Thermal Radiation From Vertical Turbulent Jet Flame: Line Source Model

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Kuibin Zhou ◽  
Juncheng Jiang
Keyword(s):  
Heat Flux ◽  
Line Source ◽  
Radiant Heat ◽  
Source Model ◽  
Radiant Heat Flux ◽  
Emissive Power ◽  
Jet Flame ◽  
New Model ◽  
Flame Shape ◽  
Line Source Model

It is often reported that a jet fire occurs in industrial installations or in the transportation of hazardous materials and could amplify the scale of accident by imposing lots of heat on people and nearby facilities. This paper presents a new semi-empirical radiation model, namely, the line source model to predict the radiant heat flux distribution around a vertical turbulent hydrocarbon jet flame. In terms of the fact that the jet flame holds the large ratio of flame length to diameter, the new model assumes that all thermal energy is emitted by a line source located inside the jet flame volume. With three typically different shapes to simulate the jet flame shape, a formula is proposed to characterize the profile of the emissive power per line length (EPPLL), by which the line source model can be closed in theory. In comparison with the point source model, the multipoint source model, and the solid flame model, the new model agrees better with the measurement of the heat flux radiated from a small jet flame. It is found that the line source model can well predict the radiant heat flux of both small and large jet flames, yet with the flame shape simulated by the back-to-back cone and the cone–cylinder combined shape, respectively. By parameter sensitivity and uncertainty analysis, the ranking by importance of input parameters is also given for the new model.

scholarly journals Heat Transfer of Buried Pipe for Heat Pump Application

1991 ◽  
Vol 113 (1) ◽  
pp. 51-55 ◽  
Author(s):  
Viung C. Mei
Keyword(s):  
Heat Pump ◽  
Line Source ◽  
Source Model ◽  
The Other ◽  
Test Results ◽  
Average Deviation ◽  
New Model ◽  
Source Theory ◽  
Soil Temperatures ◽  
Line Source Model

It is generally felt that the application of line source theory for ground coil design usually resulted in excessive overdesign. It was anticipated that in order for the ground coil heat pump systems to be economically competitive with other residential heating and cooling systems, ground coil overdesign had to be kept to a minimum. A new ground coil model was derived, which based on energy balance rather than the traditional line source theory. It was aimed to more accurately predict the operation of ground coils. It is the intention of this study to compare this ground coil model with models based on line source theory, a simple line source model and a modified line source model, by using them to simulate the same field test data for both summer and winter ground coil operations. The results indicated that for winter coil operation, the new model predicted the coil liquid exit temperature less than 2°C maximum deviation from the measured values, with an average deviation less than 1°C. The modified line source model had an average deviation of more than 1.5°C. For summer operation, all models underpredicted the measured soil temperatures because the effect of thermal backfill material was not included in the models. The new model still predicted the test results better than the other two models. However, when the effect of sand thermal backfill was included in the new model, which was not easy for the other two models, the calculated soil temperatures were almost identical to the test results.

Three-Dimensional Formulation of the Radiant Heat Flux Variation on a Cylinder Engulfed in Flames

1985 ◽  
Vol 107 (4) ◽  
pp. 949-952 ◽  
Author(s):  
M. M. Tunc¸ ◽  
A. Karakas¸
Keyword(s):  
Heat Flux ◽  
Three Dimensional ◽  
Radiant Heat ◽  
Maximum Amount ◽  
Cylinder Surface ◽  
Radiant Heat Flux ◽  
Radiation Heat ◽  
Radiation Heat Flux ◽  
Flux Variation ◽  
Flame Shape

A three-dimensional formulation is used to determine the incident radiant heat flux on a cylinder surface which is engulfed in flames. For an axisymmetric horizontal pool fire of a specified flame shape, effective flame radiation temperature and a gray flame absorption coefficient, this analysis computes the variation of the incident radiant heat flux along the length and around the circumference of the tank portrayed as a cylinder, engulfed in flames. The radiant flux density from the flame to the cylinder becomes maximum toward the center of the pool and decreases markedly toward the edges. The points which are receiving the maximum amount of radiation heat flux around the circumference of the cylinder are also determined.

