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Добірка наукової літератури з теми "Boundary heat flux"

Автор: Grafiati
Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Boundary heat flux"

1

Huang, Weichao, Jiahao Li, and Ding Liu. "Research on Unsteady Inverse Heat Conduction Based on Dynamic Matrix Control." Energies 16, no. 11 (May 30, 2023): 4420. http://dx.doi.org/10.3390/en16114420.

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For the unsteady multi-boundary inverse heat conduction problem, a real-time solution method for boundary heat flux based on dynamic matrix control is proposed in the paper. The method solves the heat flux at the boundary in real-time by measuring the temperature information at the measurement points of the heat transfer system. A two-dimensional direct heat conduction model of the heat transfer system is established in the paper, and is solved by the finite difference method to obtain the temperature information of the measurement points under any heat flux boundary. Then, the correspondence between the heat flux of boundary and the temperature information is presented by means of a step-response model. The regularization parameters are introduced into the method to improve the stability of the inversion process, and the effect of real-time inversion on the heat flux of the boundary is achieved through rolling optimization. The experimental results show that the proposed method can achieve real-time inversion of the heat fluxes of the two-dimensional boundary with good accuracy.
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2

Miao, Wenbo, Xiaoli Cheng, Bangcheng Ai, and Yonghui Dong. "Surface Slip Effect on Thermal Environment of Hypersonic Non-Equilibrium Flows." International Journal of Computational Methods 12, no. 04 (August 2015): 1540008. http://dx.doi.org/10.1142/s0219876215400083.

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Boundary slip effect caused by low gas density has an important influence on the thermal environment of the vehicles. Numerical studies on the boundary slip effect and accommodation for moment and energy have been carried out in this paper. The simulations considering slip boundary and surface catalysis are validated with Arc-jet test data. Mechanism and rules of impact on surface heat flux by different boundary slip level (Knudsen number from 0.0028 to 0.05) has been investigated in typical hypersonic flow conditions. The results show that mechanisms of boundary slip effect on mass diffusion heat flux and convective heat flux are different; slip boundary diminishes the convective heat, whereas enhances the mass diffusion heat flux. Smaller moment and energy accommodation coefficient is equivalent to more rarefaction. As Knudsen number goes up, the influences of accommodation on heatflux are enhanced, it mainly affects the convective heat flux.
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3

Wang, Fu Qiang. "Ray-Thermal Sequential Coupled Heat Transfer ANALYSIS of Porous Media Receiver for Solar Dish Collector." Applied Mechanics and Materials 442 (October 2013): 169–75. http://dx.doi.org/10.4028/www.scientific.net/amm.442.169.

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For the sake of reflecting the concentrated heat flux distribution boundary condition as genuine as possible during simulation, the sequential coupled optical-thermal heat transfer analysis is introduced for porous media receiver. During the sequential coupled numerical analysis, the non-uniform heat flux distribution on the fluid entrance surface of porous media receiver is obtained by Monte-Carlo ray tracing method. Finite element method (FEM) is adopted to solve energy equation using the calculated heat flux distribution as the third boundary condition. The dimensionless temperature distribution comparisons between uniform and non-uniform heat flux distribution boundary conditions, various porosities, and different solar dish concentrator tracking errors are investigated in this research.
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4

Wen, Jun, and M. M. Khonsari. "Analytical Formulation for the Temperature Profile by Duhamel’s Theorem in Bodies Subjected to an Oscillatory Heat Source." Journal of Heat Transfer 129, no. 2 (July 5, 2005): 236–40. http://dx.doi.org/10.1115/1.2424236.

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An analytical technique is presented for treating heat conduction problems involving a body experiencing oscillating heat flux on its boundary. The boundary heat flux is treated as a combination of many point heat sources, each of which emits heat intermittently based on the motion of the flux. The working function of the intermittent heat source with respect to time is evaluated by using the Fourier series and temperature profile of each point heat source is derived by using the Duhamel’s theorem. Finally, by superposition of the temperature fields over all the point heat sources, the temperature profile due to the original moving heat flux is determined. Prediction results and verification using finite element method are presented for an oscillatory heat flux in a rectangular domain.
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5

Alghamdi, A. "Inverse Estimation of Boundary Heat Flux for Heat Conduction Model." Journal of King Abdulaziz University-Engineering Sciences 21, no. 1 (2010): 73–95. http://dx.doi.org/10.4197/eng.21-1.5.

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6

Taylor, Robert P., Philip H. Love, Hugh W. Coleman, and M. H. Hosni. "Step heat flux effects on turbulent boundary-layer heat transfer." Journal of Thermophysics and Heat Transfer 4, no. 1 (January 1990): 121–23. http://dx.doi.org/10.2514/3.29175.

