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Sample records for oxygen transfer coefficient

  1. Effects of oxygen transfer coefficient on dihydroxyacetone production from crude glycerol

    PubMed Central

    Zheng, Xiao-juan; Jin, Kui-qi; Zhang, Lei; Wang, Gang; Liu, Yu-Peng

    2016-01-01

    The principal objective of this study was to evaluate the kinetics of dihydroxyacetone production by Gluconobacter frateurii CGMCC 5397 under different oxygen volumetric mass transfer coefficient (kLa) conditions in submerged bioreactors using biodiesel-derived crude glycerol as the carbon source. kLa is a key fermentation parameter for the production of dihydroxyacetone. Cultivations were conducted in baffled- and unbaffled-flask cultures (the kLa values were 24.32 h−1 and 52.05 h−1, respectively) and fed-batch cultures (the kLa values were held at 18.21 h−1, 46.03 h−1, and 82.14 h−1) to achieve high dihydroxyacetone concentration and productivity. The results showed that a high kLa could dramatically increase dihydroxyacetone concentrations and productivities. The baffled-flask culture (with a kLa of 52.05 h−1) favored glycerol utilization and dihydroxyacetone production, and a dihydroxyacetone concentration as high as 131.16 g/L was achieved. When the kLa was set to 82.14 h−1 in the fed-batch culture, the dihydroxyacetone concentration, productivity and yield were 175.44 g/L, 7.96 g/L/h and 0.89 g/g, respectively, all of which were significantly higher than those in previous studies and will benefit dihydroxyacetone industrial production. PMID:26887235

  2. Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Ehlers, Robert C.

    1961-01-01

    Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.

  3. Effects of soot absorption coefficient-Planck function correlation on radiative heat transfer in oxygen-enriched propane turbulent diffusion flame

    NASA Astrophysics Data System (ADS)

    Consalvi, J. L.; Nmira, F.

    2016-03-01

    The main objective of this article is to quantify the influence of the soot absorption coefficient-Planck function correlation on radiative loss and flame structure in an oxygen-enhanced propane turbulent diffusion flame. Calculations were run with and without accounting for this correlation by using a standard k-ε model and the steady laminar flamelet model (SLF) coupled to a joint Probability Density Function (PDF) of mixture fraction, enthalpy defect, scalar dissipation rate, and soot quantities. The PDF transport equation is solved by using a Stochastic Eulerian Field (SEF) method. The modeling of soot production is carried out by using a flamelet-based semi-empirical acetylene/benzene soot model. Radiative heat transfer is modeled by using a wide band correlated-k model and turbulent radiation interactions (TRI) are accounted for by using the Optically-Thin Fluctuation Approximation (OTFA). Predicted soot volume fraction, radiant wall heat flux distribution and radiant fraction are in good agreement with the available experimental data. Model results show that soot absorption coefficient and Planck function are negatively correlated in the region of intense soot emission. Neglecting this correlation is found to increase significantly the radiative loss leading to a substantial impact on flame structure in terms of mean and rms values of temperature. In addition mean and rms values of soot volume fraction are found to be less sensitive to the correlation than temperature since soot formation occurs mainly in a region where its influence is low.

  4. Improvement of oxygen transfer coefficient during Penicillium canescens culture. Influence of turbine design, agitation speed, and air flow rate on xylanase production.

    PubMed

    Gaspar, A; Strodiot, L; Thonart, P

    1998-01-01

    To improve xylanase productivity from Penicillium canescens 10-10c culture, an optimization of oxygen supply is required. Because the strain is sensitive to shear forces, leading to lower xylanase productivity as to morphological alteration, vigorous mixing is not desired. The influence of turbine design, agitation speed, and air flow rate on K1a (global mass transfer coefficient, h(-1)) and enzyme production is discussed. K1a values increased with agitation speed and air flow rate, whatever the impeller, in our assay conditions. Agitation had more influence on K1a values than air flow, when a disk-mounted blade's impeller (DT) is used; an opposite result was obtained with a hub-mounted pitched blade's impeller (PBT). Xylanase production appeared as a function of specific power (W/m3), and an optimum was found in 20 and 100 L STRs fitted with DT impellers. On the other hand, the use of a hub-mounted pitched blade impeller (PBT8), instead of a disk-mounted blade impeller (DT4), reduced the lag time of hemicellulase production and increased xylanase productivity 1.3-fold. PMID:18576019

  5. Use of Ion Beam Analysis to Study in Situ the Oxygen Diffusion and Interfacial Transfer Coefficients in Y1Ba2Cu 3O7-x Thin Films

    NASA Astrophysics Data System (ADS)

    García López, J.; Siejka, J.; Lemaitre, Y.; Mage, J. C.; Marcilhac, B.

    An experimental chamber was connected to the 2.5 MV Van de Graaff accelerator allowing in situ sample annealing at T ≤ 700°C and under pO2 ranging from 10-8 to 1 bar. For the first time to our knowledge the 16O(3He,α)15O nuclear reaction has been employed to monitor in situ the oxygen loss and uptake in Y1Ba2Cu3 O7-x (YBCO) thin films as a function of oxygen pressure and temperature (T ≤ 500°C). The role played by the presence of carbon contamination on YBCO surface was elucidated. Using the 12C(d,p)13C nuclear reaction the carbon loss was observed for T ≥ 250°C and it was associated with the oxygen loss enhancement in YBCO. It is found that in absence of carbon contamination, oxygen in-diffusion rate in YBCO is much faster than the out-diffusion rate, the later being surface reaction limited. The oxygen diffusion coefficients and the surface exchange coefficients of YBCO films have been evaluated. These results will be discussed in relation with the mechanism of high temperature YBCO thin film growth by cathodic sputtering and with the mechanism of the oxygen loss and/or uptake during the sample cooling.

  6. Heat transfer coefficient of cryotop during freezing.

    PubMed

    Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

    2013-01-01

    Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

  7. Oxygen transfer in a pressurized airlift bioreactor.

    PubMed

    Campani, Gilson; Ribeiro, Marcelo Perencin Arruda; Horta, Antônio Carlos Luperni; Giordano, Roberto Campos; Badino, Alberto Colli; Zangirolami, Teresa Cristina

    2015-08-01

    Airlift bioreactors (ALBs) offer advantages over conventional systems, such as simplicity of construction, reduced risk of contamination, and efficient gas-liquid dispersion with low power consumption. ALBs are usually operated under atmospheric pressure. However, in bioprocesses with high oxygen demand, such as high cell density cultures, oxygen limitation may occur even when operating with high superficial gas velocity and air enriched with oxygen. One way of overcoming this drawback is to pressurize the reactor. In this configuration, it is important to assess the influence of bioreactor internal pressure on the gas hold-up, volumetric oxygen transfer coefficient (k(L)a), and volumetric oxygen transfer rate (OTR). Experiments were carried out in a concentric-tube airlift bioreactor with a 5 dm(3) working volume, equipped with a system for automatic monitoring and control of the pressure, temperature, and inlet gas flow rate. The results showed that, in disagreement with previous published results for bubble column and external loop airlift reactors, overpressure did not significantly affect k(L)a within the studied ranges of pressure (0.1-0.4 MPa) and superficial gas velocity in the riser (0.032-0.065 m s(-1)). Nevertheless, a positive effect on OTR was observed: it increased up to 5.4 times, surpassing by 2.3 times the oxygen transfer in a 4 dm(3) stirred tank reactor operated under standard cultivation conditions. These results contribute to the development of non-conventional reactors, especially pneumatic bioreactors operated using novel strategies for oxygen control.

  8. Condensation heat transfer coefficient versus wettability

    NASA Astrophysics Data System (ADS)

    Roudgar, M.; De Coninck, J.

    2015-05-01

    In this paper we show how condensation on substrates can induce wetting behavior that is quite different from that of deposited or impinging drops. We describe surfaces with the same wettability in ambient conditions presenting different wetting behavior and growth of droplets in condensation. The experimental results show a rapid spread of droplets and formation of the film on the copper surface, while droplets on SU-8 surface remains on the regular shape while they grow within the time, without coalescence, as observed for Cu. Although the heat conductivity of SU-8 is much lower, due to a difference in wetting behavior, the heat transfer coefficient (h) is higher for dropwise condensation on Cu with a thin layer of SU-8 than filmwise on the bare copper.

  9. Measuring Furnace/Sample Heat-Transfer Coefficients

    NASA Technical Reports Server (NTRS)

    Rosch, William R.; Fripp, Archibald L., Jr.; Debnam, William J., Jr.; Woodell, Glenn A.

    1993-01-01

    Complicated, inexact calculations now unnecessary. Device called HTX used to simulate and measure transfer of heat between directional-solidification crystal-growth furnace and ampoule containing sample of crystalline to be grown. Yields measurement data used to calculate heat-transfer coefficients directly, without need for assumptions or prior knowledge of physical properties of furnace, furnace gas, or specimen. Determines not only total heat-transfer coefficients but also coefficients of transfer of heat in different modes.

  10. Analysis of a heat transfer device for measuring film coefficients

    NASA Technical Reports Server (NTRS)

    Medrow, R. A.; Johnson, R. L.; Loomis, W. R.; Wedeven, L. D.

    1975-01-01

    A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.

  11. Heat transfer coefficients for drying in pulsating flows

    SciTech Connect

    Fraenkel, S.L.

    1998-05-01

    Pulsating flows generated by a Rijke type combustor are studied for drying of grains and food particles. It is assumed that the velocity fluctuations are the main factor in the enhancement of the drying process. The heat transfer coefficients for drying in vibrating beds are utilized to estimate the heat transfer coefficients of fixed beds in pulsating and permeating flows and are compared to the steady flow heat transfer coefficients obtained for solid porous bodies, after perturbing the main flow. The cases considered are compared to the convective heat transfer coefficients employed in non-pulsating drying.

  12. Calculation of the mass transfer coefficient for the combustion of a carbon particle

    SciTech Connect

    Scala, Fabrizio

    2010-01-15

    In this paper we address the calculation of the mass transfer coefficient around a burning carbon particle in an atmosphere of O{sub 2}, N{sub 2}, CO{sub 2}, CO, and H{sub 2}O. The complete set of Stefan-Maxwell equations is analytically solved under the assumption of no homogeneous reaction in the boundary layer. An expression linking the oxygen concentration and the oxygen flux at the particle surface (as a function of the bulk gas composition) is derived which can be used to calculate the mass transfer coefficient. A very simple approximate explicit expression is also given for the mass transfer coefficient, that is shown to be valid in the low oxygen flux limit or when the primary combustion product is CO{sub 2}. The results are given in terms of a correction factor to the equimolar counter-diffusion mass transfer coefficient, which is typically available in the literature for specific geometries and/or fluid-dynamic conditions. The significance of the correction factor and the accuracy of the different available expressions is illustrated for several cases of practical interest. Results show that under typical combustion conditions the use of the equimolar counter-diffusion mass transfer coefficient can lead to errors up to 10%. Larger errors are possible in oxygen-enriched conditions, while the error is generally low in oxy-combustion. (author)

  13. Viscosity and thermal conductivity coefficients of gaseous and liquid oxygen

    NASA Technical Reports Server (NTRS)

    Hanley, H. J. M.; Mccarty, R. D.; Sengers, J. V.

    1974-01-01

    Equations and tables are presented for the viscosity and thermal conductivity coefficients of gaseous and liquid oxygen at temperatures between 80 K and 400 K for pressures up to 200 atm. and at temperatures between 80 K and 2000 K for the dilute gas. A description of the anomalous behavior of the thermal conductivity in the critical region is included. The tabulated coefficients are reliable to within about 15% except for a region in the immediate vicinity of the critical point. Some possibilities for future improvements of this reliability are discussed.

  14. 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.

  15. Heat-transfer coefficients in agitated vessels. Latent heat models

    SciTech Connect

    Kumpinsky, E.

    1996-03-01

    Latent heat models were developed to calculate heat-transfer coefficients in agitated vessels for two cases: (1) heating with a condensable fluid flowing through coils and jackets; (2) vacuum reflux cooling with an overhead condenser. In either case the mathematical treatment, based on macroscopic balances, requires no iterative schemes. In addition to providing heat-transfer coefficients, the models predict flow rates of service fluid through the coils and jackets, estimate the percentage of heat transfer due to latent heat, and compute reflux rates.

  16. Overall Heat and Mass Transfer Coefficient of Water Vapor Adsorption

    NASA Astrophysics Data System (ADS)

    Hamamoto, Yoshinori; Mori, Hideo; Godo, Masazumi; Miura, Kunio; Watanabe, Yutaka; Ishizawa, Toshihiko; Takatsuka, Takeshi

    A fundamental investigation was performed to develop a compact and simple desiccant ventilation unit which is one of the main components of a novel energy saving air-conditioning system. Water vapor in the air is adsorbed and/or desorbed to be controlled the humidity of supply air through a unit of an adsorbent packed bed. A numerical simulation helps to understand the phenomena of heat and mass transfer in the bed. Overall transfer coefficients of them as properties for the simulation were estimated by performing both experiment and calculation. It was clarified that the transient overall equivalent heat and mass transfer does not strongly depend on the air flow rate through the packed bed, the averaged equivalent mass transfer is governed by surface and pore diffusion in a particle of adsorbent at low flow rate. Moreover, the coefficient during the adsorption process is slightly larger than desorption. An equation of the overall mass transfer coefficient is derived. It shows five times as large as the value estimated by experiment. Therefore, the correlation and fitting parameters are presented for prediction of the overall heat and mass transfer coefficients. The estimation accuracy was improved.

  17. Heat transfer coefficient in serpentine coolant passage for CCDTL

    SciTech Connect

    Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.

    1998-12-31

    A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.

  18. 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.

  19. Determination of the heat transfer coefficients in transient heat conduction

    NASA Astrophysics Data System (ADS)

    Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.

    2013-09-01

    The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.

  20. Modeling NAPL dissolution fingering with upscaled mass transfer rate coefficients

    NASA Astrophysics Data System (ADS)

    Imhoff, Paul T.; Farthing, Matthew W.; Miller, Cass T.

    2003-10-01

    The dissolution of nonaqueous phase liquids (NAPLs) at residual saturation in porous media has sometimes resulted in the development of preferential dissolution pathways or NAPL dissolution fingers. While NAPL dissolution fingering may be modeled using numerical simulators with fine discretization, this approach is computational intensive. We derived an expression for an upscaled mass transfer rate coefficient that accounts for the growth of dissolution fingers within porous media contaminated uniformly with residual NAPL. This expression was closely related to the lengthening of the dissolution front. Data from physical experiments and numerical simulations in two dimensions were used to examine the growth of the dissolution front and the corresponding upscaled mass transfer rate coefficient. Using this upscaled mass transfer rate coefficient, the time when dissolution fingering results in a reduction in the overall mass transfer rate and thus controls the rate of NAPL dissolution was determined. This crossover time is a convenient parameter for assessing the influence of dissolution fingering on NAPL removal. For the physical experiments and numerical simulations analyzed in this study, the crossover time to dissolution fingering control always occurred before the dissolution front had moved 14 cm within NAPL-contaminated porous media, which is small compared to the scale of typical systems of concern. To verify the utility of this approach, data from a three-dimensional physical experiment were predicted reasonably well using an upscaled mass transfer rate coefficient that was determined independently from this experiment.

  1. Mass transfer coefficients determination from linear gradient elution experiments.

    PubMed

    Pfister, David; Morbidelli, Massimo

    2015-01-01

    A procedure to estimate mass transfer coefficients in linear gradient elution chromatography is presented and validated by comparison with experimental data. Mass transfer coefficients are traditionally estimated experimentally through the van Deemter plot, which represents the HETP as a function of the fluid velocity. Up to now, the HETP was obtained under isocratic elution conditions. Unfortunately, isocratic elution experiments are often not suitable for large biomolecules which suffer from severe mass transfer hindrances. Yamamoto et al. were the first to propose a semi-empirical equation to relate HETPs measured from linear gradient elution experiments to those obtained under isocratic conditions [7]. Based on his pioneering work, the approach presented in this work aims at providing an experimental procedure supported by simple equations to estimate reliable mass transfer parameters from linear gradient elution chromatographic experiments. From the resolution of the transport model, we derived a rigorous analytical expression for the HETP in linear gradient elution chromatography.

  2. Multicomponent NAPL source dissolution: evaluation of mass-transfer coefficients.

    PubMed

    Mobile, Michael A; Widdowson, Mark A; Gallagher, Daniel L

    2012-09-18

    Mass transfer rate coefficients were quantified by employing an inverse modeling technique to high-resolution aqueous phase concentration data observed following an experimental release of a multicomponent nonaqueous phase liquid (NAPL) at a field site. A solute transport model (SEAM3D) was employed to simulate advective-dispersive transport over time coupled to NAPL dissolution. Model calibration was demonstrated by accurately reproducing the observed breakthrough times and peak concentrations at multiple observation points, observed mass discharge at pumping wells, and the reported mass depletions for three soluble NAPL constituents. Vertically variable NAPL mass transfer coefficients were derived for each constituent using an optimized numerical solute transport model, ranging from 0.082 to 2.0 day(-1) across all constituents. Constituent-specific coefficients showed a positive correlation with liquid-phase diffusion coefficients. Application of a time-varying mass transfer coefficient as NAPL mass depleted showed limited sensitivity during which over 80% of the most soluble NAPL constituent dissolved from the source. Long-term simulation results, calibrated to the experimental data and rendered in terms of mass discharge versus source mass depletion, exhibited multistage behavior.

  3. A correlation for heat transfer coefficients in food extruders.

    PubMed

    Levine, L; Rockwood, J

    1986-06-01

    A dimensionless correlation of heat transfer coefficient for heat flow between the extruder barrel wall and extrudate is presented. The standard error of estimate of the correlation is 12.4%. The correlation is useful for the design and scale-up of food extruders and the design of associated temperature control systems.

  4. Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...

  5. Heat-transfer coefficients in agitated vessels. Sensible heat models

    SciTech Connect

    Kumpinsky, E.

    1995-12-01

    Transient models for sensible heat were developed to assess the thermal performance of agitated vessels with coils and jackets. Performance is quantified with the computation of heat-transfer coefficients by introducing vessel heating and cooling data into model equations. Of the two model categories studied, differential and macroscopic, the latter is preferred due to mathematical simplicity and lower sensitivity to experimental data variability.

  6. Fermentation and oxygen transfer in microgravity

    NASA Technical Reports Server (NTRS)

    Dunlop, Eric H.

    1989-01-01

    The need for high rate oxygen transfer in microgravity for a Controlled Ecological Life Support System (CELSS) environment offers a number of difficulties and challenges. The use of a phase separated bioreactor appears to provide a way of overcoming these problems resulting in a system capable of providing high cell densities with rapid fermentation rates. Some of the key design elements are discussed.

  7. CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

    NASA Technical Reports Server (NTRS)

    Yang, H. Q.; West, Jeff

    2015-01-01

    Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

  8. Determination of the heat transfer coefficients in porous media

    SciTech Connect

    Kim, L.V.

    1994-06-01

    The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.

  9. Heat transfer coefficients for staggered arrays of short pin fins

    NASA Astrophysics Data System (ADS)

    Vanfossen, G. J.

    Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

  10. Heat transfer coefficients for staggered arrays of short pin fins

    NASA Astrophysics Data System (ADS)

    Vanfossen, G. J.

    1981-03-01

    Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

  11. Oxygen transfer in membrane bioreactors treating synthetic greywater.

    PubMed

    Henkel, Jochen; Lemac, Mladen; Wagner, Martin; Cornel, Peter

    2009-04-01

    Mass transfer coefficients (k(L)a) were studied in two pilot scale membrane bioreactors (MBR) with different setup configurations treating 200L/h of synthetic greywater with mixed liquor suspended solids' (MLSS) concentrations ranging from 4.7 to 19.5g/L. Besides the MLSS concentration, mixed liquor volatile suspended solids (MLVSS), total solids (TS), volatile solids (VS), chemical oxygen demand (COD) and anionic surfactants of the sludge were measured. Although the pilot plants differed essentially in their configurations and aeration systems, similar alpha-factors at the same MLSS concentration could be determined. A comparison of the results to the published values of other authors showed that not the MLSS concentration but rather the MLVSS concentration seems to be the decisive parameter which influences the oxygen transfer in activated sludge systems operating at a high sludge retention time (SRT).

  12. Calculation of Mass Transfer Coefficients in a Crystal Growth Chamber through Heat Transfer Measurements

    SciTech Connect

    Bell, J H; Hand, L A

    2005-04-21

    The growth rate of a crystal in a supersaturated solution is limited by both reaction kinetics and the local concentration of solute. If the local mass transfer coefficient is too low, concentration of solute at the crystal-solution interface will drop below saturation, leading to a defect in the growing crystal. Here, mass transfer coefficients are calculated for a rotating crystal growing in a supersaturated solution of potassium diphosphate (KDP) in water. Since mass transfer is difficult to measure directly, the heat transfer coefficient of a scale model crystal in water is measured using temperature-sensitive paint (TSP). To the authors' knowledge this is the first use of TSP to measure temperatures in water. The corresponding mass transfer coefficient is then calculated using the Chilton- Colburn analogy. Measurements were made for three crystal sizes at two running conditions each. Running conditions include periodic reversals of rotation direction. Heat transfer coefficients were found to vary significantly both across the crystal faces and over the course of a rotation cycle, but not from one face to another. Mean heat transfer coefficients increased with both crystal size and rotation rate. Computed mass transfer coefficients were broadly in line with expectations from the full-scale crystal growth experiments. Additional experiments show that continuous rotation of the crystal results in about a 30% lower heat transfer compared to rotation with periodic reversals. The continuous rotation case also shows a periodic variation in heat transfer coefficient of about 15%, with a period about 1/20th of the rotation rate.

  13. Saponification reaction system: a detailed mass transfer coefficient determination.

    PubMed

    Pečar, Darja; Goršek, Andreja

    2015-01-01

    The saponification of an aromatic ester with an aqueous sodium hydroxide was studied within a heterogeneous reaction medium in order to determine the overall kinetics of the selected system. The extended thermo-kinetic model was developed compared to the previously used simple one. The reaction rate within a heterogeneous liquid-liquid system incorporates a chemical kinetics term as well as mass transfer between both phases. Chemical rate constant was obtained from experiments within a homogeneous medium, whilst the mass-transfer coefficient was determined separately. The measured thermal profiles were then the bases for determining the overall reaction-rate. This study presents the development of an extended kinetic model for considering mass transfer regarding the saponification of ethyl benzoate with sodium hydroxide within a heterogeneous reaction medium. The time-dependences are presented for the mass transfer coefficient and the interfacial areas at different heterogeneous stages and temperatures. The results indicated an important role of reliable kinetic model, as significant difference in k(L)a product was obtained with extended and simple approach.

  14. A study of oxygen transfer in shake flasks using a non-invasive oxygen sensor.

    PubMed

    Gupta, Atul; Rao, Govind

    2003-11-01

    We describe a study of oxygen transfer in shake flasks using a non-invasive optical sensor. This study investigates the effect of different plugs, presence of baffles, and the type of media on the dissolved oxygen profiles during Escherichia coli fermentation. We measured the volumetric mass transfer coefficient (k(L)a) under various conditions and also the resistances of the various plugs. Finally, we compared shake flask k(L)a with that from a stirred tank fermentor. By matching k(L)a's we were able to obtain similar growth and recombinant protein product formation kinetics in both a fermentor and a shake flask. These results provide a quantitative comparison of fermentations in a shake flask vs. a bench-scale fermentor and should be valuable in guiding scale-up efforts.

  15. BIOLOGICALLY ENHANCED OXYGEN TRANSFER IN THE ACTIVATED SLUDGE PROCESS (JOURNAL)

    EPA Science Inventory

    Biologically enhanced oxgyen transfer has been a hypothesis to explain observed oxygen transfer rates in activated sludge systems that were well above that predicted from aerator clean-water testing. The enhanced oxygen transfer rates were based on tests using BOD bottle oxygen ...

  16. Prediction of gas-liquid mass transfer coefficient in sparged stirred tank bioreactors.

    PubMed

    Garcia-Ochoa, Felix; Gomez, Emilio

    2005-12-20

    Oxygen mass transfer in sparged stirred tank bioreactors has been studied. The rate of oxygen mass transfer into a culture in a bioreactor is affected by operational conditions and geometrical parameters as well as the physicochemical properties of the medium (nutrients, substances excreted by the micro-organism, and surface active agents that are often added to the medium) and the presence of the micro-organism. Thus, oxygen mass transfer coefficient values in fermentation broths often differ substantially from values estimated for simple aqueous solutions. The influence of liquid phase physicochemical properties on kLa must be divided into the influence on k(L) and a, because they are affected in different ways. The presence of micro-organisms (cells, bacteria, or yeasts) can affect the mass transfer rate, and thus kLa values, due to the consumption of oxygen for both cell growth and metabolite production. In this work, theoretical equations for kLa prediction, developed for sparged and stirred tanks, taking into account the possible oxygen mass transfer enhancement due to the consumption by biochemical reactions, are proposed. The estimation of kLa is carried out taking into account a strong increase of viscosity broth, changes in surface tension and different oxygen uptake rates (OURs), and the biological enhancement factor, E, is also estimated. These different operational conditions and changes in several variables are performed using different systems and cultures (xanthan aqueous solutions, xanthan production cultures by Xanthomonas campestris, sophorolipids production by Candida bombicola, etc.). Experimental and theoretical results are presented and compared, with very good results.

  17. Transfer coefficients of radionuclides secreted in milk of dairy cows

    SciTech Connect

    Sam, D.; Williams, W.F.; Rockmann, D.D.; Allen, J.T.

    1980-09-01

    This study simulated experimentally the transfer of radionuclides to milk of dairy cows on a worst-case situation using various radionuclides known to emanate from nuclear power stations and which have been detected on particulates. Two lactating Holstein cows were administered orally one gelatin capsule containing 10 radionuclides in water-soluble form per day for 14 consecutive days. Milk samples were collected and aliquots analyzed in a germanium lithium-drifted detector coupled to a 2048-multichannel gamma-ray analyzer to measure small amounts of complex mixtures of radionuclides. The transfer coefficients of the radionuclides were calculated when their secretion in milk reached or approached a plateau of concentration. The radionuclides and their transfer coefficients to milk were: chromium/sup 51/ less than 0.01%; manganese/sup 54/ 0.033 +- 0.005%; cobalt/sup 60/ 0.01 +- 0.002%; iron/sup 59/ 0.0048 +- 0.002%; zinc/sup 65/ 0.31 +- 0.07%; selenium/sup 75/ 0.29 +- 0.1%; antimony/sup 125/ 0.011 +- 0.003%; iodine/sup 131/ 0.88 +- 0.05%; and cesium/sup 137/ 0.79 +- 0.08%.

  18. MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS

    SciTech Connect

    Leishear, R.

    2009-09-09

    Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.

  19. Influence of pluronic F68 on oxygen mass transfer.

    PubMed

    Sieblist, Christian; Jenzsch, Marco; Pohlscheidt, Michael

    2013-01-01

    Pluronic F68 is one of the most used shear protecting additives in cell culture cultivations. It is well known from literature that such surface-active surfactants lower the surface tension at the gas-liquid interface, which influences the mass transfer. In this study, the effect of Pluronic F68 on oxygen mass transfer in aqueous solutions was examined. Therefore, the gassing in/gassing out method and bubble size measurements were used. At low concentrations of 0.02 g/L, a 50% reduction on mass transfer was observed for all tested spargers and working conditions. An explanation of the observed effects by means of Higbie's penetration or Dankwerts surface renewal theory was applied. It could be demonstrated that the suppressed movement of the bubble surface layer is the main cause for the significant drop down of the kL a-values. For Pluronic F68 concentrations above 0.1 g/L, it was observed that it comes to changes in bubble appearance and bubble size strongly dependent on the sparger type. By using the bubble size measurement data, it could be shown that only small changes in mass transfer coefficient (kL ) take place above the critical micelle concentration. Further changes on overall mass transfer at higher Pluronic F68 concentrations are mainly based on increasing of gas holdup and, more importantly, by increasing of the surface area available for mass transfer.

  20. Improved transfer matrix methods for calculating quantum transmission coefficient.

    PubMed

    Biswas, Debabrata; Kumar, Vishal

    2014-07-01

    Methods for calculating the transmission coefficient are proposed, all of which arise from improved nonreflecting WKB boundary conditions at the edge of the computational domain in one-dimensional geometries. In the first, the Schrödinger equation is solved numerically, while the second is a transfer matrix (TM) algorithm where the potential is approximated by steps, but with the first and last matrix modified to reflect the new boundary condition. Both methods give excellent results with first-order WKB boundary conditions. The third uses the transfer matrix method with third-order WKB boundary conditions. For the parabolic potential, the average error for the modified third-order TM method reduces by factor of 4100 over the unmodified TM method.

  1. Ratios of transfer coefficients for radiocesium transport in ruminants

    SciTech Connect

    Assimakopoulos, P.A.; Ioannides, K.G.; Karamanis, D.

    1995-09-01

    A corollary of the multiple-compartment model for the transport of trace elements through animals was tested for cows, goats, and sheep. According to this corollary, for a given body {open_quotes}compartment{close_quotes} k of the animal (soft tissue, lung, liver, etc.), the ratio a(k)=f(k)/f(blood) of the transfer coefficients f, should exhibit similar values for physiologically similar animals. In order to verify this prediction, two experiments were performed at the Agricultural Research Station of Ioannina and at the facilities of Ria Pripyat in Pripyat, Ukranine. Eight animals in the first experiment and eighteen in the second were housed in individual pens and were artificially contaminated with a constant daily dose of radiocesium until equilibrium was reached. the animals were then sacrificed and transfer coefficients f(k) to twelve body {open_quotes}compartments{close_quotes} k were measured. These data were used to calculate the ratios a(k). The results were in accordance with predictions of the model and average values of a(k) were extracted for ruminants. It is concluded that these values may be employed for the prediction of animal contamination in any body compartment through the measurement of blood samples. 7 refs., 8 tabs.

  2. Oxygen Transfer Characteristics of Miniaturized Bioreactor Systems

    PubMed Central

    Kirk, Timothy V; Szita, Nicolas

    2013-01-01

    Since their introduction in 2001 miniaturized bioreactor systems have made great advances in function and performance. In this article the dissolved oxygen (DO) transfer performance of submilliliter microbioreactors, and 1–10 mL minibioreactors was examined. Microbioreactors have reached kLa values of 460 h-1, and are offering instrumentation and some functionality comparable to production systems, but at high throughput screening volumes. Minibioreactors, aside from one 1,440 h-1 kLa system, have not offered as high rates of DO transfer, but have demonstrated superior integration with automated fluid handling systems. Microbioreactors have been typically limited to studies with E. coli, while minibioreactors have offered greater versatility in this regard. Further, mathematical relationships confirming the applicability of kLa measurements across all scales have been derived, and alternatives to fluorescence lifetime DO sensors have been evaluated. Finally, the influence on reactor performance of oxygen uptake rate (OUR), and the possibility of its real-time measurement have been explored. Biotechnol. Bioeng. 2013; 110: 1005–1019. © 2012 Wiley Periodicals, Inc. PMID:23280578

  3. About the Role of the Bottleneck/Cork Interface on Oxygen Transfer.

    PubMed

    Lagorce-Tachon, Aurélie; Karbowiak, Thomas; Paulin, Christian; Simon, Jean-Marc; Gougeon, Régis D; Bellat, Jean-Pierre

    2016-09-01

    The transfer of oxygen through a corked bottleneck was investigated using a manometric technique. First, the effect of cork compression on oxygen transfer was evaluated without considering the glass/cork interface. No significant effect of cork compression (at 23% strain, corresponding to the compression level of cork in a bottleneck for still wines) was noticeable on the effective diffusion coefficient of oxygen. The mean value of the effective diffusion coefficient is equal to 10(-8) m(2) s(-1), with a statistical distribution ranging from 10(-10) to 10(-7) m(2) s(-1), which is of the same order of magnitude as for the non-compressed cork. Then, oxygen transfer through cork compressed in a glass bottleneck was determined to assess the effect of the glass/cork interface. In the particular case of a gradient-imposed diffusion of oxygen through our model corked bottleneck system (dry cork without surface treatment; 200 and ∼0 hPa of oxygen on both sides of the sample), the mean effective diffusion coefficient is of 5 × 10(-7) m(2) s(-1), thus revealing the possible importance of the role of the glass/stopper interface in the oxygen transfer.

  4. About the Role of the Bottleneck/Cork Interface on Oxygen Transfer.

    PubMed

    Lagorce-Tachon, Aurélie; Karbowiak, Thomas; Paulin, Christian; Simon, Jean-Marc; Gougeon, Régis D; Bellat, Jean-Pierre

    2016-09-01

    The transfer of oxygen through a corked bottleneck was investigated using a manometric technique. First, the effect of cork compression on oxygen transfer was evaluated without considering the glass/cork interface. No significant effect of cork compression (at 23% strain, corresponding to the compression level of cork in a bottleneck for still wines) was noticeable on the effective diffusion coefficient of oxygen. The mean value of the effective diffusion coefficient is equal to 10(-8) m(2) s(-1), with a statistical distribution ranging from 10(-10) to 10(-7) m(2) s(-1), which is of the same order of magnitude as for the non-compressed cork. Then, oxygen transfer through cork compressed in a glass bottleneck was determined to assess the effect of the glass/cork interface. In the particular case of a gradient-imposed diffusion of oxygen through our model corked bottleneck system (dry cork without surface treatment; 200 and ∼0 hPa of oxygen on both sides of the sample), the mean effective diffusion coefficient is of 5 × 10(-7) m(2) s(-1), thus revealing the possible importance of the role of the glass/stopper interface in the oxygen transfer. PMID:27564243

  5. Optimization of 2,3-butanediol production by Klebsiella oxytoca through oxygen transfer rate control

    SciTech Connect

    Beronio, P.B. Jr. . Amoco Research Center); Tsao, G.T. . Lab. of Renewable Resources Engineering)

    1993-12-01

    Production of 2,3-butanediol by Klebsiella oxytoca is influenced by the degree of oxygen limitation. During batch culture studies, two phases of growth are observed: energy-coupled growth, during which cell growth and oxygen supply are coupled; and, energy-uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal 2,3-butanediol productivity occurs during the energy-coupled growth phase. In this article, a control system which maintains the batch culture at a constant level of oxygen limitation in the energy-coupled growth regime has been designed. Control, which involves feedback control on the oxygen transfer coefficient, is achieved by continually increasing the partial pressure of oxygen in the feed gas, which in turn continually increases the oxygen transfer rate. Control has resulted in a balanced state of growth, a repression of ethanol formation, and an increase in 2,3-butanediol productivity of 18%.

  6. Supercritical oxygen heat transfer. [regenerative cooling

    NASA Technical Reports Server (NTRS)

    Spencer, R. G.; Rousar, D. C.

    1977-01-01

    Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%.

  7. Proton Transfer Rate Coefficient Measurements of Selected Volatile Organic Molecules

    NASA Astrophysics Data System (ADS)

    Brooke, G.; Popović, S.; Vušković, L.

    2002-05-01

    We have developed an apparatus based on the selected ion flow tube (SIFT)footnote D. Smith and N.G. Adams, Ads. At. Mol. Phys. 24, 1 (1987). that allows the study of proton transfer between various positive ions and volatile organic molecules. Reactions in the flow tube occur at pressures of approximately 300 mTorr, eliminating the requirement of thermal beam production. The proton donor molecule H_3O^+ has been produced using several types of electrical discharges in water vapor, such as a capacitively coupled RF discharge and a DC hollow cathode discharge. Presently we are developing an Asmussen-type microwave cavity discharge using the components of a standard microwave oven that has the advantages of simple design and operation, as well as low cost. We will be presenting the results of the microwave cavity ion source to produce H_3O^+, and compare it to the other studied sources. In addition, we will be presenting a preliminary measurement of the proton transfer rate coefficient in the reaction of H_3O^+ with acetone and methanol.

  8. In situ global method for measurement of oxygen demand and mass transfer

    SciTech Connect

    Klasson, K.T.; Lundbaeck, K.M.O.; Clausen, E.C.; Gaddy, J.L.

    1997-05-01

    Two aerobic microorganisms, Saccharomycopsis lipolytica and Brevibacterium lactofermentum, have been used in a study of mass transfer and oxygen uptake from a global perspective using a closed gas system. Oxygen concentrations in the gas and liquid were followed using oxygen electrodes, and the results allowed for easy calculation of in situ oxygen transport. The cell yields on oxygen for S. lipolytica and B. lactofermentum were 1.01 and 1.53 g/g respectively. The mass transfer coefficient was estimated as 10 h{sup {minus}1} at 500 rpm for both fermentations. The advantages with this method are noticeable since the use of model systems may be avoided, and the in situ measurements of oxygen demand assure reliable data for scale-up.

  9. Bioreactor scale-up and oxygen transfer rate in microbial processes: an overview.

    PubMed

    Garcia-Ochoa, Felix; Gomez, Emilio

    2009-01-01

    In aerobic bioprocesses, oxygen is a key substrate; due to its low solubility in broths (aqueous solutions), a continuous supply is needed. The oxygen transfer rate (OTR) must be known, and if possible predicted to achieve an optimum design operation and scale-up of bioreactors. Many studies have been conducted to enhance the efficiency of oxygen transfer. The dissolved oxygen concentration in a suspension of aerobic microorganisms depends on the rate of oxygen transfer from the gas phase to the liquid, on the rate at which oxygen is transported into the cells (where it is consumed), and on the oxygen uptake rate (OUR) by the microorganism for growth, maintenance and production. The gas-liquid mass transfer in a bioprocess is strongly influenced by the hydrodynamic conditions in the bioreactors. These conditions are known to be a function of energy dissipation that depends on the operational conditions, the physicochemical properties of the culture, the geometrical parameters of the bioreactor and also on the presence of oxygen consuming cells. Stirred tank and bubble column (of various types) bioreactors are widely used in a large variety of bioprocesses (such as aerobic fermentation and biological wastewater treatments, among others). Stirred tanks bioreactors provide high values of mass and heat transfer rates and excellent mixing. In these systems, a high number of variables affect the mass transfer and mixing, but the most important among them are stirrer speed, type and number of stirrers and gas flow rate used. In bubble columns and airlifts, the low-shear environment compared to the stirred tanks has enabled successful cultivation of shear sensitive and filamentous cells. Oxygen transfer is often the rate-limiting step in the aerobic bioprocess due to the low solubility of oxygen in the medium. The correct measurement and/or prediction of the volumetric mass transfer coefficient, (k(L)a), is a crucial step in the design, operation and scale-up of

  10. Secondary ion mass spectroscopy determination of oxygen diffusion coefficient in heavily Sb doped Si

    NASA Astrophysics Data System (ADS)

    Pagani, M.

    1990-10-01

    The diffusion coefficient of oxygen in heavily antimony doped Czochralski Si was measured in the temperature range 950-1100 °C by using secondary ion mass spectroscopy (SIMS). The diffusion coefficient, obtained from SIMS oxygen concentration profiles in samples submitted to out diffusion, shows no dependence on antimony concentration. The combined data give an activation energy of 2.68 eV, which is in good agreement with published results.

  11. Nanoparticulate-catalyzed oxygen transfer processes

    SciTech Connect

    Hunt, Andrew T.; Breitkopf, Richard C.

    2009-12-01

    Nanoparticulates of oxygen transfer materials that are oxides of rare earth metals, combinations of rare earth metals, and combinations of transition metals and rare earth metals are used as catalysts in a variety of processes. Unexpectedly large thermal efficiencies are achieved relative to micron sized particulates. Processes that use these catalysts are exemplified in a multistage reactor. The exemplified reactor cracks C6 to C20 hydrocarbons, desulfurizes the hydrocarbon stream and reforms the hydrocarbons in the stream to produce hydrogen. In a first reactor stage the steam and hydrocarbon are passed through particulate mixed rare earth metal oxide to crack larger hydrocarbon molecules. In a second stage, the steam and hydrocarbon are passed through particulate material that desulfurizes the hydrocarbon. In a third stage, the hydrocarbon and steam are passed through a heated, mixed transition metal/rare earth metal oxide to reform the lower hydrocarbons and thereby produce hydrogen. Stages can be alone or combined. Parallel reactors can provide continuous reactant flow. Each of the processes can be carried out individually.

  12. Experimentally Determined Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments

    NASA Technical Reports Server (NTRS)

    Bue, Grant; Watts, Carly; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vonau, Walt; Vogel, Matt; Conger, Bruce

    2015-01-01

    A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flowrate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.

  13. Distribution and mass transfer of dissolved oxygen in a multi-habitat membrane bioreactor.

    PubMed

    Tang, Bing; Qiu, Bing; Huang, Shaosong; Yang, Kanghua; Bin, Liying; Fu, Fenglian; Yang, Huiwen

    2015-04-01

    This work investigated the DO distribution and the factors influencing the mass transfer of DO in a multi-habitat membrane bioreactor. Through the continuous measurements of an on-line automatic system, the timely DO values at different zones in the bioreactor were obtained, which gave a detailed description to the distribution of oxygen within the bioreactor. The results indicated that the growth of biomass had an important influence on the distribution of oxygen. As the extension of operational time, the volumetric oxygen mass transfer coefficient (kLa) was generally decreased. With the difference in DO values, a complex environment combining anoxic and oxic state was produced within a single bioreactor, which provided a fundamental guarantee for the total removal of TN. Aeration rate, the concentration and apparent viscosity of MLSS have different influences on kLa, but adjusting the viscosity is a feasible method to improve the mass transfer of oxygen in the bioreactor.

  14. External Heat Transfer Coefficient Measurements on a Surrogate Indirect Inertial Confinement Fusion Target

    SciTech Connect

    Miles, Robin; Havstad, Mark; LeBlanc, Mary; Golosker, Ilya; Chang, Allan; Rosso, Paul

    2015-09-15

    External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m2∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.

  15. External Heat Transfer Coefficient Measurements on a Surrogate Indirect Inertial Confinement Fusion Target

    DOE PAGES

    Miles, Robin; Havstad, Mark; LeBlanc, Mary; Golosker, Ilya; Chang, Allan; Rosso, Paul

    2015-09-15

    External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m2∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.

  16. Design of experiments for measuring heat-transfer coefficients with a lumped-parameter calorimeter

    NASA Technical Reports Server (NTRS)

    Vanfossen, G. J., Jr.

    1975-01-01

    A theoretical investigation was conducted to determine optimum experimental conditions for using a lumped-parameter calorimeter to measure heat-transfer coefficients and heating rates. A mathematical model of the transient temperature response of the calorimeter was used with the measured temperature response to predict the heat-transfer coefficient and the rate of heating. A sensitivity analysis was used to determine the optimum transient experiment for simultaneously measuring the heat addition during heating and the convective heat-transfer coefficient during heating and cooling of a lumped-parameter calorimeter. Optimum experiments were also designed for measuring the convective heat-transfer coefficient during both heating and cooling and cooling only.

  17. Theoretical examination of effective oxygen diffusion coefficient and electrical conductivity of polymer electrolyte fuel cell porous components

    NASA Astrophysics Data System (ADS)

    Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki

    2016-09-01

    The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.

  18. Condensation heat transfer coefficient with noncondensible gases for heat transfer in thermal hydraulic codes

    SciTech Connect

    Banerjee, S.; Hassan, Y.A.

    1995-09-01

    Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.

  19. Transfer having a coupling coefficient higher than its active material

    NASA Technical Reports Server (NTRS)

    Lesieutre, George A. (Inventor); Davis, Christopher L. (Inventor)

    2001-01-01

    A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices.

  20. Investigation of two-phase heat transfer coefficients of argon-freon cryogenic mixed refrigerants

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

    2014-11-01

    Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has been rarely discussed so far. In this paper, condensation and evaporation heat transfer coefficients of argon-freon mixed refrigerant are measured in a microchannel heat exchanger. A Printed Circuit Heat Exchanger (PCHE) with 340 μm hydraulic diameter has been developed as a compact microchannel heat exchanger and utilized in the experiment. Several two-phase heat transfer coefficient correlations are examined to discuss the experimental measurement results. The result of this paper shows that cryogenic two-phase mixed refrigerant heat transfer coefficients can be estimated by conventional two-phase heat transfer coefficient correlations.

  1. An experimental approach to determine the heat transfer coefficient in directional solidification furnaces

    NASA Technical Reports Server (NTRS)

    Banan, Mohsen; Gray, Ross T.; Wilcox, William R.

    1992-01-01

    The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was experimentally determined using in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the theoretical value estimated by standard heat transfer calculations.

  2. A novel approach to determine the heat transfer coefficient in directional solidification furnaces

    NASA Technical Reports Server (NTRS)

    Banan, Mohsen; Gray, Ross T.; Wilcox, William R.

    1990-01-01

    The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was determined using an approach utilizing in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the value estimated by standard heat transfer calculations.

  3. Predicting oxygen transfer of fine bubble diffused aeration systems--model issued from dimensional analysis.

    PubMed

    Gillot, S; Capela-Marsal, S; Roustan, M; Héduit, A

    2005-04-01

    The standard oxygenation performances of fine bubble diffused aeration systems in clean water, measured in 12 cylindrical tanks (water depth from 2.4 to 6.1m), were analysed using dimensional analysis. A relationship was established to estimate the scale-up factor for oxygen transfer, the transfer number (N(T)) The transfer number, which is written as a function of the oxygen transfer coefficient (k(L)a(20)), the gas superficial velocity (U(G)), the kinematic viscosity of water (nu) and the acceleration due to gravity (g), has the same physical meaning as the specific oxygen transfer efficiency. N(T) only depends on the geometry of the tank/aeration system [the total surface of the perforated membrane (S(p)), the surface of the tank (S) or its diameter (D), the total surface of the zones covered by the diffusers ("aerated area", S(a)) and the submergence of the diffusers (h)]. This analysis allowed to better describe the mass transfer in cylindrical tanks. Within the range of the parameters considered, the oxygen transfer coefficient (k(L)a(20)) is an increasing linear function of the air flow rate. For a given air flow rate and a given tank surface area, k(L)a(20) decreases with the water depth (submergence of the diffusers). For a given water depth, k(L)a(20) increases with the number of diffusers, and, for an equal number of diffusers, with the total area of the zones covered by the diffusers. The latter result evidences the superiority of the total floor coverage over an arrangement whereby the diffusers are placed on separate grids. The specific standard oxygen transfer efficiency is independent of the air flow rate and the water depth, the drop in the k(L)a(20) being offset by the increase of the saturation concentration. For a given tank area, the impact of the total surface of the perforated membrane (S(p)) and of the aerated area (S(a)) is the same as on the oxygen transfer coefficient. PMID:15862338

  4. Electrocrystallization of uranium oxides from molten salt media with adjustable oxygen coefficient value

    SciTech Connect

    Smolenski, V.V.; Bovet, A.L.; Komarov, V.E.

    1993-12-31

    In order to determine the conditions necessary to produce uranium oxides with the preset oxygen coefficient value by electrolyzing salt electrolytes, we have investigated the chemical and electrochemical behavior of the oxychloride uranium compounds with various valancies in molten alkali chlorides. The electrochemical production conditions for uranium dioxide of the pre-stoichiometric composition were determined.

  5. Measurement of oxygen transfer from air into organic solvents

    PubMed Central

    Ramesh, Hemalata; Hobisch, Mathias; Borisov, Sergey; Klimant, Ingo; Krühne, Ulrich; Woodley, John M

    2015-01-01

    Abstract BACKGROUND The use of non‐aqueous organic media is becoming increasingly important in many biotechnological applications in order to achieve process intensification. Such media can be used, for example, to directly extract poorly water‐soluble toxic products from fermentations. Likewise many biological reactions require the supply of oxygen, most normally from air. However, reliable online measurements of oxygen concentration in organic solvents (and hence oxygen transfer rates from air to the solvent) has to date proven impossible due to limitations in the current analytical methods. RESULTS For the first time, online oxygen measurements in non‐aqueous media using a novel optical sensor are demonstrated. The sensor was used to measure oxygen concentration in various organic solvents including toluene, THF, isooctane, DMF, heptane and hexane (which have all been shown suitable for several biological applications). Subsequently, the oxygen transfer rates from air into these organic solvents were measured. CONCLUSION The measurement of oxygen transfer rates from air into organic solvents using the dynamic method was established using the solvent resistant optical sensor. The feasibility of online oxygen measurements in organic solvents has also been demonstrated, paving the way for new opportunities in process control. © 2015 The Authors. Journal of Chemical Technology & Biotechnology published by JohnWiley & Sons Ltd on behalf of Society of Chemical Industry.

  6. Oxygen supply in disposable shake-flasks: prediction of oxygen transfer rate, oxygen saturation and maximum cell concentration during aerobic growth.

    PubMed

    Schiefelbein, Sarah; Fröhlich, Alexander; John, Gernot T; Beutler, Falco; Wittmann, Christoph; Becker, Judith

    2013-08-01

    Dissolved oxygen plays an essential role in aerobic cultivation especially due to its low solubility. Under unfavorable conditions of mixing and vessel geometry it can become limiting. This, however, is difficult to predict and thus the right choice for an optimal experimental set-up is challenging. To overcome this, we developed a method which allows a robust prediction of the dissolved oxygen concentration during aerobic growth. This integrates newly established mathematical correlations for the determination of the volumetric gas-liquid mass transfer coefficient (kLa) in disposable shake-flasks from the filling volume, the vessel size and the agitation speed. Tested for the industrial production organism Corynebacterium glutamicum, this enabled a reliable design of culture conditions and allowed to predict the maximum possible cell concentration without oxygen limitation.

  7. Oxygen supply in disposable shake-flasks: prediction of oxygen transfer rate, oxygen saturation and maximum cell concentration during aerobic growth.

    PubMed

    Schiefelbein, Sarah; Fröhlich, Alexander; John, Gernot T; Beutler, Falco; Wittmann, Christoph; Becker, Judith

    2013-08-01

    Dissolved oxygen plays an essential role in aerobic cultivation especially due to its low solubility. Under unfavorable conditions of mixing and vessel geometry it can become limiting. This, however, is difficult to predict and thus the right choice for an optimal experimental set-up is challenging. To overcome this, we developed a method which allows a robust prediction of the dissolved oxygen concentration during aerobic growth. This integrates newly established mathematical correlations for the determination of the volumetric gas-liquid mass transfer coefficient (kLa) in disposable shake-flasks from the filling volume, the vessel size and the agitation speed. Tested for the industrial production organism Corynebacterium glutamicum, this enabled a reliable design of culture conditions and allowed to predict the maximum possible cell concentration without oxygen limitation. PMID:23592306

  8. OVERALL MASS TRANSFER COEFFICIENT FOR POLLUTANT EMISSIONS FROM SMALL WATER POOLS UNDER SIMULATED INDOOR ENVIRONMENTAL CONDITIONS

    EPA Science Inventory

    Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still water under simulated indoor-residential or occupational-environmental conditions. Fourteen tests were conducted in small environmental chambers...

  9. The oxygen transfer rate as key parameter for the characterization of Hansenula polymorpha screening cultures.

    PubMed

    Stöckmann, Christoph; Maier, Ulrike; Anderlei, Tibor; Knocke, Christof; Gellissen, Gerd; Büchs, Jochen

    2003-10-01

    Screening cultures are usually non-monitored and non-controlled due to a lack of appropriate measuring techniques. A new device for online measurement of oxygen transfer rate (OTR) in shaking-flask cultures was used for monitoring the screening of Hansenula polymorpha. A shaking frequency of 300 rpm and a filling volume of 20 ml in 250-ml flasks ensured a sufficient oxygen transfer capacity of 0.032 mol (l h)(-1) and thus a respiration not limited by oxygen. Medium buffered with 0.01 mol phosphate l(-1) (pH 6.0) resulted in pH-inhibited respiration, whereas buffering with 0.12 mol phosphate l(-1) (pH 4.1) resulted in respiration that was not inhibited by pH. The ammonium demand was balanced by establishing fixed relations between oxygen, ammonium, and glycerol consumption with 0.245+/-0.015 mol ammonium per mol glycerol. Plate precultures with complex glucose medium reduced the specific growth rate coefficient to 0.18 h(-1) in subsequent cultures with minimal glycerol medium. The specific growth rate coefficient increased to 0.26 h(-1) when exponentially growing precultures with minimal glycerol medium were used for inoculation. Changes in biomass, glycerol, ammonium, and pH over time were simulated on the basis of oxygen consumption.

  10. Experimental Studies on Carbon Dioxide Flow Boiling Heat Transfer Coefficient in Horizontal Smooth Tube

    NASA Astrophysics Data System (ADS)

    Hashimoto, Katsumi; Kiyotani, Akihiro; Sasaki, Naoe

    The CO2 heat pump water heater ”ECO CUTE” which was commercialized in 2001 has a high potential for energy conservation and greenhouse abatement. The most important element apparatus is always the evaporator in order to develop smaller and higher performance equipment. In this paper, an experimental study has been conducted to measure the pure CO2 flow boiling heat transfer coefficient (99.999 % purity, without oil) in a horizontal smooth tube (outer diameter 6 mm, thickness 0.4 mm). The measured mean heat transfer coefficients are compared with calculated value with using previous experimental heat transfer correlation equations. These two values are different from each other. Mean heat transfer coefficients are measured with varying mass velocity, pressure and heat transfer lengths. The tube length is varied to 3.0 m, 4.0 m and 5.0 m, to distinguish the influence of mass velocity and that of heat flux to the heat transfer coefficient. The test conditions were: CO2 mass velocity from about 150 to about 700 kg⁄(m2s) (heat flux from about 10 to about 40 kW⁄m2), quality at inlet of test section is 0.17, CO2 super heat at outlet of test section is 5 K and saturation temperature of CO2 ranges from 0 to 10 °C. As a result, it has been understood that heat flux has a greater influence on the heat transfer coefficient.

  11. The compressibility and the capacitance coefficient of helium-oxygen atmospheres.

    PubMed

    Imbert, G; Dejours, P; Hildwein, G

    1982-12-01

    The capacitance coefficient beta of an ideal gas mixture depends only on its temperature T, and its value is derived from the ideal gas law (i.e., beta = 1/RT, R being the ideal gas constant). But real gases behave as ideal gases only at low pressures, and this would not be the case in deep diving. High pressures of helium-oxygen are used in human and animal experimental dives (up to 7 or 12 MPa or more, respectively). At such pressures deviations from the ideal gas law cannot be neglected in hyperbaric atmospheres with respect to current accuracy of measuring instruments. As shown both theoretically and experimentally by this study, the non-ideal nature of helium-oxygen has a significant effect on the capacitance coefficient of hyperbaric atmospheres. The theoretical study is based on interaction energy in either homogeneous (He-He and O2-O2) or heterogeneous (He-O2) molecular pairs, and on the virial equation of state for gas mixtures. The experimental study is based on weight determination of samples of known volume of binary helium-oxygen mixtures, which are prepared in well-controlled pressure and temperature conditions. Our experimental results are in good agreement with theoretical predictions. 1) The helium compressibility factor ZHe increases linearly with pressure [ZHe = 1 + 0.0045 P (in MPa) at 30 degrees C]; and 2) in same temperature and pressure conditions (T = 303 K and P = 0.1 to 15 MPa), the same value for Z is valid for a helium-oxygen binary mixture and for pure helium. As derived from the equation of state of real gases, the capacitance coefficient is inversely related to Z (beta = 1/ZRT); therefore, for helium-oxygen mixtures, this coefficient would decrease with increasing pressure. A table is given for theoretical values of helium-oxygen capacitance coefficient, at pressures ranging from 0.1 to 15.0 MPa and at temperatures ranging from 25 degrees C to 37 degrees C. PMID:7168095

  12. Evaluation of oxygen transfer parameters of fine-bubble aeration system in plug flow aeration tank of wastewater treatment plant.

    PubMed

    Zhou, Xiaohong; Wu, Yuanyuan; Shi, Hanchang; Song, Yanqing

    2013-02-01

    Knowledge of the oxygen mass transfer of aerators under operational conditions in a full-scale wastewater treatment plant (WWTP) is meaningful for the optimization of WWTP, however, scarce to best of our knowledge. Through analyzing a plug flow aeration tank in the Lucun WWTP, in Wuxi, China, the oxygenation capacity of fine-bubble aerators under process conditions have been measured in-situ using the off-gas method and the non-steady-state method. The off-gas method demonstrated that the aerators in different corridors in the aeration tank of WWTP ha d significantly different oxygen transferperformance; furthermore, the aerators in the samecorridor shared almost equal oxygen transfer performance over the course of a day. Results measured by the two methods showed that the oxygen transfer performance of fine-bubble aerators in the aeration tank decreased dramatically compared with that in the clean water. The loss of oxygen transfer coefficient was over 50% under low-aeration conditions (aeration amount < 0.67 Nm3/hr). However, as the aeration amount reached 0.96 Nm3/hr, the discrepancy of oxygen transfer between the process condition and clean water was negligible. The analysis also indicated that the non-steady-state and off-gas methods resulted in comparable estimates of oxygen transfer parameters for the aerators under process conditions.

  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. 70. DETAIL OF OXYGEN TRANSFER PRESSURE GAUGE IN UPPER LEFT ...

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

    70. DETAIL OF OXYGEN TRANSFER PRESSURE GAUGE IN UPPER LEFT CORNER OF SKID ON RIGHT IN CA-133-1-C-69 - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  15. Numerical investigation of oxygen mass transfer in a helical-type artery bypass graft.

    PubMed

    Zheng, Tinghui; Wen, Jun; Jiang, Wentao; Deng, Xiaoyan; Fan, Yubo

    2014-04-01

    Local oxygen lack in arterial walls (hypoxia) plays a very important role in the initiation, progression and development of intimal hyperplasia (IH) and thrombosis. Aiming to find out whether a helical-type artery bypass graft (ABG) is hypoxia beneficial, a numerical study was carried out to compare oxygen transport between a helical-type ABG and a conventional-type ABG. The dimensionless mass transfer coefficient (Sherwood number) was introduced to evaluate the oxygen mass transfer distribution and detailed oxygen wall flux was computed. The results show that the intrinsic geometry of a helical-type ABG resulted in improved hypoxia and the oxygen-depleted fluid located proximally to the occluded section as compared with that of a conventional-type ABG. However, benefits aside, distinct double low regions (low wall shear stress (WSS) and hypoxia) which might be most prone to IH and more localised and thicker boundary layer of oxygen-depleted fluid were observed at the helical-type ABG. This may explain why the helical flow plays a detrimental role at some locations in the human body. In addition, it was observed that although low WSS region was always accompanied with low oxygen supply, the oxygen transport rate did not adjust simultaneously with flow. The change in oxygen distribution usually lagged behind the flow change. A physiological WSS region may be associated with hypoxia condition. This study captured the qualitative trend of oxygen distribution in ABGs and the effect of helical geometry on reducing hypoxia, which is useful in the structural design of swirling flow vascular devices.

  16. Study on heat transfer coefficients during cooling of PET bottles for food beverages

    NASA Astrophysics Data System (ADS)

    Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco

    2016-08-01

    The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.

  17. Measurement of local connective heat transfer coefficients of four ice accretion shapes

    NASA Technical Reports Server (NTRS)

    Smith, M. E.; Armilli, R. V.; Keshock, E. G.

    1984-01-01

    In the analytical study of ice accretions that form on aerodynamic surfaces (airfoils, engine inlets, etc.) it is often necessary to be able to calculate convective heat transfer rates. In order to do this, local convective heat transfer coefficients for the ice accretion shapes must be known. In the past, coefficients obtained for circular cylinders were used as an approximation to the actual coefficients since no better information existed. The purpose of this experimental study was to provide local convective heat transfer coefficients for four shapes that represent ice accretions. The shapes were tested with smooth and rough surfaces. The experimental method chosen was the thin-skin heat rate technique. Using this method local Nusselt numbers were determined for the ice shapes. In general it was found that the convective heat transfer was higher in regions where the model's surfaces were convex and lower in regions where the model's surfaces were concave. The effect of roughness was to increase the heat transfer in the high heat transfer regions by approximately 100% while little change was apparent in the low heat transfer regions.

