The application of temperature-sensitive paints for surface and fluid temperature measurements in both thermal developing and fully developed regions of a microchannel

This work presents the experimental analysis of heat transfer in a straight polydimethylsiloxane microchannel with cross-sectional width/depth ratio of 8.47 using the temperature-sensitive paint (TSP) technique. The TSP technique is capable of acquiring temperature profiles for both the surface and the fluid with a detailed resolution of 144 mu m per pixel through the microchannel under the constant wall temperature condition. The acquired temperature data have been analyzed to study the heat transfer and Nusselt numbers in both thermal developing and fully developed regions. The estimation of thermal entrance length from the experimental results shows good agreement with the empirical equation of the parallel-plate system, while the Nusselt numbers in the fully developed region deviate. This deviation is attributed to the small scale of the channel, which amplifies the effects of the electric double layer and the surface boundary condition. These results demonstrate the great potential of the TSP technique in providing detailed and valuable information for heat transfer investigation inside microdevices.