Natural convection and entropy generation of Fe3O4-H2O nanofluids in square cavities with cylindrical grooves under magnetic field

Abstract

Heat dissipation is crucial for the device performance, including electronic components, lithium-ion battery, solar collectors. Natural convection is regarded as one of the important ways of heat dissipation. The natural convection and entropy generation of Fe3O4-H2O nanofluids in cavities were experimentally investigated, and some influence factors including various mass fractions (0%, 0.1%, 0.3%, 0.5%) and heating powers (6 W, 12 W, 18 W, 24 W) were analyzed in detail, combining with unique square cavities and magnetic fields together. There are six square cavities with different arrangements (aligned, staggered) and depth of cylindrical grooves (1 mm, 2 mm, 3 mm), and magnetic fields have three different directions (unilateral vertical, bilateral corresponding, bilateral staggered) and intensities (0.01 T, 0.02 T, 0.03 T). The experimental data demonstrated that the optimum square cavity and magnetic field are staggered arrangement, depth h= 3 mm and bilateral staggered vertical, intensity B= 0.03 T, respectively. The cylindrical grooves and magnetic field can help decrease the thermal resistance and enhance efficiency of convection heat transfer. And mass fraction and heating power can also improve heat transfer. Furthermore, the entropy generation ṠT in the square cavity was also derived and studied. The result is really meaningful and worthwhile for designing or optimizing heat transfer system.