Vapor Mixture Research Articles

Calibrating and Graduating of Multi-Sensor Gas Analyzer

Introduction. The article is devoted to the calibration and graduation of the multi-sensor gas analyzer developed at the V.M. Glushkov Institute of Cybernetics of National Academy of Sciences of Ukraine. The modern trend in the development of medical equipment, in particular, containing built-in measuring devices, consists in its miniaturization, intellectualization, the use of information technologies, and the introduction of wireless and network means of data transmission. The purpose of the article is to design, create electronics and software for recording the concentration of three gases (oxygen, carbon dioxide and carbon monoxide), test and calibrate the device. Results. Three prototypes of sensor modules for oxygen, carbon dioxide and carbon monoxide have been created. The structure, scheme of connection of sensor modules, and the principle of operation of the gas analyzer was described. Testing and optimization of these prototypes were performed. Auxiliary pneumatic equipment for checking the performance of devices, their calibration and graduation was manufactured. Measurement technique was developed and test measurements of the specified gases were performed. The calibration technique was developed and the device was calibrated using two test gas samples such as ethanol vapor and air-gas mixture of carbon dioxide. In addition, a special software has been developed, which allow observe a registered input signal from sensor modules and store it to the file. Conclusions. As a result of the work, prototype of the device was created, its testing, calibration and graduation were carried out at the State Enterprise "Ukrmetrteststandart", 4 certificates of metrological attestation were obtained. The gas analyzer can be used for screening of healthy persons based on study of exhalation to predict the risk of diseases. Keywords: multi-sensor gas analyzer, oxygen, carbon dioxide, carbon monoxide, calibration, graduation.

Artificial olfaction based on tafel curve for quantitative detection of acetone ethanol gas mixture

This work established an artificial olfaction based on a single mixed potential type gas sensor. By identifying the Tafel curve, artificial olfaction can determine the concentration of each component in the acetone and ethanol vapor mixture. To save a long testing circle, a finite element model was built to efficiently output the Tafel curves of the sensor for different concentrations of vapor mixtures. Based on the Tafel curve data obtained from the simulation, different classification algorithms were trained to determine the operating state of the sensor. Among them, eXtreme Gradient Boosting (XGB) had a 99% accuracy in determining whether the sensor is saturated or not. Then three different regression algorithms (XGB, Gradient Boosting Decision Tree (GBDT), and Random Forest (RF)) were trained to identify acetone and ethanol vapor concentrations. The results showed that XGB and GBDT were the most effective in identifying acetone and ethanol vapor. The mean absolute percentage errors for the identified acetone and ethanol in the gas mixture were 11.3% and 23%, respectively. The above results indicated that it was feasible and effective to use Tafel curves to detect VOC gases.

Vapor sorption behavior in heptazine-based MOF featuring a brick-shaped framework

A new porous MOF, [Mg1.5(HTB)2]·2Me2NH2·3DMF·12MeOH, (1) (HTB ​= ​s-heptazine tribenzoate) was successfully synthesized by employing a π-conjugated organic ligand possessing a brick-shaped framework. The activated 1a was investigated as an adsorbent towards a series of vapors (H2O, MeOH, EtOH, n-PrOH and CH2Cl2). The H2O vapor adsorption capacity of 1a can reach 533.9 ​cm3 ​g−1. Interesting, the absorption isotherm of MeOH shows an obvious stepwise sorption phenomenon with the saturated adsorption capacity of 300.8 ​cm3 ​g−1, whereas the bulker EtOH, n-PrOH and CH2Cl2 present hardly any uptakes. Moreover, the IAST selectivities of equimolar H2O/MeOH and H2O/EtOH vapor mixtures was calculated, GCMC simulations were performed to locate the framework-vapor binding sites.

Morphofunctional reaction of leukocytes and platelets in in vitro contact with a-C:H:SiOx -coated Ti-6Al-4V substrate.

