Sample records for radiative heat flux

  1. Spectral estimates of net radiation and soil heat flux

    USGS Publications Warehouse

    Daughtry, C.S.T.; Kustas, W.P.; Moran, M.S.; Pinter, P. J., Jr.; Jackson, R. D.; Brown, P.W.; Nichols, W.D.; Gay, L.W.

    1990-01-01

    Conventional methods of measuring surface energy balance are point measurements and represent only a small area. Remote sensing offers a potential means of measuring outgoing fluxes over large areas at the spatial resolution of the sensor. The objective of this study was to estimate net radiation (Rn) and soil heat flux (G) using remotely sensed multispectral data acquired from an aircraft over large agricultural fields. Ground-based instruments measured Rn and G at nine locations along the flight lines. Incoming fluxes were also measured by ground-based instruments. Outgoing fluxes were estimated using remotely sensed data. Remote Rn, estimated as the algebraic sum of incoming and outgoing fluxes, slightly underestimated Rn measured by the ground-based net radiometers. The mean absolute errors for remote Rn minus measured Rn were less than 7%. Remote G, estimated as a function of a spectral vegetation index and remote Rn, slightly overestimated measured G; however, the mean absolute error for remote G was 13%. Some of the differences between measured and remote values of Rn and G are associated with differences in instrument designs and measurement techniques. The root mean square error for available energy (Rn - G) was 12%. Thus, methods using both ground-based and remotely sensed data can provide reliable estimates of the available energy which can be partitioned into sensible and latent heat under nonadvective conditions. ?? 1990.

  2. Figure 5. Net radiation of the study area on June 21, 2003 ESTIMATION OF HEAT FLUXES

    E-print Network

    Hall, Sharon J.

    that the influence of temperature rise on heat flux is negligible, with the exception of sensible heat. The surplus one to conclude that the influence of temperature rise on heat flux is negligible, with the exceptionFigure 5. Net radiation of the study area on June 21, 2003 at 9:40 pm ESTIMATION OF HEAT FLUXES

  3. Combined Heat Transfer by Natural Convection - Conduction and Surface Radiation in an Open Cavity Under Constant Heat Flux Heating

    Microsoft Academic Search

    Zhiyun Wang; Mo Yang; Ling Li; Yuwen Zhang

    2011-01-01

    Combined heat transfer by natural convection-conduction and surface radiation in an open cavity heated by constant flux is studied here. The laminar flow is solved numerically by employing the SIMPLE algorithm with QUICK scheme. The numerical results show that both radiation and solid conduction increase the average total Nusselt number. The average total Nusselt number is a linear increasing function

  4. Radiative Heating and the Buoyant Rise of Magnetic Flux Tubes in the Solar Interior

    E-print Network

    California at Berkeley, University of

    Radiative Heating and the Buoyant Rise of Magnetic Flux Tubes in the Solar Interior Y. Fan National tube. In the overshoot region, the radiative heating is found to cause a quasi-static rising the e ect of radiative heating on the evolution of thin magnetic ux tubes in the solar interior

  5. An Investigation of the Compatibility of Radiation and Convection Heat Flux Measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1996-01-01

    A method for determining time-resolved absorbed surface heat flux and surface temperature in radiation and convection environments is described. The method is useful for verification of aerodynamic, heat transfer and durability models. A practical heat flux gage fabrication procedure and a simple one-dimensional inverse heat conduction model and calculation procedure are incorporated in this method. The model provides an estimate of the temperature and heat flux gradient in the direction of heat transfer through the gage. This paper discusses several successful time-resolved tests of this method in hostile convective heating and cooling environments.

  6. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Hubbard, Kenneth G.; Verma, Shashi B.; Starks, Patrick; Norman, John M.; Walter-Shea, Elizabeth

    1987-01-01

    The feasibility of using radio frequency receivers to collect data from automated weather stations to model fluxes of latent heat, sensible heat, and radiation using routine weather data collected by automated weather stations was tested and the estimated fluxes were compared with fluxes measured over wheat. The model Cupid was used to model the fluxes. Two or more automated weather stations, interrogated by radio frequency and other means, were utilized to examine some of the climatic variability of the First ISLSCP (International Satellite Land-Surface Climatology Project) Field Experiment (FIFE) site, to measure and model reflected and emitted radiation streams from various locations at the site and to compare modeled latent and sensible heat fluxes with measured values. Some bidirectional reflected and emitted radiation data were collected from 23 locations throughout the FIFE site. Analysis of these data along with analysis of the measured sensible and latent heat fluxes is just beginning.

  7. Radiative forcing of the Venus mesosphere. I - Solar fluxes and heating rates

    Microsoft Academic Search

    D. Crisp

    1986-01-01

    Most of the solar energy absorbed by Venus is deposited in the atmosphere, at levels more than 60 km above the surface. This unusual flux distribution should have important consequences for the thermal structure and dynamical state of that atmosphere. A radiative transfer model was used to derive the structure and amplitude of the solar fluxes and heating rates in

  8. Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Verma, Shashi B.; Hubbard, Kenneth G.; Starks, Patrick; Hays, Cynthia; Norman, John M.; Waltershea, Elizabeth

    1988-01-01

    The primary objectives of the 1985 study were to test the feasibility of using radio frequency receivers to collect data from automated weather stations and to evaluate the use of the data collected by the automated weather stations for modeling the fluxes of latent heat, sensible heat, and radiation over wheat. The model Cupid was used to calculate these fluxes which were compared with fluxes of these entities measured using micrometeorological techniques. The primary objectives of the 1986 study were to measure and model reflected and emitted radiation streams at a few locations within the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) site and to compare modeled and measured latent heat and sensible heat fluxes from the prairie vegetation.

  9. [Research on reducing mold flux's radiative heat transfer based on FTIR and XRD].

    PubMed

    Diao, Jiang; Xie, Bing

    2009-02-01

    The mold fluxes samples containing transition metal oxides TiO2 were designed based on the composition of commercial mold fluxes in continuous casting of steel, and the relation between radiative heat transfer and the content of TiO2 was obtained through FTIR spectrum analysis and XRD analysis. The result of FTIR analysis indicates that TiO2 has a great negative effect on infrared transmittance of flux samples in the wavelength range of 1-6 microm. The result of XRD analysis indicates that crystallization of cuspidine was restrained with addition of TiO2, and CaTiO3 and other phases were found in the samples. The decrease in cuspidine phase is beneficial to strand lubrication in the mold. Radiation heat flux from the strand to the mold was calculated using a radiative heat transfer model concluded in previous study. Addition of TiO2 was found to result in a remarkable decrease in radiation heat flux for both glassy and crystalline samples, and the heat flux tended to decrease with increasing TiO2, with the maximal decrease reaching 30%. As a result of great refraction and scatter at surface and grain boundaries of samples, the negative effect of crystalline samples was much larger than that of the glassy ones. PMID:19445198

  10. Propagation of a cylindrical shock wave in a rotating dusty gas with heat conduction and radiation heat flux

    Microsoft Academic Search

    J. P. Vishwakarma; G. Nath

    2010-01-01

    A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas

  11. Similarity solution for a cylindrical shock wave in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux

    Microsoft Academic Search

    J. P. Vishwakarma; G. Nath

    2012-01-01

    The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It

  12. Heat flux microsensor measurements

    NASA Astrophysics Data System (ADS)

    Terrell, J. P.; Hager, J. M.; Onishi, S.; Diller, T. E.

    1992-12-01

    A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.

  13. Heat flux microsensor measurements

    NASA Technical Reports Server (NTRS)

    Terrell, J. P.; Hager, J. M.; Onishi, S.; Diller, T. E.

    1992-01-01

    A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.

  14. Apparatus for measuring high-flux heat transfer in radiatively heated compact exchangers

    NASA Technical Reports Server (NTRS)

    Olson, Douglas A.

    1989-01-01

    An apparatus is described which can deliver uniform heat flux densities of up to 80 W/sq cm over an area 7.8 cm x 15.2 cm for use in measuring the heat transfer and pressure drop in thin (6 mm or less), compact heat exchangers. Helium gas at flow rates of 0 to 40 kg/h and pressures to 6.9 MPa (1000 psi) is the working fluid. The instrumentation used in the apparatus and the methods for analyzing the data is described. The apparatus will be used initially to test the performance of prototype cooling jackets for the engine struts of the National Aerospace Plane (NASP).

  15. The Sensitivity of Latent Heat Flux to Changes in the Radiative Forcing: A Framework for Comparing Models and Observations

    E-print Network

    Winter, Jonathan (Jonathan Mark)

    A climate model must include an accurate surface physics scheme in order to examine the interactions between the land and atmosphere. Given an increase in the surface radiative forcing, the sensitivity of latent heat flux ...

  16. Concept of an Innovative Photoluminescent Sensor for Radiative Heat Flux Measurement During Super-Orbital Re-Entry

    NASA Astrophysics Data System (ADS)

    Conte, L.; Trifoni, E.; De Filippis, F.; Marraffa, L.

    2014-06-01

    In this work is presented the idea, the physical principle, and a first layout of an innovative sensor capable to collect the VUV contribution to radiative heat flux both for onboard flight measurements and plasma wind tunnel tests.

  17. Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile

    SciTech Connect

    Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

    2010-03-31

    The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

  18. The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates

    NASA Astrophysics Data System (ADS)

    Hinkelman, Laura M.

    The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

  19. Validation experiments to determine radiation partitioning of heat flux to an object in a fully turbulent fire.

    SciTech Connect

    Ricks, Allen; Blanchat, Thomas K.; Jernigan, Dann A.

    2006-06-01

    It is necessary to improve understanding and develop validation data of the heat flux incident to an object located within the fire plume for the validation of SIERRA/ FUEGO/SYRINX fire and SIERRA/CALORE. One key aspect of the validation data sets is the determination of the relative contribution of the radiative and convective heat fluxes. To meet this objective, a cylindrical calorimeter with sufficient instrumentation to measure total and radiative heat flux had been designed and fabricated. This calorimeter will be tested both in the controlled radiative environment of the Penlight facility and in a fire environment in the FLAME/Radiant Heat (FRH) facility. Validation experiments are specifically designed for direct comparison with the computational predictions. Making meaningful comparisons between the computational and experimental results requires careful characterization and control of the experimental features or parameters used as inputs into the computational model. Validation experiments must be designed to capture the essential physical phenomena, including all relevant initial and boundary conditions. A significant question of interest to modeling heat flux incident to an object in or near a fire is the contribution of the radiation and convection modes of heat transfer. The series of experiments documented in this test plan is designed to provide data on the radiation partitioning, defined as the fraction of the total heat flux that is due to radiation.

  20. Detection of Thermal Radiation, Sensing of Heat Flux, and Recovery of Waste Heat by the Transverse Thermoelectric Effect

    NASA Astrophysics Data System (ADS)

    Kanno, Tsutomu; Takahashi, Kouhei; Sakai, Akihiro; Tamaki, Hiromasa; Kusada, Hideo; Yamada, Yuka

    2014-06-01

    The transverse thermoelectric effect is unique in that an output voltage can be extracted in the direction perpendicular to the input temperature gradient. This paper describes how this transverse feature can be exploited to realize simple and promising configurations of thermoelectric devices. For detection of thermal radiation, two-dimensional imaging has been demonstrated by a fabricated sensor array of tilt-oriented Ca x CoO2 epitaxial thin film. We have also developed a serpentine heat flux sensor made of multilayered Bi/Cu, and Bi0.5Sb1.5Te3/Ni tubular thermoelectric devices for power generation. The fabrication processes and test results are presented.

  1. A comparison of small and larger mesoscale latent heat and radiative fluxes: December 6 case study

    NASA Technical Reports Server (NTRS)

    Gultepe, I.; Starr, David; Heymsfield, A. J.

    1993-01-01

    Because of the small amounts of water vapor, the potential for rapid changes, and the very cold temperatures in the upper troposphere, moisture measuring instruments face several problems related to calibration and response. Calculations of eddy moisture fluxes are, therefore, subject to significant uncertainty. The purpose of this study is to examine the importance of latent heat (moisture) fluxes due to small and larger mesoscale circulations in comparison to radiative fluxes within cirrus. Scale separation is made at about 1 km because of significant changes in the structures within cirrus. Only observations at warmer than -40 C are used in this study. The EG&G hygrometer that is used for measuring dewpoint temperature (Td) is believed to be fairly accurate down to -40 C. On the other hand, Lyman-Alpha (L-alpha) hygrometer measurements of moisture may include large drift errors. In order to compensate for these drift errors, the L-alpha hygrometer is often calibrated against the EG&G hygrometer. However, large errors ensue for Td measurements at temperatures less than -40 C. The cryogenic hygrometer frost point measurements may be used to calibrate L-alpha measurements at temperatures less than -40 C. In this study, however, measurements obtained by EG&G hygrometer and L-alpha measurements are used for the flux calculations.

  2. Similarity solution for a cylindrical shock wave in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux

    NASA Astrophysics Data System (ADS)

    Vishwakarma, J. P.; Nath, G.

    2012-01-01

    The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston (or inner expanding surface). The fluid velocities in the ambient medium are assume to be vary and obey power laws. The density of the ambient medium is assumed to be constant, the heat conduction is express in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. In order to obtain the similarity solutions the angular velocity of the ambient medium is assume to be decreasing as the distance from the axis increases. The effects of the variation of the heat transfer parameter and non-idealness of the gas in the mixture are investigated. The effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are also investigated.

  3. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  4. Finite difference analysis of radiative free convection flow past an impulsively started vertical plate with variable heat and mass flux

    Microsoft Academic Search

    V. R. Prasad; N. Bhaskar Reddy; R. Muthucumaraswamy; B. Vasu

    A numerical solution of the unsteady radiative free convection flow of an incompressible viscous fluid past an impulsively started vertical plate with variable heat and mass flux is presented here. This type of problem finds application in many technological and engineering fields such as rocket propulsion systems, spacecraft re- entry aerothermodynamics, cosmical flight aerodynamics, plasma physics, glass production and furnace

  5. Tuning near field radiative heat flux through surface excitations with a metal insulator transition.

    PubMed

    van Zwol, P J; Ranno, L; Chevrier, J

    2012-06-01

    The control of heat flow is a formidable challenge due to lack of good thermal insulators. Promising new opportunities for heat flow control were recently theoretically discovered for radiative heat flow in near field, where large heat flow contrasts may be achieved by tuning electronic excitations on surfaces. Here we show experimentally that the phase transition of VO2 entails a change of surface polariton states that significantly affects radiative heat transfer in near field. In all cases the Derjaguin approximation correctly predicted radiative heat transfer in near field, but it underestimated the far field limit. Our results indicate that heat flow contrasts can be realized in near field that can be larger than those obtained in far field. PMID:23003960

  6. Similarity solution for the flow behind a shock wave in a non-ideal gas with heat conduction and radiation heat-flux in magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2014-05-01

    The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock front.

  7. GEWEX Radiative Flux Assessment

    Atmospheric Science Data Center

    2013-06-27

    GEWEX Radiative Flux Assessment The ultimate goal of the Global Energy and Water Cycle Experiment ( GEWEX ) global data analysis projects is to obtain observations of the ... (atmosphere, ocean, land, cryosphere, biosphere). The GEWEX Radiative Flux Assessment (RFA) project will provide a forum for ...

  8. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W. (Espanola, NM); Borella, Henry M. (Santa Barbara, CA); Cates, Michael R. (Oak Ridge, TN); Turley, W. Dale (Santa Barbara, CA); MacArthur, Charles D. (Clayton, OH); Cala, Gregory C. (Dayton, OH)

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator wherein each thermographic layer comprises a plurality of respective thermographic phosphors. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  9. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W. (Espanola, NM); Borella, Henry M. (Santa Barbara, CA); Cates, Michael R. (Oak Ridge, TN); Turley, W. Dale (Santa Barbara, CA); MacArthur, Charles D. (Clayton, OH); Cala, Gregory C. (Dayton, OH)

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator, wherein each thermographic layer comprises a plurality of respective thermographic sensors in a juxtaposed relationship with respect to each other. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  10. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W. (Espanola, NM); Borella, Henry M. (Santa Barbara, CA); Cates, Michael R. (Oak Ridge, TN); Turley, W. Dale (Santa Barbara, CA); MaCarthur, Charles D. (Clayton, OH); Cala, Gregory C. (Dayton, OH)

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  11. Latent Heat in Soil Heat Flux Measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  12. Temporal monitoring of radiative heat flux from the craters of Tendürek volcano (East Anatolia, Turkey) using ASTER satellite imagery

    NASA Astrophysics Data System (ADS)

    Ulusoy, ?nan

    2014-05-01

    Tendürek volcano is situated in the Eastern Anatolia near Turkish-Iranian border. It is one of the youngest volcanoes of Eastern Anatolia and it is a polygenetic, basaltic shield volcano formed by successive basalt flows. Tendürek is characterized by alkaline volcanism. Holocene and historical activity has been reported. Hydrothermal activity have been observed on the twin summit craters. Fumaroles, steam vents, steam/gas emission and zones of hot grounds have been reported. In order to quantify and to determine a base value for the current thermal state of the volcano, we used ASTER Thermal Infrared spectra. Four ASTER daytime and nighttime images have been used to calculate radiative heat flux from the craters. Heat flux calculations have been made using three nighttime images and a daytime image acquired in 2002, 2004, 2008 and 2012. Images have been atmospherically corrected, temperature and emissivity have been separated and Land Surface Temperature (LST) has been calculated from 5 thermal bands. LST images have been topographically corrected. Heat flux have been calculated using corrected surface temperature data, emissivity, vapor pressure and height-dependent air temperature values. Maximum temperature anomalies observed were 9.0 °C and 15.9 °C for the western and eastern craters respectively. Heat flux is estimated between 14.4 and 25.2 W/m² at the western crater and between 16.5 and 49.4 W/m² at the eastern crater. These values are well correlated with other known low-level activity volcanoes such as Yellowstone, Stromboli and Nisyros, whereas they are lower than that of observed at Vulcano.

  13. Optical heat flux gauge

    DOEpatents

    Noel, B.W.; Borella, H.M.; Cates, M.R.; Turley, W.D.; MacArthur, C.D.; Cala, G.C.

    1991-04-09

    A heat flux gauge is disclosed comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator, wherein each thermographic layer comprises a plurality of respective thermographic sensors in a juxtaposed relationship with respect to each other. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable. 9 figures.

  14. Heat Flux Sensor Testing

    NASA Technical Reports Server (NTRS)

    Clark, D. W.

    2002-01-01

    This viewgraph presentation provides information on the following objectives: Developing secondary calibration capabilities for MSFC's (Marshall Space Flight Center) Hot Gas Facility (HGF), a Mach 4 Aerothermal Wind Tunnel; Evaluating ASTM (American Society for Testing and Materials) slug/ thinskin calorimeters against current HGF heat flux sensors; Providing verification of baselined AEDC (Arnold Engineering Development Center) / Medtherm gage calibrations; Addressing future calibration issues involving NIST (National Institute of Standards and Technology) certified radiant gages.

  15. Heat Flux Sensor Testing

    NASA Astrophysics Data System (ADS)

    Clark, D. W.

    2002-07-01

    This viewgraph presentation provides information on the following objectives: Developing secondary calibration capabilities for MSFC's (Marshall Space Flight Center) Hot Gas Facility (HGF), a Mach 4 Aerothermal Wind Tunnel; Evaluating ASTM (American Society for Testing and Materials) slug/ thinskin calorimeters against current HGF heat flux sensors; Providing verification of baselined AEDC (Arnold Engineering Development Center) / Medtherm gage calibrations; Addressing future calibration issues involving NIST (National Institute of Standards and Technology) certified radiant gages.

  16. Radiative Flux Analysis

    SciTech Connect

    Long, Chuck [NOAA

    2008-05-14

    The Radiative Flux Analysis is a technique for using surface broadband radiation measurements for detecting periods of clear (i.e. cloudless) skies, and using the detected clear-sky data to fit functions which are then used to produce continuous clear-sky estimates. The clear-sky estimates and measurements are then used in various ways to infer cloud macrophysical properties.

  17. Modeling comparison of divertor radiation from N and Ar for heat flux mitigation in JET ELMy H-modes

    NASA Astrophysics Data System (ADS)

    Monier-Garbet, P.; Hogan, J.; Corre, Y.; Thomas, P.; Andrew, P.; Coster, D.; Dumortier, P.; Eich, T.; Huber, A.; Koslowski, R.; Lawson, K.; Messiaen, A.; Nave, M.; Ongena, J.; Rapp, J.; Stober, J.

    2003-10-01

    The transient power load to divertor target plates from Type I ELMs represents a severe problem for the operation of ITER. We continue the assessment of impurity seeding as a way to reduce such heat fluxes through enhanced radiation, while maintaining good core confinement. Previous work with Ar seeded H-modes on JET found peak heat flux could be reduced by ˜2x, while confinement was only ˜5% less than for the D reference pulse [1]. Further experiments with N (to localize divertor/SOL radiation) found that dWtarget/dWdia could be reduced by 18/24% (outer/inner target) during a Type-I ELM, with a loss of confinement limited to 5% for high edge electron density. SOLPS calculations for all species of D+C+N suggested that the fraction of the ELM energy radiated before reaching the target plates depends on details of the ELM model, which are too fast to be resolved experimentally at present. With this caveat, a fraction consistent with the experiment was found for tELM >> 150_microsec , albeit with a discrepancy for the absolute values of dWtarget/dWSOL [2]. In this paper we describe development of a SOLPS model for all species of D+C+Ar and compare the Ar and N core and SOL/divertor radiation components during ELM transients on a similar basis. [1] J. Rapp et al., Proc. 19th Int. Conf. Lyon 2002, IAEA, Vienna (2003), and submitted to Nucl. Fusion. [2] P. Monier-Garbet et al EPS St. Petersburg, 2003

  18. Self-similar flow of a rotating dusty gas behind the shock wave with increasing energy, conduction and radiation heat flux

    Microsoft Academic Search

    G. Nath

    A self-similar solution is obtained for one dimensional adiabatic flow behind a cylindrical shock wave propagating in a rotating dusty gas in presence of heat conduction and radiation heat flux with increasing energy. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is

  19. Pyrolytic graphite gauge for measuring heat flux

    NASA Technical Reports Server (NTRS)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  20. Critical heat flux around strongly heated nanoparticles

    NASA Astrophysics Data System (ADS)

    Merabia, Samy; Keblinski, Pawel; Joly, Laurent; Lewis, Laurent J.; Barrat, Jean-Louis

    2009-02-01

    We study heat transfer from a heated nanoparticle into surrounding fluid using molecular dynamics simulations. We show that the fluid next to the nanoparticle can be heated well above its boiling point without a phase change. Under increasing nanoparticle temperature, the heat flux saturates, which is in sharp contrast with the case of flat interfaces, where a critical heat flux is observed followed by development of a vapor layer and heat flux drop. These differences in heat transfer are explained by the curvature-induced pressure close to the nanoparticle, which inhibits boiling. When the nanoparticle temperature is much larger than the critical fluid temperature, a very large temperature gradient develops, resulting in close to ambient temperature just a radius away from the particle surface. The behavior reported allows us to interpret recent experiments where nanoparticles can be heated up to the melting point, without observing boiling of the surrounding liquid.

  1. Heat flux microsensor measurements and calibrations

    NASA Technical Reports Server (NTRS)

    Terrell, James P.; Hager, Jon M.; Onishi, Shinzo; Diller, Thomas E.

    1992-01-01

    A new thin-film heat flux gage has been fabricated specifically for severe high temperature operation using platinum and platinum-10 percent rhodium for the thermocouple elements. Radiation calibrations of this gage were performed at the AEDC facility over the available heat flux range (approx. 1.0 - 1,000 W/cu cm). The gage output was linear with heat flux with a slight increase in sensitivity with increasing surface temperature. Survivability of gages was demonstrated in quench tests from 500 C into liquid nitrogen. Successful operation of gages to surface temperatures of 750 C has been achieved. No additional cooling of the gages is required because the gages are always at the same temperature as the substrate material. A video of oxyacetylene flame tests with real-time heat flux and temperature output is available.

  2. Atmospheric State, Cloud Microphysics and Radiative Flux

    SciTech Connect

    Mace, Gerald

    2008-01-15

    Atmospheric thermodynamics, cloud properties, radiative fluxes and radiative heating rates for the ARM Southern Great Plains (SGP) site. The data represent a characterization of the physical state of the atmospheric column compiled on a five-minute temporal and 90m vertical grid. Sources for this information include raw measurements, cloud property and radiative retrievals, retrievals and derived variables from other third-party sources, and radiative calculations using the derived quantities.

  3. Atmospheric State, Cloud Microphysics and Radiative Flux

    DOE Data Explorer

    Mace, Gerald

    Atmospheric thermodynamics, cloud properties, radiative fluxes and radiative heating rates for the ARM Southern Great Plains (SGP) site. The data represent a characterization of the physical state of the atmospheric column compiled on a five-minute temporal and 90m vertical grid. Sources for this information include raw measurements, cloud property and radiative retrievals, retrievals and derived variables from other third-party sources, and radiative calculations using the derived quantities.

  4. Radial heat flux transformer

    NASA Technical Reports Server (NTRS)

    Basiulis, A.; Buzzard, R. J.

    1971-01-01

    Unit moves heat radially from small diameter shell to larger diameter shell, or vice versa, with negligible temperature drop, making device useful wherever heating or cooling of concentrically arranged materials, substances, and structures is desired.

  5. Heating of a piezoelectric rod of semi-infinite length due to prescribed heat flux into it through radiation condition

    Microsoft Academic Search

    M. A. Khan

    1972-01-01

    A semi-infinite rod of piezoelectric material is initially at zero temperature. The deformation at any point of the rod is also zero initially. The radiation at the surface is equal to a prescribed temperature for all time. The velocity is kept zero initially. The distribution of temperature, stress, displacement, electric-field and entropy density have been worked out.

  6. Radiative flux measurements in the troposphere

    Microsoft Academic Search

    Francisco P. J. Valero; Warren J. Y. Gore; Lawrence P. M. Giver

    1982-01-01

    The results of radiative flux-density measurements in the troposphere, made using an especially designed radiometer mounted on a Cessna 402B aircraft, are reported. The radiometer incorporates several well-known principles that result in highly accurate determinations of radiative fluxes in the atmosphere. Heating rates for gases and for aerosols are calculated, using measurements and radiosonde data. Instrument performance is verified by

  7. Conical electromagnetic radiation flux concentrator

    NASA Technical Reports Server (NTRS)

    Miller, E. R.

    1972-01-01

    Concentrator provides method of concentrating a beam of electromagnetic radiation into a smaller beam, presenting a higher flux density. Smaller beam may be made larger by sending radiation through the device in the reverse direction.

  8. Impact of aerosol direct radiative forcing on the radiative budget, surface heat fluxes, and atmospheric dynamics during the heat wave of summer 2003 over western Europe: A modeling study

    NASA Astrophysics Data System (ADS)

    PéRé, J. C.; Mallet, M.; Pont, V.; Bessagnet, B.

    2011-12-01

    In this work, an off-line coupling between the chemistry-transport model CHIMERE (associated with an aerosol optical module) and the meteorological model Weather Research and Forecasting (WRF) is used to study (1) the direct radiative forcing of pollution aerosols during the heat wave of summer 2003 over western Europe and (2) the possible feedbacks of this direct radiative forcing on the surface-atmosphere system. Simulations performed for the period 7-15 August 2003 reveal a significant decrease of daily mean solar radiation reaching the surface (?FBOA = -(10-30) W/m2) because of back scattering at the top of the atmosphere (?FTOA = -(1-12) W/m2) and also absorption of solar radiation by polluted particles (?Fatm = + (5-23) W/m2). During daytime, the aerosol surface dimming induces a mean reduction of both sensible (16 W/m2) and latent (21 W/m2) heat fluxes emitted by the terrestrial surface, resulting in a radiative cooling of the air near the surface (up to 2.9 K/d at noon). Simultaneously, the absorption of solar energy by aerosols causes an atmospheric radiative heating within the planetary boundary layer reaching 1.20 K/d at noon. As a consequence, the direct radiative effect of aerosols is shown to reduce both the planetary boundary layer height (up to 30%) and the horizontal wind speed (up to 6%); that may have contributed to favor the particulate pollution during the heat wave of summer 2003.

  9. High flux heat transfer in a target environment

    E-print Network

    McDonald, Kirk

    velocity [m/s] (Mach=0.3 for gases) Pr Re Nu heat transfer coefficient [W/m 2 K] allowable temp rise [KHigh flux heat transfer in a target environment T. Davenne High Power Targets Group Rutherford · Radiation Cooling · Forced Convection · Nucleate Boiling · Critical Heat Flux · Other ideas · Summary #12

  10. Towards Improved Estimates of Ocean Heat Flux

    NASA Astrophysics Data System (ADS)

    Bentamy, Abderrahim; Hollman, Rainer; Kent, Elisabeth; Haines, Keith

    2014-05-01

    Recommendations and priorities for ocean heat flux research are for instance outlined in recent CLIVAR and WCRP reports, eg. Yu et al (2013). Among these is the need for improving the accuracy, the consistency, and the spatial and temporal resolution of air-sea fluxes over global as well as at region scales. To meet the main air-sea flux requirements, this study is aimed at obtaining and analyzing all the heat flux components (latent, sensible and radiative) at the ocean surface over global oceans using multiple satellite sensor observations in combination with in-situ measurements and numerical model analyses. The fluxes will be generated daily and monthly for the 20-year (1992-2011) period, between 80N and 80S and at 0.25deg resolution. Simultaneous estimates of all surface heat flux terms have not yet been calculated at such large scale and long time period. Such an effort requires a wide range of expertise and data sources that only recently are becoming available. Needed are methods for integrating many data sources to calculate energy fluxes (short-wave, long wave, sensible and latent heat) across the air-sea interface. We have access to all the relevant, recently available satellite data to perform such computations. Yu, L., K. Haines, M. Bourassa, M. Cronin, S. Gulev, S. Josey, S. Kato, A. Kumar, T. Lee, D. Roemmich: Towards achieving global closure of ocean heat and freshwater budgets: Recommendations for advancing research in air-sea fluxes through collaborative activities. INTERNATIONAL CLIVAR PROJECT OFFICE, 2013: International CLIVAR Publication Series No 189. http://www.clivar.org/sites/default/files/ICPO189_WHOI_fluxes_workshop.pdf

  11. Latent Heat Flux

    NSDL National Science Digital Library

    climvis.org

    This animation is available in an animated GIF or Flash formats and shows monthly variations in energy in the form of latent heat. This animation shows the energy absorbed due to evaporation. Interesting patterns to observe are higher values over the Gulf Stream and lower values in upwelling areas, like off the coasts of Labrador and Peru. In the Flash format, the animation can easily be rewound or paused to stress important points.

  12. Urban Signatures: Latent Heat Flux

    NSDL National Science Digital Library

    Jeff DeLaBeaujardiere

    2005-05-27

    Big cities influence the environment around them. For example, urban areas are typically warmer than their surroundings. Cities are strikingly visible in computer models that simulate the Earths land surface. This visualization shows latent heat flux predicted by the Land Information System (LIS) for a day in June 2001. (Latent heat flux refers to the transfer of energy from the Earths surface to the air above by evaporation of water on the surface; for a more detailed explanation see http:--www.uwsp.edu-geo-faculty-ritter-geog101-textbook-energy-energy_balance.html). Latent heat flux is lower in the cities because there is less evaporation there. Only part of the global computation is shown, focusing on the highly urbanized northeast corridor in the United States, including the cities of Boston, New York, Philadelphia, Baltimore, and Washington.

  13. Semicollisional heat flux in laser heated plasmas

    NASA Astrophysics Data System (ADS)

    Tahraoui, A.; Bendib, A.

    2002-07-01

    The semicollisional transport theory in laser heated plasmas is presented. The Fokker-Planck equation that includes the electron-electron interaction up to the first anisotropy is solved numerically for arbitrary collisionality range. The inverse bremsstrahlung absorption of the laser energy by the electrons is taken into account. Nonlocal heat flux formulas due to the thermal gradients and to the laser heating, which are in good agreement with the numerical results, are proposed. These transport coefficients are compared with the results of the literature.

  14. Non-contact heat flux measurement using a transparent sensor

    NASA Technical Reports Server (NTRS)

    Ng, Daniel; Spuckler, Charles M.

    1993-01-01

    A working non-contact heat flux sensor was demonstrated using a transparent material (sapphire) and a multiwavelength pyrometer. The pyrometer is used to measure the temperatures of the two surfaces of the sensor from the spectrum of radiation originating from them. The heat conducted through the material is determined from the temperature difference of the two surfaces and the thermal conductivity of the material. The measured heat flux is equal to the incident heat flux within experimental error indicating that no calibration would be necessary. A steady state heat flux of 100 kW/sq m was easily achieved.

  15. Coupled estimation of surface heat fluxes and vegetation dynamics from remotely sensed land surface temperature and fraction of photosynthetically active radiation

    NASA Astrophysics Data System (ADS)

    Bateni, S. M.; Entekhabi, D.; Margulis, S.; Castelli, F.; Kergoat, L.

    2014-11-01

    Remotely sensed Land Surface Temperature (LST) and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) are assimilated, respectively, into the Surface Energy Balance (SEB) equation and a Vegetation Dynamics Model (VDM) in order to estimate surface fluxes and vegetation dynamics. The problem is posed in terms of three unknown and dimensionless parameters: (1) neutral bulk heat transfer coefficient, which scales the sum of turbulent heat fluxes, (2) soil and canopy evaporative fractions that characterize partitioning among the turbulent heat fluxes over soil and vegetation, and (3) specific leaf area, which captures seasonal phenology and vegetation dynamics. The model is applied over the Gourma site in Mali, the northern region of the West African Monsoon (WAM) domain. The application of the model over the Gourma site shows that spaceborne LST observations can be used to constrain the SEB equation and obtain its key two unknown parameters (i.e., neutral bulk heat transfer coefficient and evaporative fraction). We demonstrate that the spatial patterns of estimated neutral bulk heat transfer coefficient and evaporative fraction resemble, respectively, those of independently observed vegetation index and soil moisture. The framework also yields estimates of surface energy balance components. The daily sensible, latent, and ground heat flux estimates at the Agoufou site that is located in the south of the Gourma region have, respectively, a root-mean-square error (RMSE) of 53.6, 34.4, and 45.1 Wm-2. The daily sensible heat flux estimates at the Bamba site, which is located in the north of the Gourma domain, have a RMSE of 42.6 Wm-2. The results also show that remotely sensed FPAR observations can constrain the VDM and retrieve its main unknown parameter (specific leaf area) over large-scale domains without costly in situ measurements. The results indicate that the estimated specific leaf area values vary reasonably with the expected influential environmental variables such as precipitation, air temperature, and solar radiation. Assimilating FPAR observations into the VDM can also provide an estimate of Leaf Area Index (LAI) dynamics. The estimated LAI values are comparable in magnitude, spatial pattern and temporal evolution with satellite retrievals.

  16. Mass transfer effects on the unsteady mhd radiative- convective flow of a micropolar fluid past a vertical porous plate with variable heat and mass fluxes

    NASA Astrophysics Data System (ADS)

    Reddy, M. Gnaneswara

    2013-03-01

    The problem of unsteady two-dimensional laminar flow of a viscous incompressible micropolar fluid past a vertical porous plate in the presence of a transverse magnetic field and thermal radiation with variable heat and mass fluxes is considered. The free stream velocity is subjected to exponentially increasing or decreasing small perturbations. A uniform magnetic field acts perpendicularly to a porous surface where a micropolar fluid is absorbed with a suction velocity varying with time. The Rosseland approximation is used to describe radiative heat transfer in the limit of optically thick fluids. The effects of the flow parameters and thermophysical properties on the velocity and temperature fields across the boundary layer are investigated. The effects of various parameters on the velocity, microrotation velocity, temperature, and concentration profiles are given graphically, and the values of the skin friction and couple stress coefficients are presented.

  17. Latent and sensible heat flux estimated from ERS-1 data

    NASA Technical Reports Server (NTRS)

    Iacobellis, S. F.; Gautier, C.

    1993-01-01

    Two issues regarding surface latent and sensible heat flux are addressed: its value in low wind speed conditions over the tropical oceans,and its determination solely from satellite observations. The investigation is performed with an oceanic mixed layer model operated in an 'inverse' mode. The 'normal' model is forced with the surface heat and radiative fluxes and produces the SST evolution, whereas the 'inverse' model produces the latent sensible heat flux given the SST and surface radiative flux as input. The results indicate that at low wind speeds there exists a minimum latent sensible heat flux of about 80 to 100 W/sq m. Sensitivity studies show that the latent sensible heat flux is very sensitive to random errors in the forcing SST time series. The implications of this strong sensitivity in regards to the use of satellite measurements to supply the forcing SST are discussed.

  18. Automated Heat-Flux-Calibration Facility

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    Computer control speeds operation of equipment and processing of measurements. New heat-flux-calibration facility developed at Lewis Research Center. Used for fast-transient heat-transfer testing, durability testing, and calibration of heat-flux gauges. Calibrations performed at constant or transient heat fluxes ranging from 1 to 6 MW/m2 and at temperatures ranging from 80 K to melting temperatures of most materials. Facility developed because there is need to build and calibrate very-small heat-flux gauges for Space Shuttle main engine (SSME).Includes lamp head attached to side of service module, an argon-gas-recirculation module, reflector, heat exchanger, and high-speed positioning system. This type of automated heat-flux calibration facility installed in industrial plants for onsite calibration of heat-flux gauges measuring fluxes of heat in advanced gas-turbine and rocket engines.

  19. Deployable Heat Pipe Radiator

    NASA Technical Reports Server (NTRS)

    Edelstein, F.

    1975-01-01

    A 1.2- by 1.8-m variable conductance heat pipe radiator was designed, built, and tested. The radiator has deployment capability and can passively control Freon-21 fluid loop temperatures under varying loads and environments. It consists of six grooved variable conductance heat pipes attached to a 0.032-in. aluminum panel. Heat is supplied to the radiator via a fluid header or a single-fluid flexible heat pipe header. The heat pipe header is an artery design that has a flexible section capable of bending up to 90 degrees. Radiator loads as high as 850 watts were successfully tested. Over a load variation of 200 watts, the outlet temperature of the Freon-21 fluid varied by 7 F. An alternate control system was also investigated which used a variable conductance heat pipe header attached to the heat pipe radiator panel.

  20. The Theory of Heat Flux Meters

    Microsoft Academic Search

    J. R. Philip

    1961-01-01

    For a spheroidal heat flux meter appropriately oriented in an infinite volume of a medium in which there is a steady heat flux, i, the ratio of mean flux density through the meter to the flux density through the medium is related to , the ratio of meter conductivity to medium conductivity, by an (exact) equation of the form

  1. Latent heat sink in soil heat flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface energy balance includes a term for soil heat flux. Soil heat flux is difficult to measure because it includes conduction and convection heat transfer processes. Accurate representation of soil heat flux is an important consideration in many modeling and measurement applications. Yet, the...

  2. Self-similar flow of a rotating dusty gas behind the shock wave with increasing energy, conduction and radiation heat flux

    NASA Astrophysics Data System (ADS)

    Nath, G.

    2012-01-01

    A self-similar solution is obtained for one dimensional adiabatic flow behind a cylindrical shock wave propagating in a rotating dusty gas in presence of heat conduction and radiation heat flux with increasing energy. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston (or inner expanding surface). The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature only. In order to obtain the similarity solutions the initial density of the ambient medium is assumed to be constant and the angular velocity of the ambient medium is assumed to be decreasing as the distance from the axis increases. The effects of the variation of the heat transfer parameters and non-idealness of the gas in the mixture are investigated. The effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are also investigated.

  3. Inflation driven by causal heat flux

    E-print Network

    Roy Maartens; Megan Govender; Sunil Maharaj

    1997-10-31

    We find a simple inflationary solution in an inhomogeneous spacetime with heat flux. The heat flux obeys a causal transport equation, and counteracts the inflationary decrease of energy density. At late times, the heat flux tends to zero and the fluid approaches the equation of state $p=-\\rho$.

  4. Divertor Heat Flux Control Research on DIII-D

    SciTech Connect

    Leonard, A.W. [General Atomics (United States)

    2005-10-15

    Divertor heat flux characterization and control results from DIII-D are summarized. The peak divertor heat flux is found to scale with a simple conduction model having perpendicular transport scaling with plasma current and heating power. In a double-null configuration, the heat flux sharing between divertors is very sensitive to the magnetic balance. Heat flux control in H-mode with edge-localized modes (ELMs) is obtained with deuterium gas puffing resulting in a partially detached divertor (PDD) regime. Important physical processes in the PDD regime include radiation from the intrinsic carbon impurity and deuterium, loss of electron pressure near the separatrix, parallel energy transport in the divertor dominated by convection, and particle flux reduction from deuterium recombination. Divertor neutral pressure is found to be an important control parameter to maintain the PDD regime. Divertor heat flux reduction is also obtained with impurity injection. In one approach divertor radiation is enhanced using induced scrape-off-layer flow to enrich divertor impurity concentration. Another approach uses seeded impurities to produce radiation inside the separatrix in a radiating mantle configuration. Observations of heat flux transients from ELMs and disruptions are summarized. Finally, the implications of these results for next-generation tokamaks are discussed.

  5. Observational study of relationships between incoming radiation, open water fraction, and ocean-to-ice heat flux in the Transpolar Drift: 2002-2010

    NASA Astrophysics Data System (ADS)

    Stanton, Timothy P.; Shaw, William J.; Hutchings, Jennifer K.

    2012-07-01

    Ocean/ice interface heat fluxes (F0) are calculated from upper ocean measurements obtained from autonomous systems repeatedly deployed in the Arctic Ocean Transpolar Drift between 2002 and 2010. Average F0 values over the nine summer heating season realizations varied between 4.6 and 10.5 W m-2 with an average summer value of 7.6 W m-2. Between 2002 and 2010, summer-averagedF0passed through a clear minimum, with most inter-annual variability inF0 dominated by differences in ocean heat content, rather than by differences in surface forcing. We test if Transpolar Drift F0 is supported primarily by local, radiative energy flux entering the upper ocean through areas of open water (Frw). Frwis estimated by combining re-analysis solar radiation products with satellite-borne passive microwave ice concentration products and observed divergence of drifting buoys. Inter-annual variability of summer-averaged surface insolation is relatively small (0.04 normalized standard deviation, NSTD), so differences in open water fraction (0.30 NSTD) are the most likely sources of the observedF0variability. Ensemble-averaged over the 2002-2010 summers, the satellite and buoy-divergenceFrw, are equal to 8.1, and 8.0 W m-2, respectively. Therefore, over the course of the summer season, sufficient energy enters the upper ocean through open water to wholly support the observed F0. Reasonable agreement between the two open water fraction estimates further indicates that mechanical processes, rather than lateral melting, are controlling the amount of radiation entering the upper ocean, implying that ocean ice-albedo feedbacks were not strong in the Transpolar Drift in the last decade.

  6. Spatial Scale Gaps of Turbulent Heat Fluxes in Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Fochesatto, G. J.; Gruber, M. A.; Cristóbal-Rosselló, J.; Edgar, C.; Kane, D. L.

    2013-12-01

    Large-area averaged turbulent fluxes of scalars (heat and carbon) play an important role in climate and ecosystem models by resolving the scale-gap closure defining top-down and bottom-up scaling schemes. Large Aperture Scintillometer (LAS) measurement of the refractive index structure function (CN2) allows for indirect retrieval of area-averaged (>km2) atmospheric boundary layer sensible heat fluxes. In this work we report observations of LAS in Arctic tundra at Imnavait Creek Basin. LAS-derived fluxes are compared to more localized measurements of heat fluxes obtained by an eddy-covariance (EC) system distributed across the basin. This article discusses the divergence observed in the temporal series of LAS-fluxes in comparison to spatially distributed measurements of EC-fluxes. The comparison stresses the role of the Arctic ABL structure, terrain-flow characteristics and radiative fluxes in the overall spatial representation of fluxes.

  7. Dimensional Analysis of Thermoelectric Modules Under Constant Heat Flux

    NASA Astrophysics Data System (ADS)

    Suzuki, Ryosuke O.; Fujisaka, Takeyuki; Ito, Keita O.; Meng, Xiangning; Sui, Hong-Tao

    2015-01-01

    Thermoelectric power generation is examined in the case of radiative heating. A constant heat flux is assumed in addition to consideration of the Seebeck effect, Peltier effect, and Joule heating with temperature-dependent material properties. Numerical evaluations are conducted using a combination of the finite-volume method and an original simultaneous solver for the heat transfer, thermoelectric, and electric transportation phenomena. Comparison with experimental results shows that the new solver could work well in the numerical calculations. The calculations predict that the Seebeck effect becomes larger for longer thermoelectric elements because of the larger temperature difference. The heat transfer to the cold surface is critical to determine the junction temperatures under a constant heat flux from the hot surface. The negative contribution from Peltier cooling and heating can be minimized when the current is smaller for longer elements. Therefore, a thicker TE module can generate more electric power even under a constant heat flux.

  8. Estimates of ocean heat flux at SHEBA

    Microsoft Academic Search

    Donald K. Perovich; Bruce Elder

    2002-01-01

    Observations of sea ice mass balance and temperature made during the year-long Surface HEat Budget of the Arctic Ocean (SHEBA) field experiment were used to calculate monthly estimates of the ocean heat flux for a variety of ice types. The ocean heat flux displayed a strong seasonal cycle, with values of a few W m?2 from October through June followed

  9. Dual Active Surface Heat Flux Gage Probe

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Kolodziej, Paul

    1995-01-01

    A unique plug-type heat flux gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat flux gage body to the end of a hollow metal cylindrical bolt containing a metal inner tube. Cooling air flows through the inner tube, impinges onto the back of the gage body and then flows out through the annulus formed between the inner tube and the hollow bolt wall. Heat flux was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat flux, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat fluxes measured with the probe were compared with absorbed heat fluxes measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat fluxes measured with the reference calorimeters and heat flux gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat flux measurement. A current application for dual active surface heat flux gages is for transient and steady absorbed heat flux, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.

  10. Miniature Convection Cooled Plug-type Heat Flux Gauges

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1994-01-01

    Tests and analysis of a new miniature plug-type heat flux gauge configuration are described. This gauge can simultaneously measure heat flux on two opposed active surfaces when heat flux levels are equal to or greater than about 0.2 MW/m(sup 2). The performance of this dual active surface gauge was investigated over a wide transient and steady heat flux and temperature range. The tests were performed by radiatively heating the front surface with an argon arc lamp while the back surface was convection cooled with air. Accuracy is about +20 percent. The gauge is responsive to fast heat flux transients and is designed to withstand the high temperature (1300 K), high pressure (15 MPa), erosive and corrosive environments in modern engines. This gauge can be used to measure heat flux on the surfaces of internally cooled apparatus such as turbine blades and combustors used in jet propulsion systems and on the surfaces of hypersonic vehicles. Heat flux measurement accuracy is not compromised when design considerations call for various size gauges to be fabricated into alloys of various shapes and properties. Significant gauge temperature reductions (120 K), which can lead to potential gauge durability improvement, were obtained when the gauges were air-cooled by forced convection.

  11. ORIGINAL ARTICLE Sensible and latent heat flux response to diurnal variation in soil

    E-print Network

    in latent heat flux was significant and depended mostly on solar radiation during the completely thawed stage. However, while diurnal variation in solar radiation during the completely frozen stage solar radiation on latent heat flux could not be ignored. Keywords Tibetan Plateau Á Freeze/thaw Á Soil

  12. Divertor Heat Flux Mitigation in the National Spherical Torus Experiment

    SciTech Connect

    Soukhanovskii, V A; Maingi, R; Gates, D A; Menard, J E; Paul, S F; Raman, R; Roquemore, A L; Bell, M G; Bell, R E; Boedo, J A; Bush, C E; Kaita, R; Kugel, H W; LeBlanc, B P; Mueller, D

    2008-08-04

    Steady-state handling of divertor heat flux is a critical issue for both ITER and spherical torus-based devices with compact high power density divertors. Significant reduction of heat flux to the divertor plate has been achieved simultaneously with favorable core and pedestal confinement and stability properties in a highly-shaped lower single null configuration in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 2000] using high magnetic flux expansion at the divertor strike point and the radiative divertor technique. A partial detachment of the outer strike point was achieved with divertor deuterium injection leading to peak flux reduction from 4-6 MW m{sup -2} to 0.5-2 MW m{sup -2} in small-ELM 0.8-1.0 MA, 4-6 MW neutral beam injection-heated H-mode discharges. A self-consistent picture of outer strike point partial detachment was evident from divertor heat flux profiles and recombination, particle flux and neutral pressure measurements. Analytic scrape-off layer parallel transport models were used for interpretation of NSTX detachment experiments. The modeling showed that the observed peak heat flux reduction and detachment are possible with high radiated power and momentum loss fractions, achievable with divertor gas injection, and nearly impossible to achieve with main electron density, divertor neutral density or recombination increases alone.

  13. Heat fluxes across the Antarctic Circumpolar Current

    NASA Astrophysics Data System (ADS)

    Ferrari, Ramiro; Provost, Christine; Hyang Park, Young; Sennéchael, Nathalie; Garric, Gilles; Bourdallé-Badie, Romain

    2014-05-01

    Determining the processes responsible for the Southern Ocean heat balance is fundamental to our understanding of the weather and climate systems. Therefore, in the last decades, various studies aimed at analyzing the major mechanisms of the oceanic poleward heat flux in this region. Previous works stipulated that the cross-stream heat flux due to the mesoscale transient eddies was responsible for the total meridional heat transport across the Antarctic Circumpolar Current (ACC). Several numerical modelling and current meters data studies have recently challenged this idea. These showed that the heat flux due to the mean flow in the southern part of the Antarctic Circumpolar Current could be larger than the eddy heat flux contribution by two orders of magnitude. Eddy heat flux and heat flux by the mean flow distributions of were examined in Drake Passage using in situ measurements collected during the DRAKE 2006-9 project (from January 2006 to March 2009), available observations from the historical DRAKE 79 experiment and high resolution model outputs (ORCA 12, MERCATOR). The Drake Passage estimations provided a limited view of heat transport in the Southern Ocean. The small spatial scales shown by the model derived heat flux by the mean flow indicate that circumpolar extrapolations from a single point observation are perilous. The importance of the heat flux due by the mean flow should be further investigated using other in situ observations and numerical model outputs. Similar situation has been observed, with important implication for heat flux due to the mean flow, in other topographically constricted regions with strong flow across prominent submarine ridges (choke points). We have estimated the heat flux due to the mean flow revisiting other ACC mooring sites where in situ time series are available, e.g. south of Australia (Tasmania) (Phillips and Rintoul, 2000), southeast of New Zealand (Campbell Plateau) (Bryden and Heath, 1985). Heat fluxes due to the mean flow at those choke points were compared to model outputs and provided new circumpolar estimates indicating that the choke points are a potential overwhelming contribution for the heat flux needed to balance heat lost to the atmosphere in the Southern Ocean.

  14. Comparison of the high temperature heat flux sensor to traditional heat flux gages under high heat flux conditions.

    SciTech Connect

    Blanchat, Thomas K.; Hanks, Charles R.

