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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

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

3

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

Microsoft Academic Search

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

Peter S. Cumber

2011-01-01

4

[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

5

Heat flux microsensor measurements  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

6

Simulation of solar radiation heat flux data for energy calculation  

Microsoft Academic Search

The global (or total) and diffuse solar irradiation data are not always available in many areas of the world and they have to be estimated using some sort of empirical models. This paper describes how the sequence of hourly irradiation data can be simulated using some statistical parameters of the global solar radiation intensity such as the monthly average and

A. Panek; Y. Lee; H. Tanaka

1996-01-01

7

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

8

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

9

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

E-print Network

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

Winter, Jonathan (Jonathan Mark)

10

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.

11

A Simple Method for Estimating the Latent Heat Flux over Grass from Radiative Bowen Ratio.  

NASA Astrophysics Data System (ADS)

The evaluation of crop evapotranspiration from infrared temperature is usually calculated as the residual component of the surface energy balance. This method has given good results over a full grass canopy cover with unstressed transpiration, in spite of the not well understood meaning of the aerodynamic resistance needed. A simple and more accurate method, which determines the Bowen ratio () and the latent heat flux (E) over a reference grass area without knowledge of surface resistances, is proposed. The proportionality between and a radiative Bowen ratio s is shown. The radiative Bowen ratio is derived from surface and air temperatures and vapor pressure. This relationship allows the estimation of E from temperatures, vapor pressure, and solar radiation measurements at one reference level. The new method gives an estimated error of around 10% in front of the residual one, where the wind speed has to be known, with an error of above 20%. The proposed method requires further verification for different climatological conditions.

Ibañez, M.; Pérez, P. J.; Caselles, V.; Castellvi, F.

1998-04-01

12

Experimental study of radiation power flux on the target surface during high heat plasma irradiation  

NASA Astrophysics Data System (ADS)

Some new data of the experimental study of visible radiation from the plasma shielding layer (SL) on the target surface during high heat plasma-material interaction are given in the report. The experiments were performed on the VIKA facility. Long pulse ( ?p=0.36 ms) high power ( Pirr˜100 GW m -2 plasma streams were used for irradiation of graphite and tungsten samples. The target inclination ( ?=0° normal irradiation; 45°; 70°) and magnetic field ( B=0 to 3 T) were varied in experiments. It is shown that the values of ( ???400 to 700 nm) visible radiation power flux (VRPF) on the target surface can be characterised by the level of PR˜1 GW m -2 for normal irradiation in the presence of a magnetic field B=2 to 3 T. Inclination of targets leads to the reduction of this flux in conformity with the corresponding decrease of the irradiation power. The material of the target does not influence sufficiently on the level of the incident radiation power flux in the performed experiments.

Litunovsky, V. N.; Ovchinnikov, I. B.; Titov, V. A.

2001-03-01

13

Heat flux measurements  

SciTech Connect

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, C.H.; Weikle, D.H.

1989-01-01

14

Transient combined radiation and conduction heat transfer in fibrous media with temperature and flux boundary conditions  

Microsoft Academic Search

Transient radiative and conductive heat transfer in a fibrous medium with anisotropic optical properties is investigated. Two different kinds of boundary conditions are treated: when the temperatures imposed on the boundaries vary with time and when the medium is subject to a radiation source which varies with time. A one dimensional case is considered. The non-linear transient Heat Conduction Equation

Fatmir Asllanaj; Gérard Jeandel; Jean Rodolphe Roche; David Lacroix

2004-01-01

15

UNSTEADY HYDROMAGNETIC FREE CONVECTION FLOW OF A DISSIPATIVE AND RADIATING FLUID PAST A VERTICAL PLATE WITH CONSTANT HEAT FLUX  

Microsoft Academic Search

The effect of thermal radiation absorption on an unsteady free convective flow past a vertical plate is studied in the presence of a magnetic field and constant wall heat flux. Boundary layer equations are derived, and the resulting approximate nonlinear ordinary differential equations are solved analytically using asymptotic technique. A parametric study of all parameters involved is conducted, and a

A. Ogulu; O. D. Makinde

2008-01-01

16

Role of Solar Radiation and Water Vapour Pressure Deficit in Controlling Latent Heat Flux Density in a Scots Pine Forest  

Microsoft Academic Search

We assessed in absolute and relative terms how solar radiation and water vapour pressure deficit control the latent heat flux density in a Scots pine (Pinus sylvestris L.) forest growing under boreal conditions. The absolute and relative total control can be expressed as sums of the physical and biological forms of control. Physical control is based on the direct effects

Qingguo Wang; Seppo Kellomäki

2005-01-01

17

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

PubMed

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

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

2012-06-01

18

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

E-print Network

.24(ea/Ta)1/7, where ea is the atmospheric water vapor pressure in hPa and Ta is the atmospheric is corrected based on air pressure and vapor pressure. The ra is rather complex function of various physical). Latent heat flux is expressed as where is the psychrometric constant, is the saturation vapor pressure

Hall, Sharon J.

19

A non-water-cooled heat flux measurement system under concentrated solar radiation conditions  

Microsoft Academic Search

This paper presents a brief description of a direct heat flux measurement system to measure the concentrated solar power delivered by a heliostat field onto the flat aperture of solar central receiver prototypes. The main advantages of this device are the low measurement uncertainty and the non-requirement of water-cooling. This system has been designed, mounted and used successfully on top

Jesus Ballestrin

2002-01-01

20

Scrape-off layer modeling of radiative divertor and high heat flux experiments on D3-D  

NASA Astrophysics Data System (ADS)

We use a new multispecies 1-D fluid code, NEWT-1D, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix T(sub i) with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80 percent of the SOL power input are obtained in 1-D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2-D geometries.

Campbell, R. B.; Petrie, T. W.; Hill, D. N.

1992-03-01

21

Scrape-off layer modeling of radiative divertor and high heat flux experiments on DIII-D  

NASA Astrophysics Data System (ADS)

We use a new multispecies 1D fluid code, NEWT-ID, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix Ti with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80% of the SOL power input are obtained in 1D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2D geometries.

Campbell, R. B.; Petrie, T. W.; Hill, D. N.

1992-12-01

22

INCORPORATION OF A TWO-FLUX MODEL FOR RADIATIVE HEAT TRANSFER IN A COMPREHENSIVE FLUIDIZED BED SIMULATOR PART II: NUMERICAL RESULTS AND ASSESSMENT  

Microsoft Academic Search

As shown in the first part of this paper, equations and considerations for a preliminary attempt to improve the treatment for radiative heat transfer of a previous comprehensive simulation program were presented. For that, the two-flux radiative heat transfer model was applied. In this second part, the new version of that program was tested against steady-state operations of real equipment.

J. A. Rabi; M. L. de Souza-Santos

23

Latent Heat in Soil Heat Flux Measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

24

Transient critical heat flux  

SciTech Connect

The term Critical Heat Flux (CHF) is used in boiling heat transfer to describe the local value of the heat flux at which a characteristic reduction in the heat transfer coefficient first occurs. A major limitation on the thermal design of a light-water reactor (LWR) is the necessity to maintain an adequate safety margin between the CHF and the local heat flux. Extended operations at local power levels in excess of the CHF can lead to high-temperature oxidation and embrittlement or melting of the zircaloy cladding, thus jeopardizing the fuel rod's integrity. In nuclear reactors, the CHF level is more likely to be reached during abnormal (transient) operating conditions, rather than during normal (steady) operations. For accurate nuclear reactor modeling, the accurate prediction of CHF as a function of time-dependent, thermal-hydraulic conditions is essential. This research was a two-fold study. In the first part, the quasi-steady approach in predicting the CHF is defined and analyzed. Data from blowdown experiments are compared to commonly used steady-state correlations on a local-instantaneous basis. In the second part, faster transients, where the quasi-steady approach is unable to predict the CHF, are considered. A new theory is developed to predict the CHF in power transients, which are typical of Reactivity Initiated Accidents (RIA) in LWRs.

Pasamehmetoglu, K.O.

1986-01-01

25

Surface heat fluxes in the Western Equatorial Pacific Ocean  

Microsoft Academic Search

Estimates of the components of the surface heat flux in the Western Equatorial Pacific Ocean are presented for a 22-day period, together with a critical analysis of the errors. It is shown that the errors in latent heat, and solar and longwave radiation fluxes, dominate the net heat flux for this period. It is found that the net heat flux

N. C. Wells

1995-01-01

26

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

27

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

28

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

29

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

30

GEWEX Radiative Flux Assessment  

... detail and accuracy to diagnose the causes of recent climate variations in terms of the energy and water exchanges among the main ... project will provide a forum for consistent analysis of long-term radiative flux products, primarily top-of-atmosphere (TOA) and ...

2013-06-27

31

Photovoltaic Roof Heat Flux  

NASA Astrophysics Data System (ADS)

Solar panels were mounted with different designs onto 1:800 scale building models while temperature and radiation were measured. While there have been other studies aimed at finding the optimal angles for solar panels [9], in this study both the angle and the mounting method were tested. The three PV mounting designs that were considered to provide the most insulation to a building's rooftop were flush, offset (control), and angled. The solar panel offset height became a key component for rooftop insulation as well as the performance of the actual solar panel. Experimental results were given to verify the thermal behavior of the heat loads from the different designs of the photovoltaic panel. From the results, the angled PV design needed 16Z more heat extraction than the offset and flush PV design needed 60% more heat extracted than the offset. In addition to the heat transfer analysis, thermal models were performed to incorporate main atmospheric conditions which were based on the effects of PV mounting structure.

Samady, Mezhgan Frishta

32

Heat Fluxes in Tampa Bay, FL  

NASA Astrophysics Data System (ADS)

For the period of May 2002 to present, as part of the Bay Regional Atmospheric Chemistry Experiment, an observational tower has been maintained in Middle Tampa Bay that is equipped with sensors measuring meteorological and air-water turbulent flux parameters. Data acquired from this tower include air temperature, humidity and horizontal wind velocity measured at two heights, precipitation, incoming radiation, and barometric pressure. A SeaGauge sensor monitors water temperature, salinity, and water level, and a sonic anemometer measures the three-dimensional wind speed and the turbulent flux of momentum and sensible heat. Using data gathered from the tower, sea surface albedo and upwelling and downwelling long- and shortwave radiation fluxes are determined. Heat flux due to precipitation is calculated and the directly measured sensible heat flux is compared with the sensible flux derived using bulk formula and gradient-flux methods. Latent heat flux is also computed via the latter two methods. Temporal and vertical variations, including trends connected with seasonal and shorter signal scale events, are examined. Components of the heat budget of Tampa Bay are determined through a variety of pathways in order to constrain the error associated with the calculation of these parameters.

Sopkin, K. L.; Luther, M. E.; Gilbert, S. A.; Subramanian, V.; Scudder, J.; Wetzell, L. M.

2003-12-01

33

Heat flux solarimeter  

SciTech Connect

The solarimeter presented in this work is easy to assemble. It is calibrated and its performance is validated by means of Hottel's method. Finally, the curves obtained with this solarimeter are compared to the ones obtained with a commercial solarimeter. This device is based on the evaluation of the heat flow in a metal rod. In consequence, measurements are not affected by ambient temperature variations. On the other hand, there is a linear relationship between the temperatures measured at the rod ends and the incident radiation, as can be concluded both from the theory of its operation and the calibration lines obtained. The results obtained from the global irradiance measurements in the area of Los Polvorines (Buenos Aires Province), together with a preliminary evaluation of the solarimeter's response time, are presented in this work. (author)

Sartarelli, A.; Vera, S.; Cyrulies, E. [Instituto de Desarrollo Humano, Univ. Nac. de Gral. Sarmiento (IDH, UNGS), Los Polvorines (Argentina); Echarri, R. [Instituto de Desarrollo Humano, Univ. Nac. de Gral. Sarmiento (IDH, UNGS), Los Polvorines (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Samson, I. [INTEC (Instituto Tecnologico Santo Domingo), Santo Domingo (Dominican Republic)

2010-12-15

34

Critical heat flux around strongly heated nanoparticles.  

PubMed

We study heat transfer from a heated nanoparticle into surrounding fluid using molecular dynamics simulations. We show that the fluid next to the nanoparticle can be heated well above its boiling point without a phase change. Under increasing nanoparticle temperature, the heat flux saturates, which is in sharp contrast with the case of flat interfaces, where a critical heat flux is observed followed by development of a vapor layer and heat flux drop. These differences in heat transfer are explained by the curvature-induced pressure close to the nanoparticle, which inhibits boiling. When the nanoparticle temperature is much larger than the critical fluid temperature, a very large temperature gradient develops, resulting in close to ambient temperature just a radius away from the particle surface. The behavior reported allows us to interpret recent experiments where nanoparticles can be heated up to the melting point, without observing boiling of the surrounding liquid. PMID:19391744

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

2009-02-01

35

Analytical solution for boundary heat fluxes from a radiating rectangular medium  

NASA Technical Reports Server (NTRS)

Reference is made to the work of Shah (1979) which demonstrated the possibility of partially integrating the radiative equations analytically to obtain an 'exact' solution. Shah's solution was given as a double integration of the modified Bessel function of order zero. Here, it is shown that the 'exact' solution for a rectangular region radiating to cold black walls can be conveniently derived, and expressed in simple form, by using an integral function, Sn, analogous to the exponential integral function appearing in plane-layer solutions.

Siegel, R.

1991-01-01

36

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

37

Radial heat flux transformer  

NASA Technical Reports Server (NTRS)

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

Basiulis, A.; Buzzard, R. J.

1971-01-01

38

Atmospheric State, Cloud Microphysics and Radiative Flux  

DOE Data Explorer

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

Mace, Gerald

39

Atmospheric State, Cloud Microphysics and Radiative Flux  

SciTech Connect

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

Mace, Gerald

2008-01-15

40

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

41

Heat flux limiting sleeves  

DOEpatents

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

Harris, William G. (Tampa, FL)

1985-01-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

44

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.

Jeff DeLaBeaujardiere

2005-05-27

45

Combined conduction and radiation heat transfer in porous materials heated by intense solar radiation  

Microsoft Academic Search

An analysis is presented to predict the heat transfer characteristics of a plane layer of a semitransparent, high-temperature, porous material which is irradiated by an intense solar flux. A transient, combined conduction and radiation heat transfer model, which is based on a two-flux approximation for the radiation, is used to predict the temperature distribution and heat transfer in the material.

L. K. Matthews; F. P. Incropera; R. Viskanta

1985-01-01

46

Comparing different land surface heat flux estimates  

NASA Astrophysics Data System (ADS)

Land surface heat fluxes are an important component of Earth's energy and water cycle, and quantifying these fluxes can help scientists better understand climate change. These heat fluxes are affected by factors such as cloud cover, precipitation, surface radiation, air temperature, and humidity. Different methods are used to estimate monthly mean land surface heat flux. To determine how well these different methods agree with one other, Jiménez et al. present a detailed global intercomparison of 12 such products for the period 1993-1995. Some of these products are based on combining global satellite-based data and physical formulations, while others come from atmospheric reanalysis and land surface models. The authors found that although there were some differences among the products, the products all captured the seasonality of the heat fluxes as well as the expected spatial distributions related to major climatic regimes and geographical features. Furthermore, the products correlate well with each other in general, in part due to large seasonable variability and the fact that some of the products use the same forcing data. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD014545, 2011)

Tretkoff, Ernie

2011-04-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

48

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

NASA Astrophysics Data System (ADS)

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

Reddy, M. Gnaneswara

2013-03-01

49

Coupled Estimation of Surface Heat fluxes and Vegetation Dynamics From Remotely Sensed Land Surface Temperature and Fraction of Photosynthetically Active Radiation  

NASA Astrophysics Data System (ADS)

Remotely sensed Land Surface Temperature (LST) and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) are assimilated respectively into the Surface Energy Balance (SEB) equation and a Vegetation Dynamics Model (VDM) in order to estimate surface fluxes and vegetation dynamics. The problem is posed in terms of three unknown and dimensionless parameters: (1) neutral bulk heat transfer coefficient that scales the sum of turbulent fluxes, (2) evaporative fractions for soil and canopy, which represent partitioning among the turbulent fluxes over soil and vegetation, and (3) specific leaf area, which captures seasonal phenology and vegetation dynamics. The model is applied over the Gourma site in Mali, the northern edge of the West African Monsoon (WAM) domain. The application of model over the Gourma site shows that remotely sensed FPAR observations can constrain the VDM and retrieve its main unknown parameter (specific leaf area) over large-scale domains without costly in situ measurements. The results indicate that the estimated specific leaf area values vary reasonably with the influential environmental variables such as precipitation, air temperature, and solar radiation. Assimilating FPAR observations into the VDM can also provide Leaf Area Index (LAI) dynamics. The retrieved LAI values are comparable in magnitude, spatial pattern and temporal evolution with observations. Moreover, it is demonstrated that the spatial patterns of estimated neutral bulk heat transfer coefficient resemble those of observed vegetation index even though no explicit information on vegetation phenology is used in the model. Furthermore, the day-to-day variations in the retrieved evaporative fraction values are consistent with wetting and drydown events. Finally, it is found that evaporative fraction is strongly correlated to LAI when soil surface is dry because in this condition soil evaporation is an insignificant component of latent heat flux, and therefore transpiration is the dominant component.

Castelli, F.; Bateni, S.; Entekhabi, D.

2011-12-01

50

Vertical eddy heat fluxes from model simulations  

NASA Technical Reports Server (NTRS)

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

Stone, Peter H.; Yao, Mao-Sung

1991-01-01

51

The Theory of Heat Flux Meters  

Microsoft Academic Search

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

J. R. Philip

1961-01-01

52

Latent heat sink in soil heat flux measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

53

Effects of dynamical heat fluxes on model climate sensitivity  

Microsoft Academic Search

The effect of the meridional and vertical dynamic heat fluxes on climate sensitivity is investigated using an annual mean coupled high and low latitude radiative-dynamical model of the northern hemisphere. The model was constructed by incorporating a meridonal (atmosphere and ocean) dynamical heat flux parameterization into a two-zone (flow latitude 0°-30°N and high latitude 30°-90°N) version of the vertical radiative-convective

Wei-Chyung Wang; Gyula Molnar; Todd P. Mitchell; Peter H. Stone

1984-01-01

54

Effects of Dynamical Heat Fluxes on Model Climate Sensitivity  

Microsoft Academic Search

The effect of the meridional and vertical dynamical heat fluxes on climate sensitivity is investigated using an annual mean coupled high and low latitude radiative-dynamical model of the northern hemisphere. The model was constructed by incorporating a meridional (atmosphere and ocean) dynamical heat flux parameterization into a two-zone (low latitude 0ø-30øN and high latitude 30ø-90øN) version of the vertical radiative-convective

Wei-Chyung Wang; Gyula Molnar; Todd P. Mitchell; Peter H. Stone

1984-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

56

Evaluation of factors affecting heat flux sensors  

Microsoft Academic Search

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

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

1983-01-01

57

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

58

Where do ocean eddy heat fluxes matter?  

Microsoft Academic Search

A quasi-global compilation of current meter and temperature records, along with some of the published literature, is used to assess the importance of the meridional eddy heat flux in the ocean circulation, and a comparison is made to a uniform global estimate from altimetric data. Eddy fluxes are found to be important, relative to estimated total heat fluxes, in western

Carl Wunsch

1999-01-01

59

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

2015-01-01

60

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

Microsoft Academic Search

The surface heat flux response to underlying sea surface temperature (SST) anomalies (the surface heat flux feedback) is estimated using 42 yr (1956 97) of ship-derived monthly turbulent heat fluxes and 17 yr (1984 2000) of satellite-derived monthly radiative fluxes over the global oceans for individual seasons. Net surface heat flux feedback is generally negative (i.e., a damping of the

Clara Deser; Michael A. Alexander

2005-01-01

61

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

62

Miniature Convection Cooled Plug-type Heat Flux Gauges  

NASA Technical Reports Server (NTRS)

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

Liebert, Curt H.

1994-01-01

63

High heat flux heat pipe mechanism for cooling of electronics  

Microsoft Academic Search

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

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

2001-01-01

64

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

65

In situ High Temperature Heat Flux Sensor Calibration  

Microsoft Academic Search

Recent advances in heat flux measurement have resulted in the development of a robust thermopile heat flux sensor intended for use in extreme thermal environments. The High Temperature Heat Flux Sensor (HTHFS) is capable of simultaneously measuring thermopile surface temperature and heat flux at sensor temperatures up to 1000°C. The need for high temperature heat flux calibration of the HTHFS

Clayton A. Pullins; Tom E. Diller

2010-01-01

66

Heat fluxes in Tampa Bay, Florida  

Microsoft Academic Search

The Meyers et al. (2007) Tampa Bay Model produces water level and three-dimensional current and salinity fields for Tampa Bay. It is capable of computing temperature but is presently run without active thermodynamics. Variations in water temperature are driven by heat exchange at the water-atmosphere boundary and advective heat flux at the mouth of the bay. The net heat exchange

Kristin L Sopkin

2008-01-01

67

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

68

Radiative flux opens new window on climate research  

NASA Technical Reports Server (NTRS)

For several decades, global satellite observations have been made of the rate at which electromagnetic energy (radiative flux) is emerging from the top of the atmosphere of our planet in the spectral range of about 0.2-50.0 microns. At the same time, models have been developed to infer the radiative flux at the surface from the values observed by the satellites at the upper boundary. The balance of incoming and outgoing radiative flux (radiation budget) at both boundaries, determines the net gain or loss of the radiative energy within an atmospheric column. Climate researchers can use the radiative flux as a tool to validate climate models, separate the radiative impact of clouds from surface and atmosphere contributions, and to understand the global hydrological cycle. When applied to physical processes occurring at the surface, information on the radiative flux has the potential to substantially advance our understanding of the transport of heat, moisture, and momentum across the surface/atmosphere interface. Geophysicists of many disciplines stand to benefit from efforts to improve the use of this latter untapped resource. Oceanographers can improve the representation of the selective absorption of radiation in the oceans; biologists and ecologists can improve their models for carbon dioxide exchange and biological heating in oceans; agronomists can model more realistically biomass and crop yields; and environmentalists can obtain better assessment of natural resources of radiation.

