scholarly journals Experimental and Numerical Study for the Effect of Horizontal Openings on the External Plume and Potential Fire Spread in Informal Settlements

2021 ◽  
Vol 11 (5) ◽  
pp. 2380
Author(s):  
Mohamed Beshir ◽  
Karim Omar ◽  
Felipe Roman Centeno ◽  
Samuel Stevens ◽  
Lesley Gibson ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Radiative Heat ◽  
Numerical Study ◽  
Informal Settlement ◽  
Informal Settlements ◽  
Fire Spread ◽  
Heat Fluxes ◽  
Fuel Load

According to recent UN reports, it is estimated that more than one billion people live in informal settlements globally, exposing them to a large potential fire risk. In previous research, it was found that the main fire spread mechanism between dwellings is the external flaming (plume) and radiative heat fluxes from the vertical openings at the dwelling of origin to the surroundings. In this paper, an experimental and numerical study was conducted to quantify the effect of adding horizontal roof openings to the design of informal settlement dwellings to reduce the fire spread risk by decreasing the length of flames and radiation from the external plumes at the vertical openings. In total, 19 quarter scale ISO-9705 compartment fire experiments were conducted using an identical fuel load (80 MJ/m2) of polypropylene and were used to validate a physical computational fluid dynamics model for future studies. Five different total horizontal openings areas (0.0025, 0.01, 0.04, 0.09, and 0.16 m2) were investigated using two horizontal openings designs: (1) four square openings at the four corners of the compartment and (2) one slot cut at the middle of the compartment. It was found that adding horizontal openings decreased the average heat flux measured at the door by up to 65% and 69% for corner and slot cases, respectively. Heat flux reductions were achieved at opening areas as low as 0.01 m2 for slot cases, whereas reductions were only achieved at areas of at least 0.09 m2 for corner cases. The Computational Fluid Dynamics (CFD) model was validated using the experimental results. It successfully captured the main fire dynamics within the compartment in addition to the values of the external radiative heat flux. Further, a new empirical ventilation factor was generated to describe the flow field through both openings configurations which showed strong coupling with the inlet mass of fresh air to the compartment.

scholarly journals Determination of Critical Separation Distance Between Dwellings in Informal Settlements Fire

2021 ◽  
Author(s):  
Yu Wang ◽  
Lesley Gibson ◽  
Mohamed Beshir ◽  
David Rush
Keyword(s):  
Heat Flux ◽  
Informal Settlement ◽  
Informal Settlements ◽  
Fire Risk ◽  
Fire Spread ◽  
Separation Distance ◽  
Flame Length ◽  
Critical Distance ◽  
Fire Disaster ◽  
Critical Separation

AbstractApproximately one billion people across the globe are living in informal settlements with a large potential fire risk. Due to the high dwelling density, a single informal settlement dwelling fire may result in a very serious fire disaster leaving thousands of people homeless. In this work, a simple physics-based theoretical model was employed to assess the critical fire separation distance between dwellings. The heat flux and ejected flame length were obtained from a full-scale dwelling tests with ISO 9705 dimension (3.6 m × 2.4 m × 2.4 m) to estimate the radiation decay coefficient of the radiation heat flux away from the open door. The ignition potential of combustible materials in adjacent dwellings are analyzed based on the critical heat flux from cone calorimeter tests. To verify the critical distance in real informal settlement fire, a parallel method using aerial photography within geographic information systems (GIS), was employed to determine the critical separation distances in four real informal settlement fires of 2014–2015 in Masiphumelele, Cape Town, South Africa. The fire-spread distances were obtained as well through the real fires. The probabilistic analysis was conducted by Weibull distribution and logistic regression, and the corresponding separation distances were given with different fire spread probabilities. From the experiments with the assumption of no interventions and open doors and windows, it was established that the heat flux would decay from around 36 kW/m2 within a distance of 1.0 m to a value smaller than 5 kW/m2 at a distance of 4.0 m. Both experiments and GIS results agree well and suggest the ignition probabilities at distances of 1.0 m, 2.0 m and 3.0 m are 97%, 52% and 5% respectively. While wind is not explicitly considered in the work, it is implicit within the GIS analyses of fire spread risk, therefore, it is reasonable to say that there is a relatively low fire spread risk at distances greater than 3 m. The distance of 1.0 m in GIS is verified to well and conservatively predict the fire spread risk in the informal settlements.