The article deals with the plasma-assisted chemical vapor deposition of 0.3-1.4μm thick a-C:H:SiOx films in a mixture of argon and polyphenylmethylsiloxane vapor onto the Ti-6Al-4V alloy substrate, which is often used as an implant material. The a-C:H:SiOx film structure is studied by the Fourier-transform infrared and Raman spectroscopies. The pull-off adhesion test assesses the adhesive strength of a-C:H:SiOx films, and the ball-on-disk method is employed to measure their wear rate and friction coefficient. According to these studies, a-C:H:SiOx films are highly adhesive to the Ti-6Al-4V substrate, have low (0.056) friction coefficient and wear rate (9.8 × 10-8 mm3 N-1 m-1 ) in phosphate-buffered saline at 40°C. In vitro studies show neither thrombogenicity nor cytotoxicity of the a-C:H:SiOx film for the human blood mononuclear cells (hBMNCs). The in vitro contact between the hBMNC culture and a-C:H:SiOx films 0.8-1.4μm thick deposited onto Ti-6Al-4V substrates reduces a 24-hour secretion of pro-inflammatory cytokines and chemokines IL-8, IL-17, TNFα, RANTES, and MCP-1. This reduction is more significant when the film thickness is 1.4μm and implies its potential anti-inflammatory effect and possible application in cardiovascular surgery. The dependence is suggested for the concentration of anti-inflammatory cytokines and chemokines and the a-C:H:SiOx film thickness, which correlates with the surface wettability and electrostatic potential. The article discusses the possible applications of the anti-inflammatory effect and low thrombogenicity of a-C:H:SiOx films in cardiovascular surgery.

A versatile chemical vapor synthesis reactor for in situ x-ray scattering and spectroscopy.

We describe a versatile reactor system for chemical vapor synthesis of nanoparticles, which enables in situ investigations of high temperature gas phase particle formation and transformation processes by x-ray scattering and x-ray absorption spectroscopy. The system employs an inductively heated hot wall reactor as the energy source to start nanoparticle formation from a mixture of precursor vapor and oxygen. By use of a modular set of susceptor segments, it is especially possible to change solely the residence time of the gas mixture while keeping all other process parameters (temperature, gas flow, pressure) constant. Corresponding time-temperature profiles are supported by computational fluid dynamics simulations. The operation of the system is demonstrated for two example studies: tin oxide nanoparticle formation studied by small angle x-ray scattering and iron oxide nanoparticle formation by x-ray absorption spectroscopy.

Comparative Characteristics of Evaporative Convection Regimes in Different Statements of Boundary Value Problem for Convection Equations

We analyze different statements of the boundary value problem for the convection equations in order to use Ostroumov–Birikh type exact solutions for describing the evaporative convection regimes in two-layer systems of liquids and gas–vapor mixtures filling a plane channel. The statements differ in the types of boundary conditions for the vapor concentration and temperature functions on the channel walls. We discuss the boundary value problems modeling two-layer flows in the channel, describe the characteristics of hydrodynamic, thermal, and concentration fields for the working HFE7100-nitrogen system and classify the types of flows by distinguishing three classes: purely thermocapillary, mixed, and Poiseuille type flows.

Electrochemical Air Separation and Emergency Power Fuel Cell for Aircraft

The crash of TWA Flight 800 in July 1996 was attributed to an explosion in the center fuel tank. Since then, commercial airliners have been equipped with inerting systems to prevent explosive mixtures of air and kerosene vapor from forming in fuel tanks. The incumbent technology is based on hollow-fiber membrane (HFM) separation modules that split air into an oxygen-enriched air (OEA) stream and a nitrogen- enriched air (NEA) stream. The nitrogen enriched air used to inert kerosene contains less than 12% oxygen. Other methods for separating air like cryogenic distillation and pressure swing absorption producer purer oxygen than HFM, but they do not scale down well. Another alternative is electrochemical air separation. High-temperature air separation units using solid oxide cells have been investigated for large-scale applications like oxy-combustion to facilitate carbon dioxide sequestration. However, high-temperature technologies may be less suitable for transportation applications. Electrochemical air separation at low temperatures can be accomplished with relatively compact polymer-electrolyte cells that evolve oxygen at the anode and reduce oxygen at the cathode. The effluent from the cathode is nitrogen enriched. This presentation discusses proof of concept tests and uses these to explore the relative merits of this approach versus incumbent HFM. The electrochemical air separation stack can be fed hydrogen to provide power during emergencies, potentially performing the functions of two components on commercial aircraft.