    2013-04-01

    Four types of heat flux gages (Gardon, Schmidt-Boelter, Directional Flame Temperature, and High Temperature Heat Flux Sensor) were assessed and compared under flux conditions ranging between 100-1000 kW/m2, such as those seen in hydrocarbon fire or propellant fire conditions. Short duration step and pulse boundary conditions were imposed using a six-panel cylindrical array of high-temperature tungsten lamps. Overall, agreement between all gages was acceptable for the pulse tests and also for the step tests. However, repeated tests with the HTHFS with relatively long durations at temperatures approaching 1000%C2%B0C showed a substantial decrease (10-25%) in heat flux subsequent to the initial test, likely due to the mounting technique. New HTHFS gages have been ordered to allow additional tests to determine the cause of the flux reduction.

  15. Radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Walter-Shea, Elizabeth A.; Blad, Blaine L.; Zara, Pedro; Vining, Roel; Hays, Cynthia J.; Mesarch, Mark A.

    1993-01-01

    The main objective of the International Satellite Land Surface Climatology Project (ISLSCP) has been stated as 'the development of techniques that may be applied to satellite observations of the radiation reflected and emitted from the Earth to yield quantitative information concerning land surface climatological conditions'. The major field study, FIFE (the First ISLSCP Field Experiment), was conducted in 1987-89 to accomplish this objective. Four intensive field campaigns (IFC's) were carried out in 1987 and one in 1989. Factors contributing to observed reflected radiation from the FIFE site must be understood before the radiation observed by satellites can be used to quantify surface processes. Our last report (Walter-Shea et al., 1992b) focused on slope effects on incoming and outgoing shortwave radiation and net radiation from data collected in 1989. We report here on the final analysis of the slope data as well as results from thermal radiation studies conducted during the FIFE experiment. The specific areas reported are the following: (1) analysis of slope effects on measured reflectance values and estimates of surface albedo; (2) using remotely-measured surface temperatures as a means of estimating sensible heat flux from the Konza Prairie; (3) extracting canopy temperatures from remotely-measured composite surface temperatures; (4) modeling the measured composite temperature of partially vegetated surfaces; and (5) estimating gap distribution in partially vegetated surfaces from reflectance measurements.

  16. NCEP Reanalyses Surface Heat Flux - North Atlantic

    NSDL National Science Digital Library

    Anomalous values of heat flux components (net longwave, net shortwave, sensible, and latent) for the North Atlantic Region January 1995-December 1997 are presented as color maps at this page from WOCE (World Ocean Circulation Experiment). Users can select the month and year to view. Normal values of the heat flux components were calculated using data from 1958 to 1997. These climatological norms were then removed from each of the respective monthly realizations to produce the anomalous heat flux fields shown on these pages.

  17. Surface heat flux data from energy balance Bowen ratio systems

    SciTech Connect

    Wesely, M.L.; Cook, D.R.; Coulter, R.L.

    1995-06-01

    The 350 {times} 400 km domain of the Atmospheric Radiation Measurement (ARM) Program`s Clouds and Radiation Testbed (CART) site in the southern Great Plains is equipped with 10 energy balance Bowen ratio (EBBR) stations at grassland sites; they measure the net radiation, ground heat flux, and temperature/humidity differences between 1.0 and 2.0 m heights. The latter differences provide estimates of the geometric Bowen ratio ({beta}), which are used to estimate sensible and latent heat fluxes. This paper addresses the problem that occurs when the value of {beta} is near {minus}1 and to demonstrate the effectiveness of the EBBR stations in collecting energy flux data at the CART site.

  18. New Vacuum Blackbody Cavity for Heat Flux Meter Calibration

    NASA Astrophysics Data System (ADS)

    Filtz, J.-R.; Valin, T.; Hameury, J.; Dubard, J.

    2009-02-01

    In the field of thermal radiation measurements, blackbody cavities are commonly used as reference standards for the calibration of heat flux meters. Applying the energy balance equation to the closed system including the cavity and the sensor, it is possible to predict the heat flux density absorbed by the heat flux meter. Calibration procedures developed at Laboratoire National de Métrologie et d’Essais (LNE) in recent years have allowed us to propose practical solutions for heat flux meters working below 100 kW · m-2. The best relative uncertainties ( k = 2) over the range of (10-100) kW · m-2 vary from 1.7 % to 3 %. During previous studies, three major facilities were constructed, each one with the objective to respond to different technical problems considering the measuring principle of these heat flux sensors. Following this approach, the sensitivity of these meters to radiation, the sensitivity to radiation and convection, and also the influence of the size of the source or of the positioning of the sensor (horizontally, vertically, etc.) have been investigated. As an outcome of this recent experience, a new vacuum blackbody cavity has been set up. As well as the possibility to calibrate at very low irradiance, there are also some substantive improvements in heating, thermal performance, and calibration methodology. After a summary of the state of the art of calibration methods and their limits, the article presents the preliminary results of the characterization obtained with this new facility for which the objective is to reduce the uncertainties by at least a factor of two for heat flux densities lower than 20 kW · m-2.

  19. Urban Signatures: Sensible Heat Flux (WMS)

    NSDL National Science Digital Library

    Jeff DeLaBeaujardiere

    2005-05-27

    Big cities influence the environment around them. For example, urban areas are typically warmer than their surroundings. Cities are strikingly visible in computer models that simulate the Earths land surface. This visualization shows sensible heat flux predicted by the Land Information System (LIS) for a day in June 2001. (Sensible heat flux refers to transfer of heat from the earths surface to the air above; for further explanation see http:--www.uwsp.edu-geo-faculty-ritter-geog101-textbook-energy-energy_balance.html). Sensible heat flux is higher in the cities--that is, they transfer more heat to the atmosphere--because the surface there is warmer than in the surroundings. Only part of the global computation is shown, focusing on the highly urbanized northeast corridor in the United States, including the cities of Boston, New York, Philadelphia, Baltimore, and Washington.

  20. Critical heat flux test apparatus

    DOEpatents

    Welsh, Robert E. (West Mifflin, PA); Doman, Marvin J. (McKeesport, PA); Wilson, Edward C. (West Mifflin, PA)

    1992-01-01

    An apparatus for testing, in situ, highly irradiated specimens at high temperature transients is provided. A specimen, which has a thermocouple device attached thereto, is manipulated into test position in a sealed quartz heating tube by a robot. An induction coil around a heating portion of the tube is powered by a radio frequency generator to heat the specimen. Sensors are connected to monitor the temperatures of the specimen and the induction coil. A quench chamber is located below the heating portion to permit rapid cooling of the specimen which is moved into this quench chamber once it is heated to a critical temperature. A vacuum pump is connected to the apparatus to collect any released fission gases which are analyzed at a remote location.

  1. Latent and sensible heat fluxes overestimated and net heat flux underestimated in Lake Victoria

    E-print Network

    Verburg, Piet

    2014-01-01

    Cozar et al. (2012) used remotely-sensed data to link phytoplankton growth to the net heat flux in both the northern and southern parts of Lake Victoria. However, the latent and sensible heat fluxes were overestimated by ~26% by assuming a constant air density of 1.3 kg m-3. As a result, the net heat flux was underestimated, bringing into question conclusions regarding the convective circulation.

  2. Radiative heat transfer in fibrous insulations: Part 1: Analytical study

    Microsoft Academic Search

    T. W. Tong; C. L. Tien

    1983-01-01

    The purpose of this work is to develop models for predicting the radiant heat flux in lightweight fibrous insulations (LWFI). The radiative transport process is modeled by the two-flux solution and the linear anisotropic scattering solution of the equation of transfer. The radiative properties of LWFI consistent with these solutions have been determined based on extinction of electromagnetic radiation by

  3. The effect of nonuniform axial heat flux distribution on the critical heat flux

    E-print Network

    Todreas, Neil E.

    1965-01-01

    A systematic experimental and analytic investigation of the effect of nonuniform axial heat flux distribution on critical heat rilux was performed with water in the quality condition. Utilizing a model which ascribes the ...

  4. Numerical Analysis of a Radiant Heat Flux Calibration System

    NASA Technical Reports Server (NTRS)

    Jiang, Shanjuan; Horn, Thomas J.; Dhir, V. K.

    1998-01-01

    A radiant heat flux gage calibration system exists in the Flight Loads Laboratory at NASA's Dryden Flight Research Center. This calibration system must be well understood if the heat flux gages calibrated in it are to provide useful data during radiant heating ground tests or flight tests of high speed aerospace vehicles. A part of the calibration system characterization process is to develop a numerical model of the flat plate heater element and heat flux gage, which will help identify errors due to convection, heater element erosion, and other factors. A 2-dimensional mathematical model of the gage-plate system has been developed to simulate the combined problem involving convection, radiation and mass loss by chemical reaction. A fourth order finite difference scheme is used to solve the steady state governing equations and determine the temperature distribution in the gage and plate, incident heat flux on the gage face, and flat plate erosion. Initial gage heat flux predictions from the model are found to be within 17% of experimental results.

  5. Impacts of weather variability on turbulent heat fluxes in Phoenix, AZ and Portland, OR 1 2 12 2 3 3

    E-print Network

    Hall, Sharon J.

    the partitioning of net all-wave radiation into sensible and latent heat fluxes as well as heat storageImpacts of weather variability on turbulent heat fluxes in Phoenix, AZ and Portland, OR 1 2 12 2 3 Meteorology 41: 792-810. rimmond CSB, Oke TR. 2002. Turbulent heat fluxes in urban areas: observations

  6. New technique of the local heat flux measurement in combustion chambers of steam boilers

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr

    2011-12-01

    A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

  7. Bidirectional electron heat flux events in space

    SciTech Connect

    Bame, S.J.; Gosling, J.T.

    1986-01-01

    In this paper we discuss a number of space plasma phenomena which have been illuminated by a powerful diagnostic tool provided by tracing heat flux carried by the solar wind. Measurements of this flow of heat energy from the sun and other hot plasma regions have been employed to increase our understanding of the solar wind interaction with solar system objects. Similarly, anomalies in the heat flux have helped to explain unusual plasma entities which are sometimes found in the interplanetary solar wind. The heat flux is principally carried by the solar wind electrons, since they are much more mobile than the ions. The electrons conduct heat outward from the hot solar corona and in a sense they constitute test particles that trace out the various plasma structures found in the solar wind and in the vicinities of bodies immersed in the interplanetary plasma flow. In the following sections we begin by discussing the electron heat flux which flows outward from the solar corona. This flux is ordinarily found flowing in one direction, i.e., it is unidirectional. Sometimes it is observed counterstreaming, i.e., it is bidirectional. In later sections we discuss how detection of bidirectional heat fluxes has contributed to a more complete understanding of the Earth's bow shock, the bow wave at Comet Giacobini-Zinner, interplanetary plasma structures injected into the solar wind by solar activity processes, and finally polar rain electrons that are found precipitating over the Earth's poles but are believed to originate in the hot solar corona. 37 refs., 16 figs.

  8. Heat-flux gage thermophosphor system

    NASA Astrophysics Data System (ADS)

    Tobin, K. W.

    1991-08-01

    This document describes the installation, hardware requirements, and application of the Heat-Flux Gage (Version 1.0) software package developed by the Oak Ridge National Laboratory, Applied Technology Division. The developed software is a single component of a thermographic phosphor-based temperature and heat-flux measurement system. The heat-flux transducer was developed by EG&G Energy Measurements Systems and consists of a 1 x 1 in. polymethylpentene sheet coated on the front and back with a repeating thermographic phosphor pattern. The phosphor chosen for this application is gadolinium oxysulphide doped with terbium. This compound has a sensitive temperature response from 10 to 65.6 C (50 to 150 F) for the 415- and 490-nm spectral emission lines.

  9. Bidirectional solar wind electron heat flux events

    Microsoft Academic Search

    J. T. Gosling; D. N. Baker; S. J. Bame; W. C. Feldman; R. D. Zwickl; E. J. Smith

    1987-01-01

    Normally the approx. >80-eV electrons which carry the solar wind electron heat flux are collimated along the interplanetary magnetic field (IMF) in the direction pointing outward away from the sun. Occasionally, however, collimated fluxes of approx. >80-eV electrons are observed traveling both parallel and antiparallel to the IMF. Here we present the results of a survey of such bidirectional electron

  10. Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer

    PubMed Central

    Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso

    2014-01-01

    This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758

  11. Advanced test reactor critical heat flux studies

    SciTech Connect

    Oh, C.H.; Englert, S.B.; Chapman, J.C. (Idaho National Engineering Lab., Idaho Falls (United States))

    1993-01-01

    A series of experiments has recently been completed at the Idaho National Engineering Laboratory to determine critical heat flux (CHF) in a thin aluminum rectangular channel for both upward and downward flows. This experiment simulates an advanced test reactor fuel plate and its associated flow channel. One channel face is uniformly heated using electrical heaters behind an aluminum plate; the opposite face is a Pyrex window allowing visual observation of flow patterns and test conditions in the flow channel.

  12. Critical heat flux in helically coiled tubes

    Microsoft Academic Search

    M. K. Jensen; A. E. Bergles

    1981-01-01

    A study of boiling R-113 in electrically heated coils of various diameters is reported. Sub-cooled critical heat flux (CHF) is lower with coils than with straight tubes. The differences increases as mass velocity and ratio of tube diameter to coil diameter (d\\/D) increases. On the contrary, quality CHF is enhanced in increases with d\\/D;CHF initially increases with increasing mass velocity,

  13. Rainfall and Radiative Heating Rates from TOGA COARE Atmospheric Budgets

    Microsoft Academic Search

    Richard H. Johnson; Paul E. Ciesielski

    2000-01-01

    Atmospheric heat and moisture budgets are used to determine rainfall and radiative heating rates over the western Pacific warm pool during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Results are compared to independent estimates of these quantities from the other sources. Using the COARE bulk flux algorithm to estimate surface evaporation over the intensive flux array

  14. Heat flux concentration through polymeric thermal lenses

    NASA Astrophysics Data System (ADS)

    Kapadia, R. S.; Bandaru, P. R.

    2014-12-01

    A significant contributor to energy inefficiency is the generation as well as the uneven dissipation of heat. Practical methods to adeptly channel heat flux (Q) would then have widespread applications to improved energy utilization and thermal energy management. It would be beneficial to engineer lens-like composite materials (graded in terms of length or thermal conductivity) with augmented attributes for heat control. Here, we propose and demonstrate polymeric composite based Q focusing lenses, architected through geometrical considerations. We indicate a five-fold enhancement of the Q, at the level of ˜2500 W/m2, enabled through such thermal lenses.

  15. Nanoscale heat flux between anisotropic uniaxial media

    E-print Network

    Svend-Age Biehs; Philippe Ben-Abdallah; Felipe S. S. Rosa; Karl Joulain; Jean-Jacques Greffet

    2011-03-11

    We present a theoretical study of near-field heat transfer between two anisotropic materials separated by a small vacuum gap and maintained in a stationary non-equilibrium thermal situation. By combining standard stochastic electrodynamics and the Maxwell-Garnett description for effective media, we show that heat flux can be significantly enhanced by air inclusions. This result is explained by : (a) the presence of extraordinary surface waves that give rise to supplementary channels for heat transfer throughout the gap, (b) an increase in the contribution given by the ordinary surface waves at resonance, (c) and the appearance of frustrated modes over a broad spectral range.

  16. Tropical Cloud Properties and Radiative Heating Profiles

    DOE Data Explorer

    Mather, James

    We have generated a suite of products that includes merged soundings, cloud microphysics, and radiative fluxes and heating profiles. The cloud microphysics is strongly based on the ARM Microbase value added product (Miller et al., 2003). We have made a few changes to the microbase parameterizations to address issues we observed in our initial analysis of the tropical data. The merged sounding product is not directly related to the product developed by ARM but is similar in that it uses the microwave radiometer to scale the radiosonde column water vapor. The radiative fluxes also differ from the ARM BBHRP (Broadband Heating Rate Profile) product in terms of the radiative transfer model and the sampling interval.

  17. Solid propellant combustion response to oscillatory radiant heat flux

    NASA Technical Reports Server (NTRS)

    Strand, L. D.; Weil, M. T.; Cohen, N. S.

    1989-01-01

    A progress report is given on a research project to use the microwave Doppler velocimeter technique to measure the combustion response to an oscillating thermal radiation source (CO2 laser). The test technique and supporting analyses are described, and the results are presented for an initial test series on the nonmetallized, composite propellant, Naval Weapons Center formulation A-13. It is concluded that in-depth transmission of radiant heat flux is not a factor at the CO2 laser wave length.

  18. Measuring Response Of Propellant To Oscillatory Heat Flux

    NASA Technical Reports Server (NTRS)

    Strand, Leon D.; Schwartz, Ken; Burns, Shawn P.

    1990-01-01

    Apparatus for research in combustion of solid propellants measures oscillatory response of rate of burning to oscillating thermal radiation from modulated CO2 laser. Determines response to rate of burning to equivalent oscillation in pressure. Rod of propellant mounted in burner assembly including waveguide at one end and infrared window at other end. Microwave Doppler velocimeter measures motion of combustion front. Microwave, laser-current, and heat-flux signals processed into and recorded in forms useful in determining desired response of propellent.

  19. SEBAL-based sensible and latent heat fluxes in the irrigated Gediz Basin, Turkey

    Microsoft Academic Search

    W. G. M Bastiaanssen

    2000-01-01

    Surface Energy Balance Algorithm for Land (SEBAL) is a relatively new parameterization of surface heat fluxes based on spectral satellite measurements. SEBAL requires spatially distributed, visible, near-infrared and thermal infrared data, which can be taken from Landsat Thematic Mapper. The SEBAL parameterization is an iterative and feedback-based numerical procedure that deduces the radiation, heat and evaporation fluxes. The sensible and

  20. Radiation from Kinetic Poynting Flux Acceleration

    E-print Network

    Edison Liang; Koichi Noguchi

    2007-11-18

    We derive analytic formulas for the power output and critical frequency of radiation by electrons accelerated by relativistic kinetic Poynting flux, and validate these results with Particle-In-Cell plasma simulations. We find that the in-situ radiation power output and critical frequency are much below those predicted by the classical synchrotron formulae. We discuss potential astrophysical applications of these results.

  1. Bubble dynamics in boiling under high heat flux pulse heating

    Microsoft Academic Search

    A. Asai

    1991-01-01

    A new theoretical model of bubble behavior in boiling water under high heat flux pulse is presented. The essence of the model is nucleation in the superheated liquid followed by instantaneous formation of a vapor film, rapid bubble growth due to the pressure impulse, and cavitation bubble collapse. To check the model, boiling of methanol under 5 â¼ 50 MW

  2. Contactless heat flux control with photonic devices

    E-print Network

    Ben-Abdallah, Philippe

    2015-01-01

    The ability to control electric currents in solids using diodes and transistors is undoubtedly at the origin of the main developments in modern electronics which have revolutionized the daily life in the second half of 20th century. Surprisingly, until the year 2000 no thermal counterpart for such a control had been proposed. Since then, based on pioneering works on the control of phononic heat currents new devices were proposed which allow for the control of heat fluxes carried by photons rather than phonons or electrons. The goal of the present paper is to summarize the main advances achieved recently in the field of thermal energy control with photons.

  3. The photospheric Poynting flux and coronal heating

    NASA Astrophysics Data System (ADS)

    Welsch, Brian T.

    2015-02-01

    Some models of coronal heating suppose that convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we investigate this idea by estimating the upward transport of magnetic energy-the vertical Poynting flux, Sz-across the photosphere in a plage region. To do so, we combine the following: (i) estimates of photospheric horizontal velocities, vh, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are (i) strong enough to be measured with relatively small uncertainties, (ii) not so strong that convection is heavily suppressed (as within umbrae), and (iii) unipolar, so Sz in plage is not influenced by mixed-polarity processes (e.g., flux emergence) unrelated to heating in stable, active-region fields. In this plage region, we found that the average Sz varied in space, but was positive (upward) and sufficient to explain coronal heating, with values near (5 ± 1) × 107 erg cm-2 s-1. We find the energy input per unit magnetic flux to be on the order of 105 erg s-1 Mx-1. A comparison of intensity in a Ca II image co-registered with one plage magnetogram shows stronger spatial correlations with both total field strength and unsigned vertical field, |Bz|, than either Sz or horizontal flux density, Bh. The observed Ca II brightness enhancement, however, probably contains a strong contribution from a near-photosphere hot-wall effect, which is unrelated to heating in the solar atmosphere.

  4. Prediction of Critical Heat Flux in Microchannels

    Microsoft Academic Search

    J. R. Thome; L. Consolini

    2010-01-01

    \\u000a An overview of the state-of-the-art of predicting critical heat flux during saturated flow boiling in microchannels is presented.\\u000a First, a selection of experimental results is described for single channels and for multi-channels in parallel, including\\u000a non-circular channel shapes. Next, the various empirical methods for predicting CHF are presented and discussed. Then, the\\u000a theoretically based model of Revellin and Thome for

  5. The photospheric Poynting flux and coronal heating

    NASA Astrophysics Data System (ADS)

    Welsch, Brian T.

    2015-04-01

    Some models of coronal heating suppose that convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we investigate this idea by estimating the upward transport of magnetic energy-the vertical Poynting flux, Sz-across the photosphere in a plage region. To do so, we combine the following: (i) estimates of photospheric horizontal velocities, vh, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are (i) strong enough to be measured with relatively small uncertainties, (ii) not so strong that convection is heavily suppressed (as within umbrae), and (iii) unipolar, so Sz in plage is not influenced by mixed-polarity processes (e.g., flux emergence) unrelated to heating in stable, active-region fields. In this plage region, we found that the average Sz varied in space, but was positive (upward) and sufficient to explain coronal heating, with values near (5 ± 1) × 107 erg cm-2 s-1. We find the energy input per unit magnetic flux to be on the order of 105 erg s-1 Mx-1. A comparison of intensity in a Ca II image co-registered with one plage magnetogram shows stronger spatial correlations with both total field strength and unsigned vertical field, |Bz|, than either Sz or horizontal flux density, Bh. The observed Ca II brightness enhancement, however, probably contains a strong contribution from a near-photosphere hot-wall effect, which is unrelated to heating in the solar atmosphere.

  6. Comparison of the Radiative Two-Flux and Diffusion Approximations

    NASA Technical Reports Server (NTRS)

    Spuckler, Charles M.

    2006-01-01

    Approximate solutions are sometimes used to determine the heat transfer and temperatures in a semitransparent material in which conduction and thermal radiation are acting. A comparison of the Milne-Eddington two-flux approximation and the diffusion approximation for combined conduction and radiation heat transfer in a ceramic material was preformed to determine the accuracy of the diffusion solution. A plane gray semitransparent layer without a substrate and a non-gray semitransparent plane layer on an opaque substrate were considered. For the plane gray layer the material is semitransparent for all wavelengths and the scattering and absorption coefficients do not vary with wavelength. For the non-gray plane layer the material is semitransparent with constant absorption and scattering coefficients up to a specified wavelength. At higher wavelengths the non-gray plane layer is assumed to be opaque. The layers are heated on one side and cooled on the other by diffuse radiation and convection. The scattering and absorption coefficients were varied. The error in the diffusion approximation compared to the Milne-Eddington two flux approximation was obtained as a function of scattering coefficient and absorption coefficient. The percent difference in interface temperatures and heat flux through the layer obtained using the Milne-Eddington two-flux and diffusion approximations are presented as a function of scattering coefficient and absorption coefficient. The largest errors occur for high scattering and low absorption except for the back surface temperature of the plane gray layer where the error is also larger at low scattering and low absorption. It is shown that the accuracy of the diffusion approximation can be improved for some scattering and absorption conditions if a reflectance obtained from a Kubelka-Munk type two flux theory is used instead of a reflection obtained from the Fresnel equation. The Kubelka-Munk reflectance accounts for surface reflection and radiation scattered back by internal scattering sites while the Fresnel reflection only accounts for surface reflections.

  7. Interannual Variability in Meterrancan Heat and Buoyancy Fluxes

    Microsoft Academic Search

    Curts Garrett; Richard Outerbridge; Keitu Thompson

    1993-01-01

    The flux of heat through the Strait of Gibraltar is known well enough that the Mediterranean Sea may be used as a climate test basin. After adjusting reported winds for changes in observing practice, the COADS for 1946 to 1988 was used together with standard heat flux formulas to estimate the long-term mean heat flux into the sea, giving 36

  8. Heat flux in a granular gas

    NASA Astrophysics Data System (ADS)

    Brey, J. J.; Ruiz-Montero, M. J.

    2012-11-01

    A peculiarity of the hydrodynamic Navier-Stokes equations for a granular gas is the modification of the Fourier law, with the presence of an additional contribution to the heat flux that is proportional to the density gradient. Consequently, the constitutive relation involves, in the case of a one-component granular gas, two transport coefficients: the usual (thermal) heat conductivity and a diffusive heat conductivity. A very simple physical interpretation of this effect, in terms of the mean free path and the mean free time is provided. It leads to the modified Fourier law with an expression for the diffusive Fourier coefficient that differs in a factor of the order of unity from the expression obtained by means of the inelastic Boltzmann equation. Also, some aspects of the Chapman-Enskog computation of the new transport coefficients as well as of the comparison between simulation results and theory are discussed.

  9. Global Intercomparison of 12 Land Surface Heat Flux Estimates

    NASA Technical Reports Server (NTRS)

    Jimenez, C.; Prigent, C.; Mueller, B.; Seneviratne, S. I.; McCabe, M. F.; Wood, E. F.; Rossow, W. B.; Balsamo, G.; Betts, A. K.; Dirmeyer, P. A.; Fisher, J. B.; Jung, M.; Kanamitsu, M.; Reichle, R. H.; Reichstein, M.; Rodell, M.; Sheffield, J.; Tu, K.; Wang, K.

    2011-01-01

    A global intercomparison of 12 monthly mean land surface heat flux products for the period 1993-1995 is presented. The intercomparison includes some of the first emerging global satellite-based products (developed at Paris Observatory, Max Planck Institute for Biogeochemistry, University of California Berkeley, University of Maryland, and Princeton University) and examples of fluxes produced by reanalyses (ERA-Interim, MERRA, NCEP-DOE) and off-line land surface models (GSWP-2, GLDAS CLM/ Mosaic/Noah). An intercomparison of the global latent heat flux (Q(sub le)) annual means shows a spread of approx 20 W/sq m (all-product global average of approx 45 W/sq m). A similar spread is observed for the sensible (Q(sub h)) and net radiative (R(sub n)) fluxes. In general, the products correlate well with each other, helped by the large seasonal variability and common forcing data for some of the products. Expected spatial distributions related to the major climatic regimes and geographical features are reproduced by all products. Nevertheless, large Q(sub le)and Q(sub h) absolute differences are also observed. The fluxes were spatially averaged for 10 vegetation classes. The larger Q(sub le) differences were observed for the rain forest but, when normalized by mean fluxes, the differences were comparable to other classes. In general, the correlations between Q(sub le) and R(sub n) were higher for the satellite-based products compared with the reanalyses and off-line models. The fluxes were also averaged for 10 selected basins. The seasonality was generally well captured by all products, but large differences in the flux partitioning were observed for some products and basins.

  10. The Photospheric Poynting Flux and Coronal Heating

    NASA Astrophysics Data System (ADS)

    Welsch, Brian

    2014-06-01

    Some models of coronal heating suppose that random (cf., coherent) convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we observationally test this idea by estimating the upward transport of magnetic energy --- the vertical Poynting flux, S_z --- across the photosphere in a plage region. To do so, we combine: (i) estimates of photospheric horizontal velocities, v_h, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are: (i) strong enough to be measured with relatively small uncertainties; (ii) not so strong that convection is heavily suppressed (as within umbrae); and (iii) unipolar, so S_z in plage is not influenced by mixed-polarity processes (e.g., flux emergence) that cannot explain steady heating in stable, active-region fields. In this and a previously analyzed plage region, we found that the average S_z varied between the regions, but was positive (upward) and sufficient to explain coronal heating, with values near 2 x 10^7 erg/ cm^2/ s. We find the energy input per unit magnetic flux to be on the order of a few times 10^4 erg/ s/ Mx. A comparison of intensity in a Ca II image co-registered with one plage magnetogram shows stronger spatial correlation with unsigned vertical field, |B_z|, than either S_z or horizontal flux density, |B_h|.

  11. Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer

    NASA Astrophysics Data System (ADS)

    Sirevaag, A.; de La Rosa, S.; Fer, I.; Nicolaus, M.; Tjernström, M.; McPhee, M. G.

    2011-05-01

    A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22 % of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the base of the mixed layer accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m-2) and heated by solar radiation through the ice (-2.6 W m-2). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59 % in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.

  12. Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer

    NASA Astrophysics Data System (ADS)

    Sirevaag, A.; de La Rosa, S.; Fer, I.; Nicolaus, M.; Tjernström, M.; McPhee, M. G.

    2011-02-01

    A comprehensive measurement program was conducted during 16 days of a 3 week long ice pack drift, from 15 August to 1 September 2008 in the Central Amundsen Basin, Arctic Ocean. The data, sampled as part of the Arctic Summer Cloud Ocean Study (ASCOS), included upper ocean stratification, mixing and heat transfer as well as transmittance of solar radiation through the ice. The observations give insight into the evolution of the upper layers of the Arctic Ocean in the transition period from melting to freezing. The ocean mixed layer was found to be heated from above and, for summer conditions, the net heat flux through the ice accounted for 22% of the observed change in mixed layer heat content. Heat was mixed downward within the mixed layer and a small, downward heat flux across the pycnocline accounted for the accumulated heat in the upper cold halocline during the melting season. On average, the ocean mixed layer was cooled by an ocean heat flux at the ice/ocean interface (1.2 W m-2) and heated by solar radiation through the ice (-2.6 W m-2). An abrupt change in surface conditions halfway into the drift due to freezing and snowfall showed distinct signatures in the data set and allowed for inferences and comparisons to be made for cases of contrasting forcing conditions. Transmittance of solar radiation was reduced by 59% in the latter period. From hydrographic observations obtained earlier in the melting season, in the same region, we infer a total fresh water equivalent of 3.3 m accumulated in the upper ocean, which together with the observed saltier winter mixed layer indicates a transition towards a more seasonal ice cover in the Arctic.

  13. Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Yerramilli, Vamsee K.; Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

  14. ARM Energy Balance Bowen Ratio (EBBR) station: surf. heat flux and related data, 30-min

    DOE Data Explorer

    Cook, David

    The Energy Balance Bowen Ratio (EBBR) system produces 30-min estimates of the vertical fluxes of sensible and latent heat at the local surface. Flux estimates are calculated from observations of net radiation, soil surface heat flux, and the vertical gradients of temperature and relative humidity. Meteorological data collected by the EBBR are used to calculate bulk aerodynamic fluxes, which are used in the Bulk Aerodynamic Technique (BA) EBBR value-added product (VAP) to replace sunrise and sunset spikes in the flux data. A unique aspect of the system is the automatic exchange mechanism (AEM), which helps to reduce errors from instrument offset drift.

  15. Heat pipe radiators for space. [vacuum tests

    NASA Technical Reports Server (NTRS)

    Sellers, J. P.

    1977-01-01

    An optimized flight-weight prototype fluid-header panel (heatpipe radiator system) was tested in a vacuum environment over a wide range of coolant inlet temperatures, coolant flow rates, and environmental absorbed heat fluxes. The maximum performance of the system was determined. Results are compared with earlier data obtained on a smaller fluid-header feasibility panel, and computer predictions. Freeze-thaw tests are described and the change in thaw recovery time due to the addition of a low-freezing point feeder heat pipe is evaluated. Experimental panel fin-temperature distributions are compared with calculated results.

  16. Heat flux measurements on ceramics with thin film thermocouples

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond; Anderson, Robert C.; Liebert, Curt H.

    1993-01-01

    Two methods were devised to measure heat flux through a thick ceramic using thin film thermocouples. The thermocouples were deposited on the front and back face of a flat ceramic substrate. The heat flux was applied to the front surface of the ceramic using an arc lamp Heat Flux Calibration Facility. Silicon nitride and mullite ceramics were used; two thicknesses of each material was tested, with ceramic temperatures to 1500 C. Heat flux ranged from 0.05-2.5 MW/m2(sup 2). One method for heat flux determination used an approximation technique to calculate instantaneous values of heat flux vs time; the other method used an extrapolation technique to determine the steady state heat flux from a record of transient data. Neither method measures heat flux in real time but the techniques may easily be adapted for quasi-real time measurement. In cases where a significant portion of the transient heat flux data is available, the calculated transient heat flux is seen to approach the extrapolated steady state heat flux value as expected.

  17. Prediction of Critical Heat Flux in Microchannels

    NASA Astrophysics Data System (ADS)

    Thome, J. R.; Consolini, L.

    An overview of the state-of-the-art of predicting critical heat flux during saturated flow boiling in microchannels is presented. First, a selection of experimental results is described for single channels and for multi-channels in parallel, including non-circular channel shapes. Next, the various empirical methods for predicting CHF are presented and discussed. Then, the theoretically based model of Revellin and Thome for microchannels, including prediction of CHF under hot spots, is described and discussed. Finally, some overall comments on the status of CHF modeling and experi-mentation are provided.

  18. Radiative heat transfer at nanoscale mediated by surface plasmons for highly doped silicon

    Microsoft Academic Search

    Emmanuel Rousseau; Marine Laroche; Jean-Jacques Greffet

    2009-01-01

    In this letter, we revisit the role of surface plasmons for nanoscale radiative heat transfer between doped silicon surfaces. We derive a new accurate and closed-form expression of the radiative near-field heat transfer. We also analyze the flux and find that there is a doping level that maximizes the heat flux.

  19. Thin Film Heat Flux Sensors: Design and Methodology

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Wrbanek, John D.

    2013-01-01

    Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

  20. Critical heat flux experiments in an internally heated annulus with a non-uniform, alternate high and low axial heat flux distribution (AWBA Development Program)

    SciTech Connect

    Beus, S.G.; Seebold, O.P.

    1981-02-01

    Critical heat flux experiments were performed with an alternate high and low heat flux profile in an internally heated annulus. The heated length was 84 inches (213 cm) with a chopped wave heat flux profile over the last 24 inches (61 cm) having a maximum-to-average heat flux ratio of 1.26. Three test sections were employed: one with an axially uniform heat flux profile as a base case and two with 60 inch (152 cm) uniform and 24 inch (61 cm) alternating high and low heat flux sections. The third test section had a 2.15 inch (5.46 cm) section with a peak-to-average heat flux ratio of 2.19 (hot patch) superimposed at the exit end of the alternating high and low heat flux profile.

  1. The Photospheric Poynting Flux and Coronal Heating

    E-print Network

    Welsch, B T

    2014-01-01

    Some models of coronal heating suppose that random (cf., coherent) convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we observationally test this idea by estimating the upward transport of magnetic energy --- the vertical Poynting flux, S_z --- across the photosphere in a plage region. To do so, we combine: (i) estimates of photospheric horizontal velocities, v_h, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are: (i) strong enough to be measured wit...

  2. Flux monitor diode radiation hardness testing

    NASA Astrophysics Data System (ADS)

    Lombardi, M. L.; Favalli, A.; Goda, J. M.; Ianakiev, K. D.; Moss, C. E.

    2011-10-01

    A flux monitor diode is being explored as an option for measurement of the output of an X-ray tube that is used for active transmission measurements on a pipe containing UF 6 gas. The measured flux can be used to correct for any instabilities in the X-ray tube or the high voltage power supply. For this measurement, we are using a silicon junction p-n photodiode, model AXUV100GX, developed by International Radiation Detectors, Inc. (IRD, Inc.). This diode has a silicon thickness of 104 ? and a thin (3-7 nm) silicon dioxide junction passivating, protective entrance window. These diodes have been extensively tested for radiation hardness in the UV range. However, we intend to operate mainly in the 10-40 keV X-ray region. We are performing radiation hardness testing over this energy range, with the energy spectrum that would pass through the diode during normal operation. A long-term measurement was performed at a high flux, which simulated over 80 years of operation. No significant degradation was seen over this time. Fluctuations were found to be within the 0.1% operationally acceptable error range. After irradiation, an I- V characterization showed a temporary irradiation effect which decayed over time. This effect is small because we operate the diode without external bias.

  3. High heat flux engineering in solar energy applications

    SciTech Connect

    Cameron, C.P.

    1993-07-01

    Solar thermal energy systems can produce heat fluxes in excess of 10,000 kW/m{sup 2}. This paper provides an introduction to the solar concentrators that produce high heat flux, the receivers that convert the flux into usable thermal energy, and the instrumentation systems used to measure flux in the solar environment. References are incorporated to direct the reader to detailed technical information.

  4. Remote Heat Flux Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (k = 6 gm). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 gm) radiation transmitted through the sapphire disk. The thermal conductivity of the sapphire disk and the heat transfer coefficients h, and h2 of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  5. Remote Heat Flux Measurement Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (lambda > 6 micrometers). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 micrometers) radiation transmitted through the sapphire disk. The thermal conductivity k of the sapphire disk and the heat transfer coefficients h(sub 1) and h(sub 2) of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  6. Heat pipe radiators for space

    NASA Technical Reports Server (NTRS)

    Sellers, J. P.

    1976-01-01

    Analysis of the data heat pipe radiator systems tested in both vacuum and ambient environments was continued. The systems included (1) a feasibility VCHP header heat-pipe panel, (2) the same panel reworked to eliminate the VCHP feature and referred to as the feasibility fluid header panel, and (3) an optimized flight-weight fluid header panel termed the 'prototype.' A description of freeze-thaw thermal vacuum tests conducted on the feasibility VCHP was included. In addition, the results of ambient tests made on the feasibility fluid header are presented, including a comparison with analytical results. A thermal model of a fluid header heat pipe radiator was constructed and a computer program written. The program was used to make a comparison of the VCHP and fluid-header concepts for both single and multiple panel applications. The computer program was also employed for a parametric study, including optimum feeder heat pipe spacing, of the prototype fluid header.

  7. Radiation entropy flux and entropy production of the Earth system

    Microsoft Academic Search

    Wei Wu; Yangang Liu

    2010-01-01

    The study of the Earth's radiation entropy flux at the top of the atmosphere is reviewed with an emphasis on its estimation methods. Existing expressions for calculating radiation entropy flux scattered in different disciplines are surveyed, and their applicabilities are examined. It is found that the Earth's net radiation entropy flux estimated from these various expressions can differ substantially, more

  8. Eddy fluxes of CO2, water vapor, and sensible heat over a deciduous forest

    Microsoft Academic Search

    Shashi B. Verma; Dennis D. Baldocchi; Dean E. Anderson; Detlef R. Matt; Robert J. Clement

    1986-01-01

    Fluxes of CO2, latent heat and sensible heat were measured above a fully-leafed deciduous forest in eastern Tennessee with the eddy correlation technique. These are among the first reported observations over such a surface. The influences of solar radiation, vapor pressure deficit and the aerodynamic and canopy resistances on these mass and energy exchanges are examined. Following a concept introduced

  9. Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks

    E-print Network

    Qu, Weilin

    -phase heat sink can result in an unusually large stream-wise temper- ature rise in both the cooling liquidPrediction and measurement of incipient boiling heat flux in micro-channel heat sinks Weilin Qu Abstract Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21

  10. Convectively driven shear and decreased heat flux

    E-print Network

    Goluskin, David; Flierl, Glenn R; Spiegel, Edward A

    2014-01-01

    We report on direct numerical simulations of two-dimensional, horizontally periodic Rayleigh-B\\'enard convection, focusing on its ability to drive large-scale horizontal flow that is vertically sheared. For the Prandtl numbers ($Pr$) between 1 and 10 simulated here, this large-scale shear can be induced by raising the Rayleigh number ($Ra$) sufficiently, and we explore the resulting convection for $Ra$ up to $10^{10}$. When present in our simulations, the sheared mean flow accounts for a large fraction of the total kinetic energy, and this fraction tends towards unity as $Ra\\to\\infty$. The shear helps disperse convective structures, and it reduces vertical heat flux; in parameter regimes where one state with large-scale shear and one without are both stable, the Nusselt number of the state with shear is smaller and grows more slowly with $Ra$. When the large-scale shear is present with $Pr\\lesssim2$, the convection undergoes strong global oscillations on long timescales, and heat transport occurs in bursts. N...

  11. Infrared radiometric technique for rapid quantitative evaluation of heat flux distribution over large areas

    NASA Technical Reports Server (NTRS)

    Glazer, Stuart; Siebes, Georg

    1989-01-01

    This paper describes a novel approach for rapid, quantitative measurement of spatially distributed heat flux incident on a plane. The technique utilizes the spatial temperature distribution on an opaque thin film at the location of interest, as measured by an imaging infrared radiometer. Knowledge of film radiative properties, plus quantitative estimates of convection cooling permit the steady state energy balance at any location on the film sheet to be solved for the incident heat flux. Absolute accuracies on the order of 10-15 percent have been obtained in tests performed in air. The method is particularly useful for evaluation of spatial heat flux uniformity from distributed heat sources over large areas. It has recently been used in several applications at the Jet Propulsion Laboratory, including flux uniformity measurements from large distributed quartz lamp arrays used during thermal vacuum testing of several spacecraft components, and flux mapping of a low power NdYg laser beam.

  12. Experimental Performance of a Micromachined Heat Flux Sensor

    NASA Technical Reports Server (NTRS)

    Stefanescu, S.; DeAnna, R. G.; Mehregany, M.

    1998-01-01

    Steady-state and frequency response calibration of a microfabricated heat-flux sensor have been completed. This sensor is batch fabricated using standard, micromachining techniques, allowing both miniaturization and the ability to create arrays of sensors and their corresponding interconnects. Both high-frequency and spatial response is desired, so the sensors are both thin and of small cross-sectional area. Thin-film, temperature-sensitive resistors are used as the active gauge elements. Two sensor configurations are investigated: (1) a Wheatstone-bridge using four resistors; and (2) a simple, two-resistor design. In each design, one resistor (or pair) is covered by a thin layer (5000 A) thermal barrier; the other resistor (or pair) is covered by a thick (5 microns) thermal barrier. The active area of a single resistor is 360 microns by 360 microns; the total gauge area is 1.5 mm square. The resistors are made of 2000 A-thick metal; and the entire gauge is fabricated on a 25 microns-thick flexible, polyimide substrate. Heat flux through the surface changes the temperature of the resistors and produces a corresponding change in resistance. Sensors were calibrated using two radiation heat sources: (1) a furnace for steady-state, and (2) a light and chopper for frequency response.

  13. Designing, testing, and analyzing coupled, flux transformer heat

    E-print Network

    Renzi, Kimberly Irene

    1998-01-01

    The proposed research involves designing, testing, and ics. analyzing a coupled, flux transformer heat pipe system following the patent of Oktay and Peterson (1997). Experiments were conducted utilizing four copper heat pipes, lined with copper mesh...

  14. Transient critical heat flux and blowdown heat-transfer studies

    SciTech Connect

    Leung, J.C.

    1980-05-01

    Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.

  15. Numerical and experimental analyses of the radiant heat flux produced by quartz heating systems

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Ash, Robert L.

    1994-01-01

    A method is developed for predicting the radiant heat flux distribution produced by tungsten filament, tubular fused-quartz envelope heating systems with reflectors. The method is an application of Monte Carlo simulation, which takes the form of a random walk or ray tracing scheme. The method is applied to four systems of increasing complexity, including a single lamp without a reflector, a single lamp with a Hat reflector, a single lamp with a parabolic reflector, and up to six lamps in a six-lamp contoured-reflector heating unit. The application of the Monte Carlo method to the simulation of the thermal radiation generated by these systems is discussed. The procedures for numerical implementation are also presented. Experiments were conducted to study these quartz heating systems and to acquire measurements of the corresponding empirical heat flux distributions for correlation with analysis. The experiments were conducted such that several complicating factors could be isolated and studied sequentially. Comparisons of the experimental results with analysis are presented and discussed. Good agreement between the experimental and simulated results was obtained in all cases. This study shows that this method can be used to analyze very complicated quartz heating systems and can account for factors such as spectral properties, specular reflection from curved surfaces, source enhancement due to reflectors and/or adjacent sources, and interaction with a participating medium in a straightforward manner.

  16. Radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Chapman, K.; Ramadhyani, S.; Ramamurthy, H.; Viskanta, R.

    1989-03-01

    A simple two-dimensional mathematical model was developed to predict the steady state thermal performance and combustion characteristics of a natural gas indirectly fired once-through radiant tube. Different burner geometries were studied and a grid size analysis was performed to determine the optimum grid spacing for each case. The rate of fuel burn-up was correlated using the burner geometry, the equivalence ratio, the fuel firing rate and air preheat temperatures as variables for non-swirling diffusion flames in the radiant tube. The model predictions were also compared with available experimental data for the purpose of validating the model. The transient, zero-dimensional model was used to conduct a detailed parametric study of a directly-fired batch reheating furnace. The parameters that were investigated are the load and refractory emissivities, the air preheat temperature, the heat capacity of the load, and the height of the combustion space. A one-dimensional model of a directly-fired continuous reheating furnace was also developed. A parametric study was completed to examine the effect of the local throughput on the furnace performance.

  17. NEP heat pipe radiators. [Nuclear Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Ernst, D. M.

    1979-01-01

    This paper covers improvements of heat pipe radiators for the thermionic NEP design. Liquid metal heat pipes are suitable as spacecraft radiator elements because of high thermal conductance, low mass and reliability, but the NEP thermionic system design was too large and difficult to fabricate. The current integral collector-radiator design consisting of several layers of thermionic converters, the annular-tangential collector heat pipe, the radiator heat pipe, and the transition zone designed to minimize the temperature difference between the collector heat pipe and radiator heat pipe are described. Finally, the design of micrometeoroid armor protection and the fabrication of the stainless steel annular heat pipe with a tangential arm are discussed, and it is concluded that the heat rejection system for the thermionic NEP system is well advanced, but the collector-radiator heat pipe transition and the 8 to 10 m radiator heat pipe with two bends require evaluation.

  18. Computation of radiative heat transport across a nanoscale vacuum gap

    SciTech Connect

    Budaev, Bair V., E-mail: bair@berkeley.edu; Bogy, David B., E-mail: dbogy@berkeley.edu [University of California, Etcheverry Hall, MC 1740, Berkeley, California 94720-1740 (United States)

    2014-02-10

    Radiation heat transport across a vacuum gap between two half-spaces is studied. By consistently applying only the fundamental laws of physics, we obtain an algebraic equation that connects the temperatures of the half-spaces and the heat flux between them. The heat transport coefficient generated by this equation for such structures matches available experimental data for nanoscale and larger gaps without appealing to any additional specific mechanisms of energy transfer.

  19. Thin Film Heat Flux Sensor of Improved Design

    NASA Technical Reports Server (NTRS)

    Fralick, Gus; Wrbanek, John; Blaha, Charles

    2002-01-01

    A new design for a thin film heat flux sensor is presented. It is easier to fabricate than previous designs, for a given heat flux has an order of magnitude larger signal, and is more easily scalable than previous designs. Transient and steady state data are also presented.

  20. On the Nature of Critical Heat Flux in Microchannels

    E-print Network

    Kandlikar, Satish

    On the Nature of Critical Heat Flux in Microchannels A. E. Bergles Honorary Member, ASME of Technology, Rochester, NY 14623 e-mail: sgkeme@rit.edu The critical heat flux (CHF) limit is an important. The experiments required to obtain this information pose unique challenges. Among other issues, flow dis

  1. Temporal variation of heat and moisture flux divergence in the FIFE atmospheric boundary layer during spring

    NASA Technical Reports Server (NTRS)

    Grossman, Robert L.

    1990-01-01

    A one-day investigation of the atmospheric boundary layer (ABL) is reported in which an aircraft monitors the temporal and spatial variations of heat and moisture turbulent-flux divergences. Incoming solar radiation is similar over natural prairie land and agriculturally developed land although the heat and moisture values show significant differences over the surfaces. Other temporal variations are noted which demonstrate that ABL transport of sensible and latent heat is affected by complex variables even under simple synoptic conditions.

  2. Features of Afterbody Radiative Heating for Earth Entry

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Brandis, Aaron

    2014-01-01

    Radiative heating is identified as a major contributor to afterbody heating for Earth entry capsules at velocities above 10 km/s. Because of rate-limited electron-ion recombination processes, a large fraction of the electronically-excited N and O atoms produced in the high temperature/pressure forebody remain as they expand into the afterbody region, which results in significant afterbody radiation. Large radiative heating sensitivities to electron-impact ionization rates and escape factors are identified. Ablation products from a forebody ablator are shown to increase the afterbody radiation by as much as 40%. The tangent-slab radiation transport approach is shown to over-predict the radiative flux by as much as 40% in the afterbody, therefore making the more computationally expensive ray-tracing approach necessary for accurate radiative flux predictions. For the Stardust entry, the afterbody radiation is predicted to be nearly twice as large as the convective heating during the peak heating phase of the trajectory. Comparisons between simulations and the Stardust Echelle observation measurements, which are shown to be dominated by afterbody emission, indicate agreement within 20% for various N and O lines. Similarly, calorimeter measurements from the Fire II experiment are identified as a source of validation data for afterbody radiation. For the afterbody calorimeter measurement closest to the forebody, which experiences the largest afterbody radiative heating component, the convective heating alone is shown to under-predict the measurement, even for the fullycatalytic assumption. Agreement with the measurements is improved with the addition of afterbody radiation. These comparisons with Stardust and Fire II measurements provide validation that the significant afterbody radiation values proposed in this work are legitimate.

  3. Radiative heat transfer in finite cylindrical homogeneous and nonhomogeneous scattering media exposed to collimated radiation

    SciTech Connect

    Hsu, P.F.; Tan, Z.M. [Florida Inst. of Tech., Melbourne, FL (United States); Wu, S.H.; Wu, C.Y. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Mechanical Engineering

    1999-05-14

    In recent years, many thermal engineering applications, for example, combustor and furnace designs, heat transfer in propellant plumes, thermal insulation, and scattering vapor formed by laser irradiation, require better understanding of radiative heat transfer to improve the processes or designs. Here, radiative heat transfer is studied in a finite axisymmetrical cylindrical enclosure exposed to collimated radiation. The integral equations for radiative transfer are solved by the YIX method and the quadrature method for comparison. Integrated intensity and radiative heat flux are presented in homogeneous and nonhomogeneous scattering media exposed to both uniform and Gaussian distributions of normal collimated incident radiation. The effects of aspect ratio, different incident radiation, and anisotropic scattering phase function as well as nonhomogeneous property distribution are discussed. Ray effects appear in the YIX solution for the case of a nonhomogeneous step change in the extinction coefficient. In order to eliminate the ray effect, an adaptive angular quadrature scheme is described and applied.

  4. The Influence of Ablation on Radiative Heating for Earth Entry

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Gnoffo, Peter A.; Sutton, Kenneth

    2008-01-01

    Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative heating by 30 60% and the convective heating by less than 5%.

  5. Sensible heat flux estimation by flux variance and half-order time derivative methods

    E-print Network

    Katul, Gabriel

    with greater accuracy than the half-order time derivative methods for the three experiment sites. 1Sensible heat flux estimation by flux variance and half-order time derivative methods Karen H Abstract. This study is the first to contrast two similarity theory methods, the flux variance and the half

  6. Transient heat flux shielding using thermal metamaterials

    NASA Astrophysics Data System (ADS)

    Narayana, Supradeep; Savo, Salvatore; Sato, Yuki

    2013-05-01

    We have developed a heat shield based on a metamaterial engineering approach to shield a region from transient diffusive heat flow. The shield is designed with a multilayered structure to prescribe the appropriate spatial profile for heat capacity, density, and thermal conductivity of the effective medium. The heat shield was experimentally compared to other isotropic materials.

