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in subjects: "Heat Flux"

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A theoretical prediction of critical heat flux in subcooled pool boiling during power transients

Understanding and predicting critical heat flux (CHF) behavior during steady-state and transient conditions are of fundamenatal interest in the design, operation, safety of boiling and two-phase flow devices. This paper discusses the results of a comprehensive theoretical study made specifically to model transient CHF behavior in subcooled pool boiling. This study is based upon a simplified steady-state CHF model in terms of the vapor mass growth period. The results obtained from this theory in… more

Date: January 1, 1988

Creator: Pasamehmetoglu, K. O.; Nelson, R. A. & Gunnerson, F. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Variability of surface fluxes over a heterogeneous semi-arid grassland

Efforts are increasing throughout the research community to improve the predictive capabilities of general circulation models (GCMs). The US Department of Energy's Atmospheric Radiation Measurement (ARM) program has stated its goals as improving the representation and parameterization of cloud radiative forcing and feedbacks in GCMs by a combined modeling and experimental approach. Along with ambient atmospheric conditions, including advection of water vapor and cloud nuclei from other regions,… more

Date: January 1, 1991

Creator: Barnes, F.J.; Porch, W.; Cooper, D. (Los Alamos National Lab., NM (United States)); Kunkel, K.E. (Illinois Univ., Urbana, IL (United States)); Hipps, L. & Swiatek, E. (Utah State Univ., Logan, UT (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A study of steady-state steam-water counterflow in porous media

Vapor-liquid counterflow in porous media arises in processes such as heat pipes, oil recovery and geothermal systems. Previous studies analysed these phenomena in separate contexts. This paper presents a unified description from which previous models result as limiting cases. The analysis includes capillarity, heat conduction, and Kelvin effects. The importance of each term to various processes is examined. Significantly, it is found that the critical heat flux is not constant but increases wit… more

Date: February 1, 1990

Creator: Satik, C.; Parlar, M. & Yortsos, Y.C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Further considerations of critical heat flux in saturated pool boiling during power transients

In this paper, we further evaluate our previously postulated transient CHF model. First, we verify the steady-state CHF model on which the transient model is based by using recent macrolayer-thickness data. We also include the effect of thermal storage in the heater that we previously neglected. The use of a simplified approach in the prediction of the instantaneous surface heat flux for given pwoer generation rates considerably improves the predictive capability of the transient critical heat-… more

Date: January 1, 1988

Creator: Pasamehmetoglu, K.O. & Nelson, R.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Particulate behavior in a controlled-profile pulverized coal-fired reactor: A study of coupled turbulent particle dispersion and thermal radiation transport

This report describes recent progress in a fundamental, three-year investigation of the coupled problem of turbulent particle dispersion and thermal radiation transport. The project's objective is to make measurements of particle size, velocity, number density, temperature and wall radiant heat flux in a parametrically-controlled reactor presently existent at Brigham Young University (BYU). Although the study proposed here is primarily designed to provide experimental data not currently availab… more

Date: January 1, 1992

Creator: Queiroz, M. & Webb, B.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Heat-Flux Gage thermophosphor system

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 … more

Date: August 1, 1991

Creator: Tobin, K.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Active layer hydrology for Imnavait Creek, Toolik, Alaska

The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events i… more

Date: April 1, 1987

Creator: Hinzman, L.D. & Kane, D.L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Results and predictions of scaled, nuclear large break loss-of-coolant experiments. [PWR]

Two 200% cold leg break loss-of-coolant experiments performed in the LOFT facility have exhibited early core-wide quenches which were not predicted by the RELAP4/MOD6 code. Posttest studies have shown that while the critical flow model used significantly affects the hydraulic calculation, the principal reason for not predicting the quench behavior lies in the area of post-CHF heat transfer. The ability of the code to calculate quenches using a modified heat transfer surface is demonstrated, the… more

Date: January 1, 1980

Creator: Grush, W. H.; Lin, J. C.; Linebarger, J. H. & Nelson, R. A. Jr.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Critical heat flux experiments in a circular tube with heavy water and light water.

