CO_2水平管外池沸腾换热的实验研究

对自然工质CO2在不同沸腾压力下的光管、机械加工表面强化管(Turbo-EHP)水平单管管外电加热池沸腾进行了实验研究。从核态沸腾的角度分析了光管、强化管管外沸腾换热系数随热流密度、沸腾压力的变化规律,通过对热流密度在10~50k W/m2、蒸发压力在2~4 MPa范围内的换热数据分析拟合得出光管时CO2在该范围下的换热关联式,拟合关联式的计算值和实验值的误差在±8.73%以内。新的拟合关联式的计算值与已有关联式的预测值的偏差在±15%之内。在热流密度范围内强化管的强化倍率在1.50~1.72之间。研究结果对进一步深入研究CO2池沸腾换热及蒸发器的设计具有指导意义。

Experimental Research on CO2 Pool Boiling Heat Transfer outside Horizontal Tube

The pool boiling heat transfer of natural refrigerant CO2 outside single horizontal tube is investigated experimentally under different boiling pressure. Smooth tube and enhanced tube(Turbo-EHP) are taken as the single horizontal tube with electrical heating. The relationship of boiling heat transfer coefficient along with the heat flux and the boiling pressure is analyzed, and the heat transfer correlation of smooth tube under heat flux of 10~50 kW/m2 and boiling pressure of 2~4 MPa is obtained. The maximum error is 8.73% when the experimental values are compared with fitting formula. Compared with other existing heat transfer correlations, the new fitting formula of CO2 is matching very well, and the maximum error is 15%. In the range of experimental heat flux and boiling pressure, the overall heat transfer coefficients of the enhanced tube are higher than that of the smooth tube, and its enhancement factors varies from 1.50 to 1.72. This paper makes useful exploration of CO2 pool boiling heat transfer and will benefit the design of evaporator.