Low Saturation Pressure Research Articles

Effects of Pressure, Surfactant Concentration, and Heat Flux on Pool Boiling Using Expanding Microchanneled Surface for Two-Phase Immersion Cooling.

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm2) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm-2·K-1 under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm2, the wall superheat is reduced by 12.8 K.

Evaluating the efficacy of water alternating gas injection technique in the upper jurassic hydrocarbon reservoirs, considering saturation pressure

A tertiary method of enhanced oil recovery (EOR) based on the watergas alternating injection process (WG) is examined in this article based on the ratio between saturation pressure and reservoir pressure. A hydrodynamic simulation of the WAG process was carried out using TEMPEST MORE software (version 7,1). Many hydrocarbon fields worldwide are currently experiencing declining production rates. However, by utilizing advanced technologies like alternate injection of water and associated petroleum gas, the final oil recovery factor (RF) can be significantly increased. To ensure successful water injection experiments in real fields, it is crucial to consider the ratio of saturation and reservoir pressures during injection. Any negligence in this regard can lead to failure of the experiments aimed at enhancing oil recovery through WAG application. The research examines two variations of reservoir system models with certainty. In the initial model, the saturation pressure is lower than the reservoir pressure, signifying an under-saturated state of the reservoir system containing dissolved gas. Consequently, when accompanying petroleum gas is introduced, it mixes with oil at precise thermobaric conditions. According to the second model, the reservoir is saturated with gas at a saturation pressure equivalent to the formation pressure. A thorough assessment indicates that the success of water alternating gas injection (WAG) is heavily influenced by the initial state of the reservoir. In situations where the reservoir is already saturated with gas, implementing water-gas stimulation may be ineffective as gas breakthroughs may occur rapidly. However, implementing WAG in saturated reservoirs can lead to a 1 – 8% rise in overall oil production, observable within 3 – 4 years, depending on the timing after waterflooding. Simultaneously, in the case of reservoirs with a low saturation pressure, which exhibits an undersaturated reservoir system, the implementation of water alternating gas injection can be seen as a viable approach for enhancing oil recovery. WAG is a proven method that confidently increases oil recovery up to 10% in undersaturated reservoirs compared to conventional waterflooding.

An abysmal conundrum associated with a misplaced dialysis catheter.

A 25-year-old female patient with chronic glomerulonephritis, initiated on haemodialysis presented with high-grade fever, a dysfunctional catheter, low oxygen saturation and unstable blood pressure. Upon evaluation, the patient was febrile with elevated white blood cell counts. She was intubated, started on inotropes and transferred to the intensive care unit. Chest radiography showed that the tunnelled internal jugular dialysis catheter had migrated to the inferior vena cava. Echocardiography and transoesophageal echocardiography showed severe heart dysfunction with a large thrombus attached to the catheter, indicating catheter-related atrial thrombus (CRAT). CT pulmonary angiography revealed blockage of the segmental pulmonary arteries, suggesting pulmonary embolism. Blood and tracheal cultures revealed Methicillin-resistant Staphylococcus aureus (MRSA). The patient was administered appropriate antibiotics and anticoagulants and underwent surgical removal of the thrombus and the catheter. This case demonstrates the risks associated with improper placement of dialysis catheters and highlights the brief management of CRAT.

Experimental study of ammonia nucleation boiling onset in dead-end tube segments at different boundary conditions

The nucleation boiling onset of liquid ammonia in stainless steel, aluminium, and titanium tube segments of ID 4 mm, 6 mm, and 8 mm without flow conditions has been experimentally studied at saturation pressures of 12.5–19.8 bar. It has been shown that heterogeneous nucleation is the determining mechanism for the considered cases. Maximal achievable liquid superheating at 19 K has been observed in the tests at low saturation pressure (12.5 bar), decreasing to 6 K at 19.8 bar. The heating rate in the range of 0.2–60 K min−1 (average heat fluxes of ≈0–4 kW m−2) does not impact much on boiling onset. Internal diameter (4, 6 and 8 mm), roughness (1 and 10 μm) and wettability (10°–50°) do not drastically change the level of maximum achievable superheating before boiling onset. However, quantitatively, the titanium surface with the poorest wettability (≈50°) among considered samples leads to higher overshooting of ammonia bulk temperature by several K. A stainless steel surface with artificial scratches shows a bit higher superheating than a smooth surface. The specific tests showed that ammonia boiling could start at nearly saturation level in the case of a strongly overheated wall. In particular, for ammonia at saturation pressure above 12.5 bar, the required overheating of the wall of 19 K ensures the boiling of ammonia without superheating in the bulk of the liquid.

