Buoyancy Driven Flow, Heat Transfer, and Entropy Generation Characteristics for Different Heater Geometries Placed in Cryogenic Liquid: A Computational Fluid Dynamics Study

The present work reports a 3D computational study of buoyancy-driven flow and heat transfer characteristics for a localized heater (analogous to superconductor) submerged in cryogenic liquid nitrogen in an enclosure. Seven different heater geometries are considered and the effect of heater geometry on flow and heat transfer characteristics is illustrated. The heater is generating heat at a constant rate (W/m3). Continuity, momentum, and energy equations are solved using the finite volume method. Liquid flow and heat transfer features are demonstrated with the help of velocity vector and temperature contours. Rayleigh number, average Nusselt number, the maximum vertical velocity of fluid flow, and the average velocity of fluid flow are the parameters that are considered for comparing seven different geometries of the heater. Additionally, an analysis of the entropy generation owing to the transfer of heat and friction due to fluid flow is reported. Furthermore, the dependency of average Nusselt number, maximum velocity of the fluid, entropy generation owing to transfer of heat, and fluid friction as a function of heat generation rate is illustrated graphically. The results of this study indicate that heater geometry can considerably affect the transfer of heat, fluid flow features, and entropy generation under the same heat generation rate in the heater. The highest average Nusselt number on the heater surface is obtained when heater geometry is circular, whereas the lowest value of total entropy generation in the domain is obtained when heater geometry is an equilateral triangle.