Mass Transfer Measurements Research Articles

Measuring Mass Transfer of n-Hexane and 2-Chloroethyl Ethyl Sulfide in Sorbent/Polymer Fiber Composites Using a Volumetric Adsorption Apparatus.

The integration of metal-organic frameworks (MOFs) into composite systems serves as an effective strategy to increase the processability of these materials. Notably, MOF/fiber composites have shown much promise as protective equipment for the capture and remediation of chemical warfare agents. However, the practical application of these composites requires an understanding of their mass transport properties, as both mass transfer resistance at the surface and diffusion within the materials can impact the efficacy of these materials. In this work, we synthesized composite fibers of MOF-808 and amidoxime-functionalized polymers of intrinsic microporosity (PIM-1-AX) and measured the adsorption and mass transport behavior of n-hexane and 2-chloroethyl ethyl sulfide (CEES), a sulfur mustard simulant. We developed a new Fickian diffusion model for cylindrical shapes to fit the dynamic adsorption data obtained from a commercial volumetric adsorption apparatus and found that mass transport behavior in composite fibers closely resembled that in the pure PIM fibers, regardless of MOF loading. Moreover, we found that n-hexane adsorption mirrors that of CEES, indicating that it could be used as a structural mimic for future adsorption studies of the sulfur mustard simulant. These preliminary insights and the new model introduced in this work lay the groundwork for the design of next-generation composite materials for practical applications.

Mass transfer and kinetic measurement and modeling for CO2 absorption into aqueous EAE and water-lean EAE/NMP solvents

Chemical absorption using amine solvent is currently available technology for CO2 capture from post-combustion flue gas. It is hindered by high operating cost and high capital cost due to high regeneration energy and slow CO2 absorption rate of amine solvent. Water-lean solvent of 2-(ethylamino) ethanol (EAE)/1-methyl-2-pyrrolidinone (NMP)/water could be a potential solution as it achieved significantly low regeneration energy of 2.3 GJ/tCO2 tested in a pilot plant. However, kinetics of CO2 reaction with EAE and mass transfer rate of CO2 absorption into EAE/NMP solvent are not fully understood. In this work, kinetics of CO2 absorption into unloaded aqueous EAE in 1–5 mol/L at 300–313 K and mass transfer of CO2 absorption into CO2-loaded EAE/NMP water-lean solvent in 5 mol/L with equilibrium CO2 partial pressure (PCO2*) range of 0.3–7 kPa at 312 K were studied in a wetted wall column. Kinetic data of aqueous EAE is interpreted by zwitterion mechanism, and the reaction is of first order with respect to EAE concentration in 1–5 mol/L at 300–313 K. CO2 absorption rate (kg’) of EAE/NMP water-lean solvent is 1.3–2.1 times greater than aqueous EAE due to the greater CO2 physical solubility. At lean and rich loading conditions, 5 M EAE in 3NMP/1water and 9NMP/1water show 2–7 times faster kg’ than 30 % MEA, and 1.4–2.5 times faster kg’ than 30 % PZ. It is found that EAE activity coefficient may increase in the presence of NMP in the solvent, and the estimated EAE activity coefficient in 1NMP/1water, 3NMP/1water, and 9NMP/1water are 2.13, 3.50, and 4.72, respectively. CO2 capacity of EAE/NMP solvent is 2–3.7 times greater than 30 % MEA and 1.2–2 times greater than 30 % PZ.

Inactivation Mechanisms of Escherichia coli in Simulants of Respiratory and Environmental Aerosol Droplets

The airborne transmission of disease relies on the ability of microbes to survive aerosol transport and, subsequently, cause infection when interacting with a host. The length of time airborne microorganisms remain infectious in aerosol droplets is a function of numerous variables. We present measurements of mass and heat transfer from liquid aerosol droplets combined with airborne survival data for Escherichia coli MRE162, an ACDP category 1 microorganism used as a model system, under a wide range of environmental conditions, droplet compositions and microbiological conditions. In tandem, these companion measurements demonstrate the importance of understanding the complex relationship between aerosol microphysics and microbe survival. Specifically, our data consist of the correlation of a wide range of physicochemical properties (e.g., evaporation rates, equilibrium water content, droplet morphology, compositional changes in droplet solute and gas phase, etc.), with airborne viability decay to infer the impact of aerosol microphysics on airborne bacterial survival. Thus, a mechanistic approach to support prediction of the survival of microorganisms in the aerosol phase as a function of biological, microphysical, environmental, and experimental (aerosol-generation and sampling) processes is presented. Specific findings include the following: surfactants do not increase bacteria stability in aerosol, while both the bacteria growth phase and bacteria concentration may affect the rate at which bacteria decay in aerosol.

