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Keywords = water vapor supersaturation

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18 pages, 2034 KiB  
Article
Comparison of Identified Ice Supersaturated Regions for Contrail Avoidance Using Three Standard Weather Forecast Databases
by Amy Tal Rose-Tejwani, Lance Sherry and Kayla Ebright
Atmosphere 2025, 16(2), 149; https://doi.org/10.3390/atmos16020149 - 29 Jan 2025
Viewed by 1021
Abstract
Contrails form as a result of water vapor bonding with soot emitted from jet engines at cruise altitudes, leading to contrail formation in Ice Supersaturated Regions (ISSRs). Contrails are estimated to contribute approximately 2% to total anthropogenic global warming. Some researchers have developed [...] Read more.
Contrails form as a result of water vapor bonding with soot emitted from jet engines at cruise altitudes, leading to contrail formation in Ice Supersaturated Regions (ISSRs). Contrails are estimated to contribute approximately 2% to total anthropogenic global warming. Some researchers have developed simulation models to estimate the frequency, duration, and spatial distribution of contrails. Other researchers have identified issues with the accuracy of the data for predicting the timing and precise geographic positioning of ISSRs. This study presents a systematic review of 22 peer-reviewed articles that included detailed models of ISSR identification, identifying three atmospheric data sources, four parameters, and two equations for calculating the parameters derived. A further analysis revealed differences in the temperature and RHW readings across the three databases, resulting in differences in the RHI calculations and the identification of ISSRs. Over an 18-month period in Sterling, Virginia, USA, the radiosonde data and two atmospheric forecast databases identified the ISSR conditions on 44%, 47%, and 77% of days, respectively. Broken down by a flight level between 30,000 and 39,999 feet in altitude, these differences are highlighted further. The forecast databases overestimated the presence of ISSRs compared to the radiosonde data. These findings underscore the variability inherent in atmospheric datasets and the conversion methods, highlighting potential areas for refinement in ISSR prediction, notably in the development of ensemble forecasts based on several atmospheric databases. The implications of these results, the limitations of this study, and future work are discussed. Full article
(This article belongs to the Special Issue Advance in Transportation Meteorology (2nd Edition))
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18 pages, 3218 KiB  
Article
Synthesis and Characterization of Calcium Sulfoaluminate Hydrates—Ettringite (AFt) and Monosulfate (AFm)
by Wojciech Szudek, Jakub Szydłowski, Ilona Buchała and Ewa Kapeluszna
Materials 2024, 17(21), 5216; https://doi.org/10.3390/ma17215216 - 26 Oct 2024
Cited by 1 | Viewed by 1828
Abstract
The goal of the presented work was to find the most favorable conditions for the synthesis and stabilization of chemically pure ettringite and monosulfate. The reaction was carried out by mixing pure tricalcium aluminate (C3A) and gypsum (CS¯H [...] Read more.
The goal of the presented work was to find the most favorable conditions for the synthesis and stabilization of chemically pure ettringite and monosulfate. The reaction was carried out by mixing pure tricalcium aluminate (C3A) and gypsum (CS¯H2) in an excess amount of water. The impact of hydration time (2–7 days), C3A:CS¯ molar ratio (1:1–1:3) and water vapor pressure of the selected drying agents (anhydrite-III and supersaturated CaCl2 solution) on the phase composition of the products was evaluated. After 7 days of hydration, either ettringite or monosulfate was obtained as the main product, depending on the C3A:CS¯ molar ratio. The synthesis carried out at a C3A:CS¯ molar ratio of 1:3 produced pure ettringite. In the case of the sample characterized by the ratio of 1:1 (typical of monosulfate), a considerable portion of ettringite (27.9%) was present in the final products along the AFm phase. Therefore, a different synthesis method has to be selected in order to obtain pure monosulfate. The results showed that thermal analysis, X-ray diffractometry and FTIR spectroscopy can be used to distinguish the characteristic features of ettringite and monosulfate. Full article
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17 pages, 14194 KiB  
Article
Different Mechanisms for the Northern and Southern Winter Fog Events over Eastern China
by Xiaojing Shen, Yuanlong Zhou, Jian Chen, Shuang Liu, Ming Ma and Pengfei Lin
Atmosphere 2024, 15(5), 528; https://doi.org/10.3390/atmos15050528 - 26 Apr 2024
Viewed by 1288
Abstract
Northern and southern fog events are identified over eastern China across 40 winters from 1981 to 2021. By performing composite analysis on these events, this study reveals that the formation of fog events is controlled by both dynamic and thermodynamic processes. The fog [...] Read more.
