Study On Gas-liquid Two Phase Flow And Mass Transfer In The Cap Of Combined Trapezoid Spray Tray

The trapezoid tridimensional structure caps are the key parts of Combined Trapezoid Spary Tray (CTST), which enlarge the area of gas-liquid mass transfer. The two phase flow inside the cap effects on mass transffer remarkably. Study on the gas-liquid two phase flow and the mass transfer in the cap is the basis of the cap structure optimization and the mass transfer efficiency prediction.The effect of the cap with different inclination angle (α)of spray plate and the dip length of the tray (Wb)on flowing characteristic was investigated in a experiment column with 600 mm diameter. The results showed that the optimized cap strcture was thatα=8o and Wb=10 mm. The concentration distribution, the mass transfer distribution inside the cap, and the mass transfer efficiency in lifting region and spraying region were obtained by mass transfer experiment.The different model was put forward respectively to simulate gas-liquid two phase flow on different regions inside the cap. In lifting region, the forces by surface tension and the gas-liquid interaction were considered into VOF model, so that the model can well trace two phase interface. The gas-liquid two phase flow in spraying region was simulated with particle trajectory model, and the effect of drag force, gravity, virtual-mass force was considered in the model. At the same time, the droplet turbulence diffusion was calculated with random trajectory model. In lifting region, the liquid film flow characteristic and its variability with operating conditions and the cap structure were analysed mostly. In spraying region, the droplets size distribution was mainly concerned, and the results showed that the size distribution has a good agreement with R-R distribution function. The distribution parameter and the feature size in the distribution function about the droplet size were obtained by simulation.The mass transfer models were established respectively for lifting region and spraying region. In the model of lifting region, gas phase that entrained in droplets was regarded as effective fluid and liquid phase as film. In spraying region the complex mass transfer process was treated with feature droplet's mass transfer. After that, the concentration distribution and mass transfer efficiency inside the cap were calculated with the model. It showed that the calculated results of the models have a good agreement with the experiment data in tendency.