PPE PROBLEM SET on STEAM GENERATOR

INSTRUCTION: Encircle the letter that corresponds to the correct answer of your choice.

MULTIPLE CHOICES:

1. A water tube boiler has a heating surface area of 500m2.For a developed boiler hp of 933.
Determine the percent rating of the boiler.
a. 169.81% b. 150.17% c. 160.17% d. 180.17%
2. The factor of evaporation of the boiler is 1.12 and a steam rate of 0.73kg/s. What is the developed
boiler hp?
a. 1.98hp b. 188.074hp c. 1.88hp d. 198.2hp
3. The percent rating of water tube boiler is 200%, factor of evaporation is 1.1 and heating surface area
is 300m2.Find the rate of evaporation.
a. 8,153.02kg/hr b. 8,513.02kg/hr c. 9,380.61kg/hr d. 9,830.61kg/hr
4. The actual specific evaporation of a certain boiler is 8. Factor of evaporation is 1.15. If the heating
value is 26,000 KJ/kg., find the boiler efficiency.
a. 77% b. 78% c. 79% d. 80%
5. The ASME evaporation units of a boiler is 24,827,500 KJ/hr. The boiler auxiliary consumes 2.5MW.
What is the net boiler efficiency if the heat generated by fuel is 32,000,000 KJ/hr.
a. 49.46% b. 59.40% c. 64.75% d. 60.10%
6. A 150,000 kg of coal supplied to two boilers. One has a capacity of 350 kg/hr and the other boiler
has a capacity of 100 kg/hr. How may days to consume the available fuel?
a. 15 b. 14 c. 13 d. 51
7. A boiler operates at 82.5% efficiency while the mass of steam generated is 995,000 lbs in 5 hrs. The
enthalpy of steam is 1400 Btu/lb and feed is 250 Btu/lb while the fuel used for boiler has a heating
value of 14,850 Btu/lb. Find the mass of fuel needed in short tons per day.
a. 10.78 b. 98.34 c. 224.16 d. 313.45
8. Two boilers are operating steadily on 94,000 kg of coal contained in a bunker. One boiler producing
1600 kg/hr of steam at 1.2 factor of evaporation and an efficiency of 65% and another boiler
produces 1464 kg/hr of steam at 1.15 factor of evaporation and efficiency of 60%. How many hours
will the coal in the bunker run the boilers if the heating value is 7,600 kcal/kg?
a. 240.4 b. 220.5 c. 230.09 d. 225.3
9. A typical steam generator with an efficiency of 75% is producing 10kg/s of steam. The enthalpy of
the entering water is 125.79KJ/kg and is superheated to an enthalpy of 3034.8KJ/kg. The fuel used
has heating value of 42,150KJ/kg. The A/F ratio by weight is 14. Determine the amount of air needed
in kg/hr.
a. 38371 b. 48378 c. 56873 d. 46378
10. A steam generator evaporated 20,000 kg of water per hour from feed water with enthalpy of 461.3
KJ/kg of steam with enthalpy of 2706.3 KJ/kg. Coal consumption is 2100 kg/hr. its heating value as
fired is 28,300 KJ/kg. Calculate the boiler horsepower.
a. 1271 b. 1352 c. 1578 d. 1873
11. A steam boiler on a test generates 858,000 lb of steam in a 4-hour period. The average steam
pressure is 400psia, the average steam temperature is 700oF, and the average temperature of the
feedwater supplied to the boiler is 280oF. If the boiler efficiency for the period is 82.5%, and if the
coal has a heating value of 15,350Btu per lb as fired, find the average amount of coal burned in
short tons per hour?
a. 9.43 b. 10.78 c. 12.05 d. 11.45
12. Steam is admitted to the cylinder of an engine in such a manner that the average pressure is 120psi.
The diameter of the piston is 10inch and the length of the stroke is 12inch. What is the hp of the
engine when it is making 300rpm?
a. 171.4 b. 175 c. 173.2 d. 174.4
o
13. 24.5 kg of steam per second at 5 MPa and 400 C is produced by a steam generator. The feedwater
enters the economizer at 145oC and leaves at 205oC. The steam leaves the boiler drum with a quality
of 98%. The unit consumes 2.75 kg of coal per second as received having a heating value of 30000
KJ/kg. What would be the overall efficiency of the unit in percent?
a. 65 b. 95 c. 88 d. 77
14. Determine the vacuum efficiency of a surface condenser which operates at a vacuum of 635mm Hg
and exhaust steam enters the condenser at 45.81oC. The barometric pressure is 760mm Hg.
a. 18.25 b. 20.23 c. 92.7 d. 82.7
15. If coal having a hat of combustion of 16,000 Btu per lb is used in a heating plant of 50% efficiency,
how many pounds of steam of 50% quality and 212oF temperature can be made per pound of this
coal from water whose initial temperature is 70oF?
