Numerical Simulation Of Flow And Heat Transfer In Gas-Liquid Bubbling Bed With/Without Internal Components

In recent years,gas-liquid bubbling bed has been favored by petrochemical,energy utilization and mineral processing fields due to its large interface area,excellent mass and heat transfer performance.At present,many researches have been carried out on bubble size distribution,flow pattern division,gas holdup measurement and heat and mass transfer mechanism in bubbled bed.However,most of the current research focuses on the structure of the bubble bed,and in the practical field of engineering,some bubble beds have enhanced heat transfer by adding internal components to improve the operation efficiency of equipment,such as the use of vertical tube bundles in the bubble bed to synthesize liquid phase fischer brackets.Therefore,in this paper with/without internals gas-liquid bubbling bed flow and heat transfer numerical simulation research,explore the horizontal tube bundle internals of bubbling bed flow and heat transfer,the influence of the distribution of flow parameters in the bubbling bed characteristics and different tube heat transfer capability,for gas-liquid bubbling bed structure design and safe operation for further improvement.At the same time,it provides reference for the follow-up research.In this paper,the effects of the components in horizontal tube bundles on the flow and heat transfer of the bubbling bed were investigated in a bubbling bed unit of0.48m×0.60 m.First,the Volume of Fluid（VOF）method is adopted,with water as the main phase and air as the secondary phase.The accuracy and validity of the simulation method are verified by comparing the experimental data.The formation,deformation and separation of bubbles in parallel with multiple pores were studied,the gas-liquid interface was tracked.The influence of liquid level height,hole spacing and inlet velocity on bubble movement behavior were studied.It is confirmed that the initial equivalent diameter of bubble decreases when the liquid level height increases.Similarly the diameter increases when the air inlet velocity rise.When the pore diameter is 49 mm,the effect between bubbles is minimal,so that bubbles at each pore can move vertically upward as an independent individual.In the process of formation,deformation and detachment,the bubbles mainly move in three deformation states: spherical,ellipsoidal and umbrella cap.Secondly,by changing the operating conditions and the arrangement of the horizontal tube bundle,the effect of the horizontal tube bundle on the overall gas holdup in the bubbling bed and the bubble characteristics along the different tube rows along the bed height was studied.The prediction accuracy of correlation formula with different gas holdup is discussed.The results show that the gas holdup in staggered and in-line tube bundle bubbling bed increases by 35%～50% compared with that in empty bubble bed.Under the effect of backflow,"air cushion area" is easily formed at the entrance of the bubbling bed.Along the axial height of the bed,the bubble characteristics show periodic oscillation,and there are different "peak" and "trough" points.The Reilly et al correlation and Gopal and Sharma correlation are suitable for predicting the gas holdup of the bubble beds of the cross-row and cross-row bundles,with the prediction errors of 3.76% and 3.18%,respectively.Finally,the effect of tube bundle arrangement on the heat transfer capacity of tube rows at different heights in the bubbling bed was investigated by changing the inlet temperature,inlet velocity and tube bundle arrangement.The results show that the heat transfer coefficient of staggered bubbling bed is increased by 3%～7%compared with that of sequential bubbling bed.At the same time,the simulation investigated the variation of single tube bundle along different circumferential angles The results show that,in the bubbling bed the average heat transfer coefficient of the tube row increases gradually with the augment of inlet temperature,and the heat transfer coefficient of the same tube row increases successively.In the clockwise direction,the heat transfer coefficient of single tube bundle increases first,then decreases and then increases.