竖直微槽道内沸腾换热CHF实验研究

Experimental study of the critical heat flux on boiling heat transfer in vertical micro channel

对于沸腾换热,一个主要的约束条件就是临界热流密度(Critical Heat Flux,简称CHF)。这个约束条件对沸腾换热量有一个最高值的限制。文中对矩形微槽道中的流动沸腾临界热流密度进行了实验研究。实验数据是在不同尺寸(0.15mm;0.4mm;1mm)微槽道中,在较大范围的面积质量流速和不同进口过冷度下,以去离子水为工质得到的。实验过程中发现,达到CHF时,靠近出口壁面温度会突然升高,此时传热效率迅速下降。实验数据分析结果表明:CHF随质量流量的增加而增加;进口过冷度对CHF没有明显影响;CHF随着出口干度的增加而降低。

The boiling heat transfer is constrained by a crucially important factor- the critical heat flux （CHF） condition which sets the upper limit on the boiling heat transfer and is a transition from a very efficient heat transfer mechanism to a very inefficient one. Extensive experimentation was performed in micro channels to obtain the flow boiling critical heat flux in the paper. Experimental data were obtained in narrow gap ranging from diameters as low as 0.45ram to about 3ram over a wide range of mass fluxes and inlet sub cooling, for working fluids water. There was a characteristic sharp rise in wall temperature at the point of CHF. CHF generally refers to the outcome of events that cause a sudden, appreciable decrease in the heat transfer coefficient for a surface on which boiling is occurring. The results show that CHF increases monotonically with increasing G and inlet temperature has virtually no effect on CHF.