Air Vapor Research Articles

Effects of Electronic Cigarette Vaping on Cardiac and Vascular Function, and Post-myocardial Infarction Remodeling in Rats

The effect of electronic cigarette (E-cig) vaping on cardiac and vascular function during the healing phase of myocardial infarction (MI), and post-MI remodeling was investigated. Sprague Dawley rats were subjected to left coronary artery ligation to induce MI. One week later, rats were randomized to receive either 12 weeks of exposure to purified air (n = 37) or E-cig vapor (15 mg/ml of nicotine) (n = 32). At 12 weeks, cardiac and vascular function, and post-MI remodeling were assessed. Baseline blood flow in the femoral artery did not differ between groups, but peak reperfusion blood flow was blunted in the E-cig group (1.59 ± 0.15 ml/min) vs. the air group (2.11 ± 0.18 ml/min; p = 0.034). Femoral artery diameter after reperfusion was narrower in the E-cig group (0.54 ± 0.02 mm) compared to the air group (0.60 ± 0.02 mm; p = 0.023). Postmortem left ventricular (LV) volumes were similar in the E-cig (0.69 ± 0.04 ml) and air groups (0.73 ± 0.04 ml; p = NS); and myocardial infarct expansion index did not differ between groups (1.4 ± 0.1 in E-cig group versus 1.3 ± 0.1 in air group; p = NS). LV fractional shortening by echo did not differ between groups at 12 weeks (E-cig at 29 ± 2% and air at 27 ± 1%; p = NS). Exposure to E-cig during the healing phase of MI was associated with altered vascular function with reduced femoral artery blood flow and diameter at reperfusion, but not with worsened LV dilation or worsened cardiac function.

Abstract 105: Sex Difference in Brain Energy Metabolism After Electronic Cigarette Vape Exposure May Contribute to Worsened Stroke Injury in Rats

Introduction: Electronic cigarettes (EC) are battery-powered nicotine delivery devices that have gained popularity as alternatives to tobacco cigarettes for young smokers and smokers trying to cease. Because of its relative novelty, our understanding about the effects of EC vaping on stroke outcome is limited. Here we aim to investigate the effects of EC on energy metabolism in the brain and on stroke outcome in animals of both sexes. Methods: Female and male Sprague-Dawley rats (2-3 months old; n=8) were randomly assigned to either air or EC vapor (5% nicotine Juul pods) exposure for 16 nights using the EcigAero-TM Aerosol Exposure Apparatus. After the exposure period, the rats were divided into two cohorts. The brains were collected from the first cohort of rats for unbiased metabolomic (Metabolon Inc.) or Western blot analysis. The second cohort underwent transient middle cerebral artery occlusion (tMCAO; 90 min) or sham surgery and was survived for 21 days. During the post-tMCAO/sham survival, cognition was assessed using the Morris water maze followed by brain collection for histopathological analysis. Results: Metabolomic analysis showed substantial changes in glycolytic metabolites in EC-exposed female rats in relation to air controls, implying altered brain energetics. In EC-exposed female animals, a significant increase (p<0.05) in glucose, glucose 6-phosphate, fructose-6-phosphate, and fructose 1-6 diphosphate was noted compared to air controls. However, such changes were not seen in EC-exposed male rats. Quantification of infarct volume demonstrated that, compared to air rats, EC-exposed rats displayed a significantly increased infarct volume in female rats while showing a trend of increase in male rats. In female rats, infarct volumes were 86 ± 19 mm 3 and 151 ± 25 mm 3 for air and EC groups, respectively, a significant difference (p<0.05). In the male rat air group, tMCAO resulted in an infarct volume of 80 ± 37 mm 3 , while EC yielded 130 ± 38 mm 3 . Behavioral testing showed worsened post-stroke cognitive outcome in EC groups compared to air groups in rats of both sexes. Conclusion: EC vape exposure, even for as short as two weeks, impacts glucose metabolism and worsens post-stroke cognitive deficits in female more than male rats.

