Air in a piston-cylinder device is compressed from an initial state (temperature
ID: 2997812 • Letter: A
Question
Air in a piston-cylinder device is compressed from an initial state (temperature = 40 ?C, pressure = 180 kPa, volume = 0.4 m3) to a final state (temperature = 250 ?C, pressure = 600 kPa), during a polytropic process (n = 1.74290049961219). What is the heat transfer associated with this process in kJ? (Remember, heat in is postive, heat out is negative.)
kJ
Air in a piston-cylinder device is compressed from an initial state (temperature = 40 ?C, pressure = 180 kPa, volume = 0.4 m3) to a final state (temperature = 250 ?C, pressure = 600 kPa), during a polytropic process (n = 1.74290049961219). What is the heat transfer associated with this process in kJ? (Remember, heat in is postive, heat out is negative.)Explanation / Answer
We have to calculate Cv
Cv=0.287/(1.74-1)=0.287/0.74=0.387
U=0.387*DT
T1=40+273=313K
P1=180kpa
V1=0.4 m^3
P2=600kpa
V2=?
T2=250+273k=523K
we know
(P1*V1)/T1=(P2*V2)/T2
=>V2=0.2 M^3
Now U=81.27KJ
W=(P2*V2-P1*V1)/(n-1)=66.67KJ
Q=U+W=147.94KJ
This amount of heat move away from system.
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