320 | International Journal of Thermal Technologies, Vol.4, No.4 (Dec 2014) Research Article International Journal of Thermal Technologies E-ISSN 2277 – 4114 ©2014 INPRESSCO ® , All Rights Reserved Available at http://inpressco.com/category/ijtt/ Numerical Heat Transfer Study of Turbulent Square Duct Flow through W-Type Turbulators Sagar S. Desai Ȧ* , Rupesh J. Yadav Ȧ and Omkar R. Chavan Ȧ Ȧ Mechanical Department, Pune University, MIT College of Engg. Pune-411028, India Accepted 30 Dec 2014, Available online 31 Dec 2014, Vol.4, No.4 (Dec 2014) Abstract Several cooling technique have been developed to enhance heat transfer in square duct. Different rib arrays inside square channel are widely used to enhance heat transfer rate. The reason that ribs increase the fluid flow turbulence near the wall, disrupt the boundary layer and also increase the heat transfer area. In this paper, numerical analysis is carried out three different angles of turbulators were placed in square duct. All turbulators located on bottom side wall of duct. The numerical simulation are carried on square duct having hydraulic diameter (Dh) of 0.05m. Air is working fluid with the flow rate in terms of Reynolds number ranging from 15,000 to 20,000. Details for rib height (e), pitch distance between turbulators (P) and turbulators angle are similar to experimental reference. The model is creating using Ansys ICEM software. Numerical simulations were performed using the CFD software package ANSYS 14.5 FLUENT. Turbulence closure was achieved using k-ε turbulence model, with enhance wall treatment for the simulation were used. In this, the heat transfer characteristics of square duct with internal w-shaped ribs with different angles and pitch ratio 0.3 were plotted. Keywords: Turbulators, FLUENT, Rib, Heat transfer, square duct 1. Introduction 1 The need of high performance thermal system in many engineering application. Need to find various techniques to improve heat transfer in system. In convention area heat transfer improved by means of various augmentation techniques. Means increase the heat transfer area by ribs, protrusion and roughness. However, the thermal/hydraulic performance of the ribs is affected by many factors including the holes in a rib, size and spacing. Since 1980’s many experimental and numerical work have been carried out on heat transfer in cooling passage tube and duct. Han et al.carried out combined effects of the rib angle- of-attack and the channel aspect ratio on the local heat transfer distributions in square and rectangular channels with two opposite rib-roughened walls for Reynolds numbers from 10,000 to 60,000. The rib angle-of-attack was varied from 90 0 to 60 0 , to 45 0 , and to 30 0 , whereas the corresponding channel width-to-height ratio was varied from 1 to 2 and to 4, respectively. It was concluded that the highest heat transfer and the accompanying highest pressure drop can be obtained at α = 60 0 in the square channel, the highest heat transfer and the highest pressure drop occur at α = 90 0 in the rectangular channel with a channel aspect ratio of 4. Dhanasekaran et al.carried out Computational analysis of mist/air cooling in a two-pass rectangular rotating channel with 45-deg angled rib turbulators. The results *Corresponding author: Sagar S. Desai show that the mist cooling enhancement is about 30% at the trailing surface and about 20% at the leading surface of the first passage with 2% mist injection. In the second passage, 20% enhancement is predicted for both the surfaces. Tatsumi et al.carried out detailed Numerical simulation for heat and fluid characteristics of square duct with discrete rib turbulators. It was observed that predicted stream wise distribution of Nusselt number is in good agreement with the experimental data for both arrays. Murata et al. carried out Effect of cross-sectional aspect ratio on turbulent heat transfer in an orthogonally rotating rectangular duct with angled rib turbulators. Heat transfer in a rotating rib-roughened rectangular duct was numerically simulated by using the large eddy simulation with a Lagrangian dynamic sub grid-scale model. It was observed that the effect of the rotation in the 60 0 rib- roughened duct induced the larger spatial variation in the local heat transfer, and the heat transfer was increased and decreased on the pressure and suction sides. Liu et al present an experimental study on Heat transfer characteristics in steam-cooled rectangular channels with two opposite rib-roughened walls. Most of investigation, have focused on heat transfer characteristics for rib height and spacing ratio for transverse, angled, continuous or broken, square rib. In this present work, the numerical computation for 3-D turbulent flow over the W- discrete thin ribs mounted repeatedly on one side of heated wall of square duct. The main aim being to examine the change in heat transfer characteristics.