Effect Of Vapor Pressure Research Articles

Simulation of Gas‐Particle Partitioning of Semi‐Volatile n‐Alkanes and PAHs in Nanjing, China, and Denver, United States: Effects of Vapor Pressure and Surface Adsorption Estimation

AbstractThe concentration data of semi‐volatile n‐alkanes and PAHs in the gas phase and in PM2.5 were obtained from Nanjing and Denver. First, the gas‐particle partitioning coefficients of the target compounds were calculated and compared with the predictions based on the equilibrium absorptive partitioning theory. Although the vapor pressure (poL) estimation method was selected to improve the agreement between measured and predicted partitioning coefficients, n‐alkanes in Denver and PAHs in both cities exhibited stronger sorption to PM2.5 than predicted. By including the adsorption mechanism, the average logarithms and temporal variations of the partitioning coefficients were well simulated in both Nanjing and Denver. The partitioning of n‐alkanes in Nanjing can be primarily explained by the absorption mechanism, while the adsorption mechanism dominates that for n‐alkanes in Denver and PAHs in both cities. To obtain an optimal simulation, the poL of n‐alkanes and PAHs was estimated using the SPARC and SIMPOL—two group contribution methods, respectively, and the difference between desorption and vaporization enthalpies was set between 2 and 3 kcal mol−1 for n‐alkanes in Denver and PAHs in both cities. Therefore, the estimation of poL and surface adsorption should be carefully considered when parameterizing the gas‐particle partitioning of non‐polar organic compounds in future field and modeling studies.

Swelling of Thin Graphene Oxide Film in Water Vapor Studied by In Situ Spectroscopic Ellipsometry.

Graphene oxide (GO) is obtained by the chemical treatment of graphene sheets, resulting in decoration with oxygen-containing functional groups. In the work presented here, we examined marked changes that occur in a thin film of parallel aligned GO sheets when exposed to water vapor at various pressures. It was found that exceptionally fast and substantial water uptake and release occur that is accompanied by major changes in GO interlayer spacing. These characteristics were obtained in situ with spectroscopic ellipsometry. At 99% relative humidity (RH) and 25 °C, the interlayer spacing became 1.41 nm, which recovers to ∼0.8 nm within 30 s when exposed to 10% RH. Besides layer thickness values, uniaxial optical constants for the GO vs RH were derived from the ellipsometry data. Molar refraction theory was applied that indicated monolayer water formation at ∼91% RH at 25 °C upon water adsorption. Our findings contribute to the understanding of the interaction between GO and its environment. The very outspoken effect of external water vapor pressure on GO water content, interlayer spacing, and optical properties can be utilized in sensing and separation devices, subnanometer positioning, chemical switches, and environmentally aware materials.

Numerical simulation of vapor explosion bubbles in the presence of a non-condensable gas and a phase change

The complex dynamics of two flow problems of vapor explosion bubbles near a free surface and between two parallel plates are simulated by a compressible three-phase flow code. Firstly, a coupled high-order monotonicity-preserving (MP) interface capturing scheme is developed for the numerical computation of compressible three-phase flows, which is followed by validation with previous numerical and experimental data. Phase changes are taken into consideration and the empirical condensation coefficient is calibrated with the experimental data. For both two flow problems, good agreement between the numerical results and reference data is obtained. Most physical phenomena, including the free surface spike, the liquid jet before the impact and the complex interface deformations during multiple expanding and collapsing oscillations, are reasonably well reproduced. Afterwards, the effects of the initial vapor pressure and the non-condensable gas volume fraction in the surrounding water on the behavior of vapor bubbles are analyzed and discussed. It is found that both the initial vapor pressure and the non-condensable gas volume fraction have a substantial influence on the behavior of the bubble. Higher initial vapor pressure does indeed tend to result in larger bubbles. The presence of non-condensable gases tends to hinder the transfer of heat, slowing down condensation and potentially resulting in larger bubbles. When the initial vapor pressure is in the range of 10 to 20 atmospheres and the gas volume fraction is in the range of 0 to 0.2, the maximum vapor bubble volume is found to increase linearly with an increase of the amount of non-condensable gas.

