NUMERICAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT WITH DIMPLED PARTICLES IN STRUCTURED PACKED BEDS

In packed beds, structured accumulation of particles shows more prospects due to their potential to reduce flow drag and enhance heat transfer compared with random accumulation of particles. To further strengthen heat transfer in structured packed beds, a dimpled structure was applied to particles in the present work. The three-dimensional Navier-Stokes equations and the SST k-omega turbulence model were adopted to investigate the flow and heat transfer characteristics. Spherical particles with or without the dimpled structure were compared and analyzed at four different channel-to-particle diameter ratios. It is found that the dimpled structure has an important effect on the local flow and heat transfer characteristics. Compared with the structured packed beds of smooth particles, the Nusselt number increases from 4.01% to 57.73% and the friction factor increases from 7.84% to 42.16% with channel-to-particle diameter ratios change from 1.47 to 1.00. For comprehensive evaluation of the flow drag and heat transfer performance the comprehensive heat transfer coefficient is proposed. It can be increased by up to 47.29% in the structured packed beds of dimpled particles. Furthermore, different coefficients of structured packed beds with smooth and dimpled particles are given based on the empirical formulas of the friction factor and Nusselt number, which provides reference for future applications.