<p>A double-tube heat exchanger efficiently transfers heat between two fluids, offering compact designs, easy maintenance, and enhanced heat transfer in numerous applications. In this study, perforated twisted tapes and titanium oxide (TiO₂) nanofluids are employed to enhance heat exchanger performance by overcoming limitations of conventional systems and significantly improving thermal efficiency. The turbulent flow conditions with Reynolds numbers between 7200 and 11,700 are applied with investigating the effects of introducing TiO₂ nanofluids at volume concentrations of 0.1%, 0.2%, and 0.3%. Model validation is accomplished by comparing the results with experimental data, demonstrating high accuracy. Findings indicate that both the nanofluid addition and the integration of perforated twisted tape significantly enhance the heat exchanger performance. Using perforated twisted tape alone enhances the Nusselt number ratio, ranging from 129 to 144%. Applying TiO₂ nanofluid concentrations of 0.1, 0.2, and 0.3%, the ratio further rises to 150%-164%, 157%-170%, and 162%-177%, respectively. Using only perforated twisted tape increases the pressure drop ratio, ranging from 174 to 183%. With the application of 0.3% TiO₂ nanofluid, the pressure drop ratio increases to 192%-199%. Perforated twisted tape increases pressure drop by obstructing flow, while TiO₂ nanofluid raises viscosity and friction. The results provide comprehensive insights into the temperature and pressure profiles inside the heat exchanger.</p>