Equation of polytropic process as dS=f(n)

In summary, the speaker has a program that calculates states in a Carnot cycle for a jet engine and wants to plot it on a T-S diagram. They are seeking a way to evaluate temperature as a function of entropy change, using only the states at the beginning and end of the polytropic process. The solution may involve the formula ΔS=qrev/T and knowledge of the work done in the polytropic process.
  • #1
jakub.gongol
4
0
Hej,

basicaly what I have is a program that calculates states of the gas in Carnot cycle (Jet engine). Now my intention is to plot it in T-S diagram. To do that, knowing the states after an each component of engine, I need to evaluate a temperature as a function of Enthropy change knowing only the states at the beginning and end of the polytropic process. Is there any way to do this?.
Thank you
 
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  • #2
jakub.gongol said:
Hej,

basicaly what I have is a program that calculates states of the gas in Carnot cycle (Jet engine). Now my intention is to plot it in T-S diagram. To do that, knowing the states after an each component of engine, I need to evaluate a temperature as a function of Enthropy change knowing only the states at the beginning and end of the polytropic process. Is there any way to do this?.



Thank you

ΔS=qrev/T , a reversible process...

And in polytropic process , do you know formula for work done ? After that it will be quite obvious.
 

1. What is a polytropic process?

A polytropic process is a type of thermodynamic process in which the relationship between pressure and volume can be described by a single equation. This equation is known as the polytropic equation and is represented as PVn = constant, where n is the polytropic index.

2. How is the polytropic index (n) determined?

The polytropic index (n) is determined experimentally by plotting the pressure and volume data on a log-log scale and finding the slope of the resulting straight line. This slope is equal to the polytropic index (n).

3. Why is the polytropic process important in thermodynamics?

The polytropic process is important in thermodynamics because it allows for a simplified analysis of certain thermodynamic systems. It also has practical applications in the compression and expansion of gases in various industrial processes.

4. How is the entropy change (dS) related to the polytropic process?

In a polytropic process, the entropy change (dS) is related to the polytropic index (n) by the equation dS = f(n)dV, where f(n) is a function that depends on the polytropic index. This relationship allows for the calculation of entropy changes during polytropic processes.

5. What are the limitations of using the polytropic equation to describe a process?

The polytropic equation is only applicable to ideal gases and cannot accurately describe processes involving phase changes or non-ideal behavior. It also assumes a constant polytropic index, which may not hold true in all cases. Additionally, it does not take into account external factors such as heat transfer or work done by the system.

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