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Dewar, W. K., and R. X. Huang. "Fluid flow in loops driven by freshwater and heat fluxes." Journal of Fluid Mechanics 297 (August 25, 1995): 153–91. http://dx.doi.org/10.1017/s0022112095003041.

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Thermohaline convection in a salt water loop is discussed. Fluid temperature is affected by relaxation on the loop surface and fluid salinity by a freshwater flux through the loop surface. In addition, other boundary conditions on salinity, such as the equivalent virtual salt flux or salinity relaxation condition, are examined and the dynamic role of diffusion in thermohaline convection is analysed.Both analytical and numerical analyses indicate that the system behaviour depends sensitively on the nature of the salinity boundary condition. For the saline-only loop model, analysis indicates that perturbations are advected by the mean flow, and flow stability is independent of the strength of the boundary forcing. In the full thermohaline loop problem, the virtual salt flux formulation accurately mirrors the freshwater flux results when the system is in the thermal mode. However, these formulations can differ substantially when the system is in the haline mode, especially in the strongly forced, weakly diffusive limit.For both types of loop configuration, salinity profiles governed by freshwater flux have scales determined by the internal parameters, while virtual salt flux profiles necessarily reflect the lengthscales of applied boundary conditions. Negative salinities can also appear under virtual salt flux owing to the inaccuracies inherent in the approximation, while freshwater flux ensures positive-definite salinity values.Our analysis supports the use of the physically more accurate freshwater flux boundary conditions when simulating thermohaline circulation.
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8

Voglar, Jure. "Physical Model of a Single Bubble Growth during Nucleate Pool Boiling." Fluids 7, no. 3 (February 27, 2022): 90. http://dx.doi.org/10.3390/fluids7030090.

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A simplified physical model of a single bubble growth during nucleate pool boiling was developed. The model was able to correlate the experimentally observed data of the bubble’s growth time and its radius evolution with the use of the appropriate input parameters. The calculated values of separated heat fluxes from the heater wall, thermal boundary layer, and to the bulk liquid gave us a new insight into the complex mechanisms of the nucleate pool boiling process. The thermal boundary layer was found to supply the majority of the heat to the growing bubble. The heat flux from the thermal boundary layer to the bubble was found to be close to the Zuber’s critical heat flux limit (890 kW/m2). This heat flux was substantially larger than the input heater wall heat flux of 50 kW/m2. The thermal boundary layer acts as a reservoir of energy to be released to the growing bubble, which is filled during the waiting time of the bubble growth cycle. Therefore, the thickness of the thermal boundary layer was found to have a major effect on the bubble’s growth time.
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9

Ji, Xuan, Nora Bailey, Daniel Fabrycky, Edwin S. Kite, Jonathan H. Jiang, and Dorian S. Abbot. "Inner Habitable Zone Boundary for Eccentric Exoplanets." Astrophysical Journal Letters 943, no. 1 (January 1, 2023): L1. http://dx.doi.org/10.3847/2041-8213/acaf62.

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Abstract The climate of a planet can be strongly affected by its eccentricity due to variations in the stellar flux. There are two limits for the dependence of the inner habitable zone boundary (IHZ) on eccentricity: (1) the mean stellar flux approximation ( S IHZ ∝ 1 − e 2 ), in which the temperature is approximately constant throughout the orbit, and (2) the maximum stellar flux approximation (S IHZ ∝ (1 − e)2), in which the temperature adjusts instantaneously to the stellar flux. Which limit is appropriate is determined by the dimensionless parameter Π = C BP , where C is the heat capacity of the planet, P is the orbital period, and B = ∂ Ω ∂ T s , where Ω is the outgoing long-wave radiation and T s is the surface temperature. We use the Buckingham Π theorem to derive an analytical function for the IHZ in terms of eccentricity and Π. We then build a time-dependent energy balance model to resolve the surface temperature evolution and constrain our analytical result. We find that Π must be greater than about ∼1 for the mean stellar flux approximation to be nearly exact and less than about ∼0.01 for the maximum stellar flux approximation to be nearly exact. In addition to assuming a constant heat capacity, we also consider the effective heat capacity including latent heat (evaporation and precipitation). We find that for planets with an Earthlike ocean, the IHZ should follow the mean stellar flux limit for all eccentricities. This work will aid in the prioritization of potentially habitable exoplanets with nonzero eccentricity for follow-up characterization.
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Juliano, Thomas J., Jonathan Poggie, Kevin M. Porter, Roger L. Kimmel, Joseph S. Jewell, and David W. Adamczak. "HIFIRE-5b Heat Flux and Boundary-Layer Transition." Journal of Spacecraft and Rockets 55, no. 6 (November 2018): 1315–28. http://dx.doi.org/10.2514/1.a34147.

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Дисертації з теми "Boundary heat flux"

1

Vega, Thomas. "Quantification of the Fire Thermal Boundary Condition." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/78052.

