Numerical and Experimental Determination of Thermal Performance of Perforated Variable Pitch Twisted Tape Insert

Abstract

In recent years, studies are being done to enhance heat transfer techniques to reduce the thermal resistance either by increasing the effective heat transfer surface area or by generating turbulence. To achieve this, in tube in tube heat exchangers, variety of tube inserts such as twisted tape, wire coil, swirl flow generator etc. are used. The effectiveness of a heat transfer enhancement technique is evaluated by the Thermal Performance Factor which is a ratio of the change in the heat transfer rate to change in friction factor. In this research work, different types twisted tape tube inserts with variable geometries like variable twist pitch of twisted tapes, twisted tape with perforations; winglets etc., are studied in order to comprehend the prevailing mechanism of fluid flow and heat transfer. Accordingly an attempt has been made to explore new geometry of twisted tape having perforations with variable pitch. This new geometry will be numerically and experimentally studied to elucidate the fluid flow behavior that controls the heat transfer rates across the thermal boundary layer attached to the tube wall.