PPE - PROBLEM SET # 6

1. A fuel is represented with C5 H8 is burned with 40% excess air. If mass of fuel is 0.17 kg, find the mass of air
needed.
A. 3.38 kg B. 1.638 kg C. 2.34 kg D. 5.34 kg
2. The analysis of a product of combustion on dry basis, when C 6 H18 was burned with atmospheric air, is as
follows: CO2 = 12%, CO = 1.75%, O2 = 3.01%, N2 = 83.24%. Compute the actual air-fuel ratio.
A. 12.34 B. 15.29 C. 17.35 D. 14.73
3. A boiler burns fuel oil with 15% excess air. The fuel may be represented by C 14 H30. Calculate the molal air-fuel
ratio.
A. 14 B. 117.69 C. 102.34 D. 17.14
4. Given the following ultimate analysis:
C = 71%, N2 = 4%, H2 = 4%, O2 = 3%, S2 = 5%, Ash = 6%, Moisture = 8%.
Using 20% excess air, determine the actual air-fuel ratio.

A. 11.56 B. 11.21 C. 21.21 D. 9.22

5. A certain coal has the following ultimate analysis:
C = 70%, N2 = 4%, H2 = 2.5%, O2 = 3.5%, S2 = 7%, Ash = 5%, Moisture = ?
Determine the heating value of fuel in Btu/lb.
A. 27,299.65 B. 11,735.35 C. 26,961.45 D. 27,320
6. A fuel gas has the following volumetric analysis: CH 4 = 68% C2H6 = 32% Assume complete combustion with
15% excess air at 101.325 Kpa, 21 C wet bulb and 27 C dry bulb. What is the partial pressure of water vapor in
o o

Kpa?
A. 9.62 B. 12.81 C. 17.28 D. 15.94
7. There are 23 kg of flue gases formed per kg of fuel oil burned in the combustion of a fuel oil C 12 H26. What is the
excess air in percent?
A. 46.67 B. 26.67 C. 36.67 D. 45.66
8. By how much is the change of volume of the products of combustion of benzene (C 6H6) with theoretical air?
Both volumes of reactants and products are taken at the same pressure and temperature.
A. 1.3% increase B. 1.3% decrease C. no change D. 9.2% increase
9. Calculate the amount of air in kg necessary for combustion of 1 kg of octane (C 8H18) with theoretical air.
A. 12.5 B. 14.8 C. 15.1 D. 13.5
10. Calculate the mass in kg of the combustion products of 12 kg diesel fuel oil (C 16H30) with 30% excess air.
A. 185.2 B. 284.6 C. 208.7 D. 235.44
11. Five kg-mol of octane are burned with stiochiometric amount of air. How much water is formed in the products
if the combustion is complete?
A. 15 kg-mol B. 25 kg-mol C. 35 kg-mol D. 45 kg-mol
12. Methyl alcohol (CH3OH) is burned with 30% excess air. How much unburned oxygen in kg-mol-oxygen/kg-
mol-fuel will there be in the products if the combustion is compete?
A. 0.35 B. 0.45 C. 0.55 D. 0.65
13. Dodecane (C12H26) is burned at constant pressure with 150% excess air. What is the air-fuel for this process?

A. 37.5 B. 42.3 C. 48.7 D. 51.3

14. A complete combustion of one kilogram of C 16H32 resulted to 20 kilograms of products of combustion. Calculate
the percent excess air.
A. 29.16 B. 40.5 C. 35.4 D. 55.6
15. Calculate the heating value of coal having the following composition by weight using Dulong formula. Carbon
75%, hydrogen 5%, oxygen 6%, nitrogen 1.5%, sulfur 3%, water 1.5%, ash 8%
A. 150,450 Btu/lb B. 13,658 Btu/lb C. 12,640 Btu/lb D. 14,580 Btu/lb
SITUATIONAL PROBLEM
A central station has annual factors as follows:
Load factor = 58.50% Capacity factor = 40.95% Use factor = 45.20%
The reserve carried over and above the peak load is 8900 kw. Find the following
16. Installed capacity.
A. 59,600 kw B. 49,600 kw C. 39,600 kw D. 29,667 kw
17. Annual energy production:
A. 106 x 106 kw-hrs B. 206 x 106 kw-hrs C. 306 x 106 kw-hrs D. 406 x 106 kw-hrs
18. Hours per year not in service.
A. 880 hrs. B. 823 hrs. C. 800 hrs. D. 750 hrs.
19. 19 A water tube boiler has a heating surface area of 500 m . For a developed boiler hp of 933. Determine the
2

percent rating of the boiler.

A. 169.81% B. 150.17% C. 160.17% D. 180.17%
20. 20 The factor of evaporation of the boiler is 1.12 and a steam rate of 0.73 kg/s. What is the developed boilerhp?

A. 1.98hp B. 188.074 hp C. 1.88 hp D. 198.2 hp

21. The percent rating of water tube boiler is 200%, factor of evaporation is 1.1 and heating surface are is 300 m 2.
Find the rate of evaporation.
A. 8,153.02 kg/hr B. 8513.02 kg/hr C. 9,380.61 kg/hr D. 9830.61 kg/hr
22. 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. 79% B. 78.11% C. 76.39% D. 80.00%
23. The ASME evaporation units of a boiler is 24,827,500 KJ/hr. The boiler auxiliaries consumes 2.5 MW. 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%
24. A 150,000 kg of coal supplied to two boiler. One has a capacity of 350 kg/hr and the other boiler has a capacity
of 100 kg/hr. How many days to consume the available fuel?
A. 15 B. 14 C. 51 D. 13
25. A boiler operates at 82.5% efficiency while the mass of steam generated is 995,000lbs 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
26. A coal-fired power plant has a turbine-generator rated at 1200 MW gross. The plant required about 10% of
this powerfor its internal operations. It uses 10,000 tons of coal per day. The coal has a heating value of 6,500
Kcal/kg and the steam generator efficiency is 85%. What is the net station efficiency of the plant in percent?
A. 30% B. 25% C. 33% D. 38%
27. 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
28. A typical steam generator with an efficiency of 75% is producing 10 kg/sec of steam. The enthalpy of the
entering water is 125.79 KJ/kg and is superheated to an enthalpy of 3034.8 KJ/kg. The fuel used has s heating
value of 42150 KJ/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
29. 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. 1586 D. 1873
30. A diesel power plant consumes 650 li of fuel at 26 C in 24 hrs with 28oAPI. Find the fuel rate in kg/hr.
o

A. 23.83 B. 24.85 C. 22.85 D. 26.85

31. The following data were obtained in a small power generating plant:
Power developed by the steam turbine = 2800 KW
 Heat supplied to the steam turbine generator = 3500 KJ/kg
Heat rejected by the steam to the cooling water in the condenser = 2200 KJ/kg
Power required by the feedwater pump to return the condensate to the steam generator = 12 KW
Determine the mass flow rate of steam in kg/sec.
A. 1.685 B. 2.537 C. 3.082 D. 2.145
32. A simple Rankine cycle produces 40 MW of power, 50 MW of process heated and rejects 60MW of heat to
the surroundings. What is the utilization factor of this cogeneration cycle neglecting the pump work?
A. 50% B. 60% C. 70% D. 80%

PPE - PROBLEM SET # 7

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

1. A steam engine develops 60 Bhp with saturated steam at 1034.25 Kpa absolute and exhaust at 124.11 Kpa.
Steam consumption is 736.36 kg/hr. Calculate the indicated engine efficiency based on 90% mechanical
efficiency.
A. 69.74% B. 67.74% C. 66.74% D. 68.74%
2. The crank of a double acting steam engine rotates at 220 rpm. The bore and stroke of the steam engine is300
mm x 470 mm, and the mean effective pressure acting upon the piston is 4.5 kg/cm 2. Find the
indicatedhorsepower developed in the cylinder.
A. 144.14 KW B. 144.14 hp C. 150.14 hp D. 153.51 KW
3. Steam enters a steam engine at 2 Mpa and 230 C and exit at 0.1 Mpa. Steam consumption is 1500 kg/hr.
o

Determine the equivalent Rankine efficiency.

