制冷系统中水平管降膜式蒸发器内部流动数值模拟

Numerical Simulation of Flow Inside Falling Film Evaporator with Horizontal Tubes Refrigeration System

采用FLUENT两相流VOF模型,对制冷系统中水平管降膜式蒸发器内部流场进行了数值模拟,研究了蒸发器内部蒸发管的不同布管方式对蒸发器内部流场的影响.计算结果表明:由于蒸发器入口制冷剂液体的滴落速度较小,而蒸发器内部气体流速相对较大且流场不均匀,因此导致液体垂直下落过程中受流场的影响较大;针对入口制冷剂流速不大的情况,预留水平的气流通道有助于改善蒸发器内部流场;较大宽度的气流通道有助于蒸发器内部流场的优化,该研究中满液式蒸发所占的比重较大,所以上部预留较小宽度,下部预留较大宽度有利于整体流场的优化.

Simulation on the inner flow field of a horizontal tubes of falling film evaporator in a refrigeration system was performed using two-phase flow model VOF in FLUENT, and the influence of different tube arrangements on the flow field was examined. The results show that the large vapor velocity and the non-uniform flow field inside the evaporator affect the distribution of liquid droplets significantly because of the small refrigerant liquid velocity. When the velocity of the refrigerant flowing into the evaporator is small, it seems more suitable to adopt the tube arrangement with horizontal vapor passages. It is likely that the tube arrangement with smaller space in the upper portion and larger space in the lower portion is more reasonable because of the large proportion of the vapor from flooded refrigerant inside the bottom of the evaporator.