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

1990-01-01

2

Net radiation — soil heat flux relations as influenced by soil water content variations  

Microsoft Academic Search

Net radiation, soil heat flux, incoming and reflected solar radiation, and soil water content were measured during several clear day periods following approximate 10-cm applications of water to loam soils at Phoenix, Arizona, and at Sidney, Montana. The regression of soil heat flux on net radiation changed significantly as the soil dried, with the difference between them being a linear

S. B. Idso; J. K. Aase; R. D. Jackson

1975-01-01

3

Sensitivity of Radiative Fluxes and Heating Rates To Cloud Microphysics  

NASA Astrophysics Data System (ADS)

We have investigated the sensitivity of modeled radiative fluxes to the specification of cloud microphysical parameterizations using a single-column model and measure- ments from the Atmospheric Radiation Measurement (ARM) Program. The single- column model was run for the three-month period of June-August, 2000 at the ARM Southern Great Plains and Tropical Western Pacific sites. At each site, the model was forced using 0-24 hour forecast products from the global spectral model of the U. S. National Centers for Environmental Prediction. Several model runs were performed, each with a different package of cloud microphysical parameterizations. The temporal evolution of modeled cloud amount as well as surface radiative fluxes from a control run compare well with ARM measurements at the Southern Great Plains site. The re- alism of the control run results at the Tropical West Pacific site is more difficult to evaluate due to the limited spatial resolution of the ARM observations there. Both surface and top-of-atmosphere radiative fluxes are sensitive to the scheme used to specify the ice particle effective radius. We also find that the inclusion of ice particle fallout can have a significant effect on the amount and location of high cirrus clouds. A particularly interesting finding is that the variance of the modeled ice particle effective radius is considerably smaller than that suggested by ARM cloud radar measurements at the Southern Great Plains site. This was the case for all four tested parameterizations of ice particle effective radius. Our preliminary results suggest that this theoretical underestimate of the ice particle effective radius variance can have significant effects on the modeled radiative fluxes due to the highly non-linear nature of cloud-radiation interactions.

Iacobellis, S. F.; Somerville, R. C. J.; McFarquhar, G. M.

4

Magnetogasdynamic shock waves in a nonideal gas with heat conduction and radiation heat flux  

NASA Astrophysics Data System (ADS)

The purpose of this study is to obtain a self-similar solution of the problem of propagation of a magnetogasdynamic shock wave in a nonideal gas with heat conduction and radiation heat flux in the presence of a spatially decreasing azimuthal magnetic field strength. The initial density of the medium is assumed to be constant. The heat conduction is expressed in terms of Fourier's law, and the radiation is considered to be of a diffusion type for an optically thick gray gas model. The thermal conductivity and absorption coefficients are assumed to vary with temperature and density. The shock is assumed to be driven by a piston moving with a variable velocity. Similarity solutions are obtained, and the effects of variation of the gas nonidealness parameter and Alfven-Mach number on the flow field behind the shock are investigated.

Singh, K. K.; Nath, B.

2012-09-01

5

Seasonal and Diurnal Fluxes of Radiation, Heat, Water Vapor, and Carbon Dioxide over a Suburban Area  

Microsoft Academic Search

Based on 1 yr of field measurements, the diurnal, seasonal, and annual fluxes of energy and carbon dioxide (CO2) at a residential area of Tokyo, Japan, are described. The major findings are as follows. 1) The storage heat flux G in the daytime had little seasonal variation, irrespective of significant seasonal change of net all-wave radiation Rn. 2) The latent

R. Moriwaki; M. Kanda

2004-01-01

6

[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

7

Nonequilibrium radiative heat flux modeling for the Huygens entry probe  

Microsoft Academic Search

An electronic collisional-radiative model is proposed to predict the nonequilibrium populations and the radiation of the excited electronic states CN(A, B) and N2(A, B, C) during the entry of the Huygens probe into the atmosphere of Titan. The model is loosely coupled with flow solvers using a Lagrangian method. First, the model was tested against measurements obtained with the shock-tube

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

2006-01-01

8

Radiation Effects on Oscillating Vertical Plate with Uniform Heat and Mass Flux  

NASA Astrophysics Data System (ADS)

Thermal radiation effects on flow past an impulsively started infinite vertical oscillating plate with uniform heat and mass flux is studied. The fluid considered here is a gray, absorbing-emitting radiation but a nonscattering medium. The dimensionless governing equations are solved using the Laplace-transform technique. The velocity, temperature and concentration are studied for different physical parameters such as the radiation parameter, phase angle, Schmidt number and time. The variation of the skin-friction for different values of the parameters is also shown in a table

Chandrakala, P.; Bhaskar, P. Narayana

2013-08-01

9

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

SciTech Connect

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

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

2010-03-31

10

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

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

SciTech Connect

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

Olson, D.A.

1989-10-01

12

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

SciTech Connect

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

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

2006-06-01

13

Transient critical heat flux  

Microsoft Academic Search

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

Pasamehmetoglu

1986-01-01

14

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

Microsoft Academic Search

The effect of the aerosol vertical distribution on the solar radiation profiles for idealized and measured profiles of extinction and single-scattering albedo (SSA) during the May 2003 Atmospheric Radiation Measurement Aerosol Intensive Observation Period (AIOP) is investigated using the rapid radiative transfer model shortwave code. Calculated profiles of downwelling and upwelling solar flux density during the AIOP are compared with

Hong Guan; Beat Schmid; Anthony Bucholtz; Robert Bergstrom

2010-01-01

15

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

NASA Astrophysics Data System (ADS)

A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas and small solid particles. The density of the ambient medium is assumed to be constant. The heat conduction is expressed in terms of Fourier's law and radiation is considered to be of diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. Similarity solutions are obtained, and the effects of variation of the parameter of non-idealness of the gas in the mixture, the mass concentration of solid particles and the ratio of density of solid particles to the initial density of the gas are investigated.

Vishwakarma, J. P.; Nath, G.

2010-04-01

16

Inverse solution to the net radiation heat flux of paint and coloured drawing surfaces under artificial lighting  

Microsoft Academic Search

A numerical method is used to inversely solve the net heat flux radiated to the red pine external surfaces with black and white paint and coloured drawing under four types of artificial light: high-pressure sodium lamp, tungsten halogen lamp, metal halide lamp and fluorescent lamp. Firstly, the temperature values of the external surface centre and the internal centre of the

Tian-Peng Wang; Liang-Bi Wang

2012-01-01

17

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

18

High Flux Heat Exchanger.  

National Technical Information Service (NTIS)

This interim report documents the results of the first two phases of a four-phase program to develop a high flux heat exchanger for cooling future high performance aircraft electronics. Phase I defines future needs for high flux heat removal in advanced m...

E. M. Flynn M. J. Mackowski

1993-01-01

19

Tuning Near Field Radiative Heat Flux through Surface Excitations with a Metal Insulator Transition  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

20

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

2012-06-07

21

Mechanical Heat Flux Recorder.  

National Technical Information Service (NTIS)

The patent application describes a mechanical heat flux recorder which is based upon the shape recovery properties of a nickel - titanium alloy (NiTi). A pair of nickel-titanium strips are connected between a heat sink block enclosed in an asbestos lined ...

W. K. Smith

1974-01-01

22

Optical heat flux gauge  

DOEpatents

A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator. 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 figs.

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

1989-06-07

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

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

NASA Astrophysics Data System (ADS)

The present work analyses the effect of dust aerosols on the surface and top of atmosphere radiative budget, surface temperature, sensible heat fluxes, atmospheric heating rate and convective activity over West Africa. The study is focused on the regional impact of a major dust event over the period of 7-14 March 2006 through numerical simulations performed with the mesoscale, nonhydrostatic atmospheric model MesoNH. Due to its importance on radiative budgets, a specific attention has been paid to the representation of dust single scattering albedo (SSA) in MesoNH by using inversions of the AErosol RObotic NETwork (AERONET). The radiative impacts are estimated using two parallel simulations, one including radiative effects of dust and the other without them. The simulations of dust aerosol impacts on the radiative budget indicate remarkable instantaneous (at midday) decrease of surface shortwave (SW) radiations over land, with regional (9°-17° N, 10° W-20° E) mean of -137 W/m2 during the 9 to 12 March period. The surface dimming resulting from the presence of dust is shown to cause important reduction of both surface temperature (up to 4°C) and sensible heat fluxes (up to 100 W/m2), which is consistent with experimental observations. At the top of the atmosphere, the SW cooling (regional mean of -12.0 W/m2) induced by mineral dust is shown to dominate the total net (shortwave + longwave) effect. The maximum SW heating occurs within the dusty layer with values comprised between 4 and 7° K by day and LW effect results in a cooling of -0.10/-0.20° K by day. Finally, the simulations suggest the decrease of the convective available potential energy (CAPE) over the region in the presence of mineral dust.

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

2009-09-01

26

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

SciTech Connect

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

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

2003-11-06

27

Radiation heat loss detector  

SciTech Connect

In a radiation heat loss detector, radiation from an extended surface area is detected with a sensor having a wide field of view closely matching that of an associated camera. By simultaneously photographing the surface area of interest and detecting the radiation from that same area, a clear record is provided for future use. A wide band radiation sensor is used. Compensation for environmental radiation is made by first viewing the environment with the sensor and holding the sensed signal and then subtracting that signal from the flux detected when the sensor faces the extended surface area. The date and time are also recorded on the photograph. A sonar device positioned on the camera provides a distance indication which, with a known field of view, allows for a determination of the total flux from the surface area, a determination of convective heat losses from the surface and a correction for atmospheric absorption of the radiant energy.

Pompei, F.

1982-08-10

28

Heat flux microsensor measurements and calibrations  

NASA Astrophysics Data System (ADS)

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

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

1992-09-01

29

Radiative flux measurements in the troposphere  

Microsoft Academic Search

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

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

1982-01-01

30

Radiative flux measurements in the troposphere  

SciTech Connect

The results of radiative flux-density measurements in the troposphere, made using an especially designed radiometer mounted on a Cessna 402B aircraft, are reported. The radiometer incorporates several well-known principles that result in highly accurate determinations of radiative fluxes in the atmosphere. Heating rates for gases and for aerosols are calculated, using measurements and radiosonde data. Instrument performance is verified by calculating the solar constant at the top of the atmosphere, using the radiative flux densities measured in the troposphere. Total heating rates of 0.175 and 0.377 K h/sup -1/ are determined for hazy and foggy atmospheres, respectively. Aerosol heating rates of 0.065 and 0.235 K h/sup -1/ are deduced from the total heating rates. Environmental noise measurements during data acquisition are presented. The solar constant value of 1387 +- 21 W m/sup -2/ derived from the experiments agrees within 4% of the standard value.

Valero, F.P.J.; Gore, W.J.Y.; Giver, L.P.M.

1982-03-01

31

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

SciTech Connect

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

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

2009-07-02

32

IR thermography heat flux measurement in fire safety applications  

NASA Astrophysics Data System (ADS)

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

Švantner, Michal; Vacíková, Petra; Honner, Milan

2012-07-01

33

Urban Signatures: Latent Heat Flux  

NSDL National Science Digital Library

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

Delabeaujardiere, Jeff

2005-05-27

34

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

35

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

36

High heat flux engineering III  

SciTech Connect

The main aim of this conference, as in prior years, was to provide a forum to foster a closer collaboration, exchange of information, and technology transfer among researchers involved in the design, analysis, fabrication, testing, and evaluation of high heat flux systems in areas of nuclear fusion, synchrotron x rays, high-power lasers, electronic packaging, etc. Separate abstracts were prepared for most papers in this volume.

Khounsary, A.M. [ed.] [Argonne National Lab., IL (United States)

1996-12-31

37

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

38

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

39

Radiative heating predictions for Huygens entry  

Microsoft Academic Search

Radiative heat flux predictions for the Huygens probe entry into Titan's atmosphere are presented in this paper. Radiative heating was computed with the radiation code SPECAIR, assuming a Boltzmann distribution of the excited electronic levels at a characteristic temperature taken as the vibrational temperature of the gas. CN violet is found to be the most intense emitter, followed by CN

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

2006-01-01

40

Divertor Heat Flux Control Research on DIII-D  

SciTech Connect

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

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

2005-10-15

41

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

42

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

43

Estimates of ocean heat flux at SHEBA  

Microsoft Academic Search

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

Donald K. Perovich; Bruce Elder

2002-01-01

44

Critical heat flux under choking flow conditions  

Microsoft Academic Search

Under conditions of forced convective boiling at low pressures and high mass fluxes, beyond a certain quality, choking flow may occur at the exit of a heated channel. An experimental investigation of the influence of this phenomenon on the critical heat flux (CHF) has been carried out. An analysis of the pressure distribution downstream of the heated length as well

A. Olekhnovitch; A. Teyssedou; P. Tye; P. Champagne

2001-01-01

45

Heat pipe radiators for space  

Microsoft Academic Search

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

J. P. Sellers

1977-01-01

46

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

47

Dual active surface heat flux gage probe  

Microsoft Academic Search

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

Curt H. Liebert; Paul Kolodziej

1995-01-01

48

Critical heat flux under choking flow conditions  

Microsoft Academic Search

Under conditions of forced convective boiling at low pressures and high mass fluxes, beyond a certain quality, choking flow may occur at the exit of a heated channel. An experimental investigation carried out by Olekhnovitch et al. (Olekhnovitch, A., Teyssedou, A., Tye, P., Champagne, P., 2000. Critical heat flux under choking flow conditions. Part I — Outlet pressure fluctuations. Nucl.

A. Olekhnovitch; A. Teyssedou; P. Tye

2001-01-01

49

Numerical comparison of radiative heat transfer models  

Microsoft Academic Search

A numerical comparison is presented for two mathematical models of radiative heat transfer, a direct method using the Stefan-Boltzmann law and a two step method using flux models (called the radiosity approach). The flux model equations are solved by the successive approximation technique and Hottel's matrix inversion technique, and a rectangular parallelopiped is assumed for the enclosure in order to

S. Vaidyanathan; M. Achuthan; A. Jaganmohan

1982-01-01

50

Critical heat flux tests with high pressure water in an internally heated annulus with alternating axial heat flux distribution  

Microsoft Academic Search

Critical heat flux experiments were performed with an alternating heat flux profile in an internally heated annulus. The heated length was 84 inches with a square wave alternating heat flux profile over the last 12 inches having a maximum-to-average heat flux ratio of 1.76. Test data were obtained at pressures from 800 to 2000 psia, mass velocities from 0.25 x

S. G. Beus; D. A. Humphreys

1979-01-01

51

Systematic errors in ground heat flux estimation and their correction  

NASA Astrophysics Data System (ADS)

Incoming radiation forcing at the land surface is partitioned among the components of the surface energy balance in varying proportions depending on the time scale of the forcing. Based on a land-atmosphere analytic continuum model, a numerical land surface model, and field observations we show that high-frequency fluctuations in incoming radiation (with period less than 6 h, for example, due to intermittent clouds) are preferentially partitioned toward ground heat flux. These higher frequencies are concentrated in the 0-1 cm surface soil layer. Subsequently, measurements even at a few centimeters deep in the soil profile miss part of the surface soil heat flux signal. The attenuation of the high-frequency soil heat flux spectrum throughout the soil profile leads to systematic errors in both measurements and modeling, which require a very fine sampling near the soil surface (0-1 cm). Calorimetric measurement techniques introduce a systematic error in the form of an artificial band-pass filter if the temperature probes are not placed at appropriate depths. In addition, the temporal calculation of the change in the heat storage term of the calorimetric method can further distort the reconstruction of the surface soil heat flux signal. A correction methodology is introduced which provides practical application as well as insights into the estimation of surface soil heat flux and the closure of surface energy balance based on field measurements.

Gentine, P.; Entekhabi, D.; Heusinkveld, B.

2012-09-01

52

Surface heat flux data from energy balance Bowen ratio systems  

SciTech Connect

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

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

1995-06-01

53

A mathematical model for solving three-dimensional radiative heat transfer by radiative heat ray method  

NASA Astrophysics Data System (ADS)

By introducing the wall-radiosity concept, a radiative heat ray method is developed to solve three-dimensional combined radiative and convective heat transfer problems for systems surrounded by gray walls. Parameters which influence the calculating accuracy are analyzed, and this method is applied to a cylindrical gas reformer to obtain the profiles of gas and wall temperature as well as the tube-surface heat flux. The results indicate that the jet angle of heating burner has important effects on tube-surface heat flux and gas temperature distributions.

Hiroshi, Taniguchi; Kazuhiko, Kudo; Guo, Kehui; Zhang, Yongzhao; Takao, Katayama

1990-11-01

54

Dependence of the temperature of stochastically heated electrons on the flux density of pulsed laser radiation on a target  

Microsoft Academic Search

Electron dynamics in the field of focused picosecond multimode laser radiation was considered by numerical methods. It was\\u000a found that the electron energy during stochastic perturbation of its trajectory can exceed the energy of oscillatory motion\\u000a in a plane wave by several orders of magnitude. The electron distribution function was studied based on 2D numerical simulation.\\u000a An analytical expression for

Yu. V. Krylenko; Yu. A. Mikhailov; A. S. Orekhov; G. V. Sklizkov; A. A. Filippov

2010-01-01

55

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

SciTech Connect

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

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

1991-01-01

56

A STUDY ON THE CRITICAL HEAT FLUX TEMPERATURE  

Microsoft Academic Search

A boiling curve has a functional relationship between the transferred heat flux and surface temperature of the heated wall. The maximum heat flux is usually called Critical Heat Flux in a boiling curve. Critical Heat Flux (CHF) is the maximum rate of thermal energy that can be transferred per surface area. Dryout and departure from nucleate boiling (DNB) distinguish two

Sabiha Yildiz; Gerhart Bartsch

57

Apparatus for practicing heat flux control technique  

SciTech Connect

In processes for retorting oil shale using recycled heat-carrying ceramic balls having a critical heat flux value, efficient operation, without heat shock damage to the balls, is obtained by operating at a weight ratio of balls to shale which is greater than but substantially equal to the ratio corresponding to the critical heat flux value; and this ratio is a function of both the heat transfer coefficient at the inlet to the retort and also the difference in temperature between the heat carrying balls and the oil shale. Implementing apparatus includes arrangements for controlling the ratio of heat carrying balls to shale, as by ball feed control apparatus and/or oil shale feed control apparatus, in accordance with the difference in temperature between the ceramic balls and the shale.

Barney, J.H.

1984-01-24

58

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, R.E.; Doman, M.J.; Wilson, E.C.

1990-01-01

59

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, R.E.; Doman, M.J.; Wilson, E.C.

1990-12-31

60

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

61

Advanced test reactor critical heat flux studies  

Microsoft Academic Search

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

C. H. Oh; S. B. Englert; J. C. Chapman

1993-01-01

62

Modelled and observed continental surface heat fluxes  

NASA Astrophysics Data System (ADS)

Heat fluxes in the continental subsurface were estimated from general circulation model (GCM) simulations of the climate of the last millennium and compared to those obtained from subsurface geothermal data. Since GCMs have bottom boundary conditions (BBCs) that are less than 10 m deep and thus may be thermodynamically restricted in the continental subsurface, we used an idealized land surface model (LSM) with a very deep BBC to estimate the potential for realistic subsurface heat storage in the absence of bottom boundary constraints. Results indicate that there is good agreement between observed fluxes and GCM simulated fluxes for the 1780-1980 period when the GCM simulated temperatures are coupled to the LMS with deep BBC. These results emphasize the importance of placing a deep BBC in GCM soil components for the proper simulation of the overall continental heat budget. In addition, the agreement between the LSM surface fluxes and the borehole temperature reconstructed fluxes lends additional support to the overall quality of the GCM (ECHO-G) paleoclimatic simulations. Simulations to 2100 show a divergence between the LSM simulated subsurface heat content and the heat gain in the ECHO-G soil model, with the placement of the BBCs surpassing the thermodynamical effect of the choice of emission scenario as the most important factor determining heat absorption in the simulated subsurface.

Beltrami, H.; MacDougall, A. H.; Gonzalez-Rouco, F. J.; Stevens, M. B.; Bourlon, E.

2009-12-01

63

Surface and oceanic heat fluxes in the Gulf of Oman  

NASA Astrophysics Data System (ADS)

The surface heat fluxes for the Gulf of Oman have been estimated using the bulk formulae. The average annual values of sensible, latent and net infrared radiation fluxes are -1, 100 and 64 W m -2, respectively. The annual mean of absorbed solar radiations is -219 W m -2, thus giving an annual heat surplus of 55 W m -2. In contrast, in the nearby area of the Arabian Gulf there is a yearly average of an upward flux at the sea surface, which is compensated by an advective heat flow of approximately 25 W m -2 through the strait of Hormuz. Some of the heat in the Gulf of Oman is transported into the Arabian Gulf and it is suggested that the remainder is exported by oceanic processes on a seasonal basis. The winter compensation of heat loss is probably achieved by a northward heat transport from the Arabian Sea, and during the southwest monsoon (summer) the upwelled cold water from the southern coast of Arabia appears to compensate the heat gain in the Gulf of Oman. However the manner in which these compensations are accomplished remains to be clarified.

Sultan, S. A. R.; Ahmad, F.

1993-10-01

64

Bubble dynamics in boiling under high heat flux pulse heating  

SciTech Connect

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 {approximately} 50 MW m{sup {minus}2} heat flux pulse using a small thin film heater has been experimentally investigated. When the heat flux was relatively low (< 20 MW m{sup {minus}2}), a bubble grew in a hemispherical shape. When the heat flux was extremely high (> 20 MW m{sup {minus}2}), many small bubbles nucleated and combined into a vapor film. The bubble behavior in the latter case is explained well by the model.

Asai, A. (Canon Inc. Research Center, Kanagawa (Japan))

1991-11-01

65

Bidirectional electron heat flux events in space  

SciTech Connect

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

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

1986-01-01

66

Critical heat flux in uniformly heated vertical tubes  

Microsoft Academic Search

Experimental investigations on critical heat flux have been performed in circular tubes of different diameters ranging from 2 to 16 mm. The model fluid Freon-12 was used as working fluid due to its low latent heat, low critical pressure and well-known properties. About 1700 data points have been obtained in a large range of parameters: pressure 1.0–3.0 MPa, mass flux

F. G. Pang

1997-01-01

67

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

68

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

69

RADIATION FROM COMOVING POYNTING FLUX ACCELERATION  

SciTech Connect

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

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

2009-11-10

70

Fast nanoscale heat-flux modulation with phase-change materials  

NASA Astrophysics Data System (ADS)

We introduce a concept for electrically controlled heat-flux modulation. A flux contrast larger than 10 dB is expected with switching time on the order of tens of nanoseconds. Heat-flux modulation is based on the interplay between radiative heat transfer at the nanoscale and phase-change materials. Such large contrasts are not obtainable in solids, or in far field. As such, this opens up new horizons for temperature modulation and actuation at the nanoscale.

van Zwol, P. J.; Joulain, K.; Ben Abdallah, P.; Greffet, J. J.; Chevrier, J.

2011-05-01

71

Two-dimensional heat transfer analysis of radiating plates  

Microsoft Academic Search

The strongly implicit procedure is used to solve nonlinear elliptical two-dimensional heat conduction in radiating plates. A uniform heat flux is applied at one end of the plate which dissipates heat by radiation from one end into a vacuum at 0 K and into an ambient at temperature T(i) from the other. The results are presented with reference to four

K. Badari Narayana; S. U. Kumari

1988-01-01

72

Layered heat flux gauges for aeroentry application  

NASA Astrophysics Data System (ADS)

A layered heat flux gauge, which can withstand a high temperature environment for applications such as for use on thermal protection shields on aeroentry vehicles, is analyzed, designed, fabricated, and tested. The heat flux gauge consists of two resistance temperature detectors on the top and bottom faces of a thin ceramic substrate. The heat flux is calculated from temperature measurements of the two temperature detectors. An analytical model is used to simulate the gauge response. Several numerical methods to calculate the heat flux are investigated to improve the time response of the gauge. The error due to gauge intrusiveness and the validity of one-dimensional heat transfer within the gauge is studied by solving a steady state two-dimensional composite problem using a semi-analytical approach. Gauge fabrication techniques and measurement devices are discussed. Testing apparatus, including a "close-to-entry" condition apparatus using an arcjet at low pressure and a conduction calibration furnace, are explained. Experimental data showing qualitative gauge response is presented.

