Side Mass Transfer Research Articles

Improved model for thermal transmission in evacuated tubes: Effect of non-uniform heat flux and circumferential conduction

Evacuated tubes are extensively utilized for converting solar energy into thermal energy owing to their exceptional thermal properties and affordability. The circumferential temperature gradient of the evacuated tube is significant to the heat and mass transfer inside, but it is often neglected. This research proposed an improved model incorporating non-uniform heat flux and circumferential conduction to obtain the temperature distribution. In the experiment, A thermal insulation material was inserted inside the inner tube to create an adiabatic boundary. Various conditions (non-uniform, rectangular, and uniform heat fluxes, circumferential conduction of the coating) were numerically compared. The enhanced combined thermal transmission model was validated, demonstrating a relative error of 6.45 % in temperature increase calculation and increasing the prediction accuracy by 42.15 % at least. The distribution of the heat flux and the thermal conduction of the coating were identified as the primary factors affecting the heat transfer properties of the evacuated tube. An imbalanced distribution of heat flux resulted in non-uniform heat transfer, whereas the circumferential conduction within the coating effectively modulated the temperature distribution to achieve uniformity. The local heat transfer coefficient exhibited non-uniformity, with calculated values ranging from 0.23 to 3.25 W/(m2∙K), and an error range of −16 to +3 %.

EFFECT OF MICROSTRUCTURES ON MASS TRANSFER INSIDE A HIERARCHICALLY STRUCTURED POROUS CATALYST

In this paper, the pore network model to investigate the reaction-diffusion process in the hierarchically structured porous catalyst particle is extended to consider the phenomenon of deactivation by coking. In this framework, the interaction of internal particle pore structure and mass transfer under the condition of coke deposition is examined. Then, the effect of structural features, namely macroporosity and pore size ratio, the deactivation properties, the maximum loading of coke, as well as the transport properties, the pore Damköhler number on the net reaction rate, and deactivation of the particle have been investigated. Three deactivation mechanisms are accounted for, namely, the site coverage, the pore narrowing, and the pore blockage. It is found that the deactivation of the catalyst particle can be divided into two conditions: the kinetic deactivation and the structural deactivation. It is shown that depending on the Damköhler number, increasing the macroporosity does not necessarily improve the reactivity and deactivation resistance of the catalyst. The key finding of this work is to demonstrate and quantify how changing the typical fresh catalyst microstructure into a hierarchical one influences the reactivity and deactivation.

Unraveling the mechanism and kinetics of aerobic Baeyer–Villiger oxidation of cyclohexanone

AbstractThis study explores the aerobic Baeyer–Villiger oxidation of cyclohexanone into ε‐caprolactone using metalloporphyrin and benzaldehyde, a greener process to replace hazardous concentrated peroxyacid. The reaction mechanism involves a series of free radical reactions, identified through in situ EPR. In this complex three‐component reaction, we developed an intrinsic kinetic model based on the proposed mechanism. Utilizing a hyperbolic equation, the model well fits experimental data, describing biomimetic catalytic behavior of the aerobic Baeyer–Villiger oxidation. The reaction orders for the three reactants corroborate the kinetic model, with the activation energy of oxygen (130.27 kJ/mol) surpassing cyclohexanone (94.85 kJ/mol) and benzaldehyde (40.73 kJ/mol), implying slow initial oxygen activation while rapid subsequent benzaldehyde oxidation, making oxygen transfer and activation key steps. This unified approach to elementary reaction, mechanism, and intrinsic kinetics provides robust forecasts and lays the groundwork for additional studies, such as side reactions control and mass transfer enhancement and reactor design.

Micro-interface enhanced mass transfer sodium carbonate absorption carbon dioxide reaction

Micro-interface intensified reactor (MIR) can be applied in series/parallel in the absorption of CO2 in industrial gases by Na2CO3 due to the ability to produce large numbers of stable microbubbles. This work focuses on the variation pattern of mass transfer characteristics parameters of the reaction gas in Na2CO3 solution under the influence of different solution properties and operating parameters in the reaction of CO2 absorption by Na2CO3. The mass transfer characteristics parameters include bubble Sauter mean diameter, gas holdup, interfacial area, liquid side mass transfer coefficient, and liquid side volume mass transfer coefficient kLa. The solution properties and operating parameters include Na2CO3 concentration (0.05–2.0 mol·L−1), superficial gas velocity (0.00221–0.01989 m·s−1), superficial liquid velocity (0.00332–0.02984 m·s−1), and ionic strength (1.42456–1.59588 mol·kg−1). And volumetric mass transfer coefficients kLa and superficial reaction rates r of the MIR and the bubble column reactor are compared in the reaction of sodium carbonate absorption of carbon dioxide, and the former shows a greater improvement under different solution properties and operating parameters. The enhanced role of MIR in mass transfer in non-homogeneous reactions is verified and the feasibility of industrial practical applications of MIR is demonstrated.