Northern and southern fog events are identified over eastern China across 40 winters from 1981 to 2021. By performing composite analysis on these events, this study reveals that the formation of fog events is controlled by both dynamic and thermodynamic processes. The fog events were induced by Rossby wave trains over the Eurasian continent, leading to the development of surface wind and pressure anomalies, which favor the formation of fog events. The Rossby wave trains in northern and southern fog events are characterized by their occurrence in northern and southern locations, respectively, with different strengths. The water vapor fluxes that contribute to the enhancement of the northern fog events originate from the Yellow Sea and the East China Sea, whereas the southern fog events are characterized by water vapor from the East China Sea and the South China Sea. In both northern and southern fog events, dew point depression and positive A and K index anomalies are found in northern and southern regions of eastern China, which are indicative of supersaturated air and the unstable atmospheric saturation from the low to the middle troposphere, thus providing favorable conditions for the establishment of fog events in northern and southern regions of eastern China. Full article
(This article belongs to the Section Meteorology)
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28 pages, 15405 KiB  
Article
Influence of Atmospheric Non-Uniform Saturation on Extreme Hourly Precipitation Cloud Microphysical Processes in a Heavy Rainfall Case in Zhengzhou
by Jin Xu, Liren Xu, Yufei Wang, Fan Ping and Lei Yin
Sustainability 2023, 15(20), 15047; https://doi.org/10.3390/su152015047 - 19 Oct 2023
Cited by 1 | Viewed by 1277
Abstract
Heavy rainfall not only affects urban infrastructure, it also impacts environmental changes, and which then influence the sustainability of development and ecology. Therefore, researching and forecasting heavy rainfall to prevent disaster-related damages is essential. A high-resolution numerical simulation was carried out for a [...] Read more.
Heavy rainfall not only affects urban infrastructure, it also impacts environmental changes, and which then influence the sustainability of development and ecology. Therefore, researching and forecasting heavy rainfall to prevent disaster-related damages is essential. A high-resolution numerical simulation was carried out for a heavy rainfall case in Zhengzhou, Henan Province, China, from 19–20 July 2021. The analysis of weather conditions revealed that the main cause of heavy rainfall in Zhengzhou was the supersaturation and condensation of water vapor, resulting from the invasion of dry and cold air from the upper and middle atmospheric layers. This weather condition is ideally suited for applying generalized potential temperature that is informed by the non-uniform saturation theory. Based on this, the new scheme revised the cloud microphysical scheme of the cloud water condensation parameterization process by substituting generalized potential temperature. The characteristics of the mesoscale environment and water condensates were comparatively analyzed between the original and the new scheme. Then, the quantitative mass budget and latent heat budget related to microphysical conversions were comparatively calculated over Zhengzhou. Furthermore, the possible two-scheme mechanisms through which the cloud microphysics processes affected the rainfall were investigated and discussed. It was found that: (1) The new scheme, which takes into account generalized potential temperature, produced precipitation fields more in line with observations and simulated stronger hourly precipitation compared to the original scheme. (2) The conversions of snow were the main source of microphysical processes that produced precipitation and released latent heat due to the dry and cold air invasion. (3) Given that the condensation of water vapor was hypothesized to occur at 70% relative humidity (RH) or above, rather than the original 100% RH, the new scheme simulated more supercooled water and ice-phase particles than the original scheme. This enhancement, in turn, intensified convective development owing to positive feedback within the cloud microphysics processes and cloud environment, ultimately leading to the simulation of more intense hourly precipitation. Full article
(This article belongs to the Special Issue Advances in Weather Prediction and Numerical Simulation)
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9 pages, 1688 KiB  
Communication
Increasing Antarctic Ice Mass to Help Offset Sea Level Rise
by Erik J. L. Larson, Karen H. Rosenlof and Ru-Shan Gao
Atmosphere 2023, 14(10), 1564; https://doi.org/10.3390/atmos14101564 - 15 Oct 2023
Cited by 2 | Viewed by 2700
Abstract
Global sea level is predicted to rise for centuries even if greenhouse gas emissions are greatly reduced. Sea level rise (SLR) threatens coastal communities where a large fraction of the human population lives. A possible mitigation effort is to increase the ice mass [...] Read more.
