Abstract Light-weight and high-surface-area metal foams used in phase change heat transfer may suffer flow resistance from the porous matrix and cause boiling deterioration. To alleviate the flow resistance, metal foams with pore-density gradient was proposed and significant enhancement of pool boiling heat transfer was achieved for fluids such as water and refrigerants. In this work, a self-rewetting fluid (aqueous n-butanol solution) was used for boiling on copper foams with pore-density gradient structures formed by using several layers of foam covers. The experimental results show that, comparing with the one-layer foam, the bubble departure phenomenon was substantially attenuated due to the largely increase of pore density and hence the bubble moving resistance when using a two- or three-layer foam structure. However, the increase of pore density can enhance the pool boiling of water when the foam thicknesses are the same due to more active cavity sites being formed in a denser metal foam. While the enhancement for the solution is not obvious especially for that in the foam structure with higher pore density and heat transfer deterioration may emerge at high heat fluxes, the boiling heat transfer of the solution can generally be enhanced by using the 110 ppi foam and its gradient structures as compared to the polished surface. This provides new insight into enhancing the boiling heat transfer utilizing both the surface properties formed in the pore-density gradient structure and the unique interfacial properties of the self-rewetting fluids.

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自润湿流体在具有孔密度梯度结构的泡沫铜上沸腾传热的实验研究

摘要 用于相变传热的轻质高表面积泡沫金属可能会受到多孔基体的流动阻力并导致沸腾劣化。为了减轻流动阻力，提出了具有孔密度梯度的金属泡沫，并显着增强了水和制冷剂等流体的池沸腾传热。在这项工作中，自再润湿流体（正丁醇水溶液）用于沸腾铜泡沫，该泡沫铜具有由多层泡沫覆盖层形成的孔密度梯度结构。实验结果表明，与单层泡沫相比，当使用两层或三层泡沫结构时，由于孔密度大大增加，气泡移动阻力大大增加，气泡脱离现象大大减弱。然而，当泡沫厚度相同时，由于在更致密的金属泡沫中形成更多的活性空腔位点，孔隙密度的增加可以增强水池沸腾。虽然对溶液的增强作用不明显，尤其是在孔隙密度较高的泡沫结构中，在高热通量下可能出现传热劣化，但通常使用 110 ppi 泡沫和它的泡沫可以增强溶液的沸腾传热。与抛光表面相比，梯度结构。这为利用孔隙密度梯度结构中形成的表面特性和自润湿流体的独特界面特性增强沸腾传热提供了新的见解。