Enhancement of Heat Transfer in Double-Pipe Heat Exchangers Using Wavy Edge Twisted Tape With Varying Twist Ratios and Perforated Diameters

Abstract

A computational simulation of an enhanced double-pipe heat exchanger equipped with inserted twisted tape. The Navier–Stokes, energy, and turbulence equations were employed to represent fluid flow and heat transmission, utilizing a k–ε model for turbulence. ANSYS Fluent 22 is used to solve the governing equations and investigate how the perforated wavy edge tape, along with the diameter of its holes (5, 15, and 30 mm), twisting ratio of a wavy edge twisted tape ratio (0.5, 1, 1.5, 2, 2.5, and 3), affects heat transfer and pressure drop at ranging Reynolds numbers (6957–187,837), compared to a plain tube. Hot air is utilized in the inner tube, which incorporates twisted tapes to enhance turbulence and heat transfer and cold oil in the outer tube to establish a counter-flow system and experience the improved flow's effects. Results demonstrate significant improvements in oil outlet temperature. The Nusselt number (Nu) increases with increasing Reynolds numbers and twist ratios; the enhanced tubes increase Nu and friction factor by about 41% and 2.6 times greater than the smooth tube. Increasing the Reynolds number and twisted tape ratio generally leads to higher heat transfer rates and pressure drop. Optimal configurations of PWETT with Tr = 2 and WET with a hole diameter of 30 mm gave the best thermal performance index (1.11 and 1.24) when balancing heat transfer and pressure drop. The findings provide valuable insights for designing and optimizing heat exchangers in applications demanding efficient heat transfer.