Volumetric expiratory high-resolution CT of the lung

International Nuclear Information System (INIS)

Nishino, Mizuki; Hatabu, Hiroto

2004-01-01

We developed a volumetric expiratory high-resolution CT (HRCT) protocol that provides combined inspiratory and expiratory volumetric imaging of the lung without increasing radiation exposure, and conducted a preliminary feasibility assessment of this protocol to evaluate diffuse lung disease with small airway abnormalities. The volumetric expiratory high-resolution CT increased the detectability of the conducting airway to the areas of air trapping (P<0.0001), and added significant information about extent and distribution of air trapping (P<0.0001)

Evaluation of the effect of temperature, concentration and volumetric flow in the hydrolysis of sucrose by an immobilized invertase in a spherical reactor

International Nuclear Information System (INIS)

Zamora Leiton, Maria Monserrath; Molina Cordoba, Manuel; Chacon Valle, Gerardo

2011-01-01

The effect of the volumetric flow, the temperature and the initial concentration of sucrose in the reaction of hydrolysis of sucrose by immobilized invertase were evaluated in the laboratory. Invertase was immobilized in 20 g of support of mesh size between 120 and 140. The maximum quantity of immobilized invertase obtained has been 0,130 mg/g of support at 220 min. The first experimental stage has consisted in the evaluation of the effect of the initial concentration of sucrose (1,0 and 1,5 mol/L), the volumetric flow (3,0 mL/min and 4,0 mL/min) and the temperature (45 degrees C and 50 degrees C). The effect of the above three variable has been statistically significant. The conversion has been favorable for a concentration of sucrose 1,0 mol/L, a volumetric flow of 3 mL/min and a temperature of 50 degrees C. The maximum conversion obtained has been 95,4 %. The second experimental stage has analyzed the effect of the initial concentration of sucrose (0,75 and 1,0 mol/L), the volumetric flow (2,5 mL/min and 3,0 mL/min) and the temperature (50 degrees C and 55 degrees C). The variable of volumetric flow and the interaction concentration of sucrose - temperature are found statistically significant. The conversion has been favorable for a volumetric flow of 2,5 mL/min, and it has been preferable to work at a temperature of 50 degrees C with an initial concentration of sucrose of 1,0 mol/L. The maximum conversion has been 94,8 %. The effect of the concentration was analyzed in the last experimental stage, it was found that the maximum conversion percentage was 95,0 % for a concentration of 1,1 mol/L, for a temperature of 50 degrees C and for a volumetric flow of 2,5 mL/min. (author) [es

Bridging PIV spatial and temporal resolution using governing equations and development of the coaxial volumetric velocimeter

NARCIS (Netherlands)

Schneiders, J.F.G.

2017-01-01

A series of techniques is proposed for volumetric air flow measurements that are based upon the principles of particle image velocimetry (PIV). The proposed techniques fall in two categories; part 1 of this dissertation considers measurement data processing using constitutive laws and part 2 focuses

Measurements of air entrainment by vertical plunging liquid jets

Science.gov (United States)

El Hammoumi, M.; Achard, J. L.; Davoust, L.

2002-06-01

This paper addresses the issue of the air-entrainment process by a vertical plunging liquid jet. A non-dimensional physical analysis, inspired by the literature on the stability of free jets submitted to an aerodynamic interaction, was developed and yielded two correlation equations for the laminar and the turbulent plunging jets. These correlation equations allow the volumetric flow rate of the air carryunder represented by the Weber number of entrainment We n to be predicted. The plunging jets under consideration issued from circular tubes long enough to achieve a fully developed flow at the outlet. A sensitive technique based on a rising soap meniscus was developed to measure directly the volumetric flow rate of the air carryunder. Our data are compared with other experimental data available in the literature; they also stand as a possible database for future theoretical modelling.

Measurements of air entrainment by vertical plunging liquid jets

Energy Technology Data Exchange (ETDEWEB)

El Hammoumi, M. [Faculte des Sciences et Techniques, Departement de Physique, Laboratoire de Mecanique Appliquee, Fes (Morocco); Achard, J.L.; Davoust, L. [Laboratoire des Ecoulements Geophysiques et Industriels (LEGI), Grenoble (France)

2002-06-01

This paper addresses the issue of the air-entrainment process by a vertical plunging liquid jet. A non-dimensional physical analysis, inspired by the literature on the stability of free jets submitted to an aerodynamic interaction, was developed and yielded two correlation equations for the laminar and the turbulent plunging jets. These correlation equations allow the volumetric flow rate of the air carryunder represented by the Weber number of entrainment We{sub n} to be predicted. The plunging jets under consideration issued from circular tubes long enough to achieve a fully developed flow at the outlet. A sensitive technique based on a rising soap meniscus was developed to measure directly the volumetric flow rate of the air carryunder. Our data are compared with other experimental data available in the literature; they also stand as a possible database for future theoretical modelling. (orig.)

Spatial distribution of bacterial communities on volumetric and planar anodes in single-chamber air-cathode microbial fuel cells

KAUST Repository

Vargas, Ignacio T.; Albert, Istvan U.; Regan, John M.

2013-01-01

Pyrosequencing was used to characterize bacterial communities in air-cathode microbial fuel cells across a volumetric (graphite fiber brush) and a planar (carbon cloth) anode, where different physical and chemical gradients would be expected

Determination of fan flow and water rate adjustment for off-design cooling tower tests

International Nuclear Information System (INIS)

Vance, J.M.

1984-02-01

The determination of the performance of a mechanical draft cooling tower requires that the air mass flow through the tower be known. Since this flow is not measured, it has been customary to use the manufacturer's design air flow and adjust it by the one-third power of the ratio of the design to test fan horsepower. The most nearly correct approximation of air flow through a tower can be obtained by incrementally moving through the tower from air inlet to outlet while calculating mass flows, energy balances, and pressure drops for each increment and then utilizing fan curves to determine volumetric and mass flows. This procedure would account for changes in air humidity and density through the tower, evaporation of water, effect of water rate on air pressure drop, and changes in fan characteristics. These type calculations may be within the capabilities of all in the near future, but for the interim, it is recommended that a more elementary approach be used which can be handled with a good calculator and without any proprietary data. This approach depends on certain assumptions which are acceptable if the tower test is conducted within CTI code requirements. The fan must be considered a constant suction volume blower for a given blade pitch. The total pressure at the fan, a function of volumetric flow and wet air density, must be assumed to be unaffected by other considerations, and the fan horsepower must be assumed to change only as volumetric flow and wet air density changes. Given these assumptions, along with design information normally provided with a tower, the determination of air flow through a tower in a test can be made from CTI test data. The air flow, and consequently the water rate adjustment and corrected water to air ratio, are derived and found to be direct functions of horsepower and density and an inverse function of wet air humidities

A new laboratory-scale experimental facility for detailed aerothermal characterizations of volumetric absorbers

Science.gov (United States)

Gomez-Garcia, Fabrisio; Santiago, Sergio; Luque, Salvador; Romero, Manuel; Gonzalez-Aguilar, Jose

2016-05-01

This paper describes a new modular laboratory-scale experimental facility that was designed to conduct detailed aerothermal characterizations of volumetric absorbers for use in concentrating solar power plants. Absorbers are generally considered to be the element with the highest potential for efficiency gains in solar thermal energy systems. The configu-ration of volumetric absorbers enables concentrated solar radiation to penetrate deep into their solid structure, where it is progressively absorbed, prior to being transferred by convection to a working fluid flowing through the structure. Current design trends towards higher absorber outlet temperatures have led to the use of complex intricate geometries in novel ceramic and metallic elements to maximize the temperature deep inside the structure (thus reducing thermal emission losses at the front surface and increasing efficiency). Although numerical models simulate the conjugate heat transfer mechanisms along volumetric absorbers, they lack, in many cases, the accuracy that is required for precise aerothermal validations. The present work aims to aid this objective by the design, development, commissioning and operation of a new experimental facility which consists of a 7 kWe (1.2 kWth) high flux solar simulator, a radiation homogenizer, inlet and outlet collector modules and a working section that can accommodate volumetric absorbers up to 80 mm × 80 mm in cross-sectional area. Experimental measurements conducted in the facility include absorber solid temperature distributions along its depth, inlet and outlet air temperatures, air mass flow rate and pressure drop, incident radiative heat flux, and overall thermal efficiency. In addition, two windows allow for the direct visualization of the front and rear absorber surfaces, thus enabling full-coverage surface temperature measurements by thermal imaging cameras. This paper presents the results from the aerothermal characterization of a siliconized silicon

Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density

International Nuclear Information System (INIS)

Kim, Song Soo; Seo, Joon Beom; Kim, Namkug; Chae, Eun Jin; Lee, Young Kyung; Oh, Yeon Mok; Lee, Sang Do

2014-01-01

Objectives: To determine the improvement of emphysema quantification with density correction and to determine the optimal site to use for air density correction on volumetric computed tomography (CT). Methods: Seventy-eight CT scans of COPD patients (GOLD II–IV, smoking history 39.2 ± 25.3 pack-years) were obtained from several single-vendor 16-MDCT scanners. After density measurement of aorta, tracheal- and external air, volumetric CT density correction was conducted (two reference values: air, −1000 HU/blood, +50 HU). Using in-house software, emphysema index (EI) and mean lung density (MLD) were calculated. Differences in air densities, MLD and EI prior to and after density correction were evaluated (paired t-test). Correlation between those parameters and FEV 1 and FEV 1 /FVC were compared (age- and sex adjusted partial correlation analysis). Results: Measured densities (HU) of tracheal- and external air differed significantly (−990 ± 14, −1016 ± 9, P < 0.001). MLD and EI on original CT data, after density correction using tracheal- and external air also differed significantly (MLD: −874.9 ± 27.6 vs. −882.3 ± 24.9 vs. −860.5 ± 26.6; EI: 16.8 ± 13.4 vs. 21.1 ± 14.5 vs. 9.7 ± 10.5, respectively, P < 0.001). The correlation coefficients between CT quantification indices and FEV 1 , and FEV 1 /FVC increased after density correction. The tracheal air correction showed better results than the external air correction. Conclusion: Density correction of volumetric CT data can improve correlations of emphysema quantification and PFT

Flow Characteristics of Ground Vehicle Wake and Its Response to Flow Control

Science.gov (United States)

Sellappan, Prabu; McNally, Jonathan; Alvi, Farrukh

2017-11-01

Air pollution, fuel shortages, and cost savings are some of the many incentives for improving the aerodynamics of vehicles. Reducing wake-induced aerodynamic drag, which is dependent on flow topology, on modern passenger vehicles is important for improving fuel consumption rates which directly affect the environment. In this research, an active flow control technique is applied on a generic ground vehicle, a 25°Ahmed model, to investigate its effect on the flow topology in the near-wake. The flow field of this canonical bluff body is extremely rich, with complex and unsteady flow features such as trailing wake vortices and c-pillar vortices. The spatio-temporal response of these flow features to the application of steady microjet actuators is investigated. The responses are characterized independently through time-resolved and volumetric velocity field measurements. The accuracy and cost of volumetric measurements in this complex flow field through Stereoscopic- and Tomographic- Particle Image Velocimetry (PIV) will also be commented upon. National Science Foundation PIRE Program.

Validation of the generalized model of two-phase thermosyphon loop based on experimental measurements of volumetric flow rate

Science.gov (United States)

Bieliński, Henryk

2016-09-01

The current paper presents the experimental validation of the generalized model of the two-phase thermosyphon loop. The generalized model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The theoretical analysis and the experimental data have been obtained for a new designed variant. The variant refers to a thermosyphon loop with both minichannels and conventional tubes. The thermosyphon loop consists of an evaporator on the lower vertical section and a condenser on the upper vertical section. The one-dimensional homogeneous and separated two-phase flow models were used in calculations. The latest minichannel heat transfer correlations available in literature were applied. A numerical analysis of the volumetric flow rate in the steady-state has been done. The experiment was conducted on a specially designed test apparatus. Ultrapure water was used as a working fluid. The results show that the theoretical predictions are in good agreement with the measured volumetric flow rate at steady-state.

Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density

Energy Technology Data Exchange (ETDEWEB)

Kim, Song Soo [Department of Radiology, Chungnam National University Hospital, Chungnam National University School of Medicine (Korea, Republic of); Seo, Joon Beom, E-mail: seojb@amc.seoul.kr [Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of); Kim, Namkug; Chae, Eun Jin [Department of Radiology, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of); Lee, Young Kyung [Department of Radiology, Kyung Hee University Hospital at Gangdong (Korea, Republic of); Oh, Yeon Mok; Lee, Sang Do [Division of Pulmonology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center (Korea, Republic of)

2014-01-15

Objectives: To determine the improvement of emphysema quantification with density correction and to determine the optimal site to use for air density correction on volumetric computed tomography (CT). Methods: Seventy-eight CT scans of COPD patients (GOLD II–IV, smoking history 39.2 ± 25.3 pack-years) were obtained from several single-vendor 16-MDCT scanners. After density measurement of aorta, tracheal- and external air, volumetric CT density correction was conducted (two reference values: air, −1000 HU/blood, +50 HU). Using in-house software, emphysema index (EI) and mean lung density (MLD) were calculated. Differences in air densities, MLD and EI prior to and after density correction were evaluated (paired t-test). Correlation between those parameters and FEV{sub 1} and FEV{sub 1}/FVC were compared (age- and sex adjusted partial correlation analysis). Results: Measured densities (HU) of tracheal- and external air differed significantly (−990 ± 14, −1016 ± 9, P < 0.001). MLD and EI on original CT data, after density correction using tracheal- and external air also differed significantly (MLD: −874.9 ± 27.6 vs. −882.3 ± 24.9 vs. −860.5 ± 26.6; EI: 16.8 ± 13.4 vs. 21.1 ± 14.5 vs. 9.7 ± 10.5, respectively, P < 0.001). The correlation coefficients between CT quantification indices and FEV{sub 1}, and FEV{sub 1}/FVC increased after density correction. The tracheal air correction showed better results than the external air correction. Conclusion: Density correction of volumetric CT data can improve correlations of emphysema quantification and PFT.

Optimization of recirculating laminar air flow in operating room air conditioning systems

Directory of Open Access Journals (Sweden)

Enver Yalcin

2016-04-01

Full Text Available The laminar flow air-conditioning system with 100% fresh air is used in almost all operating rooms without discrimination in Turkey. The laminar flow device which is working with 100% fresh air should be absolutely used in Type 1A operating rooms. However, there is not mandatory to use of 100% fresh air for Type 1B defined as places performed simpler operation. Compared with recirculating laminar flow, energy needs of the laminar flow with 100 % fresh air has been emerged about 40% more than re-circulated air flow. Therefore, when a recirculating laminar flow device is operated instead of laminar flow system with 100% fresh air in the Type 1B operating room, annual energy consumption will be reduced. In this study, in an operating room with recirculating laminar flow, optimal conditions have been investigated in order to obtain laminar flow form by analyzing velocity distributions at various supply velocities by using computational fluid dynamics method (CFD.

A Solar Volumetric Receiver: Influence of Absorbing Cells Configuration on Device Thermal Performance

Science.gov (United States)

Yilbas, B. S.; Shuja, S. Z.

2017-01-01

Thermal performance of a solar volumetric receiver incorporating the different cell geometric configurations is investigated. Triangular, hexagonal, and rectangular absorbing cells are incorporated in the analysis. The fluid volume fraction, which is the ratio of the volume of the working fluid over the total volume of solar volumetric receiver, is introduced to assess the effect of cell size on the heat transfer rates in the receiver. In this case, reducing the fluid volume fraction corresponds to increasing cell size in the receiver. SiC is considered as the cell material, and air is used as the working fluid in the receiver. The Lambert's Beer law is incorporated to account for the solar absorption in the receiver. A finite element method is used to solve the governing equation of flow and heat transfer. It is found that the fluid volume fraction has significant effect on the flow field in the solar volumetric receiver, which also modifies thermal field in the working fluid. The triangular absorbing cell gives rise to improved effectiveness of the receiver and then follows the hexagonal and rectangular cells. The second law efficiency of the receiver remains high when hexagonal cells are used. This occurs for the fluid volume fraction ratio of 0.5.

The measurement of low air flow velocities

NARCIS (Netherlands)

Aghaei, A.; Mao, X.G.; Zanden, van der A.J.J.; Schaik, W.H.J.; Hendriks, N.A.

2005-01-01

Air flow velocity is measured with an acoustic sensor, which can be used especially for measuring low air flow velocities as well as the temperature of the air simultaneously. Two opposite transducers send a sound pulse towards each other. From the difference of the transit times, the air flow

40 CFR 89.414 - Air flow measurement specifications.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Air flow measurement specifications... Emission Test Procedures § 89.414 Air flow measurement specifications. (a) The air flow measurement method... incorporates devices that affect the air flow measurement (such as air bleeds) that result in understated...

Augmentation of forced flow boiling heat transfer by introducing air flow into subcooled water flow

International Nuclear Information System (INIS)

Koizumi, Y.; Ohtake, H.; Yuasa, T.; Matsushita, N.

2001-01-01

The effect of air injection into a subcooled water flow on boiling heat transfer and a critical heat flux (CHF) was examined experimentally. Experiments were conducted in the range of subcooling of 50 K, a superficial velocity of water and air Ul = 0.17 ∼ 3.4 and Ug = 0 ∼ 15 m/s, respectively. A test heat transfer surface was a 5 mm wide, 40 mm long and 0.5 mm thick stainless steel sheet embedded on the bottom wall of a 10 mm high and 20 mm wide rectangular flow channel. Nine times enhancement of the heat transfer coefficient in the non-boiling region was attained at the most by introducing an air flow into a water single-phase flow. The heat transfer improvement was prominent when the water flow rate was low and the air introduction was large. The present results of the non-boiling heat transfer were well correlated with the Lockhart-Martinelli parameter X tt ; h TP /h L0 = 5.0(1/ X tt ) 0.5 . The air introduction has some effect on the augmentation of heat transfer in the boiling region, however, the two-phase flow effect was little and the boiling was dominant in the fully developed boiling region. The CHF was improved a little by the air introduction in the high water flow region. However, that was rather greatly reduced in the low flow region. Even so, the general trend by the air introduction was that qCHF increased as the air introduction was increased. The heat transfer augmentation in the non-boiling region was attained by less power increase than that in the case that only the water flow rate was increased. From the aspect of the power consumption and the heat transfer enhancement, the small air introduction in the low water flow rate region seemed more profitable, although the air introduction in the high water flow rate region and also the large air introduction were still effective in the augmentation of the heat transfer in the non-boiling region. (author)

Flow in air conditioned rooms

DEFF Research Database (Denmark)

Nielsen, Peter V.

1974-01-01

Flow in air conditioned r ooms is examined by means of model experiments . The different gearnetries giving unsteady, steady three- dimensional and steady twodimensional flow are determined . Velacity profiles and temperature profiles are measured in some of the geometries. A numerical solution...... of the flow equations is demonstrated and the flow in air conditioned rooms in case of steady two dimensional flow is predi cted. Compari son with measured results is shown i n the case of small Archimedes numbers, and predictions are shown at high Archimedes numbers. A numerical prediction of f low and heat...

Air flow management in raised floor data centers

CERN Document Server

Arghode, Vaibhav K

2016-01-01

The Brief discuss primarily two aspects of air flow management in raised floor data centers. Firstly, cooling air delivery through perforated tiles will be examined and influence of the tile geometry on flow field development and hot air entrainment above perforated tiles will be discussed. Secondly, the use of cold aisle containment to physically separate hot and cold regions, and minimize hot and cold air mixing will be presented. Both experimental investigations and computational efforts are discussed and development of computational fluid dynamics (CFD) based models for simulating air flow in data centers is included. In addition, metrology tools for facility scale air velocity and temperature measurement, and air flow rate measurement through perforated floor tiles and server racks are examined and the authors present thermodynamics-based models to gauge the effectiveness and importance of air flow management schemes in data centers.

Quantification of smoothing requirement for 3D optic flow calculation of volumetric images

DEFF Research Database (Denmark)

Bab-Hadiashar, Alireza; Tennakoon, Ruwan B.; de Bruijne, Marleen

2013-01-01

Complexities of dynamic volumetric imaging challenge the available computer vision techniques on a number of different fronts. This paper examines the relationship between the estimation accuracy and required amount of smoothness for a general solution from a robust statistics perspective. We show...... that a (surprisingly) small amount of local smoothing is required to satisfy both the necessary and sufficient conditions for accurate optic flow estimation. This notion is called 'just enough' smoothing, and its proper implementation has a profound effect on the preservation of local information in processing 3D...... dynamic scans. To demonstrate the effect of 'just enough' smoothing, a robust 3D optic flow method with quantized local smoothing is presented, and the effect of local smoothing on the accuracy of motion estimation in dynamic lung CT images is examined using both synthetic and real image sequences...

Investigation of the propagation characteristics in turbulent dispersed two-phase flow

International Nuclear Information System (INIS)

Sami, S.M.

1980-01-01

The propagation characteristics of turbulent dispersed two-phase flows have been studied experimentally using the Pitot tube associated with a conical hot-film anemometer. It is found that the mixture velocity increases with decreasing volumetric mixing ratio of the air and water. The void fraction distribution shows homogeneity across the test section in the special case of fully developed boundary layer two-phase flow. An expression is obtained which relates the local mixture velocity to the local void fraction, gas and liquid densities, and volumetric gas-liquid ratio

Turbine flow meter response in two-phase flows

International Nuclear Information System (INIS)

Shim, W.J.; Dougherty, T.J.; Cheh, H.Y.

1996-01-01

The purpose of this paper is to suggest a simple method of calibrating turbine flow meters to measure the flow rates of each phase in a two-phase flow. The response of two 50.8 mm (2 inch) turbine flow meters to air-water, two-phase mixtures flowing vertically in a 57 mm I.D. (2.25 inch) polycarbonate tube has been investigated for both upflow and downflow. The flow meters were connected in series with an intervening valve to provide an adjustable pressure difference between them. Void fractions were measured by two gamma densitometers, one upstream of the flow meters and the other downstream. The output signal of the turbine flow meters was found to depend only on the actual volumetric flow rate of the gas, F G , and liquid, F L , at the location of the flow meter

Gas bubble dimensions in Archean lava flows indicate low air pressure at 2.7 Ga

Science.gov (United States)

Som, S. M.; Buick, R.; Hagadorn, J.; Blake, T.; Perreault, J.; Harnmeijer, J.; Catling, D. C.

2014-12-01

Air pressure constrains atmospheric composition, which, in turn, is linked to the Earth system through biogeochemical cycles and fluxes of volatiles from and to the Earth's interior. Previous studies have only placed maximum levels on surface air pressure for the early Earth [1]. Here, we calculate an absolute value for Archean barometric pressure using gas bubble size (vesicle) distributions in uninflated basaltic lava flows that solidified at sea level 2.7 billion years ago in the Pilbara Craton, Western Australia. These vesicles have been filled in by secondary minerals deposited during metasomatism and so are now amydules, but thin sections show that infilling did not change vesicle dimensions. Amygdule dimensions are measured using high-resolution X-ray tomography from core samples obtained from the top and bottom of the lava flows. The modal size expressed at the top and at the bottom of an uninflated flow can be linked to atmospheric pressure using the ideal gas law. Such a technique has been verified as a paleoaltimeter using Hawaiian Quaternary lava flows [2]. We use statistical methods to estimate the mean and standard deviation of the volumetric size of the amygdules by applying 'bootstrap'resampling and the Central Limit Theorem. Our data indicate a surprisingly low atmospheric pressure. Greater nitrogen burial under anaerobic conditions likely explains lower pressure. Refs: [1] Som et al. (2012) Nature 484, 359-262. D. L. Sahagian et al. (2002) J. Geol., 110, 671-685.

Experimental investigation of the unsteady two-phase flow through perforated plates

International Nuclear Information System (INIS)

Tartaglia, G.P.

1985-07-01

The coolant flow across the perforated dip-plate during a hypothetical core disruptive accident (HCDA) in a liquid metal fast breeder reactor was simulated in a one-dimensional model. Experiments with a water-air mixture as fluid were run by varying the following parameters: geometry of the dip-plate (perforation ratio, number of the holes), height of the fluid head over the dip-plate, air volumetric fraction, size of the air bubbles, acceleration of the fluid. The pressure drop across the dip-plate, the forces acting on the dip-plate and on the upper plate, acceleration and displacement of the piston, the air volumetric fraction and the size of the air bubbles were measured in a wide range of Strouhal and acceleration numbers. The flow pattern downstream the dip-plate was filmed with a high-speed camera. The following correlations were investigated: resistance coefficients as a function of the acceleration and Strouhal number, time delay of the force on the upper plate as a function of the cavitation number, and forces and impulses acting on the upper plate compared with those acting on the dip-plate. Finally, using high-speed film pictures, the formation of fluid jets downstream the dip-plate was investigated. The following relations were obtained: displacement of the mixture surface and of the jets as a function of the perforation ratio and of the air volumetric fraction, and cavitation volume as a function of the cavitation number. (orig.) [de

Natural Flow Air Cooled Photovoltaics

Science.gov (United States)

Tanagnostopoulos, Y.; Themelis, P.

2010-01-01

Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. We performed experiments using a prototype based on three silicon photovoltaic modules placed in series to simulate a typical sloping building roof with photovoltaic installation. In this system the air flows through a channel on the rear side of PV panels. The potential for increasing the heat exchange from the photovoltaic panel to the circulating air by the addition of a thin metal sheet (TMS) in the middle of air channel or metal fins (FIN) along the air duct was examined. The operation of the device was studied with the air duct closed tightly to avoid air circulation (CLOSED) and the air duct open (REF), with the thin metal sheet (TMS) and with metal fins (FIN). In each case the experiments were performed under sunlight and the operating parameters of the experimental device determining the electrical and thermal performance of the system were observed and recorded during a whole day and for several days. We collected the data and form PV panels from the comparative diagrams of the experimental results regarding the temperature of solar cells, the electrical efficiency of the installation, the temperature of the back wall of the air duct and the temperature difference in the entrance and exit of the air duct. The comparative results from the measurements determine the improvement in electrical performance of the photovoltaic cells because of the reduction of their temperature, which is achieved by the naturally circulating air.

40 CFR 91.416 - Intake air flow measurement specifications.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Intake air flow measurement... Procedures § 91.416 Intake air flow measurement specifications. (a) If used, the engine intake air flow measurement method used must have a range large enough to accurately measure the air flow over the engine...

Characteristics of Air Flow through Windows

DEFF Research Database (Denmark)

Heiselberg, Per; Dam, Henrik; Sørensen, Lars C.

This paper describes the first results of a series of laboratory investigations that is performed to characterise three different window types. The results show the air flow conditions for different ventilation strategies and temperature differences. For one of the windows values of the discharge...... coefficient are shown for both isothermal and non-isothermal flow conditions and the thermal comfort conditions are evaluated by measurements of velocity and temperature levels in the air flow in the occupied zone.......This paper describes the first results of a series of laboratory investigations that is performed to characterise three different window types. The results show the air flow conditions for different ventilation strategies and temperature differences. For one of the windows values of the discharge...

Air conditioning system and component therefore distributing air flow from opposite directions

Science.gov (United States)

Obler, H. D.; Bauer, H. B. (Inventor)

1974-01-01

The air conditioning system comprises a plurality of separate air conditioning units coupled to a common supply duct such that air may be introduced into the supply duct in two opposite flow directions. A plurality of outlets such as registers or auxiliary or branch ducts communicate with the supply duct and valve means are disposed in the supply duct at at least some of the outlets for automatically channelling a controllable amount of air from the supply duct to the associated outlet regardless of the direction of air flow within the supply duct. The valve means comprises an automatic air volume control apparatus for distribution within the air supply duct into which air may be introduced from two opposite directions. The apparatus incorporates a freely swinging movable vane in the supply duct to automatically channel into the associated outlet only the deflected air flow which has the higher relative pressure.

Mathematical estimation of the level of microbial contamination on spacecraft surfaces by volumetric air sampling

Science.gov (United States)

Oxborrow, G. S.; Roark, A. L.; Fields, N. D.; Puleo, J. R.

1974-01-01

Microbiological sampling methods presently used for enumeration of microorganisms on spacecraft surfaces require contact with easily damaged components. Estimation of viable particles on surfaces using air sampling methods in conjunction with a mathematical model would be desirable. Parameters necessary for the mathematical model are the effect of angled surfaces on viable particle collection and the number of viable cells per viable particle. Deposition of viable particles on angled surfaces closely followed a cosine function, and the number of viable cells per viable particle was consistent with a Poisson distribution. Other parameters considered by the mathematical model included deposition rate and fractional removal per unit time. A close nonlinear correlation between volumetric air sampling and airborne fallout on surfaces was established with all fallout data points falling within the 95% confidence limits as determined by the mathematical model.

Sensitivity to draught in turbulent air flows

Energy Technology Data Exchange (ETDEWEB)

Todde, V

1998-09-01

Even though the ventilation system is designed to supply air flows at constant low velocity and controlled temperature, the resulting air movement in rooms is strongly characterised by random fluctuations. When an air flow is supplied from an inlet, a shear layer forms between the incoming and the standstill air in the room, and large scale vortices develops by coalescence of the vorticity shed at the inlet of the air supply. After a characteristically downstream distance, large scale vortices loose their identity because of the development of cascading eddies and transition to turbulence. The interaction of these vortical structures will rise a complicated three dimensional air movement affected by fluctuations whose frequencies could vary from fractions of Hz to several KHz. The perception and sensitivity to the cooling effect enhanced by these air movements depend on a number of factors interacting with each other: physical properties of the air flow, part and extension of the skin surface exposed to the air flow, exposure duration, global thermal condition, gender and posture of the person. Earlier studies were concerned with the percentage of dissatisfied subjects as a function of air velocity and temperature. Recently, experimental observations have shown that also the fluctuations, the turbulence intensity and the direction of air velocity have an important impact on draught discomfort. Two experimental investigations have been developed to observe the human reaction to horizontal air movements on bared skin surfaces, hands and neck. Attention was concentrated on the effects of relative turbulence intensity of air velocity and exposure duration on perception and sensitivity to the air movement. The air jet flows, adopted for the draught experiment in the neck, were also the object of an experimental study. This experiment was designed to observe the centre-line velocity of an isothermal circular air jet, as a function of the velocity properties at the outlet

Biventricular MR volumetric analysis and MR flow quantification in the ascending aorta and pulmonary trunk for quantification of valvular regurgitation

International Nuclear Information System (INIS)

Rominger, M.B.

2004-01-01

Purpose: To test the value of biventricular volumetric analysis and the combination of biventricular volumetric analysis with flow quantification in the ascending aorta (Ao) and pulmonary trunk (Pu) for quantification of regurgitation volume and cardiac function in valvular regurgitation (VR) according to location and presence of single or multivalvular disease. Materials and Methods: In 106 patients, the stroke volumes were assessed by measuring the biventricular volumes and the forward-stroke volumes in the great and small circulation by measuring the flow in the Ao and Pu. Valve regurgitation volumes and quotients were calculated for single and multivalvular disease and correlated with semiquantitative 2D-echocardiography (grade I-IV). For the assessment of the cardiac function in VR, the volumetric parameters of ejection fraction and end-diastolic (EDV) and end-systolic (ESV) volumes were determined. Results: The detection rate was 49% for left ventricular (LV) VR and 42% for right ventricular (RV) VR. Low LV VR and RV VR usually could not be detected quantitatively, with the detection rate improving with echocardiographically higher insufficiency grades. Quantitative MRI could detect a higher grade solitary aortic valve insufficiency (≥2) in 11 of 12 patients and higher grade mitral valve insufficiency in 4 of 10 patients. A significant increase in RV and LV ventricular EDV and ESV was seen more often with increased MR regurgitation volumes. Aortic stenosis did not interfere with flow measurements in the Ao. Conclusions: Biventricular volumetry combined with flow measurements in Ao and Pu is a robust, applicable and simple method to assess higher grade regurgitation volumes and the cardiac function in single and multivalvular regurgitation at different locations. It is an important application for the diagnosis of VR by MRI [de

Application of a vortex shedding flowmeter to the wide range measurement of high temperature gas flow

International Nuclear Information System (INIS)

Baker, S.P.; Ennis, R.M. Jr.; Herndon, P.G.

1981-01-01

A single flowmeter was required for helium gas measurement in a Gas Cooled Fast Breeder Reactor loss of coolant simulator. Volumetric flow accuracy of +-1.0% of reading was required over the Reynolds Number range 6 x 10 3 to 1 x 10 6 at flowing pressures from 0.2 to 9 MPa (29 to 1305 psia) at 350 0 C (660 0 F) flowing temperature. Because of its inherent accuracy and rangeability, a vortex shedding flowmeter was selected and specially modified to provide for a remoted thermal sensor. Experiments were conducted to determine the relationship between signal attenuation and sensor remoting geometry, as well as the relationship between gas flow parameters and remoted thermal sensor signal for both compressed air and helium gas. Based upon the results of these experiments, the sensor remoting geometry was optimized for this application. The resultant volumetric flow rangeability was 155:1. The associated temperature increase at the sensor position was 9 0 C above ambient (25 0 F) at a flowing temperature of 350 0 C. The volumetric flow accuracy was measured over the entire 155:1 flow range at parametric values of flowing density. A volumetric flow accuracy of +- % of reading was demonstrated

Characteristics of coal mine ventilation air flows.

Science.gov (United States)

Su, Shi; Chen, Hongwei; Teakle, Philip; Xue, Sheng

2008-01-01

Coal mine methane (CMM) is not only a greenhouse gas but also a wasted energy resource if not utilised. Underground coal mining is by far the most important source of fugitive methane emissions, and approximately 70% of all coal mining related methane is emitted to the atmosphere through mine ventilation air. Therefore, research and development on mine methane mitigation and utilisation now focuses on methane emitted from underground coal mines, in particular ventilation air methane (VAM) capture and utilisation. To date, most work has focused on the oxidation of very low concentration methane. These processes may be classified based on their combustion kinetic mechanisms into thermal oxidation and catalytic oxidation. VAM mitigation/utilisation technologies are generally divided into two basic categories: ancillary uses and principal uses. However, it is possible that the characteristics of ventilation air flows, for example the variations in methane concentration and the presence of certain compounds, which have not been reported so far, could make some potential VAM mitigation and utilisation technologies unfeasible if they cannot cope with the characteristics of mine site ventilation air flows. Therefore, it is important to understand the characteristics of mine ventilation air flows. Moreover, dust, hydrogen sulphide, sulphur dioxide, and other possible compounds emitted through mine ventilation air into the atmosphere are also pollutants. Therefore, this paper presents mine-site experimental results on the characteristics of mine ventilation air flows, including methane concentration and its variations, dust loadings, particle size, mineral matter of the dust, and other compounds in the ventilation air flows. The paper also discusses possible correlations between ventilation air characteristics and underground mining activities.

Kilohertz VLIF (volumetric laser induced fluorescence) measurements in a seeded free gas-phase jet in the transitionally turbulent flow regime

Science.gov (United States)

Wu, Yue; Xu, Wenjiang; Ma, Lin

2018-03-01

This paper reports the demonstration of instantaneous three-dimension (3D) measurements in turbulent flows at repetition rates up to 10 kHz using VLIF (volumetric laser induced fluorescence). The measurements were performed based on the LIF signal of iodine (I2) vapor seeded in the flow. The LIF signals of I2 vapor were generated volumetrically by a thick laser slab and then simultaneously captured by a total of seven cameras from different perspectives, based on which a 3D tomographic reconstruction was performed to obtain the 3D distribution of I2 vapor concentration. Single-shot measurements obtained in a duration of hundreds of nanoseconds (limited by the pulse duration of the excitation laser) were demonstrated in a 50 × 50 × 50 mm3 at a repetition rate up to 10 kHz. These measurements demonstrated the feasibility and potential of VLIF for resolving the 4D spatiotemporal dynamics of turbulent flows. Based on the experimental results obtained, this work also studied the VLIF signal level and its effects on the reconstruction accuracy under different the measurement conditions, illustrating the capabilities and limitations of performing high speed VLIF measurements.

Transient Air-Water Flow and Air Demand following an Opening Outlet Gate

Directory of Open Access Journals (Sweden)

James Yang

2018-01-01

Full Text Available In Sweden, the dam-safety guidelines call for an overhaul of many existing bottom outlets. During the opening of an outlet gate, understanding the transient air-water flow is essential for its safe operation, especially under submerged tailwater conditions. Three-dimensional CFD simulations are undertaken to examine air-water flow behaviors at both free and submerged outflows. The gate, hoisted by wire ropes and powered by AC, opens at a constant speed. A mesh is adapted to follow the gate movement. At the free outflow, the CFD simulations and model tests agree well in terms of outlet discharge capacity. Larger air vents lead to more air supply; the increment becomes, however, limited if the vent area is larger than 10 m2. At the submerged outflow, a hydraulic jump builds up in the conduit when the gate reaches approximately 45% of its full opening. The discharge is affected by the tailwater and slightly by the flow with the hydraulic jump. The flow features strong turbulent mixing of air and water, with build-up and break-up of air pockets and collisions of defragmented water bodies. The air demand rate is several times as much as required by steady-state hydraulic jump with free surface.

40 CFR 90.416 - Intake air flow measurement specifications.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Intake air flow measurement... Gaseous Exhaust Test Procedures § 90.416 Intake air flow measurement specifications. (a) If used, the engine intake air flow measurement method used must have a range large enough to accurately measure the...

Impact of co-flow air on buoyant diffusion flames flicker

Energy Technology Data Exchange (ETDEWEB)

Gohari Darabkhani, H., E-mail: h.g.darabkhani@gmail.com [School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester M13 9PL (United Kingdom); Wang, Q.; Chen, L.; Zhang, Y. [Mechanical Engineering Department, University of Sheffield, Mapping Street, Sheffield S1 3JD (United Kingdom)

2011-08-15

Highlights: {yields} We present the co-flow effects on flickering behaviour of diffusion flames. {yields} Co-flow air is shown to fully suppress the buoyancy driven flame oscillations. {yields} Schlieren and PIV illustrate the shift of outer vortices beyond the flame zone. {yields} Stability controlling parameter as a ratio of air to fuel velocities is presented. {yields} Equation for linear increase in flickering frequency by co-flow air is presented. - Abstract: This paper describes experimental investigation of co-flow air velocity effects on the flickering behaviour of laminar non-lifted methane diffusion flames. Chemiluminescence, high-speed photography, schlieren and Particle Imaging Velocimetry (PIV), have been used to study the changes in the flame/vortex interactions as well as the flame flickering frequency and magnitude by the co-flow air. Four cases of methane flow rates at different co-flow air velocities are investigated. It has been observed that the flame dynamics and stability of co-flow diffusion flames are strongly affected by the co-flow air velocity. When the co-flow velocity has reached a certain value the buoyancy driven flame oscillation was completely suppressed. The schlieren and PIV imaging have revealed that the co-flow of air is able to push the initiation point of the outer toroidal vortices beyond the visible flame to create a very steady laminar flow region in the reaction zone. Then the buoyancy driven instability is only effective in the plume of hot gases above the visible flame. It is observed that a higher co-flow rate is needed in order to suppress the flame flickering at a higher fuel flow rate. Therefore the ratio of the air velocity to the fuel velocity, {gamma}, is a stability controlling parameter. The velocity ratio, {gamma}, was found to be 0.72 for the range of tested flow rates. The dominant flickering frequency was observed to increase linearly with the co-flow rate (a) as; f = 0.33a + 11. The frequency amplitudes

Cavity air flow behavior during filling in microinjection molding

DEFF Research Database (Denmark)

Griffiths, C.A.; Dimov, S.S.; Scholz, S.

2011-01-01

Process monitoring of microinjection molding (μ-IM) is of crucial importance in understanding the effects of different parameter settings on the process, especially on its performance and consistency with regard to parts' quality. Quality factors related to mold cavity air evacuation can provide...... valuable information about the process dynamics and also about the filling of a cavity by a polymer melt. In this paper, a novel experimental setup is proposed to monitor maximum air flow and air flow work as an integral of the air flow over time by employing a microelectromechanical system gas sensor...... the effects of process parameters on cavity air evacuation, and the influence of air evacuation on the part flow length. © 2011 American Society of Mechanical Engineers....

Novel monorail infusion catheter for volumetric coronary blood flow measurement in humans: in vitro validation.

Science.gov (United States)

van 't Veer, Marcel; Adjedj, Julien; Wijnbergen, Inge; Tóth, Gabor G; Rutten, Marcel C M; Barbato, Emanuele; van Nunen, Lokien X; Pijls, Nico H J; De Bruyne, Bernard

2016-08-20

The aim of this study is to validate a novel monorail infusion catheter for thermodilution-based quantitative coronary flow measurements. Based on the principles of thermodilution, volumetric coronary flow can be determined from the flow rate of a continuous saline infusion, the temperature of saline when it enters the coronary artery, and the temperature of the blood mixed with the saline in the distal part of the coronary artery. In an in vitro set-up of the systemic and coronary circulation at body temperature, coronary flow values were varied from 50-300 ml/min in steps of 50 ml/min. At each coronary flow value, thermodilution-based measurements were performed at infusion rates of 15, 20, and 30 ml/min. Temperatures and pressures were simultaneously measured with a pressure/temperature sensor-tipped guidewire. Agreement of the calculated flow and the measured flow as well as repeatability were assessed. A total of five catheters were tested, with a total of 180 measurements. A strong correlation (ρ=0.976, p<0.0001) and a difference of -6.5±15.5 ml/min were found between measured and calculated flow. The difference between two repeated measures was 0.2%±8.0%. This novel infusion catheter used in combination with a pressure/temperature sensor-tipped guidewire allows accurate and repeatable absolute coronary flow measurements. This opens a window to a better understanding of the coronary microcirculation.

Correlation of volumetric flow rate and skin blood flow with cold intolerance in digital replantation.

Science.gov (United States)

Zhao, Gang; Mi, Jingyi; Rui, Yongjun; Pan, Xiaoyun; Yao, Qun; Qiu, Yang

2017-12-01

Cold intolerance is a common complication of digital replantation. The exact etiology is unclear, but it is considered to be multifactorial, including nonsurgical characteristics, vascular, and neurologic conditions. Blood flow may play a significant role in cold intolerance. This study was designed to evaluate the correlation of digital blood flow, including volumetric flow rate (VFR) and skin blood flow (SkBF), with cold intolerance in replanted fingers.A retrospective study was conducted among patients who underwent digital replantation between 2010 and 2013. Patients were selected into study cohort based on the inclusion criteria. Surgical data was collected on each patient, including age, sex, injury mechanism, amputation level, ischemia time, number of arteries repaired, and whether or not vascular crisis occurred. Patients were included as study cohort with both nerves repaired and without chronic disease. Cold intolerance was defined as a Cold Intolerance Symptom Severity (CISS) score over 30. The arterial flow velocity and caliber were measured by Color Doppler Ultrasound and the digital VFR was calculated. The SkBF was measured by Laser Speckle Imager. Both VFR and SkBF were calculated as a percentage of the contralateral fingers. Comparative study of surgical data and blood flow was performed between the patient with and without cold intolerance. Correlation between VFR and SkBF was also analyzed.A total of 93 patients met inclusion criteria for the study. Approximately, 42 patients were identified as having cold intolerance. Fingers that survived vascular crisis had a higher incidence of cold intolerance with a lower VFR and SkBF. The VFR was higher in 2-artery replantation, but the SkBF and incidence of cold intolerance did not differ significantly. No differences were found in age, sex, injury mechanism, amputation level, or ischemia time. Furthermore, no correlation was found between VFR and SkBF.Cold intolerance of digital replantation is associated

Air Flow and Gassing Potential in Micro-injection Moulding

DEFF Research Database (Denmark)

Griffithsa, C.A.; Dimova, S.S.; Scholz, S.

2011-01-01

valuable information about the process dynamics and also about the filling of a cavity by a polymer melt. In this paper, a novel experimental set-up is proposed to monitor maximum air flow and air flow work as an integral of the air flow over time by employing a MEMS gas sensor mounted inside the mould...

Effect of air flow on tubular solar still efficiency.

Science.gov (United States)

Thirugnanasambantham, Arunkumar; Rajan, Jayaprakash; Ahsan, Amimul; Kandasamy, Vinothkumar

2013-01-01

An experimental work was reported to estimate the increase in distillate yield for a compound parabolic concentrator-concentric tubular solar still (CPC-CTSS). The CPC dramatically increases the heating of the saline water. A novel idea was proposed to study the characteristic features of CPC for desalination to produce a large quantity of distillate yield. A rectangular basin of dimension 2 m × 0.025 m × 0.02 m was fabricated of copper and was placed at the focus of the CPC. This basin is covered by two cylindrical glass tubes of length 2 m with two different diameters of 0.02 m and 0.03 m. The experimental study was operated with two modes: without and with air flow between inner and outer tubes. The rate of air flow was fixed throughout the experiment at 4.5 m/s. On the basis of performance results, the water collection rate was 1445 ml/day without air flow and 2020 ml/day with air flow and the efficiencies were 16.2% and 18.9%, respectively. THE EXPERIMENTAL STUDY WAS OPERATED WITH TWO MODES: without and with air flow between inner and outer tubes. The rate of air flow was fixed throughout the experiment at 4.5 m/s. On the basis of performance results, the water collection rate was 1445 ml/day without air flow and 2020 ml/day with air flow and the efficiencies were 16.2% and 18.9%, respectively.

Coaxial volumetric velocimetry

Science.gov (United States)

Schneiders, Jan F. G.; Scarano, Fulvio; Jux, Constantin; Sciacchitano, Andrea

2018-06-01

This study describes the working principles of the coaxial volumetric velocimeter (CVV) for wind tunnel measurements. The measurement system is derived from the concept of tomographic PIV in combination with recent developments of Lagrangian particle tracking. The main characteristic of the CVV is its small tomographic aperture and the coaxial arrangement between the illumination and imaging directions. The system consists of a multi-camera arrangement subtending only few degrees solid angle and a long focal depth. Contrary to established PIV practice, laser illumination is provided along the same direction as that of the camera views, reducing the optical access requirements to a single viewing direction. The laser light is expanded to illuminate the full field of view of the cameras. Such illumination and imaging conditions along a deep measurement volume dictate the use of tracer particles with a large scattering area. In the present work, helium-filled soap bubbles are used. The fundamental principles of the CVV in terms of dynamic velocity and spatial range are discussed. Maximum particle image density is shown to limit tracer particle seeding concentration and instantaneous spatial resolution. Time-averaged flow fields can be obtained at high spatial resolution by ensemble averaging. The use of the CVV for time-averaged measurements is demonstrated in two wind tunnel experiments. After comparing the CVV measurements with the potential flow in front of a sphere, the near-surface flow around a complex wind tunnel model of a cyclist is measured. The measurements yield the volumetric time-averaged velocity and vorticity field. The measurements of the streamlines in proximity of the surface give an indication of the skin-friction lines pattern, which is of use in the interpretation of the surface flow topology.