Oishi, Tomomi

73

Energy balance analysis of ignition over a melting polymer subjected to a high radiation heat flux in a channel cross flow  

Microsoft Academic Search

A two-dimensional ignition model is examined for two different flow patterns, one with a Navier–Stokes calculation and one with an Oseen approximation. The physical phenomena include channel flow and combustion reaction in the gas phase, pyrolysis and melting in the condensed phase, and radiation heat loss and fuel injection flow at the interface. Ignition is studied by means of an

Guanyu Zheng; Indrek S. Wichman; André Bénard

2003-01-01

74

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

NASA Astrophysics Data System (ADS)

Little is known of low-latitude energy balance and its drivers in wetland ecosystems. Eddy covariance data were collected in a short-hydroperiod Everglades marsh. The dominant mode of energy dissipation from the marsh varied seasonally. Net radiation was a strong driver of sensible heat and latent energy fluxes. Everglades restoration will shift marsh fluxes toward increased latent energy fluxes.

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

2011-12-01

75

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

76

Radiative Heating of the Solar Corona  

NASA Astrophysics Data System (ADS)

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 × 10-21 to 4.0 × 10-20 W, as compared with non-loop radiative loss rates of ?1 × 10-20 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.

2011-10-01

77

EU Development of High Heat Flux Components  

Microsoft Academic Search

The development of plasma facing components for next step fusion devices in Europe is strongly focused to ITER. Here a wide spectrum of different design options for the divertor target and the first wall have been investigated with tungsten, CFC, and beryllium armor. Electron beam simulation experiments have been used to determine the performance of high heat flux components under

J. Linke; P. Lorenzetto; P. Majerus; M. Merola; D. Pitzer; M. Roedig

2005-01-01

78

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

79

Heat & Flux - Enabling the Wind Turbine Controller  

Microsoft Academic Search

Heat & Flux refers to a recently invented and patented farm control concept to increase production and to reduce loads in wind farms without causing drawbacks. This is achieved by reducing the axial induction of wind turbines at the windward side of the farm. In previous works ECN proved this concept for scaled wind farms in a boundary layer wind

P. Schaak

80

High-frequency even harmonics generation in a plasma with electron heat flux  

Microsoft Academic Search

It is shown that in a weakly nonuniform plasma with electron heat flux the generation of odd and even harmonics of high frequency radiation is possible. The even harmonics properties qualitatively differ as compared to those of odd harmonics and depend in an essential way on the heat flux value and orientation with respect to the fundamental wave polarization and

G. Ferrante; M. Zarcone; S. A Uryupin

2004-01-01

81

Heat Flux Estimation in Geothermal Areas Based on the Heat Balance of the Ground Surface  

Microsoft Academic Search

The present authors have developed a rapid method for estimation of the difference between geothermal fluxes of two adjacent places, from surface temperatures and some meteorological parameters, based on a heat budget equation for simple vegetation-free ground surfaces. As this method requires simultaneous measurements of the surface temperatures at two Places, an infrared radiation thermometer is the most suitable apparatus

Mitsuru Sekioka; Kozo Yuhara

1974-01-01

82

Rainfall and Radiative Heating Rates from TOGA COARE Atmospheric Budgets  

Microsoft Academic Search

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

Richard H. Johnson; Paul E. Ciesielski

2000-01-01

83

Loop heat pipe radiator  

SciTech Connect

This paper describes the design and testing of a Loop Heat Pipe Radiator (LHPR) which was developed as an alternative to state-of-the-art axially-grooved heat pipes for space-based heat rejection which would be usable with tubing made of aluminum foil covered with a carbon-epoxy composite. The LHPR had an aluminum envelope and a polymer wick, and used ammonia as a working fluid. It was 4 meters long with a mass of 1.4 kg. The LHPR transported 500 watts at a 2.3 meter adverse inclination and 1500 watts when horizontal. This non-optimized LHPR had a 3000 watt-meter capability, which is four times greater than an axially-grooved heat pipe of similar power-handling capability and mass. In addition to a higher power handling capability, the LHPR has a much higher capillary margin than axially-grooved pipes. That high capillary margin simplifies ground testing in a 1-g environment by reducing the need for the careful levelling and vibration reduction required by axially-grooved pipes. {copyright} {ital 1996 American Institute of Physics.}

Sarraf, D.B.; Gernert, N.J. [Thermacore, Inc., 780 Eden Rd., Lancaster, Pennsylvania (United States)

1996-03-01

84

High-heat-flux sensor calibration using calorimetry  

NASA Astrophysics Data System (ADS)

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 limited to solar irradiances of approximately 100 kW m-2. The next step is to demonstrate this methodology to higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at Plataforma Solar de Almería.

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

2004-08-01

85

Radiative and convective heat transfer coefficients of the human body in natural convection  

Microsoft Academic Search

The purpose of this study was to investigate the convective and radiative heat transfer coefficients of the human body, while focusing on the convective heat transfer area of the human body. Thermal sensors directly measuring the total heat flux and radiative heat flux were employed. The mannequin was placed in seven postures as follows: standing (exposed to the atmosphere, floor

Yoshihito Kurazumi; Tadahiro Tsuchikawa; Jin Ishii; Kenta Fukagawa; Yoshiaki Yamato; Naoki Matsubara

2008-01-01

86

Prediction of Critical Heat Flux in Microchannels  

Microsoft Academic Search

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

J. R. Thome; L. Consolini

2010-01-01

87

Burnout at very high heat fluxes  

Microsoft Academic Search

The paper provides a brief overview of the present state-of-the-art in the field of the critical heat flux (CHF) in subcooled flow conditions, with particular regard to high liquid velocity and highly subcooled conditions. These thermofluid-dynamic conditions to reach very high values of the CHF (up to 80 MW\\/m2) as requested by fusion technology requirements. After reporting the general features

G. P. Celata; M. Cumo

1992-01-01

88

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

89

Interannual Variability in Meterrancan Heat and Buoyancy Fluxes  

Microsoft Academic Search

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

Curts Garrett; Richard Outerbridge; Keitu Thompson

1993-01-01

90

ANISOTROPIC COSMIC RADIATION FLUXES OF SOLAR ORIGIN  

Microsoft Academic Search

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

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

1966-01-01

91

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

92

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

93

A long time series analysis of ocean surface momentum and heat fluxes from remotely sensed observations and General Circulation Models  

Microsoft Academic Search

The key surface parameters involved in the exchange of energy between the atmosphere and oceans are: radiative fluxes, momentum, and turbulent heat fluxes. This study aims to use and to investigate the quality of the newly estimated long time series of remotely sensed surface wind vector, specific air humidity, surface wind stress, and latent and sensible heat fluxes. For the

A. Bentamy; L. Ayina

2006-01-01

94

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

95

New low-cost high heat flux source  

NASA Astrophysics Data System (ADS)

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

Cheng, Dah Yu

1993-11-01

96

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

97

Two-flux and diffusion methods for radiative transfer in composite layers  

Microsoft Academic Search

Temperature distributions and heat fluxes are predicted in composite semitransparent layers heated or cooled on both sides by radiation and convection. Two approximate methods were used for performing spectral calculations, and the results were validated by comparison with `exact ` numerical solutions of the radiative transfer equations. The composite layers have refractive indices larger than one, and isotropic scattering is

C. M. Spuckler; R. Siegel

1996-01-01

98

High Heat Flux Two-Phase Cooling in Silicon Multimicrochannels  

Microsoft Academic Search

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

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

2008-01-01

99

Radiative Heating of the ExoMars Entry Demonstrator Module  

NASA Astrophysics Data System (ADS)

Previous Mars entry missions have not accounted for the radiative heating of the vehicle during entry, as it has been assumed small. This is indeed the case in the ultra-violet (UV) and visible wavelength ranges in which atomic and diatomic species radiate in high speed Earth return entries due to electronic transitions. The Martian atmosphere is mainly composed of carbon dioxide which radiates strongly in the infra-red at more moderate temperatures due to vibrational transitions. Simulations of the radiative fluxes to the vehicle inclusive of the infra-red (IR) CO2 radiation have been performed at three centres using independent radiation databases. The agreement between the models is good. The findings show that the radiative fluxes are very important on the afterbody, and that the radiative heat pulse occurs significantly later in the trajectory than the convective heat pulse.

Beck, J.; Omaly, P.; Lino da Silva, M.; Surzhikov, S.

2011-08-01

100

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

NASA Astrophysics Data System (ADS)

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

Selcuk, Nevin

1993-02-01

101

Critical heat flux experimentation in an annular test section. [PWR  

Microsoft Academic Search

Steady-state critical heat flux experiments have been performed in the Forced Convection Test Facility (FCTF), an annular test section containing a single electrically heated rod, for the purpose of testing the applicability of existing critical heat flux correlations. Good accuracy has been obtained using the MacBeth-Barnett critical heat flux correlation for annuli, corrected for the ''stepped cosine'' power profile of

J. D. White; A. E. Levin

1978-01-01

102

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

Microsoft Academic Search

Critical heat flux experiments were performed with an alternate high and low heat flux profile in an internally heated annulus. The heated length was 84 inches (213 cm) with a chopped wave heat flux profile over the last 24 inches (61 cm) having a maximum-to-average heat flux ratio of 1.26. Three test sections were employed: one with an axially uniform

S. G. Beus; O. P. Seebold

1981-01-01

103

Radiative heating predictions for Huygens entry  

NASA Astrophysics Data System (ADS)

Radiative heat flux predictions for the Huygens probe entry into Titan's atmosphere are presented in this paper. Radiative heating was computed with the radiation code SPECAIR, assuming a Boltzmann distribution of the excited electronic levels at a characteristic temperature taken as the vibrational temperature of the gas. CN violet is found to be the most intense emitter, followed by CN red, C2 Swan, and at early trajectory points by the first and second positive systems of N2. Solutions of the 1-D radiative transport equation along stagnation streamlines show that self-absorption by the plasma layer reduces the total emission by up to about 20%. The fine structure of the CN violet spectra (spin-splitting) was taken into account to accurately determine self-absorption by CN violet. The potential importance of argon radiation was estimated and shown to be negligible. The resulting fluxes were found to be sustainable by the Huygens's Thermal Protection System. The feasibility of the mission was deemed possible under the updated entry parameters and atmospheric composition.

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

2006-09-01

104

Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes  

SciTech Connect

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

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

1999-06-01

105

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

106

High heat flux engineering in solar energy applications  

NASA Astrophysics Data System (ADS)

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.

Cameron, Christopher P.

1993-11-01

107

Coupling heat flux dynamics with meteorological conditions in the green roof ecosystem  

Microsoft Academic Search

Green roofs can notably modify the thermal properties of the building envelope and adjacent air to bring environmental benefits. This study investigates the heat flux dynamics of the tropical green roof ecosystem to provide a scientific basis for design and management. Green roof experimental plots were established to monitor the total solar radiation, net radiation, and micrometeorological parameters. The data

C. Y. Jim; Hongming He

2010-01-01

108

Estimation of heat flux through the eastern Bering Strait  

Microsoft Academic Search

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

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

2010-01-01

109

Considerations for modeling critical heat flux behavior  

SciTech Connect

During normal and accidental operations of a light water nuclear reactor, a wide range of thermal-hydraulic conditions may be encountered for which the critical heat flux (CHF) cannot be predicted by a single correlation. An encompassing model was developed for predicting the steady-state forced convective CHF for water over a wide range of thermal-hydraulic conditions. A CHF model is postulated using a conceptual CHF map to define possible CHF mechanisms for given thermal-hydraulic conditions. Existing steadystate CHF correlations, for which the primary CHF mechanism modeled can be identified, are then used in conjunction with the conceptual CHF map to construct a predictive CHF model. The CHF correlations used as the foundation of this model are the Westinghouse-3, the Biasi, and the Modified-Barnett correlations. These correlations allow coverage of a wide range of thermal-hydraulic conditions, provide favorable comparison with experimental data, and are commonly used in the nuclear industry. The parametric ranges covered by the resultant model are 0.3flux; and X is quality. The CHF model compares favorably with available experimental data and was used to construct specific CHF maps.

Dahlquist, J.E.; Gunnerson, F.S.; Nelson, R.A.

1985-02-01

110

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

SciTech Connect

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

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

1994-08-01

111

Radiative heat exchange between a fluidized bed and heated surface  

Microsoft Academic Search

The radiative heat exchange between a fluidized bed and a heated surface was investigated via an optical experiment employing a He-Ne laser and numerical simulation analysis. A model for predicting the radiative heat transfer is proposed that considers the thermal boundary layer near the heated surface. The numerical results indicate that radiative heat transfer is enhanced when the penetration depth

Jun Yamada; Yasuo Kurosaki; Isao Satoh; Kazuhiko Shimada

1995-01-01

112

Rewetting of an infinite slab with boundary heat flux  

SciTech Connect

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

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

2000-01-01

113

Using thermal radiation detectors for studying aerodynamic heating at hypersonic flow velocities  

Microsoft Academic Search

The thermal fluxes of a cylindrical nozzle with an internal cavity have been measured using a thermal radiation detector. It is shown that heat transfer is significantly intensified in a finely dispersed heat-insulating material due to the mechanical and acoustic effect of hypersonic flow. Intense generation of heat fluxes also occurs in conical cavities forming the heat-sensitive surface of the

O. A. Gerashchenko; E. I. Averkov; M. A. Goldfeld; G. A. Kiselev; I. I. Klimenko

1986-01-01

114

Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere  

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

115

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

116

An innovative methodology in the characterization of the halogen lamp as a reference source for heat flux sensor calibration  

Microsoft Academic Search

In radiant heat flux probe calibration, the possibility of obtaining a known source is achieved by the employment of a cavity as similar as possible to a black body. That is, using common radiation laws, it is possible to monitor the produced heat flux from its temperature control and measurement. However, many drawbacks are present in traditional testing and calibration

Mario Carbonaro; Roberto Marsili; Paolo Maggiorana

2002-01-01

117

Evaluation of soil heat flux density as a function of soil management practices  

NASA Astrophysics Data System (ADS)

Soil energy is an important parameter in order to understand the flux of energy between the plant and the soil. This parameter could determine the potential for future production of soil. Pattern of surface energy flux varies depending on several factors, mainly on coverage. Also, this behaviour is strongly conditioned by the physical condition of soil. In order to evaluate the trend and behaviour of soil energy depending on soil coverage the aim of the present study was to evaluate soil heat flux density (G) in three different soil conditions depending on seasonal weather temperatures. Therefore, the authors monitored soil energy every half hour from soil located on bare soil, on soil covered by crops at root level and in between crop rows. The selected crop was corn. Soil heat flux density was measured with a heat flux plate sensor buried at a depth of 0.05 m in experimental sites. The change in heat storage in the soil layer above the heat flux plates was measured by inserting temperature sensors at an angle from near the bottom to near the top of the soil layer (above the plate sensor). The results indicated that the soil energy flux depends mainly on radiation and soil conditions. Although net radiation (Rn) was the same for all the sites, the evolution for G is different. Greater G fluctuation is produced in bared soils and decreases as soil is covered by the crops, especially at root level.

Moratiel Yugueros, R.; García Moreno, R.

2012-04-01

118

Initiation of flux jump in SC composite by heat pulse  

Microsoft Academic Search

Nonisothermal diffusion of magnetic flux after heat pulse shot on the surface of SC composite has been studied numerically taking into account smoothed transition characteristic of the superconductor. It is shown that for SC composite with poor stabilization the current and heat redistribution changes significantly the estimations of stability used on steady state functions of heat generation and heat transfer.

E. Y. Klimenko; N. N. Martovetsky

1989-01-01

119

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

120

Value of bulk heat flux parameterizations for ocean SST prediction  

Microsoft Academic Search

Bulk heat flux parameterization is an increasingly popular technique for forcing non-coupled ocean models. If sea surface temperature (SST) from the model is colder (warmer) than observed, then the net heat flux will be higher (lower) than observed; thus, bulk parameterizations tend to keep model SST close to observational SST on long time scales. However, bulk parameterizations imply neither strong

Alan J. Wallcraft; A. Birol Kara; Harley E. Hurlburt; Eric P. Chassignet; George H. Halliwell

2008-01-01

121

Structural design criteria for high heat flux components  

Microsoft Academic Search

The high temperature design rules of the ITER Structural Design Criteria (ISDC), are applied to first wall designs with high heat flux. The maximum coolant pressure and surface heat flux capabilities are shown to be determined not only by the mechanical properties of the first wall material but also by the details of the blanket design. In a high power

Majumdar

1999-01-01

122

Structural design criteria for high heat flux components  

Microsoft Academic Search

The high temperature design rules of the international thermonuclear experimental reactor (ITER) structural design criteria (ISDC) are applied to first wall designs with high heat flux. The maximum coolant pressure and surface heat flux capabilities are shown to be determined not only by the mechanical properties of the first wall material but also by the details of the blanket-design. In

Saurin Majumdar

2000-01-01

123

CALCULATED BURNOUT HEAT FLUXES FOR SANTOWAX-R  

Microsoft Academic Search

Studies were made to determine the burnout heat fluxes for Santowax-R at ; various pressures, bulk temperatures, Reynolds numbers, and high boiler compound. ; Plots of the burnout heat flux for Santowax-R are given. These values were ; obtained using the lower limit of the Griffith correlation. (W.L.H.)

Baumeister

1959-01-01

124

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

125

Decadal Changes in Surface Radiative Fluxes  

NASA Astrophysics Data System (ADS)

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

Wild, M.

2009-05-01

126

ERRORS IN SOIL HEAT FLUX MEASUREMENT: EFFECTS OF FLUX PLATE DESIGN AND VARYING SOIL THERMAL PROPERTIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The flux plate method is the most commonly employed method for measuring soil heat flux (G) in surface energy balance studies. Nonetheless, significant errors in G measured with flux plates can occur unless proper installation techniques are used and necessary corrections made. The objective of th...

127

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

128

Extension of Planck's law to steady heat flux across nanoscale gaps  

NASA Astrophysics Data System (ADS)

Recent experiments report that the radiative heat conductance through a narrow vacuum gap between two flat surfaces increases as the inverse square of the width of the gap. Such a significant increase of thermal conductivity has attracted much interest because of numerous promising applications in nanoscale heat transfer and because of the lack of its theoretical explanation. It is shown here that the radiative heat transport across narrow layers can be described in terms of conventional theory adjusted to non-equilibrium structures with a steady heat flux.

Budaev, Bair V.; Bogy, David B.

2011-06-01

129

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

SciTech Connect

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

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

2000-04-04

130

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

131

An advective atmospheric mixed layer model for ocean modeling purposes: Global simulation of surface heat fluxes  

SciTech Connect

A simple model of the lowest layer of the atmosphere is developed for coupling to ocean models used to simulate sea surface temperature (SST). The model calculates the turbulent fluxes of sensible and latent heat in terms of variables that an ocean model either calculates (SST) or is forced by (winds). It is designed to avoid the need to specify observed atmospheric data (other than surface winds), or the SST, in the surface flux calculations of ocean models and, hence, to allow a realistic representation of the feedbacks between SST and the fluxes. The modeled layer is considered to be either a dry convective layer or the subcloud layer that underlies marine clouds. The turbulent fluxes are determined through a balance of horizontal advection and diffusion, the surface flux and the flux at the mixed layer top, and, for temperature, radiative cooling. Reasonable simulations of the global distribution of latent and sensible heat flux are obtained. This includes the large fluxes that occur east of the Northern Hemisphere continents in winter that were found to be related to both diffusion (taken to be a parameterization of baroclinic eddies) and advection of cold, dry air from the continent. However, east of North America during winter the sensible heat flux is underestimated and, generally, the region of enhanced fluxes does not extend far enough east compared to observations. Reasons for these discrepancies are discussed and remedies suggested. 47 refs., 10 figs.

Seager, jR., Benno Blumenthal, M.; Kushnir, Y. [Lamont-Doherty Earth Observatory of Columbia Univ., Palisades, NY (United States)

1995-08-01

132

HIGH FLUX BOILING HEAT TRANSFER FROM A FLAT PLATE  

Microsoft Academic Search

Flat copper platcs, 1\\/8 in. thick, were heated on one side by electron ; bombardment of a 1-1\\/2 in. diameter area and cooled on the opposite side by water ; flowing in a 0.050 to 0.090-in.-wide passage. Data were obtained on plate ; temperature vs. heat flux, 'burnout'' heat flux vs. water velocity and the ; effects of various surface

C. E. Taylor; J. F. Steinhaus

1958-01-01

133

Total aerosol effect: radiative forcing or radiative flux perturbation?  

NASA Astrophysics Data System (ADS)

Uncertainties in aerosol radiative 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. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to properly define. Here we argue that fast feedbacks should be included because they 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. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.

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

2010-05-01

134

Thermic controls to regulate solar heat flux into buildings  

Microsoft Academic Search

The purpose of this project was to develop thermic controls for regulating solar heat flux into buildings. Thermics is a control discipline which uses temperature to directly control heat flow. Many independent panels, replacing building walls and roof and controlled internally by thermic devices, would perform three functions: (1) collect solar energy or dissipate internal heat, (2) control the flow

S. Buckley

1975-01-01

135

Modeling shortwave radiative fluxes from satellites  

NASA Astrophysics Data System (ADS)

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

Ma, Y.; Pinker, R. T.

2012-12-01

136

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

137

Electron Heat Transport Models and Flux Limiters in the CRASH Code  

NASA Astrophysics Data System (ADS)

The Center For Radiative Shock Hydrodynamics (CRASH) at the University of Michigan is an effort to create a radiation-hydrodynamics (RH) simulation code and quantify its predictive ability using experimental results. In the RH regime, much of the kinetic energy of the ions is expended by heating the electrons. The coefficient of electron heat conductivity can be calculated by one of several methods. When a discontinuity is encountered, many methods are prone to numerical errors. To correct for this an electron flux limiter can be used. However, flux limiters often blur real details. Simulation output in CRASH using different electron heat transport models with various flux limiters can be compared to experimental results to find the most accurate combination and its overall effect on the simulation. This research was supported by the DOE NNSA under the Predictive Science Academic Alliance Program by grant DEFC52-08NA28616.

Stewart, P. D.; Drake, R. P.; Sokolov, Igor

2010-11-01

138

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

National Technical Information Service (NTIS)

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

P. Schwerdtfeger

1970-01-01

139

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

140

Forest understory soil temperatures and heat flux calculated using a Fourier model and scaled using a digital camera  

Microsoft Academic Search

The characterization of the solar radiation environment under a forest canopy is important for both understanding temperature-dependent biological processes and validating energy balance models. A modified sinusoidal model of soil heat conductivity was used to estimate subsurface temperature and heat flux from the uneven but periodic solar heating of the soil surface due to sun flecks from a forest canopy.

Eric A. Graham; Yeung Lam; Eric M. Yuen

2010-01-01

141

Critical Heat Flux of Concentric-Tube Thermosyphon  

NASA Astrophysics Data System (ADS)

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

Kawabe, Hiromichi; Tanaka, Teimi; Fukusako, Shoichiro

142

Effect of porous coating on critical heat flux  

SciTech Connect

The critical heat flux (CHF) is studied experimentally in vertical tubes heated directly using power current (DC 2,500 A, 15 V) and cooled with water at a low mass flow rate (0--200 kg/m{sup 2}s) and at a low pressure (1.0--8.0 bar). The authors used a smooth tube and a tube with a porous coating layer sintered onto the inner surface. The results are compared with each other and with correlations by Katto and Weber. The authors determined enhancement of heat transfer as well as a negative effect of the porous coating below the expected value of critical heat flux.

