# Homework Help: Hey ! i need some help in calculating the thermal efficiency of steam turbine

1. Oct 13, 2014

### Amr Ali 33

guys i just wanted to know the formula by which i can calculate the thermal efficiency of a pass out steam turbine( a steam turbine with an extraction for process ) I've attached a simple diagram explaining my problem can anyone please help !

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2. Oct 13, 2014

### SteamKing

Staff Emeritus
You'll need more information than what is shown on the diagram, specifically the mass flow rates into the turbine and out the exhaust and extraction line, and you'll need to know the turbine work output. The exhaust conditions of 13" Hg are also a little ill-defined. Calculating the thermal efficiency of this machine is what a First Law type of analysis gives you.

3. Oct 15, 2014

### Amr Ali 33

thanks , I've adjusted the diagram and added the data u requested i hope it's ok now , i would like to say that this is a very old power plant and that's what i could get out of it so please simplify the problem as much as the first law tolerates

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Last edited: Oct 15, 2014
4. Oct 15, 2014

### SteamKing

Staff Emeritus
From this point, it's a bit of a slog with a calculator.

The thermal efficiency of the turbine = 1 - Work output / {Q(in) - [Q(out) + Q(ext)]}

You'll have to get some steam tables and look up the enthalpies of the steam at the inlet, the extraction, and the exhaust to calculate the amount of heat flowing thru the system. The generator output is turned into a heat equivalent at he rate of 3412.14 BTU/kW-hr

5. Oct 15, 2014

thank you