CFD simulation of air to air enthalpy heat exchanger

International Nuclear Information System (INIS)

Al-Waked, Rafat; Nasif, Mohammad Shakir; Morrison, Graham; Behnia, Masud

2013-01-01

Highlights: • A CFD model capable of modelling conjugate heat and mass transfer processes. • A mesh independence studies and a CFD model validation have been conducted. • Effects of flow direction on the effectiveness have been examined. • Performance parameters were sensible and latent effectiveness and pressure drop. - Abstract: A CFD model which supports conjugate heat and mass transfer problem representation across the membrane of air-to-air energy recovery heat exchangers has been developed. The model consists of one flow passage for the hot stream and another for the adjacent cold stream. Only half of each flow passage volume has been modelled on each side of the membrane surface. Three dimensional, steady state and laminar flow studies have been conducted using a commercial CFD package. The volumetric species transport model has been adopted to describe the H 2 O and air gas mixtures. Mesh dependency has been examined and followed by validation of the CFD model against published data. Furthermore, effects of flow direction at the inlet of the heat exchanger on its thermal effectiveness have been investigated. Simulation results are presented and analysed in terms of sensible effectiveness, latent effectiveness and pressure drop across the membrane heat exchanger. Results have shown that counter-flow configuration has greater sensitivity to the mesh centre perpendicular distance from the membrane when compared to the other two flow configurations (cross-/parallel-flow). However, the lateral mesh element length has shown minimal effect on the thermal effectiveness of the enthalpy heat exchanger. For the quasi-flow heat exchanger, a perpendicular flow direction to the inlets has been found to produce a higher performance in contrast to the non-perpendicular flow

Experimental investigation of the liquid volumetric mass transfer coefficient for upward gas-liquid two-phase flow in rectangular microchannels

Directory of Open Access Journals (Sweden)

X. Y. Ji

2010-12-01

Full Text Available The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure variation of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width, 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data.

Flow regime classification in air-magnetic fluid two-phase flow.

Science.gov (United States)

Kuwahara, T; De Vuyst, F; Yamaguchi, H

2008-05-21

A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors.

Modeling of air flow through a narrow crack

International Nuclear Information System (INIS)

Trojek, T.; Cechak, T.; Moucka, L.; Fronka, A.

2004-01-01

Radon transport in dwellings is governed to a significant extent by pressure differences and properties of transport pathways. A model of air flow through narrow cracks was created in order to facilitate prediction of air velocity and air flow. Theoretical calculations, based on numerical solution of a system of differential equations, were compared with measurements carried out on a window crack. (P.A.)

Experimental Setup For Study of Drop Deformation In Air Flow

Directory of Open Access Journals (Sweden)

Basalaev Sergey

2017-01-01

Full Text Available Experimental study for study of deformation of drops in air flow is considered. Experimental setup includes a module for obtaining the drops, an air flow system and measuring system. Module for formation of drops is in the form of vertically arranged dropper with capillary with the possibility of formation of fixed drops. Air flow supply system comprises an air pump coupled conduit through a regulating valve with a cylindrical pipe, installed coaxially with dropper. The measuring system includes the video camera located with possibility of visualization of drop and the Pitot gage for measurement of flow rate of air located in the output section of branch pipe. This experimental setup allows to provide reliable and informative results of the investigation of deformation of drops in the air flow.

Transition from slug to annular flow in horizontal air-water flow

International Nuclear Information System (INIS)

Reismann, J.; John, H.; Seeger, W.

1981-11-01

The transition from slug to annular flow in horizontal air-water and steam-water flow was investigated. Test sections of 50; 66.6 and 80 mm ID were used. The system pressure was 0.2 and 0.5 MPa in the air-water experiments and 2.5; 5; 7.5 and 10 MPa in the steam-water experiments. For flow pattern detection local impedance probes were used. This method was compared in a part of the experiments with differential pressure and gamma-beam measurements. The flow regime boundary is shifting strongly to smaller values of the superficial gas velocity with increasing pressure. Correlations from literature fit unsatisfactorily the experimental results. A new correlation is presented. (orig.) [de

Sodium flow distribution test of the air cooler tubes

International Nuclear Information System (INIS)

Uchida, Hiroyuki; Ohta, Hidehisa; Shimazu, Hisashi

1980-01-01

In the heat transfer tubes of the air cooler which is installed in the auxiliary core cooling system of the fast breeder prototype plant reactor ''Monju'', sodium freezing may be caused by undercooling the sodium induced by an extremely unbalanced sodium flow in the tubes. Thus, the sodium flow distribution test of the air cooler tubes was performed to examine the flow distribution of the tubes and to estimate the possibility of sodium freezing in the tubes. This test was performed by using a one fourth air cooler model installed in the water flow test facility. As the test results show, the flow distribution from the inlet header to each tube is almost equal at any operating condition, that is, the velocity deviation from normalized mean velocity is less than 6% and sodium freezing does not occur up to 250% air velocity deviation at stand-by condition. It was clear that the proposed air cooler design for the ''Monju'' will have a good sodium flow distribution at any operating condition. (author)

Discharge characteristics in inhomogeneous fields under air flow

DEFF Research Database (Denmark)

Vogel, Stephan; Holbøll, Joachim

2017-01-01

the frequency and magnitude of partial discharges in the vicinity of the electrode due to an increased rate of space charge removal around the tip of the needle and in the gap. The positive polarity shows higher dependency on air flow compared to the negative polarity. It is shown that positive breakdown......This research investigates the impact of high velocity air flow on Partial Discharge (PD) patterns generated in strongly inhomogeneous fields. In the laboratory, a needle plane electrode configuration was exposed to a high electrical DC-field and a laminar air flow up to 22 ms. The needle...

Laboratory Evaluation of Air Flow Measurement Methods for Residential HVAC Returns

Energy Technology Data Exchange (ETDEWEB)

Walker, Iain; Stratton, Chris

2015-07-01

This project improved the accuracy of air flow measurements used in commissioning California heating and air conditioning systems in Title 24 (Building and Appliance Efficiency Standards), thereby improving system performance and efficiency of California residences. The research team at Lawrence Berkeley National Laboratory addressed the issue that typical tools used by contractors in the field to test air flows may not be accurate enough to measure return flows used in Title 24 applications. The team developed guidance on performance of current diagnostics as well as a draft test method for use in future evaluations. The series of tests performed measured air flow using a range of techniques and devices. The measured air flows were compared to reference air flow measurements using inline air flow meters built into the test apparatus. The experimental results showed that some devices had reasonable results (typical errors of 5 percent or less) but others had much bigger errors (up to 25 percent).

Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study.

Science.gov (United States)

Nilsson, Anders; Revstedt, Johan; Heiberg, Einar; Ståhlberg, Freddy; Bloch, Karin Markenroth

2015-04-01

The aim of this study was to evaluate the accuracy of maximum velocity measurements using volumetric phase-contrast imaging with spiral readouts in a stenotic flow phantom. In a phantom model, maximum velocity, flow, pressure gradient, and streamline visualizations were evaluated using volumetric phase-contrast magnetic resonance imaging (MRI) with velocity encoding in one (extending on current clinical practice) and three directions (for characterization of the flow field) using spiral readouts. Results of maximum velocity and pressure drop were compared to computational fluid dynamics (CFD) simulations, as well as corresponding low-echo-time (TE) Cartesian data. Flow was compared to 2D through-plane phase contrast (PC) upstream from the restriction. Results obtained with 3D through-plane PC as well as 4D PC at shortest TE using a spiral readout showed excellent agreements with the maximum velocity values obtained with CFD (spiral sequences were respectively 14 and 13 % overestimated compared to CFD. Identification of the maximum velocity location, as well as the accurate velocity quantification can be obtained in stenotic regions using short-TE spiral volumetric PC imaging.

Gradients estimation from random points with volumetric tensor in turbulence

Science.gov (United States)

Watanabe, Tomoaki; Nagata, Koji

2017-12-01

We present an estimation method of fully-resolved/coarse-grained gradients from randomly distributed points in turbulence. The method is based on a linear approximation of spatial gradients expressed with the volumetric tensor, which is a 3 × 3 matrix determined by a geometric distribution of the points. The coarse grained gradient can be considered as a low pass filtered gradient, whose cutoff is estimated with the eigenvalues of the volumetric tensor. The present method, the volumetric tensor approximation, is tested for velocity and passive scalar gradients in incompressible planar jet and mixing layer. Comparison with a finite difference approximation on a Cartesian grid shows that the volumetric tensor approximation computes the coarse grained gradients fairly well at a moderate computational cost under various conditions of spatial distributions of points. We also show that imposing the solenoidal condition improves the accuracy of the present method for solenoidal vectors, such as a velocity vector in incompressible flows, especially when the number of the points is not large. The volumetric tensor approximation with 4 points poorly estimates the gradient because of anisotropic distribution of the points. Increasing the number of points from 4 significantly improves the accuracy. Although the coarse grained gradient changes with the cutoff length, the volumetric tensor approximation yields the coarse grained gradient whose magnitude is close to the one obtained by the finite difference. We also show that the velocity gradient estimated with the present method well captures the turbulence characteristics such as local flow topology, amplification of enstrophy and strain, and energy transfer across scales.

40 CFR 86.313-79 - Air flow measurement specifications; diesel engines.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Air flow measurement specifications... Procedures § 86.313-79 Air flow measurement specifications; diesel engines. (a) The air flow measurement... (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES...

Evaluation of Accordance of Magnetic Resonance Volumetric and Flow Measurements in Determining Ventricular Stroke Volume in Cardiac Patients

International Nuclear Information System (INIS)

Jeltsch, M.; Ranft, S.; Klass, O.; Aschoff, A.J.; Hoffmann, M.H.K.

2008-01-01

Background: Cardiovascular magnetic resonance imaging (CMR) has become an established noninvasive method for evaluating ventricular function utilizing three-dimensional volumetry. Postprocessing of volumetric measurements is still tedious and time consuming. Stroke volumes obtained by flow quantification across the aortic root or pulmonary trunk could be utilized to increase both speed of workflow and accuracy. Purpose: To assess accuracy of stroke volume quantification using MR volumetric imaging compared to flow quantification in patients with various cardiac diseases. Strategies for the augmentation of accuracy in clinical routine were deduced. Material and Methods: 78 patients with various cardiac diseases -excluding intra- or extracardiac shunts, regurgitant valvular defects, or heart rhythm disturbance -underwent cardiac function analysis with flow measurements across the aortic root and cine imaging of the left ventricle. Forty-six patients additionally underwent flow measurements in the pulmonary trunk and cine imaging of the right ventricle. Results: Left ventricular stroke volume (LVSV) and stroke volume of the aortic root (SVAo) correlated with r=0.97, and Bland-Altman analysis showed a mean difference of 0.11 ml and a standard error of estimation (SEE) of 4.31 ml. Ninety-two percent of the data were within the 95% limits of agreement. Right ventricular stroke volume (RVSV) and stroke volume of the pulmonary trunk (SVP) correlated with a factor of r=0.86, and mean difference in the Bland-Altman analysis was fixed at -2.62 ml (SEE 8.47 ml). For RVSV and SVP, we calculated r=0.82, and Bland-Altman analysis revealed a mean difference of 1.27 ml (SEE 9.89 ml). LVSV and RVSV correlated closely, with r=0.91 and a mean difference of 2.79 ml (SEE 7.17 ml). SVAo and SVP correlated with r=0.95 and a mean difference of 0.50 ml (SEE 5.56 ml). Conclusion: Flow quantification can be used as a guidance tool, providing accurate and reproducible stroke volumes of both

Patterns of a slow air-water flow in a semispherical container

DEFF Research Database (Denmark)

Balci, Adnan; Brøns, Morten; Herrada, Miguel A.

2016-01-01

This numerical study analyzes the development of eddies in a slow steady axisymmetric air-water flow in a sealed semispherical container, driven by a rotating top disk. As the water height, Hw, increases, new flow cells emerge in both water and air. First, an eddy emerges near the axis-bottom int......This numerical study analyzes the development of eddies in a slow steady axisymmetric air-water flow in a sealed semispherical container, driven by a rotating top disk. As the water height, Hw, increases, new flow cells emerge in both water and air. First, an eddy emerges near the axis...... on the air flow. In contrast to flows in cylindrical and conical containers, there is no interaction with Moffatt corner vortices here....

40 CFR 1065.225 - Intake-air flow meter.

Science.gov (United States)

2010-07-01

... as described in § 1065.650, as follows: (1) Use the actual value of calculated raw exhaust in the..., you may use an intake-air flow meter signal that does not give the actual value of raw exhaust, as... CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related Measurements § 1065.225 Intake-air...

Position paper -- Tank ventilation system design air flow rates

International Nuclear Information System (INIS)

Goolsby, G.K.

1995-01-01

The purpose of this paper is to document a project position on required ventilation system design air flow rates for the waste storage tanks currently being designed by project W-236A, the Multi-Function Waste Tank Facility (MWTF). The Title 1 design primary tank heat removal system consists of two systems: a primary tank vapor space ventilation system; and an annulus ventilation system. At the conclusion of Title 1 design, air flow rates for the primary and annulus ventilation systems were 960 scfm and 4,400 scfm, respectively, per tank. These design flow rates were capable of removing 1,250,000 Btu/hr from each tank. However, recently completed and ongoing studies have resulted in a design change to reduce the extreme case heat load to 700,000 Btu/hr. This revision of the extreme case heat load, coupled with results of scale model evaporative testing performed by WHC Thermal Hydraulics, allow for a reduction of the design air flow rates for both primary and annulus ventilation systems. Based on the preceding discussion, ICF Kaiser Hanford Co. concludes that the design should incorporate the following design air flow rates: Primary ventilation system--500 scfm maximum and Annulus ventilation system--1,100 scfm maximum. In addition, the minimum air flow rates in the primary and annulus ventilation systems will be investigated during Title 2 design. The results of the Title 2 investigation will determine the range of available temperature control using variable air flows to both ventilation systems

Real-Time Aerodynamic Parameter Estimation without Air Flow Angle Measurements

Science.gov (United States)

Morelli, Eugene A.

2010-01-01

A technique for estimating aerodynamic parameters in real time from flight data without air flow angle measurements is described and demonstrated. The method is applied to simulated F-16 data, and to flight data from a subscale jet transport aircraft. Modeling results obtained with the new approach using flight data without air flow angle measurements were compared to modeling results computed conventionally using flight data that included air flow angle measurements. Comparisons demonstrated that the new technique can provide accurate aerodynamic modeling results without air flow angle measurements, which are often difficult and expensive to obtain. Implications for efficient flight testing and flight safety are discussed.

Hypersonic Air Flow with Finite Rate Chemistry

National Research Council Canada - National Science Library

Boyd, Ian

1997-01-01

... describe the effects of non-equilibrium flow chemistry, shock interaction, and turbulent mixing and combustion on the performance of vehicles and air breathing engines designed to fly in the hypersonic flow...

Interaction of Air Flow in Complex Ventilation Systems

Directory of Open Access Journals (Sweden)

Zhorzh G. Levitskiy

2013-01-01

Full Text Available The article presents the results of study of interaction of air flow in complex ventilation systems. The study used Taylor and Maclaurin’s series and Lagrange formula to create the functional connections on estimation of the impact of changing aerodynamic parameters of one or several simultaneously working regulators on the air flow distribution in mines

A study of pipe flow rate measurement using air-coupled ultrasound

International Nuclear Information System (INIS)

Tsukada, Keisuke; Tsuzuki, Nobuyoshi; Kikura, Hiroshige

2013-01-01

A non-contact flow meter employing air-coupled ultrasound is developed in this research. Ultrasonic flow meter is applied to the higher accuracy flow rate measurement, compared with pressure difference flow meter. However, ultrasonic flow meter has difficulty to measure in severe conditions such as in the condition of high temperature, high pressure condition, and radioactive materials in fluid. Especially, in high temperature condition, piezoelectric device in ultrasonic sensors lose the piezoelectricity, and it becomes difficult to transmit or detect ultrasound. Thus, in this research, ultrasonic sensors are fixed in the air. Ultrasonic sensors transmit and detect ultrasound through air, and measure the flow rate in the pipe. However, most of ultrasound is refracted and reflected at the boundaries between air and the pipe. And detected signals are weak. To increase the signal level, we developed focusing ultrasonic sensors that was optimized for the pipe flow measurement. And employing these focusing sensors the flow rate measurement has been done in order to evaluate the air-coupled ultrasonic flow meter by the ultrasonic beam focusing technique. (author)

Time-resolved fast-neutron radiography of air-water two-phase flows in a rectangular channel by an improved detection system

Energy Technology Data Exchange (ETDEWEB)

Zboray, Robert [Paul Scherrer Institute, PSI Villigen 5232 (Switzerland); Dangendorf, Volker; Bromberger, Benjamin; Tittelmeier, Kai [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig 38116 (Germany); Mor, Ilan [Soreq NRC, Yavne 81800 (Israel)

2015-07-15

In a previous work, we have demonstrated the feasibility of high-frame-rate, fast-neutron radiography of generic air-water two-phase flows in a 1.5 cm thick, rectangular flow channel. The experiments have been carried out at the high-intensity, white-beam facility of the Physikalisch-Technische Bundesanstalt, Germany, using an multi-frame, time-resolved detector developed for fast neutron resonance radiography. The results were however not fully optimal and therefore we have decided to modify the detector and optimize it for the given application, which is described in the present work. Furthermore, we managed to improve the image post-processing methodology and the noise suppression. Using the tailored detector and the improved post-processing, significant increase in the image quality and an order of magnitude lower exposure times, down to 3.33 ms, have been achieved with minimized motion artifacts. Similar to the previous study, different two-phase flow regimes such as bubbly slug and churn flows have been examined. The enhanced imaging quality enables an improved prediction of two-phase flow parameters like the instantaneous volumetric gas fraction, bubble size, and bubble velocities. Instantaneous velocity fields around the gas enclosures can also be more robustly predicted using optical flow methods as previously.

Time-resolved fast-neutron radiography of air-water two-phase flows in a rectangular channel by an improved detection system.

Science.gov (United States)

Zboray, Robert; Dangendorf, Volker; Mor, Ilan; Bromberger, Benjamin; Tittelmeier, Kai

2015-07-01

In a previous work, we have demonstrated the feasibility of high-frame-rate, fast-neutron radiography of generic air-water two-phase flows in a 1.5 cm thick, rectangular flow channel. The experiments have been carried out at the high-intensity, white-beam facility of the Physikalisch-Technische Bundesanstalt, Germany, using an multi-frame, time-resolved detector developed for fast neutron resonance radiography. The results were however not fully optimal and therefore we have decided to modify the detector and optimize it for the given application, which is described in the present work. Furthermore, we managed to improve the image post-processing methodology and the noise suppression. Using the tailored detector and the improved post-processing, significant increase in the image quality and an order of magnitude lower exposure times, down to 3.33 ms, have been achieved with minimized motion artifacts. Similar to the previous study, different two-phase flow regimes such as bubbly slug and churn flows have been examined. The enhanced imaging quality enables an improved prediction of two-phase flow parameters like the instantaneous volumetric gas fraction, bubble size, and bubble velocities. Instantaneous velocity fields around the gas enclosures can also be more robustly predicted using optical flow methods as previously.

Compressed-air flow control system.

Science.gov (United States)

Bong, Ki Wan; Chapin, Stephen C; Pregibon, Daniel C; Baah, David; Floyd-Smith, Tamara M; Doyle, Patrick S

2011-02-21

We present the construction and operation of a compressed-air driven flow system that can be used for a variety of microfluidic applications that require rapid dynamic response and precise control of multiple inlet streams. With the use of inexpensive and readily available parts, we describe how to assemble this versatile control system and further explore its utility in continuous- and pulsed-flow microfluidic procedures for the synthesis and analysis of microparticles.

Stability and Volumetric Properties of Asphalt Mixture Containing Waste Plastic

Directory of Open Access Journals (Sweden)

Abd Kader Siti Aminah

2017-01-01

Full Text Available The objectives of this study are to determine the optimum bitumen content (OBC for every percentage added of waste plastics in asphalt mixtures and to investigate the stability properties of the asphalt mixtures containing waste plastic. Marshall stability and flow values along with density, air voids in total mix, voids in mineral aggregate, and voids filled with bitumen were determined to obtain OBC at different percentages of waste plastic, i.e., 4%, 6%, 8%, and 10% by weight of bitumen as additive. Results showed that the OBC for the plastic-modified asphalt mixtures at 4%, 6%, 8%, and 10% are 4.98, 5.44, 5.48, and 5.14, respectively. On the other hand, the controlled specimen’s shows better volumetric properties compared to plastic mixes. However, 4% additional of waste plastic indicated better stability than controlled specimen.

LABORATORY EVALUATION OF AIR FLOW MEASUREMENT METHODS FOR RESIDENTIAL HVAC RETURNS

Energy Technology Data Exchange (ETDEWEB)

Walker, Iain; Stratton, Chris

2015-02-01

This project improved the accuracy of air flow measurements used in commissioning California heating and air conditioning systems in Title 24 (Building and Appliance Efficiency Standards), thereby improving system performance and efficiency of California residences. The research team at Lawrence Berkeley National Laboratory addressed the issue that typical tools used by contractors in the field to test air flows may not be accurate enough to measure return flows used in Title 24 applications. The team developed guidance on performance of current diagnostics as well as a draft test method for use in future evaluations. The series of tests performed measured air flow using a range of techniques and devices. The measured air flows were compared to reference air flow measurements using inline air flow meters built into the test apparatus. The experimental results showed that some devices had reasonable results (typical errors of 5 percent or less) but others had much bigger errors (up to 25 percent). Because manufacturers’ accuracy estimates for their equipment do not include many of the sources of error found in actual field measurements (and replicated in the laboratory testing in this study) it is essential for a test method that could be used to determine the actual uncertainty in this specific application. The study team prepared a draft test method through ASTM International to determine the uncertainty of air flow measurements at residential heating ventilation and air conditioning returns and other terminals. This test method, when finalized, can be used by the Energy Commission and other entities to specify required accuracy of measurement devices used to show compliance with standards.

Influence of georeference for saturated excess overland flow modelling using 3D volumetric soft geo-objects

Science.gov (United States)

Izham, Mohamad Yusoff; Muhamad Uznir, Ujang; Alias, Abdul Rahman; Ayob, Katimon; Wan Ruslan, Ismail

2011-04-01

Existing 2D data structures are often insufficient for analysing the dynamism of saturation excess overland flow (SEOF) within a basin. Moreover, all stream networks and soil surface structures in GIS must be preserved within appropriate projection plane fitting techniques known as georeferencing. Inclusion of 3D volumetric structure of the current soft geo-objects simulation model would offer a substantial effort towards representing 3D soft geo-objects of SEOF dynamically within a basin by visualising saturated flow and overland flow volume. This research attempts to visualise the influence of a georeference system towards the dynamism of overland flow coverage and total overland flow volume generated from the SEOF process using VSG data structure. The data structure is driven by Green-Ampt methods and the Topographic Wetness Index (TWI). VSGs are analysed by focusing on spatial object preservation techniques of the conformal-based Malaysian Rectified Skew Orthomorphic (MRSO) and the equidistant-based Cassini-Soldner projection plane under the existing geodetic Malaysian Revised Triangulation 1948 (MRT48) and the newly implemented Geocentric Datum for Malaysia (GDM2000) datum. The simulated result visualises deformation of SEOF coverage under different georeference systems via its projection planes, which delineate dissimilar computation of SEOF areas and overland flow volumes. The integration of Georeference, 3D GIS and the saturation excess mechanism provides unifying evidence towards successful landslide and flood disaster management through envisioning the streamflow generating process (mainly SEOF) in a 3D environment.

Air flow distribution in and around a single-sided naturally ventilated room

Energy Technology Data Exchange (ETDEWEB)

Eftekhari, M.M.; Marjanovic, L.D.; Pinnock, D.J. [Loughborough University (United Kingdom). Dept. of Civil and Building Engineering

2002-03-01

The objective of this research is to compare calculated and measured air flow distributions inside a test room which is naturally ventilated. The test room is situated in a relatively sheltered location and to visualise the resultant local wind pattern around the room for all prevailing wind directions, wind tunnel trials were carried out. Both the wind tunnel and full-scale measurements show that the wind direction at the test cell was generally restricted to either a westerly or an easterly direction. To investigate air flow inside the room, the air pressures and velocities across the openings together with indoor air temperature and velocity at four locations and six different levels are measured. The experimental results demonstrate that for both winter and summer the air was entering the test room at bottom and leaving at the top louvre. Separate air flow and thermal modelling programs are used to predict the spatial distribution of the air flow and thermal comfort. The air flow distribution was predicted using a network air flow program. The predicted flow showed similar trends and the simulation results were in agreement with the measured data. An explicit finite-difference thermal modeling simulation package was used to predict the thermal comfort indices.(author)

Effects of filter housing and ductwork configuration on air flow uniformity inside air cleaning filter housings

International Nuclear Information System (INIS)

Paul, J.D.

1993-01-01

Each new HEPA filter installation presents a different physical configuration based on the system requirements, the available space and designer preference. Each different configuration can result in variations of air flow uniformity inside the filter housing across the filter banks. This paper presents the results of air flow uniformity testing for six different filter housing/ductwork configurations and discusses if any of those variations in air flow uniformity is attributable to the difference in the physical arrangements for the six cases

Dynamic methods of air traffic flow management

Directory of Open Access Journals (Sweden)

Jacek SKORUPSKI

2011-01-01

Full Text Available Air traffic management is a complex hierarchical system. Hierarchy levels can be defined according to decision making time horizon or to analyze area volume. For medium time horizon and wide analysis area, the air traffic flow management services were established. Their main task is to properly co-ordinate air traffic in European airspace, so as to minimize delays arising in congested sectors. Those services have to assure high safety level at the same time. Thus it is a very complex task, with many goals, many decision variables and many constraints.In the paper review of the methods developed for aiding air traffic flow management services is presented. More detailed description of a dynamic method is given. This method is based on stochastic capacity and scenario analysis. Some problems in utilization of presented methods are also pointed out, so are the next research possibilities.

Three-dimensional three-component particle velocimetry for microscale flows using volumetric scanning

International Nuclear Information System (INIS)

Klein, S A; Moran, J L; Posner, J D; Frakes, D H

2012-01-01

We present a diagnostic platform for measuring three-dimensional three-component (3D3C) velocity fields in microscopic volumes. The imaging system uses high-speed Nipkow spinning disk confocal microscopy. Confocal microscopy provides optical sectioning using pinhole spatial filtering which rejects light originating from out-of-focus objects. The system accomplishes volumetric scanning by rapid translation of the high numerical aperture objective using a piezo objective positioner. The motion of fluorescent microspheres is quantified using 3D3C super resolution particle-imaging velocimetry with instantaneous spatial resolutions of the order of 5 µm or less in all three dimensions. We examine 3D3C flow in a PDMS microchannel with an expanding section at 3D acquisition rates of 30 Hz, and find strong agreement with a computational model. Equations from the PIV and PTV literature adapted for a scanning objective provide estimates of maximum measurable velocity. The technique allows for isosurface visualization of 3D particle motion and robust high spatial resolution velocity measurements without requiring a calibration step or reconstruction algorithms. (paper)

Characterization of volumetric flow rate waveforms at the carotid bifurcations of older adults

International Nuclear Information System (INIS)

Hoi, Yiemeng; Xie, Yuanyuan J; Steinman, David A; Wasserman, Bruce A; Najjar, Samer S; Lakatta, Edward G; Ferruci, Luigi; Gerstenblith, Gary

2010-01-01

While it is widely appreciated that volumetric blood flow rate (VFR) dynamics change with age, there has been no detailed characterization of the typical shape of carotid bifurcation VFR waveforms of older adults. Toward this end, retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms proximal and distal to the carotid bifurcations of 94 older adults (age 68 ± 8 years) with little or no carotid artery disease, recruited from the BLSA cohort of the VALIDATE study of factors in vascular aging. Timings and amplitudes of well-defined feature points from these waveforms were extracted automatically and averaged to produce representative common, internal and external carotid artery (CCA, ICA and ECA) waveform shapes. Relative to young adults, waveforms from older adults were found to exhibit a significantly augmented secondary peak during late systole, resulting in significantly higher resistance index (RI) and flow augmentation index (FAI). Cycle-averaged VFR at the CCA, ICA and ECA were 389 ± 74, 245 ± 61 and 125 ± 49 mL min −1 , respectively, reflecting a significant cycle-averaged outflow deficit of 5%, which peaked at around 10% during systole. A small but significant mean delay of 13 ms between arrivals of ICA versus CCA/ECA peak VFR suggested differential compliance of these vessels. Sex and age differences in waveform shape were also noted. The characteristic waveforms presented here may serve as a convenient baseline for studies of VFR waveform dynamics or as suitable boundary conditions for models of blood flow in the carotid arteries of older adults

Two-phase air-water stratified flow measurement using ultrasonic techniques

International Nuclear Information System (INIS)

Fan, Shiwei; Yan, Tinghu; Yeung, Hoi

2014-01-01

In this paper, a time resolved ultrasound system was developed for investigating two-phase air-water stratified flow. The hardware of the system includes a pulsed wave transducer, a pulser/receiver, and a digital oscilloscope. The time domain cross correlation method is used to calculate the velocity profile along ultrasonic beam. The system is able to provide velocities with spatial resolution of around 1mm and the temporal resolution of 200μs. Experiments were carried out on single phase water flow and two-phase air-water stratified flow. For single phase water flow, the flow rates from ultrasound system were compared with those from electromagnetic flow (EM) meter, which showed good agreement. Then, the experiments were conducted on two-phase air-water stratified flow and the results were given. Compared with liquid height measurement from conductance probe, it indicated that the measured velocities were explainable

Computational fluid dynamics (CFD) simulation of hot air flow ...

African Journals Online (AJOL)

Computational Fluid Dynamics simulation of air flow distribution, air velocity and pressure field pattern as it will affect moisture transient in a cabinet tray dryer is performed using SolidWorks Flow Simulation (SWFS) 2014 SP 4.0 program. The model used for the drying process in this experiment was designed with Solid ...

Exergy Based Performance Analysis of Double Flow Solar Air Heater with Corrugated Absorber

OpenAIRE

S. P. Sharma; Som Nath Saha

2017-01-01

This paper presents the performance, based on exergy analysis of double flow solar air heaters with corrugated and flat plate absorber. A mathematical model of double flow solar air heater based on energy balance equations has been presented and the results obtained have been compared with that of a conventional flat-plate solar air heater. The double flow corrugated absorber solar air heater performs thermally better than the flat plate double flow and conventional flat-plate solar air heate...

Polymer electrolyte fuel cells: flow field for efficient air operation

Energy Technology Data Exchange (ETDEWEB)

Buechi, F N; Tsukada, A; Haas, O; Scherer, G G [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

A new flow field was designed for a polymer electrolyte fuel cell stack with an active area of 200 cm{sup 2} for operation at low air stoichiometry and low air over pressure. Optimum of gas flow and channel dimensions were calculated based on the required pressure drop in the fluid. Single cells and a bi-cell stack with the new flow field show an improved current/voltage characteristic when operated at low air stoichiometries as compared to that of the previous non optimized design. (author) 4 figs., 3 refs.

Performance improvement of a cross-flow hydro turbine by air layer effect

International Nuclear Information System (INIS)

Choi, Y D; Yoon, H Y; Inagaki, M; Ooike, S; Kim, Y J; Lee, Y H

2010-01-01

The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. Field test is performed in order to measure the output power of the turbine by a new air supply method. CFD analysis on the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively.The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss at the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.

Experimental investigation of air side heat transfer and fluid flow performances of multi-port serpentine cross-flow mesochannel heat exchanger

International Nuclear Information System (INIS)

Siddiqui, Faisal A.; Dasgupta, Engr Sarbadaman; Fartaj, Amir

2012-01-01

Highlights: ► Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. ► Hot ethylene glycol–water mixture (50:50) at constant mass flow rate is used against varying air flow. ► Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. ► General correlations are proposed for air side heat transfer and fluid flow parameters. - Abstract: Air side force convective heat transfer and flow characteristics of cross-flow mesochannel heat exchanger are investigated experimentally. A series of experiments representing 36 different operating conditions have been conducted on a finned mesochannel heat exchanger through the fully automated dynamic single-phase experimental facility which is capable of handling a wide variety of working fluids in air-to-liquid cross-flow orientation. The mesochannel heat exchanger is made of 15 aluminum slabs with arrays of wavy fins between slabs; 68 one millimeter circular diameter port located at each slab, and the air side frontal area of 304-mm × 304-mm. The ethylene glycol–water mixture as the working fluid in the liquid side was forced to flow through mesochannels maintaining constant inlet temperature and flow rate at 74 °C and 0.0345 kg/s respectively whereas the inlet flowing air into the arrays of wavy fins was changed at four different temperature levels from 28 °C to 43 °C. Frontal air velocity was altered in nine steps from 3 m/s to 11 m/s at each temperature level corresponding range of Reynolds number 752 a a ) and Colburn factor (j a ) were found higher in comparison with other studies.

Comparison of deliverable and exhaustible pressurized air flow rates in laboratory gloveboxes

International Nuclear Information System (INIS)

Compton, J.A.

1994-01-01

Calculations were performed to estimate the maximum credible flow rates of pressurized air into Plutonium Process Support Laboratories gloveboxes. Classical equations for compressible fluids were used to estimate the flow rates. The calculated maxima were compared to another's estimates of glovebox exhaust flow rates and corresponding glovebox internal pressures. No credible pressurized air flow rate will pressurize a glovebox beyond normal operating limits. Unrestricted use of the pressurized air supply is recommended

New sensor for measurement of low air flow velocity. Phase I final report

International Nuclear Information System (INIS)

Hashemian, H.M.; Hashemian, M.; Riggsbee, E.T.

1995-08-01

The project described here is the Phase I feasibility study of a two-phase program to integrate existing technologies to provide a system for determining air flow velocity and direction in radiation work areas. Basically, a low air flow sensor referred to as a thermocouple flow sensor has been developed. The sensor uses a thermocouple as its sensing element. The response time of the thermocouple is measured using an existing in-situ method called the Loop Current Step Response (LCSR) test. The response time results are then converted to a flow signal using a response time-versus-flow correlation. The Phase I effort has shown that a strong correlation exists between the response time of small diameter thermocouples and the ambient flow rate. As such, it has been demonstrated that thermocouple flow sensors can be used successfully to measure low air flow rates that can not be measured with conventional flow sensors. While the thermocouple flow sensor developed in this project was very successful in determining air flow velocity, determining air flow direction was beyond the scope of the Phase I project. Nevertheless, work was performed during Phase I to determine how the new flow sensor can be used to determine the direction, as well as the velocity, of ambient air movements. Basically, it is necessary to use either multiple flow sensors or move a single sensor in the monitoring area and make flow measurements at various locations sweeping the area from top to bottom and from left to right. The results can then be used with empirical or physical models, or in terms of directional vectors to estimate air flow patterns. The measurements can be made continuously or periodically to update the flow patterns as they change when people and objects are moved in the monitoring area. The potential for using multiple thermocouple flow sensors for determining air flow patterns will be examined in Phase II

Air-water two-phase flow through a pipe junction

International Nuclear Information System (INIS)

Suu, Tetsuo

1991-01-01

The distribution of the local void fraction across the section of the conduit was studied experimentally in air-water two-phase flow flowing through a pipe junction with the branching angle of 90deg and the area ratio of unity. As in the previous report, the main conduit of the junction was set up vertically and upward air-water bubbly and slug flows were arranged in the main upstream section. If the flow regime, the quality and the ratio of lateral mass flow discharge of water to total mass flow discharge of water are the same, the larger the Reynolds number is, the more violent the variety of the local void fraction distribution adjacent to the branching part in the lateral conduit is. However, the variety in the main downstream section is scarcely influenced by the Reynolds number. (author)

Study on flow rate measurement and visualization of helium-air exchange flow through a small opening

International Nuclear Information System (INIS)

Fumizawa, Motoo

1992-01-01

This paper deals with an experimental investigation on buoyancy-driven exchange flows through horizontal and inclined openings. The method of the mass increment was developed to measure the flow rate in helium-air system and a displacement fringe technique was adopted in Mach-Zehnder interferometer to visualize the flow. As the result, the followings were obtained: Flow visualization results indicate that the upward and downward plumes of helium and air break through the opening intermittently, and they swing in the lateral direction through the horizontal opening. It is clearly visualized that the exchange flows through the inclined openings take place smoothly and stably in the separated passages. The inclination angle for the maximum Froude number decreases with increasing length-to-diameter ratio in the helium-air system, on the contrary to Mercer's experimental results in the water-brine system indicating that the angle remains almost constant. (author)

Characteristics Air Flow in Room Chamber Test Refrigerator Household Energy Consumption with Inlet Flow Variation

Science.gov (United States)

Susanto, Edy; Idrus Alhamid, M.; Nasruddin; Budihardjo

2018-03-01

Room Chamber is the most important in making a good Testing Laboratory. In this study, the 2-D modeling conducted to assess the effect placed the inlet on designing a test chamber room energy consumption of household refrigerators. Where the geometry room chamber is rectangular and approaching the enclosure conditions. Inlet varied over the side parallel to the outlet and compared to the inlet where the bottom is made. The purpose of this study was to determine and define the characteristics of the airflow in the room chamber using CFD simulation. CFD method is used to obtain flow characteristics in detail, in the form of vector flow velocity and temperature distribution inside the chamber room. The result found that the position of the inlet parallel to the outlet causes air flow cannot move freely to the side of the floor, even flow of air moves up toward the outlet. While by making the inlet is below, the air can move freely from the bottom up to the side of the chamber room wall as well as to help uniform flow.

Flow rate measurement of buoyancy-driven exchange flow by laser Doppler velocimeter

International Nuclear Information System (INIS)

Fumizawa, Motoo

1993-01-01

An experimental investigation was carried out for the buoyancy-driven exchange flow in a narrow vented cylinder concerning the air ingress process during a standing pipe rupture in a high-temperature gas-cooled reactor. In the present study, the evaluation method of exchange flow was developed by measuring the velocity distribution in the cylinder using a laser Doppler velocimeter. The experiments were performed under atmospheric pressure with nitrogen as a working fluid. Rayleigh numbers ranged from 2.0x10 4 to 2.1x10 5 . The exchange flow fluctuated irregularly with time and space in the cylinder. It was found that the exchange velocity distribution along the horizontal axis changed from one-hump to two-hump distribution with increasing Rayleigh number. In the case that the hemisphere wall was cooler than the heated disk, the volumetric exchange flow rate was smaller than that in the case where the hemisphere wall and the heated disk were at the same temperature. (author)

Plenoptic Flow Imaging for Ground Testing, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Instantaneous volumetric flow imaging is crucial to aerodynamic development and testing. Simultaneous volumetric measurement of flow parameters enables accurate...

Numerical study of the air-flow in an oscillating water column wave energy converter

Energy Technology Data Exchange (ETDEWEB)

Paixao Conde, J.M. [Department of Mechanical and Industrial Engineering, Faculty of Sciences and Technology, New University of Lisbon, Monte de Caparica, 2829-516 Caparica (Portugal); IDMEC, Instituto Superior Tecnico, Technical University of Lisbon, 1049-001 Lisboa (Portugal); Gato, L.M.C. [IDMEC, Instituto Superior Tecnico, Technical University of Lisbon, 1049-001 Lisboa (Portugal)

2008-12-15

The paper presents a numerical study of the air-flow in a typical pneumatic chamber geometry of an oscillating water column (OWC)-type wave energy converter (WEC), equipped with two vertical-axis air turbines, asymmetrically placed on the top of the chamber. Outwards and inwards, steady and periodic, air-flow calculations were performed to investigate the flow distribution at the turbines' inlet sections, as well as the properties of the air-jet impinging on the water free-surface. The original design of the OWC chamber is likely to be harmful for the operation of the turbines due to the possible air-jet-produced water-spray at the water free-surface subsequently ingested by the turbine. A geometry modification of the air chamber, using a horizontal baffle-plate to deflect the air from the turbines, is proposed and proved to be very effective in reducing the risk of water-spray production from the inwards flow. The flow distribution at the turbines' inlet sections for the outwards flow was found to be fairly uniform for the geometries considered, providing good inlet flow conditions for the turbines. Steady flow was found to be an acceptable model to study the air-flow inside the pneumatic chamber of an OWC-WEC. (author)

CFD study on the effects of boundary conditions on air flow through an air-cooled condenser

Science.gov (United States)

Sumara, Zdeněk; Šochman, Michal

2018-06-01

This study focuses on the effects of boundary conditions on effectiveness of an air-cooled condenser (ACC). Heat duty of ACC is very often calculated for ideal uniform velocity field which does not correspond to reality. Therefore, this study studies the effect of wind and different landscapes on air flow through ACC. For this study software OpenFOAM was used and the flow was simulated with the use of RANS equations. For verification of numerical setup a model of one ACC cell with dimensions of platform 1.5×1.5 [m] was used. In this experiment static pressures behind fan and air flows through a model of surface of condenser for different rpm of fan were measured. In OpenFOAM software a virtual clone of this experiment was built and different meshes, turbulent models and numerical schemes were tested. After tuning up numerical setup virtual model of real ACC system was built. Influence of wind, landscape and height of ACC on air flow through ACC has been investigated.

Laser sheet light flow visualization for evaluating room air flowsfrom Registers

Energy Technology Data Exchange (ETDEWEB)

Walker, Iain S.; Claret, Valerie; Smith, Brian

2006-04-01

Forced air heating and cooling systems and whole house ventilation systems deliver air to individual rooms in a house via supply registers located on walls ceilings or floors; and occasionally less straightforward locations like toe-kicks below cabinets. Ideally, the air velocity out of the registers combined with the turbulence of the flow, vectoring of air by register vanes and geometry of register placement combine to mix the supply air within the room. A particular issue that has been raised recently is the performance of multiple capacity and air flow HVAC systems. These systems vary the air flow rate through the distribution system depending on the system load, or if operating in a ventilation rather than a space conditioning mode. These systems have been developed to maximize equipment efficiency, however, the high efficiency ratings do not include any room mixing effects. At lower air flow rates, there is the possibility that room air will be poorly mixed, leading to thermal stratification and reduced comfort for occupants. This can lead to increased energy use as the occupants adjust the thermostat settings to compensate and parts of the conditioned space have higher envelope temperature differences than for the well mixed case. In addition, lack of comfort can be a barrier to market acceptance of these higher efficiency systems To investigate the effect on room mixing of reduced air flow rates requires the measurement of mixing of supply air with room air throughout the space to be conditioned. This is a particularly difficult exercise if we want to determine the transient performance of the space conditioning system. Full scale experiments can be done in special test chambers, but the spatial resolution required to fully examine the mixing problem is usually limited by the sheer number of thermal sensors required. Current full-scale laboratory testing is therefore severely limited in its resolution. As an alternative, we used a water-filled scale model

On air-chemistry reduction for hypersonic external flow applications

International Nuclear Information System (INIS)

Ibrahim, Ashraf; Suman, Sawan; Girimaji, Sharath S.

2015-01-01

Highlights: • The existence of the slow manifold for the air-mixture system is shown. • The QSSA estimate of the slow manifold is fairly accurate. • For mid-temperature range the reduction mechanisms could be useful. - Abstract: In external hypersonic flows, viscous and compressibility effects generate very high temperatures leading to significant chemical reactions among air constituents. Therefore, hypersonic flow computations require coupled calculations of flow and chemistry. Accurate and efficient computations of air-chemistry kinetics are of much importance for many practical applications but calculations accounting for detailed chemical kinetics can be prohibitively expensive. In this paper, we investigate the possibility of applying chemical kinetics reduction schemes for hypersonic air-chemistry. We consider two chemical kinetics sets appropriate for three different temperature ranges: 2500 K to 4500 K; 4500 K to 9000 K; and above 9000 K. By demonstrating the existence of the so-called the slow manifold in each of the chemistry sets, we show that judicious chemical kinetics reduction leading to significant computational savings is possible without much loss in accuracy

Air Flow and Pressure Drop Measurements Across Porous Oxides

Science.gov (United States)

Fox, Dennis S.; Cuy, Michael D.; Werner, Roger A.

2008-01-01

This report summarizes the results of air flow tests across eight porous, open cell ceramic oxide samples. During ceramic specimen processing, the porosity was formed using the sacrificial template technique, with two different sizes of polystyrene beads used for the template. The samples were initially supplied with thicknesses ranging from 0.14 to 0.20 in. (0.35 to 0.50 cm) and nonuniform backside morphology (some areas dense, some porous). Samples were therefore ground to a thickness of 0.12 to 0.14 in. (0.30 to 0.35 cm) using dry 120 grit SiC paper. Pressure drop versus air flow is reported. Comparisons of samples with thickness variations are made, as are pressure drop estimates. As the density of the ceramic material increases the maximum corrected flow decreases rapidly. Future sample sets should be supplied with samples of similar thickness and having uniform surface morphology. This would allow a more consistent determination of air flow versus processing parameters and the resulting porosity size and distribution.

