Saturated Vapor Research Articles

High quality perovskite thin films synthesized by low-temperature supercritical carbon dioxide annealing method

Thermal annealing is a conventional method used to eliminate residual solvents in perovskite films, reducing internal and interfacial defects. However, due to the high saturation vapor pressure of the residual solvent dimethyl sulfoxide, it is difficult to quickly remove the residual solvent at low temperatures. In this paper, the high permeability and diffusion of supercritical CO2 (ScCO2) were used to quickly remove the residual solvent of film at low temperatures. The effects of ScCO2 annealing on the surface morphology, residual solvents, internal and interfacial defects of perovskite thin films were investigated. The experimental results indicate that ScCO2 annealing significantly improves the removal efficiency of residual solvents compared to low-temperature annealing, effectively minimizing internal and interfacial defects. Additionally, the interaction energy of CO2 with the perovskite crystal plane reduces the surface energy of the crystal, resulting in a significant increase in the average grain size of the crystal by about 91.2%. Notably, the average crystal size of the film prepared by chlorobenzene as an antisolvent increased from 209.35 nm to 704.57 nm. The high penetration of ScCO2 also promoted uniform crystal growth, thereby reducing crystal structure deformation and defects. The carrier lifetime of perovskite thin films after ScCO2 annealing increased by over 58.8% on average.

(+)-Nootkatone, the flavor of grapefruit

Nootkatone is one of the most valuable citrus flavors. Originally isolated from the heartwood of the Nootka cypress (Callitropsis nootkatensis), it was probably the identification of nootkatone as a minor component of grapefruit oil that catapulted this sesquiterpene into the focus of flavor research and made it a highly sought-after citrus aroma in recent decades. The odors of ( +)-nootkatone and (−)-nootkatone are perceptible in the air at threshold concentrations of 30 ppm and 66,000 ppm of saturated vapor, respectively. While ( +)-nootkatone embodies a strong grapefruit scent and has a bitter taste, (−)-nootkatone has a faint woody vetiver note and is virtually tasteless. In 2020, nootkatone was registered by the US Environmental Protection Agency as an insect repellent and natural insecticide that may repel and kill mosquitoes, fleas, ticks, mites, lice, and termites. Moreover, numerous pharmacological activities of nootkatone have been thoroughly investigated. As expected, a wealth of synthetic approaches, which are essentially based on the oxidation of valencene and on total syntheses, have been published in the last 60 years since its discovery. However, in addition to extraction from natural sources (e.g., grapefruit peel), the enzymatic oxidation of valencene and fermentative processes are the preferred production technologies today. The market is expected to grow considerably over the next 10 years, not least owing to the wide range of potential applications in the pharmaceutical, personal, and home care sector.How the reader may benefit: learn more about the total synthesis of natural products, allylic oxidation, and Robinson annulation, gain deeper insights into the biosynthesis of sesquiterpenes and finally discover how enantiopure compounds, such as ( +)-nootkatone, are produced at an industrial scale.Graphical

Energy, Exergy, and Economic Performance Comparison and Parametric Optimization of Organic Rankine Cycles Using Isobutane, Isopentane, and Their Mixtures for Waste Heat Recovery

The possibility of applying the organic Rankine cycle (ORC) to further recycle the low-grade waste heat efficiently is studied in the present work. The energy, exergy, and economic models of the ORC system are established, and the isobutane, isopentane, and their mixtures are selected as the organic working mediums (OWMs). Due to the slip characteristics of mixed OWM, four operational conditions of the ORC system are proposed, and then the contrastive analysis of energy, exergy, and economic performances under the four operational conditions are conducted. Finally, the optimal mixture mass fraction and crucial parameters of the ORC system are separately determined through the bi-objective optimization. The results show that the ORC system using the mixed OWM can achieve a larger net power output and exergy efficiency by comparing the pure OWM when the condensing temperature is set as the saturated vapor temperature during the condensation process. The electricity production cost first rises and then decreases with the rising mass fraction of isobutane in mixed OWM, and the ORC system using the isopentane can achieve the smallest electricity production cost. By taking the low-grade flue gas of 433.15 K as the ORC heat source, four operational conditions have the same optimal ORC crucial parameters, namely the evaporating temperature of 393.15 K, condensing temperature of 308.15 K, and superheat degree of 0 K. The pure OWM of isobutane can achieve better overall performance by setting the condensing temperature as the saturated liquid temperature.

