Numerical Investigation of Heat Transfer Characteristics of a Double-Pipe Heat Exchanger using Inner Corrugated Tube and Perforated Elliptical Turbulator

Abstract

This study presents the numerical analysis of thermal–hydraulic properties in a double pipe heat exchanger fitted with an inner corrugated tube and perforated elliptical strip turbulators. The three-dimensional CAD model was developed in SolidWorks, while the simulations were performed using ANSYS Fluent with the Realizable k–ε turbulence model and enhanced wall treatment. A total of eight geometric configurations were studied by changing the corrugation pitch: 15 mm, 20 mm, 25 mm, turbulator width: 3.6mm, and 4.4 m, with changing inclination angle between 15° and 20°. The computational approach has been validated against the Gnielinski and Blasius correlations for smooth tubes and experimental data from literature, ensuring accuracy below 10% for both the Nusselt number and friction factor. It was observed from the results that the heat transfer enhancement with the insertion of turbulators is very significant compared to a plain tube. For approximately the same value of Re≈18,000, the Nusselt number for Case 8 (p = 15 mm, W = 4.4 mm, α=20) is over 260, while for the smooth tube it is only 110. However, this enhancement in heat transfer is associated with higher frictional losses, since friction factor values increase up to 0.42 against 0.03 for the plain tube. As far as the thermal performance factor is concerned, in terms of an effective trade off, the best values were at low Reynolds numbers, where Case 8 gave the maximum value of 1.57 at Re=6000, although at higher flow rates its effectiveness reduces to about 1.0-1.1. In summary, the results clearly show that reducing the pitch and increasing the turbulator inclination significantly enhances the heat transfer but at the price of higher pumping power requirements. Among all the geometries tested, Case 8 gives the best configuration for maximum improvement in thermal characteristics, hence promising applicability in high performance heat exchanger systems.