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Sample records for air-water gas transfer

  1. Near-surface physics during convection affecting air-water gas transfer

    NASA Astrophysics Data System (ADS)

    Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A.

    2016-05-01

    The gas flux at the water surface is affected by physical processes including turbulence from wind shear, microscale wave breaking, large-scale breaking, and convection due to heat loss at the surface. The main route in the parameterizations of the gas flux has been to use the wind speed as a proxy for the gas flux velocity, indirectly taking into account the dependency of the wind shear and the wave processes. The interest in the contributions from convection processes has increased as the gas flux from inland waters (with typically lower wind and sheltered conditions) now is believed to play a substantial role in the air-water gas flux budget. The gas flux is enhanced by convection through the mixing of the mixed layer as well as by decreasing the diffusive boundary layer thickness. The direct numerical simulations performed in this study are shown to be a valuable tool to enhance the understanding of this flow configuration often present in nature.

  2. On the coefficients of small eddy and surface divergence models for the air-water gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Liao, Qian; Fillingham, Joseph H.; Bootsma, Harvey A.

    2015-03-01

    Recent studies suggested that under low to moderate wind conditions without bubble entraining wave breaking, the air-water gas transfer velocity k+ can be mechanistically parameterized by the near-surface turbulence, following the small eddy model (SEM). Field measurements have supported this model in a variety of environmental forcing systems. Alternatively, surface divergence model (SDM) has also been shown to predict the gas transfer velocity across the air-water interface in laboratory settings. However, the empirically determined model coefficients (α in SEM and c1 in SDM) scattered over a wide range. Here we present the first field measurement of the near-surface turbulence with a novel floating PIV system on Lake Michigan, which allows us to evaluate the SEM and SDM in situ in the natural environment. k+ was derived from the CO2 flux that was measured simultaneously with a floating gas chamber. Measured results indicate that α and c1 are not universal constants. Regression analysis showed that α˜log>(ɛ>) while the near-surface turbulence dissipation rate ɛ is approximately greater than 10-6 m2 s-3 according to data measured for this study as well as from other published results measured in similar environments or in laboratory settings. It also showed that α scales linearly with the turbulent Reynolds number. Similarly, coefficient c1 in the SDM was found to linearly scale with the Reynolds number. These findings suggest that larger eddies are also important parameters, and the dissipation rate in the SEM or the surface divergence β' in the SDM alone may not be adequate to determine k+ completely.

  3. Gas transfer velocities for quantifying methane, oxygen and other gas fluxes through the air-water interface of wetlands with emergent vegetation

    NASA Astrophysics Data System (ADS)

    Poindexter, C.; Variano, E. A.

    2012-12-01

    Empirical models for the gas transfer velocity, k, in the ocean, lakes and rivers are fairly well established, but there are few data to predict k for wetlands. We have conducted experiments in a simulated emergent marsh in the laboratory to explore the relationship between k, wind shear and thermal convection. Now we identify the implications of these results for gas transfer in actual wetlands by (1) quantifying the range of wind conditions in emergent vegetation canopies and the range of thermal convection intensities in wetland water columns, and (2) describing the non-linear interaction of these two stirring forces over their relevant ranges in wetlands. We measured mean wind speeds and wind speed variance within the shearless region of a Schoenoplectus-Typha marsh canopy in the Sacramento-San Joaquin Delta (Northern California, USA). The mean wind speed within this region, , is significantly smaller than wind above the canopy. Based on our laboratory experiments, for calm or even average wind conditions in this emergent marsh k600 is only on the order 0.1 cm hr-1 (for neutrally or stably stratified water columns). We parameterize unstable thermal stratification and the resulting thermal convection using the heat flux through the air-water interface, q. We analyzed a water temperature record for the Schoenoplectus-Typha marsh to obtain a long-term heat flux record. We used these heat flux data along with short-term heat flux data from other wetlands in the literature to identify the range of the gas transfer velocity associated with thermal convection in wetlands. The typical range of heat fluxes through water columns shaded by closed emergent canopies (-200 W m-2 to +200 W m-2) yields k600 values of 0.5 - 2.5 cm hr-1 according to the model we developed in the laboratory. Thus for calm or average wind conditions, the gas transfer velocity associated with thermal convection is significantly larger than the gas transfer velocity associated with wind

  4. The Effect of Rain on Air-Water Gas Exchange

    NASA Technical Reports Server (NTRS)

    Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

    1997-01-01

    The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.

  5. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1986-01-01

    Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components.

  6. Proton Transfers at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Mishra, Himanshu

    Proton transfer reactions at the interface of water with hydrophobic media, such as air or lipids, are ubiquitous on our planet. These reactions orchestrate a host of vital phenomena in the environment including, for example, acidification of clouds, enzymatic catalysis, chemistries of aerosol and atmospheric gases, and bioenergetic transduction. Despite their importance, however, quantitative details underlying these interactions have remained unclear. Deeper insight into these interfacial reactions is also required in addressing challenges in green chemistry, improved water quality, self-assembly of materials, the next generation of micro-nanofluidics, adhesives, coatings, catalysts, and electrodes. This thesis describes experimental and theoretical investigation of proton transfer reactions at the air-water interface as a function of hydration gradients, electrochemical potential, and electrostatics. Since emerging insights hold at the lipid-water interface as well, this work is also expected to aid understanding of complex biological phenomena associated with proton migration across membranes. Based on our current understanding, it is known that the physicochemical properties of the gas-phase water are drastically different from those of bulk water. For example, the gas-phase hydronium ion, H3O +(g), can protonate most (non-alkane) organic species, whereas H 3O+(aq) can neutralize only relatively strong bases. Thus, to be able to understand and engineer water-hydrophobe interfaces, it is imperative to investigate this fluctuating region of molecular thickness wherein the 'function' of chemical species transitions from one phase to another via steep gradients in hydration, dielectric constant, and density. Aqueous interfaces are difficult to approach by current experimental techniques because designing experiments to specifically sample interfacial layers (< 1 nm thick) is an arduous task. While recent advances in surface-specific spectroscopies have provided

  7. Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

    USGS Publications Warehouse

    Ho, David T.; Ferrón, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

    2014-01-01

    Mangrove forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 ± 0.4 and 8.1 ± 0.6 cm h−1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 ± 23.69 and 171.13 ± 20.28 mmol C m−2 d−1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

  8. Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

    NASA Astrophysics Data System (ADS)

    Ho, David T.; Ferrón, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

    2014-01-01

    forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 ± 0.4 and 8.1 ± 0.6 cm h-1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 ± 23.69 and 171.13 ± 20.28 mmol C m-2 d-1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

  9. Gas and liquid measurements in air-water bubbly flows

    SciTech Connect

    Zhou, X.; Doup, B.; Sun, X.

    2012-07-01

    Local measurements of gas- and liquid-phase flow parameters are conducted in an air-water two-phase flow loop. The test section is a vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. The measurements are performed at z/D = 10. The gas-phase measurements are performed using a four-sensor conductivity probe. The data taken from this probe are processed using a signal processing program to yield radial profiles of the void fraction, bubble velocity, and interfacial area concentration. The velocity measurements of the liquid-phase are performed using a state-of-the-art Particle Image Velocimetry (PIV) system. The raw PIV images are acquired using fluorescent particles and an optical filtration device. Image processing is used to remove noise in the raw PIV images. The statistical cross correlation is introduced to determine the axial velocity field and turbulence intensity of the liquid-phase. Measurements are currently being performed at z/D = 32 to provide a more complete data set. These data can be used for computational fluid dynamic model development and validation. (authors)

  10. Air-water gas exchange of toxaphene in Lake Superior.

    PubMed

    Jantunen, Liisa M; Bidleman, Terry F

    2003-06-01

    Parallel air and water samples were collected in Lake Superior during August 1996 and May 1997, to determine the levels and air-water exchange direction of toxaphene. Concentration of toxaphene in water did not vary across Lake Superior or between seasons (averaging 918 +/- 218 pg/L) but atmospheric levels were lower in May (12 +/- 4.6 pg/m3) than in August (28 +/- 10 pg/m3). Two recalcitrant congeners, Parlar 26 and 50, also were determined. These congeners were enriched in the air samples, compared to a standard of technical toxaphene, but not in the water. Water-air fugacity ratios varied from 1.4 to 2.6 in August and 1.3 to 4.7 in May, implying volatilization of toxaphene from the lake. Estimated net fluxes ranged from 5.4 to 13 and 1.8 to 6.4 nm/m2d, respectively. The temperature dependence of toxaphene partial pressure (P) in air was log P/Pa = -3.291/T(a) + 1.67, where T(a) is air temperature. By using this relationship, the atmospheric levels of toxaphene, fugacity ratios, and net fluxes were estimated for the entire year. Fugacity ratios were highest in the winter and lowest in the summer; thus toxaphene was predicted to undergo net volatilization from the lake during all months. A net removal of approximately 220 kg/year by gas exchange was estimated.

  11. Gas exchange in wetlands with emergent vegetation: The effects of wind and thermal convection at the air-water interface

    NASA Astrophysics Data System (ADS)

    Poindexter, Cristina M.; Variano, Evan A.

    2013-07-01

    Methane, carbon dioxide, and oxygen are exchanged between wetlands and the atmosphere through multiple pathways. One of these pathways, the hydrodynamic transport of dissolved gas through the surface water, is often underestimated in importance. We constructed a model wetland in the laboratory with artificial emergent plants to investigate the mechanisms and magnitude of this transport. We measured gas transfer velocities, which characterize the near-surface stirring driving air-water gas transfer, while varying two stirring processes important to gas exchange in other aquatic environments: wind and thermal convection. To isolate the effects of thermal convection, we identified a semiempirical model for the gas transfer velocity as a function of surface heat loss. The laboratory results indicate that thermal convection will be the dominant mechanism of air-water gas exchange in marshes with emergent vegetation. Thermal convection yielded peak gas transfer velocities of 1 cm h-1. Because of the sheltering of the water surface by emergent vegetation, gas transfer velocities for wind-driven stirring alone are likely to exceed this value only in extreme cases.

  12. Influence of current velocity and wind speed on air-water gas exchange in a mangrove estuary

    NASA Astrophysics Data System (ADS)

    Ho, David T.; Coffineau, Nathalie; Hickman, Benjamin; Chow, Nicholas; Koffman, Tobias; Schlosser, Peter

    2016-04-01

    Knowledge of air-water gas transfer velocities and water residence times is necessary to study the fate of mangrove derived carbon exported into surrounding estuaries and ultimately to determine carbon balances in mangrove ecosystems. For the first time, the 3He/SF6 dual tracer technique, which has been proven to be a powerful tool to determine gas transfer velocities in the ocean, is applied to Shark River, an estuary situated in the largest contiguous mangrove forest in North America. The mean gas transfer velocity was 3.3 ± 0.2 cm h-1 during the experiment, with a water residence time of 16.5 ± 2.0 days. We propose a gas exchange parameterization that takes into account the major sources of turbulence in the estuary (i.e., bottom generated shear and wind stress).

  13. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1984-01-01

    Heat transfer coefficients were measured using both dry and humid air in the same forced convection cooling scheme and were compared using appropriate nondimensional parameters (Nusselt, Prandtl and Reynolds numbers). A forced convection scheme with a complex flow field, two dimensional arrays of circular jets with crossflow, was utilized with humidity ratios (mass ratio of water vapor to air) up to 0.23. The dynamic viscosity, thermal conductivity and specific heat of air, steam and air/steam mixtures are examined. Methods for determining gaseous mixture properties from the properties of their pure components are reviewed as well as methods for determining these properties with good confidence. The need for more experimentally determined property data for humid air is discussed. It is concluded that dimensionless forms of forced convection heat transfer data and empirical correlations based on measurements with dry air may be applied to conditions involving humid air with the same confidence as for the dry air case itself, provided that the thermophysical properties of the humid air mixtures are known with the same confidence as their dry air counterparts.

  14. Turbulence and wave breaking effects on air-water gas exchange

    PubMed

    Boettcher; Fineberg; Lathrop

    2000-08-28

    We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in the wave dynamics. In the latter regime, the strongly enhanced aeration rate is correlated with measured acoustic emissions, indicating that bubble creation and dynamics dominate air-water exchange.

  15. Properties of amphiphilic oligonucleotide films at the air/water interface and after film transfer.

    PubMed

    Keller, R; Kwak, M; de Vries, J W; Sawaryn, C; Wang, J; Anaya, M; Müllen, K; Butt, H-J; Herrmann, A; Berger, R

    2013-11-01

    The self-assembly of amphiphilic hybrid materials containing an oligonucleotide sequence at the air/water interface was investigated by means of pressure-molecular area (Π-A) isotherms. In addition, films were transferred onto solid substrates and imaged using scanning force microscopy. We used oligonucleotide molecules with lipid tails, which consisted of a single stranded oligonucleotide 11 mer containing two hydrophobically modified 5-(dodec-1-ynyl)uracil nucleobases (dU11) at the 5'-end of the oligonucleotide sequence. The air/water interface was used as confinement for the self-assembling process of dU11. Scanning force microscopy of films transferred via Langmuir-Blodgett technique revealed mono-, bi- (Π ≥ 2 mN/m) and multilayer formation (Π ≥ 30 mN/m). The first layer was 1.6 ± 0.1 nm thick. It was oriented with the hydrophilic oligonucleotide moiety facing the hydrophilic substrate while the hydrophobic alkyl chains faced air. In the second layer the oligonucleotide moiety was found to face the air. The second layer was found to cover up to 95% of the sample area. Our measurements indicated that the rearrangement of the molecules into bi- and multiple bilayers happened already at the air/water interface. Similar results were obtained with a second type of oligonucleotide amphiphile, an oligonucleotide block copolymer, which was composed of an oligonucleotide 11 mer covalently attached at the terminus to polypropyleneoxide (PPO).

  16. Gas exchange rates across the sediment-water and air-water interfaces in south San Francisco Bay

    USGS Publications Warehouse

    Hartman, Blayne; Hammond, Douglas E.

    1984-01-01

    Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainty of the determinations, about 20%. The annual average of benthic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water interface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2–6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models.

  17. Turbulent heat and mass transfers across a thermally stratified air-water interface

    NASA Technical Reports Server (NTRS)

    Papadimitrakis, Y. A.; Hsu, Y.-H. L.; Wu, J.

    1986-01-01

    Rates of heat and mass transfer across an air-water interface were measured in a wind-wave research facility, under various wind and thermal stability conditions (unless otherwise noted, mass refers to water vapor). Heat fluxes were obtained from both the eddy correlation and the profile method, under unstable, neutral, and stable conditions. Mass fluxes were obtained only under unstable stratification from the profile and global method. Under unstable conditions the turbulent Prandtl and Schmidt numbers remain fairly constant and equal to 0.74, whereas the rate of mass transfer varies linearly with bulk Richardson number. Under stable conditions the turbulent Prandtl number rises steadily to a value of 1.4 for a bulk Richardson number of about 0.016. Results of heat and mass transfer, expressed in the form of bulk aerodynamic coefficients with friction velocity as a parameter, are also compared with field data.

  18. The effect of bubbles on air-water oxygen transfer in the breaker zone

    NASA Astrophysics Data System (ADS)

    Kakuno, Shohachi; Moog, Douglas B.; Tatekawa, Tetsuya; Takemura, Kenji; Yamagishi, Tatsuya

    The effect of bubbles entrained in the breaker zone on air-water oxygen transfer is examined. First, the area of bubbles entrained by breakers generated on a sloping bottom in a wave tank is analyzed using a color image sensor which can count the pixel number of a specific color in a frame. It was found that the time-averaged pixel number over a wave period has a strong relationship to the energy dissipation rate per unit mass of the breaker. The time-averaged pixel number is then incorporated with some modification into an equation proposed by Eckenfelder for the calculation of the mass transfer coefficient from bubble surfaces in an aeration tank. The coefficient resulting from the modified equation shows a strong relationship between the mass transfer coefficient and the dissipation rate.

  19. Influence of Gas Turbulence on the Instability of an Air-Water Mixing Layer.

    PubMed

    Matas, Jean-Philippe; Marty, Sylvain; Dem, Mohamed Seydou; Cartellier, Alain

    2015-08-14

    We present the first evidence of the direct influence of gas turbulence on the shear instability of a planar air-water mixing layer. We show with two different experiments that increasing the level of velocity fluctuations in the gas phase continuously increases the frequency of the instability, up to a doubling of frequency for the largest turbulence intensity investigated. A modified spatiotemporal stability analysis taking turbulence into account via a simple Reynolds stress closure provides the right trend and magnitude for this effect.

  20. Air-water gas exchange of organochlorine compounds in Lake Baikal, Russia

    SciTech Connect

    McConnell, L.L.; Kucklick, J.R.; Bidleman, T.F.; Ivanov, G.P.; Chernyak, S.M.

    1996-10-01

    Air and surface water samples were collected at Lake Baikal, Russia, during June 1991 to determine concentrations of organochlorine pesticides and polychlorinated biphenyl (PCB) congeners. These data were combined with Henry`s law constants to estimate the gas flux rate across the air-water interface of each compound class. Air samples were collected at Lake Baikal and from nearby Irkutsk. Water samples were collected from three mid-lake stations and at the mouth of two major tributaries. Average air concentrations of chlorinated bornanes (14 pg m{sup -3}), chlordanes (4.9 pg m{sup -3}), and hexachlorobenzene (HCB) (194 pg m{sup -3}) were similar to global backgound of Arctic levels. However, air concentrations of hexachlorocyclohexanes (HCHs), DDTs, and PCBs were closer to those observed in the Great Lakes region. Significantly higher levels of these three compound classes in air over Irkutsk suggests that regional atmospheric transport and deposition may be an important source of these persistent compounds to Lake Baikal. Air-water gas exchange calculations resulted in net depositional flux values for {alpha}-HCH, {gamma}-HCH, DDTs, and chlorinated bornanes at 112, 23, 3.6, and 2.4 ng m{sup -2} d{sup -1}, respectively. The total net flux of 22 PCB congeners, chlordanes, and HCB was from water to air (volatilization) at 47, 1.8, and 32 ng m{sup -2} d{sup -1}, respectively. 50 refs., 7 figs., 5 tabs.

  1. Visualization of oxygen transfer across the air-water interface using a fluorescence oxygen visualization method.

    PubMed

    Lee, Minhee

    2002-04-01

    Oxygen concentration fields in a water body were visualized by the fluorescence oxygen visualization (FOV) method. Pyrenebutyric acid (PBA) was used as a fluorescent indicator of oxygen, and an intensive charge coupled-device (ICCD) camera as an image detector. Sequential images (over 2000 images) of the oxygen concentration field around the surface water of the tank (1 x 1 x 0.75 m3) were produced during the 3 h experiment. From image processing, the accurate pathway of oxygen-rich, cold water at the water surface was also visualized. The amount of oxygen transferred through the air-water interface during the experiment was measured and the oxygen transfer coefficient (K(L)) was determined as 0.22 m/d, which was much higher than that is expected in molecular diffusion. Results suggest that vertical penetration of cold water was the main pathway of oxygen in the water body in the tank. The average velocity of cold water penetrating downward in water body was also measured from consecutive images and the value was 0.3-0.6 mm/s. The FOV method used in this research should have wide application in experimental fluid mechanics and can also provide a phenomenological description of oxygen transfer under physically realizable natural conditions in lakes and reservoirs.

  2. Calibration of Dissolved Noble Gas Mass Spectrometric Measurements by an Air-Water Equilibration System

    NASA Astrophysics Data System (ADS)

    Hillegonds, Darren; Matsumoto, Takuya; Jaklitsch, Manfred; Han, Liang-Feng; Klaus, Philipp; Wassenaar, Leonard; Aggarwal, Pradeep

    2013-04-01

    Precise measurements by mass spectrometry of dissolved noble gases (He, Ar, Ne, Kr, Xe) in water samples require careful calibration against laboratory standards with known concentrations. Currently, air pipettes are used for day-to-day calibrations, making estimation of overall analytical uncertainties for dissolved noble gas measurements in water difficult. Air equilibrated water (AEW) is often used as a matrix-equivalent laboratory standard for dissolved gases in groundwater, because of the well-known and constant fractions of noble gases in the atmosphere. AEW standards, however, are only useful if the temperature and pressure of the gas-water equilibrium can be controlled and measured precisely (i.e., to better than 0.5%); contamination and partial sample degassing must also be prevented during sampling. Here we present the details of a new custom air-water equilibration system which consists of an insulated 600 liter tank filled with deionized water, held isothermally at a precise target temperature (<0.05 °C) through the use of a heat exchanger. The temperature and total dissolved gas of the water in the tank are monitored continually, as are atmospheric pressure and air temperature in the laboratory. Different noble gas concentration standards can be reliably produced by accurately controlling the water temperature of the equilibration system. Equilibration characteristics and reproducibility of this system for production of copper tubes containing known amounts of noble gases will be presented.

  3. Air-Water Gas Transfer in Coastal Waters

    DTIC Science & Technology

    2016-06-07

    water currents and turbulence, air and water temperatures , visible and infrared (IR) radiative fluxes, the visco-elastic properties of surface films, and...turbulence at the ocean interface. Measuring the spatiotemporal temperature distribution on top of the aqueous mass boundary layer, heat patterns can be...interface is obtained through quantitative analysis of infrared image sequences of the water surface temperature . Our main focus during the last year

  4. Impact of Salinity on the Air-Water Partition Coefficient of Gas Tracers

    SciTech Connect

    Zhong, Lirong; Pope, Gary A.; Evans, John C.; Cameron, Richard J.

    2005-09-01

    The use of a gas partitioning interwell tracer test (PITT) has been proposed as a standard approach to the measurement of field-scale vadose zone water saturation fractions. The accuracy of the saturation measurement is largely dependent on the determination of the air-water partitioning coefficient, K, of the tracers; however, in practice, K is also strongly influenced by the physical and chemical properties of the water. In this study, column tests were conducted to investigate the impact of salinity on tracer partitioning coefficients for two promising gas phase candidate tracers, dibromomethane and dimethylether. Sodium thiosulfate was used as a salinity surrogate. The dynamic K values of the two partitioning tracers were measured for sodium thiosulfate concentrations between 0% and 36% by weight. Methane was used as the non-partitioning tracer for all experiments. K values were found to decrease significantly with increasing sodium thiosulfate concentration. Similar correlations between K values and sodium thiosulfate concentration were found for both of the partitioning tracers tested.

  5. Micrometeorological measurement of hexachlorobenzene and polychlorinated biphenyl compound air-water gas exchange in Lake Superior and comparison to model predictions

    NASA Astrophysics Data System (ADS)

    Rowe, M. D.; Perlinger, J. A.

    2012-01-01

    Air-water exchange fluxes of persistent, bioaccumulative and toxic (PBT) substances are frequently estimated using the Whitman two-film (W2F) method, but micrometeorological flux measurements of these compounds over water are rarely attempted. We measured air-water exchange fluxes of hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) on 14 July 2006 in Lake Superior using the modified Bowen ratio (MBR) method. Measured fluxes were compared to estimates using the W2F method, and to estimates from an Internal Boundary Layer Transport and Exchange (IBLTE) model that implements the NOAA COARE bulk flux algorithm and gas transfer model. We reveal an inaccuracy in the estimate of water vapor transfer velocity that is commonly used with the W2F method for PBT flux estimation, and demonstrate the effect of use of an improved estimation method. Flux measurements were conducted at three stations with increasing fetch in offshore flow (15, 30, and 60 km) in southeastern Lake Superior. This sampling strategy enabled comparison of measured and predicted flux, as well as modification in near-surface atmospheric concentration with fetch, using the IBLTE model. Fluxes estimated using the W2F model were compared to fluxes measured by MBR. In five of seven cases in which the MBR flux was significantly greater than zero, concentration increased with fetch at 1-m height, which is qualitatively consistent with the measured volatilization flux. As far as we are aware, these are the first reported micrometeorological air-water exchange flux measurements of PCBs.

  6. Air-water gas exchange of mercury in the Bay Saint François wetlands: Observation and model parameterization

    NASA Astrophysics Data System (ADS)

    Zhang, Hong H.; Poissant, Laurier; Xu, Xiaohong; Pilote, Martin; Beauvais, Conrad; Amyot, Marc; Garcia, Edenise; Laroulandie, Jerome

    2006-09-01

    Total gaseous mercury (TGM) air-water flux measurements were taken using a dynamic flux chamber (DFC) coupled with a gaseous mercury (Hg) analyzer at the Bay St. François (BSF) wetlands (Quebec, Canada) in summer 2003. The measured TGM fluxes over water exhibited a consistent diurnal pattern, with maximum emissions during daytime and minimum fluxes occurring at night. Pearson correlation analysis showed that solar radiation was the most influential environmental parameter in TGM air-water exchange. Significant correlations were also found between TGM fluxes and 1 hour time-lagged water temperature, indicating the enhancement of fluxes by bacterial activities or chemical reactions. The concentrations of dissolved gaseous mercury (DGM) in water were measured during the 2003 sampling period and indicated that DGM was always supersaturated, which implied that the water body acted primarily as a source of mercury to the atmosphere. Several empirical models of mercury air-water gas exchange were developed and evaluated. Compared to the published models, these proposed models were capable of producing good results, leading to a better agreement between the measured and modeled fluxes (improvements by 48-98%). Among these empirical models, the ones linking TGM fluxes with net radiation were superior because of their strong predictive capability. Two preferred models were selected for air-water TGM flux estimation from Lake St. Pierre's surrounding wetlands. These two models yield a mean emission of 0.19-0.24 kg mercury during May-September each year from 1999 to 2003.

  7. Forced convective flow and heat transfer of upward cocurrent air-water slug flow in vertical plain and swirl tubes

    SciTech Connect

    Chang, Shyy Woei; Yang, Tsun Lirng

    2009-10-15

    This experimental study comparatively examined the two-phase flow structures, pressured drops and heat transfer performances for the cocurrent air-water slug flows in the vertical tubes with and without the spiky twisted tape insert. The two-phase flow structures in the plain and swirl tubes were imaged using the computerized high frame-rate videography with the Taylor bubble velocity measured. Superficial liquid Reynolds number (Re{sub L}) and air-to-water mass flow ratio (AW), which were respectively in the ranges of 4000-10000 and 0.003-0.02 were selected as the controlling parameters to specify the flow condition and derive the heat transfer correlations. Tube-wise averaged void fraction and Taylor bubble velocity were well correlated by the modified drift flux models for both plain and swirl tubes at the slug flow condition. A set of selected data obtained from the plain and swirl tubes was comparatively examined to highlight the impacts of the spiky twisted tape on the air-water interfacial structure and the pressure drop and heat transfer performances. Empirical heat transfer correlations that permitted the evaluation of individual and interdependent Re{sub L} and AW impacts on heat transfer in the developed flow regions of the plain and swirl tubes at the slug flow condition were derived. (author)

  8. Micrometeorological measurement of hexachlorobenzene and polychlorinated biphenyl compound air-water gas exchange in Lake Superior and comparison to model predictions

    NASA Astrophysics Data System (ADS)

    Rowe, M. D.; Perlinger, J. A.

    2012-05-01

    Air-water exchange fluxes of persistent, bioaccumulative and toxic (PBT) substances are frequently estimated using the Whitman two-film (W2F) method, but micrometeorological flux measurements of these compounds over water are rarely attempted. We measured air-water exchange fluxes of hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) on 14 July 2006 in Lake Superior using the modified Bowen ratio (MBR) method. Measured fluxes were compared to estimates using the W2F method, and to estimates from an Internal Boundary Layer Transport and Exchange (IBLTE) model that implements the NOAA COARE bulk flux algorithm and gas transfer model. We reveal an inaccuracy in the estimate of water vapor transfer velocity that is commonly used with the W2F method for PBT flux estimation, and demonstrate the effect of use of an improved estimation method. Flux measurements were conducted at three stations with increasing fetch in offshore flow (15, 30, and 60 km) in southeastern Lake Superior. This sampling strategy enabled comparison of measured and predicted flux, as well as modification in near-surface atmospheric concentration with fetch, using the IBLTE model. Fluxes estimated using the W2F model were compared to fluxes measured by MBR. In five of seven cases in which the MBR flux was significantly greater than zero, concentration increased with fetch at 1-m height, which is qualitatively consistent with the measured volatilization flux. As far as we are aware, these are the first reported ship-based micrometeorological air-water exchange flux measurements of PCBs.

  9. Shear turbulence, Langmuir circulation and scalar transfer at an air-water interface

    NASA Astrophysics Data System (ADS)

    Hafsi, Amine; Tejada-Martinez, Andres; Veron, Fabrice

    2016-11-01

    DNS of an initially quiescent coupled air-water interface driven by an air-flow with free stream speed of 5 m/s generates gravity-capillary waves and small-scale (centimeter-scale) Langmuir circulation (LC) beneath the interface. In addition to LC, the waterside turbulence is characterized by shear turbulence with structures similar to classical "wall streaks" in wall-bounded flow. These streaks, denoted here as "shear streaks", consist of downwind-elongated vortices alternating in sign in the crosswind direction. The presence of interfacial waves causes interaction between these vortices giving rise to bigger vortices, namely LC. LES with momentum equation augmented with the Craik-Leibovich (C-L) vortex force is used to understand the roles of the shear streaks (i.e. the shear turbulence) and the LC in determining scalar flux from the airside to the waterside and vertical scalar transport beneath. The C-L force consists of the cross product between the Stokes drift velocity (induced by the interface waves) and the flow vorticity. It is observed that Stokes drift shear intensifies the shear streaks (with respect to flow without wave effects) leading to enhanced scalar flux at the air-water interface. LC leads to increased vertical scalar transport at depths below the interface.

  10. Heat transfer and fluid dynamics of air-water two-phase flow in micro-channels

    SciTech Connect

    Kaji, Masuo; Sawai, Toru; Kagi, Yosuke; Ueda, Tadanobu

    2010-05-15

    Heat transfer, pressure drop, and void fraction were simultaneously measured for upward heated air-water non-boiling two-phase flow in 0.51 mm ID tube to investigate thermo-hydro dynamic characteristics of two-phase flow in micro-channels. At low liquid superficial velocity j{sub l} frictional pressure drop agreed with Mishima-Hibiki's correlation, whereas agreed with Chisholm-Laird's correlation at relatively high j{sub l}. Void fraction was lower than the homogeneous model and conventional empirical correlations. To interpret the decrease of void fraction with decrease of tube diameter, a relation among the void fraction, pressure gradient and tube diameter was derived. Heat transfer coefficient fairly agreed with the data for 1.03 and 2.01 mm ID tubes when j{sub l} was relatively high. But it became lower than that for larger diameter tubes when j{sub l} was low. Analogy between heat transfer and frictional pressure drop was proved to hold roughly for the two-phase flow in micro-channel. But satisfactory relation was not obtained under the condition of low liquid superficial velocity. (author)

  11. Liquefied Natural Gas Transfer

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Chicago Bridge & Iron Company's tanks and associated piping are parts of system for transferring liquefied natural gas from ship to shore and storing it. LNG is a "cryogenic" fluid meaning that it must be contained and transferred at very low temperatures, about 260 degrees below Fahrenheit. Before the LNG can be pumped from the ship to the storage tanks, the two foot diameter transfer pipes must be cooled in order to avoid difficulties associated with sharp differences of temperature between the supercold fluid and relatively warm pipes. Cooldown is accomplished by sending small steady flow of the cryogenic substance through the pipeline; the rate of flow must be precisely controlled or the transfer line will be subjected to undesirable thermal stress.

  12. Photoinduced electron transfer in a monolayer at the air-water interface

    SciTech Connect

    Matsumoto, Mutsuyoshi; Ahuja, R.C.; Moebius, D.

    1992-07-09

    Photoinduced electron transfer from the amphiphilic oxacyanine (donor) to the amphiphilic viologen (acceptor) embedded on a DMPC matrix is investigated in the monolayer. Steady-state fluorescence intensity-area isotherms were measured simultaneously with surface pressure-area isotherms. In the absence of the acceptor, the fluorescence intensity normalized to surface density increased with an increase in surface pressure, which was suggested to be due to an increase in the lifetime of the excited state of the donor. Dimer formation of the donor is not found in the present case even at the donor density of 0.22 nm{sup {minus}2}, contrary to the LB film case where it is found at donor densities as low as 0.01 nm{sup {minus}2} with cadmium arachidate/methyl arachidate = 1/1 as a matrix. This shows the important role of the matrix in this type of work. In the presence of the acceptor, the relative fluorescence intensity decreases strongly with increasing surface pressure and molar fraction of the acceptor. This is due to the electron transfer from the excited state of the donor to the ground state of the acceptor. The relative fluorescence intensity depends on the densities of the donor and the acceptor and also on the lifetime of the excited state of the donor. The critical distance for the electron transfer is 0.9 nm at 2 mN m{sup {minus}1} and 1.5 nm at 40 mN m{sup {minus}1}. The close match between the observed and simulated values shows that the energy delocalization via incoherent exciton hopping is not significant in the present monolayer case as opposed to the LB film systems where the donor and acceptor are localized at the same interface. The discrepancy may be due to the larger values of the donor-to-acceptor ratio in the LB film case. 24 refs., 6 figs.

  13. 20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean.

    PubMed

    Jantunen, Liisa M; Wong, Fiona; Gawor, Anya; Kylin, Henrik; Helm, Paul A; Stern, Gary A; Strachan, William M J; Burniston, Deborah A; Bidleman, Terry F

    2015-12-01

    The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air-water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water-air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air-surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

  14. Air-water Gas Exchange Rates on a Large Impounded River Measured Using Floating Domes (Poster)

    EPA Science Inventory

    Mass balance models of dissolved gases in rivers typically serve as the basis for whole-system estimates of greenhouse gas emission rates. An important component of these models is the exchange of dissolved gases between air and water. Controls on gas exchange rates (K) have be...

  15. Gas exchange across the air - water interface determined with man-made and natural tracers

    SciTech Connect

    Wanninkhof, R.H.

    1986-01-01

    Gas exchange coefficients were determined on Rockland Lake, NY; Crowley Lake, CA; and Mono Lake, CA which have surface areas of 1 km/sup 2/, 20 km/sup 2/, and 190 km/sup 2/, respectively, by injecting a small amount of man made tracer gas, sulfur hexafluoride (SF/sub 6/) into the lake and measuring the rate of concentration decrease in the water column with time. The dependency of gas exchange on wind speed is similar for the three lakes indicating that wind fetch is not a critical parameter for the gas exchange coefficient for lakes with sizes greater than 1 km/sup 2/. Little gas exchange occurs for wind speeds less than 2.5 m/s and gas exchange increases linearly with wind speed from 2.5 to 6 m/s. The relationship of gas exchange and wind speed for the lakes agrees well with a compilation of earlier single wind speed - exchange coefficient measurements on lakes and oceans but they are lower than most results obtained in wind tunnels.

  16. Two-dimensional crystallization of proteins on lipid monolayers at the air water interface and transfer to an electron microscopy grid

    NASA Astrophysics Data System (ADS)

    Brisson, Alain; Bergsma-Schutter, Wilma; Oling, Frank; Lambert, Olivier; Reviakine, Ilya

    1999-01-01

    The two-dimensional (2-D) crystallization of proteins on lipid monolayers at the air-water interface is a well established method for crystallizing soluble proteins. The transfer of 2-D crystals from the air-water interface to an electron microscopy (EM) grid constitutes a critical and ill-controlled step in the whole procedure, which is likely to be responsible for the high variability of results obtained with this method. In this paper, we address the following questions: (1) does the material observed on EM grids constitute a true representation of the material present at the air-water interface? (2) is there an optimal method of transfer to obtain well-ordered protein 2-D crystals? To answer these questions, we combine data obtained on three different protein systems, annexin V, streptavidin and cholera toxin, using two types of EM grids, coated with either holey carbon films or continuous carbon films. These combined observations help us draw a coherent picture of the state of the interfacial films at the air-water surface and provide new insight into the perturbing influence of the transfer step. The main conclusions are: (1) both annexin V and streptavidin form crystalline monolayers at the air-water interface, which are well preserved when transfer is performed by means of holey carbon films; (2) a major reorganization of the material present at the water surface accompanies transfer with continuous carbon films; the basal monolayer is extensively damaged, transforming into domains and vesicular structures, which do not pre-exist at the water surface; with the three protein systems studied here, these domains are often crystalline; (3) the most striking structural reorganization induced by transfer with continuous carbon films is observed with annexin V, for which the native p6 crystalline assembly is transformed into another crystal form more ordered, with p3 symmetry. It is most probable that these conclusions also apply to other protein 2-D crystals

  17. Estimation of air-water gas exchange coefficient in a shallow lagoon based on 222Rn mass balance.

    PubMed

    Cockenpot, S; Claude, C; Radakovitch, O

    2015-05-01

    The radon-222 mass balance is now commonly used to quantify water fluxes due to Submarine Groundwater Discharge (SGD) in coastal areas. One of the main loss terms of this mass balance, the radon evasion to the atmosphere, is based on empirical equations. This term is generally estimated using one among the many empirical equations describing the gas transfer velocity as a function of wind speed that have been proposed in the literature. These equations were, however, mainly obtained from areas of deep water and may be less appropriate for shallow areas. Here, we calculate the radon mass balance for a windy shallow coastal lagoon (mean depth of 6m and surface area of 1.55*10(8) m(2)) and use these data to estimate the radon loss to the atmosphere and the corresponding gas transfer velocity. We present new equations, adapted to our shallow water body, to express the gas transfer velocity as a function of wind speed at 10 m height (wind range from 2 to 12.5 m/s). When compared with those from the literature, these equations fit particularly well with the one of Kremer et al. (2003). Finally, we emphasize that some gas transfer exchange may always occur, even for conditions without wind.

  18. Gas Transfer in Hydraulic Jumps.

    DTIC Science & Technology

    1981-07-01

    gas transfer based on measurements made in a hydraulic model. 5. Hydraulic jumps are flow phenomena that are part of the energy dissipation design at...gas transfer to energy dissipation. In a hydraulic jump, the energy loss is related to the Froude number of incoming flow. Fig- ures 15, 16, and 17...number in a similar manner for each of the unit discharges tested. As energy dissipation and Froude number in- creased, gas loss increased for a

  19. Heat transfer to two-phase air/water mixtures flowing in small tubes with inlet disequilibrium

    NASA Technical Reports Server (NTRS)

    Janssen, J. M.; Florschuetz, L. W.; Fiszdon, J. P.

    1986-01-01

    The cooling of gas turbine components was the subject of considerable research. The problem is difficult because the available coolant, compressor bleed air, is itself quite hot and has relatively poor thermophysical properties for a coolant. Injecting liquid water to evaporatively cool the air prior to its contact with the hot components was proposed and studied, particularly as a method of cooling for contingency power applications. Injection of a small quantity of cold liquid water into a relatively hot coolant air stream such that evaporation of the liquid is still in process when the coolant contacts the hot component was studied. No approach was found whereby heat transfer characteristics could be confidently predicted for such a case based solely on prior studies. It was not clear whether disequilibrium between phases at the inlet to the hot component section would improve cooling relative to that obtained where equilibrium was established prior to contact with the hot surface.

  20. The AirWaterGas Teacher Professional Development Program: Lessons Learned by Pairing Scientists and Teachers to Develop Curriculum on Global Climate Change and Regional Unconventional Oil and Gas Development

    NASA Astrophysics Data System (ADS)

    Gardiner, L. S.; Hatheway, B.; Rogers, J. D.; Casey, J. G.; Lackey, G.; Birdsell, D.; Brown, K.; Polmear, M.; Capps, S.; Rosenblum, J.; Sitterley, K.; Hafich, K. A.; Hannigan, M.; Knight, D.

    2015-12-01

    The AirWaterGas Teacher Professional Development Program, run by the UCAR Center for Science Education, brought together scientists and secondary science teachers in a yearlong program culminating in the development of curriculum related to the impacts of unconventional oil and gas development. Graduate students and research scientists taught about their research area and its relationship to oil and gas throughout three online courses during the 2015-16 school year, during which teachers and scientists engaged in active online discussions. Topics covered included climate change, oil and gas infrastructure, air quality, water quality, public health, and practices and policies relating to oil and gas development. Building upon their initial online interactions and a face-to-face meeting in March, teachers were paired with appropriate AirWaterGas team members as science advisors during a month-long residency in Boulder, Colorado. During the residency, graduate student scientists provided resources and feedback as teachers developed curriculum projects in collaboration with each other and UCAR science educators. Additionally, teachers and AirWaterGas researchers shared experiences on an oil and gas well site tour, and a short course on drilling methods with a drilling rig simulator. Here, we share lessons learned from both sides of the aisle, including initial results from program assessment conducted with the participating teachers.

  1. Smooth- and enhanced-tube heat transfer and pressure drop : Part I. Effect of Prandtl number with air, water, and glycol/water mixtures.

    SciTech Connect

    Obot, N. T.; Das, L.; Rabas, T. J.

    2000-11-14

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics in laminar, transitional, and turbulent flow through one smooth tube and twenty-three enhanced tubes. The working fluids for the experiments were air, water, ethylene glycol, and ethylene glycol/water mixtures; Prandtl numbers (Pr) ranged from 0.7 to 125.3. The smooth-tube experiments were carried out with Pr values of 0.7, 6.8, 24.8, 39.1, and 125.3; Pr values of 0.7, 6.8, and 24.8 were tested with enhanced tubes. Reynolds number (Re) range (based on the maximum internal diameter of a tube) was 200 to 55,000, depending on Prandtl number and tube geometry. The results are presented and discussed in this paper.

  2. Validation study of air-sea gas transfer modeling

    SciTech Connect

    Asher, W.E.; Farley, P.J.; Leifer, I.S.

    1995-07-01

    Laboratory results have demonstrated the importance of bubble plumes to air-water gas transfer (Asher et al., 1994). Bubble plumes enhance gas transfer by disrupting surface films, by directly transporting a gas, and by the creation of turbulence. Models of bubble gas transfer have been developed by different authors (Atkinson, 1973; Memery and Merlivat, 1985; Woolf and Thorpe, 1991) to determine the magnitude of gas transfer due to bubbles. Laboratory measurements of both the gas transfer rate k{sub L}, and the bubble distribution {phi} in a whitecap simulation tank (WST) have allowed these models to be validated and deficiencies in the theoretical assumptions to be explored. In the WST, each bucket tip simulates a wave breaking event. Important tests of these models include whether they can explain the experimentally determined solubility and Schmidt number dependency of k{sub L}, predict the time varying bubble concentrations, predict the evasion-invasion asymmetry, and predict the fraction of k{sub L} due to bubble plumes. Four different models were tested, a steady state model (Atkinson, 1973), a non-turbulence model with constant bubble radius (Memery and Merlivat, 1985), a turbulence model with constant bubble radius (Wolf and Thorpe, 1991), and a turbulence model with varying bubble radius. All models simulated multiple bubble tip cycles. The two turbulence models were run for sufficient tip cycles to generate statistically significant number of eddies ({number_sign}{gt}50) for bubbles affected by turbulence (V{sub B}{le}V{sub T}), found to be at least four tip cycles. The models allowed up to nine gases simultaneously and were run under different conditions of trace and major gas concentrations and partial pressures.

  3. Heat Transfer in Gas Turbines

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.

    2001-01-01

    The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.

  4. Controls on gas transfer velocities in a large river

    EPA Science Inventory

    The emission of biogenic gases from large rivers can be an important component of regional greenhouse gas budgets. However, emission rate estimates are often poorly constrained due to uncertainties in the air-water gas exchange rate. We used the floating chamber method to estim...

  5. Air/Water Purification

    NASA Technical Reports Server (NTRS)

    1992-01-01

    After 18 years of research into air/water pollution at Stennis Space Center, Dr. B. C. Wolverton formed his own company, Wolverton Environmental Services, Inc., to provide technology and consultation in air and water treatment. Common houseplants are used to absorb potentially harmful materials from bathrooms and kitchens. The plants are fertilized, air is purified, and wastewater is converted to clean water. More than 100 U.S. communities have adopted Wolverton's earlier water hyacinth and artificial marsh applications. Catfish farmers are currently evaluating the artificial marsh technology as a purification system.

  6. Gas Blowing: Mass Transfer in Gas and Melt

    NASA Astrophysics Data System (ADS)

    Sortland, Øyvind Sunde; Tangstad, Merete

    2014-09-01

    Metallurgical routes for solar grade silicon production are being developed as alternatives to chemical processes for their potential to achieve cost reductions, increased production volume, and reduced environmental and safety concerns. An important challenge in the development of metallurgical routes relates to the higher impurity concentrations in the silicon product, particularly for boron and other elements that are not efficiently segregated in solidification techniques. The reactive gas refining process is studied for its potential to remove boron below the solar grade silicon target concentration in a single step by blowing steam and hydrogen gas jets onto the melt surface. Boron in a silicon melt is extracted to HBO gas in parallel to active oxidation of silicon. The literature is not unified regarding the rate determining step in this process. Relevant theories and equations for gas blowing in induction furnaces are combined and used to explain mass transfer in experiments. Mass transfer in the melt and gas is investigated by comparing resistance and induction heating of the melt, and varying gas flow rate, crucible diameter, diameter of the gas lance, and the position of the gas lance above the melt surface. The rate of boron removal is found to increase with increasing gas flow rate and crucible diameter. A relatively high fraction of the reactive gas is utilized in the process, and supply of steam in the bulk gas is the only identified rate determining step.

  7. Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air-water interface and of the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Gonzalez, L.; Leithead, A.; Finewax, Z.; Thalman, R.; Vlasenko, A.; Vagle, S.; Miller, L. A.; Li, S.-M.; Bureekul, S.; Furutani, H.; Uematsu, M.; Volkamer, R.; Abbatt, J.

    2014-02-01

    Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acids (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air-seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) University of Colorado light-emitting diode cavity-enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas-phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon-carbon double bonds in the PUFA molecules. In addition, two highly reactive dicarbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and < 1% for n-hexanal, 3-nonenal, MDA and glyoxal, respectively, where the yields for MDA and glyoxal are likely lower limits. Heterogeneous oxidation of SML samples confirm for the first time that similar carbonyl products are formed via ozonolysis of environmental samples.

  8. Air-water oxygen exchange in a large whitewater river

    USGS Publications Warehouse

    Hall, Robert O.; Kennedy, Theodore A.; Rosi-Marshall, Emma J.

    2012-01-01

    Air-water gas exchange governs fluxes of gas into and out of aquatic ecosystems. Knowing this flux is necessary to calculate gas budgets (i.e., O2) to estimate whole-ecosystem metabolism and basin-scale carbon budgets. Empirical data on rates of gas exchange for streams, estuaries, and oceans are readily available. However, there are few data from large rivers and no data from whitewater rapids. We measured gas transfer velocity in the Colorado River, Grand Canyon, as decline in O2 saturation deficit, 7 times in a 28-km segment spanning 7 rapids. The O2 saturation deficit exists because of hypolimnetic discharge from Glen Canyon Dam, located 25 km upriver from Lees Ferry. Gas transfer velocity (k600) increased with slope of the immediate reach. k600 was -1 in flat reaches, while k600 for the steepest rapid ranged 3600-7700 cm h-1, an extremely high value of k600. Using the rate of gas exchange per unit length of water surface elevation (Kdrop, m-1), segment-integrated k600 varied between 74 and 101 cm h-1. Using Kdrop we scaled k600 to the remainder of the Colorado River in Grand Canyon. At the scale corresponding to the segment length where 80% of the O2 exchanged with the atmosphere (mean length = 26.1 km), k600 varied 4.5-fold between 56 and 272 cm h-1 with a mean of 113 cm h-1. Gas transfer velocity for the Colorado River was higher than those from other aquatic ecosystems because of large rapids. Our approach of scaling k600 based on Kdrop allows comparing gas transfer velocity across rivers with spatially heterogeneous morphology.

  9. Gas transfer in a bubbly wake flow

    NASA Astrophysics Data System (ADS)

    Karn, A.; Gulliver, J. S.; Monson, G. M.; Ellis, C.; Arndt, R. E. A.; Hong, J.

    2016-05-01

    The present work reports simultaneous bubble size and gas transfer measurements in a bubbly wake flow of a hydrofoil, designed to be similar to a hydroturbine blade. Bubble size was measured by a shadow imaging technique and found to have a Sauter mean diameter of 0.9 mm for a reference case. A lower gas flow rate, greater liquid velocities, and a larger angle of attack all resulted in an increased number of small size bubbles and a reduced weighted mean bubble size. Bubble-water gas transfer is measured by the disturbed equilibrium technique. The gas transfer model of Azbel (1981) is utilized to characterize the liquid film coefficient for gas transfer, with one scaling coefficient to reflect the fact that characteristic turbulent velocity is replaced by cross-sectional mean velocity. The coefficient was found to stay constant at a particular hydrofoil configuration while it varied within a narrow range of 0.52-0.60 for different gas/water flow conditions.

  10. Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air-water interface and of the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Gonzalez, L.; Leithead, A.; Finewax, Z.; Thalman, R.; Vlasenko, A.; Vagle, S.; Miller, L.; Li, S.-M.; Bureekul, S.; Furutani, H.; Uematsu, M.; Volkamer, R.; Abbatt, J.

    2013-07-01

    Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acid (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air-seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) and light-emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon-carbon double bonds in the PUFA molecules. In addition, two highly reactive di-carbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and <1% for n-hexanal, 3-nonenal, MDA and glyoxal, respectively, where the yields for MDA and glyoxal are likely lower limits. Heterogeneous oxidation of SML samples confirm for the first time that similar carbonyl products are formed via ozonolysis of environmental samples. The potential impact of such chemistry on the atmosphere of the marine boundary layer is discussed.

  11. Turbine airfoil gas side heat transfer

    NASA Technical Reports Server (NTRS)

    Turner, E. R.

    1984-01-01

    Work is currently underway to develop and characterize an analytical approach, based on boundary layer theory, for predicting the effects of leading edge (showerhead) film cooling on downstream gas side heat transfer rates. Parallel to this work, experiments are being conducted to build a relevant data base for present and future methods verification.

  12. Measurement of Gas and Liquid Velocities in an Air-Water Two-Phase Flow using Cross-Correlation of Signals from a Double Senor Hot-Film Probe

    SciTech Connect

    B. Gurau; P. Vassalo; K. Keller

    2002-02-19

    Local gas and liquid velocities are measured by cross-correlating signals from a double sensor hot-film anemometer probe in pure water flow and air water two-phase flow. The gas phase velocity measured in two-phase flow agrees with velocity data obtained using high-speed video to within +/-5%. A turbulent structure, present in the liquid phase, allows a correlation to be taken, which is consistent with the expected velocity profiles in pure liquid flow. This turbulent structure is also present in the liquid phase of a two-phase flow system. Therefore, a similar technique can be applied to measure the local liquid velocity in a two-phase system, when conditions permit.

  13. Gas Transfer in Cellularized Collagen-Membrane Gas Exchange Devices

    PubMed Central

    Lo, Justin H.; Bassett, Erik K.; Penson, Elliot J. N.; Hoganson, David M.

    2015-01-01

    Chronic lower respiratory disease is highly prevalent in the United States, and there remains a need for alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, provided they operate both efficiently and biocompatibly. Incorporating biomimetic materials into such devices can help replicate native gas exchange function and additionally support cellular components. In this work, we have developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in remodeling, reflected by reduced membrane thickness. Functionally, acellular collagen-membrane lung devices can mediate effective gas exchange up to ∼288 mL/min/m2 of oxygen and ∼685 mL/min/m2 of carbon dioxide, approaching the gas exchange efficiency noted in the native lung. Testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects are relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate. Finally, devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions. PMID:26020102

  14. Gas Transfer in Cellularized Collagen-Membrane Gas Exchange Devices.

    PubMed

    Lo, Justin H; Bassett, Erik K; Penson, Elliot J N; Hoganson, David M; Vacanti, Joseph P

    2015-08-01

    Chronic lower respiratory disease is highly prevalent in the United States, and there remains a need for alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, provided they operate both efficiently and biocompatibly. Incorporating biomimetic materials into such devices can help replicate native gas exchange function and additionally support cellular components. In this work, we have developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in remodeling, reflected by reduced membrane thickness. Functionally, acellular collagen-membrane lung devices can mediate effective gas exchange up to ∼288 mL/min/m(2) of oxygen and ∼685 mL/min/m(2) of carbon dioxide, approaching the gas exchange efficiency noted in the native lung. Testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects are relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate. Finally, devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions.

  15. New Mechanistic Pathways for Criegee-Water Chemistry at the Air/Water Interface.

    PubMed

    Zhu, Chongqin; Kumar, Manoj; Zhong, Jie; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng

    2016-09-07

    Understanding Criegee chemistry has become one of central topics in atmospheric research recently. The reaction of Criegee intermediates with gas-phase water clusters has been widely viewed as a key Criegee reaction in the troposphere. However, the effect of aerosols or clouds on Criegee chemistry has received little attention. In this work, we have investigated the reaction between the smallest Criegee intermediate, CH2OO, and water clusters in the gas phase, as well as at the air/water surface using ab initio quantum chemical calculations and adaptive buffered force quantum mechanics/molecular mechanics (QM/MM) dynamics simulations. Our simulation results show that the typical time scale for the reaction of CH2OO with water at the air/water interface is on the order of a few picoseconds, 2-3 orders of magnitude shorter than that in the gas phase. Importantly, the adbf-QM/MM dynamics simulations suggest several reaction pathways for the CH2OO + water reaction at the air/water interface, including the loop-structure-mediated mechanism and the stepwise mechanism. Contrary to the conventional gas-phase CH2OO reaction, the loop-structure is not a prerequisite for the stepwise mechanism. For the latter, a water molecule and the CH2OO at the air/water interface, upon their interaction, can result in the formation of (H3O)(+) and (OH)CH2(OO)(-). Thereafter, a hydrogen bond can be formed between (H3O)(+) and the terminal oxygen atom of (OH)CH2(OO)(-), leading to direct proton transfer and the formation of α-hydroxy methylperoxide, HOCH2OOH. The mechanistic insights obtained from this simulation study should motivate future experimental studies of the effect of water clouds on Criegee chemistry.

  16. Wind-driven surficial oxygen transfer and dinitrogen gas emission from treatment lagoons.

    PubMed

    Ro, K S; Hunt, P G; Poach, M E

    2006-01-01

    Surficial oxygen transfer plays an important role, when analyzing the complex biochemical and physical processes responsible for ammonia and dinitrogen gas emission in animal waste treatment lagoons. This paper analyzes if currently known nitrogen biochemical pathways can explain the enigmatic dinitrogen gas emissions recently observed from the treatment lagoons, based on the amount of wind-driven oxygen that can be transferred through the air-water interface. The stoichiometric amounts of the maximum dinitrogen gas production potential per unit mass of O(2) transferred were calculated according to three most likely biochemical pathways for ammonia removal in the treatment lagoons-classical nitrification-denitrification, partial nitrification-denitrification, and partial nitrification-Anammox. Partial nitrification-Anammox pathway would produce the largest N(2) emission, followed by partial nitrification-denitrification pathway, then by classical nitrification-denitrification pathway. In order to estimate stoichiometric amount (i.e., maximum) of N(2) emission from these pathways, we assumed that heterotrophic respiration was substantially inhibited due to high levels of free ammonia prevalent in treatment lagoons. Most observed N(2) emission data were below the maximum N(2) emission potentials by the classical nitrification-denitrification pathway. However, one value of observed N(2) emission was much higher than that could be produced by even the partial nitrification-Anammox pathway. This finding suggests yet unknown biological processes and/or non-biological nitrogen processes such as chemodenitrification may also be important in these treatment lagoons.

  17. Propagation of density disturbances in air-water flow

    NASA Technical Reports Server (NTRS)

    Nassos, G. P.

    1969-01-01

    Study investigated the behavior of density waves propagating vertically in an atmospheric pressure air-water system using a technique based on the correlation between density change and electric resistivity. This information is of interest to industries working with heat transfer systems and fluid power and control systems.

  18. The Q-sonic ultrasonic gas flowmeter for custody transfer

    SciTech Connect

    Drenthen, J.G.

    1995-12-31

    This paper presents an outline of the theory and methods applied in ultrasonic gas flow metering for custody transfer. The development of a multipath instrument for custody transfer will be discussed, and recent developments will be indicated. Practical applications are illustrated using the Servex 5-path Q.Sonic custody transfer flowmeter.

  19. The Gas Transfer through Polar Sea ice experiment: Insights into the rates and pathways that determine geochemical fluxes

    NASA Astrophysics Data System (ADS)

    Lovely, A.; Loose, B.; Schlosser, P.; McGillis, W.; Zappa, C.; Perovich, D.; Brown, S.; Morell, T.; Hsueh, D.; Friedrich, R.

    2015-12-01

    Sea ice is a defining feature of the polar marine environment. It is a critical domain for marine biota and it regulates ocean-atmosphere exchange, including the exchange of greenhouse gases such as CO2 and CH4. In this study, we determined the rates and pathways that govern gas transport through a mixed sea ice cover. N2O, SF6, 3He, 4He, and Ne were used as gas tracers of the exchange processes that take place at the ice-water and air-water interfaces in a laboratory sea ice experiment. Observation of the changes in gas concentrations during freezing revealed that He is indeed more soluble in ice than in water; Ne is less soluble in ice, and the larger gases (N2O and SF6) are mostly excluded during the freezing process. Model estimates of gas diffusion through ice were calibrated using measurements of bulk gas content in ice cores, yielding gas transfer velocity through ice (kice) of ˜5 × 10-4 m d-1. In comparison, the effective air-sea gas transfer velocities (keff) ranged up to 0.33 m d-1 providing further evidence that very little mixed-layer ventilation takes place via gas diffusion through columnar sea ice. However, this ventilation is distinct from air-ice gas fluxes driven by sea ice biogeochemistry. The magnitude of keff showed a clear increasing trend with wind speed and current velocity beneath the ice, as well as the combination of the two. This result indicates that gas transfer cannot be uniquely predicted by wind speed alone in the presence of sea ice.

  20. Direct measurements of wind-water momentum coupling in a marsh with emergent vegetation and implications for gas transfer estimates

    NASA Astrophysics Data System (ADS)

    Tse, I.; Poindexter, C.; Variano, E. A.

    2013-12-01

    Among the numerous ecological benefits of restoring wetlands is carbon sequestration. As emergent vegetation thrive, atmospheric CO2 is removed and converted into biomass that gradually become additional soil. Forecasts and management for these systems rely on accurate knowledge of gas exchange between the atmosphere and the wetland surface waters. Our previous work showed that the rate of gas transfer across the air-water interface is affected by the amount of water column mixing caused by winds penetrating through the plant canopy. Here, we present the first direct measurements of wind-water momentum coupling made within a tule marsh. This work in Twitchell Island in the California Delta shows how momentum is imparted into the water from wind stress and that this wind stress interacts with the surface waters in an interesting way. By correlating three-component velocity signals from a sonic anemometer placed within the plant canopy with data from a novel Volumetric Particle Imager (VoPI) placed in the water, we measure the flux of kinetic energy through the plant canopy and the time-scale of the response. We also use this unique dataset to estimate the air-water drag coefficient using an adjoint method.

  1. Anomalous Transmission of Infrasound Through Air-Water and Air-Ground Interfaces

    NASA Astrophysics Data System (ADS)

    Godin, O. A.

    2009-05-01

    Speed of compressional waves in air is smaller than in water and in the ground, while mass density of air is much smaller than mass densities of water and the ground. This results in a very strong acoustic impedance contrast at air-water and air-ground interfaces. Sound transmission through a boundary with a strong impedance contrast is normally very weak. This paper reports theoretical studies of the power output of localized sound sources and acoustic power fluxes through plane gas-liquid and gas-solid interfaces in a layered medium. It is found that the transparency of the interfaces increases dramatically at low frequencies. For low-frequency sound, a phenomenon of anomalous transparency can occur where most of the acoustic power generated by a source in water is radiated into the atmosphere. Contrary to the conventional wisdom based on ray-theoretical predictions and observations at higher frequencies, infrasonic energy from localized waterborne sources can be effectively transmitted into air. The main physical mechanism responsible for the anomalous transparency of air-water interface is found to be an acoustic power transfer by inhomogeneous (evanescent) waves in the plane-wave decomposition of the acoustic field in water. The effects of ocean and atmosphere stratification and of guided sound propagation in water or in air on the anomalous transparency of the air-water interface are considered. In the case of air-ground interface, the increase of the acoustic power flux into atmosphere, when a compact source approaches the interface from below, proves to be even larger than for an underwater source. The physics behind the increase of the power flux into the atmosphere, when the source depth decreases, is shown to be rather different for the air-ground and air-water interfaces. Depending on attenuation of compressional and shear waves in the ground, a leaky interface wave supported by the air-ground interface can be responsible for the bulk of acoustic power

  2. 71. DETAIL OF NITROGEN GAS STORAGE TANKS AND TRANSFER TUBING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    71. DETAIL OF NITROGEN GAS STORAGE TANKS AND TRANSFER TUBING ON SLC-3W LIQUID OXYGEN APRON - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  3. Enhancement of gas phase heat transfer by acoustic field application.

    PubMed

    Komarov, Sergey; Hirasawa, Masahiro

    2003-06-01

    This study discusses a possibility for enhancement of heat transfer between solids and ambient gas by application of powerful acoustic fields. Experiments are carried out by using preheated Pt wires (length 0.1-0.15 m, diameter 50 and 100 micro m) positioned at the velocity antinode of a standing wave (frequency range 216-1031 Hz) or in the path of a travelling wave (frequency range 6.9-17.2 kHz). A number of experiments were conducted under conditions of gas flowing across the wire surface. Effects of sound frequency, sound strength, gas flow velocity and wire preheating temperature on the Nusselt number are examined with and without sound application. The gas phase heat transfer rate is enhanced with acoustic field strength. Higher temperatures result in a vigorous radiation from the wire surface and attenuate the effect of sound. The larger the gas flow velocity, the smaller is the effect of sound wave on heat transfer enhancement.

  4. Marine bacterioplankton can increase evaporation and gas transfer bymetabolizing insoluble surfactants from the air-seawater interface.

    PubMed

    Salter, Ian; Zubkov, Mikhail V; Warwick, Phil E; Burkill, Peter H

    2009-05-01

    Hydrophobic surfactants at the air-sea interface can retard evaporative and gaseous exchange between the atmosphere and the ocean.While numerous studies have examined the metabolic role of bacterioneuston at the air-sea interface, the interactions between hydrophobic surfactants and bacterioplankton are not well constrained. A novel experimental design was developed, using Vibrio natriegens and (3)H-labelled hexadecanoic acid tracer, to determine how the bacterial metabolism of fatty acids affects evaporative fluxes. In abiotic systems, >92% of the added hexadecanoic acid remained at the air-water interface. In contrast, the presence of V. natriegens cells draws down insoluble hexadecanoic acid from the air-water interface as an exponential function of time. The exponents characterizing the removal of hexadecanoic acid from the interface co-vary with the concentration of V. natriegens cells in the underlying water, with the largest exponent corresponding to the highest cell abundance. Radiochemical budgets show that evaporative fluxes from the system are linearly proportional to the quantity of hexadecanoic acid at the interface. Thus, bacterioplankton could influence the rate of evaporation and gas transfer in the ocean through the metabolism of otherwise insoluble surfactants.

  5. Thermodynamic and transport properties of air/water mixtures

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1981-01-01

    Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.

  6. Membrane-based gas transfer: an environmental engineering laboratory.

    PubMed

    Kilduff, J; Liu, J X; Komisar, S J

    2004-01-01

    We propose an educational experience in which students design a membrane gas transfer reactor, construct a bench-scale version in the laboratory, and employ the reactor to measure mass transfer coefficients. The membrane reactor is useful for teaching mass transfer principles because the mass transfer interface is well defined and easily observed. The system can be modeled successfully using straightforward mathematics. The reactor can be designed and constructed by students, using the mathematical model as a basis, providing insight into the physical meaning of model parameters. The proposed membrane system can be readily operated to obtain data that can be employed to develop or modify existing mass transfer correlations. This can provide students with significant insight into the development of mass transfer correlations and how the constants in such correlations are typically determined. These features help promote a deeper understanding of mass transfer principles.

  7. Detectivity of gas leakage based on electromagnetic radiation transfer

    NASA Astrophysics Data System (ADS)

    Long, Yunting; Wang, Lingxue; Li, Jiakun; Zhang, Changxing; Zhang, Bei

    2011-05-01

    Standoff detection of gas leakage is a fundamental need in petrochemical and power industries. The passive gas imaging system using thermal imager has been proven to be efficient to visualize leaking gas which is not visible to the naked eye. The detection probability of gas leakage is the basis for designing a gas imaging system. Supposing the performance parameters of the thermal imager are known, the detectivity based on electromagnetic radiation transfer model to image gas leakage is analyzed. This model takes into consideration a physical analysis of the gas plume spread in the atmosphere-the interaction processes between the gas and its surrounding environment, the temperature of the gas and the background, the background surface emissivity, and also gas concentration, etc. Under a certain environmental conditions, through calculating the radiation reaching to the detector from the camera's optical field of view, we obtain an entity "Gas Equivalent Blackbody Temperature Difference (GEBTD)" which is the radiation difference between the on-plume and off-plume regions. Comparing the GEBTD with the Noise Equivalent Temperature Difference (NETD) of the thermal imager, we can know whether the system can image the gas leakage. At last, an example of detecting CO2 gas by JADE MWIR thermal imager with a narrow band-pass filter is presented.