Measurement of interfacial mass transfer of single bubbles rising in homogeneous turbulence

Accurate quantification of the mass transfer coefficient kl of bubbles under high Reynolds number conditions has been in desperate need for decades to provide insights into its fundamental physics and reach a general mass transfer model. In this paper, a state-of-the-art SI-LIF technique is developed to quantify kl indirectly based on the law of conservation of mass. The reconstruction algorithms of the required physical quantities are validated numerically, suggesting an overall uncertainty of less than ± 5 % in the estimation of kl. We perform mass transfer experiments of single oxygen bubbles with deq = 1.5 mm rising in both quiescent water and homogeneous turbulence, with turbulent Reynolds number ReT ranging from 0 to 1114. The measured kl under turbulent conditions are independent of ReT, and all collapse to the analytical solution of potential flow approximation, revealing that the flow in the immediate vicinity of the bubble interface remains undisturbed by the fluctuating liquid motions across all the turbulence settings examined in this paper.

'Dark' CO2 fixation in succinate fermentations enabled by direct CO2 delivery via hollow fiber membrane carbonation.

Anaerobic succinate fermentations can achieve high-titer, high-yield performance while fixing CO2 through the reductive branch of the tricarboxylic acid cycle. To provide the needed CO2, conventional media is supplemented with significant (up to 60g/L) bicarbonate (HCO3-), and/or carbonate (CO32-) salts. However, producing these salts from CO2 and natural ores is thermodynamically unfavorable and, thus, energetically costly, which reduces the overall sustainability of the process. Here, a series of composite hollow fiber membranes (HFMs) were first fabricated, after which comprehensive CO2 mass transfer measurements were performed under cell-free conditions using a novel, constant-pH method. Lumen pressure and total HFM surface area were found to be linearly correlated with the flux and volumetric rate of CO2 delivery, respectively. Novel HFM bioreactors were then constructed and used to comprehensively investigate the effects of modulating the CO2 delivery rate on succinate fermentations by engineered Escherichia coli. Through appropriate tuning of the design and operating conditions, it was ultimately possible to produce up to 64.5g/L succinate at a glucose yield of 0.68g/g; performance approaching that of control fermentations with directly added HCO3-/CO32- salts and on par with prior studies. HFMs were further found to demonstrate a high potential for repeated reuse. Overall, HFM-based CO2 delivery represents a viable alternative to the addition of HCO3-/CO32- salts to succinate fermentations, and likely other 'dark' CO2-fixing fermentations.

Measuring mass transfer of AM CVn binaries with a space-based gravitational wave detector

ABSTRACT The formation mechanism of AM CVn binary has not been well understood yet. Accurate measurements of the mass transfer rate can help us to determine the formation mechanism. But unfortunately such observation by electromagnetic means is quite challenging. One possible formation channel of AM CVn binary is a semidetached white dwarf binary. Such system emits strong gravitational wave radiation which could be measured by the future space-based detectors. We can simultaneously extract the mass transfer rate and the orbital period from the gravitational wave signal. We employ a post-Keplerian waveform model of gravitational wave and carry out a Fisher analysis to estimate the measurement accuracy of mass transfer rate through gravitational wave detection. Special attention is paid to the observed sources in Gaia Data Release 2. We found that we can accurately measure the mass transfer rate for those systems. Comparing to electromagnetic observations, gravitational wave detection improves the accuracy more than two orders of magnitude. Our results imply that the gravitational wave detection will help much in understanding the formation mechanism of AM CVn binaries.

