Conditions are adiabatic and reversible about a turbine

In summary, when the conditions are adiabatic and reversible about a turbine, the assumption is that the process is isentropic because in a quasi-static process, dS = dQ/T, and if dQ is equal to 0, then dS must also be equal to 0. However, this does not necessarily apply to a turbine due to the dynamic nature of the expanding gas. The equation for entropy is dS = δQ/T, where δQ is the heat absorbed in a reversible process and T is the absolute temperature.
  • #1
scott_for_the_game
28
1
Why is it when the conditions are adiabatic and reversible about a turbine, the assumption is its isentropic?
 
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  • #3
scott_for_the_game said:
Why is it when the conditions are adiabatic and reversible about a turbine, the assumption is its isentropic?
If dQ = 0, then dS = dQ/T = 0.

This would seem to imply that all adiabatic processes are isentropic (constant entropy - ie dS = 0) which is not true. The relation: dS = dQ/T assumes a quasi static process in which the system is always at equilibrium. If the process is quasi-static and adiabatic, the process is isentropic.

I don't see how this would apply to a turbine, however. The expanding gas is necessarily dynamic (in order to drive the turbine), not quasi-static/reversible.

AM
 
  • #4
you are missing a few terms in your entropy equation. You can't simply assume that dS=dQ/T.
 
  • #5
sicjeff said:
you are missing a few terms in your entropy equation. You can't simply assume that dS=dQ/T.
I am not assuming that dS = dQ/T. That is the thermodynamic definition of dS.

Wikipedia said:
"[URL
Quantitatively, entropy, symbolized by S, is defined by the differential quantity dS = δQ / T, where δQ is the amount of heat absorbed in a reversible process in which the system goes from one state to another, and T is the absolute temperature.[3][/URL]

AM
 
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1. What does it mean for a condition to be adiabatic?

Adiabatic conditions refer to a thermodynamic process in which there is no transfer of heat between the system and its surroundings. This means that the system is thermally isolated and there is no heat exchange.

2. How does a turbine operate under adiabatic conditions?

In a turbine, the adiabatic condition means that there is no heat exchange between the gas or fluid passing through the turbine and the environment. This allows the turbine to convert the fluid's kinetic energy into mechanical energy with maximum efficiency.

3. What is the significance of conditions being reversible in a turbine?

A reversible process in a turbine means that the process can be reversed without any loss of energy. This is important because it allows for the maximum amount of work to be extracted from the system, resulting in a more efficient process.

4. How are adiabatic and reversible conditions achieved in a turbine?

Adiabatic and reversible conditions can be achieved in a turbine by insulating the system to prevent heat transfer and by minimizing friction and other losses in the turbine's components. This ensures that the process is as close to an ideal, theoretical process as possible.

5. Are adiabatic and reversible conditions always possible in a turbine?

No, it is not always possible to achieve adiabatic and reversible conditions in a turbine. Real-world factors such as friction, heat transfer, and non-ideal components prevent an ideal, theoretical process from occurring. However, engineers strive to design turbines that come as close to these conditions as possible in order to maximize efficiency.

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