对水平面上通孔铜金属泡沫中的空气自然对流进行了实验研究,研究了金属泡沫孔隙率和孔密度对总传热热阻的影响。研究结果表明:与光表面相比,金属多孔表面有效地强化了自然对流散热,使总热阻至少减小209/6左右。金属泡沫传热面积和自然对流流动阻力均受孔隙率和孔密度的影响。在较小的孔隙率(ε=0.9)下,对所研究的两个孔密度(400m^-1和1600m^-1),格拉晓夫数Gr存在一个转折点,当Gr小于该转折点值时,孔密度较大的金属泡沫自然对流热阻较小,而当Gr大于该转折点值时,孔密度较小的金属泡沫热阻较小。在较大孔隙率(ε=0.95)及实验所测的Gr范围内,孔密度较大的金属泡沫热阻一直较小。在所研究的两个典型孔密度(800m^-1和1600m^-1)下,孔隙率较小的金属泡沫热阻较小,但是在1600m^-1叫时,其热阻减小量要明显大于800m^-1时对应的减小量。
Experimental study of air natural convective heat transfer in horizontally-positioned copper metallic foams with open cells was conducted. The effects of porosity and pore density on the total thermal resistance of the foam sample were quantified. It is found that the porous sur-face can enhance the natural convection and reduce the thermal resistance by about 20% in comparison with a smooth surface. The surface area density and mass flow rate in natural convection are affected by porosity and pore density simultaneously. When the porosity is relative small (ε= 0. 9), there exits a critical value of the Gr number (turning point) for two pore densities (400 m^-1 and 1 600 m^-1 ). When the Gr number is less than this critical value, the foam with a higher pore density has the lower total thermal resistance, whereas when the Gr number exceeds the turning point value, the opposite holds. If the porosity is increased to ε = 0. 95, the foam with a higher pore density has the lower thermal resistance in the whole experimental range. For the two pore densities studied (800 m^-1and 1 600 m^-1 ), the foam with a lower porosity (from 0. 95 to 0. 9) has the lower thermal resistance and the decrease is more obvious for the case of 1 600 m^-1 than the case of 800 m^-1.