Using Analogy to Overcome Misconceptions about Conservation of Matter.

ERIC Educational Resources Information Center

Stavy, Ruth

1991-01-01

This study (n=192) examined the use of analogical instruction to overcome misconceptions about conservation of matter. Students who understood the concept conservation of matter when iodine was evaporated were able to transfer their understanding to the evaporation of acetone. This indicates that teaching by analogy can be an effective tool in…

Development of a preprototype thermoelectric integrated membrane evaporation subsystem for water recovery

NASA Technical Reports Server (NTRS)

Winkler, H. E.; Roebelen, G. J., Jr.

1980-01-01

A three-man urine water recovery preprototype subsystem using a new concept to provide efficient potable water recovery from waste fluids on extended duration space flights has been designed, fabricated, and tested. Low power, compactness, and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber polysulfone membrane evaporator with a thermoelectric heat pump. Application and integration of these key elements have solved problems inherent in previous reclamation subsystem designs. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than a waste liquid recirculation pump and a product water withdrawal pump. Tubular membranes provide structural integrity, improving on previous flat sheet membrane designs. A thermoelectric heat pump provides latent energy recovery.

Computational predictions of flame spread over alcohol pools

NASA Technical Reports Server (NTRS)

Schiller, D. N.; Ross, H. D.; Sirignano, W. A.

1993-01-01

The effects of buoyancy and thermocapillarity on pulsating and uniform flame spread above n-propanol fuel pools have been studied using a numerical model. Data obtained indicate that the existence of pulsating flame spread is dependent upon the formation of a gas-phase recirculation cell which entrains evaporating fuel vapor in front of the leading edge of the flame. The size of the recirculation cell which is affected by the extent of liquid motion ahead of the flame, is shown to dictate whether flame spread is uniform or pulsating. The amplitude and period of the flame pulsations are found to be proportional to the maximum extent of the flow head. Under conditions considered, liquid motion was not affected appreciably by buoyancy. Horizontal convection in the liquid is the dominant mechanism for transporting heat ahead of the flame for both the pulsating and uniform regimes.

Quantum Evaporation from Liquid 4He by Rotons

NASA Astrophysics Data System (ADS)

Hope, F. R.; Baird, M. J.; Wyatt, A. F. G.

1984-04-01

We have shown that rotons as well as phonons can evaporate 4He atoms in a single-quantum process. Measurements of the time of flight and the angular distribution of the evaporated atoms clearly distinguish between evaporation by phonons and rotons. The results indicate that energy and the parallel component of momentum are conserved at the free liquid surface.

How research is fueling the RAS boom

USDA-ARS?s Scientific Manuscript database

The Conservation Fund’s Freshwater Institute has been researching water recirculating aquaculture system (RAS) technologies and practices for salmonids for nearly 30 years using strong funding support from the U.S. Department of Agriculture’s Agricultural Research Service. These early efforts to pio...

Gas recirculation flash drying of filtercake as a safe and economic alternative to fluidized bed drying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalb, G.W.; Sisti, D.

1996-12-31

Although approximately 50% of the thermal coal dryers in North America have been idled or demolished in the past twelve years, thermal coal dryers are currently operating at the highest yearly evaporative load in their history. This is due to the combination of idling/demolishing the marginally required thermal dryers, and replacing the evaporative capacity with more efficient centrifugal dryers while operating the remaining thermal dryers at significantly higher evaporative loads for a greater number of hours. Although previously unheard of in this industry, many of the remaining thermal coal dryers are operating at and above their design evaporative capacity. Thermalmore » coal dryers are used to meet the common moisture specifications of 6.0% in the United States and 7.5 to 8.0% in Canada and are normally required when (1) the Hardgrove grindability exceeds 90, (2) the preparation plant feed topsize is less than 1 {1/2}-inch and/or (3) for transportation reasons in northern climates. It is anticipated that thermal coal drying will be rejuvenated as a result of (1) addressing inherent moisture in low raw coals, (2) the Australian need to address their 10% moisture bituminous coal shipments, and (3) the increased ash and sulfur liberation with decreasing topsize of preparation plant feeds.« less

A SURVEY OF CONVENTIONAL STEAM BOILER EXPERIENCE APPLICABLE TO THE HTGR STEAM GENERATORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paget, J.A.

1959-10-01

BS>The steam generator of a high temperature gas-cooled reactor consists of tubular heating surface inside a shell which forms part of the primary He circuit of the reactor. When a tube fails in such a steam generator, moisture in the form of steam is released into the He steam and is carried through the reactor where it will cause corrosion and mass transfer of C in the core. A paramount consideration in the design of a steam generator for a high temperature gas-cooled reactor is the prevention of tube failures. Preference, therefore, should be given to a forced circulation design.more » The Loeffler Boiler would be the best from this standpoint alone since only steam enters the tubes, and its circulation rate can be maintained at an adequate value to insure cool tubes regardless of load fluctuations. The next type in the order of preference would be the forced recirculation boiler, since at least the boiier tubes always have an adequate cooling flow regardless of output. The third type in order of preference would be a Sulzer Type boiler since it has a separator to remove dissolved material from the water which is comparible in efficiency to a standard boiler drum and although the flow through evaporator and superheater fluctuates with load, the Sulzer Boiler can be operated as a forced recirculation boiler at low loads. The least desirable type would be a Benson or supercritical boiler which is completely dependent on input water purity for its survival. It is not claimed that Benson or supercritical boilers should not or will not be used in the future for gas-cooled reactors, but only that their use would be the least conservative choice from a tube failure standpoint at the present time. (auth)« less

Strip cell test and evaluation program

NASA Technical Reports Server (NTRS)

Gitlow, B.; Bell, W. F.; Martin, R. E.

1978-01-01

The performance characteristics of alkaline fuel cells to be used for space power systems were tested. Endurance tests were conducted on the cells during energy conversion operations. A feature of the cells fabricated and tested was the capability to evaporate the product water formed during the energy conversion reaction directly to space vacuum. A fuel cell powerplant incorporating these cells does not require a condenser and a hydrogen recirculating pump water separator to remove the product water. This simplified the fuel cell powerplant system, reduced the systems weight, and reduced the systems parasite power.

Evaporation of (quantum) black holes and energy conservation

NASA Astrophysics Data System (ADS)

Torres, R.; Fayos, F.; Lorente-Espín, O.

2013-03-01

We consider Hawking radiation as due to a tunneling process in a black hole were quantum corrections, derived from Quantum Einstein Gravity, are taken into account. The consequent derivation, satisfying conservation laws, leads to a deviation from an exact thermal spectrum. This has consequences for the information loss paradox since the non-thermal radiation is shown to carry information out of the black hole. Under the appropriate approximation, a quantum corrected temperature is assigned to the black hole. The evolution of the quantum black hole as it evaporates is then described by taking into account the full implications of energy conservation as well as the backscattered radiation. It is shown that, as a critical mass of the order of Planck's mass is reached, the evaporation process decelerates abruptly while the black hole mass decays towards this critical mass.

Steam atmosphere drying exhaust steam recompression system

DOEpatents

Becker, F.E.; Smolensky, L.A.; Doyle, E.F.; DiBella, F.A.

1994-03-08

This invention relates to a heated steam atmosphere drying system comprising dryer in combination with an exhaust recompression system which is extremely energy efficient and eliminates dangers known to air dryers. The system uses superheated steam as the drying medium, which recirculates through the system where its heat of evaporation and heat of compression is recovered, thereby providing a constant source of heat to the drying chamber. The dryer has inlets whereby feedstock and superheated steam are fed therein. High heat transfer and drying rates are achieved by intimate contact of the superheated steam with the particles being dried. The dryer comprises a vessel which enables the feedstock and steam to enter and recirculate together. When the feedstock becomes dry it will exit the dryer with the steam and become separated from the steam through the use of a curvilinear louver separator (CLS). The CLS enables removal of fine and ultrafine particles from the dryer. Water vapor separated from the particles in the CLS as superheated steam, may then be recovered and recirculated as steam through the use of a compressor to either directly or indirectly heat the dryer, and a heat exchanger or a heater to directly provide heat to the dryer. This system not only provides a very efficient heat transfer system but results in a minimum carry-over of ultrafine particles thereby eliminating any explosive hazard. 17 figures.

Steam atmosphere drying exhaust steam recompression system

DOEpatents

Becker, Frederick E.; Smolensky, Leo A.; Doyle, Edward F.; DiBella, Francis A.

1994-01-01

This invention relates to a heated steam atmosphere drying system comprising dryer in combination with an exhaust recompression system which is extremely energy efficient and eliminates dangers known to air dryers. The system uses superheated steam as the drying medium, which recirculated through the system where its heat of evaporation and heat of compression is recovered, thereby providing a constant source of heat to the drying chamber. The dryer has inlets whereby feedstock and superheated steam are fed therein. High heat transfer and drying rates are achieved by intimate contact of the superheated steam with the particles being dried The dryer comprises a vessel which enables the feedstock and steam to enter recirculate together. When the feedstock becomes dry it will exit the dryer with the steam and become separated from the steam through the use of a curvilinear louver separator (CLS). The CLS enables removal of fine and ultrafine particles from the dryer. Water vapor separated from the particles in the CLS as superheated steam, may then be recovered and recirculated as steam through the use of a compressor to either directly or indirectly heat the dryer, and a heat exchanger or a heater to directly provide heat to the dryer. This system not only provides a very efficient heat transfer system but results in a minimum carry-over of ultrafine particles thereby eliminating any explosive hazard.

Comparing volume of fluid and level set methods for evaporating liquid-gas flows

NASA Astrophysics Data System (ADS)

Palmore, John; Desjardins, Olivier

2016-11-01

This presentation demonstrates three numerical strategies for simulating liquid-gas flows undergoing evaporation. The practical aim of this work is to choose a framework capable of simulating the combustion of liquid fuels in an internal combustion engine. Each framework is analyzed with respect to its accuracy and computational cost. All simulations are performed using a conservative, finite volume code for simulating reacting, multiphase flows under the low-Mach assumption. The strategies used in this study correspond to different methods for tracking the liquid-gas interface and handling the transport of the discontinuous momentum and vapor mass fractions fields. The first two strategies are based on conservative, geometric volume of fluid schemes using directionally split and un-split advection, respectively. The third strategy is the accurate conservative level set method. For all strategies, special attention is given to ensuring the consistency between the fluxes of mass, momentum, and vapor fractions. The study performs three-dimensional simulations of an isolated droplet of a single component fuel evaporating into air. Evaporation rates and vapor mass fractions are compared to analytical results.

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

43 CFR 418.36 - Incentives for additional long term conservation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... be reduced by the incremental amount of evaporation which occurs as a result of the increased surface area of the reservoir due to the additional storage. The evaporation rate used will be either the net evaporation measured or the net historical average after precipitation is taken into account. The method of...

Development of a household waste treatment subsystem, volume 1. [with water conservation features

NASA Technical Reports Server (NTRS)

Gresko, T. M.; Murray, R. W.

1973-01-01

The domestic waste treatment subsystem was developed to process the daily liquid and non-metallic solid wastes provided by a family of four people. The subsystem was designed to be connected to the sewer line of a household which contained water conservation features. The system consisted of an evaporation technique to separate liquids from solids, an incineration technique for solids reduction, and a catalytic oxidizer for eliminating noxious gases from evaporation and incineration processes. All wastes were passed through a grinder which masticated the solids and deposited them in a settling tank. The liquids were transferred through a cleanable filter into a holding tank. From here the liquids were sprayed into an evaporator and a spray chamber where evaporation occurred. The resulting vapors were processed by catalytic oxidation. Water and latent energy were recovered in a combination evaporator/condenser heat exchanger. The solids were conveyed into an incinerator and reduced to ash while the incineration gases were passed through the catalytic oxidizer along with the processed water vapor.

Study of the Effect of Turbulence and Large Obstacles on the Evaporation from Bare Soil Surface through Coupled Free-flow and Porous-medium Flow Model

NASA Astrophysics Data System (ADS)

Gao, B.; Smits, K. M.

2017-12-01

Evaporation is a strongly coupled exchange process of mass, momentum and energy between the atmosphere and the soil. Several mechanisms influence evaporation, such as the atmospheric conditions, the structure of the soil surface, and the physical properties of the soil. Among the previous studies associated with evaporation modeling, most efforts use uncoupled models which simplify the influences of the atmosphere and soil through the use of resistance terms. Those that do consider the coupling between the free flow and porous media flow mainly consider flat terrain with grain-scale roughness. However, larger obstacles, which may form drags or ridges allowing normal convective air flow through the soil, are common in nature and may affect the evaporation significantly. Therefore, the goal of this work is to study the influence of large obstacles such as wavy surfaces on the flow behavior within the soil and exchange processes to the atmosphere under turbulent free-flow conditions. For simplicity, the soil surface with large obstacles are represented by a simple wavy surface. To do this, we modified a previously developed theory for two-phase two-component porous-medium flow, coupling it to single-phase two-component turbulent flow to simulate and analyze the evaporation from wavy soil surfaces. Detailed laboratory scale experiments using a wind tunnel interfaced with a porous media tank were carried out to test the modeling results. The characteristics of turbulent flow across a permeable wavy surface are discussed. Results demonstrate that there is an obvious recirculation zone formed at the surface, which is special because of the accumulation of water vapor and the thicker boundary layer in this area. In addition, the influences of both the free flow and porous medium on the evaporation are also analyzed. The porous medium affects the evaporation through the amount of water it can provide to the soil surface; while the atmosphere influences the evaporation through the gradients formed within the boundary layer. This study gives a primary cognition on the evaporation from bare soil surface with obstacles. Ongoing work will include a deep understanding of the mechanisms which may provide the basis for land-atmosphere study on field scale.

Diffusion Of Mass In Evaporating Multicomponent Drops

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth G.

1992-01-01

Report summarizes study of diffusion of mass and related phenomena occurring in evaporation of dense and dilute clusters of drops of multicomponent liquids intended to represent fuels as oil, kerosene, and gasoline. Cluster represented by simplified mathematical model, including global conservation equations for entire cluster and conditions on boundary between cluster and ambient gas. Differential equations of model integrated numerically. One of series of reports by same authors discussing evaporation and combustion of sprayed liquid fuels.

Energy Conservation for Low-Income Households: The Evaporative Cooler Experience.

ERIC Educational Resources Information Center

Ridge, Richard S.

1988-01-01

An econometric analysis, using a research design based on the nonequivalent control group (NECG), assessed the effectiveness of a program offering free evaporative coolers to low-income families owning air conditioners. The NECG controls for serious threats to internal validity, except for self-selection. The program successfully reduced energy…

Next-Generation Evaporative Cooling Systems for the Advanced Extravehicular Mobility Unit Portable Life Support System

NASA Technical Reports Server (NTRS)

Makinen, Janice V.; Anchondo, Ian; Bue, Grant C.; Campbell, Colin; Colunga, Aaron

2012-01-01

The development of the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support System (PLSS) is currently underway at NASA Johnson Space Center. The AEMU PLSS features two new evaporative cooling systems, the Reduced Volume Prototype Spacesuit Water Membrane Evaporator (RVP SWME), and the Auxiliary Cooling Loop (ACL). The RVP SWME is the third generation of hollow fiber SWME hardware, and like its predecessors, RVP SWME provides nominal crewmember and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crewmember and PLSS electronics. Major design improvements, including a 36% reduction in volume, reduced weight, and more flight like back-pressure valve, facilitate the packaging of RVP SWME in the AEMU PLSS envelope. In addition to the RVP SWME, the Auxiliary Cooling Loop (ACL), was developed for contingency crewmember cooling. The ACL is a completely redundant, independent cooling system that consists of a small evaporative cooler--the Mini Membrane Evaporator (Mini-ME), independent pump, independent feed-water assembly and independent Liquid Cooling Garment (LCG). The Mini-ME utilizes the same hollow fiber technology featured in the RVP SWME, but is only 25% of the size of RVP SWME, providing only the necessary crewmember cooling in a contingency situation. The ACL provides a number of benefits when compared with the current EMU PLSS contingency cooling technology; contingency crewmember cooling can be provided for a longer period of time, more contingency situations can be accounted for, no reliance on a Secondary Oxygen Vessel (SOV) for contingency cooling--thereby allowing a SOV reduction in size and pressure, and the ACL can be recharged-allowing the AEMU PLSS to be reused, even after a contingency event. The development of these evaporative cooling systems will contribute to a more robust and comprehensive AEMU PLSS.

Adaptive multigrid domain decomposition solutions for viscous interacting flows

NASA Technical Reports Server (NTRS)

Rubin, Stanley G.; Srinivasan, Kumar

1992-01-01

Several viscous incompressible flows with strong pressure interaction and/or axial flow reversal are considered with an adaptive multigrid domain decomposition procedure. Specific examples include the triple deck structure surrounding the trailing edge of a flat plate, the flow recirculation in a trough geometry, and the flow in a rearward facing step channel. For the latter case, there are multiple recirculation zones, of different character, for laminar and turbulent flow conditions. A pressure-based form of flux-vector splitting is applied to the Navier-Stokes equations, which are represented by an implicit lowest-order reduced Navier-Stokes (RNS) system and a purely diffusive, higher-order, deferred-corrector. A trapezoidal or box-like form of discretization insures that all mass conservation properties are satisfied at interfacial and outflow boundaries, even for this primitive-variable, non-staggered grid computation.

Optofluidic sensing from inkjet-printed droplets: the enormous enhancement by evaporation-induced spontaneous flow on photonic crystal biosilica†

PubMed Central

Kong, Xianming; Xi, Yuting; LeDuff, Paul; Li, Erwen; Liu, Ye; Cheng, Li-Jing; Rorrer, Gregory L.; Tan, Hua; Wang, Alan X.

2016-01-01

Novel transducers for detecting an ultra-small volume of an analyte solution play pivotal roles in many applications such as chemical analysis, environmental protection and biomedical diagnosis. Recent advances in optofluidics offer tremendous opportunities for analyzing miniature amounts of samples with high detection sensitivity. In this work, we demonstrate enormous enhancement factors (106–107) of the detection limit for optofluidic analysis from inkjet-printed droplets by evaporation-induced spontaneous flow on photonic crystal biosilica when compared with conventional surface-enhanced Raman scattering (SERS) sensing using the pipette dispensing technology. Our computational fluid dynamics simulation has shown a strong recirculation flow inside the 100 picoliter droplet during the evaporation process due to the thermal Marangoni effect. The combination of the evaporation-induced spontaneous flow in micron-sized droplets and the highly hydrophilic photonic crystal biosilica is capable of providing a strong convection flow to combat the reverse diffusion force, resulting in a higher concentration of the analyte molecules at the diatom surface. In the meanwhile, high density hot-spots provided by the strongly coupled plasmonic nanoparticles with photonic crystal biosilica under a 1.5 μm laser spot are verified by finite-difference time domain simulation, which is crucial for SERS sensing. Using a drop-on-demand inkjet device to dispense multiple 100 picoliter analyte droplets with pinpoint accuracy, we achieved the single molecule detection of Rhodamine 6G and label-free sensing of 4.5 × 10−17 g trinitrotoluene from only 200 nanoliter solution. PMID:27714122

Scenario planning for water resource management in semi arid zone

NASA Astrophysics Data System (ADS)

Gupta, Rajiv; Kumar, Gaurav

2018-06-01

Scenario planning for water resource management in semi arid zone is performed using systems Input-Output approach of time domain analysis. This approach derived the future weights of input variables of the hydrological system from their precedent weights. Input variables considered here are precipitation, evaporation, population and crop irrigation. Ingles & De Souza's method and Thornthwaite model have been used to estimate runoff and evaporation respectively. Difference between precipitation inflow and the sum of runoff and evaporation has been approximated as groundwater recharge. Population and crop irrigation derived the total water demand. Compensation of total water demand by groundwater recharge has been analyzed. Further compensation has been evaluated by proposing efficient methods of water conservation. The best measure to be adopted for water conservation is suggested based on the cost benefit analysis. A case study for nine villages in Chirawa region of district Jhunjhunu, Rajasthan (India) validates the model.

Radiation-Spray Coupling for Realistic Flow Configurations

NASA Technical Reports Server (NTRS)

El-Asrag, Hossam; Iannetti, Anthony C.

2011-01-01

Three Large Eddy Simulations (LES) for a lean-direct injection (LDI) combustor are performed and compared. In addition to the cold flow simulation, the effect of radiation coupling with the multi-physics reactive flow is analyzed. The flame let progress variable approach is used as a subgrid combustion model combined with a stochastic subgrid model for spray atomization and an optically thin radiation model. For accurate chemistry modeling, a detailed Jet-A surrogate mechanism is utilized. To achieve realistic inflow, a simple recycling technique is performed at the inflow section upstream of the swirler. Good comparison is shown with the experimental data mean and root mean square profiles. The effect of combustion is found to change the shape and size of the central recirculation zone. Radiation is found to change the spray dynamics and atomization by changing the heat release distribution and the local temperature values impacting the evaporation process. The simulation with radiation modeling shows wider range of droplet size distribution by altering the evaporation rate. The current study proves the importance of radiation modeling for accurate prediction in realistic spray combustion configurations, even for low pressure systems.

Self-assembly of colloidal particles from evaporating droplets: role of DLVO interactions and proposition of a phase diagram.

PubMed

Bhardwaj, Rajneesh; Fang, Xiaohua; Somasundaran, Ponisseril; Attinger, Daniel

2010-06-01

The shape of deposits obtained from drying drops containing colloidal particles matters for technologies such as inkjet printing, microelectronics, and bioassay manufacturing. In this work, the formation of deposits during the drying of nanoliter drops containing colloidal particles is investigated experimentally with microscopy and profilometry, and theoretically with an in-house finite-element code. The system studied involves aqueous drops containing titania nanoparticles evaporating on a glass substrate. Deposit shapes from spotted drops at different pH values are measured using a laser profilometer. Our results show that the pH of the solution influences the dried deposit pattern, which can be ring-like or more uniform. The transition between these patterns is explained by considering how DLVO interactions such as the electrostatic and van der Waals forces modify the particle deposition process. Also, a phase diagram is proposed to describe how the shape of a colloidal deposit results from the competition among three flow patterns: a radial flow driven by evaporation at the wetting line, a Marangoni recirculating flow driven by surface tension gradients, and the transport of particles toward the substrate driven by DLVO interactions. This phase diagram explains three types of deposits commonly observed experimentally, such as a peripheral ring, a small central bump, or a uniform layer. Simulations and experiments are found in very good agreement.

The third order correction on Hawking radiation and entropy conservation during black hole evaporation process

NASA Astrophysics Data System (ADS)

Yan, Hao-Peng; Liu, Wen-Biao

2016-08-01

Using Parikh-Wilczek tunneling framework, we calculate the tunneling rate from a Schwarzschild black hole under the third order WKB approximation, and then obtain the expressions for emission spectrum and black hole entropy to the third order correction. The entropy contains four terms including the Bekenstein-Hawking entropy, the logarithmic term, the inverse area term, and the square of inverse area term. In addition, we analyse the correlation between sequential emissions under this approximation. It is shown that the entropy is conserved during the process of black hole evaporation, which consists with the request of quantum mechanics and implies the information is conserved during this process. We also compare the above result with that of pure thermal spectrum case, and find that the non-thermal correction played an important role.

Radiation-stimulated explosive evaporation and burning of hydrogen droplets in hot aerosol mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osipov, V. V.; Marchenko, M. P.; Khasin, M.

2016-06-13

We present results of analytical and numerical investigation of explosive evaporation and burning scenarios of hydrogen droplets in hydrogen/oxygen aerosols. The following two scenarios have been elucidated. The first scenario, corresponding to sufficiently large droplets, is characterized by three stages: (i) an essentially homogeneous heating of a droplet to a near-critical temperature by IR radiation from the hot gas; (ii) explosive evaporation; and (iii) burning of hydrogen cloud formed by evaporation. The second scenario, corresponding to small droplets, differs in that a droplet is heated mainly by thermal conduction from the hot gas. The heating is accompanied by evaporation whichmore » can become explosive at the final stage of evaporation. The crossover droplet size separating the two scenarios is calculated. Conservative finite-difference numerical analysis is used to explore the predicted scenarios and verify analytical estimates.« less

Thermal management of advanced fuel cell power systems

NASA Technical Reports Server (NTRS)

Vanderborgh, N. E.; Hedstrom, J.; Huff, J.

1990-01-01

It is shown that fuel cell devices are particularly attractive for the high-efficiency, high-reliability space hardware necessary to support upcoming space missions. These low-temperature hydrogen-oxygen systems necessarily operate with two-phase water. In either PEMFCs (proton exchange membrane fuel cells) or AFCs (alkaline fuel cells), engineering design must be critically focused on both stack temperature control and on the relative humidity control necessary to sustain appropriate conductivity within the ionic conductor. Water must also be removed promptly from the hardware. Present designs for AFC space hardware accomplish thermal management through two coupled cooling loops, both driven by a heat transfer fluid, and involve a recirculation fan to remove water and heat from the stack. There appears to be a certain advantage in using product water for these purposes within PEM hardware, because in that case a single fluid can serve both to control stack temperature, operating simultaneously as a heat transfer medium and through evaporation, and to provide the gas-phase moisture levels necessary to set the ionic conductor at appropriate performance levels. Moreover, the humidification cooling process automatically follows current loads. This design may remove the necessity for recirculation gas fans, thus demonstrating the long-term reliability essential for future space power hardware.

Spacesuit Water Membrane Evaporator; An Enhanced Evaporative Cooling System for the Advanced Extravehicular Mobility Unit Portable Life Support System

NASA Technical Reports Server (NTRS)

Bue, Grant C.; Makinen, Janice V.; Miller, Sean; Campbell, Colin; Lynch, Bill; Vogel, Matt; Craft, Jesse; Wilkes, Robert; Kuehnel, Eric

2014-01-01

Development of the Advanced Extravehicular Mobility Unit (AEMU) portable life support subsystem (PLSS) is currently under way at NASA Johnson Space Center. The AEMU PLSS features a new evaporative cooling system, the Generation 4 Spacesuit Water Membrane Evaporator (Gen4 SWME). The SWME offers several advantages when compared with prior crewmember cooling technologies, including the ability to reject heat at increased atmospheric pressures, reduced loop infrastructure, and higher tolerance to fouling. Like its predecessors, Gen4 SWME provides nominal crew member and electronics cooling by flowing water through porous hollow fibers. Water vapor escapes through the hollow fiber pores, thereby cooling the liquid water that remains inside of the fibers. This cooled water is then recirculated to remove heat from the crew member and PLSS electronics. Test results from the backup cooling system which is based on a similar design and the subject of a companion paper, suggested that further volume reductions could be achieved through fiber density optimization. Testing was performed with four fiber bundle configurations ranging from 35,850 fibers to 41,180 fibers. The optimal configuration reduced the Gen4 SWME envelope volume by 15% from that of Gen3 while dramatically increasing the performance margin of the system. A rectangular block design was chosen over the Gen3 cylindrical design, for packaging configurations within the AEMU PLSS envelope. Several important innovations were made in the redesign of the backpressure valve which is used to control evaporation. A twin-port pivot concept was selected from among three low profile valve designs for superior robustness, control and packaging. The backpressure valve motor, the thermal control valve, delta pressure sensors and temperature sensors were incorporated into the manifold endcaps, also for packaging considerations. Flight-like materials including a titanium housing were used for all components. Performance testing of the Gen4 SWME is underway.

Warm water aquaculture using waste heat and water from zero discharge power plants in the Great Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heckmann, R.A.; Winget, R.N.; Infanger, R.C.

1984-01-31

Two series of experiments were completed to determine (a) toxicity of waste water from power plants on warm water fish and (b) multiple use of waste heat and water for aquatic animal and plant production. All three types of waste water from a typical coal-fired power plant are acceptable for growing catfish and tilapia following aeration. This growth was compared with fish raised in spring water. Closed, recirculating polyculture systems using evaporation pond water operated efficiently for plant (duckweed) and animal (fish and freshwater prawns) production. Duckweed is an excellent supplement for fish feed. Tilapia and freshwater prawns grew rapidlymore » in the tanks containing duckweed only. 10 references, 13 tables.« less

Approximate solution to the Callan-Giddings-Harvey-Strominger field equations for two-dimensional evaporating black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ori, Amos

2010-11-15

Callan, Giddings, Harvey, and Strominger (CGHS) previously introduced a two-dimensional semiclassical model of gravity coupled to a dilaton and to matter fields. Their model yields a system of field equations which may describe the formation of a black hole in gravitational collapse as well as its subsequent evaporation. Here we present an approximate analytical solution to the semiclassical CGHS field equations. This solution is constructed using the recently introduced formalism of flux-conserving hyperbolic systems. We also explore the asymptotic behavior at the horizon of the evaporating black hole.

Water budgets of Italian and Dutch gravel pit lakes: a study using a fen as a natural evaporation pan, stable isotopes and conservative tracer modeling.

NASA Astrophysics Data System (ADS)

Nella Mollema, Pauline; Antonellini, Marco

2015-04-01

Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form where the gravel pits are below the water table and fill with groundwater. Their presence changes the drainage patterns, water- and hydrochemical budgets of a watershed. We have studied the water budget of two gravel pit lakes systems using stable H and O isotopes of water as well as conservative tracer (Cl) modeling. The Dutch gravel pit lakes are a fluvial fresh water system of 70 lakes along the Meuse River and the Italian gravel pit lakes are a brackish system along the Adriatic coast. Surface water evaporation from the gravel pit lakes is larger than the actual evapotranspiration of the grass land and forests that were replaced. The ratio of evaporation to total flow into the Dutch lakes was determined by using a Fen as a natural evaporation pan: the isotope content of the Tuspeel Fen, filled with rain water and sampled in a dry and warm summer period (August 2012), is representative for the limiting isotopic enrichment under local hydro meteorological conditions. The Local Evaporation line (LEL) was determined δ2 H = 4.20 δ 18O - 14.10 (R² = 0.99) and the ratio of total inflow to evaporation for three gravel pit lakes were calculated to be 22.6 for the De Lange Vlieter lake used for drinking water production, 11.3 for the Boschmolen Lake and 8.9 for the Anna's Beemd lake showing that groundwater flow is much larger than evaporation. The Italian gravel pit lakes are characterized by high salinity (TDS = 4.6-12.3 g L-1). Stable isotope data show that these latter gravel pit lakes are fed by groundwater, which is a mix between fresh Apennine River water and brackish (Holocene) Adriatic Sea water. The local evaporation line is determined: δ2H = 5.02 δ18O - 10.49. The ratio of total inflow to evaporation is 5. Conservative tracer modeling indicates that the chloride concentration in the Italian gravel pit lakes stabilizes after a short period of rapid increase, because water leaving the lake via groundwater flow, driven by the drainage system, removes part of the Cl that accumulates in the lake due to evapo-concentration. Under climate change, rising sea levels and continuing land subsidence as well as increasing precipitation would increase the need for drainage which would enhance groundwater flow through the lake. The resulting steady-state Cl concentration of the lakes could become less than the current Cl concentration. This effect would be larger than increasing evapo- concentration. Both gravel pit lake systems have a large flux of groundwater into and out of the lakes driven by evaporation and (artificial) drainage with important consequences for the water- and hydrochemical budgets of the whole watershed and in particular on freshwater quantity and groundwater salinity.

Spark gap switch system with condensable dielectric gas

DOEpatents

Thayer, III, William J.

1991-01-01

A spark gap switch system is disclosed which is capable of operating at a high pulse rate comprising an insulated switch housing having a purging gas entrance port and a gas exit port, a pair of spaced apart electrodes each having one end thereof within the housing and defining a spark gap therebetween, an easily condensable and preferably low molecular weight insulating gas flowing through the switch housing from the housing, a heat exchanger/condenser for condensing the insulating gas after it exits from the housing, a pump for recirculating the condensed insulating gas as a liquid back to the housing, and a heater exchanger/evaporator to vaporize at least a portion of the condensed insulating gas back into a vapor prior to flowing the insulating gas back into the housing.

Development of comprehensive numerical schemes for predicting evaporating gas-droplets flow processes of a liquid-fueled combustor

NASA Technical Reports Server (NTRS)

Chen, C. P.

1990-01-01

An existing Computational Fluid Dynamics code for simulating complex turbulent flows inside a liquid rocket combustion chamber was validated and further developed. The Advanced Rocket Injector/Combustor Code (ARICC) is simplified and validated against benchmark flow situations for laminar and turbulent flows. The numerical method used in ARICC Code is re-examined for incompressible flow calculations. For turbulent flows, both the subgrid and the two equation k-epsilon turbulence models are studied. Cases tested include idealized Burger's equation in complex geometries and boundaries, a laminar pipe flow, a high Reynolds number turbulent flow, and a confined coaxial jet with recirculations. The accuracy of the algorithm is examined by comparing the numerical results with the analytical solutions as well as experimented data with different grid sizes.

Proceedings of the third annual Nevada energy forum and exposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1984-01-01

This book presents the papers given at a forum on energy conservation. The papers include subjects on the following topics: third party financing; heat recovery and indirect evaporative cooling; computer literacy; practical power factor survey methodology; the measured energy performance of buildings; casino cogeneration; employees and energy conservation; daylighting; infrared heating; peak shaving and cogeneration. These subjects were orientated toward the management, purchasing and engineering professions and coincided with the forum goal of promoting energy conservation literacy.

Contributions of local terrestrial evaporation and transpiration to precipitation using δ18O and D-excess as a proxy in Shiyang inland river basin in China

NASA Astrophysics Data System (ADS)

Zongxing, Li; Qi, Feng; Wang, Q. J.; Yanlong, Kong; Aifang, Cheng; Song, Yong; Yongge, Li; Jianguo, Li; Xiaoyan, Guo

2016-11-01

Moisture recycling by terrestrial evaporation and transpiration has recently been confirmed as an important source of precipitation, but little is known of this contribution in inland river basins of China. This study determines the fractions contributed by terrestrial evaporation and transpiration to precipitation in the Shiyang river basin, located in Gansu province of northwestern China. The basin has an area of 4.16 × 104 km2 and mean annual precipitation of 300 mm/yr. Hundreds of samples of precipitation, surface water, plant stem water and soil water were collected and analyzed for their isotopic compositions. The Craig-Gordon model and a three-end-member mixing model were used to partition precipitation into water sourced from evaporation, transpiration and advection. On average, evaporation, transpiration and advection were responsible for 9%, 14% and 77%, respectively, of precipitation, and the contribution from terrestrial evaporation and transpiration also increased with elavation; they also varied with season, being highest in August. The significant contribution from transpiration highlights the importance of vegetation conservation in this ecologically fragile basin.

Investigation of local evaporation flux and vapor-phase pressure at an evaporative droplet interface.

PubMed

Duan, Fei; Ward, C A

2009-07-07

In the steady-state experiments of water droplet evaporation, when the throat was heating at a stainless steel conical funnel, the interfacial liquid temperature was found to increase parabolically from the center line to the rim of the funnel with the global vapor-phase pressure at around 600 Pa. The energy conservation analysis at the interface indicates that the energy required for evaporation is maintained by thermal conduction to the interface from the liquid and vapor phases, thermocapillary convection at interface, and the viscous dissipation globally and locally. The local evaporation flux increases from the center line to the periphery as a result of multiple effects of energy transport at the interface. The local vapor-phase pressure predicted from statistical rate theory (SRT) is also found to increase monotonically toward the interface edge from the center line. However, the average value of the local vapor-phase pressures is in agreement with the measured global vapor-phase pressure within the measured error bar.

Tested Demonstrations.

ERIC Educational Resources Information Center

Gilbert, George L., Ed.

1987-01-01

Provides instructions on conducting four demonstrations for the chemistry classroom. Outlines procedures for demonstrations dealing with coupled oscillations, the evaporation of liquids, thioxanthone sulfone radical anion, and the control of variables and conservation of matter. (TW)

Dynamic effect of leachate recirculation on batch mode solid state anaerobic digestion: Influence of recirculated volume, leachate to substrate ratio and recirculation periodicity.

PubMed

Degueurce, Axelle; Trémier, Anne; Peu, Pascal

2016-09-01

Performances of batch mode solid state anaerobic digestion (SSAD) were investigated through several leachate recirculation strategies. Three parameters were shown to particularly influence methane production rates (MPR) and methane yields: the length of the interval between two recirculation events, the leachate to substrate (L:S) ratio and the volume of leachate recirculated. A central composite factor design was used to determine the influence of each parameter on methane production. Results showed that lengthening the interval between two recirculation events reduced methane yield. This effect can be counteracted by recirculating a large volume of leachate at a low L:S ratio. Steady methane production can be obtained by recirculating small amounts of leachate, and by lengthening the interval between two recirculations, regardless of the L:S ratio. However, several combinations of these parameters led to similar performances meaning that leachate recirculation practices can be modified as required by the specific constraints SSAD plants configurations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air.

PubMed

Jung, Heejung S; Grady, Michael L; Victoroff, Tristan; Miller, Arthur L

2017-07-01

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO 2 ) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO 2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm 3 , although CO 2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO 2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm 3 . We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO 2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO 2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50-75% maintained lower CO 2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants' exposures to particulate matter and CO 2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO 2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO 2 accumulation.

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

PubMed Central

Jung, Heejung S.; Grady, Michael L.; Victoroff, Tristan; Miller, Arthur L.

2017-01-01

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50–75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants’ exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation. PMID:28781568

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

NASA Astrophysics Data System (ADS)

Jung, Heejung S.; Grady, Michael L.; Victoroff, Tristan; Miller, Arthur L.

2017-07-01

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50-75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants' exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation.

Water-walled microfluidics for high-optical finesse cavities

NASA Astrophysics Data System (ADS)

Maayani, Shai; Martin, Leopoldo L.; Carmon, Tal

2016-01-01

In submerged microcavities there is a tradeoff between resonant enhancement for spatial water and light overlap. Why not transform the continuously resonating optical mode to be fully contained in a water microdroplet per se? Here we demonstrate a sustainable 30-μm-pure water device, bounded almost completely by free surfaces, enabling >1,000,000 re-circulations of light. The droplets survive for >16 h using a technique that is based on a nano-water bridge from the droplet to a distant reservoir to compensate for evaporation. More than enabling a nearly-perfect optical overlap with water, atomic-level surface smoothness that minimizes scattering loss, and ~99% coupling efficiency from a standard fibre. Surface tension in our droplet is 8,000 times stronger than gravity, suggesting a new class of devices with water-made walls, for new fields of study including opto-capillaries.

Ecohydrology of the wetland-forestland interface: hydrophobicity in leaf litter and its potential effect on surface evaporation

NASA Astrophysics Data System (ADS)

Probert, Samantha; Kettridge, Nicholas; Devito, Kevin; Hurley, Alexander

2017-04-01

Riparian wetlands represent an important ecotone at the interface of peatlands and forests within the Western Boreal Plain of Canada. Water storage and negative feedbacks to evaporation in these systems is crucial for the conservation and redistribution of water during dry periods and providing ecosystem resilience to disturbance. Litter cover can alter the relative importance of the physical processes that drive soil evaporation. Negative feedbacks to drying are created as the hydrophysical properties of the litter and soil override atmospheric controls on evaporation in dry conditions, subsequently dampening the effects of external forcings on the wetland moisture balance. In this study, water repellency in leaf litter has been shown to significantly correlate with surface-atmosphere interactions, whereby severely hydrophobic leaf litter is linked to the highest surface resistances to evaporation, and therefore lowest instantaneous evaporation. Decreasing moisture is associated with increasing hydrophobicity, which may reduce the evaporative flux further as the dry hydrophobic litter creates a hydrological disconnect between soil moisture and the atmosphere. In contrast, hydrophilic litter layers exhibited higher litter moistures, which is associated with reduced resistances to evaporation and enhanced evaporative fluxes. Water repellency of the litter layer has a greater control on evaporation than the presence or absence of litter itself. Litter removal had no significant effect on instantaneous evaporation or surface resistance to evaporation except under the highest evaporation conditions, where litter layers produced higher resistance values than bare peat soils. However, litter removal modified the dominant physical controls on evaporation: moisture loss in plots with leaf litter was driven by leaf and soil hydrophysical properties. Contrastingly, bare peat soils following litter removal exhibited cooler, wetter surfaces and were more strongly correlated to atmospheric controls. The interaction between evaporation, hydrophobicity and moisture of the soil surface, or litter, presents a potentially significant negative feedback to drying across wetland-forestland interfaces.

Investigation on inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet

NASA Astrophysics Data System (ADS)

Yang, Ce; Wang, Yingjun; Lao, Dazhong; Tong, Ding; Wei, Longyu; Liu, Yixiong

2016-08-01

The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct.

Design and experimental investigation of an ejector in an air-conditioning and refrigeration system

DOE Office of Scientific and Technical Information (OSTI.GOV)

AL-Khalidy, N.; Zayonia, A.

1995-12-31

This paper discusses the conservation of energy in a refrigerant ejector refrigerating machine using heat driven from the concentrator collectors. The working refrigerant was R-113. The design of an ejector operating in an air-conditioning and refrigerating system with a low thermal source (70 C to 100 C) is presented. The influence of three major parameters--boiler, condenser, and evaporator temperature--on ejector efficiency is discussed. Experimental results show that the condenser temperature is the major influence at a low evaporator temperature. The maximum ejector efficiency was 31%.

Recent Advances and Research Status in Energy Conservation of Iron Ore Sintering in China

NASA Astrophysics Data System (ADS)

Wang, Yao-Zu; Zhang, Jian-Liang; Liu, Zheng-Jian; Du, Cheng-Bo

2017-11-01

For the ferrous burden of blast furnaces in China, sinter generally accounts for more than 70% and the sintering process accounts for approximately 6-10% of the total energy consumption of the iron and steel enterprise. Therefore, saving energy during the sintering process is important to reduce the energy consumption in the iron and steel industry. This paper aims to illustrate recent advances and the research status of energy conservation of iron ore sintering in China. It focuses on the development and application of energy-saving technologies such as the composite agglomeration process, sintering with high-proportion flue gas recirculation sintering, recovery of sensible heat from the sinter cooling process, homogeneous deep-bed sintering technology, and comprehensive treatment technology of leakage of sintering. Moreover, some suggestions for the future development of energy-saving technologies are put forward.

Evaporatively cooled chiller for solar air conditioning systems design and field test

NASA Astrophysics Data System (ADS)

Merrick, R. H.; Murray, J. G.

1984-06-01

Design changes to improve reliability, part load performance, and manufacturability characteristics of the chiller are focused upon. Low heat flux was achieved by large transfer area allows scale formation without being a thermal barrier: 80 mils = 1 deg. The scaling rate is minimized by keeping surface temperatures below 100 F and a generous water recirculation flow rate. By integrating the cooling tower function into the chiller itself parasitic power consumption was reduced 35%. This system also provided the winter freeze protection without the specific manual shut down procedures required by separate water cooled units and their towers. The severe reduction in cumulative coefficient of performance (COP) due to cycling conditions has been substantially reduced using the spin down control scheme. The major disappointment was the failure to develop a satisfactory inexpensive protective coating. Hot dip galvanizing was demonstrated to be effective but costly, partially due to transportation expense.

The structure of evaporating and combusting sprays: Measurements and predictions

NASA Technical Reports Server (NTRS)

Shuen, J. S.; Solomon, A. S. P.; Faeth, G. M.

1982-01-01

An apparatus was constructed to provide measurements in open sprays with no zones of recirculation, in order to provide well-defined conditions for use in evaluating spray models. Measurements were completed in a gas jet, in order to test experimental methods, and are currently in progress for nonevaporating sprays. A locally homogeneous flow (LHF) model where interphase transport rates are assumed to be infinitely fast; a separated flow (SF) model which allows for finite interphase transport rates but neglects effects of turbulent fluctuations on drop motion; and a stochastic SF model which considers effects of turbulent fluctuations on drop motion were evaluated using existing data on particle-laden jets. The LHF model generally overestimates rates of particle dispersion while the SF model underestimates dispersion rates. The stochastic SF flow yield satisfactory predictions except at high particle mass loadings where effects of turbulence modulation may have caused the model to overestimate turbulence levels.

Nitrogen oxides emissions from the MILD combustion with the conditions of recirculation gas.

PubMed

Park, Min; Shim, Sung Hoon; Jeong, Sang Hyun; Oh, Kwang-Joong; Lee, Sang-Sup

2017-04-01

The nitrogen oxides (NO x ) reduction technology by combustion modification which has economic benefits as a method of controlling NO x emitted in the combustion process, has recently been receiving a lot of attention. Especially, the moderate or intense low oxygen dilution (MILD) combustion which applied high temperature flue gas recirculation has been confirmed for its effectiveness with regard to solid fuel as well. MILD combustion is affected by the flue gas recirculation ratio and the composition of recirculation gas, so its NO x reduction efficiency is determined by them. In order to investigate the influence of factors which determine the reduction efficiency of NO x in MILD coal combustion, this study changed the flow rate and concentration of nitrogen (N 2 ), carbon dioxide (CO 2 ) and steam (H 2 O) which simulate the recirculation gas during the MILD coal combustion using our lab-scale drop tube furnace and performed the combustion experiment. As a result, its influence by the composition of recirculation gas was insignificant and it was shown that flue gas recirculation ratio influences the change of NO x concentration greatly. We investigated the influence of factors determining the nitrogen oxides (NO x ) reduction efficiency in MILD coal combustion, which applied high-temperature flue gas recirculation. Using a lab-scale drop tube furnace and simulated recirculation gas, we conducted combustion testing changing the recirculation gas conditions. We found that the flue gas recirculation ratio influences the reduction of NO x emissions the most.

Exhaust gas recirculation system for an internal combustion engine

DOEpatents

Wu, Ko-Jen

2013-05-21

An exhaust gas recirculation system for an internal combustion engine comprises an exhaust driven turbocharger having a low pressure turbine outlet in fluid communication with an exhaust gas conduit. The turbocharger also includes a low pressure compressor intake and a high pressure compressor outlet in communication with an intake air conduit. An exhaust gas recirculation conduit fluidly communicates with the exhaust gas conduit to divert a portion of exhaust gas to a low pressure exhaust gas recirculation branch extending between the exhaust gas recirculation conduit and an engine intake system for delivery of exhaust gas thereto. A high pressure exhaust gas recirculation branch extends between the exhaust gas recirculation conduit and the compressor intake and delivers exhaust gas to the compressor for mixing with a compressed intake charge for delivery to the intake system.

Effect of integrating straw into agricultural soils on soil infiltration and evaporation.

PubMed

Cao, Jiansheng; Liu, Changming; Zhang, Wanjun; Guo, Yunlong

2012-01-01

Soil water movement is a critical consideration for crop yield in straw-integrated fields. This study used an indoor soil column experiment to determine soil infiltration and evaporation characteristics in three forms of direct straw-integrated soils (straw mulching, straw mixing and straw inter-layering). Straw mulching is covering the land surface with straw. Straw mixing is mixing straw with the top 10 cm surface soil. Then straw inter-layering is placing straw at the 20 cm soil depth. There are generally good correlations among the mulch integration methods at p < 0.05, and with average errors/biases <10%. Straw mixing exhibited the best effect in terms of soil infiltration, followed by straw mulching. Due to over-burden weight-compaction effect, straw inter-layering somehow retarded soil infiltration. In terms of soil water evaporation, straw mulching exhibited the best effect. This was followed by straw mixing and then straw inter-layering. Straw inter-layering could have a long-lasting positive effect on soil evaporation as it limited the evaporative consumption of deep soil water. The responses of the direct straw integration modes to soil infiltration and evaporation could lay the basis for developing efficient water-conservation strategies. This is especially useful for water-scarce agricultural regions such as the arid/semi-arid regions of China.

Evaporation of LOX under supercritical and subcritical conditions

NASA Technical Reports Server (NTRS)

Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

1993-01-01

The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

Biodegradation of artificial monolayers applied to water storages to reduce evaporative loss.

PubMed

Pittaway, P; Herzig, M; Stuckey, N; Larsen, K

2015-01-01

Repeat applications of an artificial monolayer to the interfacial boundary layer of large agricultural water storages during periods of high evaporative demand remains the most commercially feasible water conservation strategy. However, the interfacial boundary layer (or microlayer) is ecologically distinct from subsurface water, and repeat monolayer applications may adversely affect microlayer processes. In this study, the natural cleansing mechanisms operating within the microlayer were investigated to compare the biodegradability of two fatty alcohol (C16OH and C18OH) and one glycol ether (C18E1) monolayer compound. The C16OH and C18OH compounds were more susceptible to microbial degradation, but the C18E1 compound was most susceptible to indirect photodegradation. On clean water the surface pressure and evaporation reduction achieved with a compressed C18E1 monolayer was superior to the C18OH monolayer, but on brown water the surface pressure dropped rapidly. These results suggest artificial monolayers are readily degraded by the synergy between photo and microbial degradation. The residence time of C18OH and C18E1 monolayers on clear water is sufficient for cost-effective water conservation. However, the susceptibility of C18E1 to photodegradation indicates the application of this monolayer to brown water may not be cost-effective.

Solar-powered turbocompressor heat pump system

DOEpatents

Landerman, A.M.; Biancardi, F.R.; Melikian, G.; Meader, M.D.; Kepler, C.E.; Anderson, T.J.; Sitler, J.W.

1982-08-12

The turbocompressor comprises a power turbine and a compressor turbine having respective rotors and on a common shaft, rotatably supported by bearings. A first working fluid is supplied by a power loop and is expanded in the turbine. A second working fluid is compressed in the turbine and is circulated in a heat pump loop. A lubricant is mixed with the second working fluid but is excluded from the first working fluid. The bearings are cooled and lubricated by a system which circulates the second working fluid and the intermixed lubricant through the bearings. Such system includes a pump, a thermostatic expansion valve for expanding the working fluid into the space between the bearings, and a return conduit system for withdrawing the expanded working fluid after it passes through the bearings and for returning the working fluid to the evaporator. A shaft seal excludes the lubricant from the power turbine. The power loop includes a float operable by liquid working fluid in the condenser for controlling a recirculation valve so as to maintain a minimum liquid level in the condenser, while causing a feed pump to pump most of the working fluid into the vapor generator. The heat pump compressor loop includes a float in the condenser for operating and expansion valve to maintain a minimum liquid working fluid level in the condenser while causing most of the working fluid to be expanded into the evaporator.

Utilization of municipal wastewater for cooling in thermoelectric power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safari, Iman; Walker, Michael E.; Hsieh, Ming-Kai

2013-09-01

A process simulation model has been developed using Aspen Plus® with the OLI (OLI System, Inc.) water chemistry model to predict water quality in the recirculating cooling loop utilizing secondary- and tertiary-treated municipal wastewater as the source of makeup water. Simulation results were compared with pilot-scale experimental data on makeup water alkalinity, loop pH, and ammonia evaporation. The effects of various parameters including makeup water quality, salt formation, NH 3 and CO 2 evaporation mass transfer coefficients, heat load, and operating temperatures were investigated. The results indicate that, although the simulation model can capture the general trends in the loopmore » pH, experimental data on the rates of salt precipitation in the system are needed for more accurate prediction of the loop pH. It was also found that stripping of ammonia and carbon dioxide in the cooling tower can influence the cooling loop pH significantly. The effects of the NH 3 mass transfer coefficient on cooling loop pH appear to be more significant at lower values (e.g., k NH3 < 4×10 -3 m/s) when the makeup water alkalinity is low (e.g., <90 mg/L as CaCO 3). The effect of the CO2 mass transfer coefficient was found to be significant only at lower alkalinity values (e.g., k CO2<4×10 -6 m/s).« less

21 CFR 880.5045 - Medical recirculating air cleaner.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Medical recirculating air cleaner. 880.5045... Therapeutic Devices § 880.5045 Medical recirculating air cleaner. (a) Identification. A medical recirculating air cleaner is a device used to remove particles from the air for medical purposes. The device may...

21 CFR 880.5045 - Medical recirculating air cleaner.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Medical recirculating air cleaner. 880.5045... Therapeutic Devices § 880.5045 Medical recirculating air cleaner. (a) Identification. A medical recirculating air cleaner is a device used to remove particles from the air for medical purposes. The device may...

21 CFR 880.5045 - Medical recirculating air cleaner.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Medical recirculating air cleaner. 880.5045... Therapeutic Devices § 880.5045 Medical recirculating air cleaner. (a) Identification. A medical recirculating air cleaner is a device used to remove particles from the air for medical purposes. The device may...

21 CFR 880.5045 - Medical recirculating air cleaner.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Medical recirculating air cleaner. 880.5045 Section 880.5045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Therapeutic Devices § 880.5045 Medical recirculating air cleaner. (a) Identification. A medical recirculating...

21 CFR 880.5045 - Medical recirculating air cleaner.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Medical recirculating air cleaner. 880.5045 Section 880.5045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Therapeutic Devices § 880.5045 Medical recirculating air cleaner. (a) Identification. A medical recirculating...

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface.

PubMed

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account.

Study of the effect of wind speed on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface

PubMed Central

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa

2014-01-01

In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of wind speed on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a wind tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high wind speeds the evaporation rate becomes less dependent on the wind speed. On the contrary, the impact of wind speed on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account. PMID:25309005

Smoothed particle hydrodynamics method for evaporating multiphase flows.

PubMed

Yang, Xiufeng; Kong, Song-Charng

2017-09-01

The smoothed particle hydrodynamics (SPH) method has been increasingly used for simulating fluid flows; however, its ability to simulate evaporating flow requires significant improvements. This paper proposes an SPH method for evaporating multiphase flows. The present SPH method can simulate the heat and mass transfers across the liquid-gas interfaces. The conservation equations of mass, momentum, and energy were reformulated based on SPH, then were used to govern the fluid flow and heat transfer in both the liquid and gas phases. The continuity equation of the vapor species was employed to simulate the vapor mass fraction in the gas phase. The vapor mass fraction at the interface was predicted by the Clausius-Clapeyron correlation. An evaporation rate was derived to predict the mass transfer from the liquid phase to the gas phase at the interface. Because of the mass transfer across the liquid-gas interface, the mass of an SPH particle was allowed to change. Alternative particle splitting and merging techniques were developed to avoid large mass difference between SPH particles of the same phase. The proposed method was tested by simulating three problems, including the Stefan problem, evaporation of a static drop, and evaporation of a drop impacting a hot surface. For the Stefan problem, the SPH results of the evaporation rate at the interface agreed well with the analytical solution. For drop evaporation, the SPH result was compared with the result predicted by a level-set method from the literature. In the case of drop impact on a hot surface, the evolution of the shape of the drop, temperature, and vapor mass fraction were predicted.

Closed recirculating system for shrimp-mollusk polyculture

NASA Astrophysics Data System (ADS)

Wu, Xiongfei; Zhao, Zhidong; Li, Deshang; Chang, Kangmei; Tong, Zhuanshang; Si, Liegang; Xu, Kaichong; Ge, Bailin

2005-12-01

This paper deals with a new system of aquaculture, i.e., a closed recirculating system for shrimp-mollusk polyculture. The culture system consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir. During the production cycle, water circulated between the shrimp and mollusk ponds, and the reservoir compensated for water loss from seepage and evaporation. Constricted tagelus, Sinonovacula constricta, was selected as the cultured mollusk, and Pacific white shrimp, Litopenaeus vannamei, as the cultured shrimp. The main managing measures during the production cycle were: setting and using the aerators; introducting the probiotic products timely into the shrimp ponds; adopting a “pen-closing” method for controlling shrimp viral epidemics; setting the flow diversion barriers in the mollusk pond to keep the circulating water flowing through the pond along a sine-like curve and serve as substrate for biofilm; no direct feeding was necessary for the cultured mollusk until the co-cultured shrimp was harvested; natural foods in the water from the shrimp ponds was used for their foods. Two sets of the system were used in the experiment in 2002 and satisfactory results were achieved. The average yield of the shrimp was 11 943.5 kg/hm2, and that of the mollusk was 16 965 kg/hm2. After converting the mollusk yield into shrimp yield at their market price ratio, the food coefficient of the entire system averaged at as low as 0.81. The water quality in the ponds was maintained at a desirable level and no viral epidemics were discovered during the production cycle.

Black hole evaporation rates without spacetime.

PubMed

Braunstein, Samuel L; Patra, Manas K

2011-08-12

Verlinde recently suggested that gravity, inertia, and even spacetime may be emergent properties of an underlying thermodynamic theory. This vision was motivated in part by Jacobson's 1995 surprise result that the Einstein equations of gravity follow from the thermodynamic properties of event horizons. Taking a first tentative step in such a program, we derive the evaporation rate (or radiation spectrum) from black hole event horizons in a spacetime-free manner. Our result relies on a Hilbert space description of black hole evaporation, symmetries therein which follow from the inherent high dimensionality of black holes, global conservation of the no-hair quantities, and the existence of Penrose processes. Our analysis is not wedded to standard general relativity and so should apply to extended gravity theories where we find that the black hole area must be replaced by some other property in any generalized area theorem.

Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium.

PubMed

Fernandes, Sheryl Oliveira; Bonin, Patricia C; Michotey, Valérie D; Garcia, Nicole; LokaBharathi, P A

2012-01-01

Earlier observations in mangrove sediments of Goa, India have shown denitrification to be a major pathway for N loss. However, percentage of total nitrate transformed through complete denitrification accounted for <0-72% of the pore water nitrate reduced. Here, we show that up to 99% of nitrate removal in mangrove sediments is routed through dissimilatory nitrate reduction to ammonium (DNRA). The DNRA process was 2x higher at the relatively pristine site Tuvem compared to the anthropogenically-influenced Divar mangrove ecosystem. In systems receiving low extraneous nutrient inputs, this mechanism effectively conserves and re-circulates N minimizing nutrient loss that would otherwise occur through denitrification. In a global context, the occurrence of DNRA in mangroves has important implications for maintaining N levels and sustaining ecosystem productivity. For the first time, this study also highlights the significance of DNRA in buffering the climate by modulating the production of the greenhouse gas nitrous oxide.

High ratio recirculating gas compressor

DOEpatents

Weinbrecht, J.F.

1989-08-22

A high ratio positive displacement recirculating rotary compressor is disclosed. The compressor includes an integral heat exchanger and recirculation conduits for returning cooled, high pressure discharge gas to the compressor housing to reducing heating of the compressor and enable higher pressure ratios to be sustained. The compressor features a recirculation system which results in continuous and uninterrupted flow of recirculation gas to the compressor with no direct leakage to either the discharge port or the intake port of the compressor, resulting in a capability of higher sustained pressure ratios without overheating of the compressor. 10 figs.

Soft black hole absorption rates as conservation laws

DOE PAGES

Avery, Steven G.; Schwab, Burkhard U. W.

2017-04-10

The absorption rate of low-energy, or soft, electromagnetic radiation by spherically symmetric black holes in arbitrary dimensions is shown to be fixed by conservation of energy and large gauge transformations. Here, we interpret this result as the explicit realization of the Hawking-Perry-Strominger Ward identity for large gauge transformations in the background of a non-evaporating black hole. Along the way we rederive and extend our previous analytic results regarding the absorption rate for the minimal scalar and the photon.

Soft black hole absorption rates as conservation laws

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avery, Steven G.; Schwab, Burkhard U. W.

The absorption rate of low-energy, or soft, electromagnetic radiation by spherically symmetric black holes in arbitrary dimensions is shown to be fixed by conservation of energy and large gauge transformations. Here, we interpret this result as the explicit realization of the Hawking-Perry-Strominger Ward identity for large gauge transformations in the background of a non-evaporating black hole. Along the way we rederive and extend our previous analytic results regarding the absorption rate for the minimal scalar and the photon.

A two-scale model of radio-frequency electrosurgical tissue ablation

NASA Astrophysics Data System (ADS)

Karaki, Wafaa; Rahul; Lopez, Carlos A.; Borca-Tasciuc, Diana-Andra; De, Suvranu

2017-12-01

Radio-frequency electrosurgical procedures are widely used to simultaneously dissect and coagulate tissue. Experiments suggest that evaporation of cellular and intra-cellular water plays a significant role in the evolution of the temperature field at the tissue level, which is not adequately captured in a single scale energy balance equation. Here, we propose a two-scale model to study the effects of microscale phase change and heat dissipation in response to radiofrequency heating on the tissue level in electrosurgical ablation procedures. At the microscale, the conservation of mass along with thermodynamic and mechanical equilibrium is applied to obtain an equation-of-state relating vapor mass fraction to temperature and pressure. The evaporation losses are incorporated in the macro-level energy conservation and results are validated with mean experimental temperature distributions measured from electrosurgical ablation testing on ex vivo porcine liver at different power settings of the electrosurgical instrument. Model prediction of water loss and its effect on the temperature along with the effect of the mechanical properties on results are evaluated and discussed.

