Note: This page contains sample records for the topic radiative heat flux from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Radiative heat flux control over spherical surfaces  

Microsoft Academic Search

Tremendous efforts have been and are being devoted to control the radiative heat flux over complex spherical surfaces such as solar energy collectors. Classical energy balance methods and network analysis have been used by previous investigators to evaluate the relevant exchange-factors of any spherical collector. The complex characteristics of the radiative flux in automatic control systems of such surfaces, the

Mansoor Karimifar; Sirus Aghanajafi; Ario B. Shabani

1997-01-01

2

Spectral estimates of net radiation and soil heat flux  

USGS Publications Warehouse

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.

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

1990-01-01

3

Nonequilibrium radiative heat flux modeling for the Huygens entry probe  

NASA Astrophysics Data System (ADS)

An electronic collisional-radiative model is proposed to predict the nonequilibrium populations and the radiation of the excited electronic states CN(A, B) and N2(A, B, C) during the entry of the Huygens probe into the atmosphere of Titan. The model is loosely coupled with flow solvers using a Lagrangian method. First, the model was tested against measurements obtained with the shock-tube of NASA Ames Research Center. Then, the model was applied to the simulation of Huygen's entry. Our simulations predict that the population of the CN(B) state is lower than the Boltzmann population by a factor 40 at trajectory time t = 165 s and by a factor 2 at t = 187 s and that the population of the CN(A) state remains close to the Boltzmann population for both trajectory points. The radiative heat fluxes, driven by the CN(A, B) states, are lower than predictions based on the Boltzmann populations by a factor 15 at t = 165 s and a factor 2 at t = 187 s.

Magin, T. E.; Caillault, L.; Bourdon, A.; Laux, C. O.

2006-07-01

4

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

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.

1996-01-01

5

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

6

Measuring Radiation Heat Fluxes from a Jet Fire Using a Lumped Capacitance Model  

Microsoft Academic Search

This paper presents an experimental methodology for measuring the incident radiation heat flux distribution surrounding a\\u000a jet fire. The methodology uses a line of surface thermocouples attached to a steel bar. The thermocouples measure the temperature\\u000a time history of the steel bar in response to an imposed incident radiation heat flux. The theoretical basis of the methodology\\u000a is an energy

Peter S. Cumber

2011-01-01

7

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

8

Radiation Transfer Analysis on Heating Mechanism of Magnetohydrodynamic Emerging Magnetic Flux Tube  

NASA Astrophysics Data System (ADS)

In spite of the large number of magnetohydrodynamic (MHD) simulations of emerging flux tubes in the solar atmosphere, radiation properties of the phenomenon remain poorly understood. This is because heating at the footpoints of the emerging magnetic field lines is significant and the effects associated with heat conduction and evaporation have largely been neglected. In this study, we have performed three-dimensional (3-D) multi-wavelength radiation transfer calculations on a MHD model of an emerging flux tube in order to examine the MHD model and also to identify a possible heating mechanism for explaining the properties of observed X-ray coronal loops. It is found that the current dissipation model is difficult for reproducing the structure of X-ray loops observed by Hinode XRT and Yohkoh SXT. This suggests that alternative models of the heating process should be incorporated into our MHD models. We left unresolved issues of the heating process as future work.

Kato, Y.; Magara, T.; Shimizu, T.

2009-12-01

9

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

SciTech Connect

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.

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

2010-03-31

10

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

11

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

NASA Technical Reports Server (NTRS)

A radiative-transfer model has been used to derive the structure and amplitude of the solar fluxes and heating rates in the Venus mesosphere, accounting for absorption and scattering extinction sources that encompass CO2, H2O, SO2, and H2SO4 aerosols as well as an unidentified UV absorber. The unknown substance that causes the observed cloud-top UV contrasts is responsible for most of the absorption of sunlight within the upper cloud deck; this contributes to solar heating rates of the order of 6 K/day at levels near 65 km. These results are judged sufficiently reliable for use in numerical dynamical models of the Venus atmosphere.

Crisp, D.

1986-01-01

12

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

13

Heat flux measurements  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.; Weikle, Donald H.

1989-01-01

14

Comparison of Measured and Modeled Radiation, Heat and Water Vapor Fluxes: Fife Pilot Study. Status Report April 1, 1985-December 31, 1986.  

National Technical Information Service (NTIS)

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...

B. L. Blad K. G. Hubbard S. B. Verma P. Starks J. M. Norman

1987-01-01

15

Heat flux sensor calibrator  

NASA Astrophysics Data System (ADS)

The heat flux to space shuttle main engine (SSME) turbopump turbine blades may be as high as 10 to the 7th power. The heat flux causes thermal transients that are of the order of 1 sec as temperature varies from perhaps 1500 K to 100 K. It is suspected that these transients cause durability problems in the turbine blades. To quantitatively evaluate the effect of these transients, heat flux sensors or gauges were developed to obtain data to verify analytical models. The objective is to design and fabricate a system for steady state and transient calibration and durability testing of heat flux sensors for use in SSME turbine blades. The calibrator consists of: (1) the arc lamp, (2) a high speed positioning table for placing standard and special heat flux sensors in the incident beam of radiant heat flux, (3) provision for cooling the blade and special sensors inserted in the blade, (4) a computer for controlling the positioning table, storing electrical output values from sensors, and calculating heat flux from these values, and (5) a pyrometer for measuring sensor surface temperatures.

Liebert, C. H.

1985-05-01

16

Electrostatic heat flux instabilities  

NASA Technical Reports Server (NTRS)

The electrostatic cyclotron and ion acoustic instabilities in a plasma driven by a combined heat flux and current were investigated. The minimum critical heat conduction speed (above which the plasma is unstable) is given as a function of the ratio of electron to ion temperatures.

Morrison, P. J.; Ionson, J. A.

1980-01-01

17

A study of the behavior of composite materials under conditions of the combined effect of radiative-convective heat fluxes  

NASA Astrophysics Data System (ADS)

To investigate the stability of composite materials under conditions of high-intensity radiative-convective heat fluxes, specimens of glass/phenol formaldehyde/silica, glass/organosilicon resin/quartz, and carbon/phenol formaldehyde composites were tested by using a discharge generating a high-temperature plasma flow pressed to the specimen surface by an external magnetic field. The full sublimation energies of the materials tested are determined with allowance for the spectral absorption coefficient of the ablating surface.

Polezhaev, Iu. V.; Tlevtsezhev, V. A.; Strakhov, V. L.

1989-04-01

18

Measurement of unsteady heat flux  

NASA Astrophysics Data System (ADS)

The authors examine the influence of the volume nature of absorption of radiative flux on the operation of a heat converter with a thin-film resistive sensor. It is shown that allowing for volume absorption leads to a change in the form of the transfer function: it becomes rational (in contrast with the case of surface absorption, where the transfer function is irrational), because the converter heat-sensitive element 'integrates' the incident flux. The influence of the inertial properties of thin layers of black coating on the response time of the converter is examined.

Bautin, A. V.; Poliakov, Iu. A.

1980-07-01

19

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)

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.

Nath, G.; Vishwakarma, J. P.

2014-05-01

20

Optical heat flux gauge  

DOEpatents

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.

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

21

Optical heat flux gauge  

DOEpatents

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.

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

22

Optical heat flux gauge  

DOEpatents

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.

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

23

Heat Flux Sensor Testing  

Microsoft Academic Search

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

D. W. Clark

2002-01-01

24

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

NASA Astrophysics Data System (ADS)

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.

Ulusoy, ?nan

2014-05-01

25

Optical heat flux gauge  

DOEpatents

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.

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

1991-04-09

26

Heat Flux Sensor Testing  

NASA Astrophysics Data System (ADS)

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.

Clark, D. W.

2002-07-01

27

Heat Flux Sensor Testing  

NASA Technical Reports Server (NTRS)

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.

Clark, D. W.

2002-01-01

28

Pyrolytic graphite gauge for measuring heat flux  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

29

Spatialization of instantaneous and daily average net radiation and soil heat flux in the territory of Itaparica, Northeast Brazil  

NASA Astrophysics Data System (ADS)

This work has as aim to quantify the energy changes between atmosphere and surface by modeling both net radiation and soil heat flux related to land use and cover. The methodology took into account modeling and mapping of physical and biophysical parameters using MODIS images and SEBAL algorithm in an area of native vegetation and irrigated crops. The results showed that there are variations in the values of the estimated parameters for different land cover types and mainly in caatinga cover. The dense caatinga presents mean values of soil heat flux (Go) of 124.9 Wm-2 while sparse caatinga with incidence of erosion, present average value of 132.6 Wm-2. For irrigated plots cultivated with banana, coconut, and papaya the mean Go values were 103.8, 98.6, 113.9 Wm-2, respectively. With regard to the instantaneous net radiation (Rn), dense caatinga presented mean value of 626.1 Wm-2, while sparse caatinga a mean value of 575.2 Wm-2. Irrigated areas cultivated with banana, coconut, and papaya presented Rn of 658.1, 647.4 and 617.9 W m-2 respectively. Applying daily mean net radiation (RnDAve) it was found that dense caatinga had a mean value of 417.1 W m-2, while sparse caatinga had a mean value of 379.9 W m-2. For the irrigated crops of banana, coconut and papaya the RnDAve values were 430.9, 431.3 and 411.6 W m-2, respectively. Sinusoidal model can be applied to determine the maximum and RnDAve considering the diverse classes of LULC; however, there is a need to compare the results with field data for validation of this model.

Lopes, Helio L.; Silva, Bernardo B.; Teixeira, Antônio H. C.; Accioly, Luciano J. O.

2012-09-01

30

Critical heat flux around strongly heated nanoparticles.  

PubMed

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. PMID:19391744

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

2009-02-01

31

High heat flux single phase heat exchanger  

NASA Technical Reports Server (NTRS)

This paper presents the results obtained to date in a program to develop a high heat flux, single-phase heat exchanger for spacecraft thermal management. The intended application is a net generation interface heat exchanger to couple the crew module water thermal bus to the two-phase ammonia main thermal bus in the Space Station Freedom. The large size of the interface heat exchanger is dictated by the relatively poor water-side heat transfer characteristics. The objective of this program is to develop a single-phase heat transfer approach which can achieve heat fluxes and heat transfer coefficients comparable to those of the evaporation ammonia side. A new heat exchanger concept has been developed to meet these objecties. The main feature of this heat exchanger is that it can achieve very high heat fluxes with a pressure drop one to two orders of magnitude lower than those of previous microchannel or jet impingement high heat flux heat exchangers. This paper describes proof-of-concept experiments performed in air and water and presents analytical model of the heat exchanger.

Valenzuela, Javier A.; Izenson, Michael G.

1990-01-01

32

Heat flux microsensor measurements and calibrations  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

33

Evaluation of the radiative heat flux in absorbing, emitting and anisotropically scattering cylindrical media  

NASA Astrophysics Data System (ADS)

An exact solution is presented for radiative transfer in a gray, emitting, absorbing, and linear-anisotropically scattering medium of one-dimensional cylindrical geometry. The solution results in a first-order integral equation in the radial coordinate system, thus reducing the cylindrical case to the plane-parallel problem. Two approximate methods, differential approximation and a kernel approximation, are proposed which reduce the problem to a solution of a differential rather than an integral equation. The results presented demonstrate the accuracy and applicability of both approximate methods.

Azad, F. H.; Modest, M. F.

1980-07-01

34

Fabrication of Thin Film Heat Flux Sensors  

NASA Technical Reports Server (NTRS)

Prototype thin film heat flux sensors have been constructed and tested. The sensors can be applied to propulsion system materials and components. The sensors can provide steady state and fast transient heat flux information. Fabrication of the sensor does not require any matching of the mounting surface. Heat flux is proportional to the temperature difference across the upper and lower surfaces of an insulation material. The sensor consists of an array of thermocouples on the upper and lower surfaces of a thin insulating layer. The thermocouples for the sensor are connected in a thermopile arrangement. A 100 thermocouple pair heat flux sensor has been fabricated on silicon wafers. The sensor produced an output voltage of 200-400 microvolts when exposed to a hot air heat gun. A 20 element thermocouple pair heat flux sensor has been fabricated on aluminum oxide sheet. Thermocouples are Pt-Pt/Rh with silicon dioxide as the insulating material. This sensor produced an output of 28 microvolts when exposed to the radiation of a furnace operating at 1000 C. Work is also underway to put this type of heat flux sensor on metal surfaces.

Will, Herbert A.

1992-01-01

35

Conical electromagnetic radiation flux concentrator  

NASA Technical Reports Server (NTRS)

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.

Miller, E. R.

1972-01-01

36

Heat Flux-Based Emissivity Measurement  

NASA Astrophysics Data System (ADS)

This paper describes a heat flux-based method for measuring emissivity of a surface. In this method the emissivity of a surface is calculated using direct measurement of the heat flux passing through the surface. Unlike storage-based calorimetric methods, this method does not require application of known amounts of heat to the surface or the temperature history of a known amount of thermal mass to calculate the surface emissivity. Application and operation of this method is much simpler than calorimetric methods as it does not require careful thermal insulation of the heat radiating body from the surroundings. The low thermal capacitance and scalability of the heat flux sensors can provide good temporal and spatial resolution of the heat flux and, therefore, the emissivity. This technique allows emissivity measurements of the newly developed variable emissivity surfaces with significantly lighter and energy efficient measurement equipment that can operator for long term space missions. In this study, a commercially available thermopile heat flux sensor was used to measure the emissivity of a black paint for a temperature range of -100 to 100 °C. This paper details the concept, experimental setup, and the experiment results.

Moghaddam, Saeed; Lawler, John; McCaffery, Collin; Kim, Jungho

2005-02-01

37

Validation Experiments to Determine Radiation Partitioning of Heat Flux to an Object in a Fully Turbulent Fire.  

National Technical Information Service (NTIS)

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 ...

A. Ricks D. Jernigan T. Blanchat

2006-01-01

38

Heat flux converter  

Microsoft Academic Search

(usually by means of glue or putty). The operation of such a converter is based upon measurement of the entire quantity of heat which enters it from the start of the process. Strict fulfillment of the latter condition is guaranteed by a choice of thickness of the calorimeter such that its inner surface is heated just so much during the

B. I. Bakum; L. V. Novikov; Yu. V. Yakhlakov

1968-01-01

39

On the use of radiative surface temperature to estimate sensible heat flux over sparse shrubs in Nevada  

NASA Technical Reports Server (NTRS)

The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

Chehbouni, A.; Nichols, W. D.; Qi, J.; Njoku, E. G.; Kerr, Y. H.; Cabot, F.

1994-01-01

40

Heat flux limiting sleeves  

DOEpatents

A heat limiting tubular sleeve extending over only a portion of a tube having a generally uniform outside diameter, the sleeve being open on both ends, having one end thereof larger in diameter than the other end thereof and having a wall thickness which decreases in the same direction as the diameter of the sleeve decreases so that the heat transfer through the sleeve and tube is less adjacent the large diameter end of the sleeve than adjacent the other end thereof.

Harris, William G. (Tampa, FL)

1985-01-01

41

Towards Improved Estimates of Ocean Heat Flux  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

42

Latent Heat Flux  

NSDL National Science Digital Library

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.

Climvis.org

43

Urban Signatures: Latent Heat Flux  

NSDL National Science Digital Library

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.

Delabeaujardiere, Jeff

2005-05-27

44

Self-Similar Solution of Self-Gravitating, Magneto-Gas Dynamic Spherical Shock Wave Propagating in a Rotating Medium with Radiation Heat Flux  

SciTech Connect

Self-similar solutions for the flow behind a self-gravitating, Magneto-gas dynamic, spherical shock wave are obtained. The ambient medium is a non uniformly rotating gas of infinite electrical conductivity with uniform azimuthal magnetic field and radiation heat flux. The medium is a perfect grey gas in local thermodynamic equilibrium. The total energy of the expanding shock wave is supposed to remain constant. The effects of variations of the shock Mach number, the Alfven Mach number, the radiation parameter and the gravitation on flow field behind the shock wave are shown graphically and discussed.

Sharma, Pankaj [Department of Applied Mathematics, Jawaharlal Institute of Technology, Borawan, Khargone-451228 (India); Sharma, Vivek Kumar [Department of Applied Mathematics and Computational Science, Shri G. S. Institute of Technology and Science, 23, Park Road, Indore-452003 (India)

2009-07-02

45

Temperature and Flux Scales for Heat-Flux Sensor Calibration  

NASA Astrophysics Data System (ADS)

Methodologies for calibrating heat-flux sensors designed for direct measurement of heat-transfer at a surface are presented. These sensors, extensively used in fire-test methods and aerospace applications, vary in range from a few kW/m2 to in excess of 500 kW/m2. Traceable source- and detector-based techniques using blackbody radiation are described to cover the wide range of calibration. Calibration results on typical sensors from three blackbody facilities: 25 mm and 51 mm diameter heated graphite tubes and a 23 cm diameter spherical cavity, are presented. These results demonstrate the equivalence between the source- and detector-based techniques in the range from 50 kW/m2 to 200 kW/m2, and also the superiority of detector-based calibration when reflected radiation effects are important. The problems associated with extending the calibration techniques to high heat-flux levels by inserting the sensor inside a blackbody cavity are also discussed.

Murthy, A. V.; Dewitt, D. P.; Tsai, B. K.; Fraser, G. T.; Saunders, R. D.

2003-09-01

46

Fabrication of thin film heat flux sensors  

NASA Technical Reports Server (NTRS)

Thin-film heat-flux sensors have been constructed in the form of arrays of thermocouples on upper and lower surfaces of an insulating layer, so that flux values are proportional to the temperature difference across the upper and lower surface of the insulation material. The sensor thermocouples are connected in thermopile arrangement, and the structure is patterned with photolithographic techniques. Both chromel-alumel and Pt-Pt/Rh thermocouples have been devised; the later produced 28 microvolts when exposed to the radiation of a 1000 C furnace.

Will, Herbert

1991-01-01

47

Vertical eddy heat fluxes from model simulations  

NASA Technical Reports Server (NTRS)

Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.

Stone, Peter H.; Yao, Mao-Sung

1991-01-01

48

Spatial Scale Gaps of Turbulent Heat Fluxes in Arctic Tundra  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

49

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)

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.

Nath, G.

2012-01-01

50

Evaluation of factors affecting heat flux sensors  

Microsoft Academic Search

A program to evaluate heat-flux sensors employed in thermal measurements of passive solar structures has been performed. A guarded hot box was designed and built in accordance with ASTM Standard C236-80 to generate known heat fluxes through a variety of structural materials. These fluxes were compared with those measured by a heat flux transducer calibrated by both by the manufacturer

A. J. Darnell; L. R. McCoy; W. B. Ingle

1983-01-01

51

Remote sounding of surface radiative fluxes in cirrus cloudy conditions  

NASA Technical Reports Server (NTRS)

It has been long recognized that radiation and radiation perturbations play a critical role in the climate system. Surface radiative fluxes are useful parameters for monitoring global change, for understanding of the effects of clouds on the radiation field, and for improving parameterization of surface sensible and latent heat fluxes. Monitoring of the radiation budget at the top of the atmosphere has been one of the prime satellite programs for the last 30 years. However, monitoring radiative fluxes at the surface over the globe from space cannot be performed in a direct way at the present time. In particular, since clouds are the prime regulators of the radiative fluxes, uncertainties in the retrieved cloud parameters, which are inputs to radiative transfer models, can introduce significant errors in the computed radiative fluxes. Thus, remote sounding of surface radiative fluxes in cloudy conditions requires the development of both satellite cloud retrieval scheme and radiation models. In this paper, we present results of computed surface radiative fluxes in cirrus cloudy conditions using a cirrus cloud retrieval scheme and a detailed radiative transfer program. Comparisons have been made between the computed surface radiative fluxes and the ground-based radiometer measurements obtained during FIRE-II-IFO, which was carried out near Coffeyville, Kansas, during November and December, 1991.

Ou, S. C.; Liou, K. N.

1995-01-01

52

A comparison of ground-based and satellite-derived radiative heat flux at Mt Etna: the 12 August lava fountain case study  

NASA Astrophysics Data System (ADS)

The recent eruptive activity at Mt Etna has been characterized by quiet frequent, intermittent episodes of lava fountains associated with small lava flow output, occurring especially at the SE Crater. During 2011, 18 paroxysmal lava fountains were produced by a new cone, named "Sturiale Cone", on the east flank of the SE Crater. Given the high hazard posed by this activity, and the need of improving detection, description and knowledge of these events, remote monitoring through fixed cameras and satellites has becoming crucial, especially using thermal sensors. We here focus on the 12 August 2011 episode, the strongest of the lava fountains occurred in 2011, and also the best monitored, given the clear sky, absence of clouds, and possibility to collect also images from a close-up view. We disposed of a total of 8 fixed cameras working around the volcano, three of them offering a thermal view of the episode. Moreover, as satellite observations, we could use the complete data set from the SEVIRI sensor, which has a temporal resolution of 15 minutes. To compare the field- and satellite-derived radiative heat flux curves, thermal images were registered by taking into account a DEM, the GPS camera position, the relative camera rotations and first order lens distortion parameters. Moreover, it was performed a pixel by pixel correction from path length and atmospheric effects. Finally, a temperature threshold was fixed to identify the active lava area and the amount of heat lost by radiation from all the pixels covered by lava was computed. SEVIRI data were analyzed by the HOTSAT thermal monitoring system. Through automatic hot-spot detection algorithm based on dynamic thresholds, we are able to provide an estimate of the radiant heat flux for each thermally anomalous pixel and possibly convert it into time averaged discharge rate. Preliminary results showed a good agreement on timing, shape and amplitude of the radiative heat flux time series between thermal camera and SEVIRI data. Moreover, we could identify different phases of the eruptive activity: the initial Strombolian explosive activity, the lava fountain episode, the lava flow emission and its final cooling. Eventually, from the cooling curve the total lava volume was estimated, finding that 2.8 million of cubic meters of lava were erupted with a mean output rate of about 200 cubic meters per second.

Ganci, Gaetana; Calvari, Sonia; James, Mike; Del Negro, Ciro

2013-04-01

53

Deployable Heat Pipe Radiator  

NASA Technical Reports Server (NTRS)

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.

Edelstein, F.

1975-01-01

54

Heat Flux-Based Emissivity Measurement  

Microsoft Academic Search

This paper describes a heat flux-based method for measuring emissivity of a surface. In this method the emissivity of a surface is calculated using direct measurement of the heat flux passing through the surface. Unlike storage-based calorimetric methods, this method does not require application of known amounts of heat to the surface or the temperature history of a known amount

Saeed Moghaddam; John Lawler; Collin McCaffery; Jungho Kim

2005-01-01

55

Critical Heat Flux Tests with High Pressure Water in an Internally Heated Annulus with Alternating Axial Heat Flux Distribution.  

National Technical Information Service (NTIS)

Critical heat flux experiments were performed with an alternating heat flux profile in an internally heated annulus. The heated length was 84 inches with a square wave alternating heat flux profile over the last 12 inches having a maximum-to-average heat ...

S. G. Beus D. A. Humphreys

1979-01-01

56

Dual Active Surface Heat Flux Gage Probe  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.; Kolodziej, Paul

1995-01-01

57

Estimates of net heat fluxes over the Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Many studies have been undertaken to evaluate turbulent heat fluxes at the ocean-atmosphere interface; less was done on the total net heat flux. We will compare heat budgets at the ocean-atmosphere interface as derived from satellites and from blended products, compare them to in situ observations, identify the location of largest differences, and attempt to explain reasons for these differences. The results over the Atlantic Sector (50°S-50°N) for a 3 year period show that differences in the turbulent fluxes among two widely used approaches are overshadowed by differences in the radiative fluxes. While the maximum difference in sensible and latent heat fluxes can be about 30 W/m2, the mean values for latent heat fluxes are -2.27 W/m2 for January and 5.40 W/m2 for July. For sensible heat, they are 2.82 W/m2 for January and 5.64 W/m2 for July. We show that the maximum difference in net radiative fluxes can be as high as 55 W/m2, for January, the mean difference in net SW is 6.31 W/m2 and in net LW it is 12.14 W/m2. For July, the respective differences are -9.99 W/m2 for the SW and 14.31 W/m2 for the LW. Relationships between the fluxes and satellite derived surface wind speed, total precipitable water, and cloud cover provide insight on the dominant processes that control the net heat flux. This study is intended to present an estimate of uncertainties that still exist in the net heat flux at the ocean-atmosphere interface.

Pinker, R. T.; Bentamy, A.; Katsaros, K. B.; Ma, Y.; Li, C.

2014-01-01

58

Miniature convection cooled plug-type heat flux gauges  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.

1994-01-01

59

High heat flux heat pipe mechanism for cooling of electronics  

Microsoft Academic Search

This paper discusses an advanced heat pipe mechanism that has the potential of achieving heat flux capabilities over 250 W\\/cm2. The mechanism utilizes thermally driven pulsating two-phase flow to achieve high heat flux capability and heat transfer coefficient. A simplified hydrodynamic model in was developed to guide the proof-of-concept heat pipe design. A more detailed numerical model was also developed

Z. Jon Zuo; M. T. North; K. L. Wert

2001-01-01

60

Evaluation of Factors Affecting Heat Flux Sensors.  

National Technical Information Service (NTIS)

A program to evaluate heat-flux sensors employed in thermal measurements of passive solar structures has been performed. A guarded hot box was designed and built in accordance with ASTM Standard C236-80 to generate known heat fluxes through a variety of s...

A. J. Darnell L. R. McCoy W. B. Ingle

1983-01-01

61

Divertor Heat Flux Mitigation in the National Spherical Torus Experiment  

SciTech Connect

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.

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

62

Divertor heat flux mitigation in the National Spherical Torus Experiment  

SciTech Connect

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 , 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(-2) to 0.5-2 MW m(-2) in small-ELM 0.8-1.0 MA, 4-6 MW neutral beam injection-heated H-mode discharges. A self-consistent picture of the 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.

Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL); Maingi, R. [Oak Ridge National Laboratory (ORNL); Gates, D.A. [Princeton Plasma Physics Laboratory (PPPL); Menard, J.E. [Princeton Plasma Physics Laboratory (PPPL); Bush, C.E. [Oak Ridge National Laboratory (ORNL)

2009-01-01

63

Heat fluxes across the Antarctic Circumpolar Current  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

64

Consideration of critical heat flux margin prediction by subcooled or low quality critical heat flux correlations  

Microsoft Academic Search

The accurate prediction of the critical heat flux (CHF) margin which is a key design parameter in a variety of cooling and heating systems is of high importance. These margins are, for the low quality region, typically expressed in terms of critical heat flux ratios using the direct substitution method. Using a simple example of a heated tube, it is

Pavel Hejzlar; Neil E. Todreas

1996-01-01

65

Radiation fluxes at the FIFE site  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

66

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.

67

Ocean surface heat flux variability in the Barents Sea  

NASA Astrophysics Data System (ADS)

A 40 year (1958-1997) hindcast simulation from the regional coupled ice-ocean model HAMSOM is used to study climate relevant processes in the Barents Sea and their interannual to decadal variability. Compared to observations the model captures the variability in temperature and ice extent in a satisfying manner. The heat input through the Barents Sea Opening (BSO) is effectively lost through intense atmosphere-ocean heat exchange within the Barents Sea. Correlation analysis suggests that heat transport through the BSO leads the Barents Sea heat content by 1-10 months, while the heat content leads the air-sea heat fluxes with 1-5 months. Averaged over the period the advected heat input is 32 TW, augmented by 79 TW of shortwave radiation and reduced by 113 TW through longwave radiation and latent and sensible heat loss. Including the sensible heat loss at the ice-ocean boundary yields an oceanic heat loss in the Barents Sea of 40 TW. Cooling of Atlantic Water is very efficient just east of the BSO, and contributes to 50% of the total heat loss. Significant positive trends in both heat transport through the BSO and solar radiation, combined with a reduction in seasonal ice cover cause increased oceanic heat loss. Excess heat still enters the Barents Sea and a significant warming is observed in the northern areas. Sea-ice acts as an effective insulator against oceanic heat loss resulting in 4 TW of net heat input at the sea-ice surface. This heat flux balances the ice-ocean heat budget and the corresponding ice melt compensates for net ice production at the ice-ocean interface and ice advection into the Barents Sea.

Årthun, M.; Schrum, C.

2010-10-01

68

Evaluation of factors affecting heat flux sensors  

SciTech Connect

A program to evaluate heat-flux sensors employed in thermal measurements of passive solar structures has been performed. A guarded hot box was designed and built in accordance with ASTM Standard C236-80 to generate known heat fluxes through a variety of structural materials. These fluxes were compared with those measured by a heat flux transducer calibrated by both by the manufacturer and an independent laboratory. The guarded hot plate method, ASTM C117-76, was used in the latter case. The three sets of values were often in substantial disagreement, the extent of which varied with the substrate to which the transducer was attached. An analysis of the data indicates that the cause of disagreement lies in a local distortion of the heat flux through the substrate caused by the presence of the transducer. Disturbance of the air flow over the transducer and mismatch of surface thermal emissivities of the transducer and substrate are contributing factors. This work has demonstrated a need for a standardized procedure for heat flux sensor calibration, and the ASTM guarded hot plate method is recommended for this purpose. An approximate method for correcting the heat flux indicated by a transducer calibrated in this manner to bring it in agreement with the measured by the guarded hot box is presented.

Darnell, A.J.; McCoy, L.R.; Ingle, W.B.

1983-01-01

69

Surface heat flux data from energy balance Bowen ratio systems  

SciTech Connect

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.

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

1995-06-01

70

Scaling and profiles of heat flux during partial detachment in DIII-D  

SciTech Connect

The authors examine the scaling of the peak divertor heat flux and total divertor plate power in partially detached divertor (PDD) discharges in DIII-D, as a function of input power and radiated power. The peak divertor heat flux in the attached plasma increases linearly with input power, but saturates in the detached cases. The total divertor plate power remains linear with input power in both the attached and detached plasmas. This is consistent with the fact that the heat flux peak is reduced from the attached case but other areas receive increased radiant heating from the detached plasma. The divertor plate radiant heating is linear with input power because the total radiated power from the entire plasma is a linear function of input power in both attached and detached plasma. In the private flux region, radiated heat flux absorbed on the target plate calculated from bolometer data is enough to account for the measured plate heating. Approximately half of the overall plate heating power in detached plasma is due to absorbed radiation. By mapping the divertor heat flux before and during the PDD to flux coordinates, and comparing with a flux mapping of inserted bolometer and tangential TV data, they have verified that the radiated power is emitted from the same flux surfaces on which heat flux is reduced.

Lasnier, C.J.; Hill, D.N.; Allen, S.L.; Fenstermacher, M.E.; Porter, G.D. [Lawrence Livermore National Lab., CA (United States); Leonard, A.W.; Petrie, T.W. [General Atomics, San Diego, CA (United States); Watkins, J.G. [Sandia National Labs., Albuquerque, NM (United States)

1998-08-01

71

Direct computation of the sensible heat flux.  