Thermal Comfort Properties of 100% Cashmere Knitted Fabrics

The purpose of this research is to investigate the effects of knitting type (plain, rib, purl), knitting tightness (three different loop lengths), and plied-yarn (single-ply, two-ply and three-ply) on the thermal comfort properties of cashmere knitted fabrics. Thermal comfort properties of the sample fabrics were measured using Alambeta, Permetest, Textest 3300. Subsequently, the results were statistically evaluated with SPSS program. The findings of this research revealed that the knitting type, knitting tightness and plied-yarn usage significantly affect certain thermal comfort properties of cashmere knitted fabrics. Specifically, the plain knitted fabric exhibits the lowest thermal resistance value and the highest relative water vapor permeability value. The loose knitted fabric demonstrates the highest air permeability, while the fabric knitted with single-ply yarn has the lowest thermal conductivity and thermal resistance values, as well as the highest relative water vapor permeability and air permeability values.

Quantum control of flying doughnut terahertz pulses.

The ability to manipulate the multiple properties of light diversifies light-matter interaction and light-driven applications. Here, using quantum control, we introduce an approach that enables the amplitude, sign, and even configuration of the generated light fields to be manipulated in an all-optical manner. Following this approach, we demonstrate the generation of "flying doughnut" terahertz (THz) pulses. We show that the single-cycle THz pulse radiated from the dynamic ring current has an electric field structure that is azimuthally polarized and that the space- and time-resolved magnetic field has a strong, isolated longitudinal component. We apply the flying doughnut pulse for a spectroscopic measurement of the water vapor in ambient air. Pulses such as these will serve as unique probes for spectroscopy, imaging, telecommunications, and magnetic materials.

Development of multifunctional sustainable packaging from acetylated cellulose micro-nanofibrils (CMNF)

Cellulose micro-nanofibrils (CMNF) with different fibrillation levels were partially acetylated while preserving their morphological and native crystalline structure. The morphological changes due to fibrillation and chemical modification were observed using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and optical profilometry. The change in tensile and burst strength, barrier, and biodegradability profile were investigated which revealed that the mechanical properties of the unmodified CMNF films increased with increase in extent of fibrillation. However, the mechanical strength of the acetylated film decreased with the increase in degree of acetylation. The stretching or folding property of the film increased with the increase in both the fibrillation and acetylation. The contact angle value increased due to a higher degree of fibrillation and acetylation because they increased the hydrophobicity and consequently enhanced the air and water vapor resistance of the unmodified and modified CNF films. Furthermore, all films exhibited the highest resistance against oil and grease, and the biodegradability test substantiated that CNF films were compostable in soil. In total, this work expresses new pathways to enhance the barrier properties of biodegradable CNF films by regulating the degree of fibrillation and acetylation, thus can emerge as sustainable alternatives for packaging and agriculture applications.

NANOFLUID FILM FALLING ON A NON-DARCY POROUS VERTICAL PLATE EVAPORATOR

A numerical analysis of the falling nanofilm evaporation on a vertical porous wetted wall by mixed convection was performed. The right-wall was dry and isothermal, while the left wall was embedded in a non-Darcy porous medium filled with nanofilm (water + low fraction volume of copper nanoparticles) and exposed to a uniform heat flux from the outside. The nanofluid film made up the liquid, while dry air and water vapor comprised the gas mixture. The results obtained from this study pertain to the impact of porosity, thickness of the porous layer, concentration of nanoparticles on heat and mass exchange, and liquid film evaporation. The results indicate that mass and heat exchange, as well as liquid film evaporation, are improved in the case of nanofilm by introducing a liquid-saturated porous medium. It is shown that in the case of a porous layer, the dispersion of the nanoparticles into water film ameliorates the liquid film evaporation of the plate evaporator and weakly improves the mass and heat exchange.