Global sea level is predicted to rise for centuries even if greenhouse gas emissions are greatly reduced. Sea level rise (SLR) threatens coastal communities where a large fraction of the human population lives. A possible mitigation effort is to increase the ice mass in Antarctica. Coastal Antarctic radiosonde profiles are supersaturated with respect to ice on average 47% of the time. If all of this excess water vapor and supercooled liquid cloud water were removed from the atmosphere and deposited on the Antarctic landmass, it would offset 11 cm of SLR by 2100, or about 15 (8–17) percent of the predicted SLR. This strategy could be used to supplement other efforts to reduce climate change impacts, such as carbon dioxide removal or solar climate intervention. Full article
(This article belongs to the Section Climatology)
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22 pages, 3190 KiB  
Article
Validation of a Contrail Life-Cycle Model in Central Europe
by Judith Rosenow, Jakub Hospodka, Sébastian Lán and Hartmut Fricke
Sustainability 2023, 15(11), 8669; https://doi.org/10.3390/su15118669 - 26 May 2023
Cited by 5 | Viewed by 2574
Abstract
In an industry beset by economic and environmental crises, air transport, the safest and most efficient long-haul mode of transport, is confronted daily with multi-criteria challenges to improve its environmental performance. The formation of contrails through the emission of water vapor and condensation [...] Read more.
In an industry beset by economic and environmental crises, air transport, the safest and most efficient long-haul mode of transport, is confronted daily with multi-criteria challenges to improve its environmental performance. The formation of contrails through the emission of water vapor and condensation nuclei in what are actually dry and clean atmospheric layers represents one of the most unpredictable, or measurable, environmental impacts of air traffic. Following the bottom-up principle to evaluate individual contrails in order to derive recommendations for trajectory optimization, not only the calculation of the radiative forcing of the contrails but also the modeling of their life cycle is burdened with uncertainties. In former studies for modeling the microphysical life cycle of contrails based on a 3-D Gaussian plume model, the atmospheric conditions, specifically the turbulence, were often unknown and had to be considered as a free input variable. In this study, an innovative photographic method for identifying and tracking contrails in Central Europe, connected with database access to Automatic Dependent Surveillance—Broadcast (ADS-B) data (i.e., aircraft type, speed, altitude, track, etc.), and a combination of measured and modeled weather data are used to validate the contrail life-cycle model (i.e., the assumed Gaussian plume behavior). We found that it is challenging to model the position of ice-supersaturated layers with global forecast models, but they have the most significant impact on the contrail lifetime. On average, the contrail’s lifespan could be modeled with an error margin of 10%. Sometimes, we slightly underestimated the lifetime. With the validated and plausible contrail life-cycle model, we can apply the climate effectiveness of individual contrails with higher certainty in trajectory optimization and compare it, for example, with economic aspects such as delay costs or fuel costs. Full article
(This article belongs to the Section Sustainable Transportation)
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21 pages, 3725 KiB  
Article
On the Impact of Condensation and Liquid Water on the Radial Turbine of a Fuel Cell Turbocharger
by Tim Wittmann, Sebastian Lück, Christoph Bode and Jens Friedrichs
Machines 2022, 10(11), 1053; https://doi.org/10.3390/machines10111053 - 10 Nov 2022
Cited by 10 | Viewed by 3398
Abstract
The air-management system of a proton exchange membrane fuel cell (PEMFC) is responsible for supplying the fuel cell stack with ambient air at appropriate conditions. The compressor of the air-management system can be partly driven by utilizing the fuel cell exhaust gas in [...] Read more.