  8. Gas transfer under high wind and its dependence on wave breaking and sea state

    NASA Astrophysics Data System (ADS)

    Brumer, Sophia; Zappa, Christopher; Fairall, Christopher; Blomquist, Byron; Brooks, Ian; Yang, Mingxi

    2016-04-01

    Quantifying greenhouse gas fluxes on regional and global scales relies on parameterizations of the gas transfer velocity K. To first order, K is dictated by wind speed (U) and is typically parameterized as a non-linear functions of U. There is however a large spread in K predicted by the traditional parameterizations at high wind speed. This is because a large variety of environmental forcing and processes (Wind, Currents, Rain, Waves, Breaking, Surfactants, Fetch) actually influence K and wind speed alone cannot capture the variability of air-water gas exchange. At high wind speed especially, breaking waves become a key factor to take into account when estimating gas fluxes. The High Wind Gas exchange Study (HiWinGS) presents the unique opportunity to gain new insights on this poorly understood aspects of air-sea interaction under high winds. The HiWinGS cruise took place in the North Atlantic during October and November 2013. Wind speeds exceeded 15 m s-1 25% of the time, including 48 hrs with U10 > 20 m s-1. Continuous measurements of turbulent fluxes of heat, momentum, and gas (CO2, DMS, acetone and methanol) were taken from the bow of the R/V Knorr. The wave field was sampled by a wave rider buoy and breaking events were tracked in visible imagery was acquired from the port and starboard side of the flying bridge during daylight hours at 20Hz. Taking advantage of the range of physical forcing and wave conditions sampled during HiWinGS, we test existing parameterizations and explore ways of better constraining K based on whitecap coverage, sea state and breaking statistics contrasting pure windseas to swell dominated periods. We distinguish between windseas and swell based on a separation algorithm applied to directional wave spectra for mixed seas, system alignment is considered when interpreting results. The four gases sampled during HiWinGS ranged from being mostly waterside controlled to almost entirely airside controlled. While bubble-mediated transfer

  9. Methylglyoxal at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Wren, S. N.; Gordon, B. P.; McWilliams, L.; Valley, N. A.; Richmond, G.

    2014-12-01

    Recently, it has been suggested that aqueous-phase processing of atmospheric α-dicarbonyl compounds such as methylglyoxal (MG) could constitute an important source of secondary organic aerosol (SOA). The uptake of MG to aqueous particles is higher than expected due to the fact that its carbonyl moieties can hydrate to form diols, as well as the fact that MG can undergo aldol condensation reactions to form larger oligomers in solution. MG is known to be surface active but an improved description of its surface behaviour is crucial to understanding MG-SOA formation, in addition to understanding its gas-to-particle partitioning and cloud forming potential. Here, we employ a combined experimental and theoretical approach involving vibrational sum frequency generation spectroscopy (VSFS), surface tensiometry, molecular dynamics simulations, and density functional theory calculations to study MG's surface adsorption, in both the presence and absence of salts. We are particularly interested in determining MG's hydration state at the surface. Our experimental results indicate that MG slowly adsorbs to the air-water interface and strongly perturbs the water structure there. This perturbation is enhanced in the presence of NaCl. Together our experimental and theoretical results suggest that singly-hydrated MG is the dominant form of MG at the surface.

  10. Heat Transfer and Cooling in Gas Turbines

    DTIC Science & Technology

    1985-09-01

    ftre remplie grace A lenregistrement sur le magnutique d’un top par tour delivre par un capteur magnetique dont l’un des ergots eat our le rotor et...fluid so that the injection-to-freestream density ratio was close to unity. The question remained as to how to utilise this data in a gas turbine...oblige A refroidir louts plates-foroes en utilisant los techniques jusqu ’ ici r~servles aux aubages (convection, films.. ). Des 6tudes

  11. Cleaning verification by air/water impingement

    NASA Technical Reports Server (NTRS)

    Jones, Lisa L.; Littlefield, Maria D.; Melton, Gregory S.; Caimi, Raoul E. B.; Thaxton, Eric A.

    1995-01-01

    This paper will discuss how the Kennedy Space Center intends to perform precision cleaning verification by Air/Water Impingement in lieu of chlorofluorocarbon-113 gravimetric nonvolatile residue analysis (NVR). Test results will be given that demonstrate the effectiveness of the Air/Water system. A brief discussion of the Total Carbon method via the use of a high temperature combustion analyzer will also be given. The necessary equipment for impingement will be shown along with other possible applications of this technology.

  12. Control Decisions for Flammable Gas Hazards in Waste Transfer Systems

    SciTech Connect

    KRIPPS, L.J.

    2000-06-28

    This report describes the control decisions for flammable gas hazards in waste transfer systems (i.e., waste transfer piping and waste transfer-associated structures) made at control decision meetings on November 30, 1999a and April 19, 2000, and their basis. These control decisions, and the analyses that support them, will be documented in an amendment to the Final Safety Analysis Report (FSAR) (CHG 2000a) and Technical Safety Requirements (TSR) (CHG 2000b) to close the Flammable Gas Unreviewed Safety Question (USQ) (Bacon 1996 and Wagoner 1996). Following the Contractor Tier I review of the FSAR and TSR amendment, it will be submitted to the US. Department of Energy (DOE), Office of River Protection (ORP) for review and approval. The control decision meeting on November 30, 1999 to address flammable gas hazards in waste transfer systems followed the control decision process and the criteria for control decisions described in Section 3.3.1.5 of the FSAR. The control decision meeting agenda, attendance list, and introductory and background presentations are included in Attachments 1 through 4. The control decision discussions on existing and other possible controls for flammable gas hazards in waste transfer systems and the basis for selecting or not selecting specific controls are summarized in this report.

  13. Micrometeorological Measurement of Fetch- and Atmospheric Stability-Dependent Air- Water Exchange of Legacy Semivolatile Organic Contaminants in Lake Superior

    NASA Astrophysics Data System (ADS)

    Perlinger, J. A.; Tobias, D. E.; Rowe, M. D.

    2008-12-01

    Coastal waters including the Laurentian Great Lakes are particularly susceptible to local, regional, and long- range transport and deposition of semivolatile organic contaminants (SOCs) as gases and/or associated with particles. Recently-marketed SOCs can be expected to undergo net deposition in surface waters, whereas legacy SOCs such as polychlorinated biphenyls (PCBs) are likely to be at equilibrium with respect to air-water exchange, or, if atmospheric concentrations decrease through, e.g., policy implementation, to undergo net gas emission. SOC air-water exchange flux is usually estimated using the two-film model. This model describes molecular diffusion through the air and water films adjacent to the air-water interface. Air-water exchange flux is estimated as the product of SOC fugacity, typically based on on-shore gaseous concentration measurements, and a transfer coefficient, the latter which is estimated from SOC properties and environmental conditions. The transfer coefficient formulation commonly applied neglects resistance to exchange in the internal boundary layer under atmospherically stable conditions, and the use of on-shore gaseous concentration neglects fetch-dependent equilibration, both of which will tend to cause overestimation of flux magnitude. Thus, for legacy chemicals or in any highly contaminated surface water, the rate at which the water is cleansed through gas emission tends to be over-predicted using this approach. Micrometeorological measurement of air-water exchange rates of legacy SOCs was carried out on ships during four transect experiments during off-shore flow in Lake Superior using novel multicapillary collection devices and thermal extraction technology to measure parts-per-quadrillion SOC levels. Employing sensible heat in the modified Bowen ratio, fluxes at three over-water stations along the transects were measured, along with up-wind, onshore gaseous concentration and aqueous concentration. The atmosphere was unstable for

  14. Heat transfer across the interface between nanoscale solids and gas.

    PubMed

    Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao

    2011-12-27

    When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ∼10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments.

  15. Air-sea transfer of gas phase controlled compounds

    NASA Astrophysics Data System (ADS)

    Yang, M.; Bell, T. G.; Blomquist, B. W.; Fairall, C. W.; Brooks, I. M.; Nightingale, P. D.

    2016-05-01

    Gases in the atmosphere/ocean have solubility that spans several orders of magnitude. Resistance in the molecular sublayer on the waterside limits the air-sea exchange of sparingly soluble gases such as SF6 and CO2. In contrast, both aerodynamic and molecular diffusive resistances on the airside limit the exchange of highly soluble gases (as well as heat). Here we present direct measurements of air-sea methanol and acetone transfer from two open cruises: the Atlantic Meridional Transect in 2012 and the High Wind Gas Exchange Study in 2013. The transfer of the highly soluble methanol is essentially completely airside controlled, while the less soluble acetone is subject to both airside and waterside resistances. Both compounds were measured concurrently using a proton-transfer-reaction mass spectrometer, with their fluxes quantified by the eddy covariance method. Up to a wind speed of 15 m s-1, observed air-sea transfer velocities of these two gases are largely consistent with the expected near linear wind speed dependence. Measured acetone transfer velocity is ∼30% lower than that of methanol, which is primarily due to the lower solubility of acetone. From this difference we estimate the “zero bubble” waterside transfer velocity, which agrees fairly well with interfacial gas transfer velocities predicted by the COARE model. At wind speeds above 15 m s-1, the transfer velocities of both compounds are lower than expected in the mean. Air-sea transfer of sensible heat (also airside controlled) also appears to be reduced at wind speeds over 20 m s-1. During these conditions, large waves and abundant whitecaps generate large amounts of sea spray, which is predicted to alter heat transfer and could also affect the air-sea exchange of soluble trace gases. We make an order of magnitude estimate for the impacts of sea spray on air-sea methanol transfer.

  16. Evaluating gas transfer velocity parameterizations using upper ocean radon distributions

    NASA Astrophysics Data System (ADS)

    Bender, Michael L.; Kinter, Saul; Cassar, Nicolas; Wanninkhof, Rik

    2011-02-01

    Sea-air fluxes of gases are commonly calculated from the product of the gas transfer velocity (k) and the departure of the seawater concentration from atmospheric equilibrium. Gas transfer velocities, generally parameterized in terms of wind speed, continue to have considerable uncertainties, partly because of limited field data. Here we evaluate commonly used gas transfer parameterizations using a historical data set of 222Rn measurements at 105 stations occupied on Eltanin cruises and the Geosecs program. We make this evaluation with wind speed estimates from meteorological reanalysis products (from National Centers for Environmental Prediction and European Centre for Medium-Range Weather Forecasting) that were not available when the 22Rn data were originally published. We calculate gas transfer velocities from the parameterizations by taking into account winds in the period prior to the date that 222Rn profiles were sampled. Invoking prior wind speed histories leads to much better agreement than simply calculating parameterized gas transfer velocities from wind speeds on the day of sample collection. For individual samples from the Atlantic Ocean, where reanalyzed winds agree best with observations, three similar recent parameterizations give k values for individual stations with an rms difference of ˜40% from values calculated using 222Rn data. Agreement of basin averages is much better. For the global data set, the average difference between k constrained by 222Rn and calculated from the various parameterizations ranges from -0.2 to +0.9 m/d (average, 2.9 m/d). Averaging over large domains, and working with gas data collected in recent years when reanalyzed winds are more accurate, will further decrease the uncertainties in sea-air fluxes.

  17. Condensation heat transfer of actual flue gas on horizontal tubes

    SciTech Connect

    Osakabe, Masahiro; Itoh, Tugue; Yagi, Kiyoyuki

    1999-07-01

    In order to improve the boiler efficiency, latent heat recovery from an exhaust flue gas is a very important concept. Condensation heat transfer on horizontal stainless steel tubes was investigated experimentally using an actual flue gas from a natural gas boiler. The experiment was conducted at different air ratios and steam mass concentrations of the flue gas, and in a wide range of tube wall temperature. The condensation pattern was similar to the dropwise condensation near the dew point. As the wall temperature was decreased, the wall region covered with a thin liquid film increased. The heat and mass transfer behavior were well predicted with the simple analogy correlation in the high wall temperature region. But in the low wall temperature region, the total heat transfer rate was higher than that predicted by the simple analogy correlation. At a high steam mass concentration artificially generated with steam injection, the total heat transfer rate was higher than that predicted by the simple analogy correlation. The analogy correlation using the modified Sherwood number taking account of the mass absorption effect was proposed. The modified correlation gave a good prediction of the heat flux at the high steam mass concentration.

  18. Simultaneous measurements of air-sea gas transfer velocity and near surface turbulence at low to moderate winds (Invited)

    NASA Astrophysics Data System (ADS)

    Wang, B.; Liao, Q.; Fillingham, J. H.; Bootsma, H. A.

    2013-12-01

    Parameterization of air-sea gas transfer velocity was routinely made with wind speed. Near surface turbulent dissipation rate has been shown to have better correlation with the gas transfer velocity in a variety of aquatic environments (i.e., the small eddy model) while wind speed is low to moderate. Wind speed model may underestimate gas transfer velocity at low to moderate winds when the near surface turbulence is produced by other environmental forcing. We performed a series of field experiments to measure the CO2 transfer velocity, and the statistics of turbulence immediately below the air-water interface using a novel floating PIV and chamber system. The small eddy model was evaluated and the model coefficient was found to be a non-constant, and it varies with the local turbulent level (figure 1). Measure results also suggested an appropriate scaling of the vertical dissipation profile immediately below the interface under non-breaking conditions, which can be parameterized by the wind shear, wave height and wave age (figure 2). Figure 1. Relation between the coefficient of the small eddy model and dissipation rate. The data also include Chu & Jirka (2003) and Vachon et al. (2010). The solid regression line: α = 0.188log(ɛ)+1.158 Figure 2. Non-dimensional dissipation profiles. Symbols: measured data with the floating PIV. Solid line: regression of measured data with a -0.79 decaying rate. Dash line with -2 slope: Terray et al. (1996) relation. Dash line with two layer structure: Siddiqui & Loewen (2007) relation.

  19. Stagnation Point Heat Transfer with Gas Injection Cooling

    NASA Technical Reports Server (NTRS)

    Vancrayenest, B.; Tran, M. D.; Fletcher, D. G.

    2005-01-01

    The present paper deals with an experimental study of the stagnation-point heat transfer to a cooled copper surface with gas injection under subsonic conditions. Test were made with a probe that combined a steady-state water-cooled calorimeter that allows the capability to study convective blockage and to perform heat transfer measurements in presence of gas injection in the stagnation region. The copper probe was pierced by 52 holes, representing 2.4% of the total probe surface. The 1.2 MW high enthalpy plasma wind tunnel was operated at anode powers between 130 and 230 kW and a static pressures from 35 hPa up to 200 hPa. Air, carbon dioxide and argon were injected in the mass flow range 0-0.4 g/s in the boundary layer developed around the 50 mm diameter probe. The measured stagnation-point heat transfer rates are reported and discussed.

  20. Heat transfer and flow characteristics on a gas turbine shroud.

    PubMed

    Obata, M; Kumada, M; Ijichi, N

    2001-05-01

    The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.

  1. Gas Requirements in Pressurized Transfer of Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Gluck, D. F.; Kline, J. F.

    1961-01-01

    Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper.

  2. Heat transfer coefficients of dilute flowing gas-solids suspensions

    NASA Technical Reports Server (NTRS)

    Kane, R. S.; Pfeffer, R.

    1973-01-01

    Heat transfer coefficients of air-glass, argon-glass, and argon-aluminum suspensions were measured in horizontal and vertical tubes. The glass, 21.6 and 36.0 micron diameter particles, was suspended at gas Reynolds numbers between 11,000 and 21,000 and loading ratios between 0 and 2.5. The presence of particles generally reduced the heat transfer coefficient. The circulation of aluminum powder in the 0.870 inch diameter closed loop system produced tenacious deposits on protuberances into the stream. In the vertical test section, the Nusselt number reduction was attributed to viscous sublayer thickening; in the horizontal test section to particle deposition.

  3. Fundamental heat transfer research for gas turbine engines

    NASA Technical Reports Server (NTRS)

    Metzger, D. E. (Editor)

    1980-01-01

    Thirty-seven experts from industry and the universities joined 24 NASA Lewis staff members in an exchange of ideas on trends in aeropropulsion research and technology, basic analyses, computational analyses, basic experiments, near-engine environment experiments, fundamental fluid mechanics and heat transfer, and hot technology as related to gas turbine engines. The workshop proceedings described include pre-workshop input from participants, presentations of current activity by the Lewis staff, reports of the four working groups, and a workshop summary.

  4. Pulsatile flow and gas transfer over arrays of cylinders

    NASA Astrophysics Data System (ADS)

    Chan, Kit Yan; Fujioka, Hideki; Grotberg, James B.

    2004-11-01

    In an artificial lung device, blood passes through arrays of porous microfibers and the gas transfer occurring across the fiber surfaces strongly depends on the flow field. Pulsatile flow distribution and gas transfer over arrays of porous microfibers (modeled as cylinders) are numerically simulated for both Newtonian and Casson fluids using Finite Volume method. Different arrangements of the cylinders: square array, rectangular array, staggered array are considered in this study. For some of the studies, the average x-velocity U(t) is described by U(t) = U0 ( 1 +A sin ( ω t) ) [1], where U0 is the time-average x-velocity, A is the amplitude of the oscillation, and ω is the frequency. For other studies, half of a cycle is described by [1] and half of the cycle U(t) = 0. The inclusion of a zero average velocity period in U(t) is physiologically a better description of the time-average velocity of blood exiting the heart. Interestingly, gas transfer increases when U(t) is described this way, due to the appearance of large vortices that enhance mixing. The existence, the size and the location of the recirculation zones are found to be controlled by array geometry and flow parameters. In general, conditions that enhance the gas transfer also at the same time increase the maximum flow resistance; such as the increase of the Reynolds number, the Womersley number, A, and cylinder density, with the exception of the increase of the yield stress for a Casson fluid. This work is supported by NIH: HL 69420.

  5. 77 FR 2293 - AmeriGas Propane, L.P., AmeriGas Propane, Inc., Energy Transfer Partners, L.P., and Energy...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... AmeriGas Propane, L.P., AmeriGas Propane, Inc., Energy Transfer Partners, L.P., and Energy Transfer...'') with AmeriGas Propane, L.P. (``AmeriGas''), AmeriGas Propane, Inc., Energy Transfer Partners, L.P. (``ETP''), and Energy Transfer Partners GP, L.P. (``ETP GP''), which is designed to guard...

  6. Reacting chemistry at the air-water interface

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Morgan, Thomas; Huwel, Lutz; Graham, William

    2016-09-01

    Plasma interaction with gas-liquid interfaces is becoming increasingly important in biological applications, chemical analysis and medicine. It introduces electrons, new ionic species and reactive species and contributes to chemical and electrical self-organization at the interface. To provide insight into the associated physics and chemistry at work in the evolution of the plasma in the air-water interface (AWI), a time-dependent one-dimensional modelling has been developed. The numerical simulation is used to solve the kinetic equations and help identify the important reaction mechanisms and describe the phenomena associated with hundreds of reacting pathways in gas-phase and liquid-phase AWI chemistry. This work was partly supported by JSPS KAKENHI Grant Number 16K04998.

  7. Pulmonary gas transfer 20 years after pneumonectomy for pulmonary tuberculosis.

    PubMed Central

    Gimeno, F; Kraan, J K; Orie, N G; Peset, R

    1977-01-01

    The changes in pulmonary function after pneumonectomy in 13 patients with pulmonary tuberculosis have been studied. The data at the time of two follow-up studies are compared with those obtained before the pneumonectomy. The first follow-up was carried out between 5 and 30 months postoperatively and the second between 20 and 24 years later. The results of this second follow-up show a relatively normal arterial oxygen saturation and gas transfer factor but an increased residual volume which cannot be explained by increasing age alone. PMID:841538

  8. A modular radiative transfer program for gas filter correlation radiometry

    NASA Technical Reports Server (NTRS)

    Casas, J. C.; Campbell, S. A.

    1977-01-01

    The fundamentals of a computer program, simulated monochromatic atmospheric radiative transfer (SMART), which calculates atmospheric path transmission, solar radiation, and thermal radiation in the 4.6 micrometer spectral region, are described. A brief outline of atmospheric absorption properties and line by line transmission calculations is explained in conjunction with an outline of the SMART computational procedures. Program flexibility is demonstrated by simulating the response of a gas filter correlation radiometer as one example of an atmospheric infrared sensor. Program limitations, input data requirements, program listing, and comparison of SMART transmission calculations are presented.

  9. Gas transfer velocities of methane and carbon dioxide in a subtropical shallow pond

    NASA Astrophysics Data System (ADS)

    Xiao, Shangbin

    2015-04-01

    Two diel field campaigns under different weather patterns were carried out in the summer and autumn of 2013 to measure CO2 and CH4 fluxes and to probe the rates of gas exchange across the air-water interface in a subtropical eutrophic pond in China. Bubble emissions of CH4 accounted for 99.7% and 91.67% of the total CH4 emission measured at two sites in the summer; however, no bubble was observed in the autumn. The pond was supersaturated with CO2 and CH4 during the monitoring period, and the saturation ratios (i.e., observed concentration / equilibrium concentration) of CH4 were much higher than that of CO2. Although the concentration of dissolved CO2 in the surface water collected in the autumn was 1.24 times of that in the summer, the mean diffusive CO2 flux across the water-air interface measured in the summer is almost twice compared with that in the autumn. The mean concentration of dissolved CH4 in the surface water in the autumn was around half of that in the summer, but the mean diffusive CH4 flux in the summer is 4-5 times of that in the autumn. Our data showed that the variation in gas exchange rate was dominated by differences in weather patterns and primary production. Averaged k600-CO2 and k600-CH4 (the gas transfer velocity normalized to a Schmidt number of 600) were 0.65 and 0.55 cm/h in the autumn, and 2.83 and 1.64 cm/h in the summer respectively. No statistically significant correlation was found between k600 and U10 (wind speed at 10 m height) in the summer at low wind speeds in clear weather. Diffusive gas fluxes increased during the nights, which resulted from the nighttime cooling effect of water surface and stronger turbulent mixing in the water column. The chemical enhancements for CO2 was estimated up to 1.94-fold in the hot and clear summer with low wind speeds, which might have been resulted from the increasing hydration reactions in water due to the high water temperature and active metabolism in planktonic algae. However, both the air

  10. Air-water interfacial areas in unsaturated soils: Evaluation of interfacial domains

    NASA Astrophysics Data System (ADS)

    Costanza-Robinson, Molly S.; Brusseau, Mark L.

    2002-10-01

    A gas-phase miscible-displacement method, using decane as an interfacial tracer, was used to measure air-water interfacial areas for a sand with water contents ranging from ˜2% to 20%. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm-1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm-1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air-water interface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas-phase versus aqueous-phase methods indicates that the gas-phase method generally yields larger interfacial areas than the aqueous-phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous- and gas-phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air-water interfaces formed by "capillary water," while gas-phase tracers measure air-water interfaces formed by both capillary and surface-adsorbed (film) water. The gas- and aqueous-phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas-phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air-water interface may be significant. Conversely, the aqueous-phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary-phase behavior.

  11. Polydopamine Films from the Forgotten Air/Water Interface.

    PubMed

    Ponzio, Florian; Payamyar, Payam; Schneider, Anne; Winterhalter, Mathias; Bour, Jérôme; Addiego, Frédéric; Krafft, Marie-Pierre; Hemmerle, Joseph; Ball, Vincent

    2014-10-02

    The formation of polydopamine under mild oxidation conditions from dopamine solutions with mechanical agitation leads to the formation of films that can functionalize all kinds of materials. In the absence of stirring of the solution, we report the formation of polydopamine films at the air/water interface (PDA A/W) and suggest that it arises from an homogeneous nucleation process. These films grow two times faster than in solution and can be deposited on hydrophilic or hydrophobic substrates by the Langmuir-Schaeffer technique. Thanks to this new method, porous and hydrophobic materials like polytetrafluoroethylene (PTFE) membranes can be completely covered with a 35 nm thick PDA A/W film after only 3h of reaction. Finally the oxidation of a monomer followed by a polymerization in water is not exclusive to polydopamine since we also transferred polyaniline functional films from the air/water interface to solid substrates. These findings suggest that self-assembly from a solution containing hydrophilic monomers undergoing a chemical transformation (here oxidation and oligomerization) could be a general method to produce films at the liquid/air interface.

  12. pCO2 distributions and air-water CO2 fluxes in the Columbia River estuary

    NASA Astrophysics Data System (ADS)

    Evans, Wiley; Hales, Burke; Strutton, Peter G.

    2013-01-01

    Sources of time and space variability in the distributions of surface water carbon dioxide partial pressure (pCO2) and air-water CO2 flux were quantified in the Columbia River estuary (CRE) during five cruises in spring, summer and autumn 2007/08. The CRE is an upwelling margin river-dominated mesotidal system that is an estuary class not represented in global flux compilations. Data from the CRE show instances of pCO2 under and oversaturation with respect to the atmosphere during every season in association with tidal, wind, biological and storm-driven sources of variability. On average the CRE is a sink for atmospheric CO2 during spring and a source during summer and autumn, with large positive air-water CO2 fluxes during the snowmelt freshet coinciding with the functional transition in the estuary. It is hypothesized here that interannual variability in size of the snowmelt freshet largely influences the extent of springtime CO2 uptake in the CRE, and subsequently the magnitude of net annual CO2 emission from the estuary. Data collected during an autumn storm show that large fluxes can drop quickly, even in the presence of high gas transfer velocities, because of rapid CO2 exchange with the atmosphere in this weakly buffered system. Combining seasonal observations of CO2 exchange with an assumption of winter conditions, we estimate that the net annual emission from the CRE is approximately 1 mol C m-2 yr-1. The air-water CO2 fluxes reported here are the first from an upwelling margin river-dominated mesotidal estuary, and the estimate of net annual exchange is substantially lower than those from other tidal and/or large river systems represented in global flux compilations.

  13. Air-water fluxes of N₂O and CH₄ during microalgae (Staurosira sp.) cultivation in an open raceway pond.

    PubMed

    Ferrón, Sara; Ho, David T; Johnson, Zackary I; Huntley, Mark E

    2012-10-02

    The industrial-scale production of biofuels from cultivated microalgae has gained considerable interest in the last several decades. While the climate benefits of microalgae cultivation that result from the capture of atmospheric CO(2) are known, the counteracting effect from the potential emission of other greenhouse gases has not been well quantified. Here, we report the results of a study conducted at an industrial pilot facility in Hawaii to determine the air-water fluxes of N(2)O and CH(4) from open raceway ponds used to grow the marine diatom Staurosira sp. as a feedstock for biofuel. Dissolved O(2), CH(4), and N(2)O concentrations were measured over a 24 h cycle. During this time, four SF(6) tracer release experiments were conducted to quantify gas transfer velocities in the ponds, and these were then used to calculate air-water fluxes. Our results show that pond waters were consistently supersaturated with CH(4) (up to 725%) resulting in an average emission of 19.9 ± 5.6 μmol CH(4) m(-2) d(-1). Upon NO(3)(-) depletion, the pond shifted from being a source to being a sink of N(2)O, with an overall net uptake during the experimental period of 3.4 ± 3.5 μmol N(2)O m(-2) d(-1). The air-water fluxes of N(2)O and CH(4) expressed as CO(2) equivalents of global warming potential were 2 orders of magnitude smaller than the overall CO(2) uptake by the microalgae.

  14. Steady-state and time-resolved study of two-dimensional Foerster energy transfer between 4-heptadecyl-7-hydroxycoumarin and RhB-DPPE in phospholipid air-water monolayers

    SciTech Connect

    Urquhart, R.; Grieser, F.; Thistlethwaite, P.

    1992-09-17

    This study utilizes the Foerster energy transfer technique to examine the state of aggregation of the phospholipid N-[[(lissamine rhodamine B)sulfonyl]dipalmitoyl]-L-{alpha}-phosphatidylethanolamine triethylammonium salt in dipalmitoyl-L-{alpha}-phosphatidylcholine matrices in various phases using time-resolved and steady-state fluorescence spectroscopy.

  15. An investigation of condensation heat transfer in a closed tube containing a soluble noncondensable gas

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Hanson, R. J.

    1976-01-01

    An exact one-dimensional condensation heat transfer model for insoluble gases has been developed and compared with experimental data. Modifications to this model to accommodate soluble gas behavior have also been accomplished, and the effects on gas front behavior demonstrated. Analytical models for condensation heat transfer are documented, and a novel optical method used for measuring gas concentration profiles is outlined.

  16. Fugacity gradients of hydrophobic organics across the air-water interface measured with a novel passive sampler.

    PubMed

    Wu, Chen-Chou; Yao, Yao; Bao, Lian-Jun; Wu, Feng-Chang; Wong, Charles S; Tao, Shu; Zeng, Eddy Y

    2016-11-01

    Mass transfer of hydrophobic organic contaminants (HOCs) across the air-water interface is an important geochemical process controlling the fate and transport of HOCs at the regional and global scales. However, few studies have characterized concentration or fugacity profiles of HOCs near both sides of the air-water interface, which is the driving force for the inter-compartmental mass transfer of HOCs. Herein, we introduce a novel passive sampling device which is capable of measuring concentration (and therefore fugacity) gradients of HOCs across the air-water interface. Laboratory studies indicated that the escaping fugacity values of polycyclic aromatic hydrocarbons (PAHs) from water to air were negatively correlated to their volatilization half-lives. Results for field deployment were consistent between the passive sampler and an active method, i.e., a combination of grab sampling and liquid-liquid extraction. In general, the fugacity profiles of detected PAHs were indicative of an accumulation mechanism in the surface microlayer of the study regions (Haizhu Lake and Hailing Bay of Guangdong Province, China), while p,p'-DDD tended to volatilize from water to the atmosphere in Hailing Bay. Furthermore, the fugacity profiles of the target analytes increased towards the air-water interface, reflecting the complexity of environmental behavior of the target analytes near the air-water interface. Overall, the passive sampling device provides a novel means to better characterize the air-water diffusive transfer of HOCs, facilitating the understanding of the global cycling of HOCs.

  17. Human Regional Pulmonary Gas Exchange with Xenon Polarization Transfer (XTC)

    NASA Astrophysics Data System (ADS)

    Muradian, Iga; Butler, James; Hrovat, Mirko; Topulos, George; Hersman, Elizabeth; Ruset, Iulian; Covrig, Silviu; Frederick, Eric; Ketel, Stephen; Hersman, F. W.; Patz, Samuel

    2007-03-01

    Xenon Transfer Contrast (XTC) is an existing imaging method (Ruppert et al, Magn Reson Med, 51:676-687, 2004) that measures the fraction F of ^129Xe magnetization that diffuses from alveolar gas spaces to septal parenchymal tissue in lungs in a specified exchange time. As previously implemented, XTC is a 2-breath method and has been demonstrated in anesthetized animals. To use XTC in humans and to avoid issues associated with obtaining identical gas volumes on subsequent breath-hold experiments as well as precise image registration in post-processing, a single breath XTC method was developed that acquires three consecutive gradient echo images in an 8s acquisition. We report here initial measurements of the mean and variance of F for 5 normal healthy subjects as well as 7 asymptomatic smokers. The experiments were performed at two lung volumes (˜45 and 65% of TLC). We found that both the mean and variance of F increased with smoking history. In comparison, standard pulmonary function tests such as DLCO FEV1 showed no correlation with smoking history.

  18. Influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of persistent organic pollutants

    SciTech Connect

    Dachs, J.; Eisenreich, S.J.; Hoff, R.M.

    2000-03-15

    The influence of eutrophication on the biogeochemical cycles of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) is largely unknown. In this paper, the application of a dynamic air-water-phytoplankton exchange model to Lake Ontario is used as a framework to study the influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of POPs. The results of these simulations demonstrate that air-water exchange controls phytoplankton concentrations in remote aquatic environments with little influence from land-based sources of pollutants and supports levels in even historically contaminated systems. Furthermore, eutrophication or high biomass leads to a disequilibrium between the gas and dissolved phase, enhanced air-water exchange, and vertical sinking fluxes of PCBs. Increasing biomass also depletes the water concentrations leading to lower than equilibrium PCB concentrations in phytoplankton. Implications to future trends in PCB pollution in Lake Ontario are also discussed.

  19. Air-water flow in subsurface systems

    NASA Astrophysics Data System (ADS)

    Hansen, A.; Mishra, P.

    2013-12-01

    Groundwater traces its roots to tackle challenges of safe and reliable drinking water and food production. When the groundwater level rises, air pressure in the unsaturated Vadose zone increases, forcing air to escape from the ground surface. Abnormally high and low subsurface air pressure can be generated when the groundwater system, rainfall, and sea level fluctuation are favorably combined [Jiao and Li, 2004]. Through this process, contamination in the form of volatile gases may diffuse from the ground surface into residential areas, or possibly move into groundwater from industrial waste sites. It is therefore crucial to understand the combined effects of air-water flow in groundwater system. Here we investigate theoretically and experimentally the effects of air and water flow in groundwater system.

  20. Detachment of colloids from a solid surface by a moving air-water interface.

    PubMed

    Sharma, Prabhakar; Flury, Markus; Zhou, Jun

    2008-10-01

    Colloid attachment to liquid-gas interfaces is an important process used in industrial applications to separate suspended colloids from the fluid phase. Moving gas bubbles can also be used to remove colloidal dust from surfaces. Similarly, moving liquid-gas interfaces lead to colloid mobilization in the natural subsurface environment, such as in soils and sediments. The objective of this study was to quantify the effect of moving air-water interfaces on the detachment of colloids deposited on an air-dried glass surface, as a function of colloidal properties and interface velocity. We selected four types of polystyrene colloids (positive and negative surface charge, hydrophilic and hydrophobic). The colloids were deposited on clean microscope glass slides using a flow-through deposition chamber. Air-water interfaces were passed over the colloid-deposited glass slides, and we varied the number of passages and the interface velocity. The amounts of colloids deposited on the glass slides were visualized using confocal laser scanning microscopy and quantified by image analysis. Our results showed that colloids attached under unfavorable conditions were removed in significantly greater amounts than those attached under favorable conditions. Hydrophobic colloids were detached more than hydrophilic colloids. The effect of the air-water interface on colloid removal was most pronounced for the first two passages of the air-water interface. Subsequent passages of air-water interfaces over the colloid-deposited glass slides did not cause significant additional colloid removal. Increasing interface velocity led to decreased colloid removal. The force balances, calculated from theory, supported the experimental findings, and highlight the dominance of detachment forces (surface tension forces) over the attachment forces (DLVO forces).

  1. Biological conversion of synthesis gas. Mass transfer/kinetic studies

    SciTech Connect

    Klasson, K.T.; Basu, R.; Johnson, E.R.; Clausen, E.C.; Gaddy, J.L.

    1992-03-01

    Mass transfer and kinetic studies were carried out for the Rhodospirillum rubrum and Chlorobium thiosulfatophilum bacterial systems. R. rubrum is a photosynthetic anaerobic bacterium which catalyzes the biological water gas shift reaction: CO + H{sub 2}0 {yields} CO{sub 2} + H{sub 2}. C. thiosulfatophilum is also a H{sub 2}S and COS to elemental sulfur. The growth of R. rubrum may be satisfactorily carried out at 25{degree} and 30{degree}C, while CO uptake and thus the conversion of CO best occurs at temperatures of either 30{degree}, 32{degree} or 34{degree}C. The rate of conversion of COs and H{sub 2}O to CO{sub 2} and H{sub 2}S may be modeled by a first order rate expression. The rate constant at 30{degree}C was found to be 0.243 h{sup {minus}1}. The growth of C. thiosulfatophilum may be modeled in terms of incoming light intensity using a Monod equation: {mu} = {sub 351} + I{sub o}/{sup 0.152}I{sub o}. Comparisons of the growth of R. rubrum and C. thiosulfatophilum shows that the specific growth rate of C. thiosulfatophilum is much higher at a given light intensity.

  2. An investigation of condensation heat transfer in a closed tube containing a soluble noncondensable gas

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Hanson, R. J.

    1976-01-01

    A more exact one-dimensional condensation heat transfer model for insoluble gases was developed and compared with experimental data. Modifications to this model to accommodate soluble gas behavior were also accomplished, and the effects on gas front behavior demonstrated. Analytical models for condensation heat transfer are documented, and an optical method used for measuring gas concentration profiles is outlined. Experimental data is then presented and interpreted.

  3. Physicochemical Study of Viral Nanoparticles at the Air/Water Interface.

    PubMed

    Torres-Salgado, Jose F; Comas-Garcia, Mauricio; Villagrana-Escareño, Maria V; Durán-Meza, Ana L; Ruiz-García, Jaime; Cadena-Nava, Ruben D

    2016-07-07

    The assembly of most single-stranded RNA (ssRNA) viruses into icosahedral nucleocapsids is a spontaneous process driven by protein-protein and RNA-protein interactions. The precise nature of these interactions results in the assembly of extremely monodisperse and structurally indistinguishable nucleocapsids. In this work, by using a ssRNA plant virus (cowpea chlorotic mottle virus [CCMV]) as a charged nanoparticle we show that the diffusion of these nanoparticles from the bulk solution to the air/water interface is an irreversible adsorption process. By using the Langmuir technique, we measured the diffusion and adsorption of viral nucleocapsids at the air/water interface at different pH conditions. The pH changes, and therefore in the net surface charge of the virions, have a great influence in the diffusion rate from the bulk solution to the air/water interface. Moreover, assembly of mesoscopic and microscopic viral aggregates at this interface depends on the net surface charge of the virions and the surface pressure. By using Brewster's angle microscopy we characterized these structures at the interface. Most common structures observed were clusters of virions and soap-frothlike micron-size structures. Furthermore, the CCMV films were compressed to form monolayers and multilayers from moderate to high surface pressures, respectively. After transferring the films from the air/water interface onto mica by using the Langmuir-Blodgett technique, their morphology was characterized by atomic force microscopy. These viral monolayers showed closed-packing nano- and microscopic arrangements.

  4. Bio-inspired evaporation through plasmonic film of nanoparticles at the air-water interface.

    PubMed

    Wang, Zhenhui; Liu, Yanming; Tao, Peng; Shen, Qingchen; Yi, Nan; Zhang, Fangyu; Liu, Quanlong; Song, Chengyi; Zhang, Di; Shang, Wen; Deng, Tao

    2014-08-27

    Plasmonic gold nanoparticles self-assembled at the air-water interface to produce an evaporative surface with local control inspired by skins and plant leaves. Fast and efficient evaporation is realized due to the instant and localized plasmonic heating at the evaporative surface. The bio-inspired evaporation process provides an alternative promising approach for evaporation, and has potential applications in sterilization, distillation, and heat transfer.

  5. Fundamental mechanisms that influence the estimate of heat transfer to gas turbine blades

    NASA Technical Reports Server (NTRS)

    Graham, R. W.

    1979-01-01

    Estimates of the heat transfer from the gas to stationary (vanes) or rotating blades poses a major uncertainty due to the complexity of the heat transfer processes. The gas flow through these blade rows is three dimensional with complex secondary viscous flow patterns that interact with the endwalls and blade surfaces. In addition, upstream disturbances, stagnation flow, curvature effects, and flow acceleration complicate the thermal transport mechanisms in the boundary layers. Some of these fundamental heat transfer effects are discussed. The chief purpose of the discussion is to acquaint those in the heat transfer community, not directly involved in gas turbines, of the seriousness of the problem and to recommend some basic research that would improve the capability for predicting gas-side heat transfer on turbine blades and vanes.

  6. Heat transfer between a stationary granular packing and a descending flow of dusty gas

    SciTech Connect

    Dryabin, V.A.; Galershtein, D.M.

    1988-10-01

    The transfer of heat from a stationary granular bed (packing) to a gas-particle flow has been investigated experimentally. Heat transfer experiments were carried out on an apparatus with an open gas-particle flow system. Monodisperse packing comprised of smooth steel balls or round porcelain granules was used. Particles used in the gas flow consisted of grades of sand and electrical corundum. The external heat transfer coefficient was determined by local modeling of heat transfer in the steady temperature field regime. Calorimetry was used for determining this regime as well as the temperature of the air and dusty gas. A correlation was obtained for calculating the heat-transfer coefficient in the system.

  7. Interplay between oxygen demand reactions and kinetic gas-water transfer in porous media.

    PubMed

    Oswald, Sascha E; Griepentrog, Marco; Schirmer, Mario; Balcke, Gerd U

    2008-08-01

    Gas-water phase transfer associated with the dissolution of trapped gas in porous media is a key process that occurs during pulsed gas sparging operations in contaminated aquifers. Recently, we applied a numerical model that was experimentally validated for abiotic situations, where multi-species kinetic inter-phase mass transfer and dissolved gas transport occurred during pulsed gas penetration-dissolution events [Balcke, G.U., Meenken, S., Hoefer, C. and Oswald, S.E., 2007. Kinetic gas-water transfer and gas accumulation in porous media during pulsed oxygen sparging. Environmental Science & Technology 41(12), 4428-4434]. Here we extend the model by using a reactive term to describe dissolved oxygen demand reactions via the formation of a reaction product, and to study the effects of such an aerobic degradation process on gas-water mass transfer and dissolution of trapped gas in porous media. As a surrogate for microbial oxygen reduction, first-order oxygen demand reactions were based on the measured oxidation of alkaline pyrogallol in column experiments. This reaction allows for adjusting the rate to values close to expected biodegradation rates and detection of the reaction product. The experiments and model consistently demonstrated accelerated oxygen gas-water mass transfer with increasing oxygen demand rates associated with an influence on the partitioning of other gases. Thus, as the oxygen demand accelerates, less gas phase residues, consisting mainly of nitrogen, are observed, which is in general beneficial to the performance of field biosparging operations. Model results additionally predict how oxygen demand influences oxygen mass transfer for a range of biodegradation rates. A typical field case scenario was simulated to illustrate the observed coupling of oxygen consumption and gas bubble dissolution. The model provides a tool to improve understanding of trapped gas behavior in porous media and contributes to a model-assisted biosparging.

  8. Effect of surface roughness on rarefied-gas heat transfer in microbearings

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Ming; Meng, Guang; Wei, Xue-Yong; Peng, Zhi-Ke

    2012-01-01

    In this Letter, the rarefaction and roughness effects on the heat transfer process in gas microbearings are investigated. A heat transfer model is developed by introducing two-variable Weierstrass-Mandelbrot (W-M) function with fractal geometry. The heat transfer problem in the multiscale self-affine rough microbearings at slip flow regime is analyzed and discussed. The results show that rarefaction has more significant effect on heat transfer in rough microbearings with lower fractal dimension. The negative influence of roughness on heat transfer found to be the Nusselt number reduction. The heat transfer performance can be optimized with increasing fractal dimension of the rough surface.

  9. The potential role of sea spray droplets in facilitating air-sea gas transfer

    NASA Astrophysics Data System (ADS)

    Andreas, E. L.; Vlahos, P.; Monahan, E. C.

    2016-05-01

    For over 30 years, air-sea interaction specialists have been evaluating and parameterizing the role of whitecap bubbles in air-sea gas exchange. To our knowledge, no one, however, has studied the mirror image process of whether sea spray droplets can facilitate air-sea gas exchange. We are therefore using theory, data analysis, and numerical modeling to quantify the role of spray on air-sea gas transfer. In this, our first formal work on this subject, we seek the rate-limiting step in spray-mediated gas transfer by evaluating the three time scales that govern the exchange: τ air , which quantifies the rate of transfer between the atmospheric gas reservoir and the surface of the droplet; τ int , which quantifies the exchange rate across the air-droplet interface; and τ aq , which quantifies gas mixing within the aqueous solution droplet.

  10. Air-water interface equilibrium partitioning coefficients of aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Cheng, Wen-Hsi; Chu, Fu-Sui; Liou, Jia-Jiunn

    The single equilibration technique was used to determine the equilibrium partitioning coefficients ( pc) of an air-water interface for target aromatic volatile organic compounds (VOCs), including benzene, toluene and ethylbenzene. The tested liquid concentrations ( CL) of VOC ranged from 0.5 to 20 mg/l, and the temperatures ( Tw) of the solutions were 300, 305, 310 and 315 K, respectively. The pc values were calculated using the gaseous concentrations ( Cg*) of aromatic hydrocarbons in equilibrium with the aqueous phase and the formula pc=( Cg*/ CL). The heats of VOC of liquid and gaseous phase transfer (Δ Htr) in pure water, and the highly linear regression relationship (with squared correlation coefficients, R2, from 0.900 to 0.999) between ( ln C g*) and (1/ Tw) are also evaluated. Experimental results indicated that the pc values of the target VOC components increase with Tw but, in contrast, are not significantly affected by CL in pure water. However, pc of more soluble compounds, like iso-propanol and methyl ethyl ketone, have been evaluated to be significant with CL in the earlier investigation. Finally, the co-solute effect on pc is also evaluated in this work, as determining pc of the aromatic hydrocarbons by using aqueous ethanol (in a volume ration of 1-15%) as solutes.

  11. Dissolved gas dynamics in wetland soils: Root-mediated gas transfer kinetics determined via push-pull tracer tests

    NASA Astrophysics Data System (ADS)

    Reid, Matthew C.; Pal, David S.; Jaffé, Peter R.

    2015-09-01

    Gas transfer processes are fundamental to the biogeochemical and water quality functions of wetlands, yet there is limited knowledge of the rates and pathways of soil-atmosphere exchange for gases other than oxygen and methane (CH4). In this study, we use a novel push-pull technique with sulfur hexafluoride (SF6) and helium (He) as dissolved gas tracers to quantify the kinetics of root-mediated gas transfer, which is a critical efflux pathway for gases from wetland soils. This tracer approach disentangles the effects of physical transport from simultaneous reaction in saturated, vegetated wetland soils. We measured significant seasonal variation in first-order gas exchange rate constants, with smaller spatial variations between different soil depths and vegetation zones in a New Jersey tidal marsh. Gas transfer rates for most biogeochemical trace gases are expected to be bracketed by the rate constants for SF6 and He, which ranged from ˜10-2 to 2 × 10-1 h-1 at our site. A modified Damköhler number analysis is used to evaluate the balance between biochemical reaction and root-driven gas exchange in governing the fate of environmental trace gases in rooted, anaerobic soils. This approach confirmed the importance of plant gas transport for CH4, and showed that root-driven transport may affect nitrous oxide (N2O) balances in settings where N2O reduction rates are slow.

  12. Heat transfer between stratified immiscible liquid layers driven by gas bubbling across the interface

    SciTech Connect

    Greene, G.A.; Irvine, T.F. Jr.

    1988-01-01

    The modeling of molten core debris in the CORCON and VANESA computer codes as overlying, immiscible liquid layers is discussed as it relates to the transfer of heat and mass between the layers. This initial structure is identified and possible configurations are discussed. The stratified, gas-sparged configuration that is presently employed in CORCON and VANESA is examined and the existing literature for interlayer heat transfer is assessed. An experiment which was designed to measure interlayer heat transfer with gas sparging is described. The results are presented and compared to previously existing models. A dimensionless correlation for stratified, interlayer heat transfer with gas sparging is developed. This relationship is recommended for inclusion in CORCON-MOD2 for heat transfer between stratified, molten liquid layers. 12 refs., 6 figs., 3 tabs.

  13. Flow and heat transfer in gas turbine disk cavities subject to nonuniform external pressure field

    SciTech Connect

    Roy, R.P.; Kim, Y.W.; Tong, T.W.

    1995-12-31

    Ingestion of hot gas from the main-stream gas path into turbine disk cavities, particularly the first-stage disk cavity, has become a serious concern for the next-generation industrial gas turbines features high rotor inlet temperature. Fluid temperature in the cavities increases further due to windage generated by fluid drag at the rotating and stationary surfaces. The resulting problem of rotor disk heat-up is exacerbated by the high disk rim temperature due to adverse (relatively flat) temperature profile of the mainstream gas in the annular flow passage of the turbine. This describes an investigation into local convective heat transfer coefficient and cooling effectiveness of the rotor disk, flow field in the disk cavity, computation of the flow field and heat transfer in the disk cavity, and mainstream gas injection and rotor disk cooling effectiveness by mass transfer analogy.

  14. Regularities of asymmetric gas transfer in PVTMS- membranes

    NASA Astrophysics Data System (ADS)

    Skuridin, I. E.; Kurchatov, I. M.; Laguntsov, N. I.

    2016-09-01

    In this work the dependence of permeability of the polymer asymmetric gas- separation membrane on its orientation relative to the areas of high and low pressure was investigated. It is shown that under different directions of gas supply, permeability values are not the same due to the characteristics of the asymmetry of the object.

  15. Mass transfer from bypassed zones during gas injection

    SciTech Connect

    Burger, J.E.; Mohanty, K.K.

    1995-12-31

    Gasflooding in oil reservoirs leads to bypassing of the oil due to gravitational, viscous and/or heterogeneity effects. The bypassed oil can be recovered by the flowing solvent by pressure-driven, gravity-driven, dispersion/diffusion-driven and capillarity-driven crossflow/mass transfer. It is difficult to represent all of these mechanisms explicitly in large-scale simulations. In this work, we have studied the effect of the orientation of the bypassed region and the enrichment of the solvent on the mass transfer. Laboratory-scale mass transfer and coreflood experiments were conducted. Numerical simulation was used to identify the role of the different mechanisms. Results indicate that the mass transfer is the least for the vertical orientation, intermediate for the inverted orientation and the highest for the horizontal orientation. The mass transfer increases with enrichment for all orientations. Liquid phase diffusion controls vertical orientation mass transfer for the fluids studied. Phase behavior determines the liquid phase saturation. Capillary pumping does not contribute to the mass transfer of oil because the interfacial tension decreases towards the flowing region. Gravity-driven flow contributes the most to the mass transfer in the horizontal and the inverted orientations. The gravity-driven flow, however, is impeded by the capillarity whose magnitude decreases with solvent enrichment. Oil recovery in the horizontal gasfloods is nonmonotonic with enrichment for this fluid system in an almost homogeneous Berea core. Multiphase flow in the near-miscible floods leads to less gravity override compared to the FCM floods. In the heterogeneous core studied, the heterogeneity is very strong and the capillary forces do not prevent bypassing. The capillary forces, in fact, reduce oil recovery by diminishing mass transfer from the bypassed regions.

  16. Evolution of Nanoflowers and Nanospheres of Zinc Bisporphyrinate Tweezers at the Air/water Interface.

    PubMed

    Xie, Fan; Zhuo, Congcong; Hu, Chuanjiang; Liu, Ming Hua

    2017-03-22

    While the sophisticated Langmuir and Langmuir-Blodgett technique facilitates the fabrication of uniform ultrathin monolayer and films, it is also revealed as a powerful tool for the bottom-up constructions of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked Zinc bis-porphyrinate tweezers using the Langmuir and Langmuir-Blodgett (LB) technique. It was found that both the two tweezer type Zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates by the vertical lifting method. The atomic force microscope (AFM) revealed that at the initial spreading stage the compound formed flat disk-like domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

  17. Thermal Battery Operating Gas Atmosphere Control and Heat Transfer Optimization

    DTIC Science & Technology

    2012-09-01

    Approved for public release; distribution unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The effects of gases and gas mixtures on global...highly effective in atmospheres of pure hydrogen and are potentially useful in mixtures of hydrogen and air. Barium chromate (BaCrO4) placed in contact...15 Figure 9. Gas gettering from a 79.6/20.4 volume percent hydrogen/air mixture

  18. Gas Turbine/Solar Parabolic Trough Hybrid Design Using Molten Salt Heat Transfer Fluid: Preprint

    SciTech Connect

    Turchi, C. S.; Ma, Z.

    2011-08-01

    Parabolic trough power plants can provide reliable power by incorporating either thermal energy storage (TES) or backup heat from fossil fuels. This paper describes a gas turbine / parabolic trough hybrid design that combines a solar contribution greater than 50% with gas heat rates that rival those of natural gas combined-cycle plants. Previous work illustrated benefits of integrating gas turbines with conventional oil heat-transfer-fluid (HTF) troughs running at 390?C. This work extends that analysis to examine the integration of gas turbines with salt-HTF troughs running at 450 degrees C and including TES. Using gas turbine waste heat to supplement the TES system provides greater operating flexibility while enhancing the efficiency of gas utilization. The analysis indicates that the hybrid plant design produces solar-derived electricity and gas-derived electricity at lower cost than either system operating alone.

  19. Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures

    NASA Technical Reports Server (NTRS)

    Reid, R. S.; Martin, J. J.; Yocum, D. J.; Stewart, E. T.

    2007-01-01

    Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces.

  20. OGO-6 gas-surface energy transfer experiment

    NASA Technical Reports Server (NTRS)

    Mckeown, D.; Dummer, R. S.; Bowyer, J. M., Jr.; Corbin, W. E., Jr.

    1973-01-01

    The kinetic energy flux of the upper atmosphere was analyzed using OGO-6 data. Energy transfer between 10 microwatts/sq cm and 0.1 W/sq cm was measured by short-term frequency changes of temperature-sensitive quartz crystals used in the energy transfer probe. The condition of the surfaces was continuously monitored by a quartz crystal microbalance to determine the effect surface contamination had on energy accommodation. Results are given on the computer analysis and laboratory tests performed to optimize the operation of the energy transfer probe. Data are also given on the bombardment of OGO-6 surfaces by high energy particles. The thermoelectrically-cooled quartz crystal microbalance is described in terms of its development and applications.

  1. Radiative transfer effects on reflected shock waves. II - Absorbing gas.

    NASA Technical Reports Server (NTRS)

    Su, F. Y.; Olfe, D. B.

    1972-01-01

    Radiative cooling effects behind a reflected shock wave are calculated for an absorbing-emitting gas by means of an expansion procedure in the small density ratio across the shock front. For a gray gas shock layer with an optical thickness of order unity or less the absorption integral is simplified by use of the local temperature approximation, whereas for larger optical thicknesses a Rosseland diffusion type of solution is matched with the local temperature approximation solution. The calculations show that the shock wave will attenuate at first and then accelerate to a constant velocity. Under appropriate conditions the gas enthalpy near the wall may increase at intermediate times before ultimately decreasing to zero. A two-band absorption model yields end-wall radiant-heat fluxes which agree well with available shock-tube measurements.

  2. Optimizing Geothermal Drilling: Oil and Gas Technology Transfer

    SciTech Connect

    Denninger, Kate; Eustes, Alfred; Visser, Charles; Baker, Walt; Bolton, Dan; Bell, Jason; Bell, Sean; Jacobs, Amelia; Nagandran, Uneshddarann; Tilley, Mitch; Quick, Ralph

    2015-09-02

    There is a significant amount of financial risk associated with geothermal drilling. This study of drilling operations seeks opportunities to improve upon current practices and technologies. The scope of this study included analyzing 21 geothermal wells and 21 oil and gas wells. The goal was to determine a 'Perfect Well' using historical data to compare the best oil and gas well to the best geothermal well. Unfortunately, limitations encountered in the study included missing data (bit records, mud information, etc.) and poor data collection practices An online software database was used to format drilling data to IADC coded daily drilling reports and generate figures for analysis. Six major issues have been found in geothermal drilling operations. These problems include lost circulation, rig/ equipment selection, cementing, penetration rate, drilling program, and time management. As a result of these issues, geothermal drilling averaged 56.4 days longer than drilling comparable oil and gas wells in the wells in this study. Roughly $13.9 million was spent on non-productive time in the 21 geothermal wells, compared with only $1.3 million in the oil and gas wells, assuming a cost of $50,000 per day. Comparable events such as drilling the same sized hole, tripping in/out, cementing, and running the same size casing took substantially less time in the oil and gas wells. Geothermal wells were drilled using older and/or less advanced technology to depths less than 10,000 feet, while oil and gas wells reached 12,500 feet faster with purpose built rigs. A new approach is now underway that will optimize drilling programs throughout the drilling industry using Mechanical Specific Energy (MSE) as a tool to realize efficient drilling processes. Potential improvements for current geothermal operations are: the use of electronic records, real time services, and official glossary terms to describe rig operations, and advanced drilling rigs/technology.

  3. Recent progress in research pertaining to estimates of gas-side heat transfer in an aircraft gas turbine

    NASA Technical Reports Server (NTRS)

    Graham, Robert W.

    1989-01-01

    A decade ago several important fundamental heat transfer phenomena were identified which were considered basic to the ability to predict heat transfer loads in aircraft gas turbines. The progress in addressing these fundamentals over the past ten years is assessed. Much reseach effort has been devoted to their study in university, industry and government labs and significant progress has been achieved. Advances in computer technology have enabled the modeling of complex 3-D fluid flow in gas turbines so necessary for heat transfer calculations. Advances in instrumentation plus improved data acquisition have brought about more reliable data sets. While much has advanced in the 1980's, much challenging research remains to be done. Several of these areas are suggested.

  4. Proton transfer in gas-phase ammonium dinitramide clusters

    NASA Astrophysics Data System (ADS)

    Alavi, Saman; Thompson, Donald L.

    2003-02-01

    Proton transfer in gaseous ammonium dinitramide (ADN) clusters up to (ADN)2 is studied by using density-functional theory. Proton transfer between the hydrogen dinitramide and ammonia units does not occur in the ADN monomer, rather the ammonia-hydrogen dinitramide complex is stabilized by strong hydrogen bonding. However, proton transfer between hydrogen dinitramide and ammonia is observed in the ADN dimer [NH3HN(NO2)2]2, ADN solvated with a single ammonia molecule [NH3NH(NO2)2]NH3, and ADN solvated with a hydrogen dinitramide molecule [NH3HN(NO2)2]HN(NO2)2. Structural changes in the complexes relative to the free molecules and the binding energies of the clusters are given. Using population analysis, the total electrostatic interaction energy in each cluster is calculated. The electrostatic energy is a measure that distinguishes between the ionic or hydrogen-bonded nature of the clusters. Some implications of proton transfer in ADN clusters on the decomposition mechanism of ADN are discussed.

  5. Interaction of heat transfer and gas flow in a vertical hot tube

    NASA Astrophysics Data System (ADS)

    Abolpour, Bahador; Afsahi, M. Mehdi; Yaghobi, Mohsen; Goharrizi, Ataallah Soltani; Azizkarimi, Mehdi

    2017-02-01

    One of the main interests in industries, especially metallurgical industries, is improving the overall rate of the processes. A solution for this issue in the processes including gas phase (such as gas-solid reactions) is operating at high temperature. Mechanism of heat transfer to the gas phase at this condition is complex regarding effect of temperature on the gas properties. In this study, interaction of heat transfer and gas flow in a vertical hot tube has been investigated, experimentally and numerically. Finally, effects of inlet volumetric flow rate, gaseous type, extent of the tube wall heat flux and tube diameter on temperature and velocity distributions of the gaseous phase inside the tube have been studied.

  6. Nitrogen as an indicator of mass transfer during in-situ gas sparging

    NASA Astrophysics Data System (ADS)

    Balcke, Gerd U.; Hahn, M.; Oswald, Sascha E.

    2011-09-01

    Aiming at the stimulation of intrinsic microbial activity, pulses of pure oxygen or pressurized air were recurrently injected into groundwater polluted with chlorobenzene. To achieve well-controlled conditions and intensive sampling, a large, vertical underground tank was filled with the local unconfined sandy aquifer material. In the course of two individual gas injections, one using pure oxygen and one using pressurized air, the mass transfer of individual gas species between trapped gas phase and groundwater was studied. Field data on the dissolved gas composition in the groundwater were combined with a kinetic model on gas dissolution and transport in porous media. Phase mass transfer of individual gas components caused a temporary enrichment of nitrogen, and to a lower degree of methane, in trapped gas leading to the formation of excess dissolved nitrogen levels downgradient from the dissolving gas phase. By applying a novel gas sampling method for dissolved gases in groundwater it was shown that dissolved nitrogen can be used as a partitioning tracer to indicate complete gas dissolution in porous media.

  7. Analysis of Gas Turbine Rotor Blade Tip and Shroud Heat Transfer

    NASA Technical Reports Server (NTRS)

    Ameri, A. A.; Steinthorsson, E.

    1996-01-01

    Predictions of the rate of heat transfer to the tip and shroud of a gas turbine rotor blade are presented. The simulations are performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations. The effect of inlet boundary layer thickness as well as rotation rate on the tip and shroud heat transfer is examined. The predictions of the blade tip and shroud heat transfer are in reasonable agreement with the experimental measurements. Areas of large heat transfer rates are identified and physical reasoning for the phenomena presented.

  8. 40 CFR 63.984 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Fuel Gas System or a Process § 63.984 Fuel gas systems and processes to which storage vessel, transfer... 40 Protection of Environment 11 2013-07-01 2013-07-01 false Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak regulated material emissions are routed....

  9. 40 CFR 63.984 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Fuel Gas System or a Process § 63.984 Fuel gas systems and processes to which storage vessel, transfer... 40 Protection of Environment 11 2012-07-01 2012-07-01 false Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak regulated material emissions are routed....

  10. 40 CFR 63.984 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Fuel Gas System or a Process § 63.984 Fuel gas systems and processes to which storage vessel, transfer... 40 Protection of Environment 11 2014-07-01 2014-07-01 false Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak regulated material emissions are routed....

  11. Coupling of phytoplankton uptake and air-water exchange of persistent organic pollutants

    SciTech Connect

    Dachs, J.; Eisenreich, S.J.; Baker, J.E.; Ko, F.C.; Jeremiason, J.D.

    1999-10-15

    A dynamic model that couples air-water exchange and phytoplankton uptake of persistent organic pollutants has been developed and then applied to PCB data from a small experimental lake. A sensitivity analysis of the model, taking into account the influence of physical environmental conditions such as temperature, wind speed, and mixing depth as well as plankton-related parameters such as biomass and growth rate was carried out for a number of PCBs with different physical-chemical properties. The results indicate that air-water exchange dynamics are influenced not only by physical parameters but also by phytoplankton biomass and growth rate. New phytoplankton production results in substantially longer times to reach equilibrium. Phytoplankton uptake-induced depletion of the dissolved phase concentration maintains air and water phases out of equilibrium. Furthermore, PCBs in phytoplankton also take longer times to reach equilibrium with the dissolved water phase when the latter is supported by diffusive air-water exchange. However, both model analysis and model application to the Experimental Lakes Area of northwestern Ontario (Canada) suggest that the gas phase supports the concentrations of persistent organic pollutants, such as PCBs, in atmospherically driven aquatic environments.

  12. Thermal Analysis of the Divertor Primary Heat Transfer System Piping During the Gas Baking Process

    SciTech Connect

    Yoder Jr, Graydon L; Harvey, Karen; Ferrada, Juan J

    2011-02-01

    A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater.

  13. Optimizing Geothermal Drilling: Oil and Gas Technology Transfer

    SciTech Connect

    Tilley, Mitch; Eustes, Alfred; Visser, Charles; Baker, Walt; Bolton, Dan; Bell, Jason; Nagandran, Uneshddarann; Quick, Ralph

    2015-01-26

    There is a significant amount of financial risk associated with geothermal drilling; however, there are opportunities to improve upon current practices and technologies used. The scope of this drilling operational study included 21 geothermal wells and 21 oil and gas wells. The goal was to determine a 'perfect well' using historical data to compare the best oil and gas well to the best geothermal well. Unfortunately, limitations encountered in the study included missing data (bit records, mud information, etc.), poor data collection, and difficult to ascertain handwriting. An online software database was used to format drilling data to IADC coded daily drilling reports and generate analysis figures. Six major issues have been found in geothermal drilling operations. These problems include lost circulation, rig/equipment selection, cementing, penetration rate, drilling program, and time management. As a result of these issues, geothermal drilling averages 56.4 days longer than drilling comparable oil and gas wells in the wells in this study. Roughly $13.9 million would be lost due to non-productive time in the 21 geothermal wells and only $1.3 million in the oil and gas wells, assuming a cost of $50,000 per day. Comparable events such as drilling the same sized hole, tripping in/out, cementing, and running the same size casing took substantially less time in the oil and gas wells. Geothermal wells were drilled using older and/or less advanced technology to depths less than 10,000 feet, while oil and gas wells reached 12,500 feet faster with purpose built rigs. A new approach is now underway that will optimize drilling programs throughout the drilling industry. It is the use of Mechanical Specific Energy (MSE) as a tool to realize efficient drilling processes. However, a work-flow must also be established in order for there to be an efficient drilling program. Potential improvements for current geothermal operations are: the use of electronic records, real time

  14. A conjugate heat transfer procedure for gas turbine blades.

    PubMed

    Croce, G

    2001-05-01

    A conjugate heat transfer procedure, allowing for the use of different solvers on the solid and fluid domain(s), is presented. Information exchange between solid and fluid solution is limited to boundary condition values, and this exchange is carried out at any pseudo-time step. Global convergence rate of the procedure is, thus, of the same order of magnitude of stand-alone computations.

  15. Gas flow environmental and heat transfer nonrotating 3D program

    NASA Technical Reports Server (NTRS)

    Geil, T.; Steinhoff, J.

    1983-01-01

    A complete set of benchmark quality data for the flow and heat transfer within a large rectangular turning duct is being compiled. These data will be used to evaluate and verify three dimensional internal viscous flow models and computational codes. The analytical objective is to select such a computational code and define the capabilities of this code to predict the experimental results. Details of the proper code operation will be defined and improvements to the code modeling capabilities will be formulated.

  16. Design of Solid-Gas Interfaces for Enhanced Thermal Transfer

    DTIC Science & Technology

    2015-09-28

    solid surfaces in contact with monoatomic and diatomic gases. We demonstrated that the TAC and MAC can be significantly enhanced by proper surface...surfaces in contact with monoatomic and diatomic gases. Guided by the determined relationships and parametric dependencies we proposed and demonstrated...Au) slab in contact with Ar or N2 gas, as depicted in Fig. 1(a). The embedded-atom-method (EAM) potential [14] was used for realistic description

  17. The boomerang area: An example of oil and gas fields related to a transfer zone development

    SciTech Connect

    Specht, M.; Colletta, B.; Letouzey, J. ); Baby, P. ); Oller, J.; Montemuro, G. ); Guillier, B. )

    1993-02-01

    We present results of a study realized from petroleum data of Yacimientos Petroliferos Fiscales Bolivianos of the most important transfer zone of the Bolivian Andean belt: the Santa Cruz transfer zone. Frontal part of the Bolivian Andean belt consists of a thick series (6 to 8 km) of paleozoic to cenozoic sedimentary rocks thrusted eastwards on a sole thrust located in paleozoic series. The frontal part of the belt, globally N-S oriented, undergoes an important deviation East of Santa Cruz with a left lateral offset of 100 Km. Taking into account the E-W shortening direction, this transfer zone can be interpreted as a lateral ramp. The Santa Cruz transfer zone coincide with a set of small oil and gas fields whereas frontal structures lack hydrocarbon occurrences. We are then faced with a two-fold problem: (1) what is the origin of the transfer zone (2) why are the oil and gas concentrated in the transfer zone Our synthesis shows that the transfer zone is superimposed on the limit of a detached Paleozoic basin whose border direction is oblique to the regional shortening direction. We then interpret the oil and gas formation in two steps: (1) source rock maturation and hydrocarbon migration towards the top of the Paleozoic sedimentary wedge before Andean deformation. (2) hydrocarbon dismigration towards anticlinal structures developed during the lateral ramp propagation. In order to test our interpretation we performed a set of analog model experiments whose 3D visualization was analyzed by computerized X-ray tomography.