Pinker, R. T.; Laszlo, I.; Whitlock, C. H.; Charlock, T. P.

1995-01-01

69

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

70

New Vacuum Blackbody Cavity for Heat Flux Meter Calibration  

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

71

Surface heat flux variability over the northern  

Microsoft Academic Search

Surface heat flux components are estimated at a midshelf site over the northern California shelf using moored measurements from the 1981-1982 Coastal Ocean Dynamics Experiment (CODE) and the 1988-1989 Shelf Mixed Layer Experiment (SMILE). Time series of estimated fluxes extend from early winter through summer upwelling conditions, allowing examination of seasonal variations as well as synoptic events. On a seasonal

Steven J. Lentz; Jerome P. Dean

1998-01-01

72

Urban Signatures: Sensible Heat Flux (WMS)  

NSDL National Science Digital Library

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

Jeff DeLaBeaujardiere

2005-05-27

73

Evaluation of Global Surface Heat Fluxes From the WHOI OAFlux, ISCCP, and Atmospheric Reanalyses  

Microsoft Academic Search

The Objectively Analyzed air-sea Fluxes (OAFlux) project has been undertaken at Woods Hole Oceanographic Institution (WHOI) to develop improved surface heat flux estimates. The objective of this project is to construct daily gridded air-sea heat flux (including latent and sensible heat fluxes as well as shortwave and longwave radiation) over the global ice-free oceans for the past 50 years. At

X. Jin; L. Yu; R. Weller

2006-01-01

74

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

75

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

76

Controls on plume heat flux and plume excess temperature  

Microsoft Academic Search

Plume heat flux and plume excess temperature in the upper mantle inferred from surface observations may pose important constraints on the heat flux from the core and mantle internal heating rate. This study examined the relationship between plume heat flux Qp, core-mantle boundary (CMB) heat flux Qcmb and plume excess temperature ?Tplume in thermal convection using both numerical modeling and

Wei Leng; Shijie Zhong

2008-01-01

77

Controls on plume heat flux and plume excess temperature  

Microsoft Academic Search

Plume heat flux and plume excess temperature in the upper mantle inferred from surface observations may pose important constraints on the heat flux from the core and mantle internal heating rate. This study examined the relationship between plume heat flux Q p , core-mantle boundary (CMB) heat flux Q cmb and plume excess temperature DeltaT plume in thermal convection using

Wei Leng; Shijie Zhong

2008-01-01

78

High-heat-flux sensor calibration using calorimetry  

Microsoft Academic Search

This paper demonstrates a calorimetric procedure for calibrating high-heat-flux sensors. The results are in agreement with calibrations obtained using black-body radiation. However, the proposed method has the potential of being more accurate than traditional approaches. This new procedure calibrates sensors to measure correctly under conditions of concentrated solar radiation. At present, the thermal balance calibration technique in the laboratory is

J. Ballestrín; C. A. Estrada; M. Rodríguez-Alonso; C. Pérez-Rábago; L. W. Langley; A. Barnes

2004-01-01

79

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

80

Wave-Coherent Air Sea Heat Flux  

Microsoft Academic Search

Air-sea fluxes of heat and momentum play a crucial role in weather, climate, and the coupled general circulation of the oceans and atmosphere. Much progress has been made to quantify momentum transfer from the atmosphere to the ocean for a wide range of wind and wave conditions. Yet, despite the fact that global heat budgets are now at the forefront

Fabrice Veron; W. Kendall Melville; Luc Lenain

2008-01-01

81

Estimation of Global Ground Heat Flux  

Microsoft Academic Search

This study investigates the feasibility of a previously published algorithm for estimating global ground heat flux (GHF). The proposed method is based on an analytical solution of the diffusion equation for heat transfer in a soil layer that has been shown to be effective at local scales. The algorithm has several advantageous properties: (1) single-level input of surface (skin) temperature,

W. Bennett; J. Wang; R. Bras

2007-01-01

82

Cooling for high heat flux VLSI systems  

Microsoft Academic Search

Recent projections have suggested that heat fluxes may possibly reach 100 W\\/cm2 in future integrated circuit chips. The authors first discuss these projections and outline some of the problems associated with getting these power levels into high density packages for integrated systems. The authors then address the problem of getting the resulting heat back out of the package and look

R. C. Jaeger; J. S. Goodling

1991-01-01

83

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

84

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

Microsoft Academic Search

A theory for pyrgeometer operation is utilized for determining downwelling longwave radiation. Errors in downwelling longwave radiation measurements are due to differences in pyrgeometer body and dome temperatures compared to that of the atmosphere. Additionally, incident shortwave radiation fluxes may be important. Using the present theory along with laboratory and field observations, it appears that downwelling longwave heat fluxes can

T. D. Dickey; D. V. Manov; R. A. Weller; D. A. Siegel

1994-01-01

85

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

86

Effects of dynamic heat fluxes on model climate sensitivity: meridional sensible and latent heat fluxes  

Microsoft Academic Search

The authors incorporate physically based parameterizations of atmospheric meridional heat fluxes into the climate model of Wang et al. (1984) to study their effects on climate changes caused by increases of COâ abundance and solar constant variations. The physically based parameterizations calculate both the magnitudes and profiles of the sensible and latent heat fluxes in good agreement with observations. Comparisons

W. J. Jr. Gutowski; W.-C. Wang; Peter H. Stone

1985-01-01

87

Effects of dynamic heat fluxes on model climate sensitivity: Meridional sensible and latent heat fluxes  

Microsoft Academic Search

We incorporate physically based parameterizations of atmospheric meridional heat fluxes into the climate model of Wang et al. (1984) to study their effects on climate changes caused by increases of CO2 abundance and solar constant variations. The physically based parameterizations calculate both the magnitudes and profiles of the sensible and latent heat fluxes in good agreement with observations. Comparisons of

W. J. Gutowski; W.-C. Wang; Peter H. Stone

1985-01-01

88

Latitudinal Variations in the Solar Wind Electron Heat Flux  

Microsoft Academic Search

Ulysses measurements of the solar wind electron heat flux as a function of heliographic latitude are presented. The latitudinal in the electron heat flux presented have been normalized by the radial gradient in the electron heat flux obtained during the in-ecliptic phase of the Ulysses mission (qe˜ R-3.0). We find no significant variation in electron heat flux with latitude.

Earl E. Scime; Samuel J. Bame; John L. Phillips; Andre Balogh

1995-01-01

89

Latitudinal variations in the solar wind electron heat flux  

Microsoft Academic Search

Ulysses measurements of the solar wind electron heat flux as a function of heliographic latitude are presented. The latitudinal in the electron heat flux presented have been normalized by the radial gradient in the electron heat flux obtained during the in-ecliptic phase of the Ulysses mission (qe~ R-3.0). We find no significant variation in electron heat flux with latitude.

Earl E. Scime; Samuel J. Bame; John L. Phillips; Andre Balogh

1995-01-01

90

Heat-Flux Gage thermophosphor system  

SciTech Connect

This document describes the installation, hardware requirements, and application of the Heat-Flux Gage (Version 1.0) software package developed by the Oak Ridge National Laboratory, Applied Technology Division. The developed software is a single component of a thermographic phosphor-based temperature and heat-flux measurement system. The heat-flux transducer was developed by EG G Energy Measurements Systems and consists of a 1- by 1-in. polymethylpentene sheet coated on the front and back with a repeating thermographic phosphor pattern. The phosphor chosen for this application is gadolinium oxysulphide doped with terbium. This compound has a sensitive temperature response from 10 to 65.6{degree}C (50--150{degree}F) for the 415- and 490-nm spectral emission lines. 3 refs., 17 figs.

Tobin, K.W.

1991-08-01

91

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

92

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

93

Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer  

PubMed Central

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

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

2014-01-01

94

Heat flux apportionment to heterogeneous surfaces using flux footprint analysis  

Microsoft Academic Search

Heat flux data collected from the Baiyangdian Heterogeneous Field Experiment were analyzed using the footprint method. High\\u000a resolution (25 m) Landsat-5 satellite imaging was used to determine the land cover as one of four surface types: farmland,\\u000a lake, wetland, or village. Data from two observation sites in September 2005 were used. One site (Wangjiazhai) was characterized\\u000a by highly heterogeneous surfaces

Guliang Peng; Xuhui Cai; Hongsheng Zhang; Aiguo Li; Fei Hu; Monique Y. Leclerc

2008-01-01

95

Poleward heat flux by an ocean gyre  

NASA Astrophysics Data System (ADS)

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

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

1980-01-01

96

Covariability of SST and surface heat fluxes in reanalyses and CMIP3 climate models  

Microsoft Academic Search

The generation and dissipation of SST anomalies is mediated by the covariability of SST and surface heat fluxes. The connection\\u000a between the variability of heat flux (including its radiative and turbulent components) and that of SST is investigated using\\u000a the NCEP-NCAR and ERA-40 reanalyses and the CMIP3 multi-model collection of climate simulations. The covariance patterns of\\u000a SST and heat flux

Bin Yu; G. J. Boer; F. W. Zwiers; W. J. Merryfield

2011-01-01

97

Heat flux sensors: Calorimeters or radiometers?  

Microsoft Academic Search

Different methods may be used for measurement of very high solar irradiance on large areas, all of them are based on one or several heat flux sensors. The most common gages used for this purpose are the Gardon type, which are usually calibrated using a black body at a certain temperature as the radiant source. An alternative way to calibrate

J. Ballestrín; C. A. Estrada; M. Rodríguez-Alonso; C. Pérez-Rábago; L. W. Langley; A. Barnes

2006-01-01

98

Thermal coupling of a heat flux sensor  

NASA Technical Reports Server (NTRS)

The conditions of thermal coupling were investigated in relationship to the development of sensors for local thermal flux measurements of component surfaces. The dependence of the transfer function on heat conductivity coefficient of the measured object and the influence of the contact resistance at the sensor boundaries are discussed in terms of known results and investigations.

Kaiser, E.

1982-01-01

99

Heat flux concentration through polymeric thermal lenses  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

100

Method of predicting radiation heat transfer in turbine cooling test facilities  

NASA Technical Reports Server (NTRS)

A method is presented for calculating the average net radiation heat flux to turbine vanes and blades. The net radiation heat flux at a vane leading edge calculated by this method was compared with heat flux values independently determined from experimental tests on a vane in a cascade. The spectral emissivities of the turbine vane and the cascade wall were also measured.

Gladden, H. J.; Liebert, C. H.

1975-01-01

101

Understanding electron heat flux signatures in the solar wind  

Microsoft Academic Search

Suprathermal electrons (E > 80 eV) carry heat flux away from the Sun. Processes controlling the heat flux are not well understood. To gain insight into these processes, we model heat flux as a linear dependence on two independent parameters: electron number flux and electron pitch angle anisotropy. Pitch angle anisotropy is further modeled as a linear dependence on two

C. Pagel; N. U. Crooker; D. E. Larson; S. W. Kahler; M. J. Owens

2005-01-01

102

Development of a Remotely-sensed Soil Heat Flux Parameterization for Natural Landscapes in Semi-arid Regions  

Microsoft Academic Search

Due to the difficulties in directly measuring soil heat flux (G), research on empirical estimation has moved toward use of a strong association between soil heat flux and net radiation (Rnet). The majority of these studies are concentrated on the estimation of soil heat flux from mature agricultural areas in semi-arid regions due to the high demand for irrigation water.

J. Kim; R. Scott; T. Hogue

2007-01-01

103

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

104

Measurement of local high-level, transient surface heat flux  

SciTech Connect

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, C.H.

1988-09-01

105

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

106

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

107

Heat flux dynamics in dissipative cascaded systems  

E-print Network

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

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

2014-12-19

108

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

2007-11-18

109

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

110

The photospheric Poynting flux and coronal heating  

NASA Astrophysics Data System (ADS)

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

Welsch, Brian T.

2015-02-01

111

Progress Report Development of a High Heat Flux  

E-print Network

-metallic foam as a heat spreader, liquid wick and heat sink material for electronic package with localized highProgress Report Development of a High Heat Flux Supercooler Using Carbon Foam By Walter Yuen heat flux (in the order of 100 W/cm2 ). Based on the geometry and heating requirement of a prototype

Yuen, Walter W.

112

Partitioning of the Modern Oceanic Mass and Heat Fluxes  

Microsoft Academic Search

The modern partitioning of mass and heat fluxes between ocean basins and hemispheres is highly structured, and raises interesting questions about how they may have been distributed in the past. Today, oceanic heat fluxes are asymmetric about the equator, but the combined oceanic plus atmospheric heat flux (the real `global conveyor') is, within error bars, almost indistinguishable from perfect antisymmetry.

C. Wunsch

2005-01-01

113

Solar cycle variations in the electron heat flux: Ulysses observations  

Microsoft Academic Search

Solar wind observations by the Ulysses spacecraft now include nearly ten years of continuous ion and electron measurements. In this study, we report detailed measurements of the electron heat flux in the solar wind. In particular, we examine the heat flux measurements for long-term correlations with wave activity and solar wind speed. We find that the average heat flux, when

Earl E. Scime; J. E. Littleton; S. Peter Gary; Ruth Skoug; Naiguo Lin

2001-01-01

114

Heat flux in a granular gas  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

115

Global Intercomparison of 12 Land Surface Heat Flux Estimates  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

116

Multidecade Global Flux Datasets from the Objectively Analyzed Air-sea Fluxes (OAFlux) Project: Latent and Sensible Heat Fluxes,  

E-print Network

, and procedure used in developing the 49-year (1958-2006) analysis of global latent, sensible heat fluxes This report supports the release of the third version of global ocean-surface heat flux products (1958Multidecade Global Flux Datasets from the Objectively Analyzed Air-sea Fluxes (OAFlux) Project

Yu, Lisan

117

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

118

ACCURACY OF SOIL HEAT FLUX MEASUREMENTS MADE WITH FLUX PLATES OF CONTRASTING PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flux plate measurements of soil heat flux (G) may include significant errors unless the plates are carefully installed and known errors accounted for. The objective of this research was to quantify potential errors in G when using soil heat flux plates of contrasting designs. Five flux plates with...

119

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Diffusive heat flux at the soil surface is commonly determined as a mean value over a time period using heat flux plates buried at some depth (e.g., 5 to 8 cm) below the surface with a correction to surface flux based on the change in heat storage during the corresponding time period in the soil lay...

120

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

SciTech Connect

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

Cook, David

1993-07-04

121

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

DOE Data Explorer

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

Cook, David

122

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

123

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

124

Heat flux measurements on ceramics with thin film thermocouples  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

125

Heat pipe radiators for space. [vacuum tests  

NASA Technical Reports Server (NTRS)

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

Sellers, J. P.

1977-01-01

126

Solar Cycle Variations in the Electron Heat Flux: Ulysses Observations  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

127

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

128

Determination of regional distributions and seasonal variations of land surface heat fluxes from Landsat7 Enhanced Thematic Mapper data over the central Tibetan Plateau area  

Microsoft Academic Search

In this study, a parameterization method based on Landsat-7 ETM data and field observations has been proposed and tested for deriving surface reflectance, surface temperature, NDVI, MSAVI, vegetation coverage, LAI, net radiation flux, soil heat flux, sensible heat flux and latent heat flux over heterogeneous landscape. As a case study, the methodology was applied to the experimental area of the

Yaoming Ma; Lei Zhong; Zhongbo Su; Hirohiko Ishikawa; Massimo Menenti; Toshio Koike

2006-01-01

129

Thin Film Heat Flux Sensors: Design and Methodology  

NASA Technical Reports Server (NTRS)

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

Fralick, Gustave C.; Wrbanek, John D.

2013-01-01

130

Radiative heating in contrail cirrus  

NASA Astrophysics Data System (ADS)

In the course of analysis and modeling of aviation induced contrail cirrus, we found that observed time scales of contrail cirrus and thin cirrus in general requires particle losses by radiative heating besides other loss processes. For thin cirrus near the tropopause, radiative warming dominates over cooling in most cases, in particular in the lower part of cirrus layers. Both terrestrial and solar radiances contribute to warming, but the terrestrial part is often the larger one. The radiation is absorbed mainly by the ice particles while a smaller fraction is absorbed by water vapor and other gases inside the cirrus. The heating directly absorbed in the ice particles causes a temperature difference between the ice particles and ambient air. Because of the small heat capacity of the ice particles and because of the small particle scales, local equilibrium between radiative heating and conductive cooling is reached quickly. In agreement with Gierens (1994) and others, this causes a temperature surplus of order 0.1 K for ice particles larger than about 100 micro meters. For smaller particles, the temperature increases about linearly with the particle radius. The contribution is important for very low ice particle concentrations (below 0.1/cm**3) and solar optical depth larger 0.1. After heat exchange with the ambient air, and by additional absorption of radiation in the gas phase, the radiation also causes a bulk warming of the cirrus, again of order 0.1 K. The contribution is important for high ice particle concentrations (> 1 /cm**3) and for rather modest optical depth values (0.01 to 0.1). Quasi equilibrium is reached in proportion to the inverse heating rate, which may take hours. In case of heating the increased ice particle temperature causes reduced water vapor saturation at the ice surface and hence sublimation. Hence, both effects may contribute to a loss of ice particles in cirrus, in particular, when relative humidity inside the cirrus is close to ice saturation. In addition, the radiative heating may cause convective turbulence because of warm air masses rising and cold air masses sinking. Finally, the whole cirrus may rise slowly rise by the diabatic heating. In order to simulate these effects in contrail cirrus we developed an effective model (within our contrail cirrus prediction model, CoCiP) which computes the radiative heating rate in both the longwave and shortwave spectral ranges. The model parameterizes the impact of radiative heating on turbulent mixing and sublimation of ice particles in a thin cirrus layer. The heating rate is modeled as a function of cirrus properties (optical depth, temperature, humidity, effective particle radius, and particle habit), solar radiation, solar zenith angle, and the radiances at the top of the atmosphere (solar direct radiation, reflected solar radiation, and outgoing longwave radiation). The model parameters were determined by least square fits of the model results to the results of forward calculations with the libRadtran system using the DISORT 2.0 solver with 16 streams for about 32000 cases with different atmospheres, surface properties and cloud parameters. The model has been applied for various test cases in comparison to cirrus cover derived from SEVIRI-IR data from Meteosat (MSG) observations. The comparison shows that radiative heating may enhance vertical mixing and reduce the life time of contrail cirrus (and thin cirrus in general) by factors of order two.

Schumann, Ulrich; Mayer, Bernhard; Hamann, Ulrich; Graf, Kaspar

2010-05-01

131

Quantification of green roof carbon dioxide, heat, and water fluxes using the gradient flux technique  

NASA Astrophysics Data System (ADS)

Green roofs address several important problems associated with urbanization, but there has been limited quantification of their benefits. On the small scales necessary on a rooftop, direct eddy covariance cannot be used to measure the carbon dioxide, sensible and latent heat, and water fluxes between the plant canopy and the atmosphere. Thus, the gradient flux technique was used to calculate these fluxes between a green roof and the atmosphere over 18 days in summer, 2008. Measurements of atmospheric CO2 and H2O concentration and meteorological variables were taken in the atmospheric surface boundary layer within 35 cm of the green roof plant canopy: CO2 and H2O concentrations were sampled with one sensor at five different heights for five minutes each over the course of thirty minute intervals to construct a vertical profile, as well as a being sampled continuously with another sensor at the median height to quantify time variability; temperature and relative humidity were sampled at the highest, lowest, and median heights; wind velocity was recorded at two heights to measure shear velocity, a parameter describing atmospheric mixing; canopy temperature and moisture, and solar radiation were also measured. Results show the plant canopy was a net sink of carbon dioxide during the day and a net source of carbon dioxide during the night, as expected. Average carbon dioxide flux was approximately 0.135 ? mol m-2 s-1 into the canopy over the experiment, or about 51.1 g C m-2 year-1 into the canopy if seasonality is neglected. Long-term studies coupling this method with detailed mass and heat budgets will allow more complete quantification of carbon dioxide, water and heat fluxes on green roofs. This will aid in improving quantification of both known benefits of green roofs, as well as more speculative benefits such as carbon sequestration.

de Lanoy, J. T.; Orton, P. M.; McGillis, W. R.

