Abstract
Entropy generation in thermal convection with differentially discrete heat boundary conditions at various Rayleigh numbers (Ra) are numerically investigated using the lattice Boltzmann method. We mainly focused on the effects of Ra and discrete heat boundary conditions on entropy generation in thermal convection according to the minimal entropy generation principle. The results showed that the presence of the discrete heat source at the bottom boundary promotes the transition to a substantial convection, and the viscous entropy generation rate (Su) generally increases in magnitude at the central region of the channel with increasing Ra. Total entropy generation rate (S) and thermal entropy generation rate (Sθ) are larger in magnitude in the region with the largest temperature gradient in the channel. Our results also indicated that the thermal entropy generation, viscous entropy generation, and total entropy generation increase exponentially with the increase of Rayleigh number. It is noted that lower percentage of single heat source area in the bottom boundary increases the intensities of viscous entropy generation, thermal entropy generation and total entropy generation. Comparing with the classical homogeneous thermal convection, the thermal entropy generation, viscous entropy generation, and total entropy generation are improved by the presence of discrete heat sources at the bottom boundary.
Highlights
The thermal convection is the fundamental physical process in a variety of engineering circumstances, such as heat accumulator system, comfortable environment, grain drying unit, electron cooling, etc. [1,2,3,4,5]
Entropy is a significant quantity for assessing the energy loss in engineering applications, and entropy generation in fluid flow and heat transfer processes can be minimized based on the second law of thermodynamics [13]
We numerically studied the entropy generation in thermal convection process with discrete thermal boundary conditions based on the minimal entropy generation principle
Summary
The thermal convection is the fundamental physical process in a variety of engineering circumstances, such as heat accumulator system, comfortable environment, grain drying unit, electron cooling, etc. [1,2,3,4,5]. Entropy is a significant quantity for assessing the energy loss in engineering applications, and entropy generation in fluid flow and heat transfer processes can be minimized based on the second law of thermodynamics [13]. Based on the above discussions, it is found that the various discrete thermal boundary conditions are significant on the physical mechanism and temporal–spatial characteristics of entropy generation in thermal convection. We numerically studied the entropy generation in thermal convection process with discrete thermal boundary conditions based on the minimal entropy generation principle. The characteristics of local distributions of entropy generation are analyzed by considering the effects of Ra and the various discrete heat boundary conditions. Comparing with the classical homogeneous thermal convection, viscous entropy generation, thermal entropy generation, and total entropy generation are intensified by the discrete heat sources at the bottom boundary.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