Surface Depth Analysis of Chemical Changes in Random Copolymer Thin Films Composed of Hydrophilic and Hydrophobic Silicon-Based Monomers Induced by Plasma Treatment as Studied by Hard X-ray Photoelectron Spectroscopy and Neutron Reflectivity Measurements.

In this study, a silicon-based copolymer, poly(tris(trimethylsiloxy)-3-methacryloxypropylsilane)-co-poly(N,N-dimethyl acrylamide), thin film was subjected to plasma surface treatment to make its surface hydrophilic (biocompatible). Neutron reflectivity (NR) measurement of the plasma-treated thin film showed a decrease in the film thickness (etching width: ∼20 nm) and an increase in the scattering length density (SLD) near the surface (∼15 nm). The region with a considerably high SLD adsorbed water (D2O) from its saturated vapor, indicating its superior surface hydrophilicity. Nevertheless of the hydrophilicity, the swelling of the thin film was suppressed. Hard X-ray photoelectron spectroscopy (HAXPES) performed at various takeoff angles revealed that the thin-film surface (∼20 nm depth) underwent extensive oxidation. NR and HAXPES analysis quantitatively yielded the depth profiling of elemental compositions in a few tens of nm scale. Si oxidation and hydrogen elimination (probably CH3 groups) in the vicinity of the surface region increased the SLD and decreased the hydrophobicity. A combination of Soft X-ray photoelectron spectroscopy and NR measurements revealed the surface chemical composition and mass density. It was considered that the surface near the film was chemically composed close to SiO2, forming a gel-like (three-dimensional network) structure that is hydrophilic and suppresses swelling due to moisture, indicating it can be expected to maintain stable hydrophilicity on the film surface.

Spatiotemporal Variations and Driving Factors of Water Availability in the Arid and Semiarid Regions of Northern China

It is anticipated that global warming will modify precipitation and evapotranspiration patterns, consequently affecting water availability. Changes in water availability pose challenges to freshwater supply, food security, and ecosystem sustainability. However, the variations and driving mechanisms of water availability in the arid and semiarid regions of Northern China remain unclear. This study evaluates the accuracy of three evapotranspiration products and analyzes the changes in water availability in the arid and semiarid regions of Northern China over the past 39 years (1982–2020) along with their driving factors. The results indicate that during this period, precipitation increased at a rate of 7.5 mm/decade, while evapotranspiration rose at a higher rate of 13 mm/decade, resulting in a decline in water availability of 5.5 mm/decade. Spatially, approximately 30.17% of the area exhibited a significant downward trend in water availability, while 65.65% remained relatively stable. Evapotranspiration is the dominant factor leading to the decrease in water availability, with a contribution rate of 63.41%. The increase in evapotranspiration was primarily driven by temperature (32.53% contribution) and the saturation vapor pressure deficit (24.72% contribution). The decline in water availability may further exacerbate drought risks in arid and semiarid regions. The research results can provide a scientific basis for developing water resource management strategies and ecological restoration strategies under environmental change.

Reaction-controlled triple O-isotope exchange trajectories during experimental alteration of olivine

