Pressure change at the inlet of a steam turbine in a small electric power plant

In summary: If the turbine is designed to eject steam at 10 bar, then increasing the pressure to 20 bar will cause the turbine to eject steam at 10 bar.
  • #1
HethensEnd25
28
0

Homework Statement


A steam turbine in a small electric power plant is designed to accept 4500 kg of steam at 60 bar and 500oC and exhaust the stem at 10 bar.

Part C.

In off-peak hours, the power output of the turbine in part a) (100% efficient) is decreased by adjusting a throttling valve that reduces the turbine inlet steam pressure to 30 bar while keeping the flow rate constant. Compute T1, the steam temperature to the turbine, Tr, the steam temperature at the turbine exit, and the power output of the turbine.

Homework Equations


Sautrated steam table, superheated water table, linear interpolation

P=m (H2-H1)

Entropy balance

The Attempt at a Solution


I know a valve is isenthalpic so I worked out for the new tempature of the steam and got 484C . I know turbines are isentropic so the entropy will remain the same from inlet to outlet. My only question is will my outlet pressure change from changing my inlet pressure from 60to 30 bar? or do I keep it the same as the problem statement in the first part which is 10 bar? Or is the pressure changing at the outlet as well? If it is how is it changing?

Any and all help is appreciated
D
 
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  • #2
You could make an assumption that the output is designed to eject at 10 bar - do you have enough information to calculate that it would be different? If it is different, we would assume it would be less, since in the first situation it take energy out of 60 bar steam, then ejects 10 bar steam. Starting off at a lower pressure, if it take the same percentage of energy out, would it be close to half (5 bar) at the output. Probably not something as simple as that - atmospheric pressure is a little more than 1 bar. Since it is getting ejected, it will definitely have to be higher than that. (or is this gauge pressure?). I hope these ideas help you.
 
  • #3
They have helped me in my approach thank you. The problem statement did not clarify if there was any change in the outlet stream so I proceeded to solve it with the same outlet pressure of 10 bars.

It is also how my professor solved it.
Dylan
 
  • #4
HethensEnd25 said:
They have helped me in my approach thank you. The problem statement did not clarify if there was any change in the outlet stream so I proceeded to solve it with the same outlet pressure of 10 bars.

It
try increasing the amount of pressure from 10bars to 20 bars
 
  • #5
Jordan gyg said:
try increasing the amount of pressure from 10bars to 20 bars
On what basis.
 

Related to Pressure change at the inlet of a steam turbine in a small electric power plant

1. How does pressure change at the inlet affect the performance of a steam turbine in a small electric power plant?

The pressure at the inlet of a steam turbine is directly related to the amount of energy that can be extracted from the steam. A decrease in pressure at the inlet will result in a decrease in the amount of energy available to drive the turbine, leading to a decrease in performance.

2. What factors can cause a pressure change at the inlet of a steam turbine?

There are several factors that can cause a pressure change at the inlet of a steam turbine, including changes in steam flow rate, changes in ambient temperature, and changes in the operation of other equipment in the power plant.

3. How does the design of the steam turbine affect pressure change at the inlet?

The design of a steam turbine is crucial in maintaining a consistent pressure at the inlet. A well-designed turbine will have efficient blades and a properly sized inlet, minimizing pressure drop and ensuring consistent performance.

4. Can a pressure change at the inlet of a steam turbine be controlled?

Yes, a pressure change at the inlet of a steam turbine can be controlled through various methods, such as adjusting the steam flow rate, regulating the temperature of the steam, and using control valves to maintain a consistent pressure.

5. How does pressure change at the inlet impact the overall efficiency of a small electric power plant?

The pressure at the inlet of a steam turbine is a crucial factor in determining the overall efficiency of a small electric power plant. A decrease in pressure at the inlet can lead to a decrease in the efficiency of the turbine, resulting in lower power output and potentially higher operating costs.

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