A. 31.22% B. 21.22% C. 33% D. 22.12%
4. The indicated efficiency of a steam engine is 65%. The engine entrance is 2600 KJ/kg and exit is 2100 KJ/kg. if
steam consumption is 3000 kg/hr and mechanical efficiency is 90%, what is the brake power of theengine?
A. 55 KW B. 84 KW C. 243.75 KW D. 70 KW
5. A steam engine 18” x 24” runs at 250 rpm. The diameter of piston rod is 3.5 in. The indicator card is 3.5 in
long and the area of the head end is 1.96 sq. in. Area of the crank end card is 1.86 sq. in. Spring scale is 800 lb.
In the test, a prony brake with 10 ft lever arm registered an average load on the scale of 100 psi/in. What is the
mechanical efficiency of the engine?
A. 86.50% B. 88.00% C. 92.20% D. 84.10%
6. A steam engine has 10% brake thermal efficiency and consumes 750 kg/hr steam. The enthalpy of steam at the
entrance and exit of the engine are 2800 and 450 KJ/kg respectively. Determine the brake power of the engine
in KW.
A. 87 B. 76 C. 49 D. 35
7. Available enthalpy of turbine is ∆h = 1200 KJ/kg, turbine efficiency is 75%, full load capacity is 4,300 kw. Find
the full load steam consumption in kg/kw-hr.
A. 2.34 B. 4.51 C. 4.0 D. 7.45
8. A steam condenser receives 12 kg/s of steam with an enthalpy of 2670 KJ/kg. Steam condenses into a liquid and
leaves with an enthalpy of 260 KJ/kg. Cooling water passes through the condenser with temperature increases
from 13 degrees C to 28oC. Calculate the water flow rate in kg/s.
A. 533 B. 518 C. 460.50 D. 528
9. Steam expands adiabatically in a turbine from 2500 kpa, 400 oC to 350 kpa, 240oC. What is the effectiveness of
the process in percent assuming an atmospheric pressure of 15 oC. Neglect changes in kinetic and potential
energy. Steam Properties are: At 2500 Kpa and 400oC:
h = 3239.3 s = 7.0148 At 350 Kpa and 240oC: h = 2945.8 s = 7.4174
A. 61 B. 72 C. 80 D. 86
10. A heat exchanger was installed purposely to cool 0.80 kg of gas per second. Molecular weight is 28 and k =
1.32. The gas is cooled from 150 oC to 70oC. Water is available at the rate of 0.50 kg/s and at a temperature
of 14 C. Calculate the exit temperature of the water in C.
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A. 48 B. 42 C. 46 D. 51.44
 11. A steam turbine with 90% stage efficiency receives steam at 5 Mpa and 550 C and exhausts as 50 Kpa.
Determine the turbine work. At 5 Mpa and 550C: h1 = 3550.3 s1 = 7.1218
At 50 Kpa: hf = 340.49 hfg = 2305.4 sf = 1.091 sfg = 6.5029
A. 117 KJ/kg B. 132 KJ/kg C. 964.60 KJ/kg D. 143 KJ/kg
12. A steam turbine with 92% stage efficiency receives steam at 7 Mpa and 550 oC and exhausts as 20 Kpa.
Determine the actual exhaust enthalpy.
A. 2413.89 KJ/kg B. 2389.07 KJ/kg C. 2341.9 KJ/kg D.2541.9 KJ/kg
13. A steam turbine of 6 MW capacity has a Willan’s line equation of m s = 5.5L + 3,200 kg/hr. Determine the steam
consumption at 73% load, kg/hr.
A. 27,290 B. 26,100 C. 30,000 D. 28,920
14. A 18,000 KW geothermal plant has a generator efficiency and turbine efficiency of 90% and 80respectively. If
the quality after throttling is 16% and each well discharges 220,000 kg/hr, determine the numbers of wells are
required to produce if the change of enthalpy at entrance and exit of turbine is 500 KJ/kg.
A. 4 wells B. 5 wells C. 6 wells D. 8 wells
15. In a 10 MW geothermal power plant, the mass flow of steam entering the turbine is 20 kg/sec. The quality after
throttling is 25% and enthalpy of ground water is 750 KJ/kg. Determine the overall efficiency of theplant.
A. 7.4% B. 9.6% C. 16.67% D. 15.4%
16. A liquid dominated geothermal plant with a single flash separator receives water at 204 C. The separator
pressure is 1.04 Mpa. A direct contact condenser operates at 0.034 Mpa. The turbine has a polytropic efficiency
of 0.85. For a cycle output of 40 MW, what is the mass flow rate of the well-water in kg/s?
At 204C: hf = 870.51 KJ/kg
At 1.04 Mpa: hf = 770.38 hfg = 2009.2 hg = 2779.6 sg = 6.5729
At 0.034 Mpa: hf = 301.40 hfg = 2328.8 sf = 0.9793 sfg = 6.7463
A. 2871 B. 2100 C. 1725.31 D. 2444
17. Ground water in a Geothermal Plant has a ground water flow of 46 kg/s. If the quality of hot water entering the
flash tank is 12%, find the mass of steam entering the turbine.
A. 5.52 kg/s B. 2.54 kg/s C. 3.40 kg/s D. 4.80 kg/s
18. In a 13 MW geothermal power plant, the mass flow of steam entering the turbine is 27 kg/s. The quality after
throttling is 23% and enthalpy of ground water is 730 KJ/kg. Determine the overall efficiency of the plant.
A. 15.72% B. 15.49% C. 15.17% D. 15.38%
19. Steam in a Rankine cycle is expanded from a 200 psia saturated vapor state to 20 psia. The turbine has an
efficiency of 0.8. What is the actual enthalpy after expansion.
At 200 psia (saturated vapor): h = 1199.3 Btu/lb, s = 1.5466 Btu/lb-R
At 20 psia: sf = 0.3359 Btu/lb-R, sfg = 1.3963 Btu/lb-R, hf = 196.2 Btu/lb, hfg = 960.2 Btu/lb
A. 960.2 Btu/lb B. 986.1 Btu/lb C. 1028.7 Btu/lb D. 1062.8 Btu/lb
20. A 150 MW turbo-generator requires 700,000 kg of steam per hour at rated load and 22,000 kg per hour at
zero load. Calculate the steam rate in kg/KW-hour at 75% of its rated load.
A. 5.83 B. 4.72 C. 3.54 D. 6.32
21. A 10 MW steam turbine-generator power plant has a full load steam rate of 5.5 kg/KW-hr. No load steam
consumption is around 10% of the full load steam consumption. Calculate the hourly steam consumption at half
load in kg/hr.
A. 30250 B. 29830 C. 32510 D. 31820

22. A 5-MW steam turbine generator power plant has a full-load steam rate of 6.0 kg/KW-hr. Assuming no-load
consumption at 10% of the full-load. Compute the hourly steam consumption at 60% load in kg/hr.
A. 14500 B. 19200 C. 26500 D. 35600
PPE - PROBLEM SET # 8

