Diversity in thermal conductivity of aqueous Al2O3- and Ag-nanofluids measured by transient hot-wire and laser flash methods

Transient hot-wire and laser flash methods are the two commonly used techniques for measuring the thermal conductivity of nanofluids. However, a comparative study of these two techniques considering identical nanofluids has not been carried out. In this regard, the current study aims at comparison of two methods with identical distribution of Al2O3 and Ag nanoparticles in water. The study also accounts quantitatively for the wide difference in the measured thermal conductivities on the basis of the flux of nanoparticles across the thermal boundary layer resulting from the Brownian movement. It has been observed that the collision flux of the nanoparticle increases with increase in the initial perpendicular distance of the nanoparticle from the heat source wall. Such an increase results in higher thermal conductivity in case of transient hot-wire compared to laser flash method.