# Basic thermodynamics

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#1
Air at 5 bar, 500K is contained in a cylinder by a piston, and initially occupies a volume of 1m^3. 100kJ of heat are transferred to the air, whilst the volume is kept constant. The temperature in the cylinder after this is 540k. The mass of the air is 3.48kg.

Calculate the pressure in the cylinder at the end of the process.

Using the ideal gas law...

Using isentropic relations...

Why do I get a different answer? I'm pretty sure that both methods should work..correctly that is
0
6 years ago
#2
(Original post by Serendreamers)
Air at 5 bar, 500K is contained in a cylinder by a piston, and initially occupies a volume of 1m^3. 100kJ of heat are transferred to the air, whilst the volume is kept constant. The temperature in the cylinder after this is 540k. The mass of the air is 3.48kg.

Calculate the pressure in the cylinder at the end of the process.

Using the ideal gas law...

Using isentropic relations...

Why do I get a different answer? I'm pretty sure that both methods should work..correctly that is
I'm by no means certain but the isetropic derivation probably doesn't involve perfect gases if it gives a different answer.
2
6 years ago
#3
Why do you think the process is isentropic?

dS=dQ/T, is dQ zero?
2
6 years ago
#4
Wtf? Is this really sixth form stuffs?

Posted from TSR Mobile
2
#5
(Original post by Borek)
Why do you think the process is isentropic?

dS=dQ/T, is dQ zero?
Ahh, I'm such a fool. Thank you.

(Original post by QuantumSuicide)
Wtf? Is this really sixth form stuffs?

Posted from TSR Mobile
Nope, that was an accidental mis-labeling. Please forgive me
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