  7. Transient heat flux shielding using thermal metamaterials

    E-print Network

    Narayana, Supradeep; Sato, Yuki

    2013-01-01

    We have developed a heat shield based on a metamaterial engineering approach to shield a region from transient diffusive heat flow. The shield is designed with a multilayered structure to prescribe the appropriate spatial profile for heat capacity, density, and thermal conductivity of the effective medium. The heat shield was experimentally compared to other isotropic materials.

  8. Effects of Radiative Diffusion on Thin Flux Tubes in Turbulent Solar-like Convection

    E-print Network

    Weber, Maria A

    2015-01-01

    We study the combined effects of convection and radiative diffusion on the evolution of thin magnetic flux tubes in the solar interior. Radiative diffusion is the primary supplier of heat to convective motions in the lower convection zone, and it results in a heat input per unit volume of magnetic flux tubes that has been ignored by many previous thin flux tube studies. We use a thin flux tube model subject to convection taken from a rotating spherical shell of turbulent, solar-like convection as described by Weber, Fan, and Miesch (2011, Astrophys. J., 741, 11; 2013, Solar Phys., 287, 239), now taking into account the influence of radiative heating on flux tubes of large-scale active regions. Our simulations show that flux tubes of less than or equal to 60 kG subject to solar-like convective flows do not anchor in the overshoot region, but rather drift upward due to the increased buoyancy of the flux tube earlier in its evolution as a result of the inclusion of radiative diffusion. Flux tubes of magnetic fie...

  9. Application of heat flux transducers to determine perioperative heat exchange

    Microsoft Academic Search

    T. Perl; A. Bräuer; W. Weyland; U. Braun

    2004-01-01

    Perioperative hypothermia is a common problem in anaesthesia. To maintain a constant body heat content it is necessary to achieve a steady state of metabolic heat production and external heat exchange. During anaesthesia and surgery this balance is disturbed. The heat production is decreased to a level below resting metabolic heat production while heat losses increase due to the surgical

  10. Interannual variability in Mediterranean heat and buoyancy fluxes

    SciTech Connect

    Garrett, C.; Outerbridge, R. (Univ. of Victoria, British Columbia (Canada)); Thompson, K. (Dalhousie Univ., Halifax, Nova Scotia (Canada))

    1993-05-01

    The flux of heat through the Strait of Gibraltar is known well enough that the Mediterranean Sea may be used as a climate test basin. After adjusting reported winds for changes in observing practice, the COADS for 1946 to 1988 was used together with standard heat flux formulas to estimate the long-term mean heat flux into the sea, giving 36 W m[sup [minus]2] more than is compatible with the Gibraltar exchange, As the estimated latent heat flux is consistent with the freshwater budget, it is suggested that standard formulas overestimate insolation in the Mediterranean. If a constant adjustment factor is used for the insolation, or for the latent heat loss, interannual variability of [+-]15 Wm[sup [minus]2] is found in the total heat flux. Changes in the latent heat flux dominate, with contributions from both the humidity of the air and the saturation humidity at the temperature of the sea surface. The buoyancy flux from the sea is also examined and shows that the contributions from precipitation and runoff are important for the long-term mean, but insignificant for seasonal and interannual variability. 30 refs., 11 figs.

  11. Laminar natural convection from constant heat flux helical coiled tubes

    Microsoft Academic Search

    Mohamed E. Ali

    1998-01-01

    An experimental investigation of a steady state natural convection from uniformly heated helical coiled tubes oriented horizontally in air has been made. Average heat transfer coefficients are obtained for laminar natural convection. The experiments have been carried out for four coils and for various values of heat fluxes of 500–5000 W m?2. The data are correlated with Rayleigh number using

  12. Nonequilibrium Stagnation-Line Radiative Heating for Fire II

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Hollis, Brian R.; Sutton, Kenneth

    2007-01-01

    This paper presents a detailed analysis of the shock-layer radiative heating to the Fire II vehicle using a new air radiation model and a viscous shock-layer flowfield model. This new air radiation model contains the most up-to-date properties for modeling the atomic-line, atomic photoionization, molecular band, and non-Boltzmann processes. The applied viscous shock-layer flowfield analysis contains the same thermophysical properties and nonequilibrium models as the LAURA Navier-Stokes code. Radiation-flowfield coupling, or radiation cooling, is accounted for in detail in this study. It is shown to reduce the radiative heating by about 30% for the peak radiative heating points, while reducing the convective heating only slightly. A detailed review of past Fire II radiative heating studies is presented. It is observed that the scatter in the radiation predicted by these past studies is mostly a result of the different flowfield chemistry models and the treatment of the electronic state populations. The present predictions provide, on average throughout the trajectory, a better comparison with Fire II flight data than any previous study. The magnitude of the vacuum ultraviolet (VUV) contribution to the radiative flux is estimated from the calorimeter measurements. This is achieved using the radiometer measurements and the predicted convective heating. The VUV radiation predicted by the present model agrees well with the VUV contribution inferred from the Fire II calorimeter measurement, although only when radiation-flowfield coupling is accounted for. This agreement provides evidence that the present model accurately models the VUV radiation, which is shown to contribute significantly to the Fire II radiative heating.

  13. Heat pipe radiator. [for spacecraft waste heat rejection

    NASA Technical Reports Server (NTRS)

    Swerdling, B.; Alario, J.

    1973-01-01

    A 15,000 watt spacecraft waste heat rejection system utilizing heat pipe radiator panels was investigated. Of the several concepts initially identified, a series system was selected for more in-depth analysis. As a demonstration of system feasibility, a nominal 500 watt radiator panel was designed, built and tested. The panel, which is a module of the 15,000 watt system, consists of a variable conductance heat pipe (VCHP) header, and six isothermalizer heat pipes attached to a radiating fin. The thermal load to the VCHP is supplied by a Freon-21 liquid loop via an integral heat exchanger. Descriptions of the results of the system studies and details of the radiator design are included along with the test results for both the heat pipe components and the assembled radiator panel. These results support the feasibility of using heat pipes in a spacecraft waste heat rejection system.

  14. Effect of haze absorption and scattering on radiative-convective-conductive heat flux divergence in Martian CO2 atmosphere and ground

    NASA Technical Reports Server (NTRS)

    Pallmann, A. J.

    1977-01-01

    The paper presents some guidelines of an improved numerical modeling effort developed to investigate the effect of an absorbing and scattering particulate phase on the temperature field of the Mars atmosphere and soil in its diurnal cycle and in response to a time-dependent convective heat transfer. Some guidelines are also formulated for the re-evaluation of Mariner 9 infrared radiometer or spectrometer inverted temperature measurements of the dust-laden atmosphere.

  15. An Investigation of the Radiative Heat Transfer through Nonwoven Fibrous Materials

    Microsoft Academic Search

    Imad Qashou; Hooman Vahedi Tafreshi; Behnam Pourdeyhimi

    In this study, the surface-to-surface radiation model of the Fluent CFD code is used to investigate the response of a fibrous material to the radiative heat transfer. The unsteady state heat transfer equation is solved for the temperature and heat flux in and around the fibers that constitute a nonwoven fibrous material. For a fixed fiber diameter, it was shown

  16. A season of heat, water vapor, total hydrocarbon, and ozone fluxes at a subarctic fen

    NASA Astrophysics Data System (ADS)

    Moore, Kathleen E.; Fitzjarrald, David R.; Wofsy, Steven C.; Daube, Bruce C.; Munger, J. William; Bakwin, Peter S.; Crill, Patrick

    1994-01-01

    High-latitude environments are thought to play several critical roles in the global balance of radiatively active trace gases. Adequate documentation of the source and sink strengths for trace gases requires long time series of detailed measurements, including heat and moisture budgets. A fen near Schefferville, Quebec, was instrumented during the summer of 1990 for the measurement of the surface energy, radiation, and moisture balances as well as for eddy correlation estimates of ozone and methane flux. Despite the limited fetch at this site, analysis of the tower flux"footprint"indicates that at least 80% of the flux observed originates from sources within the fen. Sensible heat fluxes averaged 25% of the daytime net radiation at the site, while the latent heat flux, determined from the energy balance, was 63%; the Bowen ratio varied from 0.2 to 0.8 from day to day, without a seasonal trend to the variation. The competing effects of rooted macrophyte development (with concomitant effects on roughness and transpiration) and the normal shift in synoptic pattern around day 200 to warm, dry conditions results in a lack of net seasonal effect on the energy partitioning. Over the period from days 170 to 230, the evaporation (167 mm) was double the rainfall, while the decline in water level was 107 mm, leaving a net runoff of 0.44 mm/d. The total hydrocarbon flux was 75-120 mg m-2 d-1, following a diurnal pattern similar to heat or moisture flux, while the daytime ozone flux was about -1.11×1011 molecules cm-2 s-1. A period near the end of the experiment, during week 30, produced the strongest total hydrocarbon flux, associated with warmer deep (1 m) soil temperatures, lower fen water levels, and the late summer shift in wind direction at that time. An early summer"flush"of total hydrocarbon was not observed.

  17. On dryout heat flux and pressure drop of a submerged inductively heated bed flow from below

    Microsoft Academic Search

    F. F. Tsai; I. Catton

    1983-01-01

    An experimental investigation of dryout heat flux in a saturated porous medal with forced flow from below has been conducted using methanol as a coolant. The mass flux varied from 0 to 0.557 kg\\/m² sec. Particle sizes were 590-790 ..mu..m, 1.6 mm, 3.2 mm, and 4.8 mm. The dryout heat flux increases as the mass flux increases, and asymptotically goes

  18. Assessment of high-heat-flux thermal management schemes

    Microsoft Academic Search

    Issam Mudawar

    2001-01-01

    This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, microchannel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of

  19. Assessment of high-heat-flux thermal management schemes

    Microsoft Academic Search

    Issam Mudawar

    2000-01-01

    This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, micro-channel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of

  20. Using remotely sensed planetary boundary layer variables as estimates of areally averaged heat flux

    SciTech Connect

    Coulter, R.L.; Martin, T.J.; Holdridge, D.J.

    1995-06-01

    Homogeneity across the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site is an issue of importance to all facets of the Atmospheric Radiation Measurements (ARM) program. The degree to which measurements at the central facility can be used to verify, improve, or develop relationships in radiative flux models that are subsequently used in Global Circulation Models (GCMs), for example, is tied directly to the representativeness of the local measurements at the central facility for the site as a whole. The relative variation of surface energy budget terms over a 350- km X 400km domain such as the SGP CART site can be extremely large. The Planetary Boundary Layer (PBL) develops as a result of energy inputs from widely varying surfaces. The lower atmosphere effectively integrates the local inputs; measurements of PBL structure can potentially be used for estimates of surface heat flux over scales on the order of tens of kilometers. This project is focusing on two PBL quantities that are intimately tied to the surface heat flux: (1) the height of the mixed layer, z, that grows during daytime due to sensible heat flux input from the surface; and (2) the convective velocity scale, normally a scaling parameter defined by the product of the sensible heat flux and z, but in this case defined by coherent structures that connect the surface layer and the capping inversion that defines z.

  1. Critical Heat Flux of Concentric-Tube Thermosyphon

    NASA Astrophysics Data System (ADS)

    Kawabe, Hiromichi; Tanaka, Teimi; Fukusako, Shoichiro

    An experimental study has been performed to investigate the critical heat flux in a concentric-tube thermosyphon which has the straight shape of an inner tube. The outer tube was 27.4mm in diameter with 1080mm in height. Visual observations and measurments were carried out under the condition of uniform wall heat flux using R-11 and R-113 as the working liquid. The effects of inner tube diameter, insert length of inner tube into reservoir, and liquid subcooling on critical heat flux were extensively discussed. In addition, same experiments of single-tube thermosyphon were carried out for comparison. It was found that critical heat flux characteristics for concentric-tube thermosyphon were classified two regions. The correlation equations of both regions and transition condition were determined.

  2. Determination of pool boiling Critical Heat Flux enhancement in nanofluids

    E-print Network

    Truong, Bao H. (Bao Hoai)

    2007-01-01

    Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina ...

  3. Model of critical heat flux in subcooled flow boiling

    E-print Network

    Fiori, Mario P.

    1968-01-01

    The physical phenomenon occurring before and at the critical heat flux (CHF) for subcooled flow boiling has been investigated. The first phase of this study established the basic nature of the flow structure at CHF. A ...

  4. Modeling shortwave radiative fluxes from satellites

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Pinker, R. T.

    2012-12-01

    During the last two decades, significant progress has been made in assessing the Earth Radiation Balance from satellite observations. Yet, satellite based estimates differ from each other and from those provided by numerical models. Major issues are related to quality of satellite observations, such as the frequent changes in satellite observing systems, degradation of sensors, restricted spectral intervals and viewing geometry of sensors, and changes in the quality of atmospheric inputs that drive the inference schemes. To reduce differences among the satellite based estimates requires, among others, updates to inference schemes so that most recent auxiliary information can be fully utilized. This paper reports on improvements introduced to a methodology developed at the University of Maryland to estimate shortwave (SW) radiative fluxes within the atmosphere system from satellite observations, the implementation of the approach with newly available auxiliary information, evaluation of the downwelling SW flux against ground observations, and comparison with independent satellite methods and numerical models. Specifically, introduced are: new Narrow to Broadband (N/B) transformations and new Angular Distribution Models (ADM) for clear and cloudy sky that incorporate most recent land use classifications; improved aerosol treatment; separation of clouds by phase; improved sun-earth geometry; and implementation at 0.5° spatial resolution at 3-hourly intervals integrated to daily and monthly time scales. When compared to an earlier version of the model as implemented at 2.5° at global scale and against observations from the globally distributed Baseline Surface Radiation Network (BSRN) stations for a period of six years (at monthly time scale), the bias was reduced from 8.6 (4.6%) to -0.5 (0.3%) W/m2, the standard deviation from 16.6 (8.9%) to 14.5 (7.8%) W/m2while the correlation remained high at 0.98 in both cases. Evaluation was also done over oceanic sites as available from the Pilot Research Moored Array in the Tropical Atlantic (PIRATA) moorings and from the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) moorings in the tropical Pacific Ocean. Overall, results over oceans were not as good as over land for all the satellite retrievals compared in this study.

  5. Solid state radiative heat pump

    DOEpatents

    Berdahl, Paul H. (Oakland, CA)

    1986-01-01

    A solid state radiative heat pump (10, 50, 70) operable at room temperature (300.degree. K.) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of charge carriers as compared to thermal equilibrium. In one form of the invention (10, 70) an infrared semiconductor photodiode (21, 71) is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention (50), a homogeneous semiconductor (51) is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation through the active surface of the semiconductor are disclosed. In one method, an anti-reflection layer (19) is coated into the active surface (13) of the semiconductor (11), the anti-reflection layer (19) having an index of refraction equal to the square root of that of the semiconductor (11). In the second method, a passive layer (75) is spaced from the active surface (73) of the semiconductor (71) by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler (91) with a paraboloid reflecting surface (92) is in contact with the active surface (13, 53) of the semiconductor (11, 51), the coupler having an index of refraction about the same as that of the semiconductor.

  6. Solid state radiative heat pump

    DOEpatents

    Berdahl, P.H.

    1984-09-28

    A solid state radiative heat pump operable at room temperature (300 K) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of change carriers as compared equilibrium. In one form of the invention an infrared semiconductor photodiode is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention, a homogenous semiconductor is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation the active surface of the semiconductor are disclosed. In one method, an anti-refection layer is coated into the active surface of the semiconductor, the anti-reflection layer having an index of refraction equal to the square root of that of the semiconductor. In the second method, a passive layer is speaced trom the active surface of the semiconductor by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler with a paraboloid reflecting surface surface is in contact with the active surface of the semiconductor, the coupler having an index of refraction about the same as that of the semiconductor.

  7. Radiative heat transfer in fluidized-bed combustors

    Microsoft Academic Search

    1983-01-01

    A theoretical study is conducted to characterize the radiative component of heat transfer to a cooled surface in an air-fluidized bed combustor. Specifically, the effective emissivity of a fluidized bed is predicted theoretically using the two-flux model of radiative transfer theory and compared with experimental results. A gray nonisothermal model with a simple closed-form analytical solution is found to correlate

  8. A novel approach to measuring heat flux in swimming animals

    Microsoft Academic Search

    Kate Willis; Markus Horning

    2005-01-01

    We present a design for long-term or removable attachment of heat flux sensors (HFSs) to stationary or swimming animals in water that enables collection of heat flux data on both captive and free-ranging pinnipeds. HFSs were modified to allow for independent, continuous, and long-term or removable attachment to study animals. The design was tested for effects of HFSs and the

  9. ORIGINAL ARTICLE Sensible and latent heat flux response to diurnal variation in soil

    E-print Network

    in unfrozen soil water content. However, the impacts of air temperature change from solar radiation on latent the energy and water cycle processes and their effects on the Asian monsoon system. However, limitations range of latent heat flux had a similar temporal change pattern as that of unfrozen soil water at depths

  10. Numerical calculation of the radiation heat transfer between rocket motor nozzle's wall and gas

    NASA Astrophysics Data System (ADS)

    Zhou, Yipeng; Zhu, Dingqiang

    2014-11-01

    The heat flux density of radiation heat transfer between rocket motor nozzle's wall and gas is one of the most important factors to decide temperature of nozzle's wall. It also provides an invaluable references advice for choosing the material of wall and type of cooling. The numerical calculation based on finite volume method is introduced in the paper. After analysis of the formula of FVM without the influence of scattering, a formula that is used to let spectral radiant intensity that is the calculation of FVM be converted into heat flux density of radiation heat transfer is deduced. It is compiled that the program based on FVM is used to calculate the heat flux density. At the end, the heat flux density of radiation heat transfer of 3D model of double-arc nozzle's wall is calculated under different condition, then simply analysis cooling system is performed.

  11. Radiation-stagnation flow model of solid rocket motor internal insulator heat transfer

    NASA Astrophysics Data System (ADS)

    Brewster, M. Q.

    1988-01-01

    A diffusion radiation stagnation flow model of heat transfer to the forward dome internal insulator in aluminized solid rockets was developed. The dominant mode of heat transfer to the insulator surface was shown to be thermal radiation. Dimensionless heat flux was shown to be a function of three nondimensional parameters (in order of increasing sensitivity): wall-to-bulk fluid temperature ratio, conduction-radiation parameter, and boundary layer optical thickness. The effect of anisotropic scattering by molten aluminum oxide particles on heat transfer was also investigated using the Monte Carlo method. Strong forward single scattering was found to increase the net heat flux to the insulator surface over that for isotropic scattering.

  12. Radiation heat transfer in combustion systems

    Microsoft Academic Search

    R. Viskanta; M. P. Menguc

    1987-01-01

    An adequate treatment of thermal radiation heat transfer is essential to a mathematical model of the combustion process or to a design of a combustion system. This paper reviews the fundamentals of radiation heat transfer and some recent progress in its modeling in combustion systems. Topics covered include radiative properties of combustion products and their modeling and methods of solving

  13. Estimating heat fluxes by merging profile formulae and the energy budget with a variational technique

    NASA Astrophysics Data System (ADS)

    Zhang, Shuwen; Qiu, Chongjian; Zhang, Weidong

    2004-08-01

    A variational technique (VT) is applied to estimate surface sensible and latent heat fluxes based on observations of air temperature, wind speed, and humidity, respectively, at three heights (1 m, 4 m, and 10 m), and the surface energy and radiation budgets by the surface energy and radiation system (SERBS). The method fully uses all information provided by the measurements of air temperature, wind, and humidity profiles, the surface energy budget, and the similarity profile formulae as well. Data collected at Feixi experiment station installed by the China Heavy Rain Experiment and Study (HeRES) Program are used to test the method. Results show that the proposed technique can overcome the well-known unstablility problem that occurs when the Bowen method becomes singular; in comparison with the profile method, it reduces both the sensitivities of latent heat fluxes to observational errors in humidity and those of sensible heat fluxes to observational errors in temperature, while the estimated heat fluxes approximately satisfy the surface energy budget. Therefore, the variational technique is more reliable and stable than the two conventional methods in estimating surface sensible and latent heat fluxes.

  14. Measuring turbulent heat fluxes over leads using kites

    NASA Astrophysics Data System (ADS)

    Guest, Peter S.

    2007-05-01

    During the MaudNESS project in the austral winter of 2005, radiosondes attached to a kite indirectly measured surface turbulent heat fluxes from leads in the Eastern Weddell Sea near Maud Rise. Kite flights over two different leads with similar widths and upwind ice conditions are discussed. Lead mean surface fluxes were estimated by measuring the excess temperature and humidity downwind of the leads, estimating the wind speed profiles and performing a heat and moisture budget quantification. The measured sensible (latent) heat fluxes were 318 Wm-2 (158 Wm-2) and 258 Wm-2 (85 Wm-2) for the two flights; the values were lower in the second flight due to lower wind speeds. The average neutral sensible heat transfer coefficients for the two flights was (1.48 ± 0.13) × 10-3, and the average neutral latent heat flux coefficient was (1.47 ± 0.09) × 10-3. As expected, these values are enhanced from what would be expected in a typical open ocean situation with the same air-sea temperature and humidity differences. Kite radiosonde profile measurements are an economically viable method for measuring lead heat fluxes that avoid many of the logistical problems associated with other methods for measuring fluxes over leads.

  15. Characterization of local heat fluxes around ICRF antennas on JET

    NASA Astrophysics Data System (ADS)

    Campergue, A.-L.; Jacquet, P.; Bobkov, V.; Milanesio, D.; Monakhov, I.; Colas, L.; Arnoux, G.; Brix, M.; Sirinelli, A.; JET-EFDA Contributors

    2014-02-01

    When using Ion Cyclotron Range of Frequency (ICRF) heating, enhanced power deposition on Plasma-Facing Components (PFCs) close to the antennas can occur. Experiments have recently been carried out on JET with the new ITER-Like-Wall (ILW) to characterize the heat fluxes on the protection of the JET ICRF antennas, using Infra-Red (IR) thermography measurement. The measured heat flux patterns along the poloidal limiters surrounding powered antennas were compared to predictions from a simple RF sheath rectification model. The RF electric field, parallel to the static magnetic field in front of the antenna, was evaluated using the TOPICA code, integrating a 3D flattened model of the JET A2 antennas. The poloidal density variation in front of the limiters was obtained from the mapping of the Li-beam or edge reflectometry measurements using the flux surface geometry provided by EFIT equilibrium reconstruction. In many cases, this simple model can well explain the position of the maximum heat flux on the different protection limiters and the heat-flux magnitude, confirming that the parallel RF electric field and the electron plasma density in front of the antenna are the main driving parameters for ICRF-induced local heat fluxes.

  16. Sensible and Latent Heat Flux Variability and Response to Dry-Wet Soil Moisture Zones Across China

    NASA Astrophysics Data System (ADS)

    Li, Mingxing; Ma, Zhuguo

    2015-01-01

    Our understanding of the spatio-temporal variability of sensible and latent heat fluxes over land has advanced slowly due to the absence of long-term measurements. To help address this, we produced a long-term heat flux dataset by using a land-surface model driven using observation-based atmospheric forcing. We then corrected the dataset using net radiation observations, and validated the corrected dataset using multiple-source measurements. The results indicate that the corrected dataset represents the variability of these two heat fluxes well on various time scales. Based on the dataset, analyses show that, during 1951-2008, sensible heat flux decreased significantly over China, with a linear trend of 0.04 W m year, while latent heat flux increased at 0.02 W m year. Regionally, the trends appeared more significant in north-east China, south-west China, and the Tibetan Plateau. On average, the Tibetan Plateau showed the maximum sensible heat flux, especially over the south-west region, with averages 100 W m. Meanwhile, higher latent heat fluxes mainly covered the Yangtze-Huaihe river basin and southward, with averages 70 W m. Regarding the response of heat fluxes to soil moisture, the variations of sensible and latent fluxes were more sensitive to soil moisture over dry regions (arid and semi-arid soil moisture zones), while the stronger anomalies for both fluxes occurred over wet regions (semi-humid and humid soil moisture zones).

  17. Explosive Boiling at Very Low Heat Fluxes: A Microgravity Phenomenon

    NASA Technical Reports Server (NTRS)

    Hasan, M. M.; Lin, C. S.; Knoll, R. H.; Bentz, M. D.

    1993-01-01

    The paper presents experimental observations of explosive boiling from a large (relative to bubble sizes) flat heating surface at very low heat fluxes in microgravity. The explosive boiling is characterized as either a rapid growth of vapor mass over the entire heating surface due to the flashing of superheated liquid or a violent boiling spread following the appearance of single bubbles on the heating surface. Pool boiling data with saturated Freon 113 was obtained in the microgravity environment of the space shuttle. The unique features of the experimental results are the sustainability of high liquid superheat for long periods and the occurrence of explosive boiling at low heat fluxes (0.2 to 1.2 kW/sq m). For a heat flux of 1.0 kW/sq m a wall superheat of 17.9 degrees C was attained in ten minutes of heating. This was followed by an explosive boiling accompanied with a pressure spike and a violent bulk liquid motion. However, at this heat flux the vapor blanketing the heating surface could not be sustained. Stable nucleate boiling continued following the explosive boiling.

  18. Evaluation of operational ECMWF surface heat fluxes: impact of parameterisation changes during 1986 1995

    NASA Astrophysics Data System (ADS)

    Siefridt, Laure; Barnier, Bernard; Béranger, Karine; Roquet, Hervé

    1999-02-01

    Monthly mean values of ocean surface fluxes produced at the European Centre for Medium-Range Weather Forecasts (ECMWF) between 1986 and 1995 are investigated. The variations in the fluxes over this 10-year period are clearly linked to changes introduced into the analysis and forecast system, and the present study aims at documenting and understanding the sensitivity of surface flux estimates to model parameterisations. Periods are identified when properties of the ECMWF analyses can be characterized and discussed in terms of their ability to provide a forcing function for ocean circulation models. ECMWF surface fluxes are found to exhibit a sufficiently coherent geophysical behaviour from 1986 to 1988 to be considered as representing a climate state, in spite of several deficiencies characterized by weak solar and latent heat fluxes in equatorial regions. Globally, the annual mean and the seasonal cycle agree fairly well with recent observation-based climatologies. Several changes made to the model's physical parameterisations in the 1989-1991 period had a dramatic impact on the radiative fluxes. Net surface shortwave radiation were obviously over-estimated by up to 40 W m -2, and the net heat flux was clearly far from the expected geophysical values. During the 1992-1994 period, additional modifications to the radiation parameterisation scheme brought back solar radiation to a more reasonable level. However, the net input of heat in equatorial oceans appears to be low, and the uptake of heat by evaporation is insufficient at mid-latitudes in the southern hemisphere, a deficiency noticed in ECMWF analyses since the changes in cloud and radiation parameterisations of 1989. ECMWF latent and radiative fluxes show significant improvements in 1995 after the introduction of prognostic clouds in early April. This new parameterisation increases and adjusts the value of the latent heat loss at mid-latitudes in the southern hemisphere. The latent heat flux is found to be globally larger than in recent climatologies derived from ship observations. Regional deficiencies remain in the high northern latitudes (input of heat too great) and in narrow tropical bands in the inter-tropical convergence zone (ITCZ) (cooling by evaporation too great and solar heating too small), and produce a significant bias in the meridional heat transport. Over the 10-year period, latent heat loss is increased through almost 40 W m -2 by the successive model changes, apparently in the right direction, although it might be too large at the end of the period. In preparation for a study of the freshwater flux at the ocean surface (evaporation minus precipitation) in a forthcoming paper by Béranger et al. [Béranger, K., Siefridt, L., Barnier, B., Garnier, E., Roquet, H., 1998. Evaluation of operational ECMWF surface freshwater fluxes over oceans during 1991-97, and possible thermohaline effects. Submitted to J. Mar. Systems], this paper studies the climatological average of the latent heat flux over the period 1991-95. This average is characterized by a larger loss than in previous years (late 1980s), which appears to be more consistent with the current opinion that most climatologies derived from observations made by the Voluntary Observing Ship (VOS) program underestimate this type of exchange. However, the averaging does not fully correct the low evaporation at southern mid-latitudes. To conclude, the paper contributes to understanding of the accuracy currently reached in flux calculations at the global scale in the ECMWF reanalysis project.

  19. Systematic investigation of the effects of hydrophilic porosity on boiling heat transfer and critical heat flux

    E-print Network

    Tetreault-Friend, Melanie

    2014-01-01

    Predicting the conditions of critical heat flux (CHF) is of considerable importance for safety and economic reasons in heat transfer units, such as in nuclear power plants. It is greatly advantageous to increase this thermal ...

  20. Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux

    E-print Network

    Phillips, Bren Andrew

    2011-01-01

    The effects on pool boiling characteristics such as critical heat flux and the heat transfer coefficient of different surface characteristics such as surface wettability, roughness, morphology, and porosity are not well ...

  1. An Overview of the GEWEX Radiative Flux Assessment

    Microsoft Academic Search

    P. W. Stackhouse Jr.; L. M. Hinkelman; T. Wong; L. H. Chambers; B. A. Wielicki

    2009-01-01

    The Global Energy and Water Cycle Experiment (GEWEX) Radiative Flux Assessment (RFA) is an international effort to produce a community-wide evaluation of the currently available long-term radiative flux data sets derived from satellite based analysis in the context of global change detection and analysis. Its primary activity consists of assessing the uncertainties associated with these data sets by comparing TOA

  2. Unsteady heating and radiation effects of small particles in a thermal plasma

    Microsoft Academic Search

    Xi Chen; E. Pfender

    1982-01-01

    Based on exact solutions for the heat flux to a particle exposed to a thermal plasma given in a previous paper, initial unsteady heating (including heating of the solid phase, melting of the solid phase, heating of the liquid phase, and evaporation) and radiation effects are considered. Closed-form solutions can be obtained for particles with infinite thermal conductivities. The results

  3. Intercomparison of Latent Heat Fluxes Over Global Oceans

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Nelkin, Eric; Ardizzone, Joe; Atlas, Robert M.; Chou, Ming-Dah

    2003-01-01

    Turbulent fluxes of momentum, moisture, and heat at the air-sea interface are essential for climate studies. Version 2 Goddard Satellite-based Surface Turbulent Fluxes (GSSTF2) has been derived from the Special Sensor Microwave/Imager (SSM/I) radiance measurements. This dataset, covering the period July 1987-December 2000 over global oceans, has a spatial resolution of 1 deg x 1 deg lat-long and a temporal resolution of 1 day. Turbulent fluxes are derived from the SSM/I surface winds and surface air humidity, as well as the 2-m air and sea surface temperatures (SST) of the NCEP/NCAR reanalysis, using a bulk aerodynamic algorithm based on the surface layer similarity theory. The GSSTF2 bulk flux model, and retrieved daily wind stress, latent heat flux, wind speed, and surface air humidity validate well with ship observations of ten field experiments over the tropical and midlatitude oceans during 1991-99. The global distributions of 1988-2000 annual- and seasonal-mean turbulent fluxes show reasonable patterns related to the atmospheric general circulation and seasonal variations. Latent heat fluxes and related input parameters over global oceans during 1992-93 have been compared among GSSTF1 (version 1), GSSTF2, HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data), NCEP/NCAR reanalysis, and one based on COADS (Comprehensive Ocean-Atmosphere Data Set). Our analyses suggest that the GSSTF2 latent heat flux, surface air humidity, surface wind, and SST are quite realistic compared to the other four flux datasets examined. However, significant differences are found among these five flux datasets. The GSSTF2, available at http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/hydrology/hd_gsstf2.O.html, is useful for climate studies.

  4. A study of heat flux induced dryout in capillary grooves

    Microsoft Academic Search

    Timothy J. Murphy

    1992-01-01

    This is an experimental study of ethanol flowing in the narrow grooves of a copper plate which is subjected to heat fluxes sufficient to evaporate more liquid than can be replaced by capillary pumping. Three groove geometries are used: square, rectangle, and trapezoid. The objective is to simulate aspects of liquid flow in heat pipes with axial grooves. In order

  5. Advanced Micro-Heat Exchangers for High Heat Flux

    Microsoft Academic Search

    Chien-Yuh Yang; Chun-Ta Yeh; Wei-Chi Liu; Bing-Chwen Yang

    2007-01-01

    Three micro-heat exchangers for use in a liquid cooling system with a long offset strip, short offset strip, and chevron flow path based on the traditional heat transfer enhancement concepts were designed and tested. A straight channel heat exchanger was also made for comparison. The liquid crystal thermography method described by Lin and Yang (2005) was used to observe the

  6. Limitations of Using Uniform Heat Flux Assumptions in Sizing Vertical Borehole Heat Exchanger Fields

    E-print Network

    of the heat flow in the ground is used to predict the temperature rise and fall over time of the fluidLimitations of Using Uniform Heat Flux Assumptions in Sizing Vertical Borehole Heat Exchanger heat exchangers and the surrounding ground are essential for design, optimization and energy analysis

  7. Eddy heat fluxes at Drake Passage due to mesoscale motions

    E-print Network

    Rojas Recabal, Ricardo Luis

    1982-01-01

    EDDY HEAT FLUKES AT DRAKE PASSAGE DUE TO MESOSCALE MOTIONS A Thesis by RICARDO LUIS ROJAS RECABAL Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May... 1982 Major Subject: Oceanography EDDY HEAT FLUXES AT DRAKE PASSAGE DUE TO MESOSCALE NOTIONS A Thesis by RICARDO LUIS ROJAS RECABAL Approved as to style and content by: was )W-~ Member em er May 1982 ABSTRACT Eddy Heat Fluxes at Drake Passage...

  8. QUANTIFICATION OF HEAT FLUX FROM A REACTING THERMITE SPRAY

    SciTech Connect

    Eric Nixon; Michelle Pantoya

    2009-07-01

    Characterizing the combustion behaviors of energetic materials requires diagnostic tools that are often not readily or commercially available. For example, a jet of thermite spray provides a high temperature and pressure reaction that can also be highly corrosive and promote undesirable conditions for the survivability of any sensor. Developing a diagnostic to quantify heat flux from a thermite spray is the objective of this study. Quick response sensors such as thin film heat flux sensors can not survive the harsh conditions of the spray, but more rugged sensors lack the response time for the resolution desired. A sensor that will allow for adequate response time while surviving the entire test duration was constructed. The sensor outputs interior temperatures of the probes at known locations and utilizes an inverse heat conduction code to calculate heat flux values. The details of this device are discussed and illustrated. Temperature and heat flux measurements of various thermite spray conditions are reported. Results indicate that this newly developed energetic material heat flux sensor provides quantitative data with good repeatability.

  9. A diagnostic for quantifying heat flux from a thermite spray

    SciTech Connect

    E. P. Nixon; M. L. Pantoya; D. J. Prentice; E. D. Steffler; M. A. Daniels; S. P. D'Arche

    2010-02-01

    Characterizing the combustion behaviors of energetic materials requires diagnostic tools that are often not readily or commercially available. For example, a jet of thermite spray provides a high temperature and pressure reaction that can also be highly corrosive and promote undesirable conditions for the survivability of any sensor. Developing a diagnostic to quantify heat flux from a thermite spray is the objective of this study. Quick response sensors such as thin film heat flux sensors cannot survive the harsh conditions of the spray, but more rugged sensors lack the response time for the resolution desired. A sensor that will allow for adequate response time while surviving the entire test duration was constructed. The sensor outputs interior temperatures of the probes at known locations and utilizes an inverse heat conduction code to calculate heat flux values. The details of this device are discussed and illustrated. Temperature and heat flux measurements of various thermite sprays are reported. Results indicate that this newly designed heat flux sensor provides quantitative data with good repeatability suitable for characterizing energetic material combustion.

  10. Radiative heat transfer in porous uranium dioxide

    SciTech Connect

    Hayes, S.L. [Texas A and M Univ., College Station, TX (United States)] [Texas A and M Univ., College Station, TX (United States)

    1992-12-01

    Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.

  11. Turbine blade and vane heat flux sensor development, phase 1

    NASA Technical Reports Server (NTRS)

    Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

    1984-01-01

    Heat flux sensors available for installation in the hot section airfoils of advanced aircraft gas turbine engines were developed. Two heat flux sensors were designed, fabricated, calibrated, and tested. Measurement techniques are compared in an atmospheric pressure combustor rig test. Sensors, embedded thermocouple and the Gordon gauge, were fabricated that met the geometric and fabricability requirements and could withstand the hot section environmental conditions. Calibration data indicate that these sensors yielded repeatable results and have the potential to meet the accuracy goal of measuring local heat flux to within 5%. Thermal cycle tests and thermal soak tests indicated that the sensors are capable of surviving extended periods of exposure to the environment conditions in the turbine. Problems in calibration of the sensors caused by severe non-one dimensional heat flow were encountered. Modifications to the calibration techniques are needed to minimize this problem and proof testing of the sensors in an engine is needed to verify the designs.

  12. Prototype V-Groove Radiator Heat Shield

    NASA Technical Reports Server (NTRS)

    Petrick, S. Walter; Bard, Steven

    1990-01-01

    Report describes design, fabrication, and testing of heat radiator equipped with multi-V-groove radiator heat shield. Device compact, efficient structure which removes heat from infrared detectors, gamma-ray detectors, and similar instruments aboard Mars Observer spacecraft and radiates heat into outer space. Designed to maintain detector for gamma-ray spectrometer at temperature of 80 K in cold vacuum under heat load of 80 mW. Prototype made of aluminum, though production shields made of aluminized sheets of polyethylene terephthalate.

  13. Corrections of Heat Flux Measurements on Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Reinarts, Thomas R.; Matson, Monique L.; Walls, Laurie K.

    2002-01-01

    Knowledge of aerothermally induced convective heat transfer is important in the design of thermal protection systems for launch vehicles. Aerothermal models are typically calibrated via the data from circular, in-flight, flush-mounted surface heat flux gauges exposed to the thermal and velocity boundary layers of the external flow. Typically, copper or aluminum Schmidt- Boelter gauges, which take advantage of the one-dimensional Fourier's law of heat conduction, are used to measure the incident heat flux. This instrumentation, when surrounded by low-conductivity insulation, has a wall temperature significantly lower than the insulation. As a result of this substantial disturbance to the thermal boundary layer, the heat flux incident on the gauge tends to be considerably higher than it would have been on the insulation had the calorimeter not been there. In addition, radial conductive heat transfer from the hotter insulation can cause the calorimeter to indicate heat fluxes higher than actual. An overview of an effort to develop and calibrate gauge correction techniques for both of these effects will be presented.

  14. Numerical study of the effects of boundary conditions on the measurement and calibration of gardon type heat flux sensors

    NASA Technical Reports Server (NTRS)

    Krane, M.; Dybbs, A.

    1987-01-01

    To monitor the high-intensity heat flux conditions that occur in the space shuttle main engine (SSME), it is necessary to use specifically designed heat flux sensors. These sensors, which are of the Gardon-type, are exposed on the measuring face to high-intensity radiative and convective heat fluxes and on the other face to convective cooling. To improve the calibration and measurement accuracy of these gauges, researchers are studing the effect that the thermal boundary conditions have on gauge performance. In particular, they are studying how convective cooling effects the field inside the sensor and the measured heat flux. The first phase of this study involves a numerical study of these effects. Subsequent phases will involve experimental verification. A computer model of the heat transfer around a Garden-type heat flux sensor was developed. Two specific geometries are being considered are: (1) heat flux sensor mounted on a flat-plate; and (2) heat flux sensor mounted at the stagnation point of a circular cylinder. Both of these configurations are representative of the use of heat flux sensors in the components of the SSME. The purpose of the analysis is to obtain a temperature distribution as a function of the boundary conditions.

  15. Nonlinear aspects of high heat flux nucleate boiling heat transfer. Part 1, Formulation

    SciTech Connect

    Sadasivan, P.; Unal, C.; Nelson, R.

    1994-04-01

    This paper outlines the essential details of the formulation and numerical implementation of a model used to study nonlinear aspects of the macrolayer-controlled heat transfer process associated with high heat flux nucleate boiling and the critical heat flux. The model addresses the three-dimensional transient conduction heat transfer process within the problem domain comprised of the macrolayer and heater. Heat dissipation from the heater is modeled as the sum of transient transport into the macrolayer, and the heat loss resulting from evaporation of menisci associated with vapor stems.

  16. Critical Heat Flux of Butanol Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Shotaro; Shoji, Masahiro

    It is known that the addition of small amount of alcohol such as butanol to water enhances the CHF. Such aqueous solution is actively applied to heat transfer devices such as heat pipes and microchannel cooling systems, however, the fundamental characters of boiling have not been fully understood. In the present research, the experiment of boiling heat transfer is performed on a heated wire by employing butanol aqueous solution as a typical test solution and by changing concentration 1-butanol and subcooling in a wide range. Bubbling aspects were observed using high-speed video camera. It is found from the experiment that CHF is 2 to 3 times higher than that of pure water and generating bubbles are tiny even at the saturated condition. The dependence of CHF on subcooling is found to be curious showing that CHF decreases first, takes a minimum, and then increases with increasing subcooling. These results suggest that the butanol aqueous solution is a promising liquid for the application of boiling to a small-scaled cooling device.

  17. Downstream Heat Flux Profile vs. Midplane T Profile in Tokamaks

    SciTech Connect

    Robert J. Goldston

    2009-08-20

    The relationship between the midplane scrape-off-layer electron temperature profile and the parallel heat flux profile at the divertor in tokamaks is investigated. A model is applied which takes into account anisotropic thermal diffusion, in a rectilinear geometry with constant density. Eigenmode analysis is applied to the simplified problem with constant thermal diffusivities. A self-similar nonlinear solution is found for the more realistic problem with anisotropically temperature-dependent thermal diffusivities. Numerical solutions are developed for both cases, with spatially dependent heat flux emerging from the plasma. For both constant and temperature-dependent thermal diffusivities it is found that, below about one-half of its peak, the heat flux profile shape at the divertor, compared with the midplane temperature profile shape, is robustly described by the simplest two-point model. However the physical processes are not those assumed in the simplest two-point model, nor is the numerical coefficient relating q||div to Tmp ?||mp/L|| as predicted. For realistic parameters the peak in the heat flux, moreover, can be reduced by a factor of two or more from the two-point model scaling which fits the remaining profile. For temperature profiles in the SOL region above the x-point set by marginal stability, the heat flux profile to the divertor can be largely decoupled from the prediction of the two-point model. These results suggest caveats for data interpretation, and possibly favorable outcomes for divertor configurations with extended field lines.

  18. Remote sensing of heat fluxes using SEBAL: Comparison between Landsat and MODIS

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Berhane, T.; Hill, M.; Rundquist, B.

    2007-12-01

    Instantaneous heat fluxes were estimated using data obtained from Landsat 5 TM (Thematic Mapper), Landsat 7 ETM+ (Enhanced Thematic Mapper Plus) and Terra MODIS (Moderate Resolution Imaging Spectroradiometer) using Surface Energy Balance Algorithm for Land (SEBAL) model for cloud-free days. The modeled results were compared with measurements of net radiation (both incoming and outgoing short and longwave), soil, sensible and latent heat fluxes by two flux towers located in Brookings, SD and Fort Peck, MT. Flux tower data were 30 minutes averages at every half an hour and the contributing area of the air within the period was estimated for each satellite pass by taking into accounts the factors of observation height, atmospheric stability, and surface roughness as well as wind speed and directions (Hsieh et al. 2000). We found that footprints (considering 90% contributing areas) were normally larger than the size of one Landsat pixel (30 m) but smaller than that of one MODIS pixel (1 km). Therefore for Landsat the data were average for pixels within the concurrent footprint and for MODIS the data for the particular pixel covering the flux tower is used. The correlation coefficients between the modeled and the observed net radiation values for Landsat and MODIS were found to be 0.70 and 0.66 respectively. Relatively, comparisons were better at Brookings than at Fort Peck site for both sensors. This could be because the former site has a relatively flat topography and larger fetch than the latter, minimizing the possible effects of terrain heterogeneity on incoming and outgoing solar radiation modeling. Poor correlation was found for soil heat flux between satellites estimate and in-situ observations. In addition, the correlation coefficient for sensible heat flux was found to be 0.62 for Landsat. However, for MODIS, the correlation was only 0.11. On the other hand, the comparisons for latent heat flux showed improvement with correlation coefficients being 0.62 and 0.37 for Landsat and MODIS respectively. In SEBAL, cold pixels are used to estimate air temperature, which is used in computation for both net radiation and sensible heat flux. The uncertainties associated with this assumption cancelled out somehow in deriving latent heat flux. SEBAL performed better in modeling the heat fluxes with Landsat data. It is probably due to the scaling issue in comparison as the footprint areas of the flux towers have always been significantly less than a single MODIS pixel. By simulating MODIS observation using Landsat, we found the correlation coefficients for the aggregated Landsat pixels decreased from 0.62 to 0.25 with an increase of RMSE from 50.5 to 68.3 Wm-2. This suggested that poor performance of MODIS estimate of heat fluxes as compared to the flux tower measurements is due to heterogeneity of the surface within the field of view of MODIS sensor.

  19. Multi Function Heat Pulse Probes (MFHPP) to Estimate Ground Heat Flux and Reduce Surface Energy Budget Errors

    NASA Astrophysics Data System (ADS)

    Ciocca, Francesco; Sharma, Varun; Lunati, Ivan; Parlange, Marc B.

    2013-04-01

    Ground heat flux plays a crucial role in surface energy budget: an incorrect estimation of energy storage and heat fluxes in soils occur when probes such as heat flux plates are adopted, and these mistakes can account for up to 90% of the residual variance (Higgins, GRL, 2012). A promising alternative to heat flux plates is represented by Multi Function Heat Pulse Probes (MFHPP). They have proven to be accurate in thermal properties and heat fluxes estimation (e.g. Cobos, VZJ, 2003) and can be used to monitor and quantify subsurface evaporation in field experiments (Xiao et al., VZJ, 2011). We perform a laboratory experiment with controlled temperature in a small Plexiglas column (20cm diameter and 40cm height). The column is packed with homogeneously saturated sandy soil and equipped with three MFHPPs in the upper 4cm and thermocouples and dielectric soil moisture probes deeper. This configuration allows for accurate and simultaneous ground heat flux, soil moisture and subsurface evaporation measurements. Total evaporation is monitored using a precision scale, while an infrared gun and a long wave radiometer measure the soil skin temperature and the outgoing long-short wave radiation, respectively. A fan and a heat lamp placed above the column allow to mimick on a smaller and more controlled scale the field conditions induced by the diurnal cycle. At a reference height above the column relative humidity, wind speed and air temperature are collected. Results are interpreted by means of numerical simulations performed with an ad-hoc-developed numerical model that simulates coupled heat and moisture transfer in soils and is used to match and interpolate the temperature and soil moisture values got at finite depths within the column. Ground heat fluxes are then estimated by integrating over almost continuous, numerically simulated temperature profiles, which avoids errors due to use of discrete data (Lunati et al., WRR, 2012) and leads to a more reliable estimate of this crucial term. The surface energy balance is calculated and the residual decomposition approach described by Higgins, GRL, 2012 will be applied to estimate the contribution of the ground heat. Results of the matching between subsurface-surface evaporation are presented, and the applicability of the MFHPP to energy balance closure problems is discussed.

  20. Tests of scalar heat flux - roughness scale relationships from the SGS-2002 data sets

    NASA Astrophysics Data System (ADS)

    Higgins, C. W.; Parlange, M. B.; Meneveau, C.

    2003-12-01

    This study addresses relationships between sensible heat flux and dimensionless roughness scale, based on measurements at several time and length scales. The data were obtained in the summer of 2002 over the homogenous flat terrain of the Utah salt flats. The instrumentation consisted of 16 sonic anemometers arranged into a vertical 4 by 4 grid allowing for spatial resolution of 0.5 m. The temporal resolution of the data is 20 Hz. Supporting meteorological measurements including the relative humidity, latent heat flux, net radiation, soil heat flux, and skin surface temperature were also obtained. Using these data we measure the sensible heat flux and compare to predictions from a model by Brutsaert, and from a more recent improvement proposed by Cahill et al. (1997). The variability of contributing meteorological variables such as the Latent heat flux (H),the friction velocity (u*) and the Obukhov length (L) will be characterized as a function of averaging time, as well as spatial filtering scale. Thus the effects of coarse-graining in space and time upon the validity of the various models is ascertained.

  1. Variability of the latent heat flux in the Amazon over ten years of use and occupation

    NASA Astrophysics Data System (ADS)

    Furlan, D. N.; Ballester, M. V.; Andrade, R. G.; Victoria, R. L.

    2012-12-01

    An alternative to determine the latent heat flux, which is the amount of energy available for evapotranspiration, is the use of data obtained by remote sensing. Among the models that use these data, the Surface Energy Balance Algorithm for Land - SEBAL (Bastiaanssen et al., 1998) has been increasing and has become widely used because it determines the evapotranspiration from the bullet full of radiation and energy on the surface land, using remote sensing data and a few additional data collected by surface weather station, as wind speed and temperature. This study aimed to evaluate the spatial variability of the latent heat flux according to the change of use and land cover. Thus, the algorithm was used to determine the SEBAL latent heat flux rate defined as the latent heat transferred from the surface due to the evaporation process or obtained by simple evaporation difference between the radiation balance, the heat flow in the soil and latent heat flux: (?ET=RN-G-H). Where the value of the latent heat instantaneous flow, ie., its value at the time of satellite passage. To determine the latent heat flux were used Landsat 5 TM orbit and point 231/068 the following dates: 06/08/1999, 11/08/2001, 13/07/2005 and 09/08/2009.The study area is located in the central region of the Rondonia state in the Brazilian Amazon. This region has undergone an accelerated process of land use and soil in the last 30 years, which caused significant replacement of forest areas for other classes land use practices, mainly as grazing and agriculture.The results show that the area where the latent heat flux was greater decreased over ten years in analysis due to reduction of forest areas (Figure 1).These results show the latent heat flux in Rondônia in a very dry period, which is in July and August. Due to the long drought period, the topsoil dries faster and areas that are covered by pastures and agriculture have lower evapotranspiration values due to the root system are smaller and do not pick up water at greater depths. The forest areas have a different response to the dry season, they are able to draw water at greater depths, so the evaporation is constant throughout the year.The replacement of forest areas for grazing and agriculture can affect the hydrological regime in this region, especially in drought. Figure 1: Latent heat flow in the central region of Rondônia.

  2. Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

    2014-05-01

    Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

  3. Remote high-temperature insulatorless heat-flux gauge

    DOEpatents

    Noel, B.W.

    1993-12-28

    A remote optical heat-flux gauge for use in extremely high temperature environments is described. This application is possible because of the use of thermographic phosphors as the sensing media, and the omission of the need for an intervening layer of insulator between phosphor layers. The gauge has no electrical leads, but is interrogated with ultraviolet or laser light. The luminescence emitted by the two phosphor layers, which is indicative of the temperature of the layers, is collected and analyzed in order to determine the heat flux incident on the surface being investigated. The two layers of thermographic phosphor must be of different materials to assure that the spectral lines collected will be distinguishable. Spatial heat-flux measurements can be made by scanning the light across the surface of the gauge. 3 figures.

  4. Remote high-temperature insulatorless heat-flux gauge

    DOEpatents

    Noel, Bruce W. (Espanola, NM)

    1993-01-01

    A remote optical heat-flux gauge for use in extremely high temperature environments is described. This application is possible because of the use of thermographic phosphors as the sensing media, and the omission of the need for an intervening layer of insulator between phosphor layers. The gauge has no electrical leads, but is interrogated with ultraviolet or laser light. The luminescence emitted by the two phosphor layers, which is indicative of the temperature of the layers, is collected and analyzed in order to determine the heat flux incident on the surface being investigated. The two layers of thermographic phosphor must be of different materials to assure that the spectral lines collected will be distinguishable. Spatial heat-flux measurements can be made by scanning the light across the surface of the gauge.

