Presence Of Vapor Research Articles

Simultaneous solar steam and electricity generation from biochar based photothermal membranes

Clean water and energy are essential for reducing poverty, fostering economic growth and sustainable development while mitigating CO2 emissions. Considering that, solar-powered interfacial vapor or steam generation is sustainable and promising environmental technology for both water purification and energy generation while being CO2-free. Despite continuous research progress, most of the solar absorbers to capture sunlight following heat conversion for steam generation are generally made from expensive nanostructures, which in part prevents their widespread manufacturing for useful applications. Herein, we experimentally demonstrate a biomass-derived carbon composite membrane that nearly covers the entire sunlight spectrum as a solar absorber with an estimated absorptivity of 90%. As a result, the light absorbed yields a surface temperature of 55 °C at the surface of the B700 and 33 °C for water. Evaporation rates up to 1.26 and 1.16 kg/(m2 h) and solar-to-vapor efficiencies of 80 and 74% were recorded in presence of sodium chloride with two different types of biochar B700 and B300 based photothermal membranes, respectively, under 1 sun illumination. The water evaporation in presence of mixed sodium chloride/magnesium chloride reached up to 1.21 and 1.05 kg/(m2 h) with 77 and 69% efficiency with B700 and B300; due to different solar absorber geometry. Furthermore, by merging the thermoelectric technology, we exploit the concept of hybrid clean water and energy generation. At a relative humidity of 60%, the thermoelectric device may generate approximately 0.9 W/m2 power density. These results highlight the interactive effects of biochar and polyvinylidene fluoride with porous hierarchies and enhanced absorption of sunlight, thus enabling a considerable elevation of temperature with great potential for clean water and energy. Overall biochar photothermal membrane represents a significant advancement as low-cost sustainable technology, addressing both water and energy challenges by providing efficient, environmentally friendly solution for freshwater production and clean power generation.

SPIRAL TURBINE CASING - IMPELLER ASSEMBLY DESIGN AND FLUID FLOW ANALYSIS

Turbine is a hydraulic engine where energy transfer occurs both based on the kinetic energy and potential (pressure) of the water. In this article we have designed the Spiral Turbine Casing – Impeller assembly with dimensions, geometry from technical documentation forms and the articles of other authors. CAD design of this assembly is a challenge and was done using .NX SIEMENS. The study of the fluid flow was done with ANSYS CFX by importing this assembly, some conclusions were drawn regarding the fluid velocities and the pressure field. The cavitation phenomenon that may occur in the operation of the turbine was also taken into account and some conclusions were drawn regarding the effects of this phenomenon. If the presence of vapours in the hydraulic circuit is found, then the cavitation can develop and this fact can be highlighted with Vapour Volume Fraction.

Ergonomic and Olfactometric Assessment of Anti-Odour Filtering Half-Masks under Real-Life Workplace Conditions

The presence of vapours and gases of chemical compounds in the atmospheric air contributes to mental discomfort as well as irritation of the respiratory tract and eyes. The technical solutions applied, such as collective protection measures, namely the encapsulation of processes or local ventilation equipped with appropriate air filters, are often insufficient. In such a case, respiratory protective equipment (RPE) is the basic and, in many cases, the only technical means that protects humans against the harmful effects of this type of harmful substance. The study evaluated the ergonomic and anti-odour properties of a novel filtering half-mask model with an oxygen indicator in functional workplace tests. In addition, the subjective anti-odour assessment results from functional tests were statistically compared with the results of olfactometric tests. The differences identified are attributable to the fact that the olfactometric method excludes subjects with olfactory impairments. Moreover, statistical analysis indicated significant differences in anti-odour properties between a reference half-mask and the filtering half-mask model with a nonwoven adsorbent layer (91% odour reduction). The filtering half-mask developed was found to provide high and very high levels of user comfort and exhibited excellent protective and functional properties, with a filtration performance of 96% and breathing resistance of 147 Pa. Those parameters qualify the filtering half-mask presented for protection class FFP2. In addition, the half-mask effectively absorbed the vapours of malodorous substances up to 3 h and displayed oxygen concentration in the breathing zone. It should be noted that currently no such device is commercially available either in Poland or in the European Union.

