Gas Moisture Research Articles

Quantitative and Qualitative Experimental Assessment of Water Vapor Condensation in Atmospheric Air Transonic Flows in Convergent–Divergent Nozzles

Atmospheric air, being also a moist gas, is present as a working medium in various areas of technology, including the areas of airframe aerodynamics and turbomachinery. Issues related to the condensation of water vapor contained in atmospheric air have been intensively studied analytically, experimentally and numerically since the 1950s. An effort is made in this paper to present new, unique and complementary results of the experimental testing of moist air expansion in the de Laval nozzle. The results of the measurements, apart from the static pressure distribution on the nozzle wall and the images obtained using the Schlieren technique, additionally contain information regarding the quantity and quality of the condensate formed due to spontaneous condensation at the transition from the subsonic to the supersonic flow in the nozzle. The liquid phase was identified using the light extinction method (LEM). The experiments were performed for three geometries of convergent–divergent nozzles with different expansion rates of 3000, 2500 and 2000 s−1. It is shown that as the expansion rate increases, the phenomenon of water vapor spontaneous condensation appears closer to the critical cross-section of the nozzle. A study was performed of the impact of the air relative humidity and pollution on the process of condensation of the water vapor contained in the air. As indicated by the results, both these parameters have a significant effect on the flow field and the pressure distribution in the nozzle. The results of the experimental analyses show that in the case of the atmospheric air flow, in addition to the pressure, temperature and velocity, other parameters must also be taken into account as boundary parameters for possible numerical analyses. Omitting information about the air humidity and pollution can lead to incorrect results in numerical simulations of transonic flows of atmospheric air. The presented results of the measurements of the moist air transonic flow field are original and fill the research gap in the field of experimental studies on the phenomenon of water vapor spontaneous condensation.

Exhaled Anesthetic Xenon Regeneration by Gas Separation Using a Metal–Organic Framework with Sorbent‐Sorbate Induced‐Fit

AbstractNoble gas xenon (Xe) is an excellent anesthetic gas, but its rarity, high cost and constrained production prohibits wide use in medicine. Here, we have developed a closed‐circuit anesthetic Xe recovery and reusage process with highly effective CO2‐specific adsorbent CUPMOF‐5 that is promising to solve the anesthetic Xe supply problem. CUPMOF‐5 possesses spacious cage cavities interconnected in four directions by confinement throat apertures of ~3.4 Å, which makes it an ideal molecular sieving of CO2 from Xe, O2, N2 with the benchmark selectivity and high uptake capacity of CO2. In situ single‐crystal X‐ray diffraction (SCXRD) and computational simulation solidly revealed the vital sieving role of the confined throat and the sorbent‐sorbate induced‐fit strengthening binding interaction to CO2. CUPMOF‐5 can remove 5 % CO2 even from actual moist exhaled anesthetic gases, and achieves the highest Xe recovery rate (99.8 %) so far, as verified by breakthrough experiments. This endows CUPMOF‐5 great potential for the on‐line CO2 removal and Xe recovery from anesthetic closed‐circuits.

Influence of hydrogen ingress and capture on the mechanical properties of spray formed 2195 aluminum alloy

The current research has focused on the hydrogen capturing and its impact on the mechanical properties of spray-formed 2195 (SF2195) aluminum alloy. Microstructure characterization, thermal desorption spectra (TDS) and hydrogen trapping of characteristic microstructure, are used to investigate the generation, migration and trapping of hydrogen. The retention of moisture in the carrier gas is believed to induce high concentration of hydrogen and the amorphous Al2O3 layer within the SF2195 billet, and the local retention of carrier gas brings about pores with the Al2O3 layer on the inner wall. High concentration of hydrogen is captured in the hot-rolled alloy while around 60 % of the hydrogen can be eliminated during the solution-quenching. Particles of T1 phase trap large quantity of hydrogen and the high-density dislocations developed from the pre-stretch promote the migration of hydrogen towards dispersoids and precipitates. The presence of hydrogen and Al2O3 layer contributes to the reduced plasticity of SF2195 alloy. The spreading of flattened pores can induce intensified hydrogen damage effect in local regions and thus contribute to the unusually decreased ductility along the thickness direction in the T8 aged alloy.