INSTRUCTION: Encircle the letter that corresponds to the correct answer of your choice.
MULTIPLE CHOICE:
1. During the dynamometer test of an engine for 1 hr steady load, the engine consumes 40 kg fuel having 43,300
KJ/kg heating value. If the torque developed is 2.5 KN-m during the test at 600 rpm, what is the efficiency of the
engine?
A. 31.22% B. 32.65% C. 55.77% D. 25.99%
2. A 4-stroke Gasoline engine has a bore and stroke of 400 mm x 450 mm running at 750 rpm. If the clearance
volume is 0.0527 m3/s, calculate the engine efficiency.
A. 55.82% B. 65.82% C. 35.82% D. 45.82%
3. A 3 MW diesel engine consumes 240 li of 25 oAPI fuel and generates 900 KW-hr. Determine the rate of fuel
consumed by the engine.
A. 0.2 kg/s B. 0.4 kg/s C. 0.6 kg/s D. 0.8 kg/s
4. A 20 cm x 35 cm diesel engine with 4 cylinders and operating on a four stroke, has a rated power of 160 kw
and is running at 250 rpm. Find the volume displacement per brake power developed.
A. 0.9 m3/min-kw B. 0.1 m3/min-kw C. 0.06 m3/min-kw D. 0.0344 m3/min-kw
5. An engine has a power output of 8.5 hp with 70% efficiency. What will be the kw/hp? Registered to the meter?
A. 1 B. 2 C. 41.33% D. 4
6. A 2500 KW diesel engine unit uses 1 bbl oil per 550 KWH produced. Oil is 25API. Efficiency of generator 90%,
mechanical efficiency of engine 83%. What is the thermal efficiency of engine based on indicated power(%)?
A. 31.69 B. 41.33 C. 39.60 D. 35.60
7. A single-acting, four-cylinder, 4 stroke cycle diesel engine with a bore x stroke of 22 x 28 cm, operating at 375
rpm, consumes 9 kg/h of fuel whose heating value is 43,900 KJ/kg. The indicated mean effective pressure is 500
Kpa. The load on the brake arm, which is 100 cm is 115 kg. What is the brake mean effective pressure in Kpa?
A. 415.20 B. 332.98 C. 319.95 D. 645.33
8. In a double acting, 2 stroke compression ignition engine, 12-cylinder, the diameter of the cylinder is 750 mm,
stroke is 1450 mm and the piston rod diameter is 240 mm. When running at 120 rpm, the indicated mean
effective pressure above and below the pistons are 6 bar and 5 bar respectively. Calculate the brake power of
the engine with a mechanical efficiency of 80% in kilowatts.
A. 6050 B. 6030 C. 12,900 D. 8375
9. Determine the output power (KW) of a diesel power plant if the engine and generator efficiency is 80% and
96%, respectively. The engine uses 250API fuel and has a fuel consumption of 0.08 kg/s.
A. 2741.45 B. 2815 C. 1096.6 D. 9758.6
10. A four-cylinder four-stroke Diesel engine with 20 cm bore and 25 cm stroke running at 1000 rpm has a
reading of 350 kpa mean effective pressure in the indicator diagram. Calculate the indicated power generated
in KW.
A. 183.26 B. 114.54 C. 229.1 D. 91.63
11. A prony brake for measuring the power generated of a six-cylinder, two-stroke Diesel engine running 2000
rpm indicates a reading of 180 N. The length of the arm of the prony brake is a 1.25 m. In an hour operation it
consumes 14 kg of fuel with a heating value of 53,000 KJ/kg. Determine the brake thermal efficiency.
A. 0.2391 B. 0.2857 C. 0.2583 D. 0.2286
12. The following data are the results on a test of an Otto cycle engine torque = 1200 N-m; indicated mean effective
pressure = 800 kPa, fuel consumption = 0.004 kg/sec; fuel heating value = 43,816 KJ/kg;
bore x stroke = 30 cm x 32cm; speed = 300 rpm. Calculate the brake mean effective pressure.
A. 253 B. 333 C. 393 D. 287
13. A Diesel engine consumed 400 liters of fuel having a density of 860 gms/liter and a heating value of 42500
KJ/kg. If the thermal efficiency is 35%, how many hp-hrs will be generated?
A. 1678 B. 2152 C. 1812 D. 1905
14. Determine the brake power of an engine having a brake thermal efficiency of 35% and uses 25 oAPI fuel with
fuel consumption of 40 kg/hr.
A. 165.84 KW B. 173.52 KW C. 133.54 KW D. 60.67 KW
15. A diesel engine develops a torque of 5 KN-m at 1800 rpm. If the brake thermal efficiency is 31%, find theheat
generated by fuel.
A. 3050 KW B. 3040.25 KW C. 3000.25 KW D. 5000 KW
16. A 500 KW diesel engine operates at 101.3 Kpa and 27 oC in Manila. If the engine will operates in Baguio having
93 Kpa and 23oC, what new brake power developed if mechanical efficiency is 85%?
 A. 600 kw B. 754 KW C. 459 KW D. 971 KW
17. A 50 Bhp blast furnace engine uses fuel with 10 ft 3/Bhp-hr. The heating value of the gas is 33,700 KJ/m 3.
Determine the brake thermal efficiency.
A. 28.15 % B. 56% C. 28.34% D. 25.24%
18. During the dynamometer test of an engine for 1 hr steady load, the engine consumes 40kg fuel having 44,000
KJ/kg heating value. If the torque developed is 2.5 KN-m during the test at 600 rpm, what is the brake thermal
efficiency?
A. 30.11% B. 32.13% C. 34.556% D. 23.45%
19. Find the power which a 2.81MW natural gas engine can developed at an altitude of 1981.2 m taking into
consideration the pressure change alone.A. 1.975 MW B. 2.199 MW C. 1.769MW D. 1.997MW
20. A waste heat recovery boiler produces 4.8 Mpa( dry saturated ) steam from 104 C feedwater. The boiler receives
0

energy from 6 kg/s of 954 0C dry air. After passing through a waste heat boiler, the temperature of air is has been
reduced to 3430C. How much steam in kg/s produced? Note: At 4.80 Mpa dry saturated, h= 2796.
A. 1.89 B. 1.3 C. 1.55 D. 2.55
21. A water brake coupled to an engine on test absorbs 90 kw of power. Find the mass flow of fresh water through
the brake, in kg/min if the temperature increases of the water is 12 oC. Assume all the heat generated is carried
away by the cooling water.
A. 107.50 kg/min B. 110 kg/min C. 100 kg/min D. 128 kg/min
22. A 350 hp diesel engine has a cooling water that enters at 100 F and leaves at 180 oF with cp = 4.19 KJ/kg-K. Find
o

the gallons per minute of water required.

A. 10.23 B. 19.61 C. 14.56 D. 16.5
23. A 310 mm x 460 mm four stroke single acting diesel engine is rated at 170 KW at 280 rpm. Fuel consumption
at rated load is 0.28 kg/KW-hr with a heating value of 43,912 KJ/kg. Calculate brake thermal efficiency.
A. 31.53% B. 27.45% C. 29.28% D. 54.23%
24. A six cylinder, four stroke diesel engine with 76 mm bore x 89 mm stroke was run in the laboratory at 1800
rpm, when it was found that the engine torque was 163.5 N-m with all cylinders firing but 133 N-m when one
cylinder was out. The engine consumed 12.5 kg of fuel per hour with a heating value of 52,120 KJ/kg and 252
kg of air at 15.6oC per hour. Determine the indicated power.
A. 32.1 kw B. 38.4 kw C. 34.5 kw D. 48.3 kw
25. A car engine produces an average of 25 KW of power in a period of 10-min during which 1.25 kg of gasoline is
consumed. If the heating value of gasoline is 43000 KJ/kg, the efficiency of this engine during this period is:
A. 24% B. 28% C. 32% D. 36%
26. A 4 liter ( 2-liter per revolution at standard pressure and temperature) spark ignition engine has a compression
ratio of 8 and 2000 KJ/kg heat addition by the fluid combustion. Considering a cold air-standard Otto cycle
model, how much power will the engine produce when operating at 2500 rpm?
A. 50.2hp B. 73.1 hp C. 97.4 hp D. 151.39 hp
27. A pure Diesel cycle operates with a compression ratio of 15, and a cut-off ratio of 2.5. what is the rate of heat
input in KJ/sec required for this cycle to produce 300 hp?
A. 227 B. 386 C. 438 D. 556
28. A 15.24 cm x 22.86 cm single acting, 8 cylinder, 4 stroke diesel engine operates at 1200 rpm. The load on the
brake arm is 101.6 cm length is 120 kg. What is the brake mean effective pressure in kPa?
A. 451kPa B. 500 C. 625 D. 354
29. A gasoline engine generates 250 kw while consuming 0.018 kg/sec of fuel. The friction power is 25 kw. The
higher heating value of fuel is 44,000 kJ/kg. Calculate the indicated thermal efficiency.
A. 0.372 B. 0.333 C. 0.347 D. 0.316
30. Calculate the volumetric efficiency of a tour stroke six-cylinder car engine of 8.5 cm bore and 9.5 cm stroke
running at 2000 rpm with 2.0 m3/min of entering air.
A. 0.71 B. 0.75 C. 0.55 D. 0.62

