Confirmation of Gambill-Greene Straight-Flow Burnout Heat Flux Equation at Higher Flow Velocity

1964 ◽  
Vol 86 (2) ◽  
pp. 297-298 ◽  
Author(s):  
J. Mayersak ◽  
S. D. Raezer ◽  
E. A. Bunt
Keyword(s):  
Heat Flux ◽  
Ohmic Heating ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Plasma Arc ◽  
Linear Flow ◽  
Copper Electrodes ◽  
Straight Flow ◽  
Good Agreement

A test of the validity in a higher flow range of the Gunther equation (as modified by Gambill and Greene) for predicting burnout heat flux in linear flow was required during the development of copper electrodes for plasma arc heaters. An experiment employing ohmic heating of a stainless steel tube yielded a burnout value in good agreement with that predicted in the range of heat fluxes close to the maximum previously recorded.

The Effects of Nucleate Boiling Versus Film Boiling on Heat Transfer in Power Boiler Tubes

1962 ◽  
Vol 84 (4) ◽  
pp. 365-371 ◽  
Author(s):  
H. S. Swenson ◽  
J. R. Carver ◽  
G. Szoeke
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Inside Surface ◽  
Film Boiling ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Steam Quality ◽  
Heat Transfer Coefficients

In large, subcritical pressure, once-through power boilers heat is transferred to steam and water mixtures ranging in steam quality from zero per cent at the bottom of the furnace to 100 per cent at the top. In order to provide design information for this type of boiler, heat-transfer coefficients for forced convection film boiling were determined for water at 3000 psia flowing upward in a vertical stainless-steel tube, AISI Type 304, having an inside diameter of 0.408 inches and a heated length of 6 feet. Heat fluxes ranged between 90,000 and 180,000 Btu/hr-sq ft and were obtained by electrical resistance heating of the tube. The operation of the experimental equipment was controlled so that nucleate boiling, transition boiling, and stable film boiling occurred simultaneously in different zones of the tube. The film boiling data were correlated with a modified form of the equation Nu = a a(Re)m(Pr)n using steam properties evaluated at inside surface temperature. Results of a second series of heat-transfer tests with tubes having a helical rib on the inside surface showed that nucleate boiling could be maintained to much higher steam qualities with that type of tube than with a smooth-bore tube.

Nucleate Boiling Heat Transfer of Binary Mixtures at Low to Moderate Heat Fluxes

1999 ◽  
Vol 121 (2) ◽  
pp. 365-375 ◽  
Author(s):  
R. J. Benjamin ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Turbulent Natural Convection

A model for nucleate pool boiling heat transfer of binary mixtures has been proposed based on an additive mechanism. The contributing modes of heat transfer are (i) the heat transferred by microlayer evaporation, (ii) the heat transferred by transient conduction during the reformation of the thermal boundary layer, and (iii) the heat transferred by turbulent natural convection. The model takes into account the microroughness of the heating surface which has been defined quantitatively. The model compares satisfactorily with data obtained in the present study and in the literature. These data were obtained on a variety of heating surfaces such as a vertical platinum wire, a horizontal stainless steel tube and flat horizontal aluminium, and stainless steel surfaces (with various surface finishes) thereby demonstrating the validity of the model.

Flow Pattern, Heat Transfer and Pressure Drop Behaviors of Micro-Channel Flow Boiling

2018 ◽  
Author(s):  
Sira Saisorn ◽  
Pochai Srithumkhant ◽  
Pakorn Wongpromma ◽  
Maturose Suchatawat ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Boiling ◽  
Flow Direction ◽  
Saturation Pressure ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Stainless Steel Tube

Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2–26 kW/m2, and a mass flux range of 610–815 kg/m2s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.

