多孔介质中超临界压力CO2对流换热的实验研究

对超临界压力下CO2在颗粒直径为0．2～0．28mm的竖直烧结多孔介质圆管中的对流换热进行了实验研究．对热流密度、质量流量、入口压力及流动方向对对流换热规律的影响进行了研究，结果发现：准临界点附近CO2强烈的物性参数变化，尤其是定压比热的变化对对流换热的影响很大；对流换热系数随着流体局部平均温度的升高在准临界点附近达到最大；随着热流密度的增加，对流换热系数出现先增大后减小的趋势；质量流量越大，对流换热越强；流动方向对对流换热的影响不大；随着压力靠近临界压力，CO2的物性参数变化越来越剧烈，对流换热系数在准临界点附近也越来越大，但随着流体温度远离准临界点，压力对对流换热的影响逐渐减小．

Experimental Investigation on Convection Heat Transfer of Supercritical CO2 in Porous Media

Convection heat transfer of CO2 in a vertical sintered porous tube with particle diameters 0. 2-0. 28 mm at supercritical pressures was measured experimentally. The effects of heat flux, mass flow rate, inlet pressure, and flow directions on convection heat transfer were investigated. The results show that the strong variations of thermophysical properties significantly affect the convection heat transfer, especially the sharp variation of specific heat at constant pressure near pseudocritical temperature. Convection heat transfer coefficients have a maximum near the pseudocritical temperature with the increase of local fluid temperature. With the increase of heat flux, convection heat transfer coefficients increase to a maximum and then decrease continuously. Convection heat transfer is enhanced with the increase of mass flow rate, but the effect of flow directions on convection heat transfer is not significant. The convection heat transfer coefficients near the pseudocritical temperature increase with the inlet pressure decreasing to the critical pressure due to the increased variations of CO2 thermophysical properties. However, the effect of pressure on convection heat transfer is small at the fluid temperature far from the pseudocritical temperature.