Improving the efficiency of gas turbine systems with volumetric solar receivers

International Nuclear Information System (INIS)

Petrakopoulou, Fontina; Sánchez-Delgado, Sergio; Marugán-Cruz, Carolina; Santana, Domingo

2017-01-01

Highlights: • Study of small and large-scale solar-combined cycle plants with volumetric receivers. • Increase of inlet temperature of combustion air using solar energy. • The combustion exergy efficiency starts to decrease over a certain temperature. • Indications obtained from the energy and exergy analyses differ. - Abstract: The combustion process of gas turbine systems is typically associated with the highest thermodynamic inefficiencies among the system components. A method to increase the efficiency of a combustor and, consequently that of the gas turbine, is to increase the temperature of the entering combustion air. This measure reduces the consumption of fuel and improves the environmental performance of the turbine. This paper studies the incorporation of a volumetric solar receiver into existing gas turbines in order to increase the temperature of the inlet combustion air to 800 °C and 1000 °C. For the first time, detailed thermodynamic analyses involving both energy and exergy principles of both small-scale and large-scale hybrid (solar-combined cycle) power plants including volumetric receivers are realized. The plants are based on real gas turbine systems, the base operational characteristics of which are derived and reported in detail. It is found that the indications obtained from the energy and exergy analyses differ. The addition of the solar plant achieves an increase in the exergetic efficiency when the conversion of solar radiation into thermal energy (i.e., solar plant efficiency) is not accounted for in the definition of the overall plant efficiency. On the other hand, it is seen that it does not have a significant effect on the energy efficiency. Nevertheless, when the solar efficiency is included in the definition of the overall efficiency of the plants, the addition of the solar receiver always leads to an efficiency reduction. It is found that the exergy efficiency of the combustion chamber depends on the varying air

Measurement of Air Flow Rate in a Naturally Ventilated Double Skin Facade

DEFF Research Database (Denmark)

Kalyanova, Olena; Jensen, Rasmus Lund; Heiselberg, Per

2007-01-01

Air flow rate in a naturally ventilated space is extremely difficult to measure due to the stochastic nature of wind, and as a consequence non-uniform and dynamic flow conditions. This paper describes three different methods to measure the air flow in a full-scale outdoor test facility...... with a naturally ventilated double skin façade. In the first method, the air flow in the cavity is estimated on the basis of six measured velocity profiles. The second method is represented by constant injection of tracer gas and in the third method a measured relation in the laboratory is used to estimate...... the flow rate on the basis of continues measurement of the pressure difference between the surface pressure at the opening and inside pressure of the double skin façade. Although all three measurement methods are difficult to use under such dynamic air flow conditions, two of them show reasonable agreement...

Effect of Low Co-flow Air Velocity on Hydrogen-air Non-premixed Turbulent Flame Model

Directory of Open Access Journals (Sweden)

Noor Mohsin Jasim

2017-08-01

Full Text Available The aim of this paper is to provide information concerning the effect of low co-flow velocity on the turbulent diffusion flame for a simple type of combustor, a numerical simulated cases of turbulent diffusion hydrogen-air flame are performed. The combustion model used in this investigation is based on chemical equilibrium and kinetics to simplify the complexity of the chemical mechanism. Effects of increased co-flowing air velocity on temperature, velocity components (axial and radial, and reactants have been investigated numerically and examined. Numerical results for temperature are compared with the experimental data. The comparison offers a good agreement. All numerical simulations have been performed using the Computational Fluid Dynamics (CFD commercial code FLUENT. A comparison among the various co-flow air velocities, and their effects on flame behavior and temperature fields are presented.

Simulation of the air flows in many industrial pleated filters

International Nuclear Information System (INIS)

Del Fabbro, L.; Brun, P.; Laborde, J.C.; Lacan, J.; Ricciardi, L.; Renoux, A.

2000-01-01

The study presents results concerning the characterization of the charge loss and the air flow in nuclear and automobile type pleated filters. The experimental studies in correlation with the numerical models showed an homogenous distribution of the air flows in a THE nuclear type filter, whereas the distribution is heterogenous in the case of an automobile filter. (A.L.B.)

Numerical Modelling Of Humid Air Flow Around A Porous Body

Directory of Open Access Journals (Sweden)

Bohojło-Wiśniewska Aneta

2015-09-01

Full Text Available This paper presents an example of humid air flow around a single head of Chinese cabbage under conditions of complex heat transfer. This kind of numerical simulation allows us to create a heat and humidity transfer model between the Chinese cabbage and the flowing humid air. The calculations utilize the heat transfer model in porous medium, which includes the temperature difference between the solid (vegetable tissue and fluid (air phases of the porous medium. Modelling and calculations were performed in ANSYS Fluent 14.5 software.

A coupled surface/subsurface flow model accounting for air entrapment and air pressure counterflow

DEFF Research Database (Denmark)

Delfs, Jens Olaf; Wang, Wenqing; Kalbacher, Thomas

2013-01-01

wave) shallow flow and two-phase flow in a porous medium. The simultaneous mass transfer between the soil, overland, and atmosphere compartments is achieved by upgrading a fully established leakance concept for overland-soil liquid exchange to an air exchange flux between soil and atmosphere. In a new...... algorithm, leakances operate as a valve for gas pressure in a liquid-covered porous medium facilitating the simulation of air out-break events through the land surface. General criteria are stated to guarantee stability in a sequential iterative coupling algorithm and, in addition, for leakances to control...

Experimental Evaluation of Discharge Characteristics in Inhomogeneous Fields under Air Flow

DEFF Research Database (Denmark)

Vogel, Stephan; Holbøll, Joachim

2018-01-01

voltages and a laminar air flow up to 22 m/s. In the first setup, the gap was exposed to a variable DC potential of up to 100 kV in order to create space charges in the vicinity of the electrode. The impact of the air flow on partial discharges and the dynamic behavior of the space charges is evaluated...... by means of partial discharge measurement and ultraviolet photography. The results show that the air flow increases the frequency of partial discharges in the gap due to an increased rate of space charge removal in the high field area around the tip of the electrode. The partial discharge behavior shows...... higher dependency on air flow at positive tip polarity as compared to the negative polarity. In the second setup, the standard impulse voltage created by a multistage impulse voltage generator was superimposed to a DC voltage, which continuously created corona and space charges around the tip...

Startup and oxygen concentration effects in a continuous granular mixed flow autotrophic nitrogen removal reactor.

Science.gov (United States)

Varas, Rodrigo; Guzmán-Fierro, Víctor; Giustinianovich, Elisa; Behar, Jack; Fernández, Katherina; Roeckel, Marlene

2015-08-01

The startup and performance of the completely autotrophic nitrogen removal over nitrite (CANON) process was tested in a continuously fed granular bubble column reactor (BCR) with two different aeration strategies: controlling the oxygen volumetric flow and oxygen concentration. During the startup with the control of oxygen volumetric flow, the air volume was adjusted to 60mL/h and the CANON reactor had volumetric N loadings ranging from 7.35 to 100.90mgN/Ld with 36-71% total nitrogen removal and high instability. In the second stage, the reactor was operated at oxygen concentrations of 0.6, 0.4 and 0.2mg/L. The best condition was 0.2 mgO2/L with a total nitrogen removal of 75.36% with a CANON reactor activity of 0.1149gN/gVVSd and high stability. The feasibility and effectiveness of CANON processes with oxygen control was demonstrated, showing an alternative design tool for efficiently removing nitrogen species. Copyright © 2015 Elsevier Ltd. All rights reserved.

Calculation of the dynamic air flow resistivity of fibre materials

DEFF Research Database (Denmark)

Tarnow, Viggo

1997-01-01

The acoustic attenuation of acoustic fiber materials is mainly determined by the dynamic resistivity to an oscillating air flow. The dynamic resistance is calculated for a model with geometry close to the geometry of real fibre material. The model constists of parallel cylinders placed randomly.......The second procedure is an extension to oscillating air flow of the Brinkman self-consistent procedure for dc flow. The procedures are valid for volume concentrations of cylinders less than 0.1. The calculations show that for the density of fibers of interest for acoustic fibre materials the simple self...

Theoretical and numerical studies of transonic flow of moist air around a thin airfoil

Energy Technology Data Exchange (ETDEWEB)

Lee, Jang-Chang [School of Mechanical Engineering, Andong National University, Kyongbuk (Korea); Rusak, Zvi [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY (United States)

2002-07-01

Numerical studies of a two-dimensional and steady transonic flow of moist air around a thin airfoil with condensation are presented. The computations are guided by a recent transonic small-disturbance (TSD) theory of Rusak and Lee (2000) on this topic. The asymptotic model provides a simplified framework to investigate the changes in the flow field caused by the heat addition from a nonequilibrium process of condensation of water vapor in the air by homogeneous nucleation. An iterative method which is based on a type-sensitive difference scheme is applied to solve the governing equations. The results demonstrate the similarity rules for transonic flow of moist air and the effects of energy supply by condensation on the flow behavior. They provide a method to formulate various cases with different flow properties that have a sufficiently close behavior and that can be used in future computations, experiments, and design of flow systems operating with moist air. Also, the computations show that the TSD solutions of moist air flows represent the essence of the flow character computed from the inviscid fluid flow equations. (orig.)

Air-water flow measurement for ERVC conditions by LIF/PIV

International Nuclear Information System (INIS)

Yoon, Jong Woong; Jeong, Yong Hoon

2016-01-01

Critical heat flux (CHF) of the external reactor vessel wall is a safety limit that indicate the integrity of the reactor vessel during the situation. Many research conducted CHF experiments in the IVR-ERVC conditions. However, the flow velocity field which is an important factor in the CHF mechanism were not studied enough in the IVR-ERVC situations. In this study, flow measurements including velocity vector field and the liquid velocity in the IVR-ERVC conditions were studied. The air-water two phase flow loop simulating IVRERVC conditions was set up and liquid velocity field was measured by LIF/PIV technique in this study. The experiment was conducted with and without air injection conditions. For the air-water flow experiment, liquid velocity at the outside of two phase boundary layer became higher and the two phase boundary layer thickness became smaller when the mass flux increases. The velocity data obtained in this study are expected to improve the CHF correlation in the IVR-ERVC situations.

Air-water flow measurement for ERVC conditions by LIF/PIV

Energy Technology Data Exchange (ETDEWEB)

Yoon, Jong Woong; Jeong, Yong Hoon [KAIST, Daejeon (Korea, Republic of)

2016-05-15

Critical heat flux (CHF) of the external reactor vessel wall is a safety limit that indicate the integrity of the reactor vessel during the situation. Many research conducted CHF experiments in the IVR-ERVC conditions. However, the flow velocity field which is an important factor in the CHF mechanism were not studied enough in the IVR-ERVC situations. In this study, flow measurements including velocity vector field and the liquid velocity in the IVR-ERVC conditions were studied. The air-water two phase flow loop simulating IVRERVC conditions was set up and liquid velocity field was measured by LIF/PIV technique in this study. The experiment was conducted with and without air injection conditions. For the air-water flow experiment, liquid velocity at the outside of two phase boundary layer became higher and the two phase boundary layer thickness became smaller when the mass flux increases. The velocity data obtained in this study are expected to improve the CHF correlation in the IVR-ERVC situations.

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.

Experimental verification of air flow rate measurement for representative isokinetic air sampling in ventilation stacks

International Nuclear Information System (INIS)

Okruhlica, P.; Mrtvy, M.; Kopecky, Z.

2009-01-01

Nuclear facilities are obliged to monitor their discharge's influence on environment. Main monitored factions in NPP's ventilation stacks are usually noble gasses, particulates and iodine. These factions are monitored in air sampled from ventilation stack by means of sampling rosette and bypass followed with on-line measuring monitors and balance sampling devices with laboratory evaluations. Correct air flow rate measurement and representative iso-kinetic air sampling system is essential for physical correct and metrological accurate evaluation of discharge influence on environment. Pairs of measuring sensors (Anemometer, pressure gauge, thermometer and humidity meter) are symmetrically placed in horizontal projection of stack on positions based on measured air flow velocity distribution characteristic, Analogically diameter of sampling rosette nozzles and their placement in the middle of 6 - 7 annuluses are calculated for assurance of representative iso-kinetic sampling. (authors)

Experimental verification of air flow rate measurement for representative isokinetic air sampling in ventilation stacks

International Nuclear Information System (INIS)

Okruhlica, P.; Mrtvy, M.; Kopecky, Z.

2008-01-01

Nuclear facilities are obliged to monitor their discharge's influence on environment. Main monitored factions in NPP's ventilation stacks are usually noble gasses, particulates and iodine. These factions are monitored in air sampled from ventilation stack by means of sampling rosette and bypass followed with on-line measuring monitors and balance sampling devices with laboratory evaluations. Correct air flow rate measurement and representative iso-kinetic air sampling system is essential for physical correct and metrological accurate evaluation of discharge influence on environment. Pairs of measuring sensors (Anemometer, pressure gauge, thermometer and humidity meter) are symmetrically placed in horizontal projection of stack on positions based on measured air flow velocity distribution characteristic, Analogically diameter of sampling rosette nozzles and their placement in the middle of 6- 7 annuluses are calculated for assurance of representative iso-kinetic sampling. (authors)

EPA flow reference method testing and analysis: Findings report

International Nuclear Information System (INIS)

1999-06-01

This report describes an experimental program sponsored by the US Environmental Protection Agency (EPA) to evaluate potential improvements to the Agency's current reference method for measuring volumetric flow (Method 2, 40 CFR Part 60, Appendix B). Method 2 (Determination of Stack Gas Velocity and Volumetric Flow Rate (Type S Pitot Tube)) specifies measurements to determine volumetric flow, but does not prescribe specific procedures to account for yaw or pitch angles of flow when the flow in the stack is not axial. Method 2 also allows the use of only two probe types, the Type S and the Prandtl

Spirometry and volumetric capnography in lung function assessment of obese and normal-weight individuals without asthma.

Science.gov (United States)

Ferreira, Mariana S; Mendes, Roberto T; Marson, Fernando A L; Zambon, Mariana P; Antonio, Maria A R G M; Paschoal, Ilma A; Toro, Adyléia A D C; Severino, Silvana D; Ribeiro, Maria A G O; Ribeiro, José D

To analyze and compare lung function of obese and healthy, normal-weight children and adolescents, without asthma, through spirometry and volumetric capnography. Cross-sectional study including 77 subjects (38 obese) aged 5-17 years. All subjects underwent spirometry and volumetric capnography. The evaluations were repeated in obese subjects after the use of a bronchodilator. At the spirometry assessment, obese individuals, when compared with the control group, showed lower values of forced expiratory volume in the first second by forced vital capacity (FEV 1 /FVC) and expiratory flows at 75% and between 25 and 75% of the FVC (p11 years (p<0.05). Even without the diagnosis of asthma by clinical criteria and without response to bronchodilator use, obese individuals showed lower FEV 1 /FVC values and forced expiratory flow, indicating the presence of an obstructive process. Volumetric capnography showed that obese individuals had higher alveolar tidal volume, with no alterations in ventilation homogeneity, suggesting flow alterations, without affecting lung volumes. Copyright © 2017 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

Measurement and Modelling of Air Flow Rate in a Naturally Ventilated Double Skin Facade

DEFF Research Database (Denmark)

Heiselberg, Per; Kalyanova, Olena; Jensen, Rasmus Lund

2008-01-01

Air flow rate in a naturally ventilated double skin façade (DSF) is extremely difficult to measure due to the stochastic nature of wind, and as a consequence non-uniform and dynamic flow conditions. This paper describes the results of two different methods to measure the air flow in a full...... by the thermal simulation program, BSim, based on measured weather boundary conditions are compared to the measured air temperature, temperature gradient and mass flow rate in the DSF cavity. The results show that it is possible to predict the temperature distribution and airflow in the DSF although some......-scale outdoor test facility with a naturally ventilated double skin façade. Although both methods are difficult to use under such dynamic air flow conditions, they show reasonable agreement and can be used for experimental validation of numerical models of natural ventilation air flow in DSF. Simulations...

Helium-air exchange flows through partitioned opening and two-opening

International Nuclear Information System (INIS)

Kang, T. I.

1997-01-01

This paper describes experimental investigations of helium-air exchange flows through partitioned opening and two-opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature engineering test reactor. A test vessel with the two types of small opening on top of test cylinder is used for experiments. An estimation method of mass increment is developed to measure the exchange flow rate. Upward flow of the helium and downward flow of the air in partitioned opening system interact out of entrance and exit of the opening. Therefore, an experiment with two-opening system is made to investigate effect of the fluids interaction of partitioned opening system. As a result of comparison of the exchange flow rates between two types of the opening system, it is demonstrated that the exchange flow rate of the two-opening system is larger than that of the partitioned opening system because of absence of the effect of fluids interaction. (author)

Measurement of the resistivity of porous materials with an alternating air-flow method.

Science.gov (United States)

Dragonetti, Raffaele; Ianniello, Carmine; Romano, Rosario A

2011-02-01

Air-flow resistivity is a main parameter governing the acoustic behavior of porous materials for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic materials.

Visualization of the air flow behind the automotive benchmark vent

Science.gov (United States)

Pech, Ondrej; Jedelsky, Jan; Caletka, Petr; Jicha, Miroslav

2015-05-01

Passenger comfort in cars depends on appropriate function of the cabin HVAC system. A great attention is therefore paid to the effective function of automotive vents and proper formation of the flow behind the ventilation outlet. The article deals with the visualization of air flow from the automotive benchmark vent. The visualization was made for two different shapes of the inlet channel connected to the benchmark vent. The smoke visualization with the laser knife was used. The influence of the shape of the inlet channel to the airflow direction, its enlargement and position of air flow axis were investigated.

Visualization of the air flow behind the automotive benchmark vent

Directory of Open Access Journals (Sweden)

Pech Ondrej

2015-01-01

Full Text Available Passenger comfort in cars depends on appropriate function of the cabin HVAC system. A great attention is therefore paid to the effective function of automotive vents and proper formation of the flow behind the ventilation outlet. The article deals with the visualization of air flow from the automotive benchmark vent. The visualization was made for two different shapes of the inlet channel connected to the benchmark vent. The smoke visualization with the laser knife was used. The influence of the shape of the inlet channel to the airflow direction, its enlargement and position of air flow axis were investigated.

Energy recovery from air flow in underground railway systems

Energy Technology Data Exchange (ETDEWEB)

Morrone, B.; Mariani, A. [Seconda Univ. degli studi di Napoli, Aversa (Italy). Dept. of Aerospace and Mechanical Engineering; Costanzo, M.L. [Tecnosistem spa, Napoli (Italy)

2010-07-01

The 20-20-20 energy policy of the European Union commits members to reduce carbon dioxide (CO{sub 2}) emissions by 20 per cent by 2020, and stipulates that 20 per cent of final-use energy is to be supplied by renewable energy sources. This paper proposed the concept of recovering energy from underground trains by using the air flow inside tunnels to drive energy conversion systems such as turbines to generate electricity. Underground trains use much of their power to overcome the aerodynamic resistance moving the air in front of the train, creating a piston effect when travelling inside tunnels at relatively low speed. Numerical simulations were used in this study to determine how much electricity could be produced. A one-dimensional numerical analysis of a specific subway train track was used to evaluate the air flow magnitude inside the tunnel. Once the air flow features were detected, the potential electricity production was evaluated by considering the characteristics of a Wells turbine. Two types of 3-dimensional models of the tunnel and train were presented. One considered a long straight tunnel with a train running in it, and a small portion of a bypass tunnel. The other considered a large part of an opposite tunnel connected to the main one through the by-pass tunnel. Both the 3D models revealed a maximum flow rate of 2.5 x 105 m{sup 3}/h, while the 1D model showed an air flow of 1.5 x 105 m{sup 3}/h. The difference was due primarily to the presence of fans in the 1D Model and different modelling assumptions. It was concluded that one single Wells type turbine placed in a by-pass tunnel can produce 32.6 kWh per day, or about 10 MWh per year, resulting in a CO{sub 2} savings of about 5.5 tons per year. 8 refs., 1 tab., 11 figs.

VOLUMETRIC LEAK DETECTION IN LARGE UNDERGROUND STORAGE TANKS - VOLUME II: APPENDICES A-E

Science.gov (United States)

The program of experiments conducted at Griffiss Air Force Base was devised to expand the understanding of large underground storage tank behavior as it impacts the performance of volumetric leak detection testing. The report addresses three important questions about testing the ...

Investigation of effect of air flow rate on Zircaloy-4 oxidation kinetics and breakaway phenomenon in air at 850 .deg. C

International Nuclear Information System (INIS)

Maeng, Yunhwan; Lee, Jaeyoung; Park, Sanggil

2016-01-01

This paper analyzed an effect of flow rate on oxidation kinetics of Zircaloy-4 in air at 850 .deg. C. In case of the oxidation of Zircaloy-4 in air at 850 .deg. C, acceleration of oxidation kinetics from parabolic to linear (breakaway phenomenon) occurs. Oxidation and breakaway kinetics of the Zircaloy-4 in air was experimentally studied by changing a flow rate of argon/air mixture. Tests were conducted at 850 .deg. C under constant ratio of argon and air. The effects of flow rate on the oxidation and breakaway kinetics was observed. This paper is based on a revised and considerably extended presentation given at the 21 st International Quench Workshop. The effects of flow conditions on the oxidation kinetics of Zircaloy-4 samples were explained with residence time and percent flow efficiency. In addition, several issues were observed from this study, interdiffusion at breakaway and deformation of oxide structure by breakaway phenomenon

The effect of inlet conditions on the air side hydraulic resistance and flow maldistribution in industrial air heaters

Energy Technology Data Exchange (ETDEWEB)

Hoffmann-Vocke, Jonas, E-mail: jh63@waikato.ac.nz [University of Waikato, Energy Research Group, School of Science and Engineering, Private Bag 3105, Hamilton 3240 (New Zealand); Neale, James, E-mail: jamesn@waikato.ac.nz [University of Waikato, Energy Research Group, School of Science and Engineering, Private Bag 3105, Hamilton 3240 (New Zealand); Walmsley, Michael, E-mail: walmsley@waikato.ac.nz [University of Waikato, Department of Engineering, School of Science and Engineering, Private Bag 3105, Hamilton 3240 (New Zealand)

2011-08-15

Highlights: > Measured the effects of air heater inlet header geometry on hydraulic performance. > Measured the effects of inlet header flow maldistribution on hydraulic performance. > Inlet header flow maldistribution increases air heater system hydraulic resistance. - Abstract: Experimental system hydraulic resistance measurements on a scale air heater unit have highlighted the excessive hydraulic resistance of typical industry configurations. Both poor header inlet conditions and large header expansion angles are shown to contribute to system hydraulic resistance magnitudes 20-100% higher than suitable benchmark cases. Typical centrifugal fan system efficiencies well under 80% multiply the system resistance effects resulting in larger fan power penalties. Velocity profile measurements taken upstream and downstream of the test heat exchanger under flow maldistribution conditions provide insight into the flow maldistribution spreading caused by the heat exchanger resistance. The anisotropic resistance of the plate fin-and-tube heat exchanger is shown to result in resistance induced flow dispersion being concentrated in the axis parallel to the plate fins.

The effect of inlet conditions on the air side hydraulic resistance and flow maldistribution in industrial air heaters

International Nuclear Information System (INIS)

Hoffmann-Vocke, Jonas; Neale, James; Walmsley, Michael

2011-01-01

Highlights: → Measured the effects of air heater inlet header geometry on hydraulic performance. → Measured the effects of inlet header flow maldistribution on hydraulic performance. → Inlet header flow maldistribution increases air heater system hydraulic resistance. - Abstract: Experimental system hydraulic resistance measurements on a scale air heater unit have highlighted the excessive hydraulic resistance of typical industry configurations. Both poor header inlet conditions and large header expansion angles are shown to contribute to system hydraulic resistance magnitudes 20-100% higher than suitable benchmark cases. Typical centrifugal fan system efficiencies well under 80% multiply the system resistance effects resulting in larger fan power penalties. Velocity profile measurements taken upstream and downstream of the test heat exchanger under flow maldistribution conditions provide insight into the flow maldistribution spreading caused by the heat exchanger resistance. The anisotropic resistance of the plate fin-and-tube heat exchanger is shown to result in resistance induced flow dispersion being concentrated in the axis parallel to the plate fins.

Effects of air flow maldistribution on refrigeration system dynamics of air source heat pump chiller under frosting conditions

International Nuclear Information System (INIS)

Gong Jianying; Gao Tieyu; Yuan Xiuling; Huang Dong

2008-01-01

The effects of air flow maldistribution on the performance of an air source heat pump chiller under frosting conditions were investigated experimentally. The results indicated that air flow maldistribution was the dominant factor leading to hunting of the thermostatic expansion valve for medium and/or large size finned tube evaporators. With air flow maldistribution degree (AMD) increasing, frost occurred earlier, and the frost layer grew faster. The operating characteristics became lower when AMD was increased. We found such phenomenon seemed to be related to both the difference of refrigerant outlet superheat and the frosting velocity. In the hunting stage, the frost block effect became the main factor degrading the refrigeration system performance. With AMD increasing, the heat pump system pertinent performance data (suction pressure, evaporation temperature, discharge pressure, refrigerant outlet temperature, etc.) were degraded more dramatically

Pressure loss of the annular air-liquid flow in vertical tufes

Energy Technology Data Exchange (ETDEWEB)

Schmal, M [Rio de Janeiro Univ. (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia; Cantalino, A [Rio de Janeiro Univ. (Brazil). Dept. de Engenharia Quimica

1976-01-01

In this work the pressure loss of the annular air-liquid flow in vertical tubes has been determined. Correlations are presented for the frictional pressure drop. The dimensional analysis and the following fluid systems were used for this determination: air-water, air-alcohol solutions and air-water and surfactants.

A new method for controlling refrigerant flow in automobile air conditioning

Energy Technology Data Exchange (ETDEWEB)

Xuquan Li; Jiangping Chen; Zhijiu Chen [Shanghai Jiao Tong University (China). Institute of Refrigeration and Cryogenics Engineering; Weihua Liu; Wei Hu; Xiaobing Liu [Shanghai Delphi Automotive Air Conditiong Systems Co. Ltd., Changhai (China)

2004-05-01

This paper describes the improvement of the refrigerant flow control method by using an electronic expansion valve (EEV) which is driven by a stepper motor in automobile air conditioning system. An EEV can make a quick response to the abrupt change in the refrigerant flow rate during the change in automobile speed and the thermostatic on/off operation. The flow rate characteristic of the EEV for automobile air conditioning was presented. A microcontroller is used to receive the input signal and generate the output signal to control the opening of the EEV. The fuzzy self-tuning proportional-integral-derivative (PID) control method is employed. Experimental results show that the new control method can feed adequate refrigerant flow into the evaporator in various operations. The evaporator discharge air temperature has dropped by approximately 3{sup o}C as compared with that of the conventional PID control system. (author)

Horizontal Air-Water Flow Analysis with Wire Mesh Sensor

International Nuclear Information System (INIS)

De Salve, M; Monni, G; Panella, B

2012-01-01

A Wire Mesh Sensor, based on the measurement of the local instantaneous conductivity of the two-phase mixture, has been used to characterize the fluid dynamics of the gas–liquid interface in a horizontal pipe flow. Experiments with a pipe of a nominal diameter of 19.5 mm and total length of 6 m, have been performed with air/water mixtures, at ambient conditions. The flow quality ranges from 0.00016 to 0.22 and the superficial velocities range from 0.1 to 10.5 m/s for air and from 0.02 to 1.7 m/s for water; the flow pattern is stratified, slug/plug and annular. A sensor (WMS200) with an inner diameter of 19.5 mm and a measuring matrix of 16×16 points equally distributed over the cross-section has been chosen for the measurements. From the analysis of the Wire Mesh Sensor digital signals the average and the local void fraction are evaluated and the flow patterns are identified with reference to space, time and flow rate boundary conditions.

Experimental research on the flow field uniformity in the filter house of a nuclear air cleaning system

International Nuclear Information System (INIS)

Jiang Feng; Yang Jun; Ye Suisheng

2000-01-01

The filter house structure is designed using similarity laws showing that the filter house structure causes a non-uniform flow field. The flow field is also measured experimentally. The air flow field is analyzed for different conditions. The results show that: (1) The HEPA filters affect the dispersion of the air flow; (2) The appropriate angle for air input to the rectifier satisfies the requirements for uniform air flow for the test conditions; (3) The rectifier has little influence on the air flow for operating conditions

The fabrication of plastic cages for suspension in mass air flow racks.

Science.gov (United States)

Nielsen, F H; Bailey, B

1979-08-01

A cage for suspension in mass air flow racks was constructed of plastic and used to house rats. Little or no difficulty was encountered with the mass air flow rack-suspended cage system during the 4 years it was used for the study of trace elements.

A constant flow filter air sampler for workplace environments

International Nuclear Information System (INIS)

Parulian, A.; Rodgers, J.C.; McFarland, A.R.

1996-01-01

A filter air sampler has been developed for sampling radionuclide aerosol particles form the workplace environment. It provides easy filter changing, constant flow sampling, and a visual display to indicate proper operation. An experimental study was conducted to characterize the collection efficiency of the sampler as affected by variations in room air velocity, particle size, sampling flow rate, inlet geometry, and inlet orientation to the free stream. Tests were carried out in a wing tunnel at velocities between 0.3 m s -1 and 2.0 m s -1 , which is a range that covers anticipated velocities in the typical highly ventilated workplace environment of a nuclear facility. Nearly monodisperse aerosols with sizes between 5 and 20 μm aerodynamic diameter were sampled at flow rates between 28.3 and 84.9 L min -1 . Inlet orientations of 0 degree, 90 degree, and 180 degree from the horizontal were selected for evaluation. When the sampler was oriented at 0 degree over various ranges of free stream velocities, sampling flow rates and particle sizes, the transmission efficiency of aerosol was typically greater than 95%. The transmission efficiencies varied form 80% to 106% for 10-μm aerodynamic diameter particles over the previously noted range of free stream velocities and inlet orientations. Uniformity of deposits of 10 μm aerodynamic diameter particles on collection filters was examined for a sampling rate of 57 L min -1 , a sampler orientation of 90 degree into the wind and wind speeds of 0.3-2 m s -1 . The coefficients of variation for the areal density of the deposits ranged from 6.1% to 37.2%. A miniature critical flow venturi with a constant sampling flow rate of 57 L min -1 was developed for application to the new filter air sampler. It was demonstrated that the performance of the new filter air sampler is quite acceptable over a wide range of conditions. 31 refs., 8 figs., 1 tab

Volumetric B1 (+) mapping of the brain at 7T using DREAM.

Science.gov (United States)

Nehrke, Kay; Versluis, Maarten J; Webb, Andrew; Börnert, Peter

2014-01-01

To tailor and optimize the Dual Refocusing Echo Acquisition Mode (DREAM) approach for volumetric B1 (+) mapping of the brain at 7T. A new DREAM echo timing scheme based on the virtual stimulated echo was derived to minimize potential effects of transverse relaxation. Furthermore, the DREAM B1 (+) mapping performance was investigated in simulations and experimentally in phantoms and volunteers for volumetric applications, studying and optimizing the accuracy of the sequence with respect to saturation effects, slice profile imperfections, and T1 and T2 relaxation. Volumetric brain protocols were compiled for different isotropic resolutions (5-2.5 mm) and SENSE factors, and were studied in vivo for different RF drive modes (circular/linear polarization) and the application of dielectric pads. Volumetric B1 (+) maps with good SNR at 2.5 mm isotropic resolution were acquired in about 20 s or less. The specific absorption rate was well below the safety limits for all scans. Mild flow artefacts were observed in the large vessels. Moreover, a slight contrast in the ventricle was observed in the B1 (+) maps, which could be attributed to T1 and T2 relaxation effects. DREAM enables safe, very fast, and robust volumetric B1 (+) mapping of the brain at ultrahigh fields. Copyright © 2013 Wiley Periodicals, Inc.

Thermistor based, low velocity isothermal, air flow sensor

International Nuclear Information System (INIS)

Cabrita, Admésio A C M; Mendes, Ricardo; Quintela, Divo A

2016-01-01

The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms −1 ). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms −1 to 2 ms −1 with a standard uncertainty error less than 4%. (paper)

Air-Induced Drag Reduction at High Reynolds Numbers: Velocity and Void Fraction Profiles

Science.gov (United States)

Elbing, Brian; Mäkiharju, Simo; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2010-11-01

The injection of air into a turbulent boundary layer forming over a flat plate can reduce the skin friction. With sufficient volumetric fluxes an air layer can separate the solid surface from the flowing liquid, which can produce drag reduction in excess of 80%. Several large scale experiments have been conducted at the US Navy's Large Cavitation Channel on a 12.9 m long flat plate model investigating bubble drag reduction (BDR), air layer drag reduction (ALDR) and the transition between BDR and ALDR. The most recent experiment acquired phase velocities and void fraction profiles at three downstream locations (3.6, 5.9 and 10.6 m downstream from the model leading edge) for a single flow speed (˜6.4 m/s). The profiles were acquired with a combination of electrode point probes, time-of-flight sensors, Pitot tubes and an LDV system. Additional diagnostics included skin-friction sensors and flow-field image visualization. During this experiment the inlet flow was perturbed with vortex generators immediately upstream of the injection location to assess the robustness of the air layer. From these, and prior measurements, computational models can be refined to help assess the viability of ALDR for full-scale ship applications.

Macroscopic Model and Simulation Analysis of Air Traffic Flow in Airport Terminal Area

Directory of Open Access Journals (Sweden)

Honghai Zhang

2014-01-01

Full Text Available We focus on the spatiotemporal characteristics and their evolvement law of the air traffic flow in airport terminal area to provide scientific basis for optimizing flight control processes and alleviating severe air traffic conditions. Methods in this work combine mathematical derivation and simulation analysis. Based on cell transmission model the macroscopic models of arrival and departure air traffic flow in terminal area are established. Meanwhile, the interrelationship and influential factors of the three characteristic parameters as traffic flux, density, and velocity are presented. Then according to such models, the macro emergence of traffic flow evolution is emulated with the NetLogo simulation platform, and the correlativity of basic traffic flow parameters is deduced and verified by means of sensitivity analysis. The results suggest that there are remarkable relations among the three characteristic parameters of the air traffic flow in terminal area. Moreover, such relationships evolve distinctly with the flight procedures, control separations, and ATC strategies.

Dissolved methane oxidation and competition for oxygen in down-flow hanging sponge reactor for post-treatment of anaerobic wastewater treatment

OpenAIRE

Hatamoto, Masashi; Miyauchi, Tomo; Kindaichi, Tomonori; Ozaki, Noriatsu; Ohashi, Akiyoshi

2011-01-01

Post-treatment of anaerobic wastewater was undertaken to biologically oxidize dissolved methane, with the aim of preventing methane emission. The performance of dissolved methane oxidation and competition for oxygen among methane, ammonium, organic matter, and sulfide oxidizing bacteria were investigated using a lab-scale closed-type down-flow hanging sponge (OHS) reactor. Under the oxygen abundant condition of a hydraulic retention time of 2 h and volumetric air supply rate of 12.95 m(3)-air...

Helium-air counter flow in rectangular channels

International Nuclear Information System (INIS)

Fumizawa, Motoo; Tanaka, Gaku; Zhao, Hong; Hishida, Makoto; Shiina, Yasuaki

2004-01-01

This paper deals with numerical analysis of helium-air counter flow in a rectangular channel with an aspect ratio of 10. The channel has a cross sectional area of 5-50 mm and a length of 200 mm. The inclination angle was varied from 0 to 90 degree. The velocity profiles and concentration profiles were analyzed with a computer program [FLUENT]. Following main features of the counter flow are discussed based on the calculated results. (1) Time required for establishing a quasi-steady state counter flow. (2) The relationship between the inclination angle and the flow patterns of the counter flow. (3) The developing process of velocity profiles and concentration profiles. (4) The relationship between the inclination angle of the channel and the velocity profiles of upward flow and the downward flow. (5) The relationship between the concentration profile and the inclination angle. (6) The relationship between the net in-flow rate and the inclination angle. We compared the computed velocity profile and the net in-flow rate with experimental data. A good agreement was obtained between the calculation results and the experimental results. (author)

KINEMATIC STUDY OF THE AIR FLOW PRODUCED BY SOME SPRAYERS USED IN “TENDONE” VINEYARDS

Directory of Open Access Journals (Sweden)

Simone Pascuzzi

2008-09-01

Full Text Available A computerized measuring system to analyse the vector field of the air velocities in a volume surrounding the fan of air assisted sprayers usually used in tendone vineyards was designed and built. The performance of three different sprayers was tested: the first, a traditional air-convection sprayer, the other two, suitably designed for treatments in tendone vineyards. The air flow which exited through the discharge diffusers and moving towards the target sucked air from the surrounding environment that enlarged the flow rate on the target. The available flow was that which reached the vegetative and productive area, placed in a horizontal position respectively at 1.8 m and 2.0 m from the ground plane. The pneumatic sprayer produced an air flow clearly directed towards the top of the vines.

Numerical Model of Air Valve For Computation of One-dimensional Flow

Directory of Open Access Journals (Sweden)

Daniel HIMR

2014-06-01

Full Text Available The paper is focused on a numerical simulation of unsteady flow in a pipeline. The special attention is paid to a numerical model of an air valve, which has to include all possible regimes: critical/subcritical inflow and critical/subcritical outflow of air. Thermodynamic equation of subcritical mass flow was simplified to get more friendly shape of relevant equations, which enables easier solution of the problem.

CO2 Capacity Sorbent Analysis Using Volumetric Measurement Approach

Science.gov (United States)

Huang, Roger; Richardson, Tra-My Justine; Belancik, Grace; Jan, Darrell; Knox, Jim

2017-01-01

In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0C, 10C, 25C, 50C, and 75C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.

Experimental study of flow monitoring instruments in air-water, two-phase downflow

International Nuclear Information System (INIS)

Sheppard, J.D.; Hayes, P.H.; Wynn, M.C.

1976-01-01

The performance of a turbine meter, target flow meter (drag disk), and a gamma densitometer was studied in air-water, two-phase vertical downflow. Air and water were metered into an 0.0889-m-ID (3.5-in.) piping system; air flows ranged from 0.007 to 0.3 m 3 /sec (16 to 500 scfm) and water flows ranged from 0.0006 to 0.03 m 3 /sec (10 to 500 gpm). The study included effects of flow rate, quality, flow regime, and flow dispersion on the mean and fluctuating components of the instrument signals. Wire screen flow dispersers located at the inlet to the test section had a significant effect on the readings of the drag disk and gamma densitometer, but had little effect on the turbine. Further, when flow dispersers were used, mass flow rates determined from the three instrument readings and a two-velocity, slip flow model showed good agreement with actual mass flow rate over a three-fold range in quality; mass flows determined with the drag disk and densitometer readings assuming homogeneous flow were nearly as accurate. However, when mass flows were calculated using the turbine and densitometer or turbine and drag disk readings assuming homogeneous flow, results were scattered and relatively inaccurate compared to the actual mass flows. Turbine meter data were used with a two-velocity turbine model and continuity relationships for each phase to determine the void fraction and mean phase velocities in the test section. The void fraction was compared with single beam gamma densitometer results and fluid momentum calculated from a two-velocity model was compared with drag disk readings

Pressure drop and heat transfer of a mercury single-phase flow and an air-mercury two-phase flow in a helical tube under a strong magnetic field

International Nuclear Information System (INIS)

Takahashi, Minoru; Momozaki, Yoichi

2000-01-01

For the reduction of a large magneto-hydrodynamic (MHD) pressure drop of a liquid metal single-phase flow, a liquid metal two-phase flow cooling system has been proposed. As a fundamental study, MHD pressure drops and heat transfer characteristics of a mercury single-phase flow and an air-mercury two-phase flow were experimentally investigated. A strong transverse magnetic field relevant to the fusion reactor conditions was applied to the mercury single-phase flow and the air-mercury two-phase flow in a helically coiled tube that was inserted in the vertical bore of a solenoidal superconducting magnet. It was found that MHD pressure drops of a mercury single-phase flow in the helically coiled tube were nearly equal to those in a straight tube. The Nusselt number at an outside wall was higher than that at an inside wall both in the mercury single-phase flow in the absence and presence of a magnetic field. The Nusselt number of the mercury single-phase flow decreased, increased and again decreased with an increase in the magnetic flux density. MHD pressure drops did not decrease appreciably by injecting air into a mercury flow and changing the mercury flow into the air-mercury two-phase flow. Remarkable heat transfer enhancement did not appear by the air injection. The injection of air into the mercury flow enhanced heat transfer in the ranges of high mercury flow rate and low magnetic flux density, possibly due to the agitation effect of air bubbles. The air injection deteriorated heat transfer in the range of low mercury flow rates possibly because of the occupation of air near heating wall

Digital image processing based mass flow rate measurement of gas/solid two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Song Ding; Peng Lihui; Lu Geng; Yang Shiyuan [Tsinghua National Laboratory for Information Science and Technology, Department of Automation, Tsinghua University, Beijing, 100084 (China); Yan Yong, E-mail: lihuipeng@tsinghua.edu.c [University of Kent, Canterbury, Kent CT2 7NT (United Kingdom)

2009-02-01

With the rapid growth of the process industry, pneumatic conveying as a tool for the transportation of a wide variety of pulverized and granular materials has become widespread. In order to improve plant control and operational efficiency, it is essential to know the parameters of the particle flow. This paper presents a digital imaging based method which is capable of measuring multiple flow parameters, including volumetric concentration, velocity and mass flow rate of particles in the gas/solid two phase flow. The measurement system consists of a solid state laser for illumination, a low-cost CCD camera for particle image acquisition and a microcomputer with bespoke software for particle image processing. The measurements of particle velocity and volumetric concentration share the same sensing hardware but use different exposure time and different image processing methods. By controlling the exposure time of the camera a clear image and a motion blurred image are obtained respectively. The clear image is thresholded by OTSU method to identify the particles from the dark background so that the volumetric concentration is determined by calculating the ratio between the particle area and the total area. Particle velocity is derived from the motion blur length, which is estimated from the motion blurred images by using the travelling wave equation method. The mass flow rate of particles is calculated by combining the particle velocity and volumetric concentration. Simulation and experiment results indicate that the proposed method is promising for the measurement of multiple parameters of gas/solid two-phase flow.

Digital image processing based mass flow rate measurement of gas/solid two-phase flow

International Nuclear Information System (INIS)

Song Ding; Peng Lihui; Lu Geng; Yang Shiyuan; Yan Yong

2009-01-01

With the rapid growth of the process industry, pneumatic conveying as a tool for the transportation of a wide variety of pulverized and granular materials has become widespread. In order to improve plant control and operational efficiency, it is essential to know the parameters of the particle flow. This paper presents a digital imaging based method which is capable of measuring multiple flow parameters, including volumetric concentration, velocity and mass flow rate of particles in the gas/solid two phase flow. The measurement system consists of a solid state laser for illumination, a low-cost CCD camera for particle image acquisition and a microcomputer with bespoke software for particle image processing. The measurements of particle velocity and volumetric concentration share the same sensing hardware but use different exposure time and different image processing methods. By controlling the exposure time of the camera a clear image and a motion blurred image are obtained respectively. The clear image is thresholded by OTSU method to identify the particles from the dark background so that the volumetric concentration is determined by calculating the ratio between the particle area and the total area. Particle velocity is derived from the motion blur length, which is estimated from the motion blurred images by using the travelling wave equation method. The mass flow rate of particles is calculated by combining the particle velocity and volumetric concentration. Simulation and experiment results indicate that the proposed method is promising for the measurement of multiple parameters of gas/solid two-phase flow.

3-dimensional Simulation of an Air-lift Pump from Bubbly to Slug Flow

Energy Technology Data Exchange (ETDEWEB)

Jo, Hongrae; Jo, Daeseong [Kyungpook National Univ, Daegu (Korea, Republic of)

2015-10-15

The air-lift pump has been used in various applications with its merit that it can pump up without any moving parts. E.g. coffee percolator, petroleum industry, suction dredge, OTEC i.e. ocean thermal energy conversion and so on. By the merit, it has high durability for high temperature water or vapor, and fluid-solid mixture like waste water, muddy water and crude, which cause problems when it's pumped up with general pumps. In this regard, the air-lift pump has been one of the most desirable technology. A typical air-lift pump configuration is illustrated in Figure 01. The principle of this pump is very simple. When air is injected from the injector at bottom of a submerged tube, i.e., air bubbles are suspended in the liquid, the average density of the mixture in the tube is less than that of the surrounding fluid in the reservoir. Then hydrostatic pressure over the length of the tube is decreased. This buoyancy force causes a pumping action. The comparison of the simulated results, experimental result, and theoretical result is been able by data shown as Figure 04. They have similar trends but they also have a little differences because there are some limits of simulating the flow regimes. At the different flow condition, different coefficients for friction factor or pressure drop should be used, but this simulation uses a laminar condition and the theoretical equations are valid only for slug regime where the air flow rate is lower than the other regimes. From these causes, the differences has arisen, and difference comes bigger as the air flow rate increases, i.e., becoming annular flow regime or churn flow regime.

Visual study of air--water mixtures flowing inside serpentine tubes

International Nuclear Information System (INIS)

Farukhi, M.N.; Parker, J.D.

1974-01-01

Hydrodynamic behavior of air-water mixtures flowing inside serpentine tubes, with bends in the vertical plane, was investigated. Flow visualization was accomplished by injecting dye into the liquid phase and recording the events on color slides and color movies. For certain combinations of gas and liquid flow rates, in the annular type flow regime, ''film inversion'' was observed in the bend as well as in the straight section immediately downstream of the bend. A new flow regime map particularly applicable to two phase flow inside serpentine tubes is presented. (U.S.)

Quasi-steady-state model of a counter flow air-to-air heat exchanger with phase change

DEFF Research Database (Denmark)

Rose, Jørgen; Nielsen, Toke Rammer; Kragh, Jesper

2008-01-01

-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes...

Visualization of an air-water interface on superhydrophobic surfaces in turbulent channel flows

Science.gov (United States)

Kim, Hyunseok; Park, Hyungmin

2017-11-01

In the present study, three-dimensional deformation of air-water interface on superhydrophobic surfaces in turbulent channel flows at the Reynolds numbers of Re = 3000 and 10000 is measured with RICM (Reflection Interference Contrast Microscopy) technique. Two different types of roughness feature of circular hole and rectangular grate are considered, whose depth is 20 μm and diameter (or width) is varied between 20-200 μm. Since the air-water interface is always at de-pinned state at the considered condition, air-water interface shape and its sagging velocity is maintained to be almost constant as time goes one. In comparison with the previous results under the laminar flow, due to turbulent characteristics of the flow, sagging velocity is much faster. Based on the measured sagging profiles, a modified model to describe the air-water interface dynamics under turbulent flows is suggested. Supported by City of Seoul through Seoul Urban Data Science Laboratory Project (Grant No 0660-20170004) administered by SNU Big Data Institute.

