Heat Transfer and Pressure Drop Characteristics of Turbulent Flow In a Tube Fitted With Conical Ring and Twisted Tape Inserts

Abstract

The present work shows the results obtained from experimental investigations ofthe augmentation of turbulent flow heat transfer in a horizontal tube fitted withcombined conical-ring turbulators and a twisted-tape swirl generator. The air is theworking fluid for Reynolds number range of 5000-23000 under constant wall heatflux thermal boundary condition. In this study, two enhancement heat transferdevices are used. One is the conical-ring used as a turbulator and placed in thetested tube with constant diameter ratio (d/D=0.538) and the other is the twistedtapeswirl generator placed at the core of the conical-rings. Three twisted-tapes ofdifferent twist ratios, Y=2, 3, and 6, are introduced in each run. The experimentaldata obtained are compared with those obtained from the plain tube and from theliterature to ensure the validation of experimental results. Correlations for Nusseltnumber, friction factor, and enhancement efficiency are developed. It is observedthat the heat transfer process enhances by using combined conical-ring andtwisted-tape inserts or each one alone when compared to plain tube at the samemass flow rate, and this enhancement increases as twist ratio decreases for thecase of combined insertion.