分离式热管蒸发段工质流动不稳定性的试验研究

在试验台架上进行了可视化试验和模型试验,对分离式热管蒸发段工质流动的规律和工质流动的不稳定性进行了试验研究.可视化试验结果表明,对于小倾角布置的蒸发段,随着热流密度的增加,流型依次是泡状流、弹状流、波动泡沫状流;分离式热管蒸发段工质流动出现了流型转化型和密度波型两种不稳定性流动.通过模型试验确定了压力、质量流速、入口过冷度、热流密度、出口节流阻力等因素对不稳定性的影响,得出了流型转化型和密度波型不稳定性的界限.利用一维均相模型给出了计算不稳定性起始条件的无因次方程.

Experimental Investigation on the Flow Instability in Evaporator of Separated Type Heat Pipes

An experimental investigation on the working fluid flow characteristics and the flow instability in the evaporator of Separated Type Heat Pipe(STHP)was presented.Flow patterns were observed and analyzed by visualization experiment.It was found that the bubbly flow,slug flow,and wavy foam flow occurred orderly in the evaporator with a small inclination angle when the heat flux increased.Two types of flow instabilities occurred,i.e.,the flow pattern transformation instability and the density wave instability.The effects of pressure,mass velocity,inlet subcooling,heat flux,and exit throttle on the flow instability were determined in the modeling experiment.The thresholds of the flow pattern transformation instability and that of the density wave instability were obtained.Non-dimensional correlations for predicting the flow instability in STHP were given by means of one-dimension single-fluid model.The results may be used for the engineering design of largescale heat exchangers of STHP with a small inclination angle in evaporator.