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1

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, P.J., Jr.; Jackson, R.D.; Brown, P.W.; Nichols, W.D.; Gay, L.W.

1990-01-01

2

A study of the expansion of the solar corona with radiation heat flux  

Microsoft Academic Search

The expansion of the solar corona is studied using the hydrodynamic blast wave theory and the concept of the Roche model, with both solar gravity and radiation heat flux taken into consideration. Similarity solutions are developed when the radiation heat flux is more important than the radiation pressure and energy; the gas in the undisturbed field is assumed to be

J. B. Bhowmick

1980-01-01

3

Analysis of urban heat-island effect using ASTER and ETM+ Data: Separation of anthropogenic heat discharge and natural heat radiation from sensible heat flux  

Microsoft Academic Search

The urban heat-island effect occurs as a result of increased sensible heat flux from the land surface to the atmosphere near cities. Sensible heat flux consists of two components: exhausted anthropogenic heat, and heat radiation due to solar input. The latter may be enhanced by changes in the usage of artificial land surface. The authors have developed a new method

Soushi Kato; Yasushi Yamaguchi

2005-01-01

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

A study of the expansin of the solar corona with radiation heat flux  

Microsoft Academic Search

The expansion of the solar corona, with the aid of hydrodynamic blast wave theory using the concept of the Roche model, is studied here when both the solar gravity and radiation heat flux are taken into consideration.

J. B. Bhowmick

1980-01-01

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

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

PubMed

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

Diao, Jiang; Xie, Bing

2009-02-01

9

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

E-print Network

In the absence of advection or precipitation , the energy balance at the land surface is given by Rn - G - LE ­ H on vegetation, meteorological and atmospheric conditions In urban areas in addition to the net radiation the anthropogenic heat discharge also causes heat fluxes. Human activities, mainly energy production, use

Hall, Sharon J.

10

Radiative and turbulent surface heat fluxes over sea ice in the western Weddell Sea in early summer  

Microsoft Academic Search

The radiative and turbulent heat fluxes between the snow-covered sea ice and the atmosphere were analyzed on the basis of observations during the Ice Station Polarstern (ISPOL) in the western Weddell Sea from 28 November 2004 to 2 January 2005. The net heat flux to the snowpack was 3 ± 2 W m?2 (mean ± standard deviation; defined positive toward

Timo Vihma; Milla M. Johansson; Jouko Launiainen

2009-01-01

11

Temperature and Radiative Heat Flux Measurements in Microgravity Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The objective of this project is to provide detailed measurements and modeling analyses of local soot concentration, temperature and radiation heat flux distributions in laminar and turbulent jet diffusion flames under normal (1-g) and reduced gravity (0-g) conditions. Results published to date by these co-PI's and their co-workers include: 1. thermophoretic sampling and size and morphological analyses of soot aggregates in laminar flames under normal and reduced gravity conditions; 2. full-field absorption imaging for soot volume fraction maps in laminar and turbulent flames under normal and reduced gravity conditions; 3. an accurate solver module for detailed radiation heat transfer in nongray nonhomogeneous media; 4. a complete model to include flame structure, soot formation and an energy equation to couple with radiation solver.

Ku, Jerry C.; Greenberg, Paul S.

1997-01-01

12

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

NASA Technical Reports Server (NTRS)

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

Olson, Douglas A.

1989-01-01

13

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

14

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

NASA Astrophysics Data System (ADS)

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

Hinkelman, Laura M.

15

Experimental evaluation of latent heat flux during night-time radiative hoarfrost  

Microsoft Academic Search

A method to evaluate the latent heat flux during favourable conditions to frost formation has been tested with measurements made on two consecutive nights. The method is based on a surface thermal budget. Results show sign changes in the computed latent heat flux according to the observed cycle of frost formation and thaw. Flux estimates of 0.045 cal cm-2 min-1,

M. Severini; B. Olivieri

1980-01-01

16

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

17

Experimental evaluation of latent heat flux during night-time radiative hoarfrost  

NASA Astrophysics Data System (ADS)

A method to evaluate the latent heat flux during favourable conditions to frost formation has been tested with measurements made on two consecutive nights. The method is based on a surface thermal budget. Results show sign changes in the computed latent heat flux according to the observed cycle of frost formation and thaw. Flux estimates of 0.045 cal cm-2 min-1, with a mean relative error of 30%, have been obtained during the period of maximum frost accretion.

Severini, M.; Olivieri, B.

1980-08-01

18

Heat flux measurements  

Microsoft Academic Search

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

Curt H. Liebert; Donald H. Weikle

1989-01-01

19

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

20

Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006  

Microsoft Academic Search

The present work analyses the effect of dust aerosols on the surface and top of atmosphere radiative budget, surface temperature, sensible heat fluxes, atmospheric heating rate and convective activity over West Africa. The study is focused on the regional impact of a major dust event over the period of 7-14 March 2006 through numerical simulations performed with the mesoscale, nonhydrostatic

M. Mallet; P. Tulet; D. Serça; F. Solmon; O. Dubovik; J. Pelon; V. Pont; O. Thouron

2009-01-01

21

Fundamentals of heat measurement. [heat flux transducers  

NASA Technical Reports Server (NTRS)

Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

Gerashchenko, O. A.

1979-01-01

22

Heat flux sensor calibrator  

Microsoft Academic Search

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

C. H. Liebert

1985-01-01

23

An analysis of volumetric radiation heat flux and experimental comparison with arc light sensing in GTA welding process  

Microsoft Academic Search

The volumetric radiation heat flux was analyzed from a model of the entire free burning arc of GTA welding and its results were compared with measurements of the arc light intensity to find a relationship between them. Experiments were carried out for various welding currents using electrodes of different vertex angles. The results showed similar behavior for both the volumetric

J.-H. Lee; S.-J. Na

2001-01-01

24

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

25

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

26

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

27

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

28

Land use planning and surface heat island formation: A parcel-based radiation flux approach  

NASA Astrophysics Data System (ADS)

This article presents a study of residential parcel design and surface heat island formation in a major metropolitan region of the southeastern United States. Through the integration of high-resolution multispectral data (10 m) with property tax records for over 100,000 single-family residential parcels in the Atlanta, Georgia, metropolitan region, the influence of the size and material composition of residential land use on an indicator of surface heat island formation is reported. In contrast to previous work on the urban heat island, this study derives a parcel-based indicator of surface warming to permit the impact of land use planning regulations governing the density and design of development on the excess surface flux of heat energy to be measured. The results of this study suggest that the contribution of individual land parcels to regional surface heat island formation could be reduced by approximately 40% through the adoption of specific land use planning policies, such as zoning and subdivision regulations, and with no modifications to the size or albedo of the residential structure.

Stone, Brian; Norman, John M.

29

Similarity Solutions for the Flow Behind an Exponential Shock in a Rotating Nonideal Gas with Heat Conduction and Radiation Heat Fluxes  

NASA Astrophysics Data System (ADS)

A self-similar solution for the propagation of a shock wave driven by a cylindrical piston moving according to exponential temporal law in a nonideal rotating gas with heat conduction and radiation heat fluxes is investigated. The density and angular velocity of the ambient medium are assumed to be constant. Heat conduction is expressed in terms of the Fourier law, and radiation is considered to be of diffusion type for an optically thick gray gas model. The thermal conductivity and absorption coefficient are assumed to vary with temperature and density. Similarity solutions are obtained, and the effects of variations in the heat transfer parameters and gas nonidealness on the flow variables in the region behind the shock are investigated.

Singh, K. K.; Nath, B.

2014-07-01

30

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

31

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

32

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

33

Measurements of net radiation, ground heat flux and surface temperature in an urban canyon  

SciTech Connect

The Joint Urban 2003 (JU2003) field study was conducted in Oklahoma City in July 2003 to collect data to increase our knowledge of dispersion in urban areas. Air motions in and around urban areas are very complicated due to the influence of urban structures on both mechanical and thermal forcing. During JU2003, meteorological instruments were deployed at various locations throughout the urban area to characterize the processes that influence dispersion. Some of the instruments were deployed to characterize urban phenomena, such as boundary layer development. In addition, particular sites were chosen for more concentrated measurements to investigate physical processes in more detail. One such site was an urban street canyon on Park Avenue between Broadway and Robinson Avenues in downtown Oklahoma City. The urban canyon study was designed to examine the processes that control dispersion within, into and out of the urban canyon. Several towers were deployed in the Park Avenue block, with multiple levels on each tower for observing the wind using sonic anemometers. Infrared thermometers, net radiometers and ground heat flux plates were deployed on two of the towers midway in the canyon to study the thermodynamic effects and to estimate the surface energy balance. We present results from the surface energy balance observations.

Gouveia, F J; Leach, M J; Shinn, J H

2003-11-06

34

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

35

Flame Heat Fluxes in Pmma Pool Fires  

Microsoft Academic Search

A simple one-dimensional analytical model has been developed to describe the processes involved in the transient burning of non-charring thermoplastic materials. The model includes conduction, convection, and radiation effects for flaming materials. The burning rate solution is obtained by numerically solving an ordinary differential equation and an algebraic equation with flame radiative heat flux as a specified variable. The effect

Naeem Iqbal; James Quintiere

1994-01-01

36

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

37

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

38

High heat flux single phase heat exchanger  

Microsoft Academic Search

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

Javier A. Valenzuela; Michael G. Izenson

1990-01-01

39

Land use planning and surface heat island formation: A parcel-based radiation flux approach  

Microsoft Academic Search

This article presents a study of residential parcel design and surface heat island formation in a major metropolitan region of the southeastern United States. Through the integration of high-resolution multispectral data (10m) with property tax records for over 100,000 single-family residential parcels in the Atlanta, Georgia, metropolitan region, the influence of the size and material composition of residential land use

Brian Stone; John M. Norman

2006-01-01

40

Heat flux at the thermionic collector  

NASA Technical Reports Server (NTRS)

Heat flux arriving at the thermionic collector is theoretically considered to be composed of an electron heating term, proportional to the output current, plus the radiation and conduction terms. However, the measured electron heating term is always larger than what one would expect from the accepted theory. In this paper, the electron heating term at the collector is theoretically calculated as a sum of the conventional electron heating term and the heat flux which is carried into the collector by the random plasma current. The arriving random electrons and ions are considered to recombine nonradiatively at the collector surface after imparting their kinetic energies to the collector, in addition to the ionization potential energy. In this process, random electrons do not lose their potential energy equal to the collector work function, since they do not contribute to the output current.

Shimada, K.

1980-01-01

41

High heat flux loop heat pipes  

NASA Technical Reports Server (NTRS)

Loop heat pipes (LHPs) can transport very large thermal power loads over long distances, through flexible, small diameter tubes against gravitational heads. In order to overcome the evaporator limit of LHPs, which is of about 0.07 MW/sq m, work was carried out to improve the efficiency by threefold to tenfold. The vapor passage geometry for the high heat flux conditions is shown. A bidisperse wick material within the circumferential vapor passages was used. Along with heat flux enhancement, several underlying issues were demonstrated, including the fabrication of bidisperse powder with controlled properties and the fabrication of a device geometry capable of replacing vapor passages with bidisperse powder.

North, Mark T.; Sarraf, David B.; Rosenfeld, John H.; Maidanik, Yuri F.; Vershinin, Sergey

1997-01-01

42

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

43

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

Microsoft Academic Search

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

Pankaj Sharma; Vivek Kumar Sharma

2009-01-01

44

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

45

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

46

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

47

IR thermography heat flux measurement in fire safety applications  

NASA Astrophysics Data System (ADS)

The paper deals with heat flux measurement possibilities in fire safety applications. The paper presents two methods for radiation heat flux measurement - the thermography source-target measurement method, and the radiation contact target measurement method. Both the methods were used simultaneously for radiation heat flux measurement during a fire experiment on a high-density polyethylene plastic box storage stack. The theoretical background, experimental set-up, application example, and comparison of both methods are presented in this paper. Dependence of heat flux magnitude on a distance and direction from a heat source is evaluated. The possible safety risks ensuing from high temperatures inside the burning stack, and therefore high heat fluxes near the stack, are discussed.

Švantner, Michal; Vacíková, Petra; Honner, Milan

2012-07-01

48

Attenuation of Incident Heat Flux by Pyrolysis Volatiles when Heated Using Resistance Element Radiant Heater  

Microsoft Academic Search

The attenuation of an incident radiant heat flux by pyrolysis volatiles when heated under a resistance element radiant heater, a phenomenon that is not well understood, is studied by simulated experiment and mathematical models. The radiation attenuation of an incident heat flux when pine or PMMA is heated (6—14%) obviously commences before ignition, although it is not as large as

Yupeng Zhou; Lizhong Yang; Jiakun Dai; Yafei Wang; Zhihua Deng

2009-01-01

49

Non-contact heat flux measurement using a transparent sensor  

NASA Technical Reports Server (NTRS)

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

Ng, Daniel; Spuckler, Charles M.

1993-01-01

50

Sensible Heat Flux Estimated from Routine Meteorological Data by the Resistance Method  

Microsoft Academic Search

A method is described for evaluation of hourly values of the sensible heat flux from routine meteorological data. Use is made of the energy balance at the surface and of the Monteith-Penman formula for estimation of the latent heat flux. The soil heat flux is modelled as a given fraction of the sensible heat flux. The net radiation is computed

R. Berkowicz; L. P. Prahm

1982-01-01

51

Heat Flux Determination From Measured Heating Rates Using Thermographic Phosphors  

Microsoft Academic Search

A new method for measuring the heating rate (defined as the time rate of change of temperature) and estimating heat flux from the heating rate is proposed. The example problem involves analytic heat conduction in a one-dimensional slab, where the measure- ment location of temperature or heating rate coincides with the location of the estimated heat flux. The new method

D. G. Walker

2005-01-01

52

Geometrical correction factors for heat flux meters  

NASA Technical Reports Server (NTRS)

General formulas are derived for determining gage averaging errors of strip-type heat flux meters used in the measurement of one-dimensional heat flux distributions. The local averaging error e(x) is defined as the difference between the measured value of the heat flux and the local value which occurs at the center of the gage. In terms of e(x), a correction procedure is presented which allows a better estimate for the true value of the local heat flux. For many practical problems, it is possible to use relatively large gages to obtain acceptable heat flux measurements.

Baumeister, K. J.; Papell, S. S.

1974-01-01

53

External heat loads on a cryogenic radiator  

NASA Astrophysics Data System (ADS)

Cryogenic radiators are necessary for instruments on earth-orbiting spacecraft for applications in the infrared spectral regions to maintain operating temperatures of 75-100 K. The radiator size can be greatly affected by parasitic heat loads. This paper presents the results of a study which calculated the heat fluxes from solar arrays, masts, and other external appendages to a cryogenic radiator in a synchronous orbit. The analyses showed that care must be taken in the location of spacecraft components that may see a cryogenic radiator. Without proper shielding heat fluxes can easily exceed the radiators cooling capability.

Wedel, R. K.; Zingale, T.

1991-06-01

54

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

55

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

56

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

57

A nonstationary method for measuring heat fluxes  

Microsoft Academic Search

A nonstationary method for measuring heat fluxes using a hollow cylindrical probe placed in the critical cross section of a nozzle is proposed. The temperature at a fixed distance from the inner surface of the probe is measured as a function of time. The time variation of the heat flux is determined by solving the one-dimensional nonlinear heat-conduction equation.

V. S. Kulikov; G. A. Surkov; V. V. Mazak; F. B. Yurevich

1975-01-01

58

Dimensional Analysis of Thermoelectric Modules Under Constant Heat Flux  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

59

Dual active surface heat flux gage probe  

NASA Astrophysics Data System (ADS)

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

1995-02-01

60

A simple method for measuring heat flux  

Microsoft Academic Search

A method is described for the measurement of heat flux using the temperature gradient in a metal pad welded to two adjacent cooling tubes. A number of laboratory experiments have shown that the simple theoretical expression for calculating the heat flux is justified; the meter has operated successfully in an oil-fired boiler.

D. Anson; A. M. Godridge

1967-01-01

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 , 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

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 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

63

Convection calibration method for local heat flux gages  

SciTech Connect

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, which is different from the linear calibration obtained using the standard radiation technique. The degree of nonlinearity matches the analysis which accounts for the effect of the temperature distribution in the gage foil. The effect of this temperature distribution can be neglected in the standard radiation calibration but is often significant in convection applications. These results emphasize the importance of calibrating heat flux gates in thermal environments similar to those in which they will be used.

Borell, G.J.; Diller, T.E.

1987-02-01

64

Parameterization of the Diurnal Soil Heat Flux/Net Radiation Ratio Over a Range of Surface Conditions for Land Surface Energy Balance Models  

NASA Astrophysics Data System (ADS)

Many studies have demonstrated that soil heat flux (G) is strongly correlated with net radiation (Rn). Methods to parameterize G based on this relationship typically do not account for the dependency of G on soil properties and ignore the phase shift in the timing of peak G relative to Rn. In this paper, a method is described to parameterize G as a function of Rn for sparse cover or bare soil conditions that takes into account the diurnal variation in this relationship, as well as the effects of soil moisture and soil type. This approach combines information from field data and simulations from a multi-layer, diffusion-based soil model, (SHAW; Simultaneous Heat and Water model), over a range of soil types and conditions. As part of this analysis the effect of vegetation density is also considered. The resulting parameterizations for G / Rn provide a robust representation of this relationship on hourly time scales for varying soil conditions. A critical factor controlling this relationship is the relative soil moisture and the transition from stage-one (atmosphere limited) to stage-two (soil limited) evaporation. This method should provide improvement over previous simplified treatments for G in energy balance modeling in the absence of a physically-based soil model, and where diurnal energy balance closure is required.

Santanello, J. A.; Friedl, M. A.

2001-05-01

65

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

SciTech Connect

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

Blanchat, Thomas K.; Hanks, Charles R.

2013-04-01

66

Radiation entropy flux and entropy production of the Earth system  

NASA Astrophysics Data System (ADS)

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 than the typical value of the entropy production rate associated with the atmospheric latent heat process. Comparison analysis shows that the commonly used expression of radiation entropy flux as the ratio of radiation energy flux to absolute temperature underestimates the Earth's radiation entropy flux by >30%. Theoretical analysis reveals that the large difference in the Earth's reflected solar radiation entropy flux among the different expressions arises mainly from the difference of the Earth's reflection properties (i.e., Lambertian or specular) assumed in these expressions. For the Earth system with typical shortwave albedo of 0.30 and longwave emissivity between 0.50 and 1.00, the Earth's net radiation entropy flux derived from the most accurate Planck's spectral expression ranges from 1.272 to 1.284 W m-2 K-1, amounting to the overall Earth's entropy production rate from 6.481 × 1014 to 6.547 × 1014 W K-1.

Wu, Wei; Liu, Yangang

2010-05-01

67

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

68

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

69

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

70

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

E-print Network

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

Verburg, Piet

2014-01-01

71

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

72

Measuring Fluxes Of Heat To A Plasma-Arc Anode  

NASA Technical Reports Server (NTRS)

Three probes constructed to provide measurements indicative of conductive, convective, and radiative transfer of heat from free-burning plasma arc to water-cooled copper anode used in generating arc. Each probe consists mainly of copper body with two thermocouples embedded at locations 4 mm apart along length. Thermocouples provide measure of rate of conduction of heat along probe and transfers of heat from plasma to sensing surface at tip of probe. Probes identical except sensing surface of one uncoated and other two coated with different materials to make them sensitive to different components of overall flux of heat.

Sankovic, John M.; Menart, James A.; Pfender, Emil; Heberlein, Joachim

1995-01-01

73

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

E-print Network

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

Todreas, Neil E.

1965-01-01

74

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

75

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

76

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

77

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

78

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

79

RADIATION FROM COMOVING POYNTING FLUX ACCELERATION  

SciTech Connect

We derive analytic formulas for the radiation power output when electrons are accelerated by a relativistic comoving kinetic Poynting flux, and validate these analytic results with particle-in-cell simulations. We also derive analytically the critical frequency of the radiation spectrum. Potential astrophysical applications of these results are discussed. A quantitative model of gamma-ray bursts based on the breakout of kinetic Poynting flux is presented.

Liang, Edison; Noguchi, Koichi [Rice University, Houston TX 77005-1892 (United States)

2009-11-10

80

Heat flux boundary anomalies and thermal winds  

NASA Astrophysics Data System (ADS)

Several studies have shown strong effects of outer boundary heat flux patterns on the dynamo mechanism in planets. For example, the hemispherical field of the ancient Martian dynamo can be explained by a large scale sinusoidal anomaly of the core mantle boundary heat flux triggered by large scale mantle convection or giant impacts. The magnetic fields show typically the desired effect - though dynamo action is locally stronger where the underneath heat flux is higher. However, it remains an open question if these effects still apply for more realistic planetary parameters, such as vigor of the convection (Rayleigh number) or the rotation rate (Ekman). The sinusoidal variation of the CMB heat flux along the colatitude with larger heat flux in the southern and smaller in the northern hemisphere as used for Mars can lead to a concentration of magnetic field in the south. The shape of such a hemispherical dynamo matches the crustal magnetization pattern at the surface and seems therefore an admissible mode for the ancient Martian dynamo. As the consequence of the emerging latitudinal temperature gradients convection and induction are dominated by thermal winds. These zonal flows were found to be equatorial antisymmetric, axisymmetric, ageostrophic, of strong amplitude and have therefore a severe effect on core convection and especially the induction process. We measure the underlying thermal anomalies as a function of Rayleigh and Ekman number and show that they are responsible for the thermal winds. Our results suggest that temperature anomalies decrease clearly with the supercriticality of the convection due to faster stirring and mixing, but show no additional dependence on the Ekman number. Interestingly, the decline of the latitudinal temperature anomaly follows a recently suggested scaling law for the thickness of thermal boundary layers. Even though the convective supercriticality of planetary cores is rather large and therefore only a minor effect of thermal boundary disturbances is expected, we suggest thermal winds can still significantly contribute to the total kinetic energy in real planetary core.

