Investigation Concerning the Aerothermodynamic Performance Perturbation of a 19MW Intercooled Air Compressor

2000 ◽  
Author(s):  
Inam U. Haq ◽  
Ali H. Al-Jameel ◽  
Khalid N. Al-Khalidi
Keyword(s):  
Critical Role ◽  
Cooling Water ◽  
Extended Period ◽  
Evaluation Study ◽  
Plant Production ◽  
Ambient Conditions ◽  
Heavy Load ◽  
Air Compressor ◽  
Compressor Surge ◽  
Condensed Water

This paper investigates the performance problem of a large capacity multistage centrifugal air compressor when operated continuously for an extended period of time without overhauling. The compressor flow constitutes fifty percent of the plant production and plays a critical role in meeting the annual contract capacity and can not tolerate performance instability due to high intercooler temperatures, ambient conditions and, fouling of the internal components. During a recent harsh summer operation, the compressor was undergone to surge many times and prompted to initiate a performance evaluation study to identify the cause(s) of surge and the extent of performance deterioration. High cooling water supply temperature and ambient conditions crippled the performance of the compressor. Engineering analysis identified the excessive accumulation of condensed water in the water chamber of the second intercooler as the most logical reason of the compressor surge during the instances of high ambient conditions i.e. relative humidity and temperature greater than 80% and 35°C, respectively. During heavy load of condensed water, the blockage and insufficient size of the condensate drain caused build up of water level in the water collecting chamber which offered instantaneous hindrance to airflow to the next section and, hence, led to the compressor surge. During normal ambient conditions, the overall performance of the compressor was found satisfactory when compared with the commissioning after a long term of continuous operation without maintenance.

Central mineralocorticoid receptor blockade decreases plasma TNF-α after coronary artery ligation in rats

2003 ◽  
Vol 284 (2) ◽  
pp. R328-R335 ◽  
Author(s):  
Joseph Francis ◽  
Robert M. Weiss ◽  
Alan Kim Johnson ◽  
Robert B. Felder
Keyword(s):  
Heart Failure ◽  
Central Nervous System ◽  
Nervous System ◽  
Mineralocorticoid Receptor ◽  
Critical Role ◽  
Evaluation Study ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Tnf Α ◽  
The Central Nervous System

The Randomized Aldactone Evaluation Study (RALES) demonstrated a substantial clinical benefit to blocking the effects of aldosterone (Aldo) in patients with heart failure. We recently demonstrated that the enhanced renal conservation of sodium and water in rats with heart failure can be reduced by blocking the central nervous system effects of Aldo with the mineralocorticoid receptor (MR) antagonist spironolactone (SL). Preliminary data from our laboratory suggested that central MR might contribute to another peripheral mechanism in heart failure, the release of proinflammatory cytokines. In the present study, SL (100 ng/h for 21 days) or ethanol vehicle (Veh) was administered via the 3rd cerebral ventricle to one group of rats after coronary ligation (CL) or sham CL (Sham) to induce congestive heart failure (CHF). In Veh-treated CHF rats, tumor necrosis factor-α (TNF-α) levels increased during day 1 and continued to increase throughout the 3-wk observation period. In CHF rats treated with SL, started 24 h after CL, TNF-α levels rose initially but retuned to control levels by day 5 after CL and remained low throughout the study. These findings suggest that activation of MR in the central nervous system plays a critical role in regulating TNF-α release in heart failure rats. Thus some of the beneficial effect of blocking MR in heart failure could be due at least in part to a reduction in TNF-α production.

Filmwise-to-Dropwise Condensation Transition Enabled by Patterned High Wetting Contrast

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Youmin Hou ◽  
Miao Yu ◽  
Xuemei Chen ◽  
Zuankai Wang
Keyword(s):  
Liquid Film ◽  
Droplet Growth ◽  
Pinning Force ◽  
Dropwise Condensation ◽  
Ambient Conditions ◽  
Spherical Droplet ◽  
Design And Optimization ◽  
Morphology Transition ◽  
Hydrophobic Coating ◽  
Condensed Water

