Abstract
In this study, the simultaneous temperature and velocity measurements have been developed by integrating Micro Particle Image Velocimetry (μ-PIV) and Temperature-Sensitive Paint (TSP) system. The fluorescence molecule of EuTTA was chosen as temperature sensor and 3.2 m diameter fluorescence micro particles were used as tracers for velocity measurement, and they were excited by 365 nm UV LED and 532 nm laser respectively. The temperature and velocity information embedded in the luminescence images were separated by carefully distinguishing luminance difference during image processing. The molecular concentration and the acquired luminescent intensities have been adjusted to optimize the outcomes from simultaneous measurements. The modified experimental technique has been applied to a straight microchannel flow to examine and compare to the data from previous study. The simultaneous velocity and temperature measurements were later applied to microchannel flow with in-lined/staggered cavities on the side walls and Reynolds numbers varying from 25 to 200. A commercial software ANSYS FLUENT was used to examine the flow fields with velocity and temperature development. Fast developing of velocity profile at microchannel entrance was observed in the flow field due to the high Pr number (16) of the working fluid (ethanol) selected in this study. The development of temperature in the in-lined/staggered microchannel flow has reached to fully developed region at the 7th to 8th structure. The re-attachment points have been calculated by the velocity profiles acquired by the experiments and they agree with simulation data. The heat transfer of microchannel flow with in-lined cavities is growing faster than staggered in low Re number regime. As the Re number increased, the heat transfer improvement of microchannel flow with staggered cavities becomes greater than the one with in-lined cavities, which is due to the change of vortex region behind cavity structures. The heat transfer improvement of microchannel flow with staggered cavities can be more than twice of straight microchannel flow while the Re number reaches 200.