USGS Publications Warehouse

An algorithm to determine the sensible heat flux from simple field measurements (wind speed, air and ground temperatures) has been developed. It provides a direct solution, in parametric form, which can be displayed graphically or tabularly. -from Author

Watson, K.

1980-01-01

72

Graphite-Fiber Heat Radiators  

NASA Technical Reports Server (NTRS)

Heat radiators of proposed type feature thermally conductive fibers protruding from metallic surfaces to provide increased heat-dissipation surface areas. Free of leaks and more reliable than radiators incorporating heat pipes. Also lightweight and relatively inexpensive. Radial graphite fibers carry heat away from spherical shell and radiate heat into space. Radiators prove useful on Earth in special industrial and scientific applications involving dissipation of heat in vacuum or in relatively still air.

Phillips, Wayne M.

1995-01-01

73

Spatially averaged heat flux and convergence measurements at the ARM regional flux experiment  

SciTech Connect

Cloud formation and its relation to climate change is the greatest weakness in current numerical climate models. Surface heat flux in some cases causes clouds to form and in other to dissipate and the differences between these cases are subtle enough to make parameterization difficult in a numerical model. One of the goals of the DOE Atmospheric Radiation Measurement program is to make long term measurements at representative sites to improve radiation and cloud formation parameterization. This paper compares spatially averaged optical measurements of heat flux and convergence with a goal of determining how point measurements of heat fluxes scale up to the larger scale used for climate modeling. It was found that the various optical techniques used in this paper compared well with each other and with independent measurements. These results add confidence that spatially averaging optical techniques can be applied to transform point measurements to the larger scales needed for mesoscale and climate modeling. 10 refs., 6 figs. (MHB)

Porch, W.; Barnes, F.; Buchwald, M.; Clements, W.; Cooper, D.; Hoard, D. (Los Alamos National Lab., NM (United States)); Doran, C.; Hubbe, J.; Shaw, W. (Pacific Northwest Lab., Richland, WA (United States)); Coulter, R.; Martin, T. (Argonne National Lab., IL (United States)); Kunkel, K. (Illinois State Water Survey, Champaign, IL (United States))

1991-01-01

74

Urban Signatures: Sensible Heat Flux (WMS)  

NSDL National Science Digital Library

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.

Delabeaujardiere, Jeff

2005-05-27

75

Radiation flux tables for ICRCCM using the GLA GCM radiation codes  

NASA Technical Reports Server (NTRS)

Tabulated values of longwave and shortwave radiation fluxes and also cooling and heating rates in the atmosphere for standard atmospheric profiles are presented. The radiation codes used in the Goddard general circulation model were employed for the computations. These results were obtained for an international intercomparison projected called Intercomparison of Radiation Codes in Climate Models (ICRCCM).

HARSHVARDHAN

1986-01-01

76

Critical heat flux test apparatus  

DOEpatents

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.

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

1992-01-01

77

Low Temperature High Sensitivity Temperature Compensated Heat Flux Sensor  

Microsoft Academic Search

Miniature (0.74×0.71×0.14 cm thick) heat flux transducers were designed and constructed to measure heat transfer by conduction, convection, radiation, or almost any combination of these from 75 to 300 K. A high sensitivity, approximately constant at 250 mV?(W?cm2), was obtained by utilizing the semiconductor silver-antimony-telluride. Temperature compensation was achieved by matching the changing properties of the insulating material to the

E. H. Schulte; R. F. Kohl

1969-01-01

78

Radiative Heating Profiles for Tropical Cloud Regimes  

NASA Astrophysics Data System (ADS)

Radiative heating is important for its effects on atmospheric circulation and cloud evolution in addition to its central role in influencing the atmospheric temperature structure. The vertical distribution of radiative heating is determined by the vertical profile of gases such as water vapor, ozone and CO2 as well as by clouds. The Atmospheric Radiation Measurement (ARM) program operates sites around the world which provide measurements of surface radiative fluxes and various measurements of the atmospheric state that effect surface fluxes. Continuously operating millimeter cloud radars at each site provide the means to derive vertical profiles of cloud properties. In previous work, we have used these cloud profiles in combination with profiles of temperature and humidity from radiosondes to calculate radiative flux profiles using a 4-stream radiative transfer model at the three tropical ARM sites: Manus, Nauru, and Darwin. In the current study, we will use the vertical profiles of cloud properties at these sites to segregate the data into distinct cloud regimes. By compositing radiative heating profiles in different regimes, we will define characteristic radiative heating profiles of each cloud regime. Analysis of the data in terms of cloud regime provides datasets which can be more easily compared with climate model results.

Mather, J. H.; McFarlane, S. A.

2007-12-01

79

Numerical Analysis of a Radiant Heat Flux Calibration System  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

80

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

81

Heat fluxes in the Drake Passage  

NASA Astrophysics Data System (ADS)

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 [Sekma et al., 2012]. The respective contributions of the eddy and mean flows to the heat flux across the ACC in the Drake Passage are investigated using in situ measurements collected during the DRAKE 2006-9 project (from January 2006 to March 2009) and available observations from the historical DRAKE 79 experiment. DRAKE 2006-9 current meter records, obtained from a current meter array deployed on the eastern side of the Shackleton Fracture Zone (SFZ), revealed a vertical consistency of the velocity and temperature variations. However, the rotation of the mean velocity vector with depth indicated consistent downwelling through the entire water column practically all along the mooring line. In situ temperature and velocity time series from the DRAKE 2006-9 project were combined with the year-long historical DRAKE 79 experiment data set in order to analyse the eddy and mean flow contributions to the meridional heat flux across in the Drake Passage. Estimated cross-stream heat fluxes caused by the rotation of the mean flow with depth were found to be at least an order of magnitude larger than eddy heat ?uxes. Equatorward heat fluxes caused by the mean flow found downstream the SFZ were in agreement with the general downwelling observed along the DRAKE 2006-9 project mooring array. Upstream the SFZ, however, the distribution of equatorward and poleward fluxes was puzzling. This distribution was analyzed using model outputs. Heat flux due to the mean ?ow estimated from the high resolution model outputs were similar to those obtained from in situ data and exhibited small spatial scales. The rough topography in Drake Passage likely promotes associated small spatial scales of vertical velocities and heat fluxes. The model-estimated heat flux due to the mean flow across the Southern ACC Front in Drake Passage (covering about 3% of the circumpolar longitudes between 48° W and 64° W) is on the order of 10% of the heat lost to the atmosphere south of 60° S.

Ferrari, Ramiro; Provost, Christine; Hyang Park, Young; Sennéchael, Nathalie; Sekma, Hela; Garric, Gilles

2014-05-01

82

Bidirectional electron heat flux events in space  

SciTech Connect

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.

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

1986-01-01

83

Bidirectional solar wind electron heat flux events  

Microsoft Academic Search

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

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

1987-01-01

84

Critical heat flux in helically coiled tubes  

Microsoft Academic Search

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,

M. K. Jensen; A. E. Bergles

1981-01-01

85

Dryout heat fluxes for inductively heated particulate beds  

Microsoft Academic Search

Experimental observations of the dryout heat fluxes for inductively heated particulate beds have been made. The data were obtained when steel and lead particles in the size distribution 295 to 787 microns were placed in a 4.7-cm dia pyrex glass jar and inductively heated by passing radio frequency current through a 13.3-cm dia multiturn work coil encircling the jar. Distilled

V. Dhir; I. Catton

1977-01-01

86

Poleward heat flux by an ocean gyre  

NASA Astrophysics Data System (ADS)

A calculation to determine the poleward heat flux by an oceanic subtropical gyre is described. The circulation is given by Stommel's (1948) barotropic wind-driven model, and the temperature field is treated as a passive tracer. Air-sea heat exchange is parameterized as linearly proportional to the difference between air and sea temperatures. The problem so formulated reduces to the solution of the advection-diffusion (heat) equation for the temperature. The results show how ocean circulation, with a narrow western boundary layer, transports significantly more heat than does a symmetric circulation. A more intense circulation transports more heat but the increase levels off beyond a certain point. A wide ocean basin transports more of its heat by conduction than does a narrow basin. Approximate analytical solutions for both weak and strong circulations yield results that agree semiquantitatively with the numerical results.

Bye, J. A. T.; Veronis, George

1980-01-01

87

RADIATIVE HEATING OF THE SOLAR CORONA  

SciTech Connect

We investigate the effect of solar visible and infrared radiation on electrons in the Sun's atmosphere using a Monte Carlo simulation of the wave-particle interaction and conclude that sunlight provides at least 40% and possibly all of the power required to heat the corona, with the exception of dense magnetic flux loops. The simulation uses a radiation waveform comprising 100 frequency components spanning the solar blackbody spectrum. Coronal electrons are heated in a stochastic manner by low coherence solar electromagnetic radiation. The wave 'coherence time' and 'coherence volume' for each component is determined from optical theory. The low coherence of solar radiation allows moving electrons to gain energy from the chaotic wave field which imparts multiple random velocity 'kicks' to these particles causing their velocity distribution to broaden or heat. Monte Carlo simulations of broadband solar radiative heating on ensembles of 1000 electrons show heating at per particle levels of 4.0 x 10{sup -21} to 4.0 x 10{sup -20} W, as compared with non-loop radiative loss rates of {approx}1 x 10{sup -20} W per electron. Since radiative losses comprise nearly all of the power losses in the corona, sunlight alone can explain the elevated temperatures in this region. The volume electron heating rate is proportional to density, and protons are assumed to be heated either by plasma waves or through collisions with electrons.

Moran, Thomas G., E-mail: moran@grace.nascom.nasa.gov [Physics Department, Catholic University of America, 200 Hannan Hall, Washington, DC 20064 (United States) and NASA/GSFC, Code 671, Greenbelt, MD 20771 (United States)

2011-10-20

88

Measuring Response Of Propellant To Oscillatory Heat Flux  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

89

Solid propellant combustion response to oscillatory radiant heat flux  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

90

Measurement of local high-level, transient surface heat flux  

NASA Technical Reports Server (NTRS)

This study is part of a continuing investigation to develop methods for measuring local transient surface heat flux. A method is presented for simultaneous measurements of dual heat fluxes at a surface location by considering the heat flux as a separate function of heat stored and heat conducted within a heat flux gage. Surface heat flux information is obtained from transient temperature measurements taken at points within the gage. Heat flux was determined over a range of 4 to 22 MW/sq m. It was concluded that the method is feasible. Possible applications are for heat flux measurements on the turbine blade surfaces of space shuttle main engine turbopumps and on the component surfaces of rocket and advanced gas turbine engines and for testing sensors in heat flux gage calibrators.

Liebert, Curt H.

1988-01-01

91

Turbulent Exchange and Heat Fluxes in the Surface Layer of the Sea.  

National Technical Information Service (NTIS)

On the basis of experimental data and the generalized Fjeldstad method the vertical coefficients of turbulent exchange and heat flux in the surface layer of the sea were computed. The amplitudes and phases of the radiation and turbulent heat fluxes and th...

A. A. Pivovarov E. P. Anisimova L. A. Bukina

1968-01-01

92

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

Microsoft Academic Search

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

W. G. M Bastiaanssen

2000-01-01

93

HEAT TRANSFER BY COMBINED FORCED CONVECTION AND THERMAL RADIATION IN A HEATED TUBE  

Microsoft Academic Search

An analysis is made to study the heat exchange by combined forced ; convection and thermal radiation in a tube when there is a specified heat flux ; imposed at the tube wall. The gas flowing in the tube is assumed transparent to ; radiation, so that the radiation which is included takes place between the ; elemerts of the

M. Perlmutter; R. Siegel

1962-01-01

94

Transient critical heat flux and blowdown heat-transfer studies  

Microsoft Academic Search

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

1980-01-01

95

Transient critical heat flux and blowdown heat-transfer studies  

Microsoft Academic Search

Objective is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. A predictional method has been developed which 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)

1980-01-01

96

Evaluation of multi-dimensional flux models for radiative transfer in cylindrical combustion chambers  

Microsoft Academic Search

Four flux-type models for radiative heat transfer in cylindrical configurations were applied to the prediction of radiative flux density and source term of a cylindrical enclosure problem based on data reported previously on a pilot-scale experimental combustor with steep temperature gradients. The models, which are Schuster-Hamaker type four-flux model derived by Lockwood and Spalding, two Schuster-Schwarzschild type four-flux models derived

Nevin Selcuk

1993-01-01

97

Comparison of the Radiative Two-Flux and Diffusion Approximations  

NASA Technical Reports Server (NTRS)

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.

Spuckler, Charles M.

2006-01-01

98

Deployable heat-pipe radiator  

NASA Technical Reports Server (NTRS)

Loop temperatures are controlled effectively under varying load conditions. Radiator has four separate pieces of hardware: heat-pipe panel, flexible heat-pipe leader, heat exchanger, fluid header. Single-fluid transport capacities of about 850 watts, corresponding to 51,000 watt-inches, have been achieved in 90 degree bend orientation of heat-pipe header.

Edelstein, F.

1978-01-01

99

Global Intercomparison of 12 Land Surface Heat Flux Estimates  

NASA Technical Reports Server (NTRS)

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.

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

100

The Photospheric Poynting Flux and Coronal Heating  

NASA Astrophysics Data System (ADS)

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|.

Welsch, Brian

2014-06-01

101

New low-cost high heat flux source  

NASA Astrophysics Data System (ADS)

Intense heat sources are needed to address new manufacturing techniques, such as, the Rapid Thermal Process for silicon wafer manufacturing. The current technology of high heat flux sources is the laser for its ability to do welding and cutting is well-known. The laser with its coherent radiation allows an image to be focused down to very small sizes to reach extremely high heat flux. But the laser also has problems: it is inefficient in its use because of its singular wave length and brings up OSHA safety related problems. Also heavy industrial manufacturing requires much higher total energy in addition to the high heat flux which makes the current laser system too slow to be economical. The system I am proposing starts with a parabolic curve. If the curve is rotated about the axis of the parabola, it generates the classical parabolic reflector as we know it. On the other hand, when the curve is rotated about the chord, a line passing through the focal point and perpendicular to the axis, generates a new surface called the Orthogonal Parabolic Surface. A new optical reflector geometry is presented which integrates a linear white light (continuum spectra) source through a coherent path to be focused to a very small area.

Cheng, Dah Yu

1993-11-01

102

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

103

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

SciTech Connect

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.

Cook, David

1993-07-04

104

Calculations of Temperature, Conductive Heat Flux, and Heat Wave Velocities Due to Radiant Heating of Opaque Materials.  

National Technical Information Service (NTIS)

The analytic solutions of the one-dimensional Fourier conductive heat flux law and corresponding transient heat transfer equation have been used to calculate temperature, conductive heat flux, and their trajectories due to radiant heating of opaque materi...

A. Cohen

2011-01-01

105

Forced flow dryout heat flux in a stratified debris bed  

Microsoft Academic Search

The purpose of this study is to obtain qualitative information through a series of tests for forced flow dryout heat flux in a heat-generating stratified debris bed that simulates a degraded nuclear reactor core. An experimental investigation has been conducted of dryout heat flux in an inductively heated stratified debris bed with upward forced flow under atmospheric pressure. The present

J. H. Cha; M. K. Chung; Y. S. Jin

1987-01-01

106

Heat flux measurements on ceramics with thin film thermocouples  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

107

Surface energy budget over the South Pole and turbulent heat fluxes as a function of an empirical bulk Richardson number  

Microsoft Academic Search

Routine radiation and meteorological data at South Pole Station are used to investigate historical discrepancies of up to 50 W m?2 in the monthly mean surface energy budget and to investigate the behavior of turbulent heat fluxes under stable atmospheric temperature conditions. The seasonal cycles of monthly mean net radiation and turbulent heat fluxes are approximately equal, with a difference

Michael S. Town; Von P. Walden

2009-01-01

108

Solar Cycle Variations in the Electron Heat Flux: Ulysses Observations  

NASA Astrophysics Data System (ADS)

Solar wind observations by the Ulysses spacecraft now include nearly ten years of continuous ion and electron measurements. In this study, we report detailed measurements of the electron heat flux in the solar wind. In particular, we examine the heat flux measurements for long-term correlations with wave activity and solar wind speed. We find that the average heat flux, when scaled by R2.9 to account for variations due to distance from the Sun, is constant and independent of heliographic latitude or solar cycle. We find that during both solar maximum and solar minimum, there is no significant correlation between the magnitude of the electron heat flux and the solar wind speed. Comparison of the electron heat flux data with wave activity indicates that the whistler heat flux instability does not play an important role in limiting the solar wind heat flux. >http://www.as.wvu.edu/coll03/phys/users/escime/plasma.htm

Scime, E. E.; Littleton, J. E.; Gary, S. P.; Skoug, R.; Lin, N.

2001-12-01

109

Maximum allowable heat flux for a submerged horizontal tube bundle.  

National Technical Information Service (NTIS)

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. ...

D. M. McEligot

1995-01-01

110

Laboratory experiments of heat and moisture fluxes through supraglacial debris  

NASA Astrophysics Data System (ADS)

Inspired by earlier work (Reznichenko et al., 2010), we have carried out experiments within a climate chamber to explore the best ways to measure the heat and moisture fluxes through supraglacial debris. Sample ice blocks were prepared with debris cover of varying lithology, grain size and thickness and were instrumented with a combination of Gemini TinyTag temperature/relative humidity sensors and Decagon soil moisture sensors in order to monitor the heat and moisture fluxes through the overlying debris material when the experiment is exposed to specified solar lamp radiation and laminar airflow within the temperature-controlled climate chamber. Experimental results can be used to determine the optimal set up for numerical models of heat and moisture flux through supraglacial debris and also indicate the performance limitations of such sensors that can be expected in field installations. Reznichenko, N., Davies, T., Shulmeister, J. and McSaveney, M. (2010) Effects of debris on ice-surface melting rates: an experimental study. Journal of Glaciology, Volume 56, Number 197, 384-394.

Nicholson, Lindsey; Mayer, Christoph; Wirbel, Anna

2014-05-01

111

Divertor heat flux reduction by D sub 2 injection in DIII-D  

SciTech Connect

D{sub 2} gas injected into ELMing H-mode discharges in DIII-D reduced total integrated heat flux to the divertor by {approximately}2{times} and peak heat flux by {approximately}5{times}, with only modest degradation to plasma stored energy. Steady gas injection without particle pumping results in eventual degradation in stored energy. The initial reduction in peak heat flux at the divertor tiles may be primarily due to the increase in radiated power from the X-point/divertor region. The eventual formation of a high density region near the X-point appears to play a role in momentum (and energy) transfer from the flux surfaces near the outboard strike point to flux surfaces farther out into the scrapeoff. This may also contribute to further reduction in peak heat flux.

Petrie, T.W.; Groebner, R.J.; Leonard, A.W.; Lippmann, S.I.; Mahdavi, A.M.; West, W.P. (General Atomics, San Diego, CA (United States)); Buchenauer, D.; Campbell, R.B. (Sandia National Labs., Livermore, CA (United States)); Hill, D.N.; Allen, S.L.; Futch, A.H.; Resink, M.E. (Lawrence Livermore National Lab., CA (United States)); Klepper, C.C. (Oak Ridge National Lab., TN (United States))

1992-05-01

112

Divertor heat flux reduction by D{sub 2} injection in DIII-D  

SciTech Connect

D{sub 2} gas injected into ELMing H-mode discharges in DIII-D reduced total integrated heat flux to the divertor by {approximately}2{times} and peak heat flux by {approximately}5{times}, with only modest degradation to plasma stored energy. Steady gas injection without particle pumping results in eventual degradation in stored energy. The initial reduction in peak heat flux at the divertor tiles may be primarily due to the increase in radiated power from the X-point/divertor region. The eventual formation of a high density region near the X-point appears to play a role in momentum (and energy) transfer from the flux surfaces near the outboard strike point to flux surfaces farther out into the scrapeoff. This may also contribute to further reduction in peak heat flux.

Petrie, T.W.; Groebner, R.J.; Leonard, A.W.; Lippmann, S.I.; Mahdavi, A.M.; West, W.P. [General Atomics, San Diego, CA (United States); Buchenauer, D.; Campbell, R.B. [Sandia National Labs., Livermore, CA (United States); Hill, D.N.; Allen, S.L.; Futch, A.H.; Resink, M.E. [Lawrence Livermore National Lab., CA (United States); Klepper, C.C. [Oak Ridge National Lab., TN (United States)

1992-05-01

113

Annual Cycles of Surface Shortwave Radiative Fluxes  

NASA Technical Reports Server (NTRS)

The annual cycles of surface shortwave flux are investigated using the 8-yr dataset of the surface radiation budget (SRB) components for the period July 1983-June 1991. These components include the downward, upward, and net shortwave radiant fluxes at the earth's surface. The seasonal cycles are quantified in terms of principal components that describe the temporal variations and empirical orthogonal functions (EOFs) that describe the spatial patterns. The major part of the variation is simply due to the variation of the insolation at the top of the atmosphere, especially for the first term, which describes 92.4% of the variance for the downward shortwave flux. However, for the second term, which describes 4.1% of the variance, the effect of clouds is quite important and the effect of clouds dominates the third term, which describes 2.4% of the variance. To a large degree the second and third terms are due to the response of clouds to the annual cycle of solar forcing. For net shortwave flux at the surface, similar variances are described by each term. The regional values of the EOFs are related to climate classes, thereby defining the range of annual cycles of shortwave radiation for each climate class.

Wilber, Anne C.; Smith, G. Louis; Gupta, Shashi K.; Stackhouse, Paul W.

2006-01-01

114

Surface radiation fluxes in transient climate simulations  

Microsoft Academic Search

Transient CO2 experiments from five coupled climate models, in which the CO2 concentration increases at rates of 0.6–1.1% per annum for periods of 75–200 years, are used to document the responses of surface radiation fluxes, and associated atmospheric properties, to the CO2 increase. In all five models, the responses of global surface temperature and column water vapour are non-linear and

J. R. Garratt; D. M. O'Brien; M. R. Dix; J. M. Murphy; G. L. Stephens; M. Wild

1999-01-01

115

Thin Film Heat Flux Sensors: Design and Methodology  

NASA Technical Reports Server (NTRS)

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.

Fralick, Gustave C.; Wrbanek, John D.

2013-01-01

116

The dependence of critical heat flux on fuel and additive properties: a critical mass flux model  

Microsoft Academic Search

We use a mathematical model for the ignition of thermally thin thermoplastics to evaluate the critical heat flux, and the corresponding critical surface temperature, required for piloted ignition by using the concept that a sample ignites when the mass flux of fuel from the solid into the gas phase reaches a critical value. We show how the critical heat flux

M. I. Nelson; J. Brindley; A. McIntosh

1995-01-01

117

Radiation entropy flux and entropy production of the Earth system  

Microsoft Academic Search

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

Wei Wu; Yangang Liu

2010-01-01

118

Evaluation of multi-dimensional flux models for radiative transfer in cylindrical combustion chambers  

NASA Astrophysics Data System (ADS)

Four flux-type models for radiative heat transfer in cylindrical configurations were applied to the prediction of radiative flux density and source term of a cylindrical enclosure problem based on data reported previously on a pilot-scale experimental combustor with steep temperature gradients. The models, which are Schuster-Hamaker type four-flux model derived by Lockwood and Spalding, two Schuster-Schwarzschild type four-flux models derived by Siddall and Selcuk and Richter and Quack and spherical harmonics approximation, were evaluated from the viewpoint of predictive accuracy by comparing their predictions with exact solutions produced previously. The comparisons showed that spherical harmonics approximation produces more accurate results than the other models with respect to the radiative energy source term and that the four-flux models of Lockwood and Spalding and Siddall and Selcuk for isotropic radiation field are more accurate with respect to the prediction of radiative flux density to the side wall.

Selcuk, Nevin

1993-02-01

119

Method for limiting heat flux in double-wall tubes  

DOEpatents

A method of limiting the heat flux in a portion of double-wall tubes including heat treating the tubes so that the walls separate when subjected to high heat flux and supplying an inert gas mixture to the gap at the interface of the double-wall tubes.

Hwang, Jaw-Yeu (Tampa, FL)

1982-01-01

120

Critical heat flux in a closed two-phase thermosyphon  

Microsoft Academic Search

An experimental study was made of critical heat flux in a closed two-phase thermosyphon. The effects of inside diameter, heated length, working liquid, fill charge and inside temperature on the critical heat flux were investigated. The present and previously-published experimental data were correlated with expressions already proposed by other investigators but the agreements were not good. Accordingly, a new correlating

H. Imura; K. Sasaguchi; H. Kozai; S. Numata

1983-01-01

121

Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes  

SciTech Connect

We have used solar wind electron heat fluxes to determine the magnetic polarities of the interplanetary magnetic fields (IMF) during the ISEE-3 observations in 1978{endash}1982. That period included 14 magnetic clouds (MCs) identified by Zhang and Burlaga. The MCs have been modeled as single magnetic flux ropes, and it is generally assumed that they are magnetically closed structures with each end of the flux rope connected to the Sun. The flux rope model is valid only if the magnetic polarity of each MC does not change during the passage of ISEE-3 through the MC. We test this model with the heat flux data, using the dominant heat flux in bidirectional electron heat fluxes to determine the MC polarities. The polarity changes within at least 2, and possibly 6, of the 14 MCs, meaning that those MCs can not fit the model of a single flux rope. {copyright} {ital 1999 American Institute of Physics.}

Kahler, S.W. [Air Force Research Laboratory, 29 Randolph Rd, Hanscom AFB, Massachusetts 01731 (United States); Crooker, N.U. [Center for Space Physics, Boston University, 725 Commonwealth Ave., Boston, Massachusetts 02215 (United States); Gosling, J.T. [Los Alamos National Laboratory, MS D 466, Los Alamos, New Mexico 87545 (United States)

1999-06-01

122

Losses in magnetic flux compression generators. Part 2: Radiation losses  

Microsoft Academic Search

An analysis of flux losses in explosive driven magnetic flux compression generators is given. Flux loss by radiation from the outer conductor walls is treated. Flux leakage rates through walls of finite thickness are first obtained by diffusion theory. It is shown, for normal wall thicknesses, that flux leakage is determined essentially by the wall conductance, defined as the product

C. M. Fowler

1988-01-01

123

High heat flux engineering in solar energy applications  

SciTech Connect

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.

Cameron, C.P.

1993-07-01

124

Modeling Heat Transfer for Heat-resistant Fabrics Considering Pyrolysis Effect under an External Heat Flux  

Microsoft Academic Search

In the paper, a heat-transfer model considering thermal degradation of heat-resistant fabrics when subjected to the radiant heat flux has been proposed. The model incorporates the heat-induced changes in fabric thermo physical properties. The new model has been validated by experimental data from modified Radiant Protective Performance (RPP) tests of heat-resistant fabrics. Comparisons with experimental data show that the predictions

Fang-Long Zhu; Wei-Yuan Zhang

2009-01-01

125

EU Development of High Heat Flux Components  

SciTech Connect

The development of plasma facing components for next step fusion devices in Europe is strongly focused to ITER. Here a wide spectrum of different design options for the divertor target and the first wall have been investigated with tungsten, CFC, and beryllium armor. Electron beam simulation experiments have been used to determine the performance of high heat flux components under ITER specific thermal loads. Beside thermal fatigue loads with power density levels up to 20 MWm{sup -2}, off-normal events are a serious concern for the lifetime of plasma facing components. These phenomena are expected to occur on a time scale of a few milliseconds (plasma disruptions) or several hundred milliseconds (vertical displacement events) and have been identified as a major source for the production of neutron activated metallic or tritium enriched carbon dust which is of serious importance from a safety point of view.The irradiation induced material degradation is another critical concern for future D-T-burning fusion devices. In ITER the integrated neutron fluence to the first wall and the divertor armour will remain in the order of 1 dpa and 0.7 dpa, respectively. This value is low compared to future commercial fusion reactors; nevertheless, a nonnegligible degradation of the materials has been detected, both for mechanical and thermal properties, in particular for the thermal conductivity of carbon based materials. Beside the degradation of individual material properties, the high heat flux performance of actively cooled plasma facing components has been investigated under ITER specific thermal and neutron loads.

Linke, J. [Forschungszentrum Juelich GmbH (Germany); Lorenzetto, P. [EFDA Close Support Unit Garching (Germany); Majerus, P. [Forschungszentrum Juelich GmbH (Germany); Merola, M. [EFDA Close Support Unit Garching (Germany); Pitzer, D. [Forschungszentrum Juelich GmbH (Germany); Roedig, M. [Forschungszentrum Juelich GmbH (Germany)

2005-04-15

126

Heat flux measurement in SSME turbine blade tester  

SciTech Connect

Surface heat flux values were measured in the turbine blade thermal cycling tester located at NASA-Marshall. This is the first time heat flux has been measured in a space shuttle main engine turbopump environment. Plots of transient and quasi-steady state heat flux data over a range of about 0 to 15 MW/sq m are presented. Data were obtained with a miniature heat flux gage device developed at NASA-Lewis. The results from these tests are being incorporated into turbine design models. Also, these gages are being considered for airfoil surface heat flux measurement on turbine vanes mounted in SSME turbopump test bed engine nozzles at Marshall. Heat flux effects that might be observed on degraded vanes are discussed.

Liebert, C.H.

1990-11-01

127

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

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.

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

1981-02-01

128

High heat flux cooling by microbubble emission boiling.  

PubMed

In subcooled flow boiling of water in a horizontal rectangular channel, microbubble emission boiling occurred at higher subcooling of liquid in transition boiling, and the heat flux increased more than the critical heat flux. The maximum heat flux reached 10 MW/m(2) for a channel with 12 mm x 14mm cross-section at 40K liquid subcooling and 0.5 m/sec liquid velocity. For smaller rectangular channels with 14 mm x 5mm, 14mm x 3mm, and 14mm x 1mm cross-sections, the maximum heat flux was 7 MW/m(2)-more than 20 times the cooling limit of a present day CPU. Microbubble emission boiling is expected to realize high heat flux cooling for electronic devices. In convection boiling with subcooled water jet, the same boiling regime and heat flux were obtained for a downward heating surface and an upward heating surface. In subcooled flow boiling with strong convection, the hydrodynamic force is predominant for vapor-liquid exchange. Accordingly, microbubble emission boiling is expected for high heat flux cooling or high heat flux heat transfer in microgravity. PMID:12446336

Suzuki, Koichi; Saitoh, Hiroshi; Matsumoto, Kazuaki

2002-10-01

129

Estimation of heat flux through the eastern Bering Strait  

Microsoft Academic Search

We estimated the northward heat flux through the eastern channel of the Bering Strait during the ice-free seasons between\\u000a 1999 and 2008. This is likely about half of the total heat flux through the strait. The net volume transport and heat flux\\u000a through the eastern channel of the strait were estimated from multiple linear regression models with in-situ\\/satellite remotely sensed

Kohei Mizobata; Koji Shimada; Rebecca Woodgate; Sei-Ichi Saitoh; Jia Wang

2010-01-01

130

Heat-flux induced changes to multicrystalline D2 surfaces  

NASA Astrophysics Data System (ADS)

Phase-shifting interferometry reveals that a heat flux normal to the gas-solid interface reduces the surface roughness of thick (10-300 ?m) multicrystalline D2 films. The initial roughness, caused by misaligned crystals and grain boundaries produced during the initial random nucleation and rapid crystal growth used in the experiment decreases with increasing heat flux. A simple energy minimization model quantitatively explains the functional relationship between surface roughness and heat flux.

