Observations of energy transport and rate of spreads from low-intensity fires in longleaf pine habitat – RxCADRE 2012

2016 ◽  
Vol 25 (1) ◽  
pp. 76 ◽  
Author(s):  
B. Butler ◽  
C. Teske ◽  
D. Jimenez ◽  
J. O'Brien ◽  
P. Sopko ◽  
...  
Keyword(s):  
Total Energy ◽  
Energy Transport ◽  
Wildland Fire ◽  
Ground Level ◽  
Radiative Energy ◽  
Convective Heating ◽  
Emissive Power ◽  
Rate Of Spread ◽  
Heating And Cooling ◽  
Air Temperatures

Wildland fire rate of spread (ROS) and intensity are determined by the mode and magnitude of energy transport from the flames to the unburned fuels. Measurements of radiant and convective heating and cooling from experimental fires are reported here. Sensors were located nominally 0.5 m above ground level. Flame heights varied from 0.3 to 1.8 m and flaming zone depth varied from 0.3 to 3.0 m. Fire ROS derived from observations of fire transit time between sensors was 0.10 to 0.48 m s–1. ROS derived from ocular estimates reached 0.51 m s–1 for heading fire and 0.25 m s–1 for backing fire. Measurements of peak radiant and total energy incident on the sensors during flame presence reached 18.8 and 36.7 kW m–2 respectively. Peak air temperatures reached 1159°C. Calculated fire radiative energy varied from 7 to 162 kJ m–2 and fire total energy varied from 3 to 261 kJ m–2. Measurements of flame emissive power peaked at 95 kW m–2. Average horizontal air flow in the direction of flame spread immediately before, during, and shortly after the flame arrival reached 8.8 m s–1, with reverse drafts of 1.5 m s–1; vertical velocities varied from 9.9 m s–1 upward flow to 4.5 m s–1 downward flow. The observations from these fires contribute to the overall understanding of energy transport in wildland fires.

Exploring fire response to high wind speeds: fire rate of spread, energy release and flame residence time from fires burned in pine needle beds under winds up to 27 ms−1

2020 ◽  
Vol 29 (1) ◽  
pp. 81
Author(s):  
Bret Butler ◽  
Steve Quarles ◽  
Christine Standohar-Alfano ◽  
Murray Morrison ◽  
Daniel Jimenez ◽  
...  
Keyword(s):  
Wind Speed ◽  
Energy Release ◽  
Residence Time ◽  
Wildland Fire ◽  
Ground Level ◽  
Fire Spread ◽  
Convective Heating ◽  
Atmospheric Conditions ◽  
Wind Speeds ◽  
Rate Of Spread

The relationship between wildland fire spread rate and wind has been a topic of study for over a century, but few laboratory studies report measurements in controlled winds exceeding 5ms−1. In this study, measurements of fire rate of spread, flame residence time and energy release are reported for fires burning under controlled atmospheric conditions in shallow beds of pine needles subject to winds ranging from 0 to 27ms−1 (measured 5m above ground level). The data suggested that under constant flow conditions when winds are less than 10ms−1, fire rate of spread increases linearly at a rate of ~3% of the wind speed, which generally agrees with other laboratory-based models. When wind speed exceeds 10ms−1, the fire rate of spread response to wind remains linear but with a much stronger dependence, spreading at a rate of ~13% of the wind speed. Radiative and convective heating correlated directly to wind speed, with radiant heating increasing approximately three-fold as much as convective heating over the range of winds explored. The data suggested that residence time is inversely related to wind speed and appeared to approach a lower limit of ~20s as wind exceeded 15ms−1. Average flame residence time over the range of wind speeds was nominally 26s.

Measurements of radiant emissive power and temperatures in crown fires

2004 ◽  
Vol 34 (8) ◽  
pp. 1577-1587 ◽  
Author(s):  
B W Butler ◽  
J Cohen ◽  
D J Latham ◽  
R D Schuette ◽  
P Sopko ◽  
...  
Keyword(s):  
Forest Canopy ◽  
Radiant Energy ◽  
Ground Surface ◽  
Forest Stand ◽  
Radiative Energy ◽  
Fire Intensity ◽  
Energy Fluxes ◽  
Emissive Power ◽  
Radiant Intensity ◽  
Air Temperatures

This study presents spatially and temporally resolved measurements of air temperatures and radiant energy fluxes in a boreal forest crown fire. Measurements were collected 3.1, 6.2, 9.2, 12.3, and 13.8 m above the ground surface. Peak air temperatures exceeded 1330 °C, and maximum radiant energy fluxes occurred in the upper third of the forest stand and reached 290 kW·m–2. Average radiant flux from the flames across all experiments was found to be approximately 200 kW·m–2. Measured temperatures showed some variation with vertical height in the canopy. Equivalent radiometric temperatures calculated from radiant heat flux measurements exceeded thermocouple-based temperatures for all but the 10-m height, indicating that fire intensity estimates based on thermocouple measurements alone may result in underestimation of actual radiant intensity. The data indicate that the radiative energy penetration distance is significantly longer in the forest canopy than in the lower levels of the forest stand.