Experiments were performed to establish the critical heat flux (CHF) characteristics of heavy water and light water. Testing was performed with the up-flow of heavy and of light water within a 0.3744 inch inside diameter circular tube with 72.3 inches of heated length. Comparisons were made between heavy water and light water critical heat flux levels for the same local equilibrium quality at CHF, operating pressure, and nominal mass velocity. Results showed that heavy water CHF values were, on… more

Date: May 1980

Creator: Williams, C. L. & Beus, S. G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A theoretical prediction of critical heat flux in forced convection boiling during power transients

In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to the departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is favorable. The results are discussed in terms of the various parameters affecting the transient CHF. This new model also is compared with the semi-empirical… more

Date: January 1, 1988

Creator: Pasamehmetoglu, K.O.; Nelson, R.A. & Gunnerson, F.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Expected environments in high-level nuclear waste and spent fuel repositories in salt

The purpose of this report is to describe the expected environments associated with high-level waste (HLW) and spent fuel (SF) repositories in salt formations. These environments include the thermal, fluid, pressure, brine chemistry, and radiation fields predicted for the repository conceptual designs. In this study, it is assumed that the repository will be a room and pillar mine in a rock-salt formation, with the disposal horizon located approx. 2000 ft (610 m) below the surface of the earth.… more

Date: August 1, 1980

Creator: Claiborne, H.C. & Rickertsen, L.D., Graham, R.F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Bounding burnout risk power limits for the K-14 cycle

This document discusses burnout risk (BOR) power limits which are designed to protect the reactor from a significant release of fission products, due to critical heat flux (CHF) burnout of fuel and target assemblies. At expected operating power levels for the reactor restart, approximately 50% of historical full power, the risk of CHF and attendant burnout is negligible. Flow instability power limits will restrict reactor operation, and flow instability will always occur before CHF. BOR power l… more

Date: October 1, 1990

Creator: Shadday, M.A. Jr.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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The extension of solar magnetic fields into interplanetary space

The flow of coronal plasma into interplanetary space results in outward transport of the solar magnetic field. The prevailing open'' interplanetary magnetic field is rooted in the corona and wraps up into a spiral due to the rotation of the Sun. This simple configuration, however, is disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from the solar corona into interplanetary space. Observations of CMEs at 1 AU reveal electron signatures indicating a closed magnetic top… more

Date: January 1, 1991

Creator: McComas, D.J. & Phillips, J.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Quantitative analysis of bidirectional electron fluxes within coronal mass ejections at 1 AU

The solar wind electron heat flux is carried primarily by suprathermal halo'' electrons beamed antisunward along the interplanetary magnetic field (IMF), indicating magnetic connection to the Sun only in one direction. However, electron observations at 1 AU show that counterstreaming halo beams, suggesting closed magnetic structures, prevail within coronal mass ejections (CMEs). These structures might be magnetic tongues'', tied to the Sun at both ends, magnetically detached plasmoids, or compl… more

Date: January 1, 1991

Creator: Phillips, J.L.; Gosling, J.T.; McComas, D.J.; Bame, S.J. & Feldman, W.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Loss-of-coolant accident analyses of the Advanced Neutron Source Reactor

Currently in the conceptual design stage, the Advanced Neutron Source Reactor (ANSR) will operate at a high heat flux, a high mass flux, an a high degree of coolant subcooling. Loss-of-coolant accident (LOCA) analyses using RELAP5 have been performed as part of an early evaluation of ANSR safety issues. This paper discusses the RELAP5 ANSR conceptual design system model and preliminary LOCA simulation results. Some previous studies were conducted for the preconceptual design. 12 refs., 7 figs.