The measurements and application of triple O-isotope system is a relatively new and powerful tool in tracing water-rock interaction, allowing to distinguish the temperature-dependent fractionation from the water amount that interacted with the rock. While the use of 18O/16O fractionation between minerals and fluids is well-established, most natural mineral-water reactions remain uncharacterized in terms of the triple isotope fractionation (17O/16O and18O/16O). The triple O-isotope approach is especially promising when it comes to natural samples, where an array of exchanged samples constrains the fluid endmembers. However, multiple exchange mechanisms are likely to occur between the reacting rock and water, which has not been investigated for triple O-isotopes. This study examines the triple O-isotope exchange between fluid and olivine experimentally, as this is a common reaction in nature and mechanisms/rates of reaction are societally important for CO2 sequestration. Water-olivine reaction in batch experiments was investigated at 275 °C at the saturated water vapor pressure of 59.5 bar. Reactants were loaded at mass ratios 0.6 to 2 and exchanged for periods of time between 44 and 1048 h. Local meteoric water and mantle olivine were taken as the initial reactants. The mineral products are brucite, serpentine and minor magnetite that occur as coatings on unreacted olivine as well as individual crystals. The progress of this dissolution-precipitation reaction was traced with the δD-δ′18O-Δ′17O values of reacted fluids and mineral products. After 1048 h of reaction, ∼50 wt% of unreacted olivine remained. In general, experimental data conforms with the triple O-isotope fractionation factors calculated for the co-existing secondary minerals forming in equilibrium with fluid. However, there is scatter and deviations in the reacted fluid compositions likely driven by the difference in relative rates of secondary mineral formation and changing modal and chemical mineral composition. We observe that brucite and magnetite form abundant aggregates early in the progress of the reaction, while chrysotile forms fine-grained coatings that become abundant later. Since individual mineral-water fractionation 103ln18/16α range over 10 ‰ with θ ranging between 0.51 and 0.53, the dynamic behavior of dissolution-precipitation mechanism during alteration of olivine is the main factor to the “wandering” triple O-isotope trajectories in our relatively short experiments.

Substantial Increase in Sub–Daily Precipitation Extremes of Flooding Season Over China

AbstractUnderstanding sub‐daily precipitation extremes (SPEs) can provide scientific insights for taking effective measures to mitigate climate risks. Leveraging gauge observations at hourly precipitation in 2,312 meteorological stations and extreme sub‐daily precipitation indices (ESPIs), we investigate the changes of SPEs in flooding season of 1971–2022 in China. On country scale, the occurrences and intensity of SPEs have significantly increased and even accelerated since the 21st century, suggesting increases in 2010s by 15%–38% compared with that in 1970s. The SPE risks for 20‐year and 50‐year return‐period increased by 2–4 and 8–20 times in 2001–2022 compared with that in 1971–2000, respectively. Over 80% stations are found to have positive trends in all ESPIs. On regional scale, seven sub‐regions experienced significant increases in ESPIs with larger magnitudes in the East China. The enlarged 500‐hPa geopotential height, 700‐hPa pseudoequivalent potential temperature, 700‐hPa specific humidity, saturated vapor pressure and urbanization ratio may be bonded to more SPEs.

Bioaerosol emission characteristics and potential risks during composting: Focus on pathogens and antimicrobial resistance

In this study, we analyzed bioaerosol emission characteristics and potential risks of antimicrobial resistance (AMR) during composting using the impaction culture method and metagenomic sequencing. The results showed that the highly saturated water vapor in the emission gas mitigated particulate matter emission during the thermophilic period. About the bioaerosols, the airborne aerobic bacterial emissions were suppressed as composting enters the mature period, and the airborne fungi are usually present as single-cell or small-cell aggregates (< 3.3 µm). In addition, the microbial community structure in bioaerosols was stable and independent of composting time. Most importantly, the PM2.5 in bioaerosols contained large amounts of antibiotic resistance genes (ARGs), potential pathogens, and multidrug resistant pathogens, which were diverse and present in high concentrations. Among them, ARGs concentrations encoding 21 antibiotics ranged from – 4.50 to 0.70 ppm/m3 (Log10 ARGs). Among the 89 potential human pathogens detected, Escherichia coli, Salmonella enterica, Klebsiella pneumoniae, and Staphylococcus aureus were the only culturable potentially multidrug resistant pathogens carrying multiple ARGs encoding resistance at high concentrations (– 0.57 to 1.15 ppm/m3 (Log10 ARGs)), and were more likely to persist and multiply in oligotrophic environments. Our findings indicate that composting technology can transfer AMR from solid compost to gas phase and increase the risk of AMR transmission.

