HD低温蒸发系统中填料蒸发器传质传热的分析

通过研究系统中填料蒸发器的蒸发传质传热过程以及两相流动特性，采用计算流体力学（computational fluid dynamics，CFD）中离散相与连续相耦合的方法来模拟规整填料内部通道的蒸发传质传热过程，实现了填料蒸发器中两相传质传热的过程以及液滴流动的可视化，为研究气液两相在规整填料内的流动提供了一种模拟方法。通过与实验结果的比较，最终选用RNG k-ε湍流模型来分析规整填料内部气液两相传质传热以及流动情况。数值模拟研究了规整填料板间距对填料内部气液两相传质传热以及液滴运动影响，发现随着板间距的增大，填料内部压力降逐渐降低，出口空气中水蒸气的含量不断减小，液滴蒸发速率降低，液滴进出口质量差减小，气相出口温度逐渐降低，蒸发传质传热效率降低。随着气速的增大，出口空气中水蒸气的含量不断减小，液滴蒸发速率增加，气相出口温度降低，气液两相传质传热效率降低。

Analysis of mass and heat transfer process of packing evaporator in HD low temperature evaporation system

In this paper, the evaporative mass and heat transfer process and the two-phase flow characteristics of the packing evaporator were studied. The method of coupling discrete and continuous phases in computational fluid dynamics (CFD) was used to simulate mass and heat transfer of the evaporative process in the internal channels of the structured packing. The two-phase mass and heat transfer process in the packing evaporator and visualization of the droplet flow were realized. A new simulation method for studying the flow of gas-liquid two-phase in structured packing was provided. By comparing with the experimental results, the turbulence model of RNG k-ε was determined, and the mass and heat transfer and flow of gas-liquid two-phase inside the structured packing were analyzed. By changing the plate spacing of structured packing, the effect of gas-liquid two-phase mass and heat transfer and droplet movement inside the packing was simulated and analyzed. It was found that with the increase of plate spacing, the pressure drop inside the packing was gradually reduced, the content of water vapor in the outlet air was continuously reduced, the evaporation rate of the droplets was reduced, the difference between the droplet inlet and outlet quality was reduced, and the temperature at the outlet of the gas phase decreased. The efficiency of evaporation of mass transfer and heat transfer decreased. As the gas velocity increases, the content of water vapor in the outlet air decreased, the evaporation rate of the droplet increased, and the temperature at the outlet of the gas phase decreased. The efficiency of evaporation of mass transfer and heat transfer in gas-liquid two-phase decreased.