Dietrich, Wieland; Wicht, Johannes

2013-04-01

81

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

82

Coupled Heat Transfer in High Temperature Ceramic Wall with Heat Pipe under Aeroheating and Radiative Cooling  

Microsoft Academic Search

An effective heat transfer device such as heat pipe is used to reduce thermal stress and thermal gradients of inner material by transferring heat from one location to another with very large heat fluxes. Radiative transfer is important and complex at elevated temperature of the ceramic material. These temperatures in the two aeroheating regions and working fluid inside heat pipe

Du Shenghua; Ai Qing; Xia Xinlin

2010-01-01

83

Radiating spherical collapse with heat flow  

E-print Network

We present here a simple model of radiative gravitational collapse with radial heat flux which describes qualitatively the stages close to the formation of a superdense cold star. Starting with a static general solution for a cold star, the model can generate solutions for the earlier evolutionary stages. The temporal evolution of the model is specified by solving the junction conditions appropriate for radiating gravitational collapse.

M. Govender

2002-02-26

84

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

85

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

E-print Network

Surface energy budget over the South Pole and turbulent heat fluxes as a function of an empirical in the monthly mean surface energy budget and to investigate the behavior of turbulent heat fluxes under stable and one as the residual of the surface energy budget (i.e., subsurface heat fluxes minus net radiation

Walden, Von P.

86

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

87

NIST Measurement Services: Heat-Flux Sensor Calibration  

E-print Network

NIST Measurement Services: Heat-Flux Sensor Calibration NIST Special Publication 250-65 Benjamin K Special Publication 250-65 NIST MEASUREMENT SERVICES: Heat-Flux Sensor Calibration Benjamin K. Tsai Measurement Services: Heat-Flux Sensor Calibrations is a new publication. It covers the calibration of heat

88

Radiation from Kinetic Poynting Flux Acceleration  

E-print Network

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

Edison Liang; Koichi Noguchi

2007-04-13

89

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

90

Rainfall and Radiative Heating Rates from TOGA COARE Atmospheric Budgets  

Microsoft Academic Search

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

Richard H. Johnson; Paul E. Ciesielski

2000-01-01

91

Bubble dynamics in boiling under high heat flux pulse heating  

Microsoft Academic Search

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

A. Asai

1991-01-01

92

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

93

On the heating of the outer radiation belt to produce high fluxes of relativistic electrons: Measured heating rates at geosynchronous orbit for high-speed stream-driven storms  

Microsoft Academic Search

The heating rate of the outer electron radiation belt at geosynchronous orbit is determined for the interval from 36 to 72 h after the onset of high-speed stream-driven storms. Multisatellite measurements of the radiation belt temperature are used for 93 high-speed stream-driven storms. During the storms, the outer electron radiation belt temperature changes from ?120 keV to ?190 keV. The

Joseph E. Borovsky; Michael H. Denton

2010-01-01

94

On the heating of the outer radiation belt to produce high fluxes of relativistic electrons: Measured heating rates at geosynchronous orbit for high-speed stream-driven storms  

Microsoft Academic Search

The heating rate of the outer electron radiation belt at geosynchronous orbit is determined for the interval from 36 to 72 h after the onset of high-speed stream-driven storms. Multisatellite measurements of the radiation belt temperature are used for 93 high-speed stream-driven storms. During the storms, the outer electron radiation belt temperature changes from ˜120 keV to ˜190 keV. The

Joseph E. Borovsky; Michael H. Denton

2010-01-01

95

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

96

Interannual Variability in Meterrancan Heat and Buoyancy Fluxes  

Microsoft Academic Search

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

Curts Garrett; Richard Outerbridge; Keitu Thompson

1993-01-01

97

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

98

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

100

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

101

Convective heat flux in a laser-heated thruster  

NASA Technical Reports Server (NTRS)

An analysis is performed to estimate the convective heating to the wall in a laser-heated thruster on the basis of a solution of the laminar boundary-layer equations with variable transport properties. A local similiarity approximation is used, and it is assumed that the gas phase is in equilibrium. For the thruster described by Wu (1976), the temperature and pressure distributions along the nozzle are obtained from the core calculation. The similarity solutions and heat flux are obtained from the freestream conditions of the boundary layer, in order to determine if it is necessary to couple the boundary losses directly to the core calculation. In addition, the effects of mass injection on the convective heat transfer across the boundary layer with large density-viscosity product gradient are examined.

Wu, P. K. S.

1978-01-01

102

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

E-print Network

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks Weilin Qu Abstract Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 to predict the incipient boiling heat flux, accounting for the complexities of bubble formation along

Qu, Weilin

103

ANISOTROPIC COSMIC RADIATION FLUXES OF SOLAR ORIGIN  

Microsoft Academic Search

portant features of three cosmic-ray flare effects that were observed during the first thirty days of the flight of the Pioneer 6 spacecraft. It has been found that the cosmic radiation flux of mean energy 13 Mev\\/nucleon exhibited an extremely anisotropic character throughout each flare effect, the anisotropy persisting for in excess of 48 hours during one event. Subsequent flare

W. C. Bartley; R. P. Bukata; K. G. McCracken; U. R. Rao

1966-01-01

104

High Heat Flux Two-Phase Cooling in Silicon Multimicrochannels  

Microsoft Academic Search

This paper presents performances of two-phase cooling of a chip at very high heat flux with refrigerant R236fa in a silicon multimicrochannel heat sink. This heat sink was composed of 134 parallel channels, 67 mum wide, 680 mum high, and 20 mm long, with 92- mum -thick fins separating the channels. The base heat flux was varied from 3 to

Bruno Agostini; John Richard Thome; Matteo Fabbri; Bruno Michel

2008-01-01

105

High flux heat transfer in a target environment  

E-print Network

Valid for: Consider turbulent heat transfer in a 1.5mm diameter pipe ­ Dittus Boelter correlation ideas Hypervapotrons ·Water cooled finned heat exchangers developed to cope with the high heat fluxesHigh flux heat transfer in a target environment T. Davenne High Power Targets Group Rutherford

McDonald, Kirk

106

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

Microsoft Academic Search

Land heat fluxes are one of the essential components of the water and energy cycles. Despite a large body of work, there is no systematic data analysis activity underway to produce a complete, phisically consistent, global, multi-decadal land heat flux data product. The GEWEX Radiation Panel (GRP) recently launched an activity, called LandFlux , to develop the needed capabilities to

C. Jimenez; C. Prigent; F. Aires

2009-01-01

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

Experimental Measurements of Temperature and Heat Flux in a High Temperature Black Body Cavity  

NASA Technical Reports Server (NTRS)

During hypersonic flight, high temperatures and high heat fluxes are generated. The Flight Loads Laboratory (FLL) at Dryden Flight Research Center (DFRC) is equipped to calibrate high heat fluxes up to 1100 kW/sq m. There are numerous uncertainties associated with these heat flux calibrations, as the process is transient, there are expected to be interactions between transient conduction, natural and forced convection, radiation, and possibly an insignificant degree of oxidation of the graphite cavity. Better understanding, of these mechanisms during the calibration process, will provide more reliable heat transfer data during either ground testing or flight testing of hypersonic vehicles.

Abdelmessih, Amanie N.

1998-01-01

109

Radiative heat transfer in nonisothermal combustion products  

NASA Astrophysics Data System (ADS)

Radiative heat transfer plays a significant and sometimes dominant role within combustion systems. Heat flux measurements in such systems are sometimes economically disadvantaged and difficult, if not impractical to perform. To demonstrate a feasible alternative, a simplified numerical model using total transmittance data, TTNH, was developed for predicting the heat flux from nonisothermal combustion systems containing variable concentrations of water vapor, carbon dioxide, and methane. Total and spectral experimental measurements were carried out, to test the numerical model, using nonisothermal mixtures of water vapor/carbon dioxide and methane/ethene, and using isothermal mixtures of methane and ethene. In general, the TTNH model was found to be reliable to predict the total emitted energy by nonisothermal mixtures of carbon dioxide and water vapor within 10%. However, the model was found not reliable to predict the theoretical emittance of methane.

Hamdan, M. A.

1985-12-01

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

Critical heat flux around strongly-heated nanoparticles Samy Merabia1  

E-print Network

Critical heat flux around strongly-heated nanoparticles Samy Merabia1 , Pawel Keblinski2 , Laurent interfaces, where a critical heat flux is observed followed by development of a vapor layer and heat flux to the nanoparticle, which inhibits boiling. When the nanoparticle temperature is much larger than the critical fluid

Boyer, Edmond

114

Heat flux measurement in SSME turbine blade tester  

NASA Technical Reports Server (NTRS)

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, Curt H.

1990-01-01

115

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

116

Convectively driven shear and decreased heat flux  

E-print Network

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

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

2014-01-01

117

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

118

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

Microsoft Academic Search

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

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

1986-01-01

119

Experimental Performance of a Micromachined Heat Flux Sensor  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

120

Designing, testing, and analyzing coupled, flux transformer heat  

E-print Network

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

Renzi, Kimberly Irene

2012-06-07

121

Determination of the relaxtion time on a heat flux  

SciTech Connect

A method for determining the relaxation time of a heat flux is suggested for some nonlinear boundary-value problems of heat transfer. Modern representations of the applied theory of dynamical systems are employed.

Krasnyuk, I.B.; Riskiev, T.T. [S.V. Starodubtsev Physicotechnical Inst. Tashkent (Uzbekistan)

1995-04-01

122

Transient critical heat flux and blowdown heat-transfer studies  

SciTech Connect

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

Leung, J.C.

1980-05-01

123

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

124

Heat Flux and Static Stability Predictions of the Expert Vehicle  

NASA Astrophysics Data System (ADS)

The EXPERT vehicle is currently being designed to flight-test state-of-the-art instrumentation to measure transition, catalysis and real gas effects during hypersonic reentry. This paper focuses on two design issues of the EXPERT vehicle: the TPS heat flux predictions and the stability of the configuration in the transonic regime. For accuracy, the in-flight measurements require a clean, non-polluted flow field around the vehicle which motivates the use of nonablative high temperature TPS. Currently, the nose and flaps are covered with C-SiC materials, previously developed to fly on the X38 demonstrator. The rest of the vehicle is to be covered with a nickel-chromium alloy (dubbed PM1000), representative of state-of-the-art hot structure materials. The occurrence of different catalytic properties of both materials results in a significant heat flux overshoot at the C-SiC nose and PM1000 aft body junction. The magnitude of the computed overshoot justifies a thorough analysis of its implications for the design even at the current early stage of the study. Indeed, heat fluxes exceeding those computed by assuming a fully catalytic vehicle have been evidenced and are reported in this article. Aerothermal environment predictions for the EXPERT vehicle for the nominal 5 and 6 km/s re-entry trajectories, assuming radiative equilibrium, and the associated catalysis effects are presented. Finally, the static stability of the vehicle is addressed in the supersonic and transonic regime in order to assess the suitability of a transonic or supersonic descent system activation. Key words: transonic; catalysis; hypersonic.

Walpot, L.; Ottens, H.; Muylaert, J.-M.; Bayle, O.; Urmston, P.; Thomas, U.; Saccoccia, G.; Caporicci, M.; Stavrinidis, C.

2005-02-01

125

Gravitational Collapse with Heat Flux and Gravitational Waves  

NASA Astrophysics Data System (ADS)

In this paper, we investigated the cylindrical gravitational collapse with heat flux by considering the appropriate geometry of the interior and exterior spacetimes. For this purpose, we matched collapsing fluid to an exterior containing gravitational waves.The effects of heat flux on gravitational collapse are investigated and matched with the results obtained by Herrera and Santos (Class. Quantum Gravity 22:2407, 2005).

Ahmad, Zahid; Ahmed, Qazi Zahoor; Awan, Abdul Sami

2013-10-01

126

Measurement of heat flux from steaming ground  

Microsoft Academic Search

The total thermal flux at the surface of ‘steaming ground’ consists of a convective and a conductive component, even in the absence of any visible steam discharge at the surface. The total flux and its convective component can be measured separately and directly using a water-filled ground calorimeter. The conductive component is given by the difference between the two fluxes,

Manfred P. Hochstein; Christopher J. Bromley

2005-01-01

127

Tracking heat flux sensors for concentrating solar applications  

DOEpatents

Innovative tracking heat flux sensors located at or near the solar collector's focus for centering the concentrated image on a receiver assembly. With flux sensors mounted near a receiver's aperture, the flux gradient near the focus of a dish or trough collector can be used to precisely position the focused solar flux on the receiver. The heat flux sensors comprise two closely-coupled thermocouple junctions with opposing electrical polarity that are separated by a thermal resistor. This arrangement creates an electrical signal proportional to heat flux intensity, and largely independent of temperature. The sensors are thermally grounded to allow a temperature difference to develop across the thermal resistor, and are cooled by a heat sink to maintain an acceptable operating temperature.

Andraka, Charles E; Diver, Jr., Richard B

2013-06-11

128

Basic study of radiative and convective heat exchange in a room with floor heating  

SciTech Connect

Radiative heat exchange is a dominant factor in a room with a heated floor. Convective heat exchange is also important because it is increased by air circulation caused by natural convection. Surface temperatures inside the room increase when surfaces receive radiative heat flux originating from the heated floor. Since convective heat exchange takes place between the room air and the inside surfaces, it directly affects the room air temperature. Although radiative heat exchange does not influence room air temperature directly, it decreases the temperature difference between inside surfaces. These behaviors determine the wall surface temperatures and the amount of heat flux between the room air and the inside surfaces. This paper presents several basic characteristics of heat transfer on inside surfaces and temperature and velocity distribution in a room with a heated floor. Basic experiments and numerical analysis on radiative and convective heat transfer were carried out. The following conclusions were obtained: (1) a floor heating experiment produces approximately uniform air temperature except near windows where cold drafts lower the air temperature; (2) numerical analysis qualitatively predicts this kind of room air temperature distribution within 1.8 F (1 C); (3) convective heat exchange constitutes approximately half of the total heat exchange based on numerical analysis.

Hanibuchi, Haruo [Sekisui House Ltd., Kizu, Kyoto (Japan); Hokoi, Shuichi [Kyoto Univ., Sakyo, Kyoto (Japan). Dept. of Architecture and Environmental Design

1998-10-01

129

The effect of ablation injection on radiative and convective heating  

NASA Technical Reports Server (NTRS)

A viscous shock-layer analysis is for calculating high energy equilibrium flow fields about blunt axisymmetric bodies is applied to the problem of massive ablation injection with radiation transport. A nongray radiation model is used that accounts for both line and continuum radiation. The solution method is direct and provides both stagnation and downstream solutions. Results for shock heated air show that phenolic-nylon injection is substantially more effective in reducing the wall radiant flux than air injection. Also, for large included body angles, the wall radiative flux and the coupled phenolic-nylon injection rate do not continue to decrease with increasing distance downstream.

Moss, J. N.

1974-01-01

130

Reduction of Peak Heat Fluxes by Supplying Heat to the Free Stream  

Microsoft Academic Search

A supersonic flow past a blunt body in the presence of an incident oblique shock wave is considered. It is shown that by supplying heat to the free stream it is possible substantially to reduce local heat flux peaks on the body surface. The integral heat flux on the body surface increases by only a small fraction of the heat

M. N. Kogan; M. A. Starodubtsev

2003-01-01

131

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

132

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

133

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

134

Effect of the radiative background flux in convection  

E-print Network

Numerical simulations of turbulent stratified convection are used to study models with approximately the same convective flux, but different radiative fluxes. As the radiative flux is decreased, for constant convective flux: the entropy jump at the top of the convection zone becomes steeper, the temperature fluctuations increase and the velocity fluctuations decrease in magnitude, and the distance that low entropy fluid from the surface can penetrate increases. Velocity and temperature fluctuations follow mixing length scaling laws.

A. Brandenburg; K. L. Chan; A. Nordlund; R. F. Stein

2005-08-18

135

Radiative fluxes in the troposphere from upper air meteorological data in Saudi Arabia  

SciTech Connect

An attempt is made to use the empirical type of parameterization scheme for the calculations of solar radiative fluxes and atmospheric heating or cooling rates in the troposphere by using observed upper air meteorological data. This type of parameterization scheme is useful in calculating the upper air heating/cooling rate for use in planetary boundary layer modeling and in the evaluation of the surface heat budget equation. The results presented in this paper are based on the upper air data collected between 1300 to 1500 Local Standard Time (LST) in Dhahran for the year 1989. The diurnal variation of vertical profiles of radiative fluxes and heating/cooling rates is calculated by changing the solar zenith angle. The diurnal variation of annually averaged solar radiation fluxes reaching the ground is compared with the observed values of solar radiative flux at Dhahran. The calculated values are in excellent agreement with the observed values in the morning and evening times. The scheme used in this paper can be used for obtaining solar radiative fluxes and atmospheric heating or cooling rates above the earth's surface at places where only upper air meteorological data is available.

Rehman, S.; Husain, T.; Halawani, T.O. (King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia))

1992-07-01

136

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

137

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

SciTech Connect

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

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

1999-05-14

138

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

139

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

140

Determination of pool boiling Critical Heat Flux enhancement in nanofluids  

E-print Network

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

Truong, Bao H. (Bao Hoai)

2007-01-01

141

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

142

Assessment of high-heat-flux thermal management schemes  

Microsoft Academic Search

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

Issam Mudawar

2000-01-01

143

Surface Radiative Fluxes in Sub-Sahel Africa  

Microsoft Academic Search

This paper reports results of observations of radiative fluxes measured in sub-Sahel Africa during a 2-yr period (1992-94). Shortwave radiation in the solar spectrum (0.2-4.0 m), photosynthetically active radiation (0.4-0.7 m), and longwave radiation (4.0-50.0 m) were observed. In this study, the annual variability and the effects of dust on these fluxes (in particular, on the ratio of photosynthetically active

F. Miskolczi; T. O. Aro; M. Iziomon; R. T. Pinker

1997-01-01

144

Modeling pyrolysis of wet wood under external heat flux  

Microsoft Academic Search

Experiments on the thermal decomposition of wet wood in air were carried out in this work. The samples (typically 100×100mm exposed surface, 15mm thick) of several species with moisture content from 5% to 30% were subjected to a uniform heat flux 20–70kWm?2. A one-dimensional pyrolysis model is proposed to examine the influence of heat flux, species and moisture content on

D. K. Shen; M. X. Fang; Z. Y. Luo; K. F Cen

2007-01-01

145

A novel approach to measuring heat flux in swimming animals  

Microsoft Academic Search

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

Kate Willis; Markus Horning

2005-01-01

146

Traces of stable and unstable manifolds in heat flux patterns  

SciTech Connect

Experimental observations of heat fluxes on divertor plates of tokamaks show typical structures (boomerang wings) for varying edge safety factors. The heat flux patterns follow from general principles of nonlinear dynamics. The pattern selection is due to the unstable and stable manifolds of the hyperbolic fixed points of the last intact island chain. Based on the manifold analysis, the experimental observations can be explained in full detail. Quantitative results are presented in terms of the penetration depths of field lines.

Wingen, A.; Jakubowski, M.; Spatschek, K. H.; Abdullaev, S. S.; Finken, K. H.; Lehnen, M. [Institut fuer Theoretische Physik, Heinrich-Heine-Universitaet Duesseldorf, D-40225 Duesseldorf (Germany); Institut fuer Plasmaphysik, Forschungszentrum Juelich GmbH, EURATOM Association, Trilateral Euregio Cluster, D-52425 Juelich (Germany); Institut fuer Theoretische Physik, Heinrich-Heine-Universitaet Duesseldorf, D-40225 Duesseldorf (Germany); Institut fuer Plasmaphysik, Forschungszentrum Juelich GmbH, EURATOM Association, Trilateral Euregio Cluster, D-52425 Juelich (Germany)

2007-04-15

147

Characterization of local heat fluxes around ICRF antennas on JET  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

148

Explosive boiling at very low heat fluxes: A microgravity phenomenon  

SciTech Connect

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

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

1993-11-01

149

Explosive Boiling at Very Low Heat Fluxes: A Microgravity Phenomenon  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

150

MAPPING HIGH-RESOLUTION LAND SURFACE RADIATIVE FLUXES FROM MODIS  

E-print Network

pollution (Wang K. et al. 2009), and land cover and land use changes (Wang et al. 2007b). The SRB is alsoChapter 6 MAPPING HIGH-RESOLUTION LAND SURFACE RADIATIVE FLUXES FROM MODIS: ALGORITHMS-Chee Tsay, Robert Wolf, Crystal Schaaf, Alan Strahler 6.1 Introduction Land surface radiative fluxes

Liang, Shunlin

151

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

E-print Network

Sensible heat flux estimation by flux variance and half-order time derivative methods Karen H-order time derivative, over a wide range of atmospheric stability and surface roughness conditions. These two well for unstable atmospheric conditions. The half-order time derivative method was found

Katul, Gabriel

152

Surface Energy Heat Fluxes Using Remotely Sensed Parameters  

NASA Technical Reports Server (NTRS)

Realistic estimates of surface energy heat fluxes are needed for the study of water and energy interactions between the land and atmosphere. The primary objective of this work is to study the estimation of surface heat energy fluxes using remote sensing derived parameters under different spatial and temporal conditions. Surface energy fluxes and remote sensing derived data from two sources were analyzed. First, we used surface heat flux, remote sensing, and ancillary data from the International Satellite Land Surface Climatology Project (ISLSCP), mapped at a 1 deg. x 1 deg. grid. Second, we used NOAA AVHRR (1 km), weather station, and ancillary data to derive estimates of surface latent and sensible heat energy fluxes over a 100 sq kilometers area for three test sites: 1) First ISLSCP Field Experiment (FIFE) grassland site, Konza Prairie, Kansas; 2) Howland, Maine Forest Ecosystem Dynamics Site; and 3) Walnut Gulch, scrubland site, surrounding Tombstone, Arizona. Satellite derived estimates of land surface temperature, surface albedo, and spectral vegetation index are used in selected models to provide estimates of surface heat fluxes. Analysis of results from the 1 deg. x 1 deg. grid for North America indicated there were similar, overall correlations between sensible and latent heat energy fluxes versus remotely sensed vegetation index and ground temperature during dry and wet year conditions. However, there were significant differences in correlations between years when stratified by land cover class. Analysis of 100 km x 100 km data (1 km resolution) indicated partitioning the areas in to primary versus secondary cover, with the secondary cover comprising less than 5% of the area, significantly improved surface heat energy flux estimates.

Toll, David L.; Vukovich, Fred M.; Pontikes, Elizabeth G.

