CFD And Experimentalstudy On CTST-MD Tray

The spray cover of Combined Trapezoid Spray Tray (CTST) and multiple downcomerare high performance column internals, each of them has their own characteristics. Thecombination tray would be obtained by composition of CTST cover and hang downcomer.The studies of hydrodynamics performance and CFD simulation would be providedexperience and theoretical bases for the tray optimization and the structural improvement.The hydrodynamic behavior of the CTST-MD Tray was studied with air-water systemin the cold model tray with inside diameter of570mm. The variables of clear liquid heighton the tray, tray pressure drop, clear liquid height of downcomer and discharge coefficientwere obtained. It was showed that the tray pressure drop of the CTST-MD Tray is lowerthan the CTST with segment downcomer and Sieve Tray with hang downcomer. And theclear liquid height of downcomer of CTST-MD Tray is lower than Valve-MD Tray underthe condition of high liquid load. The clear liquid height of hang downcomer is lower thansegmental downcomer under the same operating condition. The orifice discharge coefficientwas mainly determined by hydraulic radius. The orifice discharge coefficient of CTST-MDwas obtained in different aperture ratio.A computational fluid dynamics model for describing the hydrodynamics ofCTST-MD Tray. It was based on RNG k-ε turbulence model, and FVM (finite volumemethod) was used to simulate the gas-liquid flow field. The result of CFD showed that nearthe trapezoid side plate the vortexes exist and decrease along with the liquid height untildisappear. The liquid velocity of CTST-MD is larger than CTST with segmentaldowncomer. However, the liquid velocity of CTST-MD is less than CTST near the base gapof plate. It implied that the lifting capacity of CTST-MD is bad. It would reduce theefficiency of mass transfer. The CFD results also showed that the gas hold-up of hangdowncomer is small and the liquid in hang downcomer is completely clear liquid layer. Theclear liquid height on tray and clear liquid height on hang downcomer determined fromthese simulations are good agreement with experimental data. It was obtained that thegreatest relative error of the orifice coefficient of experimental data and simulation data is 8.80%.In conclusion, both the experimental study of hang downcomer capacity and the CFDstudy of velocity distribution of the tray are very significant for further studies and industryapplications.