Comparison of Descemet stripping under continuous air flow, manual air injection and balanced salt solution for DMEK: a pilot study.

Science.gov (United States)

Gabbay, I E; Bahar, I; Nahum, Y; Livny, E

2017-08-01

Descemet's membrane endothelial keratoplasty (DMEK) involves removal of the recipient's Descemet membrane (DM) prior to transplanting the donor's DM. When using balanced salt solution (BSS) or ophthalmic viscosurgical devices (OVDs), visualization of the host's DM during its stripping may be inadequate and may result in Descemet remnants and could lead to sub-optimal surgical results. Previous articles described excellent visualization when utilizing air injection but this requires repeated air injection into the anterior chamber (AC). We present a pilot study that compares different techniques under which DM stripping can be performed: with continuous automated air infusion, with manual air infusion, and with BSS. We retrospectively compared video footage of DM stripping with BSS, with continuous air and with manual injection of air into the AC to determine DM stripping duration and the number of times the surgeon had to insert and retrieve a surgical instrument from the AC. Thirty videos of 10 consecutive cases of the three DM stripping techniques were evaluated. DM stripping duration was 3.26 (±1.32), 3.92 (±1.2) and 12.9 (±3.98) minutes for BSS, continuous air flow, and manual air injection, respectively. Frequency of instrument retrieval (FIR) was 3.6 (±1.71), 1.5 (±0.71) and 15.1 (±3.28) for BSS, continuous air flow, and manual air injection, respectively. Continuous air flow and BSS were both statistically different than manual air injection into the AC (p air in the AC contributes to better visualization and an efficient surgery.

The influence of air flow speed on fire propagation in object

Directory of Open Access Journals (Sweden)

Jevtić Radoje

2015-01-01

Full Text Available Fire presents the process of the uncontrolled combustion that makes material damage and endangers human lives. It is important to know the factors that fire depends on for success projecting and realization of fire protection systems. One of such factors is different air flow that could be presented as wind, draft and the like. The simulation of different air flow speeds and its influences on fire propagation in object were analyzed in this paper.

Estimation of Flow Channel Parameters for Flowing Gas Mixed with Air in Atmospheric-pressure Plasma Jets

Science.gov (United States)

Yambe, Kiyoyuki; Saito, Hidetoshi

2017-12-01

When the working gas of an atmospheric-pressure non-equilibrium (cold) plasma flows into free space, the diameter of the resulting flow channel changes continuously. The shape of the channel is observed through the light emitted by the working gas of the atmospheric-pressure plasma. When the plasma jet forms a conical shape, the diameter of the cylindrical shape, which approximates the conical shape, defines the diameter of the flow channel. When the working gas flows into the atmosphere from the inside of a quartz tube, the gas mixes with air. The molar ratio of the working gas and air is estimated from the corresponding volume ratio through the relationship between the diameter of the cylindrical plasma channel and the inner diameter of the quartz tube. The Reynolds number is calculated from the kinematic viscosity of the mixed gas and the molar ratio. The gas flow rates for the upper limit of laminar flow and the lower limit of turbulent flow are determined by the corresponding Reynolds numbers estimated from the molar ratio. It is confirmed that the plasma jet length and the internal plasma length associated with strong light emission increase with the increasing gas flow rate until the rate for the upper limit of laminar flow and the lower limit of turbulent flow, respectively. Thus, we are able to explain the increasing trend in the plasma lengths with the diameter of the flow channel and the molar ratio by using the cylindrical approximation.

An open-access modeled passenger flow matrix for the global air network in 2010.

Science.gov (United States)

Huang, Zhuojie; Wu, Xiao; Garcia, Andres J; Fik, Timothy J; Tatem, Andrew J

2013-01-01

The expanding global air network provides rapid and wide-reaching connections accelerating both domestic and international travel. To understand human movement patterns on the network and their socioeconomic, environmental and epidemiological implications, information on passenger flow is required. However, comprehensive data on global passenger flow remain difficult and expensive to obtain, prompting researchers to rely on scheduled flight seat capacity data or simple models of flow. This study describes the construction of an open-access modeled passenger flow matrix for all airports with a host city-population of more than 100,000 and within two transfers of air travel from various publicly available air travel datasets. Data on network characteristics, city population, and local area GDP amongst others are utilized as covariates in a spatial interaction framework to predict the air transportation flows between airports. Training datasets based on information from various transportation organizations in the United States, Canada and the European Union were assembled. A log-linear model controlling the random effects on origin, destination and the airport hierarchy was then built to predict passenger flows on the network, and compared to the results produced using previously published models. Validation analyses showed that the model presented here produced improved predictive power and accuracy compared to previously published models, yielding the highest successful prediction rate at the global scale. Based on this model, passenger flows between 1,491 airports on 644,406 unique routes were estimated in the prediction dataset. The airport node characteristics and estimated passenger flows are freely available as part of the Vector-Borne Disease Airline Importation Risk (VBD-Air) project at: www.vbd-air.com/data.

An experimental investigation of natural circulated air flow in the passive containment cooling system

International Nuclear Information System (INIS)

Ryu, S.H.; Oh, S.M.; Park, G.C.

2004-01-01

The objective of this study is to investigate the effects of air inlet position and external conditions on the natural circulated air flow rate in a passive containment cooling system of the advanced passive reactor. Experiments have been performed with 1/36 scaled segment type passive containment test facility. The air velocities and temperatures are measured through the air flow path. Also, the experimental results are compared with numerical calculations and show good agreement. (author)

Effect of water and air flow on concentric tubular solar water desalting system

International Nuclear Information System (INIS)

Arunkumar, T.; Jayaprakash, R.; Ahsan, Amimul; Denkenberger, D.; Okundamiya, M.S.

2013-01-01

Highlights: ► We optimized the augmentation of condense by enhanced desalination methodology. ► We measured ambient together with solar radiation intensity. ► The effect of cooling air and water flowing over the cover was studied. -- Abstract: This work reports an innovative design of tubular solar still with a rectangular basin for water desalination with flowing water and air over the cover. The daily distillate output of the system is increased by lowering the temperature of water flowing over it (top cover cooling arrangement). The fresh water production performance of this new still is observed in Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore (11° North, 77° East), India. The water production rate with no cooling flow was 2050 ml/day (410 ml/trough). However, with cooling air flow, production increased to 3050 ml/day, and with cooling water flow, it further increased to 5000 ml/day. Despite the increased cost of the water cooling system, the increased output resulted in the cost of distilled water being cut in roughly half. Diurnal variations of a few important parameters are observed during field experiments such as water temperature, cover temperature, air temperature, ambient temperature and distillate output.

Experimental and Numerical Investigation of Flow Properties of Supersonic Helium-Air Jets

Science.gov (United States)

Miller, Steven A. E.; Veltin, Jeremy

2010-01-01

Heated high speed subsonic and supersonic jets operating on- or off-design are a source of noise that is not yet fully understood. Helium-air mixtures can be used in the correct ratio to simulate the total temperature ratio of heated air jets and hence have the potential to provide inexpensive and reliable flow and acoustic measurements. This study presents a combination of flow measurements of helium-air high speed jets and numerical simulations of similar helium-air mixture and heated air jets. Jets issuing from axisymmetric convergent and convergent-divergent nozzles are investigated, and the results show very strong similarity with heated air jet measurements found in the literature. This demonstrates the validity of simulating heated high speed jets with helium-air in the laboratory, together with the excellent agreement obtained in the presented data between the numerical predictions and the experiments. The very close match between the numerical and experimental data also validates the frozen chemistry model used in the numerical simulation.

Air-water upward flow in prismatic channel of rectangular base

International Nuclear Information System (INIS)

Carvalho Tofani, P. de.

1984-01-01

Experiments had carried out to investigate the two-phase upward air-water flow structure, in a rectangular test section, by using independent measuring techniques, which comprise direct viewing and photography, electrical probes and gamma-ray attenuation. Flow pattern maps and correlations for flow pattern transitions, void fraction profiles, liquid film thickness and superficial average void fraction are proposed and compared to available data. (Author) [pt

Hologlyphics: volumetric image synthesis performance system

Science.gov (United States)

Funk, Walter

2008-02-01

This paper describes a novel volumetric image synthesis system and artistic technique, which generate moving volumetric images in real-time, integrated with music. The system, called the Hologlyphic Funkalizer, is performance based, wherein the images and sound are controlled by a live performer, for the purposes of entertaining a live audience and creating a performance art form unique to volumetric and autostereoscopic images. While currently configured for a specific parallax barrier display, the Hologlyphic Funkalizer's architecture is completely adaptable to various volumetric and autostereoscopic display technologies. Sound is distributed through a multi-channel audio system; currently a quadraphonic speaker setup is implemented. The system controls volumetric image synthesis, production of music and spatial sound via acoustic analysis and human gestural control, using a dedicated control panel, motion sensors, and multiple musical keyboards. Music can be produced by external acoustic instruments, pre-recorded sounds or custom audio synthesis integrated with the volumetric image synthesis. Aspects of the sound can control the evolution of images and visa versa. Sounds can be associated and interact with images, for example voice synthesis can be combined with an animated volumetric mouth, where nuances of generated speech modulate the mouth's expressiveness. Different images can be sent to up to 4 separate displays. The system applies many novel volumetric special effects, and extends several film and video special effects into the volumetric realm. Extensive and various content has been developed and shown to live audiences by a live performer. Real world applications will be explored, with feedback on the human factors.

Modelling of hot air chamber designs of a continuous flow grain dryer

DEFF Research Database (Denmark)

Kjær, Lotte Strange; Poulsen, Mathias; Sørensen, Kim

2018-01-01

The pressure loss, flow distribution and temperature distribution of a number of designs of the hot air chamber in a continuous flow grain dryer, were investigated using CFD. The flow in the dryer was considered as steady state, compressible and turbulent. It is essential that the grain...... is uniformly dried as uneven drying can result in damage to the end-product during storage. The original commercial design was modified with new guide vanes at the inlets to reduce the pressure loss and to ensure a uniform flow to the line burner in the hot air chamber. The new guide vane design resulted...... in a 10% reduction in pressure loss and a γ-value of 0.804. Various design changes of the hot air chamber were analysed in terms of pressure loss and temperature distribution with the aim of a temperature variation of 5 K at the outlet ducts. An obstruction design was analysed, which improved mixing...

A generalized volumetric dispersion model for a class of two-phase separation/reaction: finite difference solutions

Science.gov (United States)

Siripatana, Chairat; Thongpan, Hathaikarn; Promraksa, Arwut

2017-03-01

This article explores a volumetric approach in formulating differential equations for a class of engineering flow problems involving component transfer within or between two phases. In contrast to conventional formulation which is based on linear velocities, this work proposed a slightly different approach based on volumetric flow-rate which is essentially constant in many industrial processes. In effect, many multi-dimensional flow problems found industrially can be simplified into multi-component or multi-phase but one-dimensional flow problems. The formulation is largely generic, covering counter-current, concurrent or batch, fixed and fluidized bed arrangement. It was also intended to use for start-up, shut-down, control and steady state simulation. Since many realistic and industrial operation are dynamic with variable velocity and porosity in relation to position, analytical solutions are rare and limited to only very simple cases. Thus we also provide a numerical solution using Crank-Nicolson finite difference scheme. This solution is inherently stable as tested against a few cases published in the literature. However, it is anticipated that, for unconfined flow or non-constant flow-rate, traditional formulation should be applied.

Modeling of macrosegregation caused by volumetric deformation in a coherent mushy zone

Science.gov (United States)

Nicolli, Lilia C.; Mo, Asbjørn; M'hamdi, Mohammed

2005-02-01

A two-phase volume-averaged continuum model is presented that quantifies macrosegregation formation during solidification of metallic alloys caused by deformation of the dendritic network and associated melt flow in the coherent part of the mushy zone. Also, the macrosegregation formation associated with the solidification shrinkage (inverse segregation) is taken into account. Based on experimental evidence established elsewhere, volumetric viscoplastic deformation (densification/dilatation) of the coherent dendritic network is included in the model. While the thermomechanical model previously outlined (M. M’Hamdi, A. Mo, and C.L. Martin: Metall. Mater. Trans. A, 2002, vol. 33A, pp. 2081-93) has been used to calculate the temperature and velocity fields associated with the thermally induced deformations and shrinkage driven melt flow, the solute conservation equation including both the liquid and a solid volume-averaged velocity is solved in the present study. In modeling examples, the macrosegregation formation caused by mechanically imposed as well as by thermally induced deformations has been calculated. The modeling results for an Al-4 wt pct Cu alloy indicate that even quite small volumetric strains (≈2 pct), which can be associated with thermally induced deformations, can lead to a macroscopic composition variation in the final casting comparable to that resulting from the solidification shrinkage induced melt flow. These results can be explained by the relatively large volumetric viscoplastic deformation in the coherent mush resulting from the applied constitutive model, as well as the relatively large difference in composition for the studied Al-Cu alloy in the solid and liquid phases at high solid fractions at which the deformation takes place.

Finite element analysis of volumetrically heated fluids in an axisymmetric enclosure

International Nuclear Information System (INIS)

Gartling, D.K.

1979-01-01

A general purpose finite element computer code has been used to analyze the steady state and transient response of a confined fluid that is heated volumetrically. The numerical procedure is demonstrated to be capable of resolving flow fields of considerable complexity without undue computational expense. Results are discussed for a Grashof number range (4.0 x 10 4 to 4.0 x 10 6 ) in which the flow varies from a steady, single cell configuration to a multiple cell configuration that includes a periodic interaction

Numerical Simulation and Performance Analysis of Twin Screw Air Compressors

Directory of Open Access Journals (Sweden)

W. S. Lee

2001-01-01

Full Text Available A theoretical model is proposed in this paper in order to study the performance of oil-less and oil-injected twin screw air compressors. Based on this model, a computer simulation program is developed and the effects of different design parameters including rotor profile, geometric clearance, oil-injected angle, oil temperature, oil flow rate, built-in volume ratio and other operation conditions on the performance of twin screw air compressors are investigated. The simulation program gives us output variables such as specific power, compression ratio, compression efficiency, volumetric efficiency, and discharge temperature. Some of the above results are then compared with experimentally measured data and good agreement is found between the simulation results and the measured data.

Use of exhaust gas as sweep flow to enhance air separation membrane performance

Science.gov (United States)

Dutart, Charles H.; Choi, Cathy Y.

2003-01-01

An intake air separation system for an internal combustion engine is provided with purge gas or sweep flow on the permeate side of separation membranes in the air separation device. Exhaust gas from the engine is used as a purge gas flow, to increase oxygen flux in the separation device without increasing the nitrogen flux.

An experimental setup for the study of the steady air flow in a diesel engine chamber

Directory of Open Access Journals (Sweden)

Montanero José María

2012-04-01

Full Text Available We present an experimental setup for studying the steady air flow in a diesel engine chamber. An engine block containing the inlet manifold was placed on a test bench. A steady air stream crossed the inlet manifold and entered a glass chamber driven by a fan. A PIV system was set up around the bench to measure the in-chamber flow. An air spray gun was used as seed generator to producing sub-millimeter droplets, easily dragged by the air stream. Images of the in-flow chamber were acquired in the course of the experiments, and processed to measure the velocity field. The pressure drop driven the air current and the mass flow rate were also measured.

Flow Regimes of Air-Water Counterflow Through Cross Corrugated Parallel Plates

Energy Technology Data Exchange (ETDEWEB)

de Almeida, V.F.

2000-06-07

Heretofore unknown flow regimes of air-water counterflow through a pair of transparent vertical parallel cross corrugated plates were observed via high-speed video. Air flows upward driven by pressure gradient and water, downward driven by gravity. The crimp geometry of the corrugations was drawn from typical corrugated sheets used as filling material in modern structured packed towers. Four regimes were featured, namely, rivulet, bicontinuous, flooding fronts, and flooding waves. It is conceivable that the regimes observed might constitute the basis for understanding how gas and liquid phases contend for available space in the interstices of structured packings in packed towers. Flow regime transitions were expressed in terms of liquid load (liquid superficial velocity) and gas flow factor parameters commonly used in pressure drop and capacity curves. We have carefully examined the range of parameters equivalent to the ill-understood high-liquid-flow operation in packed towers. More importantly, our findings should prove valuable in validating improved first-principles modeling of gas-liquid flows in these industrially important devices.

Experimental investigation of droplet separation in a horizontal counter-current air/water stratified flow

International Nuclear Information System (INIS)

Gabriel, Stephan Gerhard

2015-01-01

). Measurements in the gaseous phase were carried out by conventional oil-droplets as tracer particles. The volumetric phase distribution was investigated by the new OVM method, which was developed within this work. The validation of this method was done by simultaneous measurements of the new method and an electrical conductivity probe in the WENKA channel. Finally, the droplet mass flux was measured by an isokinetic sampling probe, which was also developed within this work. The functional capability of the probe and the accuracy of isokinetic conditions were demonstrated by PIV-measurements under various flow conditions. The investigations include both supercritical and subcritical, stratified flows, with partially and fully reversed conditions. The behavior of both fluids was analyzed at four measurement sites and under 31 different volumetric flux conditions. The results include sequences of images and numerical data, providing an accurate impression of the flow behavior in the channel. This dataset can now be used for the development and validation of new turbulence and phase interaction models for stratified counter-current two-phase flows.

Volumetric formulation of lattice Boltzmann models with energy conservation

OpenAIRE

Sbragaglia, M.; Sugiyama, K.

2010-01-01

We analyze a volumetric formulation of lattice Boltzmann for compressible thermal fluid flows. The velocity set is chosen with the desired accuracy, based on the Gauss-Hermite quadrature procedure, and tested against controlled problems in bounded and unbounded fluids. The method allows the simulation of thermohydrodyamical problems without the need to preserve the exact space-filling nature of the velocity set, but still ensuring the exact conservation laws for density, momentum and energy. ...

Modelling of the flow of stable air over a complex region

CSIR Research Space (South Africa)

Scholtz, MT

1976-01-01

Full Text Available The flow of stable air over a general region of complex topography and non-uniform surface temperature has been investigated. In order to gain further understanding of the motion of surface air, it was necessary to study the vertical structure...

Catalyst volumetric fraction simulation in a riser of a cold flow pilot unit with aid of transmission gamma technique

International Nuclear Information System (INIS)

Santos, Kamylla A.L. dos; Lima Filho, Hilario J.B. de; Benachour, Mohand; Dantas, Carlos C.; Santos, Valdemir A. dos

2013-01-01

Was obtained the radial profile of the catalyst volume fraction in a riser of the cold flow pilot unit of the Fluid Catalytic Cracking (FCC) unit, which was used for adjustment of the entrance conditions of the catalyst in a simulation program by Computational Fluid Dynamics (CFD). The height of the riser of the Cold Flow Pilot Unity (CFPU) utilized is 6.0m and its inner diameter is 0.097 m. A radiation-γ source of Am-241 and a NaI (Tl) detector, with shielding made of lead, have been installed on a steel backing that maintains the geometry of the source-detector-riser and allows to vary the distance from the source to the detector and the radial position in a given cross section of the riser. The data associated with the simulation of volume fraction radial profile of the catalyst were: Fluent software, version 12.0; preprocessor GAMBIT, version 2.3.16; Eulerian approach; structured mesh, cell number of 60000; turbulence model used was k-ε and kinetic theory of granular flow (KTGF) was implemented to describe the solid phase. Comparison of radial profiles simulated and experimental of the catalyst volumetric fraction in the CFPU riser allowed the identification of needs adjustments in the simulation for the input of catalyst, with consequent validation for the proposed model simulation. (author)

Dynamic Flow Management Problems in Air Transportation

Science.gov (United States)

Patterson, Sarah Stock

1997-01-01

In 1995, over six hundred thousand licensed pilots flew nearly thirty-five million flights into over eighteen thousand U.S. airports, logging more than 519 billion passenger miles. Since demand for air travel has increased by more than 50% in the last decade while capacity has stagnated, congestion is a problem of undeniable practical significance. In this thesis, we will develop optimization techniques that reduce the impact of congestion on the national airspace. We start by determining the optimal release times for flights into the airspace and the optimal speed adjustment while airborne taking into account the capacitated airspace. This is called the Air Traffic Flow Management Problem (TFMP). We address the complexity, showing that it is NP-hard. We build an integer programming formulation that is quite strong as some of the proposed inequalities are facet defining for the convex hull of solutions. For practical problems, the solutions of the LP relaxation of the TFMP are very often integral. In essence, we reduce the problem to efficiently solving large scale linear programming problems. Thus, the computation times are reasonably small for large scale, practical problems involving thousands of flights. Next, we address the problem of determining how to reroute aircraft in the airspace system when faced with dynamically changing weather conditions. This is called the Air Traffic Flow Management Rerouting Problem (TFMRP) We present an integrated mathematical programming approach for the TFMRP, which utilizes several methodologies, in order to minimize delay costs. In order to address the high dimensionality, we present an aggregate model, in which we formulate the TFMRP as a multicommodity, integer, dynamic network flow problem with certain side constraints. Using Lagrangian relaxation, we generate aggregate flows that are decomposed into a collection of flight paths using a randomized rounding heuristic. This collection of paths is used in a packing integer

Thermal Performance Evaluation of the 200 kWth Sol Air Volumetric Solar Receiver

International Nuclear Information System (INIS)

Tellez Sufrategui, F. M.

2003-01-01

The goal of the Solair project is the design and test of a fully modular, high efficient and durable open volumetric high-flux receiver, which can be easily and safely operated at mean air outlet temperatures of up to 800 degree centigree. The project was thought in two phases, in the first one an advanced 200 kW HitRec receiver called Solair 200 was designed and tested. The Solair 200 was built like one single receiver module (subassembly), to test the thermal performance of the receiver as well as the receiver module behavior. Out of a set of these receiver modules have been developed to assemble the 3 MW t h receiver in the second phase of the project. This report describes the used procedure or methodology for data processing for thermal performance evaluation purposes and the data processing results for the first phase of the project. Test campaign started in March 2002 and produced fifty data sheets (each corresponding to a test day) and ended in February 2003. During the test phase three absorber material types (or configurations) have been tested during the test campaign. The data processing and evaluation results show that performance goals for the receiver have been fluffy accomplished: Temperatures of more than 800 degree centigree were achieved for the first two configurations in five test days. For the two absorber configurations for which incident solar power was measured the estimated efficiency at 700 degree centigree was 81 (±6)% for configuration 1 and 83 (±6) % for configuration 2 of the absorber. (Author) 20 refs

Thermal Performance Evaluation of the 200kWth SolAir Volumetric Solar Receiver

Energy Technology Data Exchange (ETDEWEB)

Tellez Sufrategui, F. M.

2003-07-01

The goal of the Solair project the design and test of a fully modular, high efficient and durable open volumetric high-flux receiver, which can be easily and safety operated at mean air outlet temperatures of up to 800 degree centigree. The project was thought in two phases, in the first one an advanced 200 kW Hitrec receiver called Solair 200 was designed and tested. The Solair 200 was built like one single receiver module (subassembly), to test the thermal performance of the receiver as well as the receiver module behavior. Out of a set of these receiver modules have been developed to assemble the 3 MWth receiver in the second phase of the project. This report describes the used procedure or methodology for data processing for thermal performance evaluation purposes and the data processing results for the first phase of the project. Test campaign started in March 2002 and produced fifty data sheets (each corresponding to a test day) and ended in February 2003. During the test phase three absorber material types (or configurations) have been tested during the test campaign. The data processing and evaluation results show that performance goals for the receiver have been fully accomplished. Temperatures of more than 800 degree centigree were achieved for the first two configurations in five test days. For the two absorber configurations for which incident solar power was measured the estimated efficiency at 700 degree centigree was 81 ({+-}6)% for configuration 1 and 83({+-}6)% for configuration 2 of the absorber. (Author). 20 refs.

Detailed evaluation of the natural circulation mass flow rate of water propelled by using an air injection

International Nuclear Information System (INIS)

Park, Rae-Joon; Ha, Kwang-Soon; Kim, Jae-Cheol; Hong, Seong-Wan; Kim, Sang-Baik

2008-01-01

One-dimensional (1D) air-water two-phase natural circulation flow in the thermohydraulic evaluation of reactor cooling mechanism by external self-induced flow - one-dimensional' (THERMES-1D) experiment has been verified and evaluated by using the RELAP5/MOD3 computer code. Experimental results on the 1D natural circulation mass flow rate of water propelled by using an air injection have been evaluated in detail. The RELAP5 results have shown that an increase in the air injection rate to 50% of the total heat flux leads to an increase in the water circulation mass flow rate. However, an increase in the air injection rate from 50 to 100% does not affect the water circulation mass flow rate, because of the inlet area condition. As the height increases in the air injection part, the void fraction increases. However, the void fraction in the upper part of the air injector maintains a constant value. An increase in the air injection mass flow rate leads to an increase in the local void fraction, but it has no influence on the local pressure. An increase in the coolant inlet area leads to an increase in the water circulation mass flow rate. However, the water outlet area does not have an influence on the water circulation mass flow rate. As the coolant outlet moves to a lower position, the water circulation mass flow rate decreases. (author)

Laboratory Evaluation of Air Flow Measurement Methods for Residential HVAC Returns for New Instrument Standards

Energy Technology Data Exchange (ETDEWEB)

Walker, Iain [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Stratton, Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2015-08-01

This project improved the accuracy of air flow measurements used in commissioning California heating and air conditioning systems in Title 24 (Building and Appliance Efficiency Standards), thereby improving system performance and efficiency of California residences. The research team at Lawrence Berkeley National Laboratory addressed the issue that typical tools used by contractors in the field to test air flows may not be accurate enough to measure return flows used in Title 24 applications. The team developed guidance on performance of current diagnostics as well as a draft test method for use in future evaluations. The study team prepared a draft test method through ASTM International to determine the uncertainty of air flow measurements at residential heating ventilation and air conditioning returns and other terminals. This test method, when finalized, can be used by the Energy Commission and other entities to specify required accuracy of measurement devices used to show compliance with standards.

Numerical investigation of the air injection effect on the cavitating flow in Francis hydro turbine

Science.gov (United States)

Chirkov, D. V.; Shcherbakov, P. K.; Cherny, S. G.; Skorospelov, V. A.; Turuk, P. A.

2017-09-01

At full and over load operating points, some Francis turbines experience strong self-excited pressure and power oscillations. These oscillations are occuring due to the hydrodynamic instability of the cavitating fluid flow. In many cases, the amplitude of such pulsations may be reduced substantially during the turbine operation by the air injection/ admission below the runner. Such an effect is investigated numerically in the present work. To this end, the hybrid one-three-dimensional model of the flow of the mixture "liquid-vapor" in the duct of a hydroelectric power station, which was proposed previously by the present authors, is augmented by the second gaseous component — the noncondensable air. The boundary conditions and the numerical method for solving the equations of the model are described. To check the accuracy of computing the interface "liquid-gas", the numerical method was applied at first for solving the dam break problem. The algorithm was then used for modeling the flow in a hydraulic turbine with air injection below the runner. It is shown that with increasing flow rate of the injected air, the amplitude of pressure pulsations decreases. The mechanism of the flow structure alteration in the draft tube cone has been elucidated, which leads to flow stabilization at air injection.

4-D flow magnetic resonance imaging: blood flow quantification compared to 2-D phase-contrast magnetic resonance imaging and Doppler echocardiography

Energy Technology Data Exchange (ETDEWEB)

Gabbour, Maya [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Medical Imaging 9, Chicago, IL (United States); Schnell, Susanne [Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States); Jarvis, Kelly [Northwestern University, Department of Biomedical Engineering, McCormick School of Engineering, Evanston, IL (United States); Robinson, Joshua D. [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Pediatrics, Division of Pediatric Cardiology, Chicago, IL (United States); Northwestern University Feinberg School of Medicine, Department of Pediatrics, Chicago, IL (United States); Markl, Michael [Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States); Northwestern University, Department of Biomedical Engineering, McCormick School of Engineering, Evanston, IL (United States); Rigsby, Cynthia K. [Ann and Robert H. Lurie Children' s Hospital of Chicago, Department of Medical Imaging 9, Chicago, IL (United States); Northwestern University Feinberg School of Medicine, Department of Radiology, Chicago, IL (United States)

2015-06-15

Doppler echocardiography (echo) is the reference standard for blood flow velocity analysis, and two-dimensional (2-D) phase-contrast magnetic resonance imaging (MRI) is considered the reference standard for quantitative blood flow assessment. However, both clinical standard-of-care techniques are limited by 2-D acquisitions and single-direction velocity encoding and may make them inadequate to assess the complex three-dimensional hemodynamics seen in congenital heart disease. Four-dimensional flow MRI (4-D flow) enables qualitative and quantitative analysis of complex blood flow in the heart and great arteries. The objectives of this study are to compare 4-D flow with 2-D phase-contrast MRI for quantification of aortic and pulmonary flow and to evaluate the advantage of 4-D flow-based volumetric flow analysis compared to 2-D phase-contrast MRI and echo for peak velocity assessment in children and young adults. Two-dimensional phase-contrast MRI of the aortic root, main pulmonary artery (MPA), and right and left pulmonary arteries (RPA, LPA) and 4-D flow with volumetric coverage of the aorta and pulmonary arteries were performed in 50 patients (mean age: 13.1 ± 6.4 years). Four-dimensional flow analyses included calculation of net flow and regurgitant fraction with 4-D flow analysis planes similarly positioned to 2-D planes. In addition, 4-D flow volumetric assessment of aortic root/ascending aorta and MPA peak velocities was performed and compared to 2-D phase-contrast MRI and echo. Excellent correlation and agreement were found between 2-D phase-contrast MRI and 4-D flow for net flow (r = 0.97, P < 0.001) and excellent correlation with good agreement was found for regurgitant fraction (r = 0.88, P < 0.001) in all vessels. Two-dimensional phase-contrast MRI significantly underestimated aortic (P = 0.032) and MPA (P < 0.001) peak velocities compared to echo, while volumetric 4-D flow analysis resulted in higher (aortic: P = 0.001) or similar (MPA: P = 0.98) peak

Study of Mouthguard Design for Endurance and Air-Flow Intake

Science.gov (United States)

Zaman, I.; Rozlan, S. A. M.; Manshoor, B.; Ngali, M. Z.; Khalid, A.; Amin, N. A. M.

2017-08-01

Mouthguard is one of the important device for athletes. Wearing a mouthguard is a must to prevent them from any orofacial injuries occurs during their sport activities. Therefore, to make sure it is safe and comfort, a study on the mouthguard design is carried out to investigate the performance of the mouthguard, in term of stress distribution and air flow path by improving the pressure difference between ambient and the oral cavity pressure. A preliminary design has been study to simulate its total deformation and stress, in terms of Von Mises Stress by using ANSYS 15.0 Workbench. From the results, the critical parts are identified on the preliminary design and later being used to improve the design to the new one. By increasing the thickness of the preliminary design, the total deformation has been decreased for about 0.20 mm to 0.16 mm for the exerted external forces ranging from 50-500 N, whereas, for internal forces ranging from 100-600 N have reduced deformation from 0.24 mm to 1.44 mm. The simulation process is then followed by the air flow study in the oral cavity with an open mouth about 0.5 mm when the athlete is doing exercise with speed 4.43 m/s of air flow into a mouth. The finding indicates that the modified mouthguard has large value of velocity streamline compared to the preliminary design which is supported by significant pressure difference of 401.86 Pa, compared to 140.09 Pa of the preliminary design. Velocity stream line also shows that the higher speeds occur in the near mouthguard, that is, between the bottom surfaces of the mouthguard and the lower teeth. The results demonstrated that the thicker the mouthguard, the better it is for prevention but less in air flow distribution into the oral cavity.

Adaptive controller for volumetric display of neuroimaging studies

Science.gov (United States)

Bleiberg, Ben; Senseney, Justin; Caban, Jesus

2014-03-01

Volumetric display of medical images is an increasingly relevant method for examining an imaging acquisition as the prevalence of thin-slice imaging increases in clinical studies. Current mouse and keyboard implementations for volumetric control provide neither the sensitivity nor specificity required to manipulate a volumetric display for efficient reading in a clinical setting. Solutions to efficient volumetric manipulation provide more sensitivity by removing the binary nature of actions controlled by keyboard clicks, but specificity is lost because a single action may change display in several directions. When specificity is then further addressed by re-implementing hardware binary functions through the introduction of mode control, the result is a cumbersome interface that fails to achieve the revolutionary benefit required for adoption of a new technology. We address the specificity versus sensitivity problem of volumetric interfaces by providing adaptive positional awareness to the volumetric control device by manipulating communication between hardware driver and existing software methods for volumetric display of medical images. This creates a tethered effect for volumetric display, providing a smooth interface that improves on existing hardware approaches to volumetric scene manipulation.

The impact of traffic-flow patterns on air quality in urban street canyons

International Nuclear Information System (INIS)

Thaker, Prashant; Gokhale, Sharad

2016-01-01

We investigated the effect of different urban traffic-flow patterns on pollutant dispersion in different winds in a real asymmetric street canyon. Free-flow traffic causes more turbulence in the canyon facilitating more dispersion and a reduction in pedestrian level concentration. The comparison of with and without a vehicle-induced-turbulence revealed that when winds were perpendicular, the free-flow traffic reduced the concentration by 73% on the windward side with a minor increase of 17% on the leeward side, whereas for parallel winds, it reduced the concentration by 51% and 29%. The congested-flow traffic increased the concentrations on the leeward side by 47% when winds were perpendicular posing a higher risk to health, whereas reduced it by 17–42% for parallel winds. The urban air quality and public health can, therefore, be improved by improving the traffic-flow patterns in street canyons as vehicle-induced turbulence has been shown to contribute significantly to dispersion. - Highlights: • CFD is used to study impact of traffic-flow patterns on urban air quality. • Facilitating free-flow patterns induce more turbulence in street canyons. • Traffic-generated turbulence alters pollutant levels in urban street canyons. - This study investigates the effect of vehicle-induced-turbulence generated during free-flow traffic pattern in reduction of air pollutant concentrations in urban street canyons.

Analysis of the air flow generated by an air-assisted sprayer equipped with two axial fans using a 3D sonic anemometer.

Science.gov (United States)

García-Ramos, F Javier; Vidal, Mariano; Boné, Antonio; Malón, Hugo; Aguirre, Javier

2012-01-01

The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study was divided into a static test and a dynamic test. During the static test, the air velocity in the working vicinity of the sprayer was measured considering the following machine configurations: (1) one activated fan regulated at three air flows (machine working as a traditional sprayer); (2) two activated fans regulated at three air flows for each fan. In the static test 72 measurement points were considered. The location of the measurement points was as follow: left and right sides of the sprayer; three sections of measurement (A, B and C); three measurement distances from the shaft of the machine (1.5 m, 2.5 m and 3.5 m); and four measurement heights (1 m, 2 m, 3 m and 4 m). The static test results have shown significant differences in the module and the vertical angle of the air velocity vector in function of the regulations of the sprayer. In the dynamic test, the air velocity was measured at 2.5 m from the axis of the sprayer considering four measurement heights (1 m, 2 m, 3 m and 4 m). In this test, the sprayer regulations were: one or two activated fans; one air flow for each fan; forward speed of 2.8 km/h. The use of one fan (back) or two fans (back and front) produced significant differences on the duration of the presence of wind in the measurement point and on the direction of the air velocity vector. The module of the air velocity vector was not affected by the number of activated fans.

Benchmark calculations for evaluation methods of gas volumetric leakage rate

International Nuclear Information System (INIS)

Asano, R.; Aritomi, M.; Matsuzaki, M.

1998-01-01

A containment function of radioactive materials transport casks is essential for safe transportation to prevent the radioactive materials from being released into environment. Regulations such as IAEA standard determined the limit of radioactivity to be released. Since is not practical for the leakage tests to measure directly the radioactivity release from a package, as gas volumetric leakages rates are proposed in ANSI N14.5 and ISO standards. In our previous works, gas volumetric leakage rates for several kinds of gas from various leaks were measured and two evaluation methods, 'a simple evaluation method' and 'a strict evaluation method', were proposed based on the results. The simple evaluation method considers the friction loss of laminar flow with expansion effect. The strict evaluating method considers an exit loss in addition to the friction loss. In this study, four worked examples were completed for on assumed large spent fuel transport cask (Type B Package) with wet or dry capacity and at three transport conditions; normal transport with intact fuels or failed fuels, and an accident in transport. The standard leakage rates and criteria for two kinds of leak test were calculated for each example by each evaluation method. The following observations are made based upon the calculations and evaluations: the choked flow model of ANSI method greatly overestimates the criteria for tests ; the laminar flow models of both ANSI and ISO methods slightly overestimate the criteria for tests; the above two results are within the design margin for ordinary transport condition and all methods are useful for the evaluation; for severe condition such as failed fuel transportation, it should pay attention to apply a choked flow model of ANSI method. (authors)

A MEMS-based Air Flow Sensor with a Free-standing Micro-cantilever Structure.

Science.gov (United States)

Wang, Yu-Hsiang; Lee, Chia-Yen; Chiang, Che-Ming

2007-10-17

This paper presents a micro-scale air flow sensor based on a free-standingcantilever structure. In the fabrication process, MEMS techniques are used to deposit asilicon nitride layer on a silicon wafer. A platinum layer is deposited on the silicon nitridelayer to form a piezoresistor, and the resulting structure is then etched to create afreestanding micro-cantilever. When an air flow passes over the surface of the cantileverbeam, the beam deflects in the downward direction, resulting in a small variation in theresistance of the piezoelectric layer. The air flow velocity is determined by measuring thechange in resistance using an external LCR meter. The experimental results indicate that theflow sensor has a high sensitivity (0.0284 ω/ms -1 ), a high velocity measurement limit (45ms -1 ) and a rapid response time (0.53 s).

Separate-effects experiments on the hydrodynamics of air ingress phenomena for the very high temperature reactor

International Nuclear Information System (INIS)

Kim, S.; Talley, J.; Yadav, M.; Ireland, A.; Bajorek, S.

2011-01-01

The present study performs scaled separate-effects experiments to investigate the hydrodynamics in the air-ingress phenomena following a Depressurized Condition Cooldown in the Very High Temperature Gas-Cooled Reactor. First, a scoping experiment using water and brine is performed. The volumetric exchange rate is measured using a hydrometer, and flow visualizations are performed. Next, Helium-air experiments are performed to obtain three-dimensional oxygen concentration transient data using an oxygen analyzer. It is found that there exists a critical density difference ratio, before which the ingress rate increases linearly with time and after which the ingress rate slows down significantly. In both the water-brine and Helium-air experiments, this critical ratio is found to be approximately 0.7. (author)

Separate-effects experiments on the hydrodynamics of air ingress phenomena for the very high temperature reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, S.; Talley, J.; Yadav, M., E-mail: skim@psu.edu [The Pennsylvania State Univ., University Park, Pennsylvania (United States); Ireland, A.; Bajorek, S. [The United States Nuclear Regulatory Commission, Washington DC (United States)

2011-07-01

The present study performs scaled separate-effects experiments to investigate the hydrodynamics in the air-ingress phenomena following a Depressurized Condition Cooldown in the Very High Temperature Gas-Cooled Reactor. First, a scoping experiment using water and brine is performed. The volumetric exchange rate is measured using a hydrometer, and flow visualizations are performed. Next, Helium-air experiments are performed to obtain three-dimensional oxygen concentration transient data using an oxygen analyzer. It is found that there exists a critical density difference ratio, before which the ingress rate increases linearly with time and after which the ingress rate slows down significantly. In both the water-brine and Helium-air experiments, this critical ratio is found to be approximately 0.7. (author)

Air-Flow-Driven Triboelectric Nanogenerators for Self-Powered Real-Time Respiratory Monitoring.

Science.gov (United States)

Wang, Meng; Zhang, Jiahao; Tang, Yingjie; Li, Jun; Zhang, Baosen; Liang, Erjun; Mao, Yanchao; Wang, Xudong

2018-06-04

Respiration is one of the most important vital signs of humans, and respiratory monitoring plays an important role in physical health management. A low-cost and convenient real-time respiratory monitoring system is extremely desirable. In this work, we demonstrated an air-flow-driven triboelectric nanogenerator (TENG) for self-powered real-time respiratory monitoring by converting mechanical energy of human respiration into electric output signals. The operation of the TENG was based on the air-flow-driven vibration of a flexible nanostructured polytetrafluoroethylene (n-PTFE) thin film in an acrylic tube. This TENG can generate distinct real-time electric signals when exposed to the air flow from different breath behaviors. It was also found that the accumulative charge transferred in breath sensing corresponds well to the total volume of air exchanged during the respiration process. Based on this TENG device, an intelligent wireless respiratory monitoring and alert system was further developed, which used the TENG signal to directly trigger a wireless alarm or dial a cell phone to provide timely alerts in response to breath behavior changes. This research offers a promising solution for developing self-powered real-time respiratory monitoring devices.

The use of air flow through water for water evaporation

International Nuclear Information System (INIS)

Lashin, A.A.

1996-01-01

In water desalination system the productivity rate is improved by increasing the rate of eater evaporation either by heating the water or by forcing air to carry more vapor before condensation. This paper describe an experimental investigation into the effect of forcing the air to flow through a hot water contained in a closed tank through a perforated end of inlet tube. When the air bubbles pass through the water, it increases the rate of vaporization. The effect of some operating parameters are investigated and the results are presented and discussed. 6 figs

Numerical simulation of air flow through turbocharger compressors with dual volute design

Energy Technology Data Exchange (ETDEWEB)

Jiao, Kui; Li, Xianguo; Wu, Hao [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON (Canada); Sun, Harold; Schram, Tim [Ford Motor Company, Dearborn, MI 48126 (United States); Krivitzky, Eric; Larosiliere, Louis M. [Concepts NREC, White River Junction, VT 05001 (United States)

2009-11-15

In this paper, turbocharger centrifugal compressors with dual volute design were investigated by using Computational Fluid Dynamics (CFD) method. The numerical simulation focused on the air flow from compressor impeller inlet to volute exit, and the overall performance level and range are predicted. The numerical investigation revealed that the dual volute design could separate the compressor into two operating regions: ''high efficiency'' and ''low efficiency'' regions with different air flow characteristics, and treating these two regions separately with dual diffuser design showed extended stable operating range and improved efficiency by comparing with conventional single volute design. The ''dual sequential volute'' concept also showed the potential to further extend the stable operating range by closing one of the volutes at low air flow rates. Furthermore, by comparing with other alternate designs such as variable diffuser vanes and variable inlet guide vanes, the operation of the dual sequential volute also features relatively simple control and calibration. (author)

Investigation of Countercurrent Helium-Air Flows in Air-ingress Accidents for VHTRs

Energy Technology Data Exchange (ETDEWEB)

Sun, Xiaodong; Christensen, Richard; Oh, Chang

2013-10-03

The primary objective of this research is to develop an extensive experimental database for the air- ingress phenomenon for the validation of computational fluid dynamics (CFD) analyses. This research is intended to be a separate-effects experimental study. However, the project team will perform a careful scaling analysis prior to designing a scaled-down test facility in order to closely tie this research with the real application. As a reference design in this study, the team will use the 600 MWth gas turbine modular helium reactor (GT-MHR) developed by General Atomic. In the test matrix of the experiments, researchers will vary the temperature and pressure of the helium— along with break size, location, shape, and orientation—to simulate deferent scenarios and to identify potential mitigation strategies. Under support of the Department of Energy, a high-temperature helium test facility has been designed and is currently being constructed at Ohio State University, primarily for high- temperature compact heat exchanger testing for the VHTR program. Once the facility is in operation (expected April 2009), this study will utilize high-temperature helium up to 900°C and 3 MPa for loss-of-coolant accident (LOCA) depressurization and air-ingress experiments. The project team will first conduct a scaling study and then design an air-ingress test facility. The major parameter to be measured in the experiments is oxygen (or nitrogen) concentration history at various locations following a LOCA scenario. The team will use two measurement techniques: 1) oxygen (or similar type) sensors employed in the flow field, which will introduce some undesirable intrusiveness, disturbing the flow, and 2) a planar laser-induced fluorescence (PLIF) imaging technique, which has no physical intrusiveness to the flow but requires a transparent window or test section that the laser beam can penetrate. The team will construct two test facilities, one for high-temperature helium tests with

Compositional and volumetric development of a monogenetic lava flow field: The historical case of Paricutin (Michoacán, Mexico)

Science.gov (United States)

Larrea, Patricia; Salinas, Sergio; Widom, Elisabeth; Siebe, Claus; Abbitt, Robbyn J. F.

2017-12-01

Paricutin volcano is the youngest and most studied monogenetic volcano in the Michoacán-Guanajuato volcanic field (Mexico), with an excellent historical record of its nine years (February 1943 to March 1952) of eruptive activity. This eruption offered a unique opportunity to observe the birth of a new volcano and document its entire eruption. Geologists surveyed all of the eruptive phases in progress, providing maps depicting the volcano's sequential growth. We have combined all of those previous results and present a new methodological approach, which utilizes state of the art GIS mapping tools to outline and identify the 23 different eruptive phases as originally defined by Luhr and Simkin (1993). Using these detailed lava flow distribution maps, the volume of each of the flows was estimated with the aid of pre- and post-eruption digital elevation models. Our procedure yielded a total lava flow volume ranging between 1.59 and 1.68 km3 DRE, which is larger than previous estimates based on simpler methods. In addition, compositional data allowed us to estimate magma effusion rates and to determine variations in the relative proportions of the different magma compositions issued during the eruption. These results represent the first comprehensive documentation of the combined chemical, temporal, and volumetric evolution of the Paricutin lava field and provide key constraints for petrological interpretations of the nature of the magmatic plumbing system that fed the eruption.

Possible effects of two-phase flow pattern on the mechanical behavior of mudstones

Science.gov (United States)

Goto, H.; Tokunaga, T.; Aichi, M.