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The thermal boundary condition to a fire exposed surface was quantified with a hybrid heat flux gage. Methods were developed to determine the net heat flux through the gage, incident heat flux, cold surface heat flux, convective heat transfer coefficient, adiabatic surface temperature, and the separated components of radiative and convective heat flux. Experiments were performed in a cone calorimeter with the hybrid gage flush mounted into UNIFRAX Duraboard LD ceramic board. The results were then compared to results obtained with a Schmidt-Boelter gage and a plate thermometer. The hybrid heat flux gage predicted a cold surface heat flux within 5% of cold surface heat fluxes measured with a Schmidt-Boelter gage. Adiabatic surface temperature measurements compared well with the plate thermometer measurements at steady state. Hybrid gage measurements were performed on flat plate samples of Aluminum 5083, Marinite P, and UNIFRAX Duraboard LD ceramic board. The gage and sample assemblies were exposed to mixed-mode heat transfer conditions in a cone calorimeter. Temperature measurements were performed at the top, center, bottom surfaces of the marinite and ceramic board samples. A single midpoint temperature was performed on the aluminum. Boundary condition details obtained with the hybrid gage were then input to the commercial finite element analysis package Abaqus. Abaqus was used to create the flat plate geometries of the sample and variable temperature dependent material properties were used for each material. Measured temperatures were then compared to the model predicted temperatures with good results. Hybrid gage measurements were verified using a new experimental apparatus. The apparatus consisted of an impinging jet assembly, a tungsten lamp, and a gage holster assembly. The impinging jet was used to expose the gage to isolated convection and the lamp was used to expose the gage to isolated radiation. The gage holster assembly was used to water cool the gage when desired. Measurements performed with the gage water cooled in isolated convection allowed for the convective heat transfer coefficient to be determined. Two methods were developed to determine the convective heat transfer coefficient in mixed-mode heat transfer conditions. These methods were then verified by comparison to the isolated heat transfer coefficient. Similarly, the incident radiation was isolated by water cooling the gage while only the lamp was on. The components of heat flux were then separated for mixed-mode comparisons and were verified against this isolated radiation. The hybrid gage predicted convective heat transfer coefficients within 10% of the isolated heat transfer coefficient and incident heat fluxes within 11% of the isolated radiation.
Master of Science
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2

Kharche, Sanjay. "Stefan problems with two-dimensional, linearised perturbations in their boundary geometry or boundary conditions." Thesis, University of Hull, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327179.

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3

Schmid, Hans Peter Emil. "Spatial scales of sensible heat flux variability : representativeness of flux measurements and surface layer structure over suburban terrain." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29385.

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The surface character of a suburban area is far from the uniform, smooth and flat planes over which current surface-layer theory is valid and where vertical eddy-fluxes can be assumed to be almost constant horizontally and vertically. The complexity of the surface introduces considerable variability into the atmosphere at small spatial scales. This variability is partly reduced and spatially-averaged by turbulent mixing but still leaves the concerns about the spatial representativeness of sensible heat flux measurements over a suburban area. The spatial scales of sensible heat flux variability are discussed in terms of the distribution of surface temperature and roughness elements. It is shown that : (1) an eddy-correlation measurement can be considered spatially representative, if its surface zone of influence (source area) is large enough to include a spatially representative sample of surface temperature and roughness elements. (2) a quantitative measure of spatial representativeness can be estimated by use of the two-dimensional Fourier transform of the surface temperature and roughness element distributions (i.e. by the normalized integrated variance spectrum). (3) the source area of an eddy correlation measurement may be evaluated by a numerical model based on a probability density function plume diffusion model. The source area model developed herein can also be used to estimate the relative influence of specific surface sources or sinks upon an eddy-flux measurement in the surface layer. These concepts are tested in a suburban residential area in Vancouver, B.C., Canada. Remotely sensed surface temperatures and a digitized roughness element inventory are used as data-bases for the Fourier transforms to develop representativeness criteria for eddy-flux measurements. A set of sensible heat flux measurements at six sites and the corresponding source area calculations are used to formulate recommendations for the objective evaluation of the spatial representativeness of sensible heat flux measurements over a suburban area. The validity of the suggested evaluation methods is confirmed by the observations. Internal boundary layer growth, estimated by the source area model, compares well with existing work. Some consequences of complex surfaces on the surface layer structure are briefly discussed.
Arts, Faculty of
Geography, Department of
Graduate
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4

Magee, Michael P. "Thermal boundary resistance in a high temperature thin-film superconductor under varying heat flux." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA326312.

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Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, December 1996.
"December 1996." Thesis advisor(s): Matthew Kelleher, Pat E. Phelan. Includes bibliographical references (p. 73-75). Also available online.
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5

Sahlée, Erik. "Fluxes of Sensible and Latent Heat and Carbon Dioxide in the Marine Atmospheric Boundary Layer." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8184.