a. 15.3 b. 11.2 c. 12.8 d. 13.5
16. Find the degree superheat of steam at 0.89MPa and 180oC.
a. 4.4 b. 4.9 c. 5.1 d. 7.4
17. The heat transferred to the engine is at a rate of 60MW. Compute the thermal efficiency of the heat
engine when the rate of waste heat rejection from a nearby reservoir is 40MW.
a. 66.67 b. 50.5 c. 33.33 d. 82
18. A typical steam generator with an efficiency of 80% is producing 15kg/s of steam. The enthalpy of
the entering water is 133.98Kj/kg and is superheated to an enthalpy of 3256.4 KJ/kg. The fuel used
has a heating value of 43,250 KJ/kg. The A/F ratio by weight is 17.5. Determine the amount of air
needed in kg/hr.
a. 4873.14 b. 78,328 c. 85,280 d. 68,317
19. A boiler uses 2000 kg of coal per hour. The amount of air needed for the combustion of one kg coal
is 20kg. If ash loss is 15%, calculate the mass of gas entering the chimney.
a. 49,350 b. 55,500 c. 36,700 d. 41,700
20. A steam generator evaporated 22,000 kg/hr of water from a feedwater with enthalpy of 481.2KJ/kg
to steam with enthalpy of 2,508.9KJ/kg. Coal consumption is 2200kg/hr. Its heating value as fired is
23,500KJ/kg. Calculate the boiler horsepower.
a. 1020 b. 1150 c. 1263 d. 1798
21. The rated boiler horsepower of a water tube generator is 164kw. The heating furnace area is?
a. 205m2 b. 2154ft2 c. 310,120in2 d. 2.1x106cm2
22. A fire tube boiler which has a heating surface area of 2960 sq. ft. at a height of 10ft is to convert to
water tube type. Feedwater temperature of 33oC and pressure of 0.1Mpa delivers to the furnace
area passing right after the economizer. Determine the heating surface area difference of the
conversion.
a. 48m2 b. 513ft2 c. 73632in2 d. 4.75x105cm2
23. A steam boiler generates 600,000 kg of steam in 4-hour period. The steam pressure is 2750kpa and
370oC. The temperature of the feedwater is 138oC. If the overall thermal efficiency is 82% and the
fuel is at 28oAPI, find the average amount of fuel burned per hour.
a. 8625.6 b. 9770.7 c. 10504.6 d. 11924.2
o
24. 25kg of steam at 5MPa and 400 C is produced per second by a steam generator. The feedwater
enters the economizer at 145oC and leaves at 205oC. Determine the overall efficiency given the
ultimate analysis of coal of: C=75.2,H=8.3,O=12,S=4.2 and Ash=0.3 where it consumes 3kg/s.
a. 88 b. 75 c. 61 d. 52
2
25. A boiler operating at 11kg/cm is required to generate a minimum of 13.89 kg per second of
saturated steam. Feedwater enters the boiler at 80oC. The furnace is designed to fire coal at an
average rate of 3 kg per second and the overall efficiency is 85%. Compute the gross calorific value.
a. 5728Btu/lb b. 8695KJ/kg c. 4829Btu/lb d. 13342KJ/kg
2
26. A boiler operating at 11kg/cm is required to generate a minimum of 19 kg per second of saturated
steam. Feedwater enters the boiler at 80oC. The furnace is designed to fire coal at an average rate of
1.5 kg per second and the boiler efficiency is 85%. Compute the rated boiler horsepower of 112%
rating.
a. 1881Btu/lb b. 4229.72KJ/kg c. 4229.27hp d. 0
27. What is boiler in a pan on a stove in sea level? During 10 minutes of boiling. It is observed that
200grams of water has evaporated. What is the rate of heat transferred?
a. 0.84KJ/s B. 45.14KJ/min c. 54.1 KJ/kgK d. 1.5KJ/s
28. Find the net boiler efficiency of a water tube boiler whose heating value is 45,000KJ/kg at 3kg/s fuel
rate, actual specific evaporation of 20 and factor of evaporation of 1.3 with auxiliaries of 60KW.
a. 130% b. 120% c. 100% d. 92%
o
29. Feedwater temperature of 78 C enters the boiler. Find the developed boiler horsepower if the
steam flow rate is 18kg/s at 11kg/cm2.
a. 4489.15 b. 3389.15 c. 2289.15 d. 1189.15
o
30. A steam boiler generating 8kg/s of 4.137kpa, 426.7 C steam is continuously blown at the rate of
0.49kg/s. Feedwater enters the economizer at 148.9oC. The furnace burns 0.7kg/s of 35322KJ/kg
heating value. Calculate the overall thermal efficiency of the boiler.
a. 0.828 b. 0.865 c. 0.712 d. 0.678
31. A steam plant operates with initial pressure of 1.7MPa and 370oC temperature and exhaust to a
heating system at 0.17MPa. The condensate from the heating system is returned to the boiler at
65.5oC and the heating system utilizes from its intended purpose 90% of the energy transferred
from the steam it receives. The turbine efficiency is 75%. If the boiler efficiency is 86%, what is the
cogeneration efficiency of the system? Neglect pump work.
a. 69.16 b. 74.24 c. 81.29 d. 89.71
32. A waste heat recovery boiler produces 4.8MPa(dry saturated )steam from 104oC feedwater. The
boiler receives energy from 5kg/s of 954oC dry air. After passing through the waste heat boiler, the
temperature of the air has been reduced to 343oC. How much steam in kg is produced per second?