1997-01-01

153

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

154

High-Resolution Satellite-Derived Dataset of the Surface Fluxes of Heat, Freshwater, and Momentum for the TOGA COARE IOP  

Microsoft Academic Search

An integrated approach is presented for determining from several different satellite datasets all of the components of the tropical sea surface fluxes of heat, freshwater, and momentum. The methodology for obtaining the surface turbulent and radiative fluxes uses physical properties of the atmosphere and surface retrieved from satellite observations as inputs into models of the surface turbulent and radiative flux

J. A. Curry; C. A. Clayson; W. B. Rossow; R. Reeder; Y.-C. Zhang; P. J. Webster; G. Liu; R.-S. Sheu

1999-01-01

155

Time and space resolved wall temperature and heat flux measurements during nucleate boiling with constant heat flux boundary conditions  

Microsoft Academic Search

The lack of time and space resolved measurements under nucleating bubbles has complicated efforts to fully explain pool-boiling phenomena. In this work, time and space resolved temperature and heat flux distributions under nucleating bubbles on a constant heat flux surface were obtained using a 10×10 microheater array with 100?m resolution along with high-speed images. A numerical simulation was used to

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

2005-01-01

156

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

E-print Network

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

Phillips, Bren Andrew

2011-01-01

157

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

NASA Astrophysics Data System (ADS)

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 (PLOSS), plasma current (Ip), and magnetic flux expansion (fexp), 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 ˜0.7 and higher Ip ? 1.2 MA. First we note that the mid-plane heat flux width mapped to the mid-plane, ?qmid, is largely independent of PLOSS for PLOSS ? 4 MW. ?qmid is also found to be relatively independent of fexp; peak heat flux is strongly reduced as fexp is increased, as expected. Finally, ?qmid is shown to strongly contract with increasing Ip such that ?qmid?Ip-1.6 with a peak divertor heat flux of qdiv, peak ˜ 15 MW/m2 when Ip = 1.2 MA and PLOSS ˜ 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, Bt = 1.0 T and Ip = 2.0 MA for 5 s.

Gray, T. K.; Maingi, R.; Soukhanovskii, V. A.; Surany, J. E.; Ahn, J.-W.; McLean, A. G.

2011-08-01

158

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

159

Warming Asymmetries due to Surface Turbulent Heat Flux Feedbacks in IPCC AR4 Climate Simulations  

NASA Astrophysics Data System (ADS)

We use the newly developed Climate Feedback Response Analysis Model (CFRAM) to evaluate the coupled atmosphere-surface temperature changes due to the surface latent and sensible heat flux feedbacks in IPCC AR4 climate simulations. The CFRAM enables us to examine the warming patterns due to both feedbacks that directly affect the TOA radiative fluxes and feedbacks that do not, such as evaporation and surface sensible flux feedbacks. We estimate the surface flux feedback patterns from the difference between the 2×CO2 and control experiments. The temperature changes attributable to the surface sensible heat flux feedback are positive over the ocean with maximum values over the southern ocean and northern hemisphere gulf currents. Over land, the surface sensible heat flux feedback causes a reduction of surface warming over southern Africa, the northeastern part of South America and around the northern hemisphere mid-latitudes, corresponding to a negative feedback. The temperature response attributable to the evaporation feedback is a warming over land with the exception of the equatorial Africa and the mid to high latitudes of the northern hemisphere. Over oceans, the evaporation feedback is negative, causing a reduction of sea surface warming except over the equatorial Pacific Ocean where the evaporation feedback is positive. Overall, the effects of evaporation and surface sensible flux feedbacks tend to cancel one another. The net temperature change patterns in response to total surface flux feedbacks are positive in the mid-latitudes, Arctic region, and equatorial Pacific, but negative in sub-tropics and over Antarctica.

Castet, C.; Lu, J.; Cai, M.

2007-12-01

160

High heat flux measurements and experimental calibrations/characterizations  

NASA Technical Reports Server (NTRS)

Recent progress in techniques employed in the measurement of very high heat-transfer rates in reentry-type facilities at the Arnold Engineering Development Center (AEDC) is described. These advances include thermal analyses applied to transducer concepts used to make these measurements; improved heat-flux sensor fabrication methods, equipment, and procedures for determining the experimental time response of individual sensors; performance of absolute heat-flux calibrations at levels above 2,000 Btu/cu ft-sec (2.27 kW/cu cm); and innovative methods of performing in-situ run-to-run characterizations of heat-flux probes installed in the test facility. Graphical illustrations of the results of extensive thermal analyses of the null-point calorimeter and coaxial surface thermocouple concepts with application to measurements in aerothermal test environments are presented. Results of time response experiments and absolute calibrations of null-point calorimeters and coaxial thermocouples performed in the laboratory at intermediate to high heat-flux levels are shown. Typical AEDC high-enthalpy arc heater heat-flux data recently obtained with a Calspan-fabricated null-point probe model are included.

Kidd, Carl T.

1992-01-01

161

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

162

A diagnostic for quantifying heat flux from a thermite spray  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

163

Advanced Micro-Heat Exchangers for High Heat Flux  

Microsoft Academic Search

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

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

2007-01-01

164

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

165

Thermal response of a flat heat pipe sandwich structure to a localized heat flux  

E-print Network

Thermal response of a flat heat pipe sandwich structure to a localized heat flux G. Carbajal a , C The temperature distribution across a flat heat pipe sandwich structure, subjected to an intense localized thermal to the evaporator side of the flat heat pipe, while the condenser side was cooled via natural convective

Wadley, Haydn

166

An analytical study of pulsating laminar heat convection in a circular tube with constant heat flux  

E-print Network

). International Journal of Heat and Mass Transfer 47 (2004) 5297­5301 www.elsevier.com/locate/ijhmt #12 form 1 June 2004 Abstract Pulsating laminar convection heat transfer in a circular tube with constant for pulsating convection heat transfer in a circular tube with constant wall heat flux. � 2004 Elsevier Ltd. All

Zhao, Tianshou

167

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

E-print Network

.ijheatmasstransfer.2003.12.006 International Journal of Heat and Mass Transfer 47 (2004) 2045­2059 www merits of boiling in micro- channels are (1) very large convective heat transfer coefficients (i.e., lowMeasurement and correlation of critical heat flux in two-phase micro-channel heat sinks Weilin Qu

Qu, Weilin

168

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

169

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

170

Experimental verification of heat flux bending in multilayered thermal metamaterials  

NASA Astrophysics Data System (ADS)

We demonstrate heat flux bending in a multilayered composite considering an effective thermal medium approximation. We show that when the orientation of the composite is physically rotated with respect to the applied temperature gradient , that the resultant thermal conductivity tensor can be modified to be anisotropic, with non-zero off- diagonal elements. The resultant anisotropy was found to be dependent on the angle of rotation as well as the ratio of the thermal conductivities of the constituent materials. We experimentally demonstrate the bending of the heat flux in three such multilayered composites made by alternately stacking 2mm layers of copper ~ 391 W/mK and alloy steel ~ 42 W/mK respectively with three different rotation angles. We show that the resultant heat flux vectors in the composites are oriented at an angle with the applied temperature gradient , due to anisotropy in the thermal conductivity. Our experiments and analysis indicate that heat flux does not have to be collinear with the applied temperature gradient, e.g. the temperature gradient in a particular direction can drive heat flux in an orthogonal direction. Our studies have implications in thermal energy management with possible utility in portable electronics, nano-combustible systems, solar energy utilization etc.

Vemuri, Krishna P.; Canbazoglu, Fatih M.; Bandaru, Prabhakar R.

2014-09-01

171

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

172

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

173

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

174

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

Microsoft Academic Search

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

Xi Chen; E. Pfender

1982-01-01

175

Initial Tile Temperature and Heat Flux Measurements in NSTX  

NASA Astrophysics Data System (ADS)

Due to their compact nature, spherical tori are projected to experience higher peak heat flux than conventional aspect ratio tokamaks of comparable heating power. For NSTX, it has been predicted[1,2] that the peak heat flux in double-null divertor configuration could reach between 10-15 MW/m2, and single-null operation would result in even higher peak heat flux. To test these predictions and support physics operations, two infrared television cameras (Inframetrics 525) have been installed on NSTX to monitor real-time tile heating and surface heat flux. The data are analyzed in real-time with a frame grabber (IMAXX) and software, and these data are also archived on videotape for future analysis. The first set of measurements will focus on thermal emission from the RF antenna, the center stack, and divertor regions. Initial data and comparison with the earlier predictions will be presented. 1 R.Maingi, et. al., "Estimates of Scrape-Off Layer and Divertor Parameters in NSTX", Proc. 1996 Int’l Workshop on the Spherical Torus, Abingdon, U.K., Dec. 4-6, 1996. 2 R. Maingi, et. al., "2-D Edge Plasma Transport Calculations for NSTX", Proc. 1997 Int’l Workshop on the Spherical Torus, St. Petersburg, Russia, Sept. 3-5, 1997.

Maingi, Rajesh; Kugel, Henry; Roquemore, Lane; Lasnier, Charles; Johnson, Dave

1999-11-01

176

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

177

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

178

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

179

Development of Advanced Thermal and Environmental Barrier Coatings Using a High-Heat-Flux Testing Approach  

NASA Technical Reports Server (NTRS)

The development of low conductivity, robust thermal and environmental barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity and cyclic resistance at very high surface temperatures (up to 1700 C) under large thermal gradients. In this study, a laser high-heat-flux test approach is established for evaluating advanced low conductivity, high temperature capability thermal and environmental barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) program. The test approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity, which initially rises under the steady-state high temperature thermal gradient test due to coating sintering, and later drops under the cyclic thermal gradient test due to coating cracking/delamination. The coating system is then evaluated based on damage accumulation and failure after the combined steady-state and cyclic thermal gradient tests. The lattice and radiation thermal conductivity of advanced ceramic coatings can also be evaluated using laser heat-flux techniques. The external radiation resistance of the coating is assessed based on the measured specimen temperature response under a laser- heated intense radiation-flux source. The coating internal radiation contribution is investigated based on the measured apparent coating conductivity increases with the coating surface test temperature under large thermal gradient test conditions. Since an increased radiation contribution is observed at these very high surface test temperatures, by varying the laser heat-flux and coating average test temperature, the complex relation between the lattice and radiation conductivity as a function of surface and interface test temperature may be derived.

Zhu, Dongming; Miller, Robert A.

2003-01-01

180

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

181

Heat flux and mixing efficiency in the surface mixing layer  

NASA Astrophysics Data System (ADS)

Fluctuations of vertical velocity and temperature, w' and T', were measured with a horizontal profiler that was towed at night in the oceanic boundary layer between 15 and 25 m depth. Stratified and convective turbulent regimes were encountered along the tow path. A direct estimate of the turbulent heat flux F was computed from the correlation of w' and T'. The concurrent measurement of the dissipation rate of turbulent kinetic energy ? allowed us to estimate the mixing efficiency ?0 = F/F?, where F? was the heat flux estimate based on the average dissipation rate. In regions where the turbulence in the stratified boundary layer was sustained by shear instabilities 0.08 ? ?0 ? 1.38. The average was ?¯0=0.46, a value close to the maximum mixing efficiency predicted by classical scaling arguments and laboratory results. The measurements of w' were significantly influenced by instrument motions and the orbital velocities induced by surface waves. A motion correction algorithm made it possible to resolve overturning length scales up to 33 m and thus to capture all scales that contributed to the heat flux F. For the surface mixing layer reported here the largest flux-supporting scales were ˜14 m. For the stably stratified regimes in particular the peak of the heat flux cospectrum was at one half of the Ozmidov wave number, 0.5ko.

Wolk, Fabian; Lueck, Rolf G.

2001-09-01

182

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

183

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

184

Heat flux instrumentation for Hyflite thermal protection system  

NASA Technical Reports Server (NTRS)

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.

1994-01-01

185

Offline GCSS Intercomparison of Cloud-Radiation Interaction and Surface Fluxes  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

186

Miniature high temperature plug-type heat flux gauges  

NASA Technical Reports Server (NTRS)

The objective is to describe continuing efforts to develop methods for measuring surface heat flux, gauge active surface temperature, and heat transfer coefficient quantities. The methodology involves inventing a procedure for fabricating improved plug-type heat flux gauges and also for formulating inverse heat conduction models and calculation procedures. These models and procedures are required for making indirect measurements of these quantities from direct temperature measurements at gauge interior locations. Measurements of these quantities were made in a turbine blade thermal cycling tester (TBT) located at MSFC. The TBT partially simulates the turbopump turbine environment in the Space Shuttle Main Engine. After the TBT test, experiments were performed in an arc lamp to analyze gauge quality.

Liebert, Curt H.

1992-01-01

187

Experimental Validation of Thermal Model of Counter Flow Microchannel Heat Exchangers Subjected to External Heat Flux  

Microsoft Academic Search

The effect of uniform external heat flux on the effectiveness of counter flow microchannel heat exchangers is experimentally studied in this article for validating an existing thermal model. The model validated in this study is a one dimensional model previously developed by the same authors. The model is validated to be independent of microchannel profile, hydraulic diameter, and heat capacity

Bobby Mathew; Hisham Hegab

2013-01-01

188

Intermittent Heating of the Solar Corona by Heat Flux-generated Ion Cyclotron Waves  

Microsoft Academic Search

Recently, we suggested that the source of ion heating in solar coronal holes is small-scale reconnection events (microflares) at the coronal base. The microflares launch intermittent heat flux up into the corona exciting ion cyclotron waves through a plasma microinstability. The ions are heated by these waves during the microflare bursts and then evolve with no energy input between the

S. A. Markovskii; Joseph V. Hollweg

2004-01-01

189

Dynamic method for measuring heat fluxes with battery-powered heat meters, using the Kalman filter  

Microsoft Academic Search

The paper deals with the problem of determining steady heat fluxes from temperature measurements made at individual points of the sensitive element of a battery-powered heat meter. An approximate model of a heat meter, consisting of a system of ordinary differential equations is derived by the method of straight lines with a view toward the application of the Kalman filter

A. S. Goltsov; D. F. Simbirskii; S. V. Kudriashov

1977-01-01

190

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

191

Strongly coupled radiative transfer and Joule heating in the cathode of an arc heater  

NASA Technical Reports Server (NTRS)

Radiation and Joule heating in the electrode region of an arc heater are discussed. Radiative transport equations for a true axisymmetric geometry are used. A subsonic code is developed to numerically solve the fluid equations with strongly coupled radiation and Joule heating representative of a high pressure and high current arc heater. Analytic expression for the divergence of radiative heat flux derived previously is used. Jacobians of the radiation term are derived. The Joule heating term is computed using a previously developed code. The equilibrium gas model consists of seven species. The fluxes are differenced using Van Leer flux splitting. Using this code, the effects of radiative cooling on the thermodynamic parameters of the arc core are discussed.

Durgapal, P.; Palmer, Grant E.

1993-01-01

192

The effect of heated wall thickness and materials on nucleate boiling at high heat flux  

SciTech Connect

The nucleate boiling heat transfer at high heat flux is of significant importance in many applications. The present work is to numerically investigate the effect of heater side factors on the nucleate boiling at high heat flux, which is characterized by the existence of macrolayer. Two-region equations are proposed to study both thermo-capillary driven flow in the liquid layer and heat conduction in the solid wall. The numerical results indicate that the thermo-capillary driven flow in the macrolayer and evaporation at the vapor-liquid interface constitute a very efficient heat transfer mechanism to explain the high heat transfer coefficient of nucleate boiling heat transfer near CHF. For a very thin wall and/or wall with a poor thermal conductivity (heat side factors) are found to have significant effect on flow pattern in the liquid layer and the temperature distribution in the heated wall.

Ma, K.T.; Pan, C.

1999-11-01

193

Transverse flux induction heating of aluminum alloy strip  

NASA Astrophysics Data System (ADS)

Transverse flux induction heating, an efficient electrical technique particularly suited to the continuous heat treatment of metal strip, is explained. Also described is a 1MW transverse flux inductor designed and built at the Electricity Council Research Centre, Capenhurst, and installed in a tension leveller line at Alcan Plate Ltd., Birmingham, UK. It has been successfully used for the continuous heat treatment of wide (1200-1250 mm) aluminum alloy strip, involving full and partial annealing at line speeds up to 2/ms as well as the solution treatment of certain high strength aluminum alloys. The advantages of this form of induction heating are compactness, controllability, hence ease of automation, and high efficiency. As a consequence, compared with existing batch and continuous heat treatment equipment, major economies in plant operation result due to reduced energy consumption as well as reduced capital and labor costs. The compactness of the technique allows the possibility of introducing transverse flux induction heat treatment furnaces into existing process lines.

Waggott, R.; Walker, D. J.; Gibson, R. C.; Johnson, R. C.

1981-07-01

194

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

195

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

196

Estimating sensible heat flux from radiometric temperature over crop canopy  

Microsoft Academic Search

The model devised by Lhommeet al. (1988) allows one to calculate the sensible heat flux over a homogeneous crop canopy from radiometric surface temperature by adding a so-called canopy aerodynamic resistance to the classical aerodynamic resistance calculated above the canopy. This model is reformulated in order to simplify the mathematical procedure needed to calculate this additional resistance. Analytical expressions of

J. P. Lhomme; N. Katerji; J. M. Bertolini

1992-01-01

197

Estimating sensible heat flux from radiometric temperature over crop canopy  

Microsoft Academic Search

The model devised by Lhomme et al. (1988) allows one to calculate the sensible heat flux over a homogeneous crop canopy from radiometric surface temperature by adding a so-called canopy aerodynamic resistance to the classical aerodynamic resistance calculated above the canopy. This model is reformulated in order to simplify the mathematical procedure needed to calculate this additional resistance. Analytical expressions

J. P. Lhomme; N. Katerji; J. M. Bertolini

1992-01-01

198

Hybrid heat flux measurement system for solar central receiver evaluation  

Microsoft Academic Search

A hybrid heat flux measurement system has been designed, built and mounted on top of the SSPS-CRS tower at the Plataforma Solar de Almería (PSA) to measure the incident solar power that is concentrated by a heliostat field on the flat aperture of a central receiver. This device is composed of two measurement systems, one direct and the other indirect.

J. Ballestrín; R. Monterreal

2004-01-01

199

Estimation of wet surface evaporation from sensible heat flux measurements  

Microsoft Academic Search

A new method is proposed to estimate wet surface evaporation by means of measurements of sensible heat flux and of air temperature, relative humidity, and wind speed at one level only. This formulation is made possible by the linearization of the Bowen ratio, a common assumption in other methods, such as Penman's model and its derivatives. The method will be

Nikki Vercauteren; Elie Bou-Zeid; Hendrik Huwald; Marc B. Parlange; Wilfried Brutsaert

2009-01-01

200

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

201

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

202

Radiative heat transfer in plastic welding process  

Microsoft Academic Search

This paper deals with a novel CO2 laser plastic welding procedure developed from the point of view of heat transfer containing simultaneous radiation and conduction processes and also gives a brief review of plastic welding development to date. The principle and features are shown by both the experiments using CO2 laser as a radiation source and numerical simulation considering heat

Yasuo Kurosaki

2005-01-01

203

Radiative heat transfer in fire safety science  

Microsoft Academic Search

In fire safety science literature thermal radiation is commonly acknowledged as the dominant mode of heat transfer for medium or large scale fires, which determines the growth and spread of a number of fires. This paper is an attempt to overview the contribution of radiative heat transfer research to fire safety science over the last decade, and to highlight the

J. F. Sacadura

2005-01-01

204

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 percent Y203 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 percent Y2O3 or ZrO2-20 percent 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

205

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

206

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 percent Y2O3 specimens survived 3000 of the 0.5 sec cycles with falling. 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 1 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-2O percent 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

207

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

208

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

209

Measurements and heat-flux transport modelling in a heated cylinder wake  

Microsoft Academic Search

Hot-wire measurements of velocity and temperature fluctuations have been made in the self-preserving turbulent wake region of a heated cylinder. Second order statistics including Reynolds fluxes, ui?, are determined along with relevant triple correlations appearing in the Reynolds stress and Reynolds flux transport equations. The primary aim with these measurements is to study different modelling levels for passive scalar quantities.

Petra M. Wikström; Magnus Hallbäck; Arne V. Johansson

1998-01-01

210

Spatial Variability of Surface Radiation Fluxes in Mountainous Terrain.  

NASA Astrophysics Data System (ADS)

This paper investigates the magnitude and causes of spatial variability of surface radiative fluxes in a complex alpine landscape in the Southern Alps of New Zealand. Radiative flux components are simulated for the Tekapo watershed at 100-m resolution for clear-sky summer days, using a surface radiation budget model in conjunction with satellite imagery and topographic modeling to derive surface parameters. Overall, the model results agree well with observations made at a range of sites, with shortwave fluxes simulated more accurately than longwave fluxes. Sensitivity studies were conducted to isolate the role of spatial variability of surface characteristics in generating variance in the radiation budget. In order of most to least important, these characteristics were found to be slope aspect, slope angle, elevation, albedo, shading, sky view factor, and leaf area index. Spatial variability was greatest in midmorning and midafternoon, as a function of optical depth. The role of landscape complexity in the spatial distribution of fluxes was investigated by considering three subareas of the watershed that contain strongly contrasting scales of autocorrelation of topography and surface cover. Increase in topographical complexity yielded a small decrease in spatial average net radiation and a large increase in spatial standard deviation, driven most significantly by incident shortwave radiation. The regional averages scaled more or less linearly, whereas subregional-scale spatial variability differed dramatically.

Oliphant, A. J.; Spronken-Smith, R. A.; Sturman, A. P.; Owens, I. F.

2003-01-01

211

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

212

Temperature and heat flux spectra in the turbulent buoyancy subrange  

NASA Astrophysics Data System (ADS)

The physical nature of motions with scales intermediate between approximately isotropic turbulence and quasi-linear internal gravity waves is not understood at the present time. Such motions play an important role in the energetics of small scales processes, both in the ocean and in the atmosphere, and in vertical transport of heat and constituents. This scale range is currently interpreted either as a saturated gravity waves field or as a buoyancy range of turbulence. We first discuss some distinctive predictions of the classical (Lumley, Phillips) buoyancy range theory, recently improved (Weinstock, Dalaudier and Sidi) to describe potential energy associated with temperature fluctuations. This theory predicts the existence of a spectral gap in the temperature spectra and of an upward mass flux (downward buoyancy and heat fluxes), strongly increasing towards large scales. These predictions are contrasted with an alternate theory, assuming “energetically insignificant” buoyancy flux, proposed by Holloway. Then we present experimental evidences of such characteristic features obtained in the lower stratosphere with an instrumented balloon. Spectra of temperature, vertical velocity, and cospectra of both, obtained in homogeneous, weakly turbulent regions, are compared with theoretical predictions. These results are strongly consistent with the improved classical buoyancy range theory and support the existence of a significant downward heat flux in the buoyancy range. The theoretical implications of the understanding of this scale range are discussed. Many experimental evidences consistently show the need for an anisotropic theory of the buoyancy range of turbulence.

