This work assesses the thermal performance of gold nanofluid as a cooling liquid in a shell and helically coiled tube (SHCT) heat exchanger (HE) built at the bench scale. Tests planned under a multi-level factorial experimental design were carried out to evaluate the effects of the volumetric fraction of the gold nanoparticles, the volumetric flowrate of the working fluid, and the inlet temperature of the hot fluid (water) on the SHCT heat exchanger effectiveness. Spherical gold nanoparticles with a mean diameter of 14 ± 2 nm were produced using Turkevich’s method to be used at two concentrations of approximately 10−5 vol%. The heat transfer tests were performed at volumetric flowrates of 20, 30, and 40 l/h for both working fluids using heated water at inlet temperatures of 40, 50, and 60 °C. Results showed that the less concentrated nanofluids were comparatively more efficient, suggesting the presence of a range of gold concentration values for improving the heat transfer effectiveness.