Marker-Free, Molecule Sensitive Mapping of Disturbed Falling Fluid Films Using Raman Imaging

Abstract

Technical liquid flow films are the basic arrangement for gas fluid transitions of all kinds and are the basis of many chemical processes, such as columns, evaporators, dryers, and different other kinds of fluid/fluid separation units. This publication presents a new method for molecule sensitive, non-contact, and marker-free localized concentration mapping in vertical falling films. Using Raman spectroscopy, no label or marker is needed for the detection of the local composition in liquid mixtures. In the presented cases, the film mapping of sodium sulfate in water on a plain surface as well as an added artificial streaming disruptor with the shape of a small pyramid is scanned in three dimensions. The results show, as a prove of concept, a clear detectable spectroscopic difference between air, back plate, and sodium sulfate for every local point in all three dimensions. In conclusion, contactless Raman scanning on falling films for liquid mapping is realizable without any mechanical film interaction caused by the measuring probe. Surface gloss or optical reflections from a metallic back plate are suppressed by using only inelastic light scattering and the mathematical removal of background noise.

Three‐Dimensional, Molecule‐Sensitive Mapping of Structured Falling Liquid Films Using Raman Scanning

“…1 displays a schematic drawing of the experimental setup. An in‐depth description of the base setup is given in 1. After the three‐dimensional pyramid measurement, the plant altered for using a pillow plate as liquid running surface.…”

“…Especially non-invasive techniques, such as optical or spectroscopic methods, offer the opportunity to determine relevant film information without disturbing its actual status. Continuing the proof-of-concept study about flow mapping in falling films using Raman spectroscopy, 3D mapping on different flow disruptors is highlighted in this publication [1]. The goal of the presented work is to demonstrate a new possibility to determine the parameters needed and to enable a better understanding of flow behavior on disturbed and structured surfaces.…”

“…There is no method for marker-free, non-contact and moleculeselective method for 3D imaging on falling films available to this date. For an in-depth description of relevant applications and publications please refer to the previous publication this communication is based on [1].…”

Liquid Mixing on Falling Films: Marker-Free, Molecule-Sensitive 3D Mapping Using Raman Imaging

“…Highlighting the state of the art, several different measurement approaches are available. The authors' previous publication presents a summary on different Raman imaging approaches [6]. In the following section, the focus will be on falling films and the available approaches to allow a more complete view on the state of the art.…”

Film Thickness and Glycerol Concentration Mapping of Falling Films Based on Fluorescence and Near-Infrared Technique

“…Bandi et al studied oxygen absorption in wavy falling films in two dimensions using a PLIL (planar laser-induced luminescence measurement technique) and a ruthenium complex as an indicator [59]. New measurement methods such as Raman spectroscopy detects local composition in falling films without marker but with the limitation of large measurement times [60].…”