Unit-2 Subject : Applied Thermodynamics : Question bank Steam Nozzle-(Theory) 1 2 3 4 5 6 7 8 1 What is steam nozzle? Why it is convergent divergent? What assumptions are adopted in analyzing flow through nozzle? Explain the significance of critical pressure ratio. What is the steady flow energy equation of nozzle? Explain its use in calculating the steam velocity at exit? Why the divergent portion of nozzle is necessary? Define nozzle efficiency. What is the effect of friction in nozzle Explain the physical concept of critical pressure ratio Explain supersaturated flow through nozzle & Wilson line? What is the metastable expansion of steam in nozzle? Explain with the help of H-S diagram.

Nozzle Problems(General)

A steam is supplied at 7 bar and 2750C.The divergent portion is 50mm long and throat diameter is 5 mm .Find the cone angle of divergent portion so that steam may leave the nozzle at 1 bar. Loss in the nozzle is 12% in divergent portion only. Determine velocity and temperature at throat. Steam at a pressure of 10 bar and dryness fraction of 0.98 is discharges through convergent divergent nozzle to a back pressure a 0.1 bar. The mass flow rate is 10 kg/kW h. If power developed is 200 kW. Determine (1) Pressure at throat (2) Number of nozzle required if throat section is rectangular 5 mm x 10 mm.(3) the cross section (with same aspect ratio at throat) at exit if the 10% enthalpy loss is in divergent part only. A steam nozzle supplied a steam at 15 bar and 350 0 C. and discharges at 1 bar.

The divergent portion of nozzle is 80 mm long and throat diameter is 6 mm. Determine the cone angle of divergent portion. Assume 12% of total enthalpy is lost in friction in divergent portion. Also determine the velocity and condition of steam at throat. A convergent-divergent nozzle is supplied a steam at 10 bar and 2700C.The divergent portion is 3.2 cm long and throat diameter is 6 mm .Find the semi cone angle of divergent portion so that steam may leave the nozzle at 1.2 bar. Loss in the nozzle is 15% in divergent portion only. A convergent-divergent nozzle is required to discharge he steam at a rate of 2 kg/sec. The nozzle is supplied a steam with a pressure at 7 bar and temp 180 0 C. The back pressure is 1 bar. The frictional resistance between throat and exit is 63 kJ/kg. Taking approach velocity 75 m/s and throat pressure is 4 bar. Estimate (1) The suitable area for the throat exit (2) OverallÂ efficiency of nozzle based on enthalpy drop between the actual inlet pressure and temperature and exit pressure.{Hint : C1=75 m/s ,Î· nozzle = (H1-H3-63)/( H1- H3) ,p2 is given so need not to calculate by maximum discharge condition} An impulse turbine develops a power of 1000 kW with a steam consumption is 7.6 kg/kW hr. The nozzle is CD .The pressure and temperature of steam entering in the nozzle is 18 bar and 3000C.The 10% enthalpy drop is in divergent portion only.

The diameter of each nozzle at exit is 10 mm and exit pressure is 0.2 bar .Determine (1) Number of nozzle (2) Throat diameter (3) Length of divergent part if the semi cone angle of divergent portion is 60. A convergent-divergent nozzle is supplied a steam at 7 bar and 2700C.The divergent portion is 50mm long and throat diameter is 5 mm .Find the cone angle of divergent portion so that steam may leave the nozzle at 1 bar. Loss in the nozzle is 10% in divergent portion only. Steam at a pressure of 11.8 bar and at 2200C is discharges through convergent divergent nozzle to a back pressure a 1.18 bar. The mass flow rate is 16.45 kg/kW h. If power developed is 184 kW. Determine (1) Number of nozzle required if throat diameter is 7 mm. (2) Exit diameter and velocity. The 8% enthalpy loss is in divergent part only. A dry saturated steam at 7 bar expanded in nozzle to 1.8 bar. The flow rate is 5 kg/sec. The 12% enthalpy loss is in divergent part only. Determine the cross sectional area at throat and exit. Take n=1.135.

2

3

4

5

6

7

8

9

Steam Nozzle-Super saturation-Metastable problems

1 In an installation 5.2 kg/s of 30 bar and 3500C is supplied to group of six nozzle in a wheel maintain pressure 4 bar. (1) Determine the dimension of nozzle at exit if the nozzle is rectangular with aspect ratio 3:1.The expansion is considered to be metastable (2) Degree of under cooling and super saturation . In an installation 5 kg/s of steam at 30 bar and 3000C is supplied with a group of six nozzle while in turbine chamber pressure is 7.5 bar. Determine the dimension of rectangular nozzle with aspect ratio of 3:1.The expansion is to be taken as metastable .

Determine the degree of under cooling and super saturation. A convergent divergent nozzle receives steam at 7 bar 2000C, expanded isentropically to 3 bar. Neglecting the inlet velocity , calculate the exit area of nozzle for mass flow rate 0.1 kg/sec.(1) when the flow is in equilibrium (2) when flow is super saturated if n=1.3.Also calculate degree of under cooling and degree of supersaturation.{Hint: Ans.(1) By Mollier chart and Ans (2) By super saturation consideration } A dry saturated steam at 2.8 bar expanded in simple convergent nozzle to 1.7 bar. Neglecting the inlet velocity, the throat area is 3 cm2.Calculate the exit velocity and mass flow. (1) When flow is in equilibrium (2) When flow is super saturated if n=1.3.{Hint: Ans.(1) By Mollier chart find H1,H2 & velocity & m (2) By super saturation consideration }