椭圆管外含不凝结气体自然对流凝结换热性能研究
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摘要
特殊的换热管型有利于加快气液膜排泄及分离,使换热器的换热性能提高,达到节能的目的。在自然对流的情况下,基于双膜理论和边界层理论,在考虑气液界面热阻的情况下,建立了椭圆管外气、液膜厚度及传热系数的数学模型,利用C++软件进行编程得到不同初始参数、曲率下的气、液膜厚度、凝液量、气、液膜热阻、气液界面热阻和传热系数沿管壁的分布规律。研究结果表明:其他条件不变,传热系数随管壁温度的增大而增大,随混合气压力的增大而减小,随不凝结气含量的增大而减小;对于当量直径相同的椭圆管,其他条件不变,曲率越大,越易发生液膜分离,传热系数越大。管外存在不凝结气体时,气膜热阻>液膜热阻》气液界面热阻。计算结果与文献基本相符,能够较好的反映实际,为强化换热提供一定理论指导。
The special heat transfer tube type is beneficial to accelerate the excretion and separation of gas and liquid membrane,which improves the heat transfer performance of the heat exchanger,thus saving energy. In the case of natural convection,this paper established a mathematic model of gas film,liquid film thickness and heat transfer coefficient of elliptical tube based on double film theory and boundary layer theory with consideration of the vapor-liquid interfacial thermal resistance. The distributions of gas film,liquid film thickness and heat transfer coefficient along the tube wall under different initial parameters and curvatures were obtained. The results indicate that under same conditions,the heat transfer coefficient increases with the increase of the wall temperature,while it decreases with the increase of the mixed gas pressure and the non-condensable gas content. For the elliptical tubes with same equivalent diameter,when other conditions remain unchanged,the larger the curvature is,the easier the liquid film separation occurs,and the greater the heat transfer coefficient becomes. When there is non-condensable gas outside the tube,interface thermal resistance of gas phase thermal resistance > liquid phase thermal resistance > > gas-liquid interface thermal resistance. The results obtained by establishing the model were in good consistent with the existing results,which can reflect the actual situation and provide theoretical guidance for heat transfer enhancement.
The special heat transfer tube type is beneficial to accelerate the excretion and separation of gas and liquid membrane,which improves the heat transfer performance of the heat exchanger,thus saving energy. In the case of natural convection,this paper established a mathematic model of gas film,liquid film thickness and heat transfer coefficient of elliptical tube based on double film theory and boundary layer theory with consideration of the vapor-liquid interfacial thermal resistance. The distributions of gas film,liquid film thickness and heat transfer coefficient along the tube wall under different initial parameters and curvatures were obtained. The results indicate that under same conditions,the heat transfer coefficient increases with the increase of the wall temperature,while it decreases with the increase of the mixed gas pressure and the non-condensable gas content. For the elliptical tubes with same equivalent diameter,when other conditions remain unchanged,the larger the curvature is,the easier the liquid film separation occurs,and the greater the heat transfer coefficient becomes. When there is non-condensable gas outside the tube,interface thermal resistance of gas phase thermal resistance > liquid phase thermal resistance > > gas-liquid interface thermal resistance. The results obtained by establishing the model were in good consistent with the existing results,which can reflect the actual situation and provide theoretical guidance for heat transfer enhancement.
引文
[1]袁世平.含有不凝性气体的蒸汽凝结现象的研究[D].北京:中国原子能科学研究院,2001.YUAN Shiping.Investigation of condensation of steam in the presence of noncondensable gases[D].Beijing:Thermalhy Draulie Laboratory China Institute of Atomic Energy,2001.
[2]沈子信.不凝性气体对制冷量影响的实验研究[J].湖南大学学报:自然科学版,1998(2):65-69.SHEN Zixin.Experimental research on effect of noncondensable gases to refrigerating capacity[J].Journal of Hunan University,1998(2):65-69.
[3]杨世铭,陶文铨.传热学[M].北京:高等教育出版社,2006.YANG Shiming,TAO Wenquan.Heat transfer[M].Beijing:Higher Education Press,2006.
[4]关秀红.气汽混合流凝结液膜厚度分布及对换热特性的影响[D].保定:华北电力大学,2013.GUAN Xiuhong.Thickness distribution of liquid film and the effect on heat transfer characteristics for the condensation of gas-vapor mixture[D].Baoding:School of Energy,Power and Mechanical Engineering,2013.
