A numerical study of fluid flow and heat/mass transfer over a stack of planks

Heat/mass transfer by air flow over a sample stack of planks ic; studied nu merically. For the simulations, the low Re k-epsilon turbulence model and b ounded QUICK scheme are used. The calculated Nusselt numbers are in good ag reement with the experimental data. The results of our study show that the low Re turbulence models have advant ages over the conventional high Re models for this type of industrial appli cation. This is mainly due to the small height of separation bubbles result ing from the selected large blockage ratios (more than 50 percent) occurrin g in such flows. Numerical simulations were carried out to study the effect of the vertical air gap due to shrinkage and non uniform sawing as well as the non uniformi ty in the height of boards on the flow field and heat/mass transfer charact eristics. The results show that the selected gap size significantly affects the local and average Nu numbers across the stack. We have suggested optim um gap sizes for maximum heat/mass for different flow velocities (Re number s).