Question 5.7: Steam initially dry and saturated is expanded in a nozzle fr...
Steam initially dry and saturated is expanded in a nozzle from 15 bar at 300°C to 1.0 bar. If the frictional loss in the nozzle is 12% of the total heat drop calculate the mass of steam discharged when exit diameter of the nozzle is 15 mm.
Refer Fig. 10.
Pressure, p_{1} = 15 bar, 300°C
Pressure, p_{2} = 1.0 bar
Frictional loss in nozzle = 12%
∴ Nozzle co-efficient, k = 1 – 0.12 = 0.88
Exit diameter of nozzle, d_{2} = 15 mm
Neglecting the velocity of steam at inlet to the nozzle, the velocity of steam at exit from the nozzle is given by
= 44.72 \sqrt{0.88 × (3037 – 2515) } = 958.5 m/s
Dryness fraction of steam at discharge pressure, x_{2} ^{′} = 0.93
Specific volume of dry saturated steam at 1.0 bar, v_{g_2} = 1.694 m³/kg
Hence mass of steam discharged through nozzle per hour
= \frac{A_{2} C_{2} ^{′} }{x_{2} v_{g_2}} × 3600 = \frac{π / 4 × (15 / 1000)² × 958.5}{0.93 × 1.694} × 3600 = 387 kg/h.
