Development and Testing of Temperature-sensitive Beads for Simultaneous Thermometry and Velocimetry

Abstract

Temperature-sensitive beads (TSBs) have been developed with promising characteristics for application to complex flows, giving the capability for flow visualization via simultaneous full-field thermometry and velocimetry. The buoyant plume resulting from natural convection was selected as the flow for preliminary testing. Of the various TSBs fabricated and tested, the best results were achieved with 5 µm-diameter polystyrene microspheres doped with Europium (III) thenoyltrifluoroacetonate (EuTTA) and Coumarin. The dual-dye sensors rely on the temperature-sensitive luminescence of EuTTA for thermometry, while the temperature-insensitive Coumarin serves as a reference dye, allowing for correction of non-uniformities in lighting and particle size/shape. The TSBs are shown to meet particle size, particle response time, particle density, and temperature sensitivity requirements for natural convection in water. Moreover, the characteristics of the TSBs are suitable for a variety of turbulent water flows. A thermal response time has yet to be measured for the TSBs, but an appropriate technique for performing this measurement is in development.