Question

ice, take us 3.26 Consider a piston-cylinder assembly that initially contains 0.5 kg of steam at 400C 100 bar. For the isothermal expansion of the steam in this system to a final pressure of 1 determine the following: (a) What is the maximum possible work (in [kj]) that can be obtained during this process and entropy change of the surroundings (in (kJ/K])? (b) Repeat part (a) using the ideal gas model for steam. Compare your answers. 11 mnt the ton of nage. It is well insulated and ini-

Answer 1

Solution state at Proobal (as using steam tables Steam is in superheated and Tz 400°C. ů z o. 0300 m² (from steam table) Steam is again in superheated state at P = 1 hae and T=4ool because saturation temperature of steam at I bar is 99.61°t which i t less than uvor. And, ♡ 23.103 m²/kg (from steam table) work done, Wz nRT ln ( 1 ) mo W z = (.5 kg), clients to (0.314 J K' mod")*(673 k) X dn (3.103 0.0300 ws 721.008 kJ

According to Itt law of thermodynamics - AU- Q - w In an isothermal process, AUZO so, ozQ-W 7 Qaw 2721.008 kJ 1 Entropy change - As = Q = 721.008 kJ 673 K As a 1.07 kJ / to be hehaning as (b) Assuming - an ideal steam gas- PN z nRT v=nRT Ř na ois kg = 27.78 mol - 18x10 -3 kg/mol V = (27,78 mod) x(0.314 Libou. Ktmort)(673 K9 (1oo bau)

V = 1554.38 L V2 = (27.78 mol) * (8.314 L. bau Klimol') x (673K) (I beu) V = 155438.ous L Nowe , W = nRT ln (V2 (27.78 mo)+(8.314 J K" mot') x (673 Koln (155430.048) 1554.38) wa 75.510 KJ) elightly less than the work done Previous is one.

Again, е – - 113. Са К Entropy change, AS = Q T - 75.518 kJ 672 к Дs 2 1. Бъ2 K. ентерт олам чао има и than the previous one.