Performance Comparison of Twisted Tape and Screw Tape Inserts in Square Duct
Effects of insertion of a full length twisted tape and full length screw tape insert in a concentric double pipe heat exchanger ,square duct inner, and circular annulus on heat transfer and pressure drop characteristics were experimentally studied. Experiments were carried out under constant wall temperature using water as working fluid. Stainless steel twisted tape and screw tape inserts have equal twist ratio(y=4.0).Cold water flows through inner square duct, and hot water flows through circular annulus, in counter current fashion. Screw tape inserts found better over twisted tape from thermal performance point of view. Results of the Isothermal friction factor for the present twisted tape and helical screw-tape are higher than those for the plain duct around 7.7 times and 14 times respectively. Experiments were conducted well within laminar region. Over entire investigated laminar range, mean Nusselt number for the present twisted tape and helical screw tape are higher than those for the plain duct around 2.85 times and 5.3 times respectively. Further, Thermal performance ratio of twisted tape and screw tape inserts were found 2.81 and 3.52 times the plain square duct on constant pumping power respectively.
Enhancement heat transfer; Square duct; Isothermal friction; Helical screw-tape with Core-rod; Twisted tape
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Published by INSIGHT - Indonesian Society for Knowledge and Human Development