Two-film Model Research Articles

Atmospheric partitioning and the air–water exchange of polycyclic aromatic hydrocarbons in a large shallow Chinese lake (Lake Chaohu)

The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in dissolved phase from Lake Chaohu were measured by (GC–MS). The composition and seasonal variation were investigated. The diffusive air–water exchange flux was estimated by a two-film model, and the uncertainty in the flux calculations and the sensitivity of the parameters were evaluated. The following results were obtained: (1) the average residual levels of all PAHs (PAH16) in the atmosphere from Lake Chaohu were 60.85±46.17ngm−3 in the gaseous phase and 14.32±23.82ngm−3 in the particulate phase. The dissolved PAH16 level was 173.46±132.89ngL−1. (2) The seasonal variation of average PAH16 contents ranged from 43.09±33.20ngm−3 (summer) to 137.47±41.69ngm−3 (winter) in gaseous phase, from 6.62±2.72ngm−3 (summer) to 56.13±22.99ngm−3 (winter) in particulate phase, and 142.68±74.68ngL−1 (winter) to 360.00±176.60ngL−1 (summer) in water samples. Obvious seasonal trends of PAH16 concentrations were found in the atmosphere and water. The values of PAH16 for both the atmosphere and the water were significantly correlated with temperature. (3) The monthly diffusive air–water exchange flux of total PAH16 ranged from −1.77×104ngm−2d−1 to 1.11×105ngm−2d−1, with an average value of 3.45×104ngm−2d−1. (4) The results of a Monte Carlo simulation showed that the monthly average PAH fluxes ranged from −3.4×103ngm−2d−1 to 1.6×104ngm−2d−1 throughout the year, and the uncertainties for individual PAHs were compared. (5) According to the sensitivity analysis, the concentrations of dissolved and gaseous phase PAHs were the two most important factors affecting the results of the flux calculations.

Kinetics of carbon dioxide absorption into aqueous [Hmim][Gly] solution

CO2 absorption performance in the [Hmim][Gly] solution was investigated in detail at 298, 303, 313, 323K within the concentration range of 0.5–1.2M under an atmospheric pressure by using a double stirred cell absorber with a planar gas–liquid interface. The density, viscosity and pH of the [Hmim][Gly] solution were obtained, and the solubility and diffusivity of CO2 in [Hmim][Gly] solution were calculated. To explore the regeneration property of the CO2-loaded solution, method under vacuum pressure was used by varying the regeneration temperature from 328 to 343K and the regeneration time in the range of 30–120min. The effect of regeneration cycles on regeneration efficiency was also determined. The kinetic results demonstrated that the reaction took place in a fast pseudo-first order regime. Hatta number Ha, the enhancement factor E, the overall reaction kinetic constant kov and the second-order rate constant k2 were obtained using the two-film model. At the absorption temperature of 303K, the enhancement factor E was linear with CIL1/2. The second-order reaction rate was determined as the following equation: k2=3.04×107exp(−3050/T).

Neutral poly- and perfluoroalkyl substances in air and seawater of the North Sea

Concentrations of neutral poly- and perfluoroalkyl substances (PFASs), such as fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamides (FASAs), perfluoroalkane sufonamidoethanols (FASEs), and fluorotelomer acrylates (FTACs), have been simultaneously determined in surface seawater and the atmosphere of the North Sea. Seawater and air samples were taken aboard the German research vessel Heincke on the cruise 303 from 15 to 24 May 2009. The concentrations of FTOHs, FASAs, FASEs, and FTACs in the dissolved phase were 2.6-74, <0.1-19, <0.1-63, and <1.0-9.0 pg L(-1), respectively. The highest concentrations were determined in the estuary of the Weser and Elbe rivers and a decreasing concentration profile appeared with increasing distance from the coast toward the central part of the North Sea. Gaseous FTOHs, FASAs, FASEs, and FTACs were in the range of 36-126, 3.1-26, 3.7-19, and 0.8-5.6 pg m(-3), which were consistent with the concentrations determined in 2007 in the North Sea, and approximately five times lower than those reported for an urban area of Northern Germany. These results suggested continuous continental emissions of neutral PFASs followed by transport toward the marine environment. Air-seawater gas exchanges of neutral PFASs were estimated using fugacity ratios and the two-film resistance model based upon paired air-seawater concentrations and estimated Henry's law constant values. Volatilization dominated for all neutral PFASs in the North Sea. The air-seawater gas exchange fluxes were in the range of 2.5×10(3)-3.6×10(5) pg m(-2) for FTOHs, 1.8×10(2)-1.0×10(5) pg m(-2) for FASAs, 1.1×10(2)-3.0×10(5) pg m(-2) for FASEs and 6.3×10(2)-2.0×10(4) pg m(-2) for FTACs, respectively. These results suggest that the air-seawater gas exchange is an important process that intervenes in the transport and fate for neutral PFASs in the marine environment.