Phase behavior and GOR evolution using a natural maturity series of lacustrine oil-prone shale: Implications from compositional modelling

For the exploration of shale oil, there is still an urgent need to relate hydrocarbon generation reactions and changing phase behavior to exact levels of thermal maturity. Six organic-rich shale samples from the Cretaceous Qingshankou Formation, Songliao Basin spanning the maturity range with vitrinite reflectance (Ro) 0.58%–1.16% were studied for petroleum generation characteristics using the PhaseKinetics, PhaseSnapshot, and GORFit approaches. All samples show very good petroleum potential and contain Type I kerogen with total organic carbon contents ranging between 1.5% and 5%. A full spectrum of light to heavy hydrocarbons, consistent with live oils, occurs in thermal extracts of all samples. Gas chromatography fingerprints of samples with Ro > 0.7% closely resemble waxy oils derived from lacustrine organic matter (OM); fingerprints of lower maturity samples are not yet as wax rich. The inferred petroleum type organofacies of all samples is paraffinic high wax with low organic sulfur levels. Hydrocarbon generation from the least mature sample is characterized by one dominant activation energy at 55 kcal/mol, accounting for 87% of the total bulk reaction. Assuming a simplified geological scenario, i.e., a 3 K/My linear heating rate, primary petroleum is generated (transformation ratio, i.e., TR: 10%–90%) over a narrow temperature interval of only 23 °C. Onset (10% TR), maximum (Tpeak), and completion (90% TR) temperatures and Ro values are 141 °C at Ro 0.85%, 155 °C at Ro 1.08%, and 164 °C at Ro 1.2%, respectively. Primary gas generation (148–172 °C) occurs 10 °C later (300 m deeper) than the generation of C6+ compounds (138–161 °C). Secondary gas formation from oil cracking begins at 182 °C, maximizes at 197 °C, and is completed well before 225 °C (beginning of late gas generation from the secondary cracking of thermally matured, macromolecular organic matter) at 206 °C. Thus, primary and secondary oil cracking processes do not overlap under geological conditions. In line with a paraffinic high-wax oil petroleum type organofacies, cumulative fluids generated from the least mature sample fall within the black oil class over most of the primary kerogen conversion range up to 90% TR as indicated by low saturation pressures (Psat) and gas-oil-ratios generally below 160 Sm3/Sm3. Maturation results in relatively heavy fluids with Psat values in the range 40–70 bar when the free hydrocarbons, i.e., already present prior to pyrolysis, are included, and in lighter fluids with Psat values in the range 70–90 bar, when the free, mostly waxy hydrocarbons, are excluded. Systematics of physical properties and fluid compositions evolution reproduce the general behavior of naturally occurring petroleum sourced from lacustrine OM very well and fit physical properties and compositions of produced shale oils in the Songliao Basin at comparable maturity levels.

Boiling heat transfer and pressure drop of R290 in a micro-fin tube

The present study focuses on the analysis of heat transfer and pressure drop of R290 in a horizontal micro-fin tube. In this regard, experiments were conducted, and flow patterns, heat transfer coefficient, and friction pressure drop were analyzed under various conditions. A wide range of conditions was studied, including saturation pressures ranging from 0.215 to 0.415 MPa, mass fluxes ranging from 70 to 190 kg m−2 s−1, heat fluxes in the range of 10.6–73.0 kW m−2, and vapor qualities from 0 to 0.96. The performed analyses revealed four flow patterns, including bubbly flow, plug flow, slug flow, and annular flow. It is found that the onset of dry-out occurs when the liquid film thickness is equal to the fin height and occurs earlier at high heat fluxes and low saturation pressures. The maximum heat transfer coefficient and friction pressure drop occur at the onset of dry-out, and the heat transfer coefficient exhibits a significant correlation with the heat flux. The obtained results were verified using the heat transfer correlation of Cavallini and the friction pressure drop correlation of Rollman, where the average relative deviation (ARD) was −24.01% and −8.65%, respectively.

