Temperature field acquisition by planar laser induced fluorescence using the two-color/two-dye technique for liquid flows in a millimetric zigzag channel

The acquisition of local temperature fields in compact reactors is essential to understand the heat transfer mechanisms in these often-complex geometry devices, and to detect the presence of any dead zones where hot or cold spots can appear during implementation of reactions. In this work, thermometry by PLIF method (Planar Laser Induced Fluorescence) is implemented in a square millimetric zigzag channel of 4 mm depth. The two-color/two-dye method is used. The advantages of this technique are that it is non-intrusive and it presents a very good spatial and temporal resolution. The method is first calibrated capturing temperature fields in flowing water at constant temperature. The sensitivity of the implemented method is good, equals to 3.3%.C-1 in terms of fluorescence signal ratio. Uncertainty of 0.6% of the measured temperature is due to the noise of the acquired images, and the global uncertainty of the measurement is estimated to be lower than 3% in the temperature range of 17-60 degrees C. The PLIF technique is then applied during heat transfer to obtain temperature fields at different positions and heights in the channel. The average temperatures measured from the local temperature fields are close to the temperature profiles calculated with a 1D heat transfer model. The obtained results show the potential of the PLIF technique to detect temperature heterogeneities in compact devices for the study and the design of intensified reactors.