Total heat release

Flammability. PhenoHcs have inherently low flammabiHty and relatively low smoke generation. For this reason they are widely used in mass transit, tiinnel-building, and mining. Fiber glass-reinforced phenoHc composites are capable of attaining the 1990 U.S. Federal Aviation Administration (FAA) regulations for total heat release and peak heat release for aircraft interior facings (1,70). 

The total heat released is the sum of the entropy contribution plus the irreversible contribution. This heat is released inside the battery at the reaction site. Heat release is not a problem for low rate appHcations however, high rate batteries must make provisions for heat dissipation. Failure to accommodate heat can lead to thermal mnaway and other catastrophic situations. 

Figure 27-13 shows the available heat in the products of combustion for various common fuels. The available heat is the total heat released during combustion minus the flue-gas heat loss (including the heat of vaporization of any water formed in the POC). 

Transient computations of methane, ethane, and propane gas-jet diffusion flames in Ig and Oy have been performed using the numerical code developed by Katta [30,46], with a detailed reaction mechanism [47,48] (33 species and 112 elementary steps) for these fuels and a simple radiation heat-loss model [49], for the high fuel-flow condition. The results for methane and ethane can be obtained from earlier studies [44,45]. For propane. Figure 8.1.5 shows the calculated flame structure in Ig and Og. The variables on the right half include, velocity vectors (v), isotherms (T), total heat-release rate ( j), and the local equivalence ratio (( locai) while on the left half the total molar flux vectors of atomic hydrogen (M ), oxygen mole fraction oxygen consumption rate... 

The total emission In the commercial heat treatment of 5 to 8 hours at 170 to 160°C varied from 0.4 to 1.2% for CO2 and 0.05 to 0.2% for CO and 0.04 to 0.1% for total acids based on dry board. Some of this emission might emanate from pyrolysis of higher molecular weight material condensed and deposited on the walls of the heat treatment chamber. The heat of formation of this CO2 and CO Is about half the total heat release measured. Part of the oxidation products might remain in the solid phase within the board material, e.g. as bound carbonyl and carboxylic groups, partly followed by heat consuming dehydration reaction. 

It appears that the rate constant for most of the boards has a smaller temperature dependence than the initial maximum rate, the corresponding "activation energy" E3 being around or less than 5 kcal/mol. An important conclusion is that the rate is diffusion limited. This has to be compared to a mean activation energy around 20 kcal/mole for the initial maximum rate of heat release for the commercial boards. As a consequence thereof the total heat release extrapolated over infinite time does increase to a significant extent with temperature from 150 to 230°C. 

For lignocellulosic boards the total heat released over infinite time under isothermal conditions based on equation (2) is... 

By substitution front Equation 1 and "Equation 3" the total heat release as a function of temperature is given by... 

Figure 18. The total heat release to infinite time QT extrapolated according to "Equation 4" versus the inverse absolute temperature. Mean for the 6 commercial hardboards of Asplund and Masonite type and a mean for the 3 semi-hardboards of Figures IS and 17, also data for the groundwood hardboard. (Reproduced with permission from ref. 10. Copyright 1989 De Gruyter.)...

Total Heat Release From Wall Assemblies. We examined the total heat release from the wall assemblies as total heat contribution. The total heat release is obtained by integrating the area under the heat release rate curve with time and it is expressed in megajoules (MJ). The total heat release data from ignition to different times are shown in Table III for the wall assemblies. 

Table III. Total Heat Release From the Wall Assemblies...

In general, walls A-l, B-l, and C-l had the highest heat release. Walls A-2, B-2, and C-2 had consistently less heat contribution because of the insulation. Walls A-3, B-3, and 03 and A-4, B-4, and C-4 had no significant heat contribution. The values in these tests vary because of initial errors associated with the perturbations at the beginning of the tests. However, total heat release did not grow, indicating zero heat release rate when gypsum was present. 

Because of the large difference in the behavior of the thin plywood and the gypsum board, the type of interior finish was the dominant factor in the statistical analysis of the total heat release data (Table III). Linear regression of the data sets for 5, 10, and 15 min resulted in squares of the correlation coefficients R = 0.88 to 0.91 with the type of interior finish as the sole variable. For the plywood, the average total heat release was 172, 292, and 425 MJ at 5, 10, and 15 min, respectively. For the gypsum board, the average total heat release was 25, 27, and 29 MJ at 5, 10, and 15 min, respectively. 

For 5 min, the type of burner (lower limit of 250 kW (series B and C) compared to 500 kW (series A)) also had a significant effect. For a linear regression model with interior finish and the burner level as the variables, the R = 0.96. Because the burner level primarily affected the total heat release from the plywood, the cross-product of burner level and type of interior finish is also a significant factor. At 10 min, the presence of insulation was more significant than the burner level. For a model with interior finish, insulation, and burner level as variables, the R = 0.95 for 10-min data. At 15 min, insulation was no longer a significant factor. This is consistent with the visual observations that the insulations in the plywood tests were gone after approximately 10 min. 

Except for the load level, which should not have an effect on the total heat release, series B and C were identical. Comparison of the results for 5, 10, and 15 min indicates very good agreement between the two sets of data. 

Rate of heat calorimeters can be used to measure a number of the most important fire hazard parameters, including the peak rate of heat release, the total heat release, the time to ignition and smoke factor (a smoke hazard measure combining the total smoke released and the peak RHR [14, 18-20]). The smoke factor will give an... 

The same hazard concept could, potentially, be used for full scale tests, multiplying the total heat released, per unit surface exposed, by the maximum smoke obscuration. This is the basis for the magnitude smoke hazard (Smoke Haz.), shown in Table II. It is of interest that smoke hazard results yield the same ranking as mass of soot formed. Cone calorimeter tests are being planned with the same materials used in the full scale tests to investigate the usefulness of this concept. 

Data measured, at each of three incident fluxes, include the maximum rate of heat release (Max RHR, in kw/m2), the total heat released after 15 min (THR015, in MJ/m2), the maximum rate of smoke release (Max RSR, in 1/s) and the total amount of smoke released after 15 min... 

It has already been shown that the Cone calorimeter smoke parameter correlates well with the obscuration in full-scale fires (Equation 1). At least four other correlations have also been found for Cone data (a) peak specific extinction area results parallel those of furniture calorimeter work [12] (b) specific extinction area of simple fuels burnt in the cone calorimeter correlates well with the value at a much larger scale, at similar fuel burning rates [15] (c)maximum rate of heat release values predicted from Cone data tie in well with corresponding full scale room furniture fire results [16] and (d) a function based on total heat release and time to ignition accurately predicts the relative rankings of wall lining materials in terms of times to flashover in a full room [22]. 

Linear correlations were thus attempted for peak rate of heat release, total heat released after 15 min. and smoke factor between both calorimeters. Furthermore, linear correlations were also attempted between OSU calorimeter smoke factors and Cone calorimeter smoke parameters and between Cone calorimeter smoke factors and Cone calorimeter smoke parameters. Figures 1-3 show some of the results. 

A summary of the results of correlation models for smoke factor and smoke parameter is shown in Table X. For comparison purposes, correlation models for OSU and Cone calorimeter peak rates of heat release are also shown in Table X, together with one of the total heat release models. 

The fire properties of PVC have been put into perspective recently [4, 5]. They show that PVC is a polymer with a high ignition temperature and low flammability. Furthermore, PVC products are associated with a low rate of heat release as well as little total heat released [4-9]. This will depend, clearly, on the type of product, since plasticised PVC products are obviously more flammable than rigid ones. 

Total heat absorbed by the calorimeter and water = Total heat released by the glucose... 

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