Effective heat of combustion

There are two intrinsic material characteristics that are related to heat release rate. These two properties are the effective heat of combustion, AHc (MJ/kg), and the heat of gasification, L (MJ/kg). The effective heat of combustion is the ratio of heat release rate to mass loss rate measured in a bench-scale calorimeter ... 

Combining data obtained by the cone calorimeter with pyrolysis combustion flow calorimeter (PCFC sometimes called microscale combustion calorimeter, MCC) results was also proposed to increase the understanding of flame retardancy and flame retardancy mechanisms.104 Dividing the fraction of the effective heat of combustion of the volatiles (THE/ML) obtained from the cone calorimeter by the heat of complete combustion of the volatiles obtained from PCFC yields the combustion efficiency %. Thus the combination of fire test and PCFC enables a quantitative... 

Propensity for Phosphorus Release and Charring Determined by Thermal Analysis for PC/ABS Materials, Combustion Efficiency Multiplied by the Effective Heat of Combustion (% hc)r Residue, PHRR, and THE Determined by Cone Calorimeter... 

FIGURE 19.18 Comparison of effective heat of combustion (EHC) for PA6-based materials at different heat fluxes. 

Figure 19.18 presents a comparison of the effective heat of combustion (EHC), calculated as the ratio of the total heat release (THR) to the total mass lost (TML), for all the formulations. An average value of... 

FIGURE 19.38 Comparisons of the predicted and experimental MLRs for different nanofiller loadings at 50kW/m2. The MLRs for 2% and 10% cases were calculated from the reported HRRs for these cases and the effective heat of combustion (EHC) determined from the HRR and MLR data for the 5% case. 

Cone calorimetry according to the ASTM E1354138 or ISO 5660139 standards are commonly used in the laboratory to screen flammability of materials by measuring heat release characteristics of the compound.116140 This device is similar to FPA but does not have the versatility of FPA. The cone calorimeter can determine the ignitability, heat release rates, effective heat of combustion, visible smoke, and C02 and CO development of cable materials. This test has been used extensively for wire and cable material evaluation. The microscale combustion calorimeter (MCC), also known as pyrolysis combustion flow calorimeter (PCFC), was recently introduced to the industry for screening heat release characteristics of FR materials.141142 This device only requires milligram quantities of test specimen to measure the heat release capacity (maximum heat release potential). Cone calorimetry and MCC have been used in product development for flammability screening of wire and cable compounds.118... 

HRR, heat release rate EHC, effective heat of combustion. (From Ref... 

This material varies in character according to the kind of wheat and the method of manufacture. For example, the soft wheat flour produced in the USA has a milling yield of 80%, contains 8.8% alubumen, 88.6% carbohydrate, 1,4% fatty material, 0.5% cellulose, 0.7% ash and the effective heat of combustion value is 339 Real per 100 g (J.Ozaki, Y. Sakurai and N.Watanabe Handbook of manufacturing confectionery, p.31... 

The ASTM procedure specifies test size as 100 X 100 mm, up to 50 mm thick (4-in. X 4-in. up to 2-in. thick). Other sizes are also considered in the procedure in case of greater or smaller thickness of the tested material. The procedure describes calculations of heat release, mass-loss rate, effective heat of combustion, and smoke obscuration. For the latter, the extinction coefficient is calculated as... 

Figures 8 and 9 show graphs for the specific extinction area and effective heat of combustion, correspondingly, for PP and PP/MWCNT(3) nanocomposites. Calculated values of effective heat of combustion for PP and PP/MWNT demonstrate invariant shift of this parameter for these nanocomposites.

FIGURE 9 Effective heat of combustion versus time for PP and PP/MWClSrr(3) nanocomposites obtained by cone calorimeter at the incident heat flux of 35 kW m. ... 

There are literature claims that phosphorus acts not only as a char promoter but also in the vapor phase, leading to a decrease in the effective heat of combustion (EHC). This activity could be either flame inhibition [i.e. incomplete combustion due to scavenging of radicals like H- or HO by phosphorus radicals in the vapor phase) or a change in the pyrolytic gases. If the decrease in the EHC is generally well observed, very few articles provide evidence of flame inhibition. 

Figure 12.2 Change in effective heat of combustion versus phosphorus weight fraction from various studies.

The effective heat of combustion (EHC) is calculated as the ratio of the total heat released over the total mass loss (for the FRCMs, the mass loss of water (35 % for ATH and 32 for MH) was subtracted from the total mass loss). The average value for the PB is about 32 kJ g, which is similar to the one reported for pure EVA by Lyon (Lyon and Janssens 2005). PB/NC has a similar but slightly lower value, implying that though it takes longer for PB/NC to bum, it bums completely. As for the FRCMs, the EHC is actually higher than the PB and PB/NC. To explain this. 

DTA Differential thermal analysis EHC Effective heat of combustion EP Epoxy resin... 

Table 6. Mass Loss Rate (MLR), Effective Heat of Combustion (HOC), and Heat Release Rate (HRR) at Ignition (Fiashpoint) and incipient Burning/Extinction (Firepoint)...

In epoxy resin, the combination of ATH and phosphonium-modified clay additives showed superposition or even synergetic behavior for nearly all fire retardancy properties. Schartel et al. suggested that the presence of ATH resulted in an increase in residues and a small decrease in effective heat of combustion because of dilution of the pyrolysis products [24], Both fire retardancy mechanisms have their primary source in the conversion of ATH into aluminum oxide, which increased the residues, and water, which diluted and cooled the flame zone. In addition, the presence of organophosphorus decreased the effective heat of combustion through a gas phase. Most of the phosphorus was liberated during polymer pyrolysis and influenced the Are behavior through flame inhibition. 

Most polymer nanocomposites show rather minor influences on decomposition of the polymer. Apart from a few exceptions, neither decomposition temperatures nor effective heat of combustion of the volatiles change relevantly. Consequently,... 

The fire behavior of the foams can be tested with a cone calorimeter, according to standard test protocols (10,12). The test method is used to determine the ignitabUity, heat release rates, mass loss rates, effective heat of combustion, and visible smoke development of materials and products. 

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