CONCENTRATING SOLAR POWERED TRANSCRITICAL CO2 POWER GENERATION CYCLE FOR THE UNION TERRITORY OF LADAKH, INDIA

High solar irradiation, cloud-free dry climate, abundant barren land, and low ambient temperature make the Union Territory of Ladakh, India, suitable for concentrating solar thermal power (CSP) plants. The present study comprehensively analyzes a 5 MW transcritical CO<sub>2</sub> Rankine cycle power tower CSP plant. Low ambient temperature of the region allows transcritical operation, which provides high cycle efficiency. The study focuses on five aspects: solar field and thermal energy storage (TES), thermodynamic cycle simulation, turbomachines, and off-design performance analysis. Modeling and optimization of the solar field are undertaken to capture the diurnal and annual variations of direct normal irradiation levels using System Advisor Model open source software. Molten salt TES is integrated to overcome the dynamic variations of solar energy by providing stable operations and additional hours. The effect of storage sizes, starting from no storage to 12 hours, on the solar field size and specifications is also assessed. An in-house algorithm is developed for thermodynamic cycle optimization, exergy analysis, and off-design operations. The turbomachines of the cycle are designed using in-house meanline codes, and 3D CFD simulations are conducted for efficiency estimations. The effects of ambient temperature variations on the low side saturation pressure, cycle efficiency, and power output are evaluated. The proposed plant offers annual optical efficiency of 54.1%, thermal efficiency of 36.5%, and overall efficiency of 19.7%.

A review on solar desalination techniques using vacuum technology

The explosion of the population is alarming as the demand increases exponentially for resources. The freshwater resources are being exploited, and innovative and economical methods are analyzed experimentally to extract freshwater from various sources. Desalination performed using solar energy is an economical method to obtain fresh water from seawater and brackish water, which are available prolifically in nature. Since the phenomenon of desalination demands solar irradiation, which is an intermittent source of energy, distillation is not feasible in some places where the solar intensity is low. In the solar desalination, the saturation temperature of the saline water is very less at low saturation pressure thereby requiring large latent heat of evaporation. Hence, vacuum pressure could be the most appropriate choice to extract drinkable water in territories where the intensity of solar irradiation is poor. In order to this, the utilization of evacuated tube collectors and vacuum technology in the solar desalination unit has been considered for discussion as it is the most sought-after subject of interest in the current scenario. Methods for implementing the vacuum technology are also introduced with plenty of experimentations. Vacuum technology implemented in the evaporator of desalination system has been supplemented with nano-fluids and phase change materials to accelerate the evaporation process, increase efficiency, and obtain a greater productivity. In this review, the performance of the solar desalination unit under the vacuum effect were discussed in detail. Furthermore, in economic analysis, the cost effectiveness and cost per liter of distillate (CPL) were discussed to estimate the payback period. Finally, this review also suggests the vision to identify the future scope for additional implementations.

Thermal nonequilibrium and mechanical forces induced breakup and droplet formation of superheated liquid jets under depressurized release

Superheated liquid jets disintegrate into numerous droplets when released into the ambient with lower saturated pressure, driven by thermal nonequilibrium induced flashing and the accompanying mechanical forces. Such a phenomenon facilitates fuel atomization in energy utilization while posing a serious threat during accidental releases. In this work, the breakup and droplet formation of superheated liquid jets under depressurized releases were investigated with an experimental 20 L tank. A high-speed camera was utilized to characterize breakup behaviors. The interaction between thermodynamic and mechanical effects during depressurization was discussed based on linear stability analysis and bubble dynamics. Furthermore, the quantitative relationship between the two driving effects under different conditions was established using dimensionless and multiple regression analyses. Results show that the thermodynamic effect increases with the decreased mechanical effect during depressurization because of the increased energy of bubble burst, regardless of the external or internal flashing regime. Non-flashing, partially flashing, and fully flashing breakup modes are identified. The dimensionless and multiple regression analyses show that in addition to thermodynamic (Ja, ρv/ρl, Rp, and ηp) and mechanical (Wev and Oh) effects, the inhibition induced by the cooling effect (Pr and Ec) should not be overlooked. The quantitative expression among them agrees well with experimental data with R2 = 0.976.

