Study of a perforated hollow cylinder and twisted tape inserts as a compound device in a circular tube for heat transfer enhancement

Abstract

In the present study, the effect of perforated hollow cylinders and twisted tapes on fluid flow and heat transfer behavior of a circular tube is presented for the Reynolds number ( Re) range of 6000–40,000. The diametrical ratio ( DR) and perforation index ( PI) of compound devices are varied to determine the Nusselt number ( Nu) and friction factor ( f) for the combined perforated hollow cylinder (PHC) and twisted tape (TT) insert. The maximum value of Nusselt number ratio is found to be 3.19 and the minimum value of the friction factor ratio is obtained as 2.24. The PHC–TT combination provides the maximum thermal enhancement factor (TEF) of 2.43 for PI = 8%, and DR = 0.5.