantai. R236fa/R32 mixed refrigerant of large glide temperature selection and experimental verification[J]. Chemical Industry and Engineering Progress, 2018, 37(11): 4190-4196.

余鹏飞, 张小松, 文先太. R236fa/R32大滑移温度混合工质的优选方法及实验验证[J]. 化工进展, 2018, 37(11): 4190-4196.

References

[1] 刘剑, 张小松. 基于大滑移温度非共沸工质的双温冷水机组[J]. 化工学报, 2016, 67(4):1186-1192. LIU Jian,ZHANG Xiaosong. Double temperature chilled water unit based on large temperature glide zeotropic mixture[J]. Journal of Chemical Engineering, 2016, 67(4):1186-1192.
[2] 余鹏飞, 张小松. 非共沸混合工质实现变蒸发温度制冷性能的理论研究[J]. 建筑科学, 2014, 30(12):75-79. YU Pengfei, ZHANG Xiaosong. Theoretical study on the variable evaporating temperature refrigeration performance of non-azeotropic refrigerant mixtures[J]. Building Science, 2014, 30(12):75-79.
[3] YU Pengfei, ZHANG Xiaosong, LIU Jian. A theoretical and experimental study on the variable evaporating temperature refrigeration performance of non-azeotropic refrigerant mixtures[C]//24th ⅡR International Congress of Refrigeration, ICR 2015:1550-1557.
[4] 余鹏飞, 张小松, 刘剑, 等. R236fa/R32混合制变浓度制冷系统的性能研究[J]. 建筑科学, 2016, 32(12):167-172 YU Pengfei, ZHANG Xiaosong, LIU Jian, et al. Study on performance of variable composition refrigerating system with R236fa/R32 mixed refrigerant[J]. Building Science, 2016, 32(12):167-172.
[5] 余鹏飞, 张小松, 张君, 等. R236fa/R32制冷系统冷凝温度和蒸发温度的确定方法[J]. 制冷与空调, 2016, 16(11):38-42. YU Pengfei, ZHANG Xiaosong, ZHANG J, et al. Determination method of condensing temperature and evaporation temperature for R236fa/R32 refrigeration system[J]. Refrigeration and Air Conditioning, 2016, 16(11):38-42.
[6] LIU Jian, SHE Xiaohui, ZHANG Xiaosong, et al. Experimental and theoretical study on a novel double evaporating temperature chiller applied in THICS using R32/R236fa[J]. International Journal of Refrigeration, 2017, 75:343-351.
[7] LIU Jian, SHE Xiaohui, ZHANG Xiaosong, et al. Experimental study of a novel double temperature chiller based on R32/R236fa[J]. Energy Conversion and Management, 2016, 124:618-626.
[8] LIU Jian, ZHANG Xiaosong. Performance analysis of a novel double temperature chilling water unit using large temperature glide zeotropic mixture[J]. Procedia Engineering, 2015, 121:1222-1229.
[9] 刘剑, 张小松. 冷冻水流量和温度对混合制冷剂双温双冷源制冷系统性能影响[J]. 制冷学报, 2015, 36(6):83-89. LIU Jian, ZHANG Xiaosong. Effect of variable chilled water flow rates and temperature on performance of double temperature chiller with large temperature glide zeotropic refrigerant[J]. Journal of Refrigeration, 2015, 36(6):83-89.
[10] CHEN Tingting, YIN Yonggao, ZHANG Xiaosong. Applicability and energy efficiency of temperature and humidity independent control systems based on dual cooling sources[J]. Energy and Buildings, 2016, 121:22-31.
[11] CHEN Yao, YIN Yonggao, ZHANG Xiaosong. Performance analysis of a hybrid air-conditioning system dehumidified by liquid desiccant with low temperature and low concentration[J]. Energy and Buildings, 2014, 77:91-102.
[12] SI Qing, ZHANG Xiaosong. Performance evaluation and experimental study of the induction radiant air-conditioning system[J]. Procedia Engineering, 2015, 121:1795-1804.
[13] 文先太, 梁彩华, 刘成兴, 等. 叉流热源塔传热传质模型的建立及实验验证[J]. 化工学报, 2012, 63(8):2398-2404. WEN Xiantai, LIANG Caihua, LIU Chengxing, et al. Verification of model for heat and mass transfer process in the cross flow heat source tower[J]. Journal of Chemical Engineering, 2012, 63(8):2398-2404.
[14] VENKATARATHNAM G, MOKASHI G, MURTHY S S. Occurrence of pinch points in condensers and evaporators for zeotropic refrigerant mixtures[J]. International Journal of Refrigeration, 1996, 19(6):361-368.