PPE - PROBLEM SET # 9

INSTRUCTION: Encircle the letter that corresponds to the correct answer of your choice.
MULTIPLE CHOICE:
1. In a hydroelectric power plant the tailwater level fixes at 480m. The net head is 27 m and head loss is 5% of the
gross head. What is the head water elevation?
A. 508.97 m B. 456.7 m C. 508.421 D. 903.9 m
2. For a proposed hydroelectric plant, the tailwater and the head water elevation is 160m and 195 m, respectively.
If the available flow is 10m3/s and head loss of 4% of available head. What is the water power?
A. 3261.825 KW B. 3678.2 KW C. 3296.16 KW D. 2425.78 KW
3. In a hydroelectric plant the brake power is 1,850 KW running at 450rpm and net head of 30m. Determine the
specific speed of the turbine.
A. 90.17 rpm B. 65.65 rpm C. 72.41 rpm D. 76.87 rpm
4. In a Francis turbine, the pressure gage leading to the turbine casing reads 400 kPa and center of spiral casing is
3m above the tail race. If the velocity of water entering the turbine is 8m/s, what is the net head of the turbine?
A. 45 m B. 65 m C. 54 m D. 47 m
5. From a height of 65m, water flows at the rate of 0.85 m 3/s and driving a water turbine connected to an electric
generator revolving at 170 rpm. Calculate the power developed by the turbine in KW if the total resisting torque
due to friction is 540 N-m and the velocity of the water leaving the turbine blades is 4.75 m/s.
A. 623.34 B. 656.89 C. 522.8 D. 541.98
6. A pelton type turbine was installed 31m below the head gate of the penstock. The head loss due to friction is 15%
of the given elevation. The length of the penstock is 80 m and the coefficient of friction is 0.00093 (Morse).
Determine the diameter in meters of the penstock and the power output in KW.
A. 0.422, 820.50 B. 2.457; 12,345.7 C. 1.899; 2,348.20 D. 1.686; 13,128.05
7. At a proposed hydroelectric plant site, the average elevation of headwater is 600 m, the tailwater elevation is
480m. The average annual water flow is determined to be equal to that volume flowing through a rectangular
channel 4m wide and 0.5 m deep and average velocity of 5.5m/s. Assuming the plant will operate 350 days/year,
find the energy Kwh that the plant site can developed if the hydraulic turbine that will be used has an efficiency
of 78% and generator efficiency of 90%. Consider a headwork loss of 4% of the available head.
A. 76,876,852 B. 76,900,353 C. 78,987,567 D. 73,304,488
8. A running at 400 rpm has a specific speed of 60 rpm and head available is 41 m. If the rating of each turbine
installed is 100 kw, how many turbines must be used?
A. 2 B. 4 C. 5 D. 7
9. The available flow of water is 25 m /s at 39 m elevation. If a hydroelectric plant is to be installed with turbine
3

efficiency of 0.86 and generator efficiency of 92%, what maximum power that the plant could generate?
A. 7567.63 kw B. 8520.3 kw C. 6520.30 kw D. 6545.90 kw
10. The difference between the head race and the tail race of a hydro-electric plant is 190 m. The friction loss
through the penstock is equivalent to 8 m. Water flow at the rate of 2.5 m 3/sec. Power loss due to friction in the
turbine is 65 kw and the leakage loss is 0.02 m 3/sec. Determine the electrical power generated in kw if the
generator efficiency is 96%.
A. 5052 B. 4188 C. 4631 D. 3942
11. A 40-m wide and 5-m deep river lows at the rate of 1.5 m/sec. A hydroplant installed nearby develops a gage
pressure of 320 kPa at the turbine entrance. Calculate the maximum power available in MW.
A. 98 B. 84 C. 96 D. 90
12. The specific speed of turbine is 75 rpm and running at 450 rpm. If the head is 28 m and generator efficiency
is 96%, what is the maximum power delivered by the generator.
A. 1610 kw B. 650.5 kw C. 750 kw D. 853 kw
13. For a generator running at 5 rps and 60 hz, find the number of generator poles.
A. 18 poles B. 8 poles C. 24 poles D. 20 poles
14. In Francis turbine, the pressure gage leading to the turbine casing reads 385 kpa and center of spiral casing is
3.5 m above the tailrace. If the velocity of water entering the turbine is 9 m/s, what is the net head of the
turbine?
A. 45 m B. 46 m C. 47 m D. 48 m
15. A Pelton type turbine has 30 m head friction loss of 5.0 m. The coefficient of friction head loss (from Morse) is
0.00093 and penstock length of 85 m. What is the penstock diameter?
A. 1.52m B. 1.69 m C. 1.58 m D. 1.89 m
 16. From a height of 70 m water flows at the rate of 0.85 m 3/s and is driving a turbine connected to 160 rpm
generator. If frictional torque is 545 N-m, calculate the turbine brake power.
A. 532.95 kw B. 574.563 kw C. 560.74 kw D. 579.48 kw
17. 17. A boiler uses 2400 kg of coal per hour and air required for combustion is 15 kg per kg coal. If ash loss is
10%, determine the mass of gas entering the chimney.
A. 42,250 kg/hr B. 38,160 kg/hr C. 40,250 kg/hr D. 37,200 kg/hr
18. 18. The gas density of chimney is o.75 kg/m and air density of 1.167 kg/m3
3
. If the driving pressure is 0.26
kpa, determine the height of the chimney.
A. 65.71 m B. 63.56 m C. 64.63 m D. 87.2 m
19. The actual velocity of gas entering in a chimney is 5 m/s . The gas temperature is 25 oC and pressure of 97 kpa
with a gas constant of 0.287 kJ/kg-k. Determine the chimney diameter if mass of gas is 53,000 kg/hr.
A. 1.82 m B. 1.37 m C. 1.58 m D. 1.92 m
20. A coal fired steam boiler uses 3,000 kg of coal per hour. Air required for combustion is 15.5 kg/kg of coal at
barometric pressure of 98.2 kpa. The flue gas has temperature of 285 oC and an average molecular weight of 30.
Assuming an ash loss of 11% and allowable gas velocity of 8.5 m/s, find the diameter of chimney.
A. 1.794 m B. 1.91 m C. 2.3 m D. 1.81 m
21. A steam generator with economizer and air heater has an overall draft loss of 22.17 cm of water. If the stack
gases are at 177oC and if the atmosphere is at 101.3 kpa and 26 oC, what theoretical height of stack in meters is
needed when no draft fan are used? Assume that the gas constant for the flue gases is the same as that for air.
A. 560 m B. 550 m C. 589 m D. 540 m
22. 22. A power plant situated at an altitude having an ambient air of 96 kpa and 24 oC . Flue gases at a rate of 5.0
kg/sec enter the stack at 200 oC and leaves at 160 oC . The flue gases gravimetric analysis are 18% CO 2, 7% O2
and 75% N2 . Calculate the height of stack necessary for a driving pressure of 0.20 kpa.
A. 57.33 m B. 52.42 m C. 59.2 m D. 50.2 m
23. A boiler uses 2500 kg of coal per hour. The amount of air needed for the combustion of one kg of coal is 16 kg.
If ash loss is 10%, calculate the mass of gas entering the chimney.
A. 42250 B. 50300 C.35600D. 48950
24. A hydro-electric power plant consumes 52,650,000 KW-hrs per annum. Expected flow is 1665 m 3/min and
overall efficiency is 65%. What is the net head in meters?
A. 52 B. 35 C. 74 D. 34
25. A hydroelectric power has the following data: catchment area -- 120 sq km, average annual rain fall -- 135 cm,
run off – 85% , available head – 350 m, overall station efficiency – 85%. Calculate the power that it can develop
in kw.
A. 12,743 B. 10,641 C. 11,435 D. 13,502

MULTIPLE CHOICE:
1. What is the required base area (ft2) of the foundation to support an engine with specific speed of 1200 rpm, and
weight of 11000 kg, assume bearing capacity of soil as 48 kpa. Use e = 0.12.
A. 11.6 B. 131.2 C. 124.803 D. 126.8
2. Determine the required speed of an engine having a weight and foundation area to be 23,750 lbs and 150 ft 2,
respectively. Assume a soil bearing capacity as 0.45 kg/cm2. Use e = 0.11.
A. 1500 rpm B. 1520 rpm C. 1820 rpm D. 1920 rpm
3. The heat transfer across a 5” wall of firebrick is 500 W/m . If the surface temperature on cold side is 30 oC and
2

thermal conductivity of brick is 0.7 Btu/hr-ft-oF, find the temperature on hot side.
A. 82.41oC B. 65.37oC C. 73.45oC D. 87.25oC
4. Two walls of a storage plant composed of insulating material (k = 0.25 KJ/hr-m- oC) with 15 cm thick
andconcrete (k = 3.2382 KJ/hr-m-oC) with 10 cm thick. The surface temperature on hot side is 35 oC and cold
side is -10oC. If the area is 8 m square, find the temperature between walls. Note: Insulating material is on cold
side.
A. 28.34oC B. 34.12oC C. 32.79oC D. -7.78oC
5. Determine the thermal conductivity of a material that is used a 4 m 2 test panel, 25 mm thick with a temperature
difference of 20oF between surfaces. During the 4 hrs of test period, the heat transmitted is KJ.
A. 0.0432 W/m-oC B. 0.0723 W/m-oC C. 0.0321 W/m-oC D. 0.0195 W/m-oC
6. Steam initially is saturated at 250oC passed through a 12 cm steel pipe for a total distance of 200 m. The steam
line is insulated with material having k = 10 W/m 2-K and thickness of 6 cm. The ambient temperature of 25 oC.
Determine the surface film conductance of air if the moisture at the discharge end is 10% and steam rate is 0.13
kg/s.
A. 0.124 W/m2-oC B. 0.872 W/m2-oC C. 0.661 W/m2-oC D. 0.452 W/m2-oC
7. At an average temperature of 110 oC, hot air flows through a 5 m pipe with outside diameter of 80 mm and pipe
thickness is 1 cm. The temperature of the tube along its entire length is 24 oC. If heat transfer is 650 W, find the
convective film coefficient, W/m2-oC .
A. 1 B. 2 C. 3 D. 4
8. A tank contains liquid nitrogen at -190 C is suspended in a vacuum shell by three stainless steel rods 0.80 cm in
o