Schroeder-Richter, D.; Yildiz, S.; Bartsch, G. [Technische Univ. Berlin (Germany). Inst. fuer Energietechnik

1996-07-01

143

Assessment of high-heat-flux thermal management schemes  

Microsoft Academic Search

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

Issam Mudawar

2001-01-01

144

Coupled air-sea interaction patterns and surface heat-flux feedback in the Bay of Biscay  

NASA Astrophysics Data System (ADS)

The coupled variability of the Sea Surface Temperature (SST) and atmosphere-ocean surface heat fluxes over the Bay of Biscay (Eastern North Atlantic) has been analyzed. Daily surface heat fluxes from different meteorological reanalyses are combined with a high resolution reconstructed satellite SST data set by means of Lagged Maximum Covariance Analysis (MCA). Lagged MCA is applied at different spatial scales. Its results are interpreted within the framework of Hasselmann's stochastic climate model. The surface heat-flux feedback on SST is confirmed to be generally negative. No clear relation is found between the first MCA expansion series and the leading Sea Level Pressure (SLP) patterns. However, a clear relation is found between the second expansion series and the leading SLP Principal Component (PC) when the atmosphere leads the ocean. Spatial patterns of anomalies of the SST and of the SST tendency are found to be related by a 4 day lag. The same reconstructed satellite SST and reanalysis heat fluxes are combined to estimate the feedbacks related to the surface heat fluxes. The traditional procedure used to compute the surface heat-flux feedbacks from monthly data is adapted for daily data. High resolution maps of the heat-flux feedback are derived for the annual and seasonal cases for the Bay of Biscay. Feedbacks related to turbulent (latent and sensible heat) fluxes are shown to dominate over the radiative ones. Special attention is paid to small-scale features present in both Lagged Covariance patterns and surface heat-flux feedback estimates.

Esnaola, G.; SáEnz, J.; Zorita, E.; Lazure, P.; Ganzedo, U.; FontáN, A.; Ibarra-Berastegi, G.; Ezcurra, A.

2012-06-01

145

Natural convection burnout heat flux limit for control rods  

SciTech Connect

Technical Standard 105-3.05, Safety Circuits, does not require the Septifoil Supply Header Pressure Very Low safety circuit for current charges. This document develops a new requirement for this circuit based on the burnout heat flux of a control rod under natural convective cooling. Specifically, the Septifoil Supply Header Pressure Very Low safety circuit will be required whenever the calculated control rod operating heat flux exceeds 155,000 pcu/ft{sup 2}-hr.

Britt, T.E.

1986-04-14

146

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

Microsoft Academic Search

Flow-excursion-induced dryout at low-heat-flux natural-convection boiling, typical of liquid-metal fast-breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of Ledinegg instability leading to flow excursion and subsequent dryout in agreement with experimental data. A flow-regime-dependent dryout heat flux relationship based upon saturated boiling criterion is also presented. Transient analysis indicates that premature flow

M. Khatib-Rahbar; E. G. Cazzoli

1983-01-01

147

On the Measurement of Soil Heat Flux to Improve Estimates of Energy Balance Closure  

NASA Astrophysics Data System (ADS)

Measurements of soil heat flux (G) are required to test for energy balance closure at many fluxnet locations. Data quality is often evaluated by comparing total available energy, composed of net radiation (Rn) and G, to the sum of latent (LE) and sensible (H) heat fluxes as measured by eddy covariance. Unfortunately, G often receives minimal attention during an experiment because other flux terms (e.g., Rn and LE) are larger or require more complex instrumentation. However, G at certain time periods can account for 10 to 30 percent of Rn, especially beneath short vegetation. Thus, errors in G can confound energy closure tests and lead to erroneous conclusions about of eddy covariance performance. Research was conducted to evaluate difference methods for automating and improving measurements of G. Automated soil heat capacity sensors were combined with heat flux plates to measure conduction and changes in heat storage at different position in the soil profile. The heat capacity sensors were also used to measure soil water content and soil temperature. Data were collected beneath turfgrass, a tallgrass prairie and a juniperous forest. Field results and numerical models were used to study the best sensor configuration and data analysis algorithms. Practical guidelines for measuring and calculating soil heat flux will be presented.

Ham, J. M.

2001-12-01

148

The Effect of Basicity on the Radiative Heat Transfer and Interfacial Thermal Resistance in Continuous Casting  

NASA Astrophysics Data System (ADS)

The basicity of mold flux has been recognized to have a significant influence on the mold flux crystallization in continuous casting, which would in turn affect the heat-transfer rate between the solidified shell and mold. The research regarding the mold flux crystallization as well as its effect on the heat transfer has been conducted intensively. However, few studies have been developed to specify the effect of basicity introduced mold flux crystallization on the radiative heat transfer and interfacial thermal resistance in continuous casting. By using an infrared radiation emitter, a radiative heat flux was applied to a copper mold covered with a solid mold flux disk to simulate the heat-transfer phenomena in continuous casting. The crystallization behaviors of mold fluxes with different basicities and their impact on the radiative heat transfer were investigated dynamically. The interfacial thermal resistance between the solid mold flux and copper mold was also studied in this article. The results suggested that the basicity tends to enhance the mold flux crystallization, leading to the reduction of radiative heat-transfer rate and enlargement of interfacial thermal resistance.

Gu, Kezhuan; Wang, Wanlin; Zhou, Lejun; Ma, Fanjun; Huang, Daoyuan

2012-08-01

149

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

150

Estimation of sensible heat, water vapor, and CO2 fluxes using the flux-variance method.  

PubMed

This study investigated the flux-variance relationships of temperature, humidity, and CO(2), and examined the performance of using this method for predicting sensible heat (H), water vapor (LE), and CO(2) fluxes (F(CO2)) with eddy-covariance measured flux data at three different ecosystems: grassland, paddy rice field, and forest. The H and LE estimations were found to be in good agreement with the measurements over the three fields. The prediction accuracy of LE could be improved by around 15% if the predictions were obtained by the flux-variance method in conjunction with measured sensible heat fluxes. Moreover, the paddy rice field was found to be a special case where water vapor follows flux-variance relation better than heat does. However, the CO(2) flux predictions were found to vary from poor to fair among the three sites. This is attributed to the complicated CO(2) sources and sinks distribution. Our results also showed that heat and water vapor were transported with the same efficiency above the grassland and rice paddy. For the forest, heat was transported 20% more efficiently than evapotranspiration. PMID:18379829

Hsieh, Cheng-I; Lai, Mei-Chun; Hsia, Yue-Joe; Chang, Tsang-Jung

2008-04-01

151

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

152

Meridional heat flux of the North Atlantic Ocean  

SciTech Connect

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

Wunsch, C.

1980-09-01

153

The heat transfer phenomenon across mold flux to copper mold in continuous casting  

NASA Astrophysics Data System (ADS)

In the development of steel technology, continuous casting has become the main process route for mass production of steel today. 1100 million tons of steel was casted annually corresponding to more than 90% of the total steel production in the world. Like any other new process, continuous casting is efficient. However, it also introduces new types of defects, like oscillation marks, corner cracks, facial cracks, macro inclusions, etc. Currently, a wealth of experience in industry has been developed to improve slab surface qualities. Most of the research has indicated that the final cast slab surface is strongly dependent upon the heat release rate from the steel strand, i.e., heat transfer rate from the partially solidified strand to caster mold. Mold fluxes have been widely used to infiltrate in between the caster mold and strand to moderate the heat transfer rate. The main goal of this study is to explore the effects of mold flux composition and solidification on heat transfer rates, especially on radiative heat transfer rates. It has been shown in the work that both solid crystalline and glassy phase films have different thermal resistance and affect the radiative heat transfer rate, and the crystallization behavior of the mold flux is the primary factor affecting the overall heat transfer rate in continuous casting. By using an infrared radiation emitter, which was developed at Carnegie Mellon University, a radiative heat flux was applied to a copper mold covered with solid mold flux disk to simulate the radiative heat transfer phenomena in continuous casting. The solid slag disk could either be glass or a mixture of glass and precipitated crystals. The kinetics of mold slag crystallization was studied by the recently developed double hot thermocouple techniques (DHTT) as well. It has been investigated that the effect of full crystallization of a slag disk is able to reduce the heat transfer rate by 20% in the meniscus area in this work. By studying the heat transfer mechanism proposed here, the hypothesis could be used in real casting industry to help moderating heat transfer rates to eliminate or minimize oscillation marks, to achieve a defects free final slab.

Wang, Wanlin

154

Radiative heat transfer in turbulent MHD channel flow  

NASA Astrophysics Data System (ADS)

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. An exponential wide band model is employed in evaluation of radiative heat flux for a real gas. The tegro-differential equation for thermal energy transport is solved by a finite difference iterative method. It is shown that radiative heat transer 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.

155

Applicability of uniform heat flux Nusselt number correlations to thermosyphon heat exchangers for solar water heaters  

SciTech Connect

Nusselt numbers are measured in three counterflow tube-in-shell heat exchangers with flow rates and temperatures representative of thermosyphon operation in solar water heating systems. Mixed convection heat transfer correlations for these tube-in-shell heat exchangers were previously developed in Dahl and Davidson (1998) from data obtained in carefully controlled experiments with uniform heat flux at the tube walls. The data presented in this paper confirm that the uniform heat flux correlations apply under more realistic conditions. Water flows in the shell and 50 percent ethylene glycol circulates in the tubes. Actual Nusselt numbers are within 15 percent of the values predicted for a constant heat flux boundary condition. The data reconfirm the importance of mixed convection in determining heat transfer rates. Under most operating conditions, natural convection heat transfer accounts for more than half of the total heat transfer rate.

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

1999-05-01

156

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

157

Preliminary measurements of heat flux in a subsonic gun simulator  

Microsoft Academic Search

Preliminary measurements of heat flux have been obtained in a subsonic gun simulator with thin film resistance thermometry for an inert, single phase flow expanding behind a projectile from an initial pressure of 8 bars and resulting in an exit projectile velocity of 40 m\\/s. The results show that heat transfer measurements at locations swept by the projectile are possible

A. F. Bicen; M. Schmidt; J. H. Whitelaw

1987-01-01

158

Performance of Thermal Barrier Coatings in High Heat Flux Environments.  

National Technical Information Service (NTIS)

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

R. A. Miller C. C. Berndt

1984-01-01

159

Critical heat flux test on saw-toothed fin duct under one-sided heating conditions  

Microsoft Academic Search

Critical heat flux (CHF) tests on a new type of rectangular cooling tube, ‘saw-toothed fin duct, SFD’ for high heat flux components were performed under one-sided heating conditions. The tube has internal triangle fins at the heating side to enhance the CHF characteristics. Hydraulic conditions were as follows: axial flow velocity ranged from 2 to 12 m\\/s. Local pressure at

K Ezato; S Suzuki; K Sato; M Taniguchi; M Hanada; M Araki; M Akiba

2001-01-01

160

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

161

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

162

Measurement of Outgoing Radiative Fluxes from Ultra Long Duration Balloons  

NASA Astrophysics Data System (ADS)

Top of Atmosphere TOA radiative fluxes W m 2 are critical to our understanding of the physics of the present climate and it is variability Recognizing this importance NASA has measured the shortwave 0 2--4 mu m fluxes reflected by the Earth-atmosphere system and longwave 4--100 mu m fluxes emitted by the Earth-atmosphere systme for almost 40 years Outgoing flux can be measured directly from satellite using wide field of view radiometers with a footprint of a few thousand kilometers In order to provide fluxes more commensurate with the increasingly fine resolution of climate models Earth radiation budget satellite the Cloud and Earth s Radiant Energy System CERES on Terra and Aqua is based entirely on narrow filed of view scanner to measure directional radiances W m 2 sr Therefore we have to rely on empirical angular directional models to convert radiance to flux which is the principle source of uncertainty in instantaneous fluxes estimated from Earth radiation budget satellites Unlike other retrieved variables emph in situ validation of outgoing fluxes has been nearly impossible for lack of platforms that operate for long periods at the top of atmosphere The NASA Ultra Long Duration Balloon ULDB program opens a new avenue for direct measurement of the Earth radiation budget Radiative transfer model shows that the outgoing flux differences between ULDB flight altitude and TOA is less than 1 W m 2 Therefore it provides a unique platform to validate the satellite retrieved TOA radiative fluxes An Earth radiation balloon package has

Su, W.; Dutton, E.; Charlock, T.; Wiscombe, W.

163

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

NASA Astrophysics Data System (ADS)

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

Li, M.; Chen, Y.

2010-12-01

164

Heat flux distribution model by sequential algorithm of inverse heat transfer for determining workpiece temperature in creep feed grinding  

Microsoft Academic Search

The purpose of this study is to determine the heat flux distribution and to estimate the workpiece temperature in creep feed grinding. The sequential algorithm of the inverse heat transfer was used for determining the heat flux distribution. The amount of heat flux to the workpiece, the energy partition and the convective heat transfer coefficients both at the front and

Hae-Ji Kim; Nam-Kyung Kim; Jae-Seob Kwak

2006-01-01

165

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

National Technical Information Service (NTIS)

Absolute radiation flux and polarization measurements of the APS undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The techniqu...

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

1994-01-01

166

Methodology for calibration and use of heat flux transducers  

NASA Astrophysics Data System (ADS)

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

Ducharme, Michel B.; Frim, John

1991-05-01

167

Horizontal Radiative Fluxes in Clouds at Absorbing Wavelengths.  

National Technical Information Service (NTIS)

We discuss the effect of horizontal fluxes on the accuracy of a conventional plane-parallel radiative transfer calculation for a single pixel, known as the Independent Pixel Approximation (IPA) at absorbing wavelengths. Vertically integrated horizontal fl...

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

1998-01-01

168

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

169

Laboratory Investigation of Electron Heat Flux Driven Whistler Instabilities  

NASA Astrophysics Data System (ADS)

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

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

1997-11-01

170

Solid state radiative heat pump  

DOEpatents

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

Berdahl, Paul H. (Oakland, CA)

1986-01-01

171

Solid state radiative heat pump  

DOEpatents

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

Berdahl, P.H.

1984-09-28

172

Using thermal radiation detectors for studying aerodynamic heating at hypersonic flow velocities  

NASA Astrophysics Data System (ADS)

The thermal fluxes of a cylindrical nozzle with an internal cavity have been measured using a thermal radiation detector. It is shown that heat transfer is significantly intensified in a finely dispersed heat-insulating material due to the mechanical and acoustic effect of hypersonic flow. Intense generation of heat fluxes also occurs in conical cavities forming the heat-sensitive surface of the radiometer.

Gerashchenko, O. A.; Averkov, E. I.; Goldfeld, M. A.; Kiselev, G. A.; Klimenko, I. I.

173

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

SciTech Connect

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

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

1994-04-01

174

The Role of Electron Heat Flux in Magnetic Reconnection  

NASA Astrophysics Data System (ADS)

Particle-in-Cell (PIC) and hybrid simulations (kinetic ions, fluid massless electrons) have been used to investigate magnetic reconnection in 2-D with no guide field. Both simulations are initialized with a Harris sheet equilibrium and the magnetic field is perturbed in order to excite a linear tearing instability. The electron momentum equation is used to calculate the electric field in the hybrid simulation, and the divergence of the full pressure tensor is included in order to break the frozen-in condition at the X-point. In order to evolve the full pressure tensor, we multiply the Vlasov equation by vivj in order to obtain an evolution equation for Pij. However, this scheme requires knowledge of the divergence of the heat flux (Q), which leads to the well known closure problem in plasma fluid theory. The Hybrid code currently solves the full evolution equation of the electron pressure tensor with the divergence of the heat flux term set to zero. In this paper, we compare the results from the hybrid code with results from the PIC code. Generally the results of the two codes agree, consistent with earlier work. However, we find differences in the evolution of the electron heating and also in the location of the heating. For example, in the hybrid code, the electrons mainly heat in the center of the diffusion region, whereas in the PIC code, the electrons heat at the edge of the diffusion region. To show the effects of the electron heat flux, we calculate it directly from a PIC code and compare with the other source terms in \\frac{? P}{? t}. We show that the heat flux term is as important in determining the electric field as all the other source terms, and therefore cannot be neglected in the calculation of the pressure tensor. Distribution functions are then presented which demonstrate kinetically the source of the heat flux. A scheme is then presented for including heat flux in the hybrid code which does not rely on taking the third moment of the Vlasov equation. Preliminary hybrid results are presented which includes heat flux in the calculation of the momentum equation.

Main, D. S.; Yin, L.; Winske, D.; Bowers, K.

2007-12-01

175

Critical Heat Flux of Butanol Aqueous Solution  

NASA Astrophysics Data System (ADS)

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

Nishiguchi, Shotaro; Shoji, Masahiro

176

Initial Tile Temperature and Heat Flux Measurements in NSTX  

NASA Astrophysics Data System (ADS)

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

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

1999-11-01

177

A critical heat flux model for tubes containing twisted tapes  

SciTech Connect

The use of subcooled flow boiling for the cooling of high-flux components is being considered for several fusion reactor designs. To enhance the critical heat flux (CHF), the insertion of twisted tapes within the cooling tubes has been proposed. A number of empirical correlations for CHF in the presence of twisted tapes have been developed. However, no phenomenological model has been available for CHF in the presence of swirling flow.

Weisman, J.; Shoaib, U. (Univ. of Cincinnati, OH (United States))

1993-01-01

178

Estimates of sensible heat flux from observations of temperature fluctuations  

NASA Astrophysics Data System (ADS)

Comparisons between sensible heat flux measured using eddy correlation instrumentation and estimated using the temperature fluctuation method are presented for four types of surface in West Africa. Agreement between measured and estimated values is good. Regression of estimated on measured sensible heat flux gave a mean slope of 0.98 with a mean r 2 of 0.94 for bare soil, mature millet, fallow savannah and tiger bush. Estimates of heat flux from temperature fluctuations measured by an instrument mounted beneath a tethered balloon are also shown to be in close agreement with eddy correlation measurements made at the surface (regression slope = 0.98, r 2 = 0.84). The results provide evidence that the ratio ??/?×is indeed a universal function of z/L for all the surface types considered.

Lloyd, C. R.; Culf, A. D.; Dolman, A. J.; Gash, J. H. C.

1991-12-01

179

Divertor Heat and Particle Fluxes During ELM Control Experiments  

NASA Astrophysics Data System (ADS)

In experiments exploring ELM suppression by resonant magnetic perturbation (RMP) as a technique for ITER, the manipulation of divertor heat and particle fluxes is of vital interest. To investigate these effects, a fast IR camera and CCD cameras equipped with D?, CII or CIII interference filters were used during RMP ELM control experiments at DIII-D. In general, a splitting of the inner and outer divertor strike lines was observed. This is caused by splitting of the invariant separatrix manifolds that form magnetic footprints on the wall elements. Parallel particle and heat fluxes are transported along these field lines forming a characteristic pattern on the divertor target. The measured patterns are compared to magnetic footprints modeled with the TRIP3D code to identify the topology of the heat and particle flux channels. Based on that, the occurrence of complete ELM suppression is correlated to the measured and modeled target patterns.

Schmitz, O.; Jakubowski, M. W.; Evans, T. E.; Schaffer, M. J.; West, W. P.; Fenstermacher, M. E.; Groth, M.; Lasnier, C. J.; Joseph, I.; Moyer, R. A.; Unterberg, B.; Frerichs, H.

2007-11-01

180

Remote high temperature insulatorless heat-flux gauge  

DOEpatents

A remote optical heat-flux gauge for use in high temperature environments. 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 light. The luminescence emitted by the two thermographic-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, B.W.

1992-12-31

181

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

182

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

PubMed

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

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

2013-08-19

183

Heat pipes for NEP spacecraft radiators  

SciTech Connect

Reliable, low mass, passive radiators for the Nuclear Electric Propulsion Spacecraft require innovative system designs and the use of high performance, high temperature liquid metal heat pipes. This paper covers the evolution of the NEP spacecraft and radiator. 1 ref.

Ernst, D.M.

1981-01-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

185

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

186

Miniature high temperature plug-type heat flux gauges  

NASA Astrophysics Data System (ADS)

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.

187

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

188

Radiative Heat Transfer in the Combustion Chamber of a Diesel Engine  

Microsoft Academic Search

Radiation is considered to be an important mode of heat transfer in diesel engines. It is mainly caused by a presence of soot particles in combustion gases. Spatial distribution of radiative heat flux on walls of the combustion chamber can be an important factor of thermal load of some parts of the engine. The paper presents a numerical method used

P. Furmanski; J. Banaszek; T. S. Wisniewski

1999-01-01

189

Distributed Temperature Sensing as a tool for measuring soil heat flux  

NASA Astrophysics Data System (ADS)

Soil heat flux is an important component of the surface energy balance. It is typically measured at a point using heat flux plates. Spatial patterns as well as temporal variability can be measured using Distributed Temperature Sensing (DTS), in which fiber-optic cable is used as an environmental temperature sensor. Previous research has demonstrated that DTS can be used to monitor soil moisture patterns and soil thermal profiles. By using a custom-built mole-plow, fiber optic cables were installed at three depths within the top 15 centimeters of a grass plot in Delft, The Netherlands. DTS was used to measure temperatures along the cable with a spatial resolution of 1 meter and a temporal resolution 5 minutes along a cable of 84 meters length. In this cable the response of soil temperature to the diurnal cycle of net radiation was measured over three months (Passive DTS). By inverse modeling of the diffusion equation, thermal properties of the soil are determined from which soil heat flux is calculated. During several more intensive campaigns, active heating experiments (Active DTS) were also carried out. In this case, a controlled electrical pulse was applied to the stainless steel armoring on the cable. The thermal response of the cable is measured for pulses of different input power, and this is related to the thermal properties of the surrounding soil. Net radiation, thermal conductivity and sensible heat flux were also measured to quantify the surface energy balance during the intensive campaigns. Results will be presented to illustrate that DTS (Active and/or Passive) is a promising and relatively inexpensive tool to measure large scale spatial patterns in temperature, soil moisture and soil heat flux at high spatial and temporal resolution.

Jansen, J.; Steele-Dunne, S. C.; Van De Giesen, N.; Selker, J. S.

2011-12-01

190

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

191

EFFECT OF CONTAMINANTS ON CRITICAL HEAT FLUX AT LOW PRESSURES  

Microsoft Academic Search

Critical heat flux (CHF) tests were performed to evaluate the effect of dissolved, nonreactive contaminants on low-pressure industrial boilers. These tests were conducted on a 2.38-inch (60.5 mm) I.D. vertical smooth bore tube with nonuniform circumferential heating at pressures between 100 and 500 psia (0.69 and 3.45 MPa). Tests were performed under two water chemistry conditions: clean (less than 1.6

JOHN B. KITTO JR

1980-01-01

192

Onset of Flow Instability and Critical Heat Flux in Horizontal, Thin, Uniformly-Heated Annuli.  

National Technical Information Service (NTIS)

Two-phase flow instability (Ledinegg Excursion) and critical heat flux in heated microchannels are of great concern in the design and operation of numerous practical systems. In order to prevent Ledinegg flow excursion and eventual burnout of the heated c...

R. M. Stoddard

2000-01-01

193

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

194

Numerical study of high heat flux pool boiling heat transfer  

Microsoft Academic Search

A new numerical simulation model of boiling heat transfer is proposed based on a numerical macrolayer model [S. Maruyama, M. Shoji, S. Shimizu, A numerical simulation of transition boiling heat transfer, in: Proceedings of the Second JSME–KSME Thermal Engineering Conference, pp. 3-345-3-348, 1992]. In this model, the boiling curve is reproduced numerically by determining the macrolayer thickness. It is found

Ying He; Masahiro Shoji; Shigeo Maruyama

2001-01-01

195

Airborne flux measurements of CO2, sensible, and latent heat over the Hudson Bay lowland  

NASA Astrophysics Data System (ADS)

As part of the Northern Wetlands Study (NOWES) in the summer of 1990, 30 flights were conducted with the National Research Council (NRC) Twin Otter research aircraft to quantify the spatial and temporal variations of CO2, H2O, and sensible heat fluxes over the Hudson Bay lowland. These consisted of two regional runs of approximately 100 km in length from James Bay to the Kinosheo Lake and 13-km runs in the form of "L" and grid patterns near the Atmospheric Environment Service (AES) tower in the Kinosheo Lake area. An examination of the average fluxes shows that day-to-day differences were larger than the spatial differences. Significant correlations were found between the fluxes of CO2, sensible heat and latent heat, and selected environmental characteristics, such as air temperature, vapor pressure deficit, surface temperature minus air temperature, and incident solar radiation, for different sections of the NOWES area. The presentation of the spatial variations of aircraft-based fluxes of CO2, sensible heat, and latent heat over a 13 km × 13 km area near Kinosheo Lake permits an evaluation of the spatial representativeness of the AES tower observations.