  18. Gas transfer velocities measured at low wind speed over a lake

    USGS Publications Warehouse

    Crusius, J.; Wanninkhof, R.

    2003-01-01

    The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ???3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ???3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

  19. Gas transfer model to design a ventilator for neonatal total liquid ventilation.

    PubMed

    Bonfanti, Mirko; Cammi, Antonio; Bagnoli, Paola

    2015-12-01

    The study was aimed to optimize the gas transfer in an innovative ventilator for neonatal Total Liquid Ventilation (TLV) that integrates the pumping and oxygenation functions in a non-volumetric pulsatile device made of parallel flat silicone membranes. A computational approach was adopted to evaluate oxygen (O2) and carbon dioxide (CO2) exchanges between the liquid perfluorocarbon (PFC) and the oxygenating gas, as a function of the geometrical parameter of the device. A 2D semi-empirical model was implemented to this purpose using Comsol Multiphysics to study both the fluid dynamics and the gas exchange in the ventilator. Experimental gas exchanges measured with a preliminary prototype were compared to the simulation outcomes to prove the model reliability. Different device configurations were modeled to identify the optimal design able to guarantee the desired gas transfer. Good agreement between experimental and simulation outcomes was obtained, validating the model. The optimal configuration, able to achieve the desired gas exchange (ΔpCO2 = 16.5 mmHg and ΔpO2 = 69 mmHg), is a device comprising 40 modules, 300 mm in length (total exchange area = 2.28 m(2)). With this configuration gas transfer performance is satisfactory for all the simulated settings, proving good adaptability of the device.

  20. Observation and modelling of dissolved gases as indicators for mass transfer during gas sparging in a contaminated aquifer

    NASA Astrophysics Data System (ADS)

    Oswald, S.; Balcke, G.

    2009-04-01

    Degradation of organic contaminants in aquifers is often limited by the availability of electron acceptors, and the attenuation of contaminants could be enhanced by additional supply of oxygen. Gas sparging is a remediation technique that supplies additional oxygen to ground water via injection of air or oxygen gas. For the performance of this method the mass transfer of gases from the gas phase trapped after injection is a key process. Our study investigated kinetic gas-water mass transfer between trapped gas phase in porous media and groundwater by spatially and temporally resolved dissolved gas measurements in an unconfined model aquifer. The aquifer model was built on-site as a 12 m tall underground tank filled with aquifer material and recharged in vertical direction by the local, contaminated groundwater. For the injection of short gas pulses, oxygen and air as injected gas phase were studied in view of interfacial mass transfer, gas transport in the aqueous phase, and accumulation of trapped gas in the porous space. At several locations dissolved nitrogen, methane and oxygen were observed at different stages of gas dissolution. Kinetic gas-water mass transfer in presence of oxygen demanding reactions in the polluted aquifer material and the transport of dissolved gases were simulated numerically for heterogeneous distribution of gas phase as was observed. Partitioning of nitrogen played an important role in the accumulation of trapped gas and contributes additional information on gas transfer processes. While injection of pure oxygen resulted in complete dissolution of trapped gas within a few meters, nitrogen and methane showed distinct patterns of mass transfer into the gas phase and back into aqueous phase. Naturally occurring gases such as methane or nitrogen were demonstrated to be valuable tracers to describe multiple compound gas-water mass transfer and to assist in predicting gas dissolution and oxygen consumption in porous media.

  1. Heat Transfer in a Turbulent Liquid or Gas Stream

    NASA Technical Reports Server (NTRS)

    Latzko, H.

    1944-01-01

    The,theory of heat.transfer from a solid body to a liquid stream could he presented previously** only with limiting assumptions about the movement of the fluid (potential flow, laminar frictional flow). (See references 1, 2, and 3). For turbulent flow, the most important practical case, the previous theoretical considerations did not go beyond dimensionless formulas and certain conclusions as to the analogy between the friction factor and the unit thermal conductance, (See references 4, 5, 6, and 7,) In order to obtain numerical results, an experimental treatment of the problem was resorted to, which gave rise to numerous investigations because of the importance of this problem in many branches of technology. However, the results of these investigations frequently deviate from one another. The experimental results are especially dependent upon the overall dimensions and the specific proportions of the equipment. In the present work, the attempt will be made to develop systematically the theory of the heat transfer and of the dependence of the unit thermal conductance upon shape and dimensions, using as a basis the velocity distribution for turbulent flow set up by Prandtl and Von Karman.

  2. Charge transfer between fullerenes and highly charged noble gas ions

    NASA Astrophysics Data System (ADS)

    Narits, A. A.

    2008-07-01

    A semiclassical model for the description of charge-exchange processes in collisions between fullerenes and multiply charged ions is developed. It is based on the decay model combined with the impact-parameter representation for the heavy particles' relative motion. The charge-transfer process in our model is treated as a transition of the active electron over and under the quasistatic potential barrier formed by the electric fields of the target and projectile. Due to the high electron delocalization on the surface of fullerene we represent it as a perfectly conducting hard sphere, whose radius is determined by the dipole polarizability of C60. The energies of the active electrons are assumed to be equal to the corresponding ionization potentials including the Stark-shift effect. We have developed an efficient technique for the evaluation of the electron transmission coefficient through the asymmetric potential barrier. It is shown that our model provides a good agreement with the available experimental data on single-electron charge-exchange processes. Moreover, it allows us to get an adequate description of multi-electron transfer processes. The first theoretical results on charge exchange between the fullerene ions and highly charged ions have been obtained.

  3. Effect of flue gas recirculation on heat transfer in a supercritical circulating fluidized bed combustor

    NASA Astrophysics Data System (ADS)

    Błaszczuk, Artur

    2015-09-01

    This paper focuses on assessment of the effect of flue gas recirculation (FGR) on heat transfer behavior in 1296t/h supercritical coal-fired circulating fluidized bed (CFB) combustor. The performance test in supercritical CFB combustor with capacity 966 MWth was performed with the low level of flue gas recirculation rate 6.9% into furnace chamber, for 80% unit load at the bed pressure of 7.7 kPa and the ratio of secondary air to the primary air SA/PA = 0.33. Heat transfer behavior in a supercritical CFB furnace between the active heat transfer surfaces (membrane wall and superheater) and bed material has been analyzed for Geldart B particle with Sauter mean diameters of 0.219 and 0.246 mm. Bed material used in the heat transfer experiments had particle density of 2700 kg/m3. A mechanistic heat transfer model based on cluster renewal approach was used in this work. A heat transfer analysis of CFB combustion system with detailed consideration of bed-to-wall heat transfer coefficient distributions along furnace height is investigated. Heat transfer data for FGR test were compared with the data obtained for representative conditions without recycled flue gases back to the furnace through star-up burners.

  4. Green's function solution to heat transfer of a transparent gas through a tube

    NASA Technical Reports Server (NTRS)

    Frankel, J. I.

    1989-01-01

    A heat transfer analysis of a transparent gas flowing through a circular tube of finite thickness is presented. This study includes the effects of wall conduction, internal radiative exchange, and convective heat transfer. The natural mathematical formulation produces a nonlinear, integrodifferential equation governing the wall temperature and an ordinary differential equation describing the gas temperature. This investigation proposes to convert the original system of equations into an equivalent system of integral equations. The Green's function method permits the conversion of an integrodifferential equation into a pure integral equation. The proposed integral formulation and subsequent computational procedure are shown to be stable and accurate.

  5. Effect of liquid distribution on gas-water phase mass transfer in an unsaturated sand during infiltration

    NASA Astrophysics Data System (ADS)

    Imhoff, Paul T.; Jaffé, Peter R.

    1994-09-01

    Gas-water phase mass transfer was examined in a homogeneous sand with both the gas and water phase mobile: water was infiltrated from the top of the sand column while benzene-laden air flowed upward from the bottom. Mass-transfer limitations for this situation may be important for applications of bioventing, where water and nutrients are added at the ground surface simultaneously with induced air movement to carry oxygen and volatile organics to microbial populations. Gas- and water-phase samples indicate that gas-water phase mass transfer was sufficiently fast that equilibrium between gas and water phases was achieved at all sampling locations within the porous medium. Lower-bound estimates for the gas-water mass-transfer rate coefficient show that mass transfer was at least 10-40 times larger than predictions made from an empirical model developed for gas-water phase mass transfer in an identical porous medium. A water-phase tracer test demonstrates that water flow was much more uniform in this study than in those earlier experiments, which is a likely explanation for the differing rates of gas-water phase mass transfer. It is hypothesized that the liquid distribution in previous laboratory experiments was less uniform because of preferential flow paths due to wetting front instabilities. Gas-water phase mass-transfer rate coefficients reported in this investigation are for an ideal situation of uniform water infiltration: mass-transfer rates in field soils are expected to be significantly smaller.

  6. Gas stream in Algol. [mass transfer in binary star systems

    NASA Technical Reports Server (NTRS)

    Cugier, H.; Chen, K.-Y.

    1977-01-01

    Additional absorption features in the red wings of the Mg II resonance lines near 2800 A are found in observations of Algol made from the Copernicus satellite. The absorption features were clearly seen only during a part of the primary eclipse, in the phase interval 0.90-0.03. The observations are interpreted as being produced by a stream of matter flowing from Algol B in the direction of Algol A. The measured Doppler shifts of the features give the value of 150 km/s as the characteristic velocity of matter in the stream. The mass transfer connected with the stream is estimated to be of the order of 10 to the -13th power solar mass per year.

  7. Heat Transfer and Pressure Distributions on a Gas Turbine Blade Tip

    NASA Technical Reports Server (NTRS)

    Azad, Gm S.; Han, Je-Chin; Teng, Shuye; Boyle, Robert J.

    2000-01-01

    Heat transfer coefficient and static pressure distributions are experimentally investigated on a gas turbine blade tip in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a first stage gas turbine rotor blade with a blade tip profile of a GE-E(sup 3) aircraft gas turbine engine rotor blade. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and exit Reynolds number based on axial chord of 1.1 x 10(exp 6). The middle 3-blade has a variable tip gap clearance. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Heat transfer measurements are also made at two different turbulence intensity levels of 6.1 % and 9.7% at the cascade inlet. Static pressure measurements are made in the mid-span and the near-tip regions as well as on the shroud surface, opposite the blade tip surface. Detailed heat transfer coefficient distributions on the plane tip surface are measured using a transient liquid crystal technique. Results show various regions of high and low heat transfer coefficient on the tip surface. Tip clearance has a significant influence on local tip beat transfer coefficient distribution. Heat transfer coefficient also increases about 15-20% along the leakage flow path at higher turbulence intensity level of 9.7% over 6.1 %.

  8. Tuning a physically-based model of the air-sea gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Jeffery, C. D.; Robinson, I. S.; Woolf, D. K.

    Air-sea gas transfer velocities are estimated for one year using a 1-D upper-ocean model (GOTM) and a modified version of the NOAA-COARE transfer velocity parameterization. Tuning parameters are evaluated with the aim of bringing the physically based NOAA-COARE parameterization in line with current estimates, based on simple wind-speed dependent models derived from bomb-radiocarbon inventories and deliberate tracer release experiments. We suggest that A = 1.3 and B = 1.0, for the sub-layer scaling parameter and the bubble mediated exchange, respectively, are consistent with the global average CO 2 transfer velocity k. Using these parameters and a simple 2nd order polynomial approximation, with respect to wind speed, we estimate a global annual average k for CO 2 of 16.4 ± 5.6 cm h -1 when using global mean winds of 6.89 m s -1 from the NCEP/NCAR Reanalysis 1 1954-2000. The tuned model can be used to predict the transfer velocity of any gas, with appropriate treatment of the dependence on molecular properties including the strong solubility dependence of bubble-mediated transfer. For example, an initial estimate of the global average transfer velocity of DMS (a relatively soluble gas) is only 11.9 cm h -1 whilst for less soluble methane the estimate is 18.0 cm h -1.

  9. Ultrasound in gas-liquid systems: effects on solubility and mass transfer.

    PubMed

    Laugier, F; Andriantsiferana, C; Wilhelm, A M; Delmas, H

    2008-09-01

    The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas-liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas-liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing.

  10. Control of interspecies electron transfer flow during anaerobic digestion: dynamic diffusion reaction models for hydrogen gas transfer in microbial flocs.

    PubMed

    Ozturk, S S; Palsson, B O; Thiele, J H

    1989-02-05

    Dynamic reaction diffusion models were used to analyze the consequences of aggregation for syntrophic reactions in methanogenic ecosystems. Flocs from a whey digestor were used to measure all model parameters under the in situ conditions of a particular defined biological system. Fermentation simulations without adjustable parameters could precisely predict the kinetics of H(2) gas production of digestor flocs during syntrophic methanogenesis from ethanol. The results demonstrated a kinetic compartmentalization of H(2) metabolism inside the flocs. The interspecies electron transfer reaction was mildly diffusion controlled. The H(2) gas profiles across the flocs showed high H (2) concentrations inside the flocs at any time. Simulations of the syntrophic metabolism at low substrate concentrations such as in digestors or sediments showed that it is impossible to achieve high H(2) gas turnovers at simultaneously low steady-state H(2) concentrations. This showed a mechanistic contradiction in the concept of postulated low H(2) microenvironments for the anaerobic digestion process. The results of the computer experiments support the conclusion that syntrophic H(2) production may only be a side reaction of H(2) independent interspecies electron transfer in methanogenic ecosystems.

  11. Transfer of dipolar gas through the discrete localized mode

    NASA Astrophysics Data System (ADS)

    Bai, Xiao-Dong; Zhang, Ai-Xia; Xue, Ju-Kui

    2013-12-01

    By considering the discrete nonlinear Schrödinger model with dipole-dipole interactions for dipolar condensate, the existence, the types, the stability, and the dynamics of the localized modes in a nonlinear lattice are discussed. It is found that the contact interaction and the dipole-dipole interactions play important roles in determining the existence, the type, and the stability of the localized modes. Because of the coupled effects of the contact interaction and the dipole-dipole interactions, rich localized modes and their stability nature can exist: when the contact interaction is larger and the dipole-dipole interactions is smaller, a discrete bright breather occurs. In this case, while the on-site interaction can stabilize the discrete breather, the dipole-dipole interactions will destabilize the discrete breather; when both the contact interaction and the dipole-dipole interactions are larger, a discrete kink appears. In this case, both the on-site interaction and the dipole-dipole interactions can stabilize the discrete kink, but the discrete kink is more unstable than the ordinary discrete breather. The predicted results provide a deep insight into the dynamics of blocking, filtering, and transfer of the norm in nonlinear lattices for dipolar condensates.

  12. External exposure to radionuclides in air, water, and soil

    SciTech Connect

    Eckerman, K.F.; Ryman, J.C.

    1996-05-01

    Federal Guidance Report No. 12 tabulates dose coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, water, and soil. The dose coefficients are intended for use by Federal Agencies in calculating the dose equivalent to organs and tissues of the body.

  13. Modeling of Aerobrake Ballute Stagnation Point Temperature and Heat Transfer to Inflation Gas

    NASA Technical Reports Server (NTRS)

    Bahrami, Parviz A.

    2012-01-01

    A trailing Ballute drag device concept for spacecraft aerocapture is considered. A thermal model for calculation of the Ballute membrane temperature and the inflation gas temperature is developed. An algorithm capturing the most salient features of the concept is implemented. In conjunction with the thermal model, trajectory calculations for two candidate missions, Titan Explorer and Neptune Orbiter missions, are used to estimate the stagnation point temperature and the inflation gas temperature. Radiation from both sides of the membrane at the stagnation point and conduction to the inflating gas is included. The results showed that the radiation from the membrane and to a much lesser extent conduction to the inflating gas, are likely to be the controlling heat transfer mechanisms and that the increase in gas temperature due to aerodynamic heating is of secondary importance.

  14. Carbon dioxide stripping in aquaculture -- part II: development of gas transfer models

    USGS Publications Warehouse

    Colt, John; Watten, Barnaby; Pfeiffer, Tim

    2012-01-01

    The basic mass transfer equation for gases such as oxygen and carbon dioxide can be derived from integration of the driving force equation. Because of the physical characteristics of the gas transfer processes, slightly different models are used for aerators tested under the non steady-state procedures, than for packed columns, or weirs. It is suggested that the standard condition for carbon dioxide should be 20 °C, 1 atm, CCO2=20 mg/kg, and XCO2=0.000285. The selection of the standard condition for carbon dioxide based on a fixed mole fraction ensures that standardized carbon dioxide transfer rates will be comparable even though the value of C*CO2 in the atmosphere is increasing with time. The computation of mass transfer for carbon dioxide is complicated by the impact of water depth and gas phase enrichment on the saturation concentration within the unit, although the importance of either factor depends strongly on the specific type of aerator. For some types of aerators, the most accurate gas phase model remains to be determined for carbon dioxide. The assumption that carbon dioxide can be treated as a non-reactive gas in packed columns may apply for cold acidic waters but not for warm alkaline waters.

  15. Properties of hydrophobic free energy found by gas-liquid transfer.

    PubMed

    Baldwin, Robert L

    2013-01-29

    The hydrophobic free energy in current use is based on transfer of alkane solutes from liquid alkanes to water, and it has been argued recently that these values are incorrect and should be based instead on gas-liquid transfer data. Hydrophobic free energy is measured here by gas-liquid transfer of hydrocarbon gases from vapor to water. The new definition reduces more than twofold the values of the apparent hydrophobic free energy. Nevertheless, the newly defined hydrophobic free energy is still the dominant factor that drives protein folding as judged by ΔCp, the change in heat capacity, found from the free energy change for heat-induced protein unfolding. The ΔCp for protein unfolding agrees with ΔCp values for solvating hydrocarbon gases and disagrees with ΔCp for breaking peptide hydrogen bonds, which has the opposite sign. The ΔCp values for the enthalpy of liquid-liquid and gas-liquid transfer are similar. The plot of free energy against the apparent solvent-exposed surface area is given for linear alkanes, but only for a single conformation, the extended conformation, of these flexible-chain molecules. The ability of the gas-liquid hydrophobic factor to predict protein stability is tested and reasonable agreement is found, using published data for the dependences on temperature of the unfolding enthalpy of ribonuclease T1 and the solvation enthalpies of the nonpolar and polar groups.

  16. Mass transfer in thin films under counter-current gas: experiments and numerical study

    NASA Astrophysics Data System (ADS)

    Lucquiaud, Mathieu; Lavalle, Gianluca; Schmidt, Patrick; Ausner, Ilja; Wehrli, Marc; O Naraigh, Lennon; Valluri, Prashant

    2016-11-01

    Mass transfer in liquid-gas stratified flows is strongly affected by the waviness of the interface. For reactive flows, the chemical reactions occurring at the liquid-gas interface also influence the mass transfer rate. This is encountered in several technological applications, such as absorption units for carbon capture. We investigate the absorption rate of carbon dioxide in a liquid solution. The experimental set-up consists of a vertical channel where a falling film is sheared by a counter-current gas flow. We measure the absorption occurring at different flow conditions, by changing the liquid solution, the liquid flow rate and the gas composition. With the aim to support the experimental results with numerical simulations, we implement in our level-set flow solver a novel module for mass transfer taking into account a variant of the ghost-fluid formalism. We firstly validate the pure mass transfer case with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we analyse the absorption rate in reactive flows, and try to reproduce the experimental results by means of numerical simulations to explore the active role of the waves at the interface.

  17. Cationic Gemini surfactant at the air/water interface.

    PubMed

    Qibin, Chen; Xiaodong, Liang; Shaolei, Wang; Shouhong, Xu; Honglai, Liu; Ying, Hu

    2007-10-15

    The surface properties and structures of a cationic Gemini surfactant with a rigid spacer, p-xylyl-bis(dimethyloctadecylammonium bromide) ([C(18)H(37)(CH(3))(2)N(+)CH(2)C(6)H(4)CH(2)N(+)(CH(3))(2)C(18)H(37)],2Br(-), abbreviated as 18-Ar-18,2Br(-1)), at the air/water interface were investigated. It is found that the surface pressure-molecular area isotherms observed at different temperatures do not exhibit a plateau region but display an unusual "kink" before collapse. The range of the corresponding minimum compressibility and maximum compressibility modulus indicates that the monolayer is in the liquid-expanded state. The monolayers were transferred onto mica and quartz plates by the Langmuir-Blodgett (LB) technique. The structures of monolayers at various surface pressures were studied by atomic force microscopy (AFM) and UV-vis spectroscopy, respectively. AFM measurements show that at lower surface pressures, unlike the structures of complex or hybrid films formed by Gemini amphiphiles with DNA, dye, or inorganic materials or the Langmuir film formed by the nonionic Gemini surfactant, in this case network-like labyrinthine interconnected ridges are formed. The formation of the structures can be interpreted in terms of the spinodal decomposition mechanism. With the increase of the surface pressure up to 35 mN/m, surface micelles dispersed in the network-like ridges gradually appear which might be caused by both the spinodal decomposition and dewetting. The UV-vis adsorption shows that over the whole range of surface pressures, the molecules form a J-aggregate in LB films, which implies that the spacers construct a pi-pi aromatic stacking. This pi-pi interaction between spacers and the van der Waals interaction between hydrophobic chains lead to the formation of both networks and micelles. The labyrinthine interconnected ridges are formed first because of the rapid evaporation of solvent during the spreading processes; with increasing surface pressure, some of the

  18. Neutral gas temperature estimates and metastable resonance energy transfer for argon-nitrogen discharges

    SciTech Connect

    Greig, A. Charles, C.; Boswell, R. W.

    2016-01-15

    Rovibrational spectroscopy band fitting of the nitrogen (N{sub 2}) second positive system is a technique used to estimate the neutral gas temperature of N{sub 2} discharges, or atomic discharges with trace amounts of a N{sub 2} added. For mixtures involving argon and N{sub 2}, resonant energy transfer between argon metastable atoms (Ar*) and N{sub 2} molecules may affect gas temperature estimates made using the second positive system. The effect of Ar* resonance energy transfer is investigated here by analyzing neutral gas temperatures of argon-N{sub 2} mixtures, for N{sub 2} percentages from 1% to 100%. Neutral gas temperature estimates are higher than expected for mixtures involving greater than 5% N{sub 2} addition, but are reasonable for argon with less than 5% N{sub 2} addition when compared with an analytic model for ion-neutral charge exchange collisional heating. Additional spatiotemporal investigations into neutral gas temperature estimates with 10% N{sub 2} addition demonstrate that although absolute temperature values may be affected by Ar* resonant energy transfer, spatiotemporal trends may still be used to accurately diagnose the discharge.

  19. Progress towards understanding and predicting convection heat transfer in the turbine gas path

    NASA Technical Reports Server (NTRS)

    Simoneau, Robert J.; Simon, Frederick F.

    1992-01-01

    A new era is drawing in the ability to predict convection heat transfer in the turbine gas path. We feel that the technical community now has the capability to mount a major assault on this problem, which has eluded significant progress for a long time. We hope to make a case for this bold statement by reviewing the state of the art in three major heat transfer, configuration-specific experiments, whose data have provided the big picture and guided both the fundamental modeling research and the code development. Following that, we review progress and directions in the development of computer codes to predict turbine gas path heat transfer. Finally, we cite examples and make observations on the more recent efforts to do all this work in a simultaneous, interactive, and more synergistic manner. We conclude with an assessment of progress, suggestions for how to use the current state of the art, and recommendations for the future.

  20. The cis-bis(decanoate)tin phthalocyanine/DPPC film at the air/water interface.

    PubMed

    Ramos, Salvador; Garza, Cristina; Beltran, Hiram I; Campos-Terán, José; Arenas-Alatorre, Jesús; Castillo, Rolando

    2012-03-01

    Films made of cis-bis-decanoate-tin(IV) phthalocyanine (PcSn10) and racemic dipalmitoylphosphatidylcholine (DPPC) are studied with compression isotherms and Brewster angle microscopy (BAM) at the air/water interface. Films enriched in PcSn10 present phase separation elliptical-shaped domains. These domains present optical anisotropy and molecular order. They are enriched in PcSn10, and the film outside these domains is enriched in DPPC, as shown in by high-angle annular dark-field transmission electron microscopy on Langmuir-Blodgett (LB) transferred films. Film collapse area and atomic force microscopy images of LB transferred films on mica indicate that the films are actually multilayers. A computational survey was performed to determine how the PcSn10 molecules prefer to self-assemble, in films basically made of PcSn10. The relative energetic stability for several dimeric assemblies was obtained, and a crystal model of the film was developed through packing and repeating the PcSn10 molecules, along the crystallographic directions of the unit cell. Our results contribute to understanding the strong interaction between PcSn10 and DPPC at the air/water interface, where even small quantities of DPPC (~1-2%) can modify the film in an important way.

  1. An investigation of channel flow with a smooth air-water interface

    NASA Astrophysics Data System (ADS)

    Madad, Reza; Elsnab, John; Chin, Cheng; Klewicki, Joseph; Marusic, Ivan

    2015-06-01

    Experiments and numerical simulation are used to investigate fully developed laminar and turbulent channel flow with an air-water interface as the lower boundary condition. Laser Doppler velocimetry measurements of streamwise and wall-normal velocity components are made over a range of Reynolds number based upon channel height and bulk velocity from 1100 to 4300, which encompasses the laminar, transitional and low Reynolds numbers turbulent regimes. The results show that the airflow statistics near the stationary wall are not significantly altered by the air-water moving interface and reflect those found in channel flows. The mean statistics on the water interface side largely exhibit results similar to simulated Poiseuille-Couette flow (PCF) with a solid moving wall. For second-order statistics, however, the simulation and experimental results show some discrepancies near the moving water surface, suggesting that a full two-phase simulation is required. A momentum and energy transport tubes analysis is investigated for laminar and turbulent PCFs. This analysis builds upon the classical notion of a streamtube and indicates that part of the energy from the pressure gradient is transported towards the stationary wall and is dissipated as heat inside the energy tubes, while the remainder is transmitted to the moving wall. For the experiments, the airflow energy is transmitted towards the water to overcome the drag force and drive the water forward; therefore, the amount of energy transferred to the water is higher than the energy transferred to a solid moving wall.

  2. Air-water ‘tornado’-type microwave plasmas applied for sugarcane biomass treatment

    NASA Astrophysics Data System (ADS)

    Bundaleska, N.; Tatarova, E.; Dias, F. M.; Lino da Silva, M.; Ferreira, C. M.; Amorim, J.

    2014-02-01

    The production of cellulosic ethanol from sugarcane biomass is an attractive alternative to the use of fossil fuels. Pretreatment is needed to separate the cellulosic material, which is packed with hemicellulose and lignin in cell wall of sugarcane biomass. A microwave ‘tornado’-type air-water plasma source operating at 2.45 GHz and atmospheric pressure has been applied for this purpose. Samples of dry and wet biomass (˜2 g) have been exposed to the late afterglow plasma stream. The experiments demonstrate that the air-water highly reactive plasma environment provides a number of long-lived active species able to destroy the cellulosic wrapping. Scanning electron microscopy has been applied to analyse the morphological changes occurring due to plasma treatment. The effluent gas streams have been analysed by Fourier-transform infrared spectroscopy (FT-IR). Optical emission spectroscopy and FT-IR have been applied to determine the gas temperature in the discharge and late afterglow plasma zones, respectively. The optimal range of the operational parameters is discussed along with the main active species involved in the treatment process. Synergistic effects can result from the action of singlet O2(a 1Δg) oxygen, NO2, nitrous acid HNO2 and OH hydroxyl radical.

  3. Effect of impeller geometry on gas-liquid mass transfer coefficients in filamentous suspensions.

    PubMed

    Dronawat, S N; Svihla, C K; Hanley, T R

    1997-01-01

    Volumetric gas-liquid mass transfer coefficients were measured in suspensions of cellulose fibers with concentrations ranging from 0 to 20 g/L. The mass transfer coefficients were measured using the dynamic method. Results are presented for three different combinations of impellers at a variety of gassing rates and agitation speeds. Rheological properties of the cellulose fibers were also measured using the impeller viscometer method. Tests were conducted in a 20 L stirred-tank fermentor and in 65 L tank with a height to diameter ratio of 3:1. Power consumption was measured in both vessels. At low agitation rates, two Rushton turbines gave 20% better performance than the Rushton and hydrofoil combination and 40% better performance than the Rushton and propeller combination for oxygen transfer. At higher agitation rates, the Rushton and hydrofoil combination gave 14 and 25% better performance for oxygen transfer than two Rushton turbines and the Rushton and hydrofoil combination, respectively.

  4. Observations of the gas stream in the mass transfer binary HR 2142 prime 1

    NASA Technical Reports Server (NTRS)

    Peters, G. J.

    1981-01-01

    The mass transfer binary system HR 2142 was observed at selected phases with the high resolution spectrograph on IUE. The observations were scheduled throughout the interval 0.91 phi 0.00 in order to allow viewing of the light of the primary star through the gas stream as it presents different orientations to the line of sight. Numerous UV lines formed in the gas stream were identified. The strengths and velocity variations displayed by these lines are compared with those observed in the ground based spectral region. As part of a preliminary analysis of the IUE data, column densities and velocities from Si III (4), Si IV (1), and Ti III (1) are used to deduce electron densities in the gas stream as well as its thickness. Possible evidence for stratification in the gas stream is presented.

  5. Dispersed bubble reactor for enhanced gas-liquid-solids contact and mass transfer

    DOEpatents

    Vimalchand, Pannalal; Liu, Guohai; Peng, WanWang; Bonsu, Alexander

    2016-01-26

    An apparatus to promote gas-liquid contact and facilitate enhanced mass transfer. The dispersed bubble reactor (DBR) operates in the dispersed bubble flow regime to selectively absorb gas phase constituents into the liquid phase. The dispersion is achieved by shearing the large inlet gas bubbles into fine bubbles with circulating liquid and additional pumped liquid solvent when necessary. The DBR is capable of handling precipitates that may form during absorption or fine catalysts that may be necessary to promote liquid phase reactions. The DBR can be configured with multistage counter current flow sections by inserting concentric cylindrical sections into the riser to facilitate annular flow. While the DBR can absorb CO.sub.2 in liquid solvents that may lead to precipitates at high loadings, it is equally capable of handling many different types of chemical processes involving solids (precipitates/catalysts) along with gas and liquid phases.

  6. A model for sound velocity in a two-phase air-water bubbly flow

    SciTech Connect

    Chung, N.M.; Lin, W.K.; Pei, B.S.; Hsu, Y.Y. )

    1992-07-01

    In this paper, wave propagation in a homogeneous, low void fraction, two-phase air-water bubbly flow is analyzed through the compressibility of a single bubble to derive a P({rho}) relation; the dispersion relation is then derived by a homogeneous model. The phase velocity and attenuation calculated from the model are compared with existing data and are in good agreement. The momentum transfer effect is considered through the virtual mass term and is significant at a higher void fraction. The interfacial heat transfer between phases is significant at low frequency, while bubble scattering effects are important at high frequency (near resonance). Bubble behavior at both low and high frequency is derived based on the isothermal and the adiabatic cases, respectively. The phase velocity occurs at the limiting condition in both cases. Furthermore, resonance is present in the model, and the resonant frequency is determined.

  7. Heat transfer between immiscible liquids enhanced by gas bubbling. [PWR; BWR

    SciTech Connect

    Greene, G.A.; Schwarz, C.E.; Klages, J.; Klein, J.

    1982-08-01

    The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments have been performed with non-reactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies have been performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non-entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model. However heat transfer data for fluid pairs which are found to entrain (water-oil), believed to be characteristic of molten reactor core-concrete conditions, were measured to be up to two orders of magnitude greater than surface renewal predictions and are calculated by a simple entrainment heat transfer model.

  8. Spatially distributed flame transfer functions for predicting combustion dynamics in lean premixed gas turbine combustors

    SciTech Connect

    Kim, K.T.; Lee, J.G.; Quay, B.D.; Santavicca, D.A.

    2010-09-15

    The present paper describes a methodology to improve the accuracy of prediction of the eigenfrequencies and growth rates of self-induced instabilities and demonstrates its application to a laboratory-scale, swirl-stabilized, lean-premixed, gas turbine combustor. The influence of the spatial heat release distribution is accounted for using local flame transfer function (FTF) measurements. The two-microphone technique and CH{sup *} chemiluminescence intensity measurements are used to determine the input (inlet velocity perturbation) and the output functions (heat release oscillation), respectively, for the local flame transfer functions. The experimentally determined local flame transfer functions are superposed using the flame transfer function superposition principle, and the result is incorporated into an analytic thermoacoustic model, in order to predict the linear stability characteristics of a given system. Results show that when the flame length is not acoustically compact the model prediction calculated using the local flame transfer functions is better than the prediction made using the global flame transfer function. In the case of a flame in the compact flame regime, accurate predictions of eigenfrequencies and growth rates can be obtained using the global flame transfer function. It was also found that the general response characteristics of the local FTF (gain and phase) are qualitatively the same as those of the global FTF. (author)

  9. Oil and gas technology transfer activities and potential in eight major producing states. Volume 1

    SciTech Connect

    Not Available

    1993-07-01

    In 1990, the Interstate Oil and Gas Compact Commission (the Compact) performed a study that identified the structure and deficiencies of the system by which oil and gas producers receive information about the potential of new technologies and communicate their problems and technology needs back to the research community. The conclusions of that work were that major integrated companies have significantly more and better sources of technology information than independent producers. The majors also have significantly better mechanisms for communicating problems to the research and development (R&D) community. As a consequence, the Compact recommended analyzing potential mechanisms to improve technology transfer channels for independents and to accelerate independents acceptance and use of existing and emerging technologies. Building on this work, the Compact, with a grant from the US Department Energy, has reviewed specific technology transfer organizations in each of eight major oil producing states to identify specific R&D and technology transfer organizations, characterize their existing activities, and identify potential future activities that could be performed to enhance technology transfer to oil and gas producers. The profiles were developed based on information received from organizations,follow-up interviews, site visit and conversations, and participation in their sponsored technology transfer activities. The results of this effort are reported in this volume. In addition, the Compact has also developed a framework for the development of evaluation methodologies to determine the effectiveness of technology transfer programs in performing their intended functions and in achieving desired impacts impacts in the producing community. The results of that work are provided in a separate volume.

  10. Studies on fluid dynamics of the flow field and gas transfer in orbitally shaken tubes.

    PubMed

    Zhu, Li-Kuan; Song, Bo-Yan; Wang, Zhen-Long; Monteil, Dominique T; Shen, Xiao; Hacker, David L; De Jesus, Maria; Wurm, Florian M

    2017-01-01

    Orbitally shaken cylindrical bioreactors [OrbShake bioreactors (OSRs)] without an impeller or sparger are increasingly being used for the suspension cultivation of mammalian cells. Among small volume OSRs, 50-mL tubes with a ventilated cap (OSR50), originally derived from standard laboratory centrifuge tubes with a conical bottom, have found many applications including high-throughput screening for the optimization of cell cultivation conditions. To better understand the fluid dynamics and gas transfer rates at the liquid surface in OSR50, we established a three-dimensional simulation model of the unsteady liquid forms (waves) in this vessel. The studies verified that the operating conditions have a large effect on the interfacial surface. The volumetric mass transfer coefficient (kL a) was determined experimentally and from simulations under various working conditions. We also determined the liquid-phase mass transfer coefficient (kL ) and the specific interfacial area (a) under different conditions to demonstrate that the value of a affected the gas transfer rate more than did the value of kL . High oxygen transfer rates, sufficient for supporting the high-density culture of mammalian cells, were found. Finally, the average axial velocity of the liquid was identified to be an important parameter for maintaining cells in suspension. Overall these studies provide valuable insights into the preferable operating conditions for the OSR50, such as those needed for cell cultures requiring high oxygen levels. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:192-200, 2017.

  11. 40 CFR 65.144 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... System or a Process § 65.144 Fuel gas systems and processes to which storage vessel, transfer rack, or... evaluation as specified in § 65.165(a)(1). (c) Statement of connection to fuel gas system. For storage... 40 Protection of Environment 16 2012-07-01 2012-07-01 false Fuel gas systems and processes...

  12. 40 CFR 65.144 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... System or a Process § 65.144 Fuel gas systems and processes to which storage vessel, transfer rack, or... evaluation as specified in § 65.165(a)(1). (c) Statement of connection to fuel gas system. For storage... 40 Protection of Environment 16 2014-07-01 2014-07-01 false Fuel gas systems and processes...

  13. 40 CFR 65.144 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... System or a Process § 65.144 Fuel gas systems and processes to which storage vessel, transfer rack, or... evaluation as specified in § 65.165(a)(1). (c) Statement of connection to fuel gas system. For storage... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Fuel gas systems and processes...

  14. 40 CFR 65.144 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... System or a Process § 65.144 Fuel gas systems and processes to which storage vessel, transfer rack, or... evaluation as specified in § 65.165(a)(1). (c) Statement of connection to fuel gas system. For storage... 40 Protection of Environment 15 2010-07-01 2010-07-01 false Fuel gas systems and processes...

  15. Examination of charge transfer in Au/YSZ for high-temperature optical gas sensing

    SciTech Connect

    Baltrus, John P.; Ohodnicki, Paul R.

    2014-01-01

    Au-nanoparticle incorporated oxide thin film materials demonstrate significant promise as functionalsensor materials for high temperature optical gas sensing in severe environments relevant for fossil andnuclear based power generation. The Au/yttria-stabilized zirconia (YSZ) system has been extensivelystudied in the literature and serves as a model system for fundamental investigations that seek to betterunderstand the mechanistic origin of the plasmonic gas sensing response. In this work, X-ray photoelec-tron spectroscopy techniques are applied to Au/YSZ films in an attempt to provide further experimentalevidence for a proposed sensing mechanism involving a change in free carrier density of Au nanoparticles due to charge transfer.

  16. A study of gas sensing behavior of metal-graphene contact with transfer length method

    NASA Astrophysics Data System (ADS)

    Li, Quanfu; Liu, Weihua; Cao, Guiming; Li, Xin; Wang, Xiaoli

    2016-05-01

    The gas sensing behavior of a metal-graphene contact is investigated by transfer length method (TLM). By simultaneously measuring the resistance of all channels in a TLM device, the time evolution of the metal-graphene contact resistance and the graphene sheet resistance are obtained. When the device is exposed to 10 ppm ammonia, the response time of the nickel-graphene contact resistance is only one-third of the pure sheet resistance, and the sensitivity of the contact resistance is about 180% and that of the graphene sheet resistance is 100%. The results of this work indicate that the contact resistance can be an effective gas sensing parameter.

  17. Resonance Energy Transfer Relates the Gas-Phase Structure and Pharmacological Activity of Opioid Peptides.

    PubMed

    Kopysov, Vladimir; Boyarkin, Oleg V

    2016-01-11

    Enkephalins are efficient pain-relief drugs that bind to transmembrane opioid receptors. One key structural parameter that governs the pharmacological activity of these opioid peptides and is typically determined from condensed-phase structures is the distance between the aromatic rings of their Tyr and Phe residues. We use resonance energy transfer, detected by a combination of cold ion spectroscopy and mass spectrometry, to estimate the Tyr-Phe spacing for enkephalins in the gas phase. In contrast to the condensed-phase structures, these distances appear to differ substantially in enkephalins with different pharmacological efficiencies, suggesting that gas-phase structures might be a better pharmacophoric metric for ligand peptides.

  18. Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade

    NASA Technical Reports Server (NTRS)

    Azad, Gm S.; Han, Je-Chin; Boyle, Robert J.

    2000-01-01

    Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modem first stage gas turbine rotor blade with a blade tip profile of a GE-E(sup 3) aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1 x 10(exp 6). A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. 'Me heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1 % case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.

  19. Determination of heat transfer coefficient for an interaction of sub-cooled gas and metal

    NASA Astrophysics Data System (ADS)

    Zaidi Sidek, Mohd; Syahidan Kamarudin, Muhammad

    2016-02-01

    Heat transfer coefficient (HTC) for a hot metal surface and their surrounding is one of the need be defined parameter in hot forming process. This study has been conducted to determine the HTC for an interaction between sub-cooled gas sprayed on a hot metal surface. Both experiments and finite element have been adopted in this work. Initially, the designated experiment was conducted to obtain temperature history of spray cooling process. Then, an inverse method was adopted to calculate the HTC value before we validate in a finite element simulation model. The result shows that the heat transfer coefficient for interaction of subcooled gas and hot metal surface is 1000 W/m2K.

  20. Hydrocarbon Release During Fuel Storage and Transfer at Gas Stations: Environmental and Health Effects.

    PubMed

    Hilpert, Markus; Mora, Bernat Adria; Ni, Jian; Rule, Ana M; Nachman, Keeve E

    2015-12-01

    At gas stations, fuel is stored and transferred between tanker trucks, storage tanks, and vehicle tanks. During both storage and transfer, a small fraction of unburned fuel is typically released to the environment unless pollution prevention technology is used. While the fraction may be small, the cumulative release can be substantial because of the large quantities of fuel sold. The cumulative release of unburned fuel is a public health concern because gas stations are widely distributed in residential areas and because fuel contains toxic and carcinogenic chemicals. We review the pathways through which gasoline is chronically released to atmospheric, aqueous, and subsurface environments, and how these releases may adversely affect human health. Adoption of suitable pollution prevention technology should not only be based on equipment and maintenance cost but also on energy- and health care-saving benefits.

  1. Heat and mass transfer rates during flow of dissociated hydrogen gas over graphite surface

    NASA Technical Reports Server (NTRS)

    Nema, V. K.; Sharma, O. P.

    1986-01-01

    To improve upon the performance of chemical rockets, the nuclear reactor has been applied to a rocket propulsion system using hydrogen gas as working fluid and a graphite-composite forming a part of the structure. Under the boundary layer approximation, theoretical predictions of skin friction coefficient, surface heat transfer rate and surface regression rate have been made for laminar/turbulent dissociated hydrogen gas flowing over a flat graphite surface. The external stream is assumed to be frozen. The analysis is restricted to Mach numbers low enough to deal with the situation of only surface-reaction between hydrogen and graphite. Empirical correlations of displacement thickness, local skin friction coefficient, local Nusselt number and local non-dimensional heat transfer rate have been obtained. The magnitude of the surface regression rate is found low enough to ensure the use of graphite as a linear or a component of the system over an extended period without loss of performance.

  2. Flow and heat transfer for gas flowing in microchannels: a review

    NASA Astrophysics Data System (ADS)

    Rostami, A. A.; Mujumdar, A. S.; Saniei, N.

    Microchannels are currently being used in many areas and have high potential for applications in many other areas, which are considered realistic by experts. The application areas include medicine, biotechnology, avionics, consumer electronics, telecommunications, metrology, computer technology, office equipment and home appliances, safety technology, process engineering, robotics, automotive engineering and environmental protection. A number of these applications are introduced in this paper, followed by a critical review of the works on the flow and heat transfer for gas flowing in microchannels. The results show that the flow and heat transfer characteristics of a gas flowing in microchannels can not be adequately predicted by the theories and correlations developed for conventional sized channels. The results of theoretical and experimental works are discussed and summarized along with suggestions for future research directions.

  3. Analysis of small scale turbulent structures and the effect of spatial scales on gas transfer

    NASA Astrophysics Data System (ADS)

    Schnieders, Jana; Garbe, Christoph

    2014-05-01

    The exchange of gases through the air-sea interface strongly depends on environmental conditions such as wind stress and waves which in turn generate near surface turbulence. Near surface turbulence is a main driver of surface divergence which has been shown to cause highly variable transfer rates on relatively small spatial scales. Due to the cool skin of the ocean, heat can be used as a tracer to detect areas of surface convergence and thus gather information about size and intensity of a turbulent process. We use infrared imagery to visualize near surface aqueous turbulence and determine the impact of turbulent scales on exchange rates. Through the high temporal and spatial resolution of these types of measurements spatial scales as well as surface dynamics can be captured. The surface heat pattern is formed by distinct structures on two scales - small-scale short lived structures termed fish scales and larger scale cold streaks that are consistent with the footprints of Langmuir Circulations. There are two key characteristics of the observed surface heat patterns: 1. The surface heat patterns show characteristic features of scales. 2. The structure of these patterns change with increasing wind stress and surface conditions. In [2] turbulent cell sizes have been shown to systematically decrease with increasing wind speed until a saturation at u* = 0.7 cm/s is reached. Results suggest a saturation in the tangential stress. Similar behaviour has been observed by [1] for gas transfer measurements at higher wind speeds. In this contribution a new model to estimate the heat flux is applied which is based on the measured turbulent cell size und surface velocities. This approach allows the direct comparison of the net effect on heat flux of eddies of different sizes and a comparison to gas transfer measurements. Linking transport models with thermographic measurements, transfer velocities can be computed. In this contribution, we will quantify the effect of small scale

  4. Heat Transfer in the Turbulent Boundary Layer of a Compressible Gas at High Speeds

    NASA Technical Reports Server (NTRS)

    Frankl, F.

    1942-01-01

    The Reynolds law of heat transfer from a wall to a turbulent stream is extended to the case of flow of a compressible gas at high speeds. The analysis is based on the modern theory of the turbulent boundary layer with laminar sublayer. The investigation is carried out for the case of a plate situated in a parallel stream. The results are obtained independently of the velocity distribution in the turbulent boundar layer.

  5. 14 CFR 1274.926 - Clean Air-Water Pollution Control Acts.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Clean Air-Water Pollution Control Acts. 1274... AGREEMENTS WITH COMMERCIAL FIRMS Other Provisions and Special Conditions § 1274.926 Clean Air-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative agreement or...

  6. Global distribution of gas hydrates in marine sediments: application of a general transfer function

    NASA Astrophysics Data System (ADS)

    Piñero, Elena; Marquardt, Mathias; Hensen, Christian; Haeckel, Matthias

    2010-05-01

    Many of the recently published estimates of the global inventory of marine methane hydrate are based on simplified diagenetic models, which were run for each grid point of a homogeneous grid of the seafloor. Since this is a very complex and time-consuming method, which may also be limited by data availability, we invented a simple transfer function, which calculates the amount of gas hydrates based on easily accessible data. The transfer function was derived from a large set of systematic runs of a numerical diagenetic model covering the wide range of environmental conditions that are typically met along the continental margins. An exhaustive parameter analysis established that the formation of gas hydrates from biogenic methane production can be sufficiently described by the total organic carbon accumulation rate and the thickness of the gas hydrate stability zone (Marquardt et al., submitted). The resulting transfer function was applied to available global datasets of 1x1-degree resolution in order to derive global estimates of the distribution and total inventory of gas hydrates. The global grids include the seafloor bathymetry, TOC input (Seiter et al., 2004), bottom water temperature, and geothermal gradient estimated from heat flow (Hamza et al., 2008). The global amount of gas hydrate is predicted to be about 2400 Gt of C and is in good agreement with previously published results (e.g. Archer et al., 2009). So far, our calculations do not consider any thermogenic methane, but only microbially produced and hence, represent only a minimum estimate of the gas hydrate budget. References: Archer et al., 2009. Ocean methane hydrates as a slow tipping point in the global carbon cycle. PNAS 106 (49), 20596-20601. Hamza et al., 2008. Spherical harmonic analysis of the Earth's conductive heat flow. Intern. J. Earth Sci., 97, 205-226 Marquardt et al. Submitted. Estimation of gas hydrate inventories in marine sediments: derivation and testing of a transfer function

  7. Amphiphilic derivatives of dextran: adsorption at air/water and oil/water interfaces.

    PubMed

    Rotureau, E; Leonard, M; Dellacherie, E; Durand, A

    2004-11-01

    Ionic amphiphilic dextran derivatives were synthesized by the attachment of sodium sulfopropyl and phenoxy groups on the native polysaccharide. A family of dextran derivatives was thus obtained with varying hydrophobic content and charge density in the polymer chains. The surface-active properties of polymers were studied at the air-water and dodecane-water interfaces using dynamic surface/interfacial tension measurements. The adsorption was shown to begin in a diffusion-limited regime at low polymer concentrations, that is to say, with the diffusion of macromolecules in the bulk solution. In contrast, at long times the interfacial adsorption is limited by interfacial phenomena: adsorption kinetics or transfer into the adsorbed layer. A semiempirical equation developed by Filippov was shown to correctly fit the experimental curves over the whole time range. The presence of ionic groups in the chains strongly lowers the adsorption kinetics. This effect can be interpreted by electrostatic interactions between the free molecules and the already adsorbed ones. The adsorption kinetics at air-water and oil-water interfaces are compared.

  8. Evaporative assembly of MEH-PPV rings using mixed solvents at the air/water interface.

    PubMed

    Chao, Kung-Po; Biswal, Sibani L

    2014-04-22

    Controlling the morphology of conjugated polymers has recently attracted considerable attention because of their applications in photovoltaic (PV) devices and organic light-emitting diodes (OLEDs). Here, we describe the self-assembly of a common conjugated polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), into ringlike structures via solvent evaporation on an air/water interface. The films are monitored using Brewster angle microscopy (BAM) and transferred onto a solid substrate by either the Langmuir-Blodgett (LB) or the Langmuir-Schaefer (LS) method and further characterized by atomic force microscopy (AFM). The morphology of the MEH-PPV thin film at the air/water interface can be controlled by the spreading solvent. By mixing solvents of varying spreading coefficients and evaporation rates, such as chloroform and chlorobenzene, MEH-PPV can be assembled into micrometer-sized ring structures. The optical properties of these MEH-PPV ring structures are also characterized. Lastly, MEH-PPV can be used as a soft template to organize microscale structures of nanoparticles.

  9. Use of silicone membranes to enhance gas transfer during microbial fuel cell operation on carbon monoxide.

    PubMed

    Hussain, A; Tartakovsky, B; Guiot, S R; Raghavan, V

    2011-12-01

    Electricity generation in a microbial fuel cell (MFC) using carbon monoxide (CO) or synthesis gas (syngas) as a carbon source has been demonstrated recently. A major challenge associated with CO or syngas utilization is the mass transfer limitation of these sparingly soluble gases in the aqueous phase. This study evaluated the applicability of a dense polymer silicone membrane and thin wall silicone tubing for CO mass transfer in MFCs. Replacing the sparger used in our previous study with the membrane systems for CO delivery resulted in improved MFC performance and CO transformation efficiency. A power output and CO transformation efficiency of up to 18 mW LR(-1) (normalized to anode compartment volume) and 98%, respectively, was obtained. The use of membrane systems offers the advantage of improved mass transfer and reduced reactor volume, thus increasing the volumetric power output of MFCs operating on a gaseous substrate such as CO.

  10. The mean coefficients of heat transfer from gas to turbine nozzle blade at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Mariev, D. I.; Lelchuk, V. L.; Balashov, Iu. A.

    1982-10-01

    The mean heat transfer in the flow section of a high-temperature gas turbine at high Reynolds number between six and seven million was examined. The experimental nozzle cascade is described and experimental velocity curves for assessing the aerodynamic efficiency of the blade profile are shown. The heat-transfer investigation involved calorimetric measurement with forward and reverse directions of the heat flux. The flow rate and temperature difference of water passing through the blade were measured, and the mean coefficients of heat transfer over the profile surface were calculated in the form of the ratio of heat flux density to the difference between the mean temperature of the surface and the inlet cascade flow temperature. The experimental results were used to derive a relation which is analyzed.

  11. A two-dimensional position sensitive gas chamber with scanned charge transfer readout

    NASA Astrophysics Data System (ADS)

    Gómez, F.; Iglesias, A.; Lobato, R.; Mosquera, J.; Pardo, J.; Pena, J.; Pazos, A.; Pombar, M.; Rodríguez, A.

    2003-10-01

    We have constructed and tested a two-dimensional position sensitive parallel-plate gas ionization chamber with scanned charge transfer readout. The scan readout method described here is based on the development of a new position-dependent charge transfer technique. It has been implemented by using gate strips perpendicularly oriented to the collector strips. This solution reduces considerably the number of electronic readout channels needed to cover large detector areas. The use of a 25 μm thick kapton etched circuit allows high charge transfer efficiency with a low gating voltage, consequently needing a very simple commutating circuit. The present prototype covers 8×8 cm2 with a pixel size of 1.27×1.27 mm2. Depending on the intended use and beam characteristics a smaller effective pixel is feasible and larger active areas are possible. This detector can be used for X-ray or other continuous beam intensity profile monitoring.

  12. Study of Mass Transfer in Gas Blowing Processes for Silicon Purification

    NASA Astrophysics Data System (ADS)

    Altenberend, Jochen; Chichignoud, Guy; Delannoy, Yves

    2017-03-01

    Boron removal processes are crucial to make the metallurgical route for silicon refining for solar cells competitive and thus reduce the cost of solar energy. The rate-limiting step was investigated in silicon purification processes for boron removal based on gas blowing, to gain better understanding that should help to improve the design of such processes. We calculate the boron concentration in the off-gas that corresponds to chemical equilibrium between the gas and silicon. The real concentration in the off-gas ranges between 9 and 30 pct of this theoretical value calculated using Gibbs free energies reported in literature. Purification experiments with varying temperature and hydrogen concentration were done to evaluate whether limited chemical reaction rates induce deviation from chemical equilibrium. The experiments and data from literature show that the chemical reactions at the surface of the melt are close to chemical equilibrium, thus the purification rate is limited by mass transfer in the gas phase near the interface. Based on this, recommendations for the design of a gas blowing purification process are given.

  13. A simple technique for continuous measurement of time-variable gas transfer in surface waters

    USGS Publications Warehouse

    Bohlke, Johnkarl F.; Harvey, Judson W.; Busenberg, Eurybiades; Tobias, Craig R.

    2009-01-01

    Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating wholeecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error-prone components of these models. Here we present a simple and efficient modification of the SF6 gas tracer approach that can be used concurrently while collecting other dissolved gas samples for dissolved gas mass balance studies in streams. It consists of continuously metering SF6-saturated water directly into the stream at a low rate of flow. This approach has advantages over pulse injection of aqueous solutions or bubbling large amounts of SF6 into the stream. By adding the SF6 as a saturated solution, we minimize the possibility that other dissolved gas measurements are affected by sparging and/or bubble injecta. Because the SF6 is added continuously we have a record of changing gas transfer velocity (GTV) that is contemporaneous with the sampling of other nonconservative ambient dissolved gases. Over a single diel period, a 30% variation in GTV was observed in a second-order stream (Sugar Creek, Indiana, USA). The changing GTV could be attributed in part to changes in temperature and windspeed that occurred on hourly to diel timescales.

  14. A simple technique for continuous measurement of time-variable gas transfer in surface waters

    USGS Publications Warehouse

    Tobias, C.R.; Böhlke, J.K.; Harvey, J.W.; Busenberg, E.

    2009-01-01

    Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating wholeecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error-prone components of these models. Here we present a simple and efficient modification of the SF6 gas tracer approach that can be used concurrently while collecting other dissolved gas samples for dissolved gas mass balance studies in streams. It consists of continuously metering SF 6-saturated water directly into the stream at a low rate of flow. This approach has advantages over pulse injection of aqueous solutions or bubbling large amounts of SF6 into the stream. By adding the SF 6 as a saturated solution, we minimize the possibility that other dissolved gas measurements are affected by sparging and/or bubble injecta. Because the SF6 is added continuously we have a record of changing gas transfer velocity (GTV) that is contemporaneous with the sampling of other nonconservative ambient dissolved gases. Over a single diel period, a 30% variation in GTV was observed in a second-order stream (Sugar Creek, Indiana, USA). The changing GTV could be attributed in part to changes in temperature and windspeed that occurred on hourly to diel timescales.

  15. Air-water two-phase flow in a 3-mm horizontal tube

    NASA Astrophysics Data System (ADS)

    Chen, Ing Youn; Chang, Yu-Juei; Wang, Chi-Chung

    2000-01-01

    Two-phase flow pattern and friction characteristics for air-water flow in a 3.17 mm smooth tube are reported in this study. The range of air-water mass flux is between 50 to 700 kg/m2.s and gas quality is between 0.0001 to 0.9. The pressure drop data are analyzed using the concept of the two-phase frictional multipliers and the Martinelli parameter. Experimental data show that the two-phase friction multipliers are strongly related to the flow pattern. Taitel & Dukler flow regime map fails to predict the stratified flow pattern data. Their transition lines between annular-wavy and annular-intermittent give fair agreement with data. A modified correlation from Klimenko and Fyodoros criterion is able to distinguish the annular and stratified data. For two-phase flow in small tubes, the effect of surface tension force should be significantly present as compared to gravitational force. The tested empirical frictional correlations couldn't predict the pressure drop in small tubes for various working fluids. It is suggested to correlate a reliable frictional multiplier for small horizontal tubes from a large database of various working fluids, and to develop the flow pattern dependent models for the prediction of two-phase pressure drop in small tubes. .

  16. Bond-Specific Dissociation Following Excitation Energy Transfer for Distance Constraint Determination in the Gas Phase

    PubMed Central

    2015-01-01

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase. PMID:25174489

  17. Bond-specific dissociation following excitation energy transfer for distance constraint determination in the gas phase.

    PubMed

    Hendricks, Nathan G; Lareau, Nichole M; Stow, Sarah M; McLean, John A; Julian, Ryan R

    2014-09-24

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase.

  18. Interspecies transfer of momentum and energy in disparate-mass gas mixtures

    NASA Astrophysics Data System (ADS)

    Riesco-Chueca, P.; Fernandez-Feria, R.; Fernandez de La Mora, J.

    1987-01-01

    A determination is made of collision integrals for the rate of exchange of momentum and tensorial energy between components of a neutral gas binary mixture, for the case where said components have very different atomic masses. Collision integral values are obtained for arbitrary temperatures and velocities of the two components, allowing for large departures of the heavy gas from equilibrium conditions. The range of present interest is that in which the system is perturbed within times of the order of magnitude of the slow relaxation time that characterizes energy transfer between unlike molecules; the light gas distribution function is then Maxwellian to lowest order. The computation is conducted in detail for the case of atomic interactions describable in terms of a Lennard-Jones potential; by combining numerical computations with optimal matching of analytical expressions valid for large and small slip velocities, a set of compact formulas is obtained that holds for high and low temperatures.

  19. Air-water exchange and dry deposition of polybrominated diphenyl ethers at a coastal site in Izmir Bay, Turkey.

    PubMed

    Cetin, Banu; Odabasi, Mustafa

    2007-02-01

    The air-water exchange of polybrominated diphenyl ethers (PBDEs), an emerging class of persistent organic pollutants (POPs), was investigated using paired air-water samples (n = 15) collected in July and December, 2005 from Guzelyali Port in Izmir Bay, Turkey. Total dissolved-phase water concentrations of PBDEs (sigma7PBDEs) were 212 +/- 65 and 87 +/- 57 pg L(-1) (average +/- SD) in summer and winter, respectively. BDE-209 was the most abundant congener in all samples, followed by BDE-99 and -47. Average ambient gas-phase sigma7PBDE concentrations were between 189 +/- 61 (summer) and 76 +/- 65 pg m(-3) (winter). Net air-water exchange fluxes ranged from -0.9 +/- 1.0 (BDE-28) (volatilization) to 11.1 +/- 5.4 (BDE-209) ng m(-2) day(-1) (deposition). The BDE-28 fluxes were mainly volatilization while the other congeners were deposited. Gas- and dissolved-phase concentrations were significantly correlated (P = 0.33-0.55, p < 0.05, except for BDE-209, r = 0.05, p > 0.05) indicating thatthe atmosphere controls the surface water PBDE levels in this coastal environment. Estimated particulate dry deposition fluxes ranged between 2.7 +/- 1.9 (BDE-154) and 116 +/- 84 ng m(-2) day(-1) (BDE-209) indicating that dry deposition is also a significant input to surface waters in the study area.

  20. Application of the gas tracer method for measuring oxygen transfer rates in subsurface flow constructed wetlands.

    PubMed

    Tyroller, Lina; Rousseau, Diederik P L; Santa, Santa; García, Joan

    2010-07-01

    The oxygen transfer rate (OTR) has a significant impact on the design, optimal operation and modelling of constructed wetlands treating wastewater. Oxygen consumption is very fast in wetlands and the OTR cannot be determined using an oxygen mass balance. This problem is circumvented in this study by applying the gas tracer method. Experiments were conducted in an unplanted gravel bed (dimensions L x W x d 125 x 50 x 35 cm filled with a 30-cm layer of 10-11-mm gravel) and a planted horizontal subsurface flow constructed wetland (HSSFCW) (L x W x d 110 x 70 x 38 cm filled with a 30-cm layer of 3.5-mm gravel with Phragmites australis). Tap water saturated with propane as gas tracer (pure or commercial cooking gas, depending on the test) was used. The mass transfer ratio between oxygen and commercial propane gas was quite constant and averaged R = 1.03, which is slightly lower than the value of R = 1.39 that is usually reported for pure propane. The OTR ranged from 0.31 to 5.04 g O(2) m(-2) d(-1) in the unplanted gravel bed and from 0.3 to 3.2 g O(2) m(-2) d(-1) in the HSSFCW, depending on the hydraulic retention time (HRT). The results of this study suggest that the OTR in HSSFCW is very low for the oxygen demand of standard wastewater and the OTR calculations based on mass balances and theoretical stoichiometric considerations overestimate OTR values by a factor that ranges from 10 to 100. The gas tracer method is a promising tool for determining OTR in constructed wetlands, with commercial gas proving to be a viable low-cost alternative for determining OTR.

  1. Simulating the Vapour Phase Air/Water Exchange of p,p′-DDE, p,p′-DDT, Lindane, and 2,3,7,8-Tetrachlorodibenzodioxin

    EPA Science Inventory

    Uncertainties in our understanding of gaseous air/water exchange have emerged as major sources of concern in efforts to construct global and regional mass balances of both the green house gas carbon dioxide and semi-volatile persistent, bioaccumulative and toxic chemicals. Hoff e...

  2. The influence of bubble plumes on air-seawater gas transfer velocities

    SciTech Connect

    Asher, W.E.; Karle, L.M.; Higgins, B.J.

    1995-07-01

    Air-sea gas exchange is an important process in the geochemical cycling of carbon dioxide (CO{sub 2}). The air-sea flux of CO{sub 2} is determined in part by the physical forcing functions, which are parameterized in terms of the air-sea transfer velocity, k{sub L}. Past studies have attempted to correlate k{sub L} with wind speed, U. Because strong winds occur in ocean regions thought to be important sources or sinks of CO{sub 2}, accurate knowledge of k{sub L} at high U is important in estimating the global air-sea flux of CO{sub 2}. Better understanding of the physical processes affecting gas transfer at large U will increase the accuracy in estimating k{sub L} in ocean regions with high CO{sub 2}, fluxes. Increased accuracy in estimating k{sub L} will increase the accuracy in calculating the net global air-sea CO{sub 2} flux and provide more accurate boundary and initial conditions for global ocean carbon cycle models. High wind speeds are associated with the presence of whitecaps, which can increase the gas flux by generating turbulence, disrupting surface films, and creating bubble plumes. Bubble plumes will create additional turbulence, prolong the surface disruption, and transfer gas to or from individual bubbles while they are beneath the surface. These turbulence and bubble processes very effectively promote gas transfer. Because of this, it is postulated that breaking waves, if present, will dominate non-whitecap related gas exchange. Under this assumption, k{sub L} Will increase linearly with increasing fractional area whitecap coverage, W{sub c}. In support of this, researchers found k{sub L} measured in a whitecap simulation tank (WSI) was linearly correlated with bubble plume coverage, B{sub c} (the laboratory analog of W{sub c}). However, it is not definitively known how the presence of breaking waves and bubble plumes affect the dependence of k{sub L} on Schmidt number, Sc, and aqueous-phase solubility, {alpha}.

  3. Precision cleaning verification of fluid components by air/water impingement and total carbon analysis

    NASA Technical Reports Server (NTRS)

    Barile, Ronald G.; Fogarty, Chris; Cantrell, Chris; Melton, Gregory S.

    1994-01-01

    NASA personnel at Kennedy Space Center's Material Science Laboratory have developed new environmentally sound precision cleaning and verification techniques for systems and components found at the center. This technology is required to replace existing methods traditionally employing CFC-113. The new patent-pending technique of precision cleaning verification is for large components of cryogenic fluid systems. These are stainless steel, sand cast valve bodies with internal surface areas ranging from 0.2 to 0.9 sq m. Extrapolation of this technique to components of even larger sizes (by orders of magnitude) is planned. Currently, the verification process is completely manual. In the new technique, a high velocity, low volume water stream impacts the part to be verified. This process is referred to as Breathing Air/Water Impingement and forms the basis for the Impingement Verification System (IVS). The system is unique in that a gas stream is used to accelerate the water droplets to high speeds. Water is injected into the gas stream in a small, continuous amount. The air/water mixture is then passed through a converging/diverging nozzle where the gas is accelerated to supersonic velocities. These droplets impart sufficient energy to the precision cleaned surface to place non-volatile residue (NVR) contaminants into suspension in the water. The sample water is collected and its NVR level is determined by total organic carbon (TOC) analysis at 880 C. The TOC, in ppm carbon, is used to establish the NVR level. A correlation between the present gravimetric CFC113 NVR and the IVS NVR is found from experimental sensitivity factors measured for various contaminants. The sensitivity has the units of ppm of carbon per mg/sq ft of contaminant. In this paper, the equipment is described and data are presented showing the development of the sensitivity factors from a test set including four NVRs impinged from witness plates of 0.05 to 0.75 sq m.

  4. Precision Cleaning Verification of Fluid Components by Air/Water Impingement and Total Carbon Analysis

    NASA Technical Reports Server (NTRS)

    Barile, Ronald G.; Fogarty, Chris; Cantrell, Chris; Melton, Gregory S.

