超临界CO_2水平管内浮升力和热加速效应评判准则
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摘要
针对超临界CO_2流体特殊的热物性所导致的奇异流动传热规律,开展了2mm内径的水平光滑圆管的传热试验研究。试验压力为7.4~8MPa,质量流速为600~1 000kg/(m~2·s),最大热流密度为94.2kW/m~2。试验获得了壁温和传热系数的变化规律,分析了不同的试验工况下无量纲浮升力和热加速的变化规律。结果表明:流体的传热系数峰值随热流密度升高逐渐向入口移动;不同无量纲浮升力的变化趋势存在较大的偏差,Kim的浮升力公式可较好地评判浮升力的大小;热加速效应在低热流密度下不显著,在高热流密度下呈现先递增后递减的趋势;当浮升力因子小于5.6×10~(-7)和热加速因子小于0.000 5时,浮升力效应和热加速效应可忽略。将浮升力和热加速因子引入新的Nusselt预测关联式,其平均误差为-2.92%,均方根误差为10.96%。
According to the complex thermophysical properties of supercritical CO_2,the heat transfer experiments on a smooth horizontal tube with a 2 mm inner diameter were carried out.The test pressure was 7.4-8 MPa,the mass flux was about 600-1 000 kg/(m~2·s),and the maximum heat flux was 94.2 kW/m~2.Through experiments,the wall temperature and local heat transfer coefficient were obtained.The non-dimensional buoyancy and thermal acceleration behavior under different experimental conditions were analyzed.The results show that the peak heat transfer coefficient of the fluid increases gradually with the heat flux and that there exists great deviation in the variation trend for different non-dimensional buoyancy.The Kim's buoyancy correlation can better judge the value of buoyancy.Three different non-dimensional thermal accelerations indicate that the effect of thermal acceleration at low heat flux is not significant,while at high heat flux the acceleration effect presents a first increasing then decreasing tendency.When the buoyancy factor and thermal acceleration factor are less than 5.6×10-7 and 0.000 5,respectively,the effects of both buoyancy and thermal acceleration can be ignored.By taking into account both buoyancy and thermal acceleration,a new Nusseltcorrelation can be established.The average error and root mean square error of the correlation is-2.92% and 10.96%,respectively.
According to the complex thermophysical properties of supercritical CO_2,the heat transfer experiments on a smooth horizontal tube with a 2 mm inner diameter were carried out.The test pressure was 7.4-8 MPa,the mass flux was about 600-1 000 kg/(m~2·s),and the maximum heat flux was 94.2 kW/m~2.Through experiments,the wall temperature and local heat transfer coefficient were obtained.The non-dimensional buoyancy and thermal acceleration behavior under different experimental conditions were analyzed.The results show that the peak heat transfer coefficient of the fluid increases gradually with the heat flux and that there exists great deviation in the variation trend for different non-dimensional buoyancy.The Kim's buoyancy correlation can better judge the value of buoyancy.Three different non-dimensional thermal accelerations indicate that the effect of thermal acceleration at low heat flux is not significant,while at high heat flux the acceleration effect presents a first increasing then decreasing tendency.When the buoyancy factor and thermal acceleration factor are less than 5.6×10-7 and 0.000 5,respectively,the effects of both buoyancy and thermal acceleration can be ignored.By taking into account both buoyancy and thermal acceleration,a new Nusseltcorrelation can be established.The average error and root mean square error of the correlation is-2.92% and 10.96%,respectively.
引文
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[16]刘光旭,黄彦平,王俊峰.浮升力和流动加速效应对超临界CO2传热影响研究[J].核动力工程,2016,37(2):48-51.LIU Guangxu,HUANG Yanping,WANG Junfeng.Experimental study on effect of buoyancy and flow acceleration on heat transfer of supercritical CO2[J].Nuclear Power Engineering,2016,37(2):48-51.
[17]KIM T H,KWON J G,YOON S H,et al.Numerical analysis of air-foil shaped fin performance in printed circuit heat exchanger in a supercritical carbon dioxide power cycle[J].Nuclear Engineering and Design,2015,288:110-118.
[18]KIM Y M,KIM C G,FAVRAT D.Transcritical or supercritical CO2cycles using both low-and high-temperature heat sources[J].Energy,2012,43(1):402-415.
[19]JACKSON J D.Fluid flow and convective heat transfer to fluids at supercritical pressure[J].Nuclear Engineering and Design,2013,264:24-40.
[20]FANG X,XU Y.Modified heat transfer equation for in-tube supercritical CO2cooling[J].Applied Thermal Engineering,2011,31(14/15):3036-3042.
[21]ADEBIYI G A,HALL W B.Experimental investigation of heat transfer to supercritical pressure carbon dioxide in a horizontal pipe[J].International Journal of Heat and Mass Transfer,1976,19(7):715-720.
[22]PETUKHOV B S,POLYAKOV A F,KULESHOV V A,et al.Turbulent flow and heat transfer in horizontal tubes with substantial influence of thermo-gravitational forces[C/OL]∥Proceedings of the 5th International Heat Transfer Conference 1974.[2017-12-25].http:∥www.dl.begellhouse.com/references/3ea7b3cd5b654406,0f1d13636fd6b121,56231ee144898242.html.
[23]KIM D E,KIM M H.Experimental study of the effects of flow acceleration and buoyancy on heat transfer in a supercritical fluid flow in a circular tube[J].Nuclear Engineering and Design,2010,240(10):3336-3349.
