Experimental Study of Heat Transfer Augmentation in Concentric Tube Heat Exchanger with Different Twist Ratio of Perforated Twisted Tape Inserts

In this study an experimental investigation has been carried out for heat transfer and pressure drop characteristics in a concentric double tube heat exchanger using perforated twisted (PT) tape inserts in inner tube of various twist ratio. The experiment was perform with perforated tape of two different twist ratio (p/w= 3, 4) and fixed axial pitch ratio (sx /w=0.625) and constant hole diameter ratio (d/w=0.208). The experiments were performed in counter flow manner of the fluid cold water flow in inner tube and hot water flow in annulus part. In this experiment Reynolds number varies from 1900 to 5200. For comparison experiments were also performed with typically twisted (TT) tape and plane tube. The experimental result shows that heat transfer rate and friction factor of plane tube and with TT tape insert. The result shows that nusselt number increases with decrease in twist ratio (p/w). PT inserts with p/w=3 and 4, provides nusselt number up to 26% and 14% higher than plane tube respectively, 10% and 8% higher than typically twisted tape respectively. In inner tube an average friction factor generated by PT tape with twist ratio d/w=3 and 4 is found up to 207% and 87% more than plane tube respectively, 46% and 38% more than TT tape respectively. The empirical correlation of nusselt number and friction factor are also developed by experimental results.