Measurement of thermal radiative and mass transfer of peristaltic pumping of electrically-conducting bio-bi-phase flow due to metachronal wave: Eukaryotic cells in biological applications

Cilia motion are commonly located in mammalian cells of living organisms which is continually grow and feature conspicuously. The ciliary apparatus is associated to cell cycle movement and proliferation, and cilia show a dynamic part in human and animal growth and in everyday life. The measurement of a solo cilium is one to tenth micrometres and width is less than 1 μm. A large number of varieties is originated such as inner ear, kidney, oviduct, eye, testes, olfactory epithelium and respiratory tract. Protozoa, algae, and several small invertebrates are examples of creatures that frequently exhibit metachronal waves in their cilia and flagella. These waves generate an overall propulsive force that enables the movement of these organisms in fluid settings. Cilia or flagella can provide fluid flow that drives the creature ahead or allows it to move particles or other materials around it by producing a travelling wave motion. Motivation of these applications, Present study is measurement of thermal and mass transfer in beating cilia of multiphase peristaltic pumping of non-Newtonian Ree-Eyring fluid in two- and three-dimensional channel using transvers magnetohydrodynamics in porous medium. Two systems of the governing equations both phases dusty and fluid phase are formulated for the non-Newtonian Ree-Eyring fluid. Calculated exact solutions for fluid phase velocity, particulate phase velocity, temperature, concentration and pressure gradient respectively. Also, physical behaviour is discussed by plotting the graph of different dimensionless parameters on both phases solid-liquid on velocity, thermal and concentration. Trapping phenomenon is visualized by plotting the stream lines of different dimensionless parameters on velocity of Ree-Eyring fluid and magnetic field.

Modelling particle dissolution in stirred vessels

Particle dissolution in stirred vessels is a unit operation commonly encountered in several production sectors, such as the mineral, pharma and chemical industries. It is commonly conducted batch-wise under time-dependent conditions, a circumstance that complicates model set-up. This paper presents a set of models for simulating batch dissolution of polydisperse particles in stirred vessels. These models cover all scenarios of particle batch dissolution, regardless of whether the initial particle quantity exceeds or falls short of achieving solution saturation. Consequently, they address cases where particles are either completely dissolved or remain partially undissolved. The models also account for both single-sized and multi-sized particles. Convenient model simplifications are also provided for the cases of final solute concentration much smaller than saturation (low final concentration models). All models are successfully experimentally validated. The single-size large final concentration model is employed to set up experimental runs that, apart from their use in predictive simulations, may be employed for simultaneously measuring mass transfer coefficient and interfacial solute concentration using suitable experimental runs. The ability to measure interfacial solute concentration is also exploited for assessing whether it coincides, or not, with the solute saturation concentration, a common assumption when dealing with solid-liquid mass transfer, which in the present case is found to hold true. The simpler single-size low-final-concentration model is very convenient for measuring the mass transfer coefficient alone. Finally, the multi-size model is utilised to evaluate the sensitivity of the estimated mass transfer coefficient in the single-size model to the particle size range employed during experimental measurements of mass transfer coefficients.

Experimental analysis of drop size distribution and nucleation site density during dropwise condensation from humid air flow

Condensation of the water vapor present in the air is a heat and mass transfer process encountered in many applications as humid air dehumidification and water harvesting. Depending on the wettability characteristics of the surface, condensation can take place in filmwise mode or in dropwise mode with the formation of discrete liquid droplets over the condensing surface. While dropwise condensation (DWC) of pure steam was found to promote a considerable enhancement of the heat transfer compared to filmwise condensation, when dealing with humid air DWC more investigation is needed. Modeling of DWC from humid air requires the calculation of the heat flow rate through a single droplet and the determination of the drop-size distribution. The heat exchanged through a single droplet depends on the heat and mass transfer resistances, while the drop-size distribution is also affected by nucleation site density and droplets mobility. Therefore, to better understand the DWC phenomenon with humid air and for the validation of the models, it is necessary to measure the heat flux (total and latent), droplet population and nucleation site density. In the present work, condensation tests from humid air are performed over two square (40 mm x 40 mm) aluminum samples that display different wettability. The experimental apparatus consists of a closed air loop with two main components: the environmental chamber and the test chamber. The air is conditioned in the environmental chamber and then it flows inside the test section where the vapor present in the humid air is condensed over the vertical metallic sample. Two variable speed fans are used to circulate the air. The test section is designed for heat and mass transfer measurements and for simultaneous visualization of the condensation process. As a peculiar characteristic of the present experimental technique, all the test section assembly is suspended on a high precision balance allowing a precise measurement of the mass of condensate. The effect of surface wettability on the heat and mass transfer during DWC is investigated. Time-lapse videos of the condensation process are acquired at different magnifications. By using a homemade MATLAB® program for droplet detection, recorded images are analysed allowing the determination of both the drop size density distribution (small and large droplet population) and the nucleation sites density.