scholarly journals ANALYSIS OF THE TURBULENCE-RADIATION INTERACTION IN A METHANE-AIR DIFFUSION FLAME

2018 ◽  
Vol 17 (1) ◽  
pp. 86
Author(s):  
G. C. Fraga ◽  
A. P. Petry ◽  
F. H. R. França
Keyword(s):  
Heat Flux ◽  
Heat Source ◽  
Diffusion Flame ◽  
Radiative Heat ◽  
Numerical Study ◽  
Heat Fluxes ◽  
Fire Dynamics ◽  
Eddy Simulation ◽  
Volume Method ◽  
Air Diffusion

The phenomenon of turbulence-radiation interaction (TRI) has been demonstrated experimentally, theoretically and numerically to be important in a great number of engineering applications. This paper presents a numerical study on the subject, focusing on a methane-air diffusion flame confined in a rectangular enclosure. An open source, Fortran-based code, Fire Dynamics Simulator, is used for the analysis. Large Eddy Simulation (LES) is adopted to model the turbulence, and to resolve the sub-grid scale terms the dynamic Smagorinsky model is employed. To solve the radiative heat transfer, the finite volume method is used alongside the Weighted-Sum-of-Gray-Gases model. The main objective of the present work is to assess the magnitude of TRI effects for the configuration proposed. For this purpose, the time-averaged wall heat fluxes and volumetric radiative heat source, calculated from the LES results, are compared with those same quantities obtained by independent simulations initialized using mean temperature and species concentration fields. TRI effects are found to be responsible for differences up to 30% between results considering and neglecting turbulent fluctuations. These differences are larger for the radiative heat source and for the radiative heat flux to the walls, smaller for the total heat flux, and almost negligible for the convective heat flux. The influence of the fuel stream Reynolds number on the TRI effects is also evaluated, and a slight decrease on the magnitude of TRI is observed with the increase of that parameter.

In-furnace temperature and heat flux mapping in a kraft recovery boiler

TAPPI Journal ◽  
2010 ◽  
Vol 9 (9) ◽  
pp. 7-11 ◽  
Author(s):  
ANDERS BRINK ◽  
TOR LAURÉN ◽  
MIKKO HUPA ◽  
RALF KOSCHACK ◽  
CHRISTIAN MUELLER
Keyword(s):  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Radiative Heat ◽  
Furnace Temperature ◽  
Ir Camera ◽  
Surface Temperatures ◽  
Validation Of Models ◽  
Recovery Boiler ◽  
Flux Probe

Gas temperatures, incident heat flux, and surface temperatures were measured in a large kraft recovery boiler. The measurements were a part of an extensive campaign planned and carried out to support validation of models based on computational fluid dynamics. The gas temperatures were measured with three different techniques: infrared (IR) pyrometer, suction pyrometer, and unshielded thermocouples. In addition to the temperature measurements, the radiative heat flux was measured in a number of locations in the boiler using a portable heat flux probe, and the surface temperatures inside the boiler were measured using a portable single-band IR camera.

A Condensed Phase Computational Fluid Dynamics Model for Polymer Melt Flow

2008 ◽  
Author(s):  
Qing Tang ◽  
Michael Bockelie
Keyword(s):  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Condensed Phase ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Polymer Materials ◽  
High Heat Flux ◽  
Time Step ◽  
Temperature Dependent Viscosity

This paper presents a condensed phase computational fluid dynamics (CFD) based tool for modeling the processes of melting, flow and gasification of thermoplastic materials exposed to a high heat flux. Potential applications of the tool include investigating the behavior of polymer materials commonly used in personal computers and computer monitors if exposed to an intense heat flux, such as occurs during a fire. The finite-volume based model uses a three-dimensional body-fitted time dependent grid formulation to solve the unsteady Navier Stokes equations. A multi-grid method is used to accelerate convergence at each time step. Sub-models are included to describe the temperature dependent viscosity relationship and in-depth gasification and absorption of thermoplastic materials, free surface flows and surface tension. A series of test cases have been performed and the model results are compared to experimental data to investigate the impacts of different sub-models, boundary conditions, material properties and problem configurations on the accuracy, efficiency and applicability of the modeling tool.