Corrosion Behaviors of Ni–Cr Alloys in O2, H2O and H2O + O2 Gases at 700°C and the Effect of Temperature

Pure nickel and four binary Ni–Cr (5, 10, 20 and 30 wt%) alloys were exposed to Ar–20O2, Ar–20O2–20H2O and Ar–20H2O (vol.%) at 700°C. In dry and wet O2, three Ni–Cr alloys (5, 10 and 20 wt%) formed a three-layered structure: an external NiO layer, an inner oxide layer of NiO + Cr2O3 and an internal oxidation zone (IOZ) with Cr2O3 dispersed. The Ni–30Cr alloy formed a continuous chromia layer, with locally outer NiO islands. In pure water vapor, all alloys underwent internal oxidation, nickel metal expulsion and NiO formation. Compared with the results at 650°C, increasing the temperature to 700°C did not alter the morphology of the oxide scale, but enhanced the scale growth kinetics. A significant difference between these two temperatures was that the strong retarding effect of water vapor on NiO formation in oxygen at 650°C became insignificant at 700°C. However, in water vapor only condition, NiO formation remained much slower at both temperatures. The effects of water vapor and oxygen partial pressure on NiO formation of different alloys and the effect of temperature on scale growth kinetics and morphology were discussed.

Spatio-temporal variation of water requirement and meteorological impact factors of maize Shaanxi, China

To quantitatively reveal the characteristics of the spatial and temporal distribution and the influencing factors of the maize water requirement in Shaanxi Province, the Penman-Monteith model and path analysis were used to systematically analyze the interannual variation and spatial distribution of the maize water requirement at different growth stages in three climatic zones in Shaanxi Province. And the relationship between the water requirement and meteorological factors based on daily meteorological data in Shaanxi Province for the past 60 years. The results showed that the maize water requirement during the whole growth period decreased from 1960 to 1989, with a rate of change of −2.08 mm/a, increased from 1989 to 2019, with a rate of change of 0.38 mm/a, and decreased from 1960 to 2019, with a rate of change of −0.46 mm/a. The water requirement of maize decreases from north to south during the whole reproductive period. That of seedling and male stage are more in the Guanzhong, followed by the north and the least in the south. The water requirement of maize at jointing stage increased from north to south. And the water requirement distribution is more in the north, followed by the south and the least in the Guanzhong area during the maturity period. The average temperature and the duration of the sunshine are the key factors that affect maize water requirement in Shaanxi Province, and have an increasing effect on water requirement, wind speed has an increasing effect on water requirement but is not obvious, water vapor pressure and relative humidity have an inhibiting effect on water requirement. For spring maize, the promoting effect of the duration of the sunshine on maize water requirement was gradually strengthened from north to south. The promoting effect of mean temperature and wind speed decreased gradually. The inhibitory effect of water vapor pressure and relative humidity decreases continuously. This study can provide a scientific basis for the management of irrigation quota in maize growing areas under similar cropping conditions.

Effect of humidity level and aspect ratio on convective heat transfer coefficient and water productivity of a solar still: Experimental and theoretical analysis

This article proposes a new correlation to estimate the convective heat transfer coefficient inside the evaporation chamber (enclosed space over the basin) of a single slope solar still with a low humidity level. The Rayleigh number, aspect ratio (width to the average height of chamber) and the relative humidity of the chamber are the main variables in proposed correlation. Existing models use only Rayleigh number to characterise the convection and neglect the effect of vapour pressure. Therefore, they fail to accurately predict the convection in higher water temperatures or in unsaturated humidity levels. In this work, the natural convection Nusselt number is generated based on a theoretical approach and the constant values in the correlation are calculated using the multiple linear regression analysis on experimental data obtained in this work. The transient thermal model of solar still using the new correlation predicts daily water yield within 7.6% of experiments under different humidity levels and aspect ratios. Higher performance is obtained in larger aspect ratio and lower humidity inside solar still. The modified solar still with a relative humidity of 62% generated 3.49 kg m−2 d−1 of water during summer in Melbourne, demonstrating an 18% increase in water yield.