Simultaneous measurement of solid concentration and solid moisture in gas–solid two-phase flow using a dual-modality electrical sensor

Abstract In a gas–solid two-phase flow system, simultaneous measurement of solid concentration and solid moisture is essential for some applications. However, during the measurement process, solid concentration and solid moisture are coupled in the measurement signals when the measurement signal is sensitive to both solid concentration and moisture. This makes it challenging to measure them simultaneously in the same measurement field. To solve this issue, a novel measurement method is proposed in this study, which uses a dual-modality electrical sensor to achieve simultaneous measurement of solid concentration and solid moisture in gas–solid two-phase flow. The dual-modality electrical sensor features a simple structure and captures measurement signals of capacitance and angle of dielectric loss within the same measurement section. With the above signals which are both sensitive to solid concentration and moisture, an iterative correction calculation method is adopted to achieve the simultaneous measurement of solid concentration and solid moisture. During the calculation process, the measured parameters are decoupled and continuously corrected until the related error values meet the threshold requirement. Numerical simulation experiments under three typical distributions and physical experiments under roping flow are carried out to verify the proposed measurement method. The results prove the effectiveness of the proposed measurement method in the simultaneous measurement of solid concentration and solid moisture for gas–solid two-phase flow.

Exhaled Anesthetic Xenon Regeneration by Gas Separation Using a Metal-Organic Framework with Sorbent-Sorbate Induced-Fit.

Noble gas xenon (Xe) is an excellent anesthetic gas, but its rarity, high cost and constrained production prohibits wide use in medicine. Here, we have developed a closed-circuit anesthetic Xe recovery and reusage process with highly effective CO2-specific adsorbent CUPMOF-5 that is promising to solve the anesthetic Xe supply problem. CUPMOF-5 possesses spacious cage cavities interconnected in four directions by confinement throat apertures of ~3.4 Å, which makes it an ideal molecular sieving of CO2 from Xe, O2, N2 with the benchmark selectivity and high uptake capacity of CO2. In situ single-crystal X-ray diffraction (SCXRD) and computational simulation solidly revealed the vital sieving role of the confined throat and the sorbent-sorbate induced-fit strengthening binding interaction to CO2. CUPMOF-5 can remove 5 % CO2 even from actual moist exhaled anesthetic gases, and achieves the highest Xe recovery rate (99.8 %) so far, as verified by breakthrough experiments. This endows CUPMOF-5 great potential for the on-line CO2 removal and Xe recovery from anesthetic closed-circuits.

Evaluation of the CH4/CO2 separation by adsorption on coconut shell activated carbon: Impact of the gas moisture on equilibrium selectivity and adsorption capacity

Upgrading biogas to biomethane is of great interest to change the energy matrix by feeding the renewable fuel produced from biomass waste into natural gas grids or directly using it to replace fossil fuels. The study aimed to assess the adsorption equilibrium of CH4, CO2, and H2O on a coconut-shell activated carbon (CAC 8X30) to provide data for further studies on its efficiency in upgrading biogas by Pressure Swing Adsorption (PSA). The adsorbent was characterized, and equilibrium parameters were estimated from monocomponent CH4, CO2, and H2O equilibrium isotherms. Binary and ternary equilibrium isotherms were simulated, and the selectivity and adsorption capacity of the CAC 8X30 were calculated in dry and wet conditions and then compared with zeolite 13X as a reference material. Regarding characterization, Nitrogen and Hydrogen Physisorption results indicated that 94 % of the pore volume is concentrated in the region of micropores. The adsorption affinity with CAC 8X30 estimated from monocomponent isotherms was in the order KH20>KCO2>KCH4. IAST-Langmuir model simulations presented good agreement with experimental binary equilibrium data. Further simulations indicated equilibrium selectivity for CO2 over CH4 (e.g., 4.7 at 1 bar and 298 K for a mixture of CH4/CO2, 60/40 vol%), which increased in the presence of moisture, indicating its suitability for upgrading humid biogas. Simulations for zeolite 13X suggested that the material is unsuitable in the presence of water vapor but presents higher selectivity than the CAC 8X30 in dry conditions. Hence, the integration of both materials might be helpful for biogas upgrading.

