Cooling capacity of magnetic nanofluid in presence of magnetic field based on first and second laws of thermodynamics analysis

Abstract

ABSTRACT In this numerical study, the cooling capacity of water/Cu magnetic nanofluids in a horizontal duct exposed to a magnetic field has been investigated. Both the first and second laws of thermodynamics analysis are conducted. All simulations have been performed for the volume fraction of 5%, Reynolds number (Re) of 100, and the Hartmann numbers (Ha) of 0, 20, 50, and 80. Temperature, velocity profiles, Nusselt number (Nu), Lorentz force (F), and thermal, frictional, and magnetic irreversibility have been studied by changing Ha. The received results indicate that as the Ha increases, the hydrodynamic boundary layer thickness decreases, while the length of the hydrodynamic entrance length increases. In addition, as the Ha increases in the range of 0 to 80, the local Nu number increases by about 7.5%, and the local wall temperature drops to 2.7%. The second law of thermodynamic analysis showed that as the Ha increases, the frictional irreversibility augments, while the thermal irreversibility decreases. Finally, the order of thermal irreversibility is larger than that of frictional and magnetic irreversibility.