对流换热条件下微钢管壁面轴向导热的实验研究

Experimental study on axial wall heat conduction for steel microtube under forced convection

以蒸馏水和氮气为工质,流过内径为168μm外径为406μm的不锈钢微管.通过直接通电法对微钢管进行加热,并采用红外成像仪及专用放大镜头来测量微钢管外壁的温度场,获得了在雷诺数恒定、不同加热功率下微钢管外壁面温度场分布.经过图像处理及修正后,得到较为精确的沿壁面的温度分布,进而求得微管沿壁面的导热量.实验结果表明,对于液体流动的微管对流换热,计算管壁的表观换热系数时可以忽略管壁轴向导热的影响.而对于微钢管的气体流动换热,在自然对流边界条件下,管壁轴向导热量与总加热量之比达到2.1%.

The wall temperature and the axial wall heat conduction for steel microtube under forced convection are experimentally studied, when distilled water and nitrogen gas, as the working fluids, flow through a stainless steel microtube with inner diameter 168μm and outer diameter 406μm. By using direct electrical heating method, the wall temperature field photos of microtube under constant Reynolds number＇s flow and different heating power are acquired by employing an infrared themoviewer and specially magnifying lens. Manipulating and amending the field photos, the exact temperature distribution along wall of the microtube is gained and the quantity of the axial conductive heat is also obtained. The experimental results show that the ratio of the quantity of the axial conductive heat to that of whole heating is about 2.1%.