Abstract:

As aircraft and spacecraft continues to evolve toward higher performance, the compactness and heat dissipation efficiency of thermal control system need to be improved. Metal foam has great potential in the application of aviation and aerospace thermal control due to its large specific area and high thermal conductivity. The pool boiling heat transfer characteristics on hydrophilic and hydrophobic metal foam covers were studied experimentally, and compared with those of uncoated metal foams. The effect of hydrophilicity and hydrophobicity on the pool boiling heat transfer performance of metal foams with different pore densities and porosities is analyzed. The test samples are copper foams with pore densities of 5 PPI, 20 PPI and 40 PPI, and porosities of 85% and 95%. The results show that hydrophobic modification can reduce the incipient boiling superheated degree by 20%—30%, while hydrophilic modification has no significant effect on the onset of nucleate boiling. Hydrophobic metal foams and hydrophilic metal foams have the optimum pool boiling heat transfer performance under low heat flux (q<4×10⁵ W/m²) and high heat flux (q≥4×10⁵ W/m²) conditions, respectively. Surface modification has a more significant effect on pool boiling heat transfer enhancement for low porosity metal foams, and hydrophilic modification is more effective than hydrophobic modification in improving thermal performance.

Key words: metal foam, hydrophilic, hydrophobic, pool boiling, heat transfer

摘要：

随着航空飞机和航天器不断向高性能发展，热控制系统的紧凑性和散热效率亟需提高。泡沫金属具有超大的比表面积和高热导率，在航空航天热控制领域具有良好的应用前景。对亲水性和疏水改性泡沫金属内的池沸腾换热特性进行了试验研究，并与未改性泡沫金属进行对比，得出了亲疏水性对不同孔密度和孔隙率泡沫金属池沸腾换热特性的影响规律。测试样件为泡沫铜，孔密度为5、20和40 PPI，孔隙率为85%和95%。结果表明，疏水改性可使泡沫金属内池沸腾的起始过热度降低20%～30%；疏水改性泡沫金属和亲水改性泡沫金属分别在低热通量（q<4×10⁵ W/m²）和高热通量（q≥4×10⁵ W/m²）条件下具有最佳的沸腾换热性能；表面改性对于低孔隙率泡沫金属内池沸腾强化换热效果更加显著，且亲水改性的强化效果优于疏水改性。

关键词: 泡沫金属, 亲水性, 疏水性, 池沸腾, 传热