Experimental investigation into flow boiling heat transfer and pressure drop in porous coated microchannels

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The flow boiling heat transfer and pressure drop in porous coated micro-channels were experimentally investigated at four porous coating particle sizes (i.e. 75 μm, 48 μm, 25 μm, and 13 μm), three mass flow rates (150 kg/m2s, 275 kg/m2s, and 400 kg/m2s), and a range of wall heat fluxes (0–1285 kW/m2). The comprehensive heat transfer (CHT) performance in the porous micro-channels was obtained and compared to the smooth micro-channel. The flow patterns in the micro-channels were visualized to analyze the flow boiling heat transfer characteristics near wall region. The results show that the heat transfer coefficient and critical heat flux were significantly enhanced and the pressure drop was increased in porous coating micro-channels as compared to the smooth micro-channel. As the size of sintered particle increases, the heat transfer coefficient on porous coating surface is increased, while the pressure drop in the micro-channel is increased. Due to its good liquid storage and re-wetting ability, the porous coating surface has a higher hydrophilicity, resulting in a higher critical heat flux in the porous micro-channel than the smooth channel. However, the CHT performance of the porous coating surface is not always better than the smooth surface. Among the studied porous-coating surfaces, the micro-channel with the averaged sintered particle size 13 μm has the best CHT, while the surface with 75 μm sintered particles has the highest critical heat flux and heat transfer coefficient. Compared to the smooth surface, the critical heat flux and heat transfer coefficient on the 75 μm porous coating surface were enhanced by 53.2 % and 114.5 %, respectively.