Design of finned spherical enclosures and thermal performance evaluation under natural convection

Abstract

Natural convection over spherical surfaces has been an important subject for numerical and experimental studies. Many applications like LED lights, optical systems, etc., housed inside the spherical enclosure, need fins on the spherical surfaces to cool the system naturally. One of the genuine usages of this research is the usage of normal convection to electronic circuits cooling. Many fascinating handy issues on regular convection heat exchange deal with the assortments of a complex shape. This present study discusses the thermal behaviour of rectangular fins of various heights and thicknesses on spherical surfaces. Fins on the spherical surface were simulated using computational fluid dynamics tool (Ansys—Fluent), the variation of Nusselt number for different fin configuration with Ra in the range of 1010 is studied. Simulation results were validated on a sector of a sphere with rectangular fins by measuring the temperature of various fin configurations. Here, the influence of fin thickness concerning the height of it is analysed at the different gap between fins is done and found that at particular fin spacing and height the thickness effects the heat transfer from the sphere. But by the current study, as thickness and spacing increase, the heat transfer rate decreases from the sphere, thus resulting in high temperature of the sphere. When heat flux over a 400 mm diameter free cooled hollow sphere varies from to 600 W/m2, the Raleigh number varies between 8.5 × 1009 and 3 × 1010, and the Nusselt number varies from 110 to 150. Hence, by the present study, it is observed that every time the heat transfer rate will not increase in increasing the fin thickness and it depends on the particular configuration as well as heat flux available at the source.