Abstract The flow boiling heat transfer mechanisms inside open-cell metal foam are investigated by Lattice Boltzmann method. The 2D reconstructed model of open-cell metal foam is proposed based on the scan image and the thermal responses of metal foam are considered. The effects of Reynolds number, porosity and Rayleigh number on bubble motion and heat transfer performance are revealed. The results show that the dominant force shifts from buoyant force to shear force with increasing Re number, thus the “sweeping off” effect is further intensified by the accelerating sliding bubbles. The superposition of enhanced boiling heat transfer and thermal conduction are responsible for the wall superheat reduction at the central heating areas. Bubble departure diameter decreases with increasing Reynolds number due to the high bubble sliding velocity. The failure of “sweeping off” effect results in the formation of vapor film which worsens the flow boiling heat transfer performance of metal foam with low porosity (e = 0.94). The convection heat transfer is depressed by bubble motion confinement inside the metal foam at low Rayleigh number.

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LBM对开孔泡沫金属中流动沸腾传热机理的孔尺度研究

摘要 采用格子Boltzmann方法研究了开孔泡沫金属内部流动沸腾传热机理。基于扫描图像提出了开孔泡沫金属的二维重建模型，并考虑了泡沫金属的热响应。揭示了雷诺数、孔隙率和瑞利数对气泡运动和传热性能的影响。结果表明，随着Re数的增加，主导力从浮力转变为剪切力，加速滑动气泡进一步加强了“扫除”效应。增强沸腾传热和热传导的叠加是集中供热区壁面过热减少的原因。由于高气泡滑动速度，气泡离开直径随着雷诺数的增加而减小。“扫除”效应的失败导致蒸汽膜的形成，这使低孔隙率（e = 0.94）的金属泡沫的流动沸腾传热性能变差。在低瑞利数下，泡沫金属内部的气泡运动限制抑制了对流热传递。