Question

A cylinder containing 2 lbm of ammonia has an externally loaded piston. Initially the ammonia is at 280 lbf/in.², 360 F and is now cooled to saturated vapor at 105 F, and then further cooled to 65 F, at which point the quality is 50%. Find the total work for the process, assuming a piecewise linear variation of P versus V.

Answer 1

State 1: (T, P) 

v₁ = 1.7672 ft³/lbm

State 2: (T, x) sat. vap.

P₂ = 229 psia, v₂ = 1.311 ft³/lbm

State 3: (T, x) P3 = 118 psia,

v₃ = (0.02614+2.52895)/2 = 1.2775