CFD study of ejector flow behavior in a blast furnace gas galvanizing plant

Science.gov (United States)

Besagni, Giorgio; Mereu, Riccardo; Inzoli, Fabio

2015-02-01

In recent years, there has been a growing interest toward Blast Furnace Gas (BFG) as a low-grade energy source for industrial furnaces. This paper considers the revamping of a galvanic plant furnace converted to BFG from natural gas. In the design of the new system, the ejector on the exhaust line is a critical component. This paper studies the flow behavior of the ejector using a Computational Fluid Dynamics (CFD) analysis. The CFD model is based on a 3D representation of the ejector, using air and exhaust gases as working fluids. This paper is divided in three parts. In the first part, the galvanic plant used as case study is presented and discussed, in the second part the CFD approach is outlined, and in the third part the CFD approach is validated using experimental data and the numerical results are presented and discussed. Different Reynolds-Averaged Navier-Stokes (RANS) turbulence models ( k-ω SST and k-ɛ Realizable) are evaluated in terms of convergence capability and accuracy in predicting the pressure drop along the ejector. Suggestions for future optimization of the system are also provided.

Shock circle model for ejector performance evaluation

International Nuclear Information System (INIS)

Zhu, Yinhai; Cai, Wenjian; Wen, Changyun; Li, Yanzhong

2007-01-01

In this paper, a novel shock circle model for the prediction of ejector performance at the critical mode operation is proposed. By introducing the 'shock circle' at the entrance of the constant area chamber, a 2D exponential expression for velocity distribution is adopted to approximate the viscosity flow near the ejector inner wall. The advantage of the 'shock circle' analysis is that the calculation of ejector performance is independent of the flows in the constant area chamber and diffuser. Consequently, the calculation is even simpler than many 1D modeling methods and can predict the performance of critical mode operation ejectors much more accurately. The effectiveness of the method is validated by two experimental results reported earlier. The proposed modeling method using two coefficients is shown to produce entrainment ratio, efficiency and coefficient of performance (COP) accurately and much closer to experimental results than those of 1D analysis methods

Experimental investigation on predictive models for motive flow calculation through ejectors for transcritical CO2 heat pumps

Science.gov (United States)

Boccardi, G.; Lillo, G.; Mastrullo, R.; Mauro, A. W.; Saraceno, L.; Pieve, M.; Trinchieri, R.

2017-11-01

Nowadays, air conditioning systems, especially those used in residential and office buildings, contribute largely to the energy consumptions and to the direct and indirect emissions of greenhouse gases. Carbon dioxide (CO2) is an interesting option to replace traditional HFCs in vapor compression systems, due to its environmentally friendly characteristics: zero ODP and extremely low GWP. In the case of heat pumps, the use of ejection systems for the expansion phase can contribute to recovery a fraction of the mechanical energy otherwise dissipated as friction, bringing to significant benefits in terms of performance. Currently, at the laboratory DTE-PCU-SPCT of the research center ENEA (Casaccia) in cooperation with the Industrial Engineering Department of Federico II University of Naples, a project is in progress, in order to evaluate experimentally the effect of several ejectors geometries on the global performance of a CO2 heat pump working with a transcritical cycle. As a part of this project, measurements of the motive flow mass flow rate have been carried out, in transcritical CO2 conditions. The ejector sizing is a crucial point for the balancing of components and the correct operation of the CO2 heat pump and therefore the availability of reliable calculation methods for the motive flowrate would be useful. This paper presents the results obtained by a comparison between the new experimental data and the predictions of some predictive semi-empirical correlations available in the open literature for transcritical CO2 conditions. Their predictions are analyzed as a function of the main physical parameters of the process to assess their reliability compared to the experimental data. Based on these indications and of the available experimental data, a new semi-empirical correlations and a calculation method based on the hypothesis of isentropic and choked two-phase flow are presented.

Rotary wave-ejector enhanced pulse detonation engine

Science.gov (United States)

Nalim, M. R.; Izzy, Z. A.; Akbari, P.

2012-01-01

The use of a non-steady ejector based on wave rotor technology is modeled for pulse detonation engine performance improvement and for compatibility with turbomachinery components in hybrid propulsion systems. The rotary wave ejector device integrates a pulse detonation process with an efficient momentum transfer process in specially shaped channels of a single wave-rotor component. In this paper, a quasi-one-dimensional numerical model is developed to help design the basic geometry and operating parameters of the device. The unsteady combustion and flow processes are simulated and compared with a baseline PDE without ejector enhancement. A preliminary performance assessment is presented for the wave ejector configuration, considering the effect of key geometric parameters, which are selected for high specific impulse. It is shown that the rotary wave ejector concept has significant potential for thrust augmentation relative to a basic pulse detonation engine.

CFD Analysis of Nozzle Exit Position Effect in Ejector Gas Removal System in Geothermal Power Plant

Directory of Open Access Journals (Sweden)

Setyo Nugroho

2015-06-01

Full Text Available The single stage ejector is used to extract the Non CondensableGas (NCG in the condenser using the working principle of the Venturi tube. Three dimensional computational simulation of the ejector according to the operating conditions was conducted to determine the flow in the ejector. Motive steam entering through the convergent – divergent nozzle with increasing flow velocity so that the low pressure exist around the nozzle. Comparison is done also in a two dimensional simulation to know the differences occurring phenomena and flow inside ejector. Different simulation results obtained between two dimensional and three dimensional simulation. Reverse flow which occurs in the mixing chamber made the static pressure in the area has increased dramatically. Then the variation performed on Exit Nozzle Position (NXP to determine the changes of the flow of the NCG and the vacuum level of the ejector. Keywords: Ejector, NCG, CFD, Compressible flow.

Evaluation of ejector performance for an organic Rankine cycle combined power and cooling system

International Nuclear Information System (INIS)

Zhang, Kun; Chen, Xue; Markides, Christos N.; Yang, Yong; Shen, Shengqiang

2016-01-01

Highlights: • The performance of an ejector in an Organic Rankine Cycle and ejector refrigeration cycle (EORC) was evaluated. • The achieved entrainment ratio and COP of an EORC system is affected significantly by the evaporator conditions (such as temperature, pressure and flow rate). • An optimum distance of 6 mm nozzle position was found that ensures a maximum entrainment ratio, the best efficiency and lowest loss in the ejector. • A reduced total pressure loss between the nozzle inlet and exit leads to a lower energy loss, a higher entrainment ratio and better overall ejector performance. - Abstract: Power-generation systems based on organic Rankine cycles (ORCs) are well suited and increasingly employed in the conversion of thermal energy from low temperature heat sources to power. These systems can be driven by waste heat, for example from various industrial processes, as well as solar or geothermal energy. A useful extension of such systems involves a combined ORC and ejector-refrigeration cycle (EORC) that is capable, at low cost and complexity, of producing useful power while having a simultaneous capacity for cooling that is highly desirable in many applications. A significant thermodynamic loss in such a combined energy system takes place in the ejector due to unavoidable losses caused by irreversible mixing in this component. This paper focuses on the flow and transport processes in an ejector, in order to understand and quantify the underlying reasons for these losses, as well as their sensitivity to important design parameters and operational variables. Specifically, the study considers, beyond variations to the geometric design of the ejector, also the role of changing the external conditions across this component and how these affect its performance; this is not only important in helping develop ejector designs in the first instance, but also in evaluating how the performance may shift (in fact, deteriorate) quantitatively when the device

An Integrated Lumped Parameter-CFD approach for off-design ejector performance evaluation

International Nuclear Information System (INIS)

Besagni, Giorgio; Mereu, Riccardo; Chiesa, Paolo; Inzoli, Fabio

2015-01-01

Highlights: • We validate a CFD approach for a convergent nozzle ejector using global and local measurement. • We evaluate seven RANS turbulence models for convergent nozzle ejector. • We introduce a lumped parameter model for on-design and off-design ejector performance evaluation. • We analyze the relationship between local flow behavior and lumped parameters of the model. • We discuss how to improve predicting capabilities of the model by variable parameters calibrated on CFD simulations. - Abstract: This paper presents an Integrated Lumped Parameter Model-Computational Fluid-Dynamics approach for off-design ejector performance evaluation. The purpose of this approach is to evaluate the entrainment ratio, for a fixed geometry, in both on-design and off-design operating conditions. The proposed model is based on a Lumped Parameter Model (LPM) with variable ejector component efficiencies provided by CFD simulations. The CFD results are used for developing maps for ejector component efficiencies in a broad range of operating conditions. The ejector component efficiency maps couple the CFD and the LPM techniques for building an Integrated LPM-CFD approach. The proposed approach is demonstrated for a convergent nozzle ejector and the paper is structured in four parts. At first, the CFD approach is validated by global and local data and seven Reynolds Averaged Navier Stokes (RANS) turbulence models are compared: the k–ω SST showed good performance and was selected for the rest of the analysis. At second, a Lumped Parameter Model (LPM) for subsonic ejector is developed and the ejector component efficiencies have been defined. At third, the CFD approach is used to investigate the flow field, to analyze its influence on ejector component efficiencies and to propose efficiency correlations and maps linking ejector component efficiencies and local flow quantities. In the last part, the efficiency maps are embedded into the lumped parameter model, thus creating

Numerical simulation of Venturi ejector reactor in yellow phosphorus purification system

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiao-jing; Tang, Lei, E-mail: alanleyfly@gmail.com; Jiang, Zeng

2014-03-15

Highlights: • Venturi ejector reactor is used in yellow phosphorus purification system to obtain high purity phosphorus. • We study the changes of vacuum region and the performances of Venturi ejector reactor with different operating pressure. • The whole study is aim to investigate the operating conditions, rather than to find out the small details of the chemical reaction. - Abstract: A novel type of Venturi ejector reactor, which was used in a pilot plant test in a factory in Guizhou in China, was developed to overcome the insufficiency of chemical reaction in the stirred-tank reactor in yellow phosphorus purification system. The effects of different working medium, the changes of vacuum region, and the performances of the Venturi ejector reactor with different operating pressure were investigated by FLUENT. Results show that the absolute value of vacuum pressure of single-phase flow was smaller than two-phase flow at the same operating conditions, which meat two-phase flow has a higher suction capability. Reflow phenomena occurred near the exit of suction pipe and nozzle. The former reflow which leads to energy loss of vacuum region was undesirable, and the latter was beneficial to the dispersion of liquid yellow phosphorus. With a flow rate ratio below 0.45, the performance of the Venturi ejector reactor was effective. By adjusting the operating pressure, a proper flow rate ratio could be satisfied to meet the production needs in yellow phosphorus purification system.

Zero-Sum Flows in Designs

International Nuclear Information System (INIS)

Akbari, S.; Khosrovshahi, G.B.; Mofidi, A.

2010-07-01

Let D be a t-(v, k, λ) design and let N i (D), for 1 ≤ i ≤ t, be the higher incidence matrix of D, a (0, 1)-matrix of size (v/i) x b, where b is the number of blocks of D. A zero-sum flow of D is a nowhere-zero real vector in the null space of N 1 (D). A zero-sum k-flow of D is a zero-sum flow with values in {±,...,±(k-1)}. In this paper we show that every non-symmetric design admits an integral zero-sum flow, and consequently we conjecture that every non-symmetric design admits a zero-sum 5-flow. Similarly, the definition of zero-sum flow can be extended to N i (D), 1 ≤ i ≤ t. Let D = t-(v,k, (v-t/k-t)) be the complete design. We conjecture that N t (D) admits a zero-sum 3-flow and prove this conjecture for t = 2. (author)

A Determinate Model of Thrust-Augmenting Ejectors

Science.gov (United States)

Whitley, N.; Krothapalli, A.; van Dommelen, L.

1996-01-01

A theoretical analysis of the compressible flow through a constant-area jet-engine ejector in which a primary jet mixes with ambient fluid from a uniform free stream is pursued. The problem is reduced to a determinate mathematical one by prescribing the ratios of stagnation properties between the primary and secondary flows. For some selections of properties and parameters more than one solution is possible and the meaning of these solutions is discussed by means of asymptotic expansions. Our results further show that while under stationary conditions the thrust-augmentation ratio assumes a value of 2 in the large area-ratio limit, for a free-stream Mach number greater than 0.6 very little thrust augmentation is left. Due to the assumptions made, the analysis provides idealized values for the thrust-augmentation ratio and the mass flux entrainment factor.

Research on CO2 ejector component efficiencies by experiment measurement and distributed-parameter modeling

International Nuclear Information System (INIS)

Zheng, Lixing; Deng, Jianqiang

2017-01-01

Highlights: • The ejector distributed-parameter model is developed to study ejector efficiencies. • Feasible component and total efficiency correlations of ejector are established. • New efficiency correlations are applied to obtain dynamic characteristics of EERC. • More suitable fixed efficiency value can be determined by the proposed correlations. - Abstract: In this study we combine the experimental measurement data and the theoretical model of ejector to determine CO 2 ejector component efficiencies including the motive nozzle, suction chamber, mixing section, diffuser as well as the total ejector efficiency. The ejector is modeled utilizing the distributed-parameter method, and the flow passage is divided into a number of elements and the governing equations are formulated based on the differential equation of mass, momentum and energy conservation. The efficiencies of ejector are investigated under different ejector geometric parameters and operational conditions, and the corresponding empirical correlations are established. Moreover, the correlations are incorporated into a transient model of transcritical CO 2 ejector expansion refrigeration cycle (EERC) and the dynamic simulations is performed based on variable component efficiencies and fixed values. The motive nozzle, suction chamber, mixing section and diffuser efficiencies vary from 0.74 to 0.89, 0.86 to 0.96, 0.73 to 0.9 and 0.75 to 0.95 under the studied conditions, respectively. The response diversities of suction flow pressure and discharge pressure are obvious between the variable efficiencies and fixed efficiencies referring to the previous studies, while when the fixed value is determined by the presented correlations, their response differences are basically the same.

Air ejector augmented compressed air energy storage system

Science.gov (United States)

Ahrens, F.W.; Kartsounes, G.T.

Energy is stored in slack demand periods by charging a plurality of underground reservoirs with air to the same peak storage pressure, during peak demand periods throttling the air from one storage reservoir into a gas turbine system at a constant inlet pressure until the air presure in the reservoir falls to said constant inlet pressure, thereupon permitting air in a second reservoir to flow into said gas turbine system while drawing air from the first reservoir through a variable geometry air ejector and adjusting said variable geometry air ejector, said air flow being essentially at the constant inlet pressure of the gas turbine system.

Turbulent Mixing of Primary and Secondary Flow Streams in a Rocket-Based Combined Cycle Engine

Science.gov (United States)

Cramer, J. M.; Greene, M. U.; Pal, S.; Santoro, R. J.; Turner, Jim (Technical Monitor)

2002-01-01

This viewgraph presentation gives an overview of the turbulent mixing of primary and secondary flow streams in a rocket-based combined cycle (RBCC) engine. A significant RBCC ejector mode database has been generated, detailing single and twin thruster configurations and global and local measurements. On-going analysis and correlation efforts include Marshall Space Flight Center computational fluid dynamics modeling and turbulent shear layer analysis. Potential follow-on activities include detailed measurements of air flow static pressure and velocity profiles, investigations into other thruster spacing configurations, performing a fundamental shear layer mixing study, and demonstrating single-shot Raman measurements.

Control-Volume Analysis Of Thrust-Augmenting Ejectors

Science.gov (United States)

Drummond, Colin K.

1990-01-01

New method of analysis of transient flow in thrust-augmenting ejector based on control-volume formulation of governing equations. Considered as potential elements of propulsion subsystems of short-takeoff/vertical-landing airplanes.

Parallel Work of CO2 Ejectors Installed in a Multi-Ejector Module of Refrigeration System

Science.gov (United States)

Bodys, Jakub; Palacz, Michal; Haida, Michal; Smolka, Jacek; Nowak, Andrzej J.; Banasiak, Krzysztof; Hafner, Armin

2016-09-01

A performance analysis on of fixed ejectors installed in a multi-ejector module in a CO2 refrigeration system is presented in this study. The serial and the parallel work of four fixed-geometry units that compose the multi-ejector pack was carried out. The executed numerical simulations were performed with the use of validated Homogeneous Equilibrium Model (HEM). The computational tool ejectorPL for typical transcritical parameters at the motive nozzle were used in all the tests. A wide range of the operating conditions for supermarket applications in three different European climate zones were taken into consideration. The obtained results present the high and stable performance of all the ejectors in the multi-ejector pack.

Computational study of variable area ejector rocket flowfields

Science.gov (United States)

Etele, Jason

Access to space has always been a scientific priority for countries which can afford the prohibitive costs associated with launch. However, the large scale exploitation of space by the business community will require the cost of placing payloads into orbit be dramatically reduced for space to become a truly profitable commodity. To this end, this work focuses on a next generation propulsive technology called the Rocket Based Combined Cycle (RBCC) engine in which rocket, ejector, ramjet, and scramjet cycles operate within the same engine environment. Using an in house numerical code solving the axisymmetric version of the Favre averaged Navier Stokes equations (including the Wilcox ko turbulence model with dilatational dissipation) a systematic study of various ejector designs within an RBCC engine is undertaken. It is shown that by using a central rocket placed along the axisymmetric axis in combination with an annular rocket placed along the outer wall of the ejector, one can obtain compression ratios of approximately 2.5 for the case where both the entrained air and rocket exhaust mass flows are equal. Further, it is shown that constricting the exit area, and the manner in which this constriction is performed, has a significant positive impact on the compression ratio. For a decrease in area of 25% a purely conical ejector can increase the compression ratio by an additional 23% compared to an equal length unconstricted ejector. The use of a more sharply angled conical section followed by a cylindrical section to maintain equivalent ejector lengths can further increase the compression ratio by 5--7% for a total increase of approximately 30%.

Study of an ejector-absorption refrigeration cycle with an adaptable ejector nozzle for different working conditions

International Nuclear Information System (INIS)

Vereda, C.; Ventas, R.; Lecuona, A.; Venegas, M.

2012-01-01

Highlights: ► An absorption refrigeration cycle with an ejector device at the absorber inlet is presented. ► This cycle is able to reduce up to 9 °C the temperature of onset of refrigerant generation without extra energy consumption. ► At very low driving temperatures it allows increasing the cooling capacity. ► The ejector device proposed has a partially variable geometry and we study its influence on the cycle performances. -- Abstract: This paper presents a numerical model of an ejector-absorption (single-effect) refrigeration cycle with ammonia–lithium nitrate solution as working fluid, operating under steady-state conditions. In this cycle, the ejector is located at the absorber inlet replacing the solution expansion valve. The liquid–gas ejector entrains refrigerant vapor from the evaporator; this way the absorber pressure becomes higher than the evaporator pressure without any additional energy consumption. The objective of this numerical model is to evaluate the influence of the ejector geometry on the cycle performances and to determine the range of the heat source temperature in which it is convenient to use a practical ejector in the absorption cycle. The simulation is based on UA-ΔT lm models for separate heat transfer regions in a novel implementation using plate-type heat exchangers and this way the results are offered as a function of the external temperatures. This study focuses on evaluating the feasibility of an ejector whose nozzle area is adjustable while the rest of the ejector dimensions are fixed, thus being more feasible than complete variable geometry ejectors. The cycle performance is reported for different mixing tube constant diameters. Results of the simulation show that the use of an ejector allows, among others, to decrease the activation temperature approximately 9 °C in respect to the conventional single-effect absorption cycle and increasing the COP for moderate temperatures. The variable ejector nozzle geometry is

Study of an innovative ejector heat pump-boosted district heating system

International Nuclear Information System (INIS)

Zhang, Bo; Wang, Yuanchao; Kang, Lisha; Lv, Jinsheng

2013-01-01

An Ejector heat pump-boosted District Heating (EDH) system is proposed to improve the heating capacity of existing district heating systems with Combined Heat and Power (CHP). In the EDH, two ejector heat pumps are installed: a primary heat pump (HP 1 ) at the heating station and a secondary heat pump (HP 2 ) at the heating substation. With the EDH, the low-grade waste heat from circulating cooling water in the CHP is recycled and the temperature difference between the water supply and the return of the primary heating network is increased. A thermodynamic model was provided. An experimental study was carried out for both HP 1 and HP 2 to verify the predicting performance. The results show that the COP of HP 1 can reach 1.5–1.9, and the return water temperature of the primary heating network could be decreased to 35 °C with HP 2 . A typical case study for the EDH was analyzed. -- Highlights: • An ejector heat pump-boosted district heating (EDH) is proposed. • The 1st ejector heat pump in EDH recycles heat from cooling water of the CHP. • The 2nd ejector heat pump in EDH boosts the thermal energy utilization of the primary heating network. • Modeling and experimental studies are presented

Steam jet ejectors are examined automatically

International Nuclear Information System (INIS)

Lardiere, C.

2013-01-01

Steam jet ejectors are used in the nuclear industry particularly for the transfer of radioactive fluids. Their working is based on the Venturi effect and the conservation of energy. A steam ejector can be considered as a thermodynamical pump without mobile parts. The Descote enterprise manufactures a broad range of steam jet ejectors and the characterization and testing of the steam ejectors was made manually and empirically so far. A new test bench has been designed, the tests are led automatically and allow a more accurate characterization and optimization of the steam jet ejectors. (A.C.)

Simplified ejector model for control and optimization

International Nuclear Information System (INIS)

Zhu Yinhai; Cai Wenjian; Wen Changyun; Li Yanzhong

2008-01-01

In this paper, a simple yet effective ejector model for a real time control and optimization of an ejector system is proposed. Firstly, a fundamental model for calculation of ejector entrainment ratio at critical working conditions is derived by one-dimensional analysis and the shock circle model. Then, based on thermodynamic principles and the lumped parameter method, the fundamental ejector model is simplified to result in a hybrid ejector model. The model is very simple, which only requires two or three parameters and measurement of two variables to determine the ejector performance. Furthermore, the procedures for on line identification of the model parameters using linear and non-linear least squares methods are also presented. Compared with existing ejector models, the solution of the proposed model is much easier without coupled equations and iterative computations. Finally, the effectiveness of the proposed model is validated by published experimental data. Results show that the model is accurate and robust and gives a better match to the real performances of ejectors over the entire operating range than the existing models. This model is expected to have wide applications in real time control and optimization of ejector systems

Determinants of systemic zero-flow arterial pressure.

Science.gov (United States)

Brunner, M J; Greene, A S; Sagawa, K; Shoukas, A A

1983-09-01

Thirteen pentobarbital-anesthetized dogs whose carotid sinuses were isolated and perfused at a constant pressure were placed on total cardiac bypass. With systemic venous pressure held at 0 mmHg (condition 1), arterial inflow was stopped for 20 s at intrasinus pressures of 50, 125, and 200 mmHg. Zero-flow arterial pressures under condition 1 were 16.2 +/- 1.3 (SE), 13.8 +/- 1.1, and 12.5 +/- 0.8 mmHg, respectively. In condition 2, the venous outflow tube was clamped at the instant of stopping the inflow, causing venous pressure to rise. The zero-flow arterial pressures were 19.7 +/- 1.3, 18.5 +/- 1.4, and 16.4 +/- 1.2 mmHg for intrasinus pressures of 50, 125, and 200 mmHg, respectively. At all levels of intrasinus pressure, the zero-flow arterial pressure in condition 2 was higher (P less than 0.005) than in condition 1. In seven dogs, at an intrasinus pressure of 125 mmHg, epinephrine increased the zero-flow arterial pressure by 3.0 mmHg, whereas hexamethonium and papaverine decreased the zero-flow arterial pressure by 2 mmHg. Reductions in the hematocrit from 52 to 11% resulted in statistically significant changes (P less than 0.01) in zero-flow arterial pressures. Thus zero-flow arterial pressure was found to be affected by changes in venous pressure, hematocrit, and vasomotor tone. The evidence does not support the literally interpreted concept of the vascular waterfall as the model for the finite arteriovenous pressure difference at zero flow.

Parametric Study of Pulse-Combustor-Driven Ejectors at High-Pressure

Science.gov (United States)

Yungster, Shaye; Paxson, Daniel E.; Perkins, Hugh D.

2015-01-01

Pulse-combustor configurations developed in recent studies have demonstrated performance levels at high-pressure operating conditions comparable to those observed at atmospheric conditions. However, problems related to the way fuel was being distributed within the pulse combustor were still limiting performance. In the first part of this study, new configurations are investigated computationally aimed at improving the fuel distribution and performance of the pulse-combustor. Subsequent sections investigate the performance of various pulse-combustor driven ejector configurations operating at highpressure conditions, focusing on the effects of fuel equivalence ratio and ejector throat area. The goal is to design pulse-combustor-ejector configurations that maximize pressure gain while achieving a thermal environment acceptable to a turbine, and at the same time maintain acceptable levels of NOx emissions and flow non-uniformities. The computations presented here have demonstrated pressure gains of up to 2.8%.

Numerical Investigation of a Liquid-Gas Ejector Used for Shipping Ballast Water Treatment

Directory of Open Access Journals (Sweden)

Xueguan Song

2014-01-01

Full Text Available Shipping ballast water can have significant ecological and economic impacts on aquatic ecosystems. Currently, water ejectors are widely used in marine applications for ballast water treatment owing to their high suction capability and reliability. In this communication, an improved ballast treatment system employing a liquid-gas ejector is introduced to clear the ballast water to reduce environmental risks. Commonly, the liquid-gas ejector uses ballast water as the primary fluid and chemical ozone as the secondary fluid. In this study, high-pressure water and air, instead of ballast water and ozone, are considered through extensive numerical and experimental research. The ejector is particularly studied by a steady three-dimensional multiphase computational fluid dynamics (CFD analysis with commercial software ANSYS-CFX 14.5. Different turbulence models (including standard k-ε, RNG k-ε, SST, and k-ω with different grid size and bubble size are compared extensively and the experiments are carried out to validate the numerical design and optimization. This study concludes that the RNG k-ε turbulence model is the most efficient and effective for the ballast water treatment system under consideration and simple change of nozzle shape can greatly improve the ejector performance under high back pressure conditions.

Ejector-Enhanced, Pulsed, Pressure-Gain Combustor

Science.gov (United States)

Paxson, Daniel E.; Dougherty, Kevin T.

2009-01-01

An experimental combination of an off-the-shelf valved pulsejet combustor and an aerodynamically optimized ejector has shown promise as a prototype of improved combustors for gas turbine engines. Despite their name, the constant pressure combustors heretofore used in gas turbine engines exhibit typical pressure losses ranging from 4 to 8 percent of the total pressures delivered by upstream compressors. In contrast, the present ejector-enhanced pulsejet combustor exhibits a pressure rise of about 3.5 percent at overall enthalpy and temperature ratios compatible with those of modern turbomachines. The modest pressure rise translates to a comparable increase in overall engine efficiency and, consequently, a comparable decrease in specific fuel consumption. The ejector-enhanced pulsejet combustor may also offer potential for reducing the emission of harmful exhaust compounds by making it practical to employ a low-loss rich-burn/quench/lean-burn sequence. Like all prior concepts for pressure-gain combustion, the present concept involves an approximation of constant-volume combustion, which is inherently unsteady (in this case, more specifically, cyclic). The consequent unsteadiness in combustor exit flow is generally regarded as detrimental to the performance of downstream turbomachinery. Among other adverse effects, this unsteadiness tends to detract from the thermodynamic benefits of pressure gain. Therefore, it is desirable in any intermittent combustion process to minimize unsteadiness in the exhaust path.

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

International Nuclear Information System (INIS)

Glenn, Autumn L.; Bulusu, Kartik V.; Shu Fangjun; Plesniak, Michael W.

2012-01-01

Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T ≈ 0.20–0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

Energy Technology Data Exchange (ETDEWEB)

Glenn, Autumn L.; Bulusu, Kartik V. [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States); Shu Fangjun [Department of Mechanical and Aerospace Engineering, New Mexico State University, MSC 3450, P.O. Box 30001, Las Cruces, NM 88003-8001 (United States); Plesniak, Michael W., E-mail: plesniak@gwu.edu [Department of Mechanical and Aerospace Engineering, George Washington University, 801 22nd Street, NW., Washington, DC 20052 (United States)

2012-06-15

Secondary flows within curved arteries with unsteady forcing result from amplified centrifugal instabilities and are expected to be driven by the rapid accelerations and decelerations inherent in physiological waveforms. These secondary flows may also affect the function of curved arteries through pro-atherogenic wall shear stresses, platelet residence time and other vascular response mechanisms. Planar PIV measurements were performed under multi-harmonic non-zero-mean and physiological carotid artery waveforms at various locations in a rigid bent-pipe curved artery model. Results revealed symmetric counter-rotating vortex pairs that developed during the acceleration phases of both multi-harmonic and physiological waveforms. An idealized stent model was placed upstream of the bend, which initiated flow perturbations under physiological inflow conditions. Changes in the secondary flow structures were observed during the systolic deceleration phase (t/T Almost-Equal-To 0.20-0.50). Proper Orthogonal Decomposition (POD) analysis of the flow morphologies under unsteady conditions indicated similarities in the coherent secondary-flow structures and correlation with phase-averaged velocity fields. A regime map was created that characterizes the kaleidoscope of vortical secondary flows with multiple vortex pairs and interesting secondary flow morphologies. This regime map in the curved artery model was created by plotting the secondary Reynolds number against another dimensionless acceleration-based parameter marking numbered regions of vortex pairs.

Theoretical studies of a hybrid ejector CO2 compression cooling system for vehicles and preliminary experimental investigations of an ejector cycle

International Nuclear Information System (INIS)

Chen, Xiangjie; Worall, Mark; Omer, Siddig; Su, Yuehong; Riffat, Saffa

2013-01-01

Highlights: ► Waste heat from vehicle exhausted gas was used as heat source for ejector. ► Ejector acts as the main interface between ejector and CO 2 VC sub-system. ► The effect of sub-cooling was analyzed. ► COP of ejector cooling system was measured between 0.2 and 0.5 during experiments. ► Enhanced ejector and vapour compression system. -- Abstract: This paper presents theoretical investigations into a hybrid ejector and CO 2 vapour compression (VC) system for road transport cooling. The purpose is to utilise the waste heat from exhaust gas and the VC sub-system to drive the ejector system, whose cooling effect will be employed to subcool the VC sub-system. Exploitation of the energy consumption ratio between ejector sub-system and CO 2 VC sub-system indicated that the more energy obtained from exhausted gas, the better system performance could be achieved for CO 2 VC sub-system, and hence higher cooling capacity of the VC sub-system at the same compression power. Thermodynamic simulations of two sub-systems and the hybrid system were presented. The results indicated that, at boiler temperature of 120 °C, evaporator temperature of 10 °C, a COP of 0.584 was achieved for hybrid system, with 22% improvement over a single ejector cycle. Preliminary experimental studies were carried out on a single ejector cycle, with boiler temperatures between 115 °C and 130 °C, and evaporator temperatures between 5 °C and 10 °C. The effects of various operation conditions on the overall ejector operation were coherently analysed. The COP of the ejector sub-system from experimental results was approximately 85% compared with simulation results, which showed a good agreement between theoretical analysis and experimental results.

State-space modelling for the ejector-based refrigeration system driven by low grade energy

International Nuclear Information System (INIS)

Xue, Binqiang; Cai, Wenjian; Wang, Xinli

2015-01-01

This paper presents a novel global state-space model to describe the ejector-based refrigeration system, which includes the dynamics of the two heat exchangers and the static properties of ejector, compressor and expansion valve. Different from the existing methods, the proposed method introduces some intermediate variables into the dynamic modelling in developing reduced order models of the heat exchangers (evaporator and condenser) based on the Number of Transfer Units (NTU) method. This global model with fewer dimensions is much simpler and can be more convenient for the real-time control system design, compared with other dynamic models. Finally, the proposed state-space model has been validated by dynamic response experiments on the ejector-based refrigeration cycle with refrigerant R134a.The experimental results indicate that the proposed model can predict well the dynamics of the ejector-based refrigeration system. - Highlights: • A low-order state-space model of ejector-based refrigeration system is presented. • Reduced-order models of heat exchangers are developed based on NTU method. • The variations of mass flow rates are introduced in multiple fluid phase regions. • Experimental results show the proposed model has a good performance

Investigation of secondary flows in turbulent pipe flows with three-dimensional sinusoidal walls

Science.gov (United States)

Chan, Leon; MacDonald, Michael; Chung, Daniel; Hutchins, Nicholas; Ooi, Andrew

2017-11-01

The occurrence of secondary flows is systematically investigated via Direct Numerical Simulations (DNS) of turbulent flow in a rough wall pipe at friction Reynolds numbers of 540. In this study, the peak-to-trough height of the roughness elements, which consist of three-dimensional sinusoidal roughness, is fixed at 120 viscous units while the wavelength of the roughness elements is varied. The solidity or effective slope (ES) of the roughness ranges from the sparse regime (ES = 0.18) to the closely packed roughness/dense regime (ES = 0.72). The time-independent dispersive stresses, which arise due to the stationary features of the flow, are analysed and are found to increase with increasing roughness wavelength. These dispersive stresses are related to the occurrence of secondary flows and are maximum within the roughness canopy. Above the crest of the roughness elements, the dispersive stresses reduce to zero at wall-normal heights greater than half of the roughness wavelength. This study has found that the size and wall-normal extent of the secondary flows scales with the roughness wavelength and can reach wall-normal heights of almost half of the pipe radius.

Design and implementation of ejector driven micropump

International Nuclear Information System (INIS)

Chuech, S.G.; Chen, C.-C.; Lu, J.-C.; Yan, M.-M.

2007-01-01

The working principle of the ejector, which converts fluid energy into suction power, was utilized for designing the miniaturized pump. The present micropump with the structure scale in the size range of microns to millimeters was fabricated through the MEMS manufacturing processes. The pump may offer portable convenience and requires no electrical power; especially it can be used in many applications where electricity is unsafe or impractical. To optimize the design, the size of the diffuser throat in the micropump was varied and used as a design parameter. The optimization results indicate that there exists an optimal width for the diffuser throat, which is critically important to the design of an ejector driven micropump. For testing the pump, the fabricated micropump was driven by compressed air from a portable can to pump water and air. In the experimental tests, the pumping flow rates of water and air were measured and compared for design optimization

Optimization of two-phase R600a ejector geometries using a non-equilibrium CFD model

International Nuclear Information System (INIS)

Lee, Moon Soo; Lee, Hoseong; Hwang, Yunho; Radermacher, Reinhard; Jeong, Hee-Moon

2016-01-01

Highlights: • Empirical mass transfer coefficient correlation is built based on Weber number. • Developed model is validated in terms of the e and DP. • A set of Pareto solutions is obtained from MOGA based OAAO method. • DP is improved up to 10,379 Pa with the same e of the baseline. • e is enhanced up to 0.782 with the same DP of the baseline case. - Abstract: A vapor compression cycle, which is typically utilized for the heat pump, air conditioning and refrigeration systems, has inherent thermodynamic losses associated with expansion and compression processes. To minimize these losses and improve the energy efficiency of the vapor compression cycle, an ejector can be applied. However, due to the occurrence of complex physics i.e., non-equilibrium flashing compressible flow in the nozzle with possible shock interactions, it has not been feasible to model or optimize the design of a two-phase ejector. In this study, a homogeneous, non-equilibrium, two-phase flow computational fluid dynamics (CFD) model in a commercial code is used with an in-house empirical correlation for the mass transfer coefficient and real gas properties to perform a geometric optimization of a two-phase ejector. The model is first validated with experimental data of an ejector with R600a as the working fluid. After that, the design parameters of the ejector are optimized using multi-objective genetic algorithm (MOGA) based online approximation-assisted optimization (OAAO) approaches to find the maximum performance.

Experimental investigation on motive nozzle throat diameter for an ejector expansion refrigeration system

International Nuclear Information System (INIS)

Bilir Sag, Nagihan; Ersoy, H. Kursad

2016-01-01

Highlights: • Effects of nozzle throat diameter and its location on performance were investigated. • The nozzle has an optimum throat diameter under the experiment condition. • The maximum performance has been achieved by using optimum nozzle throat diameter. • The variation of nozzle throat diameter with condenser water inlet temperature was examined. • Motive nozzle has no optimum position in the ejector refrigeration system. - Abstract: In this study, ejector was used to reduce throttling losses in a vapour compression refrigeration system. Effects on system performance of throat diameter and position of motive nozzle of ejector were investigated experimentally. An ejector was designed based on the established mathematical model and manufactured. The experiments were carried out by using different primary nozzle throat diameters. The experiments were further conducted by changing condenser water inlet temperature, which is one of the external parameters. The experimental results of the ejector system and those of the classic system were compared under same external operating conditions and for the same cooling capacity. In order to obtain same external operating conditions in both systems, the inlet conditions of the brine supplied to the evaporator and inlet water conditions (flow rate and temperature) to the condenser were kept constant. Maximum performance was obtained when the primary nozzle throat diameter was 2.3 mm within the areas considered in this study. When compared, it was experimentally determined that the ejector system that uses the optimum motive nozzle throat diameter exhibits higher COP than the classic system by 5–13%. Furthermore, it was found that the variation of coefficient of performance based on position of motive nozzle in two-phase ejector expander refrigeration cycle is lower than 1%.

Reduction of the suction pressure of a liquid ring vacuum pump with a supersonic gas ejector

Directory of Open Access Journals (Sweden)

Olšiak Róbert

2018-01-01

Full Text Available A supersonic gas ejector in conjunction with a liquid ring vacuum pump is used for creating and maintaining vacuum in a chamber for technological purposes. In this paper the authors submit an overview about the problematics of suction pressure reduction with a supersonic gas ejector used as a pre-stage of a liquid ring vacuum pump. This system has also the function of a cavitation protection due to the higher pressure present at the suction throat of the vacuum pump. A part of this paper is devoted to the governing equations used at the definition of the flow through an ejector. The experimental studies are then carried out in or own laboratory for verification purposes.

Combined cold compressor/ejector helium refrigerator cycle

International Nuclear Information System (INIS)

Schlafke, A.P.; Brown, D.P.; Wu, K.C.

1984-01-01

This chapter demonstrates how the use of a cold compressor in series with an ejector is an effective way to produce the desired low pressure in a helium refrigeration system. The cold compressor is tentatively located at the low pressure side below the J-T heat exchanger. The ejector is the first stage and the cold compressor is the second stage of the two-stage pumping system. A centrifugal, oil-bearing type compressor was installed on the R and D refrigerator at the Brookhaven National Laboratory. It is determined that the combined cold compressor and ejector system produces a lower temperature on the same load or more cooling at the same temperature compared with a system which uses an ejector alone. Results of the test showed a gain of 20%

Analysis of Refrigeration Cycle Performance with an Ejector

Directory of Open Access Journals (Sweden)

Wani J. R.

2016-01-01

Full Text Available A conventional refrigeration cycle uses expansion device between the condenser and the evaporator which has losses during the expansion process. A refrigeration cycle with ejector is a promising modification to improve the performance of conventional refrigeration cycle. The ejector is used to recover some of the available work so that the compressor suction pressure increases. To investigate the enhancement a model with R134a refrigerant was developed. To solve the set of equations and simulate the cycle performance a subroutine was written on engineering equation solver (EES environment. At specific conditions, the refrigerant properties are obtained from EES. At the design conditions the ejector refrigeration cycle achieved 5.141 COP compared to 4.609 COP of the conventional refrigeration cycle. This means that ejector refrigeration cycle offers better COP with 10.35% improvement compared to conventional refrigeration cycle. Parametric analysis of ejector refrigeration cycle indicated that COP was influenced significantly by evaporator and condenser temperatures, entrainment ratio and diffuser efficiency.

Ejectors of power plants turbine units efficiency and reliability increasing

Science.gov (United States)

Aronson, K. E.; Ryabchikov, A. Yu.; Kuptsov, V. K.; Murmanskii, I. B.; Brodov, Yu. M.; Zhelonkin, N. V.; Khaet, S. I.

2017-11-01

The functioning of steam turbines condensation systems influence on the efficiency and reliability of a power plant a lot. At the same time, the condensation system operating is provided by basic ejectors, which maintain the vacuum level in the condenser. Development of methods of efficiency and reliability increasing for ejector functioning is an actual problem of up-to-date power engineering. In the paper there is presented statistical analysis of ejector breakdowns, revealed during repairing processes, the influence of such damages on the steam turbine operating reliability. It is determined, that 3% of steam turbine equipment breakdowns are the ejector breakdowns. At the same time, about 7% of turbine breakdowns are caused by different ejector malfunctions. Developed and approved design solutions, which can increase the ejector functioning indexes, are presented. Intercoolers are designed in separated cases, so the air-steam mixture can’t move from the high-pressure zones to the low-pressure zones and the maintainability of the apparatuses is increased. By U-type tubes application, the thermal expansion effect of intercooler tubes is compensated and the heat-transfer area is increased. By the applied nozzle fixing construction, it is possible to change the distance between a nozzle and a mixing chamber (nozzle exit position) for operating performance optimization. In operating conditions there are provided experimental researches of more than 30 serial ejectors and also high-efficient 3-staged ejector EPO-3-80, designed by authors. The measurement scheme of the designed ejector includes 21 indicator. The results of experimental tests with different nozzle exit positions of the ejector EPO-3-80 stream devices are presented. The pressure of primary stream (water steam) is optimized. Experimental data are well-approved by the calculation results.

Effects of ejector geometries on performance of ejector-expansion R410A air conditioner considering cooling seasonal performance factor

International Nuclear Information System (INIS)

Jeon, Yongseok; Jung, Jongho; Kim, Dongwoo; Kim, Sunjae; Kim, Yongchan

2017-01-01

Highlights: •The performance of an ejector-expansion R410A air conditioner is measured. •The effect of ejector geometries on the COP and CSPF is analyzed. •The mixing-section diameter of the ejector is optimized based on the CSPF. •The mixing-section diameter is optimized based on the climatic conditions. -- Abstract: The objective of this study was to investigate the effects of ejector geometries on the performance of an ejector-expansion air conditioner (EEAC) considering the cooling seasonal performance factor (CSPF). The performance of the EEAC using R410A was measured and analyzed by varying the compressor speed, outdoor-bin temperature, operating pressures, nozzle-throat diameter, and mixing-section diameter. The EEAC in the medium-capacity mode exhibited maximum coefficient of performance (COP) improvement, i.e., 7.5%, over the baseline (conventional) cycle. The optimum mixing-section diameter was determined to be 9 mm based on the CSPF. In addition, the optimum mixing-section diameter increased with an increase in the annual average outdoor temperature. The CSPF of the EEAC with the optimized mixing-section diameter improved in the range of 16.0–20.3% over the baseline cycle depending on the climatic conditions.

Computational and experimental analysis of supersonic air ejector: Turbulence modeling and assessment of 3D effects

International Nuclear Information System (INIS)

Mazzelli, Federico; Little, Adrienne B.; Garimella, Srinivas; Bartosiewicz, Yann

2015-01-01

Highlights: • Computational and experimental assessment of computational techniques for ejector flows. • Comparisons to 2D/3D (k–ε, k–ε realizable, k–ω SST, and stress–ω RSM) turbulence models. • k–ω SST model performs best while ε-based models more accurate at low motive pressures. • Good on-design agreement across 2D and 3D models; off-design needs 3D simulations. - Abstract: Numerical and experimental analyses are performed on a supersonic air ejector to evaluate the effectiveness of commonly-used computational techniques when predicting ejector flow characteristics. Three series of experimental curves at different operating conditions are compared with 2D and 3D simulations using RANS, steady, wall-resolved models. Four different turbulence models are tested: k–ε, k–ε realizable, k–ω SST, and the stress–ω Reynolds Stress Model. An extensive analysis is performed to interpret the differences between numerical and experimental results. The results show that while differences between turbulence models are typically small with respect to the prediction of global parameters such as ejector inlet mass flow rates and Mass Entrainment Ratio (MER), the k–ω SST model generally performs best whereas ε-based models are more accurate at low motive pressures. Good agreement is found across all 2D and 3D models at on-design conditions. However, prediction at off-design conditions is only acceptable with 3D models, making 3D simulations mandatory to correctly predict the critical pressure and achieve reasonable results at off-design conditions. This may partly depend on the specific geometry under consideration, which in the present study has a rectangular cross section with low aspect ratio.

Ocular Blood Flow Measured Noninvasively in Zero Gravity

Science.gov (United States)

Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.

2003-01-01

In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.

Secondary flow in turbulent ducts with increasing aspect ratio

Science.gov (United States)

Vinuesa, R.; Schlatter, P.; Nagib, H. M.

2018-05-01

Direct numerical simulations of turbulent duct flows with aspect ratios 1, 3, 5, 7, 10, and 14.4 at a center-plane friction Reynolds number Reτ,c≃180 , and aspect ratios 1 and 3 at Reτ,c≃360 , were carried out with the spectral-element code nek5000. The aim of these simulations is to gain insight into the kinematics and dynamics of Prandtl's secondary flow of the second kind and its impact on the flow physics of wall-bounded turbulence. The secondary flow is characterized in terms of the cross-plane component of the mean kinetic energy, and its variation in the spanwise direction of the flow. Our results show that averaging times of around 3000 convective time units (based on duct half-height h ) are required to reach a converged state of the secondary flow, which extends up to a spanwise distance of around ≃5 h measured from the side walls. We also show that if the duct is not wide enough to accommodate the whole extent of the secondary flow, then its structure is modified as reflected through a different spanwise distribution of energy. Another confirmation of the extent of the secondary flow is the decay rate of kinetic energy of any remnant secondary motions for zc/h >5 (where zc is the spanwise distance from the corner) in aspect ratios 7, 10, and 14.4, which exhibits a decreasing level of energy with increasing averaging time ta, and in its rapid rate of decay given by ˜ta-1 . This is the same rate of decay observed in a spanwise-periodic channel simulation, which suggests that at the core, the kinetic energy of the secondary flow integrated over the cross-sectional area, , behaves as a random variable with zero mean, with rate of decay consistent with central limit theorem. Long-time averages of statistics in a region of rectangular ducts extending about the width of a well-designed channel simulation (i.e., extending about ≃3 h on each side of the center plane) indicate that ducts or experimental facilities with aspect ratios larger than 10 may

Theoretical analysis of ejector refrigeration system performance under overall modes

International Nuclear Information System (INIS)

Chen, Weixiong; Shi, Chaoyin; Zhang, Shuangping; Chen, Huiqiang; Chong, Daotong; Yan, Junjie

2017-01-01

Highlights: • Real gas theoretical model is used to get ejector performance at critical/sub-critical modes. • The model has a better accuracy against the experiment results compared to ideal gas model. • The overall performances of two refrigerants are analyzed based on the parameter analysis. - Abstract: The ejector refrigeration integrated in the air-conditioning system is a promising technology, because it could be driven by the low grade energy. In the present study, a theoretical calculation based on the real gas property is put forward to estimate the ejector refrigeration system performance under overall modes (critical/sub-critical modes). The experimental data from literature are applied to validate the proposed model. The findings show that the proposed model has higher accuracy compared to the model using the ideal gas law, especially when the ejector operates at sub-critical mode. Then, the performances of the ejector refrigeration circle using different refrigerants are analyzed. R290 and R134a are selected as typical refrigerants by considering the aspects of COP, environmental impact, safety and economy. Finally, the ejector refrigeration performance is investigated under variable operation conditions with R290 and R134a as refrigerants. The results show that the R290 ejector circle has higher COP under critical mode and could operate at low evaporator temperature. However, the performance would decrease rapidly at high condenser temperature. The performance of R134a ejector circle is the opposite, with relatively lower COP, and higher COP at high condenser temperature compared to R290.

Development of acoustically lined ejector technology for multitube jet noise suppressor nozzles by model and engine tests over a wide range of jet pressure ratios and temperatures

Science.gov (United States)

Atvars, J.; Paynter, G. C.; Walker, D. Q.; Wintermeyer, C. F.

1974-01-01

An experimental program comprising model nozzle and full-scale engine tests was undertaken to acquire parametric data for acoustically lined ejectors applied to primary jet noise suppression. Ejector lining design technology and acoustical scaling of lined ejector configurations were the major objectives. Ground static tests were run with a J-75 turbojet engine fitted with a 37-tube, area ratio 3.3 suppressor nozzle and two lengths of ejector shroud (L/D = 1 and 2). Seven ejector lining configurations were tested over the engine pressure ratio range of 1.40 to 2.40 with corresponding jet velocities between 305 and 610 M/sec. One-fourth scale model nozzles were tested over a pressure ratio range of 1.40 to 4.0 with jet total temperatures between ambient and 1088 K. Scaling of multielement nozzle ejector configurations was also studied using a single element of the nozzle array with identical ejector lengths and lining materials. Acoustic far field and near field data together with nozzle thrust performance and jet aerodynamic flow profiles are presented.

Coronary diastolic pressure-flow relation and zero flow pressure explained on the basis of intramyocardial compliance

NARCIS (Netherlands)

Spaan, J. A.

1985-01-01

In the controversy about the mechanisms determining the high zero flow pressures and the further interpretation of coronary diastolic pressure flow relations, this paper takes a stand in favor of intramyocardial compliance as the primary cause of the high zero flow pressures. An attempt has been

Vapour recompression by ejectors

Energy Technology Data Exchange (ETDEWEB)

Krejci, S; Komurka, J; Gemza, E; Kaspar, J; Wergner, F

1985-01-01

Thermodynamic analyses using the concept of exergy are considered very important in analysing the energy balances of processes. The way in which such a technique can be applied to ejectors is discussed. (author).

Performance evaluation of an ejector subcooled vapor-compression refrigeration cycle

International Nuclear Information System (INIS)

Xing, Meibo; Yan, Gang; Yu, Jianlin

2015-01-01

Highlights: • An ejector subcooled vapor-compression refrigeration cycle is proposed. • The performance of the cycle with ejector subcooling is evaluated theoretically. • Increase in refrigeration capacity can be achieved by the ejector subcooled cycle. • The new cycle exhibits higher COP compared to the basic single-stage cycle. • Performance of the new cycle depends on the operation pressures of the ejector. - Abstract: In this study, a novel vapor-compression refrigeration cycle with mechanical subcooling using an ejector is proposed to improve the performance of a conventional single-stage vapor-compression refrigeration cycle. In the theoretical study, a mathematical model is developed to predict the performance of the cycle by using R404A and R290, and then compared with that of the conventional refrigeration cycle. The simulation results show that the performance of the ejector subcooled cycle is better than that of the conventional cycle. When the evaporator temperature ranges from −40 to −10 °C and the condenser temperature is 45 °C, the novel cycle displays volumetric refrigeration capacity improvements of 11.7% with R404A and 7.2% with R290. And the novel cycle achieves COP improvements of 9.5% with R404A and 7.0% with R290. In addition, the improvement of the COP and cooling capacity of this novel cycle largely depends on the operation pressures of the ejector. The potential practical advantages offered by the cycle may be worth further attention in future studies

Performance test of solar-assisted ejector cooling system

KAUST Repository

Huang, Bin-Juine

2014-03-01

A solar-assisted ejector cooling/heating system (SACH-2k) is built and test result is reported. The solar-driven ejector cooling system (ECS) is connected in series with an inverter-type air conditioner (IAC). Several advanced technologies are developed in SACH-k2, including generator liquid level control in ECS, the ECS evaporator temperature control, and optimal control of fan power in cooling tower of ECS. From the field test results, the generator liquid level control performs quite well and keeps stable performance of ejector. The ECS evaporator temperature control also performs satisfactorily to keep ejector performance normally under low or fluctuating solar radiation. The fan power control system cooling tower performs stably and reduces the power consumption dramatically without affecting the ECS performance. The test results show that the overall system COPo including power consumptions of peripheral increases from 2.94-3.3 (IAC alone) to 4.06-4.5 (SACH-k2), about 33-43%. The highest COPo is 4.5. © 2013 Elsevier Ltd and IIR. All rights reserved.

Performance optimization for a variable throat ejector in a solar refrigeration system

KAUST Repository

Yen, R.H.; Huang, B.J.; Chen, C.Y.; Shiu, T.Y.; Cheng, C.W.; Chen, S.S.; Shestopalov, K.

2013-01-01

In a solar vapor ejector refrigeration system, the solar heat supply may vary because of variations in solar irradiation intensity, making it difficult to maintain a steady generator temperature. To improve ejector performance, this study proposes a variable throat ejector (VTEJ) and analyzes its performance using CFD simulations. The following conclusions can be drawn. An ejector with a greater throat area and larger solar collector allows a wider operating range of generator temperatures, but may be overdesigned and expensive. Conversely, decreasing the throat area limits the operating range of generator temperatures. Thus the ejector with a fixed throat area may be unsuitable to use solar energy as a heat source. For a VTEJ, this study derives a curve-fitting relationship between the optimum throat area ratio and the operating temperatures. Using this relationship to adjust the throat area ratio, the ejector can consistently achieve optimal and stable performances under a varying solar heat supply. © 2013 Elsevier Ltd and IIR. All rights reserved.

Performance optimization for a variable throat ejector in a solar refrigeration system

KAUST Repository

Yen, R.H.

2013-08-01

In a solar vapor ejector refrigeration system, the solar heat supply may vary because of variations in solar irradiation intensity, making it difficult to maintain a steady generator temperature. To improve ejector performance, this study proposes a variable throat ejector (VTEJ) and analyzes its performance using CFD simulations. The following conclusions can be drawn. An ejector with a greater throat area and larger solar collector allows a wider operating range of generator temperatures, but may be overdesigned and expensive. Conversely, decreasing the throat area limits the operating range of generator temperatures. Thus the ejector with a fixed throat area may be unsuitable to use solar energy as a heat source. For a VTEJ, this study derives a curve-fitting relationship between the optimum throat area ratio and the operating temperatures. Using this relationship to adjust the throat area ratio, the ejector can consistently achieve optimal and stable performances under a varying solar heat supply. © 2013 Elsevier Ltd and IIR. All rights reserved.

CFD investigations on supersonic ejectors for refrigeration applications

International Nuclear Information System (INIS)

Bartosiewicz, Y.; Aidoun, Z.; Mercadier, Y.

2004-01-01

This paper presents numerical results of a supersonic ejector for refrigeration applications. One of the interesting features is that the current model is based on the NIST properties for the R142b refrigerant: to the authors knowledge, it is the first paper dealing with a local CFD model which takes into account shock-boundary layer interactions in a real refrigerant. The numerical results put demonstrate the crucial role of the secondary nozzle for the mixing rate performance. In addition, these results point out the need of an extensive validation of the turbulence model, especially in the modeling of the off-design mode. (author)

Analysis of an Electrostatic MEMS Squeeze-film Drop Ejector

Directory of Open Access Journals (Sweden)

Edward P. Furlani

2009-10-01

Full Text Available We present an analysis of an electrostatic drop-on-demand MEMS fluid ejector. The ejector consists of a microfluidic chamber with a piston that is suspended a few microns beneath a nozzle plate. A drop is ejected when a voltage is applied between the orifice plate and the piston. This produces an electrostatic force that moves the piston towards the nozzle. The moving piston generates a squeeze-film pressure distribution that causes drop ejection. We discuss the operating physics of the ejector and present a lumped-element model for predicting its performance. We calibrate the model using coupled structural-fluidic CFD analysis.

