Natural Convection Enhancement in the Annuli Between Two Homocentric Cylinders by Using Ethylene Glycol / Water Based Titania Nanofluid

Abstract

The natural convection heat tranfer in annulate region confined  between two homocentric cylinders were numerically studied in the present work. The annulus was filled by ethylene glycol / water based Titania nanofluid. Both internal and external cylinders are presereved at an isothermal hot and cold temperatures respectively, whereas, the upper and lower walls are adiabatic. The numerical solution is obtained by applying the finite volume method along with the SIMPLER, and TDMA algorithms. In the current study, the solid volumetric fraction is varied as (0 % ? ? ? 3 %),  the volume ratios of  EG to water  are varied as (0:100 %, 40 : 60 %, 100:0 %), while both the Rayleigh number and  radii ratio are considered fixed at  (Ra = 10⁴  and  ? = 2). The obtained results indicated that, the average Nusselt number  increases as the solid volumetric fraction and the volume ratio of  ethylene glycol in the base fluid increase. Moreover, the velocity profiles reach their maximum value in the half region adjacent the internal hot wall when TiO₂ – water  nanofluid is used. Also, the temperature profiles decrease along the radial distance for all considered values of  volume ratios of  EG to water.