Numerical Studies of Thermoacoustic Convection in Near-Critical Fluids

Abstract

Thermoacoustic convection in carbon dioxide near its critical point is investigated numerically. A real-fluid model has been developed taking into account all the relevant fluid property variations near the critical point, including the bulk viscosity. The thermo-physical properties of the near-critical supercritical fluids are given as functions of both pressure and temperature due to their strong divergence near the critical point. As a layer of supercritical fluid is heated rapidly, the combination of very high thermal compressibility and vanishing thermal diffusivity near the critical points of fluids affect thermal energy propagation, leading to the formation of acoustic waves as carriers of thermal energy. The rapidity of the boundary heating is a key factor in the generation of these acoustic waves. We also study the effect of different rates of boundary heating for the temperature equilibration mechanism near the critical point. As the critically diverging bulk viscosity plays a significant role on the transport processes near the critical point, effect of bulk viscosity on the flow field and heat transport induced by thermoacoustic waves and buoyancy in supercritical fluids is also investigated numerically. The predicted results from the present study can be utilized to understand the thermal transport mechanism in near-critical fluids.