2 replies to this topic

[itsMeGenelle]

I am using Aspen Hysys v8.4. I have noticed that the stream ethalpy values are negative. The enthalpies of steam (saturated or superheated) were also negative, which is different in commonly used steam tables. I know that this is because Hysys uses different reference point, that's why enthalpy changes are just the same with the steam table.

 

My question is this: Is there a way to change the Hysys reference point? For instance, ethalpy is zero at 0 degC and 1 atm, or the same reference temperature to that of steam tables. I think it would be better if I will be working with these values.

 

Any attempt to help would be very much appreciated. Thank you!

Edited by itsMeGenelle, 13 February 2015 - 02:03 AM.

[RockDock]

I don't know the answer to your question, but I normally don't put much weight on any given stream's enthalpy value. They are completely theoretical. No matter the reference point, the important value is the deltaH, which should be the same.

[PingPong]

I fully agree with RockDock.

In the more than 30 years that I have been using various simulators (except Hysis) I have never looked at the enthalpy value of any stream.

The reference point used for H has absolutely no impact on any calculation (assuming of course that the simulator does not have a bug).