Analytical and numerical solutions of pore formation in elastic food materials during dehydration

In this paper, we describe a model for pore formation in food materials during drying. As a proxy for fruits and vegetables, we take a spherical hydrogel, with a stiff elastic skin, and a central cavity filled with air and water vapour. The model describes moisture transport coupled to large deformation mechanics. Both stress and chemical potential are derived from a free energy functional, following the framework developed by Suo and coworkers. We have compared Finite Volume and Finite Element implementations and analytical solutions with each other, and we show that they render similar solutions. The Finite Element solver has a larger range of numerical stability than the Finite Volume solver, and the analytical solution also has a limited range of validity. Since the Finite Element solver operates using the mathematically intricate weak form, we introduce the method in a tutorial manner for food scientists.Subsequently, we have explored the physics of the pore formation problem further with the Finite Element solver. We show that the presence of an elastic skin is a prerequisite for the growth of the central cavity. The elastic skin must have an elastic modulus of at least 10 times that of the hydrogel. An initial pore with 10% of the size of the gel can grow to 5 times its initial size. Such an increase in porosity has been reported in the literature on drying of vegetables, if a dense hard skin is formed, known as case hardening. We discuss that models as presented in this paper, where moisture transport is strongly coupled to large deformation mechanics, are required if one wants to describe pore/structure formation during drying and intensive heating (as baking and frying) of food materials from first principles.

Solar radiation variation weakened the boost of gross primary production by vegetation restoration in China’s most forestry engineering areas during 2001–2020

Over the past decades, ecological restoration initiatives in China have made great progress in restoring degraded forests and increasing vegetation coverage, yet the carbon sequestration effects of these initiatives in the context of climate change are not clear. In this study, we assessed the effects of vegetation restoration on gross primary production (GPP) in China’s forestry engineering areas, where large-scale vegetation restoration programmes were launched, during 2001–2020 by disentangling the respective roles of land cover change (LCC), CO2 fertilization, and climate changes using a two-leaf light use efficiency model. We found that LCC attributed by the vegetation restoration dominantly accelerated the increase of GPP in seven out of the eight areas, and CO2 fertilization played a near-equivalent role in all areas. By contrast, the changes in different climate factors contributed to GPP variations diversely. The solar radiation variation greatly inhibited the vegetation GPP over time in seven out of these areas, and the changes in air temperature and vapor pressure deficit regulated GPP inter-annual variations without clear trends in all areas. This study advances our understanding of the contribution of China’s afforestation on its forest GPP in a changing climate, which may help to better manage forests to tackle the challenge of the climate crisis in the future.

Effect of a static magnetic field on the falling-film evaporation on a vertical plate evaporator by mixed convection

The application of a magnetic field to a falling-film evaporation system can have several effects. The magnetic field can alter the liquid film's flow behavior and modify the system's heat transfer characteristics. The numerical study of falling film evaporation by mixed convection on a vertical channel under a static magnetic field has been investigated. The vertical channel is composed of two parallel plates. The right plate is dry and isothermal, while the left plate is wetted by a falling liquid film and exposed to a static, uniform heat flux from the outside. Water film makes up the liquid, while dry air and water vapor make up the gas mixture. The results relate to the effects of the magnetic field on heat and mass transfer and on liquid film evaporation. The results demonstrate that the static magnetic field has a weak effect on heat and mass transfer and water film evaporation. In fact, it is shown that an increase in the static magnetic field weakly enhances heat and mass transfer as well as liquid film evaporation.

Industrieschnee: An overview of some European anthropogenic snowfall events, with a case study from Bern (Switzerland)

AbstractIndustrieschnee or anthropogenic snowfall is a local winter hazard in many European cities and towns under suitable anticyclonic conditions and in the vicinity of persistent local water vapour sources and air pollution. Here, we overview the formation of Industrieschnee and describe a case study event from Bern, Switzerland, comparing the estimated mass of snow deposited with the water vapour emissions from a local incinerator. We speculate that previous European Industrieschnee events may have been considerably under‐reported, or falsely attributed to surface hoar frost (reif) or the accretion of rime (raureif).

