Average heat of combustion

Table 8 Average heat of combustion and yields of products for polymers from the data measured in the ASTM E 2058 fire propagation apparatus...

The heats of combustion of the volatile pyrolysis products released at various stages of volatilization were determined from untreated and chemically treated ponderosa pine (64). Fire-retardant treatments reduced the average heat of combustion for the volatile pyrolysis products released at the early stage of pyrolysis below the value associated with untreated wood at comparable stages of volatilization. At 40% volatilization, untreated wood had released 29% of its volatile products heat of combustion treated wood had only released 10-19% of its total heat. Of all the chemicals tested, only NaCl, which is known to be an ineffective fire retardant, did not reduce the heat content. This reduction in heat content of the volatiles was confirmed by using thermal evolution analysis (TEA) (55). 

For the worst case evaluation, the weight of flammable material in a vapor cloud is assumed to be the total quantity of the substance that could be released from a vessel or pipeline. For liquids, this assumption infers that the liquid is above its atmospheric-pressure boiling point and that 100% flashing to vapor occurs. Also, the entire quantity of vapor is assumed to have concentrations between the lower and upper flammability limits and that the entire quantity explodes, with an energy-conversion efficiency e of 0.10. For mixtures, the weight-average heat of combustion would be used in the above equation. 

Sample Coke remnant, wt% Max speed of heat release, kW/m Averse value of heat release, kW/m Average heat of combustion, MJ/I Specific smoke release, inVkg CO release, kg/kg... 

Table 11.12 Average Heat of Combustion and Yields of Products for Polymers from the Data Measured in the ASTM E2058 Fire Propagation Apparatus"...

The average heat of combustion is determined from the ratio of the energy, E,-, obtained from the summation of the chemical, convective, and radiative heat release rates and the total mass of gasified polymer, Wf, obtained from the summation of the mass loss rate ... 

The flame out time for nylon 6,6 with PVA oxidized by KMn04 is larger than the flame out times of nylon-6,6/PVA and nylon-6,6 (Table 5.3). The values of average heat of combustion indicate the exothermal process of smoldering provided by chelated Mn-structures (Table 5.3). That is why the authors have found an approximately equal amount of char yield for nylon-6,6/PVA and nylon-6,6/PVA oxidized by KMn04 (Table 5.2) [212]. 

Polymer Char yield (% wt.) Max.RHR (kW/m ) Average heat of combustion (MJ/kg) Total heat released (MJ/m ) Average spec. ext. area (m /kg) Average CO yield (kg/kg)... 

The insensitivity of adiabatic flame temperature to heat of combustion does not necessarily apply to the operational flame temperature, T, which is the flame temperature found in an actual furnace (remembering that this refers to some average temperature). The higher excess air requirements at higher C/H ratios coupled with greater thermal loads on longer flames generally results in markedly lower operational temperatures as the C/H ratio increases. 

J/m ) is a typical one for the heat of combustion of an average stoichiometric hydrocarbon-air mixture (Harris 1983). 

Calculate the combustion energy E (J) for each blast by multiplying the individual volumes of mixture by 3.5 x 10 J/m. Table 7.1 demonstrates that 3.5 X 10 J/m is a reasonable average value for the heat of combustion of a stoichiometric hydrocarbon-air mixture. 

C06-0127. In metric terms, a typical automobile averages 6.0 km/L of gasoline burned. Gasoline has a heat of combustion of 48 kJ/g and a density of 0.68 g/mL. How much energy is consumed in driving an automobile 1.0 km ... 

A chair burns in a room, releasing 500 kW, and the heat of combustion for the chair is estimated as 20 kJ/g. Fire and room conditions can be considered steady. The air flow rates into a door and through a window are 200 and 100 g/s respectively. Assume the room is adiabatic. The gases have constant and equal specific heats =1.5 kJ/kg K. The ambient air is 25 °C and the chair fuel gasifies at 350 °C. Compute the average temperature of the room gases. Account for all terms and show all work. 

A fire in a ship compartment bums steadily for a period of time. The average smoke layer achieves a temperature of 420 °C with the ambient temperature being 20 °C. The compartment is constructed of 1 cm thick steel having a thermal conductivity of 10 W/m2 K. Its open doorway hatch is 2.2 m high and 1.5 m wide. The compartment has an interior surface area of 60 m2. The fuel stoichiometric air to fuel mass ratio is 8 and its heat of combustion is 30 kJ/g. 

Aho [8] presented a short descriptive model of the relationship between combustion heat rate and mass loss rate of bed. He applies the same method as Koistinen et al [7]. It is clear that the method used presents time average values of combustion heat rate. No verification method is applied and no uncertainty analysis is carried out. The... 

The molecular mass of the combustion products in the ramburner is increased by the formation of the oxidized metal particles. However, the temperature in the ramburner is also increased by the oxidation. The results of thermochemical calculations indicate that the specific impulse generated by the combustion in the ramburner is more dependent on the average combustion temperature than the average molecular mass of the products when metal particles are added. Table 15.4 shows the heats of combustion and the major oxidized products of the soHd particles used in ducted rockets. 

The heat of combustion of cyclopropane, (CH2)3, to give carbon dioxide and liquid water is 499.8 kcal mole-1. Show how this value, assuming normal C-H bond strengths, can be used to calculate the average C-C bond energy of cyclopropane. 

On the other hand, and this is the most important consideration here, it has been shown above that no stoichiometrical relations exist between the quantity of fuel and the nitric oxide formed, and that the specific chemical nature of the fuel is of no account but only its heat of combustion it has been shown that the amount of nitric oxide formed is related to the oxygen content in the explosion products and not to the initial or average amount of oxygen during combustion. All this is rather difficult to reconcile with notions of chemical induction, the role of radiation, etc. and is a convincing argument in favor of the idea that the reaction of combustion is needed only to heat the mixture of 02 and N2 in which there then sets in a reversible thermal reaction (caused by the high temperature) ... 

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... 

A light fuel oil with an average chemical composition of C<,H15 is burned with oxygen in a bomb calorimeter. The heat evolved is measured as 47,730 J g-1 for the reaction at 25°C. Calculate the standard heat of combustion of the fuel oil at 25°C with H20(s) and C02(fl) as products. Note that the reaction in the bomb occurs at constant volume, produces liquid water as a product, and goes to completion. 

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