Cooling and Freezing of Cashew Apple Using Computational Fluid Dynamics

2020 ◽  
Vol 25 ◽  
pp. 114-132 ◽  
Author(s):  
V.A. Agra Brandão ◽  
R. Araújo de Queiroz ◽  
R. Lima Dantas ◽  
G. Santos de Lima ◽  
N. Lima Tresena ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nutritional Value ◽  
Fruits And Vegetables ◽  
Numerical Study ◽  
Freezing Process ◽  
Ansys Cfx ◽  
Cashew Apple ◽  
Freezing Period ◽  
Kinetics Of

Freezing is one the most efficient methods for conservation, especially, fruits and vegetables. Cashew is a fruit with high nutritional value and great economic importance in the Northeast region of Brazil, however, due to high moisture content, it is highly perishable. The numerical study of the freezing process is of great importance for the optimization of the process. In this sense, the objective of this work was to study the cooling and freezing processes of cashew apple using computational fluid dynamics technique. Experiments of cooling and freezing of the fruit, with the aid of a refrigerator,data acquisition system and thermocouples, and simulation using Ansys CFX® software for obtain the cooling and freezing kinetics of the product were realized. Results of the cooling and freezing kinetics of the cashew apple and temperature distribution inside the cashew apple are presented, compared and analyzed. The model was able to predict temperaturetransient behavior with good accuracy, except in the post-freezing period.

Numerical study of the biomass pyrolysis process in a spouted bed reactor through computational fluid dynamics

Energy ◽  
2021 ◽  
Vol 214 ◽  
pp. 118839
Author(s):  
Shiliang Yang ◽  
Ruihan Dong ◽  
Yanxiang Du ◽  
Shuai Wang ◽  
Hua Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Study ◽  
Pyrolysis Process ◽  
Biomass Pyrolysis ◽  
Spouted Bed

Development of High Speed and High Temperature Atomic Layer Thermopiles

2019 ◽  
Author(s):  
Lakshya Bhatnagar ◽  
Guillermo Paniagua
Keyword(s):  
Heat Flux ◽  
High Temperature ◽  
High Speed ◽  
Cooling System ◽  
Numerical Study ◽  
Measurement Data ◽  
Atomic Layer ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Uncertainty Estimates

Abstract This work aims to provide a technique with which high frequency heat flux measurement data can be acquired in systems with high operational temperatures and high-speed flows with quantifiable and accurate uncertainty estimates. This manuscript presents the detailed calibration and application of an atomic layer thermopile, for heat fluxes with a frequency bandwidth of 0 to 1MHz. Two calibration procedures with a detailed uncertainty analysis. The first procedure consists using a laser to deliver radiation heat flux, while the second consists of a convective heat blowdown experiment. The use of this probe is demonstrated in a high-speed environment at Mach 2. The sensor effectively captures the passage of the normal shock wave and the values are compared with those computed using surface temperature measurement. Finally, a numerical study is carried out to design a cooling system that will allow the sensor to survive in high temperature conditions of 1273K while the sensor film is maintained at 323K. A two-dimensional axisymmetric conjugate heat transfer analysis is carried out to obtain the desired geometry.

Experimental and Numerical Study of Ascending Aorta Hemodynamics Through 3D Particle Tracking Velocimetry and Computational Fluid Dynamics

2013 ◽  
Author(s):  
Utku Gülan ◽  
Diego Gallo ◽  
Raffaele Ponzini ◽  
Beat Lüthi ◽  
Markus Holzner ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Tracking ◽  
Particle Tracking Velocimetry ◽  
Numerical Study ◽  
Imaging Techniques ◽  
Ascending Aorta ◽  
Human Aorta ◽  
Wide Range

The complex hemodynamics observed in the human aorta make this district a site of election for an in depth investigation of the relationship between fluid structures, transport and pathophysiology. In recent years, the coupling of imaging techniques and computational fluid dynamics (CFD) has been applied to study aortic hemodynamics, because of the possibility to obtain highly resolved blood flow patterns in more and more realistic and fully personalized flow simulations [1]. However, the combination of imaging techniques and computational methods requires some assumptions that might influence the predicted hemodynamic scenario. Thus, computational modeling requires experimental cross-validation. Recently, 4D phase contrast MRI (PCMRI) has been applied in vivo and in vitro to access the velocity field in aorta [2] and to validate numerical results [3]. However, PCMRI usually requires long acquisition times and suffers from low spatial and temporal resolution and a low signal-to-noise ratio. Anemometric techniques have been also applied for in vitro characterization of the fluid dynamics in aortic phantoms. Among them, 3D Particle Tracking Velocimetry (PTV), an optical technique based on imaging of flow tracers successfully used to obtain Lagrangian velocity fields in a wide range of complex and turbulent flows [4], has been very recently applied to characterize fluid structures in the ascending aorta [5].

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