Examination of effective strategies on changing the amount of heat transfer and entropy during non-Newtonian magneto-nanofluid mixed convection inside a semi-ellipsoidal cavity

Abstract

Due to the application importance of convection flows under the impact of external fields such as magnetic field for non-Newtonian nanofluids, in cases such as nuclear processes, technologies related to lubrication, production and processing of food products, the modeling of these types of currents is very important. The existing research inquires the influence of heat production/absorption on the characteristics of non-Newtonian flow and entropy formation caused by convection heat transfer. For this purpose, the phenomenon of mixed convection inside the semi-elliptical chamber containing a power-law nanofluid is presumed in such a way that the Brownian motion of nanoparticles is considered. The curved and vertical walls of the enclosure are cold and under three different types of heating, respectively. The cold wall has no speed while the chamber vertical wall has a non-uniform velocity distribution (cosine) with a phase difference. The main goal of the research is to depict the impact of changing the position of applying the magnetic field and changing the phase difference of wall movement on the fluid flow. Flow modeling was accomplished via the utilization of lattice Boltzmann method and the accuracy of the findings was affirmed by comparing previous related studies. According to the research findings, enhancing the mean Nusselt number has a direct relationship with enhancing the phase difference. In addition, by enhancing the phase difference to 180, the mean Nusselt number up to 46% more is acquired, the influence of magnetic field applying becomes more conspicuous. In addition to the fact that the enhancing in Richardson number leads to increment of in the mean Nusselt number value and flow power, the effect of varying the phase difference becomes more noticeable with the enhancing in Richardson number. Enhancing in the Hartmann number, index of power-law and decreasing in the heat production/absorption coefficient lead to decrease in the entropy value and the average Nusselt number. By changing the position of applying the magnetic field, a current with various features can be acquired. Based on the results, it was demonstrated that changing the type of wall heating along with changing the heat absorption/production coefficient are very useful strategies in controlling the system thermal characteristics.