2016-12-01

To investigate the influence of two-phase flow pattern on the mechanical behavior of mudstones, laboratory experiments were conducted. In the experiment, air was injected from the bottom of the water-saturated Quaternary Umegase mudstone sample under hydrostatic external stress condition. Both axial and circumferential strains at half the height of the sample and volumetric discharge of water at the outlet were monitored during the experiment. Numerical simulation of the experiment was tried by using a simulator which can solve coupled two-phase flow and poroelastic deformation assuming the extended-Darcian flow with relative permeability and capillary pressure as functions of the wetting-phase fluid saturation. In the numerical simulation, the volumetric discharge of water was reproduced well while both strains were not. Three dimensionless numbers, i.e., the viscosity ratio, the Capillary number, and the Bond number, which characterize the two-phase flow pattern (Lenormand et al., 1988; Ewing and Berkowitz, 1998) were calculated to be 2×10-2, 2×10-11, and 7×10-11, respectively, in the experiment. Because the Bond number was quite small, it was possible to apply Lenormand et al. (1988)'s diagram to evaluate the flow regime, and the flow regime was considered to be capillary fingering. While, in the numerical simulation, air moved uniformly upward with quite low non-wetting phase saturation conditions because the fluid flow obeyed the two-phase Darcy's law. These different displacement patterns developed in the experiment and assumed in the numerical simulation were considered to be the reason why the deformation behavior observed in the experiment could not be reproduced by numerical simulation, suggesting that the two-phase flow pattern could affect the changes of internal fluid pressure patterns during displacement processes. For further studies, quantitative analysis of the experimental results by using a numerical simulator which can solve the coupled

Experimental and Numerical Analysis of Air Flow, Heat Transfer and Thermal Comfort in Buildings with Different Heating Systems

Directory of Open Access Journals (Sweden)

Sabanskis A.

2016-04-01

Full Text Available Monitoring of temperature, humidity and air flow velocity is performed in 5 experimental buildings with the inner size of 3×3×3 m3 located in Riga, Latvia. The buildings are equipped with different heating systems, such as an air-air heat pump, air-water heat pump, capillary heating mat on the ceiling and electric heater. Numerical simulation of air flow and heat transfer by convection, conduction and radiation is carried out using OpenFOAM software and compared with experimental data. Results are analysed regarding the temperature and air flow distribution as well as thermal comfort.

A MEMS-based Air Flow Sensor with a Free-standing Micro-cantilever Structure

Directory of Open Access Journals (Sweden)

Che-Ming Chiang

2007-10-01

Full Text Available This paper presents a micro-scale air flow sensor based on a free-standingcantilever structure. In the fabrication process, MEMS techniques are used to deposit asilicon nitride layer on a silicon wafer. A platinum layer is deposited on the silicon nitridelayer to form a piezoresistor, and the resulting structure is then etched to create afreestanding micro-cantilever. When an air flow passes over the surface of the cantileverbeam, the beam deflects in the downward direction, resulting in a small variation in theresistance of the piezoelectric layer. The air flow velocity is determined by measuring thechange in resistance using an external LCR meter. The experimental results indicate that theflow sensor has a high sensitivity (0.0284 ω/ms-1, a high velocity measurement limit (45ms-1 and a rapid response time (0.53 s.

Evaluations of two-phase natural circulation flow induced in the reactor vessel annular gap under ERVC conditions

Energy Technology Data Exchange (ETDEWEB)

Ha, Kwang Soon, E-mail: tomo@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Cheung, Fan-Bill [The Pennsylvania State University, University Park, PA 16802 (United States); Park, Rae Joon; Kim, Sang Baik [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

2012-12-15

volumetric air injection rate was performed using a loop integration of the momentum equation. The loop-integrated momentum equation was formulated in terms of the dimensionless mass flow rate and the area ratio. Asymptotic solutions were obtained for two limiting cases for which the dimensionless mass flow rate was either very large or very small. First-order approximate solution was also obtained and was found to agree with the experimental data within 20% in most situations. The natural circulation mass flow rate was found to increase as the water inlet area and the volumetric air injection rate were increased. For large inlet areas, the mass flow rate was found to depend almost linearly on the inlet area. By adjusting the inlet and outlet areas of the insulation in HERMES-HALF experiments, a natural circulation flow rate could be generated up to 200 kg/s, corresponding to about 1.3-1.5 MW/m{sup 2} critical heat flux at the top of the reactor lower head (90 Degree-Sign ) according to the data of KAIST and SULTAN.

Transition to chaos of a vertical collapsible tube conveying air flow

International Nuclear Information System (INIS)

Flores, F Castillo; Cros, A

2009-01-01

'Sky dancers', the large collapsible tubes used as advertising, are studied in this work through a simple experimental device. Our study is devoted to the nonlinear dynamics of this system and to its transition to chaos. Firstly, we have shown that after a collapse occurs, the air fills the tube at a different speed rate from the flow velocity. Secondly, the temporal intermittency is studied as the flow rate is increased. A statistical analysis shows that the chaotic times maintain roughly the same value by increasing air speed. On the other hand, laminar times become shorter, until the system reaches a completely chaotic state.

Transition to chaos of a vertical collapsible tube conveying air flow

Energy Technology Data Exchange (ETDEWEB)

Flores, F Castillo; Cros, A, E-mail: anne_cros@yahoo.co [Departamento de Fisica, Universidad de Guadalajara, 44430 Jalisco (Mexico)

2009-05-01

'Sky dancers', the large collapsible tubes used as advertising, are studied in this work through a simple experimental device. Our study is devoted to the nonlinear dynamics of this system and to its transition to chaos. Firstly, we have shown that after a collapse occurs, the air fills the tube at a different speed rate from the flow velocity. Secondly, the temporal intermittency is studied as the flow rate is increased. A statistical analysis shows that the chaotic times maintain roughly the same value by increasing air speed. On the other hand, laminar times become shorter, until the system reaches a completely chaotic state.

Slug flooding in air-water countercurrent vertical flow

International Nuclear Information System (INIS)

Lee, Jae Young; Raman, Roger; Chang, Jen-Shih

2000-01-01

This paper is to study slug flooding in the vertical air-water countercurrent flow loop with a porous liquid injector in the upper plenum. More water penetration into the bottom plenum in slug flooding is observed than the annular flooding because the flow regime changes from the slug flow regime or periodic slug/annular flow regime to annular flow regime due to the hysteresis between the onset of flooding and the bridging film. Experiments were made tubes of 0.995 cm, 2.07 cm, and 5.08 cm in diameter. A mechanistic model for the slug flooding with the solitary wave whose height is four time of the mean film thickness is developed to produce relations of the critical liquid flow rate and the mean film thickness. After fitting the critical liquid flow rate with the experimental data as a function of the Bond number, the gas flow rate for the slug flooding is obtained by substituting the critical liquid flow rate to the annular flooding criteria. The present experimental data evaluate the slug flooding condition developed here by substituting the correlations for mean film thickness models in the literature. The best prediction was made by the correlation for the mean film thickness of the present study which is same as Feind's correlation multiplied by 1.35. (author)

Adiabatic gas-liquid flow

International Nuclear Information System (INIS)

Mayinger, F.

1982-01-01

The author starts by discussing the gas-fluidic mixture, its application and its special characteristics. The conservation theorems for these mixtures are then presented, including the continuity equation, the impulse equation, and energy balance. The type of flow in vertical channels, vertical downwards flow and flow in horizontal and inclined tubes is discussed followed by a short section on local volumetric steam contents and slip. The expressions for the slip and for the local volumetric steam contents are explained before discussing phase separation in nonflowing fluids. Pressure loss in tubes and channels is followed by discussion of pressure loss in various types of moulded bodies with particular reference to fuel rod bundles. In conclusion the author discusses pressure wave expansion, critical discharge and cross exchange in sub-divided channels. (A.N.K.)

A test section design to simulate horizontal two-phase air-water flow

International Nuclear Information System (INIS)

Faccini, Jose Luiz H.; Cesar, Silvia B.G.; Coutinho, Jorge A.; Freitas, Sergio Carlos; Addor, Pedro N.

2002-01-01

In this work an air-water two-phase flow horizontal test section assembling at Nuclear Engineering Institute (IEN) is presented. The test section was designed to allow four-phase flow patterns to be simulated: bubble flow, stratified flow, wave flow and slug flow. These flow patterns will be identified by non-conventional ultrasonic techniques which have been developed to meet this particular application. Based on the separated flow and drift-flux models the test section design steps are shown. A description of the test section and its instrumentation and data acquisition system is also provided. (author)

Hydrodynamic study of an internal airlift reactor for microalgae culture.

Science.gov (United States)

Rengel, Ana; Zoughaib, Assaad; Dron, Dominique; Clodic, Denis

2012-01-01

Internal airlift reactors are closed systems considered today for microalgae cultivation. Several works have studied their hydrodynamics but based on important solid concentrations, not with biomass concentrations usually found in microalgae cultures. In this study, an internal airlift reactor has been built and tested in order to clarify the hydrodynamics of this system, based on microalgae typical concentrations. A model is proposed taking into account the variation of air bubble velocity according to volumetric air flow rate injected into the system. A relationship between riser and downcomer gas holdups is established, which varied slightly with solids concentrations. The repartition of solids along the reactor resulted to be homogenous for the range of concentrations and volumetric air flow rate studied here. Liquid velocities increase with volumetric air flow rate, and they vary slightly when solids are added to the system. Finally, liquid circulation time found in each section of the reactor is in concordance with those employed in microalgae culture.

Impact of heat load location and strength on air flow pattern with a passive chilled beam system

Energy Technology Data Exchange (ETDEWEB)

Kosonen, Risto [Halton Oy, Niittyvillankuja 4, 01510 Vantaa (Finland); Saarinen, Pekka; Koskela, Hannu [Finnish Institute of Occupational Health, Lemminkaisenkatu 14-18 B, 20520 Turku (Finland); Hole, Alex [Arup, Rob Leslie-Carter, Level 10, 201 Kent Street, Sydney, NSW 2000 (Australia)

2010-01-15

A passive chilled beam is a source of natural convection, creating a flow of cold air directly into the occupied zone. Experiments were conducted in a mock-up of an office room to study the air velocities in the occupied spaces. In addition, velocity profiles are registered when underneath heat loads exist and the cool and warm air flows interact. Experimental laboratory study revealed that in the case of the underneath heat gains, even no upward plume was generated and the dummy only acted as a flow obstacle, having a significant effect on the velocity profile. Furthermore, in an actual occupied office environment, the thermal plumes and the supply air diffuser mixed effectively the whole air volume. The maximum air velocity measured was still below 0.25 m/s with the extremely high heat gain of 164 W/m{sup 2}. The results demonstrate that analysis methods were the interaction of convection flow and jet are not taken into account could not accurately describe air movement and draught risk in the occupied room space. (author)

Flow-Field Characteristics of High-Temperature Annular Buoyant Jets and Their Development Laws Influenced by Ventilation System

Directory of Open Access Journals (Sweden)

Yi Wang

2013-01-01

Full Text Available The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to −5 Pa.

Flow-field characteristics of high-temperature annular buoyant jets and their development laws influenced by ventilation system.

Science.gov (United States)

Wang, Yi; Huang, Yanqiu; Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0 Pa to -5 Pa.

Comparative Study of Convective Heat Transfer Performance of Steam and Air Flow in Rib Roughened Channels

Science.gov (United States)

Ma, Chao; Ji, Yongbin; Ge, Bing; Zang, Shusheng; Chen, Hua

2018-04-01

A comparative experimental study of heat transfer characteristics of steam and air flow in rectangular channels roughened with parallel ribs was conducted by using an infrared camera. Effects of Reynolds numbers and rib angles on the steam and air convective heat transfer have been obtained and compared with each other for the Reynolds number from about 4,000 to 15,000. For all the ribbed channels the rib pitch to height ratio (p/e) is 10, and the rib height to the channel hydraulic diameter ratio is 0.078, while the rib angles are varied from 90° to 45°. Based on experimental results, it can be found that, even though the heat transfer distributions of steam and air flow in the ribbed channels are similar to each other, the steam flow can obtain higher convective heat transfer enhancement capability, and the heat transfer enhancement of both the steam and air becomes greater with the rib angle deceasing from 90° to 45°. At Reynolds number of about 12,000, the area-averaged Nusselt numbers of the steam flow is about 13.9%, 14.2%, 19.9% and 23.9% higher than those of the air flow for the rib angles of 90°, 75°, 60° and 45° respectively. With the experimental results the correlations for Nusselt number in terms of Reynolds number and rib angle for the steam and air flow in the ribbed channels were developed respectively.

Transient analysis of air-water two-phase flow in channels and bends

International Nuclear Information System (INIS)

Khan, H.J.; Ye, W.; Pertmer, G.A.

1992-01-01

The algorithm used in this paper is the Newton Block Gauss Seidel method, which has been applied to both simple and complex flow conditions in two-phase flow. This paper contains a description of difference techniques and an iterative solution algorithm that is used to solve the field and constitutive equations of the two-fluid model. In practice, this solution procedure has been proven to be stable and capable of generating solutions in problems where other schemes have failed. The method converges rapidly for reasonable error tolerances and is easily extended to three-dimensional geometries. Using air-water as the two-phase medium, transient flow behavior in several geometries of interest are shown. Flow through a vertical channel with flow obstruction, large U bends, and 90-deg bends are being demonstrated with variation of inlet void fraction and slip ratio. Significant changes in the velocity and void distribution profiles have been observed. Various regions of flow recirculation are obtained in the flow domain for each phase. The phasic velocity and void distributions are dominated by gravity-induced phase separation causing air to accumulate in the upper region. The influence of inlet slip ratio and interfacial momentum transfer on the transient flow profile has been demonstrated in detail

Numerical analysis on flows in supersonic air intakes. Choonsoku kuki toriireguchi no nagare no suchi kaiseki

Energy Technology Data Exchange (ETDEWEB)

Shimada, T.; Tamura, N.; Sekino, N.; Tsujimura, N. (Nissan Motor Co. Ltd., Tokyo (Japan))

1992-06-25

By applying computational fluid dynamics (CFD) to a flow in the supersonic air intake of rocket, appropriateness of computational result was confirmed from a comparison with the wind tunnel test result. In order for the air intake type rocket to heighten the combustion efficiency of fuel and air, it is important to possibly minimize the total pressure loss of air which has been taken in and maintain the air flow rate. A numerical analysis was made through modeling the sectional shape of wind tunnel test body and analyzing the two-dimensional flow by Reynolds-averaged Navier-Stokes equations. The computational result of analysis coincided well with the pressure measurement result in wind tunnel test. Having elucidated the main factors of total pressure loss in a two-dimensionally curved flow passage, the CFD computation gave a possibility that the total pressure loss is considerably low against that passage if improved in shape. If simultaneously used with a characteristic curve method, the CFD computation made it possible to optimize the pressure recovery characteristics in the axially symmetric air intake. The CFD can be expected to be an effective method of designing the basic shape of supersonic air intake. 9 refs., 14 figs.

Influence of ventilation structure on air flow distribution of large turbo-generator

Science.gov (United States)

Zhang, Liying; Ding, Shuye; Zhao, Zhijun; Yang, Jingmo

2018-04-01

For the 350 MW air - cooled turbo—generator, the rotor body is ventilated by sub -slots and 94 radial ventilation ducts and the end adopts arc segment and the straight section to acquire the wind. The stator is ventilated with five inlets and eight outlet air branches. In order to analyze the cooling effect of different ventilation schemes, a global physical model including the stator, rotor, casing and fan is established, and the assumptions and boundary conditions of the solution domain are given. the finite volume method is used to solve the problem, and the air flow distribution characteristics of each part of the motor under different ventilation schemes are obtained. The results show that the baffle at the end of the rotor can eliminate the eddy current at the end of the rotor, and make the flow distribution of cooling air more uniform and reasonable. The conclusions can provide reference for the design of motor ventilation structure.

Multistage open-tube trap for enrichment of part-per-trillion trace components of low-pressure (below 27-kPa) air samples

Science.gov (United States)

Ohara, D.; Vo, T.; Vedder, J. F.

1985-01-01

A multistage open-tube trap for cryogenic collection of trace components in low-pressure air samples is described. The open-tube design allows higher volumetric flow rates than densely packed glass-bead traps commonly reported and is suitable for air samples at pressures below 27 kPa with liquid nitrogen as the cryogen. Gas blends containing 200 to 2500 parts per trillion by volume each of ethane and ethene were sampled and hydrocarbons were enriched with 100 + or - 4 percent trap efficiency. The multistage design is more efficient than equal-length open-tube traps under the conditions of the measurements.

FY1999 Meeting of The Society of Heating, Air-Conditioning and Sanitary Engineering of Japan. Air flow analysis II; 1999 nendo gakujutsu koenkai gaiyo. Kiryu kaiseki 2

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-12-05

B-4 reported the result on particle size distribution experiment and numerical calculation with FEM and {kappa}- {epsilon} model using a welding simulation equipment for generation and removal of welding fume in a narrow site. Discussion was held on the position of an exhaust hood. B-5 reported the study results on indoor air flow conditions derived from a movable nozzle air conditioning system by model experiment and numerical analysis. Disagreement of both results between the experiment and calculation in the case of two diffusing nozzles attached at 30 degrees toward the inside was improved by shortening a sampling time for calculation. B-6 reported the study results on some parameters such as wind velocity, flow rate and inlet position, and the energy saving effect of an air curtain (wall outlet, floor inlet) to control air conditioning areas for a part of large spaces by numerical analysis of air flow. Discussion was held on calculation of 2-D flow and layered flow. B-7 is the 5th research report on measurement of air flow conditions such as measurement of large space environment by video camera and balloon. Study on the camera for automatic measurement, and the identification technique of balloon positions was reported. (translated by NEDO)

A three-dimensional mathematical model to predict air-cooling flow and temperature distribution of wire loops in the Stelmor air-cooling system

International Nuclear Information System (INIS)

Hong, Lingxiang; Wang, Bo; Feng, Shuai; Yang, Zhiliang; Yu, Yaowei; Peng, Wangjun; Zhang, Jieyu

2017-01-01

Highlights: • A 3-dimentioanl mathematical models for complex wire loops was set up in Stelmor. • The air flow field in the cooling process was simulated. • The convective heat transfer coefficient was simulated coupled with air flow field. • The temperature distribution with distances was predicted. - Abstract: Controlling the forced air cooling conditions in the Stelmor conveyor line is important for improving the microstructure and mechanical properties of steel wire rods. A three-dimensional mathematical model incorporating the turbulent flow of the cooling air and heat transfer of the wire rods was developed to predict the cooling process in the Stelmor air-cooling line of wire rolling mills. The distribution of cooling air from the plenum chamber and the forced convective heat transfer coefficient for the wire loops were simulated at the different locations over the conveyor. The temperature profiles and cooling curves of the wire loops in Stelmor conveyor lines were also calculated by considering the convective heat transfer, radiative heat transfer as well as the latent heat during transformation. The calculated temperature results using this model agreed well with the available measured results in the industrial tests. Thus, it was demonstrated that this model can be useful for studying the air-cooling process and predicting the temperature profile and microstructure evolution of the wire rods.

Influences of air flow on energy consumption as well as cost of investment and operation of airconditioning plants

Energy Technology Data Exchange (ETDEWEB)

Radtke, W

1981-08-01

Within research project 'RELA', tests have been made to determine the amount of entering air to be guided from bottom to top and from ceiling to ceiling in order to obtain equal cooling capacity and air quality as well as equal entering air temperature. On the basis of these results, the 'Schmidt-Reuter Ingenieurgesellschaft', Cologne/Germany, has investigated the effects of air flow on the energy consumption for the equal air conditioning of a conventional office building. Since the energy consumption is also influenced by the sort of air treatment, energy transport by air or water, the selected air temperatures and the adaption of the plant to part-load, the calculation has been performed for a larger number of air treatment and control systems customary today. Furthermore, the effects of the type of air flow on plant size, plant rooms and building construction are shown. The author reports on the resulting influences of the type of air flow on energy consumption and cost of operation.

A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

International Nuclear Information System (INIS)

Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok

1995-01-01

This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within ±8%

A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

Energy Technology Data Exchange (ETDEWEB)

Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)] [and others

1995-09-01

This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within {plus_minus}8%.

Continuous infusion thermodilution for assessment of coronary flow: Theoretical background and in vitro validation

NARCIS (Netherlands)

Veer, van 't M.; Geven, M.C.F.; Rutten, M.C.M.; Horst, van der A.; Aarnoudse, W.H.; Pijls, N.H.J.; Vosse, van de F.N.

2009-01-01

Direct volumetric assessment of coronary flow during cardiac catheterization has not been available so far. In the current study continuous infusion thermodilution, a method based on continuous infusion of saline into a selective coronary artery is evaluated. Theoretically, volumetric flow can be

Liquid velocity in upward and downward air-water flows

International Nuclear Information System (INIS)

Sun Xiaodong; Paranjape, Sidharth; Kim, Seungjin; Ozar, Basar; Ishii, Mamoru

2004-01-01

Local characteristics of the liquid phase in upward and downward air-water two-phase flows were experimentally investigated in a 50.8-mm inner-diameter round pipe. An integral laser Doppler anemometry (LDA) system was used to measure the axial liquid velocity and its fluctuations. No effect of the flow direction on the liquid velocity radial profile was observed in single-phase liquid benchmark experiments. Local multi-sensor conductivity probes were used to measure the radial profiles of the bubble velocity and the void fraction. The measurement results in the upward and downward two-phase flows are compared and discussed. The results in the downward flow demonstrated that the presence of the bubbles tended to flatten the liquid velocity radial profile, and the maximum liquid velocity could occur off the pipe centerline, in particular at relatively low flow rates. However, the maximum liquid velocity always occurred at the pipe center in the upward flow. Also, noticeable turbulence enhancement due to the bubbles in the two-phase flows was observed in the current experimental flow conditions. Furthermore, the distribution parameter and the void-weighted area-averaged drift velocity were obtained based on the definitions

Effect of flow velocity on the process of air-steam condensation in a vertical tube condenser

Science.gov (United States)

Havlík, Jan; Dlouhý, Tomáš

2018-06-01

This article describes the influence of flow velocity on the condensation process in a vertical tube. For the case of condensation in a vertical tube condenser, both the pure steam condensation process and the air-steam mixture condensation process were theoretically and experimentally analyzed. The influence of steam flow velocity on the value of the heat transfer coefficient during the condensation process was evaluated. For the condensation of pure steam, the influence of flow velocity on the value of the heat transfer coefficient begins to be seen at higher speeds, conversely, this effect is negligible at low values of steam velocity. On the other hand, for the air-steam mixture condensation, the influence of flow velocity must always be taken into account. The flow velocity affects the water vapor diffusion process through non-condensing air. The presence of air significantly reduces the value of the heat transfer coefficient. This drop in the heat transfer coefficient is significant at low velocities; on the contrary, the decrease is relatively small at high values of the velocity.

Flow measurement at the aortic root

DEFF Research Database (Denmark)

Bertelsen, Litten; Svendsen, Jesper Hastrup; Køber, Lars

2016-01-01

during CMR and aortic stenosis were excluded from the analyses. Stroke volumes were measured volumetrically (SVref) from steady-state free precision short axis images covering the entire left ventricle, excluding the papillary muscles and including the left ventricular outflow tract. Flow sequences......BACKGROUND: Cardiovascular magnetic resonance (CMR) is considered the gold standard of cardiac volumetric measurements. Flow in the aortic root is often measured at the sinotubular junction, even though placing the slice just above valve level may be more precise. It is unknown how much flow...... theoretically be equal to flow measurements, SVV and SVST were compared to SVref. RESULTS: Initially, 152 patients were included. 22 were excluded because of arrhythmias during scans and 9 were excluded for aortic stenosis. Accordingly, data from 121 patients were analysed and of these 63 had visually evident...

Study of microvascular non-Newtonian blood flow modulated by electroosmosis.

Science.gov (United States)

Tripathi, Dharmendra; Yadav, Ashu; Anwar Bég, O; Kumar, Rakesh

2018-05-01

An analytical study of microvascular non-Newtonian blood flow is conducted incorporating the electro-osmosis phenomenon. Blood is considered as a Bingham rheological aqueous ionic solution. An externally applied static axial electrical field is imposed on the system. The Poisson-Boltzmann equation for electrical potential distribution is implemented to accommodate the electrical double layer in the microvascular regime. With long wavelength, lubrication and Debye-Hückel approximations, the boundary value problem is rendered non-dimensional. Analytical solutions are derived for the axial velocity, volumetric flow rate, pressure gradient, volumetric flow rate, averaged volumetric flow rate along one time period, pressure rise along one wavelength and stream function. A plug swidth is featured in the solutions. Via symbolic software (Mathematica), graphical plots are generated for the influence of Bingham plug flow width parameter, electrical Debye length and Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity) on the key hydrodynamic variables. This study reveals that blood flow rate accelerates with decreasing the plug width (i.e. viscoplastic nature of fluids) and also with increasing the Debye length parameter. Copyright © 2018 Elsevier Inc. All rights reserved.

Analytic Intermodel Consistent Modeling of Volumetric Human Lung Dynamics.

Science.gov (United States)

Ilegbusi, Olusegun; Seyfi, Behnaz; Neylon, John; Santhanam, Anand P

2015-10-01

Human lung undergoes breathing-induced deformation in the form of inhalation and exhalation. Modeling the dynamics is numerically complicated by the lack of information on lung elastic behavior and fluid-structure interactions between air and the tissue. A mathematical method is developed to integrate deformation results from a deformable image registration (DIR) and physics-based modeling approaches in order to represent consistent volumetric lung dynamics. The computational fluid dynamics (CFD) simulation assumes the lung is a poro-elastic medium with spatially distributed elastic property. Simulation is performed on a 3D lung geometry reconstructed from four-dimensional computed tomography (4DCT) dataset of a human subject. The heterogeneous Young's modulus (YM) is estimated from a linear elastic deformation model with the same lung geometry and 4D lung DIR. The deformation obtained from the CFD is then coupled with the displacement obtained from the 4D lung DIR by means of the Tikhonov regularization (TR) algorithm. The numerical results include 4DCT registration, CFD, and optimal displacement data which collectively provide consistent estimate of the volumetric lung dynamics. The fusion method is validated by comparing the optimal displacement with the results obtained from the 4DCT registration.

Effect of variations in air speed on cross-flow cylinder frosting

International Nuclear Information System (INIS)

Monaghan, P.F.; Cassidy, S.F.; Oosthuizen, P.H.

1990-01-01

In this paper the effect of fluctuating air speed on frost growth and heat transfer to a cylinder in cross-flow is discussed. Frost-growth of up to 20 hours is simulated using an experimentally validated finite difference computer model. Graphical results are presented for frost mass, frost depth, frost surface temperature and heat transfer versus time under both steady and fluctuating air speed conditions. In general, it is found that a thinner, more dense frost layer develops under fluctuating air speed conditions giving improved heat transfer. This phenomenon may be explained by the increased frequency of frost surface thaw/freeze cycles when fluctuating air speed conditions prevail

Quantifying air distribution, ventilation effectiveness and airborne pollutant transport in an aircraft cabin mockup

Science.gov (United States)

Wang, Aijun

The health, safety and comfort of passengers during flight inspired this research into cabin air quality, which is closely related to its airflow distribution, ventilation effectiveness and airborne pollutant transport. The experimental facility is a full-scale aircraft cabin mockup. A volumetric particle tracking velocimetry (VPTV) technique was enhanced by incorporating a self-developed streak recognition algorithm. Two stable recirculation regions, the reverse flows above the seats and the main air jets from the air supply inlets formed the complicated airflow patterns inside the cabin mockup. The primary air flow was parallel to the passenger rows. The small velocity component in the direction of the cabin depth caused less net air exchange between the passenger rows than that parallel to the passenger rows. Different total air supply rate changed the developing behaviors of the main air jets, leading to different local air distribution patterns. Two indices, Local mean age of air and ventilation effectiveness factor (VEF), were measured at five levels of air supply rate and two levels of heating load. Local mean age of air decreased linearly with an increase in the air supply rate, while the VEF remained consistent when the air supply rate varied. The thermal buoyancy force from the thermal plume generated the upside plume flow, opposite to the main jet flow above the boundary seats and thus lowered the local net air exchange. The airborne transport dynamics depends on the distance between the source and the receptors, the relative location of pollutant source, and air supply rate. Exposure risk was significantly reduced with increased distance between source and receptors. Another possible way to decrease the exposure risk was to position the release source close to the exhaust outlets. Increasing the air supply rate could be an effective solution under some emergency situations. The large volume of data regarding the three-dimensional air velocities was

Investigation of flow condition on the oxidation of Zircaloy-4 in air at 850 and 1100 .deg. C

Energy Technology Data Exchange (ETDEWEB)

Maeng, Yun Hwan; Lee, Jae Young [Hangdong Global University, Pohang (Korea, Republic of); Park, Sang Gil [ACT Co. Ltd, Daejeon (Korea, Republic of)

2016-05-15

An oxidation behavior of the Zircaloy-4 was experimentally studied by varying a flow rate and partial pressure of air. Tests were conducted at two distinct temperatures in which a kinetic transition was occurred, or not: 850 .deg. C and 1100 .deg. C. The effects of flow rate and partial pressure of air was studied by a measurement of mass gain using thermogravimetric analyzer (TGA). After experiments, samples were observed with macrophotography and metallography using optical microscopy. The effect of flow rate and partial pressure of air were qualitatively analyzed with those methods. The effects of flow conditions on the oxidation kinetics of Zircaloy-4 samples were qualitatively studied. The flow rate and the partial pressure of air were changed and their effects was different when the temperature was changed.

Numerical Analysis of Flow Distribution in a Sodium Chamber of a Finned-tube Sodium-to-Air Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Jo, Youngchul; Son, Seokkwon; Kim, Hyungmo; Eoh, Jaehyuk; Jeong, Jiyoung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

DHR systems consist of two diverse heat removal loops such as passive and active DHR systems, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different kinds of sodium-to-air heat exchangers, e.g. M-shape and helical-coil type air-coolers. The former is called as an FHX(Forced-draft sodium-to-air Heat Exchanger) and the latter is simply called as an AHX(natural-draft sodium-to-Air Heat Exchanger). In a general sodium-to-air heat exchanger design, convection resistance in a shell-side air flow path becomes dominant factor affecting the mechanism of conjugate heat transfer from the sodium flow inside the tube to the air path across the sodium tube wall. Hence verification of the flow and heat transfer characteristics is one of the most important tasks to demonstrate decay heat removal performance. To confirm a kind of ultimate heat sink heat exchanger, a medium-scale Sodium thermal-hydraulic Experiment Loop for Finned-tube sodium-to-Air Heat exchanger (here after called the SELFA) has been designed and is recently being constructed at KAERI site. The introduction of the flow baffle inside the upper sodium chamber of the model FHX unit in the SELFA facility is briefly proposed and discussed as well. The present study aims at introducing a flow baffle design inside the upper sodium chamber to make more equalized flowrates flowing into each heat transfer tube of the model FHX unit. In the cases without the flow baffle geometry, it was observed lager discrepancies in flowrates at the heat transfer tubes. However it was also found that those kinds of discrepancies could be definitely decreased at around 1/10 by employing a flow baffle.

Study on heat transfer and fluid flow in the stand pipe rupture accident

International Nuclear Information System (INIS)

Fumizawa, Motoo; Hishida, Makoto

1991-09-01

This paper deals with an experimental investigation of the buoyancy driven exchange flow which takes place through a narrow cylindrical channel, during the stand pipe rupture accident in a high temperature gas-cooled reactor (HTGR). The velocity distribution through the cylindrical channel is measured by a laser Doppler velocimeter, in order to evaluate the air ingress flow rate. The experiments are performed under atmospheric pressure with nitrogen as a working fluid. Rayleigh number ranges from 1.3 x 10 7 to 7.0 x 10 7 . The following conclusions were obtained: (1) The laser Doppler velocimeter was found a good method for the measurement of the velocity of the exchange flow. (2) When the temperature of the hemisphere and the bottom heated plate, which simulate the top cover of the reactor, was kept uniform, the volumetric exchange flow rate agreed well with Epstein's result. (3) The exchange flow through a narrow cylindrical channel fluctuated irregularly with time and space. (author)

Analysis of heat flow in a tube bank of a condenser considering the influence of air

Directory of Open Access Journals (Sweden)

Joachimiak Magda

2017-09-01

Full Text Available The pressure of wet water vapor inside a condenser has a great impact on the efficiency of thermal cycle. The value of this pressure depends on the mass share of inert gases (air. The knowledge of the spots where the air accumulates allows its effective extraction from the condenser, thus improving the conditions of condensation. The condensation of water vapor with the share of inert gas in a model tube bank of a condenser has been analyzed in this paper. The models include a static pressure loss of the water vapor/air mixture and the resultant changes in the water vapor parameters. The mass share of air in water vapor was calculated using the Dalton’s law. The model includes changes of flow and thermodynamic parameters based on the partial pressure of water vapor utilizing programmed water vapor tables. In the description of the conditions of condensation the Nusselts theory was applied. The model allows for a deterioration of the heat flow conditions resulting from the presence of air. The paper contains calculations of the water vapor flow with the initial mass share of air in the range 0.2 to 1%. The results of calculations clearly show a great impact of the share of air on the flow conditions and the deterioration of the conditions of condensation. The data obtained through the model for a given air/water vapor mixture velocity upstream of the tube bank allow for identification of the spots where the air accumulates.

Estimating Probable Maximum Precipitation by Considering Combined Effect of Typhoon and Southwesterly Air Flow

Directory of Open Access Journals (Sweden)

Cheng-Chin Liu

2016-01-01

Full Text Available Typhoon Morakot hit southern Taiwan in 2009, bringing 48-hr of heavy rainfall [close to the Probable Maximum Precipitation (PMP] to the Tsengwen Reservoir catchment. This extreme rainfall event resulted from the combined (co-movement effect of two climate systems (i.e., typhoon and southwesterly air flow. Based on the traditional PMP estimation method (i.e., the storm transposition method, STM, two PMP estimation approaches, i.e., Amplification Index (AI and Independent System (IS approaches, which consider the combined effect are proposed in this work. The AI approach assumes that the southwesterly air flow precipitation in a typhoon event could reach its maximum value. The IS approach assumes that the typhoon and southwesterly air flow are independent weather systems. Based on these assumptions, calculation procedures for the two approaches were constructed for a case study on the Tsengwen Reservoir catchment. The results show that the PMP estimates for 6- to 60-hr durations using the two approaches are approximately 30% larger than the PMP estimates using the traditional STM without considering the combined effect. This work is a pioneer PMP estimation method that considers the combined effect of a typhoon and southwesterly air flow. Further studies on this issue are essential and encouraged.

Experimental measurement of fluid force coefficients for helical tube arrays in air cross flow

International Nuclear Information System (INIS)

Shen Shifang; Liu Reilan

1993-01-01

A helical coil steam generator is extensively used in the High Temperature Gas Cooled Reactor (HTGCR) and Sodium Cooled Reactor (SCR) nuclear power stations because of its compact structure, good heat-exchange, and small volume. The experimental model is established by the structure parameter of 200MW HTGCR. The fluid elastic instability of helical tube arrays in air cross flow is studied in this experiment, and the fluid force coefficients of helical tube arrays having the same notational direction of two adjacent layers in air cross flow are obtained. As compared to the fluid force coefficients of cylinder tube arrays, the fluid force coefficients of helical tube arrays are smaller in the low velocity area, and greater in the high velocity area. The experimental results help the study of the dynamic characteristics of helical tube arrays in air cross flow

Visualization of the air flow behind the automotive benchmark vent

OpenAIRE

Pech, Ondřej; Jedelský, Jan; Caletka, Petr; Jícha, Miroslav

2015-01-01

Passenger comfort in cars depends on appropriate function of the cabin HVAC system. A great attention is therefore paid to the effective function of automotive vents and proper formation of the flow behind the ventilation outlet. The article deals with the visualization of air flow from the automotive benchmark vent. The visualization was made for two different shapes of the inlet channel connected to the benchmark vent. The smoke visualization with the laser knife was used. The influence of ...

Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

Science.gov (United States)

Spanogle, J A; Moore, C S

1931-01-01

Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

A comparative study of turbulence models for dissolved air flotation flow analysis

International Nuclear Information System (INIS)

Park, Min A; Lee, Kyun Ho; Chung, Jae Dong; Seo, Seung Ho

2015-01-01

The dissolved air flotation (DAF) system is a water treatment process that removes contaminants by attaching micro bubbles to them, causing them to float to the water surface. In the present study, two-phase flow of air-water mixture is simulated to investigate changes in the internal flow analysis of DAF systems caused by using different turbulence models. Internal micro bubble distribution, velocity, and computation time are compared between several turbulence models for a given DAF geometry and condition. As a result, it is observed that the standard κ-ε model, which has been frequently used in previous research, predicts somewhat different behavior than other turbulence models

Numerical analysis of flow field formed by air bubble dischanging through a sparger

International Nuclear Information System (INIS)

Kim, H. W.; Bae, Y. Y.

2002-01-01

In both a boiling water reactor and an advanced type of pressurized water reactor APR1400 being constructed in Korea, water, air and steam successively discharge into a subcooled water pool through spargers, when a pressure relieving system is in operation. During the discharging processes, the air bubble clouds produce a low-frequency and high-amplitude oscillatory loading, which may result in significant damages to the submerged structures if the resonance between bubble clouds and structures occur. This study deals with a numerical analysis of the flow field due to the oscillation of air bubble clouds by using a commercial thermal hydraulic analysis code FLUENT, version 4.5. The VOF (Volume Of Fluid) model was used to simulate the interface of water, air and steam flows, since it is known to be suitable for the large bubble simulation and it enables to treat air as a compressible fluid. A good agreement between the analysis results and the ABB-Atom test results, which had been performed for the development of BWR sparger, was obtained

On the calculation of air flow rates to ventilate closed-type stations in subway with the double-track tunnel

Science.gov (United States)

Kiyanitsa, LA

2018-03-01

Metro is not only the most promising kind of public transport but also an important part of infrastructure in a modern city. As a place where large groups of people gather, subway is to ensure the required air exchange at the passenger platforms of the stations. The air flow rate for airing the stations is also determined based on the required temperature, humidity and MAC of gases. The present study estimates the required air flow rate at the passenger platform of the closed-type subway station with the double-track tunnel given the standard air temperature, humidity and gas concentration, as well as based on the condition of the specified air flow feed and air changes per hour. The article proposes the scheme of air recirculation from the double-track tunnel to the station.

Interfacial structures of confined air-water two-phase bubbly flow

International Nuclear Information System (INIS)

Kim, S.; Ishii, M.; Wu, Q.; McCreary, D.; Beus, S.G.

2000-01-01

The interfacial structure of the two-phase flows is of great importance in view of theoretical modeling and practical applications. In the present study, the focus is made on obtaining detailed local two-phase parameters in the air-water bubbly flow in a rectangular vertical duct using the double-sensor conductivity probe. The characteristic wall-peak is observed in the profiles of the interracial area concentration and the void fraction. The development of the interfacial area concentration along the axial direction of the flow is studied in view of the interfacial area transport and bubble interactions. The experimental data is compared with the drift flux model with C 0 = 1.35

Application of a 2D air flow model to soil vapor extraction and bioventing case studies

International Nuclear Information System (INIS)

Mohr, D.H.; Merz, P.H.

1995-01-01

Soil vapor extraction (SVE) is frequently the technology of choice to clean up hydrocarbon contamination in unsaturated soil. A two-dimensional air flow model provides a practical tool to evaluate pilot test data and estimate remediation rates for soil vapor extraction systems. The model predictions of soil vacuum versus distance are statistically compared to pilot test data for 65 SVE wells at 44 sites. For 17 of 21 sites where there was asphalt paving, the best agreement was obtained for boundary conditions with no barrier to air flow at the surface. The model predictions of air flow rates and stream lines around the well allow an estimate of the gasoline removal rates by both evaporation and bioremediation. The model can be used to quickly estimate the effective radius of influence, defined here as the maximum distance from the well where there is enough air flow to remove the contaminant present within the allowable time. The effective radius of influence is smaller than a radius of influence defined by soil vacuum only. For a case study, in situ bioremediation rates were estimated using the air flow model and compared to independent estimates based on changes in soil temperature. These estimate bioremediation rates for heavy fuel oil ranged from 2.5 to 11 mg oil degraded per kg soil per day, in agreement with values in the literature

STUDY OF THE AIR FLOWS AROUND AN AIRPLANE

Directory of Open Access Journals (Sweden)

Diaconescu Olivian

2013-06-01

Full Text Available This material presents a stage of the designing of an airplane capable to work with low capacity engines of 2.5 and 4 cmc namely the simulation of the air flow around the fuselage and the wings. The study proves the correctness of the choice made in the wing’s positioning and of the horizontal stabilizer of the airplane’s axis,for the chosen airplane type namely acrobat.

STUDY OF THE AIR FLOWS AROUND AN AIRPLANE

OpenAIRE

Diaconescu Olivian

2013-01-01

This material presents a stage of the designing of an airplane capable to work with low capacity engines of 2.5 and 4 cmc namely the simulation of the air flow around the fuselage and the wings. The study proves the correctness of the choice made in the wing’s positioning and of the horizontal stabilizer of the airplane’s axis,for the chosen airplane type namely acrobat.

40 CFR 63.801 - Definitions.

Science.gov (United States)

2010-07-01

... than 10 pounds per square inch (gauge) at the point of atomization. Airless and air assisted airless... as a fraction. (13) Qaj=the volumetric flow rate of gas stream (j) exiting the control device, in dry standard cubic meters per hour. (14) Qbi=the volumetric flow rate of gas stream (i) entering the control...

Do terrestrial hermit crabs sniff? Air flow and odorant capture by flicking antennules.

Science.gov (United States)

Waldrop, Lindsay D; Koehl, M A R

2016-01-01

Capture of odorant molecules by olfactory organs from the surrounding fluid is the first step of smelling. Sniffing intermittently moves fluid across sensory surfaces, increasing delivery rates of molecules to chemosensory receptors and providing discrete odour samples. Aquatic malacostracan crustaceans sniff by flicking olfactory antennules bearing arrays of chemosensory hairs (aesthetascs), capturing water in the arrays during downstroke and holding the sample during return stroke. Terrestrial malacostracans also flick antennules, but how their flicking affects odour capture from air is not understood. The terrestrial hermit crab, Coenobita rugosus, uses antennules bearing shingle-shaped aesthetascs to capture odours. We used particle image velocimetry to measure fine-scale fluid flow relative to a dynamically scaled physical model of a flicking antennule, and computational simulations to calculate diffusion to aesthetascs by odorant molecules carried in that flow. Air does not flow into the aesthetasc array during flick downstrokes or recovery strokes. Odorants are captured from air flowing around the outside of the array during flick downstrokes, when aesthetascs face upstream and molecule capture rates are 21% higher than for stationary antennules. Bursts of flicking followed by pauses deliver discrete odour samples to olfactory sensors, causing intermittency in odour capture by a different mechanism than aquatic crustaceans use. © 2016 The Author(s).

Three-Dimensional Mapping of Air Flow at an Urban Canyon Intersection

Science.gov (United States)

Carpentieri, Matteo; Robins, Alan G.; Baldi, Sandro

2009-11-01

In this experimental work both qualitative (flow visualisation) and quantitative (laser Doppler anemometry) methods were applied in a wind tunnel in order to describe the complex three-dimensional flow field in a real environment (a street canyon intersection). The main aim was an examination of the mean flow, turbulence and flow pathlines characterising a complex three-dimensional urban location. The experiments highlighted the complexity of the observed flows, particularly in the upwind region of the intersection. In this complex and realistic situation some details of the upwind flow, such as the presence of two tall towers, play an important role in defining the flow field within the intersection, particularly at roof level. This effect is likely to have a strong influence on the mass exchange mechanism between the canopy flow and the air aloft, and therefore the distribution of pollutants. This strong interaction between the flows inside and outside the urban canopy is currently neglected in most state-of-the-art local scale dispersion models.

Air flow quality analysis of modenas engine exhaust system

Science.gov (United States)

Shahriman A., B.; Mohamad Syafiq A., K.; Hashim, M. S. M.; Razlan, Zuradzman M.; Khairunizam W. A., N.; Hazry, D.; Afendi, Mohd; Daud, R.; Rahman, M. D. Tasyrif Abdul; Cheng, E. M.; Zaaba, S. K.

2017-09-01

The simulation process being conducted to determine the air flow effect between the original exhaust system and modified exhaust system. The simulations are conducted to investigate the flow distribution of exhaust gases that will affect the performance of the engine. The back flow pressure in the original exhaust system is predicted toward this simulation. The design modification to the exhaust port, exhaust pipe, and exhaust muffler has been done during this simulation to reduce the back flow effect. The new designs are introduced by enlarging the diameter of the exhaust port, enlarge the diameter of the exhaust pipe and created new design for the exhaust muffler. Based on the result obtained, there the pulsating flow form at the original exhaust port that will increase the velocity and resulting the back pressure occur. The result for new design of exhaust port, the velocity is lower at the valve guide in the exhaust port. New design muffler shows that the streamline of the exhaust flow move smoothly compare to the original muffler. It is proved by using the modification exhaust system, the back pressure are reduced and the engine performance can be improve.

Low-Flow Liquid Desiccant Air-Conditioning: Demonstrated Performance and Cost Implications

Energy Technology Data Exchange (ETDEWEB)

Kozubal, E.; Herrmann, L.; Deru, M.; Clark, J.; Lowenstein, A.

2014-09-01

Cooling loads must be dramatically reduced when designing net-zero energy buildings or other highly efficient facilities. Advances in this area have focused primarily on reducing a building's sensible cooling loads by improving the envelope, integrating properly sized daylighting systems, adding exterior solar shading devices, and reducing internal heat gains. As sensible loads decrease, however, latent loads remain relatively constant, and thus become a greater fraction of the overall cooling requirement in highly efficient building designs, particularly in humid climates. This shift toward latent cooling is a challenge for heating, ventilation, and air-conditioning (HVAC) systems. Traditional systems typically dehumidify by first overcooling air below the dew-point temperature and then reheating it to an appropriate supply temperature, which requires an excessive amount of energy. Another dehumidification strategy incorporates solid desiccant rotors that remove water from air more efficiently; however, these systems are large and increase fan energy consumption due to the increased airside pressure drop of solid desiccant rotors. A third dehumidification strategy involves high flow liquid desiccant systems. These systems require a high maintenance separator to protect the air distribution system from corrosive desiccant droplet carryover and so are more commonly used in industrial applications and rarely in commercial buildings. Both solid desiccant systems and most high-flow liquid desiccant systems (if not internally cooled) add sensible energy which must later be removed to the air stream during dehumidification, through the release of sensible heat during the sorption process.