diameter and 3 meters long with a thermal conductivity of 16.3 W/m- oC. If the ambient air outside the vacuum
shell is 25oC, calculate the magnitude of the conductive heat flow in watts along the support rods.
A. 0.143 B. 0.0587 C. 0.182 D. 0.176
9. The volume of concrete needed for the foundation of an engine is 12 cubic meters. The concrete mixture is 1:3:5
by volume. Calculate the number of 40 kg-bags of cement needed considering the density of cement as 1500
kg/m3.
A. 60 B. 55 C. 45 D. 50
10. A composite furnace is to be constructed. The inside wall temperature is 1300 oC while the outside wall
temperature is 40oC. Three types of bricks are available with the following properties:
Brick Thermal Thickness Maximum allowable
Conductivity temperature
(W/m K)(meters)
o
(oC)
A 1.5 0.12 2000
B 0.2 0.070 1000
C 0.7 0.10 500
The heat loss must not exceed 800W/m . Calculate the minimum wall thickness in meters.
2

A. 0.76 B. 0.88 C. 0.82 D. 0.77

11. The surface of a furnace wall is at a temperature of 1350 C. The outside wall temperature is 42 oC. The furnace
o

wall is made of 25 cm of refractory material having a thermal conductivity of 1.4 W/m oK. The outside wall is
steel, 1 cm thick with thermal conductivity of 47 W/m oK. Calculate the thickness in meters of brick to be
installed in between the refractory material and steel if its thermal conductivity is 0.28 W/m oK and the heat loss
is not to exceed 750 W/m2.
A. 0.438 B. 0.402 C. 0.481 D. 0.513
12. A counterflow heat exchanger is designed to cool 0.65 kg/sec of oil with specific heat C p = 3.4 KJ/kgoK from
150oC to 70oC. Water for cooling, Cp = 4.18 KJ/kgoK is available at 20oC and flow rate of 0.6 kg/sec. Calculate the
length of a 3.5 cm inside diameter tubing in meters. The overall coefficient of heat transfer is 90 W/m 2 oK.
A. 337 B. 452 C. 296 D. 543
13. A cold soda initially at 2 C gains 18 KJ of heat in a room at 20 oC during a 15-minute period. What is the average
o

rate of heat transfer during the process?

A. 20 W B. 18 WC. 12 W D. 10 W
14. The air contained in a room loses heat to the surroundings at a rate of 50 KJ/min while work is supplied to the
room by computer. TV, and lights at a rate of 1.2 KW. What is the net amount of energy change in KJ of air in
the room during a 30-minute period?
A. 0.36 B. 70 C. 660 D. 1100
15. Saturated steam at 500 oK flows in a 0.20 m inside diameter, 0.21 m outside diameter pipe. The pipe is covered
with 0.08 m of insulation with a thermal conductivity of 0.10 W/m-K. The pipe’s conductivity is 52 W/m-K.
The ambient temperature is 300 oK. The unit convective coefficients are h 1 = 18,000 W/m2-K and ho = 12
W/m2-K. Determine the heat loss from 4 m of pipe.
A. 778.21 watts B. 825.80 watts C. 830.80 watts D. 835.80 watts
16. An insulated steam pipe located where the ambient temperature is 32C, has an inside diameter of 50 mm with
10 mm thick wall. The outside diameter of the corrugated asbestos insulation is 125 mm and the surface
coefficient of still air, ho = 12 W/m2-K. Inside the pipe is steam having a temperature of 150C with film
 coefficient hi= 6000 W/m2-K. Thermal conductivity of pipe and asbestos insulation are 45 and 0.12 W/m-K
respectively. Determine the heat loss per unit length of pipe.
A. 110 W B. 120 W C. 130 W D. 140 W
17. Sea water for cooling enters a condenser at 25 C and leaves at 40oC. The condenser temperature is 45oC, what is
o

the log mean temperature difference?

A. 16.34oC B. 10.82 oC C. 23.34oC D. 12.34oC

18. The hot combustible gasses of a furnace are separated from the ambient air and its surrounding, which are 28 oC,
by a brick wall 120 mm thick. The brick has a thermal conductivity of 1.23 W/m- oK and a surface emissivity of
0.82. At steady state conditions the outer surface temperature is 120 oC. Air surface film conductance is 15
W/m2-oK. What is the total heat transmitted for 20 square meter area.
A. 42.15 KW B. 23.45 KW C. 45.45 KW D. 52.45 KW
19. A counterflow heat exchanger is designed to heat fuel oil from 26 oC to 100oC while the heating fluid enters at
138oC and leaves at 105oC. The fuel oil is 27oAPI and has a specific heat of 2.3 KJ/kg- oK and enters the heat
exchanger at the rate of 1000 gallons per hour. Determine the heating surface area if overall coefficient of heat
transfer is 420 Kcal/hr-m2-oK.
A. 4.21 m2 B. 3.12 m2 C. 2.34 m2 D. 5.84 m2
20. A plate-type solar energy collector with an absorbing surface covered by a glass plate is to receive an incident
radiation of 800 W/m2. The glass plate has a reflectivity of 0.12 and a transmissivity of 0.80. The absorbing
surface has an absorptivity of 0.90. The area of the collector is 5 m 2. How much solar energy in watts is
absorbed by the collector?
A. 2500 B. 2880 C. 3510 D. 3168
21. What is the log mean temperature difference in oC of a double-pipe counterflow heat exchanger where a fluid
enters at 90oC and exits at 50oC. Inside the inner pipe another fluid enters at 20oC and exits at 60oC.
A. 0 B. 30 C. 75 D. 35
22. Heat is transferred from hot water to an oil in a double-pipe counterflow heat exchanger. Water enters the
outer pipe at 95oC and exits at 40oC while the oil enters the inner pipe at 25 oC and exits at 50oC. Calculate the
log mean temperature difference.
A. 38.05 B. 30.83 C. 27.31 D. 52.5
23. The filament of a 100-watt bulb maybe considered a black body radiating into a black enclosure at 80 oC.
Considering only radiation, calculate the filament temperature in oC if the filament diameter is 0.10 mm and the
length is 6 cm.
A. 2514 B. 2837 C. 3122 D. 2674

1. A pump delivers 1000 gallons per minute of water at a head of 100 ft. Find the water power needed.
A. 12.34hp B. 34.12 hp C. 23.23 hp D. 25.28 hp
2. Find the power of motor needed to pumped the water at a head of 100 m at the rate of 400 lps if pump
efficiency is 70%.
A. 301.34 kw B. 627.56 kw C. 560.57 kw D. 426.24 kw
3. A pump has a suction condition of 50 mm Hg vacuum pressure, 100 mm diameter pipe and discharge condition
of 250 kpa at, 90 mm diameter. The discharge tank is 50 m elevation and the suction is 5 m below the pump
center line. If discharge is 0.20 m3/s, find the pump efficiency for 260 kw brake power.
A. 74.32% B. 77.12% C. 79.23% D. 82.45%
4. The suction diameter of 60 mm reads 2 psi vaccum and 50 mm diameter discharge with 250 kpag. The suction
water level is 5 m above water pump centerline and discharge water level is 25 m above pump center line. The
total head loss at suction and discharge is 2 m. If discharge is 0.01 m 3/s, find the horsepower needed to pump
the water for 80% pump efficiency.
A. 6.23hp B. 8.15 hp C. 16.23 hp D. 12.45 hp
5. The suction water level of a reservoir A is 5 m above pump centerline a and discharge water level is 50 m above
pump centerline. The discharge is 0.2 m3/s with suction pipe of 100 mm diameter and 90 mm diameter
discharge pipe. The total head loss is 50% of the velocity head at suction pipe. If pump runs at 360 rpm, find the
torque developed by the shaft of motor if pump efficiency is 76%.
 A. 3.7 KN-m B. 8.9 KN-m C. 5.4 KN-m D. 6.7 KN-m
6. A water jet has a diameter of 75 mm and has a velocity of 15 m/s. What is the horsepower exerted by the jet.
A. 12 hp B. 10 hp C. 9 hp D. 8 hp
7. A pump has a head of 20m at 450 rpm. What is the increase in head developed by the pump is speed increased
to 1000 rpm?
A. 43.23 m B. 83.56 m C. 65.23 m D. 78.76 m
8. The power developed by the pump is 30 kw. What is the percent decrease in power if speed will decrease by
40%.
A. 78.4% B. 90.1% C. 65.3% D. 82.4%
9. A reciprocating pump has 350 mm x 400 mm cylinder running at 360 rpm. If percent slip is 10%, find the
volumetric efficiency of the pump.
A. 70% B. 80% C. 90% D. 98%
10. A pump develops a power of 50 kw at 300 rpm with fluid specific gravity of 1.02 when impeller diameter is
150 mm. If increases to 650 rpm, impeller diameter of 120 mm and specific gravity of 0.8. Find the new
power.
A. 190.34 kw B. 204.19 kw C. 207.23 kw D. 302.23 kw
11. A pump has a specific speed of 42 and 600 rpm when it delivers 0.01 m 3/s. Find the head developed by the
pump.
A. 582.45ft B. 813.45 ft C. 658.69 ft D. 1015.29 ft
12. A boiler feed pump has a suction enthalpy of 2500 KJ/kg and exit of 2505 KJ/kg. Find the velocity of water in
the flowing in the pump.
A. 300 m/s B. 50 m/s C. 200 m/s D. 100 m/s
13. A swimming pool measuring 10 m by 25 m x 2 m is to be filled with water from an artesian well by a motor
pump operating with a total dynamic head of 50 m. Assuming an overall motor efficiency of 55%, energy cost
of P0.45/kw-hr, find the total cost of energy to fill up the swimming pool.
A. P23.23 B. P82.34 C. P55.74 D. P132.34
14. A 20 m tank can be filled with water in one hour by a motor driven pump. Pump efficiency is 90% and motor
3