Synergistic effects of polymaleic acid and di(dioctylpyrophosphato) ethylene titanate on B4C modification in highly filled polymer fibers for improved neutron protection safety and wear comfort of articles

Developing wearable articles with radiation protection safety and wear comfort is one of the urgent issues in that flourishing nuclear technologies are accompanied by increasing radiation threats. However, current wearable articles either display insufficient shielding performance or exhibit poor air and water vapor permeability, which are difficult to meet the growing demand of personal protection in nuclear environments. In this paper, polymaleic acid (PMA) and di(dioctylpyrophosphato) ethylene titanate (DPET) have been used to superficially modify boron carbide (B4C) particles for constructing sufficient hydrogen bonds with polyvinyl alcohol (PVA) matrix. Synergistic effects of PMA and DPET lead to enhanced interfacial interaction. As high as 55 wt% B4C/PVA fibers have been obtained with smooth wet spinning. Their multi-layered fabrics display excellent air and water vapor permeability meanwhile thermal neutron shielding. Three-layer B4C/PVA fabrics have 89.2 % thermal neutron (0.025 eV) shielding rate. In addition, 321.1 mm/s air and 2236.2 g/m2·24 h water vapor permeability have been measured. Besides, the fabrics still show great flexibility in spite of the fibers with extreme filling of inorganic particles. This work provides alternative wear articles to cope with the dilemma of radiation protection safety and wear comfort in neutron radiation environments.

Performance analysis of a novel two-bed adsorption humidification-dehumidification desalination system using Metal-organic framework 801

Adsorption desalination techniques have been increasingly studied over the last century as a sustainable option for meeting the rapidly growing demand for fresh water. One of the attractive factors for using adsorption desalination systems is the use of low-grade thermal energy normally wasted in the atmosphere. The current study introduces a novel adsorption desalination system integrated with a humidification dehumidification system for producing potable water. Four system configurations are presented. The main distinction between them is the source of hot water used for the humidifier. Scheme #1 utilizes the heat of condensation, Scheme #2 applies the heat of condensation plus the heat of adsorption, while Scheme # 3 adds the outlet of heating water from the desorber as a source of heat to the humidifier. Scheme #4 is a standalone adsorption desalination system that applies chilled water to cool the condenser. The novelty of this system is the application of the chilled water from the evaporator to the dehumidifier to create the highest possible temperature difference necessary for the humidification and dehumidification process. This advantage allows larger water productivity, especially in hot humid regions. In this case, it is possible to extract water vapour in the ambient humid air, water vapour gained from the humidification process and water vapour condensed in the condenser of the adsorption desalination system. Moreover, we have used a novel material Metal Organic Frameworks 801 as an adsorbent for a highly efficient process. Based on the results, Scheme #3 produced the maximum amount of fresh water, 210 kg/h while Scheme #2 obtained the maximum gained output ratio, 4.4 with a minimum cost of 0.0079 $/L. A standalone adsorption system produced the minimum amount of distillate water and the lowest gained output ratio. It is not advisable to use a standalone adsorption system to produce distillate water; as the full desalination potential is not achieved.

Energy Partitioning and Latent Heat Flux Driving Factors of the CAM Plant Pineapple (Ananas comosus (L.) Merril) Grown in the South Subtropical China.

