Numerical Study of Characteristics of Burning Phenomena in Equidistant Square Arrayed n-Heptane Fires

2014 ◽  
Author(s):  
Koyu Satoh ◽  
Naian Liu ◽  
Xiaodong Xie ◽  
Wei Gao
Keyword(s):  
Heat Flux ◽  
Burning Rate ◽  
Radiative Heat ◽  
Numerical Study ◽  
Simulation Method ◽  
Flame Length ◽  
Simulation Software ◽  
Radiative Heat Flux ◽  
Simulation Results ◽  
The Relationship

Merging of large-scale city fires and forest fires causes rapid acceleration of fire growth. Once a merging fire occurs, it becomes more difficult to suppress, with greater potential damages. In particular, merging fires may induce fire whirls in windy conditions. However, the details of interactions in multiple fires that cause fire merging have not been fully clarified. For the interactions in multiple fires, the inter-fire distance among fires greatly affects the merging phenomenon. The objective of this paper is to examine the detailed merging conditions, particularly the burning rate increase and total heat release rate, by numerical simulation of reduced scale fires. The burning behavior of n-heptane in n × n fire arrays is examined, using the fire simulation software, FDS by NIST. In addition, another simple model is employed. The number of array matrix, n, is varied, together with the inter-fire distance. The simulation results show that there are considerable differences between both simulations and experiments. However, the differences between the simpler simulation Method II and experiments are fewer than the simulation Method I. The following possibilities are considered: (1) The oil pan size affects the difference, but the results between simulations and experiments are so large. (2) The grid size for simulations may have some effects on the simulation results due to the resolution, (3) the experimental results may not always be precise, since the burning rates in the experiments are measured by the burn-out time and (4) the wind caused by merging fires may reduce the radiative heat flux to the adjacent fuel. The relationship between flame length and burning rate and the relationship between flame length and radiative heat flux are well-correlated.

CFD Study of a Fire Whirl of Huge Oil Tank: Burning Rate, Flame Length, Distributions of n-Heptane and Oxygen in a Fire Whirl

2014 ◽  
Author(s):  
Koyu Satoh ◽  
Naian Liu ◽  
Xiaodong Xie ◽  
Wei Gao
Keyword(s):  
Heat Flux ◽  
Radiative Heat ◽  
Flame Length ◽  
Radiative Heat Flux ◽  
Cfd Simulations ◽  
Oil Storage ◽  
Burning Rates ◽  
Oil Tank ◽  
Fire Whirl ◽  
Oil Tanks

The number of huge oil storage tanks is increasing in the world. If a fire occurs in one of these tanks, it is very difficult to suppress. Additionally, if a fire whirl occurs in an oil tank fire, it is extremely dangerous for firefighters to extinguish the fire. The authors have numerically studied huge fire whirls in a large oil tank depot and predicted the generation of those fire whirls. Here, another study is attempted to clarify the details of huge fire whirl in a large oil tank, using two kinds of fire whirl generation channels in CFD simulations using the software, FDS by NIST. Details of burning rates, velocities of whirling flames, radiative heat flux, heat release rates and whirling cycles are examined, using oil tanks with the diameters of 0.2 to 80 m. In oil tanks with a diameter of 80 m, a tall fire whirl is generated. The height is about 1000 m. In this study of oil tanks fires with small to large diameters, it has been found that fire whirl lengths are about 8 to 11 times of the oil tank diameter. The maximum radiative heat flux due to a fire whirl in 80 m diameter oil tanks exceeds 100 kW/m2. Since the maximum radiation is found at twice the distance of oil tank diameters from the tank centers, adjacent oil tanks may be ignited. This study has also examined a method used to prevent fire whirl generation in huge oil tanks.

Numerical Study of Radiative Heat Flux Emitted by Stainless Wire-Net Porous Media

2020 ◽  
Vol 861 ◽  
pp. 509-513
Author(s):  
Niwat Ketchat ◽  
Bundit Krittacom
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Porous Media ◽  
Radiative Heat ◽  
Solid Phase ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Radiative Heat Flux ◽  
Air Velocity ◽  
Lower Volume

Numerical model of the convective-radiative heat transfer of porous media was proposed. A stainless wire-net was used as porous media. The physical properties, consisting of porosity (φ) and optical thickness (τ0), of porous media were independent variables. The air velocity was reported in the form of Reynolds number (Re). Two equations of the conservative energy with local thermal non-equilibrium were analyzed. The gas (θf) and solid (θs) phases of conservative energy equation inside porous media were investigated. The radiative heat flux (ψ) at down-stream of solid phase emitted into outside was dealt by the P1 approximation. From the study, it was found that the level of θf and θs decreased as Re increased because the effect of convection heat transfer. Inversely, the level of ψ increased as increasing Re. The level of θf, θs and ψ were decreased as φ increased owing to a lower volume of material depended on the increasing level of φ resulting to the heat transfer rate became lower. The level of θf, θs and ψ gave increased with τ0 becaues a wider distance in absorping energy leading to a higher emission energy from the porous media was achieved.

A Numerical Study of Radiative Heat Transfer in a Cylindrical Furnace by Using Finite Volume Method

2016 ◽  
Author(s):  
Zhenhua Wang ◽  
Bengt Sunden ◽  
Shikui Dong ◽  
Zhihong He ◽  
Weihua Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Numerical Study ◽  
Radiative Heat Flux ◽  
Computational Time ◽  
Volume Method

In designing industrial cylindrical furnaces, it is important to predict the radiative heat flux on the wall with high accuracy. In this study, we consider CO2 and H2O which have strong absorption in the infrared range. The absorption coefficients of the gases are calculated by using the statistical narrow band (SNB) model. The spectrum is divided into 15 bands to cover all the absorption regions of the two non-gray gases. The radiative transfer equation is solved by the finite volume method (FVM) in cylindrical coordinates. To make the FVM more accurate, we discretize the solid angle into 80 directions with the S8 approximation which is found to be both efficient and less time consuming. Based on the existing species and temperature fields, which were modeled by the FLUENT commercial code, the radiative heat transfer in a cylinder combustor is simulated by an in-house code. The results show that the radiative heat flux plays a dominant part of the heat flux to the wall. Meanwhile, when the gas is considered as nongray, the computational time is very huge. Therefore, a parallel algorithm is also applied to speed up the computing process.

Nonequilibrium radiative heat flux modeling for the Huygens entry probe

2006 ◽  
Vol 111 (E7) ◽  
Author(s):  
T. E. Magin ◽  
L. Caillault ◽  
A. Bourdon ◽  
C. O. Laux
Keyword(s):  
Heat Flux ◽  
Radiative Heat ◽  
Radiative Heat Flux ◽  
Entry Probe

Handling of Collimated Irradiation on a Plane-Parallel Participating Medium

2000 ◽  
Author(s):  
Christian Proulx ◽  
Daniel R. Rousse ◽  
Rodolphe Vaillon ◽  
Jean-François Sacadura
Keyword(s):  
Heat Flux ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Radiative Heat ◽  
Radiative Heat Flux ◽  
Scattering Media ◽  
One Dimensional ◽  
Plane Parallel ◽  
Collimated Beam ◽  
Good Agreement

Abstract This article presents selected results of a study comparing two procedures for the treatment of collimated irradiation impinging on one boundary of a participating one-dimensional plane-parallel medium. These procedures are implemented in a CVFEM used to calculate the radiative heat flux and source. Both isotropically and anisotropically scattering media are considered. The results presented show that both procedures provide results in good agreement with those obtained using a Monte Carlo method, when the collimated beam impinges normally.

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