  18. Backmixing and heat transfer coefficients in bubble columns using aqueous glycerol solutions

    SciTech Connect

    Knickle, H.N.; Holcombe, N.T.; O'Dowd, W.; Smith, D.N.

    1983-01-01

    Nonisothermal bubble column experiments have been performed to determine the effect of gas and liquid velocities on steady-state viscous cocurrent upflow. Aqueous solutions of glycerol and water were used with nitrogen at 5.1 atmospheres to determine backmixing and heat transfer coefficients in a 0.078-m-diameter, 1.68-m-high bubble column. Superficial gas velocity ranged from a low of 0.0121 m/s to 0.364 m/s, and liquid superficial velocity from 0.000835 m/s to 0.0121 m/s. Nonlinear regression was used to determine the best fit for these coefficients. The backmixing coefficient varied inversely with liquid viscosity to the 0.21 power. Two regions were examined for the heat transfer coefficients depending on whether the superficial gas velocity was greater or less than 0.1 m/sec. In the lower velocity range, the heat transfer coefficient varied inversely with viscosity to the 0.25 power; and in the higher range, inversely to the 0.18 power. In the lower range the heat transfer coefficient varied directly with liquid velocity to the 0.18 power; and in the higher range, to the 0.35 power. It is thought that this marked variation with liquid velocity is due to the importance of the increased turbulence of the liquid in this viscous system.

  19. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    DOE PAGES

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibriummore » is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.« less

  20. Instrument for stable high temperature Seebeck coefficient and resistivity measurements under controlled oxygen partial pressure

    SciTech Connect

    Ihlefeld, Jon F.; Brown-Shaklee, Harlan James; Sharma, Peter Anand

    2015-04-28

    The transport properties of ceramic materials strongly depend on oxygen activity, which is tuned by changing the partial oxygen pressure (pO2) prior to and during measurement. Within, we describe an instrument for highly stable measurements of Seebeck coefficient and electrical resistivity at temperatures up to 1300 K with controlled oxygen partial pressure. An all platinum construction is used to avoid potential materials instabilities that can cause measurement drift. Two independent heaters are employed to establish a small temperature gradient for Seebeck measurements, while keeping the average temperature constant and avoiding errors associated with pO2-induced drifts in thermocouple readings. Oxygen equilibrium is monitored using both an O2 sensor and the transient behavior of the resistance as a proxy. A pO2 range of 10-25–100 atm can be established with appropriate gas mixtures. Seebeck measurements were calibrated against a high purity platinum wire, Pt/Pt–Rh thermocouple wire, and a Bi2Te3 Seebeck coefficient Standard Reference Material. To demonstrate the utility of this instrument for oxide materials we present measurements as a function of pO2 on a 1 % Nb-doped SrTiO3 single crystal, and show systematic changes in properties consistent with oxygen vacancy defect chemistry. Thus, an approximately 11% increase in power factor over a pO2 range of 10-19–10-8 atm at 973 K for the donor-doped single crystals is observed.

  1. Calculation of heat transfer coefficients at the ingot surface during DC casting

    SciTech Connect

    Kuwana, K.; Viswanathan, S.; Clark, John A, III; Sabau, A.; Hassan, M.; Saito, K.; Das, S.

    2005-02-01

    Surface heat transfer coefficients representing the various regimes of water cooling during the Direct Chill (DC) casting of aluminum 3004 alloy ingots have been calculated using the inverse heat transfer technique. ProCAST, a commercial casting simulation package, which includes heat transfer, fluid flow, solidification, and inverse heat transfer, was used for this effort. Thermocouple data from an experimental casting run, and temperature-dependent thermophysical properties of the alloy were used in the calculation. The use of a structured vs. unstructured mesh was evaluated. The calculated effective heat transfer coefficient, which is a function of temperature and time, covers three water cooling regimes, i.e., convection, nucleate boiling, and film boiling, and the change of water flow rate with time.

  2. Lewis Acid Coupled Electron Transfer of Metal-Oxygen Intermediates.

    PubMed

    Fukuzumi, Shunichi; Ohkubo, Kei; Lee, Yong-Min; Nam, Wonwoo

    2015-12-01

    Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II.

  3. Ab initio calculation of oxygen self-diffusion coefficient in uranium dioxide UO2

    NASA Astrophysics Data System (ADS)

    Dorado, Boris; Garcia, Philippe; Torrent, Marc

    Uranium dioxide UO2 is the most widely used nuclear fuel worldwide and its atomic transport properties are relevant to practically all engineering aspects of the material. Although transport properties have already been studied in UO2 by means of first-principles calculations, the ab initio determination of self-diffusion coefficients has up to now remained unreachable because the relevant computational tools were neither available or adapted. The present work reports our results related to the ab initio calculation of the oxygen self-diffusion coefficient in UO2. We first determine the Gibbs free energies of formation of oxygen charged defects by calculating both the electronic and vibrational (hence entropic) contributions. Then, we use the transition state theory in order to compute the effective jump frequency of the defects, which in turn provides us with the value of the pre-exponential factor. The results are compared to self-diffusion data obtained experimentally with a careful monitoring of the relevant thermodynamic conditions (oxygen partial pressure, temperature, impurity content).

  4. Electrocatalysis of anodic and cathodic oxygen-transfer reactions

    SciTech Connect

    Wels, B.R.

    1990-09-21

    The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalytic link between reduction of IO{sub 3}{sup {minus}} and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO{sub 3}{sup {minus}} is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN{sup {minus}} is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN{sup {minus}} is virtually nonexistent at PbO{sub 2} electrodes. The response is significantly improved by doping PbO{sub 2} with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN{sup {minus}}. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN{sup {minus}} is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.

  5. Development of a biomimetic microfluidic oxygen transfer device.

    PubMed

    Gimbel, A A; Flores, E; Koo, A; García-Cardeña, G; Borenstein, J T

    2016-08-16

    Blood oxygenators provide crucial life support for patients suffering from respiratory failure, but their use is severely limited by the complex nature of the blood circuit and by complications including bleeding and clotting. We have fabricated and tested a multilayer microfluidic blood oxygenation prototype designed to have a lower blood prime volume and improved blood circulation relative to current hollow fiber cartridge oxygenators. Here we address processes for scaling the device toward clinically relevant oxygen transfer rates while maintaining a low prime volume of blood in the device, which is required for clinical applications in cardiopulmonary support and ultimately for chronic use. Approaches for scaling the device toward clinically relevant gas transfer rates, both by expanding the active surface area of the network of blood microchannels in a planar layer and by increasing the number of microfluidic layers stacked together in a three-dimensional device are addressed. In addition to reducing prime volume and enhancing gas transfer efficiency, the geometric properties of the microchannel networks are designed to increase device safety by providing a biomimetic and physiologically realistic flow path for the blood. Safety and hemocompatibility are also influenced by blood-surface interactions within the device. In order to further enhance device safety and hemocompatibility, we have demonstrated successful coating of the blood flow pathways with human endothelial cells, in order to confer the ability of the endothelium to inhibit coagulation and thrombus formation. Blood testing results provide confirmation of fibrin clot formation in non-endothelialized devices, while negligible clot formation was documented in cell-coated devices. Gas transfer testing demonstrates that the endothelial lining does not reduce the transfer efficiency relative to acellular devices. This process of scaling the microfluidic architecture and utilizing autologous cells to

  6. Coolant-side heat-transfer rates for a hydrogen-oxygen rocket and a new technique for data correlation

    NASA Technical Reports Server (NTRS)

    Schacht, R. L.; Quentmeyer, R. J.

    1973-01-01

    An experimental investigation was conducted to determine the coolant-side, heat transfer coefficients for a liquid cooled, hydrogen-oxygen rocket thrust chamber. Heat transfer rates were determined from measurements of local hot gas wall temperature, local coolant temperature, and local coolant pressure. A correlation incorporating an integration technique for the transport properties needed near the pseudocritical temperature of liquid hydrogen gives a satisfactory prediction of hot gas wall temperatures.

  7. Determination of Radiative Heat Transfer Coefficient at High Temperatures Using a Combined Experimental-Computational Technique

    NASA Astrophysics Data System (ADS)

    Kočí, Václav; Kočí, Jan; Korecký, Tomáš; Maděra, Jiří; Černý, Robert Č.

    2015-04-01

    The radiative heat transfer coefficient at high temperatures is determined using a combination of experimental measurement and computational modeling. In the experimental part, cement mortar specimen is heated in a laboratory furnace to 600°C and the temperature field inside is recorded using built-in K-type thermocouples connected to a data logger. The measured temperatures are then used as input parameters in the three dimensional computational modeling whose objective is to find the best correlation between the measured and calculated data via four free parameters, namely the thermal conductivity of the specimen, effective thermal conductivity of thermal insulation, and heat transfer coefficients at normal and high temperatures. The optimization procedure which is performed using the genetic algorithms provides the value of the high-temperature radiative heat transfer coefficient of 3.64 W/(m2K).

  8. Chemical diffusion coefficient of oxygen in thoria-urania mixed oxide

    NASA Astrophysics Data System (ADS)

    Matsui, Tsuneo; Naito, Keiji

    1985-10-01

    The chemical diffusion coefficients of oxygen ( D˜) in sintered samples of ( Th1- yUy) O2+ x ( y = 0.2 and 0.4) were measured by means of thermogravimetry in the temperature range 1282 ⩽ T ⩽ 1373 K. The defect diffusion coefficients ( Dd) were also calculated from the chemical diffusion coefficients obtained in this study. The activation energies of D˜ or Dd for the two samples ( Th1- yUy) O2+ xwithy = 0.2 and 0.4 were observed to be nearly the same, irrespective of the y value. These activation energies also nearly coincided with those of UO 2+x reported previously, suggesting the presence of a similar diffusion mechanism to that found in UO 2+x. The magnitude of both diffusion coefficients D˜ and Dd of ( Th1- yUy) O2+ x increased with increasing uranium content and approached that of UO 2+x. The increase of Dd of ( Th1- yUy) O2+ x with y value was considered to be due to the increase of both the vibrational frequency of lattice and the entropy change of migration produced by the substitution of a U ion for a Th ion.

  9. Global rate coefficients for ionization and recombination of carbon, nitrogen, oxygen, and argon

    SciTech Connect

    Annaloro, Julien; Morel, Vincent; Bultel, Arnaud; Omaly, Pierre

    2012-07-15

    The flow field modeling of planetary entry plasmas, laser-induced plasmas, inductively coupled plasmas, arcjets, etc., requires to use Navier-Stokes codes. The kinetic mechanisms implemented in these codes involve global (effective) rate coefficients. These rate coefficients result from the excited states coupling during a quasi-steady state. In order to obtain these global rate coefficients over a wide electron temperature (T{sub e}) range for ionization and recombination of carbon, nitrogen, oxygen, and argon, the behavior of their excited states is investigated using a zero-dimensional (time-dependent) code. The population number densities of these electronic states are considered as independent species. Their relaxation is studied within the range 3000 K{<=}T{sub e}{<=}20 000 K and leads to the determination of the ionization (k{sub i}) and recombination (k{sub r}) global rate coefficients. Comparisons with existing data are performed. Finally, the ratio k{sub i}/k{sub r} is compared with the Saha equilibrium constant. This ratio increases more rapidly than the equilibrium constant for T{sub e}>15 000 K.

  10. Inverse coefficient problems for one-dimensional heat transfer with a preservation of medium temperature condition

    NASA Astrophysics Data System (ADS)

    Oralsyn, Gulaym

    2016-08-01

    We study an inverse coefficient problem for a model equation for one-dimensional heat transfer with a preservation of medium temperature. It is needed (together with finding its solution) to find time dependent unknown coefficient of the equation. So, for this inverse problem, existence of an unique generalized solution is proved. The main difficulty of the considered problems is that the eigenfunction system of the corresponding boundary value problems does not have the basis property.

  11. CFD simulation of simultaneous monotonic cooling and surface heat transfer coefficient

    NASA Astrophysics Data System (ADS)

    Mihálka, Peter; Matiašovský, Peter

    2016-07-01

    The monotonic heating regime method for determination of thermal diffusivity is based on the analysis of an unsteady-state (stabilised) thermal process characterised by an independence of the space-time temperature distribution on initial conditions. At the first kind of the monotonic regime a sample of simple geometry is heated / cooled at constant ambient temperature. The determination of thermal diffusivity requires the determination rate of a temperature change and simultaneous determination of the first eigenvalue. According to a characteristic equation the first eigenvalue is a function of the Biot number defined by a surface heat transfer coefficient and thermal conductivity of an analysed material. Knowing the surface heat transfer coefficient and the first eigenvalue the thermal conductivity can be determined. The surface heat transport coefficient during the monotonic regime can be determined by the continuous measurement of long-wave radiation heat flow and the photoelectric measurement of the air refractive index gradient in a boundary layer. CFD simulation of the cooling process was carried out to analyse local convective and radiative heat transfer coefficients more in detail. Influence of ambient air flow was analysed. The obtained eigenvalues and corresponding surface heat transfer coefficient values enable to determine thermal conductivity of the analysed specimen together with its thermal diffusivity during a monotonic heating regime.

  12. The Effect of Baffles on the Temperature Distribution and Heat-transfer Coefficients of Finned Cylinders

    NASA Technical Reports Server (NTRS)

    Schey, Oscar W; Rollin, Vern G

    1936-01-01

    This report presents the results of an investigation to determine the effect of baffles on the temperature distribution and the heat-transfer coefficient of finned cylinders. The tests were conducted in a 30-inch wind tunnel on electrically heated cylinders with fins of 0.25 and 0.31 inch pitch. The results of these tests showed that the use of integral baffles gave a reduction of 31.9 percent in the rear wall temperatures and an increase of 54.2 percent in the heat transfer coefficient as compared with a cylinder without baffles.

  13. Effect of the heating surface enhancement on the heat transfer coefficient for a vertical minichannel

    NASA Astrophysics Data System (ADS)

    Piasecka, Magdalena; Strąk, Kinga

    2016-03-01

    The aim of the paper is to estimate effect of the heating surface enhancement on FC-72 flow boiling heat transfer for a vertical minichannel 1.7 mm deep, 24 mm wide and 360 mm long. Two types of enhanced heating surfaces were used: one with minicavities distributed unevenly, and the other with capillary metal fibrous structure. It was to measure temperature field on the plain side of the heating surface by means of the infrared thermography and to observe the two-phase flow patterns on the enhanced foil side. The paper analyses mainly the impact of the microstructured heating surface on the heat transfer coefficient. The results are presented as heat transfer coefficient dependences on the distance along the minichannel length. The data obtained using two types of enhanced heating surfaces in experiments was compared with the data when smooth foil as the heating surface was used. The highest local values of heat transfer coefficient were obtained using enhanced foil with minicavities - in comparison to other cases. Local values of heat transfer coefficient received for capillary fibrous structure were the lowest, even compared with data obtained for smooth foil. Probably this porous structure caused local flow disturbances.

  14. Correlation between mass transfer coefficient kLa and relevant operating parameters in cylindrical disposable shaken bioreactors on a bench-to-pilot scale

    PubMed Central

    2013-01-01

    Background Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen kLa and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal kLa correlation. Results A Respiration Activity Monitoring System (RAMOS) was used to measure kLa values in cylindrical disposable shaken bioreactors and Buckingham’s π-Theorem was applied to define a dimensionless equation for kLa. In this way, a scale- and volume-independent kLa correlation was developed and validated in bioreactors with volumes from 2 L to 200 L. The final correlation was used to calculate cultivation parameters at different scales to allow a sufficient oxygen supply of tobacco BY-2 cell suspension cultures. Conclusion The resulting equation can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters such as the reactor diameter, the shaking frequency, the filling volume, the viscosity, the oxygen diffusion coefficient, the gravitational acceleration or the shaking diameter within an accuracy range of +/− 30%. To our knowledge, this is the first kLa correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale. PMID:24289110

  15. The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction

    NASA Astrophysics Data System (ADS)

    Luo, Benyi; Lu, Yigang

    2008-10-01

    Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

  16. Empirical correlation of volumetric mass transfer coefficient for a rectangular internal-loop airlift bioreactor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s pen...

  17. Measurements of pressure drop, heat transfer coefficient and critical energy of a bundle conductor

    SciTech Connect

    Junghans, D.

    1981-09-01

    Friction factor, saturation temperature, heat transfer coefficient and critical energy of an eight strand bundle conductor were measured in the test facility SULTAN at SIN in Switzerland. The measured values of the critical energy are in good agreement with those calculated by the computer code LONSA. 10 refs.

  18. Heat transfer coefficients in two-dimensional Yukawa systems (numerical simulations)

    SciTech Connect

    Khrustalyov, Yu. V. Vaulina, O. S.

    2013-05-15

    New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data.

  19. Measurement of convective heat transfer coefficient for a horizontal cylinder rotating in quiescent air

    SciTech Connect

    Oezerdem, B.

    2000-04-01

    Heat transfer from a rotating cylinder is one of the problems, which is drawing attention due to its wide range of engineering applications. The present paper deals with convective heat transfer from a horizontal cylinder rotating in quiescent air, experimentally. The average convective heat transfer coefficients have been measured by using radiation pyrometer, which offers a new method. According to the experimental results, a correlation in terms of the average Nusselt number and rotating Reynolds number has been established. The average Nusselt number increased with an increase in the rotating speed. Comparison of the results, with previous studies, have been showed a good agreement with each other.

  20. Computational Fluid Dynamics Based Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks

    NASA Technical Reports Server (NTRS)

    Yang, H. Q.; West, Jeff

    2015-01-01

    Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.

  1. 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. PMID:27120652

  2. Uptake, efflux, and mass transfer coefficient of fluorescent PAMAM dendrimers into pancreatic cancer cells.

    PubMed

    Opitz, Armin W; Czymmek, Kirk J; Wickstrom, Eric; Wagner, Norman J

    2013-02-01

    Targeted delivery of imaging agents to cells can be optimized with the understanding of uptake and efflux rates. Cellular uptake of macromolecules is studied frequently with fluorescent probes. We hypothesized that the internalization and efflux of fluorescently labeled macromolecules into and out of mammalian cells could be quantified by confocal microscopy to determine the rate of uptake and efflux, from which the mass transfer coefficient is calculated. The cellular influx and efflux of a third generation poly(amido amine) (PAMAM) dendrimer labeled with an Alexa Fluor 555 dye was measured in Capan-1 pancreatic cancer cells using confocal fluorescence microscopy. The Capan-1 cells were also labeled with 5-chloromethylfluorescein diacetate (CMFDA) green cell tracker dye to delineate cellular boundaries. A dilution curve of the fluorescently labeled PAMAM dendrimer enabled quantification of the concentration of dendrimer in the cell. A simple mass transfer model described the uptake and efflux behavior of the PAMAM dendrimer. The effective mass transfer coefficient was found to be 0.054±0.043μm/min, which corresponds to a rate constant of 0.035±0.023min(-1) for uptake of the PAMAM dendrimer into the Capan-1 cells. The effective mass transfer coefficient was shown to predict the efflux behavior of the PAMAM dendrimer from the cell if the fraction of labeled dendrimer undergoing non-specific binding is accounted for. This work introduces a novel method to quantify the mass transfer behavior of fluorescently labeled macromolecules into mammalian cells.

  3. Improved voltage transfer coefficients for nonconductive materials in radiofrequency glow discharge optical emission spectrometry.

    PubMed

    Therese, L; Ghalem, Z; Guillot, P; Belenguer, P

    2006-09-01

    In radiofrequency glow discharge emission spectrometry (RF-GDOES), the excitation voltage used to create the plasma is applied to the back or front end of the sample to be analyzed. In this paper we focus on back-applied voltage systems (a configuration that represents about half of the instruments available on the market), and on applied voltage problems (the power coupling efficiency and materials analysis are beyond the scope of this study). In the RF-GDOES of nonconductive samples, a voltage drop develops inside the material. The voltage transfer coefficient is defined as the ratio between the peak voltage in front of the sample (facing the plasma) and the peak voltage applied to the back of the sample. In this work, we show that it is possible to increase the voltage transfer coefficient by increasing the capacitance of the sample. The capacitance of a given nonconductive material depends on its surface, its thickness and its permittivity. Increasing the voltage transfer coefficient permits higher power deposition in the plasma. This study is based on an electrical equivalent circuit for the discharge device, which takes into account the sample and reactor capacitances as well as the voltage probes used for the measurements. This circuit, when modeled by a commercial electrical circuit simulator, gives the voltage transfer coefficient as a function of the sample capacitance. Different approaches to increasing the sample capacitance and their influence on the voltage transfer coefficient are presented and related to the 750.4 nm argon line intensity, which is correlated to the electron density. PMID:16724217

  4. Catalytic electron-transfer oxygenation of substrates with water as an oxygen source using manganese porphyrins.

    PubMed

    Fukuzumi, Shunichi; Mizuno, Takuya; Ojiri, Tetsuya

    2012-12-01

    Manganese(V)-oxo-porphyrins are produced by the electron-transfer oxidation of manganese-porphyrins with tris(2,2'-bipyridine)ruthenium(III) ([Ru(bpy)(3)](3+); 2 equiv) in acetonitrile (CH(3)CN) containing water. The rate constants of the electron-transfer oxidation of manganese-porphyrins have been determined and evaluated in light of the Marcus theory of electron transfer. Addition of [Ru(bpy)(3)](3+) to a solution of olefins (styrene and cyclohexene) in CH(3)CN containing water in the presence of a catalytic amount of manganese-porphyrins afforded epoxides, diols, and aldehydes efficiently. Epoxides were converted to the corresponding diols by hydrolysis, and were further oxidized to the corresponding aldehydes. The turnover numbers vary significantly depending on the type of manganese-porphyrin used owing to the difference in their oxidation potentials and the steric bulkiness of the ligand. Ethylbenzene was also oxidized to 1-phenylethanol using manganese-porphyrins as electron-transfer catalysts. The oxygen source in the substrate oxygenation was confirmed to be water by using (18)O-labeled water. The rate constant of the reaction of the manganese(V)-oxo species with cyclohexene was determined directly under single-turnover conditions by monitoring the increase in absorbance attributable to the manganese(III) species produced in the reaction with cyclohexene. It has been shown that the rate-determining step in the catalytic electron-transfer oxygenation of cyclohexene is electron transfer from [Ru(bpy)(3)](3+) to the manganese-porphyrins.

  5. Heat transfer coefficients in bubbly and slug flows under microgravity conditions

    SciTech Connect

    Rezkallah, K.S.; Rite, R.W.

    1996-12-31

    Experimental local heat transfer data were collected onboard NASA`s KC-135 reduced gravity aircraft for two-phase, air-water flow in vertical, upward, co-current flow through a 9.53 mm circular tube. It was found that in the bubbly and slug flow regimes (surface tension dominated regimes), reduced gravity has a tendency to lower the heat transfer coefficient by up to 50% at the lowest gas qualities. As the gas quality is increased (transition to annular flow), the difference between the 1-g and {micro}-g heat transfer coefficients is much less significant. Empirical correlations were developed in terms of the pertinent dimensionless groups; namely the superficial liquid Reynolds number, the Froude number, the Graetz number and the Morton number. The correlations predicted the experimental data within 10--25%, depending on the flow regime and the superficial gas Weber number.

  6. Techniques for obtaining detailed heat transfer coefficient measurements within gas turbine blade and vane cooling passages

    NASA Astrophysics Data System (ADS)

    Clifford, R. J.; Jones, T. V.; Dunnne, S. T.

    1983-03-01

    Techniques developed jointly by Rolls-Royce Bristol and Oxford University for determining detailed heat transfer distributions inside turbine blade and vane cooling passages are reviewed. Use is made of a low temperature phase change paint to map the heat flux distributions within models of the cooling passages; the paints change from an opaque coating to a clear liquid at a well-defined melting point. In this way the surface temperature history of a model subjected to transient convective heating is recorded. The heat transfer coefficient distribution is deduced from this history using a transient conduction analysis within the model. Results are presented on detailed heat transfer coefficient distributions within a variety of cooling passages; and data obtained from a comprehensive study of a typical engine multipass cooling geometry are examined.

  7. Experimental determination of heat transfer coefficient in the slip regime and its anomalously low value.

    PubMed

    Demsis, Anwar; Verma, Bhaskar; Prabhu, S V; Agrawal, Amit

    2009-07-01

    In this paper, the measurement of the heat transfer coefficient in rarefied gases is presented; these are among the first heat transfer measurements in the slip flow regime. The experimental setup is validated by comparing friction factor in the slip regime and heat transfer coefficient in the continuum regime. Experimental results suggest that the Nusselt number is a function of Reynolds and Knudsen numbers in the slip flow regime. The measured values for Nusselt numbers are smaller than that predicted by theoretical or simulation results, and can become a few orders of magnitude smaller than the theoretical values in the continuum regime. The results are repeatable and expected to be useful for further experimentation and modeling of flow in the slip and transition regimes.

  8. Oxygen mass transfer and hydrodynamic behaviour in wastewater: determination of local impact of surfactants by visualization techniques.

    PubMed

    Jimenez, Mélanie; Dietrich, Nicolas; Grace, John R; Hébrard, Gilles

    2014-07-01

    Powerful techniques, based on the Planar Laser Induced Fluorescence (PLIF) technique, are deployed to locally visualize and quantify the impact of surfactants in wastewaters on hydrodynamics and oxygen mass transfer. Bubble diameter, aspect ratio, rise velocity, contamination angle, as well as flux, flux density, liquid side mass transfer and diffusion coefficients of transferred oxygen are determined based on these techniques applied in the wake of rising bubbles of diameter 1 mm and through planar gas/liquid interfaces. The initial experiments were performed in demineralized water containing small amounts of surfactant. Different concentrations of surfactant were added to finally reach the Critical Micelle Concentration (CMC). Bubbles have classically been found to be more spherical with a reduced rise velocity in the presence of surfactants up to the CMC. Above the CMC, these hydrodynamic characteristics were found to be almost constant, although the oxygen mass transfer decreased due to the presence of surfactants. Experimental results were markedly lower than predicted by the well-known Frössling equation with rigid surfaces. This is believed to be caused by a barrier of surfactants hindering the oxygen mass transfer at the interface. Similar hindrance of oxygen mass transfer applies to waters from sewage plants (filtered raw water and treated water), making accurate design of aeration tanks difficult.

  9. Structure and energy transfer in photosystems of oxygenic photosynthesis.

    PubMed

    Nelson, Nathan; Junge, Wolfgang

    2015-01-01

    Oxygenic photosynthesis is the principal converter of sunlight into chemical energy on Earth. Cyanobacteria and plants provide the oxygen, food, fuel, fibers, and platform chemicals for life on Earth. The conversion of solar energy into chemical energy is catalyzed by two multisubunit membrane protein complexes, photosystem I (PSI) and photosystem II (PSII). Light is absorbed by the pigment cofactors, and excitation energy is transferred among the antennae pigments and converted into chemical energy at very high efficiency. Oxygenic photosynthesis has existed for more than three billion years, during which its molecular machinery was perfected to minimize wasteful reactions. Light excitation transfer and singlet trapping won over fluorescence, radiation-less decay, and triplet formation. Photosynthetic reaction centers operate in organisms ranging from bacteria to higher plants. They are all evolutionarily linked. The crystal structure determination of photosynthetic protein complexes sheds light on the various partial reactions and explains how they are protected against wasteful pathways and why their function is robust. This review discusses the efficiency of photosynthetic solar energy conversion.

  10. Theoretical prediction of the influence coefficients on damped simple flexible rotors using the transfer matrix method

    NASA Astrophysics Data System (ADS)

    Jun, Oh-Sung; Kim, Paul Y.

    1994-02-01

    The influence coefficients for undamped flexible rotors are analytically derived and then compared and discussed for various damping coefficients. The concept of the transfer matrix method is partially adapted in the formulation. Single-disk and single cylinder rotor models are used for one- and two-plane balancing models, respectively. The gyroscopic effect of the disk or cylinder, which has been included in the formulation, is proved important through a simplified example rotor model. Taking the gyroscopic effect into account when calculating the influence coefficient is especially important near the resonant and antiresonant frequencies of the rotor. The simplified model also shows that an increase in damping reduces the sharpness of magnitude curve of influence coefficients and smoothens the change of phase at around the resonant and antiresonant frequencies.

  11. Optimization of oxygen mass transfer in a multiphase bioreactor with perfluorodecalin as a second liquid phase.

    PubMed

    Amaral, Priscilla F F; Freire, Mara G; Rocha-Leão, Maria Helena M; Marrucho, Isabel M; Coutinho, João A P; Coelho, Maria Alice Z

    2008-02-15

    Oxygenation is an important parameter involved in the design and operation of mixing-sparging bioreactors and it can be analyzed by means of the oxygen mass transfer coefficient (k(L)a). The operational conditions of a stirred, submerged aerated 2-L bioreactor have been optimized by studying the influence of a second liquid phase with higher oxygen affinity (perfluorodecalin or olive oil) in the k(L)a. Using k(L)a measurements, the influence of the following parameters on the oxygen transfer rate was evaluated: the volume of working medium, the type of impellers and their position, the organic phase concentration, the aqueous phase composition, and the concentration of inactive biomass. This study shows that the best experimental conditions were achieved with a perfluorodecalin volume fraction of 0.20, mixing using two Rushton turbines with six vertical blades and in the presence of YPD medium as the aqueous phase, with a k(L)a value of 64.6 h(-1). The addition of 20% of perfluorodecalin in these conditions provided a k(L)a enhancement of 25% when pure water was the aqueous phase and a 230% enhancement when YPD medium was used in comparison to their respective controls (no perfluorodecalin). Furthermore it is shown that the presence of olive oil as a second liquid phase is not beneficial to the oxygen transfer rate enhancement, leading to a decrease in the k(L)a values for all the concentrations studied. It was also observed that the magnitude of the enhancement of the k(L)a values by perfluorodecalin depends on the biomass concentration present. PMID:17787007

  12. Determination of drying kinetics and convective heat transfer coefficients of ginger slices

    NASA Astrophysics Data System (ADS)

    Akpinar, Ebru Kavak; Toraman, Seda

    2016-10-01

    In the present work, the effects of some parametric values on convective heat transfer coefficients and the thin layer drying process of ginger slices were investigated. Drying was done in the laboratory by using cyclone type convective dryer. The drying air temperature was varied as 40, 50, 60 and 70 °C and the air velocity is 0.8, 1.5 and 3 m/s. All drying experiments had only falling rate period. The drying data were fitted to the twelve mathematical models and performance of these models was investigated by comparing the determination of coefficient ( R 2), reduced Chi-square ( χ 2) and root mean square error between the observed and predicted moisture ratios. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick's diffusion equation. The average effective moisture diffusivity values and activation energy values varied from 2.807 × 10-10 to 6.977 × 10-10 m2/s and 19.313-22.722 kJ/mol over the drying air temperature and velocity range, respectively. Experimental data was used to evaluate the values of constants in Nusselt number expression by using linear regression analysis and consequently, convective heat transfer coefficients were determined in forced convection mode. Convective heat transfer coefficient of ginger slices showed changes in ranges 0.33-2.11 W/m2 °C.

  13. Controlled random search technique for estimation of convective heat transfer coefficient

    NASA Astrophysics Data System (ADS)

    Mehta, R. C.; Tiwari, S. B.

    2007-09-01

    This paper is concerned with a method for solving inverse heat conduction problem. The method is based on the controlled random search (CRS) technique in conjunction with modified Newton-Raphson method. The random search procedure does not need the computation of derivative of the function to be evaluated. Therefore, it is independent of the calculation of the sensitivity coefficient for nonlinear parameter estimation. The algorithm does not depend on the future-temperature information and can predict convective heat transfer coefficient with random errors in the input temperature data. The technique is first validated against an analytical solution of heat conduction equation for a typical rocket nozzle. Comparison with an earlier analysis of inverse heat conduction problem of a similar experiment shows that the present method provides solutions, which are fully consistent with the earlier results. Once validated, the technique is used to investigate another estimation of heat transfer coefficient for an experiment of short duration, high heating rate, and employing indepth temperature measurement. The CRS procedure, in conjunction with modified Newton-Raphson method, is quite useful in estimating the value of the convective heat-transfer coefficient from the measured transient temperature data on the outer surface or imbedded thermocouple inside the rocket nozzle. Some practical examples are illustrated, which demonstrate the stability and accuracy of the method to predict the surface heat flux.

  14. Determination of the heat transfer coefficient from IRT measurement data using the Trefftz method

    NASA Astrophysics Data System (ADS)

    Maciejewska, Beata; Strąk, Kinga; Piasecka, Magdalena

    2016-03-01

    The paper presents the method of heat transfer coefficient determination for boiling research during FC-72 flow in the minichannels, each 1.7 mm deep, 24 mm wide and 360 mm long. The heating element was the thin foil, enhanced on the side which comes into contact with fluid in the minichannels. Local values of the heat transfer coefficient were calculated from the Robin boundary condition. The foil temperature distribution and the derivative of the foil temperature were obtained by solving the two-dimensional inverse heat conduction problem, due to measurements obtained by IRT. Calculations was carried out by the method based on the approximation of the solution of the problem using a linear combination of Trefftz functions. The basic property of this functions is they satisfy the governing equation. Unknown coefficients of linear combination of Trefftz functions are calculated from the minimization of the functional that expresses the mean square error of the approximate solution on the boundary. The results presented as IR thermographs, two-phase flow structure images and the heat transfer coefficient as a function of the distance from the channel inlet, were analyzed.

  15. Determination of drying kinetics and convective heat transfer coefficients of ginger slices

    NASA Astrophysics Data System (ADS)

    Akpinar, Ebru Kavak; Toraman, Seda

    2015-12-01

    In the present work, the effects of some parametric values on convective heat transfer coefficients and the thin layer drying process of ginger slices were investigated. Drying was done in the laboratory by using cyclone type convective dryer. The drying air temperature was varied as 40, 50, 60 and 70 °C and the air velocity is 0.8, 1.5 and 3 m/s. All drying experiments had only falling rate period. The drying data were fitted to the twelve mathematical models and performance of these models was investigated by comparing the determination of coefficient (R 2), reduced Chi-square (χ 2) and root mean square error between the observed and predicted moisture ratios. The effective moisture diffusivity and activation energy were calculated using an infinite series solution of Fick's diffusion equation. The average effective moisture diffusivity values and activation energy values varied from 2.807 × 10-10 to 6.977 × 10-10 m2/s and 19.313-22.722 kJ/mol over the drying air temperature and velocity range, respectively. Experimental data was used to evaluate the values of constants in Nusselt number expression by using linear regression analysis and consequently, convective heat transfer coefficients were determined in forced convection mode. Convective heat transfer coefficient of ginger slices showed changes in ranges 0.33-2.11 W/m2 °C.

  16. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    NASA Astrophysics Data System (ADS)

    Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.

    2007-05-01

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication…). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  17. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    SciTech Connect

    Moreau, P.; Gregoire, S.; Lochegnies, D.; Cesar de Sa, J.

    2007-05-17

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication...). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  18. Dimethylsulfide gas transfer coefficients from algal blooms in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Marandino, C. A.; Miller, S. D.; Law, C. S.; Smith, M. J.; Saltzman, E. S.

    2015-02-01

    Air-sea dimethylsulfide (DMS) fluxes and bulk air-sea gradients were measured over the Southern Ocean in February-March 2012 during the Surface Ocean Aerosol Production (SOAP) study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (> 15 nM). Gas transfer coefficients were considerably scattered at wind speeds above 5 m s-1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind-speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data show no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.

  19. DMS gas transfer coefficients from algal blooms in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Marandino, C. A.; Miller, S. D.; Law, C. S.; Smith, M. J.; Saltzman, E. S.

    2014-11-01

    Air/sea dimethylsulfide (DMS) fluxes and bulk air/sea gradients were measured over the Southern Ocean in February/March 2012 during the Surface Ocean Aerosol Production (SOAP) study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (>15 nM). Gas transfer coefficients were considerably scattered at wind speeds above 5 m s-1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A~flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data shows no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.

  20. Electrochemical proton-coupled electron transfer of an osmium aquo complex: theoretical analysis of asymmetric tafel plots and transfer coefficients.

    PubMed

    Ludlow, Michelle K; Soudackov, Alexander V; Hammes-Schiffer, Sharon

    2010-02-01

    Electrochemical proton-coupled electron transfer of an osmium aquo complex attached to a self-assembled monolayer on a gold electrode is studied with a recently developed theoretical formulation. The calculated hydrogen/deuterium kinetic isotope effect for the standard rate constant, the cathodic transfer coefficient at zero overpotential, and the Tafel plot are in excellent agreement with experimental data. The input quantities to the heterogeneous rate constant expressions were calculated with density functional theory in conjunction with dielectric continuum models, and no parameters were fit to experimental data. The theoretical calculations indicate that the asymmetry of the Tafel plot and the deviation of the transfer coefficient at zero overpotential from the standard value of one-half arise from the change in the equilibrium proton donor-acceptor distance upon electron transfer. The direction of the asymmetry and deviation from one-half is determined by the sign of this distance change, and the magnitude of these effects is determined by the magnitude of this distance change, as well as the reorganization energy and the distance dependence of the overlap between the initial and final proton vibrational wave functions. This theory provides experimentally testable predictions for the impact of specific system properties on the qualitative behavior of the Tafel plots. PMID:20067257

  1. Single-phase ambient and cryogenic temperature heat transfer coefficients in microchannels

    NASA Astrophysics Data System (ADS)

    Baek, S.; Bradley, P. E.

    2015-12-01

    Micro-scaling cryogenic refrigerators, in particular the Joule-Thomson (JT) variety require very good information about heat transfer characteristics of the refrigerants flowing in the microchannels for optimal design and performance. The extremely low Reynolds flow is present in a micro JT cryocooler, the heat transfer characteristics at these conditions require investigation. There are numerous studies regarding heat transfer coefficient measurements of liquid flow in microchannels at/near ambient temperature and high Reynolds flow (Re>2000), that agree well with the conventional correlations. However, results from previous studies of gaseous flow in microchannels at low Reynolds flow (Re<1000) disagree with conventional theory. Moreover, the studies performed at cryogenic temperatures are quite limited in number. In this paper, the single-phase heat transfer coefficients and friction factors for nitrogen are measured at ambient and cryogenic temperatures. The hydraulic diameters for this study are 60, 110 and 180 μm for circular microchannels. The Reynolds numbers varied from a very low value of 10 to 3000. The measured friction factors are comparable to those in macro-scale tubes. The experimental results of the heat transfer indicate that Nusselt numbers derived from measurements are significantly affected by axial conduction at low Reynolds flow (Re<500). The Nusselt numbers at high Reynolds flow (Re>1000) follow conventional theory. The detailed experiment, procedure, and measured results are presented in this paper and discussed regarding deviation from ideal theory at low Reynolds flow.

  2. Measurement of convectional heat transfer coefficients in a primary containment vessel with outer pool

    SciTech Connect

    Fukui, Toru; Kataoka, Yoshiyuki; Hatamiya, Shigeo

    1990-01-01

    New concepts with passive safety systems that use no active compounds, such as pumps, have been recently developed for next-generation nuclear power plants. In these concepts, several ideas and their combination of passive components were adopted for emergency core cooling and residual heat removal systems. For the residual heat removal system, utilization of natural circulation heat transfer in water pools was proposed as a passive containment cooling system (PCCS), which removes decay heat from the primary containment vessel (PCV) during loss-of-coolant accidents (LOCAs). This system consists of a suppression pool (S/P) and an outer pool (O/P), which are set adjacently inside and outside of the steel PCV wall. The core decay heat during LOCA is released through a break as steam and is led into the S/P. The injected steam condenses there, resulting a pool temperature rise. The adsorbed heat in the S/P is transferred to the O/P by convection in both pools and thermal conduction through the steel PCV wall. The heat transferred to the O/P is finally released to the atmosphere by vaporization of the O/P water. Estimation of the convectional heat transfer coefficients in both pools is necessary to predict the heat removal capability in this system precisely. The heat transfer coefficients measured in this study are useful for the design of the next-generation nuclear reactor as the fundamental thermal-hydraulic data in the primary containment vessel with the outer pool.

  3. On the influence of the surface heat transfer coefficient on wet underwater welds

    SciTech Connect

    Hamann, R.; Mahrenholtz, O.

    1994-12-31

    This paper deals with the influence of the surface heat transfer on the temperature distribution during wet underwater welding. A model for the heat-transfer-coefficient on a horizontal plate considering different effects is presented. The influence of undercooled boiling, surface orientation and heater material on the temperature course are discussed. Welding experiments were performed on low carbon steel plates in a shallow water basin using Plasma-MIG underwater welding technique. For the numerical simulation of the welding process a new welding model has been developed for the Plasma-MIG underwater welding technique. The temperature problem is solved using finite element method. The numerical and experimental data are compared.

  4. Survey of literature on convective heat transfer coefficients and recovery factors for high atmosphere thermometry

    NASA Technical Reports Server (NTRS)

    Chung, S.

    1973-01-01

    Heat transfer phenomena of rarefied gas flows is discussed based on a literature survey of analytical and experimental rarefied gas dynamics. Subsonic flows are emphasized for the purposes of meteorological thermometry in the high atmosphere. The heat transfer coefficients for three basic geometries are given in the regimes of free molecular flow, transition flow, slip flow, and continuum flow. Different types of heat phenomena, and the analysis of theoretical and experimental data are presented. The uncertainties calculated from the interpolation rule compared with the available experimental data are discussed. The recovery factor for each geometry in subsonic rarefied flows is also given.

  5. Moment method for the estimation of mass transfer coefficients for physiological pharmacokinetic models.

    PubMed

    Gallo, J M; Lam, F C; Perrier, D G

    1991-03-01

    In vitro and in vivo techniques have been utilized to estimate mass transfer coefficients for physiological pharmacokinetic models. No single method has been adopted for estimating this parameter, in part, due to the different model structures with which this parameter may be associated. A specific method has been derived to calculate mass transfer coefficients for non-eliminating membrane-limited tissue compartments. The present method is based on observed concentration-time data, and requires the calculation of the areas under the zero and first moment curves for plasma, and the first moment curve for the tissue. A Monte Carlo simulation technique was used to determine the percentage biases of the method based on a published model for streptozoticin and adriamycin. For the latter model, the method was compared to a non-linear regression parameter estimation technique. PMID:2031994

  6. Experimental Technique and Assessment for Measuring the Convective Heat Transfer Coefficient from Natural Ice Accretions

    NASA Technical Reports Server (NTRS)

    Masiulaniec, K. Cyril; Vanfossen, G. James, Jr.; Dewitt, Kenneth J.; Dukhan, Nihad

    1995-01-01

    A technique was developed to cast frozen ice shapes that had been grown on a metal surface. This technique was applied to a series of ice shapes that were grown in the NASA Lewis Icing Research Tunnel on flat plates. Nine flat plates, 18 inches square, were obtained from which aluminum castings were made that gave good ice shape characterizations. Test strips taken from these plates were outfitted with heat flux gages, such that when placed in a dry wind tunnel, can be used to experimentally map out the convective heat transfer coefficient in the direction of flow from the roughened surfaces. The effects on the heat transfer coefficient for both parallel and accelerating flow will be studied. The smooth plate model verification baseline data as well as one ice roughened test case are presented.

  7. Nonlinear inverse problem for the estimation of time-and-space dependent heat transfer coefficients

    NASA Astrophysics Data System (ADS)

    Osman, A. M.; Beck, J. V.

    1987-01-01

    The aim of this paper is to describe a method and an algorithm for the direct estimation of the time-and-space dependent heat transfer coefficients from transient temperature data measured at approximate points inside a heat conducting solid. This inverse estimation problem is called herein the inverse heat transfer coefficient problem. An application considered in the present is the quenching of a solid in a liquid. The solution method used here is an extension of the sequential temperature future-information method introduced by Beck for solving the inverse heat conduction problem. The finite-difference method, based on the control volume approach, was used for the discretization of the direct heat conduction problem. Numerical results show that the proposed method is accurate and efficient.

  8. Negative ion clusters in oxygen: collision cross sections and transport coefficients

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Bekstein, A.; Ducasse, O.; Ruíz-Vargas, G.; Yousfi, M.; Benhenni, M.

    2009-12-01

    Using a pulsed Townsend experiment, we have observed the formation of two negative ion species in oxygen over the pressure range 100-600 torr, and the density-normalised electric field strength, E/N, from 2 to 14 Td. The peculiar shape of these transients has led us to propose a scheme of three-body ion-molecule reactions leading to the formation of O4 - and O6 -, which is substantiated by a curve fitting procedure. The resulting mobility data of these two ionic species have been used to calculate their respective momentum transfer collision cross sections, together with the dissociation cross sections that are needed to extend the range of calculation of mobility and diffusion (transverse and longitudinal) to 1000 Td. These calculations were based on an optimised Monte Carlo algorithm, using collision cross sections obtained from a JWKB approximation (Jeffreys-Wentzel-Kramers-Brillouin) or taken from literature.

  9. Estimation of heat-transfer coefficients, the upward heat flow, and evaporation in a solar still

    SciTech Connect

    Sharma, V.B.; Mullick, S.C. . Centre of Energy Studies)

    1991-02-01

    The present work enables prediction of the performance of a solar still through simple calculations. Estimation of the temperature of the glass cover by an empirical relation developed in this work permits calculation of the heat-transfer coefficients, the upward heat flow, and evaporation. Since some of the heat-transfer coefficients vary substantially and nonlinearly with temperature, the empirical relation developed for glass cover temperature is based on an approximate solution of the heat balance equation. Hence, the overall upward heat flow factor is obtained with a maximum absolute error of three percent compared to the value obtained through a numerical solution of the heat balance equation along with the relations for vapor pressure and latent heat. The fraction of upward heat flow utilized for evaporation is determined with a maximum absolute error of 0.5 percent. The range of variables covered is 30{degrees}C to 80{degrees}C in water temperature, 5W/m{sup 2}K to 40W/M{sup 2}K in wind heat-transfer coefficient, and 5{degrees}C to 40{degrees}C in ambient temperature.

  10. Adiabatic Effectiveness and Heat Transfer Coefficient on a Film-Cooled Rotating Blade

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.

    1997-01-01

    three-dimensional Navier-Stokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotating film-cooled turbine blade. The blade chosen is the United Technologies Research Center(UTRC) rotor with five film-cooling rows containing 83 holes, including three rows on the shower head with 49 holes, covering about 86% of the blade span. The mainstream is akin to that under real engine conditions with stagnation temperature 1900 K and stagnation pressure 3 MPa. The blade speed is taken to be 5200 rpm. The adiabatic effectiveness is higher for a rotating blade as compared to that for a stationary blade. Also, the direction of coolant injection from the shower-head holes considerably affects the effectiveness and heat transfer coefficient values on both the pressure and suction surfaces. In all cases the heat transfer coefficient and adiabatic effectiveness are highly three-dimensional in the vicinity of holes but tend to become two-dimensional far downstream.

  11. Local pressure measurements and heat transfer coefficients of flow boiling in a rectangular microchannel

    NASA Astrophysics Data System (ADS)

    Mirmanto, M.

    2016-01-01

    Experiments to investigate local pressure distribution and local heat transfer coefficients during flow boiling of water in a microchannel were performed. The hydraulic diameter of the channel was 0.635 mm. The nominal mass fluxes used were varied from 200 to 700 kg/m2 s and heat fluxes ranging from 171 to 685 kW/m2 were applied. An inlet fluid temperature of 98 °C and pressure of 125 kPa were maintained at the microchannel entrance. There were six pressure tappings inserted into the channel to measure the local pressures and six thermocouple inserted into the channel block with equally distances to measure the wall local temperatures. The local pressure measurements during flow boiling show a non linear line connecting each local pressure, especially at higher heat fluxes or pressure drops. The non linear local pressure influences the value of the estimated local heat transfer coefficient. The effects of mass flux and heat flux on local heat transfer coefficient are also discussed.

  12. Transfer coefficients of selected radionuclides to animal products. II. Hen eggs and meat

    SciTech Connect

    Ennis, M.E. Jr.; Ward, G.M.; Johnson, J.E.; Boamah, K.N.

    1988-02-01

    Transfer coefficients to eggs and meat were determined after acute oral doses of /sup 95m/Tc, /sup 99/Mo, /sup 123m/Te, /sup 133/Ba, /sup 131/I, /sup 95/Zr and /sup 95/Nb to laying hens. The mean values (in units of d kg-1) to eggs and hen meat were, respectively, 3.0 and 0.03 for Tc, 0.87 and 0.18 for Mo, 5.1 and 0.60 for Te, 0.87 and 9.2 x 10(-3) for Ba, 3.2 and 0.01 for I, 2 x 10(-4) and 6 x 10(-5) for Zr, and 1 x 10(-3) and 3 x 10(-4) for Nb. For the same radionuclides administered in the same chemical form, transfer coefficients for eggs are about one to two orders of magnitude higher than for cow's milk, while the transfer coefficients for hen meat are several orders of magnitude higher than for beef.

  13. In-situ determination of field-scale NAPL mass transfer coefficients: Performance, simulation and analysis

    NASA Astrophysics Data System (ADS)

    Mobile, Michael; Widdowson, Mark; Stewart, Lloyd; Nyman, Jennifer; Deeb, Rula; Kavanaugh, Michael; Mercer, James; Gallagher, Daniel

    2016-04-01

    Better estimates of non-aqueous phase liquid (NAPL) mass, its persistence into the future, and the potential impact of source reduction are critical needs for determining the optimal path to clean up sites impacted by NAPLs. One impediment to constraining time estimates of source depletion is the uncertainty in the rate of mass transfer between NAPLs and groundwater. In this study, an innovative field test is demonstrated for the purpose of quantifying field-scale NAPL mass transfer coefficients (klN) within a source zone of a fuel-contaminated site. Initial evaluation of the test concept using a numerical model revealed that the aqueous phase concentration response to the injection of clean groundwater within a source zone was a function of NAPL mass transfer. Under rate limited conditions, NAPL dissolution together with the injection flow rate and the radial distance to monitoring points directly controlled time of travel. Concentration responses observed in the field test were consistent with the hypothetical model results allowing field-scale NAPL mass transfer coefficients to be quantified. Site models for groundwater flow and solute transport were systematically calibrated and utilized for data analysis. Results show klN for benzene varied from 0.022 to 0.60 d- 1. Variability in results was attributed to a highly heterogeneous horizon consisting of layered media of varying physical properties.

  14. Mass transfer coefficient in ginger oil extraction by microwave hydrotropic solution

    NASA Astrophysics Data System (ADS)

    Handayani, Dwi; Ikhsan, Diyono; Yulianto, Mohamad Endy; Dwisukma, Mandy Ayulia

    2015-12-01

    This research aims to obtain mass transfer coefficient data on the extraction of ginger oil using microwave hydrotropic solvent as an alternative to increase zingiberene. The innovation of this study is extraction with microwave heater and hydrotropic solvent,which able to shift the phase equilibrium, and the increasing rate of the extraction process and to improve the content of ginger oil zingiberene. The experiment was conducted at the Laboratory of Separation Techniques at Chemical Engineering Department of Diponegoro University. The research activities carried out in two stages, namely experimental and modeling work. Preparation of the model postulated, then lowered to obtain equations that were tested and validated using data obtained from experimental. Measurement of experimental data was performed using microwave power (300 W), extraction temperature of 90 ° C and the independent variable, i.e.: type of hydrotropic, the volume of solvent and concentration in order, to obtain zingiberen levels as a function of time. Measured data was used as a tool to validate the postulation, in order to obtain validation of models and empirical equations. The results showed that the mass transfer coefficient (Kla) on zingiberene mass transfer models ginger oil extraction at various hydrotropic solution attained more 14 ± 2 Kla value than its reported on the extraction with electric heating. The larger value of Kla, the faster rate of mass transfer on the extraction process. To obtain the same yields, the microwave-assisted extraction required one twelfth time shorter.

  15. In-situ determination of field-scale NAPL mass transfer coefficients: Performance, simulation and analysis.

    PubMed

    Mobile, Michael; Widdowson, Mark; Stewart, Lloyd; Nyman, Jennifer; Deeb, Rula; Kavanaugh, Michael; Mercer, James; Gallagher, Daniel

    2016-04-01

    Better estimates of non-aqueous phase liquid (NAPL) mass, its persistence into the future, and the potential impact of source reduction are critical needs for determining the optimal path to clean up sites impacted by NAPLs. One impediment to constraining time estimates of source depletion is the uncertainty in the rate of mass transfer between NAPLs and groundwater. In this study, an innovative field test is demonstrated for the purpose of quantifying field-scale NAPL mass transfer coefficients (kl(N)) within a source zone of a fuel-contaminated site. Initial evaluation of the test concept using a numerical model revealed that the aqueous phase concentration response to the injection of clean groundwater within a source zone was a function of NAPL mass transfer. Under rate limited conditions, NAPL dissolution together with the injection flow rate and the radial distance to monitoring points directly controlled time of travel. Concentration responses observed in the field test were consistent with the hypothetical model results allowing field-scale NAPL mass transfer coefficients to be quantified. Site models for groundwater flow and solute transport were systematically calibrated and utilized for data analysis. Results show kl(N) for benzene varied from 0.022 to 0.60d(-1). Variability in results was attributed to a highly heterogeneous horizon consisting of layered media of varying physical properties.

  16. A parameterization of eddy transfer coefficients for two-level seasonal statistical dynamical zonally averaged models

    NASA Technical Reports Server (NTRS)

    Neeman, Binyamin U.; Ohring, George; Joseph, Joachim H.

    1989-01-01

    This paper examines a parameterization of a quasi-geostrophic eddy transport that takes into account the time variation of eddy transfer coefficients according to Green's (1970) theory. It was found that, in the original eddy transfer relationship of Green, connecting the integral of the northward eddy entropy flux through midlatitudes with the second power of the difference in 500-mb entropy across the region of baroclinic activity, a value of 4 for the exponent is obtained when the temperature gradients at 500 mb are used. When the gradients at 1000 mb are used, an exponent of 1.5 is obtained. The differences in the powers in the eddy transfer relation were explored in a two-level zonally averaged model. It was found that an appropriate choice of power may be of special importance if the model is devised to simulate the seasonal climate cycle or to test astronomical changes inducing different seasonalities.

  17. Comparison of experimental methods for determination of the volumetric mass transfer coefficient in fermentation processes

    NASA Astrophysics Data System (ADS)

    Tobajas, M.; García-Calvo, E.

    Mass transfer in bioreactors has been examined. In the present work, dynamic methods are used for the determination of KLa values for water, model media and a fermentation broth (Candida utilis) in an airlift reactor. The conventional dynamic method is applied at the end of the microbial process in order to avoid an alteration in the metabolism of the microorganisms. New dynamic methods are used to determine KLa in an airlift reactor during the microbial growth of Candida utilis on glucose. One of the methods is based on the continuous measurement of carbon dioxide production while the other method is based on the relationship between the oxygen transfer and biomass growth rates. These methods of determining KLa does not interfere with the microorganisms action. A theoretical mass transfer model has been used for KLa estimation for the systems described above. Some differences between calculated and measured values are found for fermentation processes due to the model is developed for two-phase air-water systems. Nevertheless, the average deviation between the predicted values and those obtained from the relationship between oxygen transfer and biomass production rates are lower than 25% in any case.

  18. Oxygen transfer in the corneal-contact lens system.

    PubMed

    Garr-Peters, J M; Ho, C S

    1987-01-01

    The clinical results of contact lens wearers indicate that materials which theoretically are adequate to prevent corneal hypoxia and edema do not perform optimally under actual wearing conditions. Optimization of the cornea-tear-lens system requires an analysis of the modes of oxygen transport, mass transfer resistances, and characteristic dimensions. The lens properties are a function of polymer composition. Thus, investigations for ideal lens materials may result in limitless test copolymers and graft polymers of siloxane, methylmethacrylate, 2-hydroxyethyl-methacrylate, vinylpyrollidone, vinylacetate, and cellulose acetate butyrate of varying degrees of cross-linking and crystallinity. In an attempt to channel research efforts, this review will state the developments to date and the desirable properties of an optimal cornea-tear-lens system. The logic should encompass a theory and model whereby parameters are identified and varied within satisfactory physiological limitations, and experiments which provide data indicative of the in vivo conditions. The parameters must reflect the inherent transport properties of the corneal-contact lens system. Contact lenses may be categorized as soft, gas-permeable rigid/hydrophobic flexible, or hard. The major differences between these three categories are the properties: equilibrium water content or degree of hydration, tendency for water pervaporation and/or dehydration, surface hydrophobicity, thermal conductivity, oxygen diffusivity and solubility, lens thickness, rest height over corneal tear, flexibility, lens mobility over the cornea, cross-linking, crystallinity, stagnant boundary layer resistances, and manufacturing processes. Aside from complications presented by lens coatings and cleansing solutions, the most common problems experienced by lens wearers include corneal edema, dehydration involving the lens and the cornea, "blurry" vision due to localized corneal anoxia, debris trapped under the lens, and deposits on

  19. 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.

  20. Mass transfer in SCW extraction molecular diffusion and mass transfer coefficients of ketones and alkenes in sub- and supercritical water

    SciTech Connect

    Goemans, M.G.E.; Gloyna, E.F.

    1996-10-01

    The potential of sub- and supercritical water as extraction solvents has been demonstrated for the (reactive) extraction of coals, used car tires, organic species from residual aqueous solutions, and class selective extraction of organic pollutants with different polarities from solids. In addition, the potential of extraction of coal with supercritical aqueous solutions has been studied. However, physical transport in water at elevated temperature and pressures- and their impact on heterogenous reactions and (reactive) extraction -are not adequately understood. This situation is largely due to the limited data that is available for diffusion in high temperature, high pressure water mixture. Only the molecular diffusion of Iodine ions and hydroquinone in near-critical subcritical water and the self diffusion of coefficient of compressed supercritical water have been reported. In this paper, we present molecular diffusion coefficients of benzophenone, acetone, naphthalene, and anthracene in water at infinite dilution. Pressures ranged from 250 to 500 bar at temperatures ranging from 50{degrees}C to 500{degrees}C resulting in water densities ranging from 1000 to 150 kg/m{sup 3}. Diffusion coefficients were determined by the Taylor-Aris dispersion technique. The effects of increased diffusion on the mass transfer coefficients for emulsions and packed beds were quantified. Molecular division coefficients were 10 to 20 times faster in supercritical water than in water at ambient conditions. Experimental results were correlated with hydrodynamic and kinetic theory. This study and results to be published elsewhere show that diffusion-limited conditions are much more likely to be encountered in supercritical water than is commonly acknowledged.

  1. The Seebeck Coefficient in Oxygen Enriched La2NiO4

    NASA Astrophysics Data System (ADS)

    Bach, Paul; Leboran, Victor; Rivadulla, Francisco

    2013-03-01

    Oxide-based devices show promise for themoelectric applications due to their chemical stability and straightforward fabrication. The La2NiO4+δ system has been predicted to show an increased thermopower coupled with an increased electrical conductivity around δ = 0 . 05 [Pardo et al. PRB 86, 165114 (2012)] that could lead to a large thermoelectric figure of merit (ZT). We investigate the suitability of lanthanum nickelate as a candidate material for high-ZT devices through a systematic study of oxygenated thin films grown by pulsed laser deposition. We report the electrical conductivity, Seebeck coefficient, and structural morphology of La2NiO4 grown in a range of oxidizing atmospheres and discuss their implications for controlled engineering of thermoelectric properties. We have explored the possibility of gate-tuning these systems in order to fabricate single-oxide based devices. This work was supported by the Ministerio de Ciencia e Innovación (Spain), grant MAT2010-16157, and the European Research Council, grant ERC-2010-StG 259082 2D THERMS.