  5. Enhancement or Suppression of the Near-Field Radiative Heat Transfer Between Two Materials

    Microsoft Academic Search

    Z. H. Zheng; Y. M. Xuan

    2011-01-01

    Control of near-field radiative heat transfer is significant due to its practical applications. We propose an approach to control near-field thermal radiation between two closely spaced bodies by inserting a suspended thin film. Numerical simulations are carried out for different material combinations of doped silicon and aluminum (Al). Investigation showed that the heat flux between the two bodies can be

  6. Comparison of calculation methods and models in software for computer graphics and radiative heat exchange

    Microsoft Academic Search

    KONRAD DOMKE

    Ab stract: The paper describes the physical backgrounds for modelling in visualisation using computer graphics sof tware and in programs of radiative heat exchange. Physical phenomena in both cases (generation, propagation, reflection and absorption of light and radiative heat flux) are quite similar, provided with basic equations, typical simplification assumptions and the most frequently applied methods of resolving such issues.

  7. Variations in geothermal heat flux at Grímsvötn, Iceland

    NASA Astrophysics Data System (ADS)

    Iona Reynolds, Hannah; Tumi Gudmundsson, Magnús

    2014-05-01

    Thermal signals from sub-surface magmatic sources are difficult to quantify, as the measurement of fluxes from the ground to the atmosphere is subject to large uncertainties. Ice cauldrons are depressions which form on the surface of glaciers due to basal melting as a result of geothermal flux from the bedrock beneath, often generated by volcanic sources. The monitoring of ice cauldrons provides a unique opportunity to quantify heat flux to a much improved accuracy, as the melting ice acts as a calorimeter. Time series data of ice surface elevation at cauldrons above Grímsvötn volcano are presented over a 14 year period, with estimates of the melt volume and surface heat flux required for this melting to have occurred. Three volcanic eruptions took place at Grímsvötn during the study period, the effects of which are visible in ice surface elevation data. However, separate thermal anomalies are observed in areas unaffected by erupted products. A peak in surface heat flux is observed following the 1998 eruption, several kilometres east of the vent, with a maximum rise of ~200 W·m-2. The anomalous signal lasts for approximately three years. Possible explanations include the intrusion of a dyke beneath this area during the eruption, or increased permeability from greater dilatational strain due to regional stress, both of which would significantly increase heat flux. We investigate possible scenarios which could produce such a thermal anomaly, using finite element modelling. The effects of cooling magmatic intrusions and changes to the parameter space for country rock conductivity and permeability are considered, in relation to heat flux and the timescales and spatial extent of associated surface anomalies. Our results advance the understanding and interpretation of thermal signals observed at ice-covered volcanoes.

  8. Radiative heat transfer between inner perforated cylinder and an entire coaxial cylinder

    Microsoft Academic Search

    A. V. Rumyantsev; O. N. Bryukhanov; V. R. Bazilevich

    1979-01-01

    An equation for the radiative flux between elements of the system is obtained fay the generalized zonal method. Specific features of the heat transfer in a system with a perforated cylinder are discovered and explained.

  9. Radiative heat transfer between dielectric bodies

    E-print Network

    Svend-Age Biehs

    2011-03-16

    The recent development of a scanning thermal microscope (SThM) has led to measurements of radiative heat transfer between a heated sensor and a cooled sample down to the nanometer range. This allows for comparision of the known theoretical description of radiative heat transfer, which is based on fluctuating electrodynamics, with experiment. The theory itself is a macroscopic theory, which can be expected to break down at distances much smaller than 10-8m. Against this background it seems to be reasonable to revisit the known macroscopic theory of fluctuating electrodynamics and of radiative heat transfer.

  10. Critical heat flux in a locally heated liquid film driven by gas flow in a minichannel

    NASA Astrophysics Data System (ADS)

    Zaitsev, D. V.; Rodionov, D. A.; Kabov, O. A.

    2009-07-01

    The rupture of a liquid film driven by friction with a gas flow in a horizontal minichannel and the heat-exchange crisis in this film locally heated by a 1 × 1 cm source in the channel wall has been experimentally studied. A heat flux of 250 W/cm2 is achieved, which is greater by an order of magnitude than the limiting heat flux for a vertically falling liquid film with the same Reynolds number (Re l = 21). These experiments confirmed good prospects for using gas-flow-driven liquid films in cooling systems of devices with intense local heat evolution.

  11. Offline GCSS Intercomparison of Cloud-Radiation Interaction and Surface Fluxes

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Johnson, D.; Krueger, S.; Zulauf, M.; Donner, L.; Seman, C.; Petch, J.; Gregory, J.

    2004-01-01

    Simulations of deep tropical clouds by both cloud-resolving models (CRMs) and single-column models (SCMs) in the GEWEX Cloud System Study (GCSS) Working Group 4 (WG4; Precipitating Convective Cloud Systems), Case 2 (19-27 December 1992, TOGA-COARE IFA) have produced large differences in the mean heating and moistening rates (-1 to -5 K and -2 to 2 grams per kilogram respectively). Since the large-scale advective temperature and moisture "forcing" are prescribed for this case, a closer examination of two of the remaining external types of "forcing", namely radiative heating and air/sea hear and moisture transfer, are warranted. This paper examines the current radiation and surface flux of parameterizations used in the cloud models participating in the GCSS WG4, be executing the models "offline" for one time step (12 s) for a prescribed atmospheric state, then examining the surface and radiation fluxes from each model. The dynamic, thermodynamic, and microphysical fluids are provided by the GCE-derived model output for Case 2 during a period of very active deep convection (westerly wind burst). The surface and radiation fluxes produced from the models are then divided into prescribed convective, stratiform, and clear regions in order to examine the role that clouds play in the flux parameterizations. The results suggest that the differences between the models are attributed more to the surface flux parameterizations than the radiation schemes.

  12. Infrared Camera Diagnostic for Heat Flux Measurements on NSTX

    SciTech Connect

    D. Mastrovito; R. Maingi; H.W. Kugel; A.L. Roquemore

    2003-03-25

    An infrared imaging system has been installed on NSTX (National Spherical Torus Experiment) at the Princeton Plasma Physics Laboratory to measure the surface temperatures on the lower divertor and center stack. The imaging system is based on an Indigo Alpha 160 x 128 microbolometer camera with 12 bits/pixel operating in the 7-13 {micro}m range with a 30 Hz frame rate and a dynamic temperature range of 0-700 degrees C. From these data and knowledge of graphite thermal properties, the heat flux is derived with a classic one-dimensional conduction model. Preliminary results of heat flux scaling are reported.

  13. Combining Simultaneous Heat and Water (SHAW) with photosynthesis model to simulate water and CO2 fluxes over wheat canopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Energy, water and CO2 flux at the soil-atmosphere interface is a key interest among ecosystem researchers. The Simultaneous Heat and Water (SHAW) Model describes radiation energy balance, heat transfer and water movement within the Soil-Plant-Atmosphere Continuum, but has no provisions for carbon as...

  14. Heat flux instrumentation for Hyflite thermal protection system

    NASA Astrophysics Data System (ADS)

    Diller, T. E.

    Using Thermal Protection Tile core samples supplied by NASA, the surface characteristics of the FRCI, TUFI, and RCG coatings were evaluated. Based on these results, appropriate methods of surface preparation were determined and tested for the required sputtering processes. Sample sensors were fabricated on the RCG coating and adhesion was acceptable. Based on these encouraging results, complete Heat Flux Microsensors were fabricated on the RCG coating. The issue of lead attachment was addressed with the annnealing and welding methods developed at NASA Lewis. Parallel gap welding appears to be the best method of lead attachment with prior heat treatment of the sputtered pads. Sample Heat Flux Microsensors were submitted for testing in the NASA Ames arc jet facility. Details of the project are contained in two attached reports. One additional item of interest is contained in the attached AIAA paper, which gives details of the transient response of a Heat Flux Microsensors in a shock tube facility at Virginia Tech. The response of the heat flux sensor was measured to be faster than 10 micro-s.

  15. Heat flux instrumentation for Hyflite thermal protection system

    NASA Technical Reports Server (NTRS)

    Diller, T. E.

    1994-01-01

    Using Thermal Protection Tile core samples supplied by NASA, the surface characteristics of the FRCI, TUFI, and RCG coatings were evaluated. Based on these results, appropriate methods of surface preparation were determined and tested for the required sputtering processes. Sample sensors were fabricated on the RCG coating and adhesion was acceptable. Based on these encouraging results, complete Heat Flux Microsensors were fabricated on the RCG coating. The issue of lead attachment was addressed with the annnealing and welding methods developed at NASA Lewis. Parallel gap welding appears to be the best method of lead attachment with prior heat treatment of the sputtered pads. Sample Heat Flux Microsensors were submitted for testing in the NASA Ames arc jet facility. Details of the project are contained in two attached reports. One additional item of interest is contained in the attached AIAA paper, which gives details of the transient response of a Heat Flux Microsensors in a shock tube facility at Virginia Tech. The response of the heat flux sensor was measured to be faster than 10 micro-s.

  16. DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect

    Garrett, A; Eliel Villa-Aleman, E; Robert Kurzeja, R; Malcolm Pendergast, M; Timothy Brown, T; Saleem Salaymeh, S

    2007-12-19

    Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, {sigma}, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm{sup -2}. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and {sigma} exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm{sup -2}. The linear relationship between {sigma} and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between {sigma} and Q is improved if a correction to the measured {sigma} is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between {sigma} and Q ranged from about 0.8 to 0.9.

  17. Divertor Heat Flux Amelioration in Highly-Shaped Plasma in NSTX

    SciTech Connect

    Soukhanovskii, V; Maingi, R; Gates, D; Menard, J; Raman, R; Bell, R; Bush, C; Kaita, R; Kugel, H; LeBlanc, B; Paul, S; Roquemore, A

    2007-07-02

    Steady-state handling of divertor heat flux is a critical issue for both the International Thermonuclear Experimental Reactor and spherical torus (ST) based devices with compact high power density divertors. The ST compact divertor with a small plasma volume, a small plasma-wetted area, and a short parallel connection length can reduce the operating space of heat flux dissipation techniques based on induced edge and/or scrape-off layer (SOL) power and momentum loss, such as the radiative and dissipative divertors and radiative mantles. Access to these regimes is studied in the National Spherical Torus Experiment (NSTX) with an open geometry horizontal carbon plate divertor in 2-6 MW NBI-heated H-mode plasmas in a lower single null (LSN) configuration in a range of elongations {kappa} = 1.8-2.4 and triangularities {delta}= 0.40-0.75. Experiments conducted in a lower end {kappa}{approx}1.8-2.0 and {delta}{approx} 0.4-0.5 LSN shape using deuterium injection in the divertor region have achieved the outer strike point (OSP) peak heat flux reduction from 4-6 MW/m2 to a manageable level of 1-2 MW/m2. However, only the high-recycling radiative divertor (RD) regime was found to be compatible with good performance and H-mode confinement. A partially detached divertor (PDD) could only be obtained at a high D2 injection rate that led to an X-point MARFE formation and confinement degradation. Also in the low {kappa}{approx} 2,{delta}{approx} 0.45 shape, peak heat flux q{sub pk} and heat flux width {lambda}{sub q} scaling studies have been conducted. Similar to tokamak divertor studies, q{sub pk} was found to be a strong function of input power PNBI and plasma current Ip, and the heat flux midplane scale length {lambda}{sub q} was found to be large as compared with simple SOL models. In this paper, we report on the first experiments to assess steady-state divertor heat flux amelioration in highly shaped plasmas in NSTX.

  18. Radiative heat transfer calculations in real gases

    Microsoft Academic Search

    B. Leckner

    1974-01-01

    A general formulation for radiative heat transfer calculations is presented, based on integrated quantities such as total emissivities and absorptivities. The procedure is intended particularly for combustion chamber applications of varying degree of complexity, the radiative active medium consisting of gases such as H2O and CO2 and of soot. First, some preliminary calculations are given for the often treated radiative

  19. Quasi-exospheric heat flux of solar-wind electrons

    NASA Technical Reports Server (NTRS)

    Eviatar, A.; Schulz, M.

    1976-01-01

    Density, bulk-velocity, and heat-flow moments are calculated for truncated Maxwellian distributions representing the cool and hot populations of solar-wind electrons, as realized at the base of a hypothetical exosphere. The electrostatic potential is calculated by requiring charge quasi-neutrality and the absence of electrical current. Plasma-kinetic coupling of the cool-electron and proton bulk velocities leads to an increase in the electrostatic potential and a decrease in the heat-flow moment. If the velocities differ by the Alfven speed along the magnetic field, for example, the potential rises to 72.6 V and the heat flux falls to 0.0272 erg/sq cm per sec. In each case, the heat flux is carried mainly by the quasi-exospheric hot electrons.

  20. Maximum allowable heat flux for a submerged horizontal tube bundle

    SciTech Connect

    McEligot, D.M. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States)]|[Univ. of Arizona, Tucson, AZ (United States). Aerospace and Mechanical Engineering Dept.

    1996-12-31

    For application to industrial heating of large pools by immersed heat exchangers, the so called maximum allowable (or critical) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. This is the condition at which vapor blanketing is expected to be initiated. Phenomenological considerations demonstrate why the maximum allowable heat flux would be expected to be less than for single tubes. Hydrodynamic theory is applied to extend the results of Lienhard and Dhir to large submerged bundles and the consequent correlation is compared to the correlation of Palen and Small and the limited data available for saturated conditions. To date the main conclusion is that estimates of q{double_prime}{sub chf} are highly uncertain for this configuration.

  1. Turbulent heat flux measurements in a transitional boundary layer

    NASA Technical Reports Server (NTRS)

    Sohn, K. H.; Zaman, K. B. M. Q.; Reshotko, E.

    1992-01-01

    During an experimental investigation of the transitional boundary layer over a heated flat plate, an unexpected result was encountered for the turbulent heat flux (bar-v't'). This quantity, representing the correlation between the fluctuating normal velocity and the temperature, was measured to be negative near the wall under certain conditions. The result was unexpected as it implied a counter-gradient heat transfer by the turbulent fluctuations. Possible reasons for this anomalous result were further investigated. The possible causes considered for this negative bar-v't' were: (1) plausible measurement error and peculiarity of the flow facility, (2) large probe size effect, (3) 'streaky structure' in the near wall boundary layer, and (4) contributions from other terms usually assumed negligible in the energy equation including the Reynolds heat flux in the streamwise direction (bar-u't'). Even though the energy balance has remained inconclusive, none of the items (1) to (3) appear to be contributing directly to the anomaly.

  2. Heat-Flux Sensor For Hot Engine Cylinders

    NASA Technical Reports Server (NTRS)

    Kim, Walter S.; Barrows, Richard F.; Smith, Floyd A.; Koch, John

    1989-01-01

    Heat-flux sensor includes buried wire thermocouple and thin-film surface thermocouple, made of platinum and platinum with 13 percent rhodium. Sensor intended for use in ceramic-insulated, low-heat-rejection diesel engine at temperatures of about 1,000 K. Thermocouple junction resists environment in cylinder of advanced high-temperature diesel engine created by depositing overlapping films of Pt and 0.87 Pt/0.13 Rh on iron plug. Plug also contains internal thermocouple.

  3. Dependence of divertor heat flux widths on heating power, flux expansion, and plasma current in the NSTX

    SciTech Connect

    Maingi, Rajesh [ORNL; Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL); Ahn, J.W. [Oak Ridge National Laboratory (ORNL)

    2011-01-01

    We report the dependence of the lower divertor surface heat flux profiles, measured from infrared thermography and mapped magnetically to the mid-plane on loss power into the scrape-off layer (P{sub LOSS}), plasma current (I{sub p}), and magnetic flux expansion (f{sub exp}), as well as initial results with lithium wall conditioning in NSTX. Here we extend previous studies [R. Maingi et al., J. Nucl. Mater. 363-365 (2007) 196-200] to higher triangularity similar to 0.7 and higher I{sub p} {le} 1.2 MA. First we note that the mid-plane heat flux width mapped to the mid-plane, {lambda}{sub q}{sup mid} is largely independent of P{sub LOSS} for P{sub LOSS} {ge} 4 MW. {lambda}{sub q}{sup mid} is also found to be relatively independent of f{sub exp}; peak heat flux is strongly reduced as f{sub exp} is increased, as expected. Finally, {lambda}{sub q}{sup mid} is shown to strongly contract with increasing I{sub p} such that {lambda}{sub q}{sup mid} {alpha} I{sub p}{sup -1.6} with a peak divertor heat flux of q{sub div,peak} similar to 15 MW/m{sup 2} when I{sub p} = 1.2 MA and P{sub LOSS} similar to 6 MW. These relationships are then used to predict the divertor heat flux for the planned NSTX-Upgrade, with heating power between 10 and 15 MW, B{sub t} = 1.01 and I{sub p}= 2.0 MA for 5 s.

  4. Heat flux measurements for use in physiological and clothing research

    NASA Astrophysics Data System (ADS)

    Niedermann, R.; Psikuta, A.; Rossi, R. M.

    2014-08-01

    Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies.

  5. Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.; Gibson, M. A.; Hervol, D. S.

    2012-01-01

    A titanium-water heat pipe radiator having an innovative proprietary evaporator configuration was evaluated in a large vacuum chamber equipped with liquid nitrogen cooled cold walls. The radiator was manufactured by Advanced Cooling Technologies, Inc. (ACT), Lancaster, PA, and delivered as part of a Small Business Innovative Research effort. The radiator panel consisted of five titanium-water heat pipes operating as thermosyphons, sandwiched between two polymer matrix composite face sheets. The five variable conductance heat pipes were purposely charged with a small amount of non-condensable gas to control heat flow through the condenser. Heat rejection was evaluated over a wide range of inlet water temperature and flow conditions, and heat rejection was calculated in real-time utilizing a data acquisition system programmed with the Stefan-Boltzmann equation. Thermography through an infra-red transparent window identified heat flow across the panel. Under nominal operation, a maximum heat rejection value of over 2200 Watts was identified. The thermal vacuum evaluation of heat rejection provided critical information on understanding the radiator s performance, and in steady state and transient scenarios provided useful information for validating current thermal models in support of the Fission Power Systems Project.

  6. Estimation of net radiation flux distribution on the southern slopes of the central Himalayas using MODIS data

    NASA Astrophysics Data System (ADS)

    Amatya, Pukar Man; Ma, Yaoming; Han, Cunbo; Wang, Binbin; Devkota, Lochan Prasad

    2015-03-01

    Recent studies have highlighted the importance of the southern slopes of the Himalayas as a possible heating source driving the South Asian Summer Monsoon (SASM). The central Himalayas are characterized by a complex topography; consequently the measurements regarding land surface heat fluxes are scarce. In this study we tested the feasibility of deriving the regional net radiation flux, an essential component of the surface energy balance, from MODIS data. Three MODIS data scenes were used to derive net radiation flux, taking into account the effect of topography and a detailed extinction process within the atmosphere. This is the first time the regional net radiation flux distribution for the southern slopes of the central Himalayas has been derived from satellite data. The net shortwave radiation flux, net longwave radiation flux and net radiation flux from MODIS data agree well with field observations with mean relative errors of 6.19%, 7.72% and 6.60% respectively. We can therefore conclude that the aforementioned net radiation flux can reasonably be obtained using this method.

  7. Spatial and temporal variation of the surface temperature and heat flux for saturated pool nucleate boiling at lower heat fluxes

    SciTech Connect

    Unal, C.; Pasamehmetoglu, K.O.

    1993-10-01

    The spatial and temporal variations of local surface temperature and heat flux for saturated pool nucleate boiling are investigated parametrically using a numerical model. The numerical model consisted of solving the three-dimensional transient heat conduction equation within the heater subjected to nucleate boiling over its upper surface. The surface topography model to distribute the cavities over the boiling surface used a Monte Carlo scheme. All cavities were assumed to be conical in shape. The cavity radii are obtained using an exponential probability density function with a known mean value. Local surface temperatures showed significant spatial and temporal variations, depending upon the surface topography and the heater material and thickness. However, the surface-averaged temperature showed practically no temporal variation. The temporal variations in local temperatures caused the surface-averaged heat flux to vary significantly. The temporal variations in the surface-averaged heat flux were similar for smooth and rough and thick and thin copper and nickel plates. Results indicated that the use of a classical energy balance equation to evaluate the surface heat flux must consider the spatial variation of the temperature. Results also showed that any thermocouple embedded beneath the surface of the heater does not follow the temporal variations at the surface.

  8. Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

    1998-01-01

    Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

  9. A study of heat flux induced dryout in capillary grooves

    Microsoft Academic Search

    Timothy J. Murphy; W. J. Bowman

    1993-01-01

    This paper describes the results of an experimental study of ethanol flowing in the narrow grooves of a copper plate which was subjected to heat fluxes sufficient to evaporate more liquid than could be replaced by capillary pumping. Three groove geometries were used: square, rectangle, and trapezoid. In order to validate analytical models of capillary flow in grooves exposed to

  10. Assessing surface solar radiation fluxes in CMIP5 model simulations

    NASA Astrophysics Data System (ADS)

    Loew, Alexander; Itkin, Mikhail; Andersson, Axel; Trentmann, Jörg; Fennig, Karsten; Schröder, Marc

    2014-05-01

    Sophisticated Earth System models (ESM) are an essential research tool for better understanding the global climate system and its interactions. They are indispensable tools for providing projections about potential evolutions of the Earth climate in the future. Given the complexity of these deterministic models, it is essential to have a solid knowledge of the uncertainties of the model results in difference aspects of the models. The present paper presents results from a comprehensive study analyzing the shortwave surface radiation fluxes. State-of-the-art globals datasets of surface radiation components (surface solar radiation flux, surface albedo, surface net radiation flux) are used to benchmark results from the recent Coupled Model Intercomparison Project (CMIP5) in a standardized manner at the regional to global scale. Different skill score metrices are compared. All CMIP5 models are ranked according to their performance skill scores. The uncertainties from current observational records compared to uncertainties in climate model simulations are also analyzed. The results indicate that there are still large uncertainties (inconsistencies) among the different existing global surface radiation dataset which lead to rather different (relative) model rankings. In other words, the rank of a model is not only determined by the skill of the model itself, but also largely by the choice of a benchmarking (reference) dataset. As the differences resulting from the choice of different observational datasets are larger than between different models, progress in surface radiation flux simulations of climate models might depend on further progress in achieving consistent observations of surface radiation fluxes from space.

  11. Upward mass fluxes in tropical upper troposphere and lower stratosphere derived from radiative transfer calculations

    NASA Astrophysics Data System (ADS)

    Lin, L.; Fu, Q.; Zhang, H.; Su, J.; Yang, Q.; Sun, Z.

    2013-03-01

    Yang et al. [1] quantified vertical velocity and upward mass fluxes in tropical lower stratosphere based on radiative heating rate calculations using the Fu-Liou radiation model along with 8-year Southern Hemisphere Additional Ozonesondes balloon-borne measurements of temperature and ozone and cryogenic frost-point hygrometer measured water vapor. The impact of tropospheric clouds on stratospheric heating rates was considered using cloud distributions from the International Satellite Cloud Climatology Project. Since the radiative heating rate in the lower stratosphere can be as small as 0.1-0.2 K/day, an accurate radiative heating rate calculation including all radiatively active species is required. In this paper, we revisit the calculations in Yang et al. [1] by developing a line-by-line radiative transfer model (LBLRTM-D4S) for multiple scattering atmospheres. We consider the cloud impact using the cloud fields based on active lidar and radar observations from CALIPSO and CloudSat so that the quantification of upward mass fluxes in tropical lower stratosphere can be extended to tropical upper troposphere. The annual mean mass fluxes and vertical velocities from LBLRTM-D4S are ?14 kg m-2 day-1 and 0.77 mm s-1, respectively, at 120 hPa (15.5 km), and ?1.2 kg m-2 day-1 and 0.13 mm s-1 at 60 hPa (19.5 km). We examine the accuracy of three commonly used efficient radiation models including Fu-Liou, RRTM, and SBDART in estimating tropical upward mass fluxes against the LBLRTM-D4S results.

  12. Maximum allowable heat flux for a submerged horizontal tube bundle

    SciTech Connect

    McEligot, D.M.

    1995-08-14

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or {open_quotes}critical{close_quotes}) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration.

  13. MOC, Heat Storage and Surface Heat Flux in 2009/2010.

    NASA Astrophysics Data System (ADS)

    Wells, N. C.

    2012-04-01

    MONACO aims to study the linkages between the MOC at 26°N in the N.Atlantic , the heat and freshwater fluxes at 26N, and the seasonal and inter-annual heat and salt content changes in the upper 0-2000m of the water column between 10-70°N for the period from April 2004 to December 2010. In particular, the MOC event of 2009 when there was a 50% reduction in the overturning circulation, will be related to the changes in heat storage and surface heat flux. This unusual event will be placed in the context of longer records.

  14. Measurement of a surface heat flux and temperature

    NASA Technical Reports Server (NTRS)

    Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

    1994-01-01

    The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The superimposed thin-film pattern of all six layers is presented. The large pads are for connection with pins used to bring the signal out the back of the ceramic. In addition to the heat flux measurement, the surface temperature is measured with a platinum resistance layer (RTS). The resistance of this layer increases with increasing temperature. Therefore, these gages simultaneously measure the surface temperature and heat flux. The demonstrated applications include rocket nozzles, SCRAM jet engines, gas turbine engines, boiling heat transfer, flame experiments, basic fluid heat transfer, hypersonic flight, and shock tube testing. The laboratory involves using one of these sensors in a small combustion flame. The sensor is made on a 2.5 cm diameter piece of aluminum nitride ceramic.

  15. Robust Cooling of High Heat Fluxes Using Hybrid Loop Technology

    NASA Astrophysics Data System (ADS)

    Zuo, Jon; Park, Chanwoo; Sarraf, David; Paris, Anthony

    2005-02-01

    This paper discusses the development of an advanced hybrid loop technology that incorporates elements from both passive and active loop technologies. The result is a simple yet high performance cooling technology that can be used to remove high heat fluxes from large heat input areas. Operating principles and test results of prototype hybrid loops are discussed. Prototype hybrid loops have been demonstrated to remove heat fluxes in excess of 350W/cm2 from heat input areas over 4cm2 with evaporator thermal resistances between 0.008 and 0.065°C/W/cm2. Also importantly, this performance was achieved without the need to actively adjust or control the flows in the loops, even when the heat inputs varied between 0 and 350W/cm2. These performance characteristics represent substantial improvements over state of the art heat pipes, loop heat pipes and spray cooling devices. The hybrid loop technology was demonstrated to operate effectively at all orientations.

  16. High-heat-flux testing of helium-cooled heat exchangers for fusion applications

    SciTech Connect

    Youchison, D.L. [Sandia National Lab., Albuquerque, NM (United States); Izenson, M.G. [Creare, Inc., Hanover, NH (United States); Baxi, C.B. [General Atomics, Inc., San Diego, CA (United States); Rosenfeld, J.H. [Thermacore, Inc., Lancaster, PA (United States)

    1996-07-01

    High-heat-flux experiments on three types of helium-cooled divertor mock-ups were performed on the 30-kW electron beam test system and its associated helium flow loop at Sandia National Laboratories. A dispersion-strengthened copper alloy (DSCu) was used in the manufacture of all the mock-ups. The first heat exchanger provides for enhanced heat transfer at relatively low flow rates and much reduced pumping requirements. The Creare sample was tested to a maximum absorbed heat flux of 5.8 MW/m{sup 2}. The second used low pressure drops and high mass flow rates to achieve good heat removal. The GA specimen was tested to a maximum absorbed heat flux of 9 MW/m{sup 2} while maintaining a surface temperature below 400{degree}C. A second experiment resulted in a maximum absorbed heat flux of 34 MW/m{sup 2} and surface temperatures near 533{degree}C. The third specimen was a DSCu, axial flow, helium-cooled divertor mock-up filled with a porous metal wick which effectively increases the available heat transfer area. Low mass flow and high pressure drop operation at 4.0 MPa were characteristic of this divertor module. It survived a maximum absorbed heat flux of 16 MW/m{sup 2} and reached a surface temperature of 740{degree}C. Thermacore also manufactured a follow-on, dual channel porous metal-type heat exchanger, which survived a maximum absorbed heat flux of 14 MW/m{sup 2} and reached a maximum surface temperature of 690{degree}C. 11refs., 20 figs., 3 tabs.

  17. An assessment of buoy-derived and numerical weather prediction surface heat fluxes in the tropical Pacific

    NASA Astrophysics Data System (ADS)

    Cronin, Meghan F.; Fairall, Christopher W.; McPhaden, Michael J.

    2006-06-01

    As part of the Eastern Pacific Investigation of Climate Processes program, from 2000 through 2003, the easternmost 95°W Tropical Atmosphere Ocean (TAO) moorings were enhanced to provide time series of net surface heat flux, and the National Oceanic and Atmospheric Administration ship maintaining the 95°W and 110°W TAO lines was enhanced to monitor surface heat fluxes and atmospheric boundary layer structure. In this study we compare the ship-based and buoy-based radiative, bulk latent, and sensible heat fluxes, as well as the meteorological state variables used to compute the turbulent heat fluxes. The buoy net surface heat flux measurements appear to have an overall uncertainty near the target 10 W m-2, when careful attention is paid to the state variables. When hourly averaged data were unavailable, the telemetered daily averaged data were used in combination with an estimate of the mesoscale gustiness. In the eastern tropical Pacific a warm layer correction to account for stratification above 1-m depth was important only during the warm season (January-May) near the equator. These high-quality, cross-validated buoy heat flux time series are then used to assess the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), NCEP/Department of Energy, and 40-year European Centre for Medium-Range Weather Forecasts reanalyses' surface heat fluxes. All reanalyses show that over warm water where deep convection is prominent, latent heat loss is too large and net solar radiation is too weak; conversely, in regions of stratocumulus over cool water, net solar radiation is too strong, and for NCEP/NCAR, latent heat loss is too weak.

  18. Critical heat flux and heat transfer transition for subcooled flow boiling

    SciTech Connect

    Boyd, R.D. (Prairie View A and M Univ., TX (USA))

    1991-02-01

    The emphasis in the engineering development of fusion reactor components has been on material development. If high heat fluxes are to be accommodated with the present emphasis, low-pressure thermal data will be needed. The objectives of this experiment were to (1) expand the critical heat flux, W/cm{sup 2} data base near 4.0 kilowatts cm{sup 2} and heated coolant channel length divided by coolant chamber diameter near 100.0 (near-term application), (2) add low-pressure quantitative data to our existing knowledge of the qualitative influence of coolant exit pressure on CHF, and (3) provide thermal data in a region applicable to high heat flux components for assessing existing and evolving CHF and local heat transfer coefficient correlations (long-term).

  19. Constraints on hydrothermal heat flux through the oceanic lithosphere from global heat flow

    NASA Technical Reports Server (NTRS)

    Stein, Carol A.; Stein, Seth

    1994-01-01

    A significant discrepancy exists between the heat flow measured at the seafloor and the higher values predicted by thermal models of the cooling lithosphere. This discrepancy is generally interpreted as indicating that the upper oceanic crust is cooled significantly by hydrothermal circulation. The magnitude of this heat flow discrepancy is the primary datum used to estimate the volume of hydrothermal flow, and the variation in the discrepancy with lithospheric age is the primary constraint on how the hydrothermal flux is divided between near-ridge and off-ridge environments. The resulting estimates are important for investigation of both the thermal structure of the lithosphere and the chemistry of the oceans. We reevaluate the magnitude and age variation of the discrepancy using a global heat flow data set substantially larger than in earlier studies, and the GDHI (Global Depth and Heat Flow) model that better predicts the heat flow. We estimate that of the predicted global oceanic heat flux of 32 x 10(exp 12) W, 34% (11 x 10(exp 12) W) occurs by hydrothermal flow. Approximately 30% of the hydrothermal heat flux occurs in crust younger than 1 Ma, so the majority of this flux is off-ridge. These hydrothermal heat flux estimates are upper bounds, because heat flow measurements require sediment at the site and so are made preferentially at topographic lows, where heat flow may be depressed. Because the water temperature for the near-ridge flow exceeds that for the off-ridge flow, the near-ridge water flow will be even a smaller fraction of the total water flow. As a result, in estimating fluxes from geochemical data, use of the high water temperatures appropriate for the ridge axis may significantly overestimate the heat flux for an assumed water flux or underestimate the water flux for an assumed heat flux. Our data also permit improved estimates of the 'sealing' age, defined as the age where the observed heat flow approximately equals that predicted, suggesting that hydrothermal heat transfer has largely ceased. Although earlier studies suggested major differences in sealing ages for different ocean basins, we find that the sealing ages for the Atlantic, Pacific, and Indian oceans are similar and consistent with the sealing age for the entire data set, 65 +/- 10 Ma. The previous inference of a young (approximately 20 Ma) sealing age for the Pacific appears to have biased downward several previous estimates of the global hydrothermal flux. The heat flow data also provide indirect evidence for the mechanism by which the hydrothermal heat flux becomes small, which has often been ascribed to isolation of the igneous crust from seawater due to the hydraulic conductivity of the intervening sediment. We find, however, that even the least sedimented sites show the systematic increase of the ratio of observed to predicted heat flow with age, although the more sedimented sites have a younger sealing age. Moreover, the heat flow discrepancy persists at heavily sedimented sites until approximately 50 Ma. It thus appears that approximately 100-200 m of sediment is neither necessary nor sufficient to stop hydrothermal heat transfer. We therefore conclude that the age of the crust is the primary control on the fraction of heat transported by hydrothermal flow and that sediment thickness has a lesser effect. This inference is consistent with models in which hydrothermal flow decreases with age due to reduced crustal porosity and hence permeability.

  20. Radiative Heat Transfer between Neighboring Particles

    E-print Network

    Alejandro Manjavacas; F. Javier Garcia de Abajo

    2012-01-26

    The near-field interaction between two neighboring particles is known to produce enhanced radiative heat transfer. We advance in the understanding of this phenomenon by including the full electromagnetic particle response, heat exchange with the environment, and important radiative corrections both in the distance dependence of the fields and in the particle absorption coefficients. We find that crossed terms of electric and magnetic interactions dominate the transfer rate between gold and SiC particles, whereas radiative corrections reduce it by several orders of magnitude even at small separations. Radiation away from the dimer can be strongly suppressed or enhanced at low and high temperatures, respectively. These effects must be taken into account for an accurate description of radiative heat transfer in nanostructured environments.

  1. Two Improvements of an Operational Two-Layer Model for Terrestrial Surface Heat Flux Retrieval

    PubMed Central

    Zhang, Renhua; Tian, Jing; Su, Hongbo; Sun, Xiaomin; Chen, Shaohui; Xia, Jun

    2008-01-01

    In order to make the prediction of land surface heat fluxes more robust, two improvements were made to an operational two-layer model proposed previously by Zhang. These improvements are: 1) a surface energy balance method is used to determine the theoretical boundary lines (namely ‘true wet/cool edge’ and ‘true dry/warm edge’ in the trapezoid) in the scatter plot for the surface temperature versus the fractional vegetation cover in mixed pixels; 2) a new assumption that the slope of the Tm – f curves is mainly controlled by soil water content is introduced. The variables required by the improved method include near surface vapor pressure, air temperature, surface resistance, aerodynamic resistance, fractional vegetation cover, surface temperature and net radiation. The model predictions from the improved model were assessed in this study by in situ measurements, which show that the total latent heat flux from the soil and vegetation are in close agreement with the in situ measurement with an RMSE (Root Mean Square Error) ranging from 30 w/m2?50 w/m2, which is consistent with the site scale measurement of latent heat flux. Because soil evaporation and vegetation transpiration are not measured separately from the field site, in situ measured CO2 flux is used to examine the modeled ?Eveg. Similar trends of seasonal variations of vegetation were found for the canopy transpiration retrievals and in situ CO2 flux measurements. The above differences are mainly caused by 1) the scale disparity between the field measurement and the MODIS observation; 2) the non-closure problem of the surface energy balance from the surface fluxes observations themselves. The improved method was successfully used to predict the component surface heat fluxes from the soil and vegetation and it provides a promising approach to study the canopy transpiration and the soil evaporation quantitatively during the rapid growing season of winter wheat in northern China.

  2. A high heat flux experiment for verification of thermostructural analysis

    NASA Astrophysics Data System (ADS)

    Gladden, H. J.; Melis, M. E.

    A major concern in advancing the state of the art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of handling the high heat fluxes during flight. The leading edges of such systems must not only tolerate the maximum heating rates, but must also minimize distortions to the flow field due to excessive blunting and/or thermal warping of the conmpression surface to achieve the high inlet performance required. A combined analytical and experimental effort to study the aerothermodynamic loads on actively cooled structures for hypersonic applications was established. A hydrogen/oxygen rocket engine was modified to establish a high enthalpy high heat flux environment. The facility provides heat flux levels from about 200 up to 10000 Btu/sq ft/sec. Cross flow and parallel flow regeneratively cooled model can be tested and analyzed by using cooling fluids of water and hydrogen. Results are presented of the experiment and the characteristics of the Hot Gas Test Facility. The predicted temperature results of the cross flow model are compared with the experimental data on the first monolithic specimens and are found to be in good agreement. Thermal stress analysis results are also presented.

  3. A high heat flux experiment for verification of thermostructural analysis

    NASA Astrophysics Data System (ADS)

    Gladden, Herbert J.; Melis, Matthew E.

    1988-12-01

    A major concern in advancing the state of the art technologies for hypersonic vehicles is the development of an aeropropulsion system capable of handling the high heat fluxes during flight. The leading edges of such systems must not only tolerate the maximum heating rates, but must also minimize distortions to the flow field due to excessive blunting and/or thermal warping of the compression surface to achieve the high inlet performance required. A combined analytical and experimental effort to study the aerothermodynamic loads on actively cooled structures for hypersonic applications was established. A hydrogen/oxygen rocket engine was modified to establish a high enthalpy high heat flux environment. The facility provides heat flux levels from about 200 up to 10000 Btu/sq ft/sec. Cross flow and parallel flow regeneratively cooled model can be tested and analyzed by using cooling fluids of water and hydrogen. Results are presented of the experiment and the characteristics of the Hot Gas Test Facility. The predicted temperature results of the cross flow model are compared with the experimental data on the first monolithic specimens and are found to be in good agreement. Thermal stress analysis results are also presented.

  4. Heat flux and quantum correlations in dissipative cascaded systems

    NASA Astrophysics Data System (ADS)

    Lorenzo, Salvatore; Farace, Alessandro; Ciccarello, Francesco; Palma, G. Massimo; Giovannetti, Vittorio

    2015-02-01

    We study the dynamics of heat flux in the thermalization process of a pair of identical quantum systems that interact dissipatively with a reservoir in a cascaded fashion. Despite that the open dynamics of the bipartite system S is globally Lindbladian, one of the subsystems "sees" the reservoir in a state modified by the interaction with the other subsystem and hence it undergoes a non-Markovian dynamics. As a consequence, the heat flow exhibits a nonexponential time behavior which can greatly deviate from the case where each party is independently coupled to the reservoir. We investigate both thermal and correlated initial states of S and show that the presence of correlations at the beginning can considerably affect the heat-flux rate. We carry out our study in two paradigmatic cases—a pair of harmonic oscillators with a reservoir of bosonic modes and two qubits with a reservoir of fermionic modes—and compare the corresponding behaviors. In the case of qubits and for initial thermal states, we find that the trace distance discord is at any time interpretable as the correlated contribution to the total heat flux.

  5. A 2-D imaging heat-flux gauge

    SciTech Connect

    Noel, B.W.; Borella, H.M. (Los Alamos National Lab., NM (United States)); Beshears, D.L.; Sartory, W.K.; Tobin, K.W.; Williams, R.K. (Oak Ridge National Lab., TN (United States)); Turley, W.D. (EG and G Energy Measurements, Inc., Goleta, CA (United States). Santa Barbara Operations)

    1991-07-01

    This report describes a new leadless two-dimensional imaging optical heat-flux gauge. The gauge is made by depositing arrays of thermorgraphic-phosphor (TP) spots onto the faces of a polymethylpentene is insulator. In the first section of the report, we describe several gauge configurations and their prototype realizations. A satisfactory configuration is an array of right triangles on each face that overlay to form squares when the gauge is viewed normal to the surface. The next section of the report treats the thermal conductivity of TPs. We set up an experiment using a comparative longitudinal heat-flow apparatus to measure the previously unknown thermal conductivity of these materials. The thermal conductivity of one TP, Y{sub 2}O{sub 3}:Eu, is 0.0137 W/cm{center dot}K over the temperature range from about 300 to 360 K. The theories underlying the time response of TP gauges and the imaging characteristics are discussed in the next section. Then we discuss several laboratory experiments to (1) demonstrate that the TP heat-flux gauge can be used in imaging applications; (2) obtain a quantum yield that enumerates what typical optical output signal amplitudes can be obtained from TP heat-flux gauges; and (3) determine whether LANL-designed intensified video cameras have sufficient sensitivity to acquire images from the heat-flux gauges. We obtained positive results from all the measurements. Throughout the text, we note limitations, areas where improvements are needed, and where further research is necessary. 12 refs., 25 figs., 4 tabs.

  6. Shear heating as the origin of the plumes and heat flux on Enceladus

    E-print Network

    Nimmo, Francis

    by this heating may escape as plumes through cracks reopened by the tidal stresses10 . The ice shell thickness jetting from localized fractures (`tiger stripes') within an area of high heat flux near the south pole1 number of h2 . 0.01, suggesting that the ice shell is decoupled from the silicate interior

  7. Diamond Microchannel Heat Sink Designs For High Heat Flux Thermal Control

    NASA Astrophysics Data System (ADS)

    Corbin, Michael V.; DeBenedictis, Matthew M.; James, David B.; LeBlanc, Stephen P.; Paradis, Leo R.

    2002-08-01

    Directed energy weapons, wide band gap semiconductor based radars, and other powerful systems present significant thermal control challenges to component designers. heat Flux levels approaching 2000 W/cm(2) are encountered at the base of laser diodes, and levels as high as 500 WI /cm(2) are expected in laser slabs and power amplifier tube collectors. These impressive heat flux levels frequently combine with strict operating temperature requirements to further compound the thermal control problem. Many investigators have suggested the use of diamond heat spreaders to reduce flux levels at or near to its source, and some have suggested that diamond microchannel heat sinks ultimately may play a significant role in the solution of these problems. Design engineers at Raytheon Company have investigated the application of all-diamond microchannel heat sinks to representative high heat flux problems and have found the approach promising. Diamond microchannel fabrication feasibility has been demonstrated; integration into packaging systems and the accompanying material compatibility issues have been addressed; and thermal and hydrodynamic performance predictions have been made for selected, possible applications. An example of a practical, all diamond microchannel heat sink has been fabricated, and another is in process and will be performance tested. The heat sink assembly is made entirely of optical quality, CVD diamond and is of sufficient strength to withstand the thermal and pressure-induced mechanical loads associated with manufacture and use in tactical weapons environment. The work presented describes the development program's accomplishments to date, and highlights many of the areas for future study.

  8. Versatile beam calorimeter with a heat flux sensor

    NASA Astrophysics Data System (ADS)

    Kudomi, N.; Itahashi, T.; Takahisa, K.; Yoshida, S.; Komori, M.

    2001-07-01

    A versatile calorimeter has been developed to study astrophysical S factors for fusion reactions with gaseous targets. The number of incident projectiles are deduced from the deposited power. The principal technique employed here is based on the heat flux sensor output transferred linearly from the heat flow. Absolute values at various energies are obtained by calibration with current measurements by using a Faraday cup. This calorimeter is presently applied in measurement of the solar 3He+3He fusion reaction with an accuracy better than 2%.

  9. Method of fission heat flux determination from experimental data

    DOEpatents

    Paxton, Frank A. (Schenectady, NY)

    1999-01-01

    A method is provided for determining the fission heat flux of a prime specimen inserted into a specimen of a test reactor. A pair of thermocouple test specimens are positioned at the same level in the holder and a determination is made of various experimental data including the temperature of the thermocouple test specimens, the temperature of bulk water channels located in the test holder, the gamma scan count ratios for the thermocouple test specimens and the prime specimen, and the thicknesses of the outer clads, the fuel fillers, and the backclad of the thermocouple test specimen. Using this experimental data, the absolute value of the fission heat flux for the thermocouple test specimens and prime specimen can be calculated.

  10. Heat and Flux Configurations on Offshore Wind Farms

    NASA Astrophysics Data System (ADS)

    Kucuksahin, D.; Bot, E. T. G.

    2014-12-01

    This study aims to determine the best configurations of the Heat and Flux concept for more profitable and utilizable settings in a wind farm in terms of increase in the energy yield and reduction in loadings. The computations are performed with alteration of a single parameter at a time. The reference farm for this study is EWTW, the ECN test farm in Wieringermeer, as this farm was also the reference for the validation of both the Heat and Flux concept and the software tool FarmFlow. All the studies are performed with FarmFlow developed by ECN, which computes wake deficits and turbulence intensities, resulting in the energy yield of all turbines in the farm.

  11. A microscale thermophoretic turbine driven by external diffusive heat flux.

    PubMed

    Yang, Mingcheng; Liu, Rui; Ripoll, Marisol; Chen, Ke

    2014-11-21

    We propose a theoretical prototype of a micro-scale turbine externally driven by diffusive heat flux without the need for macroscopic particle flux, which is in sharp contrast to conventional turbines. The prototypes are described analytically and validated by computer simulations. Our results indicate that a micro-scale turbine composed of anisotropic blades can rotate unidirectionally in an external temperature gradient due to the anisotropic thermophoresis effect. The rotational direction and speed depend on the temperature gradient, the geometry and the thermophoretic properties of the turbine. The proposed thermophoretic turbines can be experimentally realized and implemented on micro-devices such as computer-chips to recover waste heat or to facilitate cooling. PMID:25268245

  12. Cosmic matter flux may turn Hawking radiation off

    NASA Astrophysics Data System (ADS)

    Firouzjaee, Javad T.; Ellis, George F. R.

    2015-02-01

    An astrophysical (cosmological) black hole forming in a cosmological context will be subject to a flux of infalling matter and radiation, which will cause the outer apparent horizon (a marginal trapping surface) to be spacelike spacelike (Ellis et al., arXiv:1407.3577). As a consequence the radiation emitted close to the apparent horizon no longer arrives at infinity with a diverging redshift. Standard calculations of the emission of Hawking radiation then indicate that no blackbody radiation is emitted to infinity by the black hole in these circumstances, hence there will also then be no black hole evaporation process due to emission of such radiation as long as the matter flux is significant. The essential adiabatic condition (eikonal approximation) for black hole radiation gives a strong limit to the black holes that can emit Hawking radiation. We give the mass range for the black holes that can radiate, according to their cosmological redshift, for the special case of the cosmic blackbody radiation (CBR) influx (which exists everywhere in the universe). At a very late stage of black hole formation when the CBR influx decays away, the black hole horizon becomes first a slowly evolving horizon and then an isolated horizon; at that stage, black hole radiation will start. This study suggests that the primordial black hole evaporation scenario should be revised to take these considerations into account.

  13. Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

    NASA Astrophysics Data System (ADS)

    Nelson, H. F.

    1981-08-01

    The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiation heating of probes entering the hydrogen helium atmospere of the major planets was investigated. At the present time, there is disagreement as to whether the radiative flux increases or decreases relative to its equilibrium value when finite rate ionization is considered. Leibowitz and Kuo content that the finite rate ionization in the hydrogen gas just behind the shock wave reduces the radiative flux to the probe, whereas Tiwari and Szema predict that it increases the radiative flux. The radiation modeling used in the calculations of both pairs of these investigators was reviewed. It is concluded that finite rate ionization in the inviscid region of the shock layer should reduce the cold wall radiative heating below the values predicted by equilibrium chemistry assumptions.

  14. [Diurnal variation of winter wheat water and heat fluxes of a simulation with photosynthesis-evapotranspiration coupled model].

    PubMed

    Wang, Jing; Yu, Qiang; Li, Xiangge; Sun, Xiaomin

    2004-11-01

    A coupled model of winter wheat photosynthesis-evapotranspiration was established based on SPAC theory. Sensible heat and latent heat fluxes were calculated by two-layer model proposed by Shuttleworth and Wallace, and photosynthesis and evapotranspiration were coupled by the parameterization of canopy resistance. The model was validated with the data measured by eddy covariance method. The results showed that the simulated and observed values were accordant, and the model could simulate the diurnal variation of sensible heat and latent heat fluxes very well. Sensitivity analysis indicated that the sensitive parameters of canopy transpiration were wilting point, stomata conductance, reflectivity of leaves to infrared radiation, and convexity of photosynthesis response to light, while the sensitive parameter of soil evaporation was soil resistance. The model could be used to study the interactions between water and heat fluxes and environmental factors, and to instruct the irrigation scheme in the field. PMID:15707316

  15. Countergradient heat flux observations during the evening transition period

    NASA Astrophysics Data System (ADS)

    Blay-Carreras, E.; Pardyjak, E. R.; Pino, D.; Alexander, D. C.; Lohou, F.; Lothon, M.

    2014-09-01

    Gradient-based turbulence models generally assume that the buoyancy flux ceases to introduce heat into the surface layer of the atmospheric boundary layer in temporal consonance with the gradient of the local virtual potential temperature. Here, we hypothesize that during the evening transition a delay exists between the instant when the buoyancy flux goes to zero and the time when the local gradient of the virtual potential temperature indicates a sign change. This phenomenon is studied using a range of data collected over several intensive observational periods (IOPs) during the Boundary Layer Late Afternoon and Sunset Turbulence field campaign conducted in Lannemezan, France. The focus is mainly on the lower part of the surface layer using a tower instrumented with high-speed temperature and velocity sensors. The results from this work confirm and quantify a flux-gradient delay. Specifically, the observed values of the delay are ~ 30-80 min. The existence of the delay and its duration can be explained by considering the convective timescale and the competition of forces associated with the classical Rayleigh-Bénard problem. This combined theory predicts that the last eddy formed while the sensible heat flux changes sign during the evening transition should produce a delay. It appears that this last eddy is decelerated through the action of turbulent momentum and thermal diffusivities, and that the delay is related to the convective turnover timescale. Observations indicate that as horizontal shear becomes more important, the delay time apparently increases to values greater than the convective turnover timescale.

  16. An overview of results from the GEWEX radiation flux assessment

    NASA Astrophysics Data System (ADS)

    Raschke, E.; Stackhouse, P.; Kinne, S.; Contributors from Europe; the USA

    2013-05-01

    Multi-annual radiative flux averages of the International Cloud Climatology Project (ISCCP), of the GEWEX - Surface Radiation Budget Project (SRB) and of the Clouds and Earth Radiative Energy System (CERES) are compared and analyzed to characterize the Earth's radiative budget, assess differences and identify possible causes. These satellite based data-sets are also compared to results of a median model, which represents 20 climate models, that participated in the 4th IPCC assessment. Consistent distribution patterns and seasonal variations among the satellite data-sets demonstrate their scientific value, which would further increase if the datasets would be reanalyzed with more accurate and consistent ancillary data.

  17. Design of a differential radiometer for atmospheric radiative flux measurements

    SciTech Connect

    LaDelfe, P.C.; Weber, P.G.; Rodriguez, C.W.

    1994-11-01

    The Hemispherical Optimized NEt Radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory for deployment on an unmanned aerospace vehicle as part of the Atmospheric Radiation Measurements (ARM/UAV) program. HONER is a differential radiometer which will measure the difference between the total upwelling and downwelling fluxes and is intended to provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into two spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4.5 micrometers and the other covering the region from approximately 4.5 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We will describe the design and operation of the sensor head and the on-board reference sources as well as the means of deployment.

