带矩形重入腔的直肋微通道内流动沸腾换热特性

Flow Boiling Heat Transfer Characteristics in a Ribbed Micro-Channel withRectangular Reentrant Cavities

为揭示矩形重入腔强化直肋微通道内流动沸腾换热的机理,采用实验方法研究了带矩形重入腔的直肋微通道内的流动沸腾换热特性,获得了不同质量流率(200~500 kg·m^(-2)·s^(-1))和不同热流密度(0~78.16 W·cm^(-2))条件下微通道内的传热系数和压降,并与无矩形重入腔的直肋微通道内的流动换热性能进行了对比。结合流态可视化测量结果,对微通道内流动沸腾过程中的流态进行了分析。实验结果表明:相比无矩形重入腔的直肋微通道,带矩形重入腔的直肋微通道内表现出更好的传热特性,尤其是在高质量流率G>400 kg·m^(-2)·s^(-1)条件下,各流态下带矩形重入腔的直肋微通道的传热性能均有所提升,G=500 kg·m^(-2)·s^(-1)时提升了14.8%;重入腔结构对液相工质的毛细牵引效应,提高了直肋微通道在高热流密度下的换热能力和临界热流密度;带矩形重入腔的直肋微通道的临界热流密度比无重入腔直肋微通道提升了15.2%;在单相区,带矩形重入腔的直肋微通道内的压降损失略高于无重入腔直肋微通道;G=500 kg·m^(-2)·s^(-1)时,在两相区带矩形重入腔的直肋微通道内的压降损失相比无重入腔直肋微通道下降了约48%。

To reveal the mechanism of enhancement of flow boiling heat transfer in ribbed microchannel by rectangular reentrant cavities,this study experimentally investigates the flow boiling heat transfer characteristic in the ribbed microchannel with rectangular reentrant cavities.It involves measuring the heat transfer coefficient and pressure drop in the rectangular reentrant microchannel(RCRM)by considering a range of mass fluxes(G=200—500 kg·m^(-2)·s^(-1))and heat fluxes(q=0—78.16 W·cm^(-2)).The thermohydraulic performance in the RCRM is compared with that in the ribbed microchannel without rectangular reentrant cavities.Incorporating visual measurements,an analysis is made regarding the flow patterns during the flow boiling process in the microchannel.The experimental results demonstrate superior heat transfer characteristics in the RCRM compared to the ribbed microchannel without rectangular reentrant cavities.Particularly,under high mass flux conditions(G>400 kg·m^(-2)·s^(-1)),the heat transfer performance in the RCRM improves across all flow regimes.At G=500 kg·m^(-2)·s^(-1),the improvement amounts to 14.8%.The presence of reentrant cavities enhances capillary traction effects on the liquid phase,boosting heat transfer capability and critical heat flux in the ribbed microchannel at high heat flux levels.The critical heat flux in the RCRM surpasses that in the ribbed microchannel without reentrant cavities by 15.2%.While the pressure drop penalty in the RCRM slightly exceeds that in the ribbed microchannel without reentrant cavities in the single-phase flow region,the pressure drop penalty in the RCRM is lower in the two-phase region.Specifically,at G=500 kg·m^(-2)·s^(-1),the pressure drop penalty in the RCRM is reduced by 48%.