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Homework Statement
A gas in a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes.
Process 1-2: adiabatic compression with pV1.4 = constant from p*1 = 50 psia and V1 = 3 ft3 to V2 = 1 ft3.
Process 2-3: isometric,
Process 3-1: isobaric with U*1 - U*3 = 46.7 Btu.
Neglect kinetic and potential energy changes. Show the pV diagram of the cycle with arrows indicating work & heat transfer during each process labeled according to the statements above. Show the direction of each process with arrows. Show all work on back of the page as needed. Determine
a. The net work.
b. The heat transfer for process 3-1 in Btu.
c. The temperature T1, if this is air as an ideal gas.
d. The change in temperature, T1 – T3, if cv = constant.
Am I correct in assuming that the mass should be provided?
Homework Equations
dU= dQ-dW
pV=RT
dW=p*dV
dH = dU + d(p*V)
The Attempt at a Solution
Found: parts a and b without trouble.
Having trouble finding T1 with given information.
I also am confused with the use of Cp and Cv in general. I know dU=Cp*dT for isobaric processes, and dU=Cv*dT for isometric processes. I do not understand why Cv should be used for an adiabatic process, when it is obviously not isometric or isobaric. I also do not understand the fact that Enthalpy and Internal Energy are seemingly interchangeable for Cp, i.e. dH=dU=Cp*dT for isobar.
I'd really appreciate some help with this, thanks guys.