Analysis of Fire Characteristics based on the Thickness and Incident Heat Flux of Wood

This study tested the wood used in building interiors; each type had various incident heat fluxes based on their thickness. The combustion characteristics measured were effective heat of combustion, heat release rate peak and arrival time, maximum average rate of heat emission, and piloted ignition temperature. The wood specimens used in the experiment were 4.8 to 18 mm thick. 25, 35, 50, and 60 kW/m<sup>2</sup> were applied to the incident heat flux that the wood specimens were exposed to. The wood specimens tested were two types of medium-density fiberboard (each with a different density), treated red pine, particle board, and plywood. A comprehensive comparison of different fire characteristics was conducted to analyze the fire patterns corresponding to each type of wood in this way, the risk of fire was studied. The risk of fire was particularly high for particle board. The results of quantifying the fire characteristics of the types of wood studied could function as important input data with which to calculate the fire load of composite combustibles.

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An Inverse Determination of Unsteady Heat Fluxes Using a Network Simulation Method

Journal of Heat Transfer ◽

10.1115/1.1597614 ◽

2003 ◽

Vol 125 (6) ◽

pp. 1178-1183 ◽

Cited By ~ 14

Author(s):

F. Alhama ◽

J. Zueco and ◽

C. F. Gonza´lez Ferna´ndez

Keyword(s):

Heat Flux ◽

Inverse Problem ◽

Heat Conduction ◽

Input Data ◽

Heat Conduction Problem ◽

Network Simulation ◽

Simulation Method ◽

Heat Fluxes ◽

Incident Heat Flux ◽

Network Simulation Method

This work addresses unsteady heat conduction in a plane wall subjected to a time-variable incident heat flux. Three different types of flux are studied (sinusoidal, triangular and step waveforms) and constant thermal properties are assumed for simplicity. First, the direct heat conduction problem is solved using the Network Simulation Method (NSM) and the collection of temperatures obtained at given instants is modified by introducing a random error. The resulting temperatures act as the input data for the inverse problem, which is also solved by a sequential approach using the NSM in a simple way. The solution is a continuous piece-wise function obtained step by step by minimizing the classical functional that compares the above input data with those obtained from the solution of the inverse problem. No prior information is used for the functional forms of the unknown heat flux. A piece-wise linear stretches of variable slope and length is used for each of the stretches of the solution. The sensitivity of the functional versus the slope of the line, at each step, is acceptable and the complete piece-wise solution is very close to the exact incident heat flux in all of the mentioned waveforms.

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Revising the definition of anthropogenic heat flux from buildings: role of human activities and building storage heat flux

10.5194/acp-2021-914 ◽

2021 ◽

Author(s):

Yiqing Liu ◽

Zhiwen Luo ◽

Sue Grimmond

Keyword(s):

Heat Flux ◽

Energy Consumption ◽

Energy Balance ◽

Human Activities ◽

Building Energy ◽

Heat Emission ◽

Heat Fluxes ◽

Anthropogenic Heat ◽

Anthropogenic Heat Flux ◽

The Difference

Abstract. Buildings are a major source of anthropogenic heat emissions, impacting energy use and human health in cities. The difference between building energy consumption and building anthropogenic heat emission magnitudes and time lag and are poorly quantified. Energy consumption (QEC) is a widely used proxy for the anthropogenic heat flux from buildings (QF,B). Here we revisit the latter’s definition. If QF,B is the heat emission to the outdoor environment from human activities within buildings, we can derive it from the changes in energy balance fluxes between occupied and unoccupied buildings. Our derivation shows the difference between QEC and QF,B is attributable to a change in the storage heat flux induced by human activities (∆So-uo) (i.e., QF,B = QEC − ∆So-uo). Using building energy simulations (EnergyPlus) we calculate the energy balance fluxes for a simplified isolated building (obtaining QF,B, QEC, ∆So-uo) with different occupancy states. The non-negligible differences in diurnal patterns between QF,B and QEC caused by thermal storage (e.g. hourly QF,B to QEC ratios vary between −2.72 and 5.13 within a year in Beijing, China). Negative QF,B can occur as human activities can reduce heat emission from building but are associated with a large storage heat flux. Building operations (e.g., open windows, use of HVAC system) modify the QF,B by affecting not only QEC but also the ∆So-uo diurnal profile. Air temperature and solar radiation are critical meteorological factors explaining day-to-day variability of QF,B. Our new approach could be used to provide data for future parameterisations of both anthropogenic heat flux and storage heat fluxes from buildings. It is evident that storage heat fluxes in cities may also be impacted by occupant behaviour.

