Gas Vapor Phase Research Articles

OLEOPHILIC SORBENTS BASED ON GRANULAR FOAMED SILICATE: PROPERTIES AND FEATURES OF REGENERATION

The solution to the problems of ecological safety when cleaning water objects from organic pollutants is indissolubly related to developing new sorbents and improving the technologies of their synthesis. Various materials in dispersed and granulated forms are successfully used in the production of sorbents. This article deals with the development and improvement of the technologies for producing the sorbents of petroleum and petroleum products. As a basis for the development of new sorbents, the properties of the granular foamed silicate obtained from the siftings of waste products from mining and processing plants were studied. The trial batches of oleophilic sorbents were obtained through thermochemical modification of hydrocarbons in the gas-vapour phase. It has been established that foamed silicate does not change its porous structure and amorphous state after thermo-chemical modification, retaining the high sorption activity. The nature of the porous structure of sorbents and the influence of porosity on their key properties, such as oil capacity, water absorption, and buoyancy, are investigated. The studies of the fractions of modified foamed silicate revealed low water-absorption capacity of the coarse- and middle-sized fractions. The minimum water absorption was determined for the fine fraction of the modified material, which is related to the absence of pores in these samples. Determination of oil capacity characteristics provides evidence of high oil receptivity and sorption capacity of the modified foamed silicate with respect to petroleum products. The results of experiments on sorbent regeneration after the end of its service life are presented. The developed semi-production experimental plant for the modification and regeneration of porous loose materials in the fixed bed is presented. The technological scheme of regeneration is proposed, allowing for regeneration and repeated modification of the used sorbent during one processing stage without any decrease in its sorption properties. The advantage of the developed technology of sorbent properties recovery is in the implementation simplicity and economic rationality. The repeatedly modified sorbent retains its characteristics and, first of all, sorption properties with respect to petroleum products. The practicability of developing new sorbents of petroleum products based on granular foamed silicate is demonstrated.

A Pyrene Coupled Azaine-linkage Chromo-fluorogenic Probe for Specific Detection of Sarin Gas Stimulant, Diethylchlorophosphate.

Owing to the extreme toxicity and easy synthesis protocol of G-series nerve agents, developing an efficient sensor for selective detection is necessary. Although various traditional methods are utilized to identify these nerve agents, chromo-fluorogenic probes have gained attractive attention from the scientific communities. In the present contribution, we have introduced a new symmetrical aza-substituted chromo-fluorogenic sensor, BPH, for specific detection of sarin gas, one of the fatal G-series nerve agents surrogate, diethylchlorophosphate (DCP). BPH shows a noticeable naked eye colorimetric change from pale yellow to light pink in the presence of DCP, displaying highly intense bright greenish cyan color photoluminosity under a 365nm UV lamp,which is also manifested from the color chromaticity diagram. A BPH-staining paper stirps-based test kit experiment has been demonstrated for the on-site detection of nerve agent mimics. A more attractive and efficient application of BPH as a sarin gas vapor phase sensor mimics DCP in solid and solution phases. The BPH-based chromo-fluorogenic sensor shows excellent selectivity toward DCP with a detection and quantification limit in the µM range. This report invokes a new way for the researchers to detect DCP employing a simple chromo-fluorogenic sensor, which could be prepared by a time-saving,straightforward, handy protocol from the cost-effective starting materials.

Key Challenges and Recommendations for In Vitro Testing of Tobacco Products for Regulatory Applications: Consideration of Test Materials and Exposure Parameters.

The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to identify, discuss and develop recommendations for optimal scientific and technical approaches for conducting in vitro assays, to assess potential toxicity within and across tobacco and various next generation nicotine and tobacco products (NGPs), including heated tobacco products (HTPs) and electronic nicotine delivery systems (ENDS). The third workshop (24-26 February 2020) summarised the key challenges and made recommendations concerning appropriate methods of test article generation and cell exposure from combustible cigarettes, HTPs and ENDS. Expert speakers provided their research, perspectives and recommendations for the three basic types of tobacco-related test articles: i) pad-collected material (PCM); ii) gas vapour phase (GVP); and iii) whole smoke/aerosol. These three types of samples can be tested individually, or the PCM and GVP can be combined. Whole smoke/aerosol can be bubbled through media or applied directly to cells at the air-liquid interface. Summaries of the speaker presentations and the recommendations developed by the workgroup are presented. Following discussion, the workshop concluded the following: that there needs to be greater standardisation in aerosol generation and collection processes; that methods for testing the NGPs need to be developed and/or optimised, since simply mirroring cigarette smoke testing approaches may be insufficient; that understanding and quantitating the applied dose is fundamental to the interpretation of data and conclusions from each study; and that whole smoke/aerosol approaches must be contextualised with regard to key information, including appropriate experimental controls, environmental conditioning, analytical monitoring, verification and performance criteria.

