压力瞬态下超临界压力CO2的传热特性  

Heat transfer characteristics of supercritical CO2 under transient pressure

作　　者：朱兵国 吴新明 张良[1] 徐进良[1] 刘欢[1] ZHU Bingguo;WU Xinming;ZHANG Liang;XU Jinliang;LIU Huan(Beijing Key Laboratory of Multiphase Flow and Heat Transfer,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学低品位能源多相流与传热北京市重点实验室

出　　处：《化工进展》2019年第10期4444-4451,共8页Chemical Industry and Engineering Progress

基　　金：国家重点研发计划(2017YFB0601801);中央高校基本科研业务费专项资金(2018QN043)

摘　　要：在均匀加热条件下,开展超临界压力二氧化碳在压力瞬态下的传热特性实验研究。实验段内径为10.0mm,实验参数范围:压力P=7.58~9.97MPa,热流密度qw=64~256kW/m^2,质量流速G=660~893kg/(m^2·s)。分析了正常传热和传热恶化条件下,瞬间泄压过程对传热的影响规律。实验结果表明,正常传热工况下,壁温随着压力的减小有降低的趋势,传热系数明显增大;传热恶化发生后壁温迅速上升,对应的传热系数减小传热恶化更加严重,且恶化壁温峰值点向着入口方向移动。最后对实验现象进行了解释,正常传热下壁温降低是由于压力的降低增大了比热容,从而改善了传热。传热恶化发生后,压力的降低减小了拟临界焓值ipc,从而增大了超临界沸腾数SBO,更大的SBO表明膨胀动量力占主导,靠近壁面低密度的vapor-like fluid在不断向外膨胀,从而使得低密度层流体的厚度增加,从而加大了传热热阻,这时壁温升高或者出现更大的恶化。Experimental study on the heat transfer characteristics of supercritical carbon dioxide under transient pressure was carried out.The experiment of supercritical CO2 heat transfer was performed in a 10.0mm inner diameter tube.The experimental conditions were:pressure,P=7.58—9.97MPa,heat flow density,qw=64—256kW/m2 and mass flow rate,G=660—893kg/(m2·s).The heat transfer characteristics during the rapid depressurization process was analyzed under normal heat transfer and heat transfer deterioration conditions.According to the experimental reaults,with the decrease of pressure,the wall temperature decreased,and heat transfer coefficients increased under normal heat transfer.The wall temperature rises rapidly in the process of pressure relief when the heat transfer deterioration occurs,and heat transfer coefficient decreases.Meanwhile,the peak point of the deteriorating wall temperature moves towards the entrance direction.Finally,the experimental phenomenon was explained.Under normal heat transfer,with the decrease of pressure,specific heat increased,and the heat transfer improved.When the heat transfer deterioration occurs,the decrease of pressure reduces the pseudo-critical enthalpy value ipc,thus increasing supercritical"boiling"number SBO.The larger SBO indicated that the vapor expansion effect was stronger compared to the inertia effect,larger SBO expands"vapor layer"thickness to increase the heat transfer resistance lead to serious heat transfer deterioration.

关 键 词：超临界二氧化碳 瞬态响应 传热 

分 类 号：TK124[动力工程及工程热物理—工程热物理]