2008-12-01

132

Standard Test Method for Measuring Heat Flux Using a Copper-Constantan Circular Foil, Heat-Flux Transducer  

E-print Network

1.1 This test method describes the measurement of radiative heat flux using a transducer whose sensing element (1,2 ) is a thin circular metal foil. These sensors are often called Gardon Gauges. 1.2 The values stated in SI units are to be regarded as the standard. The values stated in parentheses are provided for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

American Society for Testing and Materials. Philadelphia

2007-01-01

133

Electron heat flux constraints in the solar wind  

SciTech Connect

Enhanced fluctuations from electromagnetic heat flux instabilities may, through wave-particle scattering, constrain the electron heat flux which flows parallel to the background magnetic field in the solar wind. A corollary of this hypothesis is that instability thresholds should correspond to observable bounds on the heat flux. Here plasma and magnetic field data from February and March 1995 of the Ulysses mission is analyzed in terms of the core/halo electron model to yield scaling relations of dimensionless electron parameters and empirical upper bounds on the dimensionless heat flux as functions of the core {beta}. Use of these scaling relations in linear Vlasov theory for the whistler and Alfv{acute e}n heat flux instabilities in homogeneous plasmas yields threshold conditions on the dimensionless heat flux which are also functions of the electron core {beta}. The empirical bounds and the theoretical thresholds are similar and are therefore consistent with the hypothesis. {copyright} {ital 1999 American Institute of Physics.}

Gary, S.P.; Skoug, R.M.; Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1999-06-01

134

Heat flux measurement in SSME turbine blade tester  

SciTech Connect

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

Liebert, C.H.

1990-11-01

135

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

136

High heat flux engineering in solar energy applications  

SciTech Connect

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

Cameron, C.P.

1993-07-01

137

High heat flux engineering in solar energy applications  

Microsoft Academic Search

Solar thermal energy systems can produce heat fluxes in excess of 10,000 kW\\/m2. This paper provides an introduction to the solar concentrators that produce high heat flux, the receivers that convert the flux into usable thermal energy, and the instrumentation systems used to measure flux in the solar environment. References are incorporated to direct the reader to detailed technical information.

Christopher P. Cameron

1993-01-01

138

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

139

HEAT FLUX EXHAUST IN TORE SUPRA IN ERGODIC DIVERTOR AND LIMITER CONFIGURATIONS  

Microsoft Academic Search

Tore Supra being devoted to long pulse physics and technology, this paper discusses recent advances in the installation of actively cooled plasma facing components and on physics methods to mitigate the heat flux , such as edge radiation in the ergodic divertor configuration of Tore Supra. The paper also stresses the understanding requirements in terms of heat deposition , especially

A. GROSMAN

140

Heat pipe radiators for space  

NASA Technical Reports Server (NTRS)

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

Sellers, J. P.

1976-01-01

141

Critical analysis of empirical ground heat flux equations on a cereal field using micrometeorological data  

Microsoft Academic Search

The rate at which the net radiation is transferred to the soil as ground heat flux varies with surface characteristics. Surface energy balance algorithms use empirical relationships taking into account the effects of the canopy cover to insulate the soil through vegetation indexes, the soil capacity to absorb incoming net radiation via the albedo, and the surface temperature promoting the

Carmelo Cammalleri; Goffredo La Loggia; Antonino Maltese

2009-01-01

142

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

143

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

1998-01-01

144

On the net surface heat flux into the western equatorial Pacific  

NASA Astrophysics Data System (ADS)

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

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

145

High heat flux dissipation using small diameter channels  

Microsoft Academic Search

Increased heat dissipation rates from electronic chips creates the need for high heat flux cooling schemes with a special emphasis on practical considerations such as pressure drop and flow rate. Devices such as fusion reactor components and rocket nozzles have heat dissipation rates of 10,000 W cm$\\\\sp{-2}$ These heat fluxes are orders of magnitude greater than electronic devices, thus requiring

Morris Brian Bowers

1994-01-01

146

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

147

Transient critical heat flux and blowdown heat-transfer studies  

SciTech Connect

Objective is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. A predictional method has been developed which involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous local-conditions hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) 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. 234 figures, 13 tables.

Leung, J.C.

1980-05-01

148

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

NASA Astrophysics Data System (ADS)

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

Haruyama, T.

2001-05-01

149

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

NASA Astrophysics Data System (ADS)

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of deeper measurement to accurately describe the surface soil heat flux signal. Current measurement techniques lead to important errors in the surface energy budget. In addition the currently-used calorimetric method is demonstrated to be unable to characterize the variability, magnitude and phase in the surface soil heat flux. In consequence, these results call for a higher-resolution sampling of soil heat flux, both in time and vertically near the surface, in order to accurately quantify the surface soil heat flux and to account for its rapid variations, especially in cloudy situations. In addition those results demonstrate the need for high vertical and temporal resolution in the modeling of the soil surface in order to describe the diurnal course of the surface soil heat flux. Coarser resolutions are shown to miss most of the soil heat flux signal since it acts as a high-pass filter of incoming radiation. Finally this works points out important limitations of the assimilation of infrared surface temperature because of the rapid fluctuations in solar radiation (weather noise). Comparison of the soil heat flux at different depth obtained with SVAT (continuous line) and conceptual land-atmosphere model (dashed line) over 135 days of data from the SUDMED project. The conceptual model captures the emergent behavior of the soil heat flux response. Soil heat flux at the surface is mostly influenced by high frequencies, whereas the high-frequency component of the signal has almost disappeared at typical soil heat flux measurement depth (2.5 or 5cm). This shows the limitation of current soil heat flux methodology since they do not capture most of the surface signal and cannot therefore close the surface energy partitioning.

Gentine, P.; Entekhabi, D.

2010-12-01

150

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

NASA Technical Reports Server (NTRS)

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

Turner, Travis L.; Ash, Robert L.

1994-01-01

151

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

152

Atmospheric heat fluxes and restoration of the circumglobal equatorial current  

Microsoft Academic Search

An analytical model is developed for estimating the heat fluxes in the lower and upper parts of the atmosphere that would result from possible increases in the carbon dioxide (CO2) concentrations and the ensuing temperature changes. For a doubling of the CO2 concentration by volume, the net heat flux to the troposphere is estimated to increase by 22 percent, and

Blake Stevens; Magdi Ragheb

2010-01-01

153

NEP heat pipe radiators. [Nuclear Electric Propulsion  

NASA Technical Reports Server (NTRS)

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

Ernst, D. M.

1979-01-01

154

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

155

Computation of radiative heat transport across a nanoscale vacuum gap  

SciTech Connect

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

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

2014-02-10

156

On the Earth's surface energy exchange determination from ERS satellite ATSR data: Part 3. Turbulent heat flux on open sea  

Microsoft Academic Search

This is the third in a series of papers which discusses determination of the Earth's surface energy exchange from ERS satellite Along-Track Scanning Radiometer (ATSR) data. This paper focuses on estimation of turbulence heat flux exchange by using ATSR data in areas of open sea. In this paper, we present results of net longwave radiation, latent heat flux and sensible

Yong Xue; D. T. Llewellyn-Jones; S. P. Lawrence; C. T. Mutlow

2000-01-01

157

Sensitivity of model parameterizations for simulated latent heat flux at the snow surface for complex mountain sites  

Technology Transfer Automated Retrieval System (TEKTRAN)

The snowcover energy balance is typically dominated by net radiation and sensible and latent heat fluxes. Validation of the two latter components is rare and often difficult to undertake at complex mountain sites. Latent heat flux, the focus of this paper, is the primary coupling mechanism between...

158

Introduction of J-OFURO latent heat Flux Version2  

Microsoft Academic Search

Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations (J-OFURO) includes global ocean surface heat flux data derived from satellite data and are used in many studies related to air-sea interaction. Recently latent heat flux data version 2 was constructed in J-OFURO. In version 2 many points are improved compared with version 1. A bulk algorithm used for

Masahisa Kubota; Hiroyuki Tomita

159

High flux heat transfer in a target environment  

E-print Network

flow (original graph Wimblett) Burnout flux sensitive to channel thickness 10MW/m2 2MW/m2 5m/s 15m/s 10 to 50°C #12;Acoustic transducer used to detect burnout Maximum heat flux could be achieved by monitoring for burnout Heat flux may be limited by erosion due to high water velocities Wimblett & Coates 1978 #12;Other

McDonald, Kirk

160

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

SciTech Connect

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

Nakos, James Thomas

2005-12-01

161

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

NASA Technical Reports Server (NTRS)

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

Grossman, Robert L.

1990-01-01

162

Determination of the unsteady heat fluxes in the focal plane of a radiant energy concentrator  

Microsoft Academic Search

A two-dimensional nonlinear inverse heat conduction problem is examined, which consists of determining, on the basis of given temperature measurements, the law of heat flux variation at the face of a cylindrical titanium specimen during the process of radiative heat transfer in the focal plane of a solar radiant-energy concentrator. A numerical solution is obtained, using an explicit finite-difference scheme

P. G. Krukovskii; K. B. Isaev

1980-01-01

163

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

PubMed

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

Matzarakis, Andreas; Rutz, Frank; Mayer, Helmut

2010-03-01

164

Ocean-to-Ice Heat Flux and Diminished Arctic Sea Ice Cover (Invited)  

NASA Astrophysics Data System (ADS)

Ocean-to-Ice Heat Flux and the Decline of the Arctic Sea Ice Cover Heat transport from the ocean to the base of the sea ice plays a significant role in the enthalpy balance of the Arctic Ocean sea ice cover. In this presentation, we touch on two aspects of heat storage and transport in the upper Arctic Ocean: (1) the role of ocean-to-ice heat flux supported by vertical transport of heat stored below the mixed layer and (2) the vertical structure of temperature and vertical heat fluxes within the mixed layer. Inflows to the Arctic Ocean from the North Atlantic and North Pacific, carrying significant quantities of heat, circulate below the mixed layer within the Arctic. An overview analysis of ocean-to-ice heat flux estimates based on older observations (AIDJEX and SHEBA) and newer observations from autonomous systems deployed as part of the Arctic Observing Network is conducted to examine the possible contribution of these heat sources to sea ice melt. We emphasize wintertime heat fluxes, to exclude the large affects of incoming solar radiation, finding that wintertime fluxes are typically small (winter-averaged values less than 1 W/m^2), except close to bathymetric features such as the Chukchi Borderlands and the Yermak Plateau. The results indicate that vertical fluxes supported by heat below the mixed layer have a small affect on the enthalpy budget of the sea ice cover, at least in the areas where the drifting-ice-based measurements have been made. Observations from Autonomous Ocean Flux Buoys, including eddy-correlation flux measurements and a high-resolution thermistor chain, are providing detailed views of heat storage and transport within the mixed layer. The vertical structure of temperature and heat flux varies with nearby open water fraction. The vertical structure of low ice concentration conditions is more similar to that of strong entrainment than to high ice concentration conditions. Our interpretation of this observation is that large areas of leads, melt ponds, and thin ice lead to strongly heterogeneous input of solar radiation to the ocean. As ice floes move over areas that were recently heated, mixed layer vertical structure similar to entrainment conditions is produced. The observation highlights the need to better understand lateral transport and mixing processes below sea ice.

Shaw, W. J.; Stanton, T. P.

2010-12-01

165

Transient heat flux shielding using thermal metamaterials  

NASA Astrophysics Data System (ADS)

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

Narayana, Supradeep; Savo, Salvatore; Sato, Yuki

2013-05-01

166

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

167

Interannual variability in Mediterranean heat and buoyancy fluxes  

SciTech Connect

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

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

1993-05-01

168

Partitioning of Latent Heat Flux between Transpiration and Direct Evaporation  

NASA Astrophysics Data System (ADS)

The characterization of land surface fluxes is critical to enhancing our understanding of the water cycle and regional climate. The partitioning of available energy into sensible and latent heat fluxes (H and LE), as well as the partitioning of latent heat flux into vegetation transpiration (Et) and bare soil evaporation (Ed), are key elements of biosphere-atmosphere interactions. In this study empirical analyses and numerical modeling studies are carried out for a suburban grass site in Princeton NJ, focusing on a two year period from 2011 - 2013. Measurements from an Eddy-Covariance station play a central role in both empirical analyses and modeling studies. Two methods are used to partition latent heat flux into direct evaporation and transpiration components: flux similarity partitioning and partitioning based on the Penman-Monteith formulation in the Noah Land Surface Model (LSM). The former takes 10Hz water vapor and CO2 flux measurements as input, assuming that the water vapor (q) / CO2 (c)flux pair from stomatal processes (transpiration and photosynthesis) is perfectly negatively correlated. Any deviation of the correlation from -1 is contaminated by the perfect positive correlation of the q c flux pair from non-stomatal processes (soil evaporation and respiration). Thus LE can be partitioned into Et and Ed by analyzing the q c correlation. The latter method is based on a commonly used physics-based model which takes fundamental forcing time series as input, using Penman-Monteith equation. We characterize the seasonal and diurnal partitioning of latent heat flux based on flux similarity analyses and compare these results to partitioning based on Noah LSM simulations. We use wavelet decomposition to examine scale-dependent properties of latent heat flux partitioning and present sensitivity analyses of Noah LSM flux partitioning to model parameters. We also present results from a water vapor isotope analyzer that was developed with the goal of providing an empirical measurement of the Et and Ed flux components.

Wang, W.; Ramamurthy, P.; Baeck, M. L.; Bou-Zeid, E.; Scanlon, T. M.; Smith, J. A.

2013-12-01

169

Hierarchically structured surfaces for boiling critical heat flux enhancement  

NASA Astrophysics Data System (ADS)

We report large enhancements in critical heat flux (CHF) on hierarchically structured surfaces, fabricated using electrophoretic deposition of silica nanoparticles on microstructured silicon and electroplated copper microstructures covered with copper oxide (CuO) nanostructures. A critical heat flux of ?250 W/cm2 was achieved on a CuO hierarchical surface with a roughness factor of 13.3, and good agreement between the model proposed in our recent study and the current data was found. These results highlight the important role of roughness using structures at multiple length scales for CHF enhancement. This high heat removal capability promises an opportunity for high flux thermal management.

Chu, Kuang-Han; Soo Joung, Young; Enright, Ryan; Buie, Cullen R.; Wang, Evelyn N.

2013-04-01

170

UPPER AND LOWER BOUNDS ON HEAT FLUX  

Microsoft Academic Search

Some bounds on heat flow and entropy production analogous to those obtained in linear elasticity theory are discussed. The analogy is observed by introducing “mechanical” counterparts to a heat conduction process

R. Wojnar

1998-01-01

171

New Heat Transfer Correlation for an HCCI Engine Derived from Measurements of Instantaneous Surface Heat Flux  

Microsoft Academic Search

An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial

Junseok Chang; Orgun Güralp; Zoran Filipi; Dennis Assanis; Tang-Wei Kuo; Paul Najt; Rod Rask

172

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

Microsoft Academic Search

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

F. F. Tsai; I. Catton

1983-01-01

173

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

174

Model of critical heat flux in subcooled flow boiling  

E-print Network

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

Fiori, Mario P.

1968-01-01

175

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

176

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

SciTech Connect

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

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

1995-06-01

177

Development and Application of the Delta-DM Method for Computing Shortwave Radiative Fluxes in a Vertically Inhomogeneous Atmosphere  

Microsoft Academic Search

This study describes the development and application of the Delta-DM method for computing shortwave radiative fluxes planetary albedo and heating rates in vertically inhomogeneous atmospheres. Delta-DM was designed to minimize computer time requirements, furnish accurate flux estimates and permit a wide range of shortwave radiative transfer problems to be studied. Phase function approximation is variable and there is no restriction

Allan M. Sawchuk

1983-01-01

178

MHD instabilities of collisionless space plasma with heat fluxes  

NASA Astrophysics Data System (ADS)

Properties of instabilities in a collisionless plasma are considered based on 16-moment MHD equations with allowance for differences between the heat fluxes along the magnetic field due to longitudinal and transverse thermal ion motions. It is shown that the increments and thresholds appreciably depend on these two heat fluxes for all compressible instabilities arising in the MHD approach (second compressible fire-hose, mirror, and thermal instabilities).

Kuznetsov, V. D.; Dzhalilov, N. S.

2014-12-01

179

Surface heat flux variability over the northern California shelf  

Microsoft Academic Search

Surface heat flux components are estimated at a midshelf site over the northern California shelf using moored measurements from the 1981-1982 Coastal Ocean Dynamics Experiment (CODE) and the 1988-1989 Shelf Mixed Layer Experiment (SMILE). Time series of estimated fluxes extend from early winter through summer upwelling conditions, allowing examination of seasonal variations as well as synoptic events. On a seasonal

Robert C. Beardsley; Edward P. Dever; Steven J. Lentz; Jerome P. Dean

1998-01-01

180

Determination of ocean surface heat fluxes by a variational method  

Microsoft Academic Search

A new technique of determination of the ``nonsolar'' heat flux (sum of the latent, sensible, and net infrared fluxes) at the ocean surface is proposed. It applies when oceanic advection remains weak and thus relies on a one-dimensional modeling approach. It is based on a variational data assimilation scheme using the adjoint equation formalism. This allows to take advantage of

H. Roquet; S. Planton; P. Gaspar

1993-01-01

181

Heat flux distribution in the divertor-II of ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

A new divertor was installed in ASDEX Upgrade and went into operation in spring of 1997. The divertor was designed to handle heat fluxes relevant to ITER-like scenarios. For this, the tiles expected to receive the maximum load (strike point modules) are hardened by the use of carbon fibre composites covering about 20% of the total divertor area. The maximum heat flux detected by thermography in a H-mode discharge is only 4 MW/m 2 or below for a total input power of 20 MW without radiating mantle, except some ELMs showing a moderately higher heat flux. A broad distribution of the power load found in the measured poloidal distribution of the heat flux as well as the energy distribution, shows that less than half of the power flowing into the divertor is received by the strike point modules. The remaining power is loaded to other tiles of the divertor, particularly the transition module and parts of the roof baffle near to the strike point modules. The reconstructed radiation pattern reveals that the fraction of power radiated outside the divertor is comparable for both geometries. But the radiated fraction inside the divertor is increased by 10-15% in the Lyra shaped divertor.

Herrmann, A.; Fuchs, C. J.; Rohde, V.; Weinlich, M.; ASDEX Upgrade Team

182

Inaccuracies in soil heat flux measurement and modeling: a matter of vertical and temporal resolution?  

Microsoft Academic Search

We here demonstrate with a conceptual model of the land-atmosphere interaction and a high vertical resolution Soil Vegetation Atmosphere Transfer model that the high daily frequencies of incoming radiation play a fundamental role in the soil heat flux signal. These high frequencies remain concentrated in a very shallow layer at the surface of about 1cm, which precludes the use of

P. Gentine; D. Entekhabi

2010-01-01

183

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

Microsoft Academic Search

Instantaneous heat fluxes were estimated using data obtained from Landsat 5 TM (Thematic Mapper), Landsat 7 ETM+ (Enhanced Thematic Mapper Plus) and Terra MODIS (Moderate Resolution Imaging Spectroradiometer) using Surface Energy Balance Algorithm for Land (SEBAL) model for cloud-free days. The modeled results were compared with measurements of net radiation (both incoming and outgoing short and longwave), soil, sensible and

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

2007-01-01

184

Characterization of local heat fluxes around ICRF antennas on JET  

SciTech Connect

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. [Ecole Nationale des Ponts et Chaussées, F77455 Marne-la-Vallée (France); Jacquet, P.; Monakhov, I.; Arnoux, G.; Brix, M.; Sirinelli, A. [Euratom/CCFE Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Bobkov, V. [Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching (Germany); Milanesio, D. [Politecnico di Torino, Department of Electronics, Torino (Italy); Colas, L. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Collaboration: JET-EFDA Contributors

2014-02-12

185

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

NASA Astrophysics Data System (ADS)

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

Li, Mingxing; Ma, Zhuguo

2015-01-01

186

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

187

Earth's Heat Flux and Links to Chemistry  

Microsoft Academic Search

The global heat budget (or power, Qtot) and its change with time are needed for models of planetary evolution. The latest Qtot of 44 TW is 2.3 times radiogenic power provided by various chondritic (CI) models. To account for this difference, additional heat sources, processes, and various chemical models have been proposed. Most of the discrepancy originates in methods of

R. E. Criss; A. M. Hofmeister

2002-01-01

188

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

NASA Astrophysics Data System (ADS)

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

Brewster, M. Q.

1988-01-01

189

SPECTRAL data-based estimation of soil heat flux  

USGS Publications Warehouse

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

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

2011-01-01

190

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

NASA Technical Reports Server (NTRS)

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

Siegel, R.; Spuckler, C. M.