A comparison of cigarette smoke test matrices and their responsiveness in the mouse lymphoma assay: A case study.

No cigarette smoke test matrix is without limitation, due to the complexity of the starting aerosol and phase to phase dynamics. It is impossible to capture all chemicals at the same level of efficiency, therefore, any test matrix will inadvertently or by design fractionate the test aerosol. This case study examines how four different test matrices derived from cigarette smoke can be directly compared. The test matrices assessed were as follows, total particulate matter (TPM), gas vapour phase (GVP), a combination of TPM +GVP and whole aerosol (WA). Here we use an example assay, the mouse lymphoma assay (MLA) to demonstrate that data generated across four cigarette smoke test matrices can be compared. The results show that all test matrices were able to induce positive mutational events, but with clear differences in the biological activity (both potency and toxicity) between them. TPM was deemed the most potent test article and by extension, the particulate phase is interpreted as the main driver of genotoxic induced responses in the MLA. However, the results highlight that the vapour phase is also active. MLA appeared responsive to WA, with potentially lower potency, compared to TPM approaches. However, this observation is caveated in that the WA approaches used for comparison were made on a newly developed experimental method using dose calculations. The TPM +GVP matrix had comparable activity to TPM alone, but interestingly induced a greater number of mutational events at comparable relative total growth (RTG) and TPM-equivalent doses when compared to other test matrices. In conclusion, this case study highlights the importance of understanding test matrices in response to the biological assay being assessed and we note that not all test matrices are equal.

Application of ToxTracker for the toxicological assessment of tobacco and nicotine delivery products

Consumer demands and innovation have led to an increasingly diverse range of nicotine delivery systems, driven by a desire to reduce risk associated with traditional combustible cigarettes. This speed of change provides a mandate for rapid new product assessment. We have used the validated technology ToxTracker®, to assess biomarkers of DNA damage, protein misfolding, oxidative and cellular stress, across the categories of cigarette (1R6F), tobacco heating product (THP 1.4) and electronic cigarette (ePen 3). In addition, we compared the commonly used test matrices for tobacco and nicotine products; whole aerosol aqueous extracts (AqE) and gas vapour phase (GVP), determining their suitability across the product categories.We demonstrated a significant reduction in oxidative stress and cytotoxicity for THP 1.4 over cigarette, further reduced for ePen 3, when assessed by both dilution and nicotine dosimetry. We also identified that while the extraction matrices AqE and GVP from combustible products were equivalent in the induced responses, this was not true of the other category examples, moreover THP 1.4 GVP demonstrates a >50 % reduction in both toxicity and cytotoxicity endpoints over AqE. This indicates that unlike cigarette, the active components or toxicants for THP and electronic cigarette are associated with the aerosol fraction of these categories.

Estimation of corrosion aggression of aquatic media and corrosion resistance of steels of equipment of oil and gas condensate deposits

Corrosion destruction of the metal of the field equipment and gas pipelines of the oil and gas condensate field (OGCF) was revealed, the cause of which is carbon dioxide corrosion. In order to determine the corrosiveness of the OGCF equipment media, laboratory tests were carried out with periodic moisture condensation in an atmosphere of carbon dioxide, autoclave tests in the liquid phase at elevated temperatures and partial pressure of CO2, and laboratory tests in the gas-vapor phase in the presence of CO2. Tests were carried out on steel 20, the selected solutions were tested on pipe segments of 09G2S steels (well connections and loops) and J55LT (tubing) of 2 types (old, after operation in a well, and new, not operated). Studies have shown that steels used at OGCF (steel 20, J55LT and 09G2S) are not resistant to carbon dioxide corrosion. All items of equipment made of these steels will be potentially weakly resistant to corrosion in the oil and gas condensate field. It is proposed to conduct tests of corrosion inhibitors from various manufacturers in laboratory and field conditions. Recommendations are given for the corrosion inhibitor selected according to the test results. Keywords: local corrosion; aggressiveness of the environment; metal resistance; well piping; plume; tubing; laboratory tests; autoclave tests.