  2. Detailed heat transfer coefficient measurements and thermal analysis at engine conditions of a pedestal with fillet radii

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Ireland, P. T.; Jones, T. V.

    1995-04-01

    The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.

  3. COMPUTATIONAL CHEMISTRY METHOD FOR PREDICTING VAPOR PRESSURES AND ACTIVITY COEFFICIENTS OF POLAR ORGANIC OXYGENATES IN PM2.5

    EPA Science Inventory

    Parameterizations of interactions of polar multifunctional organic oxygenates in PM2.5 must be included in aerosol chemistry models for evaluating control strategies for reducing ambient concentrations of PM2.5 compounds. Vapor pressures and activity coefficients of these compo...

  4. A model for calculating heat transfer coefficient concerning ethanol-water mixtures condensation

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Yan, J. J.; Hu, S. H.; Yang, Y. S.

    2010-03-01

    The attempt of the author in this research is made to calculate a heat transfer coefficient (HTC) by combining the filmwise theory with the dropwise notion for ethanol-water mixtures condensation. A new model, including ethanol concentration, vapor pressure and velocity, is developed by introducing a characteristic coefficient to combine the two mentioned-above theories. Under different concentration, pressure and velocity, the calculation is in comparison with experiment. It turns out that the calculation value is in good agreement with the experimental result; the maximal error is within ±30.1%. In addition, the model is applied to calculate related experiment in other literature and the values obtained agree well with results in reference.

  5. Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

    NASA Astrophysics Data System (ADS)

    Gladden, H. J.; Proctor, M. P.

    A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.

  6. Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

    NASA Technical Reports Server (NTRS)

    Gladden, H. J.; Proctor, M. P.

    1985-01-01

    A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.

  7. The realistic prediction of oxygen transport in a tissue-engineered scaffold by introducing time-varying effective diffusion coefficients.

    PubMed

    Kang, Tae-Yun; Kang, Hyun-Wook; Hwang, Chang Mo; Lee, Sang Jin; Park, Jaesung; Yoo, James J; Cho, Dong-Woo

    2011-09-01

    An adequate oxygen supply is one of the most important factors needed in order to regenerate or engineer thick tissues or complex organs. To devise a method for maximizing the amount of oxygen available to cells, it is necessary to understand and to realistically predict oxygen transport within an engineered tissue. In this study, we focused on the fact that oxygen transport through a tissue-engineered scaffold may vary with time as cells proliferate. To confirm this viewpoint, effective oxygen diffusion coefficients (D(e)(,)(s)) of scaffolds were deduced from experimental measurements and simulations of oxygen-concentration profiles were performed using these D(e)(,)(s) values in a two-dimensional (2-D) perfusion model. The results of this study indicate that higher porosity, hydraulic permeability and interconnectivity of scaffolds with no cells are responsible for the prominent diffusion capability quantified using D(e)(,)(s). On the other hand, the D(e)(,)(s) of scaffolds with cells has a negative linear relationship with cell density. Cell proliferation with time leads to a significant decrease in oxygen concentration in the 2-D perfusion model. This result demonstrates the gradual restriction of oxygen transport in a porous scaffold during cell culture. Therefore, the realistic prediction of oxygen transport using a time-varying D(e)(,)(s) will provide an appropriate basis for designing optimal transport networks within a thick scaffold.

  8. Surface heat transfer coefficient, heat efficiency, and temperature of pulsed solid-state lasers

    SciTech Connect

    Mann, K.; Weber, H.

    1988-08-01

    The temperature of solid-state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air- and water-cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.

  9. Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients

    SciTech Connect

    Dan Wendt; Greg Mines

    2011-10-01

    Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients Dan Wendt, Greg Mines Idaho National Laboratory The use of mixed working fluids in binary power plants can provide significant increases in plant performance, provided the heat exchangers are designed to take advantage of these fluids non-isothermal phase changes. In the 1980's testing was conducted at DOE's Heat Cycle Research Facility (HCRF) where mixtures of different compositions were vaporized at supercritical pressures and then condensed. This testing had focused on using the data collected to verify that Heat Transfer Research Incorporated (HTRI) codes were suitable for the design of heat exchangers that could be used with mixtures. The HCRF data includes mixture compositions varying from 0% to 40% isopentane and condenser tube orientations of 15{sup o}, 60{sup o}, and 90{sup o} from horizontal. Testing was performed over a range of working fluid and cooling fluid conditions. Though the condenser used in this testing was water cooled, the working fluid condensation occurred on the tube-side of the heat exchanger. This tube-side condensation is analogous to that in an air-cooled condenser. Tube-side condensing heat transfer coefficient information gleaned from the HCRF testing is used in this study to assess the suitability of air-cooled condenser designs for use with mixtures. Results of an air-cooled binary plant process model performed with Aspen Plus indicate that that the optimal mixture composition (producing the maximum net power for the scenario considered) is within the range of compositions for which data exist. The HCRF data is used to assess the impact of composition, tube orientation, and process parameters on the condensing heat transfer coefficients. The sensitivity of the condensing coefficients to these factors is evaluated and the suitability of air-cooled condenser designs with mixtures is assessed. This paper summarizes the evaluation of the HCRF

  10. Radiative transfer theory for inhomogeneous media with random extinction and scattering coefficients

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.

    1989-01-01

    The small-angle scattering approximation of the scalar radiative transfer equation (RTE) is examined for the case where the extinction and scattering coefficients have a component that is a deterministic function of position along the propagation path and a component that is a random function of position transverse to the propagation direction. It is found that the resulting stochastic RTE can be reduced to a system of two stochastic integrodifferential equations for the average and fluctuating components of the radiant intensity. Two transfer equations are obtained describing the average radiant intensity and the spatial correlation function of the intensity fluctuations. The average intensity equation is then solved and applied to a simple propagation scenario. An approximate solution is also derived for the equation giving the correlation function. The developed equations can be applied to problems involving short wavelength electromagnetic wave propagation through media possessing the variable characteristics of turbulence and turbidity, such as plasmas, the atmosphere, and the ocean.

  11. Solution of boundary heat transfer coefficients between hot stamping die and cooling water based on FEM and optimization method

    NASA Astrophysics Data System (ADS)

    Li, Huiping; He, Lianfang; Zhang, Chunzhi; Cui, Hongzhi

    2016-04-01

    The thermal physical parameters have significant effects on the calculation accuracy of physical fields, and the boundary heat transfer coefficient between the die and water is one of the most important thermal physical parameters in the hot stamping. In order to attain the boundary heat transfer coefficient, the testing devices and test procedures are designed according to the characteristic of heat transfer in the hot stamping die. A method of estimating the temperature-dependent boundary heat transfer coefficient is presented, and an inverse heat conduction software is developed based on finite element method, advance-retreat method and golden section method. The software is used to calculate the boundary heat transfer coefficient according to the temperatures measured by NiCr-NiSi thermocouples in the experiment. The research results show that, the convergence of the method given in the paper is well, the surface temperature of sample has a significant effect on the boundary heat transfer coefficient between the die and water. The boundary heat transfer coefficient increases as the surface temperature of sample reduces, and the variation is nonlinear.

  12. Experimental and numerical study on effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer coefficient.

    PubMed

    Rong, Li; Nielsen, Peter V; Zhang, Guoqiang

    2010-04-01

    This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 x 10(4) to 5.43 x 10(4) (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.

  13. Polyoxometalate-mediated electron transfer-oxygen transfer oxidation of cellulose and hemicellulose to synthesis gas.

    PubMed

    Sarma, Bidyut Bikash; Neumann, Ronny

    2014-08-01

    Terrestrial plants contain ~70% hemicellulose and cellulose that are a significant renewable bioresource with potential as an alternative to petroleum feedstock for carbon-based fuels. The efficient and selective deconstruction of carbohydrates to their basic components, carbon monoxide and hydrogen, so called synthesis gas, is an important key step towards the realization of this potential, because the formation of liquid hydrocarbon fuels from synthesis gas are known technologies. Here we show that by using a polyoxometalate as an electron transfer-oxygen transfer catalyst, carbon monoxide is formed by cleavage of all the carbon-carbon bonds through dehydration of initially formed formic acid. In this oxidation-reduction reaction, the hydrogen atoms are stored on the polyoxometalate as protons and electrons, and can be electrochemically released from the polyoxometalate as hydrogen. Together, synthesis gas is formed. In a hydrogen economy scenario, this method can also be used to convert carbon monoxide to hydrogen.

  14. Calculating Hot Spring/Atmospheric Coupling Using the Coefficient of Convective Heat Transfer

    NASA Astrophysics Data System (ADS)

    Lindsey, C.; Price, A. N.; Fairley, J. P., Jr.; Larson, P. B.

    2015-12-01

    We calculated the correlation between discharge temperature and wind speed for multiple hydrothermal springs, both in the Alvord Basin of southeast Oregon and our primary field location in Yellowstone National Park, using spring temperatures, wind speeds, and air temperatures logged at three minute intervals for multiple days. We find that some hydrothermal springs exhibit strong coupling with wind speed and/or air temperatures. The three springs described in this work display this strong coupling, with correlations between wind speed and spring temperature as high as 70 percent; as a result, we can use the changes in spring temperature as a proxy for changes in the coefficient of convective heat transfer (h) between the springs and the atmosphere. The coefficient of convective heat transfer is a complex parameter to measure, but is a necessary input to many heat and mass flux analyses. The results of this study provide a way to estimate h for springs with strong atmospheric coupling, which is a critical component of a total energy balance for hydrothermal discharge areas.

  15. Turbulent transfer coefficient and roughness length in a high-altitude lake, Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, Zhaoguo; Lyu, Shihua; Zhao, Lin; Wen, Lijuan; Ao, Yinhuan; Wang, Shaoying

    2016-05-01

    A persistent unstable atmospheric boundary layer was observed over Lake Ngoring, caused by higher temperature on the water surface compared with the overlying air. Against this background, the eddy covariance flux data collected from Lake Ngoring were used to analyse the variation of transfer coefficients and roughness lengths for momentum, heat and moisture. Results are discussed and compared with parameterization schemes in a lake model. The drag coefficient and momentum roughness length rapidly decreased with increasing wind velocity, reached a minimum value in the moderate wind velocity and then increased slowly as wind velocity increased further. Under weak wind conditions, the surface tension or small scale capillary wave becomes more important and increases the surface roughness. The scalar roughness length ratio was much larger than unity under weak wind conditions, and it decreased to values near unity as wind velocity exceeded 4.0 m s-1. The lake model could not reproduce well the variation of drag coefficient, or momentum roughness length, versus wind velocity in Lake Ngoring, but it did simulate well the sensible heat and latent heat fluxes, as a result of complementary opposite errors.

  16. Dissolved oxygen transfer to sediments by sweep and eject motions in aquatic environments

    USGS Publications Warehouse

    O'Connor, B.L.; Hondzo, Miki

    2008-01-01

    Dissolved oxygen (DO) concentrations were quantified near the sediment-water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment-water interface. Evaluation of the DO concentration fluctuations along with detailed fluid-flow characterizations were used to quantify quasi-periodic sweep and eject motions (bursting events) near the sediments. Bursting events dominated the Reynolds shear stresses responsible for momentum and mass fluctuations near the sediment bed. Two independent methods for detecting bursting events using DO concentration and velocity data produced consistent results. The average time between bursting events was scaled with wall variables and was incorporated into a similarity model to describe the dimensionless mass transfer coefficient (Sherwood number, Sh) in terms of the Reynolds number, Re, and Schmidt number, Sc, which described transport in the flow. The scaling of bursting events was employed with the similarity model to quantify DO transfer to sediments and results showed a high degree of agreement with experimental data. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

  17. Local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a microchannel heat sink

    NASA Astrophysics Data System (ADS)

    Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.

    2016-06-01

    Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.

  18. Thermocouple error correction for measuring the flame temperature with determination of emissivity and heat transfer coefficient.

    PubMed

    Hindasageri, V; Vedula, R P; Prabhu, S V

    2013-02-01

    Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively.

  19. Electrocatalysis of anodic oxygen-transfer reactions: Evolution of ozone

    SciTech Connect

    Feng, J.; Johnson, D.C. ); Lowery, S.N.; Carey, J.J. . Kodak Research Labs.)

    1994-10-01

    Current efficiencies are compared for the generation of O[sub 3] simultaneously with O[sub 2] during anodic discharge of H[sub 2]O at pure and iron(III)-doped [beta]-lead dioxide film electrodes in phosphate buffer (pH 7.5, 10 C) containing 2.5 mM KF. Also examined is the effect of applied current density. A current efficiency of 14.6% was obtained for the Fe(III)-doped PbO[sub 2] film electrode deposited on a internally cooled (10 C) tubular titanium substrate at a current density of 200 mA cm[sup [minus]2] as compared to only 6.1% at the undoped PbO[sub 2] electrode under the same conditions. This result is tentatively explained on the basis of a mechanism involving the transfer of oxygen from hydroxyl radicals adsorbed on Pb(IV) sites adjacent to Fe(III) sites to O[sub 2] adsorbed at the Fe(III) sites in the surface of the Fe(III)-doped PbO[sub 2] electrodes.

  20. Mass transfer of SCWO processes: Molecular diffusion and mass transfer coefficients of inorganic nitrate species in sub- and supercritical water

    SciTech Connect

    Goemans, M.G.E.; Gloyna, E.F.; Buelow, S.J.

    1996-04-01

    Molecular diffusion coefficients of lithium-, sodium-, potassium-, cesium-, calcium-, and strontium nitrate in subcritical water were determined by analysis of Taylor dispersion profiles. Pressures ranged from 300 to 500 bar at temperatures ranging from 25{degrees}C to 300{degrees}C. The reported diffusion values were determined at infinite dilution. Molecular diffusion coefficients were 10 to 20 times faster in near-critical subcritical water than in water at ambient temperature and pressure (ATP). These findings implied that the diffusion rates were more liquid like than they were gas like, hence experimental results were correlated with diffusion models for liquids. The subcritical diffusion data presented in this work, and supercritical diffusion results published elsewhere were correlated with hydrodynamic diffusion equations. Both the Wilke-Chang correlation and the Stokes-Einstein equation yielded predictions within 10% of the experimental results if the structure of the diffusing species could be estimated. The effect of the increased diffusion rates on mass transfer rates in supercritical water oxidation applications was quantified, with emphasis on heterogeneous oxidation processes. This study and results published elsewhere showed that diffusion limited conditions are much more likely to be encountered in SCWO processes than commonly acknowledged.

  1. Characterization of rock matrix block size distribution, dispersivity, and mass transfer coefficients in fractured porous media

    NASA Astrophysics Data System (ADS)

    Sharifi Haddad, Amin

    characterize the slope of the linear function for different rock geometries. The final part of the study is the development of a lumped mass transfer coefficient between fractures and rock matrix blocks with different geometries. The obtained lumped mass transfer coefficient confirms that the scale of study, dispersivity, and the rate of injection of the fluid into the wellbore are important variables in solute transport in fractured rocks.

  2. Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels

    NASA Astrophysics Data System (ADS)

    Mikielewicz, Dariusz; Jakubowska, Blanka

    2016-06-01

    In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.

  3. Heat transfer coefficient for flow boiling in an annular mini gap

    NASA Astrophysics Data System (ADS)

    Hożejowska, Sylwia; Musiał, Tomasz; Piasecka, Magdalena

    2016-03-01

    The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface - fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two-phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.

  4. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport.

    PubMed

    Leung, Juliana Y; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  5. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport

    NASA Astrophysics Data System (ADS)

    Leung, Juliana Y.; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  6. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport.

    PubMed

    Leung, Juliana Y; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  7. From evolution to green chemistry: rationalization of biomimetic oxygen-transfer cascades.

    PubMed

    Deubel, Dirk V

    2004-02-01

    Thermodynamic electron-transfer potentials from biology textbooks elucidate the sequence of electron-transfer events in the respiratory chain in mitochondria. In this study, thermodynamic and kinetic oxygen-transfer potentials have been defined and predicted for oxidants and substrates using density functional theory, aiming to rationalize multiple oxygen-transfer events in chemical catalysis, particularly in current developments of the Sharpless dihydroxylation. Key transition states for competing mechanisms in a recent dihydroxylation method containing the olefin, osmium tetraoxide, methyltrioxorhenium(VII), a chiral tertiary amine, and the green terminal oxidant hydrogen peroxide have been investigated rigorously. The calculations show the amine to function as an oxygen-transfer mediator between rhenium peroxides and osma-2,5-dioxolanes, in addition to its role as a carrier of chiral information. Unique mechanistic and stereoelectronic patterns in this oxygen-transfer cascade explain the unexpected failure of reactivity predictions using simpler models such as Marcus theory. PMID:14746448

  8. Image-Based Modeling of Blood Flow and Oxygen Transfer in Feto-Placental Capillaries

    PubMed Central

    Brownbill, Paul; Janáček, Jiří; Jirkovská, Marie; Kubínová, Lucie; Chernyavsky, Igor L.; Jensen, Oliver E.

    2016-01-01

    During pregnancy, oxygen diffuses from maternal to fetal blood through villous trees in the placenta. In this paper, we simulate blood flow and oxygen transfer in feto-placental capillaries by converting three-dimensional representations of villous and capillary surfaces, reconstructed from confocal laser scanning microscopy, to finite-element meshes, and calculating values of vascular flow resistance and total oxygen transfer. The relationship between the total oxygen transfer rate and the pressure drop through the capillary is shown to be captured across a wide range of pressure drops by physical scaling laws and an upper bound on the oxygen transfer rate. A regression equation is introduced that can be used to estimate the oxygen transfer in a capillary using the vascular resistance. Two techniques for quantifying the effects of statistical variability, experimental uncertainty and pathological placental structure on the calculated properties are then introduced. First, scaling arguments are used to quantify the sensitivity of the model to uncertainties in the geometry and the parameters. Second, the effects of localized dilations in fetal capillaries are investigated using an idealized axisymmetric model, to quantify the possible effect of pathological placental structure on oxygen transfer. The model predicts how, for a fixed pressure drop through a capillary, oxygen transfer is maximized by an optimal width of the dilation. The results could explain the prevalence of fetal hypoxia in cases of delayed villous maturation, a pathology characterized by a lack of the vasculo-syncytial membranes often seen in conjunction with localized capillary dilations. PMID:27788214

  9. Characterization of the interfacial heat transfer coefficient for hot stamping processes

    NASA Astrophysics Data System (ADS)

    Luan, Xi; Liu, Xiaochuan; Fang, Haomiao; Ji, Kang; El Fakir, Omer; Wang, LiLiang

    2016-08-01

    In hot stamping processes, the interfacial heat transfer coefficient (IHTC) between the forming tools and hot blank is an essential parameter which determines the quenching rate of the process and hence the resulting material microstructure. The present work focuses on the characterization of the IHTC between an aluminium alloy 7075-T6 blank and two different die materials, cast iron (G3500) and H13 die steel, at various contact pressures. It was found that the IHTC between AA7075 and cast iron had values 78.6% higher than that obtained between AA7075 and H13 die steel. Die materials and contact pressures had pronounced effects on the IHTC, suggesting that the IHTC can be used to guide the selection of stamping tool materials and the precise control of processing parameters.

  10. Experimental Characterization of Heat Transfer Coefficients During Hot Forming Die Quenching of Boron Steel

    NASA Astrophysics Data System (ADS)

    Caron, Etienne; Daun, Kyle J.; Wells, Mary A.

    2013-04-01

    The heat transfer coefficient (HTC) between the sheet metal and the cold tool is required to predict the final microstructure and mechanical properties of parts manufactured via hot forming die quenching. Temperature data obtained from hot stamping experiments conducted on boron steel blanks were processed using an inverse heat conduction algorithm to calculate heat fluxes and temperatures at the blank/die interface. The effect of the thermocouple response time on the calculated heat flux was compensated by minimizing the heat imbalance between the blank and the die. Peak HTCs obtained at the end of the stamping phase match steady-state model predictions. At higher blank temperatures, the time-dependent deformation of contact asperities is associated with a transient regime in which calculated HTCs are a function of the initial stamping temperature.

  11. Determination of heat transfer coefficients in plastic French straws plunged in liquid nitrogen.

    PubMed

    Santos, M Victoria; Sansinena, M; Chirife, J; Zaritzky, N

    2014-12-01

    The knowledge of the thermodynamic process during the cooling of reproductive biological systems is important to assess and optimize the cryopreservation procedures. The time-temperature curve of a sample immersed in liquid nitrogen enables the calculation of cooling rates and helps to determine whether it is vitrified or undergoes phase change transition. When dealing with cryogenic liquids, the temperature difference between the solid and the sample is high enough to cause boiling of the liquid, and the sample can undergo different regimes such as film and/or nucleate pool boiling. In the present work, the surface heat transfer coefficients (h) for plastic French straws plunged in liquid nitrogen were determined using the measurement of time-temperature curves. When straws filled with ice were used the cooling curve showed an abrupt slope change which was attributed to the transition of film into nucleate pool boiling regime. The h value that fitted each stage of the cooling process was calculated using a numerical finite element program that solves the heat transfer partial differential equation under transient conditions. In the cooling process corresponding to film boiling regime, the h that best fitted experimental results was h=148.12±5.4 W/m(2) K and for nucleate-boiling h=1355±51 W/m(2) K. These values were further validated by predicting the time-temperature curve for French straws filled with a biological fluid system (bovine semen-extender) which undergoes freezing. Good agreement was obtained between the experimental and predicted temperature profiles, further confirming the accuracy of the h values previously determined for the ice-filled straw. These coefficients were corroborated using literature correlations. The determination of the boiling regimes that govern the cooling process when plunging straws in liquid nitrogen constitutes an important issue when trying to optimize cryopreservation procedures. Furthermore, this information can lead to

  12. Determination of heat transfer coefficients in plastic French straws plunged in liquid nitrogen.

    PubMed

    Santos, M Victoria; Sansinena, M; Chirife, J; Zaritzky, N

    2014-12-01

    The knowledge of the thermodynamic process during the cooling of reproductive biological systems is important to assess and optimize the cryopreservation procedures. The time-temperature curve of a sample immersed in liquid nitrogen enables the calculation of cooling rates and helps to determine whether it is vitrified or undergoes phase change transition. When dealing with cryogenic liquids, the temperature difference between the solid and the sample is high enough to cause boiling of the liquid, and the sample can undergo different regimes such as film and/or nucleate pool boiling. In the present work, the surface heat transfer coefficients (h) for plastic French straws plunged in liquid nitrogen were determined using the measurement of time-temperature curves. When straws filled with ice were used the cooling curve showed an abrupt slope change which was attributed to the transition of film into nucleate pool boiling regime. The h value that fitted each stage of the cooling process was calculated using a numerical finite element program that solves the heat transfer partial differential equation under transient conditions. In the cooling process corresponding to film boiling regime, the h that best fitted experimental results was h=148.12±5.4 W/m(2) K and for nucleate-boiling h=1355±51 W/m(2) K. These values were further validated by predicting the time-temperature curve for French straws filled with a biological fluid system (bovine semen-extender) which undergoes freezing. Good agreement was obtained between the experimental and predicted temperature profiles, further confirming the accuracy of the h values previously determined for the ice-filled straw. These coefficients were corroborated using literature correlations. The determination of the boiling regimes that govern the cooling process when plunging straws in liquid nitrogen constitutes an important issue when trying to optimize cryopreservation procedures. Furthermore, this information can lead to

  13. Determination of the metal/die interfacial heat transfer coefficient of high pressure die cast B390 alloy

    NASA Astrophysics Data System (ADS)

    Cao, Yongyou; Guo, Zhipeng; Xiong, Shoumei

    2012-07-01

    High-pressure die cast B390 alloy was prepared on a 350 ton cold chamber die casting machine. The metal/die interfacial heat transfer coefficient of the alloy was investigated. Considering the filling process, a "finger"-shaped casting was designed for the experiments. This casting consisted of five plates with different thicknesses (0.05 inch or 1.27 mm to 0.25 inch or 6.35 mm) as well as individual ingates and overflows. Experiments under various operation conditions were conducted, and temperatures were measured at various specific locations inside the die. Based on the results, the interfacial heat transfer coefficient and heat flux were determined by solving the inverse heat transfer problem. The influence of the mold-filling sequence, sensor locations, as well as processing parameters including the casting pressure, die temperature, and fast/slow shot speeds on the heat transfer coefficient were discussed.

  14. Resonant energy transfer from argon dimers to atomic oxygen in microhollow cathode discharges

    NASA Astrophysics Data System (ADS)

    Moselhy, M.; Stark, R. H.; Schoenbach, K. H.; Kogelschatz, U.

    2001-02-01

    The emission of atomic oxygen lines at 130.2 and 130.5 nm from a microhollow cathode discharge in argon with oxygen added indicates resonant energy transfer from argon dimers to oxygen atoms. The internal efficiency of the vacuum-ultraviolet (VUV) radiation was measured as 0.7% for a discharge in 1100 Torr argon with 0.1% oxygen added. The direct current VUV point source operates at voltages below 300 V and at current levels of milliamperes.

  15. Measurement of heat-transfer coefficients in shock wave-turbulent boundary layer interaction regions with a multi-layered thin film heat transfer gauge

    NASA Technical Reports Server (NTRS)

    Hayashi, M.; Sakurai, A.; Aso, S.

    1986-01-01

    A thin film heat transfer gauge is applied to the measurement of heat transfer coefficients in the interaction regions of incident shock waves and fully developed turbulent boundary layers. It was developed to measure heat flux with high spatial resolution and fast response for wind tunnels with long flow duration. To measure the heat transfer coefficients in the interaction region in detail, experiments were performed under the conditions of Mach number = 4, total pressure = 1.2 MPa, 0.59 to approximately 0.65. Reynolds number = 1.3 to approximately 1.5 x 10 to the 7th power and incident shock angles from 17.8 to 22.8 degrees. The results show that the heat transfer coefficient changes complicatedly in the interaction region. At the beginning the interaction region, the heat transfer coefficient decreases at first, reaches its minimum value at the point where the pressure begins to increase, and then increases sharply. When the boundary layer begins to separate, even a small separation bubble causes significant changes in the heat transfer coefficient, while the pressure does not show any changes which suggests that the boundary layer begins to separate.

  16. New Measurement of the Rate Coefficient for Three-Body Recombination of Oxygen Atoms in Presence of N2

    NASA Astrophysics Data System (ADS)

    Huestis, D. L.; Pejaković, D. A.; Copeland, R. A.; Kalogerakis, K. S.

    2004-12-01

    In the atmospheres of Earth, Venus, and Mars photodissociation of O2 and CO2 produces oxygen atoms that eventually undergo three-body recombination: O + O + M -> O2* + M. The competition between photodissociation, recombination, and diffusive vertical transport controls the atomic and molecular composition of the mesosphere and lower thermosphere. Knowledge of the rate coefficient for recombination of atomic oxygen is essential for modeling atmospheric composition. The most recent measurement of O-atom recombination rate coefficient is over thirty years old [1]. The published values of this rate coefficient have large divergence for both M = O2 and M = N2. For N2 as the third body, the room temperature coefficient varies between about 3 × 10-33 cm6s-1, which is the value recommended in the combustion science community, and 5 × 10-33 cm6s-1, a value used in the atmospheric modeling community. Previous laboratory investigations [2] of the process O + O + N2 -> O2* + N2 shared the same basic approach, which was to use N2 discharge flow system with NO added downstream to generate O-atoms in the absence of O2 through the reaction N + NO -> O + N2. This approach is vulnerable to heterogeneous recombination and other processes that may obscure the reaction of interest, mostly due to the low O-atom densities and, consequently, long reaction times. We employ an F2 laser with up to 50 mJ of 157 nm pulsed output to achieve nearly complete photodissociation of molecular oxygen. In a high-pressure (760 Torr) background of N2 the oxygen atoms recombine in a time scale of several milliseconds. Oxygen atom population is monitored by detecting 845-nm fluorescence, which is induced by the 226 nm output of the second laser via a two-photon process O(2p4 3P) + 2hν -> O(2p33p ^3P). Our measurements give a preliminary value for the O + O + N_2 recombination rate coefficient of approximately 3 \\times 10^{-33} cm^6s^{-1}, which favors the value recommended in the combustion community

  17. Experimental study on convective heat transfer coefficient around a vertical hexagonal rod bundle

    NASA Astrophysics Data System (ADS)

    Makhmalbaf, M. H. M.

    2012-06-01

    Research on convective heat transfer coefficient around a rod bundle has many diverse applications in industry. So far, many studies have been conducted in correlations related to internal and turbulent fully-developed flow. Comparison shows that Dittus-Boelter, Sieder-Tate and Petukhov have so far been the most practical correlations in fully-developed turbulent fluid flow heat transfer. The present study conducts an experimental examination of the validity of these frequently-applied correlations and introduces a manufactured test facility as well. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) can fulfil extensive applications. The paper also studies the major deviation sources in data measurements, calibrations and turbulence of fluid flow in this. Finally, regarding to sufficient number of experiments in a vast fluid mean velocity range (3,800 < Re < 40,000), a new curve and correlation are presented and the results are compared with the above mentioned commonly-applied correlations.

  18. Local Mass Transfer Coefficient for Idealized 2D Urban Street Canyon Models

    NASA Astrophysics Data System (ADS)

    Leung, Ka Kit; Liu, Chun-Ho

    2011-09-01

    Human activities in urban areas is one of the major sources of anthropogenic releases in the atmospheric boundary layer (ABL). The mechanism of urban morphology for the heat and mass transfer in built environment is thus an attractive topic in the research community. In this paper, a series of laboratory measurements is conducted to elucidate the mass transfer from hypothetical urban roughness constructed by idealized 2D street canyons. The experiments are carried out in the wind tunnel in the University of Hong Kong. The urban ABL structure inside the wind tunnel is controlled by placing small cubic Styrofoam blocks upstream of the test section. The street canyons are fabricated by movable rectangular acrylic blocks so that different building height to street width (aspect) ratios are examined. The height of building blocks is kept minimum to make sure that the urban ABL over the street canyons is high enough for fully developed turbulent flows. The prevailing wind is normal to the street axis, demonstrating the scenario of least pollutant removal from the street canyons to the urban ABL. The sample street canyon is covered by soaked filter papers to represent uniform mass concentrations on the building facades and ground surface. The wet bulb temperature of the filter papers is continuously monitored to ensure saturated conditions. Their weight before and after an experiment is used to measure the amount of water evaporated. Preliminary results illustrate the local mass transfer coefficient distribution for aspect ratios 1/4, 1/2, 1, and 2, which are comparable with those available in literuatre.

  19. Revised model coefficients for vibrational relaxation in a nitrogen-oxygen gas mixture

    NASA Astrophysics Data System (ADS)

    Gehre, R. M.; Wheatley, V.; Boyce, R. R.

    2012-11-01

    A numerical investigation of thermal non-equilibrium flows requires species specific relaxation rates, which are often calculated using the Landau-Teller model. This model requires the determination of collision specific relaxation times, which can be computed using Millikan and White's empirical formula. The coefficients used in this formula for each specific collision pair form a set of coefficients, which are assessed here. The focus of the investigation lies on their performance in hypersonic low-temperature (300-2,500 K) flows that occur at shock-tunnel nozzle exits or in supersonic combustion ramjets (scramjets) before combustion. Two experimental validation cases are chosen; a shock-tunnel nozzle and a sharp cone in hypersonic cross-flow experiment. A comparison of the experimentally measured vibrational temperatures at the nozzle exit against numerical data shows large discrepancies for two commonly used coefficient sets. A revised set of coefficients is proposed that greatly improves the agreement between the numerical and experimental results. Furthermore, the numerically generated shock shape over the sharp cone using the revised set of coefficients correlates well with the experimental measurements.

  20. Orbit transfer rocket engine technology program: Oxygen materials compatibility testing

    NASA Technical Reports Server (NTRS)

    Schoenman, Leonard

    1989-01-01

    Particle impact and frictional heating tests of metals in high pressure oxygen, are conducted in support of the design of an advanced rocket engine oxygen turbopump. Materials having a wide range of thermodynamic properties including heat of combustion and thermal diffusivity were compared in their resistance to ignition and sustained burning. Copper, nickel and their alloys were found superior to iron based and stainless steel alloys. Some materials became more difficult to ignite as oxygen pressure was increased from 7 to 21 MPa (1000 to 3000 psia).

  1. Correlation formulas for the frost thickness and heat transfer coefficient on a cylinder in humid air cross flow

    SciTech Connect

    Sengupta, S.; Sherif, S.A.; Wong, K.V.

    1995-12-31

    This paper reports on results of an experimental investigation where the emphasis was placed on obtaining empirical correlations for the frost thickness-time history and the heat transfer coefficient-time history for a cylinder in humid air cross flow. The facility employed for the investigation consisted of a low velocity wind tunnel comprised of a rectangular test section, a transition section and a honeycomb placed at the tunnel entrance. An external refrigerator was used to cool an antifreeze solution having a mixture of 90% methanol and 10% ethylene glycol. Measured parameters included, among other things, the heat transfer coefficient as well as the frost thickness.

  2. Experimentally Determined Overall Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments

    NASA Technical Reports Server (NTRS)

    Bue, Grant; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vogel, Matt; Vonaue, Walt; Conger, Bruce; Stein, James

    2015-01-01

    A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the overall heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flow rate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.

  3. Theoretical gas phase mass transfer coefficients for endogenous gases in the lungs.

    PubMed

    Condorelli, P; George, S C

    1999-01-01

    Gas phase mass transfer coefficients for nitric oxide (NO), ethanol (EtOH), and water vapor (H2O) were determined for typical conducting airway geometry and tracheal flows (5 x 10(-5)and 5 x 10(-4) m3 s(-1)), by solving the steady-state two-dimensional diffusion equation. A constant absolute production rate with first order consumption reactions in pulmonary tissue was assumed for NO. For EtOH and H2O, constant concentrations were assumed in the blood and tissue, respectively. Results, expressed in terms of the average Sherwood number (Sh), were correlated with the Peclet (Pe(r)) number, and the length-to-diameter (L/D) ratio for each airway branch in terms of a lumped variable, Pe(r)(L/D)n. (Sh) increases as the solubility of the gas in tissue and blood increases. In addition, Sh passes through a minimum value at Pe(r)(D/L)n equal to approximately one when axial convection and diffusion have equal but opposite magnitudes. We conclude that Sh is not a monotonic function of Pe(r)(L/D)n within the entire airway tree and that it depends on the physical properties of the gas in the tissue. This conclusion contrasts with previous experimental and theoretical correlations.

  4. Transfer coefficient of 226Ra from vegetation to meadow voles, Microtus pennsylvanicus, on U mill tailings

    SciTech Connect

    Cloutier, N.R.; Clulow, F.V.; Lim, T.P.; Dave, N.K.

    1986-06-01

    The 226Ra level in vegetation growing on U mine tailings in Elliot Lake, Ontario, Canada, was 211 + 22 mBq g-1 (dry weight) compared to less than 7 mBq g-1 (dry weight) in material from a control site. Skeletons of meadow voles (Microtus pennsylvanicus) established on the tailings had concentrations of 226Ra of 6083 +/- 673 mBq per animal in winter; 7163 +/- 1077 mBq per animal in spring; 1506 +/- 625 mBq per animal in summer; and 703 +/- 59 mBq per animal in fall, compared to less than 7 mBq per animal in controls. The /sup 226/Ra transfer coefficient from vegetation to voles (defined as total millibecquerels of /sup 226/Ra in adult vole per total millibecquerels of 226Ra consumed by the vole in its lifetime) was calculated as 4.6 +/- 2.9 X 10(-2) in summer and 2.8 +/- 0.6 X 10(-2) in fall.

  5. Liquid films on shake flask walls explain increasing maximum oxygen transfer capacities with elevating viscosity.

    PubMed

    Giese, Heiner; Azizan, Amizon; Kümmel, Anne; Liao, Anping; Peter, Cyril P; Fonseca, João A; Hermann, Robert; Duarte, Tiago M; Büchs, Jochen

    2014-02-01

    In biotechnological screening and production, oxygen supply is a crucial parameter. Even though oxygen transfer is well documented for viscous cultivations in stirred tanks, little is known about the gas/liquid oxygen transfer in shake flask cultures that become increasingly viscous during cultivation. Especially the oxygen transfer into the liquid film, adhering on the shake flask wall, has not yet been described for such cultivations. In this study, the oxygen transfer of chemical and microbial model experiments was measured and the suitability of the widely applied film theory of Higbie was studied. With numerical simulations of Fick's law of diffusion, it was demonstrated that Higbie's film theory does not apply for cultivations which occur at viscosities up to 10 mPa s. For the first time, it was experimentally shown that the maximum oxygen transfer capacity OTRmax increases in shake flasks when viscosity is increased from 1 to 10 mPa s, leading to an improved oxygen supply for microorganisms. Additionally, the OTRmax does not significantly undermatch the OTRmax at waterlike viscosities, even at elevated viscosities of up to 80 mPa s. In this range, a shake flask is a somehow self-regulating system with respect to oxygen supply. This is in contrary to stirred tanks, where the oxygen supply is steadily reduced to only 5% at 80 mPa s. Since, the liquid film formation at shake flask walls inherently promotes the oxygen supply at moderate and at elevated viscosities, these results have significant implications for scale-up.

  6. Orbital transfer vehicle oxygen turbopump technology. Volume 3: Hot oxygen testing

    NASA Technical Reports Server (NTRS)

    Urke, Robert L.

    1992-01-01

    This report covers the work done in preparation for a liquid oxygen rocket engine turbopump test utilizing high pressure hot oxygen gas for the turbine drive. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas. The goal of this test program was to demonstrate the successful operation of the TPA under simulated engine conditions including the hot oxygen turbine drive. This testing follows a highly successful series of tests pumping liquid oxygen with gaseous nitrogen as the turbine drive gas. That testing included starting of the TPA with no assist to the hydrostatic bearing. The bearing start entailed a rubbing start until the pump generated enough pressure to support the bearing. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The TPA was refurbished for the hot gas drive tests and facility work was begun, but unfortunately funding cuts prohibited the actual testing.

  7. Periodic steamwise variations of heat transfer coefficients for incline and staggered arrays of circular jets with crossflow of spent air

    NASA Technical Reports Server (NTRS)

    Florschuetz, L. W.; Metzger, D. E.; Berry, R. A.

    1979-01-01

    Heat transfer characteristics were measured for inline and staggered arrays of circular jets impinging on a surface parallel to the jet orifice plate. The impinging flow was constrained to exit in a single direction along the channel formed by the jet plate and the heat transfer surface. In this configuration the air discharged from upstream transverse rows of jet holes imposes a crossflow of increasing magnitude on the succeeding downstream jet rows. Streamwise heat transfer coefficient profiles were determined for a streamwise resolution of one-third the streamwise hole spacing, utilizing a specially constructed test surface.

  8. Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region.

    PubMed

    Karunakara, N; Ujwal, P; Yashodhara, I; Rao, Chetan; Sudeep Kumara, K; Dileep, B N; Ravi, P M

    2013-10-01

    Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium ((137)Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of (137)Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the (137)Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10(-1) and 1.8 × 10(-1) for (137)Cs and stable Cs, respectively. The Fm of (137)Cs had geometric mean values of 1.9 × 10(-2) d L(-1) and 4.6 × 10(-2) d L(-1), respectively, for adopted Cows 1 and 2; 1.7 × 10(-2) d L(-1) for the cows of local farmers, and 4.0 × 10(-3) d L(-1) for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of (137)Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for (137)Cs and stable Cs and their dependence on the potassium content ((40)K and stable K) in

  9. Data Qualification Report For DTN: MO0012RIB00065.002, Parameter Values For Transfer Coefficients

    SciTech Connect

    C.H. Tung

    2001-01-09

    A data-qualification evaluation was conducted on Reference Information Base (RIB) data set MOO0 12RIB00065.002, ''Parameter Values for Transfer Coefficients''. The corroborating data method was used to evaluate the data. This method was selected because it closely matches the literature-review method followed to select parameter values. Five criteria were considered when the corroborating method was used: adequacy of the corroborative literature, sufficiency of value-selection criteria, implementation of the selection criteria, documentation of the process, and whether the analysis was conducted in accordance with applicable quality assurance (QA) procedures. Three criteria were used when a literature review was not conducted: appropriate logic used to select parameters, documentation of the process, and whether the analysis was conducted in accordance with applicable QA procedures. The RIB data item, the associated Analysis and Model Report (AMR), the corroborative literature, and the results of an audit revision O/ICN 0 of the AMR were examined. All calculations and the selection process for all values were repeated and confirmed. The qualification team concluded: (1) A sufficient quantity of corroborative literature was reviewed and no additional literature was identified that should have been considered. (2) The selection criteria were sufficient and resulted in valid parameter values. (3) The process was well defined, adequately documented in the AMR, and correctly followed. (4) The analysis was developed in accordance with applicable QA procedures. No negative findings were documented that resulted in questions about the quality of the data. The qualification team therefore recommends that the qualification status of RIB data set MO0012RIB00065.002 be changed to qualified.

  10. Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter.

    PubMed

    Takesono, Satoshi; Onodera, Masayuki; Toda, Kiyoshi; Yoshida, Masanori; Yamagiwa, Kazuaki; Ohkawa, Akira

    2006-03-01

    This study examined a stirred-tank fermenter (STF) containing low-viscosity foaming liquids with an agitation impeller and foam-breaking impeller mounted on the same shaft. Results showed that the performance of the foam-breaking impeller can be improved by changing a conventional six-blade turbine impeller into a rod impeller as the agitation impeller. The volumetric oxygen-transfer coefficient, kLa, in the mechanical foam-control method (MFM) using a six-blade vaned disk as the foam-breaking impeller in the STF with the rod impeller was approximately five times greater than that of the chemical foam-control method (CFM) adding an anti-foaming agent in the STF with the six-blade turbine impeller. Application of the present method to the cultivation of Saccharomyces cerevisiae K-7 demonstrated that the cultivation time up to the maximum cell concentration was remarkably shorter than that achieved using a conventional CFM. PMID:16208498

  11. Confirmation of selected milk and meat radionuclide transfer coefficients. Third technical progress report, September 1984-August 1985

    SciTech Connect

    Ward, G.M.; Johnson, J.E.

    1985-08-31

    The goat milk transfer coefficient of Tc administered as TcO/sub 4//sup -/ was found to be 20 to 40 times that of Tc administered in a reduced form. The fraction of Tc, as TcO/sub 4//sup -/, transferred from gut to blood was approximately 6 to 10 times that of reduced Tc. The milk transfer coefficient of Tc administered as TcO/sub 4//sup -/ was 6 to 8 times greater for goats than cows. The fraction of Tc, as TcO/sub 4//sup -/, absorbed from the gut by cows, however, was approximately twice that absorbed by goats. The mean time for loss of Tc in cows' milk based on the average values plotted in Figure 2 was approximately 10 hours. The fraction of Tc, administered as TcO/sub 4//sup -/, absorbed from blood to mammary gland by cows was estimated to be approximately 2% that of goats. 4 refs., 15 tabs.

  12. Determination of the heat transfer coefficient at the metal-sand mold interface of lost foam casting process

    NASA Astrophysics Data System (ADS)

    Zhang, Liqiang; Tan, Wenfang; Hu, Hao

    2016-06-01

    For modeling solidification process of casting accurately, a reliable heat transfer boundary condition data is required. In this paper, an inverse conduction model was established to determine the heat flux and heat transfer coefficient at the metal-sand mold interface for cylindrical casting in the lost foam process. The numerically calculated temperature was compared with analytic solution and simulation solution obtained by commercial software ProCAST to investigate the accuracy of heat conduction model. The instantaneous cast and sand mold temperatures were measured experimentally and these values were used to determine the interfacial heat transfer coefficient (IHTC). The IHTC values during lost foam casting were shown to vary from 20 to 800 W m-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed in this study.

  13. Determinants of Oxygen and Carbon Dioxide Transfer during Extracorporeal Membrane Oxygenation in an Experimental Model of Multiple Organ Dysfunction Syndrome

    PubMed Central

    Park, Marcelo; Costa, Eduardo Leite Vieira; Maciel, Alexandre Toledo; Silva, Débora Prudêncio e; Friedrich, Natalia; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Schettino, Guilherme; Azevedo, Luciano Cesar Pontes

    2013-01-01

    Extracorporeal membrane oxygenation (ECMO) has gained renewed interest in the treatment of respiratory failure since the advent of the modern polymethylpentene membranes. Limited information exists, however, on the performance of these membranes in terms of gas transfers during multiple organ failure (MOF). We investigated determinants of oxygen and carbon dioxide transfer as well as biochemical alterations after the circulation of blood through the circuit in a pig model under ECMO support before and after induction of MOF. A predefined sequence of blood and sweep flows was tested before and after the induction of MOF with fecal peritonitis and saline lavage lung injury. In the multivariate analysis, oxygen transfer had a positive association with blood flow (slope = 66, P<0.001) and a negative association with pre-membrane PaCO2 (slope = −0.96, P = 0.001) and SatO2 (slope = −1.7, P<0.001). Carbon dioxide transfer had a positive association with blood flow (slope = 17, P<0.001), gas flow (slope = 33, P<0.001), pre-membrane PaCO2 (slope = 1.2, P<0.001) and a negative association with the hemoglobin (slope = −3.478, P = 0.042). We found an increase in pH in the baseline from 7.50[7.46,7.54] to 7.60[7.55,7.65] (P<0.001), and during the MOF from 7.19[6.92,7.32] to 7.41[7.13,7.5] (P<0.001). Likewise, the PCO2 fell in the baseline from 35 [32,39] to 25 [22,27] mmHg (P<0.001), and during the MOF from 59 [47,91] to 34 [28,45] mmHg (P<0.001). In conclusion, both oxygen and carbon dioxide transfers were significantly determined by blood flow. Oxygen transfer was modulated by the pre-membrane SatO2 and CO2, while carbon dioxide transfer was affected by the gas flow, pre-membrane CO2 and hemoglobin. PMID:23383011

  14. Determination of the external mass transfer coefficient and influence of mixing intensity in moving bed biofilm reactors for wastewater treatment.

    PubMed

    Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C

    2015-09-01

    In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies.

  15. A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

    NASA Astrophysics Data System (ADS)

    Baricci, Andrea; Casalegno, Andrea

    2016-09-01

    Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

  16. Oxygen transfer to slurries treated in a rotating drum operated at atmospheric pressure.

    PubMed

    Barrera-Cortés, Josefina; Manilla-Pérez, Efraín; Poggi-Varaldo, Héctor M

    2006-12-01

    The objective of this work was to determine (1) the effect of rotational speed (N) and lifters on the oxygen transfer coefficient (k (L)) of a mineral solution and (2) the effect of solids concentration of a slurry soil-mineral solution on k (L), at a fixed value N (0.25 s(-1)); in both cases the treatment was carried out in an aerated rotating drum reactor (RDR) operated at atmospheric pressure. First, the k (L) for the mineral solution was in the range 6.38 x 10(-4)-7.69 x 10(-4) m s(-1), which was of the same order of magnitude as those calculated for closed rotating drums supplied with air flow. In general, k (L) of RDR implemented with lifters was superior or equal to that of RDR without lifters. For RDR implemented with lifters, k (L) increased with N in the range 6.65 x 10(-4)-10.51 x 10(-4) m s(-1), whereas k (L) of RDR without lifters first increased with N up to N = 0.102 s(-1), and decreased beyond this point. Second, regarding soil slurry experiments, an abrupt fall of k (L) (ca. 50%) at low values of the solid concentration (C (v)) and an asymptotic pattern at high C (v) were observed at N = 0.25 s(-1). These results suggest that mass transfer phenomena were commanded by the slurry properties and a semi-empirical equation of the form Sh = f(Re, Sc) seems to corroborate this finding. PMID:17082914

  17. Investigation of the contact charge transfer absorption of organic solvents with oxygen for use in oxygen determination.

    PubMed

    Choi, M F; Hawkins, P

    1995-07-01

    The contact charge transfer (CCT) absorption spectra of dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), ethanol, methanol, water, benzene (Bz), N,N'-diethylaniline (DEA), N,N'-dimethyl-p-toluidine (DMT) and N,N'-diethyl-p-toluidine with molecular oxygen have been investigated. These solvents form strong ultraviolet/visible CCT absorption spectra with intensities that are related to the partial pressure of the applied oxygen. DMSO, DMF, DMA, Bz, DEA and DMT are shown to form 1:1 molecular contact complexes with molecular oxygen. A simple oxygen sensing system is described using CCT absorption spectroscopy of DMT at a wavelength of 400 nm, with a gas flow rate of 60 cm(3) min(-1) through the solvent in a cuvette with a pathlength of 1 cm. Inexpensive plastic fibres are used to relay the light from a xenon lamp source to the cuvette and back to a photo-detector. The response of the sensing system to changes in oxygen concentration is reversible, non-linear and in good agreement with the Beer-Lambert law. The most sensitive response region is from 0 to 20% O(2) with a change in signal level of about 35%. The solvent used shows no deterioration in performance over a long period and can be used to determine gaseous oxygen concentrations from 0 to 100%. It does not respond to carbon dioxide.

  18. An experimental determination of the H2S overall mass transfer coefficient from quiescent surfaces at wastewater treatment plants

    NASA Astrophysics Data System (ADS)

    Santos, Jane Meri; Kreim, Virginie; Guillot, Jean-Michel; Reis, Neyval Costa; de Sá, Leandro Melo; Horan, Nigel John

    2012-12-01

    This study has investigated overall mass transfer coefficients of hydrogen sulphide from quiescent liquid surfaces under simulated laboratory conditions. Wind flow (friction velocity) has been correlated with the overall mass transfer coefficient (KL) of hydrogen sulphide in the liquid phase using a wind tunnel study. The experimental values for this coefficient have been compared with predicted KL values obtained from three different emission models that are widely used to determine volatilization rates from the quiescent surfaces of wastewater treatment unit processes. Friction velocity (in a range of 0.11 and 0.27 m s-1) was found to have a negligible influence on the overall mass transfer coefficients for hydrogen sulphide but by contrast two of the models predicted a stronger influence of friction velocity and overestimate the KL values by up to a factor of 12.5, thus risking unnecessary expenditure on odour control measures. However, at low wind speeds or friction velocities, when more odour complaints might be expected due to poor atmospheric dispersion, a better agreement of emission rates with experimental data was found for all the models.

  19. Blood Flow Versus Hematocrit in Optimization of Oxygen Transfer to Tissue During Fluid Resuscitation.

    PubMed

    Siam, Jamal; Kadan, Marwa; Flaishon, Ron; Barnea, Ofer

    2015-12-01

    The effectiveness of fluid resuscitation regimens in hemorrhagic trauma is assessed based on its ability to increase oxygen concentration in tissue. Fluid resuscitation using both crystalloids and colloids fluids, creates a dilemma due to its opposing effects on oxygen transfer. It increases blood flow thereby augmenting oxygen transport but it also dilutes the blood simultaneously and reduces oxygen concentration thereby reducing oxygen transport. In this work we have studied these two opposing effects of fluid therapy on oxygen delivery to tissue. A mathematical model of oxygen diffusion from capillaries to tissue and its distribution in tissue was developed and integrated into a previously developed hemodynamic model. The capillary-tissue model was based on the Krogh structure. Compared to other models, fewer simplifying assumptions were made leading to different boundary conditions and less constraints, especially regarding capillary oxygen content at its venous end. Results showed that oxygen content in blood is the dominant factor in oxygen transport to tissue and its effect is greater than the effect of flow. The integration of the capillary/tissue model with the hemodynamic model that links administered fluids with flow and blood dilution indicated that fluid resuscitation may reduce oxygen transport to tissue.

  20. Orbital transfer vehicle oxygen turbopump technology. Volume 2: Nitrogen and ambient oxygen testing

    NASA Technical Reports Server (NTRS)

    Brannam, R. J.; Buckmann, P. S.; Chen, B. H.; Church, S. J.; Sabiers, R. L.

    1990-01-01

    The testing of a rocket engine oxygen turbopump using high pressure ambient temperature nitrogen and oxygen as the turbine drive gas in separate test series is discussed. The pumped fluid was liquid nitrogen or liquid oxygen. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas which will be demonstrated in a subsequent test series. Following bearing tests, the TPA was finish machined (impeller blading and inlet/outlet ports). Testing started on 15 February 1989 and was successfully concluded on 21 March 1989. Testing started using nitrogen to reduce the ignition hazard during initial TPA checkout. The Hydrostatic Bearing System requires a Bearing Pressurization System. Initial testing used a separate bearing supply to prevent a rubbing start. Two test series were successfully completed with the bearing assist supplied only by the pump second stage output which entailed a rubbing start until pump pressure builds up. The final test series used ambient oxygen drive and no external bearing assist. Total operating time was 2268 seconds. There were 14 starts without bearing assist and operating speeds up to 80,000 rpm were logged. Teardown examination showed some smearing of silverplated bearing surfaces but no exposure of the underlying monel material. There was no evidence of melting or oxidation due to the oxygen exposure. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The only anomaly was higher than predicted flow losses which were attributed to a faulty ring seal. The TPA will be refurbished prior to the 400 F oxygen test series but its condition is acceptable, as is, for continued operating. This was a highly successful test program.

  1. Micro-scale Modeling of Flow and Oxygen Transfer in Hollow Fiber Membrane Bundle

    PubMed Central

    Taskin, M. Ertan; Fraser, Katharine H.; Zhang, Tao; Griffith, Bartley P.; Wu, Zhongjun J.

    2010-01-01

    The aim of this work was to develop a modeling approach to solve the flow and oxygen transfer when the blood passes through the hollow-fiber membrane bundle. For this purpose, a “two-region” modeling approach was developed regarding the hollow fiber and blood regions. The oxygen transfer in these regions was defined with separate diffusion processes. Two dimensional single and multi-fiber geometries were created and flow solutions were obtained for a non-Newtonian fluid. The convection-diffusion-reaction equation was solved to produce the oxygen partial pressure distributions. As a benefit of coupling the interstitial flow field into the oxygen transfer through the hollow-fiber membrane bundle, the membrane resistance was taken into consideration. Thus, varying oxygen partial pressures were observed on the outer fiber surface, which is contrary to the common simplifying assumptions of negligible membrane resistance and uniform oxygen content on the fiber surface (Traditional approach). It was illustrated that, the current approach can be utilized to predict the mass transfer efficiencies without overestimating as compared to the predictions obtained with the traditional approach. Utilization of the current approach was found to be beneficial for the geometries with lower packing density which allows significant PO2 variations on the fiber surfaces. For the geometries with dense packings, the above simplifying assumptions could be applicable. The model predictions were validated with the experimental measurements taken from a benchmark device. PMID:20802783

  2. Fluorinert, an oxygen carrier, improves cell culture performance in deep square 96-well plates by facilitating oxygen transfer.

    PubMed

    Meyer, Aaron; Condon, Russell G G; Keil, Gregory; Jhaveri, Nikita; Liu, Zhong; Tsao, Yung-Shyeng

    2012-01-01

    In bioprocess development, the 96-well plate format has been widely used for high-throughput screening of production cell line or culture conditions. However, suspension cell cultures in conventional 96-well plates often fail to reach high cell density under normal agitation presumably due to constraints in oxygen transfer. Although more vigorous agitation can improve gas transfer in 96-well plate format, it often requires specialized instruments. In this report, we employed Fluorinert, a biologically inert perfluorocarbon, to improve oxygen transfer in 96-well plate and to enable the growth of a Chinese Hamster Ovary cell line expressing a recombinant monoclonal antibody. When different amounts of Fluorinert were added to the cell culture medium, a dose-dependent improvement in cell growth was observed in both conventional and deep square 96-well plates. When sufficient Fluorinert was present in the culture, the cell growth rate, the peak cell density, and recombinant protein production levels achieved in deep square 96-wells were comparable to cultures in ventilated shake flasks. Although Fluorinert is known to dissolve gases such as oxygen and CO(2), it does not dissolve nor extract medium components, such as glucose, lactate, or amino acids. We conclude that mixing Fluorinert with culture media is a suitable model for miniaturization of cell line development and process optimization. Proper cell growth and cellular productivity can be obtained with a standard shaker without the need for any additional aeration or vigorous agitation. PMID:21954223

  3. Investigation of oxygen transfer rates in full scale membrane bioreactors.

    PubMed

    Cornel, P; Wagner, M; Krause, S

    2003-01-01

    In membrane bioreactors (MBRs) for wastewater treatment the secondary clarifier is replaced by a membrane filtration. The advantage of this process is a complete removal of solids from the effluent and a small footprint due to possible high biomass concentrations (MLSS). As oxygen supply counts for more than 70% of total energy cost in municipal WWTPs the design of the aeration system is vital for efficient operation. In this respect the alpha-value is an important influencing factor. The alpha-value depends on the MLSS-concentration as shown in various publications and confirmed by own measurements in two full scale municipal MBRs with MLSS ranging from 7 and 17 kg/m3. Furthermore it must be taken into account that alpha-values are not static values; they vary with loading rates, surfactant concentrations, air flow rates, MLSS concentrations, etc. The average alpha-value at typical 12 kg/m3 MLSS for municipal MBRs is about 0.6 +/- 0.1. As submerged configured MBRs are equipped with an additional coarse bubble "crossflow" aeration system for fouling control, supplementary energy is consumed. Therefore MBRs need more energy compared to conventional treatment plants. Measurements of both aeration systems show that the fine bubble aeration system is more efficient by a factor of three concerning oxygen supply compared to the coarse bubble system.

  4. Determination of heat transfer coefficients at the polymer-mold-interface for injection molding simulation by means of calorimetry

    NASA Astrophysics Data System (ADS)

    Stricker, M.; Steinbichler, G.

    2014-05-01

    Appropriate modeling of heat transfer from the polymer material to the injection mold is essential to achieve accurate simulation results. The heat transfer is commonly modeled using convective heat transfer and applying heat transfer coefficients (HTC) to the polymer-mold-interface. The set HTC has an influence on the results for filling pressure, cooling performance and shrinkage, among others. The current paper, presents a new strategy to measure HTC in injection molding experiments using Newtons law of cooling. The heat flux is calculated out of demolding heat (measured by means of calorimetry), injection heat (measured by means of an IR-sensor), cooling time and part mass. Cavity surface area, average mold surface temperature and average part surface temperature lead to the HTC.

  5. Response coefficient analysis of a fed-batch bioreactor to dissolved oxygen perturbation in complementary cultures during PHB production

    PubMed Central

    Patnaik, Pratap R

    2008-01-01

    Background Although the production of poly-β-hydroxybutyrate (PHB) has many biological, energetic and environmental advantages over chemically synthesized polymers, synthetic polymers continue to be produced industrially since the productivities of fermentation processes fr PHB are not yet economically competitive. Improvement of a PHB fermentation requires good understanding and optimization under the realistic conditions of large bioreactors. Laboratory-scale studies have shown that co-cultures of Ralstonia eutropha and Lactobacillus delbrueckii generate better fermentation efficiencies than R. eutropha alone. In large bioreactors, incomplete dispersioin and perturbations in the dissolved oxygen (DO) concentration, both of which affect the fermentation, have to be considered. This study analyzes the effect of DO fluctuations on bioreactor performance for both ideal and optimally dispersed broths. Results Response coefficient analysis was employed to obtain quantitative information on the effect of DO perturbations on different variables. Three values of the Peclet number (Pe) cheracterized three levels of dispersion: Pe = 0.01 for nearly complete dispersion, Pe = 20 for optimum dispersion and Pe = 60 for insufficient dispersion. The response coefficients (RCs) of the pairs of bacterial concentrations and the main substrates, glucose and ammonium chloride, showed contrasting variations with time. Lactate, a critical intermediate, and PHB had similar RC profiles but those of lactate were one to two orders of magnitude larger than other RCs. Significantly, the optimum Pe also resulted in the largest RCs, suggesting a balance between productivity and reactor stability. Conclusion Since R. eutropha requires oxygen for its growth whereas L. delbrueckii does not, fluctuations in the DO concentartion have a strong influence on the fermentation. Apart from this, the mechanism of PHB biosynthesis indicates that control of lactate is a critical determinant of fermentation

  6. Promotion of multi-electron transfer for enhanced photocatalysis: A review focused on oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Changhua; Zhang, Xintong; Liu, Yichun

    2015-12-01

    Semiconductor photocatalysis has attracted significant interest for solar light induced environmental remediation and solar fuel generation. As is well known, photocatalytic performance is determined by three steps: photoexcitation, separation and transport of photogenerated charge carriers, and surface reactions. To achieve higher efficiency, significant efforts have been made on improvement of efficiency of above first two steps, which have been well documented in recent review articles. In contrast, this review intends to focus on strategies moving onto the third step of improvement for enhanced photocatalysis wherein active oxygen species including superoxide radical, hydrogen peroxide, hydroxyl radical are in situ detected. Particularly, surface electron-transfer reduction of oxygen over single component photocatalysts is reviewed and systems enabling multi-electron transfer induced oxygen reduction reaction (ORR) are highlighted. It is expected this review could provide a guideline for readers to better understand the critical role of ORR over photocatalyst in charge carrier separation and transfer and obtain reliable results for enhanced aerobic photocatalysis.