Collins, G. W.; Bernat, T. P.; Mapoles, E. R.; Kozioziemski, B. J.; Duriez, C.

2001-05-01

131

Estimation of the Surface Heat Flux Response to Sea Surface Temperature Anomalies over the Global Oceans.  

NASA Astrophysics Data System (ADS)

The surface heat flux response to underlying sea surface temperature (SST) anomalies (the surface heat flux feedback) is estimated using 42 yr (1956 97) of ship-derived monthly turbulent heat fluxes and 17 yr (1984 2000) of satellite-derived monthly radiative fluxes over the global oceans for individual seasons. Net surface heat flux feedback is generally negative (i.e., a damping of the underlying SST anomalies) over the global oceans, although there is considerable geographical and seasonal variation. Over the North Pacific Ocean, net surface heat flux feedback is dominated by the turbulent flux component, with maximum values (28 W m-2 K-1) in December February and minimum values (5 W m-2 K-1) in May July. These seasonal variations are due to changes in the strength of the climatological mean surface wind speed and the degree to which the near-surface air temperature and humidity adjust to the underlying SST anomalies. Similar features are observed over the extratropical North Atlantic Ocean with maximum (minimum) feedback values of approximately 33 W m-2 K-1 (9 W m-2 K-1) in December February (June August). Although the net surface heat flux feedback may be negative, individual components of the feedback can be positive depending on season and location. For example, over the midlatitude North Pacific Ocean during late spring to midsummer, the radiative flux feedback associated with marine boundary layer clouds and fog is positive, and results in a significant enhancement of the month-to-month persistence of SST anomalies, nearly doubling the SST anomaly decay time from 2.8 to 5.3 months in May July.Several regions are identified with net positive heat flux feedback: the tropical western North Atlantic Ocean during boreal winter, the Namibian stratocumulus deck off West Africa during boreal fall, and the Indian Ocean during boreal summer and fall. These positive feedbacks are mainly associated with the following atmospheric responses to positive SST anomalies: 1) reduced surface wind speed (positive turbulent heat flux feedback) over the tropical western North Atlantic and Indian Oceans, 2) reduced marine boundary layer stratocumulus cloud fraction (positive shortwave radiative flux feedback) over the Namibian stratocumulus deck, and 3) enhanced atmospheric water vapor (positive longwave radiative flux feedback) in the vicinity of the tropical deep convection region over the Indian Ocean that exceeds the negative shortwave radiative flux feedback associated with enhanced cloudiness.

Park, Sungsu; Deser, Clara; Alexander, Michael A.

2005-11-01

132

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

NASA Technical Reports Server (NTRS)

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.

Ng, Daniel

1998-01-01

133

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

NASA Technical Reports Server (NTRS)

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.

Ng, Daniel

1998-01-01

134

Development of a Heat Flux Meter and Measurement of the Heat Flux to the Divertor in DIVA.  

National Technical Information Service (NTIS)

In evaluating the quantity of heat flowing to the divertor, the heat flux has so far been measured with a thermocouple probe of resolving time 5 ms. To examine time variation of the heat flux to the divertor, a Ni-evapolated thin film sensor of resolving ...

N. Ueda M. Seki K. Anno H. Kawamura H. Maeda

1976-01-01

135

Wedge Heat-Flux Indicators for Flash Thermography  

NASA Technical Reports Server (NTRS)

Wedge indicators have been proposed for measuring thermal radiation that impinges on specimens illuminated by flash lamps for thermographic inspection. Heat fluxes measured by use of these indicators would be used, along with known thermal, radiative, and geometric properties of the specimens, to estimate peak flash temperatures on the specimen surfaces. These indicators would be inexpensive alternatives to high-speed infrared pyrometers, which would otherwise be needed for measuring peak flash surface temperatures. The wedge is made from any suitable homogenous material such as plastic. The choice of material is governed by the equation given. One side of the wedge is covered by a temperature sensitive compound that decomposes irreversibly when its temperature exceeds a rated temperature (T-rated). The uncoated side would be positioned alongside or in place of the specimen and exposed to the flash, then the wedge thickness at the boundary between the white and blackened portions measured.

Koshti, Ajay M.

2003-01-01

136

Rewetting of an infinite slab with boundary heat flux  

SciTech Connect

This paper deals with a numerical solution of the two-dimensional quasi-static conduction equation, governing conduction controlled rewetting of an infinitely long slab with one side flooded and the other side subjected to a constant heat flux. The solution gives the quench front temperature as a function of various model parameters such as Peclet number, Biot number, and dimensionless boundary heat flux. Also, the critical boundary heat flux is obtained by setting the Peclet number equal to zero, which gives the minimum heat flux required to prevent the hot surface being rewetted.

Satapathy, A.K.; Kar, P.K.

2000-01-01

137

Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere  

NASA Astrophysics Data System (ADS)

We discuss here the solar downward net flux in the 0.25 - 2.5 µm range in the atmosphere of Jupiter and the associated heating rates under a number of vertical cloud structure scenarios focusing in the effect of clouds and hazes. Our numerical model is based in the doubling-adding technique to solve the radiative transfer equation and it includes gas absorption by CH4, NH3 and H2, in addition to Rayleigh scattering by a mixture of H2 plus He. Four paradigmatic Jovian regions have been considered (hot-spots, belts, zones and Polar Regions). The hot-spots are the most transparent regions with downward net fluxes of 2.5±0.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.04±0.01 K/day and occurs above 1 bar. Belts and zones characterization result in a maximum net downward flux of 0.5 Wm-2 at 2 bar and 0.015 Wm-2 at 6 bar. Heating is concentrated in the stratospheric and tropospheric hazes. Finally, Polar Regions are also explored and the results point to a considerable stratospheric heating of 0.04±0.02 K/day. In all, these calculations suggest that the role of the direct solar forcing in the Jovian atmospheric dynamics is limited to the upper 1 - 2 bar of the atmosphere except in the hot-spot areas. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07.

Perez-Hoyos, Santiago; Sánchez-Lavega, A.

2009-09-01

138

Maximum power flux of auroral kilometric radiation  

NASA Astrophysics Data System (ADS)

Distant observations of intense auroral kilometric radiation (AKR) are discussed in light of the increased maximum AKR power flux registered by the 3D radio-mapping instrument on ISEE 3. Only AKR events that contain the highest frequency signals are selected, and during spacecraft rotation the spacecraft antenna gain is employed to increase the dynamic range of the instrument. The technique is found to result in the screening of false signals created by instrument overloading as well as the detection of genuine second-harmonic AKR signals while the spacecraft was 17 R(E) from earth. A very strong power flux of fundamental AKR is also reported, exceeding 3 x 10 to the -13th W/sq m/Hz at 360 kHz. The most intense source-region values detected by Isis I and Viking measurements are compared to the strong signal, and the signal is concluded to be the combined signal of a number of sources.

Benson, Robert F.; Fainberg, Joseph

1991-08-01

139

Determination of longwave heat flux at the air-sea interface using measurements from buoy platforms  

SciTech Connect

A theory for pyrgeometer operation is utilized for determining downwelling longwave radiation. Errors in downwelling longwave radiation measurements are due to differences in pyrgeometer body and dome temperatures compared to that of the atmosphere. Additionally, incident shortwave radiation fluxes may be important. Using the present theory along with laboratory and field observations, it appears that downwelling longwave heat fluxes can be measured with errors less than 6 W/sq m. Longwave heat flux observations from surface buoys deployed in four different oceanic regions suggest that (1) incoming longwave measurements from buoys are repeatable, (2) uncertainties in radiometer calibration are significant and systematic, and (3) pyrgeometers are affected by direct and indirect solar heating. A hybrid measurement method for the determination of net longwave heat flux at the air-sea interface is described. The authors recommend improvement in calibration procedures as well as development of a radiometer to be used as a transfer standard to compare with in situ measurements. Uncertainties in sea surface skin temperature and emissivity are contributors to the error in the net longwave heat flux. However, a targeted error limit goal of +/- 10 W/sq m for the monthly mean net longwave heat flux appears to be achievable.

Dickey, T.D.; Manov, D.V.; Weller, R.A.; Siegel, D.A. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States); [Woods Hole Oceanographic Institution, Woods Hole, MA (United States); [Univ. of California, Santa Barbara, CA (United States)

1994-08-01

140

Two-Flux Method for Transient Radiative Transfer in a Semitransparent Layer  

NASA Technical Reports Server (NTRS)

The two-flux method was used to obtain transient solutions for a plane layer including internal reflections and scattering. The layer was initially at uniform temperature, and was heated or cooled by external radiation and convection. The two-flux equations were examined as a means for evaluating the radiative flux gradient in the transient energy equation. Comparisons of transient temperature distributions using the two-flux method were made with results where the radiative flux gradient was evaluated from the exact radiative transfer equations. Good agreement was obtained for optical thicknesses from 0.5 to 5 and for refractive indices of 1 and 2. Illustrative results obtained with the two-flux method demonstrate the effect of isotropic scattering coupled with changing the refractive index. For small absorption with large scattering the maximum layer temperature is increased when the refractive index is increased. For larger absorption the effect is opposite, and the maximum temperature decreases with increased refractive index .

Siegel, Robert

1996-01-01

141

On the net surface heat flux into the western equatorial Pacific  

NASA Astrophysics Data System (ADS)

Downward longwave and shortwave radiation fluxes were measured for 13 days in May 1988 in the equatorial west Pacific; estimates of net radiation fluxes from these data were checked against a net radiometer over 9 days. The pyrgeometer observations were corrected to match the net radiometer measurements at night, when the latter is substantially more accurate. These measurements were compared with various empirical formulae. Three widely used empirical formulae for net longwave radiation out of the ocean consistently underestimated our observations by up to 21 ± 5 W m-2 however, the Brunt-Budyko formula had no systematic bias. Two empirical formulae for the daily mean net shortwave radiation entering the ocean both overestimated the observations by up to 17 W m-2, although the scatter of daily estimates from observation was about ±30 W m-2. Routine ship's meteorological observations were used to estimate turbulent heat fluxes, with four empirical formulae. The 18-day means differed by up to 28 W m-2, due to different treatment of the increase in bulk transfer coefficient at low wind speed. The Liu et al. (1979) algorithm gave the highest fluxes, and agreed well with direct measurements of turbulent fluxes reported elsewhere. A further systematic error in the measurement of air-sea temperature difference accounted for about 11 W m-2. These systematic errors all tend to reduce the net heat flux into the ocean; their sum is as much as 60-75 W m-2 for some choices of empirical formulae. This tends to confirm the hypothesis of Godfrey and Lindstrom (1989) that ocean mixing and advection are too weak to carry a substantial heat flux away from the mixed layer of this region. Temperature profiles collected near 4°S, 150°E showed a clear warming from May 8 to May 20 in the top 20 m, equivalent to a heat storage rate of about 30 W m-2. Directly measured radiation fluxes were available for 10 days of this period of calm, sunny weather; turbulent heat fluxes were estimated for the same period with the Liu et al. (1979) algorithm. The net heat flux into the water estimated in this way averaged 38 W m-2. While the heat flux measurements were made as much as 400 km from the site of the heat storage observations, our observations provide some support, at least in calm weather, for the hypothesis that the net heat flux into this region is only of order 10 W m-2.

Godfrey, J. S.; Nunez, M.; Bradley, E. F.; Coppin, P. A.; Lindstrom, E. J.

142

Performance of Peltier elements as a cryogenic heat flux sensor at temperatures down to 60 K  

NASA Astrophysics Data System (ADS)

An in situ heat flux measuring technique could be a good tool to investigate the mechanism of radiation heat leak and optimize the performance of multi-layer insulation. There are several types of commercially available heat flux sensors, however, most of these sensors are mainly developed for much higher heat flux measurements, e.g., radiation from an iron furnace, heat leak from LNG tanks to the ground and so on. In cryogenic systems, the typical amount of heat flux from 300 K to the first-stage radiation shield of cryogenic system is around several W/m 2, which is three or four orders of magnitude smaller than that of an iron furnace. A conventional thermoelectric element, known as a Peltier element, has been evaluated as a heat flux sensor at cryogenic temperatures and found to be suitable due to its high output voltage. In this study, the temperature dependence of the sensitivity and thermal resistance of the Peltier elements were investigated at temperatures from 200 down to 60 K for possible practical applications.

Haruyama, T.

2001-05-01

143

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

NASA Technical Reports Server (NTRS)

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.

Turner, Travis L.; Ash, Robert L.

1994-01-01

144

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

NASA Astrophysics Data System (ADS)

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.

Turner, Travis L.; Ash, Robert L.

1994-03-01

145

Heat flux measurements in the OSU rate of heat release apparatus  

Microsoft Academic Search

Thermal capacitance (slug) calorimeters were used to measure radiant and flame heat fluxes and the overall heat transfer coefficient at the sample surface in the Ohio State University (OSU) Rate of Heat Release Apparatus specified in FAR 25.853(a-1). The copper plate calorimeters gave radiant heat flux readings which were within 2% of a NIST calibrated, water-cooled, Gardon Heat Flux Sensor.

Robert Filipczak; Richard E. Lyon

2002-01-01

146

Earth's heat flux revised and linked to chemistry  

Microsoft Academic Search

Recent estimates of the heat flux from the oceanic crust rest on the validity and accuracy of the half-space cooling (HSC) model. The known discrepancies between calculated and measured heat fluxes are not due to hydrothermal circulation, as commonly assumed, because the magmatic source provides too little energy, and the Rayleigh number is too small to foster vigorous convection on

A. M. Hofmeister; R. E. Criss

2005-01-01

147

Heat Flux Measurements on Ceramics with Thin Film Thermocouples.  

National Technical Information Service (NTIS)

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 usi...

R. Holanda R. C. Anderson C. H. Liebert

1993-01-01

148

Vertical Eddy Flux of Heat in the Atmosphere  

Microsoft Academic Search

The thermodynamics of open systems is developed for a special atmospheric system in order to obtain a precise definition of the vertical eddy flux of heat. The upward eddy flux of heat per unit area is Vzh, where is density, Vz is a specially defined fluctuation of the vertical component of velocity, and h is specific enthalpy.In terms of the

R. B. Montgomery

1948-01-01

149

Heat pipe radiators for space  

NASA Technical Reports Server (NTRS)

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.

Sellers, J. P.

1976-01-01

150

Modelling radiation fluxes in simple and complex environments: basics of the RayMan model.  

PubMed

Short- and long-wave radiation flux densities absorbed by people have a significant influence on their energy balance. The heat effect of the absorbed radiation flux densities is parameterised by the mean radiant temperature. This paper presents the physical basis of the RayMan model, which simulates the short- and long-wave radiation flux densities from the three-dimensional surroundings in simple and complex environments. RayMan has the character of a freely available radiation and human-bioclimate model. The aim of the RayMan model is to calculate radiation flux densities, sunshine duration, shadow spaces and thermo-physiologically relevant assessment indices using only a limited number of meteorological and other input data. A comparison between measured and simulated values for global radiation and mean radiant temperature shows that the simulated data closely resemble measured data. PMID:19756771

Matzarakis, Andreas; Rutz, Frank; Mayer, Helmut

2010-03-01

151

Soil profile method for soil thermal diffusivity, conductivity and heat flux: Comparison to soil heat flux plates  

NASA Astrophysics Data System (ADS)

Diffusive heat flux at the soil surface is commonly determined as a mean value over a time period using heat flux plates buried at some depth (e.g., 5-8 cm) below the surface with a correction to surface flux based on the change in heat storage during the corresponding time period in the soil layer above the plates. The change in heat storage is based on the soil temperature change in the layer over the time period and an estimate of the soil thermal heat capacity that is based on soil water content, bulk density and organic matter content. One- or multiple-layer corrections using some measure of mean soil temperature over the layer depth are common; and in some cases the soil water content has been determined, although rarely. Several problems with the heat flux plate method limit the accuracy of soil heat flux values. An alternative method is presented and this flux gradient method is compared with soil heat flux plate measurements. The method is based on periodic (e.g., half-hourly) water content and temperature sensing at multiple depths within the soil profile and a solution of the Fourier heat flux equation. A Fourier sine series is fit to the temperature at each depth and the temperature at the next depth below is simulated with a sine series solution of the differential heat flux equation using successive approximation of the best fit based on changing the thermal diffusivity value. The best fit thermal diffusivity value is converted to a thermal conductivity value using the soil heat capacity, which is based on the measured water content and bulk density. A statistical analysis of the many data resulting from repeated application of this method is applied to describe the thermal conductivity as a function of water content and bulk density. The soil heat flux between each pair of temperature measurement depths is computed using the thermal conductivity function and measured water contents. The thermal gradient method of heat flux calculation compared well to values determined using heat flux plates and calorimetric correction to the soil surface; and it provided better representation of the surface spatiotemporal variation of heat flux and more accurate heat flux values. The overall method resulted in additional important knowledge including the water content dynamics in the near-surface soil profile and a soil-specific function relating thermal conductivity to soil water content and bulk density.

Evett, Steven R.; Agam, Nurit; Kustas, William P.; Colaizzi, Paul D.; Schwartz, Robert C.

2012-12-01

152

Effect of magnetic geometry on ELM heat flux profiles  

NASA Astrophysics Data System (ADS)

In this paper, we explore how precisely the magnetic up/down symmetry must be controlled to insure sharing of edge localized mode (ELM) heat flux between upper and lower divertors in a double-null tokamak. We show for DIII-D, using infrared thermography, that the spatial distribution of Type-I ELM energy is less strongly affected by variations in magnetic geometry than the time-averaged peak heat flux in attached discharges. The degree of control necessary to share ELM heat flux deposition equally between divertors was less stringent than the control needed to balance the time-averaged heat flux. ELM energy is transported more than four times further into the scrape-off layer (SOL) than the time-averaged heat flux.

Lasnier, C. J.; Leonard, A. W.; Petrie, T. W.; Watkins, J. G.

2001-03-01

153

Radiative heat transfer in emitting-absorbing-scattering spherical media  

Microsoft Academic Search

Radiative heat transfer in spherical media that emit, absorb, and scatter radiation is analyzed. Linear anisotropic scattering is considered. The spherical harmonics method is used to solve the equation of transfer. The P-1, P-2, P-3, P-7, and P-11 solutions are presented and their accuracy is discussed. Numerical results presented include the radiant heat fluxes at the inner and outer walls

Timothy W. Tong; Pananjady S. Swathi

1987-01-01

154

Decadal Changes in Surface Radiative Fluxes  

NASA Astrophysics Data System (ADS)

Recent evidence suggests that radiative fluxes incident at the Earth surface are not stable over time but undergo significant changes on decadal timescales. This is not only found in the thermal spectral range, where an increase in the downwelling flux is expected with the increasing greenhouse effect, but also in the solar range. Observations suggest that surface solar radiation, after decades of decline ("global dimming"), reversed into a "brightening" since the mid-1980s at widespread locations. This presentation gives an update on recent investigations related to the decadal variations in these fluxes, based on both observational and modeling approaches. Updated observational data, archived at the Global Energy Balance Archive (GEBA) at ETH Zurich, suggest a continuation of surface solar brightening beyond the year 2000 at numerous locations, yet less pronounced and coherent than during the 1990s, with more regions with no clear changes or declines. Current global climate models as used in the IPCC-AR4 report typically do not reproduce the observed decadal variations to their full extent. Modeling attempts to improve this situation are under way at ETH, based on a global climate model which includes a sophisticated interactive treatment of aerosol and cloud microphysics (ECHAM5-HAM). Further the impact of the decadal changes in surface radiative forcings on different aspects of the global climate system and climate change is discussed, such as 20th century day- and nighttime warming, evapotranspiration changes and the varying intensity of the hydrological cycle as well as the terrestrial carbon cycle. Selected related references: Wild, M., and Co-authors, 2005: From dimming to brightening: Decadal changes in solar radiation at the Earth's surface. Science, 308, 847-850 Wild, M., 2007: Decadal changes in surface radiative fluxes and their importance in the context of global climate change, in: Climate Variability and Extremes during the Past 100 years, Advances in Global Change Research, 140, Editors Stefan Brönnimann et al., p. 155-168. Wild, M., Ohmura A., Makowski, K., 2007: Impact of global dimming and brightening on global warming. Geophys. Res. Lett., 34, L04702, doi:10.1029/2006GL028031. Wild, M., Grieser, J. and Schär, C., 2008: Combined surface solar brightening and greenhouse effect support recent intensification of the global land-based hydrological cycle. Geophys. Res. Lett., 35, L17706, doi:10.1029/2008GL034842 Wild, M., 2009: How well do IPCC-AR4/CMIP3 climate models simulate global dimming/brightening and 20th century day- and night-time warming? To appear in J. Geophys. Res. Wild, M., Truessel, B., Ohmura, A., Long, C.N. König-Langlo G., Dutton, E.G., and Tsvetkov, A., 2009: Global Dimming and Brightening: an update beyond 2000. To appear in J. Geophys. Res. Wild, M., 2009: Global dimming and brightening: A review on decadal changes in surface solar radiation. To appear in J. Geophys. Res.

Wild, M.

2009-05-01

155

Uncertainty analysis of steady state incident heat flux measurements in hydrocarbon fuel fires.  

SciTech Connect

The objective of this report is to develop uncertainty estimates for three heat flux measurement techniques used for the measurement of incident heat flux in a combined radiative and convective environment. This is related to the measurement of heat flux to objects placed inside hydrocarbon fuel (diesel, JP-8 jet fuel) fires, which is very difficult to make accurately (e.g., less than 10%). Three methods will be discussed: a Schmidt-Boelter heat flux gage; a calorimeter and inverse heat conduction method; and a thin plate and energy balance method. Steady state uncertainties were estimated for two types of fires (i.e., calm wind and high winds) at three times (early in the fire, late in the fire, and at an intermediate time). Results showed a large uncertainty for all three methods. Typical uncertainties for a Schmidt-Boelter gage ranged from {+-}23% for high wind fires to {+-}39% for low wind fires. For the calorimeter/inverse method the uncertainties were {+-}25% to {+-}40%. The thin plate/energy balance method the uncertainties ranged from {+-}21% to {+-}42%. The 23-39% uncertainties for the Schmidt-Boelter gage are much larger than the quoted uncertainty for a radiative only environment (i.e ., {+-}3%). This large difference is due to the convective contribution and because the gage sensitivities to radiative and convective environments are not equal. All these values are larger than desired, which suggests the need for improvements in heat flux measurements in fires.

Nakos, James Thomas

2005-12-01

156

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

NASA Technical Reports Server (NTRS)

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.

Grossman, Robert L.

1990-01-01

157

An iterative procedure for estimating areally averaged heat flux using planetary boundary layer mixed layer height and locally measured heat flux  

SciTech Connect

Measurements at the central facility of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) are intended to verify, improve, and develop parameterizations in radiative flux models that are subsequently used in General Circulation Models (GCMs). The reliability of this approach depends upon the representativeness of the local measurements at the central facility for the site as a whole or on how these measurements can be interpreted so as to accurately represent increasingly large scales. The variation of surface energy budget terms over the SGP CART site is extremely large. Surface layer measurements of the sensible heat flux (H) often vary by a factor of 2 or more at the CART site (Coulter et al. 1996). The Planetary Boundary Layer (PBL) effectively integrates the local inputs across large scales; because the mixed layer height (h) is principally driven by H, it can, in principal, be used for estimates of surface heat flux over scales on the order of tens of kilometers. By combining measurements of h from radiosondes or radar wind profiles with a one-dimensional model of mixed layer height, they are investigating the ability of diagnosing large-scale heat fluxes. The authors have developed a procedure using the model described by Boers et al. (1984) to investigate the effect of changes in surface sensible heat flux on the mixed layer height. The objective of the study is to invert the sense of the model.

Coulter, R. L.; Gao, W.; Lesht, B. M.

2000-04-04

158

Convection calibration method for local heat flux gages  

Microsoft Academic Search

An apparatus for calibrating local heat flux gages in convective air flows is described. Heat transfer from a ''hot'' gage to a ''cold'' fluid was measured using a guarded hot-plate technique. The system was used to calibrate Gardon-type circular foil heat flux gates of 1\\/8 in. and 1\\/16 in. outer diameters. The reslts indicate that the calibration curves are nonlinear,

G. J. Borell; T. E. Diller

1987-01-01

159

Heat flux determination for nucleate boiling in subsurface tunnel structures  

NASA Astrophysics Data System (ADS)

The paper focuses on theoretical analysis of boiling heat transfer on surfaces with tunnel structures formed by fins with microfins and covered with perforated foil. The investigations were conducted for water, ethanol and R-123. The theoretical heat flux, based on modified Chien and Webb model, when compared to the experiments, showed satisfying agreement in low and medium ranges for water and ethanol, and in all heat flux ranges for R-123.

Pastuszko, Robert; Poniewski, Mieczyslaw E.; Koziol, Monika

2012-08-01

160

The Excess Flux in the Cosmic Submillimeter Background Radiation and the Primordial Deuterium Abundance  

Microsoft Academic Search

Recent measurements of the cosmic background radiation (CBR) show an enhanced flux in the submillimeter regime, compared to the spectrum of a 2.7 K blackbody. Thermal Comptonization of the relic radiation by a hot nonrelativistic plasma has long been known to produce distortions in the CBR spectrum, similar to what has now been observed. Heating of the primeval plasma to

C. D. Dermer; N. Guessoum

1989-01-01

161

The excess flux in the cosmic submillimeter background radiation and the primordial deuterium abundance  

Microsoft Academic Search

Recent measurements of the cosmic background radiation (CBR) show an enhanced flux in the submillimeter regime, compared to the spectrum of a 2.7 K blackbody. Thermal Comptonization of the relic radiation by a hot nonrelativistic plasma has long been known to produce distortions in the CBR spectrum, similar to what has now been observed. Heating of the primeval plasma to

Charles D. Dermer; N. Guessoum

1990-01-01

162

Interannual variability in Mediterranean heat and buoyancy fluxes  

SciTech Connect

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.

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

1993-05-01

163

Supercritical convection, critical heat flux, and coking characteristics of propane  

NASA Technical Reports Server (NTRS)

The heat transfer characteristics of propane at subcritical and supercritical pressure were experimentally evaluated using electrically heated Monel K-500 tubes. A design correlation for supercritical heat transfer coefficient was established using the approach previously applied to supercritical oxygen. Flow oscillations were observed and the onset of these oscillations at supercritical pressures was correlated with wall-to-bulk temperature ratio and velocity. The critical heat flux measured at subcritical pressure was correlated with the product of velocity and subcooling. Long duration tests at fixed heat flux conditions were conducted to evaluate coking on the coolant side tube wall and coking rates comparable to RP-1 were observed.

Rousar, D. C.; Gross, R. S.; Boyd, W. C.

1984-01-01

164

Coronal Heating and the Magnetic Flux Content of the Network  

NASA Technical Reports Server (NTRS)

Previously, from analysis of SOHO/EIT coronal images in combination with Kitt Peak magnetograms (Falconer et al 1998, ApJ, 501, 386-396), we found that the quiet corona is the sum of two components: the e-scale corona and the coronal network. The large-scale corona consists of all coronal-temperature (T approx. 10(exp 6) K) structures larger than supergranules (>approx.30,000 km). The coronal network (1) consists of all coronal-temperature structures smaller than supergranules, (2) is rooted in and loosely traces the photospheric magnetic network, (3) has its brightest features seated on polarity dividing fines (neutral lines) in the network magnetic flux, and (4) produces only about 5% of the total coronal emission in quiet regions. The heating of the coronal network is apparently magnetic in origin. Here, from analysis of EIT coronal images of quiet regions in combination with magnetograms of the same quiet regions from SOHO/MDI and from Kitt Peak, we examine the other 95% of the quiet corona and its relation to the underlying magnetic network. We find: (1) Dividing the large-scale corona into its bright and dim halves divides the area into bright "continents" and dark "oceans" having spans of 2-4 supergranules. (2) These patterns are also present in the photospheric magnetograms: the network is stronger under the bright half and weaker under the dim half. (3) The radiation from the large-scale corona increases roughly as the cube root of the magnetic flux content of the underlying magnetic network. In contrast, Fisher et A (1998, ApJ, 508, 985-998) found that the coronal radiation from an active region increases roughly linearly with the magnetic flux content of the active region. We assume, as is widely held, that nearly all of the large-scale corona is magnetically rooted in the network. Our results, together with the result of Fisher et al (1999), suggest that either the coronal heating in quiet regions has a large non-magnetic component, or, if the heating is predominantly produced via the magnetic field, the mechanism is significantly different than in active regions. This work is funded by NASA's Office of Space Science through the Solar Physics Supporting Research and Technology Program and the Sun-Earth Connection Guest Investigator Program.

Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

165

Experimental feasibility study of a thermoelectric heat flux gage  

NASA Technical Reports Server (NTRS)

An experiment was conducted to determine the feasibility of using a commercially available thermoelectric device as a heat flux gage at near ambient conditions. In certain research applications, the thermoelectric heat flux gage can provide a relatively simple means to model a warm fluid cold wall convection environment. The experiment showed that heat flux through the gage could be correlated within 2.5 percent with a simple algebraic equation which considered the thermoelectric current through the device and the hot and cold side temperatures.

Vanfossen, G. J.; Lopez, I.

1983-01-01

166

Modeling shortwave radiative fluxes from satellites  

NASA Astrophysics Data System (ADS)

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.

Ma, Y.; Pinker, R. T.

2012-12-01

167

Tools for atmospheric radiative transfer: Streamer and FluxNet  

Microsoft Academic Search

Two tools for the solution of radiative transfer problems are presented. Streamer is a flexible medium spectral resolution radiative transfer model based on the plane-parallel theory of radiative transfer. Capable of computing either fluxes or radiances, it is suitable for studying radiative processes at the surface or within the atmosphere and for the development of remote-sensing algorithms. FluxNet is a

Jeffrey R Key; Axel J Schweiger

1998-01-01

168

Heat flux modifications related to climate-induced warming of large European lakes  

NASA Astrophysics Data System (ADS)

the last decades, the water temperature of several European lakes has risen. It is assumed that these temperature increases are due to a reconfiguration of the heat-balance components. This study explores the dominant modifications of heat exchange with the atmosphere and their temporal evolutions. The objective is to identify the primary changes in heat fluxes and the sequence of events of the reconfiguration for the period 1984-2011. For this purpose, a model was applied to Lake Constance to estimate the contributions of the individual heat fluxes to the total heat balance. The results show that increasing absorption of solar radiation (+0.21 ± 0.13 W m-2 yr-1) and of longwave radiation (+0.25 ± 0.11 W m-2 yr-1) was responsible for the lake surface warming of 0.046 ± 0.011°C yr-1. Heat losses to the atmosphere by longwave emission (-0.24 ± 0.06 W m-2 yr-1) and by latent heat flux (-0.27 ± 0.12 W m-2 yr-1) have intensified in parallel due to higher lake surface temperatures. The heat budget is in a quasi-steady state, whereas incoming solar radiation and the warmer atmosphere increased the lake surface temperature; the warmer surface emits more longwave radiation and more water is evaporated. At each level of the slowly increasing water temperature, the heat fluxes are balanced. The overall change of the total heat content, however, is relatively little. Although the cooling effect of inflowing rivers decreased, this contribution is also small.