Design and evaluation of co-currently illuminated two-phase bubbly flow photochemical reactors

Current two-phase flow photochemical reactors are lacking energy efficiency required for industrial applicability. As an alternative, co-currently illuminated bubbly flow photochemical reactors are proposed. These have the advantage of running at higher absorbance values, thereby wasting less photons, improving cost efficiency, and decreasing gas holdup by separating gas and liquid residence time in the reactor. A mathematical model was used in the study in combination with photosensitized reactions, which yielded three coupled differential equations and four non-dimensional groups governing the reactor performance. A parameter study yielded an optimal operating point at a quantum photon balance (ϕtotρ) of 1, an absorbance (AS) of at least 1, a chemical quenching parameter (κA) of less than 0.1, and a sensitizer stability ratio (ϕS/fS) of less than 1. Optimal absorbance was determined via the use of a ray tracing study, yielding a theoretical optimal absorbance of 1.75 using 7 µM of rose bengal. The modelling results are experimentally validated, and the model was shown to be suitable across a wide range of operating conditions. Optimal absorbance was experimentally evaluated to match the modelling results, higher absorbance values lead to more local absorbance, throttling reactor performance. With high reagent concentrations, the reaction was found to be liquid side mass transfer limited. Guidelines are presented to design this novel type of reactor and ways to improve the reactor performance in scaled up versions. The reactor was compared against the current state-of-the-art reactors, yielding an improvement PSTY by 4.5 times and an increased reagent/sensitizer ratio by 100 times, both drastically decreasing operational cost of the reactor.

Process intensification through the application of centrifugal field: An experimental study of absorption processes using the falling film microreactor

In this work, liquid and gas side mass transfer characteristics were investigated within a centrifugal field using the falling film microreactor (FFMR). Enhancement in mass transfer rates were assessed by relating the absorption efficiency of the processes conducted within the centrifugal field to those in which liquid flows are purely-driven by gravity. The liquid side rotational mass transfer coefficients (kL) determined were considerably higher than those without rotation. Similarly, relative increase in rotational gas side mass transfer coefficient (kG) was also significantly high (up to 42%).The liquid side experimental data were well predicted by the modified correlation (a power law equation modified to consider the effect of the applied external force, geometry of the system, hydrodynamic characteristics and physical properties of the fluids employed) at lower rotational speed but deviated considerably at higher rotational speeds while, the gas side experimental data were well predicted by the correlation.

CO2 absorption using benzylamine as absorbent and promoter in a hollow fiber membrane contactor: A numerical study

Benzylamine (BZA) is a novel amine that indicates a promising potential for CO2 absorption. In this work, a mathematical model has been presented to investigate the CO2 absorption using aqueous BZA compared to aqueous monoethanolamine (MEA), diethanolamine (DEA), and 4-diethylamino-2-butanol (DEAB) in a hollow fiber membrane contactor (HFMC). Several factors such as CO2 partial pressure, amine concentration, gas velocity, liquid velocity, temperature, wettability, and mass transfer resistance of phases have been studied. According to the results, increment in the amine concentration, CO2 partial pressure, liquid velocity, gas velocity, and temperature have enhanced the CO2 absorption flux. Also, adding BZA to aqueous MDEA and K2CO3 significantly increases the CO2 absorption flux in both solutions. Moreover, the mass transfer resistance of individual phases reveals that the liquid phase mass transfer resistance is the controlling phase in non-wetted mode, while with membrane wetting, contribution of membrane side mass transfer resistance increases and become the controlling phase. In general, BZA could be a prominent potential choice as absorbent and promoter for CO2 absorption in HFMCs.

