Session: 19-02: Symposium to Honor Professor Jane Davidson II

Paper Number: 169854

169854 - Thermal Transport Dynamics in Particle-Laden Suspensions 

Abstract: 

Slurries containing suspended particles made of Phase Change Materials (PCMs) in a liquid have been proposed as effective low-temperature storage media. These slurries exhibit a high effective specific heat due to the melting and freezing processes occurring within the particles. While previous studies have characterized the heat transfer performance of such media, there is limited understanding of the fundamental processes that contribute to heat transfer, particularly in the absence of phase change. Particle-laden suspensions are complex fluids, and their effective thermal properties depend on both the particle volume fraction and the applied shear. We conducted an experimental study on thermal transport in suspensions of neutrally buoyant particles subjected to uniform shear flow. By rotating the outer cylinder of a thin gap Taylor-Couette cell, we suppressed convection and turbulence while measuring thermal diffusivity. A one-dimensional conduction model was used to derive thermal diffusivity from the inner wall, which was maintained at a fixed temperature. We utilized 3D-printed 2 mm PMMA beads to create a density-matched suspension with a glycerol-glycol mixture, achieving a viscosity of 48 mPa·s. By varying the rotation speed, we adjusted the Peclet numbers from 0 to 1600, transitioning from Stokes flow (Re < 0.06) to inertially driven flow (Re > 1). The particle Reynolds' number, Re, is defined based on the imposed shear rate, particle diameter, and base fluid viscosity.  Our findings indicate that the thermal Peclet number creates three distinct regimes: an initial linear increase, followed by saturation, and then a subsequent rise. The Reynolds number plays a significant role in the transition from shear-induced diffusion to inertial mixing. We discovered that microscale wakes formed behind particles are crucial to this transition, with complex interactions between particle spacing and these wakes influencing the Nusselt number. Furthermore, we observed a weak non-monotonic dependency on particle volume fraction across a range of 5% to 35%. Our recent results unveil the complex interaction of microconvection, shear-driven diffusion, and inertial mixing that contributes to improved heat transfer in particulate suspensions.

Presenting Author: Vinod Srinivasan University of Minnesota- Twin cities

Presenting Author Biography: Vinod Srinivasan is an assistant professor in the Department of Mechanical Engineering at the University of Minnesota. His research interests include boiling, evaporation, spray cooling, heat transfer in particle-laden flows, and shear flow instabilities. The Multiphase Transport Lab, led by Dr. Srinivasan at UMN, explores fundamental transport phenomena that are critical to energy production, storage, and conservation. Dr. Srinivasan earned both his Ph.D. and M.S. from the University of Minnesota after completing his B.Tech in Mechanical Engineering at the Indian Institute of Technology-Bombay.