Fink, Gabriel; Schmid, Martin; Wahl, Bernd; Wolf, Thomas; Wüest, Alfred

2014-03-01

169

Geometry effects on critical heat flux for subcooled convective boiling from an array of heated elements  

Microsoft Academic Search

The critical heat flux (CHF) condition was experimentally determined for subcooled flow boiling from an array of simulated microelectronic devices on one wall of a vertical rectangular passage. A test apparatus was used in these experiments that allowed visual observation of the boiling process while simultaneously measuring the heat flux and surface temperature for ten heat-dissipating elements. Using R-113 as

W. R. McGillis; V. P. Carey; B. D. Strom

1991-01-01

170

Measurement of Heat Flow in the Ground and the Theory of Heat Flux Meters.  

National Technical Information Service (NTIS)

The behavior of heat flux meters has been examined by experimental, electrical analogue and numerical means. The results indicate the more general applicability of the flux meter equation first proposed by Philip (1961) for the special case of spheroidal ...

P. Schwerdtfeger

1970-01-01

171

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

NASA Technical Reports Server (NTRS)

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(exp -2)/d, following a diurnal pattern similar to heat or moisture flux, while the daytime ozone flux was about -1.11 x 10(exp 11) molecules cm(exp -2)/s. 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.

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

1994-01-01

172

Critical Heat Flux of Concentric-Tube Thermosyphon  

NASA Astrophysics Data System (ADS)

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.

Kawabe, Hiromichi; Tanaka, Teimi; Fukusako, Shoichiro

173

Thin-Film Resistance Heat-Flux Sensors  

NASA Technical Reports Server (NTRS)

Thin-film heat-flux sensors of a proposed type would offer advantages over currently available thin-film heat flux sensors. Like a currently available thin-film heat-flux sensor, a sensor according to the proposal would be based on measurement of voltages related to the temperatures of thin metal films on the hotter and colder faces of a layer of an electrically insulating and moderately thermally conductive material. The heat flux through such a device is proportional to the difference between the temperatures and to the thermal conductivity of the layer. The advantages of the proposed sensors over the commercial ones would arise from the manner in which the temperature-related voltages would be generated and measured.

Fralick, Gustave C.; Wrbanek, John D.; Blaha, Charles A.

2005-01-01

174

Determination of surface heat flux using a single embedded thermocouple  

NASA Technical Reports Server (NTRS)

An implicit numerical procedure was developed for predicting the transient heat flux to a material using a single embedded thermocouple. The accuracy of the method was demonstrated by comparisons with analytically generated test data.

Williams, S. D.; Curry, D. M.

1976-01-01

175

Diamond Thin Film Temperature and Heat-Flux Sensors.  

National Technical Information Service (NTIS)

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...

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

1995-01-01

176

Flux-limited diffusion models in radiation hydrodynamics  

SciTech Connect

The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs.

Pomraning, G.C.; Szilard, R.H. (Univ. of California, Los Angeles (United States))

1993-01-01

177

Prediction of critical heat flux for subcooled flow boiling  

Microsoft Academic Search

A theoretical critical heat flux (CHF) prediction model is developed for the subcooled flow boiling based on the liquid sublayer dryout mechanism. The model is tested over a large data bank (about 2482 points), which is characterized by covering almost the entire physics scope, showing a general good accuracy. Parametric trends of the CHF in terms of mass flux, pressure,

W. Liu; H. Nariai; F. Inasaka

2000-01-01

178

Thermal transistor: Heat flux switching and modulating  

Microsoft Academic Search

Thermal transistor is an efficient heat control device which can act as a heat switch as well as a heat modulator. In this paper, we study systematically one-dimensional and two-dimensional thermal transistors. In particular, we show how to improve significantly the efficiency of the one-dimensional thermal transistor. The study is also extended to the design of two-dimensional thermal transistor by

Wei Chung Lo; Lei Wang; Baowen Li

2008-01-01

179

Variations of undamped rotor blade frequencies subjected to transient heat flux  

SciTech Connect

In the present work, the variation of rotor blade natural frequencies due to the radiative heat flux has been studied. The dynamic equations of motion have been obtained using curved, 20 node, solid, isoparametric finite elements. The effect of the variation of the pretwist angle on the natural frequencies also has been studied. 14 refs.

Sharan, A.M.; Bahree, R.

1989-06-01

180

Measuring turbulent heat fluxes over leads using kites  

NASA Astrophysics Data System (ADS)

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.

Guest, Peter S.

2007-05-01

181

Heat flux decay length in the midplane of ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

Power exhaust is a crucial issue for next step fusion devices since the heat flux to first wall elements has to be kept below a technically feasible limit. A crucial parameter in this context is the perpendicular heat flux decay length in the scrape-off layer (SOL). In this paper, a direct measurement of the midplane decay length in the poloidal divertor tokamak ASDEX Upgrade by continuously varying the magnetic configuration from a lower single null (SNL) through a double null configuration to upper single null (SNU), i.e., switching of the particle and heat flux continuously from the lower to the upper divertor, while monitoring the divertor particle and heat flux in the lower divertor is presented. The decrease of the signal measured at the outer lower divertor target plotted versus the midplane distance of the two separatrices results in e-folding lengths for the midplane heat flux. The decay lengths found are comparable to decay lengths derived from heat flux profiles measured at the divertor plates and mapped to the midplane.

Herrmann, A.; Carlson, A.; Fuchs, J. C.; Gruber, O.; Laux, M.; Neuhauser, J.; Pugno, R.; Sips, A.; Treutterer, W.; Schneider, W.; ASDEX Upgrade Team

2001-03-01

182

Regionalization Of Land Surface Heat Fluxes Over Heterogeneous Landscape Of Arid Area Using Landsat Etm Data  

NASA Astrophysics Data System (ADS)

Arid areas (e.g. Jidaah area of Saudi Arabia and Dunhuang area of northwestern China) with an inhomogeneous landscape are characterized by extreme gradients in land surface properties such as wetness, roughness and temperature, which have a significant but local impact on the atmospheric boundary layer (ABL). Observation of the actual extent over these areas is essential to understand the mechanisms through which inhomogeneous land surfaces may have a significant impact on the structure and dynamics of the overlying ABL. Progress in this research area requires spatial measurements of variables such as surface hemispherical reflectance, radiometric surface temperature, Normalized Difference Vegetation Index (NDVI), Modified Soil Adjusted Vegetation Index (MSAVI), vegetation coverage, leaf area index (LAI), local aerodynamic roughness length, etc. Imaging radiometric board satellites can provide useful estimates of most of these variables. Using these variables we can derive the distribution of land surface heat fluxes and evaporation over inhomogeneous landscape. In this study, a parameterization method based on Landsat-7 ETM data and field observations was described and tested for deriving the regional land surface variables, vegetation variables and land surface heat fluxes over heterogeneous landscape. As cases study, the method was applied to Jiddah area of Saudi Arabia and Dunhuang area of northwestern China. The regional distribution maps of surface reflectance, NDVI, MSAVI, vegetation coverage, LAI, surface temperature, net radiation, soil heat flux, sensible heat flux and latent heat flux have been derived over the two areas. Using the "ground truth", the derived results have been validated. The results show that the more reasonable regional distributions of land surface variables (surface reflectance, surface temperature), vegetation variables (MSAVI and vegetation coverage), net radiation, soil heat flux and sensible heat flux can be obtained by using the method proposed in this study. Further improvement of the method was also discussed.

Ma, Y.; Ishikawa, H.; Ueda, H.; Ohba, R.; Wen, J.; Su, B.

183

Nonequilibrium Stagnation-Line Radiative Heating for Fire II  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

184

Davis Strait volume, freshwater and heat fluxes  

Microsoft Academic Search

Volume, freshwater and heat transport through Davis Strait, the northern boundary of the Labrador Basin, are computed using a mooring array deployed for three con- secutive years. The net volume, freshwater and heat transports are ?2.6 ± 1.0 Sv, ?92 ± 34 mSv ,1 8± 17 ? 1012W. Both southward and northward volume and fresh- water transports are maximum in

Jerome Cuny; Peter B. Rhines; Ron Kwok

2004-01-01

185

SPECTRAL data-based estimation of soil heat flux  

USGS Publications Warehouse

Numerous existing spectral-based soil heat flux (G) models have shown wide variation in performance for maize and soybean cropping systems in Nebraska, indicating the need for localized calibration and model development. The objectives of this article are to develop a semi-empirical model to estimate G from a normalized difference vegetation index (NDVI) and net radiation (R n) for maize (Zea mays L.) and soybean (Glycine max L.) fields in the Great Plains, and present the suitability of the developed model to estimate G under similar and different soil and management conditions. Soil heat fluxes measured in both irrigated and rainfed fields in eastern and south-central Nebraska were used for model development and validation. An exponential model that uses NDVI and Rn was found to be the best to estimate G based on r2 values. The effect of geographic location, crop, and water management practices were used to develop semi-empirical models under four case studies. Each case study has the same exponential model structure but a different set of coefficients and exponents to represent the crop, soil, and management practices. Results showed that the semi-empirical models can be used effectively for G estimation for nearby fields with similar soil properties for independent years, regardless of differences in crop type, crop rotation, and irrigation practices, provided that the crop residue from the previous year is more than 4000 kg ha-1. The coefficients calibrated from particular fields can be used at nearby fields in order to capture temporal variation in G. However, there is a need for further investigation of the models to account for the interaction effects of crop rotation and irrigation. Validation at an independent site having different soil and crop management practices showed the limitation of the semi-empirical model in estimating G under different soil and environment conditions. ?? 2011 American Society of Agricultural and Biological Engineers ISSN 2151-0032.

Singh, R. K.; Irmak, A.; Walter-Shea, E. A.; Verma, S. B.; Suyker, A. E.

2011-01-01

186

Radiative Component and Combined Heat Transfer in the Thermal Calculation of Finned Tube Banks  

Microsoft Academic Search

For more exact calculation of combined heat transfer in the case of finned tube banks (e.g., in the convective section of a furnace), the radiative heat transfer cannot be neglected. A new method for relatively simple calculation of total heat flux (convection + radiation + conduction in fins) is fully compatible with that for bare tube banks\\/bundles developed earlier. It

Petr Stehlik

1999-01-01

187

Meridional heat flux of the North Atlantic Ocean  

SciTech Connect

Using self-consistent geostrophic general circulation estimates for the North Atlantic Ocean as determined by an inverse method, I calculate the geostrophic and total meridional heat flux. The result is to a large extent dictated by the assumption of a fixed volume flux through the Florida Straits. There is no fundamental discrepancy between oceanic heat fluxes deduced from atmospheric residuals and those estimated directly in the ocean, including the estimates made here, simply because the error bars on all calculations are very large.

Wunsch, C.

1980-09-01

188

Design of a Calibration System for Heat Flux Meters  

NASA Astrophysics Data System (ADS)

Accurate heat flux measurements are needed to gain a better knowledge of the thermal performance of buildings and to evaluate the heat exchange among various parts of a building envelope. Heat flux meters (HFMs) are commonly used both in laboratory applications and in situ for measuring one-dimensional heat fluxes and, thus, estimating the thermal transmittance of material samples and existing buildings components. Building applications often requires heat flux measurements below 100 W · m-2. However, a standard reference system generating such a low heat flux is available only in a few national metrology institutes (NMIs). In this work, a numerical study aimed at designing an HFM calibration apparatus operating in the heat flux range from 5 W·m-2 to 100 W · m-2 is presented. Predictions about the metrological performance of such a calibration system were estimated by numerical modeling exploiting a commercial FEM code (COMSOL®). On the basis of the modeling results, an engineered design of such an apparatus was developed and discussed in detail. The system was designed for two different purposes: (i) for measuring the thermal conductivity of insulators and (ii) for calibrating an HFM with an absolute method (i.e., by measuring the applied power from the heater and its active cross section) or by a relative method (i.e., by measuring the temperature drop across a reference material of known thickness and thermal conductivity). The numerical investigations show that in order to minimize the uncertainty of the generated heat flux, a fine temperature control on the thermal guard is needed. The predicted standard uncertainty is within 2% at 10W·m-2 and within 0.5% at 100 W · m-2.

Arpino, F.; Dell'Isola, M.; Ficco, G.; Iacomini, L.; Fernicola, V.

2011-12-01

189

Heat pipe radiator. [for spacecraft waste heat rejection  

NASA Technical Reports Server (NTRS)

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.

Swerdling, B.; Alario, J.

1973-01-01

190

Preliminary Evaluation of Sensible Heat Flux Measurements From a Large Aperture Scintillometer Using Lysimetric Data  

NASA Astrophysics Data System (ADS)

The path integrating capabilities of scintillometers over several kilometers make it a potential tool that can bridge the gap between primary point based observations (lysimeters, Bowen ratio, or eddy covariance) and the demand for large-scale spatially averaged surface fluxes. Further, the spatial scale of sensible heat flux data collected from a scintillometer is comparable to the spatial resolution of satellite images. Therefore, scintillometer data may be useful for validating evapotranspiration maps based on satellite data. Numerous studies have evaluated the measurement accuracy of scintillometers using eddy covariance systems; however, the latter has energy balance closure problems up to 30%. The main objective of this study is to test the Large Aperture Scintillometer (LAS) using lysimetric data. The LAS monitors the sensible heat flux (H) and water vapor flux (LE) is calculated as a residual of the surface energy balance equation by monitoring net radiation (Rn) and soil heat flux (G) (LE=Rn+G-H). A Large Aperture Scintillometer (LAS) was deployed across two lysimeter fields planted with grain sorghum under dryland management conditions. The orientation of LAS was selected to have the path of the LAS perpendicular to the predominant wind direction and to avoid direct sun light on the lenses. The refractive index of air was monitored during the 2007 cropping season at 15-min. intervals, synchronized with weather station and lysimeter measurements. In addition, a net radiometer and three soil heat flux plates were installed near both the receiver and transmitter of the scintillometer as well as on two large monolithic lysimeters. Predicted water vapor fluxes from the scintillometer-net radiometer-heat flux plate setup were compared with lysimeter data. Preliminary results (three months of data) indicate that the LAS is a promising tool for deriving water vapor fluxes. However, further evaluation is needed under a variety of crop/weather conditions to fully assess its capability to accurately estimate spatially distributed water vapor fluxes.

Gowda, P. H.; Howell, T. A.; Scanlon, B. R.; Copeland, K. S.; Bush, K.

2007-12-01

191

Estimation of Soil Thermal Inertia and Ground Heat Flux Based on Maximum Entropy Production Hypothesis  

NASA Astrophysics Data System (ADS)

Ground heat flux is an important component of the energy balance at the terrestrial earth surface. This study focuses on the remote sensing of areal ground heat flux G. Before, Wang and Bras (1999) suggested a method to evaluate G based on the half-order time derivatives of soil surface temperature. The method required thermal inertia of surface layer Is, which should be estimated using soil thermal properties or calculated with a few measurements of G for calibration. However, areal representative Is was difficult to obtain for the complexity of areal surface composition and lack of the direct methods of G measurement. The author developed a novel method to estimate areal Is and G, for which remotely sensible net radiation and surface temperature were only used. It depended on the assumptions that energy sharing of net radiation obeyed the maximum entropy production hypothesis in calm nights and then latent heat flux was insignificant. Validation showed thermal inertia of air Ia at the soil surface did not agree well with the theory of Wang and Bras (2009). A new empirical equation of Ia and sensitive heat flux relationship was proposed. Using this equation, net radiation was divided into sensitive heat flux and ground heat flux, and Is was obtained. For several days, systematic changes of Is could not be detected. That is, the thermal inertia of surface soil layer could be treated as a constant if not for remarkable changes of soil wetness. The method should be useful for remote sensing of other objects, for instance, soil water condition and evapotranspiration.

Kiyosawa, H.

2013-12-01

192

Enhanced Heat Flux in Non-Uniform Electric Fields  

Microsoft Academic Search

Heat transfer by convection from a thin wire to a liquid was very appreciably increased by the application of a non-uniform electric field of several hundred kilovolts per centimetre which was confocal with the temperature field. This enhancement of the heat flux was much larger in a polar, slightly conducting liquid than in a practically ion-free liquid; the behaviour of

R. Schnurmann; M. G. C. Lardge

1973-01-01

193

Heat flux from the catalyst layer of a fuel cell  

Microsoft Academic Search

We report exact solutions to the problem of heat transport in the catalyst layer (CL) of a fuel cell. The solutions are obtained for the low- and high-current regimes of CL operation. The approximate equation for the heat flux from the CL valid for the whole range of current densities is suggested. This equation is suitable for CFD calculations of

A. A. Kulikovsky; J. McIntyre

2011-01-01

194

Performance of thermal barrier coatings in high heat flux environments  

Microsoft Academic Search

Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 \\

ROBERT A. MILLER; CHRISTOPHER C. BERNDT

1984-01-01

195

Evaluation of satellite-derived latent heat fluxes  

SciTech Connect

A method of determining ocean-atmosphere latent heat flux using the Special Sensor Microwave/Imager (SSM/I) and the Advanced Very High Resolution Radiometer (AVHRR) is presented and evaluated. While sea surface temperatures are retrieved from AVHRR data with an accuracy of 0.5-1.0 K, the near-surface wind speed and the surface air humidity are retrieved from measurements of the SSM/I with accuracies of 1.4 m s{sup -1} and 1.1 g kg{sup -1}, respectively. The latent heat flux is then computed with a stability-dependent bulk parameterization model. The derived fluxes are compared to globally distributed instantaneous shipboard and buoy measurements and to monthly averages of 2{degrees} x 2{degrees} longitude and latitude bins. The standard error for instantaneous flux estimates is approximately 30 W m{sup -2}, and that for monthly averages decreases to 15 W m{sup -2}. Additionally, a 1-yr time series of latent heat flux at the weathership M in the North Atlantic and two shorter time series during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) and the Central Equatorial Pacific Experiment (CEPEX) in the tropical Pacific are compared to satellite measurements. The SSM/1-derived parameters, as well as the latent heat flux, are represented very well on the weathership M. During TOGA COARE and CEPEX, the near-surface humidity is sometimes systematically overestimated in the warm pool region, which results in an underestimation of the latent heat flux. Nevertheless, the representation of the latent heat flux is always in the range of the in situ measurements. 50 refs., 14 figs., 1 tab.

Schulz, J.; Meywerk, J.; Ewald, S. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)] [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Schluessel, P. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States)

1997-11-01

196

QUANTIFICATION OF HEAT FLUX FROM A REACTING THERMITE SPRAY  

SciTech Connect

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.

Eric Nixon; Michelle Pantoya

2009-07-01

197

The heat flux calculation for the laser-fusion problem  

NASA Astrophysics Data System (ADS)

The problem of heat flux at the critical surfaces and the surfaces of a pellet of deuterium and tritium (conduction zone) heated by laser have been considered. Ion-electron collisions are only allowed for: i.e., the linear transport equation is used to describe the problem with boundary conditions consists of isotropic and diffuse boundary conditions. The bi-variational technique has been used to calculate the electron density and temperature across the conduction zone as well as the heat flux. Numerical results are given and compared with those of Rouse and Williams (1981) results.

Elwakil, S. A.; Attia, M. T.; El-Labany, S. K.; Saad, E. A.

1989-11-01

198

Infrared Radiometery and Heat Flux Calculation for a Helicon Plasma  

NASA Astrophysics Data System (ADS)

Using an infrared camera, we measured the external temperature of a quartz tube containing a 1 kW helicon Argon plasma. An Inframetrics model 600 IR camera connected to a computer DAQ system records the temperature evolution of the quartz tube surface in the vicinity of the antenna during and after the pulse. Using these measurements, we estimated the heat flux profile from the plasma into the quartz tube walls. A MATLAB code uses pre- and post- pulse snapshot images from the video to estimate the heat flux into the quartz from the plasma. Initial results have shown a broad heating profile with localized power input into the quartz under the helical antenna. We find approximately 30% of the total RF power deposited into the tube as heat, and heating directly under the antenna accounts for about 30% of this heat input.

Berisford, Daniel; Lee, Charles A.; Raja, L. L.; Bengtson, Roger D.

2006-10-01

199

Turbine blade and vane heat flux sensor development, phase 1  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

200

Turbine blade and vane heat flux sensor development, phase 2  

NASA Technical Reports Server (NTRS)

The development of heat flux sensors for gas turbine blades and vanes and the demonstration of heat transfer measurement methods are reported. The performance of the heat flux sensors was evaluated in a cylinder in cross flow experiment and compared with two other heat flux measurement methods, the slug calorimeter and a dynamic method based on fluctuating gas and surface temperature. Two cylinders, each instrumented with an embedded thermocouple sensor, a Gardon gauge, and a slug calorimeter, were fabricated. Each sensor type was calibrated using a quartz lamp bank facility. The instrumented cylinders were then tested in an atmospheric pressure combustor rig at conditions up to gas stream temperatures of 1700K and velocities to Mach 0.74. The test data are compared to other measurements and analytical prediction.

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

1985-01-01

201

Effect of Index of Refraction on Radiation Characteristics in a Heated Absorbing, Emitting, and Scattering Layer  

NASA Technical Reports Server (NTRS)

The effect of the index of refraction on the temperature distribution and radiative heat flux in semitransparent materials, such as some ceramics, is investigated analytically. In the case considered here, a plane layer of a ceramic material is subjected to external radiative heating incident on each of its surfaces; the material emits, absorbs, and isotropically scatters radiation. It is shown that, for radiative equilibrium in a gray layer with diffuse interfaces, the temperature distribution and radiative heat flux for any index of refraction can be obtained in a simple manner from the results for an index of refraction of unity.

Siegel, R.; Spuckler, C. M.

1992-01-01

202

Solid state radiative heat pump  

DOEpatents

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.

Berdahl, Paul H. (Oakland, CA)

1986-01-01

203

Solid state radiative heat pump  

DOEpatents

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.

Berdahl, P.H.

1984-09-28

204

A constant heat flux model of the evaporating interline region  

NASA Technical Reports Server (NTRS)

An approximate procedure is developed for determining the heat sink capability of an interline region (junction of vapor, evaporating thin film, and nonevaporating thin film), with consideration of the effect of resistance of the solid to heat transfer. The formulation is based on a simple one-dimensional constant heat flux model. The solution is directed toward a limiting case in which the thermal conductance of the solid is controlling. Since the value of the ideal liquid-vapor interfacial heat transfer coefficient is very large, conductance of the solid is found to dominate the overall heat transfer coefficient in the interline region after a small increase in film thickness.

Wayner, P. C., Jr.

1978-01-01

205

Corrections of Heat Flux Measurements on Launch Vehicles  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

206

Methodology for calibration and use of heat flux transducers  

NASA Astrophysics Data System (ADS)

The direct assessment of heat flux from the body is a basic measurement in thermal physiology. Heat flux transducers (HFTs) are being used increasingly for that purpose under different environmental conditions. However, questions have been raised regarding the accuracy of the manufacturer's constant of calibration, and also about the effect of the thermal resistance of the device on the true thermal flux from the skin. Two different types of waterproofed HFTs were checked for their calibration using the Rapid-k thermal conductivity instrument. A detailed description of the methodology used during the calibration is given. A model capable of simulating a large range of tissue insulation was used to study the effect of the underlying tissue insulation on the relative error in thermal flux due to the thermal resistance of the HFTs. The data show that the deviation from the true value of thermal flux increases with the reciprocal of the underlying tissue insulation (r = 0.99, p less than 0.001). The underestimation of the heat flux through the skin measured by an HFT is minimal when the device is used on vasoconstricted skin in cool subjects (3 to 13 pct. error), but becomes important when used on warm vasodilated subjects (29 to 35 pct. error), and even more important on metallic skin mannequins (greater than 60 pct. error). In order to optimize the accuracy of the heat flux measurements by HFTs, it is important to recalibrate the HFTs and to correct the heat flux values for the thermal resistance of the HFT when used on vasodilated tissues.

Ducharme, Michel B.; Frim, John

1991-05-01

207

The partitioning between latent and sensible heat flux at FLUXNET sites  

NASA Astrophysics Data System (ADS)

The partitioning between ecosystem latent (LE) and sensible (H) heat fluxes is critical for understanding the hydrological cycle, predicting boundary layer development, weather and climate. The FLUXNET network provides a unique opportunity to investigate the partitioning of latent and sensible heat fluxes at the surface over a broad range of vegetation types and climates. This paper focuses on two aspects of surface flux partitioning at more than 20 sites worldwide. The first focus is on the relative partitioning between latent and sensible heat fluxes, or the Bowen ratio, during the warm season. We investigate the Bowen ratio across vegetation types and climates, and suggest controlling climatological and ecological factors. The surface resistance, which is related to the ability of the vegetation to supply available water and is one factor controlling the Bowen ratio, was generally lower at the agricultural and deciduous forest sites compared to coniferous forests. The ratio of the atmospheric humidity deficit to the net radiation (proportional to the climatological resistance), a second important factor controlling the Bowen ratio, was generally lower at sites near large bodies of water or over tundra vegetation, and was greater at more continental sites. The second focus of the study is on the diurnal trends of latent and sensible heat fluxes. We quantify the diurnal pattern of turbulent energy fluxes using the `diurnal centroid', which is an indicator of whether the fluxes peak in the morning or afternoon. The diurnal centroid provides useful signatures of important physiological and climatological factors that control surface fluxes. These factors include stomatal closure, advection, atmospheric stability and vegetation height. Sites with tall vegetation and/or high wind speeds in continental regions with limited affects of advection, a stable and dry atmosphere and weak stomatal sensitivity to atmospheric humidity deficits or water potential tend to have late diurnal peaks in latent heat flux relative to sensible heat flux. Alternatively, sites with short vegetation, prominent advection from maritime sources, a weakly stable and moist atmosphere and a strong stomatal sensitivity to humidity deficit or water potential will have earlier peaks in latent heat flux relative to sensible heat flux.

Wilson, K. B.

2001-12-01

208

A Semi-parametric Multivariate Gap-filling Model for Eddy Covariance Latent Heat Flux  

NASA Astrophysics Data System (ADS)

Quantitative descriptions of latent heat fluxes are important to study the water and energy exchanges between terrestrial ecosystems and the atmosphere. The eddy covariance approaches have been recognized as the most reliable technique for measuring surface fluxes over time scales ranging from hours to years. However, unfavorable micrometeorological conditions, instrument failures, and applicable measurement limitations may cause inevitable flux gaps in time series data. Development and application of suitable gap-filling techniques are crucial to estimate long term fluxes. In this study, a semi-parametric multivariate gap-filling model was developed to fill latent heat flux gaps for eddy covariance measurements. Our approach combines the advantages of a multivariate statistical analysis (principal component analysis, PCA) and a nonlinear interpolation technique (K-nearest-neighbors, KNN). The PCA method was first used to resolve the multicollinearity relationships among various hydrometeorological factors, such as radiation, soil moisture deficit, LAI, and wind speed. The KNN method was then applied as a nonlinear interpolation tool to estimate the flux gaps as the weighted sum latent heat fluxes with the K-nearest distances in the PCs’ domain. Two years, 2008 and 2009, of eddy covariance and hydrometeorological data from a subtropical mixed evergreen forest (the Lien-Hua-Chih Site) were collected to calibrate and validate the proposed approach with artificial gaps after standard QC/QA procedures. The optimal K values and weighting factors were determined by the maximum likelihood test. The results of gap-filled latent heat fluxes conclude that developed model successful preserving energy balances of daily, monthly, and yearly time scales. Annual amounts of evapotranspiration from this study forest were 747 mm and 708 mm for 2008 and 2009, respectively. Nocturnal evapotranspiration was estimated with filled gaps and results are comparable with other studies. Seasonal and daily variability of latent heat fluxes were also discussed.

Li, M.; Chen, Y.

2010-12-01

209

Reflectance-Based Estimation of Soil Heat Fluxes in the Texas High Plains  

NASA Astrophysics Data System (ADS)

Soil heat flux (G) is one of the terms required for estimating evapotranspiration 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, operational ET remote sensing programs may require locally developed/calibrated models for accurately estimating G. The objective of this study was to develop and evaluate reflectance-based empirical G models for the semi-arid Texas High Plains. Soil heat flux was measured at 0.15 hz interval and averaged every 15 minutes at five different locations within a 4.7 ha lysimeter field with Pullman clay loam soil during the 2010 summer growing season. The field was planted to soybean and managed under dryland conditions. In each location, G was measured at 8 cm depth with two Campbell Scientific HFT3 soil heat flux plates. Soil temperature was measured at 2 and 6 cm above the soil heat flux plates. Soil moisture was measured in the 2-8 cm layer using Acclima SDI-12 sensors. Hourly G fluxes at the surface were calculated by adding the measured G fluxes at 8 cm to the energy stored above the heat flux plates. A multispectral radiometer (MSR, CROPSCAN, Inc.) and hand-held thermometer (EVEREST Interscience Inc.) measured surface reflectance in red and near infrared bandwidths and surface temperature (ST), respectively, daily at 11:30 AM CST to be consistent with the Landsat 5 overpass time. Fraction crop cover (FC) was measured by digital photographs taken twice a week. A set of G models was developed for estimating hourly fluxes based on measured reflectance, net radiation, ST, NDVI, and FC,. Resulting models were compared for performance with existing models available in the literature. In this presentation, we will discuss our G models for the Texas High Plains and the statistical results.

Gowda, P. H.; Colaizzi, P. D.; O'Shaughnessy, S.; Ha, W.; Howell, T. A.

2010-12-01

210

Radiation heat transfer in combustion systems  

Microsoft Academic Search

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

R. Viskanta; M. P. Menguc

1987-01-01

211

Laboratory Investigation of Electron Heat Flux Driven Whistler Instabilities  

NASA Astrophysics Data System (ADS)

Recent observations by the Ulysses spacecraft [Scime et al., J. Geophys. Res., 99, 23401 (1994)] confirm that the thermal energy convected away from the Sun by the electron component of the solar wind, the electron heat flux, is actively regulated by some microphysical process. Comparison with theoretical predictions [Gary et al., J. Geophys. Res., 99, 23,391 (1994)] suggest that the whistler heat flux instability may be responsible for regulation of the electron heat flux. Construction of a laboratory experiment designed to investigate the electromagnetic, whistler heat flux instability is underway at West Virginia University. The experimental parameters believed necessary to excite the whistler heat flux instability will be reviewed as well as the design parameters of the steady-state, high beta, experiment. Initial measurements of the plasma density, electron temperature, background electromagnetic fluctuations, and electron beam current in the Large Experiment on Instabilities and Anisotropies (LEIA) will be presented. Work supported by the U.S. Department of Energy and the National Science Foundation

Scime, Earl E.; Balkey, Matthew M.; Keiter, Paul A.; Kline, John L.