Recent advances in condensing surfaces with hybrid architectures of superhydrophobic/hydrophilic patterns allow us to decrease the nucleation energy barrier and spatially control the water condensation. However, the condensed water is susceptible to the large pinning force of the hydrophilic area, leading to an ultimate flooding. Here, we demonstrate a hierarchical nanostructured surface with patterned high wetting contrast to achieve a natural transition from filmwise-to-dropwise condensation, which reconciles the existing problems. The energy-dispersive X-ray spectroscopy (EDX) indicates that the fluorinated hydrophobic coating conformably covers the nanostructures except for the tops of micropillars, which are covered by hydrophilic silicon dioxide (FIG 1), resulting in an extreme wetting contrast. Condensation on the hybrid surface was observed in the environmental scanning electron microscope (ESEM) and ambient conditions with controlled humidity. Water preferentially nucleates on the top of micropillars and exhibits a rapid droplet growth (FIG 2). The enhancement is attributed to the filmwise-to-dropwise transition induced by the unique architectures and wetting features of the hybrid surface (FIG 3). The water embryos initially nucleate on the hydrophilic tops and quickly grow to a liquid film covering the whole top area. Since the superhydrophobic surrounding confines the spreading of condensed water, the localized liquid film gradually transits to an isolated spherical droplet as it grows. Remarkably, the condensate morphology transition activates an unusual droplet self-propelling despite the presence of abundant hydrophilic patches. It is important to note that such coalescence-induced jumping is dependent on the size of hydrophilic patches, that is, for larger hydrophilic patches, the energy released by coalescence may not overcome the increased droplet pinning, resulting in an immobile coalescence (FIG 4). The droplet departure ensures the recurrence of filmwise-to-dropwise transition, thus prevents the water accumulation in continuous condensation. These visualizations reveal the undiscovered impact of heterogeneous wettability and architectures on the morphology transition of the condensed water, and provide important insights into the surface design and optimization for enhanced condensation.

Collecting Ethnographic Video Data for Policy Research

2019 ◽  
Vol 63 (3) ◽  
pp. 387-403 ◽  
Author(s):  
Joanne W. Golann ◽  
Zitsi Mirakhur ◽  
Thomas J. Espenshade
Keyword(s):  
Critical Role ◽  
Policy Research ◽  
Extended Period ◽  
Holistic Approach ◽  
Ethnographic Study ◽  
Video Data ◽  
Natural Environments ◽  
Home Video ◽  
Parent Child Interactions ◽  
Role Of Parents

Despite growing recognition of the critical role of parents in children’s early development, parenting education programs and interventions typically have had limited impacts on children’s outcomes. To design programs and policies that are more responsive to families’ needs and constraints, policymakers need a better understanding of the lived experiences of families. In this article, we argue that qualitative video-ethnographic approaches offer an innovative and useful supplement to policy researchers’ usual tool kit. Taking a holistic approach to parent–child interactions and filming families in their natural environments over an extended period provides policy researchers with new data to inform future parenting initiatives. To assist researchers interested in undertaking a video-ethnographic study, we discuss our experiences with the New Jersey Families Study, a 2-week, in-home video study of 21 families with a 2- to 4-year-old child. This is the first time anyone has attempted an in-home naturalistic observation of this breadth, intensity, or duration. We highlight the potential of this method for policy relevance along with its associated challenges.

scholarly journals Unraveling the complexity of iron oxides at high pressure and temperature: Synthesis of Fe5O6

2015 ◽  
Vol 1 (5) ◽  
pp. e1400260 ◽  
Author(s):  
Barbara Lavina ◽  
Yue Meng
Keyword(s):  
High Pressure ◽  
Iron Oxides ◽  
Critical Role ◽  
Ambient Conditions ◽  
Minor Phase ◽  
Planetary Interiors ◽  
High Pressure And Temperature ◽  
Systematic Behavior ◽  
Iron Coordination ◽  
Redox Equilibria

The iron-oxygen system is the most important reference of rocks’ redox state. Even as minor components, iron oxides can play a critical role in redox equilibria, which affect the speciation of the fluid phases chemical differentiation, melting, and physical properties. Until our recent finding of Fe4O5, iron oxides were assumed to comprise only the polymorphs of FeO, Fe3O4, and Fe2O3. Combining synthesis at high pressure and temperature with microdiffraction mapping, we have identified yet another distinct iron oxide, Fe5O6. The new compound, which has an orthorhombic structure, was obtained in the pressure range from 10 to 20 GPa upon laser heating mixtures of iron and hematite at ~2000 K, and is recoverable to ambient conditions. The high-pressure orthorhombic iron oxides Fe5O6, Fe4O5, and h-Fe3O4 display similar iron coordination geometries and structural arrangements, and indeed exhibit coherent systematic behavior of crystallographic parameters and compressibility. Fe5O6, along with FeO and Fe4O5, is a candidate key minor phase of planetary interiors; as such, it is of major petrological and geochemical importance. We are revealing an unforeseen complexity in the Fe-O system with four different compounds—FeO, Fe5O6, Fe4O5, and h-Fe3O4—in a narrow compositional range (0.75 < Fe/O < 1.0). New, finely spaced oxygen buffers at conditions of the Earth’s mantle can be defined.

