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# Steam as a representative fluid as per API 581- 2016 edition

## Steam as a representative fluid as per API 581- 2016 edition

(OP)
Good Day for you
I faced a problem during the application of API 581-2016 edition and I hope you could help me in this issue.

I am trying to apply RBI for a steam vessel , when I chose the representative fluid as steam , no release rate was calculated , this is because of the huge value of Cp that was calaculated for steam refer to note 3 in table 4.2 in API 581 -2016 , when using this huge value to calculate k k=Cp/(Cp-R) ,where R=8.314 the result equal to 1.

If you use k=1 in gas release rate equation (equation 3.6 or 3.7- API 581-2016) there will be no result so there will be no consequence . , temperature used is 773 K
Thanks

### RE: Steam as a representative fluid as per API 581- 2016 edition

Looking in two old textbooks, I find values of k=1.33 or 1.329 for steam. It's not clear what pressure that's at, but that could be the difference.

### RE: Steam as a representative fluid as per API 581- 2016 edition

(OP)
1.33 seems reasonable k for steam but I am talking about k that calculated as per API 581 , the problem coming from values Of ideal gas constants (A, B,C,D &E )in table 4.2 in API 581 , these values used in equation in note 3 .

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