Spatio-temporal changes in atmospheric aridity over the arid region of Central Asia during 1979–2019

The arid region of Central Asia (CA) is the largest non-zonal arid region in the world. It has experienced significant changes in climate and hydrological cycle systems owing to global warming, which has posed serious impacts on the water resources and ecological environment in this region. Although the atmospheric water vapor pressure deficit (VPD) can directly reflect the atmospheric moisture condition, studies on the change of atmospheric moisture deficit in CA are scarce. Thus, we investigated the changes in VPD in the arid region of CA from the perspective of atmospheric aridity based on the CRU TS4.04 and ERA5 data. Our results showed that the VPD in more than 95 % of grids in the arid region had a significantly increasing trend during 1979–2019. Seasonally, VPD trends were increasing in spring, summer, and autumn but decreasing in winter. The changes in saturated water vapor pressure and actual water vapor pressure determined the VPD changes. The saturated water vapor pressure showed a clearly upward trend, whereas the actual water vapor pressure did not increase at the same rate, resulting in the increase of VPD. The first four leading modes revealed by empirical orthogonal function (EOF) analysis represented the patterns by explaining 81.4 % of the total variance. The positive phase of EOF1 was characterized by a monopole pattern, and this mode continued to increase. Contrastingly, EOF2 (and EOF3) showed dipole patterns over east–west CA (and north–south CA), with a mainly interannual variability. Due to the combined effect of increasing temperatures and decreasing relative humidity, the VPD has been intensifying since the mid-to-late 1990 s in CA, and the atmosphere has become significantly drier. These research results can deepen the scientific understanding of global warming impacts on atmospheric moisture and provides a reference for revealing the VPD changes and their impacts on the climate system and ecosystem in arid regions. Our results highlight that the impacts of VPD change should be adequately considered in environmental management and policy-making processes in Central Asia.

A consistent treatment of mixed‐phase saturation for atmospheric thermodynamics

AbstractIce processes are integral to the formation and maintenance of high‐level clouds and can contribute substantially to the buoyancy of deep moist convection. These processes are represented in modern microphysics parameterisations but are commonly ignored in theoretical treatments of moist thermodynamics. While many thermodynamic variables can be defined uniquely for saturation with respect to liquid water and ice, it is desirable to account for the presence of mixed‐phase condensate, which is common in real clouds. Here, a simple yet novel representation of mixed‐phase saturation is introduced. Using this approach, analytical equations are derived for a variety of thermodynamic variables under mixed‐phase conditions. These include mixed‐phase versions of the saturation vapour pressure, saturated lapse rates, isobaric wet‐bulb temperature, and equivalent potential temperature. A new formulation of the ice–liquid water potential temperature is also presented, together with a method for calculating the mixed‐phase pseudo wet‐bulb temperature and wet‐bulb potential temperature. In addition, two new thermodynamic quantities are introduced: the isobaric saturation‐point temperature, a mixed‐phase analogue of the dew‐point and frost‐point temperatures, and the lifting saturation level, a mixed‐phase analogue of the lifting condensation and lifting deposition levels. Differences between each mixed‐phase variable and its liquid‐ and ice‐only counterparts are quantified across a wide range of atmospheric conditions. A Python library for evaluating these variables, developed during the course of this work, is also briefly introduced.

Study on the redistribution mechanism and secondary purge strategy of proton exchange membrane fuel cells

Effective control of membrane water content is essential for increasing the space for ice formation during the cold start stage and enhancing the success rate of start-up. Shutdown purge can effectively lower the membrane water content following fuel cell operation. However, during the cooling and standing process after purge, the rapid change in saturated vapor pressure can result in the redistribution of membrane dissolved water, leading to an increase in its content and a reduction in the success rate of cold start. Therefore, this study establishes a multidimensional, multiphase simulation model to comprehensively and thoroughly analyze the redistribution mechanism after purging and investigates the relationship between membrane water content and cold start. This is achieved by identifying the maximum membrane water content boundary during the cold start process and ultimately improving the success rate of cold start through a secondary purge strategy. The research results indicate that the membrane water content of the fuel cell increases from 2.31 to 8.31 after redistribution. During the cold start stage, the cold start success of the fuel cell under different environmental temperatures exhibits relatively specific boundary conditions, with the cold start process being closely related to the load current density and initial membrane water content. After implementing the secondary purging strategy, the membrane water content of the fuel cell decreases again, displaying favorable cold start characteristics in the cold start stage and successfully starting at −10 °C. This study can provide a reliable basis for the development of purging strategies during shutdown and offer a theoretical foundation for the boundary identification process of cold start.

Estimation of the Volatility and Apparent Activity Coefficient of Levoglucosan in Wood-Burning Organic Aerosols.