Competition between off-resonant and on-resonant processes in electromagnetically induced transparency in presence of magnetic field

We have analyzed and discussed the multiple Zeeman electromagnetically induced transparency (EIT) observed in R87b atomic vapor in presence of the magnetic field. We found that by tuning the power of the probe beam and magnetic field all the transmission peaks can be converted to absorption dips and vice-versa. Our theoretical analysis is based on double Λ systems formed in the presence of the magnetic field. We have argued that by limiting the interaction of various velocity classes of atoms with the probe beam, the off-resonant process can be resolved which dominates the spectra at low probe power. An alternative explanation is also provided in terms of dark and bright states which explains the quantum interference effects present in the system. Finally, our findings are also demonstrated experimentally.

Multi-Stimuli-Responsive Properties of Aggregation-Enhanced Emission-Active Unsymmetrical PtII Metallomesogens through Self-Assembly.

Herein, we report a series of unsymmetrical bispyrazolate-type PtII compounds that exhibit mesomorphism at low temperatures and photophysical multi-stimuli-responsive properties. These PtII compounds show a great ability to be self-assembled by intermolecular Pt⋅⋅⋅Pt interactions in the solid state, so generating a columnar stacking of molecules that is responsible for the formation of the mesophases. By controlling the nature of the molecular assembly through external stimuli such as the temperature, the pressure, or the presence of vapours or solvents, it is possible to modulate the luminescence behaviour of these materials. The PtII monomers emit a greenish light, whereas aggregation of molecules produces a redshifted emission. These metallomesogens also show a high stability and successive grinding/fuming cycles can be performed without degradation of the sample. The application of these materials is very attractive as rewritable luminescent platforms, and their use is already demonstrated.

Background Oriented Schlieren (BOS) imaging of condensation from humid air on wettability-engineered surfaces

Condensation of water vapor in presence of non-condensable gas is observed in several engineering applications ranging from power generation to water harvesting. Non-intrusive optical diagnostics of the thermal and vapor concentration boundary layers on a condensing surface can offer a veritable means of predicting the condensation heat transfer coefficient (CHTC), but the literature in this field is far from being well-developed. Here we perform a Schlieren imaging-based mapping of the thermogravitational density boundary layer during condensation from humid air on vertical surfaces of three different wettability, i.e., superhydrophilic, hydrophilic (control) and superhydrophobic. A lens-free, Background Oriented Schlieren (BOS) technique is used to cross-correlate the refraction of light and quantify the density gradient fields near the condenser plates for three different humidity ratios (13.5, 15.5 and 17.5 g/kg dry air) at a constant degree of subcooling (19.5 °C). CHTC measurement from condensate collection data is used to validate the non-intrusive data. The mean refraction angle and the mean density gradient near the plate are found to scale linearly with the CHTC and the condensate mass flux, respectively. The study clearly shows the potential of BOS technique in predicting the condensation heat transfer rates from humid air.

Acoustic induced flow around an evaporating drop and its influence on internal circulation

The present study provides a detailed investigation on the internal circulation of evaporating methanol and water drops in presence of an acoustic field. The drops are suspended inside an anechoic chamber, and the internal circulation of the drop with and without the acoustic field, is recorded to determine the effect of the acoustic field on the circulation. A sine wave of different frequencies and constant amplitude, with and without added white noise, is used for generating the acoustic field. The presence of the field is observed to significantly influence the circulation. Higher circulation is observed when a drop is subjected to acoustic frequency. For a given acoustic frequency, the presence of white noise enhances the circulation and hence the evaporation, compared to its absence. Maximum steady circulation is observed at 30 Hz, following which the average velocity of circulation decreases with increasing acoustic frequency. The reason for the increased circulation as well as the evaporation in presence of the acoustic field is due to the formation of an acoustic boundary layer around the evaporating drop. The presence of the layer causes higher entrainment of the surrounding air around the drop surface and thus enhances the circulation and the evaporation. The thickness of the layer determines the region subjected to motion due to acoustic waves around the drop. The present study reveals that higher effective streaming velocity is pronounced at smaller acoustic boundary layer thickness, and leads to the enhancement in the circulation as well as the evaporation. The thickness is observed to be minimum at 30 Hz and increases with the acoustic frequency, whereas, the effective streaming velocity is maximum at 30 Hz and reduces as the frequency increases.

