Gholamreza Imani

The present study conducts lattice Boltzmann simulation of flow in a duct with evolving porous layers (EPL) on the walls. The effects of elapsed time (0 < t < 125 mins), Darcy number (0.0001 < Da < 0.01), Reynolds number (100 < Re < 400), and porosity (0.85 < ε < 0.99) on the problem are studied. The time history of the average Nusselt number ratio is calculated to study thermal performance reduction of the duct. It is seen that the thermal performance is reduced as the EPL grows on the walls. Two stages in the performance reduction over time are identified in the present study, called the initial and evolution stages. At the initial stage, the performance is reduced slightly, and at the evolution stage, that starts at tev, the performance reduction occurs rapidly and approximately at a constant rate. It is shown that at Re = 200 the thermal performance is reduced by 17% and 3.2% for Da = 10−4 and 10−2, respectively, compared to the clear duct. In the present study, correlations for the evolution starting time and average Nusselt number are proposed in terms of Reynolds number, Darcy number, and elapsed time. It is also seen that the porosity has a negligible effect on thermal performance, whereas the effect of Reynolds number is significant.