Non-Darcy Hydrodynamic Model and Heat Transfer analysis of Foam Tube Heat Exchangers

In this paper a numerical model has been developed for hydrodynamic behavior and heat transfer of commonly used foam heat exchangers. The high porosity open cell metal foams are joined metallurgically to the outer wall of the tube. Forchheimer-Brinkman extended Darcy model is used for momentum equation in porous media. Also local thermal non-equilibrium (LTNE) assumption was carried out in energy equations of porous media. A set of governing equations were written for fluid inside the tube and foam matrix separately but, were solved together. Convergence of two systems of equations is very complex. SIMPLER algorithm was modified to solve the governing equations. In order to enhance the convergence rate, results were monitored each iteration. Under relaxation factor for velocity and temperature were determined with regards to the results. This modification has made this method more effective and the convergence rate enhanced. The results of the proposed model are in good agreement with the previous analytical model and predictions of boundary layer theory. Results show that using LTE instead of LTNE causes significant errors and cannot be used in the case studied in the present work

Keywords:

Foam heat exchanger , porous media , open-cell , modeling