    1995-01-01

    NASA personnel at Kennedy Space Center's Material Science Laboratory have developed new environmentally sound precision cleaning and verification techniques for systems and components found at the center. This technology is required to replace existing methods traditionally employing CFC-113. The new patent-pending technique of precision cleaning verification is for large components of cryogenic fluid systems. These are stainless steel, sand cast valve bodies with internal surface areas ranging from 0.2 to 0.9 m(exp 2). Extrapolation of this technique to components of even larger sizes (by orders of magnitude) is planned. Currently, the verification process is completely manual. In the new technique, a high velocity, low volume water stream impacts the part to be verified. This process is referred to as Breathing Air/Water Impingement and forms the basis for the Impingement Verification System (IVS). The system is unique in that a gas stream is used to accelerate the water droplets to high speeds. Water is injected into the gas stream in a small, continuous amount. The air/water mixture is then passed through a converging-diverging nozzle where the gas is accelerated to supersonic velocities. These droplets impart sufficient energy to the precision cleaned surface to place non-volatile residue (NVR) contaminants into suspension in the water. The sample water is collected and its NVR level is determined by total organic carbon (TOC) analysis at 880 C. The TOC, in ppm carbon, is used to establish the NVR level. A correlation between the present gravimetric CFC-113 NVR and the IVS NVR is found from experimental sensitivity factors measured for various contaminants. The sensitivity has the units of ppm of carbon per mg-ft(exp 2) of contaminant. In this paper, the equipment is described and data are presented showing the development of the sensitivity factors from a test set including four NVR's impinged from witness plates of 0.05 to 0.75 m(exp 2).

  5. Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank

    NASA Astrophysics Data System (ADS)

    Pereira, R.; Schneider-Zapp, K.; Upstill-Goddard, R. C.

    2016-07-01

    Understanding the physical and biogeochemical controls of air-sea gas exchange is necessary for establishing biogeochemical models for predicting regional- and global-scale trace gas fluxes and feedbacks. To this end we report the results of experiments designed to constrain the effect of surfactants in the sea surface microlayer (SML) on the gas transfer velocity (kw; cm h-1), seasonally (2012-2013) along a 20 km coastal transect (North East UK). We measured total surfactant activity (SA), chromophoric dissolved organic matter (CDOM) and chlorophyll a (Chl a) in the SML and in sub-surface water (SSW) and we evaluated corresponding kw values using a custom-designed air-sea gas exchange tank. Temporal SA variability exceeded its spatial variability. Overall, SA varied 5-fold between all samples (0.08 to 0.38 mg L-1 T-X-100), being highest in the SML during summer. SML SA enrichment factors (EFs) relative to SSW were ˜ 1.0 to 1.9, except for two values (0.75; 0.89: February 2013). The range in corresponding k660 (kw for CO2 in seawater at 20 °C) was 6.8 to 22.0 cm h-1. The film factor R660 (the ratio of k660 for seawater to k660 for "clean", i.e. surfactant-free, laboratory water) was strongly correlated with SML SA (r ≥ 0.70, p ≤ 0.002, each n = 16). High SML SA typically corresponded to k660 suppressions ˜ 14 to 51 % relative to clean laboratory water, highlighting strong spatiotemporal gradients in gas exchange due to varying surfactant in these coastal waters. Such variability should be taken account of when evaluating marine trace gas sources and sinks. Total CDOM absorbance (250 to 450 nm), the CDOM spectral slope ratio (SR = S275 - 295/S350 - 400), the 250 : 365 nm CDOM absorption ratio (E2 : E3), and Chl a all indicated spatial and temporal signals in the quantity and composition of organic matter in the SML and SSW. This prompts us to hypothesise that spatiotemporal variation in R660 and its relationship with SA is a consequence of compositional

  6. Driving force behind adsorption-induced protein unfolding: a time-resolved X-ray reflectivity study on lysozyme adsorbed at an air/water interface.

    PubMed

    Yano, Yohko F; Uruga, Tomoya; Tanida, Hajime; Toyokawa, Hidenori; Terada, Yasuko; Takagaki, Masafumi; Yamada, Hironari

    2009-01-06

    Time-resolved X-ray reflectivity measurements for lysozyme (LSZ) adsorbed at an air/water interface were performed to study the mechanism of adsorption-induced protein unfolding. The time dependence of the density profile at the air/water interface revealed that the molecular conformation changed significantly during adsorption. Taking into account previous work using Fourier transform infrared (FTIR) spectroscopy, we propose that the LSZ molecules initially adsorbed on the air/water interface have a flat unfolded structure, forming antiparallel beta-sheets as a result of hydrophobic interactions with the gas phase. In contrast, as adsorption continues, a second layer forms in which the molecules have a very loose structure having random coils as a result of hydrophilic interactions with the hydrophilic groups that protrude from the first layer.

  7. Energy transfer to Ln 3+ in GaS 1-xSe x(0 ⩽ x ⩽ 1) crystals

    NASA Astrophysics Data System (ADS)

    Tagiev, B. G.; Aidaev, F. Sh.; Abbasova, T. M.

    1988-04-01

    The paper deals with the matrix mechanism of excitation energy transfer to rare-earth centres in GaS xSe 1- x crystals. Energy transfer to Ln 3+ is shown to be radiationless in GaS 1- xSe x (0 ⩽ x ⩽ 1) single crystals and to come about predominantly by resonance, involving local states of the matrix forbidden band.

  8. Protonation, Hydrolysis, and Condensation of Mono- and Trifunctional Silanes at the Air/Water Interface

    PubMed Central

    Britt, David W.; Hlady, Vladimir

    2012-01-01

    The protonation, hydrolysis, and condensation kinetics of octadecyldimethylmethoxysilane (OMMS) and octadecyltrimethoxysilane (OTMS) at the air/water interface were investigated using a monolayer trough. OTMS chemical condensation within physically condensed phases was observed in transferred monolayers using fluorescence microscopy. Molecular area increases and decreases attributed to protonation and hydrolysis, respectively, of silane methoxy groups were measured by a surface balance. These area changes at constant surface pressure suggested a stepwise protonation and hydrolysis of the three OTMS methoxy groups. In contrast, only a single protonation and hydrolysis event was observed for monofunctional OMMS. The influences of monolayer spreading time, silane packing density, and subphase pH on the reaction kinetics are presented. PMID:25147424

  9. Evaluation of oxygen transfer efficiency under process conditions using the dynamic off-gas method.

    PubMed

    Schuchardt, A; Libra, J A; Sahlmann, C; Wiesmann, U; Gnirss, R

    2007-05-01

    The off-gas method can be used to investigate standard oxygen transfer efficiencies under process conditions (alphaSOTE) over the operating life of an aeration system. A method to evaluate alphaSOTE is described in detail by US and German standards. The standards, however, do not describe how to evaluate dynamic changes in aSOTE over a day, which can be useful to uncover problems and unfavourable process conditions. Based on over three years experience gained in off-gas testing in Berlin wastewater treatment plants (WWTPs) under operating conditions, a method to evaluate and interpret the dynamic changes in oxygen transfer is presented. The application of the dynamic off-gas method brings important additional information, which can be used to increase operational efficiency of the aeration basin and to increase process reliability, with a relatively small increase in effort. This paper shows how to perform dynamic measurements under process conditions. Some results of such measurements under dynamic process conditions, performed in a Berlin WWTP, are discussed.

  10. Characterization of carbon dioxide transfer in a hollow fiber membrane module as a solution for gas-liquid transfer in microgravity conditions.

    NASA Astrophysics Data System (ADS)

    Farges, Berangere; Duchez, David; Dussap, Claude-Gilles; Cornet, Jean-F.

    In microgravity, one of the major difficulties encountered in closed photosynthetic reactors is the gas-liquid transfer with the necessity to provide CO2 (carbon source, pH control) and to recover the produced O2 . Indeed, reduced gravity is expected to modify gas liquid transfer and liquid phase mixing characteristics inside photobioreactors conceived to regenerate atmosphere of closed life-support systems. To obtain efficient mass transfer conditions and mixing of phases, several solutions are possible: use of rotating reactor (centrifugal field), use of forced, co-current convective reactor with gas-liquid separator and use of membrane modules. In terms of space process engineering, the membrane reactor can be a valuable alternative in which the gas and liquid phases are separated with a selectively permeable membrane. The rate-limiting factors in this reactor were demonstrated to be the surface of membrane A needed for diffusion of gases and the CO2 and O2 mass transfer coefficients in the liquid phase kL. How-ever, the major advantages of the membrane reactor are that it is composed of a hydrophobic membrane (here PTFE) which showed a high hydrophobicity, an important chemical resis-tance, a very long term stability and overall which is favourable to gas transfer. Moreover, the volumetric mass transfer coefficients are sufficiently high to build compact systems with small footprints, no complex rotating devices and lighter weights. This paper describes first the development of a system enabling the accurate characterization of the mass transfer limiting step for a PTFE membrane module. This original technical apparatus, together with a technical assessment of membrane permeability to different gases, is associated with a balance model, determining thus completely the CO2 mass transfer problem between phases. First results are given and discussed for the CO2 mass transfer coefficient CO kL 2 obtained in case of an absorption experiment at pH = 8 using the

  11. Partitioning of semi-volatile organic compounds to the air/water interface

    NASA Astrophysics Data System (ADS)

    Pankow, James F.

    Partition coefficients ( Kia, m 3m -2) for sorption of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes at the air/water interface were estimated by extrapolating quartz/gas sorption data to relative humidity (RH) values of 100%. For each compound class, the log Kia values were found to be well correlated with log pLo where pLo (Torr) is the vapor pressure of the pure subcooled liquid. For the PAHs, correlation equation is log Kia = -1.20 log pLo - 5.82 ( R2 = 0.98). For the n-alkanes, the correlation equation is log Kia = -0.93 log pLo - 4.42 ( R2 = 0.95).

  12. Atmospheric photochemistry at a fatty acid-coated air-water interface

    NASA Astrophysics Data System (ADS)

    Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D. James; George, Christian

    2016-08-01

    Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

  13. Air/water two-phase flow test tunnel for airfoil studies

    NASA Astrophysics Data System (ADS)

    Ohashi, H.; Matsumoto, Y.; Ichikawa, Y.; Tsukiyama, T.

    1990-02-01

    A test tunnel for the study of airfoil performances under air/water two-phase flow condition has been designed and constructed. This facility will serve for a better understanding of the flow phenomena and characteristics of hydraulic machinery under gas/ liquid two-phase flow operating conditions. At the test section of the tunnel, a two-dimensional isolated airfoil or a cascade of airfoils is installed in a two-phase inlet flow with a uniform velocity (up to 10 m/s) and void fraction (up to 12%) distribution. The details of the tunnel structure and the measuring systems are described and the basic characteristics of the constructed tunnel are also given. As an example of the test results, void fraction distribution around a test airfoil is shown.

  14. Air/water two-phase flow test tunnel for airfoil studies

    NASA Astrophysics Data System (ADS)

    Ohashi, H.; Matsumoto, Y.; Ichikawa, Y.; Tsukiyama, T.

    1994-01-01

    A test tunnel for the study of airfoil performances under air/water two-phase flow condition has been designed and constructed. This facility will serve for a better understanding of the flow phenomena and characteristics of hydraulic machinery under gas/ liquid two-phase flow operating conditions. At the test section of the tunnel, a two-dimensional isolated airfoil or a cascade of airfoils is installed in a two-phase inlet flow with a uniform velocity (up to 10 m/s) and void fraction (up to 12%) distribution. The details of the tunnel structure and the measuring systems are described and the basic characteristics of the constructed tunnel are also given. As an example of the test results, void fraction distribution around a test airfoil is shown.

  15. Heat Transfer to Anode of Arc as Function of Transverse Magnetic Field and Lateral Gas Flow Velocity

    NASA Astrophysics Data System (ADS)

    Zama, Yoshiyuki; Shiino, Toru; Ishii, Yoko; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Gas tungsten arc welding has useful joining technology because of high-energy and high-current characteristics. It can be flexible from the transverse magnetic field and lateral gas flow velocity. In this case, the weld defect occurs. In this research, the heat transfer to the anode of the arc as a function of the transverse magnetic field and lateral gas flow velocity is elucidated. That magnetic flux density and lateral gas velocity were varied from 0 to 3 mT and 0 to 50?m?s -1, respectively. The axial plasma gas argon flow rates were 3?slm. A transverse magnetic field is applied to the arc using Helmholtz coil. The anode is used by a water-cooled copper plate, and the heat transfer is measured by temperature of cooled water. As a result, the arc is deflected by the Lorentz force and lateral gas convection. Thus, the heat transfer to the anode of the arc decreases with increasing the transverse magnetic field and lateral gas flow velocity. In addition, the heat transfer to the anode changes with different attachments modes. The lateral gas flow causes a convective heat loss from the arc to the chamber walls.

  16. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Donald Duttlinger

    1999-12-01

    During FY99, the Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and gas producers make timely, informed technology decisions. PTfC's national organization has active grassroots programs that connect with independents through its 10 Regional Lead Organizations (RLOs). These activities--including technology workshops, resource centers, websites, newsletters, and other outreach efforts--are guided by regional Producer Advisory Groups (PAGs). The role of the national headquarters (HQ) staff includes planning and managing the PTTC program, conducting nation-wide technology transfer activities, and implementing a comprehensive communications effort. This technical progress report summarizes PTTC's accomplishments during FY99, which lay the groundwork for further growth in the future.

  17. Unit operations for gas-liquid mass transfer in reduced gravity environments

    NASA Technical Reports Server (NTRS)

    Pettit, Donald R.; Allen, David T.

    1992-01-01

    Basic scaling rules are derived for converting Earth-based designs of mass transfer equipment into designs for a reduced gravity environment. Three types of gas-liquid mass transfer operations are considered: bubble columns, spray towers, and packed columns. Application of the scaling rules reveals that the height of a bubble column in lunar- and Mars-based operations would be lower than terrestrial designs by factors of 0.64 and 0.79 respectively. The reduced gravity columns would have greater cross-sectional areas, however, by factors of 2.4 and 1.6 for lunar and Martian settings. Similar results were obtained for spray towers. In contract, packed column height was found to be nearly independent of gravity.

  18. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2000-05-01

    During FY00, the Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and gas producers make timely, informed technology decisions. PTTC's national organization has active grassroots programs that connect with independents through its 10 Regional Lead Organizations (RLOs). These activities--including technology workshops, resource centers, websites, newsletters, and other outreach efforts--are guided by regional Producer Advisory Groups (PAGs). The role of the national headquarters (HQ) staff includes planning and managing the PTTC program, conducting nation-wide technology transfer activities, and implementing a comprehensive communications effort. This technical progress report summarizes PTTC's accomplishments during FY00, which lay the groundwork for further growth in the future.

  19. Microbial synthesis gas utilization and ways to resolve kinetic and mass-transfer limitations.

    PubMed

    Yasin, Muhammad; Jeong, Yeseul; Park, Shinyoung; Jeong, Jiyeong; Lee, Eun Yeol; Lovitt, Robert W; Kim, Byung Hong; Lee, Jinwon; Chang, In Seop

    2015-02-01

    Microbial conversion of syngas to energy-dense biofuels and valuable chemicals is a potential technology for the efficient utilization of fossils (e.g., coal) and renewable resources (e.g., lignocellulosic biomass) in an environmentally friendly manner. However, gas-liquid mass transfer and kinetic limitations are still major constraints that limit the widespread adoption and successful commercialization of the technology. This review paper provides rationales for syngas bioconversion and summarizes the reaction limited conditions along with the possible strategies to overcome these challenges. Mass transfer and economic performances of various reactor configurations are compared, and an ideal case for optimum bioreactor operation is presented. Overall, the challenges with the bioprocessing steps are highlighted, and potential solutions are suggested. Future research directions are provided and a conceptual design for a membrane-based syngas biorefinery is proposed.

  20. Proton transfer reaction mass spectrometry: on-line trace gas analysis at the ppb level

    NASA Astrophysics Data System (ADS)

    Hansel, A.; Jordan, A.; Holzinger, R.; Prazeller, P.; Vogel, W.; Lindinger, W.

    1995-11-01

    A system for trace gas analysis using proton transfer reaction mass spectrometry (PTR-MS) has been developed which allows for on-line measurements of components with concentrations as low as 1 ppb. The method is based on reactions of H3O+ ions, which perform non-dissociative proton transfer to most of the common organic trace constituents but do not react with any of the components present in clean air. Examples of analysis of breath taken from smokers and non-smokers as well as from patients suffering from cirrhosis of the liver, and of air in buildings as well as of ambient air taken at a road crossing demonstrate the wide range of applicability of this method. An enhanced level of acetonitrile in the breath is a most suitable indicator that a person is a smoker. Enhanced levels of propanol strongly indicate that a person has a severe liver deficiency.

  1. Effect of impeller geometry on gas-liquid mass transfer coefficients in filamentous suspensions

    SciTech Connect

    Dronawat, S.N.; Svihla, C.K.; Hanley, T.R.

    1997-12-31

    Volumetric gas-liquid mass transfer coefficients were measured in suspensions of cellulose fibers with concentrations ranging from 0 to 20 g/L. The mass transfer coefficients were measured using the dynamic method. Results are presented for three different combinations of impellers at a variety of gassing rates and agitation speeds. Rheological properties of the cellulose fibers were also measured using the impeller viscometer method. Tests were conducted in a 20 L stirred-tank fermentor and in 65 L tank with a height to diameter ratio of 3:1. Power consumption was measured in both vessels. At low agitation rates, two Rushton turbines gave 20% better performance than the Rushton and hydrofoil combination and 40% better performance than the Rushton and propeller combination for oxygen transfer. At higher agitation rates, the Rushton and hydrofoil combination gave 14 and 25% better performance for oxygen transfer than two Rushton turbines and the Rushton and hydrofoil combination, respectively. 8 refs., 11 figs., 1 tab.

  2. Computational prediction of heat transfer to gas turbine nozzle guide vanes with roughened surfaces

    SciTech Connect

    Guo, S.M.; Jones, T.V.; Lock, G.D.; Dancer, S.N.

    1998-04-01

    The local Mach number and heat transfer coefficient over the aerofoil surfaces and endwalls of a transonic gas turbine nozzle guide vane have been calculated. the computations were performed by solving the time-averaged Navier-Stokes equations using a fully three-dimensional computational code (CFDS), which is well established at Rolls-Royce. A model to predict the effects of roughness has been incorporated into CFDS and heat transfer levels have been calculated for both hydraulically smooth and transitionally rough surfaces. The roughness influences the calculations in two ways; first the mixing length at a certain height above the surface is increased; second the wall function used to reconcile the wall condition with the first grid point above the wall is also altered. The first involves a relatively straightforward shift of the origin in the van Driest damping function description, the second requires an integration of the momentum equation across the wall layer. A similar treatment applies to the energy equation. The calculations are compared with experimental contours of heat transfer coefficient obtained using both thin-film gages and the transient liquid crystal technique. Measurements were performed using both hydraulically smooth and roughened surfaces, and at engine-representative Mach and Reynolds numbers. The heat transfer results are discussed and interpreted in terms of surface-shear flow visualization using oil and dye techniques.

  3. Heat transfer analysis of fuel assemblies in a heterogeneous gas core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Watanabe, Yoichi; Appelbaum, Jacob; Diaz, Nils; Maya, Isaac

    1991-01-01

    Heat transfer problems of a heterogeneous gaseous core nuclear rocket were studied. The reactor core consists of 1.5-m long hexagonal fuel assemblies filled with pressurized uranium tetrafluoride (UF4) gas. The fuel gas temperature ranges from 3500 to 7000 K at a nominal operating condition of 40 atm. Each fuel assembly has seven coolant tubes, through which hydrogen propellant flows. The propellant temperature is not constrained by the fuel temperature but by the maximum temperature of the graphite coolant tube. For a core achieving a fission power density of 1000 MW/cu m, the propellant core exit temperature can be as high as 3200 K. The physical size of a 1250 MW gaseous core nuclear rocket is comparable with that of a NERVA-type solid core nuclear rocket. The engine can deliver a specific impulse of 1020 seconds and a thrust of 330 kN.

  4. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2003-04-30

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and natural gas producers make timely, informed technology decisions. Networking opportunities that occur with a Houston Headquarters (HQ) location are increasing name awareness. Focused efforts by Executive Director Don Duttlinger to interact with large independents, national service companies and some majors are continuing to supplement the support base of the medium to smaller industry participants around the country. PTTC is now involved in many of the technology-related activities that occur in high oil and natural gas activity areas. Access to technology remains the driving force for those who do not have in-house research and development capabilities and look to the PTTC to provide services and options for increased efficiency.

  5. Heat Transfer to Bodies in a High-speed Rarified-Gas Stream

    NASA Technical Reports Server (NTRS)

    Stalder, Jackson R; Goodwin, Glen; Creager, Marcus O

    1952-01-01

    Report presents the results of an investigation to determine the equilibrium temperature and heat-transfer coefficients for transverse cylinders in a high-speed stream of rarefied gas measured over a range of Knudsen numbers (ratio of molecular-mean-free path to cylinder diameter) from 0.025 to 11.8 and for Mach numbers from 2.0 to 3.3. The range of free-stream Reynolds numbers was from 0.28 to 203. The models tested were 0.0010-, 0.0050-, 0.030-, 0.051-, 0.080-, and 0.126-inch -diameter cylinders held normal to the stream.

  6. Gas-grain energy transfer in solar nebula shock waves: Implications for the origin of chondrules

    NASA Technical Reports Server (NTRS)

    Hood, L. L.; Horanyi, M.

    1993-01-01

    Meteoritic chondrules provide evidence for the occurrence of rapid transient heating events in the protoplanetary nebula. Astronomical evidence suggests that gas dynamic shock waves are likely to be excited in protostellar accretion disks by processes such as protosolar mass ejections, nonaxisymmetric structures in an evolving disk, and impact on the nebula surface of infalling 'clumps' of circumstellar gas. Previous detailed calculations of gas-grain energy and momentum transfer have supported the possibility that such shock waves could have melted pre-existing chondrule-sized grains. The main requirement for grains to reach melting temperatures in shock waves with plausibly low Mach numbers is that grains existed in dust-rich zones (optical depth greater than 1) where radiative cooling of a given grain can be nearly balanced by radiation from surrounding grains. Localized dust-rich zones also provide a means of explaining the apparent small spatial scale of heating events. For example, the scale size of at least some optically thick dust-rich zones must have been relatively small (less than 10 kilometers) to be consistent with petrologic evidence for accretion of hot material onto cold chondrules. The implied number density of mm-sized grains for these zones would be greater than 30 m(exp -3). In this paper, we make several improvements of our earlier calculations to include radiation self-consistently in the shock jump conditions, and we include heating of grains due to radiation from the shocked gas. In addition, we estimate the importance of momentum feedback of dust concentrations onto the shocked gas which would tend to reduce the efficiency of gas dynamic heating of grains in the center of the dust cloud.

  7. Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction.

    PubMed

    Zhu, Hongying; Huang, Guangming

    2015-03-31

    In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m(-3), ∼1.44 ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages.

  8. Regio-Selective Intramolecular Hydrogen/Deuterium Exchange in Gas-Phase Electron Transfer Dissociation

    NASA Astrophysics Data System (ADS)

    Hamuro, Yoshitomo

    2017-02-01

    Protein backbone amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) typically utilizes enzymatic digestion after the exchange reaction and before MS analysis to improve data resolution. Gas-phase fragmentation of a peptic fragment prior to MS analysis is a promising technique to further increase the resolution. The biggest technical challenge for this method is elimination of intramolecular hydrogen/deuterium exchange (scrambling) in the gas phase. The scrambling obscures the location of deuterium. Jørgensen's group pioneered a method to minimize the scrambling in gas-phase electron capture/transfer dissociation. Despite active investigation, the mechanism of hydrogen scrambling is not well-understood. The difficulty stems from the fact that the degree of hydrogen scrambling depends on instruments, various parameters of mass analysis, and peptide analyzed. In most hydrogen scrambling investigations, the hydrogen scrambling is measured by the percentage of scrambling in a whole molecule. This paper demonstrates that the degree of intramolecular hydrogen/deuterium exchange depends on the nature of exchangeable hydrogen sites. The deuterium on Tyr amide of neurotensin (9-13), Arg-Pro-Tyr-Ile-Leu, migrated significantly faster than that on Ile or Leu amides, indicating the loss of deuterium from the original sites is not mere randomization of hydrogen and deuterium but more site-specific phenomena. This more precise approach may help understand the mechanism of intramolecular hydrogen exchange and provide higher confidence for the parameter optimization to eliminate intramolecular hydrogen/deuterium exchange during gas-phase fragmentation.

  9. Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas-liquid transfer in microgravity conditions

    NASA Astrophysics Data System (ADS)

    Farges, Bérangère; Duchez, David; Dussap, Claude-Gilles; Cornet, Jean-François

    2012-01-01

    In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas-liquid transfer with, for instance, the necessity to provide CO2 (carbon source, pH control) and to recover the evolved O2 in photobioreactors used as atmosphere bioregenerative systems.This paper describes first the development of a system enabling the accurate characterization of the mass transfer limiting step for a PTFE membrane module used as a possible efficient solution to the microgravity gas-liquid transfer. This original technical apparatus, together with a technical assessment of membrane permeability to different gases, is associated with a balance model, determining thus completely the CO2 mass transfer problem between phases. First results are given and discussed for the CO2 mass transfer coefficient kLCO obtained in case of absorption experiments at pH 8 using the hollow fiber membrane module. The consistency of the proposed method, based on a gas and liquid phase balances verifying carbon conservation enables a very accurate determination of the kLCO value as a main limiting step of the whole process. Nevertheless, further experiments are still needed to demonstrate that the proposed method could serve in the future as reference method for mass transfer coefficient determination if using membrane modules for BLSS in reduced or microgravity conditions.

  10. Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence

    NASA Astrophysics Data System (ADS)

    Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

    2016-11-01

    The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, kL, and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, kL for the wind-driven wavy gas-liquid interface is generally proportional to Sc‑0.5, and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking.

  11. Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence

    PubMed Central

    Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

    2016-01-01

    The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, kL, and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, kL for the wind-driven wavy gas-liquid interface is generally proportional to Sc−0.5, and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking. PMID:27841325

  12. Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence.

    PubMed

    Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

    2016-11-14

    The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, kL, and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, kL for the wind-driven wavy gas-liquid interface is generally proportional to Sc(-0.5), and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking.

  13. Evaluation of the swell effect on the air-sea gas transfer in the coastal zone

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Loza, Lucía; Ocampo-Torres, Francisco J.

    2016-04-01

    Air-sea gas transfer processes are one of the most important factors regarding global climate and long-term global climate changes. Despite its importance, there is still a huge uncertainty on how to better parametrize these processes in order to include them on the global climate models. This uncertainty exposes the need to increase our knowledge on gas transfer controlling mechanisms. In the coastal regions, breaking waves become a key factor to take into account when estimating gas fluxes, however, there is still a lack of information and the influence of the ocean surface waves on the air-sea interaction and gas flux behavior must be validated. In this study, as part of the "Sea Surface Roughness as Air-Sea Interaction Control" project, we evaluate the effect of the ocean surface waves on the gas exchange in the coastal zone. Direct estimates of the flux of CO2 (FCO2) and water vapor (FH2O) through eddy covariance, were carried out from May 2014 to April 2015 in a coastal station located at the Northwest of Todos Santos Bay, Baja California, México. For the same period, ocean surface waves are recorded using an Acoustic Doppler Current Profiler (Workhorse Sentinel, Teledyne RD Instruments) with a sampling rate of 2 Hz and located at 10 m depth about 350 m away from the tower. We found the study area to be a weak sink of CO2 under moderate wind and wave conditions with a mean flux of -1.32 μmol/m2s. The correlation between the wind speed and FCO2 was found to be weak, suggesting that other physical processes besides wind may be important factors for the gas exchange modulation at coastal waters. The results of the quantile regression analysis computed between FCO2 and (1) wind speed, (2) significant wave height, (3) wave steepness and (4) water temperature, show that the significant wave height is the most correlated parameter with FCO2; Nevertheless, the behavior of their relation varies along the probability distribution of FCO2, with the linear regression

  14. Effects of magnetic fields on improving mass transfer in flue gas desulfurization using a fluidized bed

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Gui, Keting; Wang, Xiaobo

    2016-02-01

    The effects of magnetic fields on improving the mass transfer in flue gas desulfurization using a fluidized bed are investigated in the paper. In this research, the magnetically fluidized bed (MFB) is used as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. Lime slurry is continuously sprayed into the reactor. As a consequence, the desulfurization reaction and the slurry drying process take place simultaneously in the MFB. In this paper, the effects of ferromagnetic particles and external magnetic fields on the desulphurization efficiency are studied and compared with that of quartz particles as the fluidized particles. Experimental results show that the ferromagnetic particles not only act as a platform for lime slurry to precipitate on like quartz particles, but also take part in the desulfurization reaction. The results also show that the specific surface area of ferromagnetic particles after reaction is enlarged as the magnetic intensity increases, and the external magnetic field promotes the oxidation of S(IV), improving the mass transfer between sulphur and its sorbent. Hence, the efficiency of desulphurization under the effects of external magnetic fields is higher than that in general fluidized beds.

  15. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    1998-10-31

    In pursuing its mission of helping U.S. independent oil and gas producers make timely, informed technology decisions, the Petroleum Technology Transfer Council (PTTC) functions as a cohesive national organization that implements industry's directives through active regional programs. The role of the national headquarters (HQ) organization includes planning and managing the PTTC program, conducting nation-wide technology transfer activities, and implementing a comprehensive communications effort. PTTC relies on 10 Regional Lead Organizations (RLOs) as its main program delivery mechanism to industry. Through its regions, PTTC connects with independent oil and gas producers--through technology workshops, resources centers, websites, newsletters, and other outreach efforts. The organization effectively combines federal, state, and industry funding to achieve important goals for all of these sectors. This integrated funding base, combined with industry volunteers guiding PTTC's activities and the dedication of national and regional staff, are achieving notable results. PTTC is increasingly recognized as a critical resource for information and access to technologies, especially for smaller companies. This technical progress report summarizes PTTC's accomplishments during FY98, and its strategy for achieving further growth in the future.

  16. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2000-11-01

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and gas producers make timely, informed technology decisions during Fiscal Year 2000 (FY00). Functioning as a cohesive national organization, PTTC has active grassroots programs through its ten Regional Lead Organizations (RLOs) who bring research and academia to the table via their association with geological surveys and engineering departments. The regional directors connect with independent oil and gas producers through technology workshops, resource centers, websites, newsletters, various technical publications and other outreach efforts. These are guided by regional Producer Advisory Groups (PAGs), who are area operators and service companies working with the Regional Lead Organizations. The role of the national headquarters (HQ) staff includes planning and managing the PTTC program, conducting nation-wide technology transfer activities, and implementing a comprehensive communications effort. The organization effectively combines federal, state, and industry funding to achieve important goals for all of these sectors. This integrated funding base, combined with industry volunteers guiding PTTC's activities and the dedication of national and regional staff, are achieving notable results. PTTC is increasingly recognized as a critical resource for information and access to technologies, especially for smaller companies. This technical progress report summarizes PTTC's accomplishments during FY00, which lays the groundwork for further growth in the future. At a time of many industry changes and market movements, the organization has built a reputation and expectation to address industry needs of getting information distributed quickly which can impact the bottom line immediately.

  17. Dynamics of surfactant sorption at the air/water interface: continuous-flow tensiometry.

    PubMed

    Svitova, T F; Wetherbee, M J; Radke, C J

    2003-05-01

    Dynamic interfacial tensiometry, gauged by axisymmetric drop shape analysis of static drops or bubbles, provides useful information on surfactant adsorption kinetics. However, the traditional pendant-drop methodology is not readily amenable to the study of desorption kinetics. Thus, the question of sorption reversibility is difficult to assess by this technique. We extend classical pendant/sessile drop dynamic tensiometry by immersing a sessile bubble in a continuously mixed optical cell. Ideal-mixed conditions are established by stirring and by constant flow through the cell. Aqueous surface-active-agent solutions are either supplied to the cell (loading) or removed from the cell by flushing with water (washout), thereby allowing study of both adsorption and desorption kinetics. Well-mixed conditions and elimination of any mass transfer resistance permit direct identification of sorption kinetic barriers to and from the external aqueous phase with time constants longer than the optical-cell residence time. The monodisperse nonionic surfactant ethoxy dodecyl alcohol (C(12)E(5)), along with cationic cetyltrimethyl ammonium bromide (CTAB) in the presence of added salt, adsorbs and desorbs instantaneously at the air/water interface. In these cases, the experimentally observed dynamic-tension curves follow the local-equilibrium model precisely for both loading and washout. Accordingly, these surfactants below their critical micelle concentrations (CMC) exhibit no detectable sorption-activation barriers on time scales of order a min. However, the sorption dynamics of dilute CTAB in the absence of electrolyte is markedly different from that in the presence of KBr. Here CTAB desorption occurs at local equilibrium, but the adsorption rate is kinetically limited, most likely due to an electrostatic barrier arising as the charged surfactant accumulates at the interface. The commercial, polydisperse nonionic surfactant ethoxy nonylphenol (NP9) loads in good agreement with

  18. Flow and heat transfer in gas turbine disk cavities subject to nonuniform external pressure field

    SciTech Connect

    Roy, R.P.; Kim, Y.W.; Tong, T.W.

    1995-10-01

    Injestion of hot gas from the main-stream gas path into turbine disk cavities, particularly the first-stage disk cavity, has become a serious concern for the next-generation industrial gas turbines featuring high rotor inlet temperature. Fluid temperature in the cavities increases further due to windage generated by fluid drag at the rotating and stationary surfaces. The resulting problem of rotor disk heat-up is exacerbated by the high disk rim temperature due to adverse (relatively flat) temperature profile of the mainstream gas in the annular flow passage of the turbine. A designer is concerned about the level of stresses in the turbine rotor disk and its durability, both of which are affected significantly by the disk temperature distribution. This distribution also plays a major role in the radial position of the blade tip and thus, in establishing the clearance between the tip and the shroud. To counteract mainstream gas ingestion as well as to cool the rotor and the stator disks, it is necessary to inject cooling air (bled from the compressor discharge) into the wheel space. Since this bleeding of compressor air imposes a penalty on the engine cycle performance, the designers of disk cavity cooling and sealing systems need to accomplish these tasks with the minimum possible amount of bleed air without risking disk failure. This requires detailed knowledge of the flow characteristics and convective heat transfer in the cavity. The flow in the wheel space between the rotor and stator disks is quite complex. It is usually turbulent and contains recirculation regions. Instabilities such as vortices oscillating in space have been observed in the flow. It becomes necessary to obtain both a qualitative understanding of the general pattern of the fluid motion as well as a quantitative map of the velocity and pressure fields.

  19. An effusive molecular beam technique for studies of polyatomic gas-surface reactivity and energy transfer.

    PubMed

    Cushing, G W; Navin, J K; Valadez, L; Johánek, V; Harrison, I

    2011-04-01

    An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(T(g), T(s); ϑ), on metal surfaces for which the impinging gas temperature, T(g), and surface temperature, T(s), can be independently varied, along with the angle of incidence, ϑ, of the impinging gas. Effusive beam experiments with T(g) = T(s) = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ϑ), which when averaged over the cos (ϑ)/π angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(T(g), T(s); ϑ) measurements for which T(g) ≠ T(s) provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the T(g) of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111).

  20. Powder wettability at a static air-water interface.

    PubMed

    Dupas, Julien; Forny, Laurent; Ramaioli, Marco

    2015-06-15

    The reconstitution of a beverage from a dehydrated powder involves several physical mechanisms that determine the practical difficulty to obtain a homogeneous drink in a convenient way and within an acceptable time for the preparation of a beverage. When pouring powder onto static water, the first hurdle to overcome is the air-water interface. We propose a model to predict the percentage of powder crossing the interface in 45 s, namely the duration relevant for this application. We highlight theoretically the determinant role of the contact angle and of the particle size distribution. We validate experimentally the model for single spheres and use it to predict the wettability performance of commercial food powders for different contact angles and particles sizes. A good agreement is obtained when comparing the predictions and the wettability of the tested powders.

  1. pH effects on the molecular structure of β-lactoglobulin modified air-water interfaces and its impact on foam rheology.

    PubMed

    Engelhardt, Kathrin; Lexis, Meike; Gochev, Georgi; Konnerth, Christoph; Miller, Reinhard; Willenbacher, Norbert; Peukert, Wolfgang; Braunschweig, Björn

    2013-09-17

    Macroscopic properties of aqueous β-lactoglobulin (BLG) foams and the molecular properties of BLG modified air-water interfaces as their major structural element were investigated with a unique combination of foam rheology measurements and interfacial sensitive methods such as sum-frequency generation and interfacial dilatational rheology. The molecular structure and protein-protein interactions at the air-water interface can be changed substantially with the solution pH and result in major changes in interfacial dilational and foam rheology. At a pH near the interfacial isoelectric point BLG molecules carry zero net charge and disordered multilayers with the highest interfacial dilatational elasticity are formed at the air-water interface. Increasing or decreasing the pH with respect to the isoelectric point leads to the formation of a BLG monolayer with repulsive electrostatic interactions among the adsorbed molecules which decrease the interfacial dilational elasticity. The latter molecular information does explain the behavior of BLG foams in our rheological studies, where in fact the highest apparent yield stresses and storage moduli are established with foams from electrolyte solutions with a pH close to the isoelectric point of BLG. At this pH the gas bubbles of the foam are stabilized by BLG multilayers with attractive intermolecular interactions at the ubiquitous air-water interfaces, while BLG layers with repulsive interactions decrease the apparent yield stress and storage moduli as stabilization of gas bubbles with a monolayer of BLG is less effective.

  2. Study of heat transfer characteristics during dissociation of gas hydrates in porous media

    SciTech Connect

    Kamath, V.A.

    1984-01-01

    An experimental technique was developed to measure the rate of formation and dissociation of hydrates in porous media. In the first phase of the work, hydrates of propane and methane were studied. Propane hydrate cores were formed by contacting liquid propane with compacted porous ice cores at 274 K for 24 to 100 hours, whereas the formation of methane hydrates was achieved by contacting ice cores with gaseous methane at about 7000 kPa and 274 K, for 24 to 200 hours. These hydrate cores were dissociated by circulating warm water over the top of the core, under controlled temperatures and pressures. The major findings of these experiments are as follows: 1) the phenomena of dissociation of hydrates to liquid water and gas is similar to nucleate boiling of liquids; 2) the rate of dissociation of hydrates at constant ..delta..T, is directly proportional to the area of hydrates exposed to the warm fluid or the composition of hydrates in the core; and 3) the rate of heat transfer and dissociation increase with increase in pressure and the rate of circulation of the warm fluid. Unified correlations for heat transfer and dissociation rates were successfully obtained for both methane and propane hydrate dissociation. These correlations will be useful to predict the rate of dissociation and gas production in hydrate reservoirs. In the second phase of his work, in order to simulate the conditions of hydrate dissociation in the earth, methane hydrates were formed and dissociated in unconsolidated cores of sand. The results of these experiments have demonstrated that the heat transfer resistance of the media (rock) plays an important role in dissociation of hydrates in earth.

  3. ISSUES IN SIMULATING ELEMENTAL MERCURY AIR/WATER EXCHANGE AND AQUEOUS MONOMETHYLMERCURY SPECIATION

    EPA Science Inventory

    This presentation focuses on two areas relevant to assessing the global fate and bioavailability of mercury: elemental mercury air/water exchange and aqueous environmental monomethylmercury speciation.

  4. [Virus adsorption from batch experiments as influenced by air-water interface].

    PubMed

    Zhang, Hui; Zhao, Bing-zi; Zhang, Jia-bao; Zhang, Cong-zhi; Wang, Qiu-ying; Chen, Ji

    2007-12-01

    The presence of air-water interface in batch sorption experiments may result in inaccurate estimation of virus adsorption onto various soils. A batch sorption experiment was conducted to compare the adsorption results of MS2 in different soils under presence/absence of air-water interface. Soils with sterilization/nonterilization treatment were used. Virus recovery efficiency in a blank experiment (no soil) was also evaluated as affected by different amount of air-water interface. The presence of air-water interface altered the results of virus adsorption in different soils with different extent, with Sandy fluvo-aquic soil being the most considerably affected, followed by Red loam soil, and the least being Red clay soil, probably because of different soil properties associated with virus adsorption/inactivation. Soil sterilization resulted in more significant difference of virus adsorption onto the Sandy fluvo-aquic soil between the presence and absence of air-water interface, while a reduced difference was observed in the Red loam soil. The presence of air-water interface significantly decreased virus recovery efficiency, with the values being decreased with increase in the amount of air-water interface. Soil particles likely prohibit viruses from reaching the air-water interface or alter the forces at the solid-water-air interface so that the results from the blank experiment did not truly represent results from control blank, which probably resulted in adsorption difference between presence and absence of the air-water interface.

  5. Trajectory studies of vibrational energy transfer in gas--surface collisions

    SciTech Connect

    Lucchese, R.R.; Tully, J.C.

    1984-04-01

    We have applied the stochastic trajectory method to the scattering of NO from the (001) surface of an LiF crystal. The surface was represented by a 32 atom primary zone and the effects of the rest of the surface atoms were included using the Generalized Langevin Equation method. The forces between the surface atoms were treated using a shell model and the gas--surface interactions included short-range repulsions, attractive dispersion forces, and the interaction of the dipole moment of NO and the surface ions. The dependence of the dipole moment and the dependence of the molecular polarizability on the internuclear separation of NO were also included. The calculated vibrational energy accommodation coefficient was less than 1% when trapping of the gas diatom was negligible. By modifying the vibrational frequency of the scattered diatom we have examined the dependence of vibrational energy transfer on frequency. An exponential dependence on the ratio of the molecular frequency to the surface Debye frequency was found, similar to behavior observed for vibrational relaxation in condensed phases. We have also examined the relative efficiency of the coupling of the vibrational mode to the translational and rotational modes of the gas diatom and to the phonon modes of the surface. We found that the vibrational mode is most strongly coupled to the surface phonons with a much weaker coupling to the rotational and translational modes.

  6. Contribution of heat transfer to turbine blades and vanes for high temperature industrial gas turbines. Part 2: Heat transfer on serpentine flow passage.

    PubMed

    Takeishi, K; Aoki, S

    2001-05-01

    The improvement of the heat transfer coefficient of the 1st row blades in high temperature industrial gas turbines is one of the most important issues to ensure reliable performance of these components and to attain high thermal efficiency of the facility. This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of such gas turbines in order to attain efficient and environmentally benign engines. Following the experiments described in Part 1, a set of trials was conducted to clarify the influence of the blade's rotating motion on the heat transfer coefficient for internal serpentine flow passages with turbulence promoters. Test results are shown and discussed in this second part of the contribution.

  7. Spatially resolved air-water emissions tradeoffs improve regulatory impact analyses for electricity generation.

    PubMed

    Gingerich, Daniel B; Sun, Xiaodi; Behrer, A Patrick; Azevedo, Inês L; Mauter, Meagan S

    2017-02-21

    Coal-fired power plants (CFPPs) generate air, water, and solids emissions that impose substantial human health, environmental, and climate change (HEC) damages. This work demonstrates the importance of accounting for cross-media emissions tradeoffs, plant and regional emissions factors, and spatially variation in the marginal damages of air emissions when performing regulatory impact analyses for electric power generation. As a case study, we assess the benefits and costs of treating wet flue gas desulfurization (FGD) wastewater at US CFPPs using the two best available treatment technology options specified in the 2015 Effluent Limitation Guidelines (ELGs). We perform a life-cycle inventory of electricity and chemical inputs to FGD wastewater treatment processes and quantify the marginal HEC damages of associated air emissions. We combine these spatially resolved damage estimates with Environmental Protection Agency estimates of water quality benefits, fuel-switching benefits, and regulatory compliance costs. We estimate that the ELGs will impose average net costs of $3.01 per cubic meter for chemical precipitation and biological wastewater treatment and $11.26 per cubic meter for zero-liquid discharge wastewater treatment (expected cost-benefit ratios of 1.8 and 1.7, respectively), with damages concentrated in regions containing a high fraction of coal generation or a large chemical manufacturing industry. Findings of net cost for FGD wastewater treatment are robust to uncertainty in auxiliary power source, location of chemical manufacturing, and binding air emissions limits in noncompliant regions, among other variables. Future regulatory design will minimize compliance costs and HEC tradeoffs by regulating air, water, and solids emissions simultaneously and performing regulatory assessments that account for spatial variation in emissions impacts.

  8. Air-water CO2 exchange in five hypereutrophic lakes in Bangalore, India

    NASA Astrophysics Data System (ADS)

    Singh, G.; Ghosh, P.; Bala, G.; Bastviken, D.

    2014-12-01

    Inland water bodies play a significant role in terrestrial carbon cycling, rather than being just conduits for the transport of terrestrial carbon to the oceans. Recent syntheses estimate that freshwaters emit substantial amounts of CO2 (1.4 Pg C yr-1) (Tranvik et al. 2009) and CH4 (0.65 Pg C yr-1) (Bastviken et al. 2011), which are similar in magnitude to the global terrestrial carbon sink (2.5 ± 1.7 Pg C yr-1) (IPCC 2013). However, eutrophic waters, which constitute the majority of the global freshwater supply (ILEC/UNEP 1994, Liu et al. 2012, Carpenter et al. 1998), are vastly underrepresented in these estimates. These waters, due to high primary productivity leading to CO2 undersaturation, can act as sinks rather than sources of CO2, thus reversing the role of lakes in the carbon cycle (Balmer and Downing 2011, Pacheco et al. 2013). We are investigating the air-water CO2 exchange of five hypereutrophic lakes in urban Bangalore using a novel Non-Dispersive Infrared (NDIR)-based CO2 sensor installed in flux chambers that can be used to measure CO2 exchange in lakes in situ. This work is a part of a larger study called Bangalore Carbon Mapping Study that aims to track the spatial flows of carbon in an urban area of a developing country. Preliminary observations reveal that these lakes absorb CO2 during the photosynthetic hours, at an average rate of 3.4 mg C m-2 h-1. The ongoing study will characterize the complete diurnal cycle of CO2 exchange, its variation over different seasons, and its relationships with various limnological and catchment characteristics. The flux estimates thus produced will also be compared with those predicted by the current models for air-water gas exchange based on wind speed.

  9. Intraday evaporation and heat fluxes variation at air-water interface of extremely shallow lakes in Chilean Andean Plateau

    NASA Astrophysics Data System (ADS)

    Vergara, Jaime; de la Fuente, Alberto

    2016-04-01

    Salars are landscapes formed by evapo-concentration of salts that usually have extremely shallow terminal lagoons (de la Fuente & Niño, 2010). They are located in the altiplanic region of the Andes Mountains of Chile, Argentina, Bolivia and Peru, and they sustain highly vulnerable and isolated ecosystems in the Andean Desert. These ecosystems are sustained by benthic primary production, which is directly linked to mass, heat and momentum transfer between the water column and the atmosphere (de la Fuente, 2014). Despite the importance of these transport processes across the air-water interface, there are few studies describing their intraday variation and how they are influenced by the stability of the atmospheric boundary layer in the altiplano. The main objective of this work is to analyze the intraday vertical transport variation of water vapor, temperature and momentum between the atmosphere and a shallow water body on Salar del Huasco located in northern Chile (20°19'40"S, 68°51'25"W). To achieve this goal, we measured atmospheric and water variables in a campaign realized on late October 2015, using high frequency meteorological instruments (a sonic anemometer with an incorporated infrared gas analyzer, and a standard meteorological station) and water sensors. From these data, we characterize the intraday variation of water vapor, temperature and momentum fluxes, we quantify the influence of the atmospheric boundary layer stability on them, and we estimate transfer coefficients associated to latent heat, sensible heat, hydrodynamic drag and vertical transport of water vapor. As first results, we found that latent and sensible heat fluxes are highly influenced by wind speed rather buoyancy, and we can identify four intraday intervals with different thermo-hydrodynamic features: (1) cooling under stable condition with wind speed near 0 from midnight until sunrise; (2) free convection with nearly no wind speed under unstable condition from sunrise until midday

  10. Single lung alveolar volume and gas transfer: effect of expansion of the other lung.

    PubMed Central

    Johansen, B.; Bjørtuft, O.

    1994-01-01

    BACKGROUND--Temporary occlusion of one mainstem bronchus permits measurement of single lung function. A previous study suggested that the volume at which one lung is occluded may influence the expansion of the other. The effect of ipsilateral occlusion volume on the contralateral effective alveolar volume (VA, EFF,SL), inspired volume (VI,SL), single breath estimated residual volume (RVSB,SL), carbon monoxide (CO) transfer (TLCO,SL) and transfer coefficient (KCO,SL) has been examined. METHODS--Single breath measurements of CO transfer were made in duplicate in 12 healthy subjects aged 19-44 years, without and during occlusion of one mainstem bronchus by a balloon at RV and at total lung capacity (TLC). RESULTS--Mean VA,EFF,SL, VI,SL, and TLCO,SL were lower during occlusion at RV than during occlusion at TLC (2.84 v 3.26 l; 2.18 v 2.54 l; and 4.70 v 5.51 mmol/kPa/min respectively). RVSB,SL was independent of occlusion volume and KCO,SL not different from the KCO of both lungs (KCO,BL). Single lung values during occlusion at TLC were fairly reproducible and were, except for KCO,SL, approximately half the values for both lungs. During occlusion at RV the second TLCO,SL and KCO,SL were lower than the first. CONCLUSIONS--Occlusion of one lung permits reliable determinations of gas transfer indices of the other, provided the lung is occluded at TLC. Occlusion at RV significantly reduces VA,EFF,SL, and hence TLCO,SL, but does not affect KCO,SL of the other lung. PMID:7878561

  11. Carbon isotope evidence for the latitudinal distribution and wind speed dependence of the air-sea gas transfer velocity

    NASA Astrophysics Data System (ADS)

    Krakauer, Nir Y.; Randerson, James T.; Primeau, François W.; Gruber, Nicolas; Menemenlis, Dimitris

    2006-11-01

    The air-sea gas transfer velocity is an important determinant of the exchange of gases, including CO2, between the atmosphere and ocean, but the magnitude of the transfer velocity and what factors control it remains poorly known. Here, we use oceanic and atmospheric observations of 14C and 13C to constrain the global mean gas transfer velocity as well as the exponent of its wind speed dependence, utilizing the distinct signatures left by the air-sea exchange of 14CO2 and 13CO2. While the atmosphere and ocean inventories of 14CO2 and 13CO2 constrain the mean gas transfer velocity, the latitudinal pattern in the atmospheric and oceanic 14C and 13C distributions contain information about the wind speed dependence. We computed the uptake of bomb 14C by the ocean for different transfer velocity patterns using pulse response functions from an ocean general circulation model, and evaluated the match between the predicted bomb 14C concentrations and observationally based estimates for the 1970s-1990s. Using a wind speed climatology based on satellite measurements, we solved either for the best-fit global relationship between gas exchange and mean wind speed or for the mean gas transfer velocity over each of 11 ocean regions. We also compared the predicted consequences of different gas exchange relationships on the rate of change and interhemisphere gradient of 14C in atmospheric CO2 with tree-ring and atmospheric measurements. Our results suggest that globally, the dependence of the air-sea gas transfer velocity on wind speed is close to linear, with an exponent of 0.5 +/- 0.4, and that the global mean gas transfer velocity at a Schmidt number of 660 is 20 +/- 3 cm/hr, similar to the results of previous analyses. We find that the air-sea flux of 13C estimated from atmosphere and ocean observations also suggests a lower than quadratic dependence of gas exchange on wind speed.

  12. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2002-11-01

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of assisting U.S. independent oil and gas producers make timely, informed technology decisions by providing access to information during Fiscal Year 2002 (FY02). Functioning as a cohesive national organization, PTTC has active grassroots programs through its ten Regional Lead Organizations (RLOs) and three satellite offices that efficiently extend the program reach. They bring research and academia to the table via their association with geological surveys and engineering departments. The regional directors interact with independent oil and gas producers through technology workshops, resource centers, websites, newsletters, various technical publications and other outreach efforts. These are guided by regional Producer Advisory Groups (PAGs), who are area operators and service companies working with the regional networks. The role of the national Headquarters (HQ) staff includes planning and managing the PTTC program, conducting nation wide technology transfer activities, and implementing a comprehensive communications effort. The organization effectively combines federal funding through the Department of Energy's (DOE) Office of Fossil Energy with state and industry funding to achieve important goals for all of these sectors. This integrated funding base is combined with industry volunteers guiding PTTC's activities and the dedication of national and regional staff to achieve notable results. PTTC is increasingly recognized as a critical resource for information and access to technologies, especially for smaller companies without direct contact with R&D efforts. The DOE participation is managed through the National Energy Technology Laboratory (NETL), which deploys a national natural gas program via the Strategic Center for Natural Gas (SCNG) and a national oil program through the National Petroleum Technology Office (NTPO). This technical progress report summarizes PTTC

  13. Quasiclassical trajectory study of collisional energy transfer in toluene systems. I. Argon bath gas: Energy dependence and isotope effects

    NASA Astrophysics Data System (ADS)

    Lim, Kieran F.

    1994-05-01

    Experimental studies of collisional energy transfer from highly vibrationally excited toluene to various bath gases have recently been reported [Toselli and Barker, J. Chem. Phys. 97, 1809 (1992), and references therein]. A quasiclassical trajectory investigation for toluene in argon bath gas at 300 K for initial internal energies E'=41 000, 30 000, and 15 000 cm-1 is reported here. Collisional energy transfer is almost linearly dependent on E'. Predictions of energy transfer quantities are very sensitive to the average well depth of the assumed individual pairwise potentials, but is less sensitive to the detailed shape. Qualitative and quantitative agreement with experiment is obtained where the overall well depth is physically realistic. Isotope studies using 40Ar and pseudohelium (4Ar) bath gases indicate that energy transfer is independent of the mass of the bath-gas collider, but perdeuteration increases <ΔE2>1/2 by 13% over the undeuterated values.

  14. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2001-05-01

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and natural gas producers make timely, informed technology decisions. PTTC's Board made a strategic decision to relocate the Headquarters (HQ) office from Washington, DC to Houston, Texas. Driving force behind relocation was to better connect with independent producers, but cost savings could also be realized. Relocation was accomplished in late December 2000, with the HQ office being fully operational by January 2001. Early indications are that the HQ relocation is, in fact, enabling better networking with senior executives of independents in the Houston oil community. New Board leadership, elected in March 2001, will continue to effectively guide PTTC.

  15. Electrostatic sensors applied to the measurement of electric charge transfer in gas solids pipelines

    NASA Astrophysics Data System (ADS)

    Woodhead, S. R.; Denham, J. C.; Armour-Chelu, D. I.

    2005-01-01

    This paper describes the development of a number of electric charge sensors. The sensors have been developed specifically to investigate triboelectric charge transfer which takes place between particles and the pipeline wall, when powdered materials are conveyed through a pipeline using air. A number of industrial applications exist for such gas solids pipelines, including pneumatic conveyors, vacuum cleaners and dust extraction systems. The build-up of electric charge on pipelines and powdered materials can lead to electrostatic discharge and so is of interest from a safety viewpoint. The charging of powders can also adversely affect their mechanical handling characteristics and so is of interest to handling equipment engineers. The paper presents the design of the sensors, the design of the electric charge test rig and electric charge measurement test results.

  16. Transfer of X-rays through a spherically symmetric gas cloud

    NASA Technical Reports Server (NTRS)

    Hatchett, S.; Buff, J.; Mccray, R.

    1976-01-01

    Approximate solutions are presented for the transfer of radiation through spherically symmetric gas clouds surrounding a point source of X-rays. The approach is similar to that of Tarter and Salpeter (1969) except that heating by Compton scattering and the Auger effect is included. The temperature and ionization structure are sensitive to the source spectrum, and the solutions are not unique if soft X-rays are deficient. The emergent spectrum is rich in optical, ultraviolet, and X-ray emission lines. The radiation force due to photoelectric absorption of X-rays may exceed the force due to Compton scattering by a factor of order 10 for the radiation fields and densities likely to be encountered in galactic binary X-ray sources.

  17. Energy transfer between the shape and volume modes of a nonspherical gas bubble

    NASA Astrophysics Data System (ADS)

    Harkin, Anthony A.; Kaper, Tasso J.; Nadim, Ali

    2013-06-01

    A model of a nonspherical gas bubble is developed in which the Rayleigh-Plesset equation is augmented with second order terms that back-couple the volume mode to a single shape mode. These additional terms in the Rayleigh-Plesset equation permit oscillation energy to be transferred back and forth between the shape and volume modes. The parametric stability of the shape mode is analyzed for a driven bubble, and it is seen that the bidirectional coupling yields an enhanced, albeit minor, stabilizing effect on the shape mode when compared with a model where the shape-volume coupling is unidirectional. It is also demonstrated how a pure shape distortion can excite significant volume pulsations when the volume mode is in 2:1 internal resonance with the shape mode.

  18. Improvement and modelling of hexenal transfer in liquid-gas reactor.

    PubMed

    Ben Akacha, Najla; Guizani, Om Elkhir; Gargouri, Mohamed

    2007-12-01

    The aim of the present work is to improve the extraction of an aromatic compound, 2E-hexenal, from a continuous liquid-gas reactor. Having an improved process to recover hexenal could be of interest to obtain this chemical if produced by any biotechnological process. The experimental program proposed on the basis of a full 23 factorial design demonstrated that the conditions optima for the extraction are 40 degrees C as a reactor temperature and -10 degrees C as a temperature of trap for a nitrogen flow of 45 mL s-1. These conditions allowed to recover more than 75% of hexenal, when this compound was stripping by a nitrogen stream from the liquid phase. The mass transfer was theoretically and experimentally studied. The model predictions were validated against experimental results obtained for a reactor, and good correlation was observed for a simulation.

  19. Conjugate heat transfer with Large Eddy Simulation for gas turbine components

    NASA Astrophysics Data System (ADS)

    Duchaine, Florent; Mendez, Simon; Nicoud, Franck; Corpron, Alban; Moureau, Vincent; Poinsot, Thierry

    2009-06-01

    CHT (Conjugate Heat Transfer) is a main design constraint for GT (gas turbines). Most existing CHT tools are developed for chained, steady phenomena. A fully parallel environment for CHT has been developed and applied to two configurations of interest for the design of GT. A reactive Large Eddy Simulations code and a solid conduction solver exchange data via a supervisor. A flame/wall interaction is used to assess the precision and the order of the coupled solutions. A film-cooled turbine vane is then studied. Thermal conduction in the blade implies lower wall temperature than adiabatic results and CHT reproduces the experimental cooling efficiency. To cite this article: F. Duchaine et al., C. R. Mecanique 337 (2009).

  20. Measuring interactions between polydimethylsiloxane and serum proteins at the air-water interface.

    PubMed

    Liao, Zhengzheng; Hsieh, Wan-Ting; Baumgart, Tobias; Dmochowski, Ivan J

    2013-07-30

    The interaction between synthetic polymers and proteins at interfaces is relevant to basic science as well as a wide range of applications in biotechnology and medicine. One particularly common and important interface is the air-water interface (AWI). Due to the special energetics and dynamics of molecules at the AWI, the interplay between synthetic polymer and protein can be very different from that in bulk solution. In this paper, we applied the Langmuir-Blodgett technique and fluorescence microscopy to investigate how the compression state of polydimethylsiloxane (PDMS) film at the AWI affects the subsequent adsorption of serum protein [e.g., human serum albumin (HSA) or immunoglobulin G (IgG)] and the interaction between PDMS and protein. Of particular note is our observation of circular PDMS domains with micrometer diameters that form at the AWI in the highly compressed state of the surface film: proteins were shown to adsorb preferentially to the surface of these circular PDMS domains, accompanied by a greater than 4-fold increase in protein found in the interfacial film. The PDMS-only film and the PDMS-IgG composite film were transferred to cover glass, and platinum-carbon replicas of the transferred films were further characterized by scanning electron microscopy and atomic force microscopy. We conclude that the structure of the PDMS film greatly affects the amount and distribution of protein at the interface.

  1. Hydrocarbon transfer pathways from Smackover source rocks to younger reservoir traps in the Monroe gas field, NE Louisiana

    SciTech Connect

    Zimmerman, R.K. )

    1993-09-01

    The Monroe gas field contained more than 7 tcf of gas in its virgin state. Much of the original gas reserves have been produced through wells penetrating the Upper Cretaceous Monroe Gas Rock Formation reservoir. Other secondary reservoirs in the field area are Eocene Wilcox, the Upper Cretaceous Arkadelphia, Nacatoch, Ozan, Lower Cretaceous, Hosston, Jurassic Schuler, and Smackover. As producing zones, these secondary producing zones reservoirs have contributed an insignificant amount gas to the field. The source of much of this gas appears to have been in the lower part of the Jurassic Smackover Formation. Maturation and migration of the hydrocarbons from a Smackover source into Upper Cretaceous traps was enhanced and helped by igneous activity, and wrench faults/unconformity conduits, respectively. are present in the pre-Paleocene section. Hydrocarbon transfer pathways appear to be more vertically direct in the Jurassic and Lower Cretaceous section than the complex pattern present in the Upper Cretaceous section.

  2. An asymptotic preserving unified gas kinetic scheme for gray radiative transfer equations

    SciTech Connect

    Sun, Wenjun; Jiang, Song; Xu, Kun

    2015-03-15

    The solutions of radiative transport equations can cover both optical thin and optical thick regimes due to the large variation of photon's mean-free path and its interaction with the material. In the small mean free path limit, the nonlinear time-dependent radiative transfer equations can converge to an equilibrium diffusion equation due to the intensive interaction between radiation and material. In the optical thin limit, the photon free transport mechanism will emerge. In this paper, we are going to develop an accurate and robust asymptotic preserving unified gas kinetic scheme (AP-UGKS) for the gray radiative transfer equations, where the radiation transport equation is coupled with the material thermal energy equation. The current work is based on the UGKS framework for the rarefied gas dynamics [14], and is an extension of a recent work [12] from a one-dimensional linear radiation transport equation to a nonlinear two-dimensional gray radiative system. The newly developed scheme has the asymptotic preserving (AP) property in the optically thick regime in the capturing of diffusive solution without using a cell size being smaller than the photon's mean free path and time step being less than the photon collision time. Besides the diffusion limit, the scheme can capture the exact solution in the optical thin regime as well. The current scheme is a finite volume method. Due to the direct modeling for the time evolution solution of the interface radiative intensity, a smooth transition of the transport physics from optical thin to optical thick can be accurately recovered. Many numerical examples are included to validate the current approach.

  3. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Donald Duttlinger

    2001-11-01

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and gas producers make timely, informed technology decisions during Fiscal Year 2001 (FY01). Functioning as a cohesive national organization, PTTC has active grassroots programs through its ten Regional Lead Organizations (RLOs). They bring research and academia to the table via their association with geological surveys and engineering departments. The regional directors interact with independent oil and gas producers through technology workshops, resource centers, websites, newsletters, various technical publications and other outreach efforts. These are guided by regional Producer Advisory Groups (PAGs), who are area operators and service companies working with the regional networks. The role of the national Headquarters (HQ) staff includes planning and managing the PTTC program, conducting nation wide technology transfer activities, and implementing a comprehensive communications effort. The organization effectively combines federal funding through the Department of Energy's (DOE) Office of Fossil Energy, state, and industry funding to achieve important goals for all of these sectors. This integrated funding base, combined with industry volunteers guiding PTTC's activities and the dedication of national and regional staff, are achieving notable results. PTTC is increasingly recognized as a critical resource for information and access to technologies, especially for smaller companies without direct contact to R&D efforts. This technical progress report summarizes PTTC's accomplishments during FY01, which lays the groundwork for further growth in the future. At a time of many industry changes and wide market movements, the organization itself is adapting to change. PTTC has built a reputation and expectation among producers and other industry participants to quickly distribute information addressing technical needs. The organization efficiently has an

  4. Contribution of heat transfer to turbine blades and vanes for high temperature industrial gas turbines. Part 1: Film cooling.

    PubMed

    Takeishi, K; Aoki, S

    2001-05-01

    This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of industrial gas turbines in order to attain efficient and environmentally benign engines. High efficiency film cooling, in the form of shaped film cooling and full coverage film cooling, is one of the most important cooling technologies. Corresponding heat transfer tests to optimize the film cooling effectiveness are shown and discussed in this first part of the contribution.

  5. Mechanistic Insights on the Photosensitized Chemistry of a Fatty Acid at the Air/Water Interface

    PubMed Central

    2016-01-01

    Interfaces are ubiquitous in the environment and many atmospheric key processes, such as gas deposition, aerosol, and cloud formation are, at one stage or another, strongly impacted by physical and chemical processes occurring at interfaces. Here, the photoinduced chemistry of an air/water interface coated with nonanoic acid—a fatty acid surfactant we use as a proxy for chemically complex natural aqueous surface microlayers—was investigated as a source of volatile and semivolatile reactive organic species. The carboxylic acid coating significantly increased the propensity of photosensitizers, chosen to mimic those observed in real environmental waters, to partition to the interface and enhance reactivity there. Photochemical formation of functionalized and unsaturated compounds was systematically observed upon irradiation of these coated surfaces. The role of a coated interface appears to be critical in providing a concentrated medium allowing radical–radical reactions to occur in parallel with molecular oxygen additions. Mechanistic insights are provided from extensive analysis of products observed in both gas and aqueous phases by online switchable reagent ion-time of flight-mass spectrometry and by off-line ultraperformance liquid chromatography coupled to a Q Exactive high resolution mass spectrometer through heated electrospray ionization, respectively. PMID:27611489

  6. 14 CFR 1274.926 - Clean Air-Water Pollution Control Acts.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Clean Air-Water Pollution Control Acts...-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative... 91-604) and section 308 of the Federal Water Pollution Control Act, as amended (33 U.S.C. 1251 et...

  7. 14 CFR 1274.926 - Clean Air-Water Pollution Control Acts.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Clean Air-Water Pollution Control Acts...-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative... 91-604) and section 308 of the Federal Water Pollution Control Act, as amended (33 U.S.C. 1251 et...

  8. 14 CFR 1274.926 - Clean Air-Water Pollution Control Acts.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Clean Air-Water Pollution Control Acts...-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative... 91-604) and section 308 of the Federal Water Pollution Control Act, as amended (33 U.S.C. 1251 et...

  9. 14 CFR § 1274.926 - Clean Air-Water Pollution Control Acts.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Clean Air-Water Pollution Control Acts. Â...-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative... 91-604) and section 308 of the Federal Water Pollution Control Act, as amended (33 U.S.C. 1251 et...

  10. Numerical analysis of heat transfer in the exhaust gas flow in a diesel power generator

    NASA Astrophysics Data System (ADS)

    Brito, C. H. G.; Maia, C. B.; Sodré, J. R.

