Article

Amit Ranaware, PES’s Modern College of Engineering, Pune, India; S.Y.Bhosale ,PES’s Modern College of Engineering, Pune, India

Heat transfer augmentation without considerable pressure drop is one of the most important issues now a days. The different active and passive methods are used for the same. One of the passive technique is use of dimples. A depression forming recesses on a flat surface is considered as a dimple. Variation in dimple geometry results in various heat transfer and friction characteristics. Introducing the dimples on the surface not only increases the surface area available for heat transfer but also reduce the hydrodynamic resistance for the fluid flow over the surface, resulting in less pressure drop. The present work is based on experimental investigation of the forced convection heat transfer over the V-shaped dimpled surface. The experiments were performed on 150mm × 150mm × 15mm aluminium plate with V- shaped dimples with pitch 3.2D, where D = diameter of dimple. V-dimples with δ/D = 0.2, 0.3, 0.5 are investigated, where δ= dimple depth. The experimentation was carried over a rectangular duct with aspect ratio 3:2. Heat transfer coefficient, Nusselt Number, friction factor and overall thermal performance of dimpled surface are compared with those from flat surface under same conditions. It is found that dimpled surface show 30- 45% enhancement over a flat plate. The maximum enhancement is observed in δ=0.3D in inline pattern. The dimpled surface with δ=0.5D shows minimum enhancement. Maximum frictional losses are observed in δ=0.5D dimpled surface and minimum in δ=0.2D dimpled surface. The overall thermal efficiency goes on increasing with increasing Reynolds number for all cases. The enhancement was verified using CFD analysis using ANSYSIS-15 ICEM software using k-ε turbulence model.