[TRNSYS-users] WG: Type 619a - Wrong calculation?

Additional information: Type 619a is from the Co-Gen Library (TESS), author and editor is Jeff Thornton.

Regards,

Martin

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i. A. Martin Thur

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Von: Martin Thur [mailto:Martin.Thur@BLS-Energieplan.de]
Gesendet: Montag, 31. Mai 2010 16:30
An: trnsys-users@cae.wisc.edu
Betreff: [TRNSYS-users] Type 619a - Wrong calculation?

Hello everyone,

in my simulation i use type 619a (Open Feedwater Heater - Steam Flow Calculated to Achieve User-Designated Outlet). When I click on the more… button of output 6 (Heat Transfer Rate) it says:

“The rate at which energy is added to the de-aerating heater by the high-temperature steam inlet. The heat transfer rate is calculated by multiplying the high-temperature steam flow rate by the enthalpy difference between the high-temperature steam and the entering low-temperature steam (condensate).”

In my opinion this difference is wrong. I think the high-temperature steam flow rate should be multiplied by the enthalpy difference between the high-temperature steam and mixed outlet steam, because the high-temperature steam flow can’t “cool down” below the mixing enthalpy. One consequence is that output 5 (Required Source Steam Flow Rate) is always too low (according to my test simulation + calculation).

I am not 100 % sure about that so any thoughts on that are well appreciated.

Kind regards

Martin