Synthesis, characterization, measurement and modeling thermal conductivity and viscosity of nanofluids containing S,N-GQDs in water, ethylene glycol and their mixtures

Abstract

The objective of this article is to investigate nanofluids composed by S, N doped graphene quantum dots (S,N-GQDs) nanoparticles dispersed in water, ethylene glycol and mixture of water and ethylene glycol (60:40) in a concentration up to 0.9% in weight fraction. The S,N-GQDs have been prepared via simply chemical vapor deposition method. The characteristics of the powder are analyzed and discussed. Then the transient hot-wire technique is used to determine the thermal conductivity and the effects of both weight fraction and temperature are evaluated. The maximum thermal conductivity enhancement reaches up 66, 58 and 33% for the nanofluid containing 0.9% S,N GQDs at 50 °C in water, ethylene glycol and water- ethylene glycol mixture (60:40) as base fluids respectively. Also the viscosity of S,N-GQDs nanofluids are measured. The results showed that the viscosity of nanofluids increased with increasing weight percentage of S,N-GQDs nanoparticles and decreased with increasing of temperature. Finally, the experimental values are compared with artificial neural network (ANN) models proposed for thermal conductivity and viscosity estimation. The overall predicted thermal conductivities and viscosities of nanofluids are in excellent agreement with experimental data with AAD = 0.94% and R2 = 0.99912 for thermal conductivity and AAD = 0.95%, R2 = 0.99905 for viscosity.