Numerical Study of Heat Transfer Problems in Two-Phase Flows Involving Temperature Distribution within Dispersed Solid Particles

Heat transfer in solid-dispersed two-phase flow is simulated, and the effects of temperature distribution within the finite-sized particles on the flow structure, particle behaviour and heat transfer are studied. Temperature distribution within the particles is solved by an interfacial heat flux model with the discrete temperature field. The interfacial heat conduction model is validated through a comparison with the analytical solution of the heat conduction through eccentric cylinders of constant temperature difference. The method is applied to 2-D and 3-D natural convection problems in a confined container under relatively low Rayleigh numbers (10(4) similar to 10(6)). Particle behaviours are studied for different heat conductivity ratios (solid to fluid) ranging between 10(-3) and 10(2). With particles of relatively low heat conductivity ratios (< 10(0)), the particles show a simple circulating flow around the domain centre. By increasing the heat conductivity ratio(> 10(1)), particulate flow structure shows a transition to oscillatory modes around the domain centre. The difference in the time scales of heat transfer through the fluid and solid is found to be responsible for determining the the oscillation frequency. The results highlight the importance of temperature distributions within finite-sized particles.