Experimental and numerical simulation studies on heat transfer to calorimeters engulfed in diesel pool fires

2017 ◽  
Vol 35 (2) ◽  
pp. 156-176 ◽  
Author(s):  
Sudheer Siddapureddy ◽  
SV Prabhu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Heat Fluxes ◽  
Numerical Code ◽  
Pool Fires ◽  
Steel Pipes ◽  
Adiabatic Surface ◽  
In Fire ◽  
Good Agreement

Characterization of heat transfer to calorimeters engulfed in pool fires is extremely important. To estimate the heat flux to the calorimeters, experiments are performed with horizontal stainless steel 304L pipes engulfed in diesel pool fires. The concept of adiabatic surface temperature is applied to predict the incident heat flux to horizontally oriented calorimeters engulfed in diesel pool fires. Plate thermometers are used to measure the adiabatic surface temperature for diesel pool fires. The estimated subsurface temperatures inside the steel pipes using the adiabatic surface temperature concept and the measured temperatures are in good agreement. Adiabatic surface temperature is also computed from fire simulations. The incident heat fluxes to the steel pipes engulfed in fire predicted from the simulations are found to be in good agreement with the experiments. The fire numerical code is validated against the 1 m pool fire experimental results of centerline temperature distribution and irradiances away from fire. A correlation is provided for the estimation of adiabatic surface temperature for large diesel pool fires. These results would provide an effective way for thermal test simulations.

Heat Transfer Predictions Using Accommodation Coefficients for a Dense Gas in a Micro/Nano-Channel

2008 ◽  
Author(s):  
S. V. Nedea ◽  
A. J. Markvoort ◽  
P. Spijker ◽  
A. A. van Steenhoven
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Md Simulations ◽  
Heat Fluxes ◽  
Dense Gas ◽  
Nano Channel ◽  
Accommodation Coefficients ◽  
Gas Interactions ◽  
Wall Interactions ◽  
Good Agreement

The influence of gas-gas and gas-wall interactions on the heat flux predictions for a dense gas confined between two parallel walls of a micro/nano-channel is realized using combined Monte Carlo (MC) and Molecular Dynamics (MD) techniques. The accommodation coefficients are computed from explicit MD simulations. These MD coefficients are then used as effective accommodation coefficients in Maxwell-like boundary conditions in MC simulations. We find that heat flux predictions from MC based on these coefficients compare good with the results of explicit simulations except the case when there are hydrophobic gas-wall/gas-gas interactions. For this case an artificial wall was introduced in order to measure these MD accommodation coefficients at this artificial border. Good agreement is found then for both hydrophilic and hydrophobic gas-wall interactions and we show this by confronting the heat fluxes from explicit MD simulations with the the MC heat flux predictions for all the generic accommodation coefficients.

Evaporation of Ammonia in a Smooth Horizontal Tube: Heat Transfer Measurements and Predictions

1999 ◽  
Vol 121 (1) ◽  
pp. 89-101 ◽  
Author(s):  
O. Zu¨rcher ◽  
J. R. Thome ◽  
D. Favrat
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Two Phase

Experimental test results for flow boiling of pure ammonia inside horizontal tubes were obtained for a plain stainless steel tube. Tests were run at a nominal saturation temperature of 4°C, nine mass velocities from 20–140 kg/m2 s, vapor qualities from 1–99 percent and heat fluxes from 5–58 kW/m2. Two-phase flow observations showed that the current test data covered the following regimes: fully stratified, stratified-wavy, intermittent, annular, and annular with partial dryout. The Kattan-Thome-Favrat flow boiling model accurately predicted the local heat transfer coefficients measured in all these flow regimes with only two small modifications to their flow map (to extend its application to G < 100 kg/m2 s). Their flow boiling model was also successfully compared to the earlier ammonia flow boiling data of Chaddock and Buzzard (1986). The Gungor-Winterton (1987) correlation instead gave very poor accuracy for ammonia.

scholarly journals Calibration of thermopile heat flux gauges using a physically-based equation

2021 ◽  
pp. 095765092098210
Author(s):  
Oliver J Pountney ◽  
Mario Patinios ◽  
Hui Tang ◽  
Dario Luberti ◽  
Carl M Sangan ◽  
...  
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Likelihood Estimation ◽  
Calibration Method ◽  
Heat Fluxes ◽  
Theoretical Relationship ◽  
Voltage Output ◽  
Physically Based ◽  
Experimental Rig ◽  
Good Agreement

