管束效应对HFC245fa与HCFC123膜状凝结换热影响

Effect of Inundation on Film Condensation of HFC245fa and HCFC123 on Horizontal Tubes

建立试验系统、改进试验方法,试验研究HFC245fa与HCFC123在光管与3种强化换热管(2D-A,3D-A与3D-B)管束外冷凝换热特性。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19.05 mm、有效换热长度为500 mm。试验中,利用改进的Wilson图解法获得水侧对流传热系数,通过轮转试验方法消除管束试验中各试验管换热本构差异等因素对管束效应测试分析的影响。试验结果表明,Kern模型预测值与HFC245fa与HCFC123光管管束外凝结换热结果偏差随试验热通量升高而增大;管束效应对光管与三维表面强化管(3D-B)凝结换热影响比其对二维表面低肋管(2D-A)影响显著;管束效应对HFC245fa在3D-B管外凝结换热影响在n>3后超过Nusselt管束模型预测值;HFC245fa在3D-B管束外凝结换热性能随管排深度的变化规律与其在光管管束外的变化规律及Nusselt模型显示规律明显不同。

A test facility was constructed to perform shell-side condensation testing,and test results are presented for HFC245fa and HCFC123 using horizontal tube bundles（4 lines×5 rows） consist of smooth tubes and 2D-A,3D-A and 3D-B enhanced tubes.Effect of inundation on the condensation heat transfer coefficient（CHTC） is considered in the study.The nominal diameter of test tubes is 19.05 mm and the active length of the test section is 500 mm.In the experiment,water-side convection heat transfer coefficient of enhanced tube was gained by modified Wilson plot method and the tube row effect is studied by a designed method with high precision.The results show that the deviation between CHTC of HCFC123 and HFC245fa on smooth tube bundle and that predicted by Kern＇s model increased with the increase of heat flow rate;Inundation effect significantly affects CHTC of smooth and 3D-B tubes,but lightly affects that of 2D-A tubes;Inundation effect of HFC245fa on 3D-B tubes is more severity than that predicted by Nusselt model for smooth tube bundle,and Characteristic of CHTC of HFC245fa on 3D-B enhanced tube is obviously different from that of smooth tube and Nusselt model.