Analysis of double-diffusive hydrothermal flow in a domestic stack: The effect of side walls patterns

Domestic stack is considered to investigate the double-diffusive laminar natural convection. The working fluid is a gaseous mixture that has similar physical properties to carbon dioxide. Knowing the patterns of gaseous mixture distribution and determining the carbon deposit regions can help in carbon capture problems. The present study uses the finite element method to numerically examine the double ratio-diffusive physical phenomena in a rectangular-trapezoidal enclosure and to simulate the stack under a wide range of dimensionless parameters, such as buoyancy ratio $1\le N_{\mathit{BR}}\le 7$, Lewis number $2\le \mathit{Le}\le 8$, and Rayleigh number ${10}^3\le \mathit{Le}\le {10}^5$ for different aspect ratios. Nine different cases of the geometrical ratio are selected to cover most possible design configurations. The results indicate that increasing the Lewis number leads to augmented solutal transport but reduces heat transfer. However, both heat and mass transfer are observed by increasing the buoyancy ratio. It is worth mentioning that increasing the ratio of upper side length to base length $\left(\frac{d}{D}\right)$ from $\left(\frac{1}{4}\right)$ to $\left(\frac{3}{8}\right)$ leads to a significant increase in mass transfer by 75% and heat transfer enhancement ratio by around 50%.