Kinetic study of carbon dioxide absorption with aqueous potassium carbonate promoted by arginine

The absorption of carbon dioxide (CO2) into aqueous 35wt.% equivalent potassium carbonate (K2CO3) solution was performed using a wetted wall column at temperatures from 313K to 343K. Effect of arginine concentrations on absorption rates of CO2 into carbonate solutions was investigated and the second-order rate constant k1 was obtained using two-film model. Preliminary screening results showed that arginine was an effective promoter in aqueous K2CO3 solution for CO2 capture. The reaction of CO2 with arginine is described using zwitterionic mechanism. The overall reaction kinetic constant kov strongly increased with the increase of arginine concentration and absorption temperature under the investigated range. Based on the pseudo-first-order regime, the reaction rate parameters were obtained from the kinetic measurements and k1 was determined as 33,641 and 85,367Lmol−1s−1 at 315K and 325K, respectively with activation energy of 71.9kJmol−1. The overall reaction rate for CO2 absorption into promoted K2CO3 were described as the following equation: -rCO2=2.58×1016exp-8645TCArg+4.32×1013exp-6666TCOH-CCO2.

Effect of bidirectional mass transfer on non-isothermal gas absorption process

The simultaneous heat and mass process in a binary gas–liquid mixture is modelled by reformulating the classical two-film theory. The original expression from the two-film model is reformulated to obtain algebraic equations where all interfacial quantities are explicitly described in terms of bulk conditions. Use of the new formulation is demonstrated in the analysis of some absorbers operating under various conditions. Influence of various operating parameters is discussed including gas and liquid compositions, liquid pre-cooling, transfer coefficients and flow rates. The new formulation would provide a convenient tool in the analysis of gas–liquid contact devices in general.

Numerical study of the influence of heterogeneous kinetics on the carbon consumption by oxidation of a single coal particle

This work is devoted to the numerical study of the influence of heterogeneous kinetics on the oxidation rates of a single carbon particle in quiescent and non-quiescent environments. The coal particle is represented by moisture- and ash-free nonporous carbon while the coal rank is implemented using several kinetic rate expressions. The model includes six gaseous chemical species (O2, CO2, CO, H2O, H2, N2). Three heterogeneous reactions are employed (C+O2, C+CO2 and C+H2O), along with two homogeneous semi-global reactions, namely carbon monoxide oxidation and the water–gas shift reaction. Several semi-global reaction rate expressions taken from the literature are utilized. The Navier–Stokes equations coupled with the energy and species conservation equations are used to solve the problem by means of the pseudo-steady state approach. At the surface of the particle, the balance of mass, energy and species concentration is applied including the effect of the Stefan flow and heat loss due to radiation at the surface of the particle. The model and the code used are validated against an analytic two-film model. Good agreement is observed. The numerical simulations performed reveal that the origin of heterogeneous kinetics has a significant effect on the carbon consumption rates of the particle. In particular, the maximal discrepancy between results is achieved in a kinetically controlled regime and is proportional by a factor of 10 in respect to carbon mass flux on the particle surface. Additionally, the influence of the particle Reynolds number referring to the laminar flow regime, the ambient O2 mass fraction and the temperature on the regimes of combustion and gasification is discussed.