1997-11-01

212

Cold air outbreaks over the Northwest Florida continental shelf: Heat flux processes and hydrographic changes  

NASA Astrophysics Data System (ADS)

An experimental study of the meteorology and oceanography of the cold air outbreak cycle was conducted during the fall of 1978 off Panama City, Florida. Details of the air-sea interaction processes they induce on such upwind continental shelves are poorly known because of lack of appropriate measurements. Shallow depths and proximity to land make the processes significantly different from their deepwater counterparts. The cycle has three phases recognizable in the measurements: the prefrontal, frontal passage, and cold air outbreak/high-pressure phases. The time variability of oceanic heat fluxes was monitored through the cycle in two ways: by measuring heat content changes and by measuring turbulent and radiative heat fluxes. Advective effects on the heat budget were minimized by the site selection. A mild cold air outbreak stripped 26.8×106 J m-2 (640 cal cm-2) of heat and 1.1 cm of liquid water from the shelf in 63 hours, and a severe cold air outbreak removed 147.6×106 J m-2 (3528 cal cm-2) and 4.4 cm of liquid water in 87 hours. For these events, evaporation, sensible heat loss, and radiative heat loss were 51, 16, and 33, and 58, 25 and 17% of the totals, respectively. A simple one-dimensional shallow water heat flux model predicted temperature and heat content changes during severe cold air outbreaks to within 8%. Observations indicate the extreme time variability of heat flux processes and the hazards of extrapolating to daily rates from spot measurements or very short time series.

Huh, Oscar Karl; Rouse, Lawrence J.; Walker, Nan Delene

1984-01-01

213

Mass, heat and freshwater fluxes in the South Indian Ocean  

NASA Technical Reports Server (NTRS)

Six hydrographic sections were used to examine the circulation and property fluxes in the South Indian Ocean from 10 to 32 deg S. The calculations were made by applying an inverse method to the data. In the interior of the South Indian Ocean, the geostrophic flow is generally northward. At 18 deg S, the northward interior mass flux is balanced by the southward Ekman mass flux at the surface, whereas at 32 deg S the northward interior mass flux is balanced by the southward mass flux of the Agulhas Current. There is a weak, southward mass flux of 6 x 10 to the 9th kg/s in the Mozambique Channel. The rate of water exchange between the Pacific Ocean and the Indian Ocean is dependent on the choice of the initial reference level used in the inverse calculation. The choice of 1500 m, the depth of the deep oxygen minimum, has led to a flux of water from the Pacific Ocean to the Indian Ocean at a rate of 6.6 x 10 to the 9th kg/s. Heat flux calculations indicate that the Indian Ocean is exporting heat to the rest of the world's oceans at a rate of -0.69 x 10 to the 15th W at 18 deg S and -0.25 x 10 to the 15th W at 32 deg S (negative values being southward).

Fu, Lee-Lueng

1986-01-01

214

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

SciTech Connect

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.

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

1994-04-01

215

The ground heat flux simulated by the COSMO land surface scheme TERRA  

NASA Astrophysics Data System (ADS)

Land surface processes have a significant impact on near-surface atmospheric phenomena. They determine, among others, near-surface sensible and latent heat fluxes and the radiation budget, and thus influence atmosphere and land characteristics, such as temperature and humidity, the structure of the planetary boundary layer, and even cloud formation processes. It is therefore important to simulate the land surface processes in atmospheric models as realistically as possible. Verifications have shown that the ground heat flux computed by the land surface scheme TERRA of the COSMO atmospheric model is systematically overestimated under dry conditions. Since this flux is part of the surface energy balance it affects the other components like the turbulent heat fluxes and the surface temperature. This means, an overestimation of the ground heat flux during daytime leads to an underestimation of the other surface fluxes and a reduced surface warming. During afternoon and night this behaviour is reversed. Data from the Meteorological Observatory Lindenberg of the German Weather Service were used to analyse this model behaviour. In sensitivity experiments with the soil model TERRA it turned out that the simulated ground heat flux is particularly influenced by the shading effect of the incoming solar radiation due to the vegetation cover, but also by the thermal conductivity of the soil and its dependence on the soil moisture. Two formulations for the dependence of the thermal conductivity on soil moisture, following Johansen (1975) and McCumber and Pielke (1981), were tested in TERRA. It turned out that Johansen (1975) gives good results, while McCumber and Pielke (1981) overestimates the effect.

Schulz, Jan-Peter; Vogel, Gerd; Heret, Claudia; Ahrens, Bodo

2013-04-01

216

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

217

Urban heat fluxes in the subsurface of Cologne, Germany  

NASA Astrophysics Data System (ADS)

Urbanization during the last hundred years has led to both environmental and thermal impacts on the subsurface. The urban heat island (UHI) effect is mostly described as an atmospheric phenomenon, where the measured aboveground temperatures in cities are elevated in comparison to undisturbed rural regions. However, UHIs can be found below, as well as above ground. A large amount of anthropogenic heat migrates into the urban subsurface, which also raises the ground temperature and permanently changes the thermal conditions in shallow aquifers. The main objective of our work is to study and determine the urban heat fluxes in Cologne, Germany, and to improve our understanding of the dynamics of subsurface energy fluxes in UHIs. Ideally, our findings will contribute to strategic and more sustainable geothermal use in cities. For a quantitative analysis of the energy fluxes within the subsurface and across the atmospheric boundary, two and three-dimensional coupled numerical flow and heat transport models were developed. The simulation results indicate that during the past hundred years, an average vertical urban heat flux that ranges between 80 and 375 mW m-2 can be deduced. Thermal anomalies have migrated into the local urban aquifer system and they reach a depth of about 150 m. In this context, the influence of the regional groundwater flow on the subsurface heat transport and temperature development is comprehensively discussed.

Zhu, K.; Bayer, P.; Blum, P.

2012-04-01

218

The radiation budget of stratocumulus clouds measured by tethered balloon instrumentation: Variability of flux measurements  

NASA Technical Reports Server (NTRS)

Measurements of longwave and shortwave radiation were made using an instrument package on the NASA tethered balloon during the FIRE Marine Stratocumulus experiment. Radiation data from two pairs of pyranometers were used to obtain vertical profiles of the near-infrared and total solar fluxes through the boundary layer, while a pair of pyrgeometers supplied measurements of the longwave fluxes in the cloud layer. The radiation observations were analyzed to determine heating rates and to measure the radiative energy budget inside the stratocumulus clouds during several tethered balloon flights. The radiation fields in the cloud layer were also simulated by a two-stream radiative transfer model, which used cloud optical properties derived from microphysical measurements and Mie scattering theory.

Duda, David P.; Stephens, Graeme L.; Cox, Stephen K.

1990-01-01

219

An improved empirical method for large spatial scale surface soil heat flux estimations  

NASA Astrophysics Data System (ADS)

In this paper, a novel method to simulate soil heat flux for large spatial scale is proposed. This method is constructed with the ratio of soil heat flux and net radiation (G0/Rn) and surface characteristic parameters, such as ratio vegetation indices, surface temperature, surface shortwave infrared reflectance, soil moisture content, solar zenith angle. Field calibration is carried out using measured data in 2009 from Yingke, Huazhaizi, Arou, and Dayakou stations located in Heihe River Basin, Northwest of China. The estimated soil heat flux is compared with field observation data from Yingke and Arou stations in 2008. The overall deviation basis and correlation coefficient between the soil heat flux estimation and measured data are 13.4% and 0.804 in the Yingke station and 12.5% and 0.893 in the Arou station respectively, and also the correlation coefficient are 0.905 in the Maliantan station and 0.817 in the Binggou station respectively. Results indicated that the proposed method performed well in Heihe River Basin. This new method could be an optimal choice to estimate surface soil heat flux for large spatial scale in the future.

Zhu, Weiwei; Wu, Bingfang; Lu, Shanlong; Yan, Nana; Liu, Guoshui; Liu, Shufu; Xing, Qiang

2014-03-01

220

How Diffusion Modeling Affects Prediction of Heat Flux Loads  

NASA Astrophysics Data System (ADS)

It is customary in literature to approximate diffusion fluxes by means of a simple Fick's law approximation, that is correct only for binary mixtures. Such an approximation is computationally cheap, but can grossly violate the mass conservation constraint and leads to wrong estimation of computed wall heat flux. In this contribution we compare Fick's law approximation, Ramshaw simplified diffusion model, multicomponent diffusion formulation of Ern and Giovangigli and Stefan- axwell equations and assess their effect on computed heat. We investigate too the effect of thermal diffusion and higher order corrections to diffusion coefficients. Results show that diffusion modeling plays an important role and it is necessary to use Stefan-Maxwell, Ern and Giovangigli or at least Ramshaw formulation to obtain reliable heat flux predictions.

Barbante, P. F.

2009-01-01

221

Flow-excursion-induced dryout at low-heat-flux  

SciTech Connect

Flow-excursion-induced dryout at low-heat-flux natural-convection boiling, typical of liquid-metal fast-breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of Ledinegg instability leading to flow excursion and subsequent dryout in agreement with experimental data. A flow-regime-dependent dryout heat flux relationship based upon saturated boiling criterion is also presented. Transient analysis indicates that premature flow excursion can not be ruled out and sodium boiling is highly transient dependent. Analysis of a high-heat-flux forced convection, loss-of-flow transient shows a significantly faster flow excursion leading to dryout in excellent agreement with parallel calculations using the two-dimensional THORAX code. 17 figures.

Khatib-Rahbar, M.; Cazzoli, E.G.

1983-01-01

222

Peak pool boiling heat flux in viscous liquids  

NASA Technical Reports Server (NTRS)

The stability of a gas jet in a surrounding viscous liquid is studied. An expression is developed for the critical velocity at which the jet becomes unstable in a returning viscous liquid. The stability analysis is made to correspond with the geometrical configuration of gas jets and liquid columns similar to those observed near the peak pool boiling heat flux. The critical velocity of the gas jet is then used to obtain the functional form of the peak heat flux on flat plates and cylindrical heaters. The expressions are compared with original observations of the peak heat flux in very viscous liquids on flat plate, and cylindrical, heaters at both earth-normal, and elevated, gravities.

Dhir, V. K.; Lienhard, J. H.

1974-01-01

223

Remote high-temperature insulatorless heat-flux gauge  

DOEpatents

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.

Noel, Bruce W. (Espanola, NM)

1993-01-01

224

Remote high-temperature insulatorless heat-flux gauge  

DOEpatents

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.

Noel, B.W.

1993-12-28

225

Variations in geothermal heat flux at Grímsvötn, Iceland  

NASA Astrophysics Data System (ADS)

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.

Iona Reynolds, Hannah; Tumi Gudmundsson, Magnús

2014-05-01

226

Horizontal Radiative Fluxes in Clouds at Absorbing Wavelengths.  

National Technical Information Service (NTIS)

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 fl...

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

1998-01-01

227

Parameterisation of surface radiation flux at an Antarctic site  

NASA Astrophysics Data System (ADS)

During the Antarctic summer 1994/95 the values of downward and upward flux densities of both solar and terrestrial radiation were recorded at 1200 m for a period of 1 month on the Reeves Nevè Glacier (lat 74°39'S, long 161°35'E), near the Italian base of Terra Nova Bay. The relations proposed by Swinbank [Swinbank, W.C., 1963. Long-wave radiation from clear skies. Q. J. R. Meteorol. Soc. 89, 339-348], Idso and Jackson [Idso, S.B., Jackson, R.D., 1969. Thermal radiation from the atmosphere. J. Geophys. Res. 74, 5397-5403] and Deacon [Deacon, E.L., 1970. The derivation of Swinbank's long-wave radiation formula. Q. J. R. Meteorol. Soc. 96, 313-319] associating the long-wave atmospheric radiation flux only to the air temperature at screen level were tested in extreme Antarctic climatological condition. A relation between the long-wave radiation flux and both screen air temperature and cloud cover fraction in accordance to the height of the cloud base was defined using the Kasten and Czeplak relationship that relates the solar radiation flux and the cloud cover index. The study of the incoming short-wave radiation flux from the clear sky and that reflected by the surrounding snow cover allowed for highlighting the role of surface geometry on the albedo measurements.

Orsini, A.; Calzolari, F.; Georgiadis, T.; Levizzani, V.; Nardino, M.; Pirazzini, R.; Rizzi, R.; Sozzi, R.; Tomasi, C.

228

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

229

Validation of General Circulation Model Radiative Fluxes Using Surface Observations  

Microsoft Academic Search

The surface radiative fluxes of the ECHAM3 General Circulation Model (GCM) with T2 1, T42, and T 106 resolutions have been validated using observations from the Global Energy Balance Archive (GEBA, World Climate Program-Water Project A7). GEBA contains the most comprehensive dataset now available for worldwide instrumentally measured surface energy fluxes.The GCM incoming shortwave radiation at the surface has been

Martin Wild; Atsumu Ohmura; Hans Gilgen; Erich Roeckner

1995-01-01

230

Validation of general circulation model radiative fluxes using surface observations  

Microsoft Academic Search

The surface radiative fluxes of the ECHAM3 General Circulation Model (GCM) with T21, T42, and T106 resolutions have been validated using observations from the Global Energy Balance Archive (GEBA, World Climate Program-Water Project A7). GEBA contains the most comprehensive dataset now available for worldwide instrumentally measured surface energy fluxes. The GCM incoming shortwave radiation at the surface has been compared

M. Wild; A. Oshmura; H. Gilgen

1995-01-01

231

A modular radiation-belt electron flux model  

Microsoft Academic Search

We present a time-dependent model for the energetic electron flux in Earth's radiation belts developed from measurements by several spacecraft in the radiation belts (POLAR, SAMPEX, Akebono, HEO, and GOES) and the solar wind (ACE, WIND). The flux is a function of L shell (1-11), particle energy (0.8-6.4 MeV) and time. A different module is developed for each one of

D. Vassiliadis; D. N. Baker; S. F. Fung; S. G. Kanekal; E. J. Rigler; R. S. Selesnick; R. S. Weigel

2006-01-01

232

Long-term evolution of anthropogenic heat fluxes into a subsurface urban heat island.  

PubMed

Anthropogenic alterations in urban areas influence the thermal environment causing elevated atmospheric and subsurface temperatures. The subsurface urban heat island effect is observed in several cities. Often shallow urban aquifers exist with thermal anomalies that spread laterally and vertically, resulting in the long-term accumulation of heat. In this study, we develop an analytical heat flux model to investigate possible drivers such as increased ground surface temperatures (GSTs) at artificial surfaces and heat losses from basements of buildings, sewage systems, subsurface district heating networks, and reinjection of thermal wastewater. By modeling the anthropogenic heat flux into the subsurface of the city of Karlsruhe, Germany, in 1977 and 2011, we evaluate long-term trends in the heat flux processes. It revealed that elevated GST and heat loss from basements are dominant factors in the heat anomalies. The average total urban heat flux into the shallow aquifer in Karlsruhe was found to be ?759 ± 89 mW/m(2) in 1977 and 828 ± 143 mW/m(2) in 2011, which represents an annual energy gain of around 1.0 × 10(15) J. However, the amount of thermal energy originating from the individual heat flux processes has changed significantly over the past three decades. PMID:23895264

Menberg, Kathrin; Blum, Philipp; Schaffitel, Axel; Bayer, Peter

2013-09-01

233

Electron Flux of Radiation Belts Animation  

NASA Video Gallery

This animation shows meridional (from north-south) plane projections of the REPT-A and REPT-B electron flux values. The animation first shows the expected two-belt Van Allen zone structure; from Se...

234

Fluctuations, linear response and heat flux of an aging system  

NASA Astrophysics Data System (ADS)

We measure the fluctuations of the position of a Brownian particle confined by an optical trap in an aging gelatin droplet after a fast quench. Its linear response to an external perturbation is also measured. We compute the spontaneous heat flux from the particle to the bath due to the non-equilibrium formation of the gel. We show that the mean heat flux is quantitatively related to the violation of the equilibrium fluctuation-dissipation theorem as a measure of the broken detailed balance during the aging process.

Gomez-Solano, J. R.; Petrosyan, A.; Ciliberto, S.

2012-04-01

235

Infrared Camera Diagnostic for Heat Flux Measurements on NSTX  

SciTech Connect

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.

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

2003-03-25

236

DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY  

SciTech Connect

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.

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

2007-12-19

237

Heat flux instrumentation for Hyflite thermal protection system  

NASA Astrophysics Data System (ADS)

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.

Diller, T. E.

238

Radiative heat transfer in porous uranium dioxide  

SciTech Connect

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.

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

239

Prototype V-Groove Radiator Heat Shield  

NASA Technical Reports Server (NTRS)

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.

Petrick, S. Walter; Bard, Steven

1990-01-01

240

Sub-seasonal river heat flux partitioning in an alpine, glacierized basin  

NASA Astrophysics Data System (ADS)

In the alpine zone climate-cryosphere interactions are particularly important as seasonal dynamics in snow- and glacier-melt regulate river flow and stream water temperature. Shifts in the timing, magnitude and duration of meltwater production are predicted in response to a warming climate, which has potential to alter thermal regimes of glacier fed rivers. Current knowledge of the deterministic processes controlling alpine stream temperature dynamics is very limited. To address the research gap, this paper aims to undertake detailed hydro-meteorological investigation of the energy budget processes driving water column thermal dynamics from a glacier fed stream in the French Pyrenees over two summer melt seasons. During both summers, the heat budget was strongly positive with the majority of energy exchanged at the air - water interface. On average, net radiation was the largest heat source (~80% of total flux). Sensible heat transfer, latent heat and fluid friction were also significant heat sources. However, the latent heat flux displayed the most inter-annual variability; during 2010 (2011) it contributed to 5.2% (0.03%) of the total heat budget. This was due to windier, dryer conditions prevailing in 2011 which balanced out early season condensation gains with evaporative losses. Energy exchanges at the channel - river bed interface comprised <1% of the heat budget. However, >20% of all energy losses occurred at this interface, only latent heat transfer contributed more to total energy loss. Daily total energy fluxes were analysed to characterise sub-seasonal dynamics. Small declines in net radiation receipt and total energy available to the water column were observed as the melt season progressed. While both the sensible heat flux and bed heat flux displayed no clear patterns. Interestingly latent heat was an energy balance component in terms of heat gains and losses, showing a seasonal shift from source to sink over the melt season. This shift was driven by the retreating snowline which created changes in the thermal and humidity gradients at the air-water interface. These findings highlight the importance of considering a meltwater generation component in future heat budget models and suggests that exchanges at the river bed could be neglected when applying such models to alpine river basins.

Khamis, K.; Hannah, D. M.; Brown, L. E.; Milner, A. M.

2012-04-01

241

Divertor Heat Flux Amelioration in Highly-Shaped Plasma in NSTX  

SciTech Connect

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.

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

242

Dual-Active-Surface Miniature Plug-Type Heat-Flux Gauges  

NASA Technical Reports Server (NTRS)

Improved miniature plug-type heat-flux gauges developed for determining fluxes of heat through surfaces on both sides of heat-transfer walls. Walls are those of heat exchangers, engine housings, furnaces, chemical reactors, or any of variety of other structures in which fluxes of heat important quantities one seeks to measure.

Liebert, Curt H.; Koch, John, Jr.

1996-01-01

243

Contagious Coronal Heating from Recurring Emergence of Magnetic Flux  

NASA Technical Reports Server (NTRS)

For each of six old bipolar active regions, we present and interpret Yohkoh/SXT and SOHO/MDI observations of the development, over several days, of enhanced coronal heating in and around the old bipole in response to new magnetic flux emerge= within the old bipole. The observations show: 1. In each active region, new flux emerges in the equatorward side of the old bipole, around a lone remaining leading sunspot and/or on the equatorward end of the neutral line of the old bipole. 2. The emerging field is marked by intense internal coronal heating, and enhanced coronal heating occurs in extended loops stemming from the emergence site. 3. In five of the six cases, a "rooster tail" of coronal loops in the poleward extent of the old bipole also brightens in response to the flux emergence. 4. There are episodes of enhanced coronal heating in surrounding magnetic fields that are contiguous with the old bipole but are not directly connected to the emerging field. From these observations, we suggest that the accommodation of localized newly emerged flux within an old active region entails far reaching adjustments in the 3D magnetic field throughout the active region and in surrounding fields in which the active region is embedded, and that these adjustments produce the extensive enhanced coronal heating. We also note that the reason for the recurrence of flux emergence in old active regions may be that active region flux tends to emerge in giant-cell convection downflows. If so, the poleward "rooster tail" is a coronal flag of a long-lasting downflow in the convection zone. This work was funded by NASA's Office of Space Science through the Solar Physics Supporting Research and Technology Program and the Sun-Earth Connection Guest Investigator Program.

Moore, Ronald L.; Falconer, David; Sterling, Alphonse; Whitaker, Ann F. (Technical Monitor)

2001-01-01

244

Turbulent Heat Fluxes in Urban Areas: Observations and a Local-Scale Urban Meteorological Parameterization Scheme (LUMPS)  

Microsoft Academic Search

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

C. S. B. Grimmond; T. R. Oke

2002-01-01

245

High-sensitivity, surface-attached heat flux sensors  

Microsoft Academic Search

A new type of flat, surface-attached heat flux sensor has been developed for a variety of heat transfer measurements. This differential thermopile transducer uses new polymer-based materials and a novel patterning technology. The patterning is done using photoimageable dielectrics, allowing definition of 125?m features over a large area. Thin anodized aluminium is used as a substrate material to achieve low

L. W. Langley; A. Barnes; G. Matijasevic; P. Gandhi

1999-01-01

246

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

SciTech Connect

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.

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

2011-01-01

247

Heat flux measurements for use in physiological and clothing research.  

PubMed

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. PMID:23824222

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

2014-08-01

248

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

SciTech Connect

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.

Unal, C.; Pasamehmetoglu, K.O.

1993-10-01

249

High Heat Flux Experiment for Verification of Thermostructural Analysis.  

National Technical Information Service (NTIS)

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 maxi...

H. J. Gladden M. E. Melis

1988-01-01

250

Heat flux sensor research and development: The cool film calorimeter  

Microsoft Academic Search

The goal was to meet the measurement requirement of the NASP program for a gauge capable of measuring heat flux into a 'typical' structure in a 'typical' hypersonic flight environment. A device is conceptually described that has fast response times and is small enough to fit in leading edge or cowl lip structures. The device relies heavily on thin film

A. Abtahi; P. Dean

1990-01-01

251

Flow-Excursion-Induced Dryout at Low-Heat-Flux.  

National Technical Information Service (NTIS)

Flow-excursion-induced dryout at low-heat-flux natural-convection boiling, typical of liquid-metal fast-breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of Ledinegg instability leading...

M. Khatib-Rahbar E. G. Cazzoli

1983-01-01

252

Mechanisms of thermal nanofluids on enhanced critical heat flux (CHF)  

Microsoft Academic Search

Research on thermal nanofluids has progressed rapidly since their enhanced thermal conductivities were identified about a decade ago. Thermal nanofluids have been observed to increase the critical heat flux (CHF) remarkably under pool-boiling conditions, which could not be explained by conventional theories developed for pure fluids. This paper proposes an alternative mechanism, the long-range structural disjoining pressure arising from the

Dongsheng Wen

2008-01-01

253

Critical heat flux in thin, uniform particle coatings  

Microsoft Academic Search

Pool boiling on thin, uniform porous coatings is examined experimentally using different copper particle diameters (between 40 and 80?m), fabrications (loosely packed, shaken, or pressed), and particle characteristics (solid or porous particle) with coating thickness varying between 3 and 5 particle diameters. The results show that the critical heat flux (CHF) is about 1.8 times for all the coatings, while

G.-S. Hwang; M. Kaviany

2006-01-01

254

A critical heat flux correlation for droplet impact cooling  

Microsoft Academic Search

The characteristics of a single stream of monodispersed water droplets impacting a horizontal, upward facing flat surface have been investigated. The objective was to determine the effect of droplet diameter, impact frequency and impact velocity on the critical heat flux (CHF). A generalized correlation has been developed for the nondimensional CHF as a function of the Weber and Strouhal numbers

M. L. Sawyer; S. M. Jeter; S. I. Abdel-Khalik

1997-01-01

255

Heat flux instrumentation for HYFLITE thermal protection system  

Microsoft Academic Search

Tasks performed in this project were defined in a September 9, 1994 meeting of representatives of Vatell, NASA Lewis and Virginia Tech. The overall objective agreed upon in the meeting was 'to demonstrate the viability of thin film techniques for heat flux and temperature sensing in HYSTEP thermal protection systems'. We decided to attempt a combination of NASA's and Vatell's

T. E. Diller

1994-01-01

256

Mathematical modeling of sulfide flash smelting process: Part II. Quantitative analysis of radiative heat transfer  

Microsoft Academic Search

A mathematical model has been developed to describe the rate processes in an axisymmetric copper flash smelting furnace shaft. A particular feature of the model is the incorporation of the four-flux model to describe the radiative heat transfer by combining the absorbing, emitting, and anisotropic scattering phenomena. The importance of various subprocesses of the radiative heat transfer in a flash

Y. B. Hahn; H. Y. Sohn

1990-01-01

257

Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis  

NASA Astrophysics Data System (ADS)

Heat flux measurement is needed in many heat transfer studies. For the best unbiased heat flux sensors (HFS), the heat flux is obtained using temperature measurements at different locations and also an inverse heat conduction method (function specification...) in order to calculate the heat flux. Systematic errors can come from the uncertainty in the wire thermocouples locations and from errors in the knowledge of distances between two consecutive wire thermocouples. The main idea in this work is to use thin film thermoresistances deposited on a flexible thin polymer substrate instead of wire thermocouples welded on metallic sample. The interest of using thin film thermoresistances instead of wire thermocouples is a lower disturbance due to the smaller thickness of the thin film sensors (typically less than 1?m) and a much better knowledge of the distances between the different thin film thermoresistances which are precisely defined in the mask used for the metallic thin film pattern fabrication. In this paper, we present the fabrication of the new heat flux sensor with thin film thermoresistances, the study of the effect of the self heating (due to Joule effect in thermoresistances) and the performances of this new HFS with the comparison with classical HFS using wire thermocouples. For this study, a symmetric experimental setup is used with metallic samples equipped with an etched foil heater and both classical and new HFS. For several heating conditions, it appears that a better accuracy is always obtained with the new HFS using thin film thermoresistances.

Azerou, B.; Garnier, B.; Lahmar, J.

2012-11-01

258

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

259

Maximum allowable heat flux for a submerged horizontal tube bundle  

SciTech Connect

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.

McEligot, D.M.

1995-08-14

260

White dwarf heating and the ultraviolet flux in dwarf novae  

NASA Technical Reports Server (NTRS)

The heating of the outer layers of the white dwarf which is likely to occur during a dwarf nova outburst is investigated. It is shown that the decline in IUE flux, observed during quiescent intervals in the dwarf novae VW Hydri and WX Hydri, may be due to the outer layers cooling off once the heat source is removed. The calculations here assume uniformity of the heat source over the white dwarf surface. This is unlikely to be realized from disk accretion, and discussion is made of what further calculations are required.

Pringle, J. E.

1988-01-01

261

Measurement of a surface heat flux and temperature  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

262

Performance of thermal barrier coatings in high heat flux environments  

NASA Technical Reports Server (NTRS)

Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8%Y2O3 specimens survived 3000 of the 0.5 sec cycles with failing. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 2 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12%Y2O3 or ZrO2-20%Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.

Miller, R. A.; Berndt, C. C.

1984-01-01

263

Elucidation of the Heat-Flux Limit from Magnetic-Island Heating  

SciTech Connect

Recent experiments on heating of magnetic islands in a tokamak are analyzed to assess plasma transport characteristics. By comparing with the experimental data, both perpendicular and parallel components of the electron heat conductivity in the island are determined. As a consequence, the so-called heat-flux limit factor {xi}, the ratio of the parallel heat conduction flux in a collisionless plasma to that transferred by free-streaming electrons, can be estimated. The found factor {xi} does not contradict that established earlier by interpreting laser plasma experiments.

Tokar, M. Z.; Gupta, A. [Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster (Germany)

2007-11-30

264

Effect of pressure on critical heat flux in uniformly heated vertical annulus under low flow conditions  

Microsoft Academic Search

Critical heat flux (CHF) experiments have been carried out in a wide range of pressure for an internally heated vertical annulus. The experimental conditions covered a range of pressure from 0.57 to 15.01 MPa, mass fluxes of 0 kg m?2 s?1 and from 200 to 650 kg m?2 s?1, and inlet subcoolings from 85 to 413 kJ kg?1. Most of

Se-Young Chun; Heung-June Chung; Sang-Ki Moon; Sun-Kyu Yang; Moon-Ki Chung; Thomas Schoesse; Masanori Aritomi

2001-01-01

265

Effect of Particle Size Distribution on Wall Heat Flux in Pulverized-Coal Furnaces and Boilers  

NASA Astrophysics Data System (ADS)

A mathematical model of combustion and heat transfer within a cylindrical enclosure firing pulverized coal has been developed and tested against two sets of measured data (one is 1993 WSU/DECO Pilot test data, the other one is the International Flame Research Foundation 1964 Test (Beer, 1964)) and one independent code FURN3D from the Argonne National Laboratory (Ahluwalia and IM, 1992). The model called PILC assumes that the system is a sequence of many well-stirred reactors. A char burnout model combining diffusion to the particle surface, pore diffusion, and surface reaction is employed for predicting the char reaction, heat release, and evolution of char. The ash formation model included relates the ash particle size distribution to the particle size distribution of pulverized coal. The optical constants of char and ash particles are calculated from dispersion relations derived from reflectivity, transmissivity and extinction measurements. The Mie theory is applied to determine the extinction and scattering coefficients. The radiation heat transfer is modeled using the virtual zone method, which leads to a set of simultaneous nonlinear algebraic equations for the temperature field within the furnace and on its walls. This enables the heat fluxes to be evaluated. In comparisons with the experimental data and one independent code, the model is successful in predicting gas temperature, wall temperature, and wall radiative flux. When the coal with greater fineness is burnt, the particle size of pulverized coal has a consistent influence on combustion performance: the temperature peak was higher and nearer to burner, the radiation flux to combustor wall increased, and also the absorption and scattering coefficients of the combustion products increased. The effect of coal particle size distribution on absorption and scattering coefficients and wall heat flux is significant. But there is only a small effect on gas temperature and fuel fraction burned; it is speculated that this may be a characteristic special to the test combustor used.

