Numerical And Experimental Investigation On Gas-Liquid Two-Phase Flow In A Bubble Column

Column reactors are important facility in which the mass and heat transfer happens. Since bubbly flow is a basic flow pattern of gas-liquid two-phase flow in the column, thorough study on bubbly flow is of great scientific significance and important value for practical industry application.The present paper firstly gives a review about the developments and researching status of gas-liquid two-phase flow. The complexity and difficulties in gas-liquid two-phase flow are discussed. Based on this, the dissertation presents theoretical and experimental investigations on adiabatic gas-liquid two-phase turbulent flow in a bubble column.In theoretical study, the general governing equations for gas-liquid two-phase flow have been developed by applying the volume averaging method to the "local transient equations" of two-phase flow. In addition, by applying the time averaging operator to the above equations, the turbulent two-phase flow governing equations are obtained. According to dynamical characteristic of the bubble motion in the flow field, and under the assumptions of isothermal system without interior heat source, uniform bubble size, and ignoring surface tension, the mathematical expressions for interfacial momentum exchanges have been deduced which include drag, virtual mass force, and lift. By applying volume averaging operator to the local transient RNG k-s model, the effects of interaction between liquid and bubble on the turbulent kinetic energy and its dissipation rate are incorporated to the RNG k-s model.The finite volume approach was used to discrete the partial differential equations. The SIMPLEST algorithm was used to solve the problem of strong conjugation between velocity and pressure. And staggered-grid system was also used for the procedure of pressure discretization. The general numerical method employed for the present computations was IPSA which is a solver for multi-phase flows.In experimental study, the gas-liquid loop facility was set up. The size of bubble column is 200 4.2 2000 mm3. The velocity, turbulent intensity, and Reynolds stress of the liquid was measured with LDV, while the hold up, velocity of gas were measured with PIV. The effect of air distributor on the flow fields was studied with emphasis.The working conditions of the bubble column simulated in the numerical study were as same as in the experiments. The velocity profile at axial direction showed a peek in the center, and a backward flow near the wall when usL/uSG<19.6. The velocity profile at axial direction showed a peek near the wall when UsL/UsG>19.6.The radial velocity profile of the liquid is dependent on the superficial air velocity and the column height, and flows from the wall to the center at bottom of the column.The good agreement of predictions with experiments can be taken as evidence for the validity of the interface momentum exchange function used in the present model.