超临界压力下竖直圆管内不同流体的传热特性

Heat Transfer Characteristics of Different Fluids in Vertical Tube under Supercritical Pressure

为了深入认识超临界压力下不同流体传热中的共性反映出的传热机理及物性导致的特性差异,以水和氟利昂R134a为工质分别在SWAMUP回路和SMOTH回路上开展了竖直圆管内上升流传热试验。在正常传热、传热强化、小质量流速时浮升力导致传热恶化和大质量流速时加速效应导致传热恶化的工况中,氟利昂和水的换热系数(HTC)随无量纲温度表现出一致的变化规律。浮升力无量纲数πB增大,换热系数与经典关系式计算值之比减小;加速效应无量纲数πA较小时,换热系数比随πA的增大而增大,达到峰值后换热系数比随πA的增大而减小。πB对超临界水试验数据的相关性更佳,而πA对超临界氟利昂试验数据的相关性更好。无量纲数表征的超临界压力下传热规律的高度相似性初步验证了以模化流体氟利昂R134a研究超临界水传热特性是合理可行的。

To understand heat transfer mechanism from general character and make clear the difference caused by properties,experiments of heat transfer to water and Freon R134 aflowing upward in vertical tubes were conducted on SWAMUP and SMOTH test facilities,respectively.The variations of heat transfer coefficients of water and Freon with dimensionless temperature are coincident in the case of normal heat transfer,heat transfer enhancement and heat transfer deterioration due to buoyancy force and acceleration effect.The HTC ratio decreases with the increase of dimensionless parameterπB.The HTC ratio increases first and then decreases with the increase of dimensionless parametersπA.The dimensionless parametersπBandπA show better relevance on the supercritical water and Freon experimental data,respectively.The investigation of the heat transfer behavior of supercritical water in the SCWRs by means of model fluidFreon R134 ais proved reasonable and feasible because of the similarity dependence on dimensionless parameters.