Numerical study of the effect of aspect ratio on the entropy generation due to Rayleigh–Benard convection in 2D trapezoidal cavity

Abstract

The investigation of entropic variations in the thermal transport mechanism produced by buoyantly driven temperature gradients has attracted significant attention because of excellent physical significance. Therefore, the prime consent to manipulate the current investigation is to explore the impact of change in the aspect ratio of the trapezoidal cavity in the optimization of the entropy phenomenon. After attaining motivation from its practical essence different entropies including thermal, viscous, and local are estimated. Additionally, global quantities such as average Bejan and Nusselt numbers calculated along with total entropy are measured against flow concerning parameters (aspect ratio (AR), Rayleigh number (Ra) and irreversibility ratio ($$\phi $$ ϕ )). Numerical experiments are performed by implementing a finite element approach using open-source software renowned as COMSOL Multiphysics. Before the accomplishment of the outcomes, confirmation of the numerical technique is assured by establishing grid sensitivity testing. Comparison of results between present and previous studies is also demonstrated. A wide range of involved sundry parameters varying from $${10}^{-4}\le \phi \le {10}^{-2}$$ 10 - 4 ≤ ϕ ≤ 10 - 2 , $${10}^{2}\le {\text{Ra}}\le {10}^{5} \; {\text{and}} \; 0.25\le {\text{AR}}\le 0.75$$ 10 2 ≤ Ra ≤ 10 5 and 0.25 ≤ AR ≤ 0.75 are accounted. It is concluded that by escalating the aspect ratio from 0.50 to 0.75, the magnitude of the local entropy enhances from 3370 to 3424. It is revealed that the highest value of viscous entropy that is, 45, is achieved at Ra = 105 and by keeping the aspect ratio of enclosure equal to 0.75, whereas, the thermal entropy approaches 2 for the same situation of parameters. The magnitude of the average Bejan number reaches unity at AR = 0.5 and Ra = 105, whereas for low and high aspect ratios it depicts a magnitude less than 1 for the same Rayleigh number.