1992-01-01

191

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

192

Intercomparison of Latent Heat Fluxes Over Global Oceans  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

193

Coupled radiative and conductive heat transfer in a non-grey absorbing and emitting semitransparent media under collimated radiation  

Microsoft Academic Search

This paper deals with heat transfer in non-grey semitransparent two-dimensional sample. Considering an homogeneous purely absorbing medium, we calculated the temperature field and heat fluxes of a material irradiated under a specific direction. Coupled radiative and conductive heat transfer were considered. The radiative heat transfer equation (RTE) was solved using a S8 quadrature and a discrete ordinate method. Reflection and

David Lacroix; Gilles Parent; Fatmir Asllanaj; Gérard Jeandel

2002-01-01

194

Development of a radiative flux evaluation program with a 3-D Monte Carlo radiative transfer code  

NASA Astrophysics Data System (ADS)

In this paper, we have developed a three-dimensional (3D) Monte Carlo radiative transfer code that can treat a broadband solar flux calculation implemented with k-distribution parameters [1]. We used this code for generating the radiative flux profile and heating rate profile in the atmosphere including broken clouds. In order to construct 3-D extinction coefficient fields, we tried following three methods: 1) Minimum cloud Information Deviation Profiling Method (MIDPM), 2) numerical simulations by a non-hydrostatic model with bin cloud microphysics model and 3) idealized stochastic clouds generated by randomized extinction coefficient distribution and regularly-distributed tiled clouds. Using these constructed 3-D cloud systems, we calculated the radiation field by our Monte Carlo radiative transfer code at wavelengths of 0.5, 1.6 and 2.1 microns. We then compared the results with Plane Parallel Approximation (PPA) and a reflectivity of 3-D with Independent Pixel Approximation (IPA). In the case of wavelength 0.5 microns, as expected, all the discrepancies between 3-D clouds and equivalent IPA clouds are smaller than the discrepancies between 3-D clouds and equivalent PPA clouds. At maximum the reflectivity difference for the PPA and IPA is about equal to fluxes of 30 Wm-2 and 10 Wm-2, respectively.

Okata, Megumi; Nakajima, Teruyuki; Barker, Howard W.; Donovan, David P.

2013-05-01

195

Quantification of green roof carbon dioxide, heat, and water fluxes using the gradient flux technique  

Microsoft Academic Search

Green roofs address several important problems associated with urbanization, but there has been limited quantification of their benefits. On the small scales necessary on a rooftop, direct eddy covariance cannot be used to measure the carbon dioxide, sensible and latent heat, and water fluxes between the plant canopy and the atmosphere. Thus, the gradient flux technique was used to calculate

J. T. de Lanoy; P. M. Orton; W. R. McGillis

2008-01-01

196

Wave-Coherent Air-Sea Heat Flux  

Microsoft Academic Search

Air-sea fluxes of heat and momentum play a crucial role in weather, climate and the coupled general circulation of the oceans and atmosphere. Much progress has been made to quantify momentum transfer from the atmosphere to the ocean for a wide range of wind and wave conditions. Yet, despite the fact that global heat budgets are now at the forefront

W. Melville; F. Veron; L. Lenain

2006-01-01

197

Winter Time Heat Flux Variations in the Northern Hemispheric Stratosphere  

Microsoft Academic Search

Transport of heat in the stratosphere by the planetary waves, which is usually referred to as eddy heat flux (HF), attracted a lot of attention in the recent years. Since sources of the planetary waves are in the troposphere, HF in the stratosphere could be regarded as an external forcing. This makes HF very useful proxy for stratospheric temperature and

A. Karpetchko; G. Nikulin

2003-01-01

198

State of the Art of High Heat Flux Cooling Technologies  

Microsoft Academic Search

The purpose of this literature review is to compare different cooling technologies currently in development in research laboratories that are competing to solve the challenge of cooling the next generation of high heat flux computer chips. Today, most development efforts are focused on three technologies: liquid cooling in copper or silicon micro-geometry heat dissipation elements, impingement of liquid jets directly

Bruno Agostini; Matteo Fabbri; Jung E. Park; Leszek Wojtan; John R. Thome; Bruno Michel

2007-01-01

199

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

E-print Network

Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks Weilin Qu-channel heat sink containing 21 parallel 215 · 821 lm channels. Tests were performed with deionized water over.13 bar. As CHF was approached, flow instabilities induced vapor backflow into the heat sink's upstream

Qu, Weilin

200

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

201

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

202

Turbine blade and vane heat flux sensor development, phase 2  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

203

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

204

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

NASA Astrophysics Data System (ADS)

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

Krane, M.; Dybbs, A.

205

Downstream Heat Flux Profile vs. Midplane T Profile in Tokamaks  

SciTech Connect

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

Robert J. Goldston

2009-08-20

206

Urban heat fluxes in the subsurface of Cologne, Germany  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

207

Mean and Variability of Air-Sea Heat Fluxes in the Indian Ocean  

E-print Network

available: daily, 1º-grid, 1988-2003 #12;OAFlux (Objectively Analyzed Air-sea Heat Fluxes) For the Global. Clim., 17, 2096-2118. #12;Global Surface Heat Flux Mean Qnet (1988-2000) #12;Mean net surface heat fluxMean and Variability of Air-Sea Heat Fluxes in the Indian Ocean Lisan Yu Woods Hole Oceanographic

Yu, Lisan

208

A Local Heat Flux Measurement Technique for Inclined Heat Exchanger Tubes  

Microsoft Academic Search

This article presents the design, fabrication, and calibration of thermocouple pairs for local heat flux measurement. The intended application of the thermocouple pairs is on the tubes of phase-change heat exchangers experiencing heat fluxes on the order of 10 W\\/m. Particular advantages of this technique are that it is accurate even for thin-wall tubes, there are no restrictions on the

T. Wu; K. Vierow

2006-01-01

209

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

210

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

211

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

212

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

213

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

214

Remote high-temperature insulatorless heat-flux gauge  

DOEpatents

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

Noel, B.W.

1993-12-28

215

Fluctuations, linear response and heat flux of an aging system  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

216

Infrared Camera Diagnostic for Heat Flux Measurements on NSTX  

SciTech Connect

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

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

2003-03-25

217

Regularities of unsteady radiative–conductive heat transfer in evaporating semitransparent liquid droplets  

Microsoft Academic Search

The numerical investigation method of unsteady transfer processes in evaporating droplets in radiating media is introduced, evaluating the dependence of optical spectral properties of material upon temperature. The distribution of temperature and heat fluxes regularities in heating and simultaneously evaporating water droplets has been investigated. It is shown that as a cause of interaction of radiation and conduction processes, the

G. Miliauskas

2001-01-01

218

Radiative heat transfer in turbulent MHD channel flow  

SciTech Connect

Radiative heat transfer in a MHD channel has been studied for fully developed turbulent flow of an electrically conducting fluid. A uniform magnetic field is imposed transverse to the flow direction between the electrically insulated parallel plates. Thermal entry region is analyzed for constant wall temperature including viscous dissipation and Joulean heating. A van Dreist mixing length model with Mei and Squire correction factor is used for eddy diffusivity of momentum and a modified Cebeci model is used for eddy conductivity. Both gray and real (non-gray) gas models of radiation are examined. An exponential wide band model is employed in evaluation of radiative heat flux for a real gas. Also, the contribution of a seed material to the radiative transfer is considered. The integro-differential equation for thermal energy transport is solved by a finite difference iterative method. Effects of control parameters such as Reynolds and Hartmann numbers, wall temperature, channel height, and partial pressures of participating gases on temperature profiles and heat transfer are studied. Results for Nusselt number, bulk temperature, and temperature profiles are reported for fully developed and developing thermal profiles. Furthermore, results are presented along the channel for these quantities for various parameters. Effect of variation of electrical conductivity with temperature is considered. For practical values of parameters as found in proposed MHD generators it is shown that radiative heat transfer is a major mechanism of heat transfer in the channel and accelerates the thermal development and results in reduced gas temperature profiles.

Alipour-Haghighi, F.

1981-01-01

219

Surface heat fluxes from the NCEP\\/NCAR and NCEP\\/DOE reanalyses at the Kuroshio Extension Observatory buoy site  

Microsoft Academic Search

Surface heat fluxes from the Kuroshio Extension Observatory (KEO) buoy are compared with surface heat fluxes from the National Centers for Environmental Prediction (NCEP)\\/National Center for Atmospheric Research reanalysis (NRA1) and NCEP\\/Department of Energy reanalysis (NRA2). KEO surface measurements include downward solar and longwave radiation, wind speed and direction, relative humidity, rain rate, and air and sea surface temperature. For

Masahisa Kubota; Noriyasu Iwabe; Meghan F. Cronin; Hiroyuki Tomita

2008-01-01

220

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

221

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

222

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

223

Maximum allowable heat flux for a submerged horizontal tube bundle  

SciTech Connect

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

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

1996-12-31

224

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

225

Ground surface heat flux histories in the Urals inferred from geothermal data  

NASA Astrophysics Data System (ADS)

Ground surface temperature histories (GSTHs) inferred from borehole temperature data have been successfully used in paleoclimate investigations for a long time. More rarely geothermal data are used for estimation of the past climatic ground surface heat flux histories (SHFHs) (Beltrami et al., 2000, 2001, 2002, 2006). The determination of SHFH is important because this parameter is a fundamental one in general circulation models (GCMs). It characterizes a portion of external forcing which contributes to the change of heat content in the upper crust. And there is a set of difficulties with the experimental and theoretical evaluation of heat flux anomaly associated with its small quantity. In the report we present the reconstructions of SHFHs in the Urals calculated from GSTHs obtained using geothermal data. The investigations were conducted on several time intervals: 1) the recent 30 kyr; 2) the last millennium and 3) the 150-years reconstruction of SHFH on the basis of the Ural long-term meteorological records. Surface temperature change was preceded by heat flux change with amplitudes about several tens of mW per square meter in all periods under study. The obtained SHFH for the recent 30 kyr was compared with the insolation data at the latitude of 60º N and with the variation of carbon dioxide concentrations. The comparison gives us the timing and general similarity of the heat flux and insolation variations. Changes in carbon dioxide by its shape and chronology are much closer to temperature changes rather than to heat flux changes. The reconstructed SHFH for the last millennium is very close to the variations of total solar irradiance (TSI). A comparison of the reconstructed SHFH and TSI for the last 150 years reveals their non-synchronous oscillation against the background of general increase trend. The ratio of the surface heat flux change to radiative forcing amounts to a few percent for all time intervals and the amplitude's ratio decreases with the increase of time interval.

Gornostaeva, Anastasia; Demezhko, Dmitry

2014-05-01

226

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

SciTech Connect

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

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

2011-01-01

227

Simulated sea surface temperature and heat fluxes in different climates of the Baltic Sea.  

PubMed

The physical state of the Baltic Sea in possible future climates is approached by numerical model experiments with a regional coupled ocean-atmosphere model driven by different global simulations. Scenarios and recent climate simulations are compared to estimate changes. The sea surface is clearly warmer by 2.9 degrees C in the ensemble mean. The horizontal pattern of average annual mean warming can largely be explained in terms of ice-cover reduction. The transfer of heat from the atmosphere to the Baltic Sea shows a changed seasonal cycle: a reduced heat loss in fall, increased heat uptake in spring, and reduced heat uptake in summer. The interannual variability of surface temperature is generally increased. This is associated with a smoothed frequency distribution in northern basins. The overall heat budget shows increased solar radiation to the sea surface, which is balanced by changes of the other heat flux components. PMID:15264603

Döscher, Ralf; Meier, H E Markus

2004-06-01

228

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

229

Towards a Balanced Description of the Air-Sea Heat Exchange Through Inverse Analysis of the SOC Flux Climatology  

NASA Astrophysics Data System (ADS)

The Southampton Oceanography Centre (SOC) air-sea flux climatology, in common with other ship-based climatologies, exhibits an imbalance of 30Wm-2 in the global ocean heat budget. We have attempted to balance the climatology using linear inverse analysis. Up to ten hydrographic measurements of ocean heat transport from the Atlantic and North Pacific ocean have been used as constraints. An additional constraint that the global mean net heat flux lies in the range 0 ± 2 Wm-2 was also utilized. A solution is obtained with all ten transport constraints but without the requirement of global closure in which the global net heat bias is reduced to -5Wm-2. This change is largely due to a 15 % increase in the latent heat flux and a 9 % reduction to the shortwave flux. When the global constraint is included with the hydrographic constraints the solution requires increases in the latent heat flux, the longwave flux and the sensible heat flux of 19 % , 9 % and 7 % respectively and a decrease in the shortwave flux of 6 % . This solution results in an adjusted climatology with a global net heat flux of -2Wm-2. It also provides good agreement with recent estimates of the global ocean heat transport obtained using residual techniques and from atmospheric model reanalyses. However, additional comparisons of the adjusted fluxes with measurements made by various Woods Hole Oceanographic Institute research buoys indicate that significant regional biases still exist. Results of ongoing research, aimed at identifying the causes of these biases, will be presented. In particular, we have found that the current shortwave formula is likely to overestimate the shortwave flux by 40-50 Wm-2 in the Tropical Atlantic. The reason being that the formula was derived in regions of low aerosol concentration and does not explicitly account for the attenuation of solar radiation by high aerosol concentrations such as the Saharan dust plume.

Grist, J.; Josey, S.

2003-04-01

230

Turbulent heat transport in a circular duct with a narrow strip heat flux boundary condition  

SciTech Connect

Experiments and computations have been performed for turbulent air flow in a circular duct in which uniform heating is applied over a 60 deg arc of the circumference. The results are compared to those for both a uniform heat flux around the full circumference of the duct and for a uniform heat flux around half the circumference. The flow was hydrodynamically fully developed at the start of heating and there were negligible buoyancy effects. Both the experimental results and the computations show that the local heat transfer coefficients for the narrow strip (60 deg wide) are less than the values for uniform heating around the full circumference but greater than the values for uniform heating around half the circumference (180 deg). This rather result is a consequence of the temperature distribution in the fluid and the definition of the local heat transfer coefficient, which is based on the bulk temperature.

Baughn, J.W.; Dingus, C.A.; Hoffman, M.A. (Univ. of California, Davis (United States)); Launder, B.E. (Univ. of Manchester (England))

1989-11-01

231

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

232

Uncertainty estimates in global ocean surface heat fluxes  

Microsoft Academic Search

To date the only practical means of estimating large scale ocean surface heat fluxes is with bulk parameterization formulae. It is well known that there are many sources of uncertainties in such estimates due to sampling deficiencies, uncertainties in the field measurements and uncertainties in the parameterizations themselves. This report presents global estimates of the total uncertainties in the climatological

Gleckler

1992-01-01

233

On the Nature of Critical Heat Flux in Microchannels  

E-print Network

On the Nature of Critical Heat Flux in Microchannels A. E. Bergles Honorary Member, ASME. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher

Kandlikar, Satish

234

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

235

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

236

Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

237

Planetary heat flow limits on monopole and axion fluxes  

NASA Astrophysics Data System (ADS)

Recent improved quantitative estimates of the observed heat flow from planetary objects in the solar system are used to set a limit on the background monopole flux (less than 10 to the -19th/sq cm per s per sr) which is two orders more stringent than the Parker bound. Axion flux estimations from the giant planets are also given. A solar axion flux on earth of 10 to the 14th/s per sq cm (10 to the 8th GeV/V) squared, with solar axion energies in the soft X-ray range, and an axion flux on earth from Jupiter of 10 to the 6th/s per sq cm (10 to the 8th GeV/V) squared, with axion energies centered about 10 eV, are derived.

Sivaram, C.

1987-02-01

238

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

E-print Network

Estimation of the Surface Heat Flux Response to Sea Surface Temperature Anomalies over the Global fluxes over the global oceans for individual seasons. Net surface heat flux feedback is generally October 2004, in final form 21 February 2005) ABSTRACT The surface heat flux response to underlying sea

Hurrell, James

239

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

E-print Network

homeostasis and further affecting energy balance. Prior studies of temperature regulation in sea lions have whether they exhibit consistent spatial patterns of heat flux. Heat flux and skin temperature data were

240

Simplified Analysis of Airspike Heat Flux Into Lightcraft Thermal Management System  

Microsoft Academic Search

An approximate method is presented for estimating the airspike heat flux into a 9-meter diameter lightcraft, integrated over its flight to low Earth orbit. The super-pressure lightcraft’s exotic twin-hull, sandwich structure is assumed to be fabricated from SiC\\/SiC thin-film ceramic matrix composites of semiconductor grade purity, giving superior structural properties while being transparent to 35-GHz microwave radiation. The vehicle’s MHD

Dean R. Head; Junghwa Seo; Brice N. Cassenti; Leik N. Myrabo

2005-01-01

241

Simplified Analysis of Airspike Heat Flux Into Lightcraft Thermal Management System  

Microsoft Academic Search

An approximate method is presented for estimating the airspike heat flux into a 9-meter diameter lightcraft, integrated over its flight to low Earth orbit. The super-pressure lightcraft's exotic twin-hull, sandwich structure is assumed to be fabricated from SiC\\/SiC thin-film ceramic matrix composites of semiconductor grade purity, giving superior structural properties while being transparent to 35-GHz microwave radiation. The vehicle's MHD

Dean R. Head; Junghwa Seo; Brice N. Cassenti; Leik N. Myrabo

2005-01-01

242

S{sub n} solutions for radiative heat transfer in an L-shaped participating medium  

SciTech Connect

The Third Symposium on Solution Methods for Radiative Heat Transfer in Participating Media is a continuing effort to benchmark solutions for problems of increasing complexity. This paper presents both the statement of a problem used for the benchmarking exercise and the results obtained using a finite-element S{sub 4} solution. Cases analyzed include rectangular and L-shaped enclosures, and homogeneous and nonhomogeneous media. Calculated surface radiative heat fluxes and divergence of radiative heat fluxes are tabulated at selected coordinates within the evaluated enclosures. Computation times for each of the solutions were recorded and are presented to permit a computational efficiency test against other solution techniques.

Hoover, R.L.; Li, W.; Benmalek, A.; Tong, T.W. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering

1996-11-01

243

Cooling by Heat Conduction Inside Magnetic Flux Loops and the Moderate Cluster Cooling Flow Model  

E-print Network

I study non-radiative cooling of X-ray emitting gas via heat conduction along magnetic field lines inside magnetic flux loops in cooling flow clusters of galaxies. I find that such heat conduction can reduce the fraction of energy radiated in the X-ray band by a factor of 1.5-2. This non-radiative cooling joins two other proposed non-radiative cooling processes, which can be more efficient. These are mixing of cold and hot gas, and heat conduction initiated by magnetic fields reconnection between hot and cold gas. These processes when incorporated into the moderate cooling flow model lead to a general cooling flow model with the following ingredients. (1) Cooling flow does occur, but with a mass cooling rate about 10 times lower than in old versions of the cooling flow model. Namely, heating occurs such that the effective age of the cooling flow is much below the cluster age, but the heating can't prevent cooling altogether. (2) The cooling flow region is in a non-steady state evolution. (3) Non-radiative cooling of X-ray emitting gas can bring the model to a much better agreement with observations. (4) The general behavior of the cooling flow gas, and in particular the role played by magnetic fields, make the intracluster medium in cooling flow clusters similar in some aspects to the active solar corona.

Noam Soker

2003-11-02

244

Experimental investigation of heat transfer and burnout in condition of nonuniform megawatt heat fluxes  

SciTech Connect

In this paper burnout is investigated in tubes under nonuniform heating on the perimeter. Data on heat transfer and critical heat flux (q{sub chf}) in the case of water were obtained for ranges of mass velocity {rho}w = 200--3000 kg/m{sup 2} s, pressure p = 1--1 MPa, and inlet water temperature T = 25--98{degrees}C. The test section was a horizontal copper tube of 21 mm outer diameter, 8 mm inner diameter with a technically smooth surface and heat transfer-intensifying twisted tape and porous sintered coating. The test section was heated by bombardment with electrons. It is established that a redistribution of heat fluxes and an increase of wall temperature fluctuations occur at burnout. The range of regime parameters to prevent burnout of a heat transfer surface is determined.

Komendantov, A.S.; Kuzma-Kichta, Y.A.; Vasil'eva, L.T.; Ovodkov, A.A. (Moscow Power Engineering Inst., Moscow (SU))

1991-01-01

245

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

246

Thermal Radiation from Finned Heat Sinks  

Microsoft Academic Search

An accurate straightforward technique is presented to compute thermal radiation from finned heat sinks. A set of graphs is included to aid in the computational procedure. The analytical approach presented compares favorably with experimental data.

SAMUEL N. REA; S. E. WEST

1976-01-01

247

A high heat flux experiment for verification of thermostructural analysis  

NASA Technical Reports Server (NTRS)

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

Gladden, Herbert J.; Melis, Matthew E.

1988-01-01

248

A 2-D imaging heat-flux gauge  

SciTech Connect

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

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

1991-07-01

249

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

Microsoft Academic Search

The temperature distribution across a flat heat pipe sandwich structure, subjected to an intense localized thermal flux has been investigated both experimentally and computationally. The aluminum sandwich structure consisted of a pair of aluminum alloy face sheets, a truncated square honeycomb (cruciform) core, a nickel metal foam wick and distilled water as the working fluid. Heat was applied via a

G. Carbajal; C. B. Sobhan; G. P. Peterson; D. T. Queheillalt; H. N. G. Wadley

2006-01-01

250

A new parameterisation scheme of ground heat flux for land surface flux retrieval from remote sensing information  

NASA Astrophysics Data System (ADS)

SummaryThe objective of the study was to assess the performance of a new parameterisation scheme of ground heat flux (G) for retrieving surface fluxes from remote sensing data (MODIS-Terra). Formulae that are based on empirical relationships relating G to net radiation, Rn (G = ?Rn, ? being a function of a vegetation index, VI) are currently used, but presented drawbacks, especially in bare or sparse vegetation areas because of the poor adequacy of VI-based relationships to account for changes in soil moisture. In this study, we proposed to link ? to the evaporative fraction, EF. In a first step, using a non-dimensional form of the surface energy balance, we demonstrated that ? is functionally related to EF and to the ratio ? = G/H (H = sensible heat flux). In a second step, we proposed an EF-based parameterisation of ?, using ground fluxes data sets collected throughout the years 2005, 2006 and 2007 at four flux-tower sites in West African countries (Mali, Benin, Niger) that differ in surface conditions and Monsoon influence. The analysis indicated that the average site-specific values of ? and EF were well described by a linear relationship of the type ? = a EF + b, with a = -0.22 and b = 0.23. In a third stage, we investigated whether ET-retrieval from remote sensing information (MODIS-Terra) using the new parameterisation of ? perform better than the classical formulation through VI-based relationships. We found that the retrieved values of H using the new parameterisation supplied the best agreement with the observed ground data and significant improvement with respect to estimates from ?-VI relationships. Advantages and limitations of the proposed parameterisation scheme were discussed.