Simulation of A Solar Drier for Iroko Wood (Chlorophora Excelsa) in A Tropical Environment

In a previous study conducted by Simo Tagne to designing a solar dryer based on mathematical equations for iroko wood in Cameroon, Africa. However, there is no complete simulation of the drying process on the tool, resulting in the lack of detailed elaboration of the iroko wood drying process. The purpose of this study is to simulate in detail the drying process on the tool using an ANSYS simulation. The model used in this simulation still uses the same mathematical model that has been studied before. This research begins by setting up the ANSYS application with the previous mathematical model, environmental conditions, and tool specifications. Furthermore, simulations are carried out using the ANSYS application with measurements of pressure, temperature, velocity and mass transfer. From this simulation obtained results for the distribution of pressure, temperature, velocity, and mass transfer. From all these distributions, it is sufficient to describe the drying process of the tool according to the mathematical model that has been studied previously.

Experimental and computational characterization of mass transfer in high turndown bioreactors.

Single-use bioreactors (SUBs, or disposable bioreactors) are extensively used for the clinical and commercial production of biologics. Despite widespread application, minimal results have been reported utilizing the turndown ratio; an operation mode where the working range of the bioreactor can be expanded to include low fluid volumes. In this work, a systematic investigation into free surface mass transfer and cell growth in high turndown single-use bioreactors is presented. This approach, which combines experimental mass transfer measurements with numerical simulation, deconvolutes the combined effects of headspace mixing and the free surface convective mass transfer on cell growth. Under optimized conditions, mass transfer across the interface alone may be sufficient to satisfy oxygen demands of the cell culture. Within the context of high turndown bioreactors, this finding provides a counterpoint to traditional sparge-based bioreactor operational philosophy. Multiple monoclonal antibody-producing cell lines grown using this high turndown approach showed similar viable cell densities to those cells expanded using a traditional cell bag rocker. Furthermore, cells taken directly from the turndown expansion and placed into production showed identical growth characteristics to traditionally expanded cultures. Taken together, these results suggest that the Xcellerex SUB can be run at a 5:1 working volume as a seed to itself, with no need for system modifications, potentially simplifying preculture operations.

A comprehensive review on heat and mass transfer simulation and measurement module during the baking process

The application of computational fluid dynamics (CFD) for controlling quality boundaries in light of temperature and moisture profiling is detailed in this review. For the mapping of intricate stream design inside the baking oven and its product-based baking interaction, efficient utilization of CFD perspectives can be observed. The most crucial element in baking that affects product quality is temperature. Based on heat transfer, the CFD model proved effective in estimating the product's crumb and crust temperatures. In addition to time and temperature, the position of the dough inside the oven affects the quality of the finished product during baking. CFD demonstrating angles effectively predicts the temperature profiles inside the baked product and henceforth, assists with controlling the extreme quality of the product. Regardless, also demonstrating studies ought to be embraced including mass transport and volume extension during the baking process. A piece of the issues related to moisture and heating measures during exhibiting of bread, bun, and cookies baking process, have been included. This study exhibits CFD to be a significant tool for the simulation of the baking oven and relative expectation of temperature and moisture profiles which eventually impacts starch gelatinization and browning issue during the baking process. The mass transfer during baking and volume expansion of various bakery products can also be modelled using CFD.

Influence of Pore Size on Hydrocarbon Transport in Isostructural Metal-Organic Framework Crystallites.

Hydrocarbon separations using porous materials such as metal-organic frameworks (MOFs) have been proposed to reduce the energy demands associated with current distillation-based methods. Despite the potential of these materials to distinguish hydrocarbons through thermodynamic or kinetic mechanisms, experimental data quantifying hydrocarbon transport in MOFs is lacking. Such mass transfer measurements are vital to elucidate structure-property relationships and design future high-performing separation materials. In this work, we aim to isolate the influence of pore size on hydrocarbon diffusion by studying a pair of isoreticular MOFs, Co2Cl2BBTA and Co2Cl2BTDD. We use a volumetric method to extract mass transport coefficients for six hydrocarbon probe molecules of varying size and chemical functionality. From these nonequilibrium mass transport measurements, we determine the rate-limiting diffusion mechanism and identify trends in hydrocarbon surface permeabilities in the MOFs based on pore size, hydrocarbon chain length, and temperature.