Heat and water recovery from gaseous stream using a flat-sheet ceramic membrane as a transport membrane condenser

Ceramic-membrane technology has been employed to recover waste heat and vapor from moist gases. In addition to the hydrophilicity, pore size, and porosity of separation materials, a membrane condenser can achieve a high recovery rate. In this study, a transport membrane condenser (TMC) was successfully constructed using a flat-sheet ceramic membrane (FCM) with a large pore size of 45.54 μm. The membrane characteristics, including the mean pore size, pore size distribution, and porosity, were investigated to determine their recovery mechanism. Their water and heat fluxes, recovery rates, and thermal resistance were compared under several experimental conditions. The inlet conditions significantly affect the TMC recovery performance. Higher recovery fluxes were obtained at lower water temperatures, higher gas temperatures, and higher gas flow rates. However, when the Reynolds number of water increased, the heat flux increased rapidly, and the recovered water decreased slightly. The highest TMC water recovery rate was 84.1%. In addition, to further analyze the separation mechanisms, a two-dimensional model was developed using ANSYS Fluent code. The simulation results were compared with the experimental data to verify the accuracy of the numerical method. The comparison results showed a high degree of consistency.

Enhanced Detection of SF₆ Gas Moisture Concentration in Gas-Insulated Switchgear Utilizing Tilted Fiber Bragg Grating Coated With Multilayer Graphene Oxide Films

Enhanced Detection of SF₆ Gas Moisture Concentration in Gas-Insulated Switchgear Utilizing Tilted Fiber Bragg Grating Coated With Multilayer Graphene Oxide Films

Investigating the Impact of Hydrogen Gas Moisture Content on Electricity Generation in PEM Fuel Cells

In the realm of energy sources, non-renewable fossil fuels, such as petroleum derivatives, continue to pose a significant threat to our planet. Currently, hydrogen energy, derived from renewable sources, is under extensive research, primarily due to its high efficiency, versatile applications, and zero carbon emissions. Hydrogen gas has become an indispensable alternative energy source owing to its numerous advantages. The technology that enables efficient utilization of hydrogen gas as an energy source is fuel cells, with Polymer Electrolyte Membrane Fuel Cells (PEM Fuel Cells) being the most significant advancement in this field. In this study, anode and cathode moisture levels were investigated by experimental study on the obtained efficiency of PEM fuel cell performance. Pure hydrogen and oxygen gases were used in the anode and cathode sections of the experiment, respectively. The test stand and a 6 cell 35 watt fuel cell with 9 cm2 active area were used for the test. Temperature and water accumulation, especially humidification in PEM fuel cells, can be achieved by keeping the hydrogen flow, oxygen flow and battery temperature under control. In the experimental study, the fuel cell humidification rate is gradually increased by keeping the flow and line temperature constant. 30% - 35% - 40% - 45% - 50% - 55% - 60% - 65% - 70% of the results obtained in the voltage, amperage and their effects on watts. As a result of the experimental study, humidification rate has a significant effect on the performance of PEM fuel cell. With the increased humidification temperature, the performance of the installed system increased significantly and nominal values were found. However, it is observed that the performance decreases after a certain period of time in the values higher than 60%.

