This paper analyze the use of extended surfaces in circular tube to enhance heat transfer. Heat transfer parameters in simple circular (SC) tube without insert, with rectangular insert (RI), with twisted insert (TI) and with wave insert (WI) have been calculated and compared. The heat transfer in air for Reynolds number having range from 5000-15000 was studied experimentally and numerically in a simple circular tube and in three extended surfaces
of different design with same surface area (One insert area:0.000680m2). In present study, design of experiment (DOE) is used to develop the experiment
layout. Total five factors are selected i.e. Extended surface, velocity, heat flux, material of tube and air pressure in domain. The experimental results are
validated by CFD simulation. It is concluded that extended surfaces improve heat transfer rate in circular tubes. The rectangular insert of extended surface is optimum among all tested combinations.
Computational fluid dynamics, Forced convection, Heat transfer, Extended Surface, Nusselt number, S/N Ratio