Study on regulation mechanism of morphology and particle size of molybdenum powder in hydrogen reduction process

This study applied a novel process for manufacturing molybdenum powder to regulate the morphology and particle size. The effects of water vapor pressure, temperature, and holding time on the morphology and particle size of molybdenum powder were studied, in which bottom-blowing hydrogen was configured with a consistent flow direction of water vapor generated by hydrogen reduction. The results showed that polyhedral molybdenum powders with uniform sizes were prepared at different positions in the crucible via a single nucleation mechanism, and the water vapor pressure was identified as a key factor for controlling the particle size. By adjusting the water vapor pressure, reaction time, and temperature, the molybdenum powders with a particle size between 1 μm and 10 μm was obtained. When the hydrogen reduction temperature increased from 950 °C to 1150 °C, the average particle size increased from 1.8 μm to 3.4 μm, and particle aggregation was exacerbated. Upon extending the holding time from 60 min to 180 min, the average particle size increased marginally from 3.4 μm to 4 μm. This study provides a new method and important theoretical guidance for manufacturing molybdenum powders with a uniform morphology and particle size.

Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)

Variable-pressure electron-beam lithography (VP-EBL) employs an ambient gas at subatmospheric pressures to reduce charging during electron-beam lithography. VP-EBL has been previously shown to eliminate pattern distortion and provide improved resolution when patterning poly(methyl methacrylate) (PMMA) on insulating substrates. However, it remains unknown how water vapor affects the contrast and clearing dose nor has the effect of water vapor on the negative-tone behavior of PMMA been studied. In addition, water vapor has recently been shown to alter the radiation chemistry of the VP-EBL process for Teflon AF. Such changes in radiation chemistry have not been explored for PMMA. In this work, VP-EBL was conducted on conductive substrates to study the effect of water vapor on PMMA patterning separately from the effects of charge dissipation. In addition, both positive and negative-tone processes were studied to determine the effect of water vapor on both chain scission and cross-linking. The contrast of PMMA was found to improve significantly with increasing water vapor pressure for both positive and negative-tone patterning. The clearing dose for positive-tone patterning increases moderately with vapor pressure as would be expected for electron scattering in a gas. However, the onset set dose for negative-tone patterning increased dramatically with pressure revealing a more significant change in the exposure mechanism. X-ray photoelectron spectra and infrared transmission spectra indicate that water vapor only slightly alters the composition of exposed PMMA. Also, electron scattering in water vapor yielded a much larger clear region around negative-tone patterns. This effect could be useful for increasing the range of the developed region around cross-linked PMMA beyond the backscattered electron range. Thus, VP-EBL for PMMA introduces a new means of tuning clearing/onset dose and contrast, while allowing additional control over the size of the cleared region around negative-tone patterns.

Development of a science-based technology for the manufacture of sheet panels with fasteners

An analysis was made of the application of Stud Welding hardware welding technologies depending on the welded structures used, the duration of the process, the shape of the stud butt and the consumables used. The use of CD Stud Welding technology for welding metalware to thin-sheet panels is substantiated. The essence of the process of formation of a welded joint is described, which consists in the explosive evaporation of a protrusion at the end of a hardware during the discharge of capacitor banks, the excitation and burning of an electric arc in the metal vapors of the parts to be welded, their convergence when the spring mechanism overcomes the pressure of metal vapors, the immersion of the hardware into the weld pool of the part with subsequent crystallization molten metal in the liquid phase. The spring mechanism was calibrated using a compression dynamometer. The flowing pulsed current was registered depending on the input energy of the discharge of capacitor banks. The main parameters of the capacitor welding mode are determined and the dependences on the input energy and preliminary static pressure are established. The indicator of mechanical tests was taken as a quality parameter - the pull-off force. The effect of metal vapor pressure, which counteracts the convergence of welded parts, is revealed. Dependences of opposing pressures to the convergence of welded parts are constructed.