The efficacy of carbon molecular sieve and solid amine for CO2 separation from a simulated wet flue gas by an internally heated/cooled temperature swing adsorption process

Considering that most sources of carbon dioxide (CO2) emissions are also waste heat sources, CO2 recovery using self–generated low–temperature waste heat is desirable. This study examines CO2 enrichment and recovery via a temperature swing adsorption (TSA) process. The low–temperature heating–driven TSA process requires an alternative regeneration method to conventional air heating to avoid dilution of the desorbed CO2, and to apply it to actual gas, using an adsorbent that does not lose its CO2 adsorption capacity because of coexisting water vapor is necessary. Zeolites tested in our previous study lose their CO2 adsorption ability under a humid feed gas and a low–temperature regeneration condition. For the former, efficacy of an internally heated and cooled adsorbent–packed fin–coil heat exchanger has been confirmed. This study thus attempts to overcome the latter issue by employing carbon molecular sieve (CMS) and solid–supported polyethyleneimine (PEI) as CO2 adsorbents. The effects of moisture in the inlet gas on the separation performance of adsorbents were investigated. The study reveals that PEI required moisture to extend for CO2 adsorption, and CO2 separation performance increased with higher humidity. PEI can produce the desorbed gas with a CO2 concentration of ∼ 45 % and a recovery ratio of ∼ 70 % from feed gas (CO2 concentration of ∼ 10 %) at a dew point temperature of 15 °C. Conversely, the CMS separation performance is almost independent of humidity. The desorbed gas of CMS indicates a CO2 concentration of only ∼ 30 % and a recovery of ∼ 30 %. The flow of the volumetric desorbed gases and the CO2 concentration rate indicates that CMS has the potential for reducing heat consumption by shortening the regeneration time because most of the CO2 desorbs during the early regeneration step. For increasing the concentration of recovered CO2, a severe control valve is required to eliminate the desorbed nitrogen (N2) accompanied by CO2. In contrast, CO2 desorption from PEI is slower than that in CMS, and PEI needs a relatively longer regeneration time.

Experimental research on enhancing heat and mass transfer of porous ceramic membrane with acoustic field

Transport membrane condenser is a water heat recovery technology based on condensation mechanism. Limited by the price of ceramic membrane, it focuses on enhancing the heat and mass transfer technology of ceramic membrane. Acoustic enhancement of heat and mass transfer is an efficient enhancement method. In order to explore the heat and mass transfer characteristics of ceramic membrane enhanced by audible sound field under different condensation mechanisms, the corresponding experimental platform was built. The results show that due to the condensation characteristics of capillary condensation, the heat and mass transfer performance of the nano membrane under the action of sound field is greatly improved, with a maximum increase of 53.44% and 53.22%, respectively; This article presents an analysis of the economic advantages of utilizing acoustic waves in conjunction with ceramic membranes. It is found that the recovery period can be shortened by 3.2 years when acoustic waves are employed. The findings of this study offer a valuable foundation for improving heat and mass transfer in flue gas moisture recovery systems utilizing ceramic membranes.

Vapor Phase Electrochemistry: The Missing Science

Several aspects of physics have been adversely effected by the fact that vapor phase electrochemistry has proved impossible to quantify. By the end of the 19th century, physicists had encountered several strange observations that appeared to involve chemistry. Eventually, it was realized that, in a moist gas, no rate process involving ions is quantifiable since we possess no valid relationship between the concentrations of electrolytes and their thermodynamic activities. There are both technical and societal reasons for this problem. Until both problems have been addressed, no reliable quantitative conclusions can be drawn for any system where ionic electrostriction in a moist gas is important. The most obvious consequences of the missing science are misconceptions concerning naturally contained air plasmas such as ball lightning, tornadic lights, and unpredictable flying objects (UFOs). None of these phenomena violates any known law of physics, but this only becomes clear once the absence of applicable, strictly valid theories is accepted. Fortunately, partial solutions to the problem exist if use is made of qualitative arguments. Using this approach, it can be seen that all the apparently anomalous characteristics of atmospheric plasmas result from a balance between different physical and chemical driving forces. A better understanding of the chemical consequences of electrostriction should have two long-term benefits. One relates to understanding the corrosive properties of high-pressure steam. The other concerns the specific chemical processes that stabilize air plasmas. If stable air plasmas could be simulated, a plentiful supply of carbon-free energy would become available.

