A Numerical Investigation Based on Heat Transfer and Fluid Flow Characteristics of Air in a Circular Tube Heat Exchanger with Inclined Ribs

Abstract

This paper encapsulates the results of a numerical investigation based on heat transfer and fluid flow characteristic of water through a two-dimensional model of an isothermal-fluxed circular duct with alternating inclined ribs. The effects of artificial inclined rib’s roughness on heat transfer and fluid flow have been investigated. A 2-D numerical simulation is performed using the ANSYS FLUENT 15 code. The simulation is conducted in order to gain an understanding of physical behaviour of the thermal and fluid flow in the duct fitted artificial inclined ribs under constant wall temperature conditions for all three flow regimes—Laminar, Transitional and Turbulent; that is, for the Reynolds number ranging from 200 to 20,000. The Navier–Stokes equation in common with an energy equation is solved using the SIMPLE technique with Shear Stress Transport (SST) k–ω turbulence model. The heat transfer and thermal performance of the inclined ribs at various attack angles (θ) of 15°, 30°, 45° and 60° with different Reynolds number (200–20,000) are studied and compared with those of a plain isothermal-fluxed circular duct. The Nusselt’s number increases with the increase of attack angle (θ = 15°–60°), also increase of Reynolds number. All ribs at different angle of attack (θ = 15°, 30°, 45°, 60°) have good thermal performance with greater than unity which indicates that the compound heat transfer technique of inclined ribs with different angle of attack is commendable for the maximum enhanced heat transfer rate for higher Reynolds number.