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建立了测量微细丝表面空气自然对流换热系数3ω法模型。利用3ω法测量了直径为10.6μm水平和垂直方向铂丝表面室温下的空气换热系数。水平和垂直铂丝产生的三次谐波比较接近,结果说明,微尺度下空气的自然对流换热以导热为主,自然对流作用可以忽略。基于3ω线法原理,引入形状因子并提出了微尺度下铂丝表面换热系数的理论计算模型。空气自然对流换热系数远大于大尺度下的值,主要原因是铂丝的面积体积比值大。
The 3ω method for measuring the natural convection heat transfer coefficient was established. The 3ω method was used to measure the air heat transfer coefficient at room temperature of platinum wire with horizontal and vertical diameters of 10.6μm. The third harmonics of horizontal and vertical platinum wires are relatively close. The results show that the natural convection heat transfer of air is dominated by micro-scale and the natural convection can be neglected. Based on the principle of 3ω line method, the shape factor was introduced and a theoretical calculation model of the surface heat transfer coefficient of platinum wire was proposed. Air natural convection heat transfer coefficient is much larger than the value of large-scale, the main reason is the large area-volume ratio of platinum wire.