efficiency is 80% if the total head is 20 m, find the cost of one filling for energy cost of P0.40/kw-hr.
A. P0.606 B. P1.321 C. P0.812 D. P4.234
15. A pump delivers 4 m /min of water from 100 kPa to 300 kPa. The inlet and outlet pipe diameters are 15 cm and
3

12 cm respectively. Both pipes are on the same level. The inlet and outlet temperatures are both 25 oC and mass
density of water is 997 kg/m3. Calculate the pump work in KW.
A. 20 B. 14 C. 16 D. 12
16. A centrifugal pump delivers 1.8 m3/s of water against a head of 30m when rotating at 1200 rpm. The diameter
of its impeller is 45 cm. If a pump with the same specific speed is to discharge 6.0 m 3/sec at 1100 rpm, what is
its impeller diameter?
A. 45 cm B. 60.5 cm C. 69.2 cm D. 74.3 cm
17. A double suction centrifugal pumps delivers 25 ft /sec of water at a head of 12 m and running at 650 rpm.
3

What is the specific speed of the pump?

A. 5014.12 rpm B. 6453.12 rpm C. 3097.77 rpm D. 9968.73 rpm
18. Determine the number of stages needed for a centrifugal pump if it is used to deliver 420 gal/min of water and
pump power of 15 Hp. Each impeller develops a head of 30 ft.
A. 6 B. 4 C. 5 D. 7
19. The suction pressure of a pump reads 3.5 in. of mercury vacuum and discharge pressure reads 140 psi is use to
deliver 120 gpm of water with specific volume of 0.0163 ft3/lb. Determine the pump work.
A. 4.6 KW B. 5.7 KW C. 7.4 KW D. 8.4 KW
20. A submersible pump delivers 370 gpm of water to a height of 7 ft from the ground. The pump were installed
150 ft below the ground level and a draw down of 8 ft during the operation. If water level is 25 ft above the
pump, determine the pump power.
A. 7.13 KW B. 4.86 KW C. 7.24 KW D. 9.77 KW
21. A vacuum pump is used to drain a flooded mine shaft of 20C water. The pump pressure of water at this
temperature is 2.84 Kpa. The pump is incapable of lifting the water higher than 18 m. What is the atmospheric
pressure?
 A. 159.30 B. 132.33 C. 198.22 D. 179.4
22. A submersible, multi-stage, centrifugal deep well pump 260 gpm capacity is installed in a well 32 feet below the
static water level and running at 3000 rpm. Drawdown when pumping at rated capacity is 10 feet. The pump
delivers the water into a 25,000 gallons capacity overhead storage tank. Total discharge head developed by
pump, including friction in piping is 243 feet. Calculate the diameter of the impeller of this pump in inches if
each impeller diameter developed a head of 36 ft.
A. 3.68 B. 5.33 C. 3.71 D. 6.34
23. Pump at its best efficiency point (BEP) has a capacity of 12,500 gpm while developing a head of 60 ft at a
rotative speed of 1450 rpm. What is the specific speed of the pump?
A. 2760 B. 1450 C. 7520 D. 6892
24. A radial-flow pump operating at maximum efficiency at a specific speed of 2300 is to deliver 260 gpm against a
head of 129 ft at a rotative speed of 2100 rpm. Find the required number of stages (i.e., impellers).
A. 2 stages B. 3 stages C. 4 stages D. 5 stages
25. A 30-hp pump delivers 475 gpm of gasoline (γ = 42.5 lb/ft ) at 20oC with 78% efficiency. What pressure rise
3

result across the pump?

A. 30.2 psi B. 84.5 psi C. 120.3 psi D. 73.2 psi
26. The diameter of the discharge pipe is 7 in. and that of the intake pipe is 9 in. The pressure gage at discharge
reads 32 psi, and vacuum gage at the intake reads 12 in Hg. If the discharge flow rate = 4.0 ft 3/s of water and
the brake horsepower is 49.0, find the efficiency. The intake and the discharge are at the same elevation.
A. 82.1% B. 80.9% C. 96.0% D. 58.46%
27. A piston positive-displacement pump (PDP) has 8-in diameter and a 2.5-in. stroke. Its crankshaft rotates at 300
rpm. Calculate its output at 94 percent volumetric efficiency.
A. 12.27 cfm B. 20.51 cfm C. 10 cfm D. 11.53 cfm
28. A centrifugal pump (efficiency 86%) lifts water through a total height of 42m from reservoir to discharge.
Pumping is through 300m of 75mm diameter pipe at the rate of 20 liter/sec. If pipe friction factor, f = 0.025,
what KW is required?
A. 28.4 kW B. 33.4 kW C. 25 kW D. 9 kW
29. The speed of a centrifugal pump is triple. By what factor does the pump head change?
A. 0.125 B. 0.25 C. 4 D. 9
30. A pump delivers 5000 gallons per minute of fluid with specific gravity of 0.9 at a head of 100 ft. Find the
horsepower needed for the motor if overall efficiency is 60% and motor efficiency is 80%.
A. 142.18hp B. 178.45 hp C. 162.34 hp D. 189.54 hp

1. An air compressor takes air at 99 kpa and compress it isentropically at 700 kpa. If volume flow at discharge is 2
m3/sec, determine the capacity of air in cfm.
A. 14,153.34 B. 13,103.45 C. 15,244.24 D. 17,135.77
2. The discharge pressure of an air compressor is 5 times the suction pressure. If volume flow at suction is 0.5
m3/s, what is the compressor power using PV1.38 = C and suction pressure is 100 kpa.
A. 123.34 kw B. 136.23 kw C. 101.25 kw D. 213.23 kw
3. A 12 hp motor is used to drive an air compressor . The compressor efficiency is 70%. Find the mass of air
needed per minute if air is available at 30oC. The pressure compresses to 6 times the initial pressure.
A. 2.12 kg/min B. 1.85 kg/min C. 3.12 kg/min D. 1.43 kg/min
4. The initial condition of air in an air compressor is 98 kpa and 27 oC and discharges at 500 kpa. The bore and
stroke are 360 mm and 380 mm, respectively with percent clearance of 7% running at 300 rpm. Find the mass
flow of air at suction?
A. 0.186 kg/s B. 0.11 kg/s C. 0.33 kg/s D. 0.44 kg/s
5. An air compressor has a suction volume of 0.3 m /s at 28 C at 1 atm and discharges to 650 kpa. How much
3 o

power saved by the compressor if two staging?