Towards a sharp-interface volume-of-fluid methodology for modeling evaporation

NASA Astrophysics Data System (ADS)

Pathak, Ashish; Raessi, Mehdi

2017-11-01

In modeling evaporation, the diffuse-interface (one-domain) formulation yields inaccurate results. Recent efforts approaching the problem via a sharp-interface (two-domain) formulation have shown significant improvements. The reasons behind their better performance are discussed in the present work. All available sharp-interface methods, however, exclusively employ the level-set. In the present work, we develop a sharp-interface evaporation model in a volume-of-fluid (VOF) framework in order to leverage its mass-conserving property as well as its ability to handle large topographical changes. We start with a critical review of the assumptions underlying the mathematical equations governing evaporation. For example, it is shown that the assumption of incompressibility can only be applied in special circumstances. The famous D2 law used for benchmarking is valid exclusively to steady-state test problems. Transient is present over significant lifetime of a micron-size droplet. Therefore, a 1D spherical fully transient model is developed to provide a benchmark transient solution. Finally, a 3D Cartesian Navier-Stokes evaporation solver is developed. Some preliminary validation test-cases are presented for static and moving drop evaporation. This material is based upon work supported by the Department of Energy, Office of Energy Efficiency and Renewable Energy and the Department of Defense, Tank and Automotive Research, Development, and Engineering Center, under Award Number DEEE0007292.

Coastal recirculation potential affecting air pollutants in Portugal: The role of circulation weather types

NASA Astrophysics Data System (ADS)

Russo, Ana; Gouveia, Célia; Levy, Ilan; Dayan, Uri; Jerez, Sonia; Mendes, Manuel; Trigo, Ricardo

2016-06-01

Coastal zones are under increasing development and experience air pollution episodes regularly. These episodes are often related to peaks in local emissions from industry or transportation, but can also be associated with regional transport from neighbour urban areas influenced by land-sea breeze recirculation. This study intends to analyze the relation between circulation weather patterns, air mass recirculation and pollution levels in three coastal airsheds of Portugal (Lisbon, Porto and Sines) based on the application of an objective quantitative measure of potential recirculation. Although ventilation events have a dominant presence throughout the studied 9-yrs period on all the three airsheds, recirculation and stagnation conditions occur frequently. The association between NO2, SO2 and O3 levels and recirculation potential is evident during summer months. Under high average recirculation potential and high variability, NO2 and SO2 levels are higher for the three airsheds, whilst for O3 each airshed responds differently. This indicates a high heterogeneity among the three airsheds in (1) the type of emission - traffic or industry - prevailing for each contaminant, and (2) the response to the various circulation weather patterns and recirculation situations. Irrespectively of that, the proposed methodology, based on iterative K-means clustering, allows to identify which prevailing patterns are associated with high recirculation potential, having the advantage of being applicable to any geographical location.

Recirculating Air Filtration Significantly Reduces Exposure to Airborne Nanoparticles

PubMed Central

Pui, David Y.H.; Qi, Chaolong; Stanley, Nick; Oberdörster, Günter; Maynard, Andrew

2008-01-01

Background Airborne nanoparticles from vehicle emissions have been associated with adverse effects in people with pulmonary and cardiovascular disease, and toxicologic studies have shown that nanoparticles can be more hazardous than their larger-scale counterparts. Recirculating air filtration in automobiles and houses may provide a low-cost solution to reducing exposures in many cases, thus reducing possible health risks. Objectives We investigated the effectiveness of recirculating air filtration on reducing exposure to incidental and intentionally produced airborne nanoparticles under two scenarios while driving in traffic, and while generating nanomaterials using gas-phase synthesis. Methods We tested the recirculating air filtration in two commercial vehicles when driving in traffic, as well as in a nonventilation room with a nanoparticle generator, simulating a nanomaterial production facility. We also measured the time-resolved aerosol size distribution during the in-car recirculation to investigate how recirculating air filtration affects particles of different sizes. We developed a recirculation model to describe the aerosol concentration change during recirculation. Results The use of inexpensive, low-efficiency filters in recirculation systems is shown to reduce nanoparticle concentrations to below levels found in a typical office within 3 min while driving through heavy traffic, and within 20 min in a simulated nanomaterial production facility. Conclusions Development and application of this technology could lead to significant reductions in airborne nanoparticle exposure, reducing possible risks to health and providing solutions for generating nanomaterials safely. PMID:18629306

Simplified liquid oxygen propellant conditioning concepts

NASA Technical Reports Server (NTRS)

Cleary, N. L.; Holt, K. A.; Flachbart, R. H.

1995-01-01

Current liquid oxygen feed systems waste propellant and use hardware, unnecessary during flight, to condition the propellant at the engine turbopumps prior to launch. Simplified liquid oxygen propellant conditioning concepts are being sought for future launch vehicles. During a joint program, four alternative propellant conditioning options were studied: (1) passive recirculation; (2) low bleed through the engine; (3) recirculation lines; and (4) helium bubbling. The test configuration for this program was based on a vehicle design which used a main recirculation loop that was insulated on the downcomer and uninsulated on the upcomer. This produces a natural convection recirculation flow. The test article for this program simulated a feedline which ran from the main recirculation loop to the turbopump. The objective was to measure the temperature profile of this test article. Several parameters were varied from the baseline case to determine their effects on the temperature profile. These parameters included: flow configuration, feedline slope, heat flux, main recirculation loop velocity, pressure, bleed rate, helium bubbling, and recirculation lines. The heat flux, bleed rate, and recirculation configurations produced the greatest changes from the baseline temperature profile. However, the temperatures in the feedline remained subcooled. Any of the options studied could be used in future vehicles.

Recirculation of the Canary Current in fall 2014

NASA Astrophysics Data System (ADS)

Hernández-Guerra, Alonso; Espino-Falcón, Elisabet; Vélez-Belchí, Pedro; Dolores Pérez-Hernández, M.; Martínez-Marrero, Antonio; Cana, Luis

2017-10-01

Hydrographic measurements together with Ship mounted Acoustic Doppler Current Profilers and Lowered Acoustic Doppler Current Profilers (LADCP) obtained in October 2014 are used to describe water masses, geostrophic circulation and mass transport of the Canary Current System, as the Eastern Boundary of the North Atlantic Subtropical Gyre. Geostrophic velocities are adjusted to velocities from LADCP data to estimate an initial velocity at the reference layer. The adjustment results in a northward circulation at the thermocline layers over the African slope from an initial convergent flow. Final reference velocities and consequently absolute circulation are estimated from an inverse box model applied to an ocean divided into 13 neutral density layers. This allows us to evaluate mass fluxes consistent with the thermal wind equation and mass conservation. Ekman transport is estimated from the wind data derived from the Weather Research and Forecasting model. Ekman transport is added to the first layer and adjusted with the inverse model. The Canary Current located west of Lanzarote Island transports to the south a mass of - 1.5 ± 0.7 Sv (1 Sv = 106 m3 s- 1 ≈ 109 kg s- 1) of North Atlantic Central Water at the surface and thermocline layers ( 0-700 m). In fall 2014, hydrographic data shows that the Canary Current in the thermocline (below at about 80 m depth to 700 m) recirculates to the north over the African slope and flows through the Lanzarote Passage. At intermediate layers ( 700-1400 m), the Intermediate Poleward Undercurrent transports northward a relatively fresh Antarctic Intermediate Water in the range of 0.8 ± 0.4 Sv through the Lanzarote Passage and west of Lanzarote Island beneath the recirculation of the Canary Current.

Implementation of rooftop reciculation parameterization into the QUIC fast response urban wind model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagal, N.; Singh, B.; Pardyjak, E. R.

2004-01-01

The QUIC (Quick Urban & Industrial Complex) dispersion modeling system has been developed to provide high-resolution wind and concentration fields in cities. The fast response 3D urban wind model QUIC-URB explicitly solves for the flow field around buildings using a suite of empirical parameterizations and mass conservation. This procedure is based on the work of Rockle (1990). The current Rockle (1990) model does not capture the rooftop recirculation region associated with flow separation from the leading edge of an isolated building. According to Banks et al. (2001), there are two forms of separation depending on the incident wind angle. Formore » an incident wind angle within 20{sup o} of perpendicular to the front face of the building, 'bubble separation' occurs in which cylindrical vortices whose axis are orthogonal to the flow are generated along the rooftop surface (see Fig. 1). For a 'corner wind' flow or incident wind angle of 30{sup o} to 70{sup o} of perpendicular to the front face of the building, 'conical' or 'delta wing' vortices form along the roof surface (Fig. 3). In this work, a model for rooftop recirculation is implemented into the QUIC- URB model for the two incident wind angle regimes described above. The parameterizations for the length and height of the recirculation region are from Wilson (1979) for the case of flow perpendicular or near perpendicular to the building and from Banks et al. (2000) for the case of off-angle flow. In this paper, we describe the rooftop algorithms and show how the model results are improved through comparisons to experimental data (Snyder and Lawson 1994).« less

Comparison of recirculation configurations for biological nutrient removal in a membrane bioreactor.

PubMed

Bekir Ersu, Cagatayhan; Ong, Say Kee; Arslankaya, Ertan; Brown, Patrick

2008-03-01

A 12-L lab-scale membrane bioreactor (MBR), consisting of an anaerobic and anoxic compartment followed by an oxic plate-frame membrane compartment, was evaluated for carbonaceous and nutrient removals by varying the recirculation of mixed liquor and permeate. The hydraulic retention times (HRTs) for the anaerobic, anoxic, and oxic compartments were 2, 2, and 8h, respectively. The solids residence time (SRT) for the oxic compartment was 25 days. Five different recirculation configurations were tested by recirculating mixed liquor and/or permeate recirculation equal to the influent flow rate (identified as 100%) into different locations of the anaerobic and anoxic compartments. Of the five configurations, the configuration with 100% mixed liquor recirculation to the anaerobic compartment and 100% permeate recirculation to the anoxic compartment gave the highest percentage removal with an average 92.3+/-0.5% soluble chemical oxygen demand (sCOD), 75.6+/-0.4% total nitrogen (TN), and 62.4+/-1.3% total phosphorus (TP) removal. When the mixed liquor and permeate recirculation rates were varied for the same configuration, the highest TP removal was obtained for 300% mixed liquor recirculation and 100% permeate recirculation (300%/100%) with a TP removal of 88.1+/-1.3% while the highest TN removal (90.3+/-0.3%) was obtained for 200%/300% recirculation. TN and TP concentrations as low as 4.2+/-0.1 and 1.4+/-0.2mg/L respectively were obtained. Mass loading rates were generally low in the range of 0.11-0.22kgCOD/kgMLSS/d due to high biomass concentrations within the oxic reactor (approx. 8000mg/L). The BioWin model was calibrated against one set of the experimental data and was found to predict the experimental data of effluent TN, TP, and NO(3)(-)-N but over-predicted sCOD and NH(3)-N for various recirculation rates. The anoxic heterotrophic yield for the calibrated model was 0.2kg biomass COD/kg COD utilized while the maximum growth rates were found to be 0.45day(-1) for mu(max-autotroph), 3.2day(-1) for mu(max-heterotroph), and 1.5day(-1) for mu(max-PAO).

A comparison of precision mobile drip irrigation, LESA and LEPA

USDA-ARS?s Scientific Manuscript database

Precision mobile drip irrigation (PMDI) is a surface drip irrigation system fitted onto moving sprinkler systems that applies water through the driplines as they are dragged across the field. This application method can conserve water by limiting runoff, and reducing evaporative losses since the wat...

Behavior of sulfur mustard in sand, concrete, and asphalt matrices: Evaporation, degradation, and decontamination.

PubMed

Jung, Hyunsook; Choi, Seungki

2017-10-15

The evaporation, degradation, and decontamination of sulfur mustard on environmental matrices including sand, concrete, and asphalt are described. A specially designed wind tunnel and thermal desorber in combination with gas chromatograph (GC) produced profiles of vapor concentration obtained from samples of the chemical agent deposited as a drop on the surfaces of the matrices. The matrices were exposed to the chemical agent at room temperature, and the degradation reactions were monitored and characterized. A vapor emission test was also performed after a decontamination process. The results showed that on sand, the drop of agent spread laterally while evaporating. On concrete, the drop of the agent was absorbed immediately into the matrix while spreading and evaporating. However, the asphalt surface conserved the agent and slowly released parts of the agent over an extended period of time. The degradation reactions of the agent followed pseudo first order behavior on the matrices. Trace amounts of the residual agent present at the surface were also released as vapor after decontamination, posing a threat to the exposed individual and environment.

Design and performance considerations of evaporative-pad, waste-heat greenhouses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olszewski, M.

1978-01-01

Rising fuel costs and limited fuel availability have forced greenhouse operators to seek alternative means of heating their greenhouses in an effort to reduce production costs and conserve energy. One such alternative uses power plant reject heat, which is contained in the condenser cooling water, and a bank of evaporative pads to provide winter heating. The design technique used to size the evaporative pad system to meet both summer cooling and winter heating demands is described. Additionally, a computational scheme that simulates the system performance is presented. This analytical model is used to determine the greenhouse operating conditions that maintainmore » the vegetation in its thermal comfort zone. The evaporative pad model uses the Merkel total heat approximation and an experimentally derived transfer coefficient. Energy balance considerations on the vegetation provide a means of viewing optimal vegetation growth in terms of greenhouse environmental factors. In general, the results indicate that the vegetation can be maintained within its thermal comfort zone if sufficient warm water is available to the pads and the air stream flow is properly adjusted.« less

A comprehensive analysis of the evaporation of a liquid spherical drop.

PubMed

Sobac, B; Talbot, P; Haut, B; Rednikov, A; Colinet, P

2015-01-15

In this paper, a new comprehensive analysis of a suspended drop of a pure liquid evaporating into air is presented. Based on mass and energy conservation equations, a quasi-steady model is developed including diffusive and convective transports, and considering the non-isothermia of the gas phase. The main original feature of this simple analytical model lies in the consideration of the local dependence of the physico-chemical properties of the gas on the gas temperature, which has a significant influence on the evaporation process at high temperatures. The influence of the atmospheric conditions on the interfacial evaporation flux, molar fraction and temperature is investigated. Simplified versions of the model are developed to highlight the key mechanisms governing the evaporation process. For the conditions considered in this work, the convective transport appears to be opposed to the evaporation process leading to a decrease of the evaporation flux. However, this effect is relatively limited, the Péclet numbers happening to be small. In addition, the gas isothermia assumption never appears to be valid here, even at room temperature, due to the large temperature gradient that develops in the gas phase. These two conclusions are explained by the fact that heat transfer from the gas to the liquid appears to be the step limiting the evaporation process. Regardless of the complexity of the developed model, yet excluding extremely small droplets, the square of the drop radius decreases linearly over time (R(2) law). The assumptions of the model are rigorously discussed and general criteria are established, independently of the liquid-gas couple considered. Copyright © 2014 Elsevier Inc. All rights reserved.

Computing Evaporation Using Meteorological Data for Hydrological Budget of Lake Wapalanne in NJ School of Conservation

NASA Astrophysics Data System (ADS)

Jordan, J. J.; Barrett, K. R.; Galster, J. C.; Ophori, D. U.; Flores, D.; Kelly, S. A.; Lutey, A. M.

2011-12-01

Lake Wapalanne is small manmade lake about 5.4 hectares in northwest New Jersey in the Highlands Physiographic province within permanently protected land. The lake's surrounding area consists of forested vegetation and is relatively unoccupied which minimizes human influence. The lake's small size, minimal external influence, geographic isolation, and protected status provide an optimal research environment to record meteorological data used in calculation of potential evaporation. Between July 7h and August 3rd meteorological data was collected from a professional weather station placed on an island directly in the center of Lake Wapalanne. The Vantage Pro2 weather station provided accurate readings of temperate, humidity, wind-speed and direction, precipitation, and atmospheric pressure. A bathometric survey of the lake was conducted to determine the surface area with variations in depth of the lake's water level. Using the collected weather station data, a rate of potential evaporation was determined with several evaporation equations. A quantified volume was then derived from the rate and surface area of the lake. Using small scale evaporation measurements of known volumes of water within small pans placed in the lake water and National Oceanic and Atmospheric Administration evaporation stations near the experiment site, a comparison and validation of the calculated potential evaporation accuracy and regional evaporation is achieved. This three year study is part of an ongoing NSF Research Experience for Undergraduates (REU) project that encompasses additional topics of lake research; see abstract from Kelly et al. AGU 2011 for more information on the lake's hydrologic budget. The results and methods of this study will be of use in future forecasting and baseline measurements of hydrologic budgets for lakes and reservoirs within regional proximity, which provide drinking water to over five million people in the State of New Jersey.

Sulfur recirculation for increased electricity production in Waste-to-Energy plants.

PubMed

Andersson, Sven; Blomqvist, Evalena W; Bäfver, Linda; Jones, Frida; Davidsson, Kent; Froitzheim, Jan; Karlsson, Martin; Larsson, Erik; Liske, Jesper

2014-01-01

Sulfur recirculation is a new technology for reducing boiler corrosion and dioxin formation. It was demonstrated in full-scale tests at a Waste to Energy plant in Göteborg (Sweden) during nearly two months of operation. Sulfur was recirculated as sulfuric acid from the flue gas cleaning back to the boiler, thus creating a sulfur loop. The new technology was evaluated by extensive measurement campaigns during operation under normal conditions (reference case) and operation with sulfur recirculation. The chlorine content of both fly ash and boiler ash decreased and the sulfur content increased during the sulfur recirculation tests. The deposit growth and the particle concentration decreased with sulfur recirculation and the dioxin concentration (I-TEQ) of the flue gas was reduced by approximately 25%. Sulfuric acid dew point measurements showed that the sulfuric acid dosage did not lead to elevated SO3 concentrations, which may otherwise induce low temperature corrosion. In the sulfur recirculation corrosion probe exposures, the corrosion rate decreased for all tested materials (16Mo3, Sanicro 28 and Inconel 625) and material temperatures (450 °C and 525 °C) compared to the reference exposure. The corrosion rates were reduced by 60-90%. Sulfur recirculation prevented the formation of transition metal chlorides at the metal/oxide interface, formation of chromate and reduced the presence of zinc in the corrosion products. Furthermore, measured corrosion rates at 525 °C with sulfur recirculation in operation were similar or lower compared to those measured at 450 °C material temperature in reference conditions, which corresponds to normal operation at normal steam temperatures. This implies that sulfur recirculation allows for higher steam data and electricity production without increasing corrosion. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Calculation of recirculating flow behind flame-holders

NASA Astrophysics Data System (ADS)

Zeng, Q.; Sheng, Y.; Zhou, Q.

1985-10-01

Adoptability of standard K-epsilon turbulence model for numerical calculation of recirculating flow is discussed. Many computations of recirculating flows behind bluff-bodies used as flame-holders in afterburner of aeroengine have been completed. Blocking-off method to treat the incline walls of the flame-holder gives good results. In isothermal recirculating flows the flame-holder wall is assumed to be isolated. Therefore, it is possible to remove the inactive zone from the calculation domain in programming to save computer time. The computation for a V-shaped flame-holder exhibits an interesting phenomenon that the recirculation zone extends to the cavity of the flame-holder.

Anolyte recirculation effects in buffered and unbuffered single-chamber air-cathode microbial fuel cells.

PubMed

Zhang, Liang; Zhu, Xun; Kashima, Hiroyuki; Li, Jun; Ye, Ding-Ding; Liao, Qiang; Regan, John M

2015-03-01

Two identical microbial fuel cells (MFCs) with a floating air-cathode were operated under either buffered (MFC-B) or bufferless (MFC-BL) conditions to investigate anolyte recirculation effects on enhancing proton transfer. With an external resistance of 50 Ω and recirculation rate of 1.0 ml/min, MFC-BL had a 27% lower voltage (9.7% lower maximal power density) but a 64% higher Coulombic efficiency (CE) than MFC-B. MFC-B had a decreased voltage output, batch time, and CE with increasing recirculation rate resulting from more oxygen transfer into the anode. However, increasing the recirculation rate within a low range significantly enhanced proton transfer in MFC-BL, resulting in a higher voltage output, a longer batch time, and a higher CE. A further increase in recirculation rate decreased the batch time and CE of MFC-BL due to excess oxygen transfer into anode outweighing the proton-transfer benefits. The unbuffered MFC had an optimal recirculation rate of 0.35 ml/min. Copyright © 2014 Elsevier Ltd. All rights reserved.

The future of irrigation on the U.S. Great Plains

USDA-ARS?s Scientific Manuscript database

In the Great Plains, soil and water conservation is being achieved in both dryland and irrigated agricultural systems, and increasingly in combinations of these systems. Limiting tillage has increased the retention of crop residues on the surface and has reduced the evaporative loss of water, making...

Stirling Engine External Heat System Design with Heat Pipe Heater.

DTIC Science & Technology

1986-07-01

Figure 10. However, the evaporator analysis is greatly simplified by making the conservative assumption of constant heat flux. This assumption results in...number Cold Start Data * " ROM density of the metal, gr/cm 3 CAPM specific heat of the metal, cal./gr. K ETHG effective gauze thickness: the

Evaporator Development for an Evaporative Heat Pipe System

NASA Technical Reports Server (NTRS)

Peters, Leigh C.

2004-01-01

As fossil fuel resources continue to deplete, research for alternate power sources continues to develop. One of these alternate technologies is fuel cells. They are a practical fuel source able to provide significant amounts of power for applications from laptops to automobiles and their only byproduct is water. However, although this technology is over a century old and NASA has been working with it since the early 1960 s there is still room for improvement. The research I am involved in at NASA's Glenn Research Center is focusing on what is called a regenerative fuel cell system. The unique characteristic of this type of system is that it used an outside power source to create electrolysis of the water it produces and it then reuses the hydrogen and oxygen to continue producing power. The advantage of this type of system is that, for example, on space missions it can use solar power to recharge its gas supplies between periods when the object being orbited blocks out the sun. This particular system however is far from completion. This is because of the many components that are required to make up a fuel cell that need to be tested individually. The specific part of the system that is being worked on this summer of 2004 is the cooling system. The fuel cell stack, that is the part that actually creates the power, also produces a lot of heat. When not properly cooled, it has been known to cause fires which, needless to say are not conducive to the type of power that is trying to be created. In order to cool the fuel cell stack in this system we are developing a heat pipe cooling system. One of the main components of a heat pipe cooling system is what is known as the evaporator, and that is what happens to be the part of the system we are developing this summer. In most heat pipe systems the evaporator is a tube in which the working fluid is cooled and then re-circulated through the system to absorb more heat energy from the fuel cell stack. For this system, instead of a tube, the evaporator is made up of a stack-up of screen material and absorbent membranes inside a stainless steel shell and held together by a film adhesive and epoxy. There is an initial design for this flat plate evaporator, however is has not yet been made. The components of the stack-up are known, so all testing is focused on how it will all go together. This includes finding an appropriate epoxy to make the evaporator conductive all the way through and finding a way to hold the required tight tolerances as the stainless steel outer shell is put together. By doing the tests on smaller samples of the stack-ups and then testing the fill size component, the final flat plate evaporator will reach its final design so that research can continue on other parts of the regenerative fue1 cell system, and another step in the improvement of fue1 cell technology can be made.

A remote sensing method for estimating regional reservoir area and evaporative loss

NASA Astrophysics Data System (ADS)

Zhang, Hua; Gorelick, Steven M.; Zimba, Paul V.; Zhang, Xiaodong

2017-12-01

Evaporation from the water surface of a reservoir can significantly affect its function of ensuring the availability and temporal stability of water supply. Current estimations of reservoir evaporative loss are dependent on water area derived from a reservoir storage-area curve. Such curves are unavailable if the reservoir is located in a data-sparse region or questionable if long-term sedimentation has changed the original elevation-area relationship. We propose a remote sensing framework to estimate reservoir evaporative loss at the regional scale. This framework uses a multispectral water index to extract reservoir area from Landsat imagery and estimate monthly evaporation volume based on pan-derived evaporative rates. The optimal index threshold is determined based on local observations and extended to unobserved locations and periods. Built on the cloud computing capacity of the Google Earth Engine, this framework can efficiently analyze satellite images at large spatiotemporal scales, where such analysis is infeasible with a single computer. Our study involves 200 major reservoirs in Texas, captured in 17,811 Landsat images over a 32-year period. The results show that these reservoirs contribute to an annual evaporative loss of 8.0 billion cubic meters, equivalent to 20% of their total active storage or 53% of total annual water use in Texas. At five coastal basins, reservoir evaporative losses exceed the minimum freshwater inflows required to sustain ecosystem health and fishery productivity of the receiving estuaries. Reservoir evaporative loss can be significant enough to counterbalance the positive effects of impounding water and to offset the contribution of water conservation and reuse practices. Our results also reveal the spatially variable performance of the multispectral water index and indicate the limitation of using scene-level cloud cover to screen satellite images. This study demonstrates the advantage of combining satellite remote sensing and cloud computing to support regional water resources assessment.

40 CFR 98.468 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... applicable climate classification is determined based on the annual rainfall plus the recirculated leachate... [with appropriate unit conversions]. (1) Dry climate = precipitation plus recirculated leachate less than 20 inches/year. (2) Moderate climate = precipitation plus recirculated leachate from 20 to 40...

Hidden messenger revealed in Hawking radiation: A resolution to the paradox of black hole information loss

NASA Astrophysics Data System (ADS)

Zhang, Baocheng; Cai, Qing-yu; You, Li; Zhan, Ming-sheng

2009-05-01

Using standard statistical method, we discover the existence of correlations among Hawking radiations (of tunneled particles) from a black hole. The information carried by such correlations is quantified by mutual information between sequential emissions. Through a careful counting of the entropy taken out by the emitted particles, we show that the black hole radiation as tunneling is an entropy conservation process. While information is leaked out through the radiation, the total entropy is conserved. Thus, we conclude the black hole evaporation process is unitary.

Numerical analysis of biomass torrefaction reactor with recirculation of heat carrier

NASA Astrophysics Data System (ADS)

Director, L. B.; Ivanin, O. A.; Sinelshchikov, V. A.

2018-01-01

In this paper, results of numerical analysis of the energy-technological complex consisting of the gas piston power plant, the torrefaction reactor with recirculation of gaseous heat carrier and the heat recovery boiler are presented. Calculations of the reactor without recirculation and with recirculation of the heat carrier in torrefaction zone at different frequencies of unloading of torrefied biomass were held. It was shown that in recirculation mode the power of the gas piston power plant, required for providing given reactor productivity, is reduced several times and the consumption of fuel gas, needed for combustion of volatile torrefaction products in the heat recovery boiler, is reduced by an order.

Exhaust gas recirculation in a homogeneous charge compression ignition engine

DOEpatents

Duffy, Kevin P [Metamora, IL; Kieser, Andrew J [Morton, IL; Rodman, Anthony [Chillicothe, IL; Liechty, Michael P [Chillicothe, IL; Hergart, Carl-Anders [Peoria, IL; Hardy, William L [Peoria, IL

2008-05-27

A homogeneous charge compression ignition engine operates by injecting liquid fuel directly in a combustion chamber, and mixing the fuel with recirculated exhaust and fresh air through an auto ignition condition of the fuel. The engine includes at least one turbocharger for extracting energy from the engine exhaust and using that energy to boost intake pressure of recirculated exhaust gas and fresh air. Elevated proportions of exhaust gas recirculated to the engine are attained by throttling the fresh air inlet supply. These elevated exhaust gas recirculation rates allow the HCCI engine to be operated at higher speeds and loads rendering the HCCI engine a more viable alternative to a conventional diesel engine.

Flow field in the wake of a bluff body driven through a steady recirculating flow

NASA Astrophysics Data System (ADS)

Poussou, Stephane B.; Plesniak, Michael W.

2015-02-01

The wake produced by a bluff body driven through a steady recirculating flow is studied experimentally in a water facility using particle image velocimetry. The bluff body has a rectangular cross section of height, , and width, , such that the aspect ratio, AR = H/ D, is equal to 3. The motion of the bluff body is uniform and rectilinear, and corresponds to a Reynolds number based on width, Re D = 9,600. The recirculating flow is confined within a hemicylindrical enclosure and is generated by planar jets emanating from slots of width, , such that . Under these conditions, experiments are performed in a closed-loop facility that enables complete optical access to the near-wake. Velocity fields are obtained up to a distance of downstream of the moving body. Data include a selection of phase-averaged velocity fields representative of the wake for a baseline case (no recirculation) and an interaction case (with recirculation). Results indicate that the transient downwash flow typically observed in wakes behind finite bodies of small aspect ratio is significantly perturbed by the recirculating flow. The wake is displaced from the ground plane and exhibits a shorter recirculation zone downstream of the body. In summary, it was found that the interaction between a bluff body wake and a recirculating flow pattern alters profoundly the dynamics of the wake, which has implications on scalar transport in the wake.

Automation of water supply and recirculation-filtration of water at a swimming pool using Zelio PLC

NASA Astrophysics Data System (ADS)

Diniş, C. M.; Popa, G. N.; Iagăr, A.

2018-01-01

The paper proposes the use of the Zelio PLC for the automation of the water supply and recirculation-filtration system of a swimming pool. To do this, the Zelio SR3B261BD - 24V DC with 10 digital inputs (24V DC) and 10 digital outputs (relay contacts) was used. The proposed application makes the control of the water supply pumps and the water recirculation-filtration from a swimming pool. The recirculation-filtration systems for pools and swimming pools are designed to ensure water cleaning and recirculation to achieve optimum quality and lasting service life. The water filtration process is one of the important steps in water treatment in polls and swimming pools. It consists in recirculation of the entire volume of water and begins by absorbing the water in the pool by means of a pump followed by the passing of water through the filter, disinfectant and pH dosing, and reintroducing the water back into the pool or swimming pool through the discharge holes. Filters must to work 24 hours a day to remove pollutants from pools or swimming pools users. Filtration removes suspension particles with different origins. All newly built pools and swimming pools must be fitted with water recirculation systems, and existing ones will be equipped with water recirculation and water treatment systems.

Upgrade to the Birmingham Irradiation Facility

NASA Astrophysics Data System (ADS)

Dervan, P.; French, R.; Hodgson, P.; Marin-Reyes, H.; Parker, K.; Wilson, J.; Baca, M.

2015-10-01

The Birmingham Irradiation Facility was developed in 2013 at the University of Birmingham using the Medical Physics MC40 cyclotron. It can achieve High Luminosity LHC (HL-LHC) fluences of 1015 (1 MeV neutron equivalent (neq)) cm-2 in 80 s with proton beam currents of 1 μA and so can evaluate effectively the performance and durability of detector technologies and new components to be used for the HL-LHC. Irradiations of silicon sensors and passive materials can be carried out in a temperature controlled cold box which moves continuously through the homogenous beamspot. This movement is provided by a pre-configured XY-axis Cartesian robot scanning system. In 2014 the cooling system and cold box were upgraded from a recirculating glycol chiller system to a liquid nitrogen evaporative system. The new cooling system achieves a stable temperature of -50 °C in 30 min and aims to maintain sub-0 °C temperatures on the sensors during irradiations. This paper reviews the design, development, commissioning and performance of the new cooling system.

Precision control of drying using rhythmic dancing of sessile nanoparticle laden droplets

NASA Astrophysics Data System (ADS)

Sanyal, Apratim; Basu, Saptarshi; Chowdhuri, Subham; Kabi, Prasenjit; Chaudhuri, Swetaprovo

2014-04-01

This work analyses the unique spatio-temporal alteration of the deposition pattern of evaporating nanoparticle laden droplets resting on a hydrophobic surface through targeted low frequency substrate vibrations. External excitation near the lowest resonant mode (n = 2) of the droplet initially de-pins and then subsequently re-pins the droplet edge creating pseudo-hydrophilicity (low contact angle). Vibration subsequently induces droplet shape oscillations (cyclic elongation and flattening) resulting in strong flow recirculation. This strong radially outward liquid flow augments nanoparticle transport, vaporization, and agglomeration near the pinned edge resulting in much reduced drying time under certain characteristic frequency of oscillations. The resultant deposit exhibits a much flatter structure with sharp, defined peripheral wedge topology as compared to natural drying. Such controlled manipulation of transport enables tailoring of structural and topological morphology of the deposits and offers possible routes towards controlling the formation and drying timescales which are crucial for applications ranging from pharmaceutics to surface patterning.

Optimization of the Working Cycle for an Underwater Propulsion System Based on Aluminium-Water Combustion

NASA Astrophysics Data System (ADS)

Chen, Xianhe; Xia, Zhixun; Huang, Liya; Hu, Jianxin

2017-05-01

The working cycle of a novel underwater propulsion system based on aluminium combustion with water is researched in order to evaluate the best performance. The system exploits the exothermic reaction between aluminium and water which will produce high temperature, pressure steam and hydrogen mixture that can be used to drive turbine to generate power. Several new system configurations corresponding to different working cycles are investigated, and their performance parameters in terms of net power, energy density and global efficiency are discussed. The results of the system simulation show that using the recirculation steam rather than hydrogen as the carrier gas, the system net power, energy density and efficiency of the system are greatly increased compared, however the system performance is close either using adiabatic compression or isothermal compression. And if an evaporator component is added into system in order to take full use of the solid product heat, the system performance will be improved.

A Unique Facility For Metabolic and Thermoregulatory Studies

NASA Technical Reports Server (NTRS)

Williamson, Rebecca C.; Webbon, Bruce W.

1995-01-01

A unique exercise facility has been developed and used to perform tipper body ergometry tests for space applications. Originally designed to simulate the muscular, cardiovascular and thermoregulatory responses to working in zero gravity, this facility may be used to conduct basic thermoregulatory investigations applicable to multiple sclerosis patients. An environmental chamber houses the tipper body ergometer and permits control of temperature, air now and humidify. The chamber is a closed system and recirculate-s air after conditioning if. A Cybex Lipper body ergometer has been mounted horizontally on the wall of the environmental chamber. In this configuration, the subject lies underneath the arm crank on a supine seat in order to turn the crank. The supine seat can be removed in order to introduce other equipment into the chamber such as a stool to allow upright arm cranking, or a treadmill to allow walk-run experiments. Physiological and environmental signals are fed into a Strawberry Tree data acquisition system while being monitored and logged using the Workbench software program. Physiological monitoring capabilities include 3-lead EKG using an H-P patient monitor, 5 site skin temperature and core temperature using YSI thermistors, and O2 consumption and CO2 production using AMFTFK Applied Electrochemistry analyzers and sensors. This comprehensive data acquisition set tip allows for calculation of various thermoregulatory indices including heat storage, evaporative heat loss, latent heat loss, and metabolic rate. The current system is capable of adding more data acquisition channels if needed. Some potential studies that could be carried out using the facility include: 1) An investigation into the efficiency of cooling various segments of the body to lower Tc 1-2 F. 2) A series of heat and mass balance studies comparing various LCG configurations.

The impact of recirculating industrial air on aircraft painting operations.

PubMed

LaPuma, P T; Bolch, W E

1999-10-01

The 1990 Clean Air Act Amendments resulted in new environmental regulations for hazardous air pollutants. Industries such as painting facilities may have to treat large volumes of air, which increases the cost of an air control system. Recirculating a portion of the air back into the facility is an option to reduce the amount of air to be treated. The authors of this study developed a computer model written in Microsoft Excel 97 to analyze the impact of recirculation on worker safety and compliance costs. The model has a chemical database with over 1300 chemicals. The model will predict indoor air concentrations using mass balance calculations and results are compared to occupational exposure limits. A case study is performed on a C-130 aircraft painting facility at Hill Air Force Base, Utah. The model predicts strontium chromate concentrations found in primer paints will reach 1000 times the exposure limit. Strontium chromate and other solid particulates are nearly unaffected by recirculation because the air is filtered during recirculation. The next highest chemical, hexamethylene diisocyanate, increases from 2.6 to 10.5 times the exposure limit at 0 percent and 75 percent recirculation, respectively. Due to the level of respiratory protection required for the strontium chromate, workers are well protected from the modest increases in concentrations caused by recirculating 75 percent of the air. The initial cost of an air control system is $4.5 million with no recirculation and $1.8 million at 75 percent recirculation. The model is an excellent tool to evaluate air control options with a focus on worker safety. In the case study, the model highlights strontium chromate primers as good candidates for substitution. The model shows that recirculating 75 percent of the air at the Hill painting facility has a negligible impact on safety and could save $2.7 million on the initial expenses of a thermal treatment system.

Human skin is protected by four functionally and phenotypically discrete populations of resident and recirculating memory T cells

PubMed Central

Watanabe, Rei; Gehad, Ahmed; Yang, Chao; Campbell, Laura; Teague, Jessica E.; Schlapbach, Christoph; Elco, Christopher; Huang, Victor; Matos, Tiago R.; Kupper, Thomas S.; Clark, Rachael A.

2015-01-01

The skin of an adult human contains approximately 20 billion memory T cells. Epithelial barrier tissues are infiltrated by a combination of resident and recirculating T cells in mice but the relative proportions and functional activities of resident versus recirculating T cells have not been evaluated in human skin. We discriminated resident from recirculating T cells in human engrafted mice and lymphoma patients using alemtuzumab, a medication that depletes recirculating T cells from skin, and then analyzed these T cell populations in healthy human skin. All non-recirculating resident memory T cells (TRM) expressed CD69, but the majority were CD4+, CD103− and located in the dermis, in contrast to studies in mice. Both CD4+ and CD8+ CD103+ TRM were enriched in the epidermis, had potent effector functions and had a limited proliferative capacity compared to CD103− TRM. TRM of both types had more potent effector functions than recirculating T cells. Induction of CD103 on human T cells was enhanced by keratinocyte contact, depended on TGFβ and was independent of T cell keratinocyte adhesive interactions. We observed two distinct populations of recirculating T cells, CCR7+/L-selectin+ central memory T cells (TCM) and CCR7+/L-selectin− T cells, which we term migratory memory T cells (TMM). Circulating skin-tropic TMM were intermediate in cytokine production between TCM and effector memory T cells. In patients with cutaneous T cell lymphoma, malignant TCM and TMM induced distinct inflammatory skin lesions and TMM were depleted more slowly from skin after alemtuzumab, suggesting TMM may recirculate more slowly. In summary, human skin is protected by four functionally distinct populations of T cells, two resident and two recirculating, with differing territories of migration and distinct functional activities. PMID:25787765

Enhanced leachate recirculation and stabilization in a pilot landfill bioreactor in Taiwan.

PubMed

Huang, Fu-Shih; Hung, Jui-Min; Lu, Chih-Jen

2012-08-01

This study focused on the treatment of municipal solid waste (MSW) by modification and recirculation of leachate from a simulated landfill bioreactor. Hydrogen peroxide was added to recirculated leachate to maintain a constant oxygen concentration as the leachate passed again through the simulated landfill bioreactor. The results showed that leachate recirculation increased the dissolved oxygen concentration in the test landfill bioreactor. Over a period of 405 days, the biochemical oxygen demand (BOD(5)) in the collected leachate reduced by 99.7%, whereas the chemical oxygen demand (COD) reduced by 96%. The BOD(5)/COD ratio at the initial stage of 0.9 improved to 0.09 under aerobic conditions (leachate recirculation with added hydrogen peroxide) compared with the anaerobic test cell 0.11 (leachate recirculation alone without hydrogen peroxide). The pH increased from 5.5 to 7.6, and the degradation rate of organic carbon was 93%. Leachate recirculation brings about the biodegradation of MSW comparatively faster than the conventional landfill operation. The addition of a constant concentration of hydrogen peroxide was found to further increase the biodegradation. This increased biodegradation rate ultimately enables an MSW landfill to reach a stable state sooner and free up the land for further reuse.

Low-head saltwater recirculating aquaculture systems utilized for juvenile red drum production

USDA-ARS?s Scientific Manuscript database

Recirculating aquaculture systems reuse water with mechanical and biological treatment between each use and thus require wastewater treatment techniques for continuous waste removal. However, the traditional techniques and equipment utilized in recirculating aquaculture systems are expensive. The d...

Recirculating Aquaculture (4th edition)

USDA-ARS?s Scientific Manuscript database

Typically recirculating (closed) aquatic production systems have higher capital and operating costs than many of the extensive systems such as cage culture in natural waters and raceway and/or pond culture systems. However, when the control provided by recirculating systems and the benefits this env...

40 CFR 1065.127 - Exhaust gas recirculation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Exhaust gas recirculation. 1065.127 Section 1065.127 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.127 Exhaust gas recirculation. Use the...

40 CFR 1065.127 - Exhaust gas recirculation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Exhaust gas recirculation. 1065.127 Section 1065.127 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.127 Exhaust gas recirculation. Use the...

40 CFR 1065.127 - Exhaust gas recirculation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Exhaust gas recirculation. 1065.127 Section 1065.127 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.127 Exhaust gas recirculation. Use the...

40 CFR 1065.127 - Exhaust gas recirculation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Exhaust gas recirculation. 1065.127 Section 1065.127 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.127 Exhaust gas recirculation. Use the...

40 CFR 1065.127 - Exhaust gas recirculation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Exhaust gas recirculation. 1065.127 Section 1065.127 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.127 Exhaust gas recirculation. Use the...

Demonstration of Split-Flow Ventilation and Recirculation as Flow- Reduction Methods in an Air Force Paint Spray Booth. Volume 1

DTIC Science & Technology

1994-07-27

of the split-flow and recirculation modifications in typical Air Force painting operations; itwas a proof-of- concept study only. It is recognized...recirculating ventilation. 4 To Implement this flow-reduction concept , it must first be established that recirculation does not cause an accumulation of toxic...ventilation concept . The concentration gradient is determined by height and direction of paint application. If the concentration in the top portion is

Human skin is protected by four functionally and phenotypically discrete populations of resident and recirculating memory T cells.

PubMed

Watanabe, Rei; Gehad, Ahmed; Yang, Chao; Scott, Laura L; Teague, Jessica E; Schlapbach, Christoph; Elco, Christopher P; Huang, Victor; Matos, Tiago R; Kupper, Thomas S; Clark, Rachael A

2015-03-18

The skin of an adult human contains about 20 billion memory T cells. Epithelial barrier tissues are infiltrated by a combination of resident and recirculating T cells in mice, but the relative proportions and functional activities of resident versus recirculating T cells have not been evaluated in human skin. We discriminated resident from recirculating T cells in human-engrafted mice and lymphoma patients using alemtuzumab, a medication that depletes recirculating T cells from skin, and then analyzed these T cell populations in healthy human skin. All nonrecirculating resident memory T cells (TRM) expressed CD69, but most were CD4(+), CD103(-), and located in the dermis, in contrast to studies in mice. Both CD4(+) and CD8(+) CD103(+) TRM were enriched in the epidermis, had potent effector functions, and had a limited proliferative capacity compared to CD103(-) TRM. TRM of both types had more potent effector functions than recirculating T cells. We observed two distinct populations of recirculating T cells, CCR7(+)/L-selectin(+) central memory T cells (TCM) and CCR7(+)/L-selectin(-) T cells, which we term migratory memory T cells (TMM). Circulating skin-tropic TMM were intermediate in cytokine production between TCM and effector memory T cells. In patients with cutaneous T cell lymphoma, malignant TCM and TMM induced distinct inflammatory skin lesions, and TMM were depleted more slowly from skin after alemtuzumab, suggesting that TMM may recirculate more slowly. In summary, human skin is protected by four functionally distinct populations of T cells, two resident and two recirculating, with differing territories of migration and distinct functional activities. Copyright © 2015, American Association for the Advancement of Science.

Effects of leachate recirculation on biogas production from landfill co-disposal of municipal solid waste, sewage sludge and marine sediment.

PubMed

Chan, G Y S; Chu, L M; Wong, M H

2002-01-01

Leachate recirculation is an emerging technology associated with the management of landfill. The impact of leachate recirculation on the co-disposal of three major wastes (municipal solid waste, sewage sludge and sediment dredgings) was investigated using a laboratory column study. Chemical parameters (pH, COD, ammoniacal-N, total-P) and gas production (total gas volume, production rates and concentrations of CH4 and CO2) were monitored for 11 weeks. Leachate recirculation reduced waste-stabilization time and was effective in enhancing gas production and improving leachate quality, especially in terms of COD. The results also indicated that leachate recirculation could maximize the efficiency and waste volume reduction rate of landfill sites.

Power plant including an exhaust gas recirculation system for injecting recirculated exhaust gases in the fuel and compressed air of a gas turbine engine

DOEpatents

Anand, Ashok Kumar; Nagarjuna Reddy, Thirumala Reddy; Shaffer, Jason Brian; York, William David

2014-05-13

A power plant is provided and includes a gas turbine engine having a combustor in which compressed gas and fuel are mixed and combusted, first and second supply lines respectively coupled to the combustor and respectively configured to supply the compressed gas and the fuel to the combustor and an exhaust gas recirculation (EGR) system to re-circulate exhaust gas produced by the gas turbine engine toward the combustor. The EGR system is coupled to the first and second supply lines and configured to combine first and second portions of the re-circulated exhaust gas with the compressed gas and the fuel at the first and second supply lines, respectively.

Estimating preseason irrigation losses by characterizing evaporation of effective precipitation under bare soil conditions using large weighing lysimeters

USDA-ARS?s Scientific Manuscript database

Irrigation scheduling is one of the most cost effective means of conserving limited groundwater resources, particularly in semi-arid regions. Effective precipitation, or the net amount of water from precipitation that can be used in field water balance equations, is essential to accurate and effecti...

Accounting for green vegetation and soil spectral properties to improve remote sensing of crop residue cover

USDA-ARS?s Scientific Manuscript database

Conservation tillage methods are beneficial as they disturb soil less and leaves increased crop residue cover (CRC) after planting on the soil surface. CRC helps reduce soil erosion, evaporation, and the need for tillage operations in fields. Greenhouse gas emissions are reduced to due to less fos...

Trends in evaporation loss over the UK: 1962 to 2013

NASA Astrophysics Data System (ADS)

Blyth, Eleanor; Robinson, Emma; Martinez de la Torre, Alberto

2017-04-01

Many models of hydrology assume that an increase in air temperature will result in an increase in evaporation. However, there are some processes involved in transpiration (evaporation through the vegetation) that make the relationship more complicated: in a bid to conserve water, vegetation will reduce their stomata in response to drier soils and warmer drier air which leads to lower transpiration rates despite higher evaporative demands. In addition, the vegetation responds to increases in atmospheric carbon dioxide by closing their stomata, and this further reduces the transpiration. The JULES (Joint UK Land Environment Simulator) model, used widely in the UK to study the impacts of climate change on the environment, includes many of the processes that are likely to affect changes in water loss and its impact on large scale hydrology. A new assessment of the UK wide water balance for the last 52 years (1961 to 2013) at a 1km grid-scale has been made using this model in a system called CHESS (Climate Hydrology and Ecology research Support System). Some data is available to check the overall water balance. For instance, river flow data can be used at an annual time scale to capture the water balance, while evaporation data from flux towers can be used at some locations around the UK for the few years that it is available to evaluate the seasonal variations of evaporation. Both of these methods provide imperfect but useful evidence. Here we present the results of the modelling exercise and the evaluation: long term increasing evaporation loss trends are clearly present in the model output and these are discussed with respect to the different drivers of change.

Modeling of leachate recirculation using combined drainage blanket-horizontal trench systems in bioreactor landfills.

PubMed

Feng, Shi-Jin; Cao, Ben-Yi; Xie, Hai-Jian

2017-10-01

Leachate recirculation in municipal solid waste (MSW) landfills operated as bioreactors offers significant economic and environmental benefits. Combined drainage blanket (DB)-horizontal trench (HT) systems can be an alternative to single conventional recirculation approaches and can have competitive advantages. The key objectives of this study are to investigate combined drainage blanket -horizontal trench systems, to analyze the effects of applying two recirculation systems on the leachate migration in landfills, and to estimate some key design parameters (e.g., the steady-state flow rate, the influence width, and the cumulative leachate volume). It was determined that an effective recirculation model should consist of a moderate horizontal trench injection pressure head and supplementary leachate recirculated through drainage blanket, with an objective of increasing the horizontal unsaturated hydraulic conductivity and thereby allowing more leachate to flow from the horizontal trench system in a horizontal direction. In addition, design charts for engineering application were established using a dimensionless variable formulation.

Define of internal recirculation coefficient for biological wastewater treatment in anoxic and aerobic bioreactors

NASA Astrophysics Data System (ADS)

Rossinskyi, Volodymyr

2018-02-01

The biological wastewater treatment technologies in anoxic and aerobic bioreactors with recycle of sludge mixture are used for the effective removal of organic compounds from wastewater. The change rate of sludge mixture recirculation between bioreactors leads to a change and redistribution of concentrations of organic compounds in sludge mixture in bioreactors and change hydrodynamic regimes in bioreactors. Determination of the coefficient of internal recirculation of sludge mixture between bioreactors is important for the choice of technological parameters of biological treatment (wastewater treatment duration in anoxic and aerobic bioreactors, flow capacity of recirculation pumps). Determination of the coefficient of internal recirculation of sludge mixture requires integrated consideration of hydrodynamic parameter (flow rate), kinetic parameter (rate of oxidation of organic compounds) and physical-chemical parameter of wastewater (concentration of organic compounds). The conducted numerical experiment from the proposed mathematical equations allowed to obtain analytical dependences of the coefficient of internal recirculation sludge mixture between bioreactors on the concentration of organic compounds in wastewater, the duration of wastewater treatment in bioreactors.

Nitrogen-limited mangrove ecosystems conserve N through dissimilatory nitrate reduction to ammonium

PubMed Central

Fernandes, Sheryl Oliveira; Bonin, Patricia C.; Michotey, Valérie D.; Garcia, Nicole; LokaBharathi, P. A.

2012-01-01

Earlier observations in mangrove sediments of Goa, India have shown denitrification to be a major pathway for N loss1. However, percentage of total nitrate transformed through complete denitrification accounted for <0–72% of the pore water nitrate reduced. Here, we show that up to 99% of nitrate removal in mangrove sediments is routed through dissimilatory nitrate reduction to ammonium (DNRA). The DNRA process was 2x higher at the relatively pristine site Tuvem compared to the anthropogenically-influenced Divar mangrove ecosystem. In systems receiving low extraneous nutrient inputs, this mechanism effectively conserves and re-circulates N minimizing nutrient loss that would otherwise occur through denitrification. In a global context, the occurrence of DNRA in mangroves has important implications for maintaining N levels and sustaining ecosystem productivity. For the first time, this study also highlights the significance of DNRA in buffering the climate by modulating the production of the greenhouse gas nitrous oxide. PMID:22639727

33 CFR 159.127 - Safety coliform count: Recirculating devices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Safety coliform count....127 Safety coliform count: Recirculating devices. Thirty-eight of forty samples of flush fluid from a recirculating device must have less than 240 fecal coliform bacteria per 100 milliliters. These samples must be...

Recirculating rotary gas compressor

DOEpatents

Weinbrecht, John F.

1992-01-01

A positive displacement, recirculating Roots-type rotary gas compressor which operates on the basis of flow work compression. The compressor includes a pair of large diameter recirculation conduits (24 and 26) which return compressed discharge gas to the compressor housing (14), where it is mixed with low pressure inlet gas, thereby minimizing adiabatic heating of the gas. The compressor includes a pair of involutely lobed impellers (10 and 12) and an associated port configuration which together result in uninterrupted flow of recirculation gas. The large diameter recirculation conduits equalize gas flow velocities within the compressor and minimize gas flow losses. The compressor is particularly suited to applications requiring sustained operation at higher gas compression ratios than have previously been feasible with rotary pumps, and is particularly applicable to refrigeration or other applications requiring condensation of a vapor.

Engine with pulse-suppressed dedicated exhaust gas recirculation

DOEpatents

Keating, Edward J.; Baker, Rodney E.

2016-06-07

An engine assembly includes an intake assembly, a spark-ignited internal combustion engine, and an exhaust assembly. The intake assembly includes a charge air cooler disposed between an exhaust gas recirculation (EGR) mixer and a backpressure valve. The charge air cooler has both an inlet and an outlet, and the back pressure valve is configured to maintain a minimum pressure difference between the inlet of the charge air cooler and an outlet of the backpressure valve. A dedicated exhaust gas recirculation system is provided in fluid communication with at least one cylinder and with the EGR mixer. The dedicated exhaust gas recirculation system is configured to route all of the exhaust gas from the at least one cylinder to the EGR mixer for recirculation back to the engine.

Recirculating rotary gas compressor

DOEpatents

Weinbrecht, J.F.

1992-02-25

A positive displacement, recirculating Roots-type rotary gas compressor is described which operates on the basis of flow work compression. The compressor includes a pair of large diameter recirculation conduits which return compressed discharge gas to the compressor housing, where it is mixed with low pressure inlet gas, thereby minimizing adiabatic heating of the gas. The compressor includes a pair of involutely lobed impellers and an associated port configuration which together result in uninterrupted flow of recirculation gas. The large diameter recirculation conduits equalize gas flow velocities within the compressor and minimize gas flow losses. The compressor is particularly suited to applications requiring sustained operation at higher gas compression ratios than have previously been feasible with rotary pumps, and is particularly applicable to refrigeration or other applications requiring condensation of a vapor. 12 figs.

Cluster formation and drag reduction-proposed mechanism of particle recirculation within the partition column of the bottom spray fluid-bed coater.

PubMed

Wang, Li Kun; Heng, Paul Wan Sia; Liew, Celine Valeria

2015-04-01

Bottom spray fluid-bed coating is a common technique for coating multiparticulates. Under the quality-by-design framework, particle recirculation within the partition column is one of the main variability sources affecting particle coating and coat uniformity. However, the occurrence and mechanism of particle recirculation within the partition column of the coater are not well understood. The purpose of this study was to visualize and define particle recirculation within the partition column. Based on different combinations of partition gap setting, air accelerator insert diameter, and particle size fraction, particle movements within the partition column were captured using a high-speed video camera. The particle recirculation probability and voidage information were mapped using a visiometric process analyzer. High-speed images showed that particles contributing to the recirculation phenomenon were behaving as clustered colonies. Fluid dynamics analysis indicated that particle recirculation within the partition column may be attributed to the combined effect of cluster formation and drag reduction. Both visiometric process analysis and particle coating experiments showed that smaller particles had greater propensity toward cluster formation than larger particles. The influence of cluster formation on coating performance and possible solutions to cluster formation were further discussed. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Effects of recirculation in a three-tank pilot-scale system for pharmaceutical removal with powdered activated carbon.

PubMed

Kårelid, Victor; Larsson, Gen; Björlenius, Berndt

2017-05-15

The removal of pharmaceutically active compounds by powdered activated carbon (PAC) in municipal wastewater is a promising solution to the problem of polluted recipient waters. Today, an efficient design strategy is however lacking with regard to high-level overall, and specific, substance removal in the large scale. The performance of PAC-based removal of pharmaceuticals was studied in pilot-scale with respect to the critical parameters; contact time and PAC dose using one PAC product selected by screening in bench-scale. The goal was a minimum of 95% removal of the pharmaceuticals present in the evaluated municipal wastewater. A set of 21 pharmaceuticals was selected from an initial 100 due to their high occurrence in the effluent water of two selected wastewater treatment plants (WWTPs) in Sweden, whereof candidates discussed for future EU regulation directives were included. By using recirculation of PAC over a treatment system using three sequential contact tanks, a combination of the benefits of powdered and granular carbon performance was achieved. The treatment system was designed so that recirculation could be introduced to any of the three tanks to investigate the effect of recirculation on the adsorption performance. This was compared to use of the setup, but without recirculation. A higher degree of pharmaceutical removal was achieved in all recirculation setups, both overall and with respect to specific substances, as compared to without recirculation. Recirculation was tested with nominal contact times of 30, 60 and 120 min and the goal of 95% removal could be achieved already at the shortest contact times at a PAC dose of 10-15 mg/L. In particular, the overall removal could be increased even to 97% and 99%, at 60 and 120 min, respectively, when the recirculation point was the first tank. Recirculation of PAC to either the first or the second contact tank proved to be comparable, while a slightly lower performance was observed with recirculation to the third tank. With regards to individual substances, clarithromycin and diclofenac were ubiquitously removed according to the set goal and in contrast, a few substances (fluconazole, irbesartan, memantine and venlafaxine) required specific settings to reach an acceptable removal. Copyright © 2017 Elsevier Ltd. All rights reserved.

A remote sensing method for estimating regional reservoir area and evaporative loss

DOE PAGES

Zhang, Hua; Gorelick, Steven M.; Zimba, Paul V.; ...

2017-10-07

Evaporation from the water surface of a reservoir can significantly affect its function of ensuring the availability and temporal stability of water supply. Current estimations of reservoir evaporative loss are dependent on water area derived from a reservoir storage-area curve. Such curves are unavailable if the reservoir is located in a data-sparse region or questionable if long-term sedimentation has changed the original elevation-area relationship. In this paper, we propose a remote sensing framework to estimate reservoir evaporative loss at the regional scale. This framework uses a multispectral water index to extract reservoir area from Landsat imagery and estimate monthly evaporationmore » volume based on pan-derived evaporative rates. The optimal index threshold is determined based on local observations and extended to unobserved locations and periods. Built on the cloud computing capacity of the Google Earth Engine, this framework can efficiently analyze satellite images at large spatiotemporal scales, where such analysis is infeasible with a single computer. Our study involves 200 major reservoirs in Texas, captured in 17,811 Landsat images over a 32-year period. The results show that these reservoirs contribute to an annual evaporative loss of 8.0 billion cubic meters, equivalent to 20% of their total active storage or 53% of total annual water use in Texas. At five coastal basins, reservoir evaporative losses exceed the minimum freshwater inflows required to sustain ecosystem health and fishery productivity of the receiving estuaries. Reservoir evaporative loss can be significant enough to counterbalance the positive effects of impounding water and to offset the contribution of water conservation and reuse practices. Our results also reveal the spatially variable performance of the multispectral water index and indicate the limitation of using scene-level cloud cover to screen satellite images. Finally, this study demonstrates the advantage of combining satellite remote sensing and cloud computing to support regional water resources assessment.« less

A remote sensing method for estimating regional reservoir area and evaporative loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hua; Gorelick, Steven M.; Zimba, Paul V.

Evaporation from the water surface of a reservoir can significantly affect its function of ensuring the availability and temporal stability of water supply. Current estimations of reservoir evaporative loss are dependent on water area derived from a reservoir storage-area curve. Such curves are unavailable if the reservoir is located in a data-sparse region or questionable if long-term sedimentation has changed the original elevation-area relationship. In this paper, we propose a remote sensing framework to estimate reservoir evaporative loss at the regional scale. This framework uses a multispectral water index to extract reservoir area from Landsat imagery and estimate monthly evaporationmore » volume based on pan-derived evaporative rates. The optimal index threshold is determined based on local observations and extended to unobserved locations and periods. Built on the cloud computing capacity of the Google Earth Engine, this framework can efficiently analyze satellite images at large spatiotemporal scales, where such analysis is infeasible with a single computer. Our study involves 200 major reservoirs in Texas, captured in 17,811 Landsat images over a 32-year period. The results show that these reservoirs contribute to an annual evaporative loss of 8.0 billion cubic meters, equivalent to 20% of their total active storage or 53% of total annual water use in Texas. At five coastal basins, reservoir evaporative losses exceed the minimum freshwater inflows required to sustain ecosystem health and fishery productivity of the receiving estuaries. Reservoir evaporative loss can be significant enough to counterbalance the positive effects of impounding water and to offset the contribution of water conservation and reuse practices. Our results also reveal the spatially variable performance of the multispectral water index and indicate the limitation of using scene-level cloud cover to screen satellite images. Finally, this study demonstrates the advantage of combining satellite remote sensing and cloud computing to support regional water resources assessment.« less

Investigation of induced recirculation during planned ventilation system maintenance

PubMed Central

Pritchard, C.J.; Scott, D.F.; Noll, J.D.; Voss, B.; Leonis, D.

2015-01-01

The Office of Mine Safety and Health Research (OMSHR) investigated ways to increase mine airflow to underground metal/nonmetal (M/NM) mine working areas to improve miners’ health and safety. One of those areas is controlled recirculation. Because the quantity of mine air often cannot be increased, reusing part of the ventilating air can be an effective alternative, if implemented properly, until the capacity of the present system is improved. The additional airflow can be used to provide effective dilution of contaminants and higher flow velocities in the underground mine environment. Most applications of controlled recirculation involve taking a portion of the return air and passing it back into the intake to increase the air volume delivered to the desired work areas. OMSHR investigated a Nevada gold mine where shaft rehabilitation was in progress and one of the two main fans was shut down to allow reduced air velocity for safe shaft work. Underground booster fan operating pressures were kept constant to maintain airflow to work areas, inducing controlled recirculation in one work zone. Investigation into system behavior and the effects of recirculation on the working area during times of reduced primary ventilation system airflow would provide additional information on implementation of controlled recirculation into the system and how these events affect M/NM ventilation systems. The National Institute for Occupational Safety and Health monitored the ventilation district when both main fans were operating and another scenario with one of the units turned off for maintenance. Airflow and contaminants were measured to determine the exposure effects of induced recirculation on miner health. Surveys showed that 19% controlled recirculation created no change in the overall district airflow distribution and a small reduction in district fresh air intake. Total dust levels increased only modestly and respirable dust levels were also low. Diesel particulate matter (DPM) levels showed a high increase in district intake mass flow, but minor increases in exposure levels related to the recirculation percentage. Utilization of DPM mass flow rates allows input into ventilation modeling programs to better understand and plan for ventilation changes and district recirculation effects on miners’ health. PMID:26190862

Initialization and assimilation of cloud and rainwater in a regional model

NASA Technical Reports Server (NTRS)

Raymond, William H.; Olson, William S.

1990-01-01

The initialization and assimilation of cloud and rainwater quantities in a mesoscale regional model was examined. Forecasts of explicit cloud and rainwater are made using conservation equations. The physical processes include condensation, evaporation, autoconversion, accretion, and the removal of rainwater by fallout. These physical processes, some of which are parameterized, represent source and sink in terms in the conservation equations. The question of how to initialize the explicit liquid water calculations in numerical models and how to retain information about precipitation processes during the 4-D assimilation cycle are important issues that are addressed.

