power plant lecture notes - chapter-3 steam generator
TRANSCRIPT
كلية الھندسة –الجامعة المستنصرية يـــةانيكـــــالميكالھندســــــــة م ــــقس
ةــــــــــــــــــــــات طاقــــــــــــمحط
CHAPTER (3) Steam Generator
د. مشعل عبد االميرأ.م.
05‐Oct‐14
Chapter3
SteamGenerator
Boiler, Classification of Steam Generators: FIRE-TUBE Boilers, WATER-TUBE Boilers, Water Circulation, Types of Water Circulation: Natural Circulation, Forced Circulation, Example (1), Example (2), The Steam Drum: Gravity Separation, Mechanical Separation, Boiler Blowdown, Superheaters and Reheaters Coils, Advantige of Steam Superheating, Types of Superheaters and Reheaters: Radiant type, Convection type, Combined type, Steam Temperature Control, Heat Balance of Steam Desuperheater, Example (3), Economizer Coil, Air Heater Coil, Types of Air Heaters: Regenerative Air Heater, Recuperative Air Heater, Example (4), Steam Generator Efficiency: The Direct Method, Heat-Loss Method, Tutorial Sheet 3.
Power Plant Engineering TUTORIAL SHEET ‐ 3 كلية الھندسة –الجامعة المستنصرية
Steam Generator اقةــــــــمحطات ط –قسم الميكانيك
62
1‐ A water‐tube steam generator operating at (160 bar) has (15 m) high and (75 mm) I.D.
tubes. Assuming saturated water in the downcomer, a water‐steam mixture in the tubes
with an average density of (288.33 kg/m3), and an inlet tube velocity of (0.92 m/s).
Calculate the pump pressure necessary for the given flow. Also, calculate the mass flow
rate through the downcomer.
2‐ A drum type steam generator operates at (160 bar). (1260 kg/s) of saturated water goes
down the downcomer. The downcomer and risers are all (12 m) high. The average water‐
steam mixture density in the risers is (350 kg/m3). Calculate the power, in kilowatts,
needed to drive a forced circulation pump if the pump efficiency is (70%).
3‐ In a steam generator, a dry steam of (14 bar) enters the superheater which increase the
steam temperature by (65 Co) and reduce the flue gases temperature by (100 Co).
Calculate the flue gases mass flow rate per (1 kg/s) of steam flow rate, if the specific heat
capacity of the flue gases is (1.005 kj/kg.K).
4‐ In a steam generator, a steam of (44 bar, 370 Co) exit from the superheater which
receives steam of (99% dry). The feed water enters the economizer, saturated at (130
Co). Calculate the percentage heat transferred to the superheater, if the pressure losses
through the superheater is (2 bar).
5‐ In a steam generator, a steam of (40 bar, 350 Co) exit from the superheater which
receives steam of (80%) dry. The feed water enters the economizer, saturated at (165
Co). Draw the heat addition process in the steam generator on the (T‐s) and (h‐s)
diagrams, then calculate the percentage heat transferred to the superheater, if the
pressure losses through the superheater coil is (5%) of the inlet pressure of the
superheater.
6‐ A steam generator uses a spray‐type attemperator to control the temperature of the
superheated steam. This attemperator is supplied with feed water, saturated at (50 Co),
and (44 kg/s) of superheated steam at (30 bar), (450 Co). Calculate the mass flow rate of
the feed water to maintain the steam outlet temperature at (400 Co).
7‐ An ideal reheat steam power plant, a steam of (100 bar, 450 Co) exit from the
superheater. The feed water enters the economizer saturated at (295 Co). If (95%) of the
steam outlet from the superheater is reheated to (20 bar, 450 Co). Calculate the
percentage heat transferred to the reheater in the boiler.
Power Plant Engineering TUTORIAL SHEET ‐ 3 كلية الھندسة –الجامعة المستنصرية
Steam Generator اقةــــــــمحطات ط –قسم الميكانيك
63
8‐ A (165 MW) Electric power is generated in a Reheat‐Regenerative steam power plant.
The outlet steam rate from the boiler is (3.95 kg/kW.hr) at (40 bar, 350 Co). The inlet
boiler feed water temperature is (165 Co saturated). The boiler efficiency is (88%). The
steam is expanded in the first stage of the turbine until it is dry at (30 bar), then it is
reheated to (350 Co). (8%) of steam is extracted from the first stage of the turbine to heat
the boiler feed water. Calculate the fuel mass flow rate, if the high heat value of the fuel
is (31 Mj/kg).
9‐ During a steam generator performance test, the following data were taken:
Fuel data:
Type=Coal
Mass flow rate=2.5 kg/s
High heat value=32.5 Mj/kg
Steam data:
Pressure=13 bar
Dryness fraction=99.5%
Mass flow rate=25 kg/s
Feed water data:
Saturated at 50 Co
Calculate the steam generator efficiency.