[5]NUSSELT W.Die Oberflachenkodensation des Wasserdampfes[J].Z.vereines Deutsch.ing,1916,60.
[6]SPARROW E M,LIN S H.Condensation heat transfer in the presence of a non-condensable gas[J].Journal of Heat Transfer,1964,86(3):430-436.
[7]MINKOWYCZ W J,SPARROW E M.Condensation heat transfer in the presence of noncondensables,interfacial resistance,superheating,variable properties,and diffusion[J].International Journal of Heat and Mass Transfer,1966,9(10):1125-1144.
[8]SIDDIQUE M.The effects of noncondensable gases on steam condensation under forced convection conditions/[J].Massachusetts Institute of Technology,1991,24(2):98-107.
[9]KUHNS Z.Investigationofheat transfer from condensation steam-gasmixture and turbulent films flowing downward inside a vertical tube[D].Clifornia:University of California,1995.
[10]TANRIKUT A,YESIN O.Experimental research on Intube condensation under steady-state and transient conditions[J].Nuclear Technology,2005,149(1):88-100.
[11]欧阳新萍,舒涛,刘冰翛.R410A、R404A、R407C在水平强化换热管外的凝结换热[J].化工进展,2017,36(2):481-486.OUYANG Xinping,SHU Tao,LIU Bingxiao.Experimental study of condensation heat transfer performance of R410A,R404A and R407C on horizontal enhanced tubes[J].Chemical Industry and Engineering Progress,2017,36(2):481-486.
[12]乔宏斌,王顺,胡申华.流速对水平圆管外混合蒸汽凝结换热影响的实验研究[J].热能动力工程,2016,31(10):9-14.QIAO Hongbin,WANG Shun HU Shenua.Mixed vapor condensation outside horizontal tube under different vapor velocities[J].Journal of Engineering for Thermal Energy&Power,2016,31(10):9-14.
[13]杨丽君.管壳式换热器凝结换热实验研究[D].南京:南京工业大学,2015.YANG Lijun.Experimental investigation on condensation in shell and tube heat exchanger[D].Nanjing:Nanjing University of Technology,2015.
[14]杨宇伟.伴随有凝结发生的椭圆管外对流换热特性的数值研究[D].太原:太原理工大学,2016.YANG Yuwei.Numerical simulation on heat performance outside of elliptical tube heat exchanger with steam condensation[D].Taiyuan:Taiyuan University of Technology,2016.
[15]李慧君,彭文平.汽-气液滴形管与圆管外凝结换热的研究[J].制冷学报,2013,34(6):84-89.LI Huijun,PENG Wenping.The research on vapor-gas condensation heat transfer over a drop-shaped or circular tube[J].Journal of Refrigeration,2013,34(6):84-89.
[16]COLBURN A P,HOUGEN O A.Design of cooler condensers for mixtures of vapors with noncondensing gases[J].Ind.eng.chem,1933,26(11):1178-1182.
[17]OTHMER D F.The condensation of steam[J].Industrial&Engineering Chemistry,1929,21(6):576-583.
[18]TANG G H,HU H W,ZHUANG Z N,et al.Film condensation heat transfer on a horizontal tube in presence of a noncondensable gas[J].Applied Thermal Engineering,2012,36(1):414-425.
[19]ROHSENOW W M.Heat transfer and temperature distribution in laminar film condensation[J].Trans ASME,1956,78:1645-1648.
[20]SUKHATME S P.Heat transfer during film condensation of a liquid metal vapor[J].Journal of Heat Transfer,1964,88(1):28.
[21]沈士一,庄庆贺等.汽轮机原理[M].北京:中国电力出版社,1992.SHEN Shiyi,ZHUANG Qinghe,et al.Principles of steam turbine[M].Beijing:China Electric Power Press,1992.
[2]沈子信.不凝性气体对制冷量影响的实验研究[J].湖南大学学报:自然科学版,1998(2):65-69.SHEN Zixin.Experimental research on effect of noncondensable gases to refrigerating capacity[J].Journal of Hunan University,1998(2):65-69.
