A rigid tank contains 18 lb m of propane gas at 30 psia and 60 F. The propane ga

Question

A rigid tank contains 18 lbm of propane gas at 30 psia and 60 F. The propane gas is heated until the pressure is 45 psia. Determine:  
              (a) The final temperature in Rankine.              

              (b) The amount of heat transferred in Btu.            

              (c) The change of internal energy of the propane in Btu.              

              (d) The change of entropy of the propane in Btu/R.              

              (e) The volume of the tank in ft3.            

Assume that under these conditions propane obeys a PVT relation

Z= 1-0.4Pr/Tr and that the constant-volume heat capacity CV= 4.0+0.21T(R) Btu/lb-mole R

Explanation / Answer

a) The final temperature in Rankine

P1/T1 = P2/T2

30/60 = 45/T2

T2 = 90o F

(b) The amount of heat transferred in Btu

dQ = dU at constant volume

so heat transfer dQ = 90-60 = 30o F = 815 Btu

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