Tanguy, M.; Baille, A.; González-Real, M. M.; Lloyd, C.; Cappelaere, B.; Kergoat, L.; Cohard, J.-M.

2012-08-01

251

A Method for Monitoring the Heat Flux from an Urban District with a Single Infrared Remote Sensor  

NASA Astrophysics Data System (ADS)

The proposed methodology relies on the modelling capabilities of the thermo-radiative model Suc(olene) to simulate the heat and radiation energy exchanges between an actual urban district and the atmosphere. It is based on the comparison of the simulated upward infrared and sensible heat flux diurnal cycles that may be measured by elevated sensors above the three-dimensional scene, as a function of sensor position: the heat flux is a function of an equivalent surface temperature given by the infrared sensor and an equivalent heat transfer coefficient deduced from Suc(olene) simulations with the actual geometry. The method is tested against measurements obtained in the city centre of Toulouse, France during an experimental campaign in 2004-2005. To improve the computation of the heat exchanges between air and building surfaces a new algorithm is first implemented, based on an empirical model of the wind distribution within street canyons. This improvement is assessed by a direct comparison of the simulated brightness surface temperatures of the Toulouse city centre to measurements obtained with an airborne infrared sensor. The optimization of the infrared remote sensor position is finally analyzed as a function of its height above the mean roof level: it allows evaluation of the heat flux from an urban district when the three different classes of surfaces (roofs, walls, grounds) have similar contributions to the infrared flux towards the sensor, and to the heat flux into the atmosphere.

Hénon, Aurélien; Mestayer, Patrice G.

2014-07-01

252

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

Microsoft Academic Search

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

Weilin Qu; Issam Mudawar

2004-01-01

253

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

2014-11-21

254

Heat and Flux Configurations on Offshore Wind Farms  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

255

Study of heat flux gages using sensitivity analysis  

SciTech Connect

The response and operation of a heat flux gage is studied using sensitivity analysis. Sensitivity analysis is the process by which one determines the sensitivity of a model output to changes in the model parameters. This process uses sensitivity coefficients that are defined as partial derivatives of field variables--e.g., temperature--with respect to model parameters--e.g., thermal properties and boundary conditions. Computing sensitivity coefficients, in addition to the response of a heat flux gage, aids in identifying model parameters that significantly impact the temperature response. A control volume, finite element-based code is used to implement numerical sensitivity coefficient calculations, allowing general problems to be studied. Sensitivity coefficients are discussed for the well known Gardon gage.

Dowding, K.J.; Blackwell, B.F.; Cochran, R.J.

1998-08-01

256

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

SciTech Connect

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

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

1996-06-06

257

Evaluation of Satellite-Derived Latent Heat Fluxes  

Microsoft Academic Search

A method of determining ocean-atmosphere latent heat flux using the Special Sensor Microwave\\/Imager (SSM\\/I) and the Advanced Very High Resolution Radiometer (AVHRR) is presented and evaluated. While sea surface temperatures are retrieved from AVHRR data with an accuracy of 0.5-1.0 K, the near-surface wind speed and the surface air humidity are retrieved from measurements of the SSM\\/I with accuracies of

Jörg Schulz; Jens Meywerk; Stefan Ewald; Peter Schlüssel

1997-01-01

258

Evaluation of satellite-derived latent heat fluxes  

Microsoft Academic Search

A method of determining ocean-atmosphere latent heat flux using the Special Sensor Microwave\\/Imager (SSM\\/I) and the Advanced Very High Resolution Radiometer (AVHRR) is presented and evaluated. While sea surface temperatures are retrieved from AVHRR data with an accuracy of 0.5-1.0 K, the near-surface wind speed and the surface air humidity are retrieved from measurements of the SSM\\/I with accuracies of

J. Schulz; J. Meywerk; S. Ewald; P. Schluessel

1997-01-01

259

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

260

High heat flux cooling for silicon hybrid multichip packaging  

Microsoft Academic Search

Recent projections have suggested that heat fluxes will reach or exceed 100 W\\/cm2 in future integrated circuit chips. Research on the application of both liquid-jet impingement with boiling and direct liquid immersion to the cooling of silicon substrates used in hybrid multichip packaging is described. The authors report the first data on cooling of silicon substrates using direct immersion cooling

RICHARD C. JAEGER; JOHN S. GOODLING; MICHAEL E. BAGINSKI; CHARLES D. ELLIS; N. VINCENT WILLIAMSON; R. M. O'Barr

1989-01-01

261

Novel Surface Thermocouple Probes for Divertor Heat Flux Measurement  

NASA Astrophysics Data System (ADS)

An array of novel surface thermocouple probes have been installed and tested in the outer divertor of Alcator C-Mod. These sensors can, in principle, record divertor surface temperatures with fast time response (? >= 10 ? sec), allowing a direct estimate of the plasma heat flux to be inferred. The design is an adaptation of a commercially available device(``The Self-Renewing Thermocouple,'' Nanmac Corp., Framingham, MA), employing a coaxial-like geometry with a single tungsten-rhenium ribbon wire embedded inside a 6.35 mm diameter molybdenum rod. Various prototypes were tested, including probes with flush and 5^circ angles with respect to the divertor surface, and probes with and without protective surface coatings. Typical surface temperature rises are ~ 300-700 ^circC, corresponding to signals of ~ 3-9 mV. RC filters with 10 ms time constants are used to reduce noise introduced by the plasma environment. The surface temperature corresponding to typical RMS noise levels is ~ 25 ^circC. Using a one-dimensional, semi-infinite slab model, parallel heat fluxes in the range of 50-500 MW/m^2 are estimated. A comparison with heat flux estimates from Langmuir probes located adjacent to the thermocouple array will be presented. Supported by U.S. DOE Contract No. DE-AC02-78ET51013

Gangadhara, S.; Labombard, B.; Lipschultz, B.; Pierce, N.

1996-11-01

262

Cosmic matter flux may turn Hawking radiation off  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

263

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

NASA Technical Reports Server (NTRS)

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

Nelson, H. F.

1981-01-01

264

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

265

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

266

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

267

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

NASA Astrophysics Data System (ADS)

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.; Leonard, A. W.; Petrie, T. W.

1994-01-01

268

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

269

Cloud Properties and Radiative Heating Rates for TWP  

SciTech Connect

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

Comstock, Jennifer

2013-11-07

270

Cloud Properties and Radiative Heating Rates for TWP  

DOE Data Explorer

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

Comstock, Jennifer

271

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

272

An intercomparison between the surface heat flux feedback simulated by five coupled models  

Microsoft Academic Search

The surface heat flux feedback is estimated in the Atlantic and the extratropical North and South Pacific, using monthly heat flux and sea surface temperature (SST) anomaly data from control simulations with the five global climate models that were considered in the PREDICATE EU program. In all simulations, the net heat flux feedback is nearly everywhere negative and, at extratropical

C. Frankignoul; E. Kestenare

2003-01-01

273

Estimating air-sea fluxes of heat, freshwater, and momentum through global ocean data assimilation  

E-print Network

Estimating air-sea fluxes of heat, freshwater, and momentum through global ocean data assimilation-sea fluxes of heat, freshwater, and momentum through global ocean data assimilation, J. Geophys. Res., 109, C05023, doi:10.1029/2003JC002082. 1. Introduction [2] Air-sea fluxes of momentum, heat, and moisture

274

The balance between nonlinear inwards and outwards boundary-flux for a nonlinear heat equation  

E-print Network

The balance between nonlinear inwards and outwards boundary-flux for a nonlinear heat equation Ra that the solution is global. If i ¥ , we have the well-known heat equation. For £ ¥ the equation is called for temperature and pfAqsrut represents heat flux. Thus we have a nonlinear inwards flux at the boundary point xi

Quirós, Fernando

275

ARTICLE IN PRESS Reply to bcomments on Earth's heat flux revised and linked to  

E-print Network

the global heat flux (e.g., Pollack et al., 1993). Although related models (e.g., GDH, see Stein and Stein a singular- ity that controls the calculated value for the global heat flux. A final section addresses minorARTICLE IN PRESS Discussion Reply to bcomments on Earth's heat flux revised and linked to chemistry

Fisher, Andrew

276

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

E-print Network

and latent heat fluxes released over the Tibetan Plateau not only strongly affect global circulation patternsORIGINAL ARTICLE Sensible and latent heat flux response to diurnal variation in soil surface 2010 Ã? Springer-Verlag 2010 Abstract The relationship between sensible and latent heat flux and diurnal

277

Effect of harmonic heat flux variation on solid material piloted ignition  

E-print Network

the global trend of the incoming radiant heat flux has been taken into account. However, turbulent motionsEffect of harmonic heat flux variation on solid material piloted ignition A. Lamorlette Laboratoire) 491 113 811 Abstract This study aims at modeling the effect of incoming heat flux fluctuations

Paris-Sud XI, Université de

278

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 of the fluxes far from global equilibrium. An asymmetric set of transport coefficients is obtained, by assuming how the measurable heat flux and the heat production under isothermal conditions, as well

Kjelstrup, Signe

279

Calculation of latent and sensible heat fluxes during summer in ocean area around Antarctic  

Microsoft Academic Search

THE transfer of latent and sensible heat fluxes over the ocean surface makes an important effect on the global climatic variation. The heat fluxes can be calculated directly by using the data of fluctuations of temperature, humidity and wind speed. In addition, the heat fluxes can be calculated by bulk transfer method. The former demands accurate instruments, which are difficultly

Shiming Li; Mingyu Zhou; Lirong Su; Naping Lu

1997-01-01

280

Estimation of latent heat flux over the ocean using satellite data  

Microsoft Academic Search

Latent heat flux plays an important role in the global climate system. Though it was difficult to globally monitor latent heat flux over the ocean for many years, the situation is rapidly changing by the use of satellite data. Since a bulk formula is used to estimate turbulent heat flux using satellite data, we need wind speed, sea surface temperature

M. Kubota; H. Tomita; A. Suzuki

2002-01-01

281

Convection under a lid of finite conductivity: Heat flux scaling and application to continents  

E-print Network

Convection under a lid of finite conductivity: Heat flux scaling and application to continents C. J. Tackley (2007), Convection under a lid of finite conductivity: Heat flux scaling and application April 2007; published 1 August 2007. [1] A scaling law for the heat flux out of a convective fluid

Paris-Sud XI, Université de

282

Sensitivity of Cenozoic Antarctic ice sheet variations to geothermal heat flux  

E-print Network

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

283

Adaptation of the in-cavity calibration method for high temperature heat flux sensors  

Microsoft Academic Search

The need for in situ heat flux measurements in hot structures, used in hypersonic vehicle thermal protection system development, combustion and propulsion research, and fire testing requires that heat flux sensors are characterized over their entire operating temperature range. The in-cavity heat flux sensor calibration technique has been adapted to accommodate elevated sensor temperatures, in an effort to develop a

Clayton A. Pullins; Tom E. Diller

2011-01-01

284

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

285

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

286

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

NASA Astrophysics Data System (ADS)

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

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

1993-12-01

287

Calculation of Heating Values for the High Flux Isotope Reactor  

SciTech Connect

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

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

2012-01-01

288

Calculation of heating values for the high flux isotope reactor  

SciTech Connect

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

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

2012-07-01

289

Advanced Neutron Source design: Burnout heat flux correlation development  

SciTech Connect

In the Advanced Neutron Source Reactor (ANSR) fuel element region, heat fluxes will be elevated. Early designs corresponded to average and estimated hot-spot fluxes of 11-12 and 21-22 MW/m/sup 2/, respectively. Design changes under consideration may lower these values to about 9 and 17 MW/m/sup 2/. In either event, the development of a satisfactory burnout heat flux correlation is an important element among the many thermal-hydraulic design issues, since the critical power ration will depend in part on its validity. Relatively little work in the area of subcooled-flow burnout has been published over the past 12 years. We have compared seven burnout correlations and modifications thereof with several sets of experimental data, of which the most relevant to the ANS core are presently those referenced. The best overall agreement between the correlations tested and these data is currently provided by a modification of Thorgerson's correlation. 7 refs., 1 tab.

Gambill, W.R.; Mochizuki, T.

1988-01-01

290

Global patterns of landatmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance,  

E-print Network

Global patterns of landatmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived 2011. [1] We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields

Chen, Jiquan

291

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

Microsoft Academic Search

The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiation heating of probes entering the hydrogen helium atmospere of the major planets was investigated. At the present time, there is disagreement as to whether the radiative flux increases or decreases relative to its equilibrium value when finite rate ionization is considered.

H. F. Nelson

1981-01-01

292

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

NASA Astrophysics Data System (ADS)

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

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

1982-11-01

293

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

294

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

295

A correction method for heated length effect in critical heat flux prediction  

Microsoft Academic Search

A new correction method is developed for the effect of the length-to-diameter (L\\/D) ratio on critical heat flux (CHF) by applying artificial neural networks and conventional regression techniques to the KAIST CHF data base for water flow in uniformly-heated, vertical round tubes. It consists of two parts: (a) a threshold L\\/D over which the length effect becomes negligible; and (b)

Yong Ho Lee; Won-Pil Baek; Soon Heung Chang

2000-01-01

296

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

Microsoft Academic Search

Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 rectangular (231 ?m wide and 713 ?m deep) micro-channels. Tests were performed using deionized water with inlet liquid velocities of 0.13–1.44 m\\/s, inlet temperatures of 30, 60 and 90 °C, and an outlet pressure of 1.2 bar. Using a microscope, boiling incipience was identified

Weilin Qu; Issam Mudawar

2002-01-01

297

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

SciTech Connect

A series of tests have been performed to determine the saturated critical heat flux (CHF) in 0.5 and 0.8mm internal diameter microchannel tubes as a function of refrigerant mass velocity, heated length, saturation temperature and inlet liquid subcooling. The tested refrigerants were R-134a and R-245fa and the heated length of microchannel was varied between 20 and 70mm. The results show a strong dependence of CHF on mass velocity, heated length and microchannel diameter but no influence of liquid subcooling (2-15{sup o}C) was observed. The experimental results have been compared to the well-known CHF single-channel correlation of Y. Katto and H. Ohno [An improved version of the generalized correlation of critical heat flux for the forced convective boiling in uniformly heated vertical tubes, Int. J. Heat and Mass Transfer 27 (9) (1984) 1641-1648] and the multichannel correlation of W. Qu and I. Mudawar [Measurement and correlation of critical heat flux in two-phase microchannel heat sinks, Int. J. Heat and Mass Transfer 47 (2004) 2045-2059]. The comparison shows that the correlation of Katto-Ohno predicts microchannel data with a mean absolute error of 32.8% with only 41.2% of the data falling within a +/-15% error band. The correlation of Qu and Mudawar shows the same trends as the CHF data but significantly overpredicts them. Based on the present experimental data, a new microscale version of the Katto-Ohno correlation for the prediction of CHF during saturated boiling in microchannels has been proposed. (author)

Wojtan, Leszek; Revellin, Remi; Thome, John R. [Laboratory of Heat and Mass Transfer (LTCM), Faculty of Engineering Science (STI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2006-08-15

298

Wintertime heat flux to the underside of east Antarctic pack ice  

Microsoft Academic Search

In the sea ice zone, there is a delicate balance between the heat loss from the surface of the snow-covered sea ice and the heat supplied to the underside of the ice by the deep ocean. The difference between these two heat fluxes determines the amount of ice growth or melt. In global atmospheric models the ocean heat flux is

V. I. Lytle; R. Massom; N. Bindoff; A. Worby; I. Allison

2000-01-01

299

IR Radiative Transfer with Transient Heating  

NASA Astrophysics Data System (ADS)

In order to study the evolutionary history of most astrophysical systems an accurate account of the effects of dust is necessary. We are currently extending our radiative transfer models to include infrared emission from dust. Presently,the model tracks UV and optical photons through an arbitrary mixture of gas, stars, and dust. Emission from dust includes emission from large grains in thermodynamic equilibrium with the radiation field as well as small grains and molecules that undergo transient heating. Here we present results from our model which include the effects of the transient heating and apply it to systems with simple geometries.

Misselt, K. A.; Gordon, K. D.; Clayton, G. C.; Wolff, M. J.

1999-05-01

300

Radiative cooling in shock-heated hydrogen-helium plasmas. [for planetary entry probe heat shields  

NASA Technical Reports Server (NTRS)

Axial and off-axis radiative cooling of cylindrical shock-heated hydrogen-helium plasmas is investigated theoretically and experimentally. The coupled fluid dynamic-radiative transfer equations are solved by a combination of approximation techniques aimed at simplifying the computation of the flux divergence term, namely, the quasi-isothermal approximation and the exponential approximation developed for the solid angle integration. The accuracy of the approximation schemes has been assessed and found acceptable for applying the methods to the rapid computation of the radiatively coupled flow problem. Radiative cooling experiments were conducted in a 6-inch annular arc accelerator shock tube (ANAA) for an initial pressure of 1 torr and shock speeds from 35 to 45 Km/sec. The results indicate that the lateral cooling is small compared with the axial cooling, and that better agreement is achieved between the data and the theoretical results by inclusion of the lateral temperature gradient.

Poon, P. T. Y.; Stickford, G. H., Jr.

1978-01-01

301

Surface heat fluxes influence on medicane trajectories and intensification  

NASA Astrophysics Data System (ADS)

A few tropical-like cyclones have developed over the Mediterranean Sea during the last decades according to the inventory of images provided by Meteosat satellite. These extreme small-scale warm-core storms, also called “medicanes”, operate on the thermodynamical disequilibrium between the sea and the atmosphere, and sometimes attain hurricane intensity and threaten the islands and coastal regions. Despite their small size, mesoscale model runs at moderate horizontal resolutions (7.5 km) made with MM5 are able to simulate the formation of a subsynoptic cyclone and the general trajectory of the disturbance, and for most of the cases a warm-core axi-symmetrical structure becomes evident in the simulations. The timing and precise details of the storm trajectories are shown to be more problematic when compared against the satellite images available for the events. It is hypothesized that the small size of the systems and the crucial role of moist microphysics, deep convection and boundary layer parameterizations are the main factors behind these errors. On the other hand, a sensitivity analysis examining the role of the sea surface heat fluxes is conducted: latent and sensible heat fluxes from the Mediterranean are switched off at the beginning of the simulations to explore the effects of these factors on the medicane trajectories and deepening rate. Results show different roles of the surface heat fluxes on medicane properties (intensification and track) depending on their magnitude and spatial distribution over the Mediterranean Sea. In this way, three distinct patterns have been identified using a database of twelve events.

Tous, M.; Romero, R.; Ramis, C.

2013-04-01

302

USE OF PELTIER COOLERS AS SOIL HEAT FLUX TRANSDUCERS.  

USGS Publications Warehouse

Peltier coolers were modified and calibrated to serve as soil heat flux transducers. The modification was to fill their interiors with epoxy. The average calibration constant on 21 units was 13. 6 plus or minus 0. 8 kW m** minus **2 V** minus **1 at 20 degree C. This sensitivity is about eight times that of the two thermopile transducers with which comparisons were made. The thermal conductivity of the Peltier cooler transducers was 0. 4 W m** minus **1 degree C** minus **1, which is comparable to that of dry soil.

Weaver, H.L.; Campbell, G.S.

1985-01-01

303

Electron and proton flux models for Jupiter's radiation belts  

NASA Technical Reports Server (NTRS)

Estimates of the energetic particle distribution in Jupiter's radiation belts are presented and are compared with previous estimates. Mathematical expressions are developed for the equatorial electron and proton fluxes, shielded electron and proton dose rates, and radiation lifetimes of electronic circuits. It is calculated that a 1 g/sq cm aluminum shield will screen out all protons of energy less than 27.5 MeV, and a 2 g/sq cm shield will screen out protons less than 40.6 MeV. The radiation lifetimes are based on a maximum permissible dose value of 10 million rads, a value 1/2 to 1/3 of the flux at which electronic circuits begin to fail. Estimated increases in lifetimes by using a 3 x 50 orbit instead of a 3 x 3 orbit, and going from 1 to 2 g/sq cm are given.

Klopp, D. A.

1972-01-01

304

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

305

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

Microsoft Academic Search

The mean seasonal cycles of six state-of-the-art surface heat flux products (three based on widely available data and three based on numerical model reanalysis fields) are compared in the equatorial Pacific with heat fluxes computed from Tropical Atmosphere-Ocean (TAO) buoy data. Net surface heat flux and individual flux components derived from these products exhibit large deviations from TAO. We find

Weimin Wang; Michael J. McPhaden

2001-01-01

306

Equivalent circuit model of radiative heat transfer  

NASA Astrophysics Data System (ADS)

Here, we develop a theory of radiative heat transfer based on an equivalent electrical network representation for the hot material slabs in an arbitrary multilayered environment with arbitrary distribution of temperatures and electromagnetic properties among the layers. Our approach is fully equivalent to the known theories operating with the fluctuating current density, while being significantly simpler in analysis and applications. A practical example of the near-infrared heat transfer through the micron gap filled with an indefinite metamaterial is considered using the suggested method. The giant enhancement of the transferred heat compared to the case of the empty gap is shown.