77 FR 19740 - Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... NUCLEAR REGULATORY COMMISSION [NRC-2010-0249] Water Sources for Long-Term Recirculation Cooling... Regulatory Guide (RG) 1.82, ``Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant... regarding the sumps and suppression pools that provide water sources for emergency core cooling, containment...

An evaluation of a micro programmable logic controller for oxygen monitoring and control in tanks of a recirculating aquaculture system

USDA-ARS?s Scientific Manuscript database

Control of dissolved gases, especially oxygen is an essential component of recirculating aquaculture systems. The use of pure oxygen in a recirculating aquaculture system creates supersaturated concentrations of dissolved oxygen and can reduce fish production costs by supporting greater fish and fee...

Sensitivity of bandpass filters using recirculating delay-line structures

NASA Astrophysics Data System (ADS)

Heyde, Eric C.

1996-12-01

Recirculating delay lines have value notably as sensors and optical signal processors. Most useful applications depend on a high-finesse response from a network. A proof that, with given response parameters, more complex systems can produce behavior that is more stable to the effects of nonidealities than a single recirculating loop is presented.

10 CFR 431.306 - Energy conservation standards and their effective dates.

Code of Federal Regulations, 2014 CFR

2014-01-01

..., ceiling, and door insulation of at least R-25 for coolers and R-32 for freezers, except that this... energy consumption; (4) Contain floor insulation of at least R-28 for freezers; (5) For evaporator fan... triple-pane glass with either heat-reflective treated glass or gas fill. (2) Transparent reach-in doors...

Combustion-gas recirculation system

DOEpatents

Baldwin, Darryl Dean

2007-10-09

A combustion-gas recirculation system has a mixing chamber with a mixing-chamber inlet and a mixing-chamber outlet. The combustion-gas recirculation system may further include a duct connected to the mixing-chamber inlet. Additionally, the combustion-gas recirculation system may include an open inlet channel with a solid outer wall. The open inlet channel may extend into the mixing chamber such that an end of the open inlet channel is disposed between the mixing-chamber inlet and the mixing-chamber outlet. Furthermore, air within the open inlet channel may be at a pressure near or below atmospheric pressure.

Simultaneous carbon and nitrogen removal from anaerobic effluent of the cassava ethanol industry.

PubMed

Yin, Zhixuan; Xie, Li; Zhou, Qi; Bi, Xuejun

2018-03-01

This study investigated the simultaneous carbon and nitrogen removal from anaerobic effluent of cassava stillage using a lab-scale integrated system consisting of an upflow anaerobic sludge blanket (UASB) reactor and an activated sludge (AS) process. Simultaneous denitrification and methanogenesis (SDM) was observed in the UASB with nitrate recirculation. Compared with the blank reactor without recirculation, the overall chemical oxygen demand (COD) removal efficiencies in the combined system with nitrate recirculation were similar (80-90%), while the TN removal efficiencies were significantly improved from 4.7% to 71.0%. Additionally, the anaerobic COD removal efficiencies increased from 21% to 40% as the recirculation ratio decreased from 3 to 1. Although the influent nitrate concentrations fluctuated (60-140 mg N/L), the nitrate removal efficiencies could be maintained at about 97% under different recirculation conditions. With the decreasing recirculation ratio from 3 to 1, the CH 4 content in biogas improved from 2% to 40% while the N 2 content reduced from 95.8% to 50.6%. The 16S rDNA sequencing results indicated that bacteria diversity in anaerobic SDM granular sludge was much higher than archaea. The effect of recirculation ratios on the bacterial and archaeal communities in SDM granular sludge could be further confirmed by the relative abundance of denitrifying bacteria. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Use of a micro programmable logic controller for oxygen monitoring and control in multiple tanks of a recirculating aquaculture system

USDA-ARS?s Scientific Manuscript database

In intensive recirculating aquaculture systems the use of supplemental oxygen, specifically pure liquid oxygen, increases the mass of fish that can be supported and eliminates oxygen as a major limiting factor to a system’s carrying capacity. The use of pure oxygen in a recirculating aquaculture sys...

Apparatus for controlling air/fuel ratio for internal combustion engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, K.; Mizuno, T.

1986-07-08

This patent describes an apparatus for controlling air-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine having an intake passage, an exhaust passage, an an exhaust gas recirculation passage for recirculating exhaust gases in the exhaust passage to the intake passage therethrough. The apparatus consists of: (a) means for sensing rotational speed of the engine; (b) means for sensing intake pressure in the intake passage; (c) means for sensing atmospheric pressure; (d) means for enabling and disabling exhaust gas recirculation through the exhaust gas recirculation passage in accordance with operating condition of the engine; (e)more » means for determining required amount of fuel in accordance with the sensed rotational speed and the sensed intake pressure; (f) means for determining, when the exhaust gas recirculation is enabled, a first correction value in accordance with the sensed rotational speed, the sensed intake pressure and the sensed atmospheric pressure, the first correction factor being used for correcting fuel amount so as to compensate for the decrease of fuel due to the performance of exhaust gas recirculation and also to compensate for the change in atmospheric pressure; (g) means for determining, when the exhaust gas recirculation is disabled, a second correction value in accordance with the atmospheric pressure, the second correction factor being used so as to compensate for the change in atmospheric pressure; (h) means for correcting the required amount of fuel by the first correction value and the second correction value when the exhaust gas recirculation is enabled and disabled respectively; and (i) means for supplying the engine with the corrected amount of fuel.« less

Experimental investigation of aerodynamics, combustion, and emissions characteristics within the primary zone of a gas turbine combustor

NASA Astrophysics Data System (ADS)

Elkady, Ahmed M.

2006-04-01

The present work investigates pollutant emissions production, mainly nitric oxides and carbon monoxide, within the primary zone of a highly swirling combustion and methods with which to reduce their formation. A baseline study was executed at different equivalence ratios and different inlet air temperatures. The study was then extended to investigate the effects of utilizing transverse air jets on pollutant emission characteristics at different jet locations, jet mass ratio, and overall equivalence ratio as well as to investigate the jets' overall interactions with the recirculation zone. A Fourier Transform Infrared (FTIR) spectrometer was employed to measure emissions concentrations generated during combustion of Jet-A fuel in a swirl-cup assembly. Laser Doppler Velocimetry (LDV) was employed to investigate the mean flow aerodynamics within the combustor. Particle Image Velocimetry (PIV) was utilized to capture the instantaneous aerodynamic behavior of the non-reacting primary zone. Results illustrate that NOx production is a function of both the recirculation zone and the flame length. At low overall equivalence ratios, the recirculation zone is found to be the main producer of NOx. At near stoichiometric conditions, the post recirculation zone appears to be responsible for the majority of NOx produced. Results reveal the possibility of injecting air into the recirculation zone without altering flame stability to improve emission characteristics. Depending on the jet location and strength, nitric oxides as well as carbon monoxide can be reduced simultaneously. Placing the primary air jet just downstream of the fuel rich recirculation zone can lead to a significant reduction in both nitric oxides and carbon monoxide. In the case of fuel lean recirculation zone, reduction of nitric oxides can occur by placing the jets below the location of maximum radius of the recirculation zone.

Case study of controlled recirculation at a Wyoming trona mine

PubMed Central

Pritchard, C.; Scott, D.; Frey, G.

2015-01-01

Controlled recirculation has been used in the metal/nonmetal mining industry for energy savings when heating and cooling air, in undersea mining and for increasing airflow to mining areas. For safe and effective use of controlled district recirculation, adequate airflow to dilute contaminants must exist prior to implementation, ventilation circuit parameters must be accurately quantified, ventilation network modeling must be up to date, emergency planning scenarios must be performed and effective monitoring and control systems must be installed and used. Safety and health issues that must be considered and may be improved through the use of controlled district recirculation include blasting fumes, dust, diesel emissions, radon and contaminants from mine fires. Controlled recirculation methods are expected to become more widely used as mines reach greater working depths, requiring that these health and safety issues be well understood. The U.S. National Institute for Occupational Safety and Health (NIOSH) conducted two controlled recirculation tests over three days at a Wyoming trona mine, utilizing an inline booster fan to improve airflow to a remote and difficult-to-ventilate development section. Test results were used to determine the effect that recirculation had on air qualities and quantities measured in that section and in other adjacent areas. Pre-test conditions, including ventilation quantities and pressures, were modeled using VnetPC. During each test, ventilation quantities and pressures were measured, as well as levels of total dust. Sulfur hexafluoride (SF6) tracer gas was used to simulate a mine contaminant to monitor recirculation wave cycles. Results showed good correlation between the model results and measured values for airflows, pressure differentials, tracer gas arrival times, mine gasses and dust levels. PMID:26251567

Characterisation of recirculation zones in complex terrain using multi-lidar measurements

NASA Astrophysics Data System (ADS)

Menke, R.; Mann, J.; Vasiljevic, N.

2017-12-01

Wind fields in complex terrain show a higher complexity compared to sites with simpler geometries. It is imperative to understand well the characteristics of complex flows to account for them during the site validation to ensure the wind turbines can withstand the local flow conditions. This study focuses on the description of recirculation zones occurring on lee sides of hills. The flow recirculation can have a significant impact on the success of wind energy projects since it represents one of the main contributors to the turbulence generation. An extensive dataset of observation of flow over complex terrain is available from the Perdigão 2017 field campaign (https://www.nature.com/news/world-s-largest-wind-mapping-project-spins-up-in-portugal-1.21481). A setup of 8 long-range WindScanners (Vasiljević et al., 2016), scanning lidars deployed by DTU performed RHI scans at several positions along two parallel ridges probing the flow field in two vertical planes, in addition data from several meteorological masts is available. With the above-mentioned lidar setup we achieved simultaneous dual-Doppler scans of the recirculation zone at three positions and simultaneous observations of recirculation behind two parallel ridges. Methods are developed to identify and define the extent of recirculation bubbles. Different parameters are defined to characterise the dimensions of the recirculation zone. The change of these parameters along the ridges is studied. In particular, the impact of atmospheric stability and the changes of the wind field at the position of the downwind ridge are investigated. Furthermore, the geometry of the recirculation zone for different wind directions and in connection to the upstream wind conditions is investigated.

Altering rainfall patterns through aerosol dispersion

NASA Astrophysics Data System (ADS)

Emetere, M. E.; Bakeko, M.; Onyechekwa, L.; Ayara, W.

2017-05-01

The possibility of recirculation mechanism on rainfall patterns is salient for sustenance of the human race through agricultural produce. The peculiarity of the lower atmosphere of south west region of Nigeria was explored using theoretical and experimental approach. In the theoretical approach, the reconstruction of 1D model as an extraction from the 3D aerosol dispersion model was used to examine the physics of the recirculation theory. The experimental approach which consists of obtaining dataset from ground instruments was used to provide on-site guide for developing the new recirculation theories. The data set was obtained from the Davis weather station, Nigeria Meteorological agency and Multi-angle Imaging Spectro-radiometer (MISR). We looked at the main drivers of recirculation and propounded that recirculation is a complex process which triggers a reordering of the mixing layer- a key factor for initiating the type of rainfall in this region.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Kilean; Qiang, Ji

A recirculating superconducting linear accelerator with the advantage of both straight and circular accelerator has been demonstrated with relativistic electron beams. The acceleration concept of a recirculating proton beam was recently proposed and is currently under study. In order to further support the concept, the beam dynamics study on a recirculating proton linear accelerator has to be carried out. In this paper, we study the feasibility of a two-pass recirculating proton linear accelerator through the direct numerical beam dynamics design optimization and the start-to-end simulation. This study shows that the two-pass simultaneous focusing without particle losses is attainable including fullymore » 3D space-charge effects through the entire accelerator system.« less

Validation of enhanced stabilization of municipal solid waste under controlled leachate recirculation using FTIR and XRD.

PubMed

Sethi, Sapna; Kothiyal, N C; Nema, Arvind K

2012-07-01

Leachate recirculation at neutral PH accompanied with buffer/nutrients addition has been used successfully in earlier stabilization of municipal solid waste in bioreactor landfills. In the present study, efforts were made to enhance the stabilization rate of municipal solid waste (MSW) and organic solid waste (OSW) in simulated landfill bioreactors by controlling the pH of recirculated leachate towards slightly alkaline side in absence of additional buffer and nutrients addition. Enhanced stabilization in waste samples was monitored with the help of analytical tools like Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Predominance of bands assigned to inorganic compounds and comparatively lower intensities of bands for organic compounds in the FTIR spectra of waste samples degraded with leachate recirculation under controlled pH confirmed higher rate of biodegradation and mineralization of waste than the samples degraded without controlled leachate recirculation. XRD spectra also confirmed to a greater extent of mineralization in the waste samples degraded under leachate recirculation with controlled pH. Comparison of XRD spectra of two types of wastes pointed out higher degree of mineralization in organic solid waste as compared to municipal solid waste.

10 CFR 431.306 - Energy conservation standards and their effective dates.

Code of Federal Regulations, 2012 CFR

2012-01-01

..., ceiling, and door insulation of at least R-25 for coolers and R-32 for freezers, except that this... insulation of at least R-28 for freezers; (5) For evaporator fan motors of under 1 horsepower and less than... freezers and windows in walk-in freezer doors shall be of triple-pane glass with either heat-reflective...

10 CFR 431.306 - Energy conservation standards and their effective dates.

Code of Federal Regulations, 2013 CFR

2013-01-01

..., ceiling, and door insulation of at least R-25 for coolers and R-32 for freezers, except that this... insulation of at least R-28 for freezers; (5) For evaporator fan motors of under 1 horsepower and less than... freezers and windows in walk-in freezer doors shall be of triple-pane glass with either heat-reflective...

10 CFR 431.306 - Energy conservation standards and their effective dates.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., ceiling, and door insulation of at least R-25 for coolers and R-32 for freezers, except that this... insulation of at least R-28 for freezers; (5) For evaporator fan motors of under 1 horsepower and less than... freezers and windows in walk-in freezer doors shall be of triple-pane glass with either heat-reflective...

10 CFR 431.306 - Energy conservation standards and their effective dates.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., ceiling, and door insulation of at least R-25 for coolers and R-32 for freezers, except that this... insulation of at least R-28 for freezers; (5) For evaporator fan motors of under 1 horsepower and less than... freezers and windows in walk-in freezer doors shall be of triple-pane glass with either heat-reflective...

Hydroxyl carboxylate based non-phosphorus corrosion inhibition process for reclaimed water pipeline and downstream recirculating cooling water system.

PubMed

Wang, Jun; Wang, Dong; Hou, Deyin

2016-01-01

A combined process was developed to inhibit the corrosion both in the pipeline of reclaimed water supplies (PRWS) and in downstream recirculating cooling water systems (RCWS) using the reclaimed water as makeup. Hydroxyl carboxylate-based corrosion inhibitors (e.g., gluconate, citrate, tartrate) and zinc sulfate heptahydrate, which provided Zn(2+) as a synergistic corrosion inhibition additive, were added prior to the PRWS when the phosphate (which could be utilized as a corrosion inhibitor) content in the reclaimed water was below 1.7 mg/L, and no additional corrosion inhibitors were required for the downstream RCWS. Satisfactory corrosion inhibition was achieved even if the RCWS was operated under the condition of high numbers of concentration cycles. The corrosion inhibition requirement was also met by the appropriate combination of PO4(3-) and Zn(2+) when the phosphate content in the reclaimed water was more than 1.7 mg/L. The process integrated not only water reclamation and reuse, and the operation of a highly concentrated RCWS, but also the comprehensive utilization of phosphate in reclaimed water and the application of non-phosphorus corrosion inhibitors. The proposed process reduced the operating cost of the PRWS and the RCWS, and lowered the environmental hazard caused by the excessive discharge of phosphate. Furthermore, larger amounts of water resources could be conserved as a result. Copyright © 2015. Published by Elsevier B.V.

Recirculation of the Canary Current in Fall

NASA Astrophysics Data System (ADS)

Hernandez-Guerra, A.; Espino-Falcón, E.; Vélez-Belchí, P.; Pérez-Hernández, M. D.; Martínez, A.; Cana, L.

2015-12-01

CTD and LADCP data measured in October 2014 are used to describe water masses, geostrophic circulation and mass transport in the Eastern Boundary of the North Atlantic Subtropical Gyre. Initial geostrophic velocities are adjusted to velocities from the LADCP data to estimate an initial velocity at the reference layer. Final reference velocities and consequently circulation is estimated from an inverse box model applied to an ocean divided into 12 neutral density layers. This allows us to evaluate mass fluxes consistent with the thermal wind equation and mass conservation. Ekman transport derived from the Weather Research and Forecasting (WRF) model is added to the first layer and adjusted with the inverse model. The Canary Current (CC) transports southward a net mass of 3.8±0.7 Sv (1 Sv=106 m3/s≈109 kg/s) of North Atlantic Central Water (NACW) at the thermocline layers (~0-700 m) and 1.9±0.6 Sv of a mixture of Mediterranean Water (MW) and Antarctic Intermediate Water (AAIW) at intermediate layers (~800-1400 m). The CC recirculates northward at a rate of 4.8±0.8 Sv at the thermocline layers between the Lanzarote Island and the African coast (Lanzarote Passage) on this occasion. Separately, at intermediate layers, AAIW flows northward at a rate of 2.4±0.6 Sv through the Lanzarote Passage transported by the Intermediate Poleward Undercurrent (IPUC).

Evaluation of near field atmospheric dispersion around nuclear facilities using a Lorentzian distribution methodology.

PubMed

Hawkley, Gavin

2014-12-01

Atmospheric dispersion modeling within the near field of a nuclear facility typically applies a building wake correction to the Gaussian plume model, whereby a point source is modeled as a plane source. The plane source results in greater near field dilution and reduces the far field effluent concentration. However, the correction does not account for the concentration profile within the near field. Receptors of interest, such as the maximally exposed individual, may exist within the near field and thus the realm of building wake effects. Furthermore, release parameters and displacement characteristics may be unknown, particularly during upset conditions. Therefore, emphasis is placed upon the need to analyze and estimate an enveloping concentration profile within the near field of a release. This investigation included the analysis of 64 air samples collected over 128 wk. Variables of importance were then derived from the measurement data, and a methodology was developed that allowed for the estimation of Lorentzian-based dispersion coefficients along the lateral axis of the near field recirculation cavity; the development of recirculation cavity boundaries; and conservative evaluation of the associated concentration profile. The results evaluated the effectiveness of the Lorentzian distribution methodology for estimating near field releases and emphasized the need to place air-monitoring stations appropriately for complete concentration characterization. Additionally, the importance of the sampling period and operational conditions were discussed to balance operational feedback and the reporting of public dose.

Experimental Investigation of Combustion Stabilization in Supersonic Flow Using Free Recirculation Zones

DTIC Science & Technology

1997-08-01

NUMBERS Experimental Investigation of Combustion Stabilization in Supersonic Flow Using Free F6170896W0291 Recirculation Zones 6. AUTHOR(S) Dr...stabilization in supersonic flow using free recirculation zones Special contract (SPC-96-4043) with Air Force Office of Scientific Research (AFMC), USA, EOARD...of three quarterly reports and presents experimental results on self-ignition and combustion stabilization in supersonic flow using free

Monitoring extent of moisture variations due to leachate recirculation in an ELR/bioreactor landfill using resistivity imaging.

PubMed

Manzur, Shahed Rezwan; Hossain, Md Sahadat; Kemler, Vance; Khan, Mohammad Sadik

2016-09-01

Bioreactor or enhanced leachate recirculation (ELR) landfills are designed and operated for accelerated waste stabilization, accelerated decomposition, and an increased rate of gas generation. The major aspects of a bioreactor landfill are the addition of liquid and the recirculation of collected leachate back into the waste mass through the subsurface leachate recirculation system (LRS). The performance of the ELR landfill largely depends on the existing moisture content within the waste mass; therefore, it is of utmost importance to determine the moisture variations within the landfill. Traditionally, the moisture variation of the ELR landfill is determined by collecting samples through a bucket auger boring from the landfill, followed by laboratory investigation. Collecting the samples through a bucket auger boring is time consuming, labor intensive, and cost prohibitive. Moreover, it provides the information for a single point within the waste mass, but not for the moisture distribution within the landfill. Fortunately, 2D resistivity imaging (RI) can be performed to assess the moisture variations within the landfill and provide a continuous image of the subsurface, which can be utilized to evaluate the performance of the ELR landfill. During this study, the 2D resistivity imaging technique was utilized to determine the moisture distribution and moisture movement during the recirculation process of an ELR landfill in Denton, Texas, USA. A horizontal recirculation pipe was selected and monitored periodically for 2.5years, using the RI technique, to investigate the performance of the leachate recirculation. The RI profile indicated that the resistivity of the solid waste decreased as much as 80% with the addition of water/leachate through the recirculation pipe. In addition, the recirculated leachate traveled laterally between 11m and 16m. Based on the resistivity results, it was also observed that the leachate flow throughout the pipe was non-uniform. The non-uniformity of the leachate flow confirms that the flow of leachate through waste is primarily through preferential flow paths due the heterogeneous nature of the waste. Copyright © 2016 Elsevier Ltd. All rights reserved.

One-dimensional thermohydraulic code THESEUS and its application to chilldown process simulation in two-phase hydrogen flows

NASA Astrophysics Data System (ADS)

Papadimitriou, P.; Skorek, T.

THESUS is a thermohydraulic code for the calculation of steady state and transient processes of two-phase cryogenic flows. The physical model is based on four conservation equations with separate liquid and gas phase mass conservation equations. The thermohydraulic non-equilibrium is calculated by means of evaporation and condensation models. The mechanical non-equilibrium is modeled by a full-range drift-flux model. Also heat conduction in solid structures and heat exchange for the full spectrum of heat transfer regimes can be simulated. Test analyses of two-channel chilldown experiments and comparisons with the measured data have been performed.

Boosting devices with integral features for recirculating exhaust gas

DOEpatents

Wu, Ko-Jen

2015-12-22

According to one embodiment of the invention, a turbine housing includes a turbine inlet in fluid communication with a turbine volute configured to house a turbine wheel, the turbine inlet configured to direct an exhaust gas flow from an engine to the turbine wheel. The turbine housing also includes a turbine outlet in fluid communication with the turbine volute, the turbine outlet configured to direct the exhaust gas flow to an exhaust gas conduit and a first exhaust gas recirculation supply port located on and in fluid communication with the turbine outlet, the first exhaust gas recirculation supply port being configured to direct a portion of the exhaust gas flow to an exhaust gas recirculation supply conduit.

Prediction of recirculation zones in isothermal coaxial jet flows relevant to combustors

NASA Technical Reports Server (NTRS)

Nallasamy, M.

1987-01-01

The characteristics of the recirculation zones in confined coaxial turbulent jets are investigated numerically employing the kappa - epsilon turbulence model. The geometrical arrangement corresponds to the experimental study of Owen (AIAA J. 1976) and the investigation is undertaken to provide information for isothermal flow relevant to combustor flows. For the first time, the shape, size, and location of the recirculation zones for the above experimental configuration are correctly predicted. The processes leading to the observed results are explained. Detailed comparisons of the prediction with measurements are made. It is shown that the recirculation zones are very sensitive to the central jet exit configuration and the velocity ratio of the jets.

Multi-point optimization of recirculation flow type casing treatment in centrifugal compressors

NASA Astrophysics Data System (ADS)

Tun, Min Thaw; Sakaguchi, Daisaku

2016-06-01

High-pressure ratio and wide operating range are highly required for a turbocharger in diesel engines. A recirculation flow type casing treatment is effective for flow range enhancement of centrifugal compressors. Two ring grooves on a suction pipe and a shroud casing wall are connected by means of an annular passage and stable recirculation flow is formed at small flow rates from the downstream groove toward the upstream groove through the annular bypass. The shape of baseline recirculation flow type casing is modified and optimized by using a multi-point optimization code with a metamodel assisted evolutionary algorithm embedding a commercial CFD code CFX from ANSYS. The numerical optimization results give the optimized design of casing with improving adiabatic efficiency in wide operating flow rate range. Sensitivity analysis of design parameters as a function of efficiency has been performed. It is found that the optimized casing design provides optimized recirculation flow rate, in which an increment of entropy rise is minimized at grooves and passages of the rotating impeller.

Recirculating linacs for a neutrino factory - Arc optics design and optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alex Bogacz; Valeri Lebedev

2001-10-21

A conceptual lattice design for a muon accelerator based on recirculating linacs (Nucl. Instr. and Meth. A 472 (2001) 499, these proceedings) is presented here. The challenge of accelerating and transporting a large phase space of short-lived muons is answered here by presenting a proof-of-principle lattice design for a recirculating linac accelerator. It is the centerpiece of a chain of accelerators consisting of a 3GeV linac and two consecutive recirculating linear accelerators, which facilitates acceleration starting after ionization cooling at 190MeV/c and proceeding to 50GeV. Beam transport issues for large-momentum-spread beams are accommodated by appropriate lattice design choices. The resultingmore » arc optics is further optimized with a sextupole correction to suppress chromatic effects contributing to the emittance dilution. The presented proof-of-principle design of the arc optics with horizontal separation of multi-pass beams can be extended to all passes in both recirculating linacs.« less

Recirculating linacs for a neutrino factory - Arc optics design and optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valeri Lebedev; S. Bogacz

2001-10-25

A conceptual lattice design for a muon accelerator based on recirculating linacs (Nucl. Instr. and Meth. A 472 (2001) 499, these proceedings) is presented here. The challenge of accelerating and transporting a large phase space of short-lived muons is answered here by presenting a proof-of-principle lattice design for a recirculating linac accelerator. It is the centerpiece of a chain of accelerators consisting of a 3 GeV linac and two consecutive recirculating linear accelerators, which facilitates acceleration starting after ionization cooling at 190 MeV/c and proceeding to 50 GeV. Beam transport issues for large-momentum-spread beams are accommodated by appropriate lattice designmore » choices. The resulting arc optics is further optimized with a sextupole correction to suppress chromatic effects contributing to the emittance dilution. The presented proof-of-principle design of the arc optics with horizontal separation of multi-pass beams can be extended to all passes in both recirculating linacs.« less

Confined turbulent swirling recirculating flow predictions. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Abujelala, M. T.; Lilley, D. G.

1985-01-01

The capability and the accuracy of the STARPIC computer code in predicting confined turbulent swirling recirculating flows is presented. Inlet flow boundary conditions were demonstrated to be extremely important in simulating a flowfield via numerical calculations. The degree of swirl strength and expansion ratio have strong effects on the characteristics of swirling flow. In a nonswirling flow, a large corner recirculation zone exists in the flowfield with an expansion ratio greater than one. However, as the degree of inlet swirl increases, the size of this zone decreases and a central recirculation zone appears near the inlet. Generally, the size of the central zone increased with swirl strength and expansion ratio. Neither the standard k-epsilon turbulence mode nor its previous extensions show effective capability for predicting confined turbulent swirling recirculating flows. However, either reduced optimum values of three parameters in the mode or the empirical C sub mu formulation obtained via careful analysis of available turbulence measurements, can provide more acceptable accuracy in the prediction of these swirling flows.

Three-dimensional modelling of leachate recirculation using vertical wells in bioreactor landfills.

PubMed

Feng, Shi-Jin; Chen, Zheng-Wei; Cao, Ben-Yi

2016-12-01

Bioreactor landfills use leachate recirculation to enhance the biodegradation of municipal solid waste and accelerate landfill stabilisation, which can provide significant environmental and economic benefits. Vertical wells are operated as a major method for leachate recirculation systems. The objectives of this article are to analyse the leachate migration in bioreactor landfills using vertical wells and to offer theoretical basis for the design of leachate recirculation systems. A three-dimensional numerical model was built using FLAC-3D, and this model can consider the saturated and unsaturated flow of leachate within anisotropic waste to reflect the actual conditions. First, main influence factors of leachate migration were analysed, including the vertical well height, hydraulic conductivity, and anisotropic coefficient, in a single-well recirculation system. Then, the effects of different configurations of a group-well system were studied and the optimal well spacing was obtained. Some key design parameters (e.g. the recirculation flow rate, volume of impact zone, radius of impact zone and time to reach steady state) were also evaluated. The results show that the hydraulic conductivity has a great impact on the optimal height of vertical wells and uniform configuration is the best option in terms of both volume of impact zone and time to reach steady state. © The Author(s) 2016.

Advection-dominated Inflow/Outflows from Evaporating Accretion Disks.

PubMed

Turolla; Dullemond

2000-03-01

In this Letter we investigate the properties of advection-dominated accretion flows (ADAFs) fed by the evaporation of a Shakura-Sunyaev accretion disk (SSD). In our picture, the ADAF fills the central cavity evacuated by the SSD and extends beyond the transition radius into a coronal region. We find that, because of global angular momentum conservation, a significant fraction of the hot gas flows away from the black hole, forming a transsonic wind, unless the injection rate depends only weakly on radius (if r2sigma&d2;~r-xi, xi<1&solm0;2). The Bernoulli number of the inflowing gas is negative if the transition radius is less, similar100 Schwarzschild radii, so matter falling into the hole is gravitationally bound. The ratio of inflowing to outflowing mass is approximately 1/2, so in these solutions the accretion rate is of the same order as in standard ADAFs and much larger than in advection-dominated inflow/outflow models. The possible relevance of evaporation-fed solutions to accretion flows in black hole X-ray binaries is briefly discussed.

Implications of Advanced Crew Escape Suit Transpiration for the Orion Program

NASA Technical Reports Server (NTRS)

Bue, Grant; Kuznetz, Lawrence

2009-01-01

Human testing was conducted to more fully characterize the integrated performance of the Advanced Crew Escape Suit (ACES) with liquid cooling provide by an Individual Cooling Unit (ICU) across a broad range of environmental conditions and metabolic rates. Together with a correlation for the ACES Liquid Cooling Garment as a function of inlet temperature, metabolic rate, and crew size, a reasonably conservative correlation for core temperature was achieved for the human thermal model applied to the ACES with ICU cooling. A key observation for this correlation was accounting for transpiration of evaporated sweat through the Gortex(Registered TradeMark) liner of the ACES indicated by as much as 0.6 lbm of sweat evaporated over the course of the 1 hour test profile, most of which could not be attributed to respiration or head sweat evaporation of the crew. Historically it has been assumed that transpiration was not an important design feature of the ACES suit. The correlated human thermal model will show transpiration to be highly useful in hot survival situations for the Orion Program when adequate liquid cooling is not available.

Modeling the Dynamics of Micro- and Macroparticles in a Combined Gas-Discharge Installation

NASA Astrophysics Data System (ADS)

Astashinskii, V. V.; Bogach, M. I.; Burachevskii, A. V.

2016-05-01

We present a model of the dynamics of micro- and macroparticles in a combined gas-discharge installation that accounts for the processes of metal explosion (heating of a metal in its solid state, melting, heating of the liquid metal, intense evaporation, ionization in metal vapor), a magnetohydrodynamic description of plasma acceleration (on the basis of the mass, momentum, and energy conservation laws neglecting the plasma viscosity and thermal conductivity), and a description of the processes of energy transfer from a high-velocity stream to accelerated particles. It has been established that the process of melting terminates in 1.3 ns after the start of the discharge and that the evaporation terminates in 480 ns. The stage of cooling starts in 21 μs. The average density of the plasma upon completion of the evaporation process can be estimated to be 1.7·10-5 g/cm3, with the pressure being of the order of 1.5·104 Pa and the total time of discharge, of about 250 μs.

High-Capacity Spacesuit Evaporator Absorber Radiator (SEAR)

NASA Technical Reports Server (NTRS)

Izenson, Michael G.; Chen, Weibo; Phillips, Scott; Chepko, Ariane; Bue, Grant; Quinn, Gregory

2015-01-01

Future human space exploration missions will require advanced life support technology that can operate across a wide range of applications and environments. Thermal control systems for space suits and spacecraft will need to meet critical requirements for water conservation and multifunctional operation. This paper describes a Space Evaporator Absorber Radiator (SEAR) that has been designed to meet performance requirements for future life support systems. A SEAR system comprises a lithium chloride absorber radiator (LCAR) for heat rejection coupled with a space water membrane evaporator (SWME) for heat acquisition. SEAR systems provide heat pumping to minimize radiator size, thermal storage to accommodate variable environmental conditions, and water absorption to minimize use of expendables. We have built and tested a flight-like, high-capacity LCAR, demonstrated its performance in thermal vacuum tests, and explored the feasibility of an ISS demonstration test of a SEAR system. The new LCAR design provides the same cooling capability as prior LCAR prototypes while enabling over 30% more heat absorbing capacity. Studies show that it should be feasible to demonstrate SEAR operation in flight by coupling with an existing EMU on the space station.

High-Capacity Spacesuit Evaporator Absorber Radiator (SEAR)

NASA Technical Reports Server (NTRS)

Izenson, Michael G.; Chen, Weibo; Phillips, Scott; Chepko, Ariane; Bue, Grant; Quinn, Gregory

2014-01-01

Future human space exploration missions will require advanced life support technology that can operate across a wide range of applications and environments. Thermal control systems for space suits and spacecraft will need to meet critical requirements for water conservation and adaptability to highly variable thermal environments. This paper describes a Space Evaporator Absorber Radiator (SEAR) that has been designed to meet performance requirements for future life support systems. A SEAR system comprises a lithium chloride absorber radiator (LCAR) for heat rejection coupled with a space water membrane evaporator (SWME) for heat acquisition. SEAR systems provide heat pumping to minimize radiator size, thermal storage to accommodate variable environmental conditions, and water absorption to minimize use of expendables. We have built and tested a flightlike, high-capacity LCAR, demonstrated its performance in thermal vacuum tests, and explored the feasibility of an ISS demonstration test of a SEAR system. The new LCAR design provides the same cooling capability as prior LCAR prototypes while enabling over 30% more heat absorbing capacity. Studies show that it should be feasible to demonstrate SEAR operation in flight by coupling with an existing EMU on the space station.

The impact of recirculation, ventilation and filters on secondary organic aerosols generated by indoor chemistry

NASA Astrophysics Data System (ADS)

Fadeyi, M. O.; Weschler, C. J.; Tham, K. W.

This study examined the impact of recirculation rates (7 and 14 h -1), ventilation rates (1 and 2 h -1), and filtration on secondary organic aerosols (SOAs) generated by ozone of outdoor origin reacting with limonene of indoor origin. Experiments were conducted within a recirculating air handling system that serviced an unoccupied, 236 m 3 environmental chamber configured to simulate an office; either no filter, a new filter or a used filter was located downstream of where outdoor air mixed with return air. For otherwise comparable conditions, the SOA number and mass concentrations at a recirculation rate of 14 h -1 were significantly smaller than at a recirculation rate of 7 h -1. This was due primarily to lower ozone concentrations, resulting from increased surface removal, at the higher recirculation rate. Increased ventilation increased outdoor-to-indoor transport of ozone, but this was more than offset by the increased dilution of SOA derived from ozone-initiated chemistry. The presence of a particle filter (new or used) strikingly lowered SOA number and mass concentrations compared with conditions when no filter was present. Even though the particle filter in this study had only 35% single-pass removal efficiency for 100 nm particles, filtration efficiency was greatly amplified by recirculation. SOA particle levels were reduced to an even greater extent when an activated carbon filter was in the system, due to ozone removal by the carbon filter. These findings improve our understanding of the influence of commonly employed energy saving procedures on occupant exposures to ozone and ozone-derived SOA.

Effect of recirculation on organic matter removal in a hybrid constructed wetland system.

PubMed

Ayaz, S C; Findik, N; Akça, L; Erdoğan, N; Kinaci, C

2011-01-01

This research project aimed to determine the technologically feasible and applicable wastewater treatment systems which will be constructed to solve environmental problems caused by small communities in Turkey. Pilot-scale treatment of a small community's wastewater was performed over a period of more than 2 years in order to show applicability of these systems. The present study involves removal of organic matter and suspended solids in serially operated horizontal (HFCW) and vertical (VFCW) sub-surface flow constructed wetlands. The pilot-scale wetland was constructed downstream of anaerobic reactors at the campus of TUBITAK-MRC. Anaerobically pretreated wastewater was introduced into this hybrid two-stage sub-surface flow wetland system (TSCW). Wastewater was first introduced into the horizontal sub-surface flow system and then the vertical flow system before being discharged. Recirculation of the effluent was tested in the system. When the recirculation ratio was 100%, average removal efficiencies for TSCW were 91 +/- 4% for COD, 83 +/- 10% for BOD and 96 +/- 3% for suspended solids with average effluent concentrations of 9 +/- 5 mg/L COD, 6 +/- 3 mg/L BOD and 1 mg/L for suspended solids. Comparing non-recirculation and recirculation periods, the lowest effluent concentrations were obtained with a 100% recirculation ratio. The effluent concentrations met the Turkish regulations for discharge limits of COD, BOD and TSS in each case. The study showed that a hybrid constructed wetland system with recirculation is a very effective method of obtaining very low effluent organic matter and suspended solids concentrations downstream of anaerobic pretreatment of domestic wastewaters in small communities.

Speciation, behaviour, and fate of mercury under oxy-fuel combustion conditions.

PubMed

Córdoba, Patricia; Maroto-Valer, M; Delgado, Miguel Angel; Diego, Ruth; Font, Oriol; Querol, Xavier

2016-02-01

The work presented here reports the first study in which the speciation, behaviour and fate of mercury (Hg) have been evaluated under oxy-fuel combustion at the largest oxy-Pulverised Coal Combustion (oxy-PCC) demonstration plant to date during routine operating conditions and partial exhaust flue gas re-circulation to the boiler. The effect of the CO2-rich flue gas re-circulation on Hg has also been evaluated. Results reveal that oxy-PCC operational conditions play a significant role on Hg partitioning and fate because of the continuous CO2-rich flue gas re-circulations to the boiler. Mercury escapes from the cyclone in a gaseous form as Hg(2+) (68%) and it is the prevalent form in the CO2-rich exhaust flue gas (99%) with lower proportions of Hg(0) (1.3%). The overall retention rate for gaseous Hg is around 12%; Hg(0) is more prone to be retained (95%) while Hg(2+) shows a negative efficiency capture for the whole installation. The negative Hg(2+) capture efficiencies are due to the continuous CO2-rich exhaust flue gas recirculation to the boiler with enhanced Hg contents. Calculations revealed that 44mg of Hg were re-circulated to the boiler as a result of 2183 re-circulations of CO2-rich flue gas. Especial attention must be paid to the role of the CO2-rich exhaust flue gas re-circulation to the boiler on the Hg enrichment in Fly Ashes (FAs). Copyright © 2015 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Córdoba, Patricia, E-mail: pc247@hw.ac.uk; Maroto-Valer, M.; Delgado, Miguel Angel

The work presented here reports the first study in which the speciation, behaviour and fate of mercury (Hg) have been evaluated under oxy-fuel combustion at the largest oxy-Pulverised Coal Combustion (oxy-PCC) demonstration plant to date during routine operating conditions and partial exhaust flue gas re-circulation to the boiler. The effect of the CO{sub 2}-rich flue gas re-circulation on Hg has also been evaluated. Results reveal that oxy-PCC operational conditions play a significant role on Hg partitioning and fate because of the continuous CO{sub 2}-rich flue gas re-circulations to the boiler. Mercury escapes from the cyclone in a gaseous form asmore » Hg{sup 2+} (68%) and it is the prevalent form in the CO{sub 2}-rich exhaust flue gas (99%) with lower proportions of Hg{sup 0} (1.3%). The overall retention rate for gaseous Hg is around 12%; Hg{sup 0} is more prone to be retained (95%) while Hg{sup 2+} shows a negative efficiency capture for the whole installation. The negative Hg{sup 2+} capture efficiencies are due to the continuous CO{sub 2}-rich exhaust flue gas recirculation to the boiler with enhanced Hg contents. Calculations revealed that 44 mg of Hg were re-circulated to the boiler as a result of 2183 re-circulations of CO{sub 2}-rich flue gas. Especial attention must be paid to the role of the CO{sub 2}-rich exhaust flue gas re-circulation to the boiler on the Hg enrichment in Fly Ashes (FAs). - Highlights: • The fate of gaseous Hg has been evaluated under oxy-fuel combustion. • The Hg oxidation process is enhanced in CO{sub 2}-rich flue gas recirculation. • Hg{sup 2+} is the prevalent gas species in the CO{sub 2}-rich exhaust flue gas. • Hg{sup 2+}{sub (g)} shows a negative efficiency capture for the whole installation. • Especial attention must be paid to the Hg enrichment in Fly Ashes.« less

Summary Report on the Navy Emergency Escape Breathing Device

DTIC Science & Technology

1983-08-08

recirculated cas. The device produces pure oxygen (02) and uses a venturi to recirculate unused and expired gases through the purifier. A rubber...passing the recirculated air through a lithium hydroxide (LiOH) scrubber . The scrubber reduces the CO. level by forming either lithium bicarbonate (LiSCO...transparent visor and an elastromeric neck seal; a chlorate candle-based 02 generator; an air purification filter or scrubberl and a venturi arrangement to

Recirculating Electron Accelerators with Noncircular Electron Orbits as Radiation Sources for Applications (a Review)

NASA Astrophysics Data System (ADS)

Dubinov, Alexander E.; Ochkina, Elena I.

2018-05-01

State-of-the-art compact recirculating electron accelerators operating at intermediate energies (tens of MeV) are reviewed. The acceleration schemes implemented in the rhodotron, ridgetron, fantron, and cylindertron machines are discussed. Major accelerator components such as the electron guns, accelerating cavities, and bending magnets are described. The parameters of currently operating recirculating accelerators are tabulated, and applications of these accelerators in different processes of irradiation are exemplified.

Picosecond Pulse Recirculation for High Average Brightness Thomson Scattering-based Gamma-ray Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Semenov, V. A.

2009-06-12

Pulse recirculation has been successfully demonstrated with the interaction laser system of LLNL's Thomson-Radiated Extreme X-ray (T-REX) source. The recirculation increased twenty-eight times the intensity of the light coming out of the laser system, demonstrating the capability of increasing the gamma-ray flux emitted by T-REX. The technical approach demonstrated could conceivably increase the average gamma-ray flux output by up to a hundred times.

Beam dynamics simulation of a double pass proton linear accelerator

DOE PAGES

Hwang, Kilean; Qiang, Ji

2017-04-03

A recirculating superconducting linear accelerator with the advantage of both straight and circular accelerator has been demonstrated with relativistic electron beams. The acceleration concept of a recirculating proton beam was recently proposed and is currently under study. In order to further support the concept, the beam dynamics study on a recirculating proton linear accelerator has to be carried out. In this paper, we study the feasibility of a two-pass recirculating proton linear accelerator through the direct numerical beam dynamics design optimization and the start-to-end simulation. This study shows that the two-pass simultaneous focusing without particle losses is attainable including fullymore » 3D space-charge effects through the entire accelerator system.« less

Shallow peatland ecohydrology - the control of peat depth on moss productivity

NASA Astrophysics Data System (ADS)

Dixon, Simon; Kettridge, Nicholas; Moore, Paul; Devito, Kevin; Tilak, Amey; Petrone, Rich; Mendoza, Carl; Waddington, Mike

2017-04-01

Northern peatlands represent an important sink in the global carbon cycle. Shallow peatlands and marginal connective wetlands can be essential components of many northern peatland landscape mosaics, playing a vital role in landscape connectivity and wider landscape hydrology. However the ecohydrological function of these shallow, marginal systems has been largely overlooked, with peatland hydrology research focused on relatively deep bog systems. In order to predict landscape scale wetland function and its vulnerability to climate change we need to understand how these shallow connective systems function. The balance between moss productivity and water loss provide a key component of these systems, as water use efficiency controls the rate of moss growth and thus controls the amount of atmospheric carbon sequestered in peat. Understanding how productivity of shallow peatland systems responds to changes in evaporative stress will aid predictions of peatland landscape hydrological function in a changing climate. To determine the factors influencing peat productivity, water balance simulations using Hydrus 1-D were conducted over annual growing seasons for different soil profile depths, compositions and antecedent moisture conditions. Our results demonstrate a bimodal distribution of peatland responses; either primarily conserving water by limiting evapotranspiration or, maximizing productivity. For sustained periods of evaporative stress, shallow marginal systems are least able to buffer periods of evaporative stress due to limited labile water storage, and will limit evaporation, conserve water and be less productive. Conversely, where present, both deep water storage and a shallow initial water table prolong the onset of high vegetative stress, thus maximizing moss productivity. However, a total depth of 0.8 m is identified as the threshold above which increasing peat depth has no further effect on changing vegetative stress response and thus landscape function. These results are important as moss productivity, along with rate of organic matter decay are the two principle factors controlling the build-up of peat, and therefore sequestration of carbon. With a predicted increase in the frequency and size of rain events in northern latitudes our results indicate the productivity of shallow wetland systems may increase, but greater moisture availability will increase the likelihood they remain as wetlands in a changing climate.

Contribution of seawater recirculation to submarine groundwater discharge and related nutrient fluxes in two tropical bays

NASA Astrophysics Data System (ADS)

Vautier, Camille; Dulaiova, Henrietta

2017-04-01

Hawaiian coastal waters suffer from excess terrestrial nutrient loading, most of which comes from submarine groundwater discharge (SGD). This study quantifies and distinguishes the role of the fresh terrestrial and tidally pumped salt water components of SGD into the nearshore zone of two reefs on the island of Oahu: Maunalua Bay and Kāneohe Bay. The two components of SGD are characterized using isotopic techniques, and the study mainly focuses on the less understood recirculation component. A two-step approach is implemented: first, a conceptual model of groundwater circulation is established; second, nutrient fluxes associated with seawater recirculation are quantified. Groundwater circulation through the beach berm is quantified and characterized using 222Rn and 224Ra activity measurements. Nutrient fluxes are obtained by coupling nutrient concentration measurements and discharge estimates. The isotopic signatures inform us about the influence of the tidal cycle on groundwater circulation. 222Rn, 224Ra, and δ18O isotopes are used to derive apparent ages of the infiltrated seawater and allow us to quantify recirculation rates. The method is also complemented with the use of silicate concentration as tracers of the recirculation process. The trends in apparent ages observed in pore water in Maunalua match previously published conceptual groundwater circulation models and show a sequentially aging pore water circulation loop. However, the ages obtained in Kāneohe suggest a different tidal pumping dynamic that lacks a circulation loop, perhaps resulting from the absence of freshwater discharge. Derived nutrient fluxes show that the autochthonous production of inorganic nitrogen and phosphorus that occurs during seawater recirculation has a significant impact on nutrient cycles in the nearshore areas of the bays. This result suggests that seawater recirculation should be taken into account in biogeochemical studies of coastal areas.

A concentrated solar cavity absorber with direct heat transfer through recirculating metallic particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarker, M. R. I., E-mail: islamrabiul@yahoo.com; Saha, Manabendra, E-mail: manabendra.saha@adelaide.edu.au, E-mail: manab04me@gmail.com; Beg, R. A.

A recirculating flow solar particle cavity absorber (receiver) is modeled to investigate the flow behavior and heat transfer characteristics of a novel developing concept. It features a continuous recirculating flow of non-reacting metallic particles (black silicon carbide) with air which are used as a thermal enhancement medium. The aim of the present study is to numerically investigate the thermal behavior and flow characteristics of the proposed concept. The proposed solar particle receiver is modeled using two phase discrete particle model (DPM), RNG k-flow model and discrete ordinate (DO) radiation model. Numerical analysis is carried out considering a solar receiver withmore » only air and the mixture of non-reacting particles and air as a heat transfer as well as heat carrying medium. The parametric investigation is conducted considering the incident solar flux on the receiver aperture and changing air flow rate and recirculation rate inside the receiver. A stand-alone feature of the recirculating flow solar particle receiver concept is that the particles are directly exposed to concentrated solar radiation monotonously through recirculating flow inside the receiver and results in efficient irradiation absorption and convective heat transfer to air that help to achieve high temperature air and consequently increase in thermal efficiency. This paper presents, results from the developed concept and highlights its flow behavior and potential to enhance the heat transfer from metallic particles to air by maximizing heat carrying capacity of the heat transfer medium. The imposed milestones for the present system will be helpful to understand the radiation absorption mechanism of the particles in a recirculating flow based receiver, the thermal transport between the particles, the air and the cavity, and the fluid dynamics of the air and particle in the cavity.« less

Removal of non-biodegradable organic matter from landfill leachates by adsorption.

PubMed

Rodríguez, J; Castrillón, L; Marañón, E; Sastre, H; Fernández, E

2004-01-01

Leachates produced at the La Zoreda landfill in Asturias, Spain, were recirculated through a simulated landfill pilot plant. Prior to recirculation, three loads of different amounts of Municipal Solid Waste (MSW) were added to the plant, forming in this way consecutive layers. When anaerobic digestion was almost completed, the leachates from the landfill were recirculated. After recirculation, a new load of MSW was added and two new recirculations were carried out. The organic load of the three landfill leachates recirculated through the anaerobic pilot plant decreased from initial values of 5108, 3782 and 2560 mg/l to values of between 1500 and 1600 mg/l. Despite achieving reductions in the organic load of the leachate, a residual organic load still remained that was composed of non-biodegradable organic constituents such as humic substances. Similar values of the chemical oxygen demand (COD) were obtained when the landfill leachate was treated by a pressurised anoxic-aerobic process followed by ultrafiltration. After recirculation through the pilot plant, physico-chemical treatment was carried out to reduce the COD of the leachate. The pH of the leachate was decreased to a value of 1.5 to precipitate the humic fraction, obtaining a reduction in COD of about 13.5%. The supernatant liquid was treated with activated carbon and different resins, XAD-8, XAD-4 and IR-120. Activated carbon presented the highest adsorption capacities, obtaining COD values for the treated leachate in the order of 200mg/l. Similar results were obtained when treating with activated carbon, the leachate from the biological treatment plant at the La Zoreda landfill; in this case without decreasing the pH.

Physiological plasticity of metabolic rates in the invasive honey bee and an endemic Australian bee species.

PubMed

Tomlinson, Sean; Dixon, Kingsley W; Didham, Raphael K; Bradshaw, S Don

2015-12-01

Seasonal variation in metabolic rate and evaporative water loss as a function of ambient temperature were compared in two species of bees. The endemic blue-banded bee, Amegilla chlorocyanea, is a solitary species that is an important pollinator in the south-west Australian biodiversity hotspot. Responses were compared with the European honeybee, Apis mellifera, naturalised in Western Australia almost 200 years ago. Metabolic rate increased exponentially with temperature to a peak in both species, and then declined rapidly, with unique scaling exponents and peaks for all species-by-season comparisons. Early in the austral summer, Apis was less thermally tolerant than Amegilla, but the positions reversed later in the foraging season. There were also significant exponential increases in evaporative water loss with increasing temperature, and both season and species contributed to significantly different responses. Apis maintained relatively consistent thermal performance of metabolic rate between seasons, but at the expense of increased rates of evaporative water loss later in summer. In contrast, Amegilla had dramatically increased metabolic requirements later in summer, but maintained consistent thermal performance of evaporative water loss. Although both species acclimated to higher thermal tolerance, the physiological strategies underpinning the acclimation differed. These findings may have important implications for understanding the responses of these and other pollinators to changing environments and for their conservation management.

Heat recirculating cooler for fluid stream pollutant removal

DOEpatents

Richards, George A.; Berry, David A.

2008-10-28

A process by which heat is removed from a reactant fluid to reach the operating temperature of a known pollutant removal method and said heat is recirculated to raise the temperature of the product fluid. The process can be utilized whenever an intermediate step reaction requires a lower reaction temperature than the prior and next steps. The benefits of a heat-recirculating cooler include the ability to use known pollutant removal methods and increased thermal efficiency of the system.

An advanced anaerobic biofilter with effluent recirculation for phenol removal and methane production in treatment of coal gasification wastewater.

PubMed

Li, Yajie; Tabassum, Salma; Zhang, Zhenjia

2016-09-01

An advanced anaerobic biofilter (AF) was introduced for the treatment of coal gasification wastewater (CGW), and effluent recirculation was adopted to enhance phenol removal and methane production. The results indicated that AF was reliable in treating diluted CGW, while its efficiency and stability were seriously reduced when directly treating raw CGW. However, its performance could be greatly enhanced by effluent recirculation. Under optimal effluent recirculation of 0.5 to the influent, concentrations of chemical oxygen demand (COD) and total phenol in the effluent could reach as low as 234.0 and 14.2mg/L, respectively. Also, the rate of methane production reached 169.0mLCH4/L/day. Though CGW seemed to restrain the growth of anaerobic microorganisms, especially methanogens, the inhibition was temporary and reversible, and anaerobic bacteria presented strong tolerance. The activities of methanogens cultivated in CGW could quickly recover on feeding with glucose wastewater (GW). However, the adaptability of anaerobic bacteria to the CGW was very poor and the activity of methanogens could not be improved by long-term domestication. By analysis using the Haldane model, it was further confirmed that high effluent recirculation could result in high activity for hydrolytic bacteria and substrate affinity for toxic matters, but only suitable effluent recirculation could result in high methanogenic activity. Copyright © 2016. Published by Elsevier B.V.

Characterization of a joint recirculation of concentrated leachate and leachate to landfills with a microaerobic bioreactor for leachate treatment.

PubMed

He, Ruo; Wei, Xiao-Meng; Tian, Bao-Hu; Su, Yao; Lu, Yu-Lan

2015-12-01

With comparison of a traditional landfill, a joint recirculation of concentrated leachate and leachate to landfills with or without a microaerobic reactor for leachate treatment was investigated in this study. The results showed that the joint recirculation of concentrated leachate and leachate with a microaerobic reactor for leachate treatment could not only utilize the microaerobic reactor to buffer the fluctuation of quality and quantity of leachate during landfill stabilization, but also reduce the inhibitory effect of acidic pH and high concentrations of ammonium in recycled liquid on microorganisms and accelerate the degradation of landfilled waste. After 390 days of operation, the discharge of COD and total nitrogen (TN) from the landfill with leachate pretreatment by a microaerobic reactor was 7.4 and 0.9 g, respectively, which accounted for 0.7% and 2.6% of COD, 1.9% and 7.5% of the TN discharge from the landfills without recirculation and directly recirculated with leachate and concentrated leachate, respectively. The degradation of the organic matter and biodegradable matter (BDM) in the landfill reactors could fit well with the first-order kinetics. The highest degradation of the organic matter and BDM was observed in the joint recirculation system with a microaerobic reactor for leachate treatment with the degradation constant of the first-order kinetics of 0.001 and 0.002. Copyright © 2015 Elsevier Ltd. All rights reserved.

Suction-recirculation device for stabilizing particle flows within a solar powered solid particle receiver

DOEpatents

Kolb, Gregory J [Albuquerque, NM

2012-02-07

A suction-recirculation device for stabilizing the flow of a curtain of blackened heat absorption particles falling inside of a solar receiver with an open aperture. The curtain of particles absorbs the concentrated heat from a solar mirror array reflected up to the receiver on a solar power tower. External winds entering the receiver at an oblique angle can destabilize the particle curtain and eject particles. A fan and ductwork is located behind the back wall of the receiver and sucks air out through an array of small holes in the back wall. Any entrained particles are separated out by a conventional cyclone device. Then, the air is recirculated back to the top of the receiver by injecting the recycled air through an array of small holes in the receiver's ceiling and upper aperture front wall. Since internal air is recirculated, heat losses are minimized and high receiver efficiency is maintained. Suction-recirculation velocities in the range of 1-5 m/s are sufficient to stabilize the particle curtain against external wind speeds in excess of 10 m/s.

Recirculation zone length in renal artery is affected by flow spirality and renal-to-aorta flow ratio.

PubMed

Javadzadegan, Ashkan; Fulker, David; Barber, Tracie

2017-07-01

Haemodynamic perturbations such as flow recirculation zones play a key role in progression and development of renal artery stenosis, which typically originate at the aorta-renal bifurcation. The spiral nature of aortic blood flow, division of aortic blood flow in renal artery as well as the exercise conditions have been shown to alter the haemodynamics in both positive and negative ways. This study focuses on the combinative effects of spiral component of blood flow, renal-to-aorta flow ratio and the exercise conditions on the size and distribution of recirculation zones in renal branches using computational fluid dynamics technique. Our findings show that the recirculation length was longest when the renal-to-aorta flow ratio was smallest. Spiral flow and exercise conditions were found to be effective in reducing the recirculation length in particular in small renal-to-aorta flow ratios. These results support the hypothesis that in renal arteries with small flow ratios where a stenosis is already developed an artificially induced spiral flow within the aorta may decelerate the progression of stenosis and thereby help preserve kidney function.

Wall shear stress characterization of a 3D bluff-body separated flow

NASA Astrophysics Data System (ADS)

Fourrié, Grégoire; Keirsbulck, Laurent; Labraga, Larbi

2013-10-01

Efficient flow control strategies aimed at reducing the aerodynamic drag of road vehicles require a detailed knowledge of the reference flow. In this work, the flow around the rear slanted window of a generic car model was experimentally studied through wall shear stress measurements using an electrochemical method. The mean and fluctuating wall shear stress within the wall impact regions of the recirculation bubble and the main longitudinal vortex structures which develop above the rear window are presented. Correlations allow a more detailed characterization of the recirculation phenomenon within the separation bubble. In the model symmetry plane the recirculation structure compares well with simpler 2D configurations; specific lengths, flapping motion and shedding of large-scale vortices are observed, these similarities diminish when leaving the middle plane due to the strong three-dimensionality of the flow. A specific attention is paid to the convection processes occurring within the recirculation: a downstream convection velocity is observed, in accordance with 2D recirculations from the literature, and an upstream convection is highlighted along the entire bubble length which has not been underlined in some previous canonical configurations.

Experimental investigation of a local recirculation photobioreactor for mass cultures of photosynthetic microorganisms.

PubMed

Moroni, Monica; Cicci, Agnese; Bravi, Marco

2014-04-01

The present work deals with the experimental fluid mechanics analysis of a wavy-bottomed cascade photobioreactor, to characterize the extent and period of recirculatory and straight-flowing streams establishing therein as a function of reactor inclination and liquid flow rate. The substream characterization via Feature Tracking (FT) showed that a local recirculation zone establishes in each vane only at inclinations ≤6° and that its location changes from the lower (≤3°) to the upper part of each vane (6°). A straight-flowing stream flows opposite (above or below) the local recirculation stream. The recirculation time ranges from 0.86 s to 0.23 s, corresponding, respectively, to the minimum flow rate at the minimum inclination and to the maximum flow rate at the maximum inclination where recirculation was observed. The increase of photosynthetic activity, resulting from the entailed "flash effect", was estimated to range between 102 and 113% with respect to equivalent tubular and bubble column photobioreactors. Copyright © 2013 Elsevier Ltd. All rights reserved.

Interaction between surface water areas and groundwater in Hanoi city, Viet Nam

NASA Astrophysics Data System (ADS)

Hayashi, T.; Kuroda, K.; Do Thuan, A.; Tran Thi Viet, N.; Takizawa, S.

2012-12-01

Hanoi is the capital of Viet Nam and the second largest city in this country (population: 6.45 million in 2009). Hanoi city has developed along the Red River and has many lakes, ponds and canals. However, recent rapid urbanization of this city has reduced number of natural water areas such as ponds and lakes by reclamation not only in the central area but the suburban area. Canals also have been reclaimed or cut into pieces. Contrary, number of artificial water areas such as fish cultivation pond has rapidly increased. On the other hand, various kind of waste water flows into these natural and artificial water areas and induces pollution and eutrophication. These waste waters also have possibility of pollution of groundwater that is one of major water resources in this city. In addition, groundwater in this area has high concentrations of Arsenic, Fe and NH4. Thus, groundwater use may causes re-circulation of Arsenic. However, studies on the interaction between surface water areas and groundwater and on the role of surface water areas for solute transport with water cycle are a few. Therefore, we focused on these points and took water samples of river, pond and groundwater from four communities in suburban areas: two communities are located near the Red River and other two are far from the River. Also, columnar sediment samples of these ponds were taken and pore water was abstracted. Major dissolved ions, metals and stable isotopes of oxygen and hydrogen of water samples were analyzed. As for water cycle, from the correlation between δ18O and δD, the Red River water (after GNIR) were distributed along the LMWL (δD=8.2δ18O+14.1, calculated from precipitation (after GNIP)). On the other hand, although the pond waters in rainy season were distributed along the LMWL, that in dry season were distributed along the local evaporation line (LEL, slope=5.6). The LEL crossed with the LMWL at around the point of weighted mean values of precipitation in rainy season and of the Red river. Groundwater samples were also distributed along the LEL and there was no seasonal change. Thus, groundwater in these communities was mainly recharged by mixing of precipitation/the Red River and evaporated water bodies. Considering the land use in these communities, evaporated water bodies were considered to be not only ponds but also paddy fields. As for solute transport, concentration of dissolved Arsenic (filtered by 0.45μm) of the pond water (3 - 10 μg/L) was slightly higher than the Red River (~ 3 μg/L) and was much lower than that of groundwater (~ 60 μg/L). On the other hand, concentration of dissolved Arsenic in the pore water of sediments (10 - 85 μg/L) was close to groundwater. Also, other metal elements showed the same trend. Therefore, Arsenic and other metal elements recharged to these ponds were considered to be adsorbed by sediments (including organic matters). That is, pond sediments played an important role as a filter of metal elements. The results of this study strongly suggested that the surface water areas such as ponds and paddy fields are one of main groundwater sources. Also, ponds play important role for solute transport of metal elements. Therefore, management of these surface water areas is important to conserve groundwater environment.

