The effect of Alumina-water nanofluid on natural convection heat transfer inside vertical circular enclosure heated from above

Journal Article

Ali, Mohamed . 2013

• Magazine \ Newspaper: Heat Transfer Engineering
• Issue Number: 15
• Volume Number: 34

Publication Abstract

Experimental investigation on natural convection heat transfer has been carried out inside horizontal circular enclosures filled with Al2O3 nanofluid with different concentrations; 0.0%, 0.85% (0.21%), 1.98 (0.51%) and 2.95% (0.75%) by mass (volume).  Two enclosures are used with 0.20 m inside diameter and with two different aspect ratios.  The top surface of the enclosure is heated using a constant heat flux flexible foil heater while the bottom surface was subject to cooling using an ambient air stream.   Various heat fluxes have been used to generate the natural convection heat transfer data.  The average Nusselt number is obtained for each enclosure and correlated with the modified Rayleigh number using the concentration ratio as a parameter.  A general correlation is obtained using the volume fraction and the aspect ratio as parameters to cover both enclosures.  The results show that the Nusselt number decreases than that of the base fluid which means using the alumina-water nanofluids deteriorate the heat transfer coefficient compared to that of pure water.  It is also found that the degree of deterioration depends on the concentration ratio as well as the aspect ratio of the enclosure.