均匀电场对池沸腾换热的影响分析

对均匀高压电场作用下平板池沸腾换热的强化效果进行了试验研究,发现在较低过热度的范围内电场对换热有明显的强化效果.场强越高,相同过热度对应的换热系数越高.在相同的场强下,强化系数随着热流密度的增加而减少.结合试验结果对电场强化沸腾换热的机制进行了分析.在热流密度较小的范围内,对流换热占主导地位,电场强化对流换热使壁面过热度大大下降,导致相应过热度下汽泡的平衡半径提高,因此,抑制了核态沸腾.随着热流密度的提高,汽泡的产生和运动成为影响换热的主要因素,此时过热度的变化不是很大,在相同的过热度下,电场可以减小汽泡的临界半径,使汽泡增多.在汽泡准备区,电场会影响汽泡的核化;在汽泡成长区,电场会影响汽泡的长大、变形和脱离;在非沸腾区,电场会影响单相流体的自然对流换热.

Analysis on factors influencing electrohydrodynamics-enhanced pool boiling heat transfer

Experimental research on effects of a uniform electric field on plate pool boiling heat transfer enhancement was carried out.It's found that in the scope of lower overheat,boiling heat transfer is significantly enhanced under electric field.The higher the electric-field intensity is,the higher the coefficient of heat transfer is at the same overheat degree.With the same electric-field intensity,enhancement coefficient declines with the increase of heat flux.In the light of the experiment results,effects of electric field on pool boiling heat transfer were discussed theoretically.In the lower heat flux range,liquid convection heat transfer is dominated.Electrohydrodynamics enhancement convection heat transfer can reduce the wall superheat greatly,so the bubble equilibrium radius increases at corresponding wall superheat and nuclear boiling is delayed.While with the increase of heat flux,the generation and movement of bubbles become the main factor influencing heat transfer.At this moment,the overheat is of little variation.Under the same overheat,electric field may reduce the bubble equilibrium radius,and increase the amount of bubbles.In bubble preparing area,electric field influences the nucleation of bubbles;in bubble growing area,the growing,distortion and separation of bubbles;and in non-boiling area,the natural convection heat transfer of the single phase fluid.