Sidi, C.; Dalaudier, F.

1989-06-01

213

Feedbacks of biotically induced radiative heating on upper-ocean heat budget, circulation, and biological production in a coupled ecosystem-circulation model  

Microsoft Academic Search

A coupled ecosystem-circulation model of the North Atlantic Ocean is used to investigate the impact of radiative heating by biotically induced absorption of solar radiation on the ocean's heat budget, on water column stability and circulation, and on biological production itself. For fixed atmospheric conditions, the local sensitivity of the nonsolar heat flux to changes in sea surface temperature leads

Andreas Oschlies

2004-01-01

214

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

NASA Technical Reports Server (NTRS)

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

Stein, Carol A.; Stein, Seth

1994-01-01

215

Temperature and Heat Flux Estimation from Sampled Transient Sensor Measurements Z. C. Feng 1  

E-print Network

Page 1 Temperature and Heat Flux Estimation from Sampled Transient Sensor Measurements Z. C. Feng to calculate the front surface heat input (temperature and heat flux) from the back surface measurements (temperature and/or heat flux) when the front surface measurements are not feasible to obtain. This paper

Montgomery-Smith, Stephen

216

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

217

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

218

Nonlinear aspects of high heat flux nucleate boiling heat transfer  

SciTech Connect

This paper deals with potential nonlinear effects in nucleate boiling systems as a result of the behavior of individual nucleation sites on the heater surface. This requires detailed microscopic modeling of the surface. A computational model has been formulated for this purpose. The model addresses the three-dimensional transient conduction heat transfer process within the problem domain comprised of the macrolayer and heater. Hydrodynamic effects are represented through boundary conditions. Individual nucleation sites are activated or deactivated depending on the thermal conditions that prevail at the site. The model has been used to examine the behavior of sites on a realistic heater surface. 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 intermittently. Surface-averaged temperatures show nonlinear period-doubling behavior. A chaotic case was found. Qualitative comparisons are made to both local instantaneous temperature measurements and recent experiments that showed chaotic behavior. We believe that such nonlinear behavior is one of the reasons that mechanistic predictive capabilities for the boiling process have remained elusive. 29 refs., 8 figs., 2 tabs.

Sadasivan, P.; Unal, C.; Nelson, R. [Los Alamos National Lab., NM (United States)

1995-11-01

219

Study of Dryout Heat Fluxes in Beds of Inductively Heated Particles.  

National Technical Information Service (NTIS)

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 ...

I. Catton, V. K. Dhir

1977-01-01

220

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

221

MERLOT: a model for flow and heat transfer through porous media for high heat flux applications  

E-print Network

MERLOT: a model for flow and heat transfer through porous media for high heat flux applications A media infiltrated by the coolant. The general design strategy is to minimize the coolant flow path-cooled porous media configuration for plasma facing component application. # 2002 Elsevier Science B.V. All

Raffray, A. René

222

Round-Robin Test of Heat Flux Sensors  

NASA Astrophysics Data System (ADS)

The first intercomparison on the density of heat flow-rate measurements has been organized by MKEH (Hungarian Trade Licensing Office, Metrology Division) within the framework of EUROMET (Project No. 426). This round-robin test gives evidence about the measurement capabilities of the local realizations of a density of a heat flow-rate scale up to 100 W · m-2. Two types of heat flux plate sensors differing in their size were circulated among partner laboratories. Each one of the six partners calibrated the sensors using its own calibration system, a guarded hot plate or a heat flow meter apparatus. This article compares all the results of the round-robin test and gives the mutual differences among the partners. The participants could benefit from the measurement results by improving, in case of need, their calibration methods and procedures and by reducing their uncertainties. The impact of this comparison will go directly to the users in industry.

Turzo-Andras, E.; Blokland, H.; Hammerschmidt, U.; Rudtsch, S.; Stacey, C.; Krös, C.; Magyarlaki, T.; Nemeth, S.

2011-12-01

223

A microscale thermophoretic turbine driven by external diffusive heat flux.  

PubMed

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

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

2014-10-24

224

Method of fission heat flux determination from experimental data  

SciTech Connect

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, F.A.

1999-09-28

225

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. PMID:20368255

Wu, Wei; Liu, Yangang

2010-01-01

226

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

PubMed

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. PMID:20368255

Wu, Wei; Liu, Yangang

2010-05-12

227

Countergradient heat flux observations during the evening transition period  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

228

Eddy heat fluxes at Drake Passage due to mesoscale motions  

E-print Network

hours. His efforts can not be reoaid. TABLE OF CONTENTS ABSTRACT . ACKNOWLEDGEMENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION . l. Background . 2. Objectives of this Study OBSERVATIONS AND METHODS 1. Data Coverage 2, Calculations . RESULTS... OF RECORD-LENGTH EDDY HEAT FLUX CALCULATIONS DISCUSSION OF RESULTS 1, The 1979 FIow Field 2. Influence of a Single Frontal Shift 3. Influence of Individual Events SUMMARY AND CONCLUSIONS REFERENCES . . . . . . . . ' ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ APPENDIX...

Rojas Recabal, Ricardo Luis

2012-06-07

229

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

230

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

231

Nonstationarity of turbulent heat fluxes at Summit, Greenland  

Microsoft Academic Search

Turbulence data collected over a total of 25 days during two summers are used to describe processes responsible for the nonstationarity\\u000a of turbulent sensible heat fluxes at Summit, Greenland. A stationarity test shows that about 40% of the data are classified\\u000a as nonstationary. Three main factors are explored to account for the large fraction of nonstationary runs: (1) intermittency\\u000a of turbulence

Nicolas J. Cullen; Konrad Steffen; Peter D. Blanken

2007-01-01

232

Surface latent heat flux anomalies preceding inland earthquakes in China  

Microsoft Academic Search

Using data from the National Center for Environmental Prediction (NCEP), the paper analyzed the surface latent heat flux (SLHF)\\u000a variations for five inland earthquakes occurred in some lake area, moist area and arid area of China during recent years.\\u000a We used the SLHF daily and monthly data to differentiate the global and seasonal variability from the transient local anomalies.\\u000a The

Kai Qin; Guangmeng Guo; Lixin Wu

2009-01-01

233

A very high heat flux microchannel heat exchanger for cooling of semiconductor laser diode arrays  

Microsoft Academic Search

A low-cost, high heat flux heat exchanger for cooling of high power (of the order of 1000 W\\/cm2) semiconductor laser diode arrays has been designed and tested. The device uses a simple copper microchannel design to obtain very high fluid-to-wall heat transfer coefficients. Experimental results show that its overall thermal resistivity is less than 0.03°C\\/W, which is 2-3 times better

Sanjay K. Roy; Branko L. Avanic

1996-01-01

234

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

235

An overview of results from the GEWEX radiation flux assessment  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

236

Diapycnal heat flux and mixed layer heat budget within the Atlantic Cold Tongue  

NASA Astrophysics Data System (ADS)

Sea surface temperatures (SSTs) in the eastern tropical Atlantic are crucial for climate variability within the tropical belt. Despite this importance, state-of-the-art climate models show a large SST warm bias in this region. Knowledge about the seasonal mixed layer (ML) heat budget is a prerequisite for understanding SST mean state and its variability. Within this study all contributions to the seasonal ML heat budget are estimated at four locations within the Atlantic cold tongue (ACT) that are representative for the western (0°N, 23°W), central (0°N, 10°W) and eastern (0°N, 0°E) equatorial as well as the southern (10°S, 10°W) ACT. To estimate the contribution of the diapycnal heat flux due to turbulence an extensive data set of microstructure observations collected during ten research cruises between 2005 and 2012 is analyzed. The results for the equatorial ACT indicate that with the inclusion of the diapycnal heat flux the seasonal ML heat budget is balanced. Within the equatorial region, the diapycnal heat flux is essential for the development of the ACT. It dominates over all other cooling terms in the central and eastern equatorial ACT, while it is of similar size as the zonal advection in the western equatorial ACT. In contrast, the SST evolution in the southern ACT region can be explained entirely by air-sea heat fluxes.

Hummels, Rebecca; Dengler, Marcus; Brandt, Peter; Schlundt, Michael

2014-09-01

237

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

238

Radiative heat transfer in plastic welding process  

NASA Astrophysics Data System (ADS)

This paper deals with a novel CO2 laser plastic welding procedure developed from the point of view of heat transfer containing simultaneous radiation and conduction processes and also gives a brief review of plastic welding development to date. The principle and features are shown by both the experiments using CO2 laser as a radiation source and numerical simulation considering heat transfer phenomena in simultaneous radiation and conduction in welding process. The feasibility of the proposed procedure is confirmed by applying the overlapped same plastic films with combination of infrared radiation absorbing heating and thermal diffusion cooling processes. A solid material transparent to infrared radiation with a high thermal diffusivity is used as a heat sink in contact with the irradiated surface of overlapped thermoplastics during radiation heating. The procedure is able to achieve both high welding strength and excellent surface appearance without causing surface thermal damage as often suffered in conventional direct infrared radiation welding process. In addition, pigmentation in welding material to increase absorption of radiation is unnecessary for this method.

Kurosaki, Yasuo

2005-06-01

239

Greenhouse Micrometeorology and Estimation of Heat and Water Vapour Fluxes  

Microsoft Academic Search

Micrometeorological measurements were made within and above a potted stand of chrysanthemums in a conventional glasshouse, using high frequency sensors to detect airflow, temperature and humidity, quantum sensors to measure radiation and a digital weighing lysimeter to quantify transpiration. Analyses were conducted to evaluate the aerodynamic and thermal effects on heat and mass transfer from vegetation canopies to greenhouse air,

Xiusheng Yang

1995-01-01

240

Skyglow effects in UV and visible spectra: Radiative fluxes  

NASA Astrophysics Data System (ADS)

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

Kocifaj, Miroslav; Solano Lamphar, Hector Antonio

2013-09-01

241

Skyglow effects in UV and visible spectra: radiative fluxes.  

PubMed

Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment. PMID:23792881

Kocifaj, Miroslav; Solano Lamphar, H A

2013-09-30

242

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

243

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

244

Radiative heat transfer between neighboring particles  

NASA Astrophysics Data System (ADS)

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

Manjavacas, Alejandro; García de Abajo, F. Javier

2012-08-01

245

Longitudinal variation of tides in the MLT region: 2. Relative effects of solar radiative and latent heating  

E-print Network

) radiative fluxes (see part 1), Tropical Rainfall Measuring Mission (TRMM) latent heating profiles, and TRMM of the latent heating source vary from month to month and produce measurable diurnal amplitude variations (10 of solar radiative and latent heating Xiaoli Zhang,1 Jeffrey M. Forbes,1 and Maura E. Hagan2 Received 11

Forbes, Jeffrey

246

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

247

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

248

Efficient acceleration and radiation in Poynting flux powered GRB outflows  

Microsoft Academic Search

We investigate the effects of magnetic energy release by local magnetic dissipation processes in Poynting flux-powered GRBs. For typical GRB parameters (energy and baryon loading) the dissipation takes place mainly outside the photosphere, producing non-thermal radiation. This process converts the total burst energy into prompt radiation at an efficiency of 10-50%. At the same time the dissipation has the effect

G. Drenkhahn; H. C. Spruit

2002-01-01

249

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

250

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

Microsoft Academic Search

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

J. Quintiere; K. Bromberg

1975-01-01

251

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

E-print Network

A novel approach to measuring heat flux in swimming animals Kate Willis*, Markus Horning Laboratory measurements of heat flux from animal experiments to account for the thermal resistance of HFSs and insulative 22 September 2004 Abstract We present a design for long-term or removable attachment of heat flux

252

Fusion neutron test facility requirements for interactive effects in structural and high-heat-flux components  

NASA Astrophysics Data System (ADS)

A relevant design data base is needed for structural components in near-term and commercial fusion devices. A high-flux, high-fluence fusion neutron test facility is required for testing the failure mechanisms and lifetime-limiting features for first wall, blanket, and high-heat-flux components. We describe here the key aspects of the fusion environment which influence the response of structural and high-heat-flux components. In addition to test capabilities for fundamental radiation-effects phenomena, e.g., swelling, creep, embrittlement, and hardening, it is shown that the facility must provide an adequate range of conditions for accelerated tests to study the limitations on component lifetime due to the interaction between such fundamental phenomena. In high-heat-flux components, testing of the failure mechanisms of duplex structures is shown to require maintenance of an appropriate temperature gradient in the 14-MeV neutron field. Thermal stresses are shown to result in component failure, particularly when the degradation in the thermal conductivity and mechanical properties by irradiation are considered. Several factors are discussed for assessment of the failure modes of the first wall and blanket structures. These are displacement-damage dose and dose rate, the amount of helium gas generated, the magnitude of irradiation and thermal creep, prototypical temperature and temperature-gradient distributions, module geometry, and external mechanical constraints.

Ghoniem, N. M.; Whitley, J. B.

1989-12-01

253

Radiation and Convection from Heated Surfaces  

Microsoft Academic Search

The relative and absolute amounts of radiation and convection from surfaces heated to about 100°C. in air were measured as follows: steam was passed through the cylinders or spheres, the surface temperature being measured by a thermo-junction. The total amount of heat lost from the surface was determined from the equivalent mass of steam condensed. This was done with the

Major T Barratt; A J Scott

1919-01-01

254

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

255

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

256

Radiation heat transfer shapefactors for combustion systems  

NASA Technical Reports Server (NTRS)

The computation of radiation heat transfer through absorbing media is commonly done through the zoning method which relies upon values of the geometric mean transmittance and absorptance. The computation of these values is difficult and expensive, particularly if many spectral bands are used. This paper describes the extension of a scan line algorithm, based upon surface-surface radiation, to the computation of surface-gas and gas-gas radiation transmittances.

Emery, A. F.; Johansson, O.; Abrous, A.

1987-01-01

257

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

258

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

259

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

260

The Application of the Unit Sphere Method to the Computation of Radiant-Heat Flux for Medical Purposes  

Microsoft Academic Search

Investigations on the radiant-heat flux administered to patients by various types of clinical device led to the need for calculation of dosage. Calculation by ordinary methods is often tedious and complicated. Because the extended sources, such as `reflectors' and screens, which supply the greater part of the radiation are at a uniform temperature, it is possible to apply the unitsphere

D S Evans

1946-01-01

261

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

262

Heat Flux and Entropy Produced by Thermal Fluctuations  

NASA Astrophysics Data System (ADS)

We report an experimental and theoretical analysis of the energy exchanged between two conductors kept at different temperature and coupled by the electric thermal noise. Experimentally we determine, as functions of the temperature difference, the heat flux, the out-of-equilibrium variance, and a conservation law for the fluctuating entropy, which we justify theoretically. The system is ruled by the same equations as two Brownian particles kept at different temperatures and coupled by an elastic force. Our results set strong constraints on the energy exchanged between coupled nanosystems held at different temperatures.

Ciliberto, S.; Imparato, A.; Naert, A.; Tanase, M.

2013-05-01

263

The measurable heat flux that accompanies active transport Dick Bedeauxw and Signe Kjelstrupw  

E-print Network

The measurable heat flux that accompanies active transport by Ca2+ -ATPase Dick Bedeauxw and Signe how the measurable heat flux and the heat production under isothermal conditions, as well of measurements, that the heat production in active trans- port is significant and varies. These authors studied

Kjelstrup, Signe

264

Monte Carlo prediction of radiative heat transfer in inhomogeneous, anisotropic, nongray media  

NASA Technical Reports Server (NTRS)

A Monte Carlo solution technique has been formulated to predict the radiative heat transfer in three-dimensional, inhomogeneous participating media which exhibit spectrally dependent emission and absorption and anisotropic scattering. Details of the technique and selected numerical sensitivities are discussed. The technique was applied to a problem involving a medium composed of a gas mixture of carbon dioxide and nitrogen and suspended carbon particles. A homogeneous medium was modeled to examine the effect of total pressure and carbon-particle concentration on radiative heat transfer. Variation in total pressure, over the range studied, had minimal effect on the amount of heat radiated to the enclosure walls and on the radiative-flux distribution within the medium. Increases in the carbon particle concentration produced significantly higher heat fluxes at the boundaries and altered the radiative flux distribution. The technique was then applied to an inhomogeneous medium to examine effects of specific temperature and carbon particle concentration distributions on radiative heat transfer. For the inhomogeneous conditions examined, the largest radiative flux divergence occurs near the center of the medium and the regions near some enclosure walls act as energy sinks.

Farmer, Jeff T.; Howell, John R.

1994-01-01

265

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

266

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

267

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

268

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

E-print Network

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

269

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

270

Transectional heat transfer in thermoregulating bigeye tuna (Thunnus obesus) - a 2D heat flux model.  

PubMed

We developed a 2D heat flux model to elucidate routes and rates of heat transfer within bigeye tuna Thunnus obesus Lowe 1839 in both steady-state and time-dependent settings. In modeling the former situation, we adjusted the efficiencies of heat conservation in the red and the white muscle so as to make the output of the model agree as closely as possible with observed cross-sectional isotherms. In modeling the latter situation, we applied the heat exchanger efficiencies from the steady-state model to predict the distribution of temperature and heat fluxes in bigeye tuna during their extensive daily vertical excursions. The simulations yielded a close match to the data recorded in free-swimming fish and strongly point to the importance of the heat-producing and heat-conserving properties of the white muscle. The best correspondence between model output and observed data was obtained when the countercurrent heat exchangers in the blood flow pathways to the red and white muscle retained 99% and 96% (respectively) of the heat produced in these tissues. Our model confirms that the ability of bigeye tuna to maintain elevated muscle temperatures during their extensive daily vertical movements depends on their ability to rapidly modulate heating and cooling rates. This study shows that the differential cooling and heating rates could be fully accounted for by a mechanism where blood flow to the swimming muscles is either exclusively through the heat exchangers or completely shunted around them, depending on the ambient temperature relative to the body temperature. Our results therefore strongly suggest that such a mechanism is involved in the extensive physiological thermoregulatory abilities of endothermic bigeye tuna. PMID:19880733

Boye, Jess; Musyl, Michael; Brill, Richard; Malte, Hans

2009-11-01

271

Flow and Heat Transfer Characteristics of Turbulent Gas Flow in Microtube with Constant Heat Flux  

NASA Astrophysics Data System (ADS)

Local friction factors for turbulent gas flows in circular microtubes with constant wall heat flux were obtained numerically. The numerical methodology is based on arbitrary-Lagrangian-Eulerian method to solve two-dimensional compressible momentum and energy equations. The Lam-Bremhorst's Low-Reynolds number turbulence model was employed to calculate eddy viscosity coefficient and turbulence energy. The simulations were performed for a wide flow range of Reynolds numbers and Mach numbers with different constant wall heat fluxes. The stagnation pressure was chosen in such a way that the outlet Mach number ranged from 0.07 to 1.0. Both Darcy friction factor and Fanning friction factor were locally obtained. The result shows that the obtained both friction factors were evaluated as a function of Reynolds number on the Moody chart. The values of Darcy friction factor differ from Blasius correlation due to the compressibility effects but the values of Fanning friction factor almost coincide with Blasius correlation. The wall heat flux varied from 100 to 10000 W/m2. The wall and bulk temperatures with positive heat flux are compared with those of incompressible flow. The result shows that the Nusselt number of turbulent gas flow is different from that of incompressible flow.

Hong, Chungpyo; Asako, Yutaka; Matsushita, Shinichi; Ueno, Ichiro

2012-05-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

273

The Surface Heat Flux as a Function of Ground Cover for Climate Models  

NASA Technical Reports Server (NTRS)

Surface heat fluxes were examined as a function of surface properties and meteorological conditions in a 100 km x 100 km grid square at 1-km spatial resolution centered at the location of the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE), the Forest Ecosystem Dynamics site in central Maine, and a semiarid rangeland site around Walnut Gulch, Arizona. This investigation treats the surface heat flux variability within a GCM grid box to provide insight into methods for treating that variability in climate models. The heat fluxes were calculated using NOAA AVHRR and available meteorological data. The average heat fluxes that were estimated using the various area ground-cover representations were compared with the ensemble average heat fluxes for the entire area, which were assumed to be the best representation of the heat fluxes for the areas. Average beat fluxes were estimated for the entire 100 km x 100 km area based on a single ground-cover representation, and the mean error for the area sensible heat flux was about 10% and for the area latent heat flux, 21%. The estimation error was reduced, and in some cases significantly reduced, when the area heat fluxes were estimated by partitioning the area according to significant ground cover. The most significant effect of the partitioning was on the latent heat flux estimates.

Vukovich, Fred M.; Wayland, Robert; Toll, David

1997-01-01

274

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

275

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

276

Thermal performance of multilayer insulation. I - Derivation of a prediction-based heat-flux equation  

NASA Astrophysics Data System (ADS)

A prediction-based equation for heat flux through a multilayer insulator was derived from comparison of experimental results between room temperature and liquid nitrogen temperature. The employed multilayer insulator was a laminated material with a polyester net inserted between aluminized Mylar films. The prediction equation consists of one thermal radiation and two thermal conduction terms. The first conduction term is that of ordinary thermal contact conductance. The second conduction term depends on the self-compression of the multilayer insulation. The predicted values resulting from the obtained equation coincided fairly well with measured values.

Amano, Toshiyuki

1993-07-01

277

Radiatively heated high voltage pyroelectric crystal pulser  

NASA Astrophysics Data System (ADS)

Thin lithium tantalate pyroelectric crystals in a multi-stage pulser were heated by quartz lamps during their charging phase to generate high voltage pulses. The charging voltage was determined empirically based on the measured breakdown voltage in air and verified by the induced breakdown voltage of an external high voltage power supply. A four-stage pyroelectric crystal device generated pulse discharges of up to 86 kV using both quartz lamps (radiative) and thermoelectric (conductive) heating. Approximately 50 mJ of electrical energy was harvested from the crystals when radiatively heated in air, and up to 720 mJ was produced when the crystals were submerged in a dielectric fluid. It is anticipated that joule-level pulse discharges could be obtained by employing additional stages and optimizing the heating configuration.