Effect of Water Vapor and Oxygen Partial Pressure on Oxidation of Fe and Fe–Cr Alloys

Effect of Water Vapor and Oxygen Partial Pressure on Oxidation of Fe and Fe–Cr Alloys

Numerical investigation on the coupling effect of sessile ethanol droplet evaporation and the induced thermal flow in its pure vapor environment at low pressure

In order to reveal the coupling characteristics of sessile ethanol droplet evaporation and induced thermal flow in its pure vapor system at low pressure, a series of three-dimensional numerical simulations were carried out on the ethanol droplet evaporation on a copper substrate. The droplet radius is 2.5 mm. The droplet height ranges from 2.2 to 0.4 mm. To investigate the effect of vapor pressure, two pressure ratios (η) of 0.9 and 0.6 are chosen. The results show that, when η = 0.9, regardless of the droplet height, the surface temperature distribution in most areas is always uniform. However, when η = 0.6, several surface thermal patterns appear. Because of the evaporation, the substrate temperature distribution always has the lowest value near the contact line. The thermal pattern evolution will affect the evaporation rate and the substrate temperature distribution dynamically. When η = 0.6, the evaporation rate shows a non-monotonic variation trend with the decrease of the height. Although the droplet size is larger than the capillary length, buoyancy has little effect on the thermal pattern evolution and evaporation rate.

Effects of trimethylaluminum vapor pressure and exposure time on inorganic loading in vapor phase infiltrated PIM-1 polymer membranes

Vapor phase infiltration (VPI) is a post-polymerization modification method for infusing inorganic clusters into a polymer to create organic-inorganic hybrid materials with properties that are unique from the parent polymer. The properties of these hybrid materials can vary with the amount of VPI generated inorganic loading. However, the relationship between VPI processing conditions and inorganic loading is still not fully understood. In this paper, the effects of VPI dose pressure and exposure time on inorganic loading are explored using the technologically relevant membrane material known as “polymer of intrinsic microporosity 1” (PIM-1). At sufficiently low dose pressures and infiltration times (i.e., before saturation), inorganic loading can be controlled with both vapor pressure and exposure time. However, inorganic loading appears to saturate for this system when the polymer's functional groups become fully populated with bound VPI precursors. These experimental results can be understood with the use of a recently developed reaction-diffusion model for VPI. Critical to applying this model to these post-deposition measurements is re-normalizing the mass loading to the total number of functional groups in the polymer.

Thermodynamic research on the effect of CaO on the transformation of arsenic and sulfur in coal in different pyrolysis atmospheres

AbstractThis study investigates the influence of CaO on the transformation of arsenic and sulfur in coal in different pyrolysis atmospheres by thermodynamic equilibrium calculation by HSC Chemistry. The effect of water vapor and reaction pressure on the release of arsenic and sulfur‐related compounds was studied. The detailed As and S distribution between 0°C and 1600°C was explored. The results show that in reducing atmosphere and partly oxidative CO2 environment, arsenic and sulfur containing compounds show very different trendy with increasing temperature. CaO addition helps arsenic compounds to form Ca(AsO2)2 and Ca3(AsO4)2, and helps sulfur containing compounds to form CaSO4 and CaSO3. The temperature has a significant effect on the distribution of Ca‐As complexes and Ca‐S complexes. Ca(AsO2)2 and Ca3(AsO4)2 are formed below 600°C in N2, while in the CO2 atmosphere only Ca(AsO2)2 is found below 600°C. CaSO4 and CaSO3 exist below 600°C in N2, while they are formed above 600°C in CO2. Water vapor enhances the formation of all the Ca‐As complexes and Ca‐S complexes greatly both in N2. Organic sulfur compounds are hardly detected anymore in the N2 atmosphere with H2O addition. In both of N2 and CO2 atmosphere, rising pressure enhances the formation of Ca‐S complexes. For Ca‐As complexes, elevated pressure is favorable for As in coal to form Ca(AsO2)2.

Vapor Absorption and Marangoni Flows in Evaporating Drops.

We experimentally and analytically studied vapor-driven solutal Marangoni flow by varying volatile liquid sources on top of the water droplet. We checked and compared the effects of solubility and vapor pressures of volatile liquids on the internal flow pattern using particle image velocimetry (PIV) and the droplet shape using shadowgraphy experiments. To explain the internal flow, we explored the absorption and evaporation mechanism of the vapors and we found that Henry's constant of the volatile liquid is the primary factor. Based on the scaling arguments, we developed theoretical models to explain how much vapor is absorbed into the water droplet, and how the flow pattern occurs and evolves. The scaling models show that there is a good agreement with the experimental results. We believe that understanding this phenomenon is useful for microfluidics applications and fundamental liquid-gas interface problems where vapors can be absorbed into another liquid.

