螺旋管内超临界CO2/DME混合工质冷却换热特性研究  

Study on Heat Transfer Characteristics of Supercritical CO2/DME Mixture Flowing in Cooled Helically Coiled Tubes

作　　者：巴清心 李雪芳[1] 黄腾[1] 程林[1] BA Qing-Xin;LI Xue-Fang;HUANG Teng;CHENG Lin(Institute of Thermal Science and Technology,Shandong University,Jinan 250061,China)

机构地区：[1]山东大学热科学与工程研究中心,济南250061

出　　处：《工程热物理学报》2020年第7期1743-1750,共8页Journal of Engineering Thermophysics

基　　金：山东省自然科学基金资助项目(No.ZR2017BEE003);中国博士后科学基金(No.2017M612267)。

摘　　要：CO2/DME(Dimethyl ether二甲醚)混合工质作为制冷剂既可以降低CO2单独使用时过高的工作压力,又可抑制二甲醚的可燃性。针对跨临界热泵系统中制冷剂在超临界压力下放热时复杂的传热性能,本文对超临界CO2/DME混合工质和超临界CO2在螺旋管内流动冷却的换热过程进行了数值模拟研究。结果表明,与纯CO2相比,在高温区CO2/DME混合工质的换热性能更优;通过比较不同配比的CO2/DME混合工质的换热特性,得到了不同温度范围对应的换热性能最优的CO2/DME混合工质配比。此外,对固定质量比的CO2/DME混合工质,分别分析了不同质量流速和热流密度下的流体温度、壁面温度及传热系数的变化规律,并与纯CO2传热系数的变化进行了对比。该研究为制冷剂选取及热泵系统中气冷器的优化设计提供了理论依据。The mixture of CO2 and Dimethyl ether(DME)helps to reduce the system operating pressure and to suppress the flammability of the DME.There are complicated exothermic processes of supercritical refrigerant in a transcritical heat pump system.In this study,the heat transfer characteristics of supercritical CO2/DME mixtures and pure CO2 cooled in helically coiled tubes were modeled.The results show that the CO2/DME mixture was more favorable in high temperature zone comparing with pure CO2.The optimal compositions of CO2/DME were determined for different temperature ranges by compare the heat transfer coefficients with different DME mass fractions.Furthermore,the heat transfer performances with a given CO2/DME mixture were analyzed for different mass and heat fluxes and then compared with CO2.The present work is helpful to refrigerant selection and optimization of gas cooler in heat pump systems.

关 键 词：超临界CO2 CO2/二甲醚混合工质 数值模拟 换热特性 

分 类 号：TK124[动力工程及工程热物理—工程热物理]