In situ Raman imaging combined with computational fluid dynamics for measuring concentration profiles during mixing processes

Micro structured components for process engineering have gained increasing importance in chemical, pharmaceutical and life sciences applications. Understanding of mixing processes in those devices is of fundamental interest for their performance. Raman imaging with light sheets is a powerful tool to visualize concentration profiles. For the first time planar Raman imaging is combined with computational fluid dynamic (CFD) calculations to analyze the concentration of two components at the outlet of a micro mixer. The mixing process was monitored within an attached quartz cuvette. The laser light sheet had a thickness of 0.5 mm and a width of 10 mm matching the inner width of the cuvette. In this investigation ethanol and water were mixed. We present measured concentration maps within 10 mm × 10 mm using single shot laser pulses (6 ns). The lateral resolution is only determined by the pixel size of the CCD camera. Standard deviations and averaged data of the concentration profiles are compared with CFD calculations. The computations were done for a laminar flow at constant temperature under non-steady-state conditions.

► Creation of Nd:YAG laser light sheets with 10 mm height and 0.5 mm thickness.
► Mixing of ethanol and water at the outlet of a micro mixer in a quartz cuvette.
► Raman imaging of ethanol within the light sheet (10 mm × 10 mm) in 10 ns.
► Measurement of concentration maps within the cuvette.
► Comparison with computational fluid dynamics (CFD) calculations.