Entropy generation studies for a doubly drained square cavity filled with a hybrid nanofluid and subjected to magnetic fields

Abstract This research involved a numerical study of magnetohydrodynamic convection in a square cavity containing a hot block and filled with hybrid nanofluid, driven by cold vertical walls. The ADI method was applied to solve the governing equations and examined the effects of parameters like the volume fraction of the hybrid nanofluid ( ϕ ), Hartmann number (Ha), Richardson number (Ri) and entropy generation. The ranges of these parameters evaluated in this work are respectively 0% <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≤</mml:mo> <mml:mi mathvariant="italic">ϕ</mml:mi> <mml:mo>≤</mml:mo> <mml:mn>4</mml:mn> <mml:mo>%</mml:mo> </mml:math> , 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≤</mml:mo> <mml:mi mathvariant="italic">Ha</mml:mi> <mml:mo>≤</mml:mo> <mml:mn>80</mml:mn> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.01</mml:mn> <mml:mo>≤</mml:mo> <mml:mi mathvariant="italic">Ri</mml:mi> <mml:mo>≤</mml:mo> <mml:mn>10</mml:mn> </mml:math> . The findings include that adding 4% hybrid nanoparticles improved heat transfer by 9% compared to pure fluid. Magnetic fields reduced heat transfer by up to 16% when the block was positioned at the top and by 13% at the bottom. Increasing the Richardson number from 0.01 to 10 raised the Nusselt number around the hot block by 14% (bottom) and 8% (top). The block’s position significantly affects heat transfer, with a 70% increase when positioned at the bottom. Entropy generation was generally higher when the block was positioned at the top and decreased with an increase in the Hartmann number. Overall, a rise in the Richardson number resulted in a maximum increase in entropy generation of up to 13%.