Desjardins, R. L.; MacPherson, J. I.; Schuepp, P. H.; Hayhoe, H. N.

1994-01-01

196

Calculation of thermal fluxes of plasma torch reradiation under the action of laser radiation on a condensed target  

SciTech Connect

The problem of laser deposition with allowance for thermal radiation transport inside and outside the laser torch is considered in a multigroup approximation. The energy fluxes of laser torch thermal radiation onto a target in the far and near zones are calculated as functions of time and the character of the exposure. It is shown that absorption of thermal fluxes in the substrate and target in the course of laser deposition results in their substantial heating. The possibility of diagnosing thermal radiation fluxes from the laser torch by using photodetectors is demonstrated.

Rudenko, V. V. [Russian Federation Ministry of Defense, 12th Central Scientific Research Institute (Russian Federation)

2010-12-15

197

Calculation of thermal fluxes of plasma torch reradiation under the action of laser radiation on a condensed target  

NASA Astrophysics Data System (ADS)

The problem of laser deposition with allowance for thermal radiation transport inside and outside the laser torch is considered in a multigroup approximation. The energy fluxes of laser torch thermal radiation onto a target in the far and near zones are calculated as functions of time and the character of the exposure. It is shown that absorption of thermal fluxes in the substrate and target in the course of laser deposition results in their substantial heating. The possibility of diagnosing thermal radiation fluxes from the laser torch by using photodetectors is demonstrated.

Rudenko, V. V.

2010-12-01

198

Heat flux measurements for use in physiological and clothing research  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

199

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

200

Heat flux observations in the mesopause region above Haleakala  

Microsoft Academic Search

Horizontal and vertical heat fluxes between 85 and 100 km were computed using temperature and wind profiles observed on 21 October 1993 by the Na Wind\\/Temperature lidar operated at Haleakala during the ALOHA-93 Campaign. On this night a warm layer developed between 85 and 90 km. The temperature increased by almost 40 K near 88 km, reaching a maximum of

Xin Tao; Chester S. Gardner

1995-01-01

201

Preliminary Measurements of Heat Flux in a Subsonic Gun Simulator.  

National Technical Information Service (NTIS)

Preliminary measurements of heat flux have been obtained in a subsonic gun simulator with thin film resistance thermometry for an inert, single phase flow expanding behind a projectile from an initial pressure of 8 bars and resulting in an exit projectile...

A. F. Bicen M. Schmidt J. H. Whitelaw

1987-01-01

202

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

203

Measurement of a Surface Heat Flux and Temperature.  

National Technical Information Service (NTIS)

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. ...

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

1994-01-01

204

Measurement of a surface heat flux and temperature  

Microsoft Academic Search

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured

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

1994-01-01

205

Infrared missile domes: heat flux and thermal shock  

Microsoft Academic Search

Analytical expressions for the thermal shock resistance (TSR) of IR missile domes involve a phenomenological stress factor that is not yet available but can be either extracted from the results of aerothermal shock testing or estimated on the basis of model-related considerations. The primary purpose of this contribution is to derive a simple formula for the allowable heat flux at

Claude A. Klein

1993-01-01

206

Boundary heat flux estimation in quasi-static thermoelastic systems  

Microsoft Academic Search

The paper treats a heat flux estimation problem for a system that models the temperature evolution in a thermoelastic rod, which is allowed to come into contact with a rigid obstacle. The dynamics of the process are described by a nonlinear nonlocal PDE of parabolic type. Sensor configurations, which can provide measurements guaranteeing the problem to be uniquely solvable, and

Irina Sivergina; Michael P. Polis; Ilya V. Kolmanovsky

2005-01-01

207

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

Microsoft Academic Search

Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a

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

1994-01-01

208

Water and heat fluxes in desert soils 2. Numerical simulations  

Microsoft Academic Search

Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a

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

1994-01-01

209

Summary of Heat-Flux Sensor Calibration Data.  

National Technical Information Service (NTIS)

This paper presents a statistical evaluation of the responsivity data on a number of heat-flux sensors, calibrated using an electrical substitution radiometer as a transfer standard up to 5 W (cm.sup.-2). The sensors, furnished by the customers, were of c...

2005-01-01

210

A new critical heat flux correlation for boiling liquid metals  

Microsoft Academic Search

This paper reports on correlations for the dryout heat flux for sodium in tube and grid bundles that have been developed based on experimental results and analytical considerations. The main feature of these correlations is that they are derived from thermal, hydrodynamic, and geometrical parameters. These parameters are the subcooling, the inlet and outlet vapor quality, the mass flow rate,

H. M. Kottowski; C. Savatteri; W. Hufschmidt

1991-01-01

211

European development of prototypes for ITER high heat flux components  

Microsoft Academic Search

The extensive EU research and development, on international thermonuclear experimental reactor (ITER) high heat flux (HHF) components aims at the demonstration of prototypes for the divertor and baffle with challenging operating requirements. The recent progress of this development is summarised in the paper, particularly concerning the manufacture and testing of mock-ups and prototypes. The available results demonstrate the feasibility of

G Vieider; M Merola; F Anselmi; J. P Bonal; P Chappuis; G Dell'Orco; D Duglué; R Duwe; S Erskine; F Escourbiac; M Fèbvre; L Giancarli; M Grattarola; G LeMarois; H. D Pacher; A Pizzuto; L Plöchl; B Riccardi; M Rödig; J Schlosser; A Salito; B Schedler; C. H Wu

2000-01-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

213

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

214

Hawking Radiation and Hawking Flux from Spherical Reduction  

NASA Astrophysics Data System (ADS)

In view of the recent progress in 2D quantum gravity [1] from spherical reduction of Einstein gravity (SRG) it should be possible to also derive the correct radiative flux to infinity related to the Hawking temperature at the horizon [2] from the SRG action in D = 2. For minimally coupled scalars the correct result had been obtained a long time ago [3]. As shown first in [4] a calculation based only upon the conformal anomaly in the presence of dilaton fields leads to an unacceptable (negative) flux at infinity, requiring the addition of a nonconformally invariant piece to the effective action. A more recent calculation [5] of that anomaly disagreed with [4] and further conflicting results appeared in the literature [6, 7, 8, 9]. We (together with H. Liebl) have derived that anomaly for completely general nonminimal interaction of the scalar fields in D = 2 and for general dilaton dependent measure [8] and used the integration of the standard energy momentum conservation with Unruh vacuum at the horizon [2] to arrive at the same result for the flux as [4]. Our computation of the anomaly agreed with [6, 9, 10] in the case of SRG. After paper [11] our computation of the anomaly now is generally accepted (cf. e.g. [12]) Using the proper "extended" energy momentum conservation in the presence of dilaton interaction for matter and calculating the corresponding "dilaton anomaly" we were able to show [13] that the correct positive flux at infinity follows, completing earlier attempts in this direction [14]. Our computation was based upon a novel application of the heat kernel technique [15]. As a by-product, but not to be used in our argument, we also gave for the first time the full effective action in the presence of a dilaton field which couples arbitrarily to the scalar field and which enters in a general way in the quantum measure. This action extends the one for minimal coupling [16] to the most general case of a dilaton interaction in D = 2. Possible criticisms of our result [17, 18, 19] are discussed.

Kummer, W.; Vassilevich, D. V.

2002-12-01

215

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

Microsoft Academic Search

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

J. B. Haggard Jr.; J. B. Jr

1983-01-01

216

Simulation of induction heating process with radiative heat exchange  

Microsoft Academic Search

Purpose: Numerical modelling of induction heating process is a complex issue. It needs analysis of coupled electromagnetic and thermal fields. Calculation models for electromagnetic field analysis as well as thermal field analysis need simplifications. In case of thermal field calculations, correct modelling of radiative heat exchange between the heated charge and inductor's thermal insulation is essential. Most commercial calculation programs

A. Kachel; R. Przy?ucki

2007-01-01

217

Measurement of a surface heat flux and temperature  

NASA Astrophysics Data System (ADS)

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

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

1994-04-01

218

Mixed convection in ducts with asymmetric wall heat fluxes  

SciTech Connect

Results are presented of a numerical study dealing with combined free and forced laminar convection in a parallel plate vertical channel with asymmetric wall heating at uniform heat fluxes (UHF). The forced flow at the inlet is assumed to be spatially uniform and directed vertically upward. Quantitative information is provided pertaining to the effects of buoyancy and asymmetric heating on the hydrodynamic and thermal parameters. For values of Grashof number/Reynolds number up to 500 no flow reversal is predicted, in contrast to the case of uniform wall temperatures (UWT) recently reported. Other fundamental differences between UHF and UWT also are indicated.

Aung, Win (Howard Univ., Washington, DC (USA)); Worku, G. (Grove Engineering Inc., Gaithersburg, MD (USA))

1987-11-01

219

Maximum allowable heat flux for a submerged horizontal tube bundle  

SciTech Connect

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

McEligot, D.M.

1995-08-14

220

Downstream heat flux profile versus midplane T profile in tokamaks  

SciTech Connect

The relationship between the midplane scrape-off-layer (SOL) electron temperature profile and the parallel heat flux profile at the divertor in tokamaks is investigated. A model is applied that takes into account anisotropic thermal diffusion in rectilinear geometry with constant density. Eigenmode analysis is applied to the simplified problem with rectangular geometry and constant, but highly anisotropic, thermal diffusivities. A nonlinear solution is also 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, and geometry that includes a model for the divertor leg. 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 to the midplane temperature profile shape, is robustly described by the scaling of 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{sub paralleldiv} to T{sub mp}chi{sub parallelmp}/L{sub parallel} as predicted in that model. For realistic parameters, the peak in the heat flux, moreover, can be reduced by a factor of 2 or more relative to the two-point model scaling that 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 opportunities and caveats for data interpretation and possibly favorable outcomes for divertor configurations with extended field lines.

Goldston, Robert J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2010-01-15

221

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

National Technical Information Service (NTIS)

Cloud formation and its relation to climate change is the greatest weakness in current numerical climate models. Surface heat flux in some cases causes clouds to form and in other to dissipate and the differences between these cases are subtle enough to m...

W. Porch F. Barnes M. Buchwald W. Clements D. Cooper

1991-01-01

222

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

NASA Astrophysics Data System (ADS)

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

Lu, Jun

223

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

224

Robust Cooling of High Heat Fluxes Using Hybrid Loop Technology  

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

225

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

SciTech Connect

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

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

1996-07-01

226

Fluctuations of the heat-flux in turbulent convection  

NASA Astrophysics Data System (ADS)

We report measurements of the temporal fluctuations of the heat-flux in Rayleigh-Bénard turbulent convection. Although being a global quantity, i.e. spatially averaged on the flow field, we show that its probability density function (PDF) is non-gaussian and asymmetric. The ratio of the rms fluctuations of the heat flux to their mean display a power lax, Ra-? with ??0.25, on more than two decades in Rayleigh number (2 107< Ra A 10^9). Thus, the fluctuations are roughly proportional to the temperature difference. We discuss this law and we propose a simple mechanism to explain the non-gaussian character of the PDF. Nous présentons une étude expérimentale des fluctuations temporelles du flux de chaleur en convection turbulente de Rayleigh-Bénard. Bien que cette quantité soit globale, c'est-à-dire s'exprime comme une moyenne spatiale sur l'écoulement, nous montrons que ces fluctuations temporelles possèdent une loi de densité de probabilité non-gaussienne et asymétrique. Sur la gamme de nombres de Rayleigh explorée (2 107< Ra A 10^9), les fluctuations relatives du flux de chaleur décroissent suivant une loi de puissance en Ra-? avec ??0.25, ce qui signifie aussi que l'écart type des fluctuations du flux de chaleur est approximativement proportionnel à l'écart de température imposé. Nous discutons cette loi et présentons un mécanisme simple permettant d'expliquer le caractère non-gaussien des fluctuations.

Aumaître, S.; Fauve, S.

1999-06-01

227

Ionospheric heating for radiation-belt control  

SciTech Connect

Pitch-angle scattering interactions of electromagnetic waves in the ELF/VLF bands with trapped electrons, as formulated by Kennel and Petschek 1, describe the dynamics of the freshly filled radiation belts flux tubes. The natural existence of a slot region with electron fluxes below the Kennel-Petschek limit requires non-local wave sources. We describe a set of planned, active experiments in which VLF radiation will be injected from ground and space based transmitters in conjunction with the CRRES satellite in the radiation belts. These experiments will measure the intensity of waves driving pitch-angle diffusion and the electron energies in gyroresonance with the waves. An ability to reduce the flux of energetic particles trapped in the radiation belts by artificial means could improve the reliability of microelectronic components on earth-observing satellites in middle-altitude orbits.

Burke, W.J.; Villalon, E.

1990-10-01

228

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

229

Enhancement of the critical heat flux by using heat spreader  

Microsoft Academic Search

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon\\u000a liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper\\u000a coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the\\u000a critical heat

Yong-Sik Yoon; Hyup Yang; Ho-Young Kwak

2003-01-01

230

Indirect solar loading of waste heat radiators  

SciTech Connect

Waste heat from space based power systems must ultimately be radiated away into space. The local topology around the radiators must be considered from two stand-points: the scattering of sunlight onto the surfaces of the radiator and the heat load that the radiator may put on near-by components of the system. A view factor code (SNAP) developed at Los Alamos allows the computation of the steady-state radiation environment for complex 3-D geometries. An example of the code's utility is given. 4 refs., 2 figs., 1 tab.

Kirkpatrick, R.C.; Tabor, J.E.; Lindman, E.L.; Cooper, A.J.

1988-01-01

231

A note on vector flux models for radiation dose calculations.  

PubMed

This paper reviews and extends modelling of anisotropic fluxes for radiation belt protons to provide closed-form equations for vector proton fluxes and proton flux anisotropy in terms of standard omnidirectional flux models. These equations provide a flexible alternative to the data-based vector flux models currently available. At higher energies, anisotropy of trapped proton flux in the upper atmosphere depends strongly on the variation of atmospheric density with altitude. Calculations of proton flux anisotropies using present models require specification of the average atmospheric density along trapped particle trajectories and its variation with mirror point altitude. For an isothermal atmosphere, calculations show that in a dipole magnetic field, the scale height of this trajectory-averaged density closely approximates the scale height of the atmosphere at the mirror point of the trapped particle. However, for the earth's magnetic field, the altitudes of mirror points vary for protons drifting in longitude. This results in a small increase in longitude-averaged scale heights compared to the atmospheric scale heights at minimum mirror point altitudes. The trajectory-averaged scale heights are increased by about 10-20% over scale heights from standard atmosphere models for protons mirroring at altitudes less than 500 km in the South Atlantic Anomaly. Atmospheric losses of protons in the geomagnetic field minimum in the South Atlantic Anomaly control proton flux anisotropies of interest for radiation studies in low earth orbit. Standard atmosphere models provide corrections for diurnal, seasonal and solar activity-driven variations. Thus, determination of an "equilibrium" model of trapped proton fluxes of a given energy requires using a scale height that is time-averaged over the lifetime of the protons. The trajectory-averaged atmospheric densities calculated here lead to estimates for trapped proton lifetimes. These lifetimes provide appropriate time-averaging intervals for equilibrium models of trapped proton fluxes. PMID:11538012

Kern, J W

1994-01-01

232

Sensible and latent heat flux predictions using conditional sampling methods  

NASA Astrophysics Data System (ADS)

The conditional sampling formulation typically used in eddy accumulation flux measurements was tested at two sites using velocity, temperature, and specific humidity time series measurements. The first site was at Owen's Lake in southern California, and the second site was an irrigated bare soil field at the Campbell Tract facility in Davis, California. The constant ? relating the turbulent flux to the accumulated concentration difference between updrafts and downdrafts was related to the statistics of the vertical velocity. It was found that this formulation for ? reproduces the extreme fluxes (both sensible and latent heat) better than previous ? formulations. The overall comparison between eddy correlation measured fluxes and conditional sampling predicted fluxes for a wide range of atmospheric stability conditions was excellent (R2 = 0.97). On average, the mean ? obtained from our experiments for temperature and water vapor is in good agreement (±4%) with other reported ? values for carbon dioxide, water vapor, ozone, and temperature. These results suggest that the conditional sampling formulation used in eddy accumulation methods is useful for routine flux measurements of passive greenhouse gases.

Katul, Gabriel; Albertson, John; Chu, Chia-Ren; Parlange, Marc; Stricker, Han; Tyler, Scott

1994-11-01

233

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

234

Skyglow effects in UV and visible spectra: radiative fluxes.  

PubMed

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

Kocifaj, Miroslav; Solano Lamphar, H A

2013-06-21

235

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

236

Critical heat flux of subcooled flow boiling in swirl tubes relevant to high-heat-flux components  

SciTech Connect

It is necessary to accurately determine the critical heat flux (CHF) of cooling systems used in fusion reactors. Currently, sufficiently accurate CHF correlations for one-sided heating have not been established. A design method for subcooled boiling cooling systems using swirl tubes is described. From a review of existing work under uniform heating conditions, the correlations of Gunther and Nariai-Inasaka are recommended for smooth and swirl flow, respectively. The effects of thermal conductivity and geometry of the cooling sections on both the nouniformity factor and the peaking factor were investigated by solving a heat conduction equation. For swirl flow under one-sided heating, the CHF multiplier increases with the increasing nonuniformity factor. Design criteria for subcooled boiling swirl-tube cooling systems are presented. 33 refs., 13 figs., 4 tabs.

Inasaka, Fujio [Ship Research Inst., Tokyo (Japan); Nariai, Hideki [Univ. of Tsukuba, Ibaraki (Japan)

1996-07-01

237

Heat Flux Estimation at Heat Sources of Machine Tools by Solving Inverse Problems  

Microsoft Academic Search

An increase in frictional heat due to the increase in rotational speed and feed rate causes thermal deformation of machine tools, resulting in a decrease in machining accuracy. To establish a method for reducing thermally induced machining errors of machine tools, a method has been proposed to estimate the heat flux acting upon a machine tool body by solving inverse

Kazutake Uehara; Fumio Obata

2010-01-01

238

Heat transfer measurements in metal foam subjected to constant heat flux  

Microsoft Academic Search

The use of open-cell metal foam in numerous technologies is increasing rapidly. Heat transfer measurements inside rectangular blocks of commercially available aluminum foam subjected to constant heat flux at one side are presented. Cases for different pore velocities, porosities and pore densities of the foam are given. Each foam block is cooled by a confined stream of ambient air. The

Nihad Dukhan; Kuan-Chih Chen

2007-01-01

239

The 2007 Bering Strait oceanic heat flux and anomalous Arctic sea-ice retreat  

NASA Astrophysics Data System (ADS)

To illuminate the role of Pacific Waters in the 2007 Arctic sea-ice retreat, we use observational data to estimate Bering Strait volume and heat transports from 1991 to 2007. In 2007, both annual mean transport and temperatures are at record-length highs. Heat fluxes increase from 2001 to a 2007 maximum, 5-6 × 1020 J/yr. This is twice the 2001 heat flux, comparable to the annual shortwave radiative flux into the Chukchi Sea, and enough to melt 1/3rd of the 2007 seasonal Arctic sea-ice loss. We suggest the Bering Strait inflow influences sea-ice by providing a trigger for the onset of solar-driven melt, a conduit for oceanic heat into the Arctic, and (due to long transit times) a subsurface heat source within the Arctic in winter. The substantial interannual variability reflects temperature and transport changes, the latter (especially recently) being significantly affected by variability (> 0.2 Sv equivalent) in the Pacific-Arctic pressure-head driving the flow.

Woodgate, Rebecca A.; Weingartner, Tom; Lindsay, Ron

2010-01-01

240

Method of fission heat flux determination from experimental data  

DOEpatents

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

Paxton, Frank A. (Schenectady, NY)

1999-01-01

241

Heat flux vector in highly inhomogeneous nonequilibrium fluids  

NASA Astrophysics Data System (ADS)

We develop a simple, efficient, and general statistical mechanical technique, based upon the previously developed method of planes (MOP) technique of calculating the pressure tensor, in order to calculate the heat flux vector of an atomic fluid. The method is applied to the case of Poiseuille flow through a narrow channel and is compared to the corresponding Irving-Kirkwood heat flux vector, using the first approximation (IK1). Our exact MOP method is shown to be more efficient than the approximate IK1 approach. Additionally, for the special case of planar Poiseuille flow, we derive an alternative mesoscopic expression by integrating the energy continuity equation. This mesoscopic calculation is shown to be extremely efficient and is in excellent numerical agreement with the MOP.

Todd, B. D.; Daivis, Peter J.; Evans, Denis J.

1995-05-01

242

Phase-controlled superconducting heat-flux quantum modulator  

NASA Astrophysics Data System (ADS)

We theoretically put forward the concept of a phase-controlled superconducting heat-flux quantum modulator. Its operation relies on phase-dependent heat current predicted to occur in temperature-biased Josephson tunnel junctions. The device behavior is investigated as a function of temperature bias across the junctions, bath temperature, and junctions asymmetry as well. In a realistic Al-based setup the structure could provide temperature modulation amplitudes up to ~50 mK with flux-to-temperature transfer coefficients exceeding ~125 mK/?0 below 1 K, and temperature modulation frequency of the order of a few MHz. The proposed structure appears as a promising building-block for the implementation of caloritronic devices operating at cryogenic temperatures.

Giazotto, F.; Martínez-Pérez, M. J.

2012-09-01

243

Equivalence of a magnetohydrodynamic fluid and a viscous fluid with heat flux  

SciTech Connect

In this paper the equivalence between a perfect fluid with electromagnetic field and a viscous fluid with heat flux is considered. Heat flux, shear tensor, and other fluid parameters are readily calculated out of the magnetohydrodynamic fluid parameters.

Maiti, S.R.; Das, S.N.

1985-11-01

244

A new critical heat flux correlation for boiling liquid metals  

SciTech Connect

This paper reports on correlations for the dryout heat flux for sodium in tube and grid bundles that have been developed based on experimental results and analytical considerations. The main feature of these correlations is that they are derived from thermal, hydrodynamic, and geometrical parameters. These parameters are the subcooling, the inlet and outlet vapor quality, the mass flow rate, the latent heat of vaporization, and the aspect ratio. The correlation proposed for tube geometries is developed from a data base of 170 data points compiled from 11 sources, and the correlation for flow through rod bundles is derived from the results of 13 tests.

Kottowski, H.M.; Savatteri, C.; Hufschmidt, W. (Commission of the European Communities, Joint Research Center, Ispra Establishment, 21020 Ispra (IT))

1991-08-01

245

Infrared missile domes: heat flux and thermal shock  

NASA Astrophysics Data System (ADS)

Analytical expressions for the thermal shock resistance (TSR) of IR missile domes involve a phenomenological stress factor that is not yet available but can be either extracted from the results of aerothermal shock testing or estimated on the basis of model-related considerations. The primary purpose of this contribution is to derive a simple formula for the allowable heat flux at the stagnation point, under conditions such that the boundary-layer flow remains laminar over the entire dome surface.

Klein, Claude A.

1993-11-01

246

CRITICAL HEAT FLUX OF SANTOWAX R IN FORCED CONVECTION  

Microsoft Academic Search

The critical heat flux of Santowax R was measured for upfiow in a 0.344-; in. ID vertical tube as a function of velocity, subcooling, and pressure over ; the following ranges: V=4to 17 ft\\/sec, P = 30 to 150 psia, DELTA T\\/sub\\/ = 130to ; 280 deg F, and T\\/bulk\\/= 590 to 850 deg F. The data were correlated by

1962-01-01

247

Ion Viscous Heating and the Destruction of Magnetic Flux  

SciTech Connect

Further work on ion heating through viscous dissipation of vorticity generated by short wavelength m=0 instabilities is reported. Both heavy tungsten wire arrays and light stainless steel arrays are considered, the latter leading to record ion temperatures in the 200-300keV range. The problem of magnetic flux destruction is addressed, and this is solved by a reversible mechanism involving axially asymmetric m=0 hot spots on the axis.

