Experimental and CFD Analysis of Heat Transfer Enhancement in a Double Pipe Heat Exchanger Using Twisted Tape Inserts

Abstract

This study presents a comprehensive experimental and numerical investigation of heat transfer enhancement in a double-pipe heat exchanger equipped with twisted tape inserts. The primary objective is to quantify the impact of induced swirl flow on thermal performance and flow resistance. Experiments were conducted using water as the working fluid in a horizontal double-pipe heat exchanger with a constant heat flux boundary condition. The Reynolds number ranged from 10,000 to 20,000, ensuring turbulent flow conditions. A continuous twisted tape insert with a twist ratio of 4.7 was employed inside the inner tube.

A three-dimensional Computational Fluid Dynamics (CFD) model was developed using the standard k–ε turbulence model. The numerical results were validated against experimental data. The findings reveal that twisted tape inserts significantly enhance the Nusselt number by approximately 2.3–2.9 times compared to a smooth tube, while the friction factor increases by 1.5–2 times. The thermal performance factor exceeded unity across all operating conditions, confirming the effectiveness of the technique. The CFD analysis provided detailed insight into the flow structure, demonstrating strong swirl and secondary flow formation.

The results confirm that twisted tape inserts represent an efficient passive technique for heat transfer enhancement in compact heat exchangers.