Preferential removal of aromatics-dominated electronic industrial emissions using the integration of spray tower and photocatalysis technologies

Industrial emissions from the manufacturing of printed circuit boards (PCBs) are characterized by low concentration and high gas flow rates, and are one of the important sources of toxic and odorous volatile organic compounds (VOCs). They are deleterious to human health and considered as important precursors for the formation of ozone. Herein, we conducted a case study in which an integrated decontamination technique consisting of a spray tower (ST) and photocatalysis (PC) was applied to purify the waste gas emitted from a PCB manufacturing facility. Total of 66 VOCs including halogenated hydrocarbons (HHs), aromatic hydrocarbons (AHs), oxygen-containing hydrocarbons (OVOCs), and aliphatic hydrocarbons (AIHs) were quantified using GC-MS during four sampling events. The results showed that AHs were the largest group (contributing >85.0% of the total VOCs). The average removal efficiency (RE) of VOCs during the nine months’ continuous treatment was 72.39%. High RE was attributed to the following three aspects: the capture efficiencies of HHs with slight water solubility (50.16% of RE) and AIHs with low saturation pressure (54.75% of RE) were improved by the process consisting of ST upstream of PC, whereas AHs was preferentially degraded by PC (61.34% of RE). In addition, the ozone formation potential and the health risk (cancer and non-cancer risks) greatly decreased after the ST-PC treatment. This study suggests that ST-PC technique is a promising approach for removing continuously emitted organic waste gas with low concentration and high gas flow rates, as well as reducing the ozone formation and risk of health hazards.

Comment on Ceruti et al. Temporal Changes in the Oxyhemoglobin Dissociation Curve of Critically Ill COVID-19 Patients. J. Clin. Med. 2022, 11, 788.

Ceruti et al. describe in their article very low standard half saturation pressures (P50) in COVID-19 patients, calculated with the Dash et al. equations. By using the Hill equation and Severinghaus‘ coefficients we obtained normal values. The authors who do not present a pathophysiological cause for their results should explain this discrepancy. Independent of the absolute values a continuous moderate decrease of P50 in the surviving patients might be of clinical importance.

Preparation and thermophysical study on a super stable copper oxide/deep eutectic solvent nanofluid

Nanofluid has gained vast attention as a novel heat transfer working fluid owing to its superiority in thermal conductivity and rheological properties. Meanwhile, the liquid range and the stability of nanofluids are of great significance since it dominates the utilization scope of a working fluid. In this work, with the aim at solving the poor stability associated with short liquid range of traditional nanofluids, a novel “one-step” preparation protocol was developed using Cu(OH)2 as a precursor and deep eutectic solvents (DESs) as dispersing medium. The as-prepared nanofluid bears an extraordinary static stability that can be kept for at least two months without observation of any sedimentation thanks to the in-situ formed Cu2O nanoparticle in DESs under a microwave irradiation condition and wide liquid range attributed to the low saturated pressure of DESs. Structural analysis, such as SEM, TEM, XRD, XPS and FTIR analysis, and thermophysical properties of the nanofluids were subject to a comprehensive study. Thermal conductivity analysis indicated that the presence of Cu2O nanoparticle slightly impacts the thermal conductivity when the mass fraction of the nanoparticle is small. Notably, this DESs based nanofluid features promising photothermal conversion that can reach 83.74% with the addition of 0.1 wt% Cu2O nanoparticle. This study provides an important avenue for the preparation of nanofluids with high static stability.

Experimental study of aviation kerosene engine with PJI system

The spark-ignition (SI) piston engine has become the main power source for unmanned aerial vehicles owing to its small size and large power/weight ratio. While gasoline is the commonly used fuel in SI engines, it affords poor safety and stability. Aviation kerosene is highly suitable as an alternative to gasoline; however, its high kinematic viscosity and low saturated vapour pressure afford poor evaporation and atomisation in SI engine. Moreover, aviation kerosene has a low octane number, and easy to cause knock, particularly in four-stroke engines. Those issue limits the wide use of kerosene in SI engines. In this study, the pre-chamber jet ignition (PJI) technology is used to suppress the knock of kerosene engine. The combustion characteristics of gasoline-SI, kerosene-SI and kerosene-PJI were compared and analysed. The variation law of indicated mean effective pressure (IMEP) at different speeds is obtained. It is found that PJI system can accelerate the flame propagation speed and shorten the combustion duration, and IMEP can be increased by 10%–27%. The experimental results show that PJI can optimise kerosene combustion to a certain extent and broaden its knock limit in SI engine. It is one of the effective ways to suppress knock in kerosene engine.

