波动加热下微通道流动沸腾的格子Boltzmann模拟

Micro-channel flow boiling by Lattice Boltzmann model under fluctuating heating

中文关键词: 微通道  流动沸腾  薄液膜  波动加热

英文关键词: micro-channel  flow boiling  thin liquid film  fluctuating heating

中文摘要:

      为研究通道内的流型演变, 采用单组分多相格子玻尔兹曼模型模拟波动加热下二维微通道内的流动 沸腾。 通过速度分析解与半经验公式分别验证模型流场和温度场的准确性。 探究雷诺数(4.5 ≤Re ≤9 .0) 和 温度分布(0.01 ≤A≤0.03) 对传热和流型的影响, 分析薄液膜和温度梯度的作用机制, 揭示微通道流动沸腾 的传热机理。 模拟结果表明通道内流型将从泡状流、 塞状流, 变成拉长气泡流、 环状流。 雷诺数减小时, 气液 相变速率加快、 薄液膜厚度减小, 进而增强换热。 随着雷诺数减小, 加热壁面上热流密度的峰值点向上游转 移。 马兰戈尼对流( Marangoni convection) 的出现导致薄液膜厚度增加, 从而换热效果随着温度分布波动性 的增大而受到削弱。

英文摘要:

      In order to investigate the flow pattern evolution in micro-channel, a single component multi-phase Lattice Boltzmann model was used to simulate the flow boiling in a two-dimensional micro-channel under fluctuating heating. Firstly, the accuracy of flow and temperature field was verified by the analytical solution of velocity and semi-empirical formula respectively. The influences of Reynolds number (4.5 ≤ Re ≤ 9.0) and temperature distribution (0.01 ≤ A ≤ 0.03) on heat transfer and flow pattern were investigated, and the affecting mechanism of thin liquid film and temperature gradient was analyzed in order to reveal the heat transfer mechanism of micro-channel flow boiling. The simulating results indicate that flow patterns in the micro-channel transfer from bubbly flow /slug flow to elongated bubble flow and annular flow. The thin liquid film shows similar tendency with Reynolds number, while the rate of phase change is opposite. It is found the peak heat flux on the heating wall shifts to the upstream with the decreasing Re . Due to the Marangoni convection, the thin liquid film thickness increases and the heat transfer effect is weakened as the fluctuation of temperature distribution increases