Low-Frequency Ultrasound-Induced Transport across Non-Raft-Forming Ternary Lipid Bilayers

We examined the effect of bilayer composition on membrane sensitivity to low-frequency ultrasound (LFUS) in bilayers composed of ternary mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), dipalmitoyl-phosphocholine (DPPC), and cholesterol. The phase diagram of this system does not display macroscopic phase coexistence between liquid phases (although there are suggestions that there is coexistence between a liquid and a solid phase). Samples from across the composition space were exposed to 20 kHz, continuous wave ultrasound, and the response of the bilayer was quantified using steady-state fluorescence spectroscopy to measure the release of a self-quenching dye, calcein, from large unilamellar vesicles. Dynamic light scattering measurements indicate that, in this system, release proceeds primarily by transport through the vesicle bilayer. While vesicle destruction might account, at least in part, for the light scattering trends observed, evidence of destruction was not as obvious as in other lipid systems. Values for bilayer permeability are obtained by fitting release kinetics to a two-film theory mathematical model. The permeability due to LFUS is found to increase with increasing DPPC content, as the bilayer tends toward the solid-ordered phase. Permeability, and thus sensitivity to LFUS, decreases with either POPC or cholesterol mole fractions. In the liquid regime of this system, there is no recorded phase transition; thus cholesterol is the determining factor in release rates. However, the presence of domain boundaries between distinctly differing phases of liquid and solid is found to cause release rates to more than double. The correlation of permeability with phase behavior might prove useful in designing and developing therapies based on ultrasound and membrane interactions.

Comparison of micrometeorological and two-film estimates of air–water gas exchange for alpha-hexachlorocyclohexane in the Canadian archipelago

The air-sea gas exchange of alpha-hexachlorocyclohexane (α-HCH) in the Canadian Arctic was estimated using a micrometeorological approach and the commonly used Whitman two-film model. Concurrent shipboard measurements of α-HCH in air at two heights (1 and 15 m) and in surface seawater were conducted during the Circumpolar Flaw Lead study in 2008. Sampling was carried out during eight events in the early summer time when open water was encountered. The micrometeorological technique employed the vertical gradient in air concentration and the wind speed to estimate the flux; results were corrected for atmospheric stability using the Monin-Obukhov stability parameter. The Whitman two-film model used the concentrations of α-HCH in surface seawater, in bulk air at 1 and 15 m above the surface, and the Henry's law constant adjusted for temperature and salinity to derive the flux. Both approaches showed that the overall net flux of α-HCH was from water to air. Mean fluxes calculated using the micrometeorological technique ranged from -3.5 to 18 ng m(-2) day(-1) (mean 7.4), compared to 3.5 to 14 ng m(-2) day(-1) (mean 7.5) using the Whitman two-film model. Flux estimates for individual events agreed in direction and within a factor of two in magnitude for six of eight events. For two events, fluxes estimated by micrometeorology were zero or negative, while fluxes estimated with the two-film model were positive, and the reasons for these discrepancies are unclear. Improvements are needed to shorten air sampling times to ensure that stationarity of meteorological conditions is not compromised over the measurement periods. The micrometeorological technique could be particularly useful to estimate fluxes of organic chemicals over water in situations where no water samples are available.

Thickness-dependence of optical constants for Ta2O5 ultrathin films

An effective method for determining the optical constants of Ta2O5 thin films deposited on crystal silicon (c-Si) using spectroscopic ellipsometry (SE) measurement with a two-film model (ambient–oxide–interlayer–substrate) was presented. Ta2O5 thin films with thickness range of 1–400 nm have been prepared by the electron beam evaporation (EBE) method. We find that the refractive indices of Ta2O5 ultrathin films less than 40 nm drop with the decreasing thickness, while the other ones are close to those of bulk Ta2O5. This phenomenon was due to the existence of an interfacial oxide region and the surface roughness of the film, which was confirmed by the measurement of atomic force microscopy (AFM). Optical properties of ultrathin film varying with the thickness are useful for the design and manufacture of nano-scaled thin-film devices.

