Dispersion Optimization and Thermal Conductivity Measurement of Low Concentration Alumina Nanofluids

Dispersion stability and thermal conductivity of nanofluids obtained by dispersing of alumina nanoparticles (sizes less than 50 nm) in DI water and ethylene glycol were analyzed at several different concentrations of alumina. Optimized dispersion was achieved for the low weight percent aqueous and ethylene glycol-based alumina nanofluids by the sedimentation method. Experimental results revealed that, alumina nanofluids with ethylene glycol as base fluids had better quality dispersion compared with aqueous alumina nanofluids. Thermal conductivity of these alumina nanofluids was measured by means of hot wire technique using a LAMBDA system. For water-based alumina nanofluids, thermal conductivity was enhanced from 1.42% to 1.78% with 3 wt% alumina and from 2.29% to 3.06% with 5 wt% alumina at temperatures ranging from 15 to 40 degrees C. Whereas in case of ethylene glycol-based alumina nanofluids under the same temperature range, thermal conductivity also showed enhancement from 8.2% to 8.85% with 3 wt% and from 9.6% to 10% with 5 wt% alumina. The present research is helpful to optimize dispersion for the low weight fraction water-based and ethylene glycol-based alumina nanofluids to use further in heat transfer systems.