A control oriental model for combined compression-ejector refrigeration system

International Nuclear Information System (INIS)

Liu, Jiapeng; Wang, Lei; Jia, Lei; Li, Zhen; Zhao, Hongxia

2017-01-01

Highlights: • A control oriental model for combined compression-ejector refrigeration system is proposed. • The pressure pulsating phenomenon in the system is investigated based on the model. • The results show that the model can reflect the system performance under variable operating conditions. - Abstract: Combined compression-ejector refrigeration systems have attracted lots of attention in recent years. In order to improve the running stability of the complex refrigeration system, it is necessary to obtain a simple and accuracy mathematical model for system control. In this paper, a control oriental model for combined compression ejector system is proposed. By analyzing the inner relationship between compressor and ejector, a hybrid model is built based on thermodynamic principles and lumped parameter method. Comparing with traditional theoretical models, the model is more suitable for system control due to its simpler structure and less parameters. Then the pressure pulsating phenomenon inside the piping system between compressor and ejector is investigated based on the model. The effectiveness of the proposed model is validated by experimental data. It is shown that the model can reflect the system performance under variable operating conditions.

Two zero-flow pressure intercepts exist in autoregulating isolated skeletal muscle.

Science.gov (United States)

Braakman, R; Sipkema, P; Westerhof, N

1990-06-01

The autoregulating vascular bed of the isolated canine extensor digitorum longus muscle was investigated for the possible existence of two positive zero-flow pressure axis intercepts, a tone-dependent one and a tone-independent one. An isolated preparation, perfused with autologous blood, was used to exclude effects of collateral flow and nervous and humoral regulation while autoregulation was left intact [mean autoregulatory gain 0.50 +/- 0.24 (SD)]. In a first series of experiments, the steady-state (zero flow) pressure axis intercept [mean 8.9 +/- 2.6 (SD) mmHg, tone independent] and the instantaneous (zero flow) pressure axis intercept [mean 28.5 +/- 9.9 (SD) mmHg, tone dependent] were determined as a function of venous pressure (range: 0-45 mmHg) and were independent of venous pressure until the venous pressure exceeded their respective values. Beyond this point the relations between the venous pressure and the steady-state and instantaneous pressure axis intercept followed the line of identity. The findings agree with the predictions of the vascular waterfall model. In a second series it was shown by means of administration of vasoactive drugs that the instantaneous pressure axis intercept is tone dependent, whereas the steady-state pressure axis intercept is not. It is concluded that there is a (proximal) tone-dependent zero-flow pressure at the arteriolar level and a (distal) tone-independent zero-flow pressure at the venous level.

A Multidisciplinary Approach to Mixer-Ejector Analysis and Design

Science.gov (United States)

Hendricks, Eric, S.; Seidel, Jonathan, A.

2012-01-01

The design of an engine for a civil supersonic aircraft presents a difficult multidisciplinary problem to propulsion system engineers. There are numerous competing requirements for the engine, such as to be efficient during cruise while yet quiet enough at takeoff to meet airport noise regulations. The use of mixer-ejector nozzles presents one possible solution to this challenge. However, designing a mixer-ejector which will successfully address both of these concerns is a difficult proposition. Presented in this paper is an integrated multidisciplinary approach to the analysis and design of these systems. A process that uses several low-fidelity tools to evaluate both the performance and acoustics of mixer-ejectors nozzles is described. This process is further expanded to include system-level modeling of engines and aircraft to determine the effects on mission performance and noise near airports. The overall process is developed in the OpenMDAO framework currently being developed by NASA. From the developed process, sample results are given for a notional mixer-ejector design, thereby demonstrating the capabilities of the method.

Thermodynamic analysis of the two-phase ejector air-conditioning system for buses

International Nuclear Information System (INIS)

Ünal, Şaban; Yilmaz, Tuncay

2015-01-01

Air-conditioning compressors of the buses are usually operated with the power taken from the engine of the buses. Therefore, an improvement in the air-conditioning system will reduce the fuel consumption of the buses. The improvement in the coefficient of performance (COP) of the air-conditioning system can be provided by using the two-phase ejector as an expansion valve in the air-conditioning system. In this study, the thermodynamic analysis of bus air-conditioning system enhanced with a two-phase ejector and two evaporators is performed. Thermodynamic analysis is made assuming that the mixing process in ejector occurs at constant cross-sectional area and constant pressure. The increase rate in the COP with respect to conventional system is analyzed in terms of the subcooling, condenser and evaporator temperatures. The analysis shows that COP improvement of the system by using the two phase ejector as an expansion device is 15% depending on design parameters of the existing bus air-conditioning system. - Highlights: • Thermodynamic analysis of the two-phase ejector refrigeration system. • Analysis of the COP increase rate of bus air-conditioning system. • Analysis of the entrainment ratio of the two-phase ejector refrigeration system

Performance of an Axisymmetric Rocket Based Combined Cycle Engine During Rocket Only Operation Using Linear Regression Analysis

Science.gov (United States)

Smith, Timothy D.; Steffen, Christopher J., Jr.; Yungster, Shaye; Keller, Dennis J.

1998-01-01

The all rocket mode of operation is shown to be a critical factor in the overall performance of a rocket based combined cycle (RBCC) vehicle. An axisymmetric RBCC engine was used to determine specific impulse efficiency values based upon both full flow and gas generator configurations. Design of experiments methodology was used to construct a test matrix and multiple linear regression analysis was used to build parametric models. The main parameters investigated in this study were: rocket chamber pressure, rocket exit area ratio, injected secondary flow, mixer-ejector inlet area, mixer-ejector area ratio, and mixer-ejector length-to-inlet diameter ratio. A perfect gas computational fluid dynamics analysis, using both the Spalart-Allmaras and k-omega turbulence models, was performed with the NPARC code to obtain values of vacuum specific impulse. Results from the multiple linear regression analysis showed that for both the full flow and gas generator configurations increasing mixer-ejector area ratio and rocket area ratio increase performance, while increasing mixer-ejector inlet area ratio and mixer-ejector length-to-diameter ratio decrease performance. Increasing injected secondary flow increased performance for the gas generator analysis, but was not statistically significant for the full flow analysis. Chamber pressure was found to be not statistically significant.

Designing and simulating a nitinol-based micro ejector

Directory of Open Access Journals (Sweden)

Yesid Mora Sierra

2012-01-01

Full Text Available This paper describes pico-droplet ejector design and simulation. The actuation system was based on two interconnected nitinol membranes’ shape memory effect. Ejected volume was 12pL and it operated at 30°C to 64°C. Ejecting excitation voltage was 12V and the ejecting energy required by actuator operation was 26µJ per drop. These pico-liter ejectors could have applications in making, lubricating and cooling integrated circuits.

World's first ejector cycle for mobile refrigerators to stop global warming

Energy Technology Data Exchange (ETDEWEB)

Takeuchi, Hirotsugu [Denso Corporation, Kariya (Japan); Gyoeroeg, Tibor [DENSO AUTOMOTIVE Deutschland GmbH, Eching (Germany)

2010-07-01

The development of energy-saving technologies is in great demand recently to stop global warming. We are committed to developing the Ejector Cycle as an energy-saving technology for refrigerators and air conditioners. The ejector, which is an energy-saving technological innovation, improves the efficiency of the refrigeration cycle by effectively using the expansion energy that is lost in the conventional vapor-compression cycle, and is applicable to almost all vapor-compression refrigerating air conditioners, thus improving the efficiency of the refrigeration cycle. Concerning the application of the Ejector Cycle in truck-transport refrigerators, we released Ejector Cycle products for large and medium-size freezer trucks, which have been favorably accepted by customers in 2003. Simultaneously we also developed the domestic water supply system using heat pump with natural refrigerant (CO{sub 2}). We developed a new Ejector Cycle, completed in 2007 a cool box which uses the refrigeration cycle of the mobile air-conditioning system to cool drinks and the commercial compact refrigerator. In 2008 a domestic water supply heat pump system using a heat pump with the natural refrigerant CO{sub 2} and the next-generation Ejector Cycle II that substantially improves performance was brought to the market. A new generation of Ejector Cycle is under development which will significantly improve the efficiency of mobile air conditioning systems (orig.)

Focused RBCC Experiments: Two-Rocket Configuration Experiments and Hydrocarbon/Oxygen Rocket Ejector Experiments

Science.gov (United States)

Santoro, Robert J.; Pal, Sibtosh

2003-01-01

This addendum report documents the results of two additional efforts for the Rocket Based Combined Cycle (RBCC) rocket-ejector mode research work carried out at the Penn State Propulsion Engineering Research Center in support of NASA s technology development efforts for enabling 3 d generation Reusable Launch Vehicles (RLV). The tasks reported here build on an earlier NASA MSFC funded research program on rocket ejector investigations. The first task investigated the improvements of a gaseous hydrogen/oxygen twin thruster RBCC rocket ejector system over a single rocket system. The second task investigated the performance of a hydrocarbon (liquid JP-7)/gaseous oxygen single thruster rocket-ejector system. To gain a systematic understanding of the rocket-ejector s internal fluid mechanic/combustion phenomena, experiments were conducted with both direct-connect and sea-level static diffusion and afterburning (DAB) configurations for a range of rocket operating conditions. For all experimental conditions, overall system performance was obtained through global measurements of wall static pressure profiles, heat flux profiles and engine thrust. Detailed mixing and combustion information was obtained through Raman spectroscopy measurements of major species (gaseous oxygen, hydrogen, nitrogen and water vapor) for the gaseous hydrogen/oxygen rocket ejector experiments.

Evaluation of a contact device type ejector system for liquid-liquid extraction

International Nuclear Information System (INIS)

Schwamback, Niomedes

2002-04-01

The objective of the present work was to evaluate an ejector system, operated simultaneously with two immiscible liquid phases and a gas phase, as a contact device for liquid-liquid extraction processes. The ejector, made of perspex, has a variable geometry, although this feature was not explored in the thesis. Motivated by recent uses of liquid-liquid extraction processes for the removal of traces of heavy metal from waste waters, it was decided to carry out tests with synthetic effluents. This strategy, typical of experimental work under evaluation of technical feasibility, greatly simplifies experiments, since the nature of the chemical species involved and their feed concentrations are known exactly and do not fluctuate. The extractant used was DEHPA (diethyl hexyl phosphoric acid). The metal chosen for tests was iron with oxidation number +3, because of its high extraction coefficient towards DEHPA and also for its chemical behavior similar to americium and other heavy metals. In addition to that, iron forms soluble coloured complexes adequate to spectrophotometric determination analysis, a simple, quick and very reliable analytical technique. The effects of electrolytes of interest, namely NaCl, FeSO 4 and Al(NO 3 ) 3 , upon the extraction process were investigated. The effects resulting from the introduction of a gas phase, actually air (bubbles), in the ejector upon the extraction efficiency were studied. By coupling advanced digital photographic technique and image analysis with microcomputer, the bubble mean size was measured. It was then correlated with equipment's geometrical (characteristic diameters) and operational variables (phases' flow rates and gas hold-ups). To enable scale-up procedures, data were preferably correlated by means of dimensionless groups. For the systems and conditions investigated in this thesis and under the same operational conditions, the introduction of air bubbles by means of an ejector has greatly improved the process

Advanced exergy analyses of an ejector expansion transcritical CO_2 refrigeration system

International Nuclear Information System (INIS)

Bai, Tao; Yu, Jianlin; Yan, Gang

2016-01-01

Highlights: • Advanced exergy analyses are performed on CO_2 EERC cycle. • Compressor should be improved first, followed by ejector, evaporator and gas cooler. • Interactions among the system components are assessed with advanced exergy analysis. • Real potential for exergy destruction reduction of the system is 43.44%. - Abstract: This paper presents a thermodynamic investigation on an ejector expansion transcritical CO_2 refrigeration system with advanced exergy analysis. By splitting the exergy destruction into endogenous/exogenous and unavoidable/avoidable parts, more valuable information of the interactions among the system components and the components improvement potential is provided. The results indicate that the compressor with largest avoidable endogenous exergy destruction possesses the highest priority of improvement, followed by the ejector, evaporator and gas cooler. The system exergy destruction is dominantly endogenous, and 43.44% of the total exergy destruction can be avoided by improving the system components. The evaporator has a serious impact on the exogenous exergy destruction within the compressor and ejector, and its own exergy destruction is entirely belongs to endogenous part. The effects of the discharge pressure, compressor efficiency and ejector efficiency on the system exergetic performance are discussed. There is an optimal discharge pressure with respect to the minimum endogenous exergy destruction in the compressor. Avoidable endogenous exergy destruction rates of the compressor and ejector are respectively reduced by 93.6% and 81.7% when the corresponding component efficiency varies from 0.5 to 0.9.

On the prediction of turbulent secondary flows

Science.gov (United States)

Speziale, C. G.; So, R. M. C.; Younis, B. A.

1992-01-01

The prediction of turbulent secondary flows, with Reynolds stress models, in circular pipes and non-circular ducts is reviewed. Turbulence-driven secondary flows in straight non-circular ducts are considered along with turbulent secondary flows in pipes and ducts that arise from curvature or a system rotation. The physical mechanisms that generate these different kinds of secondary flows are outlined and the level of turbulence closure required to properly compute each type is discussed in detail. Illustrative computations of a variety of different secondary flows obtained from two-equation turbulence models and second-order closures are provided to amplify these points.

Parametric analysis for a new combined power and ejector-absorption refrigeration cycle

International Nuclear Information System (INIS)

Wang Jiangfeng; Dai Yiping; Zhang Taiyong; Ma Shaolin

2009-01-01

A new combined power and ejector-absorption refrigeration cycle is proposed, which combines the Rankine cycle and the ejector-absorption refrigeration cycle, and could produce both power output and refrigeration output simultaneously. This combined cycle, which originates from the cycle proposed by authors previously, introduces an ejector between the rectifier and the condenser, and provides a performance improvement without greatly increasing the complexity of the system. A parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the cycle performance. It is shown that heat source temperature, condenser temperature, evaporator temperature, turbine inlet pressure, turbine inlet temperature, and basic solution ammonia concentration have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. It is evident that the ejector can improve the performance of the combined cycle proposed by authors previously.

Full-scale multi-ejector module for a carbon dioxide supermarket refrigeration system: Numerical study of performance evaluation

International Nuclear Information System (INIS)

Bodys, Jakub; Palacz, Michal; Haida, Michal; Smolka, Jacek; Nowak, Andrzej J.; Banasiak, Krzysztof; Hafner, Armin

2017-01-01

Highlights: • A numerical study of the full-scale multi-ejector module performance was presented. • The module was characterised by stable operation in each considered configuration. • The module showed a high total efficiency for all the operating conditions. - Abstract: The performance of fixed ejectors installed in a multi-ejector module in a carbon dioxide refrigeration system is discussed in this paper. To analyse the module operation, three-dimensional ejector models including the inlet and outlet collecting ducts were considered. The tests were performed for three of four vapour ejectors of different sizes that compose the multi-ejector pack. The testing modes included the serial and parallel operation of the fixed units in operating conditions that are characteristic for the supermarket refrigeration unit working at high ambient temperatures. All numerical simulations were performed using the validated Homogeneous Equilibrium Model implemented on the ejectorPL computational tool for typical transcritical parameters at the motive nozzle port. The detailed analysis was executed separately for the ejectors and the ducts of the module collectors. The results discussion concerned the crucial parameters for such an installation like the pressure and vapour quality distribution. Negligible influence of the motive nozzle collector and a crucial influence of the outlet collector shape was indicated. The global performance analysis showed that the multi-ejector pack provides high and stable performance of all installed ejectors over the entire range of the considered operating conditions for supermarket application. Areas of the possible pressure loss reduction and the uniformity growth in the vapour quality distribution were presented. Finally, according to the multi-ejector pack ducts analysis, the potential areas for module shape optimisation were indicated as well.

Development of a numerical tool to study the mixing phenomenon occurring during mode one operation of a multi-mode ejector-augmented pulsed detonation rocket engine

Science.gov (United States)

Dawson, Joshua

simple and as a result of the rapid combustion process the engine cycle is more efficient compared to its combined cycle counterparts. The flow path geometry consists of an inlet system, followed just downstream by a mixing chamber where an ejector structure is placed within the flow path. Downstream of the ejector structure is a duct leading to a convergent-divergent nozzle. During mode one operation and within the ejector, products from the detonation of a stoichiometric hydrogen/air mixture are exhausted directly into the surrounding secondary air stream. Mixing then occurs between both the primary and secondary flow streams, at which point the air mass containing the high pressure, high temperature reaction products is convected downstream towards the nozzle. The engine cycle is engineered to a specific number of detonations per second, creating the pulsating characteristic of the primary flow. The pulsing nature of the primary flow serves as a momentum augmentation, enhancing the thrust and specific impulse at low speeds. Consequently it is necessary to understand the transient mixing process between the primary and secondary flow streams occurring during mode one operation. Using OPENFOAMRTM, an analytic tool is developed to simulate the dynamics of the turbulent detonation process along with detailed chemistry in order to understand the physics involved with the stream interactions. The computational code has been developed within the framework of OPENFOAMRTM, an open-source alternative to commercial CFD software. A conservative formulation of the Farve averaged Navier-Stokes equations is implemented to facilitate programming and numerical stability. Time discretization is accomplished by using the Crank-Nicolson method, achieving second order convergence in time. Species mass fraction transport equations are implemented and a Seulex ODE solver was used to resolve the system of ordinary differential equations describing the hydrogen-air reaction mechanism detailed

Smart Control System to Optimize Time of Use in a Solar-Assisted Air-Conditioning by Ejector for Residential Sector

Directory of Open Access Journals (Sweden)

Giovanna Avedian-González

2018-02-01

Full Text Available The present work provides a series of theoretical improvements of a control strategy in order to optimize the time of use of solar air-conditioning by an ejector distributed in multiple solar collectors of vacuum tubes for the residential sector, which will allow us to reduce carbon-dioxide emissions, costs and electrical energy consumption. In a solar ejector cooling system, the instability of the solar source of energy causes an operational conflict between the solar thermal system and ejector cooling cycle. A fuzzy control structure for the supervisory ejector cycle and multi-collector control system is developed: the first control is applied to control the mass flow of the generator and the evaporator for different cooling capacities (3, 3.5, 4, 4.5 and 5 kW and set a temperature reference according to the operating conditions; the second is applied to keep a constant temperature power source that feeds the low-grade ejector cooling cycle using R134aas refrigerant. For the present work, the temperature of the generator oscillates between 65 °C and 90 °C, a condenser temperature of 30 °C and an evaporator temperature of 10 °C. For the purpose of optimization, there are different levels of performance for time of use: the Mode 0 (economic gives a performance of 17.55 h, Mode 5 (maximum cooling power 14.86 h and variable mode (variable mode of capacities 16.25 h, on average. Simulations are done in MATLAB-Simulink applying fuzzy logic for a mathematical model of the thermal balance. They are compared with two different types of solar radiation: real radiation and disturbed radiation.

Determination of the ejector dimensions of a bus air-conditioning system using analytical and numerical methods

International Nuclear Information System (INIS)

Ünal, Şaban

2015-01-01

Comfortable journey with commercial buses is an essential goal of transportation companies. An air-conditioning system can play an important role for this comfortable journey but it can put extra load on the engine and extra cost in the fuel consumption. The purpose of this work is to increase the performance of air-conditioning system of the buses by reducing the load on the engine and fuel consumption. Using a two-phase ejector as an expansion valve can increase the coefficient of performance (COP) of the air-conditioning system. An improvement in the COP can reduce the empty vehicle weight and fuel consumption of buses. Two-phase ejector dimensions can be determined using the empirical methods available in the literature. In this paper, the two-phase ejector dimensions of air conditioning system for a bus are calculated using the analytical and numerical methods. First of all, the thermodynamic analysis of the vapor-compression refrigeration cycle with a two-phase ejector is performed, and then the ejector dimensions are subsequently determined. The cooling loads of the midibus and bus with R134a as a refrigerant are assumed to be 14 kW and 32 kW, respectively. The total length of the two-phase ejector for the midibuses and buses due to these cooling loads, are computed to be 480.8 mm and 793.1 mm, respectively. Also, an experimental setup is installed on a midibus air conditioner to turn it into the ejector air conditioning system to validate theoretical results with the experimental study. - Highlights: • Determination of two-phase ejector dimensions of a bus air-conditioning system. • Thermodynamic analysis of the two-phase ejector cooling system. • Experimental study on a midibus air conditioner using two-phase ejector.

Experimental study of the behavior of a hybrid ejector-based air-conditioning system with R134a

International Nuclear Information System (INIS)

Wang, Hao; Cai, Wenjian; Wang, Youyi; Yan, Jia; Wang, Lei

2016-01-01

Highlights: • We conduct experiment on two working mode of system and compare their performance. • We examine the influence of different pressure on system performance. • We examine the area ratio effect on ejector performance. • The system is sensitive to evaporating and generating pressure. • The COP improvement is around 34% under hybrid mode. - Abstract: A hybrid ejector-based air-conditioning system which combines a vapor compression cycle and a ejector refrigeration cycle was developed. The waste heat energy from automobile is applied as driven source towards ejector refrigeration cycle. Two ejectors with different mixing chamber diameters are applied separately for performance test and the system is operated under different working modes. The effect of generating, condensing and evaporating pressure on system performance are studied experimentally. The effect of ejector geometry parameters on ejector performance is also investigated. The performance comparison between two working modes is made and the results indicate that (1) the performance of proposed system is sensitive to the three pressures; (2) the coefficient of performance (COP) of hybrid ejector-based air-conditioning system is around 34% higher than that of conventional compressor based system which implies a potential energy saving ability of proposed hybrid system.

Enhancing the efficiency of a three-lobe roots blower by means of by-passing gas to the working cavity through an ejector adaptor

Science.gov (United States)

Vizgalov, S. V.; Volkov, M. V.; Chekushkin, G. N.; Khisameev, I. G.

2017-08-01

A positive displacement Roots blower with two- or three-lobe straight-tooth or twisted rotors demonstrates high performance with small specific dimensions and is used to boost internal combustion engines, aerate tanks of treatment facilities, is employed in air and gas transport systems in the food, petrochemical and metallurgical industry. It is common knowledge that several solutions have been implemented in Roots blower designs with straight-tooth with three-lobe or more-lobes rotors. It is more practical to bypass a portion of the compressed gas to the working cavity of the blower through an ejector. The purpose of developing a mathematical model for a blower working in conjunction with an ejector adapter and the further research is to determine the efficiency of this scheme un-der different discharge pressure conditions and different ejector active flow temperatures (the gas cooling effect before the nozzle).

Reverse Flow Engine Core Having a Ducted Fan with Integrated Secondary Flow Blades

Science.gov (United States)

Kisska, Michael K. (Inventor); Princen, Norman H. (Inventor); Kuehn, Mark S. (Inventor); Cosentino, Gary B. (Inventor)

2014-01-01

Secondary air flow is provided for a ducted fan having a reverse flow turbine engine core driving a fan blisk. The fan blisk incorporates a set of thrust fan blades extending from an outer hub and a set of integral secondary flow blades extending intermediate an inner hub and the outer hub. A nacelle provides an outer flow duct for the thrust fan blades and a secondary flow duct carries flow from the integral secondary flow blades as cooling air for components of the reverse flow turbine engine.

Thermodynamics analysis of a modified dual-evaporator CO2 transcritical refrigeration cycle with two-stage ejector

International Nuclear Information System (INIS)

Bai, Tao; Yan, Gang; Yu, Jianlin

2015-01-01

In this paper, a modified dual-evaporator CO 2 transcritical refrigeration cycle with two-stage ejector (MDRC) is proposed. In MDRC, the two-stage ejector are employed to recover the expansion work from cycle throttling processes and enhance the system performance and obtain dual-temperature refrigeration simultaneously. The effects of some key parameters on the thermodynamic performance of the modified cycle are theoretically investigated based on energetic and exergetic analyses. The simulation results for the modified cycle show that two-stage ejector exhibits more effective system performance improvement than the single ejector in CO 2 dual-temperature refrigeration cycle, and the improvements of the maximum system COP (coefficient of performance) and system exergy efficiency could reach 37.61% and 31.9% over those of the conventional dual-evaporator cycle under the given operating conditions. The exergetic analysis for each component at optimum discharge pressure indicates that the gas cooler, compressor, two-stage ejector and expansion valves contribute main portion to the total system exergy destruction, and the exergy destruction caused by the two-stage ejector could amount to 16.91% of the exergy input. The performance characteristics of the proposed cycle show its promise in dual-evaporator refrigeration system. - Highlights: • Two-stage ejector is used in dual-evaporator CO 2 transcritical refrigeration cycle. • Energetic and exergetic methods are carried out to analyze the system performance. • The modified cycle could obtain dual-temperature refrigeration simultaneously. • Two-stage ejector could effectively improve system COP and exergy efficiency

The application of gas ejector for road transport air conditioning system

Science.gov (United States)

Sumeru, Nasution, Henry; Ani, Farid Nasir

2012-06-01

The depletion of fossil fuel supply requires fuel and energy saving in energy utilization system. Therefore, these required the development of new and efficient technologies as to reduce fuel consumption especially in air conditioning of road vehicles. Currently, the air conditioning for road vehicles uses vapor compression system. Although the vapor compression system has high COP, the compressor is driven by vehicle engines, which take additional fuel consumption when the air conditioning system is in operation. In this study, the waste heat of radiator drives the ejector refrigeration for air conditioning. Although the ejector refrigeration system has low COP, the use of heat driven air conditioning will reduce the fuel consumption as compared with conventional system. This is because the systems do not use the mechanical engine load. The analysis of this study is based on the ejector refrigeration system using natural refrigerant (isobutene). The evaporation temperature is 10°C, condensation temperature is 35°C, generator temperature is 90°C with ejector isentropic efficiency of 0.7, and the COP system is 0.25. The heat released by the radiator of typical small road vehicles is between 60 to 100 kW and if the generator absorbs 20% of the heat, the heat contained in the generator is 12 to 20 kW. When the ejector air conditioning system has a COP 0.25, it will generate cooling capacity between 3 to 5 kW, compared with the conventional air conditioning of similar vehicles, which is approximately 2 to 4.4 kW.

Control oriented modeling of ejector in anode gas recirculation solid oxygen fuel cell systems

International Nuclear Information System (INIS)

Zhu Yinhai; Li Yanzhong; Cai Wenjian

2011-01-01

A one-equation model is proposed for fuel ejector in anode gas recirculation solid oxide fuel cell (SOFC) system. Firstly, the fundamental governing equations are established by employing the thermodynamic, fluid dynamic principles and chemical constraints inside the ejector; secondly, the one-equation model is derived by using the parameter analysis and lumped-parameter method. Finally, the computational fluid dynamics (CFD) technique is employed to obtain the source data for determining the model parameters. The effectiveness of the model is studied under a wide range of operation conditions. The effect of ejector performance on the anode gas recirculation SOFC system is also discussed. The presented model, which only contains four constant parameters, is useful in real-time control and optimization of fuel ejector in the anode gas recirculation SOFC system.

Performance evaluation of combined ejector LiBr/H2O absorption cooling cycle

Directory of Open Access Journals (Sweden)

Hasan Sh. Majdi

2016-03-01

Full Text Available The objective of this work is to develop a computer simulation program to evaluate the performance of solar-assited combined ejector absorption (single-effect cooling system using LiBr/H2O as a working fluid and operating under steady-state conditions. The ejector possess no moving parts and is simple and reliable, which makes it attractive for combination with single-stage absorption cycle for further improvement to the system's performance. In this research, improvement to the system is achieved by utilizing the potential kinetic energy of the ejector to enhance refrigeration efficiency. The effects of the entrainment ratio of the ejector, operating temperature, on the thermal loads, and system performance have been investigated. The results showed that the evaporator and condenser loads, post-addition of the ejector, is found to be permanently higher than that in the basic cycle, which indicates a significant enhancement of the proposed cycle and the cooling capacity of the system increasing with the increase in evaporator temperature and entrainment ratio. The COP of the modified cycle is improved by up to 60 % compared with that of the basic cycle at the given condition. This process stabilizes the refrigeration system, enhanced its function, and enabled the system to work under higher condenser temperatures.

Cleaning of porous filters in fluidized bed reactors. Use of one ejector for various filters

International Nuclear Information System (INIS)

Sancho Rod, J.; Rodrigo Otero, A.

1966-01-01

Tests to know the efficiency of a porous filters cleaning system by blow-back that uses on ejector for each set of simultaneously cleaned filters were carried out. A Calculation method to obtain the optimum ejector for this system was shown, taking n=2, as optimum number of working for the fluidized bed reactors belonging to the Pilot plant of the Materials Division at JEN. That is two filters for each ejector. (Author)

Solar still with ejector: Experimental phase; Destilador solar con eyector: Fase experimental

Energy Technology Data Exchange (ETDEWEB)

Morales, Juan R; Lopez, Raymundo; Diaz, Alen; Lara, Araceli; Lizardi, Arturo [Universidad Autonoma Metropolitana Azcapotzalco, Mexico, D.F. (Mexico)

2000-07-01

A model of solar still assisted by ejector has been built from a previous design. The dimensions of this model are: 0.15 m wide; 0.80 m long and 0.20 m height to the top of the double slope cover. With these dimensions the cross sectional area results in 0.12 m{sup 2}. The bottom tray was filled with water up to a height of 5 cm. In order to raise the temperature of the water in the tray to a proper value, a 500 W electrical resistance was placed into it. The solar still was built with acrylic walls and the cover was made with 3 mm glass at an angle of 20 degrees respect to the horizontal, as to adjust to Mexico's city latitude. The ejector is 25 cm long with a 0.019 mm cross section. It is placed alongside in the still and as close as possible to the free surface of the water in the tray. The driver fluid, water in this case, is made to flow through the ejector by the air pressure in a tank partially filled with water. The flow rate is regulated by means of a needle valve. The amount of water in the tank is 60 liters approximately. With this water the ejector can operate for one-hour approximately. The pressure in the tank could be adjusted to the equivalent of a 40 m-water column. The water in the still is heated to 40 Celsius degrees. When the interior of the still reaches an uniform temperature, water at 20 Celsius degrees is made to flow through the ejector. The operation of the still is intermittent. The results are presented in a table and they show that performance of the still could be greatly improved. [Spanish] A partir del diseno del destilador solar con eyector se ha construido un prototipo para simular el efecto del eyector en un medio similar al que se presentaria bajo la accion de la radiacion solar. El simulador esta integrado por un destilador tipo caseta con 0.15 m de ancho por 0.80 m de largo para poder acomodar la longitud del eyector; esto resulta en una superficie de captacion 0.12 m{sup 2}. Para llevar el agua del destilador a una

Magnetic field generation by pointwise zero-helicity three-dimensional steady flow of an incompressible electrically conducting fluid

Science.gov (United States)

Rasskazov, Andrey; Chertovskih, Roman; Zheligovsky, Vladislav

2018-04-01

We introduce six families of three-dimensional space-periodic steady solenoidal flows, whose kinetic helicity density is zero at any point. Four families are analytically defined. Flows in four families have zero helicity spectrum. Sample flows from five families are used to demonstrate numerically that neither zero kinetic helicity density nor zero helicity spectrum prohibit generation of large-scale magnetic field by the two most prominent dynamo mechanisms: the magnetic α -effect and negative eddy diffusivity. Our computations also attest that such flows often generate small-scale field for sufficiently small magnetic molecular diffusivity. These findings indicate that kinetic helicity and helicity spectrum are not the quantities controlling the dynamo properties of a flow regardless of whether scale separation is present or not.

A zero-flow microfluidics for long-term cell culture and detection

Directory of Open Access Journals (Sweden)

Shengbo Sang

2015-04-01

Full Text Available A zero-flow microfluidic design is proposed in this paper, which can be used for long-term cell culture and detection, especially for a lab-on-chip integrated with a biosensor. It consists of two parts: a main microchannel; and a circle microchamber. The Finite Element Method (FEM was employed to predict the fluid transport properties for a minimum fluid flow disturbance. Some commonly used microfluidic structures were also analysed systematically to prove the designed structure. Then the designed microfluidics was fabricated. Based on the simulations and experiments, this design provides a continuous flow environment, with a relatively stable and low shear stress atmosphere, similar to a zero-flow environment. Furthermore, the nutrients maintaining cells’ normal growth can be taken into the chamber through the diffusion effect. It also proves that the microfluidics can realize long-term cell culture and detection. The application of the structure in the field of biological microelectromechenical systems (BioMEMS will provide a research foundation for microfluidic technology.

Zero-G two phase flow regime modeling in adiabatic flow

International Nuclear Information System (INIS)

Reinarts, T.R.; Best, F.R.; Wheeler, M.; Miller, K.M.

1993-01-01

Two-phase flow, thermal management systems are currently being considered as an alternative to conventional, single phase systems for future space missions because of their potential to reduce overall system mass, size, and pumping power requirements. Knowledge of flow regime transitions, heat transfer characteristics, and pressure drop correlations is necessary to design and develop two-phase systems. This work is concerned with microgravity, two-phase flow regime analysis. The data come from a recent sets of experiments. The experiments were funded by NASA Johnson Space Center (JSC) and conducted by NASA JSC with Texas A ampersand M University. The experiment was on loan to NASA JSC from Foster-Miller, Inc., who constructed it with funding from the Air Force Phillips Laboratory. The experiment used R12 as the working fluid. A Foster-Miller two phase pump was used to circulate the two phase mixture and allow separate measurements of the vapor and liquid flow streams. The experimental package was flown 19 times for 577 parabolas aboard the NASA KC-135 aircraft which simulates zero-G conditions by its parabolic flight trajectory. Test conditions included bubbly, slug and annular flow regimes in 0-G. The superficial velocities of liquid and vapor have been obtained from the measured flow rates and are presented along with the observed flow regimes and several flow regime transition predictions. None of the predictions completely describe the transitions as indicated by the data

Ejector device for returning incomplete combustion products

Energy Technology Data Exchange (ETDEWEB)

Szule, T.; Minas, E.; Pietrowski, K.

1977-12-19

A device is proposed for separating the fine fraction of incompletely burned clinker and delivering it to the firebox for combustion. The clinker is fed into the two-chambered device from the top through an open gate. The inside chamber of the device consists of a side enclosure with an inspection hole and a hatch, and a gate with a screen on top. An ejector is located in the chamber. The case of the outside chamber, also with an inspection hole and hatch, forms a bypass channel with the enclosure of the inside chamber. Fine clinker is poured through the screen into the inside chamber, and some of it is removed by the ejector for combustion; the coarser fraction builds up on top of the gate, and is periodically passed through it. Large pieces of clinker which do not fit through the screen pass down through the bypass channel.

Development and Performance of an Advanced Ejector Cooling System for a Sustainable Built Environment

Directory of Open Access Journals (Sweden)

Paulo ePereira

2015-06-01

Full Text Available Ejector refrigeration is a promising technology for the integration into solar driven cooling systems because of its relative simplicity and low initial cost. The major drawback of such a system is associated to its relatively low coefficient of performance (COP under variable operating conditions. In order to overcome this problem, an advanced ejector was developed that changes its geometrical features depending on the upstream and downstream conditions. This paper provides a short overview of the development process and results of a small cooling capacity (1.5 kW solar driven cooling system using a variable geometry ejector. During the design steps, a number of theoretical works have been carried out, including the selection of the working fluid, the determination of the geometrical requirements and prototype design. Based on the analysis, R600a was selected as working fluid. A prototype was constructed with two independent variable geometrical factors: the area ratio and the nozzle exit position. A test rig was also assembled in order to test the ejector performance under controlled laboratory conditions and to elaborate a control algorithm for the variable geometry. Ejector performance was assessed by calculation of cooling cycle COP, entrainment ratio and critical back pressure. The results show that for a condenser pressure of 3 bar, an 80% increase in the COP was obtained when compared to the performance of a fixed geometry ejector. Experimental COP values varied between 0.4 and 0.8, depending on operating conditions. Currently the cooling cycle is being integrated into a solar driven demonstration site for long term in situ assessment.

Performance characteristics of a methanol ejector refrigeration unit

International Nuclear Information System (INIS)

Alexis, G.K.; Katsanis, J.S.

2004-01-01

This paper discusses the behavior of methanol through an ejector operating in a refrigeration system with a medium temperature thermal source. For detailed calculation of the proposed system, a method has been developed, which employs analytical functions describing the thermodynamic properties of methanol. The proposed cycle has been compared with a Carnot cycle working at the same temperature levels. The influences of three major parameters, generator, condenser and evaporator temperatures, on ejector efficiency and coefficient of performance are discussed. Also, the maximum value of COP was estimated by correlation of the above three temperatures for constant superheated temperature 150 deg. C, and it was 0.139-0.467. The design conditions were generator temperature 117.7-132.5 deg. C, condenser temperature 42-50 deg. C and evaporator temperature -10-5 deg. C

Optimization of ejector design and operation

Directory of Open Access Journals (Sweden)

Kuzmenko Konstantin

2016-01-01

Full Text Available The investigation aims at optimization of gas ejector operation. The goal consists in the improvement of the inflator design so that to enable 50 liters of gas inflation within ~30 milliseconds. For that, an experimental facility was developed and fabricated together with the measurement system to study pressure patterns in the inflator path.

Performance characteristics of low global warming potential R134a alternative refrigerants in ejector-expansion refrigeration system

Directory of Open Access Journals (Sweden)

Mishra Shubham

2016-12-01

Full Text Available Performance assessment of ejector-expansion vapor compression refrigeration system with eco-friendly R134a alternative refrigerants (R152a, R1234yf, R600a, R600, R290, R161, R32, and propylene is presented for air-conditioning application. Ejector has been modeled by considering experimental data based correlations of component efficiencies to take care of all irreversibilities. Ejector area ratio has been optimized based on maximum coefficient of performance (COP for typical air-conditioner operating temperatures. Selected refrigerants have been compared based on area ratio, pressure lift ratio, entrainment ratio, COP, COP improvement and volumetric cooling capacity. Effects of normal boiling point and critical point on the performances have been studied as well. Using ejector as an expansion device, maximum improvement in COP is noted in R1234yf (10.1%, which reduces the COP deviation with R134a (4.5% less in basic cycle and 2.5% less in ejector cycle. Hence, R1234yf seems to be best alternative for ejector expansion system due to its mild flammability and comparable volumetric capacity and cooling COP. refrigerant R161 is superior to R134a in terms of both COP and volumetric cooling capacity, although may be restricted for low capacity application due to its flammability.

Performance characteristics of low global warming potential R134a alternative refrigerants in ejector-expansion refrigeration system

Science.gov (United States)

Mishra, Shubham; Sarkar, Jahar

2016-12-01

Performance assessment of ejector-expansion vapor compression refrigeration system with eco-friendly R134a alternative refrigerants (R152a, R1234yf, R600a, R600, R290, R161, R32, and propylene) is presented for air-conditioning application. Ejector has been modeled by considering experimental data based correlations of component efficiencies to take care of all irreversibilities. Ejector area ratio has been optimized based on maximum coefficient of performance (COP) for typical air-conditioner operating temperatures. Selected refrigerants have been compared based on area ratio, pressure lift ratio, entrainment ratio, COP, COP improvement and volumetric cooling capacity. Effects of normal boiling point and critical point on the performances have been studied as well. Using ejector as an expansion device, maximum improvement in COP is noted in R1234yf (10.1%), which reduces the COP deviation with R134a (4.5% less in basic cycle and 2.5% less in ejector cycle). Hence, R1234yf seems to be best alternative for ejector expansion system due to its mild flammability and comparable volumetric capacity and cooling COP. refrigerant R161 is superior to R134a in terms of both COP and volumetric cooling capacity, although may be restricted for low capacity application due to its flammability.

Theoretical study on a novel dual-nozzle ejector enhanced refrigeration cycle for household refrigerator-freezers

International Nuclear Information System (INIS)

Zhou, Mengliu; Wang, Xiao; Yu, Jianlin

2013-01-01

Highlights: • A novel dual-nozzle ejector enhanced refrigeration cycle is proposed. • The novel cycle is evaluated by using the developed mathematical model. • The results show the performances of the novel cycle could be significantly improved. • The novel cycle shows its promise in household refrigerator-freezers applications. - Abstract: In this study, a novel dual-nozzle ejector enhanced refrigeration cycle is presented for dual evaporator household refrigerator-freezers. The proposed ejector equipped with two nozzles can efficiently recover the expansion work from cycle throttling processes and enhance cycle performances. The performances of the novel cycle are evaluated by using the developed mathematical model, and then compared with that of the conventional ejector enhanced refrigeration cycle and basic vapor-compression refrigeration cycle. The simulation results show that for the given operating conditions, the coefficient of performance (COP) of the novel cycle using refrigerant R134a is improved by 22.9–50.8% compared with that of the basic vapor-compression refrigeration cycle, and the COP improvement is 10.5–30.8% larger than that of the conventional ejector enhanced refrigeration cycle. The further simulation results of the novel cycle using refrigerant R600a indicate that the cycle COP and volumetric refrigeration capacity could be significantly improved

Analysis of secondary motions in square duct flow

Science.gov (United States)

Modesti, Davide; Pirozzoli, Sergio; Orlandi, Paolo; Grasso, Francesco

2018-04-01

We carry out direct numerical simulations (DNS) of square duct flow spanning the friction Reynolds number range {Re}τ * =150-1055, to study the nature and the role of secondary motions. We preliminarily find that secondary motions are not the mere result of the time averaging procedure, but rather they are present in the instantaneous flow realizations, corresponding to large eddies persistent in both space and time. Numerical experiments have also been carried out whereby the secondary motions are suppressed, hence allowing to quantifying their effect on the mean flow field. At sufficiently high Reynolds number, secondary motions are found to increase the friction coefficient by about 3%, hence proportionally to their relative strength with respect to the bulk flow. Simulations without secondary motions are found to yield larger deviations on the mean velocity profiles from the standard law-of-the-wall, revealing that secondary motions act as a self-regulating mechanism of turbulence whereby the effect of the corners is mitigated.

Analysis of Zero Reynolds Shear Stress Appearing in Dilute Surfactant Drag-Reducing Flow

Directory of Open Access Journals (Sweden)

Weiguo Gu

2011-01-01

Full Text Available Dilute surfactant solution of 25 ppm in the two-dimensional channel is investigated experimentally compared with water flow. Particle image velocimetry (PIV system is used to take 2D velocity frames in the streamwise and wall-normal plane. Based on the frames of instantaneous vectors and statistical results, the phenomenon of zero Reynolds shear stress appearing in the drag-reducing flow is discussed. It is found that 25 ppm CTAC solution exhibits the highest drag reduction at Re = 25000 and loses drag reduction completely at Re = 40000. When drag reduction lies in the highest, Reynolds shear stress disappears and reaches zero although the RMS of the velocity fluctuations is not zero. By the categorization in four quadrants, the fluctuations of 25 ppm CTAC solution are distributed in all four quadrants equally at Re = 25000, which indicates that turnaround transportation happens in drag-reducing flow besides Reynolds shear stress transportation. Moreover, the contour distribution of streamwise velocity and the fluctuations suggests that turbulence transportation is depressed in drag-reducing flow. The viscoelasticity is possible to decrease the turbulence transportation and cause the turnaround transportation.

Design-theoretical study of cascade CO2 sub-critical mechanical compression/butane ejector cooling cycle

KAUST Repository

Petrenko, V.O.

2011-11-01

In this paper an innovative micro-trigeneration system composed of a cogeneration system and a cascade refrigeration cycle is proposed. The cogeneration system is a combined heat and power system for electricity generation and heat production. The cascade refrigeration cycle is the combination of a CO2 mechanical compression refrigerating machine (MCRM), powered by generated electricity, and an ejector cooling machine (ECM), driven by waste heat and using refrigerant R600. Effect of the cycle operating conditions on ejector and ejector cycle performances is studied. Optimal geometry of the ejector and performance characteristics of ECM are determined at wide range of the operating conditions. The paper also describes a theoretical analysis of the CO2 sub-critical cycle and shows the effect of the MCRM evaporating temperature on the cascade system performance. The obtained data provide necessary information to design a small-scale cascade system with cooling capacity of 10 kW for application in micro-trigeneration systems. © 2010 Elsevier Ltd and IIR. All rights reserved.

Exergoeconomic analysis and multi-objective optimization of an ejector refrigeration cycle powered by an internal combustion (HCCI) engine

International Nuclear Information System (INIS)

Sadeghi, Mohsen; Mahmoudi, S.M.S.; Khoshbakhti Saray, R.

2015-01-01

Highlights: • Ejector refrigeration systems powered by HCCI engine is proposed. • A new two-dimensional model is developed for the ejector. • Multi-objective optimization is performed for the proposed system. • Pareto frontier is plotted for multi-objective optimization. - Abstract: Ejector refrigeration systems powered by low-grade heat sources have been an attractive research subject for a lot of researchers. In the present work the waste heat from exhaust gases of a HCCI (homogeneous charge compression ignition) engine is utilized to drive the ejector refrigeration system. Considering the frictional effects on the ejector wall, a new two-dimensional model is developed for the ejector. Energy, exergy and exergoeconomic analysis performed for the proposed system using the MATLAB software. In addition, considering the exergy efficiency and the product unit cost of the system as objective functions, a multi-objective optimization is performed for the system to find the optimum design variables including the generator, condenser and evaporator temperatures. The product unit cost is minimized while the exergy efficiency is maximized using the genetic algorithm. The optimization results are obtained as a set of optimal points and the Pareto frontier is plotted for multi-objective optimization. The results of the optimization show that ejector refrigeration cycle is operating at optimum state based on exergy efficiency and product unit cost when generator, condenser and evaporator work at 94.54 °C, 33.44 °C and 0.03 °C, respectively

Influence of secondary flow on meandring of rivers

NARCIS (Netherlands)

Olesen, K.W.

1982-01-01

A linear stability analysis of the governing equations for the bed and flow topography in straight alluvial channels is treated. The flow is described by a horizontal two-dimensional model, but secondary flow due to curvature of the streamlines is included. Further more knowledge about secondary

Theoretical research on the performance of the transcritical ejector refrigeration cycle with various refrigerants

International Nuclear Information System (INIS)

Wang, F.; Li, D.Y.; Zhou, Y.

2015-01-01

The transcritical ejector refrigeration cycle (TERC), which has shown an attractive alternative to the ejector refrigeration systems, can better match large variable-temperature heat sources and yields higher COP. In this paper, in order to find a proper working fluid for the TERC, the performance of the TERC with CO_2 and various working fluids with low critical temperatures including R1270, R32, R143a, R125 and R115 are studied and compared. A thermodynamic model for ejector is set up to simulate the ejector by introducing the real properties of refrigerants. The results indicate that R1270 has the highest COP at the same heat source condition and medium working pressures, and is one of environment-friendly working fluids, hence R1270 is the most proper one. The COP of the transcritical cycle is higher than that of the subcritical cycle, and The effective performance coefficient COP_m of the transcritical cycle is also better. When the heater outlet temperature is increased, its system COP_m improves, but its system COP almost does not change. - Highlights: • A thermodynamic model is used to simulate the ejector with real properties. • The performance of the TERC with various refrigerants is compared. • The environment-friendly working fluid of R1270 shows the most proper one. • The COP of the transcritical cycle is higher than that of the subcritical cycle.

Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

OpenAIRE

Najafi, Moslem; Zahednezhad, Fahimeh; Samadzadeh, Mehrban; Vaez, Haleh

2012-01-01

Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods: The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey...

Innovative application of air ejector as a pump for continuous air monitors

International Nuclear Information System (INIS)

Dhanasekaran, A.; Ajoy, K.C.; Santhanam, R.; Rajagopal, V.; Jose, M.T.

2016-01-01

Workplace monitoring, one of the key components of the radiation protection program is generally carried out by means of instruments installed permanently in respective areas or through portable air sampling instruments. Continuous air monitor (CAM) is one such monitor that constantly monitors the radionuclide concentration in air and triggers alarm as and when the air concentration goes above the pre-set levels. Conventional CAM system has a filter head, detector, display unit and a pump as four major parts. Pump may be either rotary vane or a vibrating diaphragm which are electrically driven using motors. Air lift pumps using ejectors are widely used where pump reliability and low maintenance are required, and where corrosive, abrasive, or radioactive fluids are handled. Since ejectors are uncomplicated alternative to vacuum pumps, an attempt was made to use the same as a pump for conventional CAMs. An ejector based sampling set up was made, tested and the results are represented in this paper

Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence

Science.gov (United States)

Klotz, L.; Lemoult, G.; Frontczak, I.; Tuckerman, L. S.; Wesfreid, J. E.

2017-04-01

We present an experimental setup that creates a shear flow with zero mean advection velocity achieved by counterbalancing the nonzero streamwise pressure gradient by moving boundaries, which generates plane Couette-Poiseuille flow. We obtain experimental results in the transitional regime for this flow. Using flow visualization, we characterize the subcritical transition to turbulence in Couette-Poiseuille flow and show the existence of turbulent spots generated by a permanent perturbation. Due to the zero mean advection velocity of the base profile, these turbulent structures are nearly stationary. We distinguish two regions of the turbulent spot: the active turbulent core, which is characterized by waviness of the streaks similar to traveling waves, and the surrounding region, which includes in addition the weak undisturbed streaks and oblique waves at the laminar-turbulent interface. We also study the dependence of the size of these two regions on Reynolds number. Finally, we show that the traveling waves move in the downstream (Poiseuille) direction.

Design of an ejector cycle refrigeration system

International Nuclear Information System (INIS)

Grazzini, G.; Milazzo, A.; Paganini, D.

2012-01-01

Highlights: ► A design procedure is presented for an ejection refrigeration system. ► Properties of applicable operating fluids are presented and R245fa is selected. ► Real gas properties are used. ► The diffuser is designed with a profile that controls momentum change. ► Fluid friction is accounted for along all main components. - Abstract: A design procedure, based on a one-dimensional simulation, is presented for an ejection refrigeration system. Heat exchangers are included in the calculation, accounting for temperature differences between the fluids and for pressure losses. The ideal gas assumption, which is quite common in the literature concerning ejector systems, is avoided. Furthermore, the supersonic diffuser is designed with a continuous profile, without cylindrical piece, controlling the variation of momentum along the flow path and accounting for friction. At design conditions, this should reduce the irreversibility due to the normal shock. A comparison between different operating fluids is presented and R245fa is selected. The results of the design procedure and the expected performance, in terms of first and second law efficiency, are presented.

Numerical approach to solar ejector-compression refrigeration system

Directory of Open Access Journals (Sweden)

Zheng Hui-Fan

2016-01-01

Full Text Available A model was established for solar ejector-compression refrigeration system. The influence of generator temperature, middle-temperature, and evaporator temperature on the performance of the refrigerant system was analyzed. An optimal generator temperature is found for maximal energy efficiency ratio and minimal power consumption.

Pressure Measurement and Flowfield Characterization of a Two-Dimensional Ideally Expanded, Constant Area, Air/air Ejector.

Science.gov (United States)

Benjamin, Michael Anthony

A detailed experimental investigation of a two -dimensional, Mach 1.8 air-primary, Mach 0.3 air-secondary ejector at high Reynolds number has been performed, from which a nonintrusive method for whole-field visualization using turbulent wall-pressure has been developed. The experiments were conducted using mean and time-accurate wall pressure measurements, impact-pressure measurements using a traversing probe, and Schlieren and shadowgraph visualization techniques. The time-accurate pressure measurements were recorded using a sealed Kulite miniature pressure transducer with a 0.7 mm diameter sensing diaphragm. For all except the optical methods, measurements were taken from the initial flow interface to about 13 hydraulic tube-diameters downstream in the constant-area mixing section. From the mean measurements, values of stagnation pressure, density, velocity, static pressure, Mach number, and dynamic pressure were developed and are presented. Using the time-accurate pressure measurements, a color contour plot of the rms pressure was developed that definitively shows the regions of the flow in agreement with the other measurements. Additionally, probability density functions, skewness, and kurtosis were calculated. Peak values of skewness (S) and kurtosis (K) on the centerline at about 2.5 hydraulic diameters are S = 1.85 and K = 11.5. The inlet rms pressure values, normalized by freestream dynamic pressure for the primary (~0.001), were found to be in fair agreement with previous experimental values; however, those in the secondary were much higher (~0.2), apparently due to the acoustic radiation from the primary. Fourier analysis of the time-accurate pressure measurements show that the autospectra contain k ^{-1}, k^{-7/3}, and k^{-11/3} pressure spectrum functions as predicted by prevailing theory for the overlap layer, turbulence-turbulence interaction, and turbulence-mean-shear interaction, respectively. It is believed that this is the first experiment in

First and Second Law Analyses of Trans-critical N2O Refrigeration Cycle Using an Ejector

Directory of Open Access Journals (Sweden)

Damoon Aghazadeh Dokandari

2018-04-01

Full Text Available An ejector-expansion refrigeration cycle using nitrous oxide was assessed. Thermodynamic analyses, including energy and exergy analyses, were carried out to investigate the effects on performance of several key factors in the system. The results show that the ejector-expansion refrigeration cycle (EERC has a higher maximum coefficient of performance and exergy efficiency than the internal heat exchanger cycle (IHEC, by 12% and 15%, respectively. The maximum coefficient of performance and exergy efficiency are 14% and 16.5% higher than the corresponding values for the vapor-compression refrigeration cycle (VCRC, respectively. The total exergy destruction for the N2O ejector-expansion cycle is 63% and 53% less than for IHEC and VCRC, respectively. Furthermore, the highest COPs for the vapor-compression refrigeration, the internal heat exchanger and the ejector-expansion refrigeration cycles correspond to a high side pressure of 7.3 MPa, and the highest COPs for the three types of CO2 refrigeration cycles correspond to a high side pressure of 8.5 MPa. Consequently, these lead to a lower electrical power consumption by the compressor.

Investigation of an experimental ejector refrigeration machine operating with refrigerant R245fa at design and off-design working conditions. Part 1. Theoretical analysis

KAUST Repository

Shestopalov, K.O.