Method and apparatus for control of coherent synchrotron radiation effects during recirculation with bunch compression

DOEpatents

Douglas, David R; Tennant, Christopher

2015-11-10

A modulated-bending recirculating system that avoids CSR-driven breakdown in emittance compensation by redistributing the bending along the beamline. The modulated-bending recirculating system includes a) larger angles of bending in initial FODO cells, thereby enhancing the impact of CSR early on in the beam line while the bunch is long, and 2) a decreased bending angle in the final FODO cells, reducing the effect of CSR while the bunch is short. The invention describes a method for controlling the effects of CSR during recirculation and bunch compression including a) correcting chromatic aberrations, b) correcting lattice and CSR-induced curvature in the longitudinal phase space by compensating T.sub.566, and c) using lattice perturbations to compensate obvious linear correlations x-dp/p and x'-dp/p.

A new mechanism for periodic bursting of the recirculation region in the flow through a sudden expansion in a circular pipe

NASA Astrophysics Data System (ADS)

Lebon, Benoit; Nguyen, Minh Quan; Peixinho, Jorge; Shadloo, Mostafa Safdari; Hadjadj, Abdellah

2018-03-01

We report the results of a combined experimental and numerical study of specific finite-amplitude disturbances for transition to turbulence in the flow through a circular pipe with a sudden expansion. The critical amplitude thresholds for localized turbulent patch downstream of the expansion scale with the Reynolds number with a power law exponent of -2.3 for experiments and -2.8 for simulations. A new mechanism for the periodic bursting of the recirculation region is uncovered where the asymmetric recirculation flow develops a periodic dynamics: a secondary recirculation breaks the symmetry along the pipe wall and bursts into localized turbulence, which travels downstream and relaminarises. Flow visualizations show a simple flow pattern of three waves forming, growing, and bursting.

Losing Stuff Down a Black Hole

NASA Astrophysics Data System (ADS)

Okon, Elias; Sudarsky, Daniel

2018-03-01

Over the years, the so-called black hole information loss paradox has generated an amazingly diverse set of (often radical) proposals. However, 40 years after the introduction of Hawking's radiation, there continues to be a debate regarding whether the effect does, in fact, lead to an actual problem. In this paper we try to clarify some aspect of the discussion by describing two possible perspectives regarding the landscape of the information loss issue. Moreover, we advance a fairly conservative point of view regarding the relation between evaporating black holes and the rest of physics, which leads us to advocate a generalized breakdown of unitarity. We conclude by exploring some implications of our proposal in relation with conservation laws.

Nanoengineered Surfaces for High Flux Thin Film Evaporation

DTIC Science & Technology

2013-07-15

for a variety of heat transfer and resource conserving applications. References 1. Mudawar , I., Assessment of high-heat-flux thermal...M.B. and I. Mudawar , High-flux boiling in low-flow rate, low-pressure drop mini- channel and microchannel heat sinks. International Journal of Heat...pressure drop elements and fabricated nucleation sites. Journal of Heat Transfer, 2006. 128(4): p. 389-396. 7. Qu, W. and I. Mudawar , Measurement and

Internal combustion engine fuel controls. (Latest citations from the US Patent database). Published Search

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-12-01

The bibliography contains citations of selected patents concerning fuel control devices and methods for use in internal combustion engines. Patents describe air-fuel ratio control, fuel injection systems, evaporative fuel control, and surge-corrected fuel control. Citations also discuss electronic and feedback control, methods for engine protection, and fuel conservation. (Contains a minimum of 232 citations and includes a subject term index and title list.)

Predicting the Affects of Climate Change on Evapotranspiration and Agricultural Productivity of Semi-arid Basins

NASA Astrophysics Data System (ADS)

Peri, L.; Tyler, S. W.; Zheng, C.; Pohll, G. M.; Yao, Y.

2013-12-01

Many arid and semi-arid regions around the world are experiencing water shortages that have become increasingly problematic. Since the late 1800s, upstream diversions in Nevada's Walker River have delivered irrigation supply to the surrounding agricultural fields resulting in a dramatic water level decline of the terminal Walker Lake. Salinity has also increased because the only outflow from the lake is evaporation from the lake surface. The Heihe River basin of northwestern China, a similar semi-arid catchment, is also facing losses from evaporation of terminal locations, agricultural diversions and evapotranspiration (ET) of crops. Irrigated agriculture is now experiencing increased competition for use of diminishing water resources while a demand for ecological conservation continues to grow. It is important to understand how the existing agriculture in these regions will respond as climate changes. Predicting the affects of climate change on groundwater flow, surface water flow, ET and agricultural productivity of the Walker and Heihe River basins is essential for future conservation of water resources. ET estimates from remote sensing techniques can provide estimates of crop water consumption. By determining similarities of both hydrologic cycles, critical components missing in both systems can be determined and predictions of impacts of climate change and human management strategies can be assessed.

Numerical model for thermodynamical behaviors of unsaturated soil

NASA Astrophysics Data System (ADS)

Miyamoto, Yuji; Yamada, Mitsuhide; Sako, Kazunari; Araki, Kohei; Kitamura, Ryosuke

Kitamura et al. have proposed the numerical models to establish the unsaturated soil mechanics aided by probability theory and statistics, and to apply the unsaturated soil mechanics to the geo-simulator, where the numerical model for the thermodynamical behaviors of unsaturated soil are essential. In this paper the thermodynamics is introduced to investigate the heat transfer through unsaturated soil and the evaporation of pore water in soil based on the first and second laws of thermodynamics, i.e., the conservation of energy, and increasing entropy. On the other hand the lysimeter equipment is used to obtain the data for the evaporation of pore water during fine days and seepage of rain water during rainy days. The numerical simulation is carried out by using the proposed numerical model and the results are compared with those obtained from the lysimeter test.

Design of runoff water harvesting systems and its role in minimizing water losses

NASA Astrophysics Data System (ADS)

Berliner, P.; Carmi, G.; Leake, S.; Agam, N.

2016-12-01

Precipitation is one of the major water sources for agricultural production in arid and semi-arid areas. Rainfalls are limited, erratic and not always coincide with the crop growing season. Only a part of the rain is absorbed by the soil. Soil evaporation is most severe in these regions and the large part of the absorbed water is lost to evaporation. The technique of collecting and conveying the runoff is known as runoff harvesting. Microcatchments are one of the primary techniques used for collecting, storing and conserving local surface runoff for growing trees/shrubs. In this system, runoff water is collected close-by the area in which it was generated, and trees/shrubs may utilize the water. The main objective of the present research was to estimate the effect of the design of the micro-catchment collection area (shallow basin and deep trench) has on the efficiency of the water conservation in the soil profile. The study was carried out during two years using regular micro-catchments (three replicates) with a surface area of 9 m2 (3 x 3 m) and a depth of 0.1 m and trenches (three replicates) with a surface area of 12 m2 (12 x 1 m) and 1 m depth. One and three olive trees were planted inside the trenches and micro-catchments, respectively. Access tubes for neutron probe were installed in micro-catchments and trenches (four and seven, respectively) to depths of 3m. Soil water content in the soil profile was monitored. Sap flow in trees was measured by PS-TDP8 Granier sap flow system every 0.5 hour and fluxes computed for the time intervals that correspond to the soil water measurements. The first year study included flooding trenches and regular micro-catchments once with the same amount of water (1.5 m3) and the second year study included flooding four times with 0.25 m3 each time. Flooding was followed by monitoring the water balance components and estimation of evaporation losses and water use efficiency by olive trees. Evaporation from trenches and regular micro-catchments was estimated as the difference between evapotranspiration obtained by soil water content monitoring and transpiration estimated by sap flow measurements. The results clearly show that the evaporation from the regular micro-catchments was significantly larger than that of trenches during the entire duration of the both experiments.

Constraints on evaporation and dilution of terminal, hypersaline lakes under negative water balance: The Dead Sea, Israel

NASA Astrophysics Data System (ADS)

Zilberman, Tami; Gavrieli, Ittai; Yechieli, Yoseph; Gertman, Isaac; Katz, Amitai

2017-11-01

The response of hypersaline terminal lakes to negative water balance was investigated by studying brines evaporating to extreme salinities in sinkholes along the western coast of the Dead Sea and during on-site evaporation experiments of the Dead Sea brine. Density and temperature were determined in the field and all samples were analyzed for their major and a few minor solutes. The activity of H2O (aH2O) in the brines was calculated, and the degree of evaporation (DE) was established using Sr2+as a conservative solute. The relations between density and water activity were obtained by polynomial regression, and the relation between the lake's volume and level was established using Hall's (1996) hypsographic model for the Dead Sea basin. Relating the results to the modern, long-term relative humidity (RH) over the basin shows that (a) The lowermost attainable level of a terminal lake undergoing evaporation with no inflow is dictated by the median RH; this level represents equilibrium between the brine's aH2O and RH; (b) Small, saline water bodies with high surface to volume ratios (A/V), such as the hypersaline brines in the sinkholes, are very sensitive to short term changes in RH; in these, the brines' aH2O closely follows the seasonal changes; (c) the level decline of the Dead Sea due to evaporation under present climatic conditions and assuming no inflow to the lake may continue down to 516-537 m below mean sea level (bmsl), corresponding to a water activity range of 0.46-0.39 in its brine, in equilibrium with the overlying relative air humidity; this suggests that the lake level cannot drop more than ∼100 m from its present level; and (d) The maximum RH values that existed over the precursor lake of the Dead Sea (Lake Lisan) during geologically reconstructed minima levels can be similarly calculated.

Apparatus for diffusion separation

DOEpatents

Nierenberg, William A.; Pontius, Rex B.

1976-08-10

1. The method of testing the separation efficiency of porous permeable membranes which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane.

Effect of recirculation rate on methane production and SEBAR system performance using active stage digester.

PubMed

Tubtong, Cheevanuch; Towprayoon, Sirintornthep; Connor, Michael Anthony; Chaiprasert, Pawinee; Nopharatana, Annop

2010-09-01

A project was undertaken to examine the feasibility of treating organic wastes from Thai fruit and vegetable markets using the sequential batch anaerobic digester (SEBAR) approach. A key feature of the SEBAR system is the regular interchanging, or recirculation, of portions of leachate between each freshly filled digester and a support digester to which it is coupled until it is ready to operate independently. Leachate transfer from this support digester to the fresh waste digester provides additional alkalinity to help counteract the effects of early high acid release rates; it also helps build a balanced microbial population in the fresh waste digester. To optimize the leachate recirculation process, the effect of varying the quantities of leachate interchanged between freshly filled waste digesters and the still highly active support digesters to which they were coupled was studied. It was found that increasing the recirculation rate accelerated the onset of both waste degradation and methane production. The increasing of recirculation rate from 10% to 20% and 10% to 30% could reduce the SEBAR cycle period by approximately 7% and 22% without significant reduction in the amount of methane obtained from the systems. The methane yields were 0.0063, 0.0068 and 0.0077 l g(-1) VS added in the NEW digester per day using leachate recirculation rates of 10%, 20% and 30%, respectively. This finding has potentially important practical and economic implications for those using the SEBAR system to add value to market waste.

CFD modeling of hydro-biochemical behavior of MSW subjected to leachate recirculation.

PubMed

Feng, Shi-Jin; Cao, Ben-Yi; Li, An-Zheng; Chen, Hong-Xin; Zheng, Qi-Teng

2018-02-01

The most commonly used method of operating landfills more sustainably is to promote rapid biodegradation and stabilization of municipal solid waste (MSW) by leachate recirculation. The present study is an application of computational fluid dynamics (CFD) to the 3D modeling of leachate recirculation in bioreactor landfills using vertical wells. The objective is to model and investigate the hydrodynamic and biochemical behavior of MSW subject to leachate recirculation. The results indicate that the maximum recirculated leachate volume can be reached when vertical wells are set at the upper middle part of a landfill (H W /H T  = 0.4), and increasing the screen length can be more helpful in enlarging the influence radius than increasing the well length (an increase in H S /H W from 0.4 to 0.6 results in an increase in influence radius from 6.5 to 7.7 m). The time to reach steady state of leachate recirculation decreases with the increase in pressure head; however, the time for leachate to drain away increases with the increase in pressure head. It also showed that methanogenic biomass inoculum of 1.0 kg/m 3 can accelerate the volatile fatty acid depletion and increase the peak depletion rate to 2.7 × 10 -6  kg/m 3 /s. The degradation-induced void change parameter exerts an influence on the processes of MSW biodegradation because a smaller parameter value results in a greater increase in void space.

Investigation of blood flow rheology using second-grade viscoelastic model (Phan-Thien-Tanner) within carotid artery.

PubMed

Ramiar, Abas; Larimi, Morsal Momenti; Ranjbar, Ali Akbar

2017-01-01

Hemodynamic factors, such as Wall Shear Stress (WSS), play a substantial role in arterial diseases. In the larger arteries, such as the carotid artery, interaction between the vessel wall and blood flow affects the distribution of hemodynamic factors. The fluid is considered to be non-Newtonian, whose flow is governed by the equation of a second-grade viscoelastic fluid and the effects of viscoelastic on blood flow in carotid artery is investigated. Pulsatile flow studies were carried out in a 3D model of carotid artery. The governing equations were solved using finite volume C++ based on open source code, OpenFOAM. To describe blood flow, conservation of mass and momentum, a constitutive relation of simplified Phan-Thien-Tanner (sPTT), and appropriate relations were used to explain shear thinning behavior. The first recirculation was observed at t = 0.2 s, in deceleration phase. In the acceleration phase from t = 0.3 s to t = 0.5 s, vortex and recirculation sizes in bulb regions in both ECA and ICA gradually increased. As is observed in the line graphs based on extracted data from ICA, at t = 0.2 s, τyy is the maximum amount of wall shear stress and τxy the minimum one. The maximum shear stress occurred in the inner side of the main branch (inner side of ICA and ECA) because the velocity of blood flow in the inner side of the bulb region was maximum due to the created recirculation zone in the opposite side in this area. The rheology of blood flow and shear stress in various important parts (the area that are in higher rates of WSS such as bifurcation region and the regions after bulb areas in both branches, Line1-4 in Fig. 7) were also analyzed. The investigation of velocity stream line, velocity profile and shear stress in various sections of carotid artery showed that the maximum shear stress occurred in acceleration phase and in the bifurcation region between ECA and ICA which is due to velocity gradients and changes in thinning behavior of blood and increasing strain rate in Newtonian stress part.

Energy, water and fish: biodiversity impacts of energy-sector water demand in the United States depend on efficiency and policy measures.

PubMed

McDonald, Robert I; Olden, Julian D; Opperman, Jeffrey J; Miller, William M; Fargione, Joseph; Revenga, Carmen; Higgins, Jonathan V; Powell, Jimmie

2012-01-01

Rising energy consumption in coming decades, combined with a changing energy mix, have the potential to increase the impact of energy sector water use on freshwater biodiversity. We forecast changes in future water use based on various energy scenarios and examine implications for freshwater ecosystems. Annual water withdrawn/manipulated would increase by 18-24%, going from 1,993,000-2,628,000 Mm(3) in 2010 to 2,359,000-3,271,000 Mm(3) in 2035 under the Reference Case of the Energy Information Administration (EIA). Water consumption would more rapidly increase by 26% due to increased biofuel production, going from 16,700-46,400 Mm(3) consumption in 2010 to 21,000-58,400 Mm(3) consumption in 2035. Regionally, water use in the Southwest and Southeast may increase, with anticipated decreases in water use in some areas of the Midwest and Northeast. Policies that promote energy efficiency or conservation in the electric sector would reduce water withdrawn/manipulated by 27-36 m(3)GJ(-1) (0.1-0.5 m(3)GJ(-1) consumption), while such policies in the liquid fuel sector would reduce withdrawal/manipulation by 0.4-0.7 m(3)GJ(-1) (0.2-0.3 m(3)GJ(-1) consumption). The greatest energy sector withdrawal/manipulation are for hydropower and thermoelectric cooling, although potential new EPA rules that would require recirculating cooling for thermoelectric plants would reduce withdrawal/manipulation by 441,000 Mm(3) (20,300 Mm(3) consumption). The greatest consumptive energy sector use is evaporation from hydroelectric reservoirs, followed by irrigation water for biofuel feedstocks and water used for electricity generation from coal. Historical water use by the energy sector is related to patterns of fish species endangerment, where water resource regions with a greater fraction of available surface water withdrawn by hydropower or consumed by the energy sector correlated with higher probabilities of imperilment. Since future increases in energy-sector surface water use will occur in areas of high fish endemism (e.g., Southeast), additional management and policy actions will be needed to minimize further species imperilment.

The effects of the pulsatile period on the size of recirculation bubble in the vicinity of stent struts

NASA Astrophysics Data System (ADS)

Jiang, B.; Thondapu, V.; Barlis, P.; Poon, E. K. W.; Ooi, A. S. H.

2017-04-01

Incomplete stent apposition (ISA) is sometimes found in stent deployment at complex lesions, and it is considered to be one of the causes of post-stenting complications, such as late stent thrombosis and restenosis. The presence of ISA leads to large recirculation bubbles behind the stent struts, which can reduce shear stress at the arterial wall that retards neointimal formation process and thus lead to complications. Computational fluid dynamics (CFD) simulations are performed on simplified two-dimensional axisymmetric arterial models with stents struts of square and circular cross-sectional shapes at a malapposition distance of 120 μm from the arterial wall. To investigate the effects of pulsatile flow period on the dynamics of the recirculation bubbles, high fidelity simulations are carried out with pulsatile flows of period 0.4 s and 0.8 s. Under the condition of the same flow rate, both square and circular strut cases show that shorter period provides greater flow deceleration, leading to the formation of a larger recirculation bubble. With the same thickness, circular strut has a significant improvement over the square strut in terms of the size of the recirculation bubble, and therefore less likely to lead to complications.

Correlation between Reynolds number and eccentricity effect in stenosed artery models.

PubMed

Javadzadegan, Ashkan; Shimizu, Yasutomo; Behnia, Masud; Ohta, Makoto

2013-01-01

Flow recirculation and shear strain are physiological processes within coronary arteries which are associated with pathogenic biological pathways. Distinct Quite apart from coronary stenosis severity, lesion eccentricity can cause flow recirculation and affect shear strain levels within human coronary arteries. The aim of this study is to analyse the effect of lesion eccentricity on the transient flow behaviour in a model of a coronary artery and also to investigate the correlation between Reynolds number (Re) and the eccentricity effect on flow behaviour. A transient particle image velocimetry (PIV) experiment was implemented in two silicone based models with 70% diameter stenosis, one with eccentric stenosis and one with concentric stenosis. At different times throughout the flow cycle, the eccentric model was always associated with a greater recirculation zone length, maximum shear strain rate and maximum axial velocity; however, the highest and lowest impacts of eccentricity were on the recirculation zone length and maximum shear strain rate, respectively. Analysis of the results revealed a negative correlation between the Reynolds number (Re) and the eccentricity effect on maximum axial velocity, maximum shear strain rate and recirculation zone length. As Re number increases the eccentricity effect on the flow behavior becomes negligible.

The benefits of flue gas recirculation in waste incineration.

PubMed

Liuzzo, Giuseppe; Verdone, Nicola; Bravi, Marco

2007-01-01

Flue gas recirculation in the incinerator combustion chamber is an operative technique that offers substantial benefits in managing waste incineration. The advantages that can be obtained are both economic and environmental and are determined by the low flow rate of fumes actually emitted if compared to the flue gas released when recirculation is not conducted. Simulations of two incineration processes, with and without flue gas recirculation, have been carried out by using a commercial flowsheeting simulator. The results of the simulations demonstrate that, from an economic point of view, the proposed technique permits a greater level of energy recovery (up to +3%) and, at the same time, lower investment costs as far as the equipment and machinery constituting the air pollution control section of the plant are concerned. At equal treatment system efficiencies, the environmental benefits stem from the decrease in the emission of atmospheric pollutants. Throughout the paper reference is made to the EC legislation in the field of environmental protection, thus ensuring the general validity in the EU of the foundations laid and conclusions drawn henceforth. A numerical example concerning mercury emission quantifies the reported considerations and illustrates that flue gas recirculation reduces emission of this pollutant by 50%.

Effects of aeration and leachate recirculation on methyl mercaptan emissions from landfill.

PubMed

Zhang, Siyuan; Long, Yuyang; Fang, Yuan; Du, Yao; Liu, Weijia; Shen, Dongsheng

2017-10-01

The issue of odorous volatile organic sulfur compound methyl mercaptan (MM) released from landfill sites cannot be ignored for its extremely low odor threshold and high toxicity. In this study, we focused on the formation and emission of MM in four lab-scaled simulated landfill reactors running in different operation modes, namely, R1 and R2, without leachate recirculation, running under anaerobic and semi-aerobic atmosphere, R3 and R4, with leachate recirculation, running under anaerobic and semi-aerobic atmosphere, respectively. From the perspective of odor abatement, the semi-aerobic operation mode can efficiently lower the emitted MM concentration by 87.4-94.9%, relative to the semi-aerobic operation mode. Furthermore, under semi-aerobic conditions, leachate recirculation substantially shortened the period of MM influence by 12.7%, thus reducing the risk of affecting the surrounding atmospheric environment. The formation of MM was dependent on the characteristics such as the volatile fatty acid concentration and chemical oxygen demand in the leachate and sulfide concentration of the refuse. Overall, MM release can be effectively controlled with semi-aerobic operation mode and leachate recirculation. Copyright © 2017 Elsevier Ltd. All rights reserved.

An innovative sewage sludge reduction by using a combined mesophilic anaerobic and thermophilic aerobic process with thermal-alkaline treatment and sludge recirculation.

PubMed

Cho, Hyun Uk; Park, Sang Kyu; Ha, Jeong Hyub; Park, Jong Moon

2013-11-15

Lab-scale High Efficiency Digestion (HED) systems containing a Mesophilic Anaerobic Reactor (MAR), Thermophilic Aerobic Reactor (TAR), liquid/solid separation unit, and thermal-alkaline treatment were developed to evaluate the efficiencies of sludge reduction and methane production. The HED process was divided into three phases to examine the influence of sludge pretreatment and pretreated sludge recirculation using TCOD and VSS reduction, COD solubilization, and methane production. The VSS removal with a solid/liquid separation unit, sludge recirculation, and thermal-alkaline treatment drastically increased up to 95% compared to the feed concentration. In addition, the results of COD solubilization and VSS/TSS showed that the solubilization of cells and organic matters by the thermal-alkaline treatment was highly increased, which was also consistent with the SEM images. In particular, the methane production rate increased 24-fold when the feed sludge and recirculated sludge were pretreated together. Collectively, the HED experiments performed with sludge recirculation and thermal-alkaline treatment demonstrated that the HED systems can be successfully employed for highly efficient sewage sludge reduction and methane gas production. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of flow recirculation on abdominal aortic aneurysm

NASA Astrophysics Data System (ADS)

Taib, Ishkrizat; Amirnordin, Shahrin Hisham; Madon, Rais Hanizam; Mustafa, Norrizal; Osman, Kahar

2012-06-01

The presences of flow recirculation at the abdominal aortic aneurysm (AAA) region yield the unpredictable failure of aneurismal wall. The failure of the aneurismal wall is closely related to the hemodynamic factor. Hemodynamic factor such as pressure and velocity distribution play a significance role of aneurysm growth and rupture. By using the computational approach, the influence of hemodynamic factor is investigated using computational fluid dynamic (CFD) method on the virtual AAA model. The virtual 3D AAAs model was reconstructed from Spiral Computed Tomography scan (CT-scan). The blood flow is assumed as being transient, laminar and Newtonian within a rigid section of the vessel. The blood flow also driven by an imposed of pressure gradient in the form of physiological waveform. The pulsating blood flow is also considered in this simulation. The results on pressure distribution and velocity profile are analyzed to interpret the behaviour of flow recirculation. The results show the forming of vortices is seen at the aneurysm bulge. This vortices is form at the aneurysm region then destroyed rapidly by flow recirculation. Flow recirculation is point out much higher at distal end of aneurysm closed to iliac bifurcation. This phenomenon is managed to increase the possibility of aneurysm growth and rupture.

The Weak Gravity Conjecture and the axionic black hole paradox

NASA Astrophysics Data System (ADS)

Hebecker, Arthur; Soler, Pablo

2017-09-01

In theories with a perturbatively massless 2-form (dual to an axion), a paradox may arise in the process of black hole evaporation. Schwarzschild black holes can support a non-trivial Wilson-line-type field, the integral of the 2-form around their horizon. After such an `axionic black hole' evaporates, the Wilson line must be supported by the corresponding 3-form field strength in the region formerly occupied by the black hole. In the limit of small axion decay-constant f, the energy required for this field configuration is too large. Thus, energy cannot be conserved in the process of black hole evaporation. The natural resolution of this paradox is through the presence of light strings, which allow the black hole to "shed" its axionic hair sufficiently early. This gives rise to a new Weak-Gravity-type argument in the 2-form context: small coupling, in this case f , enforces the presence of light strings or a low cutoff. We also discuss how this argument may be modified in situations where the weak coupling regime is achieved in the low-energy effective theory through an appropriate gauging of a model with a vector field and two 2-forms.

Fast Evaporation of Spreading Droplets of Colloidal Suspensions

NASA Astrophysics Data System (ADS)

Maki, Kara; Kumar, Satish

2011-11-01

When a coffee droplet dries on a countertop, a dark ring of coffee solute is left behind, a phenomenon often referred to as ``the coffee-ring effect.'' A closely related yet less-well-explored phenomenon is the formation of a layer of particles, or skin, at the surface of the droplet. In this work, we explore the behavior of a mathematical model that can qualitatively describe both phenomena. We consider a thin axisymmetric droplet of a colloidal suspension on a horizontal substrate undergoing spreading and rapid evaporation. The lubrication approximation is applied to simplify the mass and momentum conservation equations, and the colloidal particles are allowed to influence droplet rheology through their effect on the viscosity. By describing the transport of the colloidal particles with the full convection-diffusion equation, we are able to capture depthwise gradients in particle concentration and thus describe skin formation, a feature neglected in prior models of droplet evaporation. Whereas capillarity creates a flow that drives particles to the contact line to produce a coffee-ring, Marangoni flows can compete with this and promote skin formation. Increases in viscosity due to particle concentration slow down droplet dynamics, and can lead to a significant reduction in the spreading rate.

Numerical analysis of heat and mass transfer for water recovery in an evaporative cooling tower

NASA Astrophysics Data System (ADS)

Lee, Hyunsub; Son, Gihun

2017-11-01

Numerical analysis is performed for water recovery in an evaporative cooling tower using a condensing heat exchanger, which consists of a humid air channel and an ambient dry air channel. The humid air including water vapor produced in an evaporative cooling tower is cooled by the ambient dry air so that the water vapor is condensed and recovered to the liquid water. The conservation equations of mass, momentum, energy and vapor concentration in each fluid region and the energy equation in a solid region are simultaneously solved with the heat and mass transfer boundary conditions coupled to the effect of condensation on the channel surface of humid air. The present computation demonstrates the condensed water film distribution on the humid air channel, which is caused by the vapor mass transfer between the humid air and the colder water film surface, which is coupled to the indirect heat exchange with the ambient air. Computations are carried out to predict water recovery rate in parallel, counter and cross-flow type heat exchangers. The effects of air flow rate and channel interval on the water recovery rate are quantified.

Mixer assembly for a gas turbine engine having a pilot mixer with a corner flame stabilizing recirculation zone

NASA Technical Reports Server (NTRS)

Dai, Zhongtao (Inventor); Cohen, Jeffrey M. (Inventor); Fotache, Catalin G. (Inventor)

2012-01-01

A mixer assembly for a gas turbine engine is provided, including a main mixer, and a pilot mixer having an annular housing in which a corner is formed between an aft portion of the housing and a bulkhead wall in which a corner recirculation zone is located to stabilize and anchor the flame of the pilot mixer. The pilot mixer can further include features to cool the annular housing, including in the area of the corner recirculation zone.

Effect of self recirculation casing treatment on the performance of a turbocharger centrifugal compressor

NASA Astrophysics Data System (ADS)

Gancedo, Matthieu

Increase in emission regulations in the transport industry brings the need to have more efficient engines. A path followed by the automobile industry is to downsize the size of the internal combustion engine and increase the air density at the intake to keep the engine power when needed. Typically a centrifugal compressor is used to force the air into the engine, it can be powered from the engine shaft (superchargers) or extracting energy contained into the hot exhaust gases with a turbine (turbochargers). The flow range of the compressor needs to match the one of the engine. However compressors mass flow operating range is limited by choke on the high end and surge on the low end. In order to extend the operation at low mass flow rates, the use of passive devices for turbocharger centrifugal compressors was explored since the late 80's. Hence, casing treatments including flow recirculation from the inducer part of the compressor have been shown to move the surge limit to lower flows. Yet, the working mechanisms are still not well understood and thus, to optimize the design of this by-pass system, it is necessary to determine the nature of the changes induced by the device both on the dynamic stability of the pressure delivery and on the flow at the inlet. The compressor studied here features a self-recirculating casing treatment at the inlet. The recirculation passage could be blocked to carry a direct comparison between the cases with and without the flow feature. To grasp the effect on compressor stability, pressure measurements were taken in the different constituting elements of the compressor. The study of the mean pressure variations across the operating map showed that the tongue region is a limiting element. Dynamic pressure measurements revealed that the instabilities generated near the inducer when the recirculation is blocked increase the overall instability levels at the compressor outlet and propagating pressure waves starting at the tongue occurred, different in nature from rotating stall. The flow velocity was also measured at the inlet of the compressor by means of planar PIV measurements. The case without recirculation showed strong back flow occurrence at low MFR on the shroud of the inlet passage due to tip recirculation. With recirculation, this back flow was significantly reduced improving the overall stability. However, with the current recirculation channels design, there is an efficiency penalty and the recirculated flow introduces non-homogeneities in the mixing region. Finally, to explore experimentally the effect of variations of the casing treatment, several different designs were tested. It was seen that modifications of the supporting rib shape impacted the efficiency. Also, improvements on the surge line were obtained with flow reinjection near the inducer in the direction of the main flow at low speeds and with induced counter swirl for all speeds.

Impact of nitrate-enhanced leachate recirculation on gaseous releases from a landfill bioreactor cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tallec, G.; Bureau, C.; Peu, P.

2009-07-15

This study evaluates the impact of nitrate injection on a full scale landfill bioreactor through the monitoring of gaseous releases and particularly N{sub 2}O emissions. During several weeks, we monitored gas concentrations in the landfill gas collection system as well as surface gas releases with a series of seven static chambers. These devices were directly connected to a gas chromatograph coupled to a flame ionisation detector and an electron capture detector (GC-FID/ECD) placed directly on the field. Measurements were performed before, during and after recirculation of raw leachate and nitrate-enhanced leachate. Raw leachate recirculation did not have a significant effectmore » on the biogas concentrations (CO{sub 2}, CH{sub 4} and N{sub 2}O) in the gas extraction network. However, nitrate-enhanced leachate recirculation induced a marked increase of the N{sub 2}O concentrations in the gas collected from the recirculation trench (100-fold increase from 0.2 ppm to 23 ppm). In the common gas collection system however, this N{sub 2}O increase was no more detectable because of dilution by gas coming from other cells or ambient air intrusion. Surface releases through the temporary cover were characterized by a large spatial and temporal variability. One automated chamber gave limited standard errors over each experimental period for N{sub 2}O releases: 8.1 {+-} 0.16 mg m{sup -2} d{sup -1} (n = 384), 4.2 {+-} 0.14 mg m{sup -2} d{sup -1} (n = 132) and 1.9 {+-} 0.10 mg m{sup -2} d{sup -1} (n = 49), during, after raw leachate and nitrate-enhanced leachate recirculation, respectively. No clear correlation between N{sub 2}O gaseous surface releases and recirculation events were evidenced. Estimated N{sub 2}O fluxes remained in the lower range of what is reported in the literature for landfill covers, even after nitrate injection.« less

Groundwater-driven nutrient inputs to coastal lagoons: The relevance of lagoon water recirculation as a conveyor of dissolved nutrients.

PubMed

Rodellas, Valentí; Stieglitz, Thomas C; Andrisoa, Aladin; Cook, Peter G; Raimbault, Patrick; Tamborski, Joseph J; van Beek, Pieter; Radakovitch, Olivier

2018-06-16

Evaluating the sources of nutrient inputs to coastal lagoons is required to understand the functioning of these ecosystems and their vulnerability to eutrophication. Whereas terrestrial groundwater processes are increasingly recognized as relevant sources of nutrients to coastal lagoons, there are still limited studies evaluating separately nutrient fluxes driven by terrestrial groundwater discharge and lagoon water recirculation through sediments. In this study, we assess the relative significance of these sources in conveying dissolved inorganic nutrients (NO 3 - , NH 4 + and PO 4 3- ) to a coastal lagoon (La Palme lagoon; France, Mediterranean Sea) using concurrent water and radon mass balances. The recirculation of lagoon water through sediments represents a source of NH 4 + (1900-5500 mol d -1 ) and PO 4 3- (22-71 mol d -1 ), but acts as a sink of NO 3 - . Estimated karstic groundwater-driven inputs of NO 3 - , NH 4 + and PO 4 3- to the lagoon are on the order of 200-1200, 1-12 and 1.5-8.7 mol d -1 , respectively. A comparison between the main nutrient sources to the lagoon (karstic groundwater, recirculation, diffusion from sediments, inputs from a sewage treatment plant and atmospheric deposition) reveals that the recirculation of lagoon water through sediments is the main source of both dissolved inorganic nitrogen (DIN) and phosphorous (DIP) to La Palme lagoon. These results are in contrast with several studies conducted in systems influenced by terrestrial groundwater inputs, where groundwater is often assumed to be the main pathway for dissolved inorganic nutrient loads. This work highlights the important role of lagoon water recirculation through permeable sediments as a major conveyor of dissolved nutrients to coastal lagoons and, thus, the need for a sound understanding of the recirculation-driven nutrient fluxes and their ecological implications to sustainably manage lagoonal ecosystems. Copyright © 2018. Published by Elsevier B.V.

A recirculating stream aquarium for ecological studies.

Treesearch

Gordon H. Reeves; Fred H. Everest; Carl E. McLemore

1983-01-01

Investigations of the ecological behavior of fishes often require studies in both natural and artificial stream environments. We describe a large, recirculating stream aquarium and its controls, constructed for ecological studies at the Forestry Sciences Laboratory in Corvallis.

Multi-Point Interferometric Rayleigh Scattering using Dual-Pass Light Recirculation

NASA Technical Reports Server (NTRS)

Bivolaru, Daniel; Danehy, Paul M.; Cutler, Andrew D.

2008-01-01

This paper describes for the first time an interferometric Rayleigh scattering system using dual-pass light recirculation (IRS-LR) capable of simultaneously measuring at multiple points two orthogonal components of flow velocity in combustion flows using single shot laser probing. An additional optical path containing the interferometer input mirror, a quarter-wave plate, a polarization dependent beam combiner, and a high reflectivity mirror partially recirculates the light that is rejected by the interferometer. Temporally- and spatially-resolved acquisitions of Rayleigh spectra in a large-scale combustion-heated supersonic axi-symmetric jet were performed to demonstrate the technique. Recirculating of Rayleigh scattered light increases the number of photons analyzed by the system up to a factor of 1.8 compared with previous configurations. This is equivalent to performing measurements with less laser energy or performing measurements with the previous system in gas flows at higher temperatures.

Recurrent amoebic gill infestation in rainbow trout cultured in a semiclosed water recirculation system

USGS Publications Warehouse

Noble, A.C.; Herman, R.L.; Noga, E.J.; Bullock, G.L.

1997-01-01

Five lots of commercially purchased juvenile rainbow trout Oncorhynchus mykiss (17-44 g) stocked in a continuous-production water recirculation system became infested with gilt amoebae. The amoebae were introduced into the recirculation system, as evidenced by their presence on gills of fish held in quarantine tanks. Based on their morphology, as seen in histological sections and by electron microscopy, the amoebae appeared to be more closely related to the family Cochliopodiidae than to other taxa of free living amoebae. Attempts to culture the amoebae in different media, at different temperatures of incubation, and in fish cell culture were not successful. Initial treatment of the recirculation system with formalin at 167 parts per million (ppm) for 1 h eliminated amoebae from the gills. Subsequent treatments of the entire system with formalin at 50-167 ppm reduced the intensity of further infestations.

Increasing EDV Range through Intelligent Cabin Air Handling Strategies: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leighton, Daniel; Rugh, John

Computational fluid dynamics (CFD) simulations of a Ford Focus Electric demonstrated that a split flow heating, ventilating and air conditioning (HVAC) system with rear recirculation ducts can reduce cabin heating loads by up to 57.4% relative to full fresh air usage under some conditions (steady state, four passengers, ambient temperature of -5 deg C). Simulations also showed that implementing a continuous recirculation fraction control system into the original equipment manufacturer (OEM) HVAC system can reduce cabin heating loads by up to 50.0% relative to full fresh air usage under some conditions (steady state, four passengers, ambient temperature of -5 degmore » C). Identified that continuous fractional recirculation control of the OEM system can provide significant energy savings for EVs at minimal additional cost, while a split flow HVAC system with rear recirculation ducts only provides minimal additional improvement at significant additional cost.« less

Investigation of hydrocarbon oil transformation by gliding arc discharge: comparison of batch and recirculated configurations

NASA Astrophysics Data System (ADS)

Whitehead, J. Christopher; Prantsidou, Maria

2016-04-01

The degradation of liquid dodecane was studied in a gliding arc discharge (GAD) of humid argon or nitrogen. A batch or recirculating configuration was used. The products in the gaseous and liquid phase were analysed by infrared and chromatography and optical emission spectroscopy was used to identify the excited species in the discharge. The best degradation performance comes from the use of humid N2 but a GAD of humid argon produces fewer gas-phase products but more liquid-phase end-products. A wide range of products such as heavier saturated or unsaturated hydrocarbons both aliphatic and aromatic, and oxidation products mainly alcohols, but also aldehydes, ketones and esters are produced in the liquid-phase. The recirculating treatment mode is more effective than the batch mode increasing the reactivity and changing the product selectivities. Overall, the study shows promising results for the organic liquid waste treatment, especially in the recirculating mode.

A dew point signaller for conservation of works of art.

PubMed

Camuffo, D; Valcher, S

1986-03-01

All works of art, from paintings, frescoes, sculptures, to monuments and buildings, are affected by diurnal and seasonal variations of the local microclimate, which induce interactions with the environmental atmosphere. Heat and vapour exchanges cause fluxes of heat and mass between the surface and the atmosphere, and may favour the agressivity of environmental pollutants. Condensation-evaporation cycles are recognized as being very important processes which adversely affect the life-time of the work of art. The need to control the microclimate or to stop condensation processes has been resolved by means of a dew-point signaller especially designed to overcome this problem. This paper discusses the characteristics of this device as well as the environmental philosophy which should be followed when conserving works of art.

Role of Hot Water System Design on Factors Influential to Pathogen Regrowth: Temperature, Chlorine Residual, Hydrogen Evolution, and Sediment

PubMed Central

Brazeau, Randi H.; Edwards, Marc A.

2013-01-01

Abstract Residential water heating is linked to growth of pathogens in premise plumbing, which is the primary source of waterborne disease in the United States. Temperature and disinfectant residual are critical factors controlling increased concentration of pathogens, but understanding of how each factor varies in different water heater configurations is lacking. A direct comparative study of electric water heater systems was conducted to evaluate temporal variations in temperature and water quality parameters including dissolved oxygen levels, hydrogen evolution, total and soluble metal concentrations, and disinfectant decay. Recirculation tanks had much greater volumes of water at temperature ranges with potential for increased pathogen growth when set at 49°C compared with standard tank systems without recirculation. In contrast, when set at the higher end of acceptable ranges (i.e., 60°C), this relationship was reversed and recirculation systems had less volume of water at risk for pathogen growth compared with conventional systems. Recirculation tanks also tended to have much lower levels of disinfectant residual (standard systems had 40–600% higher residual), 4–6 times as much hydrogen, and 3–20 times more sediment compared with standard tanks without recirculation. On demand tankless systems had very small volumes of water at risk and relatively high levels of disinfectant residual. Recirculation systems may have distinct advantages in controlling pathogens via thermal disinfection if set at 60°C, but these systems have lower levels of disinfectant residual and greater volumes at risk if set at lower temperatures. PMID:24170969

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boreyko, Jonathan B; Mruetusatorn, Prachya; Sarles, Stephen A

Droplet interface bilayers (DIBs) are a robust platform for studying synthetic cellular membranes; however, to date no DIBs have been produced at cellular length scales. Here, we create microscale droplet interface bilayers ( DIBs) at the interface between aqueous femtoliter-volume droplets within an oil-filled microfluidic channel. The uniquely large area-to-volume ratio of the droplets results in strong evaporation effects, causing the system to transition through three distinct regimes. First, the two adjacent droplets shrink into the shape of a single spherical droplet, where an augmented lipid bilayer partitions two hemi-spherical volumes. In the second regime, the combined effects of themore » shrinking monolayers and growing bilayer force the confined bilayer to buckle to conserve its mass. Finally, at a bending moment corresponding to a critical shear stress, the buckling bilayer fissions a vesicle to regulate its shape and stress. The DIBs produced here enable evaporation-induced bilayer dynamics reminiscent of endo- and exocytosis in cells.« less

Conservation story takes to the road. [Potomac Edison Co. of Allegheny Power System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1975-02-15

Potomac Edison Co. personnel designed a compact mobile energy-conservation display that demonstrated energy conservation applications to industry, commerce, government, and educators; this van went on the road in December 1974. Among the displays in the vehicle were a working model of a liquid-heating tank that used floating plastic balls as a cover to conserve heat losses and evaporation, a microwave oven, types of insulation and their applications, and a demand controller designed to reduce consumer peak loads and demand charges. Other displays showed temperature and automatic time controls that could be used in locations unoccupied for various periods of timemore » and lighting applications that stressed use of the most efficient lamps and luminaires and emphasized equipment maintenance; a heat pump, a heat-recovery wheel, heat pipe, and model ''run-around system'' for recovering and reusing heat from various industrial processes were also included. (EAPA Ed. note: as of January 1976, plans were to refurbish, update, and put this van back on the road during the upcoming summer). (MCW)« less

Full-scale demonstration of in situ cometabolic biodegradation of trichloroethylene in groundwater 1. Dynamics of a recirculating well system

NASA Astrophysics Data System (ADS)

Gandhi, Rahul K.; Hopkins, Gary D.; Goltz, Mark N.; Gorelick, Steven M.; McCarty, Perry L.

2002-04-01

Recirculating well systems provide an engine for the in situ treatment of subsurface contaminants. Although numerous recirculating wells have been installed in the field, for such systems, there is a paucity of comprehensive monitoring data and models constrained to data appearing in the research literature. Here we present an extensive data set combined with detailed inverse and simulation analyses for a two-well groundwater recirculation system used for in situ bioremediation at Edwards Air Force Base in southern California. The ``conveyor belt'' flow system, which was established for in situ treatment of trichloroethylene (TCE) in two bioactive zones, was created by pumping water upward in one well and downward in another well, each well being screened in both the upper and lower aquifers. A bromide tracer test was conducted and extensively monitored for 60 days. Combined inverse analysis was conducted on hydraulic heads from 38 monitoring wells, 32 bromide concentration histories, and a constraint on the degree of recirculation that was based on TCE concentration data. Four different formulations involving alternative weighting schemes used in a nonlinear weighted least squares simulation-regression analysis were explored. The best formulation provided parameter estimates with tight bounds on estimated covariances, suggesting that the model provides a reasonable description of the hydrogeologic system. Our investigation indicates the geometry of the recirculation zone and the degree of recirculation under two different sets of operating conditions. Surprisingly, our analysis suggests that the effects of aquifer heterogeneity are not significant at this site under the conditions of forced recirculation. Furthermore, anomalous flow through an open monitoring well created significant vertical short-circuiting between the generally insulated aquifers. Flow through this small open conduit was equivalent to as much as 33% of the flow through the pumping wells. Using the model as a guide, we treated the aquifer system and bioactive zones as an equivalent mixed reactor to develop simple expressions relating effluent concentrations to influent concentrations. We demonstrate how these expressions are useful in predicting the removal of TCE that had undergone in situ bioremediation in the recirculatory treatment well system. The finite element model developed in this work serves as the foundation for a reactive transport simulator that we developed to analyze bioremediation which occurred during a 444 day experiment [Gandhi et al., 2002].

Better Management Practices for Recirculating Aquaculture Systems

USDA-ARS?s Scientific Manuscript database

Under the 2004 federal aquaculture effluent limitation guidelines (Federal Register 2004), recirculating aquaculture systems with an annual production exceeding 45,454 kg (100,000 pounds) are classified as concentrated aquatic animal production (CAAP) facilities and are required to obtain a National...

Production of cobia in recirculating systems

USDA-ARS?s Scientific Manuscript database

Only limited information exists with respect to rearing juvenile cobia Rachycentron canadum to stocker and marketable sizes using recirculating aquaculture systems (RAS). To investigate this topic, two rearing trials were conducted using commercial scale RAS. In Trial 1, juvenile cobia (29 g) we...

Freshwater Institute: Focused on improving recirculating aquaculture system technology

USDA-ARS?s Scientific Manuscript database

Recirculating aquaculture system (RAS) technologies help to overcome barriers to domestic aquaculture expansion and enhance the sustainability of the modern fish farming industry through reduction in environmental impacts. With RAS, fish farm expansion is no longer highly constrained by competition ...

The effect of leachate recirculation with enzyme cellulase addition on waste stability in landfill bioreactor

NASA Astrophysics Data System (ADS)

Saffira, N.; Kristanto, G. A.

2018-01-01

Landfill bioreactor with leachate recirculation is known to enhance waste stabilization. However, the composition of waste in Indonesia is comprised by organic waste which is lignocellulosic materials that considered take a long time to degrade under anaerobic condition. To accelerate the degradation process, enzyme addition is ought to do. Cellulase is an enzyme that can catalyse cellulose and other polysaccharide decomposition processes. Therefore, operation of waste degradation using leachate recirculation with a cellulase addition to enhance waste stabilization was investigated using anaerobic bioreactor landfill. The experiment was performed on 2 conditions; leachate recirculation with cellulase addition and recirculation only as a control. The addition of cellulase is reported to be significant in decreasing organic content, represented by volatile solid parameter. The volatile solid reduction in the cellulase augmented reactor and control reactor was 17.86% and 7.90%, respectively. Cellulase addition also resulted in the highest cellulose reduction. Settlement of the landfill in a bioreactor with enzyme addition (32.67%) was reported to be higher than the control (19.33%). Stabilization of landfill review by the decreasing rate constant of the cellulose and lignin ratio parameter was more rapidly achieved by the enzyme addition (0.014 day-1) compared to control (0.002 day-1).

In Situ Biotreatment of TBA with Recirculation/Oxygenation

PubMed Central

North, Katharine P.; Mackay, Douglas M.; Kayne, Julian S.; Petersen, Daniel; Rasa, Ehsan; Rastegarzadeh, Laleh; Holland, Reef B.; Scow, Kate M.

2012-01-01

The potential for in situ biodegradation of tert-butyl alcohol (TBA) by creation of aerobic conditions in the subsurface with recirculating well pairs was investigated in two field studies conducted at Vandenberg Air Force Base (VAFB). In the first experiment, a single recirculating well pair with bromide tracer and oxygen amendment successfully delivered oxygen to the subsurface for 42 days. TBA concentrations were reduced from approximately 500 μg/L to below the detection limit within the treatment zone and the treated water was detected in a monitoring transect several meters downgradient. In the second experiment, a site-calibrated model was used to design a double recirculating well pair with oxygen amendment, which successfully delivered oxygen to the subsurface for 291 days and also decreased TBA concentrations to below the detection limit. Methylibium petroleiphilum strain PM1, a known TBA-degrading bacterium, was detectable at the study site but addition of oxygen had little impact on the already low baseline population densities, suggesting that there was not enough carbon within the groundwater plume to support significant new growth in the PM1 population. Given favorable hydrogeologic and geochemical conditions, the use of recirculating well pairs to introduce dissolved oxygen into the subsurface is a viable method to stimulate in situ biodegradation of TBA or other aerobically-degradable aquifer contaminants. PMID:23358537

Low NO.sub.x multistage combustor

DOEpatents

Becker, Frederick E.; Breault, Ronald W.; Litka, Anthony F.; McClaine, Andrew W.; Shukla, Kailash

2000-01-01

A high efficiency, Vortex Inertial Staged Air (VIStA) combustor provides ultra-low NO.sub.X production of about 20 ppmvd or less with CO emissions of less than 50 ppmvd, both at 3% O.sub.2. Prompt NO.sub.X production is reduced by partially reforming the fuel in a first combustion stage to CO and H.sub.2. This is achieved in the first stage by operating with a fuel rich mixture, and by recirculating partially oxidized combustion products, with control over stoichiometry, recirculation rate and residence time. Thermal NO.sub.X production is reduced in the first stage by reducing the occurrence of high temperature combustion gas regions. This is achieved by providing the first stage burner with a thoroughly pre-mixed fuel/oxidant composition, and by recirculating part of the combustion products to further mix the gases and provide a more uniform temperature in the first stage. In a second stage combustor thermal NO.sub.X production is controlled by inducing a large flow of flue gas recirculation in the second stage combustion zone to minimize the ultimate temperature of the flame. One or both of the first and second stage burners can be cooled to further reduce the combustion temperature and to improve the recirculation efficiency. Both of these factors tend to reduce production of NO.sub.X.

Thermophysical fundamentals of cyclonic recirculating heating devices

NASA Astrophysics Data System (ADS)

Karpov, S. V.; Zagoskin, A. A.

2017-10-01

This report presents the results of experimental and theoretical research of aerodynamics and convective heat transfer in cyclone devices with the new system of external recirculation of heating gas under the influence of radial pressure gradient in a heat carrier’s swirling turbulent flow. The dynamic problem of tangential velocity distribution in a clearance volume is solved at various re-circulation ratio values including limiting quantities (kr = 0; 1) and variations in cyclonic combustion chamber’s design parameters and operating conditions (Rer); the integrated calculation ratios for fundamental aerodynamic characteristics of a recirculation device are derived. The first experimental and numerical studies of convective heat transfer on internal and external surfaces of a hollow shaft in a swirling recirculation flow are derived through the instrumentality of OpenFOAM, these studies are also conducted for a setting of several cylindrical solid inserts. The external surface heat problem of a hollow cylindrical insert is solved with integral and digital methods; generalized similarity equations for the internal and external surfaces extended in range of Reynolds number are derived. The experimental data is in reasonable agreement with the derived curves and the results of mathematic modelling of convective heat transfer. Calculation recommendations for optimal selection of kr values at various ratios of their geometric characteristics and products utilization rate are obtained.

Pilot-scale study of powdered activated carbon recirculation for micropollutant removal.

PubMed

Meinel, F; Sperlich, A; Jekel, M

Adsorption onto powdered activated carbon (PAC) is a promising technique for the removal of organic micropollutants (OMPs) from treated wastewater. To enhance the adsorption efficiency, PAC is recycled back into the adsorption stage. This technique was examined in pilot scale in comparison to a reference without recirculation. Coagulation with Fe(3+) was carried out simultaneously to adsorption. Extensive OMP measurements showed that recirculation significantly increased OMP eliminations. Thus, significant PAC savings were feasible. The PAC concentration in the contact reactor proved to be an important operating parameter that can be surrogated by the easily measurable total suspended solids (TSS) concentration. OMP eliminations increased with increasing TSS concentrations. At 20 mg PAC L(-1) and 2.8 g TSS L(-1) in the contact reactor, well-adsorbable carbamazepine was eliminated by 97%, moderately adsorbable diclofenac was eliminated by 92% and poorly-adsorbable acesulfame was eliminated by 54% in comparison to 49%, 35% and 18%, respectively, without recirculation. The recirculation system represents an efficient technique, as the PAC's adsorption capacity is practically completely used. Small PAC dosages yield high OMP eliminations. Poorly-adsorbable gabapentin was eliminated to an unexpectedly high degree. A laboratory-scale biomass inhibition study showed that aerobic biodegradation removed gabapentin in addition to adsorption.

In Situ Biotreatment of TBA with Recirculation/Oxygenation.

PubMed

North, Katharine P; Mackay, Douglas M; Kayne, Julian S; Petersen, Daniel; Rasa, Ehsan; Rastegarzadeh, Laleh; Holland, Reef B; Scow, Kate M

2012-01-01

The potential for in situ biodegradation of tert-butyl alcohol (TBA) by creation of aerobic conditions in the subsurface with recirculating well pairs was investigated in two field studies conducted at Vandenberg Air Force Base (VAFB). In the first experiment, a single recirculating well pair with bromide tracer and oxygen amendment successfully delivered oxygen to the subsurface for 42 days. TBA concentrations were reduced from approximately 500 μg/L to below the detection limit within the treatment zone and the treated water was detected in a monitoring transect several meters downgradient. In the second experiment, a site-calibrated model was used to design a double recirculating well pair with oxygen amendment, which successfully delivered oxygen to the subsurface for 291 days and also decreased TBA concentrations to below the detection limit. Methylibium petroleiphilum strain PM1, a known TBA-degrading bacterium, was detectable at the study site but addition of oxygen had little impact on the already low baseline population densities, suggesting that there was not enough carbon within the groundwater plume to support significant new growth in the PM1 population. Given favorable hydrogeologic and geochemical conditions, the use of recirculating well pairs to introduce dissolved oxygen into the subsurface is a viable method to stimulate in situ biodegradation of TBA or other aerobically-degradable aquifer contaminants.

Fall 2016 Solicitation Projects Website Info

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diachin, L.

Spark-ignition engines are the backbone behind people transportation around the world. The efficiency of spark-ignition engines is limited in practice by variations between engine cycles and cylinders within an engine that result from the manufacturing processes/tolerances. These variations impact knock limits and dilution tolerance, which results in more conservative settings for design and calibration settings, such as compression ratio, valve timing, and exhaust gas recirculation rates. Engine variations also have a significant impact on emissions generation, which can have a secondary impact on efficiency. A deeper understanding of the relative importance of these variations and their interactions on the chargemore » preparation process can guide future decisions on machining tolerances and control strategies. This project will develop simulation tools and methodology to include the effects of some key manufacturing tolerances and their impact on engine performance and emissions.« less

40 CFR 420.101 - Specialized definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Cold Forming Subcategory § 420.101 Specialized definitions. (a) The term recirculation means those cold rolling operations which include recirculation of rolling solutions at all mill stands. (b) The term combination means those cold rolling...

40 CFR 420.101 - Specialized definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Cold Forming Subcategory § 420.101 Specialized definitions. (a) The term recirculation means those cold rolling operations which include recirculation of rolling solutions at all mill stands. (b) The term combination means those cold rolling...

40 CFR 420.101 - Specialized definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Cold Forming Subcategory § 420.101 Specialized definitions. (a) The term recirculation means those cold rolling operations which include recirculation of rolling solutions at all mill stands. (b) The term combination means those cold rolling...

40 CFR 420.101 - Specialized definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Cold Forming Subcategory § 420.101 Specialized definitions. (a) The term recirculation means those cold rolling operations which include recirculation of rolling solutions at all mill stands. (b) The term combination means those cold rolling...

An Inexpensive Recirculating Aquaculture System with Multiple Use Capabilities.

ERIC Educational Resources Information Center

Scurlock, Gerald Don, Jr.; Cook, S. Bradford; Scurlock, Carrie Ann

1999-01-01

Describes the construction of an inexpensive recirculating aquaculture system that can hold up to 46 pounds of fish, invertebrates, and mussels for classroom use. The system is versatile, requires little maintenance, and can be used for both teaching and research purposes. (WRM)

Transport and recirculation of aerosols off Southern Africa—macroscale plume structure

NASA Astrophysics Data System (ADS)

Tyson, P. D.; D'Abreton, P. C.

A pall of aerosols and trace gases frequently occurs over southern Africa to a depth of ˜500 hPa, blanketing vast areas, particularly in the austral winter and spring. Large-scale offshore transport of these aerosols and trace gases in extremely large plumes from interior continental areas of the subcontinent to the Indian and Atlantic Oceans is a common occurrence. The nature of the transport plumes, their climatology, chemical composition and morphology are discussed. In the vertically integrated, surface-to-500 hPa layer, poleward of about 15° S, transport into the Indian Ocean is shown to be about 60% greater into the Indian Ocean than into the Atlantic Ocean. Recirculation of atmospheric constituents is considered and estimates of aerosol mass fluxes over central southern Africa are presented. Of the total of about 50 Mt yr -1 of aerosols being transported at the central meridian, 44% is shown to be recirculated material. The rest exits the subcontinent directly without recirculation. Preferred plume corridors of exit and entry are postulated for different localities on the east and west coasts. Two case studies of east- and west-coast plumes apparently flowing uniformly out of southern Africa are examined. The illusion of uniformity in plume structure is shown to be misleading. Both plumes are shown to be above and separated from the marine boundary layer. Each is over 1500 km in width and 3-5 km deep. Likewise, both are capped by absolutely stable layers at ˜500 hPa and exhibit a complex structure of both outflowing aerosols and trace gases and inflowing, recycled and recirculated material. Indications of the composition of the recirculated material are given and implications of the plume transports are considered.

Removal of Gross Air Embolization from Cardiopulmonary Bypass Circuits with Integrated Arterial Line Filters: A Comparison of Circuit Designs.

PubMed

Reagor, James A; Holt, David W

2016-03-01

Advances in technology, the desire to minimize blood product transfusions, and concerns relating to inflammatory mediators have lead many practitioners and manufacturers to minimize cardiopulmonary bypass (CBP) circuit designs. The oxygenator and arterial line filter (ALF) have been integrated into one device as a method of attaining a reduction in prime volume and surface area. The instructions for use of a currently available oxygenator with integrated ALF recommends incorporating a recirculation line distal to the oxygenator. However, according to an unscientific survey, 70% of respondents utilize CPB circuits incorporating integrated ALFs without a path of recirculation distal to the oxygenator outlet. Considering this circuit design, the ability to quickly remove a gross air bolus in the blood path distal to the oxygenator may be compromised. This in vitro study was designed to determine if the time required to remove a gross air bolus from a CPB circuit without a path of recirculation distal to the oxygenator will be significantly longer than that of a circuit with a path of recirculation distal to the oxygenator. A significant difference was found in the mean time required to remove a gross air bolus between the circuit designs (p = .0003). Additionally, There was found to be a statistically significant difference in the mean time required to remove a gross air bolus between Trial 1 and Trials 4 (p = .015) and 5 (p =.014) irrespective of the circuit design. Under the parameters of this study, a recirculation line distal to an oxygenator with an integrated ALF significantly decreases the time it takes to remove an air bolus from the CPB circuit and may be safer for clinical use than the same circuit without a recirculation line.

Impact of different supply air and recirculating air filtration systems on stable climate, animal health, and performance of fattening pigs in a commercial pig farm

PubMed Central

Wenke, Cindy; Pospiech, Janina; Reutter, Tobias; Altmann, Bettina; Truyen, Uwe

2018-01-01

Biosecurity is defined as the implementation of measures that reduce the risk of disease agents being introduced and/or spread. For pig production, several of these measures are routinely implemented (e.g. cleaning, disinfection, segregation). However, air as a potential vector of pathogens has long been disregarded. Filters for incoming and recirculating air were installed into an already existing ventilation plant at a fattening piggery (3,840 pigs at maximum) in Saxony, Germany. Over a period of three consecutive fattening periods, we evaluated various parameters including air quality indices, environmental and operating parameters, and pig performance. Animal data regarding respiratory diseases, presence of antibodies against influenza A viruses, PRRSV, and Actinobacillus pleuropneumoniae and lung health score at slaughter were recorded, additionally. There were no significant differences (p = 0.824) in total bacterial counts between barns with and without air filtration. Recirculating air filtration resulted in the lowest total dust concentration (0.12 mg/m3) and lung health was best in animals from the barn equipped with recirculating air filtration modules. However, there was no difference in animal performance. Antibodies against all above mentioned pathogens were detected but mostly animals were already antibody-positive at re-stocking. We demonstrated that supply air filtration as well as recirculating air filtration technique can easily be implemented in an already existing ventilation system and that recirculating air filtration resulted in enhanced lung health compared to supply air-filtered and non-filtered barns. A more prominent effect might have been obtained in a breeding facility because of the longer life span of sows and a higher biosecurity level with air filtration as an add-on measure. PMID:29558482

29 CFR 1910.1025 - Lead.

Code of Federal Regulations, 2010 CFR

2010-07-01

... reflect the current status of the program. (4) Mechanical ventilation. (i) When ventilation is used to...) Recirculation of air. If air from exhaust ventilation is recirculated into the workplace, the employer shall... protective clothing or equipment of the potentially harmful effects of exposure to lead. (vii) The employer...

