Pore-scale investigation on flow boiling heat transfer mechanisms in open-cell metal foam by LBM

摘要

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 (ε = 0.94). The convection heat transfer is depressed by bubble motion confinement inside the metal foam at low Rayleigh number.