Increase in water evaporation rate with increase in static magnetic field perpendicular to water-air interface

In the last decades many research on effects of magnetic field on water have been reported but still many arguments and doubts are present. However, increase in water evaporation due to presence of magnetic field is less in conflict. In this article, effects of static magnetic field on the amount of deionized water evaporation in presence of magnetic field with one, two or three permanent ferrite magnets perpendicular to water-air interface have been investigated and showed that tangential magnetic field at the interface does not make changes on the amount of evaporation but when magnetic field is perpendicular to the interface, up to 18.3% increase in water evaporation rate is observed. Another important effect of magnetic field is memory effect, which shows when magnetic field is applied perpendicular to the interface with three magnets for 60min after removing the magnets even up to 40min more evaporation compared to non-magnetic water is still observable. These effects are explained and discussed using the kinetic energy of water molecules and Lorentz force on these moving charged molecules at the interface which causes weakening or breaking hydrogen-bonds.

Capillary penetration in cellulose and polyethylene porous media: effect of contact with vapours and partial saturation with a non-miscible liquid

Abstract This work presents the effect of water and oil vapours and of partial liquid water saturation on the rate of capillary penetration in porous media. Two porous media were used: one made of cellulose (wettable both by oil and water) and the other made of polyethylene (wettable only by oil). Sunflower oil was the penetrating liquid. The porous structure of the porous media was characterized using SEM and surface properties were determined by FTIR. In addition, the effective pore radii and contact angles of sunflower oil against each medium were determined. The contact angle of sunflower oil against polyethylene was 0°, and no dynamic contact angle effects were observed. Capillary penetration of sunflower oil in cellulose showed contact angles around 80° in the beginning of penetration which gradually decreased to about 14°. The porous media were also put into contact with water vapours for different times and at different temperatures and results were compared with those obtained in the presence of oil vapours or in the absence of vapours. In addition, experiments were performed by fully saturating the cellulose porous medium with water and then partially drying it. The rate of capillary penetration of the oil in the polyethylene porous medium was not affected by the presence of vapours. On the contrary, the presence of water vapours and partial water saturation in the cellulose matrix significantly increased the penetration rate (up to almost three times) under most of the examined conditions. The reasons for such an effect are being discussed.

Convective Condensation of Methanol Vapor in Presence of a Non-Condensable Gas with Turbulent Flow in Vertical Tube

The problem of turbulent film condensation of methanol vapor in the presence of concentration non-condensable gas such as humid air flowing in a vertical tube under turbulent forced convection conditions is formulated theoretically. The vapor condensing at dew point temperature releases both sensible and latent heats and diffuses on to the surface of the. Thus it is treated as combined heat and mass transfer problem governed by mass, momentum and energy balance equations for the vapor-gas mixture and diffusion equation for the vapor species. The flow of the falling condensate film is governed by the momentum and energy balance equations. The effect of the influencing parameters are studied so the effect of inlet Reynolds number, the effect of temperature gradient, mass fraction are illustrated. The numerical results demonstrate that an important concentration of no-condensable gas reduces the heat transfer coefficient and film thickness considerably. The local heat flux and film thickness increase as tube surface temperature decreases at any bulk concentration of non-condensable gas. Moreover, inlet velocity increases as film thickness decreases and heat flux increases.

Pattern-based optical memory with low power switching in rubidium vapor

We report optical pattern bistability switched with ∼2μW power beam for two waves counterpropagating in warm rubidium vapor in presence of longitudinal magnetic field.

Enhancement of Evaporation in Presence of Induced Thermocapillary Convection in a Non-Isothermal Liquid Bridge

This paper examines the evaporation rate through the interface of a evaporating—convecting non-isothermal cylindrical column (liquid bridge). The liquid phase is subject to a vigorous thermocapillary convection. Experiments were performed in a wide range of the imposed temperature difference. The obtained data are compared to a theoretical model of mass transport that does not account for the bulk fluid flow. The analytical results obtained for the real experimental conditions reveal an important role of the convective heat and mass transport in evaporization. The convective process is found responsible for enhancing the evaporation rate by several times with respect to the conductive regime.