Lu, Jun

266

Validation of general circulation model radiative fluxes using surface observations  

SciTech Connect

The surface radiative fluxes of the ECHAM3 General Circulation Model (GCM) with T21, T42, and T106 resolutions have been validated using observations from the Global Energy Balance Archive (GEBA, World Climate Program-Water Project A7). GEBA contains the most comprehensive dataset now available for worldwide instrumentally measured surface energy fluxes. The GCM incoming shortwave radiation at the surface has been compared with more than 700 long-term monitoring stations. The ECHAM3 models show a clear tendency to overestimate the global annual-mean incoming shortwave radiation at the surface due to an underestimation of atmospheric absorption. The model-calculated global-mean surface shortwave absorption around 165 W M{sup -2} is estimated to be too high by 10-15 W m{sup -2}. A similar or higher overestimate is present in several other GCMs. Deficiencies in the clear-sky absorption of the ECHAM3 radiation scheme are proposed as a contributor to the flux discrepancies. A stand-alone validation of the radiation scheme under clear-sky conditions revealed overestimates of up to 50 W m{sup -2} for daily maximum values of incoming shortwave fluxes. Further, the lack of shortwave absorption by the model clouds is suggested to contribute to the overestimated surface shortwave radiation. There are indications that the incoming longwave radiation at the surface is underestimated in ECHAM3 and other GCMs. This largely offsets the overestimated shortwave flux in the global mean, so that the 102 W m{sup -2} calculated in ECHAM3 for the surface net radiation is considered to be a realistic value. A common feature of several GCMs is, therefore, a superficially correct simulation of global mean net radiation, as the overestimate in the shortwave balance is compensated by an underestimate in the longwave balance. 41 refs., 14 figs., 5 tabs.

Wild, M.; Oshmura, A.; Gilgen, H. [Swiss Federal Institute of Technology, Zurich (Switzerland)] [and others] [Swiss Federal Institute of Technology, Zurich (Switzerland); and others

1995-05-01

267

Radiative heat transfer in isothermal spherical media  

Microsoft Academic Search

Radiative heat transfer in emitting, absorbing, and scattering spherical media is analyzed. The medium is assumed to be gray, isothermal, and linear-anisotropically scattering. The medium is confined in the space between two gray concentric spheres, which diffusely emit, and specularly and diffusely reflect radiation. Approximate solutions of the equation of radiative transfer are obtained using the spherical harmonics method. Results

W. Li; T. W. Tong

1990-01-01

268

Physical mechanisms of heat, momentum and turbulence fluxes  

NASA Technical Reports Server (NTRS)

In a qualitative way, the physical mechanisms which generate fluxes of heat, momentum, and turbulence in the atmosphere are discussed. This material is presented to acquaint people with the Earth science aspects of turbulence as important processes in the atmosphere. To attempt to describe turbulent fluxes of heat, momentum, and moisture in precise mathematical detail becomes an intractable problem. It is burdened by an eighth order set of equations involving more variables than equations. It is a closure problem which requires complicated assumptions that are not necessarily always satisfied, variable boundary conditions, and sparse observational data. Therefore, we must approach the problem in a simplified manner to obtain any kind of solution involving the variables of shear, stress, and heat, moisture, and momentum fluxes. There are other problems, of course, in which the inclusion of the planetary boundary layer is extremely important. Air pollution studies, air-sea exchanges, mesoscale models, and so on, must account for the planetary layer in very specific terms. Some of the physical mechanisms that are involved in generating fluxes are described.

Theon, John S.

1987-01-01

269

Heat flux measurement from thermal infrared imagery in low-flux fumarolic zones: Example of the Ty fault (La Soufrière de Guadeloupe)  

NASA Astrophysics Data System (ADS)

Monitoring the geothermal flux of a dormant volcano is necessary both for hazard assessment and for studying hydrothermal systems. Heat from a magma body located at depth is transported by steam to the surface, where it is expelled in fumaroles if the heat flow exceeds 500 W/m2. If the heat flow is lower than 500 W/m2, steam mainly condensates in the soil close to surface and produces a thermal anomaly detectable at the surface. In this study, we propose a method to quantify low heat fluxes from temperature anomalies measured at the surface by a thermal infrared camera. Once corrected from the atmospheric and surface effects, thermal infrared images are used to compute (1) the excess of radiative flux, (2) the excess of sensible flux and (3) the steam flux from the soil to the atmosphere. These calculations require measurements of atmospheric parameters (temperature, wind velocity and humidity) and estimations of surface parameters (roughness and emissivity). This method has been tested on a low-flux fumarolic zone of the Soufrière volcano (Guadeloupe Island — Lesser Antilles), and compared to a flux estimation realized from the thermal gradient measurements into the soil. The two methods show a good agreement and a similar precision (267 ± 46 W/m2 for the thermal infrared method, and 275 ± 50 W/m2 for the vertical temperature gradient method), if surface roughness is well calibrated.

Gaudin, Damien; Beauducel, François; Allemand, Pascal; Delacourt, Christophe; Finizola, Anthony

2013-11-01

270

Heat-flux induced changes to multicrystalline D2 surfaces  

NASA Astrophysics Data System (ADS)

The surface roughness of the solid deuterium-tritium fuel in a spherical ignition target is a critical parameter in determining the target performance. Using phase shifting interferometry, we have found that the surface roughness of thick (1-300 microns) multicrystalline D2 films grown on flat substrates is dominated by misaligned crystals and grain boundaries. We show that a heat flux normal to the gas-solid interface reduces this surface roughness and converts facets to smoothly curved surfaces. The reduction in roughness is a function of applied flux. A simple energy minimization model quantitatively explains this functional relation.

Bernat, Thomas P.; Collins, Gilbert; Mapoles, Evan; Duriez, Christian

1997-11-01

271

Heat flux and oxygen consumption of the pregnant uterus.  

PubMed

Heat flux (conductive and convective heat) and oxygen consumption of the pregnant uterus and its content were measured simultaneously in the same group of pregnant ewes during the acute postoperative period, during a chronic resting period, and during alpha- and beta-adrenergic-receptor stimulation with norepinephrine and ritodrine. Results indicated four conclusions. First, an excellent correlation existed between heat flux and oxygen consumption in the acute and chronic resting condition as well as during increasing uteroplacental vascular resistance and decreasing blood flow produced by norepinephrine infusion; the correlation was not as good during ritodrine infusion. Second, during rest, about 85% of heat generated by the pregnant uterus is eliminated through the uteroplacental circulation while the remaining heat diffuses through the myometrium. Third, during decreasing uteroplacental blood flow and elevated resistance, the pregnant uterus is able to maintain a normal thermostasis by widening the temperature difference in the blood entering and leaving the uterus and by increasing the myometrial heat exchange; oxygen consumption also is maintained at normal level through increase in oxygen extraction. Fourth, with the exception of uteroplacental circulation, the circulatory, metabolic, and thermal conditions of the pregnant ewe are not different after 5 hours from 5 to 7 days after the surgical procedure. PMID:3004223

Rudelstorfer, R; Tabsh, K; Khoury, A; Nuwayhid, B; Brinkman, C R; Assali, N S

1986-02-01

272

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

PubMed Central

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.

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

2008-01-01

273

A high heat flux experiment for verification of thermostructural analysis  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

274

A high heat flux experiment for verification of thermostructural analysis  

NASA Technical Reports Server (NTRS)

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.

Gladden, Herbert J.; Melis, Matthew E.

1988-01-01

275

A new one-dimensional radiative equilibrium model for investigating atmospheric radiation entropy flux  

PubMed Central

A new one-dimensional radiative equilibrium model is built to analytically evaluate the vertical profile of the Earth's atmospheric radiation entropy flux under the assumption that atmospheric longwave radiation emission behaves as a greybody and shortwave radiation as a diluted blackbody. Results show that both the atmospheric shortwave and net longwave radiation entropy fluxes increase with altitude, and the latter is about one order in magnitude greater than the former. The vertical profile of the atmospheric net radiation entropy flux follows approximately that of the atmospheric net longwave radiation entropy flux. Sensitivity study further reveals that a ‘darker’ atmosphere with a larger overall atmospheric longwave optical depth exhibits a smaller net radiation entropy flux at all altitudes, suggesting an intrinsic connection between the atmospheric net radiation entropy flux and the overall atmospheric longwave optical depth. These results indicate that the overall strength of the atmospheric irreversible processes at all altitudes as determined by the corresponding atmospheric net entropy flux is closely related to the amount of greenhouse gases in the atmosphere.

Wu, Wei; Liu, Yangang

2010-01-01

276

Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

277

Design of a differential radiometer for atmospheric radiative flux measurements  

SciTech Connect

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.

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

1994-11-01

278

An Overview of the GEWEX Radiative Flux Assessment  

NASA Astrophysics Data System (ADS)

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 and surface radiative flux data products to each other and investigating the sources of differences. Surface measurements are also assessed and compared to the satellite based data sets. Data sets from global long-term reanalysis and global climate models are also compared against the satellite records. The assessment includes both upwelling and downwelling SW and LW fluxes, for all-sky and clear-sky conditions over all portions of the globe and at a variety of spatial and temporal scales. Its goal is to characterize variations in the fluxes over time and to establish error estimates for each product over the various temporal and spatial scales, thus facilitating use of these products in future climate studies. This presentation will discuss the current status of the Flux Assessment, including a summary of results to date, weaknesses in the current satellite and surface observation systems, and recommendations for future improvements to these systems.

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

2009-04-01

279

Diamond Microchannel Heat Sink Designs For High Heat Flux Thermal Control  

NASA Astrophysics Data System (ADS)

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.

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

2002-08-01

280

Ultrasonic temperature profiling system for detecting critical heat flux in non-uniformly heated tube bundles  

Microsoft Academic Search

A new ultrasonic instrument system was developed and applied to the problem of detecting critical heat flux (CHF) in experiments that simulate a nuclear reactor fuel assembly. This instrumentation system used the principles of ultrasonic thermometry to detect and localte CHF in a tube bundle with non-uniform axial heat generation. The technique consists of measuring the time between pairs of

A. R. Barber; K. E. Kneidel; C. S. Fitzgerald; L. C. Lynnworth

1979-01-01

281

Critical heat flux experiments and correlation in a long, sodium-heated tube  

Microsoft Academic Search

Critical heat flux (CHF) experiments were performed in the Steam Generator Test Facility (SGTF) at Argonne National Laboratory for application to liquid metal fast breeder reactor steam generators. The test section consisted of a single, straight, vertical, fullscale LMFBR steam generator tube with force-circulated water boiling upwards inside the tube heated by sodium flowing countercurrent in a surrounding annulus. The

D. M. France; R. D. Carlson; T. Chiang; W. J. Minkowycz

1981-01-01

282

Critical heat flux of water subcooled flow in one-side heated swirl tubes  

Microsoft Academic Search

This paper reports an investigation of the critical heat flux (CHF) in the subcooled flow boiling regime. Hardened copper tube is heated on one side of its external rectangular section like for fusion reactor plasma facing components. It is cooled by a subcooled water flowing in a circular channel equipped with an inserted twisted tape. During experiments, CHF is detected

J. Boscary; J. Fabre; J. Schlosser

1999-01-01

283

A theoretical model for the prediction of the critical heat flux in heated microchannels  

Microsoft Academic Search

A theoretical model for the prediction of the critical heat flux of refrigerants flowing in heated, round microchannels has been developed and presented here. The model is based on the two-phase conservation equations and includes the effect of the height of the interfacial waves of the annular film. Validation has been carried out by comparing the model, a numerical solution

Rémi Revellin; John R. Thome

2008-01-01

284

Critical heat flux in a long, curved channel subjected to concave heating  

Microsoft Academic Search

A theoretical model to predict critical heat flux in long, rectangular, curved channels is presented. Development is analogous to a model for long, straight channels previously proposed by the present authors. The model is based on the observation from a flow visualization study that vapor assumes a wavy, periodic distribution along the heated concave wall just prior to CHF such

J. Christopher Sturgis; Issam Mudawar

1999-01-01

285

Method of fission heat flux determination from experimental data  

DOEpatents

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.

Paxton, Frank A. (Schenectady, NY)

1999-01-01

286

Development of advanced high-temperature heat flux sensors  

NASA Technical Reports Server (NTRS)

Various configurations of high temperature, heat flux sensors were studied to determine their suitability for use in experimental combustor liners of advanced aircraft gas turbine engines. It was determined that embedded thermocouple sensors, laminated sensors, and Gardon gauge sensors, were the most viable candidates. Sensors of all three types were fabricated, calibrated, and endurance tested. All three types of sensors met the fabricability survivability, and accuracy requirements established for their application.

Atkinson, W. H.; Strange, R. R.

1982-01-01

287

High heat flux exposures of coated GRCop-84 substrates  

Microsoft Academic Search

The performance of several overlay coatings on Cu–8at.%Cr4%Nb alloy (GRCop-84) thermally cycled in a high heat flux hydrogen–oxygen combustion flame are reported. Finite element analyses (FEA) were conducted to evaluate the expected performances of coatings with different thermal conductivities as well as to determine a suitable thickness for coating deposition. Top coats consisting of Cu–26%Cr, NiAl and NiCrAlY along with

S. V. Raj; L. J. Ghosn; C. Robinson; D. Humphrey

2007-01-01

288

Surface sensible heat flux upscaling: examples from Alpilles in France  

NASA Astrophysics Data System (ADS)

Surface sensible heat flux upscaling is performed with an aggregation model with input of airborne optical and thermal remote sensing observations, high-resolution satellite observations, radiosounding observations and Arpège met-model data. Firstly the aggregation model results are compared to sensible heat flux field observations in various crops during the growing season in 1997 at the Alpilles site in Southern France; secondly the results are given at a kilometric scale. The upscaling is from 20 m to 1000 m resolution. The values upscaled are the surface sensible heat flux and the roughnesses for momentum and temperature, , and , respectively. All values are so-called effective values taking explicit account of non-linearity in the turbulent response function for every roughness step change between patches in the landscape as a function of wind direction and atmospheric stability. The local roughness for momentum (z0m) is assigned to each land cover type, whereas the local roughness for temperature (zot) is calculated iteratively from the momentum roughness and leaf area index (LAI) depend upon land cover type. The ratio between the upscaled roughness values are no longer proportional. The ratio is compared and discussed (in view of the kB-1). Finally the kilometric momentum roughness and NDVI values are intercompared. The aggregation model is a two-dimensional atmospheric flow model in the horizontal domain and the flow equations are linearized and solved with Fast Fourier Transform. The model is computationally fast, yet provide a sound link between surface fluxes of momentum and sensible heat from point observations to larger scales.

Hasager, C. B.; Olioso, A.; Jensen, N. O.

289

Heat flux instrumentation for HYFLITE thermal protection system  

NASA Technical Reports Server (NTRS)

Tasks performed in this project were defined in a September 9, 1994 meeting of representatives of Vatell, NASA Lewis and Virginia Tech. The overall objective agreed upon in the meeting was 'to demonstrate the viability of thin film techniques for heat flux and temperature sensing in HYSTEP thermal protection systems'. We decided to attempt a combination of NASA's and Vatell's best heat flux sensor technology in a sensor which would be tested in the Vortek facility at Lewis early in 1995. The NASA concept for thermocouple measurement of surface temperature was adopted, and Vatell methods for fabrication of sensors on small diameter substrates of aluminum nitride were used to produce a sensor. This sensor was then encapsulated in a NARloy-Z housing. Various improvements to the Vatell substrate design were explored without success. The basic NASA and Vatell sensor layouts were analyzed by finite element modeling, in an attempt to better understand the effects of material properties, dimensions and thermal differential element location on sensor symmetry, bandwidth and sensitivity. This analysis showed that, as long as the thermal resistivity of the thermal differential element material is much larger (10X) than that of the substrate material, the simplest arrangement of layer is best. During calibration of the sensor produced in this project, undesirable side-effects of combining the heat flux and temperature sensor return leads were observed. The sensor did not cleanly separate the heat flux and temperature signals, as sensors with four leads have consistently done before. Task 7 and 8 discussed in the meeting will be performed with a continuation of funding in 1995. The following is a discussion of each of the tasks performed as outlined in the statement of work dated september 26, 1994. Task 1A was added to cover further investigation into the NASA sensor concept.

Diller, T. E.

1994-01-01

290

Heat flux instrumentation for HYFLITE thermal protection system  

NASA Astrophysics Data System (ADS)

Tasks performed in this project were defined in a September 9, 1994 meeting of representatives of Vatell, NASA Lewis and Virginia Tech. The overall objective agreed upon in the meeting was 'to demonstrate the viability of thin film techniques for heat flux and temperature sensing in HYSTEP thermal protection systems'. We decided to attempt a combination of NASA's and Vatell's best heat flux sensor technology in a sensor which would be tested in the Vortek facility at Lewis early in 1995. The NASA concept for thermocouple measurement of surface temperature was adopted, and Vatell methods for fabrication of sensors on small diameter substrates of aluminum nitride were used to produce a sensor. This sensor was then encapsulated in a NARloy-Z housing. Various improvements to the Vatell substrate design were explored without success. The basic NASA and Vatell sensor layouts were analyzed by finite element modeling, in an attempt to better understand the effects of material properties, dimensions and thermal differential element location on sensor symmetry, bandwidth and sensitivity. This analysis showed that, as long as the thermal resistivity of the thermal differential element material is much larger (10X) than that of the substrate material, the simplest arrangement of layer is best. During calibration of the sensor produced in this project, undesirable side-effects of combining the heat flux and temperature sensor return leads were observed. The sensor did not cleanly separate the heat flux and temperature signals, as sensors with four leads have consistently done before. Task 7 and 8 discussed in the meeting will be performed with a continuation of funding in 1995. The following is a discussion of each of the tasks performed as outlined in the statement of work dated september 26, 1994. Task 1A was added to cover further investigation into the NASA sensor concept.

Diller, T. E.

1994-12-01

291

Spatial variability of shortwave radiative fluxes in the context of snowmelt  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

292

Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks  

Microsoft Academic Search

Critical heat flux (CHF) was measured for a water-cooled micro-channel heat sink containing 21 parallel 215×821 ?m channels. Tests were performed with deionized water over a mass velocity range of 86–368 kg\\/m2s, inlet temperatures of 30 and 60 °C, at an outlet pressure of 1.13 bar. As CHF was approached, flow instabilities induced vapor backflow into the heat sink’s upstream

Weilin Qu; Issam Mudawar

2004-01-01

293

Investigation of saturated critical heat flux in a single, uniformly heated microchannel  

Microsoft Academic Search

A series of tests have been performed to determine the saturated critical heat flux (CHF) in 0.5 and 0.8mm internal diameter microchannel tubes as a function of refrigerant mass velocity, heated length, saturation temperature and inlet liquid subcooling. The tested refrigerants were R-134a and R-245fa and the heated length of microchannel was varied between 20 and 70mm. The results show

Leszek Wojtan; Rémi Revellin; John R. Thome

2006-01-01

294

Study of dryout heat fluxes in beds of inductively heated particles. [LMFBR  

Microsoft Academic Search

Experimental observations of the dryout heat fluxes for inductively heated particulate beds have been made. The data were obtained when steel and lead particles in the size distribution 295-787 microns were placed in a 4.7 cm diameter pyrex glass jar and inductively heated by passing radio frequency current through a 13.3 cm diameter multi-turn work coil encircling the jar. Distilled

V. K. Dhir; I. Catton

1977-01-01

295

Study of dryout heat fluxes in beds of inductively heated particles. Technical report. [LMFBR  

Microsoft Academic Search

Experimental observations of the dryout heat fluxes for inductively heated particulate beds have been made. The data were obtained when steel and lead particles in the size distribution 295-787 micrometers were placed in a 4.7 cm diameter pyrex glass jar and inductively heated by passing radio frequency current through a 13.3 cm diameter multi-turn work coil encircling the jar. Distilled

V. K. Dhir; I. Catton

1977-01-01

296

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

NASA Technical Reports Server (NTRS)

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.

Siegel, Robert

1996-01-01

297

Local Heat Flux Measurements with Single Element Coaxial Injectors  

NASA Technical Reports Server (NTRS)

To support the mission for the NASA Vision for Space Exploration, the NASA Marshall Space Flight Center conducted a program in 2005 to improve the capability to predict local thermal compatibility and heat transfer in liquid propellant rocket engine combustion devices. The ultimate objective was to predict and hence reduce the local peak heat flux due to injector design, resulting in a significant improvement in overall engine reliability and durability. Such analyses are applicable to combustion devices in booster, upper stage, and in-space engines, as well as for small thrusters with few elements in the injector. In this program, single element and three-element injectors were hot-fire tested with liquid oxygen and ambient temperature gaseous hydrogen propellants at The Pennsylvania State University Cryogenic Combustor Laboratory from May to August 2005. Local heat fluxes were measured in a 1-inch internal diameter heat sink combustion chamber using Medtherm coaxial thermocouples and Gardon heat flux gauges. Injectors were tested with shear coaxial and swirl coaxial elements, including recessed, flush and scarfed oxidizer post configurations, and concentric and non-concentric fuel annuli. This paper includes general descriptions of the experimental hardware, instrumentation, and results of the hot-fire testing for three of the single element injectors - recessed-post shear coaxial with concentric fuel, flush-post swirl coaxial with concentric fuel, and scarfed-post swirl coaxial with concentric fuel. Detailed geometry and test results will be published elsewhere to provide well-defined data sets for injector development and model validatation.

Jones, Gregg; Protz, Christopher; Bullard, Brad; Hulka, James

2006-01-01

298

Spray cooling heat-transfer with subcooled trichlorotrifluoroethane (Freon-113) for vertical constant heat flux surfaces  

SciTech Connect

Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.

Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering

1996-06-06

299

First-wall heat-flux measurements during ELMing H-mode plasma  

SciTech Connect

In this report we present measurements of the diverter heat flux in DIII-D for ELMing H-mode and radiative diverter conditions. In previous work we have examined heat flux profiles in lower single-null diverted plasmas and measured the scaling of the peak heat flux with plasma current and beam power. One problem with those results was our lack of good power accounting. This situation has been improved to better than 80--90% accountability with the installation of new bolometer arrays, and the operation of the entire complement of 5 Infrared (IR) TV cameras using the DAPS (Digitizing Automated Processing System) video processing system for rapid inter-shot data analysis. We also have expanded the scope of our measurements to include a wider variety of plasma shapes (e.g., double-null diverters (DND), long and short single-null diverters (SND), and inside-limited plasmas), as well as more diverse discharge conditions. Double-null discharges are of particular interest because that shape has proven to yield the highest confinement (VH-mode) and beta of all DIII-D plasmas, so any future diverter modifications for DIII-D will have to support DND operation. In addition, the proposed TPX tokamak is being designed for double-null operation, and information on the magnitude and distribution of diverter heat flux is needed to support the engineering effort on that project. So far, we have measured the DND power sharing at the target plates and made preliminary tests of heat flux reduction by gas injection.

Lasnier, C.J.; Allen, S.L.; Hill, D.N. [Lawrence Livermore National Lab., CA (United States); Leonard, A.W.; Petrie, T.W. [General Atomics, San Diego, CA (United States)

1994-01-28

300

Arctic freshwater (and heat) fluxes: variability, and assessment  

NASA Astrophysics Data System (ADS)

Paucity of measurements means that quantifying and evaluating the Arctic hydrological cycle is problematic. For example: atmospheric reanalyses are not well constrained by observations; for river runoff measurements, there are un-gauged flows to consider; and until the relatively recent advent of autonomous measurement systems, ocean measurements outside the summer melt season were rare. It has proved possible, however, to design a metric based on sea ice and ocean measurements which captures net surface fluxes (atmosphere-ocean and land-ocean, including sea ice) of freshwater (and heat). A closed circuit is formed around the Arctic Ocean boundary by moored measurement systems (and land), supplemented by remote-sensed and other measurements. Occasionally 'patching' with coupled ice-ocean general circulation model (GCM) output is required; if so, the output water properties are validated and calibrated against climatology. This approach enables application of inverse modelling methods through the use of conservation constraints, and consequent generation of monthly-mean ocean (including sea ice) fluxes of freshwater and heat, and a draft version of a single annual cycle will be presented (2005-6). Availability of an objective metric permits subsequent intercomparison, and ultimately assessment, of the performance of GCMs and climate models in terms of Arctic ice and ocean surface fluxes. Illustrations will be given of the dependence of GCM fluxes and their dependence on model resolution and on surface forcing fields, and these in turn will be compared with an example of the same quantities calculated from a coupled climate model. This analysis will enable a view to be taken on the utility of long-term surface flux variability as derived from reanalysis fields.

Bacon, S.

2013-12-01

301

Arctic freshwater and heat fluxes: variability, and assessment  

NASA Astrophysics Data System (ADS)

Paucity of measurements means that quantifying and evaluating the Arctic thermal and hydrological cycles is problematic. For example: atmospheric reanalyses are not well constrained by observations; for river runoff measurements, there are un-gauged flows to consider; and until the relatively recent advent of autonomous measurement systems, ocean measurements outside the summer melt season were rare. It has proved possible, however, to design a metric based on sea ice and ocean measurements which captures net surface fluxes (atmosphere-ocean and land-ocean, including sea ice) of freshwater and heat. A closed circuit is formed around the Arctic Ocean boundary by moored measurement systems and land, supplemented by remote-sensed and other measurements. Occasionally "patching" with coupled ice-ocean general circulation model (GCM) output is required; if so, the output water properties are validated and calibrated against climatology. This approach enables application of inverse modelling methods through the use of conservation constraints, and consequent generation of monthly-mean ocean (including sea ice) fluxes of freshwater and heat, and a draft version of a single annual cycle will be presented (2005-6). Availability of an objective metric permits subsequent intercomparison, and ultimately assessment, of the performance of GCMs and climate models in terms of Arctic ice and ocean surface fluxes. Illustrations will be given of the dependence of both surface (air-sea-ice) and ocean boundary fluxes from GCMs and their dependence both on model resolution and on surface forcing fields, and these in turn will be compared with an example of the same quantities calculated from a coupled climate model. These are steps towards (i) designing a viable Arctic Ocean boundary observation system, and (ii) quantification of Arctic fluxes.

Bacon, Sheldon; Aksenov, Yevgeny

2014-05-01

302

Water vapour and sensible heat fluxes over forest: a multi-year study  

NASA Astrophysics Data System (ADS)

The interannual variability in water vapour and sensible heat fluxes over beech forest in Denmark is analysed. A time-series from seven years (half hourly values) are investigated in regard to extremes and the interannual variability at daily and monthly time-scales. The fluxes are measured by the eddy correlation technique from a tall mast in the center of the forest. The experimental site is part of the CARBO-EUROFLUX network and observations include precipitation, soil water, CO2, temperature, humidity, solar radiation and plant parameters. In the current study focus is on the water balance. A comparison between the water balance components, CO2 and environmental parameters is undertaken. The results are part of EO-FLUX-BUDGET project (http://www.geogr.ku.dk/projects/eoflux/) aiming for spatial and temporal predictions of the water vapour, sensible heat and CO2 balance over the island Zealand (7.200 km2) in Denmark based on satellite Earth Observation data at high resolution. The validation part is based on the in-situ heat and water vapour flux observations presented here.

Hasager, C. B.; Pilegaard, K.; Jensen, N. O.

2003-04-01

303

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

Microsoft Academic Search

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

Robert D. Watson

1993-01-01

304

Measurements of x-ray spectral flux and intensity distribution of APS/CHESS undulator radiation  

SciTech Connect

Absolute radiation flux and polarization measurements of the APS undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x-rays scattered from a well-defined He gas volume at controlled pressure.

Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z.

1994-09-01

305

Numerical study of a chemical method applied to instantaneous heat removal under high heat flux  

NASA Astrophysics Data System (ADS)

In this study, a method of chemical cooling is put forward, that is, C-CO2 endothermic reaction is applied to instantaneous heat removal under high heat flux. A method in which theoretical research is in combination with numerical simulation is used to study C-CO2 endothermic reaction. In comparison with the theoretically computational results, numerical code is validated. A high heat flux of 500 W/cm2 is applied to the research of the heat dissipation characteristics of C-CO2 endothermic reaction. The theoretical calculation results show that, under a certain temperature and pressure condition, the C-CO2 chemical endothermic reaction could remove heat from the system promptly; the product CO could be used as a supplementary medium of power source for cycling. Compared with water phase change, the C-CO2 endothermic reaction appears to have stronger heat removal ability. "Species Transport" module in FLUENT was adopted to simulate the reaction. Under the same temperature and pressure condition, the numerical simulation results are found to be well congruous with theoretical results. The C-CO2 endothermic reaction could make a high temperature in the reaction system due to a high heat flux reduce to a low temperature (below zero) promptly. The heat removal and reaction time are in consistence with theoretical calculation.

Li, Jing; He, Gao-Ming; Zeng, Cheng; Liu, Ye-Ming

2013-09-01

306

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

NASA Technical Reports Server (NTRS)

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.

Nelson, H. F.

1981-01-01

307

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

NASA Astrophysics Data System (ADS)

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.

Nelson, H. F.

1981-08-01

308

Calculation of heating values for the high flux isotope reactor  

SciTech Connect

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)

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

2012-07-01

309

Observations of net heat flux into the surface mixed layer of the Western Equatorial Pacific Ocean  

NASA Astrophysics Data System (ADS)

For a 10-day period during September 1990 the R/V Franklin worked around a drifting buoy drogued at 20-m depth in the Bismarck Sea near 4°S, 149°E. Continuous measurements were made of the air-sea fluxes of radiation and sensible and latent heat, and a conductivity/temperature/depth cast to 400 m was made about every 6 hours. The aim was to close the heat budget of a sample volume of the surface mixed layer to within 10 W m-2, in preparation for our participation in the 1992-1993 Tropical Ocean and Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). Temperature and salinity between the surface and 30-m depth were quite uniform, but below 30 m, variability was observed which suggested the possible intrusion of horizontal and vertical advection of heat. Heat content was analyzed for depths of 40 m and 20 m; bulk Richardson numbers generally greater than 0.8 and 0.4, respectively, in the two cases indicated that diapycnal mixing through the bottom of the 40-m volume could be neglected at 40 m and possibly at 20 m (Peters et al., 1988; Godfrey and Lindstrom, 1989). An eddy diffusivity for salt at 20 m was obtained to account for the steady decrease of observed freshwater content in the top 20 m over that expected from the surface flux. Using this diffusivity, the turbulent heat flux through 20 m was of order 6 W m-2, supporting the view that vertical mixing of heat was small even at this depth. Then, neglecting advection and vertical mixing, the heat budget closure to 40-m depth was satisfied to about 25 W m-2 on average over the period, but both integrated heat and freshwater time series were "noisy" because of variability below 30 m. Limited to 20-m depth, the average difference between incident energy and heat content was reduced to about 12 W m-2, with close agreement over the diurnal cycle. The model for air-sea exchange of sensible and latent heat by Liu et al. (1979) is verified at low wind speeds, although it may overestimate slightly for winds over the range 3-6 m s-1. This study has identified several possible sources of measurement, parameterization, and sampling error in determining the net heat flux into the ocean; however, with good sampling for the advective components, errors in heat budgets should be within the 10 W m-2 accuracy aimed for during COARE.

