Heat transfer enhancement in a tube with a twisted tape inserted for various length ratios

Abstract

ABSTRACT Energy efficiency is a major concern in pipe systems, particularly in applications where heat transfer is significant. Twisted tape insertion is used to enhance heat transfer in pipes. In this numerical study, twisted tapes with various length ratios (LR) (30–100%) were inserted into a tube filled with water. The tube surface was subjected to a uniform heat flux. The Nusselt number (Nu) and friction factor (f) variations were investigated for several Reynolds number values (Re) (2500–10,000) under hydrodynamically developed and thermally developing flow conditions between laminar and turbulent flows in the transition and low-turbulent regime. The results are validated with the available theoretical results and experiments. The maximum Nu enhancement is observed at an LR of 90% based on a factor of 1.55; an LR of 70% demonstrated a similar factor of ~1.5 and a friction factor 3.7 times more than that of plain tubes. This ratio provides the best results for the enhancement factor, which is 1.2 times higher at the maximum level. Consequently, an LR of 70% is considered to be sufficient to obtain an optimum combination of maximum heat transfer and minimum friction combination, and this combination is preferred over completely filling the tube with twisted tape.