Numerical simulation of the tree higro-thermal response in forest fire environment

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  
Keyword(s):  
Forest Fire ◽  
Numerical Study ◽  
Thermal Response ◽  
View Factor ◽  
Tree Model ◽  
Pine Tree ◽  
Surface Temperatures ◽  
Fire Environment ◽  
Fire Front ◽  
Heat Exchanges

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.

Comparatives study of radiative heat exchanges between fire front from fireman and pine tree in warm thermal conditions

2020 ◽  
pp. 39-49
Author(s):  
Eusébio Conceição ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Viegas ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Human Body ◽  
Thermal Conditions ◽  
Mean Radiant Temperature ◽  
Human Body Model ◽  
Tree Model ◽  
Pine Tree ◽  
Fire Front ◽  
Radiant Temperature ◽  
Heat Exchanges

This work presents the development of a numerical design in forest fire environments. A comparison between a tree body and a human body (fireman) thermal response systems is made. The three-dimensional pine tree model is constituted by trunk, branches and leaves represented by cylindrical elements. The human body model is divided into 35 elements and considers its thermoregulation. In both systems, special attention is required with conduction, convection, evaporation and radiation. There are also considered the heat exchanges by radiation between the fire front and both bodies. A vertical fire front, with 2 m of height and 20 m of length, was considered. The air temperature, air velocity, air relative humidity and mean radiant temperature are used. Two cases were studied: a pine tree and a fireman placed nearby the fire front. The results of the flame mean radiant temperature, temperature of the bodies surfaces and view factors are obtained. The results show that the fireman is most exposed than the pine tree to the fire front. Due to the human thermoregulatory and clothing systems, the fireman has a skin surface temperature much lower than the surface temperature in the trunks, branches and leaves of the tree. The evaporation in the tree is not sufficient to control the temperature.

Applicability of thermal response tests in designing standing column well system: A numerical study

Energy ◽  
2016 ◽  
Vol 109 ◽  
pp. 679-693 ◽  
Author(s):  
Jun-Seo Jeon ◽  
Seung-Rae Lee ◽  
Woo-Jin Kim
Keyword(s):  
Numerical Study ◽  
Thermal Response ◽  
System A

Experimental assessment of the influence of radiant heat transfer on the transition of a crown fire to settlements

2021 ◽  
pp. 19-26
Author(s):  
Николай Петрович Копылов ◽  
Елена Юрьевна Сушкина ◽  
Александр Евгеньевич Кузнецов ◽  
Виктория Ивановна Новикова
Keyword(s):  
Heat Flow ◽  
Forest Fire ◽  
Fire Resistance ◽  
Fire Protection ◽  
Forest Fires ◽  
Radiant Heat ◽  
Radiant Heat Transfer ◽  
Crown Fire ◽  
Fire Front ◽  
The Impact

Проведены экспериментальные исследования влияния лучистого теплообмена на переход верхового лесного пожара на постройки IV и V степеней огнестойкости. Лесной верховой пожар моделировался горением штабеля древесины с интенсивностью тепловыделения, близкой к интенсивности при реальных пожарах. Получена зависимость изменения плотности теплового потока от расстояния до кромки горения. Экспериментально определены температура воздуха с подветренной стороны пожара и плотность выпадения искр в зависимости от расстояния. Проверена эффективность защиты растворами ретардантов деревянных строений от возгорания при лучистом теплообмене между факелом пламени пожара и объектом защиты. Crown fires are the main threat of the combustion transfer from the forest to objects located in it. Fire services dealing with forest fires face the problem how to protect these objects from forest fires. It is proposed to treat the object with retardant solutions before a forest fire approaches. To assess the effectiveness of such tactics for fire protection of objects when exposed to a heat flow from the combustion front there were carried out experiments on large-scale crown fire models. A crown fire is simulated with a pile of wood with a heat release rate of ≈ 13 MW m. The wind is generated by fans, its speed is close to the speed at which a forest fire occurs. Measurements of the heat flux density, medium temperature, and the density of sparks falling downwind of the fire front at different distances and heights were carried out. Calculations were carried out to assess the impact of heat flow on buildings of IV-V degrees of fire resistance. The results obtained are compared with experimental data and they are in good agreement. There have been determined the distances from the fire front at which the fire protection with retardant solutions is effective for structures of IV-V fire resistance degrees at radiant heat exchange.