The air-management system of a proton exchange membrane fuel cell (PEMFC) is responsible for supplying the fuel cell stack with ambient air at appropriate conditions. The compressor of the air-management system can be partly driven by utilizing the fuel cell exhaust gas in a turbine. The fuel cell exhaust is partially or fully saturated with water vapor. When the exhaust gas is expanded in the turbine, supersaturation occurs. This leads to the nucleation of droplets and their subsequent growth by condensation. This study provides an overview and understanding of the various phenomena caused by condensation and liquid water in the turbine of a PEMFC air-management system. The basis for this work is previously published numerical simulations that focused on individual aspects of the above phenomena. The present work revisits these results and puts them in context to provide a comprehensive understanding. Important phenomena are the effects of condensation on turbine performance through phase change losses, release of latent heat and thermal throttling. In addition, the released latent heat offers a power potential for downstream turbine stages. Through these effects, condensation can also impact the entire air-management system. However, condensation may occur unevenly, causing a circumferential asymmetry of the turbine outflow. Liquid water in the turbine can lead to droplet erosion, corrosion, and water-induced damage. In summary, it is essential to consider condensation and liquid water when developing turbines for PEMFC air-management systems. Full article
(This article belongs to the Special Issue High Speed Air Compressor for a Fuel Cell System for Use in a Vehicle)
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25 pages, 33480 KiB  
Article
Experimental Study on a Ceramic Membrane Condenser with Air Medium for Water and Waste Heat Recovery from Flue Gas
by Da Teng, Liansuo An, Guoqing Shen, Shiping Zhang and Heng Zhang
Membranes 2021, 11(9), 701; https://doi.org/10.3390/membranes11090701 - 13 Sep 2021
Cited by 15 | Viewed by 3501
Abstract
Ceramic membrane condensers that are used for water and waste heat recovery from flue gas have the dual effects of saving water resources and improving energy efficiency. However, most ceramic membrane condensers use water as the cooling medium, which can obtain a higher [...] Read more.
Ceramic membrane condensers that are used for water and waste heat recovery from flue gas have the dual effects of saving water resources and improving energy efficiency. However, most ceramic membrane condensers use water as the cooling medium, which can obtain a higher water recovery flux, but the waste heat temperature is lower, which is difficult to use. This paper proposes to use the secondary boiler air as the cooling medium, build a ceramic membrane condenser with negative pressure air to recover water and waste heat from the flue gas, and analyze the transfer characteristics of flue gas water and waste heat in the membrane condenser. Based on the experimental results, it is technically feasible for the ceramic membrane condenser to use negative pressure air as the cooling medium. The flue gas temperature has the most obvious influence on the water and heat transfer characteristics. The waste heat recovery is dominated by latent heat of water vapor, accounting for 80% or above. The negative pressure air outlet temperature of the ceramic membrane condenser can reach 50.5 °C, and it is in a supersaturated state. The research content of this article provides a new idea for the water and waste heat recovery from flue gas. Full article
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16 pages, 5643 KiB  
Article
Aerosol–Cloud Interaction at the Summit of Mt. Fuji, Japan: Factors Influencing Cloud Droplet Number Concentrations
by Yoko Iwamoto, Ayami Watanabe, Ryota Kataoka, Mitsuo Uematsu and Kazuhiko Miura
Appl. Sci. 2021, 11(18), 8439; https://doi.org/10.3390/app11188439 - 11 Sep 2021
Cited by 11 | Viewed by 3045
Abstract
To investigate interactions between aerosols and clouds, the size and number concentrations of the cloud condensation nuclei (CCN) and the cloud droplets (CDs) were measured at the summit of Mt. Fuji (altitude 3776 m), Japan. The CCN number concentrations (NCCN) [...] Read more.