Angiotensin Converting Enzyme Inhibitors May Increase While Active Vitamin D May Decrease the Risk of Severe Pneumonia in SARS-CoV-2 Infected Patients with Chronic Kidney Disease on Maintenance Hemodialysis

The group most at risk of death due to COVID-19 are patients on maintenance hemodialysis (HD). The study aims to describe the clinical course of the early phase of SARS-CoV-2 infection and find predictors of the development of COVID-19 severe pneumonia in this population. This is a case series of HD nonvaccinated patients with COVID-19 stratified into mild pneumonia and severe pneumonia group according to the chest computed tomography (CT) pneumonia total severity score (TSS) on admission. Epidemiological, demographic, clinical, and laboratory data were obtained from hospital records. 85 HD patients with a mean age of 69.74 (13.19) years and dialysis vintage of 38 (14–84) months were included. On admission, 29.14% of patients had no symptoms, 70.59% reported fatigue followed by fever—44.71%, shortness of breath—40.0%, and cough—30.59%. 20% of the patients had finger oxygen saturation less than 90%. In 28.81% of patients, pulmonary parenchyma was involved in at least 25%. The factors associated with severe pneumonia include fever, low oxygen saturation and arterial partial pressure of oxygen, increased C-reactive protein and ferritin serum levels, low blood count of lymphocytes as well as chronic treatment with angiotensin converting enzyme inhibitors; while the chronic active vitamin D treatment was associated with mild pneumonia. In conclusion, even though nearly one-third of the patients were completely asymptomatic, while the remaining usually reported only single symptoms, a large percentage of them had extensive inflammatory changes at diagnosis with SARS-CoV-2 infection. We identified potential predictors of severe pneumonia, which might help individualize pharmacological treatment and improve clinical outcomes.

Rapid Carbon Dioxide Foaming of 3D Printed Thermoplastic Polyurethane Elastomers

Polymeric foam preparation using the carbon dioxide (CO2) foaming technique is fascinating. Until now, the CO2-based foaming process has been carried out for a long saturation time. Once it is possible to produce a polymeric foam in a low saturation time, it can enhance foam production. This study investigates the foaming behavior of 3D printed TPU samples with three different hardness values. The variation of infill density in 3D printed samples provides a macroporous range in the sample and creates a path for the gas molecules to reach the polymer. Such a gas flow path expands the foam processing technique to be carried out at low saturation time and pressure. The foaming process carried out here follows two steps: first, CO2 gas saturation in a high-pressure stainless-steel vessel; second, then hierarchical microporous generation by devising a thermodynamically unstable condition by placing the gas saturated sample in a hot water bath set up. The results showed that the increase in saturation time and pressure increases the expansion behavior of the foam samples, whereas an increase in infill density restricts the foam expansion behavior. The crystalline hard segment (HS) enhances the heterogeneous cell nucleation and reduces the shrinkage of the foam samples. The foam sample with low infill density showed low compression strength. It could be improved by filling the macroporous gap with hydrogel during printing. This hydrogel-packed low infill density foam showed an increased compression strength of 0.8 MPa at 80% strain than the neat foam sample (without hydrogel) 0.12 MPa at 80% strain, confirmed through the cyclic compression test. Hence, this 3D printing integrated subcritical solid-state foaming system offers unparalleled freedom to design and create foam and increase its production. The one-pot preparation of low-density higher compression strength foam using hydrogel makes this technique more feasible for high-end applications.