Composite Repair Performance at Elevated Temperatures

2014 ◽  
Author(s):  
Chris Alexander ◽  
Jim Souza ◽  
Casey Whalen
Keyword(s):  
Composite Materials ◽  
Elevated Temperatures ◽  
Critical Role ◽  
Ambient Conditions ◽  
Composite Repair ◽  
Repair Materials ◽  
Performance Curves ◽  
Repair Systems ◽  
Composite Repairs

For the better part of the past 20 years composite materials have been used to repair damaged piping and pressurized components in plants, refineries, and pipelines. The use of composite materials has been accompanied by comprehensive research programs focused on the development and assessment of using composite technology for restoring integrity to damaged piping and pressurized components. Of particular interest are composite repair standards such as ISO 24817 and ASME PCC-2 that provide technical guidance in how to properly design composite repair systems. The vast body of research completed to date has involved assessments at ambient conditions; however, at the present time there is significant interest in evaluating the performance of composite repair materials at elevated temperatures. This paper is focused on the topic of high temperature composite repairs and addresses the critical role of utilizing temperature-based mechanical properties to establish a composite repair design. The backbone of this effort is the development of composite performance curves that correlate change in strength as a function of temperature. A discussion on supporting full-scale pressure test results are included, along with guidance for users in how to properly design composite repair systems for applications at elevated temperatures.

scholarly journals Ab Initio Thermodynamics Reveals the Nanocomposite Structure of Ferrihydrite

2021 ◽  
Author(s):  
Michel Sassi ◽  
Anne Chaka ◽  
Kevin Rosso
Keyword(s):  
Ab Initio ◽  
Water Pressure ◽  
Critical Role ◽  
Ambient Conditions ◽  
Structural Water ◽  
X Ray ◽  
Distinct Structure ◽  
Wide Range ◽  
Lower Temperature ◽  
Individual Nanoparticles

Abstract Ferrihydrite is a poorly crystalline iron oxyhydroxide nanomineral that serves a critical role as the most bioavailable form of ferric iron for living systems. However, its atomic structure and composition remain unclear due in part to ambiguities in interpretation of X-ray scattering results. Prevailing models so far have not considered the prospect that at the level of individual nanoparticles multiple X-ray indistinguishable phases could coexist. Using ab initio thermodynamics we show that ferrihydrite is likely a nanocomposite of distinct structure types whose distribution depends on particle size, temperature, and hydration. Nanoparticles of two contrasting single-phase ferrihydrite models of Michel and Manceau are here shown to be thermodynamically equivalent across a wide range of temperature and pressure conditions despite differences in their structural water content. Higher temperature and water pressure favor the formation of the former, while lower temperature and water pressure favor the latter. For aqueous suspensions at ambient conditions, their coexistence is maximal for particle sizes up to 12 nm. The predictions can be connected to and help resolve different observations in various experiments.

Toshiba's Creative Accounting for Construction Contracts

2018 ◽  
Vol 33 (3) ◽  
pp. 117-134 ◽  
Author(s):  
Amitabh Dugar ◽  
Mahendra R. Gujarathi
Keyword(s):  
Organizational Culture ◽  
Critical Role ◽  
Extended Period ◽  
Senior Management ◽  
Revenue Recognition ◽  
Financial Reports ◽  
Case Assignment ◽  
Construction Contracts ◽  
Creative Accounting

ABSTRACT This case aims to help you understand how a world-known Japanese conglomerate—Toshiba Corporation—managed its earnings using the percentage-of-completion method to account for construction contracts in its Energy and Infrastructure division. In response to inquiries from Japan's Securities and Exchange Surveillance Commission (SESC) and internal investigations, Toshiba restated its earnings for an extended period (2008–2014) by the staggering amount of $1.86 billion. Twenty-one percent of this amount related to its improper accounting for construction contracts. The case requires you to research authoritative accounting literature, evaluate Toshiba's accounting practices, and determine which GAAP-compliant procedures Toshiba should have followed. The case assignment intends to improve your ability to (1) identify, interpret, and apply the new revenue recognition standard (ASC 606), (2) appreciate the distinction between a company's stated accounting policies and their implementation, (3) recognize the importance of estimates and judgments in the accounting process, and (4) understand the critical role played by the senior management and organizational culture in the assurance of integrity in financial reports.