[3]杨世铭,陶文铨.传热学[M].北京:高等教育出版社,2006.YANG Shiming,TAO Wenquan.Heat transfer[M].Beijing:Higher Education Press,2006.
[4]关秀红.气汽混合流凝结液膜厚度分布及对换热特性的影响[D].保定:华北电力大学,2013.GUAN Xiuhong.Thickness distribution of liquid film and the effect on heat transfer characteristics for the condensation of gas-vapor mixture[D].Baoding:School of Energy,Power and Mechanical Engineering,2013.
[5]NUSSELT W.Die Oberflachenkodensation des Wasserdampfes[J].Z.vereines Deutsch.ing,1916,60.
[6]SPARROW E M,LIN S H.Condensation heat transfer in the presence of a non-condensable gas[J].Journal of Heat Transfer,1964,86(3):430-436.
[7]MINKOWYCZ W J,SPARROW E M.Condensation heat transfer in the presence of noncondensables,interfacial resistance,superheating,variable properties,and diffusion[J].International Journal of Heat and Mass Transfer,1966,9(10):1125-1144.
[8]SIDDIQUE M.The effects of noncondensable gases on steam condensation under forced convection conditions/[J].Massachusetts Institute of Technology,1991,24(2):98-107.
[9]KUHNS Z.Investigationofheat transfer from condensation steam-gasmixture and turbulent films flowing downward inside a vertical tube[D].Clifornia:University of California,1995.
[10]TANRIKUT A,YESIN O.Experimental research on Intube condensation under steady-state and transient conditions[J].Nuclear Technology,2005,149(1):88-100.
[11]欧阳新萍,舒涛,刘冰翛.R410A、R404A、R407C在水平强化换热管外的凝结换热[J].化工进展,2017,36(2):481-486.OUYANG Xinping,SHU Tao,LIU Bingxiao.Experimental study of condensation heat transfer performance of R410A,R404A and R407C on horizontal enhanced tubes[J].Chemical Industry and Engineering Progress,2017,36(2):481-486.
[12]乔宏斌,王顺,胡申华.流速对水平圆管外混合蒸汽凝结换热影响的实验研究[J].热能动力工程,2016,31(10):9-14.QIAO Hongbin,WANG Shun HU Shenua.Mixed vapor condensation outside horizontal tube under different vapor velocities[J].Journal of Engineering for Thermal Energy&Power,2016,31(10):9-14.
[13]杨丽君.管壳式换热器凝结换热实验研究[D].南京:南京工业大学,2015.YANG Lijun.Experimental investigation on condensation in shell and tube heat exchanger[D].Nanjing:Nanjing University of Technology,2015.
[14]杨宇伟.伴随有凝结发生的椭圆管外对流换热特性的数值研究[D].太原:太原理工大学,2016.YANG Yuwei.Numerical simulation on heat performance outside of elliptical tube heat exchanger with steam condensation[D].Taiyuan:Taiyuan University of Technology,2016.
[15]李慧君,彭文平.汽-气液滴形管与圆管外凝结换热的研究[J].制冷学报,2013,34(6):84-89.LI Huijun,PENG Wenping.The research on vapor-gas condensation heat transfer over a drop-shaped or circular tube[J].Journal of Refrigeration,2013,34(6):84-89.
[16]COLBURN A P,HOUGEN O A.Design of cooler condensers for mixtures of vapors with noncondensing gases[J].Ind.eng.chem,1933,26(11):1178-1182.
[17]OTHMER D F.The condensation of steam[J].Industrial&Engineering Chemistry,1929,21(6):576-583.
[18]TANG G H,HU H W,ZHUANG Z N,et al.Film condensation heat transfer on a horizontal tube in presence of a noncondensable gas[J].Applied Thermal Engineering,2012,36(1):414-425.
[19]ROHSENOW W M.Heat transfer and temperature distribution in laminar film condensation[J].Trans ASME,1956,78:1645-1648.
[20]SUKHATME S P.Heat transfer during film condensation of a liquid metal vapor[J].Journal of Heat Transfer,1964,88(1):28.
[21]沈士一,庄庆贺等.汽轮机原理[M].北京:中国电力出版社,1992.SHEN Shiyi,ZHUANG Qinghe,et al.Principles of steam turbine[M].Beijing:China Electric Power Press,1992.