FULLY DEVELOPED CONVECTION HEAT TRANSFER IN OPEN-CELL FOAMS

摘要

Convection heat transfer in open-cell foams mainly occurs under thermally developed conditions for both uniform temperature and heat flux boundary conditions at the solid/fluid interface, since few cells are in the entrance region. Therefore, convection heat transfer needs to be thoroughly studied in order to allow reliable predictions of foam performance. A numerical analysis of fully developed laminar convection in open-cell foams at a pore scale is presented in this paper. The geometry of the cell is chosen making reference to Kelvin's tetrakaidecahedron foam model. The finite-element-based commercial code COMSOL Multiphysics (COMSOL Inc., Burlington, MA, USA) is employed in building up the numerical grid and solving the problem for different porosities and Reynolds numbers. The local velocity and local interfacial convective heat transfer coefficient in a cell in the thermal fully developed region are predicted. The results highlight the dependence of velocity on foam porosity and the effect of porosity on flow separation. They also exhibit a periodical behavior of the local convection heat transfer through the cell affected by the porosity and Reynolds number. Finally, cell-averaged heat transfer coefficients and average Nusselt numbers are presented, which highlight the effects due to scale changes.