Accurate determination of line intensity of H[formula omitted]O near 7181 cm−1 : SI-traceable measurement using primary trace-moisture standard in N[formula omitted] gas

The absorption spectra of trace water vapor in N2 gas with a mole fraction of 500 nmol/mol in the pressure range of 20 kPa to 140 kPa were obtained near 7181 cm−1 using wavelength-meter-controlled cavity ring-down spectroscopy (WMC-CRDS). The reference gas (water vapor in N2 gas) was produced using a generation system of primary measurement standards for trace moisture in gases, where the amount of water vapor was measured using a gravimetric method. The obtained spectra of H2O were analyzed using a multispectrum fitting technique with a speed-dependent asymmetric Voigt profile (SDAVP). The values of the line intensity were determined with traceability to the International System of Units (SI). We could achieve the expanded uncertainty below 2 % for the line intensities of the strong lines.

Screening, preparation, and prototyping of metal–organic frameworks for adsorptive carbon capture under humid conditions

AbstractAdsorption‐based carbon capture has been recognized as an attractive method for mitigating global warming. Metal–organic frameworks (MOFs) are promising candidate adsorbents for this purpose due to their high adsorption uptake and selectivity for carbon dioxide. However, in real‐world applications, such as direct air capture, the presence of moisture in the feed gas may pose a grand challenge for CO2 adsorption in MOFs. This paper aims to address the issue of water–CO2 co‐adsorption in MOFs and present screening criteria for selecting MOFs that preferentially adsorb CO2 under humid conditions. First, we uncover a comprehensive overview of CO2–water co‐adsorption characteristics of various MOFs. Then, the high‐throughput screening methods are summarized. Both computational and experimental efforts have been dedicated to identify the promising MOFs for humid CO2 capture. According to the screening results and adsorption mechanism, the optimal preparation strategies are proposed to modulate the effect of water on CO2 uptake in MOFs. Finally, current MOF‐based CO2 capture prototypes are presented to evaluate their practical feasibility and performance. This work could offer valuable guidance for the development and application of MOFs for CO2 capture in the presence of water and inspire further research in this field.

A Graphical Tool to Describe the Operating Point of Direct Reduction Shaft Processes

This article presents a new graphical tool for direct reduction shaft processes inspired by the Rist diagram developed for blast furnaces. The tool represents gas flows using vectors, with specific consumption and specific oxidation as components to indicate gas/iron ratios. Key features include consideration of gas chemical composition for vector directions, easy visual representation of gas mixtures, as well as reduction and carburization rates of direct reduced iron (DRI). The tool also includes thermodynamic conditions for reduction from the Chaudron diagram, analogous to the Rist diagram. Several practical applications are presented, including quantifying gas moisture, evaluating the measurement consistency of flowmeters and gas analyzers in top gas recycling, and evaluating instantaneous DRI production by analyzing reducing gas at the inlet and outlet of the shaft. This graphical tool could be useful for production teams to monitor and optimize process flows and promote understanding among students, engineers, technicians, and operators. Its potential for online use further enhances its practical value. As a result, the tool is of significant academic and industrial interest in improving process efficiency and optimization.

Application of image-based diffusion coefficients in multi-scale simulation of coalbed methane reservoirs

Gas diffusion in coalbed methane (CBM) reservoirs is a multi-scale process. It can be a dominant factor in long-term gas production performance. Producing coalbed methane requires a detailed understanding of diffusion behaviours and their contribution to production. This paper develops a core-scale model based on micro-CT images. Our model considers free and adsorbed gas diffusion, sorption, and viscous flow. It also includes the effect of swelling, gas moisture, and effective stress. Following that, it is used to simulate gas flow on micro-CT images. The simulation results quantify the influence of effective stress on gas diffusion in coal. The core-scale model is then coupled to the large-scale simulation, where we compare the gas production curves against the result based on the assumption of a constant diffusion coefficient. This model can be used to calculate the effective diffusion coefficient from a micro-CT image and to predict the production performance at the reservoir scale reliably using a coupled multi-scale approach.

