AC hot wire measurement of thermophysical properties of nanofluids with 3ω method
Mechanical Engineering Dept., Dokuz Eylul Univ., 35100 Bornova Izmir, Turkey
2 Inst. of Food Process Engineering, Univ. of Karlsruhe, 76131 Karlsruhe, Germany
3 Lab. Thermophysics, UTAP, Univ. Reims, BP. 1039, 51687 Reims Cedex 2, France
4 Food Engineering Dept., Ege Univ., 35100 Bornova Izmir, Turkey
5 Inst. fuer Experimentalphysik, Ruhr-Universitaet, 44801 Bochum, Germany
We present a new application of a hot wire sensor for simultaneous and independent measurement of thermal conductivity k and diffusivity α of (nano)fluids, based on a hot wire thermal probe with ac excitation and 3 ω lock-in detection. The theoretical modeling of imaginary part of the signal yields the k value while the phase yields the α value. Due to modulated heat flow in cylindrical geometry with a radius comparable to the thermal diffusion length, the necessary sample quantity is kept very low, typically 25μl. In the case of relative measurements, the resolution is 0.1% in k and 0.3% in α. Measurements of water-based Aerosil 200V nanofluids indicate that ultrasound treatment is more efficient than high pressure dispersion method in enhancing their thermal parameters.
© EDP Sciences, Springer-Verlag, 2008