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微细金属丝在空气中自然对流换热

Keywords: 微细丝,自然对流,数值模拟,努谢尔特数

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Abstract:

为了研究微尺度圆柱表面的自然对流换热的机理,对水平放置在空气中的微细金属丝(外径为39.9~350.1μm)的自然对流换热进行了研究.数值模拟采用二维不可压模型,对浮升力项用Boussinesq假设进行处理,并使用SIMPLER算法进行求解,考虑了浮力、贴壁层厚度及边缘效应对微自然对流换热的影响.实验采用焦耳加热的方法获得了Nusselt数(Nu),并将数值模拟得到的结果分别与经典关联式、实验结果进行了比较,计算结果与实验结果吻合较好,验证了计算方法的可行性.研究结果表明:随着微细金属丝直径的减小,表面自然对流换热系数在增大,这可能是由于尺度的缩小,使得微细金属丝的边缘效应加强,贴壁层变薄,从而强化了换热;而Nu则先减小后增大,数值计算结果与理论计算值的差别也随着直径的减小而增大.

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