SUBSTANTIATION OF APPLICATION OF UNDERGROUND REDUCTION CHAMBER IN LIQUEFIED PETROLEUM GAS SUPPLY SYSTEMS

Statement of the problem. When reducing the vapor phase of propane-butane in the pressure regulators of the above-ground closet gas control points, water falls out in free form and at subzero temperatures of ice and crystalline hydrates formation. In order to prevent this, methods are employed in the form of applying thermal insulation and heating the inner space of the cabinet, which significantly increases the cost of the structure and the reduction process. As an alternative, the authors set forth an underground reduction chamber. The article provides a scientific rationale for the use of this underground chamber in the practice of gas supply to consumers. Results. The configuration of the reduction chamber has been substantiated, mathematical modeling of the heat exchange processes of the chamber with the surrounding soil massif has been performed, the thickness of the thermal insulation of the ascending section of the vapor phase and the reduction chamber has been selected, and the process of reduction of the vapor phase in pressure regulators has been simulated. Conclusions. According to the results of the studies, the cylindrical shape is optimal for the reduction chamber, which provides the minimum total surface of the enclosing structures. The implementation of the economic and mathematical model made it possible to recommend the optimal thicknesses of the thermal insulation of the chamber and the ascending section of the vapor phase, enabling the process of throttling of the liquefied petroleum gas vapor phase in pressure regulators without the release of free water and the formation of ice and hydrate plugs.

The research on the sorption properties of the X-ray amorphous silica foam

The paper is concerned with the solution to environmental problems related to the gathering of oil and oil products from the surfaces of water bodies using the highly-porous inorganic sorbents. In the paper, the technological solutions are presented and primary results aimed at the development of new sorption materials are discussed. To develop the technologies of preparing the sorbents of oil and oil products, the properties of the granulated foam-silicate material obtained during the treatment process of technogenic raw material were investigated. A method of modifying the granulated foam silicate in the gas–vapor phase of hydrocarbons having the undoubted superiority (possibility to work out the finely-dispersed materials with the use of a wide range of modifiers) was developed. The technological scheme of the thermo-chemical modifying the foam silicates surface was presented and the operating parameters of the modification process were experimentally verified. The temperature interval of the foam-silicate porous structure and its X-ray amorphous state stability was determined. The hydrophobic properties of the modified foam-silicate are confirmed by the testing of material for moisture capacity. Determination of oil capacity characteristics suggests the high oil-receptivity and sorption capacity concerning oil products. The comparative evaluation of new oleophilic hydrophobic material regarding other sorbents confirms the possibility of using the modified granulated foam-silicate obtained from waste products of the mica-schist ore as the basis for the preparation of new sorbents for cleaning of contaminated waters from organic substances including oil products.

Modelling of mass transfer in separation of hydrocarbon mixtures and modernization of industrial columns

A system of differential equations of mass transfer with an interfacial mass source for multicomponent distillation in a column with random and structured packings in the film mode is presented. The interfacial source is associated with the matrix of volumetric mass transfer coefficients as well as a driving force for mass transfer. The diffusion fluxes of mass of components are written in the form of Fick’s law with elements of the matrix of coefficients of molecular diffusion in the gas (vapor) phase. To simplify the mathematical model, one dimensional equations for the diffusion model of the structure of flows in the gas and liquid phases with the interfacial sources and coefficients of back (longitudinal) mixing of gas and liquid flows are used. The Dankwerts boundary conditions are applied to the system of equations. To calculate the back mixing coefficients, experimental data obtained for the selected types of packings are used. When modelling mass transfer in hydrocarbon mixtures consisting of several dozen components, the system of equations for the diffusion models is solved for the key components and fractions of the oil and gas condensate (OGC) mixture stabilization column at an industrial enterprise. A brief description of the technological scheme is given. Scientific and technical solutions are developed to replace obsolete sieve trays in the stabilizer column with a new structured corrugated roll packing having a rough surface. It is found that a packing height of eight meters is sufficient for separating OGC in a given composition range. As a result of implementation of the new packing, the content of isopentane in the stable condensate decreases and its concentration in the broad fraction of light hydrocarbons increases from 9 wt.% to 11.7 wt.%. The implementation of packing in the stabilizer column meets the requirements of the technical specifications.

Smoke Chemistry, In Vitro Cytotoxicity, and Genotoxicity Demonstrates Enhanced Toxicity of Cigarillos Compared With Cigarettes.

