Thermal equilibrium time as a novel characteristic of nanofluid evaluation: An experimental investigation of distilled water-based binary and ternary nanofluids

Abstract

Nanofluids enhance thermal energy transfer in energy storage applications. Proper nanoparticles are crucial, especially regarding their thermophysical properties. This work fabricated a novel instrument to evaluate a mixture of distilled water-based ternary and binary nanofluids. This work prepared novel ternary and binary nanofluids by mixing multi-wall carbon nanotubes (MWCNTs), magnesium oxide (MgO), and boron nitride (BN) into distilled water at various volume concentrations. The instrument that has been fabricated measures the time taken by the nanofluids to reach a thermal equilibrium state as a new characteristic to evaluate and compare the thermal potential of nanofluids, which alleviates the dependence on other instruments that are occasionally inaccessible or costly for researchers. Thermodynamically, this instrument enables the assessment of nano-energy, manifested as the heat transferred to the nanofluid while reaching an equilibrium state. The results verified the purpose of the proposed instrument; the novel characteristic was affected perfectly by increasing the volume concentration of the nanoparticles in the base fluid. All nanofluids prepared with a concentration of 0.5 % emerged as the most effective in achieving thermal equilibrium in a shorter time than the other concentrations. The ternary hybrid nanofluid MWCNTs–MgO–BN with a volume concentration of 0.5 % had the shortest thermal equilibrium time, 157 s. MWCNTs–MgO–BN ternary hybrid nanofluids transferred 8.3, 5.8, and 11.8 % more heat than MWCNTs–MgO, MWCNTs–BN, and MgO–BN binary hybrid nanofluids. The thermophysical essence behind the result obtained by the created instrument lies in the fact that it generated a new approach to evaluating the nanofluids, thanks to which it was possible to evaluate and find out which fluid has the highest thermal conductivity. The uncertainty analysis showed error acceptability in the experimental instrument, with an average uncertainty value percentage for all presented composites of ± 0.936 %.