The convective heat transfer and friction factor of two different water-based nanofluids, i.e., Ag–water and SiO2–water are examined experimentally in helically coiled tube with uniform heat flux boundary condition. The dynamic viscosity and thermal conductivity of nanofluids are gauged experimentally in different volume fractions and temperatures. The Reynolds number is varied from 1040 to 2120. The effects of geometric characteristics such as pitch circle diameter and coil diameter are also inspected. The outcomes indicate that using nanoparticles in coiled tubes can be more effective in increasing the heat transfer rate than the straight tube. The performance evaluation criterion is calculated and it is found that the highest value is 3.57 for Ag nanofluid in Re = 1336. Finally for predicting the Nusselt number and friction factors, empirical correlations are extracted based on experimental data.