2015-07-01

© 2015 Elsevier Ltd and IIR.All rights reserved. The ejector refrigeration machine (ERM) offers several advantages over other heat-driven refrigeration machine, including simplicity in design and operation, high reliability and low installation cost, which enable its wide application in the production of cooling. In this paper the theoretical analysis of ejector design and ejector refrigeration cycle performance is presented. It is shown that ERM performance characteristics depend strongly on the operating conditions, the efficiency of the ejector used, and the thermodynamic properties of the refrigerant used. A 1-D model for the prediction of the entrainment ratio ω, and an optimal design for ejectors with cylindrical and conical-cylindrical mixing chambers are presented in this paper. In order to increase ERM performance values, it is necessary first of all to improve the performance of the ejector.

Dependence of charge transfer phenomena during solid-air two-phase flow on particle disperser

Science.gov (United States)

Tanoue, Ken-ichiro; Suedomi, Yuuki; Honda, Hirotaka; Furutani, Satoshi; Nishimura, Tatsuo; Masuda, Hiroaki

2012-12-01

An experimental investigation of the tribo-electrification of particles has been conducted during solid-air two-phase turbulent flow. The current induced in a metal plate by the impact of polymethylmethacrylate (PMMA) particles in a high-speed air flow was measured for two different plate materials. The results indicated that the contact potential difference between the particles and a stainless steel plate was positive, while for a nickel plate it was negative. These results agreed with theoretical contact charge transfer even if not only the particle size but also the kind of metal plate was changed. The specific charge of the PMMA particles during solid-air two-phase flow using an ejector, a stainless steel branch pipe, and a stainless steel straight pipe was measured using a Faraday cage. Although the charge was negative in the ejector, the particles had a positive specific charge at the outlet of the branch pipe, and this positive charge increased in the straight pipe. The charge decay along the flow direction could be reproduced by the charging and relaxation theory. However, the proportional coefficients in the theory changed with the particle size and air velocity. Therefore, an unexpected charge transfer occurred between the ejector and the branch pipe, which could not be explained solely by the contact potential difference. In the ejector, an electrical current in air might have been produced by self-discharge of particles with excess charge between the nickel diffuser in the ejector and the stainless steel nozzle or the stainless steel pipe due to a reversal in the contact potential difference between the PMMA and the stainless steel. The sign of the current depended on the particle size, possibly because the position where the particles impacted depended on their size. When dual coaxial glass pipes were used as a particle disperser, the specific charge of the PMMA particles became more positive along the particle flow direction due to the contact

An optimal multivariable controller for transcritical CO2 refrigeration cycle with an adjustable ejector

International Nuclear Information System (INIS)

He, Yang; Deng, Jianqiang; Yang, Fusheng; Zhang, Zaoxiao

2017-01-01

Highlights: • Dynamic model for transcritical CO 2 ejector refrigeration system is developed. • A model-driven optimal multivariable controller is proposed. • Gas cooler pressure and cooling capacity are tracked independently. • Maximal performance for a given load is achieved by the optimal controller. - Abstract: The fixed ejector has to work under a restricted operating condition to keep its positive effectiveness on the transcritical CO 2 refrigeration cycle, and a controllable ejector will be helpful. In this paper, an optimal multivariable controller based on the dynamic model is proposed to improve transcritical CO 2 refrigeration cycle with an adjustable ejector (TCRAE). A nonlinear dynamic model is first developed to model the dynamic characteristic of TCRAE. The corresponding model linearization is carried out and the simulation results reproduce transient behavior of the nonlinear model very well. Based on the developed model, an optimal multivariable controller with a tracker based linear quadratic state feedback algorithm and a predictor using steepest descent method is designed. The controller is finally applied on the experimental apparatus and the performance is verified. Using the tracker only, the gas cooler pressure and chilled water outlet temperature (cooling capacity) are well tracked rejecting the disturbances from each other. Furthermore, by the predictor, the optimal gas cooler pressure for a constant cooling capacity is actually approached on the experimental apparatus with a settling time about 700 s.

Energy and exergy analysis of a new ejector enhanced auto-cascade refrigeration cycle

International Nuclear Information System (INIS)

Yan, Gang; Chen, Jiaheng; Yu, Jianlin

2015-01-01

Highlights: • A new ejector enhanced auto-cascade refrigeration cycle using R134a/R23 is proposed. • The performance of new and basic cycles is compared by simulation method. • The new cycle outperforms the basic cycle in both energetic and exergy aspects. • Both cycles have optimum mixture compositions to obtain optimal performance. - Abstract: A new ejector enhanced auto-cascade refrigeration cycle using R134a/R23 refrigerant mixture is proposed in this paper. In the new cycle, an ejector is used to recover part of the work that would otherwise be lost in the throttling processes. The performance comparison between the new cycle and a basic auto-cascade refrigeration cycle is carried out based on the first and second laws of thermodynamics. The simulation results show that both the coefficient of performance and exergy efficiency of the new cycle can be improved by 8.42–18.02% compared with those of the basic cycle at the same operation conditions as the ejector has achieved pressure lift ratios of 1.12–1.23. It is found that in the new cycle, the highest exergy destruction occurs in the compressor followed by the condenser, cascade condenser, expansion valve, ejector and evaporator. The effect of some main parameters on the cycle performance is further investigated. The results show that for the new cycle, the achieved performance improvement over the basic cycle is also dependent on the mixture composition and the vapor quality at the condenser outlet. The coefficient of performance improvement of the new cycle over the basic cycle degrades with increasing vapor quality. In addition, there exists an optimum mixture composition to obtain the maximum coefficient of performance for the new cycle when other operation conditions are given. The optimum mixture composition of both cycles may be fixed at about 0.5 under the given evaporating temperature.

Flow Control Device Evaluation for an Internal Flow with an Adverse Pressure Gradient

Science.gov (United States)

Jenkins, Luther N.; Gorton, Susan Althoff; Anders, Scott G.

2002-01-01

The effectiveness of several active and passive devices to control flow in an adverse pressure gradient with secondary flows present was evaluated in the 15 Inch Low Speed Tunnel at NASA Langley Research Center. In this study, passive micro vortex generators, micro bumps, and piezoelectric synthetic jets were evaluated for their flow control characteristics using surface static pressures, flow visualization, and 3D Stereo Digital Particle Image Velocimetry. Data also were acquired for synthetic jet actuators in a zero flow environment. It was found that the micro vortex generator is very effective in controlling the flow environment for an adverse pressure gradient, even in the presence of secondary vortical flow. The mechanism by which the control is effected is a re-energization of the boundary layer through flow mixing. The piezoelectric synthetic jet actuators must have sufficient velocity output to produce strong longitudinal vortices if they are to be effective for flow control. The output of these devices in a laboratory or zero flow environment will be different than the output in a flow environment. In this investigation, the output was higher in the flow environment, but the stroke cycle in the flow did not indicate a positive inflow into the synthetic jet.

An experimental investigation on a novel ejector enhanced refrigeration cycle applied in the domestic refrigerator-freezer

International Nuclear Information System (INIS)

Wang, Xiao; Yu, Jianlin

2015-01-01

This paper presents an experimental investigation on a NERC (novel ejector enhanced refrigeration cycle) applied in the domestic refrigerator-freezer (BCD-249). Experimental studies were conducted to validate the NERC system feasibility in a practical NERC based refrigerator-freezer prototype. The system performances of energy consumption, ejector pressure lift ratio and compressor power were compared under different combinations of system configuration parameters. The results showed that the NERC system could effectively reduce the thermodynamic losses in the throttle processing. The minimum energy consumption of 0.520 kWh 24 h"−"1 was obtained for the NERC prototype, indicating 5.45% energy consumption reduction compared with the conventional domestic refrigerator-freezer. Furthermore, the effects of system configuration parameters including the refrigerant charge amount, the compressor displacement and the length of capillary tube were investigated. This study aims at providing deep insight into ejector-expansion technology applied in domestic refrigerator-freezers. - Highlights: • A NERC (novel ejector enhanced refrigeration cycle) was experimentally studied. • 73 experimental data points with different system configuration were acquired. • Energy consumption could be reduced with optimum system configuration. • 5.45% energy consumption reduction is obtained compared with the conventional system.

Advanced exergy analysis on a modified auto-cascade freezer cycle with an ejector

International Nuclear Information System (INIS)

Bai, Tao; Yu, Jianlin; Yan, Gang

2016-01-01

This paper presents a study on a modified ejector enhanced auto-cascade freezer cycle with conventional thermodynamic and advanced exergy analysis methods. The energetic analysis shows that the modified cycle exhibits better performance than the conventional auto-cascade freezer cycle, and the system COP and volumetric refrigeration capacity could be improved by 19.93% and 28.42%. Furthermore, advanced exergy analysis is adopted to better evaluate the performance of the proposed cycle. The exergy destruction within a system component is split into endogenous/exogenous and unavoidable/avoidable parts in the advanced exergy analysis. The results show that the compressor with the largest avoidable endogenous exergy destruction has highest improvement priority, followed by the condenser, evaporator and ejector, which is different from the conclusion obtained from the conventional exergy analysis. The evaporator/condenser greatly affects the exogenous exergy destruction within the system components, and the compressor has large impact on the exergy destruction within the condenser. Improving the efficiencies of the compressor efficiency and the ejector could effectively reduce the corresponding avoidable endogenous exergy destruction. The exergy destruction within the evaporator almost entirely belongs to the endogenous part, and reducing the temperature difference at the evaporator is the main approach of reducing its exergy destruction. - Highlights: • A modified ejector enhanced auto-cascade freezer cycle is proposed. • Conventional and advanced exergy analyses are performed in this study. • Compressor should be firstly improved first, followed by condenser and evaporator. • Interactions among the system components are assessed with advanced exergy analysis.

Flow velocity measurement by using zero-crossing polarity cross correlation method

International Nuclear Information System (INIS)

Xu Chengji; Lu Jinming; Xia Hong

1993-01-01

Using the designed correlation metering system and a high accurate hot-wire anemometer as a calibration device, the experimental study of correlation method in a tunnel was carried out. The velocity measurement of gas flow by using zero-crossing polarity cross correlation method was realized and the experimental results has been analysed

Thermodynamic analysis on a modified ejector expansion refrigeration cycle with zeotropic mixture (R290/R600a) for freezers

International Nuclear Information System (INIS)

Yan, Gang; Bai, Tao; Yu, Jianlin

2016-01-01

This study presents a modified ejector expansion cycle with zeotropic mixtures (R290/R600a) for freezers, in which an ejector and a phase-separator are employed to enhance the cycle performance. Energetic and exergetic methods are used to theoretically investigate the system operating characteristics. In addition, comparative research among the modified cycle, conventional ejector expansion cycle and basic throttling cycle is carried out. The results demonstrate that the modified cycle exhibits higher refrigeration COP (coefficient of performance), volumetric refrigeration capacity and system exergy efficiency than conventional ejector expansion cycle and basic throttling cycle. Under the given operation conditions, the system performance improvements of the modified cycle in terms of the COP, refrigeration capacity and system exergy efficiency over the basic throttling cycle could reach about 56.0%, 4.5% and 77.7%, respectively. The performance characteristics of the proposed cycle show its potential practical advantages in freezer applications. - Highlights: • A zeotropic mixture based ejector refrigeration cycle with a separator is proposed. • Comparative research among the different cycles is carried out. • Energetic and exergetic methods are used to investigate the system performance. • The COP and system exergy efficiency are improved by 56.0% and 77.7%, respectively.

Numerical simulation of secondary flow in bubbly turbulent flow in sub-channel

International Nuclear Information System (INIS)

Ikeno, Tsutomu; Kataoka, Isao

2009-01-01

Secondary flow in bubbly turbulent flow in sub-channel was simulated by using an algebraic turbulence stress model. The mass, momentum, turbulence energy and bubble diffusion equations were used as fundamental equation. The basis for these equations was the two-fluid model: the equation of liquid phase was picked up from the equation system theoretically derived for the gas-liquid two-fluid turbulent flow. The fundamental equation was transformed onto a generalized coordinate system fitted to the computational domain in sub-channel. It was discretized for the SIMPLE algorism using the finite-volume method. The shape of sub-channel causes a distortion of the computational mesh, and orthogonal nature of the mesh is sometimes broken. An iterative method to satisfy a requirement for the contra-variant velocity was introduced to represent accurate symmetric boundary condition. Two-phase flow at a steady state was simulated for different magnitude of secondary flow and void fraction. The secondary flow enhanced the momentum transport in sub-channel and accelerated the liquid phase in the rod gap. This effect was slightly mitigated when the void fraction increased. The acceleration can contribute to effective cooling in the rod gap. The numerical result implied a phenomenon of industrial interest. This suggested that experimental approach is necessary to validate the numerical model and to identify the phenomenon. (author)

Optimum selection of solar collectors for a solar-driven ejector air conditioning system by experimental and simulation study

International Nuclear Information System (INIS)

Zhang Wei; Ma Xiaoli; Omer, S.A.; Riffat, S.B.

2012-01-01

Highlights: ► Three solar collectors have been compared to drive ejector air conditioning system. ► A simulation program was constructed to study the effect parameters. ► The outdoor test were conducted to validate the solar collector modeling. ► Simulation program was found to predict solar collector performance accurately. ► The optimal design of solar collector system was carried out. - Abstract: In this paper, three different solar collectors are selected to drive the solar ejector air conditioning system for Mediterranean climate. The performance of the three selected solar collector are evaluated by computer simulation and lab test. Computer model is incorporated with a set of heat balance equations being able to analyze heat transfer process occurring in separate regions of the collector. It is found simulation and test has a good agreement. By the analysis of the computer simulation and test result, the solar ejector cooling system using the evacuated tube collector with selective surface and high performance heat pipe can be most economical when operated at the optimum generating temperature of the ejector cooling machine.

Effect of Suction Nozzle Pressure Drop on the Performance of an Ejector-Expansion Transcritical CO2 Refrigeration Cycle

Directory of Open Access Journals (Sweden)

Zhenying Zhang

2014-08-01

Full Text Available The basic transcritical CO2 systems exhibit low energy efficiency due to their large throttling loss. Replacing the throttle valve with an ejector is an effective measure for recovering some of the energy lost in the expansion process. In this paper, a thermodynamic model of the ejector-expansion transcritical CO2 refrigeration cycle is developed. The effect of the suction nozzle pressure drop (SNPD on the cycle performance is discussed. The results indicate that the SNPD has little impact on entrainment ratio. There exists an optimum SNPD which gives a maximum recovered pressure and COP under a specified condition. The value of the optimum SNPD mainly depends on the efficiencies of the motive nozzle and the suction nozzle, but it is essentially independent of evaporating temperature and gas cooler outlet temperature. Through optimizing the value of SNPD, the maximum COP of the ejector-expansion cycle can be up to 45.1% higher than that of the basic cycle. The exergy loss of the ejector-expansion cycle is reduced about 43.0% compared with the basic cycle.

TWO-PHASE EJECTOR of CARBON DIOXIDE HEAT PUMP CALCULUS

Directory of Open Access Journals (Sweden)

Sit B.M.

2010-12-01

Full Text Available It is presented the calculus of the two-phase ejector for carbon dioxide heat pump. The method of calculus is based on the method elaborated by S.M. Kandil, W.E. Lear, S.A. Sherif, and is modified taking into account entrainment ratio as the input for the calculus.

Efficiency analysis of alternative refrigerants for ejector cooling cycles

International Nuclear Information System (INIS)

Gil, Bartosz; Kasperski, Jacek

2015-01-01

Highlights: • Advantages of using alternative refrigerants as ejector refrigerants were presumed. • Computer software basing on theoretical model of Huang et al. (1999) was prepared. • Optimal temperature range of primary vapor for each working fluid was calculated. - Abstract: Computer software, basing on the theoretical model of Huang et al. with thermodynamic properties of selected refrigerants, was prepared. Investigation was focused on alternative refrigerants that belong to two groups of substances: common solvents (acetone, benzene, cyclopentane, cyclohexane and toluene) and non-flammable synthetic refrigerants applied in Organic Rankine Cycle (ORC) (R236ea, R236fa, R245ca, R245fa, R365mfc and RC318). Refrigerants were selected to detect a possibility to use them in ejector cooling system powered by a high-temperature heat source. A series of calculations were carried out for the generator temperature between 70 and 200 °C, with assumed temperatures of evaporation 10 °C and condensation 40 °C. Investigation revealed that there is no single refrigerant that ensures efficient operation of the system in the investigated temperature range of primary vapor. Each substance has its own maximum entrainment ratio and COP at its individual temperature of the optimum. The use of non-flammable synthetic refrigerants allows obtaining higher COP in the low primary vapor temperature range. R236fa was the most beneficial among the non-flammable synthetic refrigerants tested. The use of organic solvents can be justified only for high values of motive steam temperature. Among the solvents, the highest values of entrainment ratio and COP throughout the range of motive temperature were noted for cyclopentane. Toluene was found to be an unattractive refrigerant from the ejector cooling point of view

Arterial secondary blood flow patterns visualized with vector flow ultrasound

DEFF Research Database (Denmark)

Pedersen, Mads Møller; Pihl, Michael Johannes; Hansen, Jens Munk

2011-01-01

This study presents the first quantification and visualisation of secondary flow patterns with vector flow ultrasound. The first commercial implementation of the vector flow method Transverse Oscillation was used to obtain in-vivo, 2D vector fields in real-time. The hypothesis of this study...... was that the rotational direction is constant within each artery. Three data sets of 10 seconds were obtained from three main arteries in healthy volunteers. For each data set the rotational flow patterns were identified during the diastole. Each data set contains a 2D vector field over time and with the vector angles...

CFD modeling of secondary flows in fuel rod bundles

International Nuclear Information System (INIS)

Baglietto, Emilio; Ninokata, Hisashi

2004-01-01

An optimized non-linear eddy viscosity model is introduced, for calculations of detailed coolant velocity distribution in a tight lattice fuel bundle. The low Reynolds formulation has been optimized based on DNS data for channel flow. The non-linear stress-strain relationship has been modified in the coefficients to model the flow anisotropy, which causes the formation of turbulence driven secondary flows inside the bundle subchannels. Predictions of the model are first compared to experimental measurements of secondary flows in a triangularly arrayed rod bundle with p/d=1.3. Subsequently wall shear stress and velocity predictions are compared with different experimental data for a rod bundle with p/d=1.17. The model shows to be able to correctly reproduce the scale of the secondary motion, and to accurately reproduce both wall shear stress and velocity distributions inside the rod bundle subchannels. (author)

Numerical Study of an Ejector as an Expansion Device in Split-type Air Conditioners for Energy Savings

Directory of Open Access Journals (Sweden)

Kasni Sumeru

2013-07-01

Full Text Available The present study describes a numerical approach for determining both the motive nozzle and constant-area diameters of an ejector as an expansion device, based on the cooling capacity of a split-type air-conditioner using R290 as refrigerant. Previous studies have shown that replacement of HCFC R22 with HC290 (propane in the air conditioner can improve the coefficient of performance (COP. The purpose of replacing the capillary tube with an ejector as an expansion device in a split-type air conditioner using HC290 is to further improve the COP. In developing the model, conservation laws of mass, momentum and energy equations were applied to each part of the ejector. The numerical results show that the motive nozzle diameter remains constant (1.03 mm under varying condenser temperatures, whereas the diameter of the constant-area decreases as the condenser temperature increases. It was also found that improvement of the COP can reach 32.90% at a condenser temperature of 55 °C. From the results mentioned above, it can be concluded that the use of an ejector can further improve the COP of a split-type air conditioner using HC290 as working fluid.

Energy efficiency analysis of steam ejector and electric vacuum pump for a turbine condenser air extraction system based on supervised machine learning modelling

International Nuclear Information System (INIS)

Strušnik, Dušan; Marčič, Milan; Golob, Marjan; Hribernik, Aleš; Živić, Marija; Avsec, Jurij

2016-01-01

Highlights: • Steam ejector pump and electric liquid ring vacuum pump are analysed and modelled. • A supervised machine learning models by using real process data are applied. • The equation of ejector pumped mass flow from steam turbine condenser was solved. • The loss of specific energy capable of work in a SEPS or LRVP component was analysed. • The economic efficiency analysis per different coal heating values was made. - Abstract: This paper compares the vapour ejector and electric vacuum pump power consumptions with machine learning algorithms by using real process data and presents some novelty guideline for the selection of an appropriate condenser vacuum pump system of a steam turbine power plant. The machine learning algorithms are made by using the supervised machine learning methods such as artificial neural network model and local linear neuro-fuzzy models. The proposed non-linear models are designed by using a wide range of real process operation data sets from the CHP system in the thermal power plant. The novelty guideline for the selection of an appropriate condenser vacuum pumps system is expressed in the comparative analysis of the energy consumption and use of specific energy capable of work. Furthermore, the novelty is expressed in the economic efficiency analysis of the investment taking into consideration the operating costs of the vacuum pump systems and may serve as basic guidelines for the selection of an appropriate condenser vacuum pump system of a steam turbine.

Thermodynamic, Environmental and Economic Analyses of Solar Ejector Refrigeration System Application for Cold Storage

Directory of Open Access Journals (Sweden)

İbrahim ÜÇGÜL

2009-02-01

Full Text Available The refrigeration processes have been widely applied for especially in cold storages. In these plants, the systems working with compressed vapour cooling cycles have been used as a classical method. In general, electrical energy is used for compressing in these processes. Although, mainly the electricity itself has no pollution effect on the environment, the fossil fuels that are widely used to produce electricity in the most of the world, affect the nature terribly. In short, these refrigeration plants, because of the source of the electricity pollute the nature indirectly. However, for compression an ejector refrigeration system requires one of the important renewable energy sources with negligible pollution impact on the environment, namely solar energy from a thermal source. Thermodynamical, environmental and economical aspects of the ejector refrigeration system working with solar energy was investigated in this study. As a pilot case, apple cold storage plants widely used in ISPARTA city, which 1/5 th of apple production of TURKEY has been provided from, was chosen. Enviromental and economical advantages of solar ejector refrigeration system application for cold storage dictated by thermodynamic, economic and enviromental analyses in this research.

Performance Analysis of Solar Combined Ejector-Vapor Compression Cycle Using Environmental Friendly Refrigerants

Directory of Open Access Journals (Sweden)

A. B. Kasaeian

2013-04-01

Full Text Available In this study, a new model of a solar combined ejector-vapor compression refrigeration system has been considered. The system is equipped with an internal heat exchanger to enhance the performance of the cycle. The effects of working fluid and operating conditions on the system performance including COP, entrainment ratio (ω, compression ratio (rp and exergy efficiency were investigated. Some working fluids suggested are: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e and R1234ze(z. The results show that R114 and R1234ze(e yield the highest COP and exergy efficiency followed by R123, R245fa, R365mfc, R141b, R152a and R600a. It is noticed that the COP value of the new solar ejector-vapor compression refrigeration cycle is higher than that of the conventional ejector cycle with R1234ze(e for all operating conditions. This paper also demonstrates that R1234ze(e will be a suitable refrigerant in the solar combined ejector-vapor compression refrigeration system, due to its environmental friendly properties and better performance. ABSTRAK: Kajian ini menganalisa model baru sistem penyejukan mampatan gabungan ejektor-wap solar.Sistem ini dilengkapi dengan penukar haba dalaman untuk meningkatkan prestasi kitaran.Kesan bendalir bekerja dan keadaan operasi pada prestasi sistem termasuk COP, nisbah pemerangkapan (ω, nisbah mampatan (rp dan kecekapan eksergi telah disiasat.Beberapa bendalir bekerja yang dicadangkan adalah: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e dan R1234ze(z.Hasil kajian menunjukkan R114 dan R1234ze(e menghasilkan COP dan kecekapan eksergi tertinggi diikuti oleh R123, R245fa, R365mfc, R141b, R152a dan R600a.Didapati nilai COP kitaran penyejukan mampatan bagi ejektor-wap solar baru adalah lebih tinggi daripada kitaran ejektor konvensional dengan R1234ze(e bagi semua keadaan operasi.Kertas kerja ini juga menunjukkan bahawa R1234ze(e boleh menjadi penyejuk yang sesuai dalam sistem penyejukan mampatan gabungan ejektor

Analysis of Systolic Backflow and Secondary Helical Blood Flow in the Ascending Aorta Using Vector Flow Imaging

DEFF Research Database (Denmark)

Hansen, Kristoffer Lindskov; Møller-Sørensen, Hasse; Kjaergaard, Jesper

2016-01-01

echocardiography and pulmonary artery catheter thermodilution, and associated with gender, age, aortic diameter, atherosclerotic plaques, left ventricular ejection fraction and previous myocardial infarctions. Secondary flow was present for all patients. The duration and rotational frequency (p ... that backflow is injurious and that secondary flow is a normal flow phenomenon. The study also shows that transverse oscillation can provide new information on blood flow in the ascending aorta....

Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

Science.gov (United States)

Najafi, Moslem; Zahednezhad, Fahimeh; Samadzadeh, Mehrban; Vaez, Haleh

2012-01-01

Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods: The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups), respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. Results: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2%) reduced it to 39.3±11, 30.6±5.5 (Phoney concentrations and infarction size reduction was observed (R2=0.9948). In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (PHoney (0.25, 0.5 and 1 %) also lowered incidence of irreversible ventricular fibrillation (Phoney treated groups. Conclusion: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey. PMID:24312788

Thermodynamic performance of an auto-cascade ejector refrigeration cycle with mixed refrigerant R32 + R236fa

International Nuclear Information System (INIS)

Tan, Yingying; Wang, Lin; Liang, Kunfeng

2015-01-01

In this paper, an auto-cascade ejector refrigeration cycle (ACERC) is proposed to obtain lower refrigeration temperature based on conventional ejector refrigeration and auto-cascade refrigeration principle. The thermodynamic performance of ACERC is investigated theoretically. The zeotropic refrigerant mixture R32 + R236fa is used as its working fluid. A parametric analysis is conducted to evaluate the effects of some thermodynamic parameters on the cycle performance. The study shows that refrigerant mixture composition, condenser outlet temperature and evaporation pressure have effects on performance of ACERC. The theoretical results also indicate that the ACERC can achieve the lowest refrigeration temperature at the temperature level of −30 °C. The application of zeotropic refrigerant mixture auto-cascade refrigeration in the ejector refrigeration cycle can provide a new way to obtain lower refrigeration temperature utilizing low-grade thermal energy. - Highlights: • An auto-cascade ejector refrigerator with R32 + R236fa mixed refrigerant is proposed. • The cycle can obtain a refrigeration temperature at −30 °C temperature range. • The effects of some thermodynamic parameters on the cycle performance are evaluated

Turbulence and secondary motions in square duct flow

Science.gov (United States)

Pirozzoli, Sergio; Modesti, Davide; Orlandi, Paolo; Grasso, Francesco

2017-11-01

We study turbulent flows in pressure-driven ducts with square cross-section through DNS up to Reτ 1050 . Numerical simulations are carried out over extremely long integration times to get adequate convergence of the flow statistics, and specifically high-fidelity representation of the secondary motions which arise. The intensity of the latter is found to be in the order of 1-2% of the bulk velocity, and unaffected by Reynolds number variations. The smallness of the mean convection terms in the streamwise vorticity equation points to a simple characterization of the secondary flows, which in the asymptotic high-Re regime are found to be approximated with good accuracy by eigenfunctions of the Laplace operator. Despite their effect of redistributing the wall shear stress along the duct perimeter, we find that secondary motions do not have large influence on the mean velocity field, which can be characterized with good accuracy as that resulting from the concurrent effect of four independent flat walls, each controlling a quarter of the flow domain. As a consequence, we find that parametrizations based on the hydraulic diameter concept, and modifications thereof, are successful in predicting the duct friction coefficient. This research was carried out using resources from PRACE EU Grants.

零净质量射流的数值模拟%Numerical simulation of the zero mass jet flow

Institute of Scientific and Technical Information of China (English)

石清; 李桦

2011-01-01

对零净质量射流致动器的流场和有零净质量射流时翼型的绕流流场进行了数值模拟,分析了动网格与几何守恒率、边界条件、湍流模型对零净质量射流致动器流场计算的影响,分析了零净质量射流的速度幅值和驱动频率对翼型增升效果的影响.研究结果表明,在复杂计算中可以对能动部件的边界作赋值处理;随着射流速度幅值的增加,翼型的平均升力系数和阻力系数都要增加;射流频率对升力的影响呈非线性.%Numerical simulation methods are used to investigate the actuator of zero mass jet flow and the flow around airfoil with zero mass jet flow.The effects on the actuator of zero mass jet flow are analysed about dynamic grid,geometry conservation law, numerical boundary conditions, and turbulence mode.And the effects on increasing lift are analysed also, including the jet flow velocity and frequency.The results indicate that numerical boundary conditions of the actuator of zero mass jet flow can be treated with given numerical value for complicated calculation, both the average lift coefficient and the average drag coefficient are added with the increase of the jet flow velocity, and the effects of the jet flow frequency on lift are non - linear.

Investigation of an experimental ejector refrigeration machine operating with refrigerant R245fa at design and off-design working conditions. Part 1. Theoretical analysis

KAUST Repository

Shestopalov, K.O.; Huang, B.J.; Petrenko, V.O.; Volovyk, O.S.

2015-01-01

, which enable its wide application in the production of cooling. In this paper the theoretical analysis of ejector design and ejector refrigeration cycle performance is presented. It is shown that ERM performance characteristics depend strongly

Enhancement of energy performance in a boil-off gas re-liquefaction system of LNG carriers using ejectors

International Nuclear Information System (INIS)

Tan, Hongbo; Zhao, Qingxuan; Sun, Nannan; Li, Yanzhong

2016-01-01

Highlights: • An ejector-enhanced LNG boil-off gas (BOG) re-liquefaction system is proposed. • The new system has an improvement of 28% in COP over the existing system. • The specific energy consumption of the new system is reduced to 0.59 kW h/kg(BOG). • The power consumption of 754.1 kW is saved in the case study. - Abstract: An ejector-enhanced Liquefied Natural Gas (LNG) boil-off gas (BOG) re-liquefaction system is proposed to improve the energy efficiency of the existing system. In the new system, two ejectors are respectively used to reduce the energy loss in the expansion of the pressurized BOG and inject a part of fuel BOG into the compression system, and a recuperator is employed to recover the cold energy of the BOG exited from LNG tank. The performance improvement of the proposed system is analysed on the basis of the simulation in Aspen HYSYS. In the case of the re-liquefaction capacity of 4557.6 kg/h, the coefficient of performance (COP) and exergy efficiency can be increased by 28%, and the specific energy consumption (SEC) reduced from 0.756 to 0.59 kW h/kg(BOG) compared to the conventional BOG re-liquefaction system. Correspondingly, the power consumption of 754.1 kW is saved. This means that applying ejectors can effectively improve the energy efficiency of the existing BOG re-liquefaction system for LNG carriers.

Secondary Flow Phenomena in Rotating Radial Straight Pipes

OpenAIRE

Cheng, K. C.; Wang, Liqiu

1995-01-01

Flow visualization results for secondary flow phenomena near the exit of a rotating radial-axis straight pipe (length ࡁ = 82 cm, inside diameter d = 3.81 cm, ࡁ/d 21.52) are presented to study the stabilizing (relaminarization) and destabilizing (early transition from laminar to turbulent flow) effects of Coriolis forces for Reynolds numbers Re = 500 ∼ 4,500 and rotating speeds n = 0 ∼ 200 rpm. The flow visualization was realised by smoke injection method. The main features of the trans...

Numerical analysis of exhaust jet secondary combustion in hypersonic flow field

Science.gov (United States)

Yang, Tian-Peng; Wang, Jiang-Feng; Zhao, Fa-Ming; Fan, Xiao-Feng; Wang, Yu-Han

2018-05-01

The interaction effect between jet and control surface in supersonic and hypersonic flow is one of the key problems for advanced flight control system. The flow properties of exhaust jet secondary combustion in a hypersonic compression ramp flow field were studied numerically by solving the Navier-Stokes equations with multi-species and combustion reaction effects. The analysis was focused on the flow field structure and the force amplification factor under different jet conditions. Numerical results show that a series of different secondary combustion makes the flow field structure change regularly, and the temperature increases rapidly near the jet exit.

Direct Numerical Simulation of Turbulent Couette-Poiseuille Flow With Zero Skin Friction

Science.gov (United States)

Coleman, Gary N.; Spalart, Philippe R.

2015-01-01

The near-wall scaling of mean velocity U(yw) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to the square root of yw in the region just above the wall at which the mean shear dU=dy = 0.

Numerical Research on Effects of Turbine Outlet Flow Angle on Aerodynamic Performance of Wind-Ejector of Low-Speed Wind Turbine%涡轮出口气流角对低速风力引射器流场影响的数值研究

Institute of Scientific and Technical Information of China (English)

韩万龙; 颜培刚; 韩万金; 何玉荣

2015-01-01

为了开发先进的具有广泛适用性的低速风力涡轮，采用涡扇发动机喷管引射技术设计了双涵道风力涡轮，以新型低速引射式风力涡轮的引射混合器为研究对象，采用CFX商用软件基于RANS方程和k-Epsilon湍流模型，数值研究了涡轮出口气流角对风力引射器混合性能的影响。研究结果显示，涡轮出口气流与轴向夹角由0°增至30°，引起了波瓣后侧流向涡量迁移，最大正交涡量降低了1/3，波瓣内侧中部分离对涡与槽道吸力侧分离区汇合，风力引射器内流道总压损失从2.4%增大至5%，此夹角大于10°时外流场对称结构消失并失稳。%The turbofan engine nozzle ejector technology was adopted to design a high-efficiency low speed wind turbine with the double bypass for a broader areas in the world. The aerodynamic characteristics of the wind-ejector of the new wind turbine were numerically researched on turbine outlet flow angle changing based on Reyn⁃olds-averaged NS equations and k-Epsilon turbulence model, using commercial software CFX. Results show that,as the angle between turbine outlet flow and the rotation axis increased from 0°to 30°,the positive vorticity of the stream-wise vortice pairs migrated to the negative vorticity,the maximum normal vorticity was gradually reduced by 1/3,the separation vortex pairs adhesion of the lobes were gradually forced to mix with the separation vortices near the suction surface of the channels, the total pressure loss in the lobes of the wind-ejector in⁃creased from 2.4%to 5%, and if the angle was greater than 10° , the flow stability of the wind turbine outflow field rapidly disappeared.

Characterization of the secondary flow in hexagonal ducts

Science.gov (United States)

Marin, O.; Vinuesa, R.; Obabko, A. V.; Schlatter, P.

2016-12-01

In this work we report the results of DNSs and LESs of the turbulent flow through hexagonal ducts at friction Reynolds numbers based on centerplane wall shear and duct half-height Reτ,c ≃ 180, 360, and 550. The evolution of the Fanning friction factor f with Re is in very good agreement with experimental measurements. A significant disagreement between the DNS and previous RANS simulations was found in the prediction of the in-plane velocity, and is explained through the inability of the RANS model to properly reproduce the secondary flow present in the hexagon. The kinetic energy of the secondary flow integrated over the cross-sectional area yz decreases with Re in the hexagon, whereas it remains constant with Re in square ducts at comparable Reynolds numbers. Close connection between the values of Reynolds stress u w ¯ on the horizontal wall close to the corner and the interaction of bursting events between the horizontal and inclined walls is found. This interaction leads to the formation of the secondary flow, and is less frequent in the hexagon as Re increases due to the 120∘ aperture of its vertex, whereas in the square duct the 90∘ corner leads to the same level of interaction with increasing Re. Analysis of turbulence statistics at the centerplane and the azimuthal variance of the mean flow and the fluctuations shows a close connection between hexagonal ducts and pipe flows, since the hexagon exhibits near-axisymmetric conditions up to a distance of around 0.15DH measured from its center. Spanwise distributions of wall-shear stress show that in square ducts the 90∘ corner sets the location of a high-speed streak at a distance zv+≃50 from it, whereas in hexagons the 120∘ aperture leads to a shorter distance of zv+≃38 . At these locations the root mean square of the wall-shear stresses exhibits an inflection point, which further shows the connections between the near-wall structures and the large-scale motions in the outer flow.

Reynolds-Averaged Navier-Stokes Analysis of Zero Efflux Flow Control over a Hump Model

Science.gov (United States)

Rumsey, Christopher L.

2006-01-01

The unsteady flow over a hump model with zero efflux oscillatory flow control is modeled computationally using the unsteady Reynolds-averaged Navier-Stokes equations. Three different turbulence models produce similar results, and do a reasonably good job predicting the general character of the unsteady surface pressure coefficients during the forced cycle. However, the turbulent shear stresses are underpredicted in magnitude inside the separation bubble, and the computed results predict too large a (mean) separation bubble compared with experiment. These missed predictions are consistent with earlier steady-state results using no-flow-control and steady suction, from a 2004 CFD validation workshop for synthetic jets.

Multiple Payload Ejector for Education, Science and Technology Experiments

Science.gov (United States)

Lechworth, Gary

2005-01-01

The education research community no longer has a means of being manifested on Space Shuttle flights, and small orbital payload carriers must be flown as secondary payloads on ELV flights, as their launch schedule, secondary payload volume and mass permits. This has resulted in a backlog of small payloads, schedule and cost problems, and an inability for the small payloads community to achieve routine, low-cost access to orbit. This paper will discuss Goddard's Wallops Flight Facility funded effort to leverage its core competencies in small payloads, sounding rockets, balloons and range services to develop a low cost, multiple payload ejector (MPE) carrier for orbital experiments. The goal of the MPE is to provide a low-cost carrier intended primarily for educational flight research experiments. MPE can also be used by academia and industry for science, technology development and Exploration experiments. The MPE carrier will take advantage of the DARPAI NASA partnership to perform flight testing of DARPA s Falcon small, demonstration launch vehicle. The Falcon is similar to MPE fiom the standpoint of focusing on a low-cost, responsive system. Therefore, MPE and Falcon complement each other for the desired long-term goal of providing the small payloads community with a low-cost ride to orbit. The readiness dates of Falcon and MPE are complementary, also. MPE is being developed and readied for flight within 18 months by a small design team. Currently, MPE is preparing for Critical Design Review in fall 2005, payloads are being manifested on the first mission, and the carrier will be ready for flight on the first Falcon demonstration flight in summer, 2006. The MPE and attached experiments can weigh up to 900 lb. to be compatible with Falcon demonstration vehicle lift capabilities fiom Wallops, and will be delivered to the Falcon demonstration orbit - 100 nautical mile circular altitude.

Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

Directory of Open Access Journals (Sweden)

Moslem Najafi

2012-06-01

Full Text Available Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods:The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups, respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. Results: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2% reduced it to 39.3±11, 30.6±5.5 (P<0.01, 17.9±5.6 (P<0.001 and 8.7±1.1% (P<0.001, respectively. A direct linear correlation between honey concentrations and infarction size reduction was observed (R2=0.9948. In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (P<0.05 during reperfusion time. Honey (0.25, 0.5 and 1 % also lowered incidence of irreversible ventricular fibrillation (P<0.05. Moreover, number and duration of ventricular tachycardia were reduced in all honey treated groups. Conclusion: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey.

Experimental study of particle-driven secondary flow in turbulent pipe flows

OpenAIRE

Belt, R.J.; Daalmans, A.C.L.M.; Portela, L.M.

2012-01-01

In fully developed single-phase turbulent flow in straight pipes, it is known that mean motions can occur in the plane of the pipe cross-section, when the cross-section is non-circular, or when the wall roughness is non-uniform around the circumference of a circular pipe. This phenomenon is known as secondary flow of the second kind and is associated with the anisotropy in the Reynolds stress tensor in the pipe cross-section. In this work, we show, using careful laser Doppler anemometry exper...

Numerical analysis of transport phenomena for designing of ejector in PEM forklift system

DEFF Research Database (Denmark)

Hosseinzadeh, Elham; Rokni, Masoud; Jabbari, Masoud

2014-01-01

In the present study, Computational Fluid Dynamics (CFD) technique is used to design an ejector for anode recirculation in an automotive PEMFC system. A CFD model is firstly established and tested against well-documented and relevant solutions from the literature, and then used for different...

The behaviour of a hybrid compressor and ejector refrigeration system with refrigerants 134a and 142b

Energy Technology Data Exchange (ETDEWEB)

Hernandez, J.I.; Best, R.; Estrada, C.A. [UNAM, Morelos (Mexico). Centro de Investigacion en Energia; Dorantes, R.J. [UAM Azcapotzalco, Reynosa Tamaulipas (Mexico). Dpto. de Energia

2004-09-01

A complete theoretical analysis on the thermodynamic behaviour of a HYbrid Compressor and Ejector Refrigeration System - HYCERS - is carried out. An ejector under optimum performance is employed. Two working fluids were selected: refrigerant 142b (HCFC 142b) which has shown very good characteristics in air conditioning applications of ejector systems and refrigerant 134a (HFC134a) which is widely used in refrigeration applications and readily available in most countries. The variation of the generator and condenser temperatures as well as the intercooler pressure were considered for an evaporator temperature of 10{sup o}C and a unitary cooling capacity of 1 kW. The ideal efficiency, the enthalpy-based coefficient of performance, the exergy efficiency and the supplied energy ratio are obtained. With this information, at a moderate condenser and generator temperature of 30 and 85{sup o}C, respectively, the HYCERS working with R134a had the best operation with a highest coefficient of performance of 0.48 and an exergy efficiency of 0.25. On the other hand, if a higher condenser temperature is imposed, the HYCERS with 142b had its best performance at a higher generator temperature. In selecting a working fluid the ejector subsystem behaviour is determinant in system performance. If a working fluid is badly selected, despite having high entrainment ratios, the system will not function properly. Therefore, the methodology here defined becomes an effective tool for selecting adequate working fluids and optimum system design conditions. Also, the employment of a unitary cooling load allows system scaling at any capacity as it increases linearly. (author)

Secondary flow in sharp open-channel bends

NARCIS (Netherlands)

Blanckaert, K.; De Vriend, H.J.

2004-01-01

Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in

Venturi Air-Jet Vacuum Ejector For Sampling Air

Science.gov (United States)

Hill, Gerald F.; Sachse, Glen W.; Burney, L. Garland; Wade, Larry O.

1990-01-01

Venturi air-jet vacuum ejector pump light in weight, requires no electrical power, does not contribute heat to aircraft, and provides high pumping speeds at moderate suctions. High-pressure motive gas required for this type of pump bled from compressor of aircraft engine with negligible effect on performance of engine. Used as source of vacuum for differential-absorption CO-measurement (DACOM), modified to achieve in situ measurements of CO at frequency response of 10 Hz. Provides improvement in spatial resolution and potentially leads to capability to measure turbulent flux of CO by use of eddy-correlation technique.

Cleaning of porous filters in fluidized bed reactors. Use of one ejector for various filters; Limpieza de filtros porosos en reactores lecho fluidizado. Empleo de un eyector para varios filtros

Energy Technology Data Exchange (ETDEWEB)

Sancho Rod, J; Rodirgo Otero, A

1966-07-01

Tests to know the efficiency of a porous filters cleaning system by blow-back that uses on ejector for each set of simultaneously cleaned filters were carried out. A Calculation method to obtain the optimum ejector for this system was shown, taking n=2, as optimum number of working for the fluidized bed reactors belonging to the Pilot plant of the Materials Division at JEN. That is two filters for each ejector. (Author)

Comparative Analyses between the Zero-Inertia and Fully Dynamic Models of the Shallow Water Equations for Unsteady Overland Flow Propagation

Directory of Open Access Journals (Sweden)

Costanza Aricò

2018-01-01

Full Text Available The shallow water equations are a mathematical tool widely applied for the simulation of flow routing in rivers and floodplains, as well as for flood inundation mapping. The interest of many researchers has been focused on the study of simplified forms of the original set of equations. One of the most commonly applied simplifications consists of neglecting the inertial terms. The effects of such a choice on the outputs of the simulations of flooding events are controversial and are an important topic of debate. In the present paper, two numerical models recently proposed for the solution of the complete and zero-inertia forms of the shallow water equations, are applied to several unsteady flow routing scenarios. We simulate synthetic and laboratory scenarios of unsteady flow routing, starting from very simple geometries and gradually moving towards complex topographies. Unlike the studies of the range of validity of the zero-inertia model, based on a small perturbation of the linearized flow model, in unsteady flow propagation over irregular topographies, it is more difficult to specify criteria for the applicability of the simplified set of equations. In analyzing the role of the terms in the momentum equations, we try to understand the effect of neglecting the inertial terms in the zero-inertia formulation. We also analyze the computational costs.

Levy's zero-one law in game-theoretic probability

OpenAIRE

Shafer, Glenn; Vovk, Vladimir; Takemura, Akimichi

2009-01-01

We prove a game-theoretic version of Levy's zero-one law, and deduce several corollaries from it, including non-stochastic versions of Kolmogorov's zero-one law, the ergodicity of Bernoulli shifts, and a zero-one law for dependent trials. Our secondary goal is to explore the basic definitions of game-theoretic probability theory, with Levy's zero-one law serving a useful role.

Acoustic-hydrodynamic-flame coupling—A new perspective for zero and low Mach number flows

Science.gov (United States)

Pulikkottil, V. V.; Sujith, R. I.

2017-04-01

A combustion chamber has a hydrodynamic field that convects the incoming fuel and oxidizer into the chamber, thereby causing the mixture to react and produce heat energy. This heat energy can, in turn, modify the hydrodynamic and acoustic fields by acting as a source and thereby, establish a positive feedback loop. Subsequent growth in the amplitude of the acoustic field variables and their eventual saturation to a limit cycle is generally known as thermo-acoustic instability. Mathematical representation of these phenomena, by a set of equations, is the subject of this paper. In contrast to the ad hoc models, an explanation of the flame-acoustic-hydrodynamic coupling, based on fundamental laws of conservation of mass, momentum, and energy, is presented in this paper. In this paper, we use a convection reaction diffusion equation, which, in turn, is derived from the fundamental laws of conservation to explain the flame-acoustic coupling. The advantage of this approach is that the physical variables such as hydrodynamic velocity and heat release rate are coupled based on the conservation of energy and not based on an ad hoc model. Our approach shows that the acoustic-hydrodynamic interaction arises from the convection of acoustic velocity fluctuations by the hydrodynamic field and vice versa. This is a linear mechanism, mathematically represented as a convection operator. This mechanism resembles the non-normal mechanism studied in hydrodynamic theory. We propose that this mechanism could relate the instability mechanisms of hydrodynamic and thermo-acoustic systems. Furthermore, the acoustic-hydrodynamic interaction is shown to be responsible for the convection of entropy disturbances from the inlet of the chamber. The theory proposed in this paper also unifies the observations in the fields of low Mach number flows and zero Mach number flows. In contrast to the previous findings, where compressibility is shown to be causing different physics for zero and low Mach

Obtenção de concretos auto-escoantes zero-cimento a partir do controle reológico da matriz Production of self-flow zero-cement castables based on matrix rheological control

Directory of Open Access Journals (Sweden)

A. R. Studart

2000-03-01

Full Text Available Os concretos refratários auto-escoantes com reduzido teor de cimento têm se destacado pelo fato de associarem a facilidade de aplicação dos concretos de elevada fluidez, com o bom desempenho termomecânico dos refratários contendo baixo teor de CaO. Através do controle simultâneo da distribuição granulométrica e do estado de dispersão da matriz, é possível eliminar o cimento aluminoso (fonte de CaO e quaisquer outros ligantes hidráulicos do concreto, mantendo sua auto-escoabilidade. Os concretos obtidos, denominados zero-cimento, apresentam resistência mecânica a verde compatível com aplicações industriais e excelentes propriedades a altas temperaturas. Neste trabalho, são apresentadas as condições de dispersão da matriz necessárias para a obtenção dos concretos zero-cimento, após um ajuste granulométrico prévio. As faixas de pH e de teor de dispersante ideais para a otimização da reologia da matriz são apresentadas graficamente em um mapa de estabilidade, o qual mostrou-se uma ferramenta bastante útil para a formulação dos concretos auto-escoantes zero-cimento.Self-flow low-cement refractory castables have attracted much attention in the latest years because they combine the installation benefits of high-flowability castables with the good thermomechanical behaviour of low CaO-content refractories. By simultaneously controlling the castable particle size distribution and the matrix dispersion state, it becomes possible to eliminate the aluminous cement (CaO source or any other hydraulic binder in the castable, keeping its self-flow ability. Such castables, named self-flow zero-cement castables, exhibit pre-firing mechanical strength compatible with industrial applications and outstanding high temperature properties. The matrix dispersion conditions necessary to obtain these castables are presented in this work. The optimum range of pH and dispersant amount for the matrix rheological optimisation are

Internal heat exchange in an ejector-compression solar refrigeration system with R142b

Energy Technology Data Exchange (ETDEWEB)

Hernandez, Joge I; Estrada, Claudio A; Best, Roberto [Centro de Investigacion en Energia, UNAM, Temixco, Morelos (Mexico); Dorantes Ruben, J [Departamento de Energia, UNAM Azcapotzalco, Mexico, D.F. (Mexico)

2000-07-01

One way to use more efficiently the actual energy transfer in the ejector-compression system, is the use of heat exchangers between some of the components. The inclusion of two heat exchangers, preheater and precooler, is considered in a basic ejector-compression refrigeration system with refrigerant 142b. This study accounts for the energy and exergy efficiencies. COP and {epsilon}, according to parameter variations such as ejector efficiency, generation temperature with different superheating, condensation temperature and heat exchangers effectiveness. As known, the most important parameters in ejector-compression system analysis are the entrain-ment ratio U and system efficiencies COP and {epsilon}. The highest system COP and {epsilon}, as the entrainment ratio U, correspond to the highest exchangers effectiveness, highest superheating generator temperatures, highest ejector efficiency and lowest condenser temperature. For the COP and {epsilon} ratios, their maxima correspond to the same independent variables aforementioned for one of the higher superheating generator temperatures. In this case, this result indicates that the exergy efficiency {epsilon} does not contradict the information given by energy efficiency COP. So, to select correctly and optimum design condition, is enough to employ the COP ratio, which maximum value for the data shown corresponds to a superheating generator temperature of about 110 Celsius degrees, that can only be reached by evacuated tubular collectors or CPC solar concentrators. [Spanish] Una forma de usar mas eficientemente la transferencia real de energia en el sistema eyector-compresion es el uso de intercambiadores de calor entre algunos de los componentes. La inclusion de dos intercambiadores de calor precalentador y pre-enfriador se considera en un sistema de refrigeracion eyector-compresion con refrigerante 142b. Este estudio toma en cuenta las eficiencias de energia y exergia, COP y {epsilon}, de acuerdo con las variaciones

Theoretical analysis of a combined power and ejector refrigeration cycle using zeotropic mixture

International Nuclear Information System (INIS)

Yang, Xingyang; Zhao, Li; Li, Hailong; Yu, Zhixin

2015-01-01

Highlights: • A combined power and refrigeration cycle using zeotropic mixture is analyzed. • The cycle performances with different mixture compositions are compared. • Both exergy and parametric analysis of the combined cycle are conducted. - Abstract: A theoretical study on a combined power and ejector refrigeration cycle using zeotropic mixture isobutane/pentane is carried out. The performances of different mixture compositions are compared. An exergy analysis is conducted for the cycle. The result reveals that most exergy destruction happens in the ejector, where more than 40% exergy is lost. The heat exchange in generator causes the second largest exergy loss, larger than 28%. As the mass fraction of isobutane changes ranges from 100% to 0%, the relative exergy destruction of each component is also changing. And mixture isobutane/pentane (50/50) has the maximum exergy efficiency of 7.83%. The parametric analysis of generator temperature, condenser temperature and evaporator temperature for all the mixtures shows that, all these three thermodynamic parameters have a strong effect on the cycle performance.

A new oxidation flow reactor for measuring secondary aerosol formation of rapidly changing emission sources

Science.gov (United States)

Simonen, Pauli; Saukko, Erkka; Karjalainen, Panu; Timonen, Hilkka; Bloss, Matthew; Aakko-Saksa, Päivi; Rönkkö, Topi; Keskinen, Jorma; Dal Maso, Miikka

2017-04-01

Oxidation flow reactors (OFRs) or environmental chambers can be used to estimate secondary aerosol formation potential of different emission sources. Emissions from anthropogenic sources, such as vehicles, often vary on short timescales. For example, to identify the vehicle driving conditions that lead to high potential secondary aerosol emissions, rapid oxidation of exhaust is needed. However, the residence times in environmental chambers and in most oxidation flow reactors are too long to study these transient effects ( ˜ 100 s in flow reactors and several hours in environmental chambers). Here, we present a new oxidation flow reactor, TSAR (TUT Secondary Aerosol Reactor), which has a short residence time ( ˜ 40 s) and near-laminar flow conditions. These improvements are achieved by reducing the reactor radius and volume. This allows studying, for example, the effect of vehicle driving conditions on the secondary aerosol formation potential of the exhaust. We show that the flow pattern in TSAR is nearly laminar and particle losses are negligible. The secondary organic aerosol (SOA) produced in TSAR has a similar mass spectrum to the SOA produced in the state-of-the-art reactor, PAM (potential aerosol mass). Both reactors produce the same amount of mass, but TSAR has a higher time resolution. We also show that TSAR is capable of measuring the secondary aerosol formation potential of a vehicle during a transient driving cycle and that the fast response of TSAR reveals how different driving conditions affect the amount of formed secondary aerosol. Thus, TSAR can be used to study rapidly changing emission sources, especially the vehicular emissions during transient driving.

An Improved Parametrized Representation of the Secondary He Neutral Flow in its Source Region

Science.gov (United States)

Wood, Brian E.

2017-09-01

Analysis of data from the Interstellar Boundary EXplorer (IBEX) has revealed the presence of a flow of neutral helium through the inner solar system that most likely emanates from the outer heliosheath, where a distinct population of neutral He is produced by charge exchange processes. This secondary He flow has been modeled using codes designed to study interstellar flows through the heliosphere, but a laminar flow is not a good approximation for the outer heliosheath. I present a simple parametrization for a more appropriate divergent flow, and demonstrate how the secondary He particles might provide a means to remotely measure the divergence of the ISM flow around the heliopause.

The influence of thermodynamic state of mineral hydraulic oil on flow rate through radial clearance at zero overlap inside the hydraulic components

Directory of Open Access Journals (Sweden)

Knežević Darko M.