An improved method for determination of lanthanoids in environmental samples by inductively coupled plasma mass spectrometry with high matrix introduction system

The capability of ICP-MS equipped with the high matrix introduction system (HMI) for accurate analysis of lanthanoids in environmental samples was investigated. Compared to the conventional operation, the amounts of oxide and hydroxide molecular species formed in the plasma were reduced by up to 5 times. The relative yields of oxides did not exceed 0.02% for BaO + species and were as low as 0.3% for lanthanoids with the highest oxide-formation rates (LaO +, CeO +, PrO + and NdO +). Hydroxide formation was less than 0.02% when HMI system was used. In addition, two digestion procedures were evaluated by the analysis of standard reference materials (SRMs) of different matrices. The digestion efficiency and limits of detection (LOD) were improved when samples were digested with a mixture of HNO 3/H 2O 2/HCl/HF, and HF was removed by evaporation in presence of concentrated HCl. Using this procedure and HMI-ICP-MS analysis, LOD ranged from 0.1 μg kg −1 to 6 μg kg −1. Recoveries ranged from 85 to 115% for La to Ho and from 75 to 85% for the other lanthanoids. Relative standard deviations for replicate analysis of SRMs were less than 10%.

Statistical analysis of fires and explosions attributed to static electricity over the last 50 years in Japanese industry

This paper presents a statistical analysis of 153 accidents attributable to static electricity in Japanese industry over the last 50 years. A more thorough understanding of their causes could help prevent similar incidents and identify hazards that could assist in the task of risk assessment. Most of the incidents occurred during operations performed by workers. In addition, more than 70% of the flammable atmospheres resulted from the presence of vapours. A noteworthy finding is that at least 70% of the ignitions were caused by isolated conductors including operators' bodies leading to spark discharges, which could have easily been prevented with earthing. These tendencies indicate that, when operators handle flammable liquids with any conductors, the ignition risk is significantly high. A serious lack of information regarding fundamental countermeasures for static electricity seems to be the main cause of such hazards. Only organised management, including education and risk communication, would prevent them.

Towards a GC-based microsystem for benzene and 1,3 butadiene detection: Pre-concentrator characterization

The performance of a gas pre-concentrator/gas chromatographic column/gas sensor system was studied step by step towards benzene vapor in presence of 1,3 butadiene vapor. The pre-concentrator, based on an activated carbon of high adsorption capacity, was first characterized using a GC/FID system. By this way, the adsorption capacity of each pollutant was evaluated, first separately, then mixed with different proportions in air. It was shown that the affinity of the pre-concentrator for benzene was higher than for butadiene. Once the optimal pre-concentration parameters were adjusted, we replaced the FID detector by a metal oxide gas sensor. The use of such gas pre-concentrator allowed decreasing the detection limit of the system towards benzene in presence of butadiene by at least ten times.

Modifying Surface Structure to Tune Surface Properties of Vertically Aligned Carbon Nanotube Films

We report a simple etching process to modify surface of vertically aligned carbon nanotube (VACNT) arrays for their applications in superhydrophobic surface, field emission display, and sun energy conversion, etc. At a high temperature (700-800 degrees C), very low concentration water vapor in presence with Ar and hydrogen flow can be a weak oxidant, and mildly etch nanotube tips without damaging their walls. This process can be performed right after the CNT growth process. Surface of nanotube arrays becomes multi-tiered nanotube patterns with open-ended nanotubes standing straightly. Surface morphology of nanotube arrays can be tuned by changing the etching time. Water droplets on a modified nanotube surface show a large contact angle and sliding angle, which make the etched nanotube film suitable for application such as small amount liquid transport. Light absorption measurement indicated that surface roughness has no effect to improve the light absorption, indicating a different mechanism from other black material. The surface modified nanotube arrays have much increased field enhancement factor in our field emission test, showing the better field emission ability of the nanotube arrays with open tips.

