Heat transfer measurements in sheared neutrally buoyant granular suspension*

Investigating the impact of thermal microconvection on heat transfer in particulate suspensions at low-speed flows is essential for various applications, such as fluidized bed chemical reactors.Our study delves into the complex heat transfer regimes of non-brownian neutrally buoyant suspensions and seeks to examine the effective thermal diffusivity in a suspensions using a specially designed thin gap Taylor-Couette cell. The effective thermal diffusivity is quantified by introducing a thermal pulse to the stationary inner aluminum cylinder and recording the resulting temperature decay on the surface.The research utilizes spherical 1mm polystyrene and 2mm 3D printed PMMA particles in conjunction with a density-matched propylene glycol-glycerol solution to conduct the investigation. PIV imaging employed in comprehending the flow behaviors. Our observations indicate that the Reynolds number emerges as a pivotal determinant in orchestrating the transition from shear-induced diffusion to the onset of inertially driven mixing effects within the suspensions.The study identifies the microscale wakes generated behind particles as pivotal in orchestrating this transition, with the interactions between particle spacing and wake regions yielding a complex relationship for the Nusselt number. Current research unravels the intricate interplay of microconvection, shear-induced diffusion, and inertial mixing in contributing to the enhancement in heat transfer in particulate suspension.