Haines, M.G. [Blackett Laboratory, Imperial College, London (United Kingdom)

2006-01-05

248

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

SciTech Connect

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

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

1994-09-01

249

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

Microsoft Academic Search

High-heat-flux experiments on three types of helium-cooled divertor mock-ups were performed on the 30-kW electron beam test system and its associated helium flow loop at Sandia National Laboratories. A dispersion-strengthened copper alloy (DSCu) was used in the manufacture of all the mock-ups. The first heat exchanger provides for enhanced heat transfer at relatively low flow rates and much reduced pumping

D. L. Youchison; M. G. Izenson; C. B. Baxi; J. H. Rosenfeld

1996-01-01

250

Specific heat capacities of pure triglycerides by heat-flux differential scanning calorimetry  

Microsoft Academic Search

The specific heat capacities of some triglycerides commonly found in palm oil were determined with a heat-flux differential\\u000a scanning calorimeter. The specific heat capacity measurements were made under the optimum operating conditions determined\\u000a earlier: scan rate 17 deg·min?1, sample mass 21 mg and purge gas (nitrogen) flow rate 50 ml\\/min. Pure triglycerides (four simple and four mixed) were used\\u000a in

N. A. Morad; M. Idrees; A. A. Hasan

1995-01-01

251

Use of heat flux sensors for studying local heat transfer in pipes  

Microsoft Academic Search

Local heat transfer in the flow of air in a circular pipe 36 mm in diameter and 2000 mm in length was measured with single heat flux sensors and with a battery of such sensors. Data reveal an intensity of local heat transfer in the region of developed flow at Reynolds numbers in the range 10,000-120,000, length-to-diameter ratios above 50,

V. M. Legkii; O. A. Gerashchenko; V. D. Burlei

1978-01-01

252

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

SciTech Connect

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

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

1994-01-28

253

Hydrodynamics and heat transfer in swirl flow under conditions of one-side heating. Part 2: Boiling heat transfer. Critical heat fluxes  

Microsoft Academic Search

The paper gives the basic results of experimental investigation of boiling heat transfer in heat-absorbing devices of the ITER thermonuclear reactor, which are subjected to one-side heating. The experimental data on heat transfer at nucleate and film boiling and on critical heat fluxes are obtained in the following range of parameters of water flow: pressure p=0.7–2.0MPa, mass flux G=340–25000kg\\/(m2s), and

Aleksey V. Dedov; Alexander T. Komov; Alexander N. Varava; Victor V. Yagov

2010-01-01

254

Saturated critical heat flux in a multi-microchannel heat sink fed by a split flow system  

Microsoft Academic Search

An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199 m wide and 756 m deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented

A. W. Mauro; D. Toto; J. R. Thome; G. P. Vanoli

2010-01-01

255

Maximal near-field radiative heat transfer between two plates  

NASA Astrophysics Data System (ADS)

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

256

Radiative flux calculations at UV and visible wavelengths  

SciTech Connect

A radiative transfer model to calculate the short wavelength fluxes at altitudes between 0 and 80 km has been developed at LLNL. The wavelength range extends from 175--735 nm. This spectral range covers the UV-B wavelength region, 250--350 nm, with sufficient resolution to allow comparison of UV-B measurements with theoretical predictions. Validation studies for the model have been made for both UV-B ground radiation calculations and tropospheric solar radiative forcing calculations for various ozone distributions. These studies indicate that the model produces results which agree well with respect to existing UV calculations from other published models.

Grossman, A.S.; Grant, K.E.; Wuebbles, D.J.

1993-10-01

257

Reynolds stress and heat flux in spherical shell convection  

NASA Astrophysics Data System (ADS)

Context. Turbulent fluxes of angular momentum and enthalpy or heat due to rotationally affected convection play a key role in determining differential rotation of stars. Their dependence on latitude and depth has been determined in the past from convection simulations in Cartesian or spherical simulations. Here we perform a systematic comparison between the two geometries as a function of the rotation rate. Aims: Here we want to extend the earlier studies by using spherical wedges to obtain turbulent angular momentum and heat transport as functions of the rotation rate from stratified convection. We compare results from spherical and Cartesian models in the same parameter regime in order to study whether restricted geometry introduces artefacts into the results. In particular, we want to clarify whether the sharp equatorial profile of the horizontal Reynolds stress found in earlier Cartesian models is also reproduced in spherical geometry. Methods: We employ direct numerical simulations of turbulent convection in spherical and Cartesian geometries. In order to alleviate the computational cost in the spherical runs, and to reach as high spatial resolution as possible, we model only parts of the latitude and longitude. The rotational influence, measured by the Coriolis number or inverse Rossby number, is varied from zero to roughly seven, which is the regime that is likely to be realised in the solar convection zone. Cartesian simulations are performed in overlapping parameter regimes. Results: For slow rotation we find that the radial and latitudinal turbulent angular momentum fluxes are directed inward and equatorward, respectively. In the rapid rotation regime the radial flux changes sign in accordance with earlier numerical results, but in contradiction with theory. The latitudinal flux remains mostly equatorward and develops a maximum close to the equator. In Cartesian simulations this peak can be explained by the strong "banana cells". Their effect in the spherical case does not appear to be as large. The latitudinal heat flux is mostly equatorward for slow rotation but changes sign for rapid rotation. Longitudinal heat flux is always in the retrograde direction. The rotation profiles vary from anti-solar (slow equator) for slow and intermediate rotation to solar-like (fast equator) for rapid rotation. The solar-like profiles are dominated by the Taylor-Proudman balance. Movies and Appendix A are available in electronic form at http://www.aanda.org

Käpylä, P. J.; Mantere, M. J.; Guerrero, G.; Brandenburg, A.; Chatterjee, P.

2011-07-01

258

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

NASA Astrophysics Data System (ADS)

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

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

1994-03-01

259

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

260

Radiative heat transfer in plastic welding process  

NASA Astrophysics Data System (ADS)

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

Kurosaki, Yasuo

2005-06-01

261

Prediction of critical heat flux for flow boiling in subcooled and saturated regimes  

Microsoft Academic Search

A systematic investigation on the effect of major variables on critical heat flux in forced convection of flow boiling was carried out using available world data for water in a vertical round tube. A new correlation was developed to predict the critical heat flux in both subcooled boiling and saturated boiling regimes. The correlation relates critical heat flux to only

Zhijian Deng

1998-01-01

262

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

Microsoft Academic Search

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

Robert D. Watson

1993-01-01

263

Prediction of critical heat flux for annular flow in vertical pipes  

Microsoft Academic Search

A semiempirical model for adiabatic two phase annular flow is extended to predict critical heat flux in a vertical pipe for conditions of interest to boiling water reactors. The model exhibits a sharply declining curve of critical heat flux versus steam quality at low steam qualities where it is relatively independent of heat flux distribution. In this region, vaporization of

S. Levy; J. M. Healzer; D. Abdollahian

1980-01-01

264

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

265

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

Microsoft Academic Search

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

J. Quintiere; K. Bromberg

1975-01-01

266

Aram Chaos and its constraints on the surface heat flux of Mars  

Microsoft Academic Search

The surface heat flux of a planet is an important parameter to characterize its internal activity and to determine its thermal evolution. Here we report on a new method to constrain the surface heat flux of Mars during the Hesperian. For this, we explore the consequences for the martian surface heat flux from a recently presented new hypothesis for the

Sandra Schumacher; Tanja E. Zegers

2011-01-01

267

Greenhouse Micrometeorology and Estimation of Heat and Water Vapour Fluxes  

Microsoft Academic Search

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

Xiusheng Yang

1995-01-01

268

An application of the maximum entropy production principle in modeling heat fluxes over land surfaces  

NASA Astrophysics Data System (ADS)

A model of evaporation, sensible and ground heat fluxes over land surfaces is proposed based on the theory of maximum entropy production (MEP). A key element of the proposed MEP model is the formulation of a dissipation (or entropy production) function, whose extremization under the constraint of conservation of energy leads to a unique partition of net radiation into latent, sensible and ground heat fluxes. The solutions are functions of surface soil temperature, surface specific humidity (or its equivalents such as soil wetness) and net radiation. The MEP model predicts that surface heat fluxes vary monotonically and smoothly with soil wetness ranging from dry to saturation. The MEP model of transpiration over vegetated surfaces is shown to be a special case of non-vegetated surfaces. A test of the MEP model using field observations indicates that the model performs well under all soil moisture conditions and no-water-stress canopy. The proposed MEP model is an effective tool in modeling the energy budget over a land surface due to its unique features: (1) the model is built on the state-of-the-art non-equilibrium thermodynamics, (2) the model only needs input of surface variables (i.e. temperature, humidity or its equivalents, and net radiation), (3) the model covers the entire range of water states from dryness to saturation, (4) all model parameters are either physical properties of the system or universal empirical coefficients, and (5) the model formulation allows a unique solution of the fluxes with reduced sensitivity to the uncertainties in the model parameters.

Wang, Jingfeng; Bras, Rafael L.

2012-05-01

269

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

270

Infrared Radiative Heat Transfer in Nongray Gases.  

National Technical Information Service (NTIS)

The object of this investigation was to study various approximate methods of analyzing infrared radiative heat transfer in nongray nonisothermal gases. For this purpose, a very simple physical system was chosen consisting of a gas bounded by two infinite ...

R. D. Cess P. Mighdoll S. N. Tiwari

1967-01-01

271

Spectral scaling of heat fluxes in streambed sediments  

NASA Astrophysics Data System (ADS)

Advancing our predictive capabilities of heat fluxes in streams and rivers is important because of the effects on ecology and the general use of heat fluxes as analogues for solute transport. Along these lines, we derived a closed-form solution that relates the in-stream temperature spectra to the responding temperature spectra at various depths in the sediment through a physical scaling factor including the effective thermal diffusivity and the Darcy flow velocity. This analysis considers the range of frequencies in temperature fluctuations that occur due to diurnal and meteorological variation both in the long and short term. This approach provides insight regarding the key frequencies for analysing temperature responses at different depths within the sediment and also provides a simple and accurate method that offers quantitative insight into heat transport and surface water interactions with groundwater. We demonstrate for Säva Brook, Sweden, how the values of effective thermal diffusivities can be estimated based on the observed in-stream and sediment temperature time series and explain the temporal scaling of the heat transport as a function of a dimensionless frequency number. We find that the lower limit of periods of significance for the analysis increases with depth, and we recommend further research regarding appropriate frequency windows.

Wörman, A.; Riml, J.; Schmadel, N.; Neilson, B. T.; Bottacin-Busolin, A.; Heavilin, J. E.

2012-12-01

272

Performance characterization of an internally cooled window in a nonuniform high-heat-flux environment  

NASA Astrophysics Data System (ADS)

The performance of an internally cooled silicon window in a high heat flux environment has been characterized in the laboratory. The article under test was convectively/radiatively heated with a large-area-flame oxy- acetylene torch, and cooled by circulating water through internal channels. Heating rates ranging from 5 to 120 W/cm2 were achieved over the surface of the window and generated thermal gradients in the window that exceeded flight levels by an order of magnitude. This gave us a measure of window performance under stressing conditions. Thirty one heating tests were conducted to measure the thermal and optical efficiency of the windows. The degree of surface temperature uniformity was derived from midwave infrared images of the test window surface collected on a two- dimensional array, InSb camera. Optical wavefront distortion was measured with an infrared shearing interferometer. Data was collected on both a video tape recorder and a digital data acquisition system before, during, and after the period of window heating. Experimental data on two windows along with theoretical predictions are presented in this paper. The theoretical code took a given heat flux distribution into the window and predicted the surface temperature distribution, and the change in the window dimensions and index of refraction. Experimental data and theoretical predictions compared well.

Kalin, David A.; Brooks, Lori C.; Wojciechowski, Carl J.; Jones, Gregory W.

1997-06-01

273

Flux-limited heat flow in a double plasma device  

NASA Astrophysics Data System (ADS)

Electron heat flow has been studied in a double plasma device. Electrons of mean energies 5.1 eV and 2.3 eV were separated by a grid which was then pulsed to create a thermal wave moving in a large temperature gradient. Changes in the electrons' velocity distribution, concentration and energy agreed qualitatively with a simple theory based on transport in neutral gases. Thermoelectric effects reduced the heat flow by a factor of 5. This factor combined with the theory suggests a flux-limiting parameter with an upper limit of 0.15 for laser fusion. This value lies within the range found in experiments on plasma heated by lasers.

Moore, P. A. C.

1981-08-01

274

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

Microsoft Academic Search

A radial flux limit of 147 W\\/sq cm at the wetted inner tube wall has been demonstrated with a Nb-1 percent Zr\\/K heat pipe, a flux 5 times greater than the previously accepted safe design level of 25 to 30 W\\/sq cm. The wick structure was an annular gap type fabricated from 100 times 100 mesh Nb-1 percent Zr screen.

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

1989-01-01

275

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

276

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; Ilas, Germina [ORNL

2012-01-01

277

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

278

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

279

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

280

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-01-01

281

Boundary layer structure over areas of heterogeneous heat fluxes  

SciTech Connect

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

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

1993-04-01

282

Radiative MHD simulation of an Emerging Flux Region  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

283

Composite material heat pipe radiator  

Microsoft Academic Search

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness

Nelson J. Gernert; David B. Sarraf; Richard J. Guenther

1996-01-01

284

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

SciTech Connect

Critical heat flux (CHF) experiments were performed in the Steam Generator Test Facility (SGTF) at Argonne National Laboratory for application to liquid metal fast breeder reactor steam generators. The test section consisted of a single, straight, vertical, fullscale LMFBR steam generator tube with force-circulated water boiling upwards inside the tube heated by sodium flowing countercurrent in a surrounding annulus. The test section tube parameters were as follows: 10.1 mm i.d., 15.9 mm o.d., material = 2 1/4 Cr-1 Mo of 7.0 to steel, and 13.1 m heated length. Experiments were performed in the water pressure range of 7.0 to 15.3 MPa and the water mass flux range of 720 to 3200 kg/m/sup 2/xs. The data exhibited two trends: heat flux independent and heat flux dependent. Empirical correlation equations were developed from over 400 CHF tests performed in the SGTF. The data and correlation equations were compared to the results of other CHF investigations.

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

1981-02-01

285

Effects of the soil heat flux estimates on surface energy balance closure over a semi-arid grassland  

NASA Astrophysics Data System (ADS)

Soil heat flux is important for surface energy balance (SEB), and inaccurate estimation of soil heat flux often leads to surface energy imbalance. In this paper, by using observations of surface radiation fluxes and soil temperature gradients at a semi-arid grassland in Xilingguole, Inner Mongolia, China from June to September 2008, the characters of the SEB for the semi-arid grassland were analyzed. Firstly, monthly averaged diurnal variations of SEB components were revealed. A 30-min forward phase displacement of soil heat flux ( G) observed by a fluxplate at the depth of 5-cm below the soil surface was conducted and its effect on the SEB was studied. Secondly, the surface soil heat flux ( G s) was computed by using harmonic analysis and the effect of the soil heat storage between the surface and the fluxplate on the SEB was examined. The results show that with the 30-min forward phase displacement of observed G, the slope of the ordinary linear regression (OLR) of turbulent fluxes ( H+LE) against available energy ( R n- G) increased from 0.835 to 0.842, i.e., the closure ratio of SEB increased by 0.7%, yet energy imclosure of 15.8% still existed in the SEB. When G s, instead of G was used in the SEB equation, the slope of corresponding OLR of ( H+LE) against ( R n- G s) reached 0.979, thereby the imclosure ratio of SEB was reduced to only 2.1%.

Yue, Ping; Zhang, Qiang; Niu, Shengjie; Cheng, Hua; Wang, Xiyu

2011-12-01

286

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

287

Composite material heat pipe radiator  

SciTech Connect

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness (0.076 mm). The thin liner transitioned to heavier-walled ends which allowed the tubing to be sealed using conventional welding. More specifically, the heat pipe was 1.14 m long, 24 mm in diameter and had a mass of 0.165 kg. Water was the working fluid. The heat pipe was tested in a Thermacore thermal vacuum chamber under hot and cold wall operating conditions. The heat load dissipated ranged from 10 to 60 watts. Heat pipe operating temperatures varied from 278 K to 403 K. After testing, the heat pipe was delivered to NASA JSC where future thermal vacuum chamber tests are planned. {copyright} {ital 1996 American Institute of Physics.}

Gernert, N.J.; Sarraf, D.B. [Thermacore, Inc., 780 Eden Road, Lancaster, Pennsylvania 17601 (United States); Guenther, R.J. [Battelle, Pacific Northwest Laboratories, Richland, Washington 99352 (United States); Hurlbert/, K.M. [NASA Johnson Space Center, 2101 NASA Road, 1 Houston, Texas 77058-3696 (United States); EC3

1996-03-01

288

Initiation of flux jump in SC composite by heat pulse  

SciTech Connect

Nonisothermal diffusion of magnetic flux after heat pulse shot on the surface of SC composite has been studied numerically taking into account smoothed transition characteristic of the superconductor. It is shown that for SC composite with poor stabilization the current and heat redistribution changes significantly the estimations of stability used on steady state functions of heat generation and heat transfer. The critical pulsed energy strongly depends on initial current distribution over the conductor cross section and the energy may be much less for a conductor with growing current than for a conductor with the same current in steady state. It has been found that undercritical heat pulses only slightly affect current density profile but stability increases as time delay increases between the current input halt and the pulse shot. It has been found that for a SC composite with poor stabilization the transversal thermal conductivity is more important than electrical resistivity of the matrix from the stability standpoint. The critical energy decreases when the thickness of SC filaments increases and this may explain unstable behaviour of the wires with thick filaments.

Klimenko, E.Y.; Martovetaky, N.N.

1989-03-01

289

Critical heat flux correlation through the alternating conditional expectation algorithm  

SciTech Connect

Because most critical heat flux (CHF) correlations have specific ranges of application, lookup table techniques and artificial neural networks have been recently used to predict CHF for a broad range of variables. In this paper, the alternating conditional expectation (ACE) algorithm is used to generate a new CHF correlation applicable to a wide range of forced convective boiling parameters. As a generalized regression tool, the ACE algorithm does not require an initial guess for the functional form, and it guarantees the convergence of the solution.

Han Gon Kim; Lee, J.C. [Univ. of Michigan, Ann Arbor, MI (United States)

1996-12-31

290

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

291

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

292

Magnetohydrodynamic natural convection flow on a sphere with uniform heat flux in presence of heat generation  

Microsoft Academic Search

Summary  Magnetohydrodynamic natural convection boundary layer flow on a sphere with uniform heat flux in presence of heat generation\\u000a has been investigated in this paper. The governing boundary layer equations are transformed into a non-dimensional form and\\u000a the resulting nonlinear system of partial differential equations is then solved numerically by two distinct efficient methods,\\u000a namely (i) implicit finite difference method together

M. M. Molla; M. A. Hossain; M. A. Taher

2006-01-01

293

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

294

Generation of Toa Radiative Fluxes From The Gerb Instruments  

NASA Astrophysics Data System (ADS)

The first Meteosat Second Generation (MSG) satellite is planned to be launched in summer 2002. This EUMETSAT's satellite will carry 2 new instruments on a geo- stationary orbit: the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the Geostationary Earth Radiation Budget (GERB). The unique feature of GERB in comparison with previous measurements of the Earth's radiation budget (e.g. ERBE, ScaRab and CERES experiments) is the high temporal sampling afforded by the geo- stationary orbit, albeit for a limited region of the globe. The GERB will provide ac- curate broadband measurements of the radiant energy due to the reflection of the in- coming solar energy by the Earth-atmosphere system and due to the thermal emission within this system. The synergetic use of the SEVIRI data is needed to convert these directional measurements (radiances) into radiative fluxes at the top-of-atmosphere. Additionally, the SEVIRI data allows the enhancement of the spatial resolution of the GERB measurement. This contribution describes the near real-time GERB processing system that has been set up at RMIB. This includes the unfiltering of the instrument data, the radiance-to-flux conversion and the spatial resolution enhancement. The ex- pected accuracy on the resulting fluxes and their foreseen applications are also pre- sented.

Clerbaux, N.; Bertrand, C.; Dewitte, S.; Ipe, A.; Gonzalez, L.; Nicula, B.

295

Heat storage and energy balance fluxes for a temperate deciduous forest  

Microsoft Academic Search

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

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

2004-01-01

296

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

SciTech Connect

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

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

2008-09-22

297

[Characteristics and simulation of heat and CO2 fluxes over a typical cropland during the winter wheat growing in the North China Plain].  

PubMed

In order to study the surface energy budget of the cropland in North China Plain, this paper discussed the characteristics of heat and CO2 fluxes of the cropland during the winter wheat growing, and then simulated the dynamic change of the flux of heat and carbon by SiB2 (simple biosphere model Version2) based on the observational data from 2005-10-10 to 2006-06-10 of Weishan experimental station. The results showed that the heat and CO2 fluxes put up obvious inter-daily variations in the course of the wheat growing and their maximum appeared at around midday. The diurnal variations of them are obvious too, and the net radiation, latent heat flux and the heat flux of underlaying surface during the winter were minimum while they were maximum in the anthesis and maturation of wheat; and the sensible heat flux during the winter was maximum and it was minimum in the shooting and heading period of wheat; while the CO2 flux during the shooting and heading period of wheat was the maximum and it was minimum during the winter. Finally, SiB2 model was used to simulate the heat and CO2 fluxes and the surface temperature based on the data of Weishan observation station and the results showed that the model was good at simulating, the simulated net radiation, latent heat flux, sensible heat flux, the heat flux of underlaying surface, CO2 flux and surface temperature were shown to be basically in agreement with observations with their square of related coefficient being 0.985, 0.637, 0.481, 0.725, 0.499 and 0.877 respectively. In addition, the average simulated value of net radiation, latent heat flux and the heat flux of underlaying surface were lower than the observed value and others were higher than the observed ones. In addition, the fluxes and surface temperature were simulated by SiB2 in the different stages of winter wheat and the results showed that the accuracy of the model in the shooting and heading period of wheat was better than the other two stages and the leaf area index was sensitive to the model. PMID:20329514

Yuan, Zai-Jian; Shen, Yan-Jun; Chu, Ying-Min; Qi, Yong-Qing

2010-01-01

298

The function estimation in predicting heat flux of pin fins with variable heat transfer coefficients  

Microsoft Academic Search

This article solves the two dimensional inverse problem of estimating the unknown heat flux at a pin fin base by the conjugate gradient method. In the estimating processes, no prior information on the functional form of the unknown quantity is required. The accuracy of the inverse analysis is examined by simulated exact and inexact measurements of temperature at interior locations

Haw-Long Lee; Huann-Ming Chou; Yu-Ching Yang

2004-01-01

299

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

300

Fluxes of Heat and Vapor in the Lower Atmosphere Derived from Aircraft Observations  

Microsoft Academic Search

Measurements from aircraft of temperature, mixing ratio and vertical air velocity have been corrected on the basis of zero flux of mass through the flight path to yield fluxes of heat and water vapor at different levels in the lower atmosphere. A detailed examination of these fluxes indicates that most of the heat is carried by eddies much smaller than

J. W. Telford; J. Warner

1964-01-01

301

Determination of regional distributions and seasonal variations of land surface heat fluxes from Landsat-7 Enhanced Thematic Mapper data over the central Tibetan Plateau area  

NASA Astrophysics Data System (ADS)

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 CAMP/Tibet, which located at the central Tibetan Plateau. Two scenes of Landsat-7 ETM data were used in this study. The scene of 9 June 2002 was selected as a case of summer, and the scene of 2 December 2002 was selected as a case of winter. To validate the proposed methodology, the ground-measured surface reflectance, surface temperature, net radiation flux, soil heat flux, sensible heat flux and latent heat flux are compared to Landsat-7 ETM derived values. The results show that the derived surface variables and land surface heat fluxes in two different months over the study area are in good accordance with the land surface status. These parameters show a wide range due to the strong contrast of surface features. Also, the estimated land surface variables and land surface heat fluxes are in good agreement with ground measurements, and all their absolute percent difference is less than 9.9% in the validation sites. It is therefore concluded that the proposed methodology is successful for the retrieval of land surface variables and land surface heat fluxes using the Landsat-7 ETM data and filed observations over the study area.

