水平管降膜蒸发器传热系数空间分布

Distribution of heat transfer coefficient in horizontal-tube falling film evaporator

为了得到水平管降膜蒸发器传热系数,建立了水平管降膜蒸发传热实验台。通过对实验结果的归纳,分析了水平管降膜蒸发器总传热系数随顶排管喷淋密度、蒸发温度的变化规律,并给出了总传热系数在水平管降膜蒸发器内部空间的分布。结果表明,总传热系数随喷淋密度、蒸发温度的增大而增大。在空间分布上,传热系数沿管长方向受凝结过程的影响前5m先增大,后3m逐渐减小;在垂直方向由上向下逐渐减小。另外传热系数随管排数的增加而降低,并且当喷淋密度较小时,总传热系数下降的趋势更明显。

A set of experimental facilities was set up to measure the heat transfer coefficient of horizontaltube falling film evaporator. The effects of spray density on the topmost row P and evaporating temperature T on the overall heat transfer coefficient K are studied. The heat transfer coefficient distribution in the evaporator is presented. The results indicate that increase of spray density and evaporating temperature helps to enhance the value of K. Along the axial direction of the tube, K increases at the first 5 m and then decreases in the following 3 m, mainly caused by the condensation inside the tube. The K value decreases from the upper rows to the lower rows. In addition, increase of number of tube rows reduces the K value, especially at low spray density.