Biomass burning (BB) is a major source of aerosols and black carbon, thereby exerting an important impact on climate and air quality. Levoglucosan is the most well-recognized organic marker compound of BB and has been used to quantitatively assess BB's contribution to ambient aerosols. However, little is known about levoglucosan's evaporation under atmospheric conditions, primarily due to the uncertainty of its effective saturation vapor concentration (C*) and its unknown activity coefficient (γ), in the complex BB emission matrix. Here, we utilized a thermodenuder to investigate the evaporation of levoglucosan from mixtures with polyethylene glycol (PEG) or BB primary organic aerosol (BBPOA) matrices, respectively. We estimate a pure component log10(C*/[μg m-3]) of levoglucosan of 1.1 ± 0.1 at 298 K. We reveal that levoglucosan mixed with PEG or BBPOA becomes more volatile than when treated as a single component due to nonideal molecular interactions. Considering that phase separation might occur in such systems, we term γ apparent activity coefficient (γ a ). We estimate log10 C* and γ a of levoglucosan in BBPOA of 1.8 ± 0.1 and 3.8 ± 0.3, assuming a liquid phase state. Consequently, γ a must be considered to avoid significant underestimation of levoglucosan evaporation via gas-particle partitioning during transport.

Depths in a Day—a New Era of Rapid-Response Raman-Based Barometry Using Fluid Inclusions

Abstract Rapid-response petrological monitoring is a major advance for volcano observatories, allowing them to build and validate models of plumbing systems that supply eruptions in near-real time. The depth of magma storage has recently been identified as high-priority information for volcanic observatories, yet this information is not currently obtainable via petrological monitoring methods on timescales relevant to eruption response. Fluid inclusion barometry (using micro-thermometry or Raman spectroscopy) is a well-established petrological method to estimate magma storage depths and has been proposed to have potential as a rapid-response monitoring tool, although this has not been formally demonstrated. To address this deficiency, we performed a near-real-time rapid-response simulation for the September 2023 eruption of Kīlauea, Hawaiʻi. We show that Raman-based fluid inclusion barometry can robustly determine reservoir depths within a day of receiving samples—a transformative timescale that has not previously been achieved by petrological methods. Fluid inclusion barometry using micro-thermometric techniques has typically been limited to systems with relatively deep magma storage (&amp;gt;0.4 g/cm3 i.e. &amp;gt; 7 km) where measurements of CO2 density are easy and accurate because the CO2 fluid homogenizes into the liquid phase. Improvements of the accuracy of Raman spectroscopy measurements of fluids with low CO2 density over the past couple of decades has enabled measurements of fluid inclusions from shallower magmatic systems. However, one caveat of examining shallower systems is that the fraction of H2O in the fluid may be too high to reliably convert CO2 density to pressure. To test the global applicability of rapid response fluid inclusion barometry, we compiled a global melt inclusion dataset (&amp;gt;4000 samples) and calculate the fluid composition at the point of vapor saturation (${\mathrm{X}}_{{\mathrm{H}}_2\mathrm{O}}$). We show that fluid inclusions in crystal hosts from mafic compositions (&amp;lt;57 wt. % SiO2)—likely representative of magmas recharging many volcanic systems worldwide—trap fluids with ${\mathrm{X}}_{{\mathrm{H}}_2\mathrm{O}}$ low enough to make fluid inclusion barometry useful at many of the world’s most active and hazardous mafic volcanic systems (e.g. Iceland, Hawaiʻi, Galápagos Islands, East African Rift, Réunion, Canary Islands, Azores, Cabo Verde).

Visible Light-Sensitized CO2 Methanation along a Relaxed Heat Available Route.

In photocatalysis, the resulted heat by the relaxation of most of incident light no longer acts as the industrially favorite driving force back to the target photo-reaction due to more or less the negative relation between photocatalytic efficiency and temperature. Here, we reported a visible light-sensitized protocol that completely reversed the negatively temperature-dependent efficiency in photo-driven CO2 methanation with saturated water vapor. Uniform Pt/N-TiO2/PDI self-assembly material decisively injects the excited electron of PDI sensitizer into N-TiO2 forming Ti-H hydride which is crucially temperature-dependent nucleophilic species to dominate CO2 methanation, rather than conventionally separated and trapped electrons on the conductor band. Meanwhile, the ternary composite lifts itself temperature from room temperature to 305.2 °C within 400 s only by the failure excitation upon simulated sunlight of 2.5 W/cm2, and smoothly achieves CO2 methanation with a record number of 4.98 mmol g-1 h-1 rate, compared to less than 0.02 mol g-1 h-1 at classic Pt/N-TiO2/UV photocatalysis without PDI sensitization. This approach can reuse ~53.9 % of the relaxed heat energy from the incident light thereby allow high-intensity incident light as strong as possible within a flowing photo-reactor, opening the most likely gateways to industrialization.

