Simultaneous measurement of liquid-film thickness and solute concentration of aqueous solutions of two urea derivatives using NIR absorption

Lubnow, Marc; Dreier, Thomas; Schulz, Christof; Endres, Torsten

doi:10.1364/ao.440465

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…An incandescent lamp is used between 360 and 2600 nm with a filter wheel with band-pass filters at 1350, 1450, 1933, and 2200 nm. The data acquisition for all four wavelengths is almost one minute due to the mechanical function of the filter wheel [67,68].…”

Section: Introductionmentioning

confidence: 99%

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

2022

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Falling film evaporation processes involve high fluid velocities with continuous variations in local film thickness, fluid composition, and viscosity. This contribution presents a parallel and complementary film thickness and concentration mapping distribution in falling films using a non-invasive fluorescence and near-infrared imaging technique. The experiments were performed with a mixture of glycerol/water with a mass fraction from 0 to 0.65 gglycgtotal−1 and operating ranges similar to evaporation processes. The measurement system was designed by integrating two optical measurement methods for experimental image analysis. The film thickness was evaluated using a VIS camera and high-power LEDs at 470 nm. The local glycerol concentration gglycgtotal−1 was determined using a NIR camera and high-power LEDs at 1050, 1300, 1450 and 1550 nm. A multiwavelength analysis with all NIR wavelengths was implemented with a better correlation for falling films at low flow velocity. The results show an improvement in the analysis of falling films with high flow velocities up to almost 500 mm/s by using only the 1450 nm wavelength and the fluorescence measurement. Simultaneous imaging analysis of film thickness and concentration in falling films provides further insight into understanding mass and heat transport and thus supports the optimization of falling film evaporators.

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Section: Introductionmentioning

confidence: 99%

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

2022

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Nondestructive determination of SSC in an apple by using a portable near-infrared spectroscopy system

et al. 2022

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The soluble solids content (SSC) is an important factor in the internal quality detection of apples. It is essential to have reliable and high-speed measurement of the SSC. However, almost all traditional equipment is inconvenient and expensive. We designed a handheld nondestructive SSC detector based on near-infrared (NIR) spectroscopy, which is composed of a portable NIR spectrometer, cloud server, smartphone app, and prediction model of SSC. We preprocessed the spectrum with multiplicative scatter correction (MSC), standard normal variable transformation (SNV), and Savitzky–Golay (S–G) smoothing algorithms. Besides, the linear weight reduction of the particle swarm optimization algorithm is carried out, and we establish the model of an extreme learning machine optimized with the improved particle swarm optimization (IPSO-ELM) algorithm. The R 2 , root mean square error of prediction (RMSEP), and residual prediction deviation (RPD) of the model are 0.993, 0.0155, and 11.6, respectively, which are better than the traditional model obviously. In addition, the number of wavelengths reduced from 228 to 70 as the model is simplified with the uninformative variable elimination (UVE) method. The time of training is reduced by 29.30% compared with the original spectrum. It can be verified that the IPSO-ELM model has good prediction performance, and the NIR diffuse reflectance spectroscopy is a reliable nondestructive measurement of SSC in apples.

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Water-film thickness imaging based on time-multiplexed near-infrared absorption with up to 500 Hz repetition rate

et al. 2023

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We demonstrate high-repetition-rate imaging of the liquid-film thickness in the 50–1000 µm range resulting from impinging water droplets on a glass surface. The pixel-by-pixel ratio of line-of-sight absorption at two time-multiplexed near-infrared wavelengths at 1440 and 1353 nm was detected with a high-frame-rate InGaAs focal-plane array camera. Frame rates of 1 kHz and thus measurement rates of 500 Hz could be achieved, well suited to capture the fast dynamics of droplet impingement and film formation. The droplets were sprayed onto the glass surface using an atomizer. Suitable absorption wavelength bands for water droplet/film imaging were determined from Fourier-transform infrared (FTIR) spectra of pure water between 298 and 338 K. At 1440 nm, the water absorption is nearly temperature-independent, making the measurements robust against temperature fluctuations. Time-resolved imaging measurements capturing the dynamics of the water droplet impingement and evolution were successfully demonstrated.

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Simultaneous measurement of liquid-film thickness and solute concentration of aqueous solutions of two urea derivatives using NIR absorption

Abstract: We present a method to simultaneously measure the film thickness and individual concentrations of two urea derivates (urea C H 4 N 2 O and dimethylurea C 3 H 8 N 2 O ) mixed in an aqueous solution at constant temperature using near-infrared (NIR) absorption at multiple speci… Show more

Cited by 3 publications

References 21 publications

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

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

Nondestructive determination of SSC in an apple by using a portable near-infrared spectroscopy system

Water-film thickness imaging based on time-multiplexed near-infrared absorption with up to 500 Hz repetition rate

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