LBM-MRT study of a reactive porous separation on thermal and depollution efficiency in a ventilated room

Abstract

This work investigates a mixed laminar thermosolutal convection phenomenon in a cavity ventilated by air displacement, equipped with a reactive porous separation of variable height inside. The Lattice Boltzmann method with multiple relaxation times (LBM-MRT) was adopted for the mathematical resolution. The extended Darcy Brinkman-Forchheimer model was used to simulate the porous material. The objective of this work is to improve the energy efficiency of ventilation systems and optimize indoor air quality. The main novelty of this research lies in the introduction of a complement to ventilation, in the form of a fixation reaction, making it possible to develop a physical model based on both the elimination and fixation of pollutants. The model represents a rectangular cavity with heating one of its vertical walls, while the other walls are adiabatic. The geometric and flow parameters examined are the height of the porous separation (Hp), its permeability (Darcy number), the fixing reaction rate (Ak) and the Reynolds Reas well as the Rayleigh Ra numbers. The most notable result concerns the estimated improvement of around 52% in thermal efficiency. This occurs in the case of a high Darcy number (Da=10−2), a height of 0.3, a moderate flow rate (Rec=5×102) and maximum thermal heating (Ra=106). This improvement is compared to case with a low Darcy value (Da=10−6). In the same scenario, the thermal efficiency reaches its peak at a height of 0.9. The results show that the impact of the fixation reaction and the height Hp is most noticeable at low permeabilities (low Da), as the porous separation acts as a solid wall. As a result, an increase in Hp leads to an expansion of the dead zone in the second compartment, creating a zone that is both polluted and thermally uncomfortable.