    2016-09-01

    This work presents a numerical study of heat transfer in the exhaust duct of a diesel power generator. The analysis was performed using two different approaches: the Finite Difference Method (FDM) and the Finite Volume Method (FVM), this last one by means of a commercial computer software, ANSYS CFX®. In FDM, the energy conservation equation was solved taking into account the estimated velocity profile for fully developed turbulent flow inside a tube and literature correlations for heat transfer. In FVM, the mass conservation, momentum, energy and transport equations were solved for turbulent quantities by the K-ω SST model. In both methods, variable properties were considered for the exhaust gas composed by six species: CO2, H2O, H2, O2, CO and N2. The entry conditions for the numerical simulations were given by experimental data available. The results were evaluated for the engine operating under loads of 0, 10, 20, and 37.5 kW. Test mesh and convergence were performed to determine the numerical error and uncertainty of the simulations. The results showed a trend of increasing temperature gradient with load increase. The general behaviour of the velocity and temperature profiles obtained by the numerical models were similar, with some divergence arising due to the assumptions made for the resolution of the models.

  11. Mechanism of vibrational energy dissipation of free OH groups at the air-water interface.

    PubMed

    Hsieh, Cho-Shuen; Campen, R Kramer; Okuno, Masanari; Backus, Ellen H G; Nagata, Yuki; Bonn, Mischa

    2013-11-19

    Interfaces of liquid water play a critical role in a wide variety of processes that occur in biology, a variety of technologies, and the environment. Many macroscopic observations clarify that the properties of liquid water interfaces significantly differ from those of the bulk liquid. In addition to interfacial molecular structure, knowledge of the rates and mechanisms of the relaxation of excess vibrational energy is indispensable to fully understand physical and chemical processes of water and aqueous solutions, such as chemical reaction rates and pathways, proton transfer, and hydrogen bond dynamics. Here we elucidate the rate and mechanism of vibrational energy dissipation of water molecules at the air-water interface using femtosecond two-color IR-pump/vibrational sum-frequency probe spectroscopy. Vibrational relaxation of nonhydrogen-bonded OH groups occurs at a subpicosecond timescale in a manner fundamentally different from hydrogen-bonded OH groups in bulk, through two competing mechanisms: intramolecular energy transfer and ultrafast reorientational motion that leads to free OH groups becoming hydrogen bonded. Both pathways effectively lead to the transfer of the excited vibrational modes from free to hydrogen-bonded OH groups, from which relaxation readily occurs. Of the overall relaxation rate of interfacial free OH groups at the air-H2O interface, two-thirds are accounted for by intramolecular energy transfer, whereas the remaining one-third is dominated by the reorientational motion. These findings not only shed light on vibrational energy dynamics of interfacial water, but also contribute to our understanding of the impact of structural and vibrational dynamics on the vibrational sum-frequency line shapes of aqueous interfaces.

  12. Gas Flow, Particle Acceleration, and Heat Transfer in Cold Spray: A review

    NASA Astrophysics Data System (ADS)

    Yin, Shuo; Meyer, Morten; Li, Wenya; Liao, Hanlin; Lupoi, Rocco

    2016-06-01

    Cold spraying is increasingly attracting attentions from both scientific and industrial communities due to its unique `low-temperature' coating build-up process and its potential applications in the additive manufacturing across a variety of industries. The existing studies mainly focused on the following subjects: particle acceleration and heating, coating build-up, coating formation mechanism, coating properties, and coating applications, among which particle acceleration and heating can be regarded as the premise of the other subjects because it directly determines whether particles have sufficient energy to deposit and form the coating. Investigations on particle acceleration and heating behavior in cold spraying have been widely conducted both numerically and experimentally over decades, where many valuable conclusions were drawn. However, existing literature on this topic is vast; a systematical summery and review work is still lack so far. Besides, some curtail issues involved in modeling and experiments are still not quite clear, which needs to be further clarified. Hence, a comprehensive summary and review of the literature are very necessary. In this paper, the gas flow, particle acceleration, and heat transfer behavior in the cold spray process are systematically reviewed. Firstly, a brief introduction is given to introduce the early analytical models for predicting the gas flow and particle velocity in cold spraying. Subsequently, special attention is directed towards the application of computational fluid dynamics technique for cold spray modeling. Finally, the experimental observations and measurements in cold spraying are summarized.

  13. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Unknown

    2002-05-31

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of helping U.S. independent oil and natural gas producers make timely, informed technology decisions. Networking opportunities that occur with a Houston Headquarters (HQ) location are increasing name awareness. Focused efforts by Executive Director Don Duttlinger to interact with large independents, national service companies and some majors are continuing to supplement the support base of the medium to smaller industry participants around the country. PTTC is now involved in many of the technology-related activities that occur in high oil and natural gas activity areas. Access to technology remains the driving force for those who do not have in-house research and development capabilities and look to the PTTC to provide services and options for increased efficiency. Looking forward to the future, the Board, Regional Lead Organization (RLO) Directors and HQ staff developed a 10-year vision outlining what PTTC needs to accomplish in supporting a national energy plan. This vision has been communicated to Department of Energy (DOE) staff and PTTC looks forward to continuing this successful federal-state-industry partnership. As part of this effort, several more examples of industry using information gained through PTTC activities to impact their bottom line were identified. Securing the industry pull on technology acceptance was the cornerstone of this directional plan.

  14. A one-dimensional model for gas-solid heat transfer in pneumatic conveying

    NASA Astrophysics Data System (ADS)

    Smajstrla, Kody Wayne

    A one-dimensional ODE model reduced from a two-fluid model of a higher dimensional order is developed to study dilute, two-phase (air and solid particles) flows with heat transfer in a horizontal pneumatic conveying pipe. Instead of using constant air properties (e.g., density, viscosity, thermal conductivity) evaluated at the initial flow temperature and pressure, this model uses an iteration approach to couple the air properties with flow pressure and temperature. Multiple studies comparing the use of constant or variable air density, viscosity, and thermal conductivity are conducted to study the impact of the changing properties to system performance. The results show that the fully constant property calculation will overestimate the results of the fully variable calculation by 11.4%, while the constant density with variable viscosity and thermal conductivity calculation resulted in an 8.7% overestimation, the constant viscosity with variable density and thermal conductivity overestimated by 2.7%, and the constant thermal conductivity with variable density and viscosity calculation resulted in a 1.2% underestimation. These results demonstrate that gas properties varying with gas temperature can have a significant impact on a conveying system and that the varying density accounts for the majority of that impact. The accuracy of the model is also validated by comparing the simulation results to the experimental values found in the literature.

  15. Collisions of fast multicharged ions in gas targets: Charge transfer and ionization

    NASA Astrophysics Data System (ADS)

    Schlachter, A. S.

    1981-05-01

    Measurements of cross sections for charge transfer and ionization of H2 and rare-gas targets were made with fast, highly stripped projectiles in charge states as high as 59+. An empirical scaling rule for electron-capture cross section in H2 valid at energies above 275 keV/amu was found. Similar scaling might exist for other target gases. Cross sections are generally in good agreement with theory. A scaling rule was found for electron loss from H in collisions with a fast highly stripped projectile, based on Olson's classical-trajectory Monte-Carlo calculations, and confirmed by measurements in an H2 target. A similar scaling rule was for net ionization of rare-gas targets, based on Olson's CTMC calculations and the independent-electron model. Measurements are essentially consistent with the scaled cross sections. Calculations and measurements of recoil-ion charge-state spectra show large cross sections for the production of highly charged slow recoil ions.

  16. Rotational Energy Transfer and Depolarization in Rare Gas + CN (˜X, v=0) Collisions

    NASA Astrophysics Data System (ADS)

    Hall, Gregory; Forthomme, Damien; Sears, Trevor

    2014-06-01

    Rotational energy transfer and depolarization rates have been determined for fine-structure-selected rotational levels of the vibrationless ground state of CN (˜{X} ^2Σ +) radicals. Collisions with Ar, He and the photolytic precursor, {CH_3COCN have been studied with polarized transient frequency modulation (FM) absorption spectroscopy. Transient FM signals were recorded as a function of probe laser detuning across Doppler-broadened lines of the ˜{A}- ˜{X} (1-0) band, monitoring the saturation recovery kinetics after a tunable dye laser pulse selectively bleached the probed CN rotational level. The refilling kinetics of a hole in an otherwise thermalized state distribution is identical to the hypothetical decay of the corresponding isolated level in an empty manifold, even to the extent of displaying hyperfine quantum beats in the hole alignment. The Doppler-resolved kinetics reflect a competition between the speed-dependent rotational energy transfer rates, which tend to cool the velocity distribution of the hole, and velocity-changing collisions, which tend to rethermalize the velocity distribution. The observations are of relevance to speed-dependent effects in pressure broadening, but measured under Doppler-limited pressure conditions. Elastic depolarization contributes significantly to the observed signals at low rotational states, negligibly so at high J. A strongly J-dependent contribution to the relaxation kinetics due to small amounts of the photolytic precursor cannot be neglected when extracting the rare-gas-dependent rate coefficients from the observed kinetics. Some qualitative differences are thereby found with previously published energy transfer studies on He or Ar + CN (˜{X}, v=2) by Fei, et al. [J. Chem. Phys. 100, 1190 (1994); Chem. Phys. Lett. 232, 547 (1995)]. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic

  17. He Interpolation Gas Thermometry with Different Virial Coefficients and Gas Densities and Model Calculation of a Temperature Profile with Radiative Heat Transfer

    NASA Astrophysics Data System (ADS)

    Tamura, O.; Nakano, T.; Takasu, S.

    2015-08-01

    He interpolating constant-volume gas thermometer scales are compared using different virial coefficients and gas densities for a temperature range of 3 K to the triple point of Ne (24.5561 K). The differences between the International Temperature Scale of 1990 (ITS-90) and the interpolation scale, which follows the definition of the ITS-90 but uses the second and third virial coefficients of the recent ab initio calculations, have maxima of about 0.08 mK and 0.13 mK for gas densities of and , respectively. The differences between the ITS-90 and the interpolation scale using only the ab initio second virial coefficient have maxima of about 0.08 mK and 0.14 mK for the same respective sequence of gas densities. The ITS-90 temperatures obtained in eight runs with gas densities from to agree with a polynomial of the resistance of a rhodium-iron resistance thermometer within 0.2 mK. To calculate the temperature profile along the pressure-sensing tube connecting the low temperature part of the constant-volume gas thermometer to room temperature, a calculation model is proposed that takes into account not only the thermal conductivity of the tube wall but also the radiative heat transfer between the tube and the vacuum jacket enclosing it. The calculation results of this model approximate the measured profile better than the conventional calculations that neglect the radiative heat transfer.

  18. The Importance of Moving Air-Water Interfaces for Colloid Transport in Porous Media

    NASA Astrophysics Data System (ADS)

    Flury, M.

    2015-12-01

    In the vadose zone, or in unsaturated porous media in general, transport of colloids is usually less pronounced than in groundwater. An important retention mechanism for colloids in unsaturated porous media is attachment to air-water interfaces. However, air-water interfaces can also lead to colloid mobilization and enhanced transport if air-water interfaces are moving, such as during infiltration, imbibition, and drainage. Colloid attachment to air-water interfaces is caused by surface tension forces, and these forces usually exceed other interactions forces; therefore, surface tension forces play a dominant role for colloid transport in unsaturated porous media. In this presentation, experimental and theoretical evidence of surface tension forces acting on colloids will be presented, and the role of moving air-water interfaces will be discussed.

  19. Membrane gas transfer of methane and carbon dioxide in submerged coal deposits.

    PubMed

    Cramer, T A; Johnson, D W; Urynowicz, A

    2009-01-01

    Membrane degassing technology may prove to be a viable alternative to current coal bed methane recovery. The proposed approach involves supplying a CO2 sweep gas to membrane fibres placed directly within a saturated coal seam to provide simultaneous CO2 sequestration and CH4 recovery. A system of ordinary differential equations derived from a mass balance on an infinitesimal fibre element enabled the calculation of lumen gas composition as a function of fibre length. The results were verified through the use of a bench-scale vessel. The model agreement appears reasonable for CH4 recovery; however, agreement for CO2 recovery declines as liquid flow decreases and lumen flow increases. To further evaluate the feasibility of the membrane degassing technology, model predictions were normalized to an average conventional CH4 recovery rate of 1.56 x 10(4) m3 d(-1). Assuming a hypothetical coal seam with a groundwater velocity of 100 cm d(-1), thickness of 36.6 m and an average depth of 107 m, 290,000 m2 or 7.73 km of fibre fabric is required, resulting in 4.11 x 10(5) m3 of CO2 transfer daily and an outlet gas composition of 95% CH4, 4.4% CO2 and 0.6% H2O vapour. Increasing groundwater velocities reduce the required membrane surface area with diminishing effect, stabilizing at 100 cm d(-1). Greater pore pressures also reduce required membrane areas, and predictions indicate that a deeper coal seam under 4.3 times greater pressure would require 98% fewer fibres as compared with the hypothetical coal seam and only 0.206 km of membrane fabric.

  20. Nonlinear Acoustics at the Air-Water Free Surface

    NASA Astrophysics Data System (ADS)

    Pree, Seth; Naranjo, Brian; Putterman, Seth

    2016-11-01

    According to linear acoustics, airborne sound incident on a water surface transmits only a tenth of a percent of its energy. This difficulty of transmitting energy across the water surface limits the feasibility of standoff ultrasound imaging. We propose to overcome this long standing problem by developing new methods of coupling into the medium at standoff. In particular, we believe that the acoustic nonlinearity of both the air and the medium may yield a range of effects in the vicinity of the surface permitting an efficient transmission of ultrasound from the air into the medium. The recent commercial availability of parametric speakers that deliver modulated 100kHz ultrasound at 135dB to nonlinearly generate music at 95dB provides an interesting platform with which to revisit the transmission of sound across acoustic impedance mismatches. We show results of experimental studies of the behavior of the air-water free surface when subjected to large amplitude acoustic pressures from the air. This work was supported by the ARO STIR program.

  1. EFFECTS OF HOT HALO GAS ON STAR FORMATION AND MASS TRANSFER DURING DISTANT GALAXY–GALAXY ENCOUNTERS

    SciTech Connect

    Hwang, Jeong-Sun; Park, Changbom E-mail: cbp@kias.re.kr

    2015-06-01

    We use N-body/smoothed particle hydrodynamics simulations of encounters between an early-type galaxy (ETG) and a late-type galaxy (LTG) to study the effects of hot halo gas on the evolution for a case with the mass ratio of the ETG to LTG of 2:1 and the closest approach distance of ∼100 kpc. We find that the dynamics of the cold disk gas in the tidal bridge and the amount of the newly formed stars depend strongly on the existence of a gas halo. In the run of interacting galaxies not having a hot gas halo, the gas and stars accreted into the ETG do not include newly formed stars. However, in the run using the ETG with a gas halo and the LTG without a gas halo, a shock forms along the disk gas tidal bridge and induces star formation near the closest approach. The shock front is parallel to a channel along which the cold gas flows toward the center of the ETG. As a result, the ETG can accrete star-forming cold gas and newly born stars at and near its center. When both galaxies have hot gas halos, a shock is formed between the two gas halos somewhat before the closest approach. The shock hinders the growth of the cold gas bridge to the ETG and also ionizes it. Only some of the disk stars transfer through the stellar bridge. We conclude that the hot halo gas can give significant hydrodynamic effects during distant encounters.

  2. Charge transfer reactions at interfaces between neutral gas and plasma: Dynamical effects and X-ray emission

    NASA Astrophysics Data System (ADS)

    Provornikova, E.; Izmodenov, V. V.; Lallement, R.

    2012-04-01

    Charge-transfer is the main process linking neutrals and charged particles in the interaction regions of neutral (or partly ionized) gas with a plasma. In this paper we illustrate the importance of charge-transfer with respect to the dynamics and the structure of neutral gas-plasma interfaces. We consider the following phenomena: (1) the heliospheric interface - region where the solar wind plasma interacts with the partly-ionized local interstellar medium (LISM) and (2) neutral interstellar clouds embedded in a hot, tenuous plasma such as the million degree gas that fills the so-called ``Local Bubble". In (1), we discuss several effects in the outer heliosphere caused by charge exchange of interstellar neutral atoms and plasma protons. In (2) we describe the role of charge exchange in the formation of a transition region between the cloud and the surrounding plasma based on a two-component model of the cloud-plasma interaction. In the model the cloud consists of relatively cold and dense atomic hydrogen gas, surrounded by hot, low density, fully ionized plasma. We discuss the structure of the cloud-plasma interface and the effect of charge exchange on the lifetime of interstellar clouds. Charge transfer between neutral atoms and minor ions in the plasma produces X-ray emission. Assuming standard abundances of minor ions in the hot gas surrounding the cold interstellar cloud, we estimate the X-ray emissivity consecutive to the charge transfer reactions. Our model shows that the charge-transfer X-ray emission from the neutral cloud-plasma interface may be comparable to the diffuse thermal X-ray emission from the million degree gas cavity itself.

  3. Gas transfer between the atmosphere and irrigated sugarcane plantation sites under different rainfall in Hawai'i

    NASA Astrophysics Data System (ADS)

    Miyazawa, Y.; Giambelluca, T. W.; Crow, S. E.; Mudd, R. G.; Youkhana, A.; Nullet, M.; Nakahata, M.

    2015-12-01

    Sugarcane plantation land cover is increasing in area in Brazil, South Asia and the Pacific Islands because of the growing demand for sugar and biofuel production. While a large portion of sugarcane cultivated in Brazil is rain-fed and experiences drought influences on gas exchange, sugarcane in Hawai'i is thought to be buffered from drought effects because it is drip irrigated. Knowledge about carbon sequestration and evapotranspiration rates is fundamental both for the prediction of sugar and biofuel production and for water resource management for the large plantations. To understand gas transfer under spatially and temporally heterogeneous environments, we investigated the leaf- soil- and stand-scale gas transfer processes at two irrigated sugarcane plantation study sites in Hawai'i with contrasting rainfall. Gas and energy transfers were monitored using eddy covariance systems for a full- and later half- crop cycle. Leaf ecophysiological traits were measured for stands of different ages to evaluate the effects of stand age on gas transfer. Carbon sequestration rates (Fc) showed a strong relationship with solar radiation with small differences between sites. Latent heat flux expressed as the evapotranspiration rates (ET) also had a strong relationship with solar radiation, but showed seasonality due to variations in biological control (surface conductance) and atmospheric evaporative demand. The difference in ET and its responses to environments was less clear partly buffered by the differences in the stand age and seasons. The stable Fc-solar radiation relationship despite the variation in surface conductance was partly due to the saturation of net photosynthetic rates with intercellular CO2 concentration and the low sensitivity of net photosynthesis to variations in surface conductance in sugarcane with the C4 photosynthesis pathway. The response of gas transfer to periodic irrigation, rainfall and age-related changes in leaf ecophysiological traits will be

  4. Measuring air-water interfacial areas with X-ray microtomography and interfacial partitioning tracer tests.

    PubMed

    Brusseau, Mark L; Peng, Sheng; Schnaar, Gregory; Murao, Asami

    2007-03-15

    Air-water interfacial areas as a function of water saturation were measured for a sandy, natural porous medium using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. In addition, interfacial areas measured in a prior study with the gas-phase interfacial partitioning tracer-test method for the same porous medium were included for comparison. For all three methods, total air-water interfacial areas increased with decreasing water saturation. The interfacial areas measured with the tracer-test methods were generally larger than those obtained from microtomography, and the disparity increased as water saturation decreased. The interfacial areas measured by microtomography extrapolated to a value (147 cm(-1)) very similar to the specific solid surface area (151 cm(-1)) calculated using the smooth-sphere assumption, indicating that the method does not characterize the area associated with microscopic surface heterogeneity (surface roughness, microporosity). This is consistent with the method resolution of approximately 12 microm. In contrast, the interfacial areas measured with the gas-phase tracer tests approached the N2/BET measured specific solid surface area (56000 cm(-1)), indicating that this method does characterize the interfacial area associated with microscopic surface heterogeneity. The largest interfacial area measured with the aqueous-phase tracer tests was 224 cm(-1), while the extrapolated maximum interfacial area was approximately 1100 cm(-1). Both of these values are larger than the smooth-sphere specific solid surface area but much smaller than the N2/BET specific solid surface area, which suggests that the method measures a limited portion of the interfacial area associated with microscopic surface heterogeneity. All three methods provide measures of total (capillary + film) interfacial area, a primary difference being that the film-associated area is a smooth-surface equivalent for the

  5. An asymptotic preserving unified gas kinetic scheme for frequency-dependent radiative transfer equations

    SciTech Connect

    Sun, Wenjun; Jiang, Song; Xu, Kun; Li, Shu

    2015-12-01

    This paper presents an extension of previous work (Sun et al., 2015 [22]) of the unified gas kinetic scheme (UGKS) for the gray radiative transfer equations to the frequency-dependent (multi-group) radiative transfer system. Different from the gray radiative transfer equations, where the optical opacity is only a function of local material temperature, the simulation of frequency-dependent radiative transfer is associated with additional difficulties from the frequency-dependent opacity. For the multiple frequency radiation, the opacity depends on both the spatial location and the frequency. For example, the opacity is typically a decreasing function of frequency. At the same spatial region the transport physics can be optically thick for the low frequency photons, and optically thin for high frequency ones. Therefore, the optical thickness is not a simple function of space location. In this paper, the UGKS for frequency-dependent radiative system is developed. The UGKS is a finite volume method and the transport physics is modeled according to the ratio of the cell size to the photon's frequency-dependent mean free path. When the cell size is much larger than the photon's mean free path, a diffusion solution for such a frequency radiation will be obtained. On the other hand, when the cell size is much smaller than the photon's mean free path, a free transport mechanism will be recovered. In the regime between the above two limits, with the variation of the ratio between the local cell size and photon's mean free path, the UGKS provides a smooth transition in the physical and frequency space to capture the corresponding transport physics accurately. The seemingly straightforward extension of the UGKS from the gray to multiple frequency radiation system is due to its intrinsic consistent multiple scale transport modeling, but it still involves lots of work to properly discretize the multiple groups in order to design an asymptotic preserving (AP) scheme in all

  6. Greenhouse Gas Emissions from Arctic Freshwaters: Approaches for Scaling UP

    NASA Astrophysics Data System (ADS)

    MacIntyre, S.; Cortés, A.; Cooke, M.; Sadro, S.; Kushner, P. J.

    2015-12-01

    Turbulence moderates emissions of greenhouse gases on a number of scales, and it, in turn, is moderated by processes which govern the stability of boundary layers. On the smallest scale, it mediates the fluxes of gases across the air-water interface; at intermediate scales, that is, the size of within lake eddies, it brings gases to the air-water interface; on a larger scale, eddies in the unstable atmospheric boundary layers transport gases away from water bodies and maintain concentration gradients and further, help sustain fluxes by inducing within lake turbulence. The winds and cooling which induce within-lake turbulence and over-lake boundary layers are moderated by weather patterns dependent on even larger scale physical processes. Using time series measurements of lake temperatures, surface meteorology, and profiles of temperature-gradient microstructure in Alaskan arctic lakes ranging from 0.1 to 150 ha in surface area, we quantify the dependency of turbulence in the water column and at the air-water interface on surface meteorology and lake size. We show the lake size dependent variability in the stability of atmospheric boundary layers. We illustrate the resulting lake-size and weather dependent variability in gas transfer coefficients and within lake mixing. Using cluster analysis, we identify dominant weather patterns in the Alaskan Arctic Region and link them to within lake mixing dynamics. We then illustrate the dependency of greenhouse gas emissions on variability in local weather, lake size, and weather patterns.

  7. Lung cancer detection by proton transfer reaction mass-spectrometric analysis of human breath gas

    NASA Astrophysics Data System (ADS)

    Wehinger, Andreas; Schmid, Alex; Mechtcheriakov, Sergei; Ledochowski, Maximilian; Grabmer, Christoph; Gastl, Guenther A.; Amann, Anton

    2007-08-01

    Background Determination of the diagnostic usefulness of proton transfer reaction mass spectrometry (PTR-MS) for detecting primary lung cancer through analysis of volatile organic compounds (VOCs) in exhaled human breath was demonstrated in this investigation. Unlike, for example, gas-chromatographic analyses, PTR-MS can be used without time-consuming preconcentration of the gas samples.Methods By means of PTR-MS, exhaled breath samples from primary lung cancer patients (n = 17) were analyzed and compared with both an overall control collective (controls total, n = 170) and three sub-collectives: hospital personnel (controls hospital, n = 35), age-matched persons (controls age, n = 25), and smokers (controls s, n = 60), respectively.Results Among the VOCs present at reasonably high concentrations, the ones leading to the product ion at m/z = 31 (VOC-31, tentatively protonated formaldehyde) and m/z = 43 (VOC-43, tentatively a fragment of protonated iso-propanol), were found at significantly higher concentrations in the breath gas of the primary lung cancer patients as compared to the healthy controls at the following median concentrations (with interquartile distance, iqr): For VOC-31 the median concentrations were 7.0 ppb (iqr, 15.5 ppb) versus 3.0 ppb (iqr, 1.9 ppb) with P < 10-4. For VOC-43 the median concentrations were 244.1 ppb (iqr, 236.2 ppb) versus 94.1 ppb (iqr, 55.2 ppb) with P < 10-6. The discriminative power between the two collectives was further assessed by ROC-curves obtained upon variation of the chosen threshold concentration and by Fisher's Quadratic Discriminant Method.Conclusions Within the limits of pilot study, VOC-31 and -43 were found to best discriminate between exhaled breath of primary lung cancer cases and healthy controls. Simple and time-saving breath gas analysis by PTR-MS makes this method attractive for a larger clinical evaluation. It may become a new valuable tool for diagnosing primary lung cancer.

  8. Quasiclassical trajectory study of collisional energy transfer in toluene systems. II. Helium bath gas: Energy and temperature dependences, and angular momentum transfer

    NASA Astrophysics Data System (ADS)

    Lim, Kieran F.

    1994-11-01

    The collisional deactivation of highly vibrationally excited toluene-d0 and toluene-d8 by helium bath gas has been investigated using quasiclassical trajectory simulations. Collisional energy transfer was found to increase with initial toluene internal energy, in agreement with the experiments of Toselli and Barker [J. Chem. Phys. 97, 1809 (1992), and references therein]. The temperature dependence of <ΔE2>1/2 is predicted to be T(0.44±0.10), in agreement with the experiments of Heymann, Hippler, and Troe [J. Chem. Phys. 80, 1853 (1984)]. Toluene is found to have no net angular-momentum (rotational-energy) transfer to helium bath gas, although <ΔJ2>1/2 has a temperature dependence of T(0.31±0.07). Re-evaluation of earlier calculations [``Paper I:'' Lim, J. Chem. Phys. 100, 7385 (1994)] found that rotational energy transfer could be induced by increasing the mass of the collider, or by increasing the strength of the intermolecular interaction: in these cases, angular-momentum transfer depended on the initial excitation energy. In all cases, the final rotational distributions remained Boltzmann.

  9. Numerical Modeling of Flow Dynamics in The Aluminum Smelting Process: Comparison Between Air-Water and CO2-Cryolite Systems

    NASA Astrophysics Data System (ADS)

    Zhao, Zhibin; Feng, Yuqing; Schwarz, M. Philip; Witt, Peter J.; Wang, Zhaowen; Cooksey, Mark

    2016-12-01

    Air-water models have been widely applied as substitutes for CO2-cryolite systems in the study of the complex bubble dynamics and bubble-driven flow that occurs in the molten electrolyte phase in the aluminum electrolytic process, but the detailed difference between the two systems has not been studied. This paper makes a numerical comparison between the bubble dynamics for the two systems. Simulations of both single bubble and continuous bubbling were conducted using a three-dimensional computational fluid dynamics (3D CFD) modeling approach with a volume of fluid (VOF) method to capture the phase interfaces. In the single bubble simulations, it was found that bubbles sliding under an anode in a CO2-cryolite system have a smaller bubble thickness and a higher sliding velocity than those in the air-water system for bubbles of the same volume. Dimensionless analysis and numerical simulation show that contact angle is the dominant factor producing these differences; the effects of kinematic viscosity, surface tension, and density are very small. In the continuous bubbling simulations, the continuous stream of air bubbles detaches from the anode sidewall after a period of climbing, just as it does in the single bubble simulation, but bubbles have less tendency to migrate away from the wall. Quasi-stable state flow characteristics, i.e., time-averaged bath flow pattern, turbulence kinetic energy, turbulence dissipation rate, and gas volume fraction, show a remarkable agreement between the two systems in terms of distribution and magnitude. From the current numerical comparisons, it is believed that the air-water model is a close substitutive model for studying bubble-driven bath flow in aluminum smelting processes. However, because of the difference in bubble morphologies between the two systems, and also the reactive generation and growth of bubbles in the real system, there will likely be some differences in bubble coverage of the anode in the anode-cathode gap.

  10. Numerical Modeling of Flow Dynamics in The Aluminum Smelting Process: Comparison Between Air-Water and CO2-Cryolite Systems

    NASA Astrophysics Data System (ADS)

    Zhao, Zhibin; Feng, Yuqing; Schwarz, M. Philip; Witt, Peter J.; Wang, Zhaowen; Cooksey, Mark

    2017-04-01

    Air-water models have been widely applied as substitutes for CO2-cryolite systems in the study of the complex bubble dynamics and bubble-driven flow that occurs in the molten electrolyte phase in the aluminum electrolytic process, but the detailed difference between the two systems has not been studied. This paper makes a numerical comparison between the bubble dynamics for the two systems. Simulations of both single bubble and continuous bubbling were conducted using a three-dimensional computational fluid dynamics (3D CFD) modeling approach with a volume of fluid (VOF) method to capture the phase interfaces. In the single bubble simulations, it was found that bubbles sliding under an anode in a CO2-cryolite system have a smaller bubble thickness and a higher sliding velocity than those in the air-water system for bubbles of the same volume. Dimensionless analysis and numerical simulation show that contact angle is the dominant factor producing these differences; the effects of kinematic viscosity, surface tension, and density are very small. In the continuous bubbling simulations, the continuous stream of air bubbles detaches from the anode sidewall after a period of climbing, just as it does in the single bubble simulation, but bubbles have less tendency to migrate away from the wall. Quasi-stable state flow characteristics, i.e., time-averaged bath flow pattern, turbulence kinetic energy, turbulence dissipation rate, and gas volume fraction, show a remarkable agreement between the two systems in terms of distribution and magnitude. From the current numerical comparisons, it is believed that the air-water model is a close substitutive model for studying bubble-driven bath flow in aluminum smelting processes. However, because of the difference in bubble morphologies between the two systems, and also the reactive generation and growth of bubbles in the real system, there will likely be some differences in bubble coverage of the anode in the anode-cathode gap.

  11. Revealing charge-transfer effects in gas-phase water chemistry.

    PubMed

    Cappelletti, David; Ronca, Enrico; Belpassi, Leonardo; Tarantelli, Francesco; Pirani, Fernando

    2012-09-18

    An understanding of the interactions involving water and other small hydrogenated molecules such as H(2)S and NH(3) at the molecular level is an important and elusive scientific goal with potential implications for fields ranging from biochemistry to astrochemistry. One longstanding question about water's intermolecular interactions, and notably hydrogen bonding, is the extent and importance of charge transfer (CT) , which can have important implications for the development of reliable model potentials for water chemistry, among other applications. The weakly bound adducts, commonly regarded as pure van der Waals systems, formed by H(2)O, H(2)S, and NH(3) with noble gases or simple molecules such as H(2), provide an interesting case study for these interactions. Their binding energies are approximately 1 or 2 kJ/mol at most, and CT effects in these systems are thought to be negligible. Our laboratory has performed high-resolution molecular-beam scattering experiments that probe the (absolute scale) intermolecular potential of various types of these gas-phase binary complexes with extreme sensitivity. These experiments have yielded surprising and intriguing quantitative results. The key experimental measurable is the "glory" quantum interference shift that shows a systematic, anomalous energy stabilization for the water complexes and clearly points to a significant role for CT effects. To investigate these findings, we have performed very accurate theoretical calculations and devised a simple approach to study the electron displacement that accompanies gas-phase binary intermolecular interactions in extreme detail. These calculations are based on a partial progressive integration of the electron density changes. The results unambiguously show that water's intermolecular interactions are not typical van der Waals complexes. Instead, these interactions possess a definite, strongly stereospecific CT component, even when very weak, where a water molecule may act as

  12. Thermocapillary convection around gas bubbles: an important natural effect for the enhancement of heat transfer in liquids under microgravity.

    PubMed

    Betz, J; Straub, J

    2002-10-01

    In the presence of a temperature gradient at a liquid-gas or liquid-liquid interface, thermocapillary or Marangoni convection develops. This convection is a special type of natural convection that was not paid much attention in heat transfer for a long time, although it is strong enough to drive liquids against the direction of buoyancy on Earth. In a microgravity environment, however, it is the remaining mode of natural convection and supports heat and mass transfer. During boiling in microgravity it was observed at subcooled liquid conditions. Therefore, the question arises about its contribution to heat transfer without phase change. Thermocapillary convection was quantitatively studied at single gas bubbles in various liquids, both experimentally and numerically. A two-dimensional mathematical model described in this article was developed. The coupled mechanism of heat transfer and fluid flow in pure liquids around a single gas bubble was simulated with a control-volume FE-method. The simulation was accompanied and compared with experiments on Earth. The numerical results are in good accordance with the experiments performed on Earth at various Marangoni numbers using various alcohols of varying chain length and Prandtl numbers. As well as calculations on Earth, the numerical method also allows simulations at stationary spherical gas bubbles in a microgravity environment. The results demonstrate that thermocapillary convection is a natural heat transfer mechanism that can partially replace the buoyancy in a microgravity environment, if extreme precautions are taken concerning the purity of the liquids, because impurities accumulate predominantly at the interface. Under Earth conditions, an enhancement of the heat transfer in a liquid volume is even found in the case where thermocapillary flow is counteracted by buoyancy. In particular, the obstructing influence of surface active substances could be observed during the experiments on Earth in water and also in

  13. Hot-gas-side heat transfer characteristics of subscale, plug-nozzle rocket calorimeter chamber

    NASA Technical Reports Server (NTRS)

    Quentmeyer, Richard J.; Roncace, Elizabeth A.

    1993-01-01

    An experimental investigation was conducted to determine the hot-gas-side heat transfer characteristics for a liquid-hydrogen-cooled, subscale, plug-nozzle rocket test apparatus. This apparatus has been used since 1975 to evaluate rocket engine advanced cooling concepts and fabrication techniques, to screen candidate combustion chamber liner materials, and to provide data for model development. In order to obtain the data, a water-cooled calorimeter chamber having the same geometric configuration as the plug-nozzle test apparatus was tested. It also used the same two showerhead injector types that were used on the test apparatus: one having a Rigimesh faceplate and the other having a platelet faceplate. The tests were conducted using liquid oxygen and gaseous hydrogen as the propellants over a mixture ratio range of 5.8 to 6.3 at a nominal chamber pressure of 4.14 MPa abs (600 psia). The two injectors showed similar performance characteristics with the Rigimesh faceplate having a slightly higher average characteristic-exhaust-velocity efficiency of 96 percent versus 94.4 percent for the platelet faceplate. The throat heat flux was 54 MW/m(sup 2) (33 Btu/in.(sup 2)-sec) at the nominal operating condition, which was a chamber pressure of 4.14 MPa abs (600 psia), a hot-gas-side wall temperature of 730 K (1314 R), and a mixture ratio of 6.0. The chamber throat region correlation coefficient C(sub g) for a Nusselt number correlation of the form Nu =C(sub g)Re(sup 0.8)Pr(sup 0.3) averaged 0.023 for the Rigimesh faceplate and 0.026 for the platelet faceplate.

  14. Hot-gas-side heat transfer characteristics of subscale, plug-nozzle rocket calorimeter chamber

    NASA Astrophysics Data System (ADS)

    Quentmeyer, Richard J.; Roncace, Elizabeth A.

    1993-07-01

    An experimental investigation was conducted to determine the hot-gas-side heat transfer characteristics for a liquid-hydrogen-cooled, subscale, plug-nozzle rocket test apparatus. This apparatus has been used since 1975 to evaluate rocket engine advanced cooling concepts and fabrication techniques, to screen candidate combustion chamber liner materials, and to provide data for model development. In order to obtain the data, a water-cooled calorimeter chamber having the same geometric configuration as the plug-nozzle test apparatus was tested. It also used the same two showerhead injector types that were used on the test apparatus: one having a Rigimesh faceplate and the other having a platelet faceplate. The tests were conducted using liquid oxygen and gaseous hydrogen as the propellants over a mixture ratio range of 5.8 to 6.3 at a nominal chamber pressure of 4.14 MPa abs (600 psia). The two injectors showed similar performance characteristics with the Rigimesh faceplate having a slightly higher average characteristic-exhaust-velocity efficiency of 96 percent versus 94.4 percent for the platelet faceplate. The throat heat flux was 54 MW/m(sup 2) (33 Btu/in.(sup 2)-sec) at the nominal operating condition, which was a chamber pressure of 4.14 MPa abs (600 psia), a hot-gas-side wall temperature of 730 K (1314 R), and a mixture ratio of 6.0. The chamber throat region correlation coefficient C(sub g) for a Nusselt number correlation of the form Nu =C(sub g)Re(sup 0.8)Pr(sup 0.3) averaged 0.023 for the Rigimesh faceplate and 0.026 for the platelet faceplate.

  15. Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.

    PubMed

    Ringer, Joachim M

    2013-01-01

    The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS.

  16. Thermal-Flow Code for Modeling Gas Dynamics and Heat Transfer in Space Shuttle Solid Rocket Motor Joints

    NASA Technical Reports Server (NTRS)

    Wang, Qunzhen; Mathias, Edward C.; Heman, Joe R.; Smith, Cory W.

    2000-01-01

    A new, thermal-flow simulation code, called SFLOW. has been developed to model the gas dynamics, heat transfer, as well as O-ring and flow path erosion inside the space shuttle solid rocket motor joints by combining SINDA/Glo, a commercial thermal analyzer. and SHARPO, a general-purpose CFD code developed at Thiokol Propulsion. SHARP was modified so that friction, heat transfer, mass addition, as well as minor losses in one-dimensional flow can be taken into account. The pressure, temperature and velocity of the combustion gas in the leak paths are calculated in SHARP by solving the time-dependent Navier-Stokes equations while the heat conduction in the solid is modeled by SINDA/G. The two codes are coupled by the heat flux at the solid-gas interface. A few test cases are presented and the results from SFLOW agree very well with the exact solutions or experimental data. These cases include Fanno flow where friction is important, Rayleigh flow where heat transfer between gas and solid is important, flow with mass addition due to the erosion of the solid wall, a transient volume venting process, as well as some transient one-dimensional flows with analytical solutions. In addition, SFLOW is applied to model the RSRM nozzle joint 4 subscale hot-flow tests and the predicted pressures, temperatures (both gas and solid), and O-ring erosions agree well with the experimental data. It was also found that the heat transfer between gas and solid has a major effect on the pressures and temperatures of the fill bottles in the RSRM nozzle joint 4 configuration No. 8 test.

  17. Proton transport by bacteriorhodopsin in planar membranes assembled from air-water interface films

    PubMed Central

    Korenbrot, J. I.; Hwang, S. B.

    1980-01-01

    Bacteriorhodopsin, in known amounts and controlled orientation, is incorporated into planar membrane films. These films are formed by the sequential transfer of two air-water interface films onto a thin, hydrophilic, electrically conductive support cast from nitrocellulose. The films are easily accessible to electrical measurements and to control of the ionic milieu on either side of the membrane. The area of the assembled membrane films can be varied between 2.3 x 10(-2) cm2 and 0.7 cm2. Illumination of these films produces photocurrents, photovoltages, and changes in the pH of the surrounding medium. The peak amplitude of the photocurrent increases linearly with light intensity for dim lights, and it approaches a saturating value for brighter lights. In the linear range, the stoichiometry of transport is 0.65 +/- 0.06 protons/absorbed photon. The rate of transport is linearly proportional to light at all intensities tested. The amplitude and kinetics of the photovoltage measured are accurately predicted by the photocurrent generated and the passive electrical features of the film. Parallel measurements of pH and photocurrent reveal that the light-induced changes in pH are fully accounted for by the rate and amount of charge transport across the membrane. Preceding the transport of protons, a transient photovoltage is detected that exhibits no detectable latency, reaches peak in about 80 microseconds, and probably arises from light-induced intramolecular charge displacements. PMID:10822498

  18. The role of breaking wavelets in air-sea gas transfer

    NASA Astrophysics Data System (ADS)

    Csanady, G. T.

    1990-01-01

    speeds. However, in the open ocean straining by the large waves, and especially whitecapping, may significantly reduce the density of divergences and with it the area-average gas transfer rate. On the other hand, bubble and droplet production in whitecaps may diminish this effect or even reverse it.

  19. Thermal characteristics of air-water spray impingement cooling of hot metallic surface under controlled parametric conditions

    NASA Astrophysics Data System (ADS)

    Nayak, Santosh Kumar; Mishra, Purna Chandra

    2016-06-01

    Experimental results on the thermal characteristics of air-water spray impingement cooling of hot metallic surface are presented and discussed in this paper. The controlling input parameters investigated were the combined air and water pressures, plate thickness, water flow rate, nozzle height from the target surface and initial temperature of the hot surface. The effects of these input parameters on the important thermal characteristics such as heat transfer rate, heat transfer coefficient and wetting front movement were measured and examined. Hot flat plate samples of mild steel with dimension 120 mm in length, 120 mm breadth and thickness of 4 mm, 6 mm, and 8 mm respectively were tested. The air assisted water spray was found to be an effective cooling media and method to achieve very high heat transfer rate from the surface. Higher heat transfer rate and heat transfer coefficients were obtained for the lesser i.e, 4 mm thick plates. Increase in the nozzle height reduced the heat transfer efficiency of spray cooling. At an inlet water pressure of 4 bar and air pressure of 3 bar, maximum cooling rates 670°C/s and average cooling rate of 305.23°C/s were achieved for a temperature of 850°C of the steel plate.

  20. Reliable quantification of phthalates in environmental matrices (air, water, sludge, sediment and soil): a review.

    PubMed

    Net, Sopheak; Delmont, Anne; Sempéré, Richard; Paluselli, Andrea; Ouddane, Baghdad

    2015-05-15

    Because of their widespread application, phthalates or phthalic acid esters (PAEs) are ubiquitous in the environment. Their presence has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health, so their quantification has become a necessity. Various extraction procedures as well as gas/liquid chromatography and mass spectrometry detection techniques are found as suitable for reliable detection of such compounds. However, PAEs are ubiquitous in the laboratory environment including ambient air, reagents, sampling equipment, and various analytical devices, that induces difficult analysis of real samples with a low PAE background. Therefore, accurate PAE analysis in environmental matrices is a challenging task. This paper reviews the extensive literature data on the techniques for PAE quantification in natural media. Sampling, sample extraction/pretreatment and detection for quantifying PAEs in different environmental matrices (air, water, sludge, sediment and soil) have been reviewed and compared. The concept of "green analytical chemistry" for PAE determination is also discussed. Moreover useful information about the material preparation and the procedures of quality control and quality assurance are presented to overcome the problem of sample contamination and these encountered due to matrix effects in order to avoid overestimating PAE concentrations in the environment.

  1. Surface activity coefficients of spread monolayers of behenic acid salts at air-water interface.

    PubMed

    Chattoraj, D K; Halder, E; Das, K P; Mitra, A

    2006-11-16

    The pressure-area isotherms of ionized monolayers of behenic acid at air-water interface at pH 12.0 have been obtained from the Langmuir film balance experiments under various physico-chemical conditions. The value of the measured surface pressure at a given area per molecule is equal to the sum of the ideal pressure, cohesive pressure and electrical pressure. The electrical pressure term is regarded as the sum of the pressure originating from the Gouy-Chapman double layer including discrete ion effect, ion binding and monolayer hydration effect. At a given area, the deviation of the measured surface pressure from its ideal value has been calculated in terms of the apparent surface compressibility coefficients, surface fugacity coefficients for gaseous monolayer and surface activity coefficients of solute forming two-dimensional solutions in the monolayer phase respectively. Values of all these coefficients have been calculated for different compositions of the monolayer using non-ideal gas model and Raoult's and Henry's laws modified for two-dimensional non-ideal solutions respectively. Values of these coefficients may be higher or lower than unity depending upon ionic strengths and nature of inorganic salts present in the sub-phase. Using these values of surface activity coefficients, the standard free energies of formation, of spread monolayers of salts of behenic acid have been calculated at different standard states of reference.

  2. Heat Transfer Characteristics of Liquid-Driven Swirl Boiling Liquid/Gas Separator under Reduced Gravity

    NASA Astrophysics Data System (ADS)

    Oinuma, Ryoji; Nguyen, Ngoc; Dickes, Neil; Kurwitz, Richard C.; Best, Frederick R.

    2009-03-01

    Under reduced gravity conditions, conventional gravity-assisted steam generators do not function properly and shear-driven or swirl type of devices must be used. Once-through boilers with special inserts such as twisted-tapes or swirl devices and rotating boilers have been previously studied. The once-through boiler requires a liquid-vapor phase separator due to the inability to vaporize all liquid completely to avoid burn-out. These devices also encounter instabilities due to the sudden formation or collapse of vapor. The rotating boiler requires a large power input to operate and has less reliability due to moving parts and dynamic seals at high temperature. A liquid-driven vortex boiling separator is categorized as a shear-driven boiler, but creates centripetal-driven buoyancy forces to form a gas-liquid vortex by injecting liquid tangentially along the inner wall of the cylinder rather than rotating the body itself. The vortex boiling separator eliminates the disadvantages of devices mentioned above, having a low pressure drop, no moving parts and generating dry vapor at its outlet. Texas A&M University carried out a reduced gravity flight experiment on the NASA C-9 aircraft to investigate the heat transfer characteristics and performance based on similar devices developed at Texas A&M.

  3. Theoretical approach for enhanced mass transfer effects in-duct flue gas desulfurization processes

    SciTech Connect

    Jozewicz, W. . Environmental Systems Div.); Rochelle, G.T. . Dept. of Chemical Engineering)

    1992-01-29

    This report presents the results of fundamental mass transfer testing for in-duct removal of SO{sub 2}. Following this initial part of an experimental program, it became clear that the amount of initial moisture on the sorbent strongly affected the extent of Ca(OH){sub 2} conversion. Novel techniques aimed at increasing sorbent utilization were investigated and are described. Major novel technique investigated and reported on here was the reaction with SO{sub 2} of sorbents with initial free moisture (damp sorbents). The duct injection process using damp solids has the following steps: preparation of sorbent as a slurry, blending of the slurry with dry recycle materials to create damp solids, injection of the solids into the duct, reaction and drying of the solids with flue gas in the duct, collection in particulate control equipment, and finally recycle of dry solids with some bleed to disposal. The moisture content of the solids at each step affects system performance. Various factors favor high moisture whereas others favor low moisture. (VC)

  4. Global evaluation of mass transfer effects: In-duct injection flue gas desulfurization

    SciTech Connect

    Cole, J.A.; Newton, G.H.; Kramlich, J.C.; Payne, R.

    1990-09-30

    Sorbent injection is a low capital cost, low operating cost approach to SO{sub 2} control targeted primarily at older boilers for which conventional fuel gas desulfurization is not economically viable. Duct injection is one variation of this concept in which the sorbent, either a dry powder or a slurry, is injected into the cooler regions of the boiler, generally downstream of the air heaters. The attractiveness of duct injection is tied to the fact that it avoids much of the boiler heat transfer equipment and thus has minimal impact of boiler performance. Both capital and operating cost are low. This program has as its objectives three performance related issues to address: (1) experimentally identify limits on sorbent performance. (2) identify and test sorbent performance enhancement strategies. (3) develop a compute model of the duct injection process. Two major tasks are described: a laboratory-scale global experiment and development of process model. Both are aimed at understanding and quantifying the rate-limiting processes which control SO{sub 2} capture by lime slurry during boiler duct injection. 29 refs., 35 figs., 4 tabs.

  5. Modeling the Optimal Heat Transfer Fluidization Velocity in Gas-Fluidized Beds

    NASA Astrophysics Data System (ADS)

    Predey, Thomas; Bougie, Jon; Goltsiker, Aleksandr

    2014-11-01

    Fluidized beds are vital to a wide range of industrial applications and are useful for studying two-phase flow. However, modeling the optimal heat transfer fluidization velocity (OHTFV) in such beds has remained difficult. Previous investigations have commonly taken one of two approaches. One such approach attempts to find a general scaling formula for homogeneous fluidized beds by taking a harmonic average between the terminal and minimum fluidization velocities. Modern approaches using computer simulations and a wide range of parameters are more commonly used in industry today, but are generally concerned with specific applications. We propose a third approach, taking into account the inhomogeneity of the fluidized bed system while limiting the input parameters to gas velocity and particle size. We use this approach to find a general formula for OHTFV that accounts for the collective behavior of the particles rather than focusing on each individual particle in the bed. We then compare this model to previous experimental results. This research is supported by the Loyola Undergraduate Research Opportunities Program.

  6. Large eddy simulation for predicting turbulent heat transfer in gas turbines.

    PubMed

    Tafti, Danesh K; He, Long; Nagendra, K

    2014-08-13

    Blade cooling technology will play a critical role in the next generation of propulsion and power generation gas turbines. Accurate prediction of blade metal temperature can avoid the use of excessive compressed bypass air and allow higher turbine inlet temperature, increasing fuel efficiency and decreasing emissions. Large eddy simulation (LES) has been established to predict heat transfer coefficients with good accuracy under various non-canonical flows, but is still limited to relatively simple geometries and low Reynolds numbers. It is envisioned that the projected increase in computational power combined with a drop in price-to-performance ratio will make system-level simulations using LES in complex blade geometries at engine conditions accessible to the design process in the coming one to two decades. In making this possible, two key challenges are addressed in this paper: working with complex intricate blade geometries and simulating high-Reynolds-number (Re) flows. It is proposed to use the immersed boundary method (IBM) combined with LES wall functions. A ribbed duct at Re=20 000 is simulated using the IBM, and a two-pass ribbed duct is simulated at Re=100 000 with and without rotation (rotation number Ro=0.2) using LES with wall functions. The results validate that the IBM is a viable alternative to body-conforming grids and that LES with wall functions reproduces experimental results at a much lower computational cost.

  7. Large eddy simulation for predicting turbulent heat transfer in gas turbines

    PubMed Central

    Tafti, Danesh K.; He, Long; Nagendra, K.

    2014-01-01

    Blade cooling technology will play a critical role in the next generation of propulsion and power generation gas turbines. Accurate prediction of blade metal temperature can avoid the use of excessive compressed bypass air and allow higher turbine inlet temperature, increasing fuel efficiency and decreasing emissions. Large eddy simulation (LES) has been established to predict heat transfer coefficients with good accuracy under various non-canonical flows, but is still limited to relatively simple geometries and low Reynolds numbers. It is envisioned that the projected increase in computational power combined with a drop in price-to-performance ratio will make system-level simulations using LES in complex blade geometries at engine conditions accessible to the design process in the coming one to two decades. In making this possible, two key challenges are addressed in this paper: working with complex intricate blade geometries and simulating high-Reynolds-number (Re) flows. It is proposed to use the immersed boundary method (IBM) combined with LES wall functions. A ribbed duct at Re=20 000 is simulated using the IBM, and a two-pass ribbed duct is simulated at Re=100 000 with and without rotation (rotation number Ro=0.2) using LES with wall functions. The results validate that the IBM is a viable alternative to body-conforming grids and that LES with wall functions reproduces experimental results at a much lower computational cost. PMID:25024418

  8. Energetics and Dynamics of Electron Transfer and Proton Transfer in Dissociation of Metal III (salen)-Peptide Complexes in the Gas Phase

    SciTech Connect

    Laskin, Julia; Yang, Zhibo; Chu, Ivan K.

    2008-03-12

    Time- and collision energy-resolved surface-induced dissociation (SID) of ternary complexes of CoIII(salen)+, FeIII(salen)+, and MnIII(salen)+ with several angiotensin peptide analogs was studied using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially equipped to perform SID experiments. Time-resolved fragmentation efficiency curves (TFECs) were modeled using an RRKM-based approach developed in our laboratory. The approach utilizes a very flexible analytical expression for the internal energy deposition function that is capable of reproducing both single-collision and multiple-collision activation in the gas phase and excitation by collisions with a surface. The energetics and dynamics of competing dissociation pathways obtained from the modeling provides important insight on the competition between proton transfer, electron transfer, loss of neutral peptide ligand, and other processes that determine gas-phase fragmentation of these model systems. Similar fragmentation behavior was obtained for various CoIII(salen)-peptide systems of different angiotensin analogs. In contrast, dissociation pathways and relative stabilities of the complexes changed dramatically when cobalt was replaced with trivalent iron or manganese. We demonstrate that the electron transfer efficiency is correlated with redox properties of the metalIII(salen) complexes (Co > Fe > Mn), while differences in the types of fragments formed from the complexes reflect differences in the modes of binding between the metal-salen complex and the peptide ligand. RRKM modeling of time- and collision energy-resolved SID data suggests that the competition between proton transfer and electron transfer during dissociation of CoIII(salen)-peptide complexes is mainly determined by differences in entropy effects while the energetics of these two pathways are very similar.

  9. A Computational Fluid Dynamic and Heat Transfer Model for Gaseous Core and Gas Cooled Space Power and Propulsion Reactors

    NASA Technical Reports Server (NTRS)

    Anghaie, S.; Chen, G.

    1996-01-01

    A computational model based on the axisymmetric, thin-layer Navier-Stokes equations is developed to predict the convective, radiation and conductive heat transfer in high temperature space nuclear reactors. An implicit-explicit, finite volume, MacCormack method in conjunction with the Gauss-Seidel line iteration procedure is utilized to solve the thermal and fluid governing equations. Simulation of coolant and propellant flows in these reactors involves the subsonic and supersonic flows of hydrogen, helium and uranium tetrafluoride under variable boundary conditions. An enthalpy-rebalancing scheme is developed and implemented to enhance and accelerate the rate of convergence when a wall heat flux boundary condition is used. The model also incorporated the Baldwin and Lomax two-layer algebraic turbulence scheme for the calculation of the turbulent kinetic energy and eddy diffusivity of energy. The Rosseland diffusion approximation is used to simulate the radiative energy transfer in the optically thick environment of gas core reactors. The computational model is benchmarked with experimental data on flow separation angle and drag force acting on a suspended sphere in a cylindrical tube. The heat transfer is validated by comparing the computed results with the standard heat transfer correlations predictions. The model is used to simulate flow and heat transfer under a variety of design conditions. The effect of internal heat generation on the heat transfer in the gas core reactors is examined for a variety of power densities, 100 W/cc, 500 W/cc and 1000 W/cc. The maximum temperature, corresponding with the heat generation rates, are 2150 K, 2750 K and 3550 K, respectively. This analysis shows that the maximum temperature is strongly dependent on the value of heat generation rate. It also indicates that a heat generation rate higher than 1000 W/cc is necessary to maintain the gas temperature at about 3500 K, which is typical design temperature required to achieve high

  10. Excitonic splitting and coherent electronic energy transfer in the gas-phase benzoic acid dimer

    NASA Astrophysics Data System (ADS)

    Ottiger, Philipp; Leutwyler, Samuel

    2012-11-01

    The benzoic acid dimer, (BZA)2, is a paradigmatic symmetric hydrogen bonded dimer with two strong antiparallel hydrogen bonds. The excitonic S1/S2 state splitting and coherent electronic energy transfer within supersonically cooled (BZA)2 and its 13C-, d1 -, d2 -, and 13C/d1 - isotopomers have been investigated by mass-resolved two-color resonant two-photon ionization spectroscopy. The (BZA)2-(h - h) and (BZA)2-(d - d) dimers are C2h symmetric, hence only the S2 ← S0 transition can be observed, the S1 ← S0 transition being strictly electric-dipole forbidden. A single 12C/13C or H/D isotopic substitution reduces the symmetry of the dimer to Cs, so that the isotopic heterodimers (BZA)2 - 13C, (BZA)2 -(h - d), (BZA)2 -(h13C-d), and (BZA)2 -(h - d13C) show both S1 ← S0 and S2 ← S0 bands. The S1/S2 exciton splitting inferred is Δexc = 0.94 ± 0.1 cm-1. This is the smallest splitting observed so far for any H-bonded gas-phase dimer. Additional isotope-dependent contributions to the splittings, Δiso, arise from the change of the zero-point vibrational energy upon electronic excitation and range from Δiso = 3.3 cm-1 upon 12C/13C substitution to 14.8 cm-1 for carboxy H/D substitution. The degree of excitonic localization/delocalization can be sensitively measured via the relative intensities of the S1 ← S0 and S2 ← S0 origin bands; near-complete localization is observed even for a single 12C/13C substitution. The S1/ S2 energy gap of (BZA)2 is Δ ^{exc}_{calc} = 11 cm-1 when calculated by the approximate second-order perturbation theory (CC2) method. Upon correction for vibronic quenching, this decreases to Δ ^{exc}_{vibron}=2.1 cm-1 [P. Ottiger et al., J. Chem. Phys. 136, 174308 (2012)], 10.1063/1.4705119, in good agreement with the observed Δexc = 0.94 cm-1. The observed excitonic splittings can be converted to exciton hopping times τexc. For the (BZA)2-(h - h) homodimer τexc = 18 ps, which is nearly 40 times shorter than the double proton transfer time

  11. Excitonic splitting and coherent electronic energy transfer in the gas-phase benzoic acid dimer

    SciTech Connect

    Ottiger, Philipp; Leutwyler, Samuel

    2012-11-28

    The benzoic acid dimer, (BZA){sub 2}, is a paradigmatic symmetric hydrogen bonded dimer with two strong antiparallel hydrogen bonds. The excitonic S{sub 1}/S{sub 2} state splitting and coherent electronic energy transfer within supersonically cooled (BZA){sub 2} and its {sup 13}C-, d{sub 1}-, d{sub 2}-, and {sup 13}C/d{sub 1}- isotopomers have been investigated by mass-resolved two-color resonant two-photon ionization spectroscopy. The (BZA){sub 2}-(h-h) and (BZA){sub 2}-(d-d) dimers are C{sub 2h} symmetric, hence only the S{sub 2} Leftwards-Arrow S{sub 0} transition can be observed, the S{sub 1} Leftwards-Arrow S{sub 0} transition being strictly electric-dipole forbidden. A single {sup 12}C/{sup 13}C or H/D isotopic substitution reduces the symmetry of the dimer to C{sub s}, so that the isotopic heterodimers (BZA){sub 2}-{sup 13}C, (BZA){sub 2}-(h-d), (BZA){sub 2}-(h{sup 13}C-d), and (BZA){sub 2}-(h-d{sup 13}C) show both S{sub 1} Leftwards-Arrow S{sub 0} and S{sub 2} Leftwards-Arrow S{sub 0} bands. The S{sub 1}/S{sub 2} exciton splitting inferred is {Delta}{sub exc}= 0.94 {+-} 0.1 cm{sup -1}. This is the smallest splitting observed so far for any H-bonded gas-phase dimer. Additional isotope-dependent contributions to the splittings, {Delta}{sub iso}, arise from the change of the zero-point vibrational energy upon electronic excitation and range from {Delta}{sub iso}= 3.3 cm{sup -1} upon {sup 12}C/{sup 13}C substitution to 14.8 cm{sup -1} for carboxy H/D substitution. The degree of excitonic localization/delocalization can be sensitively measured via the relative intensities of the S{sub 1} Leftwards-Arrow S{sub 0} and S{sub 2} Leftwards-Arrow S{sub 0} origin bands; near-complete localization is observed even for a single {sup 12}C/{sup 13}C substitution. The S{sub 1}/ S{sub 2} energy gap of (BZA){sub 2} is {Delta}{sub calc}{sup exc}=11 cm{sup -1} when calculated by the approximate second-order perturbation theory (CC2) method. Upon correction for vibronic

  12. A CRITICAL ASSESSMENT OF ELEMENTAL MERCURY AIR/WATER EXCHANGE PARTNERS

    EPA Science Inventory

    Although evasion of elemental mercury from aquatic systems can significantly deplete net mercury accumulation resulting from atmospheric deposition, the current ability to model elemental mercury air/water exchange is limited by uncertainties in our understanding of all gaseous a...

  13. The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

    PubMed

    Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa

    2016-01-01

    A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.

  14. Application of new parameterizations of gas transfer velocity and their impact on regional and global marine CO 2 budgets

    NASA Astrophysics Data System (ADS)

    Fangohr, Susanne; Woolf, David K.

    2007-06-01

    One of the dominant sources of uncertainty in the calculation of air-sea flux of carbon dioxide on a global scale originates from the various parameterizations of the gas transfer velocity, k, that are in use. Whilst it is undisputed that most of these parameterizations have shortcomings and neglect processes which influence air-sea gas exchange and do not scale with wind speed alone, there is no general agreement about their relative accuracy. The most widely used parameterizations are based on non-linear functions of wind speed and, to a lesser extent, on sea surface temperature and salinity. Processes such as surface film damping and whitecapping are known to have an effect on air-sea exchange. More recently published parameterizations use friction velocity, sea surface roughness, and significant wave height. These new parameters can account to some extent for processes such as film damping and whitecapping and could potentially explain the spread of wind-speed based transfer velocities published in the literature. We combine some of the principles of two recently published k parameterizations [Glover, D.M., Frew, N.M., McCue, S.J. and Bock, E.J., 2002. A multiyear time series of global gas transfer velocity from the TOPEX dual frequency, normalized radar backscatter algorithm. In: Donelan, M.A., Drennan, W.M., Saltzman, E.S., and Wanninkhof, R. (Eds.), Gas Transfer at Water Surfaces, Geophys. Monograph 127. AGU,Washington, DC, 325-331; Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87-94] to calculate k as the sum of a linear function of total mean square slope of the sea surface and a wave breaking parameter. This separates contributions from direct and bubble-mediated gas transfer as suggested by Woolf [Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87-94] and allows us to quantify contributions from these two processes

  15. TECHNOLOGY TRANSFER TO U.S. INDEPENDENT OIL AND NATURAL GAS PRODUCERS

    SciTech Connect

    Donald F. Duttlinger; E. Lance Cole

    2003-12-15

    The Petroleum Technology Transfer Council (PTTC) continued pursuing its mission of assisting U.S. independent oil and gas producers to make timely, informed technology decisions. Functioning as a cohesive national organization, PTTC has active grassroots programs through its 10 Regional Lead Organizations (RLOs) and 3 Satellite Offices that encompass all of the oil- and natural gas-producing regions in the U.S. Active volunteer leadership from the Board and regional Producer Advisory Groups keeps activities focused on producer's needs. Technical expertise and personal networks of national and regional staff enable PTTC to deliver focused, technology-related information in a manner that is cost and time effective for independents. The organization effectively combines federal funding through the Department of Energy's (DOE) Office of Fossil Energy with matching state and industry funding, forming a unique partnership. This final report summarizes PTTC's accomplishments. In this final fiscal year of the contract, activities exceeded prior annual activity levels by significant percentages. Strategic planning implemented during the year is focusing PTTC's attention on changes that will bear fruit in the future. Networking and connections are increasing PTTC's sphere of influence with both producers and the service sector. PTTC's reputation for unbiased bottom-line information stimulates cooperative ventures. In FY03 PTTC's regions held 169 workshops, drawing 8,616 attendees. There were nearly 25,000 reported contacts. This represents a 38% increase in attendance and 34% increase in contacts as compared to FY02 activity. Repeat attendance at regional workshops, a measure of customer satisfaction and value received, remained strong at 50%. 39% of participants in regional workshops respond ''Yes'' on feedback forms when asked if they are applying technologies based on knowledge gained through PTTC. This feedback confirms that producers are taking action with the

  16. Scaling analysis of the coupled heat transfer process in the high-temperature gas-cooled reactor core

    SciTech Connect

    Conklin, J.C.

    1986-08-01

    The differential equations representing the coupled heat transfer from the solid nuclear core components to the helium in the coolant channels are scaled in terms of representative quantities. This scaling process identifies the relative importance of the various terms of the coupled differential equations. The relative importance of these terms is then used to simplify the numerical solution of the coupled heat transfer for two bounding cases of full-power operation and depressurization from full-system operating pressure for the Fort St. Vrain High-Temperature Gas-Cooled Reactor. This analysis rigorously justifies the simplified system of equations used in the nuclear safety analysis effort at Oak Ridge National Laboratory.

  17. Experimental study of the decrease in the temperature of an air/water-cooled turbine blade

    NASA Astrophysics Data System (ADS)

    Ryzhov, A. A.; Sereda, A. V.; Shaiakberov, V. F.; Iskakov, K. M.; Shatalov, Iu. S.

    Results of the full-scale testing of an air/water-cooled deflector-type turbine blade are reported. Data on the decrease in the temperature of the cooling air and of the blade are presented and compared with the calculated values. An analysis of the results indicates that the use of air/water cooling makes it possible to significantly reduce the temperature of the cooling air and of the blade with practically no increase in the engine weight and dimensions.