  18. Spatial variability of shortwave radiative fluxes in the context of snowmelt

    NASA Astrophysics Data System (ADS)

    Pinker, Rachel T.; Ma, Yingtao; Hinkelman, Laura; Lundquist, Jessica

    2014-05-01

    Snow-covered mountain ranges are a major source of water supply for run-off and groundwater recharge. Snowmelt supplies as much as 75% of surface water in basins of the western United States. Factors that affect the rate of snow melt include incoming shortwave and longwave radiation, surface albedo, snow emissivity, snow surface temperature, sensible and latent heat fluxes, ground heat flux, and energy transferred to the snowpack from deposited snow or rain. The net radiation generally makes up about 80% of the energy balance and is dominated by the shortwave radiation. Complex terrain poses a great challenge for obtaining the needed information on radiative fluxes from satellites due to elevation issues, spatially-variable cloud cover, rapidly changing surface conditions during snow fall and snow melt, lack of high quality ground truth for evaluation of the satellite based estimates, as well as scale issues between the ground observations and the satellite footprint. In this study we utilize observations of high spatial resolution (5-km) as available from the Moderate Resolution Imaging Spectro-radiometer (MODIS) to derive surface shortwave radiative fluxes in complex terrain, with attention to the impact of slopes on the amount of radiation received. The methodology developed has been applied to several water years (January to July during 2003, 2004, 2005 and 2009) over the western part of the United States, and the available information was used to derive metrics on spatial and temporal variability in the shortwave fluxes. It is planned to apply the findings from this study for testing improvements in Snow Water Equivalent (SWE) estimates.

  19. Cloud Properties and Radiative Heating Rates for TWP

    SciTech Connect

    Comstock, Jennifer

    2013-11-07

    A cloud properties and radiative heating rates dataset is presented where cloud properties retrieved using lidar and radar observations are input into a radiative transfer model to compute radiative fluxes and heating rates at three ARM sites located in the Tropical Western Pacific (TWP) region. The cloud properties retrieval is a conditional retrieval that applies various retrieval techniques depending on the available data, that is if lidar, radar or both instruments detect cloud. This Combined Remote Sensor Retrieval Algorithm (CombRet) produces vertical profiles of liquid or ice water content (LWC or IWC), droplet effective radius (re), ice crystal generalized effective size (Dge), cloud phase, and cloud boundaries. The algorithm was compared with 3 other independent algorithms to help estimate the uncertainty in the cloud properties, fluxes, and heating rates (Comstock et al. 2013). The dataset is provided at 2 min temporal and 90 m vertical resolution. The current dataset is applied to time periods when the MMCR (Millimeter Cloud Radar) version of the ARSCL (Active Remotely-Sensed Cloud Locations) Value Added Product (VAP) is available. The MERGESONDE VAP is utilized where temperature and humidity profiles are required. Future additions to this dataset will utilize the new KAZR instrument and its associated VAPs.

  20. Cloud Properties and Radiative Heating Rates for TWP

    DOE Data Explorer

    Comstock, Jennifer

    A cloud properties and radiative heating rates dataset is presented where cloud properties retrieved using lidar and radar observations are input into a radiative transfer model to compute radiative fluxes and heating rates at three ARM sites located in the Tropical Western Pacific (TWP) region. The cloud properties retrieval is a conditional retrieval that applies various retrieval techniques depending on the available data, that is if lidar, radar or both instruments detect cloud. This Combined Remote Sensor Retrieval Algorithm (CombRet) produces vertical profiles of liquid or ice water content (LWC or IWC), droplet effective radius (re), ice crystal generalized effective size (Dge), cloud phase, and cloud boundaries. The algorithm was compared with 3 other independent algorithms to help estimate the uncertainty in the cloud properties, fluxes, and heating rates (Comstock et al. 2013). The dataset is provided at 2 min temporal and 90 m vertical resolution. The current dataset is applied to time periods when the MMCR (Millimeter Cloud Radar) version of the ARSCL (Active Remotely-Sensed Cloud Locations) Value Added Product (VAP) is available. The MERGESONDE VAP is utilized where temperature and humidity profiles are required. Future additions to this dataset will utilize the new KAZR instrument and its associated VAPs.

  1. Two-Flux Green's Function Analysis for Transient Spectral Radiation in a Composite

    NASA Technical Reports Server (NTRS)

    Siegel, Robert

    1996-01-01

    An analysis is developed for obtaining transient temperatures in a two-layer semitransparent composite with spectrally dependent properties. Each external boundary of the composite is subjected to radiation and convection. The two-flux radiative transfer equations are solved by deriving a Green's function. This yields the local radiative heat source needed to numerically solve the transient energy equation. An advantage of the two-flux method is that isotropic scattering is included without added complexity. The layer refractive indices are larger than one. This produces internal reflections at the boundaries and the internal interface; the reflections are assumed diffuse. Spectral results using the Green's function method are verified by comparing with numerical solutions using the exact radiative transfer equations. Transient temperature distributions are given to illustrate the effect of radiative heating on one side of a composite with external convective cooling. The protection of a material from incident radiation is illustrated by adding scattering to the layer adjacent to the radiative source.

  2. Skyglow effects in UV and visible spectra: Radiative fluxes

    NASA Astrophysics Data System (ADS)

    Kocifaj, Miroslav; Solano Lamphar, Hector Antonio

    2013-09-01

    Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment.

  3. Water and heat fluxes in desert soils: 2. Numerical simulations

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.; Milly, P. C. D.

    1994-03-01

    Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a combination of laboratory measurements, models, and other published information. In the first simulation, the main drying curves were used to describe soil water retention, and hysteresis was ignored. Remarkable consistency was found between computed and measured water potentials and temperatures. Attenuation and phase shift of the seasonal cycle of water potentials below the shallow subsurface active zone (0.0- to 0.3-m depth) were similar to those of temperatures, suggesting that water potential fluctuations were driven primarily by temperature changes. Water fluxes in the upper 0.3 m of soil were dominated by downward and upward liquid fluxes that resulted from infiltration of rain and subsequent evaporation from the surface. Upward flux was vapor dominated only in the top several millimeters of the soil during periods of evaporation. Below a depth of 0.3 m, water fluxes varied slowly and were dominated by downward thermal vapor flux that decreased with depth, causing a net accumulation of water. In a second simulation, nonhysteretic water retention was instead described by the estimated main wetting curves; the resulting differences in fluxes were attributed to lower initial water contents (given fixed initial water potential) and unsaturated hydraulic conductivities that were lower than they were in the first simulation. Below a depth of 0.3 m, the thermal vapor fluxes dominated and were similar to those in the first simulation. Two other simulations were performed, differing from the first only in the prescription of different (wetter) initial water potentials. These three simulations yielded identical solutions in the upper 0.2 m of soil after infiltration of summer rain; however, the various initial water potentials were preserved throughout the year at depths greater than 0.2 m. Comparison of all four simulations showed that the predominantly upward liquid fluxes below a depth of 0.2 m were very sensitive to the differences in water retention functions and initial water potentials among simulations, because these factors strongly affected hydraulic conductivities. Comparison of numerical modeling results with chemical tracer data showed that values of downward vapor flux below the surface evaporation zone were of the same order of magnitude as those previously estimated by analysis of depth distributions of bomb 3H (volatile) and bomb 36Cl (nonvolatile).

  4. Buoyancy and chemical reaction effects on MHD mixed convection heat and mass transfer in a porous medium with thermal radiation and Ohmic heating

    Microsoft Academic Search

    Dulal Pal; Babulal Talukdar

    2010-01-01

    The combined effect of mixed convection with thermal radiation and chemical reaction on MHD flow of viscous and electrically conducting fluid past a vertical permeable surface embedded in a porous medium is analyzed. The heat equation includes the terms involving the radiative heat flux, Ohmic dissipation, viscous dissipation and the internal absorption whereas the mass transfer equation includes the effects

  5. Subgrid parameterization of surface heat and momentum fluxes over polar oceans

    NASA Astrophysics Data System (ADS)

    Vihma, Timo

    1995-11-01

    The parameterization of heat and momentum fluxes over a heterogeneous surface consisting of sea ice and large areas of open ocean (polynyas) has been studied. Various theories required to calculate grid-averaged fluxes are discussed, and a two-dimensional mesoscale boundary layer model has been applied to simulate the flow and heat exchange processes inside a single grid element of a hypothetical atmospheric general circulation model. The theories are compared with model results. Considering the surface fluxes of sensible and latent heat, a mosaic method, based on the use of estimates for local surface temperature, air temperature, specific humidity, and wind speed over the ice-covered and ice-free parts of the grid square, performed well in the comparison. Parameterizing the net longwave radiation, an estimate for the subgrid distribution of cloudiness was useful. Parameterization of surface momentum flux seemed to be most reasonable on the basis of the surface pressure field and a geostrophic drag coefficient depending on the air-surface temperature difference.

  6. Heat flux field for one spherical inhomogeneity embedded in a functionally graded material matrix

    Microsoft Academic Search

    H. M. Yin; G. H. Paulino; W. G. Buttlar; L. Z. Sun

    2008-01-01

    The heat flux field for a single particle embedded in a graded material is derived by using the equivalent inclusion method. A linearly distributed prescribed heat flux field is introduced to represent the material mismatch between the particle and the surrounding graded materials. By using Green’s function technique, an explicit solution is obtained for the heat flux field in both

  7. Calculations of radiant heat flux in the proposed floor covering flame spread test apparatus

    Microsoft Academic Search

    J. Quintiere; K. Bromberg

    1975-01-01

    Calculations were made to determine the radiant heat flux distribution to the test specimen in the proposed radiant panel flame spread test for floor covering materials. Comparison with measured heat flux indicates a significant heat transfer contribution from the enclosure of the test apparatus. Also, nonuniformities in the temperature of the radiant panel effect the resultant flux distribution. Based on

  8. Sensitivity of Cenozoic Antarctic ice sheet variations to geothermal heat flux

    E-print Network

    Sensitivity of Cenozoic Antarctic ice sheet variations to geothermal heat flux David Pollard a sheet to geothermal heat flux is investigated, using a coupled climate­ice sheet model with various prescribed values and patterns of geothermal heat flux. The sudden growth of major ice across the Eocene

  9. Vertical heat flux and lateral mass transport in nonlinear internal waves

    E-print Network

    (2010), Vertical heat flux and lateral mass transport in nonlinear internal waves, Geophys. Res. Lett and heat flux over the shelf. [3] By definition, particle speeds (uw) in NLIWs are com- parable to the waveClick Here for Full Article Vertical heat flux and lateral mass transport in nonlinear internal

  10. High heat flux issues for plasma-facing components in fusion reactors

    Microsoft Academic Search

    Robert D. Watson

    1993-01-01

    Plasma facing components in tokamak fusion reactors are faced with a number of difficult high heat flux issues. These components include: first wall armor tiles, pumped limiters, diverter plates, rf antennae structure, and diagnostic probes. Peak heat fluxes are 15 - 30 MW\\/m2 for diverter plates, which will operate for 100 - 1000 seconds in future tokamaks. Disruption heat fluxes

  11. Green's function partitioning procedure applied to foil heat flux gages

    SciTech Connect

    Beck, J.V.; Keltner, N.R.

    1987-05-01

    This paper presents a new procedure for using Green's functions for transient heat conduction problems. It is developed as part of continuing research on the unsteady surface element (USE) method; the USE method provides a means for combining solutions for two or more different basic geometries. By combining such geometries, problems involving composite media can be solved including problems associated with foil heat flux gages. The new method involves partitioning Green's function solutions over different time domains for each of which only a few terms are needed to describe the Green's function. The method is illustrated for the two-dimensional problem of a circular foil of finite thickness that is uniformly heated over a circular region and otherwise insulated. It is demonstrated that the method has the potential of providing extremely accurate values since six decimal accuracy is provided. Obtaining such accuracy using classical solution procedures is extremely difficult particularly for the extreme aspect ratios covered in this paper.

  12. Heat storage and anthropogenic heat flux in relation to the energy balance of a central European city centre

    NASA Astrophysics Data System (ADS)

    Offerle, B.; Grimmond, C. S. B.; Fortuniak, K.

    2005-08-01

    The role of net heat storage QS and anthropogenic heat QF are considered in the surface energy balance for a downtown area in ód, Poland, for a 2 year period. Eddy covariance measurements provide estimates of the turbulent heat fluxes and radiometric measurements of the net all-wave radiation. A method to determine QS based on representative surface temperature sampling is employed and compared with results from two other models. Results show that QS is an important flux on the scale of hours to days and that it can be more than 10 W m-2, on average, for periods of a week or more. By incorporating QS estimates over hourly intervals, QF was then determined as the residual of the energy balance. Using the approach, QF averaged 32 W m-2 from October to March (60% of available energy), and -3 W m-2 from June to August. The physically unrealistic negative values for the summer period may suggest underestimation of turbulent fluxes, but no causal factor was identified. Although energy balance closure was close to 100% throughout the year, there was weaker agreement in the winter. This is attributed to errors in estimates of QS and variation in QF. Results highlight the need for future investigations of the urban surface energy balance to incorporate more complete measurements and estimates of QS.

  13. Calculation of heating values for the high flux isotope reactor

    SciTech Connect

    Peterson, J.; Ilas, G. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831-6172 (United States)

    2012-07-01

    Calculating the amount of energy released by a fission reaction (fission Q value) and the heating rate distribution in a nuclear reactor is an important part of the safety analysis. However, these calculations can become very complex. One of the codes that can be used for this type of analyses is the Monte Carlo transport code MCNP5. Currently it is impossible to calculate the Q value and heating rate disposition for delayed beta and delayed gamma particles directly from MCNP5. The purpose of this paper is to outline a rigorous method for indirectly calculating the Q values and heating rates in the High Flux Isotope Reactor (HFIR), based on previous similar studies carried out for very high-temperature reactor configurations. This method has been applied in this study to calculate heating rates for the beginning of cycle (BOC) and end-of-cycle (EOC) states of HFIR. In addition, the BOC results obtained for HFIR are compared with corresponding results for the Advanced Test Reactor. The fission Q value for HFIR was calculated as 200.2 MeV for the BOC and 201.3 MeV for the EOC. It was also determined that 95.1% and 95.4% of the heat was deposited within the HFIR fuel plates for the BOC and EOC models, respectively. This methodology can also be used for heating rate calculations for HFIR experiments. (authors)

  14. Calculation of Heating Values for the High Flux Isotope Reactor

    SciTech Connect

    Peterson, Joshua L [ORNL] [ORNL; Ilas, Germina [ORNL] [ORNL

    2012-01-01

    Calculating the amount of energy released by a fission reaction (fission Q value) and the heating rate distribution in a nuclear reactor is an important part of the safety analysis. However, these calculations can become very complex. One of the codes that can be used for this type of analyses is the Monte Carlo transport code MCNP5. Currently it is impossible to calculate the Q value and heating rate disposition for delayed beta and delayed gamma particles directly from MCNP5. The purpose of this paper is to outline a rigorous method for indirectly calculating the Q values and heating rates in the High Flux Isotope Reactor (HFIR), based on previous similar studies carried out for very high-temperature reactor configurations. This method has been applied in this study to calculate heating rates for the beginning of cycle (BOC) and end-of-cycle (EOC) states of HFIR. In addition, the BOC results obtained for HFIR are compared with corresponding results for the Advanced Test Reactor. The fission Q value for HFIR was calculated as 200.2 MeV for the BOC and 201.3 MeV for the EOC. It was also determined that 95.1% and 95.4% of the heat was deposited within the HFIR fuel plates for the BOC and EOC models, respectively. This methodology can also be used for heating rate calculations for HFIR experiments.

  15. Conjugate heat transfer by natural convection, conduction and radiation in open cavities

    Microsoft Academic Search

    H. Nouanegue; A. Muftuoglu; E. Bilgen

    2008-01-01

    In this paper, we investigate conjugate heat transfer by natural convection, conduction and radiation in open cavities in which a uniform heat flux is applied to the inside surface of the solid wall facing the opening. Conservation equations are solved by finite difference–control volume numerical method. The relevant governing parameters are: the Rayleigh numbers from 109 to 1012, the Prandtl

  16. Flare loop radiative hydrodynamics. VI. Chromospheric evaporation due to heating by nonthermal electrons

    Microsoft Academic Search

    G. H. Fisher; R. C. Canfield; A. N. McClymont

    1985-01-01

    The response of the solar chromosphere to flare heating by nonthermalelectrons is examined. A number of interesting phenomena appear in our numericalsolutions of the equations of hydrodynamics and radiative transfer. Here wediscuss one aspect of these results: the phenomenon of chromosphericevaporation. We present results for a range of heating fluxes and show how thesemay be understood in simple terms. Our

  17. Radiation detector system having heat pipe based cooling

    DOEpatents

    Iwanczyk, Jan S.; Saveliev, Valeri D.; Barkan, Shaul

    2006-10-31

    A radiation detector system having a heat pipe based cooling. The radiation detector system includes a radiation detector thermally coupled to a thermo electric cooler (TEC). The TEC cools down the radiation detector, whereby heat is generated by the TEC. A heat removal device dissipates the heat generated by the TEC to surrounding environment. A heat pipe has a first end thermally coupled to the TEC to receive the heat generated by the TEC, and a second end thermally coupled to the heat removal device. The heat pipe transfers the heat generated by the TEC from the first end to the second end to be removed by the heat removal device.

  18. Dynamic instabilities in radiation-heated boiler tubes for solar central receivers

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Chan, K. C.; Chen, K.; Yadigaroglu, G.

    1982-11-01

    Density-wave instabilities have been investigated in circumferentially nonuniform radiation-heated boiler tubes, simulating solar heating. Analysis and experimental data are presented. The analysis provides the basis for a computer code, STEAMFREQ-I, for the prediction of density-wave instabilities in boiler tubes with imposed heat flux. The key model features include a drift-flux flow model in the boiling region, spatial variation of heat flux, wall dynamics, and variable steam properties in the superheat region. The experimental data include results from two radiation heated boiler panel tests. The data are applicable to central receivers for solar electric power plants. Data for stable and unstable conditions are compared with predictions from STEAMFREQ-I.

  19. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. [Pacific Northwest Lab., Richland, WA (United States); Barnes, F.J. [Los Alamos National Lab., NM (United States); Coulter, R.L. [Argonne National Lab., IL (United States); Crawford, T.L. [National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.

    1993-01-01

    In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moreover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations? To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discusses some initial findings from those campaigns.

  20. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. [Pacific Northwest Lab., Richland, WA (United States); Barnes, F.J. [Los Alamos National Lab., NM (United States); Coulter, R.L. [Argonne National Lab., IL (United States); Crawford, T.L. [National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.

    1993-04-01

    In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations within the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moveover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations? To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discuses some initial findings from those campaigns.

  1. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. (Pacific Northwest Lab., Richland, WA (United States)); Barnes, F.J. (Los Alamos National Lab., NM (United States)); Coulter, R.L. (Argonne National Lab., IL (United States)); Crawford, T.L. (National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.)

    1993-01-01

    In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moreover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discusses some initial findings from those campaigns.

  2. Boundary layer structure over areas of heterogeneous heat fluxes

    SciTech Connect

    Doran, J.C. (Pacific Northwest Lab., Richland, WA (United States)); Barnes, F.J. (Los Alamos National Lab., NM (United States)); Coulter, R.L. (Argonne National Lab., IL (United States)); Crawford, T.L. (National Oceanic and Atmospheric Administration, Oak Ridge, TN (United States). Air Resources Lab. Atmospheric Turbulence and Diffusion Div.)

    1993-01-01

    In general circulation models (GCMs), some properties of a grid element are necessarily considered homogeneous. That is, for each grid volume there is associated a particular combination of boundary layer depth, vertical profiles of wind and temperature, surface fluxes of sensible and latent heat, etc. In reality, all of these quantities may exhibit significant spatial variations within the grid area, and the larger the area the greater the likely variations. In balancing the benefits of higher resolution against increased computational time and expense, it is useful to consider what the consequences of such subgrid-scale variability may be. Moveover, in interpreting the results of a simulation, one must be able to define an appropriate average value over a grid. There are two aspects of this latter problem: (1) in observations, how does one take a set of discrete or volume-averaged measurements and relate these to properties of the entire domain, and (2) in computations, how can subgrid-scale features be accounted for in the model parameterizations To address these and related issues, two field campaigns were carried out near Boardman, Oregon, in June 1991 and 1992. These campaigns were designed to measure the surface fluxes of latent and sensible heat over adjacent areas with strongly contrasting surface types and to measure the response of the boundary layer to those fluxes. This paper discuses some initial findings from those campaigns.

  3. The effect of heat fluxes on ammonia emission from swine waste lagoon based on neural network analyses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding factors that affect ammonia emissions from swine waste lagoons or any animal waste receptacles is a necessary first step in deploying potential remediation options. In this study, we examined the various meteorological factors (i.e., air temperatures, solar radiation, and heat fluxes)...

  4. Particle and heat flux measurements in PDX edge plasmas

    SciTech Connect

    Budny, R.; Manos, D.

    1983-12-01

    This paper describes the use of novel combined Langmuir-calorimeter probes to measure edge plasma conditions near the midplane in PDX. The probes consisted of up to five Langmuir probes and up to two calorimeters. Single and double probe characteristics yield n/sub e/ and T/sub e/ which are compared with that derived from a triple probe analysis. The calorimeters measure heat flux in the electron and ion drift directions. This paper presents time-resolved radial profiles of n/sub e/, T/sub e/, V/sub F/ (floating potential), and P (heat flux) during high power neutral beam-heated, single-null discharges and circular scoop limiter discharges. The temporal dependence of these quantities displays the previous observed behavior with respect to gross discharge characteristics; however, an additional dependence on confinement mode has been observed. During the H-mode of energy confinement, a transient depression of n/sub e/, T/sub e/, and P occurs in the scrape-off plasma.

  5. Study of Solidification and Heat Transfer Behavior of Mold Flux Through Mold Flux Heat Transfer Simulator Technique: Part I. Development of the Technique

    NASA Astrophysics Data System (ADS)

    Liu, Yongzhen; Wang, Wanlin; Ma, Fanjun; Zhang, Haihui

    2015-03-01

    A Mold Flux Heat Transfer Simulator technique was developed to investigate the solidification and heat transfer behavior of mold flux in this study. The results suggested that the responding temperatures and heat fluxes increase intensively within the first second, due to the direct heating from the liquid core. It takes 1 second for the system to be heated up and to form the initial solidified mold flux shell, such that the heat fluxes and the liquid front temperature would start to reduce after that. After 2.5 seconds, the in-mold responding temperature and heat fluxes are getting attenuated with the development of the mold flux solidification and crystallization. After 15-20 seconds, the system steps into a quasi-steady state, as the cooling potential becomes identical to the heating potential due to the further development of total thermal resistance that is introduced by the further solidification and crystallization of mold flux. In addition, a mathematic model was built to calculate the interfacial thermal resistance (R int) at the mold/flux interface, and the calculated interfacial thermal resistance was around 18.9 × 10-4 m2 K W-1, which accounts for about 78.4 pct of the total thermal resistance.

  6. Modeling of a heat sink and high heat flux vapor chamber

    NASA Astrophysics Data System (ADS)

    Vadnjal, Aleksander

    An increasing demand for a higher heat flux removal capability within a smaller volume for high power electronics led us to focus on a novel cold plate design. A high heat flux evaporator and micro channel heat sink are the main components of a cold plate which is capable of removing couple of 100 W/cm2. In order to describe performance of such porous media device a proper modeling has to be addressed. A universal approach based on the volume average theory (VAT) to transport phenomena in porous media is shown. An approach on how to treat the closure for momentum and energy equations is addressed and a proper definition for friction factors and heat transfer coefficients are discussed. A numerical scheme using a solution to Navier-Stokes equations over a representative elementary volume (REV) and the use of VAT is developed to show how to compute friction factors and heat transfer coefficients. The calculation show good agreement with the experimental data. For the heat transfer coefficient closure, a proper average for both fluid and solid is investigated. Different types of heating are also investigated in order to determine how it influences the heat transfer coefficient. A higher heat fluxes in small area condensers led us to the micro channels in contrast to the classical heat fin design. A micro channel can have various shapes to enhance heat transfer, but the shape that will lead to a higher heat flux removal with a moderate pumping power needs to be determined. The standard micro-channel terminology is usually used for channels with a simple cross section, e.g. square, round, triangle, etc., but here the micro channel cross section is going to be expanded to describe more complicated and interconnected micro scale channel cross sections. The micro channel geometries explored are pin fins (in-line and staggered) and sintered porous micro channels. The problem solved here is a conjugate problem involving two heat transfer mechanisms; (1) porous media conductivity and (2) internal heat transfer coefficient. Volume averaging theory (VAT) is used to rigorously cast the point wise conservation of energy, momentum and mass equations into a form that represents the thermal and hydraulic properties of the micro channel (porous media) morphology. Using the resulting VAT based field equations, optimization of a micro channel heated from one side is used to determine the optimum micro channel morphology. A small square of 1 cm2 is chosen as an example and the thermal resistance, 0C/W, and pressure drop are shown as a function of Reynolds number. The high heat flux removal on small surfaces at moderately small temperatures is achieved by bi-porous evaporator The device was analyzed with the possibility of heat flux magnitudes exceeding 1kW/cm2 by using advantages of a dual pore structure of a bi-porous wick. The heat transfer model of a thin bi-porous wick is developed and it incorporates thermo-physical properties of a bi-porous media. It is shown that physics of heat removal is characterized in three stages; conduction, big pore drying out and small pore drying out. The operating conditions of the wick have to be in a safe margin away from the total dry out. A complete dry out of the wick inevitably leads to the burn out, therefore more concern has been added to modeling of big pore dry out, since this will be a desired operational. The construction of the boiling/evaporation curves was successfully constructed by the model showing that the physic of heat removal on two different length scales is governed by thermo-physical properties for the appropriate scale. The model shows good prediction for various combinations of big and small pores size in the bi-porous wicks tested.

  7. On the relation between coronal heating, flux tube divergence, and the solar wind proton flux and flow speed

    NASA Technical Reports Server (NTRS)

    Sandbaek, Onulf; Leer, Egil; Hansteen, Viggo H.

    1994-01-01

    A one-fluid solar wind model is used to investigate some relations between coronal heating, the flux tube divergence near the Sun, and the solar wind proton flux and flow speed. The effects of energy addition to the supersonic region of the flow are also studied. We allow for a mechanical energy flux that heats the corona, and an Alfven wave energy flux that adds energy, mainly to the supersonic flow, both as momentum and as heat. We find that the mechanical energy flux determines the solar wind mass flux, and in order to keep an almost constant proton flux at the orbit of Earth with changing flow geometry, that the mechanical energy flux must vary linearly with the magnetic field in the inner corona. This thermally driven wind generally has a low asymptotic flow speed. When Alfven waves are added to the thermally driven flow, the asymptotic flow speed is increased and is determined by the ratio of the Alfven wave and the mechanical energy fluxes at the coronal base. Flow speeds characteristic of recurrent high-speed solar wind streams can be obtained only when the Alfven wave energy flux, deposited in the supersonic flow, is larger than the mechanical energy flux heating the corona.

  8. Countergradient heat flux observations during the evening transition period

    NASA Astrophysics Data System (ADS)

    Blay-Carreras, E.; Pardyjak, E. R.; Pino, D.; Alexander, D. C.; Lohou, F.; Lothon, M.

    2014-03-01

    Gradient-based turbulence models generally assume that the buoyancy flux ceases to introduce heat into the surface layer of the atmospheric boundary layer in temporal consonance with the gradient of the local virtual potential temperature. Here, we hypothesize that during the evening transition a delay exists between the instant when the buoyancy flux goes to zero and the time when the local gradient of the virtual potential temperature indicates a sign change. This phenomenon is studied using a range of data collected over several Intensive Observational Periods (IOPs) during the Boundary Layer Late Afternoon and Sunset Turbulence field campaign conducted in Lannemezan, France. The focus is mainly on the lower part of the surface layer using a tower instrumented with high-speed temperature and velocity sensors. The results from this work confirm and quantify a flux-gradient delay. Specifically, the observed values of the delay are ~30-80 min. The existence of the delay and its duration can be explained by considering the convective time scale and the competition of forces associated with the classical Rayleigh-Bénard problem. This combined theory predicts that the last eddy formed while the sensible heat flux changes sign during the evening transition should produce a delay. It appears that this last eddy is decelerated through the action of turbulent momentum and thermal diffusivities, and that the delay is related to the convective turn - over time - scale. Observations indicate that as horizontal shear becomes more important, the delay time apparently increases to values greater than the convective turnover time-scale.

  9. Ekman heat flux variability from four wind sources

    NASA Astrophysics Data System (ADS)

    Sato, O. T.; Polito, P. S.

    2002-12-01

    The variability in the Ekman heat flux estimated from four different sources of wind is examined. The wind vectors are obtained from the European Remote Sensing (ERS), Quikscat, the Special Sensor Microwave Imager (SSM/I-Atlas) satellites, and from the National Centers for Environmental Prediction (NCEP) model. The temperature in the Ekman layer is estimated by combining the Reynolds sea surface temperature and climatological sub--surface profiles. Except for the Quikscat which span the period between 1999 and 2002, the data sets range a period over 10 years. The annual mean of the meridional Ekman heat flux (EHF) is consistently smaller when estimated with the ERS data. The NCEP tends to get larger values for the North Atlantic while the Quikscat is the largest for the North Pacific. The EHF has a better agreement at sub--tropical latitudes while the largest differences are found near the equator. To investigate the spatial variability of EHF we use a series of 2D finite impulse response filters. We quantify the role of several regions of the frequency-zonal wave number spectrum of the wind in establishing the observed Ekman heat flux. The mean component of the EHF, which keeps all the variability from the temperature field, is much higher in the low latitudes in the Atlantic. The relative variance of the mean component to the total EHF reaches up to 60% in the Atlantic while in the Pacific it explains only 30% of variance. The contribution to the variability of several bands of planetary westward propagating waves is larger in the Pacific and Indian Oceans while in the Atlantic it can explain at most 20% of the total variance. All wind sources show a change in the variability regime around 15° of latitude with lower frequencies prevailing over meso and small--scale variability within the tropics.

  10. Investigation of Instabilities and Heat Transfer Phenomena in Supercritical Fuels at High Heat Flux and Temperatures

    NASA Technical Reports Server (NTRS)

    Linne, Diane L.; Meyer, Michael L.; Braun, Donald C.; Keller, Dennis J.

    2000-01-01

    A series of heated tube experiments was performed to investigate fluid instabilities that occur during heating of supercritical fluids. In these tests, JP-7 flowed vertically through small diameter tubes at supercritical pressures. Test section heated length, diameter, mass flow rate, inlet temperature, and heat flux were varied in an effort to determine the range of conditions that trigger the instabilities. Heat flux was varied up to 4 BTU/sq in./s, and test section wall temperatures reached as high as 1950 F. A statistical model was generated to explain the trends and effects of the control variables. The model included no direct linear effect of heat flux on the occurrence of the instabilities. All terms involving inlet temperature were negative, and all terms involving mass flow rate were positive. Multiple tests at conditions that produced instabilities provided inconsistent results. These inconsistencies limit the use of the model as a predictive tool. Physical variables that had been previously postulated to control the onset of the instabilities, such as film temperature, velocity, buoyancy, and wall-to-bulk temperature ratio, were evaluated here. Film temperatures at or near critical occurred during both stable and unstable tests. All tests at the highest velocity were stable, but there was no functional relationship found between the instabilities and velocity, or a combination of velocity and temperature ratio. Finally, all of the unstable tests had significant buoyancy at the inlet of the test section, but many stable tests also had significant buoyancy forces.

  11. AOSC 621AOSC 621 Radiative Heating/CoolingRadiative Heating/Cooling

    E-print Network

    Li, Zhanqing

    of radiation on clouds: fog 2 #12;Clear-sky cooling/heating rate: longwave O3CO2 H2OO3CO O 3 #12;Clear-sky heating rate: shortwave Standard atmospherep Heating due to O3 absorption Implication on daily temp. cycle2 F 2 F 1 z1 z2 measured in W m3 m For very thin layer: 1 2 1 2 H dF dz Heating rate (H) H

  12. THERMAL DESIGN METHODOLOGY FOR HIGH-HEAT-FLUX SINGLE-PHASE AND TWO-PHASE MICRO-CHANNEL HEAT SINKS

    E-print Network

    Qu, Weilin

    boiling heat flux. A comprehensive model based on bubble departure and superheat criteria is developed-channel, heat sink, boiling, phase change, high heat flux, boiling incipience, pressure drop NOMENCLATURE Aa Point half-way from nucleation site to bubble tip f Friction factor Fd Drag force, N Fs Surface tension

  13. Heat transfer during the boiling of liquid on microstructured surfaces. Part 2: Visualization of boiling and critical heat fluxes

    NASA Astrophysics Data System (ADS)

    Popov, I. A.; Zubkov, N. N.; Kas'kov, S. I.; Shchelchkov, A. V.

    2013-04-01

    Results from visualization of boiling process and experimental study of critical heat fluxes on microstructured surfaces are presented. The studied surfaces were obtained using the deforming cutting method and have different design shapes and sizes. Mechanisms of heat transfer enhancement are substantiated. A factor of 4.1 higher value of critical heat flux is obtained.

  14. Spatial variation of heat flux in Steller sea lions: evidence for consistent avenues of heat exchange along the body trunk

    E-print Network

    Spatial variation of heat flux in Steller sea lions: evidence for consistent avenues of heat exchange along the body trunk Kate Willisa,*, Markus Horninga , David A.S. Rosenb , Andrew W. Tritesb neither quantified basic all-inclusive heat flux values for animals swimming in cold water, nor determined

  15. Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m/s), the inlet subcoolings (?Tsub, in=130 to 161K), the inlet pressure (Pin=812 to 1315kPa), the dissolved oxygen concentration (O2=5.88 and 7.34ppm) and the increasing heat input (Q0exp(t/?), ?=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test tube inner diameter (d=6mm), heated length (L=60mm), L/d=10 and wall thickness (?=0.5mm) with the rough finished inner surface (Surface roughness, Ra=3.18µm) is used in this work. The CHF data for high heating rate were compared with the quasi steady state ones previously obtained and the values calculated by the steady state CHF correlations against outlet and inlet subcoolings. Transient CHF correlation against inlet subcooling has been given based on the experimental data for wide exponentially increasing heat input (Q0exp(t/?), ?=38.1ms to 8.3s). The influence of heating rate on CHF was investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux for high heating rate was discussed.

  16. Radiation drive in laser heated hohlraums

    SciTech Connect

    Suter, L.J.; Kauffman, R.L.; Darrow, C.B. [and others

    1995-11-03

    Nearly 10 years of Nova experiments and analysis have lead to a relatively detailed quantitative and qualitative understanding of radiation drive in laser heated hohlraums. Our most successful quantitative modelling tool is 2D Lasnex numerical simulations. Analysis of the simulations provides us with insight into the details of the hohlraum drive. In particular we find hohlraum radiation conversion efficiency becomes quite high with longer pulses as the accumulated, high Z blow-off plasma begins to radiate. Extensive Nova experiments corroborate our quantitative and qualitative understanding.

  17. Near-field radiative heat transfer between closely spaced graphene and amorphous SiO2

    Microsoft Academic Search

    A. I. Volokitin; B. N. J. Persson

    2011-01-01

    We study the near-field radiative energy transfer between graphene and an amorphous SiO2 substrate. In comparison with the existing theories of near-field radiative heat transfer our theory takes into account that the free carriers in graphene are moving relative to the substrate with a drift velocity v. In this case the heat flux is determined by both thermal and quantum

  18. Radiation heating in selected NERVA engine components

    NASA Technical Reports Server (NTRS)

    Courtney, J. C.; Hertelendy, N. A.; Lindsey, B. A.

    1972-01-01

    The role of heating from nuclear radiation in design of the NERVA engine is treated. Some components are subjected to very high gamma heating rates in excess of 0.5 Btu/cubic inch/sec in steel in the primary nozzle or 0.25 Btu/cubic inch/sec in aluminum in the pressure vessel. These components must be cooled by a fraction of the liquid hydrogen propellant before it is passed through the core, heated, and expanded out the nozzle as a gas. Other components that are subjected to lower heating rates such as the thrust structure and the disk shield are designed so that they would not require liquid hydrogen cooling. Typical gamma and neutron heating rates, resulting temperatures, and their design consequences are discussed. Calculational techniques used in the nuclear and thermal analyses of the NERVA engine are briefly treated.

  19. Horizontal Radiative Fluxes in Clouds at Absorbing Wavelengths

    NASA Technical Reports Server (NTRS)

    Marshak, A.; Oreopoulos, L.; Davis, A. B.; Wiscombe, W. J.

    1998-01-01

    We discuss the effect of horizontal fluxes on the accuracy of a conventional plane-parallel radiative transfer calculation for a single pixel, known as the Independent Pixel Approximation (IPA) at absorbing wavelengths. Vertically integrated horizontal fluxes can be represented as a sum of three components; each component is the IPA accuracy on a pixel-by-pixel basis for reflectance, transmittance and absorptance, respectively. We show that IPA accuracy for reflectance always improves with more absorption, while the IPA accuracy for transmittance is less sensitive to the changes in absorption: with respect to the non-absorbing case, it may first deteriorate for weak absorption and then improve again for strongly absorbing wavelengths. EPA accuracy for absorptance always deteriorates with more absorption. As a result, vertically integrated horizontal fluxes, as a sum of IPA accuracies for reflectance, transmittance and absorptance, increase with more absorption. Finally, the question of correlations between horizontal fluxes, IPA uncertainties and radiative smoothing is addressed using wavenumber spectra of radiation fields reflected from or transmitted through fractal clouds.

  20. Numerical analysis of melting with constant heat flux heating in a thermal energy storage system

    Microsoft Academic Search

    Zhongliang Liu; Chongfang Ma

    2002-01-01

    Melting in a finite slab with a second kind boundary condition is studied numerically in order to simulate the charging process of a thermal energy storage system. A dimensionless model is given, from which it is concluded that the main factors that influence the melting process are the dimensionless heating flux, the modified Stefan number, the relative thermal diffusivity and

  1. Using Gravity Inversion to Estimate Antarctic Geothermal Heat Flux

    NASA Astrophysics Data System (ADS)

    Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; (Sasha) Golynsky, A. V.; Rogozhina, Irina

    2014-05-01

    New modelling studies for Greenland have recently underlined the importance of GHF for long-term ice sheet behaviour (Petrunin et al. 2013). Revised determinations of top basement heat-flow for Antarctica and adjacent rifted continental margins using gravity inversion mapping of crustal thickness and continental lithosphere thinning (Chappell & Kusznir 2008), using BedMap2 data have provided improved estimates of geothermal heat flux (GHF) in Antarctica where it is very poorly known. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental and oceanic lithosphere. The sensitivity of present-day Antarctic top basement heat-flow to initial continental radiogenic heat productivity, continental rift and margin breakup age has been examined. Recognition of the East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km (Ferraccioli et al. 2011) and is comparable in scale to the well-studied East African rift system, highlights that crustal variability in interior Antarctica is much greater than previously assumed. GHF is also important to understand proposed ice accretion at the base of the EAIS in the GSM and its links to sub-ice hydrology (Bell et al. 2011). References Bell, R.E., Ferraccioli, F., Creyts, T.T., Braaten, D., Corr, H., Das, I., Damaske, D., Frearson, N., Jordan, T., Rose, K., Studinger, M. & Wolovick, M. 2011. Widespread persistent thickening of the East Antarctic Ice Sheet by freezing from the base. Science, 331 (6024), 1592-1595. Chappell, A.R. & Kusznir, N.J. 2008. Three-dimensional gravity inversion for Moho depth at rifted continental margins incorporating a lithosphere thermal gravity anomaly correction. Geophysical Journal International, 174 (1), 1-13. Ferraccioli, F., Finn, C.A., Jordan, T.A., Bell, R.E., Anderson, L.M. & Damaske, D. 2011. East Antarctic rifting triggers uplift of the Gamburtsev Mountains. Nature, 479, 388-392. Petrunin, A., Rogozhina, I., Vaughan, A. P. M., Kukkonen, I. T., Kaban, M., Koulakov, I., Thomas, M. (2013): Heat flux variations beneath central Greenland's ice due to anomalously thin lithosphere. - Nature Geoscience, 6, 746-750.

  2. Radiative Heat Transfer in Fibre Insulations

    Microsoft Academic Search

    Neil Llewellyn McKay

    1984-01-01

    A first principles method of calculating combined radiative and conductive heat flow in fibrous insulation is presented. Using the measured complex refractive index for the bulk material, the scattering and absorption cross-sections are calculated for an isolated cylinder from expressions analogous to those of Mie theory for spheres. An average over fibre angles gives the cross-sections for the insulation material.

  3. Accuracy of soil heat flux plate measurements in coarse substrates - Field measurements versus a laboratory test

    NASA Astrophysics Data System (ADS)

    Weber, S.; Graf, A.; Heusinkveld, B. G.

    2007-05-01

    The in-situ performance of heat flux plates within coarse porous substrates might be limited due to poor contact between plate and substrate. We tested this behaviour with a simple laboratory set-up. Two test substrates were placed above a reference material of known thermal conductivity between a warm and a cold plate to establish a vertical heat flux. The temperature gradients and the response of a soil heat flux plate were measured. By means of the Fourier law of heat conduction the thermal conductivity of each test substrate was calculated, thus incorporating all heat transfer within the volume and representing the “effective” conductivity. The laboratory method had an accuracy of up to ±7% (±13% for a smaller set-up). In comparison, heat flux plate-derived heat fluxes showed errors of up to 26%. Use of heat flux plates in coarse substrates is not recommended without additional measurements.

  4. Modeled diurnally varying sea surface temperatures and their influence on surface heat fluxes

    NASA Astrophysics Data System (ADS)

    Weihs, Rachel R.; Bourassa, Mark. A.

    2014-07-01

    A diurnal warming model is used to create a new data set of global, diurnally varying sea surface temperatures (dSSTs) and surface turbulent heat fluxes over a 5 year period. The magnitude of diurnal warming is primarily a function of low wind speed and net heat flux. Differences between each of the surface turbulent fluxes with and without a diurnally varying SST are examined on hourly, daily, and seasonal time scales. Over a 2 month period, maximum averaged diurnal warming is as large as 0.3°C, and latent heat flux is underestimated by as much as 8 W/m2 in the Indian Ocean. They also exceed roughly 0.7°C and 10 W/m2, respectively, up to 25% of the total daytime in the Atlantic. A best-case approach validation shows the model overestimates peak warming and underestimates the duration of the cycle, though the average error is quite small. The model is tested under a variety of wind speed, solar radiation, and precipitation conditions to examine the impact of potential biases or error in the input data. To test the impact of a positive bias in the wind speeds, diurnal warming magnitudes are recomputed with an adjusted wind under near-neutral conditions. Compared to the original data, diurnal warming can increase by as much as 1.5°C on an hourly scale but generally is <0.06°C. Although precipitation effects on dSSTs are small compared to winds and radiation, the model configuration wrongly causes diurnal warming to increase by precipitation, contrary to the underlying model physics.

  5. A Radiative Transport Model for Heating Paints using High Density Plasma Arc Lamps

    SciTech Connect

    Sabau, Adrian S [ORNL; Duty, Chad E [ORNL; Dinwiddie, Ralph Barton [ORNL; Nichols, Mark [Ford Research and Advanced Engineering, Ford Motor Company; Blue, Craig A [ORNL; Ott, Ronald D [ORNL

    2009-01-01

    The energy distribution and ensuing temperature evolution within paint-like systems under the influence of infrared radiation was studied. Thermal radiation effects as well as those due to heat conduction were considered. A complete set of material properties was derived and discussed. Infrared measurements were conducted to obtain experimental data for the temperature in the paint film. The heat flux of the incident radiation from the plasma arc lamp was measured using a heat flux sensor with a very short response time. The comparison between the computed and experimental results for temperature show that the models that are based on spectral four-flux RTE and accurate optical properties yield accurate results for the black paint systems.

  6. Diamond thin film temperature and heat-flux sensors

    NASA Technical Reports Server (NTRS)

    Aslam, M.; Yang, G. S.; Masood, A.; Fredricks, R.

    1995-01-01

    Diamond film temperature and heat-flux sensors are developed using a technology compatible with silicon integrated circuit processing. The technology involves diamond nucleation, patterning, doping, and metallization. Multi-sensor test chips were designed and fabricated to study the thermistor behavior. The minimum feature size (device width) for 1st and 2nd generation chips are 160 and 5 micron, respectively. The p-type diamond thermistors on the 1st generation test chip show temperature and response time ranges of 80-1270 K and 0.29-25 microseconds, respectively. An array of diamond thermistors, acting as heat flux sensors, was successfully fabricated on an oxidized Si rod with a diameter of 1 cm. Some problems were encountered in the patterning of the Pt/Ti ohmic contacts on the rod, due mainly to the surface roughness of the diamond film. The use of thermistors with a minimum width of 5 micron (to improve the spatial resolution of measurement) resulted in lithographic problems related to surface roughness of diamond films. We improved the mean surface roughness from 124 nm to 30 nm by using an ultra high nucleation density of 10(exp 11)/sq cm. To deposit thermistors with such small dimensions on a curved surface, a new 3-D diamond patterning technique is currently under development. This involves writing a diamond seed pattern directly on the curved surface by a computer-controlled nozzle.

  7. Nonlinear aspects of high heat flux nucleate boiling heat transfer. Part 2, Results

    SciTech Connect

    Sadasivan, P.; Unal, C.; Nelson, R.

    1994-04-01

    This paper describes the results of a study aimed at understanding nonlinear aspects of the macrolayer-controlled heat transfer process associated with high heat flux nucleate boiling and the critical heat flux. Simulations of realistic heater surfaces have been carried out by detailed microscopic modeling of the surfaces. Individual nucleation sites are allowed to activate or deactivate depending on the thermal conditions that prevail at the site. The results indicate that significant spatial and temporal temperature variations can occur on the surface, and that thermal interactions among sites can result in some sites operating extremely intermittently. Surface-averaged temperatures show highly nonlinear behavior. This suggests the possibility of the system exhibiting chaotic behavior under appropriate experimental conditions. It is proposed that such nonlinear behavior is one of the reasons why mechanistic predictive capabilities for the boiling process have remained elusive.

  8. Influence of heat and mass flux conditions in hydromagnetic flow of Jeffrey nanofluid

    NASA Astrophysics Data System (ADS)

    Abbasi, F. M.; Shehzad, S. A.; Hayat, T.; Alsaedi, A.; Obid, Mustafa A.

    2015-03-01

    This article explores the hydromagnetic steady flow of Jeffrey fluid in the presence of thermal radiation. The chosen nanofluid model takes into account the Brownian motion and thermophoresis effects. Flow and heat transfer characteristics are determined by a stretching surface with flux conditions. The nonlinear boundary layer flow through partial differential systems is converted into the ordinary differential systems. The resulting reduced systems are computed for the convergent solutions of velocity, temperature and nanoparticle concentration. Graphs of dimensionless temperature and nanoparticle concentration profiles are presented for different values of emerging parameters. Skin-friction coefficient are computed and analyzed in both hydrodynamic and hydromagnetic flow situations.

  9. O+ and H+ ion heat fluxes at high altitudes and high latitudes

    NASA Astrophysics Data System (ADS)

    Barghouthi, I. A.; Nilsson, H.; Ghithan, S. H.

    2014-08-01

    Higher order moments, e.g., perpendicular and parallel heat fluxes, are related to non-Maxwellian plasma distributions. Such distributions are common when the plasma environment is not collision dominated. In the polar wind and auroral regions, the ion outflow is collisionless at altitudes above about 1.2 RE geocentric. In these regions wave-particle interaction is the primary acceleration mechanism of outflowing ionospheric origin ions. We present the altitude profiles of actual and "thermalized" heat fluxes for major ion species in the collisionless region by using the Barghouthi model. By comparing the actual and "thermalized" heat fluxes, we can see whether the heat flux corresponds to a small perturbation of an approximately bi-Maxwellian distribution (actual heat flux is small compared to "thermalized" heat flux), or whether it represents a significant deviation (actual heat flux equal or larger than "thermalized" heat flux). The model takes into account ion heating due to wave-particle interactions as well as the effects of gravity, ambipolar electric field, and divergence of geomagnetic field lines. In the discussion of the ion heat fluxes, we find that (1) the role of the ions located in the energetic tail of the ion velocity distribution function is very significant and has to be taken into consideration when modeling the ion heat flux at high altitudes and high latitudes; (2) at times the parallel and perpendicular heat fluxes have different signs at the same altitude. This indicates that the parallel and perpendicular parts of the ion energy are being transported in opposite directions. This behavior is the result of many competing processes; (3) we identify altitude regions where the actual heat flux is small as compared to the "thermalized" heat flux. In such regions we expect transport equation solutions based on perturbations of bi-Maxwellian distributions to be applicable. This is true for large altitude intervals for protons, but only the lowest altitudes for oxygen.

  10. Divertor Heat Flux Mitigation in High-Performance H-mode Plasmas in the National Spherical Torus Experiment.

    SciTech Connect

    Soukhanovskii, V A; Maingi, R; Gates, D; Menard, J; Paul, S F; Raman, R; Roquemore, A L; Bell, R E; Bush, C; Kaita, R

    2008-09-22

    Experiments conducted in high-performance 1.0-1.2 MA 6 MW NBI-heated H-mode plasmas with a high flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub p} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the lower single null configuration with higher-end elongation 2.2-2.4 and triangularity 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using high magnetic flux expansion and partial detachment of the outer strike point at several D{sub 2} injection rates, while good core confinement and pedestal characteristics were maintained. The partially detached divertor regime was characterized by a 30-60% increase in divertor plasma radiation, a peak heat flux reduction by up to 70%, measured in a 10 cm radial zone, a five-fold increase in divertor neutral pressure, and a significant volume recombination rate increase.

  11. Graphene-assisted near-field radiative heat transfer between corrugated polar materials

    SciTech Connect

    Liu, X. L.; Zhang, Z. M., E-mail: zhuomin.zhang@me.gatech.edu [G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2014-06-23

    Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

  12. Radiative Heating Methodology for the Huygens Probe

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Hollis, Brian R.; Sutton, Kenneth

    2007-01-01

    The radiative heating environment for the Huygens probe near peak heating conditions for Titan entry is investigated in this paper. The task of calculating the radiation-coupled flowfield, accounting for non-Boltzmann and non-optically thin radiation, is simplified to a rapid yet accurate calculation. This is achieved by using the viscous-shock layer (VSL) technique for the stagnation-line flowfield calculation and a modified smeared rotational band (SRB) model for the radiation calculation. These two methods provide a computationally efficient alternative to a Navier-Stokes flowfield and line-by-line radiation calculation. The results of the VSL technique are shown to provide an excellent comparison with the Navier-Stokes results of previous studies. It is shown that a conventional SRB approach is inadequate for the partially optically-thick conditions present in the Huygens shock-layer around the peak heating trajectory points. A simple modification is proposed to the SRB model that improves its accuracy in these partially optically-thick conditions. This modified approach, labeled herein as SRBC, is compared throughout this study with a detailed line-by-line (LBL) calculation and is shown to compare within 5% in all cases. The SRBC method requires many orders-of-magnitude less computational time than the LBL method, which makes it ideal for coupling to the flowfield. The application of a collisional-radiative (CR) model for determining the population of the CN electronic states, which govern the radiation for Huygens entry, is discussed and applied. The non-local absorption term in the CR model is formulated in terms of an escape factor, which is then curve-fit with temperature. Although the curve-fit is an approximation, it is shown to compare well with the exact escape factor calculation, which requires a computationally intensive iteration procedure.