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Oceans cover about 70% of the earth’s surface. They are the largest source of the atmospheric water vapour and act as enormous heat reservoirs. Thus in order to predict the future weather and climate it is of great importance to understand the processes governing the exchange of water vapour and heat between the ocean and atmosphere. This exchange is to a large extent mediated by turbulent eddies. Current numerical climate and weather forecast models are unable to resolve the turbulence, which means that the turbulent exchange needs to be simplified by using parameterizations.

Tower based measurements at the Östergarnsholm Island in the Baltic Sea have been used to study the air-sea turbulent exchange of latent and sensible heat and the heat flux parameterizations. Although the measurements are made at an island, data obtained at this site is shown to represent open ocean conditions during most situations for winds coming from the east-south sector. It is found that during conditions with small air-sea temperature differences and wind speeds above 10 m s-1, the structure of the turbulence is re-organized. Drier and colder air from aloft is transported to the surface by detached eddies, which considerably enhance the turbulent heat fluxes. The fluxes where observed to be much larger than predicted by current state-of-the-art parameterizations. The turbulence regime during these conditions is termed the Unstable Very Close to Neutral Regime, the UVCN-regime.

The global increase of the latent and sensible heat fluxes due to the UVCN-regime is calculated to 2.4 W m-2 and 0.8 W m-2 respectively. This is comparable to the current increase of the radiative forcing due to anthropogenic emissions of greenhouse gases, reported in Intergovernmental Panel on Climate Change fourth assessment report (IPCC AR4). Thus the UVCN-effect could have a significant influence when predicting the future weather and climate.

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6

Lindgren, Kristina. "The Behaviour of the Latent Heat Exchange Coefficient in the Stable Marine Boundary Layer." Thesis, Uppsala University, Department of Earth Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9140.

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Knowledge of the turbulent fluxes at the sea surface is important for understanding the interaction between atmosphere and ocean. With better knowledge, improvements in the estimation of the heat exchange coefficients can be made and hence models are able to predict the weather and future climate with higher accuracy.

The exchange coefficients of latent and sensible heat during stable stratification vary in the literature. Therefore it is necessary to investigate the processes influencing the air-sea exchange of water vapour and heat in order to estimate these values. With measurements from a tower and a directional waverider buoy at the site Östergarnsholm in the Baltic Sea, data used in this study have been sampled from the years 2005-2007. This site represents open-ocean conditions during most situations when the wind comes from the south-east sector. The neutral exchange coefficients, CEN and CHN, have been calculated along with the non-dimensional profile functions for temperature and wind to study the dependence of stability and other parameters of relevance.

It was found that CEN increased slightly with wind speed and reached a mean value of approximately 1.45×10-3. The highest values of CEN were observed during near neutral conditions and low wave ages. CHN attained a mean value of approximately 0.77×10-3 and did not show any relation to wind speed or to wave age. No significant dependence with wind or wave direction could be shown for either CEN or CHN in the sector 80-220°. The stability correction, performed to reduce the dependence on stratification for CEN and CHN, was well performed for stabilities higher than 0.15. The stability is represented by a relationship between the height and the Obukhov-length (z/L).

Validity of the non-dimensional profile functions for temperature and wind showed that, for smaller stabilities, these functions gave higher values than the corresponding functions recommended by Högström (1996). The profile funtions for temperature was shown to have a larger scatter while the profile functions for wind was less scattered and deviated more from the functions given by Högström


Kunskap om turbulenta flöden i det marina gränsskiktet är viktigt för att förstå växelverkan mellan atmosfär och hav. Med bättre kunskap kan förbättringar i bestämningen av utbyteskoefficienterna för latent och sensibelt värme erhållas. Det medför att modeller kan prognostisera väder och framtida klimat med högre noggrannhet.

Utbyteskoefficienterna för latent och sensibelt värme har för stabil skiktning olika värden i litteraturen. Detta gör det nödvändigt att undersöka de processer som påverkar utbytet av vattenånga och värme mellan luft och hav för att kunna bestämma dessa värden. Data som har använts i den här studien insamlades mellan år 2005 och 2007 från en boj och ett torn vid mätplatsen Östergarnsholm i Baltiska havet. För det flesta situationer, när vinden blåser från syd-ost, representerar mätplatsen ett förhållande likvärdigt det över öppet hav. De neutrala utbyteskoefficienterna, CEN och CHN, och de dimensionslösa profilfunktionera för temperatur och vind, och , har beräknats för att studera beroendet av stabilitet samt andra relevanta parametrar.