Elucidation of different vegetation energy partitioning and environmental control factors at the agro-ecosystem levels is critical for better understanding and scientific management of farmland. Pineapple (Ananas comosus (L.) Merril) is a tropical plant widely cultivated in the southern subtropical region of China; however, the energy partitioning of crassulacean acid metabolism (CAM) plants like pineapple and their interactions with the environment remain not well understood. In this study, we investigated the energy partitioning patterns of pineapple fields and latent heat flux (LET) response to environmental factors using the Bowen ratio energy balance system and meteorological observation field data. The results showed that the CAM plant pineapple energy partitioning was significantly different from the common C3 and C4 crops during the study period, which was mainly attributed to the complex interactions between CAM plant transpiration and the environment. Specifically, sensible heat flux was the main component of net radiation (Rn), followed by the LET, accounting for 65.0% and 30.8% of the Rn, respectively. Soil heat flux accounts for a very small fraction (4.2%). The mean values of the Bowen ratio were 2.09 and 1.41 for sunny and cloudy days during the daytime and 0.74 and 0.46 at night, respectively. LET is a key factor in responding to crop growth status and agricultural water management, and the path analysis indicates that its variation is mainly influenced directly by Rn with a direct path coefficient of 0.94 on sunny days, followed by vapor pressure deficit, air temperature and relative humidity, which indirectly affect LET through the Rn pathway, whereas soil moisture and wind speed have a low effect on LET. On cloudy days, the effect of Rn on LET was overwhelmingly dominant, with a direct path coefficient of 0.91. The direct path coefficients of the remaining factors on LET were very small and negative. Overall, this study is an important reference for enhancing the impact of pineapple as well as CAM plants on the surface energy balance and regional climate.

Critical Role of Boundary Conditions in Sorption Kinetics Measurements.

In order to characterize the hygroscopic properties of cellulose-based materials, which can absorb large amounts of water from vapor in ambient air, or the adsorption capacity of pollutants or molecules in various porous materials, it is common to rely on sorption-desorption dynamic tests. This consists of observing the mass variation over time when the sample is placed in contact with a fluid containing the elements to be absorbed or adsorbed. Here, we focus on the case of a hygroscopic material in contact with air at a relative humidity (RH) differing from that at which it has been prepared. We show that the vapor mass flux going out of the sample follows from the solution of a vapor convection-diffusion problem along the surface and is proportional to the difference between the RH of the air flux and that along the surface with a multiplicative factor (δ) depending only on the characteristics of the air flux and the geometry of the system, including the surface roughness. This factor may be determined from independent measurements in which the RH along the surface is known while keeping all other variables constant. Then we show that the apparent sorption or desorption kinetics critically depend on the competition between boundary conditions and transport through the material. For sufficiently low air flux intensities or small sample thicknesses, the moisture distribution in the sample remains uniform and evolves toward the equilibrium with a kinetics depending on the value of δ and the material thickness. For sufficiently high air flux intensities or large sample thicknesses, the moisture distribution is highly inhomogeneous, and the kinetics reflect the ability of water transport by diffusion through the material. We illustrate and validate this theoretical description on the basis of magnetic resonance imaging experiments on drying cellulose fiber stacks.

Physico-chemical surface modification of the natural leather using gliding arc discharge: An in-depth analysis of improving surface and mechanical properties

Leather, a widely used material in various industries, presents challenges in terms of dye uptake, hydrophilicity, and environmental concerns associated with chemical wet processing. In this context, non-thermal plasma technology offers a promising alternative for leather surface modification. In this study, the gliding arc, with air and water vapor plasmas, was used for the surface modification of natural leather for the first time. The influence of the treatment time and also the plasma gas chemistry on the surface chemical bonding, surface morphology, wettability, water absorption time and absorption capacity, color, and mechanical properties of the leather were investigated. The results showed that in the water vapor gliding arc discharge, the produced active oxygen and hydroxyl species can effectively react with the functional groups and break the relatively weak hydrocarbon CH bonds in the chemical composition of the natural leather. SEM images showed increased pore depth and diameter on the leather surface after air and water vapor plasma treatment with mean diameters of 76 μm and 92 μm, respectively. The tensile stress-strain curves illustrated that despite small cracks were created on the plasma treated samples, the elongation at break (ultimate strain) increased from 83.7 % to 88.5 % and 91.8 % for the samples treated with the air and the water vapor plasmas for 5 min, respectively. The water contact angle decreased from 96° to 55° and 48° after only 5-second treatment with the air and the water vapor plasmas, respectively. The same trend was also observed for the water absorption time and the absorption capacity of the treated samples. Also, the color analysis showed that the color change in the plasma treated samples was not detected by the unaided eye. It was also found that water vapor plasma has a better influence on the physico-chemical properties of the leather.