There has been limited toxicity testing of cigarillos, including comparison to cigarettes. This study compared the smoke chemistry and the cytotoxic and genotoxic potential of 10 conventional cigarettes and 10 cigarillos based on the greatest market share. Whole smoke and total particulate matter (TPM) were generated using the Canadian Intense and International Organization for Standardization puffing protocols. Tobacco-specific nitrosamines, carbonyls, and polycyclic aromatic hydrocarbons were measured using gas chromatography-mass spectrometry. TPM smoke extracts were used for the in vitro assays. Cytotoxicity was assessed in human bronchial epithelial continuously cultured cell line cells using the neutral red uptake assay. Genotoxic potential was assessed using the micronucleus (human lung adenocarcinoma continuously cultured cell line cells), Ames, and thymidine kinase assays. TPM from all cigarillos tested was more cytotoxic than cigarettes. Micronucleus formation was significantly greater for cigarillos compared with cigarettes at the highest dose of TPM, with or without rat liver S9 fraction. In the Ames test +S9, both tobacco products exhibited significant dose-dependent increases in mutation frequency, indicating metabolic activation is required for genotoxicity. In the thymidine kinase assay +S9, cigarillos showed a significantly enhanced mutation frequency although both tobacco products were positive. The levels of all measured polycyclic aromatic hydrocarbons, tobacco-specific nitrosamines, and carbonyls (except acrolein) were significantly greater in cigarillos than cigarettes. The Canadian Intense puffing protocol demonstrated increased smoke constituent levels compared with International Organization for Standardization. Even though the gas vapor phase was not tested, the results of this study showed that under the tested conditions the investigated cigarillos showed greater toxicity than comparator cigarettes. This study found that there is significantly greater toxicity in the tested U.S. marketed cigarillos than cigarettes for tobacco constituent levels, cytotoxicity, and genotoxicity. These findings are important for understanding the human health toxicity from the use of cigarillos relative to cigarettes and for building upon knowledge regarding harm from cigarillos to inform risk mitigation strategies.

Free Energy of Nucleus Formation during Growth of III–V Semiconductor Nanowires

An expression for the free energy of nucleus formation from liquid phase of a catalyst during growth of III–V semiconductor nanowires (NWs) via the vapor–liquid–solid (VLS) mechanism has been derived with allowance for depletion of the number of atoms of the group V element (As) in the drop as a result of the island growth during As deposition from the gas–vapor phase. Various regimes of island formation, including a regime with growth arrest at small As concentrations in the drop have been theoretically studied. It is established that the growth arrest takes place when the As concentration decreases to an equilibrium level. The obtained results can be used in simulations of the growth kinetics of III–V semiconductor NWs, statistics of their nucleation, and NW length distribution functions, as well as for modeling of the crystalline phase growth and doping processes.

Numerical study of the evaporative convection regimes in a three-dimensional channel for different types of liquid-phase coolant

Two-layer fluid flows with evaporation at the thermocapillary interface have been studied on the basis of the partially invariant solution of the convection equations. The modeling of the 3D fluid flows has been performed in an infinite channel of the rectangular cross section without assuming the axis-symmetrical character of the flows. The fluid flow patterns are determined by various thermal, mechanical and structural effects. Numerical investigations have been carried out for the liquid–gas system like ethanol–nitrogen and HFE-7100–nitrogen under terrestrial conditions. The solution takes into account the direct and inverse thermodiffusion effects in the gas–vapor phase. Influence of the applied thermal load, thickness of the liquid layer and thermophysical properties of the working media on topology and character of the flows is studied. It allows one to describe the formation of thermocapillary rolls and symmetrical multi-vortex structures in the systems with heat transfer liquids like the ethanol or HFE-7100. The appearance of the thermal and solutal shafts, and the near-wall condensation effects observed in real experiments are predicted by the solution.

Analysis of Characteristics of Two-Layer Convective Flows with Diffusive Type Evaporation Based on Exact Solutions

The theoretical approaches for mathematical modelling of the convective flows with mass transfer through the liquid–gas interface are discussed. The special attention is payed to modelling with use of the classical Boussinesq approximation of the Navier–Stokes equations. The diffusion equation and the effects of thermodiffusion and thermal diffusivity (the Soret and Dufour effects) are taken into account additionally to describe vapor and heat transfer processes in the gas-vapor phase. The use of the Oberbeck–Boussinesq equations allows one to apply the group-analytical methods in the theory of the evaporative convection and to construct the exact solutions of special type of the governing equations. Joint flows of the evaporating liquid and gas-vapor mixture are studied with the help of a partially invariant solution for the convection equations. The 2D and 3D solutions are demonstrated to simulate two-phase flows in the infinite channels with interface being under action of a longitudinal temperature gradient and perpendicularly directed gravity field. In the present paper the fluid flows with diffusive evaporation/condensation in the terrestrial and microgravity conditions are studied in the steady case. The new results obtained for combined thermal regime on the external rigid boundaries are presented.

