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

[mech-eng]

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?

Thank you.

 

[Dr.D]

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.

 

[mech-eng]

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.

 

[Dr.D]

Solve the equation for P and you have the shape of the curve.

 

[mech-eng]

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.