Porous media have promising attributes for the use as heat transfer enhancing structures in heat exchangers. Due to their large specific surface area, convective heat transfer can be improved and the tortuous structure of the porous solid induces mixing of the fluid flowing through the porous medium, which in turn enables increased heat dissipation. In addition to metal sponges and metal woven-wire mesh structures, periodic open cellular structures (POCS) are particularly suitable for heat transfer enhancement in applications like compact heat exchangers, since they can be ideally adapted to the desired application due to their large number of geometric degrees of freedom.
Within this contribution, the thermal enhancement factor (TEF) is used as an example of a widely adopted evaluation concept for a trade off of heat transfer and pressure drop to compare various POCS (variation of the cell morphology and porosity) with each other and with respect to a reference. A flow channel with a rectangular cross-section is chosen as that reference. To calculate the Nusselt numbers and friction factors required for the TEF, a superposition approach is used for the POCS and literature correlations are applied for the rectangular channel. Furthermore, in order to take into account the high specific surface area of the POCS, a modification of the TEF is discussed and the influence of height and width of the reference duct on the TEF is analyzed.