A. 9.84 kw B 8.23 kw C. 6.23 kw D. 7.34 kw
6. The suction condition of air compressor is 99 kpa, 27 oC and 0.21 m3/s. If surrounding air is 100 kpa and 22 oC,
determine the free air capacity in m3/s.
A. 0.345 B. 0.423 C. 0.123 D. 0.204
7. The compressor work of an air compressor in 120 kw. If piston displacement is 18 m 3/min, determine the mean
effective pressure.
A. 400kpa B. 300 kpa C. 500 kpa D. 600 kpa
8. A double acting air compressor has a cylinder dimensions of 50 cm x 60 cm, 650 rpm will have a volume
displacement of:
A. 4.12 m3/s B. 3.12 m3/s C. 2.55 m3/s D. 1.34 m3/s
9. A 2-stage air compressor has an intercooler pressure of 4 kg/cm 2. What is the discharge pressure if suction
pressure is 1 kg/cm2.
A. 14 B. 15 C. 16 D. 17
10. The piston speed of an air compressor is 150 m/min and has a volume displacement of 0.2 m 3/s. Determine the
diameter of compressor cylinder.
A. 512.34 mm B. 319.15 mm C. 354.23 mm D. 451.35 mm
11. A two stages compressor takes air at 100 kpa and 25 oC with volume flow of 0.123 m3/s and discharges to 700
kpa. What is the heat rejected by the intercooler?
A. 12.45 kw B. 13.73 C. 45.34 kw D. 32.34 kw
12. An air compressor takes air at 97 kpa at the rate of 0.4 m /sec and discharges to 600 kpa. If power input to the
3

compressor is 110 kw, determine the heat loss in the compressor.

A. 16.34 kw B. 25.80 kw C. 18.34 kw D. 17.23 kw
13. A two stage air compressor has a suction volume of 700 m 3/hr at 100 kpa and 22oC discharges to 690 kpa,
determine the heat rejected in intercooler.
A. 21.53 kw B. 23.45 kw C. 45.23 kw D. 6.34 kw
14. A single-acting compressor with a 15 cm bore and 18 cm stroke operates at 350 rpm. The clearance is 5% and
it receives air at 100 kPa and discharges it at 650 kPa. The compression is polytropic with n= 1.35. Determine
the power required in KW.
A. 4.6 B. 5.2 C. 3.1 D. 3.8
15. A two stage compressor with an ideal intercooler receives 0.2 kg/s of Helium at 150 kPa and 300 0K and
discharges it at 7,500 kPa. Calculate the intercooler pressure in kPa.
A. 2050 B. 3820 C. 1061 D. 1503
16. Calculate the compressor work in kJ required to compress 1 kg of an ideal gas from an initial volume and
pressure of 0.65 m3 and 101.3 kPa to a final pressure of 517 kPa. Compression is with n = 1.35.
A. 133.6 B. 105.8 C. 148.3 D. 142.7
17. A 3-stages air compressor compresses air from 100 kpa to 700 kpa. Find the intercooler pressure between the
2nd and 3rd stage.
A. 365.88kpa B. 375.88 kpa C. 385.88 kpa D. 395.88 kpa
18. Find the air horsepower of an industrial fan that delivers 30 m /s of air through a 700 mm x 1000 mm duct if
3

static pressure is 150 mm of water gage and air density is 1.18 kg/m 3.
A. 89.70hp B. 105.56 hp C. 102.75 hp D. 90.85 hp
19. A boiler requires 100,000 m /hr of standard air. The mechanical efficiency of fan to be installed is 70%.
3

Determine the size of driving motor needed assuming fan can deliver a pressure head of 160 mm of water and
outlet velocity of 20 m/s.
A. 60 kw B. 81.80 kw C. 75.80 kw D. 71.81 kw
20. At 1.180 kg/m air density a fan can developed a brake power of 100 kw. If it will operate at 100 kpa and 35 oC,
3

find the new brake power needed.

A. 95.87 kw B. 96.78 kw C. 100 kw D. 85.37 kw
21. A fan has suction static pressure of 40 mm of water vacuum with air velocity of 5 m/s. The discharge has 160
mm of water gage and discharge velocity of 8 m/s. What is the total head of the fan if air density is 1.2 kg/m 3,
mm of water gauge.
A. 168.66 B. 170.55 C. 218.23 D. 202.38
22. A 50 kw motor is used to drive a fan that has a total head of 120 m. If fan efficiency is 75%, what is the
maximum capacity of the motor needed if air is available at 100 kpa and 26 oC.
A. 27.34 m3/s B. 48.59 m3/s C. 50.60 m3/s D. 49.58 m3/s
23. A fan that operates at 30 oC and 101 kpa has a static pressure of 300 mm water gage. If the fan will operate at
95oC and 14 psi, find the new static pressure required.
 A. 136 mm B. 236 mm C. 250 mm D. 300 mm
24. The total head of fan is 200 m and has a static pressure of 210 mm of water gage. What is the velocity of air
flowing if density is 1.16 m3/s.
A. 20 m/s B. 18.89 m/s C. 16.25 m/s D. 19.29 m/s
25. A fan has a static head of 100 m at 1 kg/cm and 70 F. If air velocity is 15 m/s, find the total equivalent head in
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mm of water gage.
A. 120.44 mm B. 129.53 mm C. 135.53 mm D. 140.56 mm
26. The fan is rated to deliver 600 m 3/min when running at 350 rpm and required 7 kw motor to drive it. If the fan
speed is changed to 600 rpm and the air handled at 55oC instead of 28oC, find the power in kw.
A. 32.36 kw B. 40.25 kw C. 36.50 kw D. 45 kw

27. What is the horsepower required for a fan to deliver 200 ft/sec of air through a 2 ft x 4 ft duct under a total
pressure of 4 in water gage?
A. 175.83hp B. 194.24 hp C. 146.17 hp D. 204.25 hp
28. A certain fan delivers 6 m /sec of air at 25 C and 101.3 kPa is operating at 500 rpm and requires 3 kw of
3 0

power. If the air temperature is increases to 94 0C and the speed of the fan remains the same, calculate the new
power in kw.
A. 2.63 B. 3.00 C. 2.44 D. 3.7
29. 18. What is the static air powering watts of a fan designed to deliver 800 m 3/hr of air with a static pressure of 5
cm of water column on full delivery.
A. 155.3 B. 95.7 C. 105.8 D. 122.6

1. A refrigeration system is used to cooled water in the evaporator a 8 kg/s of water from 30 oC to 2oC. Find the
tons of refrigeration is required.
A. 266.75 TR B. 137.45 TR C. 120.34 TR D. 130.84 TR
2. A reversed Carnot cycle has an evaporator temperature of -5 oC and condenser temperature of 45 oC. Find the
performance factor if it will operate in a heat pump.
A. 4.45 B. 3.45 C. 6.36 D. 5.23
3. A simple saturated refrigeration cycle for R-12 system operates at an evaporating temperature of -5 oC and a
condensing temperature of 40 oC. For refrigerating capacity of 10 kw, determine the work of the compressor. At
40oC, hf = 238.5 KJ/kg; at -5oC, hg = 349.3 KJ/kg. Enthalpy entrance to the condenser is h = 375 KJ/kg.
A. 1.205 kw B. 2.32 kw C. 3.502 kw D. 4.906 kw
4. A refrigeration system using refrigerant 22 is to have a refrigerating capacity of 60 TR. The evaporating
temperature is -10oC and the condensing temperature is 42oC. Determine the heat rejected by the condenser.
Enthalpy of condenser entrance = 440 KJ/kg, exit = 254 KJ/kg. Evaporator exit = 406 KJ/kg, evaporator entrance
= 254 KJ/kg.
A. 512.34 kw B. 417.35 kw C. 315.44 kw D. 258.15 kw
5. A refrigerator has a coefficient of performance of 1.6. How much work in KJ must be supplied to this
refrigerator for it to reject 1000 KJ of heat?
A. 385 B. 627 C. 836 D. 1000
6. A Carnot heat pump uses thermal reservoirs at -27 C and 57oC. How much power does this pump consume to
o

produce a 100 KW heating effect?

