Gas Compression in a Closed System: Non-Linear vs. Horizontal P-V Diagrams

AI Thread Summary
In gas compression within a closed system, the shape of the P-V diagram can vary based on the process conditions. For isothermal processes, the graph is typically non-linear, while the possibility of a horizontal line arises if temperature decreases. The Ideal Gas Law, P * V = N * R * T, is often used to derive the relationship between pressure and volume during compression. The discussion highlights the importance of understanding the specific type of compression, such as polytropic processes, which can complicate the shape of the curve. Overall, the shape of the P-V diagram is influenced by the thermodynamic conditions and the equations governing the gas behavior.
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When a gas in a closed system is compressed, should the graph always be non-linear? If T is constant ie if the process isothermal it is clear that it should be so but I am not very sure that if the graph can be horizontal. If T decreases might not it be horizontal?

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Thank you.
 
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Unless some other constitutive equation is specified, I'd be inclined to assume that the Idea Gas Law applies. Thus,
P * V = N * R * T
This will enable you to express P(V) and thus calculate the work done.
 
Dr.D said:
Unless some other constitutive equation is specified, I'd be inclined to assume that the Idea Gas Law applies. Thus,
P * V = N * R * T
This will enable you to express P(V) and thus calculate the work done.
Yes we can calculate the work done but I especially ask for the shape of the curve.

Thank you.
 
Solve the equation for P and you have the shape of the curve.
 
Dr.D said:
Solve the equation for P and you have the shape of the curve.

But such a compression process is polytropic so the equation is also might be PVn=C and this is where I am confused.

Thank you.
 

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