[15] VENKATARATHNAM G, MURTHY S S. Effect of mixture compositeon on the formation of pinch points in condensers and evaporators for zeotropic refrigerant mixtures[J]. International Journal of Refrigeration, 1999, 22:205-215.
[16] 金星, 张小松. 非共沸制冷剂在逆流换热器中温度窄点出现的判别方法[J]. 化工学报, 2009, 60(4):848-854. JIN Xing, ZHANG Xiaosong. Identification of pinch point in countercurrent heat exchanger for zeotropic refrigerant mixtures[J]. Journal of Chemical Engineering, 2009, 60(4):848-854.
[17] YU Pengfei, ZHANG Xiaosong, WEN Xiantai. Theoretical and experimental study on the heat transfer temperature difference based on the nonlinear temperature enthalpy of the R236faR32 mixtures[J]. Procedia Engineering, 2017, 205:2126-2132.
[18] SCALABRINA G, GRIGIANTEB M, CRISTOFOLI G. Modelling enthalpy and entropy of pure and mixed refrigerants with an innovative corresponding states method[J]. International Journal of Refrigeration, 2003, 26:936-950.
[19] DENG Han, FEMAMDINO Maria. DORAO Carlos A. A numerical investigation of flow boiling of nonazeotropic and near-azeotropic binary mixtures[J]. International Journal of Refrigeration, 2015, 49:99-109.
[20] WSHAO D, GRANRYD E. Experimental and theoretical study on flow condensation with non-azeotropic refrigerant mixtures of R32/R134a[J]. International Journal of Refrigeration, 1998, 21(3):230-246.
[21] AZZOLIN M, BERTO A, BORTOLIN S, et al. Heat transfer degradation during condensation of nonazeotropic mixtures[C]//35th UIT Heat Transfer Conference, 2017:1-10.
[22] NACHIKET C, LUKE E, ACHENIE K. The optimal design of refrigerant mixtures for a two-evaporator refrigeration system[J]. Engng., 1997, 21:349-354.
[23] ZHAO P C, ZHAO L, DING G L, et al. Temperature matching method of selecting working fluids for geothermal heat pumps[J]. Applied Thermal Engineering, 2003, 23:179-195.
[24] DALKILIÇ A S. Theoretical analysis on the prediction of performance coefficient of two-stage cascade refrigeration system using various alternative refrigerants[J]. Thermal Science and Technology, 2012, 32, 1:67-79.
[25] 马一太, 吕灿仁, 严晋跃. 用非共沸混合工质R22/R142b实现劳伦兹循环代替R12的研究[J]. 工程热物理学报, 1990, 11(1):21-23. MA Yitai, LÜ Canren, YAN Jinyue. Study of realizing lorenz cycle using non-azeotropic refrigerant mixture R22/R142b for substitute of R12[J]. Journal of Engineering Thermophysics, 1990, 11(1):21-23.
[26] 赵力, 刘惠. 非共沸混合工质蒸发过程中的传热温差探讨[J]. 暖通空调, 2005, 35(6):118-121. ZHAO Li, LIU Hui. Heat transfer temperature difference of non-azeotropic mixture refrigerants in evaporating[J]. Journal of HV&AC, 2005, 35(6):118-121.
[27] 赵力, 朱禹, 王晓东. 空调工况下非共沸制冷剂在蒸发器内的传热窄点研究[J]. 低温工程, 2007(4):51-55. ZHAO Li, ZHU Yu, WANG Xiaodong. Heat transfer pinch point of zeotropic refrigerants in condenser with air-conditioning operation[J]. Journal of Chemical Industry and Engineering, 2007(4):51-55.
[28] 刘兆永, 赵力, 赵学政. 高温热泵工况下非共沸工质在换热器中的换热特性[J]. 化工学报, 2011, 62(12):3386-3393. LIU Zhaoyong, ZHAO Li, ZHAO Xuezheng. Heat exchange characteristics of zeotropic mixtures in heat exchangers in high temperature heat pump[J]. CIESC Journal, 2011, 62(12):3386-3393.
[29] ZHAO L, GAO P. Influence of zeotropic mixtures' temperature gliding on the performance of heat transfer in condenser or evaporator[J]. Transactions of Tianjin University, 2005, 11(6):400-406.
[30] ZHANG Kai, ZHU Yutong, LIU Jinxiang. et al. Exergy and energy analysis of a double evaporating temperature chiller[J]. Energy & Buildings, 2018, 165:464-471.