Experimental study on the thermal conductivity of water-based CNT-SiO2 hybrid nanofluids

Abstract This experimental study includes measurement of thermal conductivity of distilled water-based CNT-SiO 2 hybrid nanofluids. Nanofluids were prepared by using two-step method, 3 different concentrations and 4 different mass range of CNT-SiO 2 . SiO 2 has 2200 kg m −3 density, 1.4 W m −1  K −1 thermal conductivity and 7 nm average particle size. CNT has 2620 kg m −3 density, 25 W m −1  K −1 thermal conductivity and 6–10 nm average particle size. Samples were placed in ultrasonic homogenizer maximum power capacity for 3 h. Throughout sonication process temperature of nanofluids have been kept under control in order not to chance volumetric fraction of nanofluids. All measurements of thermal conductivity were done by using thermal conductivity meter. Thermal conductivity meter was calibrated by di-water. Measurements of thermal conductivity was done range from 25 °C to 60 °C for every 5 °C. Validation of measurements had been performed by using di-water and shown in a thermal conductivity-temperature figure. Minimum and maximum thermal conductivity enhancements were revealed in detail. Alteration of the thermal conductivity with temperature according to various volumetric fractions were in literature rated and it is found that the thermal conductivity increases with temperature and vol. fraction clearly. Enhancement on the thermal conductivity to di-water were also depicted for various temperatures and vol. fraction in figures. Almost well-known correlations in the literature were given with their predictable rates. Moreover, comparisons with other studies were provided in this present study. A practical correlation was proposed for other researchers.