Dry and saturated steam at 11 bar pressure enters a convergent-divergent nozzle and is discharged at 2 bar. Determine the actual enthalpy drop if he efficiency of the nozzle is 96%.

Dry and saturated steam at 11 bar pressure enters a convergent-divergent nozzle and is discharged at 2 bar. Determine the actual enthalpy drop if he efficiency of the nozzle is 96%. Correct Answer 288.14 kJ/kg

Given, P1 = 11 bar, P2 = 2 bar, η = 0.96 At 11 bar, from steam tables h1 = hg = kJ/kg s1 = sg = 6.550 kJ/kg-K At 2 bar, from steam tables hf2 = 504.7 kJ/kg, hfg2 = 2201.6 kJ/kg sf2 = 1.530 kJ/kg-K, sfg2 = 5.597 kJ/kg-K s1 = s2 s1 = sf2 + x2(sfg2) 6.550 = 1.530 + x2(5.597) x2 = 0.897 h2 = hf2 + x2(hfg2) h2 = 504.7 + 0.897(2201.6) h2 = kJ/kg Enthalpy drop, hd = h1 – h2 = 2779.7 – 2479.54 = 300.16 kJ/kg Actual enthalpy drop, hd’ = ηhd = 0.96 * 300.15 = 288.14 kJ/kg.