Free Convection in a Square Enclosure from Two Submerged Cylinders of Different Aspect Ratio in Shear-Thinning Fluids

Abstract

AbstractThe present study focuses on heat transfer due to natural convection between horizontally positioned (side-by-side) hot and cold cylinders kept in a cold non-Newtonian fluid in a square enclosure. Computation fluid dynamics (COMSOL package) was used to solve the differential equations of continuity, momentum, and energy over a wide range of 10 ≤ Gr ≤ 104, power-law index 0.2 ≤ n ≤ 1, Prandtl number 0.7 ≤ Pr ≤ 100, and an aspect ratio of 0.16 ≤ R1/L ≤ 0.24. The flow and heat characteristics have been reported in terms of streamlines and isothermal contours, respectively. The results of average Nusselt number show a positive dependence on the Prandtl number and Grashof number. No changes in local Nusselt number were observed with Prandtl number by varying Grashof number up to 100, indicating conduction is predominant for heat transfer. For a higher Grashof number (>100), the average Nusselt number increases with increasing the Prandtl number. The average Nusselt number also increases with increasing the aspect ratio for all dimensionless numbers used in the study. Effect of Prandtl number is more at lower value of aspect ratio R1/L = 0.16 with respect to that of at higher values while heat transfer is more at higher value of aspect ratio R1/L = 0.24.KeywordsEnclosureCylindersGrashof numberPrandtl number