High efficiency heat transfer and antifriction characteristics of SMWCNTs nanofluids

Abstract

In this paper, the thermal conductivity and tribological properties of ethylene glycol/water-based nanofluids with hydroxylated short multi-walled carbon nanotubes (SMWCNTs(OH)) were investigated. Long-term stable ethylene glycol/water-based nanofluids were prepared by a two-step method. The morphology and surface functional group characteristics of SMWCNTs(OH) were characterized by field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The kinematic viscosity of the base fluid and nanofluids at different temperatures was measured using a rotary rheometer. The dispersion stability of nanofluids was analyzed by dynamic light scattering. Thermal conductivity test was performed using the transient hot wire method. The reciprocating friction test was carried out by UMT5 test machine, and the appearances of wear scars were analyzed by white light morphology. Results show that a significant enhancement of thermal conductivity could be achieved by increasing the temperature of the nanofluids and adjusting the concentration of the carbon nanotubes compared with the corresponding base. At 60 °C, the thermal conductivity of the nanofluids increases significantly and reaches 6.0%at the volume fraction of 25% for ethylene glycol/water. It is shown that the SMWCNTs(OH) have good self-lubrication antifriction effect in the water base nanofluids for the GCr15 friction pair. Meanwhile, the wear loss of the wear scar is greatly reduced, and the friction coefficient is reduced by 15.4% compared with the pure water, which shows a good application prospect of nanofluids in pump drive fluid loops.