Influence of the Thermophysical Properties of a Liquid Coolant on Characteristics of the 3D Flows with Phase Transition

Regimes of the joint flows of the evaporating liquid and gas – vapor mixture induced by the action of a longitudinal temperature gradient in a three-dimensional channel of a rectangular cross-section in the terrestrial gravity field are studied in the present paper. The theoretical investigations are carried out on the basis of the partially invariant solution of rank 2 and defect 3 of the Boussinesq approximation of the Navier – Stokes equations. This solution allows one to correctly describe the two-layer flows with evapora- tion/condensation at the thermocapillary interface and to take into account the effects of thermodiffusion and diffusive thermal conductivity in the gas–vapor phase. The exact solution of governing equations are characterized by dependence of the velocity components on the transverse coordinates only. The functions of pressure, temperature and concentration of vapor linearly depend on the longitudinal coordinate and have the summands which are functions on transverse coordinates. The required functions satisfy the set of differential equations, boundary and interface conditions followed from the original three-dimensional problem statement and are found as a result of numerical technique. The presented solution of the evap- orative convection problem is very contensive. It permits to specify the 3D flow regimes with different topology, thermal and concentration characteristics observed in physical experiments. Differences of flows in the ethanol–nitrogen, HFE-7100 – nitrogen and FC-72 – nitrogen systems are studied. Impact of the thermophysical properties of the working liquids on the basic characteristics of the fluid motions (hydro- dynamical structure, temperature distribution, vapor content in the nitrogen, evaporative mass flow rate) is analyzed

Gase's thermal C onductivity C alculation by low P ressures

Data on the thermal conductivity of industrial gases (vapors) are used in chemical technology, in the processing of oil and gas for analysis, calculation, and design of thermal processes and apparatus (heat exchangers, furnaces). It is believed that information requests for this property can be satisfied due to the data and recommendations for calculation available in the reference literature. Thus, it is of interest to develop a more convenient (modified) approach to the calculation of the thermal conductivity of gases at a “reference” temperature and low pressures, bypassing the aforementioned problems of the Roy – Todos method. Reliable reference materials were used as an information database of the thermal conductivity of hydrocarbons in the gas (vapor) phase. About 40 hydrocarbons representing various classes with molecular weights of 26 ... 254.5 were selected. Physico-chemical characteristics of the substances taken according to the data. The article considers the calculation of the thermal conductivity of gases at the “reference” temperature value. The proposed formulas make it possible to determine the temperature dependence of thermal conductivity at low pressures.

Comparison of cytotoxicity of IQOS aerosols to smoke from Marlboro Red and 3R4F reference cigarettes

This study compared the cytotoxicity of IQOS aerosols to smoke from Marlboro Red (MR) and 3R4F reference cigarettes. Aerosol/smoke solutions were tested as the gas vapor phase (GVP), particulate phase (total particulate matter or TPM), or whole aerosol/smoke (WA), the latter being what smokers actually inhale. Cytotoxicities were evaluated using the LDH, MTT and neutral red uptake (NRU) assays in conjunction with eight different cell types, mainly from the respiratory system. Most test solutions did not compromise the plasma membranes of cells (LDH). However, mitochondrial activity (MTT) and dye uptake/lysosomal activity (NRU) were equally depressed by IOQS aerosols and cigarette smoke solutions at the high concentrations. Our NRU data with mouse NIH/3T3 transformed fibroblasts were similar to those previously reported by the IQOS manufacturer and showed little cytotoxicity in the NRU assay. In both studies with NIH/3T3 cells, the results were significantly different from 3RF4 cigarette smoke, suggesting reduced toxicity with IQOS. However, by expanding evaluations to a broader spectrum of cells that included respiratory system cells and by including higher concentrations of GVP, as well as WA, cytotoxicity equivalent to that of Marlboro Red and 3R4F cigarettes was frequently observed with IQOS aerosols in the MTT and NRU assays.

