3.7 Program for the calculation of the exhaust mass flow
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Statutory Documents - IMO Publications and Documents - International Codes - NOx Technical Code - Technical Code on Control of Emission of Nitrous Oxides from Marine Diesel Engines - Appendix 6 - Calculation of exhaust gas mass flow (carbon-balance method) - 3 Method 2, universal, carbon / oxygen-balance - 3.7 Program for the calculation of the exhaust mass flow

3.7 Program for the calculation of the exhaust mass flow

  3.7.1 The results of both stoichiometric calculations for carbon and oxygen calculations give the total exhaust composition and the exhaust mass flow including the water content.

  3.7.2 The formulae in the program are mainly based on wet exhaust.

  3.7.3 If dry concentrations (O2 and CO2) are measured, the dry to wet correction factor KWEXH ( = K W,r) shall be used.

  3.7.4 The program calculates the exhaust mass flow with known KWEXH and calculates the KWEXH with known exhaust gas flow. When both values are unknown, the program takes a preliminary value for KWEXH ( = K W,r ) and performs iterative calculation, until both values fit together and do not change any more.

  3.7.5 If the mass-balance formula is used without the program, the following dry to wet correction factor shall be used:

(2-44)

  3.7.6 The formula in another prepared form:

(2-44a)

  3.7.7 The general formula for dry / wet correction KWEXH = K w,r, different versions are possible.

  3.7.8 Formulae (2-44) and (2-44a) and also formulae (12) from 5.12.2.3 of this Code are not absolutely exact, because the correction for the combustion water and for the air intake water are not additive.

  3.7.9 The exact formula is:

(2-45)
where:
RhoEXHDAC = exhaust density with combustion by dry air (kg / std m3)
RhoH2O = water vapour density (kg / std m3) MWH2O / MVH2O

  3.7.10 A comparison of formula (12) from 5.12.2.3 of this Code with formula (2-45) shows very small differences of the factor Kw,r as shown in the following examples:

Humidity
g/kg 		Deviations of K w,r (compared with (2-45))
%
10.0 0.2
25.0 0.5

  3.7.11 The formula given as (2-45) is not very practical because in many cases RhoEXHDAC is not known and because the use of the fuel specific factor F FH is excluded. Therefore the more practical formulae (9), (10), (12) & (13) from 5.12.2.1 to 5.12.3.5 of this Code shall be used; the resulting error of < 0.2% (in most cases) may be neglected.

Parent topic: 3 Method 2, universal, carbon / oxygen-balance
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