同心环形管强迫流动与传热实验研究

在高温高压沸腾二相流实验系统上,实验研究了窄缝为2.05 mm的同心环形管,在不同加热条件下水的流动阻力与传热特性。2种加热方式为单内管或单外管电加热,通过处理实验测量的管壁温度获得传热系数。得到了以下结果:层流向紊流转变的临界雷诺数为2 300;环形管内的流动阻力系数小于普通圆管,外管加热时的摩擦系数小于非加热条件时的数值;窄缝环形管内换热有一定强化,高于相同条件下的圆管内紊流换热;内外管同时加热时,相比仅外管加热而言,外管的换热得到了抑制;得到了环形管内流动摩擦阻力系数与传热系数的实验关联式。

Experimental study on forced convective flow and heat transfer in a concentric annular tube

Using the high-temperature and high-pressure boiling two-phase flow test loop,the water flow resistance and heat transfer characteristics were experimentally investigated under the different heat conditions in a concentric annular tube with 2.5 mm gap size.The two heating types were individual inside-tube wall heating or individual outer-tube wall heating separately.The heat transfer coefficients were calculated with the measured tube wall temperature.The results show that the critical Reynolds number is 2 300 at the transition from laminar to turbulence flow.The flow friction coefficient is less than that in circular tube,and it becomes smaller under the condition of the outer-tube wall heating than that under the condition of non-tube wall heating.The heat transfer is enhanced in the test tube and becomes greater than that in the circular tube under the same condition.The heat transfer at the outer-tube wall is suppressed under the dual-tube walls heating comparing to that under the outer-tube wall heating.The correlations of calculating the flow friction coefficient and heat transfer coefficient under the different heating conditions were proposed based on the experimental data.