Modelling of absorption process by seawater droplets for flue gas desulfurization application

• A new model for calculating the mass transfer coefficient between the droplet and the gaseous phase has been implemented. • The new model takes additional physical parameters such as surface renewal intensity. • With the newly-implemented model in 3D CFD simulations better results are achieved. Flue gas desulfurization technology for sulfur dioxide removal from exhausts of combustion processes is becoming more widespread as allowed emission levels keep getting lowered. Spray scrubbers have gained traction in coastal and maritime applications, where seawater can be used as a scrubbing liquid. Detailed numerical models are required for accurate replication of processes in these applications, with complex physical and chemical phenomena considered. Among them, mass transfer modeling between phases has proven to be particularly important for obtaining accurate simulation results. Present work investigates a new model for calculating liquid side mass transfer coefficient in falling droplets, which considers additional parameters such as surface renewal rate, Reynolds number, and droplet diameter, compared to simplified and more common approaches. Initial modelling was performed on a single droplet level, followed by the implementation in the computational fluid dynamics framework and expansion to the entire spray. Desulfurization efficiencies for real cases modelled with the new approach were compared with the experimental data and the previously used penetration theory model results. The newly implemented model investigated the influence of operational parameters such as water and gas flow, sulfur dioxide concentration, droplet size, and distribution on desulfurization efficiency. The results obtained by the new model showed the expected trend of increased efficiency with the water flow increase, as well as greater sensitivity to operational conditions in different cases. Furthermore, compared to the previously used model, the present work more accurately replicated removal efficiencies in simulations of seawater spray scrubber applications, which is beneficial in designing new and more efficient equipment.

Design of a Combined Proportional Integral Derivative Controller to Regulate the Temperature Inside a High-Temperature Tubular Solar Reactor

Abstract Solar fuels are proven to be promising candidates for thermochemical energy storage. However, the transient nature of solar radiation is an obstacle to maintaining a stable operational temperature inside a solar reactor. To overcome this challenge, the temperature of a solar reactor can be regulated by controlling the incoming solar radiation or the feedstock flowrate inside the reactor. In this work, a combined proportional integral derivative (PID) controller is implemented to regulate the temperature inside a high-temperature tubular solar reactor with counter-current flowing gas/particles. The control model incorporates two control systems to regulate incoming solar radiation and gas flow simultaneously. The design of the controller is based on a reduced-order numerical model of a high-temperature tubular solar reactor that is vertically oriented with an upward gas flow and downward particle flow. The reactor receives heat circumferentially through its wall over a finite segment of its length. Formulation of the heat transfer model is presented by applying the energy balance for the reactor tube and considering heat and mass transfer inside. A set of governing differential equations are solved numerically by using the finite volume method to obtain reactor wall, particles, and gas temperatures along the reactor length with various boundary conditions. Simulation results are used to tune the PID controller parameters by utilizing the Ziegler–Nichols tuning method. Both the simulation results and the controller performance are visualized on the labview platform. The controller is challenged to track different temperature setpoints with different scenarios of transient solar radiation. The performance of the PID controller was compared to experimental results obtained from an industrial PID controller embedded in a 7 kW electric furnace. Results show that the combined PID controller is successful in maintaining a stable temperature inside the reactor by regulating the incoming solar radiation and the flowrate via small steady-state error and reasonable settling time and overshoot.

Taylor bubble formation and flowing in a straight millimetric channel with a cross-junction inlet geometry Part II: Gas-liquid mass transfer

• Mass transfer was studied during bubble formation at a cross-junction. • Accuracy of resazurin-based technique was improved by advanced image systems. • Different mechanisms were observed for the developing O 2 concentration fields. • Oxygen concentration fields were measured during and after bubble pinch-off. • A scaling law relating k L a and f c was proposed to gather literature data. Using the resazurin-based colorimetric technique and advanced image acquisition, the equivalent oxygen concentration fields inside the liquid slugs were measured during and after the bubble formation stage at a cross-junction in a straight millimetric channel. Firstly, two different mechanisms were identified for the development of oxygen concentration fields depending on the two-phase Reynolds numbers (Re TP ). Under low Re TP , a jet-like central oxygen concentration ‘finger’ occurred between the newly formed bubble and the gas finger at the bubble pinch-off point. Right after the bubble pinch-off, the dissolved oxygen was transported first by the entering liquid from two side inlets, and later by the developing recirculation loop inside the liquid slug. Under higher Re TP , two highly concentrated oxygen concentration spots were formed near the bubble rear and the channel wall region, and a much more complex flow structure in the liquid slug appeared. Then, whatever the operating conditions, it was observed that the averaged oxygen concentrations inside the liquid slug followed a nearly linear relation as a function of the axial position in the channel, and that the related mass flux density decreased as far as the bubbles flowed along the channel’s length. The bubble formation process could be decomposed into three stages when considering the temporal evolution of the cumulated oxygen mass and depending on the development of the liquid slug. At last, the overall volumetric liquid side mass transfer coefficients ( k L a ) were deduced from the concentration fields, and found to linearly increase with the recirculation frequencies, leading to a scaling law.

