Question

Consider the piston/cylinder arrangement shown in Fig1. A frictionless piston is free to move between two sets of stops. When 3 the piston rests on the lower stops, the enclosed volume is 0.5 m3. When the piston reaches the upper stops, the volume is 0.8 m . The cylinder initially contains water at 200 kPa, 60% quality. The mass of the piston requires 600 kPa pressure to move it against the outside ambient pressure.

a) When heat is transferred until the internal energy of water reaches 3500 kJ/kg, find the heat (kJ) transferred until then.

b) Draw this process on the p-v diagram, showing the temperature of the initial and later states (score 0 if not isothermal) and the pressure value.

Po 8 H2O Fig. 1

Answer 1

Ginen: vi m3 0.8 m? 2= 0.6 1 dictated by the motion of the Рабоо Кра 0.5 m V2 = Pi = 200 kPa ou = 3500 kg/ng The first law of thermodynamics m.ou a Ida-loky (0) Process : If P< 60o Era then = o.sm line 2-1 and below P2 600 mg then v= 0.8m3 line 3-4 and below Po Goo lepa o.5 m3 zveo-8m line 2-3 These three lines arre show in the P-v and is then diagram piston ( Perce balance)

ay State 4 | W4 = 1/2 + 2 W3434 o + 2H3 to I H4 = P2 ( V3-V2) I 14 = 600 (0-8-0.5) 1114 = 180 kJ from equation (1) 104 = m. DU + 114 at state Take properties et 200 kPa from steam fable h = Vf + 2 Upg V = 0.00106052 + 0-6 (0-88568-0-00106052) Vis 0.53183 m3/kg Vi m2 15 = 0.940 kg 0.53183 1942 0.9401 3500 + 180 164 = 3470.35 kJ

b) P-v diagram P P4 6 Pq = P₂ = 600 kPa 2 3 PA