3. Summary of Test Method
3.1 Correlations have been established between the net heat of combustion and the product of the aniline point and API gravity. These relations, assuming the sample to be sulfur free, are given by the following equations:
3.1.1 Where the net heat of combustion is required in SI units (Note 2) (megajoules per kilogram):
NOTE 2 - In SI, the unit of heat of combustion has the dimensions J/kg, but for practical use a multiple is more convenient. The megajoule per kilogram (MJ/kg) is 10(6) J/kg and is customarily used for the representation of heats of combustion of petroleum fuels, particularly for mixtures such as those covered in this International Standard.
3.1.2 Where the net heat of combustion is required in inch-pound units or British Thermal Units (Btu per pound).
3.2 To correct for the effect of the sulfur content of the sample on the net heat of combustion, apply the following equation:
3.2.1 Where the net heat of combustion is required in SI units (megajoules per kilogram):
Q' = Qp(net) x [1 - 0.01(S)] + 0.1016(S)
where:
Q' = net heat of combustion, MJ/kg, of the sample containing S % sulfur,
S = sulfur content of the sample, mass, %, and
0.1016 = a constant based on the thermo-chemical data on sulfur compounds.
3.2.2 Where the net heat of combustion is required in inch-pound units or British Thermal Units (Btu per pound):
Q' = Qp(net) x [1 - 0.01(S)] + 43.7(S)
where:
Q' = net heat of combustion, Btu/lb, of the sample containing S % sulfur,
S = sulfur content of the sample, mass %, and
43.7 = a constant based on the thermochemical data on sulfur compounds.
3.3 The empirical linear equations 1-4 and 6-9 for the estimated net heat of combustion were derived by the method of least squares from accurate data on fuels, most of which conformed at least approximately to specifications for aviation gasolines, or aircraft turbine and jet engine fuels of Types JP-4 and JP-5 and to Specification D1655, Jet A and A-1.
4. Significance and Use
4.1 This test method is intended for use as a guide in cases where an experimental determination of heat of combustion is not available and cannot be made conveniently, and where an estimate is considered satisfactory. It is not intended as a substitute for experimental measurements of heat of combustion.
NOTE 3 - The procedure for the experimental determination of the net heat of combustion is described in Test Methods D240 and D4809.