The effects of hybrid nano-powder of zinc oxide and multi walled carbon nanotubes on the thermal conductivity of an antifreeze

In the past decade, researchers have been focusing on new advanced nanofluids composed of different nanoparticles. This type of nanofluids, also referred to as hybrid nanofluids, is generally made of a combination of two different nanoparticles with a base fluid. Use of nanofluids leads to reduced production cost of metal-based nanofluids and/or carbon nanotubes. Carbon nanotubes cause magnificent thermophysical properties in nanofluids and, therefore, their addition to the base fluid can significantly affect the thermal conductivity in nanofluids. Addition of an oxide nanoparticle to carbon nanotubes or metal nanoparticles leads to their increased stability and improved suspension. This research aimed to experimentally investigate the effects of temperature and volume fraction of nanoparticles on the thermal conductivity of ZnO-MWCNT/EG-Water nanofluid. The experiments were conducted in a temperature range of 25-50°C on samples with volume fractions of 0.0375, 0.075, 0.15, 0.3, 0.6, and 1.2%. Measurements revealed that the thermal conductivity increased up to 30% by increasing the amount of nanoparticles and temperature. Finally, an experimental correlation was presented for prediction of thermal conductivity, and deviation of margin analysis was performed on the proposed correlation. The analyses results suggested a maximum deviation of margin of 1.46%, indicating an appropriate accuracy for the proposed correlations in prediction of thermal conductivity of ZnO-MWCNT/EG-Water nanofluid.