29 CFR 1910.1025 - Lead.

Code of Federal Regulations, 2012 CFR

2012-07-01

... reflect the current status of the program. (4) Mechanical ventilation. (i) When ventilation is used to...) Recirculation of air. If air from exhaust ventilation is recirculated into the workplace, the employer shall... protective clothing or equipment of the potentially harmful effects of exposure to lead. (vii) Labeling of...

29 CFR 1910.1025 - Lead.

Code of Federal Regulations, 2013 CFR

2013-07-01

... reflect the current status of the program. (4) Mechanical ventilation. (i) When ventilation is used to...) Recirculation of air. If air from exhaust ventilation is recirculated into the workplace, the employer shall... protective clothing or equipment of the potentially harmful effects of exposure to lead. (vii) Labeling of...

29 CFR 1910.1025 - Lead.

Code of Federal Regulations, 2011 CFR

2011-07-01

... reflect the current status of the program. (4) Mechanical ventilation. (i) When ventilation is used to...) Recirculation of air. If air from exhaust ventilation is recirculated into the workplace, the employer shall... protective clothing or equipment of the potentially harmful effects of exposure to lead. (vii) The employer...

29 CFR 1910.1025 - Lead.

Code of Federal Regulations, 2014 CFR

2014-07-01

... reflect the current status of the program. (4) Mechanical ventilation. (i) When ventilation is used to...) Recirculation of air. If air from exhaust ventilation is recirculated into the workplace, the employer shall... protective clothing or equipment of the potentially harmful effects of exposure to lead. (vii) Labeling of...

33 CFR 159.127 - Safety coliform count: Recirculating devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Safety coliform count: Recirculating devices. 159.127 Section 159.127 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159...

Modelling mono-digestion of grass silage in a 2-stage CSTR anaerobic digester using ADM1.

PubMed

Thamsiriroj, T; Murphy, J D

2011-01-01

This paper examines 174 days of experimental data and modelling of mono-digestion of grass silage in a two stage wet process with recirculation of liquor; the two vessels have an effective volume of 312 L each. The organic loading rate is initiated at 0.5 kg VS m(-3) d(-1) (first 74 days) and subsequently increased to 1 kg VS m(-3) d(-1). The experimental data was used to generate a mathematical model (ADM1) which was calibrated over the first 74 days of operation. Good accuracy with experimental data was found for the subsequent 100 days. Results of the model would suggest starting the process without recirculation and thus building up the solids content of the liquor. As the level of VFA increases, recirculation should be employed to control VFA. Recirculation also controls solids content and pH. Methane production was estimated at 88% of maximum theoretical production. Copyright © 2010 Elsevier Ltd. All rights reserved.

Saponification pretreatment and solids recirculation as a new anaerobic process for the treatment of slaughterhouse waste.

PubMed

Affes, R; Palatsi, J; Flotats, X; Carrère, H; Steyer, J P; Battimelli, A

2013-03-01

Different configurations of anaerobic process, adapted to the treatment of solid slaughterhouse fatty waste, were proposed and evaluated in this study. The tested configurations are based on the combination of anaerobic digestion with/without waste saponification pretreatment (70 °C during 60 min) and with/without recirculation of the digestate solid fraction (ratio=20% w/w). After an acclimation period of substrate pulses-feeding cycles, the reactors were operated in a semi-continuous feeding mode, increasing organic loading rates along experimental time. The degradation of the raw substrate was shown to be the bottleneck of the whole process, obtaining the best performance and process yields in the reactor equipped with waste pretreatment and solids recirculation. Saponification promoted the emulsification and bioavailability of solid fatty residues, while recirculation of solids minimized the substrate/biomass wash-out and induced microbial adaptation to the treatment of fatty substrates. Copyright © 2013 Elsevier Ltd. All rights reserved.

Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor

NASA Technical Reports Server (NTRS)

Roffe, G.; Raman, R. S. V.

1981-01-01

Tests were run using a perforated plate flameholder with a relatively short attached recirculation zone and a vee gutter flameholder with a relatively long attached recirculation zone. Combustor streamlines were traced in cold flow tests at ambient pressure. The amount of secondary air entrainment in the recirculation zones of the flameholders was determined by tracer gas testing at cold flow ambient pressure conditions. Combustion tests were caried out at entrance conditions of 0.5 MPa/630K and emission of NOx, CO and unburned hydrocarbons were measured along with lean stability and flashback limits. The degree of entrainment increases as dilution air injection decreases. Flashback appears to be a function of overall equivalence ratio and resistance to flashback increases with increasing combustor entrance velocity. Lean stability limit appears to be a function of both primary zone and flameholder recirculation zone equivalence ratios and resistance to lean blowout increases with increasing combustor entrance velocity.

Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

NASA Technical Reports Server (NTRS)

Coffen, Charles D.; George, Albert R.; Hardinge, Hal; Stevenson, Ryan

1991-01-01

The results are given of flow visualization studies and inflow velocity field measurements performed on a 1/12 scale model of the XV-15 tilt rotor aircraft in the hover mode. The complex recirculating flow due to the rotor-wake-body interactions characteristic of tilt rotors was studied visually using neutrally buoyant soap bubbles and quantitatively using hot wire anemometry. Still and video photography were used to record the flow patterns. Analysis of the photos and video provided information on the physical dimensions of the recirculating fountain flow and on details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Recirculating flows were also observed along the length of the fuselage. Hot wire anemometry results indicate that the wing under the rotor acts to obstruct the inflow causing a deficit in the inflow velocities over the inboard region of the model. Hot wire anemometry also shows that the turbulence intensities in the inflow are much higher in the recirculating fountain reingestion zone.

Boosting devices with integral features for recirculating exhaust gas

DOEpatents

Wu, Ko -Jen

2015-09-15

According to one embodiment of the invention, a compressor housing includes a compressor inlet in fluid communication with a compressor volute configured to house a compressor wheel, the compressor inlet configured to provide a first air flow to the compressor wheel and a compressor outlet in fluid communication with the compressor volute, the compressor outlet configured to direct a compressed gas to an intake manifold. The compressor housing further includes an exhaust gas recirculation inlet port in fluid communication with the compressor volute, the exhaust gas recirculation inlet port being configured to combine an exhaust gas flow with the air flow to the compressor wheel.

Method and device for measuring single-shot transient signals

DOEpatents

Yin, Yan

2004-05-18

Methods, apparatus, and systems, including computer program products, implementing and using techniques for measuring multi-channel single-shot transient signals. A signal acquisition unit receives one or more single-shot pulses from a multi-channel source. An optical-fiber recirculating loop reproduces the one or more received single-shot optical pulses to form a first multi-channel pulse train for circulation in the recirculating loop, and a second multi-channel pulse train for display on a display device. The optical-fiber recirculating loop also optically amplifies the first circulating pulse train to compensate for signal losses and performs optical multi-channel noise filtration.

A transient analysis of frost formation on a parallel plate evaporator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Frias, J.; Aceves, S.M.; Hernandez-Guerrero, A.

1996-12-31

This paper presents the development of a transient model for evaluating frost formation on a parallel plate evaporator for heat pump applications. The model treats the frost layer as a porous substance, and applies the equations of conservation of mass, momentum and energy to calculate the growth and densification of the frost layer. Empirical correlations for thermal conductivity and tortuosity as a function of density are incorporated from previous studies. Frost growth is calculated as a function of time, Reynolds number, longitudinal location, plate temperature, and ambient air temperature and humidity. The main assumptions are: ideal gas behavior for airmore » and water vapor, uniform frost density and thermal conductivity across the thickness of the frost layer; and quasi-steady conditions during the whole process. The mathematical model is validated by comparing the predicted values of frost thickness and frost density with results obtained in recent experimental studies. A good agreement was obtained in the comparison. The frost formation model calculates pressure drop and heat transfer resistance that result from the existence of the frost layer, and it can therefore be incorporated into a heat pump model to evaluate performance losses due to frosting as a function of weather conditions and time of operation since the last evaporator defrost.« less

Physiological regulation of evaporative water loss in endotherms: is the little red kaluta (Dasykaluta rosamondae) an exception or the rule?

PubMed Central

Withers, Philip C.; Cooper, Christine E.

2014-01-01

It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick's law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and linearly proportional to the water vapour pressure deficit (Δwvp) between animal and air. However, we show here for a small dasyurid marsupial, the little kaluta (Dasykaluta rosamondae), that EWL is essentially independent of RH (and Δwvp) at low RH (as are metabolic rate and thermal conductance). These results suggest regulation of a constant EWL independent of RH, a hitherto unappreciated capacity of endothermic vertebrates. Independence of EWL from RH conserves water and heat at low RH, and avoids physiological adjustments to changes in evaporative heat loss such as thermoregulation. Re-evaluation of previously published data for mammals and birds suggests that a lesser dependence of EWL on RH is observed more commonly than previously thought, suggesting that physiological independence of EWL of RH is not just an unusual capacity of a few species, such as the little kaluta, but a more general capability of many mammals and birds. PMID:24741015

Interactions between plant nutrients, water and carbon dioxide as factors limiting crop yields

PubMed Central

Gregory, P. J.; Simmonds, L. P.; Warren, G. P.

1997-01-01

Biomass production of annual crops is often directly proportional to the amounts of radiation intercepted, water transpired and nutrients taken up. In many places the amount of rainfall during the period of rapid crop growth is less than the potential rate of evaporation, so that depletion of stored soil water is commonplace. The rate of mineralization of nitrogen (N) from organic matter and the processes of nutrient loss are closely related to the availability of soil water. Results from Kenya indicate the rapid changes in nitrate availability following rain.
Nutrient supply has a large effect on the quantity of radiation intercepted and hence, biomass production. There is considerable scope for encouraging canopy expansion to conserve water by reducing evaporation from the soil surface in environments where it is frequently rewetted, and where the unsaturated hydraulic conductivity of the soil is sufficient to supply water at the energy limited rate (e.g. northern Syria). In regions with high evaporative demand and coarse-textured soils (e.g. Niger), transpiration may be increased by management techniques that reduce drainage.
Increases in atmospheric [CO2] are likely to have only a small impact on crop yields when allowance is made for the interacting effects of temperature, and water and nutrient supply.

Generation and Maintenance of Recirculations by Gulf Stream Instabilities

DTIC Science & Technology

1999-02-01

Francois Primeau for endless discus- sions of various scientific problems, Kirill Pankratov for useful advice on the numerical methods in fluid...recirculation. J. Phys. Oceanogr., 18, 662-682. [7] Davis C. A. and K. A. Emanuel, 1991 : Potential vorticity diagnostics of cyclo- genesis. Mon. Weather. Rev

Nitrate removal effectiveness of fluidized sulfur-based autotrophic denitrification biofilters for recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

There is a need to develop practical methods to reduce nitrate -nitrogen loads from recirculating aqua-culture systems to facilitate increased food protein production simultaneously with attainment of water quality goals. The most common wastewater denitrification treatment systems utilize methanol-...

Disinfection of water in recirculating aquaculture systems with peracetic acid (PAA)

USDA-ARS?s Scientific Manuscript database

The disinfection behaviour of peracetic acid (PAA) in recirculating aquaculture systems (RAS) was investigated. Peracetic acid is a strong oxidizing agent found in various concentrations in different products. Three Wofasteril PAA products (E400 (c), Lspecical; AC 150) were tested in vitro for the...

Experimental Bleaching of a Reef-Building Coral Using a Simplified Recirculating Laboratory Exposure System

EPA Science Inventory

Determining stressor-response relationships in reef building corals is a critical need for researchers because of global declines in coral reef ecosystems. A simplified recirculating coral exposure system for laboratory testing of a diversity of species and morphologies of reef b...

Delineating sources of groundwater recharge in an arsenic-affected Holocene aquifer in Cambodia using stable isotope-based mixing models

NASA Astrophysics Data System (ADS)

Richards, Laura A.; Magnone, Daniel; Boyce, Adrian J.; Casanueva-Marenco, Maria J.; van Dongen, Bart E.; Ballentine, Christopher J.; Polya, David A.

2018-02-01

Chronic exposure to arsenic (As) through the consumption of contaminated groundwaters is a major threat to public health in South and Southeast Asia. The source of As-affected groundwaters is important to the fundamental understanding of the controls on As mobilization and subsequent transport throughout shallow aquifers. Using the stable isotopes of hydrogen and oxygen, the source of groundwater and the interactions between various water bodies were investigated in Cambodia's Kandal Province, an area which is heavily affected by As and typical of many circum-Himalayan shallow aquifers. Two-point mixing models based on δD and δ18O allowed the relative extent of evaporation of groundwater sources to be estimated and allowed various water bodies to be broadly distinguished within the aquifer system. Model limitations are discussed, including the spatial and temporal variation in end member compositions. The conservative tracer Cl/Br is used to further discriminate between groundwater bodies. The stable isotopic signatures of groundwaters containing high As and/or high dissolved organic carbon plot both near the local meteoric water line and near more evaporative lines. The varying degrees of evaporation of high As groundwater sources are indicative of differing recharge contributions (and thus indirectly inferred associated organic matter contributions). The presence of high As groundwaters with recharge derived from both local precipitation and relatively evaporated surface water sources, such as ponds or flooded wetlands, are consistent with (but do not provide direct evidence for) models of a potential dual role of surface-derived and sedimentary organic matter in As mobilization.

Changing Demands from Riparian Evapotranspiration and Free-Water Evaporation in the Lower Colorado River Basin Under Different Climate Scenarios

NASA Astrophysics Data System (ADS)

Bunk, D. A.; Piechota, T. C.

2012-12-01

Observed and projected trends in riparian evapotranspiration (ET) and free-water evaporation are examined to improve water demand forecasting for use in modeling of lower Colorado River system reservoir operations. While most previous research has focused on the impacts of climate change and climate variability on water supply, the impacts on water demand under changing climate conditions have not been adequately addressed (NRC, 2007 and Reclamation, 2009). Increases in temperatures and changes in precipitation and wind patterns are expected to increase evaporative demands (Bates and others, 2008), potentially increasing free-water evaporation and ET from riparian vegetation; increasing infiltration rates; altering cropping patterns; and changing the temporal and spatial distribution of water deliveries. This study uses observations and projections under changing climate scenarios of hydroclimatic variables, such as temperature, wind, and precipitation, to analyze their impacts on riparian ET and free-water evaporation in the lower Colorado River mainstream downstream of Lake Mead and Hoover Dam. The projected changes in evaporative demands were assessed to determine their impacts on water supply and reservoir operations in the Colorado River basin under changing climate conditions. Based on analysis of observed and projected hydroclimatic data from the Variable Infiltration Capacity (VIC) hydrologic model, mean annual daily temperature in the lower Colorado River mainstream reach has increased by 0.8° Celsius (C) from the 30-year period ending in 1980 to period ending in 2010 and is projected to increase by an additional 1.7° C by 30-year period ending in 2060. Analysis of riparian ET derived from the ASCE Penman-Monteith method (Allen et al., 2005, from Monteith, 1965 and 1981) and Westenburg et al. (2006) and free-water evaporation derived from the Penman combination model in Dingman (2008) indicates that combined evaporative demand in the lower Colorado River mainstream increased by 14,800 acre-feet, or 1.8 percent, during the 30-year period ending in 2010, and may increase by an additional 16,600 acre-feet, or 2.0 percent, during the 30-year period ending in 2060, when compared to the period from 1951 to 1980. With this projected increase in evaporative demands, the combined storage of Lake Powell and Lake Mead are projected to decrease by a cumulative volume of 75,400 acre-feet, or 0.15 percent of total conservation capacity, based on 10-year running averages ending in years 2020 to 2060. In addition, average annual shortage volumes in the lower Colorado River basin are projected to increase by 40,000 acre-feet, or 0.30 percent, from 2013 to 2060.

Effect of exhaust gas recirculation on emissions from a flame-tube combustor using Liquid Jet A fuel

NASA Technical Reports Server (NTRS)

Marek, C. J.; Tacina, R. R.

1976-01-01

The effects of uncooled exhaust gas recirculation as an inert diluent on emissions of oxides of nitrogen (NO + NO2) and on combustion efficiency were investigated. Ratios of recirculated combustion products to inlet airflow were varied from 10 to 80 percent by using an inlet air ejector nozzle. Liquid Jet A fuel was used. The flame-tube combustor was 10.2 cm in diameter. It was operated with and without a flameholder present. The combustor pressure was maintained constant at 0.5 MPa. The equivalence ratio was varied from 0.3 to 1.0. The inlet air temperature was varied from 590 to 800 K, and the reference velocity from 10 to 30 m/sec. Increasing the percent recirculation from 10 to 25 had the following effects: (1) the peak NOx emission was decreased by 37 percent, from 8 to 5 g NO2/kg fuel, at an inlet air temperature of 590 K and a reference velocity of 15 m/sec; (2) the combustion efficiency was increased, particularly at the higher equivalence ratios; and (3) for a high combustion efficiency of greater than 99.5 percent, the range of operation of the combustor was nearly doubled in terms of equivalence ratio. Increasing the recirculation from 25 to 50 percent did not change the emissions significantly.

Ocean Bottom Pressure Variation Associated with the Large Meander of the Kuroshio South of Japan in 2004-2005

NASA Astrophysics Data System (ADS)

Nagano, A.; Hasegawa, T.; Matsumoto, H.; Ariyoshi, K.

2016-02-01

The Kuroshio, the western boundary current of the North Pacific subtropical gyre, takes a stable meandering path off the southern coast of Japan, called the large meander (LM), on interannual to decadal timescales. The LM of the Kuroshio formed in July 2004 associated with the intensified anticyclonic recirculation gyre south of the Kuroshio, and gradually decayed in the latter half of 2005. The variations of the Kuroshio and the southern recirculating currents may be related to deep currents, which are expected to be associated with bottom pressure (BP) variation. In order to examine the variation of BP associated with the variations of the sea surface currents, we analyzed data of eleven pressure sensors equipped to inverted echo sounders deployed from July 2004 to October 2006. An abrupt enhancement of BP is found on the continental slope off Shikoku, lagging a few months behind an elevation of sea surface height (SSH) due to the onshore shift of the recirculation gyre associated with the LM formation. Subsequently, BP beneath the recirculation gyre dwindles, leading the gradual depression of SSH due to the decay of the LM. The relationship between BP and SSH may suggest that the occurrence and decay of the LM depend on the extension of the recirculation gyre current down to the ocean bottom.

Cooling Tower (Evaporative Cooling System) Measurement and Verification Protocol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurnik, Charles W.; Boyd, Brian; Stoughton, Kate M.

This measurement and verification (M and V) protocol provides procedures for energy service companies (ESCOs) and water efficiency service companies (WESCOs) to determine water savings resulting from water conservation measures (WCMs) in energy performance contracts associated with cooling tower efficiency projects. The water savings are determined by comparing the baseline water use to the water use after the WCM has been implemented. This protocol outlines the basic structure of the M and V plan, and details the procedures to use to determine water savings.

Reservoir Control Center: Activities and Accomplishments of the Southwestern Division of the Army Corps of Engineers Related to Reservoir Regulation and Water Management. Part 2.

DTIC Science & Technology

1981-01-01

entered the low flow pipe, cloggea the control valve, and died. Although the Kansas Fish and Game Commission felt the loss of the fish was not...Guadalupe River above Canyon Lake in March *1980. The equipment installed was a Handar data collection platform (dcp) with an emergency transmission channel...continued high evaporation losses resulted in * the lakes averaging about 72 percent full conservation storage. Most projects, * except those with

Investigation of Saltwater Intrusion and Recirculation of Seawater for Henry Constant Dispersion and Velocity-Dependent Dispersion Problems and Field-Scale Problem

NASA Astrophysics Data System (ADS)

Motz, L. H.; Kalakan, C.

2013-12-01

Three problems regarding saltwater intrusion, namely the Henry constant dispersion and velocity-dependent dispersion problems and a larger, field-scale velocity-dependent dispersion problem, have been investigated to determine quantitatively how saltwater intrusion and the recirculation of seawater at a coastal boundary are related to the freshwater inflow and the density-driven buoyancy flux. Based on dimensional analysis, saltwater intrusion and the recirculation of seawater are dependent functions of the independent ratio of freshwater advective flux relative to the density-driven vertical buoyancy flux, defined as az (or a for an isotropic aquifer), and the aspect ratio of horizontal and vertical dimensions of the cross-section. For the Henry constant dispersion problem, in which the aquifer is isotropic, saltwater intrusion and recirculation are related to an additional independent dimensionless parameter that is the ratio of the constant dispersion coefficient treated as a scalar quantity, the porosity, and the freshwater advective flux, defined as b. For the Henry velocity-dependent dispersion problem, the ratio b is zero, and saltwater intrusion and recirculation are related to an additional independent dimensionless parameter that is the ratio of the vertical and horizontal dispersivities, or rα = αz/αx. For an anisotropic aquifer, saltwater intrusion and recirculation are also dependent on the ratio of vertical and horizontal hydraulic conductivities, or rK = Kz/Kx. For the field-scale velocity-dependent dispersion problem, saltwater intrusion and recirculation are dependent on the same independent ratios as the Henry velocity-dependent dispersion problem. In the two-dimensional cross-section for all three problems, freshwater inflow occurs at an upgradient boundary, and recirculated seawater outflow occurs at a downgradient coastal boundary. The upgradient boundary is a specified-flux boundary with zero freshwater concentration, and the downgradient boundary is a specified-head boundary with a specified concentration equal to seawater. Equivalent freshwater heads are specified at the downstream boundary to account for density differences between freshwater and saltwater at the downstream boundary. The three problems were solved using the numerical groundwater flow and transport code SEAWAT for two conditions, i.e., first for the uncoupled condition in which the fluid density is constant and thus the flow and transport equations are uncoupled in a constant-density flowfield, and then for the coupled condition in which the fluid density is a function of the total dissolved solids concentration and thus the flow and transport equations are coupled in a variable-density flowfield. A wide range of results for the landward extent of saltwater intrusion and the amount of recirculation of seawater at the coastal boundary was obtained by varying the independent dimensionless ratio az (or a in problem one) in all three problems. The dimensionless dispersion ratio b was also varied in problem one, and the dispersivity ratio rα and the hydraulic conductivity ratio rK were also varied in problems two and three.

Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

USGS Publications Warehouse

Schmidt, John C.; Graf, Julia B.

1990-01-01

Alluvial sand deposits along the Colorado River in Grand Canyon National Park are used as campsites and are substrate for vegetation. The largest and most numerous of these deposits are formed in zones of recirculating current that are created downstream from where the channel is constricted by debris fans at tributary mouths. Alluvial sand deposits are classified by location and form. Separation and reattachment deposits are downstream from constrictions within recirculation zones. Separation deposits are near the point of flow separation and typically mantle large debris fans. Reattachment deposits are near the point of flow reattachment and project upstream beneath much of the zone of recirculating current. Upper-pool deposits are upstream from a constriction and are associated with backwaters. Channel-margin deposits line the channel and have the form of terraces. Some are created in small recirculation zones. Reattachment and channel-margin deposits are largest and most numerous in wide reaches, although small channel-margin deposits are used as campsites in the narrow Muav Gorge. Separation deposits are more uniformly distributed throughout Grand Canyon National Park than are other types of deposits. In some narrow reaches where the number of alluvial sand deposits used as campsites is small, separation deposits are a high percentage of the total. During high flows, both separation and reattachment deposits are initially scoured but are subsequently redeposited during flow recession. Sand is also exchanged between the main channel and recirculation zones. The rate of recession of high flows can affect the elevation of alluvial deposits that are left exposed after a flood has passed. Fluctuating flows that follow a period of steady discharge cause initial erosion of separation and reattachment deposits. A part of this eroded sand is transported to the main channel. Therefore, sand is exchanged between the main channel and recirculation zones and redistributed within recirculation zones over a broad range of discharges. Comparison of aerial photographs and reinterpretation of published data concerning changes of alluvial sand deposits following recession of high flows in 1983 and 1984 indicate that sand was eroded from recirculation zones in narrow reaches. In wide reaches, however, aggradation in recirculation zones may have occurred. In narrow reaches, the decrease of reattachment deposits was greater than that of separation deposits. In all reaches, the percentage of separation deposits that maintained a constant area was greater than for other deposits. Separation deposits, therefore, appear to be the most stable of the deposit types. Fluctuating flows between October 1985 and January 1986, which followed the higher and steadier flows of 1983 to 1985, caused erosion throughout the park. For separation deposits, erosion was greatest at those sites where deposition from the 1983 high flows had been greatest. The existing pattern of low campsite availability in narrow reaches and high campsite availability in wide reaches was thus accentuated by the sequence of flows between 1983 and 1985.

Process Requirements for Achieving Full-Flow Disinfection of Recirculating Water Using Ozonation and UV Irradiation

USDA-ARS?s Scientific Manuscript database

A continuous water disinfection process can be used to prevent the introduction and accumulation of obligate and opportunistic fish pathogens in recirculating aquaculture systems (RAS), especially during a disease outbreak when the causative agent would otherwise proliferate within the system. To p...

Evaluation of commercial marine fish feeds for production of juvenile cobia in recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

The effect of feeding three commercially available diets manufactured by three U.S. feed companies on production characteristics and body composition of juvenile cobia Rachycentron canadum reared in recirculating aquaculture systems (RAS) was evaluated in a 57 d growth trial. Juvenile cobia (26.7 +...

End-to-end 9-D polarized bunch transport in eRHIC energy-recovery recirculator, some aspects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meot, F.; Meot, F.; Brooks, S.

2015-05-03

This paper is a brief overview of some of the numerous beam and spin dynamics investigations undertaken in the framework of the design of the FFAG based electron energy recovery re-circulator ring of the eRHIC electron-ion collider project

Confined Turbulent Swirling Recirculating Flow Predictions. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Abujelala, M. T.

1984-01-01

Turbulent swirling flow, the STARPIC computer code, turbulence modeling of turbulent flows, the k-xi turbulence model and extensions, turbulence parameters deduction from swirling confined flow measurements, extension of the k-xi to confined swirling recirculating flows, and general predictions for confined turbulent swirling flow are discussed.

Low head oxygenator performance characterization for marine recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

This study evaluated the effect of temperature (20 and 25 ºC), salinity (10, 15, and 20 ppt), and dissolved oxygen levels within low head oxygenator (LHO) outlet water on oxygen transfer efficiency (OTE) of LHOs for a planned marine recirculating aquaculture system (RAS). Test results indicated tha...

Observations on side-swimming rainbow trout Oncorhynchus mykiss in water recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

During a controlled 6-month study using six replicated water recirculation aquaculture systems (WRAS), it was observed that rainbow trout Oncorhynchus mykiss in all WRAS exhibited a higher-than-normal prevalence of side-swimming (i.e. controlled, forward swimming, but with misaligned orientation suc...

Improvement of anaerobic digester performance by wastewater recirculation through an aerated membrane.

USDA-ARS?s Scientific Manuscript database

Swine wastewater from an anaerobic digester was recirculated through a silicone hose located in an external aeration chamber to determine its effect on wastewater malodorants and biogas composition. The silicone hose acted as a semipermeable membrane for the passage of small molecules. In the first...

40 CFR Table Hh-1 to Subpart Hh of... - Emissions Factors, Oxidation Factors and Methods

Code of Federal Regulations, 2011 CFR

2011-07-01

... evapotranspiration rate exceeds the mean annual precipitation rate plus recirculated leachate. Use the greater value when the potential evapotranspiration rate does not exceed the mean annual precipitation rate plus... value rather than assessing the potential evapotranspiration rate or recirculated leachate rate. [75 FR...

40 CFR Table Hh-1 to Subpart Hh of... - Emissions Factors, Oxidation Factors and Methods

Code of Federal Regulations, 2014 CFR

2014-07-01

... value when the potential evapotranspiration rate exceeds the mean annual precipitation rate plus recirculated leachate. Use the greater value when the potential evapotranspiration rate does not exceed the... recirculation can elect to use the greater value rather than assessing the potential evapotranspiration rate or...

40 CFR Table Hh-1 to Subpart Hh of... - Emissions Factors, Oxidation Factors and Methods

Code of Federal Regulations, 2013 CFR

2013-07-01

... evapotranspiration rate exceeds the mean annual precipitation rate plus recirculated leachate. Use the greater value when the potential evapotranspiration rate does not exceed the mean annual precipitation rate plus... value rather than assessing the potential evapotranspiration rate or recirculated leachate rate. [75 FR...

40 CFR Table Hh-1 to Subpart Hh of... - Emissions Factors, Oxidation Factors and Methods

Code of Federal Regulations, 2012 CFR

2012-07-01

... evapotranspiration rate exceeds the mean annual precipitation rate plus recirculated leachate. Use the greater value when the potential evapotranspiration rate does not exceed the mean annual precipitation rate plus... value rather than assessing the potential evapotranspiration rate or recirculated leachate rate. [75 FR...

Off-flavor characterization and depuration in Atlantic salmon cultured to food-size within closed-containment systems

USDA-ARS?s Scientific Manuscript database

Atlantic salmon are typically cultured in marine net pens. However, technological advancements in recirculating aquaculture systems have increased the feasibility of culturing Atlantic salmon in land-based systems. One problem encountered when fish are harvested from recirculating systems is the pre...

Can positive matrix factorization help to understand patterns of organic trace gases at the continental Global Atmosphere Watch site Hohenpeissenberg?

NASA Astrophysics Data System (ADS)

Leuchner, M.; Gubo, S.; Schunk, C.; Wastl, C.; Kirchner, M.; Menzel, A.; Plass-Dülmer, C.

2015-02-01

From the rural Global Atmosphere Watch (GAW) site Hohenpeissenberg in the pre-alpine area of southern Germany, a data set of 24 C2-C8 non-methane hydrocarbons over a period of 7 years was analyzed. Receptor modeling was performed by positive matrix factorization (PMF) and the resulting factors were interpreted with respect to source profiles and photochemical aging. Differing from other studies, no direct source attribution was intended because, due to chemistry along transport, mass conservation from source to receptor is not given. However, at remote sites such as Hohenpeissenberg, the observed patterns of non-methane hydrocarbons can be derived from combinations of factors determined by PMF. A six-factor solution showed high stability and the most plausible results. In addition to a biogenic and a background factor of very stable compounds, four additional anthropogenic factors were resolved that could be divided into two short- and two long-lived patterns from evaporative sources/natural gas leakage and incomplete combustion processes. The volume or mass contribution at the site over the entire period was, in decreasing order, from the following factor categories: background, gas leakage and long-lived evaporative, residential heating and long-lived combustion, short-lived evaporative, short-lived combustion, and biogenic. The importance with respect to reactivity contribution was generally in reverse order, with the biogenic and the short-lived combustion factors contributing most. The seasonality of the factors was analyzed and compared to results of a simple box model using constant emissions and the photochemical decay calculated from the measured annual cycles of OH radicals and ozone. Two of the factors, short-lived combustion and gas leakage/long-lived evaporative, showed winter/summer ratios of about 9 and 7, respectively, as expected from constant source estimations. Contrarily, the short-lived evaporative emissions were about 3 times higher in summer than in winter, while residential heating/long-lived combustion emissions were about 2 times higher in winter than in summer.

CFD Analysis of the 24-inch JIRAD Hybrid Rocket Motor

NASA Technical Reports Server (NTRS)

Liang, Pak-Yan; Ungewitter, Ronald; Claflin, Scott

1996-01-01

A series of multispecies, multiphase computational fluid dynamics (CFD) analyses of the 24-inch diameter joint government industry industrial research and development (JIRAD) hybrid rocket motor is described. The 24-inch JIRAD hybrid motor operates by injection of liquid oxygen (LOX) into a vaporization plenum chamber upstream of ports in the hydroxyl-terminated polybutadiene (HTPB) solid fuel. The injector spray pattern had a strong influence on combustion stability of the JIRAD motor so a CFD study was initiated to define the injector end flow field under different oxidizer spray patterns and operating conditions. By using CFD to gain a clear picture of the flow field and temperature distribution within the JIRAD motor, it is hoped that the fundamental mechanisms of hybrid combustion instability may be identified and then suppressed by simple alterations to the oxidizer injection parameters such as injection angle and velocity. The simulations in this study were carried out using the General Algorithm for Analysis of Combustion SYstems (GALACSY) multiphase combustion codes. GALACSY consists of a comprehensive set of droplet dynamic submodels (atomization, evaporation, etc.) and a computationally efficient hydrocarbon chemistry package built around a robust Navier-Stokes solver optimized for low Mach number flows. Lagrangian tracking of dispersed particles describes a closely coupled spray phase. The CFD cases described in this paper represent various levels of simplification of the problem. They include: (A) gaseous oxygen with combusting fuel vapor blowing off the walls at various oxidizer injection angles and velocities, (B) gaseous oxygen with combusting fuel vapor blowing off the walls, and (C) liquid oxygen with combusting fuel vapor blowing off the walls. The study used an axisymmetric model and the results indicate that the injector design significantly effects the flow field in the injector end of the motor. Markedly different recirculation patterns are observed in the vaporization chamber as the oxygen velocity and/or spray pattern is varied. The ability of these recirculation patterns to stabilize the diffusion flame above the surface of the solid fuel gives a plausible explanation for the experimentally determined combustion stability characteristics of the JIRAD motor, and suggests how combustion stability can be assured by modifications to the injector design.

A dented LH2 recirculation line is removed from Discovery

NASA Technical Reports Server (NTRS)

1999-01-01

Workers with United Space Alliance remove Shuttle Discovery's dented main propulsion system liquid hydrogen recirculation line. From left are James Stickley, George Atkins, and Todd Biddle. The 12-inch-long dent was discovered during routine aft compartment inspections Tuesday, Dec. 7. The line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. The line is being replaced and managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope.

Reduced bleed air extraction for DC-10 cabin air conditioning

NASA Technical Reports Server (NTRS)

Newman, W. H.; Viele, M. R.; Hrach, F. J.

1980-01-01

It is noted that a significant fuel savings can be achieved by reducing bleed air used for cabin air conditioning. Air in the cabin can be recirculated to maintain comfortable ventilation rates but the quality of the air tends to decrease due to entrainment of smoke and odors. Attention is given to a development system designed and fabricated under the NASA Engine Component Improvement Program to define the recirculation limit for the DC-10. It is shown that with the system, a wide range of bleed air reductions and recirculation rates is possible. A goal of 0.8% fuel savings has been achieved which results from a 50% reduction in bleed extraction from the engine.

Applications of a new wall function to turbulent flow computations

NASA Astrophysics Data System (ADS)

Chen, Y. S.

1986-01-01

A new wall function approach is developed based on a wall law suitable for incompressible turbulent boundary layers under strong adverse pressure gradients. This wall law was derived from a one-dimensional analysis of the turbulent kinetic energy equation with gradient diffusion concept employed in modeling the near-wall shear stress gradient. Numerical testing cases for the present wall functions include turbulent separating flows around an airfoil and turbulent recirculating flows in several confined regions. Improvements on the predictions using the present wall functions are illustrated. For cases of internal recirculating flows, one modification factor for improving the performance of the k-epsilon turbulence model in the flow recirculation regions is also included.

Bioturbation, advection, and diffusion of a conserved tracer in a laboratory flume

NASA Astrophysics Data System (ADS)

Work, P. A.; Moore, P. R.; Reible, D. D.

2002-06-01

Laboratory experiments indicating the relative influences of advection, diffusion, and bioturbation on transport of NaCl tracer between a stream and streambed are described. Data were collected in a recirculating flume housing a box filled with test sediments. Peclet numbers ranged from 0 to 1.5. Sediment components included a medium sand (d50 = 0.31 mm), kaolinite, and topsoil. Lumbriculus variegatus were introduced as bioturbators. Conductivity probes were employed to document the flux of the tracer solution out of the bed. Measurements are compared to one-dimensional effective diffusion models assuming one or two horizontal sediment layers. These simple models provide a good indication of tracer half-life in the bed if a suitable effective diffusion coefficient is chosen but underpredict initial flux and overpredict flux at long times. Organism activity was limited to the upper reaches of the sediment test box but eventually exerts a secondary influence on flux from deeper regions.

Barriers to Achieving Textbook Multigrid Efficiency (TME) in CFD

NASA Technical Reports Server (NTRS)

Brandt, Achi

1998-01-01

As a guide to attaining this optimal performance for general CFD problems, the table below lists every foreseen kind of computational difficulty for achieving that goal, together with the possible ways for resolving that difficulty, their current state of development, and references. Included in the table are staggered and nonstaggered, conservative and nonconservative discretizations of viscous and inviscid, incompressible and compressible flows at various Mach numbers, as well as a simple (algebraic) turbulence model and comments on chemically reacting flows. The listing of associated computational barriers involves: non-alignment of streamlines or sonic characteristics with the grids; recirculating flows; stagnation points; discretization and relaxation on and near shocks and boundaries; far-field artificial boundary conditions; small-scale singularities (meaning important features, such as the complete airplane, which are not visible on some of the coarse grids); large grid aspect ratios; boundary layer resolution; and grid adaption.

Conceptual model of turbulent flameholding for scramjet combustors

NASA Technical Reports Server (NTRS)

Huber, P. W.

1980-01-01

New concepts and approaches to scramjet combustor design are presented. Blowoff was from failure of the recirculation-zone (RZ) flame to reach the dividing streamline (DS) at the rear stagnation zone. Increased turbulent exchange across the DS helped flameholding due to forward movement of the flame anchor point inside the RZ. Modeling of the blowoff phenomenon was based on a mass conservation concept involving the traverse of a flame element across the RZ and a flow element along the DS. The scale required to achieve flameholding, predicted by the model, showed a strong adverse effect of low pressure and low fuel equivalence ratio, moderate effect of flight Mach number, and little effect of temperature recovery factor. Possible effects of finite rate chemistry on flameholding and flamespreading in scramjets are discussed and recommendations for approaches to engine combustor design as well as for needed research to reduce uncertainties in the concepts are made.

Production characteristics and body composition of juvenile cobia fed three different commercial diets in recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

The effect of feeding three commercial diets on production characteristics and body composition of juvenile cobia Rachycentron canadum reared using recirculating aquaculture systems (RAS) was evaluated in a 56 d growth trial. Juvenile cobia (29.2 +/= 0.7 g, mean weight +/= SE) were stocked into thr...

Stocking density effects on production characteristics and body composition of market size cobia, Rachycentron canadum, reared in recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

Production density in excess of a critical threshold can result in a negative relationship between stocking density and fish production. This study was conducted to evaluate production characteristics of juvenile cobia Rachycentron canadum, reared to market size in production-scale recirculating aq...

Assessing peracetic acid as a means to control post-vaccination Saprolegniasis in Atlantic salmon Salmo salar parr in recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Land-based closed containment facilities, utilizing recirculation aquaculture system (RAS) technologies, can reduce or eliminate the introduction of obligate fish pathogens. Regardless, the presence of opportunistic pathogens must be assumed, and these agents can cause disease during unfavorable con...

Abnormal swimming behavior and increased deformities in rainbow trout Oncorhynchus mykiss cultured in low exchange water recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Two studies were conducted to determine if accumulating water quality parameters would negatively impact rainbow trout Oncorhynchus mykiss health and welfare within water recirculation aquaculture systems (WRAS) that were operated at low and near-zero water exchange, with and without ozonation, and ...

Systemic granuloma observed in Atlantic salmon Salmo salar raised to market size in a freshwater recirculation aquaculture system

USDA-ARS?s Scientific Manuscript database

Systemic granuloma was observed in sampled adult Atlantic salmon Salmo salar raised to harvest size in a freshwater recirculation aquaculture system. The prevalence of this condition was estimated at 10-20% of the population, with affected individuals grossly demonstrating pathology in varying degre...

Effects of semi-continous peracetic acid dosing on rainbow trout Oncorhynchus mykiss performance, water quality, and off-flavor compounds in recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Water clarifying and disinfection techniques such as ozonation and ultraviolet irradiation are commonly used in recirculation aquaculture systems (RAS); however, the capital and operating costs of these technologies are expensive. Cost-effective treatment options that maintain fish health and simult...

Researchers evaluate low-energy recirculating system for inland production of marine finfish juveniles

USDA-ARS?s Scientific Manuscript database

The low-energy recirculating aquaculture system consists of nine separate modules which utilize the double drain fish culture tank paired to a moving bed biofilter. The nine fiberglass tanks are five feet in diameter and normal water depth is about three feet for a total tank volume of approximately...

Temperature effects on biomass, geosmin, and 2-methylisoborneol production and cellular activity by Nocardia spp. and Streptomyces spp. isolated from rainbow trout recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

Isolates of Nocardia cummidelens, Nocardia fluminea, Streptomyces albidoflavus, and Streptomyces luridiscabiei attributing to geosmin-related off-flavor in rainbow trout (Oncorhynchus mykiss) raised in recirculating aquaculture systems (RAS) were evaluated for the effect of temperature (10-30 degree...

Alternative Bio-Derived JP-8 Class Fuel and JP-8 Fuel: Flame Tube Combustor Test Results Compared using a GE TAPS Injector Configuration

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Tedder, Sarah A.; Anderson, Robert C.

2016-01-01

This paper presents results from tests in a flame tube facility, where a bio-derived alternate fuel was compared with JP-8 for emissions and general combustion performance. A research version of General Electric Aviation (GE) TAPS injector was used for the tests. Results include combustion efficiency from gaseous emission measurements, 2D planar laser-based imaging as well as basic flow visualization of the flame. Four inlet test conditions were selected that simulate various engine power conditions relevant to NASA Fundamental Aeronautics Supersonics Project and Environmentally Responsible Aviation Program. One inlet condition was a pilot-only test point. The other three inlet conditions incorporated fuel staging via a split between the pilot and main circuits of either 10%/90% or 20%/80%. For each engine power condition, three fuel mixes were used: 100% JP-8; 100% alternative; and a blend of the two, containing 75% alternative. Results for the inlet cases that have fuel split between pilot and main, indicate that fuel from the pilot appears to be evaporated by the time it reaches the dome exit. Main circuit liquid evaporates within a downstream distance equal to annulus height, no matter the fuel. Some fuel fluorescence images for a 10%/90% fuel staging case show a distinct difference between JP-8 and bio-derived fuel. OH PLIF results indicate that OH forms in a region more centrally-located for the JP-8 case downstream of the pilot, in its central recirculation region (CRZ). For the bio-derived Hydrotreated Renewable Jet (HRJ) fuel, however, we do not see much OH in the CRZ. The OH image structure near the dome exit is similar for the two fuels, but farther downstream the OH in the CRZ is much more apparent for the JP-8 than for the alternate fuel. For all conditions, there was no discernable difference between fuel types in combustion efficiency or emissions.

The study of recirculating aquaculture system in pond and its purification effect

NASA Astrophysics Data System (ADS)

Qu, Jiangqi; Zhang, Qingjing; Jia, Chengxia; Liu, Pan; Yang, Mu

2017-05-01

In this paper, a recirculating aquaculture purification system (RAPS) was designed to solve the problems of aquaculture pollution and shortage of freshwater resource according to the characteristic of northern freshwater ponds of China. The system were arranged in series and composed of high density culture pond, deposit pond, floating and submerged plant pond, ecological floating bed pond and biofilm filtrate pond. At the fish density of 20~30kg/m3 in the high density culture pond, the water quality parameters were monitored seasonally. The results indicated that the removal rate of total nitrogen, total phosphorus, ammonia nitrogen and nitrite nitrogen in the recirculating aquaculture system were 69.59%, 77.89%, 72.54% and 68.68%, respectively. The floating and submerged plant pond and ecological floating bed pond can remove TN and TP obviously, and increase dissolved oxygen and transparency significantly. And the biofilm filtrate pond has good effect of removing ammonium nitrogen and nitrite nitrogen, meanwhile, the microbial communities in the recirculating aquaculture system regulate on the water quality. Therefore, the RAPS show significant effects on water saving and pollution emission reducing.

Recirculation or artificial aeration in vertical flow constructed wetlands: a comparative study for treating high load wastewater.

PubMed

Foladori, Paola; Ruaben, Jenny; Ortigara, Angela R C

2013-12-01

Vertical subsurface-flow constructed wetlands at pilot-scale have been applied to treat high hydraulic and organic loads by implementing the following configurations: (1) intermittent recirculation of the treated wastewater from the bottom to the top of the bed, (2) intermittent artificial aeration supplied at the bottom of the bed and (3) the combination of both. These configurations were operated with a saturated bottom layer for a 6h-treatment phase, followed by a free drainage phase prior to a new feeding. COD removal efficiency was 85-90% in all the configurations and removed loads were 54-70 gCOD m(-2)d(-1). The aerated and recirculated wetland resulted in a higher total nitrogen removal (8.6 gN m(-2)d(-1)) due to simultaneous nitrification/denitrification, even in the presence of intermittent aeration (6.8 Nm(3)m(-2)d(-1)). The extra investment needed for implementing aeration/recirculation would be compensated for by a reduction of the surface area per population equivalent, which decreased to 1.5m(2)/PE. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hydrodynamic and chemical effects of hydrogen dilution on soot evolution in turbulent nonpremixed bluff body ethylene flames

NASA Astrophysics Data System (ADS)

Deng, Sili; Mueller, Michael E.; Chan, Qing N.; Qamar, Nader H.; Dally, Bassam B.; Alwahabi, Zeyad T.; Nathan, Graham J.

2015-11-01

A turbulent nonpremixed bluff body ethylene/hydrogen (volume ratio 2:1) flame is studied and compared with the ethylene counterpart [Mueller et al., Combust. Flame, 160, 2013]. Similar to the ethylene buff body flame, a low-strain recirculation zone, a high-strain neck region, and a downstream jet-like region are observed. However, the maximum soot volume fraction in the recirculation zone of the hydrogen diluted case is significantly lower than the ethylene case. Large Eddy Simulation is used to further investigate soot evolution in the recirculation zone and to elucidate the role of hydrogen dilution. Since the central jet Reynolds numbers in both cases are the same (approximately 30,900), the jet velocity of the hydrogen diluted case is higher, resulting in a shorter and leaner recirculation zone. In addition, hydrogen dilution chemically suppresses soot formation due to the reduction of C/H ratio. Consequently, the reduction of the soot volume fraction for the hydrogen diluted ethylene flame is attributed to two major effects: hydrodynamic and chemical effects.

Contribution of 3-D time-lapse ERT to the study of leachate recirculation in a landfill

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clement, R., E-mail: remi.clement@hmg.inpg.fr; Grenoble Universite, B.P. 53, 38041 Grenoble Cedex 9; Oxarango, L.

2011-03-15

Leachate recirculation is a key process in the operation of municipal waste landfills as bioreactors. It aims at increasing the moisture content to optimise the biodegradation. Because waste is a very heterogeneous and anisotropic porous media, the geometry of the leachate plume recirculation is difficult to delineate from the surface at the scale of the bioreactor site. In this study, 3-D time-lapse electrical resistivity tomography (ERT) was used to obtain useful information for understanding leachate recirculation hydrodynamics. The ERT inversion methodology and the electrode arrays were optimised using numerical modelling simulating a 3-D leachate injection scenario. Time-lapse ERT was subsequentlymore » applied at the field scale during an experimental injection. We compared ERT images with injected volumes to evaluate the sensitivity of time-lapse ERT to delineate the plume migration. The results show that time-lapse ERT can accomplish the following: (i) accurately locate the injection plume, delineating its depth and lateral extension; (ii) be used to estimate some hydraulic properties of waste.« less

Turbulence characteristics of swirling flowfields. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Jackson, T. W.; Lilley, D. G.

1985-01-01

The time mean and turbulence properties of a confined swirling jet using the six orientation, single hot wire technique were obtained. The effect of swirl on a confined, expanding jet is to reduce the size of the corner recirculation zone and generate a central recirculation zone followed by a precessing vortex core. The effect of introducing a contraction nozzle of area ratio four, located two test section diameters downstream of the inlet, is to dramatically reduce the size and shape of the central recirculation zone for the swirling flows considered. The shear stresses are found to increase by an order of magnitude in the region of the contraction nozzle because of large radial gradients of axial velocity. Reduction of the expansion ratio to D/o = 1 causes the time mean flow field to be homogeneous throughout the entire test section with the tangential velocity dominating in the swirling cases. No recirculation zones were observed for these particular flows. Turbulence levels and dissipation rates were found to be low except in the entrance regions and in areas of acceleration in the swirling flow cases.

Five-hole pitot probe time-mean velocity measurements in confined swirling flows

NASA Technical Reports Server (NTRS)

Yoon, H. K.; Lilley, D. G.

1983-01-01

Nonswirling and swirling nonreacting flows in an axisymmetric test section with an expansion ratio D/d = 2, which may be equipped with contraction nozzles of area ratios 2 and 4, are investigated. The effects of a number of geometric parameters on the flow-field are investigated, among them side-wall expansion angles of 90 and 45 deg, swirl vane angles of 0, 38, 45, 60, and 70 deg, and contraction nozzle locations L/D = 1 and 2 (if present). Data are acquired by means of a five-hole pitot probe enabling three time-mean velocity components in the axial, radial, and azimuthal directions to be measured. The velocities are extensively plotted and artistic impressions of recirculation zones are set forth. The presence of a swirler is found to shorten the corner recirculation zone and to generate a central recirculation zone followed by a precessing vortex core. A gradual inlet expansion has the effect of encouraging the flow to remain close to the sidewall and shortening the extent of the corner recirculation zone in all cases investigated.

Building America Case Study: Control Retrofits for Multifamily Domestic Hot Water Recirculation Systems, Brooklyn, New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7 percent after implementing the demand control technique, 2 percent after implementing temperature modulation, and 15 percent after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8 percent, 1 percent, and 14 percent for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Building America Case Study: Control Retrofits for Multifamily Domestic Hot Water Recirculation Systems, Brooklyn, New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Dentz; E. Ansanelli, H. Henderson, Jr.; K. Varshney

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Pilot-scale experiment on anaerobic bioreactor landfills in China.

PubMed

Jiang, Jianguo; Yang, Guodong; Deng, Zhou; Huang, Yunfeng; Huang, Zhonglin; Feng, Xiangming; Zhou, Shengyong; Zhang, Chaoping

2007-01-01

Developing countries have begun to investigate bioreactor landfills for municipal solid waste management. This paper describes the impacts of leachate recirculation and recirculation loadings on waste stabilization, landfill gas (LFG) generation and leachate characteristics. Four simulated anaerobic columns, R1-R4, were each filled with about 30 tons of waste and recirculated weekly with 1.6, 0.8 and 0.2m(3) leachate and 0.1m(3) tap water. The results indicated that the chemical oxygen demand (COD) half-time of leachate from R1 was about 180 days, which was 8-14 weeks shorter than that of R2-R4. A large amount of LFG was first produced in R1, and its generation rate was positively correlated to the COD or volatile fatty acid concentrations of influent leachates after the 30th week. By the 50th week of recirculation, the waste in R1 was more stabilized, with 931.2 kg COD or 175.6 kg total organic carbon released and with the highest landfill gas production. However, this contributed mainly to washout by leachate, which also resulted in the reduction of LFG generation potential and accumulation of ammonia and/or phosphorus in the early stage. Therefore, the regimes of leachate recirculation should be adjusted to the phases of waste stabilization to enhance efficiency of energy recovery. Integrated with the strategy of in situ leachate management, extra pre-treatment or post-treatment methods to remove the nutrients are recommended.

Production of Tuber-Inducing Factor

NASA Technical Reports Server (NTRS)

Stutte, Gary W.; Yorio, Neil C.

2006-01-01

A process for making a substance that regulates the growth of potatoes and some other economically important plants has been developed. The process also yields an economically important by-product: potatoes. The particular growth-regulating substance, denoted tuber-inducing factor (TIF), is made naturally by, and acts naturally on, potato plants. The primary effects of TIF on potato plants are reducing the lengths of the main shoots, reducing the numbers of nodes on the main stems, reducing the total biomass, accelerating the initiation of potatoes, and increasing the edible fraction (potatoes) of the overall biomass. To some extent, these effects of TIF can override environmental effects that typically inhibit the formation of tubers. TIF can be used in the potato industry to reduce growth time and increase harvest efficiency. Other plants that have been observed to be affected by TIF include tomatoes, peppers, radishes, eggplants, marigolds, and morning glories. In the present process, potatoes are grown with their roots and stolons immersed in a nutrient solution in a recirculating hydroponic system. From time to time, a nutrient replenishment solution is added to the recirculating nutrient solution to maintain the required nutrient concentration, water is added to replace water lost from the recirculating solution through transpiration, and an acid or base is added, as needed, to maintain the recirculating solution at a desired pH level. The growing potato plants secrete TIF into the recirculating solution. The concentration of TIF in the solution gradually increases to a range in which the TIF regulates the growth of the plants.

Numerical Modeling of Liquid-Vapor Phase Change

NASA Technical Reports Server (NTRS)

Esmaeeli, Asghar; Arpaci, Vedat S.

2001-01-01

We implemented a two- and three-dimensional finite difference/front tracking technique to solve liquid-vapor phase change problems. The mathematical and the numerical features of the method were explained in great detail in our previous reports, Briefly, we used a single formula representation which incorporated jump conditions into the governing equations. The interfacial terms were distributed as singular terms using delta functions so that the governing equations would be the same as conventional conservation equations away from the interface and in the vicinity of the interface they would provide correct jump conditions. We used a fixed staggered grid to discretize these equations and an unstructured grid to explicitly track the front. While in two dimensions the front was simply a connection of small line segments, in three dimensions it was represented by a connection of small triangular elements. The equations were written in conservative forms and during the course of computations we used regriding to control the size of the elements of the unstructured grid. Moreover, we implemented a coalescence in two dimensions which allowed the merging of different fronts or two segments of the same front when they were sufficiently close. We used our code to study thermocapillary migration of bubbles, burst of bubbles at a free surface, buoyancy-driven interactions of bubbles, evaporation of drops, rapid evaporation of an interface, planar solidification of an undercooled melt, dendritic solidification, and a host of other problems cited in the reference.

Production of polycaprolactone nanoparticles with low polydispersity index in a tubular recirculating system by using a multifactorial design of experiments

NASA Astrophysics Data System (ADS)

Colmenares Roldán, Gabriel Jaime; Agudelo Gomez, Liliana María; Carlos Cornelio, Jesús Antonio; Rodriguez, Luis Fernando; Pinal, Rodolfo; Hoyos Palacio, Lina Marcela

2018-03-01

Encapsulation and controlled release of substances using polymeric nanoparticles require that these have a high reproducibility, homogeneity, and control over their properties (diameter and polydispersity), especially when they are to be used in medical, pharmaceutical, or nutritional applications among others. In conventional production systems, it is tough to ensure these characteristics; hence, the cost increases when we try to control these properties. This paper shows a comparison between a recirculating system and the standard nanoprecipitation technique for producing polymeric nanoparticles. In previous investigations, we evaluate the effect of recirculating flow and the ratio between the organic and aqueous phase. For this paper, we evaluated the effect of polymer and surfactant concentrations using a multifactorial design of experiments on the recirculating system and on the standard nanoprecipitation system. The response of the design was the average diameter of the nanoparticles and polydispersity index. Finally, we found that the polymer and surfactant concentrations could change the average diameter and polydispersity index of the nanoparticles obtained. On the other hand, it was found that the effect of the polymer concentration was stronger than the surfactant concentration to reduce the average diameter of the nanoparticles. The results of the present study show that the proposed recirculation system presents a high potential to produce polymer nanoparticles with good morphological characteristics, particle size distributions in the nano range, and with a low polydispersity. The average mean size of nanoparticles of polycaprolactone for the design using the recirculating system was of 61 to 140 nm and the values of polydispersity index PDI for this design were between 0.097 and 0.22, while for the design using the standard nanoprecipitation technique, the obtained diameters were 74 to 176 nm and the polydispersity was between 0.26 and 0.41.

Effect of high-pressure homogenization preparation on mean globule size and large-diameter tail of oil-in-water injectable emulsions.

PubMed

Peng, Jie; Dong, Wu-Jun; Li, Ling; Xu, Jia-Ming; Jin, Du-Jia; Xia, Xue-Jun; Liu, Yu-Ling

2015-12-01

The effect of different high pressure homogenization energy input parameters on mean diameter droplet size (MDS) and droplets with > 5 μm of lipid injectable emulsions were evaluated. All emulsions were prepared at different water bath temperatures or at different rotation speeds and rotor-stator system times, and using different homogenization pressures and numbers of high-pressure system recirculations. The MDS and polydispersity index (PI) value of the emulsions were determined using the dynamic light scattering (DLS) method, and large-diameter tail assessments were performed using the light-obscuration/single particle optical sensing (LO/SPOS) method. Using 1000 bar homogenization pressure and seven recirculations, the energy input parameters related to the rotor-stator system will not have an effect on the final particle size results. When rotor-stator system energy input parameters are fixed, homogenization pressure and recirculation will affect mean particle size and large diameter droplet. Particle size will decrease with increasing homogenization pressure from 400 bar to 1300 bar when homogenization recirculation is fixed; when the homogenization pressure is fixed at 1000 bar, the particle size of both MDS and percent of fat droplets exceeding 5 μm (PFAT 5 ) will decrease with increasing homogenization recirculations, MDS dropped to 173 nm after five cycles and maintained this level, volume-weighted PFAT 5 will drop to 0.038% after three cycles, so the "plateau" of MDS will come up later than that of PFAT 5 , and the optimal particle size is produced when both of them remained at plateau. Excess homogenization recirculation such as nine times under the 1000 bar may lead to PFAT 5 increase to 0.060% rather than a decrease; therefore, the high-pressure homogenization procedure is the key factor affecting the particle size distribution of emulsions. Varying storage conditions (4-25°C) also influenced particle size, especially the PFAT 5 . Copyright © 2015. Published by Elsevier B.V.

Microfiltration: Effect of retentate protein concentration on limiting flux and serum protein removal with 4-mm-channel ceramic microfiltration membranes.

PubMed

Hurt, E E; Adams, M C; Barbano, D M

2015-04-01

The objective of our study was to determine if the limiting flux and serum protein (SP) removal were different at 8, 9, or 10% true protein (TP) in the microfiltration (MF) retentate recirculation loop using 0.1-µm ceramic graded permeability membranes with 4-mm-channel diameters operated at 50 °C using a diluted milk protein concentrate with 85% protein on a total solids basis (MPC85) as the MF feed. The limiting flux for the MF of diluted MPC85 was determined at 3 TP concentrations in the recirculation loop (8, 9, and 10%). The experiment was replicated 3 times for a total of 9 runs. On the morning of each run, MPC85 was diluted with reverse osmosis water to an MF feed TP concentration of 5.4%. In all runs, the starting flux was 55 kg/m(2) per hour, the flux was increased in steps until the limiting flux was reached. The minimum flux increase was 10 kg/m(2) per hour. The limiting flux decreased as TP concentration in the recirculation loop increased. The limiting flux was 154 ± 0.3, 133 ± 0.7, and 117 ± 3.3 kg/m(2) per hour at recirculation loop TP concentrations of 8.2 ± 0.07, 9.2 ± 0.04, and 10.2 ± 0.09%, respectively. No effect of recirculation loop TP concentration on the SP removal factor was detected. However, the SP removal factor decreased from 0.80 ± 0.02 to 0.75 ± 0.02 as flux was increased from the starting flux of 55 kg/m(2) per hour to the limiting flux, with a similar decrease seen at all recirculation loop TP concentrations. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

A study of the liquid-vapor phase change of mercury based on irreversible thermodynamics.

NASA Technical Reports Server (NTRS)

Adt, R. R., Jr.; Hatsopoulos, G. N.; Bornhorst, W. J.

1972-01-01

The object of this work is to determine the transport coefficients which appear in linear irreversible-thermodynamic rate equations of a phase change. An experiment which involves the steady-state evaporation of mercury was performed to measure the principal transport coefficient appearing in the mass-rate equation and the coupling transport coefficient appearing in both the mass-rate equation and the energy-rate equation. The principal transport coefficient sigma, usually termed the 'condensation' or 'evaporation' coefficient, is found to be approximately 0.9, which is higher than that measured previously in condensation-of-mercury experiments. The experimental value of the coupling coefficient K does not agree with the value predicted from Schrage's kinetic analysis of the phase change. A modified kinetic analysis in which the Onsager reciprocal law and the conservation laws are invoked is presented which removes this discrepancy but which shows that the use of Schrage's equation for predicting mass rates of phase change is a good approximation.

The flushing and exchange of the South China Sea derived from salt and mass conservation

NASA Astrophysics Data System (ADS)

Liu, Yang; Bye, John A. T.; You, Yuzhu; Bao, Xianwen; Wu, Dexing

2010-07-01

In this paper, we use two kinds of hydrographic data, historical cruise data, Array for Real-time Geostrophic Oceanography (Argo) float data, and atmospheric data to study the water exchange between the South China Sea (SCS) and the Pacific Ocean through the Luzon Strait. The annual mean distributions of temperature and salinity at five different levels in the SCS and the adjacent Pacific Ocean are presented, which indicate the occurrence of active water exchange through the Luzon Strait. The flushing and exchange of the SCS are then determined by the application of salt and mass conservation in a multi-layered thermohaline system, using an estimate of the net rainfall obtained from reanalysis data. The results show that the annual mean flushing time is 44±8 months with an inflow rate of 11±2 Sv (1 Sv=10 6 m 3 s -1), part of which recirculates at a deeper level through the Luzon Strait, the remainder (6±2 Sv) forming the SCS throughflow. The diffusive influx of salt is also estimated and accounts for about 10% of the total influx, and hence advection dominates over diffusion in the water exchange through the Luzon Strait. The seasonal cycle of exchange shows a maximum in autumn and winter of about twice the annual mean rate.

