Convective heat transfer in different porous passages

This presentation concerns with the reported development of the exact series solutions for the computation of temperature in porous passages. Preliminary consideration is given to rapid heating within biological systems. Then, parallel plate and circular porous passages received significant considerations. These porous passages are filled with solids having relatively different thermal conductivity from that of the fluid materials. Therefore, this study includes the contribution of axial conduction for selected cases. This is to demonstrate the mathematical procedure leading to exact series solutions for selected cases. This leads to the exact solutions for a set of modified Graetz type problems for parallel plate channels and circular pipes. In general, when solid material has higher thermal conductivity, the numerical procedure yields a Nusselt number that changes significantly when the Peclet number changes. To show this phenomenon, the Nusselt number is computed for selected values of the Peclet number. Another application deals with rapidly switched heat regenerators in counterflow where the phenomenon of the so-called ‘flush’ phase plays an important role and affects the regenerator effectiveness.