  7. Entrance effect and gas-film mass-transfer coefficient in a large-diameter packed column

    SciTech Connect

    Doan, H.D.; Fayed, M.E.

    2000-04-01

    The effects of the bed height and the entrance section below the packing support on mass transfer in a 1.2-m diameter packed bed of 50-mm ceramic Intalox saddles were investigated under various gas flow rates from 1,957 to 7,828 kg/h {sm_bullet}m{sup 2} and liquid flow rates from 12,200 to 46,700 kg/h {sm_bullet}m{sup 2}. The entrance effect accounted for 17% of the overall water vapor transferred from moist air to a calcium chloride solution in the tower, regardless of the packing height. For a 0.91-m high bed, the average mass-transfer coefficient was directly proportional to the gas rate and was proportional to the liquid rate to the power of 0.24. For a 1.8-m high bed, the average mass-transfer coefficient was proportional to the gas rate to the power of 0.89 and appeared to be independent of the liquid rate. The height of a transfer unit (HTU) for 50-mm ceramic Intalox saddles remained relatively constant under various gas rates used in the present study. The HTU was about 0.5 m for the short bed and 0.8 m for the tall bed.

  8. A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors.

    PubMed

    Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L

    2013-04-01

    Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed.

  9. A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors.

    PubMed

    Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L

    2013-04-01

    Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed. PMID:23434811

  10. Impact of hydrogen peroxide oxygen transfer tests on the performance of the biological nutrient removal process.

    PubMed

    Mahendraker, V; Mavinic, D S; Rabinowitz, B

    2002-02-01

    Knowledge of in-process oxygen transfer is essential to the optimum design and operation of aeration systems in activated sludge processes. In this study, non-steady state H2O2 oxygen transfer tests were performed in a laboratory scale, University of Cape Town configuration biological nutrient removal process (BNR) to measure the in-process oxygen transfer rates. Given the small quantity (about 1 ml @30% concentration) of H2O2 used in the aerobic reactor with a mixed liquor volume of 161 (total system working volume of 33.65 l), no effect on the process performance itself was expected. However, the process performance data obtained indicated results to the contrary. Use of H2O2 in measuring process oxygen transfer rates may not be suitable for BNR processes, as all the major process performance indicators (carbon, nitrogen and phosphorus removal by the system and carbon uptake and phosphorus release in the anaerobic zone) were negatively affected. Evidence in thiswork leads to the conclusion that external addition of H2O2 leads to excessive production of the hydroxyl radical. Since microorganisms do not have enzyme systems capable of acting upon this additional reactive radical, it resulted in loss of process performance. It is also possible that H2O2 could have upset the normal aerobic respiration process by introducing oxidative stress conditions on the catalase, peroxidase and superoxide dismutase enzymes that deal with other oxygen radicals generated as part of the overall process of reducing oxygen to water. Any test that interferes with the system in which the test is being performed is suspect. Therefore, in light of these results, the H2O2 method to test in-process oxygen transfer should be re-evaluated.

  11. Turbulent Transfer Coefficients and Calculation of Air Temperature inside Tall Grass Canopies in Land Atmosphere Schemes for Environmental Modeling.

    NASA Astrophysics Data System (ADS)

    Mihailovic, D. T.; Alapaty, K.; Lalic, B.; Arsenic, I.; Rajkovic, B.; Malinovic, S.

    2004-10-01

    A method for estimating profiles of turbulent transfer coefficients inside a vegetation canopy and their use in calculating the air temperature inside tall grass canopies in land surface schemes for environmental modeling is presented. The proposed method, based on K theory, is assessed using data measured in a maize canopy. The air temperature inside the canopy is determined diagnostically by a method based on detailed consideration of 1) calculations of turbulent fluxes, 2) the shape of the wind and turbulent transfer coefficient profiles, and 3) calculation of the aerodynamic resistances inside tall grass canopies. An expression for calculating the turbulent transfer coefficient inside sparse tall grass canopies is also suggested, including modification of the corresponding equation for the wind profile inside the canopy. The proposed calculations of K-theory parameters are tested using the Land Air Parameterization Scheme (LAPS). Model outputs of air temperature inside the canopy for 8 17 July 2002 are compared with micrometeorological measurements inside a sunflower field at the Rimski Sancevi experimental site (Serbia). To demonstrate how changes in the specification of canopy density affect the simulation of air temperature inside tall grass canopies and, thus, alter the growth of PBL height, numerical experiments are performed with LAPS coupled with a one-dimensional PBL model over a sunflower field. To examine how the turbulent transfer coefficient inside tall grass canopies over a large domain represents the influence of the underlying surface on the air layer above, sensitivity tests are performed using a coupled system consisting of the NCEP Nonhydrostatic Mesoscale Model and LAPS.


  12. Experiment 2028: Flowing Temperature Logs and Evaluation of Wellbore Heat Transfer Coefficients with the Nitrogen Blankets – Revision I

    SciTech Connect

    Zyvoloski, George A.; Dash, Zora V.; Murphy, Hugh D.

    1983-06-20

    The accurate assessment of temperatures in the casing and liner is critical to the safety of EE-3 during the upcoming fracturing experiment. The purpose of this experiment is to obtain heat transfer coefficients for the nitrogen filled annulus as well as the water filled annulus below the nitrogen water interface. In addition the flowing temperature logs that were not obtained during Experiment 2026 because of an obstruction; will now be obtained in this experiment.

  13. Impact of heterogeneity on oxygen transfer in a fluctuating capillary fringe.

    PubMed

    Haberer, Christina M; Rolle, Massimo; Cirpka, Olaf A; Grathwohl, Peter

    2015-01-01

    We performed quasi-two-dimensional flow through laboratory experiments to study the effect of a coarse-material inclusion, located in the proximity of the water table, on flow and oxygen transfer in the capillary fringe. The experiments investigate different phases of mass transfer from the unsaturated zone to anoxic groundwater under both steady-state and transient flow conditions, the latter obtained by fluctuating the water table. Monitoring of flow and transport in the different experimental phases was performed by visual inspection of the complex flow field using a dye tracer solution, measurement of oxygen profiles across the capillary fringe, and determination of oxygen fluxes in the effluent of the flow-through chamber. Our results show significant effects of the coarse-material inclusion on oxygen transfer during the different phases of the experiments. At steady state, the oxygen flux across the unsaturated/saturated interface was considerably enhanced due to flow focusing in the fully water-saturated coarse-material inclusion. During drainage, a zone of higher water saturation formed in the fine material overlying the coarse lens. The entrapped oxygen-rich aqueous phase contributed to the total amount of oxygen supplied to the system when the water table was raised back to its initial level. In case of imbibition, pronounced air entrapment occurred in the coarse lens, causing oxygen to partition between the aqueous and gaseous phases. The oxygen mass supplied to the anoxic groundwater following the imbibition event was found to be remarkably higher (approximately seven times) in the heterogeneous system compared with a similar experiment performed in a homogeneous porous medium.

  14. A Study of the Heat Transfer Coefficient of a Mini Channel Evaporator with R-134a as Refrigerant

    NASA Astrophysics Data System (ADS)

    Dollera, E. B.; Villanueva, E. P.

    2015-09-01

    The present study is to evaluate the heat transfer coefficient of the minichannel copper blocks used as evaporator with R-134a as the refrigerant. Experiments were conducted using three evaporator specimens of different channel hydraulic diameters (1.0mm, 2.0mm, 3.0mm). The total length for each channel is 640 mm. The dimension of each is 100mm.x50mm.x20mm. and the outside surfaces were machined to have fins. They were connected to a standard vapour compression refrigeration system. During each run of the experiment, the copper block evaporator was placed inside a small wind tunnel where controlled flow of air from a forced draft fan was introduced for the cooling process. The experimental set-up used data acquisition software and computer-aided simulation software was used to simulate the pressure drop and temperature profiles of the evaporator during the experimental run. The results were then compared with the Shah correlation. The Shah correlation over predicted and under predicted the values as compared with the experimental results for all of the three diameters and high variation for Dh=1.0mm. This indicates that the Shah correlation at small diameters is not the appropriate equation for predicting the heat transfer coefficient. The trend of the heat transfer coefficient is increasing as the size of the diameter increases.

  15. Numerical investigation of the convective heat transfer coefficient with longitudinal pitch variation in a staggered tube bank

    NASA Astrophysics Data System (ADS)

    Alfandi, Ashraf; Yoon, Juhyeon; Abusaleem, Khalifeh; Albati, Mohammad; Khafaji, Salih

    2015-11-01

    In this study, the effect on a shell-side heat transfer coefficient is investigated using the CFD code FLUENT with a variation in longitudinal pitch to diameter ratio, SL, in the range of 1.15 to 2.6 with a fixed transverse pitch to diameter ratio. For the benchmark purposes with the available empirical correlation, typical thermal-hydraulic conditions for the Zukauskas correlation are assumed. Many sensitivity calculations for different mesh sizes and turbulent models are performed to check the accuracy of the numerical solution. A realizable κ- ɛ turbulence model was found to be in good agreement with results of the Zukauskas correlation among the other turbulence models, at least for the staggered tube bank. It was found that the average heat transfer coefficient of a crossflow over a staggered tube bank calculated using FLUENT is in good agreement with the Zukauskas correlation-calculated heat transfer coefficient in the range of 1.15 - 2.6. For a staggered tube bank, using the Zukauskas correlation seems to be valid down to SL = 1.15.

  16. Electrocatalysis of anodic, oxygen-transfer reactions at noble metal electrodes

    SciTech Connect

    Vitt, J.E.

    1992-06-09

    Voltammetry at rotated disk and rotated ring-disk electrodes was applied to the study of several aspects of anodic, oxygen-transfer reactions at noble electrodes. Anodic reactions which involve the transfer of oxygen from H{sub 2}O to the oxidation products generally exhibit a voltammetric response characterized by severe kinetic limitations. Mechanistic studies were performed at noble electrodes in order to contrive strategies for improving the kinetics of these reactions. Competitive adsorption studies were used to devise an adsorption hierarchy for Au rotated disk electrodes. It was concluded that adsorption was a prerequisite for oxidations involving the transfer of oxygen present on the electrodes surface as adsorbed hydroxyl radicals. The electrogenerated chemiluminescence (ECL) of luminol was studied at Au, Pt, Pd, glassy carbon, PbO{sub 2}, and Bi-doped PbO{sub 2} electrodes. The ECL intensity was determined to be inversely related to electrochemical activity for the oxidation of luminol. It was concluded that the oxygen-transfer oxidation of luminol to 3-aminophthalate ( n = 4 eq mol{sup {minus}1}) corresponded to the dark reaction, whereas the electron-transfer oxidation of luminol with n = 1 eq mol{sup {minus}1} initiated the chemiluminescent reaction in solution.

  17. Energy transfer enhancement by oxygen perturbation of spin-forbidden electronic transitions in aromatic systems

    NASA Astrophysics Data System (ADS)

    Monguzzi, A.; Tubino, R.; Salamone, M. M.; Meinardi, F.

    2010-09-01

    Triplet-triplet energy transfer in multicomponent organic systems is usually entirely ascribed to a Dexter-type mechanism involving only short-range donor/acceptor interactions. We demonstrate that the presence of molecular oxygen introduces a perturbation to the electronic structure of one of the involved moieties which can induce a large increase in the spin-forbidden transition oscillator strength so that the otherwise negligible Förster contribution dominates the overall energy transfer rate.

  18. Two Experiments for Estimating Free Convection and Radiation Heat Transfer Coefficients

    ERIC Educational Resources Information Center

    Economides, Michael J.; Maloney, J. O.

    1978-01-01

    This article describes two simple undergraduate heat transfer experiments which may reinforce a student's understanding of free convection and radiation. Apparatus, experimental procedure, typical results, and discussion are included. (Author/BB)

  19. OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE SOUTH SHORE WASTEWATER TREATMENT PLANT - 1985-1987

    EPA Science Inventory

    Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. They have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initi...

  20. OXYGEN TRANSFER EFFICIENCY SURVEYS AT THE JONES ISLAND TREATMENT PLANTS - 1985-1988

    EPA Science Inventory

    Ceramic plate diffusers were among the earliest forms of fine pore diffusers used for oxygen transfer in activated sludge treatment. They have been successfully used for over 60 years in the Jones Island West Plant of the Milwaukee Metropolitan Sewerage District and, since initia...

  1. Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes.

    PubMed

    Karimi, Ali; Golbabaei, Farideh; Mehrnia, Momammad Reza; Neghab, Masoud; Mohammad, Kazem; Nikpey, Ahmad; Pourmand, Mohammad Reza

    2013-01-07

    In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor.

  2. Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes.

    PubMed

    Karimi, Ali; Golbabaei, Farideh; Mehrnia, Momammad Reza; Neghab, Masoud; Mohammad, Kazem; Nikpey, Ahmad; Pourmand, Mohammad Reza

    2013-01-01

    In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581

  3. Synthesis, characterisation, and oxygen atom transfer reactions involving the first gold(I)-alkylperoxo complexes.

    PubMed

    Collado, Alba; Gómez-Suárez, Adrián; Oonishi, Yoshihiro; Slawin, Alexandra M Z; Nolan, Steven P

    2013-11-25

    The synthesis of a new class of organogold species containing a peroxo moiety is reported. Complexes [Au(IPr)(OO(t)Bu)] and [Au(SIPr)(OO(t)Bu)] have been synthesised via a straightforward methodology using the parent gold(I) hydroxide complexes as synthons. These complexes have been successfully used in oxygen-transfer reactions to triphenylphosphine.

  4. Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes

    PubMed Central

    2013-01-01

    In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581

  5. Arterial oxygen saturation in anaesthetised patients during transfer from induction room to operating room.

    PubMed

    Riley, R H; Davis, N J; Finucane, K E; Christmas, P

    1988-05-01

    There is no published study that examines oxygenation of anaesthetised patients during transport from anaesthesia induction room to operating room. Arterial oxygen saturation (SaO2) was measured in twenty-five anaesthetised patients before and during transfer to an adjacent operating room and continuously recorded on a calibrated chart recorder. A telemetry ECG recorder was used to detect cardiac dysrhythmias. All anaesthetists followed their usual anaesthetic practice. Patients ventilated via face-mask and via endotracheal tube were studied. During transfer patients were either apnoeic (n = 8) or breathing room air spontaneously (n = 17). Mean SaO2 before induction was 95.4 (SD 2.5)%, was higher after induction of anaesthesia, 98.5 (SD 1.4)% and fell after transfer, 95.7 (SD 2.6)%. A fall in SaO2 was recorded for 21 patients. No SaO2 value below 90% was seen. The decrease in SaO2 was related to the time taken to transfer the patients and spontaneous ventilation (Multiple regression analysis); it was not related to the body mass index although two of the greatest decreases were seen in obese patients. Transfer time averaged 51 seconds (range: 24-97 s). No changes in cardiac rhythm were seen. Transfer of anaesthetised patients was accompanied by variable falls in SaO2 which related to duration of transfer and spontaneous breathing of room air and which were not associated with new dysrhythmias.

  6. Nonthermal radiative transfer of oxygen 98.9 nm ultraviolet emission: Solving an old mystery

    NASA Astrophysics Data System (ADS)

    Hubert, B.; Gérard, J.-C.; Shematovich, V. I.; Bisikalo, D. V.; Chakrabarti, S.; Gladstone, G. R.

    2015-12-01

    Sounding rocket measurements conducted in 1988 under high solar activity conditions revealed that the intensity of thermospheric OI emissions at 98.9 nm presents an anomalous vertical profile, showing exospheric intensities much higher than expected from radiative transfer model results, which included the known sources of excited oxygen. All attempts based on modeling of the photochemical processes and radiative transfer were unable to account for the higher than predicted brightnesses. More recently, the SOHO-Solar Ultraviolet Measurements of Emitted Radiation instrument measured the UV solar flux at high-spectral resolution, revealing the importance of a significant additional source of oxygen emission at 98.9 nm that had not been accounted for before. In this study, we simulate the radiative transfer of the OI-98.9 nm multiplet, including the photochemical sources of excited oxygen, the resonant scattering of solar photons, and the effects of nonthermal atoms, i.e., a population of fast-moving oxygen atoms in excess of the Maxwellian distribution. Including resonance scattering of the 98.9 nm solar multiplet, we find good agreement with the previous sounding rocket observation. The inclusion of a nonthermal oxygen population with a consistent increase of the total density produces a larger intensity at high altitude that apparently better accounts for the observation, but such a correction cannot be demonstrated given the uncertainties of the observations. A good agreement between model and sounding rocket observation is also found with the triplet at 130.4 nm. We further investigate the radiative transfer of the OI-98.9 nm multiplet and the oxygen emissions at 130.4 and 135.6 nm using observations from the STP78-1 satellite. We find a less satisfying agreement between the model and the STP78-1 data that can be accounted for by scaling the modeled intensity within a range acceptable given the uncertainties on the STP78-1 absolute calibration.

  7. Determination of thermal accommodation coefficients from heat transfer measurements between parallel plates.

    SciTech Connect

    Gallis, Michail A.; Castaneda, Jaime N.; Rader, Daniel John; Torczynski, John Robert; Trott, Wayne Merle

    2010-10-01

    Thermal accommodation coefficients have been derived for a variety of gas-surface combinations using an experimental apparatus developed to measure the pressure dependence of the conductive heat flux between parallel plates at unequal temperature separated by a gas-filled gap. The heat flux is inferred from temperature-difference measurements across the plates in a configuration where the plate temperatures are set with two carefully controlled thermal baths. Temperature-controlled shrouds provide for environmental isolation of the opposing test plates. Since the measured temperature differences in these experiments are very small (typically 0.3 C or less over the entire pressure range), high-precision thermistors are used to acquire the requisite temperature data. High-precision components have also been utilized on the other control and measurement subsystems in this apparatus, including system pressure, gas flow rate, plate alignment, and plate positions. The apparatus also includes the capability for in situ plasma cleaning of the installed test plates. Measured heat-flux results are used in a formula based on Direct Simulation Monte Carlo (DSMC) code calculations to determine the thermal accommodation coefficients. Thermal accommodation coefficients have been determined for three different gases (argon, nitrogen, helium) in contact with various surfaces. Materials include metals and alloys such as aluminum, gold, platinum, and 304 stainless steel. A number of materials important to fabrication of Micro Electro Mechanical Systems (MEMS) devices have also been examined. For most surfaces, coefficient values are near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Only slight differences in accommodation as a function of surface roughness have been seen. Surface contamination appears to have a more significant effect: argon plasma treatment has been observed to reduce thermal accommodation by as much as 0.10 for helium. Mixtures of argon and

  8. Transferability in the natural linear-scaled coupled-cluster effective Hamiltonian approach: Applications to dynamic polarizabilities and dispersion coefficients.

    PubMed

    Hughes, Thomas F; Bartlett, Rodney J

    2008-08-01

    A natural linear-scaled coupled-cluster (CC) method has been developed to calculate the response properties of large molecules, for example, dynamic polarizabilities and dispersion coefficients. The method is based on the transferability of the CC effective Hamiltonian from the equation-of-motion (EOM)-CC methods, subject to its representation in terms of highly transferable natural localized molecular orbitals. This transferability allows the interactions among regions in a molecule to be classified according to their important inter-region excitations and de-excitations. Dynamic polarizabilities determined in this way provide insight into calculating the excited states of large molecules using localized orbital concepts. Dispersion coefficients for the interactions within large molecules can be similarly determined. These could be useful in constructing corrective long-range potentials. Applications to alkanes, tryptophan, and polyglycine are presented. For those cases which are possible, conventional results can be reproduced. Dynamic polarizabilities of tryptophan indicate that the first excited state is localized to the indole group, while the second is localized to the carboxyl group.

  9. The oxygen transfer rate influences the molecular mass of the alginate produced by Azotobacter vinelandii.

    PubMed

    Díaz-Barrera, A; Peña, C; Galindo, E

    2007-09-01

    The influence of oxygen transfer rate (OTR) on the molecular mass of alginate was studied. In batch cultures without dissolved oxygen tension (DOT) control and at different agitation rates, the DOT was nearly zero and the OTR was constant during biomass growth, hence the cultures were oxygen-limited. The OTR reached different maximum levels (OTR(max)) and enabled to establish various relative respiration rates. Overall, the findings showed that OTR influences alginate molecular mass. The mean molecular mass (MMM) of the alginate increased as OTR(max) decreased. The molecular mass obtained at 3.0 mmol l(-1) h(-1) was 7.0 times higher (1,560 kDa) than at 9.0 mmol l(-1) h(-1) (220 kDa). An increase in molecular mass can be a bacterial response to adverse nutritional conditions such as oxygen limitation.

  10. Effect of porous structure of catalyst layer on effective oxygen diffusion coefficient in polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Inoue, Gen; Kawase, Motoaki

    2016-09-01

    It is important to reduce the oxygen diffusion resistance through PEFC porous electrode, because it is the key to reduce the PEFC cost. However, the gas diffusion coefficient of CL is lower than MPL in spite of framework consisted of same carbon blacks. In this study, in order to understand the reasons of the lower gas diffusion performance of CL, the relationship between a carbon black agglomerate structure and ionomer adhesion condition is evaluated by a numerical analysis with an actual reconstructed structure and a simulated structure. As a result, the gas diffusion property of CL strongly depends on the ionomer adhesion shape. In the case of adhesion shape with the same curvature of ionomer interface, each pore can not be connected enough. So the pore tortuosity increases. Moreover, in the case of existence of inefficient large pores formed by carbon black agglomerate and ununiformly coated ionomer, the gas diffusion performance decrease rapidly. As the measurement values in actual CL are almost equal to that with model structure with inefficient large pores. These characteristics can be confirmed by actual cross-section image obtained by FIB-SEM.

  11. Partition coefficients for iron between plagioclase and basalt as a function of oxygen fugacity - Implications for Archean and lunar anorthosites

    NASA Technical Reports Server (NTRS)

    Phinney, W. C.

    1992-01-01

    As a prelude to determinations of the content of total iron as FeO(T) in melts in equilibrium with calcic anorthosites, the partition coefficients (Ds) for FeO(T) between calcic plagioclase and basaltic melt were determined, as a function of oxygen fugacity (f(O2)), for a basaltic composition that occurs as matrices for plagioclase megacrysts. Results showed that, at the liquidus conditions, the value of D for FeO(T) between calcic plagioclase and tholeiitic basalt changed little (from 0.030 to 0.044) between the very low f(O2) of the iron-wustite buffer and that of the quartz-fayalite-magnetite (QFM) buffer. At fugacities above QFM, the value for D increased rapidly to 0.14 at the magnetite-hematite buffer and to 0.33 in air. The increase in D results from the fact that, at f(O2) below QFM, nearly all of the Fe is in the Fe(2+) state; above QFM, the Fe(3+)/Fe(2+) ratio in the melt increases rapidly, causing more Fe to enter the plagioclase which accepts Fe(3+) more readily than Fe(2+).

  12. Measurement of Charge Transfer Rate Coefficient Between Ground-State N(2+) Ion and He at Electron-Volt Energies

    NASA Technical Reports Server (NTRS)

    Fang, Z.; Kwong, Victor H. S.

    1997-01-01

    The charge transfer rate coefficient for the reaction N(2+)(2p(sup 2)P(sup 0)) + He yields products is measured by recording the time dependence of the N(2+) ions stored in an ion trap. A cylindrical radio-frequency ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The decay of the ion signals was analyzed by single exponential least-squares fits to the data. The measured rate coefficient is 8.67(0.76) x 10(exp -11)sq cm/s. The N(2+) ions were at a mean energy of 2.7 eV while He gas was at room temperature, corresponding to an equivalent temperature of 3.9 x 10(exp 3) K. The measured value is in good agreement with a recent calculation.

  13. Differentiation of the functional in an optimization problem for diffusion and convective transfer coefficients of elliptic imperfect contact interface problems

    NASA Astrophysics Data System (ADS)

    Manapova, Aigul

    2016-08-01

    We consider optimal control problems for second order elliptic equations with non-self-adjoint operators-convection-diffusion problems. Control processes are described by semi-linear convection-diffusion equation with discontinuous data and solutions (states) subject to the boundary interface conditions of imperfect type (i.e., problems with a jump of the coefficients and the solution on the interface; the jump of the solution is proportional to the normal component of the flux). Controls are involved in the coefficients of diffusion and convective transfer. We prove differentiability and Lipshitz continuity of the cost functional, depending on a state of the system and a control. The calculation of the gradients uses the numerical solutions of direct problems for the state and adjoint problems.

  14. A step-forward in the characterization and potential applications of solid and liquid oxygen transfer vectors.

    PubMed

    Quijano, Guillermo; Hernandez, Maria; Villaverde, Santiago; Thalasso, Frederic; Muñoz, Raul

    2010-01-01

    Silicone oil 20 and 200 cSt, a perfluorocarbon (FC40TM), heptamethylnonane, Kraton, Elvax, and Desmopan were evaluated for their ability to enhance oxygen transfer in stirred tank and airlift reactors (STR and ALR, respectively). None of the vectors tested was either toxic or biodegradable and they exhibited a moderate affinity for oxygen (gas/vector partitioning coefficients K(g)/(v) = C(g) times C(v)(-1) ranging from 3 to 5.1). FC40 was highly volatile, while KratonTM and ElvaxTM exhibited a low thermal stability, which constitutes a serious handicap for their implementation in fermentations. Silicone oil 20 cSt and Desmopan supported the highest oxygen transfer rates under abiotic conditions in both STR and ALR designs, with enhancement factors of up to 90% and 250%, respectively, compared to control tests (deprived of vector). The fact that these vectors showed the highest K (g/v) proved that, besides the classical selection criteria, the in situ hydrodynamic behavior (which affects K ( L ) a) must be considered for vector selection. The use of silicone oil 20 cSt and Desmopan in glucose-supplemented Saccharomyces cerevisiae fermentations resulted in a two- and threefold increase in biomass productions, respectively. The better performance of Desmopan in terms of biomass growth enhancement, together with the absence of the operational problems inherent to the use of liquid vectors (such as intensive foaming, high cost, and difficult solvent recovery), make solid vectors a promising and cost-effective alternative in the future developments of two-phase partitioning bioreactors.

  15. [Oxygen transfer efficiency of four kinds substrates applied in artificial aeration vertical-flow wetland].

    PubMed

    Pan, Ji-Zheng; Li, Wen-Chao; Ke, Fan; Wang, Lei; Li, Xue-Juan

    2009-02-15

    In subsurface flow constructed wetlands, artificial aeration plays an important role in enhancing the ability of pollutant removal. Oxygenation capacity of four substrates, limestone, vesuvianite, 500 grade ceramisite and high-strength ceramisite, are tested under three kinds of gas volume [0.19, 0.38, 0.76 m3 x (m2 x h)(-1)] in artificial aeration vertical-flow wetland. When the gas volume is 0.19 m3 x (m2 x h)(-1), the results demonstrate that the oxygen utilization of 500 grade ceramisite and high-strength ceramisite are highest as 14.39% and 14.21%, and the oxygen utilization of limestone and vesuvianite are 11.68% and 13.11% respectively. With the increase of aeration intensity, oxygen transfer efficiency parameter KLa rises accordingly. However, the oxygen utilization of vesuvianite and two other kinds of ceramisite decreases with the increase of aeration intensity. The oxygen utilization of vesuvianite, 500 grad ceramisite and high-strength ceramisite are lower as 7.67%, 10.46% and 10.77% respectively when the aeration intensity is 0.76 m3 x (m2 x h)(-1). On the contrary, the oxygen utilization of limestone get its maximum value of 14.04% as the aeration intensity is 0.38 m3 x (m2 x h)(-1).

  16. Determination of the mass-transfer coefficient in liquid phase in a stream-bubble contact device

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Dmitrieva, O. S.; Madyshev, I. N.

    2016-09-01

    One of the most effective energy saving technologies is the improvement of existing heat and mass exchange units. A stream-bubble contact device is designed to enhance the operation efficiency of heat and mass exchange units. The stages of the stream-bubble units that are proposed by the authors for the decarbonization process comprise contact devices with equivalent sizes, whose number is determined by the required performance of a unit. This approach to the structural design eliminates the problems that arise upon the transition from laboratory samples to industrial facilities and makes it possible to design the units of any required performance without a decrease in the effectiveness of mass exchange. To choose the optimal design that provides the maximum effectiveness of the mass-exchange processes in units and their intensification, the change of the mass-transfer coefficient is analyzed with the assumption of a number of parameters. The results of the study of the effect of various structural parameters of a stream-bubble contact device on the mass-transfer coefficient in the liquid phase are given. It is proven that the mass-transfer coefficient increases in the liquid phase, in the first place, with the growth of the level of liquid in the contact element, because the rate of the liquid run-off grows in this case and, consequently, the time of surface renewal is reduced; in the second place, with an increase in the slot diameter in the downpipe, because the jet diameter and, accordingly, their section perimeter and the area of the surface that is immersed in liquid increase; and, in the third place, with an increase in the number of slots in the downpipe, because the area of the surface that is immersed in the liquid of the contact element increases. Thus, in order to increase the mass-transfer coefficient in the liquid phase, it is necessary to design the contact elements with a minimum width and a large number of slots and their increased diameter; in

  17. Oxygen mass transfer and scale-up studies in baffled roller bioreactors.

    PubMed

    Nikakhtari, H; Song, W; Nemati, M; Hill, G A

    2014-02-01

    Oxygen mass transfer was studied in conventional, bead mill and baffled roller bioreactors. Using central composite rotational design, impacts of size, rotation speed and working volume on the oxygen mass transfer were evaluated. Baffled roller bioreactor outperformed its conventional and bead mill counterparts, with the highest k(L)a obtained in these configurations being 0.58, 0.19, 0.41 min(-1), respectively. Performances of the bead mill and baffled roller bioreactor were only comparable when a high bead loading (40%) was applied. Regardless of configuration increase in rotation speed and decrease in working volume improved the oxygen mass transfer rate. Increase in size led to enhanced mass transfer and higher k(L)a in baffled roller bioreactor (0.49 min(-1) for 2.2 L and 1.31 min(-1) for 55 L bioreactors). Finally, the experimentally determined k(L)a in the baffled roller bioreactors of different sizes fit reasonably well to an empirical correlation describing the k(L)a in terms of dimensionless numbers.

  18. The effect of the liquid-solid system properties on the interline heat transfer coefficient

    NASA Technical Reports Server (NTRS)

    Wayner, P. C., Jr.

    1977-01-01

    A theoretical procedure to determine the heat transfer characteristics of the interline region of an evaporating meniscus using the macroscopic optical and thermophysical properties of the system is outlined. The analysis is based on the premise that the interline transport processes are controlled by the London-van der Waals forces between condensed phases (solid and liquid). The procedure is used to compare the relative size of the interline heat sink of various systems using a constant heat flux model. This solution demonstrates the importance of the interline heat flow number which is evaluated for various systems. The heat transfer characteristics of the decane-steel system are numerically compared with those of the carbon tetrachloride-quartz system.

  19. Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime.

    PubMed

    Fielitz, Peter; Borchardt, Günter

    2016-08-10

    In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively.

  20. Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime.

    PubMed

    Fielitz, Peter; Borchardt, Günter

    2016-08-10

    In the dedicated literature the oxygen surface exchange coefficient KO and the equilibrium oxygen exchange rate [Fraktur R] are considered to be directly proportional to each other regardless of the experimental circumstances. Recent experimental observations, however, contradict the consequences of this assumption. Most surprising is the finding that the apparent activation energy of KO depends dramatically on the kinetic regime in which it has been determined, i.e. surface exchange controlled vs. mixed or diffusion controlled. This work demonstrates how the diffusion boundary condition at the gas/solid interface inevitably entails a correlation between the oxygen surface exchange coefficient KO and the oxygen self-diffusion coefficient DO in the bulk ("on top" of the correlation between KO and [Fraktur R] for the pure surface exchange regime). The model can thus quantitatively explain the range of apparent activation energies measured in the different regimes: in the surface exchange regime the apparent activation energy only contains the contribution of the equilibrium exchange rate, whereas in the mixed or in the diffusion controlled regime the contribution of the oxygen self-diffusivity has also to be taken into account, which may yield significantly higher apparent activation energies and simultaneously quantifies the correlation KO ∝ DO(1/2) observed for a large number of oxides in the mixed or diffusion controlled regime, respectively. PMID:27460608

  1. Consider a non-spherical elephant: computational fluid dynamics simulations of heat transfer coefficients and drag verified using wind tunnel experiments.

    PubMed

    Dudley, Peter N; Bonazza, Riccardo; Porter, Warren P

    2013-07-01

    Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry.

  2. Triplet-triplet energy transfer and protection mechanisms against singlet oxygen in photosynthesis

    NASA Astrophysics Data System (ADS)

    Kihara, Shigeharu

    individual BChl pigments within that photosynthetic antenna complex are accessed via their triplet state dynamics. It is found that the currently used exciton model of FMO needs to be revised. It is also shown that triplet excited states can be readily transferred between the molecules. It is proposed that the triplet energy transfer between the BChl molecules can also serve as a protection mechanism. Finally, it is inferred that at least one of the BChl molecules within the FMO has a triplet state energy that is lower than that of singlet oxygen. This effectively prevents the formation of singlet oxygen and protects the complex from oxidative damage. The energy of BChl is apparently lowered by the specific protein environment, as in solution its energy is measured to be somewhat higher than the energy of singlet oxygen. Finally, the results of the triplet energy transfer within the cytochrome b6f complex are presented. This part of the work is not conclusive, and some of the problems encountered in experiments are described, as well as a new method of sample degassing developed for this type of study is presented.

  3. Transfer coefficients of selected radionuclides to animal products. I. Comparison of milk and meat from dairy cows and goats

    SciTech Connect

    Johnson, J.E.; Ward, G.M.; Ennis, M.E. Jr.; Boamah, K.N.

    1988-02-01

    The diet-milk transfer coefficient, Fm (Bq L-1 output in milk divided by Bq d-1 intake to the animal) was studied for eight radionuclides that previously had been given little attention. The Fm values for cows and goats, respectively, were: 2.3 x 10(-5) and 1.5 x 10(-4) for /sup 99m/Tc, 1.4 x 10(-4) and 8.5 x 10(-4) for /sup 95m/Tc, 1.1 x 10(-2) for /sup 99/Tc (goats only); 1.7 x 10(-3) and 9 x 10(-3) for /sup 99/Mo; 4.8 x 10(-4) and 4.4 x 10(-3) for /sup 123m/Te; 4.8 x 10(-4) and 4.6 x 10(-3) for /sup 133/Ba; 5.5 x 10(-7) and 5.5 x 10(-6) for /sup 95/Zr; and 4.1 x 10(-7) and 6.4 x 10(-6) for /sup 95/Nb. The goat/cow transfer coefficient ratios for milk were approximately 10, but the goat/cow ratios for meat varied by three orders of magnitude.

  4. The simultaneous retrieval of surface evaporative fraction and heat transfer coefficients using variational data assimilation and surface radiometric temperature observations

    NASA Astrophysics Data System (ADS)

    Crow, W. T.; Kustas, W. P.

    2003-12-01

    Recent advances in land data assimilation have yielded data assimilation techniques designed to solve the surface energy balance based on remote observations of surface radiometric temperature and a simple prognostic equation for surface temperature. These approaches have a number of potential advantages over existing diagnostic models, including the ability to make energy flux predictions between satellite overpass times, more physically realistic representations of ground heat flux, and reduced requirements for ancillary parameter estimation. Of particular interest is the variational approach presented by Caparrini et al. (Journal of Hydrometeorology, 2003) which uses a force-restore equation for surface temperature as a constraint for the simultaneous estimation of both evaporative fraction and bulk heat transfer coefficients from sequences of surface radiometric temperature observations. Using eddy correlation flux tower data and analogous energy balance results obtained from the diagnostic Two-Source Model (TSM), this presentation will examine the performance of the Caparrini et al. algorithm over a range of vegetative and hydrologic conditions in the southern United States. Results identify circumstances under which the simultaneous - and unambiguous - retrieval of both surface evaporation fraction and heat transfer coefficients is possible and clarify parameter interpretation issues associated with the single-source geometry of the variational approach. Inter-comparison with the TSM model illustrates circumstances under which the increased parameter complexity of the TSM model is justified by its more accurate two-source representation of thermal emission from partial vegetation canopies. Potential improvements to current variational data assimilation techniques will also be discussed.

  5. Convective Heat Transfer Coefficients of Automatic Transmission Fluid Jets with Implications for Electric Machine Thermal Management: Preprint

    SciTech Connect

    Bennion, Kevin; Moreno, Gilberto

    2015-09-29

    Thermal management for electric machines (motors/ generators) is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. Cooling of the electric machine(s) in some electric vehicle traction drive applications is accomplished by impinging automatic transmission fluid (ATF) jets onto the machine's copper windings. In this study, we provide the results of experiments characterizing the thermal performance of ATF jets on surfaces representative of windings, using Ford's Mercon LV ATF. Experiments were carried out at various ATF temperatures and jet velocities to quantify the influence of these parameters on heat transfer coefficients. Fluid temperatures were varied from 50 degrees C to 90 degrees C to encompass potential operating temperatures within an automotive transaxle environment. The jet nozzle velocities were varied from 0.5 to 10 m/s. The experimental ATF heat transfer coefficient results provided in this report are a useful resource for understanding factors that influence the performance of ATF-based cooling systems for electric machines.

  6. Performance and heat transfer characteristics of a carbon monoxide/oxygen rocket engine

    NASA Technical Reports Server (NTRS)

    Linne, Diane L.

    1993-01-01

    The combustion and heat transfer characteristics of a carbon monoxide and oxygen rocket engine were evaluated. The test hardware consisted of a calorimeter combustion chamber with a heat sink nozzle and an eighteen element concentric tube injector. Experimental results are given at chamber pressures of 1070 and 3070 kPa, and over a mixture ratio range of 0.3 to 1.0. Experimental C efficiency was between 95 and 96.5 percent. Heat transfer results are discussed both as a function of mixture ratio and axial distance in the chamber. They are also compared to a Nusselt number correlation for fully developed turbulent flow.

  7. Using eddy covariance to estimate air-sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  8. Using eddy covariance to estimate air–sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  9. Instantaneous heat transfer coefficient based upon two-dimensional analyses of Stirling space engine components

    NASA Technical Reports Server (NTRS)

    Ibrahim, Mounir; Kannapareddy, Mohan; Tew, Roy C.; Dudenhoefer, James E.

    1991-01-01

    Twelve different cases of multidimensional models of Stirling engine components for space applications have been numerically investigated for oscillating, incompressible laminar flow with heat transfer. The cases studied covered wide ranges of Valensi number (from 44 to 700), Re(max) number (from 8250 to 60,000), and relative amplitude of fluid motion of 0.686 and 1.32. The Nusselt numbers obtained from the present study indicate a very complex shape with respect to time and axial location in the channel. The results indicate that three parameters can be used to define the local Nusselt number variation, namely: time average, amplitude, and phase angle. These parameters could be correlated respectively using: Re(max), Va and Re(max), and the relative amplitude of fluid motion.

  10. Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Taler, Dawid; Kowal, Andrzej

    2011-04-01

    The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surfaces of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.

  11. Drag and Bulk Transfer Coefficients Over Water Surfaces in Light Winds

    NASA Astrophysics Data System (ADS)

    Wei, Zhongwang; Miyano, Aiko; Sugita, Michiaki

    2016-08-01

    The drag coefficient (CD), experimentally determined from observed wind speed and surface stress, has been reported to increase in the low wind-speed range (<3 m s^{-1}) as wind speed becomes smaller. However, until now, the exact causes for its occurrence have not been determined. Here, possible causes for increased CD values in near-calm conditions are examined using high quality datasets selected from three-year continuous measurements obtained from the centre of Lake Kasumigaura, the second largest lake in Japan. Based on our analysis, suggested causes including (i) measurement errors, (ii) lake currents, (iii) capillary waves, (iv) the possibility of a measurement height within the interfacial/transition sublayer, and (v) a possible mismatch in the representative time scale used for mean and covariance averaging, are not considered major factors. The use of vector-averaged, instead of scalar-averaged, wind speeds and the presence of waves only partially explain the increase in CD under light winds. A small increase in turbulent kinetic energy due to buoyant production at low wind speeds is identified as the likely major cause for this increase in CD in the unstable atmosphere dominant over inland water surfaces.

  12. Full surface local heat transfer coefficient measurements in a model of an integrally cast impingement cooling geometry

    SciTech Connect

    Gillespie, D.R.H.; Wang, Z.; Ireland, P.T.; Kohler, S.T.

    1998-01-01

    Cast impingement cooling geometries offer the gas turbine designer higher structural integrity and improved convective cooling when compared to traditional impingement cooling systems, which rely on plate inserts. In this paper, it is shown that the surface that forms the jets contributes significantly to the total cooling. Local heat transfer coefficient distributions have been measured in a model of an engine wall cooling geometry using the transient heat transfer technique. The method employs temperature-sensitive liquid crystals to measure the surface temperature of large-scale perspex models during transient experiments. Full distributions of local Nusselt number on both surfaces of the impingement plate, and on the impingement target plate, are presented at engine representative Reynolds numbers. The relative effects of the impingement plate thermal boundary condition and the coolant supply temperature on the target plate heat transfer have been determined by maintaining an isothermal boundary condition at the impingement plate during the transient tests. The results are discussed in terms of the interpreted flow field.

  13. Theoretical and experimental study of the rule for heat transfer coefficient in hot stamping of high strength steels

    SciTech Connect

    Han, Xianhong; Hao, Xin; Yang, Kun; Zhong, Yaoyao

    2013-12-16

    Heat transfer is a crucial aspect for hot stamping process, the fully austenitized boron steel blank with temperature about 900°C is transferred to the tool, then formed rapidly and quenched in the cooled tool. The desired fully martensitic transformation will happen only if the cooling rate exceeds a critical value approximately 27 K/s. During such process, the heat transfer coefficient (abbreviated as HTC) between the tool and blank plays a decisive role for the variation of the blank temperature. In this work, a theoretical formula based on the joint-roughness model is presented to describe the law of HTC, which relies on the roughness, hardness, and other material parameters of the tool and blank. Moreover, a non-contact temperature measuring system based on the infrared thermal camera is built to catch the temperature change course, and then the HTC value is derived through the inverse analysis. Based on the theoretical and experimental results, the change rule of HTC especially its dependence on the process pressure will be discussed in detail.

  14. Experimental verification of the Einstein A-coefficient used for evaluation of O2(1Δg) concentration in the chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Spalek, O.; Kodymová, J.; Stopka, P.; Micek, I.

    1999-04-01

    This paper is a contribution to the current discussion on the Einstein coefficient for spontaneous emission (A-coefficient) of singlet delta oxygen, O2(1Δg), that is often used for an evaluation of O2(1Δg) concentration in a chemical oxygen-iodine laser (COIL). The published values of the A-coefficient vary in a wide range, corresponding to a radiative lifetime of O2(1Δg), τ_Δ^rad, from ~53 to ~151 min. This could make an evaluation of COIL operation questionable. In this paper, the Einstein A-coefficient is estimated, based on the comparison of O2(1Δg) concentrations determined by two independent methods: electron paramagnetic resonance and emission spectroscopy. Within the accuracy of the experimental techniques used, the value of the A-coefficient resulting from our investigation is (2.24±0.40) × 10-4 s-1, corresponding to τ_Δ^rad of ~74 min. This result is more consistent with the value of 2.58 × 10-4 s-1 of Badger et al [1] than with the value of 1.47 × 10-4 s-1 reported recently by Mlynczak and Nesbitt [2], who raised doubt about the Badger et al value.

  15. Simple transfer calibration method for a Cimel Sun-Moon photometer: calculating lunar calibration coefficients from Sun calibration constants.

    PubMed

    Li, Zhengqiang; Li, Kaitao; Li, Donghui; Yang, Jiuchun; Xu, Hua; Goloub, Philippe; Victori, Stephane

    2016-09-20

    The Cimel new technologies allow both daytime and nighttime aerosol optical depth (AOD) measurements. Although the daytime AOD calibration protocols are well established, accurate and simple nighttime calibration is still a challenging task. Standard lunar-Langley and intercomparison calibration methods both require specific conditions in terms of atmospheric stability and site condition. Additionally, the lunar irradiance model also has some known limits on its uncertainty. This paper presents a simple calibration method that transfers the direct-Sun calibration constant, V0,Sun, to the lunar irradiance calibration coefficient, CMoon. Our approach is a pure calculation method, independent of site limits, e.g., Moon phase. The method is also not affected by the lunar irradiance model limitations, which is the largest error source of traditional calibration methods. Besides, this new transfer calibration approach is easy to use in the field since CMoon can be obtained directly once V0,Sun is known. Error analysis suggests that the average uncertainty of CMoon over the 440-1640 nm bands obtained with the transfer method is 2.4%-2.8%, depending on the V0,Sun approach (Langley or intercomparison), which is comparable with that of lunar-Langley approach, theoretically. In this paper, the Sun-Moon transfer and the Langley methods are compared based on site measurements in Beijing, and the day-night measurement continuity and performance are analyzed.

  16. Simple transfer calibration method for a Cimel Sun-Moon photometer: calculating lunar calibration coefficients from Sun calibration constants.

    PubMed

    Li, Zhengqiang; Li, Kaitao; Li, Donghui; Yang, Jiuchun; Xu, Hua; Goloub, Philippe; Victori, Stephane

    2016-09-20

    The Cimel new technologies allow both daytime and nighttime aerosol optical depth (AOD) measurements. Although the daytime AOD calibration protocols are well established, accurate and simple nighttime calibration is still a challenging task. Standard lunar-Langley and intercomparison calibration methods both require specific conditions in terms of atmospheric stability and site condition. Additionally, the lunar irradiance model also has some known limits on its uncertainty. This paper presents a simple calibration method that transfers the direct-Sun calibration constant, V0,Sun, to the lunar irradiance calibration coefficient, CMoon. Our approach is a pure calculation method, independent of site limits, e.g., Moon phase. The method is also not affected by the lunar irradiance model limitations, which is the largest error source of traditional calibration methods. Besides, this new transfer calibration approach is easy to use in the field since CMoon can be obtained directly once V0,Sun is known. Error analysis suggests that the average uncertainty of CMoon over the 440-1640 nm bands obtained with the transfer method is 2.4%-2.8%, depending on the V0,Sun approach (Langley or intercomparison), which is comparable with that of lunar-Langley approach, theoretically. In this paper, the Sun-Moon transfer and the Langley methods are compared based on site measurements in Beijing, and the day-night measurement continuity and performance are analyzed. PMID:27661591

  17. Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps

    NASA Technical Reports Server (NTRS)

    Hippensteele, Steven A.; Poinsatte, Philip E.

    1993-01-01

    In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence

  18. The generalized correlation for the evaluation of the influence of the Stefan flow on the heat transfer coefficient

    NASA Astrophysics Data System (ADS)

    Baskakov, A. P.; Rakov, O. A.

    2013-11-01

    The analytical equations for the steady-state heat-and-mass transfer in the steam evaporation/condensation processes from the steam-gas mixtures on the planar and spherical surfaces are derived. The vapor flow through the motionless dry gas is considered according to the method proposed by Maxwell for the solution of the diffusion problems. The relationships for the calculation of the coefficients taking into account an increase in the mass output and an increase or a decrease in the heat emission (depending on the directions of the heat-and-mass flows) as a result of the influence of the Stefan flow are presented. The derived relationships can be used to calculate the apparatuses in which the steam evaporation or condensation from the steam-gas mixture occurs (the coolers of the vapor from deaerators, the apparatuses for the deep utilization of the heat of the combustion products, the condensation boilers, etc.).

  19. Turbulence at the Air-Water Interface in Lakes of Different Sizes: Consequences for Gas Transfer Coefficients

    NASA Astrophysics Data System (ADS)

    MacIntyre, S.; Crowe, A. T.; Amaral, J. H.; Arneborg, L.; Bastviken, D.; Forsberg, B. R.; Melack, J. M.; Tota, J.; Tedford, E. W.; Karlsson, J.; Podgrajsek, E.; Andersson, A.; Rutgersson, A.

    2014-12-01

    Similarity scaling predicts that wind induced shear will be the dominant source of turbulence near the air-water interface in lakes with low to moderate wind forcing. Turbulence is expected to be enhanced with wave activity; results are conflicting on the effects of heating and cooling. We measured turbulence with an acoustic Doppler velocimeter (ADV) and / or a temperature-gradient microstructure profiler and obtained correlative time series measurements of meteorology and water column temperature in a 800 m2 arctic pond, a 1 ha boreal lake, and a large tropical reservoir. Turbulence measurements with both instruments corroborated those calculated from similarity scaling in the boreal lake. Within the arctic pond, dissipation rates obtained with the ADV were in agreement with those from similarity scaling when winds exceeded ~1.5 m/s with a greater frequency of measurable dissipation rates when surface waves were present. Dissipation rates in the tropical reservoir reached and often exceeded 10-6 m2 s-3 in the upper meter under light winds and decreased by an order of magnitude with cooling or rainfall. Under cooling, dissipation rates were at least an order of magnitude higher in the uppermost 25 cm bin than in the water column below. Gas transfer coefficients calculated from concurrent measurements of greenhouse gas fluxes with floating chambers and the surface renewal model using the estimates of turbulence were in agreement. These results support the predictions of Monin-Obuhov similarity scaling in that shear dominates turbulence production near the air-water interface under heating and cooling, illustrate spatial variability in turbulence production in small water bodies due to the intermittency of wind interacting with the water's surface, are in agreement with prior oceanic observations that shear and associated turbulence can be intensified in shallow mixing layers under heating with light winds, and illustrate the utility of similarity scaling for

  20. Wind-chill-equivalent temperatures: regarding the impact due to the variability of the environmental convective heat transfer coefficient.

    PubMed

    Shitzer, Avraham

    2006-03-01

    The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published "new" WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a "gold standard" for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized. PMID:16397760

  1. Wind-chill-equivalent temperatures: regarding the impact due to the variability of the environmental convective heat transfer coefficient.

    PubMed

    Shitzer, Avraham

    2006-03-01

    The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published "new" WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a "gold standard" for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized.

  2. Wind-chill-equivalent temperatures: regarding the impact due to the variability of the environmental convective heat transfer coefficient

    NASA Astrophysics Data System (ADS)

    Shitzer, Avraham

    2006-03-01

    The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published “new” WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a “gold standard” for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized.

  3. 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.

  4. Ultrafast and ultraslow oxygen atom transfer reactions between late metal centers.

    PubMed

    Fortner, Kevin C; Laitar, David S; Muldoon, John; Pu, Lihung; Braun-Sand, Sonja B; Wiest, Olaf; Brown, Seth N

    2007-01-24

    Oxotrimesityliridium(V), (mes)3Ir=O (mes = 2,4,6-trimethylphenyl), and trimesityliridium(III), (mes)3Ir, undergo extremely rapid degenerate intermetal oxygen atom transfer at room temperature. At low temperatures, the two complexes conproportionate to form (mes)3Ir-O-Ir(mes)3, the 2,6-dimethylphenyl analogue of which has been characterized crystallographically. Variable-temperature NMR measurements of the rate of dissociation of the mu-oxo dimer combined with measurements of the conproportionation equilibrium by low-temperature optical spectroscopy indicate that oxygen atom exchange between iridium(V) and iridium(III) occurs with a rate constant, extrapolated to 20 degrees C, of 5 x 107 M-1 s-1. The oxotris(imido)osmium(VIII) complex (ArN)3Os=O (Ar = 2,6-diisopropylphenyl) also undergoes degenerate intermetal atom transfer to its deoxy partner, (ArN)3Os. However, despite the fact that its metal-oxygen bond strength and reactivity toward triphenylphosphine are nearly identical to those of (mes)3Ir=O, the osmium complex (ArN)3Os=O transfers its oxygen atom 12 orders of magnitude more slowly to (ArN)3Os than (mes)3Ir=O does to (mes)3Ir (kOsOs = 1.8 x 10-5 M-1 s-1 at 20 degrees C). Iridium-osmium cross-exchange takes place at an intermediate rate, in quantitative agreement with a Marcus-type cross relation. The enormous difference between the iridium-iridium and osmium-osmium exchange rates can be rationalized by an analogue of the inner-sphere reorganization energy. Both Ir(III) and Ir(V) are pyramidal and can form pyramidal iridium(IV) with little energetic cost in an orbitally allowed linear approach. Conversely, pyramidalization of the planar tris(imido)osmium(VI) fragment requires placing a pair of electrons in an antibonding orbital. The unique propensity of (mes)3Ir=O to undergo intermetal oxygen atom transfer allows it to serve as an activator of dioxygen in cocatalyzed oxidations, for example, acting with osmium tetroxide to catalyze the aerobic

  5. The effect of aeration conditions, characterized by the volumetric mass transfer coefficient K(L)a, on the fermentation kinetics of Bacillus thuringiensis kurstaki.

    PubMed

    Mounsef, Jihane Rahbani; Salameh, Dominique; Louka, Nicolas; Brandam, Cedric; Lteif, Roger

    2015-09-20

    The aeration is a key factor for Bacillus thuringiensis growth, sporulation and δ-endotoxins production. The objective of our work was to study the effect of aeration on the fermentation kinetics of Bacillus thuringiensis kurstaki (Btk), cultivated in a cereal milling byproduct (CMB) mono-component medium, in order to improve the δ-endotoxins productivity. Aeration conditions were systematically characterized by the volumetric mass transfer coefficient KLa. In the 6% CMB culture medium, different values of the maximal specific oxygen uptake rate were obtained at different values of KLa. For KLa of 7.2 h(-1), the growth was inhibited and the sporulation was defective. There was a linear increase of the average specific growth rate and faster sporulation and liberation of spores and δ-endotoxins crystals when KLa was increased between 13.3 h(-1) and 65.5 h(-1). Similar kinetic was observed in cultures performed at KLa equal to 65.5 h(-1) and 106.2 h(-1). The highest toxins productivity of 96.1 mg L(-1) (h)-1 was obtained in the 9% CMB culture medium for KLa of 102 h(-1). It was possible to track the evolution of the bacterial cells between vegetative growth, sporulation and liberation of mature spores by following the variation of the CO2 percent in the effluent gas.

  6. Comparison of different oxygen transfer testing procedures in full-scale membrane bioreactors.

    PubMed

    Krause, S; Cornel, P; Wagner, M

    2003-01-01

    Membrane bioreactors (MBRs) for wastewater treatment offer the advantage of a complete removal of solids from the effluent. The secondary clarifier is replaced by a membrane filtration and therefore high biomass concentrations (MLSS) in the reactor are possible. The design of the aeration system is vital for an energy efficient operation of any wastewater treatment plant. Hence the exact measurement of oxygen transfer rates (OTR) and alpha-values is important. For MBRs these values reported in literature differ considerably. The OTR can be measured using non-steady state methods or using the off-gas method. The non-steady state methods additionally require the determination of the respiration rate (oxygen uptake rate OUR), which usually is measured in lab scale units. As there are differences of OUR between lab scale and full scale measurements, off-gas tests (which do not require an additional respiration test) were performed in order to compare both methods at high MLSS concentrations. Both methods result in the same average value of OTR. Due to variations in loading and wastewater composition variations of OTR in time can be pointed out using the off-gas method. For the first time a comparison of different oxygen transfer tests in full scale membrane bioreactors is presented.

  7. Measurement of enhanced heat transfer coefficient with perforated twisted tape inserts during condensation of R-245fa

    NASA Astrophysics Data System (ADS)

    Khatua, A. K.; Kumar, P.; Singh, H. N.; Kumar, R.

    2016-04-01

    The experimental conductive heat transfer results for flow through inserted perforated twisted tapes in a horizontal tube during condensation of pure R-245fa vapor. The test section consisting of two separate coaxial double pipes assembled in series, acted like a counter flow heat exchanger, where the refrigerant condensed inside the inner tube by rejecting heat to the cooling water flowing inside the outer tube in reversed direction. Data for three perforated twisted tapes having constant twist ratio of 7.1 mm and pitch of perforation as 12.5, 25.0 and 37.5 mm, inserted one by one in full length of test condenser by varying refrigerant mass flux from 100 to 200 kg/m2 s in steps of 50 kg/m2 s for the range of vapor quality from 0.1 to 0.9, were collected together with flow and without insert (plain tube). It has been found that the perforated twisted tape insert having pitch of perforation equal to in order of 12.5 mm gives the highest value of average heat transfer coefficient and is of the order of 37.5 % more than that of the plain one and the correlation predicts the experimental data within an error band of ±15 %.

  8. Electric transport coefficients in highly epitaxial LaBaCo2O5 + δ films with "p-to-n" transition induced by oxygen deficiency

    NASA Astrophysics Data System (ADS)

    Shaibo, J.; Zhang, Q. Y.; Wang, Y. Q.; Hu, H. C.; Li, X. N.; Pan, L. J.

    2016-08-01

    Electric transport coefficients such as carrier type, density, and mobility are the important physical parameters in designing functional devices. In this work, we report the study on the electric transport coefficients of the highly epitaxial LaBaCo2O5 + δ (LBCO) films, which were discussed as a function of electric conductivity for the first time and compared with the results calculated by the theory for mixed conduction. The mobility in the LBCO films was determined to be ˜0.85 and ˜40 cm2/V s for holes and electrons, respectively, and the density of p-type carriers strongly depends on the oxygen deficiency. Solid evidence is presented to demonstrate that the oxygen deficiency cannot make LBCO materials changed from p- to n-type. The n-type conduction observed in experiment is a counterfeit phenomenon caused by the deficiency in Hall measurement, rather than a realistic transition induced by oxygen deficiency. In addition, the temperature-dependent conductivity was discussed using the differential coefficients, which might be useful in the study of the samples with magnetic transition.

  9. Rheology, oxygen transfer, and molecular weight characteristics of poly(glutamic acid) fermentation by Bacillus subtilis.

    PubMed

    Richard, Andrew; Margaritis, Argyrios

    2003-05-01

    Poly(glutamic acid) (PGA) is a water-soluble, biodegradable biopolymer that is produced by microbial fermentation. Recent research has shown that PGA can be used in drug delivery applications for the controlled release of paclitaxel (Taxol) in cancer treatment. A fundamental understanding of the key fermentation parameters is necessary to optimize the production and molecular weight characteristics of poly(glutamic acid) by Bacillus subtilis for paclitaxel and other applications of pharmaceuticals for controlled release. Because of its high molecular weight, PGA fermentation broths exhibit non-Newtonian rheology. In this article we present experimental results on the batch fermentation kinetics of PGA production, mass transfer of oxygen, specific oxygen uptake rate, broth rheology, and molecular weight characterization of the PGA biopolymer.

