Question

A vertical cylinder fitted with a piston contains 10 lbm of R-22 at 50 F, Heat is transferred to the system causing the piston to rise until it reaches a set of stops at which point the volume has doubled. Additional heat is transferred until the temperature inside reaches 120 F, at which point the pressure inside the cylinder is 200 lbf/in.2.

a. What is the quality at the initial state?

b. Calculate the heat transfer for the overall process.

Answer 1

C.V. R-22. Control mass goes through process: 1 -> 2 -> 3 As piston floats pressure is constant (1 -> 2) and the volume is constant for the second part (2 -> 3).

So we have: v3 = v2 = 2 × v1

State 3: (P,T) v3 = 0.2959 ft3/kg,

u3 = h - Pv = 117.0 - 200 x 0.2959 x 144/778

= 106.1 Btu/lbm