Heat Exchanger Cleaning in Support of Ocean Thermal Energy Conversion (OTEC) - Mechanical Subsystem.

DTIC Science & Technology

1980-12-01

sponge rubber ball, and chlorination systems. In addition, the maintenance procedures utilized at the NCSC test site are provided. jAN 7 1473 EDITION OF...Recirculating Sponge Rubber Balls .. .... ............. 17 Chlorination .. .............. ............. 19 OTEC MAINTENANCE PROCEDURES...C-1 APPENDIX D - RECIRCULATING SPONGE RUBBER BALL. ............... D-1 APPENDIX E - CHLORINATION SYSTEM .. .. ................. E-1 i 1

Periodic bacterial control with peracetic acid in a recirculating aquaculture system and its long-term beneficial effect on fish health

USDA-ARS?s Scientific Manuscript database

Peracetic acid (PAA) is being introduced to aquaculture as a sustainable disinfectant. It is suitable for recirculating aquaculture systems (RAS) because of the low effective concentrations and its minimal impact on biofilter function. The application of PAA in a RAS has a combined impact on fish an...

The impact of water exchange rate on the health and performance of rainbow trout Oncorhynchus mykiss in recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Fish mortality in recirculating aquaculture systems (RAS) has been observed by the authors to increase when RAS are managed at low makeup water exchange rates with relatively high feed loading. The precise etiology of this elevated mortality was unknown, all typical water quality parameters were wit...

The effects of ozonation on select waterborne steroid hormones in recirculation aquaculture systems containing sexually mature Atlantic salmon Salmo salar

USDA-ARS?s Scientific Manuscript database

A controlled 3-month study was conducted in 6 replicated water recirculation aquaculture systems (RAS) containing a mixture of sexually mature and immature Atlantic salmon Salmo salar to determine whether water ozonation is associated with a reduction in waterborne hormones. Post-smolt Atlantic salm...

Investigating the effectiveness of peracetic acid to reduce post-vaccination Saprolegnia spp.-associated mortality in Atlantic salmon parr while assessing impact on nitrification in recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Closed containment operations utilizing recirculation aquaculture systems (RAS) can provide critical barriers to the introduction of obligate fish pathogens (Timmons and Ebeling, 2010); however, opportunistic pathogens will be present and can cause disease when conditions favor these agents. One par...

29 CFR 1910.124 - General requirements for dipping and coating operations.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Chemical reaction. (c) What requirements must I follow to recirculate exhaust air into the workplace? (1) You may not recirculate exhaust air when any substance in that air poses a health hazard to employees... Liquids. (5) When you use mechanical ventilation, it must draw the flow of air into a hood or exhaust duct...

Evaluating the chronic effects of nitrate on the health and performance of post-smolt Atlantic salmon Salmo salar in freshwater recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Commercial production of Atlantic salmon smolts, post-smolts, and market-size fish using land-based recirculation aquaculture systems (RAS) is expanding. RAS generally provide a nutrient-rich environment in which nitrate accumulates as an end-product of nitrification. An 8-month study was conducted ...

Membrane biological reactors to remove nitrate, digest biosolids, and eliminate water flushing requirements within replicated recirculation systems culturing rainbow trout

USDA-ARS?s Scientific Manuscript database

Nutrients, particularly nitrate (NO3), can accumulate to very high levels within low exchange recirculation aquaculture systems (RAS) and negatively impact a number of cultured species. To prevent the harmful effects of nitrate accumulation and to dispose of concentrated waste biosolids, many RAS ar...

40 CFR 258.42 - Approval of site-specific flexibility requests in Indian country.

Code of Federal Regulations, 2012 CFR

2012-07-01

... VI. (2) The owner and/or operator may operate Phase VI as a bioreactor by recirculating leachate and... IVA by recirculating leachate and landfill gas condensate, and by adding storm water and groundwater... than a 30-cm depth of leachate on the liner. (5) The owner and/or operator shall submit reports to the...

40 CFR 258.42 - Approval of site-specific flexibility requests in Indian country.

Code of Federal Regulations, 2013 CFR

2013-07-01

... VI. (2) The owner and/or operator may operate Phase VI as a bioreactor by recirculating leachate and... IVA by recirculating leachate and landfill gas condensate, and by adding storm water and groundwater... than a 30-cm depth of leachate on the liner. (5) The owner and/or operator shall submit reports to the...

40 CFR 258.42 - Approval of site-specific flexibility requests in Indian country.

Code of Federal Regulations, 2014 CFR

2014-07-01

... VI. (2) The owner and/or operator may operate Phase VI as a bioreactor by recirculating leachate and... IVA by recirculating leachate and landfill gas condensate, and by adding storm water and groundwater... than a 30-cm depth of leachate on the liner. (5) The owner and/or operator shall submit reports to the...

Evaluating standard operating procedures to mitigate off-flavor from Atlantic salmon Salmo salar cultured in a semi-commercial scale recirculating aquaculture system

USDA-ARS?s Scientific Manuscript database

Fish cultured within water recirculating aquaculture systems (RAS) can acquire “earthy” or “musty” off-flavors due to bioaccumulation of the compounds geosmin and 2-methylisoborneol (MIB), respectively, which are produced by certain bacterial species present in RAS biosolids and microbial biofilms. ...

Achromatic recirculated chicane with fixed geometry and independently variable path length and momentum compaction

DOEpatents

Douglas, David R.; Neil, George R.

2005-04-26

A particle beam recirculated chicane geometry that, through the inducement of a pair of 180 degree bends directed by the poles of a pair of controllable magnetic fields allows for variation of dipole position, return loop radii and steering/focussing, thereby allowing the implementation of independent variation of path length and momentum compaction.

Production of market-size North American strain Atlantic salmon Salmo salar in a land-based recirculation aquaculture system using freshwater

USDA-ARS?s Scientific Manuscript database

There is interest in culturing Atlantic salmon Salmo salar to market-size in land-based, closed containment systems that use recirculation aquaculture systems (RAS), as this technology often enables facilities to locate near major markets, obtain permits, exclude obligate pathogens, and/or reduce en...

Fillet quality and processing attributes of postsmolt Atlantic salmon, Salmo salar, fed a fishmeal-free diet and a fishmeal-based diet in recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Many studies have evaluated the adequacy of alternate ingredient diets for Atlantic salmon, Salmo salar, mainly with focus on fish performance and health; however, comprehensive analysis of fillet quality is lacking, particularly for salmon fed these diets in recirculation aquaculture systems (RAS)....

Circulation of the gyres of the world ocean: Observation modeling using TOPEX/Poseidon altimeter data

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Zlotnicki, V.; Holland, W. R.; Malanotte-Rizzoli, P.

1991-01-01

The overall objectives of the proposed investigation are to study the dynamics of the large-scale recirculating cells of water in the ocean, which are loosely defined as 'gyres' in this study. A gyre is normally composed of a swift western boundary current (e.g., the Gulf Stream and the Kuroshio), a tight recirculating cell attached to the current, and a large-scale sluggish return flow. The water, of course, is not entirely recirculating within a gyre. The exchange of water among gyres is an important process in maintaining the meridional heat transport of the ocean. The gyres constitute a major mode of water movement in the ocean and play significant roles in the global climate system.

A replacement LH2 recirculation line before installation in Discovery

NASA Technical Reports Server (NTRS)

1999-01-01

A spare four-inch diameter LH2 recirculation line (shown in photo) will be used to replace a damaged LH2 line in the orbiter Discovery. The line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. Workers noted a dent in the line during routine aft compartment inspections Tuesday, Dec. 7. The dent measures 12 inches long and about =-inch deep. Managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope.

A portable gas recirculation unit for gaseous detectors

NASA Astrophysics Data System (ADS)

Guida, R.; Mandelli, B.

2017-10-01

The use of greenhouse gases (usually C2H2F4, CF4 and SF6) is sometimes necessary to achieve the required performance for some gaseous detectors. The consumption of these gases in the LHC systems is reduced by recycling the gas mixture thanks to a complex gas recirculation system. Beyond greenhouse gas consumption due to LHC systems, a considerable contribution is generated by setups used for LHC detector upgrade projects, R&D activities, detector quality assurance or longevity tests. In order to minimise this emission, a new flexible and portable gas recirculation unit has been developed. Thanks to its low price, flexibility and user-friendly operation it can be easily adapted for the different types of detector systems and set-ups.

Removal of sodium chloride from human urine via batch recirculation electrodialysis at constant applied voltage

NASA Technical Reports Server (NTRS)

Gordils-Striker, Nilda E.; Colon, Guillermo

2003-01-01

The removal of sodium chloride (NaCl) from human urine using a six-compartment electrodialysis cell with batch recirculation mode of operation for use in advanced life support systems (ALSS) was studied. From the results obtained, batch recirculation at constant applied voltage yields high values (approximately 94% of NaCl removal. Based on the results, the initial rate of NaCl removal was correlated to a power function of the applied voltage: -r=2.0 x 10(-4)E(3.8). With impedance spectroscopy methods, it was also found that the anion membranes were more affected by fouling with an increase of the ohmic resistance of almost 11% compared with 7.4% for the cationic ones.

Characterization of Mycobacterium salmoniphilum as causal agent of mycobacteriosis in Atlantic salmon, Salmo salar L., from a freshwater recirculation system.

PubMed

Aro, L; Correa, K; Martínez, A; Ildefonso, R; Yáñez, J M

2014-04-01

Thirty Atlantic salmon, Salmo salar L., with low corporal condition relative to other fish present in the culture system, were sampled from a freshwater recirculation pisciculture located in Chile. The most characteristic signs and lesions were cachexia and presence of multiple greyish-white granulomas within internal organs. The external and internal lesions, along with the microscopic, histologic and biochemical findings, were consistent with mycobacteriosis. The identification of Mycobacterium salmoniphilum as the causal agent of the lesions was possible through the use of molecular analyses. This study represents the first report of Mycobacterium salmoniphilum in a freshwater recirculation system and the first case of fish mycobacteriosis described in Chile. © 2013 John Wiley & Sons Ltd.

Evaporative oxidation treatability test report

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1995-04-01

In 1992, Congress passed the Federal Facilities Compliance Act that requires the U.S. Department of Energy (DOE) to treat and dispose of its mixed waste in accordance with the Resource Conservation and Recovery Act (RCRA) land disposal restrictions (LDRs). In response to the need for mixed-waste treatment capacity where available off-site commercial treatment facilities do not exist or cannot be used, the DOE Albuquerque Operations Office (DOE-AL) organized a Treatment Selection Team to match mixed wastes with treatment options and develop a strategy for treatment of its mixed wastes. DOE-AL manages operations at nine sites with mixed-waste inventories. The Treatmentmore » Selection Team determined a need to develop mobile treatment capacity to treat wastes at the sites where the wastes are generated. Treatment processes used for mixed waste not only must address the hazardous component (i.e., meet LDRs) but also must contain the radioactive component in a form that allows final disposal while protecting workers, the public, and the environment. On the basis of recommendations of the Treatment Selection Team, DOE-AL assigned projects to the sites to bring mixed-waste treatment capacity on-line. The three technologies assigned to the DOE Grand Junction Projects Office (GJPO) are evaporative oxidation, thermal desorption, and treated wastewater evaporation. Rust Geotech, the DOE-GJPO prime contractor, was assigned to design and fabricate mobile treatment units (MTUs) for these three technologies and to deliver the MTUs to selected DOE-AL sites. To conduct treatability tests at the GJPO, Rust leased a pilot-scale evaporative oxidation unit from the Clemson Technical Center (CTC), Anderson, South Carolina. The purpose of this report is to document the findings and results of tests performed using this equipment.« less

Breathing of a coral cay: Tracing tidally driven seawater recirculation in permeable coral reef sediments

NASA Astrophysics Data System (ADS)

Santos, Isaac R.; Erler, Dirk; Tait, Douglas; Eyre, Bradley D.

2010-12-01

Coral reefs are characterized by high gross productivity in spite of low nutrient concentrations. This apparent paradox may be partially reconciled if seawater recirculation in permeable sediments over large (meters) and long (hours to days) scales is an important source of recycled nitrogen and phosphorus to coral reefs. In this paper we use radon (222Rn, a natural tracer) to quantify tidally driven pore water (or groundwater) exchange between (1) an offshore coral cay island and its fringing reef lagoon and (2) a reef lagoon and the surrounding ocean. As seawater infiltrates Heron Island at high tide, it acquires a radon signal that can be detected when pore waters emerge from carbonate sands at low tide. A nonsteady state model indicated that vertical pore water upwelling rates (or saline submarine groundwater discharge) were >40 cm/d within the reef lagoon and >100 cm/d outside the lagoon at low tide. Within the lagoon, tidal pumping and temperature-driven convection were the main driving forces of pore water advection. At low tide, the reef lagoon level is about 1 m higher than the surrounding ocean. As a result, a steep hydraulic gradient develops at the reef edge, driving unidirectional filtration through the reef framework. Groundwaters were highly enriched in nitrate (average of 530 μmol, likely influenced by bird guano) relative to lagoon waters (1.9 μmol). Rough but conservative estimates indicated that groundwater-derived nitrate fluxes (7.9 mmol/m2/d) can replace the entire lagoon nitrate inventory every <19 days. We speculate that as offshore coral islands "breath" (inhale seawater at high tide and exhale groundwater at low tide), they release nutrients that lead to sustained productivity within coral reefs.

Dispersal and fallout simulations for urban consequences management (u)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grinstein, Fernando F; Wachtor, Adam J; Nelson, Matt

2010-01-01

Hazardous chemical, biological, or radioactive releases from leaks, spills, fires, or blasts, may occur (intentionally or accidentally) in urban environments during warfare or as part of terrorist attacks on military bases or other facilities. The associated contaminant dispersion is complex and semi-chaotic. Urban predictive simulation capabilities can have direct impact in many threat-reduction areas of interest, including, urban sensor placement and threat analysis, contaminant transport (CT) effects on surrounding civilian population (dosages, evacuation, shelter-in-place), education and training of rescue teams and services. Detailed simulations for the various processes involved are in principle possible, but generally not fast. Predicting urban airflowmore » accompanied by CT presents extremely challenging requirements. Crucial technical issues include, simulating turbulent fluid and particulate transport, initial and boundary condition modeling incorporating a consistent stratified urban boundary layer with realistic wind fluctuations, and post-processing of the simulation results for practical consequences management. Relevant fluid dynamic processes to be simulated include, detailed energetic and contaminant sources, complex building vortex shedding and flows in recirculation zones, and modeling of particle distributions, including particulate fallout, as well as deposition, re-suspension and evaporation. Other issues include, modeling building damage effects due to eventual blasts, addressing appropriate regional and atmospheric data reduction.« less

Leachate management design in Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lange, D.A.; Broscious, J.C.; Zullo, E.G.

1996-02-01

As part of a project to provide solid waste master plans for 25 cities in Mexico, an American engineering firm, Paul C. Rizzo Associates (Monroeville, Pa.), was contracted to design a comprehensive leachate management system for landfills in the chosen cities. The solid waste master plan project was administered by the Mexican federal government Secretaria de Desarrollo Social (SEDESOL) with funding from the World Bank. While Paul C. Rizzo was the prime contractor for the project, which was completed in 1994, work was also subcontracted to a local Mexican engineering firm. The lack of specific design criteria for leachate managementmore » in current Mexican regulations enabled the use of a creative design for the system based on experience and technical judgment. Important design considerations included the current, primitive open-dump/burning/scavenging method of disposal and recycling of wastes, and the need for a minimal-cost solution in this developing country. The economic situation made the need for minimal expenditures to upgrade infrastructure equally important. The purpose of the design effort was to use evaporation and recirculation methods of landfill leachate management to minimize the amount of leachate that required treatment. Engineers in the project sought an ultimate goal of achieving zero excess leachate at the landfill sites.« less

Realizing the geothermal electricity potential—water use and consequences

NASA Astrophysics Data System (ADS)

Shankar Mishra, Gouri; Glassley, William E.; Yeh, Sonia

2011-07-01

Electricity from geothermal resources has the potential to supply a significant portion of US baseload electricity. We estimate the water requirements of geothermal electricity and the impact of potential scaling up of such electricity on water demand in various western states with rich geothermal resources but stressed water resources. Freshwater, degraded water, and geothermal fluid requirements are estimated explicitly. In general, geothermal electricity has higher water intensity (l kWh - 1) than thermoelectric or solar thermal electricity. Water intensity decreases with increase in resource enthalpy, and freshwater gets substituted by degraded water at higher resource temperatures. Electricity from enhanced geothermal systems (EGS) could displace 8-100% of thermoelectricity generated in most western states. Such displacement would increase stress on water resources if re-circulating evaporative cooling, the dominant cooling system in the thermoelectric sector, is adopted. Adoption of dry cooling, which accounts for 78% of geothermal capacity today, will limit changes in state-wide freshwater abstraction, but increase degraded water requirements. We suggest a research and development focus to develop advanced energy conversion and cooling technologies that reduce water use without imposing energy and consequent financial penalties. Policies should incentivize the development of higher enthalpy resources, and support identification of non-traditional degraded water sources and optimized siting of geothermal plants.

Study of the Effect of Wind Speed on Evaporation from Soil Through Integrated Modeling of Atmospheric Boundary Layer and Shallow Subsurface

NASA Astrophysics Data System (ADS)

Smits, K. M.; Davarzani, H.; Illangasekare, T. H.

2012-12-01

The study of the interaction between the land and atmosphere is paramount to our understanding of many emerging problems to include climate change and the movement of green house gases such as possible leaking of sequestered CO2. Soil moisture distribution in the shallow subsurface becomes a critical factor in these problems. The heat and mass flux in the form of soil evaporation across the land surface couples the atmospheric boundary layer to the shallow subsurface. The coupling between land and the atmosphere leads to highly dynamic interactions between the porous media properties, transport processes and boundary conditions, resulting in dynamic evaporative behavior. However, the coupling at the land-atmospheric interface is rarely considered in most current models and their validation for practical applications. This is due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining coupled energy and mass transfer theories. In most efforts to compute evaporation from soil, only indirect coupling is provided to characterize the interaction between non-isothermal multiphase flows under realistic atmospheric conditions even though heat and mass flux are controlled by the coupled dynamics of the land and the atmospheric boundary layer. In earlier drying modeling concepts, imposing evaporation flux (kinetic of relative humidity) and temperature as surface boundary condition is often needed. With the goal of improving our understanding of the land/atmospheric coupling, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model consists of the coupled equations of mass conservation for the liquid phase (water) and gas phase (water vapor and air) in porous medium with gas phase (water vapor and air) in free flow domain under non-isothermal, non-equilibrium conditions. The boundary conditions at the porous medium-free flow medium interface include dynamical, thermal and solutal equilibriums, and using the Beavers-Joseph slip boundary condition. What is unique about this model is that the evaporation rate and soil surface temperature conditions come directly from the model output. In order to experimentally validate the numerical results, we developed and used a unique two dimensional wind tunnel placed above a soil tank equipped with a network of different sensors. A series of experiments under varying boundary conditions were performed. Precision data under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate that the coupling concept can predict the different stages of the drying process in porous media with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time at low velocity values; then, at high values of wind speed the evaporation rate becomes less dependent of flow in free fluid. In the opposite, the impact of the wind speed on the second stage evaporation (diffusion dominant stage) is not significant. The proposed theoretical model can be used to predict the evaporation process where a porous medium flow is coupled to a free flow for different practical applications.

Asphaltene content and composition as a measure of Deepwater Horizon oil spill losses within the first 80 days

USGS Publications Warehouse

Lewan, M.D.; Warden, A.; Dias, R.F.; Lowry, Z.K.; Hannah, T.L.; Lillis, P.G.; Kokaly, R.F.; Hoefen, T.M.; Swayze, G.A.; Mills, C.T.; Harris, S.H.; Plumlee, G.S.

2014-01-01

The composition and content of asphaltenes in spilled and original wellhead oils from the Deepwater Horizon (DWH) incident provide information on the amount of original oil lost and the processes most responsible for the losses within the first 80 days of the active spill. Spilled oils were collected from open waters, coastal waters and coastal sediments during the incident. Asphaltenes are the most refractory component of crude oils but their alteration in the spilled oils during weathering prevents them from being used directly as a conservative component to calculate original oil losses. The alteration is reflected by their increase in oxygen content and depletion in 12C. Reconnaissance experiments involving evaporation, photo-oxidation, microbial degradation, dissolution, dispersion and burning indicate that the combined effects of photo-oxidation and evaporation are responsible for these compositional changes. Based on measured losses and altered asphaltenes from these experiments, a mean of 61 ± 3 vol% of the original oil was lost from the surface spilled oils during the incident. This mean percentage of original oil loss is considerably larger than previous estimates of evaporative losses based on only gas chromatography (GC) amenable hydrocarbons (32–50 vol%), and highlights the importance of using asphaltenes, as well as GC amenable parameters in evaluating original oil losses and the processes responsible for the losses.

Merriam's kangaroo rats (Dipodomys merriami) voluntarily select temperatures that conserve energy rather than water.

PubMed

Banta, Marilyn R

2003-01-01

Desert endotherms such as Merriam's kangaroo rat (Dipodomys merriami) use both behavioral and physiological means to conserve energy and water. The energy and water needs of kangaroo rats are affected by their thermal environment. Animals that choose temperatures within their thermoneutral zone (TNZ) minimize energy expenditure but may impair water balance because the ratio of water loss to water gain is high. At temperatures below the TNZ, water balance may be improved because animals generate more oxidative water and reduce evaporative water loss; however, they must also increase energy expenditure to maintain a normal body temperature. Hence, it is not possible for kangaroo rats to choose thermal environments that simultaneously minimize energy expenditure and increase water conservation. I used a thermal gradient to test whether water stress, energy stress, simultaneous water and energy stress, or no water/energy stress affected the thermal environment selected by D. merriami. During the night (i.e., active phase), animals in all four treatments chose temperatures near the bottom of their TNZ. During the day (i.e., inactive phase), animals in all four treatments settled at temperatures near the top of their TNZ. Thus, kangaroo rats chose thermal environments that minimized energy requirements, not water requirements. Because kangaroo rats have evolved high water use efficiency, energy conservation may be more important than water conservation to the fitness of extant kangaroo rats.

Evaluating leachate recirculation with cellulase addition to enhance waste biostabilisation and landfill gas production.

PubMed

Frank, R R; Davies, S; Wagland, S T; Villa, R; Trois, C; Coulon, F

2016-09-01

The effect of leachate recirculation with cellulase augmentation on municipal solid waste (MSW) biostabilisation and landfill gas production was investigated using batch bioreactors to determine the optimal conditions of moisture content, temperature and nutrients. Experimentation was thereafter scaled-up in 7L bioreactors. Three conditions were tested including (1) leachate recirculation only, (2) leachate recirculation with enzyme augmentation and (3) no leachate recirculation (control). Cumulative biogas production of the batch tests indicated that there was little difference between the leachate and control test conditions, producing on average 0.043m(3)biogaskg(-1) waste. However the addition of cellulase at 15×10(6)Utonne(-1) waste doubled the biogas production (0.074m(3)biogaskg(-1) waste). Similar trend was observed with the bioreactors. Cellulase addition also resulted in the highest COD reduction in both the waste and the leachate samples (47% and 42% COD reduction, respectively). In both cases, the quantity of biogas produced was closer to the lower value of theoretical and data-based biogas prediction indicators (0.05-0.4m(3)biogaskg(-1) waste). This was likely due to a high concentration of heavy metals present in the leachate, in particular Cr and Mn, which are known to be toxic to methanogens. The cost-benefit analysis (CBA) based on the settings of the study (cellulase concentration of 15×10(6)Utonne(-1) waste) showed that leachate bioaugmentation using cellulase is economically viable, with a net benefit of approximately €12.1million on a 5Mt mixed waste landfill. Copyright © 2016 Elsevier Ltd. All rights reserved.

Conditions for coherent-synchrotron-radiation-induced microbunching suppression in multibend beam transport or recirculation arcs

NASA Astrophysics Data System (ADS)

Tsai, C.-Y.; Di Mitri, S.; Douglas, D.; Li, R.; Tennant, C.

2017-02-01

The coherent synchrotron radiation (CSR) of a high-brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in beam phase space degradation. On one hand, CSR can perturb electron transverse motion in dispersive regions along the beam line and possibly cause emittance growth. On the other hand, the CSR effect on the longitudinal beam dynamics could result in microbunching instability. For transport arcs, several schemes have been proposed to suppress the CSR-induced emittance growth. Correspondingly, a few scenarios have been introduced to suppress CSR-induced microbunching instability, which however mostly aim for linac-based machines. In this paper we provide sufficient conditions for suppression of CSR-induced microbunching instability along transport or recirculation arcs. Examples are presented with the relevant microbunching analyses carried out by our developed semianalytical Vlasov solver [C.-Y. Tsai, D. Douglas, R. Li, and C. Tennant, Linear microbunching analysis for recirculation machines, Phys. Rev. ST Accel. Beams 19, 114401 (2016), 10.1103/PhysRevAccelBeams.19.114401]. The example lattices include low-energy (˜100 MeV ) and high-energy (˜1 GeV ) recirculation arcs, and medium-energy compressor arcs. Our studies show that lattices satisfying the proposed conditions indeed have microbunching gain suppressed. Beam current dependences of maximal CSR microbunching gains are also demonstrated, which should help outline a beam line design for different scales of nominal currents. We expect this analysis can shed light on the lattice design approach that aims to control the CSR-induced microbunching.

Design of two-column batch-to-batch recirculation to enhance performance in ion-exchange chromatography.

PubMed

Persson, Oliver; Andersson, Niklas; Nilsson, Bernt

2018-01-05

Preparative liquid chromatography is a separation technique widely used in the manufacturing of fine chemicals and pharmaceuticals. A major drawback of traditional single-column batch chromatography step is the trade-off between product purity and process performance. Recirculation of impure product can be utilized to make the trade-off more favorable. The aim of the present study was to investigate the usage of a two-column batch-to-batch recirculation process step to increase the performance compared to single-column batch chromatography at a high purity requirement. The separation of a ternary protein mixture on ion-exchange chromatography columns was used to evaluate the proposed process. The investigation used modelling and simulation of the process step, experimental validation and optimization of the simulated process. In the presented case the yield increases from 45.4% to 93.6% and the productivity increases 3.4 times compared to the performance of a batch run for a nominal case. A rapid concentration build-up product can be seen during the first cycles, before the process reaches a cyclic steady-state with reoccurring concentration profiles. The optimization of the simulation model predicts that the recirculated salt can be used as a flying start of the elution, which would enhance the process performance. The proposed process is more complex than a batch process, but may improve the separation performance, especially while operating at cyclic steady-state. The recirculation of impure fractions reduces the product losses and ensures separation of product to a high degree of purity. Copyright © 2017 Elsevier B.V. All rights reserved.

Turbulence measurements of high shear flow fields in a turbomachine seal configuration

NASA Technical Reports Server (NTRS)

Morrison, Gerald L.; Deotte, Robert E., Jr.; Thames, H. Davis, III.

1992-01-01

The mean velocity and Reynolds stress tensor throughout a whirling annular seal are presented. The data was collected with a three dimensional laser Doppler velocimeter using phase averaging. Two axial flow conditions (Re = 12,000 and 24,000) were studied at one shaft speed (Ta = 6,600). The eccentricity and whirl ratios were 50 and 100 percent, respectively. There is a region of high axial momentum in this region is higher in the low Reynolds number case due to an axial recirculation zone that occurs on the suction side of the rotor at the inlet. The recirculation zone does not occur in the high Reynolds number case. At both Reynolds numbers, there is a recirculation zone on the rotor surface in the pressure side of the inlet. This recirculation zone extends from 20 to 200 degrees rotor zenith in the tangential direction, and is one third of a clearance wide radially. The high Reynolds number recirculation zone is 1.5 mean clearances long, while the low Reynolds number zone extends 2 mean clearances downstream. When compared to previous studies, it is apparent that the tangential momentum is no greater for a seal with whirl than for one without if other parameters are constant. Areas of high tangential momentum occur in the clearance where the axial momentum is low. Average exit plane tangential velocities in the high Reynolds number case are 1.5 times greater than those in the other flow case. These results are in general agreement with predictions made by other investigators.

Semi-continuous anaerobic co-digestion of cow manure and steam-exploded Salix with recirculation of liquid digestate.

PubMed

Estevez, Maria M; Sapci, Zehra; Linjordet, Roar; Schnürer, Anna; Morken, John

2014-04-01

The effects of recirculating the liquid fraction of the digestate during mesophilic anaerobic co-digestion of steam-exploded Salix and cow manure were investigated in laboratory-scale continuously stirred tank reactors. An average organic loading rate of 2.6 g VS L(-1) d(-1) and a hydraulic retention time (HRT) of 30 days were employed. Co-digestion of Salix and manure gave better methane yields than digestion of manure alone. Also, a 16% increase in the methane yield was achieved when digestate was recirculated and used instead of water to dilute the feedstock (1:1 dilution ratio). The reactor in which the larger fraction of digestate was recirculated (1:3 dilution ratio) gave the highest methane yields. Ammonia and volatile fatty acids did not reach inhibitory levels, and some potentially inhibitory compounds released during steam explosion (i.e., furfural and 5-hydroxy methyl furfural) were only detected at trace levels throughout the entire study period. However, accumulation of solids, which was more pronounced in the recycling reactors, led to decreased methane yields in those systems after three HRTs. Refraining from the use of fresh water to dilute biomass with a high-solids content and obtaining a final digestate with increased dry matter content might offer important economic benefits in full-scale processes. To ensure long-term stability in such an approach, it would be necessary to optimize separation of the fraction of digestate to be recirculated and also perform proper monitoring to avoid accumulation of solids. Copyright © 2014 Elsevier Ltd. All rights reserved.

A detached eddy simulation model for the study of lateral separation zones along a large canyon-bound river

NASA Astrophysics Data System (ADS)

Alvarez, Laura V.; Schmeeckle, Mark W.; Grams, Paul E.

2017-01-01

Lateral flow separation occurs in rivers where banks exhibit strong curvature. In canyon-bound rivers, lateral recirculation zones are the principal storage of fine-sediment deposits. A parallelized, three-dimensional, turbulence-resolving model was developed to study the flow structures along lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model employs the detached eddy simulation (DES) technique, which resolves turbulence structures larger than the grid spacing in the interior of the flow. The DES-3D model is validated using Acoustic Doppler Current Profiler flow measurements taken during the 2008 controlled flood release from Glen Canyon Dam. A point-to-point validation using a number of skill metrics, often employed in hydrological research, is proposed here for fluvial modeling. The validation results show predictive capabilities of the DES model. The model reproduces the pattern and magnitude of the velocity in the lateral recirculation zone, including the size and position of the primary and secondary eddy cells, and return current. The lateral recirculation zone is open, having continuous import of fluid upstream of the point of reattachment and export by the recirculation return current downstream of the point of separation. Differences in magnitude and direction of near-bed and near-surface velocity vectors are found, resulting in an inward vertical spiral. Interaction between the recirculation return current and the main flow is dynamic, with large temporal changes in flow direction and magnitude. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer becoming three-dimensional without preferred orientation downstream.

Design and performance of recirculating systems for Atlantic salmon (Salmo salar) at the USDA ARS National Cold Water Marine Aquaculture Center (Franklin, Maine)

USDA-ARS?s Scientific Manuscript database

Atlantic salmon cultured in the NCWMAC breeding program have grown well in the fish culture systems during the first 3 years of operation. The systems were operated at approximately 98% reuse (2% makeup water on the basis of flow rate). The water recirculating systems maintained acceptable water qua...

Engine bleed air reduction in DC-10

NASA Technical Reports Server (NTRS)

Newman, W. H.; Viele, M. R.

1980-01-01

An 0.8 percent fuel savings was achieved by a reduction in engine bleed air through the use of cabin air recirculation. The recirculation system was evaluated in revenue service on a DC-10. The cabin remained comfortable with reductions in cabin fresh air (engine bleed air) as much as 50 percent. Flight test verified the predicted fuel saving of 0.8 percent.

Removal of Nutrients from Septic Effluent with Re-circulated Hybrid Tidal Flow Constructed Wetland

Treesearch

Lihua Cui; Jigkun Feng; Ying Ouyang; Peiwen Deng

2012-01-01

Hybrid tidal flow constructed wetland (CW) with recirculation is an improved biological and engineering technique for removal of excess nutrients and certain pollutants from wastewater. This study investigated the removal efficiency of total phosphorus (TP), ammonia-nitrogen (NH3-N), and total nitrogen (TN) from septic tank effluent with the hybrid tidal flow CW system...

Use of low temperature blowers for recirculation of hot gases

DOEpatents

Maru, H.C.; Forooque, M.

1982-08-19

An apparatus is described for maintaining motors at low operating temperatures during recirculation of hot gases in fuel cell operations and chemical processes such as fluidized bed coal gasification. The apparatus includes a means for separating the hot process gas from the motor using a secondary lower temperature gas, thereby minimizing the temperature increase of the motor and associated accessories.

Evaluation of depuration procedures to mitigate the off-flavor compounds geosmin and 2-methylisoborneol from Atlantic salmon Salmo salar raised to market-size in recirculating aquaculture systems

USDA-ARS?s Scientific Manuscript database

Fish cultured within water recirculating aquaculture systems (RAS) can acquire “earthy” or “musty” off-flavors due to bioaccumulation of the compounds geosmin and 2-methylisoborneol (MIB), respectively, which are produced by certain bacterial species present in RAS biosolids and microbial biofilms. ...

Effects of pH on biomass, geosmin, and 2-methylisoborneol production and cellular activity by Streptomyces luridiscabiei isolated from a rainbow trout recirculating aquaculture system

USDA-ARS?s Scientific Manuscript database

Rainbow trout (Oncorhynchus mykiss) grown in recirculating aquaculture systems (RAS) can acquire “earthy” and “musty” taints due to bioaccumulation of geosmin and 2-methyisoborneol (MIB), respectively, in the fish flesh. Certain species of actinomycetes which produce these compounds are attributed a...

The effects of long-term 20 mg/L carbon dioxide exposure on the health and performance of Atlantic salmon Salmo salar post-smolts in water recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

Previous research and experience has linked elevated dissolved carbon dioxide (CO2) to reduced growth performance, poor feed conversion, and a variety of health issues in farm-raised fish, including Atlantic salmon Salmo salar. Supplemental control measures in water recirculation aquaculture systems...

Impacts of coronary artery eccentricity on macro-recirculation and pressure drops using computational fluid dynamics

NASA Astrophysics Data System (ADS)

Poon, Eric; Thondapu, Vikas; Barlis, Peter; Ooi, Andrew

2017-11-01

Coronary artery disease remains a major cause of mortality in developed countries, and is most often due to a localized flow-limiting stenosis, or narrowing, of coronary arteries. Patients often undergo invasive procedures such as X-ray angiography and fractional flow reserve to diagnose flow-limiting lesions. Even though such diagnostic techniques are well-developed, the effects of diseased coronary segments on local flow are still poorly understood. Therefore, this study investigated the effect of irregular geometries of diseased coronary segments on the macro-recirculation and local pressure minimum regions. We employed an idealized coronary artery model with a diameter of stenosis of 75%. By systematically adjusting the eccentricity and the asymmetry of the coronary stenosis, we uncovered an increase in macro-recirculation size. Most importantly, the presence of this macro-recirculation signifies a local pressure minimum (identified by λ2 vortex identification method). This local pressure minimum has a profound effect on the pressure drops in both longitudinal and planar directions, which has implications for diagnosis and treatment of coronary artery disease. Supported by Australian Research Council LP150100233 and National Computational Infrastructure m45.

Linear microbunching analysis for recirculation machines

DOE PAGES

Tsai, C. -Y.; Douglas, D.; Li, R.; ...

2016-11-28

Microbunching instability (MBI) has been one of the most challenging issues in designs of magnetic chicanes for short-wavelength free-electron lasers or linear colliders, as well as those of transport lines for recirculating or energy-recovery-linac machines. To quantify MBI for a recirculating machine and for more systematic analyses, we have recently developed a linear Vlasov solver and incorporated relevant collective effects into the code, including the longitudinal space charge, coherent synchrotron radiation, and linac geometric impedances, with extension of the existing formulation to include beam acceleration. In our code, we semianalytically solve the linearized Vlasov equation for microbunching amplification factor formore » an arbitrary linear lattice. In this study we apply our code to beam line lattices of two comparative isochronous recirculation arcs and one arc lattice preceded by a linac section. The resultant microbunching gain functions and spectral responses are presented, with some results compared to particle tracking simulation by elegant (M. Borland, APS Light Source Note No. LS-287, 2002). These results demonstrate clearly the impact of arc lattice design on the microbunching development. Lastly, the underlying physics with inclusion of those collective effects is elucidated and the limitation of the existing formulation is also discussed.« less

Fan Performance From Duct Rake Instrumentation on a 1.294 Pressure Ratio, 725 ft/sec Tip Speed Turbofan Simulator Using Vaned Passage Casing Treatment

NASA Technical Reports Server (NTRS)

Fite, E. Brian

2006-01-01

A 1.294 pressure ratio, 725 ft/sec tip speed, variable pitch low noise fan was designed and tested in the NASA Glenn 9- by 15-foot Wind Tunnel. The design included a casing treatment that used recirculation to extend the fan stall line and provide an acceptable operating range. Overall aerodynamic experimental results are presented for this low tip speed, low noise fan without casing treatment as well as using several variants of the casing treatment that moved the air extraction and insertion axial locations. Measurements were made to assess effects on performance, operability, and noise. An unusual instability was discovered near the design operating line and is documented in the fan operating range. Measurements were made to compare stall margin improvements as well as measure the performance impact of the casing treatments. Experimental results in the presence of simulated inlet distortion, via screens, are presented for the baseline and recirculation casing treatment configurations. Estimates are made for the quantity of recirculation weight flow based on limited instrumentation in the recirculation system along with discussion of results and conclusions

Biofouling reduction in recirculating cooling systems through biofiltration of process water.

PubMed

Meesters, K P H; Van Groenestijn, J W; Gerritse, J

2003-02-01

Biofouling is a serious problem in industrial recirculating cooling systems. It damages equipment, through biocorrosion, and causes clogging and increased energy consumption, through decreased heat transfer. In this research a fixed-bed biofilter was developed which removed assimilable organic carbon (AOC) from process water, thus limiting the major substrate for the growth of biofouling. The biofilter was tested in a laboratory model recirculating cooling water system, including a heat exchanger and a cooling tower. A second identical model system without a biofilter served as a reference. Both installations were challenged with organic carbon (sucrose and yeast extract) to provoke biofouling. The biofilter improved the quality of the recirculating cooling water by reducing the AOC content, the ATP concentration, bacterial numbers (30-40 fold) and the turbidity (OD660). The process of biofouling in the heat exchangers, the process water pipelines and the cooling towers, was monitored by protein increase, heat transfer resistance, and chlorine demanded for maintenance. This revealed that biofouling was lower in the system with the biofilter compared to the reference installation. It was concluded that AOC removal through biofiltration provides an attractive, environmental-friendly means to reduce biofouling in industrial cooling systems.

Short tests to couple N₂O emission mitigation and nitrogen removal strategies for landfill leachate recirculation.

PubMed

Wu, Dong; Wang, Chao; Dolfing, Jan; Xie, Bing

2015-04-15

Landfills implemented with onsite leachate recirculation can efficiently remove pollutants, but currently they are reckoned as N2O emission hot spots. In this project, we evaluated the relationship between N2O emission and nitrogen (N) removal efficiency with different types of leachate recirculated. Nitrate supplemented leachate showed low N2O emission rates with the highest N removal efficiency (~70%), which was equivalent to ~1% nitrogen emitted as N2O. Although in nitrite containing leachates' N removal efficiencies also reached to ~60%, their emitted N2O comprised ~40% of total removed nitrogen. Increasing nitrogen load promoted N2O emission and N removal efficiency, except in ammonia type leachate. When the ratio of BOD to total nitrogen increased from 0.2 to 0.4, the N2O emission flux from nitrate supplemented leachate decreased from ~25 to <0.5 μg N/kg-soil·h. We argue prior to leachate in situ recirculation, sufficient pre-aeration is critical to mitigate N2O surges and simultaneously enhance nitrogen removal efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Simultaneous Raman-Rayleigh-LIF Measurements and Numerical Modeling Results of a Lifted H2/N2 Turbulent Jet Flame in a Vitiated Coflow

NASA Technical Reports Server (NTRS)

Cabra, R.; Chen, J. Y.; Dibble, R. W.; Hamano, Y.; Karpetis, A. N.; Barlow, R. S.

2002-01-01

An experimental and numerical investigation is presented of a H2/N2 turbulent jet flame burner that has a novel vitiated coflow. The vitiated coflow emulates the recirculation region of most combustors, such as gas turbines or furnaces. Additionally, since the vitiated gases are coflowing, the burner allows for exploration of recirculation chemistry without the corresponding fluid mechanics of recirculation. Thus the vitiated coflow burner design facilitates the development of chemical kinetic combustion models without the added complexity of recirculation fluid mechanics. Scalar measurements are reported for a turbulent jet flame of H2/N2 in a coflow of combustion products from a lean ((empty set) = 0.25) H2/Air flame. The combination of laser-induced fluorescence, Rayleigh scattering, and Raman scattering is used to obtain simultaneous measurements of the temperature, major species, as well as OH and NO. Laminar flame calculation with equal diffusivity do agree when the premixing and preheating that occurs prior to flame stabilization is accounted for in the boundary conditions. Also presented is an exploratory pdf model that predicts the flame's axial profiles fairly well, but does not accurately predict the lift-off height.

Computational fluid dynamics assessment: Volume 2, Isothermal simulations of the METC bench-scale coal-water slurry combustor: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celik, I.; Chattree, M.

1988-09-01

The isothermal turbulent, swirling flow inside the METC pressurized bench-scale combustor has been simulated using ISOPCGC-2. The effects of the swirl numbers, the momentum ratio of the primary to secondary streams, the annular wall thickness, and the quarl angle on the flow and mixing patterns have been investigated. The results that with the present configuration of the combustor, an annular recirculation zone is present up to secondary swirl number of four. A central (on axis) recirculation zone can be obtained by increasing the momentum of the secondary stream by decreasing the annular area at the reactor inlet. The mixing ofmore » the primary (fuel carrier) air with the secondary air improves only slightly due to swirl unless a central recirculation zone is present. Good mixing is achieved in the quarl region when a central recirculation zone is present. A preliminary investigation of the influence of placing flow regulators inside the the combustor shows that they influence the flow field significantly and that there is a potential of obtaining optimum flow conditions using these flow regulators. 58 refs., 47 figs., 12 tabs.« less

Tilt rotor hover aeroacoustics

NASA Technical Reports Server (NTRS)

Coffen, Charles David

1992-01-01

The methodology, results, and conclusions of a study of tilt rotor hover aeroacoustics and aerodynamics are presented. Flow visualization and hot wire velocity measurement were performed on a 1/12-scale model of the XV-15 Tilt Rotor Aircraft in hover. The wing and fuselage below the rotor cause a complex recirculating flow. Results indicate the physical dimensions and details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Discrete frequency harmonic thickness and the loading noise mechanism were predicted using WOPWOP for the standard metal blades and the Advanced Technology Blades. The recirculating flow created by the wing below the rotor is a primary sound mechanism for a hovering tilt rotor. The effects of dynamic blade response should be included for fountain flow conditions which produce impulsive blade loading. Broadband noise mechanisms were studied using Amiet's method with azimuthally varying turbulence characteristics derived from the measurements. The recirculating fountain flow with high turbulence levels in the recirculating zone is the dominant source of broadband noise for a hovering rotor. It is shown that tilt rotor hover aeroacoustic noise mechanisms are now understood. Noise predictions can be made based on reasonably accurate aerodynamic models developed here.

Energy, Water and Fish: Biodiversity Impacts of Energy-Sector Water Demand in the United States Depend on Efficiency and Policy Measures

PubMed Central

McDonald, Robert I.; Olden, Julian D.; Opperman, Jeffrey J.; Miller, William M.; Fargione, Joseph; Revenga, Carmen; Higgins, Jonathan V.; Powell, Jimmie

2012-01-01

Rising energy consumption in coming decades, combined with a changing energy mix, have the potential to increase the impact of energy sector water use on freshwater biodiversity. We forecast changes in future water use based on various energy scenarios and examine implications for freshwater ecosystems. Annual water withdrawn/manipulated would increase by 18–24%, going from 1,993,000–2,628,000 Mm3 in 2010 to 2,359,000–3,271,000 Mm3 in 2035 under the Reference Case of the Energy Information Administration (EIA). Water consumption would more rapidly increase by 26% due to increased biofuel production, going from 16,700–46,400 Mm3 consumption in 2010 to 21,000–58,400 Mm3 consumption in 2035. Regionally, water use in the Southwest and Southeast may increase, with anticipated decreases in water use in some areas of the Midwest and Northeast. Policies that promote energy efficiency or conservation in the electric sector would reduce water withdrawn/manipulated by 27–36 m3GJ−1 (0.1–0.5 m3GJ−1 consumption), while such policies in the liquid fuel sector would reduce withdrawal/manipulation by 0.4–0.7 m3GJ−1 (0.2–0.3 m3GJ−1 consumption). The greatest energy sector withdrawal/manipulation are for hydropower and thermoelectric cooling, although potential new EPA rules that would require recirculating cooling for thermoelectric plants would reduce withdrawal/manipulation by 441,000 Mm3 (20,300 Mm3 consumption). The greatest consumptive energy sector use is evaporation from hydroelectric reservoirs, followed by irrigation water for biofuel feedstocks and water used for electricity generation from coal. Historical water use by the energy sector is related to patterns of fish species endangerment, where water resource regions with a greater fraction of available surface water withdrawn by hydropower or consumed by the energy sector correlated with higher probabilities of imperilment. Since future increases in energy-sector surface water use will occur in areas of high fish endemism (e.g., Southeast), additional management and policy actions will be needed to minimize further species imperilment. PMID:23185581

Assessment of artificial recharge at Sand Hollow Reservoir, Washington County, Utah, Updated to Conditions through 2006

USGS Publications Warehouse

Heilweil, Victor M.; Susong, David D.

2007-01-01

Sand Hollow, Utah, is the site of a surface-water reservoir completed in March 2002 and operated by the Washington County Water Conservancy District (WCWCD) primarily as an aquifer storage and recovery project. The reservoir is an off-channel facility that receives water from the Virgin River, diverted near the town of Virgin, Utah. Hydrologic data collected are described and listed in this report, including ground-water levels, reservoir stage, reservoir-water temperature, meteorology, evaporation, and estimated ground-water recharge. Since the construction of the reservoir in 2002, diversions from the Virgin River have resulted in generally rising stage and surface area. Large spring run-off volumes during 2005-06 allowed the WCWCD to fill the reservoir to near capacity, with a surface area of about 1,300 acres in 2006. Reservoir stage reached a record altitude of about 3,060 feet in May 2006, resulting in a depth of nearly 90 feet and a reservoir storage of about 51,000 acre-feet. Water temperature in the reservoir shows large seasonal variation and has ranged from about 5 to 32?C. Estimated ground-water recharge rates have ranged from 0.01 to 0.43 feet per day. Estimated recharge volumes have ranged from about 200 to about 3,500 acre-feet per month. Total ground-water recharge from March 2002 through August 2006 is estimated to be about 51,000 acre-feet. Estimated evaporation rates have varied from 0.05 to 0.97 feet per month, resulting in evaporation losses of 20 to 1,200 acre-feet per month. Total evaporation from March 2002 through August 2006 is estimated to be about 17,000 acre-feet. The combination of generally declining recharge rates and increasing reservoir altitude and area explains the trend of an increasing ratio of evaporation to recharge volume over time, with the total volume of water lost through evaporation nearly as large as the volume of ground-water recharge during the first 8 months of 2006. With removal of the viscosity effects (caused by seasonal water temperature variations), the intrinsic permeability indicates a large seasonal variation in clogging, with large winter increases likely caused by a combination of both decreased biofilms and the reduced volume of trapped gas bubbles.

A replacement LH2 recirculation line before installation in Discovery

NASA Technical Reports Server (NTRS)

1999-01-01

Gary Hamilton (left) and James Stickley, both with United Space Alliance, check out a spare four-inch diameter LH2 recirculation line that will be used to replace a damaged LH2 line in the orbiter Discovery. The line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. Workers noted a dent in the line during routine aft compartment inspections Tuesday, Dec. 7. The dent measures 12 inches long and about =-inch deep. Managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope.

A replacement LH2 recirculation line before installation in Discovery

NASA Technical Reports Server (NTRS)

1999-01-01

James Stickley (left) and Derry Dilby (right), who are with United Space Alliance, check over a spare four-inch diameter LH2 recirculation line that will be used to replace a damaged LH2 line in the orbiter Discovery. The line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. Workers noted a dent in the line during routine aft compartment inspections Tuesday, Dec. 7. The dent measures 12 inches long and about =-inch deep. Managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope.

Back to the Thymus: Peripheral T Cells Come Home

PubMed Central

Hale, J. Scott; Fink, Pamela J.

2009-01-01

The thymus has long been known as the generative organ for the T cell arm of the immune system. To perform this role, the thymus was thought to require protection from antigenic and cellular insult from the “outside world”, with the notable exception of the continual influx of progenitor cells required to initiate the complicated process of T cell differentiation. Overwhelming evidence that mature T cells can recirculate and persist in the thymus has required us to revamp this earlier view of the thymus as detached from outside influence. In this review, we consider the evidence for T cell recirculation into the thymus, discuss the likely means and location of mature T cell entry, and speculate on the potential consequences of such close apposition between differentiating thymocytes and mature recirculating lymphocytes. PMID:19030016

Back to the thymus: peripheral T cells come home.

PubMed

Hale, J Scott; Fink, Pamela J

2009-01-01

The thymus has long been known as the generative organ for the T-cell arm of the immune system. To perform this role, the thymus was thought to require protection from antigenic and cellular insult from the 'outside world', with the notable exception of the continual influx of progenitor cells required to initiate the complicated process of T-cell differentiation. Overwhelming evidence that mature T cells can recirculate and persist in the thymus has required us to revamp this earlier view of the thymus as detached from outside influence. In this review, we consider the evidence for T-cell recirculation into the thymus, discuss the likely means and location of mature T-cell entry, and speculate on the potential consequences of such close apposition between differentiating thymocytes and mature recirculating lymphocytes.

Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance.

PubMed

Kern, P; Cramp, R L; Gordos, M A; Watson, J R; Franklin, C E

2018-01-01

This study compared the critical swimming speed (U crit ) and endurance performance of three Australian freshwater fish species in different swim-test apparatus. Estimates of U crit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free-surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory-based measures to the design of fish passage infrastructure. © 2017 The Fisheries Society of the British Isles.

Turbulent transport modeling of shear flows around an aerodynamic wing. Development of turbulent near-wall model and its application to recirculating flows

NASA Technical Reports Server (NTRS)

Amano, R. S.

1982-01-01

Progress in implementing and refining two near-wall turbulence models in which the near-wall region is divided into either two or three zones is outlined. These models were successfully applied to the computation of recirculating flows. The research was further extended to obtaining experimental results of two different recirculating flow conditions in order to check the validity of the present models. Two different experimental apparatuses were set up: axisymmetric turbulent impinging jets on a flat plate, and turbulent flows in a circular pipe with a abrupt pipe expansion. It is shown that generally better results are obtained by using the present near-wall models, and among the models the three-zone model is superior to the two-zone model.

Zero-G Thermodynamic Venting System (TVS) Performance Prediction Program

NASA Technical Reports Server (NTRS)

Nguyen, Han

1994-01-01

This report documents the Zero-g Thermodynamic Venting System (TVS) performance prediction computer program. The zero-g TVS is a device that destratifies and rejects environmentally induced zero-g thermal gradients in the LH2 storage transfer system. A recirculation pump and spray injection manifold recirculates liquid throughout the length of the tank thereby destratifying both the ullage gas and liquid bulk. Heat rejection is accomplished by the opening of the TVS control valve which allows a small flow rate to expand to a low pressure thereby producing a low temperature heat sink which is used to absorb heat from the recirculating liquid flow. The program was written in FORTRAN 77 language on the HP-9000 and IBM PC computers. It can be run on various platforms with a FORTRAN compiler.

Investigating the influence of nitrate nitrogen on post-smolt Atlantic salmon Salmo salar reproductive physiology in freshwater recirculation aquaculture systems

USDA-ARS?s Scientific Manuscript database

An 8-month trial was carried out to assess the effects of NO3-N on a variety of performance and physiological outcomes in post-smolt Atlantic salmon Salmo salar (initial weight 102 plus or minus 1 g) reared in six replicated laboratory-scale water recirculation aquaculture systems (RAS). Three RAS r...

Effects of alkalinity on ammonia removal, carbon dioxide stripping, and system pH in semi-commercial scale water recirculating aquaculture systems operated with moving bed bioreactors

USDA-ARS?s Scientific Manuscript database

When operating water recirculating systems (RAS) with high make-up water flushing rates in locations that have low alkalinity in the raw water, such as Norway, knowledge about the required RAS alkalinity concentration is important. Flushing RAS with make-up water containing low alkalinity washes out...

Walleye Sander vitreus performance, water quality, and waste production in replicated recirculation aquaculture systems when feeding a low phosphorus diet without fishmeal versus a traditional fishmeal-based diet

USDA-ARS?s Scientific Manuscript database

Walleye Sander vitreus is a popular sport- and food-fish in areas surrounding the Great Lakes. Walleye are mainly provided as food-fish by limited capture fisheries, but have potential for profitable production to market-size in recirculation aquaculture systems (RAS). Walleye are piscivorous with a...

Impact of capillary rise and recirculation on simulated crop yields

NASA Astrophysics Data System (ADS)

Kroes, Joop; Supit, Iwan; van Dam, Jos; van Walsum, Paul; Mulder, Martin

2018-05-01

Upward soil water flow is a vital supply of water to crops. The purpose of this study is to determine if upward flow and recirculated percolation water can be quantified separately, and to determine the contribution of capillary rise and recirculated water to crop yield and groundwater recharge. Therefore, we performed impact analyses of various soil water flow regimes on grass, maize and potato yields in the Dutch delta. Flow regimes are characterized by soil composition and groundwater depth and derived from a national soil database. The intermittent occurrence of upward flow and its influence on crop growth are simulated with the combined SWAP-WOFOST model using various boundary conditions. Case studies and model experiments are used to illustrate the impact of upward flow on yield and crop growth. This impact is clearly present in situations with relatively shallow groundwater levels (85 % of the Netherlands), where capillary rise is a well-known source of upward flow; but also in free-draining situations the impact of upward flow is considerable. In the latter case recirculated percolation water is the flow source. To make this impact explicit we implemented a synthetic modelling option that stops upward flow from reaching the root zone, without inhibiting percolation. Such a hypothetically moisture-stressed situation compared to a natural one in the presence of shallow groundwater shows mean yield reductions for grassland, maize and potatoes of respectively 26, 3 and 14 % or respectively about 3.7, 0.3 and 1.5 t dry matter per hectare. About half of the withheld water behind these yield effects comes from recirculated percolation water as occurs in free-drainage conditions and the other half comes from increased upward capillary rise. Soil water and crop growth modelling should consider both capillary rise from groundwater and recirculation of percolation water as this improves the accuracy of yield simulations. This also improves the accuracy of the simulated groundwater recharge: neglecting these processes causes overestimates of 17 % for grassland and 46 % for potatoes, or 63 and 34 mm yr-1, respectively.

Yield Stress Reduction of DWPF Melter Feed Slurries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, M.E.; Smith, M.E.

2007-07-01

The Defense Waste Processing Facility (DWPF) at the Savannah River Site vitrifies High Level Waste for repository internment. The process consists of three major steps: waste pretreatment, vitrification, and canister decontamination/sealing. The HLW consists of insoluble metal hydroxides and soluble sodium salts. The pretreatment process acidifies the sludge with nitric and formic acids, adds the glass formers as glass frit, then concentrates the resulting slurry to approximately 50 weight percent (wt%) total solids. This slurry is fed to the joule-heated melter where the remaining water is evaporated followed by calcination of the solids and conversion to glass. The Savannah Rivermore » National Laboratory (SRNL) is currently assisting DWPF efforts to increase throughput of the melter. As part of this effort, SRNL has investigated methods to increase the solids content of the melter feed to reduce the heat load required to complete the evaporation of water and allow more of the energy available to calcine and vitrify the waste. The process equipment in the facility is fixed and cannot process materials with high yield stresses, therefore increasing the solids content will require that the yield stress of the melter feed slurries be reduced. Changing the glass former added during pretreatment from an irregularly shaped glass frit to nearly spherical beads was evaluated. The evaluation required a systems approach which included evaluations of the effectiveness of beads in reducing the melter feed yield stress as well as evaluations of the processing impacts of changing the frit morphology. Processing impacts of beads include changing the settling rate of the glass former (which effects mixing and sampling of the melter feed slurry and the frit addition equipment) as well as impacts on the melt behavior due to decreased surface area of the beads versus frit. Beads were produced from the DWPF process frit by fire polishing. The frit was allowed to free fall through a flame, then quenched with a water spray. Approximately 90% of the frit was converted to beads by this process. Yield stress reduction was measured by preparing melter feed slurries (using nonradioactive HLW simulants) that contain beads and comparing the yield stress with melter feed containing frit. A second set of tests was performed with beads of various diameters to determine if a decrease in diameter affected the results. Smaller particle size was shown to increase yield stress when frit is utilized. The settling rate of the beads was required to match the settling rate of the frit, therefore a decrease in particle size was anticipated. Settling tests were conducted in water, xanthan gum solutions, and in non-radioactive simulants of the HLW. The tests used time-lapse video-graphy as well as solids sampling to evaluate the settling characteristics of beads compared to frit of the same particle size. A preliminary melt rate evaluation was performed using a dry-fed Melt Rate Furnace (MRF) developed by SRNL. Preliminary evaluation of the impact of beading the frit on the frit addition system were completed by conducting flow loop testing. A recirculation loop was built with a total length of about 30 feet. Pump power, flow rate, outlet pressure, and observations of the flow in the horizontal upper section of the loop were noted. The recirculation flow was then gradually reduced and the above items recorded until settling was noted in the recirculation line. Overall, the data shows that the line pressure increased as the solids were increased for the same flow rate. In addition, the line pressure was higher for Frit 320 than the beads at the same solids level and flow. With the observations, a determination of minimum velocity to prevent settling could be done, but a graph of the line pressures versus velocity for the various tests was deemed to more objective. The graph shows that the inflection point in pressure drop is about the same for the beads and Frit 320. This indicates that the bead slurry would not require higher flows rates than frit slurry at DWPF during transfers. Another key finding was that the pump impeller was not significantly damaged by the bead slurry, while the Frit 320 slurry rapidly destroyed the impeller. Evidence of this was first observed when black particles were seen in the Frit 320 slurry being recirculated and then confirmed by a post-test inspection of the impeller. Finally, the pumping of bead slurry could be recovered even if flow is stopped. The Frit 320 slurry could not be restarted after stopping flow due to the nature of the frit to pack tightly when settled. Beads were shown to represent a significant process improvement versus frit for the DWPF process in lowering yield stress of the melter feed. Lower erosion of process equipment is another expected benefit.« less

A simple approach to distinguish land-use and climate-change effects on watershed hydrology

USGS Publications Warehouse

Tomer, M.D.; Schilling, K.E.

2009-01-01

Impacts of climate change on watershed hydrology are subtle compared to cycles of drought and surplus precipitation (PPT), and difficult to separate from effects of land-use change. In the US Midwest, increasing baseflow has been more attributed to increased annual cropping than climate change. The agricultural changes have led to increased fertilizer use and nutrient losses, contributing to Gulf of Mexico hypoxia. In a 25-yr, small-watershed experiment in Iowa, when annual hydrologic budgets were accrued between droughts, a coupled water-energy budget (ecohydrologic) analysis showed effects of tillage and climate on hydrology could be distinguished. The fraction of PPT discharged increased with conservation tillage and time. However, unsatisfied evaporative demand (PET - Hargreaves method) increased under conservation tillage, but decreased with time. A conceptual model was developed and a similar analysis conducted on long-term (>1920s) records from four large, agricultural Midwest watersheds underlain by fine-grained tills. At least three of four watersheds showed decreases in PET, and increases in PPT, discharge, baseflow and PPT:PET ratios (p < 0.10). An analysis of covariance showed the fraction of precipitation discharged increased, while unsatisfied evaporative demand decreased with time among the four watersheds (p < 0.001). Within watersheds, agricultural changes were associated with ecohydrologic shifts that affected timing and significance, but not direction, of these trends. Thus, an ecohydrologic concept derived from small-watershed research, when regionally applied, suggests climate change has increased discharge from Midwest watersheds, especially since the 1970s. By inference, climate change has increased susceptibility of nutrients to water transport, exacerbating Gulf of Mexico hypoxia.

Does an Open Recirculation Line Affect the Flow Rate and Pressure in a Neonatal Extracorporeal Life Support Circuit With a Centrifugal or Roller Pump?