A numerical study on the thermal response in multi-layer of skin tissue subjected to heating and cooling procedures

2022 ◽  
Vol 137 (1) ◽  
Author(s):  
Rajneesh Kumar Chaudhary ◽  
Vikas Chaurasiya ◽  
Mohamed M. Awad ◽  
Jitendra Singh
Keyword(s):  
Numerical Study ◽  
Thermal Response ◽  
Skin Tissue ◽  
Heating And Cooling

Axisymmetric numerical study on thermal response of composites to laser irradiation

2014 ◽  
Vol 26 (9) ◽  
pp. 91024
Author(s):  
张家雷 Zhang Jialei ◽  
王伟平 Wang Weiping ◽  
刘仓理 Liu Cangli
Keyword(s):  
Laser Irradiation ◽  
Numerical Study ◽  
Thermal Response

Possible effects of Mercury surface temperatures on the exosphere

2020 ◽  
Author(s):  
Edoardo Rognini ◽  
Alessandro Mura ◽  
Maria Teresa Capria ◽  
Angelo Zinzi ◽  
Anna Milillo ◽  
...  
Keyword(s):  
Internal Heat ◽  
Thermal Response ◽  
Circulation Model ◽  
Sodium Content ◽  
Heat Propagation ◽  
Conductive Heat ◽  
High Porosity ◽  
Surface Temperatures ◽  
Thermophysical Model ◽  
The One

<div> <p>The BepiColombo mission is the first European mission to Mercury; the spacecraft will reach its destination in December 2025, and will study in detail the surface, the exosphere and the magnetosphere of the planet. </p> </div> <div> <p>We have developed a thermophysical model with the aim to analyze the dependence of the temperature of the surface and of the layers close to it on the assumptions on the thermophysical properties of the soil. The code solves the one-dimensional heat equation, assumes purely conductive heat propagation and no internal heat sources; the surface is assumed to be composed of a regolith layer with high porosity and density increasing with depth. The illumination conditions are calculated by using a Mercury shape model and the SPICE routines [1]. </p> </div> <div> <p>The model will help us to interpret the data that will be provided by the instruments onboard the BepiColombo mission. Preliminary calculations have been carried out to analyze the thermal response of the soil as a function of thermal conductivity. The model is currently also used to study the sodium content in the planet's exosphere, whose origin is under investigation [2]; the MESSENGER mission has measured the exospheric sodium content as a function of time, detecting an increase at the "cold poles" (so called because of their lower than average temperature). We therefore want to study the effect of surface temperatures on the sodium content in the exosphere; for this purpose, the temperature distribution calculated with the code is used together with an atmospheric circulation model that calculates the exospheric sodium content [3]. </p> </div> <div> <p>A simplified version of the thermophysical code is almost ready to be available to the scientific community through MATISSE [4], the software developed at the SSDC in ASI and available at https://tools.ssdc.asi.it/Matisse. </p> </div> <p>[1] Acton, C. H. (1996), Planetary and Space Science, 44, 65-70<br />[2] Cassidy, T., et al. (2016), GRL, 43, 11 121-128<br />[3] Mura, A., et al. (2009), Icarus, 1, 1-11<br />[4] Zinzi, A., et al. (2016), Astronomy & Computing, 15, 16-28</p>

Numerical Study on Forced Convective Heat Transfer in Porous Pin Fin Channels

2008 ◽  
Author(s):  
Jian Yang ◽  
Min Zeng ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Porous Metal ◽  
Transfer Model ◽  
Transfer Performance ◽  
Pin Fin ◽  
Heat Exchanges

Pin fin heat exchanges are often used in cooling of high thermal loaded electronic components due to their excellent heat transfer performance. However, the pressure drop in such heat exchanges is usually much higher than that in others, so their overall heat transfer performance is seriously reduced. In order to reduce the pressure drop and improve the overall heat transfer performance for pin fin heat exchangers, porous metal pin arrays are used and the performance of fluid flow and heat transfer in heat exchanger unit cells are numerically studied. The Forchheimer-Brinkman extended Darcy model and two-equation heat transfer model for porous media are employed and the effects of Reynolds number (Re), permeability (K) and pin fin cross-section forms are studied in detail. The results show that, with proper selection of governing parameters, the overall heat transfer performance of porous pin fin heat exchanger is much better than that of traditional solid pin fin heat exchanger; the overall heat transfer performance of long elliptic porous pin fin heat exchanger is the best, that is, the heat transfer per unit pressure drop of such heat exchanger is the highest and the maximum value of the heat transfer over pressure drop is obtained at K = 2×10−7 m2.

Calculating and interpreting forest fire intensities

1982 ◽  
Vol 60 (4) ◽  
pp. 349-357 ◽  
Author(s):  
Martin E. Alexander
Keyword(s):  
Forest Fire ◽  
International System ◽  
Unit Length ◽  
Fire Behavior ◽  
Energy Output ◽  
Fire Intensity ◽  
Linear Rate ◽  
Fire Front ◽  
Quantitative Basis ◽  
The Impact

Frontal fire intensity is a valid measure of forest fire behavior that is solely a physical attribute of the fire itself. It is defined as the energy output rate per unit length of fire front and is directly related to flame size. Numerically, it is equal to the product of net heat of combustion, quantity of fuel consumed in the active combustion zone, and a spreading fire's linear rate of advance. The recommended International System (SI) units are kilowatts per metre. This concept of fire intensity provides a quantitative basis for fire description useful in evaluating the impact of fire on forest ecosystems.

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