<p>Double-pipe helical heat exchangers are known for their enhanced heat transfer efficiency and compact design, making them ideal for applications where space is limited, and high performance is critical. This study enhances the thermal performance and compactness of double-pipe helical heat exchangers by integrating twisted tape inserts (TTI) and tungsten carbide/water nanofluids, which collectively boost turbulence, augment heat transfer rates, and optimize system efficiency. It is indicated that tungsten carbide has not been used as nanoparticles in double-pipe helical heat exchangers. The effects on the Nusselt number, thermal enhancement factor, pressure drop, and exergy efficiency are investigated across Reynolds numbers (Re) ranging from 5400 to 8400. Nanofluid concentrations of 0.1%, 0.2%, and 0.3% are examined. The numerical model’s accuracy is confirmed by comparing the results with the experimental findings, showing considerable agreement. Results show that both TTI and tungsten carbide/water nanofluids significantly boost heat transfer by increasing turbulence and enhancing thermal properties, leading to higher Nusselt numbers. The Nu enhancement ratio peaks at 130–153% with a 0.3% nanofluid concentration and TTI. The maximum pressure drop occurs with TTI and 0.3% nanofluid concentration. Nu ratios range from 118 to 147% with varying TTI and nanofluid concentrations. Exergy efficiency improves with increase in nanoparticle concentration, reaching a peak of 48–61% at 0.3%. The combination of TTI and 0.3% tungsten carbide/water nanofluid provides the highest thermal enhancement factor, outperforming the use of nanofluids alone. The numerical findings of temperature velocity, and pressure drop explain that the incorporation of TTI and nanofluids enhances turbulence and induces swirl flow, significantly improving heat transfer performance.</p>