Study of Pressure Retarded Osmosis Process in Hollow Fiber Membrane: Cylindrical Model for Description of Energy Production

A new mathematical model was developed to predict the cylindrical effect of the membrane performance in the pressure retarded osmosis process. The cylindrical membrane transport layers (the draw side boundary and the porous membrane) were divided into very thin sublayers with constant mass transport parameters, among others with a constant radius in every sublayer. The obtained second-order differential mass balance equations were solved analytically, with constant parameters written for every sublayer. The algebraic equation system involving 2N equations was then solved for the determinant solution. It was shown that the membrane properties, water permeability (A), salt permeability (B), structural parameter (S) and the operating conditions (inlet draw side solute concentration and draw side mass transfer coefficient) affect the water flux strongly, and thus the membrane performance, due to the cylindrical effect caused by the variable surface and volume of the sublayers. This effect significantly depends on the lumen radius. The lower radius means a larger change in the internal surface/volume of sublayers with ΔR thickness. The predicted results correspond to that of the flat-sheet membrane layer at ro = 10,000 μm. At the end of this manuscript, the calculated mass transfer rates were compared to those measured. It was stated that the curvature effect in using a capillary membrane must not be left out of consideration when applying hollow fiber membrane modules due to their relatively low lumen radius. The presented model provides more precise prediction of the performance in the case of hollow fiber membranes.

Numerical analysis of a counter-flow wet cooling tower and its plume

A one-dimensional model to study the heat and mass transfer inside and immediately above a wet counter-flow cooling tower is described. The wet cooling tower thermodynamic model assigns zone-specific Merkel numbers to each of the rain, fill, and spray zones, and it includes an atmospheric plume model. Using the present formulation, zone-by-zone rates of heat rejection and water evaporation can be estimated, as can the visible plume height. The model is validated against the well-established Poppe and Merkel methods as well as select field data. Cooling tower performance and plume visibility are evaluated under a variety of climatic conditions (hot-dry, hot-humid, cool-dry and cool-humid), cooling tower designs (e.g. fill zone height, H f z ), and operating conditions (e.g. water-to-air mass flow rate ratio, L / G ). The parametric study in question highlights the ability of the proposed model to predict the impact of ambient conditions, cooling tower design parameters, and operating conditions on overall performance and patterns of atmospheric dispersion. The proposed model is ideal for numerical optimization of cooling towers that need to meet stringent thermal performance and plume visibility requirements. • A coupled one-dimensional cooling tower and plume model is developed. • Heat transfer in each zone of the tower analyzed at varying ambient conditions. • Plume visibility at different air flow rates studied at varying ambient conditions.

Effect of vacuum environment on air side heat and mass transfer characters of plain fin-tube heat exchangers

Air-side heat and mass transfer performance of plain fin-tube heat exchangers at different vacuum degree have been experimentally investigated. In this experiment, influence of air inlet humidity on air-side heat and mass transfer under vacuum environment is studied by controlling vacuum degree and air inlet humidity. Results show that: variation trend of air-side sensible heat transfer coefficient (ha), heat transfer j-factor (jh), mass transfer coefficient (hm) and mass transfer j-factor (jm) are not all time remain the same. Variation trend of ha, jh are the same with increase of vacuum degree when air inlet humidity changes, ha is gradually decreased and jh is gradually increased. Variation trend of hm is opposite with the increase of vacuum degree when the air inlet humidity changes. Under constant air inlet relative humidity conditions, hm is gradually increased. Under constant air inlet moisture content conditions, hm is gradually decreased. However, variation trend of jm is the same with increase of vacuum degree when air inlet humidity changes, both are increased. But slope of jm is greater under constant air inlet relative humidity conditions. Overall heat transfer performance is greatly affected by air inlet humidity changes. Under constant air inlet relative humidity conditions, when air inlet relative humidity increases from 50% to 70% and then to 90%, proportion of latent heat transfer increases from 30.98%∼53.99% to 36.53%∼56.95% and then increases to 44.19%∼64.04% with vacuum degree increases. As proportion of latent heat transfer increases, air-side total heat transfer performance is not obviously reduced. Under constant air inlet moisture content conditions, when air inlet moisture content increases from 15 to 20 g/kg, proportion of latent heat transfer is basically unchanged with increase of vacuum degree, at about 36% and 37%, respectively. So, total heat transfer performance on air side decreases obviously. In order to model air-side heat and mass transfer performance of the complex structure fin-tube heat exchangers, a simplified model is investigated under vacuum environment. Results show that influence of pressure changes on heat and mass transfer based on theory is basically consistent with the results of regression analysis based on experimental results. This study can provide guiding suggestions for the design of heat exchangers under vacuum environment.

