Combined heat and mass transfer by mixed convection MHD flow along a porous plate with chemical reaction in presence of heat source

An exact and a numerical solutions to the problem of a steady mixed convective MHD flow of an incompressible viscous electrically conducting fluid past an infinite vertical porous plate with combined heat and mass transfer are presented.A uniform magnetic field is assumed to be applied transversely to the direction of the flow with the consideration of the induced magnetic field with viscous and magnetic dissipations of energy.The porous plate is subjected to a constant suction velocity as well as a uniform mixed stream velocity.The governing equations are solved by the perturbation technique and a numerical method.The analytical expressions for the velocity field,the temperature field,the induced magnetic field,the skin-friction,and the rate of heat transfer at the plate are obtained.The numerical results are demonstrated graphically for various values of the parameters involved in the problem.The effects of the Hartmann number,the chemical reaction parameter,the magnetic Prandtl number,and the other parameters involved in the velocity field,the temperature field,the concentration field,and the induced magnetic field from the plate to the fluid are discussed.An increase in the heat source/sink or the Eckert number is found to strongly enhance the fluid velocity values.The induced magnetic field along the x-direction increases with the increase in the Hartmann number,the magnetic Prandtl number,the heat source/sink,and the viscous dissipation.It is found that the flow velocity,the fluid temperature,and the induced magnetic field decrease with the increase in the destructive chemical reaction.Applications of the study arise in the thermal plasma reactor modelling,the electromagnetic induction,the magnetohydrodynamic transport phenomena in chromatographic systems,and the magnetic field control of materials processing.

Effect of Operating Parameters on Carbon Dioxide Depressurized Regeneration in Circulating Fluidized Bed Downer using Computational Fluid Dynamics

Typically,heating or high-temperature treatment has been used to regenerate solid sorbent.In this study,the depressurized regeneration using a circulating fluidized bed downer was proposed and the significance of its operating parameters was identified.Two-dimensional computational fluid dynamics were employed to systematically investigate the effects of operating parameters on carbon dioxide depressurized regeneration with potassium carbonate solid sorbent particles.The simulated model was based on a laboratory scale circulating fluidized bed downer.The chemical equilibrium model for predicting the highest outlet carbon dioxide mass fraction was then used.A central composite design was employed to identify the main,quadratic,and interaction effects of operating parameters to the regeneration process.The operating parameters consisted of the outlet system pressure,inlet gas velocity,and inlet solid circulation rate,while the response variable was the released outlet carbon dioxide mass fraction.Among the multiple operating parameters,there were two main operating parameters and their combinations,namely the inlet gas velocity,outlet system pressure,square of inlet gas velocity,and interaction between inlet gas velocity and outlet system pressure,which had great impacts on the regeneration.All the main,quadratic,and interaction effects were explained.Then,the optimal operating conditions were obtained through the response surface method.

Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite

In this work,the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production,and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome.However,the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2.The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production,with both reforming and sorbent regeneration occurring simultaneously.The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system.The reforming riser and bubbling bed regenerator are studied separately but related to each other.Two-dimensional transient models using the Euler-Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite,to investigate a conceptual regenerator system and determine its key conditions.A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200 kg/(m2 s) and a catalyst to sorbent ratio of 2.54 kg/kg.A double-stage bubbling bed regenerator system was designed with 1.2 m width,0.8 m bed height,a gas inlet velocity of 0.2 m/s and solid preheating at 950 ℃.The used dolomite was regenerated with an assumed CaO conversion of 3%;the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.