Чисельне моделювання нестаціонарної течії в гідравлічній системі за каві-туючою шайбою

This paper addresses the construction of an efficient mathematical model to be used in the numerical simulation of unsteady liquid flows in hydraulic systems with cavitating restrictors. Existing approaches to cavitation simulation are based either on accounting for a two-phase flow structure or on representing a cavitating flow as a homogeneous medium of variable density. In the latter case, the pressure and the density are related via the barotropic equation of liquid–vapor mixture state. The goal of this work is to verify the applicability of a cavitation model based on the barotropic equation of liquid–vapor mixture state to the numerical simulation of an unsteady flow in a hydraulic system with a cavitating ring plate. The method employed is a numerical flow simulation in the axisymmetric approximation using the complete averaged Navier–Stokes equations. It is shown that the use of the barotropic equation of liquid–vapor mixture state provides a satisfactory agreement between the computed results and the experimental data available in the literature. In agreement are the peak-to-valley values of the oscillating pressure on the pipe wall immediately downstream of the cavitating ring plate and the presence of a pronounced periodic component in the pressure vs. time relationship. It is shown that the parameters of the unsteady flow downstream of the cavitating ring plate vary when going from the ring plate to the cavity collapse location: the peak-to-valley value of the oscillating pressure on the pipe wall increases and so does the contribution of high-frequency periodic components to the pressure vs. time relationship. It seems desirable that the turbulence model employed be refined further to correctly simulate cavitation oscillations generated by periodically detached cavitation in Venturi tubes, which are used in various cavitation pulse plants.

Dissolution losses of metallurgical cokes in CO2-H2O mixtures

ABSTRACT Influences of the gas mixtures of carbon dioxide and water vapor with different water vapor content on the thermal properties of cokes were studied at 1,373 k using a high-temperature gas-solid reaction device to clarify the action mechanism of water vapor in the dissolution loss of metallurgical coke in the blast furnace. Furthermore, the reaction depth and the microstructure of coke samples with different water vapor content were studied. The results showed that the reactivity of cokes was significantly improved by steam, and coke strength after the reaction was significantly weakened. Cokes with strong reactivity were more affected by water vapor. When H2O content was 0 and 11.1%, the reactivity indices of cokes with strong reactivity were 2.03 and 1.67 times that of cokes with poor reactivity, respectively. The influence of H2O on the strength ratio of two kinds of cokes after the reaction was ignored when H2O content exceeded 50.1%. The analysis of coke reaction depth after the reaction under different H2O content showed that the solution loss reaction between H2O and coke is mainly concentrated on the coke surface, while CO2 can penetrate into the coke to react. In addition, by comparing two kinds of coke with different reactivity, it is found that coke with higher reactivity is more sensitive to water vapor. The micromorphologies of cokes after reactions showed that water vapor significantly affected the pore and pore sizes of cokes. When water vapor content increased, the pore sizes of cokes increased, with the thinner pore wall and the increased number of new pores.