To investigate interactions between aerosols and clouds, the size and number concentrations of the cloud condensation nuclei (CCN) and the cloud droplets (CDs) were measured at the summit of Mt. Fuji (altitude 3776 m), Japan. The CCN number concentrations (NCCN) are significantly higher in continental air masses than in air masses from the Pacific Ocean. The hygroscopicity parameter κ did not change much for different air mass origins, indicating that aerosol particles in the free troposphere are well mixed. Based on the CD number concentrations (NCD), the degree of supersaturation in the ambient air during the cloud-shrouded period was estimated to be 0.15% (25th percentile) to 0.44% (75th percentile). To evaluate factors influencing the NCD, measured NCD were compared to ones calculated based on the Köhler theory using aerosol number size distributions, κ, and the degree of supersaturation. The results showed that NCD could not be reproduced satisfyingly when the mean number size distribution or the mean effective supersaturation were used for the calculation. This study highlights the importance of obtaining information about the degree of supersaturation to predict NCD in the atmosphere. Full article
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19 pages, 1017 KiB  
Review
Review on Applications of 17O in Hydrological Cycle
by Yalalt Nyamgerel, Yeongcheol Han, Minji Kim, Dongchan Koh and Jeonghoon Lee
Molecules 2021, 26(15), 4468; https://doi.org/10.3390/molecules26154468 - 24 Jul 2021
Cited by 6 | Viewed by 3739
Abstract
The triple oxygen isotopes (16O, 17O, and 18O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of 17O [...] Read more.
The triple oxygen isotopes (16O, 17O, and 18O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of 17O in hydrological studies. Dual-inlet isotope ratio mass spectrometry and laser absorption spectroscopy have been used to measure 17O, which provides information on atmospheric conditions at the moisture source and isotopic fractionations during transport and deposition processes. The variations of δ17O from the developed global meteoric water line, with a slope of 0.528, indicate the importance of regional or local effects on the 17O distribution. In polar regions, factors such as the supersaturation effect, intrusion of stratospheric vapor, post-depositional processes (local moisture recycling through sublimation), regional circulation patterns, sea ice concentration and local meteorological conditions determine the distribution of 17O-excess. Numerous studies have used these isotopes to detect the changes in the moisture source, mixing of different water vapor, evaporative loss in dry regions, re-evaporation of rain drops during warm precipitation and convective storms in low and mid-latitude waters. Owing to the large variation of the spatial scale of hydrological processes with their extent (i.e., whether the processes are local or regional), more studies based on isotopic composition of surface and subsurface water, convective precipitation, and water vapor, are required. In particular, in situ measurements are important for accurate simulations of atmospheric hydrological cycles by isotope-enabled general circulation models. Full article
(This article belongs to the Special Issue Applications of Stable Isotope Analysis)
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12 pages, 2714 KiB  
Article
A Study of Moist Air Condensation Characteristics in a Transonic Flow System
by Jie Wang and Hongfang Gu
Energies 2021, 14(13), 4052; https://doi.org/10.3390/en14134052 - 5 Jul 2021
Cited by 5 | Viewed by 2912
Abstract
When water vapor in moist air reaches supersaturation in a transonic flow system, non-equilibrium condensation forms a large number of droplets which may adversely affect the operation of some thermal-hydraulic equipment. For a better understanding of this non-equilibrium condensing phenomenon, a numerical model [...] Read more.
When water vapor in moist air reaches supersaturation in a transonic flow system, non-equilibrium condensation forms a large number of droplets which may adversely affect the operation of some thermal-hydraulic equipment. For a better understanding of this non-equilibrium condensing phenomenon, a numerical model is applied to analyze moist air condensation in a transonic flow system by using the theory of nucleation and droplet growth. The Benson model is adopted to correct the liquid-plane surface tension equation for realistic results. The results show that the distributions of pressure, temperature and Mach number in moist air are significantly different from those in dry air. The dry air model exaggerates the Mach number by 19% and reduces both the pressure and the temperature by 34% at the nozzle exit as compared with the moist air model. At a Laval nozzle, for example, the nucleation rate, droplet number and condensation rate increase significantly with increasing relative humidity. The results also reveal the fact that the number of condensate droplets increases rapidly when moist air reaches 60% relative humidity. These findings provide a fundamental approach to account for the effect of condensate droplet formation on moist gas in a transonic flow system. Full article
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16 pages, 3259 KiB  
Article
Porous Hydrophobic–Hydrophilic Composite Hollow Fiber and Flat Membranes Prepared by Plasma Polymerization for Direct Contact Membrane Distillation
by Ashok K. Sharma, Adam Juelfs, Connor Colling, Saket Sharma, Stephen P. Conover, Aishwarya A. Puranik, John Chau, Lydia Rodrigues and Kamalesh K. Sirkar
Membranes 2021, 11(2), 120; https://doi.org/10.3390/membranes11020120 - 8 Feb 2021
Cited by 20 | Viewed by 4070
Abstract
High water vapor flux at low brine temperatures without surface fouling is needed in membrane distillation-based desalination. Brine crossflow over surface-modified hydrophobic hollow fiber membranes (HFMs) yielded fouling-free operation with supersaturated solutions of scaling salts and their precipitates. Surface modification involved an ultrathin [...] Read more.