2016-01-01

Full Text Available In control hydraulic components (servo valves, LS regulators, etc. there is a need for precise mathematical description of fluid flow through radial clearances between the control piston and body of component at zero overlap, small valve opening and small lengths of overlap. Such a mathematical description would allow for a better dynamic analysis and stability analysis of hydraulic systems. The existing formulas in the literature do not take into account the change of the physical properties of the fluid with a change of thermodynamic state of the fluid to determine the flow rate through radial clearances in hydraulic components at zero overlap, a small opening, and a small overlap lengths, which leads to the formation of insufficiently precise mathematical models. In this paper model description of fluid flow through radial clearances at zero overlap is developed, taking into account the changes of physical properties of hydraulic fluid as a function of pressure and temperature. In addition, the experimental verification of the mathematical model is performed.

Suppression of secondary flows in a double suction centrifugal pump with different loading distributions

International Nuclear Information System (INIS)

Leng, H F; Wang, F J; Zhang, Z C; Yao, Z F; Zhou, P J

2013-01-01

Secondary flow is one of the main reasons for low efficiency in double suction centrifugal pump. In a 3-D inverse design method, the pump blade could be designed by a specified loading distribution to control the flow field in pump. In order to study the influence of loading distribution on secondary flow of a double suction centrifugal pump, the external characteristics and the internal flow field of the pump with three kinds of loading distributions are analysed by using CFD approach. According to the simulation results, it is found that the form of fore-loading distribution at shroud and aft-loading distribution at hub could improve the optimal efficiency and broaden the high efficiency area of the pump. Furthermore, the secondary flow in impeller exit region and volute could be significantly suppressed if the slope of loading distribution curve of shroud is set to be −0.7

Spatial characteristics of secondary flow in a turbulent boundary layer over longitudinal surface roughness

Science.gov (United States)

Hwang, Hyeon Gyu; Lee, Jae Hwa

2017-11-01

Direct numerical simulations of turbulent boundary layers (TBLs) over spanwise heterogeneous surface roughness are performed to investigate the characteristics of secondary flow. The longitudinal surface roughness, which features lateral change in bed elevation, is described by immersed boundary method. The Reynolds number based on the momentum thickness is varied in the range of Reθ = 300-900. As the TBLs over the roughness elements spatially develop in the streamwise direction, a secondary flow emerges in a form of counter-rotating vortex pair. As the spanwise spacing between the roughness elements and roughness width vary, it is shown that the size of the secondary flow is determined by the valley width between the roughness elements. In addition, the strength of the secondary flow is mostly affected by the spanwise distance between the cores of the secondary flow. Analysis of the Reynolds-averaged turbulent kinetic energy transport equation reveals that the energy redistribution terms in the TBLs over-the ridge type roughness play an important role to derive low-momentum pathways with upward motion over the roughness crest, contrary to the previous observation with the strip-type roughness. This research was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1A1A09000537) and the Ministry of Science, ICT & Future Planning (NRF-2017R1A5A1015311).

Large Eddy Simulation of turbulence induced secondary flows in stationary and rotating straight square ducts

Science.gov (United States)

Sudjai, W.; Juntasaro, V.; Juttijudata, V.

2018-01-01

The accuracy of predicting turbulence induced secondary flows is crucially important in many industrial applications such as turbine blade internal cooling passages in a gas turbine and fuel rod bundles in a nuclear reactor. A straight square duct is popularly used to reveal the characteristic of turbulence induced secondary flows which consists of two counter rotating vortices distributed in each corner of the duct. For a rotating duct, the flow can be divided into the pressure side and the suction side. The turbulence induced secondary flows are converted to the Coriolis force driven two large circulations with a pair of additional vortices on the pressure wall due to the rotational effect. In this paper, the Large Eddy Simulation (LES) of turbulence induced secondary flows in a straight square duct is performed using the ANSYS FLUENT CFD software. A dynamic kinetic energy subgrid-scale model is used to describe the three-dimensional incompressible turbulent flows in the stationary and the rotating straight square ducts. The Reynolds number based on the friction velocity and the hydraulic diameter is 300 with the various rotation numbers for the rotating cases. The flow is assumed fully developed by imposing the constant pressure gradient in the streamwise direction. For the rotating cases, the rotational axis is placed perpendicular to the streamwise direction. The simulation results on the secondary flows and the turbulent statistics are found to be in good agreement with the available Direct Numerical Simulation (DNS) data. Finally, the details of the Coriolis effects are discussed.

A Summary/Overview of Ejector Augmentor Theory and Performance. Volume 2. Bibliography

Science.gov (United States)

1979-09-01

229. 1/3 DPDF A, E,T Brown, G. A., and Levy, E. K., "Liquid Metal Magnetohydrodynamic SS F, Power Generation with Condensing Ejector Cycles’’, Paper SM ...SPSF C, Duvvuri, T., and Raghunath , B., "Theoretical Study of Turbulent SS F Mixing Along Curved Jet Boundaries", Duvvuri Research Associates Tech. Rep...Engine Cooling System for a Turbojet Powered Aircraft, Report No. SM -14020, Douglas Aircraft Company, Incorporated, Santa Monica, California, May

Secondary flow structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2017-11-01

Secondary flow vortical structures were investigated in an elastic 180° curved pipe with and without torsion under steady and pulsatile flow using particle image velocimetry (PIV). The elastic thin-walled curved pipes were constructed using Sylgard 184, and inserted into a bath of refractive index matched fluid to perform PIV. A vortex identification method was employed to identify various vortical structures in the flow. The secondary flow structures in the planar compliant model with dilatation of 0.61%-3.23% under pulsatile flow rate were compared with the rigid vessel model results, and it was found that local vessel compliance has a negligible effect on secondary flow morphology. The secondary flow structures were found to be more sensitive to out of plane curvature (torsion) than to vessel compliance. Torsion distorts the symmetry of secondary flow and results in more complex vortical structures in both steady and pulsatile flows. In high Re number steady flow with torsion, a single dominant vortical structure can be detected at the middle of the 90° cross section. In pulsatile flow with torsion, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together. supported by GW Center for Biomimetics and Bioinspired Engineering.

Exergy analysis, parametric analysis and optimization for a novel combined power and ejector refrigeration cycle

International Nuclear Information System (INIS)

Dai Yiping; Wang Jiangfeng; Gao Lin

2009-01-01

A new combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces both power output and refrigeration output simultaneously. It can be driven by the flue gas of gas turbine or engine, solar energy, geothermal energy and industrial waste heats. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. And a parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the performance of the combined cycle. In addition, a parameter optimization is achieved by means of genetic algorithm to reach the maximum exergy efficiency. The results show that the biggest exergy loss due to the irreversibility occurs in heat addition processes, and the ejector causes the next largest exergy loss. It is also shown that the turbine inlet pressure, the turbine back pressure, the condenser temperature and the evaporator temperature have significant effects on the turbine power output, refrigeration output and exergy efficiency of the combined cycle. The optimized exergy efficiency is 27.10% under the given condition.

Predicted macroinvertebrate response to water diversion from a montane stream using two-dimensional hydrodynamic models and zero flow approximation

Science.gov (United States)

Holmquist, Jeffrey G.; Waddle, Terry J.

2013-01-01

We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.

Axial velocity profiles and secondary flows of developing laminar flows in a straight connected exit region of a 180 .deg. square curved duct

Energy Technology Data Exchange (ETDEWEB)

Sohn, Hyun Chull; Lee, Heang Nam; Park, Gil Moon [Chosun Univ., Gwangju (Korea, Republic of)

2005-10-01

In the present study, characteristics of steady state laminar flows of a straight duct connected to a 180 .deg. curved duct were examined in the entrance region through experimental and numerical analyses. For the analysis, the governing equations of laminar flows in the Cartesian coordinate system were applied. Flow characteristics such as velocity profiles and secondary flows were investigated numerically and experimentally in a square cross-sectional straight duct by the PIV system and a CFD code (STARCD). For the PIV measurement, smoke particles produced from mosquito coils. The experimental data were obtained at 9 points dividing the test sections by 400 mm. Experimental and numerical results can be summarized as follows. 1) Reynolds number, Re was increased, dimensionless velocity profiles at the outer wall were increased due to the effect of the centrifugal force and secondary flows. 2) The intensity of a secondary flow became stronger at the inner wall rather than the outer wall regardless of Reynolds number. Especially, fluid dynamic phenomenon called conner impact were observed at dimensionless axial position, x/D{sub h}=50.

Theoretical statistics of zero-age cataclysmic variables

International Nuclear Information System (INIS)

Politano, M.J.

1988-01-01

The distribution of the white dwarf masses, the distribution of the mass ratios and the distribution of the orbital periods in cataclysmic variables which are forming at the present time are calculated. These systems are referred to as zero-age cataclysmic variables. The results show that 60% of the systems being formed contain helium white dwarfs and 40% contain carbon-oxygen white dwarfs. The mean dwarf mass in those systems containing helium white dwarfs is 0.34. The mean white dwarf mass in those systems containing carbon-oxygen white dwarfs is 0.75. The orbital period distribution identifies four main classes of zero-age cataclysmic variables: (1) short-period systems containing helium white dwarfs, (2) systems containing carbon-oxygen white dwarfs whose secondaries are convectively stable against rapid mass transfer to the white dwarf, (3) systems containing carbon-oxygen white dwarfs whose secondaries are radiatively stable against rapid mass transfer to the white dwarf and (4) long period systems with evolved secondaries. The white dwarf mass distribution in zero-age cataclysmic variables has direct application to the calculation of the frequency of outburst in classical novae as a function of the mass of the white dwarf. The method developed in this thesis to calculate the distributions of the orbital parameters in zero-age cataclysmic variables can be used to calculate theoretical statistics of any class of binary systems. This method provides a theoretical framework from which to investigate the statistical properties and the evolution of the orbital parameters of binary systems

FEASIBILITY STUDY OF GAS TREATMENT PLANT BASED ON AN EJECTOR SCRUBBER

Directory of Open Access Journals (Sweden)

S. Iu. Panov

2014-01-01

Full Text Available Summary. The article executed the feasibility study of various options for gas treatment. Rapid development of industry and transport worldwide in recent times raises the problem in the protection of habitat environment from harmful waste. In solving problems of flue gas treatment great attention is given to the economic characteristics and recycling techniques for capturing emissions and disposal must also meet the sanitary health requirements: flue gas treatment plants should not cause air or water pollution. The set objective is solved by developing a two-stage wet treatment system for pyrolysis gas based on ejector scrubbers. Their advantage - a central nozzle supply that allows the scrubber to operate on the principle of an ejector pump. Projected plant can be used in enterprises for processing of solid domestic and industrial waste, where there are steam and hot water boilers, whose operations result in contaminated gases emissions obtained with high temperatures. In particular, this installation can be applied at a cement plant in which a large amount of waste gases containing sulfur oxides is emitted. Assessment of market potential for the plant designed to treat waste gases in the cement factory is performed through a SWOT analysis. SWOT analysis results indicate the possibility of the treatment of exhaust gases without a high cost and with high gas treatment efficiency. Plant competitive analysis was done using an expert method in comparison with market competitors. Technical and economic indicators of the plant are presented. Return on investments is 46% and payback period of capital investments - 2.7 years.

Performance of a Code Migration for the Simulation of Supersonic Ejector Flow to SMP, MIC, and GPU Using OpenMP, OpenMP+LEO, and OpenACC Directives

Directory of Open Access Journals (Sweden)

C. Couder-Castañeda

2015-01-01

Full Text Available A serial source code for simulating a supersonic ejector flow is accelerated using parallelization based on OpenMP and OpenACC directives. The purpose is to reduce the development costs and to simplify the maintenance of the application due to the complexity of the FORTRAN source code. This research follows well-proven strategies in order to obtain the best performance in both OpenMP and OpenACC. OpenMP has become the programming standard for scientific multicore software and OpenACC is one true alternative for graphics accelerators without the need of programming low level kernels. The strategies using OpenMP are oriented towards reducing the creation of parallel regions, tasks creation to handle boundary conditions, and a nested control of the loop time for the programming in offload mode specifically for the Xeon Phi. In OpenACC, the strategy focuses on maintaining the data regions among the executions of the kernels. Experiments for performance and validation are conducted here on a 12-core Xeon CPU, Xeon Phi 5110p, and Tesla C2070, obtaining the best performance from the latter. The Tesla C2070 presented an acceleration factor of 9.86X, 1.6X, and 4.5X compared against the serial version on CPU, 12-core Xeon CPU, and Xeon Phi, respectively.

Zero entropy continuous interval maps and MMLS-MMA property

Science.gov (United States)

Jiang, Yunping

2018-06-01

We prove that the flow generated by any continuous interval map with zero topological entropy is minimally mean-attractable and minimally mean-L-stable. One of the consequences is that any oscillating sequence is linearly disjoint from all flows generated by all continuous interval maps with zero topological entropy. In particular, the Möbius function is linearly disjoint from all flows generated by all continuous interval maps with zero topological entropy (Sarnak’s conjecture for continuous interval maps). Another consequence is a non-trivial example of a flow having discrete spectrum. We also define a log-uniform oscillating sequence and show a result in ergodic theory for comparison. This material is based upon work supported by the National Science Foundation. It is also partially supported by a collaboration grant from the Simons Foundation (grant number 523341) and PSC-CUNY awards and a grant from NSFC (grant number 11571122).

Uncertainty Flow Facilitates Zero-Shot Multi-Label Learning in Affective Facial Analysis

Directory of Open Access Journals (Sweden)

Wenjun Bai

2018-02-01

Full Text Available Featured Application: The proposed Uncertainty Flow framework may benefit the facial analysis with its promised elevation in discriminability in multi-label affective classification tasks. Moreover, this framework also allows the efficient model training and between tasks knowledge transfer. The applications that rely heavily on continuous prediction on emotional valance, e.g., to monitor prisoners’ emotional stability in jail, can be directly benefited from our framework. Abstract: To lower the single-label dependency on affective facial analysis, it urges the fruition of multi-label affective learning. The impediment to practical implementation of existing multi-label algorithms pertains to scarcity of scalable multi-label training datasets. To resolve this, an inductive transfer learning based framework, i.e.,Uncertainty Flow, is put forward in this research to allow knowledge transfer from a single labelled emotion recognition task to a multi-label affective recognition task. I.e., the model uncertainty—which can be quantified in Uncertainty Flow—is distilled from a single-label learning task. The distilled model uncertainty ensures the later efficient zero-shot multi-label affective learning. On the theoretical perspective, within our proposed Uncertainty Flow framework, the feasibility of applying weakly informative priors, e.g., uniform and Cauchy prior, is fully explored in this research. More importantly, based on the derived weight uncertainty, three sets of prediction related uncertainty indexes, i.e., soft-max uncertainty, pure uncertainty and uncertainty plus are proposed to produce reliable and accurate multi-label predictions. Validated on our manual annotated evaluation dataset, i.e., the multi-label annotated FER2013, our proposed Uncertainty Flow in multi-label facial expression analysis exhibited superiority to conventional multi-label learning algorithms and multi-label compatible neural networks. The success of our

The structure of single-phase turbulent flows through closely spaced rod arrays

International Nuclear Information System (INIS)

Hooper, J.D.; Rehme, K.

1983-02-01

The axial and azimuthal turbulence intensity in the rod gap region has been shown, for developed single-phase turbulent flow through parallel rod arrays, to strongly increase with decreasing rod spacing. Two array geometries are reported, one constructed from a rectangular cross-section duct containing four rods and spaced at five p/d or w/d ratios. The second test section, constructed from six rods set in a regular square-pitch array, represented the interior flow region of a large array. The mean axial velocity, wall shear stress variation and axial pressure distribution were measured, together with hot-wire anemometer measurements of the Reynolds stresses. No significant non-zero secondary flow components were detected, using techniques capable of resolving secondary flow velocities to 1% of the local axial velocity. For the lowest p/d ratio of 1.036, cross-correlation measurements showed the presence of an energetic periodic azimuthal turbulent velocity component, correlated over a significant part of the flow area. The negligible contribution of secondary flows to the axial momentum balance, and the large azimuthal turbulent velocity component in the rod gap area, suggest a different mechanism than Reynolds stress gradient driven secondary flows for the turbulent transport process in the rod gap. (orig.) [de

Secondary flows occurring in a whirlpool separator – A study of phenomena – observation, simulation and measurements

Directory of Open Access Journals (Sweden)

Jakubowski Marek

2015-09-01

Full Text Available The whirlpool separator, used for hot trub separation, is prevalent in the brewing industry. It is a kind of a hydrocyclone inside of which a tea leaf effect occurs, which is sediment accumulation into a cone shape at the central part of the tank’s bottom. This manner of sediment accumulation is caused by the secondary flow occurring in the so-called Ekman boundary layer. This article is a summary of the research, which has been conducted for many years and involved observation, simulation and experimental research on the recognition and formation of the secondary flow accumulating the sediment cone. Secondary flows occurring in a whirlpool were identified through CFD simulation and PIV experiments, and are presented in this paper. Based on their location and direction, an attempt to determine their impact on the separation process taking place in the whirlpool has been made. The secondary flow identification methods proposed in this paper can be successfully applied in other solutions, e. g. structural ones, which involve rotational-flow-based separation.

CROSS-FLOW ULTRAFILTRATION OF SECONDARY EFFLUENTS. MEMBRANE FOULING ANALYSIS

Directory of Open Access Journals (Sweden)

Luisa Vera

2014-12-01

Full Text Available The application of cross-flow ultrafiltration to regenerate secondary effluents is limited by membrane fouling. This work analyzes the influence of the main operational parameters (transmembrane pressure and cross-flow velocity about the selectivity and fouling observed in an ultrafiltration tubular ceramic membrane. The experimental results have shown a significant retention of the microcolloidal and soluble organic matter (52 – 54% in the membrane. The fouling analysis has defined the critical operational conditions where the fouling resistance is minimized. Such conditions can be described in terms of a dimensionless number known as shear stress number and its relationship with other dimensionless parameter, the fouling number.

Intuitions and Undefined Operations: The Cases of Division by Zero.

Science.gov (United States)

Tsamir, Pessia; Sheffer, Ruth; Tirosh, Dina

2000-01-01

Describes a study that explores secondary school students' conceptions of division by zero. Examines whether students identify expressions involving division by zero as undefined or tend to assign them numerical values. Studies students' justifications and analyzes the effects of age and level of achievement in mathematics on students' responses…

Design and Thermodynamic Analysis of a Steam Ejector Refrigeration/Heat Pump System for Naval Surface Ship Applications

Directory of Open Access Journals (Sweden)

Cüneyt Ezgi

2015-12-01

Full Text Available Naval surface ships should use thermally driven heating and cooling technologies to continue the Navy’s leadership role in protecting the marine environment. Steam ejector refrigeration (SER or steam ejector heat pump (SEHP systems are thermally driven heating and cooling technologies and seem to be a promising technology to reduce emissions for heating and cooling on board naval surface ships. In this study, design and thermodynamic analysis of a seawater cooled SER and SEHP as an HVAC system for a naval surface ship application are presented and compared with those of a current typical naval ship system case, an H2O-LiBr absorption heat pump and a vapour-compression heat pump. The off-design study estimated the coefficient of performances (COPs were 0.29–0.11 for the cooling mode and 1.29–1.11 for the heating mode, depending on the pressure of the exhaust gas boiler at off-design conditions. In the system operating at the exhaust gas boiler pressure of 0.2 MPa, the optimum area ratio obtained was 23.30.

Characteristics of buoyancy force on stagnation point flow with magneto-nanoparticles and zero mass flux condition

Directory of Open Access Journals (Sweden)

Iftikhar Uddin

2018-03-01

Full Text Available This attempt dedicated to the solution of buoyancy effect over a stretching sheet in existence of MHD stagnation point flow with convective boundary conditions. Thermophoresis and Brownian motion aspects are included. Incompressible fluid is electrically conducted in the presence of varying magnetic field. Boundary layer analysis is used to develop the mathematical formulation. Zero mass flux condition is considered at the boundary. Non-linear ordinary differential system of equations is constructed by means of proper transformations. Interval of convergence via numerical data and plots are developed. Characteristics of involved variables on the velocity, temperature and concentration distributions are sketched and discussed. Features of correlated parameters on Cf and Nu are examined by means of tables. It is found that buoyancy ratio and magnetic parameters increase and reduce the velocity field. Further opposite feature is noticed for higher values of thermophoresis and Brownian motion parameters on concentration distribution. Keywords: Stagnation point, MHD, Nanoparticles, Zero mass flux condition

Secondary flow vortical structures in a 180∘ elastic curved vessel with torsion under steady and pulsatile inflow conditions

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2018-01-01

Secondary flow structures in a 180∘ curved pipe model of an artery are studied using particle image velocimetry. Both steady and pulsatile inflow conditions are investigated. In planar curved pipes with steady flow, multiple (two, four, six) vortices are detected. For pulsatile flow, various pairs of vortices, i.e., Dean, deformed-Dean, Lyne-type, and split-Dean, are present in the cross section of the pipe at 90∘ into the bend. The effects of nonplanar curvature (torsion) and vessel dilatation on these vortical structures are studied. Torsion distorts the symmetric secondary flows (which exist in planar curvatures) and can result in formation of more complex vortical structures. For example, the split-Dean and Lyne-type vortices with same rotation direction originating from opposite sides of the cross section tend to merge together in pulsatile flow. The vortical structures in elastic vessels with dilatation (0.61%-3.23%) are also investigated and the results are compared with rigid model results. It was found that the secondary flow structures in rigid and elastic models are similar, and hence the local compliance of the vessel does not affect the morphology of secondary flow structures.

Air injection evaluation in open steam discharge pipes based on ejector equipment theory

International Nuclear Information System (INIS)

Bigu, M.; Nita, I.; Tenescu, M.

2005-01-01

The paper starts from the finding that the calculation method proposed by ANSI B31.1 for open steam discharge pipes (normative 'ANSI/ASMF B31.1-1980 appendix II Non-Mandatory rules for the design of safety valve installation') shows an air injection in steam system without making a quantitative evaluation of this process of air injection in the exhaust steam. For this it is proposed an assimilation of process with an ejection process in which either steam or air is the ejected fluid. The reason of using opened exhaust systems instead of closed exhaust systems is the fact that expansions and especially shock load from discharge valves and especially in exhaust elbow, are not conducted over the pipe system (ventilation tube). In order to estimate the quantity of air flow which enters through the ejection effect the present paper makes use of gas-gas ejectors. The interest for optimal operating of the system is that the air mixture have a value low in comparison with steam flow (i.e. 2-3% or upmost 5-7%). These percents of mixture lead to properly choosing of the ratio of the two pipe diameters (ventilation tube D/ exhaust elbow d). The results show that optimum ratio is between D/d = 1.10 to 1.15 and in extreme cases 1.20. A lower value of ratio is not acceptable because the pipes come in direct contact when expansion and/or hydraulic hammer occur and stresses from exhaust elbow of safety valve are propagated towards ventilation tube. A higher value of the ratio D/d leads to great air injection in ventilation tube and so to an unjustified large diameter of ventilation tube. It must be mention that the optimal ratio is obtained at sub critical flow of ejected air with Mach number lower then unity, at a static pressure between 0.6 to 1.0 bar in mixture zone of the two fluids. (authors)

Air injection evaluation in open steam discharge pipes based on ejector equipment theory

International Nuclear Information System (INIS)

Bigu, M.; Nita, I.; Tenescu, M.

2005-01-01

Full text: The paper starts from the finding that the calculation method proposed by ANSI B31.1 for open steam discharge pipes (normative 'ANSI/ASMF B31.1-1980 appendix II Non-Mandatory rules for the design of safety valve installation') shows an air injection in steam system without making a quantitative evaluation of this process of air injection in the exhaust steam. For this it is proposed an assimilation of process with an ejection process in which either steam or air is the ejected fluid. The reason of using opened exhaust systems instead of closed exhaust systems is the fact that expansions and especially shock load from discharge valves and especially in exhaust elbow, are not conducted over the pipe system (ventilation tube). In order to estimate the quantity of air flow which enters through the ejection effect the present paper makes use of gas-gas ejectors. The interest for optimal operating of the system is that the air mixture have a value low in comparison with steam flow (i.e. 2-3% or upmost 5-7%). These percents of mixture lead to properly choosing of the ratio of the two pipe diameters (ventilation tube D/ exhaust elbow d). The results show that optimum ratio is between D/d = 1.10 to 1.15 and in extreme cases 1.20. A lower value of ratio is not acceptable because the pipes come in direct contact when expansion and/or hydraulic hammer occur and stresses from exhaust elbow of safety valve are propagated towards ventilation tube. A higher value of the ratio D/d leads to great air injection in ventilation tube and so to an unjustified large diameter of ventilation tube. It must be mention that the optimal ratio is obtained at sub critical flow of ejected air with Mach number lower then unity, at a static pressure between 0.6 to 1.0 bar in mixture zone of the two fluids

Numerical Calculation of Secondary Flow in Pump Volute and Circular Casings using 3D Viscous Flow Techniques

Directory of Open Access Journals (Sweden)

K. Majidi

2000-01-01

Full Text Available The flow field in volute and circular casings interacting with a centrifugal impeller is obtained by numerical analysis. In the present study, effects of the volute and circular casings on the flow pattern have been investigated by successively combining a volute casing and a circular casing with a single centrifugal impeller. The numerical calculations are carried out with a multiple frame of reference to predict the flow field inside the entire impeller and casings. The impeller flow field is solved in a rotating frame and the flow field in the casings in a stationary frame. The static pressure and velocity in the casing and impeller, and the static pressures and secondary velocity vectors at several cross-sectional planes of the casings are calculated. The calculations show that the curvature of the casings creates pressure gradients that cause vortices at cross-sectional planes of the casings.

Operability of an Ejector Enhanced Pulse Combustor in a Gas Turbine Environment

Science.gov (United States)

Paxson, Daniel E.; Dougherty, Kevin

2008-01-01

A pressure-gain combustor comprised of a mechanically valved, liquid fueled pulsejet, an ejector, and an enclosing shroud, was coupled to a small automotive turbocharger to form a self-aspirating, thrust producing gas turbine engine. The system was constructed in order to investigate issues associated with the interaction of pulsed combustion devices and turbomachinery. Installed instrumentation allowed for sensing of distributed low frequency pressure and temperature, high frequency pressure in the shroud, fuel flow rate, rotational speed, thrust, and laboratory noise. The engine ran successfully and reliably, achieving a sustained thrust of 5 to 6 lbf, and maintaining a rotor speed of approximately 90,000 rpm, with a combustor pressure gain of approximately 4 percent. Numerical simulations of the system without pressure-gain combustion indicated that the turbocharger would not operate. Thus, the new combustor represented a substantial improvement in system performance. Acoustic measurements in the shroud and laboratory indicated turbine stage sound pressure level attenuation of 20 dB. This is consistent with published results from detonative combustion experiments. As expected, the mechanical reed valves suffered considerable damage under the higher pressure and thermal loading characteristics of this system. This result underscores the need for development of more robust valve systems for this application. The efficiency of the turbomachinery components did not appear to be significantly affected by unsteadiness associated with pulsed combustion, though the steady component efficiencies were already low, and thus not expected to be particularly sensitive.

Analysis of experimental characteristics of multistage steam-jet electors of steam turbines

Science.gov (United States)

Aronson, K. E.; Ryabchikov, A. Yu.; Brodov, Yu. M.; Brezgin, D. V.; Zhelonkin, N. V.; Murmanskii, I. B.

2017-02-01

A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multistage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the "sound tube" zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the "sound tube" define optimal axial sizes of the ejector. According to measurement results, the part of steam condensing in the first-stage coolant constitutes 70-80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of ejector of the next stage after coolant of steam-jet stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the ejector's mixing chamber. The influence of change of wall roughness on ejector characteristic is similar to the influence of reverse pressure of the steam-jet stage. Until some roughness value, injection coefficient of the ejector stage operating in superlimiting regime hardly changed. After reaching critical roughness, the ejector switches to prelimiting operating regime.

Numerical investigation into the unsteady effects of non-axisymmetric turbine endwall contouring on secondary flows

CSIR Research Space (South Africa)

Dunn, Dwain I

2011-08-01

Full Text Available with the rotor leading edge, i.e. the location that the wake impinges on the leading edge of the rotor. It can be seen that there was not much fluctuation in time in the pressure profiles. With regards to the annular case the pressure surface shows... and lighter for a given b) (1) (A) (b) (1) (A) 2 thrust rating, the stronger secondary flows become. Therefore a reduction in secondary flow leads to an increase in performance of the turbine engine. One of the methods currently being investigated...

3D Measurements of coupled freestream turbulence and secondary flow effects on film cooling

Science.gov (United States)

Ching, David S.; Xu, Haosen H. A.; Elkins, Christopher J.; Eaton, John K.

2018-06-01

The effect of freestream turbulence on a single round film cooling hole is examined at two turbulence levels of 5 and 8% and compared to a baseline low freestream turbulence case. The hole is inclined at 30° and has length to diameter ratio L/D=4 and unity blowing ratio. Turbulence is generated with grid upstream of the hole in the main channel. The three-dimensional, three-component mean velocity field is acquired with magnetic resonance velocimetry (MRV) and the three-dimensional temperature field is acquired with magnetic resonance thermometry (MRT). The 8% turbulence grid produces weak mean secondary flows in the mainstream (peak crossflow velocities are 7% of U_bulk) which push the jet close to the wall and significantly change the adiabatic effectiveness distribution. By contrast, the 5% grid has a simpler structure and does not produce a measurable secondary flow structure. The grid turbulence causes little change to the temperature field, indicating that the turbulence generated in the shear layers around the jet dominates the freestream turbulence. The results suggest that secondary flows induced by complex turbulence generators may have caused some of the contradictory results in previous works.

Development of air pulsed ejector mixer settlers of different capacities

Energy Technology Data Exchange (ETDEWEB)

Rajagopalan, C V; Periasamy, K; Koganti, S B [Reprocessing Programme, Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

1994-06-01

Nuclear industry has made significant contributions in the development of liquid-liquid contactors, for the separation of one or more solutes from feed solutions wherein they provide a more economical alternative compared to other unit operations. The various equipment that are used can be broadly classified into three categories: (1) mixer settlers (2) liquid pulsed sieve plate columns (3) centrifugal contactors. Each one has its own merits and demerits. Mixer settlers score over the other contactors in their simple design and reliable operation over a wide range of process conditions. Air pulsed mixer settlers of different designs are in use in the fuel reprocessing industry. The present paper describes the development of a new type of mixer settler based on ejector as the mixing device. (author). 7 refs., 3 figs., 1 tab.

3D flow visualizations by means of laser beam sweeps

International Nuclear Information System (INIS)

Prenel, J.P.; Porcar, R.; Diemunsch, G.

1987-01-01

A method in which two-dimensional aperiodic or periodic sweeps are used to produce three-dimensional light sweeps makes possible the quasi-simultaneous recording of different specific planes of a flow, or the characterization of a fluid without revolution symmetry. The optical device consists of two scanners (whose axes are orthogonal) set into a telescope, allowing fine focusing of the light sheets in the study zone. The method also allows visualizations on skewed surfaces, particularly those of flows without a cylindrical geometry; it is applicable from low velocity, as in heat convection, to supersonic velocity, as in the analysis of a nonaxisymmetric ejector. 8 references

A case of atherosclerotic inferior mesenteric artery aneurysm secondary to high flow state.

Science.gov (United States)

Troisi, Nicola; Esposito, Giovanni; Cefalì, Pietro; Setti, Marco

2011-07-01

Inferior mesenteric artery aneurysms are very rare and they are among the rarest of visceral artery aneurysms. Sometimes, the distribution of the blood flow due to chronic atherosclerotic occlusion of some arteries can establish an increased flow into a particular supplying district (high flow state). A high flow state in a stenotic inferior mesenteric artery in compensation for a mesenteric occlusive disease can produce a rare form of aneurysm. We report the case of an atherosclerotic inferior mesenteric aneurysm secondary to high flow state (association with occlusion of the celiac trunk and severe stenosis of the superior mesenteric artery), treated by open surgical approach. Copyright © 2011 Society for Vascular Surgery. Published by Mosby, Inc. All rights reserved.

Recent Experimental Results Related to Ejector Mode Studies of Rocket-Based Combined Cycle (RBCC) Engines

Science.gov (United States)

Cramer, J. M.; Pal, S.; Marshall, W. M.; Santoro, R. J.

2003-01-01

Contents include the folloving: 1. Motivation. Support NASA's 3d generation launch vehicle technology program. RBCC is promising candidate for 3d generation propulsion system. 2. Approach. Focus on ejector mode p3erformance (Mach 0-3). Perform testing on established flowpath geometry. Use conventional propulsion measurement techniques. Use advanced optical diagnostic techniques to measure local combustion gas properties. 3. Objectives. Gain physical understanding of detailing mixing and combustion phenomena. Establish an experimental data set for CFD code development and validation.

Transmit Antenna Selection for Multi-User Underlay Cognitive Transmission with Zero-Forcing Beamforming

KAUST Repository

Hanif, Muhammad; Yang, Hong-Chuan; Alouini, Mohamed-Slim

2017-01-01

We present a transmit antenna subset selection scheme for an underlay cognitive system serving multiple secondary receivers. The secondary system employs zero-forcing beamforming to nullify the interference to multiple primary users and eliminate

Secondary flows in the cooling channels of the high-performance light-water reactor

Energy Technology Data Exchange (ETDEWEB)

Laurien, E.; Wintterle, Th. [Stuttgart Univ., Institute for Nuclear Technolgy and Energy Systems (IKE) (Germany)

2007-07-01

The new design of a High-Performance Light-Water Reactor (HPLWR) involves a three-pass core with an evaporator region, where the compressed water is heated above the pseudo-critical temperature, and two superheater regions. Due to the strong dependency of the supercritical water density on the temperature significant mass transfer between neighboring cooling channels is expected if the temperature is unevenly distributed across the fuel element. An inter-channel flow is then superimposed to the secondary flow vortices induced by the non-isotropy of turbulence. In order to gain insight into the resulting flow patterns as well as into temperature and density distributions within the various subchannels of the fuel element CFD (Computational Fluid Dynamics) calculations for the 1/8 fuel element are performed. For simplicity adiabatic boundary conditions at the moderator box and the fuel element box are assumed. Our investigation confirms earlier results obtained by subchannel analysis that the axial mass flux is significantly reduced in the corner subchannel of this fuel element resulting in a net mass flux towards the neighboring subchannels. Our results provide a first estimation of the magnitude of the secondary flows in the pseudo-critical region of a supercritical light-water reactor. Furthermore, it is demonstrated that CFD is an efficient tool for investigations of flow patterns within nuclear reactor fuel elements. (authors)

Parametric analysis of diffuser requirements for high expansion ratio space engine

Science.gov (United States)

Wojciechowski, C. J.; Anderson, P. G.

1981-01-01

A supersonic diffuser ejector design computer program was developed. Using empirically modified one dimensional flow methods the diffuser ejector geometry is specified by the code. The design code results for calculations up to the end of the diffuser second throat were verified. Diffuser requirements for sea level testing of high expansion ratio space engines were defined. The feasibility of an ejector system using two commonly available turbojet engines feeding two variable area ratio ejectors was demonstrated.

Validating and improving a zero-dimensional stack voltage model of the Vanadium Redox Flow Battery

Science.gov (United States)

König, S.; Suriyah, M. R.; Leibfried, T.

2018-02-01

Simple, computationally efficient battery models can contribute significantly to the development of flow batteries. However, validation studies for these models on an industrial-scale stack level are rarely published. We first extensively present a simple stack voltage model for the Vanadium Redox Flow Battery. For modeling the concentration overpotential, we derive mass transfer coefficients from experimental results presented in the 1990s. The calculated mass transfer coefficient of the positive half-cell is 63% larger than of the negative half-cell, which is not considered in models published to date. Further, we advance the concentration overpotential model by introducing an apparent electrochemically active electrode surface which differs from the geometric electrode area. We use the apparent surface as fitting parameter for adapting the model to experimental results of a flow battery manufacturer. For adapting the model, we propose a method for determining the agreement between model and reality quantitatively. To protect the manufacturer's intellectual property, we introduce a normalization method for presenting the results. For the studied stack, the apparent electrochemically active surface of the electrode is 41% larger than its geometrical area. Hence, the current density in the diffusion layer is 29% smaller than previously reported for a zero-dimensional model.

Secondary flow in a curved artery model with Newtonian and non-Newtonian blood-analog fluids

Science.gov (United States)

Najjari, Mohammad Reza; Plesniak, Michael W.

2016-11-01

Steady and pulsatile flows of Newtonian and non-Newtonian fluids through a 180°-curved pipe were investigated using particle image velocimetry (PIV). The experiment was inspired by physiological pulsatile flow through large curved arteries, with a carotid artery flow rate imposed. Sodium iodide (NaI) and sodium thiocyanate (NaSCN) were added to the working fluids to match the refractive index (RI) of the test section to eliminate optical distortion. Rheological measurements revealed that adding NaI or NaSCN changes the viscoelastic properties of non-Newtonian solutions and reduces their shear-thinning property. Measured centerline velocity profiles in the upstream straight pipe agreed well with an analytical solution. In the pulsatile case, secondary flow structures, i.e. deformed-Dean, Dean, Wall and Lyne vortices, were observed in various cross sections along the curved pipe. Vortical structures at each cross section were detected using the d2 vortex identification method. Circulation analysis was performed on each vortex separately during the systolic deceleration phase, and showed that vortices split and rejoin. Secondary flow structures in steady flows were found to be morphologically similar to those in pulsatile flows for sufficiently high Dean number. supported by the George Washington University Center for Biomimetics and Bioinspired Engineering.

Error analysis of supersonic air-to-air ejector schlieren pictures

Directory of Open Access Journals (Sweden)

Kolář J.

2013-04-01

Full Text Available The scope of this article is focused on general analysis of errors and uncertainties possibly arising from CFD-to-schlieren pictures matching. Analysis is based on classic analytical equations. These are firstly evaluated with the presumption of constant density gradient along the ray course. In other words, the deflection of light-ray caused by density gradient is negligible in compare to the cross size of constant gradient area. It is the aim of this work to determine, whether this presumption is applicable in case of supersonic air-to-air ejector. The colour and black and white schlieren pictures are carried out and compared to CFD results. Simulations had covered various eddy viscosities. Computed pressure gradients are transformed into deflection angles and further to ray displacement. Resulting computed light- ray deflection is matched to experimental results

Flow development through HP & LP turbines, Part II: Effects of the hub endwall secondary sealing air flow on the turbine's mainstream flow

Science.gov (United States)

Hu, Jialin; Du, Qiang; Liu, Jun; Wang, Pei; Liu, Guang; Liu, Hongrui; Du, Meimei

2017-08-01

Although many literatures have been focused on the underneath flow and loss mechanism, very few experiments and simulations have been done under the engines' representative working conditions or considering the real cavity structure as a whole. This paper aims at realizing the goal of design of efficient turbine and scrutinizing the velocity distribution in the vicinity of the rim seal. With the aid of numerical method, a numerical model describing the flow pattern both in the purge flow spot and within the mainstream flow path is established, fluid migration and its accompanied flow mechanism within the realistic cavity structure (with rim seal structure and considering mainstream & secondary air flow's interaction) is used to evaluate both the flow pattern and the underneath flow mechanism within the inward rotating cavity. Meanwhile, the underneath flow and loss mechanism are also studied in the current paper. The computational results show that the sealing air flow's ingestion and ejection are highly interwound with each other in both upstream and downstream flow of the rim seal. Both the down-stream blades' potential effects as well as the upstream blades' wake trajectory can bring about the ingestion of the hot gas flow within the cavity, abrupt increase of the static pressure is believed to be the main reason. Also, the results indicate that sealing air flow ejected through the rear cavity will cause unexpected loss near the outlet section of the blades in the downstream of the HP rotor passages.

Equivalent Temperature-Enthalpy Diagram for the Study of Ejector Refrigeration Systems

Directory of Open Access Journals (Sweden)

Mohammed Khennich

2014-05-01

Full Text Available The Carnot factor versus enthalpy variation (heat diagram has been used extensively for the second law analysis of heat transfer processes. With enthalpy variation (heat as the abscissa and the Carnot factor as the ordinate the area between the curves representing the heat exchanging media on this diagram illustrates the exergy losses due to the transfer. It is also possible to draw the paths of working fluids in steady-state, steady-flow thermodynamic cycles on this diagram using the definition of “the equivalent temperature” as the ratio between the variations of enthalpy and entropy in an analyzed process. Despite the usefulness of this approach two important shortcomings should be emphasized. First, the approach is not applicable for the processes of expansion and compression particularly for the isenthalpic processes taking place in expansion valves. Second, from the point of view of rigorous thermodynamics, the proposed ratio gives the temperature dimension for the isobaric processes only. The present paper proposes to overcome these shortcomings by replacing the actual processes of expansion and compression by combinations of two thermodynamic paths: isentropic and isobaric. As a result the actual (not ideal refrigeration and power cycles can be presented on equivalent temperature versus enthalpy variation diagrams. All the exergy losses, taking place in different equipments like pumps, turbines, compressors, expansion valves, condensers and evaporators are then clearly visualized. Moreover the exergies consumed and produced in each component of these cycles are also presented. The latter give the opportunity to also analyze the exergy efficiencies of the components. The proposed diagram is finally applied for the second law analysis of an ejector based refrigeration system.

Numerical simulation of the gas-solid flow in a square circulating fluidized bed with secondary air injection

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhengyang [Harbin Institute of Technology, Harbin (China). Post-doctor Station of Civil Engineering; Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Sun, Shaozeng; Zhao, Ningbo; Wu, Shaohua [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Tan, Yufei [Harbin Institute of Technology, Harbin (China). School of Municipal and Environmental Engineering

2013-07-01

The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m x 0.25 m x 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with secondary injection and without air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the secondary air injection ports when air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

The blood flow changes associated with idiopathic and secondary intracranial hypertension

International Nuclear Information System (INIS)

Bateman, G.

2002-01-01

Full text: The radiological diagnosis of idiopathic intracranial hypertension (IIH) is one of exclusion and as the MR venogram is prone to flow artefacts, the diagnosis of secondary intracranial hypertension (SIH) can also be problematic. The purpose of this paper is to define the blood flow characteristics, which are useful in the diagnosis of these conditions. Twelve patients with clinical findings suggestive of IIH and 12 control subjects were investigated with MR venography and MR flow quantification studies of the cerebral arteries and veins. Total cerebral blood flow, superior sagittal sinus (SSS) and straight sinus (ST) blood flows were measured. MR venography confirmed 7 of the 12 patients had venous outflow obstruction and thus SIH. The remaining 5 patients had IIH. The control patients mean total blood flow was 855 ml/min, the SSS flow was 400ml/min and the ST flow 117 ml/min. The total blood flow in the IIH patients was 46% higher (P = 0.0002) and the ST blood flow 38% higher (P = 0.05) than the control group, the SSS flow was 17% higher but this failed to reach significance. In SIH the SSS flow was reduced by 25% (P = 0.003) compared with the control group, the total and ST blood flow were not significantly altered. In IIH there is hyperaemia and the SSS appears limited in its ability to increase flow, therefore venous collaterals carry a greater load. In SIH, selective obstruction of the SSS reduces flow in this vessel but total blood flow is normal indicating there is also increased flow in collateral veins. Presumably the limited ability of the SSS to drain blood away from the brain in each condition raises venous sinus pressure and alters CSF resorption giving raised CSF pressure. Copyright (2002) Blackwell Science Pty Ltd

Density of Real Zeros of the Tutte Polynomial

DEFF Research Database (Denmark)

Ok, Seongmin; Perrett, Thomas

2018-01-01

The Tutte polynomial of a graph is a two-variable polynomial whose zeros and evaluations encode many interesting properties of the graph. In this article we investigate the real zeros of the Tutte polynomials of graphs, and show that they form a dense subset of certain regions of the plane. This ....... This is the first density result for the real zeros of the Tutte polynomial in a region of positive volume. Our result almost confirms a conjecture of Jackson and Sokal except for one region which is related to an open problem on flow polynomials.......The Tutte polynomial of a graph is a two-variable polynomial whose zeros and evaluations encode many interesting properties of the graph. In this article we investigate the real zeros of the Tutte polynomials of graphs, and show that they form a dense subset of certain regions of the plane...

Density of Real Zeros of the Tutte Polynomial

DEFF Research Database (Denmark)

Ok, Seongmin; Perrett, Thomas

2017-01-01

The Tutte polynomial of a graph is a two-variable polynomial whose zeros and evaluations encode many interesting properties of the graph. In this article we investigate the real zeros of the Tutte polynomials of graphs, and show that they form a dense subset of certain regions of the plane. This ....... This is the first density result for the real zeros of the Tutte polynomial in a region of positive volume. Our result almost confirms a conjecture of Jackson and Sokal except for one region which is related to an open problem on flow polynomials.......The Tutte polynomial of a graph is a two-variable polynomial whose zeros and evaluations encode many interesting properties of the graph. In this article we investigate the real zeros of the Tutte polynomials of graphs, and show that they form a dense subset of certain regions of the plane...

Gravity and Zero Point Energy

Science.gov (United States)

Massie, U. W.

When Planck introduced the 1/2 hv term to his 1911 black body equation he showed that there is a residual energy remaining at zero degree K after all thermal energy ceased. Other investigators, including Lamb, Casimir, and Dirac added to this information. Today zero point energy (ZPE) is accepted as an established condition. The purpose of this paper is to demonstrate that the density of the ZPE is given by the gravity constant (G) and the characteristics of its particles are revealed by the cosmic microwave background (CMB). Eddies of ZPE particles created by flow around mass bodies reduce the pressure normal to the eddy flow and are responsible for the force of gravity. Helium atoms resonate with ZPE particles at low temperature to produce superfluid helium. High velocity micro vortices of ZPE particles about a basic particle or particles are responsible for electromagnetic forces. The speed of light is the speed of the wave front in the ZPE and its value is a function of the temperature and density of the ZPE.

Transmit Antenna Selection for Multi-User Underlay Cognitive Transmission with Zero-Forcing Beamforming

KAUST Repository

Hanif, Muhammad

2017-03-20

We present a transmit antenna subset selection scheme for an underlay cognitive system serving multiple secondary receivers. The secondary system employs zero-forcing beamforming to nullify the interference to multiple primary users and eliminate inter-user interference to the secondary users simultaneously. Simulation results show that the proposed scheme achieves near-optimal performance with low computational complexity. Lastly, an optimal power allocation strategy is also introduced to improve the secondary network throughput.

Conference on Fluid Machinery, 8th, Budapest, Hungary, Sept. 1987, Proceedings. Volumes 1 & 2

Science.gov (United States)

Szabo, A.; Kisbocskoi, L.

The present conference on turbomachine fluid mechanics gives attention to the analysis of labyrinth seals, irrigation turbomachinery, axial-flow fans, poppet valves, the generation of Karman vortices, self-rectifying Wells-type air turbines, computer simulations for water-supply systems, the computation of meridional flow in turbomachines, entrained air effects on vortex pump performance, the three-dimensional potential flow in a draft tube, and hydro powerplant diagnostic methods. Also discussed are a mathematical model for the initiation of cavitation wear, cryogenic flow in ejectors, flow downstream of guide vanes in a Kaplan turbine, unsteady flow in rotating cascades, novel methods for turbomachine vibration monitoring, cavitation breakdown in centrifugal pumps, test results for Banki turbines, centrifugal compressor return-channel flow, performance predictions for regenerative turbomachines, and secondary flows in a centrifugal pump.

Multi-ejector concept for R-744 supermarket refrigerators; Multi-Ejektoren Konzept fuer R-744 Supermarkt-Kaelteanlagen

Energy Technology Data Exchange (ETDEWEB)

Hafner, Armin [SINTEF Energy Research, Trondheim (Norway); Foersterling, Sven [TLK-Thermo GmbH, Braunschweig (Germany); Banasiak, Krzystof [Silesian Univ. of Technology, Gliwice (Poland)

2012-07-01

Supermarkets are commercial buildings with major energy consumption and contribute also to relatively large direct emissions of greenhouse (GHG) through emissions of refrigerants from the refrigeration plants and the air conditioning system installed. The huge majority of these systems, which are installed in European supermarkets, are applying HFC-404A as working fluid. Average annual leakage rates in Europe are in the range of 15-20 % of the total charge. Worldwide the figure is about 30 % and HCFC-22 being the main refrigerant in use. Restrictions on the use of synthetic refrigerants are coming into force in several countries. There is a need for a natural refrigerant which allows for a safe investment in efficient refrigeration systems which will not be forced to be retrofitted by legislation in the future. Systems applying R-744 as the only refrigerant have been developed and more than 500 supermarkets exist in Europe, mainly in northern and mid-European countries. However, the systems still have large potential in development with respect to energy efficiency, heat recovery and cost efficiency. The paper describes the calculation method to identify the possible annual energy savings for different supermarket systems layout. The adoption of non-controlled ejectors and additional function such as heat recovery are evaluated. Results show relevant improvements in system efficiency when heat recovery has been adopted. Ejector usage is not widely spread at the moment. Thus, a theoretical analysis applying the programming language Modelica has been carried out. (orig.)

AERODYNAMIC CHARACTERISTICS OF “FAN-IN-FIN” SYSTEM IN CONDITION OF FLOWING UNDER ZERO ATTACK ANGLE

Directory of Open Access Journals (Sweden)

2016-01-01

Full Text Available Fan-in-fin system can be used as single-rotor helicopter fenestrons propulsion system of low-speed airplanes and dirigibles as well as vehicles with remote control.The article suggests way to continue the author’s research in the field of fan-in-fin system aerodynamics.It also offers a method of aerodynamic characteristics of “fan-in-fin” (fenestron system with cylindrical diffuser of limited length in flow regime under zero angle of attack calculation. The article gives some formula to calculate the flow velocity through the disk area which decrease with the increase of the defusser and air speed.Correlation between fan thrust power and ring thrust on these regimes and momentum drag are found. Momentum drag is high enough, this fact leads to back deviation of total aerodynamic force system. This angle increases with increase of the diffuser length and at medium speed it can reach 30°.Certainty of suggested algorithms is proved by comparison with experiments for helicopter fenestron and un- manned air vehicle by tests in wind tunnel of MAI.

Numerical Estimation Method for the NonStationary Thrust of Pulsejet Ejector Nozzle

Directory of Open Access Journals (Sweden)

A. Yu. Mikushkin

2016-01-01

Full Text Available The article considers a calculation method for the non-stationary thrust of pulsejet ejector nozzle that is based on detonation combustion of gaseous fuel.To determine initial distributions of the thermodynamic parameters inside the detonation tube was carried out a rapid analysis based on x-t-diagrams of motion of glowing combustion products. For this purpose, the section with transparent walls was connected to the outlet of the tube to register the movement of products of combustion.Based on obtained images and gas-dynamic and thermodynamic equations the velocity distribution of the combustion products, its density, pressure and temperature required for numerical analysis were calculated. The world literature presents data on distribution of parameters, however they are given only for direct initiation of detonation at the closed end and for chemically "frozen" gas composition. The article presents the interpolation methods of parameters measured at the temperatures of 2500-2800K.Estimation of the thermodynamic parameters is based on the Chapman-Jouguet theory that the speed of the combustion products directly behind the detonation wave front with respect to the wave front is equal to the speed of sound of these products at a given point. The method of minimizing enthalpy of the final thermodynamic state was used to calculate the equilibrium parameters. Thus, a software package «IVTANTHERMO», which is a database of thermodynamic properties of many individual substances in a wide temperature range, was used.An integral thrust was numerically calculated according to the ejector nozzle surface. We solved the Navier-Stokes equations using the finite-difference Roe scheme of the second order. The combustion products were considered both as an inert mixture with "frozen" composition and as a mixture in chemical equilibrium with the changing temperature. The comparison with experimental results was made.The above method can be used for rapid

Optimization of gas mixing system of premixed burner based on CFD analysis

International Nuclear Information System (INIS)

Zhang, Tian-Hu; Liu, Feng-Guo; You, Xue-Yi

2014-01-01

Highlights: • New multi-ejectors gas mixing system for premixed combustion burner is provided. • Two measures are proposed to improve the flow uniformity at the outlet of GMS. • Small improvement of uniformity induces significant decrease of pollutant emission. • Uniformity of velocity and fuel–gas mixing of ejector increases 234.2% and 2.9%. • Uniformity of flow rate and fuel–gas mixing of ejectors increases 1.9% and 2.2%. - Abstract: The optimization of gas mixing system (GMS) of premixed burner is presented by Computational Fluid Dynamics (CFD) and the uniformity at the outlet of GMS is proved experimentally to have strong influence on pollutant emission. To improve the uniformity at the outlet of GMS, the eleven distribution orifice plates and a diversion plate are introduced. The quantified analysis shows that the uniformity at the outlet of GMS is improved significantly. With applying the distribution orifice plates, the uniformity of velocity and fuel–gas mixing of single ejector is increased by 234.2% and 2.9%, respectively. With applying the diversion plate, the uniformity of flow rate and fuel–gas mixing of different ejectors is increased by 1.9% and 2.2%, respectively. The optimal measures and geometrical parameters provide an applicable guidance for the design of commercial premixed burner

Essential Development of Streamwise Vortical/Secondary Flows in All Ducts with Corners or Slope Discontinuities in Perimeter

Science.gov (United States)

Nagib, Hassan; Vidal, Alvaro; Vinuesa, Ricardo; Schlatter, Philipp

2017-11-01

Direct numerical simulations of fully-developed turbulent flow through various straight ducts with sharp or rounded corners of various radii were performed to study influence of corner geometry on secondary flows. Unexpectedly, increased rounding of corners in rectangular ducts does not lead to monotonic trend towards pipe case. Instead, secondary vortices relocate close to regions of wall-curvature change. This behavior is connected to inhomogeneous interaction between near-wall bursting events, which are further characterized in this work with definition of their local preferential direction, and vorticity fluxes. Although these motions are relatively weak compared to streamwise velocity their effect on turbulence statistics and shear-stress distribution is very important and has not been sufficiently documented or fully understood. Flow through spanwise-periodic channels, with sinusoidal function to define the geometry of wall, yw = +/- h + A cos(ωz) , was also studied as model flow that is parametrically changed using A and ω, while taking advantage of many resulting symmetries. Consequences on experimental facilities and comparisons between experiments and various numerical and theoretical models are discussed revealing the uniqueness of pipe flow.

