Mathematical Investigation on Laminar Forced Convection in Square Channel with

U-Shaped Rib Turbulator

 Withada Jedsadaratanachai

Department of Mechanical Engineering, Faculty of Engineering

King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand

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and Amnart boonloi

Department of Mechanical Engineering Technology, College of Industrial Technology

King Mongkut’s University of Technology North Bangkok, Bangkok 10800, Thailand

Manuscript received May 2, 2014

Revised May 20, 2014

Abstract

Periodic laminar flow and heat transfer characteristics in a three–dimensional (3D) isothermal square channel walls with 45° U-shaped rib turbulators, URT, were investigated numerically. The computations are based on the finite volume method (FVM), and the SIMPLE algorithm has been implemented. The fluid flow and heat transfer characteristics are shown for Reynolds numbers based on the hydraulic diameter of the square channel, Re = 100 to 1000. To generate main longitudinal vortices flows through the tested section, URT with an attack angle of 45° are inserted in the tested square channel. Effects of different blockage ratio (b/H, BR) with a single pitch ratio (P/H, PR) of 1 on heat transfer and pressure loss in the channel are studied. It is apparent that in each of the main vortex flows, longitudinal twisted vortex flows can induce impinging flows on a wall of the interbaffle cavity leading to a drastic increase in heat transfer rate over the channel. In addition, the rise in the URT height results in the increase in the Nusselt number and friction factor values. The flow structures with common–flow–down are appeared by using URT. The computational results show that the optimum thermal enhancement factor is around 2.5 at BR = 0.25 and, Re = 1000. 

Keywords: Forced convection; Heat transfer; Laminar flow; Periodic flow; Turbulators;

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