  18. Secondary flow and heat transfer control in gas turbine inlet nozzle guide vanes

    NASA Astrophysics Data System (ADS)

    Burd, Steven Wayne

    1998-12-01

    Endwall heat transfer is a very serious problem in the inlet nozzle guide vane region of gas turbine engines. To resolve heat transfer concerns and provide the desired thermal protection, modern cooling flows for the vane endwalls tend to be excessive leading to lossy and inefficient designs. Coolant introduction is further complicated by the flow patterns along vane endwall surfaces. They are three-dimensional and dominated by strong, complex secondary flows. To achieve performance goals for next-generation engines, more aerodynamically efficient and advanced cooling concepts, including combustor bleed cooling, must be investigated. To this end, the overall performance characteristics of several combustor bleed flow designs are assessed in this experimental study. In particular, their contributions toward secondary flow control and component cooling are documented. Testing is performed in a large-scale, guide vane simulator comprised of three airfoils encased between one contoured and one flat endwall. Core flow is supplied to this simulator at an inlet chord Reynolds number of 350,000 and turbulence intensity of 9.5%. Combustor bleed cooling flow is injected through the contoured endwall via inclined slots. The slots vary in cross-sectional area, have equivalent slot widths, and are positioned with their leeward edges 10% of the axial chord ahead of the airfoil leading edges. Measurements with hot-wire anemometry characterize the inlet and exit flow fields of the cascade. Total and static pressure measurements document aerodynamic performance. Thermocouple measurements detail thermal fields and permit evaluation of surface adiabatic effectiveness. To elucidate the effects of bleed injection, data are compared to an experiment taken without bleed. The influence of bleed mass flow rate and slot geometry on the aerodynamic losses and thermal protection arc given. This study suggests that such combustor bleed flow cooling offers significant thermal protection without

  19. Capillary forces between sediment particles and an air-water interface.

    PubMed

    Chatterjee, Nirmalya; Lapin, Sergey; Flury, Markus

    2012-04-17

    In the vadose zone, air-water interfaces play an important role in particle fate and transport, as particles can attach to the air-water interfaces by action of capillary forces. This attachment can either retard or enhance the movement of particles, depending on whether the air-water interfaces are stationary or mobile. Here we use three standard PTFE particles (sphere, circular cylinder, and tent) and seven natural mineral particles (basalt, granite, hematite, magnetite, mica, milky quartz, and clear quartz) to quantify the capillary forces between an air-water interface and the different particles. Capillary forces were determined experimentally using tensiometry, and theoretically assuming volume-equivalent spherical, ellipsoidal, and circular cylinder shapes. We experimentally distinguished between the maximum capillary force and the snap-off force when the air-water interface detaches from the particle. Theoretical and experimental values of capillary forces were of similar order of magnitude. The sphere gave the smallest theoretical capillary force, and the circular cylinder had the largest force due to pinning of the air-water interface. Pinning was less pronounced for natural particles when compared to the circular cylinder. Ellipsoids gave the best agreement with measured forces, suggesting that this shape can provide a reasonable estimation of capillary forces for many natural particles.

  20. Effect of pattern and severity of respiratory muscle weakness on carbon monoxide gas transfer and lung volumes.

    PubMed

    Hart, N; Cramer, D; Ward, S P; Nickol, A H; Moxham, J; Polkey, M I; Pride, N B

    2002-10-01

    In clinical practice, an elevated carbon monoxide (CO) transfer coefficient (KCO) and restrictive ventilatory defect are taken as features of respiratory muscle weakness (RMW). However, the authors hypothesised that both pattern and severity of RMW effect gas transfer and lung volumes. Measurements of CO transfer and lung volumes were performed in patients with isolated diaphragm weakness (n=10), inspiratory muscle weakness (n=12), combined inspiratory and expiratory muscle weakness (n=5) and healthy controls (n=6). Patients with diaphragm weakness and inspiratory muscle weakness had reduced total lung capacity (TLC) (83.6% predicted and 68.9% pred, respectively), functional residual capacity (FRC) (83.9% pred and 83.6% pred) and transfer factor of the lung for CO (TL,CO) (86.2% pred and 66.2% pred) with increased KCO (114.1% pred and 130.2% pred). Patients with combined inspiratory and expiratory muscle weakness had reduced TLC (80.9% pred) but increased FRC (109.9% pred) and RV (157.4% pred) with decreased TL,CO (58.0% pred) and KCO (85.5% pred). In patients with diaphragm weakness, the increase in carbon monoxide transfer coefficient was similar to that of normal subjects when alveolar volume was reduced. However, the increase in carbon monoxide transfer coefficient in inspiratory muscle weakness was often less than expected, while in combined inspiratory and expiratory muscle weakness, the carbon monoxide transfer coefficient was normal/reduced despite further reductions in alveolar volume, which may indicate subtle abnormalities of the lung parenchyma or pulmonary vasculature. Thus, this study demonstrates the limitations of using carbon monoxide transfer coefficient in the diagnosis of respiratory muscle weakness, particularly if no account is taken of the alveolar volume at which the carbon monoxide transfer coefficient is made.

  1. Heat transfer technology for internal passages of air-cooled blades for heavy-duty gas turbines.

    PubMed

    Weigand, B; Semmler, K; von Wolfersdorf, J

    2001-05-01

    The present review paper, although far from being complete, aims to give an overview about the present state of the art in the field of heat transfer technology for internal cooling of gas turbine blades. After showing some typical modern cooled blades, the different methods to enhance heat transfer in the internal passages of air-cooled blades are discussed. The complicated flows occurring in bends are described in detail, because of their increasing importance for modern cooling designs. A short review about testing of cooling design elements is given, showing the interaction of the different cooling features as well. The special focus of the present review has been put on the cooling of blades for heavy-duty gas turbines, which show several differences compared to aero-engine blades.

  2. Advanced online monitoring of cell culture off-gas using proton transfer reaction mass spectrometry.

    PubMed

    Schmidberger, Timo; Gutmann, Rene; Bayer, Karl; Kronthaler, Jennifer; Huber, Robert

    2014-01-01

    Mass spectrometry has been frequently applied to monitor the O₂ and CO₂ content in the off-gas of animal cell culture fermentations. In contrast to classical mass spectrometry the proton transfer reaction mass spectrometry (PTR-MS) provides additional information of volatile organic compounds by application of a soft ionization technology. Hence, the spectra show less fragments and can more accurately assigned to particular compounds. In order to discriminate between compounds of non-metabolic and metabolic origin cell free experiments and fed-batch cultivations with a recombinant CHO cell line were conducted. As a result, in total eight volatiles showing high relevance to individual cultivation or cultivation conditions could be identified. Among the detected compounds methanethiol, with a mass-to-charge ratio of 49, qualifies as a key candidate in process monitoring due to its strong connectivity to lactate formation. Moreover, the versatile and complex data sets acquired by PTR MS provide a valuable resource for statistical modeling to predict non direct measurable parameters. Hence, partial least square regression was applied to the complete spectra of volatiles measured and important cell culture parameters such as viable cell density estimated (R²  = 0.86). As a whole, the results of this study clearly show that PTR-MS provides a powerful tool to improve bioprocess-monitoring for mammalian cell culture. Thus, specific volatiles emitted by cells and measured online by the PTR-MS and complex variables gained through statistical modeling will contribute to a deeper process understanding in the future and open promising perspectives to bioprocess control.

  3. A survey of gas-side fouling in industrial heat-transfer equipment

    NASA Technical Reports Server (NTRS)

    Marner, W. J.; Suitor, J. W.

    1983-01-01

    Gas-side fouling and corrosion problems occur in all of the energy intensive industries including the chemical, petroleum, primary metals, pulp and paper, glass, cement, foodstuffs, and textile industries. Topics of major interest include: (1) heat exchanger design procedures for gas-side fouling service; (2) gas-side fouling factors which are presently available; (3) startup and shutdown procedures used to minimize the effects of gas-side fouling; (4) gas-side fouling prevention, mitigation, and accommodation techniques; (5) economic impact of gas-side fouling on capital costs, maintenance costs, loss of production, and energy losses; and (6) miscellaneous considerations related to gas-side fouling. The present state-of-the-art for industrial gas-side fouling is summarized by a list of recommendations for further work in this area.

  4. A survey of gas-side fouling in industrial heat-transfer equipment

    NASA Astrophysics Data System (ADS)

    Marner, W. J.; Suitor, J. W.

    1983-11-01

    Gas-side fouling and corrosion problems occur in all of the energy intensive industries including the chemical, petroleum, primary metals, pulp and paper, glass, cement, foodstuffs, and textile industries. Topics of major interest include: (1) heat exchanger design procedures for gas-side fouling service; (2) gas-side fouling factors which are presently available; (3) startup and shutdown procedures used to minimize the effects of gas-side fouling; (4) gas-side fouling prevention, mitigation, and accommodation techniques; (5) economic impact of gas-side fouling on capital costs, maintenance costs, loss of production, and energy losses; and (6) miscellaneous considerations related to gas-side fouling. The present state-of-the-art for industrial gas-side fouling is summarized by a list of recommendations for further work in this area.

  5. Radiative transfer modelling for the NOMAD-UVIS instrument on the ExoMars Trace Gas Orbiter mission

    NASA Astrophysics Data System (ADS)

    Dawson, D. G.; Patel, M. R.; Lewis, S. R.; Mason, J. P.; Irwin, P. G. J.

    2013-09-01

    The NOMAD (Nadir and Occultation for MArs Discovery) instrument is a 3-channel (2 IR, 1 UV/Vis) spectrometer due to fly on the 2016 ExoMars Trace Gas Orbiter mission. A radiative transfer model for Mars has been developed providing synthetic spectra to simulate observations of the UVIS channel in both solar occultation and nadir viewing geometries. This will allow for the characterization and mitigation of the influence of dust on retrievals of ozone abundance.

  6. A diffusion-kinetic model for pulverized-coal combustion and heat-and-mass transfer in a gas stream

    SciTech Connect

    E.A. Boiko; S.V. Pachkovskii

    2008-12-15

    A diffusion-kinetic model for pulverized-coal combustion and heat-and-mass transfer in a gas stream is proposed, and the results of numerical simulation of the burnout dynamics of Kansk-Achinsk coals in the pulverized state at different treatment conditions and different model parameters are presented. The mathematical model describes the dynamics of thermochemical conversion of solid organic fuels with allowance for complex physicochemical phenomena of heat-and-mass exchange between coal particles and the gaseous environment.

  7. Slip conditions with wall catalysis and radiation for multicomponent, nonequilibrium gas flow. [for predicting heat transfer to the space shuttle

    NASA Technical Reports Server (NTRS)

    Hendricks, W. L.

    1974-01-01

    The slip conditions for a multicomponent mixture with diffusion, wall-catalyzed atom recombination and thermal radiation are derived, and simplified expressions for engineering applications are presented. The gas mixture may be in chemical nonequilibrium with finite-rate catalytic recombination occurring on the wall. These boundary conditions, which are used for rarefied flow regime flow field calculations, are shown to be necessary for accurate predictions of skin friction and heat transfer coefficients in the rarefied portion of the space shuttle trajectory.

  8. EPRI High-Sulfur Test Center: Wet FGD (flue gas desulfurization) sodium carbonate mass-transfer tests: Final report

    SciTech Connect

    Jarvis, J.B.; Burke, J.M.

    1988-10-01

    HSTC contains pilot- and mini-pilot-scale systems for investigating wet FGD technologies, as well as dry-injection and spray-drying pilot systems for investigating dry FGD technologies. A series of sodium carbonate (Na/sub 2/CO/sub 3/) mass-transfer tests is the first step in characterizing the SO/sub 2/ removal capabilities of wet FGD systems at HSTC. By using sodium as the SO/sub 2/ absorbent, an excess of liquid-phase alkalinity is provided to assure that gas-limited mass transfer alone will control SO/sub 2/ removal. Objectives of this project were to determine the maximum possible SO/sub 2/ removal capabilities of the HSTC wet FGD systems under different configurations; to provide data for modeling SO/sub 2/ absorption under gas-limited mass-transfer conditions. Sodium mass-transfer tests were conducted using slurry with a high concentration of liquid-phase alkalinity, established by adding sodium carbonate and maintained with a unique, in situ, dual-alkali operating system that continuously regenerated slurry alkalinity with slaked quicklime (Ca(OH)/sub 2/). This process allows testing of a slurry, simulating a lime or limestone scrubber, while maintaining an excess of liquid-phase alkalinity to assure gas-limited mass-transfer conditions. SO/sub 2/ removal efficiencies were measured of the mini-pilot and pilot systems for three absorber configurations---spray tower, tray tower, and packed tower. More than 300 tests were conducted over a wide range of operating conditions, using various types of spray nozzles characterized for spray distribution patterns. 5 refs., 74 figs., 23 tabs.

  9. A transient liquid crystal thermography technique for gas turbine heat transfer measurements

    NASA Astrophysics Data System (ADS)

    Ekkad, Srinath V.; Han, Je-Chin

    2000-07-01

    This paper presents in detail the transient liquid crystal technique for convective heat transfer measurements. A historical perspective on the active development of liquid crystal techniques for convective heat transfer measurement is also presented. The experimental technique involves using a thermochromic liquid crystal coating on the test surface. The colour change time of the coating at every pixel location on the heat transfer surface during a transient test is measured using an image processing system. The heat transfer coefficients are calculated from the measured time responses of these thermochromic coatings. This technique has been used for turbine blade internal coolant passage heat transfer measurements as well as turbine blade film cooling heat transfer measurements. Results can be obtained on complex geometry surfaces if visually accessible. Some heat transfer results for experiments with jet impingement, internal cooling channels with ribs, flow over simulated TBC spallation, flat plate film cooling, cylindrical leading edge and turbine blade film cooling are presented for demonstration.

  10. Visualization of gas-liquid mass transfer and wake structure of rising bubbles using pH-sensitive PLIF

    NASA Astrophysics Data System (ADS)

    Stöhr, M.; Schanze, J.; Khalili, A.

    2009-07-01

    A planar laser-induced fluorescence (PLIF) technique for visualizing gas-liquid mass transfer and wake structure of rising gas bubbles is described. The method uses an aqueous solution of the pH-sensitive dye Naphthofluorescein and CO2 as a tracer gas. It features a high spatial resolution and frame rates of up to 500 Hz, providing the ability to capture cinematographic image sequences. By steering the laser beam with a set of two programmable scanning mirrors, sequences of three-dimensional LIF images can be recorded. The technique is applied to freely rising bubbles with diameters between 0.5 and 5 mm, which perform rectilinear, oscillatory or irregular motions. The resulting PLIF image sequences reveal the evolution of characteristic patterns in the near and far wake of the bubbles and prove the potential of the technique to provide new and detailed insights into the spatio-temporal dynamics of mass transfer of rising gas bubbles. The image sequences further allow the estimation of bubble size and rise velocity. The analysis of bubble rise velocities in the Naphthofluorescein solution indicates that surfactant-contaminated conditions are encountered.

  11. Mechanism of kinetic energy transfer in homogeneous bidisperse gas-solid flow and its implications for segregation

    NASA Astrophysics Data System (ADS)

    Mehrabadi, Mohammad; Subramaniam, Shankar

    2017-02-01

    Most gas-solid flows encountered in nature and industrial applications are polydisperse, and the segregation or mixing of particle classes in polydisperse gas-solid flows is a phenomenon of great practical importance. A statistically homogeneous gas-solid flow with a bidisperse distribution (in size or density) of particles is a canonical representation of polydisperse flows. A key feature that distinguishes the bidisperse flow from its monodisperse counterpart is the exchange of momentum and kinetic energy between the particle classes due to collisions, which are important for applications outside the very dilute regime. The average exchange of linear momentum between particle classes due to collisions occurs through the particle-particle drag term. The conservation equations for average momentum corresponding to each particle class can be used to deduce the average slip velocity between the particle size and density classes, which is the signature of particle segregation. In this canonical problem, the steady value of particle mean slip velocity results from a balance between three terms, each in turn involving the body force or the mean fluid pressure gradient, the gas-particle drag, and the particle-particle drag. The particle-particle drag depends on the particle velocity fluctuations in each class [Louge, M. Y. et al., "The role of particle collisions in pneumatic transport," J. Fluid Mech. 231, 345-359 (1991)], thereby coupling the mean and second-moment equations. For monodisperse gas-solid flows the transfer of kinetic energy from the mean to second-moment equations was explained by Subramaniam and co-workers who proposed the conservation of interphase turbulent kinetic energy transfer principle [Xu, Y. and Subramaniam, S., "Consistent modeling of interphase turbulent kinetic energy transfer in particle-laden turbulent flows," Phys. Fluids 19(8), 085101 (2007)], and this was subsequently verified by particle-resolved direct numerical simulation [Mehrabadi

  12. Viscoelastic Drag Forces and Crossover from No-Slip to Slip Boundary Conditions for Flow near Air-Water Interfaces

    NASA Astrophysics Data System (ADS)

    Maali, A.; Boisgard, R.; Chraibi, H.; Zhang, Z.; Kellay, H.; Würger, A.

    2017-02-01

    The "free" water surface is generally prone to contamination with surface impurities, be they surfactants, particles, or other surface active agents. The presence of such impurities can modify flow near such interfaces in a drastic manner. Here we show that vibrating a small sphere mounted on an atomic force microscope cantilever near a gas bubble immersed in water is an excellent probe of surface contamination. Both viscous and elastic forces are exerted by an air-water interface on the vibrating sphere even when very low doses of contaminants are present. The viscous drag forces show a crossover from no-slip to slip boundary conditions while the elastic forces show a nontrivial variation as the vibration frequency changes. We provide a simple model to rationalize these results and propose a simple way of evaluating the concentration of such surface impurities.

  13. Characterization of atmospheric nanosecond discharge under highly inhomogeneous and transient electric field in air/water mixture

    NASA Astrophysics Data System (ADS)

    Ouaras, Karim; Tardiveau, Pierre; Magne, Lionel; Jeanney, Pascal; Bournonville, Blandine

    2016-09-01

    We report the studies of a centimeter range pin-to-plane nanosecond repetitively discharge (<30 ns and 10 Hz) in standard conditions of pressure and temperature under very high positive voltage pulses (20 to 100 kV). In these typical conditions, plasma exhibit unusual diffuse and large structure. This kind of discharge is not well understood and in first approach, it requires (i) a description of plasma dynamic and (ii) behavior under relevant context (environmental issues ...) using pertinent gas (humid air). Thus, we will first present sub-nanosecond imaging of the discharge obtained for typical conditions of stabilized plasma. Then we will focus on determination of rotational and vibrational temperature (OES) and preliminary results concerning the production and evolution of OH radical in temporal post-discharge in air/water mixture (PLIF). Theses spectroscopic measurements are undertaken as function of most influent parameters, i . e . voltage pulses features (amplitude, rise time and length) and water concentration.

  14. Surfactant-Induced Flow in Unsaturated Porous Media: Implications for Air-Water Interfacial Area Determination

    NASA Astrophysics Data System (ADS)

    Costanza-Robinson, M. S.; Zheng, Z.; Estabrook, B.; Henry, E. J.; Littlefield, M. H.

    2011-12-01

    Air-water interfacial area (AI) in porous media is an important factor governing equilibrium contaminant retention, as well as the kinetics of interphase mass transfer. Interfacial-partitioning tracer (IPT) tests are a common technique for measuring AI at a given moisture saturation (SW), where AI is calculated based on the ratio of arrival times of a surfactant and a non-reactive tracer. At surfactant concentrations often used, the aqueous surface tension of the interfacial tracer solution is ~30% lower than that of the resident porewater in the system, creating transient surface tension gradients during the IPT measurement. Because surface tension gradients create capillary pressure gradients, surfactant-induced unsaturated flow may occur during IPT tests, a process that would violate fundamental assumptions of constant SW, of steady-state flow, and of nonreactive and surfactant tracers experiencing the same transport conditions. To examine the occurrence and magnitude of surfactant-induced flow, we conducted IPT tests for unsaturated systems at ~84% initial SW using surfactant input concentrations that bracket concentrations commonly used. Despite constant boundary conditions (constant inlet flux and outlet pressure), the introduction of the surfactant solution induced considerable transience in column effluent flowrate and SW. Real-time system mass measurements revealed drainage of 20-40% SW, with the amount of drainage and the maximum rate of drainage proportional to the influent surfactant concentration, as would be expected. Because AI is inversely related to SW, the use of higher surfactant concentrations should yield larger AI estimates. Measured AI values, however, showed no clear relationship to surfactant concentration or the time-averaged SW of the system. These findings cast doubt on the reliability of IPT for AI determination.

  15. Advances in simulating radiance signatures for dynamic air/water interfaces

    NASA Astrophysics Data System (ADS)

    Goodenough, Adam A.; Brown, Scott D.; Gerace, Aaron

    2015-05-01

    The air-water interface poses a number of problems for both collecting and simulating imagery. At the surface, the magnitude of observed radiance can change by multiple orders of magnitude at high spatiotemporal frequency due to glinting effects. In the volume, similarly high frequency focusing of photons by a dynamic wave surface significantly changes the reflected radiance of in-water objects and the scattered return of the volume itself. These phenomena are often manifest as saturated pixels and artifacts in collected imagery (often enhanced by time delays between neighboring pixels or interpolation between adjacent filters) and as noise and greater required computation times in simulated imagery. This paper describes recent advances made to the Digital Image and Remote Sensing Image Generation (DIRSIG) model to address the simulation issues to better facilitate an understanding of a multi/hyper-spectral collection. Glint effects are simulated using a dynamic height field that can be driven by wave frequency models and generates a sea state at arbitrary time scales. The volume scattering problem is handled by coupling the geometry representing the surface (facetization by the height field) with the single scattering contribution at any point in the water. The problem is constrained somewhat by assuming that contributions come from a Snell's window above the scattering point and by assuming a direct source (sun). Diffuse single scattered and multiple scattered energy contributions are handled by Monte Carlo techniques employed previously. The model is compared to existing radiative transfer codes where possible, with the objective of providing a robust movel of time-dependent absolute radiance at many wavelengths.

  16. Mass transfer phenomena of gaseous hydrocarbons and nitrogen dioxide across gas-inorganic pigments boundaries

    NASA Astrophysics Data System (ADS)

    Birbatakou, S.; Pagopoulou, I.; Kalantzopoulos, A.; Roubani-Kalantzopoulou, F.

    1998-11-01

    Reversed-flow gas chromatography was used to study the kinetics of the action of five hydrocarbons namely, ethane, ethene, ethyne, propene and butene and of the nitrogen dioxide, on three known and widely used pigments, the white one TiO2, and the yellows CdS and PbCrO4. The calculation of kinetic parameters and mass transfer coefficients is based on an experimental adsorption isotherm. All these calculations are based on a non linear adsorption isotherm model as it is well accepted that the linear one is inadequate for inorganic substances like these mentioned in this work. The inadequacy is mainly attributed to the non-uniformity of the solid surface. Five physicochemical parameters have been obtained for each of the twenty heterogeneous reactions studied. With these systematic experiments under conditions which are similar to the atmospheric ones, an extrapolation of the results obtained to “real" atmospheres with a high degree of confidence is possible. Some of the calculations were based on the linear model for comparison. La cinétique de la réaction de cinq hydrocarbures (éthane, éthylène, acétylène, propène, boutène) et du dioxyde d'azote avec trois pigments (le blanc de TiO2 et les jaunes de CdS et PbCrO4) a été étudiée par chromatographie en phase gazeuse a flux inversé. Le calcul des paramètres cinétiques et des coefficients de transfert de masse a été effectué à partir des isothermes d'adsorption expérimentales en faisant l'hypothèse d`un modèle d'adsorption non-linéaire, qui résulte de la non-uniformité de la surface. Cinq paramètres physico-chimiques ont été obténus pour chacune des vingt réaction hétérogènes étudiées. À partir de ces résultats obténus dans des conditions similaires aux conditions atmosphériques, l'extrapolation à des atmosphères réelles paraît possible avec une bonne confiance. Quelques calculs ont été effectués avec un modèle linéaire pour comparaison.

  17. Gas Transfer in the Pluto-Charon System: A Charon Atmosphere

    NASA Astrophysics Data System (ADS)

    Tucker, O. J.; Johnson, R. E.; Young, L. A.; Jia, X.; Tenishev, V.

    2014-12-01

    Recent hybrid fluid/molecular kinetic models demonstrated that Pluto's upper atmosphere is warmer and more extended than previously thought (Erwin et al., 2013; Tucker et al. 2012). This extended atmosphere is a source of molecules to Charon's surface. For approximate solar medium conditions at ~33AU about ~0.2% of the flux from Pluto's exobase impinges on Charon at a rate of ~5.7×1025 N2/s. This is a source of condensed N2 for Charon's night side, and molecules re-emitted from warmer (>20 K) surface regions form a tenuous atmosphere. For the approximate range of surface temperatures, the residence time of N2 on the surface can range from a fraction of a second to 10's of years with the near surface line of sight column densities varying from ~3×1018 N2/m2 up to >6×1019N2/m2. Additional mechanisms that can eject N2molecules from the surface include cometary impacts (Stern et al. 2014) and electronic sputtering (Johnson et al., 2013). A Charon atmosphere could be detectable during the solar occultation that will occur during the New Horizon encounter providing a measure of the transfer of gas between bodies in this binary system. Tucker, O.J., Erwin, J.T., Deighan, J.I., Volkov, A.N., Johnson, R.E., 2012. Thermally driven escape from Pluto's atmosphere: A combined fluid/kinetic model. Icarus 217, pp 408-415.; Erwin, J.T., Tucker, O.J., Johnson, R.E., 2013. Hybrid fluid/kinetic modeling of Pluto's escapingatmosphere. Icarus 226, 375-384. Stern, S.A., R. Gladstone, A. Zangari, D. Goldstein,T.Fleming 2014. Transient Atmospheres on Charon and Other Water-Ice Covered KBOs, Resulting from Comet Impacts, Icarus. DOI: 10.1016/j.icarus.2014.03.008 Johnson, R.E., R. Carlson, T.A. Cassidy, M. Fama, "Sputtering of ices", Chapter in The Science of Solar System Ices. ed. M. Gutopati, J. Castillo-Rogez, Astrophysics and Space Science Library, 356, pp551-581 (2013).

  18. Gas hold-up and oxygen mass transfer in three pneumatic bioreactors operating with sugarcane bagasse suspensions.

    PubMed

    Esperança, M N; Cunha, F M; Cerri, M O; Zangirolami, T C; Farinas, C S; Badino, A C

    2014-05-01

    Sugarcane bagasse is a low-cost and abundant by-product generated by the bioethanol industry, and is a potential substrate for cellulolytic enzyme production. The aim of this work was to evaluate the effects of air flow rate (QAIR), solids loading (%S), sugarcane bagasse type, and particle size on the gas hold-up (εG) and volumetric oxygen transfer coefficient (kLa) in three different pneumatic bioreactors, using response surface methodology. Concentric tube airlift (CTA), split-cylinder airlift (SCA), and bubble column (BC) bioreactor types were tested. QAIR and %S affected oxygen mass transfer positively and negatively, respectively, while sugarcane bagasse type and particle size (within the range studied) did not influence kLa. Using large particles of untreated sugarcane bagasse, the loop-type bioreactors (CTA and SCA) exhibited higher mass transfer, compared to the BC reactor. At higher %S, SCA presented a higher kLa value (0.0448 s−1) than CTA, and the best operational conditions in terms of oxygen mass transfer were achieved for %S < 10.0 g L−1 and QAIR > 27.0 L min−1. These results demonstrated that pneumatic bioreactors can provide elevated oxygen transfer in the presence of vegetal biomass, making them an excellent option for use in three-phase systems for cellulolytic enzyme production by filamentous fungi.

  19. Estimation of internal heat transfer coefficients and detection of rib positions in gas turbine blades from transient surface temperature measurements

    NASA Astrophysics Data System (ADS)

    Heidrich, P.; Wolfersdorf, J. v.; Schmidt, S.; Schnieder, M.

    2008-11-01

    This paper describes a non-invasive, non-destructive, transient inverse measurement technique that allows one to determine internal heat transfer coefficients and rib positions of real gas turbine blades from outer surface temperature measurements after a sudden flow heating. The determination of internal heat transfer coefficients is important during the design process to adjust local heat transfer to spatial thermal load. The detection of rib positions is important during production to fulfill design and quality requirements. For the analysis the one-dimensional transient heat transfer problem inside of the turbine blade's wall was solved. This solution was combined with the Levenberg-Marquardt method to estimate the unknown boundary condition by an inverse technique. The method was tested with artificial data to determine uncertainties with positive results. Then experimental testing with a reference model was carried out. Based on the results, it is concluded that the presented inverse technique could be used to determine internal heat transfer coefficients and to detect rib positions of real turbine blades.

  20. OXYGEN TRANSFER ACROSS THE AIR-WATER INTERFACE DUE TO NATURAL CONVECTION IN LAKES. (R825428)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  1. Effect of particle shape on capillary forces acting on particles at the air-water interface.

    PubMed

    Chatterjee, Nirmalya; Flury, Markus

    2013-06-25

    The capillary forces exerted by moving air-water interfaces can dislodge particles from stationary surfaces. The magnitude of the capillary forces depends on particle shape, orientation, and surface properties, such as contact angle and roughness. The objective was to quantify, both experimentally and theoretically, capillary force variations as an air-water interface moves over the particles. We measured capillary forces as a function of position, i.e., force-position curves, on particles of different shape by using force tensiometry. The particles (5 mm nominal size) were made of polyacrylate and were fabricated using a 3D printer. Experimental measurements were compared with theoretical calculations. We found that force-position curves could be classified into in three categories according to particle shapes: (1) curves for particles with round cross sections, such as spheroidal particles, (2) curves for particles with fixed cross sections, such cylindrical or cubical particles, and (3) curves for particles with tapering cross sections, such as prismatic or tetrahedral particles. Spheroidal particles showed a continuously varying capillary force. Cylindrical or cubical particles showed pronounced pinning of the air-water interface line at edges. The pinning led to an increased capillary force, which was relaxed when the interface snapped off from the edges. Particles with tapering cross section did not show pinning and showed reduced capillary forces as the air-water interface line perimeter and displacement cross section continuously decrease when the air-water interface moved over the particles.

  2. Convective Heat Transfer in Internal Gas Flows with Temperature-Dependent Properties.

    DTIC Science & Technology

    1982-06-30

    effects of variable properties have been provided by Petukhov [1970],specifically for turbulent flow in circular tubes.and by Leontiev o for the...243-249. Leontiev , A. I., 1966. Heat and mass transfer in turbulent boundary layers, Adv. Heat Transfer, 3, pp. 33-100. Leung, E. Y., V. M. Kays and W

  3. Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions

    NASA Technical Reports Server (NTRS)

    Gray, Vernon H.

    1950-01-01

    The effect of modifying the gas passage of hollow metal airfoils by the additIon of internal fins and partitions was experimentally investigated and comparisons were made among a basic unfinned airfoil section and two airfoil designs having metal fins attached at the leading edge of the internal gas passage. An analysis considering the effects of heat conduction in the airfoil metal was made to determine the internal modification effectiveness that may be obtained in gas-heated components, such as turbojet-inlet guide vanes, support struts, hollow propeller blades, arid. thin wings. Over a wide range of heated-gas flow and tunnel-air velocity, the increase In surface-heating rates with internal finning was marked (up to 3.5 times), with the greatest increase occurring at the leading edge where anti-icing heat requirements are most critical. Variations in the amount and the location of internal finning and. partitioning provided. control over the local rates of surface heat transfer and permitted efficient anti-icing utilization of the gas-stream heat content.

  4. Flow and heat transfer characteristics of assisting gas impingining onto an alumina coated hole in relation to laser drilling

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    Flow and heat transfer characteristics of the assisting gas impinging onto the coated holes are investigated in relation to the laser drilling process. The alumina coating with thickness of 250 μm is considered at the surface of the carbon steel substrate. Three cases are considered by incorporating different locations of the coating on the carbon steel. These cases include coating at the top of the workpiece, coating at the bottom of the workpiece, and coating both at the top and at the bottom of the workpiece. A no-coating situation of the hole is also presented for the comparison reason. To resemble the laser drilling process, the wall temperature of the coating and the carbon steel substrate is kept at the melting temperatures during the simulations. A numerical scheme incorporating the control volume approach is introduced and the Reynolds stress turbulence model is used to account for the turbulence effect of the impinging assisting gas. An experiment is carried out in line with the simulation conditions to examine the morphological changes at the coating-carbon steel interface. It is found that the assisting gas temperature exceeds the melting temperature of the steel substrate along the coating thickness and as the assisting gas progresses further into the hole, heat transfer from the assisting gas to the hole wall takes place. This, in turn, increases thermal erosion at the hole wall in the vicinity of the coating-steel substrate interface. The Nusselt number and the skin friction attain large values along the coating thickness in the hole.

  5. Experimental investigation of heat transfer and flow using V and broken V ribs within gas turbine blade cooling passage

    NASA Astrophysics Data System (ADS)

    Kumar, Sourabh; Amano, R. S.

    2015-05-01

    Gas turbines are extensively used for aircraft propulsion, land-based power generation, and various industrial applications. With an increase in turbine rotor inlet temperatures, developments in innovative gas turbine cooling technology enhance the efficiency and power output; these advancements of turbine cooling have allowed engine designs to exceed normal material temperature limits. For internal cooling design, techniques for heat extraction from the surfaces exposed to hot stream of gas are based on an increase in the heat transfer areas and on the promotion of turbulence of the cooling flow. In this study, an improvement in performance is obtained by casting repeated continuous V- and broken V-shaped ribs on one side of the two pass square channels into the core of the blade. A detailed experimental investigation is done for two pass square channels with a 180° turn. Detailed heat transfer distribution occurring in the ribbed passage is reported for a steady state experiment. Four different combinations of 60° V- and broken 60° V-ribs in a channel are considered. A series of thermocouples are used to obtain the temperature on the channel surface and local heat transfer coefficients are obtained for Reynolds numbers 16,000, 56,000 and 85,000 within the turbulent flow regime. Area averaged data are calculated in order to compare the overall performance of the tested ribbed surface and to evaluate the degree of heat transfer enhancement induced by the rib. Flow within the channels is characterized by heat transfer enhancing ribs, bends, rotation and buoyancy effects. A series of experimental measurements is performed to predict the overall performance of the channel. This paper presents an attempt to collect information about the Nusselt number, the pressure drop and the overall performance of the eight different ribbed ducts at the specified Reynolds number. The main contribution of this study is to evaluate the best combination of rib arrangements

  6. Gas-liquid transfer data used to analyze hydrophobic hydration and find the nature of the Kauzmann-Tanford hydrophobic factor.

    PubMed

    Baldwin, Robert L

    2012-05-08

    Hydrophobic free energy for protein folding is currently measured by liquid-liquid transfer, based on an analogy between the folding process and the transfer of a nonpolar solute from water into a reference solvent. The second part of the analogy (transfer into a nonaqueous solvent) is dubious and has been justified by arguing that transfer out of water probably contributes the major part of the free energy change. This assumption is wrong: transfer out of water contributes no more than half the total, often less. Liquid-liquid transfer of the solute from water to liquid alkane is written here as the sum of 2 gas-liquid transfers: (i) out of water into vapor, and (ii) from vapor into liquid alkane. Both gas-liquid transfers have known free energy values for several alkane solutes. The comparable values of the two different transfer reactions are explained by the values, determined in 1991 for three alkane solutes, of the cavity work and the solute-solvent interaction energy. The transfer free energy is the difference between the positive cavity work and the negative solute-solvent interaction energy. The interaction energy has similar values in water and liquid alkane that are intermediate in magnitude between the cavity work in water and in liquid alkane. These properties explain why the transfer free energy has comparable values (with opposite signs) in the two transfers. The current hydrophobic free energy is puzzling and poorly defined and needs a new definition and method of measurement.

  7. Gas-liquid transfer data used to analyze hydrophobic hydration and find the nature of the Kauzmann-Tanford hydrophobic factor

    PubMed Central

    Baldwin, Robert L.

    2012-01-01

    Hydrophobic free energy for protein folding is currently measured by liquid-liquid transfer, based on an analogy between the folding process and the transfer of a nonpolar solute from water into a reference solvent. The second part of the analogy (transfer into a nonaqueous solvent) is dubious and has been justified by arguing that transfer out of water probably contributes the major part of the free energy change. This assumption is wrong: transfer out of water contributes no more than half the total, often less. Liquid-liquid transfer of the solute from water to liquid alkane is written here as the sum of 2 gas-liquid transfers: (i) out of water into vapor, and (ii) from vapor into liquid alkane. Both gas-liquid transfers have known free energy values for several alkane solutes. The comparable values of the two different transfer reactions are explained by the values, determined in 1991 for three alkane solutes, of the cavity work and the solute-solvent interaction energy. The transfer free energy is the difference between the positive cavity work and the negative solute-solvent interaction energy. The interaction energy has similar values in water and liquid alkane that are intermediate in magnitude between the cavity work in water and in liquid alkane. These properties explain why the transfer free energy has comparable values (with opposite signs) in the two transfers. The current hydrophobic free energy is puzzling and poorly defined and needs a new definition and method of measurement. PMID:22529345

  8. Critical air/water blow-down in safety valves at low qualities.

    PubMed

    Moncalvo, D; Friedel, L

    2011-02-28

    Critical air/water blow-downs in safety valves for qualities from 0.01 to 0.113 and mass flow rates from 1.5 up to 4.3 kg/s have been observed in our test facility. These critical blow-downs are characterized by a large void fraction and by an intense mixing of the phases both in the valve body and in the outlet pipe. A qualitative estimation of the flow pattern in the outlet pipe using the map of Taitel and Dukler suggests that these air/water flows are intermittent flows--presumably slug flows--evolving to annular flows for qualities above 0.1. Intermittent flows are also predicted for critical air/water and air/glycerine flows taken from the literature for the same safety valve at slightly larger relieving pressures.

  9. Surface behavior of malonic acid adsorption at the air/water interface.

    PubMed

    Blower, Patrick G; Shamay, Eric; Kringle, Loni; Ota, Stephanie T; Richmond, Geraldine L

    2013-03-28

    The presence of organic materials adsorbed to the surfaces of aerosol particles has been demonstrated to be a determining factor in relevant atmospheric processes. Malonic acid is a small, water-soluble organic acid that is common in aerosols and is surface-active. A comprehensive investigation of the adsorption of malonic acid to the air/water interface was accomplished using vibrational sum frequency spectroscopy (VSFS) and surface tension measurements as functions of concentration and pH. Malonic acid was found to be weakly solvated at the air/water interface, and its orientation as a function of concentration was explored through different VSFS polarization schemes. pH-dependent experiments revealed that the surface-active species is the fully protonated species. Computational analyses were used to obtain depth-specific geometries of malonic acid at the air/water interface that confirm and enrich the experimental results.

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

    SciTech Connect

    Fan, Shiwei; Yan, Tinghu; Yeung, Hoi

    2014-04-11

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

  11. Heat transfer in gas turbine engines and three-dimensional flows; Proceedings of the Symposium, ASME Winter Annual Meeting, Chicago, IL, Nov. 27-Dec. 2, 1988

    NASA Astrophysics Data System (ADS)

    Elovic, E.; O'Brien, J. E.; Pepper, D. W.

    The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.

  12. Does colloid shape affect detachment of colloids by a moving air-water interface?

    PubMed

    Aramrak, Surachet; Flury, Markus; Harsh, James B; Zollars, Richard L; Davis, Howard P

    2013-05-14

    Air-water interfaces interact strongly with colloidal particles by capillary forces. The magnitude of the interaction force depends on, among other things, the particle shape. Here, we investigate the effects of particle shape on colloid detachment by a moving air-water interface. We used hydrophilic polystyrene colloids with four different shapes (spheres, barrels, rods, and oblong disks), but otherwise identical surface properties. The nonspherical shapes were created by stretching spherical microspheres on a film of polyvinyl alcohol (PVA). The colloids were then deposited onto the inner surface of a glass channel. An air bubble was introduced into the channel and passed through, thereby generating a receding followed by an advancing air-water interface. The detachment of colloids by the air-water interfaces was visualized with a confocal microscope, quantified by image analysis, and analyzed statistically to determine significant differences. For all colloid shapes, the advancing air-water interface caused pronounced colloid detachment (>63%), whereas the receding interface was ineffective in colloid detachment (<1.5%). Among the different colloid shapes, the barrels were most readily removed (94%) by the advancing interface, followed by the spheres and oblong disks (80%) and the rods (63%). Colloid detachment was significantly affected by colloid shape. The presence of an edge, as it occurs in a barrel-shaped colloid, promoted colloid detachment because the air-water interface is being pinned at the edge of the colloid. This suggests that the magnitude of colloid mobilization and transport in porous media is underestimated for edged particles and overestimated for rodlike particles when a sphere is used as a model colloid.

  13. Product distributions for some thermal energy charge transfer reactions of rare gas ions

    NASA Technical Reports Server (NTRS)

    Anicich, V. G.; Laudenslager, J. B.; Huntress, W. T., Jr.; Futrell, J. H.

    1977-01-01

    Ion cyclotron resonance methods were used to measure the product distributions for thermal-energy charge-transfer reactions of He(+), Ne(+), and Ar(+) ions with N2, O2, CO, NO, CO2, and N2O. Except for the He(+)-N2 reaction, no molecular ions were formed by thermal-energy charge transfer from He(+) and Ne(+) with these target molecules. The propensity for dissociative ionization channels in these highly exothermic charge-transfer reactions at thermal energies contrasts with the propensity for formation of parent molecular ions observed in photoionization experiments and in high-energy charge-transfer processes. This difference is explained in terms of more stringent requirements for energy resonance and favorable Franck-Condon factors at thermal ion velocities.

  14. EFFECTS OF ALTERNATE ANTIFOAM AGENTS, NOBLE METALS, MIXING SYSTEMS AND MASS TRANSFER ON GAS HOLDUP AND RELEASE FROM NONNEWTONIAN SLURRIES

    SciTech Connect

    Guerrero, H; Mark Fowley, M; Charles Crawford, C; Michael Restivo, M; Robert Leishear, R

    2007-12-24

    Gas holdup tests performed in a small-scale mechanically-agitated mixing system at the Savannah River National Laboratory (SRNL) were reported in 2006. The tests were for a simulant of waste from the Hanford Tank 241-AZ-101 and featured additions of DOW Corning Q2-3183A Antifoam agent. Results indicated that this antifoam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter intuitively, that the holdup increased as the simulant shear strength decreased (apparent viscosity decreased). These results raised questions about how the AFA might affect gas holdup in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs). And whether the WTP air supply system being designed would have the capacity to handle a demand for increased airflow to operate the sparger-PJM mixing systems should the AFA increase retention of the radiochemically generated flammable gases in the waste by making the gas bubbles smaller and less mobile, or decrease the size of sparger bubbles making them mix less effectively for a given airflow rate. A new testing program was developed to assess the potential effects of adding the DOW Corning Q2-3183A AFA to WTP waste streams by first confirming the results of the work reported in 2006 by Stewart et al. and then determining if the AFA in fact causes such increased gas holdup in a prototypic sparger-PJM mixing system, or if the increased holdup is just a feature of the small-scale agitation system. Other elements of the new program include evaluating effects other variables could have on gas holdup in systems with AFA additions such as catalysis from trace noble metals in the waste, determining mass transfer coefficients for the AZ-101 waste simulant, and determining whether other AFA compositions such as Dow Corning 1520-US could also increase gas holdup in Hanford waste. This new testing program was split into two investigations, prototypic sparger

  15. Rotational Energy Transfer of N2 Gas Determined Using a New Ab Initio Potential Energy Surface

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Stallcop, James R.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    Rotational energy transfer between two N2 molecules is a fundamental process of some importance. Exchange is expected to play a role, but its importance is somewhat uncertain. Rotational energy transfer cross sections of N2 also have applications in many other fields including modeling of aerodynamic flows, laser operations, and linewidth analysis in nonintrusive laser diagnostics. A number of N2-N2 rigid rotor potential energy surface (PES) has been reported in the literature.

  16. Femtosecond-laser-induced shockwaves in water generated at an air-water interface.

    PubMed

    Strycker, B D; Springer, M M; Traverso, A J; Kolomenskii, A A; Kattawar, G W; Sokolov, A V

    2013-10-07

    We report generation of femtosecond-laser-induced shockwaves at an air-water interface by millijoule femtosecond laser pulses. We document and discuss the main processes accompanying this phenomenon, including light emission, development of the ablation plume in the air, formation of an ablation cavity, and, subsequently, a bubble developing in water. We also discuss the possibility of remotely controlling the characteristics of laser-induced sound waves in water through linear acoustic superposition of sound waves that results from millijoule femtosecond laser-pulse interaction with an air-water interface, thus opening up the possibility of remote acoustic applications in oceanic and riverine environments.

  17. Interaction of Charged Colloidal Particles at the Air-Water Interface.

    PubMed

    Girotto, Matheus; Dos Santos, Alexandre P; Levin, Yan

    2016-07-07

    We study, using Monte Carlo simulations, the interaction between charged colloidal particles confined to the air-water interface. The dependence of force on ionic strength and counterion valence is explored. For 1:1 electrolyte, we find that the electrostatic interaction at the interface is very close to the one observed in the bulk. On the other hand, for salts with multivalent counterions, an interface produces an enhanced attraction between like charged colloids. Finally, we explore the effect of induced surface charge at the air-water interface on the interaction between colloidal particles.

  18. Optimizing gas transfer to improve growth rate of Haematococcus pluvialis in a raceway pond with chute and oscillating baffles.

    PubMed

    Yang, Zongbo; Cheng, Jun; Li, Ke; Zhou, Junhu; Cen, Kefa

    2016-08-01

    Up-down chute and oscillating (UCO) baffles were used to generate vortex and oscillating flow field to improve growth rate of Haematococcus pluvialis in a raceway pond. Effects of gas flow rate, solution velocity, and solution depth on solution mass transfer coefficient and mixing time were evaluated using online pH and dissolved oxygen probes. Mass transfer coefficient increased by 1.3 times and mixing time decreased by 33% when UCO baffles were used in the H. pluvialis solution, resulting in an 18% increase in biomass yield with 2% CO2. The H. pluvialis biomass yield further increased to 1.5g/L, and astaxanthin composition accumulated to 29.7mg/L under relatively higher light intensity and salinity.

  19. Equations for nickel-chromium wire heaters of column transfer lines in gas chromatographic-electroantennographic detection (GC-EAD).

    PubMed

    Byers, John A

    2004-05-30

    Heating of chromatographic columns, transfer lines, and other devices is often required in neuroscience research. For example, volatile compounds passing through a capillary column of a gas chromatograph (GC) can be split, with half exiting the instrument through a heated transfer line to an insect antenna or olfactory sensillum for electroantennographic detector (GC-EAD) recordings. The heated transfer line is used to prevent condensation of various chemicals in the capillary that would otherwise occur at room temperature. Construction of such a transfer line heater is described using (80/20%) nickel-chromium heating wire wrapped in a helical coil and powered by a 120/220 V ac rheostat. Algorithms were developed in a computer program to estimate the voltage at which a rheostat should be set to obtain the desired heater temperature for a specific coil. The coil attributes (radius, width, number of loops, or length of each loop) are input by the user, as well as AWG size of heating wire and desired heater temperature. The program calculates total length of wire in the helix, resistance of the wire, amperage used, and the voltage to set the rheostat. A discussion of semiochemical isolation methods using the GC-EAD and bioassays is presented.

  20. A novel high-heat transfer low-NO{sub x} natural gas combustion system. Phase 1 final report

    SciTech Connect

    Rue, D.M.; Fridman, A.; Viskanta, R.; Neff, D.

    1997-11-01

    Phase I of the project focused on acquiring the market needs, modeling, design, and test plan information for a novel high-heat transfer low-NO{sub x} natural gas combustion system. All goals and objectives were achieved. The key component of the system is an innovative burner technology which combines high temperature natural gas preheating with soot formation and subsequent soot burnout in the flame, increases the system`s energy efficiency and furnace throughput, while minimizing the furnace air emissions, all without external parasitic systems. Work has included identifying industry`s needs and constraints, modeling the high luminosity burner system, designing the prototype burner for initial laboratory-scale testing, defining the test plan, adapting the burner technology to meet the industry`s needs and constraints, and outlining the Industrial Adoption Plan.

  1. Probing ‘Spin-Forbidden’ Oxygen Atom Transfer: Gas-Phase Reactions of Chromium-Porphyrin Complexes

    PubMed Central

    Fornarini, Simonetta; Lanucara, Francesco; Warren, Jeffrey J.

    2010-01-01

    Oxygen-atom transfer reactions of metalloporphyrin species play an important role in biochemical and synthetic oxidation reactions. An emerging theme in this chemistry is that spin-state changes can play important roles, and a ‘two-state’ reactivity model has been extensively applied especially in iron-porphyrin systems. Herein we explore the gas phase oxygen-atom transfer chemistry of meso-tetrakis(pentafluorophenyl)porphyrin (TPFPP) chromium complexes, as well as some other tetradentate macrocyclic ligands. Electrospray ionization in concert with Fourier transform ion cyclotron resonance (FT-ICR) spectrometry has been used to characterize and observe reactivity of the ionic species [(TPFPP)CrIII]+ (1) and [(TPFPP)CrVO]+ (2). These are an attractive system to examine the effects of spin state change on oxygen atom transfer because the d1 CrV species are doublets while the CrIII complexes have quartet ground states with high-lying doublet excited states. In the gas phase, [(TPFPP)CrIII]+ forms adducts with a variety of neutral donors but O-atom transfer is only observed for NO2. Pyridine N-oxide adducts of 1 do yield 2 upon collision induced dissociation (CID), but the ethylene oxide, DMSO, and TEMPO analogs do not. [(TPFPP)CrVO]+ is shown by its reactivity and by CID experiments to be a terminal metal-oxo with a single vacant coordination site. It also displays limited reaction chemistry, being deoxygenated only by the very potent reductant P(OMe)3. In general, [(TPFPP)CrVO]+ species are much less reactive than the Fe and Mn analogs. Thermochemical analysis of the reactions points towards the involvement of spin issues in the lower observed reactivity of the chromium complexes. PMID:20218631

  2. Effects of outlet blade angle of centrifugal pump on the pump performance under air-water two-phase flow conditions

    SciTech Connect

    Minemura, Kiyoshi; Kinoshita, Katsuhiko; Ihara, Masaru; Furukawa, Hironori; Egashira, Kazuyuki

    1995-12-31

    To establish the optimum design parameters of offshore oil well centrifugal pumps, which should deliver crude oil containing a large amount of gas, various shapes of pump impeller with different outlet blade angles, locations of leading-edge and numbers of impeller blades as the design parameters were tested with various rotating speeds and suction pressures under air-water two-phase flow conditions. The greater the outlet blade angle, the less the degradation of the pump performance becomes, showing the optimum blade angle approximately equals to 90{degree}.

  3. Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase.

    PubMed

    Chai, Yunfeng; Xiong, Xingchuang; Yue, Lei; Jiang, You; Pan, Yuanjiang; Fang, Xiang

    2016-01-01

    The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R(1)R(2)R(3)N(+)CH2(CH2)nX, where X = F, Cl, Br, I, n = 1, 2, 3, 4) was studied by electrospray ionization tandem mass spectrometry. A characteristic fragment ion (R(1)R(2)R(3)N(+)X) resulting from halogen transfer was observed in collision-induced dissociation. A new mechanism for the intramolecular halogen transfer was proposed that involves a reactive intermediate, [amine/halonium ion]. A potential energy surface scan using DFT calculation for CH2-N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the five- and six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine.

  4. Effect of internal pressure and gas/liquid interface area on the CO mass transfer coefficient using hollow fibre membranes as a high mass transfer gas diffusing system for microbial syngas fermentation.

    PubMed

    Yasin, Muhammad; Park, Shinyoung; Jeong, Yeseul; Lee, Eun Yeol; Lee, Jinwon; Chang, In Seop

    2014-10-01

    This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A(S)/V(L)) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k(L)a) values. We found a k(L)a of 135.72 h(-1) when P was 93.76 kPa and AS/VL was fixed at 27.5m(-1). A higher k(L)a of 155.16 h(-1) was achieved by increasing AS/VL to 62.5m(-1) at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO2 fermentation using Eubacterium limosum KIST612.

  5. Application of convection heat transfer in near-wall jets to electron-beam-pumped gas lasers

    NASA Astrophysics Data System (ADS)

    Lu, Bo

    Heating of the transmission foil separating the vacuum diodes from the laser gas in electron-beam-pumped gas lasers due to high-energy electron beam attenuation necessitates an external cooling scheme to prevent its failure under repetitively pulsed operating conditions. Attenuation of the electron beam (typically 500 kV, 100 kA and 100 ns pulse duration) produces a strong and pulsed volumetric heat source in the relatively thin stainless-steel foil (thickness of ˜25 mum) causing it to fail. An experimental and numerical investigation has been conducted to study the cooling effectiveness of near-wall high-speed jets for a single stainless-steel foil strip that simulates the actual foil geometry between two neighboring support ribs in the Electra KrF gas laser developed by the Naval Research Laboratory. The foil is placed inside a rectangular channel with continuous gas flow to simulate the circulating laser gas. The foil is electrically heated with the heating power input adjusted to achieve the same foil temperatures observed in Electra when no active cooling is applied. Detailed studies include two jet geometries (planar and circular) and two injection methods (tangential/parallel or obliquely impinging jets) for two hibachi foil structure designs (flat and scalloped). The planar jet of ˜1mm thickness flows parallel to the circulating laser gas across the entire foil span. The other configuration uses circular jets of small diameters (0.8 mm, 1.2 mm and 1.6 mm) positioned in two staggered rows located on the foil's two vertical edges with a pitch of 1.25 cm over the entire height of the foil. For both configurations, experiments have been conducted at various jet velocities (or jet Reynolds numbers), impingement angles and jet-foil spacing with an aim to identify the optimal operating parameters for the actual hibachi foil cooling. Numerous investigations have been performed that covered a wide range of operating parameters. Local and average heat transfer

  6. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    NASA Astrophysics Data System (ADS)

    Dukler, A. E.; Fabre, J. A.; McQuillen, J. B.; Vernon, R.

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  7. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    NASA Technical Reports Server (NTRS)

    Dukler, A. E.; Fabre, J. A.; Mcquillen, J. B.; Vernon, R.

    1987-01-01

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  8. A Novel High-Heat Transfer Low-NO{sub x} Natural Gas Combustion System. Final Technical Report

    SciTech Connect

    Abbasi, H.

    2004-01-01

    A novel high-heat transfer low NO(sub x) natural gas combustion system. The objectives of this program are to research, develop, test, and commercialize a novel high-heat transfer low-NO{sub x} natural gas combustion system for oxygen-, oxygen-enriched air, and air-fired furnaces. This technology will improve the process efficiency (productivity and product quality) and the energy efficiency of high-temperature industrial furnaces by at least 20%. GTI's high-heat transfer burner has applications in high-temperature air, oxygen-enriched air, and oxygen furnaces used in the glass, metals, cement, and other industries. Development work in this program is focused on using this burner to improve the energy efficiency and productivity of glass melting furnaces that are major industrial energy consumers. The following specific project objectives are defined to provide a means of achieving the overall project objectives. (1) Identify topics to be covered, problems requiring attention, equipment to be used in the program, and test plans to be followed in Phase II and Phase III. (2) Use existing codes to develop models of gas combustion and soot nucleation and growth as well as a thermodynamic and parametric description of furnace heat transfer issues. (3) Conduct a parametric study to confirm the increase in process and energy efficiency. (4) Design and fabricate a high-heat transfer low-NOx natural gas burners for laboratory, pilot- and demonstration-scale tests. (5) Test the high-heat transfer burner in one of GTI's laboratory-scale high-temperature furnaces. (6) Design and demonstrate the high-heat transfer burner on GTI's unique pilot-scale glass tank simulator. (7) Complete one long term demonstration test of this burner technology on an Owens Corning full-scale industrial glass melting furnace. (8) Prepare an Industrial Adoption Plan. This Plan will be updated in each program Phase as additional information becomes available. The Plan will include technical and

  9. Mass transfer across combustion gas thermal boundary layers - Power production and materials processing implications

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.

    1985-01-01

    The effects of Soret diffusion (for vapors) and thermophoresis (for particles) are illustrated using recent optical experiments and boundary layer computations. Mass transfer rate augmentations of up to a factor of 1000 were observed and predicted for submicron-particle capture by cooled solid surfaces, while mass transfer suppressions of more than 10 to the -10th-fold were predicted for 'overheated' surfaces. It is noted that the results obtained are of interest in connection with such technological applications as fly-ash capture in power generation equipment and glass droplet deposition in optical-waveguide manufacture.

  10. It's Alive!: Students Observe Air-Water Interface Samples Rich with Organisms

    ERIC Educational Resources Information Center

    Avant, Thomas

    2002-01-01

    This article describes an experiment, designed by Cindy Henk, manager of the Socolofsky Microscopy Center at Louisiana State University (LSU), that involved collecting and viewing microorganisms in the air-water interface. The experiment was participated by Leesville High School microbiology students. The students found that the air-water…

  11. Effects of flow on insulin fibril formation at an air/water interface

    NASA Astrophysics Data System (ADS)

    Posada, David; Heldt, Caryn; Sorci, Mirco; Belfort, Georges; Hirsa, Amir

    2009-11-01

    The amyloid fibril formation process, which is implicated in several diseases such as Alzheimer's and Huntington's, is characterized by the conversion of monomers to oligomers and then to fibrils. Besides well-studied factors such as pH, temperature and concentration, the kinetics of this process are significantly influenced by the presence of solid or fluid interfaces and by flow. By studying the nucleation and growth of a model system (insulin fibrils) in a well-defined flow field with an air/water interface, we can identify the flow conditions that impact protein aggregation kinetics both in the bulk solution and at the air/water interface. The present flow system (deep-channel surface viscometer) consists of an annular region bounded by stationary inner and outer cylinders, an air/water interface, and a floor driven at constant rotation. We show the effects of Reynolds number on the kinetics of the fibrillation process both in the bulk solution and at the air/water interface, as well as on the structure of the resultant amyloid aggregates.

  12. Oil lenses on the air-water surface and the validity of Neumann's rule.

    PubMed

    Nikolov, Alex; Wasan, Darsh

    2016-05-10

    Many studies have focused on the mechanisms of oil spreading over the air-water surface, oil lens formation, and lens dynamics: Franklin et al.(1774), Rayleigh (1890), Neumann and Wangerin (1894), Hardy (1912), Lyons (1930), Langmuir (1933), Miller (1941), Zisman (1941), Pujado and Scriven (1972), Seeto et al. (1983), and Takamura et al. (2012). Despite all of these studies, the phenomenon of the oil lens's air-water surface equilibrium is still under discussion. Here, we highlight an accurate method to study the oil lens's three-phase-contact angle by reflected light interferometry, using both common (CRLI) and differential reflected light interferometry (DRLI) to verify Neumann's rule (the vectorial sum of the three tensions is zero). For non-spreading oils, the validity of Neumann's rule is confirmed for small lenses when the role of the oil film tension around the lens's meniscus is taken into consideration. Neumann's rule was also validated when the monolayer surface pressure isotherm was taken into consideration for oil spreading on the air-water surface. The periodic monolayer surface pressure oscillation of the oil phase monolayer created by the air-evaporating biphilic oil was monitored with time. The monolayer's surface pressure periodic oscillation was attributed to the instability of the aqueous film covering the oil drop phase. The knowledge gained from this study will benefit the fundamental understanding of the oil lens's air-water surface equilibrium and oil spill mechanisms, thereby promoting better methods for the prevention and clean-up of oil spills.

  13. Understanding the structure of hydrophobic surfactants at the air/water interface from molecular level.

    PubMed

    Zhang, Li; Liu, Zhipei; Ren, Tao; Wu, Pan; Shen, Jia-Wei; Zhang, Wei; Wang, Xinping

    2014-11-25

    Understanding the behavior of fluorocarbon surfactants at the air/water interface is crucial for many applications, such as lubricants, paints, cosmetics, and fire-fighting foams. In this study, molecular dynamics (MD) simulations were employed to investigate the microscopic properties of non-ionic fluorocarbon surfactants at the air/water interface. Several properties, including the distribution of head groups, the distribution probability of the tilt angle between hydrophobic tails with respect to the xy plane, and the order parameter of surfactants, were computed to probe the structure of hydrophobic surfactants at the air/water interface. The effects of the monomer structure on interfacial phenomena of non-ionic surfactants were investigated as well. It is observed that the structure of fluorocarbon surfactants at the air/water interface is more ordered than that of hydrocarbons, which is dominated by the van der Waals interaction between surfactants and water molecules. However, replacing one or two CF2 with one or two CH2 group does not significantly influence the interfacial structure, suggesting that hydrocarbons may be promising alternatives to perfluorinated surfactants.

  14. Hydrodynamics of a self-propelled camphor boat at the air-water interface

    NASA Astrophysics Data System (ADS)

    Akella, Sathish; Singh, Dhiraj; Singh, Ravi; Bandi, Mahesh

    2015-11-01

    A camphor tablet, when placed at the air-water interface undergoes sublimation and camphor vapour spreads radially outwards across the surface due to Marangoni forces. This steady camphor influx from tablet onto the air-water interface is balanced by the camphor outflux due to evaporation. When spontaneous fluctuations in evaporation break the axial symmetry of Marangoni force acting radially outwards, the camphor tablet is propelled like a boat along the water surface. We report experiments on the hydrodynamics of a self-propelled camphor boat at air-water interfaces. We observe three different modes of motion, namely continuous, harmonic and periodic, due to the volatile nature of camphor. We explain these modes in terms of ratio of two time-scales: the time-scale over which viscous forces are dominant over the Marangoni forces (τη) and the time-scale over which Marangoni forces are dominant over the viscous forces (τσ). The continuous, harmonic and periodic motions are observed when τη /τσ ~ 1 , τη /τσ >= 1 and τη /τσ >> 1 respectively. Experimentally, the ratio of the time scales is varied by changing the interfacial tension of the air-water interface using Sodium Dodecyl Sulfate. This work was supported by the Collective Interactions Unit, OIST Graduate University.

  15. THE EFFECT OF SALINITY ON RATES OF ELEMENTAL MERCURY AIR/WATER EXCHANGE

    EPA Science Inventory

    The U.S. EPA laboratory in Athens, Georgia i spursuing the goal of developing a model for describing toxicant vapor phase air/water exchange under all relevant environmental conditions. To date, the two-layer exchange model (suitable for low wind speed conditions) has been modif...

  16. Gas transfer rates from airlifts used for concurrent aeration, carbon dioxide stripping, and recirculation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Airlifts simplify recirculating aquaculture systems and can potentially reduce capital costs and minimize maintenance issues. Airlifts have the ability to move and aerate water as well as degass the water of any carbon dioxide. This study evaluated the oxygen transfer and carbon dioxide removal abil...

  17. Heat Transfer to Vertical Flat Plates in a Rectangular Gas-Fluidized Bed.

    DTIC Science & Technology

    1984-06-01

    a Fluidized Bed," Journal of Engineering Physics, V. 28, pp. 698-700, June 1975. 205 AIL Kunii, D. and Levenspiel , 0., Fluidization Engineering...Wiley, 1969. Levenspiel , 0. and Walton, J. S., "Bed-Wall Heat Transfer in Fluidized Systems, Chemical Engineering Progress Symposium Series Number 9, V

  18. Mass Transfer Study of Chlorine Dioxide Gas Through Polymeric Packaging Materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A continuous system for measuring the mass transfer of gaseous chlorine dioxide (ClO2), a strong oxidizing agent and used in food and pharmaceutical packaging, through 10 different types of polymeric packaging material was developed utilizing electrochemical sensor as a detector. Permeability, diff...

  19. Chiral discrimination of a gemini-type surfactant with rigid spacer at the air-water interface.

    PubMed

    Shankar, B Vijai; Patnaik, Archita

    2007-10-04

    Spontaneous separation of chiral phases was observed in the monolayers of a racemate of gemini-type twin-tailed, twin-chiral amphiphiles, (2R,3R)-(+)-bis(decyloxy)succinic acid and (2S,3S)-(-)-bis(decyloxy)succinic acid. The pressure-area isotherms of the interfacial monolayers formed at the liquid-air interface, and the 2D lattice structures studied through surface probe measurements revealed that the racemate exhibits a homochiral discrimination of the enantiomers in two dimensions. An enantiomeric excess (e,e) of 20% was sufficient to break the chiral symmetry at the air-water interface for a homochiral interaction. Langmuir monolayers on ZnCl2 and CaCl2 subphases manifested chiral discrimination with Zn2+ evidencing homochiral interaction with a chelate-type complex, whereas Ca2+ resulted in a heterochiral interaction forming an ionic-type complex. For the chiral asymmetric units, oblique and rectangular unit cells of the racemic monolayer had exclusive requirements of homo- and heterochiral recognitions for Zn2+ and Ca2+ ions, respectively. Monolayers transferred from the condensed phase at 25 mN/m onto hydrophilic Si(100) and quartz substrates revealed the formation of bilayers through transfer-induced monolayer buckling. The emergence of homochiral discrimination was explained using the effective-pair-potential (EPP) approach.

  20. Charge dependent condensation of macro-ions at air-water interfaces

    NASA Astrophysics Data System (ADS)

    Bera, Mrinal; Antonio, Mark

    2015-03-01

    Ordering of ions at and near air-water interfaces is a century old problem for researchers and has implications on a host of physical, chemical and biological processes. The dynamic nature of water surface and the surface fluctuations created by thermally excited capillary waves have always limited measurement of near surface ionic-distributions. We demonstrate that this limitation can be overcome by using macro-ions of sizes larger than the capillary wave roughness ~3Å. Our attempts to measure distributions of inorganic macro-ions in the form of Keggin heteropolyanions (HPAs) of sizes ~10Å have unraveled novel charge-dependent condensation of macro-ions beneath air-water interfaces. Our results demonstrate that HPAs with -3 charges condense readily beneath air-water interfaces. This is in contrast to the absence of surface preference for HPAs with -4 charges. The similarity of HPA-HPA separations near air-water interfaces and in bulk crystal structures suggests the presence of the planar Zundel ions (H5O2+), which interact with HPAs and the water surface to facilitate the charge dependent condensation beneath the air-water interfaces.This work and the use of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility at Argonne National Laboratory, is based upon work supported by the U.S. DOE, Office of Science, Office of Basic Energy Science, Division of Chemical Sciences, Biosciences and Geosciences, under contract No DE-AC02-06CH11357.

  1. Exploiting charge-transfer complexation for selective measurement of gas-phase olefins with nanoparticle-coated chemiresistors.

