Nonlinear Heat Transfer From Particles in Supercritical Carbon Dioxide Near the Critical Point

Particle to fluid heat transfer in supercritical carbon dioxide (sCO₂) is encountered in energy technologies and in materials synthesis. Near the critical point, the extreme pressure and temperature sensitivity of sCO₂'s thermal conductivity will change the expected heat transfer in these systems. The current work combines the Kirchoff transformation for thermal conductivity with the conduction shape factor for a sphere, allowing prediction of heat transfer in these systems and quantification of the impact of these property changes. Results show that the heat transfer is nonlinear for supercritical heat transfer, with the non-linearity particularly significant near the critical point. The results also show that approaches such as an average thermal conductivity based on film temperature are unlikely to accurately predict heat transfer in this region. The methods described in this paper can be applied to fluid-particle heat transfer at low Reynolds number in other fluids with large variations in thermal conductivity.