Enhancing natural convection in a cube using a strong magnetic field — Experimental heat transfer rate measurements and flow visualization

The effect of a strong magnetic field on the average heat transfer rate and flow profiles of joint gravitational and thermo-magnetic convection of a paramagnetic fluid in a cubic enclosure heated from below and cooled from above was experimentally investigated. The working fluid consisted of 80% mass glycerol aqueous solution with a concentration of 0.8 mol/kg gadolinium nitrate hexahydrate making it paramagnetic. The cubic enclosure of 32-mm sides was located in the 10-cm bore of a horizontally oriented 5-Tesla super-conducting magnet at a position where the magnetic force distribution was relatively uniform. Under this configuration, the magnetic field imposed in the horizontal direction acted perpendicularly to gravity. It was found that the heat transfer rate through the cube increased with the increase of the magnetic induction. Furthermore, steady and transient state flow visualizations were carried out with a 10-Tesla super-conducting magnet to show a change in the temperature field when magnet-thermo convection dominated. Visualization was made using thermo-chromic liquid crystal slurry added to the working fluid and illuminated in a vertical cross-section of the cube.