Experimental Study of Horizontal Flow Boiling Heat Transfer Coefficient and Pressure Drop of R134a from Subcooled Liquid Region to Superheated Vapor Region

For the past few years, research in the field of flow boiling heat transfer has gained immense popularity for unravelling the dominant mechanism responsible for controlling heat transfer and identifying a parametric trend for understanding the characteristics of flow boiling heat transfer. This has led to several assumptions and models for predicting heat transfer during flow boiling without any known generalized mechanism. This study therefore seeks to experimentally study the characteristics of heat transfer during flow boiling over a wide range but small increase in vapor quality from a single-phase subcooled region through to a two-phase superheated vapor region. The study was performed with an R134a refrigerant in a single horizontal circular stainless-steel smooth tube that had an internal diameter of 5 mm. In this experimental study, local heat transfer coefficients and frictional pressure drop were measured for low heat fluxes of 4.6–8.5 kW/m2, mass fluxes of 200–300 kg/(m2s), vapor quality from −0.1 to 1.2 and a low constant saturation pressure of 460 kPa. Flow patterns observed during the study were recorded with a high-speed camera at 2000 fps. In covering a wide range of vapor quality, a peak of heat transfer coefficient near a vapor quality of zero and a local minimum observed in the low vapor quality region were observed, and both were sensitive to heat flux and mildly sensitive to mass flux. Generally, at low vapor quality, the heat transfer coefficient deteriorated with vapor quality and this was sensitive to heat flux but insensitive to mass flux and vapor quality, indicating nucleate boiling dominance in low vapor quality regions. In high vapor quality regions, the heat transfer coefficient was sensitive to mass flux and insensitive to heat flux. This indicates the dominance of convective boiling. In the low vapor quality regions, the flow patterns observed were slug and intermittent, while in the high vapor quality region, annular and mist flow patterns were observed. Generally, frictional pressure drop increased with increasing mass flux and vapor quality in the two-phase region.

Ultra-Wide Range Pressure Sensor Based on a Microstructured Conductive Nanocomposite for Wearable Workout Monitoring.

Conventional flexible pressure sensors are not suitable for high-pressure applications due to their low saturation pressure. In this study, an ultra-wide range pressure sensor is designed based on the optimized microstructure of the polyimide/carbon nanotubes (PI/CNT) nanocomposite film. The sensing range of the pressure sensor is expanded by adopting polyimide (PI) with a high elastic modulus as a matrix material and its sensitivity is improved through functional sensing film with tip-flattened microdome arrays. As a result, the pressure sensor can measure a wide pressure range (≈ 0-3000kPa) and possesses the sensitivity of ≈ 5.66 × 10-3 -0.23 × 10-3 kPa-1 with high reliability and durability up to 1000 cycles. The proposed sensor is integrated into the hand and foot pressure monitoring systems for workout monitoring. The representative values of the pressure distribution in the hands and feet during the powerlifting are acquired and analyzed through Pearson's correlation coefficient (PCC). The analyzed results suggest that the pressure sensor can provide useful real-time information for healthcare and sports performance monitoring.

Effect of Young's modulus of active materials on ion transport through solid electrolyte in all-solid-state lithium-ion battery

An all-solid-state lithium-ion battery with sulfide solid electrolyte is expected to be operated and fabricated under pressure to achieve high ionic conductivity. However, the varying mechanical properties of the constituent materials of composite electrodes generate a non-uniform stress distribution, which affects the ionic conductivity. Moreover, because of the presence of various active materials with different Young's moduli, the correlation between the Young's modulus of the active material and ion-conduction characteristics of a composite electrode is considered. In this study, to elucidate the effect of the Young's modulus of the active material on the ionic conductivity of a composite electrode, electrochemical impedance spectroscopy measurements and finite element method stress simulations based on X-ray computed tomography images are performed for model composite electrodes. The model composite electrodes are fabricated by mixing the solid electrolyte with zirconia or nylon in different volumetric fractions. The experimental results demonstrate that a composite electrode containing an active material with lower Young's modulus exhibits a higher ionic conductivity and lower saturation pressure. The finite element method stress simulation indicates that the change in the ion-conduction characteristics originates from the stress concentration induced by the active material's Young's modulus and volumetric fraction.