Bradley, E. F.; Godfrey, J. S.; Coppin, P. A.; Butt, J. A.

1993-12-01

310

Entropy Flux and Entropy Production of Stationary Black-Body Radiation  

NASA Astrophysics Data System (ADS)

More than a century after Max Planck's 1906 book Theorie der Wärmestrahlung, alternative expressions for the entropy flux as related to thermal black-body radiation under non-equilibrium conditions are still controversially discussed in the scientific literature. In this paper, we consider the radiative heat exchange between two planar black bodies of different temperatures. Solely by exploiting the Second Law, it is shown that the mathematical formula for the related non-equilibrium entropy flux can uniquely be inferred from the Stefan-Boltzmann law, without taking advantage of the statistical Planck distribution. Expressions for the entropy production at the emitting surfaces are derived and an effective temperature associated with the radiation between the two bodies is suggested.

Feistel, Rainer

2011-06-01

311

Radiative heat transfer in rotary kilns  

Microsoft Academic Search

Radiative heat transfer between a nongray freeboard gas and the interior surfaces of a rotary kiln has been studied by evaluating\\u000a the fundamental radiative exchange integrals using numerical methods. Direct gas-to-surface exchange, reflection of the gas\\u000a radiation by the kiln wall, and kiln wall-to-solids exchange have been considered. Graphical representations of the results\\u000a have been developed which facilitate the determination

J. P. Gorog; J. K. Brimacombe; T. N. Adams

1981-01-01

312

2D divertor heat flux distribution using a 3D heat conduction solver in National Spherical Torus Experiment.  

PubMed

The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated. PMID:23464209

Gan, K F; Ahn, J-W; Park, J-W; Maingi, R; McLean, A G; Gray, T K; Gong, X; Zhang, X D

2013-02-01

313

2D divertor heat flux distribution using a 3D heat conduction solver in National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated.

Gan, K. F.; Ahn, J.-W.; Park, J.-W.; Maingi, R.; McLean, A. G.; Gray, T. K.; Gong, X.; Zhang, X. D.

2013-02-01

314

Boiling Heat-Transfer Processes and Their Application in the Cooling of High Heat Flux Devices.  

National Technical Information Service (NTIS)

Water cooling is used extensively at AEDC to prevent the failure of high-enthalpy arc heater components at elevated heat loads where cooling by radiation, conduction, and natural convection from air circulation are ineffective. Other cooling techniques su...

G. R. Beitel

1993-01-01

315

Horizontal Radiative Fluxes in Clouds at Absorbing Wavelengths  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

316

Observations of SST, heat flux and North Atlantic Ocean-atmosphere interaction  

NASA Astrophysics Data System (ADS)

The relationship between the observed North Atlantic atmosphere and the forcing of SST and heat flux is investigated using the lagged MCA analysis. The dominant heat flux forcing to the North Atlantic Oscillation is associated with the later summer horseshoe SST forcing. The horseshoe SST is generated largely by the surface heat flux, and then forces the early winter atmosphere through the release of oceanic heat flux into the atmosphere. Independent of the horseshoe SST, there is no significant heat flux forcing on the atmosphere with a lead of longer than 1 month.

Wen, Na; Liu, Zhengyu; Liu, Qinyu; Frankignoul, Claude

2005-12-01

317

High heat flux flow boiling in silicon multi-microchannels – Part III: Saturated critical heat flux of R236fa and two-phase pressure drops  

Microsoft Academic Search

New experimental critical heat flux results for saturated boiling conditions have been obtained for R236fa flowing in a silicon multi-microchannel heat sink composed of 67 parallel channels, 223?m wide, 680?m high and with 80?m thick fins separating the channels. The microchannel length was 20mm. The footprint critical heat fluxes measured varied from 112 to 250W\\/cm2 and the wall critical heat

Bruno Agostini; Rémi Revellin; John Richard Thome; Matteo Fabbri; Bruno Michel; Daniele Calmi; Urs Kloter

2008-01-01

318

Radiative MHD simulation of an Emerging Flux Region  

NASA Astrophysics Data System (ADS)

We present a radiation magnetohydrodynamics (MHD) simulation of the birth of an active region. The simulation models the rise of a magnetic flux bundle from the convection zone into the solar photosphere. Observational properties of the simulation are consistent with recent, high-cadence and high spatial resolution observations of emerging flux regions taken by Hinode/SOT. Observational properties common to both simulation and observation include the hierarchical formation of progressively larger photospheric magnetic structures, the formation and disappearance of light bridges, umbral dots as well as penumbral filaments.

Cheung, C.; Rempel, M.; Title, A. M.; Schuessler, M.

2009-12-01

319

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

NASA Astrophysics Data System (ADS)

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 by McNaughton and Jarvis (1983), examination of our data suggest that the water vapor exchange of a deciduous forest is not as strongly coupled with net radiation as is that of agricultural crops. The degree of decoupling is smaller than in the case of a coniferous forest. This difference may be attributable in part to the greater aerodynamic resistance to water vapor transfer in a deciduous forest. It appears that the concept of decoupling may be extended to the CO2 exchange of a deciduous forest as well.

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

1986-07-01

320

Strong electron heat flux modes in Jupiter's foreshock  

NASA Technical Reports Server (NTRS)

Analysis of Voyager plasma wave data from the Jovian foreshock has revealed the existence of a new oscillation with center frequency below fp and typically lying above the upper limit Doppler shift frequency for ion acoustic waves. The properties of these waves are consistent with modes generated by a strong electron heat flux in an unmagnetized plasma. Such modes become unstable when the effective drift velocity exceeds n(cold)/(hot) exp 1/2 times the thermal speed of the hot component. The occasional simultaneous appearance of more than one frequency band is a possible indication of multiple magnetic connection with the shock.

Moses, S. L.; Coroniti, F. V.; Kennel, C. F.; Scarf, F. L.

1984-01-01

321

Method of producing a plug-type heat flux gauge  

NASA Technical Reports Server (NTRS)

A method of making a plug-type heat flux gauge in a material specimen in which a thermoplug is integrally formed in the specimen is disclosed. The thermoplug and concentric annulus are formed in the material specimen by electrical discharge machining and trepanning procedures. The thermoplug is surrounded by a concentric annulus through which thermocouple wires are routed. The end of each thermocouple wire is welded to the thermoplug, with each thermocouple wire welded at a different location along the length of the thermoplug.

Liebert, Curt H. (inventor); Koch, John, Jr. (inventor)

1992-01-01

322

Modeling of a heat sink and high heat flux vapor chamber  

NASA Astrophysics Data System (ADS)

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.

Vadnjal, Aleksander

323

Simplified Analysis of Radiation Heat Exchange in Boiler Superheaters  

Microsoft Academic Search

This article describes the determination of the radiation heat transfer coefficient in radiant platen superheaters and on convective heating surfaces. A new simple formula for determination of the heat transfer coefficient is derived on the basis of a diffusivity model of radiation heat exchange. The radiation heat transfer coefficients are determined on the tube surface in a convective evaporator, in

Dawid Taler; Jan Taler

2009-01-01

324

Novel Magnetic Geometries to Cure the Divertor Heat Flux Problem for Reactors  

NASA Astrophysics Data System (ADS)

A novel magnetic divertor geometry with a second axi-symmetric x-point and flux expansion region along the separatrix is analysed. It can provide a stable, completely detached plasma state compatible with reactor operation; avoiding serious physics and engineering problems: 1) extreme divertor heat fluxes, 2) poor global confinement and high disruptivity due to low edge temperatures, 3) lack of access to lower edge densities with acceptable power exhaust, 4) high radiation fractions in the main chamber, and 5) first wall heat fluxes in the high neutron fluence region. In traditional divertors, detachment results in the propagation of the ionization-recombination front towards the main plasma energy source, cooling the bulk plasma boundary. Simple robust physical arguments imply that the extra x-point will act as a local attractor for the front. Thus, a high bulk edge temperature would be maintained at the bulk boundary, and the completely detached/highly radiating region can be programmed to occur at whatever location is convenient. Complete detachment would also be enabled for a much lower bulk boundary density and/or higher SOL exhaust power. See adjacent related posters.

Valanju, P.; Kotschenreuther, M.; Wiley, J. C.; Pekker, M.

2004-11-01

325

a Conceptual Model of Integrating Sensor Network and Radiative Heat Transfer Equation for Ethylene Furnace  

Microsoft Academic Search

A conceptual model of integrating the sensor network and the radiative heat transfer equation is developed and presented in this paper. The idea is to present possible deployment of sensor networks in the Ethylene furnace so that valuable input in the form of boundary value can be generated in order to produce intensity distribution and heat flux distribution. Once the

Z. Abal Abas; S. Salleh; A. S. Hassan Basari; Nuzulha Khilwani Ibrahim

2010-01-01

326

A CONCEPTUAL MODEL OF INTEGRATING SENSOR NETWORK AND RADIATIVE HEAT TRANSFER EQUATION FOR ETHYLENE FURNACE  

Microsoft Academic Search

A conceptual model of integrating the sensor network and the radiative heat transfer equation is developed and presented in this paper. The idea is to present possible deployment of sensor networks in the Ethylene furnace so that valuable input in the form of boundary value can be generated in order to produce intensity distribution and heat flux distribution. Once the

Z. Abal Abas; S. Salleh; A. S. Hassan Basari; Nuzulha Khilwani Ibrahim

2010-01-01

327

Dependence of Convective Heat Flux Calculations on Roughness Lengths  

NASA Technical Reports Server (NTRS)

The zero plane displacement height (d) and aerodynamic roughness length (z0) can be determined separately for momentum, heat, and humidity by using a procedure based on the Levenberg-Marquardt method for solving non-linear equations. This procedure is used to analyze profile data previously collected by Lo (1977) in a forested area in Canada and by Morgan et al (1971) on a field at the University of California at Davis (UCD) in the United States. The UCD data base is used to show the effects of allowing for different roughness lengths (zom,z0h,z0q) in calculating sensible and latent heat flux densities from bulk transfer coefficients.

Schieldge, John P.

1995-01-01

328

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

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

329

Heat flux through a geothermally heated fluidized bed at the bottom of a lake.  

PubMed

Heat fluxes and the underground inflow through a natural fluidized bed within the main sub-basin of Lake Banyoles are studied and parameterized. In the upper part of this fluidized bed, at a depth of about 30 m, the vertical gradients of particle concentration and temperature are very sharply located within an interface a few centimeters thick. Within this interface (lutocline), the depths where the temperature and the concentration gradients are maximum match exactly. On the other hand, the lutocline determines a flat, horizontal surface dividing the water column into a hot, turbid medium at the bottom and clear, colder, bulk water above. Through this interface the flow regime also varies from being laminar just below it, to turbulent due to convective processes developing above it. More precisely, in studied main sub-basin a buoyant plume develops above the lutocline, as a result of the heat flux, and affects the lake's water quality due to particles dragged along by it. In this paper it is proposed to determine the temperature at the depth of maximum gradient within the interface by means of measured temperature profiles, and consider the stationary heat transport equation in the laminar region below it, in order to obtain the water velocity and the heat flux. Heat flux parameterization is given based on a large number of thermal high-resolution profiles, covering six campaigns in different years and seasons. Furthermore, and in consideration of the fact that high-resolution thermal profiles are not always available, some alternative parameterizations for the heat flux are presented based only on the temperature of the fluidized bed and that of the lower hypolimnion. PMID:19457537

Sanchez, Xavier; Roget, Elena; Planella, Jesus

2009-07-01

330

Simplified model for determining local heat flux boundary conditions for slagging wall  

SciTech Connect

In this work, two models for calculating heat transfer through a cooled vertical wall covered with a running slag layer are investigated. The first one relies on a discretization of the velocity equation, and the second one relies on an analytical solution. The aim is to find a model that can be used for calculating local heat flux boundary conditions in computational fluid dynamics (CFD) analysis of such processes. Two different cases where molten deposits exist are investigated: the black liquor recovery boiler and the coal gasifier. The results show that a model relying on discretization of the velocity equation is more flexible in handling different temperature-viscosity relations. Nevertheless, a model relying on an analytical solution is the one fast enough for a potential use as a CFD submodel. Furthermore, the influence of simplifications to the heat balance in the model is investigated. It is found that simplification of the heat balance can be applied when the radiation heat flux is dominant in the balance. 9 refs., 7 figs., 10 tabs.

Bingzhi Li; Anders Brink; Mikko Hupa [Aabo Akademi University, Turku (Finland). Process Chemistry Centre

2009-07-15

331

Using Gravity Inversion to Estimate Antarctic Geothermal Heat Flux  

NASA Astrophysics Data System (ADS)

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.

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

332

Experimental study on the critical heat flux in varying acceleration field, (2). The measurement of critical heat flux under varying acceleration field, 2.  

National Technical Information Service (NTIS)

In designing a marine reactor, it is very important to understand the effect of varying acceleration induced by ship motion on critical heat flux. The purpose of this study is to clarify quantitatively the relationship between the critical heat flux and v...

T. Kusunoki N. Teshima O. Suzuki

1993-01-01

333

Critical heat flux in saturated forced convective boiling on a heated disk with multiple impinging jets  

Microsoft Academic Search

The existing data for critical heat flux (CHF) on a disk heater cooled by multiple impinging jets have been correlated successfully by deriving a generalized correlation that can predict the CHF on a disk heater cooled by a single impinging jet with high accuracy. The generalized correlation for the CHF for the single jet can be applied to predict the

M. Monde; T. Inoue

1991-01-01

334

Effect of nanoparticles on critical heat flux of water in pool boiling heat transfer  

Microsoft Academic Search

The present study is to enhance the critical heat flux (CHF) in pool boiling from a flat square heater immersed in nanofluid (water mixed with extremely small amount of nanosized particles). The test results show that the enhancement of CHF was drastic when nanofluid is used as a cooling liquid instead of pure water. The experiment was performed to measure

S. M. You; J. H. Kim; K. H. Kim

2003-01-01

335

Flux divergence of thermal radiation within stratiform clouds  

NASA Technical Reports Server (NTRS)

A longwave radiative transfer model based on the narrow-band transmission functions of Lowtran 6 has been developed to investigate the profile of radiative flux divergence at the tops of stratiform clouds. The model has a vertical resolution of 1 m and a spectral resolution of 20/cm. These features are shown to permit modeling of broadband radiative transfer in the presence of a cloud top inversion and finite liquid water gradient. Radiative cooling rates in excess of 40 K/hr are shown to be possible for extreme conditions, with values of 10 K/hr being representative of more typical conditions. The values obtained are shown to be strongly influenced by the magnitude of liquid water concentration, by the gradient of liquid water in the top 50 m, and by the strength of the temperature inversion.

Davies, Roger; Alves, Adil R.

1989-01-01

336

The Global Character of the Flux of Downward Longwave Radiation  

NASA Technical Reports Server (NTRS)

Four different types of estimates of the surface downwelling longwave radiative flux (DLR) are reviewed. One group of estimates synthesizes global cloud, aerosol, and other information in a radiation model that is used to calculate fluxes. Because these synthesis fluxes have been assessed against observations, the global-mean values of these fluxes are deemed to be the most credible of the four different categories reviewed. The global, annual mean DLR lies between approximately 344 and 350 W/sq m with an error of approximately +/-10 W/sq m that arises mostly from the uncertainty in atmospheric state that governs the estimation of the clear-sky emission. The authors conclude that the DLR derived from global climate models are biased low by approximately 10 W/sq m and even larger differences are found with respect to reanalysis climate data. The DLR inferred from a surface energy balance closure is also substantially smaller that the range found from synthesis products suggesting that current depictions of surface energy balance also require revision. The effect of clouds on the DLR, largely facilitated by the new cloud base information from the CloudSat radar, is estimated to lie in the range from 24 to 34 W/sq m for the global cloud radiative effect (all-sky minus clear-sky DLR). This effect is strongly modulated by the underlying water vapor that gives rise to a maximum sensitivity of the DLR to cloud occurring in the colder drier regions of the planet. The bottom of atmosphere (BOA) cloud effect directly contrast the effect of clouds on the top of atmosphere (TOA) fluxes that is maximum in regions of deepest and coldest clouds in the moist tropics.

Stephens, Graeme L.; Wild, Martin; Stackhouse, Paul W., Jr.; L'Ecuyer, Tristan; Kato, Seiji; Henderson, David S.

2012-01-01

337

Radiative heat transfer and water content in atmosphere of Venus  

SciTech Connect

The authors present the procedure for calculating optical characteristics of the main components and the effective fluxes in the atmosphere of Venus, and concrete results of the calculations. They are compared to the results of other authors and to the experimantal data. Integration was carried out by the Simpson method with automatic selection of the step or interval for a given relative integrating accuracy delta. The calculations were done with a BESM-6 computer. Using this procedure and data on absorbtion coefficients, calculations of the spectrum of effective flux were carried out for a pure carbon dioxide atmosphere and for an atmosphere containing water vapor at various relative admixtures, for different altitude profiles of temperature and cloudiness albedo. Thus, the comparisons made, enable the authors to judge about the degree of agreement of the F(z) altitude profile, in some regions of the planet where measurements have been made, rather than about the absolute values of the heat fluxes. In conclusion, the authors point out that the task of calculating in detail the radiation balance in Venus' lower atmosphere, as also the problem of a more reliable interpretation of the experimantal data, is coupled with the necessity of elaborating reliable models of the atmospheric components' optical characteristics, which determine the radiative transfer of heat.

Yarov, M.Y.; Gal'stev, A.P.; Shari, V.P.

1985-07-01

338

Diamond thin film temperature and heat-flux sensors  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

339

Parameterizing the Wind 3DP Heat Flux Electron Data  

NASA Astrophysics Data System (ADS)

Solar wind heat flux (HF) electrons are valuable as tracers of the interplanetary magnetic field (IMF) topology, distinguishing positive from negative solar polarities and indicating the presence of magnetically closed CMEs when the flows are counterstreaming. All past applications of heat fluxes to determine field topologies have been based on visual inspection of color spectrograms of electron pitch angle distributions (PADs). However, HF PADs can take a range of shapes and amplitudes, which challenges the visual analysis. We now take a quantitative approach to HF analysis by parameterizing the HF PADs of the UC Berkeley 3DP data with a Fourier harmonic analysis. We have calculated the harmonic cosine coefficients A0 through A4 for a five-year period of the Wind 3DP data set with a 10-min time resolution. With these data we intend to derive quantitative criteria for unidirectional and bi-directional flows and other possible diagnostics of interplanetary field dynamics or configurations. Some initial considerations and results of the 3DP parameterization are presented.

Kahler, S. W.; Crooker, N. U.; Larson, D. E.

2003-09-01

340

a Parameterization of Mesoscale Heat Fluxes for General Circulation Models  

NASA Astrophysics Data System (ADS)

This study addresses the parameterization of mesoscale heat fluxes generated by landscape discontinuities. The realistic representation of the planetary boundary layer (PBL) is one of the most important aspects of climate modelling (e.g., Shukla and Mintz, 1982; Avissar, 1992). Former research in the field of planetary boundary layer modelling is explored. It is suggested that current representations of boundary layer processes in large-scale models (e.g., General Circulation Models (GCMs)) are unrealistic when there are land discontinuities 10-200 km wide. These land discontinuities generate mesoscale circulations which can be as strong as sea-breezes. Given the relevance of climate change to human welfare and the environment, current efforts should be directed towards improvement in boundary layer modelling. A set of equations by Avissar and Chen (1993) is reviewed. They suggested a set of equations for GCMs which includes the impact of both turbulent and mesoscale processes on the mean variables. They derived prognostic equations for the mesoscale fluxes, which present a closure problem. Thus, they emphasized a need to develop a parameterization of these fluxes. A mesoscale atmospheric model was used to evaluate the impact of subgrid-scale landscape discontinuities on the vertical profiles of resolved temperature, moisture, and moist static energy in the planetary boundary layer of GCMs. Profiles of the mean variables were produced with a three-dimensional (3D) version of the model by averaging horizontally the various atmospheric variables over a domain about the size of a single grid element in a GCM. They were compared to corresponding vertical profiles produced with a one-dimensional (1D) version of the model, which simulates the PBL, as in a GCM, over a single horizontal grid element. The differences between the horizontally -averaged atmospheric variables produced with the 3D simulations and the 1D simulations emphasize the impact of subgrid -scale landscape discontinuities on GCM resolved variables. Landscape discontinuities, characterized by horizontal contrasts of surface wetness and size of land patches, were simulated under various background-wind conditions. Differences of air temperature, specific humidity, and moist static energy as large as 4 K, 6 g kg^{-1 }, and 10 kJ kg^{-1} were obtained, respectively, in some cases. These differences were not affected significantly by moderate winds, but were sensitive to the spatial distribution of surface wetness. Similarity theory was then used to develop a parameterization of mesoscale heat fluxes induced by landscape discontinuities in GCMs. For this purpose, Buckingham Pi Theory, a systematic method for performing dimensional analysis, was used to derive a set of dimensionless groups, which describes the large-scale atmospheric background conditions, the spatial variability of surface sensible heat flux, and the characteristic structure of the landscape. These dimensionless groups were used to calculate the coefficients of a fourth-order Chebyshev polynomial, which represents the vertical profiles of dimensionless mesoscale heat fluxes obtained for a broad range of large-scale atmospheric conditions and different landscapes. The numerous three-dimensional numerical experiments performed to evaluate the proposed parameterization suggests that it is quite robust.

Lynn, Barry Hugh

341

Heat storage and energy balance fluxes for a temperate deciduous forest  

Microsoft Academic Search

Hourly observations of forest-atmosphere energy balance components are presented for the Morgan-Monroe State Forest, south-central Indiana, USA for the period March 1998 to December 2001, with particular emphasis on the storage heat flux (?QS). The sub-components of ?QS showed strong diurnal variability, although ground heat flux dominated the seasonal change of storage heat flux. The annual storage heat balance for

A. J. Oliphant; C. S. B. Grimmond; H. N. Zutter; H. P. Schmid; H.-B. Su; S. L. Scott; B. Offerle; J. C. Randolph; J. Ehman

2004-01-01

342

Analysis of ocean surface heat fluxes in a NOGAPS climate simulation: Influences from convection, clouds and dynamical processes  

NASA Astrophysics Data System (ADS)

This study examines the simulation quality of the surface heat flux fields produced during a climate simulation of the Navy Operational Global Atmospheric Prediction System, version 3.4, with a reduced spectral truncation of T63 and 18 levels (herineafter referred to as NOGAPS-CL). Comparisons are made between a 17-year NOGAPS-CL simulation using monthly sea surface temperatures as surface boundary conditions and a number of validating data sets consisting of ship, satellite, and/or reanalysis-based surface heat fluxes, precipitation, top of the atmosphere radiation budget, water vapor, cloud frequency, surface wind stress, and tropospheric winds. In this extended, long-range integration, NOGAPS-CL underpredicts the net surface shortwave flux in much of the subtropical oceans and overpredicts the net shortwave flux in the western Pacific warm pool and the midlatitude oceans, when compared to several satellite-derived climatological data sets. In addition, NOGAPS-CL over predicts the latent heat flux in much of the subtropics and under predicts the latent heat flux over the northern ocean western boundary currents and under the storm track regions that extend eastward from them. These shortwave and evaporation biases combine to produce errors in the surface net heat flux, with too little heat entering the subtropical/tropical oceans and too much heat loss in the midlatitudes oceans. Examination of related quantities indicates that the tropical climate biases are coupled to shortcomings in the convective cloud and/or boundary layer parameterizations which leads to the premature release of moist instability from the boundary layer in regions just outside the deep convective zones. This leads to enhanced climatological cloudiness, rainfall, and surface evaporation, as well as to a reduction in the surface shortwave flux and outgoing longwave radiation (OLR), in the subtropical regions. Furthermore, because of this early release of the moist static energy, there is a reduction in clouds, rainfall and water vapor content, as well as enhanced surface shortwave flux and outgoing longwave radiation, in the deep convective zones. The reduction in rainfall and enhanced OLR reduces the strength of the tropical large-scale circulation, which in turn reduces the strength of the subsidence in the subtropical regions which normally acts to suppress the convection processes in these regions. The implications of these results are discussed in terms of the relationship among the forecast model climatological surface fluxes, convection, clouds, and the dynamical processes, as well as their similarities to other climate models and their possible impact on the simulation of transient systems.

Waliser, Duane E.; Hogan, Timothy F.

2000-02-01

343

The Sensitivity of Radiative Fluxes to Parameterized Cloud Microphysics.  

NASA Astrophysics Data System (ADS)

The sensitivity of modeled radiative fluxes to the specification of cloud microphysical parameterizations of effective radius and fallout are investigated using a single-column model and measurements from the Atmospheric Radiation Measurement (ARM) Program. The single-column model was run with data for the 3-month period of June-August 2000 at the ARM Southern Great Plains site forced with operational numerical weather prediction data. Several different packages of cloud microphysical parameterizations were used in the single-column model. The temporal evolution of modeled cloud amount as well as surface radiative fluxes from a control run compare well with ARM measurements.Mean ice particle fall speeds varied significantly with respect to the assumed ice particle habit. As particle fall speeds increased, the overall cloud fraction, cloud height, and grid-averaged ice water path decreased. The outgoing longwave radiation (OLR) differs by up to 4 W m2 over the range of fall speeds examined, while shortwave fluxes varied little as most of the changes in cloud properties occurred at times of minimal solar radiation.Model results indicate that surface and top-of-atmosphere radiative fluxes are sensitive to the scheme used to specify the ice particle effective radius. On the seasonal timescale this sensitivity is on the order of 4 W m2 and on the daily timescale can be as large as 32 W m2. A conclusive statement as to which microphysical scheme is performing best is not achievable until cloud microphysical measurements include an accurate representation of small ice particles. The modeled variance of the ice particle effective radius at any given height in the model is considerably smaller than that suggested by measurements. Model results indicate that this underestimation of the ice particle effective radius variance can alter the seasonal mean top-of-atmosphere radiative fluxes by up to 5 W m2 and the mean longwave cooling rate by up to 0.2° K day1 near the location of maximum cloud amount.These seemingly modest flux sensitivities may have important implications for numerical climate simulations. These numerical experiments and observational comparisons have provided valuable physical insight into ice cloud-radiation physics and also into the mechanisms through which contemporary cloud microphysical parameterizations interact with climate model radiation schemes. In particular, the results demonstrate the importance of the smaller ice particles and emphasize the critical role played by not only the average particle size and shape but also the width of the ice particle effective radius distribution about its mean. In fact, the results show that this variability in particle size can sometimes play a greater role in cloud-radiation interactions than the more obvious variations in cloud amount due to changes in ice particle fall speed.

Iacobellis, Sam F.; McFarquhar, Greg M.; Mitchell, David L.; Somerville, Richard C. J.

2003-09-01

344

Subglacial topography and geothermal heat flux: Potential interactions with drainage of the Greenland ice sheet  

Microsoft Academic Search

Many of the outlet glaciers in Greenland overlie deep and narrow trenches cut into the bedrock. It is well known that pronounced topography intensifies the geothermal heat flux in deep valleys and attenuates this flux on mountains. Here we investigate the magnitude of this effect for two subglacial trenches in Greenland. Heat flux variations are estimated for idealized geometries using

C. J. van der Veen; T. Leftwich; R. von Frese; B. M. Csatho; J. Li

2007-01-01

345

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

SciTech Connect

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.

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

1994-04-01

346

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

SciTech Connect

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.

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

347

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

Microsoft Academic Search

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

Judith A. Curry; Elizabeth E. Ebert

1992-01-01

348

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

349

Estimating Antarctic Geothermal Heat Flux using Gravity Inversion  

NASA Astrophysics Data System (ADS)

Geothermal heat flux (GHF) in Antarctica is very poorly known. We have determined (Vaughan et al. 2012) 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). 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. Knowing GHF distribution for East Antarctica and the Gamburtsev Subglacial Mountains (GSM) region in particular is critical because: 1) The GSM likely acted as key nucleation point for the East Antarctic Ice Sheet (EAIS); 2) the region may contain the oldest ice of the EAIS - a prime target for future ice core drilling; 3) GHF is 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). An integrated multi-dataset-based GHF model for East Antarctica is planned that will resolve the wide range of estimates previously published using single datasets. The new map and existing GHF distribution estimates available for Antarctica will be evaluated using direct ice temperature measurements obtained from deep ice cores, estimates of GHF derived from subglacial lakes, and a thermodynamic ice-sheet model of the Antarctic Ice Sheet driven by past climate reconstructions and each of analysed heat flow maps, as has recently been done for the Greenland region (Rogozhina et al. 2012). 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. Golynsky, A.V. & Golynsky, D.A. 2009. Rifts in the tectonic structure of East Antarctica (in Russian). Russian Earth Science Research in Antarctica, 2, 132-162. Rogozhina, I., Hagedoorn, J.M., Martinec, Z., Fleming, K., Soucek, O., Greve, R. & Thomas, M. 2012. Effects of uncertainties in the geothermal heat flux distribution on the Greenland Ice Sheet: An assessment of existing heat flow models. Journal of Geophysical Research-Earth Surface, 117 (F2), F02025. Vaughan, A.P.M., Kusznir, N.J., Ferraccioli, F. & Jordan, T.A.R.M. 2012. Regional heat-?ow prediction for Antarctica using gravity inversion mapping of crustal thickness and lithosphere thinning. Geophysical Research Abstracts, 14, EGU2012-8095.

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

2013-04-01

350

Critical heat flux in a long, rectangular channel subjected to one-sided heating—II. Analysis of critical heat flux data  

Microsoft Academic Search

A theoretical model to predict critical heat flux in long, rectangular channels is presented. The theoretical development is complemented by an extensive flow visualization analysis presented in Part I of this study. The observation of a periodic distribution of increasingly larger vapor patches along the surface just prior to CHF is idealized as a sinusoidal interface with amplitude and wavelength

J. C. Sturgis; I. Mudawar

1999-01-01

351

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

352

Mathematical modeling of sulfide flash smelting process: Part II. Quantitative analysis of radiative heat transfer  

Microsoft Academic Search

A mathematical model has been developed to describe the rate processes in an axisymmetric copper flash smelting furnace shaft.\\u000a A particular feature of the model is the incorporation of the four-flux model to describe the radiative heat transfer by combining\\u000a the absorbing, emitting, and anisotropic scattering phenomena. The importance of various subprocesses of the radiative heat\\u000a transfer in a flash

Y. B. Hahn; H. Y. Sohn

1990-01-01

353

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

SciTech Connect

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.

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

354

Meshless approach for coupled radiative and conductive heat transfer in one-dimensional graded index medium  

NASA Astrophysics Data System (ADS)

A meshless local Petrov Galerkin (MLPG) approach is employed for solving the coupled radiative and conductive heat transfer in a one-dimensional slab with graded index media. The angular distribution term in discrete ordinate equation of radiative transfer within a one-dimensional graded index slab is discretized by a step scheme, and the meshless approach for radiative transfer is based on the discrete ordinate equation. A moving least-squares approximation is used to construct the shape function. Two particular test cases for coupled radiative and conductive heat transfer within a one-dimensional graded index slab are examined to verify this new approximate method. The temperatures and the radiative heat fluxes are obtained. The results are compared with the other benchmark approximate solutions. By comparison, the results show that the MLPG approach has a good accuracy in solving the coupled radiative and conductive heat transfer in one-dimensional graded index media.