Maslovski, Stanislav I.; Simovski, Constantin R.; Tretyakov, Sergei A.

2013-04-01

307

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

308

Net surface heat flux over the North and South Atlantic in 1985-1986 from Day 1 predictions of the European Center for Medium Range Weather Forecast  

Microsoft Academic Search

Twelve months of data on surface heat fluxes (shortwave radiation, longwave radiation, latent heat and sensible heat, from August 1985 to July 1986), obtained from the European Center for Medium-Range Weather Forecast (ECMWF) on a grid of 1.125° latitude by 1.125° longitude were analyzed. Comparison with older data from ECMWF (Simonot and Le Treut, 1987) indicates the occurrence of significant

B. Barnier; J.-Y. Simonot

1990-01-01

309

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

SciTech Connect

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

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

2009-01-01

310

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

311

Critical heat flux prediction for water boiling in vertical tubes of a steam generator  

Microsoft Academic Search

This paper presents a methodology for the prediction of the critical heat flux (CHF) for the boiling of water in vertical tubes operating under typical conditions found in steam generators. At the furnace, the water flows through long vertical tubes under an axially non-uniform heat flux and with relatively low mass fluxes. This fact causes that the recent theories and

L. A. Payan-Rodriguez; A. Gallegos-Muñoz; G. L. Porras-Loaiza; M. Picon-Nuñez

2005-01-01

312

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

313

AOSC 621AOSC 621 Radiative Heating/CoolingRadiative Heating/Cooling  

E-print Network

? Why drop off near sfc? 4 #12;Net flux Net flux: F = F+ - F- 1 2 F-(1) F+(1) F-(2) F+(2) Net energy at the top of the atmosphere is zero. Then we can write 1' ' )',( )'()0,()( 0 * dz dz zzdT zBzTBzF z z F F · The heating rate at z is defined as follows: )( )( d zdF zH net four termsofconsistwilland dz A

Li, Zhanqing

314

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

SciTech Connect

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

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

2014-06-23

315

Radiative Heating Methodology for the Huygens Probe  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

316

Measuring Longwave Radiative Flux Divergence in an Urban Canyon  

NASA Astrophysics Data System (ADS)

There has been very little measurement of longwave radiation divergence since the urban studies of Fuggle, Oke and Nunez in the mid 1970's or the rural work of Funk in the early 1960's. Although radiative divergence has been widely ignored for sometime there is the belief that it may play an important role in balancing nocturnal energy budgets in a range of environments. For example, in urban environments surface temperature relates well to the energy balance whereas air temperature does not, even in non-turbulent conditions. This is probably due at least in part to the effects of longwave divergence. To help answer issues related to longwave divergence a new dual-channel infrared radiometer (DCIR) has been developed. The DCIR, as the name implies, measures the directional infrared radiation in two wavebands and can, through differencing of the signals and further signal processing, give a direct measurement of longwave radiative flux divergence. The DCIR was deployed for the first time as part of a larger study (BUBBLE) of the urban boundary layer of Basel, Switzerland. The objective is to further study the thermal regime of a city at the canyon scale. To this end, a street canyon was carefully selected, in the city of Basel. The canyon surface and air volume were instrumented, including turbulent and conductive fluxes, and standard meteorological variables in addition to radiation. A unique data set was obtained to allow the complete energy balance of the canyon system to be evaluated without the need to resort to using residuals to quantify the magnitude of the longwave radiative flux divergence. Measured values of longwave flux-divergence are converted to cooling rates to compare with measured air temperature cooling. Preliminary results show that at the onset of canyon air-volume cooling, measured cooling rates are slightly lower than radiative cooling rates. The differences are less than 0.5° C. This contrasts sharply with previously measured above roof level and rural differences of greater than 5° C. The difference between the rural and above-canyon case and the in-canyon case is most likely a result of differences in radiative environments and wind and temperature fields. The differences illustrate the strong role of urbanization on the surface energy budget.

Soux, A.; Oke, T. R.; Nunez, M.; Wilson, M.

2003-12-01

317

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

318

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

319

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

Microsoft Academic Search

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

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

2005-01-01

320

Inter-annual to Intra-decadal Variability in the Ekman Heat Flux from Scatterometer Winds  

Microsoft Academic Search

The heat transported poleward by the oceans is a major contributor to inter-annual, long-term, and possibly to climate changes. Depending on the latitude the Ekman heat flux is comparable with the total oceanic heat flux. The high spatial and temporal resolution and the directional information of the wind provided by the scatterometer satellite data can improve the estimates of the

O. T. Sato; P. S. Polito; W. Liu

2001-01-01

321

The Effect of Heat Flux Limiting on Divertor Fluid Models a  

E-print Network

that the classical expres­ sions for thermal conductivities lead to significantly overestimated electron heat fluxes effort to develop nonlocal heat conduction models[2]. Reference 3 includes a critique of a large classThe Effect of Heat Flux Limiting on Divertor Fluid Models a M. Day b , B. Merriman c , F. Najmabadi

Bell, John B.

322

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

Microsoft Academic Search

The high-latitude ionosphere interfaces with the hot, tenuous, magnetospheric plasma, and a heat flow into the ionosphere is expected, which has a large impact on the plasma densities and temperatures in the high-latitude ionosphere. The value of this magnetospheric heat flux is unknown. In an effort to estimate the value of the magnetospheric heat flux into the ionosphere and, and

H. Bekerat; R. Schunk; L. Scherliess

2005-01-01

323

Heat fluxes at the Earth's surface and coremantle boundary since Pangea formation and their implications for the geomagnetic superchrons  

E-print Network

ago, while global CMB heat flux is a maximum at ~100 Ma ago. These extrema in CMB heat fluxes coincideHeat fluxes at the Earth's surface and core­mantle boundary since Pangea formation Editor: Y. Ricard Keywords: mantle convection heat flux supercontinent Pangea magnetic polarity reversals

Zhong, Shijie

324

CFD Analysis of Radiative Heat Transfer in the SSME Main Combustion Chamber Using Advanced Spectral Models  

NASA Astrophysics Data System (ADS)

In this work, enhanced Weighted Sum of Gray Gases Models for spectral integration of radiative heat transfer are identified and implemented in the Computational Fluid Dynamics solver ANSYS CFX. The models are applicable to both homogeneous and nonhomogeneous conditions in temperature, pressure and molar fraction of radiating species. A simulation of the Space Shuttle Main Engine Main Combustion Chamber is done using these models combined with the P1 Model and the Discrete Transfer Model. Results in Radiative Wall Heat Flux are then compared to benchmark solutions. The results show that the model by Denison & Webb comes close to the benchmark results with vanishing difference between its applications for homogeneous and nonhomogeneous conditions. Both models by Modest predict a smaller radiative wall heat flux than the benchmarks, whereas the results of the nonhomogeneous Full- pectrum-Correlated-k- Distribution-Model are closer to the benchmarks than those of the homogeneous Full-Spectrum-k- Distribution-Model.

Göbel, F.; Mundt, C.

2011-08-01

325

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

E-print Network

THERMAL DESIGN METHODOLOGY FOR HIGH-HEAT-FLUX SINGLE-PHASE AND TWO-PHASE MICRO-CHANNEL HEAT SINKS to the thermal design of single-phase and two-phase micro-channel heat sinks. The first part of the paper is developed to predict pressure drop across a two-phase micro-channel heat sink. This model provides

Qu, Weilin

326

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

327

Eddy heat fluxes at Drake Passage due to mesoscale motions  

E-print Network

981. 7 598. 1 383. 6 3790. 7 61. 6 NT 948. 9 1235. 7 910. 3 325. 5 2540. 3 50. 4 NLl 810. 0 1331. 1 481. 4 849. 7 44490. 8 210. 9 NL1 ML 2 h1L2 ML 6 ML 6 2732. 6 2972. 3 2556. 7 415. 5 14523. 3 120. 5 882. 2 1417. 1 571. 3 845. 8 29196. 1 170. 9... corrected with the mean gradient plus and minus the standard error. Using the mean temperature gradient (-3. 83 x 10 C/db) the eddy heat flux is -1. 5 kW m for MLS at 647 m and -25. 4 kW m for ML 6 at 688 m. The mean gradient plus the standard error (-2...

Rojas Recabal, Ricardo Luis

2012-06-07

328

High heat flux mirror design for an undulator beamline  

NASA Astrophysics Data System (ADS)

A-high-heat-load, horizontally deflecting/focusing mirror is designed for installation on an APS undulator beamline. The main design objective has been to keep the total tangential RMS slope error, including the thermally induced component, to less than 2 (mu) rad with an absorbed beam power on the mirror of 2 kW and a peak flux of 3.2 W/mm2. Extensive examination of various design parameters and detailed thermal/structural analyses has resulted in a mirror design that meets the tight slope-error requirement. Design features include a silicon substrate, a tailored pin-post cooling scheme, a moderate coolant flow rate, primary and secondary cooling areas, a multi-strip coating on the reflecting surface, and inlet/outlet cooling manifolds through an attached Ni-Fe mounting structure.

Tonnessen, Thomas W.; Fisher, Steven E.; Anthony, Frank M.; Lunt, David L.; Khounsary, Ali M.; Randall, Kevin J.; Gluskin, Efim S.; Yun, Wenbing

1993-11-01

329

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

330

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

PubMed

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

Li, Xiantao

2014-09-01

331

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

SciTech Connect

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

Nakos, James Thomas

2010-12-01

332

Total aerosol effect: forcing or radiative flux perturbation?  

SciTech Connect

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

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

2009-09-25

333

Shaping solar concentrator mirrors by radiative heating  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

334

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

335

Heat pump augmented radiator for low-temperature space applications  

Microsoft Academic Search

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

M. Olszewski; U. Rockenfeller

1988-01-01

336

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

337

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

338

Elementary heating events - magnetic interactions between two flux sources. II. Rates of flux reconnection  

NASA Astrophysics Data System (ADS)

Magnetic fragments in the photosphere are in continuous motion and, due to the complex nature of the magnetic field in the solar atmosphere, these motions are likely to drive a lucrative coronal energy source: the passing of initially-unconnected opposite-polarity fragments that release energy through both closing and then re-opening the same fieldlines. Three-dimensional, time-dependent MHD and potential models are used to investigate the passing of fragments in an overlying field. The processes of closing and opening the field generally occur through separator and separatrix reconnection, respectively. The rates of flux reconnection in these processes are determined. They are found to be dependent on the direction of the surrounding magnetic field relative to the motion of the fragments and the velocity of the sources. In particular, separator reconnection rates (closing) and separatrix-surface reconnection rates (opening) are directly related to the rate of flux transport perpendicular to the current sheet (overlying field). The results suggest that both types of reconnection are fast with the peak rates of separator and separatrix reconnection occurring at 58% and 29% of the peak potential reconnection rate, respectively, when the sources are driven at a hundredth of the peak Alfvén velocity in the box. Moreover, the slower the system is driven the closer the flux reconnection rates are to the instantaneous potential rates. Furthermore, there is a maximum reconnection rate for both types of reconnection as the driving speed tends to the Alfvén speed with the separatrix reconnection rate typically half that of separator reconnection. These results suggest that, on the Sun, reconnection driven by the passing of small-scale network and intranetwork fragments is a highly efficient process that is very likely to contribute significantly to the heating of the background solar corona. The three-dimensional reconnection processes are efficient because, unlike in two-dimensions, there are many places within the current sheets where reconnection can take place simultaneously giving rise to fine-scale structure along the boundaries between the open, closed and re-opened flux. Furthermore, due to the complexity of the magnetic field above the photosphere the reconnection all takes place low down at less than a quarter of the separation of the initial fragments above the photosphere.

Parnell, C. E.; Galsgaard, K.

2004-12-01

339

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

340

TWO-DIMENSIONAL TRANSIENT RADIATIVE HEAT TRANSFER USING DISCRETE ORDINATES METHOD  

E-print Network

TWO-DIMENSIONAL TRANSIENT RADIATIVE HEAT TRANSFER USING DISCRETE ORDINATES METHOD Zhixiong Guo Metrotech Center, Brooklyn, NY 11201, USA ABSTRACT. The S-N discrete ordinates (DO) method is developed, in which discrete ordinates method, P-N model, diffuse approximation, and two-flux method have been

Guo, Zhixiong "James"

341

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

342

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

ERIC Educational Resources Information Center

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

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

2009-01-01

343

Heat transfer performance of an external receiver pipe under unilateral concentrated solar radiation  

SciTech Connect

The heat transfer and absorption characteristics of an external receiver pipe under unilateral concentrated solar radiation are theoretically investigated. Since the heat loss ratio of the infrared radiation has maximum at moderate energy flux, the heat absorption efficiency will first increase and then decrease with the incident energy flux. The local absorption efficiency will increase with the flow velocity, while the wall temperature drops quickly. Because of the unilateral concentrated solar radiation and different incident angle, the heat transfer is uneven along the circumference. Near the perpendicularly incident region, the wall temperature and absorption efficiency slowly approaches to the maximum, while the absorption efficiency sharply drops near the parallelly incident region. The calculation results show that the heat transfer parameters calculated from the average incident energy flux have a good agreement with the average values of the circumference under different boundary conditions. For the whole pipe with coating of Pyromark, the absorption efficiency of the main region is above 85%, and only the absorption efficiency near the parallelly incident region is below 80%. In general, the absorption efficiency of the whole pipe increases with flow velocity rising and pipe length decreasing, and it approaches to the maximum at optimal concentrated solar flux. (author)

Jianfeng, Lu; Jing, Ding [School of Engineering, Sun Yat-Sen University, Guangzhou 510006 (China); Jianping, Yang [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

2010-11-15

344

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

345

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

346

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

E-print Network

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

347

Uncertainties in Global Ocean Surface Heat Flux Climatologies Derived from Ship Observations  

Microsoft Academic Search

A methodology to define uncertainties associated with ocean surface heat flux calculations has been developed and applied to a global climatology that utilizes a summary of the Comprehensive Ocean-Atmosphere Data Set surface observations. Systematic and random uncertainties in the net oceanic heat flux and each of its four components at individual grid points and for zonal averages have been estimated

Peter J. Gleckler; Bryan C. Weare

1997-01-01

348

Sensible heat flux estimated by using satellite data over the North Pacific  

Microsoft Academic Search

Turbulent heat fluxes over a wide region are generally estimated by an aerodynamic bulk formula. Though a remote sensing technique can be expected to estimate global heat flux, it is difficult to obtain every physical parameter included in aerodynamic formulae by a remote sensor. In particular it is difficult to obtain air temperature at sea surface by a remote sensor,

Masahisa Kubota; Shoichi Mitsumori

1997-01-01

349

Low heat flux and large variations of lithospheric thickness in the Canadian Shield  

Microsoft Academic Search

Ten new heat flux determinations have been made using measurements in 22 mining exploration boreholes located at latitudes higher than 51°N in the Canadian Shield. They provide data in poorly sampled regions near the core of the North American craton where one expects the lithosphere to be thickest. The new heat flux values are all smaller than 34 mW m?2

F. Lévy; C. Jaupart; J.-C. Mareschal; G. Bienfait; A. Limare

2010-01-01

350

Intra-decadal variability in the Ekman heat flux from scatterometer winds  

Microsoft Academic Search

We examine evidences of low frequency variability in the Ekman heat flux due to changes in the global temperature and wind patterns. The 10-year long time series of high resolution surface wind vectors was provided by the European Remote Sensing Satellites 1 and 2. A linear regression of the zonally averaged Ekman heat flux shows a latitudinal trend for the

O. T. Sato; P. S. Polito; W. Timothy Liu

2002-01-01

351

The whistler heat flux instability: Threshold conditions in the solar wind  

Microsoft Academic Search

Solar wind electrons are observed often to consist of two components: a core and a halo. The anisotropics and relative average speeds of these components correspond to a heat flux that has the potential to excite several different electromagetic instabilities; wave-particle scattering by the resulting enhanced fluctuations can limit this heat flux. This manuscript describes theoretical studies using the linear

S. Peter Gary; Earl E. Scime; John L. Phillips; William C. Feldman

1994-01-01

352

Uncertainties in global ocean surface heat flux climatologies derived from ship observations  

Microsoft Academic Search

A methodology to define uncertainties associated with ocean surface heat flux calculations has been developed and applied to a revised version of the Oberhuber global climatology, which utilizes a summary of the COADS surface observations. Systematic and random uncertainties in the net oceanic heat flux and each of its four components at individual grid points and for zonal averages have

P. J. Gleckler; B. C. Weare

1995-01-01

353

Intra-decadal variability in the Ekman heat flux from scatterometer winds  

Microsoft Academic Search

(1) We examine evidences of low frequency variability in the Ekman heat flux due to changes in the global temperature and wind patterns. The 10-year long time series of high resolution surface wind vectors was provided by the European Remote Sensing Satellites 1 and 2. A linear regression of the zonally averaged Ekman heat flux shows a latitudinal trend for

O. T. Sato; P. S. Polito

2002-01-01

354

A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents seas  

Microsoft Academic Search

This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations

Sirpa Häkkinen; Donald J. Cavalieri

1989-01-01

355

The whistler heat flux instability: Threshold conditions in the solar wind  

Microsoft Academic Search

Solar wind electrons are observed often to consist of two components: a core and a halo. The anisotropies and relative average speeds of these two components correspond to a heat flux that has the potential to excite several different electromagnetic instabilities; wave-particle scattering by the resulting enhanced fluctuations can limit this heat flux. This manuscript describes theoretical studies using the

S. Peter Gary; Earl E. Scime; John L. Phillips; William C. Feldman

1994-01-01

356

Analytical estimate of critical heat flux for water boiling in a tube  

Microsoft Academic Search

An approximate equation for the critical heat flux is obtained. The formula is compared with test data on critical heat fluxes at pressures in the range 9.8–196 bar, water mass velocities larger than 4000 kg\\/m2\\/sec, and superheat temperatures of more than 50°C.

A. A. Ivashkevich

1977-01-01

357

Regulation of the solar wind electron heat flux from 1 to 5 AU: Ulysses observations  

SciTech Connect

In this study the authors use observations from the three-dimensional electron spectrometer and magnetometer aboard the Ulysses spacecraft to examine the solar wind electron heat flux from 1.2 to 5.4 AU in the ecliptic plane. Throughout Ulysses` transit to 5.4 AU, the electron heat flux decreases more rapidly ({approximately}R{sup {minus}3.0}) than simple collisionless expansion along the local magnetic field and is smaller than expected for a thermal gradient heat flux, q{sub {parallel}}e(r)={minus}k{sub {parallel}}{del}{sub {parallel}}T{sub e}(r). The radial gradients and magnitudes expected for a number of electron heat flux regulatory mechanisms are examined and compared to the observations. The best agreement is found for heat flux regulation by the whistler heat flux instability. The upper bound and radial scaling for the electron heat flux predicted for the whistler heat flux instability are consistent with observations.

Scime, E.E.; Bame, S.J.; Feldman, W.C.; Gary, S.P.; Phillips, J.L. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States); Balogh, A. [Imperial College, London (United Kingdom)] [Imperial College, London (United Kingdom)

1994-12-01

358

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

Microsoft Academic Search

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

C. K. Rice

1987-01-01

359

Effects of spray characteristics on critical heat flux in subcooled water spray cooling  

Microsoft Academic Search

Effects of spray parameters (mean droplet size, droplet flux, and droplet velocity) on critical heat flux (CHF) were studied while these parameters were systematically varied. The effect of each parameter was studied while keeping the other two nearly constant. The mean droplet velocity (V) had the most dominant effect on CHF and the heat transfer coefficient at CHF (hc), followed

Ruey-Hung Chen; Louis C Chow; Jose E Navedo

2002-01-01

360

AIAA 94-2478 The Method of Heat Flux Simulating in  

E-print Network

AIAA 94-2478 The Method of Heat Flux Simulating in Hypersonic Aerothermodynamics V. V. Riabov Worcester Polytechnic Institute Worcester, MA 18th AIAA Aerospace Ground Testing Conference June 20-23, 1994 and Astronautics 370 L'Enfant Promenade,S.W., Washington, D.C. 20024 I #12;AIAA-94-2478- THE METHOD OF HEAT FLUX

Riabov, Vladimir V.

361

Surface heat flux histories from inversion of geothermal data: Energy balance at the Earth's surface  

Microsoft Academic Search

Past changes in the Earth's surface energy balance propagate into the subsurface and appear as perturbations of the subsurface thermal regime. This paper presents a singular value decomposition inversion method used to reconstruct surface heat flux histories (SHFH) from the heat flux anomalies detected in the shallow subsurface. Synthetic tests were used to assess the robustness of the inversion procedure.

