Experimental investigation on pH and stability of distilled water ethylene glycol mixture with graphene nanoplatelets

Abstract

An efficient heat transfer medium improves the overall efficiency of the equipment, and the main difficulty is with making well-dispersed nanoparticles in base fluids. The current research is focused to study the effect of different surfactants on nanoparticle dispersion and enhancement through property modifications. The stability and pH value of various surfactants with varying sonication duration were studied and compared with the graphene nanofluids. The graphene nanofluids were prepared by a two-step method by dispersing 0.1 wt% graphene nanoparticles in distilled water and ethylene glycol with a ratio of 70:30. The surfactants namely Cetyltrimethylammonium bromide (CTAB), Polyvinylpyrrolidone (PVP K-30), and Polysorbate 60 (Tween 60) of each 0.1 wt% were used for stabilizing the nanofluids. The duration of the sonication process was set as 60, 90, and 120 min respectively followed by the magnetic stirring for 60 min duration. The stability behavior of nanofluids was studied through visual inspection, UV spectrum, and zeta potential techniques, and the corresponding pH values were measured to correlate with the performance of the heat transfer equipment. The results showed that the dispersion of graphene nanofluids strongly depends on the type and amount of dispersant in the absolute value of zeta potential. Finally, the optimum conditions were found based on the enhanced stability, pH, and sonication time of graphene nanoplatelets in distilled water-ethylene glycol mixture with Polyvinylpyrrolidone (PVP K-30) as a surfactant for the battery thermal management systems (BTMS) in electric vehicles.