High water vapor flux at low brine temperatures without surface fouling is needed in membrane distillation-based desalination. Brine crossflow over surface-modified hydrophobic hollow fiber membranes (HFMs) yielded fouling-free operation with supersaturated solutions of scaling salts and their precipitates. Surface modification involved an ultrathin porous polyfluorosiloxane or polysiloxane coating deposited on the outside of porous polypropylene (PP) HFMs by plasma polymerization. The outside of hydrophilic MicroPES HFMs of polyethersulfone was also coated by an ultrathin coating of porous plasma-polymerized polyfluorosiloxane or polysiloxane rendering the surface hydrophobic. Direct contact membrane distillation-based desalination performances of these HFMs were determined and compared with porous PP-based HFMs. Salt concentrations of 1, 10, and 20 wt% were used. Leak rates were determined at low pressures. Surface and cross-sections of two kinds of coated HFMs were investigated by scanning electron microscopy. The HFMs based on water-wetted MicroPES substrate offered a very thin gas gap in the hydrophobic surface coating yielding a high flux of 26.4–27.6 kg/m2-h with 1 wt% feed brine at 70 °C. The fluxes of HFMs on porous PP substrates having a long vapor diffusion path were significantly lower. Coated HFM performances have been compared with flat hydrophilic membranes of polyvinylidene fluoride having a similar plasma-polymerized hydrophobic polyfluorosiloxane coating. Full article
(This article belongs to the Special Issue Membrane Distillation Process)
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12 pages, 1777 KiB  
Article
Hybrid Membrane Distillation and Wet Scrubber for Simultaneous Recovery of Heat and Water from Flue Gas
by Mohd Hizami Mohd Yusoff, Ein K. Nyunt, Muhammad Roil Bilad, Nasrul Arahman, Sri Mulyati, Samsul Rizal, Nik Abdul Hadi Nordin, Jia Jia Leam, Asim Laeeq Khan and Juhana Jaafar
Entropy 2020, 22(2), 178; https://doi.org/10.3390/e22020178 - 4 Feb 2020
Cited by 7 | Viewed by 4787
Abstract
Flue gas contains high amount of low-grade heat and water vapor that are attractive for recovery. This study assesses performance of a hybrid of water scrubber and membrane distillation (MD) to recover both heat and water from a simulated flue gas. The former [...] Read more.
Flue gas contains high amount of low-grade heat and water vapor that are attractive for recovery. This study assesses performance of a hybrid of water scrubber and membrane distillation (MD) to recover both heat and water from a simulated flue gas. The former help to condense the water vapor to form a hot liquid flow which later used as the feed for the MD unit. The system simultaneously recovers water and heat through the MD permeate. Results show that the system performance is dictated by the MD performance since most heat and water can be recovered by the scrubber unit. The scrubber achieved nearly complete water and heat recovery because the flue gas flows were supersaturated with steam condensed in the water scrubber unit. The recovered water and heat in the scrubber contains in the hot liquid used as the feed for the MD unit. The MD performance is affected by both the temperature and the flow rate of the flue gas. The MD fluxes increases at higher flue gas temperatures and higher flow rates because of higher enthalpy of the flue gas inputs. The maximum obtained water and heat fluxes of 12 kg m2 h1 and 2505 kJm2 h1 respectively, obtained at flue gas temperature of 99 °C and at flow rate of 5.56 L min−1. The MD flux was also found stable over the testing period at this optimum condition. Further study on assessing a more realistic flue gas composition is required to capture complexity of the process, particularly to address the impacts of particulates and acid gases. Full article
(This article belongs to the Special Issue Entropy in Renewable Energy Systems)
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17 pages, 7291 KiB  
Article
Bifunctional TiO2/AlZr Thin Films on Steel Substrate Combining Corrosion Resistance and Photocatalytic Properties
by Caroline Villardi de Oliveira, Akram Alhussein, Juan Creus, Frédéric Schuster, Michel L. Schlegel, Zhili Dong, Carmen Jiménez and Frédéric Sanchette
Coatings 2019, 9(9), 564; https://doi.org/10.3390/coatings9090564 - 3 Sep 2019
Cited by 9 | Viewed by 3750
Abstract
A novel multi-functional bilayer coating combining an anti-corrosion Al–Zr (4 at.% Zr) underlayer and an anti-biofouling TiO2 top layer was deposited on high-speed steel (HSS) substrates. Al–Zr (4 at.% Zr) film, deposited by DC magnetron sputtering, which is a single phased supersaturated [...] Read more.