[24]JACKSON J D.An semi-empirical model of turbulent convective heat transfer to fluids at supercritical pressure[C/OL]∥Proceedings of the 16th International Conference on Nuclear Engineering.[2017-12-25].DOI:10.1115/ICONE16-48914.
[2]DOSTAL V,DRISCOLL M J.A supercritical carbon dioxide cycle for next generation nuclear reactors:MIT-ANP-TR-100[R].Boston,USA:Advanced Nuclear Power Technology Program,2004:39-42.
[3]SHIRALKAR B,GRIFFITH P.The effect of swirl,inlet conditions,flow direction,and tube diameter on the heat transfer to fluids at supercritical pressure[J].Journal of Heat Transfer,1970,92(3):465-471.
[4]SHIRALKAR B,GRIFFITH P.Deterioration in heat transfer to fluids at supercritical pressure and high heat fluxes[J].Journal of Heat Transfer,1969,91(1):27-36.
[5]PETUKHOV B S.Heat transfer and flow resistance in the turbulent pipe flow of a fluidwith near-critical state parameters[J].Teplofizika Vysokikh of Temperature,1983,21:92-100.
[6]PETUKHOV B S,POLYAKOV A V.Boundaries of regimes with worsened/heat transfer for supercritical pressure of coolant[J].Teplofizika Vysokikh of Temperature,1970,12(1):221-224.
[7]PETUKHOV B S.Heat transfer and friction in turbulent pipe flow with variable physical properties[J].Advances in Heat Transfer,2011,6:503-564.
[8]BAE Y Y,KIM H Y,KANG D J.Forced and mixed convection heat transfer to supercritical CO2 vertically flowing in a uniformly-heated circular tube[J].Experiment of Thermal Fluid Science,2010,34(8):1295-1308.
[9]KIM H Y,KIM H,SONG J H,et al.Heat transfer test in a vertical tube using CO2at supercritical pressures[J].Journal of Nuclear Science and Technology,2007,44(3):285-293.
[10]KIM J K,JEON H K,LEE J S.Wall temperature measurement and heat transfer correlation of turbulent supercritical carbon dioxide flow in vertical circular/non-circular tubes[J].Nuclear Engineering and Design,2007,237(15/16/17):1795-1802.
[11]KIM J K,JEON H K,LEE J S.Wall temperature measurements with turbulent flow in heated vertical circular/non-circular channels of supercritical pressure carbon-dioxide[J].International Journal of Heat and Mass Transfer,2007,50(23/24):4908-4911.
[12]HALL W B,JACKSON J D.Heat transfer near the critical point[J].Advances in Heat Transfer,1971,7(1):86.
[13]LIAO S M,ZHAO T S.Measurements of heat transfer coefficients from supercritical carbon dioxide flowing in horizontal mini/micro channels[J].ASME J Heat Transfer,2002,124(3):413-420.
[14]MCELIGOT D,JACKSON D.“Deterioration”criteria for convective heat transfer in gas flow through noncircular ducts[J].Nuclear Engineering and Design,2004,232(3):327-333.
[15]刘波.超临界压力流体在圆管内对流换热及热裂解研究[D].北京:清华大学,2013:5-6.
[16]刘光旭,黄彦平,王俊峰.浮升力和流动加速效应对超临界CO2传热影响研究[J].核动力工程,2016,37(2):48-51.LIU Guangxu,HUANG Yanping,WANG Junfeng.Experimental study on effect of buoyancy and flow acceleration on heat transfer of supercritical CO2[J].Nuclear Power Engineering,2016,37(2):48-51.
[17]KIM T H,KWON J G,YOON S H,et al.Numerical analysis of air-foil shaped fin performance in printed circuit heat exchanger in a supercritical carbon dioxide power cycle[J].Nuclear Engineering and Design,2015,288:110-118.
[18]KIM Y M,KIM C G,FAVRAT D.Transcritical or supercritical CO2cycles using both low-and high-temperature heat sources[J].Energy,2012,43(1):402-415.
[19]JACKSON J D.Fluid flow and convective heat transfer to fluids at supercritical pressure[J].Nuclear Engineering and Design,2013,264:24-40.
[20]FANG X,XU Y.Modified heat transfer equation for in-tube supercritical CO2cooling[J].Applied Thermal Engineering,2011,31(14/15):3036-3042.
[21]ADEBIYI G A,HALL W B.Experimental investigation of heat transfer to supercritical pressure carbon dioxide in a horizontal pipe[J].International Journal of Heat and Mass Transfer,1976,19(7):715-720.
[22]PETUKHOV B S,POLYAKOV A F,KULESHOV V A,et al.Turbulent flow and heat transfer in horizontal tubes with substantial influence of thermo-gravitational forces[C/OL]∥Proceedings of the 5th International Heat Transfer Conference 1974.[2017-12-25].http:∥www.dl.begellhouse.com/references/3ea7b3cd5b654406,0f1d13636fd6b121,56231ee144898242.html.
[23]KIM D E,KIM M H.Experimental study of the effects of flow acceleration and buoyancy on heat transfer in a supercritical fluid flow in a circular tube[J].Nuclear Engineering and Design,2010,240(10):3336-3349.
[24]JACKSON J D.An semi-empirical model of turbulent convective heat transfer to fluids at supercritical pressure[C/OL]∥Proceedings of the 16th International Conference on Nuclear Engineering.[2017-12-25].DOI:10.1115/ICONE16-48914.