Nanofluid Convection in Microtubes

Abstract

While there has been much previous research on the thermal conductivity and convection performance of nanofluids, these data are rarely reported together with effective viscosity data that govern the relevance for heat exchanger applications. We report here the effective convection coefficient and viscosity in microtubes (D=0.5 mm) along with stationary thermal conductivity measurements for nanofluids based on spherical particles (Al2O3, ZnO, and CuO) and carbon nanotubes. Sample data include an effective convection coefficient increase of 5% for 3 vol %Al2O3/DI water nanofluid, 13.3% for 4 vol % CuO/DI water nanofluid, and 11.6% for 0.2 vol % Carbon nanotube(CNT)/DI water nanofluid. When considered together with our viscosity measurement on the same fluids, we find that the only the CNT-based nanofluids are promising for microfluidic heat exchangers.