Graphene has piqued the interest of many researchers due to its superior mechanical, thermal, and physiochemical properties. Graphene nanoplatelets with covalently functionalized surfaces (CF-GNPs) were employed in turbulent-heated pipes to undertake thermal and economic studies. CF-GNPs and distilled water were used to make the current nanofluids at various mass percentages, such as 0.025, 0.05, 0.075%, and 0.1 wt.%. In the range of 6, 401 Re 11, 907, the thermal system was heated up to 11, 205 W/m2 under fully developed turbulent flow conditions. Field emission scanning electron microscopy (FE-SEM), zeta potential, nanoparticle sizer, and field emission transmission electron microscopy (FE-TEM) were used to examine the morphological features and characterise the particles. In addition, the current thermal system's economic performance was assessed to estimate its price-to-operate ratio. There was a 16.10% reduction in heat exchanger size for 0.025 weight percent, 0.05 weight percent, 0.075 weight percent, and 0.1 weight percent. In addition, the power needed for the base fluid was 422 W, which was then lowered to 354 W, 326 W, 315 W, and 298 W for 0.025 wt.%, 0.05 wt.%, 0.075 wt.%, and 0.1 wt.%, respectively.
