CFD ANALYSIS OF CONTAMINANT TRANSPORT IN AN ENCLOSURE

Abstract

The air flow pattern and temperature distribution within a room play important roles in determining the quality of indoor environment and the amount of energy needed to condition the air for human comfort. Recent advances in computational fluid dynamics (CFD) and computer technology have provided powerful tools to predict air flow characteristics within a room that would almost be impossible to evaluate using experimental procedures. While using a CFD simulation, the reliability and accuracy of results depend on several factors, such as the numerical scheme, and the modelling of the boundary conditions. A numerical study has been conducted to investigate the double diffusive mixed convection in a two-dimensional rectangular cavity with a high concentrated contaminant on the horizontal wall and a part of the left wall subjected to high temperature. The remaining parts of walls are assumed to be adiabatic. Cold fluid is blown into the cavity from an inlet in the left side wall of the cavity and is exited through three different outlets i.e., bottom, middle and top in the opposite side wall. This configuration of double diffusive mixed convective heat transfer has application in building energy systems, cooling of electronic circuit boards, and solar collectors, among others. The objective of the research is to optimize the relative locations of outlet in order to have most effective cooling in the core of the cavity by maximizing the heat-removal rate and reducing the overall temperature and contaminant in the enclosure. This thesis reports the results of the numerical study of heat and contaminant transport in a rectangular ventilated enclosure. The Governing equations consist of velocity-Poisson equations, vorticity transport equation, energy equation and species concentration equation. Galerkin's finite element method has been employed to solve the governing equations to obtain the solution for flow field, temperature and concentration of the contaminant. Simulation results are obtained for the effect of variation of Reynolds number and buoyancy ratio (N) on contaminant distribution inside the enclosure with a high concentrated contaminant on the horizontal wall and a part of the left wall subjected to high temperature. Results obtained for 0.1 < Ri < 10 , 100 < Re <500 and 0.1 <N < 10 indicate that increase in Reynolds number results in enhancement in the dispersion of contaminants and pronounced effects are observed on the downstream of the flow field. Increase in buoyancy ratio also increases the convective transport of contaminant transport within the enclosure.