Experimental investigation on flow boiling heat transfer of R290, R600a and their mixtures in a horizontal minichannel

The flow boiling heat transfer characteristics of R290, R600a and their mixtures were experimentally investigated in a horizontal minichannel with an inner diameter of 1.54 mm. In order to investigate the effects of mass flux and vapor quality, heat flux, saturation temperature, and component concentration on the flow boiling heat transfer coefficients, experiments were conducted with mass fluxes ranging from 200 to 400 kg/(m2·s), heat fluxes ranging from 20 to 30 kW/m2, saturation temperatures of 22 °C, 24 °C, and 26 °C, vapor qualities ranging from 0 to 1, and mass ratios of 70/30, 50/50, and 30/70 for R290/R600a. The experimental results indicate that with the increase of vapor quality, the mass flux promotes the heat transfer coefficient more obviously, and the heat transfer coefficient tends to increase first and then decrease. The heat transfer coefficients of both pure and mixed refrigerants increase with increasing the heat flux. The effect of saturation temperature on the heat transfer coefficients of pure and mixed refrigerants is not significant in this study. In the low vapor quality region, the heat transfer coefficients of R290/R600a mixtures are between those of R290 and R600a. As vapor quality increases, the heat transfer coefficients of the mixtures increase more slowly than those of pure refrigerants. In addition, experimental data were compared with the predictions of the empirical correlations. Among all the correlations, the Tran et al. correlation predicts the heat transfer coefficients for R290 and R600a best. The Lim and Kim correlation gives the best predictions of the heat transfer coefficients for R290/R600a mixtures.

Low‐temperature bubble formation in silica glass

AbstractPhase separation was observed in silica glass following low‐temperature heat treatment in high water vapor pressure through the formation of bubbles. Although the 6 day diffusion treatment in saturated water vapor pressure at 250°C does not normally cause phase separation, the reactive fracture surface and subsurface damage caused by polishing with cerium oxide (CeO2) allowed for an increase in water absorption during treatment and heterogeneous nucleation of the bubbles at damaged sites. The sub‐surface damage, characteristic of blunt contact damage, was only revealed when the polished sample was etched. The formation of bubbles and polishing damage were observed in two silica glasses—one containing chlorine impurities and the other containing OH impurities. Raman spectra collected after fracture or polishing and water diffusion treatment demonstrated an increase in the abundance of –OH species including silanol (SiOH) groups and an evolution in the glass structure in the bubble regions compared with the bubble‐free regions. These results indicate an increase in the reactivity between water and glass fracture surfaces relative to the bulk.

Simulation study on the cavitation flow characteristics of liquid ammonia in the nozzle under high-pressure injection conditions

In this study, a non-isothermal compressible cavitating flow simulation model for liquid ammonia in high-pressure injector, accounting for the phase change properties, was established. The model was validated using experimental data from existing literature. The cavitation phase change process of liquid ammonia within the injector nozzle was investigated, and the differences in cavitation distribution between ammonia and diesel were explored. The results indicate that with increasing injection pressure, the vapor volume fraction of ammonia increases linearly, while that of diesel fuel shows a rapid initial rise followed by a decelerating trend. In terms of flow coefficient, ammonia is lower than diesel, though the two values converge at higher injection pressures. Under low injection pressure, the heat absorbed by the cavitation phase change of ammonia exceeded the heat generated by the high-speed friction of ammonia flow against the nozzle wall, leading to a temperature drop at the nozzle inlet. Conversely, at high injection pressure, the temperature of ammonia on the nozzle wall increases by more than 20 K, resulting in a rapid rise in saturated vapor pressure and significantly intensifying the cavitation effect. Compared to ammonia, diesel experienced a higher temperature rise within the nozzle but exhibited smaller variations in saturated vapor pressure, making the temperature effect on cavitation less pronounced. Diesel’s higher density and viscosity resulted in lower flow velocities compared to ammonia, leading to more developed cavitation in the lower wall region of the nozzle and creating a higher pressure region on the upper wall of the nozzle, which was more distant from the nozzle inlet and inhibited cavitation development there. The research results provide theoretical support for the design of liquid ammonia injectors.

