An insulated cylinder/piston contains R-134a at 150 lbf/in.2, 120 F, with a volume of 3.5 ft3. The R-134a expands, moving the piston until the pressure in the cylinder has dropped to 15 lbf/in.2. It is claimed that the R-134a does 180 Btu of work against the piston during the process. Is that possible?
C.V. R-134a in cylinder. Insulated so assume Q = 0.
State 1: v1 = 0.3332 ft3/lbm, u1
= 175.33 Btu/lbm,
s1 = 0.41586 Btu/lbm R, m = V1/v1
= 3.5/0.3332 = 10.504 lbm
This is possible since 1S2 gen > 0
