Development and Calibration of a Two-Dye Fluorescence System for Use in Two-Phase Micro Flow Thermometry

The increasing need for more effective cooling in electronic devices has led to research into the use and modeling of two-phase cooling strategies in micro-scale geometries. In order to verify these models it is necessary to reliably determine local parameters such as fluid temperature in boiling flows, which cannot be easily obtained due to micro-scale geometries. A convenient and non-contact method of thermometry is the use of fluorescence where the emitted intensity is a function of the local temperature. Previous work has verified the ability to use single dyes to measure void fraction in isothermal cases and suggested the possibility of simultaneous thermometry using a system of two dyes. In the present work, we verify the ability to measure the temperature of a single-phase liquid system using pairs of dyes and to this end also determine if two-dye temperature-intensity calibration curves could be accurately constructed from single dye calibration curves. The experimental set-up and procedure yield calibration results from 300K to 400K for Stilbene 420, Kiton Red, Rhodamine B and Fluorescein. Two-dye calibration curves are constructed from single-dye calibration curves and compared experimentally to a system containing two dyes in mixture. The small variation in predicted and actual responses suggest that two-dye systems should be calibrated in mixture form, and if done accurately, have the potential to measure the liquid temperature of a two-phase system