Multifunctional sensing ability of a new Pt/Zn-based luminescent coordination polymer

We synthesized a new Pt/Zn-based coordination polymer, {Zn[Pt(CN)(2)(5,5'-dcbpy)].4H(2)O}(n), (5,5'-H(2)dcbpy = 5,5'-dicarboxy-2,2'-bipyridine), which exhibits reversible colour changes in response to temperature change or exposure to chemical vapours and liquids. Such chromic behaviour shows promise for sensing not only changes in temperature but also for detecting chemical solvents and vapours. The single crystal X-ray structure indicates that one-dimensional coordination polymeric chains formed by an alternating arrangement of [Zn(H(2)O)(3)](2+) and [Pt(CN)(2)(5,5'-dcbpy)](2-) stacked to produce moderate metallophilic interactions between the Pt(ii) ions. Thermogravimetric analysis and water vapour adsorption measurements show that both the crystal water and water coordinated to Zn(ii) ions can be removed and re-adsorbed reversibly by heating or under vacuum. Emission spectra at various temperatures and/or in the presence of vapours or liquids reveal that the complex exhibits thermochromic and solvatochromic-like behaviours, with the emission band shifting between 616 and 671 nm. IR spectroscopy and powder X-ray diffraction measurements suggest that this multichromic behaviour is a result of the cooperative phenomena of water adsorption/desorption around the Zn(ii) ions and the modification of the metallophilic interaction.

Combination of sealed source and radiotracer technique to understand malfunctioning in a chemical plant

Pure terphthalic acid (PTA) is produced by the oxidation of paraxylene in an oxidation reactor of a PTA plant. Since the reaction is exothermic, the temperature rises above 210 °C. Vapours formed in the reactor are passed through a series of heat exchangers and the cooled liquid is fed back to the reactor, which flows to the reactor by gravity. In one of the heat exchangers, improper flow distribution in the inlet and outlet pipelines was suspected. Maldistribution of flow in the heat exchanger was also suspected. Gamma scanning of the pipelines and a radiotracer experiment were carried out in the heat exchanger to study the malfunctioning. A specially fabricated pipe scanner was used to scan both 24 in diameter and 16 in diameter pipelines. From gamma scanning of the pipelines mostly on the bends, absence of the full bore flow of the liquid was observed. Presence of vapours along with the liquid could be obstructing the liquid flow, thereby causing the malfunctioning. A radiotracer experiment was also carried out to study the flow pattern in the heat exchanger. From the experiment, mean residence time of the heat exchanger was estimated as 470 s, which theoretically should be about 102 s. It indicated that the flow is decelerated in the heat exchanger because of the presence of vapour lock in the tube side.

Laboratory studies about the interaction of ammonia with ice crystals at temperatures between 0 and −20°C

In laboratory experiments the interactions of ammonia with ice crystals were studied within the temperature range between 0 and −20°C. In a first series of experiments dendritic ice crystals were grown from water vapor in presence of ammonia gas in various concentrations between 4 and 400 ppbv. In a second series of experiments pure ice crystals were exposed to a humidified ammonia–air mixture inside a horizontal flow tube. The influence of temperature, ammonia gas concentration (0.6, 1.5, and 10 ppmv), exposure time, and the presence of impurities such as sulfate on the ammonia uptake by the ice surface was investigated by determining the ammonium content in the melt water of the ice crystals by ion chromatography. During the growth of ice crystals significant amounts of ammonia (around 200 μg/l) were taken up even at small gas concentrations. In contrast, even at high gas concentrations the uptake of ammonia by non-growing ice crystals was lower by approximately one order of magnitude. The presence of sulfate on the ice surface affected an enhanced uptake of ammonia by a factor of 5–10. A model is presented which describes the uptake of ammonia by ice considering the chemical processes occurring in the ice surface layer and simultaneous diffusion of ammonia into bulk ice. Even the increased uptake of ammonia by growing ice is rather small compared to the uptake by water droplets; thus, the major process for scavenging of ammonia from the atmosphere via the ice phase might not be the direct uptake by ice crystals but the riming involving super-cooled droplets containing ammonia.

On the number of droplets in aerosols

The number of droplets which may be formed with a supersaturated vapor in presence of a gas cannot exceed a number proportional to ( p v− p v 0 ) 4 where p v and p v 0 denote at the same temperature the pressure of the supersaturated vapor–gas mixture and the pressure of the saturated vapor–gas mixture. The energy necessary to the droplet formation is also bounded by a number proportional to ( p v− p v 0 ) 2.