ABSTRACT. The present study addresses an experimental investigation on the influence of the concentration of nanoparticles and temperature on nanofluid's viscosity and establishes a numerical correlation for predicting the nanofluid's viscosity. In this study, silver nanoparticles (Ag) with a size of 20 nm were used to prepare the nanofluid with water as the base fluid. The concentrations of silver nanoparticles were fixed as 0.01, 0.05, and 0.1% by volume in the range of temperature from 20 to 60oC. The findings of the current investigations report that the nanofluid's viscosity increases with volume fractions of nanoparticles and decreases as the temperature increases. The theoretical correlations in the literature under predict the viscosity of silver-water nanofluids, which has led to the development of a new relationship for determining the nanofluids' effective viscosity from the experimental findings of this research. The proposed model as outcome of the current investigation confirms a reasonable agreement with the experimental data.
 
 KEY WORDS: Silver nanoparticles, Nanofluid, Viscosity, Volume Concentration, Temperature
 
 Bull. Chem. Soc. Ethiop. 2023, 37(2), 505-514. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i2.18