Liu, L. H.; Tan, J. Y.; Li, B. X.

2006-09-01

355

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

SciTech Connect

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.

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

1996-07-01

356

ANL ITER high-heat-flux blanket-module heat transfer experiments. Fusion Power Program  

SciTech Connect

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.

Kasza, K.E.

1992-02-01

357

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

SciTech Connect

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.

Kasza, K.E.

1992-02-01

358

Radiation heating in selected NERVA engine components  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

359

Radial heat flux limits in potassium heat pipes: An experimental and analytical investigation  

NASA Astrophysics Data System (ADS)

A radial flux limit of 147 W/sq cm at the wetted inner tube wall has been demonstrated with a Nb-1 percent Zr/K heat pipe, a flux 5 times greater than the previously accepted safe design level of 25 to 30 W/sq cm. The wick structure was an annular gap type fabricated from 100 times 100 mesh Nb-1 percent Zr screen. Rigorous fabrication and cleaning procedures are believed to be critical to good wetting, resulting in significantly reduced active nucleation site size and a higher boiling limit. The procedure used to clean this heat pipe included acid wash, Freon-TF degrease, ethanol wash, high-vacuum firing, and operation as a lithium heat pipe. A heat pipe boiling limit model, based on the active nucleation site radius, is described. An active nucleation site radius of 6 times 10(exp -6) m 2.4 times 10(exp -4) in. correlates the radial flux boiling limit measured in these tests.

Woloshun, K. A.; Sena, J. Tom; Keddy, E. S.; Merrigan, Michael A.

360

Mathematical modeling of sulfide flash smelting process: Part II. Quantitative analysis of radiative heat transfer  

NASA Astrophysics Data System (ADS)

A mathematical model has been developed to describe the rate processes in an axisymmetric copper flash smelting furnace shaft. A particular feature of the model is the incorporation of the four-flux model to describe the radiative heat transfer by combining the absorbing, emitting, and anisotropic scattering phenomena. The importance of various subprocesses of the radiative heat transfer in a flash smelting furnace has been studied. Model predictions showed that the radiation from the furnace walls and between the particles and the surrounding is the dominant mode of heat transfer in a flash smelting furnace.

Hahn, Y. B.; Sohn, H. Y.

1990-12-01

361

Mathematical modeling of sulfide flash smelting process. Part 2; Quantitative analysis of radiative heat transfer  

SciTech Connect

This paper reports on a mathematical model developed to describe the rate processes in an axisymmetric copper flash smelting furnace shaft. A particular feature of the model is the incorporation of the four-flux model to describe the radiative heat transfer by combining the absorbing, emitting, and anisotropic scattering phenomena. The importance of various subprocesses of the radiative heat transfer in a flash smelting furnace has been studied. Model predictions showed that the radiation from the furnace walls and between the particles and the surrounding is the dominant mode of heat transfer in a flash smelting furnace.

Hahn, Y.B. (Lucky Metals Corp., Seoul (KR)); Sohn, H.Y. (Dept. of Metallurgical Engineering, Univ. of Utah, Salt Lake City, UT (US))

1990-12-01

362

Analysis of the heat flux distribution at the anode of a TIG welding arc  

Microsoft Academic Search

The correlation of the heat flux on the anode surface with the plasma properties at the free-fall edge was developed. By using the models of the tungsten inert gas (TIG) welding arc and the anode boundary layer, the heat transfer contributions to the anode heat flux in TIG welding were analyzed. The percentages of the electron flow contribution and the

C. S Wu; J. Q Gao

2002-01-01

363

Monitor for Radiation-Induced Heating.  

National Technical Information Service (NTIS)

The patent relates to a susceptive material that is to be examined with respect to radiation-induced heating sealed within a capsule composed of a material such as stainless steel. The remaining capsule volume is filled with a liquid metal that has a grea...

W. R. Wallin V. W. Lowery R. R. Smith

1974-01-01

364

Strong near-field enhancement of radiative heat transfer between metallic surfaces.  

PubMed

Near-field heat transfer across a gap between plane-parallel tungsten layers in vacuo was studied experimentally with the temperature of the cold sample near 5 K and the temperature of the hot sample in the range 10-40 K as a function of the gap size d. At gaps smaller than one-third of the peak wavelength ?(m) given by Wien's displacement law, the near-field effect was observed. In comparison with blackbody radiation, hundred times higher values of heat flux were achieved at d?1 ?m. Heat flux normalized to the radiative power transferred between black surfaces showed scaling (?(m)/d)(n), where n?2.6. This Letter describes the results of experiment and a comparison with present theory over 4 orders of magnitude of heat flux. PMID:23368126

Kralik, Tomas; Hanzelka, Pavel; Zobac, Martin; Musilova, Vera; Fort, Tomas; Horak, Michal

2012-11-30

365

Heat flux sensor research and development: The cool film calorimeter  

NASA Technical Reports Server (NTRS)

The goal was to meet the measurement requirement of the NASP program for a gauge capable of measuring heat flux into a 'typical' structure in a 'typical' hypersonic flight environment. A device is conceptually described that has fast response times and is small enough to fit in leading edge or cowl lip structures. The device relies heavily on thin film technology. The main conclusion is the description of the limitations of thin film technology both in the art of fabrication and in the assumption that thin films have the same material properties as the original bulk material. Three gauges were designed and fabricated. Thin film deposition processes were evaluated. The effect of different thin film materials on the performance and fabrication of the gauge was studied. The gauges were tested in an arcjet facility. Survivability and accuracy were determined under various hostile environment conditions.

Abtahi, A.; Dean, P.

1990-01-01

366

Estimation of sensible heat flux from remotely sensed canopy temperatures  

NASA Technical Reports Server (NTRS)

Temperatures of tallgrass priarie vegetation were measured with infrared thermometers (IRT) at different view zenith and azimuth angles. The optimum IRT view zenith angle for estimating sensible heat fluxes (H) was determined by comparing H estimated with eddy correlation and/or Bowen ratio techniques to H calculated by a method suggested by Hatfield et al. (1984). For wind speeds of 5 m/s or greater, H estimated with surface temperatures measured at a 0 deg or 20 deg view zenith angle gave the best agreement, but for wind speeds of less than 4 m/s the best estimate of H was made with surface temperatures measured at a 40 deg or 60 deg view zenith angle.

Vining, R. C.; Blad, B. L.

1992-01-01

367

Estimation of sensible heat flux from remotely sensed canopy temperatures  

NASA Astrophysics Data System (ADS)

Temperatures of tallgrass prairie vegetation were measured with infrared thermometers (IRT) at different view zenith and azimuth angles. The optimum IRT view zenith angle for estimating sensible heat fluxes (H) was determined by comparing H estimated with eddy correlation and/or Bowen ratio techniques to H calculated by a method suggested by Hatfield et al. (1984). For wind speeds of 5 m s-1 or greater, H estimated with surface temperatures measured at a 0° or 20° view zenith angle gave the best agreement, but for wind speeds of less than 4 m s-1 the best estimate of H was made with surface temperatures measured at a 40° or 60° view zenith angle.

Vining, R. C.; Blad, B. L.

1992-11-01

368

Interannual changes in the Bering Strait fluxes of volume, heat and freshwater between 1991 and 2004  

Microsoft Academic Search

Year-round moorings (1990 to 2004) illustrate interannual variability of Bering Strait volume, freshwater and heat fluxes, which affect Arctic systems including sea-ice. Fluxes are lowest in 2001 and increase to 2004. Whilst 2004 freshwater and volume fluxes match previous maxima (1998), the 2004 heat flux is the highest recorded, partly due to ~ 0.5ºC warmer temperatures since 2002. The Alaskan

Rebecca A. Woodgate; Knut Aagaard; Thomas J. Weingartner

2006-01-01

369

Regional differences in surface sensible and latent heat fluxes in China  

NASA Astrophysics Data System (ADS)

This study documents the variability of surface sensible and latent heat fluxes in five regions of China (Northwest China, the Tibetan Plateau, Northeast China, North China, and Southeast China) using the ERA-40 reanalysis for the years 1960-2000. The surface sensible and latent heat flux variations are remarkably different in Northwest and Southeast China. The seasonal variation of the surface sensible heat fluxes is largest in Northwest China and smallest in Southeast China. In contrast, the seasonal variation in latent heat flux is largest in Southeast China and smallest in Northwest China. The interdecadal variation of surface sensible and surface latent heat fluxes strongly depends on both the region and season. The trends in surface sensible and latent heat fluxes in all four seasons are mainly caused by variations in both the land-air temperature difference and in the specific humidity. There is also a limited contribution of wind speed in some regions, depending on the season.

Zhou, Lian-Tong; Huang, Ronghui

2014-05-01

370

Heat Flow on Hotspot Swells Reflect Fluid Flow Masking Potential Variations in Mantle Heat Flux  

NASA Astrophysics Data System (ADS)

The origin of hotspot swells is poorly understood. Heat flow data collected on hotspot swells have been used to argue for and against sublithospheric thermal anomalies. The presence of sublithospheric thermal anomalies has been inferred from interpretations of anomalously high heat flow determinations, whereas the contention that hotspot swells result from normal melting processes within the lithosphere is based on `normal' heat flow values. These arguments depend in part on the choice of a thermal reference model, but more importantly assume conductive heat transfer through the lithosphere. We provide evidence that heat flow measurements collected on hotspot swells likely reflect shallow fluid flow rather than deep thermal variations within or at the base of the lithosphere. Discriminating between environments where heat is transferred conductively or convectively requires closely spaced heat flow determinations (1-2 km) collocated with seismic reflection profiles. Only Hawaii and Reunion have surveys meeting these requirements. The Hawaiian survey consists of two profiles, one north of Oahu and one north of Maro Reef. The Reunion survey also consists of two profiles, both north of Mauritius. These heat flow profiles reveal greater scatter than anticipated with spectral peaks on the order of 10 km consistent with fluid flow. Root mean square variations along the Oahu and Maro Reef profiles are 15 and 5 mW m-2, respectively, and along both Reunion profiles are about13 mW m-2. Coupled heat and fluid flow models demonstrate that thermal buoyancy due to bathymetric relief is capable of driving significant fluid flow that may suppress the background thermal field. These models are consistent with heat flow patterns observed at individual seamounts and oceanic basement highs that are more easily sampled and characterized than large hotspot swells. We caution that the ability of fluid flow to mask variations in sublithospheric heat flux make surface heat-flow values a poor discriminator between geodynamic models for hotspot swells.

Harris, R. N.; McNutt, M. K.

2004-12-01

371

High Temperature Titanium-Water Heat Pipe Radiator  

Microsoft Academic Search

Space nuclear systems require large area radiators to reject the unconverted heat to space. System optimizations with Brayton cycles lead to radiators with radiator temperatures in the 400 to 550 K range. To date, nearly all space radiator systems have used aluminum\\/ammonia heat pipes but these components cannot function at the required temperatures. A Graphite Fiber Reinforced Composites (GFRC) radiator

William G. Anderson; Richard Bonner; John Hartenstine; Jim Barth

2006-01-01

372

High Temperature Water-Titanium Heat Pipe Radiator  

Microsoft Academic Search

Space nuclear systems require large area radiators to reject the unconverted heat to space. System optimizations with Brayton cycles lead to radiators with radiator temperatures in the 400 to 550 K range. To date, nearly all space radiator systems have used aluminum\\/ammonia heat pipes but these components cannot function at the required temperatures. A Graphite Fiber Reinforced Composites (GFRC) radiator

William G. Anderson; David B. Sarraf; Scott D. Garner; Jim Barth

373

Controls on sensible heat and latent energy fluxes from a short-hydroperiod Florida Everglades marsh  

NASA Astrophysics Data System (ADS)

SummaryLittle is known of energy balance in low latitude wetlands where there is a year-round growing season and a climate best defined by wet and dry seasons. The Florida Everglades is a highly managed and extensive subtropical wetland that exerts a substantial influence on the hydrology and climate of the south Florida region. However, the effects of seasonality and active water management on energy balance in the Everglades ecosystem are poorly understood. An eddy covariance and micrometeorological tower was established in a short-hydroperiod Everglades marsh to examine the dominant environmental controls on sensible heat ( H) and latent energy ( LE) fluxes, as well as the effects of seasonality on these parameters. Seasonality differentially affected H and LE fluxes in this marsh, such that H was principally dominant in the dry season and LE was strongly dominant in the wet season. The Bowen ratio was high for much of the dry season (1.5-2.4), but relatively low (<0.7) in the wet season. Net radiation strongly influenced H and LE fluxes across nearly all seasons and years ( Radj2=0.48-0.79). However, the 2009 dry season LE data were not consistent with this relationship ( Radj2=0.08) because of low seasonal variation in LE following a prolonged end to the previous wet season. In addition to net radiation, H and LE fluxes were significantly related to soil volumetric water content (VWC), water depth, air temperature, and occasionally vapor pressure deficit. Given that VWC and water depth were determined in part by water management decisions, it is clear that human actions have the ability to influence the mode of energy dissipation from this ecosystem. Impending modifications to water management under the Comprehensive Everglades Restoration Plan may shift the dominant turbulent flux from this ecosystem further toward LE, and this change will likely affect local hydrology and climate.

Schedlbauer, Jessica L.; Oberbauer, Steven F.; Starr, Gregory; Jimenez, Kristine L.

2011-12-01

374

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

NASA Astrophysics Data System (ADS)

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

Taler, Jan; Taler, Dawid; Kowal, Andrzej

2011-04-01

375

An experimental investigation into the feasibility of a thermoelectric heat flux gage  

NASA Technical Reports Server (NTRS)

An experiment was conducted to determine the feasibility of using a commerically available thermoelectric device as a heat flux gage. In certain research applications, the thermoelectric heat flux gage can provide a relatively simple means to model a warm fluid--cold wall. The experiment showed that heat flux through the gage could be correlated within two percent to the applied thermoelectric current through the device and the hot and cold side temperature with a simple algebraic equation.

Jones, J. C.; Vanfossen, G. J., Jr.

1981-01-01

376

Divertor heat flux reduction by D2 injection in DIII-D  

Microsoft Academic Search

D2 gas injected into ELMing H-mode discharges in DIII-D reduced the total integrated heat flux to the divertor ˜2× and the peak heat flux ˜5×, with only modest degradation to plasma stored energy. Steady gas injection without particle pumping results in eventual degradation in stored energy. The initial reduction in peak heat flux at the divertor tiles may be primarily

T. W. Petrie; D. Buchenauer; D. N. Hill; C. Klepper; S. Allen; R. Campbell; A. Futch; R. J. Groebner; A. Leonard; S. Lippmann; M. Ali Mahdavi; M. E. Resink

1992-01-01

377

Divertor heat flux reduction by D sub 2 injection in DIII-D  

Microsoft Academic Search

Dâ gas injected into ELMing H-mode discharges in DIII-D reduced total integrated heat flux to the divertor by â¼2Ã and peak heat flux by â¼5Ã, with only modest degradation to plasma stored energy. Steady gas injection without particle pumping results in eventual degradation in stored energy. The initial reduction in peak heat flux at the divertor tiles may be primarily

T. W. Petrie; R. J. Groebner; A. W. Leonard; S. I. Lippmann; A. M. Mahdavi; W. P. West; D. Buchenauer; R. B. Campbell; D. N. Hill; S. L. Allen; A. H. Futch; M. E. Resink; C. C. Klepper

1992-01-01

378

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

NASA Astrophysics Data System (ADS)

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.

Song, Xiangzhou; Yu, Lisan

2013-07-01

379

Critical heat flux analysis and R&D for the design of the ITER divertor  

Microsoft Academic Search

The vertical target and dump target of the ITER divertor have to be designed for high heat fluxes (up to 20 MW\\/m2 over ?10 s). Accommodation of such high heat fluxes gives rise to several issues, including the critical heat flux (CHF) margin which is a key requirement influencing the choice of cooling channel geometry and coolant conditions. An R&D

A. R. Raffray; J. Schlosser; M. Akiba; M. Araki; S. Chiocchio; D. Driemeyer; F. Escourbiac; S. Grigoriev; M. Merola; R. Tivey; G. Vieider; D. Youchison

1999-01-01

380

Divertor heat flux mitigation in high-performance H-mode discharges in the National Spherical Torus Experiment  

SciTech Connect

Experiments conducted in high-performance 1.0 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(t) = 15-25%, a high bootstrap current fraction f(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 = 0.7-0.8. Divertor peak heat fluxes were reduced from 6-12 to 0.5-2 MW m(-2) in ELMy H-mode discharges using the inherently high magnetic flux expansion f(m) = 15-25 and the partial detachment of the outer strike point at several D-2 injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z(eff) were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction in ion flux to the plate and a large neutral compression ratio. Spectroscopic measurements indicated the formation of a high-density, low-temperature region adjacent to the outer strike point, where substantial increases in the volume recombination rate and C II, CIII emission rates were measured.

Soukhanovskii, V. A. [Lawrence Livermore National Laboratory (LLNL); Maingi, R. [Oak Ridge National Laboratory (ORNL); Gates, D.A. [Princeton Plasma Physics Laboratory (PPPL); Menard, J. [Princeton Plasma Physics Laboratory (PPPL); Paul, S.F. [Princeton Plasma Physics Laboratory (PPPL); Raman, R. [University of Washington, Seattle; Roquemore, A. L. [Princeton Plasma Physics Laboratory (PPPL); Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Bush, C.E. [Oak Ridge National Laboratory (ORNL); Kaita, R. [Princeton Plasma Physics Laboratory (PPPL); Kugel, H. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Mueller, D. [Princeton Plasma Physics Laboratory (PPPL)

2009-01-01

381

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

Microsoft Academic Search

The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, 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\\/tau), tau=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test

Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

2006-01-01

382

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

383

Radiative Heating Methodology for the Huygens Probe  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

384

Critical heat flux in saturated forced convective boiling on a heated disk with an impinging jet  

Microsoft Academic Search

The present study introduces a new correlation predicting critical heat flux (CHF) for a saturated forced convective boiling with an impinging jet. The new correlation is able to predict all the CHF data inV-regime with a good accuracy of +-20% to which the correlations existing until now could not be applicable for 15l\\/?r36. The new correlation seems to support a

M. Monde

1985-01-01

385

Hydrodynamic and heat transfer characteristics of laminar flow past a parabolic cylinder with constant heat flux  

Microsoft Academic Search

Steady, two-dimensional, symmetric, laminar and incompressible flow past parabolic bodies in a uniform stream with constant heat flux is investigated numerically. The full Navier-Stokes and energy equations in parabolic coordinates with stream function, vorticity and temperature as dependent variables were solved. These equations were solved using a second order accurate finite difference scheme on a non-uniform grid. The leading edge

M. Abu-Qudais; O. M. Haddad; A. M. Maqableh

2001-01-01

386

Hydrodynamic and heat transfer characteristics of laminar flow past a parabolic cylinder with constant heat flux  

Microsoft Academic Search

Steady, two-dimensional, symmetric, laminar and incompressible flow past parabolic bodies in a uniform stream with constant\\u000a heat flux is investigated numerically. The full Navier–Stokes and energy equations in parabolic coordinates with stream function,\\u000a vorticity and temperature as dependent variables were solved. These equations were solved using a second order accurate finite\\u000a difference scheme on a non-uniform grid. The leading edge

M. Abu-Qudais; O. M. Haddad; A. M. Maqableh

2001-01-01

387

Report of the Joint Scientific Commitee AD Hoc Working Group on Radiative Flux Measurements.  

National Technical Information Service (NTIS)

A strategy for studying radiation flux as part of the World Climate Research Program is outlined. Key elements are the Earth radiation budget at the top of the atmosphere; solar irradiance; and the surface radiation budget.

1987-01-01

388

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

SciTech Connect

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.

Holcomb, G.R.

2008-04-01

389

Quantitative method for measuring heat flux emitted from a cryogenic object  

DOEpatents

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.

Duncan, R.V.

1993-03-16

390

Quantitative method for measuring heat flux emitted from a cryogenic object  

DOEpatents

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.

Duncan, Robert V. (Tijeras, NM)

1993-01-01

391

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

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

D. C. Wadsworth; I. Mudawar

1992-01-01

392

Characterization of surface heat fluxes in the Mediterranean Sea from a 44-year high-resolution atmospheric data set  

NASA Astrophysics Data System (ADS)

We examine 44 years (1958-2001) of model data with the aim of characterizing the low frequency (the seasonal cycle and lower) variability of surface heat fluxes. The data set was produced in the framework of the HIPOCAS project through a dynamical downscaling (1/2? × 1/2?) from the NCEP/NCAR global reanalysis using the atmospheric limited area model REMO. The added value of this data set is the better representation of regional and local aspects related to thermal and dynamical effects resulting from its higher resolution. The basin mean values of the heat fluxes have been estimated in 168 W/m 2 for the solar radiation ( QS), 73 W/m 2 for the longwave net radiation ( QB), 8 W/m 2 for the sensible heat ( QH) and 88 W/m 2 for the latent heat ( QE), giving a total heat budget of about - 1 W/m 2. The main differences with respect to previous results are the reduced QS and QE terms. The seasonal cycle accounts for a significant fraction of the variability (75%, 20% and 10% for QS, QE and QH) except for QB (less than 1%). The total heat budget has an amplitude of 164 W/m 2 and peaks by middle June, in agreement with previous works and observations. The interannual variability of each component has been first quantified by the standard deviation of the annual mean values, obtaining ± 2.0 W/m 2 for QS, ± 1.1 W/m 2 for QB, ± 4.7 W/m 2 for QE and ± 1.1 W/m 2 for QH. The dominant modes have been obtained through an EOF analysis, which is shown to be robust with respect to the analysis domain. The correlation between the amplitudes of the radiation terms ( QS and QB) and MOI winter values is higher than 0.7 (in absolute value) in the Eastern basin. For the other flux components the correlation with the MOI is less than 0.7 everywhere. The correlation between the heat flux terms and the NAO is smaller than 0.7 for all terms. From the evaluation analysis, HIPCOAS fluxes show stronger correlations with the observation based NOC fields than are obtained with the original NCEP/NCAR fluxes for the full set of interannually varying heat flux estimates. Thus, the downscaling has led to an improved representation of the interannual variability when compared with observations.

Ruiz, Simón; Gomis, Damià; Sotillo, Marcos G.; Josey, Simon A.

2008-09-01

393

Discussion on calculation methods of sensible heat flux during GAME/Tibet in 1998  

NASA Astrophysics Data System (ADS)

Based on previous research on sensible heat flux, we investigate it from different aspects using GAME/Tibet data measured during 6 June-13 September, 1998. This work consists of the derivation of the surface heat flux equation, analysis on counter-gradient heat transference, comparison between two different methods to compute the sensible heat flux, and investigation on the calculation scheme of sensible heat flux in the Simple Biosphere model 2 (SiB2) with relevant simulation. By improving two previous formulations, an integrated formulation for calculating surface heat flux is given. Secondly, using the measured data, the counter-gradient heat flux is clarified, leading to the fact that buoyancy plays an important role in the sensible heat transfer process. It is concluded that (1) energy imbalance is a common phenomenon resulting from the use of the traditional closure scheme on the heterogeneous underlying surface because the measured ensemble heat fluxes by eddy correlation contain the effect of nonlocal parcel movements; and (2) nonlocal parcel movement deserves more attention in any future heat flux study.

Gao, Z. Q.; Bian, L. G.; Wang, J. X.; Lu, L. G.

2003-05-01

394

Estimation of the High-Latitude Topside Heat Flux Using DMSP In Situ Plasma Densities  

NASA Astrophysics Data System (ADS)

The high-latitude ionosphere interfaces with the hot, tenuous, magnetospheric plasma, and a heat flow into the ionosphere is expected, which has a large impact on the plasma densities and temperatures in the high-latitude ionosphere. The value of this magnetospheric heat flux is unknown. In an effort to estimate the value of the magnetospheric heat flux into the ionosphere and, and show its effect on the high-latitude plasma densities, we ran an ensemble of model runs using the Ionosphere Forecast Model (IFM) with different values of the heat flux through the upper boundary. These model runs included both auroral and solar heating. For each heat flux value, the plasma densities obtained from the model run at 840 Km were compared to the corresponding values measured by the DMSP F13 satellite. The heat flux value that gave the best compariosn between the measured and calculated plasma densities is considered to be the best estimated to the topside heat flux. The comparison was conducted for a one-year data set of the DMSP F13 measured plasma densities. In this paper, we show the effect of the topside heat flux on the plasma densities, and show realistic estimates for the topside heat flux values through the upper boundary of the high-latitude ionosphere.

Bekerat, H.; Schunk, R.; Scherliess, L.

2005-12-01

395

Impact of clouds on radiative heating rates in the tropical lower stratosphere  

NASA Astrophysics Data System (ADS)

We quantify the impact of tropospheric clouds on radiative heating rates in the tropical lower stratosphere using the data collected from the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) sites Manus and Nauru. The cloud fields are retrieved from ground-based millimeter cloud radar observations. We find that the radiative heating rate change due to enhanced upwelling shortwave fluxes only partially compensates that due to reduced upwelling longwave fluxes, resulting in a net change of about -0.2 K/day in the 70-30 hPa layer during the periods of frequent high cloud occurrence. The impact of clouds is particularly large relative to clear sky radiative heating rates around 60 hPa (435-475 K, the base of the "tropical pipe") where they show a local minimum. The radiative heating rates in this layer with the consideration of cloud effects are close to zero and can be even negative (i.e., diabatic descent). The seasonal and spatial structures of tropical convection, and associated high cloud coverage, suggest that their effect, leading to longitudinal (in addition to the well known latitudinal) gradients in radiative heating rates, may be partially responsible for stratospheric mixing. It is suggested that the effect of high tropospheric clouds on radiative heating rates cannot fully explain the amplitude of diabatic descent in the lower stratosphere over the maritime continent reported in previous studies.

Fueglistaler, S.; Fu, Q.

2006-12-01

396

Estimation of surface heat fluxes and evapotranspiration using community land model  

NASA Astrophysics Data System (ADS)

Land surface heat and water fluxes are key components of water and energy cycles between land and atmosphere. Information about these surface fluxes can guide agricultural production and environmental preservation, and manage different ecosystems to mitigate climate change. The main objective of this work is to estimate the surface heat fluxes and evapotranspiration. For this purpose, the Community Land Model Version 3 was used, atmospheric forcing data and flux observation were extracted from AmeriFlux standardized Level 2 database, then surface heat fluxes under two different underlying surfaces were modeled. The results showed that the model works well regarding the simulation of daily surface fluxes and diurnal surface fluxes although these values were underestimated relative to the values observed from eddycovariance. After validation, evapotranspiration was chosen as the indicator for specific comparison. CLM3.0 showed a better performance in simulating the moisture and evapotranspiration.

Du, Juan; Liu, Chaoshun; Shi, Runhe; Shu, Shijie; Gao, Wei

2013-09-01

397

Critical Heat Flux (CHF) Phenomenon on a Downward Facing Curved Surface: Effects of Thermal Insulation.  

National Technical Information Service (NTIS)

The phenomena of natural convection boiling and critical heat flux on the outer surface of a heated hemispherical vessel surrounded by a thermal insulation structure were investigated experimentally in the subscale boundary layer boiling (SBLB) test facil...

F. B. Cheung Y. C. Liu

1998-01-01

398

Facility for high heat flux testing of irradiated fusion materials and components using infrared plasma arc lamps  

SciTech Connect

A new high-heat flux testing facility using water-wall stabilized high-power high-pressure argon Plasma Arc Lamps (PALs) has been developed for fusion applications. It can handle irradiated plasma facing component materials and mock-up divertor components. Two PALs currently available at ORNL can provide maximum incident heat fluxes of 4.2 and 27 MW/m2 over a heated area of 9x12 and 1x10 cm2, respectively, which are fusion-prototypical steady state heat flux conditions. The facility will be described and the main differences between the photon-based high-heat flux testing facilities, such as PALs, and the e-beam and particle beam facilities more commonly used for fusion HHF testing are discussed. The components of the test chamber were designed to accommodate radiation safety and materials compatibility requirements posed by high-temperature exposure of low levels irradiated tungsten articles. Issues related to the operation and temperature measurements during testing are presented and discussed.

Sabau, Adrian S [ORNL] [ORNL; Ohriner, Evan Keith [ORNL] [ORNL; Kiggans, Jim [ORNL] [ORNL; Harper, David C [ORNL] [ORNL; Snead, Lance Lewis [ORNL] [ORNL; Schaich, Charles Ross [ORNL] [ORNL

2014-01-01

399

Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites  

NASA Astrophysics Data System (ADS)

The warm season (mid-June through late August) partitioning between sensible (H) and latent (LE) heat flux, or the Bowen ratio (? = H/LE), was investigated at 27 sites over 66 site years within the international network of eddy covariance sites (FLUXNET). Variability in ? across ecosystems and climates was analyzed by quantifying general climatic and surface characteristics that control flux partitioning. The climatic control on ? was quantified using the climatological resistance (Ri), which is proportional to the ratio of vapor pressure deficit (difference between saturation vapor pressure and atmospheric vapor pressure) to net radiation (large values of Ri decrease ?). The control of flux partitioning by the vegetation and underlying surface was quantified by computing the surface resistance to water vapor transport (Rc, with large values tending to increase ?). There was a considerable range in flux partitioning characteristics (Rc, Ri and ?) among sites, but it was possible to define some general differences between vegetation types and climates. Deciduous forest sites and the agricultural site had the lowest values of Rc and ? (0.25-0.50). Coniferous forests typically had a larger Rc and higher ? (typically between 0.50 and 1.00 but also much larger). However, there was notable variability in Rc and Ri between coniferous site years, most notably differences between oceanic and continental climates and sites with a distinct dry summer season (Mediterranean climate). Sites with Mediterranean climates generally had the highest net radiation, Rc, Ri, and ?. There was considerable variability in ? between grassland site years, primarily the result of interannual differences in soil water content and Rc.

Wilson, Kell B.; Baldocchi, Dennis D.; Aubinet, Marc; Berbigier, Paul; Bernhofer, Christian; Dolman, Han; Falge, Eva; Field, Chris; Goldstein, Allen; Granier, Andre; Grelle, Achim; Halldor, Thorgeirsson; Hollinger, Dave; Katul, Gabriel; Law, B. E.; Lindroth, Anders; Meyers, Tilden; Moncrieff, John; Monson, Russ; Oechel, Walter; Tenhunen, John; Valentini, Riccardo; Verma, Shashi; Vesala, Timo; Wofsy, Steve

2002-12-01

400

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

NASA Technical Reports Server (NTRS)

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.

Abdelmessih, Amanie N.; Horn, Thomas J.

2008-01-01