Beräkningarna visade att CEN ökade något med vindhastighet och hamnade på ett medelvärde av ungefär 1.45×10-3. De högsta värdena på CEN observerades vid nära neutrala förhållanden och låga vågåldrar. CHN uppmättes till att ha ett medelvärde på ungefär 0.77×10-3 och uppvisade inget beroende med vindhastighet eller vågålder. Inget märkbart beroende med vind- eller vågriktning kunde visas för CEN eller CHN i sektorn 80-220°. Stabilitetskorrektionen, utförd för att reducera beroendet av atmosfärens skiktning för CEN och CHN, var bra för stabiliteter högre än 0.15. Stabiliteten representeras av förhållandet mellan höjden och Obukhov-längden (z/L).

Utvärdering av de dimensionslösa funktionerna för temperatur och vind visade att dessa funktioner, för små stabiliteter, gav högre värden än motsvarande funktioner som rekommenderas av Högström (1996). Värdena på profilfunktionerna för temperatur hade större spridning än värdena på profilfunktionerna för vind och avvek mer från funktionerna givna av Högström.

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7

Moosbrugger, John C. "Numerical computation of metal/mold boundary heat flux in sand castings using a finite element enthalpy model." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/16365.

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8

Brunner, Daniel Frederic. "Development of probes for assessment of ion heat transport and sheath heat flux in the boundary of the Alcator C-Mod Tokamak." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/86420.

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Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2013.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. Pages [228-229] blank.
Includes bibliographical references.
Progress towards a viable fusion reactor will require comprehensive understanding of boundary plasma physics. Knowledge in this area has been growing, yet there are critical gaps. Measurements of the sheath heat flux transmission coefficient-a fundamental physical quantity whose theoretical value is ~ 7-have varied from 2 to 20. Values below 5 are physically impossible and have challenged the understanding of this very basic theory. In addition, measurements of ion temperature are sparse and ion energy transport is poorly understood. To this end a set of new diagnostics, including a surface thermocouple, ion sensitive probe, and retarding field analyzer, have been developed that can tolerate the extreme heat fluxes in the Alcator C-Mod boundary plasma. These probes are used to asses issues of heat flux and ion energy transport. Systematic studies with these new tools reveal the following: A comparison of surface thermocouples and Langmuir probes confirms standard sheath heat flux theory in a tokamak for the first time. The measurement of unphysically low sheath heat flux transmission coefficients and an anomalous increase in measured divertor pressure by Langmuir probes, which is also unphysical, are found the be linked. Plasma-neutral simulations indicate that these artifacts are due to the Langmuir probe bias modifying the local plasma. Important space charge limits to measurements with ion sensitive probes are found experimentally and explored in depth with a 1D kinetic simulation. These results clarify the plasma conditions under which an ion sensitive probe may be used to measure ion temperature and/or plasma potential. The retarding field analyzer is demonstrated to be a viable ion temperature diagnostic up to the last closed flux surface in C-Mod. A ₁D fluid simulations is built to interpret edge ion heat transport. At high collisionality-where the fluid approximations are valid: the simulation reproduces the measured edge ion-to-electron temperature ratio (~ 2). However, at low collisionality-where fluid approximation is not valid-the simulation is not able to reproduce the experimental temperature ratio (~ 4). The addition of kinetic heat flux limiters can bring the simulated ratio into agreement with measurements. The value of heat flux limiter is found to be consistent with that expected from kinetic theory.
by Daniel Frederic Brunner.
Ph. D.
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9

Nilsson, Erik. "Flux Attenuation due to Sensor Displacement over Sea." Thesis, Uppsala University, Department of Earth Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8024.

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In this study the flux attenuation due to sensor displacement has been investigated over sea using an extensive set of data from the "Ocean Horizontal Array Turbulence Study". All previous investigations of the flux attenuation have been performed over land.

A function developed for correcting fluxes in the homogenous surface layer was compared to measured flux attenuation. This investigation revealed the possibility to find new functions describing the flux attenuation when measurements are carried out over sea. From the measured flux attenuation studied here a change in the form of correction functions was required to improve the estimated flux loss. The most significant difference found in this report compared to the previous landbased study Horst (2006) is for stable conditions, where significantly less flux loss is found over sea. Two new functions describing the attenuation due to sensor displacement over sea have been constructed.

One of these expressions has a discontinuity at z/L = 0. This is supported by measured flux attenuation. A reasonable interpretation is; however, that this discontinuity is caused by two separate turbulence regimes near neutrality on the stable and unstable side respectively. The discontinuity is thus not believed to be an effect merely of stability. A second correction function which is continuous over all stabilities has therefore also been constructed. These two functions and the correction function from Horst (2006) have been compared to measured flux loss. Based on this comparison the continuous correction function is recommended for correcting scalar fluxes measured over sea. It should be noted, however, that this expression only describes the mean attenuation and has been constructed from measurements at 5 and 5.5 m above mean sea level.

The theoretical basis used in the development of the function for flux attenuation over land allows for a direct link between a spectral shape and the attenuation expression. This link has been preserved for the new expressions presented in this report. The spectral shape corresponding to the continuous correction function has been compared to measured mean cospectra and also to the cospectra from Horst (2006) corresponding to crosswind displacements.

