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Heat transfer and pressure drop characteristics in a circular tube fitted with regularly spaced twisted-tape elements have been investigated experimentally. Laminar swirl flow of a viscous fluid having intermediate Prandtl number range was considered. The swirl was generated by regularly spaced twisted-tape elements with single twist in the tape module and connected by thin circular rods. The tape-width and the rod diameter were both varied. The effect of higher-than-zero phase angle between consecutive tape elements have been studied. Heated as well as isothermal friction factor data has been generated. The heat transfer test section was heated electrically imposing axially and circumferentially constant wall heat flux (UHF) boundary condition. Reynolds number, Prandtl number, twist ratio, space ratio, tape-width, rod-diameter and phase angle govern the characteristics. `Pinching' of the tapes in place rather …