Critical assessment of gassing-in methods to determine mass transfer coefficient in miniature and microbioreactors with gas-liquid flow

Accurate measurements of mass transfer coefficients are critical for reliable characterization of bioreactors. While standardized methods to measure mass transfer coefficients have been established for simple stirred tank reactors, existing methods to characterize mass transfer coefficients have not yet been standardized for alternative reactor types such as miniaturized and biofiltration reactors, leading to inconsistencies in implementation and confusion about the validity of comparisons across different methodologies, volume scales, or reactor types. This study evaluated the accuracy of two commonly used lab-scale methods for the measurement of mass transfer coefficients in a miniature plug-flow reactor: the Dynamic Gassing-In and the Steady State Gassing-In Methods were evaluated. Results revealed that while both experimental methods can be equally accurate and applicable at small scales, there must be careful consideration of mass transfer and volumes peripheral to the reactor itself. To address these findings, a detailed mathematical model was developed and applied to each experimental method, which enabled accurate calculation of the mass transfer coefficients. This approach can be used to analyze experimental data and determine mass transfer coefficients for many reactor types and at any scale. We also propose best practices for mass transfer methods which will enable more consistency in testing and clarity in comparisons between studies.

Development of enhanced three‐dimensional printed packings for scale‐up of distillation columns: A successful case study

AbstractThis publication presents a general approach for the enhancement of packings regarding scalability, separation efficiency, and fluid dynamic properties using three‐dimensional (3D) printing. The methodology is used to develop miniaturized, scalable packings for process development, and scale‐up applications. For this purpose, a 3D printable computer‐aided design version of the Rombopak 9M industrial packing (RP9M‐3D), which is known for its positive scalability properties, was created. An initial characterization by means of computational fluid dynamics simulations and mass transfer measurements reveals positive but also negative design properties. These findings are used to create a more advanced, miniaturized packing structure, the XW‐Pak. The evolved structure is compared to the RP9M‐3D. The simulation and experimental results show that the enhanced packing, which is still in the early stages of development, exhibits higher separation efficiencies with improved scalability properties at the same void fraction and surface area than the RP9M‐3D.

Onset of instabilities in rotating flows by direct numerical simulation

A rotating disk is the canonical experiment for measuring surface reaction rates in geochemical and electrochemical systems. Using the similarity solution for laminar flow around an infinite disk, the mass transfer coefficient can be simply related to the intrinsic reaction rate at the surface. However, measurements of mass transfer rates use a finite-size disk within a larger container of solution; here the flow is no longer strictly laminar, but there must always be some recirculation. Our interest was initially in the assumption of a uniform radial concentration field, how this breaks down near the perimeter of the disk, and what effect that might have on the measured mass transfer rates. However, our numerical simulations suggest that the flow around a finite-size disk becomes time dependent at Reynolds number ( $Re$ ) below 1000, which is much smaller than the typical values in mass-transfer measurements ( ${Re} \sim 10^4$ ). We observe the formation of coherent structures in the flow, which suggest a non-uniform mass transfer at the disk surface. The rotating-disk flow follows a similar sequence of instabilities to the Taylor–Couette flow: a centrifugal instability leading an axisymmetric, time-invariant flow, followed by a Hopf bifurcation to a time-periodic flow. To minimise the possibility that our results are a numerical artefact, we have also simulated the instability in the stationary boundary layer of a rotor–stator flow, comparing with self-similar solutions at low ${Re}$ and with spectral methods near the critical Reynolds number.

Investigation of the Effect of Cutting Directions On the Improvement of Mechanical Parameters of Treated Cork by THT: Experimental Measurement, Modelling and Optimization of Mass Transfer

This work aims to investigate the impact of the cutting direction on the transfer properties of both the native cork and the treated by an optimized cycle at high temperature and boiling for the purpose to improve its mechanical characteristics in all three orthotropic directions. The study of the insulation performance is based on tracking the apparent mass diffusion coefficient (Dapp) variation in order to evolve a new material with the thermal, mass, acoustic and vibratory properties needed for various applications. TGA, IR and SEM analyzes are used to confirm the enhancement of the treated cork. The Dapp of the diffusing chemical species, NaCl (0.7M), is determined by conductimetric method. In transient mode, a mathematical model of mass transfer, which includes the diffusion parameters of the chemical species, is developed. Through the calibration of the model with the experimental measurements the Dapp values ​​were determined and then refined numerically by optimization using the Bat-Algorithm. The obtained results showed that the treatment improves the diffusion property of the native (DN) compared to the treaty (DA) with the values in the order of 10-12 and 10-13 m2.s-1 respectively with a relative uncertainty of 10-7. In addition, this investigation reveals that the radial diffusion coefficient (DR) is significantly higher than the tangential diffusion (DT) and longitudinal (DL) diffusion coefficients which both are almost of the same.