Antolak, A. J.; Chen, A. X.; Leung, K.-N.; Morse, D. H.; Raber, T. N.

2014-01-01

278

Spatial distribution of air-sea heat fluxes over the sub-polar North Atlantic Ocean  

E-print Network

Spatial distribution of air-sea heat fluxes over the sub-polar North Atlantic Ocean G. W. K. Moore circulations. This is particularly true in the sub-polar North Atlantic Ocean, where these fluxes drive water-sea turbulent heat fluxes over the sub-polar North Atlantic Ocean. As has been previously recognized

Pickart, Robert S.

279

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

280

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

281

Buoyant magnetic flux tubes enhance radiation in Z pinches  

PubMed

In numerous experiments, magnetic energy coupled to strongly radiating Z-pinch plasmas exceeds the thermalized kinetic energy, sometimes by a factor of 2-3. We demonstrate that the enhanced energy coupling may be due to the buoyancy rise of toroidal magnetic flux tubes converging to the axis through the unstable pinch plasma. We derive an explicit formula for the enhanced dissipation rate and apply this formula to reconsider an old problem of power balance in a steady-state Z pinch, and then to analyze a new challenge of producing K-shell 3 to 10 keV radiation in long-pulse Z-pinch implosions. PMID:11019081

Rudakov; Velikovich; Davis; Thornhill; Giuliani; Deeney

2000-04-10

282

Heat flux calculations for Mackenzie and Yukon Rivers  

NASA Astrophysics Data System (ADS)

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

Yang, Daqing; Marsh, Philip; Ge, Shaoqing

2014-09-01

283

The surface latent heat flux anomalies related to major earthquake  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

284

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

E-print Network

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

Edwards, Bronwyn K

2009-01-01

285

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

286

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation  

Microsoft Academic Search

This study is to investigate the critical heat transfer characteristics of an insulated sphere considering heat radiation. It is found that the results considering heat radiation are very big different from those of neglecting heat radiation. The critical heat transfer characteristics deeply depend on the sphere surface emissivity, &Vegr;0, and insulation surface emissivity &Vegr;, surrounding temperature Tsur and the internal

King Leung Wong; Jose´ Luis Leo´n Salazar

2010-01-01

287

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation  

Microsoft Academic Search

This study is to investigate the critical heat transfer characteristics of an insulated sphere considering heat radiation. It is found that the results considering heat radiation are very big different from those of neglecting heat radiation. The critical heat transfer characteristics deeply depend on the sphere surface emissivity, epsilo0, and insulation surface emissivity V, surrounding temperature Tsur and the internal

King Leung Wong; José Luis León Salazar

2010-01-01

288

The development of a new direct-heat-flux gauge for heat-transfer facilities  

NASA Astrophysics Data System (ADS)

A new type of direct-heat-flux gauge (DHFG) comprising an insulating layer mounted on a metal substrate has been developed. The gauge measures the heat flux across the insulating layer by measuring the top surface temperature employing a sputtered thin-film gauge (TFG) and the metal temperature using a thermocouple. The TFGs are platinum temperature sensors with physical thickness less than 0.1 µm. They are instrumented on the insulating layer. The thermal properties and the ratio of the thickness over the thermal conductivity of the insulating layer have been calibrated. A detailed method of analysis for calculating the surface heat flux from DHFG temperature traces is presented. The advantages of the DHFG include its high accuracy, its wide range of frequency response (from dc to 100 kHz) and, most significantly, that there is no requirement for knowledge of the structure of the metal substrate. Since the metal substrate is of high conductivity, few thermocouples are required to monitor the small spatial variation of the metal temperature, whereas multiple thin-film gauges may be employed. The DHFGs have been applied to a gas turbine nozzle guide vane and tested in the Oxford Cold Heat Transfer Tunnel successfully.

Piccini, E.; Guo, S. M.; Jones, T. V.

2000-04-01

289

Sensitivity of Cenozoic Antarctic ice sheet variations to geothermal heat flux  

E-print Network

-long simulations spanning the transition is performed, with various geothermal heat flux magnitudes and spatial: Antarctica; Cenozoic; ice sheets; geothermal heat flow 1. Introduction Physical properties at the baseSensitivity of Cenozoic Antarctic ice sheet variations to geothermal heat flux David Pollard a

290

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

E-print Network

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

291

Neural Computation to Estimate Heat Flux in an Atmospheric Plasma Spray Process  

Microsoft Academic Search

Temperature is a key parameter in the thermal spray process and is a consequence of the heat flux experienced by the workpiece. This paper deals with the estimation of the heat flux transmitted to a workpiece from an atmospheric plasma spray torch during the preheating process often implemented in thermal spraying. An inverse heat conduction problem solution using a conjugate

Sofiane Guessasma; Deng Hao; Larbi Moulla; Hanlin Liao; Christian Coddet

2005-01-01

292

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

293

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

E-print Network

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

Bateni, Sayed Mohyeddin

2011-01-01

294

Scaling of shortwave radiation fluxes for sub grid topography  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

295

Retrieval of Surface Heat and Moisture Fluxes from Slow-launched Radiosondes.  

NASA Astrophysics Data System (ADS)

Recently, there has been growing emphasis on improving surface flux inputs to mesoscale models and general circulation models. Since there is presently no operational network providing this information, we have conducted a feasibility experiment to determine whether the Bowen ratio (and indirectly surface heat and moisture fluxes) can be reasonably and accurately derived from thermodynamic measurements obtained from balloon-launched radiosondes.The experiment took place during July 1988 at the Regional Airport in Tallahassee, Florida using an Atmospheric Instrumentation Research, Inc. (AIR) airsonde system and a surface radiation and energy budget station (SREBS) developed at Florida State University. The AIR system consists of a balloon-launched airsonde, which measures vertical profiles of atmospheric pressure, temperature, and relative humidity, and an automatic data acquisition system, which receives and records sensor output from the airsonde package. The SREBS is a compact, self-contained, battery-powered system used to measure approximately 100 surface parameters. For this experiment, the system was used to monitor in situ surface energy fluxes at the time of the radiosonde flights. The data recorded from the airsonde launches were used to create mixing-line profiles for each launch. Using the profiles, an objective technique for choosing the appropriate surface-layer mixing lines was developed, and from these the associated Bowen ratios within the surface layer were deduced.Intercomparisons were made between Bowen ratios derived from the airsonde profiles and the Bowen ratios measured directly by the surface radiation and energy budget station. The results show that this technique produces estimates of the Bowen ratios within 9% of measured values, and a sensitivity analysis indicates that estimates of sensible and latent heat fluxes have root-mean-square differences of less than 6 W m2.

Smith, Eric A.; Cooper, Harry J.; Crosson, William L.; Delorey, Donald D.

1991-12-01

296

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

297

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

298

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

NASA Astrophysics Data System (ADS)

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

Xiao, Bo-Qi

2013-01-01

299

Efficient acceleration and radiation in Poynting flux powered GRB outflows  

E-print Network

We investigate the effects of magnetic energy release by local magnetic dissipation processes in Poynting flux-powered GRBs. For typical GRB parameters (energy and baryon loading) the dissipation takes place mainly outside the photosphere, producing non-thermal radiation. This process converts the total burst energy into prompt radiation at an efficiency of 10-50%. At the same time the dissipation has the effect of accelerating the flow to a large Lorentz factor. For higher baryon loading, the dissipation takes place mostly inside the photosphere, the efficiency of conversion of magnetic energy into radiation is lower, and an x-ray flash results instead of a GRB. We demonstrate these effects with numerical one-dimensional steady relativistic MHD calculations.

Drenkhahn, G

2002-01-01

300

Efficient acceleration and radiation in Poynting flux powered GRB outflows  

NASA Astrophysics Data System (ADS)

We investigate the effects of magnetic energy release by local magnetic dissipation processes in Poynting flux-powered GRBs. For typical GRB parameters (energy and baryon loading) the dissipation takes place mainly outside the photosphere, producing non-thermal radiation. This process converts the total burst energy into prompt radiation at an efficiency of 10-50%. At the same time the dissipation has the effect of accelerating the flow to a large Lorentz factor. For higher baryon loading, the dissipation takes place mostly inside the photosphere, the efficiency of conversion of magnetic energy into radiation is lower, and an X-ray flash results instead of a GRB. We demonstrate these effects with numerical one-dimensional steady relativistic MHD calculations.

Drenkhahn, G.; Spruit, H. C.

2002-09-01

301

Efficient acceleration and radiation in Poynting flux powered GRB outflows  

E-print Network

We investigate the effects of magnetic energy release by local magnetic dissipation processes in Poynting flux-powered GRBs. For typical GRB parameters (energy and baryon loading) the dissipation takes place mainly outside the photosphere, producing non-thermal radiation. This process converts the total burst energy into prompt radiation at an efficiency of 10-50%. At the same time the dissipation has the effect of accelerating the flow to a large Lorentz factor. For higher baryon loading, the dissipation takes place mostly inside the photosphere, the efficiency of conversion of magnetic energy into radiation is lower, and an X-ray flash results instead of a GRB. We demonstrate these effects with numerical one-dimensional steady relativistic MHD calculations.

G. Drenkhahn; H. C. Spruit

2002-02-21

302

A laser-induced heat flux technique for convective heat transfer measurements in high speed flows  

NASA Technical Reports Server (NTRS)

A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

1991-01-01

303

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

304

Heat conduction in nanoscale materials: A statistical-mechanics derivation of the local heat flux  

NASA Astrophysics Data System (ADS)

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

Li, Xiantao

2014-09-01

305

Quantitative method for measuring heat flux emitted from a cryogenic object  

Microsoft Academic Search

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

Robert V

1993-01-01

306

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

307

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

NASA Astrophysics Data System (ADS)

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 ?t = 15-25%, a high bootstrap current fraction fBS = 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 ? = 2.2-2.4 and triangularity ? = 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 fm = 15-25 and the partial detachment of the outer strike point at several D2 injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Zeff 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, C III emission rates were measured.

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

2009-09-01

308

Critical Heat Flux In Inclined Rectangular Narrow Long Channel  

SciTech Connect

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

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

2005-05-01

309

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

310

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

311

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

E-print Network

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

Burg, Brian R.

312

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

313

Fluxes of energy, heat, momentum, and mass due to gravity waves in the meteor zone  

Microsoft Academic Search

Wave flux data derived from Obninsk radiometer observations of 1979-1980 are examined. The procedure for calculating the wave fluxes is described. It is observed that the energy vertical flux changes from 0.006 W\\/sq m in winter to 0.001 W\\/sq m in summer; the mass vertical flux corresponds to the ascent with velocities of 1-4 cm\\/sec; and the heat flux is

N. M. Gavrilov; E. D. Kalov

1986-01-01

314

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

315

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

SciTech Connect

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

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

2005-07-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

317

Satellite estimates of ocean-air heat fluxes during cold air outbreaks  

NASA Technical Reports Server (NTRS)

A method for estimating the heat and moisture fluxes of coastal waters using the cloud free path, the sea surface temperature, and the saturation water vapor mixing ratio is presented. Generalized nomograms for the surface sensible and latent heat fluxes are developed using the Stage and Businger (1981) mixed-layer model. The fluxes are found to be slightly dependent on wind speed. The results are found to be applicable to any path within the cloud-free region, with heat fluxes obtainable by multiplication of the mean heating by the mean wind speed in the boundary layer. Higher stability causes lowered heating. It is shown that the latent heat flux is linear. Applications of the method to lake-effect snowstorms and for verification of boundary-layer models are indicated.

Chou, S.-H.; Atlas, D.

1982-01-01

318

Heat pump processes induced by laser radiation  

NASA Technical Reports Server (NTRS)

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

Garbuny, M.; Henningsen, T.

1980-01-01

319

Effects of tropospheric aerosols on radiative flux calculations at UV and visible wavelengths  

SciTech Connect

The surface fluxes in the wavelength range 175 to 735nm have been calculated for an atmosphere which contains a uniformly mixed aerosol layer of thickness 1km at the earth`s surface. Two different aerosol types were considered, a rural aerosol, and an urban aerosol. The visibility range for the aerosol layers was 95 to 15 km. Surface flux ratios (15km/95km) were in agreement with previously published results for the rural aerosol layer to within about 2%. The surface flux ratios vary from 7 to 14% for the rural aerosol layer and from 13 to 23% for the urban aerosol layer over the wavelength range. A tropospheric radiative forcing of about 1.3% of the total tropospheric flux was determined for the 95km to 15km visibility change in the rural aerosol layer, indicating the potential of tropospheric feedback effects on the surface flux changes. This effect was found to be negligible for the urban aerosol layer. Stratospheric layer heating rate changes due to visibility changes in either the rural or urban aerosol layer were found to be negligible.

Grossman, A.S.; Grant, K.E.

1994-08-01

320

Remote Measurement of Heat Flux from Power Plant Cooling Lakes  

SciTech Connect

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

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

2013-01-01

321

Thermal Chaotic Mixing With Imposed Heat Flux In a Mixer With Alternately Rotating Walls  

E-print Network

used for heat transfer [4], especially in twisted- pipe heat exchangers [5]. Even if the flowThermal Chaotic Mixing With Imposed Heat Flux In a Mixer With Alternately Rotating Walls Kamal El.elomari@univ-pau.fr & yves.leguer@univ-pau.fr November 24, 2009 Abstract We investigated mixing and heat transfer enhancement

322

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

323

Latent and Sensible Heat Flux Anomalies over the Northern Oceans: The Connection to Monthly Atmospheric Circulation  

Microsoft Academic Search

The influence of the atmospheric circulation on monthly anomalies of ocean surface latent and sensible heat fluxes is explored. The fluxes are estimated using bulk formulas applied to a set of about four decades of marine observations over 1946-1986. Monthly averaging over 5° `square' reduces errors contained in individual observations. The focus is on behavior of the flux anomalies over

Daniel R. Cayan

1992-01-01

324

Sensible and latent heat flux estimates in Antarctica  

NASA Technical Reports Server (NTRS)

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

Stearns, Charles R.; Weidner, George A.

1993-01-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

326

Electron parameter correlations in high-speed streams and heat flux instabilities. [in solar wind  

NASA Technical Reports Server (NTRS)

Statistical electron parameter correlations associated with high-speed streams are determined with the aim of identifying one or more locally active solar wind heat flux instabilities. Evidence that points toward local regulation of the heat flux at 1 AU is presented, and the results of a search for special signatures expected from the action of the Alfven, magnetosonic, and whistler flux instabilities are discussed. It is shown that under certain conditions, the whistler mode can be active in regulating the heat flux at 1 AU.

Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gary, S. P.; Montgomery, M. D.

1976-01-01

327

High Flux Heat Removal with Microchannels---A Roadmap of Challenges and Opportunities  

Microsoft Academic Search

Heat fluxes in IC chips and other electronics equipment have reached the current limits of air cooling technology. Some of the applications require heat fluxes well beyond the limit of 100 W\\/cm2, requiring advanced cooling solutions. Liquid cooling technology has been receiving attention as th e advances in single -phase liquid cooling in mic rochannels have shown considerable promise. The

Satish G. Kandlikar

2005-01-01

328

Electron heat flux dropouts in the solar wind: evidence for interplanetary magnetic field reconnection  

Microsoft Academic Search

Electron heat flux dropout events have been observed in the solar wind using the ISEE 3 plasma electron data set. These events manifest themselves as dropouts of the solar wind halo electrons which are normally found streaming outward along the local magnetic field. These dropouts leave nearly isotropic distributions of solar wind halo electrons, and consequently, the heat flux in

D. J. McComas; J. T. Gosling; J. L. Phillips; S. J. Bame; J. G. Luhmann; E. J. Smith

1989-01-01

329

Hot-Spot Detection in Integrated Circuits by Substrate Heat-Flux Sensing  

Microsoft Academic Search

This letter presents a novel approach to detect hot spots (HSs) in active integrated circuits (ICs) and devices. It is based on sensing the HS heat flux within the chip substrate with a probe-laser beam. As the beam passes through the die, it experiences a deflection directly proportional to the heat flux found along its trajectory (internal infrared laser deflection

X. Perpina; J. Altet; X. Jorda; M. Vellvehi; J. Millan; N. Mestres

2008-01-01

330

A method of measuring heat fluxes across nickel surfaces using the metal oxide on the surface  

Microsoft Academic Search

The feasibility of using the semiconducting oxide film on a metal surface to measure the heat flux through that surface and to measure the temperature of the surface has been demonstrated for nickel. The output compares favourably with other available heat flux meters.

P L Weickhardt; I M Ritchie; R J Batterham; D G Wood

1969-01-01

331

Ir Thermographic Measurements of Temperatures and Heat Fluxes in Hypersonic Plasma Flow  

Microsoft Academic Search

The technological development achieved in instruments and methodology concerning both flights and ground hypersonic experiment (employed in space plane planning) goes towards an updating and a standardization of the heat flux technical measurements. In fact, the possibility to simulate high enthalpy flow relative to reentry condition by hypersonic arc-jet facility needs devoted methods to measure heat fluxes. Aim of this

G. Cardone; G. Tortora; A. del Vecchio

2005-01-01

332

Increasing trends for the surface heat flux and fresh water flux in the North Pacific eastern subtropical region  

NASA Astrophysics Data System (ADS)

We investigated trends for surface net heat flux (NET) and fresh water flux (FWF) over the eastern subtropical region in the North Pacific for the period of 1988-2005 using satellite-based data set. It is concluded that NET and FWF remarkably increased during this period. Latent heat flux (LHF) mainly contributes to the increase in NET. Moreover, in order to clarify which flux has larger contribution to the increase in LHF, we investigated four LHF products. Both of the increase in the wind speed (U) and the decrease in the air specific humidity (Qa) have critical contribution to the increase in LHF. In contrast, the decrease of the sea surface temperature (SST) which contributes the decrease in LHF is also found. Also, we proposed a possible mechanism that the increase in U and the decrease in Qa are induced by the strengthened descending branch of local Hadley circulation, associated with change of SST around this region.

Iwasaki, Shinsuke; Kubota, Masahisa

2011-05-01

333

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

334

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

Microsoft Academic Search

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

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

2000-01-01

335

Preliminary investigation of changes in x-ray multilayer optics subjected to high radiation flux  

SciTech Connect

A variety of metal multilayers was exposed to high x-ray flux using Sandia National Laboratories' PROTO II machine in the gas puff mode. Fluxes incident on the multilayers above 700 MW/cm/sup 2/ in total radiation, in nominal 20 ns pulses, were realized. The neon hydrogen- and helium-like resonance lines were used to probe the x-ray reflectivity properties of the multilayers as they underwent change of state during the heating pulse. A fluorescer-fiber optic-streak camera system was used to monitor the changes in x-ray reflectivity as a function of time and irradiance. Preliminary results are presented for a W/C multilayer. Work in progress to model the experiment is discussed. 13 refs., 4 figs.

Hockaday, M.P.; Blake, R.L.; Grosso, J.S.; Selph, M.M.; Klein, M.M.; Matuska, W. Jr.; Palmer, M.A.; Liefeld, R.J.

1985-01-01

336

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

NASA Technical Reports Server (NTRS)

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

Haggard, J. B., Jr.

1983-01-01

337

Comparison of Heat Flux Measurements and Calculations at an Arctic Site  

NASA Astrophysics Data System (ADS)

The complex exchanges between the atmosphere and the surface are one of the primary drivers of the changes that are occurring in the Arctic environment. These exchanges are exceedingly difficult to parameterize or observe remotely, and it is clear that flux parameterizations developed for lower latitudes and oceans are not representative in the Arctic. In response, several Arctic sites have recently installed micrometeorological flux towers with suites of instruments to produce measurements that can be used to calculate turbulent and sensible heat fluxes. These towers typically also have surface heat flux plates and active layer thermistor strings as part of the suite of instruments characterizing the near surface boundary layer. In this presentation we compare measurements from two surface heat flux plates and a one meter thermistor probe that is installed near the micrometeorological flux tower at the Tiksi Hydrometeorological Observatory in the Sakha Republic of Russia. Theoretically the direct measurement of heat flux from the plates and the calculated flux from the thermistor temperature profiles should be identical, however, it is expected that a number of biases and inconsistencies will result from inhomogeneity in surface characteristics, and within the underlying active layer, including snow cover, standing water, vegetation, soil characteristics as well as instrument measurement limitations. Quantification and error analysis of these measurement limitations are important as the surface heat flux is an important parameter in achieving closure between the heat budgets of the atmosphere and the underlying surface.

Crepinsek, S.; Uttal, T.; Sandoval, C.; Persson, O. P.; Grachev, A. A.

2013-12-01

338

Effect of combined heat and radiation on microbial destruction  

NASA Technical Reports Server (NTRS)

A series of experiments at several levels of relative humidity and radiation dose rates was carried out using spores of Bacillus subtilis var. niger to evaluate the effect of heat alone, radiation alone, and a combination of heat and radiation. Combined heat and radiation treatment of microorganisms yields a destruction rate greater than the additive rates of the independent agents. The synergistic mechanism shows a proportional dependency on radiation dose rate, an Arrhenius dependence on temperature, and a dependency on relative humidity. Maximum synergism occurs under conditions where heat and radiation individually destroy microorganisms at approximately equal rates. Larger synergistic advantage is possible at low relative humidities rather than at high relative humidities.

Fisher, D. A.; Pflug, I. J.

