Mixed convective heat transfer in an enclosure containing a heat-generating porous bed under the influence of bottom injection

- Mixed convection is analysed in an enclosure with a heat generating porous bed.
- Cold fluid injection takes place from the bottom of the porous bed.
- Energy transfer is visualised with the help of energy flux vectors.
- Da affects the evolution of inertial flow at low Ri into buoyancy-driven flow at very high Ri.
- Lateral flow spreading is observed near the fluid inlet at low Da.

The present study numerically models the process of heat removal from a heat-generating porous bed with cold fluid injection from the bottom of the bed. This type of situation is encountered during post-accident situations in nuclear reactors and involves augmentation of heat removal capacity with forced coolant injection from the bottom. A steady-state analysis is carried out with the assumption of laminar flow regime and without accounting for phase change. Darcy-Brinkmann-Forchheimer approximation and local thermal equilibrium assumption are adopted for modelling the momentum and energy equations in porous media, respectively. It is observed that the fluid flow is determined based on the dominancy of the two co-existing flow mechanisms viz. inertial flow due to forced fluid injection and buoyancy-driven flow due to heat generation within the porous bed. In addition, permeability of the porous media significantly affects the flow mechanism, especially near the fluid inlet. Heat transfer characteristics closely follow the flow mechanism established within the enclosure.