New experimental correlation for the thermal conductivity of MWCNTs-SiO2/water-EG in various solid volume fractions and temperatures

Abstract

In recent years, studies on rheological behavior and heat transfer of nanofluids have been greatly increased and results show significant progress in this field. In this study, thermal conductivity of nanofluid consisting of SiO2 and MWCNTs suspended in water and ethylene glycol as the base fluid was experimentally studied. Using nanofluid in energy systems is going to spread more day after day, therefore, measuring its properties has significant importance. To do so 50:50 mass fraction of SiO2 and MWCNTs nanoparticles has been dispersed in water and ethylene glycol (60–40) with various solid volume fractions (0.0625%, 0.125%, 0.25%, 0.5%, 0.75% and 1%) in different temperatures from 25 to 50 °C. Nanoparticles were suspended in base fluid using the two-stage method. Results suggest that the thermal conductivity of nanofluid is higher than the base fluid and the changes have a direct relation with increase or decrease of solid volume fraction and temperature. The highest increase in thermal conductivity occurred in solid volume fraction of 1% in a temperature between 25 and 50 °C amounting 13.1% and in a temperature of 50 °C and solid volume fraction between 0 and 1% was 29.8%. Eventually, a relation provided based on solid volume fraction and temperature. Margin of deviation in this relation is less than 1.9% that demonstrated the good accuracy.