  10. Preparation of a silanone through oxygen atom transfer to a stable cyclic silylene.

    PubMed

    Linden, Michael M; Reisenauer, Hans Peter; Gerbig, Dennis; Karni, Miriam; Schäfer, Annemarie; Müller, Thomas; Apeloig, Yitzhak; Schreiner, Peter R

    2015-10-12

    We report the evaporation of a stable cyclic silylene and its oxidation (with ozone or N2 O) through oxygen atom transfer to form the corresponding silanone under matrix isolation conditions. As uncomplexed silanones are rare owing to their very high reactivity, this method provides an alternative route to these sought-after molecules. The silanone, as well as a novel bicyclic silane with a bridgehead silicon atom derived from an intramolecular silylene CH bond insertion, were characterized by comparison of high-resolution infrared spectra with density functional theory (DFT) computations at the M06-2X/cc-pVDZ level of theory. PMID:26315924

  11. Preparation of a silanone through oxygen atom transfer to a stable cyclic silylene.

    PubMed

    Linden, Michael M; Reisenauer, Hans Peter; Gerbig, Dennis; Karni, Miriam; Schäfer, Annemarie; Müller, Thomas; Apeloig, Yitzhak; Schreiner, Peter R

    2015-10-12

    We report the evaporation of a stable cyclic silylene and its oxidation (with ozone or N2 O) through oxygen atom transfer to form the corresponding silanone under matrix isolation conditions. As uncomplexed silanones are rare owing to their very high reactivity, this method provides an alternative route to these sought-after molecules. The silanone, as well as a novel bicyclic silane with a bridgehead silicon atom derived from an intramolecular silylene CH bond insertion, were characterized by comparison of high-resolution infrared spectra with density functional theory (DFT) computations at the M06-2X/cc-pVDZ level of theory.

  12. An application of the non-continuous Trefftz method to the determination of heat transfer coefficient for flow boiling in a minichannel

    NASA Astrophysics Data System (ADS)

    Maciejewska, Beata; Piasecka, Magdalena

    2016-08-01

    The paper presents an application of the semi-analytical method, called the non-continuous Trefftz method, to the calculation of the heat transfer coefficients. It is very effective method for solving direct and inverse problems. The results obtained by this method are consistent with the results obtained by using complicated methods: the FEM and Beck method. Sought local heat transfer coefficients between the heating surface and the boiling liquid flowing through 1 mm deep minichannel were calculated from the Robin boundary condition. The temperature of the heating surface and the derivative of the temperature were was found from solving the inverse problem. The study is limited to the identification of the heat transfer coefficient in the subcooled and the saturated nucleate boiling regions. The article presents also the measurement stand and methodology of conducting the experiment. Presented issues allows verification of state-of-the-art methods of solving the inverse problem by using the authors' empirical data from the experiment.

  13. Time efficient way to calculate oxygen transfer areas and power input in cylindrical disposable shaken bioreactors.

    PubMed

    Klöckner, Wolf; Lattermann, Clemens; Pursche, Franz; Büchs, Jochen; Werner, Sören; Eibl, Dieter

    2014-01-01

    Disposable orbitally shaken bioreactors are a promising alternative to stirred or wave agitated systems for mammalian and plant cell cultivation, because they provide a homogeneous and well-defined liquid distribution together with a simple and cost-efficient design. Cultivation conditions in the surface-aerated bioreactors are mainly affected by the size of the volumetric oxygen transfer area (a) and the volumetric power input (P∕VL ) that both result from the liquid distribution during shaking. Since Computational Fluid Dynamics (CFD)-commonly applied to simulate the liquid distribution in such bioreactors-needs high computing power, this technique is poorly suited to investigate the influence of many different operating conditions in various scales. Thus, the aim of this paper is to introduce a new mathematical model for calculating the values of a and P∕VL for liquids with water-like viscosities. The model equations were derived from the balance of centrifugal and gravitational forces exerted during shaking. A good agreement was found among calculated values for a and P∕VL , CFD simulation values and empirical results. The newly proposed model enables a time efficient way to calculate the oxygen transfer areas and power input for various shaking frequencies, filling volumes and shaking and reactor diameters. All these parameters can be calculated fast and with little computing power.

  14. Quantification of surface area and intrinsic mass transfer coefficient for ultrasound-assisted dissolution process of a sparingly soluble solid dispersed in aqueous solutions.

    PubMed

    Durbha, Krishna Sandilya; Aravamudan, Kannan

    2012-05-01

    The efficacy of power ultrasound of 20 kHz in enhancing the volumetric mass transfer coefficient was investigated in this study. Breakage and dissolution of sparingly soluble benzoic acid dispersed in either water or 24% aqueous glycerol was monitored as a function of time and ultrasound power input. Particle size measurements were carried out at intermediate times during the experiment to estimate the mean particle size and surface area. Linear combination of lognormal distributions was found to fit the experimental particle size distribution data. The De Brouckere mean diameters (d(43)) obtained from the particle size distributions decreased with increase in the ultrasonic power level. Empirical correlations were developed for the evolution of surface area as a function of ultrasonic energy input per unit mass. The effect of ultrasound on the intrinsic mass transfer coefficient (k(c)) could be decoupled from the volumetric mass transfer coefficient (k(c)a) as the surface area was also estimated. Different approaches involving either constant or variable intrinsic mass transfer coefficients were employed when carrying out the delineation. Mass transfer rates were enhanced due to both higher ultrasound induced intrinsic convective mass transfer coefficient and additional surface area created from particle breakage. To delineate the effects of particle breakage from solid dissolution, experiments were also carried out under non-mass transfer conditions by pre-saturating the solvents with benzoic acid. Both the solid-liquid systems examined in the present study attained saturation concentration when the ultrasonic energy input per unit mass was approximately 60 kJ/kg, irrespective of the ultrasonic power level setting.

  15. Nitrogen-doped graphene prepared by a transfer doping approach for the oxygen reduction reaction application

    NASA Astrophysics Data System (ADS)

    Mo, Zaiyong; Zheng, Ruiping; Peng, Hongliang; Liang, Huagen; Liao, Shijun

    2014-01-01

    Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm-2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.

  16. Empirical relationship between Kubelka-Munk and radiative transfer coefficients for extracting optical parameters of tissues in diffusive and nondiffusive regimes

    NASA Astrophysics Data System (ADS)

    Roy, Arindam; Ramasubramaniam, Rajagopal; Gaonkar, Harshavardhan A.

    2012-11-01

    Kubelka-Munk (K-M) theory is a phenomenological light transport theory that provides analytical expressions for reflectance and transmittance of diffusive substrates such as tissues. Many authors have derived relations between coefficients of K-M theory and that of the more fundamental radiative transfer equations. These relations are valid only in diffusive light transport regime where scattering dominates over absorption. They also fail near boundaries where incident beams are not diffusive. By measuring total transmittance and total reflectance of tissue phantoms with varying optical parameters, we have obtained empirical relations between K-M coefficients and the radiative transport coefficients for integrating sphere-based spectrophotometers that use uniform, nondiffusive incident beams. Our empirical relations show that the K-M scattering coefficients depend only on reduced scattering coefficient (μs‧), whereas the K-M absorption coefficient depends on both absorption (μa) and reduced scattering (μs‧) coefficients of radiative transfer theory. We have shown that these empirical relations are valid in both the diffusive and nondiffusive regimes and can predict total reflectance within an error of 10%. They also can be used to solve the inverse problem of obtaining multiple optical parameters such as chromophore concentration and tissue thickness from the measured reflectance spectra with a maximum accuracy of 90% to 95%.

  17. Effect of temperature-dependent surface heat transfer coefficient on the maximum surface stress in ceramics during quenching

    NASA Astrophysics Data System (ADS)

    Shao, Y. F.; Song, F.; Jiang, C. P.; Xu, X. H.; Wei, J. C.; Zhou, Z. L.

    2016-02-01

    We study the difference in the maximum stress on a cylinder surface σmax using the measured surface heat transfer coefficient hm instead of its average value ha during quenching. In the quenching temperatures of 200, 300, 400, 500, 600 and 800°C, the maximum surface stress σmmax calculated by hm is always smaller than σamax calculated by ha, except in the case of 800°C; while the time to reach σmax calculated by hm (fmmax) is always earlier than that by ha (famax). It is inconsistent with the traditional view that σmax increases with increasing Biot number and the time to reach σmax decreases with increasing Biot number. Other temperature-dependent properties also have a small effect on the trend of their mutual ratios with quenching temperatures. Such a difference between the two maximum surface stresses is caused by the dramatic variation of hm with temperature, which needs to be considered in engineering analysis.

  18. High heat flux sensor for infrared thermography determination of heat transfer coefficient of liquid metal cooled target's wall

    NASA Astrophysics Data System (ADS)

    Patorski, Jacek A.; Gindrat, Malko

    2009-05-01

    The proton beam passing through the wall area of a liquid metal (LM) target container, called entrance window, is causing deposition of maximum high heat flux amount 140 W/cm2.Previous experimental thermo-hydraulics investigations for the MEGAPIE LM-target at the SINQ facility of Heat- Transfer-Coefficient (HTC) using InfraRed-Thermography (IRT) have been presented at Thermosense 2006 and 2007 [1], [2] and references therein. During these investigations the IRT active sensors with applied heat fluxes of the small and low range from 2.5 to 15.2 W/cm2 are used. The heating shell foil of the sensor has been connected to steel dish enclosing LM target container by using electrical insulation ceramic glue. A higher, then achieved 15 W/cm2, heat flux has lead to delaminating of the heater. Because of interest to determinate the HTC-chart under real heat flux conditions and investigate some positive effect of heat flux buoyancy on cooling, the idea for the High Heat Flux (HHF) IRT Sensors, using of the Low Pressure Plasma Spraying - Thin Film (LPPS-TF) technology of the Sulzer Metco Company has been created. The paper presents the idea of multilayer thermal sprayed construction of HHF-IRT-Sensor, few realizations and some results of the first pre-test performed at the PSI LBE Double Pump Loop using the new sensor and the 2DD IRT methodology presented in [1].

  19. Measurement of Heat Flux and Heat Transfer Coefficient Due to Spray Application for the Die Casting Process

    SciTech Connect

    Sabau, Adrian S

    2007-01-01

    Lubricant spray application experiments were conducted for the die casting process. The heat flux was measured in situ using a differential thermopile sensor for three application techniques. First, the lubricant was applied under a constant flowrate while the nozzle was held in the same position. Second, the lubricant was applied in a pulsed, static manner, in which the nozzle was held over the same surface while it was turned on and off several times. Third, the lubricant was applied in a sweeping manner, in which the nozzle was moved along the die surface while it was held open. The experiments were conducted at several die temperatures and at sweep speeds of 20, 23, and 68 cm/s. The heat flux data, which were obtained with a sensor that was located in the centre of the test plate, were presented and discussed. The sensor can be used to evaluate lubricants, monitor the consistency of die lubrication process, and obtain useful process data, such as surface temperature, heat flux, and heat transfer coefficients. The heat removed from the die surface during lubricant application is necessary for (a) designing the cooling channels in the die, i.e. their size and placement, and (b) performing accurate numerical simulations of the die casting process.

  20. Mass transfer coefficients for volatilization of polychlorinated biphenyls from the Hudson River, New York measured using micrometeorological approaches.

    PubMed

    Sandy, Andy L; Guo, Jia; Miskewitz, Robert J; McGillis, Wade R; Rodenburg, Lisa A

    2013-02-01

    Air-water exchange is an important process controlling the fate of many organic chemicals in the environment. Modeling this process is hampered by the lack of direct observations. Thus, the purpose of this work was to derive direct measurements of the mass transfer coefficients for air-water exchange (v(aw)) of polychlorinated biphenyls (PCBs) that may be used to check the validity of values derived from tracer gas experiments. v(aw) values for PCBs were determined using previously published turbulent fluxes divided by the corresponding dissolved phase concentrations. The median v(aw) values for each homolog decreased with increasing molecular weight and ranged from 0.29 for hexachlorobiphenyls to 2.2 m d(-1) for monochlorobiphenyls with a propagated uncertainty of about 70%, lower than in previous studies. Due to relatively low wind speeds and possible sorption of PCBs to colloids, these numbers may be biased low. These field measurements of v(aw) differ by as much as a factor of 23 from predictions based on the widely-used Whitman two-film model. Therefore a new formulation for the calculation of v(aw) based on field measurements is needed. This study demonstrates that micrometeorological approaches are a viable option for the measurement of v(aw) for hydrophobic organics such as PCBs and should be used to generate enough field data on the air-water exchange of hydrophobic organics to allow the development of new predictive models. PMID:23040647

  1. Measurements of momentum transfer coefficients for H2, N2, CO and CO2 incident upon spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Cook, S. R.; Hoffbauer, M. A.

    1997-01-01

    Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H2, N2, CO, and CO2 incident upon the solar array material, Kapton, SiO2-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that scattering behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.

  2. Measurement of Momentum Transfer Coefficients for H2, N2, CO, and CO2 Incident Upon Spacecraft Surfaces

    NASA Technical Reports Server (NTRS)

    Cook, Steven R.; Hoffbauer, Mark A.

    1997-01-01

    Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H2, N2, CO, and CO2 incident upon the solar array material, Kapton, SiO2-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that the scattering behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.

  3. Electrocatalysis of anodic oxygen-transfer reactions at modified lead dioxide electrodes

    SciTech Connect

    Hsiao, Yun-Lin.

    1990-09-21

    The electrocatalytic activities were compared for pure and chloride-doped beta-PbO{sub 2} (Cl-PbO{sub 2}) films on gold and platinum substrates. Rate constants were increased significantly for oxidations of Mn{sup 2+}, toluene, benzyl alcohol, dimethylsulphoxide (DMSO) and benzaldehyde in acidic media by the incorporation of Cl{sup {minus}} into the oxide films. These reactions are concluded to occur by the electrocatalytic transfer of oxygen from H{sub 2}O to the reaction products. Results of x-ray diffraction studies indicate the Cl-PbO{sub 2} film continues to have the slightly distorted rutile structure of pure beta-PbO{sub 2}. The observed electrocatalytic phenomena are concluded to be the beneficial consequence of surface defects generated when Cl{sup {minus}} serves for charge compensation within the surface matrix and, thereby, increases the number of surface sites capable of adsorbing hydroxyl radicals which are transferred in the electrocatalytic O-transfer reactions. 91 refs., 44 figs., 10 tabs.

  4. Solvent-dependent singlet oxygen lifetimes: temperature effects implicate tunneling and charge-transfer interactions.

    PubMed

    Bregnhøj, Mikkel; Westberg, Michael; Jensen, Frank; Ogilby, Peter R

    2016-08-17

    The effect of solvent on the lifetime of singlet oxygen, O2(a(1)Δg), particularly the pronounced H/D solvent isotope effect, has drawn the attention of chemists for almost 50 years. The currently accepted model for this phenomenon is built on a foundation in which the electronic excitation energy of O2(a(1)Δg) is transferred to vibrational modes in a solvent molecule, with oxygen returning to its ground electronic state, O2(X(3)Σg(-)). This model of electronic-to-vibrational (e-to-v) energy transfer specifically focusses on the solvent as a "sink" for the excitation energy of O2(a(1)Δg). On the basis of temperature-dependent changes in the solvent-mediated O2(a(1)Δg) lifetime, we demonstrate that this energy-sink-based model has limitations and needs to be re-formulated. We now show that the effect of solvent on the O2(a(1)Δg) lifetime is more reasonably interpreted by considering an activation barrier that reflects the extent to which a solvent molecule perturbs the forbidden O2(a(1)Δg) → O2(X(3)Σg(-)) transition. For a given solvent molecule, this barrier reflects contributions from (a) the oxygen-solvent charge transfer state that mediates nonradiative coupling between the O2(a(1)Δg) and O2(X(3)Σg(-)) states, and (b) vibrations of specific bonds in the solvent molecule. The latter establishes connectivity to the desirable features of the energy-sink-based model. Moreover, temperature-dependent H/D solvent isotope effects imply that tunneling through this barrier plays a role in the mechanism for O2(a(1)Δg) deactivation, even at room temperature. Although we focus on a long-standing problem involving O2(a(1)Δg), our results and interpretation touch fundamental issues of interest to chemists at large. PMID:27484979

  5. A stability-dependent parametrization of transfer coefficients for momentum and heat over polar sea ice to be used in climate models

    NASA Astrophysics Data System (ADS)

    Lüpkes, Christof; Gryanik, Vladimir M.

    2015-01-01

    The interaction between sea ice and atmosphere depends strongly on the near-surface transfer coefficients for momentum and heat. A parametrization of these coefficients is developed on the basis of an existing parametrization of drag coefficients for neutral stratification that accounts for form drag caused by the edges of ice floes and melt ponds. This scheme is extended to better account for the dependence of surface wind on limiting cases of high and low ice concentration and to include near-surface stability effects over open water and ice on form drag. The stability correction is formulated on the basis of stability functions from Monin-Obukhov similarity theory and also using the Louis concept with stability functions depending on the bulk Richardson numbers. Furthermore, a parametrization is proposed that includes the effect of edge-related turbulence also on heat transfer coefficients. The parametrizations are available in different levels of complexity. The lowest level only needs sea ice concentration and surface temperature as input, while the more complex level needs additional sea ice characteristics. An important property of our parametrization is that form drag caused by ice edges depends on the stability over both ice and water which is in contrast to the skin drag over ice. Results of the parametrization show that stability has a large impact on form drag and, thereby, determines the value of sea ice concentration for which the transfer coefficients reach their maxima. Depending on the stratification, these maxima can occur anywhere between ice concentrations of 20 and 80%.

  6. A tale of two solutes: Dual-domain flow and the role of the mass transfer coefficient

    NASA Astrophysics Data System (ADS)

    Callaghan, M. V.; Bishop, J. M.; Cey, E. E.; Bentley, L. R.

    2011-12-01

    ' histories were different because of the difference in their distribution at the beginning of the experiment. Dual-permeability water flow and solute transport has been modeled using the HYDRUS software package. The numerical model was calibrated to both the observed salt and tracer concentrations, and, consequently, the distinct behavior of the two solutes. The numerical modeling results indicate that salt and tracer transport are sensitive to the mass transfer coefficient between matrix and macropore domains and, consequently, proper selection of the coefficient value is key to the accurate prediction of transport in dual permeability media.

  7. Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

    NASA Astrophysics Data System (ADS)

    Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

    1987-05-01

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  8. Henry’s Law Constant and Overall Mass Transfer Coefficient for Formaldehyde Emission from Small Water Pools under Simulated Indoor Environmental Conditions

    EPA Science Inventory

    The Henry’s law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for aqueous formaldehyde solutions were determined in the concentration range from 0....

  9. Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

    NASA Technical Reports Server (NTRS)

    Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.

    1987-01-01

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  10. Influence of tube-entrance configuration on average heat-transfer coefficients and friction factors for air flowing in an Inconel tube

    NASA Technical Reports Server (NTRS)

    Lowdermilk, Warren H; Grele, Milton D

    1950-01-01

    A heat-transfer investigation was conducted with air flowing through an electrically heated Inconel tube having either a long-approach or a right-angle-edge entrance, an inside diameter of 0.402 inch, and a length of 24 inches over a range of Reynolds numbers up to 375,000 and average inside-tube-wall temperatures up to 2000 degrees R. Good correlation of heat-transfer data was obtained for both entrances, which substantiates work previously reported. A fair correlation of friction data was obtained for both entrances. The entrance configuration had little effect on the average heat-transfer and friction coefficients.

  11. Effect of mass transfer on the oxygen reduction reaction catalyzed by platinum dendrimer encapsulated nanoparticles.

    PubMed

    Dumitrescu, Ioana; Crooks, Richard M

    2012-07-17

    Here we report on the effect of the mass transfer rate (k(t)) on the oxygen reduction reaction (ORR) catalyzed by Pt dendrimer-encapsulated nanoparticles (DENs) comprised of 147 and 55 atoms (Pt(147) and Pt(55)). The experiments were carried out using a dual-electrode microelectrochemical device, which enables the study of the ORR under high k(t) conditions with simultaneous detection of H(2)O(2). At low k(t) (0.02 to 0.12 cm s(-1)) the effective number of electrons involved in ORR, n(eff), is 3.7 for Pt(147) and 3.4 for Pt(55). As k(t) is increased, the mass-transfer-limited current for the ORR becomes significantly lower than the value predicted by the Levich equation for a 4-electron process regardless of catalyst size. However, the percentage of H(2)O(2) detected remains constant, such that n(eff) barely changes over the entire k(t) range explored (0.02 cm s(-1)). This suggests that mass transfer does not affect n(eff), which has implications for the mechanism of the ORR on Pt nanoparticles. Interestingly, there is a significant difference in n(eff) for the two sizes of Pt DENs (n(eff) = 3.7 and 3.5 for Pt(147) and Pt(55), respectively) that cannot be assigned to mass transfer effects and that we therefore attribute to a particle size effect.

  12. Metallized Gelled Propellants: Oxygen/RP-1/Aluminum Rocket Engine Calorimeter Heat Transfer Measurements and Analysis

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    1997-01-01

    A set of analyses was conducted to determine the heat transfer characteristics of metallized gelled liquid propellants in a rocket engine. The analyses used the data from experiments conducted with a small 30- to 40-lbf thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-wt %, 5-wt%, and 55-wt% loadings of aluminum with silicon dioxide gellant, and gaseous oxygen as the oxidizer. Heat transfer was computed based on measurements using calorimeter rocket chamber and nozzle hardware with a total of 31 cooling channels. A gelled fuel coating formed in the 0-, 5- and 55-wt% engines, and the coating was composed of unburned gelled fuel and partially combusted RP-1. The coating caused a large decrease in calorimeter engine heat flux in the last half of the chamber for the 0- and 5-wt% RP-1/Al. This heat flux reduction effect was analyzed by comparing engine runs and the changes in the heat flux during a run as well as from run to run. Heat transfer and time-dependent heat flux analyses and interpretations are provided. The 5- and 55-wt% RP-1/Al fueled engines had the highest chamber heat fluxes, with the 5-wt% fuel having the highest throat flux. This result is counter to the predicted result, where the 55 wt% fuel has the highest combustion and throat temperature, and therefore implies that it would deliver the highest throat heat flux. The 5-wt% RP-1/Al produced the most influence on the engine heat transfer and the heat flux reduction was caused by the formation of a gelled propellant layer in the chamber and nozzle.

  13. Exceedingly Fast Oxygen Atom Transfer to Olefins via a Catalytically Competent Nonheme Iron Species.

    PubMed

    Serrano-Plana, Joan; Aguinaco, Almudena; Belda, Raquel; García-España, Enrique; Basallote, Manuel G; Company, Anna; Costas, Miquel

    2016-05-17

    The reaction of [Fe(CF3 SO3 )2 (PyNMe3 )] with excess peracetic acid at -40 °C leads to the accumulation of a metastable compound that exists as a pair of electromeric species, [Fe(III) (OOAc)(PyNMe3 )](2+) and [Fe(V) (O)(OAc)(PyNMe3 )](2+) , in fast equilibrium. Stopped-flow UV/Vis analysis confirmed that oxygen atom transfer (OAT) from these electromeric species to olefinic substrates is exceedingly fast, forming epoxides with stereoretention. The impact of the electronic and steric properties of the substrate on the reaction rate could be elucidated, and the relative reactivities determined for the catalytic oxidations could be reproduced by kinetic studies. The observed fast reaction rates and high selectivities demonstrate that this metastable compound is a truly competent OAT intermediate of relevance for nonheme iron catalyzed epoxidations.

  14. Exceedingly Fast Oxygen Atom Transfer to Olefins via a Catalytically Competent Nonheme Iron Species.

    PubMed

    Serrano-Plana, Joan; Aguinaco, Almudena; Belda, Raquel; García-España, Enrique; Basallote, Manuel G; Company, Anna; Costas, Miquel

    2016-05-17

    The reaction of [Fe(CF3 SO3 )2 (PyNMe3 )] with excess peracetic acid at -40 °C leads to the accumulation of a metastable compound that exists as a pair of electromeric species, [Fe(III) (OOAc)(PyNMe3 )](2+) and [Fe(V) (O)(OAc)(PyNMe3 )](2+) , in fast equilibrium. Stopped-flow UV/Vis analysis confirmed that oxygen atom transfer (OAT) from these electromeric species to olefinic substrates is exceedingly fast, forming epoxides with stereoretention. The impact of the electronic and steric properties of the substrate on the reaction rate could be elucidated, and the relative reactivities determined for the catalytic oxidations could be reproduced by kinetic studies. The observed fast reaction rates and high selectivities demonstrate that this metastable compound is a truly competent OAT intermediate of relevance for nonheme iron catalyzed epoxidations. PMID:27071372

  15. Theory of Triplet Excitation Transfer in the Donor-Oxygen-Acceptor System: Application to Cytochrome b6f.

    PubMed

    Petrov, Elmar G; Robert, Bruno; Lin, Sheng Hsien; Valkunas, Leonas

    2015-10-20

    Theoretical consideration is presented of the triplet excitation dynamics in donor-acceptor systems in conditions where the transfer is mediated by an oxygen molecule. It is demonstrated that oxygen may be involved in both real and virtual intramolecular triplet-singlet conversions in the course of the process under consideration. Expressions describing a superexchange donor-acceptor coupling owing to a participation of the bridging twofold degenerate oxygen's virtual singlet state are derived and the transfer kinetics including the sequential (hopping) and coherent (distant) routes are analyzed. Applicability of this theoretical description to the pigment-protein complex cytochrome b6f, by considering the triplet excitation transfer from the chlorophyll a molecule to distant β-carotene, is discussed. PMID:26488665

  16. Experimental determination of transfer coefficients of sup 137 Cs and sup 131 I from fodder into milk of cows and sheep after the Chernobyl accident

    SciTech Connect

    Voigt, G.; Mueller, H.P.; Proehl, G.P.; Paretzke, H.G.; Propstmeier, G.; Roehrmoser, G.H.; Hofmann, P. )

    1989-12-01

    Following the Chernobyl accident in April 1986, the transfer of {sup 131}I and {sup 137}Cs from feed to milk was studied under experimental and common agricultural conditions. From measurements in different dairy farms in Southern Bavaria, equilibrium transfer coefficients for cow's milk were calculated to be 0.003 d L-1 (range 0.0015 to 0.005) for {sup 131}I and 0.003 d L-1 (range 0.0025 to 0.004) for {sup 137}Cs. In feeding experiments with cows and sheep under more controlled conditions, milk transfer coefficients of 0.007 d L-1 (range 0.0055 to 0.0081) for {sup 131}I and 0.003 d L-1 (range 0.0023 to 0.0053) for {sup 137}Cs were obtained for cows, while for sheep the {sup 137}Cs transfer coefficient was higher: 0.06 d L-1. The kinetics of the Cs transfer from fodder to cow's milk can be described by two exponential terms assuming biological half-lives in milk of 1-2 d and 10-20 d. The use of a fast component with 1.5 d and a fraction of 0.8, and a slow component with 15 d, gives a good approximation to the kinetics for all cows in this experiment.

  17. Effect of soybean oil on oxygen transfer in the production of tetracycline with an airlift bioreactor.

    PubMed

    Jia, S; Chen, G; Kahar, P; Choi, D B; Okabe, M

    1999-01-01

    Corn starch and soybean oil are suitable carbon sources for the production of tetracycline by Streptomyces aureofacience CG-1. However, it could not produce more than 6 g/l of tetracycline even if initial corn starch concentration was increased to more than 100 g/l. It was confirmed by shaking flask experiments that the k(L)a in a mixture of 2% soybean oil in water was four folds compared with that without soybean oil. With the addition of soybean oil to the starch medium in a shaking flask, tetracycline production was significantly improved. By scaling-up to a 5.5-l airlift bioreactor from 500-ml Erlenmeyer flask, more than 10 g/l of tetracycline was produced with the addition of 60 g/l of soybean oil to the medium containing 100 g/l of corn starch. The dissolved oxygen level in the airlift bioreactor containing soybean oil was higher than that without soybean oil. This suggests that soybean oil is not only a suitable carbon source but is also a surface-active agent which may accelerate the oxygen transfer. This may lead to the possibility of the enhanced production of tetracycline at a low cost in airlift bioreactor.

  18. Influence of oxygen transfer on Pseudomonas putida effects on growth rate and biodesulfurization capacity.

    PubMed

    Escobar, S; Rodriguez, A; Gomez, E; Alcon, A; Santos, V E; Garcia-Ochoa, Felix

    2016-04-01

    The growth rate and desulfurization capacity accumulated by the cells during the growth of Pseudomonas putida KTH2 under different oxygen transfer conditions in a stirred and sparged tank bioreactor have been studied. Hydrodynamic conditions were changed using different agitation conditions. During the culture, several magnitudes associated to growth, such as the specific growth rate, the dissolved oxygen concentration and the carbon source consumption have been measured. Experimental results indicate that cultures are influenced by the fluid dynamic conditions into the bioreactor. An increase in the stirrer speed from 400 to 700 rpm has a positive influence on the cell growth rate. Nevertheless, the increase of agitation from 700 to 2000 rpm hardly has any influence on the growth rate. The effect of fluid dynamics on the cells development of the biodesulfurization (BDS) capacity of the cells during growth is different. The activities of the intracellular enzymes involved in the 4S pathway change with dissolved oxygen concentration. The enzyme activities have been evaluated in cells at several growth time and different hydrodynamic conditions. An increase of the agitation from 100 to 300 rpm has a positive influence on the development of the overall BDS capacity of the cells during growth. This capacity shows a decrease for higher stirrer speeds and the activity of the enzymes monooxygenases DszC and DszA decreases dramatically. The highest value of the activity of DszB enzyme was obtained with cells cultured at 100 rpm, while this activity decreases when the stirrer speed was increased higher than this value. PMID:26762940

  19. Electron transfer between the heme bound oxygen and the tetrahydrobiopterin cofactor of nitric oxide synthase: a DFT study

    NASA Astrophysics Data System (ADS)

    Menyhárd, Dóra K.

    2004-07-01

    Nitric oxide is synthesized from L-Arg by nitric oxide synthases (NOSs). DFT calculations carried out in the present study demonstrate that there is direct coupling between the heme bound oxygen and the tetrahydrobiopterin (H 4B) cofactor in the activated state of NOS. Results indicate that radicalization of H 4B causes the coupled reduction of heme bound oxygen. In our model system H 3B rad radical formation is prompted by proton dissociation from the N5 site of the cofactor; spin density is transferred to the heme bound oxygen, which we found in an orientation preconditioned for H abstraction from the substrate.

  20. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hallacoglu, Bertan; Sassaroli, Angelo; Wysocki, Michael; Guerrero-Berroa, Elizabeth; Schnaider Beeri, Michal; Haroutunian, Vahram; Shaul, Merav; Rosenberg, Irwin H.; Troen, Aron M.; Fantini, Sergio

    2012-08-01

    We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85±6 years) and 19 young adults (mean age, 28±4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (μa), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10±4 μM, 4±3 μM, 14±5 μM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.

  1. Determination of time-of-travel, dispersion characteristics, and oxygen reaeration coefficients during low streamflows--Lower Tacony/Frankford Creek, Philadelphia, Pennsylvania

    USGS Publications Warehouse

    Senior, Lisa A.; Gyves, Matthew C.

    2010-01-01

    Time-of-travel, dispersion characteristics, and oxygen reaeration coefficients were determined by use of dye and gas tracing for a 2-mile reach of Tacony/Frankford Creek in Philadelphia, southeastern Pennsylvania. The reach frequently has concentrations of dissolved oxygen (DO) below the water-quality standard of 4 milligrams per liter during warm months. Several large combined sewer overflows (CSOs), including one of the largest in Philadelphia (former Wingohocking Creek), discharge to the study reach in this urbanized watershed, affecting water quality and the timing and magnitude of storm peaks. In addition, a dam that commonly results in backwater conditions and reduced natural reaeration is present a few hundred feet from the end of the study reach. Time-of-travel and reaeration data were collected under base-flow conditions in August and September 2009 for three sub-reaches from Roosevelt Boulevard (U.S. Route 1) to Castor Avenue. Determination of traveltimes to the centroid of the dye cloud were needed for calculation of the reaeration coefficients. Results of the dye study in Tacony/Frankford Creek indicate that traveltimes were affected by the presence of man-made structures, such as the large scour hole and pool developed at the outfall of the T14 CSO and the dam, both of which reduce stream velocities. Mean stream velocities during the dye-tracer tests ranged from a maximum of 0.44 to 0.04 foot per second through a large pool. The dispersion efficiency of the stream was determined from relations between normalized unit concentrations to time to peak for use in water-quality modeling. Oxygen reaeration coefficients determined by a constant rate-injection method using propane as the tracer gas were as low as 0.04 unit per hour in a long pool affected by backwater conditions behind a dam. The highest reaeration coefficient was 2.29 units per hour for a steep-gradient reach with multiple winding channels through gravel deposits, just downstream of a large

  2. Charts Adapted from Van Driest's Turbulent Flat-plate Theory for Determining Values of Turbulent Aerodynamic Friction and Heat-transfer Coefficients

    NASA Technical Reports Server (NTRS)

    Lee, Dorothy B; Faget, Maxime A

    1956-01-01

    A modified method of Van Driest's flat-plate theory for turbulent boundary layer has been found to simplify the calculation of local skin-friction coefficients which, in turn, have made it possible to obtain through Reynolds analogy theoretical turbulent heat-transfer coefficients in the form of Stanton number. A general formula is given and charts are presented from which the modified method can be solved for Mach numbers 1.0 to 12.0, temperature ratios 0.2 to 6.0, and Reynolds numbers 0.2 times 10 to the 6th power to 200 times 10 to the 6th power.

  3. Effect of the oxygen transfer rate (OSR) on the formation of cellulases by Trichoderma viride in submersion culture

    SciTech Connect

    Skachova, H.; Gottvaldova, M.; Kucera, J.; Podrazky, V.

    1981-12-01

    The formation of cellulases by Trichoderma viride in a medium containing cellulose as a sole source of carbon depends on the oxygen transfer rate (OSR); the OSR, on the other hand, depends on the concentration of cellulose in the medium because the concentration of cellulose strongly affects the viscosity of the medium. In the work presented here, the dependence has been determined for the oxygen transfer rate on geometric relations and viscosity in cellulose-containing media during cultivation in shaken flasks, and the oxygen transfer rates on NRE, NG, and Na during cultivation in a laboratory fermentor of 3000-mL volume. Two cellulosic materials have been compared with a different effect on viscosity; microcrystalline beach cellulose and fibrous cellulose. It has been found that, in an applicable range of concentration, microcrystalline cellulose does not affect the oxygen transfer rate (at concentrations up to 3%). Fibrous cellulose increases the OSR during cultivation in shake flasks but decreases its during cultivation in fermentors. On the basis of these results, the optimizing has been carried out on the cultivation conditions in fermentors. (Refs. 50).

  4. Advancement in recombinant protein production using a marine oxygen carrier to enhance oxygen transfer in a CHO-S cell line.

    PubMed

    Le Pape, Fiona; Bossard, Morgane; Dutheil, Delphine; Rousselot, Morgane; Polard, Valérie; Férec, Claude; Leize, Elisabeth; Delépine, Pascal; Zal, Franck

    2015-06-01

    Recombinant proteins, particularly proteins used as therapeutics, are widely expressed for bioprocessing manufacturing processes. Mammalian cell lines represent the major host cells for bioproduction, according to their capacities of post-translational modifications and folding of secreted proteins. Many parameters can affect cell productivity, especially the rate of oxygen transfer. Dissolved oxygen, in high or low proportions, is a crucial parameter which can affect cell viability and thus productivity. HEMARINA has developed a new technology, commercially proposed as HEMOXCell(®), to improve cell culture at a large production scale. HEMOXCell(®) is a marine oxygen carrier having properties of high oxygen sensitivity, to be used as an oxygen additive during cell culture manufacturing. In this study, we investigated the effects of HEMOXCell(®) on the culture of the commonly used CHO-S cell line. Two main objectives were pursued: 1) cell growth rate and viability during a batch mode process, and 2) the determination of the effect of this oxygen carrier on recombinant protein production from a CHO-transfected cell line. Our results show an increase of CHO-S cellular growth at a rate of more than four-fold in culture with HEMOXCell(®). Moreover, an extension of the growth exponential phase and high cell viability were observed. All of these benefits seem to contribute to the improvement of recombinant protein production. This work underlines several applications using this marine-type oxygen carrier for large biomanufacturing. It is a promising cell culture additive according to the increasing demand for therapeutic products such as monoclonal antibodies.

  5. Heat transfer coefficients and pressure drops for R-134a and an ester lubricant mixture in a smooth tube and a micro-fin tube

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1998-10-01

    This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.

  6. Mass transfer coefficients for carbon dioxide and oxygen for a polygeyser biofilter using airlift in an aquaculture reuse system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aquaculture is a rapidly growing industry, accounting for over one-third of all direct fisheries consumption. In recirculating aquaculture systems the primary technology being used is energy intensive because water must be moved continuously through the culture and treatment units to remove wastes ...

  7. Metallized Gelled Propellants: Oxygen/RP-1/Aluminum Rocket Heat Transfer and Combustion Measurements

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan; Zakany, James S.

    1996-01-01

    A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted. These experiments used a small 20- to 40-lb/f thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-percentage by weight loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Three different injectors were used during the testing: one for the baseline O(2)/RP-1 tests and two for the gelled and metallized gelled fuel firings. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each chamber used a water flow to carry heat away from the chamber and the attached thermocouples and flow meters allowed heat flux estimates at each of the 31 stations. The rocket engine Cstar efficiency for the RP-1 fuel was in the 65-69 percent range, while the gelled 0 percent by weight RP-1 and the 5-percent by weight RP-1 exhibited a Cstar efficiency range of 60 to 62% and 65 to 67%, respectively. The 55-percent by weight RP-1 fuel delivered a 42-47% Cstar efficiency. Comparisons of the heat flux and temperature profiles of the RP-1 and the metallized gelled RP-1/A1 fuels show that the peak nozzle heat fluxes with the metallized gelled O2/RP-1/A1 propellants are substantially higher than the baseline O2/RP-1: up to double the flux for the 55 percent by weight RP-1/A1 over the RP-1 fuel. Analyses showed that the heat transfer to the wall was significantly different for the RP-1/A1 at 55-percent by weight versus the RP-1 fuel. Also, a gellant and an aluminum combustion delay was inferred in the 0 percent and 5-percent by weight RP-1/A1 cases from the decrease in heat flux in the first part of the chamber. A large decrease in heat flux in the last half of the chamber was caused by fuel deposition in the chamber and nozzle. The engine combustion occurred well downstream of the injector face

  8. Experimental investigation of the unusual behavior of local heat transfer coefficient in the transition region of a circular tube with a bell-mouth entrance

    SciTech Connect

    Tam, L.M.; Ghajar, A.J.

    1996-12-31

    The local heat transfer characteristics for ethylene glycol water mixtures flowing in a horizontal circular straight tube with a bell-mouth inlet have been determined experimentally over a flow Reynolds number range of 1,500 to 27,000. A wall-boundary heating condition of uniform heat flux was imposed. The variation of local heat transfer coefficient with length in the transition and turbulent flow regimes is very unusual. For the bell-mouth inlet, the boundary layer along the tube wall is at first laminar and then changes through a transition region to the turbulent condition causing a dip in the Nu-x/D curve. The length of the dip in the transition region is much longer than that in the turbulent region. For the experiments the length of the dip in the transition region varied from x/D = 100 to 175 in comparison to an x/D < 25 for the turbulent region. The presence of the dip in the transition region causes a significant influence on both the local and the average heat transfer coefficients. This is particularly important for heat transfer calculations in short tubes with a bell-mouth inlet.

  9. ASRDI oxygen technology survey. Volume 3: Heat transfer and fluid dynamics. Abstracts of selected technical reports and publications

    NASA Technical Reports Server (NTRS)

    Schmidt, A. F. (Editor)

    1972-01-01

    Selected information is presented from an assemblage of reports and publications on heat transfer and fluid dynamics with direct applicability to oxygen systems. For each document cited, an abstract has been prepared together with key words and a listing of most important references found in the document. Additionally, an author index, a subject index, and a key word index have been provided to simplify the retrieval of specific information from this work. In each subject area - e.g., boiling heat transfer - the individual citations are listed alphabetically by first author, with review papers dually noted under the appropriate subject category and under review papers. Of the documents reviewed and evaluated for inclusion in this publication, coverage of existing information directly concerned with oxygen was given primary emphasis. However, work not specifically oxygen-designated but considered applicable to oxygen by the reviewer e.g., a two-phase friction factor correlation derived from nitrogen experiments is occasionally given where no actual oxygen data exist, as an aid to the reader. Approximately 130 abstracts are listed.

  10. Assessment of external heat transfer coefficient during oocyte vitrification in liquid and slush nitrogen using numerical simulations to determine cooling rates.

    PubMed

    Santos, M V; Sansinena, M; Zaritzky, N; Chirife, J

    2012-01-01

    In oocyte vitrification, plunging directly into liquid nitrogen favor film boiling and strong nitrogen vaporization. A survey of literature values of heat transfer coefficients (h) for film boiling of small metal objects with different geometries plunged in liquid nitrogen revealed values between 125 to 1000 W per per square m per K. These h values were used in a numerical simulation of cooling rates of two oocyte vitrification devices (open-pulled straw and Cryotop), plunged in liquid and slush nitrogen conditions. Heat conduction equation with convective boundary condition was considered a linear mathematical problem and was solved using the finite element method applying the variational formulation. COMSOL Multiphysics was used to simulate the cooling process of the systems. Predicted cooling rates for OPS and Cryotop when cooled at -196 degree C (liquid nitrogen) or -207 degree C (average for slush nitrogen) for heat transfer coefficients estimated to be representative of film boiling, indicated lowering the cooling temperature produces only a maximum 10 percent increase in cooling rates; confirming the main benefit of plunging in slush over liquid nitrogen does not arise from their temperature difference. Numerical simulations also demonstrated that a hypothetical four-fold increase in the cooling rate of vitrification devices when plunging in slush nitrogen would be explained by an increase in heat transfer coefficient. This improvement in heat transfer (i.e., high cooling rates) in slush nitrogen is attributed to less or null film boiling when a sample is placed in slush (mixture of liquid and solid nitrogen) because it first melts the solid nitrogen before causing the liquid to boil and form a film.

  11. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2016-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  12. Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

    SciTech Connect

    Kelly, Sean M; Kromer, Brian R; Litwin, Michael M; Rosen, Lee J; Christie, Gervase Maxwell; Wilson, Jamie R; Kosowski, Lawrence W; Robinson, Charles

    2014-01-07

    A method and apparatus for producing heat used in a synthesis gas production is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the stream reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5.

  13. Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

    DOEpatents

    Kelly, Sean M.; Kromer, Brian R.; Litwin, Michael M.; Rosen, Lee J.; Christie, Gervase Maxwell; Wilson, Jamie R.; Kosowski, Lawrence W.; Robinson, Charles

    2016-01-19

    A method and apparatus for producing heat used in a synthesis gas production process is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the steam reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5

  14. Singlet oxygen triplet energy transfer-based imaging technology for mapping protein-protein proximity in intact cells.

    PubMed

    To, Tsz-Leung; Fadul, Michael J; Shu, Xiaokun

    2014-01-01

    Many cellular processes are carried out by large protein complexes that can span several tens of nanometres. Whereas forster resonance energy transfer has a detection range of <10 nm, here we report the theoretical development and experimental demonstration of a new fluorescence-imaging technology with a detection range of up to several tens of nanometres: singlet oxygen triplet energy transfer. We demonstrate that our method confirms the topology of a large protein complex in intact cells, which spans from the endoplasmic reticulum to the outer mitochondrial membrane and the matrix. This new method is thus suited for mapping protein proximity in large protein complexes.

  15. Singlet oxygen Triplet Energy Transfer based imaging technology for mapping protein-protein proximity in intact cells

    PubMed Central

    To, Tsz-Leung; Fadul, Michael J.; Shu, Xiaokun

    2014-01-01

    Many cellular processes are carried out by large protein complexes that can span several tens of nanometers. Whereas Forster resonance energy transfer has a detection range of <10 nm, here we report the theoretical development and experimental demonstration of a new fluorescence imaging technology with a detection range of up to several tens of nanometers: singlet oxygen triplet energy transfer. We demonstrate that our method confirms the topology of a large protein complex in intact cells, which spans from the endoplasmic reticulum to the outer mitochondrial membrane and the matrix. This new method is thus suited for mapping protein proximity in large protein complexes. PMID:24905026

  16. Ion-transfer voltammetry of local anesthetics at an organic solvent/water interface and pharmacological activity vs. ion partition coefficient relationship.

    PubMed

    Kubota, Y; Katano, H; Senda, M

    2001-01-01

    The ion-transfer reaction of local anesthetics at an organic solvent/water interface has been studied using cyclic voltammetry (CV) with a stationary nitrobenzene (NB)/water (W) interface. Procaine and seven other local anesthetics gave reversible or quasi-reversible voltammograms at the NB/W interface in the pH range between 0.9 and 9.6. These drugs are present in aqueous solution in either neutral or ionic form, or both forms. The half-wave potential, as determined by the midpoint potential in CV, vs. pH curves, were determined and analyzed to determine the partition coefficients of both neutral and ionic forms of the drugs between NB and W. The partition coefficients of the ionic forms were derived from their formal potential of transfer at an NB/W interface. The dissociation constants of ionic forms of the drugs in NB were also deduced. A high correlation between the pharmacological activity and the partition coefficient of the ionic form of amide-linked local anesthetics has been shown.

  17. Detailed measurements of local heat transfer coefficient in the entrance to normal and inclined film cooling holes

    SciTech Connect

    Gillespie, D.R.H.; Byerley, A.R.; Ireland, P.T.; Wang, Z.; Jones, T.V.; Kohler, S.T.

    1996-04-01

    The local heat transfer inside the entrance to large-scale models of film cooling holes has been measured using the transient heat transfer technique. The method employs temperature-sensitive liquid crystals to measure the surface temperature of large-scale perspex models. Full distributions of local Nusselt number were calculated based on the cooling passage centerline gas temperature ahead of the cooling hole. The circumferentially averaged Nusselt number was also calculated based on the local mixed bulk driving gas temperature to aid interpretation of the results, and to broaden the potential application of the data. Data are presented for a single film cooling hole inclined at 90 and 150 deg to the coolant duct wall. Both holes exhibited entry length heat transfer levels that were significantly lower than those predicted by entry length data in the presence of crossflow. The reasons for the comparative reduction are discussed in terms of the interpreted flow field.

  18. Oxygen configurations and their effect on charge transfer in YBa[sub 2]Cu[sub 3]O[sub z

    SciTech Connect

    McCormack, R.; Fontaine, D. de ); Ceder, G. )

    1992-04-01

    The relationship between oxygen structure, charge transfer (hole count), and oxygen content in the YBa[sub 2]Cu[sub 3]O[sub z] superconductor is studied by combining Monte-Carlo simulation with existing electronic structure calculations. The present model proposed an expansion of the hole count in terms of oxygen configuration variables for states of an arbitrary degree of order. Calculations of hole count as a function of oxygen content suggest that oxygen ordering is, at least in part, responsible for the observed plateau structure of T[sub c] vs. oxygen content z.

  19. Oxygen configurations and their effect on charge transfer in YBa{sub 2}Cu{sub 3}O{sub z}

    SciTech Connect

    McCormack, R.; Fontaine, D. de; Ceder, G.

    1992-04-01

    The relationship between oxygen structure, charge transfer (hole count), and oxygen content in the YBa{sub 2}Cu{sub 3}O{sub z} superconductor is studied by combining Monte-Carlo simulation with existing electronic structure calculations. The present model proposed an expansion of the hole count in terms of oxygen configuration variables for states of an arbitrary degree of order. Calculations of hole count as a function of oxygen content suggest that oxygen ordering is, at least in part, responsible for the observed plateau structure of T{sub c} vs. oxygen content z.

  20. Monitoring the variations of the oxygen transfer rate in a full scale membrane bioreactor using daily mass balances.

    PubMed

    Racault, Y; Stricker, A-E; Husson, A; Gillot, S

    2011-01-01

    Oxygen transfer in biological wastewater treatment processes with high sludge concentration, such as membrane bioreactor (MBR), is an important issue. The variation of alpha-factor versus mixed liquor suspended solids (MLSS) concentration was investigated in a full scale MBR plant under process conditions, using mass balances. Exhaustive data from the Supervisory Control And Data Acquisition (SCADA) and from additional online sensors (COD, DO, MLSS) were used to calculate the daily oxygen consumption (OC) using a non-steady state mass balance for COD and total N on a 24-h basis. To close the oxygen balance, OC has to match the total oxygen transfer rate (OTRtot) of the system, which is provided by fine bubble (FB) diffusers in the aeration tank and coarse bubbles (CB) in separate membrane tanks. First assessing OTR(CB) then closing the balance OC = OTRtot allowed to calculate OTR(FB) and to fit an exponential relationship between OTR(FB) and MLSS. A comparison of the alpha-factor obtained by this balance method and by direct measurements with the off-gas method on the same plant is presented and discussed. PMID:22049761

  1. Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing

    NASA Technical Reports Server (NTRS)

    Buckmann, P. S.; Hayden, W. R.; Lorenc, S. A.; Sabiers, R. L.; Shimp, N. R.

    1990-01-01

    The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers.

  2. Strategies to overcome oxygen transfer limitations during hairy root cultivation of Azadiracta indica for enhanced azadirachtin production.

    PubMed

    Srivastava, Smita; Srivastava, Ashok Kumar

    2012-07-01

    The vast untapped potential of hairy root cultures as a stable source of biologically active chemicals has focused the attention of scientific community toward its commercial exploitation. However, the major bottleneck remains its successful scale-up. Due to branching, the roots form an interlocked matrix that exhibits resistance to oxygen transfer. Thus, present work was undertaken to develop cultivation strategies like optimization of inlet gas composition (in terms of % (v/v) O(2) in air), air-flow rate and addition of oxygen vectors in the medium, to curb the oxygen transfer limitations during hairy root cultivation of Azadirachta indica for in vitro azadirachtin (a biopesticide) production. It was found that increasing the oxygen fraction in the inlet air (in the range, 20-100% (v/v) O(2) in air) increased the azadirachtin productivity by approximately threefold, to a maximum of 4.42 mg/L per day (at 100% (v/v) O(2) in air) with respect to 1.68 mg/L per day in control (air with no oxygen supplementation). Similarly, increasing the air-flow rate (in the range, 0.3-2 vvm) also increased the azadirachtin productivity to a maximum of 1.84 mg/L per day at 0.8 vvm of air-flow rate. On the contrary, addition of oxygen vectors (in the range, 1-4% (v/v); hydrogen peroxide, toluene, Tween 80, kerosene, silicone oil, and n-hexadecane), decreased the azadirachtin productivity with respect to control (1.76 mg/L per day). PMID:22246729

  3. Measurement of local convective heat transfer coefficients from a smooth and roughened NACA-0012 airfoil: Flight test data

    NASA Technical Reports Server (NTRS)

    Newton, James E.; Vanfossen, G. James; Poinsatte, Phillip E.; Dewitt, Kenneth J.

    1988-01-01

    Wind tunnels typically have higher free stream turbulence levels than are found in flight. Turbulence intensity was measured to be 0.5 percent in the NASA Lewis Icing Research Tunnel (IRT) with the cloud making sprays off and around 2 percent with cloud making equipment on. Turbulence intensity for flight conditions was found to be too low to make meaningful measurements for smooth air. This difference between free stream and wing tunnel conditions has raised questions as to the validity of results obtained in the IRT. One objective of these tests was to determine the effect of free stream turbulence on convective heat transfer for the NASA Lewis LEWICE ice growth prediction code. These tests provide in-flight heat transfer data for a NASA-0012 airfoil with a 533 cm chord. Future tests will measure heat transfer data from the same airfoil in the Lewis Icing Research Tunnel. Roughness was obtained by the attachment of small, 2 mm diameter hemispheres of uniform size to the airfoil in three different patterns. Heat transfer measurements were recorded in flight on the NASA Lewis Twin Otter Icing Research Aircraft. Measurements were taken for the smooth and roughened surfaces at various aircraft speeds and angles of attack up to four degrees. Results are presented as Frossling number versus position on the airfoil for various roughnesses and angles of attack.

  4. A METHOD FOR ESTIMATING DISTRIBUTIONS OF MASS TRANSFER RATE COEFFICIENTS WITH APPLICATION TO PURGING AND BATCH EXPERIMENTS. (R825825)

    EPA Science Inventory

    Mass transfer between aquifer material and groundwater is often modeled as first-order rate-limited sorption or diffusive exchange between mobile zones and immobile zones with idealized geometries. Recent improvements in experimental techniques and advances in our understanding o...

  5. Scale-up from shake flasks to fermenters in batch and continuous mode with Corynebacterium glutamicum on lactic acid based on oxygen transfer and pH.

    PubMed

    Seletzky, Juri M; Noak, Ute; Fricke, Jens; Welk, Eike; Eberhard, Werner; Knocke, Christof; Büchs, Jochen

    2007-11-01

    Scale-up from shake flasks to fermenters has been hampered by the lack of knowledge concerning the influence of operating conditions on mass transfer, hydromechanics, and power input. However, in recent years the properties of shake flasks have been described with empirical models. A practical scale-up strategy for everyday use is introduced for the scale-up of aerobic cultures from shake flasks to fermenters in batch and continuous mode. The strategy is based on empirical correlations of the volumetric mass transfer coefficient (k(L) a) and the pH. The accuracy of the empirical k(L) a correlations and the assumptions required to use these correlations for an arbitrary biological medium are discussed. To determine the optimal pH of the culture medium a simple laboratory method based on titration curves of the medium and a mechanistic pH model, which is solely based on the medium composition, is applied. The effectiveness of the scale-up strategy is demonstrated by comparing the behavior of Corynebacterium glutamicum on lactic acid in shake flasks and fermenters in batch and continuous mode. The maximum growth rate (micro(max) = 0.32 h(-1)) and the oxygen substrate coefficient (Y O2 /S= 0.0174 mol/l) of C. glutamicum on lactic acid were equal for shake flask, fermenter, batch, and continuous cultures. The biomass substrate yield was independent of the scale, but was lower in batch cultures (Y(X/S) = 0.36 g/g) than in continuous cultures (Y(X/S) = 0.45 g/g). The experimental data (biomass, respiration, pH) could be described with a simple biological model combined with a mechanistic pH model.

  6. Transverse heat transfer coefficient in the dual channel ITER TF CICCs Part II. Analysis of transient temperature responses observed during a heat slug propagation experiment

    NASA Astrophysics Data System (ADS)

    Lewandowska, Monika; Herzog, Robert; Malinowski, Leszek

    2015-01-01

    A heat slug propagation experiment in the final design dual channel ITER TF CICC was performed in the SULTAN test facility at EPFL-CRPP in Villigen PSI. We analyzed the data resulting from this experiment to determine the equivalent transverse heat transfer coefficient hBC between the bundle and the central channel of this cable. In the data analysis we used methods based on the analytical solutions of a problem of transient heat transfer in a dual-channel cable, similar to Renard et al. (2006) and Bottura et al. (2006). The observed experimental and other limits related to these methods are identified and possible modifications proposed. One result from our analysis is that the hBC values obtained with different methods differ by up to a factor of 2. We have also observed that the uncertainties of hBC in both methods considered are much larger than those reported earlier.

  7. Transfer coefficients for L-valine and the rate of incorporation of L-(1-/sup 14/C) valine into proteins in normal adult rat brain

    SciTech Connect

    Kirikae, M.; Diksic, M.; Yamamoto, Y.L.

    1988-08-01

    An autoradiographic method for the measurement of the rate of valine incorporation into brain proteins is described. The transfer coefficients for valine into and out of the brain and the rate of valine incorporation into normal rat brain proteins are given. The valine incorporation and the transfer constants of valine between different biological compartments are provided for 14 gray matter and 2 white matter structures of an adult rat brain. The rate of valine incorporation varies between 0.52 +/- 0.19 nmol/g/min in white matter and 1.94 +/- 0.47 in inferior colliculus (gray matter). Generally, the rate of valine incorporation is about three to four times higher in the gray matter than in the white matter structures.

  8. Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

    SciTech Connect

    Brett Kimball Simpson

    2002-08-27

    Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO{sub 2} films] revealed that MnO{sub 2} film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO{sub 2} films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO{sub 2} films showed that the Fe(III)-doped RuO{sub 2}-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO{sub 2} films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H{sub 2}O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb{sub 10}Sn{sub 20}Ti{sub 70}, Cu{sub 63}Ni{sub 37} and Cu{sub 25}Ni{sub 75} alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu{sub 63}Ni{sub 37} alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO{sub 3}{sup -} at the Cu-Ni alloy electrode is superior to the response at the pure Cu and Ni electrodes. This is explained on the basis of the

  9. Senstitivity analysis of horizontal heat and vapor transfer coefficients for a cloud-topped marine boundary layer during cold-air outbreaks. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Chang, Y. V.

    1986-01-01

    The effects of external parameters on the surface heat and vapor fluxes into the marine atmospheric boundary layer (MABL) during cold-air outbreaks are investigated using the numerical model of Stage and Businger (1981a). These fluxes are nondimensionalized using the horizontal heat (g1) and vapor (g2) transfer coefficient method first suggested by Chou and Atlas (1982) and further formulated by Stage (1983a). In order to simplify the problem, the boundary layer is assumed to be well mixed and horizontally homogeneous, and to have linear shoreline soundings of equivalent potential temperature and mixing ratio. Modifications of initial surface flux estimates, time step limitation, and termination conditions are made to the MABL model to obtain accurate computations. The dependence of g1 and g2 in the cloud topped boundary layer on the external parameters (wind speed, divergence, sea surface temperature, radiative sky temperature, cloud top radiation cooling, and initial shoreline soundings of temperature, and mixing ratio) is studied by a sensitivity analysis, which shows that the uncertainties of horizontal transfer coefficients caused by changes in the parameters are reasonably small.

  10. Exponential Sum Absorption Coefficients of Phosphine from 2750 to 3550/cm for Application to Radiative Transfer Analyses on Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Temma, T.; Baines, K. H.; Butler, R. A. H.; Brown, L. R.; Sagui, L.; Kleiner, I.

    2006-01-01

    PH3 exponential sum k coefficients were computed between 2750 and 3550/cm (2.82-3.64 (microns), in view of future application to radiative transfer analyses of Jupiter and Saturn in a phosphine absorption band near 3 microns. The temperature and pressure of this data set cover the ranges from 80 to 350 K and from 10 (exp -3)to 10(exp 1) bars, respectively. Transmission uncertainty incurred by the use of the k coefficients is smaller than a few percent as long as the radiation is confined above an altitude of a few bars in the giant planets. In spectral regions of weak absorption at high pressures close to 10 bars, contributions from far wings of strong absorption lines must be carefully taken into account. Our data set helps map the three-dimensional distribution of PH3 on the giant planets, revealing their global atmospheric dynamics extending down to the deep interior. The complete k coefficient data set of this work is available at the Web site of the NASA Planetary Data System Atmospheres Node.

  11. Bulk heat transfer coefficient in the ice-upper ocean system in the ice melt season derived from concentration-temperature relationship

    NASA Astrophysics Data System (ADS)

    Nihashi, Sohey; Ohshima, Kay I.

