What is the difference between Hs and Hz?
The enthalpy of a specie, or stream at Temperature, T, and Pressure, P, is calculated using the specific heats with a reference temperature of 0°C and 101.325kPa. • SysCAD assigns ALL species an Hs value of 0J/mol at 0°C and 101.325kPa. • SysCAD assigns most species an Hz of 0J/mol at 0°C and 101.325kPa. • However the exception is species that exist in 2 or more phases, where Hz at 0°C and 101.325kPa is calculated as follows: Hz = Energy of Formation at 0°C and 101.325kPa of the specie – Energy of Formation at 0°C and 101.325kPa of the specie in the ‘lowest’ energy phase (g > l > s) Therefore, if the project contains any species that occur in 2 or more phases, the Hs and Hz values will be different by this amount.
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