Abstract:

To explore the flow boiling heat transfer mechanism in the micro-rib array channel with different cross-sections, the deionized water is used as the working medium, the mass flow rate is 96-224 kg·m^-2·s^-1, and the effective heat flux density is 10-240 W·cm^-2. The instability of flow boiling in microchannel was also analyzed in the experiment. The experimental results showed that the dominant heat transfer mechanism is nucleate boiling in the low heat flux region, while it is convective heat transfer of a thin liquid film evaporation in the medium and high heat flux regions. With the increase of heat flux and outlet quality, the boiling heat transfer coefficient decreases, but the two-phase pressure drop increases. The secondary channel width between the micro pin fins has a great influence on the heat transfer and the two-phase pressure drop. The wider the secondary channel is, the easier the bubble is to break out, the better the heat transfer effect, and the greater the pressure drop. The existence of micro fin inhibits the reverse flow of bubbles, which reduces the flow boiling instability and delays the occurrence of critical heat flux. The flow boiling stability of the elliptical micro pin fins is the best, while the flow boiling stability of the circular micro pin fins is the worst.

Key words: microchannel, micro pin fins, boiling, heat transfer, pressure drop, instability

摘要：

为探究不同截面微肋阵通道内的流动沸腾换热机理，以去离子水为工质，在质量流速为96～224 kg·m^-2·s^-1，有效热通量为10～240 W·cm^-2的范围内，对圆形、菱形、椭圆形微肋阵通道内流动沸腾换热及压降特性进行了实验研究，同时对微通道内流动沸腾的不稳定性进行了分析。通过实验发现：在低热通量下，核态沸腾占主导地位，而在中高热通量下，薄膜蒸发对流换热为主要沸腾机制；沸腾传热系数随着热通量和出口干度的增加而减小，两相压降随着热通量和出口干度的增加而增大；微肋阵肋间形成的次级通道宽度对换热和两相压降有很大的影响，次级通道越宽，气泡越容易脱离，换热效果越好，压降越大；微肋的存在抑制了气泡的反向流动，减小了沸腾不稳定性，推迟了临界热通量的发生，椭圆形微肋阵通道的流动沸腾稳定性最好，而圆形微肋阵通道的流动沸腾稳定性最差。

关键词: 微通道, 微肋阵, 沸腾, 传热, 压降, 不稳定性