Electro-scrubbing volatile organic carbons in the air stream with a gas diffusion electrode

Energy Technology Data Exchange (ETDEWEB)

Yang Ji, E-mail: yangji@ecust.edu.cn [School of Resources and Environmental Engineering, State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237 (China); School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu Kaichen; Jia Jinping; Cao Limei [School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

2011-04-15

It is demonstrated that exposing the VOC air streams to the electro-scrubbing reactor with a gas diffusion electrode leads to an efficient removal of organics. The importance order of the influence factors on the electro-scrubbing reactor performance is: conductivity, voltage and air stream flow-rate. The effective conductivity and high voltages generally are beneficial to the removal process and the air flow-rate is not a significant factor compared with the other two, indicating that the reactor might have a consistently satisfying performance within a wide range of gas volumetric load. The mass transfer of both organics and oxygen in the reactor is estimated by mathematical model, and the calculation determines the concentration boundary conditions for the 2-ethoxyethyl acetate removal: if the 2-ethoxyethyl acetate concentration in the inflow air stream holds C{sub G,i} {<=} 0.7198 % , the removal in the electro-scrubbing reactor is electrochemical reaction controlled; if C{sub G,i} > 0.7198 % , the controlling step will be the oxygen mass transfer from the air to the liquid in the electro-scrubbing reactor. The Apparent Current Efficiency of the electro-scrubbing reactor was also determined using COD data, which is significantly higher than some commercial metal oxide electrodes, showing that the reactor is energy efficient and has the promise for the future scale-up.

Natural convection in wavy enclosures with volumetric heat sources

International Nuclear Information System (INIS)

Oztop, H.F.; Varol, Y.; Abu-Nada, E.; Chamkha, A.

2011-01-01

In this paper, the effects of volumetric heat sources on natural convection heat transfer and flow structures in a wavy-walled enclosure are studied numerically. The governing differential equations are solved by an accurate finite-volume method. The vertical walls of enclosure are assumed to be heated differentially whereas the two wavy walls (top and bottom) are kept adiabatic. The effective governing parameters for this problem are the internal and external Rayleigh numbers and the amplitude of wavy walls. It is found that both the function of wavy wall and the ratio of internal Rayleigh number (Ra I ) to external Rayleigh number (Ra E ) affect the heat transfer and fluid flow significantly. The heat transfer is predicted to be a decreasing function of waviness of the top and bottom walls in case of (IRa/ERa)>1 and (IRa/ERa)<1. (authors)

Numerical investigation on turbulence mixing characteristics under thermal striping flows. Investigations on fluid temperature fluctuation phenomena in air and sodium

Energy Technology Data Exchange (ETDEWEB)

Murakami, Satoshi [Customer System Co. Ltd., Tokai, Ibaraki (Japan); Muramatsu, Toshiharu

1999-05-01

A three-dimensional thermal striping analysis was carried out using a direct numerical simulation code DINUS-3, for a coaxial jet configuration using air and sodium as a working fluid, within the framework of the EJCC thermo-hydraulic division. From the analysis, the following results have been obtained: (1) Calculated potential core length in air and sodium turbulence flows agreed with a theoretical value (5d - 7d ; d : diameter of jet nozzle) in the two-dimensional free jet theory. (2) Hydraulic characteristics in sodium flows as the potential core length can be estimated by the use of that of air flow characteristics. (3) Shorter thermally potential core length defined by spatial temperature distribution was evaluated in sodium flows, compared with that in air flows. This is due to the higher thermal conductivity of sodium. (4) Thermal characteristics in sodium flows as the thermally potential core length can not be evaluated, based on that air thermal characteristics. (author)

Volumetric CT-images improve testing of radiological image interpretation skills

Energy Technology Data Exchange (ETDEWEB)

Ravesloot, Cécile J., E-mail: C.J.Ravesloot@umcutrecht.nl [Radiology Department at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, Room E01.132 (Netherlands); Schaaf, Marieke F. van der, E-mail: M.F.vanderSchaaf@uu.nl [Department of Pedagogical and Educational Sciences at Utrecht University, Heidelberglaan 1, 3584 CS Utrecht (Netherlands); Schaik, Jan P.J. van, E-mail: J.P.J.vanSchaik@umcutrecht.nl [Radiology Department at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, Room E01.132 (Netherlands); Cate, Olle Th.J. ten, E-mail: T.J.tenCate@umcutrecht.nl [Center for Research and Development of Education at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht (Netherlands); Gijp, Anouk van der, E-mail: A.vanderGijp-2@umcutrecht.nl [Radiology Department at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, Room E01.132 (Netherlands); Mol, Christian P., E-mail: C.Mol@umcutrecht.nl [Image Sciences Institute at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht (Netherlands); Vincken, Koen L., E-mail: K.Vincken@umcutrecht.nl [Image Sciences Institute at University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht (Netherlands)

2015-05-15

Rationale and objectives: Current radiology practice increasingly involves interpretation of volumetric data sets. In contrast, most radiology tests still contain only 2D images. We introduced a new testing tool that allows for stack viewing of volumetric images in our undergraduate radiology program. We hypothesized that tests with volumetric CT-images enhance test quality, in comparison with traditional completely 2D image-based tests, because they might better reflect required skills for clinical practice. Materials and methods: Two groups of medical students (n = 139; n = 143), trained with 2D and volumetric CT-images, took a digital radiology test in two versions (A and B), each containing both 2D and volumetric CT-image questions. In a questionnaire, they were asked to comment on the representativeness for clinical practice, difficulty and user-friendliness of the test questions and testing program. Students’ test scores and reliabilities, measured with Cronbach's alpha, of 2D and volumetric CT-image tests were compared. Results: Estimated reliabilities (Cronbach's alphas) were higher for volumetric CT-image scores (version A: .51 and version B: .54), than for 2D CT-image scores (version A: .24 and version B: .37). Participants found volumetric CT-image tests more representative of clinical practice, and considered them to be less difficult than volumetric CT-image questions. However, in one version (A), volumetric CT-image scores (M 80.9, SD 14.8) were significantly lower than 2D CT-image scores (M 88.4, SD 10.4) (p < .001). The volumetric CT-image testing program was considered user-friendly. Conclusion: This study shows that volumetric image questions can be successfully integrated in students’ radiology testing. Results suggests that the inclusion of volumetric CT-images might improve the quality of radiology tests by positively impacting perceived representativeness for clinical practice and increasing reliability of the test.

On the design criteria for the evaporated water flow rate in a wet air cooler

International Nuclear Information System (INIS)

Bourillot, C.

1982-01-01

The author discusses Poppe's formulation used for the modelling of heat exchangers between air and water, in Electricite de France's TEFERI numerical wet atmospheric cooler model: heat transfer laws in unsaturated and saturated air, Bosnjakivic's formula, evaporation coefficient. The theorical results show good agreement with the measurements taken on Neurath's cooler C in West Germany, whatever the ambient temperature (evaporated water flow rate, condensate content of warm air). The author then demonstrates the inadequacy of Merkel's method for calculating evaporated water flow rates, and estimates the influence of the assumptions made on the total error [fr

Improving the performance of a compression ignition engine by directing flow of inlet air

Science.gov (United States)

Kemper, Carlton

1946-01-01

The object of this report is to present the results of tests performed by the National Advisory Committee for Aeronautics to determine the effect on engine performance of directing the flow of the inlet air to a 5-inch by 7-inch cylinder, solid injection, compression ignition engine, After a few preliminary tests, comparative runs were made at a speed of 1500 r.p.m. with and without directed air flow. It was found that directing the flow of the inlet air toward the fuel injection valve gave steadier engine operation, and an appreciable increase in power, and decreased fuel consumption. The results indicate the possibility of improving the performance of a given type of combustion chamber without changing its shape and with no change in valve timing. They would also seem to prove that directional turbulence, set up before the inlet valve of a four-stroke cycle engine, continues in the engine cylinder throughout the compression stroke.

An air flow sensor for neonatal mechanical ventilation applications based on a novel fiber-optic sensing technique.

Science.gov (United States)

Battista, L; Sciuto, S A; Scorza, A

2013-03-01

In this work, a simple and low-cost air flow sensor, based on a novel fiber-optic sensing technique has been developed for monitoring air flows rates supplied by a neonatal ventilator to support infants in intensive care units. The device is based on a fiber optic sensing technique allowing (a) the immunity to light intensity variations independent by measurand and (b) the reduction of typical shortcomings affecting all biomedical fields (electromagnetic interference and patient electrical safety). The sensing principle is based on the measurement of transversal displacement of an emitting fiber-optic cantilever due to action of air flow acting on it; the fiber tip displacement is measured by means of a photodiode linear array, placed in front of the entrance face of the emitting optical fiber in order to detect its light intensity profile. As the measurement system is based on a detection of the illumination pattern, and not on an intensity modulation technique, it results less sensitive to light intensity fluctuation independent by measurand than intensity-based sensors. The considered technique is here adopted in order to develop two different configurations for an air flow sensor suitable for the measurement of air flow rates typically occurring during mechanical ventilation of newborns: a mono-directional and a bi-directional transducer have been proposed. A mathematical model for the air flow sensor is here proposed and a static calibration of two different arrangements has been performed: a measurement range up to 3.00 × 10(-4) m(3)∕s (18.0 l∕min) for the mono-directional sensor and a measurement range of ±3.00 × 10(-4) m(3)∕s (±18.0 l∕min) for the bi-directional sensor are experimentally evaluated, according to the air flow rates normally encountered during tidal breathing of infants with a mass lower than 10 kg. Experimental data of static calibration result in accordance with the proposed theoretical model: for the mono

An Eulerian-Eulerian CFD Simulation of Air-Water Flow in a Pipe Separator

Directory of Open Access Journals (Sweden)

E.A. Afolabi

2014-06-01

Full Text Available This paper presents a three dimensional Computational Fluid Dynamics (CFD of air-water flow using Eulerian –Eulerian multiphase model and RSM mixture turbulence model to investigate its hydrodynamic flow behaviour in a 30 mm pipe separator. The simulated results are then compared with the stereoscopic PIV measurements at different axial positions. The comparison shows that the velocity distribution can be predicted with high accuracy using CFD. The numerical velocity profiles are also found to be in good qualitative agreement with the experimental measurements. However, there were some discrepancies between the CFD results and the SPIV measurements at some axial positions away from the inlet section. Therefore, the CFD model could provide good physical understanding on the hydrodynamics flow behaviour for air-water in a pipe separator.

Fine PM measurements: personal and indoor air monitoring.

Science.gov (United States)

Jantunen, M; Hänninen, O; Koistinen, K; Hashim, J H

2002-12-01

This review compiles personal and indoor microenvironment particulate matter (PM) monitoring needs from recently set research objectives, most importantly the NRC published "Research Priorities for Airborne Particulate Matter (1998)". Techniques and equipment used to monitor PM personal exposures and microenvironment concentrations and the constituents of the sampled PM during the last 20 years are then reviewed. Development objectives are set and discussed for personal and microenvironment PM samplers and monitors, for filter materials, and analytical laboratory techniques for equipment calibration, filter weighing and laboratory climate control. The progress is leading towards smaller sample flows, lighter, silent, independent (battery powered) monitors with data logging capacity to store microenvironment or activity relevant sensor data, advanced flow controls and continuous recording of the concentration. The best filters are non-hygroscopic, chemically pure and inert, and physically robust against mechanical wear. Semiautomatic and primary standard equivalent positive displacement flow meters are replacing the less accurate methods in flow calibration, and also personal sampling flow rates should become mass flow controlled (with or without volumetric compensation for pressure and temperature changes). In the weighing laboratory the alternatives are climatic control (set temperature and relative humidity), and mechanically simpler thermostatic heating, air conditioning and dehumidification systems combined with numerical control of temperature, humidity and pressure effects on flow calibration and filter weighing.

Experimental and numerical study of flow deflection effects on electronic air-cooling

International Nuclear Information System (INIS)

Arfaoui, Ahlem; Ben Maad, Rejeb; Hammami, Mahmoud; Rebay, Mourad; Padet, Jacques

2009-01-01

This work present a numerical and experimental investigation of the influence of transversal flow deflector on the cooling of a heated block mounted on a flat plate. The deflector is inclined and therefore it guides the air flow to the upper surface of the block. This situation is simulating the air-cooling of a rectangular integrated circuit or a current converter mounted on an electronic board. The electronic component are assumed dissipating a low or medium heat flux (with a density lower than 5000 W/m 2 ), as such the forced convection air cooling without fan or heat sink is still sufficient. The study details the effects of the angle of deflector on the temperature and the heat transfer coefficient along the surface of the block and around it. The results of the numerical simulations and the InfraRed camera measurements show that the deviation caused by deflector may significantly enhance the heat transfer on the top face of block

Relating water and air flow characteristics in coarse granular materials

DEFF Research Database (Denmark)

Andreasen, Rune Røjgaard; Canga, Eriona; Poulsen, Tjalfe Gorm

2013-01-01

Water pressure drop as a function of velocity controls w 1 ater cleaning biofilter operation 2 cost. At present this relationship in biofilter materials must be determined experimentally as no 3 universal link between pressure drop, velocity and filter material properties have been established. 4...... Pressure drop - velocity in porous media is much simpler and faster to measure for air than for water. 5 For soils and similar materials, observations show a strong connection between pressure drop – 6 velocity relations for air and water, indicating that water pressure drop – velocity may be estimated 7...... from air flow data. The objective of this study was, therefore, to investigate if this approach is valid 8 also for coarse granular biofilter media which usually consists of much larger particles than soils. In 9 this paper the connection between the pressure drop – velocity relationships for air...

Interfacial structures of confined air-water two-phase bubbly flow

Energy Technology Data Exchange (ETDEWEB)

Kim, S.; Ishii, M.; Wu, Q.; McCreary, D.; Beus, S.G.

2000-08-01

The interfacial structure of the two-phase flows is of great importance in view of theoretical modeling and practical applications. In the present study, the focus is made on obtaining detailed local two-phase parameters in the air-water bubbly flow in a rectangular vertical duct using the double-sensor conductivity probe. The characteristic wall-peak is observed in the profiles of the interracial area concentration and the void fraction. The development of the interfacial area concentration along the axial direction of the flow is studied in view of the interfacial area transport and bubble interactions. The experimental data is compared with the drift flux model with C{sub 0} = 1.35.

Velocity measurements and identification of the flow pattern of vertical air-water flows with light-beam detectors

International Nuclear Information System (INIS)

Luebbesmeyer, D.; Leoni, B.

1980-07-01

A new detector for measuring fluid velocities in two-phase flows by means of Noise-Analysis (especially Transient-Cross-Correlation-technique) has been developed. The detector utilizes a light-beam which is modulated by changes in the transparency of the two-phase flow. The results of nine measurements for different flow-regimes of vertical air/water-flows are shown. A main topic of these investigations was to answer the question if it is possible to identify the flow-pattern by looking at the shape of different 'Noise-Analytical-functions' (like APSD, CPSD, CCF etc.). The results prove that light-beam sensors are good detectors for fluid-velocity measurements in different flow regimes and in a wide range of fluid velocities starting with values of about 0.08 m/s up to values of 40 m/s. With respect to flow-pattern identification only the time-signals and the shape of the cross-power-density-function (CPSD) seem to be useful. (Auth.)

Two dimensional numerical analysis of aerodynamic characteristics for rotating cylinder on concentrated air flow

Science.gov (United States)

Alias, M. S.; Rafie, A. S. Mohd; Marzuki, O. F.; Hamid, M. F. Abdul; Chia, C. C.

2017-12-01

Over the years, many studies have demonstrated the feasibility of the Magnus effect on spinning cylinder to improve lift production, which can be much higher than the traditional airfoil shape. With this characteristic, spinning cylinder might be used as a lifting device for short take-off distance aircraft or unmanned aerial vehicle (UAV). Nonetheless, there is still a gap in research to explain the use of spinning cylinder as a good lifting device. Computational method is used for this study to analyse the Magnus effect, in which two-dimensional finite element numerical analysis method is applied using ANSYS FLUENT software to examine the coefficients of lift and drag, and to investigate the flow field around the rotating cylinder surface body. Cylinder size of 30mm is chosen and several configurations in steady and concentrated air flows have been evaluated. All in all, it can be concluded that, with the right configuration of the concentrated air flow setup, the rotating cylinder can be used as a lifting device for very short take-off since it can produce very high coefficient of lift (2.5 times higher) compared with steady air flow configuration.

Reference method for total water in lint cotton by automated oven drying combined with volumetric Karl Fischer titration

Science.gov (United States)

In a preliminary study to measure total water in lint cotton we demonstrated that volumetric Karl Fischer Titration of moisture transported by a carrier gas from an attached small oven is more accurate than standard oven drying in air. The objective of the present study was to assess the measuremen...

Mitigating the Impacts of Uncontrolled Air Flow on Indoor Environmental Quality and Energy Demand in Non-Residential Buildings

Energy Technology Data Exchange (ETDEWEB)

Hugh I. Henderson; Jensen Zhang; James B. Cummings; Terry Brennan

2006-07-31

This multi-faceted study evaluated several aspects of uncontrolled air flows in commercial buildings in both Northern and Southern climates. Field data were collected from 25 small commercial buildings in New York State to understand baseline conditions for Northern buildings. Laboratory wall assembly testing was completed at Syracuse University to understand the impact of typical air leakage pathways on heat and moisture transport within wall assemblies for both Northern and Southern building applications. The experimental data from the laboratory tests were used to verify detailed heat and moisture (HAM) simulation models that could be used to evaluate a wider array of building applications and situations. Whole building testing at FSEC's Building Science Laboratory (BSL) systematically evaluated the energy and IAQ impacts of duct leakage with various attic and ceiling configurations. This systematic test carefully controlled all aspects of building performance to quantify the impact of duct leakage and unbalanced flow. The newest features of the EnergyPlus building simulation tool were used to model the combined impacts of duct leakage, ceiling leakage, unbalanced flows, and air conditioner performance. The experimental data provided the basis to validate the simulation model so it could be used to study the impact of duct leakage over a wide range of climates and applications. The overall objective of this project was to transfer work and knowledge that has been done on uncontrolled air flow in non-residential buildings in Florida to a national basis. This objective was implemented by means of four tasks: (1) Field testing and monitoring of uncontrolled air flow in a sample of New York buildings; (2) Detailed wall assembly laboratory measurements and modeling; (3) Whole building experiments and simulation of uncontrolled air flows; and (4) Develop and implement training on uncontrolled air flows for Practitioners in New York State.

Air sampling to assess potential generation of aerosolized viable bacteria during flow cytometric analysis of unfixed bacterial suspensions

Science.gov (United States)

Carson, Christine F; Inglis, Timothy JJ

2018-01-01

This study investigated aerosolized viable bacteria in a university research laboratory during operation of an acoustic-assisted flow cytometer for antimicrobial susceptibility testing by sampling room air before, during and after flow cytometer use. The aim was to assess the risk associated with use of an acoustic-assisted flow cytometer analyzing unfixed bacterial suspensions. Air sampling in a nearby clinical laboratory was conducted during the same period to provide context for the existing background of microorganisms that would be detected in the air. The three species of bacteria undergoing analysis by flow cytometer in the research laboratory were Klebsiella pneumoniae, Burkholderia thailandensis and Streptococcus pneumoniae. None of these was detected from multiple 1000 L air samples acquired in the research laboratory environment. The main cultured bacteria in both locations were skin commensal and environmental bacteria, presumed to have been disturbed or dispersed in laboratory air by personnel movements during routine laboratory activities. The concentrations of bacteria detected in research laboratory air samples were reduced after interventional cleaning measures were introduced and were lower than those in the diagnostic clinical microbiology laboratory. We conclude that our flow cytometric analyses of unfixed suspensions of K. pneumoniae, B. thailandensis and S. pneumoniae do not pose a risk to cytometer operators or other personnel in the laboratory but caution against extrapolation of our results to other bacteria and/or different flow cytometric experimental procedures. PMID:29608197

Volumetric PIV behind mangrove-type root models

Science.gov (United States)

Kazemi, Amirkhosro; van de Riet, Keith; Curet, Oscar M.

2017-11-01

Mangrove trees form dense networks of prop roots in coastal intertidal zones. The interaction of mangroves with the tidal flow is fundamental in estuaries and shoreline by providing water filtration, protection against erosion and habitat for aquatic animals. In this work, we modeled the mangrove prop roots with a cluster of rigid circular cylinders (patch) to investigate its hydrodynamics. We conducted 2-D PIV and V3V in the near- and far-wake in the recirculating water channel. Two models were considered: (1) a rigid patch, and (2) a flexible patch modeled as rigid cylinders with a flexible hinge. We found that Strouhal number changes with porosity while the patch diameter is constant. Based on the wake signature, we defined an effective diameter length scale. The volumetric flow measurements revealed a regular shedding forming von Kármán vortices for the rigid patch while the flexible patch produced a less uniform wake where vortices were substantially distorted. We compare the wake structure between that 2-D PIV and V3V. This analysis of the hydrodynamics of mangrove-root like models can also be extended to understand other complex flows including bio-inspired coastal infrastructures, damping-wave systems, and energy harvesting devices.

Evaluation of air flow rates through spargers for optimization of KNGR IRWST and SDVS design

International Nuclear Information System (INIS)

Jung, J. S.; Rha, I. S.; Jang, Y. S.; Koh, H. J.; Park, J. N.; Lee, S. W.

1999-01-01

In KNGR in the event of POSRVs actuation water, air and steam discharged from the RCS impose the dynamic loads on IRWST walls and submerged structures. The largest load is air clearing load. The main factors having an effect on the air clearing load are steam mass flux, the pressure and air volume in the POSRV discharge line. It is practically difficult to make the amount of air mass and its flow rates discharged through each sparger evenly distributed because several spargers are branched from one horizontal header. For an optimization of KNGR IRWST and SDVS design to minimize the T/H loads, the pressure in the discharge pipe and the air mass flow rates through spargers are evaluated using RELAP5/MOD3 code with changing the POSRV opening time and line and sparger arrangement. It is shown that as the opening time is the longer, the pressure in the discharge line is decreased and difference of the amount of air mass between spargers is reduced. And sparger headers with three spargers show better performance rather than those with six ones

Role of mixed boundaries on flow in open capillary channels with curved air-water interfaces.

Science.gov (United States)

Zheng, Wenjuan; Wang, Lian-Ping; Or, Dani; Lazouskaya, Volha; Jin, Yan

2012-09-04

Flow in unsaturated porous media or in engineered microfluidic systems is dominated by capillary and viscous forces. Consequently, flow regimes may differ markedly from conventional flows, reflecting strong interfacial influences on small bodies of flowing liquids. In this work, we visualized liquid transport patterns in open capillary channels with a range of opening sizes from 0.6 to 5.0 mm using laser scanning confocal microscopy combined with fluorescent latex particles (1.0 μm) as tracers at a mean velocity of ∼0.50 mm s(-1). The observed velocity profiles indicate limited mobility at the air-water interface. The application of the Stokes equation with mixed boundary conditions (i.e., no slip on the channel walls and partial slip or shear stress at the air-water interface) clearly illustrates the increasing importance of interfacial shear stress with decreasing channel size. Interfacial shear stress emerges from the velocity gradient from the adjoining no-slip walls to the center where flow is trapped in a region in which capillary forces dominate. In addition, the increased contribution of capillary forces (relative to viscous forces) to flow on the microscale leads to increased interfacial curvature, which, together with interfacial shear stress, affects the velocity distribution and flow pattern (e.g., reverse flow in the contact line region). We found that partial slip, rather than the commonly used stress-free condition, provided a more accurate description of the boundary condition at the confined air-water interface, reflecting the key role that surface/interface effects play in controlling flow behavior on the nanoscale and microscale.

Simulation analysis of air flow and turbulence statistics in a rib grit roughened duct.

Science.gov (United States)

Vogiatzis, I I; Denizopoulou, A C; Ntinas, G K; Fragos, V P

2014-01-01

The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations.

Structure of two-phase air-water flows. Study of average void fraction and flow patterns

International Nuclear Information System (INIS)

Roumy, R.

1969-01-01

This report deals with experimental work on a two phase air-water mixture in vertical tubes of different diameters. The average void fraction was measured in a 2 metre long test section by means of quick-closing valves. Using resistive probes and photographic techniques, we have determined the flow patterns and developed diagrams to indicate the boundaries between the various patterns: independent bubbles, agglomerated bubbles, slugs, semi-annular, annular. In the case of bubble flow and slug flow, it is shown that the relationship between the average void fraction and the superficial velocities of the phases is given by: V sg = f( ) * g(V sl ). The function g(V sl ) for the case of independent bubbles has been found to be: g(V sl ) = V sl + 20. For semi-annular and annular flow conditions; it appears that the average void fraction depends, to a first approximation only on the ratio V sg /V sl . (author) [fr

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.

A Coupled Thermo-Hydro-Mechanical Model of Jointed Hard Rock for Compressed Air Energy Storage

Directory of Open Access Journals (Sweden)

Xiaoying Zhuang

2014-01-01

Full Text Available Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared.

Toward the Experimental Characterization of an Unmanned Air System Flow Field

Science.gov (United States)

Velarde, John-Michael; Connors, Jacob; Glauser, Mark

2017-11-01

The velocity flow field around a small unmanned air system (sUAS) is investigated in a series of experiments at Syracuse University. Experiments are conducted in the 2'x2' sub-sonic wind tunnel at Syracuse University and the Indoor Flow Lab. The goal of these experiments is to gain a better understanding of the rich, turbulent flow field that a sUAS creates. Comparison to large, multi-rotor manned vehicles is done to gain a better understanding of the flow physics that could be occurring with the sUAS. Regions of investigation include the downwash, above the vehicle, and far downstream. Characterization of the flow is performed using hotwire anemometry. Investigation of several locations around the sUAS show that dominant frequencies exist within the flow field. Analysis of the flow field using power spectral density will be presented as well as looking at which parameters have an effect on these dominant frequencies.

Heat transfer to air-water two-phase flow in slug/churn region

International Nuclear Information System (INIS)

Wadekar, V.V.; Tuzla, K.; Chen, J.C.

1996-01-01

Measured heat transfer data for air-water two-phase flow in the slug/churn flow region are reported. The measurements were obtained from a 1.3 m tall, 15.7 mm diameter vertical tube test-section. It is observed that the data exhibit different heat transfer characteristics to those predicted by the standard correlations for the convective component of flow boiling heat transfer. Comparison with the predictions of a slug flow model for evaporation shows a significant overprediction of the data. The reason for the overprediction is attributed to the sensible heating requirement of the gas phase. The slug flow model is therefore suitably modified for non-evaporating two-phase flow. This specially adapted model is found to give reasonably good predictions of the measured data

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

Radiative effects on turbulent buoyancy-driven air flow in open square cavities

International Nuclear Information System (INIS)

Zamora, B.; Kaiser, A.S.

2016-01-01

The effects of the radiative effects and the air variable properties (density, viscosity and thermal conductivity) on the buoyancy-driven flows established in open square cavities are investigated. Two-dimensional, laminar, transitional and turbulent simulations are obtained, considering both uniform wall temperature and uniform heat flux heating conditions. In transitional and turbulent cases, the low- Reynolds k-ω turbulence model is employed. The average Nusselt number and the dimensionless mass-flow rate have been obtained for a wide range of the Rayleigh number varying from 10 3 to 10 16 . The results obtained taking into account the variable thermophysical properties of air are compared to those calculated assuming constant properties and the Boussinesq approximation. In addition, the influence of considering surface radiative effects on the differences reached for the Nusselt number and the mass flow rate obtained with several intensities of heating is studied; specifically, the effects of thermal radiation on the appearance of the burnout phenomenon is analyzed. The changes produced in the flow patterns into the cavity when the radiative heat transfer and the effects of variation of properties are relevant, are also shown. (authors)

Fluid flow and fuel-air mixing in a motored two-dimensional Wankel rotary engine

Science.gov (United States)

Shih, T. I.-P.; Nguyen, H. L.; Stegeman, J.

1986-01-01

The implicit-factored method of Beam and Warming was employed to obtain numerical solutions to the conservation equations of mass, species, momentum, and energy to study the unsteady, multidimensional flow and mixing of fuel and air inside the combustion chambers of a two-dimensional Wankel rotary engine under motored conditions. The effects of the following engine design and operating parameters on fluid flow and fuel-air mixing during the intake and compression cycles were studied: engine speed, angle of gaseous fuel injection during compression cycle, and speed of the fuel leaving fuel injector.

Performance analysis of air conditioning system and airflow simulation in an operating theater

Science.gov (United States)

Alhamid, Muhammad Idrus; Budihardjo, Rahmat

2018-02-01

The importance of maintaining performance of a hospital operating theater is to establish an adequate circulation of clean air within the room. The parameter of air distribution in a space should be based on Air Changes per Hour (ACH) to maintain a positive room pressure. The dispersion of airborne particles in the operating theater was governed by regulating the air distribution so that the operating theater meets clean room standards ie ISO 14664 and ASHRAE 170. Here, we introduced several input parameters in a simulation environment to observe the pressure distribution in the room. Input parameters were air temperature, air velocity and volumetric flow rate entering and leaving room for existing and designed condition. In the existing operating theatre, several observations were found. It was found that the outlet air velocity at the HEPA filter above the operating table was too high thus causing a turbulent airflow pattern. Moreover, the setting temperature at 19°C was found to be too low. The supply of air into the room was observed at lower than 20 ACH which is under the standard requirement. Our simulation using FloVent 8.2™ program showed that not only airflow turbulence could be reduced but also the amount of particle contamination could also be minimized.

High-frame rate imaging of two-phase flow in a thin rectangular channel using fast neutrons.

Science.gov (United States)

Zboray, R; Mor, I; Dangendorf, V; Stark, M; Tittelmeier, K; Cortesi, M; Adams, R

2014-08-01

We have demonstrated the feasibility of performing high-frame-rate, fast neutron radiography of air-water two-phase flows in a thin channel with rectangular cross section. The experiments have been carried out at the accelerator facility of the Physikalisch-Technische Bundesanstalt. A polychromatic, high-intensity fast neutron beam with average energy of 6 MeV was produced by 11.5 MeV deuterons hitting a thick Be target. Image sequences down to 10 ms exposure times were obtained using a fast-neutron imaging detector developed in the context of fast-neutron resonance imaging. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two phase flow parameters like the volumetric gas fraction, bubble size and mean bubble velocities have been measured. The first results are promising, improvements for future experiments are also discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Water flow and energy balance for a tropical dry semideciduous forest

Science.gov (United States)

Andrade, J. L.; Garruña-Hernandez, R.; Leon-Palomo, M.; Us-Santamaria, R.; Sima, J. L.

2013-05-01

Tropical forests cool down locally because increase water evaporation from the soil to the atmosphere, reduce albedo and help forming clouds that reflect solar radiation back to the atmosphere; this, aligned to the carbon catchment, increase forests value. We will present an estimation of the sap flow and energy balance for the tropical dry semideciduous forest at Kiuic, Yucatan, Mexico during a year. We use a meteorological tower equipped with a rain gauge, temperature and relative humidity, heat flow plates, thermocouples and volumetric soil water content. We recorded net radiation and soil heat flux and estimated sensible heat and latent heat. Besides, we estimated latent heat by measuring sap flow directly in tres using disispation constant heat probes during the rainy season. Results show the influence of the seasonality on net radiation, air temperatura and vapor pressure deficit, because during the dry season his variables were higher and with more duation than during the rainy and early dry season. Sap flow was different for trees belonging to the family Fabaceae compared to trees from other families.

Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

Directory of Open Access Journals (Sweden)

Alejandro López

2013-08-01

Full Text Available Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1, and at low wind speed (≈ 1.8 m s-1 the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening to the windward side and two side vents, the windward one being blocked by another greenhouse close to it, while the leeward one is free of obstacles. When no fans are used, air enters through the roof vent and exits through both side vents, thus flowing contrary to the thermal effect which causes hot air to rise and impairing the natural ventilation of the greenhouse. Using fans inside the greenhouse helps the air to circulate and mix, giving rise to a more homogeneous inside temperature and increasing the average value of normalized air velocity by 365 %. These fans also increase the average values of kinetic turbulence energy inside the greenhouse by 550 % compared to conditions of natural ventilation. As the fans are placed 4 m away from the side vents, their effect on the entrance of outside air is insufficient and they do not help to reduce the inside temperature on hot days with little wind. It is therefore recommended to place the fans closer to the side vents to allow an additional increase of the air exchange rate of greenhouses.

40 CFR 204.54 - Test procedures.

Science.gov (United States)

2010-07-01

... measure portable air compressor engine speed. (6) A gauge accurate to within ±5 percent shall be used to... used to measure the portable air compressor compressed air volumetric flow rate. (8) A barometer for...

High accuracy acoustic relative humidity measurement in duct flow with air

NARCIS (Netherlands)

Schaik, van W.; Grooten, M.H.M.; Wernaart, T.; Geld, van der C.W.M.

2010-01-01

An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and

Relationship between spontaneous expiratory flow-volume curve pattern and air-flow obstruction in elderly COPD patients.

Science.gov (United States)

Nozoe, Masafumi; Mase, Kyoshi; Murakami, Shigefumi; Okada, Makoto; Ogino, Tomoyuki; Matsushita, Kazuhiro; Takashima, Sachie; Yamamoto, Noriyasu; Fukuda, Yoshihiro; Domen, Kazuhisa

2013-10-01

Assessment of the degree of air-flow obstruction is important for determining the treatment strategy in COPD patients. However, in some elderly COPD patients, measuring FVC is impossible because of cognitive dysfunction or severe dyspnea. In such patients a simple test of airways obstruction requiring only a short run of tidal breathing would be useful. We studied whether the spontaneous expiratory flow-volume (SEFV) curve pattern reflects the degree of air-flow obstruction in elderly COPD patients. In 34 elderly subjects (mean ± SD age 80 ± 7 y) with stable COPD (percent-of-predicted FEV(1) 39.0 ± 18.5%), and 12 age-matched healthy subjects, we measured FVC and recorded flow-volume curves during quiet breathing. We studied the SEFV curve patterns (concavity/convexity), spirometry results, breathing patterns, and demographics. The SEFV curve concavity/convexity prediction accuracy was examined by calculating the receiver operating characteristic curves, cutoff values, area under the curve, sensitivity, and specificity. Fourteen subjects with COPD had a concave SEFV curve. All the healthy subjects had convex SEFV curves. The COPD subjects who had concave SEFV curves often had very severe airway obstruction. The percent-of-predicted FEV(1)% (32.4%) was the most powerful SEFV curve concavity predictor (area under the curve 0.92, 95% CI 0.83-1.00), and had the highest sensitivity (0.93) and specificity (0.88). Concavity of the SEFV curve obtained during tidal breathing may be a useful test for determining the presence of very severe obstruction in elderly patients unable to perform a satisfactory FVC maneuver.

Three-dimensional DEM–CFD analysis of air-flow-induced detachment of API particles from carrier particles in dry powder inhalers

Directory of Open Access Journals (Sweden)

Jiecheng Yang

2014-02-01

Full Text Available Air flow and particle–particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs. Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM–CFD (discrete element method–computational fluid dynamics is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force.

Three-dimensional DEM–CFD analysis of air-flow-induced detachment of API particles from carrier particles in dry powder inhalers

Science.gov (United States)

Yang, Jiecheng; Wu, Chuan-Yu; Adams, Michael

2014-01-01

Air flow and particle–particle/wall impacts are considered as two primary dispersion mechanisms for dry powder inhalers (DPIs). Hence, an understanding of these mechanisms is critical for the development of DPIs. In this study, a coupled DEM–CFD (discrete element method–computational fluid dynamics) is employed to investigate the influence of air flow on the dispersion performance of the carrier-based DPI formulations. A carrier-based agglomerate is initially formed and then dispersed in a uniformed air flow. It is found that air flow can drag API particles away from the carrier and those in the downstream air flow regions are prone to be dispersed. Furthermore, the influence of the air velocity and work of adhesion are also examined. It is shown that the dispersion number (i.e., the number of API particles detached from the carrier) increases with increasing air velocity, and decreases with increasing the work of adhesion, indicating that the DPI performance is controlled by the balance of the removal and adhesive forces. It is also shown that the cumulative Weibull distribution function can be used to describe the DPI performance, which is governed by the ratio of the fluid drag force to the pull-off force. PMID:26579364

Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

OpenAIRE

López, Alejandro; Valera, Diego Luis; Molina-Aiz, Francisco Domingo; Peña, Araceli

2013-01-01

Natural ventilation is the most important method of climate control in Mediterranean greenhouses. In this study, the microclimate and air flow inside a Mediterranean greenhouse were evaluated by means of sonic anemometry. Experiments were carried out in conditions of moderate wind (≈ 4.0 m s-1), and at low wind speed (≈ 1.8 m s-1) the natural ventilation of the greenhouse was supplemented by two horizontal air flow fans. The greenhouse is equipped with a single roof vent opening t...

Electro-osmotic flows inside triangular microchannels

International Nuclear Information System (INIS)

Vocale, P; Spiga, M; Geri, M; Morini, G L

2014-01-01

This work presents a numerical investigation of both pure electro-osmotic and combined electro-osmotic/pressure-driven flows inside triangular microchannels. A finite element analysis has been adopted to solve the governing equations for the electric potential and the velocity field, accounting for a finite thickness of the electric double layer. The influence of non-dimensional parameters such as the aspect ratio of the cross-section, the electrokinetic diameter and the ratio of the pressure force to the electric force on the flow behavior has been investigated. Numerical results point out that the velocity field is significantly influenced by the aspect ratio of the cross section and the electrokinetic diameter. More specifically, the aspect ratio plays an important role in determining the maximum volumetric flow rate, while the electrokinetic diameter is crucial to establishing the range of pressures that may be sustained by the electro-osmotic flow. Numerical results are also compared with two correlations available in the literature which enable to assess the volumetric flow rate and the pressure head for microchannels featuring a rectangular, a trapezoidal or an elliptical cross-section.

Control of multi-evaporator air-conditioning systems for flow distribution

International Nuclear Information System (INIS)

Lin, J.-L.; Yeh, T.-J.

2009-01-01

Modern air-conditioners incorporate variable-speed compressors and variable-opening expansion valves as the actuators for improving cooling performance and energy efficiency. These actuators have to be properly feedback-controlled; otherwise the systems may exhibit even poorer performance than the conventional machines which use fixed-speed compressors and mechanical expansion valves. In this paper, a control strategy with flow distribution capability is proposed for multi-evaporator air-conditioners to accommodate different thermal demands in different rooms. The structure in the control strategy is based on a low-order, linear model obtained from system identification. To determine appropriate control parameters, theorems regarding stability of the closed-loop system are given. Moreover, by performing steady-state analysis on the control system and utilizing characteristics of the identified system parameters, one can analytically explain the mechanics of flow distribution. Experiments indicate that the proposed strategy can successfully regulate the indoor temperatures regardless that the reference settings for respective rooms are different and the settings are switched in the middle of the control process.

7Q10 flows for SRS streams

International Nuclear Information System (INIS)

Chen, K.F.

1996-01-01

The Environmental Transport Group of the Environmental Technology Section was requested to predict the seven-day ten-year low flow (7Q10 flow) for the SRS streams based on historical stream flow records. Most of the historical flow records for the SRS streams include reactor coolant water discharged from the reactors and process water released from the process facilities. The most straight forward way to estimate the stream daily natural flow is to subtract the measured upstream reactor and/or facility daily effluents from the measured downstream daily flow. Unfortunately, this method does not always work, as indicated by the fact that sometimes the measured downstream volumetric flow rates are lower than the reactor effluent volumetric flow rates. For those cases that cannot be analyzed with the simple subtracting method, an alternative method was used to estimate the stream natural flows by statistically separating reactor coolant and process water flow data. The correlation between the calculated 7Q10 flows and the watershed areas for Four Mile Branch and Pen Branch agrees with that calculated by the USGS for Upper Three Runs and Lower Three Runs Creeks. The agreement between these two independent calculations lends confidence to the 7Q10 flow calculations presented in this report

Numerical study of the thermo-flow performances of novel finned tubes for air-cooled condensers in power plant

Science.gov (United States)

Guo, Yonghong; Du, Xiaoze; Yang, Lijun

2018-02-01

Air-cooled condenser is the main equipment of the direct dry cooling system in a power plant, which rejects heat of the exhaust steam with the finned tube bundles. Therefore, the thermo-flow performances of the finned tubes have an important effect on the optimal operation of the direct dry cooling system. In this paper, the flow and heat transfer characteristics of the single row finned tubes with the conventional flat fins and novel jagged fins are investigated by numerical method. The flow and temperature fields of cooling air for the finned tubes are obtained. Moreover, the variations of the flow resistance and average convection heat transfer coefficient under different frontal velocity of air and jag number are presented. Finally, the correlating equations of the friction factor and Nusselt number versus the Reynolds number are fitted. The results show that with increasing the frontal velocity of air, the heat transfer performances of the finned tubes are enhanced but the pressure drop will increase accordingly, resulting in the average convection heat transfer coefficient and friction factor increasing. Meanwhile, with increasing the number of fin jag, the heat transfer performance is intensified. The present studies provide a reference in optimal designing for the air-cooled condenser of direct air cooling system.

Flow characteristics of centrifugal gas-liquid separator. Investigation with air-water two-phase flow experiment

International Nuclear Information System (INIS)

Yoneda, Kimitoshi; Inada, Fumio

2004-01-01

Air-water two-phase flow experiment was conducted to examine the basic flow characteristics of a centrifugal gas-liquid separator. Vertical transparent test section, which is 4 m in height, was used to imitate the scale of a BWR separator. Flow rate conditions of gas and liquid were fixed at 0.1 m 3 /s and 0.033 m 3 /s, respectively. Radial distributions of two-phase flow characteristics, such as void fraction, gas velocity and bubble chord length, were measured by traversing dual optical void probes in the test section, horizontally. The flow in the standpipe reached to quasi-developed state within the height-to-diameter aspect ratio H/D=10, which in turn can mean the maximum value for an ideal height design of a standpipe. The liquid film in the barrel showed a maximum thickness at 0.5 to 1 m in height from the swirler exit, which was a common result for three different standpipe length conditions, qualitatively and quantitatively. The empirical database obtained in this study would contribute practically to the validation of numerical analyses for an actual separator in a plant, and would also be academically useful for further investigations of two-phase flow in large-diameter pipes. (author)

Performance of a combined three-hole conductivity probe for void fraction and velocity measurement in air-water flows

Energy Technology Data Exchange (ETDEWEB)

Borges, Joao Eduardo [IDMEC, Instituto Superior Tecnico, Technical University of Lisbon, Department of Mechanical Engineering, Lisbon (Portugal); Pereira, Nuno H.C. [EST Setubal, Polytechnic Institute of Setubal, Department of Mechanical Engineering, Setubal (Portugal); Matos, Jorge [Instituto Superior Tecnico, Technical University of Lisbon, Department of Civil Engineering and Architecture, Lisbon (Portugal); Frizell, Kathleen H. [U.S. Bureau of Reclamation, Denver, CO (United States)

2010-01-15

The development of a three-hole pressure probe with back-flushing combined with a conductivity probe, used for measuring simultaneously the magnitude and direction of the velocity vector in complex air-water flows, is described in this paper. The air-water flows envisaged in the current work are typically those occurring around the rotors of impulse hydraulic turbines (like the Pelton and Cross-Flow turbines), where the flow direction is not known prior to the data acquisition. The calibration of both the conductivity and three-hole pressure components of the combined probe in a rig built for the purpose, where the probe was placed in a position similar to that adopted for the flow measurements, will be reported. After concluding the calibration procedure, the probe was utilized in the outside region of a Cross-Flow turbine rotor. The experimental results obtained in the present study illustrate the satisfactory performance of the combined probe, and are encouraging toward its use for characterizing the velocity field of other complex air-water flows. (orig.)

Performance of a combined three-hole conductivity probe for void fraction and velocity measurement in air-water flows

Science.gov (United States)

Borges, João Eduardo; Pereira, Nuno H. C.; Matos, Jorge; Frizell, Kathleen H.

2010-01-01

The development of a three-hole pressure probe with back-flushing combined with a conductivity probe, used for measuring simultaneously the magnitude and direction of the velocity vector in complex air-water flows, is described in this paper. The air-water flows envisaged in the current work are typically those occurring around the rotors of impulse hydraulic turbines (like the Pelton and Cross-Flow turbines), where the flow direction is not known prior to the data acquisition. The calibration of both the conductivity and three-hole pressure components of the combined probe in a rig built for the purpose, where the probe was placed in a position similar to that adopted for the flow measurements, will be reported. After concluding the calibration procedure, the probe was utilized in the outside region of a Cross-Flow turbine rotor. The experimental results obtained in the present study illustrate the satisfactory performance of the combined probe, and are encouraging toward its use for characterizing the velocity field of other complex air-water flows.

The effect of compressed air massage on skin blood flow and temperature.

Science.gov (United States)

Mars, Maurice; Maharaj, Sunil S; Tufts, Mark

2005-01-01

Compressed air massage is a new treatment modality that uses air under pressure to massage skin and muscle. It is claimed to improve skin blood flow but this has not been verified. Several pilot studies were undertaken to determine the effects of compressed air massage on skin blood flow and temperature. Skin blood flow (SBF), measured using laser Doppler fluxmetry and skin temperature was recorded under several different situations: (i) treatment, at 1 Bar pressure using a single-hole (5-mm) applicator head, for 1 min at each of several sites on the right and left lower legs, with SBF measured on the dorsum of the left foot; (ii) at the same treatment pressure, SBF was measured over the left tibialis anterior when treatment was performed at different distances from the probe; (iii) SBF and skin temperature of the lower leg were measured with treatment at 0 or 1 Bar for 45 min, using two different applicator heads; (iv) SBF was measured on the dorsum of the foot of 10 subjects with treatment for 1 min at 0, 0.5, 1, 1.5 and 2 Bar using three different applicator heads. (i) SBF of the left foot was not altered by treatment of the right leg or chest, but was significantly increased during treatment of the left sole and first web, p Compressed air massage causes an immediate increase in SBF, and an immediate fall in SBF when treatment is stopped. The effect appears to be locally and not centrally mediated and is related to the pressure used. Treatment cools the skin for at least 15 min after a 45-min treatment.