    PubMed

    Rowe, Michael P; Steinecker, William H; Zellers, Edward T

    2007-02-01

    Charge-transfer-mediated olefin-selective sensing by use of chemiresistors (CR) coated with composite films of n-octanethiolate-monolayer-protected gold nanoparticles (C8-MPN) and each of several square-planar PtCl2(olefin)(pyridine) coordination complexes is described. Where the gas-phase olefin analyte differs from that initially coordinated to Pt, olefin substitution occurs and is accompanied by a persistent shift in the composite film resistance. Commensurate changes in film mass are also observed with a similarly coated thickness shear mode resonator. Regeneration is possible by exposure to the initially complexed olefin gas or vapor. If the olefin analyte is the same as that initially coordinated to Pt, then a reversible charge-transfer interaction occurs that is accompanied by a decrease in film resistance (increase in film mass), which recovers spontaneously after removal of the olefin from the atmosphere above the sensor. This behavior differs from that of MPN-coated CRs lacking such Pt complexes, which invariably yield resistance increases upon exposure to nonpolar vapors. Red shifts in the UV-vis absorbance spectra of the PtCl2(olefin)(pyridine) complexes in solution upon addition of free olefin support the hypothesis that Pt-olefin coordination in the composite films creates temporary low-resistance pathways that compete effectively with the concurrent increase in tunneling resistance associated with swelling-induced separation of C8-MPN cores. Structurally analogous non-olefins produce only increases in film resistance. Selective measurement of styrene, ethylene, 1-octene, and 1,3-butadiene is illustrated. Olefin detection limits are reduced as much as 23 000-fold by inclusion of the corresponding Pt complex in the CR interface film. Composite films suffer a gradual loss of selectivity from decomposition of the Pt-olefin complex, apparently facilitated by a Au-Pt charge transfer.

  2. Experimental and numerical investigations of high temperature gas heat transfer and flow in a VHTR reactor core

    NASA Astrophysics Data System (ADS)

    Valentin Rodriguez, Francisco Ivan

    High pressure/high temperature forced and natural convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. VHTRs are designed with the capability to withstand accidents by preventing nuclear fuel meltdown, using passive safety mechanisms; a product of advanced reactor designs including the implementation of inert gases like helium as coolants. The present experiments utilize a high temperature/high pressure gas flow test facility constructed for forced and natural circulation experiments. This work examines fundamental aspects of high temperature gas heat transfer applied to VHTR operational and accident scenarios. Two different types of experiments, forced convection and natural circulation, were conducted under high pressure and high temperature conditions using three different gases: air, nitrogen and helium. The experimental data were analyzed to obtain heat transfer coefficient data in the form of Nusselt numbers as a function of Reynolds, Grashof and Prandtl numbers. This work also examines the flow laminarization phenomenon (turbulent flows displaying much lower heat transfer parameters than expected due to intense heating conditions) in detail for a full range of Reynolds numbers including: laminar, transition and turbulent flows under forced convection and its impact on heat transfer. This phenomenon could give rise to deterioration in convection heat transfer and occurrence of hot spots in the reactor core. Forced and mixed convection data analyzed indicated the occurrence of flow laminarization phenomenon due to the buoyancy and acceleration effects induced by strong heating. Turbulence parameters were also measured using a hot wire anemometer in forced convection experiments to confirm the existence of the flow laminarization phenomenon. In particular, these results demonstrated the influence of pressure on delayed transition between laminar and turbulent flow. The heat

  3. The simplest equivalent circuit of a pulsed dielectric barrier discharge and the determination of the gas gap charge transfer

    NASA Astrophysics Data System (ADS)

    Pipa, A. V.; Koskulics, J.; Brandenburg, R.; Hoder, T.

    2012-11-01

    The concept of the simplest equivalent circuit for a dielectric barrier discharge (DBD) is critically reviewed. It is shown that the approach is consistent with experimental data measured either in large-scale sinusoidal-voltage driven or miniature pulse-voltage driven DBDs. An expression for the charge transferred through the gas gap q(t) is obtained with an accurate account for the displacement current and the values of DBD reactor capacitance. This enables (i) the significant reduction of experimental error in the determination of q(t) in pulsed DBDs, (ii) the verification of the classical electrical theory of ozonizers about maximal transferred charge qmax, and (iii) the development of a graphical method for the determination of qmax from charge-voltage characteristics (Q-V plots, often referred as Lissajous figures) measured under pulsed excitation. The method of graphical presentation of qmax is demonstrated with an example of a Q-V plot measured under pulsed excitation. The relations between the discharge current jR(t), the transferred charge q(t), and the measurable parameters are presented in new forms, which enable the qualitative interpretation of the measured current and voltage waveforms without the knowledge about the value of the dielectric barrier capacitance Cd. Whereas for quantitative evaluation of electrical measurements, the accurate estimation of the Cd is important.

  4. Numerical simulation of gas flow and heat transfer in a rough microchannel using the lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Dorari, Elaheh; Saffar-Avval, Majid; Mansoori, Zohreh

    2015-12-01

    In microfluidics, two important factors responsible for the differences between the characteristics of the flow and heat transfer in microchannels and conventional channels are rarefaction and surface roughness which are studied in the present work. An incompressible gas flow in a microchannel is simulated two dimensionally using the lattice Boltzmann method. The flow is in the slip regime and surface roughness is modeled by both regular and Gaussian random distribution of rectangular modules. The effects of relative surface roughness height and Knudsen number on gaseous flow and heat transfer are studied. It was shown that as the relative roughness height increases, the Poiseuille number increases and the Nusselt number has a decreasing or increasing trend, depending on the degree of rarefaction. A comparison between the flow and heat transfer characteristics in regular and random distribution of surface roughness demonstrates that in regular roughness, circular flows are more pronounced; Poiseuille number is higher and Nusselt number is lower than that of its equivalent random roughness.

  5. Numerical simulation of gas flow and heat transfer in a rough microchannel using the lattice Boltzmann method.

    PubMed

    Dorari, Elaheh; Saffar-Avval, Majid; Mansoori, Zohreh

    2015-12-01

    In microfluidics, two important factors responsible for the differences between the characteristics of the flow and heat transfer in microchannels and conventional channels are rarefaction and surface roughness which are studied in the present work. An incompressible gas flow in a microchannel is simulated two dimensionally using the lattice Boltzmann method. The flow is in the slip regime and surface roughness is modeled by both regular and Gaussian random distribution of rectangular modules. The effects of relative surface roughness height and Knudsen number on gaseous flow and heat transfer are studied. It was shown that as the relative roughness height increases, the Poiseuille number increases and the Nusselt number has a decreasing or increasing trend, depending on the degree of rarefaction. A comparison between the flow and heat transfer characteristics in regular and random distribution of surface roughness demonstrates that in regular roughness, circular flows are more pronounced; Poiseuille number is higher and Nusselt number is lower than that of its equivalent random roughness.

  6. Extension of weighted sum of gray gas data to mathematical simulation of radiative heat transfer in a boiler with gas-soot media.

    PubMed

    Gharehkhani, Samira; Nouri-Borujerdi, Ali; Kazi, Salim Newaz; Yarmand, Hooman

    2014-01-01

    In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

  7. Extension of Weighted Sum of Gray Gas Data to Mathematical Simulation of Radiative Heat Transfer in a Boiler with Gas-Soot Media

    PubMed Central

    Nouri-Borujerdi, Ali; Kazi, Salim Newaz

    2014-01-01

    In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site. PMID:25143981

  8. Air-water partition coefficients for a suite of polycyclic aromatic and other C10 through C20 unsaturated hydrocarbons.

    PubMed

    Rayne, Sierra; Forest, Kaya

    2016-09-18

    The air-water partition coefficients (Kaw) for 86 large polycyclic aromatic hydrocarbons and their unsaturated relatives were estimated using high-level G4(MP2) gas and aqueous phase calculations with the SMD, IEFPCM-UFF, and CPCM solvation models. An extensive method validation effort was undertaken which involved confirming that, via comparisons to experimental enthalpies of formation, gas-phase energies at the G4(MP2) level for the compounds of interest were at or near thermochemical accuracy. Investigations of the three solvation models using a range of neutral and ionic compounds suggested that while no clear preferential solvation model could be chosen in advance for accurate Kaw estimates of the target compounds, the employment of increasingly higher levels of theory would result in lower Kaw errors. Subsequent calculations on the polycyclic aromatic and unsaturated hydrocarbons at the G4(MP2) level revealed excellent agreement for the IEFPCM-UFF and CPCM models against limited available experimental data. The IEFPCM-UFF-G4(MP2) and CPCM-G4(MP2) solvation energy calculation approaches are anticipated to give Kaw estimates within typical experimental ranges, each having general Kaw errors of less than 0.5 log10 units. When applied to other large organic compounds, the method should allow development of a broad and reliable Kaw database for multimedia environmental modeling efforts on various contaminants.

  9. Distribution of air-water mixtures in parallel vertical channels as an effect of the header geometry

    SciTech Connect

    Marchitto, Annalisa; Fossa, Marco; Guglielmini, Giovanni

    2009-07-15

    Uneven phase distribution in heat exchangers is a cause of severe reductions in thermal performances of refrigeration equipment. To date, no general design rules are available to avoid phase separation in manifolds with several outlet channels, and even predicting the phase and mass distribution in parallel channels is a demanding task. In the present paper, measurements of two-phase air-water distributions are reported with reference to a horizontal header supplying 16 vertical upward channels. The effects of the operating conditions, the header geometry and the inlet port nozzle were investigated in the ranges of liquid and gas superficial velocities of 0.2-1.2 and 1.5-16.5 m/s, respectively. Among the fitting devices used, the insertion of a co-axial, multi-hole distributor inside the header confirmed the possibility of greatly improving the liquid and gas flow distribution by the proper selection of position, diameter and number of the flow openings between the supplying distributor and the system of parallel channels connected to the header. (author)

  10. Laser absorption, power transfer, and radiation symmetry during the first shock of inertial confinement fusion gas-filled hohlraum experiments

    NASA Astrophysics Data System (ADS)

    Pak, A.; Dewald, E. L.; Landen, O. L.; Milovich, J.; Strozzi, D. J.; Berzak Hopkins, L. F.; Bradley, D. K.; Divol, L.; Ho, D. D.; MacKinnon, A. J.; Meezan, N. B.; Michel, P.; Moody, J. D.; Moore, A. S.; Schneider, M. B.; Town, R. P. J.; Hsing, W. W.; Edwards, M. J.

    2015-12-01

    Temporally resolved measurements of the hohlraum radiation flux asymmetry incident onto a bismuth coated surrogate capsule have been made over the first two nanoseconds of ignition relevant laser pulses. Specifically, we study the P2 asymmetry of the incoming flux as a function of cone fraction, defined as the inner-to-total laser beam power ratio, for a variety of hohlraums with different scales and gas fills. This work was performed to understand the relevance of recent experiments, conducted in new reduced-scale neopentane gas filled hohlraums, to full scale helium filled ignition targets. Experimental measurements, matched by 3D view factor calculations, are used to infer differences in symmetry, relative beam absorption, and cross beam energy transfer (CBET), employing an analytic model. Despite differences in hohlraum dimensions and gas fill, as well as in laser beam pointing and power, we find that laser absorption, CBET, and the cone fraction, at which a symmetric flux is achieved, are similar to within 25% between experiments conducted in the reduced and full scale hohlraums. This work demonstrates a close surrogacy in the dynamics during the first shock between reduced-scale and full scale implosion experiments and is an important step in enabling the increased rate of study for physics associated with inertial confinement fusion.

  11. Study of hydrodynamics and heat transfer in non-Newtonian liquid-gas two-phase flow in horizontal pipes

    SciTech Connect

    Deshpande, S.D.

    1985-01-01

    Non-Newtonian liquid-gas stratified flow data in 0.026- and 0.052-m-diameter pipes were obtained. Interfacial level gradients between the two phases were observed. The Heywood-Charles model is found to be valid for pseudoplastic liquid-gas uniform stratified flow. Two-phase drag reduction in non-Newtonian systems was not achieved as the transition to semi-slug flow occurred before the model criteria were reached. Interfacial liquid and gas shear stresses were compared. A new parameter ..sigma../sup 2/ is introduced which is a numerical indication of the interfacial level gradient. Two-phase drag reduction was experimentally observed in polymer solution-air plug-slug flow in 0.026- and 0.052-m-diameter pipes. The Hubbard-Dukler pressure drop model was extended to non-Newtonian systems. Reasonable agreement between the experiment and the model predictions is obtained. However, more work needs to be done in order to better understand the two-phase drag reduction phenomena. Liquid holdup correlations were developed for both Newtonian and non-Newtonian systems which successfully correlate the holdup over a wide range of parameters. The Petukhov correlation is found to be better than the Dittus-Boelter correlation in predicting the single-phase water heat-transfer coefficients.

  12. Exploring salt bridge structures of gas-phase protein ions using multiple stages of electron transfer and collision induced dissociation.

    PubMed

    Zhang, Zhe; Browne, Shaynah J; Vachet, Richard W

    2014-04-01

    The gas-phase structures of protein ions have been studied by electron transfer dissociation (ETD) and collision-induced dissociation (CID) after electrospraying these proteins from native-like solutions into a quadrupole ion trap mass spectrometer. Because ETD can break covalent bonds while minimally disrupting noncovalent interactions, we have investigated the ability of this dissociation technique together with CID to probe the sites of electrostatic interactions in gas-phase protein ions. By comparing spectra from ETD with spectra from ETD followed by CID, we find that several proteins, including ubiquitin, CRABP I, azurin, and β-2-microglobulin, appear to maintain many of the salt bridge contacts known to exist in solution. To support this conclusion, we also performed calculations to consider all possible salt bridge patterns for each protein, and we find that the native salt bridge pattern explains the experimental ETD data better than nearly all other possible salt bridge patterns. Overall, our data suggest that ETD and ETD/CID of native protein ions can provide some insight into approximate location of salt bridges in the gas phase.

  13. Laser absorption, power transfer, and radiation symmetry during the first shock of inertial confinement fusion gas-filled hohlraum experiments

    SciTech Connect

    Pak, A.; Dewald, E. L.; Landen, O. L.; Milovich, J.; Strozzi, D. J.; Berzak Hopkins, L. F.; Bradley, D. K.; Divol, L.; Ho, D. D.; MacKinnon, A. J.; Meezan, N. B.; Michel, P.; Moody, J. D.; Moore, A. S.; Schneider, M. B.; Town, R. P. J.; Hsing, W. W.; Edwards, M. J.

    2015-12-15

    Temporally resolved measurements of the hohlraum radiation flux asymmetry incident onto a bismuth coated surrogate capsule have been made over the first two nanoseconds of ignition relevant laser pulses. Specifically, we study the P2 asymmetry of the incoming flux as a function of cone fraction, defined as the inner-to-total laser beam power ratio, for a variety of hohlraums with different scales and gas fills. This work was performed to understand the relevance of recent experiments, conducted in new reduced-scale neopentane gas filled hohlraums, to full scale helium filled ignition targets. Experimental measurements, matched by 3D view factor calculations, are used to infer differences in symmetry, relative beam absorption, and cross beam energy transfer (CBET), employing an analytic model. Despite differences in hohlraum dimensions and gas fill, as well as in laser beam pointing and power, we find that laser absorption, CBET, and the cone fraction, at which a symmetric flux is achieved, are similar to within 25% between experiments conducted in the reduced and full scale hohlraums. This work demonstrates a close surrogacy in the dynamics during the first shock between reduced-scale and full scale implosion experiments and is an important step in enabling the increased rate of study for physics associated with inertial confinement fusion.

  14. Theoretical approach for enhanced mass transfer effects in-duct flue gas desulfurization processes

    SciTech Connect

    Not Available

    1990-10-24

    During the reporting of July 1 to September 30, 1990, bench- and pilot-scale experiments were conducted to measure mass transfer and kinetic rates under simulated duct-injection conditions. This report describes the results of stirred-tank modelling experiments; experiments with moist solids in a short-time differential reactor in order to study and compare SO{sub 2} conversions; an investigation of the agglomeration of damp Ca(OH)-based solids; and evaluation of speciality sorbents.

  15. Comparison of the hydrodynamics and mass transfer characteristics in internal-loop airlift bioreactors utilizing either a novel membrane-tube sparger or perforated plate sparger.

    PubMed

    Wei, Ce; Wu, Bing; Li, Ganlu; Chen, Kequan; Jiang, Min; Ouyang, Pingkai

    2014-11-01

    Two gas spargers, a novel membrane-tube sparger and a perforated plate sparger, were compared in terms of hydrodynamics and mass transfer (or oxygen transfer) performance in an internal-loop airlift bioreactor. The overall gas holdup ε T, downcomer liquid velocity V d, and volumetric mass transfer coefficient K L a were examined depending on superficial gas velocity U G increased in Newtonian and non-Newtonian fluids for the both spargers. Compared with the perforated plate sparger, the bioreactor with the membrane-tube sparger increased the values of ε T by 4.9-48.8% in air-water system when the U G was from 0.004 to 0.04 m/s, and by 65.1-512.6% in air-CMC solution system. The V d value for the membrane-tube sparger was improved by 40.0-86.3%. The value of K L a was increased by 52.8-84.4% in air-water system, and by 63.3-836.3% in air-CMC solution system. Empirical correlations of ε T, V d, and K L a were proposed, and well corresponding with the experimental data with the deviation of 10%.

  16. Comparison of pulsating DC and DC power air-water plasma jet: A method to decrease plume temperature and increase ROS

    NASA Astrophysics Data System (ADS)

    Liu, K.; Hu, H.; Lei, J.; Hu, Y.; Zheng, Z.

    2016-12-01

    Most air-water plasma jets are rich in hydroxyl radicals (•OH), but the plasma has higher temperatures, compared to that of pure gas, especially when using air as working gas. In this paper, pulsating direct current (PDC) power was used to excite the air-water plasma jet to reduce plume temperature. In addition to the temperature, other differences between PDC and DC plasma jets are not yet clear. Thus, comparative studies of those plasmas are performed to evaluate characteristics, such as breakdown voltage, temperature, and reactive oxygen species. The results show that the plume temperature of PDC plasma is roughly 5-10 °C lower than that of DC plasma in the same conditions. The •OH content of PDC is lower than that of DC plasma, whereas the O content of PDC plasma is higher. The addition of water leads in an increase in the plume temperature and in the production of •OH with two types of power supplies. The production of O inversely shows a declining tendency with higher water ratio. The most important finding is that the PDC plasma with 100% water ratio achieves lower temperature and more abundant production of •OH and O, compared with DC plasma with 0% water ratio.

  17. Different Apparent Gas Exchange Coefficients for CO2 and CH4: Comparing a Brown-Water and a Clear-Water Lake in the Boreal Zone during the Whole Growing Season.

    PubMed

    Rantakari, Miitta; Heiskanen, Jouni; Mammarella, Ivan; Tulonen, Tiina; Linnaluoma, Jessica; Kankaala, Paula; Ojala, Anne

    2015-10-06

    The air-water exchange of carbon dioxide (CO2) and methane (CH4) is a central process during attempts to establish carbon budgets for lakes and landscapes containing lakes. Lake-atmosphere diffusive gas exchange is dependent on the concentration gradient between air and surface water and also on the gas transfer velocity, often described with the gas transfer coefficient k. We used the floating-chamber method in connection with surface water gas concentration measurements to estimate the gas transfer velocity of CO2 (kCO2) and CH4 (kCH4) weekly throughout the entire growing season in two contrasting boreal lakes, a humic oligotrophic lake and a clear-water productive lake, in order to investigate the earlier observed differences between kCO2 and kCH4. We found that the seasonally averaged gas transfer velocity of CH4 was the same for both lakes. When the lakes were sources of CO2, the gas transfer velocity of CO2 was also similar between the two study lakes. The gas transfer velocity of CH4 was constantly higher than that of CO2 in both lakes, a result also found in other studies but for reasons not yet fully understood. We found no differences between the lakes, demonstrating that the difference between kCO2 and kCH4 is not dependent on season or the characteristics of the lake.

  18. Intermediate Heat Transfer Loop Study for High Temperature Gas-Cooled Reactor

    SciTech Connect

    C. H. Oh; C. Davis; S. Sherman

    2008-08-01

    A number of possible configurations for a system that transfers heat between the nuclear reactor and the hydrogen and/or electrical generation plants were identified. These configurations included both direct and indirect cycles for the production of electricity. Both helium and liquid salts were considered as the working fluid in the intermediate heat transport loop. Methods were developed to perform thermal-hydraulic and cycleefficiency evaluations of the different configurations and coolants. The thermal-hydraulic evaluations estimated the sizes of various components in the intermediate heat transport loop for the different configurations. This paper also includes a portion of stress analyses performed on pipe configurations.

  19. Heat Transfer Measurements and Predictions on a Power Generation Gas Turbine Blade

    NASA Technical Reports Server (NTRS)

    Giel, Paul W.; Bunker, Ronald S.; VanFossen, G. James; Boyle, Robert J.

    2000-01-01

    Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 129 deg of nominal turning and an axial chord of 137 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the design point of 628,000, -20%, +20%, and +40%. Three ideal exit pressure ratios were examined including the design point of 1.378, -10%, and +10%. Inlet incidence angles of 0 deg and +/-2 deg were also examined. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.

  20. Ion/Ion Reactions with "Onium" Reagents: An Approach for the Gas-phase Transfer of Organic Cations to Multiply-Charged Anions

    NASA Astrophysics Data System (ADS)

    Gilbert, Joshua D.; Prentice, Boone M.; McLuckey, Scott A.

    2015-05-01

    The use of ion/ion reactions to effect gas-phase alkylation is demonstrated. Commonly used fixed-charge "onium" cations are well-suited for ion/ion reactions with multiply deprotonated analytes because of their tendency to form long-lived electrostatic complexes. Activation of these complexes results in an SN2 reaction that yields an alkylated anion with the loss of a neutral remnant of the reagent. This alkylation process forms the basis of a general method for alkylation of deprotonated analytes generated via electrospray, and is demonstrated on a variety of anionic sites. SN2 reactions of this nature are demonstrated empirically and characterized using density functional theory (DFT). This method for modification in the gas phase is extended to the transfer of larger and more complex R groups that can be used in later gas-phase synthesis steps. For example, N-cyclohexyl- N'-(2-morpholinoethyl)carbodiimide (CMC) is used to transfer a carbodiimide functionality to a peptide anion containing a carboxylic acid. Subsequent activation yields a selective reaction between the transferred carbodiimide group and a carboxylic acid, suggesting the carbodiimide functionality is retained through the transfer process. Many different R groups are transferable using this method, allowing for new possibilities for charge manipulation and derivatization in the gas phase.

  1. Ion/ion reactions with "onium" reagents: an approach for the gas-phase transfer of organic cations to multiply-charged anions.

    PubMed

    Gilbert, Joshua D; Prentice, Boone M; McLuckey, Scott A

    2015-05-01

    The use of ion/ion reactions to effect gas-phase alkylation is demonstrated. Commonly used fixed-charge "onium" cations are well-suited for ion/ion reactions with multiply deprotonated analytes because of their tendency to form long-lived electrostatic complexes. Activation of these complexes results in an SN2 reaction that yields an alkylated anion with the loss of a neutral remnant of the reagent. This alkylation process forms the basis of a general method for alkylation of deprotonated analytes generated via electrospray, and is demonstrated on a variety of anionic sites. SN2 reactions of this nature are demonstrated empirically and characterized using density functional theory (DFT). This method for modification in the gas phase is extended to the transfer of larger and more complex R groups that can be used in later gas-phase synthesis steps. For example, N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide (CMC) is used to transfer a carbodiimide functionality to a peptide anion containing a carboxylic acid. Subsequent activation yields a selective reaction between the transferred carbodiimide group and a carboxylic acid, suggesting the carbodiimide functionality is retained through the transfer process. Many different R groups are transferable using this method, allowing for new possibilities for charge manipulation and derivatization in the gas phase.

  2. Ecosystem Metabolism and Air-Water Fluxes of Greenhouse Gases in High Arctic Wetland Ponds

    NASA Astrophysics Data System (ADS)

    Lehnherr, I.; Venkiteswaran, J.; St. Louis, V. L.; Emmerton, C.; Schiff, S. L.

    2012-12-01

    Freshwater lakes and wetlands can be very productive systems on the Arctic landscape compared to terrestrial tundra ecosystems and provide valuable resources to many organisms, including waterfowl, fish and humans. Rates of ecosystem productivity dictate how much energy flows through food webs, impacting the abundance of higher-level organisms (e.g., fish), as well as the net carbon balance, which determines whether a particular ecosystem is a source or sink of carbon. Climate change is predicted to result in warmer temperatures, increased precipitation and permafrost melting in the Arctic and is already altering northern ecosystems at unprecedented rates; however, it is not known how freshwater systems are responding to these changes. To predict how freshwater systems will respond to complex environmental changes, it is necessary to understand the key processes, such as primary production and ecosystem respiration, that are driving these systems. We sampled wetland ponds (n=8) and lakes (n=2) on northern Ellesmere Island (81° N, Nunavut, Canada) during the open water season for a suite of biogeochemical parameters, including concentrations of dissolved gases (O2, CO2, CH4, N2O) as well as stable-isotope ratios of dissolved inorganic carbon (δ13C-DIC), dissolved oxygen (δ18O-DO), and water (δ18O-H2O). We will present rates of primary production and ecosystem respiration, modeled from the concentration and stable isotope ratios of DIC and DO, as well as air-water gas exchange of greenhouse gases in these high Arctic ponds and lakes. Preliminary results demonstrate that ecosystem metabolism in these ponds was high enough to result in significant deviations in the isotope ratios of DIC and DO from atmospheric equilibrium conditions. In other words ecosystem rates of primary production and respiration were faster than gas exchange even in these small, shallow, well-mixed ponds. Furthermore, primary production was elevated enough at all sites except Lake Hazen, a

  3. WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1979-01-01

    A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.

  4. Structure of phospholipid monolayers containing poly(ethylene glycol) lipids at the air-water interface

    SciTech Connect

    Majewski, J.; Smith, G.S.; Kuhl, T.L.; Israelachvili, J.N.; Gerstenberg, M.C.

    1997-04-17

    The density distribution of a lipid monolayer at the air-water interface mixed with varying amounts of lipid with poly(ethylene glycol)polymer headgroups (polymer-lipid or PEG-lipid) was measured using neutron reflectometry. The structure of the monolayer at the interface was greatly perturbed by the presence of the bulky polymer-lipid headgroups resulting in a large increase in the thickness of the headgroup region normal to the interface and a systematic roughening of the interface with increasing polymer-lipid content. These results show how bulky hydrophilic moieties cause significant deformations and out-of-place protrusions of phospholipid monolayers and presumably bilayers, vesicles and biological membranes. In terms of polymer physics, very short polymer chains tethered to the air-water interface follow scaling behavior with a mushroom to brush transition with increasing polymer grafting density. 34 refs., 9 figs., 1 tab.

  5. Behavior of pH-sensitive core shell particles at the air-water interface.

    PubMed

    Mathew, Mark D'Souza; Manga, Mohamed S; Hunter, Timothy N; Cayre, Olivier J; Biggs, Simon

    2012-03-20

    In this article, the adsorption of latex core-responsive polymer-shell nanoparticles at the air-water interface is investigated using a Langmuir trough. Phase transition isotherms are used to explore their responsive behavior at the interface as a function of changes in the pH of the subphase. By adjusting the pH of the water prior to particle deposition, we probe the effect of the stabilizing polymer wetting by the water subphase on the stability of these particles at the air-water interface. In addition, by initially compressing a stable film of adsorbed particles and then subsequently changing the pH of the subphase we study desorption of these particles into the water phase.

  6. Effect of surfactants on bubble collisions with an air-water interface

    NASA Astrophysics Data System (ADS)

    Wang, Shiyan; Guo, Tianqi; Dabiri, Sadegh; Vlachos, Pavlos P.; Ardekani, Arezoo M.

    2016-11-01

    Collisions of bubbles on an air-water interface are frequently observed in natural environments and industrial applications. We study the coefficient of restitution of a bubble colliding on an air-water interface in the presence of surfactants through a combination of experimental and numerical approaches. In a high concentration surfactant solution, bubbles experience perfectly inelastic collisions, and bubbles are arrested by the interface after the collision. As the surfactant concentration decreases, collisions are altered to partially inelastic, and eventually, elastic collisions occur in the pure water. In a high concentration surfactant solution, the reduced bouncing is attributed to the Marangoni stress. We identify the Langmuir number, the ratio between absorption and desorption rates, as the fundamental parameter to quantify the Marangoni effect on collision processes in surfactant solutions. The effect of Marangoni stress on the bubble's coefficient of restitution is non-monotonic, where the coefficient of restitution first decreases with Langmuir number, and then increases.

  7. Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gas-chromatographic preseparation method.

    PubMed

    Warneke, Carsten; De Gouw, Joost A; Kuster, William C; Goldan, Paul D; Fall, Ray

    2003-06-01

    Proton-transfer-reaction mass spectrometry (PTR-MS) has emerged as a useful tool to study volatile organic compounds (VOCs) in the atmosphere. In PTR-MS, proton-transfer reactions with H30+ ions are used to ionize and measure VOCs in air with a high sensitivity and fast time response. Only the masses of the ionized VOCs and their fragments, if any, are determined, and these product ions are not unique indicators of VOC identities. Here, a combination of gas chromatography and PTR-MS (GC-PTR-MS) is used to validate the measurements by PTR-MS of a number of common atmospheric VOCs. We have analyzed 75 VOCs contained in standard mixtures by GC-PTR-MS, which allowed detected masses to be unambiguously related to a specific compound. The calibration factors for PTR-MS and GC-PTR-MS were compared and showed that the loss of VOCs in the sample acquisition and GC system is small. GC-PTR-MS analyses of 56 air samples from an urban site were used to address the specificity of PTR-MS in complex air masses. It is demonstrated that the ions associated with methanol, acetonitrile, acetaldehyde, acetone, benzene, toluene, and higher aromatic VOCs are free from significant interference. A quantitative intercomparison between PTR-MS and GC-PTR-MS measurements of the aforementioned VOCs was performed and shows that they are accurately measured by PTR-MS.

  8. Adsorption, folding, and packing of an amphiphilic peptide at the air/water interface.

    PubMed

    Engin, Ozge; Sayar, Mehmet

    2012-02-23

    Peptide oligomers play an essential role as model compounds for identifying key motifs in protein structure formation and protein aggregation. Here, we present our results, based on extensive molecular dynamics simulations, on adsorption, folding, and packing within a surface monolayer of an amphiphilic peptide at the air/water interface. Experimental results suggest that these molecules spontaneously form ordered monolayers at the interface, adopting a β-hairpin-like structure within the surface layer. Our results reveal that the β-hairpin structure can be observed both in bulk and at the air/water interface. However, the presence of an interface leads to ideal partitioning of the hydrophobic and hydrophilic residues, and therefore reduces the conformational space for the molecule and increases the stability of the hairpin structure. We obtained the adsorption free energy of a single β-hairpin at the air/water interface, and analyzed the enthalpic and entropic contributions. The adsorption process is favored by two main factors: (1) Free-energy reduction due to desolvation of the hydrophobic side chains of the peptide and release of the water molecules which form a cage around these hydrophobic groups in bulk water. (2) Reduction of the total air/water contact area at the interface upon adsorption of the peptide amphiphile. By performing mutations on the original molecule, we demonstrated the relative role of key design features of the peptide. Finally, by analyzing the potential of mean force among two peptides at the interface, we investigated possible packing mechanisms for these molecules within the surface monolayer.

  9. Foam and cluster structure formation by latex particles at the air/water interface

    NASA Astrophysics Data System (ADS)

    Ruiz-Garcia, Jaime; Gámez-Corrales, Rogelio; Ivlev, Boris I.

    1997-02-01

    We report the formation of two-dimensional foam and cluster structures by spherical polystyrene particles trapped at the air/water interface. The colloidal foam is a transient structure that evolves to the formation of clusters, but clusters can also be formed after deposition of the sample. We also observed the formation of small aggregates, whose formation along with the cluster stabilization can be explained in terms of a balance between electrostatic repulsive and van der Waals attractive interactions.

  10. Rheology and microrheology of materials at the air-water interface

    NASA Astrophysics Data System (ADS)

    Walder, Robert Benjamin

    2008-10-01

    The study of materials at the air-water interface is an important area of research in soft condensed matter physics. Films at the air-water interface have been a system of interest to physics, chemistry and biology for the last 20 years. The unique properties of these surface films provide ideal models for 2-d films, surface chemistry and provide a platform for creating 2 dimensional analogue materials to cellular membranes. Measurements of the surface rheology of cross-linked F-actin networks associated with a lipid monolayer at the air-water interface of a Langmuir monolayer have been performed. The rheological measurements are made using a Couette cell. These data demonstrate that the network has a finite elastic modulus that grows as a function of the cross-linking concentration. We also note that under steady-state flow the system behaves as a power law fluid in which the effective viscosity decreases with imposed shear. A Langmuir monolayer trough that is equipped for simultaneous microrheology and standard rheology measurements has been constructed. The central elements are the trough itself with a full range of optical tools accessing the air-water interface from below the trough and a portable knife-edge torsion pendulum that can access the interface from above. The ability to simultaneously measure the mechanical response of Langmuir monolayers on very different length scales is an important step for our understanding of the mechanical response of two-dimensional viscoelastic networks. The optical tweezer microrheometer is used to study the micromechanical properties of Langmuir monolayers. Microrheology measurements are made a variety of surface pressures that correspond to different ordered phases of the monolayer. The complex shear modulus shows an order of magnitude increase for the liquid condensed phase of DPPC compared to the liquid expanded phase.

  11. Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Aircraft Turbine Engines.

    PubMed

    Kilic, Dogushan; Brem, Benjamin T; Klein, Felix; El-Haddad, Imad; Durdina, Lukas; Rindlisbacher, Theo; Setyan, Ari; Huang, Rujin; Wang, Jing; Slowik, Jay G; Baltensperger, Urs; Prevot, Andre S H

    2017-04-04

    Nonmethane organic gas emissions (NMOGs) from in-service aircraft turbine engines were investigated using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at an engine test facility at Zurich Airport, Switzerland. Experiments consisted of 60 exhaust samples for seven engine types (used in commercial aviation) from two manufacturers at thrust levels ranging from idle to takeoff. Emission indices (EIs) for more than 200 NMOGs were quantified, and the functional group fractions (including acids, carbonyls, aromatics, and aliphatics) were calculated to characterize the exhaust chemical composition at different engine operation modes. Total NMOG emissions were highest at idling with an average EI of 7.8 g/kg fuel and were a factor of ∼40 lower at takeoff thrust. The relative contribution of pure hydrocarbons (particularly aromatics and aliphatics) of the engine exhaust decreased with increasing thrust while the fraction of oxidized compounds, for example, acids and carbonyls increased. Exhaust chemical composition at idle was also affected by engine technology. Older engines emitted a higher fraction of nonoxidized NMOGs compared to newer ones. Idling conditions dominated ground level organic gas emissions. Based on the EI determined here, we estimate that reducing idle emissions could substantially improve air quality near airports.

  12. Contribution of Liquid/Gas Mass-Transfer Limitations to Dissolved Methane Oversaturation in Anaerobic Treatment of Dilute Wastewater.

    PubMed

    Yeo, Hyeongu; An, Junyeong; Reid, Robertson; Rittmann, Bruce E; Lee, Hyung-Sool

    2015-09-01

    The mechanisms controlling the accumulation of dissolved methane in anaerobic membrane bioreactors (AnMBRs) treating a synthetic dilute wastewater (a glucose medium) were assessed experimentally and theoretically. The AnMBR was maintained at a temperature of 24-26 °C as the organic loading rate increased from 0.39 to 1.1 kg COD/m(3)-d. The measured concentration of dissolved methane was consistently 2.2- to 2.5-fold larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH4 partial pressure, and the fraction of dissolved methane was as high as 76% of the total methane produced. The low gas production rate in the AnMBR significantly slowed the mass transport of dissolved methane to the gas phase. Although the production rate of total methane increased linearly with the COD loading rate, the concentration of dissolved methane only slightly increased with an increasing organic loading rate, because the mass-transfer rate increased by almost 5-fold as the COD loading increased from 0.39 to 1.1 kg COD/m(3)-d. Thus, slow mass transport kinetics exacerbated the situation in which dissolved methane accounted for a substantial fraction of the total methane generated from the AnMBR.

  13. Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Cooking Emissions.

    PubMed

    Klein, Felix; Platt, Stephen M; Farren, Naomi J; Detournay, Anais; Bruns, Emily A; Bozzetti, Carlo; Daellenbach, Kaspar R; Kilic, Dogushan; Kumar, Nivedita K; Pieber, Simone M; Slowik, Jay G; Temime-Roussel, Brice; Marchand, Nicolas; Hamilton, Jacqueline F; Baltensperger, Urs; Prévôt, André S H; El Haddad, Imad

    2016-02-02

    Cooking processes produce gaseous and particle emissions that are potentially deleterious to human health. Using a highly controlled experimental setup involving a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), we investigate the emission factors and the detailed chemical composition of gas phase emissions from a broad variety of cooking styles and techniques. A total of 95 experiments were conducted to characterize nonmethane organic gas (NMOG) emissions from boiling, charbroiling, shallow frying, and deep frying of various vegetables and meats, as well as emissions from vegetable oils heated to different temperatures. Emissions from boiling vegetables are dominated by methanol. Significant amounts of dimethyl sulfide are emitted from cruciferous vegetables. Emissions from shallow frying, deep frying and charbroiling are dominated by aldehydes of differing relative composition depending on the oil used. We show that the emission factors of some aldehydes are particularly large which may result in considerable negative impacts on human health in indoor environments. The suitability of some of the aldehydes as tracers for the identification of cooking emissions in ambient air is discussed.

  14. Studies of momentum and energy transfer across wavy gas-liquid interfaces. Final report

    SciTech Connect

    Dukler, A.E.

    1993-06-01

    Two phase gas-liquid flow and its associated interfaces exist in a wide variety of situations of importance to the Navy and this has prompted the study of the basic flow mechanics which underlie this complex process. The existence of wind-wave interactions over large bodies of water have long been recognized as a special case of two phase flow where the presence of the deformable interface plays a complex role in the generation of waves due to the action of the wind. Less well recognized, but of great importance, are situations of two phase flow which are found in components of power systems such as condensers, boilers refrigeration loops and cryogen lines. Here the characteristics of two phase flow are critical to the reliable design and safe operation of such systems.

  15. Heat transfer in a compact tubular heat exchanger with helium gas at 3.5 MPa

    NASA Technical Reports Server (NTRS)

    Olson, Douglas A.; Glover, Michael P.

    1990-01-01

    A compact heat exchanger was constructed consisting of circular tubes in parallel brazed to a grooved base plate. This tube specimen heat exchanger was tested in an apparatus which radiatively heated the specimen on one side at a heat flux of up to 54 W/sq cm, and cooled the specimen with helium gas at 3.5 MPa and Reynolds numbers of 3000 to 35,000. The measured friction factor of the tube specimen was lower than that of a circular tube with fully developed turbulent flow, although the uncertainty was high due to entrance and exit losses. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in circular tubes.

  16. Interaction between graphene oxide and Pluronic F127 at the air-water interface.

    PubMed

    Li, Shanghao; Guo, Jingru; Patel, Ravi A; Dadlani, Anup L; Leblanc, Roger M

    2013-05-14

    Triblock copolymer Pluronic F127 (PF127) has previously been demonstrated to disperse graphene oxide (GO) in electrolyte solution and block the hydrophobic interaction between GO and l-tryptophan and l-tyrosine. However, the nature of this interaction between PF127 and GO remains to be characterized and elucidated. In the present study, we aimed to characterize and understand the interaction between GO and PF127 using a 2-dimensional Langmuir monolayer methodology at the air-water interface by surface pressure-area isotherm measurement, stability, adsorption, and atomic force microscopy (AFM) imaging. Based on the observation of surface pressure-area isotherms, adsorption, and stability of PF127 and PF127/GO mixture at the air-water interface, GO is suggested to change the conformation of PF127 at the air-water interface and also drag PF127 from the interface to the bulk subphase. Atomic force microscopy (AFM) image supports this assumption, as GO and PF127 can be observed by spreading the subphase solution outside the compressing barriers, as shown in the TOC graphic.

  17. Anisotropic orientational motion of molecular adsorbates at the air-water interface

    SciTech Connect

    Zimdars, D.; Dadap, J.I.; Eisenthal, K.B.; Heinz, T.F.

    1999-04-29

    The ultrafast orientational motions of coumarin 314 (C314) adsorbed at the air/water interface were investigated by time-resolved surface second harmonic generation (TRSHG). The theory and method of using TRSHG to detect both out-of-plane and in-plane orientational motions are discussed. The interfacial solute motions were found to be anisotropic, with differing out-of-plane and in-plane reorientation time constants. This report presents the first direct observation of in-plane orientational motion of a molecule (C314) at the air/water interface using TRSHG. The in-plane reorientation time constant is 600 {+-} 40 ps. The out-of-plane reorientation time constant is 350 {+-} 20 ps. The out-of-plane orientational motion of C314 is similar to the previous results on rhodamine 6G at the air/water interface which indicated increased interfacial friction compared with bulk aqueous solution. The surface reorientation times are 2--3 times slower than the bulk isotropic orientational diffusion time.

  18. Drag reductions and the air-water interface stability of superhydrophobic surfaces in rectangular channel flow

    NASA Astrophysics Data System (ADS)

    Zhang, Jingxian; Yao, Zhaohui; Hao, Pengfei

    2016-11-01

    Flow in a rectangular channel with superhydrophobic (SH) top and bottom walls was investigated experimentally. Different SH surfaces, including hierarchical structured surfaces and surfaces with different micropost sizes (width and spacing) but the same solid fraction, were fabricated and measured. Pressure loss and flow rate in the channel with SH top and bottom walls were measured, with Reynolds number changing from 700 to 4700, and the corresponding friction factor for the SH surface was calculated. The statuses of the air plastron on different SH surfaces were observed during the experiment. In our experiment, compared with the experiment for the smooth surface, drag reductions were observed for all SH surfaces, with the largest drag reduction of 42.2%. It was found that the hierarchy of the microstructure can increase the drag reduction by decreasing the solid fraction and enhancing the stability of the air-water interface. With a fixed solid fraction, the drag reduction decreases as the post size (width and spacing) increases, due to the increasing curvature and instability effects of the air-water interface. A correlation parameter between the contact angle hysteresis, the air-water interface stability, and the drag reduction of the SH surfaces was found.

  19. Morphological variation of stimuli-responsive polypeptide at air-water interface

    NASA Astrophysics Data System (ADS)

    Shin, Sungchul; Ahn, Sungmin; Cheng, Jie; Chang, Hyejin; Jung, Dae-Hong; Hyun, Jinho

    2016-12-01

    The morphological variation of stimuli-responsive polypeptide molecules at the air-water interface as a function of temperature and compression was described. The surface pressure-area (π-A) isotherms of an elastin-like polypeptide (ELP) monolayer were obtained under variable external conditions, and Langmuir-Blodgett (LB) monolayers were deposited onto a mica substrate for characterization. As the compression of the ELP monolayer increased, the surface pressure increased gradually, indicating that the ELP monolayer could be prepared with high stability at the air-water interface. The temperature in the subphase of the ELP monolayer was critical in the preparation of LB monolayers. The change in temperature induced a shift in the π-A isotherms as well as a change in ELP secondary structures. Surprisingly, the compression of the ELP monolayer influenced the ELP secondary structure due to the reduction in the phase transition temperature with decreasing temperature. The change in the ELP secondary structure formed at the air-water interface was investigated by surface-enhanced Raman scattering. Moreover, the morphology of the ELP monolayer was subsequently imaged using atomic force microscopy. The temperature responsive behavior resulted in changes in surface morphology from relatively flat structures to rugged labyrinth structures, which suggested conformational changes in the ELP monolayers.

  20. Studies of Athabasca asphaltene Langmuir films at air-water interface.

    PubMed

    Zhang, Li Yan; Lawrence, Steven; Xu, Zhenghe; Masliyah, Jacob H

    2003-08-01

    Asphaltenes are present in heavy oils and bitumen. They are a mixture of hydrocarbons having complex structures of polyaromatic rings and short side chains. In general, the high-molecular-weight asphaltene is the most aromatic fraction with the highest number of side chains and the low-molecular-weight asphaltene contains the lowest number of side chains, while the number of side chains of the whole asphaltene fraction lies in between. In this study, asphaltenes were extracted and/or fractionated from Athabasca oil sand bitumen. Subfractions of high and low molecular weight and the whole asphaltenes were characterized using a Langmuir trough and complementary techniques such as VPO, FTIR, AFM, and contact angle measurements. At an air-water interface, amphiphilic asphaltene molecules can form a monolayer. Various fractions (high, low, and whole) of the asphaltene molecules behave similarly at the air-water interface, characterized by close resemblance of their surface pressure-area, hysteresis, and relaxation isotherms. The high-molecular-weight asphaltene is the most expanded fraction, while the low-molecular-weight asphaltene fraction is the most condensed, with the whole asphaltene lying in between. At the air-water interface a monolayer of the low-molecular-weight asphaltene relaxes at a faster rate than one of the high-molecular-weight asphaltene.

  1. Drag reductions and the air-water interface stability of superhydrophobic surfaces in rectangular channel flow.

    PubMed

    Zhang, Jingxian; Yao, Zhaohui; Hao, Pengfei

    2016-11-01

    Flow in a rectangular channel with superhydrophobic (SH) top and bottom walls was investigated experimentally. Different SH surfaces, including hierarchical structured surfaces and surfaces with different micropost sizes (width and spacing) but the same solid fraction, were fabricated and measured. Pressure loss and flow rate in the channel with SH top and bottom walls were measured, with Reynolds number changing from 700 to 4700, and the corresponding friction factor for the SH surface was calculated. The statuses of the air plastron on different SH surfaces were observed during the experiment. In our experiment, compared with the experiment for the smooth surface, drag reductions were observed for all SH surfaces, with the largest drag reduction of 42.2%. It was found that the hierarchy of the microstructure can increase the drag reduction by decreasing the solid fraction and enhancing the stability of the air-water interface. With a fixed solid fraction, the drag reduction decreases as the post size (width and spacing) increases, due to the increasing curvature and instability effects of the air-water interface. A correlation parameter between the contact angle hysteresis, the air-water interface stability, and the drag reduction of the SH surfaces was found.

  2. Hydrodynamics of a fixed camphor boat at the air-water interface

    NASA Astrophysics Data System (ADS)

    Singh, Dhiraj; Akella, Sathish; Singh, Ravi; Mandre, Shreyas; Bandi, Mahesh

    2015-11-01

    A camphor tablet, when introduced at the air-water interface undergoes sublimation and the camphor vapour spreads radially outwards across the surface. This radial spreading of camphor is due to Marangoni forces setup by the camphor concentration gradient. We report experiments on the hydrodynamics of this process for a camphor tablet held fixed at the air-water interface. During the initial transient, the time-dependent spread radius R (t) of camphor scales algebraically with time t (R (t) ~t 1 / 2) in agreement with empirical scalings reported for spreading of volatile oils on water surface. But unlike surfactants, the camphor stops spreading when the influx of camphor from the tablet onto the air-water interface is balanced by the outflux of camphor due to evaporation, and a steady-state condition is reached. The spreading camphor however, shears the underlying fluid and sets up bulk convective flow. We explain the coupled steady-state dynamics between the interfacial camphor spreading and bulk convective flow with a boundary layer approximation, supported by experimental evidence. This work was supported by the Collective Interactions Unit, OIST Graduate University.

  3. Spatiotemporal patterns in methane flux and gas transfer velocity at low wind speeds: Implications for upscaling studies on small lakes

    NASA Astrophysics Data System (ADS)

    Schilder, J.; Bastviken, D.; Hardenbroek, M.; Heiri, O.

    2016-06-01

    Lakes contribute significantly to the global natural emissions of methane (CH4) and carbon dioxide. However, to accurately incorporate them into the continental carbon balance more detailed surveys of lacustrine greenhouse gas emissions are needed, especially in respect to spatiotemporal variability and to how this affects the upscaling of results. We investigated CH4 flux from a small, wind-shielded lake during 10 field trips over a 14 month period. We show that floating chambers may be used to calibrate the relationship between gas transfer velocity (k) and wind speed at 10 m height (U10) to the local system, in order to obtain more accurate estimates of diffusive CH4 flux than by applying general models predicting k based on U10. We confirm earlier studies indicating strong within-lake spatial variation in this relationship and in ebullitive CH4 flux within the lake basin. However, in contrast to the pattern reported in other studies, ebullitive CH4 flux was highest in the central parts of the lake. Our results indicate positive relationships between k and U10 at very low U10 (0-3 m s-1), which disagrees with earlier suggestions that this relationship may be negligible at low U10 values. We estimate annually averaged open water CH4 emission from Lake Gerzensee to be 3.6-5.8 mmol m-2 d-1. Our data suggest that estimates of greenhouse gas emissions from aquatic systems to the atmosphere based on the upscaling of short-term and small-scale measurements can be improved if both spatial and temporal variabilities of emissions are taken into account.

  4. Liquid Surface X-ray Studies of Gold Nanoparticle-Phospholipid Films at the Air/Water Interface.

    PubMed

    You, Siheng Sean; Heffern, Charles T R; Dai, Yeling; Meron, Mati; Henderson, J Michael; Bu, Wei; Xie, Wenyi; Lee, Ka Yee C; Lin, Binhua

    2016-09-01

    Amphiphilic phospholipids and nanoparticles functionalized with hydrophobic capping ligands have been extensively investigated for their capacity to self-assemble into Langmuir monolayers at the air/water interface. However, understanding of composite films consisting of both nanoparticles and phospholipids, and by extension, the complex interactions arising between nanomaterials and biological membranes, remains limited. In this work, dodecanethiol-capped gold nanoparticles (Au-NPs) with an average core diameter of 6 nm were incorporated into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers with surface densities ranging from 0.1 to 20% area coverage at a surface pressure of 30 mN/m. High resolution liquid surface X-ray scattering studies revealed a phase separation of the DPPC and Au-NP components of the composite film, as confirmed with atomic force microscopy after the film was transferred to a substrate. At low Au-NP content, the structural organization of the phase-separated film is best described as a DPPC film containing isolated islands of Au-NPs. However, increasing the Au-NP content beyond 5% area coverage transforms the structural organization of the composite film to a long-range interconnected network of Au-NP strands surrounding small seas of DPPC, where the density of the Au-NP network increases with increasing Au-NP content. The observed phase separation and structural organization of the phospholipid and nanoparticle components in these Langmuir monolayers are useful for understanding interactions of nanoparticles with biological membranes.

  5. Spectroscopic investigation of H atom transfer in a gas-phase dissociation reaction: McLafferty rearrangement of model gas-phase peptide ions.

    PubMed

    Van Stipdonk, Michael J; Kerstetter, Dale R; Leavitt, Christopher M; Groenewold, Gary S; Steill, Jeffrey; Oomens, Jos

    2008-06-14

    Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D(2)O and CH(3)OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm(-1) to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in situ, for subsequent investigation of intramolecular proton migration during peptide fragmentation studies.

  6. Spectroscopic Investigation of H Atom Transfer in a Gas-phase Dissociation Reaction: McLafferty Rearrangement of Model Gas-phase Peptide Ions

    SciTech Connect

    Michael J. Van Stipdonk; Dale R. Kersetter; Christopher M. Leavitt; Gary S. Groenewold; Jeffrey Steill; Jos Oomens

    2008-07-01

    Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D2O and CH3OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD technique to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm-1 to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in-situ, for subsequent investigation of intra-molecular proton migration during peptide fragmentation studies.

  7. Keto-enol tautomerization and intermolecular proton transfer in photoionized cyclopentanone dimer in the gas phase

    SciTech Connect

    Ghosh, Arup K.; Chatterjee, Piyali; Chakraborty, Tapas

    2014-07-28

    Time-of-flight mass spectra of cyclopentanone and its clusters cooled in a supersonic jet expansion have been measured following 4-, 3-, and 2-photon ionizations by the 2nd, 3rd, and 4th harmonic wavelengths, respectively, of a Q-switched Nd:YAG laser. The mass spectra reveal signatures of energetically favored keto to enol tautomerization of the molecular ion leading to intermolecular proton transfer, and this observation is found sharply dependent on the ionization wavelengths used. Electronic structure calculation predicts that in spite of the energetic preference, keto-enol conversion barrier of isolated molecular ion is high. However, the barrier is significantly reduced in a CH⋯O hydrogen-bonded dimer of the molecule. The transition states associated with tautomeric conversion of both cyclopentanone monomer and dimer cations have been identified by means of intrinsic reaction co-ordinate calculation. In a supersonic jet expansion, although a weakly bound dimer is readily generated, the corresponding cation and also the protonated counterpart are observed only for ionization by 532 nm. For other two ionization wavelengths, these species do not register in the mass spectra, where the competing reaction channels via α-cleavage of the ring become dominant. In contrast to the report of a recent study, we notice that the intact molecular ion largely survives fragmentations when ionized from the 2-photon resonant 3p Rydberg state as intermediate using nanosecond laser pulses, and the corresponding resonant 3-photon ionization spectrum has been recorded probing the intact molecular ion.

  8. Heat transfer in a compact heat exchanger containing rectangular channels and using helium gas

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1991-01-01

    Development of a National Aerospace Plane (NASP), which will fly at hypersonic speeds, require novel cooling techniques to manage the anticipated high heat fluxes on various components. A compact heat exchanger was constructed consisting of 12 parallel, rectangular channels in a flat piece of commercially pure nickel. The channel specimen was radiatively heated on the top side at heat fluxes of up to 77 W/sq cm, insulated on the back side, and cooled with helium gas flowing in the channels at 3.5 to 7.0 MPa and Reynolds numbers of 1400 to 28,000. The measured friction factor was lower than that of the accepted correlation for fully developed turbulent flow, although the uncertainty was high due to uncertainty in the channel height and a high ratio of dynamic pressure to pressure drop. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in channels. Flow nonuniformity from channel-to-channel was as high as 12 pct above and 19 pct below the mean flow.

  9. Phase diagram, design of monolayer binary colloidal crystals, and their fabrication based on ethanol-assisted self-assembly at the air/water interface.

    PubMed

    Dai, Zhengfei; Li, Yue; Duan, Guotao; Jia, Lichao; Cai, Weiping

    2012-08-28

    Flexible structural design and accurate controlled fabrication with structural tunability according to need for binary or multicomponent colloidal crystals have been expected. However, it is still a challenge. In this work, the phase diagram of monolayer binary colloidal crystals (bCCs) is established on the assumption that both large and small polystyrene (PS) colloidal spheres can stay at the air/water interface, and the range diagram for the size ratio and number ratio of small to large colloidal spheres is presented. From this phase diagram, combining the range diagram, we can design and relatively accurately control fabrication of the bCCs with specific structures (or patterns) according to need, including single or mixed patterns with the given relative content. Further, a simple and facile approach is presented to fabricate large-area (more than 10 cm(2)) monolayer bCCs without any surfactants, using differently sized PS spheres, based on ethanol-assisted self-assembly at the air/water interface. bCCs with different patterns and stoichiometries are thus designed from the established phase diagram and then successfully fabricated based on the volume ratios (V(S/L)) of the small to large PS suspensions using the presented colloidal self-assembling method. Interestingly, these monolayer bCCs can be transferred to any desired substrates using water as the medium. This study allows us to design desired patterns of monolayer bCCs and to more accurately control their structures with the used V(S/L).

  10. Interaction between heterogeneous environmental quality domains (air, water, land, socio-demographic and built environment) on preterm birth.

    EPA Science Inventory

    Environmental exposures are often measured individually, though many occur in tandem. To address aggregate exposures, a county-level Environmental Quality Index (EQI) representing five environmental domains (air, water, land, built and sociodemographic) was constructed. Recent st...

  11. Modelling of heat and mass transfer in a granular medium during high-temperature air drying. Effect of the internal gas pressure

    NASA Astrophysics Data System (ADS)

    Othmani, Hammouda; Hassini, Lamine; Lamloumi, Raja; El Cafsi, Mohamed Afif

    2016-02-01

    A comprehensive internal heat and water transfer model including the gas pressure effect has been proposed in order to improve the industrial high-temperature air drying of inserts made of agglomerated sand. In this model, the internal gas phase pressure effect was made perfectly explicit, by considering the liquid and vapour transfer by filtration and the liquid expulsion at the surface. Wet sand enclosed in a tight cylindrical glass bottle dried convectively at a high temperature was chosen as an application case. The model was validated on the basis of the experimental average water content and core temperature curves for drying trials at different operating conditions. The simulations of the spatio-temporal distribution of internal gas pressure were performed and interpreted in terms of product potential damage. Based on a compromise between the drying time and the pressure increase, a simple drying cycle was implemented in order to optimize the drying process.

  12. Simultaneous multi-determination and transfer of eight pesticide residues from green tea leaves to infusion using gas chromatography.

    PubMed

    Cho, Soon-Kil; Abd El-Aty, A M; Rahman, Md Musfiqur; Choi, Jeong-Heui; Shim, Jae-Han

    2014-12-15

    A method for determining eight pesticide (cyhalothrin, flufenoxuron, fenitrothion, EPN, bifenthrin, difenoconazole, triflumizole, and azoxystrobin) residues in made green tea as well as a tea infusion (under various brewing water temperatures; 60, 80, and 100°C) using gas chromatography (GC) micro-electron capture detector (μECD) was developed and validated. The extraction method adopted the relatively commonly used approach of solid sample hydration, with the green tea hydrated before being extracted through salting out with acetonitrile followed by a cleanup procedure. The analytes were confirmed using GC-coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole. The linearity of the calibration curves yielded determination coefficients (R(2)) >0.995. Recoveries were carried out using blank samples spiked with all analytes at two levels. The results demonstrated that all pesticides were recovered within the range of 77-116% with a relative standard deviation (RSD) ⩽14%. The quantification limits of 0.015-0.03 mg/kg were lower than the maximum residue limits (MRLs) set by the Korea Food and Drug Administration (KFDA) for all analytes (0.05-10mg/kg). The infusion study indicated that cyhalothrin, flufenoxuron, and bifenthrin did not infuse into the tea brew from the made tea. Increases in brewing time resulted in increased transfer of azoxystrobin, fenitrothion, and difenoconazole from the made tea to the brew; however, this was not the case with triflumizole or EPN. We conclude that transfer of pesticides appeared to be dependent on their water solubilities and drinking a cup of tea is recommended to be at a water temperature of 60°C.

  13. Submm Observations of Massive Star Formation in the Giant Molecular Cloud NGC 6334 : Gas Kinematics with Radiative Transfer Models

    NASA Astrophysics Data System (ADS)

    Zernickel, A.

    2015-05-01

    Context. How massive stars (M>8 Ms) form and how they accrete gas is still an open research field, but it is known that their influence on the interstellar medium (ISM) is immense. Star formation involves the gravitational collapse of gas from scales of giant molecular clouds (GMCs) down to dense hot molecular cores (HMCs). Thus, it is important to understand the mass flows and kinematics in the ISM. Aims. This dissertation focuses on the detailed study of the region NGC 6334, located in the Galaxy at a distance of 1.7 kpc. It is aimed to trace the gas velocities in the filamentary, massive star-forming region NGC 6334 at several scales and to explain its dynamics. For that purpose, different scales are examined from 0.01-10 pc to collect information about the density, molecular abundance, temperature and velocity, and consequently to gain insights about the physio-chemical conditions of molecular clouds. The two embedded massive protostellar clusters NGC 6334I and I(N), which are at different stages of development, were selected to determine their infall velocities and mass accretion rates. Methods. This astronomical source was surveyed by a combination of different observatories, namely with the Submillimeter Array (SMA), the single-dish telescope Atacama Pathfinder Experiment (APEX), and the Herschel Space Observatory (HSO). It was mapped with APEX in carbon monoxide (13CO and C18O, J=2-1) at 220.4 GHz to study the filamentary structure and turbulent kinematics on the largest scales of 10 pc. The spectral line profiles are decomposed by Gaussian fitting and a dendrogram algorithm is applied to distinguish velocity-coherent structures and to derive statistical properties. The velocity gradient method is used to derive mass flow rates. The main filament was mapped with APEX in hydrogen cyanide (HCN) and oxomethylium (HCO+, J=3-2) at 267.6 GHz to trace the dense gas. To reproduce the position- velocity diagram (PVD), a cylindrical model with the radiative transfer

  14. Circulation in gas-slurry column reactors

    SciTech Connect

    Clark, N.; Kuhlman, J.; Celik, I.; Gross, R.; Nebiolo, E.; Wang, Yi-Zun.

    1990-08-15

    Circulation in bubble columns, such as those used in fischer-tropsch synthesis, detracts from their performance in that gas is carried on average more rapidly through the column, and the residence time distribution of the gas in the column is widened. Both of these factors influence mass-transfer operations in bubble columns. Circulation prediction and measurement has been undertaken using probes, one-dimensional models, laser Doppler velocimetry, and numerical modeling. Local void fraction was measured using resistance probes and a newly developed approach to determining air/water threshold voltage for the probe. A tall column of eight inch diameter was constructed of Plexiglas and the distributor plate was manufactured to distribute air evenly through the base of the column. Data were gathered throughout the volume at three different gas throughputs. Bubble velocities proved difficult to measure using twin probes with cross-correlation because of radial bubble movement. A series of three-dimensional mean and RMS bubble and liquid velocity measurements were also obtained for a turbulent flow in a laboratory model of a bubble column. These measurements have been made using a three-component laser Doppler velocimeter (LDV), to determine velocity distributions non-intrusively. Finally, the gas-liquid flow inside a vertically situated circular isothermal column reactor was simulated numerically. 74 refs., 170 figs., 5 tabs.

  15. Comparison of positional surfactant isomers for displacement of rubisco protein from the air-water interface.

    PubMed

    He, Lizhong; Onaizi, Sagheer A; Dimitrijev-Dwyer, Mirjana; Malcolm, Andrew S; Shen, Hsin-Hui; Dong, Chuchuan; Holt, Stephen A; Thomas, Robert K; Middelberg, Anton P J

    2011-08-15

    Protein-surfactant interaction, which is a function of the protein and surfactant characteristics, is a common phenomenon in a wide range of industrial applications. In this work, we used rubisco, the most abundant protein in nature, as a model protein and sodium dodecylbenzenesulfonate (SDOBS), one of the most widely used commercial surfactants, with two positional isomers (SDOBS-2 and SDOBS-6), as a model surfactant. We first examined the surface tension and the mechanical properties of interfacial mixed rubisco-SDOBS films adsorbed at the air-water interface. The concentration of rubisco in solution was fixed at 0.1 mg mL(-1) while the SDOBS concentration varied from 0 to 150 μM. Both the surface tension and the mechanical strength of the interfacial film decreased with increasing SDOBS concentration. Overall, the surface tension of a rubisco-SDOBS-6 mixture is lower than that of rubisco-SDOBS-2, while the mechanical strength of both systems is similar. Neutron reflection data suggest that rubisco protein is likely denatured at the interface. The populations of rubisco and SDOBS of the mixed systems at the interface were determined by combining non-deuterated and deuterated SDOBS to provide contrast variation. At a low surfactant concentration, SDOBS-6 has a stronger ability to displace rubisco from the air-water interface than SDOBS-2. However, when surfactant concentration reaches 50 μM, SDOBS-2 has a higher population than SDOBS-6, with more rubisco displaced from the interface. The results presented in this work suggest that the extent of protein displacement from the air-water interface, and hence the nature of the protein-surfactant interactions at the interface, are strongly affected by the position of surfactant isomerisation, which might allow the design of formulations for efficient removal of protein stains.

  16. Monolayer film behavior of lipopolysaccharide from Pseudomonas aeruginosa at the air-water interface.

    PubMed

    Abraham, Thomas; Schooling, Sarah R; Beveridge, Terry J; Katsaras, John

    2008-10-01

    Lipopolysaccharide (LPS) is an essential biomacromolecule making up approximately 50% of the outer membrane of gram-negative bacteria. LPS chemistry facilitates cellular barrier and permeability functions and mediates interactions between the cell and its environment. To better understand the local interactions within LPS membranes, the monolayer film behavior of LPS extracted from Pseudomonas aeruginosa, an opportunistic pathogen of medical importance, was investigated by Langmuir film balance. LPS formed stable monolayers at the air-water interface and the measured lateral stresses and modulus (rigidity) of the LPS film in the compressed monolayer region were found to be appreciable. Scaling theories for two-dimensional (2D) polymer chain conformations were used to describe the pi-A profile, in particular, the high lateral stress region suggested that the polysaccharide segments reside at the 2D air-water interface. Although the addition of monovalent and divalent salts caused LPS molecules to adopt a compact conformation at the air-water interface, they did not appear to have any influence on the modulus (rigidity) of the LPS monolayer film under biologically relevant stressed conditions. With increasing divalent salt (CaCl2) content in the subphase, however, there is a progressive reduction of the LPS monolayer's collapse pressure, signifying that, at high concentrations, divalent salts weaken the ability of the membrane to withstand elevated stress. Finally, based on the measured viscoelastic response of the LPS films, we hypothesize that this property of LPS-rich outer membranes of bacteria permits the deformation of the membrane and may consequently protect bacteria from catastrophic structural failure when under mechanical-stress.

  17. Transfer-matrix study of a hard-square lattice gas with two kinds of particles and density anomaly

    NASA Astrophysics Data System (ADS)

    Oliveira, Tiago J.; Stilck, Jürgen F.

    2015-09-01

    Using transfer matrix and finite-size scaling methods, we study the thermodynamic behavior of a lattice gas with two kinds of particles on the square lattice. Only excluded volume interactions are considered, so that the model is athermal. Large particles exclude the site they occupy and its four first neighbors, while small particles exclude only their site. Two thermodynamic phases are found: a disordered phase where large particles occupy both sublattices with the same probability and an ordered phase where one of the two sublattices is preferentially occupied by them. The transition between these phases is continuous at small concentrations of the small particles and discontinuous at larger concentrations, both transitions are separated by a tricritical point. Estimates of the central charge suggest that the critical line is in the Ising universality class, while the tricritical point has tricritical Ising (Blume-Emery-Griffiths) exponents. The isobaric curves of the total density as functions of the fugacity of small or large particles display a minimum in the disordered phase.

  18. Formation of H-type liquid crystal dimer at air-water interface

    SciTech Connect

    Karthik, C. Gupta, Adbhut Joshi, Aditya Manjuladevi, V. Gupta, Raj Kumar; Varia, Mahesh C.; Kumar, Sandeep

    2014-04-24

    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.

  19. Air-Water Exchange of Legacy and Emerging Organic Pollutants across the Great Lakes

    NASA Astrophysics Data System (ADS)

    Lohmann, R.; Ruge, Z.; Khairy, M.; Muir, D.; Helm, P.

