One kg of air as an ideal gas executes a Carnot power cycle having a thermal efficiency of 60%. The heat transfer to the air during the isothermal expansion is 40 kJ. At the end of the isothermal expansion, the pressure is 5.6 bar and the volume is 0.3 m3. Determine...
a.) The maximum and mininmum temperatures for the cycle in Kelvin.
b.) The pressure in bar and volume in m3 at the beginning of the isothermal expansion.
c.) The work and heat transfer for each of the four processes in kJ.
Assume: CV,air = 0.731 kJ/kg-K (constant).
d.) Sketch the cycle on a PV diagram.
9 comments:
I'm completely lost on how to do part B. Should the boundary work here be equal to the incoming heat?
confused:
Step 12 is isothermal. For an ideal gas, U = fxn(T) only. Therefore U2 = U1 and the 1st Law becomes Q12 = W12. Because this is an ideal gas we can evaluate W12 from integral of P dV. The resulting formula is in the book and in the chapter 4 summary. Solve this equation for P1 or V1 and then use the ideal gas EOS to determine the other one (V1 or P1).
Professor,
Do I really have to draw another diagram for part d? I drew one at the beginning when I started doing the problem. However, if I do have to draw it again, could you tell me what I should put on it (P,V,W...)? Thank you very much!
how do you find Tmin and Tmax?
y:
Determin the T at each state and Tmax is the biggest one and Tmin is the smallest one.
I used Ideal Gas EOS to calculate the
Tmax but I don't know the molar weight of air.
the mw of air is .02891 kg/mol
Y:
The MW of air is 28.97 g/mole = 28.97 lbm/lbmole.
I:
Thanks for helping !
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