Atmospheric effects are stronger than soil moisture in restricting net CO2 uptake of managed grasslands in New Zealand

Climate change is exposing agricultural systems to more frequent weather extremes, threatening production and challenging the sustainability of current management practices. However, isolating the climatic drivers of CO2 exchange in managed systems can be complicated by the periodic removal of aboveground biomass through grazing or harvesting, abruptly shifting the potential for plant uptake and associated ecosystem biogeochemistry. We used eddy covariance datasets from managed grasslands across New Zealand to determine the relative effects of temperature, vapour pressure deficit, and soil moisture on net CO2 uptake. Using time since grazing or harvest as a proxy for above-ground biomass, we accounted for the shifting potential CO2 exchange associated with these management actions. We then fit light response curves to the outer envelope of data to estimate maximal potential NEE, and subsequently calculate NEE deficit for every measured half hour. Using this analytical framework, we combined data from seven locations making up sixteen individual flux datasets comprising >600 site months and found that high air temperature and vapour pressure deficit were stronger controls over NEE deficit than soil moisture. These results were also consistent with a controlled leaf-level experiment demonstrating increasing photosynthesis deficit as VPD increased under constant temperature. The dominance of atmospheric effects over soil moisture in determining grassland response to dry conditions has important implications because it may be more difficult to mitigate these responses with typical management approaches (e.g., irrigation). We found these patterns were consistent across a diverse range of managed grassland operations, but subtle differences suggest that expanding the approach to a wider array of climatic regions and soil types could provide additional insights into how we might avoid the worst effects of future drying on managed systems.

The Seasonal Variability and Environmental Factors Influencing the Transpiration of Western Juniper (Juniperus occidentalis) Saplings

There is scarce information regarding the interactions between young tree water uptake and the environment in water-limited ecosystems. This study was conducted in a semiarid rangeland ecosystem in central Oregon, Pacific Northwest Region, USA. We measured the tree transpiration of western juniper (Juniperus occidentalis) saplings using the stem heat balance (SHB) method. We analyzed the correlation between transpiration and environmental factors affecting the saplings’ water use from May to October for 2017, 2018, 2019, 2021, and 2022. The study results showed that total annual precipitation for all but one year was below the long-term (2005 to 2022) mean precipitation value of 307 mm for the study site. Significantly higher transpiration rates were observed in the wet vs. dry years. The highest monthly averaged transpiration rates (2.95 L d−1) were obtained in August during the above-average precipitation year (2017). Peak transpiration rates for the below-average precipitation years were generally reached in June or July, ranging from 0.91 to 1.65 L d−1. The seasonal response of transpiration to different environmental factors varied. For all years, vapor pressure deficit (VPD), solar radiation (SR), and air temperature (AT) showed a positive correlation with transpiration, whereas precipitation (Pr) and relative humidity (RH) indicated a negative correlation with transpiration. Soil moisture (SM) and soil temperature (ST) positively correlated with transpiration for most years. A strong association between VPD and transpiration was observed during the wettest (2017; 327 mm) and driest (2021; 198 mm) years. Results from this study add to the limited literature on sapling transpiration and can contribute to the improved management of cool-climate rangeland ecosystems through an enhanced understanding of water use by young-stage trees and its potential impacts on the water balance of restored juniper landscapes.

Cardiovascular dysfunction induced by combined exposure to nicotine inhalation and high-fat diet.