Fire shelter performance in simulated wildfires: an exploratory study

2001 ◽  
Vol 10 (1) ◽  
pp. 29 ◽  
Author(s):  
Bret W. Butler ◽  
Ted Putnam
Keyword(s):  
Prescribed Fire ◽  
Burn Injury ◽  
Energy Levels ◽  
Strong Dependence ◽  
The United States ◽  
Convective Heating ◽  
Radiant Heating ◽  
Emissive Power ◽  
Air Temperatures ◽  
Current Design

Fire shelters are required equipment for most wildland firefighters in the United States. In this study we report flame emissive power and temperatures inside and outside fire shelters placed in one prescribed fire, five experimental field fires, and one laboratory fire. Energy levels radiated by flames varied from 70 to 150 kW m–2 and lasted less than 10 min. Maximum fire shelter internal air temperatures reached 250˚C and occurred during the test with the maximum external air temperatures (1000˚C). Air temperatures inside the fire shelters did not show a strong dependence on flame radiant power, rather they correlated most strongly with external air temperature. We compare measurements from these tests with results reported by others. The data clearly indicate (1) the capability of the fire shelter to protect the occupant from radiant heating; (2) the susceptibility of the current design to convective heating; and (3) the significant decrease in burn injury when fire shelters are used.

Radiant flux density, energy density and fuel consumption in mixed-oak forest surface fires

2012 ◽  
Vol 21 (6) ◽  
pp. 722 ◽  
Author(s):  
R. L. Kremens ◽  
M. B. Dickinson ◽  
A. S. Bova
Keyword(s):  
Energy Density ◽  
Fuel Consumption ◽  
Energy Transport ◽  
Heat Budget ◽  
Wildland Fire ◽  
Linear Increase ◽  
Dual Band ◽  
Radiative Energy ◽  
Eastern United States ◽  
Soil Heating

Closing the wildland fire heat budget involves characterising the heat source and energy dissipation across the range of variability in fuels and fire behaviour. Meeting this challenge will lay the foundation for predicting direct ecological effects of fires and fire–atmosphere coupling. In this paper, we focus on the relationships between the fire radiation field, as measured from the zenith, fuel consumption and the behaviour of spreading flame fronts. Experiments were conducted in 8 × 8-m outdoor plots using preconditioned wildland fuels characteristic of mixed-oak forests of the eastern United States. Using dual-band radiometers with a field of view of ~18.5 m2 at a height of 4.2 m, we found a near-linear increase in fire radiative energy density over a range of fuel consumption between 0.15 and 3.25 kg m–2. Using an integrated heat budget, we estimate that the fraction of total theoretical combustion energy density radiated from the plot averaged 0.17, the fraction of latent energy transported in the plume averaged 0.08, and the fraction accounted for by the combination of fire convective energy transport and soil heating averaged 0.72. Future work will require, at minimum, instantaneous and time-integrated estimates of energy transported by radiation, convection and soil heating across a range of fuels.

scholarly journals PLANHEAT’s Satellite-Derived Heating and Cooling Degrees Dataset for Energy Demand Mapping and Planning

2019 ◽  
Vol 11 (17) ◽  
pp. 2048
Author(s):  
Sismanidis ◽  
Keramitsoglou ◽  
Barberis ◽  
Dorotić ◽  
Bechtel ◽  
...  
Keyword(s):  
Energy Demand ◽  
Near Infrared ◽  
Accuracy Assessment ◽  
Surface Air Temperature ◽  
Software Tool ◽  
Base Temperature ◽  
Low Carbon ◽  
Heating And Cooling ◽  
Air Temperatures ◽  
Infrared Imager

The urban heat island (UHI) effect influences the heating and cooling (H&C) energy demand of buildings and should be taken into account in H&C energy demand simulations. To provide information about this effect, the PLANHEAT integrated tool—which is a GIS-based, open-source software tool for selecting, simulating and comparing alternative low-carbon and economically sustainable H&C scenarios—includes a dataset of 1 × 1 km hourly heating and cooling degrees (HD and CD, respectively). HD and CD are energy demand proxies that are defined as the deviation of the outdoor surface air temperature from a base temperature, above or below which a building is assumed to need heating or cooling, respectively. PLANHEAT’s HD and CD are calculated from a dataset of gridded surface air temperatures that have been derived using satellite thermal data from Meteosat-10 Spinning Enhanced Visible and Near-Infrared Imager (SEVIRI). This article describes the method for producing this dataset and presents the results for Antwerp (Belgium), which is one of the three validation cities of PLANHEAT. The results demonstrate the spatial and temporal information of PLANHEAT’s HD and CD dataset, while the accuracy assessment reveals that they agree well with reference values retrieved from in situ surface air temperatures. This dataset is an example of application-oriented research that provides location-specific results with practical utility.

