MODEL FOR HEAT AND MOISTURE TRANSFER IN ARBITRARILY-SHAPED 2-DIMENSIONAL POROUS-MEDIA

A model was developed to predict heat and moisture transfer due to nat ural convection and diffusion in arbitrarily shaped two-dimensional po rous media. Boundary conditions were diurnally varying ambient tempera ture on the outside of walls with moderate Blot number. Other importan t boundary conditions were developed for typical storage and transport ation situations. A two-energy equation model was used to allow for th e difference between the fluid and solid temperatures and its effect o n mass transfer in the porous medium. The governing equations were sol ved with a finite-difference method in a generalized coordinate system using a stream function formulation. It was found that the energy and moisture transport equations were best solved using a modified Crank- Nicolson method that was developed to control the tendency for instabi lity caused by the source terms in these equations. All of the boundar y conditions that were developed worked satisfactorily The two-energy equation model predicted small differences between the fluid and solid particle temperatures and natural convection only impacted the temper ature solution significantly in the upper comers of the porous media.