Numerical Analysis of Helical Coil‐Inserted Tubes Based on Thermohydraulic Performance and Development of Correlations for Heat and Fluid Flow

ABSTRACT This study presents a numerical investigation on the thermohydraulic performance of tubes fitted with wire coil inserts under turbulent flow conditions to enhance heat transfer (HT) efficiency in compact thermal systems. Conventional smooth tubes face limitations due to boundary‐layer formation, which resists convective HT; therefore, wire coil inserts are employed to disrupt this layer and increase turbulence. The objective of this research is to determine the influence of wire coil geometry on HT and pressure drop and to develop empirical correlations for predicting the Nusselt number and friction factor. Numerical simulations were carried out using ANSYS Fluent with the renormalization group k – ε turbulence model validated against the Dittus–Boelter correlation. Water was used as the working fluid, and wire coil diameters of 0.5, 1, and 1.5 mm with pitches of 21, 24, 28, and 31 mm were analyzed for Reynolds numbers ranging from 4500 to 9000. Results indicated that a wire coil of 1 mm diameter and 24 mm pitch provided the best combination of HT enhancement and moderate pressure drop, achieving an average Nusselt number improvement of about 110% compared with a smooth tube. The thermohydraulic performance factor ranged between 1.62 and 1.20, confirming significant enhancement up to a Reynolds number of 10,000. Regression‐based correlations for Nusselt number and friction factor were developed, showing strong agreement with simulation data ( R 2 = 0.94 and 0.89, respectively). The developed correlations serve as reliable tools for predicting the performance of coil‐inserted tubes in practical heat exchanger design.