Dryout Heat Fluxes in Particulate Beds Heated Through the Base

1984 ◽  
Vol 106 (1) ◽  
pp. 176-183 ◽  
Author(s):  
S. W. Jones ◽  
M. Epstein ◽  
S. G. Bankoff ◽  
D. R. Pedersen
Keyword(s):  
Heat Flux ◽  
Heat Fluxes ◽  
Countercurrent Flow ◽  
Empirical Correlations ◽  
Flux Data ◽  
Experimental Heat ◽  
Bed Height ◽  
Data Points ◽  
Semi Empirical

A laboratory study of dryout heat fluxes in particulate beds heated through the base is reported. More than two hundred experimental heat flux data points were measured. Semi-empirical correlations of the dryout heat flux data for both deep and shallow particulate beds are developed, based on flooding in countercurrent flow in deep beds and a boiling crises in shallow beds. The role of capillary forces in bed dryout is discussed and an explanation for the variation of dryout heat flux with bed height in volumetrically heated particulate beds is presented.

Pool Boiling Critical Heat Flux in Reduced Gravity

1999 ◽  
Vol 121 (4) ◽  
pp. 865-873 ◽  
Author(s):  
D. P. Shatto ◽  
G. P. Peterson
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Qualitative Data ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Reduced Gravity ◽  
Empirical Correlations ◽  
Using Data ◽  
Semi Empirical ◽  
Reduced Pressures

An experimental investigation has been conducted to measure pool boiling critical heat fluxes in reduced gravity. A horizontal cylindrical cartridge heater immersed in water at reduced pressures during parabolic flights on NASA’s KC-135 resulted in boiling on the heater surface. Visual observations and qualitative data trends indicate that the conventional Taylor-Helmholtz. instability model still governs the critical heat flux mechanism over the range of gravitational accelerations of the current study, which range from 0.0005 < g/go < 0.044. Using data from more than 40 individual tests, two semi-empirical correlations have been developed to account for the effect of thermocapillary flow, which tends to decrease the critical heat flux below the predictions of previous correlations.

An Experimental Study of Subcooled Film Boiling on a Vertical Surface—Thermal Aspects

1992 ◽  
Vol 114 (1) ◽  
pp. 169-178 ◽  
Author(s):  
R. Vijaykumar ◽  
V. K. Dhir
Keyword(s):  
Heat Flux ◽  
Vertical Wall ◽  
Leading Edge ◽  
Vertical Surface ◽  
Heat Fluxes ◽  
Heated Wall ◽  
Film Boiling ◽  
Copper Block ◽  
Thermal Layer

Wall and liquid side heat fluxes near the leading edge of a vertical wall 6.3 cm wide and 10.3 cm high were measured during subcooled film boiling of water at 1 atm pressure. The heat flux from the interface into the liquid and temperature profiles in the liquid thermal layer were measured using real time holographic interferometry. The wall heat flux was measured with thermocouples embedded in a copper block, one face of which served as the heated wall. The role of the leading edge vapor layer, ripples, and large bulges in modifying the liquid side heat transfer is quantified.

A Comparison of Analytical and Experimental Local Heat Fluxes in Liquid-Propellant Rocket Thrust Chambers

1962 ◽  
Vol 84 (1) ◽  
pp. 19-28 ◽  
Author(s):  
William E. Welsh ◽  
Arvel B. Witte
Keyword(s):  
Heat Flux ◽  
Flow Characteristics ◽  
Heat Fluxes ◽  
Chamber Pressure ◽  
Liquid Propellant ◽  
Nitrogen Tetroxide ◽  
Thrust Chamber ◽  
Experimental Heat ◽  
Rocket Thrust ◽  
Propellant Rocket

Experimental data are presented showing heat-flux distributions measured calorimetrically with several liquid-propellant rocket thrust-chamber configurations. Thrust levels of the experimental chambers were from 300 to 5000 lb. Enzian-type and axial-stream showerhead propellant injectors were utilized with hydrazine (N2H4) and nitrogen tetroxide (N2O4) propellants. Nozzle-contraction-area ratios of 8 to 1, 4 to 1, and 1.64 to 1 were tested, each having a 5-in. inlet diameter. Characteristic chamber lengths ranged from 16.95 to 62.8 in. The comparison between the experimental heat flux and the analytical heat flux using the method of Bartz [1] was found to be closest in the nozzle-expansion region. The experimental heat-flux measurements ranged between 80 per cent above and 45 per cent below the analytical estimates at the nozzle throat, however. These differences were dependent upon thrust-chamber configuration, injector type, and chamber pressure, and apparently resulted from nonideal combustion and flow characteristics. It is concluded that a priori determination of heat-flux distribution along the thrust-chamber length was possible only to a first approximation for the conditions of these tests.

scholarly journals Using Transformation and Formation Maps to Study the Role of Air–Sea Heat Fluxes in North Atlantic Eighteen Degree Water Formation

2009 ◽  
Vol 39 (8) ◽  
pp. 1818-1835 ◽  
Author(s):  
Guillaume Maze ◽  
Gael Forget ◽  
Martha Buckley ◽  
John Marshall ◽  
Ivana Cerovecki
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Gulf Stream ◽  
Spatial Information ◽  
Formation Rate ◽  
Heat Fluxes ◽  
Subtropical Gyre ◽  
Sea Surface ◽  
Transformation Rate

