The effects of temperature, volume fraction and vibration time on the thermo-physicalproperties of a carbon nanotube suspension (carbon nanofluid)

Abstract

In this investigation, nanofluids of carbon nanotubes are prepared and the thermalconductivity and volumetric heat capacity of these fluids are measured using a thin layertechnique as a function of time of ultrasonication, temperature, and volume fraction. It hasbeen observed that after using the ultrasonic disrupter, the size of agglomeratedparticles and number of primary particles in a particle cluster was significantlydecreased and that the thermal conductivity increased with elapsed ultrasonicationtime. The clustering of carbon nanotubes was also confirmed microscopically.The strong dependence of the effective thermal conductivity on temperature and volumefraction of nanofluids was attributed to Brownian motion and the interparticle potential,which influences the particle motion.The effect of temperature will become much more evident with an increase in the volumefraction and the agglomeration of the nanoparticles, as observed experimentally.The data obtained from this work have been compared with those of other studies andalso with mathematical models at present proven for suspensions. Using a 2.5%volumetric concentration of carbon nanotubes resulted in a 20% increase in thethermal conductivity of the base fluid (ethylene glycol).The volumetric heat capacityalso showed a pronounced increase with respect to that of the pure base fluid.