The heat transfer performance of a particle-laden flow has design implications for a wide range of industries. The objective of this thesis is to improve a previously proposed Eulerian CFD model for the heat transfer of a highly mass loaded high Reynolds number particle-laden flow. Experimentation had shown that a layer of copper particles accumulated on the bottom of the flow channel. The previous two field (gas + dispersed particle) model was extended to include a third field to represent this particle layer. Mass transfer models were developed to account for the deposition of particles from dispersed to particle layer and from particle layer back to dispersed. New drag and heat transfer models were developed to account for the interaction of the particle layer field with the core gas flow. The model is tested and implemented using NPHASE, an Eulerian Multiphase flow CFD solver, and suggestions for improvement are proposed.

The goal of this research is to understand heat transfer in particle-laden flows. Particle-laden flows are prevalent in multiple industries, including chemical, pharmaceutical, plastics, food, and agriculture. In many applications, it is necessary to heat or cool the particle-laden flow to achieve desired process conditions. It is therefore important to understand the heat transfer characteristics of particle-laden flows under varying process conditions. This research seeks to experimentally investigate how the concentration of particles in turbulent, particle-laden flow effect the heat transfer properties of the flow. An experimental setup to observe the heat transfer properties of particle-laden flows was designed and built in house. A MARK XV-HP powder feeder system was used to entrain copper particles (-325 mesh) into a flow of nitrogen gas. The particle-laden flow then traveled through a horizontal pipe with a constant heat flux applied to the wall. Surface and fluid temperatures along the test section were measured and used to calculate the heat transfer coefficient and Nusselt number of the flow. A range of Reynolds numbers from 30,000 to 65,000 as well as a range of solids loadings from 0.0 to 1.0 were tested. For solids loadings of 0.5, the Nusselt number increased at lower Reynolds numbers and then decreased at higher Reynolds numbers. For solids loadings of 1.0, the Nusselt number was lower at low Reynolds numbers and then increased at higher Reynolds numbers. A transition in Nusselt number occurred for both solids loadings, but they occurred at different Reynolds numbers. The Nusselt number for particle-laden flows did show a variance from the Nusselt number for gas only flows. The direction and quantity of this difference was dependent on solids loading and Reynolds number. These trends are proposed to be a result of different turbulence modulation effects, which are discussed herein.

Turbulent particle-laden flows are common in many natural phenomena and engineering applications. While particle-laden turbulence is a relatively well-studied subject, not many studies address the concurrent effect of an radiative heat transfer on the multiphase system. Understanding such an interaction can be key to designing effective spray combustors, fire suppression systems, and particle solar receivers. Using the particle solar receiver as a test bed for investigation, this work aims to experimentally investigate the coupling between radiation, turbulence, and particles in such a system using two different flow configurations of a duct flow and an isokinetic co-flowing jet. The goals of the work are to examine the effects of preferential concentration on the behavior of the radiation transport through the disperse medium and the convective heat transfer between the carrier and disperse phase. In addition, it also aims to study the converse effect of how the radiative heating can effect the clustering behavior of the particles by examining measures of preferential concentration of particles in the flow in the presence of radiative heating. The study finds that the preferential concentration of particles can cause the radiation transmission to deviate from a classical Beer's Law extinction behavior, due to increased line of sight distances in the medium. Measurements of the carrier phase temperature statistics show that large coherent particles clusters dominate the modulation of the gas phase temperature, especially in the boundary layer in wall-bounded flows. Measurements of the radial distribution function, clustering index, and Voronoi cell area PDFs all indicated a reduction of preferential concentration within clusters, particularly in denser clusters with smaller associated separation length scales, which correspond to the most intensely heated regions of the flow. Particle velocity statistics showed evidence of bulk turbulence modification by radiative heating, as particle velocity fluctuations were dampened. This was likely caused by variable property effects from temperature-dependent properties, specifically from the increase in fluid kinematic viscosity. Buoyancy and dilatation effects were identified as possible mechanisms for turbulence modification at the smaller cluster scales, supported by scaling analyses and directional measures of preferential concentration.