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Development and calibration of reduced-size plate thermometer for measuring incident heat flux

Journal of Fire Sciences ◽

10.1177/0734904120958602 ◽

2020 ◽

pp. 073490412095860

Author(s):

Hong-Seok Yun ◽

Ho-Sik Han ◽

Cheol-Hong Hwang

Keyword(s):

Heat Flux ◽

Heat Fluxes ◽

Empirical Constant ◽

Incident Heat Flux ◽

Wide Range ◽

Plate Thermometer ◽

Plate Area ◽

Conventional Plate ◽

Heat Flux Meter ◽

In Fire

This study proposes a new reduced-size plate thermometer with a modified shape and improved insulation performance in order to resolve problems commonly found when using conventional plate thermometers to measure incident heat flux in fire environments, for example, a low spatial resolution caused by the large plate area and a non-uniform temperature distribution on the plate. The main results of this study showed that the new plate thermometer exhibits high spatial temperature uniformity, and that the plate thermometer can be reduced in size to 30 mm. Moreover, it was found that the relative error of the incident heat flux of the plate thermometer was substantially reduced compared to that of a heat flux meter using a conduction correction factor expressed as a third-order polynomial function of heat flux, rather than using an average empirical constant calculated from measurement over a wide range of heat fluxes. Finally, it was confirmed that the incident heat flux measured by the new reduced-size plate thermometer in a heptane pool fire was in good agreement with the heat flux meter measurements during the rapid-fire growth, fully developed and decay phases of a fire.

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Fire Characteristics of Selected Tropical Woods without and with Fire Retardant

Coatings ◽

10.3390/coatings10060527 ◽

2020 ◽

Vol 10 (6) ◽

pp. 527 ◽

Cited By ~ 2

Author(s):

Linda Makovicka Osvaldova ◽

Patricia Kadlicova ◽

Jozef Rychly

Keyword(s):

Average Rate ◽

Fire Retardant ◽

Heat Emission ◽

South American ◽

Three Samples ◽

Wood Fire ◽

Lower Maximum ◽

Fire Characteristics ◽

Tropical Woods ◽

Ferrous Phosphate

The flammability of tropical woods and the effect of a selected fire protection coating were evaluated using a cone calorimeter at a cone radiancy of 35 kW/m2. Three samples were from the South American continent (Cumaru, Garapa, Ipe), and two were from the Asian continent (Kempas and Merbau). Samples were treated with commercial fire retardant (FR) containing ferrous phosphate as an essential component. The untreated samples were used as reference materials that were of particular interest concerning their flammability. It was shown that there is unambiguous correlation between the effective heat of combustion (EHC) and total oxygen consumed (TOC) related to mass lost during burning for both the untreated and treated samples. In the case of Cumaru and Garapa, there exists an inverse relation between the amount of smoke and carbon residue. The decisive effect on the time of ignition was performed by the initial mass of the sample. This is valid for the spruce and the Cumaru, Ipe, and Kempas, both treated and untreated with retardant, while Garapa and Merbau were found to decline. According to the lower maximum average rate of heat emission (MARHE) parameter, a lower flammability was observed for the treated samples of wood, except for Garapa wood. Fire-retardant treated Garapa and Merbau also have a significantly lower time to ignition than untreated ones.

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THE EFFECT OF NONUNIFORM AXIAL HEAT FLUX DISTRIBUTION ON CRITICAL HEAT FLUXES WITH POTASSIUM IN TUBES

10.1615/ihtc4.850 ◽

1970 ◽

Author(s):

I. T. Aladyev ◽

I. G. Gorlov ◽

O. S. Fedynsky

Keyword(s):

Heat Flux ◽

Flux Distribution ◽

Heat Fluxes ◽

Heat Flux Distribution ◽

Axial Heat

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Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽

10.3390/fluids6070246 ◽

2021 ◽

Vol 6 (7) ◽

pp. 246

Author(s):

Rozie Zangeneh

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Large Eddy Simulation ◽

Skin Friction ◽

Heat Fluxes ◽

Separated Flows ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Large Eddy ◽

Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

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Drift kinetic theory of alpha transport by tokamak perturbations

Journal of Plasma Physics ◽

10.1017/s0022377820001671 ◽

2021 ◽

Vol 87 (2) ◽

Author(s):

Elizabeth A. Tolman ◽

Peter J. Catto

Keyword(s):

Heat Flux ◽

Kinetic Theory ◽

Alpha Particle ◽

Heat Fluxes ◽

Alpha Particles ◽

Alpha Power ◽

Mode Amplitude ◽

Effective Collision Frequency ◽

Perturbation Frequency ◽

Particle Confinement

Upcoming tokamak experiments fuelled with deuterium and tritium are expected to have large alpha particle populations. Such experiments motivate new attention to the theory of alpha particle confinement and transport. A key topic is the interaction of alpha particles with perturbations to the tokamak fields, including those from ripple and magnetohydrodynamic modes like Alfvén eigenmodes. These perturbations can transport alphas, leading to changed localization of alpha heating, loss of alpha power and damage to device walls. Alpha interaction with these perturbations is often studied with single-particle theory. In contrast, we derive a drift kinetic theory to calculate the alpha heat flux resulting from arbitrary perturbation frequency and periodicity (provided these can be studied drift kinetically). Novel features of the theory include the retention of a large effective collision frequency resulting from the resonant alpha collisional boundary layer, correlated interactions over many poloidal transits and finite orbit effects. Heat fluxes are considered for the example cases of ripple and the toroidal Alfvén eigenmode (TAE). The ripple heat flux is small. The TAE heat flux is significant and scales with the square of the perturbation amplitude, allowing the derivation of constraints on mode amplitude for avoidance of significant alpha depletion. A simple saturation condition suggests that TAEs in one upcoming experiment will not cause significant alpha transport via the mechanisms in this theory. However, saturation above the level suggested by the simple condition, but within numerical and experimental experience, which could be accompanied by the onset of stochasticity, could cause significant transport.

