Numerical investigation on the effects of the positional variation of porosity in thin porous layers

The application of pressure in the assembly of devices containing thin porous layers has shown significant effects with the presence of a solid boundary contact. During this process, pore diameters of the thin porous layers are reduced. Thus, the porosity in the near wall region is effectively reduced. The reduced porosity significantly lowers the overall performance of the devices because of the limited fluid dynamic variables. A new method for the positional variation of porosity is proposed to compensate the fluid dynamic disadvantages and mass transport characteristics in the industrial devices such as filters, porous electroosmotic pump and fuel cells. In the present study, the novel method introduces a composite porous layer with high porosity in the outer region rather than in the central region of the porous media. A three-dimensional numerical simulation is performed to investigate the effects of this positional variation of porosity and the performance of the composite porous layer. A reasonable increase in flow rate is found in the wall region and in the central region, depending on the increment in the porosity in the outer region and on the orientation of the porous layer to the fluid flow.