investigation of nanoparticles morphology on viscosity of nanofluids and new correlation for prediction

this article presents an experimental investigation on effects of morphology of nanoparticles on the viscosity nanofluids (nfs). water and ethylene glycol were used as base fluids. a two step method was used for preparation of nfs. sio2 nanoparticles, cnt and graphene nano sheets were dispersed in the base fluids separately with the volume fraction ranging from 0.05% to 1.5%. stability of the nanoparticles was established by adding adequate surfactant and sonication enough time. then viscosity of the nfs was measured by brookfield viscometer at fix ambient temperature. first, it has been concluded that, viscosity of nfs increases significantly with increasing of nanoparticle volume fraction. then the results of theoretical models (einstein, brinkman, batchelor and wang) were compared with experimental data and the deviation of theme was calculated. in order to reduce of this deviation, a correlation was developed based on the geometry of nanoparticles. the modified models showed reasonably better agreement with the experimental results