  13. Near-field radiative heat transfer in mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Jing, Li; Yan-Hui, Feng; Xin-Xin, Zhang; Cong-Liang, Huang; Ge, Wang

    2015-01-01

    The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2˜4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. Project supported by the National Natural Science Foundation of China (Grant No. 51422601), the National Basic Research Program of China (Grant No. 2012CB720404), and the National Key Technology Research and Development Program of China (Grant No. 2013BAJ01B03).

  14. ESTIMATION OF BARE-SOIL EVAPORATION USING A CALORIMETRIC APPROACH WITH HEAT FLUX MEASURED AT MULTIPLE DEPTHS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An assumption in calorimetric methods for soil heat flux is that sensible heat terms can be balanced (i.e., if the heat flux is known at one depth, the heat flux at another depth may be determined by monitoring the change in heat storage). Latent heat from water evaporation is assigned to the energy...

  15. Development of advanced high-temperature heat flux sensors. Phase 2: Verification testing

    NASA Technical Reports Server (NTRS)

    Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

    1985-01-01

    A two-phase program is conducted to develop heat flux sensors capable of making heat flux measurements throughout the hot section of gas turbine engines. In Phase 1, three types of heat flux sensors are selected; embedded thermocouple, laminated, and Gardon gauge sensors. A demonstration of the ability of these sensors to operate in an actual engine environment is reported. A segmented liner of each of two combustors being used in the Broad Specification Fuels Combustor program is instrumented with the three types of heat flux sensors then tested in a high pressure combustor rig. Radiometer probes are also used to measure the radiant heat loads to more fully characterize the combustor environment. Test results show the heat flux sensors to be in good agreement with radiometer probes and the predicted data trends. In general, heat flux sensors have strong potential for use in combustor development programs.

  16. Effect of combined nanoparticle and polymeric dispersions on critical heat flux, nucleate boiling heat transfer coefficient, and coating adhesion

    E-print Network

    Edwards, Bronwyn K

    2009-01-01

    An experimental study was performed to determine thermal performance and adhesion effects of a combined nanoparticle and polymeric dispersion coating. The critical heat flux (CHF) values and nucleate boiling heat transfer ...

  17. Relations for local radiative heat transfer between rectangular boundaries of an absorbing-emitting medium

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1993-01-01

    An analytical solution was obtained by Siegel (1991, 1992) for local boundary heat fluxes by a radiating medium at uniform temperature in a 2D rectangular region. It is shown here that, after local fluxes from the medium to the walls have been evaluated, it is very easy to compute local fluxes arriving from the adjacent and opposite walls. This extends the previous analysis and provides convenient relations to include radiation from a black boundary, each side of the rectangle being at a different uniform temperature. The final expressions are helpful in performing spectral calculations that must be made for many spectral bands.

  18. ANL ITER high-heat-flux blanket-module heat transfer experiments

    SciTech Connect

    Kasza, K.E.

    1992-02-01

    An Argonne National Laboratory facility for conducting tests on multilayered slab models of fusion blanket designs is being developed; some of its features are described. This facility will allow testing under prototypic high heat fluxes, high temperatures, thermal gradients, and variable mechanical loadings in a helium gas environment. Steady and transient heat flux tests are possible. Electrical heating by a two-sided, thin stainless steel (SS) plate electrical resistance heater and SS water-cooled cold panels placed symmetrically on both sides of the heater allow achievement of global one-dimensional heat transfer across blanket specimen layers sandwiched between the hot and cold plates. The heat transfer characteristics at interfaces, as well as macroscale and microscale thermomechanical interactions between layers, can be studied in support of the ITER engineering design effort. The engineering design of the test apparatus has shown that it is important to use multidimensional thermomechanical analysis of sandwich-type composites to adequately analyze heat transfer. This fact will also be true for the engineering design of ITER.

  19. Critical-heat-flux experiment on the screw tube under one-sided-heating conditions

    SciTech Connect

    Araki, Masanori; Sato, Kazuyoshi; Suzuki, Satoshi; Akiba, Masato [Japan Atomic Energy Research Inst., Ibaraki (Japan)

    1996-07-01

    Development of high-heat-flux components such as the divertor plate of fusion experimental machines is essential for removal of high heat loads with heating on one side. For this purpose, the authors machined a tube with an inside wall like a nut, namely, a screw tube, to enhance heat transfer efficiency and simplify the machining process. The screw tube is compared with a swirl tube, originally developed by Oak Ridge National Laboratory, and the Hypervapotron, developed by Joint European Torus (JET). The spirally machined inside wall can enlarge the heat transfer area and make a little vortex flow only close to the wall. The performance of the screw tube is characterized by a critical-heat-flux experiment that uses water flow velocities ranging from 4 to 20 m/s with a water inlet pressure of 1.0 MPa. As a result, the screw tube has a higher incidence of CHFs compared with the smooth tube and the Hypervapotron and performs similarly to the swirl tube at identical flow velocities. 15 refs., 10 figs., 2 tabs.

  20. The surface latent heat flux anomalies related to major earthquake

    NASA Astrophysics Data System (ADS)

    Jing, Feng; Shen, Xuhui; Kang, Chunli; Xiong, Pan; Hong, Shunying

    2011-12-01

    SLHF (Surface Latent Heat Flux) is an atmospheric parameter, which can describe the heat released by phase changes and dependent on meteorological parameters such as surface temperature, relative humidity, wind speed etc. There is a sharp difference between the ocean surface and the land surface. Recently, many studies related to the SLHF anomalies prior to earthquakes have been developed. It has been shown that the energy exchange enhanced between coastal surface and atmosphere prior to earthquakes can increase the rate of the water-heat exchange, which will lead to an obviously increases in SLHF. In this paper, two earthquakes in 2010 (Haiti earthquake and southwest of Sumatra in Indonesia earthquake) have been analyzed using SLHF data by STD (standard deviation) threshold method. It is shows that the SLHF anomaly may occur in interpolate earthquakes or intraplate earthquakes and coastal earthquakes or island earthquakes. And the SLHF anomalies usually appear 5-6 days prior to an earthquake, then disappear quickly after the event. The process of anomaly evolution to a certain extent reflects a dynamic energy change process about earthquake preparation, that is, weak-strong-weak-disappeared.

  1. Heat flux calculations for Mackenzie and Yukon Rivers

    NASA Astrophysics Data System (ADS)

    Yang, Daqing; Marsh, Philip; Ge, Shaoqing

    2014-09-01

    This study analyzes long-term (40-60 years) discharge and water temperature records collected near the basin outlets of the Yukon and Mackenzie Rivers. It defines seasonal cycles of discharge, water temperature (WT), and heat flux (HF) for the basins, and compares their main features to understand their similarity and difference. Both rivers have similar hydrographs, i.e. low flows in winter and high discharge in summer, with the peak flood in June due to snowmelt runoff. Mackenzie River has many large lakes and they sustain the higher base flows over the fall/winter season. Mackenzie basin is large with high precipitation, thus producing 50% more discharge than the Yukon River to the Arctic Ocean. The WT regimes are also similar between the two rivers. Yukon River WT is about 2-3 °C warmer than the Mackenzie over the open water months. Both rivers have the highest WT in the mid summer and they transport large amount of heat to the polar ocean system. Yukon River monthly HF is lower by 10-60% than the Mackenzie mainly due to smaller discharge. Mackenzie River heat transport peaks in July, while the Yukon HF reaches the maximum in June and July. These results provide critical knowledge of river thermal condition and energy transport to the northern seas. They are useful for large-scale climate and ocean model development and validation, and climate/hydrology change research in the northern regions.

  2. A Comparison of Latent Heat Fluxes over Global Oceans for Four Flux Products

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Nelkin, Eric; Ardizzone, Joe; Atlas, Robert M.

    2003-01-01

    To improve our understanding of global energy and water cycle variability, and to improve model simulations of climate variations, it is vital to have accurate latent heat fluxes (LHF) over global oceans. Monthly LHF, 10-m wind speed (U10m), 10-m specific humidity (Q10h), and sea-air humidity difference (Qs-Q10m) of GSSTF2 (version 2 Goddard Satellite-based Surface Turbulent Fluxes) over global Oceans during 1992-93 are compared with those of HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data), NCEP (NCEP/NCAR reanalysis). The mean differences, standard deviations of differences, and temporal correlation of these monthly variables over global Oceans during 1992-93 between GSSTF2 and each of the three datasets are analyzed. The large-scale patterns of the 2yr-mean fields for these variables are similar among these four datasets, but significant quantitative differences are found. The temporal correlation is higher in the northern extratropics than in the south for all variables, with the contrast being especially large for da Silva as a result of more missing ship data in the south. The da Silva has extremely low temporal correlation and large differences with GSSTF2 for all variables in the southern extratropics, indicating that da Silva hardly produces a realistic variability in these variables. The NCEP has extremely low temporal correlation (0.27) and large spatial variations of differences with GSSTF2 for Qs-Q10m in the tropics, which causes the low correlation for LHF. Over the tropics, the HOAPS LHF is significantly smaller than GSSTF2 by approx. 31% (37 W/sq m), whereas the other two datasets are comparable to GSSTF2. This is because the HOAPS has systematically smaller LHF than GSSTF2 in space, while the other two datasets have very large spatial variations of large positive and negative LHF differences with GSSTF2 to cancel and to produce smaller regional-mean differences. Our analyses suggest that the GSSTF2 latent heat flux, surface air humidity, and winds are likely to be more realistic than the other three flux datasets examined, although those of GSSTF2 are still subject to regional biases.

  3. Annual Cycle of Radiation Fluxes over the Arctic Ocean: Sensitivity to Cloud Optical Properties

    Microsoft Academic Search

    Judith A. Curry; Elizabeth E. Ebert

    1992-01-01

    The relationship between cloud optical properties and the radiative fluxes over the Arctic Ocean is explored by conducting a series of modeling experiments. The annual cycle of arctic cloud optical properties that are required to reproduce both the outgoing radiative fluxes at the top of the atmosphere as determined from satellite observations and the available determinations of surface radiative fluxes

  4. Mixed convection heat transfer and pressure drop correlations for tube-in-shell thermosyphon heat exchangers with uniform heat flux

    SciTech Connect

    Dahl, S.D.; Davidson, J.H. [Univ. of Minnesota, Minneapolis, MN (United States). Mechanical Engineering Dept.

    1998-11-01

    An important issue arising from prior studies of thermosyphon heat exchangers for use in solar water heaters is the need for heat transfer and pressure drop correlations for the laminar, mixed-convection regime in which these many of these heat exchangers operate. In this paper, the authors present empirical correlations for tube-in-shell heat exchangers with the thermosyphon flow on the shell side. The correlations are determined for uniform heat flux on the tube walls. Ranges of Reynolds and Grashof numbers are 130 to 2,000 and 4 {times} 10{sup 5} to 8 {times} 10{sup 7}, respectively. Nusselt number correlations are presented in a form that combines the contributions of forced and natural convection. Mixed convection dominates forced convection heat transfer in these geometries. Pressure drop is not significantly affected by mixed convection.

  5. Surface Solar Radiation Flux and Cloud Radiative Forcing for the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP): A Satellite, Surface Observations, and Radiative Transfer Model Study

    Microsoft Academic Search

    Catherine Gautier; Martin Landsfeld

    1997-01-01

    This study presents surface solar radiation flux and cloud radiative forcing results obtained by using a combination of satellite and surface observations interpreted by means of a simple plane-parallel radiative transfer model called 2001. This model, a revised version of a model initially introduced by Gautier et al., relates calibrated radiance observations from space to incoming surface solar flux. After

  6. Heat Flux From the Endeavour Segment of the Juan de Fuca Ridge

    Microsoft Academic Search

    W. J. Thompson; R. E. McDuff; F. R. Stahr; D. R. Yoerger; M. Jakuba

    2005-01-01

    The very essence of a hydrothermal system is transfer of heat by a convecting fluid, yet the flux of heat remains a poorly known quantity. Past studies of heat flux consisted primarily of point measurements of temperature and fluid flow at individual vent sites and inventories of the neutrally buoyant plume above the field. In 2000 the Flow Mow project

  7. An inverse method to estimate stem surface heat flux in wildland fires

    Microsoft Academic Search

    Anthony S. BovaA; Matthew B. DickinsonA

    Models of wildland fire-induced stem heating and tissue necrosis require accurate estimates of inward heat flux at the bark surface. Thermocouple probes or heat flux sensors placed at a stem surface do not mimic the thermal response of tree bark to flames. We show that data from thin thermocouple probes inserted just below the bark can be used, by means

  8. Reconstruction of local heat fluxes in pool boiling experiments along the entire boiling curve from high

    E-print Network

    Reconstruction of local heat fluxes in pool boiling experiments along the entire boiling curve from conduction problem (IHCP) defined on an irregular three-dimensional (3D) domain in pool boiling experiments heating foil pressed to the bottom of the heater. The heat flux at the inaccessible boiling side

  9. Tangential force, Frictional Torque and Heating Rate of a Small Neutral Rotating Particle Moving through the Equilibrium Background Radiation

    E-print Network

    G. V. Dedkov; A. A. Kyasov

    2013-02-04

    For the first time, based on the fluctuation-electromagnetic theory, we have calculated the drug force, the radiation heat flux and the frictional torque on a small rotating particle moving at a relativistic velocity through the equilibrium background radiation (photon gas). The particle and background radiation are characterized by different temperatures corresponding to the local thermodynamic equilibrium in their own reference frames.

  10. Scaling of shortwave radiation fluxes for sub grid topography

    NASA Astrophysics Data System (ADS)

    Helbig, N.; Loewe, H.; Adams, E. E.

    2011-12-01

    Shortwave radiation plays an important role in the surface energy balance for understanding mass balances, snow cover distribution as well as snow melt. Incident shortwave radiation is greatly altered by mountainous terrain. While distributed radiation balance models can account for all topographic influences at small scales, for larger scale applications, such as climate and hydrological models, physically based sub grid parameterizations are required. We present a complete shortwave radiation parameterization scheme for sub grid topography accounting for shading, limited sky view and terrain reflections. Each radiative flux is parameterized individually. The parameters required are sun elevation angle, domain-averaged surface albedo and terrain parameters such as slope angle, slope distribution and sky view factor. We show that the domain-averaged sky view factor as an important parameter of the scheme can be theoretically related to the slope distribution. This suggests that the parametrization can solely be computed from slope characteristics and the numerically expensive computation of horizons angles can be abandoned. To validate the parameterization scheme we used domain-averaged values from a detailed radiation balance model for the three-dimensional radiative transfer in complex terrain. In order to minimize influences in the modeled distributed radiation arising from specific geomorphology and climate we compiled a large ensemble of several thousand Gaussian topographies with a broad range of characteristic scales and used fixed sun positions. Overall, modeled radiation from the simulated topographies compared well with parameterized values. We found that depending on sun elevation angles, shading and limited sky view alter direct beam and diffuse sky radiation by up to 40% each. We confirmed that when using domain-averaged values, multiple, anisotropic terrain reflections can be approximated with single, isotropic terrain reflections.

  11. Development of Low Conductivity and Ultra High Temperature Ceramic Coatings Using A High-Heat-Flux Testing Approach

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1990-01-01

    The development of low conductivity, robust thermal and environmental barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity and cyclic resistance at very high surface temperatures (up to 17OOOC) under large thermal gradients. In this study, a laser high-heat-flux test approach is established for evaluating advanced low conductivity, ultra-high temperature ceramic thermal and environmental barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) program. The test approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity: the initial conductivity rise under a steady-state high temperature thermal gradient test due to coating sintering, and the later coating conductivity reduction under a subsequent cyclic thermal gradient test due to coating cracking/delamination. The coating system is then evaluated based on the damage accumulations and failure after the combined steady-state and cyclic thermal gradient tests. The lattice and radiation thermal conductivity of advanced ceramic coatings can also be evaluated using laser heat-flux techniques. The coating external radiation resistance is assessed based on the measured specimen temperature response under a laser heated intense radiation flux source. The coating internal radiation contribution is investigated based on the measured apparent coating conductivity increases with the coating surface test temperature under large thermal gradient test conditions. Since an increased radiation contribution is observed at these very high surface test temperatures, by varying the laser heat-flux and coating average test temperature, the complex relation between the lattice and radiation conductivity as a function of surface and interface test temperature is derived.

  12. Fusion Engineering and Design 45 (1999) 377407 Critical heat flux analysis and R&D for the design of the

    E-print Network

    Raffray, A. René

    of such high heat fluxes gives rise to several issues, including the critical heat flux (CHF) margin whichFusion Engineering and Design 45 (1999) 377­407 Critical heat flux analysis and R&D for the design of the ITER divertor have to be designed for high heat fluxes (up to 20 MW/m2 over :10 s). Accommodation

  13. Gamma heating measurements in a mixed radiation field

    SciTech Connect

    Chiu, H.K. (Illinois Univ., Urbana, IL (USA). Dept. of Nuclear Engineering); Bennett, E.F.; Micklich, B.J. (Argonne National Lab., IL (USA))

    1990-09-01

    Gamma hearing measurements have been made in a low-Z assembly irradiated with 14-MeV neutrons and (n,n{prime}) gammas produced by a Texas Nuclear Model 9400 neutron generator. The assembly is composed of 144 magnesium sleeves (5cm {times} 5cm {times} 60cm {times} 3 mm thick) filled with graphite to simulate a fusion blanket test module. Heating measurements were made in the mid-line of the assembly using a proportional counter operating in the Continuously-varied Bias-voltage Acquisition (CBA) mode. The neutron induced atomic recoil signal was rejected by observing the signal rise-time differences inherent to radiations of different LET. The experiment was modelled using the one-dimensional radiation transport code ANISN/PC. The operating limits of this technique were identified by comparing measurements made at different positions in the assembly and then comparing these measurements to the calculated flux. 7 refs., 5 figs., 1 tab.

  14. Estimation of turbulent surface heat fluxes using sequences of remotely sensed land surface temperature

    E-print Network

    Bateni, Sayed Mohyeddin

    2011-01-01

    Fluxes of heat and moisture at the land-surface play a significant role in the climate system. These fluxes interact with the overlying atmosphere and influence the characteristics of the planetary boundary layer (e.g. ...

  15. Theory and methods of calculating radiative heat transfer

    Microsoft Academic Search

    Iu. A. Surinov

    1976-01-01

    Attention is given to the solution of integral equations of radiative heat transfer in an absorbing and isotropically scattering medium, unsteady problems of thermoelasticity, solar activity effects on the earth atmosphere, radiative heat transfer between a conical body and a shock front, and the local characteristics of radiative heat transfer between concentric cylinders separated by an absorbing medium. Also considered

  16. Prediction of heat transfer of nanofluid on critical heat flux based on fractal geometry

    NASA Astrophysics Data System (ADS)

    Xiao, Bo-Qi

    2013-01-01

    Analytical expressions for nucleate pool boiling heat transfer of nanofluid in the critical heat flux (CHF) region are derived taking into account the effect of nanoparticles moving in liquid based on the fractal geometry theory. The proposed fractal model for the CHF of nanofluid is explicitly related to the average diameter of the nanoparticles, the volumetric nanoparticle concentration, the thermal conductivity of nanoparticles, the fractal dimension of nanoparticles, the fractal dimension of active cavities on the heated surfaces, the temperature, and the properties of the fluid. It is found that the CHF of nanofluid decreases with the increase of the average diameter of nanoparticles. Each parameter of the proposed formulas on CHF has a clear physical meaning. The model predictions are compared with the existing experimental data, and a good agreement between the model predictions and experimental data is found. The validity of the present model is thus verified. The proposed fractal model can reveal the mechanism of heat transfer in nanofluid.

  17. Heat pump processes induced by laser radiation

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.

    1980-01-01

    A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

  18. Total aerosol effect: forcing or radiative flux perturbation?

    SciTech Connect

    Lohmann, Ulrike; Storelvmo, Trude; Jones, Andy; Rotstayn, Leon; Menon, Surabi; Quaas, Johannes; Ekman, Annica; Koch, Dorothy; Ruedy, Reto

    2009-09-25

    Uncertainties in aerosol forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. Traditionally these feedbacks were not included in estimates of total aerosol forcing. Here we argue that they should be included because these feedbacks act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Thus we propose replacing the direct and indirect aerosol forcing in the IPCC forcing chart with RFP estimates. This implies that it is better to evaluate the total anthropogenic aerosol effect as a whole.

  19. Heat conduction in nanoscale materials: a statistical-mechanics derivation of the local heat flux.

    PubMed

    Li, Xiantao

    2014-09-01

    We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples. PMID:25314400

  20. Shaping solar concentrator mirrors by radiative heating

    NASA Astrophysics Data System (ADS)

    Angel, Roger; Stalcup, Thomas; Wheelwright, Brian; Warner, Stephen; Hammer, Kimberly; Frenkel, Mira

    2014-10-01

    Here we report a newly developed method for gravity sag molding of large glass solar reflectors, 1.65 m x 1.65 m square, with either line or point focus, and short focal length. The method is designed for high volume manufacture when incorporated into a production line with separate pre-heating and cooling. The tests reported here have been made in a custom batch furnace, with high power radiative heating to soften the glass for slumping. The mold surface is machined to the required shape as grooves which intersect the glass at cusps, reducing the mold contact area to <1%. Optical metrology of replicas made with the system has been carried out with a novel test using a linear array of coaligned lasers translated in a perpendicular direction across the reflector while the deviation of each beam from perfect focus is measured. Slopes measured over an array of 4000 points show an absolute accuracy of <0.3 mrad rms in sx and sy. The most accurate replicas we have made are from a 2.6 m2 point focus mold, showing slope errors in x and y of 1.0 mrad rms. The slump cycle, starting with rigid flat glass at 500C, uses a 350 kW burst of radiative heating for 200 seconds, followed by radiative and convective cooling.

  1. How much net surface heat flux should go into the Western Pacific Warm Pool?

    NASA Astrophysics Data System (ADS)

    Song, Xiangzhou; Yu, Lisan

    2013-07-01

    The western tropical Pacific warm pool, with the surface area bounded by the 28°C isotherm, receives heat from the atmosphere through the year. However, the exact amount of net surface heat flux into this area remains to be determined. A survey of nine heat flux climatologies (including three latest atmospheric reanalyses, three early reanalyses, and three analyzed products) shows that the estimates are clustered into two groups, with a mean of 18 Wm-2 for the five-member low net heat flux group (ERA-Interim, CORE.2, NCEP 1 and 2, and ERA-40) and of 49 Wm-2 for the four-member high net heat flux group (CFSR, OAFlux+ISCCP, NOCSv2.0, and MERRA). This study used a pool-area based heat budget analysis together with in situ air-sea and subsurface measurements to examine the physical consistency of the nine flux climatologies and to ascribe the statistical uncertainty of each product. The heat budget analysis indicates that the annual mean net surface heat flux should be 28 ± 10 Wm-2. The observed eddy coefficient along the 28°C isotherm is 1.5 cm2s-1 based on the TAO/TRION buoys and the historical records. The ocean cannot dissipate the excessive high heat fluxes, while the low fluxes cannot balance the estimated diffusive heat flux across the isotherm. Both the one-point direct comparison and pool integrated eddy diffusive heat flux analysis demonstrate that, the high net heat flux climatologies have high bias; on the other hand, the low fluxes have low bias. These biases and uncertainties are given and documented in this paper.

  2. Combining satellite data and land model outputs to advance in the estimation of global land surface heat fluxes

    NASA Astrophysics Data System (ADS)

    Jimenez, C.; Prigent, C.; Aires, F.

    2009-04-01

    Land heat fluxes are one of the essential components of the water and energy cycles. Despite a large body of work, there is no systematic data analysis activity underway to produce a complete, phisically consistent, global, multi-decadal land heat flux data product. The GEWEX Radiation Panel (GRP) recently launched an activity, called LandFlux , to develop the needed capabilities to produce such data product. In this context, we have started to study the sensitivity of a suite of satellite observations to land surface turbulent fluxes and to investigate the possibility of estimating the fluxes from the satellite measurements. The satellite data were selected for their expected sensitivity to the surface properties that affect the fluxes, and includes: active microwave backscatter (ERS scatterometer), passive microwave emissivities (SSM/I), visible and near-infrared reflectances (AVHRR), and thermal infrared surface skin temperature (ISCCP) and the corresponding amplitude of its diurnal cycle. The fluxes calculated from some land surface models were adopted as estimates of land surface fluxes at a global scale: the GSWP-2 multi-model analysis and the NCEP/NCAR reanalysis were used, at a monthly time scale for the 1993-1995 period. To link the satellite observations to the fluxes, a statistical model based on a neural network is trained to find the global relationships between the fluxes and the satellite observations. Comparing the fluxes predicted by the statistical model and the original land model fluxes shows that the satellite data can reproduce the fluxes with global RMS errors of less than 25 W/m2. Geographical and temporal patterns of the fluxes are realtively well captured. When there are large differences related to local departures from the global relationships, they can be used to reveal potential modelling problems. The original and estimated fluxes are also compared with climatological AmeriFlux tower flux measurements (2002-2006 annual averages), with similar correlations of ~0.7, but the comparison cannot be regarded as conclusive. It is outside of the relatively well modeled mid-latitude regions where the differences between the original and estimated fluxes are the largest, but lack of tower fluxes precludes a more extensive comparison. This methodology is general and can also be applied to link other land model outputs and global satellite observations. However, it is tightly related to the model outputs and cannot be considered as a method to derive independent land surface products from satellite observations. Nevertheless, this statistical analysis can be an efficient tool to diagnose modelling difficulties or to combine satellite data and land models to produce global surface products maximizing their relational consistency.

  3. Description of heat flux measurement methods used in hydrocarbon and propellant fuel fires at Sandia.

    SciTech Connect

    Nakos, James Thomas

    2010-12-01

    The purpose of this report is to describe the methods commonly used to measure heat flux in fire applications at Sandia National Laboratories in both hydrocarbon (JP-8 jet fuel, diesel fuel, etc.) and propellant fires. Because these environments are very severe, many commercially available heat flux gauges do not survive the test, so alternative methods had to be developed. Specially built sensors include 'calorimeters' that use a temperature measurement to infer heat flux by use of a model (heat balance on the sensing surface) or by using an inverse heat conduction method. These specialty-built sensors are made rugged so they will survive the environment, so are not optimally designed for ease of use or accuracy. Other methods include radiometers, co-axial thermocouples, directional flame thermometers (DFTs), Sandia 'heat flux gauges', transpiration radiometers, and transverse Seebeck coefficient heat flux gauges. Typical applications are described and pros and cons of each method are listed.

  4. Enhancement of single-phase heat transfer and critical heat flux from an ultra-high-flux simulated microelectronic heat source to a rectangular impinging jet of dielectric liquid

    Microsoft Academic Search

    D. C. Wadsworth; I. Mudawar

    1992-01-01

    Jet impingement is encountered in numerous applications demanding high heating or cooling fluxes. Examples include annealing of metal sheets and cooling of turbine blades, x-ray medical devices, laser weapons, and fusion blankets. The attractive heat transfer attributes of jet impingement have also stimulated research efforts on cooling of high-heat-flux microelectronic devices. These devices are fast approaching heat fluxes in excess

  5. Decoupled cantilever arms for highly versatile and sensitive temperature and heat flux measurements

    E-print Network

    Burg, Brian R.

    Microfabricated cantilever beams have been used in microelectromechanical systems for a variety of sensor and actuator applications. Bimorph cantilevers accurately measure temperature change and heat flux with resolutions ...

  6. Effects of Temperature Gradients and Heat Fluxes on High-Temperature Oxidation

    SciTech Connect

    Holcomb, G.R.

    2008-04-01

    The effects of a temperature gradient and heat flux on point defect diffusion in protective oxide scales were examined. Irreversible thermodynamics were used to expand Fick’s first law of diffusion to include a heat-flux term—a Soret effect. Oxidation kinetics were developed for the oxidation of cobalt and of nickel doped with chromium. Research is described to verify the effects of a heat flux by oxidizing pure cobalt in a temperature gradient at 900 °C, and comparing the kinetics to isothermal oxidation. No evidence of a heat flux effect was found.

  7. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, Robert V. (Tijeras, NM)

    1993-01-01

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infra-red sensing devices.

  8. Quantitative method for measuring heat flux emitted from a cryogenic object

    DOEpatents

    Duncan, R.V.

    1993-03-16

    The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infrared sensing devices.

  9. Critical Heat Flux In Inclined Rectangular Narrow Long Channel

    SciTech Connect

    J. L. Rempe; S. W. Noh; Y. H. Kim; K. Y. Suh; F.B.Cheung; S. B. Kim

    2005-05-01

    In the TMI-2 accident, the lower part of the reactor pressure vessel had been overheated and then rather rapidly cooled down, as was later identified in a vessel investigation project. This accounted for the possibility of gap cooling feasibility. For this reason, several investigations were performed to determine the critical heat flux (CHF) from the standpoint of invessel retention. The experiments are conducted to investigate the general boiling phenomena, and the triggering mechanism for the CHF in a narrow gap using a 5 x 105 mm2 crevice type heater assembly and de-mineralized water. The test parameters include the gap size of 5 mm, and the surface orientation angles from the downward facing position (180o) to the vertical position (90o). The orientation angle affects the bubble layer and escape from the narrow gap. The CHF is less than that in a shorter channel, compared with the previous experiments having a heated length of 35 mmin the copper test section.

  10. Measuring and modeling near-surface reflected and emitted radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Walter-Shea, Elizabeth A.; Starks, Patrick J.; Vining, Roel C.; Hays, Cynthia J.; Mesarch, Mark A.

    1990-01-01

    Information is presented pertaining to the measurement and estimation of reflected and emitted components of the radiation balance. Information is included about reflectance and transmittance of solar radiation from and through the leaves of some grass and forb prairie species, bidirectional reflectance from a prairie canopy is discussed and measured and estimated fluxes are described of incoming and outgoing longwave and shortwave radiation. Results of the study showed only very small differences in reflectances and transmittances for the adaxial and abaxial surfaces of grass species in the visible and infrared wavebands, but some differences in the infrared wavebands were noted for the forbs. Reflectance from the prairie canopy changed as a function of solar and view zenith angles in the solar principal plane with definite asymmetry about nadir. The surface temperature of prairie canopies was found to vary by as much as 5 C depending on view zenith and azimuth position and on the solar azimuth. Aerodynamic temperature calculated from measured sensible heat fluxes ranged from 0 to 3 C higher than nadir-viewed temperatures. Models were developed to estimate incoming and reflected shortwave radiation from data collected with a Barnes Modular Multiband Radiometer. Several algorithms for estimating incoming longwave radiation were evaluated and compared to actual measures of that parameter. Net radiation was calculated using the estimated components of the shortwave radiation streams, determined from the algorithms developed, and from the longwave radiation streams provided by the Brunt, modified Deacon, and the Stefan-Boltzmann models. Estimates of net radiation were compared to measured values and found to be within the measurement error of the net radiometers used in the study.

  11. A radiative transport model for heating paints using high density plasma arc lamps

    NASA Astrophysics Data System (ADS)

    Sabau, Adrian S.; Duty, Chad E.; Dinwiddie, Ralph B.; Nichols, Mark; Blue, Craig A.; Ott, Ronald D.

    2009-04-01

    The energy distribution and temperature evolution within paintlike systems that are exposed to spectral radiant energy were studied. A complete set of material properties was derived and discussed. Infrared measurements were conducted to obtain experimental data for the temperature in the paint film. The heat flux due to the incident radiation from the plasma arc lamp was measured using a heat flux sensor with a very short response time. A radiative transport model based on spectral four-flux radiation transport equations has been developed for multilayered and semitransparent material systems. Comparisons between the computed and experimental results for temperature show that the energy transport model yields accurate results for a black painted substrate.

  12. Critical Heat Flux in Inclined Rectangular Narrow Gaps

    SciTech Connect

    Jeong J. Kim; Yong H. Kim; Seong J. Kim; Sang W. Noh; Kune Y. Suh; Joy L. Rempe; Fan-Bill Cheung; Sang B. Kim

    2004-06-01

    In light of the TMI-2 accident, in which the reactor vessel lower head survived the attack by molten core material, the in-vessel retention strategy was suggested to benefit from cooling the debris through a gap between the lower head and the core material. The GAMMA 1D (Gap Apparatus Mitigating Melt Attack One Dimensional) tests were conducted to investigate the critical heat flux (CHF) in narrow gaps with varying surface orientations. The CHF in an inclined gap, especially in case of the downward-facing narrow gap, is dictated by bubble behavior because the departing bubbles are squeezed. The orientation angle affects the bubble layer and escape of the bubbles from the narrow gap. The test parameters include gap sizes of 1, 2, 5 and 10 mm and the open periphery, and the orientation angles range from the fully downward-facing (180o) to the vertical (90o) position. The 15 ×35 mm copper test section was electrically heated by the thin film resistor on the back. The heater assembly was installed to the tip of the rotating arm in the heated water pool at the atmospheric pressure. The bubble behavior was photographed utilizing a high-speed camera through the Pyrex glass spacer. It was observed that the CHF decreased as the surface inclination angle increased and as the gap size decreased in most of the cases. However, the opposing results were obtained at certain surface orientations and gap sizes. Transition angles, at which the CHF changed in a rapid slope, were also detected, which is consistent with the existing literature. A semi-empirical CHF correlation was developed for the inclined narrow rectangular channels through dimensional analysis. The correlation provides with best-estimate CHF values for realistically assessing the thermal margin to failure of the lower head during a severe accident involving relocation of the core material.

  13. Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling

    SciTech Connect

    J. Yang; F. B. Cheung; J. L. Rempe; K. Y. Suh; S. B. Kim

    2005-07-01

    Four types of steady-state boiling experiments were conducted to investigate the efficacy of two distinctly different heat transfer enhancement methods for external reactor vessel cooling under severe accident conditions. One method involved the use of a thin vessel coating and the other involved the use of an enhanced insulation structure. By comparing the results obtained in the four types of experiments, the separate and integral effect of vessel coating and insulation structure were determined. Correlation equations were obtained for the nucleate boiling heat transfer and the critical heat flux. It was found that both enhancement methods were quite effective. Depending on the angular location, the local critical heat flux could be enhanced by 1.4 to 2.5 times using vessel coating alone whereas it could be enhanced by 1.8 to 3.0 times using an enhanced insulation structure alone. When both vessel coating and insulation structure were used simultaneously, the integral effect on the enhancement was found much less than the product of the two separate effects, indicating possible competing mechanisms (i.e., interference) between the two enhancement methods.

  14. Coupled conductive radiative heat transfer problem for two-layer slab

    NASA Astrophysics Data System (ADS)

    Elghazaly, A.

    2006-12-01

    The coupled conductive radiative transfer problem in two homogeneous layers slab of anisotropic scattering with specularly reflecting boundaries has been considered. A Galerkin-iterative technique is used to solve the coupled conductive radiative heat equations in integral forms for the two layers. Numerical results are obtained for the temperature, the conductive, radiative and the total heat fluxes for the two homogeneous layers with isotropic and anisotropic scattering. The calculations are also carried out for homogeneous plane parallel medium with anisotropic scattering which show good agreement with the published calculations.

  15. What is the mean seasonal cycle of surface heat flux in the equatorial Pacific?

    NASA Astrophysics Data System (ADS)

    Wang, Weimin; McPhaden, Michael J.

    2001-01-01

    The mean seasonal cycles of six state-of-the-art surface heat flux products (three based on widely available data and three based on numerical model reanalysis fields) are compared in the equatorial Pacific with heat fluxes computed from Tropical Atmosphere-Ocean (TAO) buoy data. Net surface heat flux and individual flux components derived from these products exhibit large deviations from TAO. We find that a significant contribution to these differences, which are often 50 W m-2 or more for net flux, is the use of systematically biased bulk variables in the computation of turbulent surface heat fluxes. We also find that for some products, compensating errors in bulk variables lead to fortuitous agreement with turbulent heat fluxes estimated from TAO. Finally, comparisons of TAO-derived fluxes with tuned and untuned heat flux estimates from the Comprehensive Ocean Atmosphere Data Set indicate better agreement with untuned fluxes, suggesting that commonly used ad hoc strategies to close the global ocean heat budget are not strictly valid.

  16. Heat Flux From the Endeavour Segment of the Juan de Fuca Ridge

    NASA Astrophysics Data System (ADS)

    Thompson, W. J.; McDuff, R. E.; Stahr, F. R.; Yoerger, D. R.; Jakuba, M.

    2005-12-01

    The very essence of a hydrothermal system is transfer of heat by a convecting fluid, yet the flux of heat remains a poorly known quantity. Past studies of heat flux consisted primarily of point measurements of temperature and fluid flow at individual vent sites and inventories of the neutrally buoyant plume above the field. In 2000 the Flow Mow project used the Autonomous Benthic Explorer (ABE) to determine heat flux from Main Endeavour Field (MEF) on the Juan de Fuca Ridge by intersecting the stems of rising buoyant plumes. ABE carries instruments to measure conductivity, temperature and depth, and a MAVS current meter to determine the vertical velocity of the fluid, after correcting for vehicle motion. Complementary work on horizontal fluxes suggests that the vertical flux measured by ABE includes both the primary high buoyancy focused "smoker" sources and also entrained diffuse flow. In 2004, ABE was again used to determine heat flux not only from MEF, but also from the other four fields in the Endeavour Segment RIDGE 2000 Integrated Study Site. In this four year interval the flux of heat from MEF has declined by approximately a factor of two. The High Rise vent field has the greatest heat flux, followed by MEF, then Mothra, Salty Dawg and Sasquatch (of order 500, 300, 100, 50 MW respectively; heat flux at Sasquatch was below detection).

  17. Energy Balance Comparison and Closure at a Moist Desert Playa: The Importance of Ground Heat Storage and Flux Estimation

    NASA Astrophysics Data System (ADS)

    Huntington, J. L.; Rajagopal, S.; Allen, R. G.; Mihevc, T. M.; Schumer, R.; Caldwell, T.; deBruin, H.

    2012-12-01

    Given increasing demands on finite water supplies in arid environments, the need for accurate estimates of sustainable groundwater resources is greater than ever. Many drainages in desert environments are considered hydrologically closed, where the entire groundwater recharge volume is consumed by evaporation and evapotranspiration along mountain front and valley floor areas. The amount of groundwater recharge that occurs in a given hydrographic basin is difficult to accurately estimate and is therefore commonly quantified by estimating the groundwater discharge using micrometeorological, and remote and in situ energy balance methods. Large playas are common features in desert environments, and the phreatic surface is often less than a few meters below land surface, creating nearly saturated conditions at the land surface through capillary rise. At first glance one might conclude that evaporation is high due to the nearly saturated surface, however, playa surfaces are commonly sealed by thin salt crusts, inhibiting evaporation. In this work we use eddy covariance, scintillometer, and four component radiometer measurements, and present a novel ground heat flux analysis using multiple ground heat flux plates and heat-pulse sensors to assess energy balance closure and uncertainties on estimated evaporation in Dixie Valley, Nevada. Results indicate that greater than 50 percent of daytime net radiation is partitioned into ground heat flux, and almost all of the available energy is portioned into sensible heat as determined from eddy covariance, and confirmed with scintillometer estimates. Utilizing heat pulse derived soil thermal properties and high density discrete soil temperature measurements allowed for estimation of soil heat storage and flux using a finite difference solution to the transient heat flow equation. This approach improved energy balance closure by 20 percent (achieving 90 percent closure) when compared to traditional calorimetric soil heat storage and flux estimates. We found that underestimation of energy balance closure occurs due to phase lags between 30 minute average available energy and turbulent fluxes, and is primarily due to inaccurate accounting of soil heat storage. Our work highlights the importance of accurate ground heat storage and flux estimation and provides insight into solving the surface energy imbalance problem in complex desert environments.

  18. Controls on plume heat flux and plume excess temperature and Shijie Zhong1

    E-print Network

    Zhong, Shijie

    constraints on the heat flux from the core and mantle internal heating rate. This study examined%. Subadiabatic temperature from our models with >50% internal heating rate ranges from 35 K to 170 K for CMB temperature of 3400°C. (5) Our results confirms that $70% internal heating rate for the mantle or Qcmb of $11

  19. Remote Measurement of Heat Flux from Power Plant Cooling Lakes

    SciTech Connect

    Garrett, A.; Kurzeja, R.; Villa-Aleman, E.; Bollinger, J.

    2013-01-01

    Laboratory experiments have demonstrated a correlation between the rate of heat loss q? from an experimental fluid to the air above and the standard deviation ? of the thermal variability in images of the fluid surface. These experimental results imply that q? can be derived directly from thermal imagery by computing ?. This paper analyses thermal imagery collected over two power plant cooling lakes to determine if the same relationship exists. Turbulent boundary layer theory predicts a linear relationship between q? and ? when both forced (wind driven) and free (buoyancy driven) convection are present. Datasets derived from ground- and helicopter-based imagery collections had correlation coefficients between ? and q? of 0.45 and 0.76, respectively. Values of q? computed from a function of ? and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q? (0.84 and 0.89). This research may be applicable to the problem of calculating losses of heat from the ocean to the atmosphere during high-latitude cold-air outbreaks because it does not require the information typically needed to compute sensible, evaporative, and thermal radiation energy losses to the atmosphere.

  20. Design of a steady-state heat flux probe for measurements in an induction-heated plasma flow [wind tunnels

    Microsoft Academic Search

    J. F. Lumens; B. Bottin; M. Carbonaro

    1997-01-01

    The design of a steady-state heat flux probe for high-enthalpy plasma flows was performed using empirical and numerical methods. A commercial code has been used to assess the local heat transfer inside the probe, at the stagnation point. The study led to the optimization of the cooling circuit geometry and to the quantification of the convective heat transfer coefficient. A

  1. The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a Tube with a Uniform Wall Heat Flux

    ERIC Educational Resources Information Center

    Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…

  2. Radiative heat transfer in nonlinear Kerr media

    NASA Astrophysics Data System (ADS)

    Khandekar, Chinmay; Pick, Adi; Johnson, Steven G.; Rodriguez, Alejandro W.

    2015-03-01

    We obtain a fluctuation-dissipation theorem describing thermal electromagnetic fluctuation effects in nonlinear media that we exploit in conjunction with a stochastic Langevin framework to study thermal radiation from Kerr (?(3 )) photonic cavities coupled to external environments at and out of equilibrium. We show that, in addition to thermal broadening due to two-photon absorption, the emissivity of such cavities can exhibit asymmetric, non-Lorentzian line shapes due to self-phase modulation. When the local temperature of the cavity is larger than that of the external bath, we find that the heat transfer into the bath exceeds the radiation from a corresponding linear blackbody at the same local temperature. We predict that these temperature-tunable thermal processes can be observed in practical, nanophotonic cavities operating at relatively small temperatures.

  3. Experimental and Numerical Characterization of High Heat Fluxes During Transient Blackbody Calibrations

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.; Horn, Thomas J.

    2008-01-01

    High heat fluxes are encountered in numerous applications, such as hypersonic vehicles in flight, fires, and engines, Calibration of heat flux gages may be performed in a dual cavity cylindrical blackbody resulting in a transient calibration environment. To characterize the transient heat fluxes. experiments were performed on a dual cavity cylindrical blackbody at nominal temperatures varying from 800 C to 1900 C in increments of 100 C. Based on experiments, the optimum heat flux sensor insertion location as measured from the center partition was determined. The pre-insertion steady state axial temperature profile is compared experimentally, numerically, and analytically. The effect of convection in the blackbody cavity during the insertion is calculated and found to be less than 2 per cent. Also, an empirical correlation for predicting the emissivity of the blackbody is included. Detailed transient thermal models have been developed to simulate the heat flux calibration process at two extreme fluxes. The high (1MW/sq m) and relatively low (70 kw/sq m) fluxes are reported in this article. The transient models show the effect of inserting a heat flux gage at room temperature on the thermal equilibrium of the blackbody at 1800 C and 800 C nominal temperatures, respectively. Also, heat flux sensor outputs are derived from computed sensor temperature distributions and compared to experimental results.

  4. Quantifying the heat flux regulation of metropolitan land use/land cover components by coupling remote sensing modeling with in situ measurement

    NASA Astrophysics Data System (ADS)

    Kuang, Wenhui; Dou, Yinyin; Zhang, Chi; Chi, Wenfeng; Liu, Ailin; Liu, Yue; Zhang, Renhua; Liu, Jiyuan

    2015-01-01

    the effects of urban land use/land cover with regard to surface radiation and heat flux regulation is important to ecological planning and heat stress mitigation. To retrieve the spatial pattern of heat fluxes in the Beijing metropolitan area, China, a remote sensing-based energy balance model was calibrated with synchronously measured energy fluxes including net radiation, latent heat flux (LE), and sensible heat flux (H). Our model calibration approach avoided the uncertainties due to subjective judgments in previous empirical parameterization methods. The land surface temperature (LST), H, and Bowen ratio (?) of Beijing were found to increase along the outskirt-suburban-urban gradient, with strong spatial variation. LST and H were negatively correlated with vegetation fraction cover (VFC). For example, the modern high-rise residential areas with relatively higher VFC had lower H and ? than the traditional low-rise residential areas. Our findings that indicate thermal dissipation through vegetation transpiration might play an important role in urban heat regulation. Notably, the thermal dissipating strength of vegetation (calculated as LE/VFC) declined exponentially with increased VFC. For the purpose of heat stress regulation, we recommend upgrading the traditional low-rise residential areas to modern high-rise residential areas and focusing urban greenery projects in areas whose VFC < 0.1, where the heat regulating service by urban vegetation could be twice as effective as in other places.

  5. The effect of void fraction correlation and heat flux assumption on refrigerant charge inventory predictions

    Microsoft Academic Search

    C. K. Rice

    1987-01-01

    Ten void fraction correlations and four heat flux assumptions are evaluated for their effect on refrigerant charge inventory predictions. Comparisons between mass inventory predictions are made for condensers and evaporators over representative heat pump operating ranges of saturation temperature, mass quality, and mass flux. The choice of void fraction model is found to have a major effect on refrigerant inventory

  6. Finite element based design optimization of WENDELSTEIN 7-X divertor components under high heat flux loading

    Microsoft Academic Search

    A. Plankensteiner; A. Leuprecht; B. Schedler; K.-H. Scheiber; H. Greuner

    2007-01-01

    In the divertor of the nuclear fusion experiment WENDELSTEIN 7-X (W7-X) plasma facing high heat flux target elements have to withstand severe loading conditions. The thermally induced mechanical stressing turns out to be most critical with respect to lifetime predictions of the target elements. Therefore, different design variants of those CFC flat tile armoured high heat flux components have been

  7. PUBLISHED VERSION Characterization of local heat fluxes around ICRF antennas on JET

    E-print Network

    PUBLISHED VERSION Characterization of local heat fluxes around ICRF antennas on JET A.-L. Campergue at : http://dx.doi.org/10.1063/1.4864538 #12;Characterization of local heat fluxes around ICRF antennas Antennas on JET AL. Camperguea , P. Jacquetb , V. Bobkovc , D. Milanesiod , I. Monakhovb , L. Colase , G

  8. Correlation of sauter mean diameter and critical heat flux for spray cooling of small surfaces

    Microsoft Academic Search

    Kurt A. Estes; Issam Mudawar

    1995-01-01

    Experiments were performed to understand better nucleate boiling heat transfer and critical heat flux (CHF) for full cone sprays. The effects of spray nozzle, volumetric flux, subcooling and working fluid were investigated. Dense sprays greatly reduced evaporation efficiency, and their boiling curves exhibited an unusually small increase in slope upon transition between the single phase and nucleate boiling regimes. Sauter

  9. Generalization of data on critical heat fluxes for flow swirled using a tape

    NASA Astrophysics Data System (ADS)

    Krug, A. F.; Kuzma-Kichta, Yu. A.; Komendantov, A. S.

    2010-03-01

    The available data on critical heat fluxes for boiling of subcooled and saturated liquid in tubes with twisted tape inserts are considered. Experimental data obtained by different researchers are generalized, and an equation for calculating critical heat fluxes for both smooth tubes and tubes with flow swirling by means of a tape is proposed.

  10. A novel approach to measuring heat flux in swimming animals Kate Willis*, Markus Horning

    E-print Network

    sensors (HFSs) to stationary or swimming animals in water that enables collection of heat flux data and the attachment mechanism on resultant heat flux. Effects were insulative and consistent across water temperatures lion; Thermoregulation; Weddell seal 1. Introduction Aquatic homeotherms of the order Pinnipedia (seals

  11. FIELD TESTS OF THE SOIL HEAT FLUX PLATE METHOD AND SOME ALTERNATIVES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat flux plates are commonly used to measure soil heat flux, a component of the surface energy balance. The plate method is simple and precise, but several previous studies have demonstrated the potential for relatively large errors. Here we present the results of in situ tests of the plate method,...

  12. Multi-Scale Sensible Heat Fluxes in the Suburban Environment from Large-Aperture Scintillometry and Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Ward, H. C.; Evans, J. G.; Grimmond, C. S. B.

    2014-07-01

    Sensible heat fluxes () are determined using scintillometry and eddy covariance over a suburban area. Two large-aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 , whilst the long path extends from the rural outskirts to the town centre and has a source area of around 5-10 . These large-scale heat fluxes are compared with local-scale eddy-covariance measurements. Clear seasonal trends are revealed by the long duration of this dataset and variability in monthly is related to the meteorological conditions. At shorter time scales the response of to solar radiation often gives rise to close agreement between the measurements, but during times of rapidly changing cloud cover spatial differences in the net radiation () coincide with greater differences between heat fluxes. For clear days lags , thus the ratio of to increases throughout the day. In summer the observed energy partitioning is related to the vegetation fraction through use of a footprint model. The results demonstrate the value of scintillometry for integrating surface heterogeneity and offer improved understanding of the influence of anthropogenic materials on surface-atmosphere interactions.

  13. Eddy Heat Fluxes across the Antarctic Circumpolar Current in Northern Drake Passage

    NASA Astrophysics Data System (ADS)

    Watts, D. R.; Tracey, K. L.; Donohue, K. A.; Chereskin, T. K.

    2012-12-01

    A local dynamics array of 24 current and pressure recording inverted echo sounders (CPIES) was deployed as part of the cDrake experiment for 4 years centered near 57S, 63W spanning a local maximum eddy kinetic energy region between the Subantarctic Front and Polar Front. The CPIES array provides full water-column estimates of velocity and temperature that were mapped to quantify and characterize eddy heat flux. Objective mapping was used to separate the total eddy heat fluxes into a nondivergent (rotational) part that recirculates around mean temperature-variance structures and a divergent part that accounts for the net eddy flux of heat across the Antarctic Circumpolar Current. The vertical shear, aligned along isotherms, is equivalent-barotropic and contributes only nondivergent heat flux. In contrast, the dynamically important component of eddy heat flux that transfers energy from the mean to the eddy field is driven by nearly depth-independent geostrophic currents that can cross the temperature front. Thus as in Bishop [2012], the coupling between the nearly depth-independent currents measured at the bottom and the temperatures in the baroclinic front accounts for all the divergent component of eddy heat flux. The separation reveals divergent heat fluxes that typically are oriented differently and have magnitudes a few times smaller than the total eddy heat fluxes. The mapped annual-mean eddy heat fluxes have a spatial structure that is relatively consistent from year-to-year and exhibit a region of strong poleward divergent fluxes just downstream of a prominent topographic ridge (Shackleton Fracture Zone). The fluxes peak in the upper water column at 100-200 kW m^{-2} near 200 m depth and decrease to 10-15% as large by 600 m depth, below which they are relatively constant and coherent to the sea floor. In these "hot spots" of eddy heat flux the vertically-integrated poleward divergent fluxes are 50 - 100 MW m^{-1}. The time series of daily heat flux show that the means arise as the sum of many short-period interactions between the deep barotropic eddies and the upper baroclinic jet, whose peak directions are mainly poleward and periodicities are typically 10-40 days. This explains why the time-averages of divergent heat flux are rather stable after only 1-2 years. Bishop, Stuart P. [2012] "The Role of Eddy Fluxes in the Kuroshio Extension at 144-148E," PhD Dissertation, University of Rhode Island.