The basaltic plinian eruption of the ~6 ka San Antonio Tephra and formation of the Masaya caldera, Nicaragua

Masaya is unusual for a basaltic caldera because it formed by piston-subsidence in response to large-volume magma withdrawal by highly explosive eruptions, i.e. in a fashion typical of silicic calderas. The first and most voluminous of the three explosive eruptions formed the 6 ka old basaltic San Antonio Tephra (SAT). This eruption is also unusual in that most of the 9 km3 DRE basaltic magma was discharged by a plinian eruption. The subsequent eruptions of the basaltic Masaya Triple Layer (MTL, 2.1 ka) and the Masaya Tuff/Ticuantepe Lapilli (MT-TIL, 1.9 ka) each discharged 2 km3 DRE magma and enlarged the Masaya caldera.The SAT consists of a lower sequence of alternating scoria lapilli and ash layers, interpreted as an alternation between more or less phreatomagmatically influenced fallout events. These are followed by two prominent well-sorted lapilli layers: the first one formed by a climactic plinian eruption whose column height reached 21–29 km and discharged most of the total erupted mass including about 35 Mt SO2. The second, lithic-rich lapilli layer probably formed by a phreatoplinian event when partial collapse of the magma chamber roof initiated increasing magma-water interaction which ultimately formed the upper sequence of phreatomagmatic cross-bedded surge deposits, accretionary lapilli-rich tuffs and a final fallout of dense lapilli. Phreatomagmatic activity may have been related to disruption of a hydrothermal system reflected in hydrothermally altered lithics, and/or by the caldera floor subsiding closer to the groundwater table.The bulk-rock chemical composition of the SAT is basaltic but the bimodal glass compositions demonstrate mixing of a basaltic with an andesitic melt probably in the conduit during eruption. The SAT basalt differentiated in a reservoir near the MOHO at 20 km depth by fractional crystallization of olivine, plagioclase, and minor clinopyroxene forming a tholeiitic fractionation trend. Minor intermediate-An plagioclase crystallized from the basaltic melt at H2O concentrations of about 2 wt% as measured by FTIR in melt inclusions. However, a key observation is that the melt inclusions are not in equilibrium with the high-An plagioclases hosting them. Re-equilibration of the inclusions requires initially higher water contents (about 5–6 wt%) which also fits the high Ba/La ~ 80 indicating input from the strongly hydrated subducting slab. Therefore, while the SAT magma evolved under hydrous conditions at depth, it was then stored at shallow level long enough to adjust to the low saturation pressure and to precipitate some intermediate-An plagioclase but still preserving its high temperature (around 1100 °C) and phenocryst-poor composition. Large overpressure due to connection to the deep-seated reservoir and water degassing during ascent limited the storage time at shallow level and drove the unusually intense and voluminous plinian-style eruption that facilitated piston-type collapse of the chamber roof.

Internal Nozzle Flow Simulations of the ECN Spray C Injector under Realistic Operating Conditions

<div class="section abstract"><div class="htmlview paragraph">In this study, three-dimensional large eddy simulations were performed to study the internal nozzle flow of the ECN Spray C diesel injector. Realistic nozzle geometry, full needle motion, and internal flow imaging data obtained from X-ray measurements were employed to initialize and validate the CFD model. The influence of injection pressure and fuel properties were investigated, and the effect of mesh size was discussed. The results agreed well with the experimental data of mass flow rate and correctly captured the flow structures inside the orifice. Simulations showed that the pressure drop near the sharp orifice inlet triggered flow separation, resulting in the ingestion of ambient gas into the orifice via a phenomenon known as hydraulic flip. At higher injection pressure, the pressure drop was more significant as the liquid momentum increased and the stream inertia was less prone to change its direction. Two fuels were tested in both experiments and simulations, namely iso-octane and n-dodecane. With the former, the gas species in the low-pressure region consisted of both fuel vapor and non-condensable gas. With n-dodecane, due to its low saturation pressure, fuel vapor was practically absent. Furthermore, it was found that fuel cavitation might not be the only phenomenon able to trigger flow separation, as “pseudo-cavitation” caused by non-condensable gas expansion played a similar role in promoting the conditions that led the flow to detach from the wall. Finally, it was found that a minimum mesh size of 10 μm within the orifice was sufficient to ensure the main flow features were captured. However, it was shown that finer meshes allowed for better resolution of the near-wall gas layer, resulting in more flow features to be resolved.</div></div>