Suppression of the secondary flow in a suction channel of a large centrifugal pump

International Nuclear Information System (INIS)

Torii, D; Nagahara, T; Okihara, T

2013-01-01

The suction channel configuration of a large centrifugal pump with a 90-degree bend was studied in detail to suppress the secondary flow at the impeller inlet for improving suction performance. Design of experiments (DOE) and computational fluid dynamics (CFD) were used to evaluate the sensitivity of several primary design parameters of the suction channel. A DOE is a powerful tool to clarify the sensitivity of objective functions to design parameters with a minimum of trials. An L9 orthogonal array was adopted in this study and nine suction channels were designed, through which the flow was predicted by steady state calculation. The results indicate that a smaller bend radius with a longer straight nozzle, distributed between the bend and the impeller, suppresses the secondary flow at the impeller inlet. An optimum ratio of the cross sectional areas at the bend inlet and outlet was also confirmed in relationship to the contraction rate of the downstream straight nozzle. These findings were obtained by CFD and verified by experiments. The results will aid the design of large centrifugal pumps with better suction performance and higher reliability

Improvement of the thermal and mechanical flow characteristics in the exhaust system of piston engine through the use of ejection effect

Science.gov (United States)

Plotnikov, L. V.; Zhilkin, B. P.; Brodov, Yu M.

2017-11-01

The results of experimental research of gas dynamics and heat transfer in the exhaust process in piston internal combustion engines are presented. Studies were conducted on full-scale models of piston engine in the conditions of unsteady gas-dynamic (pulsating flows). Dependences of the instantaneous flow speed and the local heat transfer coefficient from the crankshaft rotation angle in the exhaust pipe are presented in the article. Also, the flow characteristics of the exhaust gases through the exhaust systems of various configurations are analyzed. It is shown that installation of the ejector in the exhaust system lead to a stabilization of the flow and allows to improve cleaning of the cylinder from exhaust gases and to optimize the thermal state of the exhaust pipes. Experimental studies were complemented by numerical simulation of the working process of the DM-21 diesel engine (production of “Ural diesel-motor plant”). The object of modeling was the eight-cylinder diesel with turbocharger. The simulation was performed taking into account the processes nonstationarity in the intake and exhaust pipes for the various configurations of exhaust systems (with and without ejector). Numerical simulation of the working process of diesel was performed in ACTUS software (ABB Turbo Systems). The simulation results confirmed the stabilization of the flow due to the use of the ejection effect in the exhaust system of a diesel engine. The use of ejection in the exhaust system of the DM-21 diesel leads to improvement of cleaning cylinders up to 10 %, reduces the specific fuel consumption on average by 1 %.

Convective boundary layer flow and heat transfer in a nanofluid in the presence of second order slip, constant heat flux and zero nanoparticles flux

Energy Technology Data Exchange (ETDEWEB)

Rahman, M.M., E-mail: mansurdu@yahoo.com [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Al-Rashdi, Maryam H. [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Pop, I. [Department of Mathematics, Faculty of Mathematics and Computer Science, Babeş-Bolyai University, Cluj-Napoca 400084 (Romania)

2016-02-15

Highlights: • Convective boundary layer flow and heat transfer in a nanofluid is investigated. • Second order slip increases the rate of shear stress and decreases the rate of heat transfer in a nanofluid. • In nanofluid flow zero normal flux of the nanoparticles at the surface is realistic to apply. • Multiple solutions are identified for certain values of the parameter space. • The upper branch solution is found to be stable, hence physically realizable. - Abstract: In this work, the effects of the second order slip, constant heat flux, and zero normal flux of the nanoparticles due to thermophoresis on the convective boundary layer flow and heat transfer characteristics in a nanofluid using Buongiorno's model over a permeable shrinking sheet is studied theoretically. The nonlinear coupled similarity equations are solved using the function bvp4c using Matlab. Similarity solutions of the flow, heat transfer and nanoparticles volume fraction are presented graphically for several values of the model parameters. The results show that the application of second order slip at the interface is found to be increased the rate of shear stress and decreased the rate of heat transfer in a nanofluid, so need to be taken into account in nanofluid modeling. The results further indicate that multiple solutions exist for certain values of the parameter space. The stability analysis provides guarantee that the lower branch solution is unstable, while the upper branch solution is stable and physically realizable.

Technological processing waste water using the dressing the ejector system for pretreament

Directory of Open Access Journals (Sweden)

Božović Milan

2017-01-01

Full Text Available Slaughter industry produces large amounts of waste water, which endanger and degrade the natural recipients - recipients, given that the waste vode najčešće discharged without any form of treatment or purification. Wastewater slaughter industry carry faeces, straw, unprocessed animal feed, various stomach secretions, blood, fat, a variety of solid waste and other organic matter present. Many applied technical and technological solutions in order to prevent harming the recipients are not given adequate results from the ecological aspect. The reconstruction of a system for pre-treatment and slaughter waste water by applying technological solutions ejector - pump, not only have obtained good results required by the project, but also pointed to the possibility of their use in many types of agro-industrial waste water, especially with the growing number of small agro-industrial drive .

Forced flow cooling of ISABELLE dipole magnets

International Nuclear Information System (INIS)

Bamberger, J.A.; Aggus, J.; Brown, D.P.; Kassner, D.A.; Sondericker, J.H.; Strobridge, T.R.

1976-01-01

The superconducting magnets for ISABELLE will use a forced flow supercritical helium cooling system. In order to evaluate this cooling scheme, two individual dipole magnets were first tested in conventional dewars using pool boiling helium. These magnets were then modified for forced flow cooling and retested with the identical magnet coils. The first evaluation test used a l m-long ISA model dipole magnet whose pool boiling performance had been established. The same magnet was then retested with forced flow cooling, energizing it at various operating temperatures until quench occurred. The magnet performance with forced flow cooling was consistent with data from the previous pool boiling tests. The next step in the program was a full-scale ISABELLE dipole ring magnet, 4.25 m long, whose performance was first evaluated with pool boiling. For the forced flow test the magnet was shrunk-fit into an unsplit laminated core encased in a stainless steel cylinder. The high pressure gas is cooled below 4 K by a helium bath which is pumped below atmospheric pressure with an ejector nozzle. The performance of the full-scale dipole magnet in the new configuration with forced flow cooling, showed a 10 percent increase in the attainable maximum current as compared to the pool boiling data

Performance analysis of ejector absorption heat pump using ozone safe fluid couple through artificial neural networks

International Nuclear Information System (INIS)

Soezen, Adnan; Arcaklioglu, Erol; Oezalp, Mehmet

2004-01-01

Thermodynamic analysis of absorption thermal systems is too complex because the analytic functions calculating the thermodynamic properties of fluid couples involve the solution of complex differential equations and simulation programs. This study aims at easing this complex situation and consists of three cases: (i) A special ejector, located at the absorber inlet, instead of the common location at the condenser inlet, to increase overall performance was used in the ejector absorption heat pump (EAHP). The ejector has two functions: Firstly, it aids the pressure recovery from the evaporator and then upgrades the mixing process and pre-absorption by the weak solution of the methanol coming from the evaporator. (ii) Use of artificial neural networks (ANNs) has been proposed to determine the properties of the liquid and two phase boiling and condensing of an alternative working fluid couple (methanol/LiCl), which does not cause ozone depletion. (iii) A comparative performance study of the EAHP was performed between the analytic functions and the values predicted by the ANN for the properties of the couple. The back propagation learning algorithm with three different variants and logistic sigmoid transfer function were used in the network. In order to train the neural network, limited experimental measurements were used as training and test data. In the input layer, there are temperature, pressure and concentration of the couples. Specific volume is in the output layer. After training, it was found that the maximum error was less than 3%, the average error was less than 1.2% and the R 2 values were about 0.9999. Additionally, in comparison of the analysis results between analytic equations obtained by using experimental data and by means of the ANN, the deviations of the refrigeration effectiveness of the system for cooling (COP r ), exergetic coefficient of performance of the system for cooling (ECOP r ) and circulation ratio (F) for all working temperatures were

Experimental investigation of zero phase shift effects for Coriolis flowmeters due to pipe imperfections

DEFF Research Database (Denmark)

Enz, Stephanie; Thomsen, Jon Juel; Neumeyer, Stefan

2011-01-01

mass as well as temperature changes could be causes contributing to a time-varying measured zero shift, as observed with some commercial CFMs. The conducted experimental tests of the theoretically based hypotheses have shown that simple mathematical models and approximate analysis allow general......, the flexural vibrations of two bent, parallel, non-fluid-conveying pipes are studied experimentally, employing an industrial CFM. Special attention has been paid on the phase shift in the case of zero mass flow, i.e. the zero shift, caused by various imperfections to the ‘‘perfect’’ CFM, i.e. non-uniform pipe...... damping and mass, and on ambient temperature changes. Experimental observations confirm the hypothesis that asymmetry in the axial distribution of damping will induce zero shifts similar to the phase shifts due to fluid flow. Axially symmetrically distributed damping was observed to influence phase shift...

A Spatial-Filtering Zero-Inflated Approach to the Estimation of the Gravity Model of Trade

Directory of Open Access Journals (Sweden)

Rodolfo Metulini

2018-02-01

Full Text Available Nonlinear estimation of the gravity model with Poisson-type regression methods has become popular for modelling international trade flows, because it permits a better accounting for zero flows and extreme values in the distribution tail. Nevertheless, as trade flows are not independent from each other due to spatial and network autocorrelation, these methods may lead to biased parameter estimates. To overcome this problem, eigenvector spatial filtering (ESF variants of the Poisson/negative binomial specifications have been proposed in the literature on gravity modelling of trade. However, no specific treatment has been developed for cases in which many zero flows are present. This paper contributes to the literature in two ways. First, by employing a stepwise selection criterion for spatial filters that is based on robust (sandwich p-values and does not require likelihood-based indicators. In this respect, we develop an ad hoc backward stepwise function in R. Second, using this function, we select a reduced set of spatial filters that properly accounts for importer-side and exporter-side specific spatial effects, as well as network effects, both at the count and the logit processes of zero-inflated methods. Applying this estimation strategy to a cross-section of bilateral trade flows between a set of 64 countries for the year 2000, we find that our specification outperforms the benchmark models in terms of model fitting, both considering the AIC and in predicting zero (and small flows.

Zero Boil Off System for Cryogen Storage, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This work proposes to develop a zero boil off (ZBO) dewar using a two-stage pulse-tube cooler together with two innovative, continuous-flow cooling loops and an...

Cooling joint width and secondary mineral infilling characteristics in four Grande Ronde Basalt flows at the Hanford Site, Washington

International Nuclear Information System (INIS)

Lindberg, J.W.

1988-09-01

Widths were measured and percentages of secondary mineral infilling types were estimated 3194 cooling joints in basalt core of the Rocky Coulee, Cohassett, McCoy Canyon, and Umtanum basalt flows. The core was from core holes RRL-2, RRL-6, RRL-14, and DC-16 on the Hanford Site in Washington State. Joint width was characterized by determining the frequency distribution in each of 16 flow/core hole combination samples (4 flows by 4 core holes = 16 samples) and comparing the distributions between intraflow structures, between basalt flows, and between core holes. Joint infilling was characterized by determining the percentage of joints with each secondary mineral type present and then comparing flows and comparing intraflow instructures. Basalt flows, intraflow structures, and core holes cannot be differentiated consistently on the basis of joint width. There is only one population of widths that can be characterized by a log-normal distribution, an arithmetic mean of 0. 23 mm(9.0E-04in.), and a standard deviation of 0.49 mm (1.9E-03in.). Clay is the predominant infilling type followed by silica and zeolite. For example, 98.1% of the randomly selected joints from the Cohassett flow are filled predominately with clay, 6.5% have zeolite predominating, and 4.0% have silica predominating. Only 19(0.6%) of the 3194 joints measured have observable void space. Basalt flows and intraflow structures cannot be differentiated on the basis joint infilling types, except for the Umtanum entablature. Joint width and infilling types are correlated, and secondary minerals fill basalt cooling joints in a particular sequence

EFFECTS OF SLOTTED BLADING ON SECONDARY FLOW IN HIGHLY LOADED COMPRESSOR CASCADE

Directory of Open Access Journals (Sweden)

RAMZI MDOUKI

2013-10-01

Full Text Available With the aim to increase allowable blade loadings and enlarge stable operating range in highly loaded compressor, this work is carried out in order to explore the potential of passive control via slotted bladings in linear cascade configurations under both design and stall conditions. Through an extensive 2D-numerical study, the effects of location, width and slope of slots were analysed and the best configuration was identified. Based on the optimal slot, the 3D aerodynamic performances of cascade were studied and the influence of slotted blading to control endwall flow was investigated. Both 2D and 3D calculations are performed on steady RANS solver with standard k-epsilon turbulence model and low Mach number regime. The total loss coefficient, turning angle and flow visualizations on the blade and end-wall surfaces are adopted to describe the different configurations. The obtained results show, for 2D situation, that a maximum of 28.3% reduction in loss coefficient had been reached and the flow turning was increased with approximately 5°. Concerning 3D flow fields the slots marked their benefit at large incoming flow angles which delays the separation on both end wall and blade suction surface at mid span. However, at design conditions, the slotted blades are not able to control secondary flows near the wall and so, lose their potential.

Power ramp rate capabilities of a 5 kW proton exchange membrane fuel cell system with discrete ejector control

Science.gov (United States)

Nikiforow, K.; Pennanen, J.; Ihonen, J.; Uski, S.; Koski, P.

2018-03-01

The power ramp rate capabilities of a 5 kW proton exchange membrane fuel cell (PEMFC) system are studied theoretically and experimentally for grid support service applications. The fuel supply is implemented with a fixed-geometry ejector and a discrete control solution without any anode-side pressure fluctuation suppression methods. We show that the stack power can be ramped up from 2.0 kW to 4.0 kW with adequate fuel supply and low anode pressure fluctuations within only 0.1 s. The air supply is implemented with a centrifugal blower. Air supply ramp rates are studied with a power increase executed within 1 and 0.2 s after the request, the time dictated by grid support service requirements in Finland and the UK. We show that a power ramp-up from 2.0 kW to 3.7 kW is achieved within 1 s with an initial air stoichiometry of 2.5 and within 0.2 s with an initial air stoichiometry of 7.0. We also show that the timing of the power ramp-up affects the achieved ancillary power capacity. This work demonstrates that hydrogen fueled and ejector-based PEMFC systems can provide a significant amount of power in less than 1 s and provide valuable ancillary power capacity for grid support services.

Zero Gravity Research Facility (Zero-G)

Data.gov (United States)

Federal Laboratory Consortium — The Zero Gravity Research Facility (Zero-G) provides a near weightless or microgravity environment for a duration of 5.18 seconds. This is accomplished by allowing...

Method and apparatus for condensing radioactive rare gases by means of use of ejector and selective adsorption and desorption process including cycles

International Nuclear Information System (INIS)

Kanazawa, Toshio; Tsuda, Koji; Watanabe, Yukio; Miharada, Hassui; Tani, Akira.

1975-01-01

Object: To recover rare gases in waste gases at one stage as high density as possible while effectively utilizing adsorption beds. Structure: The waste gases pass through an ejector and are subject to treatment of dehumidification and decarbonization in a pretreatment station, after which the gases enter a first low temperature adsorption bed through a heat exchanger and a first valve. If breaking should occur in the first adsorption bed, the waste gases would be introduced into a second adsorption bed for adsorption treatment. The first adsorption bed, which has completed adsorption, is heated to a regenerative temperature while adsorption is being performed at the second adsorption bed, and degases containing rare gases are recycled through a second and third valves and are mixed into raw waste gases by the action of the ejector. After the above adsorption and desorption have been repeated several times by alternately using the first and second adsorption bed the adsorption bed is heated to a temperature lower than the regenerative temperature to recycle the desorption gases to feed and then heated to the regenerative temperature, and the desorbed rare gases are fed to the succeeding system through a pump. (Yoshihara, H.)

SIMULACIÓN HORARIA DE UN SISTEMA DE REFRIGERACIÓN COMBINADO EYECTOR-COMPRESIÓN DE VAPOR ASISTIDO POR ENERGÍA SOLAR Y GAS NATURAL HOURLY SIMULATION OF A COMBINED EJECTOR-VAPOR COMPRESSION REFRIGERATION SYSTEM ASSISTED BY SOLAR ENERGY AND NATURAL GAS

Directory of Open Access Journals (Sweden)

Humberto Vidal

2009-04-01

Full Text Available Entre los sistemas de refrigeración movidos térmicamente asistidos por energía solar y gas natural, el sistema de refrigeración con eyector ha recibido especial atención. Este sistema se caracteriza por su simplicidad constructiva, ausencia de partes móviles, operación en bajas temperaturas y bajo costo operacional. Sin embargo, el ciclo de refrigeración por eyector tiene usualmente un bajo coeficiente de desempeño. Una alternativa de solución a este problema lo constituye el sistema de refrigeración con eyector combinado. La primera etapa está constituida por un ciclo de compresión mecánica de vapor convencional con R134a, mientras que la segunda etapa la constituye un ciclo termo-movido con eyector usando R141b como fluido de trabajo. Colectores de placa plana y un quemador de energía auxiliar entregan calor al ciclo de eyector. Este artículo describe la simulación en base horaria de un sistema de refrigeración combinado eyector-compresión de vapor asistido por energía solar y gas natural. El sistema de refrigeración solar combinado es modelado usando la herramienta de simulación TRNSYS-EES y los datos climáticos de un año típico de Florianópolis, Brasil. Los resultados obtenidos con la modelación computacional desarrollada para este sistema muestran la ventaja del ciclo de refrigeración combinado eyector-compresión de vapor por sobre el ciclo simple con eyector. Finalmente, el modelo computacional desarrollado en este artículo podría ser usado para realizar una optimización termo-económica del sistema en trabajos futuros.Among the thermally driven cooling systems assisted by solar energy and natural gas, the ejector cooling system has received special attention. This system is an interesting refrigeration technology due to its construction simplicity, absence of moving parts, operation at lower temperatures and a low operational cost. However, the coefficient of performance of ejector cycle is usually low. The

Gas pollutants removal in a single- and two-stage ejector-venturi scrubber.

Science.gov (United States)

Gamisans, Xavier; Sarrà, Montserrrat; Lafuente, F Javier

2002-03-29

The absorption of SO(2) and NH(3) from the flue gas into NaOH and H(2)SO(4) solutions, respectively has been studied using an industrial scale ejector-venturi scrubber. A statistical methodology is presented to characterise the performance of the scrubber by varying several factors such as gas pollutant concentration, air flowrate and absorbing solution flowrate. Some types of venturi tube constructions were assessed, including the use of a two-stage venturi tube. The results showed a strong influence of the liquid scrubbing flowrate on pollutant removal efficiency. The initial pollutant concentration and the gas flowrate had a slight influence. The use of a two-stage venturi tube considerably improved the absorption efficiency, although it increased energy consumption. The results of this study will be applicable to the optimal design of venturi-based absorbers for gaseous pollution control or chemical reactors.

A study on prediction of metal loss by flow-accelerated corrosion in the CANDU NPP secondary piping systems

International Nuclear Information System (INIS)

Shim, S. H.; Song, J. S.; Yoon, K. B.; Hwang, K. M.; Jin, T. E.; Lee, S. H.; Kim, W. S.

2001-01-01

Flow-Accelerated Corrosion(FAC) is a phenomenon that results in metal loss from piping, vessels, and equipment made of carbon steel. FAC occurs only under certain conditions of flow, chemistry, geometry, and material. Unfortunately, those conditions are in much of the high-energy piping in nuclear and fossil-fueled power plants. Also, for domestic NPP secondary pipings whose operating time become longer, more evidences of FAC have been reported. The authors are studying on FAC management using CHECWORKS, computer code developed by EPRI. This paper is on the prediction results of metal loss by FAC in the one of CANDU type NPP secondary piping systems

Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen.

Science.gov (United States)

Ushakov, Dmitry B; Gilmore, Kerry; Kopetzki, Daniel; McQuade, D Tyler; Seeberger, Peter H

2014-01-07

Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Micron-Size Zero-Valent Iron Emplacement in Porous Media Using Polymer Additives: Column and Flow Cell Ex-periments

Energy Technology Data Exchange (ETDEWEB)

Oostrom, Mart; Wietsma, Thomas W.; Covert, Matthew A.; Vermeul, Vince R.

2006-03-20

At the Hanford Site, an extensive In Situ Redox Manipulation (ISRM) permeable reactive barrier was installed to prevent chromate from reaching the Columbia River. However, chromium has been detected in several wells, indicating a premature loss of the reductive capacity in the aquifer. Laboratory experiments have been conducted to investigate whether barrier reductive capacity can be enhanced by adding micron-scale zero-valent iron to the high-permeability zones within the aquifer using shear-thinning fluids containing polymers. Porous media were packed in a wedge-shaped flow cell to create either a heterogeneous layered system with a high-permeability zone between two low-permeability zones or a high-permeability channel sur-rounded by low-permeability materials. The injection flow rate, polymer type, polymer concentration, and injected pore volumes were determined based on preliminary short- and long-column experiments. The flow cell experiments indicated that iron concentration enhancements of at least 0.6% (w/w) could be obtained using moderate flow rates and injection of 30 pore volumes. The 0.6% amended Fe0 concentration would provide approximately 20 times the average reductive capacity that is provided by the dithionite-reduced iron in the ISRM barrier. Calculations show that a 1-m-long Fe0 amended zone with an average concentration of 0.6% w/w iron subject to a groundwater velocity of 1 m/day will have an estimated longevity of 7.2 years.

A methodology for the measure of secondary homes tourist flows at municipal level

Directory of Open Access Journals (Sweden)

Andrea Guizzardi

2007-10-01

Full Text Available The present public statistical system does not provide information concerning second houses touristic flows at sub-regional level. The lack limits local administrations' capabilities to take decisions about either: environmental, territorial and productive development, as well as regional governments in fair allocation of public financing. In the work, this information lack is overcome by proposing an indirect estimation methodology. Municipalities electric power consumption is proposed as an indicator of the stays on secondary homes. The indicator is connected to tourism flows considering both measurement errors and factors, modifying the local power demand. The application to Emilia-Romagna regional case allow to verify results’ coherence with officials statistics, as weel as to assess municipalities’ tourist vocation.

Oil spillage recovery by vacuum trawl

International Nuclear Information System (INIS)

Birkett, H.

1992-01-01

In this invention, floating oil is sucked from the surface of the sea under a skirt and into a tubular floating boom, along whose interior it is carried to water-oil separation means. The suction is produced by one or more ejectors which are supplied with sea water under pressure and may be located inside the boom, or immediately below it and connected into a separate pipe. The boom is used to enclose an oil slick and drawn tighter to increase the thickness of the oil layer. The oil enters the boom through holes in its upper half and then flows to the ejector(s) along separate internal tubes or between buoyancy balls. A fraction of the oil-water mixture withdrawn from the boom is pressurised and returned to ejector(s) and the rest is diverted to the separation means. (author)

Performance estimation of ejector cycles using heavier hydrocarbon refrigerants

International Nuclear Information System (INIS)

Kasperski, Jacek; Gil, Bartosz

2014-01-01

Computer software basing on theoretical model of Huang et al. with thermodynamic properties of hydrocarbons was prepared. Investigation was focused on nine hydrocarbons: propane, butane, iso-butane, pentane, iso-pentane, hexane, heptane and octane. A series of calculations was carried out for the generator temperature between 70 and 200 °C, with assumed temperatures of evaporation 10 °C and condensation 40 °C. Calculation results show that none of the hydrocarbons enables high efficiency of a cycle in a wide range of temperature. Each hydrocarbon has its own maximal entrainment ratio at its individual temperature of optimum. Temperatures of entrainment ratios optimum increase according to the hydrocarbon heaviness with simultaneous increase of entrainment ratio peak values. Peak values of the COP do not increase according to the hydrocarbons heaviness. The highest COP = 0.32 is achieved for iso-butane at 102 °C and the COP = 0.28 for pentane at 165 °C. Heptane and octane can be ignored. - Highlights: • Advantages of use of higher hydrocarbons as ejector refrigerants were presumed. • Computer software basing on theoretical model of Huang et al. (1999) was prepared. • Optimal temperature range of vapor generation for each hydrocarbon was calculated

Low flow and drought spatial analysis

International Nuclear Information System (INIS)

Dakova, Snejana

2004-01-01

The hydrological characteristics of Bulgarian rivers reflect to the climate variability. Nearly all precipitation is received during the spring and/or winter months, with negligible precipitations in summer. Thus, peak flows occur in spring and/or winter, and during the summer, the flow is significant lower with many rivers being ephemeral. Therefore, 2210 reservoirs for satisfaction the water needs have been constructed during the last sixty years. In spit of that, Bulgaria is facing to a new insufficiency of water. The recent climate change investigations and climate scenarios determine the area of Balkan Peninsula as territories with decreasing of rainfalls and increasing of air temperature. In view of that, research the low flow in the light of climate changing together with the water management is required. In this study the definitions of low flow and drought are developed using available data obtained in Bulgarian area, which has semiarid zone conditions. The difference between the terms of drought and low flow is describing and clarified also. The low flow and drought variables are investigated on two levels: first on long-year's variability using annual data and than monthly and seasonal data series-for enabling the within-year effects to be determined. The relationship between the probability of river's dry up and mean annual and seasonal rainfalls is quantified using multiple regressions applied to logarithmic- transformed data. This paper presets also analyses of minimum flow series with zero values. The exceed probability above which stream flow is zero and conditional probability of non-zero flow (non-zero-duration curve) is obtained by the principals of total probability. A different kind of adjusting duration curves are proposed depending of the number of zero values in the series.(Author)

Zero-One Law for Regular Languages and Semigroups with Zero

OpenAIRE

Sin'ya, Ryoma

2015-01-01

A regular language has the zero-one law if its asymptotic density converges to either zero or one. We prove that the class of all zero-one languages is closed under Boolean operations and quotients. Moreover, we prove that a regular language has the zero-one law if and only if its syntactic monoid has a zero element. Our proof gives both algebraic and automata characterisation of the zero-one law for regular languages, and it leads the following two corollaries: (i) There is an O(n log n) alg...

Interdependencies of aortic arch secondary flow patterns, geometry, and age analysed by 4-dimensional phase contrast magnetic resonance imaging at 3 Tesla

Energy Technology Data Exchange (ETDEWEB)

Frydrychowicz, Alex [University Hospital Schleswig-Holstein, Clinic for Radiology and Nuclear Medicine, Luebeck (Germany); Berger, Alexander; Russe, Maximilian F.; Bock, Jelena [University Hospital Freiburg, Department of Radiology, Medical Physics, Freiburg (Germany); Munoz del Rio, Alejandro [University of Wisconsin - Madison, Departments of Radiology and Medical Physics, Madison, WI (United States); Harloff, Andreas [University Hospital Freiburg, Department of Neurology and Clinical Neurophysiology, Freiburg (Germany); Markl, Michael [University Hospital Freiburg, Department of Radiology, Medical Physics, Freiburg (Germany); Northwestern University, Departments of Radiology and Biomedical Engineering, Chicago, IL (United States)

2012-05-15

It was the aim to analyse the impact of age, aortic arch geometry, and size on secondary flow patterns such as helix and vortex flow derived from flow-sensitive magnetic resonance imaging (4D PC-MRI). 62 subjects (age range = 20-80 years) without circumscribed pathologies of the thoracic aorta (ascending aortic (AAo) diameter: 3.2 {+-} 0.6 cm [range 2.2-5.1]) were examined by 4D PC-MRI after IRB-approval and written informed consent. Blood flow visualisation based on streamlines and time-resolved 3D particle traces was performed. Aortic diameter, shape (gothic, crook-shaped, cubic), angle, and age were correlated with existence and extent of secondary flow patterns (helicity, vortices); statistical modelling was performed. Helical flow was the typical pattern in standard crook-shaped aortic arches. With altered shapes and increasing age, helicity was less common. AAo diameter and age had the highest correlation (r = 0.69 and 0.68, respectively) with number of detected vortices. None of the other arch geometric or demographic variables (for all, P {>=} 0.177) improved statistical modelling. Substantially different secondary flow patterns can be observed in the normal thoracic aorta. Age and the AAo diameter were the parameters correlating best with presence and amount of vortices. Findings underline the importance of age- and geometry-matched control groups for haemodynamic studies. (orig.)

Interdependencies of aortic arch secondary flow patterns, geometry, and age analysed by 4-dimensional phase contrast magnetic resonance imaging at 3 Tesla

International Nuclear Information System (INIS)

Frydrychowicz, Alex; Berger, Alexander; Russe, Maximilian F.; Bock, Jelena; Munoz del Rio, Alejandro; Harloff, Andreas; Markl, Michael

2012-01-01

It was the aim to analyse the impact of age, aortic arch geometry, and size on secondary flow patterns such as helix and vortex flow derived from flow-sensitive magnetic resonance imaging (4D PC-MRI). 62 subjects (age range = 20-80 years) without circumscribed pathologies of the thoracic aorta (ascending aortic (AAo) diameter: 3.2 ± 0.6 cm [range 2.2-5.1]) were examined by 4D PC-MRI after IRB-approval and written informed consent. Blood flow visualisation based on streamlines and time-resolved 3D particle traces was performed. Aortic diameter, shape (gothic, crook-shaped, cubic), angle, and age were correlated with existence and extent of secondary flow patterns (helicity, vortices); statistical modelling was performed. Helical flow was the typical pattern in standard crook-shaped aortic arches. With altered shapes and increasing age, helicity was less common. AAo diameter and age had the highest correlation (r = 0.69 and 0.68, respectively) with number of detected vortices. None of the other arch geometric or demographic variables (for all, P ≥ 0.177) improved statistical modelling. Substantially different secondary flow patterns can be observed in the normal thoracic aorta. Age and the AAo diameter were the parameters correlating best with presence and amount of vortices. Findings underline the importance of age- and geometry-matched control groups for haemodynamic studies. (orig.)

Application of nano-structured coatings to mitigate flow-accelerated corrosion in secondary pipe systems of nuclear power plants

International Nuclear Information System (INIS)

Kim, Seung Hyun; Kim, Jong Jin; Yoo, Seung Chang; Kim, Ji Hyun

2014-01-01

Carbon steel is widely used as a structural material in secondary pipe systems. However, the passivity of carbon steel is not sufficient for protection in secondary water chemistry with a very fast-flowing fluid because of the dissolution of ferrous and magnetite ions and surface friction at the interface of the coolant and pipe surface. There have been many efforts to mitigate flow-accelerated corrosion through adoption of advanced water chemistries such as optimized dissolve oxygen (DO) concentration and temperature, as well as usage of new additives such as monoethanol amine (ETA) to adjust pH. However, these mitigation techniques pose certain challenges relating to the compatibility of new water chemistries with the steam generator, the thermal efficiency of the secondary side, etc. In this study, to improve the passivity of carbon steel, nanostructured coatings especially nanoparticle-enhanced surface coatings were adopted to improve resistance to corrosion and wear. Nanoparticles in the coating matrix help decrease the electrochemical potential compared coatings without nanoparticles, and thus help improve the mechanical properties, especially hardness, through precipitation. In other words, nanoparticle-enhanced surface coatings have the potential to mitigate flow-accelerated corrosion in secondary pipe systems. As candidate coatings, TiO 2 - and SiC-enhanced electrolytic and electroless nickel plating and Fe-Cr-W amorphous metallic coatings (AMC) were selected by acquiring the Pourbaix diagram with thermodynamic calculations. Both TiO 2 and SiC show a stable state in secondary water chemistry, and it is estimated that Fe-Cr-W can be applied to secondary water chemistry because it has a similar chemical composition to carbon steel. Electron microscopic analysis results with scanning electron microscopy (SEM) and tunneling electron microscopy (TEM) show the distribution of TiO 2 nanoparticles in the nickel matrix coating layer, whereas the SiC nanoparticles

A Two-Temperature Open-Source CFD Model for Hypersonic Reacting Flows, Part One: Zero-Dimensional Analysis

Directory of Open Access Journals (Sweden)

Vincent Casseau

2016-10-01

Full Text Available A two-temperature CFD (computational fluid dynamics solver is a prerequisite to any spacecraft re-entry numerical study that aims at producing results with a satisfactory level of accuracy within realistic timescales. In this respect, a new two-temperature CFD solver, hy2Foam, has been developed within the framework of the open-source CFD platform OpenFOAM for the prediction of hypersonic reacting flows. This solver makes the distinct juncture between the trans-rotational and multiple vibrational-electronic temperatures. hy2Foam has the capability to model vibrational-translational and vibrational-vibrational energy exchanges in an eleven-species air mixture. It makes use of either the Park TTv model or the coupled vibration-dissociation-vibration (CVDV model to handle chemistry-vibration coupling and it can simulate flows with or without electronic energy. Verification of the code for various zero-dimensional adiabatic heat baths of progressive complexity has been carried out. hy2Foam has been shown to produce results in good agreement with those given by the CFD code LeMANS (The Michigan Aerothermodynamic Navier-Stokes solver and previously published data. A comparison is also performed with the open-source DSMC (direct simulation Monte Carlo code dsmcFoam. It has been demonstrated that the use of the CVDV model and rates derived from Quantum-Kinetic theory promote a satisfactory consistency between the CFD and DSMC chemistry modules.

Improving COIL Efficiency By Iodine Pre-Dissociation Via Corona Discharge In The Transonic Section Of The Secondary Flow

National Research Council Canada - National Science Library

Rosenwaks, Zamik; Barmashenko, Boris

2006-01-01

...: We intend to carry out a comprehensive experimental study of I2 pre-dissociation, based on applying corona discharge in the transonic section of the secondary flow in the COIL supersonic nozzle...

Determination and removal of antibiotics in secondary effluent using a horizontal subsurface flow constructed wetland.

Science.gov (United States)

Zhang, Chunhui; Ning, Ke; Zhang, Wenwen; Guo, Yuanjie; Chen, Jun; Liang, Chen

2013-04-01

Increased attention is currently being directed towards the potential negative effects of antibiotics and other PPCPs discharged into the aquatic environment via municipal WWTP secondary effluents. A number of analytical methods, such as high performance liquid chromatography technologies, including a high performance liquid chromatography-fluorescence method (HPLC-FLD), high performance liquid chromatography-UV detection method (HPLC-UV) and high performance liquid chromatography-mass spectrometry method (HPLC-MS), have been suggested as determination technologies for antibiotic residues in water. In this study, we implement a HPLC-MS/MS combined method to detect and analyze antibiotics in WWTP secondary effluent and apply a horizontal subsurface flow constructed wetland (CW) as an advanced wastewater treatment for removing antibiotics in the WWTP secondary effluent. The results show that there were 2 macrolides, 2 quinolones and 5 sulfas in WWTP secondary effluent among all the 22 antibiotics considered. After the CW advanced treatment, the concentration removal efficiencies and removal loads of 9 antibiotics were 53-100% and 0.004-0.7307 μg m(-2) per day, respectively.

A text zero-watermarking method based on keyword dense interval

Science.gov (United States)

Yang, Fan; Zhu, Yuesheng; Jiang, Yifeng; Qing, Yin

2017-07-01

Digital watermarking has been recognized as a useful technology for the copyright protection and authentication of digital information. However, rarely did the former methods focus on the key content of digital carrier. The idea based on the protection of key content is more targeted and can be considered in different digital information, including text, image and video. In this paper, we use text as research object and a text zero-watermarking method which uses keyword dense interval (KDI) as the key content is proposed. First, we construct zero-watermarking model by introducing the concept of KDI and giving the method of KDI extraction. Second, we design detection model which includes secondary generation of zero-watermark and the similarity computing method of keyword distribution. Besides, experiments are carried out, and the results show that the proposed method gives better performance than other available methods especially in the attacks of sentence transformation and synonyms substitution.

Technical definition for nearly zero energy buildings nZEB

DEFF Research Database (Denmark)

Kurnitski, Jarek; Allard, Francis; Braham, Derrick

or maximum harmonized requirements as well as details of energy performance calculation framework, it will be up to the Member States to define what these for them exactly constitute. In the definition local conditions are to be obviously taken into account, but the uniform methodology can be used in all......This REHVA Task Force proposes a technical definition for nearly zero energy buildings required in the implementation of the Energy performance of buildings directive recast. Energy calculation framework and system boundaries associated with the definition are provided to specify which energy flows...... in which way are taken into account in the energy performance assessment. The intention of the Task Force is to help the experts in the Member States in defining the nearly zero energy buildings in a uniform way. The directive requires nearly zero energy buildings, but since it does not give minimum...

Non-zero total correlation means non-zero quantum correlation

International Nuclear Information System (INIS)

Li, Bo; Chen, Lin; Fan, Heng

2014-01-01

We investigated the super quantum discord based on weak measurements. The super quantum discord is an extension of the standard quantum discord defined by projective measurements and also describes the quantumness of correlations. We provide some equivalent conditions for zero super quantum discord by using quantum discord, classical correlation and mutual information. In particular, we find that the super quantum discord is zero only for product states, which have zero mutual information. This result suggests that non-zero correlations can always be detected using the quantum correlation with weak measurements. As an example, we present the assisted state-discrimination method.

Compact time-zero detector for heavy ions

International Nuclear Information System (INIS)

Weissenberger, E.; Kast, W.; Goennenwein, F.

1979-01-01

A time-zero detector for flight-time measurements with heavy ions is described. The ions traverse a thin foil and the secondary electrons splashed from the foil are detected in a channel plate multiplier. A timing signal is derived from the multiplier pulse. The novel features of the detector are its simplicity and compactness of design. The time resolution achieved for the full energy and mass span of fission fragments from the spontaneous fission of 252 Cf used as a heavy ion source is 115 ps (fwhm). (Auth.)

R744 ejector technology future perspectives

Science.gov (United States)

Hafner, Armin; Banasiak, Krzysztof

2016-09-01

Carbon Dioxide, CO2 (R744) was one of the first commonly applied working fluids in the infancy of refrigeration more than 100 years ago. In contrast to ammonia it mainly disappeared after the first generation of synthetic refrigerants have been introduced to the market after 1930. One reason was that the transition from low-rpm belt driven compressors towards the direct electrical motor driven compressors (50-60 Hz) was not performed for CO2 compressors before the revival introduced by Gustav Lorentzen in the 90is of last century. Since 1988 an enormous R & D effort has been made to further develop CO2 refrigeration technology in spite of the opposition from the chemical industry. Today CO2 refrigeration and heat pumping technologies are accepted as viable and sustainable alternatives for several applications like commercial refrigeration, transport refrigeration, vehicle air conditioning & heat pumping, domestic hot water heat pumps and industrial applications. For some applications, the current threshold to introduce R744 technology can be overcome when the system design takes into account the advantage of the thermo dynamical- and fluid properties of CO2. I.e. the system is designed for transcritical operation with all it pros and cons and takes into consideration how to minimize the losses, and to apply the normally lost expansion work. Shortcut-designs, i.e. drop in solutions, just replacing the H(C)FC refrigeration unit with an CO2 systems adapted for higher system pressures will not result in energy efficient products. CO2 systems do offer the advantage of enabling flooded evaporators supported with adapted ejector technology. These units offer high system performances at low temperature differences and show low temperature air mal-distributions across evaporators. This work gives an overview for the development possibilities for several applications during the next years. Resulting in a further market share increase of CO2 refrigeration and heat pump

Secondary coolant purification system

International Nuclear Information System (INIS)

Stiteler, F.Z.; Donohue, J.P.

1978-01-01

The present invention combines the attributes of volatile chemical addition, continuous blowdown, and full flow condensate demineralization. During normal plant operation (defined as no primary to secondary leakage) condensate from the condenser is pumped through a full flow condensate demineralizer system by the condensate pumps. Volatile chemical additions are made. Dissolved and suspended solids are removed in the condensate polishers by ion exchange and/or filtration. At the same time a continuous blowdown of approximately 1 percent of the main steaming rate of the steam generators is maintained. Radiation detectors monitor the secondary coolant. If these monitors indicate no primary to secondary leakage, the blowdown is cooled and returned directly to the condensate pump discharge. If one of the radiation monitors should indicate a primary to secondary leak, when the temperature of the effluent exiting from the blowdown heat exchanger is compatible with the resin specifications of the ion exchangers, the bypass valve causes the blowdown flow to pass through the blowdown ion exchangers

CONCENTRATION OF HARMFUL SUBSTANCES REDUCING IN SURFACE LAYER OF ATMOSPHERE AT RHEOSTAT LOCOMOTIVE TESTS

Directory of Open Access Journals (Sweden)

E. A. Bondar

2010-06-01

Full Text Available It is shown that at present an acceptable way of reducing the concentration of harmful substances in the surface layer of the atmosphere at rheostat tests of locomotives is their dispersion in a large volume of air. Channels, installed above an exhaust pipe of diesel locomotive with a break at the gas flow, work as ejectors. We have solved jointly the equation of aerodynamic characteristics of the ejector device and the equation of diffusion of gases; as a result the calculated dependence for determining the necessary height of ejector device has been obtained.

Local, zero-power void coefficient measurements in the ACPR

Energy Technology Data Exchange (ETDEWEB)

Rivard, J B; Thome, F V [Sandia Laboratories (United States)

1974-07-01

Changes in reactivity may be stimulated in the ACPR by the local introduction of voids into the reactor coolant. The local void coefficients of reactivity which describe this effect are of interest from a reactor safety point-of-view, and their determination is the subject of this presentation. Bottled nitrogen gas was used to produce the voids. The gas was forced out of a small diameter tube which was positioned vertically in the core lattice with its open end below the fuel. The gas was passed through a pressure regulator, a valve, and a flowmeter to establish a steady flow condition, following which a delayed-critical (zero-power) reactor state was established. Correlation of the average volume of core void created by the nitrogen flow with the reactivity worth of the delayed-critical control-rod bank position produced the values of the zero-power void coefficients of reactivity. The void coefficients were determined at various core positions from {approx}6 mm to 142 mm beyond the central irradiation space and for three different flow rates. For the range of void fractions investigated, these coefficients are negative, with values ranging between -$0.02 and -$0.12. Tabular and graphical results of the measurements are presented, and details of the coefficient determination are explained. (author)

Local, zero-power void coefficient measurements in the ACPR

International Nuclear Information System (INIS)

Rivard, J.B.; Thome, F.V.

1974-01-01

Changes in reactivity may be stimulated in the ACPR by the local introduction of voids into the reactor coolant. The local void coefficients of reactivity which describe this effect are of interest from a reactor safety point-of-view, and their determination is the subject of this presentation. Bottled nitrogen gas was used to produce the voids. The gas was forced out of a small diameter tube which was positioned vertically in the core lattice with its open end below the fuel. The gas was passed through a pressure regulator, a valve, and a flowmeter to establish a steady flow condition, following which a delayed-critical (zero-power) reactor state was established. Correlation of the average volume of core void created by the nitrogen flow with the reactivity worth of the delayed-critical control-rod bank position produced the values of the zero-power void coefficients of reactivity. The void coefficients were determined at various core positions from ∼6 mm to 142 mm beyond the central irradiation space and for three different flow rates. For the range of void fractions investigated, these coefficients are negative, with values ranging between -$0.02 and -$0.12. Tabular and graphical results of the measurements are presented, and details of the coefficient determination are explained. (author)

Visualization study of flow in axial flow inducer.

Science.gov (United States)

Lakshminarayana, B.

1972-01-01

A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory.

Mapping fracture flow paths with a nanoscale zero-valent iron tracer test and a flowmeter test

Science.gov (United States)

Chuang, Po-Yu; Chia, Yeeping; Chiu, Yung-Chia; Teng, Mao-Hua; Liou, Sofia Ya Hsuan

2018-02-01

The detection of preferential flow paths and the characterization of their hydraulic properties are important for the development of hydrogeological conceptual models in fractured-rock aquifers. In this study, nanoscale zero-valent iron (nZVI) particles were used as tracers to characterize fracture connectivity between two boreholes in fractured rock. A magnet array was installed vertically in the observation well to attract arriving nZVI particles and identify the location of the incoming tracer. Heat-pulse flowmeter tests were conducted to delineate the permeable fractures in the two wells for the design of the tracer test. The nZVI slurry was released in the screened injection well. The arrival of the slurry in the observation well was detected by an increase in electrical conductivity, while the depth of the connected fracture was identified by the distribution of nZVI particles attracted to the magnet array. The position where the maximum weight of attracted nZVI particles was observed coincides with the depth of a permeable fracture zone delineated by the heat-pulse flowmeter. In addition, a saline tracer test produced comparable results with the nZVI tracer test. Numerical simulation was performed using MODFLOW with MT3DMS to estimate the hydraulic properties of the connected fracture zones between the two wells. The study results indicate that the nZVI particle could be a promising tracer for the characterization of flow paths in fractured rock.

The ''Flight Chamber'': A fast, large area, zero-time detector

International Nuclear Information System (INIS)

Trautner, N.

1976-01-01

A new, fast, zero-time detector with an active area of 20 cm 2 has been constructed. Secondary electrons from a thin self-supporting foil are accelerated onto a scinitllator. The intrinsic time resolution (fwhm) was 0.85 for 5.5 MeV α-particles and 0.42 ns for 17 MeV 16 O-ions, at an efficiency of 97.5% and 99.6%, respectively. (author)

Secondary motion in three-dimensional branching networks

Science.gov (United States)

Guha, Abhijit; Pradhan, Kaustav

2017-06-01

A major aim of the present work is to understand and thoroughly document the generation, the three-dimensional distribution, and the evolution of the secondary motion as the fluid progresses downstream through a branched network. Six generations (G0-G5) of branches (involving 63 straight portions and 31 bifurcation modules) are computed in one go; such computational challenges are rarely taken in the literature. More than 30 × 106 computational elements are employed for high precision of computed results and fine quality of the flow visualization diagrams. The study of co-planar vis-à-vis non-planar space-filling configurations establishes a quantitative evaluation of the dependence of the fluid dynamics on the three-dimensional arrangement of the same individual branches. As compared to the secondary motion in a simple curved pipe, three distinctive features, viz., the change of shape and size of the flow-cross-section, the division of non-uniform primary flow in a bifurcation module, and repeated switchover from clockwise to anticlockwise curvature and vice versa in the flow path, make the present situation more complex. It is shown that the straight portions in the network, in general, attenuate the secondary motion, while the three-dimensionally complex bifurcation modules generate secondary motion and may alter the number, arrangement, and structure of vortices. A comprehensive picture of the evolution of quantitative flow visualizations of the secondary motion is achieved by constructing contours of secondary velocity | v → S | , streamwise vorticity ω S , and λ 2 iso-surfaces. It is demonstrated, for example, that for in-plane configuration, the vortices on any plane appear in pair (i.e., for each clockwise rotating vortex, there is an otherwise identical anticlockwise vortex), whereas the vortices on a plane for the out-of-plane configuration may be dissimilar, and there may even be an odd number of vortices. We have formulated three new parameters

The flows structure in unsteady gas flow in pipes with different cross-sections

OpenAIRE

Plotnikov Leonid; Nevolin Alexandr; Nikolaev Dmitrij

2017-01-01

The results of numerical simulation and experimental study of the structure of unsteady flows in pipes with different cross sections are presented in the article. It is shown that the unsteady gas flow in a circular pipe is axisymmetric without secondary currents. Steady vortex structures (secondary flows) are observed in pipes with cross sections in the form of a square and an equilateral triangle. It was found that these secondary flows have a significant impact on gas flows in pipes of com...

Fisher's Zeros as the Boundary of Renormalization Group Flows in Complex Coupling Spaces

International Nuclear Information System (INIS)

Denbleyker, A.; Du Daping; Liu Yuzhi; Meurice, Y.; Zou Haiyuan

2010-01-01

We propose new methods to extend the renormalization group transformation to complex coupling spaces. We argue that Fisher's zeros are located at the boundary of the complex basin of attraction of infrared fixed points. We support this picture with numerical calculations at finite volume for two-dimensional O(N) models in the large-N limit and the hierarchical Ising model. We present numerical evidence that, as the volume increases, the Fisher's zeros of four-dimensional pure gauge SU(2) lattice gauge theory with a Wilson action stabilize at a distance larger than 0.15 from the real axis in the complex β=4/g 2 plane. We discuss the implications for proofs of confinement and searches for nontrivial infrared fixed points in models beyond the standard model.

Constitutive model of discontinuous plastic flow at cryogenic temperatures

CERN Document Server

Skoczen, B; Bielski, J; Marcinek, D

2010-01-01

FCC metals and alloys are frequently used in cryogenic applications, nearly down to the temperature of absolute zero, because of their excellent physical and mechanical properties including ductility. Some of these materials, often characterized by the low stacking fault energy (LSFE), undergo at low temperatures three distinct phenomena: dynamic strain ageing (DSA), plastic strain induced transformation from the parent phase (gamma) to the secondary phase (alpha) and evolution of micro-damage. The constitutive model presented in the paper is focused on the discontinuous plastic flow (serrated yielding) and takes into account the relevant thermodynamic background. The discontinuous plastic flow reflecting the DSA effect is described by the mechanism of local catastrophic failure of Lomer-Cottrell (LC) locks under the stress fields related to the accumulating edge dislocations (below the transition temperature from the screw dislocations to the edge dislocations mode T-1). The failure of LC locks leads to mass...

Recycling Potentials of Critical Metals-Analyzing Secondary Flows from Selected Applications

Directory of Open Access Journals (Sweden)

Till Zimmermann

2014-03-01

Full Text Available Metal mobilization in general, as well as the number of metals used in products to increase performance and provide sometimes unique functionalities, has increased steadily in the past decades. Materials, such as indium, gallium, platinum group metals (PGM, and rare earths (RE, are used ever more frequently in high-tech applications and their criticality as a function of economic importance and supply risks has been highlighted in various studies. Nevertheless, recycling rates are often below one percent. Against this background, secondary flows of critical metals from three different end-of-life products up to 2020 are modeled and losses along the products’ end-of-life (EOL chain are identified. Two established applications of PGM and RE–industrial catalysts and thermal barrier coatings–and CIGS photovoltaic cells as a relatively new product have been analyzed. In addition to a quantification of future EOL flows, the analysis showed that a relatively well working recycling system exists for PGM-bearing catalysts, while a complete loss of critical metals occurs for the other applications. The reasons include a lack of economic incentives, technologically caused material dissipation and other technological challenges.

Zero Thermal Noise in Resistors at Zero Temperature

Science.gov (United States)

Kish, Laszlo B.; Niklasson, Gunnar A.; Granqvist, Claes-Göran

2016-06-01

The bandwidth of transistors in logic devices approaches the quantum limit, where Johnson noise and associated error rates are supposed to be strongly enhanced. However, the related theory — asserting a temperature-independent quantum zero-point (ZP) contribution to Johnson noise, which dominates the quantum regime — is controversial and resolution of the controversy is essential to determine the real error rate and fundamental energy dissipation limits of logic gates in the quantum limit. The Callen-Welton formula (fluctuation-dissipation theorem) of voltage and current noise for a resistance is the sum of Nyquist’s classical Johnson noise equation and a quantum ZP term with a power density spectrum proportional to frequency and independent of temperature. The classical Johnson-Nyquist formula vanishes at the approach of zero temperature, but the quantum ZP term still predicts non-zero noise voltage and current. Here, we show that this noise cannot be reconciled with the Fermi-Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. Consequently, Johnson noise must be nil at zero temperature, and non-zero noise found for certain experimental arrangements may be a measurement artifact, such as the one mentioned in Kleen’s uncertainty relation argument.

Removal of halogenated organic compounds in landfill gas by top covers containing zero-valent iron

DEFF Research Database (Denmark)

Scheutz, Charlotte; Winther, K.; Kjeldsen, Peter

2000-01-01

Transformation of gaseous CCl3F and CCl4 by zero-valent iron was studied in systems unsaturated with water under anaerobic conditionssin an N2 gas and in a landfill gas atmosphere. The transformation was studied in batch as well as flow-through column tests. In both systems, the transformation....... During continuous aerobic conditions, the transformation of CCl3F decreased toward zero. Model calculations show that use of zero-valent iron in landfill top covers is a potential treatment technology for emission reduction of halogenated trace compounds from landfills....

How to Define Nearly Net Zero Energy Buildings nZEB

DEFF Research Database (Denmark)

Kurnitski, Jarek; Allard, Francis; Braham, Derrick

2011-01-01

or maximum harmonized requirements as well as details of energy performance calculation framework, it will be up to the Member State to define what these for them exactly constitute. In the definition, local conditions are to be obviously taken into account, but the uniform methodology can be used in all......This REHVA Task Force proposes a technical definition for nearly zero energy buildings required in the implementation of the Energy performance of buildings directive recast. Energy calculation framework and system boundaries associated with the definition are provided to specify which energy flows...... in which way are taken into account in the energy performance assessment. The intention of the Task Force is to help the experts in the Member States in defining the nearly zero energy buildings in a uniform way. The directive requires nearly zero energy buildings, but since it does not give minimum...

Enhanced removal of ethanolamine from secondary system of nuclear power plant wastewater by novel hybrid nano zero-valent iron and pressurized ozone initiated oxidation process.

Science.gov (United States)

Lee, Son Dong; Mallampati, Srinivasa Reddy; Lee, Byoung Ho

2017-07-01

Monoethanolamine (shortly ethanolamine (ETA)), usually used as a corrosion inhibitor, is a contaminant of wastewater from the secondary cooling system of nuclear power plants (NPPs) and is not readily biodegradable. We conducted various experiments, including treatments with nano zero-valent iron (nZVI), nano-iron/calcium, and calcium oxide (nFe/Ca/CaO) with ozone (O 3 ) or hydrogen peroxide (H 2 O 2 ) to reduce the concentration of ETA and to decrease the chemical demand of oxygen (COD) of these wastewaters. During this study, wastewater with ETA concentration of 7465 mg L -1 and COD of 6920 mg L -1 was used. As a result, the ETA concentration was reduced to 5 mg L -1 (a decrease of almost 100%) and COD was reduced to 2260 mg L -1 , a reduction of 67%, using doses of 26.8 mM of nZVI and 1.5 mM of H 2 O 2 at pH 3 for 3 h. Further treatment for 48 h allowed a decrease of COD by almost 97%. Some mechanistic considerations are proposed in order to explain the degradation pathway. The developed hybrid nano zero-valent iron-initiated oxidation process with H 2 O 2 is promising in the treatment of ETA-contaminated wastewaters.

PERFORMANCE OF A SURFACE FLOW CONSTRUCTED WETLAND SYSTEM USED TO TREAT SECONDARY EFFLUENT AND FILTER BACKWASH WATER

Directory of Open Access Journals (Sweden)

Juan Antonio Vidales-Contreras

2011-05-01

The performance of a surface flow wetland system used to treat activated sludge effluent and filter backwash water from a tertiary treatment facility was evaluated. Samples were collected before and after vegetation removal from the system which consists of two densely vegetated settling basins (0.35 ha, an artificial stream, and a 3-ha surface flow wetland. Bulrush (Scripus spp. and cattail (Typha domingensis were the dominant plant species. The average inflow of chlorinated secondary effluent during the first two months of the actual study was 1.9  m3 min-1 while the inflow for backwash water treatment ranged from 0.21 to 0.42 m3 min-1. The system was able to reduce TSS and BOD5 to tertiary effluent standards; however, monitoring of chloride concentrations revealed that wetland evapotranspiration is probably enriching pollutant concentrations in the wetland outflow. Coliphage removal from the filter backwash was 97 and 35% during 1999 and 2000, respectively. However, when secondary effluent entered the system, coliphage removal averaged 65%. After vegetation removal, pH and coliphage density increased significantly (p

Controlling the Flow past a Semicircular Airfoil at Zero Angle of Attack Using Slot Suction in One or Two Vortex Cells for Attaining Extremal Lift

Science.gov (United States)

Isaev, S. A.; Baranov, P. A.; Sudakov, A. G.; Popov, I. A.; Usachov, A. E.