Consistent and flexible thermodynamics in atmospheric models using internal energy as a thermodynamic potential. Part I: Equilibrium regime

Approximations in the moist thermodynamics of atmospheric models can often be inconsistent; different parts of numerical models may handle the thermodynamics in different ways, or the approximations may disagree with the laws of thermodynamics. To address these problems, all relevant thermodynamic quantities may be derived from a defined thermodynamic potential; approximations are instead made to the potential itself—this guarantees self‐consistency, as well as flexibility. Previous work showed that this concept is viable for vapour and liquid water mixtures in a moist atmospheric system using the Gibbs potential. However, on extension to include the ice phase, an ambiguity is encountered at the triple point. To resolve this ambiguity, here the internal energy is used instead. Constrained maximisation methods on the entropy can then be used to solve for the system equilibrium state. Nevertheless, a further extension is necessary for realistic atmospheric systems, where many importantnon‐equilibriumprocesses take place; for example, freezing of supercooled water and evaporation into subsaturated air. To capture processes such as these fully, the equilibrium method must be reformulated to involve finite rates of approach towards equilibrium. Here the principles of non‐equilibrium thermodynamics are used, beginning with a set of phenomenological equations, to show how non‐equilibrium moist processes may be coupled to a semi‐implicit semi‐Lagrangian dynamical core. Standard bubble test cases and simulations of idealised cloudy thermals are presented to demonstrate the viability of the approach for the equilibrium regime. Further details and results for non‐equilibrium regimes are presented in Part II.

Ignition Delay Time of a Vapor Mixture of Structurally Strained High-Density Hydrocarbons with Air

Ignition Delay Time of a Vapor Mixture of Structurally Strained High-Density Hydrocarbons with Air

Water vapor absorption line parameters in the 6760–7430 cm–1 region for application to CO2-rich planetary atmosphere

The absorption spectra of the mixtures of water vapor and carbon dioxide at five different partial pressures of both gasses have been recorded using the Bruker IFS 125 HR FTIR spectrometer at room temperature in the 6760–7430 cm–1 spectral region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. To obtain the spectral lines parameters the quadratic speed-dependent Voigt profile was used. The water vapor line broadening and shift coefficients for lines of three vibrational bands ν1+ν3, 2ν2+ν3, and 2ν1 were obtained.

Membrane Unit for Integrated Gas Separation – Membrane Bioreactor (GS-MBR) System

One of the research directions of renewable energy sources is the production of biohydrogen from the dark fermentation of organic matter. During this fermentation process, since hydrogen is produced along with a complex mixture of other gases and vapors, hydrogen gas requires further purification. One relatively easy solution to this problem might be the utilization of gas separation membrane modules given their low energy consumption, simple operation and ease of upscaling. In this work, hollow fiber (HF) membranes based on polyetherimide (PEI) were developed and tested. HF membranes were spun from a polymer solution of PEI using the wet phase inversion process into a water bath using a pilot-scale spinning device. Gas transport measurements showed that membranes exhibited permeances of between 9.3 and 19.2 GPU with CO2/H2 selectivities within the range of 3.3 - 5.6. Morphology studies showed regular shapes resembling hollow fibers with outer diameters within the range of 250-320 microns, depending on various parameters of the spinning process. The best performing membranes were selected and a morphological analysis carried out. Selected fibers were incorporated into two types of membrane modules. One type was a laboratory-scale membrane mini-module used for preliminary tests, while the other membrane module was designed for the treatment of larger amounts of biohydrogen. Two types of laboratory-scale membrane separation units were constructed. For laboratory use, the low-pressure unit proved more accurate regulation to match the fermenters performance with the separation unit in comparison with the high-pressure one.

Stimuli‐Responsive of Flexible Silver–Organic Framework Film with Molecular Rotors Based on Methylene Rotation

Environmental stimuli‐responsive materials exhibit immense potential in various applications. Herein, three stable silver‐based organic frameworks (MOF‐Ag‐1, MOF‐Ag‐2, and MOF‐Ag‐3) are constructed connecting by the same [Ag2(CN4)2] secondary building blocks. The MOF‐Ag‐3 shows controllable molecular rotation driven by water vapor due to the flexible framework and methylene molecular rotor. Meanwhile, the soft materials (MOF‐Ag‐3@PVDF film, PVDF = polyvinylidene fluoride) that enable visible shape transformation have been prepared by integrating deformable MOF‐Ag‐3 crystals into polymer films. Moreover, the vertical distribution of MOF‐Ag‐3 crystals is adjusted by acid etching to prepare a double‐layer structure actuator, containing alternant moving layer and fixed layer. The smart actuator presents bending deformation in the water vapor (folding angle φ = 451°, RH = 80%), performing “pull‐ups” and “sit‐ups” stimuli‐responsive behaviors as the “arms” or “waist” part. In addition, the MOF‐Ag‐3@PVDF film not only produces distortion under a CH3SH vapor but also shows fluorescence quenching to the CH3SH/water mixture vapor (0.5% CH3SH) with a low detection limit of 0.48 μm. This work indicates the molecular‐level construction of stimuli‐responsive materials for pollutant monitoring.