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Air–Sea Interaction in the Central Mediterranean Sea: Assessment of Reanalysis and Satellite Observations

Remote Sensing ◽

10.3390/rs13112188 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2188

Author(s):

Salvatore Marullo ◽

Jaime Pitarch ◽

Marco Bellacicco ◽

Alcide Giorgio di Sarra ◽

Daniela Meloni ◽

...

Keyword(s):

Heat Flux ◽

Mediterranean Sea ◽

Seasonal Cycle ◽

Heat Fluxes ◽

Meteorological Variables ◽

Central Mediterranean ◽

High Quality ◽

Central Mediterranean Sea ◽

In Situ Observations

Air–sea heat fluxes are essential climate variables, required for understanding air–sea interactions, local, regional and global climate, the hydrological cycle and atmospheric and oceanic circulation. In situ measurements of fluxes over the ocean are sparse and model reanalysis and satellite data can provide estimates at different scales. The accuracy of such estimates is therefore essential to obtain a reliable description of the occurring phenomena and changes. In this work, air–sea radiative fluxes derived from the SEVIRI sensor onboard the MSG satellite and from ERA5 reanalysis have been compared to direct high quality measurements performed over a complete annual cycle at the ENEA oceanographic observatory, near the island of Lampedusa in the Central Mediterranean Sea. Our analysis reveals that satellite derived products overestimate in situ direct observations of the downwelling short-wave (bias of 6.1 W/m2) and longwave (bias of 6.6 W/m2) irradiances. ERA5 reanalysis data show a negligible positive bias (+1.0 W/m2) for the shortwave irradiance and a large negative bias (−17 W/m2) for the longwave irradiance with respect to in situ observations. ERA5 meteorological variables, which are needed to calculate the air–sea heat flux using bulk formulae, have been compared with in situ measurements made at the oceanographic observatory. The two meteorological datasets show a very good agreement, with some underestimate of the wind speed by ERA5 for high wind conditions. We investigated the impact of different determinations of heat fluxes on the near surface sea temperature (1 m depth), as determined by calculations with a one-dimensional numerical model, the General Ocean Turbulence Model (GOTM). The sensitivity of the model to the different forcing was measured in terms of differences with respect to in situ temperature measurements made during the period under investigation. All simulations reproduced the true seasonal cycle and all high frequency variabilities. The best results on the overall seasonal cycle were obtained when using meteorological variables in the bulk formulae formulations used by the model itself. The derived overall annual net heat flux values were between +1.6 and 40.4 W/m2, depending on the used dataset. The large variability obtained with different datasets suggests that current determinations of the heat flux components and, in particular, of the longwave irradiance, need to be improved. The ENEA oceanographic observatory provides a complete, long-term, high resolution time series of high quality in situ observations. In the future, more similar sites worldwide will be needed for model and satellite validations and to improve the determination of the air–sea exchange and the understanding of related processes.

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Inverse Heat Conduction Applied to the Measurement of Heat Fluxes on a Rotating Cylinder: Comparison Between an Analytical and a Numerical Technique

Journal of Heat Transfer ◽

10.1115/1.2928013 ◽

2008 ◽

Vol 130 (8) ◽

Cited By ~ 8

Author(s):

Fabien Volle ◽

Michel Gradeck ◽

Denis Maillet ◽

Arsène Kouachi ◽

Michel Lebouché

Keyword(s):

Heat Flux ◽

Numerical Technique ◽

Rotating Cylinder ◽

Local Heat ◽

Heat Fluxes ◽

Inverse Heat Conduction ◽

Analytical Technique ◽

Inner Radius ◽

Direct Model ◽

Stable Estimation

A method using either a one-dimensional analytical or a two-dimensional numerical inverse technique is developed for measurement of local heat fluxes at the surface of a hot rotating cylinder submitted to the impingement of a subcooled water jet. The direct model calculates the temperature field inside the cylinder that is submitted to a given nonuniform and time dependent heat flux on its outer surface and to a uniform surface heat source on an inner radius. In order to validate the algorithms, simulated temperature measurements inside the cylinder are processed and used by the two inverse techniques to estimate the wall heat flux. As the problem is improperly posed, regularization methods have been introduced into the analytical and numerical inverse algorithms. The numerical results obtained using the analytical technique compare well with the results obtained using the numerical algorithm, showing a good stable estimation of the available test solutions. Furthermore, real experimental data are used for the estimation, and local boiling curves are plotted and discussed.

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