水平管降膜蒸发器壳程流场和温度场数值研究

Numerical research on flow field and temperature field in shell side of horizontal-tube falling-film evaporator

为了探究水平管降膜蒸发器壳程区域流场与温度场的分布特性,基于三维分布参数模型开发蒸发器整体数值模拟程序,获得蒸发器内热力参数分布,并分析壳程区域流场和温度场以及其他各主要参数的变化。研究结果表明:采用前密后疏的喷头布置方式可以有效改善海水的流场,使1管程下部海水分布更加均匀;在文中结构下海水流经2管程后已经达到饱和状态;1管程和2管程蒸汽进口区总传热系数最大;在1管程进口的下半区,海水盐度最大值已达到56 g/kg;为避免结垢发生,应当控制海水浓缩比不超过2.5,最高温度低于70℃。

In order to study distribution characteristics of flow field and temperature field in the shell side of the horizontal-tube falling-film evaporator,the self-built numerical software for the whole evaporator was developed based on a three-dimensional distributed parameter model.The distributions of thermal parameters were obtained.The variations of flow field,temperature field and other important parameters were also analyzed in detail.The results show that it is possible to achieve uniform liquid distribution at the bottom row of the first-tube-pass bundle by selecting uneven placement of the spray nozzles.The temperature of seawater reaches the saturation temperature in the present geometrical dimensions and working conditions after it has escaped from second-tube-pass bundle.The maximum of overall heat transfer coefficient tends to locate at the inlet positions of the bundle.Furthermore,the maximum salinity of seawater is 56 g/kg,which locates at the bottom row of the first-tube-pass bundle.The concentration factor of seawater should be no more than 2.5 and the temperature is below 70 ℃ to prevent the scale formation on the heat transfer surfaces.