水平管外降膜蒸发传热实验研究

HEAT TRANSFER OF FALLING-FILM EVAPORATION OUTSIDE HORIZONTAL TUBE

以水为工质,对直径为19 mm的铝黄铜管外降膜蒸发传热过程进行实验研究。实验通过测量管表面和饱和蒸气温度,计算得到平均和局部传热系数。由实验数据分析喷淋密度、蒸发温度、热流密度、管间距等参数对管外平均传热系数的影响,并与直径25.4 mm铝黄铜管降膜蒸发传热系数进行比较,讨论局部传热系数随周向角度的变化。结果表明,在实验范围内,管外平均传热系数随温度的升高而增大,随喷淋密度的增大先增大,后略微下降。小管径管的降膜蒸发传热系数大于大管径管的传热系数。

Taking water as working fluid, an experimental study was conducted to investigate the heat transfer characteristics of falling film evaporation outside horizontal aluminum brass tube with diameter 19 mm. The average and local heat transfer coefficients were calculated by measuring the surface temperature outside the tube and saturation steam temperature. The effect of spray density, evaporation temperature, heat flux and tube spacing etc. on average heat transfer coefficient outside the tube was analyzed according to experimental data, which was compared with the heat transfer coefficient of falling film evaporation outside horizontal aluminum brass tube with diameter 25.4 mm, and the change of local heat transfer coefficient with circumferential angle was discussed. The results show that the average heat transfer coefficient increases with evaporation temperature, and increases with the spray density firstly, then decreases slightly. In addition, the heat transfer coefficient of small tube is larger than that of large diameter tube.