EBSILON®Professional Online Documentation
The heating value of a fluid (NCV: net calorific value, GCV:Gross calorific value) is defined via component 1 or component 33.
Open the ”Material Fractions” tab of the property sheet of component 1 or 33.
On the left there is a table with the headings "Option" and "Value". A combo box is arranged above this. The right table is the composition table.
The content of both tables depends on the type of the stream the component is connected to.
The ”Reference Temperature for heating value” (TNCVREF) indicates the temperature, for which net calorific values are specified. This temperature is a model setting and can be overridden in this field. The specification of the reference temperature is ONLY possible here with simultaneous explicit specification of the method (i.e. not with "According to model options").
FNCVCALC, FNCVCALCELEM and TNCVREF are then forwarded in flow direction and, for this purpose, saved in the individual stream. In the case of mixer-components, the specifications of the main line (Inlet 1) are transmitted to the outlet. If streams with different specifications are to be connected, the stream with the specifications to be retained must therefore be connected to Port 1.
By the way, the same applies to the "water/steam calculation" or the water/steam table FSTEAMFORMULATION , for the gas/flue gas calculation" or the gas table FGASFORMULATION and the real gas correction FREALGC.
Ebsilon always regards the heat of vaporisation as sensible heat, which means that the latent heat and thus the calorific value are basically the same in the liquid and gaseous phases. With Ebsilon, the gas phase has an enthalpy of 0 at 0°C, both for starting materials (e.g. methanol and oxygen) and for products (e.g. CO2 and H2O). If the zero point of methanol and/or water were to be placed in the liquid phase, the calorific value would have to be reduced or increased accordingly.
The ”NCV / GCV according to composition shows the calorific value that EBSILON®Professional calculates for and from the given composition. This is not the specified heating value that is used for the calculation, unless "No, always use the heating values calculated from the composition" is selected.
The reason for this is, that heating value calculations, especially for solid and liquid fuels, are only an approximation. If you know the NCV of your fuel, you can insert this value into the field ”NCV/GCV input (if required)"
In the case of gases it is possible to calculate the calorific value rather precisely due to the specification of the molecular composition.
In the case of solid and liquid fuels there usually is an elementary analysis that merely allows to estimate the calorific value.
Ebsilon provides different methods for both, estimating the calorific value from the elementary analysis and calculating the calorific value from the the chemical composition.
The default method for NCV/GCV calculation according to FDBR implemented in Ebsilon uses empirical formulae that are based on elementary analysis. For logical reasons it should therefore only be used for solid and liquid fuels where only an elementary analysis can be specified.
Possible methods (FNCVCALCELEM) for the calorific value calculation due to the elementary analysis (line: Method used for heating value calculation for solids (elementary analysis: C, H, O, N, S,Cl).
0: FDBR
1: Dulong
2: Boie
3: Grummel/Davis
4: Mott/Spooner
5: IGT
6: Seyler
7: Neavel
8: Given
9: Francis/Lloyd
10: Channiwala
Methods 1 to 10 all refer to the gross calorific value. It is then calculated into the net calorific value with the evaporation enthalpy of the water at the reference temperature.
In the case of gaseous fuels, the chemical composition is usually known. Therefore more precise methods can be used here; these are available in Ebsilon as well. The method is defined in the model settings, but you can override it here by changing the value of line "Method used for heating value calculation for gases" :
However, not all substances available in Ebsilon are covered by ISO 6976 and ASTM 3588. If the fluid contains substances that are not covered by the selected standard, the procedure will be as follows:
• No NCV calculation will be carried out if a specification is effected via an elementary analysis (C, H, O, N, S, Cl), or if solids (Ca and Mg compounds) are available.
Ash is acceptable, it is allocated an NCV of 0.
In the input screen, no NCV is suggested in this case (“0“ is displayed), the user has to enter the NCV on their own then. As no conversion of the reference temperature according to the standard can be effected either, the NCV has to be specified for the reference temperature 0°C.
• For all other substances that are not covered by ISO 6976, chemical reaction equations can be compiled by means of which these substances can be attributed to ISO 6976 substances. The NCV is then calculated on the basis of the standard enthalpies of formation.
• For substances that are not covered by ASTM 3588 but in ISO 6976, the ISO 6976 value is used as a substitute value when selecting ASTM 3588.
• In ASTM 3588, the NCVs are only defined for a reference temperature of 60°F. When selecting ASTM 3588, ISO 6976 is used for the conversion of the reference temperature.