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

2006-05-01

302

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

PubMed

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

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

2009-11-01

303

Glacier winds and parameterisation of the related surface heat fluxes  

NASA Astrophysics Data System (ADS)

The katabatic flow over glaciers is studied with data from automatic weather stations (AWS). We analyse data from the Morteratschgletscher (Switzerland), Vatnajökull (Iceland) and West Greenland, and conclude that katabatic flow is very common over melting glacier surfaces and rarely disrupted by the large-scale flow. Over small and medium-size glaciers the height of the wind maximum is generally low (typically 10 m), and vertical temperature differences near the surface are very large (up to 15 K over 4 m). In glacier mass-balance models there is a great need for parameterisations of the surface heat flux. We develop a simple method to estimate the sensible heat flux Fh associated with the glacier wind. It is based on the classical Prandtl model for slope flows. We set the turbulent exchange coefficient proportional to the maximum wind speed (velocity scale) and the height of the wind maximum (length scale). The resulting theory shows that Fh increases quadratically with the temperature difference between the surface and the ambient atmosphere; Fh decreases with the square root of the potential temperature gradient of the ambient atmosphere; and Fh is independent of the surface slope.

Oerlemans, J.; Grisogono, B.

2002-10-01

304

a Parameterization of Mesoscale Heat Fluxes for General Circulation Models  

NASA Astrophysics Data System (ADS)

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

Lynn, Barry Hugh

305

Evaluation of momentum and sensible heat fluxes in constant density coordinates: Application to superpressure balloon data during the VORCORE campaign  

NASA Astrophysics Data System (ADS)

Expressions for momentum and heat fluxes using density as the vertical coordinate are derived. These are applied in the evaluation of fluxes using data from super-pressure balloons drifting on constant density surfaces in the Antarctic lower stratosphere during the VORCORE campaign (September 2005 to February 2006). We focus on the core months of October and November. Vertical fluxes of zonal and meridional momentum are calculated using wind, pressure and height data and the vertical flux of sensible heat is calculated using temperature and height data. Calculations were performed in three band passes covering 1-13 h. We find that the largest fluxes are in the vicinity of the Antarctic Peninsula. In October the fluxes in the low period band pass (1-5 h) account for the main part of the total flux of zonal momentum, consistent with topographically forced waves. During November the vertical fluxes of zonal momentum are found mainly in longer period band passes, consistent with weaker winds. The peak campaign-averaged flux of zonal momentum in the vicinity of the Antarctic Peninsula is ˜-30 mPa. These values are ˜60% larger over the peninsula than those inferred by other authors. The flux of zonal momentum provides a zonal body force of ˜5 m s-1 day-1 assuming a saturated spectrum. We infer downward sensible heat fluxes of ˜3 W m-2. The corresponding cooling rates assuming a saturated spectrum are ˜0.6 K day-1, a significant fraction of the net radiative imbalance in the springtime Antarctic lower stratosphere.

Walterscheid, R. L.; Gelinas, L. J.; Mechoso, C. R.; Schubert, G.

2012-05-01

306

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

SciTech Connect

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

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

1994-04-01

307

Steady-state post-critical heat flux heat transfer to a refrigerant  

SciTech Connect

Heat transfer in the post-critical heat flux (CHF) regime was studied experimentally under steady-state conditions producing low superheat temperature of the heated surface. Experiments were performed with the vertical flow of refrigerant-12 in a tube with inside diameter of 7.75 mm over the mass flux range of 182 to 808 kg/sq m s at a pressure of 1 MPa. Liquid heating produced the low wall-superheat in the post-CHF region at steady state, which is typical of heat exchanger operation. Superheated vapor measured at the test section exit in most tests ensured that the entire post-CHF region was included. Heat transfer results were compared to predictions from nine post-CHF correlations and models. The potential for thermodynamic nonequilibrium diminishes and direct wall-drop heat transfer is enhanced when wall-superheat is low. These two phenomena were considered in the comparisons, and the best predictions of independent data for two fluids, refrigerant-12 and water, were obtained from a single correlation that included both phenomena explicitly. 15 refs.

Paske, J.M.; Papadopoulos, P.; George, C.M.; France, D.M.; Minkowycz, W.J. (Illinois, University, Chicago (United States))

1992-06-01

308

Strong Near-Field Enhancement of Radiative Heat Transfer between Metallic Surfaces  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

309

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

PubMed

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

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

2012-11-27

310

Saturated critical heat flux in a multi-microchannel heat sink fed by a split flow system  

Microsoft Academic Search

An extensive experimental campaign has been carried out for the measurement of saturated critical heat flux in a multi-microchannel copper heat sink. The heat sink was formed by 29 parallel channels that were 199?m wide and 756?m deep. In order to increase the critical heat flux and reduce the two-phase pressure drop, a split flow system was implemented with one

A. W. Mauro; J. R. Thome; D. Toto; G. P. Vanoli

2010-01-01

311

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

Microsoft Academic Search

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

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

2006-01-01

312

Estimation of TOA radiative fluxes from the GERB instrument data  

NASA Astrophysics Data System (ADS)

The first Meteosat Second Generation (MSG) satellite was launched in August 2002. This EUMETSAT satellite carries 2 new instruments on the geostationary orbit: the Spinning Enhanced Visible and InfraRed Imager, SEVIRI, and the Geostationary Earth Radiation Budget, GERB. The unique feature of GERB in comparison with previous measurement missions of the Earth's radiation budget (e.g. ERBE, ScaRab and CERES experiments) is the high temporal sampling afforded by the geostationary orbit, albeit for a limited region of the globe. The GERB instrument provides accurate broadband measurements of the radiant energy originating in the reflection of the incoming solar energy by the Earth-atmosphere system and in the thermal emission within this system. The synergetic use of the SEVIRI data is needed to convert these directional measurements (radiances) into radiative fluxes at the top-of-atmosphere. Additionally, the SEVIRI data allows the enhancement of the spatial resolution of the GERB measurement. This paper describes the near real-time GERB processing system that has been set up at the Royal Meteorological Institute of Belgium (RMIB). This includes the unfiltering of the instrument data, the radiance-to-flux conversions and the enhancement of the instrument spatial resolution. An early validation of the instrument data by comparison with CERES data is presented. Finally, the different data formats, the way to access them and their expected accuracy are presented.

Clerbaux, Nicolas; Bertrand, Cedric; Dewitte, Steven; Gonzalez, Luis; Ipe, Alessandro; Nicula, Bogdan

2003-12-01

313

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

SciTech Connect

Experiments conducted in high-performance 1.0 and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor in NSTX demonstrate that significant divertor peak heat flux reduction and access to detachment may be facilitated naturally in a highly shaped spherical torus (ST) configuration. Improved plasma performance with high beta(t) = 15-25%, a high bootstrap current fraction f(BS) = 45-50%, longer plasma pulses and an H-mode regime with smaller ELMs has been achieved in the strongly shaped lower single null configuration with elongation kappa = 2.2-2.4 and triangularity delta = 0.7-0.8. Divertor peak heat fluxes were reduced from 6-12 to 0.5-2 MW m(-2) in ELMy H-mode discharges using the inherently high magnetic flux expansion f(m) = 15-25 and the partial detachment of the outer strike point at several D-2 injection rates. A good core confinement and pedestal characteristics were maintained, while the core carbon concentration and the associated Z(eff) were reduced. The partially detached divertor regime was characterized by an increase in divertor radiated power, a reduction in ion flux to the plate and a large neutral compression ratio. Spectroscopic measurements indicated the formation of a high-density, low-temperature region adjacent to the outer strike point, where substantial increases in the volume recombination rate and C II, CIII emission rates were measured.

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

2009-01-01

314

Heat radiation from long cylindrical objects.  

PubMed

The heat radiated by objects smaller than or comparable in size to the thermal wavelength can be very different from the classical blackbody radiation as described by the Planck and Stefan-Boltzmann laws. We use methods based on scattering of electromagnetic waves to explore the dependence on size, shape, and material properties. In particular, we explore the radiation from a long cylinder at uniform temperature, discussing in detail the degree of polarization of the emitted radiation. If the radius of the cylinder is much smaller than the thermal wavelength, the radiation is polarized parallel to the cylindrical axis and becomes perpendicular when the radius is comparable to the thermal wavelength. For a cylinder of uniaxial material (a simple model for carbon nanontubes), we find that the influence of uniaxiality on the polarization is most pronounced if the radius is larger than a few micrometers, and quite small for the submicrometer sizes typical for nanotubes. PMID:22680594

Golyk, Vladyslav A; Krüger, Matthias; Kardar, Mehran

2012-04-09

315

Prediction of critical heat flux for annular flow in vertical pipes. Final report  

Microsoft Academic Search

A previously developed semi-empirical model for adiabatic two-phase annular flow (EPRI-NP-1521) is extended to predict critical heat flux in a vertical pipe for conditions of interest to boiling water reactors. The model exhibits a sharply declining curve of critical heat flux versus steam quality at low steam qualities where it is relatively independent of heat flux distribution. In this region,

S. Levy; J. M. Healzer; D. Abdollahian

1980-01-01

316

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

NASA Astrophysics Data System (ADS)

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

Song, Xiangzhou; Yu, Lisan

2013-07-01

317

Technical assessment of thermal-hydraulics for high heat flux fusion components  

Microsoft Academic Search

A technical assessment of three possible thermal-hydraulic high heat flux (HHF) heat removal techniques which will result in adequate heat removal from fusion components with minimum penalty is presented. The heat removal alternatives discussed are: (1) subcooled flow boiling (SFB) with water; (2) high velocity helium gas convection (HGC); and (3) liquid metal (LM) heat transfer in the presence of

R. D. Boyd; C. P. C. Wong; Y. S. Cha

1985-01-01

318

The application of computational fluid dynamics to critical heat flux  

SciTech Connect

The estimation of critical heat flux (CHF) in nuclear reactors is based largely on empirical relations that have a physical limiting conditions, a narrow range of applicability, and are inadequate for transient conditions. It is generally agreed that a more physically based approach is needed. Evidence is presented supporting the importance of boiling-induced fluid flow o the CHF process. Computational fluid dynamics (CFD) is used to model the microscale, transient dynamics of a vapor bubble growing in a subcooled liquid, resulting in qualitative reproduction of vapor blanket growth and CHF. The same CFD techniques are used to evaluate the macroscale thermal diffusion caused by spacers, resulting in qualitative reproduction of previous empirical results. This work forms the basis for a systematic investigation of CHF that could result in improved and less costly procedures for nuclear fuel design. This work is relevant for BWR and PWR reactors.

Stuhmiller, J.H.; Masiello, P.J. [JAYCOR, San Diego, CA (United States); Srikantiah, G.S.; Agee, L.J. [Electric Power Research Inst., Palo Alto, CA (United States). Nuclear Power Div.

1995-12-01

319

Seasonal and interannual variation in water vapor and heat fluxes in a West Siberian continental bog  

NASA Astrophysics Data System (ADS)

The seasonal and interannual variation in the energy fluxes of a West Siberian continental bog were measured from April to October in 1999 and 2000 using the eddy covariance method. The energy balance closure rate (=[sensible + latent heat fluxes]/[available energy]) ranged from ˜0.8 to 0.9 and showed a better energy balance and less scattering using the soil heat flux estimated from an area-averaged soil thermal parameter rather than from a plot-based measurement. The net radiation (Rn) increased drastically after snowmelt because the surface albedo (a) dropped from its highest value to its lowest value over the course of the snowmelt. The snowmelt water raised the water table (zwt) to its highest level; it then gradually decreased. The seasonal and interannual variation in a, which ranged from 0.09-0.19, depended on zwt, because surface wetness was closely related to zwt through the capillary uptake of Sphagnum moss. The seasonal variation in the latent heat flux (lE) was similar to that in Rn. The largest lE was observed in the middle of June, and was ˜120 Wm-2 (4.2 mm d-1) in both years. Conversely, the sensible heat flux (H) did not show an obvious seasonal pattern and was lower than lE during the growing season. The Bowen ratio (Br) in the early growing season was 0.57 and 0.60, and the values in the peak growing season were 0.65 and 0.78, in 1999 and 2000, respectively. The lower Br was related to the higher zwt; specifically, it was due to the wetter surface conditions. An interannual comparison of the monthly mean atmospheric water vapor deficit (?e) and lE showed a significant relationship with a higher lE observed in the year with a higher ?e. Therefore in the bog studied the interannual variation in the water vapor flux was controlled mainly by zwt and ?e.

Shimoyama, K.; Hiyama, T.; Fukushima, Y.; Inoue, G.

2003-10-01

320

EXPERIMENTAL INVESTIGATION OF RADIATION HEATING IN MATERIALS  

Microsoft Academic Search

An experimental study was performed to measure the nuclear-reactor ; radiation-induced heating rates in lead, 1018 steel, Marlex Type 2 Polyethylene, ; and an 80% lithium hydride-polyethylene matrix material. The data obtained from ; this study are compared with data predicted by methods employing computer ; techniques. Thermal transducers of the material types were fabricated to provide ; for the

O. H. Hill; E. E. Kerlin

1961-01-01

321

Infrared Radiative Heat Transfer in Nongray Gases.  

National Technical Information Service (NTIS)

The object of the investigation was to study various approximate methods of analyzing infrared radiative heat transfer in nongray nonisothermal gases. For this purpose, a very simple physical system was chosen, and this consists of a gas bounded by two in...

R. D. Cess P. Mighdoll S. N. Tiwari

1967-01-01

322

High Temperature Titanium-Water Heat Pipe Radiator  

Microsoft Academic Search

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

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

2006-01-01

323

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

324

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

325

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

SciTech Connect

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

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

1998-11-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

327

Estimation of surface heat fluxes and evapotranspiration using community land model  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

328

Hydromagnetic flow and heat transfer adjacent to a stretching vertical sheet with prescribed surface heat flux  

Microsoft Academic Search

The similarity solution for the problem of mixed convection boundary layer flow adjacent to a stretching vertical sheet in\\u000a an incompressible electrically conducting fluid in the presence of a transverse magnetic field is presented. It is assumed\\u000a that the sheet is stretched with a power-law velocity and is subjected to a variable surface heat flux. The governing partial\\u000a differential equations

Fazlina Aman; Anuar Ishak

2010-01-01

329

Critical Heat Flux in a Thin Annular Channel  

NASA Astrophysics Data System (ADS)

The improved accuracy in predicting critical heat flux (CHF) for specific reactor core geometry would allow for increased power output. The objectives of this project were to incorporate a scale model test to determine the feasibility of generating high power density in an annular fuel arrangement in a reactor. The desired power density was 100W/cm2. This would be accomplished by using resistive heating on the outer cylinder of an annular flow channel between concentric cylinders. The inner cylinder consists of a hemispherical shape in the upstream direction to condition the flow. The second objective was to study the behavior of two-phase flow through a simulated reactor core. The CHF would be measured and compared with existing correlations. Finally, the concept of a future full scale testing would be investigated. The results of this project are not only applicable to nuclear reactors, but can be used to increase the efficiency of other applications such as fuel cells, combustion engines, turbines and polymer processes.

Habtour, Ahmed; Anderson, Elgin

2002-11-01

330

A mathematical model for solving three-dimensional radiative heat transfer by radiative heat ray method  

Microsoft Academic Search

By introducing the wall-radiosity concept, a radiative heat ray method is developed to solve three-dimensional combined radiative and convective heat transfer problems for systems surrounded by gray walls. Parameters which influence the calculating accuracy are analyzed, and this method is applied to a cylindrical gas reformer to obtain the profiles of gas and wall temperature as well as the tube-surface

Taniguchi Hiroshi; Kudo Kazuhiko; Kehui Guo; Yongzhao Zhang; Katayama Takao

1990-01-01

331

Gamma heating measurements in a mixed radiation field  

SciTech Connect

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

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

1990-09-01

332

Critical Heat Flux Tests of a Simulated Power Burst Facility Rod Bundle.  

National Technical Information Service (NTIS)

Critical heat flux (CHF) tests were performed at low pressure in a close-packed rod bundle. The test bundle was electrically heated with geometrical configurations the same as the Power Burst Facility nuclear core. Existing low pressure CHF correlations, ...

R. G. Ambrosek R. P. Wadkins M. W. Young

1978-01-01

333

Critical Heat Flux in Inclined Rectangular Narrow Gaps  

SciTech Connect

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

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

2004-06-01

334

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

SciTech Connect

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

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

1985-01-01

335

Cutaneous heat flux models do not reliably predict metabolic rates of marine mammals.  

PubMed

Heat flux models have been used to predict metabolic rates of marine mammals, generally by estimating conductive heat transfer through their blubber layer. Recently, Kvadsheim et al. (1997) found that such models tend to overestimate metabolic rates, and that such errors probably result from the asymmetrical distribution of blubber. This problem may be avoided if reliable estimates of heat flux through the skin of the animals are obtained by using models that combine calculations of conductive heat flux through the skin and fur, and convective heat flux from the surface of the animal to the environment. We evaluated this approach based on simultaneous measurements of metabolic rates and of input parameters necessary for heat flux calculations, as obtained from four harp seals (Phoca groenlandica) resting in cold water. Heat flux estimates were made using two free convection models (double-flat-plate and cylindrical geometry) and one forced convection model (single-flat-plate geometry). We found that heat flux estimates generally underestimated metabolic rates, on average by 26-58%, and that small variations in input parameters caused large variations in these estimates. We conclude that cutaneous heat flux models are too inaccurate and sensitive to small errors in input parameters to provide reliable estimates of metabolic rates of marine mammals. PMID:11082302

Boily, P; Kvadsheim, P H; Folkow, L P

2000-12-01

336

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

SciTech Connect

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

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

2005-07-01

337

Longitudinal variation of tides in the MLT region: 1. Tides driven by tropospheric net radiative heating  

NASA Astrophysics Data System (ADS)

This study demonstrates that the diurnal cycle of net radiative heating in the troposphere accounts for considerable longitudinal variability of diurnal and semidiurnal tidal fields in the mesosphere and lower thermosphere (MLT) (˜80-120 km), whereas previously it was thought that latent heating associated with deep tropical convection is the predominant driver of this variability. The heating rates used for this study are derived from radiative flux products by NASA Goddard Institute for Space Studies (GISS), and the model employed to estimate the corresponding MLT tides is the Global-Scale Wave Model (GSWM). The radiative flux products by NASA GISS utilize improved International Satellite Cloud Climatology Project (ISCCP) cloud climatology and ancillary data sets and were validated by Earth radiation Budget Experiment (ERBE) and Clouds and the Earth's Radiant Energy System (CERES) radiative flux (0.2-200.0 microns) measurements at the top of the atmosphere and the Earth surface. Typical magnitudes of tidal temperature longitude variations at, e.g., 95 km or 110 km are 20 ± 5 K for the diurnal tide and 6 ± 2 K for the semidiurnal tide. The computed tides and their longitude variability are of comparable amplitude to those derived from TIMED SABER temperature measurements. Part 2 of this study provides new estimates of tidal forcing by latent heating and assesses the total MLT tidal response to these combined heat sources in comparison to tidal climatologies derived from TIMED SABER measurements.

Zhang, Xiaoli; Forbes, Jeffrey M.; Hagan, Maura E.

2010-06-01

338

Effects of heat absorption and thermal radiation on heat transfer in a fluid–particle flow past a surface in the presence of a gravity field  

Microsoft Academic Search

A continuum two-phase fluid–particle model accounting for fluid-phase heat generation or absorption and thermal radiation is developed and applied to the problem of heat transfer in a particulate suspension flow over a horizontal heated surface in the presence of a gravity field. Analytical solutions for the temperature distributions and the wall heat fluxes for both phases are obtained. Two cases

Ali J. Chamkha

2000-01-01

339

Ion heat flux and energy transport near the magnetotail neutral sheet  

Microsoft Academic Search

Ten-year averages of energy transport rates near the neutral sheet showed that the enthalpy flux density or thermal energy term QT = (5\\/2)PV was the largest, where P is the isotropic pressure and V is the bulk flow velocity. The ion heat flux, qi, was the next largest term. Sorting data using a magnetic flux transport parameter showed that qi

Richard L. Kaufmann; William R. Paterson

2008-01-01

340

Design, fabrication, and testing of helium-cooled high heat flux module  

NASA Astrophysics Data System (ADS)

Helium cooling is an attractive alternative to water cooling for high heat flux components. Helium offers advantages from safety considerations, such as excellent radiation stability and chemical inertness. General Atomics (GA) has considerable expertise in use of helium cooling due to its high temperature gas cooled reactor experience. In order to prove the feasibility of helium cooling at high heat flux levels of above 5 MW/m2, GA designed, fabricated, and tested a helium cooled module. The module was sized to have a heat flux surface of 25 mm wide and 80 mm long due to test setup limitations on maximum deposited power. WIth a smooth flow channel, a flow rate of 0.23 kg/s, and a pumping power of 2300 W was required to keep the copper module surface temperature below 500 degrees C at a heat flux level of 10 MW/m2. Hence, different techniques were examined to enhance the heat transfer, which in turn reduced the flow and pumping power required. It was concluded that an extended surface was the most practical solution. An optimization study was performed to find the best parameters. The module with an optimized extended surface geometry was estimated to require a flow of about 0.032 kg/s and a pumping power of 50 W to remove 20 kW of power. This is more than an order of magnitude reduction in pumping power required compared to the smooth channel. The module was made from dispersion strengthened copper. The fabricated geometry was slightly different than the optimized design due to constraints of machining. The fabrication was done by electro discharge matching. The testing was carried out at the electron beam test facility of Sandia National Laboratory, Albuquerque. The specifications of the loop and the electron beam testing facility were: 4 MPa pressure, 32 g/s of helium flow, and 30 kW beam power. The testing was carried out during August 1993 and again in December 1994. The testing confirmed the design calculations.

Baxi, Chandu B.; Redler, K. M.; Smith, J. P.

1996-11-01

341

An analytical study of the critical heat flux of a two-phase thermosiphon  

Microsoft Academic Search

An analytical study has been made of the critical heat flux of a two-phase thermosiphon, in which liquid and vapor form a countercurrent annular flow. An equation governing the flow of the liquid film and other equations for mass and energy balances in the thermosiphon are solved together under two conditions: first, the critical heat flux takes place when the

Masonori Monde; Shinnichi Mihara; Toshiaki Inoue

1994-01-01

342

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

343

Modeling and analysis of low heat flux natural convection sodium boiling in LMFBRs  

Microsoft Academic Search

Flow excursion induced dryout at low heat flux natural convection boiling, typical of liquid metal fast breeder reactor, is addressed. Steady state calculations indicate that low quality boiling is possible up to the point of Ledinegg instability leading to flow excursion and subsequent dryout in agreement with experimental data. A flow regime-dependent dryout heat flux relationship based upon saturated boiling

M. Khatib-Rahbar; E. G. Cazzoli

1982-01-01

344

Peak Heat Fluxe Reduction Using Aerospikes Installed on Multimodule Launch Vehicle  

NASA Astrophysics Data System (ADS)

Based on the experimental data in the supersonic wind tunnels the flow patterns, which cause peak pressure and peak heat fluxes on the heavy space rocket surfaces, were researched. Physical interpretations for each flow pattern are presented. Peak areas dimensions were specified. Influence of aerospike attached to on lateral rocket module to the heat fluxes was investigated .

Kudinov, A.; Yurchenko, L.; Karakotin, I.; Vaganov, A.; Drozdov, S.; Skuratov, A.