  14. Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2003-01-01

    Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms. Recent investigations by Yaddanapyddi and Kim and Demiray and Kim have obtained time and space resolved heat transfer information at the bubble/heater interface under constant temperature conditions using a novel micro-heater array (10x10 array, each heater 100 microns on a side) that is semi-transparent and doubles as a measurement sensor. By using active feedback to maintain a state of constant temperature at the heater surface, they showed that the area of influence of bubbles generated in FC-72 was much smaller than predicted by standard models and that micro-conduction/micro-convection due to re-wetting dominated heat transfer effects. This study seeks to expand on the previous work by making time and space resolved measurements under bubbles nucleating on a micro-heater array operated under constant heat flux conditions. In the planned investigation, wall temperature measurements made under a single bubble nucleation site will be synchronized with high-speed video to allow analysis of the bubble energy removal from the wall.

  15. Design considerations for a thermophotovoltaic energy converter using heat pipe radiators

    SciTech Connect

    Ashcroft, J.; DePoy, D. [Lockheed Martin Corp., Schenectady, NY (United States)

    1997-06-01

    The purpose of this paper is to discuss concepts for using high temperature heat pipes to transport energy from a heat source to a thermophotovoltaic (TPV) converter. Within the converter, the condenser portion of each heat pipe acts as a photon radiator, providing a radiant flux to adjacent TPV cells, which in turn create electricity. Using heat pipes in this way could help to increase the power output and the power density of TPV systems. TPV systems with radiator temperatures in the range of 1,500 K are expected to produce as much as 3.6 W/cm{sup 3} of heat exchanger volume at an efficiency of 20% or greater. Four different arrangements of heat pipe-TPV energy converters are considered. Performance and sizing calculations for each of the concepts are presented. Finally, concerns with this concept and issues which remain to be considered are discussed.

  16. Sensible and latent heat flux estimates in Antarctica

    NASA Technical Reports Server (NTRS)

    Stearns, Charles R.; Weidner, George A.

    1993-01-01

    The assumption has been made that the net annual contribution of water by the processes of deposition and sublimation to the Antarctic Ice Sheet is zero. The U.S. Antarctic Program started installing reliable automatic weather stations on the Antarctic Continent in 1980. The initial units were equipped to measure wind speed, wind direction, air pressure, and air temperature. During the 1983-1984 field season in Antarctica, three units were installed that measured a vertical air temperature difference between the nominal heights of 0.5 m and 3.0 m and relative humidity at a nominal height of 3 m. The measurements of the vertical air temperature difference and the relative humidity are the minimum required to estimate the sensible and latent heat fluxes to the air, while not exceeding the available energy requirements for the weather stations. The estimates of the net annual sublimation and deposition on the Ross Ice Shelf amount to 20 to 80 percent of the annual accumulation. We conclude that the assumption that annual sublimation and deposition are zero is not valid under Antarctic conditions.

  17. Self-similar electron distribution, inverse bremsstrahlung, and heat flux inhibition in high-Z nonuniform plasmas

    NASA Astrophysics Data System (ADS)

    Uryupin, S. A.; Kato, S.; Mima, K.

    1995-08-01

    The self-similar distribution of electrons is found for a nonuniform underdense plasma that is heated by an intensive laser field. The distribution function is flat-topped for the low-energy electrons. And in the high-energy region, it has a well-pronounced high-energy tail. It is also found how the electron heat flux and the absorption coefficient depend upon both the ratios of electron mean-free path to the inhomogeneity scale of effective temperature and of the oscillation velocity to the thermal velocity. The actual shapes of electron energy distribution, the heat flux limitation, and the electromagnetic radiation absorption rate are given, both for a currentless plasma and for a plasma with a finite electric current.

  18. Partial moment entropy approximation to radiative heat transfer

    Microsoft Academic Search

    Martin. Frank; Bruno. Dubroca; Axel. Klar

    2006-01-01

    We extend the half moment entropy closure for the radiative heat transfer equations presented in Dubroca and Klar [B. Dubroca, A. Klar, Half moment closure for radiative transfer equations, J. Comput. Phys. 180 (2002) 584–596] and Turpault et al. [R. Turpault, M. Frank, B. Dubroca, A. Klar, Multigroup half space moment approximations to the radiative heat transfer equations, J. Comput.

  19. Radiative heat transfer in participating media — A review

    Microsoft Academic Search

    Subhash C Mishra; Manohar Prasad

    1998-01-01

    This paper presents an overview of various exact analytic and approximate numerical methods for the solution of radiative\\u000a heat transfer problems in participating media. Review of each method is followed by its strengths and limitations. Importance\\u000a of radiative heat transfer analysis and difficulties in the solution of radiative transfer problems have been emphasized.

  20. Analogous studies of simultaneous conductive and radiative heat transfer

    Microsoft Academic Search

    D W Stops; R E Pearson

    1966-01-01

    The process of radiative heat transfer is electrically simulated by using voltage-dependent resistors in conjunction with current transference circuits, and so an analogue is devised which shows how the overall uni-directional heat transfer by simultaneous conduction and radiation across a transparent gas space is a function of the positions of radiation shields which may be interposed between the bounding surfaces.

  1. Effects of broadened property fuels on radiant heat flux to gas turbine combustor liners

    NASA Technical Reports Server (NTRS)

    Haggard, J. B., Jr.

    1983-01-01

    The effects of fuel type, inlet air pressure, inlet air temperature, and fuel/air ratio on the combustor radiation were investigated. Combustor liner radiant heat flux measurements were made in the spectral region between 0.14 and 6.5 microns at three locations in a modified commercial aviation can combustor. Two fuels, Jet A and a heavier distillate research fuel called ERBS were used. The use of ERBS fuel as opposed to Jet A under similar operating conditions resulted in increased radiation to the combustor liner and hence increased backside liner temperature. This increased radiation resulted in liner temperature increases always less than 73 C. The increased radiation is shown by way of calculations to be the result of increased soot concentrations in the combustor. The increased liner temperatures indicated can substantially affect engine maintenance costs by reducing combustor liner life up to 1/3 because of the rapid decay in liner material properties when operated beyond their design conditions.

  2. Net Fluid and Heat Fluxes for the Hyporheic Zone of a Gravel Bar on the Willamette River, Oregon

    NASA Astrophysics Data System (ADS)

    Squeochs, G. M.; Haggerty, R.; Lancaster, S. T.

    2009-12-01

    Stream temperature is a vital component of riverine ecosystems; as higher stream temperatures can negatively impact biotic components (i.e., reduced dissolved oxygen due to increased temperatures severely stresses salmonid species). Like many rivers throughout the Western United States, the Willamette River, OR has become impaired by thermal pollution. Studies have indicated that hyporheic exchange in large gravel bed rivers may mitigate thermal pollution and garner greater attention as tools to buffer stream temperature fluxuations. While the thermodynamics of processes dominating heat transport in streams (incoming short-wave radiation, long-wave radiation, evaporation, bed conduction, groundwater inputs) have been extensively studied, hyporheic zone heat transfer has largely been neglected. Thus, we are presenting a physically based study to determine the net water and heat fluxes occurring in a hyporheic zone of a gravel bar. The gravel bar was instrumented with a piezometer network and fiber optic distributed temperature sensing system to monitor the spatial extent of the thermal flux over time. Using detailed topographic surveys of the gravel bar and the adjacent river channel, river shoreline elevations, and piezometer groundwater levels, a groundwater flow model was created via the GMS 6.0 interface to determine the flow geometry and hyporheic zone volume. The result of the flow model was then input into HYDRUS 3D modeling software to simulate the heat transport through the hyporheic zone. Results of gravel bar flow geometry and net hyporheic fluxes will be presented.

  3. Thin film heat flux sensor for Space Shuttle Main Engine turbine environment

    NASA Technical Reports Server (NTRS)

    Will, Herbert

    1991-01-01

    The Space Shuttle Main Engine (SSME) turbine environment stresses engine components to their design limits and beyond. The extremely high temperatures and rapid temperature cycling can easily cause parts to fail if they are not properly designed. Thin film heat flux sensors can provide heat loading information with almost no disturbance of gas flows or of the blade. These sensors can provide steady state and transient heat flux information. A thin film heat flux sensor is described which makes it easier to measure small temperature differences across very thin insulating layers.

  4. Evaporation on/in Capillary Structures of High Heat Flux Two-Phase Devices

    NASA Technical Reports Server (NTRS)

    Faghri, Amir; Khrustalev, Dmitry

    1996-01-01

    Two-phase devices (heat pipes, capillary pumped loops, loop heat pipes, and evaporators) have become recognized as key elements in thermal control systems of space platforms. Capillary and porous structures are necessary and widely used in these devices, especially in high heat flux and zero-g applications, to provide fluid transport and enhanced heat transfer during vaporization and condensation. However, some unexpected critical phenomena, such as dryout in long heat pipe evaporators and high thermal resistance of loop heat pipe evaporators with high heat fluxes, are possible and have been encountered in the use of two-phase devices in the low gravity environment. Therefore, a detailed fundamental investigation is proposed to better understand the fluid behavior in capillary-porous structures during vaporization at high heat fluxes. The present paper addresses some theoretical aspects of this investigation.

  5. A review of the criteria for people exposure to radiant heat flux from fires.

    PubMed

    Raj, Phani K

    2008-11-15

    The NFPA 59A Standard and the Federal Regulation, 49 CFR Part 193, stipulate a level of 5 kW/m(2) as the criterion for determining the hazard distance to people exposure from a LNG fire. Another regulation (24CFR, Section 51.204) while stipulating a lower exposure limit of 1.42 kW/m(2) provides administrative relief from the regulation if mitigation measures are provided. Several countries in Europe and the Far East have adopted both a specified heat flux value (generally, 5 kW/m(2)) as well as modified dose criteria for human exposure hazard calculation in risk assessments. In some cases, the regulations in Europe require the use of lower values for children and physically challenged persons. This paper reviews the available literature on the phenomenon of skin burn caused by radiant heat exposure. The associated thermal and spectral properties of human skin are reviewed. The basis for regulatory setting, of 5 kW/m(2) and other exposure criteria (as a part of hazard and risk calculations) for evaluating distances to hazards from the exposure of people to radiant heat effects of large fires, is evaluated. An example calculation is provided to show the extent of reduction in the hazard distance to specified radiant heat flux from a fire when the spectral reflection and absorption properties of skin are considered with and without the inclusion of the mitigating effects of clothing. The results indicate that hazard distances calculated including the reflective and band absorptive properties (in IR wavelength) of skin results in a reduction of between 30 and 50% in the hazard distances obtained with current methodology, which ignores these effects. Unfortunately, there are no test results, from full-scale human-exposure-to-IR radiation, with which these predictions can be compared. PMID:18035487

  6. Heat flux decay length during RF power operation in the Tore Supra tokamak

    NASA Astrophysics Data System (ADS)

    Corre, Y.; Gunn, J. P.; Firdaouss, M.; Carpentier, S.; Chantant, M.; Colas, L.; Ekedahl, A.; Gardarein, J.-L.; Lipa, M.; Loarer, T.; Courtois, X.; Guilhem, D.; Saint-Laurent, F.

    2014-01-01

    The upgrade of its ion cyclotron resonance (ICRH) and lower hybrid current drive (LHCD) heating systems makes the Tore Supra (TS) tokamak particularly well suited to address the physics and technology of high-power and steady-state plasma-surface interactions. High radio frequency (RF) heating powers have been successfully applied up to 12.2 MW coupled to the plasma, in which about 7.85 MW flows through the scrape-off layer. Thermal calculation based on thermography measurements gives the heat flux density distribution on the TS toroidal limiter located at the bottom of the machine. The target heat flux densities are divided by the incidence angle of the field lines with the surface and mapped to the magnetic flux surface to evaluate the power flowing in the scrape-off layer (SOL). The power profile shows a narrow component near the last closed flux surface and a wide component in the rest of the SOL. The narrow component is attributed to significant cross-field heat flux density around the plasma contact point, about 0.8% of the parallel heat flux density in the SOL, when incident angles are nearly tangential to the surface. The wide component is used to derive the experimental heat flux decay length (?q) and parallel heat flux in the SOL. The power widths are measured for a series of 1 MA/3.8 T discharges involving a scan of RF injected power 3.5 ? Ptot ? 12.2 MW. Independently of the heating power, we measured ?q,OMP = 14.5 ± 1.5 mm at the outer mid-plane and parallel heat flux in the SOL in the range 130\\le Q_{\\parallel}^{LCFS}\\le 490\\,MW\\,m^{-2} . TS values obtained with L-mode limiter plasmas are broader than those derived from L-mode divertor plasmas, confirming earlier results obtained with an ohmically heated plasma leaning on the inboard wall of TS.

  7. Analytical and experimental studies of heat pipe radiation cooling of hypersonic propulsion systems

    SciTech Connect

    Martin, R.A.; Merrigan, M.A.; Elder, M.G.; Sena, J.T.; Keddy, E.S. [Los Alamos National Lab., NM (United States); Silverstein, C.C. [CCS Associates, Bethel Park, PA (United States)

    1992-06-01

    Preliminary, research-oriented, analytical and experimental studies were completed to assess the feasibility of using high-temperature heat pipes to cool hypersonic engine components. This new approach involves using heat pipes to transport heat away from the combustor, nozzle, or inlet regions, and to reject it to the environment by thermal radiation from an external heat pipe nacelle. For propulsion systems using heat pipe radiation cooling (HPRC), it is possible to continue to use hydrocarbon fuels into the Mach 4 to Mach 6 speed range, thereby enhancing the economic attractiveness of commercial or military hypersonic flight. In the second-phase feasibility program recently completed, we found that heat loads produced by considering both convection and radiation heat transfer from the combustion gas can be handled with HPRC design modifications. The application of thermal insulation to ramburner and nozzle walls was also found to reduce the heat load by about one-half and to reduce peak HPRC system temperatures to below 2700{degrees}F. In addition, the operation of HPRC at cruise conditions of around Mach 4.5 and at an altitude of 90, 000 ft lowers peak hot section temperatures to around 2800{degrees}F. An HPRC heat pipe was successfully fabricated and tested at Mach 5 conditions of heat flux, heat load, and temperature. 24 refs.

  8. Analytical and experimental studies of heat pipe radiation cooling of hypersonic propulsion systems

    SciTech Connect

    Martin, R.A.; Merrigan, M.A.; Elder, M.G.; Sena, J.T.; Keddy, E.S. (Los Alamos National Lab., NM (United States)); Silverstein, C.C. (CCS Associates, Bethel Park, PA (United States))

    1992-01-01

    Preliminary, research-oriented, analytical and experimental studies were completed to assess the feasibility of using high-temperature heat pipes to cool hypersonic engine components. This new approach involves using heat pipes to transport heat away from the combustor, nozzle, or inlet regions, and to reject it to the environment by thermal radiation from an external heat pipe nacelle. For propulsion systems using heat pipe radiation cooling (HPRC), it is possible to continue to use hydrocarbon fuels into the Mach 4 to Mach 6 speed range, thereby enhancing the economic attractiveness of commercial or military hypersonic flight. In the second-phase feasibility program recently completed, we found that heat loads produced by considering both convection and radiation heat transfer from the combustion gas can be handled with HPRC design modifications. The application of thermal insulation to ramburner and nozzle walls was also found to reduce the heat load by about one-half and to reduce peak HPRC system temperatures to below 2700{degrees}F. In addition, the operation of HPRC at cruise conditions of around Mach 4.5 and at an altitude of 90, 000 ft lowers peak hot section temperatures to around 2800{degrees}F. An HPRC heat pipe was successfully fabricated and tested at Mach 5 conditions of heat flux, heat load, and temperature. 24 refs.

  9. Critical heat flux experiments in a heated rod bundle with upward crossflow of Freon 114

    SciTech Connect

    Symolon, P.D.; Moore, W.E.; Wolf, D.F.

    1997-02-01

    Critical heat flux (CHF) data were obtained for upward crossflow of R-114 in a heated staggered rod bundle. Data were obtained over a broad range of mass fluxes (135 to 1,221 kg/m{sup 2} sec), inlet subcooling (0 to 55 C), and qualities ({minus}0.42 to 0.92). The present work extends the available database to higher quality, inlet subcooling, and mass flux. The test section is 3.43 cm x 15.24 cm (1.35 in. x 6 in.) in cross section with a total length of 55.88 cm (22 inches) from the top of the inlet flow straightener to the perforated plate at the test section exit. The rod bundle has a triangular pitch with a diameter (D) of 0.635 cm (0.25 in), and a pitch to diameter (P/D) ratio of 1.5. The rod bundle has 165 rods with a 15.24 cm (6 in.) heated length arranged in 55 rows of three rods each. Unheated half rods were positioned on the walls of the test section to maintain the regular rod arrangement and prevent flow bypass along the gaps between the window and the first column of heated rods. A single instrumented heater was positioned five rows upstream from the bundle exit to determine CHF. The last three rows of rods in the bundle were unheated to prevent undetected dryout downstream of the CHF position. Temperature excursions due to CHF were sensed using four imbedded thermocouples (TC) in the heater rod. The four TC temperatures were continuously monitored on a strip chart recorder. The rod heat was gradually increased until CHF was detected. Overall, the data are in good agreement with the Jensen and Tang correlation in the range of application of this correlation. The local minima in CHF which occurs near zero quality is slightly lower in the present experiment than for the Jensen and Tang correlation. At high quality, CHF drops off more rapidly than the Jensen-Tang prediction. Data are now available to extend the existing correlations to higher quality, and higher inlet subcooling.

  10. Critical heat flux experiments in a heated rod bundle with upward crossflow of freon 114

    SciTech Connect

    Symolon, P.D.; Moore, W.E.; Wolf, D.F.

    1997-07-01

    Critical heat flux (CHF) data were obtained for upward crossflow of R-114 in a heated staggered rod bundle. Data were obtained over a broad range of mass fluxes (135 to 1,221 kg/m{sup 2}sec), inlet subcooling (0 to 55 C), and qualities ({minus}0.42 to 0.92). The present work extends the available database to higher quality, inlet subcooling, and mass flux. The test section is 3.43 cm x 15.24 cm (1.35in. x 6in.) in cross section with a total length of 55.88 cm (22in.) from the top of the inlet flow straightener to the perforated plate at the test section exit. The rod bundle has a triangular pitch with a diameter (D) of 0.635 cm (0.25in.), and a pitch to diameter (P/D) ratio of 1.5. The rod bundle has 165 rods with a 15.24 cm (6in.) heated length arranged in 55 rows of three rods each. Unheated half rods were positioned on the walls of the test section to maintain the regular rod arrangement and prevent flow bypass along the gaps between the window and the first column of heated rods. A single instrumented heater was positioned five rows upstream from the bundle exit to determine CHF. The last three rows of rods in the bundle were unheated to prevent undetected dryout downstream of the CHF position. Temperature excursions due to CHF were sensed using four imbedded thermocouples (TC) in the heater rod. The four TC temperatures were continuously monitored on a strip chart recorder. The rod heat was gradually increased until CHF was detected. Overall, the data are in good agreement with the Jensen and Tang correlation in the range of application of this correlation. The local minima in CHF which occurs near zero quality is slightly lower in the present experiment than for the Jensen and Tang correlation. At high quality, CHF drops off more rapidly than the Jensen-Tang prediction. Data are now available to extend the existing correlations to higher quality, and higher inlet subcooling.

  11. Plasmon enhanced near-field radiative heat transfer for graphene covered dielectrics

    NASA Astrophysics Data System (ADS)

    Svetovoy, V. B.; van Zwol, P. J.; Chevrier, J.

    2012-04-01

    It is shown that a graphene layer on top of a dielectric slab can dramatically influence the ability of this dielectric for radiative heat exchange turning a poor heat emitter/absorber into a good one and vice versa. The effect of graphene is related to thermally excited plasmons. The frequency of these resonances lies in the terahertz region and can be tuned by varying the Fermi level through doping or gating. It makes possible the fast modulation of the heat flux by electrical means, which opens up new possibilities for very fast manipulations with the heat flux. The heat transfer between two dielectrics covered with graphene can be larger than that between best known materials and becomes especially efficient below the room temperature.

  12. Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Miller, Robert A.

    2004-01-01

    The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

  13. Steady-State and Frequency Response of a Thin-Film Heat Flux Gauge

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Bhatt, Hemanshu D.; Cho, Chistopher S.

    1997-01-01

    A new and simpler design of thin-film heat flux gauge has been developed for use In high-heat-flux environments. Heat flux gauges of the same design were fabricated on three different substrates and tested. The heat flux gauge comprises a thermopile and a thermocouple junction, which measures the surface temperature. The thermopile has 40 pairs of S-type thermocouples and is covered by two thermal resistance layers. Calibration and testing of these gauges were first carried out in an arc-lamp calibration facility. Sensitivity of the gauge was discussed in terms of the relative conductivity and surface temperature. The heat flux calculated from the gauge output was In good agreement with the precalibrated standard sensor. The steady-state and the transient response characteristics of the heat flux gauge were also investigated using a carbon dioxide pulse laser as a heat source. The dynamic frequency response was evaluated in terms of the nondimensional amplitude ratio with respect to the frequency spectrum of a chopped laser bcam. The frequency response of the gauge was determined to be about 3 kHz. The temperature profiles in the thin-film heat flux gauge were obtained numerically in steady-state conditions using FLUENT and compared with the experimental results.

  14. Modulation and amplification of radiative far field heat transfer : towards a simple radiative thermal transistor

    E-print Network

    Joulain, Karl; Drevillon, Jeremie; Ben-Abdallah, Philippe

    2015-01-01

    We show in this article that phase change materials (PCM) exhibiting a phase transition between a dielectric state and a metallic state are good candidates to perform modulation as well as amplification of radiative thermal flux. We propose a simple situation in plane parallel geometry where a so-called radiative thermal transistor could be achieved. In this configuration, we put a PCM between two blackbodies at different temperatures. We show that the transistor effect can be achieved easily when this material has its critical temperature between the two blackbody temperatures. We also see, that the more the material is reflective in the metallic state, the more switching effect is realized whereas the more PCM transition is stiff in temperature, the more thermal amplification is high. We finally take the example of VO2 that exhibits an insulator-metallic transition at 68{\\textdegree}C. We show that a demonstrator of a radiative transistor could easily be achieved in view of the heat flux levels predicted. F...

  15. Estimation of the average surface heat flux over an inhomogeneous terrain from the vertical velocity variance

    NASA Technical Reports Server (NTRS)

    Eilts, M. D.; Sundara-Rajan, A.; Evans, R. J.

    1987-01-01

    An indirect method of estimating the surface heat flux from observations of vertical velocity variance at the lower mid-levels of the convective atmospheric boundary layer is described. Comparison of surface heat flux estimates with those from boundary-layer heating rates is good, and this method seems to be especially suitable for inhomogeneous terrain for which the surface-layer profile method cannot be used.

  16. Distribution of the heat and current fluxes in gas tungsten arcs

    Microsoft Academic Search

    N. S. Tsai; T. W. Eagar

    1985-01-01

    The distribution of heat flux on a water-cooled copper anode as a function of welding process parameters has been determined\\u000a experimentally following an experimental technique developed previously. The results indicate that arc length is the primary\\u000a variable governing heat distribution and that the distribution is closely approximated by a gaussian function. The half width\\u000a of the heat flux is defined

  17. Subcooled flow boiling heat transfer and critical heat flux in water-based nanofluids at low pressure

    E-print Network

    Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology

    2009-01-01

    A nanofluid is a colloidal suspension of nano-scale particles in water, or other base fluids. Previous pool boiling studies have shown that nanofluids can improve the critical heat flux (CHF) by as much as 200%. In this ...

  18. Heat transfer by natural convection, conduction and radiation in an inclined square enclosure bounded with a solid wall

    Microsoft Academic Search

    H. F. Nouanegue; A. Muftuoglu; E. Bilgen

    2009-01-01

    We study in this paper conjugate heat transfer by natural convection, conduction and radiation in an inclined square enclosure bounded by a solid wall with its outer boundary at constant temperature while the opposing active wall is with a constant heat flux. We solved two-dimensional coupled equations of conservation of mass, momentum and energy, with the Boussinesq approximation using finite

  19. Heat pump augmented radiators for spacecraft thermal management

    SciTech Connect

    Merrigan, M.A.; Reid, R.S.

    1988-01-01

    Because future space missions will require heat rejection subsystems having megawatt capacity, the development of lightweight heat rejection techniques is desirable. Closed systems for waste heat rejection in space are radiative and their capacity is proportional to the fourth power of absolute temperature. Reductions in the surface area and therefore, in the mass of a space radiator are possible by increasing the heat rejection temperature above the temperature of the thermal source. One proposed method of increasing the heat rejection temperature uses a heat pump powered by a cyclic heat engine operating at a temperature above the waste heat source. This heat pumping technique reduces the required direct radiator surface area, but it introduces mass penalties associated with its power supply and its heat rejection system. The use of a heat pump augmented heat rejection system will generally be practical if it reduces the total radiator mass requirement over a suitable baseline design. The mass penalties of the heat pump augmented radiator over a baseline (a flat plate radiator) are considered in this analysis. 2 refs., 8 figs., 1 tab.

  20. TRANSIENT RADIATION HEAT TRANSFER WITHIN A NONGRAY NONISOTHERMAL ABSORBING-EMITTING-SCATTERING SUSPENSION OF REACTING PARTICLES UNDERGOING SHRINKAGE

    Microsoft Academic Search

    W. Lipinski; A. ZGraggen; A. Steinfeld

    2005-01-01

    A nonisothermal, nongray, absorbing, emitting, and anisotropically scattering suspension of reacting particles exposed to concentrated thermal radiation is considered. The steam gasification of coal is selected as the model thermochemical reaction. The unsteady energy equation that couples the radiative heat flux with the chemical kinetics is solved by means of a numerical model that incorporates Monte Carlo ray tracing, the

  1. Transient Radiation Heat Transfer Within a Nongray Nonisothermal Absorbing-Emitting Suspension of Reacting Particles Undergoing Shrinkage

    Microsoft Academic Search

    W. Lipinski; A. Z'graggen; A. Steinfeld

    2005-01-01

    A nonisothermal, nongray, absorbing, emitting, and anisotropically scattering suspension of reacting particles exposed to concentrated thermal radiation is considered. The steam gasi- fication of coal is selected as the model thermochemical reaction. The unsteady energy equation that couples the radiative heat flux with the chemical kinetics is solved by means of a numerical model that incorporates Monte Carlo ray tracing,

  2. The first critical heat-flux density of kerosene in stepwise and steady-state releases of heat

    NASA Astrophysics Data System (ADS)

    Obukhov, D. S.

    2006-11-01

    Experimental results on determination of stationary and nonstationary first critical densities of heat fluxes for the TS-1 hydrocarbon fuel are presented. As a consequence of the investigations carried out in a wide range of subcoolings and pressures, it has been established that for kerosene, just as for water, hydrogen, and helium, the first nonstationary critical heat-flux density qcr.1n coincides with the stationary one qcr1.

  3. Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Schunk, Richard G.

    2011-01-01

    An active thermal control system architecture has been modified to include a regenerative heat exchanger (regenerator) inboard of the radiator. Rather than using a radiator bypass valve a regenerative heat exchanger is placed inboard of the radiators. A regenerator cold side bypass valve is used to set the return temperature. During operation, the regenerator bypass flow is varied, mixing cold radiator return fluid and warm regenerator outlet fluid to maintain the system setpoint. At the lowest heat load for stable operation, the bypass flow is closed off, sending all of the flow through the regenerator. This lowers the radiator inlet temperature well below the system set-point while maintaining full flow through the radiators. By using a regenerator bypass flow control to maintain system setpoint, the required minimum heat load to avoid radiator freezing can be reduced by more than half compared to a radiator bypass system.

  4. Long-term energy flux and radiation balance observations over Lake Ngoring, Tibetan Plateau

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    It remains unclear what are the characteristics of the surface energy budget and the radiation balance over the lake at high altitudes. Here we report a nearly two-year ice-free time measurement (2011-2012) of energy flux and radiation balance using the eddy covariance method over Lake Ngoring, Tibetan Plateau. A persistent unstable atmospheric boundary layer was maintained over the lake, caused by a higher water surface temperature compared with the overlying atmosphere. As a result, the positive sensible heat (H) and latent heat (LE) fluxes almost lasted throughout the entire observation period. The heat storage period of the lake could last until September, and the strongest heating occurred in October from the lake to the atmosphere. Compared with the subtropical lake, Bowen ratios were larger in Lake Ngoring, caused by a large temperature difference and a small specific humidity difference between the water surface and the overlying air. The patterns of H versus the atmospheric stability differed from those of LE. H was large under unstable stratification conditions and significantly decreased in the nearly neutral and stable atmospheric stratification. By contrast, the large LE concentrated in the weak unstable to the nearly neutral atmospheric stratification, and clearly declined with increased atmospheric instability. Overall, the vertical specific humidity difference contributed more to LE than the wind speed. As regards H, the major contributors varied with the atmospheric stability. The intrusion of dry, cold air with strong wind could result in significant increases in H and LE (approximately 2.0-4.5 times as much as those of normal days); during this period, the stored energy in water dramatically decreased and even could provide 70% of the energy for H and LE.

  5. Elastic thickness and heat flux estimates for the uranian satellite Ariel

    NASA Astrophysics Data System (ADS)

    Peterson, G.; Nimmo, F.; Schenk, P.

    2015-04-01

    The surface of Ariel, an icy satellite orbiting Uranus, shows extensional tectonic features suggesting an episode of endogenic heating in the satellite's past. Using topography derived from stereo-photoclinometry, we identified flexural uplift at a rift zone suggesting elastic thickness values in the range 3.8-4.4 km. We estimate the temperature at the base of the lithosphere to be in the range 99-146 K, depending on the strain rate assumed, with corresponding heat fluxes of 28-92 mW/m2. Neither tidal heating, assuming Ariel's current eccentricity, nor radiogenic heat production from the silicate core are enough to cause the inferred heat fluxes. None of three proposed ancient mean-motion resonances produce equilibrium tidal heating values in excess of 4.3 mW/m2. Thus, the origin of the inferred high heat fluxes is currently mysterious.

  6. Estimation of Surface Heat Flux and Surface Temperature during Inverse Heat Conduction under Varying Spray Parameters and Sample Initial Temperature

    PubMed Central

    Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong

    2014-01-01

    An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27?mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2?MPa to 1.8?MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024?MW/m2 was estimated for a thickness of 8.5?mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8?MPa. PMID:24977219

  7. Estimation of surface heat flux and surface temperature during inverse heat conduction under varying spray parameters and sample initial temperature.

    PubMed

    Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong; Zubair, Muhammad

    2014-01-01

    An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m(2) was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa. PMID:24977219

  8. Turbulent Heat Fluxes in Urban Areas: Observations and a Local-Scale Urban Meteorological Parameterization Scheme (LUMPS).

    NASA Astrophysics Data System (ADS)

    Grimmond, C. S. B.; Oke, T. R.

    2002-07-01

    A linked set of simple equations specifically designed to calculate heat fluxes for the urban environment is presented. This local-scale urban meteorological parameterization scheme (LUMPS), which has similarities to the hybrid plume dispersion model (HPDM) scheme, requires only standard meteorological observations and basic knowledge of surface cover. LUMPS is driven by net all-wave radiation. Heat storage by the urban fabric is parameterized from net all-wave radiation and surface cover information using the objective hysteresis model (OHM). The turbulent sensible and latent heat fluxes are calculated using the available energy and are partitioned using the approach of de Bruin and Holtslag, and Holtslag and van Ulden. A new scheme to define the Holtslag and van Ulden and parameters for urban environments is presented; is empirically related to the plan fraction of the surface that is vegetated or irrigated, and a new urban value of captures the observed delay in reversal of the sign of the sensible heat flux in the evening. LUMPS is evaluated using field observations collected in seven North American cities (Mexico City, Mexico; Miami, Florida; Tucson, Arizona; Los Angeles and Sacramento, California; Vancouver, British Columbia, Canada; and Chicago, Illinois). Performance is shown to be better than that for the standard HPDM preprocessor scheme. Most improvement derives from the inclusion of the OHM for the storage heat flux and the revised coefficient. The scheme is expected to have broad utility in models used to calculate air pollution dispersion and the mixing depths of urban areas or to provide surface forcing for mesoscale models of urban regions.

  9. A Flux Tube Tectonics Model for Solar Coronal Heating Driven by the Magnetic Carpet.

    E-print Network

    Priest, Eric

    A Flux Tube Tectonics Model for Solar Coronal Heating Driven by the Magnetic Carpet. Eric R. Priest heating. The dissipation of energy along sharp boundaries we call, by analogy with geophysi- cal plate tectonics, the tectonics model of coronal heating. Similar to the case on Earth, the relative motions

  10. Depth of faulting on Mercury: Implications for heat flux and crustal and effective elastic thickness

    Microsoft Academic Search

    F. Nimmo; T. R. Watters

    2004-01-01

    Topographic profiles across a lobate fault scarp on Mercury have been used to constrain the depth of faulting to 30–40 km. Here we use this depth to place constraints on the crustal thickness and heat flow into the base of the crust. With no crustal heat production, the mantle heat flux on Mercury at the time of scarp formation was

  11. Depth of faulting on Mercury: Implications for heat flux and crustal and effective elastic thickness

    Microsoft Academic Search

    F. Nimmo; T. R. Watters

    2004-01-01

    Topographic profiles across a lobate fault scarp on Mercury have been used to constrain the depth of faulting to 30-40 km. Here we use this depth to place constraints on the crustal thickness and heat flow into the base of the crust. With no crustal heat production, the mantle heat flux on Mercury at the time of scarp formation was

  12. Solar wind stream interaction - Electron temperature and heat flux rise in the low-speed stream

    Microsoft Academic Search

    P. Alexander; S. Duhau

    1990-01-01

    The strong compression produced in the two-stream interaction regions in the solar wind is a local source of heating. The study of the distribution of that energy between heat and internal energy provides valuable information about transport processes. In the present work, the electron heat flux and temperature rise in the compression produced within the low-speed portion of the interaction

  13. Heat fluxes across the Antarctic Circumpolar Current in Drake Passage: Mean flow and eddy contributions

    NASA Astrophysics Data System (ADS)

    Ferrari, Ramiro; Provost, Christine; Park, Young-Hyang; Sennéchael, Nathalie; Koenig, Zoé; Sekma, Hela; Garric, Gilles; Bourdallé-Badie, Romain

    2014-09-01

    In contrast to a long-standing belief, observations in the Antarctic Circumpolar Current (ACC) show that mean velocity vectors rotate with depth, thus suggesting a possible importance of the time-mean flow for the local poleward heat transport. The respective contributions of the eddy and mean flows to the heat flux across the ACC in Drake Passage (DP) are investigated using recently acquired and historical time series of velocity and temperature from a total of 24 current meter moorings and outputs of a high-resolution (1/12°) model with realistic topography. Only 11 out of the 24 depth-integrated eddy heat flux estimates are found to be significant, and they are poleward. Model depth-integrated eddy heat fluxes have similar signs and amplitudes as the in situ estimates at the mooring sites. They are mostly poleward or nonsignificant, with amplitude decreasing to the south. The cross-stream temperature fluxes caused by the mean flow at the moorings have a sign that varies with location and corresponds to the opposite of the vertical velocity estimates. The depth-integrated temperature fluxes due to the mean flow in the model exhibit small spatial scales and are of opposite sign to the bottom vertical velocities. This suggests that the rotation of the mean velocity vectors with depth is mainly due to bottom topography. The rough hilly topography in DP likely promotes the small-scale vertical velocities and temperature fluxes. Eddy heat fluxes and cross-stream temperature fluxes are integrated over mass-balanced regions defined by the model transport streamlines. The contribution of the mean flow to the ocean heat fluxes across the Southern ACC Front in DP (covering about 4% of the circumpolar longitudes) is about four times as large as the eddy heat flux contribution and the sum of the two represent on the order of 10% of the heat loss to the atmosphere south of 60°S.

  14. New technique for the fabrication of miniature thin film heat flux gauges

    NASA Astrophysics Data System (ADS)

    Collins, Matthew; Chana, Kam; Povey, Thomas

    2015-02-01

    This paper details the improvements made to the design and fabrication of thin-film heat flux gauges at Oxford. These improvements have been driven by the desire to improve measurement accuracy and resolution in short duration wind-tunnel experiments. A thin-film heat flux gauge (TFHFG) measures heat flux by recording the temperature history of thin film resistive temperature sensors sputtered onto an insulating substrate. The heat flux can then be calculated using Fourier’s law of heat conduction. A new fabrication process utilising technology from the manufacture of flexible printed circuit boards is outlined, which enables the production of significantly smaller and more robust gauges than those previously used.

  15. Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

    2013-01-01

    Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

  16. E × B shear pattern formation by radial propagation of heat flux waves

    SciTech Connect

    Kosuga, Y., E-mail: kosuga@riam.kyushu-u.ac.jp [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); IAS and RIAM, Kyushu University, Fukuoka (Japan); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of) [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CASS and CMTFO, University of California, San Diego, California 92093 (United States); Dif-Pradalier, G. [CEA, IRFM, Paul-lez-Durance Cedex (France)] [CEA, IRFM, Paul-lez-Durance Cedex (France); Gürcan, Ö. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)] [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)

    2014-05-15

    A novel theory to describe the formation of E×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E×B staircase is discussed.

  17. E × B shear pattern formation by radial propagation of heat flux wavesa)

    NASA Astrophysics Data System (ADS)

    Kosuga, Y.; Diamond, P. H.; Dif-Pradalier, G.; Gürcan, Ã.-. D.

    2014-05-01

    A novel theory to describe the formation of E ×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E ×B staircase is discussed.

  18. A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents Seas

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa; Cavalieri, Donald J.

    1989-01-01

    This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Numerical Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations provides particularly good data coverage in this region for a comparison with the gridded Navy winds and air temperatures. The standard errors of estimate between the Navy and FGGE IIb winds and air temperatures are 3.6 m/s and 2.5 C, respectively. The computations for the latent and sensible heat fluxes are based on bulk formulas with the same constant heat exchange coefficient of 0.0015. The results show extremely strong wintertime heat fluxes in the northern Greenland Sea and especially in the Barents Sea in contrast to previous studies.

  19. Extended hydrodynamic theory of the peak and minimum pool boiling heat fluxes

    NASA Technical Reports Server (NTRS)

    Linehard, J. H.; Dhir, V. K.

    1973-01-01

    The hydrodynamic theory of the extreme pool boiling heat fluxes is expanded to embrace a variety of problems that have not previously been analyzed. These problems include the prediction of the peak heat flux on a variety of finite heaters, the influence of viscosity on the Taylor and Helmoltz instability mechanisms with application to film boiling and to the peak heat flux in viscous liquids, the formalization of the analogy between high-current-density electrolysis and boiling, and the description of boiling in the low-gravity limit. The predictions are verified with a large number of new data.

  20. Electron heat flux dropouts in the solar wind - Evidence for interplanetary magnetic field reconnection?

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.; Bame, S. J.; Luhmann, J. G.; Smith, E. J.

    1989-01-01

    An examination of ISEE-3 data from 1978 reveal 25 electron heat flux dropout events ranging in duration from 20 min to over 11 hours. The heat flux dropouts are found to occur in association with high plasma densities, low plasma velocities, low ion and electron temperatures, and low magnetic field magnitudes. It is suggested that the heat flux dropout intervals may indicate that the spacecraft is sampling plasma regimes which are magnetically disconnected from the sun and instead are connected to the outer heliosphere at both ends.

  1. High-heat flux testing of an interceptive device for an intense proton beam

    SciTech Connect

    Valdiviez, R. (Robert); Martinez, F. A. (Felix A.); Rendon, Armando M.; Nguyen, D. C. (Dinh C.); Earley, L. M. (Lawrence M.); La Fave, R. P. (Richard P.)

    2001-04-01

    An interceptive device referred to here as a scraper has been designed and tested for use in a diagnostic device [1]. The scraper will be used to probe a proton beam in order to detect the formation of beam halo [2]. Probing the proton beam exposes the scraper to high heat fluxes on the order of 610 kW/cm{sup 2}. The high-heat flux exposure is cyclic since the beam is probed while in pulsed mode. In order to test the design repetitive high-heat flux testing has been performed on a prototype design of the scraper. This paper describes the design, analysis, and testing of the scraper.

  2. Pyrotechnic hazards classification and evaluation program test report. Heat flux study of deflagrating pyrotechnic munitions

    NASA Technical Reports Server (NTRS)

    Fassnacht, P. O.

    1971-01-01

    A heat flux study of deflagrating pyrotechnic munitions is presented. Three tests were authorized to investigate whether heat flux measurements may be used as effective hazards evaluation criteria to determine safe quantity distances for pyrotechnics. A passive sensor study was conducted simultaneously to investigate their usefulness in recording events and conditions. It was concluded that heat flux measurements can effectively be used to evaluate hazards criteria and that passive sensors are an inexpensive tool to record certain events in the vicinity of deflagrating pyrotechnic stacks.

  3. Parameterization of surface heat fluxes above a forest with satellite thermal sensing

    NASA Technical Reports Server (NTRS)

    Brutsaert, Wilfried; Hsu, A. Y.; Schmugge, Thomas J.

    1992-01-01

    The authors discuss the feasibility of determining the surface flux of sensible heat from forests with surface temperatures measured by satellites together with temperature soundings in the unstable atmospheric boundary layer (ABL). The latent heat flux is derived from the sensible heat flux by means of the energy budget. The study makes use of data collected during HAPEX-MOBILHY (Hydrologic Atmospheric Pilot Experiment-Modelization du Bilan Hydrique). The methodology is based on turbulence similarity for the unstable ABL. The surface temperature data were derived from measurements by the advanced very high resolution radiometer (AVHRR) aboard the NOAA-9 satellite; the atmospheric profiles were obtained by radiosondes.

  4. Heat flux as a source of ion-acoustic oscillations in the transition region of the solar atmosphere

    NASA Astrophysics Data System (ADS)

    Bespalov, P. A.; Savina, O. N.

    2009-05-01

    Based on model calculations, we show that ion-acoustic oscillations can be excited by heat fluxes in a plasma. We discuss the probable effect of ion-acoustic oscillations on the formation of temperature gradients at critical heat fluxes. The local critical heat flux in the transition region of the solar atmosphere is close to the well-known experimental heat flux from the corona into the chromosphere.

  5. Spectrally enhancing near-field radiative heat transfer by exciting magnetic polariton in SiC gratings

    E-print Network

    Yang, Yue

    2015-01-01

    In the present work, we theoretically demonstrate, for the first time, that near field radiative transport between 1D periodic grating microstructures separated by subwavelength vacuum gaps can be significantly enhanced by exciting magnetic resonance or polariton. Fluctuational electrodynamics that incorporates scattering matrix theory with rigorous coupled wave analysis is employed to exactly calculate the near field radiative heat flux between two SiC gratings. Besides the well known coupled surface phonon polaritons (SPhP), an additional spectral radiative heat flux peak, which is due to magnetic polariton, is found within the phonon absorption band of SiC. The mechanisms, behaviors and interplays between magnetic polariton, coupled SPhP, single interface SPhP, and Wood's anomaly in the near field radiative transport are elucidated in detail. The findings will open up a new way to control near field radiative heat transfer by magnetic resonance with micro or nanostructured metamaterials.

  6. Radiative Heat Conduction and the Magnetorotational Instability

    E-print Network

    Rafael A. Araya-Gochez; Ethan Vishniac

    2003-11-21

    A photon or neutrino gas--semi-contained by a baryonic species through scattering--comprises a rather peculiar MHD fluid where the magnetic field is truly frozen only to the co-moving volume associated with the mass density. Although radiative diffusion precludes an adiabatic treatment of compressive perturbations, we show that the energy equation may be cast in "quasi-adiabatic" form for exponentially growing non-propagating wave modes. Defining a generalized quasi-adiabatic index leads to a relatively straightforward dispersion relation for non-axisymmetric magnetorotational modes in the horizontal regime when an accretion disk has comparable stress contributions from diffusive and non-diffusive particle species. This analysis is generally applicable to optically thick, neutrino-cooled disks since the pressure contributions from photons, pairs and neutrinos, all have the same temperature dependence whereas only the neutrino component has radiative heat conduction properties on the time and length scales of the instability. We discuss the energy deposition process and the temporal and spatial properties of the ensuing turbulent disk structure on the basis of the derived dispersion relation.

  7. The effects of orientation angle, subcooling, heat flux, mass flux, and pressure on bubble growth and detachment in subcooled flow boiling

    E-print Network

    Sugrue, Rosemary M

    2012-01-01

    The effects of orientation angle, subcooling, heat flux, mass flux, and pressure on bubble growth and detachment in subcooled flow boiling were studied using a high-speed video camera in conjunction with a two-phase flow ...

  8. Multiphase Science and Technology, Vol. 13, No. 3, pp. 207-232, 2001 CRITICAL HEAT FLUX IN SUBCOOLED FLOW

    E-print Network

    Kandlikar, Satish

    controlled systems) followed by a drastic rise in wall temperature, or considerable degradation in heat fluxMultiphase Science and Technology, Vol. 13, No. 3, pp. 207-232, 2001 CRITICAL HEAT FLUX Abstract. Critical Heat Flux, or CHF, is an important condition that defines the upper limit of safe

  9. Thermal barrier coatings (TBC's) for high heat flux thrust chambers

    NASA Astrophysics Data System (ADS)

    Bradley, Christopher M.

    The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot-section components has become critical, but at the same time the service conditions have put our best alloy systems to their limits. As a result, implementation of cooling holes and thermal barrier coatings are new advances in hot-section technologies now looked at for modifications to reach higher temperature applications. Current thermal barrier coatings used in today's turbine applications is known as 8%yttria-stabilized zirconia (YSZ) and there are no coatings for current thrust chambers. Current research is looking at the applicability of 8%yttria-stabilized hafnia (YSH) for turbine applications and the implementation of 8%YSZ onto thrust chambers. This study intends to determine if the use of thermal barrier coatings are applicable for high heat flux thrust chambers using industrial YSZ will be advantageous for improvements in efficiency, thrust and longer service life by allowing the thrust chambers to be used more than once.

  10. Critical heat flux and boiling heat transfer to water in a 3-mm-diameter horizontal tube.

    SciTech Connect

    Yu, W.; Wambsganss, M. W.; Hull, J. R.; France, D. M.

    2000-12-04

    Boiling of the coolant in an engine, by design or by circumstance, is limited by the critical heat flux phenomenon. As a first step in providing relevant engine design information, this study experimentally addressed both rate of boiling heat transfer and conditions at the critical point of water in a horizontal tube of 2.98 mm inside diameter and 0.9144 m heated length. Experiments were performed at system pressure of 203 kPa, mass fluxes in range of 50 to 200 kg/m{sup z}s, and inlet temperatures in range of ambient to 80 C. Experimental results and comparisons with predictive correlations are presented.

  11. Divertor Heat Flux Mitigation in High-Performance H-mode Discharges in the National Spherical Torus Experiment.

    SciTech Connect

    Soukhanovskii, V A; Maingi, R; Gates, D; Menard, J

    2008-12-31

    Experiments conducted in high-performance 1.0 MA and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub t} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the strongly-shaped lower single null configuration with elongation {kappa} = 2.2-2.4 and triangularity {delta} = 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using the inherently high magnetic flux expansion f{sub m} = 16-25 and the partial detachment of the outer strike point at several D{sub 2} injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z{sub eff} were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction of ion flux to the plate, and a large neutral compression ratio. Spectroscopic measurements indicated a formation of a high-density, low temperature region adjacent to the outer strike point, where substantial increases in the volume recombination rate and CII, CIII emission rates was measured.

  12. Analytical study of the heat loss attenuation by clothing on thermal manikins under radiative heat loads.

    PubMed

    Den Hartog, Emiel A; Havenith, George

    2010-01-01

    For wearers of protective clothing in radiation environments there are no quantitative guidelines available for the effect of a radiative heat load on heat exchange. Under the European Union funded project ThermProtect an analytical effort was defined to address the issue of radiative heat load while wearing protective clothing. As within the ThermProtect project much information has become available from thermal manikin experiments in thermal radiation environments, these sets of experimental data are used to verify the analytical approach. The analytical approach provided a good prediction of the heat loss in the manikin experiments, 95% of the variance was explained by the model. The model has not yet been validated at high radiative heat loads and neglects some physical properties of the radiation emissivity. Still, the analytical approach provides a pragmatic approach and may be useful for practical implementation in protective clothing standards for moderate thermal radiation environments. PMID:20540843

  13. Influence of heat generation and heat flux on peristaltic flow with interacting nanoparticles

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher; Raza, M.; Ellahi, R.

    2014-08-01

    In the current study, we have examined the peristaltic flow of three different nanoparticles with water as base fluid under the influence of slip boundary conditions through a vertical asymmetric porous channel in the presence of MHD. The selected nanoparticles are titanium dioxide ( TiO2 , copper oxide (CuO) and silicon dioxide ( SiO2 . The Brownian motion shows that the effective conductivity increases to result in a lower temperature gradient for a given heat flux. To examine these transport phenomena thoroughly, we also consider the thermal conductivity model of Brownian motion for nanofluids, this increases the effect of the particle size, particle volume fraction and temperature dependence. The mathematical formulation is presented. Exact solutions are obtained from the resulting equations. The obtained expressions for pressure gradient, temperature and velocity profile are described through graphs for the various relevant parameters. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon.

  14. RADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS

    E-print Network

    . The radiative heat exchange in such a reactor is a function of the geometry of the problem, the spectralRADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS A. Kersch1 W. Moroko2 A. Schuster1 1Siemens wafers, as well as many other industrial processes. Several factors are considered including surface ab

  15. RADIATIVE HEAT TRANSFER WITH QUASIMONTE CARLO METHODS \\Lambda

    E-print Network

    , corresponding to an area of 8.64 cm 2 . The radiative heat exchange in such a reactor is a functionRADIATIVE HEAT TRANSFER WITH QUASI­MONTE CARLO METHODS \\Lambda A. Kersch 1 W. Morokoff 2 A of semiconductor wafers, as well as many other industrial processes. Several factors are considered including

  16. Longitudinal Water Temperature and Heat Flux Patterns within a Semi-Natural Forested Stream Reach

    NASA Astrophysics Data System (ADS)

    Garner, G.; Malcolm, I.; Hannah, D. M.; Sadler, J. P.

