Evaporation of nanofluids

• Main Author: Choong, Clarrisa Yu Ying.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/53961
• Institution: Nanyang Technological University

Nanofluids are suspensions of nanoparticles in fluids that exhibit significant enhancement of their properties at modest nanoparticle concentrations. They are utilized in electronic applications as cooling devices in combination with thin film evaporation and in industrial applications where overheated surfaces in power plants are cooled down more quickly. In an effort to elucidate nanofluid droplet evaporation characteristics, this study presents experimentation on the evaporation of nanofluids. The main objective is to examine how varying parameters affect the evaporation of nanofluids in terms of contact angle, base diameter and volume. Graphite nanoparticles suspended in a binary mixture of ethanol and DI water is used as the working fluid. By varying the concentrations of ethanol at 10 wt%, 25 wt% and 50 wt% and concentrations of nanoparticles at 0.5mg/ml, 1mg/ml 1.5mg/ml and 2mg/ml, as well as the duration of ultrasonication at 1 hour and 2 hours, the nanofluids are then deposited as droplets onto silicon wafer substrates and analyzed with the use of goniometer. It is found that higher ethanol concentration in base solvents leads to faster evaporation rate and a three-phase evaporation behavior can be observed. The overall evaporation time for base solvent droplets is also found to be about two times longer than for nanofluids. Evaporation rate is the slowest for 2mg/ml nanofluid droplet, suggesting that evaporation rate declines with an increase in the nanoparticle concentration and causes deviation from the classical D^2-law. The wetting dynamics of the droplets throughout the evaporation process shows major influence of nanoparticles. Agglomeration of nanoparticles occurs over time and even more actively in nanofliuds with higher nanoparticle concentration, thus slowing down the evaporation rate of nanofluids. However, evaporation of nanofluids seems to be insensitive to ultrasonication experimental conditions. Henceforth, the use of surfactants preventing agglomeration of nanoparticles in prepared colloidal solution and investigation on temperature and surface tension can be recommended for future works in the evaporation of nanofluids.