2017-12-01

Calculations using multiblock computational technologies and a model of shear-stress transport modified with allowance for the curvature of streamlines in turbulent airflow were performed at a zero angle of attack for a semicircular airfoil containing one or two surface vortex cells with slot suction. The results showed evidence of stabilization of a nearly undetached flow and attainment of an extremal lift of C y = 5.2 and a lift-to-drag ratio of K = 24 with allowance for energy losses for suction in the vortex cells.

CANDU channel flow verification

International Nuclear Information System (INIS)

Mazalu, N.; Negut, Gh.

1997-01-01

The purpose of this evaluation was to obtain accurate information on each channel flow that enables us to assess precisely the level of reactor thermal power and, for reasons of safety, to establish which channel is boiling. In order to assess the channel flow parameters, computer simulations were done with the NUCIRC code and the results were checked by measurements. The complete channel flow measurements were made in the zero power cold condition. In hot conditions there were made flow measurements using the Shut Down System 1 (SDS 1) flow devices from 0.1 % F.P. up to 100 % F.P. The NUCIRC prediction for CANDU channel flows and the measurements by Ultrasonic Flow Meter at zero power cold conditions and SDS 1 flow channel measurements at different reactor power levels showed an acceptable agreement. The 100 % F.P. average errors for channel flow of R, shows that suitable NUCIRC flow assessment can be made. So, it can be done a fair prediction of the reactor power distribution. NUCIRC can predict accurately the onset of boiling and helps to warn at the possible power instabilities at high powers or it can detect the flow blockages. The thermal hydraulic analyst has in NUCIRC a suitable tool to do accurate predictions for the thermal hydraulic parameters for different steady state power levels which subsequently leads to an optimal CANDU reactor operation. (authors)

Performance and environmental impact assessment of pulse detonation based engine systems

Science.gov (United States)

Glaser, Aaron J.

Experimental research was performed to investigate the feasibility of using pulse detonation based engine systems for practical aerospace applications. In order to carry out this work a new pulse detonation combustion research facility was developed at the University of Cincinnati. This research covered two broad areas of application interest. The first area is pure PDE applications where the detonation tube is used to generate an impulsive thrust directly. The second focus area is on pulse detonation based hybrid propulsion systems. Within each of these areas various studies were performed to quantify engine performance. Comparisons of the performance between detonation and conventional deflagration based engine cycles were made. Fundamental studies investigating detonation physics and flow dynamics were performed in order to gain physical insight into the observed performance trends. Experimental studies were performed on PDE-driven straight and diverging ejectors to determine the system performance. Ejector performance was quantified by thrust measurements made using a damped thrust stand. The effects of PDE operating parameters and ejector geometric parameters on thrust augmentation were investigated. For all cases tested, the maximum thrust augmentation is found to occur at a downstream ejector placement. The optimum ejector geometry was determined to have an overall length of LEJECT/DEJECT =5.61, including an intermediate-straight section length of LSTRT /DEJECT=2, and diverging exhaust section with 4 deg half-angle. A maximum thrust augmentation of 105% was observed while employing the optimized ejector geometry and operating the PDE at a fill-fraction of 0.6 and a frequency of 10 Hz. When operated at a fill-fraction of 1.0 and a frequency of 30 Hz, the thrust augmentation of the optimized PDE-driven ejector system was observed to be 71%. Static pressure was measured along the interior surface of the ejector, including the inlet and exhaust sections. The

The Trouble with Zero

Science.gov (United States)

Lewis, Robert

2015-01-01

The history of the number zero is an interesting one. In early times, zero was not used as a number at all, but instead was used as a place holder to indicate the position of hundreds and tens. This article briefly discusses the history of zero and challenges the thinking where divisions using zero are used.

Power flow control based solely on slow feedback loop for heart pump applications.

Science.gov (United States)

Wang, Bob; Hu, Aiguo Patrick; Budgett, David

2012-06-01

This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz.

Sewerage force adjustment technology for energy conservation in vacuum sanitation systems

Science.gov (United States)

Guo, Zhonghua; Li, Xiaoning; Kagawa, Toshiharu

2013-03-01

The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not adjustable and the energy consumption does not adapt to the real time sewerage requirement. Therefore, it is important to study the sewerage force adjustment to improve the energy efficiency. This paper proposes an energy conservation design in vacuum sanitation systems with pneumatic ejector circuits. The sewerage force is controlled by changing the systematic vacuum degree according to the amount of the excreta. In particular, the amount of the excreta is tested by liquid level sensor and mass sensor. According to the amount of the excreta, the relationship between the excreta amount and the sewerage force is studied to provide proper propulsive force. In the other aspect, to provide variable vacuum degrees for different sanitation requirements, the suction and discharge system is designed with pneumatic vacuum ejector. On the basis of the static flow-rate characteristics and the vacuum generation model, the pressure response in the ejector circuit is studied by using the static flow rate characteristics of the ejector and air status equation. The relationship is obtained between supplied compressed air and systematic vacuum degree. When the compressed air is supplied to the ejector continuously, the systematic vacuum degree increases until the vacuum degree reaches the extreme value. Therefore, the variable systematic vacuum degree is obtained by controlling the compressed air supply of the ejector. To verify the effect of energy conservation, experiments are carried out in the artificial excreta collection, and the variable vacuum-degree design saves more than 30% of the energy supply. The energy conservation is realized effectively in the new vacuum sanitation systems with good application prospect. The proposed technology provides technological

Performance parameters of an ejector-absorption heat transformer

International Nuclear Information System (INIS)

Soezen, Adnan; Arcaklioglu, Erol; Oezalp, Mehmet; Yuecesu, Serdar

2005-01-01

Ejector-absorption heat transformers (EAHTs) are attractive for increasing a solar-pond's temperature and for recovering low-level waste-heat. Thermodynamic analysis of the performance of an EAHT is complicated due to the associated complex differential equations and simulation programs. This paper proposes the use of artificial neural-networks (ANNs) as a new approach to determine the performance parameters, as functions of only the working temperatures of the EAHT, which is used to increase the solar pond's temperature under various working conditions. Thus, this study is helpful in predicting the performance of an EAHT where the temperatures are known. Scaled conjugate gradient (SCG) and Levenberg-Marquardt (LM) learning algorithms and a logistic sigmoid transfer-function were used in the network. The best approach was investigated for performance parameters with developed software using various algorithms. The best statistical coefficients of multiple determinations (R 2 -values) equal 0.99995, 0.99997 and 0.99995 for the coefficient of performance (COP), exergetic coefficient of performance (ECOP) and circulation ratio (F), respectively obtained by the LM algorithm with seven neurons. In the comparison of performances, results obtained via analytic equations and by means of the ANN, the COP, ECOP and F for all working situations differ by less than 1.05%, 0.7% and 3.07%, respectively. These accuracies are acceptable in the design of the EAHT. The ANN approach greatly reduces the time required by design engineers to find the optimum solution. Apart from reducing the time required, it is possible to find solutions that make solar-energy applications more viable and thus more attractive to potential users. Also, this approach has the advantages of high computational speed, low cost for feasibility, rapid turn-around, which is especially important during iterative design phases, and ease of design by operators with little technical experience

Flow Pattern Identification of Horizontal Two-Phase Refrigerant Flow Using Neural Networks

Science.gov (United States)

2015-12-31

classification of liquid–vapor structures into flow patterns is useful for predicting heat transfer rates and, ultimately, system performance. Most flow and...Here, ~x represents the spa- tial variables, x and y, and t is time. This normalization assigns εð~x; tÞ to be zero for only vapor (εg) and one for...tube surface [17,22]. As in stratified wavy flow, interfacial waves were also present in stratified wavy transitional flow. The waves were more fre

Zero current measurements using the Rogowski coil

International Nuclear Information System (INIS)

Gregor, J.; Jakubova, I.; Kadlec, P.; Senk, J.; Vavra, Z.

1997-01-01

The zero current measurements using the Rogowski coil carried out on the model of the extinguishing chamber of hv SF 6 circuit breaker with self-flow generation are presented in the paper. The time course of the post-arc current obtained by numerical integration of the measured induced voltage of the Rogowski coil gives information not only about the value of the residual current after the successful interruption but also about the current changes connected with the dynamic behaviour of the arc during its quenching. (author)

Numerical analysis of gas-liquid two-phase flow in secondary side of steam generator

Energy Technology Data Exchange (ETDEWEB)

Murase, Michio; Nakamura, Akira; Yagi, Yoshinori [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2002-09-01

The steam generator (SG) in a pressurized water reactor (PWR) is an important two-phase flow component as the boundary between the primary loop and the secondary loop. In this study, we performed gas-liquid two-phase flow analyses for SG reliability tests conduced by Nuclear Power Engineering Corporation (NUPEC) using the two-fluid model of a thermal-hydraulic computer code PHOENICS. In order to calculate the location of the boiling initiation accurately, detailed inputs were required for the friction coefficients affecting the velocity distribution and the heat transfer distribution. However, the velocity and heat transfer distributions did not greatly affect the void fractions in the upper region of the heat transfer tubes. The calculated void fractions agreed with the measured values within 4% as the local average and within 2% as an average in a cross-section, except the region of low void fractions. (author)

Secondary circulation in river junctions even at very low flow momentum ratios : The legacy effects of point bar formation

NARCIS (Netherlands)

Moradi, Gelare; Rennie, Colin; Vermeulen, Bart; Cardot, Romain; Lane, Stuart

2018-01-01

River confluences remain a challenging subject because of their 3D geometry which leads to a complex, three-dimensional mean and turbulent velocity processes. Since secondary circulation plays an important role in flow hydrodynamics and the development of bank erosion, bed scour and bar formation,

Theoretical study and design of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane and intended for cooling of gas transported in a gas-main pipeline

KAUST Repository

Petrenko, V.O.

2011-11-01

This paper describes the construction and performance of a novel combined system intended for natural gas transportation and power production, and for cooling of gas transported in a gas-main pipeline. The proposed system includes a gas turbine compressor, a combined electrogenerating plant and an ejector refrigeration unit operating with a hydrocarbon refrigerant. The combined electrogenerating plant consists of a high-temperature steam-power cycle and a low-temperature hydrocarbon vapor power cycle, which together comprise a binary vapor system. The combined system is designed for the highest possible effectiveness of power generation and could find wide application in gas-transmission systems of gas-main pipelines. Application of the proposed system would enable year-round power generation and provide cooling of natural gas during periods of high ambient temperature operation. This paper presents the main results of a theoretical study and design performance specifications of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane. © 2010 Elsevier Ltd and IIR. All rights reserved.

Directional Secondary Emission of a Semiconductor Microcavity

DEFF Research Database (Denmark)

Langbein, Wolfgang; Jensen, Jacob Riis; Hvam, Jørn Märcher

2000-01-01

We investigate the time-resolved secondary emission of a homogeneously broadened microcavity after resonant excitation. The sample consists of a 25nm GaAs single quantum well (QW) in the center of a wedged ¥ë cavity with AlAs/AlGaAs Bragg reflectors, grown by molecular beam epitaxy. At zero detun...

Secondary Flow in Cascades.

Science.gov (United States)

1984-06-01

Int. .7. Neat adMs rnfr 9 the auction Vo1. iS. p. 1.157, 12 1.7r aeTase WOW ugte 0In the comuted 2. Briley# V.R., umenrical Method for AW16 wereo at...S. ft, C.R., -A General Theory of Three saemnit u thecsg the rotation Dimensional Flow in subsonic -a super- injoes Wer sonic Turhasachines of Axial

On the skin friction coefficient in viscoelastic wall-bounded flows

International Nuclear Information System (INIS)

Housiadas, Kostas D.; Beris, Antony N.

2013-01-01

Highlights: ► We decompose the skin friction coefficient to its individual contributions. ► The contributions are evaluated using simulation results in turbulent channel flow. ► We present a fitting curve for the drag reduction. ► A new formula for the skin friction coefficient is also developed. ► The results agree well with experimental data from the literature. -- Abstract: Analysis of the skin friction coefficient for wall bounded viscoelastic flows is performed by utilizing available direct numerical simulation (DNS) results for viscoelastic turbulent channel flow. The Oldroyd-B, FENE-P and Giesekus constitutive models are used. First, we analyze the friction coefficient in viscous, viscoelastic and inertial stress contributions, as these arise from suitable momentum balances, for the flow in channels and pipes. Following Fukagata et al. (Phys. Fluids, 14, p. L73, 2002) and Yu et al. (Int. J. Heat. Fluid Flow, 25, p. 961, 2004) these three contributions are evaluated averaging available numerical results, and presented for selected values of flow and rheological parameters. Second, based on DNS results, we develop a universal function for the relative drag reduction as a function of the friction Weissenberg number. This leads to a closed-form approximate expression for the inverse of the square root of the skin friction coefficient for viscoelastic turbulent pipe flow as a function of the friction Reynolds number involving two primary material parameters, and a secondary one which also depends on the flow. The primary parameters are the zero shear-rate elasticity number, El 0 , and the limiting value for the drag reduction at high Weissenberg number, LDR, while the secondary one is the relative wall viscosity, μ w . The predictions reproduce both types A and B of drag reduction, as first introduced by Virk (Nature, 253, p. 109, 1975), corresponding to partially and fully extended polymer molecules, respectively. Comparison of the results for the

Flight Operations . [Zero Knowledge to Mission Complete

Science.gov (United States)

Forest, Greg; Apyan, Alex; Hillin, Andrew

2016-01-01

Outline the process that takes new hires with zero knowledge all the way to the point of completing missions in Flight Operations. Audience members should be able to outline the attributes of a flight controller and instructor, outline the training flow for flight controllers and instructors, and identify how the flight controller and instructor attributes are necessary to ensure operational excellence in mission prep and execution. Identify how the simulation environment is used to develop crisis management, communication, teamwork, and leadership skills for SGT employees beyond what can be provided by classroom training.

Zeroing of the TL signal of sediment undergoing fluvial transportation: a laboratory experiment

International Nuclear Information System (INIS)

Gemmell, A.M.D.

1985-01-01

Rates of bleaching of suspended sediment undergoing fluvial transportation in a closed laboratory flume beneath a u.v. lamp were measured. It was found that the speed of zeroing is inversely related to the speed of flow. This is attributed to the effects of flow turbulence in keeping sediment in suspension, thereby reducing the penetration of u.v. radiation, and to the re-entrainment of partially bleached or unbleached sediment into the flow. The time required to reduce TL to the residual levels indicated by sunlamp bleaching experiments are such as to suggest that at faster flows sediments in a heavily-laden stream may never attain a complete bleaching. (author)

Exergy analysis of an ejector-absorption heat transformer using artificial neural network approach

International Nuclear Information System (INIS)

Soezen, Adnan; Arcaklioglu, Erol

2007-01-01

This paper proposes artificial neural networks (ANNs) technique as a new approach to determine the exergy losses of an ejector-absorption heat transformer (EAHT). Thermodynamic analysis of the EAHT is too complex due to complex differential equations and complex simulations programs. ANN technique facilitates these complicated situations. This study is considered to be helpful in predicting the exergetic performance of components of an EAHT prior to its setting up in a thermal system where the working temperatures are known. The best approach was investigated using different algorithms with developed software. The best statistical coefficient of multiple determinations (R 2 -value) for training data equals to 0.999715, 0.995627, 0.999497, and 0.997648 obtained by different algorithms with seven neurons for the non-dimensional exergy losses of evaporator, generator, absorber and condenser, respectively. Similarly these values for testing data are 0.999774, 0.994039, 0.999613 and 0.99938, respectively. The results show that this approach has the advantages of computational speed, low cost for feasibility, rapid turnaround, which is especially important during iterative design phases, and easy of design by operators with little technical experience

Normally-Closed Zero-Leak Valve with Magnetostrictive Actuator

Science.gov (United States)

Ramspacher, Daniel J. (Inventor); Richard, James A. (Inventor)

2017-01-01

A non-pyrotechnic, normally-closed, zero-leak valve is a replacement for the pyrovalve used for both in-space and launch vehicle applications. The valve utilizes a magnetostrictive alloy for actuation, rather than pyrotechnic charges. The alloy, such as Terfenol-D, experiences magnetostriction, i.e. a gross elongation, when exposed to a magnetic field. This elongation fractures a parent metal seal, allowing fluid flow through the valve. The required magnetic field is generated by redundant coils that are isolated from the working fluid.

A study on flow development in an APU-style inlet and its effect on centrifugal compressor performance

Science.gov (United States)

Lou, Fangyuan

The objectives of this research were to investigate the flow development inside an APU-style inlet and its effect on centrifugal compressor performance. The motivation arises from the increased applications of gas turbine engines installed with APU-style inlets such as unmanned aerial vehicles, auxiliary power units, and helicopters. The inlet swirl distortion created from these complicated inlet systems has become a major performance and operability concern. To improve the integration between the APU-style inlet and gas turbine engines, better understanding of the flow field in the APU-style inlet and its effect on gas turbine is necessary. A research facility for the purpose of performing an experimental investigation of the flow field inside an APU-style inlet was developed. A subcritical air ejector is used to continuously flow the inlet at desired corrected mass flow rates. The facility is capable of flowing the APU inlet over a wide range of corrected mass flow rate that matches the same Mach numbers as engine operating conditions. Additionally, improvement in the system operational steadiness was achieved by tuning the pressure controller using a PID control method and utilizing multi-layer screens downstream of the APU inlet. Less than 1% relative unsteadiness was achieved for full range operation. The flow field inside the rectangular-sectioned 90? bend of the APU-style inlet was measured using a 3-Component LDV system. The structures for both primary flow and the secondary flow inside the bend were resolved. Additionally, the effect of upstream geometry on the flow development in the downstream bend was also investigated. Furthermore, a Single Stage Centrifugal Compressor research facility was developed at Purdue University in collaboration with Honeywell to operate the APU-style inlet at engine conditions with a compressor. To operate the facility, extensive infrastructure for facility health monitoring and performance control (including lubrication

Critical heat flux under zero flow conditions in a vertical 3 X 3 rod bundle with a non-uniform axial heat flux

Energy Technology Data Exchange (ETDEWEB)

Cho, Seok; Chun, Se Young; Moon, Sang Ki; Baek, Won Pil

2003-11-01

KAERI has performed an experimental study of water Critical Heat Flux (CHF) under zero flow conditions with a non-uniformly heated 3 by 3 rod bundle. Experimental conditions are in the range of a system pressure from 0.5 to 15.0 MPa and inlet water subcooling enthalpies from 67.5 to 351.5 kJ/kg. The test section used in the present experiments consisted of a vertical flow channel, upper and lower plenums, and a non-uniformly heated 3 by 3 rod bundle. The experimental results show that the CHFs in low-pressure conditions are somewhat scattered within a narrow range. As the system pressure increases, however, the CHFs show a consistent parametric trend. The CHFs occur in the upper region of the heated section, but the vertical distances of the detected CHFs from the bottom of the heated section are reduced as the system pressure increases. Even though the effects of the inlet water subcooling enthalpies and system pressure in the flooding CHF are relatively smaller than those of the flow boiling CHF, the CHF increases by increasing the inlet water subcooling enthalpies. Several existing correlations for the countercurrent flooding CHF based on Wallis's flooding correlation and Kutateladze's criterion for the onset of flooding are compared with the CHF data obtained in the present experiments to examine the applicability of the correlations.

Compact mass flow meter based on a micro coriolis flow sensor

NARCIS (Netherlands)

Sparreboom, Wouter; van de Geest, Jan; Katerberg, Marcel; Postma, F.M.; Haneveld, J.; Groenesteijn, Jarno; Lammerink, Theodorus S.J.; Wiegerink, Remco J.; Lötters, Joost Conrad

2013-01-01

In this paper we demonstrate a compact ready-to-use micro Coriolis mass flow meter. The full scale flow is 1 g/h (for water at a pressure drop < 1 bar). It has a zero stability of 2 mg/h and an accuracy of 0.5% reading for both liquids and gases. The temperature drift between 10 and 50 °C is below 1

Secondary organic aerosol from VOC mixtures in an oxidation flow reactor

Science.gov (United States)

Ahlberg, Erik; Falk, John; Eriksson, Axel; Holst, Thomas; Brune, William H.; Kristensson, Adam; Roldin, Pontus; Svenningsson, Birgitta

2017-07-01

The atmospheric organic aerosol is a tremendously complex system in terms of chemical content. Models generally treat the mixtures as ideal, something which has been questioned owing to model-measurement discrepancies. We used an oxidation flow reactor to produce secondary organic aerosol (SOA) mixtures containing oxidation products of biogenic (α-pinene, myrcene and isoprene) and anthropogenic (m-xylene) volatile organic compounds (VOCs). The resulting volume concentration and chemical composition was measured using a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. The SOA mass yield of the mixtures was compared to a partitioning model constructed from single VOC experiments. The single VOC SOA mass yields with no wall-loss correction applied are comparable to previous experiments. In the mixtures containing myrcene a higher yield than expected was produced. We attribute this to an increased condensation sink, arising from myrcene producing a significantly higher number of nucleation particles compared to the other precursors. Isoprene did not produce much mass in single VOC experiments but contributed to the mass of the mixtures. The effect of high concentrations of isoprene on the OH exposure was found to be small, even at OH reactivities that previously have been reported to significantly suppress OH exposures in oxidation flow reactors. Furthermore, isoprene shifted the particle size distribution of mixtures towards larger sizes, which could be due to a change in oxidant dynamics inside the reactor.

Net zero water

CSIR Research Space (South Africa)

Lindeque, M

2013-01-01

Full Text Available the national grid. The unfortunate situation with water is that there is no replacement technology for water. Water can be supplied from many different sources. A net zero energy development will move closer to a net zero water development by reducing...

The Three Dimensional Flow Field at the Exit of an Axial-Flow Turbine Rotor

Science.gov (United States)

Lakshminarayana, B.; Ristic, D.; Chu, S.

1998-01-01

A systematic and comprehensive investigation was performed to provide detailed data on the three dimensional viscous flow phenomena downstream of a modem turbine rotor and to understand the flow physics such as origin, nature, development of wakes, secondary flow, and leakage flow. The experiment was carried out in the Axial Flow Turbine Research Facility (AFTRF) at Penn State, with velocity measurements taken with a 3-D LDV System. Two radial traverses at 1% and 10% of chord downstream of the rotor have been performed to identify the three-dimensional flow features at the exit of the rotor blade row. Sufficient spatial resolution was maintained to resolve blade wake, secondary flow, and tip leakage flow. The wake deficit is found to be substantial, especially at 1% of chord downstream of the rotor. At this location, negative axial velocity occurs near the tip, suggesting flow separation in the tip clearance region. Turbulence intensities peak in the wake region, and cross- correlations are mainly associated with the velocity gradient of the wake deficit. The radial velocities, both in the wake and in the endwall region, are found to be substantial. Two counter-rotating secondary flows are identified in the blade passage, with one occupying the half span close to the casino and the other occupying the half span close to the hub. The tip leakage flow is well restricted to 10% immersion from the blade tip. There are strong vorticity distributions associated with these secondary flows and tip leakage flow. The passage averaged data are in good agreement with design values.

Flow accelerated corrosion and its control measures for the secondary circuit pipelines in Indian nuclear power plants

International Nuclear Information System (INIS)

Kain, Vivekanand; Roychowdhury, S.; Mathew, Thomas; Bhandakkar, Atul

2008-01-01

A plain carbon steel feeder pipeline in the secondary circuit failed downstream of a flow measurement device (orifice meter) during operation at nuclear power plant. A detailed failure analysis done on the failed pipeline is described in this paper. The results established the fine surface pattern of 'Horseshoe pits' at the affected regions. X-ray diffraction analysis on the samples far from the failed regions showed presence of magnetite but on the sample from the failed region showed peaks due to base metal only, indicating dissolution of the oxide. Thickness profiling of the pipeline indicated reduction of thickness from the design 7.62 mm to a minimum of 0.4-1.4 mm at the location of the failure. These observations are characteristic of single phase flow accelerated corrosion. This paper details the extent of flow accelerated corrosion in various Indian power plants and the remedial measures for replacement and possible design and water chemistry changes to combat it

Contribution to the study of the exchanges to the interface liquid bubble, resulting from an ejector venturi, for the treatment of dust; Contribution a l'etude des echanges a l'interface bulle liquide, issue d'un ejecteur venturi, horizontal en vue du traitement des poussieres

Energy Technology Data Exchange (ETDEWEB)

Giovannacci, D.

2002-06-15

A great number of industrial processes generate aerosols that the legislation prohibited to reject too great quantities (Decree no 98-360, 6 may 1998). Among the processes of elimination but also of recovery of these pollutants, washing by means of selective solvent is widespread. This operation is realized in contactors gas-liquid that one can classify out of absorbers with columns and absorbers venturi. Among the latter, one distinguishes the ejector venturi, the venturi high energy and the venturi with emulsion. In this work, we proposed to study the ejector venturi on the plans of hydrodynamics and transfer of matter, in the case of pollutants in the form of dust. At the time of the hydrodynamic study, we determine experimentally using fast camera the characteristics of the interface, the surface of exchange a and the diameter of the bubbles. We then could establish the law of distribution of the diameters of the bubbles. The introduction of a model of evolution in three phases of the current of bubbles enabled us to understand the evolution of the diameter during the course of the bubble and to characterize the influence of coalescence. With regard to the study of transfer of matter, we introduced a new model characterizing the trapping of dust included into bubbles. The dominating mechanism in the trapping is then with the inertial effects with the range of diameter of dust [ 2;4 ] {mu}m for which the trapping is optimum. We measured in experiments the effectiveness of trapping of the ejector, and its variations with the temperature of two effluents, the time of course and the density of the particles. The results from this study make it possible to work out a new type of particle filter, based on the technique of the ejector venturi. (author)

Compact mass flow meter based on a micro Coriolis flow sensor

NARCIS (Netherlands)

Sparreboom, Wouter; Katerberg, M.R.; Lammerink, Theodorus S.J.; Postma, F.M.; Haneveld, J.; Groenesteijn, Jarno; Wiegerink, Remco J.; Lötters, Joost Conrad

2012-01-01

In this paper we present a compact ready-to-use micro Coriolis mass flow meter. The full scale flow is 2 g/h (for water at a pressure drop of 2 bar). It has a zero stability of 2 mg/h and an accuracy of 0.5% reading. The temperature drift between 10 and 50 ºC is below 1 mg/h/ºC. The meter is robust,

Quantifying spatial and temporal patterns of flow intermittency using spatially contiguous runoff data

Science.gov (United States)

Yu (于松延), Songyan; Bond, Nick R.; Bunn, Stuart E.; Xu, Zongxue; Kennard, Mark J.

2018-04-01

River channel drying caused by intermittent stream flow is a widely-recognized factor shaping stream ecosystems. There is a strong need to quantify the distribution of intermittent streams across catchments to inform management. However, observational gauge networks provide only point estimates of streamflow variation. Increasingly, this limitation is being overcome through the use of spatially contiguous estimates of the terrestrial water-balance, which can also assist in estimating runoff and streamflow at large-spatial scales. Here we proposed an approach to quantifying spatial and temporal variation in monthly flow intermittency throughout river networks in eastern Australia. We aggregated gridded (5 × 5 km) monthly water-balance data with a hierarchically nested catchment dataset to simulate catchment runoff accumulation throughout river networks from 1900 to 2016. We also predicted zero flow duration for the entire river network by developing a robust predictive model relating measured zero flow duration (% months) to environmental predictor variables (based on 43 stream gauges). We then combined these datasets by using the predicted zero flow duration from the regression model to determine appropriate 'zero' flow thresholds for the modelled discharge data, which varied spatially across the catchments examined. Finally, based on modelled discharge data and identified actual zero flow thresholds, we derived summary metrics describing flow intermittency across the catchment (mean flow duration and coefficient-of-variation in flow permanence from 1900 to 2016). We also classified the relative degree of flow intermittency annually to characterise temporal variation in flow intermittency. Results showed that the degree of flow intermittency varied substantially across streams in eastern Australia, ranging from perennial streams flowing permanently (11-12 months) to strongly intermittent streams flowing 4 months or less of year. Results also showed that the

Zero-Based Budgeting.

Science.gov (United States)

Wichowski, Chester

1979-01-01

The zero-based budgeting approach is designed to achieve the greatest benefit with the fewest undesirable consequences. Seven basic steps make up the zero-based decision-making process: (1) identifying program goals, (2) classifying goals, (3) identifying resources, (4) reviewing consequences, (5) developing decision packages, (6) implementing a…

CFD Study of Turbo-Ramjet Interactions in Hypersonic Airbreathing Propulsion System

Science.gov (United States)

Chang, Ing; Hunter, Louis G.

1996-01-01

also decreases slightly as the sidewall is approached. Other difference between the 2-D and 3-D solutions were a lowering of the nozzle thrust coefficient value from 0.9850 (2-D) to 0.9807 (3-D), where the experimental value was 0.9790. In the third phase of our study, a different turbo-ramjet configuration was analyzed. The confluence of a supersonic turbojet and a subsonic ramjet in the turbine based combined-cycle (TBCC) propulsion system was studied by a 2-D CFD code. In the analysis, Mach 1.4 primary turbojet was mixed with the subsonic ramjet secondary flow in an ejector mode operation. Reasonable agreements were obtained with the supplied I-D TBCC solutions. For low downstream backpressure, the Fabri choke condition (Break-Point condition) was observed in the secondary flow within mixing zone. For sufficient high downstream backpressure, the Fabri choke no longer exist, the ramjet flow was reduced and the ejector flow became backpressure dependent. Highly non-uniform flow at ejector exit were observed, indicated that for smooth downstream combustion, the mixing of the two streams probably required some physical devices.

Inertia-driven particle migration and mixing in a wall-bounded laminar suspension flow

Energy Technology Data Exchange (ETDEWEB)

Loisel, V.; Abbas, M., E-mail: micheline.abbas@ensiacet.fr; Masbernat, O. [Université de Toulouse INPT-UPS: Laboratoire de Génie Chimique and CNRS, Fédération de Recherche FERMaT, Toulouse (France); Climent, E. [Université de Toulouse INPT-UPS: Institut de Mécanique des Fluides de Toulouse and CNRS, Fédération de Recherche FERMaT, Toulouse (France)

2015-12-15

Laminar pressure-driven suspension flows are studied in the situation of neutrally buoyant particles at finite Reynolds number. The numerical method is validated for homogeneous particle distribution (no lateral migration across the channel): the increase of particle slip velocities and particle stress with inertia and concentration is in agreement with former works in the literature. In the case of a two-phase channel flow with freely moving particles, migration towards the channel walls due to the Segré-Silberberg effect is observed, leading to the development of a non-uniform concentration profile in the wall-normal direction (the concentration peaks in the wall region and tends towards zero in the channel core). The particle accumulation in the region of highest shear favors the shear-induced particle interactions and agitation, the profile of which appears to be correlated to the concentration profile. A 1D model predicting particle agitation, based on the kinetic theory of granular flows in the quenched state regime when Stokes number St = O(1) and from numerical simulations when St < 1, fails to reproduce the agitation profile in the wall normal direction. Instead, the existence of secondary flows is clearly evidenced by long time simulations. These are composed of a succession of contra-rotating structures, correlated with the development of concentration waves in the transverse direction. The mechanism proposed to explain the onset of this transverse instability is based on the development of a lift force induced by spanwise gradient of the axial velocity fluctuations. The establishment of the concentration profile in the wall-normal direction therefore results from the combination of the mean flow Segré-Silberberg induced migration, which tends to stratify the suspension and secondary flows which tend to mix the particles over the channel cross section.

Inertia-driven particle migration and mixing in a wall-bounded laminar suspension flow

International Nuclear Information System (INIS)

Loisel, V.; Abbas, M.; Masbernat, O.; Climent, E.

2015-01-01

Laminar pressure-driven suspension flows are studied in the situation of neutrally buoyant particles at finite Reynolds number. The numerical method is validated for homogeneous particle distribution (no lateral migration across the channel): the increase of particle slip velocities and particle stress with inertia and concentration is in agreement with former works in the literature. In the case of a two-phase channel flow with freely moving particles, migration towards the channel walls due to the Segré-Silberberg effect is observed, leading to the development of a non-uniform concentration profile in the wall-normal direction (the concentration peaks in the wall region and tends towards zero in the channel core). The particle accumulation in the region of highest shear favors the shear-induced particle interactions and agitation, the profile of which appears to be correlated to the concentration profile. A 1D model predicting particle agitation, based on the kinetic theory of granular flows in the quenched state regime when Stokes number St = O(1) and from numerical simulations when St < 1, fails to reproduce the agitation profile in the wall normal direction. Instead, the existence of secondary flows is clearly evidenced by long time simulations. These are composed of a succession of contra-rotating structures, correlated with the development of concentration waves in the transverse direction. The mechanism proposed to explain the onset of this transverse instability is based on the development of a lift force induced by spanwise gradient of the axial velocity fluctuations. The establishment of the concentration profile in the wall-normal direction therefore results from the combination of the mean flow Segré-Silberberg induced migration, which tends to stratify the suspension and secondary flows which tend to mix the particles over the channel cross section

Operational analysis of the coupling between a multi-effect distillation unit with thermal vapor compression and a Rankine cycle power block using variable nozzle thermocompressors

International Nuclear Information System (INIS)

Ortega-Delgado, Bartolomé; Cornali, Matteo; Palenzuela, Patricia; Alarcón-Padilla, Diego C.

2017-01-01

Highlights: •Variable nozzle steam ejectors are used for operation flexibility of MED plants. •The power block breaking points have been investigated by simulations in Thermoflex. •An operational model of the MED-TVC process is developed for part load operation. •Efficiency and fresh water production are studied at nominal and partial loads. -- Abstract: In Multi-Effect Distillation with Thermal Vapor Compression (MED-TVC) plants, fixed steam ejectors are usually designed for constant motive steam pressures. When these distillation units are integrated into Concentrating Solar Power (CSP) plants, the available motive steam pressure is normally lower than the design value (due to the partial load operation of the power cycle under different solar radiation conditions), being the efficiency of the steam ejectors drastically reduced. Also, it has a negative impact on the fresh water production from the desalination plant because of a decrease in the mass flow of the motive steam. All this can be avoided by using variable nozzle steam ejectors, which can adjust the mass flow rate of steam according to the variable pressure so that they are always operating with the maximum efficiency and therefore they can maintain the freshwater production of the desalination plant near to the nominal value. This work presents a study of the coupling between CSP plants and MED-TVC units using variable nozzle steam ejectors in a wide range of operating conditions (on and off-design). For this purpose, simulations of a Rankine cycle power block in a typical commercial CSP plant have been firstly performed at different thermal loads to investigate the operational limits that allow keeping the motive steam mass flow rates constant. Then, the efficiency and fresh water production of an MED-TVC unit coupled to the different extractions available at the CSP plant have been studied in a wide range of operating conditions, covering both nominal and partial loads. To this end, an

Zero-truncated negative binomial - Erlang distribution

Science.gov (United States)

Bodhisuwan, Winai; Pudprommarat, Chookait; Bodhisuwan, Rujira; Saothayanun, Luckhana

2017-11-01

The zero-truncated negative binomial-Erlang distribution is introduced. It is developed from negative binomial-Erlang distribution. In this work, the probability mass function is derived and some properties are included. The parameters of the zero-truncated negative binomial-Erlang distribution are estimated by using the maximum likelihood estimation. Finally, the proposed distribution is applied to real data, the number of methamphetamine in the Bangkok, Thailand. Based on the results, it shows that the zero-truncated negative binomial-Erlang distribution provided a better fit than the zero-truncated Poisson, zero-truncated negative binomial, zero-truncated generalized negative-binomial and zero-truncated Poisson-Lindley distributions for this data.

Steady Secondary Flows Generated by Periodic Compression and Expansion of an Ideal Gas in a Pulse Tube

Science.gov (United States)

Lee, Jeffrey M.

1999-01-01

This study establishes a consistent set of differential equations for use in describing the steady secondary flows generated by periodic compression and expansion of an ideal gas in pulse tubes. Also considered is heat transfer between the gas and the tube wall of finite thickness. A small-amplitude series expansion solution in the inverse Strouhal number is proposed for the two-dimensional axisymmetric mass, momentum and energy equations. The anelastic approach applies when shock and acoustic energies are small compared with the energy needed to compress and expand the gas. An analytic solution to the ordered series is obtained in the strong temperature limit where the zeroth-order temperature is constant. The solution shows steady velocities increase linearly for small Valensi number and can be of order I for large Valensi number. A conversion of steady work flow to heat flow occurs whenever temperature, velocity or phase angle gradients are present. Steady enthalpy flow is reduced by heat transfer and is scaled by the Prandtl times Valensi numbers. Particle velocities from a smoke-wire experiment were compared with predictions for the basic and orifice pulse tube configurations. The theory accurately predicted the observed steady streaming.

The modelling of an SF6 arc in a supersonic nozzle: II. Current zero behaviour of the nozzle arc

International Nuclear Information System (INIS)

Zhang, Q; Liu, J; Yan, J D; Fang, M T C

2016-01-01

The present work (part II) forms the second part of an investigation into the behaviour of SF 6 nozzle arc. It is concerned with the aerodynamic and electrical behaviour of a transient nozzle arc under a current ramp specified by a rate of current decay (d i /d t ) before current zero and a voltage ramp (d V /d t ) after current zero. The five flow models used in part I [1] for cold gas flow and DC nozzle arcs have been applied to study the transient arc at three stagnation pressures ( P 0 ) and two values of d i /d t for the current ramp, representing a wide range of arcing conditions. An analysis of the physical mechanisms encompassed in each flow model is given with an emphasis on the adequacy of a particular model in describing the rapidly varying arc around current zero. The critical rate of rise of recovery voltage (RRRV) is found computationally and compared with test results of Benenson et al [2]. For transient nozzle arcs, the RRRV is proportional to the square of P 0 , rather than to the square root of P 0 for DC nozzle arcs. The physical mechanisms responsible for the strong dependence of RRRV on P 0 have been investigated. The relative merits of the flow models employed are discussed. (paper)

How is flow experienced and by whom? Testing flow among occupations.

Science.gov (United States)

Llorens, Susana; Salanova, Marisa; Rodríguez, Alma M

2013-04-01

The aims of this paper are to test (1) the factorial structure of the frequency of flow experience at work; (2) the flow analysis model in work settings by differentiating the frequency of flow and the frequency of its prerequisites; and (3) whether there are significant differences in the frequency of flow experience depending on the occupation. A retrospective study among 957 employees (474 tile workers and 483 secondary school teachers) using multigroup confirmatory factorial analyses and multiple analyses of variance suggested that on the basis of the flow analysis model in work settings, (1) the frequency of flow experience has a two-factor structure (enjoyment and absorption); (2) the frequency of flow experience at work is produced when both challenge and skills are high and balanced; and (3) secondary school teachers experience flow more frequently than tile workers. Copyright © 2012 John Wiley & Sons, Ltd.

Secondary amenorrhea (image)

Science.gov (United States)

Secondary amenorrhea is the cessation of menstrual flow for a period of 6 months or more in the absence ... as anxiety can be the root cause of amenorrhea. Treatment can range from behavior modification for excessive ...

Characterization of flow in a scroll duct

Science.gov (United States)

Begg, E. K.; Bennett, J. C.

1985-01-01

A quantitative, flow visualization study was made of a partially elliptic cross section, inward curving duct (scroll duct), with an axial outflow through a vaneless annular cutlet. The working fluid was water, with a Re(d) of 40,000 at the inlet to the scroll duct, this Reynolds number being representative of the conditions in an actual gas turbine scroll. Both still and high speed moving pictures of fluorescein dye injected into the flow and illuminated by an argon ion laser were used to document the flow. Strong secondary flow, similar to the secondary flow in a pipe bend, was found in the bottom half of the scroll within the first 180 degs of turning. The pressure field set up by the turning duct was strong enough to affect the inlet flow condition. At 90 degs downstream, the large scale secondary flow was found to be oscillatory in nature. The exit flow was nonuniform in the annular exit. By 270 degs downstream, the flow appeared unorganized with no distinctive secondary flow pattern. Large scale structures from the upstream core region appeared by 90 degs and continued through the duct to reenter at the inlet section.

The flows structure in unsteady gas flow in pipes with different cross-sections

Science.gov (United States)

Plotnikov, Leonid; Nevolin, Alexandr; Nikolaev, Dmitrij

2017-10-01

The results of numerical simulation and experimental study of the structure of unsteady flows in pipes with different cross sections are presented in the article. It is shown that the unsteady gas flow in a circular pipe is axisymmetric without secondary currents. Steady vortex structures (secondary flows) are observed in pipes with cross sections in the form of a square and an equilateral triangle. It was found that these secondary flows have a significant impact on gas flows in pipes of complex configuration. On the basis of experimental researches it is established that the strong oscillatory phenomena exist in the inlet pipe of the piston engine arising after the closing of the intake valve. The placement of the profiled plots (with a cross section of a square or an equilateral triangle) in the intake pipe leads to the damping of the oscillatory phenomena and a more rapid stabilization of pulsating flow. This is due to the stabilizing effect of the vortex structures formed in the corners of this configuration.

The flows structure in unsteady gas flow in pipes with different cross-sections

Directory of Open Access Journals (Sweden)

Plotnikov Leonid

2017-01-01

Full Text Available The results of numerical simulation and experimental study of the structure of unsteady flows in pipes with different cross sections are presented in the article. It is shown that the unsteady gas flow in a circular pipe is axisymmetric without secondary currents. Steady vortex structures (secondary flows are observed in pipes with cross sections in the form of a square and an equilateral triangle. It was found that these secondary flows have a significant impact on gas flows in pipes of complex configuration. On the basis of experimental researches it is established that the strong oscillatory phenomena exist in the inlet pipe of the piston engine arising after the closing of the intake valve. The placement of the profiled plots (with a cross section of a square or an equilateral triangle in the intake pipe leads to the damping of the oscillatory phenomena and a more rapid stabilization of pulsating flow. This is due to the stabilizing effect of the vortex structures formed in the corners of this configuration.

Prediction of transverse asymmetries in MHD ducts with zero net Hall current

International Nuclear Information System (INIS)

Swean, T.F. Jr.; Oliver, D.A.; Maxwell, C.D.; Demetriades, S.T.

1981-01-01

A new class of fluid-electrical asymmetries in MHD generator channel flow are predicted. It is shown that the existence of interelectrode asymmetries is not confined to generators in which there exists a nonzero net axial current, but rather they are induced even in the case of the Faraday generators. Also demonstrated is the impact of these asymmetries upon the generator and diffuser flow. It is concluded that in MHD generators, the net axial current in the cross plane is identically zero, while at any given point in the plane, the local Hall current density is in general nonzero

Initial ratio optimization for the ejector cooling system with thermal pumping effect (ECSTPE)

International Nuclear Information System (INIS)

He, Yijian; Sun, Yongjun; Zhang, Sheng; Lyu, Yuanli; Chen, Guangming

2016-01-01

Graphical abstract: The existing ejector cooling systems with thermal pumping effect (ECSTPEs) have severe problems of thermal energy and chilling load waste. The deviations of the initial ratio from its optimal value would lead to the deviations of the time length of cooling stage (TLCS), and finally, result in the performance deteriorations of the ECSTPEs. The results of the case study showed that, for an ECSTPE with R134a, a 10-second deviation from the optimal TLCS led to a decrease of 5.6% in the COP value and an increase of 23.7% in the chilling load, when the generation temperature, the condensing temperature and the evaporation temperature were 85 °C, 35 °C and 10 °C, respectively. Therefore, accurately controlling the TLCS corresponding to the optimal TLCS, which is derived on the basis of the optimal initial ratio, can effectively improve the performance of ECSPTEs. - Highlights: • ECSTPEs encounter challenges for a great waste of heat and chilling water. • Initial ratio optimization is proposed to improve the performance of ECSTPEs. • Based on the optimal initial ratio, the optimal TLCS control strategy is obtained. • With the optimal TLCS control, COP values of the ECSTPEs are effectively enhanced. • Accordingly, the chilling loads of the ECSTPEs are greatly reduced. - Abstract: An ejector cooling system with thermal pumping effect (ECSTPE) could operate without consumption of electric power, but it discards a great amount of thermal energy, which generally results in a lower COP value and a greater chilling load. An innovative concept for the optimal initial ratio is therefore proposed to develop the optimal time length of cooling stage (TLCS) control method. The optimal TLCS control method effectively improves the ECSTPE performance. First, in this context, it was theoretically proven that the optimal initial ratio could be used to reduce the energy loss and the chilling load. Second, it was formulated how to achieve the optimal initial

Taylor-Couette flow stability with toroidal magnetic field

International Nuclear Information System (INIS)

Shalybkov, D

2005-01-01

The linear stability of the dissipative Taylor-Couette flow with imposed azimuthal magnetic field is considered. Unlike to ideal flow, the magnetic field is fixed function of radius with two parameters only: a ratio of inner to outer cylinder radii and a ratio of the magnetic field values on outer and inner cylinders. The magnetic field with boundary values ratio greater than zero and smaller than inverse radii ratio always stabilizes the flow and called stable magnetic field below. The current free magnetic field is the stable magnetic field. The unstable magnetic field destabilizes every flow if the magnetic field (or Hartmann number) exceeds some critical value. This instability survives even without rotation (for zero Reynolds number). For the stable without the magnetic field flow, the unstable modes are located into some interval of the vertical wave numbers. The interval length is zero for critical Hartmann number and increases with increasing Hartmann number. The critical Hartmann numbers and the length of the unstable vertical wave numbers interval is the same for every rotation law. There are the critical Hartmann numbers for m = 0 sausage and m = 1 kink modes only. The critical Hartmann numbers are smaller for kink mode and this mode is the most unstable mode like to the pinch instability case. The flow stability do not depend on the magnetic Prandtl number for m = 0 mode. The same is true for critical Hartmann numbers for m = 0 and m = 1 modes. The typical value of the magnetic field destabilizing the liquid metal Taylor-Couette flow is order of 100 Gauss

Beyond Zero Based Budgeting.

Science.gov (United States)

Ogden, Daniel M., Jr.

1978-01-01

Suggests that the most practical budgeting system for most managers is a formalized combination of incremental and zero-based analysis because little can be learned about most programs from an annual zero-based budget. (Author/IRT)

Zero modes and entanglement entropy

Energy Technology Data Exchange (ETDEWEB)

Yazdi, Yasaman K. [Perimeter Institute for Theoretical Physics,31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada); Department of Physics and Astronomy, University of Waterloo,200 University Avenue West, Waterloo, ON, N2L 3G1 (Canada)

2017-04-26

Ultraviolet divergences are widely discussed in studies of entanglement entropy. Also present, but much less understood, are infrared divergences due to zero modes in the field theory. In this note, we discuss the importance of carefully handling zero modes in entanglement entropy. We give an explicit example for a chain of harmonic oscillators in 1D, where a mass regulator is necessary to avoid an infrared divergence due to a zero mode. We also comment on a surprising contribution of the zero mode to the UV-scaling of the entanglement entropy.

A Ulysses Detection of Secondary Helium Neutrals

Science.gov (United States)

Wood, Brian E.; Müller, Hans-Reinhard; Witte, Manfred

2017-12-01

The Interstellar Boundary EXplorer (IBEX) mission has recently studied the flow of interstellar neutral He atoms through the solar system and discovered the existence of a secondary He flow that likely originates in the outer heliosheath. We find evidence for this secondary component in Ulysses data. By coadding hundreds of Ulysses He beam maps together to maximize signal-to-noise ratio, we identify a weak signal that is credibly associated with the secondary component. Assuming a laminar flow from infinity, we infer the following He flow parameters: V=12.8+/- 1.9 km s-1, λ =74\\buildrel{\\circ}\\over{.} 4+/- 1\\buildrel{\\circ}\\over{.} 8, β =-10\\buildrel{\\circ}\\over{.} 5+/- 4\\buildrel{\\circ}\\over{.} 1, and T=3000+/- 1100 K; where λ and β are the ecliptic longitude and latitude direction in J2000 coordinates. The secondary component has a density that is 4.9 ± 0.9% that of the primary component. These measurements are reasonably consistent with measurements from IBEX, with the exception of temperature, where our temperature is much lower than IBEX’s T = 9500 K. Even the higher IBEX temperature is suspiciously low compared to expectactions for the outer heliosheath source region. The implausibly low temperatures are due to the incorrect assumption of a laminar flow instead of a diverging one, given that the flow in the outer heliosheath source region will be deflecting around the heliopause. As for why the IBEX and Ulysses T values are different, difficulties with background subtraction in the Ulysses data are a potential source of concern, but the discrepancy may also be another effect of the improper laminar flow assumption, which could affect the IBEX and Ulysses analyses differently.

Stress corrosion cracking susceptibility of steam generator tubing on secondary side in restricted flow areas

International Nuclear Information System (INIS)

Fulger, M.; Lucan, D.; Radulescu, M.; Velciu, L.

2003-01-01

Nuclear steam generator tubes operate in high temperature water and on the secondary side in restricted flow areas many nonvolatile impurities accidentally introduced into circuit tend to concentrate. The concentration process leads to the formation of highly aggressive alkaline or acid solutions in crevices, and these solutions can cause stress corrosion cracking (SCC) on stressed tube materials. Even though alloy 800 has shown to be highly resistant to general corrosion in high temperature water, it has been found that the steam generator tubes may crack during service from the primary and/or secondary side. Stress corrosion cracking is still a serious problem occurring on outside tubes in operating steam generators. The purpose of this study was to evaluate the environmental factors affecting the stress corrosion cracking of steam generators tubing. The main test method was the exposure for 1000 hours into static autoclaves of plastically stressed C-rings of Incoloy 800 in caustic solutions (10% NaOH) and acidic chloride solutions because such environments may sometimes form accidentally in crevices on secondary side of tubes. Because the kinetics of corrosion of metals is indicated by anodic polarization curves, in this study, some stressed specimens were anodically polarized in caustic solutions in electrochemical cell, and other in chloride acidic solutions. The results presented as micrographs, potentiokinetic curves, and electrochemical parameters have been compared to establish the SCC behavior of Incoloy 800 in such concentrated environments. (authors)

Diastolic coronary artery pressure-flow velocity relationships in conscious man.

Science.gov (United States)

Dole, W P; Richards, K L; Hartley, C J; Alexander, G M; Campbell, A B; Bishop, V S

1984-09-01

We characterised the diastolic pressure-flow velocity relationship in the normal left coronary artery of conscious man before and after vasodilatation with angiographic contrast medium. Phasic coronary artery pressure and flow velocity were measured in ten patients during individual diastoles (0.5 to 1.0 s) using a 20 MHz catheter-tipped, pulsed Doppler transducer. All pressure-flow velocity curves were linear over the diastolic pressure range of 110 +/- 15 (SD) mmHg to 71 +/- 7 mmHg (r = 0.97 +/- 0.01). In the basal state, values for slope and extrapolated zero flow pressure intercept averaged 0.35 +/- 0.12 cm X s-1 X mmHg-1 and 51.7 +/- 8.6 mmHg, respectively. Vasodilatation resulted in a 2.5 +/- 0.5 fold increase in mean flow velocity. The diastolic pressure-flow velocity relationship obtained during peak vasodilatation compared to that during basal conditions was characterised by a steeper slope (0.80 +/- 0.48 cm X s-1 X mmHg-1, p less than 0.001) and lower extrapolated zero flow pressure intercept (37.9 +/- 9.8 mmHg, p less than 0.05). Mean right atrial pressure for the group averaged 4.4 +/- 1.7 mmHg, while left ventricular end-diastolic pressure averaged 8.7 +/- 2.8 mmHg. These observations in man are similar to data reported in the canine coronary circulation which are consistent with a vascular waterfall model of diastolic flow regulation. In this model, coronary blood flow may be regulated by changes in diastolic zero flow pressure as well as in coronary resistance.

Four-level time decomposition quasi-static power flow and successive disturbances analysis. [Power system disturbances

Energy Technology Data Exchange (ETDEWEB)

Jovanovic, S M [Nikola Tesla Inst., Belgrade (YU)

1990-01-01

This paper presents a model and an appropriate numerical procedure for a four-level time decomposition quasi-static power flow and successive disturbances analysis of power systems. The analysis consists of the sequential computation of the zero, primary, secondary and tertiary quasi-static states and of the estimation of successive structural disturbances during the 1200 s dynamics after a structural disturbance. The model is developed by detailed inspection of the time decomposition characteristics of automatic protection and control devices. Adequate speed of the numerical procedure is attained by a specific application of the inversion matrix lemma and the decoupled model constant coefficient matrices. The four-level time decomposition quasi-static method is intended for security and emergency analysis. (author).

Zero-gravity movement studies

Science.gov (United States)

Badler, N. I.; Fishwick, P.; Taft, N.; Agrawala, M.

1985-01-01

The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms.

NASA Net Zero Energy Buildings Roadmap

Energy Technology Data Exchange (ETDEWEB)

Pless, S.; Scheib, J.; Torcellini, P.; Hendron, B.; Slovensky, M.

2014-10-01

In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategic approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.

Getting to Net Zero

Energy Technology Data Exchange (ETDEWEB)

2016-09-01

The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.