    2008-06-01

    The bulk heat transfer coefficient in the ice-upper ocean system (Kb) in the ice melt season is estimated by a new method at 18 areas that cover much of the Antarctic seasonal ice zone. The method is based on a model in which ice melting is caused only by heat input through open water and is treated in a bulk fashion in the ice-upper ocean system. Kb is estimated by fitting a convergent curve derived from the model to an observed ice concentration-temperature plot (CT-plot). Estimated Kb is 1.15 ± 0.72 × 10-4 m s-1 on average. If Kb can be expressed by the product of the heat transfer coefficient (ch) and the friction velocity (uτ), ch is 0.0113 ± 0.0055. This value is about two times larger than that estimated at the ice bottom. The relationship between Kb and the geostrophic wind speed (Uw), which is roughly proportional to uτ, shows a significant positive correlation, as expected. Further, Kb seems more likely to be proportional to the square or cube of Uw rather than a linear relationship. Since Kb estimated from our method is associated with ice melting in a bulk fashion in the ice-upper ocean system, this relationship likely indicates both the mixing process of heat in the upper ocean (proportional to uτ3) and the local heat transfer process at the ice-ocean interface (proportional to uτ).

  12. Proposal for new best estimates for the soil solid-liquid distribution coefficient and soil-to-plant transfer of nickel.

    PubMed

    Vandenhove, Hildegarde; Van Hees, May; Olyslaegers, Geert; Vidal, Miquel

    2009-04-01

    The objective of this study was to compile data, based on an extensive literature survey, for the soil solid-liquid distribution coefficient (K(d)) and soil-to-plant transfer factor (TF) for nickel. The K(d) best estimates were calculated for soils grouped according to texture and organic matter content (sand, loam, clay and organic) and soil cofactors affecting soil-nickel interaction, such as pH, organic matter, and clay content. Variability in K(d) was better explained by pH than by soil texture. Nickel TF estimates were presented for major crop groups (cereals, leafy vegetables, non-leafy vegetables, root crops, tubers, fruits, herbs, pastures/grasses and fodder), and also for plant compartments within crop groups. Transfer factors were also calculated per soil group, as defined by their texture and organic matter content. Furthermore an evaluation of transfer factor dependency on specific soil characteristics was performed following regression analysis. The derived estimates were compared with parameter estimates currently in use.

  13. Proposal for new best estimates for the soil solid-liquid distribution coefficient and soil-to-plant transfer of nickel.

    PubMed

    Vandenhove, Hildegarde; Van Hees, May; Olyslaegers, Geert; Vidal, Miquel

    2009-04-01

    The objective of this study was to compile data, based on an extensive literature survey, for the soil solid-liquid distribution coefficient (K(d)) and soil-to-plant transfer factor (TF) for nickel. The K(d) best estimates were calculated for soils grouped according to texture and organic matter content (sand, loam, clay and organic) and soil cofactors affecting soil-nickel interaction, such as pH, organic matter, and clay content. Variability in K(d) was better explained by pH than by soil texture. Nickel TF estimates were presented for major crop groups (cereals, leafy vegetables, non-leafy vegetables, root crops, tubers, fruits, herbs, pastures/grasses and fodder), and also for plant compartments within crop groups. Transfer factors were also calculated per soil group, as defined by their texture and organic matter content. Furthermore an evaluation of transfer factor dependency on specific soil characteristics was performed following regression analysis. The derived estimates were compared with parameter estimates currently in use. PMID:19223096

  14. Thermal expansion of UO2+x nuclear fuel rods from a model coupling heat transfer and oxygen diffusion

    SciTech Connect

    Mihaila, Bogden; Zubelewicz, Aleksander; Stan, Marius; Ramirez, Juan

    2008-01-01

    We study the thermal expansion of UO{sub 2+x} nuclear fuel rod in the context of a model coupling heat transfer and oxygen diffusion discussed previously by J.C. Ramirez, M. Stan and P. Cristea [J. Nucl. Mat. 359 (2006) 174]. We report results of simulations performed for steady-state and time-dependent regimes in one-dimensional configurations. A variety of initial- and boundary-value scenarios are considered. We use material properties obtained from previously published correlations or from analysis of previously published data. All simulations were performed using the commercial code COMSOL Multiphysics{sup TM} and are readily extendable to include multidimensional effects.

  15. Oxygen isotope effects as probes of electron transfer mechanisms and structures of activated O2.

    PubMed

    Roth, Justine P

    2009-03-17

    Competitively determined oxygen ((18)O) isotope effects can be powerful probes of chemical and biological transformations involving molecular oxygen as well as superoxide and hydrogen peroxide. They play a complementary role to crystallography and spectroscopy in the study of activated oxygen intermediates by forging a link between electronic/vibrational structure and the bonding that occurs within ground and transition states along the reaction coordinate. Such analyses can be used to assess the plausibility of intermediates and their catalytic relevance in oxidative processes. This Account describes efforts to advance oxygen kinetic isotope effects ((18)O KIEs) and equilibrium isotope effects ((18)O EIEs) as mechanistic probes of reactive, oxygen-derived species. We focus primarily on transition metal mediated oxidations, outlining both advances over the past five years and current limitations of this approach. Computational methods are now being developed to probe transition states and the accompanying kinetic isotope effects. In particular, we describe the importance of using a full-frequency model to accurately predict the magnitudes as well as the temperature dependence of the isotope effects. Earlier studies have used a "cut-off model," which employs only a few isotopic vibrational modes, and such models tend to overestimate (18)O EIEs. Researchers in mechanistic biological inorganic chemistry would like to differentiate "inner-sphere" from "outer-sphere" reactivity of O(2), a designation that describes the extent of the bonding interaction between metal and oxygen in the transition state. Though this problem remains unsolved, we expect that this isotopic approach will help differentiate these processes. For example, comparisons of (18)O KIEs to (18)O EIEs provide benchmarks that allow us to calibrate computationally derived reaction coordinates. Once the physical origins of heavy atom isotope effects are better understood, researchers will be able to apply

  16. Design and Testing of an Automated System using Thermochromatic Liquid Crystals to Determine Local Heat Transfer Coefficients for an Impinging Jet

    NASA Technical Reports Server (NTRS)

    Tan, Benjamin

    1995-01-01

    Using thermochromatic liquid crystal to measure surface temperature, an automated transient method with time-varying free-stream temperature is developed to determine local heat transfer coefficients. By allowing the free-stream temperature to vary with time, the need for complicated mechanical components to achieve a step temperature change is eliminated, and by using the thermochromatic liquid crystals as temperature indicators, the labor intensive task of installing many thermocouples is omitted. Bias associated with human perception of the transition of the thermochromatic liquid crystal is eliminated by using a high speed digital camera and a computer. The method is validated by comparisons with results obtained by the steady-state method for a circular Jet impinging on a flat plate. Several factors affecting the accuracy of the method are evaluated.

  17. Near-field krypton-85 measurements in stable meteorological conditions around the AREVA NC La Hague reprocessing plant: estimation of atmospheric transfer coefficients.

    PubMed

    Connan, O; Solier, L; Hébert, D; Maro, D; Lamotte, M; Voiseux, C; Laguionie, P; Cazimajou, O; Le Cavelier, S; Godinot, C; Morillon, M; Thomas, L; Percot, S

    2014-11-01

    The aim of this work was to study the near-field dispersion of (85)Kr around the nuclear fuel reprocessing plant at La Hague (AREVA NC La Hague - France) under stable meteorological conditions. Twenty-two (85)Kr night-time experimental campaigns were carried out at distances of up to 4 km from the release source. Although the operational Gaussian models predict for these meteorological conditions a distance to plume touchdown of several kilometers, we almost systematically observed a marked ground signal at distances of 0.5-4 km. The calculated atmospheric transfer coefficients (ATC) show values (1) higher than those observed under neutral conditions, (2) much higher than those proposed by the operational models, and (3) higher than those used in the impact assessments.

  18. A method of computing the transient temperature of thick walls from arbitrary variation of adiabatic-wall temperature and heat-transfer coefficient

    NASA Technical Reports Server (NTRS)

    Hill, P R

    1958-01-01

    A method of calculating the temperature of thick walls has been developed in which the time series and the response to a unit triangle variation of surface temperature concepts are used, together with essentially standard formulas for transient temperature and heat flow into thick walls. The method can be used without knowledge of the mathematical tools of its development. The method is particularly suitable for determining the wall temperature in one-dimensional thermal problems in aeronautics where there is a continuous variation of the heat-transfer coefficient and adiabatic-wall temperature. The method also offers a convenient means for solving the inverse problem of determining the heat-flow history when temperature history is known.

  19. Transverse heat transfer coefficient in the dual channel ITER TF CICCs. Part I: Analysis of steady state temperature profiles resulting from annular heating

    NASA Astrophysics Data System (ADS)

    Lewandowska, Monika; Herzog, Robert

    2011-10-01

    Two ITER TF dual channel Cable-in-Conduit Conductors (CICCs) have been tested in the SULTAN test facility. The samples were heated either by foil heaters mounted on the outside of the conductor jacket or by induced AC losses. The steady-state temperature response of several thermometers installed on the jacket surface as well as inside the cable were analyzed using the two-channel analytical model proposed by Renard et al. to obtain the equivalent transverse heat transfer coefficient between the bundle and central channel as a function of the mass flow rate. In addition, on the basis of the measured pressure drop and helium flow velocities, the friction factors for helium flow in the bundle and in the central channel were determined. The obtained results may serve as a reference for these cables.

  20. Improved Results for the H-2(d, n)(3) He Transverse Vector Polarization- Transfer Coefficient K-y(y)' (0 degrees) at Low Energies

    SciTech Connect

    Roper, C. D.; Dunham, J. D.; Tornow, W.

    2010-01-01

    Measurements of the H-2(d, n)(3) He transverse vector polarization-transfer coefficient K-y(y)' at 0 degrees. are reported for 29 outgoing neutron energies between 3.94 and 8.47MeV. Our new results determine K-y(y)' (0 degrees) more accurately than previous data, especially for neutron energies below 5MeV. Low-energy data for this reaction are important both as a high-intensity source of highly polarized neutrons for nuclear physics studies with polarized neutron beams, and as a test of the emerging theoretical descriptions of the four-body system, where recently substantial progress has been made.

  1. Near-field krypton-85 measurements in stable meteorological conditions around the AREVA NC La Hague reprocessing plant: estimation of atmospheric transfer coefficients.

    PubMed

    Connan, O; Solier, L; Hébert, D; Maro, D; Lamotte, M; Voiseux, C; Laguionie, P; Cazimajou, O; Le Cavelier, S; Godinot, C; Morillon, M; Thomas, L; Percot, S

    2014-11-01

    The aim of this work was to study the near-field dispersion of (85)Kr around the nuclear fuel reprocessing plant at La Hague (AREVA NC La Hague - France) under stable meteorological conditions. Twenty-two (85)Kr night-time experimental campaigns were carried out at distances of up to 4 km from the release source. Although the operational Gaussian models predict for these meteorological conditions a distance to plume touchdown of several kilometers, we almost systematically observed a marked ground signal at distances of 0.5-4 km. The calculated atmospheric transfer coefficients (ATC) show values (1) higher than those observed under neutral conditions, (2) much higher than those proposed by the operational models, and (3) higher than those used in the impact assessments. PMID:25078471

  2. A method for mapping regional oxygen and CO2 transfer in the lung.

    PubMed

    Johansen, Troels; Winkler, Tilo; Kelly, Vanessa Jane; Osorio-Valencia, Juan Sebastian; Greenblatt, Elliot Eliyahu; Harris, Robert Scott; Venegas, Jose Gabriel

    2016-02-01

    This paper presents a novel approach to visualizing regional lung function, through quantitative three-dimensional maps of O2 and CO2 transfer rates. These maps describe the contribution of anatomical regions to overall gas exchange and demonstrate how transfer rates of the two gas species' differ regionally. An algorithm for generating such maps is presented, and for illustration, regional gas transfer maps were generated using values of ventilation and perfusion imaged by PET/CT for a healthy subject and an asthmatic patient after bronchoprovocation. In a sensitivity analysis, compartment values of gas transfer showed minor sensitivity to imaging noise in the ventilation and perfusion data, and moderate sensitivity to estimation errors in global lung input values, chiefly global alveolar ventilation, followed by cardiac output and arterial-venous O2 content difference. Gas transfer maps offer an intuitive display of physiologically relevant lung function at a regional level, the potential for an improved understanding of pulmonary gas exchange in health and disease, and potentially a presurgical evaluation tool. PMID:26563454

  3. A method for mapping regional oxygen and CO2 transfer in the lung.

    PubMed

    Johansen, Troels; Winkler, Tilo; Kelly, Vanessa Jane; Osorio-Valencia, Juan Sebastian; Greenblatt, Elliot Eliyahu; Harris, Robert Scott; Venegas, Jose Gabriel

    2016-02-01

    This paper presents a novel approach to visualizing regional lung function, through quantitative three-dimensional maps of O2 and CO2 transfer rates. These maps describe the contribution of anatomical regions to overall gas exchange and demonstrate how transfer rates of the two gas species' differ regionally. An algorithm for generating such maps is presented, and for illustration, regional gas transfer maps were generated using values of ventilation and perfusion imaged by PET/CT for a healthy subject and an asthmatic patient after bronchoprovocation. In a sensitivity analysis, compartment values of gas transfer showed minor sensitivity to imaging noise in the ventilation and perfusion data, and moderate sensitivity to estimation errors in global lung input values, chiefly global alveolar ventilation, followed by cardiac output and arterial-venous O2 content difference. Gas transfer maps offer an intuitive display of physiologically relevant lung function at a regional level, the potential for an improved understanding of pulmonary gas exchange in health and disease, and potentially a presurgical evaluation tool.

  4. The prediction of nozzle performance and heat transfer in hydrogen/oxygen rocket engines with transpiration cooling, film cooling, and high area ratios

    NASA Technical Reports Server (NTRS)

    Kacynski, Kenneth J.; Hoffman, Joe D.

    1993-01-01

    An advanced engineering computational model has been developed to aid in the analysis and design of hydrogen/oxygen chemical rocket engines. The complete multi-species, chemically reacting and diffusing Navier-Stokes equations are modelled, finite difference approach that is tailored to be conservative in an axisymmetric coordinate system for both the inviscid and viscous terms. Demonstration cases are presented for a 1030:1 area ratio nozzle, a 25 lbf film cooled nozzle, and transpiration cooled plug-and-spool rocket engine. The results indicate that the thrust coefficient predictions of the 1030:1 nozzle and the film cooled nozzle are within 0.2 to 0.5 percent, respectively, of experimental measurements when all of the chemical reaction and diffusion terms are considered. Further, the model's predictions agree very well with the heat transfer measurements made in all of the nozzle test cases. The Soret thermal diffusion term is demonstrated to have a significant effect on the predicted mass fraction of hydrogen along the wall of the nozzle in both the laminar flow 1030:1 nozzle and the turbulent plug-and-spool rocket engine analysis cases performed. Further, the Soret term was shown to represent a significant fraction of the diffusion fluxes occurring in the transpiration cooled rocket engine.

  5. Seasonal transfer of oxygen isotopes from precipitation and soil to the tree ring: source water versus needle water enrichment.

    PubMed

    Treydte, Kerstin; Boda, Sonja; Graf Pannatier, Elisabeth; Fonti, Patrick; Frank, David; Ullrich, Bastian; Saurer, Matthias; Siegwolf, Rolf; Battipaglia, Giovanna; Werner, Willy; Gessler, Arthur

    2014-05-01

    For accurate interpretation of oxygen isotopes in tree rings (δ(18) O), it is necessary to disentangle the mechanisms underlying the variations in the tree's internal water cycle and to understand the transfer of source versus leaf water δ(18) O to phloem sugars and stem wood. We studied the seasonal transfer of oxygen isotopes from precipitation and soil water through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites in the Lötschental (Switzerland). Weekly resolved δ(18) O records of precipitation, soil water, xylem and needle water, phloem organic matter and tree rings were developed. Week-to-week variations in needle-water (18) O enrichment were strongly controlled by weather conditions during the growing season. These short-term variations were, however, not significantly fingerprinted in tree-ring δ(18) O. Instead, seasonal trends in tree-ring δ(18) O predominantly mirrored trends in the source water, including recent precipitation and soil water pools. Modelling results support these findings: seasonal tree-ring δ(18) O variations are captured best when the week-to-week variations of the leaf water signal are suppressed. Our results suggest that climate signals in tree-ring δ(18) O variations should be strongest at temperate sites with humid conditions and precipitation maxima during the growing season.

  6. Formation of a long-lived electron-transfer state in mesoporous silica-alumina composites enhances photocatalytic oxygenation reactivity

    PubMed Central

    Fukuzumi, Shunichi; Doi, Kaoru; Itoh, Akinori; Suenobu, Tomoyoshi; Ohkubo, Kei; Yamada, Yusuke; Karlin, Kenneth D.

    2012-01-01

    A simple donor-acceptor linked dyad, 9-mesityl-10-methylacridinium ion (Acr+-Mes) was incorporated into nanosized mesoporous silica-alumina to form a composite, which in acetonitrile is highly dispersed. In this medium, upon visible light irradiation, the formation of an extremely long-lived electron-transfer state (Acr•-Mes•+) was confirmed by EPR and laser flash photolysis spectroscopic methods. The composite of Acr+-Mes-incorporated mesoporous silica-alumina with an added copper complex [(tmpa)CuII] (tmpa = tris(2-pyridylmethyl)amine) acts as an efficient and robust photocatalyst for the selective oxygenation of p-xylene by molecular oxygen to produce p-tolualdehyde and hydrogen peroxide. Thus, incorporation of Acr+-Mes into nanosized mesoporous silica-alumina combined with an O2-reduction catalyst ([(tmpa)CuII]2+) provides a promising method in the development of efficient and robust organic photocatalysts for substrate oxygenation by dioxygen, the ultimate environmentally benign oxidant. PMID:22543164

  7. Oxygen-atom transfer chemistry and thermolytic properties of a di-tert-butylphosphate-ligated Mn4O4 cubane.

    PubMed

    Van Allsburg, Kurt M; Anzenberg, Eitan; Drisdell, Walter S; Yano, Junko; Tilley, T Don

    2015-03-16

    [Mn4O4{O2P(OtBu)2}6] (1), an Mn4O4 cubane complex combining the structural inspiration of the photosystem II oxygen-evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen-atom acceptor (PEt3), to give the butterfly complex [Mn4O2{O2P(OtBu)2}6(OPEt3)2]. The cubane structure is restored by reaction of the latter complex with the O-atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X-ray absorption spectroscopy to determine the fate of the Mn4O4 unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn(II) species. Finally, the related butterfly complex [Mn4O2{O2P(pin)}6(bpy)2] (pin = pinacolate) is described.

  8. Multiple electron transfer systems in oxygen reducing biocathodes revealed by different conditions of aeration/agitation.

    PubMed

    Rimboud, Mickaël; Bergel, Alain; Erable, Benjamin

    2016-08-01

    Oxygen reducing biocathodes were formed at -0.2V/SCE (+0.04V/SHE) from compost leachate. Depending on whether aeration was implemented or not, two different redox systems responsible for the electrocatalysis of oxygen reduction were evidenced. System I was observed at low potential (-0.03V/SHE) on cyclic voltammetries (CVs). It appeared during the early formation of the biocathode (few hours) and resisted the hydrodynamic conditions induced by the aeration. System II was observed at higher potential on CV (+0.46V/SHE); it required a longer lag time (up to 10days) and quiescent conditions to produce an electrochemical signal. The hydrodynamic effects produced by the forced aeration led to its extinction. From their different behaviors and examples in the literature, system I was identified as being a membrane-bound cytochrome-related molecule, while system II was identified as a soluble redox mediator excreted by the biofilm. This study highlighted the importance of controlling the local hydrodynamics to design efficient oxygen reducing biocathodes able to operate at high potential.

  9. Soil-water distribution coefficients and plant transfer factors for (134)Cs, (85)Sr and (65)Zn under field conditions in tropical Australia.

    PubMed

    Twining, J R; Payne, T E; Itakura, T

    2004-01-01

    Measurements of soil-to-plant transfer of (134)Cs, (85)Sr and (65)Zn from two tropical red earth soils ('Blain' and 'Tippera') to sorghum and mung crops have been undertaken in the north of Australia. The aim of the study was to identify factors that control bioaccumulation of these radionuclides in tropical regions, for which few previous data are available. Batch sorption experiments were conducted to determine the distribution coefficient (K(d)) of the selected radionuclides at pH values similar to natural pH values, which ranged from about 5.5 to 6.7. In addition, K(d) values were obtained at one pH unit above and below the soil-water equilibrium pH values to determine the effect of pH. The adsorption of Cs showed no pH dependence, but the K(d) values for the Tippera soils (2300-4100 ml/g) exceeded those for the Blain soils (800-1200 ml/g) at equilibrium pH. This was related to the greater clay content of the Tippera soil. Both Sr and Zn were more strongly adsorbed at higher pH values, but the K(d) values showed less dependence on the soil type. Strontium K(d)s were 30-60 ml/g whilst Zn ranged from 160 to 1630 ml/g for the two soils at equilibrium pH. With the possible exception of Sr, there was no evidence for downward movement of radionuclides through the soils during the course of the growing season. There was some evidence of surface movement of labelled soil particles. Soil-to-plant transfer factors varied slightly between the soils. The average results for sorghum were 0.1-0.3 g/g for Cs, 0.4-0.8 g/g for Sr and 18-26 g/g for Zn (dry weight) with the initial values relating to Blain and the following values to Tippera. Similar values were observed for the mung bean samples. The transfer factors for Cs and Sr were not substantially different from the typical values observed in temperate studies. However, Zn transfer factors for plants grown on both these tropical soils were greater than for soils in temperate climates (by more than an order of magnitude

  10. 3D discrete angiogenesis dynamic model and stochastic simulation for the assessment of blood perfusion coefficient and impact on heat transfer between nanoparticles and malignant tumors.

    PubMed

    Yifat, Jonathan; Gannot, Israel

    2015-03-01

    Early detection of malignant tumors plays a crucial role in the survivability chances of the patient. Therefore, new and innovative tumor detection methods are constantly searched for. Tumor-specific magnetic-core nano-particles can be used with an alternating magnetic field to detect and treat tumors by hyperthermia. For the analysis of the method effectiveness, the bio-heat transfer between the nanoparticles and the tissue must be carefully studied. Heat diffusion in biological tissue is usually analyzed using the Pennes Bio-Heat Equation, where blood perfusion plays an important role. Malignant tumors are known to initiate an angiogenesis process, where endothelial cell migration from neighboring vasculature eventually leads to the formation of a thick blood capillary network around them. This process allows the tumor to receive its extensive nutrition demands and evolve into a more progressive and potentially fatal tumor. In order to assess the effect of angiogenesis on the bio-heat transfer problem, we have developed a discrete stochastic 3D model & simulation of tumor-induced angiogenesis. The model elaborates other angiogenesis models by providing high resolution 3D stochastic simulation, capturing of fine angiogenesis morphological features, effects of dynamic sprout thickness functions, and stochastic parent vessel generator. We show that the angiogenesis realizations produced are well suited for numerical bio-heat transfer analysis. Statistical study on the angiogenesis characteristics was derived using Monte Carlo simulations. According to the statistical analysis, we provide analytical expression for the blood perfusion coefficient in the Pennes equation, as a function of several parameters. This updated form of the Pennes equation could be used for numerical and analytical analyses of the proposed detection and treatment method.

  11. 3D discrete angiogenesis dynamic model and stochastic simulation for the assessment of blood perfusion coefficient and impact on heat transfer between nanoparticles and malignant tumors.

    PubMed

    Yifat, Jonathan; Gannot, Israel

    2015-03-01

    Early detection of malignant tumors plays a crucial role in the survivability chances of the patient. Therefore, new and innovative tumor detection methods are constantly searched for. Tumor-specific magnetic-core nano-particles can be used with an alternating magnetic field to detect and treat tumors by hyperthermia. For the analysis of the method effectiveness, the bio-heat transfer between the nanoparticles and the tissue must be carefully studied. Heat diffusion in biological tissue is usually analyzed using the Pennes Bio-Heat Equation, where blood perfusion plays an important role. Malignant tumors are known to initiate an angiogenesis process, where endothelial cell migration from neighboring vasculature eventually leads to the formation of a thick blood capillary network around them. This process allows the tumor to receive its extensive nutrition demands and evolve into a more progressive and potentially fatal tumor. In order to assess the effect of angiogenesis on the bio-heat transfer problem, we have developed a discrete stochastic 3D model & simulation of tumor-induced angiogenesis. The model elaborates other angiogenesis models by providing high resolution 3D stochastic simulation, capturing of fine angiogenesis morphological features, effects of dynamic sprout thickness functions, and stochastic parent vessel generator. We show that the angiogenesis realizations produced are well suited for numerical bio-heat transfer analysis. Statistical study on the angiogenesis characteristics was derived using Monte Carlo simulations. According to the statistical analysis, we provide analytical expression for the blood perfusion coefficient in the Pennes equation, as a function of several parameters. This updated form of the Pennes equation could be used for numerical and analytical analyses of the proposed detection and treatment method. PMID:24462603

  12. Oxidation of Aryl Diphenylmethyl Sulfides Promoted by a Nonheme Iron(IV)-Oxo Complex: Evidence for an Electron Transfer-Oxygen Transfer Mechanism.

    PubMed

    Barbieri, Alessia; De Carlo Chimienti, Rosemilia; Del Giacco, Tiziana; Di Stefano, Stefano; Lanzalunga, Osvaldo; Lapi, Andrea; Mazzonna, Marco; Olivo, Giorgio; Salamone, Michela

    2016-03-18

    The oxidation of a series of aryl diphenylmethyl sulfides (4-X-C6H4SCH(C6H5)2, where X = OCH3 (1), X = CH3 (2), X = H (3), and X = CF3 (4)) promoted by the nonheme iron(IV)-oxo complex [(N4Py)Fe(IV)═O](2+) occurs by an electron transfer-oxygen transfer (ET-OT) mechanism as supported by the observation of products (diphenylmethanol, benzophenone, and diaryl disulfides) deriving from α-C-S and α-C-H fragmentation of radical cations 1(+•)-4(+•), formed besides the S-oxidation products (aryl diphenylmethyl sulfoxides). The fragmentation/S-oxidation product ratios regularly increase through a decrease in the electron-donating power of the aryl substituents, that is, by increasing the fragmentation rate constants of the radical cations as indicated by a laser flash photolysis (LFP) study of the photochemical oxidation of 1-4 carried out in the presence of N-methoxyphenanthridinium hexafluorophosphate (MeOP(+)PF6(-)). PMID:26886491

  13. Oxidation of Aryl Diphenylmethyl Sulfides Promoted by a Nonheme Iron(IV)-Oxo Complex: Evidence for an Electron Transfer-Oxygen Transfer Mechanism.

    PubMed

    Barbieri, Alessia; De Carlo Chimienti, Rosemilia; Del Giacco, Tiziana; Di Stefano, Stefano; Lanzalunga, Osvaldo; Lapi, Andrea; Mazzonna, Marco; Olivo, Giorgio; Salamone, Michela

    2016-03-18

    The oxidation of a series of aryl diphenylmethyl sulfides (4-X-C6H4SCH(C6H5)2, where X = OCH3 (1), X = CH3 (2), X = H (3), and X = CF3 (4)) promoted by the nonheme iron(IV)-oxo complex [(N4Py)Fe(IV)═O](2+) occurs by an electron transfer-oxygen transfer (ET-OT) mechanism as supported by the observation of products (diphenylmethanol, benzophenone, and diaryl disulfides) deriving from α-C-S and α-C-H fragmentation of radical cations 1(+•)-4(+•), formed besides the S-oxidation products (aryl diphenylmethyl sulfoxides). The fragmentation/S-oxidation product ratios regularly increase through a decrease in the electron-donating power of the aryl substituents, that is, by increasing the fragmentation rate constants of the radical cations as indicated by a laser flash photolysis (LFP) study of the photochemical oxidation of 1-4 carried out in the presence of N-methoxyphenanthridinium hexafluorophosphate (MeOP(+)PF6(-)).

  14. A biocompatible cobaltporphyrin-based complex micelle constructed via supramolecular assembly for oxygen transfer.

    PubMed

    Shen, Liangliang; Qu, Rui; Shi, Hejin; Huang, Fan; An, Yingli; Shi, Linqi

    2016-05-26

    Herein, a complex micelle as an oxygen nano-carrier is constructed through the hierarchical assembly of the diblock copolymer poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLys), tetrakis(4-sulfonatophenyl)porphinato cobalt(ii) (Co(ii)TPPS), a heptapeptide (Cys-His-His-His-His-His-His) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). Co(ii)TPPS was encapsulated into the cavities of TM-β-CDs driven by the host-guest interaction so that the irreversible formation of a μ-oxo-dimer of Co(ii)TPPS can be effectively prevented. The imidazole groups of the heptapeptide were selected as good axial ligands coordinating to the centric cobalt of Co(ii)TPPS, which subtly constituted the five-coordinated precursor serving as an active functional centre for oxygen binding. The sixth position of Co(ii)TPPS can bind oxygen. Furthermore, the host-guest inclusion (TM-β-CD/Co(ii)TPPS) was loaded into the hydrophobic core of the complex micelle and tightly fixed with PLys chains. The hydrophilic PEG blocks stretched in the aqueous solution constitute the shells which stabilize the structure of the complex micelle as well as impart the complex micelle sufficient blood circulation time. Moreover, the complex micelle exhibited excellent biocompatibility and cellular uptake. Therefore, the rationally designed amphiphilic structure can work as promising artificial O2 carriers in vivo. Potentially, the complex micelle can be expected to change the anaerobic microenvironment and find applications in the repair of the cells damaged by cellular hypoxia. PMID:27009911

  15. Modeling ozone mass transfer in reclaimed wastewater.

    PubMed

    Jiang, Pan; Chen, Hsiao-Ting; Babcock, Roger W; Stenstrom, Michael K

    2009-01-01

    Ozone mass transfer in reclaimed water was evaluated at pilot scale to determine mass-transfer characteristics and reaction kinetics and to assess the use of oxygen as a surrogate to measure this process. Tests were conducted in a 40-L/min pilot plant over a 3-year period. Nonsteady-state mass-transfer analyses for both oxygen and ozone were performed for superficial gas flow rates ranging from 0.13m/min to 0.40m/min. The psi factor, which is the ratio of volumetric mass-transfer coefficients of ozone to oxygen, was determined. The decrease in oxygen transfer rate caused by contaminants in reclaimed water was only 10 to 15% compared to tap water. A simple mathematical model was developed to describe transfer rate and steady state ozone concentration. Ozone decay was modeled accurately as a pseudo first-order reaction between ozone and ozone-demanding materials.

  16. ETON 1 - A data base pertinent to the study of energy transfer in the oxygen nightglow

    NASA Astrophysics Data System (ADS)

    Greer, R. G. H.; Murtagh, D. P.; McDade, I. C.; Dickinson, P. H. G.; Thomas, L.

    1986-09-01

    A comprehensive group of experiments, assembled and flown on a series of Petrel rockets in March 1982 for the primary purpose of investigating the extent to which energy transfer is important in the excitation of the oxgen nightglow, is briefly described. Aspects of the data reduction methods are summarised and the bulk of the processed data is presented in profile and tabular form as a base for modelling and analyses in papers to follow and in evidence of the quality and success of this memorable international collaborative campaign.

  17. Low-pressure airlift fermenter for single cell protein production. I. Design and oxygen transfer studies

    SciTech Connect

    Chen, N.Y.; Kondis, E.F.; Srinivasan, S.

    1987-03-01

    The energy consumption of a fermenter constitutes a major part of the operating expense of a single cell protein process. A low-pressure airlift fermenter was designed to reduce this cost. In this new design, the fermenter broth is kept below 120 cm in depth, and air alone is employed to fulfil the need of supplying oxygen, and cooling and agitating the broth. The use of low-pressure air from air blowers instead of air compressors lowers the capital cost of air delivery and reduces the energy consumption in the fermenter section to below 1 kWh/kg protein, a saving of over 70% as compared to a conventional stirred tank fermenter. It also eliminates the investment of mechanical agitators, heat exchangers, and air compressors. Sulfite oxidation studies confirmed the design concepts. 30 references.

  18. Mechanism of inhibition and decoupling of oxygen evolution from electron transfer in photosystem II by fluoride, ammonia and acetate.

    PubMed

    Lovyagina, E R; Semin, B K

    2016-05-01

    Ca(2+) extraction from oxygen-evolving complex (OEC) of photosystem II (PSII) is accompanied by decoupling of oxygen evolution/electron transfer processes [Semin et al. Photosynth. Res. 98 (2008) 235] and appearance of a broad EPR signal at g=2 (split "S3" signal) what can imply the relationship between these effects. Split signal have been observed not only in Ca-depleted PSII but also in PSII membranes treated by fluoride anions, sodium acetate, and NH4Cl. Here we investigated the question: can such compounds induce the decoupling effect during treatment of PSII like Ca(2+) extraction does? We found that F(-), sodium acetate, and NH4Cl inhibit O2 evolution in PSII membranes more effectively than the reduction of artificial electron acceptor 2,6-dichlorophenolindophenol, i.e. the action of these compounds is accompanied by decoupling of these processes in OEC. Similarity of effects observed after Ca(2+) extraction and F(-), CH3COO(-) or NH4Cl treatments suggests that these compounds can inactivate function of Ca(2+). Such inactivation could originate from disturbance of the network of functionally active hydrogen bonds around OEC formed with participation of Ca(2+). This inhibition effect is observed in the region of low concentration of inhibitors. Increasing of inhibitor concentration is accompanied by appearance of other sites of inhibition. PMID:26971280

  19. Xanthohumol induces generation of reactive oxygen species and triggers apoptosis through inhibition of mitochondrial electron transfer chain complex I.

    PubMed

    Zhang, Bo; Chu, Wei; Wei, Peng; Liu, Ying; Wei, Taotao

    2015-12-01

    Xanthohumol is a prenylflavonoid extracted from hops (Humulus lupulus). It possesses anti-cancer and anti-inflammatory activities in vitro and in vivo, and offers therapeutic benefits for treatment of metabolic syndromes. However, the precise mechanisms underlying its pharmacological effects remain to be elucidated, together with its cellular target. Here, we provide evidence that xanthohumol directly interacts with the mitochondrial electron transfer chain complex I (NADH dehydrogenase), inhibits the oxidative phosphorylation, triggers the production of reactive oxygen species, and induces apoptosis. In addition, we show that as a result of the inhibition of the mitochondrial oxidative phosphorylation, xanthohumol exposure causes a rapid decrease of mitochondrial transmembrane potential. Furthermore, we showed that xanthohumol up-regulates the glycolytic capacity in cells, and thus compensates cellular ATP generation. Dissection of the multiple steps of aerobic respiration by extracellular flux assays revealed that xanthohumol specifically inhibits the activity of mitochondrial complex I, but had little effect on that of complex II, III and IV. Inhibition of complex I by xanthohumol caused the overproduction of reactive oxygen species, which are responsible for the induction of apoptosis in cancer cells. We also found that isoxanthohumol, the structural isomer of xanthohumol, is inactive to cells, suggesting that the reactive 2-hydroxyl group of xanthohumol is crucial for its targeting to the mitochondrial complex I. Together, the remodeling of cell metabolism revealed here has therapeutic potential for the use of xanthohumol.

  20. Potential technology transfers of research on low-temperature carbon monoxide-oxygen recombination catalysts

    NASA Technical Reports Server (NTRS)

    Poziomek, Edward J.

    1990-01-01

    Results from research on catalytic recombination of CO-O2 for stable closed-cycle operation of CO2 lasers hold much promise for a variety of technology transfer. Expansion of CO2 laser remote sensing applications toward chemical detection and pollution monitoring would certainly be expected. However, the catalysts themselves may be especially effective in low-temperature oxidation of a number of chemicals in addition to CO. It is therefore of interest to compare the CO-O2 catalysts with chemical systems designed for chemical sensing, air purification and process catalysis. Success in understanding the catalytic mechanisms of the recombination of CO-O2 could help to shed light on how catalyst systems operate. New directions in low-temperature oxidation catalysts, coatings for chemical sensors and sorbents for air purification could well emerge.

  1. Testing models of fatty acid transfer and lipid synthesis in spinach leaf using in vivo oxygen-18 labeling

    SciTech Connect

    Pollard, M.; Ohlrogge, J.

    1999-12-01

    Oxygen-18 labeling has been applied to the study of plant lipid biosynthesis for the first time. [{sup 13}C{sub 2}{sup 18}O{sub 2}]Acetate was incubated with spinach (Spinacia oleracea) leaves and the {sup 18}O content in fatty acid methyl esters isolated from different lipid classes measured by gas chromatography-mass spectrometry. Fatty acids isolated from lipids synthesized within the plastid, such as monogalactosyldiacylglycerol, show an {sup 18}O content consistent with the exogenous acetate undergoing a single activation step and with the direct utilization of acyl-acyl carrier protein by the acyl transferases of the chloroplast. In contrast, fatty acids isolated from lipids assembled in the cytosol, such as phosphatidylcholine, show a 50% reduction in the {sup 18}O content. This is indicative of export of the fatty acyl groups from the plastid via a free carboxylate anion, and is consistent with the acyl-acyl carrier protein thioesterase:acyl-coenzyme A (CoA) synthetase mediated export mechanism. If this were not the case and the acyl group was transferred directly from acyl-acyl carrier protein to an acyl acceptor on the cytosolic side, there would be either complete retention of {sup 18}O or, less likely, complete loss of {sup 18}O, but not a 50% loss of {sup 18}O. Thus, existing models for fatty acid transfer from the plastid and for spatially separate synthesis of prokaryotic and eukaryotic lipids have both been confirmed.

  2. Electrocatalysis of anodic oxygen-transfer reactions: The electrochemical incineration of benzoquinone

    SciTech Connect

    Feng, J.; Houk, L.L.; Johnson, D.C. |; Lowery, S.N.; Carey, J.J.

    1995-11-01

    The electrochemical performance of several anode materials is compared for the electrochemical incineration of p-benzoquinone in acetate buffer media (pH 5). The chemical oxygen demand (COD) estimated for benzoquinone by titration with standard permanganate solution can be decreased to virtually zero by electrolysis at electrodes comprised of Fe(III)-doped {beta}-PbO{sub 2} films on Ti substrates. Carbon dioxide is a product of the electrochemical process; however, the possibility of other volatile products cannot be dismissed. Addition of solid benzoquinone to acetate media is followed by slow formation of a brownish black color that is concluded to result from one or more humic compounds produced by condensation of benzoquinone; however, it cannot be concluded whether the condensation reaction is a necessary prerequisite to successful electrochemical incineration of benzoquinone. Optimal operating conditions suggested for electrochemical incineration of benzoquinone in acetate buffer include heating of the anode (e.g., 60 C) to increase the rate of anodic discharge of H{sub 2}O and, thereby, decrease the anodic overpotential. Evidence also is presented that the rate of electrochemical incineration is enhanced slightly by the addition of a traces of Fe(III) with reduction of dioxygen (O{sub 2}) to hydrogen peroxide (H{sub 2}O{sub 2}) at a cooled stainless steel cathode (e.g., 15 C) in an undivided cell.

  3. The study on the heat transfer characteristics of oxygen fuel combustion boiler

    NASA Astrophysics Data System (ADS)

    Wu, Haibo; Liu, Zhaohui; Liao, Haiyan

    2016-10-01

    According to 350MW and 600MW boilers, under oxygen fuel condition, through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model, the temperature distribution, heat flux distribution and absorption heat distribution, etc. was obtained which compared with those under air condition. Through calculation, it is obtained that the primary and secondary flow mixed well, good tangentially fired combustion in furnace was formed, the temperature under air condition obviously higher than the temperature under O26 condition. The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle. The maximum heat load appeared on the waterwall around the burner area. The heat load gradually decreased along the furnace height up and down in burner area. The heat absorption capacity of the furnace under O26 was lower than that under the air condition. The heat absorption capacity of the platen heating surface under O26 was equal to that under air condition. And the heat absorbing capacity of waterwall under O26 was about7%~12% less than that under air condition.

  4. Measurements of momentum transfer coefficients for H{sub 2}, N{sub 2}, CO and CO{sub 2} incident upon spacecraft surfaces

    SciTech Connect

    Cook, S.R.; Hoffbauer, M.A.

    1997-07-16

    Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H{sub 2}, N{sub 2}, CO, and CO{sub 2} incident upon the solar array material, Kapton, SiO{sub 2}-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that scattering behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.

  5. Structural and magnetic features of oxygen inserted [Co-O/Pt]n multi-layer matrix for spin transfer torque memory applications.

    PubMed

    Lee, Ja Bin; An, Gwang Guk; Yang, Seung Mo; Hong, Jin Pyo

    2013-11-01

    We describe the influence of inserted oxygen atoms on the structural and magnetic properties of a [Co/Pt]n multi-layer matrix. The correlation of magnetic properties with oxygen gas flow rate was studied as an alternative perpendicular medium in spin transfer torque magnetic random access memory applications. Experimental analysis suggests that the addition of a small amount of oxygen atoms into the [Co/Pt]n multi-layer matrix leads to a high coercivity and proper magnetization performance, together with high thermal stability. Finally, the nature of the improved perpendicular medium behaviors is also discussed.

  6. Predicting diffusive alveolar oxygen transfer from carbon monoxide-diffusing capacity in exercising foxhounds

    PubMed Central

    Hsia, Connie C. W.; Wagner, Peter D.; Dane, D. Merrill; Wagner, Harrieth E.; Johnson, Robert L.

    2008-01-01

    Although lung diffusing capacity for carbon monoxide (DlCO) is a widely used test of diffusive O2 transfer, few studies have directly related DlCO to O2-diffusing capacity (DlO2); none has used the components of DlCO, i.e., conductance of alveolar membrane and capillary blood, to predict DlO2 from rest to exercise. To understand the relationship between DlCO and DlO2 at matched levels of cardiac output, we analyzed cumulative data from rest to heavy exercise in 43 adult dogs, with normal lungs or reduced lung capacity following lung resection, that were studied by two techniques. 1) A rebreathing (RB) technique was used to measure DlCO and pulmonary blood flow at two O2 tensions, independent of O2 exchange. DlCO was partitioned into CO-diffusing capacity of alveolar membrane and pulmonary capillary blood volume using the Roughton-Forster equation and converted into an equivalent DlO2, [DlO2(RB)]. 2) A multiple inert-gas elimination technique (MIGET) was used to measure ventilation-perfusion distributions, O2 and CO2 exchange under hypoxia, to derive DlO2 [DlO2(MIGET)] by the Lilienthal-Riley technique and Bohr integration. For direct comparisons, DlO2(RB) was interpolated to the cardiac output measured by the Fick principle corresponding to DlO2(MIGET). The DlO2-to-DlCO ratio averaged 1.61. Correlation between DlO2(RB) and DlO2(MIGET) was similar in normal and post-resection groups. Overall, DlO2(MIGET) = 0.975 DlO2(RB); mean difference between the two techniques was under 5% for both animal groups. We conclude that, despite various uncertainties inherent in these two disparate methods, the Roughton-Forster equation adequately predicts diffusive O2 transfer from rest to heavy exercise in canines with normal, as well as reduced, lung capacities. PMID:18719238

  7. 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.

  8. Organization of the electron transfer chain to oxygen in the obligate human pathogen Neisseria gonorrhoeae: roles for cytochromes c4 and c5, but not cytochrome c2, in oxygen reduction.

    PubMed

    Li, Ying; Hopper, Amanda; Overton, Tim; Squire, Derrick J P; Cole, Jeffrey; Tovell, Nicholas

    2010-05-01

    Although Neisseria gonorrhoeae is a prolific source of eight c-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes c(2), c(4), and c(5), encoded by the genes cccA, cycA, and cycB, respectively, have been investigated. Single mutations in genes for either cytochrome c(4) or c(5) resulted in an increased sensitivity to growth inhibition by excess oxygen and small decreases in the respiratory capacity of the parent, which were complemented by the chromosomal integration of an ectopic, isopropyl-beta-d-thiogalactopyranoside (IPTG)-inducible copy of the cycA or cycB gene. In contrast, a cccA mutant reduced oxygen slightly more rapidly than the parent, suggesting that cccA is expressed but cytochrome c(2) is not involved in electron transfer to cytochrome oxidase. The deletion of cccA increased the sensitivity of the cycB mutant to excess oxygen but decreased the sensitivity of the cycA mutant. Despite many attempts, a double mutant defective in both cytochromes c(4) and c(5) could not be isolated. However, a strain with the ectopically encoded, IPTG-inducible cycB gene with deletions in both cycA and cycB was constructed: the growth and survival of this strain were dependent upon the addition of IPTG, so gonococcal survival is dependent upon the synthesis of either cytochrome c(4) or c(5). These results define the gonococcal electron transfer chain to oxygen in which cytochromes c(4) and c(5), but not cytochrome c(2), provide alternative pathways for electron transfer from the cytochrome bc(1) complex to the terminal oxidase cytochrome cbb(3).

  9. Effect of oxygen transfer rate on the composition of the pectolytic enzyme complex of Aspergillus niger

    SciTech Connect

    Zetelaki-Horvath, K.; Vas, K.

    1981-01-01

    Optimal agitation and aeration conditions (assuring O/sub 2/ transfer rates (OTR) of 12-179 mmol/L-h) were determined for pectin lyase (PL) synthesis of an Aspergillus niger strain. Components of the pectolytic enzyme complex were also investigated in order to determine whether their O/sub 2/ demand is identical with or different from that of pectin lyase. Should the latter be the case, a possibility would be given to produce enzyme complexes of different agitation and aeration conditions. The mycelium yield of Aspergillus niger was maximum at an OTR of 100 mmol/L-h. The yields of the various pectolytic enzymes reached maximum at different OTRs. PL production was highest (0.555 mumol/min-mL) at an OTR of 60 mmol/L-h. Endopolygalacturonase (PG) production has a maximum at OTR 49 mmol/L-h, with a 2nd peak at 100-135 mmol O2/L-h. Pectin esterase (PE) synthesis showed a maximum at an OTR of 12-14 mmol/L-h, while both apple juice clarifying and macerating activities gave 2 maximum at 14 and 60 mmol/L-h due to the optima of PE and endo-PG. Macerating activity showed a high value at OTR optimal for PL production as well.

  10. Metal ion effect on the switch of mechanism from direct oxygen transfer to metal ion-coupled electron transfer in the sulfoxidation of thioanisoles by a non-heme iron(IV)-oxo complex.

    PubMed

    Park, Jiyun; Morimoto, Yuma; Lee, Yong-Min; Nam, Wonwoo; Fukuzumi, Shunichi

    2011-04-13

    The mechanism of sulfoxidation of thioaniosoles by a non-heme iron(IV)-oxo complex is switched from direct oxygen transfer to metal ion-coupled electron transfer by the presence of Sc(3+). The switch in the sulfoxidation mechanism is dependent on the one-electron oxidation potentials of thioanisoles. The rate of sulfoxidation is accelerated as much as 10(2)-fold by the addition of Sc(3+).

  11. Structural Snapshots of Yeast Alkyl Hydroperoxide Reductase Ahp1 Peroxiredoxin Reveal a Novel Two-cysteine Mechanism of Electron Transfer to Eliminate Reactive Oxygen Species*

    PubMed Central

    Lian, Fu-Ming; Yu, Jiang; Ma, Xiao-Xiao; Yu, Xiao-Jie; Chen, Yuxing; Zhou, Cong-Zhao

    2012-01-01

    Peroxiredoxins (Prxs) are thiol-specific antioxidant proteins that protect cells against reactive oxygen species and are involved in cellular signaling pathways. Alkyl hydroperoxide reductase Ahp1 belongs to the Prx5 subfamily and is a two-cysteine (2-Cys) Prx that forms an intermolecular disulfide bond. Enzymatic assays and bioinformatics enabled us to re-assign the peroxidatic cysteine (CP) to Cys-62 and the resolving cysteine (CR) to Cys-31 but not the previously reported Cys-120. Thus Ahp1 represents the first 2-Cys Prx with a peroxidatic cysteine after the resolving cysteine in the primary sequence. We also found the positive cooperativity of the substrate t-butyl hydroperoxide binding to Ahp1 homodimer at a Hill coefficient of ∼2, which enabled Ahp1 to eliminate hydroperoxide at much higher efficiency. To gain the structural insights into the catalytic cycle of Ahp1, we determined the crystal structures of Ahp1 in the oxidized, reduced, and Trx2-complexed forms at 2.40, 2.91, and 2.10 Å resolution, respectively. Structural superposition of the oxidized to the reduced form revealed significant conformational changes at the segments containing CP and CR. An intermolecular CP-CR disulfide bond crossing the A-type dimer interface distinguishes Ahp1 from other typical 2-Cys Prxs. The structure of the Ahp1-Trx2 complex showed for the first time how the electron transfers from thioredoxin to a peroxidase with a thioredoxin-like fold. In addition, site-directed mutagenesis in combination with enzymatic assays suggested that the peroxidase activity of Ahp1 would be altered upon the urmylation (covalently conjugated to ubiquitin-related modifier Urm1) of Lys-32. PMID:22474296

  12. Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

    NASA Astrophysics Data System (ADS)

    Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  13. Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

    NASA Technical Reports Server (NTRS)

    Hippensteele, S. A.; Russell, L. M.; Torres, F. J.

    1987-01-01

    Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

  14. Diffusion of oxygen in cork.

    PubMed

    Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Simon, Jean-Marc; Paulin, Christian; Bellat, Jean-Pierre

    2012-04-01

    This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.

  15. Diffusion of oxygen through cork stopper: is it a Knudsen or a Fickian mechanism?

    PubMed

    Lagorce-Tachon, Aurélie; Karbowiak, Thomas; Simon, Jean-Marc; Gougeon, Régis; Bellat, Jean-Pierre

    2014-09-17

    The aim of this work is to identify which law governs oxygen transfer through cork: Knudsen or Fickian mechanism. This is important to better understand wine oxidation during post-bottling aging. Oxygen transfer through cork wafers is measured at 298 K using a manometric permeation technique. Depending on the mechanism, we can extract the transport coefficients. Increasing the initial pressure of oxygen from 50 to 800 hPa leads to a change in the values of the transport coefficients. This implies that oxygen transport through cork does not obey the Knudsen law. From these results, we conclude that the limiting step of oxygen transport through cork occurs in the cell wall following Fickian law. From the diffusion dependence's coefficients with pressure, we also extract by applying transition state theory an apparent activation volume of 45 ± 4 nm(3). This high value indicates that oxygen molecules also diffuse from one site to another by passing through a gas phase.

  16. Singlet molecular oxygen ( sup 1. Delta. sub g O sub 2 ) formation upon irradiation of an oxygen ( sup 3. Sigma. sub g sup minus O sub 2 )-organic molecule charge-transfer absorption band

    SciTech Connect

    Scurlock, R.D.; Ogilby, P.R. )

    1989-07-13

    Singlet molecular oxygen ({sup 1}{Delta}{sub g}O{sub 2}) phosphorescence ({sup 3}{Sigma}{sub g}{sup {minus}}O{sub 2} {l arrow} {sup 1}{Delta}{sub g}O{sub 2}: 1270 nm) has been observed in a time-resolved experiment subsequent to pulsed UV laser irradiation of the oxygen ({sup 3}{Sigma}{sub g}{sup {minus}}O{sub 2})-organic molecule charge-transfer bands of liquid aromatic hydrocarbons (mesitylene, p-xylene, o-xylene, toluene, benzene), ethers (tetrahydrofuran, 1,4-dioxane, glyme, diglyme, triglyme), alcohols (methanol, propanol), and aliphatic hydrocarbons (cyclohexane, cyclooctane, decahydronaphthalene). Although {sup 1}{Delta}{sub g}O{sub 2} could originate from a variety of different processes in these oxygenated solvent systems, we have used the results of several independent experiments to indicate that an oxygen-solvent charge-transfer (CT) state is the {sup 1}{Delta}{sub g}O{sub 2} precursor. Other transient species have also been observed in time-resolved absorption experiments subsequent to pulsed UV irradiation of the oxygen-solvent CT bands. Some of these molecular transients, or species derived from these intermediates, may be responsible for an observed increase in the rate of {sup 1}{Delta}{sub g}O{sub 2} decay under certain conditions.

  17. Impaired alveolar-arterial oxygen transfer is associated with reduced milk yield in primiparous post-partum dairy heifers at moderate altitude.

    PubMed

    Neary, Joseph M; Garry, Franklyn B

    2014-11-01

    Domestic cattle have limited cardiopulmonary reserve for their body size and oxygen requirements. Therefore, it is plausible that impaired alveolar-arterial gas exchange may be detrimental to energetically expensive traits such as milk production which, like all aerobic processes, requires oxygen. The degree of alveolar-arterial oxygen transfer impairment can be determined by estimating the alveolar-arterial oxygen (A-a O2) pressure gradient from arterial blood-gas tensions. The degree of oxygen transfer impairment is proportional to the A-a O2 pressure gradient: the higher the A-a O2 pressure gradient the less oxygen is transferred to the blood for a given ventilation rate. In this study two cohorts of Holstein-Friesian heifers were followed on one northern Colorado dairy farm. Arterial blood-gas analyses were performed up to 9 d post-calving. Heifers were grouped into quartiles based on A-a O2 pressure gradient so that relative comparisons could be made. Heifers in the lowest (Q1) and highest (Q4) quartile had the least and greatest impairment of alveolar-arterial oxygen transfer, respectively. We hypothesised that milk yield over 60 d would be greatest for heifers in Q1 and would decrease with quartile increments. Hyperventilation, as indicated by hypocapnia, was notable. Despite hypoxia, haematocrit was low. Alveolar-arterial O2 pressure gradient was associated with milk production (P=0·03) when controlling for cohort, treatment for disease and calving difficulty score. Heifers in Q1 produced 1992 kg (95% CI=1858, 2127 kg) of milk when controlling for all other variables. Relative to heifers in Q1, heifers in Q2, Q3 and Q4 produced 130 kg (95% CI=313, -52 kg; P=0·45), 285 kg (95% CI=474, 96 kg; P=0·004) and 169 kg (95% CI=395, -57 kg; P=0.14) less milk, respectively. In conclusion, efficacy of alveolar-arterial oxygen transfer was associated with milk yield in dairy heifers on one farm at moderate altitude.

  18. Ceria-Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity.

    PubMed

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-11-16

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2-ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities. PMID:26448053

  19. Ceria–Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity

    PubMed Central

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-01-01

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2–ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities. PMID:26448053

  20. How dangerous are phthalate plasticizers? Integrated approach to toxicity based on metabolism, electron transfer, reactive oxygen species and cell signaling.

    PubMed

    Kovacic, Peter

    2010-04-01

    Phthalate plasticizers are the most abundant man-made pollutants that have recently received wide-spread attention. There is uncertainty concerning the toxicity to humans. During the debate, scant attention has been paid to adverse effects at the molecular level which is the focus of this article. Most metabolic reports are concerned only with ester hydrolysis. In addition to that aspect, an important study deals with formation of catechol carboxylic acids which have the potential to redox cycle with the o-quinone counterparts. This electron transfer (ET) process is capable of generating reactive oxygen species (ROS) which are well known toxic agents at elevated levels. Substantial numbers of investigations find the presence of ROS leading to oxidative stress (OS) in living systems containing phthalates. Insults occur to various organs, including the reproductive system, pulmonary, central nervous system, immune system and liver. Toxic reactions are also reported involving inflammation, mitochondria and carcinogenicity. Generally, OS evidently plays a role. Of relevance are prior reviews which document extensive evidence for association of ET-ROS-OS with organ toxicity, and other deleterious reactions. In addition, cell signaling has been related to the physiological effects of phthalates. Various signaling processes participate together with involvement of ROS and association with biological effects. Suggestions for future work are offered.

  1. The roles of polycarboxylates in Cr(VI)/sulfite reaction system: Involvement of reactive oxygen species and intramolecular electron transfer.

    PubMed

    Jiang, Bo; Wang, Xianli; Liu, Yukun; Wang, Zhaohui; Zheng, Jingtang; Wu, Mingbo

    2016-03-01

    In this study, the effects of polycarboxylates on both Cr(VI) reduction and S(IV) consumption in Cr(VI)/S(IV) system was investigated in acidic solution. Under aerobic condition, the productions of reactive oxygen species (ROS), i.e., SO4(-) and OH, have been confirmed in S(IV) reducing Cr(VI) process by using electron spin resonance and fluorescence spectrum techniques, leading to the excess consumption of S(IV). However, when polycarboxylates (oxalic, citric, malic and tartaric acid) were present in Cr(VI)/S(IV) system, the affinity of polycarboxylates to CrSO6(2-) can greatly promote the reduction of Cr(VI) via expanding the coordination of Cr(VI) species from tetrahedron to hexahedron. Besides, as alternatives to S(IV), these polycarboxylates can also act as electron donors for Cr(VI) reduction via intramolecular electron transfer reaction, which is dependent on the energies of the highest occupied molecular orbital of these polycarboxylates. Notably, the variant electron donating capacity of these polycarboxylates resulted in different yield of ROS and therefore the oxidation efficiencies of other pollutants, e.g., rhodamine B and As(III). Generally, this study does not only shed light on the mechanism of S(IV) reducing Cr(VI) process mediated by polycarboxylates, but also provides an escalated, cost-effective and green strategy for the remediation of Cr(VI) using sulfite as a reductant. PMID:26610099

  2. Ceria-Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity.

    PubMed

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-11-16

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2-ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities.

  3. Ototoxicity and noise trauma: electron transfer, reactive oxygen species, cell signaling, electrical effects, and protection by antioxidants: practical medical aspects.

    PubMed

    Kovacic, Peter; Somanathan, Ratnasamy

    2008-01-01

    Ototoxins are substances of various structures and classes. This review provides extensive evidence for involvement of electron transfer (ET), reactive oxygen species (ROS) and oxidative stress (OS) as a unifying theme. Successful application is made to the large majority of ototoxins, as well as noise trauma. We believe it is not coincidental that these toxins generally incorporate ET functionalities (quinone, metal complex, ArNO(2), or conjugated iminium) either per se or in metabolites, potentially giving rise to ROS by redox cycling. Some categories, e.g., peroxides and noise, appear to operate via non-ET routes in generating OS. These highly reactive entities can then inflict injury via OS upon various constituents of the ear apparatus. The theoretical framework is supported by the extensive literature on beneficial effects of antioxidants, both for toxins and noise. Involvement of cell signaling and electrical effects are discussed. This review is the first comprehensive one based on a unified mechanistic approach. Various practical medical aspects are also addressed. There is extensive documentation for beneficial effects of antioxidants whose use might be recommended clinically for prevention of ototoxicity and noise trauma. Recent research indicates that catalytic antioxidants may be more effective. In addition to ototoxicity, a widespread problem consists of ear infections by bacteria which are demonstrating increasing resistance to conventional therapies. A recent, novel approach to improved drugs involves use of agents which inhibit quorum sensors that play important roles in bacterial functioning. Prevention of ear injury by noise trauma is also discussed, along with ear therapeutics.

  4. Low oxygen tension and relative defined culture medium with 3, 4-dihydroxyflavone are beneficial for yak-bovine interspecies somatic cell nuclear transfer embryo.

    PubMed

    Xiong, X; Li, J; Wang, L; Zhong, J; Zi, X; Wang, Y

    2014-02-01

    With an aim to improve the efficiency of yak-bovine interspecies somatic cell nuclear transfer (iSCNT), this study investigated the effect of different culture systems on the development, quality and gene expression profile of yak-bovine iSCNT embryo. Reconstructed embryos were cultured in modified synthetic oviductal fluid (mSOF) or relative defined culture medium (RDCM) with 5% or 20% oxygen tension. Relative mRNA abundance of Oct-4, IFNT, IGF-2, Bax, GPX-1, SOD-1, CAT and GSS was analysed in blastocysts with qRT-PCR. The blastocyst formation rate in RDCM under 5% oxygen tension was significantly higher than that under 20% oxygen tension (P < 0.05). The total cell number of blastocyst derived from RDCM with 20% oxygen tension was lower than that of other groups, whereas the group of RDCM with 5% oxygen tension showed a beneficial effect on apoptosis index and tolerance to cryopreservation (P < 0.05). However, under the same oxygen tension, the mRNA abundance of IFNT of RDCM groups was higher than that of the mSOF groups. In addition, high oxygen tension during in vitro culture (IVC) with RDCM significantly increases the mRNA expression of oxidative stress-related genes (GPX-1, SOD-1, CAT and GSS) (P < 0.05). 3, 4-Dihydroxyflavone (DHF) during high oxygen tension was able to improve the cloned blastocyst formation rate in RDCM (P < 0.05). These results for the first time showed that low oxygen tension and RDCM could improve the developmental competence and quality and alleviate the oxidative stress for yak-bovine iSCNT embryo during IVC.