At a height of 10 m and a sensor displacement of 0.2 m the mean flux attenuation is about 1.3-4% in the stability interval −1 < z/L < 1.5 when using the new correction functions presented in this report.

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10

Lammert, Andrea, and Armin Raabe. "Berechnung sensibler Wärmeströme mit der Surface Renewal Analysis und der Eddy - Korrelations - Methode." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-215495.

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Die Surface Renewal Analysis wurde zur Bestimmung sensibler Wärmeflußdichten im bodennahen Bereich der atmosphärischen Grenzschicht genutzt und mit der Eddy - Korrelations - Methode verglichen. Dazu wurden beide Berechnungsmethoden auf Temperatur - und Vertikalwinddaten angewandt, die unter Verwendung von Strukturfunktionen simuliert wurden. Zur Überprüfung der Resultate wurden über zwei verschiedenen Unterlagen (Wiese und Düne) hochfrequente Zeitreihen von Temperatur und Vertikalwind gemessen und mit der Surface Renewal Analysis und der Eddy - Korrelations - Methode analysiert
The Surface Renewal Analysis was used to estimate the sensible heat flux density in the ground near area of the boundary layer. The results were compared with eddy correlation method. For it both methods were used to analyse temperature- and vertical velocity-data, which were simulated by the application of structure functions. Time series of high frequency temperature- and vertical velocity-data over two different canopies (meadow and dune) were measured to examine the results. The data were analysed with surface renewal analysis and eddy correlation
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Книги з теми "Boundary heat flux"

1

Zaman, K. B. M. O., Reshotko Eli, and United States. National Aeronautics and Space Administration., eds. Turbulent heat flux measurements in a transitional boundary layer. [Washington, DC]: National Aeronautics and Space Administration, 1992.

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2

Zaman, K. B. M. Q., Reshotko E, and United States. National Aeronautics and Space Administration., eds. Turbulent heat flux measurements in a transitional boundary layer. [Washington, DC]: National Aeronautics and Space Administration, 1992.

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3

Bradley, E. F. A guide to making climate quality meteorological and flux measurements at sea. Boulder, Colo: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Office of Oceanic and Atmospheric Research, Earth System Research Laboratory, Physical Sciences Division, 2007.

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4

Bradley, E. F. A guide to making climate quality meteorological and flux measurements at sea. Boulder, CO: National Oceanic and Atmospheric Administration, Office of Oceanic and Atmospheric Research, Earth System Research Laboratory, Physical Sciences Division, 2006.

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5

Michels, Berenice I. Fluxes of heat and water vapour in a convective mixed layer during EFEDA. Köln: Deutsche Forschungsanstalt für Luft- und Raumfahrt, 1992.

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6

Jankovsky, Robert S. High-area-ratio rocket nozzle at high combustion chamber pressure--experimental and analytical validation. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

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7

D, Smith Timothy, Pavli Albert J, and NASA Glenn Research Center, eds. High-area-ratio rocket nozzle at high combustion chamber pressure--experimental and analytical validation. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

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8

D, Smith Timothy, Pavli Albert J, and NASA Glenn Research Center, eds. High-area-ratio rocket nozzle at high combustion chamber pressure--experimental and analytical validation. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

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9

D, Smith Timothy, Pavli Albert J, and NASA Glenn Research Center, eds. High-area-ratio rocket nozzle at high combustion chamber pressure--experimental and analytical validation. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

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10

Foken, Th. Turbulenter Energieaustausch zwischen Atmosphäre und Unterlage: Methoden, messtechnische Realisierung sowie ihre Grenzen und Anwendungsmöglichkeiten. Offenbach am Main: Selbstverlag des Deutschen Wetterdienstes, 1990.

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Частини книг з теми "Boundary heat flux"

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Burton, Ralph A. "Coupling of Waviness and Boundary Heat Flux in Reynolds Flow." In Heat, Bearings, and Lubrication, 90–97. New York, NY: Springer New York, 2000. http://dx.doi.org/10.1007/978-1-4612-1248-5_12.

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Desjardins, R. L., J. I. Macpherson, P. H. Schuepp, and F. Karanja. "An Evaluation of Aircraft Flux Measurements of CO2, Water Vapor and Sensible Heat." In Boundary Layer Studies and Applications, 55–69. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0975-5_5.

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3

Amar, M., D. Andreucci, R. Gianni, and C. Timofte. "Homogenization of a Heat Conduction Problem with a Total Flux Boundary Condition." In Lecture Notes in Mechanical Engineering, 1475–87. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-41057-5_119.

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Hasebe, Norio. "Thermal Stress for Mixed Heat Conduction Boundary Around an Arbitrarily Shaped Hole Under Uniform Heat Flux." In Encyclopedia of Thermal Stresses, 5204–8. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_117.

