Thermal Wave in Thermal Properties Measurements and Flow Diagnostics

The thermal wave technique has been explored for the use of liquid thermal conductivity measurement and flow property diagnostics in this dissertation. For liquid thermal conductivity measurements, an experimental technique based on the thermal wave approach is developed. An aqueous fluid consisting of gold nanoparticles was tested and anomalous thermal conductivity enhancement was observed. Our measurement results also showed a divergence of thermal transport behavior between nanofluids and pure liquids. For the study of flow property diagnostics, a heat transfer system with a periodic boundary condition in a steady flow field is examined. Due to linearity and homogeneity of the heat transfer system under certain conditions, a thermal wave field generated by a periodic heating flux at the boundary of the flow field may be used to detect important flow field parameters, such as the velocity gradient at the wall, and therefore, the wall shear stress.