Entropy Generation in Unsteady Flow of a Ternary Nanofluid With Chemical Reaction, Thermal Radiation, Magnetic Field, and Darcy Effects in a Porous Microchannel Subject to Convective Cooling and Uniform Suction/Injection

ABSTRACT The present study investigates the behavior of two fundamental thermodynamic characteristics, namely, entropy generation and thermal runaway, in the unsteady flow of a ternary hybrid nanofluid (THNF) through a vertical microchannel. The THNF is composed of a mixture of molybdenum disulfide (), silver (Ag), and multi‐walled carbon nanotube (MWCNT) nanoparticles suspended in a water‐base fluid. The microchannel has permeable walls, and the interior of the microchannel is filled with a porous material. The flow inside the microchannel is subjected to exothermic reactions, thermal radiation, and a transverse magnetic field. The microchannel walls are exposed to fluid injection/suction at uniform rates and are also subjected to convective cooling. The resultant governing model equations and corresponding initial and boundary conditions are solved numerically using robust and efficient semi‐implicit finite difference methods (SIFDM). Key findings of the study demonstrate that the THNFs perform best in thermal runaway mitigation as compared to hybrid nanofluids (HNFs), conventional nanofluids (NFs), and the nanoparticle‐free base fluid. With regard to entropy generation, key observations indicate that entropy generation rates are highest at the microchannel walls with the lowest values recorded inside the microchannel; that entropy generation would be minimized by using THNFs as compared to either HNFs or NFs; and that the combined forms of irreversibility (arising from the magnetic field, porous medium, and viscous dissipation) dominate over heat transfer irreversibility. The current study therefore demonstrates practical implications in the design and operation of efficient industrial and engineering thermo‐mechanical systems, emphasizing the role of nanoparticle composition and operational considerations for optimal thermal performance.