Steam Megawatt-hours calculation

[33JMAC]

Hi All,

I have been tasked to specify a function block for our control system that uses the pressure (bar a), temperature (degC) and flow (kg s-1) to obtain a Megawatt-hours (energy) value for steam exported. I have had a look at various research papers and cant find a straight cut answer. Any help would be greatly appreciated.

Thanks

James

 

[TD2K]

Is this for an extraction turbine or simply steam that you export and doesn't go through the steam turbine producing electricity?

 

[katmar]

Have you asked your instrument supplier if they have a standard module for this? You might get lucky.

If you can't get a ready made module, you could probably make a simple linear model yourself if the pressure and temperature ranges aren't too wide. Do a linear regression of the data from the steam tables for the steam enthalpy over the ranges (Excel will do this for you), and then multiply by the mass flow rate to give the energy per time.

Katmar Software - Uconeer 3.0

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[33JMAC]

Thanks for the feedback!

Since posting this I have contacted our site DCS guys who have made a block in fb cad for this purpose!

 

[Raphlinz]

You querry is very unclear. Do you mean that you have ben asked to form a model for calculating energy output in mega-watt of steam? If give people the data regarding that process, that problem can be solved.

 

[33JMAC]

The solution is:

Enthalpy of steam * flow * 2.7E-7 = Energy in MWh

The enthalpy of steam is calculated by our DCS using a function block with inputs: pressure and temperature.

This allows the use of the temp, pressure and flow to calculate the energy in a steam process stream.

 

[dcasto]

Unless you input the steam tables and you specify the base T&P for the steam (ie is it bubble point water at 14.65 psia or is it water at 60F and 14.65 psia) you cannot get the exact value.