Heat Transfer Due to Particle-Wall Collisions in Suspension Flows

A numerical study was undertaken to clarify the mechanisms of heat transfer in fluid-particle suspension flows. Such flows, including fluidization, are of considerable industrial importance. The present research focuses on heat transfer due to particle-wall collisions, of which three mechanisms can be unambiguously identified: (1) Direct solid-solid conduction through the contact area during particle-wall collisions. (2) Gas-mediated conduction between the particle and the wall. (3) Convection due to induced flow associated with particle collision. The first of these mechanisms had been previously studied by Sun and Chen. The present study examines the latter two mechanisms through the use of 2-D and 3-D numerical computations of collisions of normal incidence between a spherical (or cylindrical) particle and a wall. By comparing the results using (a) adiabatic boundary conditions on the particle and (b) uniform, elevated temperature conditions on the particle, the contributions of fluid-mediated conduction and particle induced convection were successfully separated. Asymptotic solutions were used to insure numerical accuracy when the particle is near the surface. Computational expedience led to the use of a transient conduction thermal layer as the background thermal field for the analysis. The results showed that the energy exchange due to gas-mediated conduction scales as the gas conductivity, the square of the particle diameter, the temperature difference, and the inverse of the velocity. The results are independent of the Prandtl number and the Peclet number, but approximately proportional to the square root of δ/D, the ratio of background thermal boundary layer thickness and the particle diameter. The energy exchange due to particle-induced convection scales approximately as the mass of the displaced fluid, the enthalpy difference, and \rm(δ/D)\sp{0.28}Pr\sp{0.21}Pe\sp{-0.56}.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Kwon, Oh Boong

Contributors dc:contributor

• Chen, M.M.,

• Engineering, Mechanical

Identifier

(UMI)AAI9305592

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/72233