水-水降膜蒸发器的模拟仿真和优化

Modeling and optimization of water-to-water falling film evaporator

由于具有换热性能突出、制冷剂充注量小等优点,降膜蒸发器已被广泛应用于海水淡化等行业。然而,由于存在液位控制和干斑效应等实际操作问题,在压缩式制冷系统中,降膜蒸发器的设计还需要进一步优化。为解决这个问题,构建了水-水降膜蒸发器的仿真模型。采用有限元方法,获得了沿管程的温度、热流变化情况。对于现有的四管程降膜蒸发器,在80℃蒸发沸腾和0.4kg·s^(-1)的喷淋量下,为获得最大的换热量,进行了详细的模拟计算,基于模型的计算结果,建议采用两管程降膜、两管程满液的液位控制方式。本模型同时给出了沿管程换热时的传热系数分布情况,提出了满液降膜分界线,为后续的降膜蒸发器结构设计优化提供了新思路。

With the advantages of excellent heat transfer performance and less refrigerant charge,falling film evaporator has been widely used in seawater desalination and other industries.However,due to the practical problems of liquid level control and dry patches interactions,the structure design of falling film evaporator should be optimized for refrigeration applications.To resolve those problems,a simulation model for water-to-water falling film evaporator was conducted in this paper.Through the finite volume method,the temperature distribution along the working tubes and the heat exchanger has been obtained.For an existed falling film evaporator with 4-pass working tubes under boiling temperature of 80℃ and spraying mass of 0.4kg·s^-1,it is suggested that 2-pass working tubes should be in falling film region in order to arrive the largest heating capacity.The distribution of heat transfer coefficient along the tube is also investigated.Finally,it is proposed that there exits an optimal boundary line between full liquid and falling film region.It may provide a new idea for optimal design of falling film evaporators.