Cooling of Two Hot Half-Cylinders through MHD Non-Newtonian Ferrofluid Free Convection under Heat Absorption; Investigation of Methods to Improve Thermal Performance via LBM

The cooling process of parts in limited spaces is of great interest to researchers due to its many applications in industries such as electronics. Therefore, achieving the best performance of such systems has always been one of the challenges facing researchers. Due to this necessity, in the present simulation via the lattice Boltzmann method (LBM), the cooling of two hot semi-cylinders via magnetohydrodynamics (MHD) free convection has been interrogated. The novelty of the available study compared to antecedent studies is the effect of a magnetic field (MF) in different types and heat absorption for cooling two hot objects embedded within a triangular enclosure comprising non-Newtonian ferrofluid, which has not been studied so far. The accuracy of the obtained results was guaranteed via the validation of the written code in comparison with other studies qualitatively and quantitatively. Based on the results, To have a larger the Nusselt (Nu) value, at the highest Rayleigh (Ra) value, it is sufficient to decline the fluid power-law (PL) index, heat absorption index and the Hartmann (Ha) value. The reduction of in the mean Nu value due to rise of the Ha value for the shear thinning fluid is about ۵۹%, while it is about ۳۸% and ۲۱% for the Newtonian and the shear thickening fluids, respectively. The existence of heat absorption, in addition to reducing the Nu value by about ۷۵% in highest value, for the shear thinning fluid, results in a decrease in the value of thermal performance index (ITP), which is very insignificant for the shear thickening fluid at Ha=۶۰. The predominance of conduction over convection is the result of enhancing the PL index, which diminishes the effect of type and power of MF. For Ra=۱۰۴, due to low convection effects, changing the type of MF is ineffective, while for Ra=۱۰۶, this effect is highest. By changing the angle of inclination of the chamber and changing the arrangement of hot objects on the walls of the cavity, by changing the flow patterns, the thermal characteristics of the system can be strongly affected. In all cases, the trend of the ITP changes is in accordance with the trend of the mean Nu changes, which exhibits that HT has the largest share to production entropy (PE).

کلیدواژه ها:

Non-Newtonian ferrofluid free convection ، Heat absorption ، Entropy Generation ، Changing the hot objects position ، Changing the form of applied magnetic field ، Tilted right-triangular cavity