Numerical Investigation of the Piston Effect of Supercritical Fluid under Microgravity Conditions Using Lattice Boltzmann Method

Piston effect is an important mechanism of heat transfer in a supercritical fluid flow under microgravity condition. In this study, a Lattice Boltzmann Model (LBM) has been introduced to simulate the piston effect. Variations of diffusion coefficient has been accounted for by adding a corresponding term to equilibrium distribution function. To calculate the intermolecular forces and compressibility in the LBM, a van der Waals equation of estate has been employed. Boundary conditions corresponding to compressible LBM at the presence of van der Waals forces have been set to eliminate the speed jump at the wall. It has been shown that such boundary conditions provide high accuracy in problems involving forces with an error of second order of magnitude in terms of space. The developed thermal LBM together with compressible LBM have been applied to simulate the heat transfer to supercritical fluid flows. The piston effect has been modeled by considering van der Waals inter molecular forces. The errors associated with each of the schemes used have been evaluated. A comparison between a pure conduction case and heat transfer due to piston effect has been made. It has been shown that the heat transfer occurs faster once the piston effect is in effect.