Gross heat of combustion

Heat of combustion, gross (including thermal energy 286.0 kJ/mol... 

Ratio of specific heats, Cp/Cv Gross heat of combustion Gross heat after vaporization Flammable limits in oxygen Flammable limits in air... 

The Atwater procedure, in brief, was to adjust the heats of combustion (gross calories) of the fat, protein, and carbohydrate in a food to allow for the losses in digestion and metabolism found for human subjects, and to apply the adjusted caloric factors to the amounts of protein, fat, and carbohydrate in the food. The contents of protein and fat were determined by chemical analysis, and the percentage of carbohydrate was obtained by difference that is, it was taken as the remainder after the sum of the fat, protein, ash, and moisture had been deducted from 100. This so-called total carbohydrate, therefore, included fiber (an all-inclusive term for carbohydrates that are not digested by people) as well as any noncarbohydrate residue present... 

Heat of combustion is the heat liberated or absorbed when one gram mole of the substance is completely oxidized to liquid water and CO2 gas at one atmosphere and 20°C or 25°C. (Cj-C hydrocarbons and cyclohexane at 25°C, others at 20°C). The gross heating value in Btu/ft could be calculated as follows ... 

Latent heat of sublimation at -84°C Latent heat of fusion at triple point Flammable limits in air Auto-ignition temperature Gross heat of combustion at 15.6°C, 1 atm Specific heat, gas at 25°C, 1 atm Cp Cv... 

Heat Release Rate From Fuel Gas. The fuel gas used in these tests was a mixture of natural gas supplied by the local gas company. This gas mixture contains approximately 90 percent methane and small fractions of ethane, propane, butane, C02, and nitrogen, as analyzed by Brenden and Chamberlain (6). Although composition of the gas changes with time, the changes were small in our case. A statistical sample of gross heat of combustion of fuel gas over several months showed a coefficient of variation of 0.7 percent. Also, the gross heat of combustion of natural gas reported by the gas company on the day of the test did not vary significantly from test to test. Thus, we assumed that the net heat of combustion was constant. 

Net heat of combustion was calculated based on the gross heat of combustion and the stoichiometry of combustion of the fuel mixture and a typical composition of the fuel mixture. The rate of heat release from burning fuel gas (<3ruei) is... 

While the high, or gross, heat of combustion can be accurately determined by established (ASTM) procedures, direct determination of the low heat of combuslion Is difficult. Therefore, it is usually calculated using the following formula ... 

The calorific value is a direct indication of the heat content (energy value) of the coal and represents the combined heats of combustion of the carbon, hydrogen, nitrogen, and sulfur in the organic matter and of the sulfur in pyrite and is the gross calorific value with a correction applied if the net calorific value is of interest. 

Gross calorific value (gross heat of combustion at constant volume) heat produced by combustion of a unit quantity of a solid or liquid fuel when burned at constant volume in an oxygen bomb calorimeter under specified conditions, with the resulting water condensed to a liquid not applied to gaseous fuels and applies to a volatile liquid fuel only if it is suitably contained during the measurement closely related to the internal energy of combustion for the same reaction at constant standard temperature and pressure. 

The heating values of petroleum, heavy oil, and bitumen are measured as the gross heats of combustion that are given with reasonable accuracy by the equation ... 

Oil or Ester Viscosity (mm2/S) Cetane No. Gross Heat of Combustion (kJ/kg) Cloud Point fC) Pour Point fC)... 

Gross energy (E, GE) is the energy released as heat when a substance is completely oxidized to carbon dioxide and water. It is generally measured at 25-30 atmospheres of oxygen in a bomb calorimeter and is called the heat of combustion. 

Enthalpies of combustion and physiological fuel values. The heat of combustion -AH,) of an organic substance is usually determined from AE,., which is measured in a bomb calorimeter. Since AE and AEp are nearly identical, it follows that AHp = AEy + P AV. Here AV is the volume change which would have occurred if the reaction were carried out at constant pressure P thus, AHp can be estimated by calculation. Since AH is desired for combustion to carbon dioxide, water, elemental nitrogen (N2), and sulfur, correction must be made for the amounts of the latter elements converted into oxides. By these procedures, it has been possible to obtain highly accurate values of AH both for biochemical compounds and for mixed foodstuffs. In nutrition, -AH, is sometimes referred to as the gross energy. Values are usually expressed in kilocalories (kcal) by chemists but often as Cal (with a capital C) in the nutritional literature. 

A general equation for the gross heat of combustion of vegetable oils developed by Bertram (1946) is ... 

Because m/n values for various test gases containing saturated hydrocarbons are related to their chemieal composition, they can serve as the basis for direct determination of heats of combustion. Table 11 lists the gross heats of combustion of several ptrre saturated hydrocarbons (refs. 1,2,4,9). 

TABLE II. GROSS HEATS OF COMBUSTION AH OF SELECTED SATURATED HYDROCARBONS... 

From the data summarized in Tables IV and V, it is apparent that the calculated and experimental values of m/n for various types of mixtures are in excellent agreement. As indicated earlier, the m/n values for the mixtures can be used to infer their heats of combustion. The reported (refs. 2,4,9) gross heat of combustion values for saturated hydrocarbons Usted in Table II were used to derive the following relationship between m/n values and heat of combustion expressed in kilocalories per mole ... 

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