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对水力直径为0.715 mm的方孔及0.86 mm的圆孔多孔扁管内液相流体对流换热特性进行了实验研究,Re数范围为50~2300,入口温度为5~45℃,加热热流密度为3~9 kW/m~2。实验结果表明,对流换热在Re=2000附近发生过渡;入口段效应明显;在Re数较小时,Nu数明显小于充分发展流动的预测值;热流密度越大、入口温度越高,对流换热强度越低。两种管型扁管的实验值变化趋势一致,但圆孔Nu数高于方孔。基于尺度效应的影响及经典层流换热理论对实验结果进行了修正。
The convective heat transfer characteristics of liquid flow in a square hole with a diameter of 0.715 mm and a circular hole with a diameter of 0.86 mm were studied. The Reynolds number ranges from 50 to 2300, the inlet temperature is from 5 to 45 ℃, and the heating flux density is 3 ~ 9 kW / m ~ 2. The experimental results show that the convective heat transfer takes place near Re = 2000, and the entrance section effect is obvious. When the Re number is small, the Nu number is obviously smaller than that of the fully developed flow. The larger the heat flux, the higher the inlet temperature, the convective heat transfer The lower the intensity. The experimental results of the two tube flat tubes showed the same trend, but the number of round holes Nu was higher than the square holes. Based on the effect of scale effect and the classical theory of laminar heat transfer, experimental results were revised.