Heat transfer performance evaluation based on local thermal non-equilibrium for air forced convection in channels filled with metal foam and spherical particles

摘要

A local thermal non-equilibrium heat transfer analysis was conducted for air forced convection in channels filled with metal foam and particles. A general analytical expression was obtained for evaluating Nusselt numbers for the hydro-dynamically and thermal fully developed channel flows subject to constant heat flux, which can be used to investigate heat transfer performances of various porous media under equal pumping power. Such performance evaluations were made for aluminum metal foams of the porosity ranging from 0.85 to 0.95 and the pore diameter to channel half height ratio ranging from 0.01 to 0.20, and also for various packed aluminum particles of the diameter to channel half height ranging from 0.01 to 0.20. It has been found that the conventional local thermal equilibrium model leads to substantial overestimation of Nusselt number in the range of moderate pumping power, especially when the metal foam with large pore diameter is used to fill the channel. The analysis also revealed that in the moderate range of pumping power, the metal foam of comparatively low porosity performs better, while, in the high range of pumping power, the packed bed with large particle diameter gives higher heat transfer performance due to enhanced thermal dispersion.