Thermal Simulation of a Zero Energy Glazed Pavilion in Sofia, Bulgaria. New Strategies for Energy Management by Means of Water Flow Glazing

Science.gov (United States)

del Ama Gonzalo, Fernando; Hernandez Ramos, Juan A.; Moreno, Belen

2017-10-01

The building sector is primarily responsible for a major part of total energy consumption. The European Energy Performance of Buildings Directives (EPBD) emphasized the need to reduce the energy consumption in buildings, and put forward the rationale for developing Near to Zero Energy Buildings (NZEB). Passive and active strategies help architects to minimize the use of active HVAC systems, taking advantage of the available natural resources such as solar radiation, thermal variability and daylight. The building envelope plays a decisive role in passive and active design strategies. The ideal transparent façade would be one with optical properties, such as Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT), that could readily adapt in response to changing climatic conditions or occupant preferences. The aim of this article consists of describing the system to maintain a small glazed pavilion located in Sofia (Bulgaria) at the desired interior temperature over a whole year. The system comprises i) the use of Water Flow Glazing facades (WFG) and Radiant Interior Walls (RIW), ii) the use of free cooling devices along with traditional heat pump connected to photo-voltaic panels and iii) the use of a new Energy Management System that collects data and acts accordingly by controlling all components. The effect of these strategies and the use of active systems, like Water Flow Glazing, are analysed by means of simulating the prototype over one year. Summer and Winter energy management strategies are discussed in order to change the SHGC value of the Water Flow Glazing and thus, reduce the required energy to maintain comfort conditions.

Zero-Valent Iron Permeable Reactive Barriers: A Review of Performance

International Nuclear Information System (INIS)

Korte, NE

2001-01-01

This report briefly reviews issues regarding the implementation of the zero-valent iron permeable reactive barrier (PRB) technology at sites managed by the U.S. Department of Energy (DOE). Initially, the PRB technology, using zero-valent iron for the reactive media, was received with great enthusiasm, and DOE invested millions of dollars testing and implementing PRBs. Recently, a negative perception of the technology has been building. This perception is based on the failure of some deployments to satisfy goals for treatment and operating expenses. The purpose of this report, therefore, is to suggest reasons for the problems that have been encountered and to recommend whether DOE should invest in additional research and deployments. The principal conclusion of this review is that the most significant problems have been the result of insufficient characterization, which resulted in poor engineering implementation. Although there are legitimate concerns regarding the longevity of the reactive media, the ability of zero-valent iron to reduce certain chlorinated hydrocarbons and to immobilize certain metals and radionuclides is well documented. The primary problem encountered at some DOE full-scale deployments has been an inadequate assessment of site hydrology, which resulted in misapplication of the technology. The result is PRBs with higher than expected flow velocities and/or incomplete plume capture

Numerical study of jets secondary instabilities

International Nuclear Information System (INIS)

Brancher, Pierre

1996-01-01

The work presented in this dissertation is a contribution to the study of the transition to turbulence in open shear flows. Results from direct numerical simulations are interpreted within the framework of hydrodynamic stability theory. The first chapter is an introduction to the primary and secondary instabilities observed in jets and mixing layers. The numerical method used in the present study is detailed in the second chapter. The dynamics of homogeneous circular jets subjected to stream wise and azimuthal perturbations are investigated in the third chapter. A complete scenario describing the evolution of the jet is proposed with emphasis on the dynamics of vorticity within the flow. In the fourth chapter a parametric study reveals a three-dimensional secondary instability mainly controlled in the linear regime by the Strouhal number of the primary instability. In the nonlinear regime the dynamics of the azimuthal harmonies are described by means of model equations and are linked to the formation of stream wise vortices in the braid. The fifth chapter is dedicated to the convective or absolute nature of the secondary instabilities in plane shear layers. It is shown that there are flow configurations for which the two-dimensional secondary instability (pairing) is absolute even though the primary instability (Kelvin-Helmholtz) is convective. Some preliminary results concerning the three-dimensional secondary instabilities arc presented at the end of this chapter. The last chapter summarizes the main results and examines possible extensions of this work. (author) [fr

A Zero-Dimensional Model of a 2nd Generation Planar SOFC Using Calibrated Parameters

DEFF Research Database (Denmark)

Petersen, Thomas Frank

2006-01-01

This paper presents a zero-dimensional mathematical model of a planar 2nd generation co-flow SOFC developed for simulation of power systems. The model accounts for the electrochemical oxidation of hydrogen as well as the methane reforming reaction and the water-gas shift reaction. An important part...... SOFC-based power systems....

Zero-knowledge using garbled circuits

DEFF Research Database (Denmark)

Jawurek, Marek; Kerschbaum, Florian; Orlandi, Claudio

2013-01-01

Zero-knowledge protocols are one of the fundamental concepts in modern cryptography and have countless applications. However, after more than 30 years from their introduction, there are only very few languages (essentially those with a group structure) for which we can construct zero......-party computation (i.e., any protocol for generic secure computation can be used to do zero-knowledge). The main contribution of this paper is to construct an efficient protocol for the special case of secure two-party computation where only one party has input (like in the zero-knowledge case). The protocol......-knowledge protocols that are efficient enough to be used in practice. In this paper we address the problem of how to construct efficient zero-knowledge protocols for generic languages and we propose a protocol based on Yao's garbled circuit technique. The motivation for our work is that in many cryptographic...

Large-Scale V/STOL Experimental Investigations of an Ejector-Lift Fighter and a Twin Tilt-Nacelle Transport

Science.gov (United States)

Dudley, Michael R.

2016-01-01

In the 1980s NASA Aeronautics was actively involved in full-scale wind tunnel testing of promising VSTOL aircraft concepts. This presentation looks at two, a multi-role fighter and a subsonic tactical transport. Their strengths and weaknesses are discussed with some of the rationale that ultimately led to the selection of competing concepts for production, namely the V-22 Osprey and the F-35 Lightning. The E7-A STOVL multi-role fighter was the product of an aircraft development program in the late 1980s by NASA, the Defense Advanced Research Projects Agency (DARPA), the Canadian Department of Industry Science and Technology (DIST), and industry partners General Dynamics and Boeing Dehavilland. The program was conducted an in response to increasing US-UK interest in supersonic STOVL fighters. The objective was to design an aircraft that could replace most existing close air support-air combat fighters with a single aircraft that had some of the qualities of an air superiority fighter and the deployment flexibility of a VSTOL aircraft. The resulting E7-A concept was a delta-wing supersonic fighter that used a fuselage-mounted thrust augmenting ejector and a ventral deflecting jet nozzle for vertical lift. The Grumman Aircraft Company, the Navy, and NASA developed the Design-698 (D-698) subsonic tactical transport in response to the Navy's Type A VSTOL utility aircraft requirement. The objective was to develop a subsonic utility transport with the operational flexibility of a helicopter, but with greater speed and range. The D-698 employs two high-bypass turbofan engines mounted on a dumbbell that rotates through ninety degrees for vertical takeoff and cruise flight. Movable vanes positioned in the exhaust flow provide control in hover with the need for reaction control jets. The presentations concluding comments suggest that technology advances in the last thirty-years may justify the value of revisiting some of these concepts.

Reduction and Immobilization of Radionuclides and Toxic Metal Ions Using Combined Zero Valent Iron and Anaerobic Bacteria

International Nuclear Information System (INIS)

Weathers, Lenly J.; Katz, Lynn E.

2002-01-01

The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. AN exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes are functional. This work evaluated the hypothesis that a system combining a mixed culture of sulfate reducing bacteria (SRB) with zero valent iron would have a greater cr(VI) removal efficiency and a greater total Cr(VI) removal capacity than a zero valent iron system without the microorganisms. Hence, the overall goal of this research was to compare the performance of these types of systems with regard to their Cr(VI) removal efficiency and total Cr(VI) removal capacity. Both batch and continuous flow reactor systems were evaluated

Reduction and Immobilization of Radionuclides and Toxic Metal Ions Using Combined Zero Valent Iron and Anaerobic Bacteria

Energy Technology Data Exchange (ETDEWEB)

Lenly J. Weathers; Lynn E. Katz

2002-05-29

The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. AN exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes are functional. This work evaluated the hypothesis that a system combining a mixed culture of sulfate reducing bacteria (SRB) with zero valent iron would have a greater cr(VI) removal efficiency and a greater total Cr(VI) removal capacity than a zero valent iron system without the microorganisms. Hence, the overall goal of this research was to compare the performance of these types of systems with regard to their Cr(VI) removal efficiency and total Cr(VI) removal capacity. Both batch and continuous flow reactor systems were evaluated.

Zero energy Tunnel-concept

NARCIS (Netherlands)

Dzhusupova, R.

2012-01-01

Creating a zero energy environment is a hot topic. The developments in this field are based on the concept of the "Trias Energetica": reducing energy consumption, using renewable energy sources, and efficiently using fossil fuels. A zero energy concept can also be applied to road tunnels to improve

Development of Flow Accelerated Corrosion Reduction Technology

Energy Technology Data Exchange (ETDEWEB)

Heo, Min Bum; Choi, Won Yeol; Lee, Jong Chan; Lim, Dong Seok; Kwon, Byung Il; Ku, Hee Kwon; Kim, Jong Uk [FNC Tech, Yongin (Korea, Republic of)

2015-10-15

Development of flow accelerated corrosion reduction technology is necessary for prevent this kind of accidents. This study deals with development of flow accelerated corrosion reduction technology through platinum injection and developed of flow accelerated corrosion reduction technology by imitating water chemical condition in PWR secondary system in practice. In addition, in order to get reliability of water chemical simulator in PWR secondary system, analyzed and compared with test result through CFD analysis. This study composed test device that can simulate water chemical environment in PWR secondary system, in order to develop flow accelerated corrosion reduction , and evaluated the ratio of corrosion in water chemical environment in PWR secondary system. In conclusion, corrosion ratio of low alloy steel material that includes more Cr and Mo was lower. And the results were confirmed to be the maximum corrosion rate in the case that replicate the 90 elbow. Additionally, inserted Pt nano particle for developing flow accelerated corrosion rate reduction technology, the test results, it was confirmed for about 80% of the flow accelerated corrosion rate reduction than before input.

Three dimensional steady subsonic Euler flows in bounded nozzles

Science.gov (United States)

Chen, Chao; Xie, Chunjing

The existence and uniqueness of three dimensional steady subsonic Euler flows in rectangular nozzles were obtained when prescribing normal component of momentum at both the entrance and exit. If, in addition, the normal component of the voriticity and the variation of Bernoulli's function at the entrance are both zero, then there exists a unique subsonic potential flow when the magnitude of the normal component of the momentum is less than a critical number. As the magnitude of the normal component of the momentum approaches the critical number, the associated flows converge to a subsonic-sonic flow. Furthermore, when the normal component of vorticity and the variation of Bernoulli function are both small, the existence and uniqueness of subsonic Euler flows with non-zero vorticity are established. The proof of these results is based on a new formulation for the Euler system, a priori estimate for nonlinear elliptic equations with nonlinear boundary conditions, detailed study for a linear div-curl system, and delicate estimate for the transport equations.

Adsorptive removal of arsenate from aqueous solutions by biochar supported zero-valent iron nanocomposite: Batch and continuous flow tests

International Nuclear Information System (INIS)

Wang, Shengsen; Gao, Bin; Li, Yuncong; Creamer, Anne Elise; He, Feng

2017-01-01

Highlights: • Biochar supported nZVI (nZVI/BC) was synthesized. • nZVI/BC showed excellent As(V) removal efficiency in batch and CMR experiments. • 100% removal efficiency was achieved in CMRs. • Surface adsorption was the dominant removal mechanism. - Abstract: Arsenate (As(V)) removal ability by nanoscale zero-valent iron (nZVI) is compromised by aggregation of nZVI particles. In this work, pine derived biochar (PB) was used as a supporting material to stabilize nZVI for As(V) removal. The biochar supported nZVI (nZVI/BC) was synthesized by precipitating the nanoparticles on carbon surfaces. Experiments using batch and continuous flow, completely mixed reactors (CMRs) were carried out to investigate the removal of As(V) by the nZVI/BC from aqueous solutions. Batch experiments showed that nZVI/BC had high As(V) removal capacity in a wide range of pH (3–8). Kinetic data revealed that equilibrium was reached within 1 h and the isotherm data showed that the Langmuir maximum adsorption capacity of the nZVI/BC for As(V) at pH 4.1 was 124.5 g kg −1 . As(V) (100 mg L −1 ) adsorption in anoxic condition was about 8% more than in oxic conditions, where As(V) reduction was observed in anoxic condition. The performance of the nZVI/BC in flowing condition was evaluated in CMRs at influent As(V) concentrations of 2.1 and 5.5 mg L −1 and the adsorbent removed 100% and 90% of the As(V), respectively. Furthermore, the nZVI/BC composite is magnetic which facilitates collection from aqueous solutions.

Adsorptive removal of arsenate from aqueous solutions by biochar supported zero-valent iron nanocomposite: Batch and continuous flow tests

Energy Technology Data Exchange (ETDEWEB)

Wang, Shengsen [Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611 (United States); Gao, Bin, E-mail: bg55@ufl.edu [Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611 (United States); Li, Yuncong [Tropical Research and Education Center, University of Florida, Homestead, FL 33031 (United States); Creamer, Anne Elise [Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611 (United States); He, Feng [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310014 (China)

2017-01-15

Highlights: • Biochar supported nZVI (nZVI/BC) was synthesized. • nZVI/BC showed excellent As(V) removal efficiency in batch and CMR experiments. • 100% removal efficiency was achieved in CMRs. • Surface adsorption was the dominant removal mechanism. - Abstract: Arsenate (As(V)) removal ability by nanoscale zero-valent iron (nZVI) is compromised by aggregation of nZVI particles. In this work, pine derived biochar (PB) was used as a supporting material to stabilize nZVI for As(V) removal. The biochar supported nZVI (nZVI/BC) was synthesized by precipitating the nanoparticles on carbon surfaces. Experiments using batch and continuous flow, completely mixed reactors (CMRs) were carried out to investigate the removal of As(V) by the nZVI/BC from aqueous solutions. Batch experiments showed that nZVI/BC had high As(V) removal capacity in a wide range of pH (3–8). Kinetic data revealed that equilibrium was reached within 1 h and the isotherm data showed that the Langmuir maximum adsorption capacity of the nZVI/BC for As(V) at pH 4.1 was 124.5 g kg{sup −1}. As(V) (100 mg L{sup −1}) adsorption in anoxic condition was about 8% more than in oxic conditions, where As(V) reduction was observed in anoxic condition. The performance of the nZVI/BC in flowing condition was evaluated in CMRs at influent As(V) concentrations of 2.1 and 5.5 mg L{sup −1} and the adsorbent removed 100% and 90% of the As(V), respectively. Furthermore, the nZVI/BC composite is magnetic which facilitates collection from aqueous solutions.

Secondary Voltage Unbalance Compensation for Three-Phase Four-Wire Islanded Microgrids

DEFF Research Database (Denmark)

Tang, Fen; Zhou, Xiao; Meng, Lexuan

2014-01-01

This paper proposes a secondary voltage unbalance control approach that compensate voltage unbalances in three-phase four-wire islanded microgrid systems. It is implemented in the secondary control level of the microgrid hierarchical control structure. By sending information through low......-bandwidth communication links to the primary control level, the required unbalanced factors at sensitive buses are achieved. Also, negative and zero sequence equivalent circuits and unbalance compensation principle are derived. Finally, real-time hardware-in-the-loop results show the feasibility of the proposed approach...

Marginalized multilevel hurdle and zero-inflated models for overdispersed and correlated count data with excess zeros.

Science.gov (United States)

Kassahun, Wondwosen; Neyens, Thomas; Molenberghs, Geert; Faes, Christel; Verbeke, Geert

2014-11-10

Count data are collected repeatedly over time in many applications, such as biology, epidemiology, and public health. Such data are often characterized by the following three features. First, correlation due to the repeated measures is usually accounted for using subject-specific random effects, which are assumed to be normally distributed. Second, the sample variance may exceed the mean, and hence, the theoretical mean-variance relationship is violated, leading to overdispersion. This is usually allowed for based on a hierarchical approach, combining a Poisson model with gamma distributed random effects. Third, an excess of zeros beyond what standard count distributions can predict is often handled by either the hurdle or the zero-inflated model. A zero-inflated model assumes two processes as sources of zeros and combines a count distribution with a discrete point mass as a mixture, while the hurdle model separately handles zero observations and positive counts, where then a truncated-at-zero count distribution is used for the non-zero state. In practice, however, all these three features can appear simultaneously. Hence, a modeling framework that incorporates all three is necessary, and this presents challenges for the data analysis. Such models, when conditionally specified, will naturally have a subject-specific interpretation. However, adopting their purposefully modified marginalized versions leads to a direct marginal or population-averaged interpretation for parameter estimates of covariate effects, which is the primary interest in many applications. In this paper, we present a marginalized hurdle model and a marginalized zero-inflated model for correlated and overdispersed count data with excess zero observations and then illustrate these further with two case studies. The first dataset focuses on the Anopheles mosquito density around a hydroelectric dam, while adolescents' involvement in work, to earn money and support their families or themselves, is

Generalized zero point anomaly

International Nuclear Information System (INIS)

Nogueira, Jose Alexandre; Maia Junior, Adolfo

1994-01-01

It is defined Zero point Anomaly (ZPA) as the difference between the Effective Potential (EP) and the Zero point Energy (ZPE). It is shown, for a massive and interacting scalar field that, in very general conditions, the renormalized ZPA vanishes and then the renormalized EP and ZPE coincide. (author). 3 refs

Three Dimensional Viscous Flow Field in an Axial Flow Turbine Nozzle Passage

Science.gov (United States)

Ristic, D.; Lakshminarayana, B.

1997-01-01

The objective of this investigation is experimental and computational study of three dimensional viscous flow field in the nozzle passage of an axial flow turbine stage. The nozzle passage flow field has been measured using a two sensor hot-wire probe at various axial and radial stations. In addition, two component LDV measurements at one axial station (x/c(sum m) = 0.56) were performed to measure the velocity field. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. A three dimensional boundary layer code, with a simple intermittency transition model, was used to predict the viscous layers along the blade and endwall surfaces. The boundary layers on the blade surface were found to be very thin and mostly laminar, except on the suction surface downstream of 70% axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong cross flow components in the trailing edge regions of the blade. On the end-walls the boundary layers were much thicker, especially near the suction corner of the casing surface, caused by secondary flow. The secondary flow region near the suction-casing surface corner indicates the presence of the passage vortex detached from the blade surface. The corner vortex is found to be very weak. The presence of a closely spaced rotor downstream (20% of the nozzle vane chord) introduces unsteadiness in the blade passage. The measured instantaneous velocity signal was filtered using FFT square window to remove the periodic unsteadiness introduced by the downstream rotor and fans. The filtering decreased the free stream turbulence level from 2.1% to 0.9% but had no influence on the computed turbulence length scale. The computation of the three dimensional boundary layers is found to be accurate on the nozzle passage blade surfaces, away from the end-walls and the secondary flow region. On

The three-dimensional distributions of tangential velocity and total- temperature in vortex tubes

DEFF Research Database (Denmark)

Linderstrøm-Lang, C.U.

1971-01-01

The axial and radial gradients of the tangential velocity distribution are calculated from prescribed secondary flow functions on the basis of a zero-order approximation to the momentum equations developed by Lewellen. It is shown that secondary flow functions may be devised which meet pertinent...... physical requirements and which at the same time lead to realistic tangential velocity gradients. The total-temperature distribution in both the axial and radial directions is calculated from such secondary flow functions and corresponding tangential velocity results on the basis of an approximate...

Note on the End Game in Homotopy Zero Curve Tracking

OpenAIRE

Sosonkina, Masha; Watson, Layne T.; Stewart, David E.

1995-01-01

Homotopy algorithms to solve a nonlinear system of equations f(x)=0 involve tracking the zero curve of a homotopy map p(a,theta,x) from theta=0 until theta=1. When the algorithm nears or crosses the hyperplane theta=1, an "end game" phase is begun to compute the solution x(bar) satisfying p(a,theta,x(bar))=f(x(bar))=0. This note compares several end game strategies, including the one implemented in the normal flow code FIXPNF in the homotopy software package HOMPACK.

Zero-voltage DC/DC converter with asymmetric pulse-width modulation for DC micro-grid system

Science.gov (United States)

Lin, Bor-Ren

2018-04-01

This paper presents a zero-voltage switching DC/DC converter for DC micro-grid system applications. The proposed circuit includes three half-bridge circuit cells connected in primary-series and secondary-parallel in order to lessen the voltage rating of power switches and current rating of rectifier diodes. Thus, low voltage stress of power MOSFETs can be adopted for high-voltage input applications with high switching frequency operation. In order to achieve low switching losses and high circuit efficiency, asymmetric pulse-width modulation is used to turn on power switches at zero voltage. Flying capacitors are used between each circuit cell to automatically balance input split voltages. Therefore, the voltage stress of each power switch is limited at Vin/3. Finally, a prototype is constructed and experiments are provided to demonstrate the circuit performance.

Critical heat flux and flow pattern for water flow in annular geometry

International Nuclear Information System (INIS)

Park, Jae Wook; Baek, Won Pil; Chang, Soon Heung

1996-01-01

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced-circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m, inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, churn-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow

Classification of pulsating flow patterns in curved pipes.

Science.gov (United States)

Tada, S; Oshima, S; Yamane, R

1996-08-01

The fully developed periodic laminar flow of incompressible Newtonian fluids through a pipe of circular cross section, which is coiled in a circle, was simulated numerically. The flow patterns are characterized by three parameters: the Womersley number Wo, the Dean number De, and the amplitude ratio beta. The effect of these parameters on the flow was studied in the range 2.19 secondary flow evolved with increasing Womersley number and Dean number is explained. The secondary flow patterns are classified into three main groups: the viscosity-dominated type, the inertia-dominated type, and the convection-dominated type. It was found that when the amplitude ratio of the volumetric flow rate is equal to 1.0, four to six vortices of the secondary flow appear at high Dean numbers, and the Lyne-type flow patterns disappear at beta > or = 0.50.

Self-organization in three-dimensional compressible magnetohydrodynamic flow

International Nuclear Information System (INIS)

Horiuchi, Ritoku; Sato, Tetsuya.

1987-07-01

A three-dimensional self-organization process of a compressible dissipative plasma with a velocity-magnetic field correlation is investigated in detail by means of a variational method and a magnetohydrodynamic simulation. There are two types of relaxation, i.e., fast relaxation in which the cross helicity is not conserved, and slow relaxation in which the cross helicity is approximately conserved. In the slow relaxation case the cross helicity consists of two components with opposite sign which have almost the same amplitude in the large wavenumber region. In both cases the system approaches a high correlation state, dependent on the initial condition. These results are consistent with an observational data of the solar wind. Selective dissipation of magnetic energy, normal cascade of magnetic energy spectrum and inverse cascade of magnetic helicity spectrum are observed for the sub-Alfvenic flow case as was previously observed for the zero flow case. When the flow velocity is super-Alfvenic, the relaxation process is significantly altered from the zero flow case. (author)

Zero point and zero suffix methods with robust ranking for solving fully fuzzy transportation problems

Science.gov (United States)

Ngastiti, P. T. B.; Surarso, Bayu; Sutimin

2018-05-01

Transportation issue of the distribution problem such as the commodity or goods from the supply tothe demmand is to minimize the transportation costs. Fuzzy transportation problem is an issue in which the transport costs, supply and demand are in the form of fuzzy quantities. Inthe case study at CV. Bintang Anugerah Elektrik, a company engages in the manufacture of gensets that has more than one distributors. We use the methods of zero point and zero suffix to investigate the transportation minimum cost. In implementing both methods, we use robust ranking techniques for the defuzzification process. The studyresult show that the iteration of zero suffix method is less than that of zero point method.

Zero-dimensional mathematical model of the torch ignited engine

International Nuclear Information System (INIS)

Cruz, Igor William Santos Leal; Alvarez, Carlos Eduardo Castilla; Teixeira, Alysson Fernandes; Valle, Ramon Molina

2016-01-01

Highlights: • Publications about the torch ignition system are mostly CFD or experimental research. • A zero-dimensional mathematical model is presented. • The model is based on classical thermodynamic equations. • Approximations are based on empirical functions. • The model is applied to a prototype by means of a computer code. - Abstract: Often employed in the analysis of conventional SI and CI engines, mathematical models can also be applied to engines with torch ignition, which have been researched almost exclusively by CFD or experimentally. The objective of this work is to describe the development and application of a zero-dimensional model of the compression and power strokes of a torch ignited engine. It is an initial analysis that can be used as a basis for future models. The processes of compression, combustion and expansion were described mathematically and applied to an existing prototype by means of a computer code written in MATLAB language. Conservation of energy and mass and the ideal gas law were used in determining gas temperature, pressure, and mass flow rate within the cylinder. Gas motion through the orifice was modelled as an isentropic compressible flow. The thermodynamic properties of the mixture were found by a weighted arithmetic mean of the data for each component, computed by polynomial functions of temperature. Combustion was modelled by the Wiebe function. Heat transfer to the cylinder walls was estimated by Annand’s correlations. Results revealed the behaviour of pressure, temperature, jet velocity, energy transfer, thermodynamic properties, among other variables, and how some of these are influenced by others.

Flow accelerated corrosion and life management of the secondary circuit of the Embalse nuclear power plant

International Nuclear Information System (INIS)

Chocron, Mauricio; La Gamma, Ana M.; Fernandez, Narciso; Moyano, Ricardo; Schiersmann, Christian; Ovando, Luis E.; Sainz, Ricardo A.; Keitelman, Alberto

2003-01-01

Flow accelerated corrosion is a matter of concern in secondary circuits of nuclear power plants as well as in fossil fired plants. It contributes to the piping wall thinning and to the corrosion products transport to the steam generators. Because it is a generalized corrosion phenomena, could address to extensive failures. In that sense the plants conduct extensive programs of surveillance of piping degradation. Because the problem involves many variables like alloys, water chemistry and hydrodynamics several models have been proposed in the literature. In the present paper the variables have been organized in a spreadsheet which allows the calculation of normalized risk factors. (author)

Zero-birefringence pressure-sensitive adhesives

Directory of Open Access Journals (Sweden)

Hiroto Ito

2012-06-01

Full Text Available We have developed zero-birefringence pressure-sensitive adhesives (PSAs that exhibit almost no birefringence at any orientation of polymer chains. To evaluate the birefringence of PSAs quantitatively, we report a novel birefringence-measurement method utilizing zero–zero-birefringence polymers that exhibit no birefringence at any orientation of polymer chains and in elastic deformation. By employing this method, we designed and synthesized poly(butyl acrylate/phenoxyethyl acrylate/acrylic acid/hydroxyethyl acrylate = 80.0:20.0:1.5:1.0 (by weight that contains 1.8 wt% isocyanate-type crosslinker that exhibited almost zero birefringence. Furthermore, we demonstrated that after the accelerated aging test by applying heat, this zero-birefringence PSA almost completely prevented light leakage through crossed polarizers.

Optimizing Urban Material Flows and Waste Streams in Urban Development through Principles of Zero Waste and Sustainable Consumption

Directory of Open Access Journals (Sweden)

Steffen Lehmann

2011-01-01

Full Text Available Beyond energy efficiency, there are now urgent challenges around the supply of resources, materials, energy, food and water. After debating energy efficiency for the last decade, the focus has shifted to include further resources and material efficiency. In this context, urban farming has emerged as a valid urban design strategy, where food is produced and consumed locally within city boundaries, turning disused sites and underutilized public space into productive urban landscapes and community gardens. Furthermore, such agricultural activities allow for effective composting of organic waste, returning nutrients to the soil and improving biodiversity in the urban environment. Urban farming and resource recovery will help to feed the 9 billion by 2050 (predicted population growth, UN-Habitat forecast 2009. This paper reports on best practice of urban design principles in regard to materials flow, material recovery, adaptive re-use of entire building elements and components (‘design for disassembly’; prefabrication of modular building components, and other relevant strategies to implement zero waste by avoiding waste creation, reducing wasteful consumption and changing behaviour in the design and construction sectors. The paper touches on two important issues in regard to the rapid depletion of the world’s natural resources: the built environment and the education of architects and designers (both topics of further research. The construction and demolition (C&D sector: Prefabricated multi-story buildings for inner-city living can set new benchmarks for minimizing construction wastage and for modular on-site assembly. Today, the C&D sector is one of the main producers of waste; it does not engage enough with waste minimization, waste avoidance and recycling. Education and research: It’s still unclear how best to introduce a holistic understanding of these challenges and to better teach practical and affordable solutions to architects, urban

On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

Energy Technology Data Exchange (ETDEWEB)

Shaha, Poly Rani; Poddar, Nayan Kumar; Mondal, Rabindra Nath, E-mail: rnmondal71@yahoo.com [Department of Mathematics, Jagannath University, Dhaka-1100 (Bangladesh); Rudro, Sajal Kanti [Department of Mathematics, Notredame Colleage, Motijheel, Dhaka (Bangladesh)

2016-07-12

The study of flows through coiled ducts and channels has attracted considerable attention not only because of their ample applications in Chemical, Mechanical, Civil, Nuclear and Biomechanical engineering but also because of their ample applications in other areas, such as blood flow in the veins and arteries of human and other animals. In this paper, a numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a loosely coiled rectangular duct of large aspect ratio. Numerical calculations are carried out by using a spectral method, and covering a wide range of the Dean number, Dn, for two types of curvatures of the duct. The main concern of the present study is to find out effects of curvature as well as formation of secondary vortices on unsteady solutions whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if Dn is increased. Time evolution calculations as well as their phase spaces are performed with a view to study the non-linear behavior of the unsteady solutions, and it is found that the steady-state flow turns into chaotic flow through various flow instabilities, if Dn is increased no matter what the curvature is. It is found that the unsteady flow is a steady-state solution for small Dn’s and oscillates periodically or non-periodically (chaotic) between two- and twelve-vortex solutions, if Dn is increased. It is also found that the chaotic solution is weak for small Dn’s but strong as Dn becomes large. Axial flow distribution is also investigated and shown in contour plots.

On the onset of secondary flow and unsteady solutions through a loosely coiled rectangular duct for large aspect ratio

International Nuclear Information System (INIS)

Shaha, Poly Rani; Poddar, Nayan Kumar; Mondal, Rabindra Nath; Rudro, Sajal Kanti

2016-01-01

The study of flows through coiled ducts and channels has attracted considerable attention not only because of their ample applications in Chemical, Mechanical, Civil, Nuclear and Biomechanical engineering but also because of their ample applications in other areas, such as blood flow in the veins and arteries of human and other animals. In this paper, a numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a loosely coiled rectangular duct of large aspect ratio. Numerical calculations are carried out by using a spectral method, and covering a wide range of the Dean number, Dn, for two types of curvatures of the duct. The main concern of the present study is to find out effects of curvature as well as formation of secondary vortices on unsteady solutions whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if Dn is increased. Time evolution calculations as well as their phase spaces are performed with a view to study the non-linear behavior of the unsteady solutions, and it is found that the steady-state flow turns into chaotic flow through various flow instabilities, if Dn is increased no matter what the curvature is. It is found that the unsteady flow is a steady-state solution for small Dn’s and oscillates periodically or non-periodically (chaotic) between two- and twelve-vortex solutions, if Dn is increased. It is also found that the chaotic solution is weak for small Dn’s but strong as Dn becomes large. Axial flow distribution is also investigated and shown in contour plots.

ACS Zero Point Verification

Science.gov (United States)

Dolphin, Andrew

2005-07-01

The uncertainties in the photometric zero points create a fundamental limit to the accuracy of photometry. The current state of the ACS calibration is surprisingly poor, with zero point uncertainties of 0.03 magnitudes. The reason for this is that the ACS calibrations are based primarily on semi-emprical synthetic zero points and observations of fields too crowded for accurate ground-based photometry. I propose to remedy this problem by obtaining ACS images of the omega Cen standard field with all nine broadband ACS/WFC filters. This will permit the direct determination of the ACS zero points by comparison with excellent ground-based photometry, and should reduce their uncertainties to less than 0.01 magnitudes. A second benefit is that it will facilitate the comparison of the WFPC2 and ACS photometric systems, which will be important as WFPC2 is phased out and ACS becomes HST's primary imager. Finally, three of the filters will be repeated from my Cycle 12 observations, allowing for a measurement of any change in sensitivity.

Zero-point oscillations, zero-point fluctuations, and fluctuations of zero-point oscillations

International Nuclear Information System (INIS)

Khalili, Farit Ya

2003-01-01

Several physical effects and methodological issues relating to the ground state of an oscillator are considered. Even in the simplest case of an ideal lossless harmonic oscillator, its ground state exhibits properties that are unusual from the classical point of view. In particular, the mean value of the product of two non-negative observables, kinetic and potential energies, is negative in the ground state. It is shown that semiclassical and rigorous quantum approaches yield substantially different results for the ground state energy fluctuations of an oscillator with finite losses. The dependence of zero-point fluctuations on the boundary conditions is considered. Using this dependence, it is possible to transmit information without emitting electromagnetic quanta. Fluctuations of electromagnetic pressure of zero-point oscillations are analyzed, and the corresponding mechanical friction is considered. This friction can be viewed as the most fundamental mechanism limiting the quality factor of mechanical oscillators. Observation of these effects exceeds the possibilities of contemporary experimental physics but almost undoubtedly will be possible in the near future. (methodological notes)

Reduction and Immobilization of Radionuclides and Toxic Metal Ions Using Combined Zero Valent Iron and Anaerobic Bacteria; FINAL

International Nuclear Information System (INIS)

Lenly J. Weathers; Lynn E. Katz

2002-01-01

The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. AN exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes are functional. This work evaluated the hypothesis that a system combining a mixed culture of sulfate reducing bacteria (SRB) with zero valent iron would have a greater cr(VI) removal efficiency and a greater total Cr(VI) removal capacity than a zero valent iron system without the microorganisms. Hence, the overall goal of this research was to compare the performance of these types of systems with regard to their Cr(VI) removal efficiency and total Cr(VI) removal capacity. Both batch and continuous flow reactor systems were evaluated

Effect of non-condensable gas on heat transfer in steam turbine condenser and modelling of ejector pump system by controlling the gas extraction rate through extraction tubes

International Nuclear Information System (INIS)

Strušnik, Dušan; Golob, Marjan; Avsec, Jurij

2016-01-01

Graphical abstract: Control of the amount of the pumped gases through extraction tubes. The connecting locations interconnect the extraction tubes for STC gas pumping. The extraction tubes are fitted with 3 control valves to control the amount of the pumped gas depending on the temperature of the pumped gas. The amount of the pumped gas increases through the extraction tubes, where the pumped gases are cooler and decreases, at the same time, through the extraction tubes, where the pumped gases are warmer. As a result, pumping of a larger amount of NCG is ensured and of a smaller amount of CG, given that the NCG concentration is the highest on the colder places. This way, the total amount of the pumped gases from the STC can be reduced, the SEPS operates more efficiently and consumes less energy for its operation. - Highlights: • Impact of non-condensable gas on heat transfer in a steam turbine condenser. • The ejector system is optimised by selecting a Laval nozzle diameter. • Simulation model of the control of the amount of pumped gases through extraction tubes. • Neural network and fuzzy logic systems used to control gas extraction rate. • Simulation model was designed by using real process data from the thermal power plant. - Abstract: The paper describes the impact of non-condensable gas (NCG) on heat transfer in a steam turbine condenser (STC) and modelling of the steam ejector pump system (SEPS) by controlling the gas extraction rate through extraction tubes. The ideal connection points for the NCG extraction from the STC are identified by analysing the impact of the NCG on the heat transfer and measuring the existing system at a thermal power plant in Slovenia. A simulation model is designed using the Matlab software and Simulink, Neural Net Work, Fuzzy Logic and Curve Fitting Toolboxes, to control gas extraction rate through extraction tubes of the gas pumped from the STC, thus optimising the operation of the steam ejector pump system (SEPS). The

Resolution function normalisation and secondary extinction in neutron triple-axis spectrometry

International Nuclear Information System (INIS)

Tindle, G.L.

1987-01-01

The theory of resolution correction in triple-axis spectrometry is developed from first principles. It is demonstrated that for ideally imperfect thin crystals the formulation coincides with that introduced initially by Cooper and Nathans and subsequently considered by Dorner. The predicted energy variation of peak Bragg reflectivities of monochromator and analyser crystals in Bragg case scattering is such as to confirm experimental data. In the Laue case to obtain results compatible with experiment one has to invoke theories of secondary extinction. In an attempt to accommodate these observations a new finite threshold model of secondary extinction is proposed which interpolates thin crystals formulas and conventional secondary extinction formulas obtained in the zero threshold limit. (orig.)

40 CFR Table 3 to Subpart Uuu of... - Continous Monitoring Systems for Metal HAP Emissions From Catalytic Cracking Units

Science.gov (United States)

2010-07-01

... scrubbing liquor) flow rate to the control device. (2) If you use a wet scrubber of the non-venturi jet... liquor) flow rate to the control device. (2) If you use a wet scrubber of the non-venturi jet-ejector... size Electrostatic precipitator or wet scrubber or no control device Continuous opacity monitoring...

Zero expression of arguments in Old Danish

DEFF Research Database (Denmark)

Heltoft, Lars

2014-01-01

arguments in Scanic are semantically different from pronouns, and therefore pronouns and zero arguments are not variants. At one level, zero arguments and pronouns are similar with respect to function, namely to supply means for establishing co-reference in text; however, they are not semantically...... equivalent. By reducing these two categories to one single underlying category, such as pro, one would miss this point. On the contrary, zero arguments are arguably full-bodied signs with their own content, thus corresponding to Melčuk’s Zero Sign Introduction Principle.......Old Scandinavian (represented here by Old Danish) allowed zero arguments (null-arguments) in any nominal (argument) position, that is: for NPs as subjects, objects and in PPs. In generative grammar, zero arguments are held to be variants of pronouns, but in this article, I shall claim that zero...

Minimizing secondary coolant blowdown in HANARO

International Nuclear Information System (INIS)

Park, Y. C.; Woo, J. S.; Ryu, J. S.; Cho, Y. G.; Lim, N. Y.

2000-01-01

There is about 80m 3 /h loss of the secondary cooling water by evaporation, windage and blowdown during the operation of HANARO, 30MW research reactor. The evaporation and the windage is necessary loss to maintain the performance of cooling tower, but the blowdown is artificial lose to get rid of the foreign material and to maintain the quality of the secondary cooling water. Therefore, minimizing the blowdown loss was studied. It was confirmed, through the relation of the number of cycle and the loss rate of secondary coolant, that the number of cycle is saturated to 12 without blowdown because of the windage loss. When the secondary coolant is treated by high Ca-hardness treatment program (the number of cycle > 10) to maintain the number of cycle around 12 without blowdown, only the turbidity exceeds the limit. By adding filtering system it was confirmed, through the relation of turbidity and filtering rate of secondary cooling water, that the turbidity is reduced below the limit (5 deg.) by 2% of filtering rate without blowdown. And it was verified, through the performance test of back-flow filtering unit, that this unit gets rid of foreign material up to 95% of the back-flow and that the water can be reused as coolant. Therefore, the secondary cooling water can be treated by the high Ca-hardness program and filter system without blowdown

Uncertainty analysis for secondary energy distributions

International Nuclear Information System (INIS)

Gerstl, S.A.W.

1978-01-01

In many transport calculations the integral design parameter of interest (response) is determined mainly by secondary particles such as gamma rays from (n,γ) reactions or secondary neutrons from inelastic scattering events or (n,2n) reactions. Standard sensitivity analysis usually allows to calculate the sensitivities to the production cross sections of such secondaries, but an extended formalism is needed to also obtain the sensitivities to the energy distribution of the generated secondary particles. For a 30-group standard cross-section set 84% of all non-zero table positions pertain to the description of secondary energy distributions (SED's) and only 16% to the actual reaction cross sections. Therefore, any sensitivity/uncertainty analysis which does not consider the effects of SED's is incomplete and neglects most of the input data. This paper describes the methods of how sensitivity profiles for SED's are obtained and used to estimate the uncertainty of an integral response due to uncertainties in these SED's. The detailed theory is documented elsewhere and implemented in the LASL sensitivity code SENSIT. SED sensitivity profiles have proven particularly valuable in cross-section uncertainty analyses for fusion reactors. Even when the production cross sections for secondary neutrons were assumed to be without error, the uncertainties in the energy distribution of these secondaries produced appreciable uncertainties in the calculated tritium breeding rate. However, complete error files for SED's are presently nonexistent. Therefore, methods will be described that allow rough error estimates due to estimated SED uncertainties based on integral SED sensitivities

Investigative Research on the Effect of Zero-Mass Jets on the Base Drag of Axisymmatric Bodies at Sunersonic Speeds

National Research Council Canada - National Science Library

Fasel, Hermann

2000-01-01

... out. For low subsonic Mach numbers, we have found that zero-mass jets that are generated by high-frequency forcing can have a significant effect on the flow structures that develop downstream of the base...

Reversed Extension Flow of Polymer melts

DEFF Research Database (Denmark)

Rasmussen, Henrik K.; Nielsen, Jens Kromann

2007-01-01

The measurement of the startup of uni axial elongational flow (potentially until steady state) followed by reversed bi axial flow, both with a constant elongational rate was made possible using a Filament Stretching Rheometer (FSR). The filament stretching rheometer rheometer is surrounded...... by a thermostated environment and allows measurements on polymeric melts and liquids from room temperatures until 200 °C. In the experiments the Hencky strain at which the stress becomes zero (the recovery strain) of the reversed flow can be identified....

A New Flow Control Technique Using Diluted Epinephrine in the N-butyl-2-cyanoacrylate Embolization of Visceral Artery Pseudoaneurysms Secondary to Chronic Pancreatitis

Energy Technology Data Exchange (ETDEWEB)

Morishita, Hiroyuki, E-mail: hmorif@koto.kpu-m.ac.jp [Japan Red Cross Kyoto Daiichi Hospital, Department of Diagnostic Radiology (Japan); Yamagami, Takuji [Kyoto Prefectural University of Medicine, Department of Radiology, Graduate School of Medical Science (Japan); Takeuchi, Yoshito [National Cancer Center, Division of Diagnostic Radiology (Japan); Matsumoto, Tomohiro; Asai, Shunsuke; Masui, Koji [Japan Red Cross Kyoto Daiichi Hospital, Department of Diagnostic Radiology (Japan); Sato, Hideki [Japan Red Cross Kyoto Daiichi Hospital, Department of Gastroenterology (Japan); Taniguchi, Fumihiro [Japan Red Cross Kyoto Daiichi Hospital, Department of Surgery (Japan); Sato, Osamu [Japan Red Cross Kyoto Daiichi Hospital, Department of Diagnostic Radiology (Japan); Nishimura, Tsunehiko [Kyoto Prefectural University of Medicine, Department of Radiology, Graduate School of Medical Science (Japan)

2012-08-15

Although n-butyl-2-cyanoacrylate (NBCA) has been used as an effective liquid embolization material, its indication for pseudoaneurysms has seemingly been limited because of the technical difficulties of using NBCA, such as reflux to the parent artery and causing significant infarction. Thus, considerable skill in using NBCA or a device to control blood flow during its polymerization is required to achieve embolization without severe complications. We report our new technique for controlling blood flow using diluted epinephrine in transcatheter arterial NBCA embolization of five pseudoaneurysms in four cases secondary to hemosuccus pancreaticus.

Local expansion flows of galaxies: quantifying acceleration effect of dark energy

Science.gov (United States)

Chernin, A. D.; Teerikorpi, P.

2013-08-01

The nearest expansion flow of galaxies observed around the Local group is studied as an archetypical example of the newly discovered local expansion flows around groups and clusters of galaxies in the nearby Universe. The flow is accelerating due to the antigravity produced by the universal dark energy background. We introduce a new acceleration measure of the flow which is the dimensionless ``acceleration parameter" Q (x) = x - x-2 depending on the normalized distance x only. The parameter is zero at the zero-gravity distance x = 1, and Q(x) ∝ x, when x ≫ 1. At the distance x = 3, the parameter Q = 2.9. Since the expansion flows have a self-similar structure in normalized variables, we expect that the result is valid as well for all the other expansion flows around groups and clusters of galaxies on the spatial scales from ˜ 1 to ˜ 10 Mpc everywhere in the Universe.

Quantitative analysis of the aqueductal CSF flow dynamics with FLASH sequence

International Nuclear Information System (INIS)

Seki, Kouji; Tsuji, Shoji; Yuasa, Tatsuhiko; Miyatake, Tadashi.

1993-01-01

Aqueductal cerebrospinal fluid (CSF) flow image and its dynamics were analyzed with 1.5 T MR system using ECG-gated Fast Low Flip Angle Shot (FLASH). High flip angle (90 degree) and short echo time (10 ms) were applicated. Seventeen ECG gated nine images were obtained in one cardiac cycle from the inferior midbrain. Axial imaging plane (across at 60 degree to the aqueduct) and 6 mm of slice thickness is available. The CSF flow velocity was estimated by a standard curve of signal intensity ratio, obtained by the running water in model tubes. Examinations of five normal subjects (male/female=2/3, 48.4±15 years old) were performed. The aqueductal flow signal had two peaks in one cardiac cycle. The latter oval signals within the diastolic phase represent the caudal (downward) CSF flow, and the former wedge shaped signals represent the cephalad (reverse) flow. The peak velocity of the caudal CSF flow is about 6.5 mm/s, the cephalad flow is about 4.5 mm/s. We defined two zero points of the to-and-fro curve as turning points, the first (caudal to cephalad) zero point as the 'first turning point', the second (cephalad to caudal) zero point as the 'second turning point'. In normal subjects, the first turning points are at 236±28 ms (±SD), the second turning points are at 723±67 ms (±SD) after ECG R wave. This new method is highly useful for the analyzing disorders with CSF flow abnormalities. (author)

Secondary fuel delivery system

Science.gov (United States)

Parker, David M.; Cai, Weidong; Garan, Daniel W.; Harris, Arthur J.

2010-02-23

A secondary fuel delivery system for delivering a secondary stream of fuel and/or diluent to a secondary combustion zone located in the transition piece of a combustion engine, downstream of the engine primary combustion region is disclosed. The system includes a manifold formed integral to, and surrounding a portion of, the transition piece, a manifold inlet port, and a collection of injection nozzles. A flowsleeve augments fuel/diluent flow velocity and improves the system cooling effectiveness. Passive cooling elements, including effusion cooling holes located within the transition boundary and thermal-stress-dissipating gaps that resist thermal stress accumulation, provide supplemental heat dissipation in key areas. The system delivers a secondary fuel/diluent mixture to a secondary combustion zone located along the length of the transition piece, while reducing the impact of elevated vibration levels found within the transition piece and avoiding the heat dissipation difficulties often associated with traditional vibration reduction methods.

Feasibility Study on Nano-structured Coatings to Mitigate Flow-accelerated Corrosion in Secondary System of Nuclear Power Plants

Energy Technology Data Exchange (ETDEWEB)

Kim, Seunghyun; Kim, Jeong Won; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Banyeon-ri, Eonyang-eup, Ulju-gun, Ulsan (Korea, Republic of)

2015-05-15

There have been many efforts to mitigate FAC through the adoption of the advanced and modified water chemistries such as optimized dissolved oxygen (DO) concentration and temperature. However, these mitigation techniques pose certain challenges relating to the compatibility of new water chemistries with the steam generator, the thermal efficiency of the secondary side, etc. In this context, nano-particle reinforced electroless nickel plating (NP ENP) could help solve the FAC issues in secondary pipe systems. This does not require modification of water chemistry or structural materials, and hence, its application is reasonable and time-saving compared to previous FAC mitigation techniques. The main parameters of FAC are known as electrochemical reaction at the interface, dissolution of magnetite and ferrous ions due to concentration gradient between carbon steels and water and wear due to a fast-flowing fluid. High-temperature corrosion characteristics of the both coatings have potential as FAC barrier for carbon steel. Feasibility study will be carried out with FAC simulation experiments.

A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

Energy Technology Data Exchange (ETDEWEB)

Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

1998-12-31

This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

A study on the instability criterion for the stratified flow in horizontal pipe at cocurrent flow conditions

Energy Technology Data Exchange (ETDEWEB)

Sung, Chang Kyung [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

1997-12-31

This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow. Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al. [1] experimental data of pipes, it is shown that they are in good agreement with data. 4 refs., 2 figs. (Author)

A variational EM method for pole-zero modeling of speech with mixed block sparse and Gaussian excitation

DEFF Research Database (Denmark)

Shi, Liming; Nielsen, Jesper Kjær; Jensen, Jesper Rindom

2017-01-01

The modeling of speech can be used for speech synthesis and speech recognition. We present a speech analysis method based on pole-zero modeling of speech with mixed block sparse and Gaussian excitation. By using a pole-zero model, instead of the all-pole model, a better spectral fitting can...... be expected. Moreover, motivated by the block sparse glottal flow excitation during voiced speech and the white noise excitation for unvoiced speech, we model the excitation sequence as a combination of block sparse signals and white noise. A variational EM (VEM) method is proposed for estimating...... in reconstructing of the block sparse excitation....

Logic circuits from zero forcing.

Science.gov (United States)

Burgarth, Daniel; Giovannetti, Vittorio; Hogben, Leslie; Severini, Simone; Young, Michael

We design logic circuits based on the notion of zero forcing on graphs; each gate of the circuits is a gadget in which zero forcing is performed. We show that such circuits can evaluate every monotone Boolean function. By using two vertices to encode each logical bit, we obtain universal computation. We also highlight a phenomenon of "back forcing" as a property of each function. Such a phenomenon occurs in a circuit when the input of gates which have been already used at a given time step is further modified by a computation actually performed at a later stage. Finally, we show that zero forcing can be also used to implement reversible computation. The model introduced here provides a potentially new tool in the analysis of Boolean functions, with particular attention to monotonicity. Moreover, in the light of applications of zero forcing in quantum mechanics, the link with Boolean functions may suggest a new directions in quantum control theory and in the study of engineered quantum spin systems. It is an open technical problem to verify whether there is a link between zero forcing and computation with contact circuits.

The LISA zero-signal solution

International Nuclear Information System (INIS)

Tinto, Massimo; Larson, Shane L

2005-01-01

We derive a time-delay interferometric (TDI) combination that has zero-response to a gravitational wave signal. This combination, which we have called the zero-signal solution, is a two-parameter family of linear combinations of the generators of the TDI space that has null gravitational wave response when its two parameters coincide with the values of the angles of the source location in the sky. Remarkably, the zero-signal solution does not rely on any assumptions about the gravitational waveform, and in fact it works for waveforms of any kind

Homogeneous purely buoyancy driven turbulent flow

Science.gov (United States)

Arakeri, Jaywant; Cholemari, Murali; Pawar, Shashikant

2010-11-01

An unstable density difference across a long vertical tube open at both ends leads to convection that is axially homogeneous with a linear density gradient. We report results from such tube convection experiments, with driving density caused by salt concentration difference or temperature difference. At high enough Rayleigh numbers (Ra) the convection is turbulent with zero mean flow and zero mean Reynolds shear stresses; thus turbulent production is purely by buoyancy. We observe different regimes of turbulent convection. At very high Ra the Nusselt number scales as the square root of the Rayleigh number, giving the so-called "ultimate regime" of convection predicted for Rayleigh-Benard convection in limit of infinite Ra. Turbulent convection at intermediate Ra, the Nusselt number scales as Ra^0.3. In both regimes, the flux and the Taylor scale Reynolds number are more than order of magnitude larger than those obtained in Rayleigh-Benard convection. Absence of a mean flow makes this an ideal flow to study shear free turbulence near a wall.

Zero point energy of renormalized Wilson loops

International Nuclear Information System (INIS)

Hidaka, Yoshimasa; Pisarski, Robert D.

2009-01-01

The quark-antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to the zero point energy vanishes in the Nambu model, but is nonzero when terms for extrinsic curvature are included. At one loop order, the nonperturbative contribution to the zero point energy is negative, regardless of the sign of the extrinsic curvature term.

Designing of zero energy office buildings in hot arid climate

Energy Technology Data Exchange (ETDEWEB)

Abdel-Gwad, Mohamed

2011-07-01

The designing of office buildings by using large glass areas to have a transparent building is an attractive approach in the modern office building architecture. This attitude increases the energy demand for cooling specially in the hot arid region which has long sun duration time, while the use of small glazing areas increases the energy demand for lighting. The use of uncontrolled natural ventilation increases the rate of hot ambient air flow which increases the building energy demand for cooling. At the same time, the use of mechanical ventilation to control the air change rate may increase the energy demand for fans. Some ideas such as low energy design concept are introduced for improving the building energy performance and different rating systems have been developed such as LEED, BREEAM and DGNB for evaluating building energy performance system. One of the new ideas for decreasing the dependence on fossil fuels and improving the use of renewable energy is the net zero-energy building concept in which the building generates enough renewable energy on site to equal or exceed its annual energy use. This work depends on using the potentials of mixing different energy strategies such as hybrid ventilation strategy, passive night cooling, passive chilled ceiling side by side with the integrating of photovoltaic modules into the building facade to produce energy and enrich the architectural aesthetics and finally reaching the Net Zero Energy Building. There are different definitions for zero energy buildings, however in this work the use of building-integrated Photovoltaic (BIPV) to provide the building with its annual energy needs is adopted, in order to reach to a Grid-Connected Net-Zero Energy Office Building in the hot arid desert zone represented by Cairo, Egypt. (orig.)

Improvements in or relating to pumps

Energy Technology Data Exchange (ETDEWEB)

Strong, R E; Boyle, K

1976-06-30

A pump is described that has what is termed a fluid diode in the inlet and outlet. Each such diode has non-moving parts and is operable to allow fluid to flow therethrough easily in one direction and to give restricted flow in the reverse direction. A suction leg is provided, connected to an ejector having a passage for compressed gas, and a valve is provided in the passage downstream of the ejector operable to open and close the passage periodically, thereby creating alternate negative and positive pumping pressures within the pump chamber. The valve may take the form of a solenoid valve and may include electrically linked means for sensing liquid levels. The pump is stated to be particularly attractive for plants in which it is desirable to avoid pump maintenance. Examples of its application includes the transfer of toxic and radioactive liquids. The exhaust from the ejector can be fed into a containment vessel from which it can be extracted through a normal venting system for plant handling such materials. It is also suitable for sludge pumping. The solenoid valve does not come into contact with the fluid being pumped, and can be located so that it is accessible for maintenance. Stainless steel is normally a convenient constructional material.

Pre-equilibrium Longitudinal Flow in the IP-Glasma Framework for Pb+Pb Collisions at the LHC

Science.gov (United States)

McDonald, Scott; Shen, Chun; Fillion-Gourdeau, François; Jeon, Sangyong; Gale, Charles

2017-08-01

In this work, we debut a new implementation of IP-Glasma and quantify the pre-equilibrium longitudinal flow in the IP-Glasma framework. The saturation physics based IP-Glasma model naturally provides a non-zero initial longitudinal flow through its pre-equilibrium Yang-Mills evolution. A hybrid IP-Glasma+MUSIC+UrQMD frame-work is employed to test this new implementation against experimental data and to make further predictions about hadronic flow observables in Pb+Pb collisions at 5.02 TeV. Finally, the non-zero pre-equilibrium longitudinal flow of the IP-Glasma model is quantified, and its origin is briefly discussed.

