Heat of Formation
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|Standard Species Model||Stream Properties||Special Cases|
|Density||Heat of Formation||Heat of Dilution||Specific Heat |
|Solubility||Boiling Point Elevation||pH||Charge||Steam and Water||Sulfuric Acid|
The Heat of Formation at 25 °C for each species is defined in the Species Table.
All elements in their Standard State should have zero heat of formation at 25 °C.
The heat of formation value is used:
- Calculate the Stream Heat of Formation (Hf)
- For a given stream temperature, the stream Heat of Formation values are calculated using the mass weighted mean method: see Stream Heat of Formation values (Hf) for more information.
- Calculate the Heat of Reaction (HOR)
- The Heat of Formation at 25 °C, dH25, is used to calculate heats of reaction for chemical reactions specified in SysCAD.
- If the compound is used in chemical reactions, the heat of reaction will be determined using the heat of formation values from its products and reactants. If the heat of formation value is missing for any species involved in the reaction, then the energy balance may not be correct. If this happens, the user needs to define a Heat of Reaction (HOR) value for the reaction. See Heat of Reaction for more information.
Implementation in SysCAD
- Entering Heat of Formation Data in the Species Properties Database - Heat of formation data is entered as Enthalpy of Formation at 25°C (H25) in the Species Properties Database.
- Heat of Reaction - Heats of formation are used to calculate the heat of reaction.
- Heat of Formation Information in a Project - The Heat of Formation information can be seen in the Species Properties Access Window (Species - View Properties). The value of H@T will be equal to the H25 value when the specified Temperature is set to 25°C.
- Stream Heat of Formation values (Hf) - This shows an example on how to calculate the Heat of Formation of the stream at a given temperature.