Date: January 1, 1991

Creator: Chen, N.C.J.; Yoder, G.L. (Oak Ridge National Lab., TN (USA)) & Wendel, M.W. (Martin Marietta Energy Systems, Inc., Oak Ridge, TN (USA))

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

On the hot-spot-controlled critical heat flux mechanism in pool boiling of saturated fluids

In this paper, we further investigate the hypothesis that the critical heat flux (CHF) occurs when some point on the heated surface reaches a high enough temperature that liquid can no longer contact that point, resulting in a gradual but continuous increase in the overall surface temperature. This hypothesis unifies the occurrence of the CHF and the quenching of hot surfaces by relating both to the same concept, i.e., the ability of a liquid to contact a hot surface. We use a two-dimensional t… more

Date: January 1, 1992

Creator: Unal, C.; Sadasivan, P. & Nelson, R.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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

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

Date: January 1, 1988

Creator: O'Rourke, P.J. & Collins, L.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Limits of helium cooling in fusion reactor first walls and blankets

This study explores the practical limits of helium cooling in a simple geometry unconstrained by a particular conceptual design. Specifically, the configuration was chosen to be an externally heated straight tube considering both uniform heating and heating of half the external parimeter. Both thermal hydraulic and structural limits to the heat flux have been investigated. Curves are presented to show the heat flux and tube length which simultaneously attain both a well temperature and pressure… more

Date: January 1, 1978

Creator: Stewart, C. W.; Bampton, M .C. C.; Aase, D. T. & Sutey, A. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Critical heat flux concerns during the flow instability phase of a DEGB LOCA

Arguments are presented that support the proposal that a separate burnout risk analysis, for the Flow Instability (FI) phase of a LOCA, not be required for reactor restart. With expected reactor power limits, flow instability will occur before critical heat flux (CHF). Since FI power limits preclude the occurrence of flow instability in a bounding accident, a DEGB LOCA, the risk of CHF and attendant burnout is negligible. A review of RDAP data revealed that in the past reactor assemblies operat… more

Date: August 1, 1990

Creator: Shadday, M.A. Jr.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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An X-point ergodic divertor

A new ergodic divertor is proposed. It utilizes a system of external (n = 3) coils arranged to generate overlapping magnetic islands in the edge region of a diverted tokamak and connect the randomized field lines to the external (cold) divertor plate. The novel feature in the configuration is the placement of the external coils close to the X-point. A realistic design of the external coil set is studied by using the field line tracing method for a low aspect ratio (A {approx equal} 3) tokamak. … more

Date: October 1, 1991

Creator: Chu, M. S.; Jensen, T. H.; La Haye, R. J.; Taylor, T. S. & Evans, T. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Post CHF heat transfer and quenching. [PWR]

This paper describes quantitatively new mechanisms in the post-CHF regime which provide understanding and predictive capability for several current two-phase forced convective heat transfer problems. These mechanisms are important in predicting rod temperature turnaround and quenching during the reflood phase of either a hypothetical loss-of-coolant accident (LOCA) or the FLECHT and Semiscale experiments. The mechanisms are also important to the blowdown phase of a LOCA or the recent Loss-of-Fl… more

Date: January 1, 1980

Creator: Nelson, R.A. & Condie, K.G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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

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 criterion is also presented. Transient analysis indicates that premature flow excurs… more

Date: September 1, 1982

Creator: Khatib-Rahbar, M. & Cazzoli, E. G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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

A radial flux limit of 147 W/cm{sup 2} at the wetted inner tube wall has been demonstrated with a Nb-1%Zr/K heat pipe, a flux 5 times greater than the previously accepted safe design level of 25-30 W/cm{sup 2}. The wick structure was an annular gap type fabricated from 100 {times} 100 mesh Nb-1%Zr screen. Rigorous fabrication and cleaning procedures are believed to be critical to good wetting, resulting in significantly reduced active nucleation site size and a higher boiling limit. The procedu… more

Date: January 1, 1989

Creator: Woloshun, K.A.; Sena, J.T.; Keddy, E.S. & Merrigan, M.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The DIII-D summary contribution to the final INTOR workshop

In SIII-D, good H-mode confinement has been obtained with up to 6 MW of neutral-beam injection (NBI). In this report we summarize the essential features of divertor operation for DIII-D H-mode plasma. Briefly, our measurements show that: Large edge density and temperarture gradients are obtained with scale lengths of a few cm at the midplane; In the steady state, approximately 10-20% of the input power is deposited on the divertor plates in a region that is peaked on the separatrix and extends … more

Date: February 26, 1988

Creator: Hill, D. N.; Allen, S. L.; Brooks, N. H.; Content, D.; DeBoo, J. C.; Gohil, P. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department