HFC245fa水平光管与强化管管束外冷凝换热  

Condensation heat transfer coefficient of HFC245fa on horizontal smooth and enhanced tube bundles

作　　者：马志先[1] 张吉礼[1,2] 孙德兴[1] 

机构地区：[1]哈尔滨工业大学市政环境工程学院,黑龙江哈尔滨150090 [2]大连理工大学建设工程学部土木学院,辽宁大连110064

出　　处：《化工学报》2010年第5期1097-1106,共10页CIESC Journal

基　　金：国家自然科学基金项目(50578049);'十一五'国家科技部支撑计划项目(2006BAJ01A09; 2008 BAJ12B05)~~

摘　　要：试验研究了新型环保工质HFC245fa在光管与强化换热管管束上的冷凝换热特性。试验管束由4列排深为5排的列管构成,换热管公称外径为19.05mm、有效换热长度为1000mm。试验中,通过改进的Wilson图解法获得强化换热管水侧对流传热系数,利用2接点温差电偶测试蒸气与冷却水温差(±0.025℃),利用热电偶通过小周期标定法获取试验管进出水温差(±0.01℃);考察了冷凝温度、热通量对冷凝换热的影响。研究结果表明:HFC245fa在光管单管外冷凝传热系数与Nusselt模型预测值一致性较好;同热通量下,强化换热管单管上的冷凝传热系数为光管的13.5倍;光管管束上的试验结果比Nusselt管束模型预测值高20%～50%;强化管冷凝换热性能受作用热通量的影响较大。试验结果对工质与新管材推广、应用具有指导意义。The characteristics of condensation heat transfer of HFC245fa were investigated experimentally on horizontal tube bundles,which consist of 4-column and 5-row smooth tubes and enhanced tubes.All tubes in the test had the same equivalent outside diameter of 19.05 mm and effective length of 1000 mm.The water-side convection heat transfer coefficient of enhanced tube was obtained by modified Wilson plot method.The temperature difference between saturated vapor and cooling water was obtained by two-junction thermopiles （precision,±0.025℃） and the temperature difference of cooling water was obtained by thermocouples with small period standardization method （precision,±0.01℃）.The effects of saturate temperature and heat flux on the condensation heat transfer were examined.The results show that the condensation heat transfer coefficients of HFC245fa on single smooth tube can be well predicted by Nusselt model under lower heat flux,but the deviation increases with the increase of heat flux.The heat transfer coefficient of single enhanced tube is 13.5 times that of smooth tube under the same heat flux.The coefficient of smooth tube bundle is higher than that estimated by Nusselt model （nearly 20%—50% according to row 2 to row 5）.The condensation heat transfer of the enhanced tube bundle is sensitive to the quantity of condensate.The results may provide some guidelines for the design of shell-tube condenser for HFC245fa.

关 键 词：HFC245fa 冷凝换热 水平管束 强化管 管束效应 

分 类 号：TK124[动力工程及工程热物理—工程热物理]