    2014-12-01

    Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are transported to great water bodies via long-range atmospheric transport and released from the surface water as air concentrations continue to diminish. As the largest fresh water bodies in North America, the Great Lakes have both the potential to accumulate and serve as a secondary source of persistent bioaccumulative toxins. OCP and PCB concentrations were sampled at 30+ sites across Lake Superior, Ontario and Erie in the summer of 2011. Polyethylene passive samplers (PEs) were simultaneously deployed in surface water and near surface atmosphere to determine air-water gaseous exchange of OCPs and PCBs. In Lake Superior, surface water and atmospheric concentrations were dominated by α-HCH (average 250 pg/L and 4.2 pg/m3, respectively), followed by HCB (average 17 pg/L and 89 pg/m3, respectively). Air-water exchange varied greatly between sites and individual OCPs, however α-endosulfan was consistently deposited into the surface water (average 19 pg/m2/day). PCBs in the air and water were characterized by penta- and hexachlorobiphenyls with distribution along the coast correlated with proximity to developed areas. Air-water exchange gradients generally yielded net volatilization of PCBs out of Lake Superior. Gaseous concentrations of hexachlorobenzene, dieldrin and chlordanes were significantly higher (p < 0.05) at Lake Erie than Lake Ontario. A multiple linear regression that incorporated meteorological, landuse and population data was used to explain variability in the atmospheric concentrations. Results indicated that landuse (urban and/or cropland) greatly explained the variability in the data. Freely dissolved concentrations of OCPs (

  20. Rediscovering the Schulze-Hardy Rule in Competitive Adsorption to an Air-Water Interface

    PubMed Central

    Stenger, Patrick C.; Isbell, Stephen G.; Hillaire, Debra St.; Zasadzinski, Joseph A.

    2009-01-01

    The ratio of divalent to monovalent ion concentration necessary to displace the surface-active protein, albumin, by lung surfactant monolayers and multilayers at an air-water interface scales as 2−6, the same concentration dependence as the critical flocculation concentration (CFC) for colloids with a high surface potential. Confirming this analogy between competitive adsorption and colloid stability, polymer-induced depletion attraction and electrostatic potentials are additive in their effects; the range of the depletion attraction, twice the polymer radius of gyration, must be greater than the Debye length to have an effect on adsorption. PMID:19705897

  1. Regularities pertinent to heat transfer between torch gas layers and steam boiler firebox waterwalls. Part I. Geometrical and physical torch model as a source of heat radiation

    NASA Astrophysics Data System (ADS)

    Makarov, A. N.

    2014-09-01

    The progress seen in the 19th-21st centuries in the development of methods for calculating heat transfer in torch furnaces, fireboxes, and combustion chambers is analyzed. Throughout the 20th century, calculations of heat transfer were carried out based on the law for radiation from solid bodies deduced by Y. Stefan and L. Boltzmann. It is shown that the use of this law for calculating heat transfer of a torch (a gaseous source of radiation) in heating furnaces and power-generating installations leads to incorrect results. It is substantiated that there is crisis of methods for calculating heat transfer in torch furnaces and power-generating installations. Geometrical and physical torch models in the form of radiating cylindrical gas volumes as sources of heat radiation are proposed for overcoming this crisis.

  2. Influence of forced internal air circulation on airflow distribution and heat transfer in a gas double-dynamic solid-state fermentation bioreactor.

    PubMed

    Chen, Hongzhang; Qin, Lanzhi; Li, Hongqiang

    2014-02-01

    Internal air circulation affects the temperature field distribution in a gas double-dynamic solid-state fermentation bioreactor (GDSFB). To enhance heat transfer through strengthening internal air circulation in a GDSFB, we put an air distribution plate (ADP) into the bioreactor and studied the effects of forced internal air circulation on airflow, heat transfer, and cellulase activity of Trichoderma viride L3. Results showed that ADP could help form a steady and uniform airflow distribution, and with gas-guide tubes, air reversal was formed inside the bioreactor, thus resulting in a smaller temperature difference between medium and air by enhancing convective heat transfer inside the bioreactor. Using an ADP of 5.35 % aperture ratio caused a 1 °C decrease in the average temperature difference during the solid-state fermentation process of T. viride L3. Meanwhile, the cellulase activity of T. viride L3 increased by 13.5 %. The best heat-transfer effect was attained when using an ADP of 5.35 % aperture ratio and setting the fan power to 125 V (4.81 W) in the gas double-dynamic solid-state fermentation (GDSF) process. An option of suitable aperture ratio and fan power may be conducive to ADPs' industrial amplification.

  3. Three-Legged 2,2'-Bipyridine Monomer at the Air/Water Interface: Monolayer Structure and Reactions with Ni(II) Ions from the Subphase.

    PubMed

    Dai, Wenyang; Lee, Lay-Theng; Schütz, Andri; Zelenay, Benjamin; Zheng, Zhikun; Borgschulte, Andreas; Döbeli, Max; Abuillan, Wasim; Konovalov, Oleg V; Tanaka, Motomu; Schlüter, A Dieter

    2017-02-21

    The behavior of compound 2 [1,3,5-tri(2,2'-bipyridin-5-yl)benzene] with three bipyridine units arranged in a star geometry is investigated in the presence and absence of Ni(ClO4)2. Its properties at the air-water interface as well as after transfer onto a solid substrate are studied by several techniques including Brewster angle microscopy, X-ray reflectivity, neutron reflectivity, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and atomic force microscopy combined with optical microscopy. It is found that compound 2 within the monolayers formed stays almost vertical at the interface and that at high Ni(2+)/2 (Ni(2+)/2 = 4000, 20'000) ratios two of the three bipyridine units of 2 are complexed, resulting in supramolecular sheets that are likely composed of arrays of linear metal-organic complexation polymers.

  4. The effects of channel diameter on flow pattern, void fraction and pressure drop of two-phase air-water flow in circular micro-channels

    SciTech Connect

    Saisorn, Sira; Wongwises, Somchai

    2010-05-15

    Two-phase air-water flow characteristics are experimentally investigated in horizontal circular micro-channels. Test sections are made of fused silica. The experiments are conducted based on three different inner diameters of 0.53, 0.22 and 0.15 mm with the corresponding lengths of 320, 120 and 104 mm, respectively. The test runs are done at superficial velocities of gas and liquid ranging between 0.37-42.36 and 0.005-3.04 m/s, respectively. The flow visualisation is facilitated by systems mainly including stereozoom microscope and high-speed camera. The flow regime maps developed from the observed flow patterns are presented. The void fractions are determined based on image analysis. New correlation for two-phase frictional multiplier is also proposed for practical applications. (author)

  5. Through-space and through-bond mixed charge transfer mechanisms on the hydrazine oxidation by cobalt(II) phthalocyanine in the gas phase.

    PubMed

    Paredes-García, V; Cardenas-Jirón, G I; Venegas-Yazigi, D; Zagal, J H; Paez, M; Costamagna, J

    2005-02-17

    Two quantum chemistry theoretical models in the gas phase at the density functional theory B3LYP/LACVP(d) level of calculation are proposed to rationalize the hydrazine oxidation by cobalt(II) phthalocyanine (Co(II)Pc). This oxidation reaction involves the net transfer of four electrons. These theoretical models that are described in terms of energy profiles include a through-space mechanism for the transfer of the first electron of the hydrazine and a through-bond mechanism proposed for the transfer of the three electrons remaining. The main difference between both models arises from a one-electron and one-proton alternate transfer for model 1 and a two-electron and two-proton alternate transfer for model 2. The main problem for experimental studies is to determine if the first transfer corresponds to an electron or a chemical transfer. Under this point of view, we proposed two models which deal with this problem. We conclude that model 1 is more reasonable than model 2 because the whole oxidation process is always exergonic.

  6. Effect of Particulate Contaminants on the Development of Biofilms at Air/Water Interfaces.

    PubMed

    Zhang, Zhenhuan; Christopher, Gordon

    2016-03-22

    The development of biofilms at air/water or oil/water interfaces has important ramifications on several applications, but it has received less attention than biofilm formation on solid surfaces. A key difference between the growth of biofilms on solid surfaces versus liquid interfaces is the range of complicated boundary conditions the liquid interface can create that may affect bacteria, as they adsorb onto and grow on the interface. This situation is exacerbated by the existence of complex interfaces in which interfacially adsorbed components can even more greatly affect interfacial boundary conditions. In this work, we present evidence as to how particle-laden interfaces impact biofilm growth at an air/water interface. We find that particles can enhance the rate of growth and final strength of biofilms at liquid interfaces by providing sites of increased adhesive strength for bacteria. The increased adhesion stems from creating localized areas of hydrophobicity that protrude in the water phase and provide sites where bacteria preferentially adhere. This mechanism is found to be primarily controlled by particle composition, with particle size providing a secondary effect. This increased adhesion through interfacial conditions creates biofilms with properties similar to those observed when adhesion is increased through biological means. Because of the generally understood ubiquity of increased bacteria attachment to hydrophobic surfaces, this result has general applicability to pellicle formation for many pellicle-forming bacteria.

  7. Interfacial characterization of Pluronic PE9400 at biocompatible (air-water and limonene-water) interfaces.

    PubMed

    Pérez-Mosqueda, Luis M; Maldonado-Valderrama, Julia; Ramírez, Pablo; Cabrerizo-Vílchez, Miguel A; Muñoz, José

    2013-11-01

    In this work, we provide an accurate characterization of non-ionic triblock copolymer Pluronic PE9400 at the air-water and limonene-water interfaces, comprising a systematic analysis of surface tension isotherms, dynamic curves, dilatational rheology and desorption profiles. The surface pressure isotherms display two different slopes of the Π-c plot suggesting the existence of two adsorption regimes for PE9400 at both interfaces. Application of a theoretical model, which assumes the coexistence of different adsorbed states characterized by their molar areas, allows quantification of the conformational changes occurring at the adsorbed layer, indentifying differences between the conformations adopted at the air-water and the limonene-water interface. The presence of two maxima in the dilatational modulus vs. interfacial pressure importantly corroborates this conformational change from a 2D flat conformation to 3D brush one. Moreover, the dilatational response provides mechanical diferences between the interfacial layers formed at the two interfaces analyzed. Dynamic surface pressure data were transformed into a dimensionless form and fitted to another model which considers the influence of the reorganization process on the adsorption dynamics. Finally, the desorption profiles reveal that Pluronic PE9400 is irreversibly adsorbed at both interfaces regardless of the interfacial conformation and nature of the interface. The systematic characterization presented in this work provides important new findings on the interfacial properties of pluronics which can be applied in the rational development of new products, such as biocompatible limonene-based emulsions and/or microemulsions.

  8. NOVEL METHODS FOR MEASURING AIR-WATER INTERFACIAL AREA IN UNSATURATED POROUS MEDIA

    PubMed Central

    Brusseau, Mark L.; Ouni, Asma El; Araujo, Juliana B.; Zhong, Hua

    2015-01-01

    Interfacial partitioning tracer tests (IPTT) are used to measure air-water interfacial area for unsaturated porous media. The standard IPTT method involves conducting tests wherein an aqueous surfactant solution is introduced into a packed column under unsaturated flow conditions. Surfactant-induced drainage has been observed to occur for this method in some cases, which can complicate data analysis and impart uncertainty to the measured values. Two novel alternative approaches for conducting IPTTs are presented herein that are designed in part to prevent surfactant-induced drainage. The two methods are termed the dual-surfactant IPTT (IPTT-DS) and the residual-air IPTT (IPTT-RA). The two methods were used to measure air-water interfacial areas for two natural porous media. System monitoring during the tests revealed no measurable surfactant-induced drainage. The measured interfacial areas compared well to those obtained with the standard IPTT method conducted in such a manner that surfactant-induced drainage was prevented. PMID:25732632

  9. Surface properties and morphology of mixed POSS-DPPC monolayers at the air/water interface.

    PubMed

    Rojewska, Monika; Skrzypiec, Marta; Prochaska, Krystyna

    2017-02-01

    From the point of view of the possible medical applications of POSS (polyhedral oligomeric silsesquioxanes), it is crucial to analyse interactions occurring between POSS and model biological membrane at molecular level. Knowledge of the interaction between POSS and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) allows prediction of the impact of POSS contained in biomaterials or cosmetics on a living organism. In the study presented, the surface properties and morphology of Langmuir monolayers formed by mixtures of POSS and the phospholipid (DPPC) at the air/water surface are examined. We selected two POSS derivatives, with completely different chemical structure of substituents attached to the corner of the silicon open cage, which allowed the analysis of the impact of the character of organic moieties (strongly hydrophobic or clearly hydrophilic) on the order of POSS molecules and their tendency to form self-aggregates at the air/water surface. POSS derivatives significantly changed the profile of the π-A isotherms obtained for DPPC but in different ways. On the basis of the regular solution theory, the miscibility and stability of the two components in the monolayer were analysed in terms of compression modulus (Cs(-1)), excess Gibbs free energy (ΔGexc), activity coefficients (γ) and interaction parameter (ξ). The results obtained indicate the existence of two different interaction mechanisms between DPPC and POSS which depend on the chemical character of moieties present in POSS molecules.

  10. Molecular Adsorption Steers Bacterial Swimming at the Air/Water Interface

    PubMed Central

    Morse, Michael; Huang, Athena; Li, Guanglai; Maxey, Martin R.; Tang, Jay X.

    2013-01-01

    Microbes inhabiting Earth have adapted to diverse environments of water, air, soil, and often at the interfaces of multiple media. In this study, we focus on the behavior of Caulobacter crescentus, a singly flagellated bacterium, at the air/water interface. Forward swimming C. crescentus swarmer cells tend to get physically trapped at the surface when swimming in nutrient-rich growth medium but not in minimal salt motility medium. Trapped cells move in tight, clockwise circles when viewed from the air with slightly reduced speed. Trace amounts of Triton X100, a nonionic surfactant, release the trapped cells from these circular trajectories. We show, by tracing the motion of positively charged colloidal beads near the interface that organic molecules in the growth medium adsorb at the interface, creating a high viscosity film. Consequently, the air/water interface no longer acts as a free surface and forward swimming cells become hydrodynamically trapped. Added surfactants efficiently partition to the surface, replacing the viscous layer of molecules and reestablishing free surface behavior. These findings help explain recent similar studies on Escherichia coli, showing trajectories of variable handedness depending on media chemistry. The consistent behavior of these two distinct microbial species provides insights on how microbes have evolved to cope with challenging interfacial environments. PMID:23823220

  11. Research on measurement-device-independent quantum key distribution based on an air-water channel

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan-yuan; Zhou, Xue-jun; Xu, Hua-bin; Cheng, Kang

    2016-11-01

    A measurement-device-independent quantum key distribution (MDI-QKD) method with an air-water channel is researched. In this method, the underwater vehicle and satellite are the legitimate parties, and the third party is at the airwater interface in order to simplify the unilateral quantum channel to water or air. Considering the condition that both unilateral transmission distance and transmission loss coefficient are unequal, a perfect model of the asymmetric channel is built. The influence of asymmetric channel on system loss tolerance and secure transmission distance is analyzed. The simulation results show that with the increase of the channel's asymmetric degree, the system loss tolerance will descend, one transmission distance will be reduced while the other will be increased. When the asymmetric coefficient of channel is between 0.068 and 0.171, MDI-QKD can satisfy the demand of QKD with an air-water channel, namely the underwater transmission distance and atmospheric transmission distance are not less than 60 m and 12 km, respectively.

  12. Dipole Moment of a Charged Particle Trapped at the Air-Water Interface.

    PubMed

    Bossa, Guilherme Volpe; Bohinc, Klemen; Brown, Matthew A; May, Sylvio

    2016-07-07

    The interaction between two charged particles (such as nanoparticles or colloids) trapped at the air-water interface becomes dipolar at large separations. The corresponding dipole moment can be modeled by considering a single point charge located exactly at the interface, but this model fails to correctly predict the dipole moment's dependence on the salt concentration in the aqueous medium. We extend the single point charge model to two point charges that are separated by a fixed distance and are located at the air-water interface, with one charge being immersed in air and the other in the solvent. The two point charges represent the surface charges at the air-exposed and water-exposed regions of an interface-trapped particle. The two point charges also account for the spatial extension of the particle. On the basis of the Debye-Hückel model, we derive mathematical expressions for the interaction between two pairs of charges and discuss the salt concentration dependence of the dipolar moment at large separations. Our results reveal a residual dipole moment in the limit of large salt content that originates from the charge attached to the air-exposed region of the particle. We discuss nonlinear screening effects and compare the predicted dipolar moments with recent experimental results.

  13. Separating Octadecyltrimethoxysilane Hydrolysis and Condensation at the Air/Water Interface through Addition of Methyl Stearate

    PubMed Central

    Britt, David W.; Hlady, Vladimir

    2012-01-01

    The hydrolysis and condensation of octadecyltrimethoxysilane (OTMS) at the air/water interface were monitored through molecular area changes at a constant surface pressure of 10 mN/m. The onset of condensation was delayed through the addition of methyl stearate (SME) acting as an inert filler molecule. In the absence of SME, complete gelation of OTMS required 30 h, during which time OTMS condensation occurred concomitantly with hydrolysis. In the presence of SME, the OTMS monolayer gelation rate increased in proportion to the amount of SME present. A 1:6 OTMS:SME molar ratio resulted in monolayer gelation within 30 min, suggesting completion of monomer hydrolysis prior to condensation. These findings indicate that lability of OTMS to hydrolysis at the air/water interface is governed by steric and conformational constraints at the silicon atom site, with monomeric OTMS being much more reactive than oligomeric OTMS. Fluorescence microscope images demonstrated that the OTMS condensed domain size also decreased with increasing SME concentrations, further implicating SME’s role as an inert filler. PMID:25132807

  14. Mechanisms of Polyelectrolyte Enhanced Surfactant Adsorption at the Air-Water Interface

    PubMed Central

    Stenger, Patrick C.; Palazoglu, Omer A.; Zasadzinski, Joseph A.

    2009-01-01

    Chitosan, a naturally occurring cationic polyelectrolyte, restores the adsorption of the clinical lung surfactant Survanta to the air-water interface in the presence of albumin at much lower concentrations than uncharged polymers such as polyethylene glycol. This is consistent with the positively charged chitosan forming ion pairs with negative charges on the albumin and lung surfactant particles, reducing the net charge in the double-layer, and decreasing the electrostatic energy barrier to adsorption to the air-water interface. However, chitosan, like other polyelectrolytes, cannot perfectly match the charge distribution on the surfactant, which leads to patches of positive and negative charge at net neutrality. Increasing the chitosan concentration further leads to a reduction in the rate of surfactant adsorption consistent with an over-compensation of the negative charge on the surfactant and albumin surfaces, which creates a new repulsive electrostatic potential between the now cationic surfaces. This charge neutralization followed by charge inversion explains the window of polyelectrolyte concentration that enhances surfactant adsorption; the same physical mechanism is observed in flocculation and re-stabilization of anionic colloids by chitosan and in alternate layer deposition of anionic and cationic polyelectrolytes on charged colloids. PMID:19366599

  15. Molecular adsorption steers bacterial swimming at the air/water interface.

    PubMed

    Morse, Michael; Huang, Athena; Li, Guanglai; Maxey, Martin R; Tang, Jay X

    2013-07-02

    Microbes inhabiting Earth have adapted to diverse environments of water, air, soil, and often at the interfaces of multiple media. In this study, we focus on the behavior of Caulobacter crescentus, a singly flagellated bacterium, at the air/water interface. Forward swimming C. crescentus swarmer cells tend to get physically trapped at the surface when swimming in nutrient-rich growth medium but not in minimal salt motility medium. Trapped cells move in tight, clockwise circles when viewed from the air with slightly reduced speed. Trace amounts of Triton X100, a nonionic surfactant, release the trapped cells from these circular trajectories. We show, by tracing the motion of positively charged colloidal beads near the interface that organic molecules in the growth medium adsorb at the interface, creating a high viscosity film. Consequently, the air/water interface no longer acts as a free surface and forward swimming cells become hydrodynamically trapped. Added surfactants efficiently partition to the surface, replacing the viscous layer of molecules and reestablishing free surface behavior. These findings help explain recent similar studies on Escherichia coli, showing trajectories of variable handedness depending on media chemistry. The consistent behavior of these two distinct microbial species provides insights on how microbes have evolved to cope with challenging interfacial environments.

  16. Bovine insulin-phosphatidylcholine mixed Langmuir monolayers: behavior at the air-water interface.

    PubMed

    Pérez-López, S; Blanco-Vila, N M; Vila-Romeu, N

    2011-08-04

    The behavior of the binary mixed Langmuir monolayers of bovine insulin (INS) and phosphatidylcholine (PC) spread at the air-water interface was investigated under various subphase conditions. Pure and mixed monolayers were spread on water, on NaOH and phosphate-buffered solutions of pH 7.4, and on Zn(2+)-containing solutions. Miscibility and interactions between the components were studied on the basis of the analysis of the surface pressure (π)-mean molecular area (A) isotherms, surface compression modulus (C(s)(-1))-π curves, and plots of A versus mole fraction of INS (X(INS)). Our results indicate that intermolecular interactions between INS and PC depend on both the monolayer state and the structural characteristics of INS at the interface, which are strongly influenced by the subphase pH and salt content. Brewster angle microscopy (BAM) was applied to investigate the peptide aggregation pattern at the air-water interface in the presence of the studied lipid under any experimental condition investigated. The influence of the lipid on the INS behavior at the interface strongly depends on the subphase conditions.

  17. Studies on behaviors of dipalmitoylposphatidylcholine and bilirubin in mixed monolayer at the air/water interface

    NASA Astrophysics Data System (ADS)

    Shen, Yuhua; Tang, Yufeng; Xie, Anjian; Zhu, Jinmiao; Li, Shikuo; Zhang, Yong

    2006-06-01

    Mixed monolayers of dipalmitoylposphatidylcholine (DPPC) and bilirubin (BR) were prepared on different subphases. The properties of DPPC/BR monolayer, such as collapse pressure ( πcoll), limiting area per molecule ( Alim), surface compressibility modulus, free energy (Δ Gmix) and excess free energy (Δ Gex), were investigated based on the analysis of the surface pressure-area isotherms on pure water. The results showed that DPPC and BR were miscible and formed non-ideal mixed monolayers at the air/water interface. With the molar fraction of BR ( XBR) increasing, the LE-LC coexistence region of DPPC monolayer was eliminated gradually. The DPPC/BR complex (M D-B) of 1:2 stoichiometry formed as a result of the strong hydrogen bonds between the polar groups of DPPC and BR. The studies of effects of pH values and calcium ions in subphase on the DPPC/BR monolayers showed that the mixed monolayer became expanded on alkali aqueous solution and on 1 mmol/L CaCl 2 aqueous solution. The orientation of DPPC and BR at air/water interface was also discussed.

  18. An air-water interfacial area based variable tortuosity model for unsaturated sands

    SciTech Connect

    Khaleel, Raziuddin; Saripalli, Prasad

    2006-05-01

    Based on Kozeny-Carman equation for saturated media permeability, a new model is developed for the prediction of unsaturated hydraulic conductivity, K as a function of moisture content, ?. The K(???) estimates are obtained using laboratory measurements of moisture retention and saturated hydraulic conductivity, and a saturation-dependent tortuosity based on the immiscible fluid (air-water) interfacial area. Tortuosity (?a) for unsaturated media is defined as aaw/aaw,o (ratio of the specific air-water interfacial area of a real and the corresponding idealized porous medium). A correspondence between the real and idealized media is established by using the laboratory-measured soil moisture retention curve to calculate the interfacial area. The general trend in prediction of ?a as a function water saturation is in agreement with similar recent predictions based on diffusion theory. Unsaturated hydraulic conductivities measured for a number of coarse-textured, repacked Hanford sediments agree well with predictions based on the modified Kozeny-Carman relation. Because of the use of saturated hydraulic conductivity, a slight bias is apparent in measured and predicted K at low ?. While the modified Kozeny-Carman relation was found to be reasonably accurate in predicting K(??) for the repacked, sandy soils considered in this study, a further testing of the new model for undisturbed sediments and other soil textures would be useful.

  19. Transient natural and surface-tension-driven convection in a two-layer gas-and-liquid enclosure with nonuniform radiative transfer

    NASA Technical Reports Server (NTRS)

    Abramzon, B.; Edwards, D. K.; Sirignano, W. A.

    1986-01-01

    A numerical study has been made of transient heat transfer and fluid flow in a cylindrical enclosure containing a two-layer gas-and-liquid system. The geometric configuration and the boundary conditions of the problem are relevant to the analysis of the preignition processes during the fire accident situation involving a pool of liquid fuel in the vicinity of an ignition source. It is demonstrated that the effects of the natural and thermocapillary convection, radiative transfer, thermal inertia and conduction of the walls bounding the enclosure, as well as, the magnitude of the gravity field play important roles in the development of the temperature and velocity fields in the container.

  20. Air-Water Exchange of N2 and O2 from In Situ Measurements in the Subarctic and Subtropical Pacific Oceans: Oxygen Flux and Net Biological Production

    NASA Astrophysics Data System (ADS)

    Emerson, S.

    2008-12-01

    In-situ measurements of wind speed, atmospheric pressure, surface-ocean total dissolved gas pressure and oxygen concentration are used to determine the flux of nitrogen and oxygen between the ocean and atmosphere in the subarctic and subtropical Pacific Oceans. Measurements were made hourly over a period of about one year on surface moorings at the Hawaii Ocean Time series (HOT) in 2005 and at Station P in 2007. Gas pressures in the mixed layer were determined using a gas tension device (GTD) and an oxygen sensor calibrated by Winkler O2 titrations. The pressures of nitrogen and oxygen vary smoothly within a few percent of atmospheric saturation in the subtropical Pacific Ocean, but in the subarctic surface waters these values are punctuated by very rapid excursions caused by storms. The primary flux of oxygen in the upper ocean is between the ocean and atmosphere. We use a simple ocean mixed-layer model to determine this flux and estimate the net biological oxygen production at these sites. Assuming that the net biological oxygen and carbon production are stoichiometrically related over an annual cycle, this method provides a measure of the annual carbon export from the mixed layer, an important component of the ocean's role in the global carbon cycle. There is net biological O2 production most of the year in the subtropical ocean; however, little evidence of net O2 production in the wintertime in the subarctic Pacific. This contrasts with earlier 14C primary production measurements which indicate that wintertime production is about half that in summer at both locations. Annual estimates of biologically produced carbon export at these two sites will be contrasted at the presentation in the fall meeting. This research indicates that it should be possible to derive estimates of the net annual air-water oxygen fluxes caused by biological production at any location of the open ocean where there is a surface mooring. Large, abrupt atmospheric pressure changes (up to 50

  1. Particle monolayer formation with arrayed structure by PMMA-grafted polystyrene Latex at the air-water interface.

    PubMed

    Mouri, Emiko; Terada, Motokazu; Koga, Ryosuke; Karakawa, Hiroyuki; Yoshinaga, Kohji

    2010-09-01

    The structure of the particle monolayer formed by the polymer-grafted latex particle at the air-water interface was estimated mainly by pi--A isotherm measurement and SEM observation to examine the effect of core particle characteristics and to generalize the key factors in determining the polymer-grafted particle monolayer structure. Methyl methacrylate (MMA) was polymerized from the polystyrene latex (PSL) surface by atom transfer radical polymerization to give a PMMA-grafted PSL (PSL-PMMA) with a relatively high graft density of about 0.2 nm-2. We obtained PSL-PMMA with PMMA of different molecular weights but almost the same graft density. The onset area of increasing surface pressure in pi-A isotherm was in agreement with the value of effective radius of PSL-PMMA with quite extended PMMA chains. The particle monolayer structure deposited on the substrate was strongly dependent on the molecular weight of the grafted PMMA. The aggregation size was reduced with increasing molecular weight and a lattice-like structure was observed for PSL-PMMA monolayer with a high molecular weight PMMA. The interparticle distance was decreased and structure becomes ordered with increasing surface pressure. The monolayer structure obtained here was consistent with that of the PMMA-grafted silica particle system. We also synthesized polystyrene (PS)-grafted PMMA latex (PML-PS) and compared the two systems. We confirmed that the lattice-like structure depended on the nature of the grafted PMMA chain, not the core particle characteristics.

  2. The Influence of Surface Tension Gradients on Surfactant Tracer Measurement of Air-Water Interfacial Area in Porous Media

    NASA Astrophysics Data System (ADS)

    Costanza-Robinson, M. S.; Estabrook, B. D.; Henry, E. J.

    2009-12-01

    Air-water interfacial area (AI) in porous media is an important factor governing equilibrium contaminant retention, as well as the kinetics of interphase mass transfer, such as delivery of oxygen to roots and volatilization of methane from landfills. Despite this importance, significant method-dependence is observed among techniques used to determine AI in porous media. In this work, possible low bias in conventional aqueous interfacial-partitioning tracer methodology (IPT) was examined by comparison of IPT-AI estimates with more direct estimates obtained using synchrotron X-ray microtomographic (µCT) imaging. Sodium dodecyl benzene sulfonate and pentafluorobenzoate were used as interfacial and nonreactive tracers, respectively, to measure AI at three water saturations (Sw) in a natural fine sand. IPT-AI exhibited expected trends, with higher areas associated with drier conditions, but the magnitude of AI was as much as 50% lower than those measured by µCT. IPT-AI values for the driest system agreed most closely with microtomography data. Real-time system mass measurements revealed that upon introduction of the surfactant tracer, system Sw decreased by 15-30%; the driest system exhibited the least drainage. This drainage is consistent with a reduction in capillarity caused by the lower surface tension of the surfactant solution as compared to the surfactant-free resident fluid. Drainage in the direction of flow would lead to earlier breakthrough of the surfactant tracer and a lower AI-estimate. In fact, the magnitude of drainage and magnitude of AI-underestimation relative to µCT were qualitatively correlated. Although this effect was expected, its magnitude and potential influence on AI was previously unknown and was larger than anticipated.

  3. Determining Spatial Distribution And Air-Water Exchange Of Polycyclic Aromatic Hydrocarbons In Stormwater Runoff Catchment Basins

    NASA Astrophysics Data System (ADS)

    Kasaraneni, V. K.; Schifman, L. A.; Craver, V.; Boving, T. B.

    2014-12-01

    Stormwater runoff is a conduit for several pollutants such as polycyclic aromatic hydrocarbons (PAHs) in to surface and ground water bodies. The control of runoff and pollutants is typically addressed by best management practices (BMPs), such as retention/detention ponds or catchment basins in general. The effectiveness of catchment basins in reducing the volume of runoff and removal of some contaminants has been established. However, very little is known about the fate of the contaminants settled within these structures. In coastal regions and places with shallow groundwater tables accumulation of high concentrations of PAHs in the bottom sediments poses a potential threat for groundwater contamination. The concentrations of PAHs accumulated in the sediments of these catchment basins will primarily depend on the sources of runoff origin and the surrounding land use. Due to the physico-chemical characteristics of PAHs, their transport not only can occur in the liquid and solid phase, but it is also possible that gaseous emissions can be produced from BMP systems. For the purpose of this study, five stormwater catchment basins along the I-95 corridor in Rhode Island were selected based on the stormwater runoff origin and covering (industrial, urban, highway, and commercial) land uses. To study the stratification of PAHs sediment cores one foot were collected and analyzed for 31PAHs (16 EPA parent PAH and 15 methylated PAHs). In order to determine whether the catchment basins are a source of atmospheric pollution polyethylene passive samplers were deployed to determine the freely dissolved PAHs in the water column and gas phase PAHs at the air-water interface. This presentation will describe how PAH fluxes move between three environmental compartments (sediments, water column, atmosphere) within the five stormwater catchment basins. Further, it will be investigated whether these BMP structures can act as contaminant sources rather than sinks and whether BMP

  4. An experimental and analytical investigation into the performance of centrifugal pumps operating with air-water mixtures

    NASA Astrophysics Data System (ADS)

    Sterrett, John Douglas

    1994-01-01

    An investigation was made into the performance of centrifugal pumps when two-phase non-condensable mixtures of gas and liquid are flowing. This problem is encountered during loss-of-coolant accidents in nuclear reactor systems and in the pumping of oil where natural gas may be present in the mixture. Analytical and experimental techniques were used to address the issues of scaling between a model and a prototype pump and the validity of the single-phase pump affinity laws when two-phase flows are present. The results from this effort have also provided insight into the physical phenomena which cause the degradation in pump performance. An analytical model for the motion of a single bubble through a pump impeller is provided. The results from this fundamental problem show that the Coriolis and buoyancy forces are important in describing the kinematics of a gas phase. These results show that dynamic similitude is not preserved between a model and prototype impeller when the standard single-phase pump scaling relationships are used. The motion of a single bubble is also shown to be influenced by the magnitude of the pump suction pressure. The results from an extensive series of air-water two phase pump tests are provided. A 1/4 scale pump, modeled after the Savannah River Site K-reactor pumps, was tested over a wide range of pump speeds, flow rates, and suction pressures. These results indicate that the single-phase pump affinity laws are not applicable to two-phase pump flows and that the magnitude of the pump suction pressure is an important quantity in determining the pump performance. A second analytical model is developed for two-phase flow through a pump impeller. The results from this one-dimensional, two-fluid, non-homogeneous streamline model show good agreement with the experimental data. The model results support the experimental data in showing that the single-phase pump affinity relationships are not valid for two-phase pump flows and that dynamic

  5. Monitoring gas retention and slurry transport during the transfer of waste from Tank 241-C-106 to Tank 241-AY-102

    SciTech Connect

    Stewart, C.W.; Erian, F.F.; Meyer, P.A.

    1997-07-01

    The retained gas volume can be estimated by several methods. All of these methods have significant uncertainties, but together they form a preponderance of evidence that describes the gas retention behavior of the tank. The methods are (1) an increase in nonconvective layer thickness; (2) a waste surface level rise (surface level effect [SLE] model); (3) the barometric pressure effect (BPE model); (4) direct void measurement; and (5) the consequences of the transfer process. The nonconvective layer thickness can be determined with sufficient accuracy to describe the overall waste configuration by means of temperature profiles or densitometer indications. However, the presence of a nonconvective layer does not necessarily indicate significant gas retention, and small changes in layer thickness that could quantify gas retention cannot be detected reliably with the methods available. The primary value of this measurement is in establishing the actual {open_quotes}fluffing factor{close_quotes} for thermal calculations. Surface level rise is not a useful measure of gas retention in Tank 241-C-106 (C-106) since the waste level fluctuates with regular makeup water additions. In Tank 241-AY-102 (AY-102) with the existing ventilation system it should be possible to determine the gas retention rate within 30-60% uncertainty from the surface level rise, should a significant rise be observed. The planned ventilation system upgrades in AY- 102 will greatly reduce the exhaust flow and the headspace humidity, and the evaporation rate should be significantly lower when transfers begin. This could reduce the uncertainty in gas retention rate estimates to around {+-} 10%.

  6. 40 CFR 65.144 - Fuel gas systems and processes to which storage vessel, transfer rack, or equipment leak...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... vapors to a fuel gas system or process shall open to the atmosphere during loading. Pressure relief... to the atmosphere. (b) Fuel gas system and process compliance determination. (1) If emissions...

  7. Estimating the gas transfer velocity: a prerequisite for more accurate and higher resolution GHG fluxes (lower Aare River, Switzerland)

    NASA Astrophysics Data System (ADS)

    Sollberger, S.; Perez, K.; Schubert, C. J.; Eugster, W.; Wehrli, B.; Del Sontro, T.

    2013-12-01

    Currently, carbon dioxide (CO2) and methane (CH4) emissions from lakes, reservoirs and rivers are readily investigated due to the global warming potential of those gases and the role these inland waters play in the carbon cycle. However, there is a lack of high spatiotemporally-resolved emission estimates, and how to accurately assess the gas transfer velocity (K) remains controversial. In anthropogenically-impacted systems where run-of-river reservoirs disrupt the flow of sediments by increasing the erosion and load accumulation patterns, the resulting production of carbonic greenhouse gases (GH-C) is likely to be enhanced. The GH-C flux is thus counteracting the terrestrial carbon sink in these environments that act as net carbon emitters. The aim of this project was to determine the GH-C emissions from a medium-sized river heavily impacted by several impoundments and channelization through a densely-populated region of Switzerland. Estimating gas emission from rivers is not trivial and recently several models have been put forth to do so; therefore a second goal of this project was to compare the river emission models available with direct measurements. Finally, we further validated the modeled fluxes by using a combined approach with water sampling, chamber measurements, and highly temporal GH-C monitoring using an equilibrator. We conducted monthly surveys along the 120 km of the lower Aare River where we sampled for dissolved CH4 (';manual' sampling) at a 5-km sampling resolution, and measured gas emissions directly with chambers over a 35 km section. We calculated fluxes (F) via the boundary layer equation (F=K×(Cw-Ceq)) that uses the water-air GH-C concentration (C) gradient (Cw-Ceq) and K, which is the most sensitive parameter. K was estimated using 11 different models found in the literature with varying dependencies on: river hydrology (n=7), wind (2), heat exchange (1), and river width (1). We found that chamber fluxes were always higher than boundary

  8. Sensitivity of Global Sea-Air CO2 Flux to Gas Transfer Algorithms, Climatological Wind Speeds, and Variability of Sea Surface Temperature and Salinity

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.; Signorini, Sergio

    2002-01-01

    Sensitivity analyses of sea-air CO2 flux to gas transfer algorithms, climatological wind speeds, sea surface temperatures (SST) and salinity (SSS) were conducted for the global oceans and selected regional domains. Large uncertainties in the global sea-air flux estimates are identified due to different gas transfer algorithms, global climatological wind speeds, and seasonal SST and SSS data. The global sea-air flux ranges from -0.57 to -2.27 Gt/yr, depending on the combination of gas transfer algorithms and global climatological wind speeds used. Different combinations of SST and SSS global fields resulted in changes as large as 35% on the oceans global sea-air flux. An error as small as plus or minus 0.2 in SSS translates into a plus or minus 43% deviation on the mean global CO2 flux. This result emphasizes the need for highly accurate satellite SSS observations for the development of remote sensing sea-air flux algorithms.

  9. Development of Negative Ion Proton Transfer Reaction Time-of-Flight Mass Spectrometry (NI-PTR TOFMS) for the Measurement of Gas Phase Acids in the Troposphere

    NASA Astrophysics Data System (ADS)

    Cochran, A. K.; Begashaw, I.; Jessamy, C.; Bililign, S.

    2008-12-01

    We report on the progress and feasibility tests of an on-line time-of-flight (TOF) technique for negative ion proton transfer reactive mass spectrometry (NI-PTRMS) for the measurement of trace gas phase carboxylic acids. Acetate ions are produced via alpha particle ionization of acetic acid through a polonium-210. The target carboxylic gases undergo proton transfer reactions with the acetate ions due to the affinity differences. This technique has the potential for improvement in mass resolution as well as shorter integration periods which lead to faster measurements with greater sensitivity. We report on initial instrument sensitivity, calibrations, and clustering effects of some known gases as well as some carboxylic acids for some comparisons with recent negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) results. This work is supported in part by both NOAA (Award NA06OAR4810187) and NSF (award 0803016).

  10. Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column

    SciTech Connect

    Gbewonyo, K.; Wang, D.I.C.

    1983-12-01

    The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (k /SUB L/ a) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.

  11. Experimental Heat Transfer Coefficients and Friction Factors in a Rib-Roughened Leading-Edge Cooling Cavity of a Gas Turbine Airfoil

    NASA Astrophysics Data System (ADS)

    Hagan, Peter

    A gas turbine airfoil contains multiple coolant passageways. These passages usually have rib roughened wall surfaces in order to increase the heat transfer from the blade to the cooling air. Auxiliary power and compressed air is very valuable in a gas turbine, therefore low pumping power requirements are crucial. The thermal performance of three different coolant channel geometries with three different rib sizes was investigated. Heat transfer calculations were performed for Reynolds numbers ranging from 6,000 to 40,000. The performance characteristics were calculated through the use of the convective heat transfer coefficient and the friction factor. In this study, the most desirable characteristics are a high heat transfer coefficient and minimal pumping power requirements. The thermal performance of each case was determined by comparing the average Nusselt numbers to the friction factor ratio. The resulting value was then plotted against the Reynolds number for each case. The trending data indicated thermal efficiency decreases with an increasing Reynolds number for all cases. The picture data shows increased thermal efficiency at larger distances from the nose portion of the cavity. In addition, thermal efficiency was higher at the half distance of the rib pitch while areas close to the ribs saw a lower thermal efficiency. The following experimental data will show that Rig 2 and 3 are the most thermally efficient geometries, with Rig 2 requiring lower pumping power and Rig 3 having a higher average Nusselt number.

  12. Partially ionized gas flow and heat transfer in the separation, reattachment, and redevelopment regions downstream of an abrupt circular channel expansion.

    NASA Technical Reports Server (NTRS)

    Back, L. H.; Massier, P. F.; Roschke, E. J.

    1972-01-01

    Heat transfer and pressure measurements obtained in the separation, reattachment, and redevelopment regions along a tube and nozzle located downstream of an abrupt channel expansion are presented for a very high enthalpy flow of argon. The ionization energy fraction extended up to 0.6 at the tube inlet just downstream of the arc heater. Reattachment resulted from the growth of an instability in the vortex sheet-like shear layer between the central jet that discharged into the tube and the reverse flow along the wall at the lower Reynolds numbers, as indicated by water flow visualization studies which were found to dynamically model the high-temperature gas flow. A reasonably good prediction of the heat transfer in the reattachment region where the highest heat transfer occurred and in the redevelopment region downstream can be made by using existing laminar boundary layer theory for a partially ionized gas. In the experiments as much as 90 per cent of the inlet energy was lost by heat transfer to the tube and the nozzle wall.

  13. Ionic Nature of a Gemini Surfactant at the Air/Water Interface.

    PubMed

    Phan, Chi M; Nguyen, Cuong V; Nakahara, Hiromichi; Shibata, Osamu; Nguyen, Thanh V

    2016-12-06

    The ionic state of an adsorbed gemini surfactant at the air/water interface was investigated using a combination of surface potential and surface tension data. The combined model was developed and successfully described the experimental data. The results verified the existence of three ionic states of the gemini surfactant in the interfacial zone. Furthermore, the model can quantify the adsorbed concentrations of these species. At low concentrations, the fully dissociated state dominates the adsorption. At high concentrations, the fully associated state dominates, accounting for up to 80% of the total adsorption. In the middle range, the adsorption is dominated by the partially associated state, which has a maximum percentage of 80% at a critical micelle concentration of 0.5. The variation in the ionic state is a unique characteristic of gemini surfactants, which can be the underlying mechanism for their advantages over conventional surfactants.

  14. Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface

    PubMed Central

    Banerjee, R.; Sanyal, M. K.; Bera, M. K.; Gibaud, A.; Lin, B.; Meron, M.

    2015-01-01

    We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initial monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate. PMID:25687953

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

    SciTech Connect

    Vassallo, P.

    1997-07-01

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

  16. Study of interfacial area transport and sensitivity analysis for air-water bubbly flow

    SciTech Connect

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

    2000-09-01

    The interfacial area transport equation applicable to the bubbly flow is presented. The model is evaluated against the data acquired by the state-of-the-art miniaturized double-sensor conductivity probe in an adiabatic air-water co-current vertical test loop under atmospheric pressure condition. In general, a good agreement, within the measurement error of plus/minus 10%, is observed for a wide range in the bubbly flow regime. The sensitivity analysis on the individual particle interaction mechanisms demonstrates the active interactions between the bubbles and highlights the mechanisms playing the dominant role in interfacial area transport. The analysis employing the drift flux model is also performed for the data acquired. Under the given flow conditions, the distribution parameter of 1.076 yields the best fit to the data.

  17. Novel Behavior in Self-Assembled Superparamagnetic Nanoparticle Monolayers at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Stanley, Jacob; Boucheron, Leandra; Dai, Yeling; Lin, Binhua; Meron, Mati; Shpyrko, Oleg

    2013-03-01

    Iron oxide nanoparticles, coated with an oleic acid ligand, have been found to form self-assembled monolayers when deposited at the air-water interface. Even for low particle densities these particles aggregate into hexagonally close-packed islands which merge into a uniform layer at higher densities. Using Grazing Incidence Small Angle X-Ray Scattering (GISAXS) we were able to measure the first through fifth order diffraction peaks. By analyzing the positions and shapes of these peaks we investigated the in-plane structure of these monolayers and characterized how the structure changes as a function of compression in a Langmuir-Blodgett trough. Since iron oxide nanoparticles are known to be super-paramagnetic, we sought to investigate the role magnetic effects may have on the interparticle interactions and ordering within the film. We performed Grazing Incidence Diffraction (GID) measurements on the film while varying an external magnetic field. We will discuss the results of our findings.

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

    SciTech Connect

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

    2000-08-01

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

  19. Denaturation resistance of beta-lactoglobulin in monomolecular films at the air-water interface.

    PubMed

    Lin, Jhih-Min; White, John W

    2009-10-29

    Using X-ray reflectometry we report strong differences in the denaturation response of beta-lactoglobulin adsorbed as a monomolecular film at the air-water interface from that observed in mixed denaturant/beta-lactoglobulin bulk solutions. Using the "flow trough" technique an isolated monomolecular film of the protein showed little change in structure when subjected to a 4.0 M guanidinium hydrochloride substrate. Unlike the bulk solution where a new protein layer structure appears, small changes in the protein packing and the roughness of the film are the only evidence of change. These parameters have been studied as a function of denaturant concentration and film quality. The strength of the response depends on the degree of perfection of the originally formed film; quickly formed films are more easily denatured. As the response is so subtle, possible interfering effects such as denaturant release of protein adsorbed on the trough have been quantified.

  20. Robust Gold Nanoparticle Sheets by Ligand Cross-Linking at the Air-Water Interface.

    PubMed

    Kosif, Irem; Kratz, Katrina; You, Siheng Sean; Bera, Mrinal K; Kim, Kyungil; Leahy, Brian; Emrick, Todd; Lee, Ka Yee C; Lin, Binhua

    2017-02-28

    We report the results of cross-linking of two-dimensional gold nanoparticle (Au-NP) assemblies at the air-water interface in situ. We introduce an aqueous soluble ruthenium benzylidene catalyst into the water subphase to generate a robust, elastic two-dimensional network of nanoparticles containing cyclic olefins in their ligand framework. The most striking feature of the cross-linked Au-NP assemblies is that the extended connectivity of the nanoparticles enables the film to preserve much of its integrity under compression and expansion, features that are absent in its non-cross-linked counterparts. The cross-linking process appears to "stitch" the nanoparticle crystalline domains together, allowing the cross-linked monolayers to behave like a piece of fabric under lateral compression.

  1. Structure of hydroxylated galactocerebrosides from myelin at the air-water interface.

    PubMed Central

    Graf, Karlheinz; Baltes, Hubert; Ahrens, Heiko; Helm, Christiane A; Husted, Cynthia A

    2002-01-01

    Hydroxy-galactocerebrosides (mixed chain length, constituent of myelin membranes) from bovine brain are investigated as monolayers at the air-water interface with isotherms, fluorescence microscopy, x-ray reflectivity and grazing incidence diffraction. With grazing incidence diffraction a monoclinic tilted chain lattice is found in the condensed phase. According to x-ray reflectivity, the longest chains protrude above the chain lattice and roughen the lipid/air interface. On compressing the chain lattice, the correlation length increases by approximately 65%; obviously, the sugar headgroups are flexible enough to allow for lattice deformation. With fluorescence experiments, small coexisting fluid and ordered domains are observed, and there is lipid dissolution into the subphase as well. The dissolved hydroxy-galactocerebroside molecules reenter on monolayer expansion. The electron density profiles derived from x-ray reflectometry (coherent superposition) show that the chain-ordering transition causes the molecules to grow into the subphase. PMID:11806931

  2. Two-dimensional crystallization of phthalocyanine pigments at the air/water interface

    SciTech Connect

    Gregory, B.W.; Vaknin, D.; Gray, J.D.; Cotton, T.M.; Struve, W.S. |; Ocko, B.M.

    1999-01-21

    Two-dimensional crystallization of highly planar phthalocyanine (Pc) pigments underneath the headgroups of a lipid Langmuir monolayer was observed and characterized by synchrotron X-ray diffraction at grazing angles of incidence (GID). The crystallization was achieved through spontaneous adsorption of positively charged, water-soluble Pc`s to a spread dihexadecyl phosphate (DHDP) monolayer at the air/water interface. Analysis of the GID and rod profiles show that the lipid, pigment, and counterions form a complex in which the pigment plane is tilted with respect to the liquid surface; this is consistent with previous independent X-ray reflectivity investigations. In addition, the two-dimensional crystalline order of DHDP monolayers on pure H{sub 2}O has been determined and an analysis of its structure both before and after complexation is presented.

  3. Measuring Air-water Interfacial Area for Soils Using the Mass Balance Surfactant-tracer Method

    PubMed Central

    Araujo, Juliana B.; Mainhagu, Jon; Brusseau, Mark L.

    2015-01-01

    There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the mass balance surfactant tracer method. An advantage of the mass-balance method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The mass-balance method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the mass-balance method for application to more complex porous media. The results indicate that interfacial areas measured with the mass-balance method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. PMID:25950136

  4. Crystalline self-assembly into monolayers of folded oligomers at the air-water interface

    PubMed

    Lederer; Godt; Howes; Kjaer; Als-Nielsen; Lahav; Wegner; Leiserowitz; Weissbuch

    2000-06-16

    Insertion of the 1,3-bis(ethynylene)benzene unit as a rigid spacer into a linear alkyl chain, thus separating the two resulting stems by 9 A. induces chain folding at the air-water interface. These folded molecules self-assemble into crystalline monolayers at this interface, with the plane of the folding unit almost perpendicular to the water surface, as determined by synchrotron grazing-incidence X-ray diffraction. Three distinct molecular shapes, of the types U, inverted U, and M, were obtained in the two-dimensional crystalline state, depending upon the number of spacer units, and the number and position of the hydrophilic groups in the molecule. The molecules form ribbons with a higher crystal coherence in the direction of stacking between the molecular ribbons, and a lower coherence along the ribbon direction. A similar molecule, but with a spacer unit that imposes a 5 A separation between alkyl chains, yields the conventional herringbone arrangement.

  5. Surface enhanced Raman scattering of a lipid Langmuir monolayer at the air-water interface.

    PubMed

    Mangeney, C; Dupres, V; Roche, Y; Felidj, N; Levi, G; Aubard, J; Bernard, S

    Surface enhanced Raman spectra were recorded from a phospholipid monolayer directly at the air-water interface. We used an organized monolayer of negatively charged tetramyristoyl cardiolipins as a template for the electrochemical generation of silver deposits. This two-dimensional electrodeposition of silver under potentiostatic control was the substrate for enhancement of Raman spectra. We report the optimized conditions for the Raman enhancement, the microscopic observations of the deposits, and their characterization by atomic force microscopy. Laser excitation at 514.5 nm leads to intense and reproducible surface enhanced Raman scattering spectra recorded in situ from one monolayer of cardiolipin, using 0.5 mol % of 10N nonyl acridine orange or 5 mol % of acridine in the film, and demonstrates the possibility of estimating the pH at the metal/phospholipidic film interface.

  6. Conformational changes of a calix[8]arene derivative at the air-water interface.

    PubMed

    de Miguel, Gustavo; Pedrosa, José M; Martín-Romero, María T; Muñoz, Eulogia; Richardson, Tim H; Camacho, Luis

    2005-03-10

    The particular behavior of a p-tert-butyl calix[8]arene derivative (C8A) has been studied at the air-water interface using surface pressure-area isotherms, surface potential-area isotherms, film relaxation measurements, Brewster angle microscopy (BAM), and infrared spectroscopy for Langmuir-Blodgett films. Thus, it is observed that the properties of the film, for example, isotherms, domain formation, and FTIR spectra, recorded during the first compression cycle differ appreciably from those during the second compression and following cycles. The results obtained are interpreted on the basis of the conformational changes of the C8A molecules by surface pressure, allowing us to inquire into the inter- and intramolecular interactions (hydrogen bonds) of those molecules. Thus, the compression induces changes in the kind of hydrogen bonds from intra- and intermolecular with other C8A molecules to hydrogen bonds with water molecules.

  7. Mechanical Stability of Polystyrene and Janus Particle Monolayers at the Air/Water Interface.

    PubMed

    Lenis, Jessica; Razavi, Sepideh; Cao, Kathleen D; Lin, Binhua; Lee, Ka Yee C; Tu, Raymond S; Kretzschmar, Ilona

    2015-12-16

    The compressional instability of particle-laden air/water interfaces is investigated with plain and surface-anisotropic (Janus) particles. We hypothesize that the amphiphilic nature of Janus particles leads to both anisotropic particle-particle and particle-interface interactions that can yield particle films with unique collapse mechanisms. Analysis of Langmuir isotherms and microstructural characterization of the homogeneous polystyrene particle films during compression reveal an interfacial buckling instability followed by folding, which is in good agreement with predictions from classical elasticity theory. In contrast, Janus particle films exhibit a different behavior during compression, where the collapse mode occurs through the subduction of the Janus particle film. Our results suggest that particle-laden films comprised of surface-anisotropic particles can be engineered to evolve new material properties.

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

    SciTech Connect

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

    1995-09-01

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

  9. Entropy of adsorption of mixed surfactants from solutions onto the air/water interface

    USGS Publications Warehouse

    Chen, L.-W.; Chen, J.-H.; Zhou, N.-F.

    1995-01-01

    The partial molar entropy change for mixed surfactant molecules adsorbed from solution at the air/water interface has been investigated by surface thermodynamics based upon the experimental surface tension isotherms at various temperatures. Results for different surfactant mixtures of sodium dodecyl sulfate and sodium tetradecyl sulfate, decylpyridinium chloride and sodium alkylsulfonates have shown that the partial molar entropy changes for adsorption of the mixed surfactants were generally negative and decreased with increasing adsorption to a minimum near the maximum adsorption and then increased abruptly. The entropy decrease can be explained by the adsorption-orientation of surfactant molecules in the adsorbed monolayer and the abrupt entropy increase at the maximum adsorption is possible due to the strong repulsion between the adsorbed molecules.

  10. Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface

    DOE PAGES

    Banerjee, R.; Sanyal, M. K.; Bera, M. K.; ...

    2015-02-17

    We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initialmore » monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.« less

  11. Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface

    SciTech Connect

    Banerjee, R.; Sanyal, M. K.; Bera, M. K.; Gibaud, A.; Lin, B.; Meron, M.

    2015-02-17

    We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initial monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.

  12. Thermodynamics of iodide adsorption at the instantaneous air-water interface

    NASA Astrophysics Data System (ADS)

    Stern, Abraham C.; Baer, Marcel D.; Mundy, Christopher J.; Tobias, Douglas J.

    2013-03-01

    We performed molecular dynamics simulations using both polarizable and non-polarizable force fields to study the adsorption of iodide to the air-water interface. A novel aspect of our analysis is that the progress of ion adsorption is measured as the distance from the instantaneous interface, which is defined by a coarse-graining scheme proposed recently by Willard and Chandler ["Instantaneous liquid interfaces," J. Phys. Chem. B 114, 1954-1958 (2010), 10.1021/jp909219k]. Referring structural and thermodynamic quantities to the instantaneous interface unmasks molecular-scale details that are obscured by thermal fluctuations when the same quantities are referred to an average measure of the position of the interface, such as the Gibbs dividing surface. Our results suggest that an ion adsorbed at the interface resides primarily in the topmost water layer, and the interfacial location of the ion is favored by enthalpy and opposed by entropy.

  13. Diffusive exchange of PAHs across the air-water interface of the Kaohsiung Harbor lagoon, Taiwan.

    PubMed

    Fang, Meng-Der; Lee, Chon-Lin; Jiang, Jheng-Jie; Ko, Fung-Chi; Baker, Joel E

    2012-11-15

    Instantaneous air-water polycyclic aromatic hydrocarbons (PAHs) exchange fluxes were calculated in 22 pairs of ambient air and water samples from Kaohsiung Harbor lagoon, from December 2003 to January 2005. The highest net volatilization (3135 ng m(-2) day(-1)) and absorptive (-1150 ng m(-2) day(-1)) fluxes in the present study were obtained for the three-ring PAH phenanthrene on 7 April and 27 January 2004, respectively. All PAH diffusive fluxes for three-ring PAHs except phenanthrene were mainly volatilization exchange across the air-water interface. Phenanthrene and the four-ring PAHs were absorbed primarily from the atmosphere and deposited to the surface water, although some minor volatilization fluxes were also observed. Differences in flux magnitude and direction between the dry and wet seasons were also evident for PAHs. Strong absorptive/weaker volatilization PAH fluxes occurred in the dry season, but the opposite was found in the wet season. The mean daily PAH diffusive fluxes were an in flux of -635 ng m(-2) day(-1) in the dry season and an efflux of 686 ng m(-2) day(-1) in the wet season. The integrated absorbed and emitted fluxes of PAHs for harbor lagoon surface waters in the dry and wet seasons were 3.1 kg and 3.4 kg, respectively. Different from water bodies located in temperate zone, phenanthrene diffusive fluxes in Kaohsiung Harbor lagoon was favored in volatilization from surface waters during the wet season (April to September) because of scavenging by precipitation and dilution by prevailing southwesterly winds. In addition, this study used both of salinity and temperature to improve estimation of Henry's law constants (H) of PAHs in a tropical coastal area and show that correction for salinity produced 13-15% of differences in H values.

  14. Catechol oxidation by ozone and hydroxyl radicals at the air-water interface.

    PubMed

    Pillar, Elizabeth A; Camm, Robert C; Guzman, Marcelo I

    2014-12-16

    Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air-water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon the encounter of 40 ppbv-6.0 ppmv O3(g) with microdroplets containing [catechol] = 1-150 μM. While the previous pathway results in the instantaneous formation of mono- and polyhydroxylated aromatic rings (PHA) and chromophoric mono- and polyhydroxylated quinones (PHQ), a different channel produces oxo- and dicarboxylic acids of low molecular weight (LMW). The cleavage of catechol occurs at the 1,2 carbon-carbon bond at the air-water interface through the formation of (1) an ozonide intermediate, (2) a hydroperoxide, and (3) cis,cis-muconic acid. However, variable [catechol] and [O3(g)] can affect the ratio of the primary products (cis,cis-muconic acid and trihydroxybenzenes) and higher order products observed (PHA, PHQ, and LMW oxo- and dicarboxylic acids). Secondary processing is confirmed by mass spectrometry, showing the production of crotonic, maleinaldehydic, maleic, glyoxylic, and oxalic acids. The proposed pathway can contribute precursors to aqueous SOA (AqSOA) formation, converting aromatic hydrocarbons into polyfunctional species widely found in tropospheric aerosols with light-absorbing brown carbon.

  15. Numerical and experimental study of dissociation in an air-water single-bubble sonoluminescence system.

    PubMed

    Puente, Gabriela F; Urteaga, Raúl; Bonetto, Fabián J

    2005-10-01

    We performed a comprehensive numerical and experimental analysis of dissociation effects in an air bubble in water acoustically levitated in a spherical resonator. Our numerical approach is based on suitable models for the different effects considered. We compared model predictions with experimental results obtained in our laboratory in the whole phase parameter space, for acoustic pressures from the bubble dissolution limit up to bubble extinction. The effects were taken into account simultaneously to consider the transition from nonsonoluminescence to sonoluminescence bubbles. The model includes (1) inside the bubble, transient and spatially nonuniform heat transfer using a collocation points method, dissociation of O2 and N2, and mass diffusion of vapor in the noncondensable gases; (2) at the bubble interface, nonequilibrium evaporation and condensation of water and a temperature jump due to the accommodation coefficient; (3) in the liquid, transient and spatially nonuniform heat transfer using a collocation points method, and mass diffusion of the gas in the liquid. The model is completed with a Rayleigh-Plesset equation with liquid compressible terms and vapor mass transfer. We computed the boundary for the shape instability based on the temporal evolution of the computed radius. The model is valid for an arbitrary number of dissociable gases dissolved in the liquid. We also obtained absolute measurements for R(t) using two photodetectors and Mie scattering calculations. The robust technique used allows the estimation of experimental results of absolute R0 and P(a). The technique is based on identifying the bubble dissolution limit coincident with the parametric instability in (P(a),R0) parameter space. We take advantage of the fact that this point can be determined experimentally with high precision and replicability. We computed the equilibrium concentration of the different gaseous species and water vapor during collapse as a function of P(a) and R0. The

  16. Numerical and experimental study of dissociation in an air-water single-bubble sonoluminescence system

    NASA Astrophysics Data System (ADS)

    Puente, Gabriela F.; Urteaga, Raúl; Bonetto, Fabián J.

    2005-10-01

    We performed a comprehensive numerical and experimental analysis of dissociation effects in an air bubble in water acoustically levitated in a spherical resonator. Our numerical approach is based on suitable models for the different effects considered. We compared model predictions with experimental results obtained in our laboratory in the whole phase parameter space, for acoustic pressures from the bubble dissolution limit up to bubble extinction. The effects were taken into account simultaneously to consider the transition from nonsonoluminescence to sonoluminescence bubbles. The model includes (1) inside the bubble, transient and spatially nonuniform heat transfer using a collocation points method, dissociation of O2 and N2 , and mass diffusion of vapor in the noncondensable gases; (2) at the bubble interface, nonequilibrium evaporation and condensation of water and a temperature jump due to the accommodation coefficient; (3) in the liquid, transient and spatially nonuniform heat transfer using a collocation points method, and mass diffusion of the gas in the liquid. The model is completed with a Rayleigh-Plesset equation with liquid compressible terms and vapor mass transfer. We computed the boundary for the shape instability based on the temporal evolution of the computed radius. The model is valid for an arbitrary number of dissociable gases dissolved in the liquid. We also obtained absolute measurements for R(t) using two photodetectors and Mie scattering calculations. The robust technique used allows the estimation of experimental results of absolute R0 and Pa . The technique is based on identifying the bubble dissolution limit coincident with the parametric instability in (Pa,R0) parameter space. We take advantage of the fact that this point can be determined experimentally with high precision and replicability. We computed the equilibrium concentration of the different gaseous species and water vapor during collapse as a function of Pa and R0 . The model

  17. Coherent motions and time scales that control heat and mass transfer at wind-swept water surfaces

    NASA Astrophysics Data System (ADS)

    Turney, D. E.

    2016-12-01

    Forecast of the heat and chemical budgets of lakes, rivers, and oceans requires improved predictive understanding of air-water interfacial transfer coefficients. Here we present laboratory observations of the coherent motions that occupy the air-water interface at wind speeds (U10) 1.1-8.9 m/s. Spatiotemporal near-surface velocity data and interfacial renewal data are made available by a novel flow tracer method. The relative activity, velocity scales, and time scales of the various coherent interfacial motions are measured, namely for Langmuir circulations, streamwise streaks, nonbreaking wind waves, parasitic capillary waves, nonturbulent breaking wind waves, and turbulence-generating breaking wind waves. Breaking waves exhibit a sudden jump in streamwise interfacial velocity wherein the velocity jumps up to exceed the wave celerity and destroys nearby parasitic capillary waves. Four distinct hydrodynamic regimes are found to exist between U10 = 0 and 8.9 m/s, each with a unique population balance of the various coherent motions. The velocity scales, time scales, and population balance of the different coherent motions are input to a first-principles gas transfer model to explain the waterside transfer coefficient (kw) as well as experimental patterns of temperature and gas concentration. The model mixes concepts from surface renewal and divergence theories and requires surface divergence strength (β), the Lagrangian residence time inside the upwelling zone (tLu), and the total lifetime of new interface before it is downwelled (tLT). The model's output agrees with time-averaged measurements kw, patterns of temperature in infrared photographs, and spatial patterns of gas concentration and kw from direct numerical simulations. Several nondimensional parameters, e.g. βtLu and τstLT where τs is the interfacial shear rate, determine the effectiveness of a particular type of coherent motion for affecting kw.

  18. In situ air-water and particle-water partitioning of perfluorocarboxylic acids, perfluorosulfonic acids and perfluorooctyl sulfonamide at a wastewater treatment plant.

    PubMed

    Vierke, Lena; Ahrens, Lutz; Shoeib, Mahiba; Palm, Wolf-Ulrich; Webster, Eva M; Ellis, David A; Ebinghaus, Ralf; Harner, Tom

    2013-08-01

    In situ measurements of air and water phases at a wastewater treatment plant (WWTP) were used to investigate the partitioning behavior of perfluorocarboxylic acids (PFCAs), perfluorosulfonic acids (PFSAs) and perfluorooctyl sulfonamide (HFOSA) and their conjugate bases (PFC(-)s, PFS(-)s, and FOSA(-), respectively). Particle-dissolved (Rd) and air-water (QAW) concentration ratios were determined at different tanks of a WWTP. Sum of concentrations of C4-12,14 PFC(A)s, C4,6,8,10 PFS(A)s and (H)FOSA were as high as 50 pg m(-3) (atmospheric gas phase), 2300 ng L(-1) (aqueous dissolved phase) and 2500 ng L(-1) (aqueous particle phase). Particle-dissolved concentration ratios of total species, log Rd, ranged from -2.9 to 1.3 for PFS(A)s, from -1.9 to 1.1 for PFC(A)s and was 0.71 for (H)FOSA. These field-based values agree well with equilibrium partitioning data reported in the literature, suggesting that any in situ generation from precursors, if they are present in this system, occurs at a slower rate than the rate of approach to equilibrium. Acid QAW were also estimated. Good agreement between the QAW and the air-water equilibrium partition coefficient for C8PFCA suggests that the air above the WWTP tanks is at or near equilibrium with the water. Uncertainties in these QAW values are attributed mainly to variability in pKa values reported in the literature. The WWTP provides a unique environment for investigating environmental fate processes of the PFCAs and PFSAs under 'real' conditions in order to better understand and predict their fate in the environment.

  19. Electron Transfer Reduction of the Diazirine Ring in Gas-Phase Peptide Ions. On the Peculiar Loss of [NH4O] from Photoleucine

    NASA Astrophysics Data System (ADS)

    Marek, Aleš; Shaffer, Christopher J.; Pepin, Robert; Slováková, Kristina; Laszlo, Kenneth J.; Bush, Matthew F.; Tureček, František

    2015-03-01

    Electron transfer to gas-phase peptide ions with diazirine-containing amino acid residue photoleucine (L*) triggers diazirine ring reductio