Smoking and high-fat diet (HFD) consumption are two modifiable risk factors for cardiovascular (CV) diseases, and individuals who are overweight or obese due to unhealthy diet are more likely to use tobacco products. In this study, we aim to investigate the combined effects of nicotine (the addictive component of all tobacco products) and HFD on CV health, which are poorly understood. C57BL/6N male mice were placed on either HFD (60 kcal% fat) or regular diet (22 kcal% fat) and exposed to air or nicotine vapor for 10-12 wk. CV function was monitored by echocardiography and radiotelemetry, with left ventricular (LV) catheterization and aortic ring vasoreactivity assays performed at end point. Mice on HFD exhibited increased heart rate and impaired parasympathetic tone, whereas nicotine exposure increased sympathetic vascular tone as evidenced by increased blood pressure (BP) response to ganglionic blockade. Although neither nicotine nor HFD alone or in combination significantly altered BP, nicotine exposure disrupted circadian BP regulation with reduced BP dipping. LV catheterization revealed that combined exposure to nicotine and HFD led to LV diastolic dysfunction with increased LV end-diastolic pressure (LVEDP). Moreover, combined exposure resulted in increased inhibitory phosphorylation of endothelial nitric oxide synthase and greater impairment of endothelium-dependent vasodilation. Finally, a small cohort of C57BL/6N females with combined exposure exhibited similar increases in LVEDP, indicating that both sexes are susceptible to the combined effect of nicotine and HFD. In summary, combined exposure to nicotine and HFD leads to greater CV harm, including both additive and new-onset CV dysfunction.NEW & NOTEWORTHY Nicotine product usage and high-fat diet consumption are two modifiable risk factors for cardiovascular diseases. Here, we demonstrate that in mice, combined exposure to inhaled nicotine and high-fat diet results in unique cardiovascular consequences compared with either treatment alone, including left ventricular diastolic dysfunction, dysregulation of blood pressure, autonomic dysfunction, and greater impairment of endothelium-dependent vasorelaxation. These findings indicate that individuals who consume both nicotine products and high-fat diet have distinctive cardiovascular risks.

Stability of an aqueous foam lamella at simulated fire conditions containing surfactants relevant to firefighting foams

To better understand interactions between firefighting foams and a fire environment, we isolated interactions to a single surfactant containing bubble lamellae. A horizontal thin liquid film experiment was designed to study film rupture in the presence of heated air and heptane vapors. Thin films were formed from aqueous solutions of alkylpolyglycosides (APGs, G215 and G225), trisiloxane (502W and L77), and fluorinated (Cap) surfactants and their mixtures. The Cap surfactant film was the most stable to heat but in the presence of heptane, the surfactant film had a comparable (and the Cap:G215 mixture had a shorter) rupture time to the fluorine-free surfactant films. APG films showed the least destabilization with heptane followed by the trisiloxane films and the Cap film which was the most destabilized by heptane. L77, Cap, and their respective mixtures formed possible emulsions with the fuel vapors, turning cloudy with vapor introduction. The correlation between film rupture behavior and fuel induced foam lifetime may be better defined by minimizing error in lifetime and producing longer film lifetimes. This thin film experiment represents a new way of observing surfactant/fuel interactions that may elucidate important surfactant properties for firefighting foams.

Coupled heat transfer analysis of U-type tube module of LNG ambient air vaporizer under dry conditions

Liquefied natural gas (LNG) ambient air vaporizer (AAV) utilizes renewable aerothermal energy from ambient air to regasify LNG, which is usually chosen as the first choice in gas stations. Its gasification efficiency depends on the heat transfer performance of U-type finned tube which is composed of multiple straight finned tubes connected in series by U-bends. This paper developed a two-way coupled heat transfer model of AAV U-type module considering the conjugated interaction between different fluid domains and the phase interactions during the vaporization process of LNG. Experiments were conducted to validate the numerical model, and the results are in good agreement. The coupled heat transfer analysis indicates that mutually interference of the heat transfer process between two adjacent finned tubes in a U-type tube module occurs and gets more obvious as closer to the entrance of LNG. The heat flux of the inner tube surface decreases along the flow direction of LNG on the whole, yet there exists an obvious drop on the inner surface of the U-bend due to lack of fins. Besides, the heat transfer performance of the vertical straight finned tube is superior to U-type tube, and the difference is more obvious with higher LNG velocity.