1977-01-01

339

A New Facility for Measurements of Three-Dimensional, Local Subcooled Flow Boiling Heat Flux and Related Critical Heat Flux for PFCs  

SciTech Connect

In the development of plasma-facing components for fusion reactors and high-heat-flux heat sinks (or components) for electronic applications, the components are usually subjected to a peripherally nonuniform heat flux. Even if the applied heat flux is uniform in the axial direction (which is unlikely), both intuition and recent investigations have clearly shown that both the local heat flux and the eventual critical heat flux (CHF) in this three-dimensional (3-D) case will differ significantly from similar quantities found in the voluminous body of data for uniformly heated flow channels. Although this latter case has been used in the past as an estimate for the former case, more study has become necessary to examine the 3-D temperature and heat flux distributions and related CHF. Work thus far has shown that the nonuniform peripheral heat flux condition enhances CHF in some cases.To avoid the excess costs associated with using electron or ion beams to produce the nonuniform heat flux, a new facility was developed that will allow 3-D conjugate heat transfer measurements and two-dimensional, local subcooled flow boiling heat flux and related CHF measurements.The configurations under study for this work consist of (a) a nonuniformly heated cylinder-like test section with a circular coolant channel bored through the center and (b) a monoblock that is a square cross-section parallelepiped with a circular drilled flow channel along the channel centerline. The theoretical or ideal cylinder-like test section would be a circular cylinder with half (-90 to 90 deg) of its outside boundary subjected to a uniform heat flux and the remaining half insulated. For the monoblock, a uniform heat flux is applied to one of the outside surfaces, and the remaining surfaces are insulated. The outside diameter of the cylinder-like test section is 30.0 mm, and its length is 200.0 mm. The monoblock square is 30.0 mm long. The inside diameter of the flow channel for both types of test sections is 10.0 mm. Water is the coolant. The inlet water temperature can be set at any level in the range from 26.0 to 130.0 deg. C, and the exit pressure can be set at any level in the range from 0.4 to 4.0 MPa. Thermocouples were placed at 48 locations inside the solid cylinder-like or monoblock test section to obtain 3-D wall temperature variations and related local heat flux. Finally, the mass velocity can be set at any level in the range from 0.4 to 10.0 Mg/m{sup 2}.s for the 10.0-mm-diam channel.

Boyd, Ronald D. Sr.; Cofie, Penrose; Li Qingyuan; Ekhlassi, Ali A

2002-01-15

340

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

NASA Technical Reports Server (NTRS)

Two-phase devices (heat pipes, capillary pumped loops, loop heat pipes, and evaporators) have become recognized as key elements in thermal control systems of space platforms. Capillary and porous structures are necessary and widely used in these devices, especially in high heat flux and zero-g applications, to provide fluid transport and enhanced heat transfer during vaporization and condensation. However, some unexpected critical phenomena, such as dryout in long heat pipe evaporators and high thermal resistance of loop heat pipe evaporators with high heat fluxes, are possible and have been encountered in the use of two-phase devices in the low gravity environment. Therefore, a detailed fundamental investigation is proposed to better understand the fluid behavior in capillary-porous structures during vaporization at high heat fluxes. The present paper addresses some theoretical aspects of this investigation.

Faghri, Amir; Khrustalev, Dmitry

1996-01-01

341

A review of the criteria for people exposure to radiant heat flux from fires.  

PubMed

The NFPA 59A Standard and the Federal Regulation, 49 CFR Part 193, stipulate a level of 5 kW/m(2) as the criterion for determining the hazard distance to people exposure from a LNG fire. Another regulation (24CFR, Section 51.204) while stipulating a lower exposure limit of 1.42 kW/m(2) provides administrative relief from the regulation if mitigation measures are provided. Several countries in Europe and the Far East have adopted both a specified heat flux value (generally, 5 kW/m(2)) as well as modified dose criteria for human exposure hazard calculation in risk assessments. In some cases, the regulations in Europe require the use of lower values for children and physically challenged persons. This paper reviews the available literature on the phenomenon of skin burn caused by radiant heat exposure. The associated thermal and spectral properties of human skin are reviewed. The basis for regulatory setting, of 5 kW/m(2) and other exposure criteria (as a part of hazard and risk calculations) for evaluating distances to hazards from the exposure of people to radiant heat effects of large fires, is evaluated. An example calculation is provided to show the extent of reduction in the hazard distance to specified radiant heat flux from a fire when the spectral reflection and absorption properties of skin are considered with and without the inclusion of the mitigating effects of clothing. The results indicate that hazard distances calculated including the reflective and band absorptive properties (in IR wavelength) of skin results in a reduction of between 30 and 50% in the hazard distances obtained with current methodology, which ignores these effects. Unfortunately, there are no test results, from full-scale human-exposure-to-IR radiation, with which these predictions can be compared. PMID:18035487

Raj, Phani K

2008-11-15

342

Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach  

NASA Technical Reports Server (NTRS)

The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

343

Discrete Ordinates Radiation Element Method for Radiative Heat Transfer in Three-Dimensional Participating Media  

Microsoft Academic Search

A new algorithm, the discrete ordinates radiation element method (DOREM), for modeling radiative heat transfer in inhomogeneous three-dimensional participating media is described. The DOREM uses advantages of the both the radiation element method (REM) and the discrete ordinates method. Benchmark comparisons are conducted against several radiation models. The DOREM successfully implements radiative heat transfer simulations precisely, since false scattering never

Shigenao Maruyama; Atsushi Sakurai; Atsuki Komiya

2007-01-01

344

Subcooled flow boiling heat transfer and critical heat flux in water-based nanofluids at low pressure  

E-print Network

A nanofluid is a colloidal suspension of nano-scale particles in water, or other base fluids. Previous pool boiling studies have shown that nanofluids can improve the critical heat flux (CHF) by as much as 200%. In this ...

Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology

2009-01-01

345

Liquid jet impingement cooling with diamond substrates for extremely high heat flux applications  

SciTech Connect

The combination of impinging jets and diamond substrates may provide an effective solution to a class of extremely high heat flux problems in which very localized heat loads must be removed. Some potential applications include the cooling of high-heat-load components in synchrotron x-ray, fusion, and semiconductor laser systems. Impinging liquid jets are a very effective vehicle for removing high heat fluxes. The liquid supply arrangement is relatively simple, and low thermal resistances can be routinely achieved. A jet`s cooling ability is a strong function of the size of the cooled area relative to the jet diameter. For relatively large area targets, the critical heat fluxes can approach 20 W/mm{sup 2}. In this situation, burnout usually originates at the outer edge of the cooled region as increasing heat flux inhibits the liquid supply. Limitations from liquid supply are minimized when heating is restricted to the jet stagnation zone. The high stagnation pressure and high velocity gradients appear to suppress critical flux phenomena, and fluxes of up to 400 W/mm{sup 2} have been reached without evidence of burnout. Instead, the restrictions on heat flux are closely related to properties of the cooled target. Target properties become an issue owing to the large temperatures and large temperature gradients that accompany heat fluxes over 100 W/mm{sup 2}. These conditions necessitate a target with both high thermal conductivity to prevent excessive temperatures and good mechanical properties to prevent mechanical failures. Recent developments in synthetic diamond technology present a possible solution to some of the solid-side constraints on heat flux. Polycrystalline diamond foils can now be produced by chemical vapor deposition in reasonable quantity and at reasonable cost. Synthetic single crystal diamonds as large as 1 cm{sup 2} are also available.

Lienhard, J.H. V [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Mechanical Engineering; Khounsary, A.M. [Argonne National Lab., IL (United States)

1993-09-01

346

Induced convective enhancement of the critical heat flux from partially heated horizontal flat plates in saturated pool boiling  

SciTech Connect

Current developments in high-power electronics and other energy-intensive applications have accentuated the need for higher performance heat transfer. Nucleate boiling heat transfer is one of the most effective modes of heat transfer, with pool boiling being perhaps the simplest type of passive two-phase cooling. Unfortunately, the maximum heat flux attainable in nucleate pool boiling is limited by the relatively low critical heat flux at the onset of film boiling. Several methods have been suggested to enhance the critical heat flux. In particular, Costello et al. showed that the critical heat flux in saturated pool boiling could be enhanced by simply increasing the width of the pool while maintaining a fixed heater size. Elkassabgi and Lienhard examined the combined effects of immersion depth and pool size on the critical heat flux for a small-diameter horizontal cylinder in saturated pool boiling. No similar study for flat plate heaters appears in the literature. While as noted above the effect of heater appears in the literature. While as noted above the effect of heater appears in the literature. While as noted above the effect of heater size and immersion depth have been studied independently, no systematic investigation of the combined effects has been conducted previously. This paper presents the results of such a study.

Bockwoldt, T.S.; Jeter, S.M.; Abdel-Khalik, S.I.; Hartley, J.G. (Georgia Inst. of Tech., Atlanta (United States))

1992-05-01

347

Radiative heat transfer in two-phase media  

Microsoft Academic Search

Physical processes occurring in radiating two-phase media are examined with emphasis on radiative heat transfer in the combustion chambers of thermal power plants. In particular, correct effective temperatures are determined for radiating and dissipating media with reflecting and radiating boundary surfaces; radiation characteristics and thermal efficiencies of the surfaces are calculated. An approximate method is developed for taking account of

Kazimir Serafimovich Adzerikho; Evgenii Fomich Nogotov; Vladimir Petrovich Trofimov

1987-01-01

348

Transient conductive, radiative heat transfer coupled with moisture transport in attic insulations  

NASA Astrophysics Data System (ADS)

A transient, one-dimensional thermal model that incorporates combined conduction, radiation heat transfer, and moisture transport for residential attic insulations has been developed. The governing equations are the energy equation, the radiative transport equation for volumetric radiation within the insulation batt, and the species equations for bound H2O and vapor H2O. A simultaneous solution procedure with a Eulerian control volume-based finite difference method was used to solve the energy equation and the species equations. The method of discrete ordinates was used in solving the radiative transport equation. For H2O transport, both diffusion of vapor H2O and bound H2O and moisture adsorption/desorption within the insulation binder are included in the model. The experimental data measured at an occupied North Mississippi residence for R19STD (standard R19 fiberglass insulation batt without a foil radiant barrier) were used to validate the model which predicted heat fluxes for summer, spring, winter, and fall seasonal conditions. These predictions were compared with the measured heat flux data and the predictions from the dry model (without the moisture transport). Various profiles such as temperature-time histories, relative humidity time histories, spatial H2O concentrations, spatial temperatures, and spatial heat fluxes are presented to explain the overall heat transfer behavior.

Gorthala, R.; Harris, K. T.; Roux, J. A.; McCarty, T. A.

1994-01-01

349

Method of high heat flux removal by usage of liquid spray cooling  

NASA Astrophysics Data System (ADS)

High heat flux removal are important issue in many perspective applications such as computer chips, laser diode arrays, or boilers working on supercritical parameters. Electronic microchips constructed nowadays are model example of high heat flux removal, where the cooling system have to maintain the temperature below 358 K and take heat flux up to 300 W/cm2. One of the most efficient methods of microchips cooling turns out to be the spray cooling method. Review of installations has been accomplished for removal at high heat flux with liquid sprays. In the article are shown high flux removal characteristic and dependences, boiling critical parameters, as also the numerical method of spray cooling analysis.

Smakulski, Przemys?aw

2013-09-01

350

Modelling of heat flux received by a bubble pump of absorption-diffusion refrigeration cycles  

NASA Astrophysics Data System (ADS)

In the present study, the heat flux received by a bubble pump, which was simulated to a vertical tube 1 m long and with a variable diameter, was optimized. A numerical study was carried out in order to solve balance equations concerning the water-ammonia mixture in the up flow. The two-fluid model was used to derive the equations. A numerical study was carried out on a heat flux between 1 and 70 kW m-2 and the liquid velocity was determined. The optimum flux was determined for a tube diameter equal to 4, 6, 8 and 10 mm and a mass flow rate ranging from 10 to 90 kg m-2 s-1. The optimum heat flux was correlated as a function of the tube diameter and mass flow rate, while the minimum heat flux required for pumping was correlated as a function of the tube diameter.

Benhmidene, Ali; Chaouachi, Béchir; Gabsi, Slimane; Bourouis, Mahmoud

2011-11-01

351

Heat Fluxes and Evaporation Measurements by Multi-Function Heat Pulse Probe: a Laboratory Experiment  

NASA Astrophysics Data System (ADS)

Multi Functional Heat Pulse Probes (MFHPP) are multi-needles probes developed in the last years able to measure temperature, thermal properties such as thermal diffusivity and volumetric heat capacity, from which soil moisture is directly retrieved, and electric conductivity (through a Wenner array). They allow the simultaneous measurement of coupled heat, water and solute transport in porous media, then. The use of only one instrument to estimate different quantities in the same volume and almost at the same time significantly reduces the need to interpolate different measurement types in space and time, increasing the ability to study the interdependencies characterizing the coupled transports, especially of water and heat, and water and solute. A three steps laboratory experiment is realized at EPFL to investigate the effectiveness and reliability of the MFHPP responses in a loamy soil from Conthey, Switzerland. In the first step specific calibration curves of volumetric heat capacity and thermal conductivity as function of known volumetric water content are obtained placing the MFHPP in small samplers filled with the soil homogeneously packed at different saturation degrees. The results are compared with literature values. In the second stage the ability of the MFHPP to measure heat fluxes is tested within a homemade thermally insulated calibration box and results are matched with those by two self-calibrating Heatflux plates (from Huxseflux), placed in the same box. In the last step the MFHPP are used to estimate the cumulative subsurface evaporation inside a small column (30 centimeters height per 8 centimeters inner diameter), placed on a scale, filled with the same loamy soil (homogeneously packed and then saturated) and equipped with a vertical array of four MFHPP inserted close to the surface. The subsurface evaporation is calculated from the difference between the net sensible heat and the net heat storage in the volume scanned by the probes, and the values obtained are matched with the overall evaporation, estimated through the scale in terms of weight loss. A numerical model able to solve the coupled heat-moisture diffusive equations is used to interpolate the obtained measures in the second and third step.

Sharma, V.; Ciocca, F.; Hopmans, J. W.; Kamai, T.; Lunati, I.; Parlange, M. B.

2012-04-01

352

Estimation of surface heat flux and surface temperature during inverse heat conduction under varying spray parameters and sample initial temperature.  

PubMed

An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m(2) was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa. PMID:24977219

Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong; Zubair, Muhammad

2014-01-01

353

Estimation of Surface Heat Flux and Surface Temperature during Inverse Heat Conduction under Varying Spray Parameters and Sample Initial Temperature  

PubMed Central

An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27?mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2?MPa to 1.8?MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024?MW/m2 was estimated for a thickness of 8.5?mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8?MPa. PMID:24977219

Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong

2014-01-01

354

Heat fluxes across the Antarctic Circumpolar Current in Drake Passage: Mean flow and eddy contributions  

NASA Astrophysics Data System (ADS)

contrast to a long-standing belief, observations in the Antarctic Circumpolar Current (ACC) show that mean velocity vectors rotate with depth, thus suggesting a possible importance of the time-mean flow for the local poleward heat transport. The respective contributions of the eddy and mean flows to the heat flux across the ACC in Drake Passage (DP) are investigated using recently acquired and historical time series of velocity and temperature from a total of 24 current meter moorings and outputs of a high-resolution (1/12°) model with realistic topography. Only 11 out of the 24 depth-integrated eddy heat flux estimates are found to be significant, and they are poleward. Model depth-integrated eddy heat fluxes have similar signs and amplitudes as the in situ estimates at the mooring sites. They are mostly poleward or nonsignificant, with amplitude decreasing to the south. The cross-stream temperature fluxes caused by the mean flow at the moorings have a sign that varies with location and corresponds to the opposite of the vertical velocity estimates. The depth-integrated temperature fluxes due to the mean flow in the model exhibit small spatial scales and are of opposite sign to the bottom vertical velocities. This suggests that the rotation of the mean velocity vectors with depth is mainly due to bottom topography. The rough hilly topography in DP likely promotes the small-scale vertical velocities and temperature fluxes. Eddy heat fluxes and cross-stream temperature fluxes are integrated over mass-balanced regions defined by the model transport streamlines. The contribution of the mean flow to the ocean heat fluxes across the Southern ACC Front in DP (covering about 4% of the circumpolar longitudes) is about four times as large as the eddy heat flux contribution and the sum of the two represent on the order of 10% of the heat loss to the atmosphere south of 60°S.

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

2014-09-01

355

Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets  

NASA Technical Reports Server (NTRS)

Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

2013-01-01

356

E × B shear pattern formation by radial propagation of heat flux wavesa)  

NASA Astrophysics Data System (ADS)

A novel theory to describe the formation of E ×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E ×B staircase is discussed.

Kosuga, Y.; Diamond, P. H.; Dif-Pradalier, G.; Gürcan, Ã.-. D.

2014-05-01

357

Microscale liquid cooling system for high heat flux processor cooling applications  

Microsoft Academic Search

The requirements for thermal management in high performance computers are rapidly outpacing the capabilities of the best commercial heat sinks, including those with integrated heat pipes. The problem lies in three compounding trends: a) higher total chip power, b) higher local heat flux in chip hotspots, and c) smaller system enclosures. Pumped liquid cooling is a promising alternative, but this

Girish Upadhya; Mark Munch; Peng Zhou; J. Horn; Douglas Werner; Mark McMaster

2006-01-01

358

A FLUX-TUBE TECTONICS MODEL FOR SOLAR CORONAL HEATING DRIVEN BY THE MAGNETIC CARPET  

E-print Network

-scale corona. This suggests that unresolved observations of coronal loops should exhibit enhanced heating nearA FLUX-TUBE TECTONICS MODEL FOR SOLAR CORONAL HEATING DRIVEN BY THE MAGNETIC CARPET Eric R. Priest May 1 ABSTRACT We explore some of the consequences of the magnetic carpet for coronal heating

Priest, Eric

359

Critical heat flux prediction for saturated flow boiling of water in vertical tubes  

Microsoft Academic Search

This study presents a new analytical model for the prediction of the critical heat flux (CHF) in water saturated flow boiling in round vertical and uniformly heated pipes. The CHF is assumed to occur in annular flow when the liquid film vanishes at the exit section of the heated channel. Channel pressure drop is calculated using the Friedel correlation. Liquid

Gian Piero Celata; Kaichiro Mishima; Giuseppe Zummo

2001-01-01

360

Deep-Sea Research I 52 (2005) 519542 Davis Strait volume, freshwater and heat fluxes  

E-print Network

Deep-Sea Research I 52 (2005) 519­542 Davis Strait volume, freshwater and heat fluxes Je´ ro^ me 2005 Abstract Volume, freshwater and heat transport through Davis Strait, the northern boundary, freshwater and heat transports are �2:6 � 1:0 Sv; �92 � 34 mSv; 18 � 17 � 1012 W: Both southward

361

A Flux Tube Tectonics Model for Solar Coronal Heating Driven by the Magnetic Carpet.  

E-print Network

A Flux Tube Tectonics Model for Solar Coronal Heating Driven by the Magnetic Carpet. Eric R. Priest heating. The dissipation of energy along sharp boundaries we call, by analogy with geophysi- cal plate tectonics, the tectonics model of coronal heating. Similar to the case on Earth, the relative motions

Priest, Eric

362

A novel temperature based flat-plate heat flux sensor for high accuracy measurement  

Microsoft Academic Search

This paper presents a novel flat-plate heat flux sensor for thermal control systems of airborne electronic equipments and actuators. The sensor consists of a pair of high and low conductivity materials to enable the temperature difference between the heat source and heat sink to be measured by resistance temperature detectors (RTDs) and an auxiliary conditioning circuit. Because high accuracy RTDs

Dongxiao Liu; Yun-Ze Li; Yunhua Li; Kok-Meng Lee

2009-01-01

363

Time and space resolved wall temperature and heat flux measurements during nucleate boiling with constant  

E-print Network

Time and space resolved wall temperature and heat flux measurements during nucleate boiling used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic al. [4]. Yaddanapudi and Kim [5] measured local heat trans- fer underneath single bubbles nucleating

Kim, Jungho

364

Innovative Divertor Development to Solve the Plasma Heat-Flux Problem  

SciTech Connect

Large, localized plasma heat exhaust continues to be one of the critical problems for the development of tokamak fusion reactors. Excessive heat flux erodes and possibly melts plasma-facing materials, thereby dramatically shortening their lifetime and increasing the impurity contamination of the core plasma. A detailed assessment by the ITER team for their divertor has revealed substantial limitations on the operational space imposed by the divertor performance. For a fusion reactor, the problem becomes worse in that the divertor must accommodate 20% of the total fusion power (less any broadly radiated loss), while not allowing excess buildup of tritium in the walls nor excessive impurity production. This is an extremely challenging set of problems that must be solved for fusion to succeed as a power source; it deserves a substantial research investment. Material heat-flux constraints: Results from present-day tokamaks show that there are two major limitations of peak plasma heat exhaust. The first is the continuous flow of power to the divertor plates and nearby surfaces that, for present technology, is limited to 10-20 MW/m{sup 2}. The second is the transient peak heat-flux that can be tolerated in a short time, {tau}{sub m}, before substantial ablation and melting of the surface occurs; such common large transient events are Edge Localized Mode (ELMs) and disruptions. The material limits imposed by these events give a peak energy/{tau}{sub m}{sup 1/2} parameter of {approx} 40 MJ/m{sup 2}s{sup 1/2} [1]. Both the continuous and transient limits can be approached by input powers in the largest present-day devices, and future devices are expected to substantially exceed the limits unless a solution can be found. Since the early 90's LLNL has developed the analytic and computational foundation for analyzing divertor plasmas, and also suggested and studied a number of solid and liquid material concepts for improving divertor/wall performance, with the most recent being the Snowflake divertor concept [2] and generating Resonant Magnetic Perturbations by the SOL currents [3]. However, the specific approaches discussed here are part of a wider class of innovative divertor ideas that have come from the community in the last several years, and we certainly advocate the need to consider a range of options. Indeed, the most effective solution to the heat-flux problem may well contain features of various ideas. For example, there are the X-divertor (Kotschenreuther et al. [4]) that expands the magnetic flux surface in the vicinity of the near-X-point divertor plate, and the super X-divertor (Valanju et al. [5]) that guides the near-separatrix SOL flux tubes to a larger major radius to increase the surface area available for power deposition. These approaches have the common feature of manipulation of the edge magnetic geometry. Another approach is the use of liquid divertor surfaces that can increase the heat-flux capability by flowing the heated material to a cooling region and eventually out of the machine, and/or by being able to withstand a higher peak heat flux [6]. All of these areas are only emerging concepts that require substantially more analysis and definitive experimental tests, and given the need for a large improvement in this area, we advocate a substantial program to systematically assess the approaches. Because of space limitation here, we present some details of one of the concepts, namely the Snowflake divertor configuration. The Snowflake (SF) divertor [2] exploits a tokamak geometry in which the poloidal magnetic field varies quadratically with distance from the X-point null, {Delta}r. The name stems from the characteristic hexagonal, snowflake-like, shape of the multi-branched separatrix for this exact second-order null. In contrast, the standard X-point configuration has a poloidal field varying linearly with ?r. The different variations mean that a flux expansion is much larger in the vicinity of a null of a snowflake divertor, and one can try to exploit this fact for reducing the divertor heat load. A uniqu

Rognlien, T; Ryutov, D; Makowski, M; Soukhanovskii, V; Umansky, M; Cohen, R; HIll, D; Joseph, I

2009-02-26

365

Nozzle flow of laser-heated radiating hydrogen with application to a laser-heated rocket  

NASA Technical Reports Server (NTRS)

This paper presents a model for the steady heating of flowing hydrogen by a CW 10.6 micron laser, to consider the feasibility of a laser-heated rocket. The hydrogen flow and the laser beam are parallel, and move into a converging-diverging nozzle. The absorption of laser energy is initiated by a laser-supported combustion wave. The hydrogen is in chemical equilibrium, absorbs laser energy by inverse Bremsstrahlung, and loses energy by radiation. The hydrogen flow was calculated from the rear of the LSC wave to the throat. Estimates of convective heat losses were made using a hydrogen boundary layer analysis. Specific impulse, obtained by expanding isentropically from the throat to 1 atm or a vacuum, varies from 1400 to 3000 s. Radiation losses are 5 to 20%, though the energy fluxes to the walls are quite high. Convective loss estimates are high enough to indicate that coupling to the hot gas flow is required for a 10 kW engine, but not for a 5 MW engine.

