亚临界压力下二氧化碳传热特性及临界热流密度预测模型研究

Study on heat transfer characteristics and critical heat flux prediction model of carbon dioxide under subcritical pressure

二氧化碳(CO_(2))布雷顿循环系统有着紧凑、高效、灵活的特点在第三代光热系统和第四代核电系统中具有良好的应用前景,而CO_(2)传热恶化现象影响着机组的安全运行。为研究竖直上升管内CO_(2)的传热恶化现象,在实验室建立了CO_(2)传热特性系统,对比了亚临界与超临界状态下CO_(2)传热特性,获得了热工参数对CO_(2)传热恶化的影响规律,并建立了CO_(2)临界热流密度预测关联,预测值与实验值吻合良好,误差在±30%以内。研究结果表明:亚临界压力下,CO_(2)发生传热恶化时壁温峰值更高;远离临界压力,增加质量流量均有利于抑制传热恶化的发生。

The carbon dioxide(CO_(2))Brayton cycle system is compact,efficient and flexible,and has a good application prospect in the third generation photothermal system and the fourth generation nuclear power system.The deterioration of CO_(2)heat transfer affects the safe operation of the unit.In order to study the deterioration of CO_(2)heat transfer in the vertical riser,a CO_(2)heat transfer characteristic system is established for experimental research,and the CO_(2)heat transfer characteristics under subcritical and supercritical conditions are compared.The influence of thermal parameters on the deterioration of CO_(2)heat transfer is obtained,and the prediction correlation of CO_(2)critical heat flux is established.The predicted value is in good agreement with the experimental value(error±30%).It is found that the peak value of wall temperature is higher when CO_(2)heat transfer deteriorates at subcritical pressure.Far away from the critical pressure and increasing the mass flow rate are conducive to restraining the occurrence of heat transfer deterioration.