Temperature Dependency of Ceramic Nanofluids Shows Classical Behavior

Nanofluids have become one of the most exciting options to enhance heat transfer. However, despite the large number of investigations published recently, the knowledge about the thermophysical properties of these special fluids is still limited. Here, the thermal conductivity of three water-based ceramic nanofluids in a temperature range between 20 and 60 degrees C is investigated experimentally. For that purpose, a ring-gap apparatus was very carefully designed, built, and analyzed numerically. No anomalous enhancement of the thermal conductivity of nanofluids was found. Rather, the thermal conductivity was increased by a constant value over the entire temperature range investigated here, or over parts of it. The nanofluids investigated here are in agreement with the extension of Maxwell's classical theory by Nan et al. [Nan, C.-W., Birringer, R., Clarke, D. R., and Gleiter, H, "Effective Thermal Conductivity of Particulate Composites with Interfacial Thermal Resistance," Journal of Applied Physics, Vol. 81, 1997, pp. 6692-6699].