Hugo Beltrami

2001-01-01

362

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

NASA Astrophysics Data System (ADS)

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

Patorski, Jacek A.; Gindrat, Malko

2009-05-01

363

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

364

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

365

Design considerations for a thermophotovoltaic energy converter using heat pipe radiators  

SciTech Connect

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

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

1997-06-01

366

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

367

High heat flux removal using water subcooled flow boiling in a single-side heated circular channel  

Microsoft Academic Search

High heat flux removal from plasma-facing components and electronic heat sinks involves conjugate heat transfer analysis of the applicable substrate and flowing fluid. For the present case of subcooled flow boiling inside a single-side heated circular channel, the dimensional results show the significant radial, circumferential and axial variations in all thermal quantities for the present radial aspect ratio (Ro=outside radius

Ronald D. Boyd; Marcella Strahan; Penrose Cofie; Ali Ekhlassi; Rashad Martin

2003-01-01

368

Distribution of the heat and current fluxes in gas tungsten arcs  

Microsoft Academic Search

The distribution of heat flux on a water-cooled copper anode as a function of welding process parameters has been determined\\u000a experimentally following an experimental technique developed previously. The results indicate that arc length is the primary\\u000a variable governing heat distribution and that the distribution is closely approximated by a gaussian function. The half width\\u000a of the heat flux is defined

N. S. Tsai; T. W. Eagar

1985-01-01

369

Estimation of the high-latitude topside electron heat flux using DMSP plasma density measurements  

Microsoft Academic Search

The high-latitude ionosphere interfaces with the hot, tenuous, magnetospheric plasma, and a heat flow into the ionosphere is expected, which has a large impact on the plasma densities and temperatures in the high-latitude ionosphere. The value of this magnetospheric heat flux is unknown. In an effort to estimate the value of the magnetospheric heat flux into the high-latitude ionosphere, and

Hamed A. Bekerat; Robert W. Schunk; Ludger Scherliess

2007-01-01

370

Consistency Between Tropical Divergent Circulations from Reanalysis Data Sets and Satellite-Derived Precipitation, Radiation, and Surface Fluxes  

NASA Technical Reports Server (NTRS)

Large-scale divergent circulations are part of the atmospheric dynamic response to diabatic heating from condensation, radiative processes, and surface heat fluxes. Vertical motion and the associated divergent wind is thus intimately tied to the hydrologic cycle and the global heat balance. Vertical motions are recovered diagnostically from reanalyses and, as such, are subject to shortcommings in model physics, numerics, and data availability. We use several Global Energy and Water Cycle Experiment (GEWEX) Earth Observation System (EOS) data sets derived from satellite data to assess interannual divergent flow anomalies in the National Centers for Environmental Prediction (NCEP), Goddard Space Flight Center (GSFC), and GSFC Data Assimilation Office (DAO) analyses. Among the data sets are monthly, 2.5 degree gridded precipitation (Microwave Sounding Unit (MSU) and Special Sensor Microwave Imager (SSM/I-based)), Top or the atmosphere (TOA) radiative fluxes from ERBS, surface radiative fluxes from the SRB project, and surface latent and sensible flux estimates from SSM/I. These data sets can be considered as independent of the reanalysis fields. We focus largely on the period 1987-1989 encompassing a strong El Nino / la Nina couplet. Consequently we emphasize interannual changes as well as climatological aspects of the reanalyses. In the processes of this study we use simple integral constraints enforced through the satellite-derived data sets to derive corrections to the divergent circulation produced from the reanalyses. We examine the implications of these corrections in describing how perturbations to the tropical heat balance evolve during a warm / cool couplet. In particular the perturbations to the planetary scale water vapor transport, and the resulting changes in TOA and surface radiative fluxes are considered.

Robertson, Franklin R.; Roads, John; McCaul, Eugene W.

1999-01-01

371

Consistency Between Divergent Circulations from Reanalysis Data Sets and Satellite-Derived Precipitation, Radiation, and Surface Fluxes  

NASA Technical Reports Server (NTRS)

Large-scale divergent circulations are part of the atmospheric dynamic response to diabatic heating from condensation, radiative processes, and surface heat fluxes. Vertical motion and the associated divergent wind is thus intimately tied to the hydrologic cycle and the global heat balance. Despite its importance, the divergent circulation is too small in comparison to the rotational flow to measure directly with any accuracy. Vertical motions are recovered diagnostically from reanalyses and, as such, are subject to shortcomings in model physics, numerics, and data availability. We use several GEWEX pre-EOS data sets derived from satellite data to assess interannual divergent flow anomalies in the NCEP, GSFC, and GSFC DAO analyse. Among the data sets are monthly, 2.5 degree gridded precipitation (MSU and SSM/I-based), TOA radiative fluxes from ERBS, surface radiative fluxes from the SRB project, and surface latent and sensible flux estimates from SSM/I. Most of these data sets can be considered as independent of the reanalysis fields. We focus largely on the period 1987-1989 encompassing a strong El Nino / la Nina couplet. Consequently we emphasize interannual changes rather than climatological aspects of the reanalyses. In the processes of this study we use simple integral constraints enforced through the satellite-derived data sets to derive corrections to the divergent circulation produced from the reanalyses. We examine the implications of these corrections in describing how perturbations to the tropical heat balance evolve during a warm / cool couplet. In particular the perturbations to the planetary scale water vapor transport, and the resulting changes in TOA and surface radiative fluxes are considered.

Robertson, Franklin R.; Fitzjarrald, Dan; McCaul, Eugene W.

1997-01-01

372

Convective currents in nucleate pool boiling and their effects on the heat flux from varying diameter flat plate heating elements  

E-print Network

) was boiled from flat circular copper surfaces at one atmosohere absolute pressure. The critical flux was found to incr ase with decreas- ing diameter. Convection currents across the heating sur- face were produced by auxiliary heaters located to the side... of the main heater . Vapor bubbles escaping from the auxiliary heaters caused a circular flow the test surface. it was shown that inc pattern across reasing flow over the surface increased the critical flux The critical flux was hypothesized...

Morford, Peter Stephen

1980-01-01

373

Calibration of high-heat-flux sensors in a solar furnace  

NASA Astrophysics Data System (ADS)

The most common sensors used for the measurement of high solar irradiance are the Gardon gauges, which are usually calibrated using a black body at a certain temperature as the radiant source. This calibration procedure is assumed to produce a systematic error when solar irradiance measurements are taken using these sensors. This paper demonstrates a calorimetric method for calibrating these high-heat-flux gauges in a solar furnace. This procedure has enabled these sensors to be calibrated under concentrated solar radiation at higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at the Plataforma Solar de Almería. Working at higher irradiances has allowed the uncertainty in the calibration constant of these sensors to be reduced. This work experimentally confirms the predicted systematic errors committed when measuring high solar irradiances using Gardon sensors calibrated with a black body.

Ballestrín, J.; Rodríguez-Alonso, M.; Rodríguez, J.; Cañadas, I.; Barbero, F. J.; Langley, L. W.; Barnes, A.

2006-12-01

374

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

375

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

376

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

377

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

378

Measurement of Heat Flux at Metal-Mold Interface during Casting Solidification  

SciTech Connect

All previous studies on interfacial heat transfer coefficient have been based on indirect methods for estimating the heat flux that employed either inverse heat transfer analysis procedures or instrumentation arrangements to measure temperatures and displacements near the metal-mold interface. In this paper, the heat transfer at the metal-mold interfaces is investigated using a sensor for the direct measurement of heat flux. The heat flux sensor (HFS) was rated for 700oC and had a time response of less than 10 ms. Casting experiments were conducted using graphite molds for aluminum alloy A356. Several casting experiments were performed using a graphite coating and a boron nitride coating. The measurement errors were estimated. The temperature of the mold surface was provided by the HFS while the temperature of the casting surface was measured using a thermocouple. Results for the heat transfer coefficients were obtained based on measured heat flux and temperatures. Four stages were clearly identified for the variation in time of the heat flux. Values of the heat transfer coefficient were in good agreement with data from previous studies.

Sabau, Adrian S [ORNL

2006-01-01

379

Inferring surface heat flux distributions guided by a global seismic model: particular application to Antarctica  

E-print Network

Inferring surface heat flux distributions guided by a global seismic model: particular application a global seismic model of the crust and upper mantle to guide the extrapolation of existing heat regions. We apply this procedure world-wide using the global heat-flow data base of Pollack et al. [Rev

Shapiro, Nikolai

380

Ocean-to-Ice Heat Flux and Diminished Arctic Sea Ice Cover (Invited)  

Microsoft Academic Search

Ocean-to-Ice Heat Flux and the Decline of the Arctic Sea Ice Cover Heat transport from the ocean to the base of the sea ice plays a significant role in the enthalpy balance of the Arctic Ocean sea ice cover. In this presentation, we touch on two aspects of heat storage and transport in the upper Arctic Ocean: (1) the role

W. J. Shaw; T. P. Stanton

2010-01-01

381

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

382

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

383

A study of oceanic surface heat fluxes in the Greenland, Norwegian, and Barents Seas  

NASA Technical Reports Server (NTRS)

This study examines oceanic surface heat fluxes in the Norwegian, Greenland, and Barents seas using the gridded Navy Fleet Numerical Oceanography Central surface analysis and the First GARP Global Experiment (FGGE) IIc cloudiness data bases. Monthly and annual means of net and turbulent heat fluxes are computed for the FGGE year 1979. The FGGE IIb data base consisting of individual observations provides particularly good data coverage in this region for a comparison with the gridded Navy winds and air temperatures. The standard errors of estimate between the Navy and FGGE IIb winds and air temperatures are 3.6 m/s and 2.5 C, respectively. The computations for the latent and sensible heat fluxes are based on bulk formulas with the same constant heat exchange coefficient of 0.0015. The results show extremely strong wintertime heat fluxes in the northern Greenland Sea and especially in the Barents Sea in contrast to previous studies.

Hakkinen, Sirpa; Cavalieri, Donald J.

1989-01-01

384

New technique for the fabrication of miniature thin film heat flux gauges  

NASA Astrophysics Data System (ADS)

This paper details the improvements made to the design and fabrication of thin-film heat flux gauges at Oxford. These improvements have been driven by the desire to improve measurement accuracy and resolution in short duration wind-tunnel experiments. A thin-film heat flux gauge (TFHFG) measures heat flux by recording the temperature history of thin film resistive temperature sensors sputtered onto an insulating substrate. The heat flux can then be calculated using Fourier’s law of heat conduction. A new fabrication process utilising technology from the manufacture of flexible printed circuit boards is outlined, which enables the production of significantly smaller and more robust gauges than those previously used.

Collins, Matthew; Chana, Kam; Povey, Thomas

2015-02-01

385

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

SciTech Connect

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., E-mail: kosuga@riam.kyushu-u.ac.jp [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); IAS and RIAM, Kyushu University, Fukuoka (Japan); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of) [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CASS and CMTFO, University of California, San Diego, California 92093 (United States); Dif-Pradalier, G. [CEA, IRFM, Paul-lez-Durance Cedex (France)] [CEA, IRFM, Paul-lez-Durance Cedex (France); Gürcan, Ö. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)] [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)

2014-05-15

386

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

387

Parametric representation of heat and moisture fluxes in cloud-topped mixed layers  

NASA Technical Reports Server (NTRS)

The Betts (1973, 1978) parametrization of heat and moisture fluxes is tested using measurements made in thin, broken, and solid stratocumulus clouds by the NCAR Electra off the California coast in June 1976. The turbulence data are used to determine updraft-downdraft properties, heat and moisture fluxes, spectra, and cospectra. From the convective properties, vertical mass flux profiles are obtained and examined for consistency. A convective scaling which is appropriate for cloud-topped mixed layers is discussed. The results demonstrate the usefulness of a mass flux formulation in modeling applications for cloud conditions varying between solid and broken.

Penc, Richard S.; Albrecht, Bruce A.

1987-01-01

388

80 60 40 20 0 20 40 60 80 GLOBAL MERIDIONAL HEAT FLUX  

E-print Network

80 60 40 20 0 20 40 60 80 2 1.5 1 0.5 0 0.5 1 1.5 2 HeatfluxPW GLOBAL MERIDIONAL HEAT FLUX 20 0 20 40 60 80 2 1.5 1 0.5 0 0.5 1 1.5 2 HeatfluxPW INDOPACIFIC MERIDIONAL HEAT FLUX 20 0 20 40 60 80 2 1.5 1 0.5 0 0.5 1 1.5 2 HeatfluxPW latitude ATLANTIC MERIDIONAL HEAT FLUX total overturning (including

Tokmakian, Robin

389

Intraseasonal variability of latent-heat flux in the South China Sea  

Microsoft Academic Search

Intraseasonal variability (ISV) of latent-heat flux in the South China Sea (SCS) is examined using 9 years of weekly data\\u000a from January 1998 to December 2006. Using harmonic and composite analysis, some fundamental features of the latent-heat flux\\u000a ISVs are revealed. Intraseasonal latent-heat flux has two spectral peaks around 28–35 and 49–56 days, comparable with the\\u000a timescales of the atmospheric ISV in

Lili Zeng; Dongxiao Wang

2009-01-01

390

Heat flux characteristics in an atmospheric double arc argon plasma jet  

SciTech Connect

In this study, the axial evolution of heat flux excited by a double arc argon plasma jet impinging on a flat plate is determined, while the nonstationary behavior of the heat flux is investigated by combined means of the fast Fourier transform, Wigner distribution, and short-time Fourier transform. Two frequency groups (<1 and 2-10 kHz) are identified in both the Fourier spectrum and the time-frequency distributions, which suggest that the nature of fluctuations in the heat flux is strongly associated with the dynamic behavior of the plasma arc and the engulfment of ambient air into different plasma jet regions.

Tu Xin; Yu Liang; Yan Jianhua; Cen Kefa [Zhejiang University, Hangzhou 310027 (China); Cheron, Bruno [UMR 6614 CNRS CORIA, Saint Etienne du Rouvray 76801 (France)

2008-10-13

391

Parameterization of surface heat fluxes above forest with satellite thermal sensing and boundary-layer soundings  

NASA Technical Reports Server (NTRS)

The paper is concerned with the feasibility of determining the surface flux of sensible heat from forest using surface temperatures measured by a satellite together with soundings of temperature aloft in the unstable atmospheric boundary layer. Consideration is also given to the effect of the spatial scale of the surface temperature measurement on the parameterization by means of the scalar roughness. The latent heat flux is derived from the sensible heat flux by means of the energy budget. The data used in the study have been obtained during the HAPEX-MOBILHY experiment of 1986. The approach is based on turbulence similarity for the unstable atmospheric boundary layer.

Brutsaert, Wilfried; Hsu, A. Y.; Schmugge, Thomas J.

1993-01-01

392

Analysis of the transient calibration of heat flux sensors: One dimensional case  

NASA Technical Reports Server (NTRS)

The effect of transient heat flux on heat flux sensor response and calibration is analyzed. A one dimensional case was studied in order to elucidate the key parameters and trends for the problem. It has the added advantage that the solutions to the governing equations can be obtained by analytic means. The analytical results obtained to date indicate that the transient response of a heat flux sensor depends on the thermal boundary conditions, the geometry and the thermal properties of the sensor. In particular it was shown that if the thermal diffusivity of the sensor is small, then the transient behavior must be taken into account.

Dybbs, A.; Ling, J. X.

1989-01-01

393

On the Effect of Surface Heat-Flux Heterogeneities on the Mixed-Layer-Top Entrainment  

NASA Astrophysics Data System (ADS)

We used a set of large-eddy simulations to investigate the effect of one-dimensional stripe-like surface heat-flux heterogeneities on mixed-layer top entrainment. The profiles of sensible heat flux and the temporal evolution of the boundary-layer depth revealed decreased entrainment for small heat-flux amplitudes and increased entrainment for large heat-flux amplitudes, compared to the homogeneously-heated mixed layer. For large heat-flux amplitudes the largest entrainment was observed for patch sizes in the order of the boundary-layer depth, while for significantly smaller or larger patch sizes entrainment was similar as in the homogeneous case. In order to understand the underlying physics of this impact, a new approach was developed to infer local information on entrainment by means of the local flux divergence. We found an entrainment maximum over the centre of the stronger heated surface patch, where thermal energy is accumulated by the secondary circulation (SC) that was induced by the surface heterogeneity. Furthermore, we observed an entrainment maximum over the less heated patch as well, which we suppose is to be linked to the SC-induced horizontal flow convergence at the top of the convective boundary layer (CBL). For small heat-flux amplitudes a counteracting effect dominates that decreases entrainment, which we suppose is the horizontal advection of cold air in the lower, and warm air in the upper, CBL by the SC, stabilizing the CBL and thus weakening thermal convection. Moreover, we found that a mean wind can reduce the heterogeneity-induced impact on entrainment. If the flow is aligned perpendicular to the border between the differentially-heated patches, the SC and thus its impact on entrainment vanishes due to increased horizontal mixing, even for moderate wind speeds. However, if the flow is directed parallel to the border between the differentially-heated patches, the SC and thus its impact on entrainment persists.

Sühring, Matthias; Maronga, Björn; Herbort, Florian; Raasch, Siegfried

2014-06-01

394

The DRESOR method for radiative heat transfer in semitransparent graded index cylindrical medium  

NASA Astrophysics Data System (ADS)

During a numerical analysis of radiative transfer in some cylindrical optical thermal analysis and thermal design, applying a cylindrical coordinate system would be much more convenient and precise than that using a Cartesian coordinate system. In this paper, the DRESOR method under a cylindrical coordinate system is proposed to address radiative transfer in a semitransparent graded index cylindrical medium. The dimensionless incident radiation and net radiative heat flux are obtained using the DRESOR method. The accuracy and validity of the proposed method is verified by comparison with other techniques. The effects of isotropic scattering albedo and graded index on radiative transfer are also considered. Additionally, the high directional radiative intensity information is obtained to show the performance of the DRESOR method. It shows that the DRESOR method is an effective technique to address the radiative transfer problem in the graded index cylindrical medium with complex surface temperature characteristics.

Cheng, Qiang; Zhang, Xian; Huang, Zhifeng; Wang, Zhichao; Zhou, Huaichun

2014-08-01

395

An intercomparison between the surface heat flux feedback in five coupled models, COADS and the NCEP reanalysis  

Microsoft Academic Search

The surface heat flux feedback is estimated in the Atlantic and the extra-tropical Indo-Pacific, using monthly heat flux and sea surface temperature anomaly data from control simulations with five global climate models, and it is compared to estimates derived from COADS and the NCEP reanalysis. In all data sets, the heat flux feedback is negative nearly everywhere and damps the

C. Frankignoul; E. Kestenare; M. Botzet; A. F. Carril; H. Drange; A. Pardaens; L. Terray; R. Sutton

2004-01-01

396

GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1029/, The hemispheric dichotomy of surface tectonics and heat flux on  

E-print Network

and heat flux. With a spherical core, convection produces global overturn- ing, which cannot explain tectonics and heat flux on Enceladus Adam P. Showman1 , Lijie Han2 , and William B. Hubbard1 Enceladus., 2011], corresponding to a heat flux averaged over the SPT area of 200 mW m-2 . Jets of salty ice par

397

Estimating net air-sea fluxes from ocean bulk data: Methodology and application to the heat cycle  

E-print Network

parameterization, which generally require constraints to ensure a global net heat flux of zero. We also findEstimating net air-sea fluxes from ocean bulk data: Methodology and application to the heat cycle annual mean heat, water, and gas exchange fluxes between the ocean and the atmosphere is proposed

Gruber, Nicolas

398

ensl-00151647,version1-5Jun2007 Lagrangian temperature, velocity and local heat flux measurement in  

E-print Network

laws which relate global heat flux and flow velocities to fluid properties, flow boundary geom- etryensl-00151647,version1-5Jun2007 Lagrangian temperature, velocity and local heat flux measurement.1 C). The Nusselt number, defined as the total heat flux normalized by T/H, is Nu = 167.9 ± 0.2. Under

Paris-Sud XI, Université de

399

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

Microsoft Academic Search

turbulent heat fluxes are approximately equal, with a difference of 40 W m?2 between summer and winter, while the seasonal cycle of subsurface heat fluxes is only a few Wm ?2 . For an 8-month period (the winter of 2001), we calculate two estimates of turbulent heat fluxes, one from Monin-Obukhov (MO) similarity theory and one as the residual of

Michael S. Town; Von P. Walden

2009-01-01

400

Estimation of sensible heat flux by a hybrid method of temperature profile and light-beam deflection  

NASA Astrophysics Data System (ADS)

A new method of sensible heat flux estimation by a hybrid use of temperature profile and light-beam deflection is proposed and tested over an asphalt pavement on fine days. A helium-neon gas laser with wavelength 0.6328 ?m was used as a light-beam source. Temperature gradient near the surface was measured by the deflection of a light-beam propagated nearly horizontally at a distance of 25 m. Measurement of the air temperature profile in the upper part of the surface layer was made by means of a copper-constantan thermocouple thermometer. The sensible heat flux was estimated from the temperature profile using profile-flux relationships. The surface temperature of the asphalt pavement rose to as high as 63 °C in the daytime and never decreased below the air temperature even in the morning in summer. The maximum value of heat flux obtained from this observation attained 365 W m-2, which was about 48% of incoming solar radiation.