Online application oriented dynamic modeling for the flue gas desulfurization tower in coal-fired power plants

A dynamic model for the flue gas desulfurization tower in coal-fired power plants is proposed. The model is validated with the data from a 350 MW unit. The penetration theory is adopted in modeling. The movement and the size of the slurry droplets, the temperature and the flow rate of the flue gas, as well as the chemical reactions have been taken into account. Three parameters in the model are found to have a critical impact on the model accuracy, i.e., the droplets’ initial velocity, the number of droplets leaving all nozzles in a single spray layer per unit time, and the liquid side mass transfer coefficient of sulfur dioxide. These parameters need to be identified periodically in real applications. The quantitative relationship between pH and liquid side mass transfer coefficient is given. The main hypotheses and parameters of the model were discussed in order to quantify their respective influence. The model may be used to simulate the desulfurization process across the entire load range. Specifically, it may be used to predict the desulfurization efficiency online, so that applied potentially for the operational optimization.

New electroscrubbing process for desulfurization

A new process for removing sulfur from gas using electricity is presented. The process combines electrochemical production of active oxidizing species with an oxidative scrubber for desulfurization. Reactions for the electrochemical cell and the scrubbing tower are presented and a scrubbing set-up with a continuous electrolyte recirculation is validated on synthetic biogas. The test shows that a gas flow of 200 L/h with 1330 ppm H 2 S can be cleaned down to non-detectable levels of sulfur in a single step, at a current efficiency of 29%. This is a very high removal percentage for a high concentration of H 2 S. Solid sulfur can be removed from the system after the experiments. The sulfur has traces of NaClO and no other products were detected. A simple model based on estimated gas side mass transfer coefficients were used to estimate a scrubber height of only a few centimeters. The experiments supports the model. This technology allows for a robust implementation of sulfur free applications in a future green fuel and green chemistry like Power-to-X (PtX) and carbon capture and utilization (CCU). Sulfur compounds are poison for most heterogeneous catalysts, thus for carbon utilization, the carbon gas source has to be desulfurized .

Analysis of low-grade heat driven ethanol-silica gel adsorption chiller

The main objective of this study is to design a low-grade heat driven ethanol-silica gel adsorption chiller. The low-grade waste heat is utilized in an adsorption chiller. For this purpose, an innovative bed heat exchanger including a condenser embedded inside the adsorbent bed is uniquely designed. The silica gel/ethanol pair is examined both analytically and numerically in this article. The cycles of the adsorption chiller are performed experimentally. The obtained isotherm for the silica gel/ethanol fitted to Type III isotherm behavior. The obtained equations of isotherm are also validated numerically. The new adsorption chiller design used in this study has reduced the desorption temperature for silica gel/ethanol pair to 37 °C which will widen the application area of adsorption chillers. The COMSOL Multiphysics program is used for 2-D numerical analysis of adsorbent bed. The mass transfer inside of the particle, the heat transfer in porous media, and Darcy law are used for analyzing the heat and mass transfer of the bed. Temperature and concentration distributions of adsorbent bed during the duration of adsorption and desorption processes are examined numerically. The specific cooling power and volumetric cooling power values of the system are found as 20.2 Wkg−1 and 4.5 kWm−3, respectively.

Advanced ammonia nitrogen removal and recovery technology using electrokinetic and stripping process towards a sustainable nitrogen cycle: A review

