三维变形管内降膜蒸发特性

Characteristics of falling film evaporation in three-dimensional deformed tube

为了提高降膜蒸发器的传热性能,将三维变形管用于MVR降膜蒸发器中,利用FLUENT软件探究了管内液膜的分布特点,分析了长、短轴比对三维变形管的传热性能的影响。结果表明:相比圆管,三维变形管内液膜的厚度会逐渐减小,流体速度场与温度场的协同性相对来说也更好;随着长、短轴比的增大,三维变形管内液膜的厚度会逐渐减小,液膜速度更为缓慢,而且进一步提高了速度场与温度场的协同性,还增强了液膜的扰动性,最终努塞尔数从0.249提高到0.276。将三维变形管应用于MVR蒸发器中,具有良好的换热效果,可节省换热材料。

In order to improve the heat transfer performance of the falling film evaporator,a three-dimensional deformed tube was used in the MVR falling film evaporator.The distribution characteristics of the liquid film in the tube were explored by FLUENT,and the influence of major-minor axis ratio on the heat transfer performance of the three-dimensional deformed tube was analyzed.The research results show that the thickness of the liquid film in the three-dimensional deformed tube will gradually decrease compared with the round tube,and the synergy between the fluid velocity field and the temperature field is relatively better;with the increase in the major-minor axis ratio,the thickness of the liquid film in the three-dimensional deformed tube will gradually decrease.The thickness of the liquid film will gradually decrease,the speed of the liquid film is slower,and the synergy between the velocity field and the temperature field is further improved,and the turbulence of the liquid film is enhanced.Finally,the Nusselt number is increased from 0.249 to 0.276.Applying three-dimensional deformed tube in MVR evaporator has good heat exchange effect and can save heat exchange material.