    2013-12-01

    It is hypothesised that riparian vegetation offers potential to mitigate water temperature thermal extremes and provide refugia for temperature sensitive organisms in a warming climate. Daytime cooling gradients have been observed for stream reaches shaded by coniferous trees downstream of clear cuts; however many of these studies are confounded by cool groundwater inflows and there is a lack of research for semi-natural forest cover. This study addresses this research gap, it aims to quantify and subsequently model observed longitudinal water temperature and heat flux patterns in a semi-natural forested reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) throughout which heat exchange across the bed-water column interface accounted for < 1% of the net energy budget. Observations were made along a 1500 m reach using a spatially-distributed network of ten water temperature micro-loggers and three automatic weather stations. The reach is located below open moorland and bounded by deciduous semi-natural riparian woodland with varying canopy density and tree species composition. For periods when daytime net radiation gains were high (i.e. clear skies), downstream cooling of up to 2.5 °C was observed. Longitudinal thermal gradients were not distinct at night or on days when net radiation gains were low (i.e. over-cast sky conditions). A Lagrangian stream temperature model driven by a reach-averaged deterministic net radiation model using hemispherical photographs provided good predictions of longitudinal water temperature change. The modelling exercise demonstrates the processes which produce longitudinal cooling patterns in a reach without significant groundwater inputs. Consequently, this research provides process based evidence for the potential of riparian vegetation to mitigate thermal extremes and thus improves the scientific basis for management decisions regarding stream temperature under a changing climate.

  17. The Effect of Cumulus Cloud Field Anisotropy on Domain-Averaged Solar Fluxes and Atmospheric Heating Rates

    NASA Technical Reports Server (NTRS)

    Hinkelman, Laura M.; Evans, K. Franklin; Clothiaux, Eugene E.; Ackerman, Thomas P.; Stackhouse, Paul W., Jr.

    2006-01-01

    Cumulus clouds can become tilted or elongated in the presence of wind shear. Nevertheless, most studies of the interaction of cumulus clouds and radiation have assumed these clouds to be isotropic. This paper describes an investigation of the effect of fair-weather cumulus cloud field anisotropy on domain-averaged solar fluxes and atmospheric heating rate profiles. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of cloud scenes from a large eddy simulation. Progressively greater degrees of x-z plane tilting and horizontal stretching were imposed on each of these scenes, so that an ensemble of scenes was produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo radiative transfer model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. The mechanisms by which anisotropy interacts with solar fluxes were investigated by comparisons to independent pixel approximation and tilted independent pixel approximation computations for the same scenes. Cumulus anisotropy was found to most strongly impact solar radiative transfer by changing the effective cloud fraction, i.e., the cloud fraction when the field is projected on a surface perpendicular to the direction of the incident solar beam.

  18. Experimental and Numerical Characterization of Transient Insertion of Heat Flux Gages in a Cylindrical Black Body Cavity at 1100 C

    NASA Technical Reports Server (NTRS)

    Abdelmessih, A. N.; Horn, T.

    2006-01-01

    Initial transient thermal models have been developed to simulate a heat flux gage calibration process capable of generating high heat flux levels of interest to reciprocating and gas turbine engine industries as well as the aerospace industry. These transient models are based on existing, experimentally validated, steady state models of the cylindrical blackbody calibration system. The steady state models were modified to include insertion of a heat flux gage into the hot zone of the calibration system and time varying electrical current passing through the resistance heated blackbody. Heat fluxes computed using the initial transient models were compared to experimental measurements. The calculated and measured transient heat fluxes were within 5% indicating that the major physical phenomena in the transient calibration had been captured by the models. The predicted and measured transient heat fluxes were also compared at two different gage insertion depths. These results indicated that there is an optimum insertion position which maximizes heat flux and minimizes cavity disturbance.

  19. SURFACE HEAT FLUX DERIVED FROM SODAR AMPLITUDE AND FREQUENCY DATA: A COMPARISON

    EPA Science Inventory

    Sensible heat flux measurements were made in an agricultural setting near Champaign, Illinois by using doppler sodar, eddy correlations and profile methods during convective conditions during an experimental study called VOICE, (Vertical Observations Involving Convective Exchange...

  20. Sensitivity of a climatologically-driven sea ice model to the ocean heat flux

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Good, M. R.

    1982-01-01

    Ocean heat flux sensitivity was studied on a numerical model of sea ice covering the Weddell Sea region of the southern ocean. The model is driven by mean monthly climatological atmospheric variables. For each model run, the ocean heat flux is uniform in both space and time. Ocean heat fluxes below 20 W m to the minus 2 power do not provide sufficient energy to allow the ice to melt to its summertime thicknesses and concentrations by the end of the 14 month simulation, whereas ocean heat fluxes of 30 W m to the minus 2 power and above result in too much ice melt, producing the almost total disappearance of ice in the Weddell Sea by the end of the 14 months. These results are dependent on the atmospheric forcing fields.

  1. Alumina Nanoparticle Pre-coated Tubing Ehancing Subcooled Flow Boiling Cricital Heat Flux

    E-print Network

    Truong, Bao H.

    Nanofluids are engineered colloidal dispersions of nano-sized particle in common base fluids. Previous pool boiling studies have shown that nanofluids can improve critical heat flux (CHF) up to 200% for pool boiling and ...

  2. Numerical Study of Spatial Surface Temperature and Nucleation Site Density At High Heat Flux Pool Boiling

    E-print Network

    Maruyama, Shigeo

    ] . The results indicate that nucleate boiling curve and critical heat flux point move to the lower superheat region with increasing surface roughness, which is in a good agreement with Bereson[1] 's experiment

  3. Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux

    E-print Network

    O'Hanley, Harry

    The separate effects of surface wettability, porosity, and roughness on the critical heat flux (CHF) of water were examined using engineered surfaces. Values explored were 0, 5, 10, and 15??m for Rz (roughness), <5°, ?75°, ...

  4. An experimental investigation of critical heat flux in subcooled internal flow

    E-print Network

    Shatto, Donald Patrick

    1997-01-01

    diameters, tube lengths, and mass flow rates. Methods of developing predictive correlations for subcooled critical heat flux based on dimensional analysis, and the sublayer dryout model, are described and applied to the data from these experiments. When...

  5. The role of the geothermal heat flux in driving the abyssal ocean circulation

    E-print Network

    Mashayek, A.

    The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based ...

  6. Thermal conductivity in nanostructured materials and analysis of local angle between heat fluxes

    NASA Astrophysics Data System (ADS)

    Fu, B.; Tang, G. H.; Bi, C.

    2014-09-01

    The phonon Boltzmann transport equation with the frequency-dependent model is solved numerically to study the thermal conductivity in nanoporous thin film and nanocomposite. Local angle between heat fluxes, defined as the angle between the directions of heat flux component qx and the local heat flux q, is introduced. At a fixed porosity or interface area, the thermal conductivity, local angle distribution, and the average angle of the two-dimensional nanoporous thin films with circular, hexagonal, square, and triangular pores are reported, and the thermal conductivity decreases with the increase in the interface area or porosity. Furthermore, the relationship between the thermal conductivity and average angle is also discussed for the three-dimensional nanoporous thin films with aligned or staggered pores, and silicon-germanium embedded and compacted nanocomposites. All the results show that the nanostructured material with a larger average angle between heat fluxes has a lower thermal conductivity.

  7. Solar heating system, and improved heat collecting and radiating components, for livestock-confining buildings

    Microsoft Academic Search

    1983-01-01

    A system is disclosed for heating a building adapted to confine animals includes a solar collector, means for storing the heat absorbed by the collector and heat radiating floor mats which use such heat. The collector includes panels each having lightweight, clear, parallel plastic tubes secured at their ends to headers of similar material. The tubes are disposed in troughs

  8. Solar heating system, and improved heat collecting and radiating components, for livestock-confining buildings

    Microsoft Academic Search

    1984-01-01

    A system for heating a building adapted to confine animals includes a solar collector, means for storing the heat absorbed by the collector and heat radiating floor mats which use such heat. The collector includes panels each having lightweight, clear, parallel plastic tubes secured at their ends to headers of similar material. The tubes are disposed in troughs in the

  9. Radiation Heat Transfer Between Diffuse-Gray Surfaces Using Higher Order Finite Elements

    NASA Technical Reports Server (NTRS)

    Gould, Dana C.

    2000-01-01

    This paper presents recent work on developing methods for analyzing radiation heat transfer between diffuse-gray surfaces using p-version finite elements. The work was motivated by a thermal analysis of a High Speed Civil Transport (HSCT) wing structure which showed the importance of radiation heat transfer throughout the structure. The analysis also showed that refining the finite element mesh to accurately capture the temperature distribution on the internal structure led to very large meshes with unacceptably long execution times. Traditional methods for calculating surface-to-surface radiation are based on assumptions that are not appropriate for p-version finite elements. Two methods for determining internal radiation heat transfer are developed for one and two-dimensional p-version finite elements. In the first method, higher-order elements are divided into a number of sub-elements. Traditional methods are used to determine radiation heat flux along each sub-element and then mapped back to the parent element. In the second method, the radiation heat transfer equations are numerically integrated over the higher-order element. Comparisons with analytical solutions show that the integration scheme is generally more accurate than the sub-element method. Comparison to results from traditional finite elements shows that significant reduction in the number of elements in the mesh is possible using higher-order (p-version) finite elements.

  10. Flux and brightness calculations for various synchrotron radiation sources

    SciTech Connect

    Weber, J.M.; Hulbert, S.L.

    1991-11-01

    Synchrotron radiation (SR) storage rings are powerful scientific and technological tools. The first generation of storage rings in the US., e.g., SURF (Washington, D.C.), Tantalus (Wisconsin), SSRL (Stanford), and CHESS (Cornell), revolutionized VUV, soft X-ray, and hard X-ray science. The second (present) generation of storage rings, e.g. the NSLS VUV and XRAY rings and Aladdin (Wisconsin), have sustained the revolution by providing higher stored currents and up to a factor of ten smaller electron beam sizes than the first generation sources. This has made possible a large number of experiments that could not performed using first generation sources. In addition, the NSLS XRAY ring design optimizes the performance of wigglers (high field periodic magnetic insertion devices). The third generation storage rings, e.g. ALS (Berkeley) and APS (Argonne), are being designed to optimize the performance of undulators (low field periodic magnetic insertion devices). These extremely high brightness sources will further revolutionize x-ray science by providing diffraction-limited x-ray beams. The output of undulators and wigglers is distinct from that of bending magnets in magnitude, spectral shape, and in spatial and angular size. Using published equations, we have developed computer programs to calculate the flux, central intensity, and brightness output bending magnets and selected wigglers and undulators of the NSLS VUV and XRAY rings, the Advanced Light Source (ALS), and the Advanced Photon Source (APS). Following is a summary of the equations used, the graphs and data produced, and the computer codes written. These codes, written in the C programming language, can be used to calculate the flux, central intensity, and brightness curves for bending magnets and insertion devices on any storage ring.

  11. Comparison of surface radiative flux data sets over the Arctic Ocean Jiping Liu,1,2

    E-print Network

    Comparison of surface radiative flux data sets over the Arctic Ocean Jiping Liu,1,2 Judith A. Curry in the Arctic Ocean. To assess how well we can reconstruct the variations of surface radiative fluxes used of the Arctic Ocean (SHEBA) over the seasonal cycle and during particular storm events. The CASPR and NCEP-R2

  12. Galileo probe measurements of thermal and solar radiation fluxes in the Jovian atmosphere

    Microsoft Academic Search

    L. A. Sromovsky; A. D. Collard; P. M. Fry; G. S. Orton; M. T. Lemmon; M. G. Tomasko; R. S. Freedman

    1998-01-01

    The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements

  13. An improved time-dependent nonlocal electron heat-flux model and its verification by laser-driven Al foil acceleration experiment

    NASA Astrophysics Data System (ADS)

    Sijoy, C. D.; Chaurasia, Shivanand; Mishra, Vinayak; Leshma, P.; Sakthivel, N.; Chaturvedi, Shashank; Sharma, S. M.; Basu, Sekhar

    2014-06-01

    In hydrodynamics simulation of laser driven systems, the time-dependent nonlocal electron heat-flux models predict the saturation (flux inhibition) and delocalization of the heat-flux automatically. Therefore it avoids commonly used time and space-independent ad hoc flux limiting. Previously proposed analytical nonlocal heat-flux model of Luciani et al. [Phys. Rev. Lett., 51, p-1664, (1983)] which fits the results of numerical Fokke-Planck calculations is simple and straight forward to implement in a fluid code. The proposed expression, however, is a convolution of Spitze-Harm heat-flux with a delocalization kernel which depends on classical electron collision mean free path. This is rigorously valid for high temperature non-degenerate plasmas. However, in laser driven systems, the energy transport due to electron thermal conduction is important in regions between the critical density and ablation surface where the plasma is mostly degenerate. We have improved this nonlocal heat-flux model by using a wide-range electron collision frequency model valid from warm-dense matter (degenerate plasmas) to fully ionized plasmas. The effect of this improved nonlocal heat-flux model on the free-surface velocity of laser-accelerated Al foils of thickness 2-10 ?m is studied by using a two-dimensional radiation hydrodynamics code. The simulated free surface velocities are compared with our experimental results for laser intensities in the range 4 × 1013-3 × 1014 W/cm2. Preliminary analysis shows that the simulation results obtained with improved nonlocal heat-flux model yields better agreement with our experimental values.

  14. Research concerning the net flux of radiation in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Tomasko, M. G.

    1996-01-01

    The plan of the NFR (Net Flux of Radiation) team is for the data from the two solar channels (B and E) of NFR to be reduced with the goal of determining the solar heating rate. In order to determine the solar heating rate from the NFR measurements, effects due to the instrument's spatial and spectral response functions, to the temperature variation of the instrument (and associated drift of calibration), to the setting sun, and to the rotation of the probe (initially at a rate comparable to the NFR sampling frequency), all must be well modelled. In the past year, a forward modeling routine was created to simulate NFR data return in the B and E channels. The effects of varying parameters describing the atmospheric model (such as cloud location and thickness) and the descent profile (such as rotation rate) were investigated and an inversion routine was developed. For the forward modeling, existing radiative transfer codes were used to determine intensity fields within the Jovian atmosphere. A routine was developed to determine instantaneous instrument response by integrating the intensity field over the instrument response functions. A second routine was developed to determine the actual output of the NFR by integrating along an arbitrary descent trajectory. Near the top of the atmosphere, the upflux data alone are used to constrain the cloud structure of he atmosphere. To accomplish this, models are used to describe the variation in up flux between consecutive measurements in terms of variations of cloud opacity and variations in known parameters such as the solar zenith angle. This allows us to develop a zero-order model of cloud structure. Lower in the atmosphere, at levels where there is little or no azimuthal structure to the net flux measurements, both the up flux and net flux are used to derive layer transmission and reflection functions, which then determine layer opacity and single scattering albedo. A preliminary analysis of the data began in December 1995. In these data we could see the rapid oscillations expected at the beginning of the data due to probe rotation and the sun passing through the edge of the field of view. In addition, the time when this oscillation stopped was clearly visible. This sets the rough optical depth above the probe at this time.

  15. Empirical Modeling of Radiative versus Magnetic Flux for the Sun-as-a-Star

    E-print Network

    Preminger, Dora; Chapman, Gary; Martens, Petrus C H; 10.1007/s11207-010-9560-1

    2010-01-01

    We study the relationship between full-disk solar radiative flux at different wavelengths and average solar photospheric magnetic-flux density, using daily measurements from the Kitt Peak magnetograph and other instruments extending over one or more solar cycles. We use two different statistical methods to determine the underlying nature of these flux-flux relationships. First, we use statistical correlation and regression analysis and show that the relationships are not monotonic for total solar irradiance and for continuum radiation from the photosphere, but are approximately linear for chromospheric and coronal radiation. Second, we use signal theory to examine the flux-flux relationships for a temporal component. We find that a well-defined temporal component exists and accounts for some of the variance in the data. This temporal component arises because active regions with high magnetic field strength evolve, breaking up into small-scale magnetic elements with low field strength, and radiative and magnet...

  16. Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow

    NASA Astrophysics Data System (ADS)

    Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

    2015-03-01

    Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

  17. Streambed temperature dynamics and corresponding heat fluxes in small streams experiencing seasonal ice cover

    NASA Astrophysics Data System (ADS)

    Caissie, Daniel; Kurylyk, Barret L.; St-Hilaire, André; El-Jabi, Nassir; MacQuarrie, Kerry T. B.

    2014-11-01

    Streambed temperature and heat fluxes are important for aquatic habitats as well as in the development and improvement of water temperature models. In the present study, measured streambed temperatures at different depths were used as a tracer to predict the magnitude and direction of groundwater flow using an advection-conduction heat transport model. This analysis was carried out under different conditions, namely under natural surface water temperature conditions (i.e., as measured in the field), under steady-state conditions (e.g. under stream ice cover) and for conditions where the surface water temperatures followed a sinusoidal function. In Catamaran Brook, results from the advection-conduction numerical model showed good agreement between predicted and observed streambed temperatures with root-mean-square errors (RMSEs) ranging between 0.07 °C to 0.6 °C. A comparison of streambed fluxes showed that the heat flux by conduction was more important during the summer period for upwelling conditions (mean value 96 W m-2 at 25 °C), but was also present in winter (-20 W m-2). Variability in heat flux by conduction was also greater when the diel surface water temperature variability was high (e.g. range of 6 °C). The heat flux by advection varied between -120 and 145 W m-2 (for typical water temperatures and vertical flow conditions within Catamaran Brook, 0-25 °C and ±0.005 m h-1). Short-term heat exchange (diel) occurred within the thermally active depth, typically <0.7 m. The long-term annual streambed heat flux by conduction was also calculated and daily mean was generally less than ±11 W m-2. Winter conditions provided a unique opportunity to analyse streambed heat fluxes under steady-state conditions when both conduction and advection fluxes were present.

  18. Modeling near-field radiative heat transfer from sharp objects using a general 3d numerical scattering technique

    Microsoft Academic Search

    Alexander P. McCauley; M. T. Homer Reid; Matthias Krüger; Steven G. Johnson

    2011-01-01

    We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objects including corners or tips. We find qualitatively different scaling laws for conical shapes at small separations, and in contrast to a flat\\/slightly-curved object, a

  19. Wafer-grown heat flux sensor arrays for plasma etch processes

    Microsoft Academic Search

    Mason Freed; Michiel V. P. Krüger; Kameshwar Poolla; Costas J. Spanos

    2005-01-01

    This work treats the design, fabrication, and testing of a wafer-grown thermal flux sensor for use in plasma etch processes. This sensor is capable of separately resolving the heating due to ion flux from that due to surface chemical reactions. The sensor is constructed using a modified Gardon gauge structure with an added antenna structure. This addition allows the exposed

  20. Reflectance-Based Estimation of Soil Heat Fluxes in the Texas High Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil heat flux (G) is one of the terms required for estimating evapotranspiration (ET) rates using an energy balance. Numerous reflectance-based models are available in the literature for estimating G fluxes. However, these models have shown wide variation in their performance. Therefore, operationa...

  1. Measurement of Local Heat Flux to Membrane Water-Walls in Steam Boilers

    Microsoft Academic Search

    Dawid Taler

    2008-01-01

    1. Abstract A heat flux entering steam generating tubes in power station boilers may be a critical factor in considering the safety of the tubes. The knowledge of the distribution and magnitude of this flux during the operation of the power boiler is very important. The design of a modern boiler furnace requires the computation of furnace wall metal temperatures

  2. Changes in fluxes of heat, H2O, CO2 caused by a large wind farm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Crop Wind Energy Experiment (CWEX) provides a platform to investigate the effect of wind turbines and large wind farms on surface fluxes of momentum, heat, moisture and carbon dioxide (CO2). In 2010 and 2011, eddy covariance flux stations were installed between two lines of turbines at the south...

  3. Radiative Heat Transfer During Atmosphere Entry at Parabolic Velocity

    NASA Technical Reports Server (NTRS)

    Yoshikawa, Kenneth K.; Wick, Bradford H.

    1961-01-01

    Stagnation point radiative heating rates for manned vehicles entering the earth's atmosphere at parabolic velocity are presented and compared with corresponding laminar convective heating rates. The calculations were made for both nonlifting and lifting entry trajectories for vehicles of varying nose radius, weight-to-area ratio, and drag. It is concluded from the results presented that radiative heating will be important for the entry conditions considered.

  4. Application of ray tracing in radiation heat transfer

    NASA Technical Reports Server (NTRS)

    Baumeister, Joseph F.

    1993-01-01

    This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.

  5. Thermal evaluation of uranium silicide miniplates irradiated at high heat flux

    SciTech Connect

    Donna P. Guillen

    2012-09-01

    The Gas Test Loop (GTL)-1 irradiation experiment was conducted in the Advanced Test Reactor (ATR) to assess corrosion performance of proposed booster fuel at heat flux levels ~30% above the design operating condition. Sixteen miniplates fabricated from 25% enriched, high-density (4.8 g U/cm3) U3Si2/Al dispersion fuel with 6061 aluminum cladding were subjected to peak beginning of cycle (BOC) heat fluxes ranging from 411 to 593 W/cm2. No adverse impacts to the miniplates were observed at these high heat flux levels. A detailed finite element model was constructed to calculate temperatures and heat flux for an as-run cycle average effective ATR south lobe power of 25.4 MW(t). Miniplate heat flux levels and fuel, cladding, hydroxide, and coolant–hydroxide interface temperatures were calculated using the average hydroxide thickness on each miniplate measured during post-irradiation examination. The purpose of this study was to obtain a best estimate of the as-run experiment temperatures to aid in establishing acceptable heat flux levels and designing fuel qualification experiments for this fuel type.

  6. Kilometric radiation power flux dependence on area of discrete aurora

    NASA Technical Reports Server (NTRS)

    Saflekos, N. A.; Burch, J. L.; Gurnett, D. A.; Anderson, R. R.; Sheehan, R. E.

    1989-01-01

    Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

  7. Apparatus development for measuring heat flux in a direct coal-liquefaction preheater

    SciTech Connect

    Kornosky, R.M.; Perlmutter, M.; Fuchs, W.; Ruether, J.A.

    1982-04-01

    A device is evaluated for determining heat flux in a direct coal liquefaction preheater for a planned experimental program. The heat fluxmeter determines heat flux from measurements of temperature difference across the preheater tube wall at a given plane perpendicular to the tube axis. In the present work, six fluxmeters were installed in a 5.08 m length of nominal 1-1/2-inch-diameter, schedule XX pipe enclosed in stacked electric furnaces. Heat flux to a heat transfer fluid flowing through the pipe was measured and compared to values predicted by the fluxmeters. Fair agreement was observed, and the method could be used as an empirical calibration procedure for fluxmeters. A number of apparatus improvements were identified that will be incorporated in the planned experimental program.

  8. Apparatus development for measuring heat flux in a direct coal-liquefaction preheater

    NASA Astrophysics Data System (ADS)

    Kornosky, R. M.; Perlmutter, M.; Fuchs, W.; Ruether, J. A.

    1982-04-01

    A device is evaluated for determining heat flux in a direct coal liquefaction preheater. The heat fluxmeter determines heat flux from measurements of temperature difference across the preheater tube wall at a given plane perpendicular to the tube axis. Six fluxmeters were installed in a 5.08 m length of nominal 1 1/2 inch diameter, schedule XX pipe enclosed in stacked electric furnaces. Heat flux to a heat transfer fluid flowing through the pipe was measured and compared to values predicted by the fluxmeters. Fair agreement was observed, and the method can be used as an empirical calibration procedure for fluxmeters. A number of apparatus improvements were identified that will be incorporated in the planned experimental program.

  9. Development of a shuttle plume radiation heating indicator

    NASA Technical Reports Server (NTRS)

    Reardon, John E.

    1988-01-01

    The primary objectives were to develop a Base Heating Indicator Code and a new plume radiation code for the Space Shuttle. Additional work included: revision of the Space Shuttle plume radiation environment for changes in configuration and correction of errors, evaluation of radiation measurements to establish a plume radiation model for the SRB High Performance Motor (HPM) plume, radiation predictions for preliminary designs, and participation in hydrogen disposal analysis and testing for the VAFB Shuttle launch site. The two most significant accomplishments were the development of the Base Heating Indicator Code and the Shuttle Engine Plume Radiation (SEPRAD) Code. The major efforts in revising the current Shuttle plume radiation environment were for the Orbiter base heat shield and the ET components in the Orbiter-ET interface region. The work performed is summarized in the technical discussion section with references to the documents containing detailed results. The technical discussion is followed by a summary of conclusions and recommendations for future work.

  10. On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

    SciTech Connect

    Kazil, J.; Feingold, G.; Wang, Hailong; Yamaguchi, T.

    2014-01-02

    The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. It is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.

  11. Coupling heat conduction, radiation and convection in complex geometries

    Microsoft Academic Search

    I. Rupp; C. Péniguel

    1999-01-01

    In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a

  12. Radiative heating and cooling with spectrally selective surfaces

    Microsoft Academic Search

    C. G. Granqvist

    1981-01-01

    Ambient radiative properties are examined. For the temperatures of interest in connection with natural heating and cooling, the Planck spectrum is confined to the wavelength range from 3 to 50 micrometers. Solar radiation is limited to the range from 0.25 to 3 micrometers. A surface may, therefore, have different properties with respect to solar and thermal radiation. Attention is given

  13. Critical heat flux during natural circulation boiling of saturated liquid in annulus with uniformly heat outer tube

    SciTech Connect

    Monde, M.; Mitsutake, Y.

    2000-02-01

    Critical heat flux has been measured during natural circulation boiling of water and R113 on a uniformly heated outer tube in a vertical annular tube. The experiment was carried out using water at atmospheric pressure and R113 at a pressure of 0.1--0.4 MPa for the annular gap width of S = 1.0--4.0 mm, the heated tube diameter of 9--17 mm, and the annular tube length of 100--1,000 mm. The similarity of critical heat flux between annular configurations of either inner or outer heated tubes and a simple heated tube can be clearly elucidated based on the characteristics of the heated equivalent diameter. The critical heat flux measured for S = 1 mm can be predicted accurately by existing correlation for the annular tube and for clearance larger than S = 4 mm by existing correlation for the single tube. A new correlation for medium clearances from S = 1 to 4 mm has been developed to connect between both the existing correlations.

  14. ANALYSIS OF A HEAT-FLUX DIFFERENTIAL SCANNING CALORIMETRY INSTRUMENTS

    SciTech Connect

    Sabau, Adrian S [ORNL; Porter, Wallace D [ORNL

    2007-01-01

    Differential Scanning Calorimetry (DSC) measurements are used to estimate the fractional latent heat release during phase changes. There are temperature lags inherent to the instruments due to the temperature measurement at a different location than that of the sample and reference materials. Recently, Dong and Hunt[1] showed that significant improvement in estimating the fractional latent heat can be obtained when detailed simulations of the heat transfer within the instrument are performed. The Netzsch DSC 404C instrument, with a high accuracy heat capacity sensor, is considered in this study. This instrument had a different configuration than that studied by Dong and Hunt[1]. The applicability of Dong and Hunt's approach to this instrument is investigated. It was found that the DSC instrument could be described by numerous parameters but that model parameters were difficult to estimate. Numerical simulation results are presented and compared with experimental results for the fractional latent heat of a commercial A356 aluminum alloy.

  15. Effects of marine cloud brightening on polar regions and the meridional heat flux

    NASA Astrophysics Data System (ADS)

    Parkes, B.; Gadian, A.; Latham, J.

    2011-12-01

    Marine cloud brightening is one of several proposed solar radiation management geoengineering schemes designed to avert some of the undesirable effects of climate change (Latham et al. 2008). Such changes include ice loss, desertification and increased sea levels. Polar sea ice fraction has been recorded by satellite data for the last 40 years. This data shows a general long term reduction in sea ice thickness and area and this reduction has been attributed to climate change. Changes in climate have been argued to be disproportionately larger in polar regions. The HadGEM1 (UK Met Office Climate Model, V6.1) is a fully coupled climate model. It is used to project changes in polar ice cover and temperatures as a result of increasing carbon dioxide and geoengineering using marine cloud brightening scenario. The meridional heat flux is the mechanism for moving energy from the tropics to the polar regions. The results show that for a comparison between a control (~ 2020 Carbon Dioxide concentrations) and a double pre-industrial Carbon Dioxide simulation, the maximum meridional heat flux is found to increase from 5.8PW to 6.1PW. With three-region seeding of marine Stratocumulus, this is reduced to 5.7PW. The annual North Polar sea ice cover, initially 11.5M sq km, is reduced by 3.6M sq km as a result of the increased Carbon Dioxide. Application of a three region seeding scenario, results in an increase in sea ice cover of 0.20M sq km above the initial (2020) values. Reference: Latham J. et al.. (2008) Global temperature stabilization via controlled albedo enhancement of low-level maritime clouds. Phil. Trans. R. Soc. A doi:10.1098/rsta.2008.0137.

  16. The GEWEX LandFlux Initiative: development and analysis of a global land surface heat flux product

    NASA Astrophysics Data System (ADS)

    McCabe, M. F.; Wood, E. F.; Jimenez, C.; Miralles, D. G.; Ershadi, A.; Liang, M.; Mueller, B.; Seneviratne, S. I.; Kummerow, C. D.

    2013-12-01

    The GEWEX Data and Assessments Panel (GDAP) has recently released Version 0 of a new global terrestrial land surface heat flux product. Developed as part of the GDAP LandFlux Project, one of the major motivations behind this effort was the need to provide an independent and (largely) observationally based product that could be used to, amongst other applications, evaluate an increasing variety of global flux simulations - particularly those being delivered as part of global climate models (GCM), reanalyses and land surface modeling (LSM) activities. The dataset also features as one of the outstanding elements of the GDAP mission to provide observationally based measures of the global water and energy cycles, facilitating the capacity for independent assessment of change and variability within regional to global scale exchanges. Numerous challenges presented themselves during product development, including issues of consistency in forcing data, difficulties in discriminating forcing from model induced error, undertaking independent/unbiased evaluation and the inherent compromises in algorithm choice and intercomparison. While there are inevitably issues that remain unresolved and require ongoing investigation, the project has provided some important insights into the characterization, assessment and development of global flux data sets. Here we will explore some of the key outcomes of this work, including the spatial and temporal development of flux response across a number of key continental scale basins, the evaluation of flux retrievals using available in-situ and other data sets, and the influence of model induced variability introduced via algorithm choice.

  17. Assessment of land surface temperature and heat fluxes over Delhi using remote sensing data.

    PubMed

    Chakraborty, Surya Deb; Kant, Yogesh; Mitra, Debashis

    2015-01-15

    Surface energy processes has an essential role in urban weather, climate and hydrosphere cycles, as well in urban heat redistribution. The research was undertaken to analyze the potential of Landsat and MODIS data in retrieving biophysical parameters in estimating land surface temperature & heat fluxes diurnally in summer and winter seasons of years 2000 and 2010 and understanding its effect on anthropogenic heat disturbance over Delhi and surrounding region. Results show that during years 2000-2010, settlement and industrial area increased from 5.66 to 11.74% and 4.92 to 11.87% respectively which in turn has direct effect on land surface temperature (LST) and heat fluxes including anthropogenic heat flux. Based on the energy balance model for land surface, a method to estimate the increase in anthropogenic heat flux (Has) has been proposed. The settlement and industrial areas has higher amounts of energy consumed and has high values of Has in all seasons. The comparison of satellite derived LST with that of field measured values show that Landsat estimated values are in close agreement within error of ±2 °C than MODIS with an error of ±3 °C. It was observed that, during 2000 and 2010, the average change in surface temperature using Landsat over settlement & industrial areas of both seasons is 1.4 °C & for MODIS data is 3.7 °C. The seasonal average change in anthropogenic heat flux (Has) estimated using Landsat & MODIS is up by around 38 W/m(2) and 62 W/m(2) respectively while higher change is observed over settlement and concrete structures. The study reveals that the dynamic range of Has values has increased in the 10 year period due to the strong anthropogenic influence over the area. The study showed that anthropogenic heat flux is an indicator of the strength of urban heat island effect, and can be used to quantify the magnitude of the urban heat island effect. PMID:24360191

  18. Combined buoyancy and flow direction effects on saturated boiling critical heat flux in liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.

    1972-01-01

    Buoyancy effects on the critical heat flux and general data trends for a liquid nitrogen internal flow system were determined by comparison of upflow and downflow data under identical test conditions. The test section had a 1.28 cm diameter flow passage and a 30.5 cm heated length which was subjected to uniform heat fluxes through resistance heating. Test conditions covered a range of pressures from 3.4 to 10.2 atm, inlet velocities from 0.23 to 3.51 m/sec, with the liquid nitrogen temperature at saturated inlet conditions. Data comparisons showed that the critical heat flux for downflow could be up to 36 percent lower than for upflow. A nonmonotonic relationship between the critical heat flux and velocity was determined for upflow but not for downflow. A limiting inlet velocity of 4.12 m/sec was determined to be the minimum velocity required to completely suppress the influence of buoyancy on the critical heat flux for this saturated inlet flow system. A correlation of this limiting fluid velocity is presented that was developed from previously published subcooled liquid nitrogen data and the saturated data of this investigation.

  19. Two-Flux and Green's Function Method for Transient Radiative Transfer in a Semi-Transparent Layer

    NASA Technical Reports Server (NTRS)

    Siegel, Robert

    1995-01-01

    A method using a Green's function is developed for computing transient temperatures in a semitransparent layer by using the two-flux method coupled with the transient energy equation. Each boundary of the layer is exposed to a hot or cold radiative environment, and is heated or cooled by convection. The layer refractive index is larger than one, and the effect of internal reflections is included with the boundaries assumed diffuse. The analysis accounts for internal emission, absorption, heat conduction, and isotropic scattering. Spectrally dependent radiative properties are included, and transient results are given to illustrate two-band spectral behavior with optically thin and thick bands. Transient results using the present Green's function method are verified for a gray layer by comparison with a finite difference solution of the exact radiative transfer equations; excellent agreement is obtained. The present method requires only moderate computing times and incorporates isotropic scattering without additional complexity. Typical temperature distributions are given to illustrate application of the method by examining the effect of strong radiative heating on one side of a layer with convective cooling on the other side, and the interaction of strong convective heating with radiative cooling from the layer interior.

  20. Two-phase flow in high-heat-flux micro-channel heat sink for refrigeration cooling applications: Part II—heat transfer characteristics

    Microsoft Academic Search

    Jaeseon Lee; Issam Mudawar

    2005-01-01

    This paper is the second of a two-part study concerning two-phase flow and heat transfer characteristics of R134a in a micro-channel heat sink incorporated as an evaporator in a refrigeration cycle. Boiling heat transfer coefficients were measured by controlling heat flux (q?=15.9?93.8W\\/cm2) and vapor quality (xe=0.26?0.87) over a broad range of mass velocity. While prior studies point to either nucleate

  1. Numerical prediction of radiative heat transfer in reciprocating superadiabatic combustion in porous media.

    PubMed

    Du, Liming; Xie, Maozhao

    2011-06-01

    A numerical study of Reciprocating Superadiabatic Combustion of Premixed gases in porous media (hereafter, referred to as RSCP) is performed. In this system the transient combustion of methane-air mixture is stabilized in a porous media combustor by periodically switching flow directions. The mass, momentum, energy and species conservation equations are solved using a two-dimensional control volume method. Local thermal non-equilibrium between the gas and the solid phases is considered by solving separate energy equations for the two phases and coupling them through a convective heat transfer coefficient. The porous media is assumed to emit, absorb and isotropically scatter radiation. The influences of the dominating operating parameters, such as filtration velocity, equivalence ratio and half cycle on the temperature profile, heat release rate, radiant flux, radiant efficiency and combustion efficiency are discussed. The results show that coupling calculating of flow field, combustion reaction and volume radiation of the optically thick media is successively achieved and heat radiation plays an important role in the overall performance of the burner. The temperature profile inside the RSCP combustor has a typical trapezoidal shape and the profile of radiation flux is similar to sinusoidal shape. Compared with the conventional premixed combustion in porous medium, combustion behavior in RSCP combustor is superior, such as better thermal structure and higher radiation efficiency and combustion efficiency. PMID:25084588

  2. How Well are Recent Climate Variability Signals Resolved by Satellite Radiative Flux Estimates?

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Lu, H.-L.

    2004-01-01

    One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. Understanding the character of radiative flux estimates and relating them to variations in other energy fluxes and climate state variables is key to improving our understanding of climate. In this work we will evaluate several recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from rnid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and HlRS operational soundings profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Several estimates of downward LW flux at the surface inferred from microwave data are also examined. Since these products have been evaluated with Baseline Surface Radiation Network data over land we focus over ocean regions and use the DOE/NOAA/NASA Shipboard Ocean Atmospheric Radiation (SOAR) surface flux measurements to characterize performance of these data sets under both clear and cloudy conditions. Some aspects of performance are stratified according to SST and vertical motion regimes. Comparisons to the TRMM/CERES SRB data in 1998 are also interpreted. These radiative fluxes are then analyzed to determine how surface (and TOA) radiative exchanges respond to interannual signals of ENS0 warm and cold events. Our analysis includes regional changes as well as integrated signals over land, ocean and various latitude bands. Changes in water vapor and cloud forcing signatures are prominent on interannual time scales. Prominent signals are also found in the SW fluxes for the Pinatubo volcanic event. These systematic changes in fluxes are related to changes in large-scale circulations and energy transport in the atmosphere and ocean. Some estimates of signal-to-noise and reliability are discussed to place our results in context.

  3. The CERES\\/ARM\\/GEWEX experiment (CAGEX) for the retrieval of radiative fluxes with satellite data

    Microsoft Academic Search

    T. P. Charlock; T. L. Alberta

    1996-01-01

    Results from a temporally intensive, limited area, radiative transfer model experiment are on-line for investigating the vertical profile of shortwave and longwave radiative fluxes from the surface to the top of the atmosphere (TOA). The CERES\\/ARM\\/GEWEX Experiment (CAGEX) Version 1 provides a record of fluxes that have been computed with a radiative transfer code; the atmospheric sounding, aerosol, and satellite-retrieved

  4. The CERES\\/ARM\\/GEWEX Experiment (CAGEX) for the Retrieval of Radiative Fluxes with Satellite Data

    Microsoft Academic Search

    Thomas P. Charlock; Timothy L. Alberta

    1996-01-01

    Results from a temporally intensive, limited area, radiative transfer model experiment are on-line for investigating the vertical profile of shortwave and longwave radiative fluxes from the surface to the top of the atmosphere (TOA). The CERES\\/ARM\\/GEWEX Experiment (CAGEX) Version 1 provides a record of fluxes that have been computed with a radiative transfer code; the atmospheric sounding, aerosol, and satellite-retrieved

  5. A Freezable Heat Exchanger for Space Suit Radiator Systems

    NASA Technical Reports Server (NTRS)

    Nabity, James A.; Mason, Georgia R.; Copeland, Robert J.; Trevino, Luis a.

    2008-01-01

    During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut s metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Radiators have no moving parts and are thus highly reliable. Past freezable radiators have been too heavy, but the weight can be greatly reduced by placing a small and freeze tolerant heat exchanger between the astronaut and radiator, instead of making the very large radiator freeze tolerant. Therefore, the key technological innovation to improve space suit radiator performance was the development of a lightweight and freezable heat exchanger that accommodates the variable heat load generated by the astronaut. Herein, we present the heat transfer performance of a newly designed heat exchanger that endured several freeze / thaw cycles without any apparent damage. The heat exchanger was also able to continuously turn down or turn up the heat rejection to follow the variable load.

  6. Synergistic inactivation of viruses by heat and ionizing radiation.

    NASA Technical Reports Server (NTRS)

    Trujillo, R.; Dugan, V. L.

    1972-01-01

    Viral inactivation by heat and/or ionizing radiation is analyzed in terms of a kinetic model. The phenomenon of synergistic viral inactivation observed when viruses are exposed to the simultaneous application of heat and ionizing radiation is interpreted within the framework provided by this three-term model. Data on the inactivation of T4 bacteriophage by heat and/or ionizing radiation is presented, and the kinetic model is used to provide a description of observed dose rate and temperature dependences. Extension of the model to other viral systems inactivated by heat and ionizing radiation is considered, and the general applicability of these analyses suggests that the kinetic model may well serve as an extension of target theory in describing the radiobiological effects of ionizing radiation.

  7. Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest

    NASA Astrophysics Data System (ADS)

    Starkenburg, Derek; Fochesatto, Gilberto J.; Cristóbal, Jordi; Prakash, Anupma; Gens, Rudiger; Alfieri, Joseph G.; Nagano, Hirohiko; Harazono, Yoshinobu; Iwata, Hiroki; Kane, Douglas L.

    2015-02-01

    We evaluate local differences in thermal regimes and turbulent heat fluxes across the heterogeneous canopy of a black spruce boreal forest on discontinuous permafrost in interior Alaska. The data were taken during an intensive observing period in the summer of 2013 from two micrometeorological towers 600 m apart in a central section of boreal forest, one in a denser canopy (DC) and the other in a sparser canopy, but under approximately similar atmospheric boundary layer (ABL) flow conditions. Results suggest that on average 34% of the half-hourly periods in a day are nonstationary, primarily during night and during ABL transitions. Also, thermal regimes differ between the two towers; specifically between midnight and 0500 Alaska Standard Time (AKST) it is about 3°C warmer at DC. On average, the sensible heat flux at DC was greater. For midday periods, the difference between those fluxes exceeded 30% of the measured flux and over 30 W m-2 in magnitude more than 60% of the time. These differences are due to higher mechanical mixing as a result of the increased density of roughness elements at DC. Finally, the vertical distribution of turbulent heat fluxes verifies a maximum atop the canopy crown (2.6 h) when compared with the subcanopy (0.6 h) and above canopy (5.1 h), where h is the mean canopy height. We argue that these spatial and vertical variations of sensible heat fluxes result from the complex scale aggregation of energy fluxes over a heterogeneous canopy.

  8. Be/C layer appears to form `beads' in response to heat flux.

    E-print Network

    Princeton Plasma Physics Laboratory

    Be/C layer appears to form `beads' in response to heat flux. `Globules' of Be formed after laser heating. 21 temperature excursions above 1000 C, peak temperature 2,100 C. Subsequent scans at same laser power and speed resulted in lower temperatures (1,601 C then 1,314 C) as layer became more thermally

  9. Interactive initialization of heat flux parameters for numerical models using satellite temperature measurements

    NASA Technical Reports Server (NTRS)

    Carlson, T. N. (principal investigator)

    1981-01-01

    Day/night Heat Capacity Mapping Mission image pairs over Kansas and Indiana were used to examine the spatial variation of moisture availability on the mesoscale. Of particular concern was whether patterns of moisture availability and thermal inertia, as well as surface heat fluxes, respond to significant spatial variations in the rainfall pattern. A temperature analysis for the Indiana case is presented.

  10. Transient heat flux shielding using thermal metamaterials Supradeep Narayana,a)

    E-print Network

    Sato, Yuki

    Transient heat flux shielding using thermal metamaterials Supradeep Narayana,a) Salvatore Savo based on a metamaterial engineering approach to shield a region from transient diffusive heat flow compared to other isotropic materials. VC 2013 AIP Publishing LLC. [http://dx.doi.org/10

  11. A FLUX-TUBE TECTONICS MODEL FOR SOLAR CORONAL HEATING DRIVEN BY THE MAGNETIC CARPET

    E-print Network

    Priest, Eric

    . The dissipation of energy along sharp boundaries we call, by analogy with geophysical plate tectonicsA FLUX-TUBE TECTONICS MODEL FOR SOLAR CORONAL HEATING DRIVEN BY THE MAGNETIC CARPET Eric R. Priest, the tectonics model of coronal heating. Simi- lar to the case on Earth, the relative motions of the photospheric

  12. Surface Skin Temperature and the Interplay between Sensible and Ground Heat Fluxes over Arid Regions

    E-print Network

    Surface Skin Temperature and the Interplay between Sensible and Ground Heat Fluxes over Arid the diurnal cycle of surface skin temperature. Based on theoretical arguments and synthesis of previous of the coefficients in computing roughness length for heat significantly reduces the underestimate of daytime skin

  13. Study of heat flux induced dryout in capillary grooves. Master's thesis

    Microsoft Academic Search

    1992-01-01

    This is an experimental study of ethanol flowing in the narrow grooves of a copper plate which is subjected to heat fluxes sufficient to evaporate more liquid than can be replaced by capillary pumping. Three groove geometries are used: square, rectangle, and trapezoid. The objective is to simulate aspects of liquid flow in heat pipes with axial grooves. In order

  14. IMPLICATIONS OF RADIOMETRIC-AERODYNAMIC TEMPERATURE DIFFERENCES FOR HEAT FLUX ESTIMATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the application of radiometric surface temperature observations for heat flux computations in numerical models, it is necessary to consider differences between the so-called “aerodynamic” temperature, which is the model-derived temperature that relates to the efficiency of heat exchange between t...

  15. Parametric trends analysis of the critical heat flux based on artificial neural networks

    Microsoft Academic Search

    Sang Ki Moon; Won-Pil Baek; Soon Heung Chang

    1996-01-01

    Parametric trends of the critical heat flux (CHF) are analyzed by applying artificial neural networks (ANNs) to a CHF data base for upward flow of water in uniformly heated vertical round tubes. The analyses are performed from three viewpoints, i.e., for fixed inlet conditions, for fixed exit conditions, and based on local conditions hypothesis. Katto's and Groeneveld et al. dimensionless

  16. Study of channel-type systems for solar-energy radiative heat transport

    Microsoft Academic Search

    A. A. Khudenko

    1974-01-01

    Results of a study of channel-type systems for direct heating of industrial premises by solar energy. A description is given of a channel-type system in which a high-power radiative-energy flux is created by a solar-energy concentrator and is then fed into horizontal channels, where it is directed by rotating reflectors to outlets located uniformly over the area of the premises

  17. Time-dependent modeling of solar wind acceleration from turbulent heating in open flux tubes

    NASA Astrophysics Data System (ADS)

    Woolsey, Lauren Nicole; Cranmer, Steven R.

    2015-04-01

    The acceleration of the solar wind, particularly from open flux tubes, remains an open question in solar physics. Countless physical processes have been suggested to explain all or parts of the coupled problem of coronal heating and wind acceleration, but the current generation of observations have been so far unable to distinguish which mechanism(s) dominates. In this project, we consider heating by Alfvén waves in a three-dimensional, time-dependent reduced magnetohydrodynamics model. This model solves for the heating rate as a function of time due to the twisting and braiding of magnetic field lines within a flux tube, which is caused by Alfvén waves generated at the single footpoint of the flux tube. We investigate three specific structures commonly found in the corona: 1) an open flux tube in a coronal hole, 2) an open flux tube on the edge of an equatorial streamer, and 3) an open flux tube directly neighboring an active region. We present the time-dependent heating rate, power spectra of fluctuations, and the time-averaged properties of the solar wind arising from each magnetic structure. We compare the time-averaged properties from the present modeling with previous results from a one-dimensional, time-steady code (Cranmer et al. 2007) to better calibrate the physics in the lower-dimensional code and get a better understanding of the intricate role that bursty, transient heating from Alfvén-wave-driven turbulence plays in the acceleration of the solar wind from different magnetic structures.

  18. [Variation patterns of soil wall temperature and heat flux in sunken solar greenhouse].

    PubMed

    Huang, Xue; Wang, Xiu-Feng; Wei, Min; Hou, Jia-Lin; Liu, Fu-Sheng; Li, Qing-Ming; Yang, Feng-Juan; Shi, Qing-Hua

    2013-06-01

    From December 2011 to March 2012, a consecutive test was conducted on the temperature and heat flux of different thickness of the soil backwall of sunken solar greenhouse in Shouguang of Shandong Province, East China, aimed to analyze the variation patterns of soil wall temperature and heat flux of the sunken solar greenhouse and to confirm the suitable wall thickness. In winter, the temperature and heat flux of the wall inner surface and outer surface varied over a wide range, which was in accordance with the variation trend of indoor and outdoor air temperature. Overall, the wall temperature decreased from the inner to the outer surface, and the layers of the inner wall with higher variation range of temperature and heat flux were more than those of the outer wall. The variation range of temperature and heat flux decreased gradually from the shallow layers to deep layers of the wall. In successive cloudy days, the temperature of each layer of inner wall decreased to different degrees, and the layers releasing heat to the indoor deepened constantly, whereas the heat in the layers of outer wall was mainly released to the outdoor. According to the variation patterns of temperature and heat flux in the wall, the wall from inside to outside could be divided into heat storage layer, transitional layer, and cold resistant layer, and their thickness was 0.8-1.0 m, 2.2-2.6 m, and 0.4-0.6 m, respectively, under the condition of the outer surface being covered. Without considering the transitional layer, the suitable thickness of the soil wall in Shouguang solar greenhouse would be 1.4-1.6 m. PMID:24066556

  19. Prediction of critical heat flux in water-cooled plasma facing components using computational fluid dynamics.

    SciTech Connect

    Bullock, James H.; Youchison, Dennis Lee; Ulrickson, Michael Andrew

    2010-11-01

    Several commercial computational fluid dynamics (CFD) codes now have the capability to analyze Eulerian two-phase flow using the Rohsenow nucleate boiling model. Analysis of boiling due to one-sided heating in plasma facing components (pfcs) is now receiving attention during the design of water-cooled first wall panels for ITER that may encounter heat fluxes as high as 5 MW/m2. Empirical thermalhydraulic design correlations developed for long fission reactor channels are not reliable when applied to pfcs because fully developed flow conditions seldom exist. Star-CCM+ is one of the commercial CFD codes that can model two-phase flows. Like others, it implements the RPI model for nucleate boiling, but it also seamlessly transitions to a volume-of-fluid model for film boiling. By benchmarking the results of our 3d models against recent experiments on critical heat flux for both smooth rectangular channels and hypervapotrons, we determined the six unique input parameters that accurately characterize the boiling physics for ITER flow conditions under a wide range of absorbed heat flux. We can now exploit this capability to predict the onset of critical heat flux in these components. In addition, the results clearly illustrate the production and transport of vapor and its effect on heat transfer in pfcs from nucleate boiling through transition to film boiling. This article describes the boiling physics implemented in CCM+ and compares the computational results to the benchmark experiments carried out independently in the United States and Russia. Temperature distributions agreed to within 10 C for a wide range of heat fluxes from 3 MW/m2 to 10 MW/m2 and flow velocities from 1 m/s to 10 m/s in these devices. Although the analysis is incapable of capturing the stochastic nature of critical heat flux (i.e., time and location may depend on a local materials defect or turbulence phenomenon), it is highly reliable in determining the heat flux where boiling instabilities begin to dominate. Beyond this threshold, higher heat fluxes lead to the boiling crisis and eventual burnout. This predictive capability is essential in determining the critical heat flux margin for the design of complex 3d components.

  20. Viscous hydrodynamic instability theory of the peak and minimum pool boiling heat fluxes

    NASA Technical Reports Server (NTRS)

    Dhir, V. K.

    1972-01-01

    Liquid viscosity was included in the Bellman-Pennington theory of the Taylor wave in a liquid vapor interface. Predictions of the most susceptible wavelength, and of the wave frequency, were made as a function of a liquid viscosity parameter and the Bond number. The stability of a gas jet in a viscous liquid was studied and the result is used to predict the peak heat flux on large horizontal heaters. Experimental measurements of the dominant Taylor wave and its growth rate were made during the film boiling of cyclohexanol on cylindrical heaters. The results bear out the predictions quite well. The thickness of the vapor blanket surrounding a cylindrical heater was measured and a correlation suggested. The effect of large fluxes of vapor volume on the dominant wavelength was also noted. Theoretical results of the peak heat flux are compared with the experimental data, and the effect of finite geometry of flat plate heaters on the peak heat flux is also discussed.