Soft bilateral filtering volumetric shadows using cube shadow maps.

Directory of Open Access Journals (Sweden)

Hatam H Ali

Full Text Available Volumetric shadows often increase the realism of rendered scenes in computer graphics. Typical volumetric shadows techniques do not provide a smooth transition effect in real-time with conservation on crispness of boundaries. This research presents a new technique for generating high quality volumetric shadows by sampling and interpolation. Contrary to conventional ray marching method, which requires extensive time, this proposed technique adopts downsampling in calculating ray marching. Furthermore, light scattering is computed in High Dynamic Range buffer to generate tone mapping. The bilateral interpolation is used along a view rays to smooth transition of volumetric shadows with respect to preserving-edges. In addition, this technique applied a cube shadow map to create multiple shadows. The contribution of this technique isreducing the number of sample points in evaluating light scattering and then introducing bilateral interpolation to improve volumetric shadows. This contribution is done by removing the inherent deficiencies significantly in shadow maps. This technique allows obtaining soft marvelous volumetric shadows, having a good performance and high quality, which show its potential for interactive applications.

Effect of Number of Blades on Performance of Ceiling Fans

Directory of Open Access Journals (Sweden)

Adeeb Ehsan

2015-01-01

Full Text Available In this paper, the effect of number of blades on ceiling fan performance is discussed. This approach helps to satisfy tradeoff between high air flow (performance and power consumption (energy efficiency. Specifically, variation from two to six blades is considered with nonlinear forward sweep profile. Reynolds Averaged Navier-Stokes (RANS technique is used to model the flow field induced by the ceiling fan inside a generic room. The performance is gauged through response parameters namely volumetric flow rate, mass flow rate, torque and energy efficiency. The results indicate that mass and volumetric flow rates are maximized for six blade configuration and energy efficiency is maximized for two blade configuration. The study indicates the importance of tradeoff between high air flow through ceiling fan and associated energy efficiency.

Helium-air exchange flow through an opening with a partition

International Nuclear Information System (INIS)

Kang, Tae-il; Okamoto, Koji; Madarame, Haruki; Fumizawa, Motoo.

1993-01-01

The helium-air exchange flow through a small vertical opening with a partition was experimentally investigated. The vertical partition was aligned with the center line of the small opening to evaluate the effects of the multiple openings. The dimensionless exchange flow rates, i.e., Froude numbers, were experimentally obtained with several opening ratios (H 1 /D f ), i.e., the ratio of the height to the effective diameter of the opening. In the case of low opening ratios (H 1 /D f 1 /D f ≥ 0.75), the measured Froude numbers for the multiple openings were larger than those for the single opening, because the upward and downward flows were separated by the vertical partition. Based on the balance between the pressure losses in the openings and the driving force due to density difference, the exchange flow rate was calculated, and found to agree qualitatively with the measured Froude numbers. The effect of the upward and downward flow interaction at the exit of the opening was found to play an important role in the prediction of the Froude number. (author)

Volumetric formulation for a class of kinetic models with energy conservation.

Science.gov (United States)

Sbragaglia, M; Sugiyama, K

2010-10-01

We analyze a volumetric formulation of lattice Boltzmann for compressible thermal fluid flows. The velocity set is chosen with the desired accuracy, based on the Gauss-Hermite quadrature procedure, and tested against controlled problems in bounded and unbounded fluids. The method allows the simulation of thermohydrodyamical problems without the need to preserve the exact space-filling nature of the velocity set, but still ensuring the exact conservation laws for density, momentum, and energy. Issues related to boundary condition problems and improvements based on grid refinement are also investigated.

Behavior of cross flow heat exchangers during the cooling and dehumidification of air

Energy Technology Data Exchange (ETDEWEB)

Ober, C [Karlsruhe Univ. (TH) (Germany, F.R.). Inst. fuer Mess- und Regelungstechnik mit Maschinenlaboratorium

1980-09-01

The task of cross flow heat exchangers in room air engineering consists on the one hand in heating up the air and, on the other hand, in the simultaneous cooling and dehumidification. The facilities used for this purpose generally are multi-row finned pipe heat exchangers which when used for cooling contain cold water or brine as the working fluid. The use of directly evaporating freezing mixtures may not be included in this consideration. The model establishment for the dynamic and the static behavior of multi-row cross flow heat exchangers during cooling and dehumidification of air has been derived in this contribution. The representation is performed for the dynamic case in the complex, display range of the Laplace transformation. A comparison with experimental results can be done very simply by means of measurements of the frequency-responce curves in the form of Bode diagrams. The description of the static behaviour may be applied as a basis for humidity controls with more favourable energy utilization.

Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first.

Science.gov (United States)

Bartol, Ian K; Krueger, Paul S; Jastrebsky, Rachel A; Williams, Sheila; Thompson, Joseph T

2016-02-01

Squids use a pulsed jet and fin movements to swim both arms-first (forward) and tail-first (backward). Given the complexity of the squid multi-propulsor system, 3D velocimetry techniques are required for the comprehensive study of wake dynamics. Defocusing digital particle tracking velocimetry, a volumetric velocimetry technique, and high-speed videography were used to study arms-first and tail-first swimming of brief squid Lolliguncula brevis over a broad range of speeds [0-10 dorsal mantle lengths (DML) s(-1)] in a swim tunnel. Although there was considerable complexity in the wakes of these multi-propulsor swimmers, 3D vortex rings and their derivatives were prominent reoccurring features during both tail-first and arms-first swimming, with the greatest jet and fin flow complexity occurring at intermediate speeds (1.5-3.0 DML s(-1)). The jet generally produced the majority of thrust during rectilinear swimming, increasing in relative importance with speed, and the fins provided no thrust at speeds >4.5 DML s(-1). For both swimming orientations, the fins sometimes acted as stabilizers, producing negative thrust (drag), and consistently provided lift at low/intermediate speeds (swimming orientation, and η for swimming sequences with clear isolated jet vortex rings was significantly greater (η=78.6±7.6%, mean±s.d.) than that for swimming sequences with clear elongated regions of concentrated jet vorticity (η=67.9±19.2%). This study reveals the complexity of 3D vortex wake flows produced by nekton with hydrodynamically distinct propulsors. © 2016. Published by The Company of Biologists Ltd.

Internal air flow analysis of a bladeless micro aerial vehicle hemisphere body using computational fluid dynamic

Science.gov (United States)

Othman, M. N. K.; Zuradzman, M. Razlan; Hazry, D.; Khairunizam, Wan; Shahriman, A. B.; Yaacob, S.; Ahmed, S. Faiz; Hussain, Abadalsalam T.

2014-12-01

This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors and the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity.

Internal air flow analysis of a bladeless micro aerial vehicle hemisphere body using computational fluid dynamic

International Nuclear Information System (INIS)

Othman, M. N. K.; Zuradzman, M. Razlan; Hazry, D.; Khairunizam, Wan; Shahriman, A. B.; Yaacob, S.; Ahmed, S. Faiz

2014-01-01

This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors and the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity

Internal air flow analysis of a bladeless micro aerial vehicle hemisphere body using computational fluid dynamic

Energy Technology Data Exchange (ETDEWEB)

Othman, M. N. K., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Zuradzman, M. Razlan, E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Hazry, D., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Khairunizam, Wan, E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Shahriman, A. B., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Yaacob, S., E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my; Ahmed, S. Faiz, E-mail: najibkhir86@gmail.com, E-mail: zuradzman@unimap.edu.my, E-mail: hazry@unimap.edu.my, E-mail: khairunizam@unimap.edu.my, E-mail: shahriman@unimap.edu.my, E-mail: s.yaacob@unimap.edu.my, E-mail: syedfaiz@unimap.edu.my, E-mail: abadal@unimap.edu.my [Centre of Excellence for Unmanned Aerial Systems, Universiti Malaysia Perlis, 01000 Kangar, Perlis (Malaysia); and others

2014-12-04

This paper explain the analysis of internal air flow velocity of a bladeless vertical takeoff and landing (VTOL) Micro Aerial Vehicle (MAV) hemisphere body. In mechanical design, before produce a prototype model, several analyses should be done to ensure the product's effectiveness and efficiency. There are two types of analysis method can be done in mechanical design; mathematical modeling and computational fluid dynamic. In this analysis, I used computational fluid dynamic (CFD) by using SolidWorks Flow Simulation software. The idea came through to overcome the problem of ordinary quadrotor UAV which has larger size due to using four rotors and the propellers are exposed to environment. The bladeless MAV body is designed to protect all electronic parts, which means it can be used in rainy condition. It also has been made to increase the thrust produced by the ducted propeller compare to exposed propeller. From the analysis result, the air flow velocity at the ducted area increased to twice the inlet air. This means that the duct contribute to the increasing of air velocity.

Experimental study on two-phase flow natural circulation in a core catcher cooling channel for EU-APR1400 using air-water system

Energy Technology Data Exchange (ETDEWEB)

Song, Ki Won [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Nguyen, Thanh Hung [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906 (United States); Ha, Kwang Soon; Kim, Hwan Yeol; Song, Jinho [Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Park, Hyun Sun [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Revankar, Shripad T., E-mail: shripad@postech.ac.kr [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906 (United States); Kim, Moo Hwan [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Institute of Nuclear Safety, Daejeon 305-338 (Korea, Republic of)

2017-05-15

Highlights: • Two-phase flow regimes and transition behavior were observed in the coolant channel. • Test were conducted for natural circulation with air-water. • Data were obtained on flow regime, void fraction, flow rates and re-wetting time. • The data were related to a cooling capability of core catcher system. - Abstract: Ex-vessel core catcher cooling system driven by natural circulation is designed using a full scaled air-water system. A transparent half symmetric section of a core catcher coolant channel of a pressurized water reactor was designed with instrumentations for local void fraction measurement and flow visualization. Two designs of air-water top separator water tanks are studied including one with modified ‘super-step’ design which prevents gas entrainment into down-comer. In the experiment air flow rates are set corresponding to steam generation rate for given corium decay power. Measurements of natural circulation flow rate, spatial local void fraction distribution and re-wetting time near the top wall are carried out for various air flow rates which simulate boiling-induced vapor generation. Since heat transfer and critical heat flux are strongly dependent on the water mass flow rate and development of two-phase flow on the heated wall, knowledge of two-phase flow characteristics in the coolant channel is essential. Results on flow visualization showing two phase flow structure specifically near the high void accumulation regions, local void profiles, rewetting time, and natural circulation flow rate are presented for various air flow rates that simulate corium power levels. The data are useful in assessing the cooling capability of and safety of the core catcher system.

Numerical analysis of thermal environment control in high density data center

Energy Technology Data Exchange (ETDEWEB)

Kwon, Oh Kyung; Kim, Hyeon Joong; Cha, Dong An [Korea Institute of Industrial Technology, Cheonan (Korea, Republic of)

2012-08-15

Increasing heat generation in CPUs can hamper effective recirculation and by pass because of the large temperature difference between the exhaust and the intake air through a server room. This increases the overall temperature inside a data center and decreases the efficiency of the data center's cooling system. The purpose of the data center's cooling system is to separate the intake and exhaust air by controlling the computer room air conditioner(CRAC). In this study, ICEPAK is used to conduct a numerical analysis of a data center's cooling system. The temperature distribution and the entire room are analyzed for different volumetric flow rates. The optimized volumetric flow rate is found for each CPU power. The heat removal and temperature distribution for CPU powers of 100, 120, and 140W are found to be the best for a volumetric flow rate of 0.15m'3'/s. The numerical analysis is verified through RTI indicators, and the results appear to be the most reliable when the RTI value is 81.

Regulation of pulpal blood flow

International Nuclear Information System (INIS)

Kim, S.

1985-01-01

The regulation of blood flow of the dental pulp was investigated in dogs and rats anesthetized with sodium pentobarbital. Pulpal blood flow was altered by variations of local and systemic hemodynamics. Macrocirculatory blood flow (ml/min/100 g) in the dental pulp was measured with both the 133 Xe washout and the 15-microns radioisotope-labeled microsphere injection methods on the canine teeth of dogs, to provide a comparison of the two methods in the same tooth. Microcirculatory studies were conducted in the rat incisor tooth with microscopic determination of the vascular pattern, RBC velocity, and intravascular volumetric flow distribution. Pulpal resistance vessels have alpha- and beta-adrenergic receptors. Activation of alpha-receptors by intra-arterial injection of norepinephrine (NE) caused both a reduction in macrocirculatory Qp in dogs and decreases in arteriolar and venular diameters and intravascular volumetric flow (Qi) in rats. These responses were blocked by the alpha-antagonist PBZ. Activation of beta-receptors by intra-arterial injection of isoproterenal (ISO) caused a paradoxical reduction of Qp in dogs. In rats, ISO caused a transient increase in arteriolar Qi followed by a flow reduction; arteriolar dilation was accompanied by venular constriction. These macrocirculatory and microcirculatory responses to ISO were blocked by the alpha-antagonist propranolol

Methods of Visually Determining the Air Flow Around Airplanes

Science.gov (United States)

Gough, Melvin N; Johnson, Ernest

1932-01-01

This report describes methods used by the National Advisory Committee for Aeronautics to study visually the air flow around airplanes. The use of streamers, oil and exhaust gas streaks, lampblack and kerosene, powdered materials, and kerosene smoke is briefly described. The generation and distribution of smoke from candles and from titanium tetrachloride are described in greater detail because they appear most advantageous for general application. Examples are included showing results of the various methods.

Volumetric dispenser for small particles from plural sources

International Nuclear Information System (INIS)

Bradley, R.A.; Miller, W.H.; Sease, J.D.

1975-01-01

Apparatus is described for rapidly and accurately dispensing measured volumes of small particles from a supply hopper. The apparatus includes an adjustable, vertically oriented measuring tube and orifice member defining the volume to be dispensed, a ball plug valve for selectively closing the bottom end of the orifice member, and a compression valve for selectively closing the top end of the measuring tube. A supply hopper is disposed above and in gravity flow communication with the measuring tube. Properly sequenced opening and closing of the two valves provides accurate volumetric discharge through the ball plug valve. A dispensing system is described wherein several appropriately sized measuring tubes, orifice members, and associated valves are arranged to operate contemporaneously to facilitate blending of different particles

Dynamic model of counter flow air to air heat exchanger for comfort ventilation with condensation and frost formation

DEFF Research Database (Denmark)

Nielsen, Toke Rammer; Rose, Jørgen; Kragh, Jesper

2009-01-01

must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements......In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer...

Flowing Air-Water Cooled Slab Nd: Glass Laser

Science.gov (United States)

Lu, Baida; Cai, Bangwei; Liao, Y.; Xu, Shifa; Xin, Z.

1989-03-01

A zig-zag optical path slab geometry Nd: glass laser cooled through flowing air-water is developed by us. Theoretical studies on temperature distribution of slab and rod configurations in the unsteady state clarify the advantages of the slab geometry laser. The slab design and processing are also reported. In our experiments main laser output characteristics, e. g. laser efficiency, polarization, far-field divergence angle as well as resonator misalignment are investigated. The slab phosphate glass laser in combination with a crossed Porro-prism resonator demonstrates a good laser performance.

Countercurrent air/water and steam/water flow above a perforated plate. Report for October 1978-October 1979

International Nuclear Information System (INIS)

Hsieh, C.; Bankoff, S.G.; Tankin, R.S.; Yuen, M.C.

1980-11-01

The perforated plate weeping phenomena have been studied in both air/water and steam/cold water systems. The air/water experiment is designed to investigate the effect of geometric factors of the perforated plate on the rate of weeping. A new dimensionless flow rate in the form of H star is suggested. The data obtained are successfully correlated by this H star scaling in the conventional flooding equation. The steam/cold water experiment is concentrated on locating the boundary between weeping and no weeping. The effects of water subcooling, water inlet flow rate, and position of water spray are investigated. Depending on the combination of these factors, several types of weeping were observed. The data obtained at high water spray position can be related to the air/water flooding correlation by replacing the stream flow rate to an effective stream flow rate, which is determined by the mixing efficiency above the plate

Mechanical Design of a Performance Test Rig for the Turbine Air-Flow Task (TAFT)

Science.gov (United States)

Forbes, John C.; Xenofos, George D.; Farrow, John L.; Tyler, Tom; Williams, Robert; Sargent, Scott; Moharos, Jozsef

2004-01-01

To support development of the Boeing-Rocketdyne RS84 rocket engine, a full-flow, reaction turbine geometry was integrated into the NASA-MSFC turbine air-flow test facility. A mechanical design was generated which minimized the amount of new hardware while incorporating all test and instrumentation requirements. This paper provides details of the mechanical design for this Turbine Air-Flow Task (TAFT) test rig. The mechanical design process utilized for this task included the following basic stages: Conceptual Design. Preliminary Design. Detailed Design. Baseline of Design (including Configuration Control and Drawing Revision). Fabrication. Assembly. During the design process, many lessons were learned that should benefit future test rig design projects. Of primary importance are well-defined requirements early in the design process, a thorough detailed design package, and effective communication with both the customer and the fabrication contractors.

Aspects of volumetric efficiency measurement for reciprocating engines

Directory of Open Access Journals (Sweden)

Pešić Radivoje B.

2013-01-01

Full Text Available The volumetric efficiency significantly influences engine output. Both design and dimensions of an intake and exhaust system have large impact on volumetric efficiency. Experimental equipment for measuring of airflow through the engine, which is placed in the intake system, may affect the results of measurements and distort the real picture of the impact of individual structural factors. This paper deals with the problems of experimental determination of intake airflow using orifice plates and the influence of orifice plate diameter on the results of the measurements. The problems of airflow measurements through a multi-process Otto/Diesel engine were analyzed. An original method for determining volumetric efficiency was developed based on in-cylinder pressure measurement during motored operation, and appropriate calibration of the experimental procedure was performed. Good correlation between the results of application of the original method for determination of volumetric efficiency and the results of theoretical model used in research of influence of the intake pipe length on volumetric efficiency was determined. [Acknowledgments. The paper is the result of the research within the project TR 35041 financed by the Ministry of Science and Technological Development of the Republic of Serbia

Bubble-size distributions produced by wall injection of air into flowing freshwater, saltwater and surfactant solutions

Science.gov (United States)

Winkel, Eric S.; Ceccio, Steven L.; Dowling, David R.; Perlin, Marc

2004-12-01

As air is injected into a flowing liquid, the resultant bubble characteristics depend on the properties of the injector, near-wall flow, and flowing liquid. Previous research has shown that near-wall bubbles can significantly reduce skin-friction drag. Air was injected into the turbulent boundary layer on a test section wall of a water tunnel containing various concentrations of salt and surfactant (Triton-X-100, Union Carbide). Photographic records show that the mean bubble diameter decreased monotonically with increasing salt and surfactant concentrations. Here, 33 ppt saltwater bubbles had one quarter, and 20 ppm Triton-X-100 bubbles had one half of the mean diameter of freshwater bubbles.

Influence of air flow rate on structural and electrical properties of undoped indium oxide thin films

International Nuclear Information System (INIS)

Mirzapour, S.; Rozati, S.M.; Takwale, M.G.; Marathe, B.R.; Bhide, V.G.

1993-01-01

Using the spray pyrolysis technique thin films of indium oxide were prepared on Corning glass (7059) at a substrate temperature of 425 C at different flow rates. The electrical and structural properties of these films were studied. The Hall measurements at room temperature showed that the films prepared in an air flow rate of 7 litre min -1 have the highest mobility of 47 cm 2 V -1 s -1 and a minimum resistivity of 1.125 x 10 -3 Ω cm. The X-ray diffraction patterns showed that the films have a preferred orientation of [400] which peaks at the air flow rate of 7 litre min -1 . (orig.)

Velocity and phase distribution measurements in vertical air-water annular flows

International Nuclear Information System (INIS)

Vassallo, P.

1997-07-01

Annular flow topology for three air-water conditions in a vertical duct is investigated through the use of a traversing double-sensor hot-film anemometry probe and differential pressure measurements. Near wall measurements of mean and fluctuating velocities, as well as local void fraction, are taken in the liquid film, with the highest turbulent fluctuations occurring for the flow condition with the largest pressure drop. A modified law-of-the-wall formulation for wall shear is presented which, using near wall values of mean velocity and kinetic energy, agrees reasonably well with the average stress obtained from direct pressure drop measurements. The linear profile using wall coordinates in the logarithmic layer is preserved in annular flow; however, the slope and intercept of the profile differ from the single-phase values for the annular flow condition which has a thicker, more turbulent, liquid film

Air flow measurement techniques applied to noise reduction of a centrifugal blower

Science.gov (United States)

Laage, John W.; Armstrong, Ashli J.; Eilers, Daniel J.; Olsen, Michael G.; Mann, J. Adin

2005-09-01

The air flow in a centrifugal blower was studied using a variety of flow and sound measurement techniques. The flow measurement techniques employed included Particle Image Velocimetry (PIV), pitot tubes, and a five hole spherical probe. PIV was used to measure instantaneous and ensemble-averaged velocity fields over large area of the outlet duct as a function of fan position, allowing for the visualization of the flow as it leave the fan blades and progressed downstream. The results from the flow measurements were reviewed along side the results of the sound measurements with the goal of identifying sources of noise and inefficiencies in flow performance. The radiated sound power was divided into broadband and tone noise and measures of the flow. The changes in the tone and broadband sound were compared to changes in flow quantities such as the turbulent kinetic energy and Reynolds stress. Results for each method will be presented to demonstrate the strengths of each flow measurement technique as well as their limitations. Finally, the role that each played in identifying noise sources is described.

Mid-section of a can-annular gas turbine engine with an improved rotation of air flow from the compressor to the turbine

Science.gov (United States)

Little, David A.; Schilp, Reinhard; Ross, Christopher W.

2016-03-22

A midframe portion (313) of a gas turbine engine (310) is presented and includes a compressor section with a last stage blade to orient an air flow (311) at a first angle (372). The midframe portion (313) further includes a turbine section with a first stage blade to receive the air flow (311) oriented at a second angle (374). The midframe portion (313) further includes a manifold (314) to directly couple the air flow (311) from the compressor section to a combustor head (318) upstream of the turbine section. The combustor head (318) introduces an offset angle in the air flow (311) from the first angle (372) to the second angle (374) to discharge the air flow (311) from the combustor head (318) at the second angle (374). While introducing the offset angle, the combustor head (318) at least maintains or augments the first angle (372).

Single-Shot, Volumetrically Illuminated, Three-Dimensional, Tomographic Laser-Induced-Fluorescence Imaging in a Gaseous Free Jet

Science.gov (United States)

2016-04-28

Single-shot, volumetrically illuminated, three- dimensional, tomographic laser-induced- fluorescence imaging in a gaseous free jet Benjamin R. Halls...acquisition; (110.6955) Tomographic imaging ; (110.6960) Tomography; (280.2490) Flow diagnostics; (300.2530) Fluorescence , laser-induced...84 (1983). 2. I. van Cruyningen, A. Lozano, and R. K. Hanson, “Quantitative imaging of concentration by planar laser-induced fluorescence ,” Exp

Experimental study for flow regime of downward air-water two-phase flow in a vertical narrow rectangular channel

Energy Technology Data Exchange (ETDEWEB)

Kim, T. H.; Yun, B. J.; Jeong, J. H. [Pusan National University, Geunjeong-gu, Busan (Korea, Republic of)

2015-05-15

Studies were mostly about flow in upward flow in medium size circular tube. Although there are great differences between upward and downward flow, studies on vertical upward flow are much more active than those on vertical downward flow in a channel. In addition, due to the increase of surface forces and friction pressure drop, the pattern of gas-liquid two-phase flow bounded to the gap of inside the rectangular channel is different from that in a tube. The downward flow in a rectangular channel is universally applicable to cool the plate type nuclear fuel in research reactor. The sub-channel of the plate type nuclear fuel is designed with a few millimeters. Downward air-water two-phase flow in vertical rectangular channel was experimentally observed. The depth, width, and length of the rectangular channel is 2.35 mm, 66.7 mm, and 780 mm, respectively. The test section consists of transparent acrylic plates confined within a stainless steel frame. The flow patterns of the downward flow in high liquid velocity appeared to be similar to those observed in previous studies with upward flow. In downward flow, the transition lines for bubbly-slug and slug-churn flow shift to left in the flow regime map constructed with abscissa of the superficial gas velocity and ordinate of the superficial liquid velocity. The flow patterns observed with downward flow at low liquid velocity are different from those with upward flow.

Online optimal control of variable refrigerant flow and variable air volume combined air conditioning system for energy saving

International Nuclear Information System (INIS)

Zhu, Yonghua; Jin, Xinqiao; Du, Zhimin; Fang, Xing

2015-01-01

The variable refrigerant flow (VRF) and variable air volume (VAV) combined air conditioning system can solve the problem of the VRF system in outdoor air ventilation while taking advantage of its high part load energy efficiency. Energy performance of the combined air conditioning system can also be optimized by joint control of both the VRF and the VAV parts. A model-based online optimal control strategy for the combined air conditioning system is presented. Simplified adaptive models of major components of the combined air conditioning system are firstly developed for predicting system performances. And a cost function in terms of energy consumption and thermal comfort is constructed. Genetic algorithm is used to search for the optimal control sets. The optimal control strategy is tested and evaluated through two case studies based on the simulation platform. Results show that the optimal strategy can effectively reduce energy consumption of the combined air conditioning system while maintaining acceptable thermal comfort. - Highlights: • A VRF and VAV combined system is proposed. • A model-based online optimal control strategy is proposed for the combined system. • The strategy can reduce energy consumption without sacrificing thermal comfort. • Novel simplified adaptive models are firstly developed for the VRF system

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

International Nuclear Information System (INIS)

Sun, X.; Kim, S.; Cheng, L.; Ishii, M.; Beus, S.G.

2001-01-01

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in a cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 20-cm in width and 1-cm in gap. The miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

International Nuclear Information System (INIS)

Xiaodong Sun; Seungjin Kim; Ling Cheng; Mamoru Ishii; Beus, Stephen G.

2002-01-01

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 200-mm in width and 10-mm in gap. Miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions. (authors)

Methods for preparation of mixtures of gases in air at the parts-per-billion to parts-per-million concentration range for calibration of monitors

International Nuclear Information System (INIS)

Karpas, Z.; Melloul, S.; Pollevoy, Y.; Matmor, A.

1992-05-01

Static and dynamic methods for generating mixture of gases and vapors in air at the parts-per-billion (ppb) to parts-per-million (ppm) concentration range were surveyed. The dynamic methods include: a dynamic flow and mixing system; injection of samples into large volumes of air; exponential dilution; permeation and diffusion tubes; and generation of the target gas by chemical reaction or electrolysis. The static methods include preparation of mixtures by weighing the components, by volumetric mixing and by partial pressure method. The principles governing the utilization of these methods for the appropriate applications were discussed, and examples in which they were used to calibrate an ion mobility spectrometer (IMS) were given. (authors)

Transport coefficients in high-temperature ionized air flows with electronic excitation

Science.gov (United States)

Istomin, V. A.; Oblapenko, G. P.

2018-01-01

Transport coefficients are studied in high-temperature ionized air mixtures using the modified Chapman-Enskog method. The 11-component mixture N2/N2+/N /N+/O2/O2+/O /O+/N O /N O+/e- , taking into account the rotational and vibrational degrees of freedom of molecules and electronic degrees of freedom of both atomic and molecular species, is considered. Using the PAINeT software package, developed by the authors of the paper, in wide temperature range calculations of the thermal conductivity, thermal diffusion, diffusion, and shear viscosity coefficients for an equilibrium ionized air mixture and non-equilibrium flow conditions for mixture compositions, characteristic of those in shock tube experiments and re-entry conditions, are performed. For the equilibrium air case, the computed transport coefficients are compared to those obtained using simplified kinetic theory algorithms. It is shown that neglecting electronic excitation leads to a significant underestimation of the thermal conductivity coefficient at temperatures higher than 25 000 K. For non-equilibrium test cases, it is shown that the thermal diffusion coefficients of neutral species and the self-diffusion coefficients of all species are strongly affected by the mixture composition, while the thermal conductivity coefficient is most strongly influenced by the degree of ionization of the flow. Neglecting electronic excitation causes noticeable underestimation of the thermal conductivity coefficient at temperatures higher than 20 000 K.

Effect of real-time boundary wind conditions on the air flow and pollutant dispersion in an urban street canyon—Large eddy simulations

Science.gov (United States)

Zhang, Yun-Wei; Gu, Zhao-Lin; Cheng, Yan; Lee, Shun-Cheng

2011-07-01

Air flow and pollutant dispersion characteristics in an urban street canyon are studied under the real-time boundary conditions. A new scheme for realizing real-time boundary conditions in simulations is proposed, to keep the upper boundary wind conditions consistent with the measured time series of wind data. The air flow structure and its evolution under real-time boundary wind conditions are simulated by using this new scheme. The induced effect of time series of ambient wind conditions on the flow structures inside and above the street canyon is investigated. The flow shows an obvious intermittent feature in the street canyon and the flapping of the shear layer forms near the roof layer under real-time wind conditions, resulting in the expansion or compression of the air mass in the canyon. The simulations of pollutant dispersion show that the pollutants inside and above the street canyon are transported by different dispersion mechanisms, relying on the time series of air flow structures. Large scale air movements in the processes of the air mass expansion or compression in the canyon exhibit obvious effects on pollutant dispersion. The simulations of pollutant dispersion also show that the transport of pollutants from the canyon to the upper air flow is dominated by the shear layer turbulence near the roof level and the expansion or compression of the air mass in street canyon under real-time boundary wind conditions. Especially, the expansion of the air mass, which features the large scale air movement of the air mass, makes more contribution to the pollutant dispersion in this study. Comparisons of simulated results under different boundary wind conditions indicate that real-time boundary wind conditions produces better condition for pollutant dispersion than the artificially-designed steady boundary wind conditions.

Fluid-elastic instability in tube arrays subjected to air-water and steam-water cross-flow

Science.gov (United States)

Mitra, D.; Dhir, V. K.; Catton, I.

2009-10-01

Flow induced vibrations in heat exchanger tubes have led to numerous accidents and economic losses in the past. Efforts have been made to systematically study the cause of these vibrations and develop remedial design criteria for their avoidance. In this research, experiments were systematically carried out with air-water and steam-water cross-flow over horizontal tubes. A normal square tube array of pitch-to-diameter ratio of 1.4 was used in the experiments. The tubes were suspended from piano wires and strain gauges were used to measure the vibrations. Tubes made of aluminum; stainless steel and brass were systematically tested by maintaining approximately the same stiffness in the tube-wire systems. Instability was clearly seen in single phase and two-phase flow and the critical flow velocity was found to be proportional to tube mass. The present study shows that fully flexible arrays become unstable at a lower flow velocity when compared to a single flexible tube surrounded by rigid tubes. It is also found that tubes are more stable in steam-water flow as compared to air-water flow. Nucleate boiling on the tube surface is also found to have a stabilizing effect on fluid-elastic instability.

Visualization and volumetric structures from MR images of the brain

Energy Technology Data Exchange (ETDEWEB)

Parvin, B.; Johnston, W.; Robertson, D.

1994-03-01

Pinta is a system for segmentation and visualization of anatomical structures obtained from serial sections reconstructed from magnetic resonance imaging. The system approaches the segmentation problem by assigning each volumetric region to an anatomical structure. This is accomplished by satisfying constraints at the pixel level, slice level, and volumetric level. Each slice is represented by an attributed graph, where nodes correspond to regions and links correspond to the relations between regions. These regions are obtained by grouping pixels based on similarity and proximity. The slice level attributed graphs are then coerced to form a volumetric attributed graph, where volumetric consistency can be verified. The main novelty of our approach is in the use of the volumetric graph to ensure consistency from symbolic representations obtained from individual slices. In this fashion, the system allows errors to be made at the slice level, yet removes them when the volumetric consistency cannot be verified. Once the segmentation is complete, the 3D surfaces of the brain can be constructed and visualized.

Two-phase flow models

International Nuclear Information System (INIS)

Delaje, Dzh.

1984-01-01

General hypothesis used to simplify the equations, describing two-phase flows, are considered. Two-component and one-component models of two-phase flow, as well as Zuber and Findlay model for actual volumetric steam content, and Wallis model, describing the given phase rates, are presented. The conclusion is made, that the two-component model, in which values averaged in time are included, is applicable for the solving of three-dimensional tasks for unsteady two-phase flow. At the same time, using the two-component model, including values, averaged in space only one-dimensional tasks for unsteady two-phase flow can be solved

A Numerical Assessment of the Air Flow Behaviour in a Conventional Compact Dry Kiln

OpenAIRE

Paulo Zdanski; Daniel Possamai; Miguel Vaz Jr.

2015-01-01

Convective drying is the most common drying strategy used in timber manufacturing industries in the developing world. In convective drying, the reduction rate of the moisture content is directly affected by the flow topology in the inlet and exit plenums and the air flow velocity in the channels formed by timber layers.Turbulence, boundary layer separation, vortex formation and recirculation regions are flow features that are intrinsically associated with the kiln geometry, which in turn dict...

Preliminary Calculations of Bypass Flow Distribution in a Multi-Block Air Test

International Nuclear Information System (INIS)

Kim, Min Hwan; Tak, Nam Il

2011-01-01

The development of a methodology for the bypass flow assessment in a prismatic VHTR (Very High Temperature Reactor) core has been conducted at KAERI. A preliminary estimation of variation of local bypass flow gap size between graphite blocks in the NHDD core were carried out. With the predicted gap sizes, their influence on the bypass flow distribution and the core hot spot was assessed. Due to the complexity of gap distributions, a system thermo-fluid analysis code is suggested as a tool for the core thermo-fluid analysis, the model and correlations of which should be validated. In order to generate data for validating the bypass flow analysis model, an experimental facility for a multi-block air test was constructed at Seoul National University (SNU). This study is focused on the preliminary evaluation of flow distribution in the test section to understand how the flow is distributed and to help the selection of experimental case. A commercial CFD code, ANSYS CFX is used for the analyses

Graphical User Interface Development for Representing Air Flow Patterns

Science.gov (United States)

Chaudhary, Nilika

2004-01-01

In the Turbine Branch, scientists carry out experimental and computational work to advance the efficiency and diminish the noise production of jet engine turbines. One way to do this is by decreasing the heat that the turbine blades receive. Most of the experimental work is carried out by taking a single turbine blade and analyzing the air flow patterns around it, because this data indicates the sections of the turbine blade that are getting too hot. Since the cost of doing turbine blade air flow experiments is very high, researchers try to do computational work that fits the experimental data. The goal of computational fluid dynamics is for scientists to find a numerical way to predict the complex flow patterns around different turbine blades without physically having to perform tests or costly experiments. When visualizing flow patterns, scientists need a way to represent the flow conditions around a turbine blade. A researcher will assign specific zones that surround the turbine blade. In a two-dimensional view, the zones are usually quadrilaterals. The next step is to assign boundary conditions which define how the flow enters or exits one side of a zone. way of setting up computational zones and grids, visualizing flow patterns, and storing all the flow conditions in a file on the computer for future computation. Such a program is necessary because the only method for creating flow pattern graphs is by hand, which is tedious and time-consuming. By using a computer program to create the zones and grids, the graph would be faster to make and easier to edit. Basically, the user would run a program that is an editable graph. The user could click and drag with the mouse to form various zones and grids, then edit the locations of these grids, add flow and boundary conditions, and finally save the graph for future use and analysis. My goal this summer is to create a graphical user interface (GUI) that incorporates all of these elements. I am writing the program in

Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

Science.gov (United States)

Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

1999-01-01

forming bubble decreases, as the superficial liquid velocity is in-creased. Furthermore, it is shown that the void fraction of the resulting two-phase flow increases with volumetric gas flow rate Q(sub d), pipe diameter and gas injection nozzle diameter, while they decrease with surrounding liquid flow. The important role played by flowing liquid in detaching bubbles in a reduced gravity environment is thus emphasized. We observe that the void fraction can be accurately controlled by using single nozzle gas injection, rather than by employing multiple port injection, since the later system gives rise to unpredictable coalescence of adjacent bubbles. It is of interest to note that empirical bubble size and corresponding void fraction are somewhat smaller for the co-flow geometry than the cross-flow configuration at similar flow conditions with similar pipe and nozzle diameters. In order to supplement the empirical data, a theoretical model is employed to study single bubble generation in the dynamic (Q(sub d) = 1 - 1000 cu cm/s) and bubbly flow regime within the framework of the co-flow configuration. This theoretical model is based on an overall force balance acting on the bubble during the two stages of generation, namely the expansion and the detachment stage. Two sets of forces, one aiding and the other inhibiting bubble detachment are identified. Under conditions of reduced gravity, gas momentum flux enhances, while the surface tension force at the air injection nozzle tip inhibits bubble detachment. In parallel, liquid drag and inertia can act as both attaching and detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with our experimental results. However, at higher superficial liquid velocities, as the bubble loses its spherical form, empirical bubble size no longer matches the theoretical predictions. In summary, we have developed a combined experimental and

FLOW VISUALIZATION OF RECTANGULAR SLOT AIR JET IMPINGEMENT ON FLAT SURFACES

OpenAIRE

Satheesha V *1, B. K. Muralidhra2, Abhilash N3, C. K. Umesh4

2018-01-01

Jet impingement near the mid-chord of the gas turbine blade is treated as a flat plate. Experimental and numerical investigations are carried out for a single slot air jet impinging on flat surface for two different rectangular slots of dimension (3mm x 65 mm) and (5mm x 65 mm). Experimentation is done to study the flow pattern topography on the flat target plate, with varying the flow rate from 20 LPM to 50 LPM by varying the nozzle to plate distance from 9 mm to 24 mm for slot jet of 3mm an...

Stopping times in cessation flows of Bingham plastics with slip at the wall

Science.gov (United States)

Philippou, Maria; Damianou, Yiolanda; Kaoullas, George; Georgiou, Georgios C.

2012-09-01

We solve numerically the cessation of axisymmetric Poiseuille flow of a Bingham plastic assuming that slip occurs along the wall. A power-law expression is used to relate the wall shear stress to the slip velocity. The numerical results show that the velocity becomes and remains uniform before complete cessation and that the stopping time is finite only when the exponent sBingham number and the volumetric flow rate decays exponentially. When s>1, the decay is much slower, i.e. polynomial. The asymptotic expressions for the volumetric flow rate in the case of full-slip are also derived.

Identify temporal trend of air temperature and its impact on forest stream flow in Lower Mississippi River Alluvial Valley using wavelet analysis.

Science.gov (United States)

Ouyang, Ying; Parajuli, Prem B; Li, Yide; Leininger, Theodor D; Feng, Gary

2017-08-01

Characterization of stream flow is essential to water resource management, water supply planning, environmental protection, and ecological restoration; while air temperature variation due to climate change can exacerbate stream flow and add instability to the flow. In this study, the wavelet analysis technique was employed to identify temporal trend of air temperature and its impact upon forest stream flows in Lower Mississippi River Alluvial Valley (LMRAV). Four surface water monitoring stations, which locate near the headwater areas with very few land use disturbances and the long-term data records (60-90 years) in the LMRAV, were selected to obtain stream discharge and air temperature data. The wavelet analysis showed that air temperature had an increasing temporal trend around its mean value during the past several decades in the LMRAV, whereas stream flow had a decreasing temporal trend around its average value at the same time period in the same region. Results of this study demonstrated that the climate in the LMRAV did get warmer as time elapsed and the streams were drier as a result of warmer air temperature. This study further revealed that the best way to estimate the temporal trends of air temperature and stream flow was to perform the wavelet transformation around their mean values. Published by Elsevier Ltd.

Air-cooled, hydrogen-air fuel cell

Science.gov (United States)

Shelekhin, Alexander B. (Inventor); Bushnell, Calvin L. (Inventor); Pien, Michael S. (Inventor)

1999-01-01

An air-cooled, hydrogen-air solid polymer electrolyte (SPE) fuel cell with a membrane electrode assembly operatively associated with a fluid flow plate having at least one plate cooling channel extending through the plate and at least one air distribution hole extending from a surface of the cathode flow field into the plate cooling channel.

Ring waves as a mass transport mechanism in air-driven core-annular flows.

Science.gov (United States)

Camassa, Roberto; Forest, M Gregory; Lee, Long; Ogrosky, H Reed; Olander, Jeffrey

2012-12-01

Air-driven core-annular fluid flows occur in many situations, from lung airways to engineering applications. Here we study, experimentally and theoretically, flows where a viscous liquid film lining the inside of a tube is forced upwards against gravity by turbulent airflow up the center of the tube. We present results on the thickness and mean speed of the film and properties of the interfacial waves that develop from an instability of the air-liquid interface. We derive a long-wave asymptotic model and compare properties of its solutions with those of the experiments. Traveling wave solutions of this long-wave model exhibit evidence of different mass transport regimes: Past a certain threshold, sufficiently large-amplitude waves begin to trap cores of fluid which propagate upward at wave speeds. This theoretical result is then confirmed by a second set of experiments that show evidence of ring waves of annular fluid propagating over the underlying creeping flow. By tuning the parameters of the experiments, the strength of this phenomenon can be adjusted in a way that is predicted qualitatively by the model.

The air flow and heat transfer in gravel embankment in permafrost areas

Institute of Scientific and Technical Information of China (English)

JIANG Fan; LIU Shi; WANG Haigang; CHEN Huanzhuo

2004-01-01

A comparative numerical investigation of transient temperature profile and pore-air velocities in horizontal rock block embankments are conducted using the "gravels model", in which the embankment is composed of stones and air, and the "porous media model" respectively. As the velocities from the "gravels model" directly reflect the true flow of air and winter-time convection, in this paper it can be concluded that computational results from the "gravels model"are superior to the "porous media model". In addition, the "gravels model" has the advantages of reflecting the effect of the dimensions and collocation of gravels upon the temperature fields.Therefore, the computation of the gravels embankment is mainly based on the gravels model.Simulation results show that in summer, a clockwise circulation of the pore-air extends throughout most of the embankment. However its motion is very weak that results in relatively straight horizontal isotherm lines. And heat transfer is mainly maintained through conduction. But in winter, the pore-air velocities are higher and multiple vortexes are formed in the embankment.Natural convection then becomes the dominant influence on the isotherm shapes within the embankment. The isotherms are complex and alternative upward and downward flowing plumes exist. The winter-time convection can further reduce the temperature of the foundation soil beneath the gravel embankment. In addition, the effects of the gravel dimensions within the embankment have been analyzed and compared in the gravels model. It shows that in winter, large stones, e.g. 200 mm, lead to stronger vortexes than those of small stones, say 60 mm. Consequently, the zone of low-temperature beneath the large-stone embankment extends deeper into the ground.

Hybridized electromagnetic-triboelectric nanogenerator for scavenging air-flow energy to sustainably power temperature sensors.

Science.gov (United States)

Wang, Xue; Wang, Shuhua; Yang, Ya; Wang, Zhong Lin

2015-04-28

We report a hybridized nanogenerator with dimensions of 6.7 cm × 4.5 cm × 2 cm and a weight of 42.3 g that consists of two triboelectric nanogenerators (TENGs) and two electromagnetic generators (EMGs) for scavenging air-flow energy. Under an air-flow speed of about 18 m/s, the hybridized nanogenerator can deliver largest output powers of 3.5 mW for one TENG (in correspondence of power per unit mass/volume: 8.8 mW/g and 14.6 kW/m(3)) at a loading resistance of 3 MΩ and 1.8 mW for one EMG (in correspondence of power per unit mass/volume: 0.3 mW/g and 0.4 kW/m(3)) at a loading resistance of 2 kΩ, respectively. The hybridized nanogenerator can be utilized to charge a capacitor of 3300 μF to sustainably power four temperature sensors for realizing self-powered temperature sensor networks. Moreover, a wireless temperature sensor driven by a hybridized nanogenerator charged Li-ion battery can work well to send the temperature data to a receiver/computer at a distance of 1.5 m. This work takes a significant step toward air-flow energy harvesting and its potential applications in self-powered wireless sensor networks.

Canyon air flow measurement utilizing ASME standard pitot tube arrays

International Nuclear Information System (INIS)

Moncrief, B.R.

1990-01-01

The Savannah River Site produces nuclear materials for national defense. In addition to nuclear reactors, the site has separation facilities for reprocessing irradiated nuclear fuel. The chemical separation of highly radioactive materials takes place by remote control in large buildings called canyons. Personnel in these buildings are shielded from radiation by thick concrete walls. Contaminated air is exhausted from the canyons and contaminants are removed by sand filters prior to release to the atmosphere through a stack. When these facilities were built on a crash basis in the early 1950's, inadequate means were provided for pressure and air flow measurement. This presentation describes the challenge we faced in retrofitting a highly radioactive, heavily shielded facility with instrumentation to provide this capability

Process conditions and volumetric composition in composites

DEFF Research Database (Denmark)

Madsen, Bo

2013-01-01

The obtainable volumetric composition in composites is linked to the gravimetric composition, and it is influenced by the conditions of the manufacturing process. A model for the volumetric composition is presented, where the volume fractions of fibers, matrix and porosity are calculated...... as a function of the fiber weight fraction, and where parameters are included for the composite microstructure, and the fiber assembly compaction behavior. Based on experimental data of composites manufactured with different process conditions, together with model predictions, different types of process related...... effects are analyzed. The applied consolidation pressure is found to have a marked effect on the volumetric composition. A power-law relationship is found to well describe the found relations between the maximum obtainable fiber volume fraction and the consolidation pressure. The degree of fiber...

Interfacial area, velocity and void fraction in two-phase slug flow

International Nuclear Information System (INIS)

Kojasoy, G.; Riznic, J.R.

