experimental investigation on the thermal conductivity and viscosity of zno nanofluid and development of new correlations

in this paper, the measurement of the viscosity of zno in ethylene glycol, propylene glycol, mixture of ethylene glycol and water (60:40 by weight), and a mixture of propylene glycol and water (60:40 by weight) and the thermal conductivity in ethylene glycol and propylene glycol as base fluids in the range of temperature from 25 ºc to 60 ºc are investigated. the results indicate that as the temperature increase the viscosity of nanofluid decrease and the thermal conductivity of both base fluid and nanofluid increase. several existing models for thermal conductivity and viscosity are compared with the experimental data, and they do not demonstrate good comparison agreement. finally, some new models for predicting the effective viscosity and thermal conductivity are proposed. furthermore, the viscosity of the base fluid affects the thermal conductivity variation of the nanofluids. the results indicate that the largest enhancements in thermal conductivity are 15% and 9% for eg and pg as base fluids, respectively.