Radiative Energy Transport

2021 ◽  
pp. 73-83
Author(s):  
Tianshu Liu ◽  
John P. Sullivan ◽  
Keisuke Asai ◽  
Christian Klein ◽  
Yasuhiro Egami
Keyword(s):  
Energy Transport ◽  
Radiative Energy ◽  
Radiative Energy Transport

scholarly journals Estimation of sensible and latent heat based on measurements for non-typical large room

2019 ◽  
Vol 116 ◽  
pp. 00085
Author(s):  
Sylwia Szczęśniak ◽  
Juliusz Walaszczyk
Keyword(s):  
Latent Heat ◽  
Air Temperature ◽  
Historical Data ◽  
Operation Mode ◽  
Ventilation System ◽  
Thermal Conditions ◽  
Existing Building ◽  
Heating And Cooling ◽  
Air Temperatures ◽  
Heating And Cooling Load

The knowledge about dynamic changing heating and cooling load in existing building is essential for proper energy management. Whenever existing building is analyzed or ventilation system is going optimized, it’s essential to estimate temporary sensible and latent heat based on historical data. The basic conditions for heat calculations are quasi-stable thermal conditions. If supply air temperature significantly varies in short time, what happens very often, the calculations can give untrue results. The procedure described in this article improves usability of measured data affected by rapid supply air temperature changing. Therefore real sensible and latent heat can be calculated, what it is important for future optimization process. Specified, on the basis of varying supply and exhaust air temperatures, thermal loads range from -55.8 kW to 40.7 kW was substitute to more authentic range from -14.1 kW to 51.2 kW received from the conducted simulations. In addition, the data obtained from the simulation showed that latent heat gains were associated with the air temperature in the room, and not with the operation mode of the ventilation unit (day/night) as observed on the basis of historical data.

Buoyancy-driven flows of a radiatively participating fluid in a vertical cylinder heated from below

1993 ◽  
Vol 442 (1915) ◽  
pp. 313-341 ◽  
Keyword(s):  
Rayleigh Number ◽  
Energy Transport ◽  
Vertical Cylinder ◽  
Side Wall ◽  
Radiative Energy ◽  
Parameter Study ◽  
Internal Radiation ◽  
Static State ◽  
Buoyancy Driven Flows ◽  
Radiative Energy Transport

The effect of radiative energy transport on the onset and evolution of natural convective flows is studied in a Rayleigh–Bénard system. Steady, axisymmetric flows of a radiatively participating fluid contained in a rigid-walled, vertical cylinder which is heated on the base, cooled on top, and insulated on the side wall are calculated by using the Galerkin finite element method. Bifurcation analysis techniques are used to investigate the changes in the flow structure due to internal radiation. The results of this two-parameter study – where the Rayleigh number, Ra and optical thickness, ז , are varied – apply to fluids ranging from opaque to nearly transparent with respect to infrared radiation. For any non-opaque fluid, internal radiation eliminates the static state that, without radiation, exists for all values of the Rayleigh number. This heat transfer mechanism also destroys a symmetry of the system that relates clockwise and counter-clockwise flows. The connectivity between characteristic flow families and the range of Ra where families are stable are found to depend greatly on ז . Results demonstrate the inadequacy of characterizing the behaviour of this system using simple notions of radiative transfer in optically thick or thin media; the nonlinear interaction of radiation and flow are far more complicated than these asymptotic limits would imply.

Thermodynamic structure of a grass fire plume

2010 ◽  
Vol 19 (7) ◽  
pp. 895 ◽  
Author(s):  
Craig B. Clements
Keyword(s):  
Short Duration ◽  
Combustion Zone ◽  
Rapid Heating ◽  
Ground Level ◽  
Heating Rates ◽  
Fire Plume ◽  
Thermodynamic Structure ◽  
Rate Of Spread ◽  
Fire Front ◽  
Plume Temperature

High-frequency thermocouple measurements were made during an experimental grass fire conducted during ideal weather with overcast and windy conditions. Analysis of the thermodynamic structure of the fire plume showed that a maximum plume temperature of 295.2°C was measured directly above the combustion zone. Plume heating rates were on the order of 26–45 kW m–2 and occurred in the region just above the combustion zone between 10 and 15 m above ground level and were followed by cooling of approximately –37 and –44 kW m–2. The observed cooling was caused by strong entrainment that occurred behind the fire front and plume. The rapid heating and subsequent cooling indicate that the heating caused by a fire front is limited to a small volume around the flaming front and that the rates of heat gain occur for a short duration. The short duration of plume heating is due to the fast rate of spread of the fire front and ambient wind.

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