Thermal characterization of microheated microchannels with spatially resolved two-color fluorescence thermometry

Two-color fluorescence thermometry is a well known, noninvasive, and accurate technique used to measure temperature in liquids. In this paper, we present an improved methodology that enhances the spatial accuracy of the technique by minimizing image-pair distortion errors and its subsequent use in the characterization of heated microchannels. In order to spatially calibrate the image-pair and to quantify the distortion of one image with respect to the other, particle image velocimetry was performed with sandpaper. Results show that the objective lens and the primary dichroic mirror does not significantly affect the beam path and that the main source of distortion is likely to occur between the secondary dichroic mirror and the reflective mirrors within the emission splitting system. This spatial calibration and correlation methodology was used to map the temperature distribution in microheated microchannels. The experimentally calculated advective efficiency results showed good agreement against their numerically computed counterparts. These results suggest that the power supplied to the microheaters should be varied accordingly to maintain fixed heat flux conditions through the microchannel walls as a function of flow rate.