Improving the thermal conductivity of ethylene glycol by addition of hybrid nano-materials containing multi-walled carbon nanotubes and titanium dioxide: applicable for cooling and heating

Abstract

In this research, thermal conductivity of a hybrid nanofluid containing multi-walled carbon nanotubes (MWCNTs) and titanium dioxide (TiO2) has been examined. Many samples were prepared by loading MWCNTs and TiO2 at 50:50 mass% into the ethylene glycol (EG) to measure the thermal conductivity at temperatures within 25–50 °C and solid volume fractions of 0–1%. The amount of positive nanoparticles incorporation efficacy on the thermal conductivity was influenced by the volume fraction as well as the temperature. As the temperature augmented from 25 to 50 °C, the EG thermal conductivity was intensified by 9.6%, while this figure for nanofluid at 1 vol.% was 18.2%. Therefore, it is concluded that the loading nanoparticles amplified the thermal conductivity sensitivity to temperature. Statistical analysis showed that the positive effects of loading nanoparticles on thermal conductivity are amplified by rising temperature. At 25 °C, loading nanoparticles (1 vol.%) can amplify the thermal conductivity by 16%, while at 50 °C, this figure was 25.18% (maximum thermal conductivity enhancement). A correlation was developed using response surface methodology (RSM), and the input parameters significance was specified applying analysis of variance (ANOVA). Finally, using 28 machine learning-based algorithms, the hybrid nanofluid thermal conductivity has been predicted and compared with the RSM outputs.