Heat transfer enhancement of heat exchanger tube with multiple square perforated twisted tape inserts: Experimental investigation and correlation development

The present study examines the augmentation in heat transfer and friction in a flow through heat exchanger tube with multiple square perforated twisted tape inserts. The experimental outcomes pertaining to Reynolds number (Re-n) from 5000 to 27000, perforation width ratio (a/W-T) from 0.083-0.333 and twist ratio (T-L/W-T) from 2.0-3.5 have been presented and discussed. Multiple square perforated twist tape brought out considerable enhancement in heat transfer rates over without square perforated multiple twisted tape and plain tube. The maximum enhancement is observed at a a/WT of 0.250 and T-L/W-T of 2.5. Correlations of Nusselt number, friction factor and thermal hydraulic performance are established in term of Reynolds number and geometrical parameter of twisted tape which can be used to predict the values of Nusselt number, friction factor and thermal hydraulic performance with considerably good accuracy. (C) 2017 Elsevier B.V. All rights reserved.