Experimental Study on MWCNT–Graphene/Water Hybrid Nanofluids Preparation, Characterization, Thermophysical Characteristics, and Rheology for Heat Transfer

Abstract In many applications, conventional process fluids are insufficient to achieve high-intensity heat transfer. Hybrid nanofluids (HNFs) are advanced heat transfer fluids primarily utilized for thermal energy transportation in various applications. This study aims to characterize multiwalled carbon nanotube (MWCNT) and graphene nanoparticles with scanning electron microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared using instrument QUANTA 450, Rigaku Ultima IV, and SHIMADZU IRSprit, respectively. Different concentrations of HNFs were prepared consisting of MWCNT and graphene in water. The two-step technique employed for HNFs preparation involves stirring and sonication. Moreover, ultraviolet (UV) spectroscopy and particle size analysis (PSA) are used to characterize HNFs. Furthermore, the thermal and physical properties of HNFs are examined by experimental methods, covering a temperature range of 25 °C–75 °C. The investigational results demonstrate that the thermal conductivity improves by 32.87% for 0.03 vol. %, as temperature rises to 75 °C, when compared to water. Specific heat rises with temperature, while it reduces with nanoparticles' loading. The HNF's dynamic viscosity decreases with an increase in temperature. Density improves with the addition of nanoparticles. Rheology shows Newtonian behavior across the entire range of shear rates. Prepared HNFs are commended as a medium for heat transfer in numerous fields.