Question

Steam undergoes an isentropic compression in an insulated piston–cylinder assembly from an initial state where T1 5 1208C, p1 5 1 bar to a final state where the pressure p2 5 100 bar. Determine the final temperature, in 8C, and the work, in kJ per kg of steam.

Answer 1

Answer:

temperature T2 = 826.9°C

$\frac{W}{m}$ = -1142.7 kJ/kg

Explanation:

given data

initial state temperature = 120°C

final state pressure p1 = 1 bar

pressure p2 =  100 bar

solution

we use here super heated water table A6 that is

specific internal energy u1 = 2537.3 kJ/kg

specific entropy s1 = 7.4668 kJ/kg.K

and

here specific entropy stage 1 = stage 2

so for specific entropy and pressure 100 bar

specific internal energy u2 = 3680 kJ/kg

and temperature T2 = 826.9°C

so here now we get specific work of steam is

ΔU = -W     ...........1

m ( u1 - u2) = W

$\frac{W}{m}$ = u1 - u2

$\frac{W}{m}$ = 2537.3 - 3680

$\frac{W}{m}$ = -1142.7 kJ/kg