Study Of Motion And Heat Transfer Characteristics Of Regular Tetrahedral Particles In Vertical Riser Heat Exchange Tube

The liquid-solid fluidized bed heat exchanger has high heat exchange efficiency,and the motion state of the solid phase in the two-phase flow in the tube plays a crucial role in the heat exchange effect.In this paper,the numerical simulation method of CFD-DEM coupling will be used to explore the specific motion state of non-spherical regular tetrahedral shaped particles based on the combination of experimental verification,and further prove the motion characteristics and heat transfer characteristics of two-phase flow in the riser pipe.The research content of this paper mainly includes the following parts:(1)The vertical ascending pipe model and the regular tetrahedral particle model are established,and the regular tetrahedral particle model is established after the multi-sphere simulation method is improved by the method of spatial coordination.And the PIV experimental method is used to measure the flow field distribution information of the self-prepared regular tetrahedral particle group at the upper section of the vertical heat exchange tube to verify the simulation model experimentally.(2)The effects of particle shape,particle inlet concentration α,and liquid inlet flow velocity v on the force,velocity distribution and concentration distribution of irregular-shaped particles in the tube were explored.In terms of force,the force of regular tetrahedral particles is always larger than that of spherical particles.In terms of velocity distribution,the particle velocity distribution in the axial direction first increases sharply and then fluctuates,and the fluctuation range becomes wider as the liquid inlet velocity v increases;in the radial direction,as the liquid inlet velocity v increases,the velocity distribution converges in every working condition.In terms of concentration distribution,in the axial direction,the relative volume concentration of particles at the inlet is greater than that at the outlet,and the difference decreases with the increase of the liquid inlet flow velocity;in the radial direction,the relative volume concentration distribution of the particle phase presents a " double peak " structure.(3)Under the premise of the above research,the effects of particle shape,particle inlet concentration α,and liquid inlet velocity v on the pressure field,velocity field,Nusselt number and friction coefficient were explored,and combined with the parameter PEC index to evaluate the economic performance of the enhanced heat transfer by the particle group in the tube.Within the research parameters,under the condition that the particle inlet concentration α is 1% and the liquid inlet velocity v is2.0 m/s,the liquid-solid two-phase flow using regular tetrahedral particles has the best economical efficiency.