Effect of differentially heated tubes on natural convection heat transfer in a space between two adiabatic horizontal concentric cylinders using nano-fluid

Journal: International Journal of Mechanical Sciences
Author: Masoud Afrand
Link: https://www.sciencedirect.com/science/article/pii/S0020740319328954
Abstract

In the present numerical study, the free convective flow between several differentially hot and cold tubes enclosed in a space between two horizontal adiabatic coaxial cylinders which filled with three different kinds of nano-fluids is investigated. The effects of influential aspects including; location of heat source/sink, number of tubes, Rayleigh number (Ra), volume concentration (ϕ) and type of the nanoadditives on the isotherms, streamline, stream function and average Nusselt number () are explored. The governing equations are solved numerically employing control-volume based finite volume technique. For pressure-velocity coupling, the Semi-Implicit Method is utilized. According to the obtained results, usage of nano-fluid leads to the considerable enhancement of heat transfer in the studied cavity. For all the examined configurations with two cylinders, the configuration 30° has the most  values which is followed by configurations 60° or 0°, 90°, 120°, 150° and 180°, respectively. It is clearly seen that for all the assessed configurations with three cylinders, the highest to lowest  respectively belongs to the Case 2C, Case 2A and Case 2B. Moreover, for all the investigated configurations with four cylinders, the highest and lowest  respectively occurs at Case 3B and Case 3A.