Analysis of heat and mass transfer of pollutant inside a partially heated and concentrated vented cavity

Abstract

In this thesis, a numerical analysis has been performed to investigate the heat and mass transfer inside a partially heated and concentrated vented cavity. Numerical simulation has been done to carry out an investigation on the mixed convection of air under double-diffusive conditions in a square shaped cavity. A flow of air is passing inside a square enclosure with a heat source and a pollutant source on the right and bottom wall, creating double-diffusion, as well as two ventilation ducts on the upper sides asserting mixed convection. The physical problems are represented mathematically by different sets of governing equations along with the initial and boundary conditions. Using a class of appropriate transformations, the governing equations along with the initial and boundary conditions are transformed into non-dimensional form, which are then solved by employing a finite-element scheme based on the Galerkin method of weighted residuals. Numerical calculations are carried out for different parameters namely Reynolds number (Re = 50 to 500), Richardson number (Ri = 0.1 to 10), Prandtl number (Pr = 0.071 to 7.1), Lewis number (Le = 0.01 to 5) and Buoyancy ratio (Br = -10 to 20) at = 0.1, 0.5 and 1. Results are presented in terms of isotherms, isoconcentration, streamlines, heat and mass transfer rate in terms of Nusselt number and Sherwood number respectively, average fluid temperature at the exit port and average mass concentration inside the cavity is for the aforesaid parameters graphically. Comparisons with previously published work are performed and the result are found to be in excellent agreement. The findings have been discussed to ensure understanding of the changes in parameters, and an enhancement in heat as well as mass transfer was seen with the rapid change in dimensionless time. The computational results also indicate that the average Nusselt number at the hot wall, average temperature of the fluid in the cavity and temperature at the cavity depending on the aforementioned dimensionless parameters. Moreover, when the thermal diffusivity is higher than the mass diffusivity, the average fluid temperature and mass concentration become lower. This study will be a guide on double-diffusive system design, like roof-based air ventilation systems with partial heat and mass generation.