Transient heat transfer analysis in supercritical fluids
Amanda Furtado Pinheiro1; Leonardo Santos de Brito Alves1
1 Universidade Federal Fluminense
doi:10.20906/CPS/COB-2015-2235
Resumo
The supercritical fluids have shown remarkable effects in physics and hydrodynamics, which take advantage of the unique properties of supercritical fluids. The heat transfer into a one dimensional cavity containing a supercritical fluid at zero gravity occurs unexpectedly fast. This phenomenon, called as piston effect, will be analyzed for different cases. A thermodynamic model for this specific happening will be used, and it consists in the general heat equation with an addition source term containing the bulk temperature time derivative. The normal expression for the piston effect relaxation time $t_{PE}$ for this model is $t_{PE} = t_D / (\gamma-1)^2$, where $t_D$ is the thermal diffusion relaxation time and $\gamma$ is the ratio between specific heats. Motivated by the fact that this formulation is an approximate solution, a previous work showed, for different boundary conditions for the piston effect, that the correct piston effect relaxation time should be $t_{PE} = t_D / \gamma$ instead, cause is rigorously satisfied by the exact solution when Dirichlet boundary conditions are imposed. A previous work of the same group employed Dirichlet, Neumann and Robin boundary conditions on the left wall, with prescribed temperature on the right wall in all three cases. As a continuation of this study, is intended to analyze again the heat transfer using the exact solution for three different boundary conditions for the right wall: Dirichlet, Neumann and Robin, with temperature prescribed on the left wall for all of the cases
Palavras-chave: supercritical fluids; state equations; heat transfer; thermodynamics