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Helmig, Thorsten, Hui Liu, Simon Winter, Thomas Bergs, and Reinhold Kneer. "Development of a Tool Temperature Simulation During Side Milling." In Lecture Notes in Production Engineering, 308–17. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34486-2_22.

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AbstractCurrent modeling approaches of cutting processes require on the one hand extensive numerical and analytical simulations and further an experienced user in the field of numerical simulations, which makes a large-scale application time-consuming to apply.Therefore, the goal is to implement existing models into an established side-milling simulation program aiming for a computationally fast and user-friendly simulation approach capable of predicting transient tool temperatures along the cutting edge. Aim of this work is the development of the thermal model, which can later be implemented into existing programs. The model process involves the following two major steps: First, a geometric engagement simulation of the milling process with a parameterizable tool geometry is performed. These results are used to form a database linking the specific cutting force components with the heat flux components. Second, a three-dimensional transient heat conduction model of the cutter is established, applying the calculated heat flux components as boundary conditions in the simulation. Finally, first results of the performed simulation are presented and evaluated, in particular to validate the work flow and user accessibility. Future studies will then focus on further parameter analysis and experimental validation.
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Vaka, Ananda S., Pedduri Jayakrishna, Saurav Chakraborty, Suvankar Ganguly, and Prabal Talukdar. "Application of Inverse Heat Transfer Technique in Thin Slab Continuous Casting for Estimating the Interfacial Boundary Heat Flux." In Lecture Notes in Mechanical Engineering, 385–98. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-7214-0_32.

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Ferdows, M., and Sakawat Hossain. "Local Non-similar Solution of Induced Magnetic Boundary Layer Flow with Radiative Heat Flux." In Flow and Transport in Subsurface Environment, 343–65. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-8773-8_12.

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Fuselier, S. A., W. C. Feldman, S. J. Bame, E. J. Smith, and F. L. Scarf. "Heat Flux Observations and the Location of The Transition Region Boundary of Giacobini-Zinner." In Special Publications, 1. Washington, D.C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/sp027p0165.

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Prajapati, Ravi, Viral Thakkar, Sanil Shah, and Ajit Kumar Parwani. "Estimation of Transient Boundary Heat Flux Using Modified JAYA Algorithm in Laminar Duct Flow." In Recent Advances in Mechanical Infrastructure, 331–42. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4176-0_29.

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Sathavara, Parth, Ajit Kumar Parwani, Maulik Panchal, and Paritosh Chaudhuri. "Estimation of Boundary Heat Flux with Conjugate Gradient Method by Experimental Transient Temperature Data." In Recent Advances in Mechanical Infrastructure, 343–52. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4176-0_30.

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Тези доповідей конференцій з теми "Boundary heat flux"

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Juliano, Thomas J., Jonathan Poggie, Kevin Porter, Roger L. Kimmel, Joseph S. Jewell, and David Adamczak. "HIFiRE-5b Heat Flux and Boundary-Layer Transition." In 47th AIAA Fluid Dynamics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2017. http://dx.doi.org/10.2514/6.2017-3134.

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Saidi, Arash, and Jungho Kim. "Heat Flux Sensor With Minimal Impact on Boundary Conditions." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47567.

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A technique for determining the heat transfer on the far surface of a wall based on measuring the heat transfer and temperature on the near wall is presented. Although heat transfer measurements have previously been used to augment temperature measurements in inverse heat conduction methods, the sensors used alter the heat flow through the surface, disturbing the very quantity that is desired to be measured. The ideal sensor would not alter the boundary condition that would exist were the sensor not present. The innovation of this technique in that it has minimal impact on the wall boundary condition. Since the sensor is placed on the surface of the wall, no alteration of the wall is needed. The theoretical basis for the experimental technique as well as experimental results showing the heat flux sensor performance is presented.
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3

Walsh, P. A., E. J. Walsh, and Y. S. Muzychka. "Laminar Slug Flow: Heat Transfer Characteristics With Constant Heat Flux Boundary." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88428.