2011-08-01

345

Surface heat fluxes and marine boundary layer modification in the Agulhas Retroflection Region  

Microsoft Academic Search

The Subtropical Convergence Agulhas Retroflection Cruise, from February 12 to March 4, 1987, provided an opportunity for studying variability of surface heat fluxes and marine boundary layer modification within an ocean area where few atmospheric measurements have been made. From 3-hourly surface observations it has been ascertained that surface heat flux processes are enhanced under cold air outbreak, postfrontal synoptic

Rosemary D. Mey; Nan D. Walker; Mark R. Jury

1990-01-01

346

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

347

Critical Heat Flux During Flow Boiling in Microchannels: A Parametric Study  

Microsoft Academic Search

The application of flow boiling in microchannels in copper cooling elements for very high heat flux dissipation from microprocessor chips is one of the promising technologies to replace air cooling and water cooling of these units, particularly in mainframes and servers. Recently, the authors have proposed a new theoretical model to predict the critical heat flux (CHF) in microchannels, and

Remi Revellin; John R. Thome

2009-01-01

348

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

349

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

NASA Astrophysics Data System (ADS)

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

Iwasaki, Shinsuke; Kubota, Masahisa

2011-05-01

350

Homotopy analysis method for heat radiation equations  

Microsoft Academic Search

Here, the homotopy analysis method (HAM), one of the newest analytical methods which is powerful and easy-to-use, is applied to solve heat transfer problems with high nonlinearity order. Also, the results are compared with the perturbation and numerical Runge–Kutta methods and homotopy perturbation method (HPM). Here, homotopy analysis method is used to solve an unsteady nonlinear convective–radiative equation containing two

S. Abbasbandy

2007-01-01

351

Stationary shape of bodies ablating in hypersonic flow under the action of radiation heating  

Microsoft Academic Search

The stationary shape of axisymmetrical blunt bodies subjected to ablation as a result of radiative aerodynamic heating in an equilibrium hypersonic air flow is analyzed on the basis of a method proposed previously for calculating the radiant flux distribution over the surface of bodies. It is found that the stationary shape depends slightly on the governing parameters of the problem

M. V. Brykin

1982-01-01

352

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

353

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

354

Experimental study of heat transfer in pipes for the case of variable heat flux at the wall  

Microsoft Academic Search

Experiments were conducted to study local heat transfer in a water flow and a turbulent flow of nitrogen in circular ducts for the case of linear increase or decrease of wall heat flux and small variations in physical properties. Local heat transfer correlations were obtained for the thermal entrance regions of a pipe for Prandtl numbers of 0.7 with consideration

B. S. Petukhov; V. S. Grigorev; A. F. Poliakov; S. V. Rosnovskii

1976-01-01

355

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

356

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

SciTech Connect

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.

1983-12-01

357

The validation of ocean surface heat fluxes in AMIP  

SciTech Connect

Recent intercomparisons of Atmospheric General Circulation Models (AGCMS) constrained with sea-surface temperatures have shown that while there are substantial differences among various models (with each other and available observations), overall the differences between them have been decreasing. The primary goal of AMIP is to enable a systematic intercomparison and validation of state-of-the- art AGCMs by supporting in-depth diagnosis of and interpretation of the model results. Official AMIP simulations are 10 years long, using monthly mean Sea-Surface Temperatures (SSTs) and sea ice conditions which are representative of the 1979--1988 decade. Some model properties are also dictated by the design of AMIP such as the solar constant, the atmospheric CO{sub 2} concentration, and the approximate horizontal resolution. In this paper, some of the preliminary results of AMIP Subproject No. 5 will be summarized. The focus will be on the intercomparison and validation of ocean surface heat fluxes of the AMIP simulations available thus far.

Gleckler, P.J. [Lawrence Livermore National Lab., CA (United States); Randall, D.A. [Colorado State Univ., Fort Collins, CO (United States)

1993-09-01

358

Comparisons of fixation of heat, radiation, and heat plus radiation damage by anisotonic sodium chloride solutions  

SciTech Connect

Heat treatment at temperatures greater than 40 degrees C synergistically enhanced damage produced by ionizing radiation. Researchers experiments indicated that radiation damage in exponentially growing Chinese hamster cells could be fixed in a dose-dependent manner by postirradiation treatment with both hypertonic and hypotonic NaCl solutions. At a 1,000-rad dose level, survival could be depressed by a factor of about 260. For various treatments at either 42 or 45 degrees C, exposure after heating to anisotonic solutions did not result in the fixation of heat damage. When cells were heated at 45 degrees C for 5 minutes and irradiated with 500 rad before or after heating or given 500 rad without heating and then exposed to 0.05 M NaCl solutions for 120 minutes, survival was reduced by factors of 875, 667, and 12, respectively. For heat treatments at lower temperatures, such as 41.5 or 42 degrees C, less damage fixation for the combined treatments was observed. The data indicated that heat and radiation damage were different and damage from the combined treatments was not the same for low- and high-treatment temperatures.

Raaphorst, G.P.; Azzam, E.I.

1982-06-01

359

Results of an experimental determination of limiting heat fluxes in two-phase thermosiphons  

NASA Astrophysics Data System (ADS)

Experiments were carried out on closed two-phase thermosiphons made of Kh18N10T steel to investigate the limiting heat fluxes, with emphasis on the effects of the length of the heating zone and thermosiphon diameter. Experimental results support the conclusion that changing the degree of filling of the thermosiphon with coolant over a wide range (30-100%) has no effect on the limiting heat flux. A similarity equation is obtained which makes it possible to determine the limiting heat fluxes of two-phase thermosiphons over a wide range of process variables and geometric parameters for various coolants.

Tolubinskii, V. I.; Pioro, I. L.

1983-04-01

360

The vertical eddy-heat flux as a stabilizer of cold accretion disks  

NASA Astrophysics Data System (ADS)

The time-dependent vertical structure of cold accretion disks and their thermal stability have been studied with turbulent heat transfer being included. A strong turbulent heat transport enforces a nearly adiabatic stratification and the disk evolves quasi-homologously, although homology is broken by the outer boundary condition. The radiative energy loss scales with the disk's optical depth tau like Q(-~) T_c(4/tau ^m) with T_c the midplane temperature. The disk is only stable if the resulting m fulfills the stability criterion 3+mleft({n/2}-qright ) > 0, with n and q taken from the opacity law kappa ~rho (n) T(q) . For rather cool disks with n=1/3 and q=10 the vertical structure proves to be thermally unstable unless the turbulent Prandtl number (the ratio between the eddy viscosity and turbulent heat conductivity) is less than, say, 0.1. For weaker temperature power-laws of the opacity (smaller q) the disks become more and more stable even without the stabilizing support of the eddy-heat flux. Numerical simulations confirm the quasi-analytically derived stability criterion.

Fröhlich, H.-E.; Rüdiger, G.

1999-03-01

361

Nanoscale Radiative Heat Flow due to Surface Plasmons in Graphene and Doped Silicon  

NASA Astrophysics Data System (ADS)

Owing to its two-dimensional electronic structure, graphene exhibits many unique properties. One of them is a wave vector and temperature dependent plasmon in the infrared range. Theory predicts that due to these plasmons, graphene can be used as a universal material to enhance nanoscale radiative heat exchange for any dielectric substrate. Here we report on radiative heat transfer experiments between SiC and a SiO2 sphere that have nonmatching phonon polariton frequencies, and thus only weakly exchange heat in near field. We observed that the heat flux contribution of graphene epitaxially grown on SiC dominates at short distances. The influence of plasmons on radiative heat transfer is further supported with measurements for doped silicon. These results highlight graphene’s strong potential in photonic near field and energy conversion devices.

van Zwol, P. J.; Thiele, S.; Berger, C.; de Heer, W. A.; Chevrier, J.

2012-12-01

362

Nanoscale radiative heat flow due to surface plasmons in graphene and doped silicon.  

PubMed

Owing to its two-dimensional electronic structure, graphene exhibits many unique properties. One of them is a wave vector and temperature dependent plasmon in the infrared range. Theory predicts that due to these plasmons, graphene can be used as a universal material to enhance nanoscale radiative heat exchange for any dielectric substrate. Here we report on radiative heat transfer experiments between SiC and a SiO2 sphere that have nonmatching phonon polariton frequencies, and thus only weakly exchange heat in near field. We observed that the heat flux contribution of graphene epitaxially grown on SiC dominates at short distances. The influence of plasmons on radiative heat transfer is further supported with measurements for doped silicon. These results highlight graphene's strong potential in photonic near field and energy conversion devices. PMID:23368565

van Zwol, P J; Thiele, S; Berger, C; de Heer, W A; Chevrier, J

2012-12-27

363

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

PubMed

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

Raj, Phani K

2007-10-07

364

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

SciTech Connect

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

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

2002-01-15

365

Radiative Heating Profiles in the Convective Tropics: A Comparison of Observations and Models  

SciTech Connect

Radiative heating is one of the principal drivers of tropical circulation. While we have good knowledge of radiative fluxes at the top-of-atmosphere and at specific surface sites, observations of atmospheric profiles of radiative heating, particular in cloudy conditions, have been largely unavailable. The Atmospheric Radiation Measurement (ARM) Program has begun a program to compute radiative heating profiles routinely at its observational sites at Nauru and Manus Island, Papua New Guinea, using observed and retrieved inputs of water vapor and condensed water phase, particle size, and mass. The accuracy of these profiles can be assessed by comparing the calculated TOA and surface fluxes with observations. We have computed radiative heating profiles every 20 minutes for several months at each of these two sites in the 1999-2000 time period, which represent a unique dataset for model comparison. Here, we compare this dataset to model output from the European Center for Medium-Range Weather Forecasting (ECMWF) analysis, the NCAR Community Atmosphere Model (CAM 3.0) and the Multi-Scale Modeling Framework (MMF). These three models, all run using observed SST for this comparison, provide an interesting range of resolution from the 4 km cloud resolving model in the MMF to the approximately 280 km grid-scale of the CAM and a contrast between forecasting and climate models. In general, the model results fail to capture the structure of the observed heating in the upper troposphere because of their failure to simulate cirrus and stratiform cloud adequately.

McFarlane, Sally A.; Mather, Jim H.; Ackerman, Thomas P.

2005-01-10

366

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

SciTech Connect

The existing data for critical heat flux (CHF) on a disk heater cooled by multiple impinging jets have been correlated successfully by deriving a generalized correlation that can predict the CHF on a disk heater cooled by a single impinging jet with high accuracy. The generalized correlation for the CHF for the single jet can be applied to predict the CHF for multiple jets with an accuracy of {plus minus}20 percent, in spite of a great difference in the flow situation on a disk between a single jet and multiple jets.

Monde, M. (Saga Univ. (Japan)); Inoue T. (Kurume Inst. of Tech. (Japan))

1991-08-01

367

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

368

Incipient boiling superheat and critical heat flux in liquid sodium. Effect of the pre-pressure on the heated surface.  

National Technical Information Service (NTIS)

Incipient boiling superheat and critical heat flux on a horizontal cylinder in liquid sodium have been systematically measured to know effects of the history of experimental condition, the cold-trap temperature, subcooling of the liquid sodium. The effect...

M. Shiotsu Y. Shirai K. Hata Y. Takeuchi K. Hama

1998-01-01

369

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

370

Critical heat flux experiments in a heated rod bundle with upward crossflow of Freon 114  

SciTech Connect

Critical heat flux (CHF) data were obtained for upward crossflow of R-114 in a heated staggered rod bundle. Data were obtained over a broad range of mass fluxes (135 to 1,221 kg/m{sup 2} sec), inlet subcooling (0 to 55 C), and qualities ({minus}0.42 to 0.92). The present work extends the available database to higher quality, inlet subcooling, and mass flux. The test section is 3.43 cm x 15.24 cm (1.35 in. x 6 in.) in cross section with a total length of 55.88 cm (22 inches) from the top of the inlet flow straightener to the perforated plate at the test section exit. The rod bundle has a triangular pitch with a diameter (D) of 0.635 cm (0.25 in), and a pitch to diameter (P/D) ratio of 1.5. The rod bundle has 165 rods with a 15.24 cm (6 in.) heated length arranged in 55 rows of three rods each. Unheated half rods were positioned on the walls of the test section to maintain the regular rod arrangement and prevent flow bypass along the gaps between the window and the first column of heated rods. A single instrumented heater was positioned five rows upstream from the bundle exit to determine CHF. The last three rows of rods in the bundle were unheated to prevent undetected dryout downstream of the CHF position. Temperature excursions due to CHF were sensed using four imbedded thermocouples (TC) in the heater rod. The four TC temperatures were continuously monitored on a strip chart recorder. The rod heat was gradually increased until CHF was detected. Overall, the data are in good agreement with the Jensen and Tang correlation in the range of application of this correlation. The local minima in CHF which occurs near zero quality is slightly lower in the present experiment than for the Jensen and Tang correlation. At high quality, CHF drops off more rapidly than the Jensen-Tang prediction. Data are now available to extend the existing correlations to higher quality, and higher inlet subcooling.

Symolon, P.D.; Moore, W.E.; Wolf, D.F.

1997-02-01

371

Uncertainty analysis of heat flux measurements estimated using a one-dimensional, inverse heat-conduction program.  

SciTech Connect

The measurement of heat flux in hydrocarbon fuel fires (e.g., diesel or JP-8) is difficult due to high temperatures and the sooty environment. Un-cooled commercially available heat flux gages do not survive in long duration fires, and cooled gages often become covered with soot, thus changing the gage calibration. An alternate method that is rugged and relatively inexpensive is based on inverse heat conduction methods. Inverse heat-conduction methods estimate absorbed heat flux at specific material interfaces using temperature/time histories, boundary conditions, material properties, and usually an assumption of one-dimensional (1-D) heat flow. This method is commonly used at Sandia.s fire test facilities. In this report, an uncertainty analysis was performed for a specific example to quantify the effect of input parameter variations on the estimated heat flux when using the inverse heat conduction method. The approach used was to compare results from a number of cases using modified inputs to a base-case. The response of a 304 stainless-steel cylinder [about 30.5 cm (12-in.) in diameter and 0.32-cm-thick (1/8-in.)] filled with 2.5-cm-thick (1-in.) ceramic fiber insulation was examined. Input parameters of an inverse heat conduction program varied were steel-wall thickness, thermal conductivity, and volumetric heat capacity; insulation thickness, thermal conductivity, and volumetric heat capacity, temperature uncertainty, boundary conditions, temperature sampling period; and numerical inputs. One-dimensional heat transfer was assumed in all cases. Results of the analysis show that, at the maximum heat flux, the most important parameters were temperature uncertainty, steel thickness and steel volumetric heat capacity. The use of a constant thermal properties rather than temperature dependent values also made a significant difference in the resultant heat flux; therefore, temperature-dependent values should be used. As an example, several parameters were varied to estimate the uncertainty in heat flux. The result was 15-19% uncertainty to 95% confidence at the highest flux, neglecting multidimensional effects.

Nakos, James Thomas; Figueroa, Victor G.; Murphy, Jill E. (Worcester Polytechnic Institute, Worcester, MA)

2005-02-01

372

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

373

High heat flux flow boiling in silicon multi-microchannels – Part II: Heat transfer characteristics of refrigerant R245fa  

Microsoft Academic Search

This article is the second in a three-part study. This second part focuses on flow boiling heat transfer of refrigerant R245fa in a silicon multi-microchannel heat sink and their comparison with the results presented in part I for refrigerant R236fa. This heat sink was the same as utilized in part I. The test conditions covered base heat fluxes from 3.6

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

2008-01-01

374

Modeling thermal behavior and work flux in finite-rate systems with radiation  

Microsoft Academic Search

We apply thermodynamic analysis in modeling, simulation and optimization of radiation engines as non-linear energy converters. We also perform critical analysis of available data for photon flux and photon density that leads to exact numerical value of photon flux constant. Basic thermodynamic principles lead to expressions for converter’s efficiency and generated work in terms of driving energy flux in the

Stanislaw Sieniutycz; Piotr Kuran

2006-01-01

375

RADIATION DOSIMETRY AT THE BNL HIGH FLUX BEAM REACTOR AND MEDICAL RESEARCH REACTOR  

Microsoft Academic Search

RADIATION DOSIMETRY MEASUREMENTS HAVE BEEN PERFORMED OVER A PERIOD OF MANY YEARS AT THE HIGH FLUX BEAM REACTOR (HFBR) AND THE MEDICAL RESEARCH REACTOR (BMRR) AT BROOKHAVEN NATIONAL LABORATORY TO PROVIDE INFORMATION ON THE ENERGY DISTRIBUTION OF THE NEUTRON FLUX, NEUTRON DOSE RATES, GAMMA-RAY FLUXES AND GAMMA-RAY DOSE RATES. THE MCNP PARTICLE TRANSPORT CODE PROVIDED MONTE CARLO RESULTS TO COMPARE

1999-01-01

376

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

Microsoft Academic Search

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

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

1995-01-01

377

Thin-cavity interferometric sensors for detection of weak radiation flux and microvibrations  

Microsoft Academic Search

Novel optical sensors for the detection of weak radiation flux transients and mechanical micro-vibrations have been developed. The sensors are based on the modulation of an interference pattern created during the optical interrogation of a thin air cavity similar to a low finesse Fabry-Perot or Fizeau interferometer, formed between two parallel glass holographic plates. In the detection of radiation flux

Maurice Whelan; Robert P. Kenny; John T. Sheridan; Constantin T. Coutsomitros

1996-01-01

378

Forestation of boreal peatlands: Impacts of changing albedo and greenhouse gas fluxes on radiative forcing  

Microsoft Academic Search

We estimated the magnitude of the radiative forcing (RF) due to changes in albedo following the forestation of peatlands, and calculated the net RF by taking into account the changes in both the albedo and the greenhouse gas (GHG) fluxes during one forest rotation. Data on radiation, tree biomass, and soil GHG fluxes were combined with models for canopy cover,

Annalea Lohila; Kari Minkkinen; Jukka Laine; Ilkka Savolainen; Juha-Pekka Tuovinen; Lauri Korhonen; Tuomas Laurila; Hanna Tietäväinen; Ari Laaksonen

2010-01-01

379

Comparison of three radiative formulations for radiative and convective heat transfer interactions in three dimensional turbulent boundary layers  

SciTech Connect

The effects of an external source of thermal radiation on a three-dimensional hypersonic turbulent boundary layer over a sharp cone at an angle of attack are evaluated using three radiative interaction formulations: (1) an optically thin limit approximation, (2) an optically thick limit approximation, and (3) a band approximation for the wavelength-dependent properties of the medium. Interactions between radiation and the boundary layer are determined by solving numerically three-dimensional compressible turbulent boundary layer equations together with the energy equation modified to include thermal radiation. It is shown that the total heat flux to the wall is increased by an order of magnitude due to the external source of radiation as compared with the case in which there is no radiation.The band approximation, in general, gives the most accurate results, but requires excessive computer time the optically thin formulation gives reasonably accurate results with moderate computer times.

Kumar, G.N. (Tuskegee Institute, Tuskegee, AL); Vachon, R.I. (Vachon, Nix and Associates, Atlanta, GA)

1982-01-01

380

Heat transfer science and technology  

Microsoft Academic Search

This book presents the papers given at a conference on heat transfer. Topics considered at the conference included two-phase flow, freezing, heat flux, natural heat convection, forced heat convection, flow visualization, boiling heat transfer, condensation heat transfer, thermal radiation, heat and mass transfer in porous media, nuclear reaction heat transfer, combustion heat transfer, high-temperature heat transfer, heat exchangers, and industrial

1987-01-01

381

High heat flux flow boiling apparatus for the study of cooling effectiveness. Final report, October 1989September 1994  

Microsoft Academic Search

Backside water cooling is used extensively to transfer heat from critical elements in high heat flux devices such as hypersonic test facilities and nuclear reactors. In such devices, efficient cooling is accomplished with high heat transfer coefficients resulting from the transition of the coolant from single phase convection to nucleate boiling at higher heat flux. Analytical modeling of the heat-transfer

Beitel

1995-01-01

382

Applying the Variational Analysis Method to Construct Daily Air-sea Heat Fluxes Over the Atlantic Ocean  

Microsoft Academic Search

Errors in surface heat flux products can result from errors in basic surface meteorological variables, errors in flux parameterization schemes, or a combination of both. For example, the overestimation of latent heat loss from the NCEP1 reanalysis over the North Atlantic Subduction region is an offset resulting from biases in the flux algorithm and in basic variables. The NCEP flux

B. Sun

2001-01-01

383

Innovative Divertor Development to Solve the Plasma Heat-Flux Problem  

SciTech Connect

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

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

2009-02-26

384

On the interaction between marine boundary layer cellular cloudiness and surface heat fluxes  

NASA Astrophysics Data System (ADS)

The interaction between marine boundary layer cellular cloudiness and surface fluxes 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 closed-cell state imposes its horizontal spatial structure on surface air temperature and water vapor, and, to a lesser degree, on the surface sensible and latent heat flux. The responsible mechanism is the entrainment of dry free tropospheric air into the boundary layer. The open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible heat, latent heat, and of sea salt aerosol. Here, the responsible mechanism is the periodic formation of clouds, rain, and of cold and moist pools with elevated wind speed. 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 structure of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that the open-cell state creates conditions conducive to its maintenance by enhancing the surface sensible heat flux. The open-cell state also enhances the sea-salt flux relative to the closed-cell state. While the open-cell state under consideration is not depleted in aerosol and is insensitive to variations in sea-salt fluxes, in aerosol-depleted conditions, the enhancement of the sea-salt flux may replenish the aerosol needed for cloud formation and hence contribute to the maintenance of the open-cell state. 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, H.; Yamaguchi, T.

2013-07-01

385

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

Microsoft Academic Search

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

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

2009-01-01

386

The effects of pressure gradients on convective heat flux predictions in engine environments  

Microsoft Academic Search

Accurate convective heat transfer predictions inside engines is important to improvements in performance, reduction of harmful exhaust emissions, and structural and material design. Current heat transfer models used in engine simulations do not incorporate the effects of pressure gradients. In this study, wall functions that use local pressure gradients to correct the friction velocity, wall shear stress, and heat flux

I.-Ping Chang; Iping

1991-01-01

387

Constraints on Thermochemical Mantle Convection From Plume Excess Temperature, Plume Heat Flux and Upper Mantle Temperature  

Microsoft Academic Search

Mantle convection is responsible for releasing about 36 TW heat from the mantle. However, how much of the 36 TW mantle heat flux is from the core (i.e., Qcmb), mantle radiogenic heating and mantle secular cooling remains poorly understood. This question is further complicated if the mantle is compositionally heterogeneous or layered as suggested by seismic and geochemical observations. The

S. Zhong

2005-01-01

388

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

Treesearch

Description: Models of wildland fire-induced stem heating and tissue necrosis ... at a stem surface do not mimic the thermal response of tree bark to flames. ... to estimate net heat flux (inward minus outward heat flow) and temperature at the ...

389

Recent advances in evaluating critical heat flux conditions in LMFBR steam generators  

Microsoft Academic Search

An experimental program was conducted at two independent laboratories to characterize critical heat flux (CHF) in sodium-heated steam generator tubes for application to Liquid Metal Fast Breeder Reactor (LMFBR) steam generator design. Three models of about the same inside tube diameter, wall thickness, and material have been tested. Water was circulated vertically upward in the tube models heated by sodium

S. Wolf; D. M. France; D. H. Holmes

1977-01-01

390

Lava discharge rates from satellite-measured heat flux  

Microsoft Academic Search

A commonly used method to convert lava flow area to volume flux using low spatial resolution satellite data rests on two primary assumptions, that: (1) volume flux is related to flow area, and (2) lava surfaces cool exponentially with time and distance from the source. Field data show that both assumptions are valid. The ensuing relationship is an empirical one

Andrew J. L. Harris; Stephen M. Baloga

2009-01-01

391

THE HIGH-HEAT FLUX TESTING OF AN INTERCEPTIVE DEVICE FOR AN INTENSE PROTON BEAM  

SciTech Connect

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

R. VALDIVIEZ; F. A. MARTINEZ; ET AL

2001-04-01

392

Snow temperature profiles and heat fluxes measured on the Greenland crest by an automatic weather station  

SciTech Connect

In June 1989 three automatic weather station (AWS) units were installed on the Greenland crest at the GISP2 (78.58 N, 38.46 W, 3265 m) and GRIP (78.57 N, 37.62 W, 3230 m) ice coring sites and at Kenton (72.28 N, 38.80 W, 3185 m), the air sampling site. The purpose of the AWS units is to measure the local meteorological variables, including snow temperatures at various depths, in support of ice coring studies. The AWS units measure wind speed and direction, air temperature, and relative humidity at a nominal height of 3.6 meters, air pressure at the electronics enclosure, and air temperature difference between 3.6 m and 0.5 m. The AWS units at GISP2 and GRIP also measure solar radiation, and seven snow temperatures from the surface to a depth of approximately 4 m in the snow. The data are updated at 10-minute intervals and transmitted to the ARGOS data collection system on board the NOAA series of polar-orbiting satellites. The air temperature and snow temperatures are presented as a function of time for the period from June 8, 1989 to August 31, 1990 and as tautochrones at 30-day intervals. The heat flux into the snow is determined from the daily mean snow temperature between the day after and the day before using the volumetric heat capacity of the snow assuming a snow density of 300 kg m-3. The daily mean heat flux into the snow between the highest and the lowest levels of snow temperature is presented as a function of time.