PubMed

Wang, Shigang; Spencer, Shannon B; Woitas, Karl; Glass, Kristen; Kunselman, Allen R; Ündar, Akif

2017-01-01

The objective of this study is to evaluate the impact of an open or closed recirculation line on flow rate, circuit pressure, and hemodynamic energy transmission in simulated neonatal extracorporeal life support (ECLS) systems. The two neonatal ECLS circuits consisted of a Maquet HL20 roller pump (RP group) or a RotaFlow centrifugal pump (CP group), Quadrox-iD Pediatric oxygenator, and Biomedicus arterial and venous cannulae (8 Fr and 10 Fr) primed with lactated Ringer's solution and packed red blood cells (hematocrit 35%). Trials were conducted at flow rates ranging from 200 to 600 mL/min (200 mL/min increments) with a closed or open recirculation line at 36°C. Real-time pressure and flow data were recorded using a custom-based data acquisition system. In the RP group, the preoxygenator flow did not change when the recirculation line was open while the prearterial cannula flow decreased by 15.7-20.0% (P < 0.01). Circuit pressure, total circuit pressure drop, and hemodynamic energy delivered to patients also decreased (P < 0.01). In the CP group, the prearterial cannula flow did not change while preoxygenator flow increased by 13.6-18.8% (P < 0.01). Circuit pressure drop and hemodynamic energy transmission remained the same. The results showed that the shunt of an open recirculation line could decrease perfusion flow in patients in the ECLS circuit using a roller pump, but did not change perfusion flow in the circuit using a centrifugal pump. An additional flow sensor is needed to monitor perfusion flow in patients if any shunts exist in the ECLS circuit. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Using mushroom farm and anaerobic digestion wastewaters as supplemental fertilizer sources for growing container nursery stock in a closed system.

PubMed

Chong, C; Purvis, P; Lumis, G; Holbein, B E; Voroney, R P; Zhou, H; Liu, H-W; Alam, M Z

2008-04-01

Wastewaters from farm and composting operations are often rich in select nutrients that potentially can be reutilized in crop production. Liners of silverleaf dogwood (Cornus alba L. 'Argenteo-marginata'), common ninebark [Physocarpus opulifolius (L.) Maxim.], and Anthony Waterer spirea (Spiraeaxbumalda Burvénich 'Anthony Waterer') were grown in 6L containers filled with a bark-based commercial mix. Plants were fertigated daily via a computer-controlled multi-fertilizer injector with three recirculated fertilizer treatments: (1) a stock (control) solution with complete macro- and micro-nutrients, electrical conductivity (EC) 2.2 dS m(-1); (2) wastewater from a mushroom farm; and (3) process wastewater from anaerobic digestion of municipal solid waste. The wastewaters used in both treatments 2 and 3 were diluted with tap water, and the computer was programmed to amend, dispense and recirculate nutrients based on the same target EC as in treatment 1. For comparison, there was a traditional controlled-release fertilizer treatment [Nutryon 17-5-12 (17N-2P-10K) plus micro-nutrients topdressed at a rate of 39 g/plant, nutrients not recirculated]. All three species responded similarly to the three recirculated fertilizer treatments. Growth with the recirculated treatments was similar and significantly higher than that obtained with controlled-release fertilizer. Throughout the study, the EC measured in wastewater-derived nutrient solutions, and also in the container substrate, were similar or close to those of the control treatment, although there were small to large differences among individual major nutrients. There was no sign of nutrient deficiency or toxicity symptoms to the plants. Small to moderate excesses in concentrations of SO(4), Na, and/or Cl were physiologically tolerable to the species.

Modeling Episodic Ephemeral Brine Lake Evaporation and Salt Crystallization on the Bonneville Salt Flats, Utah

NASA Astrophysics Data System (ADS)

Liu, T.; Harman, C. J.; Kipnis, E. L.; Bowen, B. B.

2017-12-01

Public concern about apparent reductions in the areal extent of the Bonneville Salt Flat (BSF) and perceived changes in inundation frequency has motivated renewed interest in the hydrologic and geochemical behavior of this salt playa. In this study, we develop a numerical modeling framework to simulate the relationship between hydrometeorologic variability, brine evaporation and salt crystallization processes on BSF. The BSF, locates in Utah, is the remnant of paleo-lake Bonneville, and is capped by up to 1 meter of salt deposition over a 100 km2 area. The BSF has two distinct hydrologic periods each year: a winter wet periods with standing surface brine and the summer dry periods when the brine is evaporated, exposing the surface salt crust. We develop a lumped non-linear dynamical models coupling conservation expressions from water, dissolved salt and thermal energy to investigate the seasonal and diurnal behavior of brine during the transition from standing brine to exposed salt at BSF. The lumped dynamic models capture important nonlinear and kinetic effects introduced by the high ionic concentration of the brine, including the pronounced effect of the depressed water activity coefficient on evaporation. The salt crystallization and dissolution rate is modeled as a kinetic process linearly proportional to the degree of supersaturation of brine. The model generates predictions of the brine temperature and the solute and solvent masses controlled by diurnal net radiation input and aerodynamic forcing. Two distinct mechanisms emerge as potential controls on salt production and dissolution: (1) evapo-concentration and (2) changes in solubility related to changes in brine temperature. Although the evaporation of water is responsible for ultimate disappearance of the brine each season ,variation in solubility is found to be the dominant control on diurnal cycles of salt precipitation and dissolution in the BSF case. Most salt is crystallized during nighttime, but the long-term salt production is driven by the seasonal evapo-concentration. Moreover, we find that the timing of the brine temperature fluctuations and salt production lags the diurnal net radiation input. The key controls on the magnitudes of these effects and phase lags are determined by analytical periodic analysis of linearized forms of the model.

A dented LH2 recirculation line is removed from Discovery

NASA Technical Reports Server (NTRS)

1999-01-01

In the Payload Changeout Room, Launch Pad 39B, United Space Alliance and NASA workers look at the replacement main propulsion system liquid hydrogen recirculation line (left) to be installed in Shuttle Discovery's aft compartment. At right is the dented line that has been removed. The 12-inch-long dent was discovered during routine aft compartment inspections Tuesday, Dec. 7. The line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. The line is being replaced and managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope.

NASA Langley Low Speed Aeroacoustic Wind Tunnel: Background Noise and Flow Survey Results Prior to FY05 Construction of Facilities Modifications

NASA Technical Reports Server (NTRS)

Booth, Earl R., Jr.; Henderson, Brenda S.

2005-01-01

The NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel is a premier facility for model-scale testing of jet noise reduction concepts at realistic flow conditions. However, flow inside the open jet test section is less than optimum. A Construction of Facilities project, scheduled for FY 05, will replace the flow collector with a new design intended to reduce recirculation in the open jet test section. The reduction of recirculation will reduce background noise levels measured by a microphone array impinged by the recirculation flow and will improve flow characteristics in the open jet tunnel flow. In order to assess the degree to which this modification is successful, background noise levels and tunnel flow are documented, in order to establish a baseline, in this report.

Design Concept for a Compact ERL to Drive a VUV/Soft X-Ray FEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christopher Tennant ,David Douglas

2011-03-01

We explore possible upgrades of the existing Jefferson Laboratory IR/UV FEL driver to higher electron beam energy and shorter wavelength through use of multipass recirculation to drive an amplifier FEL. The system would require beam energy at the wiggler of 600 MeV with 1 mA of average current. The system must generate a high brightness beam, configure it appropriately, and preserve beam quality through the acceleration cycle ? including multiple recirculations ? and appropriately manage the phase space during energy recovery. The paper will discuss preliminary design analysis of the longitudinal match, space charge effects in the linac, and recirculatormore » design issues, including the potential for the microbunching instability. A design concept for the low energy recirculator and an emittance preserving lattice solution will be presented.« less

Study of the effect of wind speed on evaporation from soil through integrated modeling of atmospheric boundary layer and shallow subsurface

NASA Astrophysics Data System (ADS)

Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan; Illangasekare, Tissa

2013-04-01

The study of the interaction between the land and atmosphere is paramount to our understanding of many emerging problems to include climate change, the movement of green house gases such as possible leaking of sequestered CO2 and the accurate detection of buried objects such as landmines. Soil moisture distribution in the shallow subsurface becomes a critical factor in all these problems. The heat and mass flux in the form of soil evaporation across the land surface couples the atmospheric boundary layer to the shallow subsurface. The coupling between land and the atmosphere leads to highly dynamic interactions between the porous media properties, transport processes and boundary conditions, resulting in dynamic evaporative behavior. However, the coupling at the land-atmospheric interface is rarely considered in most current models and their validation for practical applications. This is due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining coupled energy and mass transfer theories. In most efforts to compute evaporation from soil, only indirect coupling is provided to characterize the interaction between non-isothermal multiphase flows under realistic atmospheric conditions even though heat and mass flux are controlled by the coupled dynamics of the land and the atmospheric boundary layer. In earlier drying modeling concepts, imposing evaporation flux (kinetic of relative humidity) and temperature as surface boundary condition is often needed. With the goal of improving our understanding of the land/atmospheric coupling, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model consists of the coupled equations of mass conservation for the liquid phase (water) and gas phase (water vapor and air) in porous medium with gas phase (water vapor and air) in free flow domain under non-isothermal, non-equilibrium conditions. The boundary conditions at the porous medium-free flow medium interface include dynamical, thermal and solutal equilibriums, and using the Beavers-Joseph slip boundary condition. What is unique about this model is that the evaporation rate and soil surface temperature conditions come directly from the model output. In order to experimentally validate the numerical results, we developed and used a unique two dimensional wind tunnel placed above a soil tank equipped with a network of different sensors. A series of experiments under varying boundary conditions, using a test sand for which the hydraulic and thermal properties were well characterized, were performed. Precision data for soil moisture, soil and air temperature and relative humidity, and also wind velocity under well-controlled transient heat and wind boundary conditions was generated. Results from numerical simulations were compared with experimental data. Results demonstrate that the coupling concept can predict the different stages of the drying process in porous media with good accuracy. Increasing the wind speed increases the first stage evaporation rate and decreases the transition time at low velocity values; then, at high values of wind speed the evaporation rate becomes less dependent of flow in free fluid. In the opposite, the impact of the wind speed on the second stage evaporation (diffusion dominant stage) is not significant. The proposed theoretical model can be used to predict the evaporation process where a porous medium flow is coupled to a free flow for different practical applications.

Changes in sex steroids, growth hormone, and insulin-like growth factor-I during ovarian development in Rainbow Trout cultured within a recirculating system with 24-hour Light

USDA-ARS?s Scientific Manuscript database

Female rainbow trout (Onchorynchus mykiss) were cultured within a freshwater recirculating aquaculture system under 24-h constant lighting in 13oC water, and they were fed every six hours to near satiation. An opaque roof allowed surface light intensity to vary between <200 to ~1500 lx. Growth per...

National Combustion Code Validated Against Lean Direct Injection Flow Field Data

NASA Technical Reports Server (NTRS)

Iannetti, Anthony C.

2003-01-01

Most combustion processes have, in some way or another, a recirculating flow field. This recirculation stabilizes the reaction zone, or flame, but an unnecessarily large recirculation zone can result in high nitrogen oxide (NOx) values for combustion systems. The size of this recirculation zone is crucial to the performance of state-of-the-art, low-emissions hardware. If this is a large-scale combustion process, the flow field will probably be turbulent and, therefore, three-dimensional. This research dealt primarily with flow fields resulting from lean direct injection (LDI) concepts, as described in Research & Technology 2001. LDI is a concept that depends heavily on the design of the swirler. The LDI concept has the potential to reduce NOx values from 50 to 70 percent of current values, with good flame stability characteristics. It is cost effective and (hopefully) beneficial to do most of the design work for an LDI swirler using computer-aided design (CAD) and computer-aided engineering (CAE) tools. Computational fluid dynamics (CFD) codes are CAE tools that can calculate three-dimensional flows in complex geometries. However, CFD codes are only beginning to correctly calculate the flow fields for complex devices, and the related combustion models usually remove a large portion of the flow physics.

Open-RAC: Open-Design, Recirculating and Auto-Cleaning Zebrafish Maintenance System.

PubMed

Nema, Shubham; Bhargava, Yogesh

2017-08-01

Zebrafish is a vertebrate animal model. Their maintenance in large number under laboratory conditions is a daunting task. Commercially available recirculating zebrafish maintenance systems are used to efficiently handle the tasks of automatic sediment cleaning from zebrafish tanks with minimal waste of water. Due to their compact nature, they also ensure the maximal use of available lab space. However, the high costs of commercial systems present a limitation to researchers with limited funds. A cost-effective zebrafish maintenance system with major features offered by commercially available systems is highly desirable. Here, we describe a compact and recirculating zebrafish maintenance system. Our system is composed of cost-effective components, which are available in local markets and/or can be procured via online vendors. Depending on the expertise of end users, the system can be assembled in 2 days. The system is completely customizable as it offers geometry independent zebrafish tanks that are capable of auto-cleaning the sediments. Due to these features, we called our setup as Open-RAC (Open-design, Recirculating and Auto-Cleaning zebrafish maintenance system). Open-RAC is a cost-effective and viable alternative to the currently available zebrafish maintenance systems. Thus, we believe that the use of Open-RAC could promote the zebrafish research by removing the cost barrier for researchers.

Cyclone reactor with internal separation and axial recirculation

DOEpatents

Becker, F.E.; Smolensky, L.A.

1988-07-19

A cyclone combustor apparatus contains a circular partition plate containing a central circular aperture is described. The partition plate divides the apparatus into a cylindrical precombustor chamber and a combustor chamber. A coal-water slurry is passed axially into the inlet end of the precombustor chamber, and primary air is passed tangentially into said chamber to establish a cyclonic air flow. Combustion products pass through the partition plate aperture and into the combustor chamber. Secondary air may also be passed tangentially into the combustor chamber adjacent the partition plate to maintain the cyclonic flow. Flue gas is passed axially out of the combustor chamber at the outlet end and ash is withdrawn tangentially from the combustor chamber at the outlet end. A first mixture of flue gas and ash may be tangentially withdrawn from the combustor chamber at the outlet end and recirculated to the axial inlet of the precombustor chamber with the coal-water slurry. A second mixture may be tangentially withdrawn from the outlet end and passed to a heat exchanger for cooling. Cooled second mixture is then recirculated to the axial inlet of the precombustor chamber. In another embodiment a single cyclone combustor chamber is provided with both the recirculation streams of the first mixture and the second mixture. 10 figs.

Cyclone reactor with internal separation and axial recirculation

DOEpatents

Becker, Frederick E.; Smolensky, Leo A.

1989-01-01

A cyclone combustor apparatus contains a circular partition plate containing a central circular aperture. The partition plate divides the apparatus into a cylindrical precombustor chamber and a combustor chamber. A coal-water slurry is passed axially into the inlet end of the precombustor chamber, and primary air is passed tangentially into said chamber to establish a cyclonic air flow. Combustion products pass through the partition plate aperture and into the combustor chamber. Secondary air may also be passed tangentially into the combustor chamber adjacent the partition plate to maintain the cyclonic flow. Flue gas is passed axially out of the combustor chamber at the outlet end and ash is withdrawn tangentially from the combuston chamber at the outlet end. A first mixture of flue gas and ash may be tangentially withdrawn from the combustor chamber at the outlet end and recirculated to the axial inlet of the precombustor chamber with the coal-water slurry. A second mixture of flue gas and ash may be tangentially withdrawn from the outlet end of the combustor chamber and passed to a heat exchanger for cooling. Cooled second mixture is then recirculated to the axial inlet of the precombustor chamber. In another embodiment a single cyclone combustor chamber is provided with both the recirculation streams of the first mixture and the second mixture.

Organic compounds in re-circulated leachates of aerobic biological treated municipal solid waste.

PubMed

Franke, Matthias; Jandl, Gerald; Leinweber, Peter

2006-10-01

Biodegradation of organic matter is required to reduce the potential of municipal solid waste for producing gaseous emissions and leaching contaminants. Therefore, we studied leachates of an aerobic-treated waste from municipal solids and a sewage sludge mixture that were re-circulated to decrease the concentration of biodegradable organic matter in laboratory-scale reactors. After 12 months, the total organic C and biological and chemical oxygen demands were reduced, indicating the biodegradation of organic compounds in the leachates. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that phenols, alkylaromatic compounds, N-containing compounds and carbohydrates were the predominate compounds in the leachates and solid waste. Leachate re-circulation led to a higher thermal stability of the residual organic matter as indicated by temperature-resolved Py-FIMS. Admixture of sewage sludge to solid waste was less effective in removing organic compounds from the leachates. It resulted in drastic higher and more bio-resistant loads of organic matter in the leachates and revealed increased proportions of alkylaromatic compounds. The biodegradation of organic matter in leachates, re-circulated through municipal solid waste, offers the potential for improved aerobic waste treatments and should be investigated on a larger scale.

The evaporation of dense sprays as a mixing process

NASA Astrophysics Data System (ADS)

de Rivas, Alois; Villermaux, Emmanuel

2014-11-01

A dense spray of micron-sized droplets (water or ethanol) is formed in air by a pneumatic atomizer in a closed chamber, and is then conveyed through a nozzle in ambient air, forming a plume whose extension depends on the relative humidity of the diluting medium. We focus on the dry ambient medium, and large plume Reynolds number limit. Standard shear instabilities develop at the plume edge, forming the stretched lamellar structures familiar with passive scalars, except that these vanish in a finite time, because individual droplets evaporate at their border. Experiments also demonstrate that the lifetime of an individual droplet embedded in a lamellae is much larger than expected from the usual d-square law for an isolated droplet. By analogy with the way mixing times are understood from the convection-diffusion equation for passive scalars, we show that the lifetime of a lamellae stretched at a rate γ is tv =1/γ ln (1/+ ϕ ϕ ) where ϕ is a parameter which incorporates the thermodynamic and diffusional properties of the vapor in the diluting phase. The droplets field thus behaves as a -non conserved- passive scalar.

Brazilian solar saltworks - ancient uses and future possibilities

PubMed Central

2012-01-01

Coastal solar saltworks of Brazil are exploited for sea salt, which becomes progressively concentrated by evaporation. This study aimed to review the current and new potential uses of these systems, in order to provide more dynamic for this activity. The first evaporation ponds are also used for artisanal fisheries, ensuring the livelihood of many families. All the brine rich in secondary salts (bittern) can be widely used by the chemical industry, while the Brazil shows an incipient production of "flower of salt", a salt with distinct characteristics with higher market value than sodium chloride. On the other hand, the saltponds have a high potential for management and obtaining of large populations of Artemia spp., purifying the brine through the action as biological filter. This microcrustacean occurs naturally in intermediate salinity ponds, being commonly used in aquaculture. Species of microalgae and halobacteria found in the saltworks are employed for extraction of beta-carotene and glycerol, used in an extensive list of products with high commercial value. These ecosystems represent refuge zones for many species of migratory birds, becoming imperative to promote the conservation of these hypersaline wetlands. PMID:22490329

High performance incandescent lighting using a selective emitter and nanophotonic filters

NASA Astrophysics Data System (ADS)

Leroy, Arny; Bhatia, Bikram; Wilke, Kyle; Ilic, Ognjen; Soljačić, Marin; Wang, Evelyn N.

2017-09-01

Previous approaches for improving the efficiency of incandescent light bulbs (ILBs) have relied on tailoring the emitted spectrum using cold-side interference filters that reflect the infrared energy back to the emitter while transmitting the visible light. While this approach has, in theory, potential to surpass light-emitting diodes (LEDs) in terms of luminous efficiency while conserving the excellent color rendering index (CRI) inherent to ILBs, challenges such as low view factor between the emitter and filter, high emitter (>2800 K) and filter temperatures and emitter evaporation have significantly limited the maximum efficiency. In this work, we first analyze the effect of non-idealities in the cold-side filter, the emitter and the view factor on the luminous efficiency. Second, we theoretically and experimentally demonstrate that the loss in efficiency associated with low view factors can be minimized by using a selective emitter (e.g., high emissivity in the visible and low emissivity in the infrared) with a filter. Finally, we discuss the challenges in achieving a high performance and long-lasting incandescent light source including the emitter and filter thermal stability as well as emitter evaporation.

Urban outdoor water use and response to drought assessed through mobile energy balance and vegetation greenness measurements

NASA Astrophysics Data System (ADS)

Liang, L. L.; Anderson, R. G.; Shiflett, S. A.; Jenerette, G. D.

2017-08-01

Urban vegetation provides many highly valued ecosystem services but also requires extensive urban water resources. Increasingly, cities are experiencing water limitations and managing outdoor urban water use is an important concern. Quantifying the water lost via evapotranspiration (ET) is critical for urban water management and conservation, especially in arid or semi-arid regions. In this study, we deployed a mobile energy balance platform to measure evaporative fraction throughout Riverside, California, a warm, semi-arid, city. We observed the relationship between evaporative fraction and satellite derived vegetation index across 29 sites, which was then used to map whole-city ET for a representative mid-summer period. Resulting ET distributions were strongly associated with both neighborhood population density and income. By comparing 2014 and 2015 summer-period water uses, our results show 7.8% reductions in evapotranspiration, which were also correlated with neighborhood demographic characteristics. Our findings suggest a mobile energy balance measurement platform coupled with satellite imagery could serve as an effective tool in assessing the outdoor water use at neighborhood to whole city scales.

Numerical and experimental studies on effects of moisture content on combustion characteristics of simulated municipal solid wastes in a fixed bed.

PubMed

Sun, Rui; Ismail, Tamer M; Ren, Xiaohan; Abd El-Salam, M

2015-05-01

In order to reveal the features of the combustion process in the porous bed of a waste incinerator, a two-dimensional unsteady state model and experimental study were employed to investigate the combustion process in a fixed bed of municipal solid waste (MSW) on the combustion process in a fixed bed reactor. Conservation equations of the waste bed were implemented to describe the incineration process. The gas phase turbulence was modeled using the k-ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. The rate of moisture evaporation, devolatilization rate, and char burnout was calculated according to the waste property characters. The simulation results were then compared with experimental data for different moisture content of MSW, which shows that the incineration process of waste in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data. Due to the high moisture content of fuel, moisture evaporation consumes a vast amount of heat, and the evaporation takes up most of the combustion time (about 2/3 of the whole combustion process). The whole bed combustion process reduces greatly as MSW moisture content increases. The experimental and simulation results provide direction for design and optimization of the fixed bed of MSW. Copyright © 2015 Elsevier Ltd. All rights reserved.

Compact Fuel-Cell System Would Consume Neat Methanol

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram; Kindler, Andrew; Valdez, Thomas

2007-01-01

In a proposed direct methanol fuel-cell electric-power-generating system, the fuel cells would consume neat methanol, in contradistinction to the dilute aqueous methanol solutions consumed in prior direct methanol fuel-cell systems. The design concept of the proposed fuel-cell system takes advantage of (1) electro-osmotic drag and diffusion processes to manage the flows of hydrogen and water between the anode and the cathode and (2) evaporative cooling for regulating temperature. The design concept provides for supplying enough water to the anodes to enable the use of neat methanol while ensuring conservation of water for the whole fuel-cell system.

Steam drum design for direct steam generation

NASA Astrophysics Data System (ADS)

Willwerth, Lisa; Müller, Svenja; Krüger, Joachim; Succo, Manuel; Feldhoff, Jan Fabian; Tiedemann, Jörg; Pandian, Yuvaraj; Krüger, Dirk; Hennecke, Klaus

2017-06-01

For the direct steam generation in solar fields, the recirculation concept has been demonstrated in several installations. Water masses in the solar field vary during transient phases, such as passing clouds. The volume of the steam drum can serve as a buffer during such transients by taking in excess water and providing water storage. The saturated steam mass flow to the superheating section or the consumer can be maintained almost constant during short transients; therefore the steam drum plays a key role for constant steam supply. Its buffer effect depends on the right sizing of the steam drum for the prevailing situations. Due to missing experiences, steam drums have been sized under conservative assumptions and are thereby usually oversized. With this paper, experiences on the steam drum of the 5 MWel TSE1 power plant are discussed for optimized future plant design. The results are also of relevance for process heat installations, in which saturated steam is produced by the solar field.

A magnetically driven piston pump for ultra-clean applications

NASA Astrophysics Data System (ADS)

LePort, F.; Neilson, R.; Barbeau, P. S.; Barry, K.; Bartoszek, L.; Counts, I.; Davis, J.; deVoe, R.; Dolinski, M. J.; Gratta, G.; Green, M.; Díez, M. Montero; Müller, A. R.; O'Sullivan, K.; Rivas, A.; Twelker, K.; Aharmim, B.; Auger, M.; Belov, V.; Benitez-Medina, C.; Breidenbach, M.; Burenkov, A.; Cleveland, B.; Conley, R.; Cook, J.; Cook, S.; Craddock, W.; Daniels, T.; Dixit, M.; Dobi, A.; Donato, K.; Fairbank, W.; Farine, J.; Fierlinger, P.; Franco, D.; Giroux, G.; Gornea, R.; Graham, K.; Green, C.; Hägemann, C.; Hall, C.; Hall, K.; Hallman, D.; Hargrove, C.; Herrin, S.; Hughes, M.; Hodgson, J.; Juget, F.; Kaufman, L. J.; Karelin, A.; Ku, J.; Kuchenkov, A.; Kumar, K.; Leonard, D. S.; Lutter, G.; Mackay, D.; MacLellan, R.; Marino, M.; Mong, B.; Morgan, P.; Odian, A.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Pushkin, K.; Rollin, E.; Rowson, P. C.; Schmoll, B.; Sinclair, D.; Skarpaas, K.; Slutsky, S.; Stekhanov, V.; Strickland, V.; Swift, M.; Vuilleumier, J.-L.; Vuilleumier, J.-M.; Wichoski, U.; Wodin, J.; Yang, L.; Yen, Y.-R.

2011-10-01

A magnetically driven piston pump for xenon gas recirculation is presented. The pump is designed to satisfy extreme purity and containment requirements, as is appropriate for the recirculation of isotopically enriched xenon through the purification system and large liquid xenon time projection chamber of EXO-200. The pump, using sprung polymer gaskets, is capable of pumping more than 16 standard liters per minute of xenon gas with 750 Torr differential pressure.

A magnetically driven piston pump for ultra-clean applications.

PubMed

LePort, F; Neilson, R; Barbeau, P S; Barry, K; Bartoszek, L; Counts, I; Davis, J; deVoe, R; Dolinski, M J; Gratta, G; Green, M; Montero Díez, M; Müller, A R; O'Sullivan, K; Rivas, A; Twelker, K; Aharmim, B; Auger, M; Belov, V; Benitez-Medina, C; Breidenbach, M; Burenkov, A; Cleveland, B; Conley, R; Cook, J; Cook, S; Craddock, W; Daniels, T; Dixit, M; Dobi, A; Donato, K; Fairbank, W; Farine, J; Fierlinger, P; Franco, D; Giroux, G; Gornea, R; Graham, K; Green, C; Hägemann, C; Hall, C; Hall, K; Hallman, D; Hargrove, C; Herrin, S; Hughes, M; Hodgson, J; Juget, F; Kaufman, L J; Karelin, A; Ku, J; Kuchenkov, A; Kumar, K; Leonard, D S; Lutter, G; Mackay, D; MacLellan, R; Marino, M; Mong, B; Morgan, P; Odian, A; Piepke, A; Pocar, A; Prescott, C Y; Pushkin, K; Rollin, E; Rowson, P C; Schmoll, B; Sinclair, D; Skarpaas, K; Slutsky, S; Stekhanov, V; Strickland, V; Swift, M; Vuilleumier, J-L; Vuilleumier, J-M; Wichoski, U; Wodin, J; Yang, L; Yen, Y-R

2011-10-01

A magnetically driven piston pump for xenon gas recirculation is presented. The pump is designed to satisfy extreme purity and containment requirements, as is appropriate for the recirculation of isotopically enriched xenon through the purification system and large liquid xenon time projection chamber of EXO-200. The pump, using sprung polymer gaskets, is capable of pumping more than 16 standard liters per minute of xenon gas with 750 Torr differential pressure.

A Lagrangian Analysis of a Developing and Non-Developing Disturbance Observed During the PREDICT Experiment

DTIC Science & Technology

2012-12-03

paper provides an introduction of Lagrangian techniques for locating flow boundaries that encompass regions of recirculation in time- dependent flows...the low- to mid- level embryonic vortex from adverse conditions, while the 1The glossary on NOAA’s Hurricane Research Division’s web - site uses...wave or disturbance. This paper provides an introduction of Lagrangian techniques for locating flow boundaries that encompass regions of recirculation

Dedicated exhaust gas recirculation control systems and methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sczomak, David P.; Narayanaswamy, Kushal; Keating, Edward J.

An engine control system of a vehicle includes a fuel control module that controls fuel injection of a first cylinder of an engine based on a first target air/fuel ratio that is fuel lean relative to a stoichiometric air/fuel ratio and that controls fuel injection of a second cylinder of the engine based on a second target air/fuel ratio that is fuel rich relative to stoichiometry. The first cylinder outputs exhaust to a first three way catalyst (TWC), and the second cylinder outputs exhaust to an exhaust gas recirculation (EGR) valve. An EGR control module controls opening of the EGRmore » valve to: (i) a second TWC that reacts with nitrogen oxides (NOx) in the exhaust and outputs ammonia to a selective catalytic reduction (SCR) catalyst; and (ii) a conduit that recirculates exhaust back to an intake system of the engine.« less

Using Solar Hot Water to Address Piping Heat Losses in Multifamily Buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Springer, David; Seitzler, Matt; Backman, Christine

2015-10-01

Solar thermal water heating is most cost effective when applied to multifamily buildings and some states offer incentives or other inducements to install them. However, typical solar water heating designs do not allow the solar generated heat to be applied to recirculation losses, only to reduce the amount of gas or electric energy needed for hot water that is delivered to the fixtures. For good reasons, hot water that is recirculated through the building is returned to the water heater, not to the solar storage tank. The project described in this report investigated the effectiveness of using automatic valves tomore » divert water that is normally returned through the recirculation piping to the gas or electric water heater instead to the solar storage tank. The valves can be controlled so that the flow is only diverted when the returning water is cooler than the water in the solar storage tank.« less

Copper emissions from a high volume air sampler

NASA Technical Reports Server (NTRS)

King, R. B.; Toma, J.

1975-01-01

High volume air samplers (hi vols) are described which utilize a brush-type electric motor to power the fans used for pulling air through the filter. Anomalously high copper values were attributed to removal of copper from the commutator into the air stream due to arcing of the brushes and recirculation through the filter. Duplicate hi vols were set up under three operating conditions: (1) unmodified; (2) gasketed to prevent internal recirculation; and (3) gasketed and provided with a pipe to transport the motor exhaust some 20 feet away. The results of 5 days' operation demonstrate that hi vols can suddenly start emitting increased amounts of copper with no discernible operational indication, and that recirculation and capture on the filter can take place. Copper levels found with hi vols whose exhaust was discharged at a distance downwind were among the lowest found, and apparently provides a satisfactory solution to copper contamination.

Enhancing biogas production from anaerobic biodegradation of the organic fraction of municipal solid waste through leachate blending and recirculation.

PubMed

Nair, Arjun; Sartaj, Majid; Kennedy, Kevin; Coelho, Nuno M G

2014-10-01

Leachate recirculation has a profound advantage on biodegradation of the organic fraction of municipal solid waste in landfills. Mature leachate from older sections of landfills (>10 years) and young leachate were blended and added to organic fraction of municipal solid waste in a series of biomethane potential assay experiments with different mixing ratios of mature and young leachate and their effect on biogas production was monitored. The improvement in biogas production was in the range of 19%-41% depending on the ratio of mixing old and new leachate. The results are conclusive that the biogas generation could be improved by blending the old and new leachate in a bioreactor landfill system as compared with a conventional system employed in bioreactor landfills today for recirculating the same age leachate. © The Author(s) 2014.

Research on leachate recirculation from different types of landfills

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Qi; Matsufuji, Yasushi; Dong Lu

2006-07-01

Landfills can produce a great amount of leachate containing highly concentrated organic matter. This is especially true for the initial leachate from landfilled municipal solid wastes (MSW) that generally has concentrations of COD{sub Cr} and BOD{sub 5} up to 80,000 and 50,000 mg/L, respectively. The leachate could be disposed by means of recirculating technique, which decomposes the organics through the action of proliferating microorganisms and thereby purifies the leachate, and simultaneously accelerates organic decomposition through water saturation control. Data from experimental results indicated that leachate recirculating could reduce the organic concentration considerably, with a maximum reduction rate of COD{sub Cr}more » over 95%; and, using a semi-aerobic process, NH{sub 3}-N concentration of treated leachate could be under 10 mg/L. In addition, the organic concentration in MSW decreased greatly.« less

Engine with exhaust gas recirculation system and variable geometry turbocharger

DOEpatents

Keating, Edward J.

2015-11-03

An engine assembly includes an intake assembly, an internal combustion engine defining a plurality of cylinders and configured to combust a fuel and produce exhaust gas, and an exhaust assembly in fluid communication with a first subset of the plurality of cylinders. Each of the plurality of cylinders are provided in fluid communication with the intake assembly. The exhaust assembly is provided in fluid communication with a first subset of the plurality of cylinders, and a dedicated exhaust gas recirculation system in fluid communication with both a second subset of the plurality of cylinders and with the intake assembly. The dedicated exhaust gas recirculation system is configured to route all of the exhaust gas from the second subset of the plurality of cylinders to the intake assembly. Finally, the engine assembly includes a turbocharger having a variable geometry turbine in fluid communication with the exhaust assembly.

Hemodynamically driven stent strut design.

PubMed

Jiménez, Juan M; Davies, Peter F

2009-08-01

Stents are deployed to physically reopen stenotic regions of arteries and to restore blood flow. However, inflammation and localized stent thrombosis remain a risk for all current commercial stent designs. Computational fluid dynamics results predict that nonstreamlined stent struts deployed at the arterial surface in contact with flowing blood, regardless of the strut height, promote the creation of proximal and distal flow conditions that are characterized by flow recirculation, low flow (shear) rates, and prolonged particle residence time. Furthermore, low shear rates yield an environment less conducive for endothelialization, while local flow recirculation zones can serve as micro-reaction chambers where procoagulant and pro-inflammatory elements from the blood and vessel wall accumulate. By merging aerodynamic theory with local hemodynamic conditions we propose a streamlined stent strut design that promotes the development of a local flow field free of recirculation zones, which is predicted to inhibit thrombosis and is more conducive for endothelialization.

Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagel, S. R.; Chen, H.; Park, J.

Time resolved x-ray images with 7 ps resolution are recorded on relativistic short-pulse laser-plasma experiments using the dilation x-ray imager, a high-speed x-ray framing camera, sensitive to x-rays in the range of ≈1-17 keV. Furthermore, this capability enables a series of 2D x-ray images to be recorded at picosecond scales, which allows for the investigation of fast electron transport within the target with unprecedented temporal resolution. With an increase in the Kα-emission spot size over time we found that targets were thinner than the recirculation limit and is absent for thicker targets. Together with the observed polarization dependence of themore » spot size increase, this indicates that electron recirculation is relevant for the x-ray production in thin targets.« less

Possible interactions between recirculated landfill leachate and the stabilized organic fraction of municipal solid waste.

PubMed

Calabrò, Paolo S; Mancini, Giuseppe

2012-05-01

The stabilized organic fraction of municipal solid waste (SOFMSW) is a product of the mechanical/biological treatment (MBT) of mixed municipal solid waste (MMSW). SOFMSW is considered a 'grey' compost and the presence of pollutants (particularly heavy metals) and residual glass and plastic normally prevents agricultural use, making landfills the typical final destination for SOFMSW. Recirculation of leachate in landfills can be a cost-effective management option, but the long-term sustainability of such a practice must be verified. Column tests were carried out to examine the effect of SOFMSW on leachate recirculation. The results indicate that organic matter may be biologically degraded and metals (copper and zinc) are effectively entrapped through a combination of physical (adsorption), biological (bacterial sulfate reduction), and chemical (precipitation of metal sulfides) processes, while other chemicals (i.e. ammonia nitrogen and chloride) are essentially unaffected by filtration through SOFMSW.

Leachate pre-treatment strategies before recirculation in landfill bioreactors.

PubMed

Vigneron, V; Bouchez, T; Bureau, C; Mailly, N; Mazeas, L; Duquennoi, C; Audic, J M; Hébé, L; Bernet, N

2005-01-01

Nitrified leachate recirculation represents a promising strategy for a more sustainable landfill management. Our objective was to determine the reactions involved in nitrate reduction in municipal solid waste batch biodegradation tests. Anaerobic digestion of waste in the three control reactors showed a good reproducibility. In two test reactors, nitrate was added at various moments of the waste degradation process. We observed that: (1) H2S concentration controlled the nitrate reduction pathway: above a certain threshold of H2S, dissimilatory nitrate reduction to ammonium (DNRA) replaced denitrification. (2) N2O/N2 ratio varied with the organic carbon concentration: the lower the easily biodegradable carbon concentration, the higher the N2O/N2 ratio. (3) N2 was consumed after denitrification. The possibility of a nitrogen fixation reaction in the presence of NH4 is discussed. Nitrified leachate recirculation during acidogenesis should be avoided because of higher H2S production which could induce DNRA.

Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation

DOE PAGES

Nagel, S. R.; Chen, H.; Park, J.; ...

2017-04-04

Time resolved x-ray images with 7 ps resolution are recorded on relativistic short-pulse laser-plasma experiments using the dilation x-ray imager, a high-speed x-ray framing camera, sensitive to x-rays in the range of ≈1-17 keV. Furthermore, this capability enables a series of 2D x-ray images to be recorded at picosecond scales, which allows for the investigation of fast electron transport within the target with unprecedented temporal resolution. With an increase in the Kα-emission spot size over time we found that targets were thinner than the recirculation limit and is absent for thicker targets. Together with the observed polarization dependence of themore » spot size increase, this indicates that electron recirculation is relevant for the x-ray production in thin targets.« less

Conservative water management in the widespread conifer genus Callitris

PubMed Central

Brodribb, Timothy J.; Bowman, David M. J. S.; Grierson, Pauline F.; Murphy, Brett P.; Nichols, Scott; Prior, Lynda D.

2013-01-01

Water management by woody species encompasses characters involved in seeking, transporting and evaporating water. Examples of adaptation of individual characters to water availability are common, but little is known about the adaptability of whole-plant water management. Here we use plant hydration and growth to examine variation in whole-plant water management characteristics within the conifer genus Callitris. Using four species that cover the environmental extremes in the Australian continent, we compare seasonal patterns of growth and hydration over 2 years to determine the extent to which species exhibit adaptive variation to the local environment. Detailed measurements of gas exchange in one species are used to produce a hydraulic model to predict changes in leaf water potential throughout the year. This same model, when applied to the remaining three species, provided a close representation of the measured patterns of water potential gradient at all sites, suggesting strong conservation in water management, a conclusion supported by carbon and oxygen isotope measurements in Callitris from across the continent. We conclude that despite its large range in terms of rainfall, Callitris has a conservative water management strategy, characterized by a high sensitivity of growth to rainfall and a delayed (anisohydric) closure of stomata during soil drying.

Recirculation of Laser Power in an Atomic Fountain

NASA Technical Reports Server (NTRS)

Enzer, Daphna G.; Klipstein, WIlliam M.; Moore, James D.

2007-01-01

A new technique for laser-cooling atoms in a cesium atomic fountain frequency standard relies on recirculation of laser light through the atom-collection region of the fountain. The recirculation, accomplished by means of reflections from multiple fixed beam-splitter cubes, is such that each of two laser beams makes three passes. As described below, this recirculation scheme offers several advantages over prior designs, including simplification of the laser system, greater optical power throughput, fewer optical and electrical connections, and simplification of beam power balancing. A typical laser-cooled cesium fountain requires the use of six laser beams arranged as three orthogonal pairs of counter-propagating beams to decelerate the atoms and hold them in a three-dimensional optical trap in vacuum. Typically, these trapping/cooling beams are linearly polarized and are positioned and oriented so that (1) counter-propagating beams in each pair have opposite linear polarizations and (2) three of the six orthogonal beams have the sum of their propagation directions pointing up, while the other three have the sum of their propagation directions pointing down. In a typical prior design, two lasers are used - one to generate the three "up" beams, the other to generate the three "down" beams. For this purpose, the output of each laser is split three ways, then the resulting six beams are delivered to the vacuum system, independently of each other, via optical fibers. The present recirculating design also requires two lasers, but the beams are not split before delivery. Instead, only one "up" beam and one oppositely polarized "down" beam are delivered to the vacuum system, and each of these beams is sent through the collection region three times. The polarization of each beam on each pass through the collection region is set up to yield the same combination of polarization and propagation directions as described above. In comparison with the prior design, the present recirculating design utilizes the available laser light more efficiently, making it possible to trap more atoms at a given laser power or the same number of atoms at a lower laser power. The present design is also simpler in that it requires fewer optical fibers, fiber couplings, and collimators, and fewer photodiodes for monitoring beam powers. Additionally, the present design alleviates the difficulty of maintaining constant ratios among power levels of the beams within each "up" or "down" triplet.

Carbon and nutrient removal from on-site wastewater using extended-aeration activated sludge and ion exchange.

PubMed

Safferman, Steven I; Burks, Bennette D; Parker, Robert A

2004-01-01

The need to improve on-site wastewater treatment processes is being realized as populations move into more environmentally sensitive regions and regulators adopt the total maximum daily load approach to watershed management. Under many conditions, septic systems do not provide adequate treatment; therefore, advanced systems are required. These systems must remove significant amounts of biochemical oxygen demand (BOD) and suspended solids, and substantially nitrify, denitrify, and remove phosphorus. Many existing advanced on-site wastewater systems effectively remove BOD, suspended solids, and ammonia, but few substantially denitrify and uptake phosphorus. The purpose of this research was to design and test modifications to an existing on-site wastewater treatment system to improve denitrification and phosphorus removal. The Nayadic (Consolidated Treatment Systems, Inc., Franklin, Ohio), an established, commercially available, extended-aeration, activated sludge process, was used to represent a typical existing system. Several modifications were considered based on a literature review, and the option with the best potential was tested. To improve denitrification, a supplemental treatment tank was installed before the Nayadic and a combination flow splitter, sump, and pump box with a recirculation system was installed after it. A recirculation pump returned a high proportion of the system effluent back to the supplemental treatment tank. Two supplemental treatment tank sizes, three flowrates, and three recirculation rates were tested. Actual wastewater was dosed as brief slugs to the system in accordance with a set schedule. Several ion-exchange resins housed in a contact column were tested on the effluent for their potential to remove phosphorus. Low effluent levels of five-day biochemical oxygen demand, suspended solids, and total nitrogen were achieved and substantial phosphorous removal was also achieved using a 3780-L supplemental treatment tank, a recirculation ratio of 5:1, and a fine-grain activated aluminum-oxide-exchange media. Good results were also obtained with an 1890-L supplemental treatment tank and a recirculation ratio of 3:1. The most significant benefit of the supplemental treatment tank, in combination with the recirculation system, appears to be the low nitrogen concentration dosed to the Nayadic. By reducing the nitrogen concentration and spreading out its mass over time during no-flow periods, the Nayadic's inherent low-level denitrifying capacity was more closely matched and effective treatment was achieved.

Sodium Hydroxide Production from Seawater Desalination Brine: Process Design and Energy Efficiency.

PubMed

Du, Fengmin; Warsinger, David M; Urmi, Tamanna I; Thiel, Gregory P; Kumar, Amit; Lienhard V, John H

2018-05-15

The ability to increase pH is a crucial need for desalination pretreatment (especially in reverse osmosis) and for other industries, but processes used to raise pH often incur significant emissions and nonrenewable resource use. Alternatively, waste brine from desalination can be used to create sodium hydroxide, via appropriate concentration and purification pretreatment steps, for input into the chlor-alkali process. In this work, an efficient process train (with variations) is developed and modeled for sodium hydroxide production from seawater desalination brine using membrane chlor-alkali electrolysis. The integrated system includes nanofiltration, concentration via evaporation or mechanical vapor compression, chemical softening, further ion-exchange softening, dechlorination, and membrane electrolysis. System productivity, component performance, and energy consumption of the NaOH production process are highlighted, and their dependencies on electrolyzer outlet conditions and brine recirculation are investigated. The analysis of the process also includes assessment of the energy efficiency of major components, estimation of system operating expense and comparison with similar processes. The brine-to-caustic process is shown to be technically feasible while offering several advantages, that is, the reduced environmental impact of desalination through lessened brine discharge, and the increase in the overall water recovery ratio of the reverse osmosis facility. Additionally, best-use conditions are given for producing caustic not only for use within the plant, but also in excess amounts for potential revenue.

Influence of net freshwater supply on salinity in Florida Bay

USGS Publications Warehouse

Nuttle, William K.; Fourqurean, James W.; Cosby, Bernard J.; Zieman, Joseph C.; Robblee, Michael B.

2000-01-01

An annual water budget for Florida Bay, the large, seasonally hypersaline estuary in the Everglades National Park, was constructed using physically based models and long‐term (31 years) data on salinity, hydrology, and climate. Effects of seasonal and interannual variations of the net freshwater supply (runoff plus rainfall minus evaporation) on salinity variation within the bay were also examined. Particular attention was paid to the effects of runoff, which are the focus of ambitious plans to restore and conserve the Florida Bay ecosystem. From 1965 to 1995 the annual runoff from the Everglades into the bay was less than one tenth of the annual direct rainfall onto the bay, while estimated annual evaporation slightly exceeded annual rainfall. The average net freshwater supply to the bay over a year was thus approximately zero, and interannual variations in salinity appeared to be affected primarily by interannual fluctuations in rainfall. At the annual scale, runoff apparently had little effect on the bay as a whole during this period. On a seasonal basis, variations in rainfall, evaporation, and runoff were not in phase, and the net freshwater supply to the bay varied between positive and negative values, contributing to a strong seasonal pattern in salinity, especially in regions of the bay relatively isolated from exchanges with the Gulf of Mexico and Atlantic Ocean. Changes in runoff could have a greater effect on salinity in the bay if the seasonal patterns of rainfall and evaporation and the timing of the runoff are considered. One model was also used to simulate spatial and temporal patterns of salinity responses expected to result from changes in net freshwater supply. Simulations in which runoff was increased by a factor of 2 (but with no change in spatial pattern) indicated that increased runoff will lower salinity values in eastern Florida Bay, increase the variability of salinity in the South Region, but have little effect on salinity in the Central and West Regions.

Rotor Aerodynamics in Ground Effect at Low Advance Ratios.

DTIC Science & Technology

1982-07-27

the rotor wake flows entirely downstream. At test conditions were the recirculating flow or ground vortex is present there are marked departures...ILLUSTRATIONS Figure Page 1 Cross Section of Test Facilty 12 2 Overall View of Test Facility and Rotor Model 13 3 Flow Pattern in Ground Vortex Regime, (v...entirely flowing downstream splits and a portion of the rotor wake flows forward (upstream) and then recirculates through the rotor or forms a vortex or

Project W-320, 241-C-106 sluicing HVAC calculations, Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, J.W.

1998-08-07

This supporting document has been prepared to make the FDNW calculations for Project W-320, readily retrievable. The report contains the following calculations: Exhaust airflow sizing for Tank 241-C-106; Equipment sizing and selection recirculation fan; Sizing high efficiency mist eliminator; Sizing electric heating coil; Equipment sizing and selection of recirculation condenser; Chiller skid system sizing and selection; High efficiency metal filter shielding input and flushing frequency; and Exhaust skid stack sizing and fan sizing.

Improved numerical methods for turbulent viscous recirculating flows

NASA Technical Reports Server (NTRS)

Turan, A.

1985-01-01

The hybrid-upwind finite difference schemes employed in generally available combustor codes possess excessive numerical diffusion errors which preclude accurate quantative calculations. The present study has as its primary objective the identification and assessment of an improved solution algorithm as well as discretization schemes applicable to analysis of turbulent viscous recirculating flows. The assessment is carried out primarily in two dimensional/axisymetric geometries with a view to identifying an appropriate technique to be incorporated in a three-dimensional code.

Elucidation and visualization of solid-state transformation and mixing in a pharmaceutical mini hot melt extrusion process using in-line Raman spectroscopy.

PubMed

Van Renterghem, Jeroen; Kumar, Ashish; Vervaet, Chris; Remon, Jean Paul; Nopens, Ingmar; Vander Heyden, Yvan; De Beer, Thomas

2017-01-30

Mixing of raw materials (drug+polymer) in the investigated mini pharma melt extruder is achieved by using co-rotating conical twin screws and an internal recirculation channel. In-line Raman spectroscopy was implemented in the barrels, allowing monitoring of the melt during processing. The aim of this study was twofold: to investigate (I) the influence of key process parameters (screw speed - barrel temperature) upon the product solid-state transformation during processing of a sustained release formulation in recirculation mode; (II) the influence of process parameters (screw speed - barrel temperature - recirculation time) upon mixing of a crystalline drug (tracer) in an amorphous polymer carrier by means of residence time distribution (RTD) measurements. The results indicated a faster mixing endpoint with increasing screw speed. Processing a high drug load formulation above the drug melting temperature resulted in the production of amorphous drug whereas processing below the drug melting point produced solid dispersions with partially amorphous/crystalline drug. Furthermore, increasing the screw speed resulted in lower drug crystallinity of the solid dispersion. RTD measurements elucidated the improved mixing capacity when using the recirculation channel. In-line Raman spectroscopy has shown to be an adequate PAT-tool for product solid-state monitoring and elucidation of the mixing behavior during processing in a mini extruder. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of the injection dose of exhaust gases, on work parameters of combustion engine

NASA Astrophysics Data System (ADS)

Marek, W.; Śliwiński, K.

2016-09-01

This article is another one from the series in which were presented research results indicated the possible areas of application of the pneumatic injection using hot combustion gases proposed by Professor Jarnuszkiewicz. This publication present the results of the control system of exhaust gas recirculation. The main aim of this research was to determine the effect of exhaust gas recirculation to the operating parameters of the internal combustion engine on the basis of laboratory measurements. All measurements were performed at a constant engine speed. These conditions correspond to the operation of the motor operating an electrical generator. The study was conducted on the four-stroke two-cylinder engine with spark ignition. The study were specifically tested on the air injection system and therefore the selection of the rotational speed was not bound, as in conventional versions of operating parameters of the electrical machine. During the measurement there were applied criterion which used power control corresponding to the requirements of load power, at minimal values of engine speed. Recirculation value determined by the following recurrent position control valve of the injection doses inflator gas for pneumatic injection system. They were studied and recorded, the impact of dose of gases recirculation to the operating and ecological engine parameters such as power, torque, specific fuel consumption, efficiency, air fuel ratio, exhaust gas temperature and nitrogen oxides and hydrocarbons.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dentz, Jordan; Ansanelli, Eric; Henderson, Hugh

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Advanced Horizontal Well Recirculation Systems for Geothermal Energy Recovery in Sedimentary and Crystalline Formations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruno, Mike S.; Detwiler, Russell L.; Lao, Kang

2012-12-13

There is increased recognition that geothermal energy resources are more widespread than previously thought, with potential for providing a significant amount of sustainable clean energy worldwide. Recent advances in drilling, completion, and production technology from the oil and gas industry can now be applied to unlock vast new geothermal resources, with some estimates for potential electricity generation from geothermal energy now on the order of 2 million megawatts. The primary objectives of this DOE research effort are to develop and document optimum design configurations and operating practices to produce geothermal power from hot permeable sedimentary and crystalline formations using advancedmore » horizontal well recirculation systems. During Phase I of this research project Terralog Technologies USA and The University of California, Irvine (UCI), have completed preliminary investigations and documentation of advanced design concepts for paired horizontal well recirculation systems, optimally configured for geothermal energy recovery in permeable sedimentary and crystalline formations of varying structure and material properties. We have also identified significant geologic resources appropriate for application of such technology. The main challenge for such recirculation systems is to optimize both the design configuration and the operating practices for cost-effective geothermal energy recovery. These will be strongly influenced by sedimentary formation properties, including thickness and dip, temperature, thermal conductivity, heat capacity, permeability, and porosity; and by working fluid properties.« less

Recirculation cells for granular flow in cylindrical rotating tumblers

NASA Astrophysics Data System (ADS)

D'Ortona, Umberto; Thomas, Nathalie; Lueptow, Richard M.

2018-05-01

To better understand the velocity field and flowing layer structure, we have performed a detailed discrete element method study of the flow of monodisperse particles in a partially filled three-dimensional cylindrical rotating tumblers. Similar to what occurs near the poles in spherical and conical tumblers, recirculation cells (secondary flows) develop near the flat endwalls of a cylindrical tumbler in which particles near the surface drift axially toward the endwall, while particles deeper in the flowing layer drift axially toward the midlength of the tumbler. Another recirculation cell with the opposite sense develops next to each endwall recirculation cell, extending to the midlength of the tumbler. For a long enough tumbler, each endwall cell is about one quarter of the tumbler diameter in length. Endwall cells are insensitive to tumbler length and relatively insensitive to rotation speed (so long as the flowing layer remains flat and continuously flowing) or fill level (from 25% to 50% full). However, for shorter tumblers (0.5 to 1.0 length/diameter aspect ratio) the endwall cell size does not change much, while center cells reduce their size and eventually disappear for the shortest tumblers. For longer tumblers (length/diameter aspect ratio larger than 2), a stagnation zone appears in between the central cells. These results provide insight into the mixing of monodisperse particles in rotating cylindrical tumblers as well as the frictional effects of the tumbler endwalls.

Large-Eddy Simulations of Atmospheric Flows Over Complex Terrain Using the Immersed-Boundary Method in the Weather Research and Forecasting Model

NASA Astrophysics Data System (ADS)

Ma, Yulong; Liu, Heping

2017-12-01

Atmospheric flow over complex terrain, particularly recirculation flows, greatly influences wind-turbine siting, forest-fire behaviour, and trace-gas and pollutant dispersion. However, there is a large uncertainty in the simulation of flow over complex topography, which is attributable to the type of turbulence model, the subgrid-scale (SGS) turbulence parametrization, terrain-following coordinates, and numerical errors in finite-difference methods. Here, we upgrade the large-eddy simulation module within the Weather Research and Forecasting model by incorporating the immersed-boundary method into the module to improve simulations of the flow and recirculation over complex terrain. Simulations over the Bolund Hill indicate improved mean absolute speed-up errors with respect to previous studies, as well an improved simulation of the recirculation zone behind the escarpment of the hill. With regard to the SGS parametrization, the Lagrangian-averaged scale-dependent Smagorinsky model performs better than the classic Smagorinsky model in reproducing both velocity and turbulent kinetic energy. A finer grid resolution also improves the strength of the recirculation in flow simulations, with a higher horizontal grid resolution improving simulations just behind the escarpment, and a higher vertical grid resolution improving results on the lee side of the hill. Our modelling approach has broad applications for the simulation of atmospheric flows over complex topography.

Marginal costs of water savings from cooling system retrofits: a case study for Texas power plants

NASA Astrophysics Data System (ADS)

Loew, Aviva; Jaramillo, Paulina; Zhai, Haibo

2016-10-01

The water demands of power plant cooling systems may strain water supply and make power generation vulnerable to water scarcity. Cooling systems range in their rates of water use, capital investment, and annual costs. Using Texas as a case study, we examined the cost of retrofitting existing coal and natural gas combined-cycle (NGCC) power plants with alternative cooling systems, either wet recirculating towers or air-cooled condensers for dry cooling. We applied a power plant assessment tool to model existing power plants in terms of their key plant attributes and site-specific meteorological conditions and then estimated operation characteristics of retrofitted plants and retrofit costs. We determined the anticipated annual reductions in water withdrawals and the cost-per-gallon of water saved by retrofits in both deterministic and probabilistic forms. The results demonstrate that replacing once-through cooling at coal-fired power plants with wet recirculating towers has the lowest cost per reduced water withdrawals, on average. The average marginal cost of water withdrawal savings for dry-cooling retrofits at coal-fired plants is approximately 0.68 cents per gallon, while the marginal recirculating retrofit cost is 0.008 cents per gallon. For NGCC plants, the average marginal costs of water withdrawal savings for dry-cooling and recirculating towers are 1.78 and 0.037 cents per gallon, respectively.

Understanding Drought and Regional Conservation Efforts on Urban Ecohydrology in Southern California

NASA Astrophysics Data System (ADS)

Hogue, T. S.

2015-12-01

Cities in the western U.S. are under increasing pressure to reduce the demand of imported water through increasing conservation efforts, altering non-native landscapes, and enhancing local water supplies. The State of California adopted emergency regulations implementing a mandatory 25% statewide reduction in potable urban water use and agricultural restrictions have also been enacted. The complexities in urban water flows and lack of granular data make understanding the impact of conservation and demand change on regional ecohydrology difficult. This presentation highlights ongoing work to better understand the coupling between humans, water and ecosystems in semi-arid urban cities, using metropolitan southern California as a case study. We evaluate historical and contemporary ecohydrologic behavior and human impacts through intensive data collection, remote sensing and high resolution modeling. The change in outdoor irrigation rates due to recent conservation measures (2008-2010) has resulted in overall decreased greenness and reduced dry season streamflow; however significant variability in conservation response is observed. Groundwater recharge, artificially supported by landscape irrigation, is also being impacted. In general, anthropogenic water fluxes (irrigation, pipe leakage, spreading grounds) are not parameterized in hydrologic and land surface models applied over urban areas. Inclusion of landscape irrigation significantly improves neighborhood scale simulations of evaporative fluxes and land surface temperatures and results in shifts in the energy partitioning. The cooling effects of irrigation on daily air temperatures has the largest influence over low intensity residential areas, with an average 2°C decrease observed in coupled model simulations (WRF-Noah-UCM). Ultimately, we strive to improve predictions of human-water interactions in semi-arid cities to better understand the effectiveness and impacts of ongoing drought and conservation efforts and guide demand strategies under future climate variability.

Selection of flooded agricultural fields and other landscapes by female northern pintails wintering in Tulare Basin, California

USGS Publications Warehouse

Fleskes, Joseph P.; Jarvis, Robert L.; Gilmer, David S.

2003-01-01

Habitat selection and use are measures of relative importance of habitats to wildlife and necessary information for effective wildlife conservation. To measure the relative importance of flooded agricultural fields and other landscapes to northern pintails (Anas acuta) wintering in Tulare Basin (TB), California, we radiotagged female pintails during late August-early October, 1991-1993 in TB and other San Joaquin Valley areas and determined use and selection of these TB landscapes through March each year. Availability of landscape and field types in TB changed within and among years. Pintail use and selection (based upon use-to-availability log ratios) of landscape and field types differed among seasons, years, and diel periods. Fields flooded after harvest and before planting (i.e., pre-irrigated) were the most available, used, and selected landscape type before the hunting season (Prehunt). Safflower was the most available, used, and-except in 1993, when pre-irrigated fallow was available-selected pre-irrigated field type during Prehunt. Pre-irrigated barley-wheat received 19-22% of use before hunting season, but selection varied greatly among years and diel periods. During and after hunting season, managed marsh was the most available, used, and, along with floodwater areas, selected landscape type; pre-irrigated cotton and alfalfa were the least selected field types and accounted for <13% of pintail use. Agricultural drainwater evaporation ponds, sewage treatment ponds, and reservoirs accounted for 42-48% of flooded landscape available but were little used and least selected. Exodus of pintails from TB coincided with drying of pre-irrigated fallow, safflower, and barley-wheat fields early in winter, indicating that preferred habitats were lacking in TB during late winter. Agriculture conservation programs could improve TB for pintails by increasing flooding of fallow and harvested safflower and grain fields. Conservation of remaining wetlands should concentrate on increasing the amount and productivity of marsh that is shallow-flooded as pre-irrigated grain fields dry. If pin- tails were provided with adequate preferred field and marsh habitats, including hunt-day sanctuaries, contaminant risks associated with exposure to drainwater evaporation ponds probably should remain low for these waterfowl even if their abundance in TB increased.

Four-Nozzle Benchmark Wind Tunnel Model USA Code Solutions for Simulation of Multiple Rocket Base Flow Recirculation at 145,000 Feet Altitude

NASA Technical Reports Server (NTRS)

Dougherty, N. S.; Johnson, S. L.

1993-01-01

Multiple rocket exhaust plume interactions at high altitudes can produce base flow recirculation with attendant alteration of the base pressure coefficient and increased base heating. A search for a good wind tunnel benchmark problem to check grid clustering technique and turbulence modeling turned up the experiment done at AEDC in 1961 by Goethert and Matz on a 4.25-in. diameter domed missile base model with four rocket nozzles. This wind tunnel model with varied external bleed air flow for the base flow wake produced measured p/p(sub ref) at the center of the base as high as 3.3 due to plume flow recirculation back onto the base. At that time in 1961, relatively inexpensive experimentation with air at gamma = 1.4 and nozzle A(sub e)/A of 10.6 and theta(sub n) = 7.55 deg with P(sub c) = 155 psia simulated a LO2/LH2 rocket exhaust plume with gamma = 1.20, A(sub e)/A of 78 and P(sub c) about 1,000 psia. An array of base pressure taps on the aft dome gave a clear measurement of the plume recirculation effects at p(infinity) = 4.76 psfa corresponding to 145,000 ft altitude. Our CFD computations of the flow field with direct comparison of computed-versus-measured base pressure distribution (across the dome) provide detailed information on velocities and particle traces as well eddy viscosity in the base and nozzle region. The solution was obtained using a six-zone mesh with 284,000 grid points for one quadrant taking advantage of symmetry. Results are compared using a zero-equation algebraic and a one-equation pointwise R(sub t) turbulence model (work in progress). Good agreement with the experimental pressure data was obtained with both; and this benchmark showed the importance of: (1) proper grid clustering and (2) proper choice of turbulence modeling for rocket plume problems/recirculation at high altitude.

