STEAM NOZZLES

1. Dry saturated steam at 5 bar with negligible velocity expands isentropically in a convergent nozzle to a 1 bar and dryness fraction 0.94. Determine the velocity of steam leaving the nozzle. Ans:-644m/s

2. Dry saturated steam at a pressure of 15 bar enters in a nozzle and is discharged at a pressure of 1.5 bar. Find the final velocity of the steam, when the initial velocity of the steam is negligible. Ans:-439.3 m/s , 5.1%

3. Dry saturated steam at 10bar is expanded isentropically in a nozzle to 0.1bar. Using steam tables only, find the dryness fraction of the steam at exit. Also find the velocity steam leaving the nozzle when 1. Initial velocity is negligible, and 2. Initial velocity of the steam is 135 m/s. Ans:- 0.791, 1176m/s, 1184 m/s

4. Dry saturated steam at a pressure of 10 bar is expanded in a nozzle to a pressure of 0.7bar. With the help of Mollier diagram find the velocity and dryness fraction of steam issuing from the nozzle, if the friction is neglected. Also find the velocity and dryness fraction of the steam, if 15% of the heat drop is lost in friction. Ans:-961 m/s, 0.848, 886m/s

5. Dry air at a temperature of 27C and pressure of 20bar enters a nozzle and leaves at a pressure of 4 bar. Find the mass of air discharged, if the area of the nozzle is 200mm2. Ans:- 0.72kg/s

6. Steam enters a group of nozzles of a steam turbine at 12 bar and 220C and leaves at 1.2 bar. The steam turbine develops 220kW with a specific steam consumption of 13.5kg/kWh. If the diameter of nozzles at throat is 7 mm, calculate the number of nozzles. Ans=13.1 ~14

7Estimate the mass flow rate of steam in a nozzle with the following data: Inlet pressure and temperature =10 bar and 200 C; Back pressure= 0.5 bar; Throat diameter = 12mm. Ans-576kg/h

8Dry saturated steam enters a nozzle at a pressure of 10 bar and with an initial velocity of 90 m/s. The outlet pressure is 6 bar and the outlet velocity is 435 m/s. The heat loss from the nozzle is 9kJ/kg of steam flow. Calculate the dryness fraction and the area at the exit, if the area at the inlet is 1256 mm2. Ans:- 0.962, 406 mm2

9Dry saturated steam at a pressure of 8 bar enters a convergent- divergent nozzle and leaves it at a pressure of 1.5 bar, If the flow is isentropic, and the corresponding expansion index is 1.135; find the ratio of cross-sectional area at exit and throat for maximum discharge. Ans:-1.7

10Steam at a pressure of 10 bar and 0.9 dry discharge through a nozzle having throat area of 450 mm2. If the back pressure is 1 bar, find1. Final velocity of the steam, and 2. Cross-section area of nozzle at exit for maximum discharge. Ans:-842.6m/s; 1114mm2

11A chimney is 28m high and the temperature of the hot gases in the chimney is 320C. The temperature of outside air is 23C and the furnace is supplied with 15kg of air per kg of coal burnt. Calculate draught in mm of water. Ans:- 15.6mm

12A boiler uses 18 kg air of fuel. Determine the minimum height of chimney required to produce a draught of 25mm of water. The mean temperature of chimney gases is 315C and that of outside air 27C. Ans:- 47.2m

13The following data pertain to a steam power plant: Height of chimney= 30m ; Draught produced =16.5mm of water gauge; Temperature of flue gas= 360C; Temperature of boiler house= 28C; Atmospheric pressure =1.013bar. Determine the quantity of air used per kg of fuel burnt in the boiler. Ans:-8.772kg/kg of fuel

14A 30m high chimney is used to discharge hot gases at 297C to the atmosphere which is at 27C. Find the mass of air actually used per kg of fuel, if the draught produced is 15mm of water. If the coal burnt in the combustion chamber contains 80% carbon, 6% moisture and remaining ash, determine the % of excess air supplied. Ans:-11.11kg/kg of fuel, 19.7%