Directive line source model: A new model for sound diffraction by half planes and wedges

2000 ◽  
Vol 107 (6) ◽  
pp. 2973-2986 ◽  
Author(s):  
Penelope Menounou ◽  
Ilene J. Busch-Vishniac ◽  
David T. Blackstock
Keyword(s):  
Line Source ◽  
Source Model ◽  
New Model ◽  
Sound Diffraction ◽  
Line Source Model

Investigation on the Thermal Radiation Distribution of Oil Tank Fires

2014 ◽  
Vol 530-531 ◽  
pp. 349-352
Author(s):  
Shan Shan Li ◽  
Jian Gang Sun ◽  
Zhen Wang ◽  
Li Fu Cui
Keyword(s):  
Heat Flux ◽  
Thermal Radiation ◽  
Point Source ◽  
Crude Oil ◽  
Radiant Heat ◽  
Source Model ◽  
Target Point ◽  
Radiant Heat Flux ◽  
Radiation Distribution ◽  
Oil Tank

A thermal radiation monitoring system was established to measure the thermal radiation distribution of the crude oil tank fires, and the effect of open area, horizontal and vertical distance on the radiant heat flux was analyzed. The experimental results are compared with the calculated values by the point source model. It shows that the point source model have a high accuracy to calculate the radiant heat flux of the crude oil tank fire when the distance between the target point and the flame center is larger than the diameter of the tank.

scholarly journals A Novel Model Concerning the Independence of Emissivity and Absorptivity for Enhancing the Sustainability of Radiant Cooling Technology

2021 ◽  
Author(s):  
Fan Zhang ◽  
Guoqiang Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiant Heat ◽  
Radiant Heat Transfer ◽  
Radiant Heat Flux ◽  
New Model ◽  
The Past ◽  
Radiant Cooling ◽  
Cooling Technology ◽  
Kirchhoff's Law

Abstract Radiant cooling technology is a sustainable technology for improving built environment. The past research only studied the performance (e.g., radiant heat flux) based on Kirchhoff’s law while the accuracy and its reasons were seldom analyzed. In order to study the mechanism deeply, a new model of radiant heat transfer is derived theoretically which considers emissivity and absorptivity independently. This model is validated by the experimental data then applied in a reference case for further analysis. The analyzing methods of sensitivity and relative deviation are performed to investigate the reasons for the errors. The results of sensitivity analysis show that it is about 20% − 40% more sensitive for the emissivity to the heat flux than the absorptivity. Furthermore, the deviation of the heat flux can reach up to 20% when the absorptivity is in the range from 0.4 to 0.9. This deviation is close to the estimated error range of 21.8% in the past studies. Therefore, the discussion based on the theoretical analysis, shows that the errors in past studies are highly due to the oversimplified preconditions for applying Kirchhoff’s law and they ignored the impact of surface absorption. Additionally, the validation in the previous experiments was highly coincidence, since they neglected the key independent tests of the absorptivity and radiant heat flux. Comprehensively, the new model is valuable to provide a more reliable solution for analyzing the radiant heat transfer and for the future design of an independent test of radiant heat flux.

scholarly journals Лучистый тепловой поток от возбужденных атомов в высокочастотном ионном двигателе

2021 ◽  
Vol 47 (4) ◽  
pp. 45
Author(s):  
В.К. Абгарян ◽  
М.В. Абгарян ◽  
А.Б. Надирадзе ◽  
В.В. Нигматзянов ◽  
А.А. Семенов
Keyword(s):  
Heat Flux ◽  
Radio Frequency ◽  
Spontaneous Emission ◽  
Discharge Plasma ◽  
Radiant Heat ◽  
Numerical Calculations ◽  
Radiant Heat Flux ◽  
Ion Thrusters

The radiant heat flux coming from the discharge plasma on the surfaces of radio frequency ion thrusters is considered. Spontaneous emission of photons is formed when the excitation of plasma atoms and ions is removed. The distributions of the densities of the heat flux brought by radiation to the surface in the thrusters are calculated. The distributions can be used in numerical calculations of temperatures in thrusters design.

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