Yokoi, Takehisa

1991-12-01

401

Spectrally enhancing near-field radiative heat transfer by exciting magnetic polariton in SiC gratings  

E-print Network

In the present work, we theoretically demonstrate, for the first time, that near field radiative transport between 1D periodic grating microstructures separated by subwavelength vacuum gaps can be significantly enhanced by exciting magnetic resonance or polariton. Fluctuational electrodynamics that incorporates scattering matrix theory with rigorous coupled wave analysis is employed to exactly calculate the near field radiative heat flux between two SiC gratings. Besides the well known coupled surface phonon polaritons (SPhP), an additional spectral radiative heat flux peak, which is due to magnetic polariton, is found within the phonon absorption band of SiC. The mechanisms, behaviors and interplays between magnetic polariton, coupled SPhP, single interface SPhP, and Wood's anomaly in the near field radiative transport are elucidated in detail. The findings will open up a new way to control near field radiative heat transfer by magnetic resonance with micro or nanostructured metamaterials.

Yang, Yue

2015-01-01

402

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.

403

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

404

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

405

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

406

RF-sheath heat flux estimates on Tore Supra and JET ICRF antennae. Extrapolation to ITER  

SciTech Connect

RF-sheath induced heat loads are identified from infrared thermography measurements on Tore Supra ITER-like prototype and JET A2 antennae, and are quantified by fitting thermal calculations. Using a simple scaling law assessed experimentally, the estimated heat fluxes are then extrapolated to the ITER ICRF launcher delivering 20 MW RF power for several plasma scenarios. Parallel heat fluxes up to 6.7 MW/m{sup 2} are expected very locally on ITER antenna front face. The role of edge density on operation is stressed as a trade-off between easy RF coupling and reasonable heat loads. Sources of uncertainty on the results are identified.

Colas, L.; Portafaix, C.; Goniche, M. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Jacquet, Ph. [EURATOM/UKAEA Fusion Association, Culham, OX14 3DB (United Kingdom); Agarici, G. [Fusion for Energy, C/Josep Pla 2, E-08019 Barcelona (Spain)

2009-11-26

407

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

408

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.

409

The role of the geothermal heat flux in driving the abyssal ocean circulation  

E-print Network

The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based ...

Mashayek, A.

410

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

411

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

412

The Effect of Cumulus Cloud Field Anisotropy on Domain-Averaged Solar Fluxes and Atmospheric Heating Rates  

NASA Technical Reports Server (NTRS)

Cumulus clouds can become tilted or elongated in the presence of wind shear. Nevertheless, most studies of the interaction of cumulus clouds and radiation have assumed these clouds to be isotropic. This paper describes an investigation of the effect of fair-weather cumulus cloud field anisotropy on domain-averaged solar fluxes and atmospheric heating rate profiles. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of cloud scenes from a large eddy simulation. Progressively greater degrees of x-z plane tilting and horizontal stretching were imposed on each of these scenes, so that an ensemble of scenes was produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo radiative transfer model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. The mechanisms by which anisotropy interacts with solar fluxes were investigated by comparisons to independent pixel approximation and tilted independent pixel approximation computations for the same scenes. Cumulus anisotropy was found to most strongly impact solar radiative transfer by changing the effective cloud fraction, i.e., the cloud fraction when the field is projected on a surface perpendicular to the direction of the incident solar beam.

Hinkelman, Laura M.; Evans, K. Franklin; Clothiaux, Eugene E.; Ackerman, Thomas P.; Stackhouse, Paul W., Jr.

2006-01-01

413

Analytical study of the heat loss attenuation by clothing on thermal manikins under radiative heat loads.  

PubMed

For wearers of protective clothing in radiation environments there are no quantitative guidelines available for the effect of a radiative heat load on heat exchange. Under the European Union funded project ThermProtect an analytical effort was defined to address the issue of radiative heat load while wearing protective clothing. As within the ThermProtect project much information has become available from thermal manikin experiments in thermal radiation environments, these sets of experimental data are used to verify the analytical approach. The analytical approach provided a good prediction of the heat loss in the manikin experiments, 95% of the variance was explained by the model. The model has not yet been validated at high radiative heat loads and neglects some physical properties of the radiation emissivity. Still, the analytical approach provides a pragmatic approach and may be useful for practical implementation in protective clothing standards for moderate thermal radiation environments. PMID:20540843

Den Hartog, Emiel A; Havenith, George

2010-01-01

414

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

415

Calculation of the sensible heat flux of the global ocean using satellite data  

Microsoft Academic Search

The sensible heat flux of the global ocean is derived using satellite data of Special Sensor Microwave\\/Imager (SSM\\/I) precipitable water, Advanced Very High Resolution Radiometer (AVHRR) sea-surface temperature (SST) and scatterometer wind speed. Prior to heat flux derivation, the air temperature over the sea surface in the global ocean is obtained with an iterative solving technique applied to a simplified

Jiayi Pan; Hui Lin

2012-01-01

416

Regulation of the solar wind electron heat flux from 1 to 5 AU: Ulysses observations  

Microsoft Academic Search

In this study the authors use observations from the three-dimensional electron spectrometer and magnetometer aboard the Ulysses spacecraft to examine the solar wind electron heat flux from 1.2 to 5.4 AU in the ecliptic plane. Throughout Ulysses` transit to 5.4 AU, the electron heat flux decreases more rapidly (â¼R{sup -3.0}) than simple collisionless expansion along the local magnetic field and

Earl E. Scime; Samuel J. Bame; William C. Feldman; S. Peter Gary; John L. Phillips; Andre Balogh

1994-01-01

417

Heat flux characteristics in an atmospheric double arc argon plasma jet  

Microsoft Academic Search

In this study, the axial evolution of heat flux excited by a double arc argon plasma jet impinging on a flat plate is determined, while the nonstationary behavior of the heat flux is investigated by combined means of the fast Fourier transform, Wigner distribution, and short-time Fourier transform. Two frequency groups (<1 and 2-10 kHz) are identified in both the

Xin Tu; Liang Yu; Jianhua Yan; Kefa Cen; Bruno Chéron

2008-01-01

418

Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow  

NASA Astrophysics Data System (ADS)

Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

2014-09-01

419

Comparison of in-situ measured ground heat fluxes within a heteorogeneous urban ballast layer  

Microsoft Academic Search

Summary  This study concentrates on measurements of ground heat fluxes within a porous urban ballast layer that were conducted from\\u000a June to September 2002 at the goods station in Osnabrück, Germany. To account for the limitation of accurately installing\\u000a sensors within the heterogeneous and porous ballast bulk, the heat fluxes were calculated from four different methods to compare\\u000a their variability, dynamics

S. Weber

2006-01-01

420

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

421

The turbulent heat flux in low Mach number flows with large density variations  

NASA Technical Reports Server (NTRS)

A transport equation has been derived which is the difference between the volume- and mass-averaged velocities and is simply related to the turbulent heat flux phi sup h. Using this equation and an assumption analogous to the drift flux approximation of two-phase flow modeling, an algebraic closure relation for phi sup h that exibits fluxes due to directed transport proportional to -del anti p and due to gradient transport proportional to -del tau has been obtained.

Orourke, Peter J.; Collins, Lance R.

1988-01-01

422

409MARCH 2004AMERICAN METEOROLOGICAL SOCIETY | cean surface fluxes of heat, moisture, and mo-  

E-print Network

409MARCH 2004AMERICAN METEOROLOGICAL SOCIETY | O cean surface fluxes of heat, moisture, and mo, P. J. WEBSTER, G. A. WICK, AND X. ZENG Satellite-based datasets of surface turbulent fluxes over; FAIRALL AND WICK--NOAA ETL, Boulder, Colorado; KUBOTA--School of Marine Science and Technology, Tokai

423

EMERGING FLUX AND THE HEATING OF CORONAL LOOPS B. Schmieder,1,2  

E-print Network

and evolved rapidly $6 Ã? 2 hr after the first detection of emerging magnetic flux. In the low chromosphere, flux emergence resulted in intense Ellerman bomb activity. Besides the chromosphere, we find that Ellerman bombs may also heat the transition region, which showed ``moss'' $100% brighter in areas

Demoulin, Pascal

424

Changes in fluxes of heat, H2O, CO2 caused by a large wind farm  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Crop Wind Energy Experiment (CWEX) provides a platform to investigate the effect of wind turbines and large wind farms on surface fluxes of momentum, heat, moisture and carbon dioxide (CO2). In 2010 and 2011, eddy covariance flux stations were installed between two lines of turbines at the south...

425

Inverse Analysis Adjustment of the SOC Air-Sea Flux Climatology Using Ocean Heat Transport Constraints  

Microsoft Academic Search

Results are presented from a linear inverse analysis of the Southampton Oceanography Centre (SOC) air-sea flux climatology using 10 hydrographic ocean heat transport constraints distributed throughout the Atlantic and North Pacific Oceans. A solution is found that results in an adjusted set of fluxes that is consistent with all of the available constraints within their estimated error bounds. The global

Jeremy P. Grist; Simon A. Josey

2003-01-01

426

Simulation of the outer radiation belt electron flux decrease during the March 26, 1995, magnetic storm  

Microsoft Academic Search

In this paper we study the variation of the relativistic electron fluxes in the Earth's outer radiation belt during the March 26, 1995, magnetic storm. Using observations by the radiation environment monitor (REM) on board the space technology research vehicle (STRV-1b), we discuss the flux decrease and possible loss of relativistic electrons during the storm main phase. In order to

L. Desorgher; P. Bühler; A. Zehnder; E. O. Flückiger

2000-01-01

427

Research concerning the net flux of radiation in the atmosphere of Jupiter  

NASA Technical Reports Server (NTRS)

The plan of the NFR (Net Flux of Radiation) team is for the data from the two solar channels (B and E) of NFR to be reduced with the goal of determining the solar heating rate. In order to determine the solar heating rate from the NFR measurements, effects due to the instrument's spatial and spectral response functions, to the temperature variation of the instrument (and associated drift of calibration), to the setting sun, and to the rotation of the probe (initially at a rate comparable to the NFR sampling frequency), all must be well modelled. In the past year, a forward modeling routine was created to simulate NFR data return in the B and E channels. The effects of varying parameters describing the atmospheric model (such as cloud location and thickness) and the descent profile (such as rotation rate) were investigated and an inversion routine was developed. For the forward modeling, existing radiative transfer codes were used to determine intensity fields within the Jovian atmosphere. A routine was developed to determine instantaneous instrument response by integrating the intensity field over the instrument response functions. A second routine was developed to determine the actual output of the NFR by integrating along an arbitrary descent trajectory. Near the top of the atmosphere, the upflux data alone are used to constrain the cloud structure of he atmosphere. To accomplish this, models are used to describe the variation in up flux between consecutive measurements in terms of variations of cloud opacity and variations in known parameters such as the solar zenith angle. This allows us to develop a zero-order model of cloud structure. Lower in the atmosphere, at levels where there is little or no azimuthal structure to the net flux measurements, both the up flux and net flux are used to derive layer transmission and reflection functions, which then determine layer opacity and single scattering albedo. A preliminary analysis of the data began in December 1995. In these data we could see the rapid oscillations expected at the beginning of the data due to probe rotation and the sun passing through the edge of the field of view. In addition, the time when this oscillation stopped was clearly visible. This sets the rough optical depth above the probe at this time.

Tomasko, M. G.

1996-01-01

428

The whistler heat flux instability: Threshold conditions in the solar wind  

NASA Technical Reports Server (NTRS)

Solar wind electrons are observed often to consist of two components: a core and a halo. The anisotropics and relative average speeds of these components correspond to a heat flux that has the potential to excite several different electromagetic instabilities; wave-particle scattering by the resulting enhanced fluctuations can limit this heat flux. This manuscript describes theoretical studies using the linear Vlasco dispersion equation for drifting bi-Maxwellian component distributions in a homogeneous plasma to examine the threshold of the whistler heat flux instability. Expressions for this threshold are obtained from two different parametric baselines: a local model that yields scalings as functions of local dimensionless plasma paramaters, and a global model based on average electron properties observed during the in-eliptic phase of the Ulysses mission. The latter model yields an expression for the heat flux at threshold of the whistler instability as a function of helisopheric radius that scales in the same way as the average heat flux observed form Ulysses and that provides an approximate upper bound for that same quantity. This theoretical scaling is combined with the observational results to yield a semi-empirical closure relation for the average electron heat flux in the solar wind between 1 and 5 AU.

Gary, S. Peter; Scime, Earl E.; Phillips, John L.; Feldman, William C.

1994-01-01

429

The whistler heat flux instability: Threshold conditions in the solar wind  

SciTech Connect

Solar wind electrons are observed often to consist of two components: a core and a halo. The anisotropies and relative average speeds of these two components correspond to a heat flux that has the potential to excite several different electromagnetic instabilities; wave-particle scattering by the resulting enhanced fluctuations can limit this heat flux. This manuscript describes theoretical studies using the linear Vlasov dispersion equation for drifting bi-Maxwellian component distributions in a homogeneous plasma to examine the threshold of the whistler heat flux instability. Expressions for this threshold are obtained from two different parametric baselines: a local model that yields scalings as functions of local dimensionless plasma parameters, and a global model based on average electron properties observed during the in-ecliptic phase of the Ulysses mission. The latter model yields an expression for the heat flux at threshold of the whistler instability as a function of heliospheric radius that scales in the same way as the average heat flux observed from Ulysses and that provides an approximate upper bound for that same quantity. This theoretical scaling is combined with the observational results to yield a semiempirical closure relation for the average electron heat flux in the solar wind between 1 and 5 AU. 29 refs., 9 figs., 2 tabs.

Gary, S.P.; Scime, E.E.; Phillips, J.L.; Feldman, W.C. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1994-12-01

430

Broadening of divertor heat flux profile with increasing number of ELM filaments in NSTX  

NASA Astrophysics Data System (ADS)

Edge localized modes (ELMs) represent a challenge to future fusion devices, owing to cyclical high peak heat fluxes on divertor plasma facing surfaces. One ameliorating factor has been that the heat flux characteristic profile width has been observed to broaden with the size of the ELM, as compared with the inter-ELM heat flux profile. In contrast, the heat flux profile has been observed to narrow during ELMs under certain conditions in NSTX. Here we show that the ELM heat flux profile width increases with the number of filamentary striations observed, i.e. profile narrowing is observed with zero or very few striations. Because NSTX often lies on the long wavelength current-driven mode side of ideal MHD instabilities, few filamentary structures can be expected under many conditions. ITER is also projected to lie on the current driven low-n stability boundary, and therefore detailed projections of the unstable modes expected in ITER and the heat flux driven in ensuing filamentary structures is needed.

Ahn, J.-W.; Maingi, R.; Canik, J. M.; Gan, K. F.; Gray, T. K.; McLean, A. G.

2014-12-01

431

Effect of combined heat and radiation on microbial destruction.  

PubMed Central

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 independence agents. The synergistic mechanism shows a proportional dependency on radiation dose rate an Arrhenius dependency 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. PMID:406843

Fisher, D A; Pflug, I J

1977-01-01

432

Modeling near-field radiative heat transfer from sharp objects using a general 3d numerical scattering technique  

Microsoft Academic Search

We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objects including corners or tips. We find qualitatively different scaling laws for conical shapes at small separations, and in contrast to a flat\\/slightly-curved object, a

Alexander P. McCauley; M. T. Homer Reid; Matthias Krüger; Steven G. Johnson

2011-01-01

433

On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes  

SciTech Connect

The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. It is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.

Kazil, J.; Feingold, G.; Wang, Hailong; Yamaguchi, T.

2014-01-02

434

The theoretical basis of heat flux sensor pen  

Microsoft Academic Search

Measuring heat ux out or into a process surface is of signican t practi- cal interest. Miniaturization of the sensor and the capability of dynamic sensing are highly desirable. In this paper, the theoretical basis of a heat ux sensor 'pen' idea has been established, which allows for real-time measurements. Here the thin temperature measuring wires (thermocouple) are used as

Xiao Dong Chen; Sing Kiong Nguang

2003-01-01

435

Extended cryogenic performance of Lobar Wick heat pipe\\/radiator  

Microsoft Academic Search

Two series of cryogenic-vacuum tests were performed as part of a continuing research program aimed at developing lightweight, reliable, and efficient Lobar Wick heat pipe\\/radiator or heat pipe\\/solid cryogen cooling systems for earth resource and meteorological spaceborne detectors. In the first series, a 640 cm long nitrogen heat pipe\\/radiator was tested from 74 to 116 K; pipe performance was isothermal

A. A. Cenkner Jr.; B. E. Nelson; W. Petrie

1976-01-01

436

Application of ray tracing in radiation heat transfer  

NASA Technical Reports Server (NTRS)

This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.

Baumeister, Joseph F.

1993-01-01

437

Assessment of land surface temperature and heat fluxes over Delhi using remote sensing data.  

PubMed

Surface energy processes has an essential role in urban weather, climate and hydrosphere cycles, as well in urban heat redistribution. The research was undertaken to analyze the potential of Landsat and MODIS data in retrieving biophysical parameters in estimating land surface temperature & heat fluxes diurnally in summer and winter seasons of years 2000 and 2010 and understanding its effect on anthropogenic heat disturbance over Delhi and surrounding region. Results show that during years 2000-2010, settlement and industrial area increased from 5.66 to 11.74% and 4.92 to 11.87% respectively which in turn has direct effect on land surface temperature (LST) and heat fluxes including anthropogenic heat flux. Based on the energy balance model for land surface, a method to estimate the increase in anthropogenic heat flux (Has) has been proposed. The settlement and industrial areas has higher amounts of energy consumed and has high values of Has in all seasons. The comparison of satellite derived LST with that of field measured values show that Landsat estimated values are in close agreement within error of ±2 °C than MODIS with an error of ±3 °C. It was observed that, during 2000 and 2010, the average change in surface temperature using Landsat over settlement & industrial areas of both seasons is 1.4 °C & for MODIS data is 3.7 °C. The seasonal average change in anthropogenic heat flux (Has) estimated using Landsat & MODIS is up by around 38 W/m(2) and 62 W/m(2) respectively while higher change is observed over settlement and concrete structures. The study reveals that the dynamic range of Has values has increased in the 10 year period due to the strong anthropogenic influence over the area. The study showed that anthropogenic heat flux is an indicator of the strength of urban heat island effect, and can be used to quantify the magnitude of the urban heat island effect. PMID:24360191

Chakraborty, Surya Deb; Kant, Yogesh; Mitra, Debashis

2015-01-15

438

Effects of marine cloud brightening on polar regions and the meridional heat flux  

NASA Astrophysics Data System (ADS)

Marine cloud brightening is one of several proposed solar radiation management geoengineering schemes designed to avert some of the undesirable effects of climate change (Latham et al. 2008). Such changes include ice loss, desertification and increased sea levels. Polar sea ice fraction has been recorded by satellite data for the last 40 years. This data shows a general long term reduction in sea ice thickness and area and this reduction has been attributed to climate change. Changes in climate have been argued to be disproportionately larger in polar regions. The HadGEM1 (UK Met Office Climate Model, V6.1) is a fully coupled climate model. It is used to project changes in polar ice cover and temperatures as a result of increasing carbon dioxide and geoengineering using marine cloud brightening scenario. The meridional heat flux is the mechanism for moving energy from the tropics to the polar regions. The results show that for a comparison between a control (~ 2020 carbon dioxide concentrations) and a double pre-industrial carbon dioxide simulation, the maximum meridional heat flux is found to change from 5.8 PW to 6.1 PW. With three region seeding of marine stratocumulus, this is reduced to 5.7 PW. The annual North Polar sea ice cover, initially 11.5 x106 sq km, is reduced by 3.6 x106 sq km as a result of the increased carbon dioxide. Application of a three region seeding scenario, results an increase in sea ice cover of 0.20 x106 sq km above the initial values. Reference: Latham J. et al.. (2008) Global temperature stabilization via controlled albedo enhancement of low-level maritime clouds. Phil. Trans. R. Soc. A doi:10.1098/rsta.2008.0137.

Parkes, B.; Gadain, A.; Latham, J.

2012-04-01

439

Effects of marine cloud brightening on polar regions and the meridional heat flux  

NASA Astrophysics Data System (ADS)

Marine cloud brightening is one of several proposed solar radiation management geoengineering schemes designed to avert some of the undesirable effects of climate change (Latham et al. 2008). Such changes include ice loss, desertification and increased sea levels. Polar sea ice fraction has been recorded by satellite data for the last 40 years. This data shows a general long term reduction in sea ice thickness and area and this reduction has been attributed to climate change. Changes in climate have been argued to be disproportionately larger in polar regions. The HadGEM1 (UK Met Office Climate Model, V6.1) is a fully coupled climate model. It is used to project changes in polar ice cover and temperatures as a result of increasing carbon dioxide and geoengineering using marine cloud brightening scenario. The meridional heat flux is the mechanism for moving energy from the tropics to the polar regions. The results show that for a comparison between a control (~ 2020 Carbon Dioxide concentrations) and a double pre-industrial Carbon Dioxide simulation, the maximum meridional heat flux is found to increase from 5.8PW to 6.1PW. With three-region seeding of marine Stratocumulus, this is reduced to 5.7PW. The annual North Polar sea ice cover, initially 11.5M sq km, is reduced by 3.6M sq km as a result of the increased Carbon Dioxide. Application of a three region seeding scenario, results in an increase in sea ice cover of 0.20M sq km above the initial (2020) values. Reference: Latham J. et al.. (2008) Global temperature stabilization via controlled albedo enhancement of low-level maritime clouds. Phil. Trans. R. Soc. A doi:10.1098/rsta.2008.0137.

Parkes, B.; Gadian, A.; Latham, J.

2011-12-01

440