Turbulent flow in a partially filled pipe

Science.gov (United States)

Ng, Henry; Cregan, Hope; Dodds, Jonathan; Poole, Robert; Dennis, David

2017-11-01

Turbulent flow in a pressure driven pipe running partially full has been investigated using high-speed 2D-3C Stereoscopic Particle Imaging Velocimetry. With the field-of-view spanning the entire pipe cross section we are able to reconstruct the full three dimensional quasi-instantaneous flow field by invoking Taylor's hypothesis. The measurements were carried out over a range of flow depths at a constant Reynolds number based on hydraulic diameter and bulk velocity of Re = 32 , 000 . In agreement with previous studies, the ``velocity dip'' phenomenon, whereby the location of the maximum streamwise velocity occurs below the free surface was observed. A mean flow secondary current is observed near the free surface with each of the counter-rotating rollers filling the half-width of the pipe. Unlike fully turbulent flow in a rectangular open channel or pressurized square duct flow where the secondary flow cells appear in pairs about a corner bisector, the mean secondary motion observed here manifests only as a single pair of vortices mirrored about the pipe vertical centreline.

New approach to the suction force at the leading edge of a profile with zero thickness

NARCIS (Netherlands)

Sparenberg, JA; de Jager, EM

2004-01-01

This paper considers the suction force at the leading edge of a profile with zero thickness in an incompressible and inviscid fluid flow. The theory is linear, and the approach to the suction force is from the innerside of the profile. It is shown that the suction force can be considered as an

Enhancing Near Zero Volt Storage Tolerance of Lithium-ion Batteries

Science.gov (United States)

Crompton, Kyle R.

There are inherent safety risks associated with inactive lithium ion batteries leading to greater restrictions and regulations on shipping and storage. Maintaining all cells of a lithium ion battery at near zero voltage with an applied fixed resistive load is one promising approach which can lessen (and potentially eliminate) the risk of a lithium ion battery entering thermal runaway when in an inactive state. However, in a conventional lithium ion cell, a near zero cell voltage can be damaging if the anode electrochemical potential increases to greater than the potential where dissolution of the standard copper current collector occurs (i.e. 3.1 V vs. Li/Li+ at room temperature). Past approaches to yield lithium ion cells that are resilient to a near zero volt state of charge involve use of secondary active materials or alternative current collectors which have anticipated tradeoffs in terms of cell performance and cost. In the the present dissertation work the approach of managing the amount of reversible lithium in a cell during construction to prevent the anode potential from increasing to greater than 3.1 V vs. Li/Li+ during near zero volt storage is introduced. Anode pre-lithiation was used in LiCoO 2/MCMB pouch cells to appropriately manage the amount of reversible lithium so that there is excess reversible lithium compared to the cathodes intercalation capacity (reversible lithium excess cell or RLE cell). RLE LiCoO 2/MCMB cells maintained 99% of their original capacity after three, 3-day and three, 7-day storage periods at near zero volts under fixed load. A LiCoO2/MCMB pouch cell fabricated with a pre-lithiated anode also maintained its original discharge performance after three, 3-day storage periods under fixed load at 45°C. The strong recharge performance after near zero volt storage is attributed to the anode potential remaining below the copper dissolution potential during near zero volt storage as informed by reference electrode measurements. Pulse

The possibility of non-synchronism of convective secondaries in close binary stars

International Nuclear Information System (INIS)

Campbell, C.G.; Papaloizou, J.

1983-01-01

The non-synchronous velocity field is calculated for a low mass convective secondary in a close binary system, taking rotation into account. It is found that, contrary to previous belief, the velocity tends to zero as the L 1 point is approached. It is also found that the use of tidal lobes is inappropriate when the secondary is asynchronous. The action of a turbulent viscosity on the velocity field is considered and it is found that, when convection is inefficient, synchronization times can approach the lifetime of the system. (author)

Radioactivity release vs probability for a steam generator tube rupture accident

International Nuclear Information System (INIS)

Buslik, A.J.; Hall, R.E.

1978-01-01

A calculation of the probability of obtaining various radioactivity releases from a steam generator tube rupture (SGTR) is presented. The only radioactive isotopes considered are Iodine-131 and Xe-133. The particular accident path considered consists of a double-ended guillotine SGTR followed by loss of offsite power (LOSP). If there is no loss of offsite power, and no system fault other than the SGTR, it is judged that the consequences will be minimal, since the amount of iodine released through the condenser air ejector is expected to be quite small; this is a consequence of the fact that the concentration of iodine in the vapor released from the condenser air ejector is very small compared to that dissolved in the condensate water. In addition, in some plants the condenser air ejector flow is automatically diverted to containment or a high-activity alarm. The analysis presented here is for a typical Westinghouse PWR such as described in RESAR-3S

Properties of Zero-Free Transfer Function Matrices

Science.gov (United States)

D. O. Anderson, Brian; Deistler, Manfred

Transfer functions of linear, time-invariant finite-dimensional systems with more outputs than inputs, as arise in factor analysis (for example in econometrics), have, for state-variable descriptions with generic entries in the relevant matrices, no finite zeros. This paper gives a number of characterizations of such systems (and indeed square discrete-time systems with no zeros), using state-variable, impulse response, and matrix-fraction descriptions. Key properties include the ability to recover the input values at any time from a bounded interval of output values, without any knowledge of an initial state, and an ability to verify the no-zero property in terms of a property of the impulse response coefficient matrices. Results are particularized to cases where the transfer function matrix in question may or may not have a zero at infinity or a zero at zero.

Zero Point Energy of Renormalized Wilson Loops

OpenAIRE

Hidaka, Yoshimasa; Pisarski, Robert D.

2009-01-01

The quark antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to the zero point energy vanishes in the Nambu model, but is nonzero wh...

Resin bleed improvement on surface mount semiconductor device

Science.gov (United States)

Rajoo, Indra Kumar; Tahir, Suraya Mohd; Aziz, Faieza Abdul; Shamsul Anuar, Mohd

2018-04-01

Resin bleed is a transparent layer of epoxy compound which occurs during molding process but is difficult to be detected after the molding process. Resin bleed on the lead on the unit from the focused package, SOD123, can cause solderability failure at end customer. This failed unit from the customer will be considered as a customer complaint. Generally, the semiconductor company has to perform visual inspection after the plating process to detect resin bleed. Mold chase with excess hole, split cavity & stepped design ejector pin hole have been found to be the major root cause of resin bleed in this company. The modifications of the mold chase, changing of split cavity to solid cavity and re-design of the ejector pin proposed were derived after a detailed study & analysis conducted to arrive at these solutions. The solutions proposed have yield good results during the pilot run with zero (0) occurrence of resin bleed for 3 consecutive months.

Regularizing properties of Complex Monge-Amp\\`ere flows

OpenAIRE

Tô, Tat Dat

2016-01-01

We study the regularizing properties of complex Monge-Amp\\`ere flows on a K\\"ahler manifold $(X,\\omega)$ when the initial data are $\\omega$-psh functions with zero Lelong number at all points. We prove that the general Monge-Amp\\`ere flow has a solution which is immediately smooth. We also prove the uniqueness and stability of solution.

On the instability of convective flow in cylinder and possible secondary regimes

Energy Technology Data Exchange (ETDEWEB)

Bekezhanova, V B; Andreev, V K, E-mail: bekezhanova@mail.ru, E-mail: andr@icm.krasn.ru [Institute of Computational Modelling SB RAS, Akademgorodok, 50/44, Krasnoyarsk, Institute of Mathematics and Fundamental Informatics, Siberian Federal University, Svobodny, 79, Krasnoyarsk, 660041 (Russian Federation)

2014-08-01

A new exact solution of equations of free convection is constructed in the framework of the Oberbeck–Boussinesq approximation. The solution contains an independent parameter and describes the flow of a viscous heat-conducting liquid in the vertical cylinder with large radius. Complex rheology and radiative heating are taken into account. The considered problem reduces to the operator equation with strongly nonlinear operator. The solvability of the operator problem is proved. The iterative procedure for finding the free parameter is suggested. Three different classes of solution are obtained with the help of the procedure. The linear stability of all classes of solutions is studied numerically. Critical thermal mode is isolated. Evolution of oscillatory mode depending on Prandtl number is investigated. It is shown that under small Prandtl numbers oscillatory modes decay. If Prandtl numbers are not small a new instability type appears. This instability is connected with growing thermal disturbances. Another instability mechanism is discovered in the short waves domain. In this case the crisis is attributed to growing hydrodynamical disturbances. Secondary regimes arising in the hydrodynamical mechanism of the stability loss are calculated. (paper)

Flow induced vibration of secondary piping of LMFBR

International Nuclear Information System (INIS)

Gibert, R.J.; Axisa, F.

1977-01-01

This paper presents a method for evaluating the characteristics of vibrations caused by internal flow in three-dimensional piping systems conveying high density fluids. The excitation of the circuit is mainly caused by the flow singularities, and it is shown that the problem may be reduced to calculate the response of the circuit to an acoustical pressure discontinuity, localised at each flow singularity. The paper is divided into two main parts: First part is devoted to the theoretical formulation of the coupled acoustical-mechanical problem and to its numerical solution by the french computer code TEDEL. Second part describes an experimental test of the method. The tested piping system consists of a stainless steel tube circuit comprising four 909 bends, conveying water. Vibrations are excited by a half closed gate valve. Satisfactory results are obtained concerning both the frequencies of resonance of the circuit and the level of the vibrations observed

Application of Nano-Structured Coatings for Mitigation of Flow-Accelerated Corrosion in Secondary Pipe Systems of Nuclear Power Plants

Energy Technology Data Exchange (ETDEWEB)

Kim, Seung Hyun; Kim, Jong Jin; Yoo, Seung Chang; Huh, Jae Hoon; Kim, Ji Hyun [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

2014-05-15

Flow-accelerated corrosion (FAC) is a complex corrosion process combined with mechanical reaction with fluid. There were lots of research to mitigate FAC such as controlling temperature or water chemistry but in this research, we adopt active coating techniques especially nano-particle reinforced coatings. One of the general characteristics of FAC and its mitigation is that surface friction due to surface morphology makes a significant effect on FAC. Therefore to form a uniform coating layers, nano-particles including TiO2, SiC, Fe-Cr-W and Graphene were utilized. Those materials are known as greatly improve the corrosion resistance of substrates such as carbon steels but their effects on mitigation of FAC are not revealed clearly. Therefore in this research, the FAC resistive performance of nano-structured coatings were tested by electrochemical impedance spectroscopy (EIS) in room temperature 15 wt% sulfuric acid. As the flow-accelerated corrosion inhibitors in secondary piping system of nuclear power plants, various kinds of nano-structured coatings were prepared and tested in room-temperature electrochemical cells. SHS7740 with two types of Densifiers, electroless nickel plating with TiO2 are prepared. Electropolarization curves shows the outstanding corrosion mitigation performance of SHS7740 but EIS results shows the promising potential of Ni-P and Ni-P-TiO2 electroless nickel plating. For future work, high-temperature electrochemical analysis system will be constructed and in secondary water chemistry will be simulated.

A Secondary Flow Effect on the Heat and Mass Transfer Processes in the Finned Rod Bundles of Gas-cooled Reactors

Directory of Open Access Journals (Sweden)

A. A. Dunaitsev

2017-01-01

Full Text Available In nuclear power engineering a need to justify an operability of products and their components is of great importance. In high-temperature gas reactors, the critical element affecting the facility reliability is the fuel rod cladding, which in turn leads to the need to gain knowledge in the field of gas dynamics and heat transfer in the reactor core and to increase the detail of the calculation results. For the time being, calculations of reactor core are performed using the proven techniques of per-channel calculations, which show good representativeness and count rate. However, these techniques require additional experimental studies to describe correctly the inter-channel exchange, which, being taken into account, largely affects the pattern of the temperature fields in the region under consideration. Increasingly more relevant and demandable are numerical simulation methods of fluid and gas dynamics, as well as of heat exchange, which consist in the direct solution of the system of differential equations of mass balance, kinetic moment, and energy. Calculation of reactor cores or rod bundles according these techniques does not require additional experimental studies and allows us to obtain the local distributions of flow characteristics in the bundle and the flow characteristics that are hard to measure in the physical experiment.The article shows the calculation results and their analysis for an infinite rod lattice of the reactor core. The results were obtained by the technique of modelling one rod of a regular lattice using the periodic boundary conditions, followed by translating the results to the neighbouring rods. In channels of complex shape, there are secondary flows caused by changes in the channel geometry along the flow and directed across the main front of the flow. These secondary flows in the reactor cores with rods spaced by the winding wire lead to a redistribution of the coolant along the channel section, which in turn

More about unphysical zeroes in quark mass matrices

Energy Technology Data Exchange (ETDEWEB)

Emmanuel-Costa, David, E-mail: david.costa@tecnico.ulisboa.pt [Departamento de Física and Centro de Física Teórica de Partículas - CFTP, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa (Portugal); González Felipe, Ricardo, E-mail: ricardo.felipe@tecnico.ulisboa.pt [Departamento de Física and Centro de Física Teórica de Partículas - CFTP, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa (Portugal); ISEL - Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, Rua Conselheiro Emídio Navarro, 1959-007 Lisboa (Portugal)

2017-01-10

We look for all weak bases that lead to texture zeroes in the quark mass matrices and contain a minimal number of parameters in the framework of the standard model. Since there are ten physical observables, namely, six nonvanishing quark masses, three mixing angles and one CP phase, the maximum number of texture zeroes in both quark sectors is altogether nine. The nine zero entries can only be distributed between the up- and down-quark sectors in matrix pairs with six and three texture zeroes or five and four texture zeroes. In the weak basis where a quark mass matrix is nonsingular and has six zeroes in one sector, we find that there are 54 matrices with three zeroes in the other sector, obtainable through right-handed weak basis transformations. It is also found that all pairs composed of a nonsingular matrix with five zeroes and a nonsingular and nondecoupled matrix with four zeroes simply correspond to a weak basis choice. Without any further assumptions, none of these pairs of up- and down-quark mass matrices has physical content. It is shown that all non-weak-basis pairs of quark mass matrices that contain nine zeroes are not compatible with current experimental data. The particular case of the so-called nearest-neighbour-interaction pattern is also discussed.

Storage and transmission of secondary energy

International Nuclear Information System (INIS)

Taube, M.

1979-09-01

In the area of the total energy flow, possibilities and limits of shifts in time (storage) and in space (transfer) of secondary energy, i.e. electrical, chemical and thermal energy are examined and formulated. These shifts are linked to the qualitative conversions of secondary energy. The multiple technological possibilities, the spectrum of governing factors and the numerous technical and economical parameters show that only a complex optimization is possible. (Auth.)

Queijo gorgonzola fabricado com leite pasteurizado por ejetor de vapor e HTST: parâmetros físico-químicos e sensoriais Gorgonzola type cheese manufactured with milk pasteurized by the HTST and steam ejector systems: physic-chemical and sensory parameters

Directory of Open Access Journals (Sweden)

Cristiane Gattini Sbampato

2000-01-01

Full Text Available Este trabalho teve como objetivo avaliar a influência de dois sistemas de pasteurização (High Temperature Short Time ¾ HTST¾ e ejetor de vapor nas características físico-químicas e sensoriais do queijo tipo Gorgonzola. As coletas de amostras de queijo e análises foram realizadas aos 5, 25, 45, 65 e 85 dias de maturação. Durante o período de maturação ocorreu aumento gradual de pH, sal/umidade e índice de acidez nos dois tratamentos. Os queijos fabricados com leite pasteurizado pelo sistema HTST obtiveram valores médios de pH superiores aos dos queijos fabricados com leite pasteurizado pelo sistema ejetor de vapor; os queijos fabricados com leite pasteurizado pelo sistema ejetor de vapor, obtiveram teores de índice de acidez e metilcetonas superiores aos dos queijos fabricados com leite pasteurizado pelo sistema HTST, indicando maior atividade lipolítica nesses queijos. Pela análise sensorial realizada aos 65 dias de maturação, pode se observar que não houve diferença significativa entre os tratamentos em relação à aparência, cor, consistência, textura e sabor. Porém foi observada diferença significativa com relação ao desenvolvimento do mofo e aroma. Os queijos fabricados com leite pasteurizado pelo sistema ejetor de vapor apresentaram maior atividade lipolítica e massa mais macia e fechada.The objective of this work was to evaluate the influence of two pasteurization systems (HTST and steam ejector on the physic-chemical and sensory characteristics of Gorgonzola type cheese. Sampling and analysis were conducted at 5, 25, 45, 65 and 85 days of ripening. Along the maturation period, pH, acidity index, salt/humidity, gradually increased. Cheeses manufactured with milk pasteurized by the HTST system had average values of pH higher than those manufactured with milk pasteurized by the steam ejector system. Milk pasteurized by the steam ejector system produced cheeses with higher acidity index (lipolysis and

Characteristics of zero-absenteeism in hospital care.

Science.gov (United States)

Schreuder, J A H; Roelen, C A M; van der Klink, J J L; Groothoff, J W

2013-06-01

Literature on sickness presenteeism is emerging, but still little is known about employees who are never absent from work due to injuries or illness. Insight into the determinants and characteristics of such zero-absentees may provide clues for preventing sickness absence. To investigate the characteristics of zero-absentees, defined as employees without sickness absence over a period of 5 years. A mixed-method qualitative study comprising semi-structured interviews and focus groups for which Azjen and Fishbein's theory of planned behaviour was used as a framework. Zero-absentees working in hospital care were invited for semi-structured interviews until saturation was reached. The results of semi-structured interviews were validated in two focus groups. Of 1053 hospital employees, 47 were zero-absentees of whom 31 (66%) agreed to participate in the study. After 16 semi-structured interviews, no new insights or information were gathered from the interviews. The remaining 15 employees were invited to two (n = 8 and n = 7) focus groups. Personal attitudes and self-efficacy were more important in zero-absenteeism than social pressures of managers, colleagues or patients. Zero-absentees were found to be intrinsically motivated to try attending work when ill. In the present study population of hospital employees, we found indications that zero-absenteeism and sickness presenteeism might be different types of work attendance. Managers should realize that zero-absentees are driven by intrinsic motivation rather than social pressures to attend work.

Compact Mass Flow Meter Based on a Micro Coriolis Flow Sensor

Directory of Open Access Journals (Sweden)

Remco Wiegerink

2013-03-01

Full Text Available In this paper we demonstrate a compact ready-to-use micro Coriolis mass flow meter. The full scale flow is 1 g/h (for water at a pressure drop < 1 bar. It has a zero stability of 2 mg/h and an accuracy of 0.5% reading for both liquids and gases. The temperature drift between 10 and 50 °C is below 1 mg/h/°C. The meter is robust, has standard fluidic connections and can be read out by means of a PC or laptop via USB. Its performance was tested for several common gases (hydrogen, helium, nitrogen, argon and air and liquids (water and isopropanol. As in all Coriolis mass flow meters, the meter is also able to measure the actual density of the medium flowing through the tube. The sensitivity of the measured density is ~1 Hz.m3/kg.

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs

Science.gov (United States)

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2006-01-01

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.

ACS Photometric Zero Point Verification

Science.gov (United States)

Dolphin, Andrew

2003-07-01

The uncertainties in the photometric zero points create a fundamental limit to the accuracy of photometry. The current state of the ACS calibration is surprisingly poor, with zero point uncertainties of 0.03 magnitudes in the Johnson filters. The reason for this is that ACS observations of excellent ground-based standard fields, such as the omega Cen field used for WFPC2 calibrations, have not been obtained. Instead, the ACS photometric calibrations are based primarily on semi-emprical synthetic zero points and observations of fields too crowded for accurate ground-based photometry. I propose to remedy this problem by obtaining ACS broadband images of the omega Cen standard field with both the WFC and HRC. This will permit the direct determination of the ACS transformations, and is expected to double the accuracy to which the ACS zero points are known. A second benefit is that it will facilitate the comparison of the WFPC2 and ACS photometric systems, which will be important as WFPC2 is phased out and ACS becomes HST's primary imager.

Next generation Zero-Code control system UI

CERN Multimedia

CERN. Geneva

2017-01-01

Developing ergonomic user interfaces for control systems is challenging, especially during machine upgrade and commissioning where several small changes may suddenly be required. Zero-code systems, such as *Inspector*, provide agile features for creating and maintaining control system interfaces. More so, these next generation Zero-code systems bring simplicity and uniformity and brake the boundaries between Users and Developers. In this talk we present *Inspector*, a CERN made Zero-code application development system, and we introduce the major differences and advantages of using Zero-code control systems to develop operational UI.

Systems and methods for tracking a device in zero-infrastructure and zero-power conditions, and a tracking device therefor

KAUST Repository

Shamim, Atif

2017-03-23

Disclosed are embodiments for a tracking device having multiple layers of localization and communication capabilities, and particularly having the ability to operate in zero-infrastructure or zero-power conditions. Also disclosed are methods and systems that enhance location determination in zero-infrastructure and zero-power conditions. In one example, a device, system and/or method includes an infrastructure-based localization module, an infrastructure-less localization module and a passive module that can utilize at least two of the modules to determine a location of the tracking device.

Symmetry realization of texture zeros

International Nuclear Information System (INIS)

Grimus, W.; Joshipura, A.S.; Lavoura, L.; Tanimoto, M.

2004-01-01

We show that it is possible to enforce texture zeros in arbitrary entries of the fermion mass matrices by means of Abelian symmetries; in this way, many popular mass-matrix textures find a symmetry justification. We propose two alternative methods which allow one to place zeros in any number of elements of the mass matrices that one wants. They are applicable simultaneously in the quark and lepton sectors. They are also applicable in grand unified theories. The number of scalar fields required by our methods may be large; still, in many interesting cases this number can be reduced considerably. The larger the desired number of texture zeros is, the simpler are the models which reproduce the texture. (orig.)

Calorimetric and reactor coolant system flow uncertainty

International Nuclear Information System (INIS)

Bates, L.; McLean, T.

1991-01-01

This paper describes a methodology for the quantification of errors associated with the determination of a feedwater flow, secondary power, and Reactor Coolant System (RCS) flow used at the Trojan Nuclear Plant to ensure compliance with regulatory requirements. The sources of error in Plant indications and process measurement are identified and tracked, using examples, through the mathematical processes necessary to calculate the uncertainty in the RCS flow measurement. An error of approximately 1.4 percent is calculated for secondary power. This error results, along with the consideration of other errors, in an uncertainty of approximately 3 percent in the RCS flow determination

Reciprocity and its utilization in ultrasonic flow meters

Energy Technology Data Exchange (ETDEWEB)

Lunde, Per; Vestrheim, Magne; Boe, Reidar; Smoergrav, Skule; Abrahamsen, Atle K.

2005-07-01

In ultrasonic transit time flow meters for gas and liquid (USMs), the flow direction, the flow velocity and the sound velocity are estimated from the measured up- and downstream transit times. At no-flow conditions, the up- and downstream transit times of such meters should ideally be the same, or the difference should be negligible. This may not be the case unless special precautions are made. In order to reduce the possibility of the meter to detect a false flow at no-flow conditions, USMs are typically ''dry calibrated'' before being installed in the field. ''Dry calibration'' (which may be made in different ways), in general involves measurement of (a) the time delays due to electronics, cables and transducers, (b) the so called ''{delta}t-correction'' (for each acoustic path, also denoted ''zero flow offset factor''), and (c) geometrical parameters. Various {delta}t-correction approaches may be used by different manufacturers, but these are basically similar and have the same purpose: to reduce the false flow detection and improve the accuracy at low and no-flow conditions (''zero flow adjustment''), without significantly affecting the accuracy at the high velocity measurements. The AGA-9 report and the API MPMS Ch. 5.8 standard both prescribe need for ''zero flow verification test (zero test)'' or ''zeroing the meter'', for gas and liquid USMs, respectively. Advances in USM technology based on the electro acoustic reciprocity principle have provided methods for reduction or even neglect ion of the need for ''{delta} t-correction'' of USMs. That means, if the USM measurement system is reciprocal, and operated in a ''sufficiently reciprocal'' way, the ''{delta}t-correction'' may be negligibly small over the operational range of pressure and temperature, and

Performance of nanoscale zero-valent iron in nitrate reduction from water using a laboratory-scale continuous-flow system.

Science.gov (United States)

Khalil, Ahmed M E; Eljamal, Osama; Saha, Bidyut Baran; Matsunaga, Nobuhiro

2018-04-01

Nanoscale zero-valent iron (nZVI) is a versatile treatment reagent that should be utilized in an effective application for nitrate remediation in water. For this purpose, a laboratory-scale continuous-flow system (LSCFS) was developed to evaluate nZVI performance in removal of nitrate in different contaminated-water bodies. The equipment design (reactor, settler, and polisher) and operational parameters of the LSCFS were determined based on nZVI characterization and nitrate reduction kinetics. Ten experimental runs were conducted at different dosages (6, 10 and 20 g) of nZVI-based reagents (nZVI, bimetallic nZVI-Cu, CuCl 2 -added nZVI). Effluent concentrations of nitrogen and iron compounds were measured, and pH and ORP values were monitored. The major role exhibited by the recirculation process of unreacted nZVI from the settler to the reactor succeeded in achieving overall nitrate removal efficiency (RE) of >90%. The similar performance of both nZVI and copper-ions-modified nZVI in contaminated distilled water was an indication of LSCFS reliability in completely utilizing iron nanoparticles. In case of treating contaminated river water and simulated groundwater, the nitrate reduction process was sensitive towards the presence of interfering substances that dropped the overall RE drastically. However, the addition of copper ions during the treatment counteracted the retardation effect and greatly enhanced the nitrate RE. Copyright © 2018 Elsevier Ltd. All rights reserved.

Zero-Power Radio Device.

Energy Technology Data Exchange (ETDEWEB)

Brocato, Robert W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2018-02-01

This report describes an unpowered radio receiver capable of detecting and responding to weak signals transmit ted from comparatively long distances . This radio receiver offers key advantages over a short range zero - power radio receiver previously described in SAND2004 - 4610, A Zero - Power Radio Receiver . The device described here can be fabricated as an integrated circuit for use in portable wireless devices, as a wake - up circuit, or a s a stand - alone receiver operating in conjunction with identification decoders or other electroni cs. It builds on key sub - components developed at Sandia National Laboratories over many years. It uses surface acoustic wave (SAW) filter technology. It uses custom component design to enable the efficient use of small aperture antennas. This device uses a key component, the pyroelectric demodulator , covered by Sandia owned U.S. Patent 7397301, Pyroelectric Demodulating Detector [1] . This device is also described in Sandia owned U.S. Patent 97266446, Zero Power Receiver [2].

"Zeroing" in on mathematics in the monkey brain.

Science.gov (United States)

Beran, Michael J

2016-03-01

A new study documented that monkeys showed selective neuronal responding to the concept of zero during a numerical task, and that there were two distinct classes of neurons that coded the absence of stimuli either through a discrete activation pattern (zero or not zero) or a continuous one for which zero was integrated with other numerosities in the relative rate of activity. These data indicate that monkeys, like humans, have a concept of zero that is part of their analog number line but that also may have unique properties compared to other numerosities.

Flow Control in a Compact Inlet

Science.gov (United States)

Vaccaro, John C.

2011-12-01

An experimental investigation of flow control, via various control jets actuators, was undertaken to eliminate separation and secondary flows in a compact inlet. The compact inlet studied was highly aggressive with a length-to-diameter ratio of 1.5. A brand new facility was designed and built to enable various actuation methodologies as well as multiple measurement techniques. Techniques included static surface pressure, total pressure, and stereoscopic particle image velocimetry. Experimental data were supplemented with numerical simulations courtesy of Prof. Kenneth Jansen, Dr. Onkar Sahni, and Yi Chen. The baseline flow field was found to be dominated by two massive separations and secondary flow structures. These secondary structures were present at the aerodynamic interface plane in the form of two counter-rotating vortices inducing upwash along centerline. A dominant shedding frequency of 350 Hz was measured both at the aerodynamic interface plane and along the lower surface of the inlet. Flow control experiments started utilizing a pair of control jets placed in streamwise locations where flow was found to separate. Tests were performed for a range of inlet Mach numbers from 0.2 to 0.44. Steady and unsteady static pressure measurements along the upper and lower walls of the duct were performed for various combinations of actuation. The parameters that were tested include the control jets momentum coefficient, their blowing ratio, the actuation frequency, as well as different combinations of jets. It was shown that using mass flux ratio as a criterion to define flow control is not sufficient, and one needs to provide both the momentum coefficient and the blowing ratio to quantify the flow control performance. A detailed study was undertaken on controlling the upstream separation point for an inlet Mach number of 0.44. Similar to the baseline flow field, the flow field associated with the activation of a two-dimensional control jet actuator was dominated by

Flow and edge scour in current adjacent to stone covers

DEFF Research Database (Denmark)

Petersen, Thor U.; Sumer, B. Mutlu; Bøgelund, Jon

2015-01-01

This paper presents the results of an experimental investigation on edge scour adjacent to a stone cover laid on a sandy bed. The three-dimensional flow over the edge of the stone layer has been investigated by the use of particle image velocimetry. The flow measurements show a significant amount...... of turbulence in the primary flow near the junction between the stone layer and the sand bed and the formation of complex secondary-flow structures. The results show that the flow and the edge scour process in a steady current are governed by the size of the roughness elements and to some extent the side slope...... of the berm. The edge scour is caused by the combined action of the primary flow and the secondary flow. The primary flow stirs up the sediment and puts it into suspension, and the secondary flow carries it away from the junction between the stone layer and the sand bed, resulting in a scour hole forming...

Zero Tolerance: Advantages and Disadvantages. Research Brief

Science.gov (United States)

Walker, Karen

2009-01-01

What are the positives and negatives of zero tolerance? What should be considered when examining a school's program? Although there are no definitive definitions of zero tolerance, two commonly used ones are as follows: "Zero tolerance means that a school will automatically and severely punish a student for a variety of infractions" (American Bar…

Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors

Directory of Open Access Journals (Sweden)

Peter Busche

2012-10-01

Full Text Available A sensor concept for detection of boundary layer separation (flow separation, stall and reattachment on airfoils is introduced in this paper. Boundary layer separation and reattachment are phenomena of fluid mechanics showing characteristics of extinction and even inversion of the flow velocity on an overflowed surface. The flow sensor used in this work is able to measure the flow velocity in terms of direction and quantity at the sensor’s position and expected to determine those specific flow conditions. Therefore, an array of thermal flow sensors has been integrated (flush-mounted on an airfoil and placed in a wind tunnel for measurement. Sensor signals have been recorded at different wind speeds and angles of attack for different positions on the airfoil. The sensors used here are based on the change of temperature distribution on a membrane (calorimetric principle. Thermopiles are used as temperature sensors in this approach offering a baseline free sensor signal, which is favorable for measurements at zero flow. Measurement results show clear separation points (zero flow and even negative flow values (back flow for all sensor positions. In addition to standard silicon-based flow sensors, a polymer-based flexible approach has been tested showing similar results.

Topology of helical fluid flow

DEFF Research Database (Denmark)

Andersen, Morten; Brøns, Morten

2014-01-01

function for the topology of the streamline pattern in incompressible flows. On this basis, we perform a comprehensive study of the topology of the flow field generated by a helical vortex filament in an ideal fluid. The classical expression for the stream function obtained by Hardin (Hardin, J. C. 1982...... the zeroes of a single real function of one variable, and we show that three different flow topologies can occur, depending on a single dimensionless parameter. By including the self-induced velocity on the vortex filament by a localised induction approximation, the stream function is slightly modified...... and an extra parameter is introduced. In this setting two new flow topologies arise, but not more than two critical points occur for any combination of parameters....

Large-eddy simulation of flow over a grooved cylinder up to transcritical Reynolds numbers

KAUST Repository

Cheng, W.; Pullin, D. I.; Samtaney, Ravi

2017-01-01

for flow past a cylinder with different surface topographies is the result of a change in the global flow state generated by an interaction of primary flow separation with secondary flow recirculating motions that manifest as a mean-flow secondary bubble

Induced gravity and Planck zeros

International Nuclear Information System (INIS)

Khuri, N.N.

1982-01-01

Starting with an asymptotically free gauge theory with dynamical symmetry breaking and a mass hierarchy, we investigate the Adler-Zee formula for the induced gravitational constant. We study the two-point function psi(q 2 ), constructed with the trace of the energy-momentum tensor. First, we show that if the zeros of psi are at a mass scale significantly below the leading scale, then G/sub ind/ - 1 = 0 (m/sub zero/ 2 ) making it impossible to get a realistic G/sub ind/ from the Adler-Zee formula with low-mass zeros. Next we use the Jensen formula to derive a sum rule for Vertical Barm/sub zero/Vertical Bar. The analysis of this sum rule coupled with the result above leads to a dilemma with only one reasonable resolution. To get a realistic G/sub ind/ from the Adler-Zee formula, psi(q 2 ) must have a pair of complex-conjugate zeros at q 2 = M 0 2 +- 2iνM 0 , where M 0 is large and of the maximal scale and ν/M 0 - 1 . It gives a lower bound, which with our previously derived general upper bound gives [π 2 /4(ln10)288] C/sub psi/M 0 2 - 1 2 /288) C/sub psi/M 0 2 , where C/sub psi/ is the anomaly coefficient, a number easily determined by low-order perturbation theory for any group

Vortex diode jet

Science.gov (United States)

Houck, Edward D.

1994-01-01

A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

A novel approach for quantifying the zero-plane displacement of rough-wall boundary layers

Science.gov (United States)

Ferreira, Manuel; Rodriguez-Lopez, Eduardo; Ganapathisubramani, Bharath; Aerodynamics; Flight Mechanics Team

2017-11-01

Indirect methods of wall shear stress (WSS) estimation are frequently used to characterise rough wall boundary-layer flows. The zero-plane displacement, hypothesised to be the vertical location where it acts, is often treated as a fitting parameter. However, it would be preferrable to measure both these quantities directly, especially for surfaces with large roughness elements where established scaling and similarity laws may not hold. In this talk we present a novel floating element balance that is able to measure not only the WSS but also the wall normal location at which it acts. While allowing compensation for mild static pressure gradients by means of a first-order analytical model. Its architecture is based on a parallel-shift linkage and it's fitted with custom built force transducers and a data acquisition system especially designed to achieve high Signal-to-Noise Ratios (SNR). The smooth-wall boundary-layer flow is used as benchmark to assess the accuracy of this balance. The values of skin friction coefficient show an agreement with hot-wire anemometry to within 2 % at a local Reynolds number Reθ = 4 ×103 up to 104. A rough surface of regularly distributed large elements is used to investigate the ability to infer the zero-plane displacement.

Secondary instability and transition in three-dimensional boundary layers

Energy Technology Data Exchange (ETDEWEB)

Stolte, A.; Bertolotti, F.P.; Koch, W. (Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Goettingen (Germany). Inst. fuer Stroemungsmechanik)

1999-01-01

Stationary and traveling crossflow modes are the most prominent disturbances in the highly accelerated three-dimensional flow near the leading edge of a swept wing. Near transition onset, secondary three-dimensional instabilities of high frequency can be observed in such flows. A model flow on the basis of a DLR swept plate experiment allows a detailed study of transition scenarios triggered by crossflow instabilities, since the favorable pressure gradient over the whole plate inhibits instabilities of Tollmien-Schlichting type. In order to shed some light upon the role of the high-frequency secondary instabilities, the saturation characteristics of crossflow vortices in this model flow are investigated using the parabolized stability equations. In contrast to nonlinear equilibrium solutions of steady crossflow vortices, the nonlinear Polarized Stability Equations (PSE) results yield different maximal disturbance amplitudes for different initial amplitudes. (orig./AKF)

Secondary instability and transition in three-dimensional boundary layers

Energy Technology Data Exchange (ETDEWEB)

Stolte, A.; Bertolotti, F.P.; Koch, W. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Goettingen (Germany). Inst. fuer Stroemungsmechanik

1999-12-01

Stationary and traveling crossflow modes are the most prominent disturbances in the highly accelerated three-dimensional flow near the leading edge of a swept wing. Near transition onset, secondary three-dimensional instabilities of high frequency can be observed in such flows. A model flow on the basis of a DLR swept plate experiment allows a detailed study of transition scenarios triggered by crossflow instabilities, since the favorable pressure gradient over the whole plate inhibits instabilities of Tollmien-Schlichting type. In order to shed some light upon the role of the high-frequency secondary instabilities, the saturation characteristics of crossflow vortices in this model flow are investigated using the parabolized stability equations. In contrast to nonlinear equilibrium solutions of steady crossflow vortices, the nonlinear Polarized Stability Equations (PSE) results yield different maximal disturbance amplitudes for different initial amplitudes. (orig./AKF)

A screen-printed flexible flow sensor

International Nuclear Information System (INIS)

Moschos, A; Kaltsas, G; Syrovy, T; Syrova, L

2017-01-01

A thermal flow sensor was printed on a flexible plastic substrate using exclusively screen-printing techniques. The presented device was implemented with custom made screen-printed thermistors, which allows simple, cost-efficient production on a variety of flexible substrates while maintaining the typical advantages of thermal flow sensors. Evaluation was performed for both static (zero flow) and dynamic conditions using a combination of electrical measurements and IR imaging techniques in order to determine important characteristics, such as temperature response, output repeatability, etc. The flow sensor was characterized utilizing the hot-wire and calorimetric principles of operation, while the preliminary results appear to be very promising, since the sensor was successfully evaluated and displayed adequate sensitivity in a relatively wide flow range. (paper)

Zero forcing parameters and minimum rank problems

NARCIS (Netherlands)

Barioli, F.; Barrett, W.; Fallat, S.M.; Hall, H.T.; Hogben, L.; Shader, B.L.; Driessche, van den P.; Holst, van der H.

2010-01-01

The zero forcing number Z(G), which is the minimum number of vertices in a zero forcing set of a graph G, is used to study the maximum nullity/minimum rank of the family of symmetric matrices described by G. It is shown that for a connected graph of order at least two, no vertex is in every zero

Large zero-tension plate lysimeters for soil water and solute collection in undisturbed soils

Directory of Open Access Journals (Sweden)

A. Peters

2009-09-01

Full Text Available Water collection from undisturbed unsaturated soils to estimate in situ water and solute fluxes in the field is a challenge, in particular if soils are heterogeneous. Large sampling devices are required if preferential flow paths are present. We present a modular plate system that allows installation of large zero-tension lysimeter plates under undisturbed soils in the field. To investigate the influence of the lysimeter on the water flow field in the soil, a numerical 2-D simulation study was conducted for homogeneous soils with uni- and bimodal pore-size distributions and stochastic Miller-Miller heterogeneity. The collection efficiency was found to be highly dependent on the hydraulic functions, infiltration rate, and lysimeter size, and was furthermore affected by the degree of heterogeneity. In homogeneous soils with high saturated conductivities the devices perform poorly and even large lysimeters (width 250 cm can be bypassed by the soil water. Heterogeneities of soil hydraulic properties result into a network of flow channels that enhance the sampling efficiency of the lysimeter plates. Solute breakthrough into zero-tension lysimeter occurs slightly retarded as compared to the free soil, but concentrations in the collected water are similar to the mean flux concentration in the undisturbed soil. To validate the results from the numerical study, a dual tracer study with seven lysimeters of 1.25×1.25 m area was conducted in the field. Three lysimeters were installed underneath a 1.2 m filling of contaminated silty sand, the others deeper in the undisturbed soil. The lysimeters directly underneath the filled soil material collected water with a collection efficiency of 45%. The deeper lysimeters did not collect any water. The arrival of the tracers showed that almost all collected water came from preferential flow paths.

One Terminal Digital Algorithm for Adaptive Single Pole Auto-Reclosing Based on Zero Sequence Voltage

Directory of Open Access Journals (Sweden)

S. Jamali

2008-10-01

Full Text Available This paper presents an algorithm for adaptive determination of the dead timeduring transient arcing faults and blocking automatic reclosing during permanent faults onoverhead transmission lines. The discrimination between transient and permanent faults ismade by the zero sequence voltage measured at the relay point. If the fault is recognised asan arcing one, then the third harmonic of the zero sequence voltage is used to evaluate theextinction time of the secondary arc and to initiate reclosing signal. The significantadvantage of this algorithm is that it uses an adaptive threshold level and therefore itsperformance is independent of fault location, line parameters and the system operatingconditions. The proposed algorithm has been successfully tested under a variety of faultlocations and load angles on a 400KV overhead line using Electro-Magnetic TransientProgram (EMTP. The test results validate the algorithm ability in determining thesecondary arc extinction time during transient faults as well as blocking unsuccessfulautomatic reclosing during permanent faults.

Analysis of the VVER-440 reactor steam generator secondary side with the RELAP5/MOD3 code

International Nuclear Information System (INIS)

Tuunanen, J.

1993-01-01

Nuclear Engineering Laboratory of the Technical Research Centre of Finland has widely used RELAP5/MOD2 and -MOD3 codes to simulate horizontal steam generators. Several models have been developed and successfully used in the VVER-safety analysis. Nevertheless, the models developed have included only rather few nodes in the steam generator secondary side. The secondary side has normally been divided into about 10 to 15 nodes. Since the secondary side at the steam generators of VVER-440 type reactors consists of a rather large water pool, these models were only roughly capable to predict secondary side flows. The paper describes an attempt to use RELAP5/MOD3 code to predict secondary side flows in a steam generator of a VVER-440 reactor. A 2D/3D model has been developed using RELAP5/MOD3 codes cross-flow junctions. The model includes 90 volumes on the steam generator secondary side. The model has been used to calculate steady state flow conditions in the secondary side of a VVER-440 reactor steam generator. (orig.) (1 ref., 9 figs., 2 tabs.)

Applied thermodynamics of the real gas with respect to the thermodynamic zeros of the entropy and internal energy

International Nuclear Information System (INIS)

Elsner, Albrecht

2012-01-01

Gibbs's work on the thermodynamic properties of substances presented a complete thermodynamic theory. The formulations of the entropy S and internal energy U as extensive quantities allow the zeros of the real gas to be given: S=0 at absolute zero (Nernst, Planck) and U=0 at the critical point. Consequently, every thermodynamic function is unique and absolutely specified. Interdependences among quantities such as temperature, vapor pressure, chemical potential, volume, entropy, internal energy, and heat capacity are likewise unique and numerically well defined. This is shown for the saturated fluid, water, in the region between absolute zero and the critical point. As a consequence of the calculation of the chemical potential, it follows that the free particle flow in an inhomogeneous system is essentially governed by the difference in chemical potential, and not through the difference in pressure, this effect being of importance for meteorology and oceanography.

Finite element analysis of helical flows in human aortic arch: A novel index

OpenAIRE

Lee, Cheng-Hung; Liu, Kuo-Sheng; Jhong, Guan-Heng; Liu, Shih-Jung; Hsu, Ming-Yi; Wang, Chao-Jan; Hung, Kuo-Chun

2014-01-01

This study investigates the helical secondary flows in the aortic arch using finite element analysis. The relationship between helical flow and the configuration of the aorta in patients of whose three-dimensional images constructed from computed tomography scans was examined. A finite element model of the pressurized root, arch, and supra-aortic vessels was developed to simulate the pattern of helical secondary flows. Calculations indicate that most of the helical secondary flow was formed i...

Off-wall boundary conditions for turbulent flows obtained from buffer-layer minimal flow units

Science.gov (United States)

Garcia-Mayoral, Ricardo; Pierce, Brian; Wallace, James

2012-11-01

There is strong evidence that the transport processes in the buffer region of wall-bounded turbulence are common across various flow configurations, even in the embryonic turbulence in transition (Park et al., Phys. Fl. 24). We use this premise to develop off-wall boundary conditions for turbulent simulations. Boundary conditions are constructed from DNS databases using periodic minimal flow units and reduced order modeling. The DNS data was taken from a channel at Reτ = 400 and a zero-pressure gradient transitional boundary layer (Sayadi et al., submitted to J . FluidMech .) . Both types of boundary conditions were first tested on a DNS of the core of the channel flow with the aim of extending their application to LES and to spatially evolving flows. 2012 CTR Summer Program.

Zero-base budgeting and the library.

Science.gov (United States)

Sargent, C W

1978-01-01

This paper describes the application of zero-base budgeting to libraries and the procedures involved in setting up this type of budget. It describes the "decision packages" necessary when this systmem is employed, as well as how to rank the packages and the problems which are related to the process. Zero-base budgeting involves the entire staff of a library, and the incentive engendered makes for a better and more realistic budget. The paper concludes with the problems which one might encounter in zero-base budgeting and the major benefits of the system. PMID:626795

Experimental study of particle-driven secondary flow in turbulent pipe flows

NARCIS (Netherlands)

Belt, R.J.; Daalmans, A.C.L.M.; Portela, L.M.

2012-01-01

In fully developed single-phase turbulent flow in straight pipes, it is known that mean motions can occur in the plane of the pipe cross-section, when the cross-section is non-circular, or when the wall roughness is non-uniform around the circumference of a circular pipe. This phenomenon is known as

ALICE Zero Degree Calorimeter

CERN Multimedia

De Marco, N

2013-01-01

Two identical sets of calorimeters are located on both sides with respect to the beam Interaction Point (IP), 112.5 m away from it. Each set of detectors consists of a neutron (ZN) and a proton (ZP) Zero Degree Calorimeter (ZDC), positioned on remotely controlled platforms. The ZN is placed at zero degree with respect to the LHC beam axis, between the two beam pipes, while the ZP is positioned externally to the outgoing beam pipe. The spectator protons are separated from the ion beams by means of the dipole magnet D1.

Net Zero Energy Buildings

DEFF Research Database (Denmark)

Marszal, Anna Joanna; Bourrelle, Julien S.; Gustavsen, Arild

2010-01-01

and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...

Torsion effect on fully developed flow in a helical pipe

Science.gov (United States)

Kao, Hsiao C.

1987-01-01

Two techniques, a series expansion method of perturbed Poiseuille flow valid for low Dean numbers and a solution of the complete Navier-Stokes equation applicable to intermediate Dean values, are used to investigate the torsion effect on the fully developed laminar flow in a helical pipe of constant circular cross section. For the secondary flow patterns, the results show that the presence of torsion can produce a significant effect if the ratio of the curvature to the torsion is of order unity. The secondary flow is distorted in these cases. It is noted that the torsion effect is, however, usually small, and that the secondary flow has the usual pattern of a pair of counter-rotating vortices of nearly equal strength.

'Zero-time' detectors using microchannel plates for charged particle detection

International Nuclear Information System (INIS)

Girard, J.

1977-01-01

The mass identification of the reaction products detected in heavy ion nuclear reactions is generally obtained by the time-of-flight method. This method requires a device giving first the 'start' signal (zero time at the passage of the particle) and then the stop 'signal'. The interest lying in 'zero-time' detectors using a secondary electron emission has been considerably increased with using microchannel electron multipliers. Nevertheless such a device was shown to induce either fluctuations in the distance of flight or the use of detectors of different type in the 'start' and 'stop' channels respectively. In both cases, it remains an ambiguity as the access to time resolution, in the channel including the electron multiplier, is not direct and the effect of the different parameters on this resolution are masked. To palliate this drawback and study the qualities of microchannel plate multipliers in time measurement field, some devices mechanically and electronically symmetric have been developed. The resolution measurement in time of flight is obtained for electrons generated by the same particle and emitted from either side of a thin film. The distances of flight of the electrons on each side of the film are same, and so are the accelerating potentials. The microchannel electron multipliers and the processing electronic units are the same in each channel [fr

Transonic Performance Characteristics of Several Jet Noise Suppressors

Science.gov (United States)

Schmeer, James W.; Salters, Leland B., Jr.; Cassetti, Marlowe D.

1960-01-01

An investigation of the transonic performance characteristics of several noise-suppressor configurations has been conducted in the Langley 16-foot transonic tunnel. The models were tested statically and over a Mach number range from 0.70 to 1.05 at an angle of attack of 0 deg. The primary jet total-pressure ratio was varied from 1.0 (jet off) to about 4.5. The effect of secondary air flow on the performance of two of the configurations was investigated. A hydrogen peroxide turbojet-engine simulator was used to supply the hot-jet exhaust. An 8-lobe afterbody with centerbody, short shroud, and secondary air had the highest thrust-minus-drag coefficients of the six noise-suppressor configurations tested. The 12-tube and 12-lobe afterbodies had the lowest internal losses. The presence of an ejector shroud partially shields the external pressure distribution of the 8-lobe after-body from the influence of the primary jet. A ring-airfoil shroud increased the static thrust of the annular nozzle but generally decreased the thrust minus drag at transonic Mach numbers.

Transition from steady to periodic liquid-metal magnetohydrodynamic flow in a sliding electrical contact

Science.gov (United States)

Talmage, Gita; Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.

1993-09-01

In homopolar motors and generators, large dc electric currents pass through the sliding electrical contacts between rotating copper disks (rotors) and static copper surfaces shrouding the rotor tips (stators). A liquid metal in the small radial gap between the rotor tip and concentric stator surface can provide a low-resistance, low-drag electrical contact. Since there is a strong magnetic field in the region of the electrical contacts, there are large electromagnetic body forces on the liquid metal. The primary, azimuthal motion consists of simple Couette flow, plus an electromagnetically driven flow with large extremes of the azimuthal velocity near the rotor corners. The secondary flow involves the radial and axial velocity components, is driven by the centrifugal force associated with the primary flow, and is opposed by the electromagnetic body force, so that the circulation varies inversely as the square of the magnetic-field strength. Three flow regimes are identified as the angular velocity Ω of the rotor is increased. For small Ω, the primary flow is decoupled from the secondary flow. As Ω increases, the secondary flow begins to convect the azimuthal-velocity peaks radially outward, which in turn changes the centrifugal force driving the secondary flow. At some critical value of Ω, the flow becomes periodic through the coupling of the primary and secondary flows. The azimuthal-velocity peaks begin to move radially in and out with an accompanying oscillation in the secondary-flow strength.

Anatomy of zero-norm states in string theory

International Nuclear Information System (INIS)

Chan, C.-T.; Lee, J.-C.; Yi Yang

2005-01-01

We calculate and identify the counterparts of zero-norm states in the old covariant first quantized (OCFQ) spectrum of open bosonic string in two other quantization schemes of string theory, namely, the light-cone Del Giudice-Di Vecchia-Fubine zero-norm states and the off-shell Becchi-Rouet-Stora-Tyutin (BRST) zero-norm states (with ghost) in the Witten string field theory (WSFT). In particular, special attention is paid to the interparticle zero-norm states in all quantization schemes. For the case of the off-shell BRST zero-norm states, we impose the no-ghost conditions and recover exactly two types of on-shell zero-norm states in the OCFQ string spectrum for the first few low-lying mass levels. We then show that off-shell gauge transformations of WSFT are identical to the on-shell stringy gauge symmetries generated by two types of zero-norm states in the generalized massive σ-model approach of string theory. The high-energy limit of these stringy gauge symmetries was recently used to calculate the proportionality constants, conjectured by Gross, among high-energy scattering amplitudes of different string states. Based on these zero-norm state calculations, we have thus related gauge symmetry of WSFT to the high-energy stringy symmetry of Gross

Influence of Stationary Crossflow Modulation on Secondary Instability

Science.gov (United States)

Choudhari, Meelan M.; Li, Fei; Paredes, Pedro

2016-01-01

A likely scenario for swept wing transition on subsonic aircraft with natural laminar flow involves the breakdown of stationary crossflow vortices via high frequency secondary instability. A majority of the prior research on this secondary instability has focused on crossflow vortices with a single dominant spanwise wavelength. This paper investigates the effects of the spanwise modulation of stationary crossflow vortices at a specified wavelength by a subharmonic stationary mode. Secondary instability of the modulated crossflow pattern is studied using planar, partial-differential-equation based eigenvalue analysis. Computations reveal that weak modulation by the first subharmonic of the input stationary mode leads to mode splitting that is particularly obvious for Y-type secondary modes that are driven by the wall-normal shear of the basic state. Thus, for each Y mode corresponding to the fundamental wavelength of results in unmodulated train of crossflow vortices, the modulated flow supports a pair of secondary modes with somewhat different amplification rates. The mode splitting phenomenon suggests that a more complex stationary modulation such as that induced by natural surface roughness would yield a considerably richer spectrum of secondary instability modes. Even modest levels of subharmonic modulation are shown to have a strong effect on the overall amplification of secondary disturbances, particularly the Z-modes driven by the spanwise shear of the basic state. Preliminary computations related to the nonlinear breakdown of these secondary disturbances provide interesting insights into the process of crossflow transition in the presence of the first subharmonic of the dominant stationary vortex.

Geothermal heat exchanger with coaxial flow of fluids

Directory of Open Access Journals (Sweden)

Pejić Dragan M.

2005-01-01

Full Text Available The paper deals with a heat exchanger with coaxial flow. Two coaxial pipes of the secondary part were placed directly into a geothermal boring in such a way that geothermal water flows around the outer pipe. Starting from the energy balance of the exchanger formed in this way and the assumption of a study-state operating regime, a mathematical model was formulated. On the basis of the model, the secondary circle output temperature was determined as a function of the exchanger geometry, the coefficient of heat passing through the heat exchange areas, the average mass isobaric specific heats of fluid and mass flows. The input temperature of the exchanger secondary circle and the temperature of the geothermal water at the exit of the boring were taken as known values. Also, an analysis of changes in certain factors influencing the secondary water temperature was carried out. The parameters (flow temperature of the deep boring B-4 in Sijarinska Spa, Serbia were used. The theoretical results obtained indicate the great potential of this boring and the possible application of such an exchanger.

Comparison of secondary flows predicted by a viscous code and an inviscid code with experimental data for a turning duct

Science.gov (United States)

Schwab, J. R.; Povinelli, L. A.

1984-01-01

A comparison of the secondary flows computed by the viscous Kreskovsky-Briley-McDonald code and the inviscid Denton code with benchmark experimental data for turning duct is presented. The viscous code is a fully parabolized space-marching Navier-Stokes solver while the inviscid code is a time-marching Euler solver. The experimental data were collected by Taylor, Whitelaw, and Yianneskis with a laser Doppler velocimeter system in a 90 deg turning duct of square cross-section. The agreement between the viscous and inviscid computations was generally very good for the streamwise primary velocity and the radial secondary velocity, except at the walls, where slip conditions were specified for the inviscid code. The agreement between both the computations and the experimental data was not as close, especially at the 60.0 deg and 77.5 deg angular positions within the duct. This disagreement was attributed to incomplete modelling of the vortex development near the suction surface.