Numerical simulation of adiabatic/cooled/heated spherical particles with Stefan flow in supercritical water

When droplets or particles are in complex fluid-temperature-environment conditions, the spatial variation in temperature-dependent properties affects the overall particle-laden flow behavior. Particularly, in a high-temperature environment, the components on the particle surface are heated and volatilize to form a mass flow, named the Stefan flow, that influences the mass, momentum, and energy transfer between particles and the fluid. For supercritical fluids, small changes in temperature and pressure cause substantial changes in thermophysical properties. Hence, in this work, we study the characteristics of supercritical water flowing past an adiabatic/cooled/heated sphere for Re=10-200 with and without Stefan flow. The three-dimensional numerical simulations that are conducted consider the exact water thermophysical properties. The flow field, the Nusselt number (Nu), the drag coefficient (Cd), and the velocity and temperature distribution around the particle are analyzed. The results demonstrate that the vortex is strongly influenced by the variation in viscosity near the particle. The Cd and Nu values of the cooled and heated spheres show different deviations in different conditions. The influence of Stefan flow cannot be ignored as it increases the vortex size and decreases both Cd and Nu. Finally, the effect of Stefan flow on both Cd and Nu of the cooled sphere is greater than that of the heated sphere. Published under an exclusive license by AIP Publishing.

Automated summary

The study highlights the significant impact of Stefan flow on particle-laden flow behavior in high-temperature environments and the substantial changes in thermophysical properties of supercritical fluids under small variations in temperature and pressure. The numerical simulations reveal that the vortex is strongly influenced by viscosity variations near the particle, and the cooled and heated spheres show distinct deviations in Cd and Nu values under different conditions. The influence of Stefan flow cannot be disregarded, as it affects the vortex size and reduces both Cd and Nu, with a greater effect on the cooled sphere compared to the heated sphere.