A thermopile, in which a number of thermocouple junctions are arranged on either side of a thin layer of insulation, is commonly used to determine the heat flux for steady-state measurements. Gauges using this method are available commercially and a new, generic calibration method is described here. For this purpose, an equation based on physical properties has been derived to determine the theoretical relationship between the measured voltage output of the gauge and the heat flux through it. An experimental rig has been built and used to calibrate gauges under steady-state conditions for heat fluxes between 0.5 and 8 kW/m2. The gauge temperature was controlled between 30 and 110 °C, and voltage-flux correlation – based on the theoretical relationship – was determined using maximum likelihood estimation (MLE). For tests with constant gauge temperature, there was a linear relationship between the voltage and heat flux; owing to the temperature dependency of the Seebeck constants of the thermoelectric materials, the voltage increased with increasing gauge temperature. In all cases, there was very good agreement between the measured and correlated values, and the overall uncertainty of the correlation was estimated to be less than 5% of the measured heat flux.

scholarly journals Towards a better understanding in acrylamide formation, degradation and reduction in model systems (and foodstuffs)

2004 ◽  
Vol 22 (SI - Chem. Reactions in Foods V) ◽  
pp. S11-S14 ◽  
Author(s):  
F. Mestdagh ◽  
B. De Meulenaer ◽  
C. Van Peteghem ◽  
C. Cromphout ◽  
O. Thas
Keyword(s):  
Heat Flux ◽  
Stainless Steel ◽  
Steel Tube ◽  
Model Systems ◽  
Water Evaporation ◽  
Stainless Steel Tube ◽  
Tube Reactor ◽  
Acrylamide Formation ◽  
Fat Hydrolysis ◽  
Artificial Mixtures

A new baking methodology to study acrylamide formation, based on a closed stainless steel tube reactor, was tested on its repeatability. The main advantage of this frying procedure includes the possibility to study the acrylamide formation mechanism in different artificial mixtures, eliminating some variable factors during frying, such as heat flux, degradation of the frying oil and water evaporation. As a first application of this optimized heating concept, the influence of fat oxidation and fat hydrolysis on acrylamide formation was tested during baking of French fries, as well as during heating in the tube reactor. In both cases, no differences in acrylamide formation could be found between fresh oil and oxidized or hydrolyzed heating oils.

Film Boiling on a Horizontal Tube in Increased Gravity Fields

1964 ◽  
Vol 86 (2) ◽  
pp. 213-218 ◽  
Author(s):  
M. L. Pomerantz
Keyword(s):  
High Speed ◽  
Horizontal Tube ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Acceleration Data ◽  
Liquid Heat

The influence of acceleration on saturated pool film boiling from the outside of a horizontal 0.188 in. OD, stainless-steel tube is reported. Freon-113 at approximately atmospheric pressure was used as the test liquid. Heat-transfer coefficients were determined for the experimental ranges: (a) temperature differences of 200 to 500 deg F; (b) heat fluxes of 5000 to 25000 Btu/hr-ft2; and (c) accelerations of 1 to 10 times normal acceleration. Data were correlated by adding a dimensionless parameter to the theoretical equation derived by Bromley for film boiling. High-speed motion pictures were taken from which interbubble distances, bubble periods, and bubble breakoff diameters were measured.

Wettability of Horizontal Stainless Steel Tube by Nanofluid Droplets

2013 ◽  
Vol 597 ◽  
pp. 21-27
Author(s):  
Janusz T. Cieśliński ◽  
Katarzyna Krygier
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Stainless Steel ◽  
Solid Surface ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Natural Processes ◽  
Hydrophilic Surfaces ◽  
Nucleation Sites ◽  
Boiling Process

Wetting is the interaction of a liquid with a solid and is found in numerous natural processes as well as being of extreme importance to many industrial and engineering processes, such as absorption, distillation, flotation, gas scrubbing, condensation. Wetting is of key importance in boiling process, because contact angle, that is the measure of the degree of wetting, affects density of active nucleation sites, bubble departure diameter, and finally critical heat flux [. If the liquid will completely spread out on the solid surface and the contact angle will be close to zero degrees, the surface is called superhydrophilic. Less hydrophilic surfaces will have contact angle below 90o. If the surface is hydrophobic, the contact angle will be larger than 90o. Surfaces with contact angle larger than 150o are called superhydrophobic Fig. 1.

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