Abstract The Walin water mass framework quantifies the rate at which water is transformed from one temperature class to another by air–sea heat fluxes (transformation). The divergence of the transformation rate yields the rate at which a given temperature range is created or destroyed by air–sea heat fluxes (formation). Walin’s framework provides a precise integral statement at the expense of losing spatial information. In this study the integrand of Walin’s expression to yield transformation and formation maps is plotted and used to study the role of air–sea heat fluxes in the cycle of formation–destruction of the 18° ± 1°C layer in the North Atlantic. Using remotely sensed sea surface temperatures and air–sea heat flux estimates based on both analyzed meteorological fields and ocean data–model syntheses for the 3-yr period from 2004 to 2006, the authors find that Eighteen Degree Water (EDW) is formed by air–sea heat fluxes in the western part of the subtropical gyre, just south of the Gulf Stream. The formation rate peaks in February when the EDW layer is thickened by convection owing to buoyancy loss. EDW is destroyed by air–sea heat fluxes from spring to summer over the entire subtropical gyre. In the annual mean there is net EDW formation in the west to the south of the Gulf Stream, and net destruction over the eastern part of the gyre. Results suggest that annual mean formation rates of EDW associated with air–sea fluxes are in the range from 3 to 5 Sv (Sv ≡ 106 m3 s−1). Finally, error estimates are computed from sea surface temperature and heat flux data using an ensemble perturbation method. The transformation/formation patterns are found to be robust and errors mostly affect integral quantities.

Dryout Heat Fluxes for Inductively Heated Particulate Beds

1977 ◽  
Vol 99 (2) ◽  
pp. 250-256 ◽  
Author(s):  
V. Dhir ◽  
I. Catton
Keyword(s):  
Heat Flux ◽  
Flow Rate ◽  
Gravitational Force ◽  
Heat Fluxes ◽  
Distilled Water ◽  
Hydrodynamic Models ◽  
Gas Jets ◽  
Bed Height ◽  
Dry Out ◽  
Frequency Current

Experimental observations of the dryout heat fluxes for inductively heated particulate beds have been made. The data were obtained when steel and lead particles in the size distribution 295–787 microns were placed in a 4.7-cm dia pyrex glass jar and inductively heated by passing radio frequency current through a 13.3-cm dia multiturn work coil encircling the jar. Distilled water, methanol and acetone were used as coolants in the experiments, while the bed height was varied from 1.9 to 8.9 cm. Different mechanisms for the dryout in deep and shallow beds have been identified. Dryout in shallow beds is believed to occur when the vapor velocity in the gas jets exceeds a certain critical velocity at which choking of the vapor, leading to obstruction in the flow of the liquid towards the bed occurs. However, deep beds dry out when gravitational force can no longer maintain a downward coolant flow rate necessary to dissipate the heat generated in the bed. Finally, the heat flux data of the present investigation and that from two previous investigations made at Argonne Laboratory and at UCLA have been correlated with semitheoretical correlations based on the proposed hydrodynamic models.

Intraseasonal Variability of Upper Ocean Heat Fluxes in the Central Bay of Bengal

2021 ◽  
Keyword(s):  
Heat Flux ◽  
Bay Of Bengal ◽  
Intraseasonal Variability ◽  
Heat Content ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Upper Ocean ◽  
Flux Divergence ◽  
Intraseasonal Oscillations

Abstract Upper-ocean heat content and heat fluxes of 10-60-day intraseasonal oscillations (ISOs) were examined using high-resolution currents and hydrographic fields measured at five deep-water moorings in the central Bay of Bengal (BoB) and satellite observations as part of an international effort examining the role of the ocean on monsoon intraseasonal oscillations (MISOs) in the BoB. Currents, temperature and salinity were sampled over the upper 600 to 1200 m from July 2018 -June 2019. The 10-60-day velocity ISOs of magnitudes 20-30 cm s−1 were observed in the upper 200 m, and temperature ISOs as large as 3°C were observed in the thermocline near 100 m. The wavelet co-spectral analysis reveals multiple periods of ISOs carrying heat southward. The meridional heat-flux divergence associated with the 10-60-day band was strongest in the central BoB at depths between 40 and 100 m, where the averaged flux divergence over the observational period is as large as 10−7 ° C s−1. The vertically-integrated heat-flux-divergence in the upper 200 m is about 20-30 Wm−2, which is comparable to the annual-average net surface heat flux in the northern BoB. Correlations between the heat content over the 26° C isotherm and the outgoing longwave radiation indicate that the atmospheric forcing typically leads changes of the oceanic-heat content, but in some instances, during fall-winter months, oceanic-heat content leads the atmospheric convection. Our analyses suggest that ISOs play an important role in the upper-ocean heat balance by transporting heat southward, while aiding the air-sea coupling at ISO time scales.

On the Role of Marangoni Effects on the Critical Heat Flux for Pool Boiling of Binary Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 103-109 ◽  
Author(s):  
W. R. McGillis ◽  
V. P. Carey
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Full Range ◽  
Pool Boiling ◽  
Marangoni Effect ◽  
Restoring Force ◽  
Marangoni Effects

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has been quantitatively estimated with a modified model derived from hydrodynamics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evidence, accurate mixture properties, and phase equilibrium revealing a correlation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid restoring force caused by surface tension gradients. The CHF condition was determined experimentally for saturated methanol/water, 2-propanol/water, and ethylene glycol/water mixtures, over the full range of concentrations, and compared to the model. The evidence in this study demonstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.

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