The following table provides an overview of the treatment of the substances:
| Substance | ISO-6976 calculation | ASTM-3588 calculation |
| Nitrogen (N2) | yes | yes |
| Oxygen (O2) | yes | yes |
| Argon (Ar) | yes | yes |
| Water (H2O) | yes | replaced by ISO-6976 |
| Carbon dioxide (CO2) | yes | yes |
| Carbon monoxide (CO) | yes | yes |
| Carbon oxide sulfide (COS) | yes | replaced by ISO-6976 |
| Hydrogen (H2) | yes | yes |
| Hydrogen sulfide (H2S) | yes | yes |
| Methane (CH4) | yes | yes |
| Ethane (C2H6) | yes | yes |
| Propane (C3H8) | yes | yes |
| n-Butane (C4H10) | yes | yes |
| n-Pentane (C5H12) | yes | yes |
| n-Hexane (C6H14) | yes | yes |
| n-Heptane (C7H16) | yes | yes |
| Acetylene (C2H2) | yes | yes |
| Benzene (C6H6) | yes | yes |
| Sulfur dioxide (SO2) | yes | replaced by ISO-6976 |
| Hydrogen chloride (HCl) | with default enthalpy of formation | with default enthalpy of formation |
| Ash (incombustible solids) | NCV = 0 | NCV = 0 |
| Lime (Ca(OH)2) | no | no |
| Elemental carbon (C) | no | no |
| Methanol (CH3OH) | yes | replaced by ISO-6976 |
| n-Octane (C8H18) | yes | yes |
| n-Nonane (C9H20) | yes | yes |
| n-Decane (C10H22) | yes | yes |
| n-Dodecane (C12H26) | with default enthalpy of formation | with default enthalpy of formation |
| Isobutane (2-Methylpropane) | yes | yes |
| Isopentane (2-Methylbutane) | yes | replaced by ISO-6976 |
| Neopentane (2,2-Dimethylpropane) | yes | yes |
| Neohexane (2,2-Dimethylbutane) | yes | yes |
| 2,3-Dimethylbutane | yes | yes |
| Cyclopentane (C5H10) | yes | yes |
| Isohexane (2-Methylpentane) | yes | yes |
| 3-Methylpentane | yes | yes |
| Methylcyclopentane (CH3-C5H9) | yes | replaced by ISO-6976 |
| Cyclohexane (C6H12) | yes | yes |
| Methylcyclohexane (CH3-C6H11) | yes | yes |
| Ethylcyclopentane (C2H5-C5H9) | yes | replaced by ISO-6976 |
| Ethylcyclohexane (C2H5-C6H11) | yes | replaced by ISO-6976 |
| Toluene (Methylbenzene, CH3-C6H5) | yes | replaced by ISO-6976 |
| Ethylbenzol (C2H5-C6H5) | yes | replaced by ISO-6976 |
| Ortho-xylene (1,2-Dimethylbenzene) | yes | replaced by ISO-6976 |
| cis-Decalin (Decahydronaphthalene, C10H18) | with default enthalpy of formation | with default enthalpy of formation |
| trans-Decalin (Decahydronaphthalene, C10H18) | with default enthalpy of formation | with default enthalpy of formation |
| Ethene (Ethylene, C2H4) | yes | yes |
| Propene (Propylene, C3H6) | yes | yes |
| 1-Butene (C4H8) | yes | yes |
| cis-2-Butene | yes | yes |
| trans-2-Butene | yes | replaced by ISO-6976 |
| Isobutene (2-Methylpropene) | yes | replaced by ISO-6976 |
| 1-Pentene (C5H10) | yes | yes |
| Propadiene (Allene, C3H4) | yes | replaced by ISO-6976 |
| 1,2-Butadiene (Methylallene, C4H6) | yes | replaced by ISO-6976 |
| 1,3-Butadiene (Vinyl ethylene, C4H6) | yes | replaced by ISO-6976 |
| Ethanol (C2H5OH) | with default enthalpy of formation | with default enthalpy of formation |
| Methanethiol (Methyl mercaptan, CH3SH) | yes | replaced by ISO-6976 |
| HCN (hydrocyanic acid) | yes | replaced by ISO-6976 |
| Carbon disulfide (CS2) | yes | replaced by ISO-6976 |
| Air | yes | yes |
| Helium (He) | yes | yes |
| Neon (Ne) | yes | yes |
| Krypton (Kr) | yes | yes |
| Xenon (Xe) | yes | yes |
| N2O (laughing gas) | yes | replaced by ISO-6976 |
| Elemental hydrogen (H) | no | no |
| Elemental oxygen (O) | no | no |
| Elemental nitrogen (N) | no | no |
| Elemental sulfur (S) | no | no |
| Chlorine (Cl) | no | no |
| Ash (g) | no | no |
| Nitrogen monoxide (NO) | with default enthalpy of formation | with default enthalpy of formation |
| Nitrogen dioxide (NO2) | with default enthalpy of formation | with default enthalpy of formation |
| Ammonia (NH3) | yes | replaced by ISO-6976 |
| Calcium carbonate (CaCO3) | no | no |
| Calcium oxide (CaO) | no | no |
| Calcium sulfate (CaSO4) | no | no |
| Magnesium carbonate (MgCO3) | no | no |
| Magnesium oxide (MgO) | no | no |
| Water in the fuel (H2OB) | no | no |