Ammonia removal and recovery from wastewater have been a critical issue worldwide and a key to achieve a sustainable nitrogen cycle and circular economy. Conventional ammonia removal via air stripping needs pH adjustment pretreatment with chemical additives while electrokinetic technologies can provide electrochemically in-situ pH control without chemicals needed. The integration of electrokinetic and air stripping technologies is a potential process for the simultaneous removal/recovery of ammonia/ammonium from wastewater. This study consolidates research findings of the separate research domains of electrokinetic and air stripping technologies and aims to identify an integrated process for the simultaneous nitrogen removal/recovery from waste streams. Process integration involves research on improved ammonia removal efficiencies and liquid side mass transfer performances using innovative air stripping system designs and gas-liquid contactors, e.g., rotating packed beds and membrane contactors, compared with the conventional stripping tower process. Findings in the applications and performances of electrokinetic separation processes, including electrodialysis, electrodeionization, capacitive deionization, electrochemical cell, and bio-electrochemical systems, on the removal/recovery of ammonia/ammonium, are a crucial link to integration as well. Energy consumptions between 5–20.4 kWh/kg–NH4-N with a removal ratio of around 90% for electrokinetic processes are currently achievable, and some groups can be implemented on the biodegradable organic substrates from urine. Innovative hybrid technologies of ammonia nitrogen removal/recovery with energy production and co-product valorization that reduce the overall cost and energy consumption via integrated processes optimization, and discussions on the environmental impact assessment (via life cycle assessment) and economic benefit analysis (via techno-economic analysis) of ammonia recovery practices on waste streams are investigated.

A coarse-grained simulation of heat and mass transfer through a graphene oxide-based composite membrane

Composite porous membranes have been widely used in various applications. The modeling and manipulation of heat and mass through a composite membrane is challenging. Previous methods for simulating heat conductivity and mass diffusivity in membranes, either the micro-scale all atom molecular dynamics simulation (MDS), or macro-scale resistance-in-series models, cannot accurately reflect the mesoscale feature in the membrane structure. To solve this issue, here, a new approach, a mesoscale coarse-grained simulation of heat conduction and moisture diffusion in a graphene-oxide based composite porous membrane (GO-PVP/PVDF) is performed. A “template” method based on the Fast Fourier transformation (FFT) is proposed for the setting up of coarse-grained models of the rough contact surfaces between different layers/components. The mesoscale dissipative particle dynamics (DPD) method is used to control the dynamics of the coarse-grained beads. Then, the heat and mass transfer inside, as well as the wetting behavior on the surface, are modeled. It is shown that the heat and mass transfer performance can be optimized by adjusting the membrane structures and functional groups in the materials. This approach can be used to directly evaluate and manipulate membrane performance by simultaneously considering its mesoscale properties like roughness and pore sizes, and its micro scale properties like molecular group information in materials.

An intensification of mass transfer process for gas-liquid counter-current flow in a novel microchannel with limited path for CO2 capture

Microchemical technology shows prospect in the process intensification field of carbon capture and storage, however, there remain great challenges in microchemical technology for gas-liquid mass transfer with counter-current flow. In this work, we proposed a micro-apparatus with confined structure for gas-liquid counter-current flow mass transfer. The flow patterns on the confined structure, steady flow and bead flow, were observed, furthermore, the critical flow rate between them was measured. The influences of confined structure geometry, surface tension and viscosity of liquid on the meniscus at the gas-liquid interface were studied. The operation window of micro-apparatus with different types of confined structures was examined. The liquid loading and gas loading of micro-apparatus with S1005 were tested to be 230 μL/min and 500 mL/min, respectively. The system of absorption of pure CO2 in a 1 M NaOH solution was used to study the mass transfer. The average liquid side mass transfer coefficient of 25.1 × 10−5 m/s was measured at liquid flow rate of 30 μL/min and gas flow rate of 300 μL/min, which proves that the micro-apparatus achieves the process intensification of CO2 absorption.

Gas–Liquid Mass Transfer around a Rising Bubble: Combined Effect of Rheology and Surfactant

The influence of viscosity and surface tension on oxygen transfer was investigated using planar laser-induced fluorescence with inhibition (PLIF-I). The surface tension and the viscosity were modified using Triton X-100 and polyacrylamide, respectively. Changes in the hydrodynamic parameters of millimetric bubbles were identified, and transfer parameters were calculated. The results revealed a decrease in the mass transferred in the presence of a contaminant. For modified viscosity, the decrease in mass transferred was allowed for by current correlations, but the presence of surfactant led to a sharp decrease in the liquid side mass transfer coefficient, which became even lower when polymer was added. An explanation for the gap between classical correlations and experimental values of kL is discussed, and a hypothesis of the existence of an accumulation of contaminant in the diffusion layer is proposed. This led to the possibility of a decrease in the diffusion coefficient and oxygen saturation concentration in the liquid film, explaining the discrepancy between models and experience. Adapted values of DO2 and [O2] * in this layer were estimated. This original study unravels the complexity of mass transfer from an air bubble in a complex medium.