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The problem of elevated heat flux in modern electronics has led to the development of numerous liquid cooling devices which yield superior heat transfer coefficients over their air based counterparts. This study investigates the use of liquid/gas slug flows where a liquid coolant is segregated into discrete slugs, resulting in a segmented flow, and heat transfer rates are enhanced by an internal circulation within slugs. This circulation directs cooler fluid from the center of the slug towards the heated surface and elevates the temperature difference at the wall. An experimental facility is built to examine this problem in circular tube flow with a constant wall heat flux boundary condition. This was attained by Joule heating a thin walled stainless steel tube. Water was used as the coolant and air as the segregating phase. The flow rates of each were controlled using high precision syringe pumps and a slug producing mechanism was introduced for segmenting the flow into slugs of various lengths at any particular flow rate. Tube flows with Reynolds numbers in the range 10 to 1500 were examined ensuring a well ordered segmented flow throughout. Heat transfer performance was calculated by measuring the exterior temperature of the thin tube wall at various locations using an Infrared camera. Nusselt number results are presented for inverse Graetz numbers over four decades, which spans both the thermally developing and developed regions. The results show that Nu in the early thermally developing region are slightly inferior to single phase flows for heat transfer performance but become far superior at higher values of inverse Gr. Additionally, the slug length plays an important role in maximizing Nusselt number in the fully developed region as Nu plateaus at different levels for slugs of differing lengths. Overall, this paper provides a new body of experimental findings relating to segmented flow heat transfer in constant heat flux tubes without boiling. Put abstract text here.
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Wu, Zhijian, Jing Feng, Xueyan Zhang, and Aixia Zhou. "Study on Reconstruction of Heat Flux in Moving Boundary." In 2012 National Conference on Information Technology and Computer Science. Paris, France: Atlantis Press, 2012. http://dx.doi.org/10.2991/citcs.2012.203.

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Molavi, Hosein, Ali Hakkaki-Fard, Alireza Pourshaghaghy, Mehdi Molavi, and Ramin K. Rahmani. "Heat Flux Estimation in a Nonlinear Inverse Heat Conduction Problem With Moving Boundary." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88501.

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Estimation of heat flux in the nonlinear heat conduction problem becomes more challenging when the material at the boundary loses its mass due to phase change, chemical erosion, oxidation, or mechanical removal. In this paper, a new gradient-type method with adjoint problem is employed to predict the unknown time-varying heat flux at the receding surface in the nonlinear heat conduction problem. Particular features of this novel approach are discussed and examined. Results obtained by the new method for several test cases are benchmarked and analyzed using the numerical experiments with the simulated exact and noisy measurements. Exceedingly reliable estimation on the heat flux can be obtained from the knowledge of the transient temperature recordings, even in the case with measurement errors. In order to evaluate the performance characteristics of the present inverse scheme, simulations are conducted to analyze the effects of this technique with regard to conjugate gradient method with adjoint problem and variable metric method with adjoint problem. The obtained results show that the present inverse scheme distinguishably accelerates the convergence rate, which approve the well capability of the method for this type of heat conduction problems.
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Park, Chul. "Radiative to Convective Heat Flux Conversion by Boundary Layer Absorption." In 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-1583.

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Breidenthal, R. E. "Wall Heat Flux Under Persistent Vortices." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31244.

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It is commonly perceived that turbulent flows yield turbulent wall fluxes, while laminar flows yield correspondingly laminar wall fluxes. Experiments support a recent theory that turbulent flows can yield laminar wall fluxes if the flow is “persistent.” Adding strong, stationary vortices to a turbulent boundary layer lowers the wall heat flux to a laminar value.
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Wang, Q. W., Q. W. He, X. N. Suo, and Y. N. Wu. "GASEOUS FLOW AND HEAT TRANSFER IN MICRO-CHANNEL WITH HEAT FLUX SPECIFIED BOUNDARY CONDITION." In Annals of the Assembly for International Heat Transfer Conference 13. Begell House Inc., 2006. http://dx.doi.org/10.1615/ihtc13.p14.130.

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Lee, Man, Luthur Siu Lun Cheung, Yi-Kuen Lee, and Yitshak Zohar. "Two-Phase Flow in Microchannel Heat Sink with Nearly Uniform Heat Flux Boundary Condition." In 2006 1st IEEE International Conference on Nano/Micro Engineered and Molecular Systems. IEEE, 2006. http://dx.doi.org/10.1109/nems.2006.334888.

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Lu, Wen-Qiang, and Qing-Mei Fan. "Non-Fourier Heat Conduction Phenomena Applied Different Temperature and Heat Flux Pulses on Boundary." In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52287.

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A new numerical method [1], which combines the dual reciprocity boundary element method with Laplace transforms, has been used to solve ultrafast heat conduction problems. By this method, the time micro scale heat transfer problems applied different extreme high frequency temperature and heat flux pulses (the width of a single pulse is less than 10−12 s) on the boundary are simulated in this paper. Numerical results open out some phenomena of non-Fourier heat conduction. “Thermal accumulation (TA)” as a typical phenomenon of non-Fourier heat conduction takes on different characteristics under different pulsed conditions. The pulse time-width has important effect on the non-Fourier characteristics for single pulse, while different pulse periods for seriate pulse make obvious different non-Fourier characteristics.
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Звіти організацій з теми "Boundary heat flux"

1

Mahrt, Larry, and Jielun Sun. A New Heat Flux Formulation Based on Effective Surface Temperatures, With Extension to the Nocturnal Boundary Layer. Fort Belvoir, VA: Defense Technical Information Center, August 1999. http://dx.doi.org/10.21236/ada369931.

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