Transient heating and entropy generation of a fluid inside a large aspect ratio cavity

► Transient heating of a fluid in a vertical cavity of large aspect ratio was studied. ► Two vertical plates located in the side walls, near the bottom, heated the cavity. ► Defining fields and the vortices dynamics of the process are obtained. ► Ways of symmetry break and heat transfer are found depending on the Rayleigh number. ► The overall entropy production increases with the square root of the Rayleigh number.