1997-01-01

The internal flow structure of air-water plug/slug flow in a 50.3 mm dia transparent pipeline has been experimentally investigated by using a four-sensor resistivity probe. Liquid and gas volumetric superficial velocities ranged from 0.55 to 2.20 m/s and 0.27 to 2.20 m/s, respectively, and area-averaged void fractions ranged from about 10 to 70%. The local distributions of void fractions, interfacial area concentration and interface velocity were measured. Contributions from small spherical bubbles and large elongated slug bubbles toward the total void fraction and interfacial area concentration were differentiated. It was observed that the small bubble void contribution to the overall void fraction was small indicating that the large slug bubble void fraction was a dominant factor in determining the total void fraction. However, the small bubble interfacial area contribution was significant in the lower and upper portions of the pipe cross sections

Sensitivity study of poisson corruption in tomographic measurements for air-water flows

International Nuclear Information System (INIS)

Munshi, P.; Vaidya, M.S.

1993-01-01

An application of computerized tomography (CT) for measuring void fraction profiles in two-phase air-water flows was reported earlier. Those attempts involved some special radial methods for tomographic reconstruction and the popular convolution backprojection (CBP) method. The CBP method is capable of reconstructing void profiles for nonsymmetric flows also. In this paper, we investigate the effect of corrupted CT data for gamma-ray sources and aCBP algorithm. The corruption in such a case is due to the statistical (Poisson) nature of the source

Modeling Flow Rate to Estimate Hydraulic Conductivity in a Parabolic Ceramic Water Filter

Directory of Open Access Journals (Sweden)

Ileana Wald

2012-01-01

Full Text Available In this project we model volumetric flow rate through a parabolic ceramic water filter (CWF to determine how quickly it can process water while still improving its quality. The volumetric flow rate is dependent upon the pore size of the filter, the surface area, and the height of water in the filter (hydraulic head. We derive differential equations governing this flow from the conservation of mass principle and Darcy's Law and find the flow rate with respect to time. We then use methods of calculus to find optimal specifications for the filter. This work is related to the research conducted in Dr. James R. Mihelcic's Civil and Environmental Engineering Lab at USF.

Managing the Drivers of Air Flow and Water Vapor Transport in Existing Single Family Homes (Revised)

Energy Technology Data Exchange (ETDEWEB)

Cummings, J.; Withers, C.; Martin, E.; Moyer, N.

2012-10-01

This document focuses on managing the driving forces which move air and moisture across the building envelope. While other previously published Measure Guidelines focus on elimination of air pathways, the ultimate goal of this Measure Guideline is to manage drivers which cause air flow and water vapor transport across the building envelope (and also within the home), control air infiltration, keep relative humidity (RH) within acceptable limits, avoid combustion safety problems, improve occupant comfort, and reduce house energy use.

Three dimensional turbulence structure measurements in air/water two phase flow

International Nuclear Information System (INIS)

Wang, S.K.L.

1986-01-01

The phenomena of turbulent air/water two phase upward and downward flows in a circular test section were investigated. Important flow quantities such as void fraction, liquid velocity, and Reynolds stresses were measured by using both single sensor and three sensor hot film probes. A digital data processing technique based on combined derivative and level thresholding was developed to determine the local void fraction from hot-film anemometer signals. The measured local void fraction was integrated and the result was compared with the chordal averaged void fraction measured by a gamma ray densitometer. It was found that the local measurement underestimated local void fraction due to surface tension effects and bubble deflection by the probe. A correlation based on local parameters characterizing probe/bubble interaction was developed, and it corrected the measured void fraction successfully. The measured void fraction profiles in upward flow and downward flow showed two distinct patterns. In upward flow, bubbles tend to migrate toward the wall and the void fraction profile shows a sharp peak near the wall. In downward flow, as the liquid velocity increases, the wall peaking phenomenon fades out and bubbles tend to migrate toward the center of the pipe

Soil volumetric water content measurements using TDR technique

Directory of Open Access Journals (Sweden)

S. Vincenzi

1996-06-01

Full Text Available A physical model to measure some hydrological and thermal parameters in soils will to be set up. The vertical profiles of: volumetric water content, matric potential and temperature will be monitored in different soils. The volumetric soil water content is measured by means of the Time Domain Reflectometry (TDR technique. The result of a test to determine experimentally the reproducibility of the volumetric water content measurements is reported together with the methodology and the results of the analysis of the TDR wave forms. The analysis is based on the calculation of the travel time of the TDR signal in the wave guide embedded in the soil.

Two-phase upward air water flow in a prismatic channel with rectangular base

International Nuclear Information System (INIS)

Carvalho Tofani, P. de

1984-01-01

Two-phase liquid-gas mixtures provide suitable means to simulate water-water vapor flows, which may occur in nuclear reactor cores. The mastery of physical transport phenomena is of great importance, as far as the analysis of such thermal systems is concerned. Within the framework of thermal-hydraulic programs, experiments have been carried out to investigate the two-phase upward air-water flow structure, in a rectangular test section, by using independent measuring techniques, which comprise direct viewing and photography, electrical probes and gamma-ray attenuation. In this paper, flow pattern maps and correlations for flow pattern transitions, void fraction profiles, liquid film thickness and superficial average void fraction are proposed and compared to available data. (Author) [pt

Simultaneous velocity and pressure quantification using pressure-sensitive flow tracers in air

Science.gov (United States)

Zhang, Peng; Peterson, Sean; Porfiri, Maurizio

2017-11-01

Particle-based measurement techniques for assessing the velocity field of a fluid have advanced rapidly over the past two decades. Full-field pressure measurement techniques have remained elusive, however. In this work, we aim to demonstrate the possibility of direct simultaneous planar velocity and pressure measurement of a high speed aerodynamic flow by employing novel pressure-sensitive tracer particles for particle image velocimetry (PIV). Specifically, the velocity and pressure variations of an airflow through a converging-diverging channel are studied. Polystyrene microparticles embedded with a pressure-sensitive phosphorescent dye-platinum octaethylporphyrin (PtOEP)-are used as seeding particles. Due to the oxygen quenching effect, the emission lifetime of PtOEP is highly sensitive to the oxygen concentration, that is, the partial pressure of oxygen, in the air. Since the partial pressure of oxygen is linearly proportional to the air pressure, we can determine the air pressure through the phosphorescence emission lifetime of the dye. The velocity field is instead obtained using traditional PIV methods. The particles have a pressure resolution on the order of 1 kPa, which may be improved by optimizing the particle size and dye concentration to suit specific flow scenarios. This work was supported by the National Science Foundation under Grant Number CBET-1332204.

GENERATION, TRANSPORT AND DEPOSITION OF TUNGSTEN-OXIDE AEROSOLS AT 1000 C IN FLOWING AIR-STEAM MIXTURES.

Energy Technology Data Exchange (ETDEWEB)

GREENE,G.A.; FINFROCK,C.C.

2001-10-01

Experiments were conducted to measure the rates of oxidation and vaporization of pure tungsten rods in flowing air, steam and air-steam mixtures in laminar flow. Also measured were the downstream transport of tungsten-oxide condensation aerosols and their region of deposition, including plateout in the superheated flow tube, rainout in the condenser and ambient discharge which was collected on an array of sub-micron aerosol filters. The nominal conditions of the tests, with the exception of the first two tests, were tungsten temperatures of 1000 C, gas mixture temperatures of 200 C and wall temperatures of 150 C to 200 C. It was observed that the tungsten oxidation rates were greatest in all air and least in all steam, generally decreasing non-linearly with increasing steam mole fraction. The tungsten oxidation rates in all air were more than five times greater than the tungsten oxidation rates in all steam. The tungsten vaporization rate was zero in all air and increased with increasing steam mole fraction. The vaporization rate became maximum at a steam mole fraction of 0.85 and decreased thereafter as the steam mole fraction was increased to unity. The tungsten-oxide was transported downstream as condensation aerosols, initially flowing upwards from the tungsten rod through an 18-inch long, one-inch diameter quartz tube, around a 3.5-inch radius, 90{sup o} bend and laterally through a 24-inch horizontal run. The entire length of the quartz glass flow path was heated by electrical resistance clamshell heaters whose temperatures were individually controlled and measured. The tungsten-oxide plateout in the quartz tube was collected, nearly all of which was deposited at the end of the heated zone near the entrance to the condenser which was cold. The tungsten-oxide which rained out in the condenser as the steam condensed was collected with the condensate and weighed after being dried. The aerosol smoke which escaped the condenser was collected on the sub

Mechanistic understanding of monosaccharide-air flow battery electrochemistry

Science.gov (United States)

Scott, Daniel M.; Tsang, Tsz Ho; Chetty, Leticia; Aloi, Sekotilani; Liaw, Bor Yann

Recently, an inexpensive monosaccharide-air flow battery configuration has been demonstrated to utilize a strong base and a mediator redox dye to harness electrical power from the partial oxidation of glucose. Here the mechanistic understanding of glucose oxidation in this unique glucose-air power source is further explored by acid-base titration experiments, 13C NMR, and comparison of results from chemically different redox mediators (indigo carmine vs. methyl viologen) and sugars (fructose vs. glucose) via studies using electrochemical techniques. Titration results indicate that gluconic acid is the main product of the cell reaction, as supported by evidence in the 13C NMR spectra. Using indigo carmine as the mediator dye and fructose as the energy source, an abiotic cell configuration generates a power density of 1.66 mW cm -2, which is greater than that produced from glucose under similar conditions (ca. 1.28 mW cm -2). A faster transition from fructose into the ene-diol intermediate than from glucose likely contributed to this difference in power density.

Volumetric fat-water separated T2-weighted MRI

International Nuclear Information System (INIS)

Vasanawala, Shreyas S.; Sonik, Arvind; Madhuranthakam, Ananth J.; Venkatesan, Ramesh; Lai, Peng; Brau, Anja C.S.

2011-01-01

Pediatric body MRI exams often cover multiple body parts, making the development of broadly applicable protocols and obtaining uniform fat suppression a challenge. Volumetric T2 imaging with Dixon-type fat-water separation might address this challenge, but it is a lengthy process. We develop and evaluate a faster two-echo approach to volumetric T2 imaging with fat-water separation. A volumetric spin-echo sequence was modified to include a second shifted echo so two image sets are acquired. A region-growing reconstruction approach was developed to decompose separate water and fat images. Twenty-six children were recruited with IRB approval and informed consent. Fat-suppression quality was graded by two pediatric radiologists and compared against conventional fat-suppressed fast spin-echo T2-W images. Additionally, the value of in- and opposed-phase images was evaluated. Fat suppression on volumetric images had high quality in 96% of cases (95% confidence interval of 80-100%) and were preferred over or considered equivalent to conventional two-dimensional fat-suppressed FSE T2 imaging in 96% of cases (95% confidence interval of 78-100%). In- and opposed-phase images had definite value in 12% of cases. Volumetric fat-water separated T2-weighted MRI is feasible and is likely to yield improved fat suppression over conventional fat-suppressed T2-weighted imaging. (orig.)

Air flow optimization for energy efficient blower of biosafety cabinet class II A2

Science.gov (United States)

Ibrahim, M. D.; Mohtar, M. Z.; Alias, A. A.; Wong, L. K.; Yunos, Y. S.; Rahman, M. R. A.; Zulkharnain, A.; Tan, C. S.; Thayan, R.

2017-04-01

An energy efficient Biosafety Cabinet (BSC) has become a big challenge for manufacturers to develop BSC with the highest level of protection. The objective of research is to increase air flow velocity discharge from centrifugal blower. An aerodynamic duct shape inspired by the shape of Peregrine Falcon’s wing during diving flight is added to the end of the centrifugal blower. Investigation of air movement is determined by computational fluid dynamics (CFD) simulation. The results showed that air velocity can be increased by double compared to typical manufactured BSC and no air recirculation. As conclusion, a novel design of aerodynamic duct shape successfully developed and proved that air velocity can be increase naturally with same impeller speed. It can contribute in increasing energy efficiency of the centrifugal blower. It is vital to BSC manufacturer and can be apply to Heating, Air Ventilation and Air Conditioning (HVAC) industries.

Air-water two-phase flow in a four by four rod bundle with partial length rods

International Nuclear Information System (INIS)

Ohta, Motoki; Kamei, Akihiro; Mizutani, Yoshitaka; Hosokawa, Shigeo; Tomiyama, Akio

2009-01-01

Partial length rods (PLR) are used in fuel bundles of BWR to reduce pressure drops in two-phase regions and to optimize the power distribution. Since little is known about effects of PLR on two-phase flows, air-water two-phase flow around PLRs in a four by four rod bundle is visualized by using a high-speed video camera. The experimental apparatus consists of acrylic channel box and transparent rods. Air and water at atmospheric pressure and room temperature are used for the gas and liquid phases, respectively. The ranges of the gas and liquid volume fluxes, J G and J L , are 0.4 L G L , the flow pattern in the downstream of PLR transits to slug flow, and the flow patterns in the surrounding subchannels transit to bubbly flow due to the redistribution of gas flow. (2) In annular flow, the liquid film on the PLR forms a liquid column above the end cap of PLR. Droplets are generated by column breakup and deposit on liquid films on the neighboring rods. (3) The liquid film thickness on the surface of neighbor rods facing the PLR increases and it reduces that on their opposite surface in the downstream of PLR. (author)

CFD model of air movement in ventilated facade: comparison between natural and forced air flow

Energy Technology Data Exchange (ETDEWEB)

Mora Perez, Miguel; Lopez Patino, Gonzalo; Lopez Jimenez, P. Amparo [Hydraulic and Environmental Engineering Department, Universitat Politècnica de Valencia (Spain)

2013-07-01

This study describes computational fluid dynamics (CFD) modeling of ventilated facade. Ventilated facades are normal facade but it has an extra channel between the concrete wall and the (double skin) facade. Several studies found in the literature are carried out with CFD simulations about the behavior of the thermodynamic phenomena of the double skin facades systems. These studies conclude that the presence of the air gap in the ventilated facade affects the temperature in the building skin, causing a cooling effect, at least in low-rise buildings. One of the most important factors affecting the thermal effects of ventilated facades is the wind velocity. In this contribution, a CFD analysis applied on two different velocity assumptions for air movement in the air gap of a ventilated facade is presented. A comparison is proposed considering natural wind induced velocity with forced fan induced velocity in the gap. Finally, comparing temperatures in the building skin, the differences between both solutions are described determining that, related to the considered boundary conditions, there is a maximum height in which the thermal effect of the induced flow is significantly observed.

Exploring interaction with 3D volumetric displays

Science.gov (United States)

Grossman, Tovi; Wigdor, Daniel; Balakrishnan, Ravin

2005-03-01

Volumetric displays generate true volumetric 3D images by actually illuminating points in 3D space. As a result, viewing their contents is similar to viewing physical objects in the real world. These displays provide a 360 degree field of view, and do not require the user to wear hardware such as shutter glasses or head-trackers. These properties make them a promising alternative to traditional display systems for viewing imagery in 3D. Because these displays have only recently been made available commercially (e.g., www.actuality-systems.com), their current use tends to be limited to non-interactive output-only display devices. To take full advantage of the unique features of these displays, however, it would be desirable if the 3D data being displayed could be directly interacted with and manipulated. We investigate interaction techniques for volumetric display interfaces, through the development of an interactive 3D geometric model building application. While this application area itself presents many interesting challenges, our focus is on the interaction techniques that are likely generalizable to interactive applications for other domains. We explore a very direct style of interaction where the user interacts with the virtual data using direct finger manipulations on and around the enclosure surrounding the displayed 3D volumetric image.

Volumetric composition in composites and historical data

DEFF Research Database (Denmark)

Lilholt, Hans; Madsen, Bo

2013-01-01

The obtainable volumetric composition in composites is of importance for the prediction of mechanical and physical properties, and in particular to assess the best possible (normally the highest) values for these properties. The volumetric model for the composition of (fibrous) composites gives...... guidance to the optimal combination of fibre content, matrix content and porosity content, in order to achieve the best obtainable properties. Several composite materials systems have been shown to be handleable with this model. An extensive series of experimental data for the system of cellulose fibres...... and polymer (resin) was produced in 1942 – 1944, and these data have been (re-)analysed by the volumetric composition model, and the property values for density, stiffness and strength have been evaluated. Good agreement has been obtained and some further observations have been extracted from the analysis....

Hot-wire air flow meter for gasoline fuel-injection system. Calculation of air mass in cylinder during transient condition; Gasoline funsha system yo no netsusenshiki kuki ryuryokei. Kato untenji no cylinder juten kukiryo no keisan

Energy Technology Data Exchange (ETDEWEB)

Oyama, Y [Hitachi Car Engineering, Ltd., Tokyo (Japan); Nishimura, Y; Osuga, M; Yamauchi, T [Hitachi, Ltd., Tokyo (Japan)

1997-10-01

Air flow characteristics of hot-wire air flow meters for gasoline fuel-injection systems with supercharging and exhaust gas recycle during transient conditions were investigated to analyze a simple method for calculating air mass in cylinder. It was clarified that the air mass in cylinder could be calculated by compensating for the change of air mass in intake system by using aerodynamic models of intake system. 3 refs., 6 figs., 1 tab.

Cost-effectiveness of volumetric alcohol taxation in Australia.

Science.gov (United States)

Byrnes, Joshua M; Cobiac, Linda J; Doran, Christopher M; Vos, Theo; Shakeshaft, Anthony P

2010-04-19

To estimate the potential health benefits and cost savings of an alcohol tax rate that applies equally to all alcoholic beverages based on their alcohol content (volumetric tax) and to compare the cost savings with the cost of implementation. Mathematical modelling of three scenarios of volumetric alcohol taxation for the population of Australia: (i) no change in deadweight loss, (ii) no change in tax revenue, and (iii) all alcoholic beverages taxed at the same rate as spirits. Estimated change in alcohol consumption, tax revenue and health benefit. The estimated cost of changing to a volumetric tax rate is $18 million. A volumetric tax that is deadweight loss-neutral would increase the cost of beer and wine and reduce the cost of spirits, resulting in an estimated annual increase in taxation revenue of $492 million and a 2.77% reduction in annual consumption of pure alcohol. The estimated net health gain would be 21 000 disability-adjusted life-years (DALYs), with potential cost offsets of $110 million per annum. A tax revenue-neutral scenario would result in an 0.05% decrease in consumption, and a tax on all alcohol at a spirits rate would reduce consumption by 23.85% and increase revenue by $3094 million [corrected]. All volumetric tax scenarios would provide greater health benefits and cost savings to the health sector than the existing taxation system, based on current understandings of alcohol-related health effects. An equalized volumetric tax that would reduce beer and wine consumption while increasing the consumption of spirits would need to be approached with caution. Further research is required to examine whether alcohol-related health effects vary by type of alcoholic beverage independent of the amount of alcohol consumed to provide a strong evidence platform for alcohol taxation policies.

Simplified model for a ventilated glass window under forced air flow conditions

International Nuclear Information System (INIS)

Ismail, K.A.R.; Henriquez, J.R.

2006-01-01

This paper presents a study on a ventilated window composed of two glass sheets separated by a spacing through which air is forced to flow. The proposed model is one dimensional and unsteady based upon global energy balance over the glass sheets and the flowing fluid. The external glass sheet of the cavity is subjected to variable heat flow due to the solar radiation as well as variable external ambient temperature. The exchange of radiation energy (infrared radiation) between the glass sheets is also included in the formulation. Effects of the spacing between the glass sheets, variation of the forced mass flow rate on the total heat gain and the shading coefficients are investigated. The results show that the effect of the increase of the mass flow rate is found to reduce the mean solar heat gain and the shading coefficients while the increase of the fluid entry temperature is found to deteriorate the window thermal performance

Simplified model for a ventilated glass window under forced air flow conditions

Energy Technology Data Exchange (ETDEWEB)

Ismail, K.A.R. [Depto. de Engenharia Termica e de Fluidos-FEM-UNICAMP CP: 6122 CEP 13083-970 Campinas, SP (Brazil); Henriquez, J.R. [Depto. de Eng. Mecanica-DEMEC, UFPE Av. Academico Helio Ramos, S/N CEP 50740-530, Recife, PE (Brazil)

2006-02-01

This paper presents a study on a ventilated window composed of two glass sheets separated by a spacing through which air is forced to flow. The proposed model is one dimensional and unsteady based upon global energy balance over the glass sheets and the flowing fluid. The external glass sheet of the cavity is subjected to variable heat flow due to the solar radiation as well as variable external ambient temperature. The exchange of radiation energy (infrared radiation) between the glass sheets is also included in the formulation. Effects of the spacing between the glass sheets, variation of the forced mass flow rate on the total heat gain and the shading coefficients are investigated. The results show that the effect of the increase of the mass flow rate is found to reduce the mean solar heat gain and the shading coefficients while the increase of the fluid entry temperature is found to deteriorate the window thermal performance. (author)

Performance and Internal Flow of a Dental Air Turbine Handpiece

Directory of Open Access Journals (Sweden)

Yasuyuki Nishi

2018-01-01

Full Text Available An air turbine handpiece is a dental abrasive device that rotates at high speed and uses compressed air as the driving force. It is characterized by its small size, light weight, and painless abrading due to its high-speed rotation, but its torque is small and noise level is high. Thus, to improve the performance of the air turbine handpiece, we conducted a performance test of an actual handpiece and a numerical analysis that modeled the whole handpiece; we also analyzed the internal flow of the handpiece. Results show that experimental and calculated values were consistent for a constant speed load method with the descending speed of 1 mm/min for torque and turbine output. When the tip of the blade was at the center of the nozzle, the torque was at its highest. This is likely because the jet from the nozzle entered the tip of the blade from a close distance that would not reduce the speed and exited along the blade.

Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning

DEFF Research Database (Denmark)

Kærn, Martin Ryhl; Brix, Wiebke; Elmegaard, Brian

2011-01-01

Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution....

Conjugate transient natural convection in a cylindrical enclosure with internal volumetric heat generation

International Nuclear Information System (INIS)

Sharma, Anil Kumar; Velusamy, K.; Balaji, C.

2008-01-01

This paper reports the results of a numerical investigation of transient turbulent natural convection heat transfer from a volumetric energy generating source placed inside a cylindrical enclosure filled with low Prandtl number fluid (liquid sodium, Pr = 0.005). Two-dimensional conservation equations of mass, momentum and energy, coupled with the Boussinesq approximation, are solved using a finite volume based discretisation method employing the SIMPLE algorithm for the pressure velocity coupling. Turbulence is modeled using the k-ε model with physical boundary conditions. The study presents the transient features of confined turbulent natural convection, due to time varying generation of heat in the volumetric source. The intensity of heat source exponentially decays with time and the source is placed over circular plates with a central opening. Results obtained from the numerical model compare favorably with those reported in the literature for steady state natural convection. Numerical simulations are carried out to display the sequential evolution of flow and thermal fields and the maximum temperature reached in the source. The advantages of distributing the heat source on multi trays have been quantified

Effect of reference conditions on flow rate, modifier fraction and retention in supercritical fluid chromatography.

Science.gov (United States)

De Pauw, Ruben; Shoykhet Choikhet, Konstantin; Desmet, Gert; Broeckhoven, Ken

2016-08-12

When using compressible mobile phases such as fluidic CO2, the density, the volumetric flow rates and volumetric fractions are pressure dependent. The pressure and temperature definition of these volumetric parameters (referred to as the reference conditions) may alter between systems, manufacturers and operating conditions. A supercritical fluid chromatography system was modified to operate in two modes with different definition of the eluent delivery parameters, referred to as fixed and variable mode. For the variable mode, the volumetric parameters are defined with reference to the pump operating pressure and actual pump head temperature. These conditions may vary when, e.g. changing the column length, permeability, flow rate, etc. and are thus variable reference conditions. For the fixed mode, the reference conditions were set at 150bar and 30°C, resulting in a mass flow rate and mass fraction of modifier definition which is independent of the operation conditions. For the variable mode, the mass flow rate of carbon dioxide increases with system pump operating pressure, decreasing the fraction of modifier. Comparing the void times and retention factor shows that the deviation between the two modes is almost independent of modifier percentage, but depends on the operating pressure. Recalculating the set volumetric fraction of modifier to the mass fraction results in the same retention behaviour for both modes. This shows that retention in SFC can be best modelled using the mass fraction of modifier. The fixed mode also simplifies method scaling as it only requires matching average column pressure. Copyright © 2016 Elsevier B.V. All rights reserved.

Critical properties and high-pressure volumetric behavior of the carbon dioxide+propane system at T=308.15 k. Krichevskii function and related thermodynamic properties.

Science.gov (United States)

Blanco, Sofía T; Gil, Laura; García-Giménez, Pilar; Artal, Manuela; Otín, Santos; Velasco, Inmaculada

2009-05-21

Critical properties and volumetric behavior for the {CO2(1)+C3H8(2)} system have been studied. The critical locus was measured with a flow apparatus and detected by critical opalescence. For the mixtures, repeatabilities in critical temperature and pressure are rTcStructural properties such as direct and total correlation function integrals and cluster size were calculated using the Krichevskii function concept. Both the critical and volumetric behavior have been compared with literature data and with those obtained from the PC-SAFT and Patel-Teja equations of state.

Flow visualization study of two phase flow in a single bend outlet feeder pipe and horizontal annulus of outlet end-fitting of a CANDU reactor

International Nuclear Information System (INIS)

Supa-Amornkul, S.; Lister, D.H.; Steward, F.R.

2005-01-01

'Full text:' In CANDU-6 reactors, the pressurized high-temperature coolant flows through 380 fuel channels passing horizontally through the core. Each end of a fuel channel has a stainless steel annular end-fitting connected to a carbon steel feeder pipe. The outlet coolant, which is at 310 o C with up to 0.30 steam voidage, turns through 90 o as it passes from flow in the annular end-fitting to pipe flow in the feeder via a Grayloc connector. Since 1996, several CANDU stations have reported excessive corrosion of their outlet feeder pipes; especially between the first metre, which consisted of single or double bends. Early studies related the attack to the hydrodynamics of the coolant and verified that it was a type of flow accelerated corrosion. In order to understand the hydrodynamics of the coolant in the outlet feeders by flow-visualization, a full-scale transparent test section simulating the geometry and orientation of an outlet feeder bend with its upstream annular end-fitting were fabricated. The feeder consisted of a 54 mm inside diameter acrylic pipe with a 73 o bend, connecting to an acrylic simulation of a Grayloc flanged fitting and annular end-fitting. The annular end-fitting consisted of an inner pipe, 110 mm outer diameter, and an outer pipe, 150 mm inner diameter, both 190.7 cm long in length. The tests were performed with water and air at atmospheric pressure and room temperature. The maximum water volumetric flow rate was 19 L/s and the volume fraction of air varied from 0.05 to 0.56. The phase distributions within the feeder pipe and along the length of the annulus were investigated with a digital video recorder. Size, concentration and velocity of the air bubbles at particular locations were studied with a high-speed digital still camera and a high-speed digital video camera. Phase distributions and variations in bubble size with velocity were determined. Particular attention was paid to the flow pattern at the inside of the bend, where a CFD

Flow visualization study of two phase flow in a single bend outlet feeder pipe and horizontal annulus of outlet end-fitting of a CANDU reactor

Energy Technology Data Exchange (ETDEWEB)

Supa-Amornkul, S.; Lister, D.H.; Steward, F.R. [Univ. of New Brunswick, Fredericton, New Brunswick (Canada)]. E-mail: h796e@unb.ca; dlister@unb.ca; fsteward@unb.ca

2005-07-01

'Full text:' In CANDU-6 reactors, the pressurized high-temperature coolant flows through 380 fuel channels passing horizontally through the core. Each end of a fuel channel has a stainless steel annular end-fitting connected to a carbon steel feeder pipe. The outlet coolant, which is at 310{sup o}C with up to 0.30 steam voidage, turns through 90{sup o} as it passes from flow in the annular end-fitting to pipe flow in the feeder via a Grayloc connector. Since 1996, several CANDU stations have reported excessive corrosion of their outlet feeder pipes; especially between the first metre, which consisted of single or double bends. Early studies related the attack to the hydrodynamics of the coolant and verified that it was a type of flow accelerated corrosion. In order to understand the hydrodynamics of the coolant in the outlet feeders by flow-visualization, a full-scale transparent test section simulating the geometry and orientation of an outlet feeder bend with its upstream annular end-fitting were fabricated. The feeder consisted of a 54 mm inside diameter acrylic pipe with a 73{sup o} bend, connecting to an acrylic simulation of a Grayloc flanged fitting and annular end-fitting. The annular end-fitting consisted of an inner pipe, 110 mm outer diameter, and an outer pipe, 150 mm inner diameter, both 190.7 cm long in length. The tests were performed with water and air at atmospheric pressure and room temperature. The maximum water volumetric flow rate was 19 L/s and the volume fraction of air varied from 0.05 to 0.56. The phase distributions within the feeder pipe and along the length of the annulus were investigated with a digital video recorder. Size, concentration and velocity of the air bubbles at particular locations were studied with a high-speed digital still camera and a high-speed digital video camera. Phase distributions and variations in bubble size with velocity were determined. Particular attention was paid to the flow pattern at the inside

Polyarene mediators for mediated redox flow battery

Science.gov (United States)

Delnick, Frank M.; Ingersoll, David; Liang, Chengdu

2018-01-02

The fundamental charge storage mechanisms in a number of currently studied high energy redox couples are based on intercalation, conversion, or displacement reactions. With exception to certain metal-air chemistries, most often the active redox materials are stored physically in the electrochemical cell stack thereby lowering the practical gravimetric and volumetric energy density as a tradeoff to achieve reasonable power density. In a general embodiment, a mediated redox flow battery includes a series of secondary organic molecules that form highly reduced anionic radicals as reaction mediator pairs for the reduction and oxidation of primary high capacity redox species ex situ from the electrochemical cell stack. Arenes are reduced to stable anionic radicals that in turn reduce a primary anode to the charged state. The primary anode is then discharged using a second lower potential (more positive) arene. Compatible separators and solvents are also disclosed herein.

Available online Efficiency potential of indirectly heated solar reforming with different types of solar air receivers

International Nuclear Information System (INIS)

Storch, Henrik von; Roeb, Martin; Stadler, Hannes; Sattler, Christian; Hoffschmidt, Bernhard

2016-01-01

Highlights: • A process for indirectly heated solar reforming of natural gas with air as heat transfer fluid is proposed. • Different solar receivers are modeled and implemented into the reforming process. • The overall efficiency of the process with different solar receivers is determined. • Optimum solar receiver characteristics for application in a solar reforming process are determined. - Abstract: In solar reforming, the heating value of natural gas is increased by utilization of concentrated solar radiation. Hence, it is a process for storing solar energy in a stable and transportable form that also permits further conversion into liquid fuels like methanol. This process has the potential to significantly decrease the natural gas consumption and the associated CO_2-emissions of methanol production with only few open questions to be addressed prior to commercialization. In the medium and long term, it has the potential to generate methanol as an environmentally friendly fuel for both transport as well as flexible electricity production in combined cycle gas turbines, when biogas is used as reactant. In a previous study the high potential of indirectly heated solar reforming with solar air receivers was shown; however, the efficiency is limited when using state of the art open volumetric receivers. Therefore, different types of air receivers are implemented into an indirectly heated solar reforming process and the overall efficiency potential is assessed in the present study. The implemented receivers are an open volumetric cavity receiver, a closed volumetric cavity receiver and a tubular cavity receiver. The open volumetric cavity receiver and tubular cavity receiver achieve the best results due to their capability of operating efficiently at temperatures well above 700 °C. For these receivers peak efficiencies up to 29% and 27% respectively are predicted. As the utilization of an open volumetric cavity receiver constitutes an open heat transfer

Influence of air flow parameters on nanosecond repetitively pulsed discharges in a pin-annular electrode configuration

KAUST Repository

Heitz, Sylvain A

2016-03-16

The effect of various air flow parameters on the plasma regimes of nanosecond repetitively pulsed (NRP) discharges is investigated at atmospheric pressure. The two electrodes are in a pin-annular configuration, transverse to the mean flow. The voltage pulses have amplitudes up to 15 kV, a duration of 10 ns and a repetition frequency ranging from 15 to 30 kHz. The NRP corona to NRP spark (C-S) regime transition and the NRP spark to NRP corona (S-C) regime transition are investigated for different steady and harmonically oscillating flows. First, the strong effect of a transverse flow on the C-S and S-C transitions, as reported in previous studies, is verified. Second, it is shown that the azimuthal flow imparted by a swirler does not affect the regime transition voltages. Finally, the influence of low frequency harmonic oscillations of the air flow, generated by a loudspeaker, is studied. A strong effect of frequency and amplitude of the incoming flow modulation on the NRP plasma regime is observed. Results are interpreted based on the cumulative effect of the NRP discharges and an analysis of the residence times of fluid particles in the inter-electrode region. © 2016 IOP Publishing Ltd.

Influence of air flow parameters on nanosecond repetitively pulsed discharges in a pin-annular electrode configuration

KAUST Repository

Heitz, Sylvain A; Moeck, Jonas P; Schuller, Thierry; Veynante, Denis; Lacoste, Deanna

2016-01-01

The effect of various air flow parameters on the plasma regimes of nanosecond repetitively pulsed (NRP) discharges is investigated at atmospheric pressure. The two electrodes are in a pin-annular configuration, transverse to the mean flow. The voltage pulses have amplitudes up to 15 kV, a duration of 10 ns and a repetition frequency ranging from 15 to 30 kHz. The NRP corona to NRP spark (C-S) regime transition and the NRP spark to NRP corona (S-C) regime transition are investigated for different steady and harmonically oscillating flows. First, the strong effect of a transverse flow on the C-S and S-C transitions, as reported in previous studies, is verified. Second, it is shown that the azimuthal flow imparted by a swirler does not affect the regime transition voltages. Finally, the influence of low frequency harmonic oscillations of the air flow, generated by a loudspeaker, is studied. A strong effect of frequency and amplitude of the incoming flow modulation on the NRP plasma regime is observed. Results are interpreted based on the cumulative effect of the NRP discharges and an analysis of the residence times of fluid particles in the inter-electrode region. © 2016 IOP Publishing Ltd.

A semi-automated volumetric software for segmentation and perfusion parameter quantification of brain tumors using 320-row multidetector computed tomography: a validation study

Energy Technology Data Exchange (ETDEWEB)

Chae, Soo Young; Suh, Sangil; Ryoo, Inseon; Park, Arim; Seol, Hae Young [Korea University Guro Hospital, Department of Radiology, Seoul (Korea, Republic of); Noh, Kyoung Jin [Soonchunhyang University, Department of Electronic Engineering, Asan (Korea, Republic of); Shim, Hackjoon [Toshiba Medical Systems Korea Co., Seoul (Korea, Republic of)

2017-05-15

We developed a semi-automated volumetric software, NPerfusion, to segment brain tumors and quantify perfusion parameters on whole-brain CT perfusion (WBCTP) images. The purpose of this study was to assess the feasibility of the software and to validate its performance compared with manual segmentation. Twenty-nine patients with pathologically proven brain tumors who underwent preoperative WBCTP between August 2012 and February 2015 were included. Three perfusion parameters, arterial flow (AF), equivalent blood volume (EBV), and Patlak flow (PF, which is a measure of permeability of capillaries), of brain tumors were generated by a commercial software and then quantified volumetrically by NPerfusion, which also semi-automatically segmented tumor boundaries. The quantification was validated by comparison with that of manual segmentation in terms of the concordance correlation coefficient and Bland-Altman analysis. With NPerfusion, we successfully performed segmentation and quantified whole volumetric perfusion parameters of all 29 brain tumors that showed consistent perfusion trends with previous studies. The validation of the perfusion parameter quantification exhibited almost perfect agreement with manual segmentation, with Lin concordance correlation coefficients (ρ {sub c}) for AF, EBV, and PF of 0.9988, 0.9994, and 0.9976, respectively. On Bland-Altman analysis, most differences between this software and manual segmentation on the commercial software were within the limit of agreement. NPerfusion successfully performs segmentation of brain tumors and calculates perfusion parameters of brain tumors. We validated this semi-automated segmentation software by comparing it with manual segmentation. NPerfusion can be used to calculate volumetric perfusion parameters of brain tumors from WBCTP. (orig.)

A semi-automated volumetric software for segmentation and perfusion parameter quantification of brain tumors using 320-row multidetector computed tomography: a validation study.

Science.gov (United States)

Chae, Soo Young; Suh, Sangil; Ryoo, Inseon; Park, Arim; Noh, Kyoung Jin; Shim, Hackjoon; Seol, Hae Young

2017-05-01

We developed a semi-automated volumetric software, NPerfusion, to segment brain tumors and quantify perfusion parameters on whole-brain CT perfusion (WBCTP) images. The purpose of this study was to assess the feasibility of the software and to validate its performance compared with manual segmentation. Twenty-nine patients with pathologically proven brain tumors who underwent preoperative WBCTP between August 2012 and February 2015 were included. Three perfusion parameters, arterial flow (AF), equivalent blood volume (EBV), and Patlak flow (PF, which is a measure of permeability of capillaries), of brain tumors were generated by a commercial software and then quantified volumetrically by NPerfusion, which also semi-automatically segmented tumor boundaries. The quantification was validated by comparison with that of manual segmentation in terms of the concordance correlation coefficient and Bland-Altman analysis. With NPerfusion, we successfully performed segmentation and quantified whole volumetric perfusion parameters of all 29 brain tumors that showed consistent perfusion trends with previous studies. The validation of the perfusion parameter quantification exhibited almost perfect agreement with manual segmentation, with Lin concordance correlation coefficients (ρ c ) for AF, EBV, and PF of 0.9988, 0.9994, and 0.9976, respectively. On Bland-Altman analysis, most differences between this software and manual segmentation on the commercial software were within the limit of agreement. NPerfusion successfully performs segmentation of brain tumors and calculates perfusion parameters of brain tumors. We validated this semi-automated segmentation software by comparing it with manual segmentation. NPerfusion can be used to calculate volumetric perfusion parameters of brain tumors from WBCTP.

The Effect of Volumetric Porosity on Roughness Element Drag

Science.gov (United States)

Gillies, John; Nickling, William; Nikolich, George; Etyemezian, Vicken

2016-04-01

Much attention has been given to understanding how the porosity of two dimensional structures affects the drag force exerted by boundary-layer flow on these flow obstructions. Porous structures such as wind breaks and fences are typically used to control the sedimentation of sand and snow particles or create micro-habitats in their lee. Vegetation in drylands also exerts control on sediment transport by wind due to aerodynamic effects and interaction with particles in transport. Recent research has also demonstrated that large spatial arrays of solid three dimensional roughness elements can be used to reduce sand transport to specified targets for control of wind erosion through the effect of drag partitioning and interaction of the moving sand with the large (>0.3 m high) roughness elements, but porous elements may improve the effectiveness of this approach. A thorough understanding of the role porosity plays in affecting the drag force on three-dimensional forms is lacking. To provide basic understanding of the relationship between the porosity of roughness elements and the force of drag exerted on them by fluid flow, we undertook a wind tunnel study that systematically altered the porosity of roughness elements of defined geometry (cubes, rectangular cylinders, and round cylinders) and measured the associated change in the drag force on the elements under similar Reynolds number conditions. The elements tested were of four basic forms: 1) same sized cubes with tubes of known diameter milled through them creating three volumetric porosity values and increasing connectivity between the tubes, 2) cubes and rectangular cylinders constructed of brass screen that nested within each other, and 3) round cylinders constructed of brass screen that nested within each other. The two-dimensional porosity, defined as the ratio of total surface area of the empty space to the solid surface area of the side of the element presented to the fluid flow was conserved at 0.519 for

On the potential importance of transient air flow in advective radon entry into buildings

International Nuclear Information System (INIS)

Narasimhan, T.N.; Tsang, Y.W.; Holman, H.Y.

1990-01-01

The authors have investigated, using a mathematical model, the temporal variations of air flux within the soil mass surrounding a basement in the presence of time dependent periodic variations of barometric pressure and a persistent under-pressure at the basement. The results of transient air flow show that for a homogeneous soil medium, the effects of barometric fluctuations are most significant in the cases where soil permeability to air is low and the fluctuation frequency is high. In these cases, the barometric fluctuation can greatly enhance the magnitude of fluxes as well as introduce flow direction reversals from surrounding soil into the basement. These large fluxes with direction reversals have strong implications in regard to advective transport of radon. The results suggest that the transient oscillations have to be accounted for in quantifying radon entry into buildings. In the actual field set up, the transient behavior will be further influenced by soil permeability heterogeneity, by soil moisture variations, and by the effects of multiple periodic components in the barometric pressure fluctuations

Influence of air flow, temperature and agitation speed in the batch acetification process to obtain orange vinegar (Citrus sinensis var.W. Navel

Directory of Open Access Journals (Sweden)

María Ferreyra

2012-03-01

Full Text Available This paper describes the influence of process variables to produce orange vinegar. Orange juice was fermented with Saccharomyces cerevisiae until reach 14% v/v. The biooxidation was carried out with Acetobacter sp., in submerge culture using a laboratory scale fermentor. In order to avoid the inhibitory effect of ethanol on acetic acid bacteria, the orange wine was diluted to 6% v/v with a mineral solution. It was performed a factorial design 2k to study the influence of variables. It was studied air flow rate/agitation at levels of 0.3-0.6 vvm and 200-400 rpm and the effect of air flow rate/temperature at 0.4-0.6 vvm and 25- 30°C, respectively. Duplicate treatments were carried out and the results were evaluated in terms of productivity and fermentation yield. Statistical design (p-value<0.05 was analyzed using Statgraphics Centurion XV Corporate software. Treatments performed at 200 rpm and different air flow levels, did not show significant differences on acetification rate. At higher agitation speed and air flow rates, the productivity was high. The best yields were obtained at lower air flows levels and higher agitation speed. Temperature did not present statistically differences on studied variables. The best yield was obtained at 400 rpm and 0.3 vvm at 25°C. It can be concluded that agitation speed plays an important role for a better acetification rate however higher air flow rates causes less yields.

Hydrodynamic characteristics of the two-phase flow field at gas-evolving electrodes: numerical and experimental studies

Science.gov (United States)

Liu, Cheng-Lin; Sun, Ze; Lu, Gui-Min; Yu, Jian-Guo

2018-05-01

Gas-evolving vertical electrode system is a typical electrochemical industrial reactor. Gas bubbles are released from the surfaces of the anode and affect the electrolyte flow pattern and even the cell performance. In the current work, the hydrodynamics induced by the air bubbles in a cold model was experimentally and numerically investigated. Particle image velocimetry and volumetric three-component velocimetry techniques were applied to experimentally visualize the hydrodynamics characteristics and flow fields in a two-dimensional (2D) plane and a three-dimensional (3D) space, respectively. Measurements were performed at different gas rates. Furthermore, the corresponding mathematical model was developed under identical conditions for the qualitative and quantitative analyses. The experimental measurements were compared with the numerical results based on the mathematical model. The study of the time-averaged flow field, three velocity components, instantaneous velocity and turbulent intensity indicate that the numerical model qualitatively reproduces liquid motion. The 3D model predictions capture the flow behaviour more accurately than the 2D model in this study.

Effect of air flow rate on the polyphenols content and antioxidant capacity of convective dried cactus pear cladodes (Opuntia ficus indica).

Science.gov (United States)

Gallegos-Infante, José-Alberto; Rocha-Guzman, Nuria-Elizabeth; González-Laredo, Ruben-Francisco; Reynoso-Camacho, Rosalia; Medina-Torres, Luis; Cervantes-Cardozo, Veronica

2009-01-01

The interest in nopal has encouraged the use of dehydration; there are few studies about the effect of process parameters on the nopal polyphenol content and antioxidant activity. The objective of the present work was to evaluate the effect of air-drying flow rates on the amount and antioxidant capacity of extracts of Opuntia ficus indica cladodes. Nopal was dried at 45 degrees C and air flow rates of 3 and 5 m/sec. Samples were analyzed for moisture, total polyphenol, flavonoid, and flavonol contents, chain-breaking activity, inhibition of low-density lipoprotein and deoxyribose oxidation. Nopal drying at an air flow rate of 3 m/sec showed higher values of phenols, flavonoids and flavonols. The best value of low-density lipoprotein inhibition and deoxyribose was found at 1,000 microg/ml. The air flow rate affected the amount of polyphenols and the OH( . ) radical scavenging, but did not modify the chain-breaking activity and the low-density lipoprotein inhibition activity.

Novel Volumetric Size and Velocity Measurement of Particles Using Interferometric Laser Imaging

Science.gov (United States)

Gunawardana, R.; Zarzecki, M.; Diez, F. J.

2008-11-01

Global Sizing Velocimetry (GSV) is a recently developed technique for characterizing the particle size distribution and flow velocity in a plane and in this research we extend this measurement to a volume through a laser scanning system. In GSV, a LASER sheet is used to illuminate translucent particles in a spray or flow field and the camera image is de-focused a known distance to create interference patterns. The diameters of the particles in the flow field are calculated by measuring the inter-fringe spacing in the resulting interferogram. Particle Imaging Velocimetry (PIV) techniques are used to compute velocity by measuring the particle displacement over a known short time interval. Researchers have recently begun applying GSV techniques to characterize sprays in a plane as it offers a larger area of investigation than other well known techniques such as Phase Doppler Anemometry (PDA). In this paper we extend GSA techniques from the current planar measurements to a volumetric measurement. The approach uses a high speed camera to acquire GSA images by scanning multiple planes in a volume of the flow field within a short period of time and obtain particle size distribution and velocity measurements in the entire volume.

VOF Simulations of Countercurrent Gas-Liquid Flow in a PWR Hot Leg

Directory of Open Access Journals (Sweden)

Michio Murase

2012-12-01

Full Text Available In order to evaluate flow patterns and CCFL (countercurrent flow limitation characteristics in a PWR hot leg under reflux condensation, numerical simulations have been done using a two-fluid model and a VOF (volume of fluid method implemented in the CFD software, FLUENT6.3.26. The two-fluid model gave good agreement with CCFL data under low pressure conditions but did not give good results under high pressure steam-water conditions. On the other hand, the VOF method gave good agreement with CCFL data for tests with a rectangular channel but did not give good results for calculations in a circular channel. Therefore, in this paper, the computational grid and schemes were improved in the VOF method, numerical simulations were done for steam-water flows at 1.5 MPa under PWR full-scale conditions with the diameter of 0.75 m, and the calculated results were compared with the UPTF data at 1.5 MPa. As a result, the calculated flow pattern was found to be similar to the flow pattern observed in small-scale air-water tests, and the calculated CCFL characteristics agreed well with the UPTF data at 1.5 MPa except in the region of a large steam volumetric flux.