Question

Find the specific volume, enthalpy and internal energy of wet steam at 18 bar, dryness fraction 0.85.

Answer 1

Pressure of steam, p = 18 bar 

Dryness fraction, x = 0.85 

From steam tables corresponding to 18 bar pressure : 

h_f = 884.6 kJ/kg, 

hfg = 1910.3 kJ/kg, 

vg = 0.110 m³/kg, 

u_f = 883 kJ/kg, 

ug = 2598 kJ/kg. 

(i) Specific volume of wet steam, 

v = xvg = 0.85 × 0.110 = 0.0935 m³/kg. 

(ii) Specific enthalpy of wet steam, 

h = h_f + xhfg = 884.6 + 0.85 × 1910.3 

= 2508.35 kJ/kg.

(iii) Specific internal energy of wet steam, 

u = (1 – x)uf + xu_g 

= (1 – 0.85) × 883 + 0.85 × 2598 

= 2340.75 kJ/kg.