A set of experiments wereperformed to investigate the effect of two different techniques of heat transfer enhancement: nanofluidics and helical coiling. The convectionheat transfer behavior of multi-walled carbon nanotube (MWCNT)/water nanofluids through helical coiled tubes with different geometries was reported. 0.1, 0.3 and 0.5% particle weight concentration of MWCNT in distilled water were prepared using two-step method and the effects of a wide range of different parameters such as Reynolds and Helical numbers, geometrical parameters of the coils and nanofluid weight fractions were studied. It was observed that by increasing the Reynolds number or weight concentration of nanofluid, the Nusselt number increases considerably. The maximum thermal performance factor at 4.24 was achieved in this study. Also, the helical coiling technique showed better performance than nanofluidics in these experiments. In addition, the empirical correlations were developed for Nusselt number and pressure drop in terms of Helical number, Prandtl number and weight concentration fit to the experimental data within +25% and -20%.

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