Reactive Fluids

The use of optical in-situ measurement technology in reactive flows requires optical accessibility to the equipment used. While this is always possible in the case of equipment that operates at atmospheric pressure and does not have to meet any special safety requirements, as it is operated openly, optical accessibility poses greater challenges in other types of equipment.

Reactors for nanomaterial synthesis usually have to be operated in a closed system to prevent contamination of the laboratory and personnel by potentially toxic aerosols. For the application of macroscopic optical measurement technology (i.e., with comparatively low magnification), the installation of quartz glass windows on the reactor is usually sufficient. Light, e.g., from a laser or LED, can be coupled in through one side. Through another window, the signal, e.g., scattered light, fluorescence, or incandescence, can be imaged onto a camera sensor through a lens.

The use of microscopic measurement technology (see cover image) usually requires very short working distances (3-5 cm from the object plane), which is why imaging through a window (usually about 30 cm) from the object plane is unsuitable. In these cases, the reactors are either operated openly, if safety can still be guaranteed, or by designing appropriate adapters. The latter enable closed operation while simultaneously using a microscope.

When setting up optical access, it is important to consider the extent to which the process is “disrupted,” i.e., a process without optical access is no longer comparable. This happens, for example, due to different heat capacities and thermal conductivities of the materials or bulges in the system for setting up access, which influence the flow field. In some test facilities, even parts that are crucial to the process are made optically accessible, such as the piston and cylinder wall in a combustion engine or, as shown in the following figure, the bipolar plate of an electrolysis cell.

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