Abstract
Natural convection in an inclined rectangular cavity filled with air is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls of the cavity are adiabatic. Entropy generation due to heat transfer and fluid friction has been determined in transient state for laminar natural convection by solving numerically: the continuity, momentum and energy equations, using a Control Volume Finite Element Method. The structure of the studied flows depends on four dimensionless parameters which are: the thermal Grashof number, the inclination angle, the irreversibility distribution ratio and the aspect ratio of the cavity. The obtained results show that entropy generation tends towards asymptotic values for lower thermal Grashof number values, whereas it takes an oscillative behavior for higher values of thermal Grashof number. Transient entropy generation increases towards a maximum value, then decreases asymptotically to a constant value that depends on aspect ratio of the enclosure. Entropy generation increases with the increase of thermal Grashof number, irreversibility distribution ratio and aspect ratio of the cavity. Bejan number is used to measure the predominance of either thermal or viscous irreversibility. At local level, irreversibility charts show that entropy generation is mainly localized on bottom corner of the left heated wall and upper corner of the right cooled wall.
Highlights
Today, thermodynamic studies are not limited to the knowledge of exchanges between work and heat
The aim of the present study is to investigate the influence of the operating parameters such as the thermal Grashof number, the irreversibility distribution and the aspect ratios and the inclination angle of a rectangular enclosure on entropy generation behavior for the case of an incompressible viscous fluid
Entropy generation increases at the beginning of the transient state where the conduction is the dominant mode of heat transfer, reaches a maximum value which is more important as the aspect ratio of the cavity is more important
Summary
Thermodynamic studies are not limited to the knowledge of exchanges between work and heat. The field of investigation is being extended, namely in applications of exchanges between mechanical, chemical and electromagnetic forms of energy. Thermodynamics is not restricted to equilibrium state studies but domains near and far from equilibrium which describe thermodynamics of irreversible processes have become of great practical importance. Thermodynamic systems submitted to thermal gradients and friction effects are subjected to energy loss, which induces entropy generation in the system. Many studies have been published concerning entropy generation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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