  5. Activity and Activity Coefficient of Iron Oxides in the Liquid FeO-Fe2O3-CaO-SiO2 Slag Systems at Intermediate Oxygen Partial Pressures

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Itagaki, Kimio

    2007-10-01

    At present, there is a scarcity of data on the activities of iron oxides in the FeO-Fe2O3-CaO-SiO2 slag system at intermediate oxygen partial pressures and temperatures relevant to sulfide smelting and nonferrous metallurgy. The present study provides relevant data at temperatures between 1573 and 1673 K and partial pressures of oxygen between 10-9 and 10-4 atm. The experiments were carried out by equilibrating the slag in a CO-CO2 gas mixture in a platinum crucible, after which the phases of all the experimental samples, including the platinum foil, were analyzed by electron probe microanalysis (EPMA). Where only liquid phase or liquid phase and tridymite (SiO2) were observed, wet chemical analysis was used to determine the ratio of (mass pct Fe2+)/(mass pct Fe3+). Activity and activity coefficients for FeO (liquid) and FeO1.33 (solid) were calculated. Tendencies of the effect of the (CaO/SiO2) ratio, temperature, and oxygen partial pressure on these thermochemical quantities are discussed in this article.

  6. Teaching the fundamentals of electron transfer reactions in mitochondria and the production and detection of reactive oxygen species

    PubMed Central

    Mailloux, Ryan J.

    2015-01-01

    Mitochondria fulfill a number of biological functions which inherently depend on ATP and O2−•/H2O2 production. Both ATP and O2−•/H2O2 are generated by electron transfer reactions. ATP is the product of oxidative phosphorylation whereas O2−• is generated by singlet electron reduction of di-oxygen (O2). O2−• is then rapidly dismutated by superoxide dismutase (SOD) producing H2O2. O2−•/H2O2 were once viewed as unfortunately by-products of aerobic respiration. This characterization is fitting considering over production of O2−•/H2O2 by mitochondria is associated with range of pathological conditions and aging. However, O2−•/H2O2 are only dangerous in large quantities. If produced in a controlled fashion and maintained at a low concentration, cells can benefit greatly from the redox properties of O2−•/H2O2. Indeed, low rates of O2−•/H2O2 production are required for intrinsic mitochondrial signaling (e.g. modulation of mitochondrial processes) and communication with the rest of the cell. O2−•/H2O2 levels are kept in check by anti-oxidant defense systems that sequester O2−•/H2O2 with extreme efficiency. Given the importance of O2−•/H2O2 in cellular function, it is imperative to consider how mitochondria produce O2−•/H2O2 and how O2−•/H2O2 genesis is regulated in conjunction with fluctuations in nutritional and redox states. Here, I discuss the fundamentals of electron transfer reactions in mitochondria and emerging knowledge on the 11 potential sources of mitochondrial O2−•/H2O2 in tandem with their significance in contributing to overall O2−•/H2O2 emission in health and disease. The potential for classifying these different sites in isopotential groups, which is essentially defined by the redox properties of electron donator involved in O2−•/H2O2 production, as originally suggested by Brand and colleagues is also surveyed in detail. In addition, redox signaling mechanisms that control O2−•/H2O2

  7. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    PubMed

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

  8. The beneficial role of rubble mound coastal structures on seawater oxygenation

    NASA Astrophysics Data System (ADS)

    Daniil, E. I.; Tsoukala, V. K.; Moutzouris, C. I.

    2000-10-01

    The beneficial role of rubble mound coastal structures on oxygenation under the effect of waves is discussed, based on analytical considerations and experimental data from laboratory experiments with permeable and impermeable structures. Significant oxygenation of the wave-protected area was observed as a result of horizontal transport through the permeable structure. A two-cell model describing the transport of dissolved oxygen (DO) near a rubble mound breakwater structure was developed and used for the determination of the oxygen transfer coefficients from the experimental data. Oxygen transfer through the air-water interface is considered a source term in the transport equation and the oxygen flux through the structure is taken into account. The mass transport equations for both sides of the structure are solved analytically in terms of time evolution of DO concentration. The behaviour of the solution is illustrated for three different characteristic cases of initial conditions. The oxygen transfer through the air-water interface in the wave-influenced area increases the DO content in the area; the resulting oxygen flux through the structure is discussed. The analytical results depend on the initial conditions, the oxygen transfer coefficient and the exchange flow rate through the structure. Experiments with impermeable structures show that air water oxygen transfer in the harbour area is negligible in the absence of waves. In addition the ratio of the horizontal DO flux to the vertical flux into the seaward side tends towards a constant value, independent of the initial conditions.

  9. Charge transfer, bonding conditioning and solvation effect in the activation of the oxygen reduction reaction on unclustered graphitic-nitrogen-doped graphene.

    PubMed

    Ferre-Vilaplana, Adolfo; Herrero, Enrique

    2015-07-01

    The monodentate associative chemisorption of molecular oxygen on unclustered graphitic-nitrogen-doped graphene requires two nitrogen dopants per activated molecule. Significant charge transfers from regions corresponding to distant nitrogen-dopants, the presence of a nitrogen-dopant adjacent to the carbon atom acting as an active site, which favours its transition from a sp(2) hybridization state to sp(3), and the solvation effect turn the investigated mechanism to a favourable process.

  10. The Determination of Soil-plant Transfer Coefficients of Cesium-137 and Other Elements by γ-Ray Measurement and PIXE Analysis, for use in the Remediation of Fukushima

    NASA Astrophysics Data System (ADS)

    Ishii, K.; Fujita, A.; Toyama, S.; Terakawa, A.; Matsuyama, S.; Arai, H.; Osada, N.; Takyu, S.; Matsuyama, T.; Koshio, S.; Watanabe, K.; Ito, S.; Kasahara, K.

    Edible wild plants growing in the area around the Fukushima Daiichi nuclear power plant remain contaminated. It is important to identify plants with low levels of contamination for the restoration of agriculture in the area. We collected specimens of 10 wild plant species growing in Iitate village which is one of the most highly contaminated areas and also sampled the soil beneath each plant. We measured the specific activity of 137Cs and the concentrations of Na, Mg, Al, Si, P, S, K, Ca, Fe, Zn, Rb and Sr in these samples using a germanium detector and PIXE analysis, respectively. We compared the soil-plant transfer coefficient of 137Cs with those of each element and determined their correlation with 137Cs. It was found that a low Sr transfer coefficient could be used to determine the plants with a low 137Cs transfer coefficient. We suggest that PIXE analysis is a useful analysis technique for agricultural remediation projects in highly contaminated areas around the Fukushima Daiichi nuclear power plant.

  11. Three-dimensional three-phase model for simulation of hydrodynamics, oxygen mass transfer, carbon oxidation, nitrification and denitrification in an oxidation ditch.

    PubMed

    Lei, Li; Ni, Jinren

    2014-04-15

    A three-dimensional three-phase fluid model, supplemented by laboratory data, was developed to simulate the hydrodynamics, oxygen mass transfer, carbon oxidation, nitrification and denitrification processes in an oxidation ditch. The model provided detailed phase information on the liquid flow field, gas hold-up distribution and sludge sedimentation. The three-phase model described water-gas, water-sludge and gas-sludge interactions. Activated sludge was taken to be in a pseudo-solid phase, comprising an initially separated solid phase that was transported and later underwent biological reactions with the surrounding liquidmedia. Floc parameters were modified to improve the sludge viscosity, sludge density, oxygen mass transfer rate, and carbon substrate uptake due to adsorption onto the activated sludge. The validation test results were in very satisfactory agreement with laboratory data on the behavior of activated sludge in an oxidation ditch. By coupling species transport and biological process models, reasonable predictions are made of: (1) the biochemical kinetics of dissolved oxygen, chemical oxygen demand (COD) and nitrogen variation, and (2) the physical kinematics of sludge sedimentation.

  12. Heat transfer, diffusion, and evaporation

    NASA Technical Reports Server (NTRS)

    Nusselt, Wilhelm

    1954-01-01

    Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.

  13. Olefin epoxidation by the hydrogen peroxide adduct of a novel non-heme mangangese(IV) complex: demonstration of oxygen transfer by multiple mechanisms.

    PubMed

    Yin, Guochuan; Buchalova, Maria; Danby, Andrew M; Perkins, Chris M; Kitko, David; Carter, John D; Scheper, William M; Busch, Daryle H

    2006-04-17

    Olefin epoxidations are a class of reactions appropriate for the investigation of oxygenation processes in general. Here, we report the catalytic epoxidation of various olefins with a novel, cross-bridged cyclam manganese complex, Mn(Me2EBC)Cl2 (Me2EBC is 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane), using hydrogen peroxide as the terminal oxidant, in acetone/water (ratio 4:1) as the solvent medium. Catalytic epoxidation studies with this system have disclosed reactions that proceed by a nonradical pathway other than the expected oxygen-rebound mechanism that is characteristic of high-valent, late-transition-metal catalysts. Direct treatment of olefins with freshly synthesized [Mn(IV)(Me2EBC)(OH)2](PF6)2 (pKa = 6.86) in either neutral or basic solution confirms earlier observations that neither the oxo-Mn(IV) nor oxo-Mn(V) species is responsible for olefin epoxidization in this case. Catalytic epoxidation experiments using the 18O labels in an acetone/water (H2(18)O) solvent demonstrate that no 18O from water (H2(18)O) is incorporated into epoxide products even though oxygen exchange was observed between the Mn(IV) species and H2(18)O, which leads to the conclusion that oxygen transfer does not proceed by the well-known oxygen-rebound mechanism. Experiments using labeled dioxygen, (18)O2, and hydrogen peroxide, H2(18)O2, confirm that an oxygen atom is transferred directly from the H2(18)O2 oxidant to the olefin substrate in the predominant pathway. The hydrogen peroxide adduct of this high-oxidation-state manganese complex, Mn(IV)(Me2EBC)(O)(OOH)+, was detected by mass spectra in aqueous solutions prepared from Mn(II)(Me2EBC)Cl2 and excess hydrogen peroxide. A Lewis acid pathway, in which oxygen is transferred to the olefin from that adduct, Mn(IV)(Me2EBC)(O)(OOH)+, is proposed for epoxidation reactions mediated by this novel, non-heme manganese complex. A minor radical pathway is also apparent in these systems.

  14. Scope and limitations of the TEMPO/EPR method for singlet oxygen detection: the misleading role of electron transfer.

    PubMed

    Nardi, Giacomo; Manet, Ilse; Monti, Sandra; Miranda, Miguel A; Lhiaubet-Vallet, Virginie

    2014-12-01

    For many biological and biomedical studies, it is essential to detect the production of (1)O2 and quantify its production yield. Among the available methods, detection of the characteristic 1270-nm phosphorescence of singlet oxygen by time-resolved near-infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with a singlet oxygen probe. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6-tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been widely employed, it can produce misleading data. This is demonstrated by the present study, in which the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method are compared for a set of well-known photosensitizers. The results reveal that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizer is efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP(+) radical cation, followed by deprotonation and reaction with molecular oxygen, gives rise to an EPR-detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological, and medical studies.

  15. Oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives by nitrous oxide via selective oxygen atom transfer reactions: insights from quantum chemistry calculations.

    PubMed

    Xie, Hujun; Liu, Chengcheng; Yuan, Ying; Zhou, Tao; Fan, Ting; Lei, Qunfang; Fang, Wenjun

    2016-01-21

    The mechanisms for the oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives (Cp* = η(5)-C5Me5) by nitrous oxide via selective oxygen atom transfer reactions have been systematically studied by means of density functional theory (DFT) calculations. On the basis of the calculations, we investigated the original mechanism proposed by Hillhouse and co-workers for the activation of N2O. The calculations showed that the complex with an initial O-coordination of N2O to the coordinatively unsaturated Hf center is not a local minimum. Then we proposed a new reaction mechanism to investigate how N2O is activated and why N2O selectively oxidize phenyl and hydride ligands of . Frontier molecular orbital theory analysis indicates that N2O is activated by nucleophilic attack by the phenyl or hydride ligand. Present calculations provide new insights into the activation of N2O involving the direct oxygen atom transfer from nitrous oxide to metal-ligand bonds instead of the generally observed oxygen abstraction reaction to generate metal-oxo species.

  16. Influence of methanol/sorbitol co-feeding rate on pAOX1 induction in a Pichia pastoris Mut+ strain in bioreactor with limited oxygen transfer rate.

    PubMed

    Carly, F; Niu, H; Delvigne, F; Fickers, P

    2016-04-01

    High Pichia pastoris biomass density could be obtained using high co-feeding rate of methanol and sorbitol in a fed-batch or continuous culture, while further higher feeding rate finally leads to oxygen limitation in bioreactor. In the literature, there is lack of report about AOX1 promoter regulation with regard to dissolved oxygen level (DO). Therefore, in this work, chemostat cultures were performed to investigate the cell growth, metabolism and regulation of the AOX1 promoter (pAOX1) regarding co-feeding rate of optimized methanol/sorbitol mixture (methanol fraction 0.60 C-mol/C-mol) using a P. pastoris Mut+/pAOX1-lacZ strain. The oxygen transfer rates (OTR) in bioreactor were kept in the range of typical values of large bioreactor, i.e., 4-8 g/(L h) if DO equals 30 % saturation or 5-10 g/(L h) if DO nears zero. For DO >0, an increase of the carbon fed led to an increase of pAOX1 induction. By contrast, when dissolved oxygen was completely depleted, methanol accumulated, causing a 30 % decrease of pAOX1 induction. However, this decrease is more likely to be lined to methanol accumulation than to low level of dissolved oxygen (<4 % DO). Methanol/sorbitol co-feeding allowed cells to adapt to oxygen transient limitations that often occur at industrial scale with reduced effect on pAOX1 induction. The optimal feeding rate tested here was 6.6 mmol C (DCW h)(-1) at an OTR of 8.28 g O2(L h)(-1) with over fivefold pAOX1 induction (probably directly associated with target protein productivity) compared with previous work.

  17. Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion-Clipperton Fracture Zone

    NASA Astrophysics Data System (ADS)

    Mewes, K.; Mogollón, J. M.; Picard, A.; Rühlemann, C.; Eisenhauer, A.; Kuhn, T.; Ziebis, W.; Kasten, S.

    2016-01-01

    The Clarion-Clipperton Fracture Zone (CCFZ) in the Pacific Ocean is characterized by organic carbon-starved sediments and meter-scale oxygen penetration into the sediment. Furthermore, numerous seamounts occur throughout its deep-sea plain, which may serve as conduits for low-temperature hydrothermal seawater circulation through the oceanic crust. Recent studies in deep-sea environments of the Pacific and Atlantic Oceans have suggested and presented evidence of dissolved constituent exchange between the seawater flowing in the basaltic crust and the pore water of the overlying sediments. Through high-resolution pore-water oxygen and nutrient measurements, we examined fluxes and geochemical interactions between the seamount basaltic basement and pore waters of the overlying sediments at three sites located on a radial transect from the foot of Teddy Bare, a small seamount in the CCFZ. At three sites, located 1000, 700 and 400 m away from the foot of the seamount, we found that oxygen concentrations initially decrease with sediment depth but start to increase at depths of 3 and 7 m toward the basaltic basement. Nitrate (NO3-) concentrations mirror the oxygen concentration profiles, as they increase with sediment depth but decrease towards the basement. These profiles suggest an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments and a downward diffusion of NO32- from sediment pore water into the basaltic crust. At one site, we determined that the 87Sr/86Sr ratios of the bottom water and of the deep sediment near the basaltic crust are similar, further supporting diffusive exchange between basaltic crust fluids and sediment pore water. Transport-reaction modeling performed at two of the study sites revealed that (1) the diffusive flux of oxygen from the basaltic basement outpaces the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange

  18. Oxygen transfer from an intramolecularly coordinated diaryltellurium oxide to acetonitrile. Formation and combined AIM and ELI-D analysis of a novel diaryltellurium acetimidate.

    PubMed

    Mallow, Ole; Bolsinger, Jens; Finke, Pamela; Hesse, Malte; Chen, Yu-Sheng; Duthie, Andrew; Grabowsky, Simon; Luger, Peter; Mebs, Stefan; Beckmann, Jens

    2014-08-01

    The reaction of the intramolecularly coordinated diaryltellurium(IV) oxide (8-Me2NC10H6)2TeO with acetonitrile proceeds with oxygen transfer and gives rise to the formation of the novel zwitterionic diaryltelluronium(IV) acetimidate (8-Me2NC10H6)2TeNC(O)CH3 (1) in 57% yield. Hydrolysis of 1 with hydrochloric acid affords acetamide and the previously known diarylhydroxytelluronium(IV) chloride [(8-Me2NC10H6)2Te(OH)]Cl.

  19. Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings

    NASA Technical Reports Server (NTRS)

    Kannel, J. W.; Dufrane, K. F.; Zugaro, F. F.

    1981-01-01

    Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.

  20. The Unique Gas-Phase Chemistry of the [AuO](+) /CH4 Couple: Selective Oxygen-Atom Transfer to, Rather than Hydrogen-Atom Abstraction from, Methane.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-08-26

    The thermal reaction of [AuO](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied congener [CuO](+) , and to [AgO](+) , [AuO](+) reacts with CH4 exclusively via oxygen-atom transfer to form CH3 OH, and a novel mechanistic scenario for this selective oxidation process has been revealed. Also, the origin of the inertness of the [AgO](+) /CH4 couple has been addressed computationally. PMID:27390885

  1. Oxygen transfer from an intramolecularly coordinated diaryltellurium oxide to acetonitrile. Formation and combined AIM and ELI-D analysis of a novel diaryltellurium acetimidate.

    PubMed

    Mallow, Ole; Bolsinger, Jens; Finke, Pamela; Hesse, Malte; Chen, Yu-Sheng; Duthie, Andrew; Grabowsky, Simon; Luger, Peter; Mebs, Stefan; Beckmann, Jens

    2014-08-01

    The reaction of the intramolecularly coordinated diaryltellurium(IV) oxide (8-Me2NC10H6)2TeO with acetonitrile proceeds with oxygen transfer and gives rise to the formation of the novel zwitterionic diaryltelluronium(IV) acetimidate (8-Me2NC10H6)2TeNC(O)CH3 (1) in 57% yield. Hydrolysis of 1 with hydrochloric acid affords acetamide and the previously known diarylhydroxytelluronium(IV) chloride [(8-Me2NC10H6)2Te(OH)]Cl. PMID:25026100

  2. Home Oxygen Therapy

    MedlinePlus

    ... important advantage of liquid oxygen is you can transfer some of the liquid oxygen into a smaller, ... from gas stoves, candles, lighted fireplaces, or other heat sources. Don't use any flammable products like ...

  3. Low effective activation energies for oxygen release from metal oxides: evidence for mass-transfer limits at high heating rates.

    PubMed

    Jian, Guoqiang; Zhou, Lei; Piekiel, Nicholas W; Zachariah, Michael R

    2014-06-01

    Oxygen release from metal oxides at high temperatures is relevant to many thermally activated chemical processes, including chemical-looping combustion, solar thermochemical cycles and energetic thermite reactions. In this study, we evaluated the thermal decomposition of nanosized metal oxides under rapid heating (~10(5) K s(-1)) with time-resolved mass spectrometry. We found that the effective activation-energy values that were obtained using the Flynn-Wall-Ozawa isoconversional method are much lower than the values found at low heating rates, indicating that oxygen transport might be rate-determining at a high heating rate.

  4. In situ study of mass transfer in aqueous solutions under high pressures via Raman spectroscopy: A new method for the determination of diffusion coefficients of methane in water near hydrate formation conditions

    USGS Publications Warehouse

    Lu, W.J.; Chou, I.-Ming; Burruss, R.C.; Yang, M.Z.

    2006-01-01

    A new method was developed for in situ study of the diffusive transfer of methane in aqueous solution under high pressures near hydrate formation conditions within an optical capillary cell. Time-dependent Raman spectra of the solution at several different spots along the one-dimensional diffusion path were collected and thus the varying composition profile of the solution was monitored. Diffusion coefficients were estimated by the least squares method based on the variations in methane concentration data in space and time in the cell. The measured diffusion coefficients of methane in water at the liquid (L)-vapor (V) stable region and L-V metastable region are close to previously reported values determined at lower pressure and similar temperature. This in situ monitoring method was demonstrated to be suitable for the study of mass transfer in aqueous solution under high pressure and at various temperature conditions and will be applied to the study of nucleation and dissolution kinetics of methane hydrate in a hydrate-water system where the interaction of methane and water would be more complicated than that presented here for the L-V metastable condition. ?? 2006 Society for Applied Spectroscopy.

  5. Ground-state oxygen holes and the metal–insulator transition in the negative charge-transfer rare-earth nickelates

    PubMed Central

    Bisogni, Valentina; Catalano, Sara; Green, Robert J.; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Strocov, Vladimir N.; Zubko, Pavlo; Balandeh, Shadi; Triscone, Jean-Marc; Sawatzky, George; Schmitt, Thorsten

    2016-01-01

    The metal–insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal–insulator transition in terms of bond disproportionation. PMID:27725665

  6. A study of boiling heat transfer as applied to the cooling of ball bearings in the high pressure oxygen turbopump of the space shuttle main engine

    NASA Technical Reports Server (NTRS)

    Schreiber, Will

    1986-01-01

    Two sets of ball bearings support the main shaft within the High Pressure Oxygen Turbopump (HPOTP) in the Space Shuttle Main Engine (SSME). In operation, these bearings are cooled and lubricated with high pressure liquid oxygen (LOX) flowing axially through the bearing assembly. Currently, modifications in the assembly design are being contemplated in order to enhance the lifetime of the bearings and to allow the HPOTP to operate under larger loads. An understanding of the fluid dynamics and heat transfer characteristics of the flowing LOX is necessary for the implementation of these design changes. The proposed computational model of the LOX fluid dynamics, in addition to dealing with a turbulent flow in a complex geometry, must address the complication associated with boiling and two-phase flow. The feasibility of and possible methods for modeling boiling heat transfer are considered. The theory of boiling as pertains to this particular problem is reviewed. Recommendations are given for experiments which would be necessary to establish validity for correlations needed to model boiling.

  7. Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus.

    PubMed

    Pandelia, Maria-Eirini; Nitschke, Wolfgang; Infossi, Pascale; Giudici-Orticoni, Marie-Thérèse; Bill, Eckhard; Lubitz, Wolfgang

    2011-04-12

    Iron-sulfur clusters are versatile electron transfer cofactors, ubiquitous in metalloenzymes such as hydrogenases. In the oxygen-tolerant Hydrogenase I from Aquifex aeolicus such electron "wires" form a relay to a diheme cytb, an integral part of a respiration pathway for the reduction of O(2) to water. Amino acid sequence comparison with oxygen-sensitive hydrogenases showed conserved binding motifs for three iron-sulfur clusters, the nature and properties of which were unknown so far. Electron paramagnetic resonance spectra exhibited complex signals that disclose interesting features and spin-coupling patterns; by redox titrations three iron-sulfur clusters were identified in their usual redox states, a [3Fe4S] and two [4Fe4S], but also a unique high-potential (HP) state was found. On the basis of (57)Fe Mössbauer spectroscopy we attribute this HP form to a superoxidized state of the [4Fe4S] center proximal to the [NiFe] site. The unique environment of this cluster, characterized by a surplus cysteine coordination, is able to tune the redox potentials and make it compliant with the [4Fe4S](3+) state. It is actually the first example of a biological [4Fe4S] center that physiologically switches between 3+, 2+, and 1+ oxidation states within a very small potential range. We suggest that the (1 + /2+) redox couple serves the classical electron transfer reaction, whereas the superoxidation step is associated with a redox switch against oxidative stress.

  8. Ground-state oxygen holes and the metal-insulator transition in the negative charge-transfer rare-earth nickelates

    NASA Astrophysics Data System (ADS)

    Bisogni, Valentina; Catalano, Sara; Green, Robert J.; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Strocov, Vladimir N.; Zubko, Pavlo; Balandeh, Shadi; Triscone, Jean-Marc; Sawatzky, George; Schmitt, Thorsten

    2016-10-01

    The metal-insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal-insulator transition in terms of bond disproportionation.

  9. High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel

    NASA Technical Reports Server (NTRS)

    Jones, T. V.; Hippensteele, S. A.

    1987-01-01

    Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained.

  10. High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel

    NASA Technical Reports Server (NTRS)

    Jones, Terry V.; Hippensteele, Steven A.

    1988-01-01

    Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained.

  11. Oxygen safety

    MedlinePlus

    COPD - oxygen safety; Chronic obstructive pulmonary disease - oxygen safety; Chronic obstructive airways disease - oxygen safety; Emphysema - oxygen safety; Heart failure - oxygen-safety; Palliative care - oxygen safety; ...

  12. Measurements of average heat-transfer and friction coefficients for subsonic flow of air in smooth tubes at high surface and fluid temperatures

    NASA Technical Reports Server (NTRS)

    Humble, Leroy V; Lowdermilk, Warren H; Desmon, Leland G

    1951-01-01

    An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through smooth tubes for an over-all range of surface temperature from 535 degrees to 3050 degrees r, inlet-air temperature from 535 degrees to 1500 degrees r, Reynolds number up to 500,000, exit Mach number up to 1, heat flux up to 150,000 btu per hour per square foot, length-diameter ratio from 30 to 120, and three entrance configurations. Most of the data are for heat addition to the air; a few results are included for cooling of the air. The over-all range of surface-to-air temperature ratio was from 0.46 to 3.5.

  13. A New Global Potential Energy Surface for the Hydroperoxyl Radical, HO2: Reaction Coefficients for H + O2 and Vibrational Splittings for H Atom Transfer

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher E.; Arnold, James O. (Technical Monitor)

    1994-01-01

    A new analytic global potential energy surface describing the hydroperoxyl radical system H((sup 2)S) + O2(X (sup 3)Sigma((sup -)(sub g))) (reversible reaction) HO2 ((X-tilde) (sup 2)A'') (reversible reaction) O((sup 3)P) + O H (X (sup 2)Pi) has been fitted using the ab initio complete active space SCF (self-consistent-field)/externally contracted configuration interaction (CASSCF/CCI) energy calculations of Walch and Duchovic. Results of quasiclassical trajectory studies to determine the rate coefficients of the forward and reverse reactions at combustion temperatures will be presented. In addition, vibrational energy levels were calculated using the quantum DVR-DGB (discrete variable representation-distributed Gaussian basis) method and the splitting due to H atom migration is investigated. The material of the proposed presentation was reviewed and the technical content will not reveal any information not already in the public domain and will not give any foreign industry or government a competitive advantage.

  14. Scale-down assessment of the sensitivity of Yarrowia lipolytica to oxygen transfer and foam management in bioreactors: investigation of the underlying physiological mechanisms.

    PubMed

    Kar, Tambi; Destain, Jacqueline; Thonart, Philippe; Delvigne, Frank

    2012-02-01

    A scale-down investigation of the impact of local dissolved oxygen limitation on lipase production by Y. lipolytica has been performed. One of the major issues encountered during this kind of process is foam formation, requiring a reduction of the overall oxygen transfer efficiency of the system in order to keep antifoam consumption to a reasonable level. A regulation strategy involving oxygen enrichment of the air flow through the reactor has allowed this issue to be partly overcome. For a second time, the scale dependency of the process operated with air enrichment has been investigated by a combination of scale-down and pilot-scale cultivation tests. The scale-down apparatus considered in this work comprised a well-mixed part connected to a plug-flow part subjected to dissolved oxygen limitation. Surprisingly, foaming intensity was greatly reduced in the case of the test performed in scale-down reactors (SDRs) while maintaining the same stirring and aeration intensities in the stirred part of the reactor. For mean residence time of 100 s in the recycle loop of the reactor, foam formation was significantly reduced while cell growth and lipase production were both unaltered. When the residence time in the recycle loop was raised to 200 s, the foam phenomena was also reduced, but the lipase yield was altered as well as lip2 gene transcription and translation as shown by real-time quantitative polymerase chain reaction (RT-qPCR) and reporter gene activity, respectively. Our results clearly show the importance of primarily taking into account cell physiology for the scaling-up procedure.

  15. Replacement of tyrosine D with phenylalanine affects the normal proton transfer pathways for the reduction of P680+ in oxygen-evolving photosystem II particles from Chlamydomonas.

    PubMed

    Jeans, C; Schilstra, M J; Ray, N; Husain, S; Minagawa, J; Nugent, J H A; Klug, D R

    2002-12-31

    We have probed the electrostatics of P680(+) reduction in oxygenic photosynthesis using histidine-tagged and histidine-tagged Y(D)-less Photosystem II cores. We make two main observations: (i) that His-tagged Chlamydomonas cores show kinetics which are essentially identical to those of Photosystem II enriched thylakoid membranes from spinach; (ii) that the microsecond kinetics, previously shown to be proton/hydrogen transfer limited [Schilstra et al. (1998) Biochemistry 37, 3974-3981], are significantly different in Y(D)-less Chlamydomonas particles when compared with both the His-tagged Chlamydomonas particles and the spinach membranes. The oscillatory nature of the kinetics in both Chlamydomonas samples is normal, indicating that S-state cycling is unaffected by either the histidine-tagging or the replacement of tyrosine D with phenylalanine. We propose that the effects on the proton-coupled electron transfers of P680(+) reduction in the absence of Y(D) are likely to be due to pK shifts of residues in a hydrogen-bonded network of amino acids in the vicinity of Y(Z). Tyrosine D is 35 A from Y(Z) and yet has a significant influence on proton-coupled electron transfer events in the vicinity of Y(Z). This finding emphasizes the delicacy of the proton balance that Photosystem II has to achieve during the water splitting process. PMID:12501204

  16. Successful 2,000-Kilometer International Transfer of an Infant Receiving Extracorporeal Membrane Oxygenation for Severe Respiratory Failure.

    PubMed

    Brown, Kilian; Dunne, Ben; Festa, Marino; La Hei, Erik; Karpelowsky, Jonathan; Dando, Hayden; Orr, Yishay

    2016-08-01

    There is minimal reported experience with long-range retrieval of pediatric patients receiving extracorporeal membrane oxygenation (ECMO) support. We report the case of a 10-month old boy with necrotizing staphylococcal pneumonia complicated by a bronchopleural fistula, who was successfully retrieved and transported while receiving ECMO to our unit in Sydney, Australia, from a referring hospital 2,000 kilometers away in the Pacific Islands. He was successfully weaned from ECMO to receive single-lung ventilation after 13 days, and he underwent surgical repair of his bronchopleural fistula through a thoracotomy 3 days after decannulation. He has made a full recovery.

  17. Successful 2,000-Kilometer International Transfer of an Infant Receiving Extracorporeal Membrane Oxygenation for Severe Respiratory Failure.

    PubMed

    Brown, Kilian; Dunne, Ben; Festa, Marino; La Hei, Erik; Karpelowsky, Jonathan; Dando, Hayden; Orr, Yishay

    2016-08-01

    There is minimal reported experience with long-range retrieval of pediatric patients receiving extracorporeal membrane oxygenation (ECMO) support. We report the case of a 10-month old boy with necrotizing staphylococcal pneumonia complicated by a bronchopleural fistula, who was successfully retrieved and transported while receiving ECMO to our unit in Sydney, Australia, from a referring hospital 2,000 kilometers away in the Pacific Islands. He was successfully weaned from ECMO to receive single-lung ventilation after 13 days, and he underwent surgical repair of his bronchopleural fistula through a thoracotomy 3 days after decannulation. He has made a full recovery. PMID:27449448

  18. Computational investigation of longitudinal diffusion, eddy dispersion, and trans-particle mass transfer in bulk, random packings of core-shell particles with varied shell thickness and shell diffusion coefficient.

    PubMed

    Daneyko, Anton; Hlushkou, Dzmitry; Baranau, Vasili; Khirevich, Siarhei; Seidel-Morgenstern, Andreas; Tallarek, Ulrich

    2015-08-14

    In recent years, chromatographic columns packed with core-shell particles have been widely used for efficient and fast separations at comparatively low operating pressure. However, the influence of the porous shell properties on the mass transfer kinetics in core-shell packings is still not fully understood. We report on results obtained with a modeling approach to simulate three-dimensional advective-diffusive transport in bulk random packings of monosized core-shell particles, covering a range of reduced mobile phase flow velocities from 0.5 up to 1000. The impact of the effective diffusivity of analyte molecules in the porous shell and the shell thickness on the resulting plate height was investigated. An extension of Giddings' theory of coupled eddy dispersion to account for retention of analyte molecules due to stagnant regions in porous shells with zero mobile phase flow velocity is presented. The plate height equation involving a modified eddy dispersion term excellently describes simulated data obtained for particle-packings with varied shell thickness and shell diffusion coefficient. It is confirmed that the model of trans-particle mass transfer resistance of core-shell particles by Kaczmarski and Guiochon [42] is applicable up to a constant factor. We analyze individual contributions to the plate height from different mass transfer mechanisms in dependence of the shell parameters. The simulations demonstrate that a reduction of plate height in packings of core-shell relative to fully porous particles arises mainly due to reduced trans-particle mass transfer resistance and transchannel eddy dispersion.

  19. Computational investigation of longitudinal diffusion, eddy dispersion, and trans-particle mass transfer in bulk, random packings of core-shell particles with varied shell thickness and shell diffusion coefficient.

    PubMed

    Daneyko, Anton; Hlushkou, Dzmitry; Baranau, Vasili; Khirevich, Siarhei; Seidel-Morgenstern, Andreas; Tallarek, Ulrich

    2015-08-14

    In recent years, chromatographic columns packed with core-shell particles have been widely used for efficient and fast separations at comparatively low operating pressure. However, the influence of the porous shell properties on the mass transfer kinetics in core-shell packings is still not fully understood. We report on results obtained with a modeling approach to simulate three-dimensional advective-diffusive transport in bulk random packings of monosized core-shell particles, covering a range of reduced mobile phase flow velocities from 0.5 up to 1000. The impact of the effective diffusivity of analyte molecules in the porous shell and the shell thickness on the resulting plate height was investigated. An extension of Giddings' theory of coupled eddy dispersion to account for retention of analyte molecules due to stagnant regions in porous shells with zero mobile phase flow velocity is presented. The plate height equation involving a modified eddy dispersion term excellently describes simulated data obtained for particle-packings with varied shell thickness and shell diffusion coefficient. It is confirmed that the model of trans-particle mass transfer resistance of core-shell particles by Kaczmarski and Guiochon [42] is applicable up to a constant factor. We analyze individual contributions to the plate height from different mass transfer mechanisms in dependence of the shell parameters. The simulations demonstrate that a reduction of plate height in packings of core-shell relative to fully porous particles arises mainly due to reduced trans-particle mass transfer resistance and transchannel eddy dispersion. PMID:26162667

  20. Solid state oxygen sensor

    DOEpatents

    Garzon, Fernando H.; Chung, Brandon W.; Raistrick, Ian D.; Brosha, Eric L.

    1996-01-01

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer.

  1. Solid state oxygen sensor

    DOEpatents

    Garzon, F.H.; Chung, B.W.; Raistrick, I.D.; Brosha, E.L.

    1996-08-06

    Solid state oxygen sensors are provided with a yttria-doped zirconia as an electrolyte and use the electrochemical oxygen pumping of the zirconia electrolyte. A linear relationship between oxygen concentration and the voltage arising at a current plateau occurs when oxygen accessing the electrolyte is limited by a diffusion barrier. A diffusion barrier is formed herein with a mixed electronic and oxygen ion-conducting membrane of lanthanum-containing perovskite or zirconia-containing fluorite. A heater may be used to maintain an adequate oxygen diffusion coefficient in the mixed conducting layer. 4 figs.

  2. Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

    PubMed Central

    Díaz-Barrera, Alvaro; Martínez, Fabiola; Guevara Pezoa, Felipe; Acevedo, Fernando

    2014-01-01

    Alginates are polysaccharides used as food additives and encapsulation agents in biotechnology, and their functional properties depend on its molecular weight. In this study, different steady-states in continuous cultures of A. vinelandii were established to determine the effect of the dilution rate (D) and the agitation rate on alginate production and expression of genes involved in alginate polymerization and depolymerization. Both, the agitation and dilution rates, determined the partitioning of the carbon utilization from sucrose into alginate and CO2 under oxygen-limiting conditions. A low D (0.07 h−1) and 500 rpm resulted in the highest carbon utilization into alginate (25%). Quantitative real-time polymerase chain reaction was used to determine the transcription level of six genes involved in alginate polymerization and depolymerization. In chemostat cultures at 0.07 h−1, the gene expression was affected by changes in the agitation rate. By increasing the agitation rate from 400 to 600 rpm, the algE7 gene expression decreased tenfold, whereas alyA1, algL and alyA2 gene expression increased between 1.5 and 2.8 times under similar conditions evaluated. Chemostat at 0.07 h−1 showed a highest alginate molecular weight (580 kDa) at 500 rpm whereas similar molecular weights (480 kDa) were obtained at 400 and 600 rpm. The highest molecular weight was not explained by changes in the expression of alg8 and alg44 (genes involved in alginate polymerization). Nonetheless, a different expression pattern observed for lyases could explain the highest alginate molecular weight obtained. Overall, the results suggest that the control of alginate molecular weight in A. vinelandii cells growing in continuous mode is determined by a balance between the gene expression of intracellular and extracellular lyases in response to oxygen availability. These findings better our understanding of the biosynthesis of bacterial alginate and help us progress toward obtain tailor

  3. Evaluation of gene expression and alginate production in response to oxygen transfer in continuous culture of Azotobacter vinelandii.

    PubMed

    Díaz-Barrera, Alvaro; Martínez, Fabiola; Pezoa, Felipe Guevara; Acevedo, Fernando

    2014-01-01

    Alginates are polysaccharides used as food additives and encapsulation agents in biotechnology, and their functional properties depend on its molecular weight. In this study, different steady-states in continuous cultures of A. vinelandii were established to determine the effect of the dilution rate (D) and the agitation rate on alginate production and expression of genes involved in alginate polymerization and depolymerization. Both, the agitation and dilution rates, determined the partitioning of the carbon utilization from sucrose into alginate and CO2 under oxygen-limiting conditions. A low D (0.07 h(-1)) and 500 rpm resulted in the highest carbon utilization into alginate (25%). Quantitative real-time polymerase chain reaction was used to determine the transcription level of six genes involved in alginate polymerization and depolymerization. In chemostat cultures at 0.07 h(-1), the gene expression was affected by changes in the agitation rate. By increasing the agitation rate from 400 to 600 rpm, the algE7 gene expression decreased tenfold, whereas alyA1, algL and alyA2 gene expression increased between 1.5 and 2.8 times under similar conditions evaluated. Chemostat at 0.07 h(-1) showed a highest alginate molecular weight (580 kDa) at 500 rpm whereas similar molecular weights (480 kDa) were obtained at 400 and 600 rpm. The highest molecular weight was not explained by changes in the expression of alg8 and alg44 (genes involved in alginate polymerization). Nonetheless, a different expression pattern observed for lyases could explain the highest alginate molecular weight obtained. Overall, the results suggest that the control of alginate molecular weight in A. vinelandii cells growing in continuous mode is determined by a balance between the gene expression of intracellular and extracellular lyases in response to oxygen availability. These findings better our understanding of the biosynthesis of bacterial alginate and help us progress toward obtain tailor

  4. High-yield production of biologically active recombinant protein in shake flask culture by combination of enzyme-based glucose delivery and increased oxygen transfer

    PubMed Central

    2011-01-01

    This report describes the combined use of an enzyme-based glucose release system (EnBase®) and high-aeration shake flask (Ultra Yield Flask™). The benefit of this combination is demonstrated by over 100-fold improvement in the active yield of recombinant alcohol dehydrogenase expressed in E. coli. Compared to Terrific Broth and ZYM-5052 autoinduction medium, the EnBase system improved yield mainly through increased productivity per cell. Four-fold increase in oxygen transfer by the Ultra Yield Flask contributed to higher cell density with EnBase but not with the other tested media, and consequently the product yield per ml of EnBase culture was further improved. PMID:22152005

  5. Enhancement of oxygen mass transfer and gas holdup using palm oil in stirred tank bioreactors with xanthan solutions as simulated viscous fermentation broths.

    PubMed

    Mohd Sauid, Suhaila; Krishnan, Jagannathan; Huey Ling, Tan; Veluri, Murthy V P S

    2013-01-01

    Volumetric mass transfer coefficient (kLa) is an important parameter in bioreactors handling viscous fermentations such as xanthan gum production, as it affects the reactor performance and productivity. Published literatures showed that adding an organic phase such as hydrocarbons or vegetable oil could increase the kLa. The present study opted for palm oil as the organic phase as it is plentiful in Malaysia. Experiments were carried out to study the effect of viscosity, gas holdup, and kLa on the xanthan solution with different palm oil fractions by varying the agitation rate and aeration rate in a 5 L bench-top bioreactor fitted with twin Rushton turbines. Results showed that 10% (v/v) of palm oil raised the kLa of xanthan solution by 1.5 to 3 folds with the highest kLa value of 84.44 h(-1). It was also found that palm oil increased the gas holdup and viscosity of the xanthan solution. The kLa values obtained as a function of power input, superficial gas velocity, and palm oil fraction were validated by two different empirical equations. Similarly, the gas holdup obtained as a function of power input and superficial gas velocity was validated by another empirical equation. All correlations were found to fit well with higher determination coefficients.

  6. Quenching of electron transfer reactions through coadsorption: A study of oxygen photodesorption from TiO2(110)

    DOE PAGES

    Petrik, Nikolay G.; Kimmel, Greg A.; Shen, Mingmin; Henderson, Michael A.

    2016-01-11

    Using temperature programmed desorption (TPD) and photon-stimulated desorption (PSD), we show that coadsorbates of varying binding energies on the rutile TiO2(110) surface exert a commensurate inhibiting influence on the hole-mediated photodesorption of adsorbed O2. A variety of coadsorbates (Ar, Kr, Xe, N2, CO, CO2, CH4, N2O, acetone, methanol or water) were shown to quench O2 photoactivity, with the extent correlating with the coadsorbate's gas phase basicity, which in turn determines the strength of the coadsorbate–Ti4+ bond. Coadsorbed rare gases inhibited the photodesorption of O2 by ~ 10–25%, whereas strongly bound species (water, methanol, and acetone) nearly completely inhibited O2 PSD.more » We suggest that coadsorption of these molecules inhibit the arrival probability of holes to the surface. Band-bending effects, which vary with the extent of charge transfer between the coadsorbate and the TiO2(110) surface, are not expected to be significant in the cases of the rare gases and physisorbed species. Furthermore, these results indicate that neutral coadsorbates can exert a significant influence on charge transfer events by altering the interfacial dipole in the vicinity of the target molecule.« less

  7. Quenching of electron transfer reactions through coadsorption: A study of oxygen photodesorption from TiO2(110)

    NASA Astrophysics Data System (ADS)

    Petrik, Nikolay G.; Kimmel, Greg A.; Shen, Mingmin; Henderson, Michael A.

    2016-10-01

    Using temperature programmed desorption (TPD) and photon-stimulated desorption (PSD), we show that coadsorbates of varying binding energies on the rutile TiO2(110) surface exert a commensurate inhibiting influence on the hole-mediated photodesorption of adsorbed O2. A variety of coadsorbates (Ar, Kr, Xe, N2, CO, CO2, CH4, N2O, acetone, methanol or water) were shown to quench O2 photoactivity, with the extent correlating with the coadsorbate's gas phase basicity, which in turn determines the strength of the coadsorbate-Ti4 + bond. Coadsorbed rare gases inhibited the photodesorption of O2 by ~ 10-25%, whereas strongly bound species (water, methanol, and acetone) nearly completely inhibited O2 PSD. We suggest that coadsorption of these molecules inhibit the arrival probability of holes to the surface. Band-bending effects, which vary with the extent of charge transfer between the coadsorbate and the TiO2(110) surface, are not expected to be significant in the cases of the rare gases and physisorbed species. These results indicate that neutral coadsorbates can exert a significant influence on charge transfer events by altering the interfacial dipole in the vicinity of the target molecule.

  8. Covalent versus Charge Transfer Modification of Graphene/Carbon-Nanotubes with Vitamin B1: Co/N/S-C Catalyst toward Excellent Oxygen Reduction.

    PubMed

    Vij, Varun; Tiwari, Jitendra N; Kim, Kwang S

    2016-06-29

    High-performance nonprecious cathodic catalysts for oxygen reduction are highly demanded for low-temperature polymer electrolyte membrane fuel cells (PEMFCs). Here, we report a noble-meta- free, nitrogen and sulfur codoped graphene(G)/carbon-nanotube(CNT) material decorated with Co nanoparticles (NPs), which serve as catalytic sites for excellent oxygen reduction reaction (ORR) in basic and acidic media. Out of the cathodic catalysts synthesized by either covalent (cov) or charge transfer (CT) modification of graphen oxide (GO) with thiamine (Th: Vitamin B1), ThG/CNT/Co-cov shows more promising ORR properties than ThG/CNT/Co-CT. Catalyst ThG/CNT/Co-cov exhibits onset/halfwave potentials of 0.95/0.86 V in 0.1 M KOH and 0.92/0.83 V in 0.1 M HClO4, which are comparable to those of commercial catalyst Pt/C (0.95/0.86 V). As compared to Pt/C, our catalyst shows higher current densities of 6.72 mA cm(-2) in basic medium and 7.08 mA cm(-2) in acidic medium at 0.55 V (vs reversible hydrogen electrode (RHE)). It also exhibits better catalytic stability and methanol tolerance. High catalytic efficiency and stability of ThG/CNT/Co-cov show a promising prospect of materialization of PEMFCs for clean energy production. PMID:27255326

  9. The Molybdenum Active Site of Formate Dehydrogenase Is Capable of Catalyzing C-H Bond Cleavage and Oxygen Atom Transfer Reactions.

    PubMed

    Hartmann, Tobias; Schrapers, Peer; Utesch, Tillmann; Nimtz, Manfred; Rippers, Yvonne; Dau, Holger; Mroginski, Maria Andrea; Haumann, Michael; Leimkühler, Silke

    2016-04-26

    Formate dehydrogenases (FDHs) are capable of performing the reversible oxidation of formate and are enzymes of great interest for fuel cell applications and for the production of reduced carbon compounds as energy sources from CO2. Metal-containing FDHs in general contain a highly conserved active site, comprising a molybdenum (or tungsten) center coordinated by two molybdopterin guanine dinucleotide molecules, a sulfido and a (seleno-)cysteine ligand, in addition to a histidine and arginine residue in the second coordination sphere. So far, the role of these amino acids in catalysis has not been studied in detail, because of the lack of suitable expression systems and the lability or oxygen sensitivity of the enzymes. Here, the roles of these active site residues is revealed using the Mo-containing FDH from Rhodobacter capsulatus. Our results show that the cysteine ligand at the Mo ion is displaced by the formate substrate during the reaction, the arginine has a direct role in substrate binding and stabilization, and the histidine elevates the pKa of the active site cysteine. We further found that in addition to reversible formate oxidation, the enzyme is further capable of reducing nitrate to nitrite. We propose a mechanistic scheme that combines both functionalities and provides important insights into the distinct mechanisms of C-H bond cleavage and oxygen atom transfer catalyzed by formate dehydrogenase. PMID:27054466

  10. The Prediction of Nozzle Performance and Heat Transfer in Hydrogen/Oxygen Rocket Engines with Transpiration Cooling, Film Cooling, and High Area Ratios

    NASA Technical Reports Server (NTRS)

    Kacynski, Kenneth J.; Hoffman, Joe D.

    1994-01-01

    An advanced engineering computational model has been developed to aid in the analysis of chemical rocket engines. The complete multispecies, chemically reacting and diffusing Navier-Stokes equations are modelled, including the Soret thermal diffusion and Dufour energy transfer terms. Demonstration cases are presented for a 1030:1 area ratio nozzle, a 25 lbf film-cooled nozzle, and a transpiration-cooled plug-and-spool rocket engine. The results indicate that the thrust coefficient predictions of the 1030:1 nozzle and the film-cooled nozzle are within 0.2 to 0.5 percent, respectively, of experimental measurements. Further, the model's predictions agree very well with the heat transfer measurements made in all of the nozzle test cases. It is demonstrated that thermal diffusion has a significant effect on the predicted mass fraction of hydrogen along the wall of the nozzle and was shown to represent a significant fraction of the diffusion fluxes occurring in the transpiration-cooled rocket engine.

  11. Metallized Gelled Propellants: Heat Transfer of a Rocket Engine Fueled by Oxygen/RP-1/Aluminum Was Measured by a Calorimeter

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan A.

    1998-01-01

    A set of analyses was conducted to determine the heat transfer characteristics of metallized gelled liquid propellants in a rocket engine. These analyses used data from experiments conducted with a small 30- to 40-lbf thrust engine composed of a modular injector, igniter, chamber, and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum (Al) with gaseous oxygen as the oxidizer. Heat transfer measurements were made with a calorimeter chamber and nozzle setup that had a total of 31 cooling channels. A gelled fuel coating, composed of unburned gelled fuel and partially combusted RP-1, formed in the 0-, 5- and 55-wt % engines. For the 0- and 5-wt % RP-1/Al, the coating caused a large decrease in calorimeter engine heat flux in the last half of the chamber. This heat flux reduction was analyzed by comparing engine firings and the changes in the heat flux during a firing at NASA Lewis Research Center's Rocket Laboratories. This work is part of an ongoing series of analyses of metallized gelled propellants.

  12. Transient free radicals in iron/oxygen reconstitution of mutant protein R2 Y122F. Possible participants in electron transfer chains in ribonucleotide reductase.

    PubMed

    Sahlin, M; Lassmann, G; Pötsch, S; Sjöberg, B M; Gräslund, A

    1995-05-26

    Ferrous iron/oxygen reconstitution of the mutant R2 apoprotein Y122F leads to formation of a diferric center similar to that of the wild-type R2 protein of Escherichia coli ribonucleotide reductase. This reconstitution reaction requires two extra electrons, supplied or transferred by the protein matrix of R2. We observed several transient free radical species using stopped flow and freeze quench EPR and stopped flow UV-visible spectroscopy. Three of the radicals occur in the time window 0.1-2 s, i.e. concomitant with formation of the diferric site. They include a strongly iron-coupled radical (singlet EPR signal) observed only at < or = 77 K, a singlet EPR signal observed only at room temperature, and a radical at Tyr-356 (light absorption at 410 nm), an invariant residue proposed to be part of an electron transfer chain in catalysis. Three additional transient radicals species are observed in the time window 6 s to 20 min. Two of these are conclusively identified, by specific deuteration, as tryptophan radicals. Comparing side chain geometry and distance to the iron center with EPR characteristics of the radicals, we propose certain Trp residues in R2 as likely to harbor these transient radicals.

  13. Air-water transfer of MTBE, its degradation products, and alternative fuel oxygenates: the role of temperature.

    PubMed

    Arp, Hans Peter H; Schmidt, Torsten C

    2004-10-15

    The gasoline oxygenate methyl tert-butyl ether (MTBE) has become one of the world's mostwidespread groundwater and surface water contaminants. As a result, there has been increasing interest in the environmental behavior of MTBE and its degradation products, mainly tert-butyl formate (TBF) and tert-butyl alcohol (TBA). In contrast, the environmental behavior of the proposed alternatives to MTBE, namely ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and diisopropyl ether (DIPE) has hardly been studied yet, although some of them are already in substantial use in various countries. A key parameter for the assessment of the fate, transport, and possible remediation of these contaminants is the air-water partitioning constant (KiH). The KiH is highly temperature dependent, and it is therefore necessary to obtain reliable experimental values at relevant temperatures. Hence, the KiH of MTBE, ETBE, TAME, and DIPE, along with the degradation products, TBF and methyl acetate, were determined from 5 degrees C-40 degrees C. The alternatives to MTBE generally had a higher KiH, which implies that, upon emission into the environment, the alternatives partition more readily into the air phase than MTBE. This may favor their use, as it is in the air phase where dilution and degradation are the most effective. The degradation products of MTBE, with the exception of TBF, have much lower KiH values at all temperatures. Hence, the degradation products will have a stronger affinity for the water phase. The temperature dependency of the kinetics of air-watertransfer is discussed using a boundary layer model. Only for TBA but not for the ethers a significant effect of temperature was found.

  14. DFT study on the oxygen transfer mechanism in nitroethenediamine based H2-receptor antagonists using the bis-dithiolene complex as the model catalyst for N-oxide reductase enzyme.

    PubMed

    Dhaked, Devendra K; Bharatam, Prasad V

    2015-01-01

    Nitroethenediamine is an important functional unit, which is present in H2-receptor antagonists. These drugs show low bioavailability due to the bacterial degradation caused by the N-oxide reductase type of enzymes present in the human colon. Quantum chemical studies have been carried out to elucidate the mechanism of metabolic degradation of nitroethenediamine in the active site of N-oxide reductase. Three different pathways have been explored for the N-oxide bond cleavage by the model system, Mo(IV) bis-dithiolene complex [Mo(OMe)(mdt)2](-), (where mdt=1,2-dimethyl-ethene-1,2-dithiolate) using B3LYP/6-311+G(d,p) and M06/6-311+G(d,p) Density Functional Theory methods. The oxygen atom transfer from the nitrogen atom of nitroethenediamine to the Mo(IV) complex, involves simultaneous weakening of the N-oxide bond and the formation of Mo-O bond through a least motion path. During this transfer, Mo center is converted from a square pyramidal geometry to a distorted octahedral geometry, to facilitate the process of oxygen atom transfer. The energy barrier for the oxygen atom transfer from the imine tautomer has been estimated to be 25.9kcal/mol however, the overall reaction has been found to be endothermic. On the other hand, oxygen transfer reaction from the nitronic acid tautomer requires 30.5kcal/mol energy leading to a highly exothermic metabolite (M-1) directly hence, this path can be considered thermodynamically favorable for this metabolite. The alternative path involving the oxygen atom transfer from the enamine tautomer requires comparatively a higher energy barrier (32.6kcal/mol) and leads to a slightly endothermic metabolite. This study established the structural and energetic details associated with the Mo(IV) bis-dithiolene complex that catalyzes the degradation of nitroethenediamine based drug molecules.

  15. Characterization of oxygen transfer in miniature and lab-scale bubble column bioreactors and comparison of microbial growth performance based on constant k(L)a.

    PubMed

    Doig, Steven D; Ortiz-Ochoa, Kenny; Ward, John M; Baganz, Frank

    2005-01-01

    This work describes the engineering characterization of miniature (2 mL) and laboratory-scale (100 mL) bubble column bioreactors useful for the cultivation of microbial cells. These bioreactors were constructed of glass and used a range of sintered glass gas diffusers with differently sized pores to disperse humidified air within the liquid biomedium. The effect of the pressure of this supplied air on the breakthrough point for gas diffusers with different pore sizes was examined and could be predicted using the Laplace-Young equation. The influence of the superficial gas velocity (u(g)) on the volumetric mass transfer coefficient (k(L)a) was determined, and values of up to 0.09 s(-1) were observed in this work. Two modeling approaches were considered in order to predict and provide comparison criteria. The first related the volumetric power consumption (P/V) to the k(L)a and a good correlation was obtained for differently sized reactors with a given pore size, but this correlation was not satisfactory for bubble columns with different gas diffusers. Values for P/V ranged from about 10 to 400 W.m(-3). Second, a model was developed predicting bubble size (d(b)), bubble rising velocity (u(b)), gas hold-up (phi), liquid side mass transfer coefficient (k(L)), and thus the k(L)a using established theory and empirical correlations. Good agreement was found with our experimental data at different scales and pore sizes. Values for d(b) varied from 0.1 to 0.6 mm, and k(L) values between 1.7 and 9.8 x 10(-4) m.s(-1) were determined. Several E. coli cultivations were performed in the miniature bubble column at low and high k(L)a values, and the results were compared to those from a conventional stirred tank operated under identical k(L)a values. Results from the two systems were similar in terms of biomass growth rate and carbon source utilization.

  16. Factor Scores, Structure Coefficients, and Communality Coefficients

    ERIC Educational Resources Information Center

    Goodwyn, Fara

    2012-01-01

    This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…

  17. Atomic Oxygen Textured Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Hunt, Jason D.; Drobotij, Erin; Cales, Michael R.; Cantrell, Gidget

    1995-01-01

    Atomic oxygen can be used to microscopically alter the surface morphology of polymeric materials in space or in ground laboratory facilities. For polymeric materials whose sole oxidation products are volatile species, directed atomic oxygen reactions produce surfaces of microscopic cones. However, isotropic atomic oxygen exposure results in polymer surfaces covered with lower aspect ratio sharp-edged craters. Isotropic atomic oxygen plasma exposure of polymers typically causes a significant decrease in water contact angle as well as altered coefficient of static friction. Such surface alterations may be of benefit for industrial and biomedical applications. The results of atomic oxygen plasma exposure of thirty-three (33) different polymers are presented, including typical morphology changes, effects on water contact angle, and coefficient of static friction.

  18. Development of a novel electrochemical system for oxygen control (ESOC) to examine dissolved oxygen inhibition on algal activity.

    PubMed

    Keymer, Philip C; Pratt, Steven; Lant, Paul A

    2013-09-01

    The development of an Electrochemical System for Oxygen Control (ESOC) for examining algal photosynthetic activity as a function of dissolved oxygen (DO) is outlined. The main innovation of the tool is coulombic titration in order to balance the electrochemical reduction of oxygen with the oxygen input to achieve a steady DO set-point. ESOC allows quantification of algal oxygen production whilst simultaneously maintaining a desired DO concentration. The tool was validated abiotically by comparison with a mass transfer approach for quantifying oxygenation. It was then applied to quantify oxygen inhibition of algal activity. Five experiments, using an enriched culture of Scenedesmus sp. as the inoculum, are presented. For each experiment, ESOC was used to quantify algal activity at a series of DO set-points. In all experiments substantial oxygen inhibition was observed at DO >30 mgO2 L-1. Inhibition was shown to fit a Hill inhibition model, with a common Hill coefficient of 0.22±0.07 L mg-1 and common log10  CI50 of 27.2±0.7 mg L-1. This is the first time that the oxygen inhibition kinetic parameters have been quantified under controlled DO conditions.

  19. Oxygen atom transfer between rhenium, sulfur, and phosphorus. Characterization and reactivity of Re(O)Cl/sub 3/(Me/sub 2/S)(OPPh/sub 3/) and Re(O)Cl/sub 3/(CNCMe/sub 3/)/sub 2/

    SciTech Connect

    Bryan, J.C.; Stenkamp, R.E.; Tulip, T.H.; Mayer, J.M.

    1987-07-15

    Re(O)Cl/sub 3/(PPh/sub 3/)/sub 2/ (I) reacts with Me/sub 2/SO to form OPPh/sub 3/ and Re(O)Cl/sub 3/(Me/sub 2/S)(OPPh/sub 3/) (II), not Re(O)Cl/sub 3/(Me/sub 2/SO)(PPh/sub 3/) as had been previously reported. Compounds I and II are catalysts for oxygen atom transfer from Me/sub 2/SO to PPh/sub 3/. The mechanism of these oxygen atom transfer reactions has been studied with oxygen-18 labeling experiments. The rhenium oxo group does not appear to be involved; rather, the rhenium center acts as a Lewis acid activator for a Me/sub 2/SO ligand. The rhenium oxo group does, however, exchange oxygen atoms with Me/sub 2/S/sup 18/O, probably by a similar mechanism. Compound II is an excellent starting material for compounds of the form Re(O)Cl/sub 3/L/sub 2/, with L = isonitriles, phosphines, bipyridine, etc. The compounds Re(O)Cl/sub 3/-(CNR)/sub 2/ (R = CMe/sub 3/ (IV), CHMe/sub 2/, C/sub 6/H/sub 11/) are rare examples of high-valent isonitrile complexes. Data from an X-ray crystal structure of IV are reported. 36 references, 2 figures, 3 tables.