Thermodynamics and kinetics of evaporation and thermal decomposition of 1-ethyl- and 1-butyl-3-methylimidazolium methanesulfonate ionic liquids: Experimental and computational study

Knudsen cell mass spectrometry was used to study the evaporation of two ionic liquids, 1-ethyl-3-methylimidazolium methanesulfonate ([EtMIm][MS], MS = CH3SO3) and 1-butyl-3-methylimidazolium methanesulfonate ([BuMIm][MS]), accompanied by thermal decomposition (thermolysis). The independent occurrence of evaporation and thermolysis reactions made it possible to determine their thermodynamic and kinetic characteristics under identical experimental conditions. The saturated vapor pressures were measured and the standard enthalpies of vaporization of [EtMIm][MS](l) and [BuMIm][MS](l) were obtained. The standard thermodynamic functions of formation in the liquid and gaseous states at 298.15 K were estimated from the available experimental data and the results of quantum chemical calculations. The gaseous decomposition products of ionic liquids were identified and the pressures of the thermolysis products of [EtMIm][MS](l) were determined. According to the experimental data and quantum chemical calculations, the thermolysis of [EtMIm][MS](l) occurs through heterogeneous reactions far from the equilibrium state. The kinetics of the reactions is described in two ways. When the degree of sample conversion is used as a variable, the constant reaction rates at the initial stage of thermolysis correspond to a pseudo-zero order reaction with a monotonic increase in the degree of conversion. In the proposed alternative approach, the reaction rates are estimated from the fluxes of thermolysis products and are expressed in terms of ionic liquid concentration.

Numerical investigation on cavitation erosion and evolution of choked flow in a tri-eccentric butterfly valve

The tri-eccentric butterfly valve is widely utilized in the petrochemical, nuclear, and metallurgy industries due to its robust sealing performance and great pressure resistance. When the local static pressure is lower than the saturation vapor pressure, the fluid phase is transformed into vapor, and cavitation occurs. Cavitation intensifies and the bubbles generated by cavitation severely hinder the flow when the inlet pressure remains constant and the outlet pressure further decreases. This phenomenon is known as choked flow. Choked flow is a derivative phenomenon of cavitation, which seriously threatens the lifetime of valves and the safety of the operation system. In this paper, a multiphase flow of the tri-eccentric butterfly valve is modeled to investigate the choked flow characteristics. The numerical results based on the proposed model are in good agreement with the experiments. The effect of the pressure drop on the mass flow rate and flow coefficient is studied and the liquid pressure recovery factor of the tri-eccentric butterfly is determined at the certain valve opening degree based on the Schnerr and Sauer cavitation model. The relationship between the pressure ratio and choked flow is studied by pressure and velocity contours. The susceptible erosion locations and primary causes of erosion for the tri-eccentric butterfly valve at the certain valve opening degree are investigated. By comparison of the distribution of the vapor volume fraction and vortex structures, the spatial correlation between vortex and choked flow is revealed. Meanwhile, the effect of the pressure ratios on the average vapor volume fraction at 70 % and 100 % valve opening degrees is studied. The evolution of choked flow in the tri-eccentric butterfly is revealed and the cause of choking is pointed out.

Thermal and sublimation properties of cardiovascular drugs sotalol and ivabradine hydrochlorides

The saturated vapor pressure of sotalol and ivabradine hydrochlorides was measured in the temperature range (413.15–437.15) K by the transpiration method. The sublimation thermodynamic functions (Gibbs energy, enthalpy and entropy) of the compounds were calculated from the temperature dependencies of saturated vapor pressure. The standard molar enthalpy of sublimation for sotalol and ivabradine hydrochlorides is (157.5 ± 1.4) kJ·mol−1 and (143.2 ± 1.2) kJ·mol−1, respectively. The thermal properties and crystal state of the drugs were studied by the DSC, TG/DTG and X-ray diffraction methods.