Experimental Studies And CFD Simulations Of Hydrodynamics And Heat-Mass Transfer In New Sieve Baffle Tray Column

The tray and packed columns are the main devices in the course of gas/liquid mass transfer operation. The tray column is advantageous in processing high viscosity fluid, high pressure operation etc. But in the case of large liquid/gas ratio, such as cooling, humidification, absorption, high pressure distillation, due to the large liquid flux, the use of tray column is not suitable because the downcomer area will be increased drastically, leading to the reducing of mass transfer area, tray efficiency and column processing capacity. In overcoming these shortcomings of tray column, new sieve baffle tray column is invented by New Tianjin Technology & Development Co. The experimental equipment is designed by the author for investigating the hydrodynamics and mass transfer characteristics of the new sieve baffle tray. The experimental result is as follows: The maximum entrainment is only 0.06% and much less than the allowable 10%(for the traditional tray), which means that the operational flexibility of the new tray is large. Under the same operation condition, its pressure drop is lower than the traditional tray, even adding baffle in column, which means that the new tray has the advantage of operating at high liquid/gas ratio. Experimental work was done to obtain the mass transfer efficiency by the humidification of air. The Experimental result shows that the efficiency of mass transfer becomes lower when the velocity of empty column is increasing and when the liquid load is increasing. Increasing the height of weir, the efficiency of mass transfer becomes low down. When adding the baffles, the mass transfer efficiency becomes higher. The efficiency of mass transfer in 60% fraction of hole is higher than in 40% fraction of hole. When gas/liquid ratio is lower 10, the efficiency of mass transfer in new sieve baffle tray is higher than in traditional tray.A three-dimensional quasi-single phase computational fluid dynamics (CFD) program with the RNG- turbulence model is presented for evaluating the performance of the new sieve baffle tray. The special feature of this model is taking into account the influence of heat transfer during the mass transfer and the influence of mass transfer in computing the flow field. The model built in this work considers the coupling of mass transfer and heat transfer adequately.The finite volume method and the FLUENT 6.0 software are used to compute the fluid flow, mass and heat transfer processes. The comparison of the experimental data and computing result shows that our model is correct.By analyzing the stability of parallel flow, where the liquid flow is two dimensional, and the mass transfer is one dimensional, the relationship of eddy diffusion is obtained. The computing result for eddy diffusivity is somewhat lower than the experimental, but the theoretical finding of eddy diffusion is being tried firstly. It is of significance in both theoretical research and practical work.