  20. Unifying mechanism for bacterial cell signalers (4,5-dihydroxy-2,3-pentanedione, lactones and oligopeptides): electron transfer and reactive oxygen species. Practical medical features.

    PubMed

    Kovacic, Peter

    2007-01-01

    Cell signaling has attracted much attention involving higher organisms, and more recently is of considerable interest concerning involvement in the bacterial realm. Many aspects can apply, including quorum sensing. Of the participating molecules, designated autoinducers, 4,5-dihydroxy-2,3-pentanedione (DPD) is one of the most important. It is in equilibrium with a furanone and a furanosyl-borate diester (AI-2). A prior hypothesis for cell signaling in higher organisms invoked a key role for electron transfer (ET) and reactive oxygen species (ROS), as well as conduits, relays and electrical effects. The principal ET functionalities are quinones, metal complexes, ArNO(2), and iminium species. A lesser known type is the alpha-dicarbonyl class. Diacetyl, a member, as well as its imine derivatives, can serve as a model for DPD, since the parent possesses a reduction potential amenable to ET in the biological domain. Hence, it is conceivable that DPD and its imine derivatives may be involved in ET-ROS processes. Presence of hydroxy groups should facilitate ET by DPD vs. diacetyl. Extensive prior literature supports participation of ET functionalities in action of therapeutic drugs, toxins and various illnesses. This biochemical behavior also applies to the alpha-dicarbonyl parent models. A second important bacterial autoinducer is the lactone category. Although ET functionality is lacking, the presence of the 1,3-dicarbonyl structure can provide a site for avid chelation with redox metal, e.g., iron or copper, followed by ET-ROS. Findings with added iron furnish support for the proposal. Oligopeptides comprise the third principal type of bacterial signaling agent. A prior review incorporates these within the theoretical framework based on ET by redox amino acids and redox enzymes. In recent years there has been a rapid increase in resistance to antibiotics by pathogenic bacteria. Infectious diseases are the leading cause of death worldwide and the third leading cause in

  1. Oxygen Therapy

    MedlinePlus

    Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb ... in your home. A different kind of oxygen therapy is called hyperbaric oxygen therapy. It uses oxygen ...

  2. Molecular Diffusion Coefficients: Experimental Determination and Demonstration.

    ERIC Educational Resources Information Center

    Fate, Gwendolyn; Lynn, David G.

    1990-01-01

    Presented are laboratory methods which allow the demonstration and determination of the diffusion coefficients of compounds ranging in size from water to small proteins. Included are the procedures involving the use of a spectrometer, UV cell, triterated agar, and oxygen diffusion. Results including quantification are described. (CW)

  3. Oxygen Sag and Stream Purification.

    ERIC Educational Resources Information Center

    Neal, Larry; Herwig, Roy

    1978-01-01

    Presents a literature review of water quality related to oxygen sag and stream purification, covering publications of 1976-77. This review includes: (1) self-purification models; (2) oxygen demand; and (3) reaeration and oxygen transfer. A list of 60 references is also presented. (HM)

  4. Dicobalt-μ-oxo polyoxometalate compound, [(α(2)-P2W17O61Co)2O](14-): a potent species for water oxidation, C-H bond activation, and oxygen transfer.

    PubMed

    Barats-Damatov, Delina; Shimon, Linda J W; Weiner, Lev; Schreiber, Roy E; Jiménez-Lozano, Pablo; Poblet, Josep M; de Graaf, Coen; Neumann, Ronny

    2014-02-01

    High-valent oxo compounds of transition metals are often implicated as active species in oxygenation of hydrocarbons through carbon-hydrogen bond activation or oxygen transfer and also in water oxidation. Recently, several examples of cobalt-catalyzed water oxidation have been reported, and cobalt(IV) species have been suggested as active intermediates. A reactive species, formally a dicobalt(IV)-μ-oxo polyoxometalate compound [(α2-P2W17O61Co)2O](14-), [(POMCo)2O], has now been isolated and characterized by the oxidation of a monomeric [α2-P2W17O61Co(II)(H2O)](8-), [POMCo(II)H2O], with ozone in water. The crystal structure shows a nearly linear Co-O-Co moiety with a Co-O bond length of ∼1.77 Å. In aqueous solution [(POMCo)2O] was identified by (31)P NMR, Raman, and UV-vis spectroscopy. Reactivity studies showed that [(POMCo)2O]2O] is an active compound for the oxidation of H2O to O2, direct oxygen transfer to water-soluble sulfoxides and phosphines, indirect epoxidation of alkenes via a Mn porphyrin, and the selective oxidation of alcohols by carbon-hydrogen bond activation. The latter appears to occur via a hydrogen atom transfer mechanism. Density functional and CASSCF calculations strongly indicate that the electronic structure of [(POMCo)2O]2O] is best defined as a compound having two cobalt(III) atoms with two oxidized oxygen atoms.

  5. Toward a Full Simulation of the Basic Oxygen Furnace: Deformation of the Bath Free Surface and Coupled Transfer Processes Associated with the Post-Combustion in the Gas Region

    NASA Astrophysics Data System (ADS)

    Doh, Y.; Chapelle, P.; Jardy, A.; Djambazov, G.; Pericleous, K.; Ghazal, G.; Gardin, P.

    2013-06-01

    The present article treats different phenomena taking place in a steelmaking converter through the development of two separate models. The first model describes the cavity produced at the free surface of the metal bath by the high-speed impinging oxygen jet. The model is based on a zonal approach, where gas compressibility effects are taken into account only in the high velocity jet region, while elsewhere the gas is treated as incompressible. The volume of fluid (VOF) method is employed to follow the deformation of the bath free surface. Calculations are presented for two- and three-phase systems and compared against experimental data obtained in a cold model experiment presented in the literature. The influence on the size and shape of the cavity of various parameters and models (including the jet inlet boundary conditions, the VOF advection scheme, and the turbulence model) is studied. Next, the model is used to simulate the interaction of a supersonic oxygen jet with the surface of a liquid steel bath in a pilot-scale converter. The second model concentrates on fluid flow, heat transfer, and the post-combustion reaction in the gas phase above the metal bath. The model uses the simple chemical reaction scheme approach to describe the transport of the chemical species and takes into account the consumption of oxygen by the bath and thermal radiative transfer. The model predictions are in reasonable agreement with measurements collected in a laboratory experiment and in a pilot-scale furnace.

  6. Monolithic solid electrolyte oxygen pump

    DOEpatents

    Fee, Darrell C.; Poeppel, Roger B.; Easler, Timothy E.; Dees, Dennis W.

    1989-01-01

    A multi-layer oxygen pump having a one-piece, monolithic ceramic structure affords high oxygen production per unit weight and volume and is thus particularly adapted for use as a portable oxygen supply. The oxygen pump is comprised of a large number of small cells on the order of 1-2 millimeters in diameter which form the walls of the pump and which are comprised of thin, i.e., 25-50 micrometers, ceramic layers of cell components. The cell components include an air electrode, an oxygen electrode, an electrolyte and interconnection materials. The cell walls form the passages for input air and for exhausting the oxygen which is transferred from a relatively dilute gaseous mixture to a higher concentration by applying a DC voltage across the electrodes so as to ionize the oxygen at the air electrode, whereupon the ionized oxygen travels through the electrolyte and is converted to oxygen gas at the oxygen electrode.

  7. Experimental study of dissolved oxygen transport by regular waves through a perforated breakwater

    NASA Astrophysics Data System (ADS)

    Yin, Zegao; Yu, Ning; Liang, Bingchen; Zeng, Jixiong; Xie, Shaohua

    2016-02-01

    The perforated breakwater is an environmentally friendly coastal structure, and dissolved oxygen concentration levels are an important index to denote water quality. In this paper, oxygen transport experiments with regular waves through a vertical perforated breakwater were conducted. The oxygen scavenger method was used to reduce the dissolved oxygen concentration of inner water body with the chemicals Na2SO3 and CoCl2. The dissolved oxygen concentration and wave parameters of 36 experimental scenarios were measured with different perforated arrangements and wave conditions. It was found that the oxygen transfer coefficient through wave surface, K1 a 1, is much lower than the oxygen transport coefficient through the perforated breakwater, K2 a 2. If the effect of K1 a 1 is not considered, the dissolved oxygen concentration computation for inner water body will not be greatly affected. Considering the effect of a permeable area ratio a, relative location parameter of perforations δ and wave period T, the aforementioned data of 30 experimental scenarios, the dimensional analysis and the least squares method were used to derive an equation of K2 a 2 (K2 a 2=0.0042 a 0.5 δ 0.2 T -1). It was validated with 6 other experimental scenarios data, which indicates an approximate agreement. Therefore, this equation can be used to compute the DO concentration caused by the water transport through perforated breakwater.

  8. Experimental Studies of Liquefaction and Densification of Liquid Oxygen

    NASA Technical Reports Server (NTRS)

    Partridge, Jonathan Koert

    2010-01-01

    The propellant combination that offers optimum performance is very reactive with a low average molecular weight of the resulting combustion products. Propellant combinations such as oxygen and hydrogen meet the above criteria, however, the propellants in gaseous form require large propellant tanks due to the low density of gas. Thus, rocketry employs cryogenic refrigeration to provide a more dense propellant stored as a liquid. In addition to propellant liquefaction, cryogenic refrigeration can also conserve propellant and provide propellant subcooling and propellant densification. Previous studies analyzed vapor conditioning of a cryogenic propellant, with the vapor conditioning by either a heat exchanger position in the vapor or by using the vapor in a refrigeration cycle as the working fluid. This study analyzes the effects of refrigeration heat exchanger located in the liquid of the common propellant oxidizer, liquid oxygen. This study predicted and determined the mass condensation rate and heat transfer coefficient for liquid oxygen.

  9. Oxygen limitation is a pitfall during screening for industrial strains.

    PubMed

    Zimmermann, Hartmut F; Anderlei, Tibor; Büchs, Jochen; Binder, Michael

    2006-10-01

    Oxygen supply is a key parameter in aerobic fermentation processes like the industrial production of amino acids. Although the oxygen transfer rate (OTR; or the volumetric oxygen transfer coefficient k(L)a) is routinely analyzed by engineers during stirred tank fermentations, it is often not taken into account by biologists conducting screening experiments in shake flasks. To show the importance of knowing how to avoid oxygen transfer limitations during primary screenings, Corynebacterium glutamicum ATCC 13032 (wild-type strain) and DSM 12866 (lysine-producing strain) were cultivated in shake flasks with different culture liquid volumes and under different shaking conditions. With the Respiration Activity Monitoring System, the OTR was determined quasi-continuously. Optical density as well as concentrations of lysine and byproducts (lactate, acetate, succinate) were determined off-line and correlated with the OTR signal. From the results, design criteria for improved screening in shaken bioreactors that help to avoid selection of suboptimal strains during early process development steps can be derived. Finally, the suitability of DSM 12866 as a strain for industrial processes with a high space-time yield is discussed.

  10. Diffusive Transfer of Oxygen From Seamount Basaltic Crust Into Overlying Sediments: an Example From the Clarion-Clipperton Fracture Zone, Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Kasten, S.; Mewes, K.; Mogollón, J.; Picard, A.; Rühlemann, C.; Eisenhauer, A.; Kuhn, T.; Ziebis, W.

    2015-12-01

    Within the Clarion-Clipperton Fracture Zone (CCFZ) located in the equatorial Pacific Ocean numerous seamounts, with diameters ranging from 3 to 30 km and varying heights above the surrounding seafloor of up to 2500 m, occur throughout the deep-sea plain. There is evidence that these may serve as conduits for low-temperature hydrothermal circulation of seawater through the oceanic crust. During RV SONNE cruise SO205 in April/May 2010 and BIONOD cruise with RV ĹATALANTE in spring 2012 we took piston and gravity cores for geochemical analyses, as well as for high-resolution pore-water oxygen and nutrient measurements. Specifically, we took cores along a transect at three sites, located 400, 700 and 1000 m away from the foot of a 240 m high seamount, called 'Teddy Bare'. At all 3 sites oxygen penetrates the entire sediment column of the organic carbon-poor sediment. More importantly, oxygen concentrations initially decrease with sediment depth but increase again at depths of 3 m and 7 m above the basaltic basement, suggesting an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments. This is the first time this has been shown for the deep subsurface in the Pacific Ocean. Mirroring the oxygen concentrations nitrate concentrations accumulate with sediment depth but decrease towards the basement. Transport-reaction modeling revealed that (1) the diffusive flux of oxygen from the basaltic basement exceeds the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange between the sediment and the underlying basaltic crust occurs at orders-of-magnitude lower rates than between the sediment surface and the overlying bottom water. We furthermore show that the upward diffusion of oxygen from the basaltic basement affects the preservation of organic compounds within the oxic sediment column at all 3 sites. Our investigations indicate that an upward

  11. Outgassing of oxygen from polycarbonate.

    PubMed

    Moon, Sung In; Monson, L; Extrand, C W

    2009-07-01

    A manometric permeation apparatus was used to study the "outgassing" or desorption of oxygen from polycarbonate (PC). A PC film was placed in the apparatus. Both sides were exposed to oxygen until the film was saturated. To simulate inert gas purging of a closed container or "microenvironment", oxygen was pumped from one side of the apparatus to reduce the concentration on that side to nearly zero. Oxygen concentrations on the freshly purged side rose quickly at first but then slowed. Eventually, a steady state was established and oxygen concentrations increased linearly with time. Mass-transport coefficients (permeation, diffusion, and solubility coefficients) were also estimated and then used to successfully predict the postpurge rise of the oxygen concentration.

  12. Cobalt(iii) catalyzed C-8 selective C-H and C-O coupling of quinoline N-oxide with internal alkynes via C-H activation and oxygen atom transfer.

    PubMed

    Barsu, Nagaraju; Sen, Malay; Premkumar, J Richard; Sundararaju, Basker

    2016-01-25

    An efficient, scalable, atom-economical, regio-selective air stable Cp*Co(iii) catalyzed C-H and C-O coupling via a C-H activation/oxygen atom transfer reaction of quinoline N-oxide and an internal alkyne is reported. Such a catalytic transformation is witnessed for the first time with a cobalt catalyst and using N-oxide as a traceless directing group, in contrast to the existing literature. The developed synthetic methodology is straightforward and possesses various functional group tolerances, including heterocycles.

  13. Internal photopumping of Nd3+ (2H9/2, 4F5/2) states in yttrium aluminum garnet by excitation transfer from oxygen deficiency centers and Fe3+ continuum emission

    NASA Astrophysics Data System (ADS)

    Hewitt, J. D.; Spinka, T. M.; Senin, A. A.; Eden, J. G.

    2011-07-01

    Photoexcitation of Nd3+ (2H9/2, 4F5/2) states by the broad (˜70 nm FWHM), near-infrared continuum provided by Fe3+ has been observed at 300 K in bulk yttrium aluminum garnet (YAG) crystals doped with trace concentrations (<50 ppm) of Fe, Cr, and Eu. Irradiation of YAG at 248 nm with a KrF laser, which excites the oxygen deficiency center (ODC) in YAG having peak absorption at ˜240 nm, culminates in ODC→Fe3+ excitation transfer and subsequent Fe3+ emission. This internal optical pumping mechanism for rare earth ions is unencumbered by the requirement for donor-acceptor proximity that constrains conventional Förster-Dexter excitation transfer in co-doped crystals.

  14. Oxygen uptake induced by electron transfer from donors to the triplet state of methylene blue and xanthene dyes in air-saturated aqueous solution.

    PubMed

    Görner, Helmut

    2008-03-01

    The effects of oxygen in the photolysis of rose bengal, eosin, erythrosin and methylene blue were studied in the presence of formate and electron donors, such as ascorbic acid, aromatic amino acids or aliphatic amines, e.g. triethylamine (TEA). The overall reaction is conversion of oxygen via the hydroperoxyl/superoxide ion radical into hydrogen peroxide. The quantum yield of oxygen uptake (Phi(-O2)) increases with the donor concentration. The photoinduced formation of H2O2 is initiated by quenching of the triplet state of the dye by the donor and subsequent reactions of both the dye and donor radicals with oxygen. For methylene blue and the xanthene dyes in the presence of 10 mM ascorbic acid or 0.1 M TEA Phi(-O2)=0.07-0.25. The spectral and kinetic properties of the specific dye transients, including the radicals involved and the pH and concentration dependences, are discussed. PMID:18389155

  15. Application of computational fluid dynamics to closed-loop bioreactors: I. Characterization and simulation of fluid-flow pattern and oxygen transfer.

    PubMed

    Littleton, Helen X; Daigger, Glen T; Strom, Peter F

    2007-06-01

    A full-scale, closed-loop bioreactor (Orbal oxidation ditch, Envirex brand technologies, Siemens, Waukesha, Wisconsin), previously examined for simultaneous biological nutrient removal (SBNR), was further evaluated using computational fluid dynamics (CFD). A CFD model was developed first by imparting the known momentum (calculated by tank fluid velocity and mass flowrate) to the fluid at the aeration disc region. Oxygen source (aeration) and sink (consumption) terms were introduced, and statistical analysis was applied to the CFD simulation results. The CFD model was validated with field data obtained from a test tank and a full-scale tank. The results indicated that CFD could predict the mixing pattern in closed-loop bioreactors. This enables visualization of the flow pattern, both with regard to flow velocity and dissolved-oxygen-distribution profiles. The velocity and oxygen-distribution gradients suggested that the flow patterns produced by directional aeration in closed-loop bioreactors created a heterogeneous environment that can result in dissolved oxygen variations throughout the bioreactor. Distinct anaerobic zones on a macroenvironment scale were not observed, but it is clear that, when flow passed around curves, a secondary spiral flow was generated. This second current, along with the main recirculation flow, could create alternating anaerobic and aerobic conditions vertically and horizontally, which would allow SBNR to occur. Reliable SBNR performance in Orbal oxidation ditches may be a result, at least in part, of such a spatially varying environment.

  16. Application of computational fluid dynamics to closed-loop bioreactors: I. Characterization and simulation of fluid-flow pattern and oxygen transfer.

    PubMed

    Littleton, Helen X; Daigger, Glen T; Strom, Peter F

    2007-06-01

    A full-scale, closed-loop bioreactor (Orbal oxidation ditch, Envirex brand technologies, Siemens, Waukesha, Wisconsin), previously examined for simultaneous biological nutrient removal (SBNR), was further evaluated using computational fluid dynamics (CFD). A CFD model was developed first by imparting the known momentum (calculated by tank fluid velocity and mass flowrate) to the fluid at the aeration disc region. Oxygen source (aeration) and sink (consumption) terms were introduced, and statistical analysis was applied to the CFD simulation results. The CFD model was validated with field data obtained from a test tank and a full-scale tank. The results indicated that CFD could predict the mixing pattern in closed-loop bioreactors. This enables visualization of the flow pattern, both with regard to flow velocity and dissolved-oxygen-distribution profiles. The velocity and oxygen-distribution gradients suggested that the flow patterns produced by directional aeration in closed-loop bioreactors created a heterogeneous environment that can result in dissolved oxygen variations throughout the bioreactor. Distinct anaerobic zones on a macroenvironment scale were not observed, but it is clear that, when flow passed around curves, a secondary spiral flow was generated. This second current, along with the main recirculation flow, could create alternating anaerobic and aerobic conditions vertically and horizontally, which would allow SBNR to occur. Reliable SBNR performance in Orbal oxidation ditches may be a result, at least in part, of such a spatially varying environment. PMID:17605329

  17. Theoretical and observational determinations of the ionization coefficient of meteors

    NASA Astrophysics Data System (ADS)

    Jones, William

    1997-07-01

    We examine the problem of the determination of the ionization coefficient beta from both the theoretical and observational points of view. In the past, theoretical evaluations of beta in terms of the relevant scattering cross-sections have used the Massey-Sida formula, which we show to give results which are plainly incorrect. We derive an integral equation for beta and compare the results of its application to copper and iron with laboratory simulations. Agreement for the variation of the ionization coefficient with velocity is good. The ionization coefficient has been determined observationally by Verniani & Hawkins from a comparison of radar and visual observations, employing the luminous efficiency tau also obtained observationally by Verniani. However, this determination of tau would appear to be invalidated by fragmentation. There is good evidence that the radiation of cometary meteors is dominated by that of iron in the visual range, and we have accordingly re-analysed the data of Verniani & Hawkins using the luminous efficiency of iron obtained in simulation experiments. However, it is not possible to choose an iron concentration which gives agreement between the determination of the ionization coefficient by this means and its determination from the theoretical equation in terms of either scattering coefficients or simulation methods. The observational ionization coefficients are much lower than predicted by the present theory and we provisionally explain this as a consequence of transfer of charge from the meteoric ion to a molecule of the air. It is now possible for the meteoric atom to be re-ionized, but it is also possible at sufficiently high initial line densities for significant dissociative recombination of the electrons and nitrogen or oxygen to take place. This recombination will not take place in meteor trains simulated in an ionization chamber. We thus conclude that the present theory is limited to faint radio meteors at lower velocities (v<~35

  18. Performance Testing of Molten Regolith Electrolysis with Transfer of Molten Material for the Production of Oxygen and Metals on the Moon

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Sadoway, Donald; Tripathy, Prabhat; Standish, Evan; Sirk, Aislinn; Melendez, Orlando; Stefanescu, Doru

    2010-01-01

    Previously, we have demonstrated the production of oxygen by electrolysis of molten regolith simulants at temperatures near 1600 C. Using an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in the production of molten metallic products at the cathode and oxygen gas at the anode. Initial direct measurements of current efficiency have confirmed that the process offer potential advantages of high oxygen production rates in a smaller footprint facility landed on the moon, with a minimum of consumables brought from Earth. We now report the results of a scale-up effort toward the goal of achieving production rates equivalent to 1 metric ton O2/year, a benchmark established for the support of a lunar base. We previously reported on the electrochemical behavior of the molten electrolyte as dependent on anode material, sweep rate and electrolyte composition in batches of 20-200g and at currents of less than 0.5 A. In this paper, we present the results of experiments performed at currents up to 10 Amperes) and in larger volumes of regolith simulant (500 g - 1 kg) for longer durations of electrolysis. The technical development of critical design components is described, including: inert anodes capable of passing continuous currents of several Amperes, container materials selection, direct gas analysis capability to determine the gas components co-evolving with oxygen. To allow a continuous process, a system has been designed and tested to enable the withdrawal of cathodically-reduced molten metals and spent molten oxide electrolyte. The performance of the withdrawal system is presented and critiqued. The design of the electrolytic cell and the configuration of the furnace were supported by modeling the thermal environment of the system in an effort to realize a balance between external heating and internal joule heating. We will discuss the impact these simulations and experimental findings have

  19. Measuring Seebeck Coefficient

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor)

    2015-01-01

    A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.

  20. Oxygen uptake after electron transfer from amines, amino acids and ascorbic acid to triplet flavins in air-saturated aqueous solution.

    PubMed

    Görner, Helmut

    2007-05-25

    The photolysis of lumichrome, riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) was studied in air-saturated aqueous solution at room temperature in the presence of appropriate electron donors: ascorbic acid, aromatic amino acids or amines, e.g. ethylenediaminetetraacetate (EDTA). The overall reaction is conversion of oxygen via the hydroperoxyl/superoxide radical into hydrogen peroxide. The quantum yield of oxygen uptake increases with the donor concentration, e.g. up to 0.3 for riboflavin, FMN or FAD in the presence of EDTA or ascorbic acid (0.3-10mM). The formation of H(2)O(2) is initiated by quenching of the acceptor triplet state by the electron donor and subsequent reaction of the semiquinone radical with oxygen. Specific properties of flavins are discussed including the radicals involved and the pH and concentration dependences. The quantum yield of photodegradation is low under air, but substantial under argon, where the major product absorbing in the visible spectral range is the corresponding hydroquinone. PMID:17395476

  1. Catalytic transfer hydrogenation for stabilization of bio-oil oxygenates: reduction of p-cresol and furfural over bimetallic Ni-Cu catalysts using isopropanol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transfer hydrogenation and hydrodeoxygenation of model bio-oil compounds (p-cresol and furfural) and bio-oils derived from biomass via traditional pyrolysis and tail-gas reactive pyrolysis (TGRP) were conducted. Mild batch reaction conditions were employed, using isopropanol as a hydrogen donor over...

  2. Modeling the signal transfer of sea water δ18O to the δ18O of atmospheric oxygen using a diagnostic box model for the terrestrial and marine biosphere

    NASA Astrophysics Data System (ADS)

    Leuenberger, Markus C.

    1997-11-01

    We make use of a simple diagnostic box model to determine the sensitivities of the influencing parameters for the isotopic signal transfer of seawater oxygen to atmospheric oxygen. We calculate the δ18O of atmospheric oxygen from prescribed oxygen fluxes of the living and dead biomes on land and in the ocean, respectively. The model is driven by an assumed (experiment 1) or measured (experiments 2 and 3) temporal seawater δ18O signal and a land biomass estimation. In experiment 1, we calculated the required changes of several model parameters in order to study fast variations of δ18O of atmospheric oxygen as seen in the Greenland Ice Core Project (GRIP) ice at depths assigned to the Eemian time period. Our calculations support evidence of stratigraphic problems at these depths in the GRIP ice core. In experiment 2, we adjusted the model output, which was driven by the benthic seawater δ18O record from V19-30, to the measured Greenland Ice Sheet Project 2 δ18O record of atmospheric oxygen for the last 110,000 years, by varying the model parameter. Single and multi-parameter matchings were performed. The results for single-parameter runs exceed the uncertainty ranges for most of the parameters, while multiparameter variations are well within these ranges. The model calculations are most sensitive to the land respiration factor. Our results support the findings of Van de Water et al. [1994] that the fractionations associated with biomes activities were most probably lower during cold periods, which could point to a combination of fractionations with different temperature dependencies. The model results indicate periods of higher marine biological activity during the ice age than today. Temporal variations of the model parameters show a double peak around 10000 and 8000 years ago, which could be associated with meltwater pulses, as shown in experiment 3. However, they are hardly the well-known Fairbanks [Fairbanks et al., 1992] pulses since these occur 3000 to

  3. NQR investigation of pressure-induced charge transfer in oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} ({delta} = 0.38)

    SciTech Connect

    Reyes, A.P.; Ahrens, E.T.; Hammel, P.C.; Heffner, R.H.; Takigawa, M.

    1992-03-01

    Measurements of the pressure dependence of {sup 63}Cu nuclear quadrupole frequency in YBa{sub 2}Cu{sub 3}O{sub 6.62} from ambient pressure up to 1.5 GPa at 4k have been performed. {Tc} was found to increase with pressure: d{Tc}/dp {approximately} 5 K/GPa. All observed NQR lines are linear in pressure: dln{nu}{sub Q}/dp=z. We found positive z for the empty chain sites, consistent with ionic (Cu{sup 1+}) configuration in which the atom simply feels a squeezing lattice. Planar coppers close to the empty chains have positive z, while those that are close to full chains have z {approximately} 0. We present an analysis of the NQR result on the basis of the charge transfer model in which the mobile charges migrate from the chain to the plane sites. We deduced that a transfer of 0.021 holes to the O(2,3) sites would explain the result in YBa{sub 2}Cu{sub 3}O{sub 6.62}, whereas only 0.007 holes transfer in fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7}.

  4. Oxygen Therapy

    MedlinePlus

    ... 85-95% pure oxygen. The concentrator runs on electricity or a battery. A concentrator for home usually ... systems deliver 100% oxygen, and do not require electricity. A small canister can be filled from the ...

  5. Oxygen analyzer

    DOEpatents

    Benner, William H.

    1986-01-01

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  6. Effect of system variables involved in packed column SFC of nevirapine as model analyte using response surface methodology: application to retention thermodynamics, solute transfer kinetic study and binary diffusion coefficient determination.

    PubMed

    Kaul, Neerej; Agrawal, Himani; Paradkar, A R; Mahadik, K R

    2005-08-31

    A multifactor optimization technique is successfully applied to study the effect of simultaneously varying the system variables on feasibility of nevirapine analysis by packed column supercritical fluid chromatography (PC-SFC). The optimal conditions were determined with the aid of the response surface methodology using 3(3) factorial designs. The method is based on methanol-modified carbon dioxide as the mobile phase at flow rate of 3.0 ml/min with elution through a JASCO Finepak SIL-5, [C18 (5-micron, 25 cm x 4.6 mm, i.d.)] column using photodiode array detection. The method has been successfully used to analyze commercial solid dosage form to assess the chromatographic performance of SFC system. The present work briefs the thermodynamic applications of PC-SFC with an emphasis on the results of nevirapine. The foremost of such applications is the determination of solute diffusion coefficient in supercritical mobile phase by Taylor-Aris peak broadening technique.

  7. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS Painlevé Integrability of Nonlinear Schrödinger Equations with both Space- and Time-Dependent Coefficients

    NASA Astrophysics Data System (ADS)

    Kyoung, Ho Han; H. J., Shin

    2010-12-01

    We investigate the Painlevé integrability of nonautonomous nonlinear Schrödinger (NLS) equations with both space- and time-dependent dispersion, nonlinearity, and external potentials. The Painlevé analysis is carried out without using the Kruskal's simplification, which results in more generalized form of inhomogeneous equations. The obtained equations are shown to be reducible to the standard NLS equation by using a point transformation. We also construct the corresponding Lax pair and carry out its Kundu-type reduction to the standard Lax pair. Special cases of equations from choosing limited form of coefficients coincide with the equations from the previous Painlevé analyses and/or become unknown new equations.

  8. Exergy Transfer Characteristics on Low Temperature Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Wu, S. Y.; Yuan, X. F.; Li, Y. R.; Peng, L.

    By analyzing exergy transfer process of the low temperature heat exchangers operating below the surrounding temperature, the concept of exergy transfer coefficient is put forward and the expressions which involving relevant variables for the exergy transfer coefficient, the heat transfer units number and the ratio of cold to hot fluids heat capacity rate, etc. are derived. Taking the parallel flow, counter flow and cross flow low temperature heat exchangers as examples, the numerical results of exergy transfer coefficient are given and the comparison of exergy transfer coefficient with heat transfer coefficient is analyzed.

  9. Oxygen analyzer

    DOEpatents

    Benner, W.H.

    1984-05-08

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N/sub 2/), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable obtained by decomposing the sample at 1135/sup 0/C, or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135/sup 0/C as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N/sub 2/, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  10. Bubble rise velocities and drag coefficients in non-Newtonian polysaccharide solutions.

    PubMed

    Margaritis, A; te Bokkel, D W; Karamanev, D G

    1999-08-01

    Microbially produced polysaccharides have properties which are extremely useful in different applications. Polysaccharide producing fermentations start with liquid broths having Newtonian rheology and end as highly viscous non-Newtonian solutions. Since aerobic microorganisms are used to produce these polysaccharides, it is of great importance to know the mass transfer rate of oxygen from a rising air bubble to the liquid phase, where the microorganisms need the oxygen to grow. One of the most important parameters determining the oxygen transfer rate is the terminal rise velocity of air bubble. The dynamics of the rise of air bubbles in the aqueous solutions of different, mostly microbially produced polysaccharides was studied in this work. Solutions with a wide variety of polysaccharide concentrations and rheological properties were studied. The bubble sizes varied between 0.01 mm3 and 10 cm3. The terminal rise velocities as a function of air bubble volume were studied for 21 different polysaccharide solutions with different rheological properties. It was found that the terminal velocities reached a plateau at higher bubble volumes, and the value of the plateau was nearly constant, between 23 and 27 cm/s, for all solutions studied. The data were analyzed to produce the functional relationship between the drag coefficient and Reynolds number (drag curves). It was found out that all the experimental data obtained from 21 polysaccharide solutions (431 experimental points), can be represented by a new single drag curve. At low values of Reynolds numbers, below 1.0, this curve could be described by the modofoed Hadamard-Rybczynski model, while at Re > 60 the drag coefficient was a constant, equal to 0.95. The latter finding is similar to that observed for bubble rise in Newtonian liquids which was explained on the basis of the "solid bubble" approach. PMID:10397862

  11. Determination of stream reaeration coefficients by use of tracers

    USGS Publications Warehouse

    Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.

    1987-01-01

    Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed in which a radioactive tracer gas was injected into a stream--the tracer gas being desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. The slug-injection and constant-rate injection methods of performing gas tracer desorption measurements are described. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, methods of injection, sampling and analysis, and computational techniques to compute desorption and reaeration coefficients. (Author 's abstract)

  12. 41 CFR 50-204.67 - Oxygen.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 1 2013-07-01 2013-07-01 false Oxygen. 50-204.67..., Vapors, Fumes, Dusts, and Mists § 50-204.67 Oxygen. The in-plant transfer, handling, storage, and utilization of oxygen as a liquid or a compressed gas shall be in accordance with Compressed Gas...

  13. 41 CFR 50-204.67 - Oxygen.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 41 Public Contracts and Property Management 1 2011-07-01 2009-07-01 true Oxygen. 50-204.67 Section..., Vapors, Fumes, Dusts, and Mists § 50-204.67 Oxygen. The in-plant transfer, handling, storage, and utilization of oxygen as a liquid or a compressed gas shall be in accordance with Compressed Gas...

  14. Dynamics of oxygen sorption from water by copper-containing fibrous porous redox ion-exchangers

    SciTech Connect

    Ul'eva, L.S.; Burinskii, S.V.; Grebennikov, S.F.

    1985-08-10

    A most important field of practical application of oxidation-reduction (redox) polymers is the sorption of dissolved oxygen from water in order to prevent corrosion of power equipment. Copper-containing redox polymers, which have fairly high capacity and good swelling characteristics were used. Values of the dynamic exchange capacity (DEC) for copper ions, the redox capacity (ROC) for the reducing metal, and the dynamic reduction capacity for oxygen are given. It can be seen from these data that fibrous porous reactive materials (FPRM) in which the mass fiber content is 60% have somewhat better characteristics. The authors conclude that despite the fibrous porous material's considerably lower coefficient of internal diffusion, it is superior to granular EI-21 in the length of the masstransfer zone and in the coefficient of utilization of capacity, in consequence of the low linear density of the fibers. Their mass transfer zone is shorter by a factor of about 5.

  15. Catalytic recombination of nitrogen and oxygen on iron-cobalt-chromia spinel

    NASA Technical Reports Server (NTRS)

    Scott, C. D.

    1983-01-01

    The energy-transfer catalytic recombination coefficient for nitrogen and oxygen recombination on iron-cobalt-chromia spinel is inferred from stagnation-point heat flux measurements in dissociated arc-jet flow. This material was coated on several Space Shuttle Orbiter thermal protection tiles. The resulting coefficients are correlated with an Arrhenius model for convenience, and these expressions may be used to account for catalytic recombination in predictions of the heat flux on the spinel-coated tiles flown on several Space Shuttle Orbiter flights. The results are compared with those inferred by Rakich, Stewart, and Lanfranco from an Orbiter flight and arc-jet experiments. Good agreement is obtained for oxygen recombination, but agreement for nitrogen is poor.

  16. Oxygen electrode in molten carbonate fuel cells. Ninth quarterly technical progress report, August 1, 1989--October 31, 1989

    SciTech Connect

    Dave, B.B.; Srinivasan, S.; White, R.E.; Appleby, A.J.

    1989-12-31

    The oxygen reduction reaction on a gold electrode in lithium carbonate melt was investigated to determine the influence of partial pressure of carbon dioxide and temperature on electrode kinetics and oxygen solubility by using cyclic Voltammetry and impedance analysis techniques. During this quarter, the impedance data were analyzed by a Complex Nonlinear Least Square (CNLS) Parameter estimation program to determine the kinetic and the mass transfer related parameters such as charge transfer resistance, double layer capacitance, solution resistance, and Warburg coefficient. The estimated parameters were used to obtain the C0{sub 2} reaction orders and apparent activation energies for the exchange current density and the mass transfer parameter (D{sub o}{sup {1/2}}C{sub o}*).

  17. Optical absorption coefficients of pure water

    NASA Astrophysics Data System (ADS)

    Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.

    2002-10-01

    The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.

  18. Appreciating Oxygen

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2008-01-01

    Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

  19. Catalytic recombination of nitrogen and oxygen on high-temperature reusable surface insulation

    NASA Technical Reports Server (NTRS)

    Scott, C. D.

    1980-01-01

    The energy transfer catalytic recombination coefficient for nitrogen and oxygen recombination on the surface coating of high-temperature reusable surface insulation (HRSI) is inferred from stagnation point heat flux measurements in a high-temperature dissociated arc jet flow. The resulting catalytic recombination coefficients are correlated with an Arrhenius model for convenience, and these expressions may be used to account for catalytic recombination effects in predictions of the heat flux on the HRSI thermal protection system of the Space Shuttle Orbiter during reentry flight. Analysis of stagnation point pressure and total heat balance enthalpy measurements indicates that the arc heater reservoir conditions are not in chemical equilibrium. This is contrary to what is usually assumed for arc jet analysis and indicates the need for suitable diagnostics and analyses, especially when dealing with chemical reaction phenomena such as catalytic recombination heat transfer effects.

  20. Averaging Internal Consistency Reliability Coefficients

    ERIC Educational Resources Information Center

    Feldt, Leonard S.; Charter, Richard A.

    2006-01-01

    Seven approaches to averaging reliability coefficients are presented. Each approach starts with a unique definition of the concept of "average," and no approach is more correct than the others. Six of the approaches are applicable to internal consistency coefficients. The seventh approach is specific to alternate-forms coefficients. Although the…

  1. New method to determine the mass transfer resistance of sterile closures for shaken bioreactors.

    PubMed

    Anderlei, Tibor; Mrotzek, Christian; Bartsch, Stefan; Amoabediny, Ghassem; Peter, Cyril P; Büchs, Jochen

    2007-12-01

    In this paper a novel and easily applied method to measure the mass transfer resistance of the sterile closures (e.g. cotton plug) of shaken bioreactors is introduced. This method requires no investment in special equipment (e.g. an oxygen sensor) and can be performed with the materials usually available in typical laboratories. The method is based on the model of Henzler et al. (1986), which mechanistically describes mass transfer through the sterile closure of a shaken bioreactor based on diffusion coupled with Stefan convection. The concentration dependency of the multi-component diffusion coefficients is taken into account. The water loss from two equivalent shaken bioreactors equipped with sterile closures during several days of shaking is measured. One flask contains distilled water, the other a saturated salt solution. From the water evaporation rate in each of the two flasks, the new model presented calculates the relative humidity in the environment, the average diffusion coefficient of oxygen in the sterile closure (D(O2)), and the diffusion coefficient of carbon dioxide (D(CO2)) . The diffusion coefficient of carbon dioxide (D(CO2)) only depends on the density and material properties of the sterile closure and not on the gas concentrations and is, therefore, an ideal parameter for the characterization of the mass transfer resistance. This new method is validated experimentally by comparing the diffusion coefficient of oxygen (D(O2)) to a measurement by the classic dynamic method; and by comparing the calculated relative humidity in the environment to a humidity sensor measurement. PMID:17497734

  2. Measurements and Analysis of Oxygen Bubble Distributions in LiCl-KCl Molten Salt

    SciTech Connect

    Ryan W. Bezzant; Supathorn Phongikaroon; Michael F. Simpson

    2013-03-01

    Transparent system experimental studies have been performed to provide measurement and analysis of oxygen bubble distributions and mass transfer coefficients at different sparging rates ranging from 0.05 to 0.20 L/min in LiCl-KCl molten salt at 500 degrees C using a high-speed digital camera and an oxygen sensor. The results reveal that bubble sizes and rise velocities increased with an increase in oxygen sparging rate. The bubbles observed were ellipsoidal in shape, and an equivalent diameter based on the ellipsoid volume was calculated. The average equivalent bubble diameters at 500 degrees C and these oxygen sparging rates range from 2.63 to 4.07 mm. Results show that the bubble equivalent diameters at each respective sparging rate are normally distributed. A Fanning friction factor correlation was produced to predict a bubble’s rise velocity based on its equivalent diameter. The oxygen mass transfer coefficients for four sparging rates were calculated using the oxygenation model. These calculated values were within the order of magnitude of 10-2 cm/sec and followed a decreasing trend corresponding to an increasing bubble size and sparging rate. The diffusivities were calculated based on two different types of mechanisms, one based on physics of the bubbles and the other on systematic properties. The results reveal that diffusivity values calculated from bubble physics are 1.65 to 8.40 x 10-5 cm2/sec, which are within the range suggested by literature for gases in liquids of a similar viscosity.

  3. Enzymic phosphoryl transfer to carbon and oxygen acceptors: An investigation of the biosynthesis of 2-aminoethylphosphonic acid in Tetrahymena pyriformis W. and the kinetic mechanism and cofactor controlled substrate specificity of yeast inorganic pyrophosphatase

    SciTech Connect

    Barry, R.J.

    1987-01-01

    This research is concerned with the study of two enzymatic systems which catalyze phosphoryl transfer reactions to carbon and oxygen acceptors. The first portion of this study is concerned with the elucidation of the T. pyriformis 2-aminoethylphosphonate (AEP) biosynthetic pathway. The de novo formation of AEP from exogenously added precursors in Tetrahymena cell-free preparations was evaluated by using radioisotopic techniques and NMR spectral analysis. Incubation of ({sup 32}P)-phosphoenolpyruvate (PEP) with cell-free preparations yielded ({sup 32}P)-labelled material that was chromatographically identical to authentic phosphonopyruvate (p-pry). A reexamination of AEP biosynthesis was initiated. In the second portion of this study the kinetic mechanism of yeast inorganic pyrophosphatase (PPase) was examined by carrying-out initial velocity studies. Ca{sup 2+} and Rh(H{sub 2}O){sub 4} (methylenediphosphonate) (Rh(H{sub 2}O){sub 4}PCP) were used as dead-end inhibitors to study the order of binding of Cr(H{sub 2}O){sub 4}PP to the substrate site and Mg{sup 2+} to the low affinity activator site on the enzyme.

  4. Transfer of a proton between H2 and O2.

    PubMed

    Kluge, Lars; Gärtner, Sabrina; Brünken, Sandra; Asvany, Oskar; Gerlich, Dieter; Schlemmer, Stephan

    2012-11-13

    The proton affinities of hydrogen and oxygen are very similar. Therefore, it has been discussed that the proton transfer from the omnipresent H(3)(+) to molecular oxygen in the near thermoneutral reaction H(3)(+) + O(2) <--> O(2)H(+) + H(2) effectively binds the interstellar oxygen in O(2)H(+). In this work, the proton transfer reaction has been investigated in a low-temperature 22-pole ion trap from almost room temperature (280 K) down to the lowest possible temperature limited by freeze out of oxygen gas (about 40 K at a low pressure). The Arrhenius behaviour of the rate coefficient for the forward reaction shows that it is subject to an activation energy of E(A)/k=113 K. Thus, the forward reaction can proceed only in higher temperature molecular clouds. Applying laser-induced reactions to the given reaction (in the backward direction), a preliminary search for spectroscopic signatures of O(2)H(+) in the infrared was unsuccessful, whereas the forward reaction has been successfully used to probe the population of the lowest ortho and para levels of H(3)(+).

  5. Atomic oxygen transport in the thermosphere.

    NASA Technical Reports Server (NTRS)

    Johnson, F. S.; Gottlieb, B.

    1973-01-01

    The photodissociation of oxygen in the lower thermosphere is evaluated to obtain its global average value and the hemispheric imbalance. The observed concentrations of atomic oxygen do not reflect this imbalance in production due to the effect of seasonal wind patterns redistributing the atomic oxygen. The wind system necessary to compensate for the imbalance in solar thermal input into the lower thermosphere is found to transport an amount of atomic oxygen sufficient to compensate for the hemispheric imbalance in production. Ionospheric data indicate a winter enhancement in atomic oxygen concentration; to produce this, a higher degree of oxygen dissociation than that normally accepted (i.e., higher than an atomic to molecular oxygen ratio of unity at 120 km) is needed. The concept that the concentrations of atomic oxygen observed over the winter polar region are maintained by transport from lower latitudes requires that eddy diffusion coefficients derived from vertical transport at low latitudes (ignoring horizontal transport) be reduced by about 25%.

  6. Reference Material for Seebeck Coefficients

    NASA Astrophysics Data System (ADS)

    Edler, F.; Lenz, E.; Haupt, S.

    2015-03-01

    This paper describes a measurement method and a measuring system to determine absolute Seebeck coefficients of thermoelectric bulk materials with the aim of establishing reference materials for Seebeck coefficients. Reference materials with known thermoelectric properties are essential to allow a reliable benchmarking of different thermoelectric materials for application in thermoelectric generators to convert thermal into electrical energy or vice versa. A temperature gradient (1 to 8) K is induced across the sample, and the resulting voltage is measured by using two differential Au/Pt thermocouples. On the basis of the known absolute Seebeck coefficients of Au and Pt, the unknown Seebeck coefficient of the sample is calculated. The measurements are performed in inert atmospheres and at low pressure (30 to 60) mbar in the temperature range between 300 K and 860 K. The measurement results of the Seebeck coefficients of metallic and semiconducting samples are presented. Achievable relative measurement uncertainties of the Seebeck coefficient are on the order of a few percent.

  7. 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.

  8. Coefficient Alpha: A Reliability Coefficient for the 21st Century?

    ERIC Educational Resources Information Center

    Yang, Yanyun; Green, Samuel B.

    2011-01-01

    Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…

  9. Turbine heat transfer

    NASA Technical Reports Server (NTRS)

    Rohde, J. E.

    1982-01-01

    Objectives and approaches to research in turbine heat transfer are discussed. Generally, improvements in the method of determining the hot gas flow through the turbine passage is one area of concern, as is the cooling air flow inside the airfoil, and the methods of predicting the heat transfer rates on the hot gas side and on the coolant side of the airfoil. More specific areas of research are: (1) local hot gas recovery temperatures along the airfoil surfaces; (2) local airfoil wall temperature; (3) local hot gas side heat transfer coefficients on the airfoil surfaces; (4) local coolant side heat transfer coefficients inside the airfoils; (5) local hot gas flow velocities and secondary flows at real engine conditions; and (6) local delta strain range of the airfoil walls.

  10. The anomaly of oxygen diffusion in aqueous xanthan solutions.

    PubMed

    Ho, C S; Ju, L K; Baddour, R F

    1988-06-20

    A membrane-covered polarographic oxygen electrode was used to measure oxygen diffusion coefficients in aqueous polyelectrolyte solutions of xanthan gum, sodium alginate, and sodium carboxymethylcellulose (CMC). In sodium alginate solutions, dilute xanthan solutions, and solutions containing more than 0.3 wt % CMC, oxygen diffusion coefficients decrease with increasing polymer concentrations. Interestingly, in dilute CMC solutions and concentrate xanthan solutions containing more than 0.5 wt % xanthan gum, oxygen diffusion coefficients increase with increasing polymer concentrations, and values exceeding that in pure water are generally observed.

  11. Altitude Dependent Auroral Ion Diffusion Coefficients

    NASA Astrophysics Data System (ADS)

    Ludlow, G. R.

    2011-12-01

    Simultaneous upgoing auroral H+ and O+ ion beams generate ion acoustic waves which have both parallel and oblique wave vectors with respect to the ambient magnetic field. A parallel mode is investigated with phase velocity UO + CO in the direction of beam propagation, where UO is the oxygen beam velocity and CO is the oxygen ion sound speed. Due to the mass difference, this mode preferentially resonates with the oxygen beam through the n = 1 cyclotron resonance, causing O+ ions to diffuse in a direction that is primarily perpendicular to the background magnetic field. The Landau resonance (n = 0) is very narrow in parallel velocity and does not interact with either ion beam. In one case study the parallel acoustic mode begins to resonate with O+ ions within the auroral acceleration region and this resonant region in velocity space sweeps through the entire O+ beam as it moves into weaker magnetic field regions. The O+ quasilinear diffusion coefficients are examined during this process. Perpendicular diffusion becomes significant when the parallel resonant velocity is close to the parallel group velocity of the waves. This selects regions of velocity space where perpendicular diffusion is maximum which occurs at the leading edge of the resonant region as it sweeps through the O+ beam. In k - space these resonant velocities correspond to the regions of peak growth rate. The relevance of this work to the selective energization of heavy auroral ion beams will be discussed.

  12. Reactions of the unsaturated ditungsten complexes [W2Cp2(μ-PPh2)2(CO)x] (x = 1, 2) with nitric oxide: stereoselective carbonyl displacement and oxygen-transfer reactions of a nitrite ligand.

    PubMed

    Alvarez, M Angeles; García, M Esther; García-Vivó, Daniel; Melón, Sonia; Ruiz, Miguel A; Toyos, Adrián

    2014-05-01

    The dicarbonyl complex trans-[W2Cp2(μ-PPh2)2(CO)2] (Cp = η(5)-C5H5) reacted rapidly with NO (5% in N2) at 273 K to give selectively cis-[W2Cp2(μ-PPh2)2(NO)2]. In contrast, the analogous reactions of monocarbonyl [W2Cp2(μ-PPh2)2(μ-CO)] yielded either trans-[W2Cp2(μ-PPh2)2(NO)2] or the nitrito complex [W2Cp2(μ-PPh2)2(ONO)(CO)(NO)] (W-W = 2.9797(4) Å), depending on experimental conditions, with the latter presumably arising from reaction with trace amounts of oxygen in the medium. The stereoselectivity of the above reactions can be rationalized by assuming the participation of 33-electron [W2Cp2(μ-PPh2)2(CO)(NO)] intermediates which rapidly add a second molecule of NO via η(2)-C5H5 intermediates to eventually yield the corresponding dinitrosyls with inversion of the stereochemistry at the dimetal center, as supported by density functional theory (DFT) calculations. The nitrito complex was thermally unstable and evolved through oxygen transfer either to the carbonyl ligand, to yield the above dinitrosyls with release of CO2, or to the phosphide ligand, to give the phosphinito derivative cis-[W2Cp2(μ-OPPh2)(μ-PPh2)(NO)2], depending on experimental conditions. According to DFT calculations, the first process would involve transient dissociation/recombination of the nitrite ligand followed by coupling to carbonyl to give an intermediate with a chelate W{C,N-C(O)ON(O)} ring. Indeed, the nitrite ligand could be easily removed upon reaction of the nitrito complex with Na(BAr'4), but immediate decomposition also took place to render the electron-precise dicarbonyl [W2Cp2(μ-PPh2)2(CO)2(NO)]BAr'4 (W-W = 2.9663(3) Å) as the unique product (Ar' = 3,5-C6H3(CF3)2). Attempts to decarbonylate the latter complex photochemically yielded instead the oxo derivatives cis- and trans-[W2Cp2(μ-PPh2)2(O)(NO)]BAr'4 as the only isolable products (W-W = 2.980(2) and 3.0077(3) Å, respectively). PMID:24739068

  13. Oxygen transfer in circular surface aeration tanks.

    PubMed

    Rao, Achanta Ramakrishna; Patel, Ajey Kumar; Kumar, Bimlesh

    2009-06-01

    Surface aeration systems employed in activated sludge plants are the most energy-intensive units of the plants and typically account for a higher percentage of the treatment facility's total energy use. The geometry of the aeration tank imparts a major effect on the system efficiency. It is said that at optimal geometric conditions, systems exhibits the maximum efficiency. Thus the quantification of the optimal geometric conditions in surface aeration tanks is needed. Optimal geometric conditions are also needed to scale up the laboratory result to the field installation. In the present work, experimental studies have been carried out on baffled and unbaffled circular surface aeration tanks to ascertain the optimal geometric conditions. It is found that no optimal geometric conditions exist for the liquid/water depth in circular surface aeration tanks; however, for design purposes, a standard value has been assumed. Based on the optimal geometric conditions, a scale-up equation has been developed for the baffled circular surface aeration tanks.

  14. Graph characterization via Ihara coefficients.

    PubMed

    Ren, Peng; Wilson, Richard C; Hancock, Edwin R

    2011-02-01

    The novel contributions of this paper are twofold. First, we demonstrate how to characterize unweighted graphs in a permutation-invariant manner using the polynomial coefficients from the Ihara zeta function, i.e., the Ihara coefficients. Second, we generalize the definition of the Ihara coefficients to edge-weighted graphs. For an unweighted graph, the Ihara zeta function is the reciprocal of a quasi characteristic polynomial of the adjacency matrix of the associated oriented line graph. Since the Ihara zeta function has poles that give rise to infinities, the most convenient numerically stable representation is to work with the coefficients of the quasi characteristic polynomial. Moreover, the polynomial coefficients are invariant to vertex order permutations and also convey information concerning the cycle structure of the graph. To generalize the representation to edge-weighted graphs, we make use of the reduced Bartholdi zeta function. We prove that the computation of the Ihara coefficients for unweighted graphs is a special case of our proposed method for unit edge weights. We also present a spectral analysis of the Ihara coefficients and indicate their advantages over other graph spectral methods. We apply the proposed graph characterization method to capturing graph-class structure and clustering graphs. Experimental results reveal that the Ihara coefficients are more effective than methods based on Laplacian spectra.

  15. Measurement of the Convective Heat-Transfer Coefficient

    ERIC Educational Resources Information Center

    Conti, Rosaria; Gallitto, Aurelio Agliolo; Fiordilino, Emilio

    2014-01-01

    We propose an experiment for investigating how objects cool down toward the thermal equilibrium with their surroundings. We describe the time dependence of the temperature difference of the cooling objects and the environment with an exponential decay function. By measuring the thermal constant t, we determine the convective heat-transfer…

  16. Hyperthermal atomic oxygen generator

    NASA Technical Reports Server (NTRS)

    Khandelwal, Govind S.; Wu, Dongchuan

    1990-01-01

    Characterization of the transport properties of oxygen through silver was continued. Specifically, experiments measuring the transport through Ag(111), Ag(110), Ag(100) single crystals and through Ag0.05 Zr alloy were completed. In addition, experiments using glow discharge excitation of oxygen to assist in the transport were completed. It was found that the permeability through the different orientations of single crystal Ag was the same, but significant differences existed in the diffusivity. The experimental ratio of diffusivities, however, was in reasonable agreement with theoretical estimates. Since the solubilities of orientations must be the same, this suggests some problems with the assumption K = DS. The glow discharge experiments show that there is a substantial increase in transport (factor of six) when the upstream pressure is dissociated to some fraction of atoms (which have a much higher sticking coefficient). These results indicate that there is a significant surface limitation because of dissociative adsorption of the molecules. Experiments with the Ag0.05 Zr alloy and its high-grain boundary and defect density show a permeability of greater than a factor of two over ordinary polycrystalline Ag, but it is unclear as to whether this is because of enhanced transport through these defects or whether the Zr and defects on the surface increased the sticking coefficient and therefore the transport.

  17. Thermodynamic and kinetic study of cleavage of the N-O bond of N-oxides by a vanadium(III) complex: enhanced oxygen atom transfer reaction rates for adducts of nitrous oxide and mesityl nitrile oxide.

    PubMed

    Palluccio, Taryn D; Rybak-Akimova, Elena V; Majumdar, Subhojit; Cai, Xiaochen; Chui, Megan; Temprado, Manuel; Silvia, Jared S; Cozzolino, Anthony F; Tofan, Daniel; Velian, Alexandra; Cummins, Christopher C; Captain, Burjor; Hoff, Carl D

    2013-07-31

    Thermodynamic, kinetic, and computational studies are reported for oxygen atom transfer (OAT) to the complex V(N[t-Bu]Ar)3 (Ar = 3,5-C6H3Me2, 1) from compounds containing N-O bonds with a range of BDEs spanning nearly 100 kcal mol(-1): PhNO (108) > SIPr/MesCNO (75) > PyO (63) > IPr/N2O (62) > MesCNO (53) > N2O (40) > dbabhNO (10) (Mes = mesityl; SIPr = 1,3-bis(diisopropyl)phenylimidazolin-2-ylidene; Py = pyridine; IPr = 1,3-bis(diisopropyl)phenylimidazol-2-ylidene; dbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene). Stopped flow kinetic studies of the OAT reactions show a range of kinetic behavior influenced by both the mode and strength of coordination of the O donor and its ease of atom transfer. Four categories of kinetic behavior are observed depending upon the magnitudes of the rate constants involved: (I) dinuclear OAT following an overall third order rate law (N2O); (II) formation of stable oxidant-bound complexes followed by OAT in a separate step (PyO and PhNO); (III) transient formation and decay of metastable oxidant-bound intermediates on the same time scale as OAT (SIPr/MesCNO and IPr/N2O); (IV) steady-state kinetics in which no detectable intermediates are observed (dbabhNO and MesCNO). Thermochemical studies of OAT to 1 show that the V-O bond in O≡V(N[t-Bu]Ar)3 is strong (BDE = 154 ± 3 kcal mol(-1)) compared with all the N-O bonds cleaved. In contrast, measurement of the N-O bond in dbabhNO show it to be especially weak (BDE = 10 ± 3 kcal mol(-1)) and that dissociation of dbabhNO to anthracene, N2, and a (3)O atom is thermodynamically favorable at room temperature. Comparison of the OAT of adducts of N2O and MesCNO to the bulky complex 1 show a faster rate than in the case of free N2O or MesCNO despite increased steric hindrance of the adducts.

  18. Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

    PubMed

    Yang, Zongbo; Cheng, Jun; Lin, Richen; Zhou, Junhu; Cen, Kefa

    2016-07-01

    A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%. PMID:27035474

  19. Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

    PubMed

    Yang, Zongbo; Cheng, Jun; Lin, Richen; Zhou, Junhu; Cen, Kefa

    2016-07-01

    A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%.

  20. From Source to Sink: Integration and Alteration of Oxygen Isotope Signals during the Transfer from Precipitation to Leaf Water, Leaf Sugars, Twig Phloem Sugars into the Stem Phloem Sugars of Four Mature European Tree Species

    NASA Astrophysics Data System (ADS)

    Brinkmann, N.; Werner, R. A.; Buchmann, N. C.; Kahmen, A.

    2014-12-01

    Stable oxygen isotope ratios (δ18O) of stem cellulose record physiological and ecohydrological information and are increasingly being used for the reconstruction of past environments. Studies that have investigated the environmental and physiological drivers of δ18O values in tree ring cellulose have typically focused either on the source of the signal, e.g. the leaf and the water therein, or on the sink, e.g. the cellulose in the stem. In contrast, hardly any research has investigated the transfer of the δ18O signal from precipitation, to soil water, xylem water, leaf water, leaf sugars, phloem sugars all the way to cellulose in the tree ring. As such, critical uncertainties remain regarding the seasonal integration and precision by which precipitation and leaf water δ18O signals are recorded in the tree ring cellulose δ18O values. In our talk, we will present a unique three year dataset that shows the seasonal variation of δ18O values in precipitation, soil water, xylem water, leaf water, leaf sugars, twig and stem phloem sugars for four common European tree species, which are growing in a mature temperature Swiss mixed broadleaf/evergreen forest. This dataset allows us to assess, (i) to what degree the substantial seasonal variation in precipitation δ18O values influences the δ18O values of tree ring cellulose and (ii) if physiological and environmental δ18O signals imprinted on the tree's leaf water δ18O values and the assimilates formed therein are altered on their way downstream to the tree stem. The new insight that we provide into the integration and possible alteration of δ18O signals along the leaf-stem pathway will contribute significantly to a better understanding of the environmental and physiological signals that can be obtained from tree ring δ18O chronologies. In addition it will be relevant for the incorporation and parameterization of tree ring isotope models into dynamic global vegetation models.