Ultrafine bubble generation by rapid condensation of mixed vapor of non-condensable gas and steam

Although the mechanism of ultrafine bubble generation has not yet been elucidated, we believe that the state of gas-saturated water before the generation of ultrafine bubbles is the most important factor in the mechanism of ultrafine bubble generation. Therefore, we proposed the hypothesis that the spatial distribution of dissolved gas molecules among the water molecules before the ultrafine bubble formation is stared has a significant effect on the formation of ultrafine bubble suspending water. Based on this hypothesis, we succeeded in generating ultrafine bubbles of sufficient number concentration in the condensate by rapidly condensing a well mixture of non-condensable gas and vapor by cooling. The number concentration of the generated ultrafine bubbles increased almost in proportion to the condensation rate of the vapor. Therefore, it was found that promoting the formation of bubble nuclei from dissolved gas molecules existing between water molecules in the condensate and suppressing bubble growth led to an increase in the number concentration of ultrafine bubbles. The principle of ultrafine bubble generation in this invention not only simplifies the generation of ultrafine bubble water but also enables the control of the number concentration of ultrafine bubbles in water.

Radiation source with enhanced virucide effectiveness based on a mixture of helium and iodine vapor

Subject of study. A source of spontaneous emission (a lamp) in the ultraviolet spectral range excited by a capacitive discharge was investigated. Iodine vapor and mixtures of iodine vapor with inert gases were used as the operating gas medium of the lamp. Conditions for enhancements in specific output parameters of the lamp emission were investigated. Excitation conditions under which the lamp emits predominantly at the iodine atomic line with a wavelength of 206.16 nm were determined. Aim of study. The primary aim of the study was to investigate the spectral and energy characteristics of the lamp based on the iodine vapor, which is promising for the development of a radiation source with enhanced virucidal effectiveness for ultraviolet disinfection of a human environment contaminated with pathogenic microorganisms including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Method. In this study, the composition and pressure of the operating medium were optimized. In addition, the excitation mode of the lamp emission was optimized by changing the repetition rate of voltage pulses. Main results. At a specific excitation power of approximately 1.3mW/cm3 and partial pressures of iodine vapor and helium of approximately 2.5 and 7 Torr, respectively, the line of an iodine atom with a wavelength of 206.16 nm dominates in the output lamp spectrum, and the specific emission power at the outer surface of the lamp tube is approximately 3mW/cm2. Practical significance. The emission of the investigated lamp is in the spectral range of 200–225 nm, which is promising in terms of developing technology for safe ultraviolet inactivation of pathogenic microorganisms including SARS-CoV-2.

A phenomenological-based dynamic model for a polymer electrolyte membrane fuel-cell humidifier assembly

This paper presents the deduction of a phenomenological-based semi-physical model (PBSM) for the gas humidification in a fuel-cell assembly. Unlike previously published models, the one proposed here includes the momentum transfer effects and their influences over simultaneous heat and mass transfers occurring into the process as a whole. These effects strongly affect the model precision due to the compressible characteristics of the air. High sensitivity of gas properties regarding changes in both pressure and temperature are also included by modelling the gas as a compressible fluid. The model reproduces the air–water vapour mixture behaviour from the compressor discharge to the fuel-cell inlet port. Since the air humidity and temperature conditions must be maintained at their set-points to guarantee an optimal fuel-cell performance, a model such as the one presented here can be used for designing any model-based control strategy towards achieving desirable operative conditions taking also into account the operational context of the considered assembly. The comparative assessment done with experimental data from a real test bench has shown the effectiveness of the proposed model in accurately reproduce the behaviour of such complex systems.