Thermocapillary Convection with Phase Transition in the 3D Channel in a Weak Gravity Field

The regimes of joint flows of the evaporating liquid and vapor-gas mixture in a 3D rectangular channel are studied with the help of a partially invariant solution for the convection equations. The effects of thermodiffusion and diffusive thermal conductivity in the gas–vapor phase are additionally taken into account in the governing equations and under interface conditions. A numerical simulation of the 3D fluid flows is carried out for the liquid–gas system like ethanol–nitrogen and HFE-7100–nitrogen under microgravity conditions. The influence of the thermal load, liquid layer thickness and heat-transfer liquid type on the structure of the fluid flows and evaporation characteristics is investigated. The solution allows one to describe the formation of longitudinal thermocapillary rolls observed in the experiments. The evaporative mass flow rate depends essentially on the thermophysical properties of the working liquid. Spatial size and a shape of thermal patterns are determined by the applied thermal load and they can be varied with the change in the liquid layer thickness. Topological structure of the flows (double or quadruple vortex composition) is defined by the combined influence of the thermocapillary and convective mechanisms and phase transition effects. The results discussed in the paper provide motivation for the development of a classification of the 3D flow regimes similar to the Napolitano’s classification for 2D flows.

In vitro mutagenicity of gas-vapour phase extracts from flavoured and unflavoured heated tobacco products.

The in vitro mutagenic and genotoxic potential of Heated Tobacco Products (HTPs) has already been studied with the particulate phase and reported previously. This study has been designed to complement the in vitro assessment of the HTP and to determine whether the inclusion of potential flavourings would alter the in vitro response by testing the other phase of the aerosol, the gas-vapour phase (GVP). Both flavoured and unflavoured Neostik GVP samples did not show any sign of mutagenic activity in the Ames test but induced a mutagenic response in the mouse lymphoma assay (MLA), however, these responses were significantly less than those of the reference cigarette, 3R4F. The results demonstrated that GVP emissions of this HTP did not induce either new qualitative or quantitative mutagenic hazards compared to 3R4F, as assessed by the Ames test (no new responsive strains) and MLA (a lower mutagenic response), respectively. A statistical comparative analysis of the responses showed that the addition of flavourings that may thermally decompose under the conditions of use did not add to the in vitro baseline responses of the unflavoured Neostik.

Development of a quantitative method for assessment of dose in in vitro evaluations using a VITROCELL® VC10® smoke exposure system

The assessment of potential cytotoxicity or genotoxicity of combustible tobacco products has historically been performed using partitioned exposures (i.e. total particulate matter [TPM], gas vapor phase [GVP]) rather than whole smoke. The VITROCELL® VC10® smoke exposure system offers multiple platforms for air liquid interface (ALI) or air agar interface (AAI) exposure to mimic in vivo-like conditions for assessing the toxicological impact of whole smoke using in vitro assays (e.g. cytotoxicity, mutagenicity and DNA modifications).The aims of this study were to investigate dosimetry during whole smoke exposure in the VITROCELL® VC10® smoking robot using quartz crystal microbalances (QCMs) and to support the use of photometers for concurrent assessment of ‘dose’ during whole smoke exposures. QCM results showed consistent deposition across different exposure chambers, between dilution bars, experiments and modules. Higher levels of variation were noted at higher airflows (i.e., >8 L/min). Dosimetry assessed using photometers also showed a high level of consistency between experiments, with no notable impact on deposition on the QCM when the photometers were placed ‘in-line’ between the dilution bar and the exposure module. However, the use of photometers alone may be not be sufficient to estimate deposition; the predictability of the data-generated equation was poor. Further development of dosimetry methodology and information for use in validated in vitro biological test methods is needed to facilitate on-going aerosol-based research and relative assessment.

Influence of Gravity on the Stability of Evaporative Convection Regimes

The characteristics of convective regimes in a two-layer system have been investigated in the framework of the Boussinesq approximation of the Navier–Stokes equations. An exact invariant solution of the convection equations is used to describe a joint stationary flow of an evaporating liquid and a gas-vapor mixture in a horizontal channel. Thermodiffusion effects in the gas-vapor phase are additionally taken into account in the governing equations and interface conditions. The influence of gravity and thickness of the liquid layer on the hydrodynamical, thermal and concentration characteristics of the regimes has been investigated. Flows of the pure thermocapillary, mixed and Poiseuille’s types are specified for different values of the problem parameters. The linear stability of the evaporative convection regimes has been studied. The types and properties of the arising perturbations have been investigated and the critical characteristics of the stability have been obtained. Disturbances can lead to the formation of deformed convective cells, vortex and thermocapillary structures. The change of the instability types and threshold thermal loads occurs with the increasing thickness of the liquid layer and gravity action.