Fixed-grid method for the modelling of unsteady partial oxidation of a spherical coal particle

The main goal of this work is the development of a fixed-grid method to model unsteady partial oxidation of a solid with implicit tracking of the interface. As a first step diffusive oxidation of a spherical coal particle is considered. The energy and species conservation equations formulated in spherical coordinates are discretised using the finite-volume approach. The boundary conditions for the temperature and species mass fractions at the solid–gas interface are modelled via special source terms activated in the interface cells. The numerical model was validated against analytic one- and two-film models for coal combustion in a dry-air atmosphere. Very good agreement was obtained. Based on the model developed a numerical study was carried out on the influence of water vapour on the partial oxidation of a spherical coal particle. Numerous numerical simulations were performed for particle diameters in the range 200×10−6 m to 2×10−2 m. The ambient temperature was varied in the range between 700 and 3000 K. The analysis of results showed that the addition of H2O has an influence on the solution convergence due to the catalytic effect of water in the coal monoxide oxidation reaction making the whole system stiffer. However, at the same time, it was found that if the ambient mass fraction of water vapour is below 1×10−3, its influence on combustion rates is minimal. The results of numerical simulations obtained for higher H2O concentration (>1×10−3) are discussed.

Characterization and kinetics of carbon dioxide absorption into aqueous tetramethylammonium glycinate solution

An advanced aqueous amine solvent of tetramethylammonium glycinate ([N1111][Gly]) was characterized for carbon dioxide (CO2) absorption purposes. Density, viscosity and pH of the [N1111][Gly] solution, with concentrations ranging from 5% to 30%, were determined at temperatures from 298 to 323K. Solubility and diffusivity of CO2 in [N1111][Gly] solution at the same temperatures and concentrations was estimated. Absorption of CO2 into [N1111][Gly] aqueous solution was investigated using a double stirred-cell absorber with a planar gas–liquid interface. The effects of the [N1111][Gly] concentration, temperature and CO2 concentration of absorption CO2 into aqueous [N1111][Gly] were studied. The kinetics study showed that absorption CO2 into aqueous [N1111][Gly] was the fast pseudo-first order reaction regime. Based on the reaction regime, the enhancement factor E, the overall reaction kinetic constant kov and the second-order rate constant k2 were obtained using the two-film model. The results showed that E was linear with CB01/2, and the activation energy of 15% aqueous [N1111][Gly] absorbing CO2 was 15.431kJmol−1.

Air−Water Exchange of Anthropogenic and Natural Organohalogens on International Polar Year (IPY) Expeditions in the Canadian Arctic

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: α-hexachlorocyclohexane (α-HCH) 465-1013, γ-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: α-HCH 7.5-48, γ-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of α-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The α-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic α-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: α-HCH 6.8 ± 3.2 (2.7-13), γ-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0).

Evolution of optical constants of silicon dioxide on silicon from ultrathin films to thick films

A series of SiO2 films with thickness range 1–600 nm have been deposited on crystal silicon (c-Si) substrates by electron beam evaporation (EBE) method. Variable-angle spectroscopic ellipsometry (VASE) in combination with a two-film model (ambient-oxide-interlayer substrate) was used to determine the optical constants and thicknesses of the investigated films. The refractive indices of SiO2 films thicker than 60 nm are close to those of bulk SiO2. For the thin films deposited at the rate of ∼1.0 nm s−1, the refractive indices increase with decreasing thickness from ∼60 to ∼10 nm and then drop sharply with decreasing thickness below ∼10 nm. However, for thin films deposited at the rates of ∼0.4 and ∼0.2 nm s−1, the refractive indices monotonically increase with decreasing thickness below 60 nm. The optical constants of the ultrathin film depend on the morphology of the film, the stress exerted on the film, as well as the stoichiometry of the oxide film.