Stearns, C.R.; Weidner, G A.

1992-03-01

393

Flux and brightness calculations for various synchrotron radiation sources  

SciTech Connect

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

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

1991-11-01

394

Studies on a cooling of high heat flux surface in fusion reactor by impinging planar jet flow  

Microsoft Academic Search

Divertor surface of a fusion reactor is exposed to strong surface heating by high flux charged particles. According to typical design of ITER, the heat flux on divertor surface becomes locally near 20 MW m?2. Then, it is necessary to establish a cooling method to cool such high heat flux surface. A cooling by a planar impinging jet has been

A Inoue; A Ui; Y Yamazaki; H Matsusita; S. R Lee

2000-01-01

395

Heat pump augmented radiators for spacecraft thermal management  

Microsoft Academic Search

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

M. A. Merrigan; R. S. Reid

1988-01-01

396

Analysis of the thermal performance of heat pipe radiators  

Microsoft Academic Search

A comprehensive mathematical model and computational methodology are presented to obtain numerical solutions for the transient behavior of a heat pipe radiator in a space environment. The modeling is focused on a typical radiator panel having a long heat pipe at the center and two extended surfaces attached to opposing sides of the heat pipe shell in the condenser section.

J. H. Boo; J. G. Hartley

1990-01-01

397

Direct Retrieval of Radiative Flux-Divergence and Radiative Forcing from Satellite Spectral Measurements.  

NASA Astrophysics Data System (ADS)

We explore the concept of a retrieval of the thermal infrared radiative flux divergence and cooling rate profile using top-of-atmosphere spectral radiance measurements and demonstrate that the retrieval of this quantity can be performed directly. We show that the inversion encountered in this problem is sensitive to the initial atmospheric state vector assumed a priori. However, the direct approach has specific advantageous in terms of accuracy and computational speed, as compared to the conventional indirect approach using the retrieved atmospheric state vector coupled with a line-by-line radiative transfer model in cooling rate calculations. Furthermore, we show that the spectrally-resolved radiative forcing at the tropopause can be derived directly from the retrieved flux-divergence profile. As a test case, we carried out retrieval in the strong cooling band associated with the 15 ?m band of CO2 employing the Atmospheric Infrared Sounder (AIRS, 2002-present) on board the Aqua satellite, along with validation campaign data and underflight Scanning High-Resolution Interferometer (S-HIS) zenith and nadir spectra taken aboard a high-altitude aircraft. Retrieval sensitivity analyses have been performed for AIRS and the Infrared Interferometer Sounder (IRIS-D, 1970-1971) instruments. It is anticipated that the large changes in stratospheric temperature and CO2 values between the two missions would lead to detectable changes in the CO2 radiative forcing at the tropopause so long as the IRIS-D instrument could be appropriately characterized.

Feldman, D.; Liou, K.; Yung, Y.; Tobin, D.; Berk, L.

2005-12-01

398

Modeling of radiative heat transfer in 3D complex boiler with non-gray sooting media  

NASA Astrophysics Data System (ADS)

The radiative heat transfer problem is solved for 3D complex industrial boiler with five baffles containing a mixture of carbon dioxide and water vapor for non-uniform temperature fields. A numerical formulation using the FTn finite volume method coupled with the bounded high-order resolution CLAM scheme, the blocked-off-region procedure and the narrow-band based weighted-sum-of-gray-gases (WSGG) [Kim OJ, Song T-H. Data base of WSGGM-based spectral model for radiation properties of combustion products, JQSRT 2000; 64: 379 94] model is adapted. The effect of soot volumetric fraction, particle temperature and uniform particle concentration on the radiative heat flux and radiative heat source is investigated and discussed. Also the advantages, in non-gray media, of the FTnFVM compared to the classical FVM are highlighted.

Borjini, Mohamed Naceur; Guedri, Kamel; Saïd, Rachid

2007-06-01

399

Ultra lightweight unfurlable radiator for lunar base heat rejection  

SciTech Connect

A proof-of-concept (POC) ultra lightweight lunar radiator was fabricated and tested. The POC radiator has a specific weight of 5 kg/kW one quarter the specific weight of current ambient temperature space radiators. The significant weight reduction was due to the radiator's unique design. It is a multi-cellular heat pipe radiator utilizing the lunar gravity for condensate return. The innovation of this radiator is the laminated film material used as the heat pipe envelope. By utilizing a flexible, durable, leak tight laminate structure instead of the typical ridge heat pipe envelope, significant weight reductions were achieved. In addition, the resulting radiator is extremely flexible, allowing it to be rolled or folded and compactly stored during transit to the lunar surface. Testing demonstrated that a laminated film heat pipe radiator offers improved performance and significant weight savings over conventional space radiators.

Garner, S.D.; Gernert, N.J. (Thermacore, Inc., 780 Eden Road, Lancaster, Pennsylvania 17601 (United States))

1993-01-10

400

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

401

Fin effect and radiative heat transfer of the unheated region of an asymmetrically heated tube  

NASA Astrophysics Data System (ADS)

The heat transfer rate in an asymmetrically heated tube is enhanced by heat conduction within the tube wall, i.e., the fin effect of the unheated region. The fin effects of the unheated regions on heat transfer rates and the temperature distributions of circumferentially partially heated tubes were numerically obtained for this paper; the flow in a tube was assumed to be turbulent and the radiation from the tube wall was taken into account. The circumferential heat conduction within the wall, the radiative heat exchange between walls, and the size of the heated region, were seen to affect the fin efficiency of the unheated region. Without radiative heat transfer, the unheated region of the asymmetrically heated tube can be considered to be a straight fin which has a constant thickness and height. The fin efficiency of the unheated region is increased with the radiative heat transfer of the wall.

Satoh, Isao; Kurosaki, Yasuo

402

A Revised Estimate of Earth's Surface Heat Flux: 47TW ± 2TW  

NASA Astrophysics Data System (ADS)

Earth's surface heat flux provides a fundamental constraint on solid Earth dynamics. However, deriving an estimate of the total surface heat flux is complex, due to the inhomogeneous distribution of heat flow measurements and difficulties in measuring heat flux in young oceanic crust, arising due to hydrothermal circulation. We derive a revised estimate of Earth's surface heat flux using a database of 38347 measurements (provided by G. Laske and G. Masters), representing a 55% increase on the number of measurements used previously, and the methods of Geographical Information Science (GIS) (Davies & Davies, 2010). To account for hydrothermal circulation in young oceanic crust, we use a model estimate of the heat flux, following the work of Jaupart et al., 2007; while for the rest of the globe, in an attempt to overcome the inhomogeneous distribution of measurements, we develop an average for different geological units. Two digital geology data sets are used to define the global geology: (i) continental geology - Hearn et al., 2003; and (ii) the global data-set of CCGM - Commission de la Carte Géologique du Monde, 2000. This leads to > 93,000 polygons defining Earth's geology. To limit the influence of clustering, we intersect the geology polygons with a 1 by 1 degree (at the equator) equal area grid. For each geology class the average heat flow in the resulting polygons is evaluated. The contribution of that geology class to the global surface heat flow is derived by multiplying the estimated surface heat flux with the area of that geology class. The total surface heat flow contributions of all the geology classes are summed. For Antarctica we use an estimate based on depth to Curie temperature and include a 1TW contribution from hot-spots in young ocean age. Geology classes with less than 50 readings are excluded. The raw data suggests that this method of correlating heat flux with geology has some power. Our revised estimate for Earth's global surface heat flux is 47 ± 2 TW, which is similar but slightly higher than previous estimates (e.g. Pollack et al., 1993 - 45 ± 1 TW; and Jaupart et al., 2007, - 46 ± 3 TW). It is challenging to reconcile such a high heat flow with estimates of internal heat sources in a monotonically cooling mantle. We will discuss alternative explanations and also how this work can be extended to produce a best estimate of the local heat flux globally.

Davies, J.; Davies, R.

2011-12-01

403

Retrieving latent heat flux from MODIS Aqua and its comparison with ARM CLASIC 2007 observations, LDAS and recent reanalyses products over US Southern Great Plains  

NASA Astrophysics Data System (ADS)

We present a new method for retrieving the terrestrial latent heat flux by exploiting the vertical soundings of MODIS Aqua in conjugation with visible and infrared geophysical land products at 5 km x 5 km spatial resolution over the US Southern Great Plains (SGP) during the DOE ARM CLASIC 2007 field campaign. The method focuses first on specifying the evaporative fraction fields through the profile measurements of air and dew-point temperature obtained from MODIS IR soundings. The evaporative fraction is then combined with satellite based surface net available energy to obtain an estimate of the surface latent heat flux. Both net radiation and latent heat flux estimates were evaluated against in-situ flux measurements from the ARM CART and CLASIC field sites for June 2007. The validated satellite-based radiative and latent heat fluxes were then compared with the simulated fluxes from a land data assimilation system (LDAS) and reanalyses estimates such as from MERRA, NARR, and NCEP CFSR. The potential advantage and deficits from this approach will be discussed along with an update on a ongoing study involving the AIRS based retrievals using a similar method.

Mallick, K.; Jarvis, A.; Niyogi, D.; Fall, S.; Charusambot, U.; Bhattacharya, B.

2010-12-01

404

Explanation of how to run the global local optimization code (GLO) to find surface heat flux  

SciTech Connect

From the evaluation[1] of the inverse techniques available, it was determined that the Global Local Optimization Code[2] can determine the surface heat flux using known experimental data at various points in the geometry. This code uses a whole domain approach in which an analysis code (such as TOPAZ2D or ABAQUS) can be run to get the appropriate data needed to minimize the heat flux function. This document is a compilation of our notes on how to run this code to find the surface heat flux. First, the code is described and the overall set-up procedure is reviewed. Then, creation of the configuration file is described. A specific configuration file is given with appropriate explanation. Using this information, the reader should be able to run GLO to find the surface heat flux.

Aceves, S; Sahai, V; Stein, W

1999-03-01

405

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

EPA Science Inventory

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

406

Oxidation and Volatilization from Tungsten Brush High Heat Flux Armor During High Temperature Steam Exposure.  

National Technical Information Service (NTIS)

Tungsten brush accommodates thermal stresses and high heat flux in fusion reactor components such as plasma facing surfaces or armor. However, inherently higher surface areas are introduced with the brush design. We have tested a specific design of tungst...

G. R. Smolik R. J. Pawelko R. A. Anderl D. A. Petti

2000-01-01

407

Chaotic Terrain and Its Constraints on the Surface Heat Flux of Mars  

NASA Astrophysics Data System (ADS)

Geological analysis of Aram Chaos on Mars suggests that this chaotic terrain could have formed by the collapse of an underground lake. We show how this concept can be used to constrain the surface heat flux during the Hesperian.

Schumacher, S.; Zegers, T. E.

2010-03-01

408

Chaotic Terrain and Its Constraints on the Surface Heat Flux of Mars  

Microsoft Academic Search

Geological analysis of Aram Chaos on Mars suggests that this chaotic terrain could have formed by the collapse of an underground lake. We show how this concept can be used to constrain the surface heat flux during the Hesperian.

S. Schumacher; T. E. Zegers

2010-01-01

409

Thermally driven acoustic oscillations, part III: Second-order heat flux  

Microsoft Academic Search

Summary The second-order heat flux in thermally driven oscillations of gas columns is calculated and given in a form suitable for numerical evaluation. Order-of-magnitude estimates are made in the case of steep temperature gradients.

Nikolaus Rott

1975-01-01

410

The Thermal Conductivity Measurements of Solid Samples by Heat Flux Differantial Scanning Calorimetry  

NASA Astrophysics Data System (ADS)

The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.

Kök, M.; Aydo?du, Y.

2007-04-01

411

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

412

Effects of heat and water vapor transport on eddy covariance measurement of CO2 fluxes  

Microsoft Academic Search

Flux densities of carbon dioxide were measured over an arid, vegetation-free surface by eddy covariance techniques and by a heat budget-profile method, in which CO2 concentration gradients were specified in terms of mixing ratios. This method showed negligible fluxes of CO2, consistent with the bareness of the experimental site, whereas the eddy covariance measurements indicated large downward fluxes of CO2.

R. Leuning; O. T. Denmead; A. R. G. Lang; E. Ohtaki

1982-01-01

413

Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL  

SciTech Connect

An analytical evaluation of the vertical heat fluxes associated with the mesoscale flow generated by thermal inhomogeneities in the PBL in the absence of a synoptic wind is presented. Results show that the mesoscale fluxes are of the same order as the diabatic beat fluxes. In the sea-breeze case, results show that in the lower layer of the atmosphere the heat flux is positive over the land and negative over the sea with an overall positive horizontal average. In the free atmosphere above the PBL, the mesoscale vertical heat flux is negative over the land and over the sea. The mesoscale flow contributes to the weakening of the atmospheric stability within a region that extends a Rossby radius distance from the coastline and up to an altitude larger than twice the depth of the convective PBL. The average momentum flux equals zero. Sinusoidally periodic thermal inhomogeneities induce periodic atmospheric cells of the same horizontal scale. The intensity of mesoscale cells increases for increasing values of the wavenumber, maximizes when the wavelength of the forcing is of the order of the local Rossby radius, and then decreases as the wavelength of the forcing decreases. The intensity of the vertical velocity and vertical fluxes is only a weak function of the wavenumber, at large wavenumber. The intensity of the mesoscale heat flux does not decrease substantially at high wavenumbers; however, the transport of cool air over small heated patches of land may cut off the temperature gradient in the atmosphere between the land and water early in the day, thereby reducing the duration of the mesoscale activity. Horizontal diffusion of heat in the convective boundary layer can significantly weaken horizontal temperature gradients for large wavenumbers. Periodic square-wave thermal inhomogeneities are more effective than sinusoidal waves in generating mesoscale cells. When dealing with low resolution models the mesoscale heat fluxes have to be introduced in a parametric form.

Dalu, G.A. (Colorado State Univ., Fort Collins (United States) IFA-CNR, Rome (Italy)); Pielke, R.A. (Colorado State Univ., Fort Collins (United States))

1993-03-15

414

Differences between two estimates of air-sea turbulent heat fluxes over the Atlantic Ocean  

Microsoft Academic Search

Uncertainties in turbulent ocean-atmosphere heat flux estimates, both among the estimates and between them and ground truth, suggest that further comparisons are needed. We analyze estimates from the French Research Institute for Exploitation of the Sea (IFREMER) and the Woods Hole Oceanographic Institution's Objectively Analyzed air-sea Fluxes (WHOI OAFlux). The IFREMER products are based on satellite observations and the WHOI

A. Santorelli; R. T. Pinker; A. Bentamy; K. B. Katsaros; W. M. Drennan; A. M. Mestas-Nuñez; J. A. Carton

2011-01-01

415

Wafer-grown heat flux sensor arrays for plasma etch processes  

Microsoft Academic Search

This work treats the design, fabrication, and testing of a wafer-grown thermal flux sensor for use in plasma etch processes. This sensor is capable of separately resolving the heating due to ion flux from that due to surface chemical reactions. The sensor is constructed using a modified Gardon gauge structure with an added antenna structure. This addition allows the exposed

Mason Freed; Michiel V. P. Krüger; Kameshwar Poolla; Costas J. Spanos

2005-01-01

416

Heat-Transfer Phenomena Across Mold Flux by Using the Inferred Emitter Technique  

NASA Astrophysics Data System (ADS)

An investigation was carried out to study the heat-transfer phenomena across mold flux film by using infrared emitter technique (IET). With IET, it is possible to develop the mold fluxes with a liquid layer at the top and a solid layer in contact with copper mold with the degree of varying crystallization. The dynamic crystallization and melting process of the mold fluxes as well as their effects on the overall heat-transfer rate in the mold were successfully conducted. The single hot thermocouple technique (SHTT) was also employed in this investigation to study the melting and crystallization behaviors of mold fluxes for the interpretation of IET results. The results suggested that the interfacial thermal resistance between the solidified mold flux and copper mold would significantly influence the heat-transfer rate in continuous casting and the melting of the mold flux tends to enhance the overall heat-transfer rate. The technique established in this article by utilizing the IET can be well applied to the investigation of mold flux thermal properties, which in turn gives guidelines for the design of new mold flux for continuous casting.

Gu, Kezhuan; Wang, Wanlin; Wei, Juan; Matsuura, Hiroyuki; Tsukihashi, Fumitaka; Sohn, Il; Min, Dong Joon

2012-12-01

417

Sensors for physical fluxes at the sea surface: energy, heat, water, salt  

Microsoft Academic Search

The current status of meteorological sensors used aboard ships and buoys to measure the air-sea fluxes of momentum, heat, and freshwater is reviewed. Methods of flux measurement by the bulk aerodynamic, inertial dissipation and eddy-correlation methods are considered; and areas are identified where improvements are needed in measurement of the basic variables. In some cases, what is required is the

R. A. Weller; E. F. Bradley; J. B. Edson; C. W. Fairall; I. Brooks; M. J. Yelland; R. W. Pascal

2008-01-01

418

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

SciTech Connect

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

Massoudi, Mehrdad

2006-09-10

419

Effect of rod bow to partial closure on critical heat flux in PWR fuel assembly  

Microsoft Academic Search

The effects of partial closure due to bowed rods on critical heat flux (CHF) in a pressurized water reactor rod bundle were evaluated by conducting tests in an electrically heated test section. The test section consisted of a 5x5 square rod array with 24 heated rods of 9.14 mm (0.360 in) diameter, each with a heated length of 3.66 m

R. B. Macbuff; C. F. Fighetti

1983-01-01

420

Lidar Measurement of Boundary Layer Evolution to Determine Sensible Heat Fluxes  

NASA Astrophysics Data System (ADS)

The estimation of large scale fluxes of heat and water vapor is crucial for a number of reasons, including weather prediction, climate, agriculture, and water resources management. It is known that these fluxes are not uniform and that the distribution of the surface heat fluxes is a major factor in producing and modifying mesoscale atmospheric flows, turbulence and evaporation. Local variability in the values is the result of variations in soil type, moisture content, type of vegetative cover, and wind speed, among other factors. Obtaining high quality data requires expensive equipment that needs periodic maintenance and attention. So while point sensors cannot be extensively deployed because of cost, conventional measurements represent the surface fluxes over very limited areas. This work evaluates a method where, with a relatively simple, vertically staring lidar, larger scale estimates of the sensible heat flux can be inferred. The estimation of a spatially integrated sensible surface heat flux and the determination of regional heat fluxes over heterogeneous land surfaces is needed to address a number of problems concerning long-range and mesoscale transport models of pollutants and parameterizations in climate models.

Nichols, J. J.; Eichinger, W. E.; Cooper, D. I.; Hipps, L. E.; Holder, H. E.; Kustas, W. P.; Prueger, J. H.

2004-12-01

421

Activity of the European high heat flux test facility: FE200  

Microsoft Academic Search

FE200 is an electron beam (EB) 200kW test facility resulting since 1991 from partnership between Framatome Technical Centre in Le Creusot (France) and Tore Supra team in CEA Cadarache (France). It is dedicated to high heat flux testing of small and medium-sized plasma facing components. The performed tests are thermal fatigue tests (100,000 since 1992), critical heat fluxes, disruptions, glancing

I. Bobin-Vastra; F. Escourbiac; M. Merola; P. Lorenzetto

2005-01-01

422

Application of the gradient heat flux sensor to study pulsed processes in a shock tube  

NASA Astrophysics Data System (ADS)

The surface temperature of a model body of revolution placed in a pulsed supersonic nitrogen flow is measured with the help of a gradient heat flux sensor. From the measured temperature, a heat flux toward the surface of the body is determined. The steady flow of a viscous transcalent gas about the body is numerically calculated. The results of the numerical calculation and measuring data are in good agreement.

Bobashev, S. V.; Golovachov, Yu. P.; Mende, N. P.; Popov, P. A.; Reznikov, B. I.; Sakharov, V. A.; Schmidt, A. A.; Chernyshev, A. S.; Sapozhnikov, S. Z.; Mityakov, V. Yu.; Mityakov, A. V.

2008-12-01

423

An urban canyon energy budget model and its application to urban storage heat flux modeling  

Microsoft Academic Search

To obtain a local-scale urban energy balance by either measurement or modeling it is necessary to determine storage heat flux (?Qs). This flux cannot be measured directly due to the complexity of the urban surface. The Grimmond et al. Objective Hysteresis Model (OHM) [C.S.B. Grimmond, H.A. Cleugh, T.R. Oke, An objective urban heat storage model and its comparison with other

A. John Arnfield; C. S. B. Grimmond

1998-01-01

424

Correlation between air-sea heat fluxes over the Aegean Sea and the total precipitable water over Europe and North Africa.  

NASA Astrophysics Data System (ADS)

The relationship between the air-sea heat fluxes at two sites in the Aegean Sea and the total precipitable water (TPW) over Europe and North Africa is investigated. The four components of heat flux (shortwave and longwave radiation, latent and sensible heat) originate from two independent and widely used data sets. At first a comparison is carried out between in situ observations, and various available dataset in order to select the most suitable for the Aegean Sea area. Thus, the Mediterranean HIPOCAS dataset (1958-2001) is used for the radiative components of air-sea heat fluxes while the OAFlux dataset is used for the turbulent ones. The TPW data were retrieved from the European Centre for Medium-Range Weather Forecasts data archive (ERA-40 dataset, 1958-2002) covering the area from 15W to 35E and 20N to 70N with a 2.5oX2.5o grid resolution. Then, correlation coefficients were estimated between the monthly mean heat flux anomalies at each one of the two sites in the Aegean Sea (one in the north and one in the south) and the monthly TPW anomalies at each grid point of the aforementioned area for winter (November-March) and summer (May-September). Finally, the eight correlation patterns were constructed, revealing the following: For the shortwave radiation, in winter, a dipole of opposite correlation (see-saw teleconnection), is observed between northeast Europe and East Mediterranean Sea. This pattern is inverted for the longwave radiation during winter and is limited to a strong positive south pole during the summer. Both correlation patterns indicate that an increase of TPW over northern Europe and the simultaneous decrease over eastern Mediterranean imply a decrease of total cloud coverage over the Aegean Sea and vice-versa. Regarding the turbulent air-sea heat flux components -latent and sensible heat-a different correlation pattern is appeared. The winter pattern exhibits a strong positive correlation (r>0.75) over the Balkan Peninsula indicating a simultaneous TPW decrease/increase and turbulent fluxes increase/decrease (flux anomaly arithmetically decrease when heat losses increase as latent and sensible heat are both negative during winter). The latter is in accordance with the effect of the strong northeastern cold and dry winds dominating the area throughout winter. These winds strengthen the turbulent heat loss over the Aegean Sea transferring cold and dry air masses from the Balkans. The identified correlation patterns weaken during summer although they still remain prominent. Regarding to the sensible heat the summer correlation pattern forms a weak dipole between the Northern Balkans and the Eastern Mediterranean.

Papadopoulos, V. P.; Bartzokas, A.; Chronis,