Abstract This paper presents the findings of a numerical study on the flow boiling in a micro-channel heat sink. The Navier-Stokes equations, energy equation, and the continuity equation are solved in a finite-volume framework using the front-tracking method. The numerical method is validated by comparison with the experimental results for a slug bubble growth, and vertical flow boiling. The numerical method is then used to study the effect of changing the inflow mass-velocity on the heat transfer coefficient, bubble size distribution, and the bubble nucleation frequency for a constant heat flux. The mean heat transfer coefficient of all the cases is found to be nearly twice that of the single-phase heat transfer coefficient. The bubble nucleation frequency is found to increase monotonically with the inflow mass-velocity. The bubble size distribution along the channel is found to become flatter as the mass-velocity is increased. We identify three distinct phases of the bubble evolution, namely the initial rapid growth phase, the boiling dominant phase, and finally the condensation dominant phase. Subsequently, the numerical method is used to study the effect of having a hot-spot near the bubble nucleation site on the heat transfer characteristics. It is found that the bubble nucleation frequency increases and the bubbles’ maximum volume decreases as the intensity of the hot-spot is increased for a fixed inlet flow rate. It is also observed that the average heat transfer coefficient does not change significantly with changing the intensity of the hot-spot, and that the bubble size distribution along the channel becomes flatter as the intensity of the hot-spot is increased.

中文翻译：

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微通道中流动沸腾的模拟：入口流速和热点的影响

摘要 本文介绍了微通道散热器中流动沸腾的数值研究结果。Navier-Stokes 方程、能量方程和连续性方程在有限体积框架中使用前向追踪法求解。通过与段塞气泡生长和垂直流动沸腾的实验结果进行比较，验证了该数值方法。然后使用数值方法研究改变流入质量速度对传热系数、气泡尺寸分布和恒定热通量的气泡成核频率的影响。发现所有情况的平均传热系数几乎是单相传热系数的两倍。发现气泡成核频率随着流入质量速度单调增加。随着质量速度的增加，发现沿通道的气泡尺寸分布变得更平坦。我们确定了气泡演化的三个不同阶段，即初始快速增长阶段、沸腾主导阶段和最终冷凝主导阶段。随后，利用数值方法研究了气泡形核点附近的热点对传热特性的影响。结果表明，对于固定的入口流速，随着热点强度的增加，气泡成核频率增加，气泡的最大体积减小。还观察到平均传热系数不会随着热点强度的变化而显着变化，