Solar-driven thermo-photocatalytic CO2 methanation over a structured RuO2:TiO2/SBA-15 nanocomposite at low temperature

A new hybrid catalyst composed of mesostructured silica SBA-15 functionalized with TiO2 and further loaded with RuO2 was developed to efficiently promote thermo-photocatalytic CO2 hydrogenation into methane at low temperatures. The catalytic activity was assessed with respect to TiO2:RuO2 loading, catalyst dosage, illumination source (polychromatic sunlight and monochromatic LEDs) and power, [H2]:[CO2] molar ratio, temperature, and catalyst reusability. The best methanation yields were attained for the RuO2(6.4%):TiO2(16.9%)/SBA-15 nanocomposite at 150 ºC, under simulated sunlight (0.21 W) and stoichiometric [H2]:[CO2] molar ratio, reaching: a specific CH4 production rate of 13.6 mmol gcat-1 h-1; 99.8 % selectivity; 96.8 % CO2 conversion (110-min; 40 mL); and apparent photonic efficiency/quantum yield of 39.5 %/42.1 %. Considering only the active RuO2:TiO2 photocatalyst mass (23.3 %), the CH4 production rate increased to 58.6 mmol gactive_cat-1 h-1. Besides, this highly-active photocatalyst featured excellent UV-Vis-IR light absorbance, high surface area, and stability for reuse when moist gas was removed between cycles.

Effects of trace moisture content on tribofilm formation, friction and wear of CF-filled PTFE in hydrogen

This study investigated the effects of trace moisture in hydrogen gas on the tribological behavior of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites by examining 20 wt% polyacrylonitrile-based CF-reinforced PTFE composites against stainless-steel disks in gaseous hydrogen environments, where moisture content was controlled at 1, 10, 20, and 40 ppm. The results revealed tribological characteristics of the sliding couples were significantly affected by the moisture content. Wear rates of pin specimens tended to increase gradually with moisture content. Similarly, average coefficient of friction increased as moisture content increased from 1 to 20 ppm. However, it decreased upon further increasing the water content. Moreover, surface analyses of the formed tribofilms at varying moisture contents revealed significant variations in terms of the amount and structure.

Experimental study on liquid-gas phase separation driven by pressure gradient in transport membrane condenser

Flue gas moisture recovery from coal-fired power plants has always been an important topic in the fields of energy and building and gas dehumidification. Moisture and waste heat recovery in a transport membrane condenser (TMC) involves heat transfer, mass transfer and intermolecular interactions. This study, an experiment was designed based on TMC, which revealed the process of vapor condensation on the membrane surface and mass transfer across the membrane, and clarified the driving mechanism of mass transfer. It is found that the main driving force affecting the mass transfer is related to the recovery mechanism and the flowing working fluid. The main driving force influencing mass transfer on the flue gas side is the pressure gradient caused by the vapor pressure difference, whereas on the condensation side, mass transfer is influenced through the heat transfer gradient. Furthermore, high vacuum levels on the permeate side may enhance gas cross-membrane transport, but do not improve mass transfer performance. Compared with a longitudinal spacing of 30 mm, the condensation mass transfer rate of TMC with a longitudinal spacing of 80 mm increased by 107%–174%. The research results have an important role in promoting the realization of resource recovery and energy efficiency.

Physisorption of SO2 by carbonaceous model adsorbents with tunable hierarchical pore configurations: Experiment and simulation

Adsorption removal of SO2 using activated carbons has attracted enormous attention due to its relatively low water consumption and environmental friendliness. The physisorption of SO2 is regarded as the prerequisite step of SO2 chemisorption (i.e., SO2 reacting with oxygen and moisture in the flue gas). In this study, a series of carbonaceous model adsorbents (i.e., activated carbons, ACs) with various pore hierarchy degrees and similar surface chemistry were synthesized by simply regulating the conditions of catalytic activation. The physical and chemical characteristics of the ACs were elucidated by N2 physisorption, XPS, TEM and SEM. Both dynamic breakthrough performances and isotherms of SO2 adsorption on ACs were investigated, presenting a negative correlation between pore hierarchy and SO2 saturated adsorption capacity. Compared with the fitting of semi-empirical isotherm models, classical molecular dynamic (MD) simulation can better demonstrate the spatial distribution and the local density of SO2 molecules in nanopores of ACs with diameters <2 nm.