泡沫铜孔隙率和孔密度对流动与沸腾换热特性的影响

以去离子水作为工质,设计并搭建了以泡沫铜为研究对象的单相和两相换热实验系统。对于单相流动换热,当Re数较小时,孔隙率80%、孔密度90PPI的泡沫铜样品换热性能最好;当Re数较大时,孔隙率80%、孔密度45PPI的泡沫铜样品换热性能最好。泡沫铜最大换热系数为空通道的6倍,但同时需付出更大的泵功损耗为代价。对于两相流沸腾换热,低孔隙率样品70%~80%能有效地降低壁面过热度和强化沸腾换热性能。孔隙率对沸腾换热性能起决定性作用,孔隙率越低,沸腾换热系数越大;孔密度对沸腾换热性能起次要作用。90PPI泡沫铜样品,因其成核址密度高和毛细力较大,有助于提升泡沫铜的沸腾换热性能。

Influence of porosity and pore density on heat transfer performance for copper foam heat sink

Using the deionized-water as the working fluid, both single-phase and two-phase heat dissipation systems for copper foams were designed. For low Re number, the copper foam sample with 80% porosity and 90PPI presented the maximum heat transfer coefficient, while for large Re number, the copper foam sample with 80% porosity and 45PPI outweighed. The copper foam sample could show six times larger than the bare channel in heat transfer coefficient, but consume more pump power. For the two-phase heat transfer, experiments found that low porosity samples (70%~80%) could effectively reduce the wall superheat and enhance boiling heat transfer. Porosity plays a more important role than pore density. Larger pore density would be helpful to provide more nucleation site density and larger capillary force. The samples with 90PPI have better heat transfer performance in flow boiling process.