Heat Of Combustion Unit

The Heat Of Combustion Unit has one inlet material stream and one outlet material stream. It copies the content of the inlet material stream to the outlet material stream. It performs a P-VF flash in case the feed is at a phase boundary, and the resulting temperature is less then 0.1 K from the feed temperature. Otherwise it performs a P-H flash for a stream that is near enough to pure, or a T-P flash.

The Heat Of Combustion Unit measures the following properties of a mixture, at reference conditions of 298.15 K and 1 atm:

• Higher Heating Value (HHV): the mixture is combusted, and the combustion products are brought back to the equilibrium phase at their pre-combustion conditions; this implies that water is brought back to the liquid phase.
• Lower Heating Value (LHV): the heat of vaporization of water is not realized; water is in the vapor phase.

The Heat Of Combustion Unit requires pure compound values for the LLV to function. These are automatically picked up from the PCD files if a match is found. If a match is not found, values can be entered manually. Or you can specify a custom PCD file to scan for missing values. Compounds in a PCD file are matched if either name or CAS number matches.

For the water vaporization term, the Heat Of Combustion Unit requires to know how many hydrogen atoms are present in each molecule of each compound. If the chemical formula is available from the simulator, this value will be automatically determined. Values can also be entered manually.

Calculations are provided on a per-mole basis. If the molecular weights are available, values are calculated on per-mass basis as well.

The pure compounds LHV values are mixed using the feed mole ratios. This value is corrected for the enthalpy difference between the mixture at reference conditions and the pure compounds at the reference conditions. Enthalpy calculations supplied by the simulation environment (using thermodynamic from the object connected to the feed) are used for this. The phases in which the pure compounds and mixture are at reference conditions are reported in the Calculation Report.