Development of heat dissipation system for electronic devices using flow boiling heat transfer

本研究的目的在于获得如何利用流动沸腾热传递来开发创新的散热系统的基础知识，以用于高热负荷的电子设备。本研究是在实际应用中遇到的工作流路狭窄、流量小的情况下进行的，以水作为工作流体，以满足高源功率和环境问题的要求。在研究中，压降，传热系数，和最大热通量，这是重要的设计因素进行了实验研究。一个是提出的压降和传热系数的实验数据在我们的实验室以前获得的细圆管方面的关联式。另一个是对窄缝矩形通道（1.0 mm和1.5 mm，宽20 mm，长80 mm，加热长度40 mm）内的换热和压降进行了实验研究，得到了换热和压降随时间的变化规律，并与实验结果进行了比较 关于我们 在考虑汽相流动影响的基础上，建立了一个适用于常规尺寸细圆管的沸腾换热系数关联式，并对细圆管的沸腾换热系数进行了预测。在第二项研究中，进行了测量压降、传热系数和最大热通量的实验，质量通量为16至76 kg/m^2s。实验的主要发现如下。建议间隙尺寸小于1.0 mm，因为最大压降高达500 Pa，然后压降远低于圆管。然而，压降的波动比管内的大得多。在热流密度与壁面粗糙度的关系上，管与通道的换热系数基本相同，但矩形通道的换热系数与局部干度的关系与圆管不同。圆管的关联式大大高估了最大热流密度，而矩形通道的关联式给出了更好的预测。通道截面上的液相分布对换热系数和最大热流密度有重要影响。少

The purpose of this study is to obtain fundamental knowledge how to make use of flow boiling heat transfer to develop innovated heat dissipation system for high heat loaded electronic devices. This study was performed under conditions of narrow working flow path and low flow rate which are encountered in practical cases and used water as a working fluid to meet requirements of high source power and environmental issues. In the study pressure drop, heat transfer coefficient, and maximum heat flux which are important design factors are experimentally examined.Two types of studies were performed. One was to propose correlations for pressure drop and heat transfer coefficient in terms of experimental data in a fine circular tube previously obtained in our laboratory. The other was an experimental investigation about heat transfer and pressure drop in narrow rectangular channels, 1.0 and 1.5 mm gap and 20 mm width and 80 mm length (40 mm heated length).From the first study, the pressure dro … More p and boiling heat transfer coefficient in a fine circular tube could be predicted by correlations developed in a normal size tube by taking additional account of large effect of vapor flow. In the second study, experiments were performed to measure pressure drop, heat transfer coefficient, and maximum heat flux at mass flux of 16 to 76 kg/m^2s. The major findings of the experiments are as follows. Smaller gap size, than 1.0 mm was suggested since the maximum pressure drop as much as 500 Pa and then the pressure drop is much lower than the circular tube. However, the fluctuation of the pressure drop is much larger than that in the tube. The heat transfer coefficients are similar between the tube and the channel in the relationship between heat flux and wall superheat, but the relationship in the rectangular channel between the coefficient and local quality is different form that in the circular tube. The correlation developed for circular tubes highly overpredicted the maximum heat flux and the correlation developed by using data of rectangular channels give much better prediction. The liquid phase distribution in the cross section of the channel significantly affects the heat transfer coefficient and maximum heat flux. Less