Nanoparticle Aggregation and Thermophoretic Particle Deposition Process in the Flow of Micropolar Nanofluid over a Stretching Sheet.

The purpose of this research is to investigate the consequence of thermophoretic particle deposition (TPD) on the movement of a TiO2/water-based micropolar nanoliquid surface in the existence of a porous medium, a heat source/sink, and bioconvection. Movement, temperature, and mass transfer measurements are also performed in the attendance and nonappearance of nanoparticle aggregation. The nonlinear partial differential equations are transformed into a system of ordinary differential equations using appropriate similarity factors, and numerical research is carried out using the Runge-Kutta-Felhberg 4th/5th order and shooting technique. The obtained results show that improved values of the porous constraint will decline the velocity profile. Improvement in heat source/sink parameter directly affects the temperature profile. Thermophoretic parameter, bioconvection Peclet number, and Lewis number decrease the concentration and bioconvection profiles. Increases in the heat source/sink constraint and solid volume fraction will advance the rate of thermal dispersion. Nanoparticle with aggregation exhibits less impact in case of velocity profile, but shows a greater impact on temperature, concentration, and bioconvection profiles.

Determination of mass transfer coefficient in flow assisted corrosion of steel in liquid Pb[sbnd]Bi. Rotating cylinder geometry

The aim of this experimental and numerical work is to determine the mass transfer at the wall of a steel cylinder rotating within liquid Lead-Bismuth blend. This is a crucial parameter for the analysis of corrosion tests performed in the CICLAD experimental set-up for the investigation of flow assisted corrosion of steel by liquid metals. As a reliable numerical modelling must rely on experimental validation, and since no direct wall mass transfer measurement is possible in CICLAD, a scaled electrochemical model has been achieved. Modelling the turbulence in this rotating configuration is shown to require the use of a Reynolds-Stress Model. A sensitivity to the Schmidt number is observed in the numerical simulations representing the measured mass transfer in the electrochemical model. Simulations dedicated to liquid PbBi are thus presented in addition to those dedicated to the aqueous solution used in the electrochemical model. Following correlations are proposed for the prediction of Fe mass transfer at the wall of a steel rotating cylinder in liquid Pb-Bi:Sh = 1.9 × 10−1(Re2Sc)0.31 for 2 × 109 < Re2Sc < 5.3 × 1010;Sh = 1.4 × 10−3(Re2Sc)0.51 for 5.3 × 1010 < Re2Sc < 8.5 × 1011;Sh = 1.1 × 10−2(Re2Sc)0.43 for 8.5 × 1011 < Re2Sc < 1013.This mass transfer coefficient has recently been used to get a better understanding of corrosion in PbBi [1].

Gas-liquid mass transfer characterization in a thin shrinking film at an atomization nozzle

In this paper, a light absorption method is applied to estimate the thickness of an atomizing liquid film at microscale that exits a spraying nozzle. By using a dioxygen sensitive dye, called resazurin, it is also possible to determine the local profile of dioxygen concentration resulting from the gas-liquid transfer from air into the liquid film. The method relies on the use of the well-known Beer-Lambert law, the linearity of which has been experimentally proved for the optical system and the dye concentration used in this study. From thickness and dye concentration measurements in the liquid film formed at the outlet of the nozzle, a mass transfer analysis is performed, providing a local description of the dioxygen mass transfer (concentration fluxes, etc.) occurring in this film. This optical method, leading to a dual measurement of thickness and mass transfer, is the first to be successfully implemented in this type of thin liquid film in sprays (≈ 30 µm) at microscale and with such high velocities (≈ 8 m/s). The method is non-invasive and does not disturb the flow, in comparison with classical liquid phase measurements where the liquid is collected to be titrated. The values of the mass transfer coefficients, kL, deduced from our analysis for the liquid film (2.2 × 10−3–1.2 × 10−2 m/s) are consistent with global measurements already obtained, validating our measurement and giving more insight into the mass transfer occurring in this film.