Two-phase analysis of heat transfer of nanofluid flow in a wavy channel heat exchanger: A numerical approach

Abstract

The heat transfer improvement by using CuO/water nanofluid (NF) in a wavy channel is evaluated numerically using the turbulent two-phase mixture and the κ - ε models. The numerical work is a 2-dimensional model created and analyzed in Gambit and Ansys Fluent software, respectively. The flow Reynolds (Re) numbers of 8000 – 40,000, wavelength ranging from 0 – 0.4 m, and solid volume fraction (SVF) of 0 % to 4 % are investigated. In all cases, a constant heat flux of q′′=5000 W/m2 is applied on the outer surface of the heat exchanger. The heat transfer and fluid flow were analyzed by the flow visualization method and heat transfer evaluation indexes. The results show that by increasing the Re number, the vortices increase and more turbulence are generated in the vicinity of the waves near the channel inlet. As the amplitude of the channel waves increased, the velocity at the top of the wave increased, and the resulting pressure gradient behind the wave is intensified and the reverse flow is generated. The improving effect of using NF is more prominent where the effect of other enhancing factors is weak. For wall amplitude of 0.1 m, by increasing the SVF from 1 – 4 % the average Nu number (Nuavg) increased by 35 % and 22 % in Re = 8,000 and 40,000, respectively.

Keywords

• Two-phase analysis
• Nanofluid flow
• Wavy channel heat exchanger