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.

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.

Differents Methods to Estimate the Mean Radiant Temperature in an Urban Canyon

2013 ◽  
Vol 650 ◽  
pp. 647-651 ◽  
Author(s):  
R. de Lieto Vollaro ◽  
A. Vallati ◽  
S. Bottillo
Keyword(s):  
Human Body ◽  
Street Canyon ◽  
The Other ◽  
Radiation Environment ◽  
Mean Radiant Temperature ◽  
Radiation Fluxes ◽  
Human Energy ◽  
Environment Simulation ◽  
The Mean ◽  
Radiant Temperature

The mean radiant temperature is one of the meteorological key parameters governing human energy balance and the thermal comfort of human body. This variable can be considered as the sum of all direct and reflected radiation fluxes to which the human body is exposed. After the basics of the Tmrt calculation a comparison between two methods suitable for obtaining Tmrt in a street canyon will be presented. One of the discussed methods of obtaining Tmrt is based on the utilization of a globe thermometer. The other method is the radiation environment simulation through three PC software (RayMan, ENVI-met and SOLWEIG).

scholarly journals Evaluation and modelling the micro-bioclimatological conditions of a popular playground in Szeged, Hungary

2013 ◽  
Vol 4 (1) ◽  
pp. 57-61 ◽  
Author(s):  
L. A. Égerházi ◽  
N. Kántor ◽  
T. Gál
Keyword(s):  
Land Cover ◽  
Thermal Comfort ◽  
Meteorological Parameters ◽  
Thermal Sensation ◽  
Thermal Conditions ◽  
Radiation Environment ◽  
Mean Radiant Temperature ◽  
Predicted Mean Vote ◽  
Typical Summer ◽  
Radiant Temperature

Abstract This paper presents a thermal comfort study of a popular playground in Szeged, Hungary in order to find its optimal land cover and vegetation options. For this assessment simulated micro- and bioclimatological conditions recorded on a typical summer day (12th July 2011) were analysed. The thermal and radiation features of the study area were quantified by two biometeorological indices, Predicted Mean Vote (PMV) and Mean Radiant Temperature (Tmrt). For the simulation of the meteorological parameters and the bioclimate indices, ENVI-met microclimate model was used. The results confirmed that the modelled areas with different land cover provide a variety of thermal conditions for the visitors; moreover, human thermal sensation was significantly affected by the change of the radiation environment.

scholarly journals Integrated Weather Effects on Cycling Shares, Frequencies, and Durations in Rotterdam, the Netherlands

2014 ◽  
Vol 6 (4) ◽  
pp. 468-481 ◽  
Author(s):  
Lars Böcker ◽  
Sofia Thorsson
Keyword(s):  
Wind Speed ◽  
The Netherlands ◽  
Air Temperature ◽  
Panel Study ◽  
Thermal Conditions ◽  
Meteorological Variables ◽  
Mean Radiant Temperature ◽  
Physiological Equivalent Temperature ◽  
Transport Modes ◽  
Radiant Temperature

Abstract With the increasing societal interest in climate change, health, accessibility, and liveability and subsequent policy aims to promote active transport modes over car usage, many scholars have investigated the relationship between weather and cycling. Existing studies, however, hardly address the effects of weather on cycling durations and often lack assessments of the combined effects of different meteorological variables and potential nonlinearity of these effects. Drawing on travel diary data from a panel study of 945 Greater Rotterdam respondents (the Netherlands), this paper investigates and compares the effects of different meteorological variables, singly as well as combined, on cycling frequencies, cycling durations, and the exchange between cycling and other transport modes. Results show linear negative effects of precipitation sum and wind speed and nonlinear bell-shaped effects of thermal variables on cycling and opposite effects on car usage. Out of three thermal variables investigated, mean radiant temperature (radiant heat exchange between humans and the environment) and physiological equivalent temperature (an index combining the effects of air temperature, mean radiant temperature, air humidity, and wind speed) better explain cycling behavior than just air temperature. Optimum thermal conditions for cycling were found on days with maximum air temperatures around 24°C, mean radiant temperatures around 52°C, and physiological equivalent temperatures around 30°C. Policy and planning implications are highlighted that could reduce cyclists’ exposures to disadvantageous weather conditions such as heat, precipitation, and wind, at present and in a potentially changing climate.

Consideration of Operative Temperature in Design and Operation

2016 ◽  
Vol 861 ◽  
pp. 438-445
Author(s):  
Attila Kerekes ◽  
András Zöld
Keyword(s):  
Regression Analysis ◽  
Air Temperature ◽  
Indoor Air ◽  
Thermal Conditions ◽  
Mean Radiant Temperature ◽  
Operative Temperature ◽  
Pros And Cons ◽  
Radiant Temperature ◽  
Overall Heat Loss Coefficient ◽  
Simplified Calculation

In order to provide appropriate thermal conditions current national regulations prescribe operative temperature as the base of design and operation. In simplified calculation procedure prescribed operative temperature can be provided using a corrected air temperature. Interrelation of operative and indoor air temperature has been investigated in function of overall heat loss coefficient and glazed ratio. Based on regression analysis necessary corrections in function of the above parameters are investigated, the consequences of neglected Mean Radiant Temperature are analysed. Operative temperature represents a control problem, too: disregarding the sensor itself its position in the room, the uneven distribution of radiant field in one room and in the rooms of a flat requires compromises. The possible solutions, their pros and cons are presented.

scholarly journals Modeling Mean Radiant Temperature Distribution in Urban Landscapes Using DART

2021 ◽  
Vol 13 (8) ◽  
pp. 1443
Author(s):  
Maria Angela Dissegna ◽  
Tiangang Yin ◽  
Hao Wu ◽  
Nicolas Lauret ◽  
Shanshan Wei ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Thermal Comfort ◽  
Leaf Area ◽  
Remote Sensing Data ◽  
Outdoor Thermal Comfort ◽  
Transfer Model ◽  
Mean Radiant Temperature ◽  
Area Index ◽  
Sensing Data ◽  
Radiant Temperature

The microclimatic conditions of the urban environment influence significantly the thermal comfort of human beings. One of the main human biometeorology parameters of thermal comfort is the Mean Radiant Temperature (Tmrt), which quantifies effective radiative flux reaching a human body. Simulation tools have proven useful to analyze the radiative behavior of an urban space and its impact on the inhabitants. We present a new method to produce detailed modeling of Tmrt spatial distribution using the 3-D Discrete Anisotropic Radiation Transfer model (DART). Our approach is capable to simulate Tmrt at different scales and under a range of parameters including the urban pattern, surface material of ground, walls, roofs, and properties of the vegetation (coverage, shape, spectral signature, Leaf Area Index and Leaf Area Density). The main advantages of our method are found in (1) the fine treatment of radiation in both short-wave and long-wave domains, (2) detailed specification of optical properties of urban surface materials and of vegetation, (3) precise representation of the vegetation component, and (4) capability to assimilate 3-D inputs derived from multisource remote sensing data. We illustrate and provide a first evaluation of the method in Singapore, a tropical city experiencing strong Urban Heat Island effect (UHI) and seeking to enhance the outdoor thermal comfort. The comparison between DART modelled and field estimated Tmrt shows good agreement in our study site under clear-sky condition over a time period from 10:00 to 19:00 (R2 = 0.9697, RMSE = 3.3249). The use of a 3-D radiative transfer model shows promising capability to study urban microclimate and outdoor thermal comfort with increasing landscape details, and to build linkage to remote sensing data. Our methodology has the potential to contribute towards optimizing climate-sensitive urban design when combined with the appropriate tools.

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