A pore-scale investigation of the transient response of forced convection in porous media to inlet ramp inputs

This paper investigates the transient response of forced convection of heat in a reticulated porous medium through taking a pore-scale approach. The thermal system is subject to a ramp disturbance superimposed on the entrance flow temperature/velocity. The developed model consisted of ten cylindrical obstacles aligned in a staggered arrangement with set isothermal boundary conditions. A few types of fluids, along with different values of porosity and Reynolds number are considered. Assuming a laminar flow, the unsteady Navier Stokes and energy equations are solved numerically. The temporally developing flow and temperature fields as well as the surface averaged Nusselt numbers are used to explore the transient response of the system. Further, a Response Lag Ratio (RLR) is defined to compare the transient response and the input. The results reveal that an increase in amplitude increases the RLR. Nonetheless, an increase in ramp duration decreases the RLR, particularly for high density fluids. Interestingly, it is found that Reynolds number has almost negligible effects upon RLP. This study clearly reflects the importance of conducting pore-scale analyses for understanding the transient response of heat convection in porous media