An Experimental Study of Swirling Flows as Applied to Annular Combustors

NASA Technical Reports Server (NTRS)

Seal, Michael Damian, II

1997-01-01

This thesis presents an experimental study of swirling flows with direct applications to gas turbine combustors. Two separate flowfields were investigated: a round, swirling jet and a non-combusting annular combustor model. These studies were intended to allow both a further understanding of the behavior of general swirling flow characteristics, such as the recirculation zone, as well as to provide a base for the development of computational models. In order to determine the characteristics of swirling flows the concentration fields of a round, swirling jet were analyzed for varying amount of swirl. The experimental method used was a light scattering concentration measurement technique known as marker nephelometry. Results indicated the formation of a zone of recirculating fluid for swirl ratios (rotational speed x jet radius over mass average axial velocity) above a certain critical value. The size of this recirculation zone, as well as the spread angle of the jet, was found to increase with increase in the amount of applied swirl. The annular combustor model flowfield simulated the cold-flow characteristics of typical current annular combustors: swirl, recirculation, primary air cross jets and high levels of turbulence. The measurements in the combustor model made by the Laser Doppler Velocimetry technique, allowed the evaluation of the mean and rms velocities in the three coordinate directions, one Reynold's shear stress component and the turbulence kinetic energy: The primary cross jets were found to have a very strong effect on both the mean and turbulence flowfields. These cross jets, along with a large step change in area and wall jet inlet flow pattern, reduced the overall swirl in the test section to negligible levels. The formation of the strong recirculation zone is due mainly to the cross jets and the large step change in area. The cross jets were also found to drive a four-celled vortex-type motion (parallel to the combustor longitudinal axis) near the cross jet injection plane.

Controlling flows in microchannels with patterned surface charge and topography.

PubMed

Stroock, Abraham D; Whitesides, George M

2003-08-01

This Account reviews two procedures for controlling the flow of fluids in microchannels. The first procedure involves patterning the density of charge on the inner surfaces of a channel. These patterns generate recirculating electroosmotic flows in the presence of a steady electric field. The second procedure involves patterning topography on an inner surface of a channel. These patterns generate recirculation in the cross-section of steady, pressure-driven flows. This Account summarizes applications of these flow to mixing and to controlling dispersion (band broadening).

Spectral Structure Of Phase-Induced Intensity Noise In Recirculating Delay Lines

NASA Astrophysics Data System (ADS)

Tur, M.; Moslehi, B.; Bowers, J. E.; Newton, S. A.; Jackson, K. P.; Goodman, J. W.; Cutler, C. C.; Shaw, H. J.

1983-09-01

The dynamic range of fiber optic signal processors driven by relatively incoherent multimode semiconductor lasers is shown to be severely limited by laser phase-induced noise. It is experimentally demonstrated that while the noise power spectrum of differential length fiber filters is approximately flat, processors with recirculating loops exhibit noise with a periodically structured power spectrum with notches at zero frequency as well as at all other multiples of 1/(loop delay). The experimental results are aug-mented by a theoretical analysis.

A recirculating hydroponic system for studying peanut (Arachis hypogaea L.)

NASA Technical Reports Server (NTRS)

Mackowiak, C. L.; Wheeler, R. M.; Stutte, G. W.; Yorio, N. C.; Ruffe, L. M.; Sager, J. C. (Principal Investigator)

1998-01-01

Peanut (Arachis hypogaea L.) plants were grown hydroponically, using continuously recirculating nutrient solution. Two culture tray designs were tested; one tray design used only nutrient solution, while the other used a sphagnum-filled pod development compartment just beneath the cover and above the nutrient solution. Both trays were fitted with slotted covers to allow developing gynophores to reach the root zone. Peanut seed yields averaged 350 gm-2 dry mass, regardless of tray design, suggesting that substrate is not required for hydroponic peanut production.

High gradient magnetic beneficiation of dry pulverized coal via upwardly directed recirculating fluidization

DOEpatents

Eissenberg, David M.; Liu, Yin-An

1980-01-01

This invention relates to an improved device and method for the high gradient magnetic beneficiation of dry pulverized coal, for the purpose of removing sulfur and ash from the coal whereby the product is a dry environmentally acceptable, low-sulfur fuel. The process involves upwardly directed recirculating air fluidization of selectively sized powdered coal in a separator having sections of increasing diameters in the direction of air flow, with magnetic field and flow rates chosen for optimum separations depending upon particulate size.

Improved numerical methods for turbulent viscous recirculating flows

NASA Technical Reports Server (NTRS)

Vandoormaal, J. P.; Turan, A.; Raithby, G. D.

1986-01-01

The objective of the present study is to improve both the accuracy and computational efficiency of existing numerical techniques used to predict viscous recirculating flows in combustors. A review of the status of the study is presented along with some illustrative results. The effort to improve the numerical techniques consists of the following technical tasks: (1) selection of numerical techniques to be evaluated; (2) two dimensional evaluation of selected techniques; and (3) three dimensional evaluation of technique(s) recommended in Task 2.

Soft Hair on Black Holes

NASA Astrophysics Data System (ADS)

Hawking, Stephen W.; Perry, Malcolm J.; Strominger, Andrew

2016-06-01

It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

Water conservation benefits of urban heat mitigation.

PubMed

Vahmani, Pouya; Jones, Andrew D

2017-10-20

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite-supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areas is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.

Soft Hair on Black Holes.

PubMed

Hawking, Stephen W; Perry, Malcolm J; Strominger, Andrew

2016-06-10

It has recently been shown that Bondi-van der Burg-Metzner-Sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically Minkowskian spacetimes. These laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. The presence of a Maxwell field similarly implies soft electric hair. This Letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. Charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. It is further argued that soft hair which is spatially localized to much less than a Planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in Planck units.

Water conservation benefits of urban heat mitigation

DOE PAGES

Vahmani, Pouya; Jones, Andrew D.

2017-10-20

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite-supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areasmore » is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.« less

Water conservation benefits of urban heat mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahmani, Pouya; Jones, Andrew D.

Many cities globally are seeking strategies to counter the consequences of both a hotter and drier climate. While urban heat mitigation strategies have been shown to have beneficial effects on health, energy consumption, and greenhouse gas emissions, their implications for water conservation have not been widely examined. Here we use a suite of satellite-supported regional climate simulations in California to show that broad implementation of cool roofs, a heat mitigation strategy, not only results in significant cooling, but can also meaningfully decrease outdoor water consumption by reducing evaporative and irrigation water demands. Irrigation water consumption across the major metropolitan areasmore » is reduced by up to 9% and irrigation water savings per capita range from 1.8 to 15.4 gallons per day across 18 counties examined. Total water savings are found to be the highest in Los Angeles county, reaching about 83 million gallons per day. Cool roofs are a valuable solution for addressing the adaptation and mitigation challenges faced by multiple sectors in California.« less

A numerical method for shock driven multiphase flow with evaporating particles

NASA Astrophysics Data System (ADS)

Dahal, Jeevan; McFarland, Jacob A.

2017-09-01

A numerical method for predicting the interaction of active, phase changing particles in a shock driven flow is presented in this paper. The Particle-in-Cell (PIC) technique was used to couple particles in a Lagrangian coordinate system with a fluid in an Eulerian coordinate system. The Piecewise Parabolic Method (PPM) hydrodynamics solver was used for solving the conservation equations and was modified with mass, momentum, and energy source terms from the particle phase. The method was implemented in the open source hydrodynamics software FLASH, developed at the University of Chicago. A simple validation of the methods is accomplished by comparing velocity and temperature histories from a single particle simulation with the analytical solution. Furthermore, simple single particle parcel simulations were run at two different sizes to study the effect of particle size on vorticity deposition in a shock-driven multiphase instability. Large particles were found to have lower enstrophy production at early times and higher enstrophy dissipation at late times due to the advection of the particle vorticity source term through the carrier gas. A 2D shock-driven instability of a circular perturbation is studied in simulations and compared to previous experimental data as further validation of the numerical methods. The effect of the particle size distribution and particle evaporation is examined further for this case. The results show that larger particles reduce the vorticity deposition, while particle evaporation increases it. It is also shown that for a distribution of particles sizes the vorticity deposition is decreased compared to single particle size case at the mean diameter.

Increased evaporation following widespread tree mortality limits streamflow response

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Harpold, A. A.; Gochis, D. J.; Ewers, B. E.; Reed, D. E.; Papuga, S. A.; Brooks, P. D.

2014-07-01

A North American epidemic of mountain pine beetle (MPB) has disturbed over 5 million ha of forest containing headwater catchments crucial to water resources. However, there are limited observations of MPB effects on partitioning of precipitation between vapor loss and streamflow, and to our knowledge these fluxes have not been observed simultaneously following disturbance. We combined eddy covariance vapor loss (V), catchment streamflow (Q), and stable isotope indicators of evaporation (E) to quantify hydrologic partitioning over 3 years in MPB-impacted and control sites. Annual control V was conservative, varying only from 573 to 623 mm, while MPB site V varied more widely from 570 to 700 mm. During wet periods, MPB site V was greater than control V in spite of similar above-canopy potential evapotranspiration (PET). During a wet year, annual MPB V was greater and annual Q was lower as compared to an average year, while in a dry year, essentially all water was partitioned to V. Ratios of 2H and 18O in stream and soil water showed no kinetic evaporation at the control site, while MPB isotope ratios fell below the local meteoric water line, indicating greater E and snowpack sublimation (Ss) counteracted reductions in transpiration (T) and sublimation of canopy-intercepted snow (Sc). Increased E was possibly driven by reduced canopy shading of shortwave radiation, which averaged 21 W m-2 during summer under control forest as compared to 66 W m-2 under MPB forest. These results show that abiotic vapor losses may limit widely expected streamflow increases.

Structural basis of the alternating-access mechanism in a bile acid transporter

NASA Astrophysics Data System (ADS)

Zhou, Xiaoming; Levin, Elena J.; Pan, Yaping; McCoy, Jason G.; Sharma, Ruchika; Kloss, Brian; Bruni, Renato; Quick, Matthias; Zhou, Ming

2014-01-01

Bile acids are synthesized from cholesterol in hepatocytes and secreted through the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for resecretion. In humans, there are two Na+-dependent bile acid transporters involved in enterohepatic recirculation, the Na+-taurocholate co-transporting polypeptide (NTCP; also known as SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT; also known as SLC10A2) expressed on enterocytes in the terminal ileum. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolaemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. However, a lack of three-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data. The crystal structure of an ASBT homologue from Neisseria meningitidis (ASBTNM) in detergent was reported recently, showing the protein in an inward-open conformation bound to two Na+ and a taurocholic acid. However, the structural changes that bring bile acid and Na+ across the membrane are difficult to infer from a single structure. To understand the structural changes associated with the coupled transport of Na+ and bile acids, here we solved two structures of an ASBT homologue from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives the conserved `crossover' region, where two discontinuous helices cross each other, alternating accessibility from either side of the cell membrane. This result has implications for the location and orientation of the bile acid during transport, as well as for the translocation pathway for Na+.

Structural basis of the alternating-access mechanism in a bile acid transporter

PubMed Central

Zhou, Xiaoming; Levin, Elena J.; Pan, Yaping; McCoy, Jason G.; Sharma, Ruchika; Kloss, Brian; Bruni, Renato; Quick, Matthias; Zhou, Ming

2014-01-01

Bile acids are synthesized from cholesterol in hepatocytes and secreted via the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for re-secretion1. In humans, there are two Na+-dependent bile acid transporters involved in enterohepatic recirculation, the Na+-taurocholate co-transporting polypeptide (NTCP or SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT or SLC10A2) expressed on enterocytes in the terminal ileum2. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption3,4. However, a lack of 3-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data2,5-8. The crystal structure of an ASBT homolog from Neisseria meningitidis (ASBTNM) in detergent was reported recently9, showing the protein in an inward-open conformation bound to two Na+ and a taurocholic acid. However, the structural changes that bring bile acid and Na+ across the membrane are difficult to infer from a single structure. To understand better the structural changes associated with the coupled transport of Na+ and bile acids, we crystallized and solved two structures of a ASBT homolog from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives alternate accessibility to the highly conserved “crossover” region, where two discontinuous transmembrane helices cross each other. This result has implications for the location and orientation of the bile acid during transport, as well as for the translocation pathway for Na+. PMID:24317697

Water-quality modeling of Klamath Straits Drain recirculation, a Klamath River wetland, and 2011 conditions for the Link River to Keno Dam reach of the Klamath River, Oregon

USGS Publications Warehouse

Sullivan, Annett B.; Sogutlugil, I. Ertugrul; Deas, Michael L.; Rounds, Stewart A.

2014-01-01

The upper Klamath River and adjacent Lost River are interconnected basins in south-central Oregon and northern California. Both basins have impaired water quality with Total Maximum Daily Loads (TMDLs) in progress or approved. In cooperation with the Bureau of Reclamation, the U.S. Geological Survey (USGS) and Watercourse Engineering, Inc., have conducted modeling and research to inform management of these basins for multiple purposes, including agriculture, endangered species protection, wildlife refuges, and adjacent and downstream water users. A water-quality and hydrodynamic model (CE-QUAL-W2) of the Link River to Keno Dam reach of the Klamath River for 2006–09 is one of the tools used in this work. The model can simulate stage, flow, water velocity, ice cover, water temperature, specific conductance, suspended sediment, nutrients, organic matter in bed sediment and the water column, three algal groups, three macrophyte groups, dissolved oxygen, and pH. This report documents two model scenarios and a test of the existing model applied to year 2011, which had exceptional water quality. The first scenario examined the water-quality effects of recirculating Klamath Straits Drain flows into the Ady Canal, to conserve water and to decrease flows from the Klamath Straits Drain to the Klamath River. The second scenario explicitly incorporated a 2.73×106 m2 (675 acre) off-channel connected wetland into the CE-QUAL-W2 framework, with the wetland operating from May 1 through October 31. The wetland represented a managed treatment feature to decrease organic matter loads and process nutrients. Finally, the summer of 2011 showed substantially higher dissolved-oxygen concentrations in the Link-Keno reach than in other recent years, so the Link-Keno model (originally developed for 2006–09) was run with 2011 data as a test of model parameters and rates and to develop insights regarding the reasons for the improved water-quality conditions.

CFD analysis of a rotary kiln using for plaster production and discussion of the effects of flue gas recirculation application

NASA Astrophysics Data System (ADS)

Gürtürk, Mert; Oztop, Hakan F.; Pambudi, Nugroho Agung

2018-04-01

In this study, the CFD analysis of the rotary kiln is carried out for examining effects of various parameters on energy consumption and efficiency of the rotary kiln. The flue gas recirculation using in many applications is a useful method for combusting of fuel unburned in the flue gas. Also, effects of flue gas recirculation on the combusting of fuel, operating temperature and efficiency of the rotary kiln are discussed in this study. The rotary kiln, which is considered in this study, is used in plaster plant. Two different CFD models were created and these models are compared according to many parameters such as temperature distribution, mixture fraction, the mass fraction of O2, CO, CO and CH4 in the combustion chamber. It is found that the plaster plant has a great potential for an increase in energy efficiency. Results obtained for producers of rotary kiln and burner will be useful for determining better design parameters.

On Orbit ISS Oxygen Generation System Operation Status

NASA Technical Reports Server (NTRS)

Diderich, Greg S.; Polis, Pete; VanKeuren, Steven P.; Erickson, Robert; Mason, Richard

2011-01-01

The International Space Station (ISS) United States Orbital Segment (USOS) Oxygen Generation System (OGS) has accumulated almost a year of operation at varied oxygen production rates within the US Laboratory Module (LAB) since it was first activated in July 2007. It was operated intermittently through 2009 and 2010, due to filter clogging and acid accumulation in the recirculation loop. Since the installation of a deionizing bed in the recirculation loop in May of 2011 the OGA has been operated continuously. Filters in the recirculation loop have clogged and have been replaced. Hydrogen sensors have drifted apart, and a power failure may have condensed water on a hydrogen sensor. A pump delta pressure sensor failed, and a replacement new spare pump failed to start. Finally, the voltage across the cell stack increased out of tolerance due to cation contamination, and the cell stack was replaced. This paper will discuss the operating experience and characteristics of the OGS, as well as operational issues and their resolution.

Investigations of Multiple Swirl-Venturi Fuel Injector Concepts: Recent Experimental Optical Measurement Results for 1-Point, 7-Point, and 9-Point Configurations

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Anderson, Robert C.; Tedder, Sarah A.; Tacina, Kathleen M.

2015-01-01

This paper presents results obtained during testing in optically-accessible, JP8-fueled, flame tube combustors using swirl-venturi lean direct injection (LDI) research hardware. The baseline LDI geometry has 9 fuel/air mixers arranged in a 3 x 3 array within a square chamber. 2-D results from this 9-element array are compared to results obtained in a cylindrical combustor using a 7-element array and a single element. In each case, the baseline element size remains the same. The effect of air swirler angle, and element arrangement on the presence of a central recirculation zone are presented. Only the highest swirl number air swirler produced a central recirculation zone for the single element swirl-venturi LDI and the 9-element LDI, but that same swirler did not produce a central recirculation zone for the 7-element LDI, possibly because of strong interactions due to element spacing within the array.

Conceptual design of the cryogenic system and estimation of the recirculated power for CFETR

NASA Astrophysics Data System (ADS)

Liu, Xiaogang; Qiu, Lilong; Li, Junjun; Wang, Zhaoliang; Ren, Yong; Wang, Xianwei; Li, Guoqiang; Gao, Xiang; Bi, Yanfang

2017-01-01

The China Fusion Engineering Test Reactor (CFETR) is the next tokamak in China’s roadmap for realizing commercial fusion energy. The CFETR cryogenic system is crucial to creating and maintaining operational conditions for its superconducting magnet system and thermal shields. The preliminary conceptual design of the CFETR cryogenic system has been carried out with reference to that of ITER. It will provide an average capacity of 75 to 80 kW at 4.5 K and a peak capacity of 1300 kW at 80 K. The electric power consumption of the cryogenic system is estimated to be 24 MW, and the gross building area is about 7000 m2. The relationships among the auxiliary power consumed by the cryogenic system, the fusion power gain and the recirculated power of CFETR are discussed, with the suggestion that about 52% of the electric power produced by CFETR in phase II must be recirculated to run the fusion test reactor.

Two Devices for Removing Sludge From Bioreactor Wastewater

NASA Technical Reports Server (NTRS)

Archer, Shivaun; Hitchens, G. DUncan; Jabs, Harry; Cross, Jennifer; Pilkinton, Michelle; Taylor, Michael

2007-01-01

Two devices a magnetic separator and a special filter denoted a self-regenerating separator (SRS) have been developed for separating sludge from the stream of wastewater from a bioreactor. These devices were originally intended for use in microgravity, but have also been demonstrated to function in normal Earth gravity. The magnetic separator (see Figure 1) includes a thin-walled nonmagnetic, stainless-steel cylindrical drum that rotates within a cylindrical housing. The wastewater enters the separator through a recirculation inlet, and about 80 percent of the wastewater flow leaves through a recirculation outlet. Inside the drum, a magnet holder positions strong permanent magnets stationary and, except near a recirculation outlet, close to the inner drum surface. To enable magnetic separation, magnetite (a ferromagnetic and magnetically soft iron oxide) powder is mixed into the bioreactor wastewater. The magnetite becomes incorporated into the sludge by condensation, onto the powder particles, of microbe flocks that constitute the sludge. As a result, the magnets inside the drum magnetically attract the sludge onto the outer surface of the drum.

Effect of hydrothermal liquefaction aqueous phase recycling on bio-crude yields and composition.

PubMed

Biller, Patrick; Madsen, René B; Klemmer, Maika; Becker, Jacob; Iversen, Bo B; Glasius, Marianne

2016-11-01

Hydrothermal liquefaction (HTL) is a promising thermo-chemical processing technology for the production of biofuels but produces large amounts of process water. Therefore recirculation of process water from HTL of dried distillers grains with solubles (DDGS) is investigated. Two sets of recirculation on a continuous reactor system using K2CO3 as catalyst were carried out. Following this, the process water was recirculated in batch experiments for a total of 10 rounds. To assess the effect of alkali catalyst, non-catalytic HTL process water recycling was performed with 9 recycle rounds. Both sets of experiments showed a large increase in bio-crude yields from approximately 35 to 55wt%. The water phase and bio-crude samples from all experiments were analysed via quantitative gas chromatography-mass spectrometry (GC-MS) to investigate their composition and build-up of organic compounds. Overall the results show an increase in HTL conversion efficiency and a lower volume, more concentrated aqueous by-product following recycling. Copyright © 2016 Elsevier Ltd. All rights reserved.

A recirculation aerosol wind tunnel for evaluating aerosol samplers and measuring particle penetration through protective clothing materials.

PubMed

Jaques, Peter A; Hsiao, Ta-Chih; Gao, Pengfei

2011-08-01

A recirculation aerosol wind tunnel was designed to maintain a uniform airflow and stable aerosol size distribution for evaluating aerosol sampler performance and determining particle penetration through protective clothing materials. The oval-shaped wind tunnel was designed to be small enough to fit onto a lab bench, have optimized dimensions for uniformity in wind speed and particle size distributions, sufficient mixing for even distribution of particles, and minimum particle losses. Performance evaluation demonstrates a relatively high level of spatial uniformity, with a coefficient of variation of 1.5-6.2% for wind velocities between 0.4 and 2.8 m s(-1) and, in this range, 0.8-8.5% for particles between 50 and 450 nm. Aerosol concentration stabilized within the first 5-20 min with, approximately, a count median diameter of 135 nm and geometric standard deviation of 2.20. Negligible agglomerate growth and particle loss are suggested. The recirculation design appears to result in unique features as needed for our research.

High speed exhaust gas recirculation valve

DOEpatents

Fensom, Rod; Kidder, David J.

2005-01-18

In order to minimize pollutants such as Nox, internal combustion engines typically include an exhaust gas recirculation (EGR) valve that can be used to redirect a portion of exhaust gases to an intake conduit, such as an intake manifold, so that the redirected exhaust gases will be recycled. It is desirable to have an EGR valve with fast-acting capabilities, and it is also desirable to have the EGR valve take up as little space as possible. An exhaust gas recirculation valve is provided that includes an exhaust passage tube, a valve element pivotally mounted within the exhaust passage tube, a linear actuator; and a gear train. The gear train includes a rack gear operatively connected to the linear actuator, and at least one rotatable gear meshing with the rack gear and operatively connected to the valve element to cause rotation of the valve element upon actuation of the linear actuator. The apparatus provides a highly compact package having a high-speed valve actuation capability.

Characteristics of a trapped-vortex (TV) combustor

NASA Technical Reports Server (NTRS)

Hsu, K.-Y.; Gross, L. P.; Trump, D. D.; Roquemore, W. M.

1994-01-01

The characteristics of a Trapped-Vortex (TV) combustor are presented. A vortex is trapped in the cavity established between two disks mounted in tandem. Fuel and air are injected directly into the cavity in such a way as to increase the vortex strength. Some air from the annular flow is also entrained into the recirculation zone of the vortex. Lean blow-out limits of the combustor are determined for a wide range of annular air flow rates. These data indicate that the lean blow-out limits are considerably lower for the TV combustor than for flames stabilized using swirl or bluff-bodies. The pressure loss through the annular duct is also low, being less than 2% for the flow conditions in this study. The instantaneous shape of the recirculation zone of the trapped vortex is measured using a two-color PIV technique. Temperature profiles obtained with CARS indicate a well mixed recirculation zone and demonstrate the impact of primary air injection on the local equivalence ratio.

Analysis of tropospheric ozone concentration on a Western Mediterranean site: Castellon (Spain).

PubMed

Castell, Nuria; Mantilla, Enrique; Millan, Millan M

2008-01-01

Ozone dynamics in our study area (Castellon, Spain) is both strongly bound to the mesoscale circulations that develop under the effect of high insolation (especially in summer) and conditioned by the morphological characteristics of the Western Mediterranean Basin. In this work we present a preliminary analysis of ozone time series on five locations in Castellon for the period 1997-2003. We study their temporal and spatial variations at different scales: daily, weekly, seasonally and interannually. Because both the O3 concentration and its temporal variation depend on the topographic location of the observing station, they can show large differences within tens of kilometer. We also contrast the variation in the ozone concentration with the variations found for meteorological variables such as radiation, temperature, relative humidity and recirculation of the air mass. The link between elevated ozone concentrations and high values of the recirculation factor (r=0.7-0.9) shown the importance of recirculating flows on the local air pollution episodes.

Effect of oxygen dosing point and mixing on the microaerobic removal of hydrogen sulphide in sludge digesters.

PubMed

Díaz, I; Pérez, S I; Ferrero, E M; Fdz-Polanco, M

2011-02-01

Limited oxygen supply to anaerobic sludge digesters to remove hydrogen sulphide from biogas was studied. Micro-oxygenation showed competitive performance to reduce considerably the additional equipment necessary to perform biogas desulphurization. Two pilot-plant digesters with an HRT of ∼ 20 d were micro-oxygenated at a rate of 0.25 NL per L of feed sludge with a removal efficiency higher than 98%. The way of mixing (sludge or biogas recirculation) and the point of oxygen supply (headspace or liquid phase) played an important role on hydrogen sulphide oxidation. While micro-oxygenation with sludge recirculation removed only hydrogen sulphide from the biogas, dissolved sulphide was removed if micro-oxygenation was performed with biogas recirculation. Dosage in the headspace resulted in a more stable operation. The result of the hydrogen sulphide oxidation was mostly elemental sulphur, partially accumulated in the headspace of the digester, where different sulphide-oxidising bacteria were found. Copyright © 2010 Elsevier Ltd. All rights reserved.

Building America Case Study: Addressing Multifamily Piping Losses with Solar Hot Water, Davis, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

2016-12-01

Solar thermal water heating is most cost effective when applied to multifamily buildings and some states offer incentives or other inducements to install them. However, typical solar water heating designs do not allow the solar generated heat to be applied to recirculation losses, only to reduce the amount of gas or electric energy needed for hot water that is delivered to the fixtures. For good reasons, hot water that is recirculated through the building is returned to the water heater, not to the solar storage tank. The project described in this report investigated the effectiveness of using automatic valves tomore » divert water that is normally returned through the recirculation piping to the gas or electric water heater instead to the solar storage tank. The valves can be controlled so that the flow is only diverted when the returning water is cooler than the water in the solar storage tank.« less

Improving indoor air quality and thermal comfort in office building by using combination filters

NASA Astrophysics Data System (ADS)

Kabrein, H.; Yusof, M. Z. M.; Hariri, A.; Leman, A. M.; Afandi, A.

2017-09-01

Poor indoor air quality and thermal comfort condition in the workspace affected the occupants’ health and work productivity, especially when adapting the recirculation of air in heating ventilation and air-conditioning (HVAC) system. The recirculation of air was implemented in this study by mixing the circulated returned indoor air with the outdoor fresh air. The aims of this study are to assess the indoor thermal comfort and indoor air quality (IAQ) in the office buildings, equipped with combination filters. The air filtration technique consisting minimum efficiency reporting value (MERV) filter and activated carbon fiber (ACF) filter, located before the fan coil units. The findings of the study show that the technique of mixing recirculation air with the fresh air through the combination filters met the recommended thermal comfort condition in the workspace. Furthermore, the result of the post-occupancy evaluation (POE) and the environmental measurements comply with the ASHRAE 55 standard. In addition, the level of CO2 concentration continued to decrease during the period of the measurement.

Self-Recirculating Casing Treatment Concept for Enhanced Compressor Performance

NASA Technical Reports Server (NTRS)

Hathaway, Michael D.

2002-01-01

A state-of-the-art CFD code (APNASA) was employed in a computationally based investigation of the impact of casing bleed and injection on the stability and performance of a moderate speed fan rotor wherein the stalling mass flow is controlled by tip flow field breakdown. The investigation was guided by observed trends in endwall flow characteristics (e.g., increasing endwall aerodynamic blockage) as stall is approached and based on the hypothesis that application of bleed or injection can mitigate these trends. The "best" bleed and injection configurations were then combined to yield a self-recirculating casing treatment concept. The results of this investigation yielded: 1) identification of the fluid mechanisms which precipitate stall of tip critical blade rows, and 2) an approach to recirculated casing treatment which results in increased compressor stall range with minimal or no loss in efficiency. Subsequent application of this approach to a high speed transonic rotor successfully yielded significant improvements in stall range with no loss in compressor efficiency.

Investigation of Microbunching Instabilities in Modern Recirculating Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, Cheng

Particle accelerators are machines to accelerate and store charged particles, such as electrons or protons, to the energy levels for various scientific applications. A collection of charged particles usually forms a particle beam. There are three basic types of particle accelerators: linear accelerators (linac), storage-ring (or circular) accelerators, and recirculating accelerators. In a linac, particles are accelerated and pass through once along a linear or straight beamline. Storage-ring accelerators propel particles around a circular track and repetitively append the energy to the stored beam. The third type, also the most recent one in chronology, the recirculating accelerator, is designed tomore » accelerate the particle beam in a short section of linac, circulate the beam, and then either continue to accelerate for energy boost or decelerate it for energy recovery. The beam properties of a linac machine are set at best by the initial particle sources. For storage rings, the beam equilibria are instead determined by the overall machine design. The modern recirculating machines share with linacs the advantages to both accelerate and preserve the beam with high beam quality, as well as efficiently reuse the accelerating components. The beamline design in such a machine configuration can however be much more complicated than that of linacs. As modern accelerators push toward the high-brightness or high-intensity frontier by demanding particles in a highly charged bunch (about nano-Coulomb per bunch) to concentrate in an ever-decreasing beam phase space (transverse normalized emittance about 1 μm and relative energy spread of the order of 10^-5 in GeV beam energy), the interaction amongst particles via their self-generated electromagnetic fields can potentially lead to coherent instabilities of the beam and thus pose significant challenges to the machine design and operation. In the past decade and a half, microbunching instability (MBI) has been one of the most challenging issues for such high-brightness or high-intensity beam transport, as it would degrade lasing performance in the fourth-generation light sources, reduce cooling efficiency in electron cooling facilities, and compromise the luminosity of colliding beams in lepton or lepton-hadron colliders. The dissertation work will focus on the MBI in modern recirculating electron accelerators. It has been known that the collective interactions, the coherent synchrotron radiation (CSR) and the longitudinal space charge (LSC) forces, can drive MBI. The CSR effect is a collective phenomenon in which the electrons in a curved motion, e.g. a bending dipole, emit radiation at a scale comparable to the micro-bunched structure of the bunch distribution. The LSC effect stems from non-uniformity of the charge distribution, acts as plasma oscillation, and can eventually accumulate an amount of energy modulation when the beam traverses a long section of a beamline. MBI can be seeded by non-uniformity or shot noise of the beam, which originates from granularity of the elementary charge. Through the aforementioned collective effects, the modulation of the bunch sub-structure can be amplified and, once the beam-wave interaction formed a positive feedback, can result in MBI. The problem of MBI has been intensively studied for linac-based facilities and for storage-ring accelerators. However, systematic studies for recirculation machines are still very limited and form a knowledge gap. Because of the much more complicated machine configuration of the recirculating accelerators than that of linacs, the existing MBI analysis needs to be extended to accommodate the high-brightness particle beam transport in modern recirculating accelerators. This dissertation is focused on theoretical investigation of MBI in such machine configuration in the following seven themes: (1) Development and generalization of MBI theory The theoretical formulation has been extended so as to be applicable to a general linear beamline lattice including horizontal and vertical transport bending elements, and beam acceleration or deceleration. These featured generalizations are required for MBI analysis in recirculation accelerators. (2) Construction of CSR impedance models In addition to the steady-state CSR interaction, it has been found that the exit transient effect (or CSR drift) can even result in more serious MBI in high-brightness recirculation arcs. The onedimensional free-space CSR impedances, especially the exit transients, are derived. The steady-state CSR impedance is also extended to non-ultrarelativistic beam energy for MBI analysis of low-energy merger sections in recirculating accelerators. (3) Numerical implementation of the derived semi-analytical formulation This includes the development of a semi-analytical Vlasov solver for MBI analysis, and also benchmarking of the solver against massive particle tracking simulations. (4) Exploration of multistage amplification behavior of CSR microbunching development The CSR-induced MBI acts as an amplifier, which amplifies the sub-bunch modulation of a beam. The amplification is commonly quantified by the amplification gain. A beam transport system can be considered as a cascaded amplifier. Unlike the two-stage amplification of four-dipole bunch compressor chicanes employed in linacs, the recirculation arcs, which are usually constituted by several tens of bending magnets, show a distinguishing feature of up to six-stage microbunching amplification for our example arc lattices. That is, the maximal CSR amplification gain can be proportional to the peak bunch current up to sixth power. A method to compare lattice performance has been developed in terms of gain coefficients, which nearly depend on the lattice properties only. This method has also proven to be an effective way to quantify the current dependence of the maximal (5) Control of CSR MBI in multibend transport or recirculation arcs The existing mitigation schemes of MBI mostly aim to linac-based accelerators and may not be practical to the recirculating accelerator facilities. Thus a set of conditions for suppression of CSR MBI was proposed and examined for example lattices from low (~100 MeV) to high (~1 GeV) energies. (6) Study of more aspects of microbunched structures in beam phase spaces For a cascaded amplifier in circuit electronics, the total amplification gain can be estimated as the product of individual gains. In a beam transport line of an accelerator, the (scalar) gain multiplication was examined and found to under-estimate the overall microbunching amplification. The concept of gain matrix was developed, which includes the density, energy and transverse-longitudinal modulations in a beam phase space, and used to analyze MBI for a proposed recirculating machine. Throughout the gain matrix approach, it reasonably gives the upper limit of spectral MBI gain curves. This extended analysis can be employed to study multi-pass recirculation. (7) Study of MBI for magnetized beams Driven by a recent energy-recovery-linac based cooler design for electron cooling at Jefferson Lab Electron-Ion Collider Project, the generalized theoretical formulation for MBI to a transversely coupled beam has been developed and applied to this study. A magnetized beam in general features non-zero canonical angular momentum, thus considered to be a transversely coupled beam. A novel idea of utilizing magnetized beam transport was proposed for improvement of cooling efficiency and possible mitigation of collective effects. A concern of MBI regarding this design was studied and excluded. The large transverse beam size associated with the beam magnetization is found to help suppress MBI via the transverse-longitudinal correlation.« less

Unravelling the active microbial community in a thermophilic anaerobic digester-microbial electrolysis cell coupled system under different conditions.

PubMed

Cerrillo, Míriam; Viñas, Marc; Bonmatí, August

2017-03-01

Thermophilic anaerobic digestion (AD) of pig slurry coupled to a microbial electrolysis cell (MEC) with a recirculation loop was studied at lab-scale as a strategy to increase AD stability when submitted to organic and nitrogen overloads. The system performance was studied, with the recirculation loop both connected and disconnected, in terms of AD methane production, chemical oxygen demand removal (COD) and volatile fatty acid (VFA) concentrations. Furthermore, the microbial population was quantitatively and qualitatively assessed through DNA and RNA-based qPCR and high throughput sequencing (MiSeq), respectively to identify the RNA-based active microbial populations from the total DNA-based microbial community composition both in the AD and MEC reactors under different operational conditions. Suppression of the recirculation loop reduced the AD COD removal efficiency (from 40% to 22%) and the methane production (from 0.32 to 0.03 m 3  m -3  d -1 ). Restoring the recirculation loop led to a methane production of 0.55 m 3  m -3  d -1 concomitant with maximum MEC COD and ammonium removal efficiencies of 29% and 34%, respectively. Regarding microbial analysis, the composition of the AD and MEC anode populations differed from really active microorganisms. Desulfuromonadaceae was revealed as the most active family in the MEC (18%-19% of the RNA relative abundance), while hydrogenotrophic methanogens (Methanobacteriaceae) dominated the AD biomass. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comprehensive Evaluation of Biological Growth Control by Chlorine-Based Biocides in Power Plant Cooling Systems Using Tertiary Effluent

PubMed Central

Chien, Shih-Hsiang; Dzombak, David A.; Vidic, Radisav D.

2013-01-01

Abstract Recent studies have shown that treated municipal wastewater can be a reliable cooling water alternative to fresh water. However, elevated nutrient concentration and microbial population in wastewater lead to aggressive biological proliferation in the cooling system. Three chlorine-based biocides were evaluated for the control of biological growth in cooling systems using tertiary treated wastewater as makeup, based on their biocidal efficiency and cost-effectiveness. Optimal chemical regimens for achieving successful biological growth control were elucidated based on batch-, bench-, and pilot-scale experiments. Biocide usage and biological activity in planktonic and sessile phases were carefully monitored to understand biological growth potential and biocidal efficiency of the three disinfectants in this particular environment. Water parameters, such as temperature, cycles of concentration, and ammonia concentration in recirculating water, critically affected the biocide performance in recirculating cooling systems. Bench-scale recirculating tests were shown to adequately predict the biocide residual required for a pilot-scale cooling system. Optimal residuals needed for proper biological growth control were 1, 2–3, and 0.5–1 mg/L as Cl2 for NaOCl, preformed NH2Cl, and ClO2, respectively. Pilot-scale tests also revealed that Legionella pneumophila was absent from these cooling systems when using the disinfectants evaluated in this study. Cost analysis showed that NaOCl is the most cost-effective for controlling biological growth in power plant recirculating cooling systems using tertiary-treated wastewater as makeup. PMID:23781129

Recirculating, passive micromixer with a novel sawtooth structure.

PubMed

Nichols, Kevin P; Ferullo, Julia R; Baeumner, Antje J

2006-02-01

A microfluidic device capable of recirculating nano to microlitre volumes in order to efficiently mix solutions is described. The device consists of molded polydimethyl siloxane (PDMS) channels with pressure inlet and outlet holes sealed by a glass lid. Recirculation is accomplished by a repeatedly reciprocated flow over an iterated sawtooth structure. The sawtooth structure serves to change the fluid velocity of individual streamlines differently depending on whether the fluid is flowing backwards or forward over the structure. Thus, individual streamlines can be accelerated or decelerated relative to the other streamlines to allow sections of the fluid to interact that would normally be linearly separated. Low Reynolds numbers imply that the process is reversible, neglecting diffusion. Computer simulations were carried out using FLUENT. Subsequently, fluorescent indicators were employed to experimentally verify these numerical simulations of the recirculation principal. Finally, mixing of a carboxyfluorescein labeled DMSO plug with an unlabeled DMSO plug across an immiscible hydrocarbon plug was investigated. At cycling rates of 1 Hz across five sawtooth units, the time was recorded to reach steady state in the channels, i.e. until both DMSO plugs had the same fluorescence intensity. In the case of the sawtooth structures, steady state was reached five times faster than in channels without sawtooth structures, which verified what would be expected based on numerical simulations. The microfluidic mixer is unique due to its versatility with respect to scaling, its potential to also mix solutions containing small particles such as beads and cells, and its ease of fabrication and use.

Comprehensive Evaluation of Biological Growth Control by Chlorine-Based Biocides in Power Plant Cooling Systems Using Tertiary Effluent.

PubMed

Chien, Shih-Hsiang; Dzombak, David A; Vidic, Radisav D

2013-06-01

Recent studies have shown that treated municipal wastewater can be a reliable cooling water alternative to fresh water. However, elevated nutrient concentration and microbial population in wastewater lead to aggressive biological proliferation in the cooling system. Three chlorine-based biocides were evaluated for the control of biological growth in cooling systems using tertiary treated wastewater as makeup, based on their biocidal efficiency and cost-effectiveness. Optimal chemical regimens for achieving successful biological growth control were elucidated based on batch-, bench-, and pilot-scale experiments. Biocide usage and biological activity in planktonic and sessile phases were carefully monitored to understand biological growth potential and biocidal efficiency of the three disinfectants in this particular environment. Water parameters, such as temperature, cycles of concentration, and ammonia concentration in recirculating water, critically affected the biocide performance in recirculating cooling systems. Bench-scale recirculating tests were shown to adequately predict the biocide residual required for a pilot-scale cooling system. Optimal residuals needed for proper biological growth control were 1, 2-3, and 0.5-1 mg/L as Cl 2 for NaOCl, preformed NH 2 Cl, and ClO 2 , respectively. Pilot-scale tests also revealed that Legionella pneumophila was absent from these cooling systems when using the disinfectants evaluated in this study. Cost analysis showed that NaOCl is the most cost-effective for controlling biological growth in power plant recirculating cooling systems using tertiary-treated wastewater as makeup.

Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

PubMed

Giri, Rajiv K; Reddy, Krishna R

2014-03-01

In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

Experimental and Numerical Analysis of Performance Discontinuity of a Pump-Turbine under Pumping Mode

NASA Astrophysics Data System (ADS)

Zhang, X.; Burgstaller, R.; Lai, X.; Gehrer, A.; Kefalas, A.; Pang, Y.

2016-11-01

The performance discontinuity of a pump-turbine under pumping mode is harmful to stable operation of units in hydropower station. In this paper, the performance discontinuity phenomenon of the pump-turbine was studied by means of experiment and numerical simulation. In the experiment, characteristics of the pump-turbine with different diffuser vane openings were tested in order to investigate the effect of pumping casing to the performance discontinuity. While other effects such as flow separation and rotating stall are known to have an effect on the discontinuity, the present studied test cases show that prerotation is the dominating effect for the instability, positions of the positive slope of characteristics are almost the same in different diffuser vane opening conditions. The impeller has principal effect to the performance discontinuity. In the numerical simulation, CFD analysis of tested pump-turbine has been done with k-ω and SST turbulence model. It is found that the position of performance curve discontinuity corresponds to flow recirculation at impeller inlet. Flow recirculation at impeller inlet is the cause of the discontinuity of characteristics curve. It is also found that the operating condition of occurrence of flow recirculation at impeller inlet is misestimated with k-ω and SST turbulence model. Furthermore, the original SST model has been modified. We predict the occurrence position of flow recirculation at impeller inlet correctly with the modified SST turbulence model, and it also can improve the prediction accuracy of the pump- turbine performance at the same time.

Microfluidic device capable of medium recirculation for non-adherent cell culture

PubMed Central

Dixon, Angela R.; Rajan, Shrinidhi; Kuo, Chuan-Hsien; Bersano, Tom; Wold, Rachel; Futai, Nobuyuki; Takayama, Shuichi; Mehta, Geeta

2014-01-01

We present a microfluidic device designed for maintenance and culture of non-adherent mammalian cells, which enables both recirculation and refreshing of medium, as well as easy harvesting of cells from the device. We demonstrate fabrication of a novel microfluidic device utilizing Braille perfusion for peristaltic fluid flow to enable switching between recirculation and refresh flow modes. Utilizing fluid flow simulations and the human promyelocytic leukemia cell line, HL-60, non-adherent cells, we demonstrate the utility of this RECIR-REFRESH device. With computer simulations, we profiled fluid flow and concentration gradients of autocrine factors and found that the geometry of the cell culture well plays a key role in cell entrapping and retaining autocrine and soluble factors. We subjected HL-60 cells, in the device, to a treatment regimen of 1.25% dimethylsulfoxide, every other day, to provoke differentiation and measured subsequent expression of CD11b on day 2 and day 4 and tumor necrosis factor-alpha (TNF-α) on day 4. Our findings display perfusion sensitive CD11b expression, but not TNF-α build-up, by day 4 of culture, with a 1:1 ratio of recirculation to refresh flow yielding the greatest increase in CD11b levels. RECIR-REFRESH facilitates programmable levels of cell differentiation in a HL-60 non-adherent cell population and can be expanded to other types of non-adherent cells such as hematopoietic stem cells. PMID:24753733

Simulation and stability analysis of oblique shock-wave/boundary-layer interactions at Mach 5.92

NASA Astrophysics Data System (ADS)

Hildebrand, Nathaniel; Dwivedi, Anubhav; Nichols, Joseph W.; Jovanović, Mihailo R.; Candler, Graham V.

2018-01-01

We investigate flow instability created by an oblique shock wave impinging on a Mach 5.92 laminar boundary layer at a transitional Reynolds number. The adverse pressure gradient of the oblique shock causes the boundary layer to separate from the wall, resulting in the formation of a recirculation bubble. For sufficiently large oblique shock angles, the recirculation bubble is unstable to three-dimensional perturbations and the flow bifurcates from its original laminar state. We utilize direct numerical simulation (DNS) and global stability analysis to show that this first occurs at a critical shock angle of θ =12 .9∘ . At bifurcation, the least-stable global mode is nonoscillatory and it takes place at a spanwise wave number β =0.25 , in good agreement with DNS results. Examination of the critical global mode reveals that it originates from an interaction between small spanwise corrugations at the base of the incident shock, streamwise vortices inside the recirculation bubble, and spanwise modulation of the bubble strength. The global mode drives the formation of long streamwise streaks downstream of the bubble. While the streaks may be amplified by either the lift-up effect or by Görtler instability, we show that centrifugal instability plays no role in the upstream self-sustaining mechanism of the global mode. We employ an adjoint solver to corroborate our physical interpretation by showing that the critical global mode is most sensitive to base flow modifications that are entirely contained inside the recirculation bubble.

Control Strategies to Reduce the Energy Consumption of Central Domestic Hot Water Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dentz, Jordan; Ansanelli, Eric; Henderson, Hugh

Domestic hot water (DHW) heating is the second largest energy end use in U.S. buildings, exceeded only by space conditioning. Recirculation systems consisting of a pump and piping loop(s) are commonly used in multifamily buildings to reduce wait time for hot water at faucets; however, constant pumping increases energy consumption by exposing supply and return line piping to continuous heat loss, even during periods when there is no demand for hot water. In this study, ARIES installed and tested two types of recirculation controls in a pair of buildings in order to evaluate their energy savings potential. Demand control, temperaturemore » modulation controls, and the simultaneous operation of both were compared to the baseline case of constant recirculation. Additionally, interactive effects between DHW control fuel reductions and space conditioning (heating and cooling) were estimated in order to make more realistic predictions of the payback and financial viability of retrofitting DHW systems with these controls. Results showed that DHW fuel consumption reduced by 7% after implementing the demand control technique, 2% after implementing temperature modulation, and 15% after implementing demand control and temperature modulation techniques simultaneously; recirculation pump runtime was reduced to 14 minutes or less per day. With space heating and cooling interactions included, the estimated annual cost savings were 8%, 1%, and 14% for the respective control techniques. Possible complications in the installation, commissioning and operation of the controls were identified and solutions offered.« less

Experimental and numerical study of spatter formation and composition change in fiber laser welding of aluminum alloy

NASA Astrophysics Data System (ADS)

Wu, Dongsheng; Hua, Xueming; Ye, Youxiong; Huang, Lijin; Li, Fang; Huang, Ye

2018-05-01

A laser welding experiment with glass is conducted to directly observe the keyhole behavior and spatter formation in fiber laser welding of aluminum alloy. A 3D model is developed to investigate the spatter formation and composition change. An additional conservation equation is introduced to describe the Mg element distribution, and the Mg element loss due to evaporation is also considered. Based on numerical and experimental results, it is found that the keyhole geometry in laser welding of aluminum alloy is different from that in laser welding of steel. There are three required steps for spatter formation around the keyhole. The high momentum of the molten metal, the high recoil pressure and vapor shear stress, and the low surface tension around the keyhole contribute to the easy formation of spatter. The in-homogeneous distribution of Mg element in the weld can be attributable to the continuous evaporation of Mg element at the top surface of keyhole rear, the upward flow of low Mg element region from the bottom of the keyhole to the top surface of keyhole rear along the fusion line, the collapse of the keyhole, and the ejection of spatters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mruetusatorn, Prachya; Boreyko, Jonathan B; Sarles, Stephen A

Droplet interface bilayers (DIBs) are a powerful platform for studying the dynamics of synthetic cellular membranes; however, very little has been done to exploit the unique dynamical features of DIBs. Here, we generate microscale droplet interface bilayers ( DIBs) by bringing together femtoliter-volume water droplets in a microfluidic oil channel, and characterize morphological changes of the DIBs as the droplets shrink due to evaporation. By varying the initial conditions of the system, we identify three distinct classes of dynamic morphology. (1) Buckling and Fission: When forming DIBs using the lipid-out method (lipids in oil phase), lipids in the shrinking monolayersmore » continually pair together and slide into the bilayer to conserve their mass. As the bilayer continues to grow, it becomes confined, buckles, and eventually fissions one or more vesicles. (2) Uniform Shrinking: When using the lipid-in method (lipids in water phase) to form DIBs, lipids uniformly transfer from the monolayers and bilayer into vesicles contained inside the water droplets. (3) Stretching and Unzipping: Finally, when the droplets are pinned to the wall(s) of the microfluidic channel, the droplets become stretched during evaporation, culminating in the unzipping of the bilayer and droplet separation. These findings offer a better understanding of the dynamics of coupled lipid interfaces.« less

Advanced deep sea diving equipment

NASA Technical Reports Server (NTRS)

Danesi, W. A.

1972-01-01

Design requirements are generated for a deep sea heavy duty diving system to equip salvage divers with equipment and tools that permit work of the same quality and in times approaching that done on the surface. The system consists of a helmet, a recirculator for removing carbon dioxide, and the diver's dress. The diver controls the inlet flow by the recirculatory control valve and is able to change closed cycle operation to open cycle if malfunction occurs. Proper function of the scrubber in the recirculator minimizes temperature and humidity effects as it filters the returning air.

In-tank recirculating arsenic treatment system

DOEpatents

Brady, Patrick V [Albuquerque, NM; Dwyer, Brian P [Albuquerque, NM; Krumhansl, James L [Albuquerque, NM; Chwirka, Joseph D [Tijeras, NM

2009-04-07

A low-cost, water treatment system and method for reducing arsenic contamination in small community water storage tanks. Arsenic is removed by using a submersible pump, sitting at the bottom of the tank, which continuously recirculates (at a low flow rate) arsenic-contaminated water through an attached and enclosed filter bed containing arsenic-sorbing media. The pump and treatment column can be either placed inside the tank (In-Tank) by manually-lowering through an access hole, or attached to the outside of the tank (Out-of-Tank), for easy replacement of the sorption media.

Commercialization of the Stone and Webster/Conoco SCB technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, R.C.; Johnson, W.B.; Ratliff, B.D.

1982-06-01

Stone and Webster have developed a second generation recirculating fluidized bed boiler system, named Solids Circulation Boiler (SCB). The heart of the system is the recirculating fluidized bed, which is schematized, and explained. In November 1981 Conoco announced plans to construct an SCB at Lake Charles LA. Preliminary plot plan and elevation drawings are provided. The advantages of SCB are its rapid and controlled turn on and turn down capability, high carbon efficiency, simple coal and limestone feed system, high sulphur capture, compact design, and low NOx emission.

Non-conservation of global charges in the Brane Universe and baryogenesis

NASA Astrophysics Data System (ADS)

Dvali, Gia; Gabadadze, Gregory

1999-08-01

We argue that global charges, such as baryon or lepton number, are not conserved in theories with the Standard Model fields localized on the brane which propagates in higher-dimensional space-time. The global-charge non-conservation is due to quantum fluctuations of the brane surface. These fluctuations create ``baby branes'' that can capture some global charges and carry them away into the bulk of higher-dimensional space. Such processes are exponentially suppressed at low-energies, but can be significant at high enough temperatures or energies. These effects can lead to a new, intrinsically high-dimensional mechanism of baryogenesis. Baryon asymmetry might be produced due either to ``evaporation'' into the baby branes, or creation of the baryon number excess in collisions of two Brane Universes. As an example we discuss a possible cosmological scenario within the recently proposed ``Brane Inflation'' framework. Inflation is driven by displaced branes which slowly fall on top of each other. When the branes collide inflation stops and the Brane Universe reheats. During this non-equilibrium collision baryon number can be transported from one brane to another one. This results in the baryon number excess in our Universe which exactly equals to the hidden ``baryon number'' deficit in the other Brane Universe. © 1999

Large eddy simulation of soot evolution in an aircraft combustor

NASA Astrophysics Data System (ADS)

Mueller, Michael E.; Pitsch, Heinz

2013-11-01

An integrated kinetics-based Large Eddy Simulation (LES) approach for soot evolution in turbulent reacting flows is applied to the simulation of a Pratt & Whitney aircraft gas turbine combustor, and the results are analyzed to provide insights into the complex interactions of the hydrodynamics, mixing, chemistry, and soot. The integrated approach includes detailed models for soot, combustion, and the unresolved interactions between soot, chemistry, and turbulence. The soot model is based on the Hybrid Method of Moments and detailed descriptions of soot aggregates and the various physical and chemical processes governing their evolution. The detailed kinetics of jet fuel oxidation and soot precursor formation is described with the Radiation Flamelet/Progress Variable model, which has been modified to account for the removal of soot precursors from the gas-phase. The unclosed filtered quantities in the soot and combustion models, such as source terms, are closed with a novel presumed subfilter PDF approach that accounts for the high subfilter spatial intermittency of soot. For the combustor simulation, the integrated approach is combined with a Lagrangian parcel method for the liquid spray and state-of-the-art unstructured LES technology for complex geometries. Two overall fuel-to-air ratios are simulated to evaluate the ability of the model to make not only absolute predictions but also quantitative predictions of trends. The Pratt & Whitney combustor is a Rich-Quench-Lean combustor in which combustion first occurs in a fuel-rich primary zone characterized by a large recirculation zone. Dilution air is then added downstream of the recirculation zone, and combustion continues in a fuel-lean secondary zone. The simulations show that large quantities of soot are formed in the fuel-rich recirculation zone, and, furthermore, the overall fuel-to-air ratio dictates both the dominant soot growth process and the location of maximum soot volume fraction. At the higher fuel-to-air ratio, the maximum soot volume fraction is found inside the recirculation zone; at the lower fuel-to-air ratio, turbulent fluctuations in the mixture fraction promote the oxidation of soot inside the recirculation zone and suppress the accumulation of a large soot volume fraction. Downstream, soot exits the combustor in intermittent fuel-rich pockets that are not mixed during the injection of dilution air and subsequent secondary fuel-lean combustion. At the higher fuel-to-air ratio, the frequency of these fuel-rich pockets is increased, leading to higher soot emissions from the combustor. Quantitatively, the soot emissions from the combustor are overpredicted by about 50%, which is a substantial improvement over previous works utilizing RANS to predict such emissions. In addition, the ratio between the two fuel-to-air ratios predicted by LES compares very favorably with the experimental measurements. Furthermore, soot growth is dominated by an acetylene-based pathway rather than an aromatic-based pathway, which is usually the dominant mechanism in nonpremixed flames. This finding is the result of the interactions between the hydrodynamics, mixing, chemistry, and soot in the recirculation zone and the resulting residence times of soot at various mixture fractions (compositions), which are not the same in this complex recirculating flow as in nonpremixed jet flames.

Protective isolation in single-bed rooms: studies in a modified hospital ward

PubMed Central

Ayliffe, G. A. J.; Collins, B. J.; Lowbury, E. J. L.; Wall, Mary

1971-01-01

Studies were made in a modified hospital ward containing 19 beds, 14 of them in the open ward, one in a window-ventilated side-room, two in rooms with partial-recirculation ventilators giving 7-10 air changes per hour, and two in self-contained isolation suites with plenum ventilation (20 air changes per hour), ultra-violet (UV) barriers at doorways and airlocks. Preliminary tests with aerosols of tracer bacteria showed that few bacteria entered the plenum or recirculation-ventilated rooms. Bacteria released inside mechanically ventilated cubicles escaped into the corridor, but this transfer was reduced by the presence of an airlock. UV barriers at the entrance to the airlock and the cubicle reduced the transfer of bacteria from cubicle to corridor. During a period of 4 years while the ward was in use for surgical and gynaecological patients, the incidence of post-operative sepsis and colonization of wounds by multiple-resistant Staphylococcus aureus was lower (though not significantly lower) in the plenum-ventilated rooms than in the open ward, the recirculator-ventilated cubicles and the window-ventilated cubicles. Nasal acquisition of multiple-resistant Staph. aureus was significantly less common in the plenum-ventilated than in the recirculator-ventilated cubicles and in the other areas. Mean counts of bacteria on settle-plates were significantly lower in the plenum-ventilated cubicles than in the other areas; mean settle-plate counts in the recirculator-ventilated cubicles were significantly lower than in the open ward and in the window-ventilated side-room; similar results were shown by slit-sampling of air. Mean settle-plate counts were significantly lower in all areas when the ward was occupied by female patients. Staph. aureus was rarely carried by air from plenum-ventilated or other cubicles to the open ward, or from the open ward to the cubicles; though staphylococci were transferred from one floor area to another, they did not appear to be redispersed into the air in sufficient numbers to infect the patients. Ultra-violet irradiation caused a significant reduction in the total and staphylococcal counts from the floors of airlocks, and a significant reduction of total counts in the air. PMID:5289715

Recirculation of reverse osmosis concentrate in lab-scale anaerobic and aerobic landfill simulation reactors.

PubMed

Morello, Luca; Cossu, Raffaello; Raga, Roberto; Pivato, Alberto; Lavagnolo, Maria Cristina

2016-10-01

Leachate treatment is a major issue in the context of landfill management, particularly in view of the consistent changes manifested over time in the quality and quantity of leachate produced, linked to both waste and landfill characteristics, which renders the procedure technically difficult and expensive. Leachate recirculation may afford a series of potential advantages, including improvement of leachate quality, enhancement of gas production, acceleration of biochemical processes, control of moisture content, as well as nutrients and microbe migration within the landfill. Recirculation of the products of leachate treatment, such as reverse osmosis (RO) concentrate, is a less common practice, with widespread controversy relating to its suitability, potential impacts on landfill management and future gaseous and leachable emissions. Scientific literature provides the results of only a few full-scale applications of concentrate recirculation. In some cases, an increase of COD and ammonium nitrogen in leachate was observed, coupled with an increase of salinity; which, additionally, might negatively affect performance of the RO plant itself. In other cases, not only did leachate production not increase significantly but the characteristics of leachate extracted from the well closest to the re-injection point also remained unchanged. This paper presents the results of lab-scale tests conducted in landfill simulation reactors, in which the effects of injection of municipal solid waste (MSW) landfill leachate RO concentrate were evaluated. Six reactors were managed with different weekly concentrate inputs, under both anaerobic and aerobic conditions, with the aim of investigating the short and long-term effects of this practice on landfill emissions. Lab-scale tests resulted in a more reliable identification of compound accumulation and kinetic changes than full-scale applications, further enhancing the development of a mass balance in which gaseous emissions and waste characteristics were also taken into consideration. Results showed that RO concentrate recirculation did not produce consistent changes in COD emissions and methane production. Simultaneously, ammonium ion showed a consistent increase in leachate (more than 25%) in anaerobic reactors, free ammonia gaseous emissions doubled with concentrate injection, while chloride resulted accumulated inside the reactor. Copyright © 2016 Elsevier Ltd. All rights reserved.

Numerical model of turbulence, sediment transport, and morphodynamics tested in the Colorado River at Grand Canyon

NASA Astrophysics Data System (ADS)

Alvarez, L. V.; Grams, P.

2017-12-01

We present a parallelized, three-dimensional, turbulence-resolving model using the Detached-Eddy Simulation (DES) technique, tested at the scale of the river-reach in the Colorado River. DES is a hybrid large eddy simulation (LES) and Reynolds-averaged Navier Stokes (RANS). RANS is applied to the near-bed grid cells, where grid resolution is not sufficient to fully resolve wall turbulence. LES is applied in the flow interior. We utilize the Spalart-Allmaras one equation turbulence closure with a rough wall extension. The model resolves large-scale turbulence using DES and simultaneously integrates the suspended sediment advection-diffusion equation. The Smith and McLean suspended sediment boundary condition is used to calculate the upward and downward settling of sediment fluxes in the grid cells attached to the bed. Model results compare favorably with ADCP measurements of flow taken on the Colorado River in Grand Canyon during the High Flow Experiment (HFE) of 2008. The model accurately reproduces the size and position of the major recirculation currents, and the error in velocity magnitude was found to be less than 17% or 0.22 m/s absolute error. The mean deviation of the direction of velocity with respect to the measured velocity was found to be 20 degrees. Large-scale turbulence structures with vorticity predominantly in the vertical direction are produced at the shear layer between the main channel and the separation zone. However, these structures rapidly become three-dimensional with no preferred orientation of vorticity. Cross-stream velocities, into the main recirculation zone just upstream of the point of reattachment and out of the main recirculation region just downstream of the point of separation, are highest near the bed. Lateral separation eddies are more efficient at storing and exporting sediment than previously modeled. The input of sediment to the eddy recirculation zone occurs in the interface of the eddy and main channel. Pulsation of the strength of the return current becomes a key factor to determine the rates of erosion and deposition in the main recirculation zone.