High-performance perovskite/Cu(In,Ga)Se2 monolithic tandem solar cells

Science ◽  
2018 ◽  
Vol 361 (6405) ◽  
pp. 904-908 ◽  
Author(s):  
Qifeng Han ◽  
Yao-Tsung Hsieh ◽  
Lei Meng ◽  
Jyh-Lih Wu ◽  
Pengyu Sun ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Efficiency ◽  
Short Circuit ◽  
Critical Role ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Transport Layer ◽  
Ambient Conditions ◽  
Photovoltaic Properties ◽  
Tandem Solar Cells

The combination of hybrid perovskite and Cu(In,Ga)Se2 (CIGS) has the potential for realizing high-efficiency thin-film tandem solar cells because of the complementary tunable bandgaps and excellent photovoltaic properties of these materials. In tandem solar device architectures, the interconnecting layer plays a critical role in determining the overall cell performance, requiring both an effective electrical connection and high optical transparency. We used nanoscale interface engineering of the CIGS surface and a heavily doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) hole transport layer between the subcells that preserves open-circuit voltage and enhances both the fill factor and short-circuit current. A monolithic perovskite/CIGS tandem solar cell achieved a 22.43% efficiency, and unencapsulated devices under ambient conditions maintained 88% of their initial efficiency after 500 hours of aging under continuous 1-sun illumination.

Paper 3: The Effect of Ambient and Environmental Atmospheric Conditions

1969 ◽  
Vol 184 (16) ◽  
pp. 18-24 ◽  
Author(s):  
W. Lowe
Keyword(s):  
Diesel Engines ◽  
Cooling Water ◽  
Engine Performance ◽  
International Standards ◽  
Atmospheric Conditions ◽  
Ambient Conditions ◽  
Turbo Charger ◽  
Air Cooler ◽  
Air Intake ◽  
Charge Cooling

The basis of existing national and international standards for derating naturally aspirated and turbo-charged diesel engines for temperature, altitude, and humidity is recapitulated. The effect of site ambient conditions on the permissible rating of modern turbo-charged and charge-air cooled engines, with fixed and rematched turbo-chargers, is discussed. The effect of turbo-charger and charge-air cooler limitations on the engine rating is examined, including the use of air-to-air charge cooling. Consideration is given to the installation details which affect the engine performance, e.g. air-intake temperature, cooling water, etc.

Demonstration of Bleed Air Recirculation System to Improve Part Load Efficiency of Solar Mars® 100 DLE Industrial Gas Turbine

2018 ◽  
Author(s):  
Luke Cowell ◽  
Simon Reynolds ◽  
Tim Caron ◽  
Donghui Zhang
Keyword(s):  
Gas Turbines ◽  
Flame Temperature ◽  
Heat Rate ◽  
Ambient Conditions ◽  
Engine Exhaust ◽  
Part Load ◽  
Air Inlet ◽  
Recirculation System ◽  
Compressor Surge ◽  
Site Evaluation

On two-shaft DLE (Dry Low Emissions) gas turbines compressor air is often bled off the combustor housing to control the combustor flame temperature for part load emissions management. The bleed air is typically directed into the exhaust ducting, bypassing the turbine, causing engine efficiency to decrease. A prototype bleed air recirculation system was fitted onto a compressor package in the field that redirects bleed flow from the engine exhaust to the air inlet to raise the air temperature entering the engine. This system is designed to reduce the amount of bleed air required at a given ambient operating condition, while not compromising emissions, to increase part load efficiency. The bleed air recirculation system was designed, built, installed, and tested on a Mars 16000S compressor package at a station in northern Pennsylvania. A control algorithm was developed and validated to control bleed air recirculation so that package durability was not impacted. Over an evaluation period of 12 months, no significant durability issues or degradation were noted. The on-site evaluation indicated that the engine’s heat rate is significantly improved by using bleed air recirculation. The heat rate was reduced by as much as 7% during testing at site with a strong dependency on the engine operating load and ambient temperature. As predicted the best case was demonstrated at 50% load and at colder ambient conditions. The NOx emissions were also improved with bleed air recirculation. In addition, using this system extended the range of low emissions operation to lower loads. No effects on compressor surge or sound emissions were detected.

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