Kinetic study on the synthesis of ethyl nitrite by the reaction of C 2H 5OH, O 2, and NO in a trickle bed reactor

The synthesis of ethyl nitrite by the reaction of C 2H 5OH, O 2, and NO, called the regeneration reaction in the synthesis of ethylene glycol (EG) by the coupling reaction-hydrogenation process, is carried out in a trickle bed reactor filled with θ-mesh rings at 313–343 K and atmospheric pressure. It is shown that the conversion of O 2 increases with the NO/O 2 and the EtOH/NO molar ratios, and decreases with the N 2 volume fraction and the liquid hourly space velocity (LHSV). O 2 conversion reaches a maximum (∼90.9%) at 333 K, NO/O 2 molar ratio of 6:1, EtOH/NO molar ratio of 3:1, N 2 volume fraction of 50%, and LHSV of 2.65 h −1. The synthesis reaction is a fast one and takes place in a liquid film. A kinetics model based on the two-film model of gas–liquid reaction is proposed. The experiment data fit the kinetics model very well and statistical tests also show their reliability.

Effect of Wind Tunnel Air Velocity on VOC Flux from Standard Solutions and CAFO Manure/Wastewater

Researchers and practitioners have used wind tunnels and flux chambers to quantify the flux of volatile organic compounds (VOCs), ammonia, and hydrogen sulfide and estimate emission factors from animal feeding operations (AFOs) without accounting for effects of air velocity or sweep air flow rate. Laboratory experiments were conducted using a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). The objectives of the research were to (1) quantify the effect of wind velocity on VOC flux rates, (2) compare and contrast a two-film model with different wind speed corrections, and (3) provide insight into methods for either selecting appropriate wind tunnel velocities or conducting post-sampling wind velocity corrections to simulate field emission rates. Fluxes were measured on standard solutions and on manure/wastewater from beef cattle and dairy AFOs. Volumetric air exchange rates were varied between 0.6 and 44 exchanges per minute, corresponding to calculated longitudinal air velocities of 0.003 to 0.23 m s-1. Exhaust air was sampled using stainless steel sorbent tubes and analyzed for eleven volatile organic compounds comprised of seven volatile fatty acids (VFAs: acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic) and four heavier molecular weight semivolatile organic compounds (sVOCs: phenol, p-cresol, indole, and skatole) using gas chromatography/mass spectrometry. Sulfur-containing VOCs were quantified using a portable total reduced sulfur meter. Flux rates for VOCs with small dimensionless Henry's law constants (i.e., those found at AFOs) increased with increasing air velocity. The two-film model with an experimentally derived reference gas-film transfer coefficient was found to reliably predict VOC flux at velocities between 0.003 and 0.23 m s-1. However, the two-film model did not reliably predict VOC flux with other air velocity correction formulae, an indication that flux is a function of wind tunnel geometry and turbulence factors, and not just average air velocity or sweep air flow rate. These results corroborate other studies that show that air velocity is a major factor affecting VOC fluxes from AFOs, verifying that an air velocity correction factor is required for estimating accurate VOC emission factors using wind tunnels and flux chambers.

Ellipsometric Measurements of Plastically Deformed Copper

Chemically pure copper (99.99) prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm was extremely plastically deformed with the repeated application of equal channel angular pressing. Equal channel angular pressing was applied as an effective technique for producing bulk nanoscaled structures. It is well known that severe plastic deformation of metallic materials often leads to microstructure with ultrafine grains and cross-sections which remain about equal before and after deformation. Optical properties of the sample were studied using spectroscopic ellipsometry in UV-VIS range. The parameters of the sample like copper oxide and surface roughness overlayer were calculated using two-film model together with the Bruggeman effective medium approximation.