Mathematical Modelling of Binary Distillation Column for Petrochemical Industries

Abstract: Distillation is a method of separating mixtures based on differences in volatility of components in a boiling liquid mixture. It is defined as a process in which a liquid or vapour mixture of two or more substance is separated in to component fractions of desired purity by the application and removal of heat. In this work importance is given to Binary distillation columns. In the Binary Distillation, the feed to the process consist of mixture of two components (A & B) and after the distillation two products will be generated. It is very important to model a distillation column and perform its analysis before the distillation column is practically implemented. Distillation columns are generally considered as chemical systems, for modelling chemical systems one can use mass balance equations

Ignition of thermally-thick blunt body PMMA samples using a heated wire

Ignition limits and ignition delay times of thermally-thick polymethyl methacrylate (PMMA) spheres (4-cm diameter) and cylinders (5.08-cm diameter) are investigated by placing an electrically-heated wire coil beneath the sample in a slow forced flow. The wire serves as both a heater for the solid sample and a gas-phase hot spot to ignite the oxidizer-fuel vapor mixture. In the experiments, the wire's electrical current and power-on time, its distance from the sample surface, the forced flow velocity, oxygen percentage, and pressure are systematically varied. Ignition limits as a function of the oxygen percentage, pressure, and igniter current are determined. Two ignition delay times are determined: igniter-assisted ignition and self-sustained ignition. These critical times are also functions of the degree of heat-up of the sample interior. Solid temperature profiles are measured using embedded thermocouples to determine the sub-surface temperature gradients at the moment of ignition. The heat transfer modes from the igniter to the solid sample are numerically investigated during the pre-pyrolysis heat-up period. At the forward stagnation-point region where ignition occurs, radiation is greater than convection and accounts for approximately 60% of the total heat input. This is consistent with the experimental findings on ignition delay times and heat flux measurements.

Decrements in lung function and respiratory abnormalities associated with exposure to diacetyl and 2,3-pentanedione in coffee production workers.

Coffee production workers are exposed to complex mixtures of gases, dust, and vapors, including the known respiratory toxins, diacetyl, and 2,3-pentanedione, which occur naturally during coffee roasting and are also present in flavorings used to flavor coffee. This study evaluated the associations of these two α-diketones with lung function measures in coffee production workers. Workers completed questionnaires, and their lung function was assessed by spirometry and impulse oscillometry (IOS). Personal exposures to diacetyl, 2,3-pentanedione, and their sum (SumDA+PD) were assigned to participants, and metrics of the highest 95th percentile (P95), cumulative, and average exposure were calculated. Linear and logistic regression models for continuous and binary/polytomous outcomes, respectively, were used to explore exposure-response relationships adjusting for age, body mass index, tenure, height, sex, smoking status, race, or allergic status. Decrements in percent predicted forced expiratory volume in 1 second (ppFEV1) and forced vital capacity (ppFVC) were associated with the highest-P95 exposures to 2,3-pentanedione and SumDA+PD. Among flavoring workers, larger decrements in ppFEV1 and ppFVC were associated with highest-P95 exposures to diacetyl, 2,3-pentanedione, and SumDA+PD. Abnormal FEV1, FVC, and restrictive spirometric patterns were associated with the highest-P95, cumulative, and average exposures for all α-diketone metrics; some of these associations were also present among flavoring and non-flavoring workers. The combined category of small and peripheral airways plus small and large airways abnormalities on IOS had elevated odds for highest-P95 exposure to α-diketones. These results may be affected by the small sample size, few cases of abnormal spirometry, and the healthy worker effect. Associations between lung function abnormalities and exposure to α-diketones suggest it may be prudent to consider exposure controls in both flavoring and non-flavoring settings.