Note: At 4.80MPa dry saturated, h=2796KJ/kg
a. 0.9 b. 1.3 c. 1.8 d. 2.5
33. Steam enters the superheaters of a boiler at a pressure of 25bar and dryness of 0.98 and leaves at
the same pressure at a temperature of 370oC. Calculate the heat energy supplied per kg steam
supplied in the superheaters.
a. 276.63 b. 346.25 c. 405.51 d. 523.12
34. A double pass condenser with a mass flow rate of 1000000kg/hr has a leaving flow velocity of
1.5m/s. The area of the condenser tube is 0.0003m2. Calculate the number of tubes.
a. 618 b. 816 c. 982 d. 1235
35. From the furnace, heat is transferred to a heat engine at a rate of 75MW. The rate of rejection of
waste heat to a sink is 40MW. Compute the thermal efficiency of the heat engine.
a. 34.48 b. 46.67 c. 55.23 d. 62.12
36. A water tube condenser has a total of 60tubes. If these are three passes, compute the number of
tubes per pass.
a. 30 b. 20 c. 15 d. 60
37. A water tube boiler evaporated5.05kg/s of water from a feedwater temperature of 104.44 oC to
steam at 1241.1kPa and quality of 0.97; weight of the coal per second is 0.57; heating value of coal
as fired is 11,800Btu/lb. Determine the rate of heat absorption in KW.
a. 9800 b. 10526 c. 11558 d. 12698
38. A water tube boiler evaporated5.05kg/s of water from a feedwater temperature of 104.44 oC to
steam at 1241.1kPa and quality of 0.97; weight of the coal per second is 0.57; heating value of coal
as fired is 11,800Btu/lb. Find the boiler horsepower.
a. 9256.23 b. 1177.97 c. 5684.21 d. 3268.45
39. A water tube boiler evaporated5.05kg/s of water from a feedwater temperature of 104.44 oC to
steam at 1241.1kPa and quality of 0.97; weight of the coal per second is 0.57; heating value of coal
as fired is 11,800Btu/lb. Find the boiler efficiency.
a. 56 b. 68 c. 74 d. 82
40. A steam condenser receives 18kg/s of steam with an enthalpy of 2750KJ/kg. Steam condenses into
liquid and leaves an enthalpy of 160KJ/kg. Cooling water passes through the condenser with
temperature increase from 13oC to 24oC. Calculate the cooling water flow rate.
a. 523.2 b.858.1 c.9412.5 d.1012.2
41. A boiler plant is to furnish steam for a 100hp engine using 17lb of steam per hp-hr. The auxiliaries
used 25% as much as the engine. The efficiency of the boiler, furnace and grate is 70%. Steam
pressure is 100psi, quality is 98%, feedwater temperature is 200oF. Coal contains 13,000Btu/lb. How
much coal will the plant use in an hour.
a. 187.3 b. 201.7 c. 234.5 d. 340.3
2
42. A steam boiler having 153.4m of heating surface has a steaming capacity of 6800kg/hr. Steam is
generated at 1.724MPa and 249oC from 138oC feedwater. Calculate the rated boiler horsepower.
a. 138 b. 169 c. 187 d. 200
43. A fuel of 12300Btu was burned in the furnace of a 2400sq.ft water tube boiler which was generating
12000lb steam per hr at 200psi, dry and saturated from 228oF feed at a time when fuel consumption
was 1350lb/hr. Determine the percent rating of the boiler.
a. 89 b. 110 c. 149 d. 190
44. A fuel of 12300Btu was burned in the furnace of a 2400sq.ft water tube boiler which was generating
12000lb steam per hr at 200psi, dry and saturated from 228oF feed at a time when fuel consumption
was 1350lb/hr. Determine the overall thermal efficiency.
a. 25 b. 50 c. 72 d. 89
2
45. A simple water tube boiler of 20,000ft heating surface is offered by a salesman for installation in a
steam plant where 80,000 lb per hour of dry and saturated steam are to be produced at 190psig
from 210oF feedwater. Using the babcock formula calculate the area by assuming mass flow of
5000lb/hr-ft2. Furnace and chimney temperatures of 1800oF and 450oF respectively.
a. 20016 b. 20100 c. 20600 d. 21200