A novel multi-functional bilayer coating combining an anti-corrosion Al–Zr (4 at.% Zr) underlayer and an anti-biofouling TiO2 top layer was deposited on high-speed steel (HSS) substrates. Al–Zr (4 at.% Zr) film, deposited by DC magnetron sputtering, which is a single phased supersaturated solid solution of Zr in Al, is used to provide sacrificial corrosion resistance of steels and TiO2 is added as a top layer to induce photocatalytic activity and hydrophilic behavior which can generate antifouling properties in order to slow down the biofouling process. The top TiO2 films, deposited at 550 °C by AACVD (aerosol-assisted chemical vapor deposition), consisting of anatase TiO2 microflowers physically attached to the TiO2 thin films present a high decomposition rate of Orange G dye (780 × 10−10 mol L−1·min−1). The enhanced photocatalytic performance is associated with the rough network and the presence of TiO2 microflowers capable of supporting the enhanced loading of organic contaminants onto the film surface. Electrochemical tests in saline solution have revealed that bilayer films provide cathodic protection for the steel substrate. The Al–Zr/TiO2 bilayer presents a lower corrosion current density of 4.01 × 10−7 A/cm2 and a corrosion potential of −0.61 V vs. Ag/AgCl, offering good protection through the preferential oxidation of the bilayer and an increased pitting resistance. The proposed functionalized coating combining anticorrosion and photocatalytic properties is a promising candidate for an anti-fouling system in sea water. Full article
(This article belongs to the Special Issue Magnetron Sputtering Deposited Thin Films and Its Applications)
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12 pages, 2002 KiB  
Article
Recent Insights into Protein Crystal Nucleation
by Christo N. Nanev
Crystals 2018, 8(5), 219; https://doi.org/10.3390/cryst8050219 - 17 May 2018
Cited by 14 | Viewed by 4399
Abstract
Homogeneous nucleation of protein crystals in solution is tackled from both thermodynamic and energetic perspectives. The entropic contribution to the destructive action of water molecules which tend to tear up the crystals and to their bond energy is considered. It is argued that, [...] Read more.
Homogeneous nucleation of protein crystals in solution is tackled from both thermodynamic and energetic perspectives. The entropic contribution to the destructive action of water molecules which tend to tear up the crystals and to their bond energy is considered. It is argued that, in contrast to the crystals’ bond energy, the magnitude of destructive energy depends on the imposed supersaturation. The rationale behind the consideration presented is that the critical nucleus size is determined by the balance between destructive and bond energies. By summing up all intra-crystal bonds, the breaking of which is needed to disintegrate a crystal into its constituting molecules, and using a crystallographic computer program, the bond energy of the closest-packed crystals is calculated (hexagonal closest-packed crystals are given as an example). This approach is compared to the classical mean work of separation (MWS) method of Stranski and Kaischew. While the latter is applied merely for the so-called Kossel-crystal and vapor grown crystals, the approach presented can be used to establish the supersaturation dependence of the protein crystal nucleus size of arbitrary lattice structures. Full article
(This article belongs to the Special Issue Biological Crystallization)
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