Stability and Thermal Conductivity of Ethylene Glycol and Water Nanofluid Containing Graphite Nanoparticles

Abstract

Heat transfer enhancement in a heat exchanger using conventional fluids such as water, ethylene glycol and engine oils is limited due to lower thermal conductivity of fluids. Addition of nanoparticles to these fluids can provide better heat transfer due to improved thermophysical properties. In this study, thermal conductivity and stability of ethylene glycol (EG) and water (35:65 in terms of volume)-based graphite nanofluids were investigated experimentally. Nanofluids containing graphite nanoparticles in weight concentrations in the range of 0.5–2 wt% were prepared using ultrasonication method. Thermal conductivity of nanofluids was measured at each weight concentration in the temperature range of 30–50 °C using transient hot wire method. Subsequently, the stability of EG and water-based graphite nanofluids was evaluated by visual observation and thermal conductivity measurement over a period of 30 days at 30 °C. The results showed that thermal conductivity enhances by adding graphite nanoparticles to the ethylene glycol and water. It was found from the study that thermal conductivity of prepared nanofluid increases with increase in temperature. Addition of 2 wt% of graphite nanoparticles in EG: water showed an enhancement of 22% and 26.67% in thermal conductivity at 30 and 50 °C, respectively. Stability study overtime reveals that there is no considerable difference in thermal conductivity for 30 days indicating a stable nanofluid dispersion. A correlation was developed to predict the thermal conductivity of EG: water-based graphite nanofluids.