Influence of meteorological parameters on the propagation of lightning electromagnetic fields

Lightning electromagnetic field computation is essential in determining the impact of lightning discharge on various systems, equipment, and structures. In this regard, it is essential to know the factors affecting field propagation, and among these, the climatic conditions are essential to consider. This paper discusses the effect of different meteorological parameters on the propagation of lightning electromagnetic fields.The effect of temperature, vapor pressure, and relative humidity fluctuation on the change in the medium parameter is assessed, and the electric and magnetic field alteration is calculated. From the analysis, inconsequential variation is noted in permittivity for a temperature change from C to C and relative humidity from 0% to full saturation of 100%. Upon computing the variation in the field, the peak value of electric field and its time of arrival shows insignificant change. In line with this, the magnetic field propagation also remains unaffected by the weather conditions.

Effect of guest-dependent reference hydrate vapor pressure in thermodynamic modeling of gas hydrate phase equilibria, with various combinations of equations of state and activity coefficient models

Using the van der Waals solid solution theory and the fugacity-based approach of Klauda and Sandler, a thermodynamic model to predict the phase equilibria of gas hydrates using an Equation of State (EOS) and an Activity Coefficient Model (ACM) is presented. Here, we have studied five EOS models, that are, Peng-Robinson-Stryjek-Vera (PRSV), Patel-Teja (PT), Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), and Redlich-Kwong (RK) to calculate the gas phase fugacity and four ACMs, that are, modified UNIFAC (mUNIFAC), UNIQUAC, Wilson and NRTL to model the liquid phase non-ideality. The Wilson and NRTL activity coefficient models have previously been used for systems containing additional chemicals in the liquid phase but not for pure water in coexistence with gas hydrates, to the best of our knowledge, and this has been explored in this work. By making the empty hydrate vapor pressure parameters guest dependent, the model improves upon the predictions from our previous model for sI and sII hydrates significantly and has drastically reduced the errors especially in modeling sII hydrates. The best combinations of EOS and ACM in L-H-V equilibrium and best EOS for I-H-V equilibrium, respectively, for each compound, to be used in the guest dependent model from the 100 combinations of EOS and ACM (for L-H-V equilibrium) and 25 possible EOS options (for I-H-V equilibrium) examined are: RK–mUNIFAC and SRK for CH4, RK–mUNIFAC and PRSV for CO2, RK–mUNIFAC and PR for C2H6, SRK–mUNIFAC and SRK for N2, and PR–NRTL and RK for C3H8. While different EOS work well for CH4, CO2, C2H6 and C3H8 hydrates in L-H-V and I-H-V equilibria, the SRK EOS works well for N2 hydrates in both L-H-V and I-H-V equilibria. We have also reported the solubilities of guest species in liquid water in equilibrium with hydrates and the hydrate cage occupancies from the models producing the least error as data on these facets is limited.

Solar-thermal energy conversion prediction of building envelope using thermochemical sorbent based on established reaction kinetics

In this paper, the dehydration (heat charge) and hydration (discharge) reaction kinetics of thermochemical sorbents synthesised in previous work by the author is established by using the isothermal method, with the aim of understanding their thermochemical conversion behaviour and developing reaction models for numerical simulations. The effects of temperature, reaction advancement, and vapour pressure are fully considered and employed in a thermochemical energy storage model. The derived dehydration reaction activation energies of the LiOH/LiCl@ expanded graphite (LiO2C1@EG and LiO3C1@EG) sorbents are 54.7 and 52.2 kJ/mol, respectively, which are lower than that of pure LiOH·H2O. To achieve the dual-function of space heating and air purification in an efficient manner, a novel solar building envelope combining thermochemical energy storage and photocatalysis is proposed and studied numerically based on the established reaction kinetics. Fresh air can be produced during solar harvesting. The porous wall, which is made of a composite sorbent, absorbs thermal energy to heat air near the wall and thus creates a chimney effect in the channel for continuous space heating. During discharge, the desorbed heat storage wall adsorbs the moist air and the hydration reaction enthalpy can be used again for air heating. The total efficiency including the equivalent formaldehyde degradation efficiency and the thermal efficiency is around 81% when the solar radiation is 600 W/m2. Results indicate that this passive building envelope can achieve a higher heat harvesting and utilisation efficiency in a more compact space compared to previous studies. Moreover, the influence of radiation intensity on air purification and thermal performance is investigated. The present work provides new insights and promotes the integration of passive solar building envelopes and thermochemical energy storage.

