Natural convection enhancement in the annuli between two homocentric cylinders by using ethylene glycol / water based titania nanofluid

The natural convection heat transfer 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 preserved 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 % ≤ φ ≤ 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 λ = 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.