Kemp, N. H.; Root, R. G.

1977-01-01

366

Heat pump augmented radiator for low-temperature space applications  

SciTech Connect

Closed-cycle, space-based heat rejection systems depend solely on radiation to achieve their heat dissipation function. Since the payload heat rejection temperature is typically 50 K above that of the radiation sink in near earth orbit, the size and mass of these systems can be appreciable. Size (and potentially mass) reductions are achievable by increasing the rejection temperature via a heat pump. Two heat pump concept were examined to determine if radiator area reductions could be realized without increasing the mass of the heat rejection system. The first was a conventional, electrically-driven vapor compression system. The second is an innovative concept using a solid-vapor adsorption system driven by reject heat from the prime power system. The mass and radiator area of the heat pumpradiator systems were compared to that of a radiator only system to determine the merit of the heat pump concepts. Results for the compressor system indicated that the mass minimum occured at a temperature lift of about 50 K and radiator area reductions of 35% were realized. With a radiator specific mass of 10 kgm/sup 2/, the heat pump system is 15% higher than the radiator only baseline system. The complex compound chemisorption systems showed more promising results. Using water vapor as the working fluid in a single stage heat amplifier resulted in optimal temperature lifts exceeding 150 K. This resulted in a radiator area reduction of 83% with a mass reduction of 64%. 7 refs., 9 figs.

Olszewski, M.; Rockenfeller, U.

1988-01-01

367

Radiative heat transfer in inhomogeneous, nongray, and anisotropically scattering media  

E-print Network

and anisotropic scattering medium. Thus, the REM2 International Journal of Heat and Mass Transfer 43 (2000) 2325Radiative heat transfer in inhomogeneous, nongray, and anisotropically scattering media Zhixiong Radiative heat transfer in three-dimensional inhomogeneous, nongray and anisotropically scattering

Guo, Zhixiong "James"

368

Radiative heat transfer in participating media — A review  

Microsoft Academic Search

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

Subhash C Mishra; Manohar Prasad

1998-01-01

369

High-heat flux testing of an interceptive device for an intense proton beam  

SciTech Connect

An interceptive device referred to here as a scraper has been designed and tested for use in a diagnostic device [1]. The scraper will be used to probe a proton beam in order to detect the formation of beam halo [2]. Probing the proton beam exposes the scraper to high heat fluxes on the order of 610 kW/cm{sup 2}. The high-heat flux exposure is cyclic since the beam is probed while in pulsed mode. In order to test the design repetitive high-heat flux testing has been performed on a prototype design of the scraper. This paper describes the design, analysis, and testing of the scraper.

Valdiviez, R. (Robert); Martinez, F. A. (Felix A.); Rendon, Armando M.; Nguyen, D. C. (Dinh C.); Earley, L. M. (Lawrence M.); La Fave, R. P. (Richard P.)

2001-04-01

370

Electron heat flux dropouts in the solar wind - Evidence for interplanetary magnetic field reconnection?  

NASA Technical Reports Server (NTRS)

An examination of ISEE-3 data from 1978 reveal 25 electron heat flux dropout events ranging in duration from 20 min to over 11 hours. The heat flux dropouts are found to occur in association with high plasma densities, low plasma velocities, low ion and electron temperatures, and low magnetic field magnitudes. It is suggested that the heat flux dropout intervals may indicate that the spacecraft is sampling plasma regimes which are magnetically disconnected from the sun and instead are connected to the outer heliosphere at both ends.

Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.; Bame, S. J.; Luhmann, J. G.; Smith, E. J.

1989-01-01

371

Parameterization of subsurface heating for soil and concrete using net radiation data  

SciTech Connect

The variability of surface sensible heat flux depend strongly on the rate of heating of the underlying surfaces. The variability is expected to be large in urban areas where the surfaces are layered with a variety of man-made materials. Parameterization of the ground heat storage as a function of surface materials is presented based on analyses of the U.S. Environmental Protection Agency's Regional Air Pollution Study (RAPS) conducted in St. Louis, MO. Ground heat flux data are derived from observations of surface and subsurface temperatures for a soil layer and for concrete slabs resting on soil. Simple mathematical expressions giving the ratio of ground heat storage to net radiation as a function of time are presented.

Doll, D.; Ching, J.K.S.; Kaneshiro, J.

1985-01-01

372

Plasmon enhanced near-field radiative heat transfer for graphene covered dielectrics  

NASA Astrophysics Data System (ADS)

It is shown that a graphene layer on top of a dielectric slab can dramatically influence the ability of this dielectric for radiative heat exchange turning a poor heat emitter/absorber into a good one and vice versa. The effect of graphene is related to thermally excited plasmons. The frequency of these resonances lies in the terahertz region and can be tuned by varying the Fermi level through doping or gating. It makes possible the fast modulation of the heat flux by electrical means, which opens up new possibilities for very fast manipulations with the heat flux. The heat transfer between two dielectrics covered with graphene can be larger than that between best known materials and becomes especially efficient below the room temperature.

Svetovoy, V. B.; van Zwol, P. J.; Chevrier, J.

2012-04-01

373

Thermal barrier coatings (TBC's) for high heat flux thrust chambers  

NASA Astrophysics Data System (ADS)

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot-section components has become critical, but at the same time the service conditions have put our best alloy systems to their limits. As a result, implementation of cooling holes and thermal barrier coatings are new advances in hot-section technologies now looked at for modifications to reach higher temperature applications. Current thermal barrier coatings used in today's turbine applications is known as 8%yttria-stabilized zirconia (YSZ) and there are no coatings for current thrust chambers. Current research is looking at the applicability of 8%yttria-stabilized hafnia (YSH) for turbine applications and the implementation of 8%YSZ onto thrust chambers. This study intends to determine if the use of thermal barrier coatings are applicable for high heat flux thrust chambers using industrial YSZ will be advantageous for improvements in efficiency, thrust and longer service life by allowing the thrust chambers to be used more than once.

Bradley, Christopher M.

374

Analytical and experimental studies of heat pipe radiation cooling of hypersonic propulsion systems  

SciTech Connect

Preliminary, research-oriented, analytical and experimental studies were completed to assess the feasibility of using high-temperature heat pipes to cool hypersonic engine components. This new approach involves using heat pipes to transport heat away from the combustor, nozzle, or inlet regions, and to reject it to the environment by thermal radiation from an external heat pipe nacelle. For propulsion systems using heat pipe radiation cooling (HPRC), it is possible to continue to use hydrocarbon fuels into the Mach 4 to Mach 6 speed range, thereby enhancing the economic attractiveness of commercial or military hypersonic flight. In the second-phase feasibility program recently completed, we found that heat loads produced by considering both convection and radiation heat transfer from the combustion gas can be handled with HPRC design modifications. The application of thermal insulation to ramburner and nozzle walls was also found to reduce the heat load by about one-half and to reduce peak HPRC system temperatures to below 2700{degrees}F. In addition, the operation of HPRC at cruise conditions of around Mach 4.5 and at an altitude of 90, 000 ft lowers peak hot section temperatures to around 2800{degrees}F. An HPRC heat pipe was successfully fabricated and tested at Mach 5 conditions of heat flux, heat load, and temperature. 24 refs.

Martin, R.A.; Merrigan, M.A.; Elder, M.G.; Sena, J.T.; Keddy, E.S. (Los Alamos National Lab., NM (United States)); Silverstein, C.C. (CCS Associates, Bethel Park, PA (United States))

1992-01-01

375

Analytical and experimental studies of heat pipe radiation cooling of hypersonic propulsion systems  

SciTech Connect

Preliminary, research-oriented, analytical and experimental studies were completed to assess the feasibility of using high-temperature heat pipes to cool hypersonic engine components. This new approach involves using heat pipes to transport heat away from the combustor, nozzle, or inlet regions, and to reject it to the environment by thermal radiation from an external heat pipe nacelle. For propulsion systems using heat pipe radiation cooling (HPRC), it is possible to continue to use hydrocarbon fuels into the Mach 4 to Mach 6 speed range, thereby enhancing the economic attractiveness of commercial or military hypersonic flight. In the second-phase feasibility program recently completed, we found that heat loads produced by considering both convection and radiation heat transfer from the combustion gas can be handled with HPRC design modifications. The application of thermal insulation to ramburner and nozzle walls was also found to reduce the heat load by about one-half and to reduce peak HPRC system temperatures to below 2700{degrees}F. In addition, the operation of HPRC at cruise conditions of around Mach 4.5 and at an altitude of 90, 000 ft lowers peak hot section temperatures to around 2800{degrees}F. An HPRC heat pipe was successfully fabricated and tested at Mach 5 conditions of heat flux, heat load, and temperature. 24 refs.

Martin, R.A.; Merrigan, M.A.; Elder, M.G.; Sena, J.T.; Keddy, E.S. [Los Alamos National Lab., NM (United States); Silverstein, C.C. [CCS Associates, Bethel Park, PA (United States)

1992-06-01

376

Experimental Study of Heat Transfer from a Yawed Cylinder to Air with a Constant Wall Heat Flux.  

National Technical Information Service (NTIS)

The heat transfer from a yawed cylinder to air for constant wall heat flux boundary condition has been studied experimentally. Yaws of 0 exp 0 , 20 exp 0 , 40 exp 0 , and 60 exp 0 were used with a Reynolds number based on a freestream velocity of 1.1 x 10...

C. A. Pura

1979-01-01

377

Generalized Thermoelasticity for an Isotropic Solid Sphere Indual-Phase-Lag of Heat Transfer with Surface Heat Flux  

Microsoft Academic Search

The dual-phase-lag heat transfer model is applied for an isotropic solid sphere. The solution of the problem is carried out when the boundary of the sphere is maintained at constant heat flux and the displacement of the surface is constrained. The analytical solutions of the displacement, temperature, and stresses are determined. Laplace transform technique is used to obtain the solution.

Ahmed E. Abouelregal

2011-01-01

378

An Experimental Study of a Radially Arranged Thin Film Heat Flux Gauge  

NASA Technical Reports Server (NTRS)

A new thin-film heat-flux gauge was designed and fabricated on three different substrate materials. Forty pairs of Pt-Pt/10% Rh thermocouple junctions were deposited in a circular pattern on the same plane of the substrate. Over the thermocouples, 5 and 10 micron thick thermal resistance layers were deposited to create a temperature gradient across those layers. Calibration and testing of these gauges were carried out in an arc-lamp calibration facility. The heat flux calculated from the gauge output is in good agreement with the value obtained from the pre-calibrated standard sensor. A CO2 laser was also used to test the steady-state and dynamic responses of the heat-flux gauge. During the steady-state test, the time constant for the heating period was 30 s. The frequency response of the heat-flux gauge was measured in the frequency domain using a CO2 laser and a chopper. The responses from an infrared detector and the heat-flux gauge were measured simultaneously and compared. It was found that the thin-film heat-flux gauge has a dynamic frequency response of 3 kHz.

Cho, Christoper S. K.; Fralick, Gustave C.; Bhatt, Hemanshu D.

1997-01-01

379

Icebase: A suborbital survey to map geothermal heat flux under an ice sheet  

NASA Astrophysics Data System (ADS)

NASA will solicit suborbital missions as part of its Earth Venture program element in the coming year. These missions are designed as complete PI-led investigations to conduct innovative hypothesis or scientific question-driven approaches to pressing questions in Earth System science. We propose to carry out a suborbital magnetic survey of Greenland using NASA's Global Hawk unmanned aerial vehicle to produce the first-ever map of the geothermal heat flux under an ice sheet. Better constraints on geothermal heat flux will reduce the uncertainty in future sea level rise, in turn allowing a more informed assessment of its impact on society. The geothermal heat flux depends on conditions such as mantle heat flux, and the tectonic history and heat production of the crust, all of which vary spatially. Underneath ice sheets, the geothermal heat flux influences the basal ice. Therefore heat flux is an important boundary condition in ice sheet modeling. Using magnetic data to constrain heat flux is possible because the magnetic properties of rocks are temperature dependent until they reach the Curie temperature. The technique has applications to understanding the response of Greenland ice sheet to climate forcing because the basal heat flux provides one of the boundary conditions. The technique also helps to locate the oldest ice. The oldest ice in Greenland should be found in areas of very low heat flux, and the identification of those areas is provided by this technique. Ice cores from the areas of oldest ice help to decipher past temperatures and CO2 contents. Our latest model of the geothermal heat flux under the Greenland ice sheet (http://websrv.cs.umt.edu/isis/index.php/Greenland_Basal_Heat_Flux) is based on low- resolution satellite observations collected by the CHAMP satellite between 2000 and 2010. Those observations will be enhanced by the upcoming Swarm gradient satellite mission, but the resolution will improve by less than a factor of two, from 400 km resolution to approximately 250 km resolution. A high altitude, suborbital magnetic survey of Greenland would provide a heat flux model with resolution comparable to the crustal thickness, and would provide details of the high heat flux region associated with the Iceland mantle plume in E /SE Greenland, and the low heat flux region in NW Greenland, adjacent to the Canadian Shield. Magnetic field measurements from 20 km altitude are strongly preferred over lower altitude observations because of their ability to sample the longest wavelengths, provide uniform calibration with sufficient sensitivity, and suppress local remanent magnetic field signatures. We validate our heat flux estimates by assessing the possible contributions from remanent magnetism and variable susceptibility, and from other lithospheric processes such as structure, volcanism and impact, from unmodeled external magnetic fields, and from the assumptions utilized in the heat flux model.

Purucker, Michael E.; Connerney, John E. P.; Blakely, Richard J.; Bracken, Robert E.; Nowicki, Sophie; Le, Guan; Sabaka, Terence J.; Bonalsky, Todd M.; Kuang, Weijia; Ravat, Dhananjay; Ritz, Catherine; Vaughan, Alan P. M.; Gaina, Carmen; McEnroe, Suzanne; Lesur, Vincent

2013-04-01

380

Influence of Infrared Radiation on Attic Heat Transfer  

E-print Network

surface to rneasure the ceiling heat flux. The flux meters were constructed of 318'" inch bakelite sandwiched between two 3,'~'~ inch thick aluminum plates of 6 " 6 'I. Ther- mocouples were placed between the bakelite and both alu- minum plates.... By measuring the temperature drop across the bakeli~e the heat flux can be computed, since the ther- mal conductivity of the bakelite was known. A 4 ' .. 4 ' x 114" aluminum sheet heated by a 555 watt. 1 lo\\' electric coil was mounted on the to of the box...

Katipamula, S.; Turner, W. D.; Murphy, W. E.; O'Neal, D. L.

1985-01-01

381

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 MA and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly-shaped spherical torus (ST) configuration. Improved plasma performance with high {beta}{sub t} = 15-25%, a high bootstrap current fraction f{sub BS} = 45-50%, longer plasma pulses, and an H-mode regime with smaller ELMs has been achieved in the strongly-shaped lower single null configuration with elongation {kappa} = 2.2-2.4 and triangularity {delta} = 0.6-0.8. Divertor peak heat fluxes were reduced from 6-12 MW/m{sup 2} to 0.5-2 MW/m{sup 2} in ELMy H-mode discharges using the inherently high magnetic flux expansion f{sub m} = 16-25 and the partial detachment of the outer strike point at several D{sub 2} injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z{sub eff} were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction of ion flux to the plate, and a large neutral compression ratio. Spectroscopic measurements indicated a formation of a high-density, low temperature region adjacent to the outer strike point, where substantial increases in the volume recombination rate and CII, CIII emission rates was measured.

Soukhanovskii, V A; Maingi, R; Gates, D; Menard, J

2008-12-31

382

Influence of heat generation and heat flux on peristaltic flow with interacting nanoparticles  

NASA Astrophysics Data System (ADS)

In the current study, we have examined the peristaltic flow of three different nanoparticles with water as base fluid under the influence of slip boundary conditions through a vertical asymmetric porous channel in the presence of MHD. The selected nanoparticles are titanium dioxide ( TiO2 , copper oxide (CuO) and silicon dioxide ( SiO2 . The Brownian motion shows that the effective conductivity increases to result in a lower temperature gradient for a given heat flux. To examine these transport phenomena thoroughly, we also consider the thermal conductivity model of Brownian motion for nanofluids, this increases the effect of the particle size, particle volume fraction and temperature dependence. The mathematical formulation is presented. Exact solutions are obtained from the resulting equations. The obtained expressions for pressure gradient, temperature and velocity profile are described through graphs for the various relevant parameters. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon.

Akbar, Noreen Sher; Raza, M.; Ellahi, R.

2014-08-01

383

Longitudinal Water Temperature and Heat Flux Patterns within a Semi-Natural Forested Stream Reach  

NASA Astrophysics Data System (ADS)

It is hypothesised that riparian vegetation offers potential to mitigate water temperature thermal extremes and provide refugia for temperature sensitive organisms in a warming climate. Daytime cooling gradients have been observed for stream reaches shaded by coniferous trees downstream of clear cuts; however many of these studies are confounded by cool groundwater inflows and there is a lack of research for semi-natural forest cover. This study addresses this research gap, it aims to quantify and subsequently model observed longitudinal water temperature and heat flux patterns in a semi-natural forested reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) throughout which heat exchange across the bed-water column interface accounted for < 1% of the net energy budget. Observations were made along a 1500 m reach using a spatially-distributed network of ten water temperature micro-loggers and three automatic weather stations. The reach is located below open moorland and bounded by deciduous semi-natural riparian woodland with varying canopy density and tree species composition. For periods when daytime net radiation gains were high (i.e. clear skies), downstream cooling of up to 2.5 °C was observed. Longitudinal thermal gradients were not distinct at night or on days when net radiation gains were low (i.e. over-cast sky conditions). A Lagrangian stream temperature model driven by a reach-averaged deterministic net radiation model using hemispherical photographs provided good predictions of longitudinal water temperature change. The modelling exercise demonstrates the processes which produce longitudinal cooling patterns in a reach without significant groundwater inputs. Consequently, this research provides process based evidence for the potential of riparian vegetation to mitigate thermal extremes and thus improves the scientific basis for management decisions regarding stream temperature under a changing climate.

Garner, G.; Malcolm, I.; Hannah, D. M.; Sadler, J. P.

2013-12-01

384

Heat pump augmented radiators for spacecraft thermal management  

SciTech Connect

Because future space missions will require heat rejection subsystems having megawatt capacity, the development of lightweight heat rejection techniques is desirable. Closed systems for waste heat rejection in space are radiative and their capacity is proportional to the fourth power of absolute temperature. Reductions in the surface area and therefore, in the mass of a space radiator are possible by increasing the heat rejection temperature above the temperature of the thermal source. One proposed method of increasing the heat rejection temperature uses a heat pump powered by a cyclic heat engine operating at a temperature above the waste heat source. This heat pumping technique reduces the required direct radiator surface area, but it introduces mass penalties associated with its power supply and its heat rejection system. The use of a heat pump augmented heat rejection system will generally be practical if it reduces the total radiator mass requirement over a suitable baseline design. The mass penalties of the heat pump augmented radiator over a baseline (a flat plate radiator) are considered in this analysis. 2 refs., 8 figs., 1 tab.

Merrigan, M.A.; Reid, R.S.

1988-01-01

385

Alumina Nanoparticle Pre-coated Tubing Ehancing Subcooled Flow Boiling Cricital Heat Flux  

E-print Network

Nanofluids are engineered colloidal dispersions of nano-sized particle in common base fluids. Previous pool boiling studies have shown that nanofluids can improve critical heat flux (CHF) up to 200% for pool boiling and ...

Truong, Bao H.

386

SURFACE HEAT FLUX DERIVED FROM SODAR AMPLITUDE AND FREQUENCY DATA: A COMPARISON  

EPA Science Inventory

Sensible heat flux measurements were made in an agricultural setting near Champaign, Illinois by using doppler sodar, eddy correlations and profile methods during convective conditions during an experimental study called VOICE, (Vertical Observations Involving Convective Exchange...

387

High temperature thermocouple and heat flux gauge using a unique thin film-hardware hot juncture  

NASA Technical Reports Server (NTRS)

A special thin film-hardware material thermocouple (TC) and heat flux gauge concept for a reasonably high temperature and high flux flat plate heat transfer experiment was fabricated and tested to gauge temperatures of 911 K. This concept was developed for minimal disturbance of boundary layer temperature and flow over the plates and minimal disturbance of heat flux through the plates. Comparison of special heat flux gauge Stanton number output at steady-state conditions with benchmark literature data was good and agreement was within a calculated uncertainty of the measurement system. Also, good agreement of special TC and standard TC outputs was obtained and the results are encouraging. Oxidation of thin film thermoelements was a primary failure mode after about 5 of operation.

Liebert, C. H.; Holanda, R.; Hippensteele, S. A.; Andracchio, C. A.

1984-01-01

388

Separate effects of surface roughness, wettability, and porosity on the boiling critical heat flux  

E-print Network

The separate effects of surface wettability, porosity, and roughness on the critical heat flux (CHF) of water were examined using engineered surfaces. Values explored were 0, 5, 10, and 15??m for Rz (roughness), <5°, ?75°, ...

O'Hanley, Harry

389

Multi-Dimensional, Inviscid flux Reconstruction for Simulation of Hypersonic Heating on Tetrahedral Grids.  

National Technical Information Service (NTIS)

The quality of simulated hypersonic stagnation region heating on tetrahedral meshes is investigated by using a three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. Two test problems are investigated: hypersonic flow over a thre...

