HEAT TRANSFER ENHANCEMENT OF TURBULENT FLOW THROUGH A CIRCULAR DUCT WITH TWISTED TAPE INSERT. Suvanjan Bhattacharyya 1 , Vivek Kumar Roy 2 , Anirban Roy 2 , Sushovan Chatterjee 2 1 Assistant Professor, Mechanical Engineering Department, MCKV Institute of Engineering, Howrah. West Bengal. 2 Undergraduate Student of Mechanical Engineering Dept, Seacom Engineering College, Howrah. West Bengal. 2 Undergraduate Student of Mechanical Engineering Dept, MCKV Institute of Engineering, Howrah. West Bengal. 2 Undergraduate Student of Mechanical Engineering Dept, Adamas Institute of Technology, Barasat. Kolkata. 1 Email id - suvanjanr@gmail.com, Mob - 09477410056 Absrract - 3-D numerical simulations are performed for heat transfer and fluid flow characteristics of the tubes fitted with twisted-tape inserts. The principle of heat transfer enhancement in the core flow of tube has been proposed to improve the temperature uniformity and reduce flow resistance. Twisted inserts widths w = 12 mm have been investigated for different inlet volume-flow rates. The simulation results show that the average overall heat transfer coefficients in circular plain tubes are enhanced with twisted- tape of widths by as much as 100% at a constant tube-side temperature and the friction factor are enhanced. The twisted-tape-induced swirl flow heat transfer due to exponentially increasing heat inputs with various exponential periods and twisted-tape-induced pressure drop were sytematically meseared. Keywords: Twisted-tape, Swril Flow, Turbulence, Heat transfer enhancement. 1. Introduction: Turbulent flow is encountered in many industrial applications. In case of turbulent flow, there is major thermal resistance in the bulk flow in addition to the dominant thermal resistance in the thin boundary layer adjacent to the flow. Twisted-tape inserts are, therefore, used to mix the gross flow effectively in turbulent flow to reduce the thermal resistance in the core flow through the channel. Resistance to heat transfer from or to a fluid is mainly due to the slowly moving layers of fluid near the hot or cold wall, so as to enhance the heat transfer these layers should be disturbed or disturbed. In passive enhancement, to create this disturbance we provide some irregularities to the solid surface or wall. Transverse rib is made as integral surface to the duct wall. Farrel et al. [1] tested one fully- ribbed and two broken ribbed flat radiator tube. Olsson and Sunden [2] tested two ribbed radiator tubes with airflow. The enhanced tubes showed higher friction factors than the smooth tube in both laminar and turbulent regions. Olsson and Sunden [3] investigated the effect of rib configurations for the multiple V-ribbed channel. Initially, only full-length twisted-tape extending all over the length of the duct had been used. Subsequently, many variations of twisted tapes have been used to improve the thermohydraulic performance. Also, twisted tapes in combination with other enhancement techniques have been used. Saha and Dutta [4] have observed that, for regularly spaced twisted-tape elements, thermohydraulic performance of twisted tapes with multiple twists in the tape module is not much different from that with single twist in the tape module. Twisted