Kinetics of SO2 Absorption with Fly Ash Slurry with Concomitant Production of a Useful Wastewater Coagulant

This research was aimed at recovering Fe and Al compounds to produce a useful complex coagulant from fly ash using H2 SO4 and SO2 from flue gas oxidized to SO3 by NaClO3 . The reaction kinetics of wet SO2 scrubbing from simulated flue gas with fly ash slurry was studied. The SO2 scrubbing experiments were carried out in a jacketed glass reactor system with a simulated flue gas containing SO2 and N2 in the gas phase and fly ash slurry in the liquid phase. Sodium chlorate was added to oxidize SO2 to SO3 , adding H2 SO4 in the slurry. The reaction orders of both Fe2 O3 and Al2 O3 extraction from fly ash slurry were shown to be 1.5. The empirical Arrhenius expressions were also derived from the reaction rate constants obtained at each reaction temperature. The mass transfer process of SO2 with ClO 3− was evaluated using a two-film theory model.

A comparison of mercury cycling in Lakes Michigan and Superior

Mercury cycling in Lake Superior and Lake Michigan was evaluated based on measurements of mercury levels, modeling of evasional fluxes, and development of first-order mass balance models. Total mercury, methylmercury, and dissolved gaseous mercury were measured on sampling cruises in Lake Michigan (2005) and Lake Superior (2006). Average total mercury concentrations in unfiltered surface water were higher in Lake Michigan (420 ± 40 pg/L) compared to Lake Superior (210 ± 20 pg/L). Methylmercury levels were below the detection limit in Lake Michigan. Larger sample volumes were collected to lower detection limits in Lake Superior in 2006 and methylmercury levels averaged 7 ± 6 pg/L. Dissolved gaseous mercury concentrations were also higher in Lake Michigan (27 ± 7 pg/L) compared to Lake Superior (14 ± 8 pg/L). Evasional fluxes were estimated using a two-film model for air–water exchange. The annual evasional flux in Lake Michigan was determined to be ~ 380 kg/yr from Lake Michigan and ~ 160 kg/yr from Lake Superior. Total mercury burdens in each lake were estimated to be ~ 2500 kg in Superior and ~ 2100 kg in Lake Michigan demonstrating that evasional fluxes play an important role in the mass balance of each lake, particularly Lake Michigan. A simple first-order mass balance model demonstrates the importance of air–water exchange and sedimentation as primary removal processes for Hg in each lake. Uncertainties in the mass balance model are highlighted due to lack of key data, particularly in Lake Superior.

안면도에서 대기 중 가스상 PAHs의 계절적 변동

Passive air samplers with polyurethane foam (PUF) disks were employed to determine seasonal gas phase variation of polycyclic aromatic hydrocarbons (PAHs) in ambient air on Anmyeon island from March 2007 to January 2008. Sum of 13 PAHs ranged between <TEX>$3.5\;ng/m^3$</TEX> and <TEX>$27.6\;ng/m^3$</TEX>. Total PAHs during the heating season was 6.2 times higher than non-heating season. The dominant PAHs components during sampling periods were low and middle molecular weight PAHs including phenanthrene, fluoranthene, pyrene and chrysene. Gas exchange fluxes of PAHs across the air-water interface of the Yellow Sea were calculated using a modified two-film exchange model. PAHs fluxes ranged from <TEX>$196\;ng/m^2/d$</TEX> net volatilization during summer to <TEX>$3830\;ng/m^2/d$</TEX> net absorption during winter. Passive air sampler provides a convenient and cost-effective tool for measuring averaged gas phase PAHs, which was successfully used for calculation of gas exchange flux of PAHs in the Yellow Sea.

Modeling liquid–gas iodine mass transfer under evaporative conditions during severe accidents

During postulated severe accidents transfer of volatile iodine dissolved in containment water sumps to atmosphere can be fostered under pool evaporative conditions. Scarcity of representative data has resulted in semi-empirical models that relies on fitting parameters and still need of further validation. This paper presents a mechanistic model based on: the two-film model, the heat-mass transfer analogy and the surface renewal theory. Comparison to data from the SISYPHE program, performed at the French “Institut de Radioprotection et de Sûreté Nucléaire”, has resulted in an accurate response, the error band being 9–25% for the aqueous steady state concentration. Likewise, the model performance has been compared to the model implemented in the ASTEC code. In addition to yield similar results, some advantages have been highlighted: the mechanistic nature, the estimates conservatism, and the thorough documentation of model grounds and assumptions.