P. A. Gnoffo

2009-01-01

390

Ir Thermographic Measurements of Temperatures and Heat Fluxes in Hypersonic Plasma Flow  

NASA Astrophysics Data System (ADS)

The technological development achieved in instruments and methodology concerning both flights and ground hypersonic experiment (employed in space plane planning) goes towards an updating and a standardization of the heat flux technical measurements. In fact, the possibility to simulate high enthalpy flow relative to reentry condition by hypersonic arc-jet facility needs devoted methods to measure heat fluxes. Aim of this work is to develop an experimental numerical technique for the evaluation of heat fluxes over Thermal Protection System (TPS) by means of InfraRed (IR) thermographic temperature measurements and a new heat flux sensor (IR-HFS). We tackle the numerical validation of IR-HFS, apply the same one to the Hyflex nose cap model and compare the obtained results with others ones obtained by others methodology.

Cardone, G.; Tortora, G.; del Vecchio, A.

2005-02-01

391

Sensitivity of a climatologically-driven sea ice model to the ocean heat flux  

NASA Technical Reports Server (NTRS)

Ocean heat flux sensitivity was studied on a numerical model of sea ice covering the Weddell Sea region of the southern ocean. The model is driven by mean monthly climatological atmospheric variables. For each model run, the ocean heat flux is uniform in both space and time. Ocean heat fluxes below 20 W m to the minus 2 power do not provide sufficient energy to allow the ice to melt to its summertime thicknesses and concentrations by the end of the 14 month simulation, whereas ocean heat fluxes of 30 W m to the minus 2 power and above result in too much ice melt, producing the almost total disappearance of ice in the Weddell Sea by the end of the 14 months. These results are dependent on the atmospheric forcing fields.

Parkinson, C. L.; Good, M. R.

1982-01-01

392

Flux and brightness calculations for various synchrotron radiation sources  

SciTech Connect

Synchrotron radiation (SR) storage rings are powerful scientific and technological tools. The first generation of storage rings in the US., e.g., SURF (Washington, D.C.), Tantalus (Wisconsin), SSRL (Stanford), and CHESS (Cornell), revolutionized VUV, soft X-ray, and hard X-ray science. The second (present) generation of storage rings, e.g. the NSLS VUV and XRAY rings and Aladdin (Wisconsin), have sustained the revolution by providing higher stored currents and up to a factor of ten smaller electron beam sizes than the first generation sources. This has made possible a large number of experiments that could not performed using first generation sources. In addition, the NSLS XRAY ring design optimizes the performance of wigglers (high field periodic magnetic insertion devices). The third generation storage rings, e.g. ALS (Berkeley) and APS (Argonne), are being designed to optimize the performance of undulators (low field periodic magnetic insertion devices). These extremely high brightness sources will further revolutionize x-ray science by providing diffraction-limited x-ray beams. The output of undulators and wigglers is distinct from that of bending magnets in magnitude, spectral shape, and in spatial and angular size. Using published equations, we have developed computer programs to calculate the flux, central intensity, and brightness output bending magnets and selected wigglers and undulators of the NSLS VUV and XRAY rings, the Advanced Light Source (ALS), and the Advanced Photon Source (APS). Following is a summary of the equations used, the graphs and data produced, and the computer codes written. These codes, written in the C programming language, can be used to calculate the flux, central intensity, and brightness curves for bending magnets and insertion devices on any storage ring.

Weber, J.M.; Hulbert, S.L.

1991-11-01

393

Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger  

NASA Technical Reports Server (NTRS)

An active thermal control system architecture has been modified to include a regenerative heat exchanger (regenerator) inboard of the radiator. Rather than using a radiator bypass valve a regenerative heat exchanger is placed inboard of the radiators. A regenerator cold side bypass valve is used to set the return temperature. During operation, the regenerator bypass flow is varied, mixing cold radiator return fluid and warm regenerator outlet fluid to maintain the system setpoint. At the lowest heat load for stable operation, the bypass flow is closed off, sending all of the flow through the regenerator. This lowers the radiator inlet temperature well below the system set-point while maintaining full flow through the radiators. By using a regenerator bypass flow control to maintain system setpoint, the required minimum heat load to avoid radiator freezing can be reduced by more than half compared to a radiator bypass system.

Ungar, Eugene K.; Schunk, Richard G.

2011-01-01

394

Comparison of surface radiative flux data sets over the Arctic Ocean Jiping Liu,1,2  

E-print Network

Comparison of surface radiative flux data sets over the Arctic Ocean Jiping Liu,1,2 Judith A. Curry in the Arctic Ocean. To assess how well we can reconstruct the variations of surface radiative fluxes used of the Arctic Ocean (SHEBA) over the seasonal cycle and during particular storm events. The CASPR and NCEP-R2

395

Galileo probe measurements of thermal and solar radiation fluxes in the Jovian atmosphere  

Microsoft Academic Search

The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements

L. A. Sromovsky; A. D. Collard; P. M. Fry; G. S. Orton; M. T. Lemmon; M. G. Tomasko; R. S. Freedman

1998-01-01

396

Experimental and Numerical Characterization of Transient Insertion of Heat Flux Gages in a Cylindrical Black Body Cavity at 1100 C  

NASA Technical Reports Server (NTRS)

Initial transient thermal models have been developed to simulate a heat flux gage calibration process capable of generating high heat flux levels of interest to reciprocating and gas turbine engine industries as well as the aerospace industry. These transient models are based on existing, experimentally validated, steady state models of the cylindrical blackbody calibration system. The steady state models were modified to include insertion of a heat flux gage into the hot zone of the calibration system and time varying electrical current passing through the resistance heated blackbody. Heat fluxes computed using the initial transient models were compared to experimental measurements. The calculated and measured transient heat fluxes were within 5% indicating that the major physical phenomena in the transient calibration had been captured by the models. The predicted and measured transient heat fluxes were also compared at two different gage insertion depths. These results indicated that there is an optimum insertion position which maximizes heat flux and minimizes cavity disturbance.

Abdelmessih, A. N.; Horn, T.

2006-01-01

397

On the heat flux vector for flowing granular materials--part II: derivation and special cases  

SciTech Connect

Heat transfer plays a major role in the processing of many particulate materials. The heat flux vector is commonly modelled by the Fourier's law of heat conduction and for complex materials such as non-linear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematical parameters such as temperature, shear rate, porosity or concentration, etc. In Part I, we will give a brief review of the basic equations of thermodynamics and heat transfer to indicate the importance of the modelling of the heat flux vector. We will also discuss the concept of effective thermal conductivity (ETC) in granular and porous media. In Part II, we propose and subsequently derive a properly frame-invariant constitutive relationship for the heat flux vector for a (single phase) flowing granular medium. Standard methods in continuum mechanics such as representation theorems and homogenization techniques are used. It is shown that the heat flux vector in addition to being proportional to the temperature gradient (the Fourier's law), could also depend on the gradient of density (or volume fraction), and D (the symmetric part of the velocity gradient) in an appropriate manner. The emphasis in this paper is on the idea that for complex non-linear materials it is the heat flux vector which should be studied; obtaining or proposing generalized form of the thermal conductivity is not always appropriate or sufficient.

Massoudi, Mehrdad

2006-09-10

398

New Equations For Sonic Temperature Variance And Buoyancy Heat Flux With An Omnidirectional Sonic Anemometer  

Microsoft Academic Search

Many new types of sonic anemometer obtain sonic temperature from an average value of temperature measured along three paths, unlike previous sonic anemometers that generally used one path. New equations are derived to calculate temperature variance from sonic temperature variance and sensible heat flux from buoyancy flux considering the influence of a crosswind. These equations can be applied to CSAT3,

Heping Liu; Gerhard Peters; Thomas Foken

2001-01-01

399

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

Microsoft Academic Search

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

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

2004-01-01

400

Carbon dioxide, water vapor and sensible heat fluxes over a tallgrass prairie  

Microsoft Academic Search

Fluxes of CO2, water vapor and sensible heat were measured in a grassland ecosystem near Manhattan, Kansas, employing the eddy correlation technique. The vegetation at this site is dominated by big bluestem ( Andropogon gerardii), switchgrass ( Panicum virgatum), and indiangrass ( Sorghastrum nutans). Diurnal patterns of the energy budget components and CO2 fluxes are evaluated on a few selected

Shashi B. Verma; Joon Kim; Robert J. Clement

1989-01-01

401

Carbon dioxide, water vapor and sensible heat fluxes over a tallgrass prairie  

Microsoft Academic Search

Fluxes of CO2, water vapor and sensible heat were measured in a grassland ecosystem near Manhattan, Kansas, employing the eddy correlation technique. The vegetation at this site is dominated by big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum), and indiangrass (Sorghastrum nutans). Diurnal patterns of the energy budget components and CO2 fluxes are evaluated on a few selected days. Influence of

Shashi B. Verma; Joon Kim; Robert J. Clement

1989-01-01

402

High heat flux experiments of plasma facing components for next fusion devices  

Microsoft Academic Search

To develop plasma facing components (PFC) for the next fusion devices, JAERI has been carrying out high heat flux and high particle flux experiments on the divertor modules and candidate materials in JAERI Electron Beam Irradiation System (JEBIS). (1) To investigate the feasibility and the advantage of a saddle type divertor modules, which has unidirectional (1-D) carbon fiber reinforced carbon

K. Nakamura; M. Akiba; S. Suzuki; K. Satoh; K. Yokoyama; M. Dairaku; M. Araki; Y. Ohara; T. Inoue; Y. Okumura; I. Smid

1993-01-01

403

Streambed temperature dynamics and corresponding heat fluxes in small streams experiencing seasonal ice cover  

NASA Astrophysics Data System (ADS)

Streambed temperature and heat fluxes are important for aquatic habitats as well as in the development and improvement of water temperature models. In the present study, measured streambed temperatures at different depths were used as a tracer to predict the magnitude and direction of groundwater flow using an advection-conduction heat transport model. This analysis was carried out under different conditions, namely under natural surface water temperature conditions (i.e., as measured in the field), under steady-state conditions (e.g. under stream ice cover) and for conditions where the surface water temperatures followed a sinusoidal function. In Catamaran Brook, results from the advection-conduction numerical model showed good agreement between predicted and observed streambed temperatures with root-mean-square errors (RMSEs) ranging between 0.07 °C to 0.6 °C. A comparison of streambed fluxes showed that the heat flux by conduction was more important during the summer period for upwelling conditions (mean value 96 W m-2 at 25 °C), but was also present in winter (-20 W m-2). Variability in heat flux by conduction was also greater when the diel surface water temperature variability was high (e.g. range of 6 °C). The heat flux by advection varied between -120 and 145 W m-2 (for typical water temperatures and vertical flow conditions within Catamaran Brook, 0-25 °C and ±0.005 m h-1). Short-term heat exchange (diel) occurred within the thermally active depth, typically <0.7 m. The long-term annual streambed heat flux by conduction was also calculated and daily mean was generally less than ±11 W m-2. Winter conditions provided a unique opportunity to analyse streambed heat fluxes under steady-state conditions when both conduction and advection fluxes were present.

Caissie, Daniel; Kurylyk, Barret L.; St-Hilaire, André; El-Jabi, Nassir; MacQuarrie, Kerry T. B.

2014-11-01

404

Properties of the flux of momentum, heat, and moisture in the boundary layer  

E-print Network

PROPERTIES OF THE FLUX OF MOMENTUM, HEAT, AND MOISTURE IN THE BOUNDARY LAYER A Thesis by SARA SUZANNE SCHMIEDEKAMP Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE August 1985 Major Subject: Meteorology PROPERTIES OF THE FLUX OF MOMENTUM, HEAT AND MOISTURE IN THE BOUNDARY LAYER A Thesis by SARA SUZANNE SCHMIEDEKAMP Approved as to style and content by: Dr. James R. Sc ns (Chairman of Committee) Dr...

Schmiedekamp, Sara Suzanne

2012-06-07

405

An improved time-dependent nonlocal electron heat-flux model and its verification by laser-driven Al foil acceleration experiment  

NASA Astrophysics Data System (ADS)

In hydrodynamics simulation of laser driven systems, the time-dependent nonlocal electron heat-flux models predict the saturation (flux inhibition) and delocalization of the heat-flux automatically. Therefore it avoids commonly used time and space-independent ad hoc flux limiting. Previously proposed analytical nonlocal heat-flux model of Luciani et al. [Phys. Rev. Lett., 51, p-1664, (1983)] which fits the results of numerical Fokke-Planck calculations is simple and straight forward to implement in a fluid code. The proposed expression, however, is a convolution of Spitze-Harm heat-flux with a delocalization kernel which depends on classical electron collision mean free path. This is rigorously valid for high temperature non-degenerate plasmas. However, in laser driven systems, the energy transport due to electron thermal conduction is important in regions between the critical density and ablation surface where the plasma is mostly degenerate. We have improved this nonlocal heat-flux model by using a wide-range electron collision frequency model valid from warm-dense matter (degenerate plasmas) to fully ionized plasmas. The effect of this improved nonlocal heat-flux model on the free-surface velocity of laser-accelerated Al foils of thickness 2-10 ?m is studied by using a two-dimensional radiation hydrodynamics code. The simulated free surface velocities are compared with our experimental results for laser intensities in the range 4 × 1013-3 × 1014 W/cm2. Preliminary analysis shows that the simulation results obtained with improved nonlocal heat-flux model yields better agreement with our experimental values.

Sijoy, C. D.; Chaurasia, Shivanand; Mishra, Vinayak; Leshma, P.; Sakthivel, N.; Chaturvedi, Shashank; Sharma, S. M.; Basu, Sekhar

2014-06-01

406

A new parameterization scheme for estimating surface energy fluxes with continuous surface temperature, air temperature, and surface net radiation measurements  

NASA Astrophysics Data System (ADS)

study develops a method for estimating surface energy fluxes (surface sensible heat flux (H), latent heat flux (LE), and soil heat flux (G)) simultaneously from continuous observations of surface temperature (Ts), air temperature (Ta), and net radiation (Rn) without calculating various resistances. First, H, LE, and G are parameterized by some constant parameters that remain fairly invariant during a given day and some known functions related to Ts and Ta. Second, these constant parameters are solved by a minimization technique based on surface energy balance. Data from ground-based measurements at the Yucheng station were used to evaluate the performance of the developed method. Results show that the simplified parameterization schemes well reproduce H, LE, and G with a root mean square error (RMSE) of ˜20 W/m2 at the instantaneous time scale, and perform better at the daily scale. For the estimates of H, LE, and G using the known Ts, Ta, and Rn measured at the Yucheng station as inputs, the RMSE is ˜60 W/m2 at the instantaneous time scale and ˜20 W/m2 at the daily scale. The requirement of continuous observations throughout a day in the developed method could be met by remotely sensed data from geostationary meteorological satellites. Fewer input variables and the obviation of calculating various resistances give the method the potential to generate surface fluxes over a large area.

Lu, Jing; Tang, Ronglin; Tang, Huajun; Li, Zhao-Liang

2014-02-01

407

Measurement of XUV-absorption spectra of ZnS radiatively heated foils  

NASA Astrophysics Data System (ADS)

Time-resolved absorption of zinc sulfide (ZnS) and aluminum in the XUV-range has been measured. Thin foils in conditions close to local thermodynamic equilibrium were heated by radiation from laser-irradiated gold spherical cavities. Analysis of the aluminum foil radiative hydrodynamic expansion, based on the detailed atomic calculations of its absorption spectra, showed that the cavity emitted flux that heated the absorption foils corresponds to a radiation temperature in the range 55-60 eV. Comparison of the ZnS absorption spectra with calculations based on a superconfiguration approach identified the presence of species Zn 6+-Zn 8+ and S 5+-S 6+. Based on the validation of the radiative source simulations, experimental spectra were then compared to calculations performed by post-processing the radiative hydrodynamic simulations of ZnS. Satisfying agreement is found when temperature gradients are accounted for.

Kontogiannopoulos, N.; Bastiani-Ceccotti, S.; Thais, F.; Chenais-Popovics, C.; Sauvan, P.; Schott, R.; Fölsner, W.; Arnault, Ph.; Poirier, M.; Blenski, T.

2007-05-01

408

Evaluation of sensible heat fluxes derived from Large Aperture Scintillometer measurements over irrigated and dryland cotton during BEAREX08  

NASA Astrophysics Data System (ADS)

The path integrating capabilities of scintillometer over heterogeneous landscapes makes it a powerful tool for validating satellite-based evapotranspiration (ET) maps. Numerous studies have evaluated the accuracy of sensible heat fluxes (H) derived from Large Aperture Scintillometer (LAS) measurements using eddy covariance (EC) measurements. EC systems have the energy balance closure problem (Rn-H-LE-G?0) up to 20 percent. For that reason we chose to evaluate the accuracy of the LAS-based ET fluxes against lysimeter data. Data used in this study was collected during the Bushland Evapotranspiration and Agricultural Remote Sensing Experiment 2008 (BEAREX08). The BEAREX08 was conducted at the USDA-ARS Conservation and Production Research Laboratory (CPRL) in Bushland [350 11' N, 1020 06' W; 1,170 m elevation MSL] located in the semi-arid Southern High Plains of Texas, USA during the 2008 summer cropping season. The CPRL is equipped with four large (3 x 3 x 2.5 m) monolithic lysimeters, with each lysimeter located in the center of 210 x 225 m fields arranged in a block pattern. One LAS was deployed across two dryland lysimeter fields (designated as NW and SW) and another on two irrigated lysimeter fields (designated as NE and SE), and all four fields were planted to cotton. The structure parameter of the refractive index of air was monitored at a 1-min interval and averaged for 15-minute periods between 10 July and 30 August, synchronized with weather station and lysimeter measurements. In addition, net radiation (Rn) and soil heat fluxes (G) were measured in all four lysimeter fields. Sensible heat fluxes (H) were derived from LAS measurements using a heat flux source area function and estimated ET fluxes as a residual from the energy balance were compared against lysimeter data. Trends in the LAS-based ET fluxes closely followed those in the observed data. However, LAS-based ET fluxes were over predicted by 10-35%. Differences between lysimeter- and LAS-based ET estimates over dryland cotton may be partly due to non-uniform vegetation growth on the NW and SW lysimeter fields. Overall, results indicate that the LAS is a promising tool for estimating ET fluxes.

Gowda, P.; Hartogensis, O.; Howell, T.; Scanlon, B.

2009-09-01

409

Thermal evaluation of uranium silicide miniplates irradiated at high heat flux  

SciTech Connect

The Gas Test Loop (GTL)-1 irradiation experiment was conducted in the Advanced Test Reactor (ATR) to assess corrosion performance of proposed booster fuel at heat flux levels ~30% above the design operating condition. Sixteen miniplates fabricated from 25% enriched, high-density (4.8 g U/cm3) U3Si2/Al dispersion fuel with 6061 aluminum cladding were subjected to peak beginning of cycle (BOC) heat fluxes ranging from 411 to 593 W/cm2. No adverse impacts to the miniplates were observed at these high heat flux levels. A detailed finite element model was constructed to calculate temperatures and heat flux for an as-run cycle average effective ATR south lobe power of 25.4 MW(t). Miniplate heat flux levels and fuel, cladding, hydroxide, and coolant–hydroxide interface temperatures were calculated using the average hydroxide thickness on each miniplate measured during post-irradiation examination. The purpose of this study was to obtain a best estimate of the as-run experiment temperatures to aid in establishing acceptable heat flux levels and designing fuel qualification experiments for this fuel type.

Donna P. Guillen

2012-09-01

410

The ice flow sensitivity to geothermal heat flux of Pine Island Glacier, Antarctica.  

NASA Astrophysics Data System (ADS)

Model projections of ice flow in a changing climate are dependent on model inputs such as surface altimetry, bedrock position, surface temperatures, etc. Of all these inputs, geothermal heat flux is the one for which uncertainty is greatest. Specifically, in the area of Pine Island Glacier, Antarctica, available dataset differ by up to a factor of 2.5 . Here, we evaluate the impact of such uncertainty on ice flow, using sampling analyses based on the Latin-Hypercube method. First, we quantify the impact of geothermal heat flux errors on ice hardness, a thermal parameter which critically controls the magnitude of ice flow. Second, we quantify the impact of the same errors on mass balance, specifically on the mass flux advecting through thirteen flux gates distributed across Pine Island Glacier. We contrast our results with similar uncertainties generated by errors in the specification of ice thickness. Model outputs indicate that geothermal heat flux errors yield uncertainties on ice hardness on the order of 5-7%, with maximum uncertainty reaching 15%. Resulting uncertainties in mass balance remain however below 1%. We discuss the uncertainty distribution and its relationship to the amount of heat available at the base of the ice sheet from friction, viscous and geothermal heating. We also show that comparatively, errors in ice thickness contribute more to model uncertainty than errors in geothermal heat flux, especially for fast-flowing ice streams.

Larour, E. Y.; Morlighem, M.; Seroussi, H. L.; Schiermeier, J.; Rignot, E. J.

2012-12-01

411

Kilometric radiation power flux dependence on area of discrete aurora  

NASA Technical Reports Server (NTRS)

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

Saflekos, N. A.; Burch, J. L.; Gurnett, D. A.; Anderson, R. R.; Sheehan, R. E.

1989-01-01

412

Characterization of a heat flux sensor using short pulse laser calibration  

SciTech Connect

A method to calibrate classical heat flux sensors is presented. The classical approach to measure the temperature inside a known material by using a thermocouple fails when the measurement time is very short. In this work the surface heat flux is determined by solving the inverse heat conduction problem using a noninteger identified system as a direct model for the estimation process. Using short pulse laser calibration measurements the crucial design aspects of the sensor that play a significant role when assuming one-dimensional, semi-infinite heat transfer have been accounted for. The theoretical approach as well as the calibration results are presented and comparisons to the classical approach and results from finite element modeling are shown. It is concluded that the new method ameliorate the heat flux sensor significantly and extend its application to very short measurement times.

Loehle, Stefan; Battaglia, Jean-Luc; Batsale, Jean-Christophe; Enouf, Olivier; Dubard, Jimmy; Filtz, Jean-Remy [TREFLE Universite de Bordeaux I, Esplanade des Arts et Metiers, 33405 Talence (France); Laboratoire National de Metrologie et d'Essais, 29, Avenue Roger Hennequin, 78197 Trappes (France)<