Engineering Steam Turbine with Open Regenerative Feed Heater

AI Thread Summary
The discussion revolves around calculating the mass of steam bled from a steam turbine to produce 1 kg of saturated feedwater at 2 bar using an open-type regenerative feed heater. Key assumptions include negligible energy input from the heater pump and no energy loss, with enthalpy values provided for the steam and feedwater. The initial calculation yields a mass of 0.26259 kg, but a correction to the equation suggests the correct mass should be 0.179 kg. Participants are encouraged to review the calculations for accuracy and provide feedback. The inquiry highlights the complexities involved in thermodynamic calculations within steam turbine systems.
PaxFinnica96
Messages
14
Reaction score
0
Homework Statement
A steam turbine operates with a condenser pressure of 0.04 bar and has a single open-type regenerative feed heater. How much steam, at a pressure of 2 bar and a dryness fraction of 0.98, must be bled from the turbine to produce 1 kg of saturated feedwater at 2 bar?
Relevant Equations
m h3 + (1 – m) h6 = h7
I would very much appreciate anyone to cast their eye over my attempt at solving this problem which I've been struggling with the past few days. Many thanks in advance.

Assuming that:

  • energy input from open-type regenerative feed heater pump is negligible
  • no energy is lost
  • the heater pressure is the same as the bled pressure
h6 = hf at 0.04 bar = 121.41 kJ kg-1

h7 = hf at 2 bar = 505 kJ kg-1
Enthalpy at exit of turbine…

h3 = hf + x hfg at 2 bar (from steam tables)

h3 = 505 + 0.98 (1795) = 2264.1
Balancing the

m (2264.1) = (1 – m) (121.41) + 505

m = 0.26259

So, mass of steam bled from the turbine to produce 1kg of saturated feedwater as 2 bar would be 0.26259 kg
 
Physics news on Phys.org
PaxFinnica96 said:
Homework Statement:: A steam turbine operates with a condenser pressure of 0.04 bar and has a single open-type regenerative feed heater. How much steam, at a pressure of 2 bar and a dryness fraction of 0.98, must be bled from the turbine to produce 1 kg of saturated feedwater at 2 bar?
Relevant Equations:: m h3 + (1 – m) h6 = h7

I would very much appreciate anyone to cast their eye over my attempt at solving this problem which I've been struggling with the past few days. Many thanks in advance.

Assuming that:

  • energy input from open-type regenerative feed heater pump is negligible
  • no energy is lost
  • the heater pressure is the same as the bled pressure
h6 = hf at 0.04 bar = 121.41 kJ kg-1

h7 = hf at 2 bar = 505 kJ kg-1
Enthalpy at exit of turbine…

h3 = hf + x hfg at 2 bar (from steam tables)

h3 = 505 + 0.98 (1795) = 2264.1
Balancing the

m (2264.1) = (1 – m) (121.41) + 505
This equation should read

m (2264.1) + (1 – m) (121.41) = 505
 
Many thanks for your help, I get 0.179 kg
 
Back
Top