Eur. Phys. J. Plus (2022) 137: 668
https://doi.org/10.1140/epjp/s13360-022-02782-9

Regular Article

The dual behavior of the dynamic viscosity of multiwalled carbon nanotubes–Al₂O₃ (3:7)/ethylene glycol hybrid nanofluids: an experimental study

Department of Mechanical Engineering, Imam Hossein University, Tehran, Iran

^a M.hemmatesfe@semnan.ac.ir

Received: 16 January 2022
Accepted: 29 April 2022
Published online: 7 June 2022

Abstract

This study investigates the behavior of nanofluids containing multiwalled carbon nanotubes (MWCNT) and Al₂O₃ nanoparticles based on ethylene glycol. To that end, the MWCNT and Al₂O₃ nanoparticles were combined in 3:7 ratios. The nanofluids in solid volume fractions (SVFs) of 0.04–0.3%, at a temperature range of 25–50 °C and different shear rates, were prepared and investigated. The nanofluids displayed two different behaviors: non-Newtonian behavior in 0.3% SVF and Newtonian behavior in all other SVFs. Increasing the nanofluid temperature at constant SVF decreased its viscosity. Response surface methodology was used to develop a model to predict nanofluid viscosity with a regression coefficient of 0.96, which indicates the model's suitability. The viscosity sensitivity to SVFs indicated the significant impact of the concentration on nanofluid in 0.3% SVF.