Experimental studies are performed to evaluate the stability of zinc oxide (ZnO) nanoparticles suspended in a mixture of ethylene glycol and water with weight ratio of 40–60 as the base fluid. Different methods have been employed to disperse ZnO nanoparticles. It is found that using Gum Arabic leads to clustering and settle the nanoparticles. Also, the use of DI ammonium hydrogen citrate with weight ratio 1:1 (surfactant:nanoparticles) gives the acceptable stability. The density of nanofluids is measured and the results are compared with theoretical results. A helpful correlation for the measured densities of the stable nanofluids in a temperature range of 25–40 C is presented which can used in practical applications. Finally based on the correlation a sensitivity analysis has been done. It is found that at higher temperatures the density is more sensitive to the increases in volume fraction.

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