Energy storage and photosensitivity of in-situ formed silver-copper (Ag-Cu) heterogeneous nanoparticles generated using multi-tool micro electro discharge machining process

The present work focused on the energy storage and photosensitivity of in-situ formed segregated type silver-copper (Ag-Cu) heterogeneous nanoparticles generated by using the developed Micro-Electro Discharge Machining (Micro-EDM) process. The investigation includes analysis of useful heat gain, temperature gain, and thermal efficiencies by the nanofluids using fabricated mini parabolic solar trough collector. Photosensitivity of nanoparticles are studied by evaluating light absorbance and bandgap energies at different light intensities. Theoretical study includes understanding of the effects of the metallic vapor pressure, dielectric temperature, and the material properties on heterogeneous particle formation mechanisms. The experimentation work comprises of conduction of ten experiments by keeping silver plate (workpiece) at anode terminal and varying copper multi-tool pins from 1, 2, 3…10 at cathode terminal submerged in deionized water with 0.7 mM concentration of CTAB surfactant. Particles generated are found to be well dispersed, heterogeneously arranged structures with average particle size ranging from (4.83 ± 3.35 in 3rd experiment) nm to (15.37 ± 5.46 in 5th experiment) nm. XRD crystallographic studies confirmed the presence of the FCC structure of Ag and BCC structure of Cu2O. The maximum particle synthesis is from the 9th experiment producing 5.4 g/L for 30 min of machining with the spark energy of 2.88 mJ. The highest useful heat gain is obtained by the 3rd experiment due to higher silver content whereas highest overall thermal efficiency of 14.5% and bandgap energy of 2.75 eV is obtained by the 7th experiment nanofluid.

Effects of Vapor Pressure of Desiccant Solution on Mass Transfer Performance for a Spray-Bed Absorber

The depression in vapor pressure caused by adding desiccant to liquid water can be regarded as the driving force for the dehumidification process. The vapor pressure depends on the temperature and the concentration. Therefore, the purpose in this study is to discuss the mass transfer performance affected by operating variables and to show that the vapor pressure is a key factor affecting the mass transfer performance for absorbing water vapor by triethylene glycol (TEG) solution. The experimental results showed that the mass transfer coefficients were decreased with increases in the temperature and increased with increases in the concentration, respectively, while the mass transfer coefficients were increased with increases in the vapor pressure depression. Although both the average error is within 5% among the mass transfer correlation involving the vapor pressure and that involving the temperature and the concentration in predicting the mass transfer coefficient, there are just two terms, those are vapor pressure and fluid flow rate, associated with operating variables used in the mass transfer correlation. The depression in vapor pressure was not only proved to be the driving force for absorbing water vapor by a desiccant solution, but also a key factor affecting the mass transfer performance.

Medium effect on acid degradation of cotton and wood celluloses

Degradation of cotton and wood celluloses treated with hydrogen chloride in different media at 65 °C for 1−120 h was studied. Results showed the use of alcohol increased the cellulosic sugar content of hydrolysate as compared to water. Additionally, the recovery of celluloses treated in alcohols was lower than that of water, particularly when using 2-propanol and 1-butanol. After degradation, the crystallinity indices of celluloses changed slightly, and increased with treatment duration. The initial degradation rates of celluloses were in the order of 1-butanol > methanol > 2-propanol > ethanol > water. However, the decreases in weight-average degree of polymerization (DPw) plateaued after approximately 72 h for cotton cellulose and 5 h for wood cellulose, and the DPw after 120 h treatment were in the range of 98–195 and 196–364 AGU (anhydrous glucose unit), respectively. This study demonstrates the acid-degradation extent of cellulose can be tailored by the selection of degradation medium. Moreover, the alcohols tend to increase the penetration of acid and consequently facilitate the degradation, especially by using alcohols with higher carbon numbers. Additionally, the vapor pressure effect of methanol at 65 °C improved the degradation of cellulose.