A. 9.1 KW B. 12.7 KW C. 15.3 KW D. 20.7 KW
7. A manufacturer claims that its has a COP of 1.4 when cooling food at 7 oC using ambient air at 23 oC as a heat
sink. Is his claim valid?
A. Yes B. No. C. Probably D. None of the above
8. A reversed Carnot cycle is used for cooling. The input work is 12 kw, while the COP is 3.8 . Calculate the
refrigerating effect in tons of refrigeration.
A. 12.97 B. 10.6 C. 15.4 D. 9.65
9. Consider a refrigeration whose 40 watts light bulb remains on continuously as a result of a malfunction of the
switch. If the refrigerator has a COP of 1.5 and the cost of electricity is 10 cents per kw-hr, determine the
increase in the energy consumption of the refrigerator and its cost per year if the switch is not fixed.
A. P58.40 B. P47.59 C. P65.40 D. P83.59
10. A household refrigerator that has a power input of 450 watts and a COP of 2.5 is to cool six large watermelons,
12 kg each, to 8oC. If the watermelons are initially at 20 oC, determine how long will take for the refrigerator to
cool them. The watermelons can be treated as water whose specific heat is 4.2 KJ/kg- oK.
A. 1220 seconds B. 2230 seconds C. 3226 seconds D. 4250 seconds
11. When a man returns to his wall-sealed house on a summer day, he finds that the house is at 32 oC. He returns
on the air conditioner which cools the entire house to 20oC in 20 minutes. If COP is 2.7, determine the power
drawn by the airconditoner. Assume the entire mass within the house is 800 kg of air for which c v = 0.72 KJ/kg-
K, cp = 1.0 KJ/kg-K
A. 1.072 KW B. 2.130 KW C. 3.072 KW D. 4.072 KW
12. A Carnot refrigerator operates in a room in which the temperature is 25 C and consumes 3 KW of power when
o

operating. If the food compartment of the refrigerator is to be maintained at 3 oC, determine the rate of heat
removal from the food compartment.
A. 1504.8 kJ/min B. 12.86 kJ/min C. 1625 kJ/min D. 2258.18 KJ/min
13. A household refrigerator with EER of 10 removes heat from the refrigerated space at a rate of 100 kJ/min.
Determine the rate of heat transfer to the kitchen air.
A. 101.25 kJ/min B. 134.12 kJ/min C. 128.46 kJ/min D. 80 kJ/min
14. A house that was heated by electric resistance heaters consumed 1300 kWh of electric energy in a winter
month. If this house were heated instead by a heat pump that has an average performance factor, PF of 2.5,
determine how much money the homeowner would be saved that month. Assume a price of 0.090$/kWh for
electricity.
A. $42.5 B. $70.20 C. $102 D. $97.75
15. 15. A Freon 22 air conditioning under standard operating conditions of 35 oC condensing and 5oCevaporating
temperatures. The volume flow rate entering the compressor is 25 L/s Determine the refrigerating capacity if
the refrigerating effect is 164 kJ/kg. From the table for R22 the specific volume at the compressor entrance is 42
L/kg.
A. 339.3 TR B. 79.3 TR C. 96.4 TR D. 27.76 TR
16. A refrigeration system consumed 30,800 kw-hr per month of energy. There are 20% of energy is lost due to
cooling system of compressor and motor efficiency is 90%. If COP of the system is 6, find the tons of
refrigeration of the system.
A. 63.15 TR B. 46.15 TR C. 52.56TR D. 41.15 TR
17. A refrigeration system is to be used to cool 45,000 kg of water from 29 oC to 8oC in 8 hours. The refrigerant is
ammonia and the operating conditions are 616 Kpa evaporating pressure and 1737 kpa liquefaction pressure.
Determine the quantity of cooling water in the condenser for an increase in temperature of 10 oC.Enthalpy at
condenser entrance = 1650 and exit = 410.4 KJ/kg. Evaporator entrance = 410.4, exit = 1471.6 KJ/kg.
A. 4.59 kg/s B. 3.83 kg/s C. 5.94 kg/s D. 8.54 kg/s
18. A 60 tons refrigeration system has COP of 4.5. Find the gallons per minute of cooling water required in the
condenser for a temperature rise of 12 oC.
A. 81.35gpm B. 90.34 gpm C. 74.56 gpm D. 64.67 gpm
19. A vapor compression cycle is designed to have a capacity of 90 tons of refrigeration. It produces chilled water
from 25oC to 2oC. Its coefficient of performance is 5 and 30% of the power supplied is lost. Determine the size
of electric motor required to drive the compressor in kw.
A. 60.5 kw B. 92.5 kw C. 100. 5 kw D. 90.41 kw
20. A reversed Carnot cycle that operates between -2 C and 50 C needs 45 Kw compressor power. Find the tons of
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refrigeration system needed.

A. 56.34 B. 73.45 C. 60.34 D. 68.51
21. An ammonia compressor operates at an evaporator pressure of 316 kpa and a condenser pressure of 1514.2
kpa. The refrigerant is subcooled by 5 oC and is superheated by 8 oC. For an evaporator load of 85 kw, determine
the quantity of cooling water in the condenser if the increase in temperature of water is 6 oC. Condenser
entrance = 1715 KJ/kg, exit = 361.2 KJ/kg. Evaporator entrance = 361.2, exit = 1472 KJ/kg.
A. 11,350 kg/hr B. 12,845 kg/hr C. 13,100 kg/hr D. 14,845 kg/hr
22. A refrigeration compressor has a volume flow of 0.15 m /s. The percent clearance is 8% and has a compression
3

ratio of 6. The bore and stroke are equal running at 360 rpm. Find the bore of the compressor.
A. 375.75 mm B. 275.78 mm C. 303.37 mm D. 343.45 mm
23. An ammonia refrigeration system operates at 316 Kpa pressure evaporator and 1514.2 kpa condenser
pressure. Find the fraction of water evaporized. Condenser exit = 362 KJ/kg, Evaporator at 310 Kpahf = 163; hg
= 1127 KJ/kg.
A. 10.23 % B. 13.35 % C. 15.34 % D. 20.64 %
24. Find the performance factor of a heat pump that operates between -4 oC and 30oC.
A. 8.91 B. 9.58 C. 7.30 D. 6.20
25. A heat pump has a compressor power of 10 kw and heat rejected of 50 kw to the low temperature region. Find
the temperature of the low temperature region if high temperature region is 40 oC.
A. -.8.45oC B. 15.04oC C. -22.60oC D. -34.23oC
26. A heat pump operates between 36 oF and 120oF. If heat added from the low temperature region is 500 Btu/min,
find the horsepower needed of the compressor.
A. 2.0 B. 3.0 C. 4.0 D. 5.0
27. A heat pump operates between -4 oC and 28oC.If the compressor power needed is 6 kw, find the KJ/min added
from the low temperature source.
A. 2395 B. 2522 C. 2798 D. 2984
28. A refrigeration system has an evaporator temperature of -4 C and compressor suction temperature is 8 oC. Find
o

the degree superheat, oF.

A. 12 B. 14 C. 16 D. 18
29. A cascade refrigeration system operates between 100 kpa and 800 kpa. Find the cascade condenser pressure.

A. 269.34kpa B. 276.45 kpa C. 282.84 kpa D. 298.45 kpa

30. Find the mass of water that can be cooled from 26 C to -10 C from a 15 tons refrigeration system for 14 hrs.
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A. 5447 kg B. 6383 kg C. 5719 kg D. 4923 kg

31. The refrigerant volume flow rate at the entrance of compressor were obtained from a test on a twin cylinder,
single acting 15 cm x 20 cm, 350 rpm compressor ammonia refrigerating plant to be 35 L/s. Determine the
volumetric efficiency of the compressor.
A. 77.65% B. 84.88% C. 97.6 % D. 65.65%
32. A twin cylinder ammonia compressor with volume displacement of 15,726 cm 3 operates at 320 rpm. Condenser
and evaporator pressure are 1200 kPa and 227 kPa respectively. Specific volume of refrigerant at the entrance
of compressor is 528.26 L/kg. Compression process is polytropic with n = 1.20 and clearance factor of
compressor is 2 percent. Determine horsepower required.
A. 60hp B. 70 hp C. 80 hp D. 92 hp
33. A reversed Carnot cycle has a refrigerating COP of 3.0. Determine the ratio TH/TL?
A. 1.4 B. 1.5 C. 1.33 D. 1.2
34. Saturated vapor ammonia at –16 C ( h7 = 1442.60 kJ/kg) leaves the evaporator and enters the compressor at –
o

6oC (h1 = 1465 kJ/kg). The refrigerant leaves the condenser as saturated liquid at 40 oC (h4 = 390.6 kJ/kg) and
enter the expansion valve at 35 oC ( h5 = 366.1 kJ/kg). Heat rejected from the condenser amount to 60 kW. The
work to compressor is 208 kJ/kg, while the heat loss from compressor is 33 kJ/kg. If 95 kJ/kg of heat are lost in
the piping between the compressor discharge and condenser inlet, determine the refrigerating capacity of the
system.
A. 49.5 TR B. 15.91 TR C. 12.88 TR D. 13.24 TR

1. A refrigeration system is to cool bread loaves with an average mass of 600 g from 22 oC to –12oC at a rate of 500
loaves per hour by refrigerated air. Taking the average specific and latent heats of bread to be 2.93 kJ/kg. oC
and 109.3 kJ/kg, respectively, determine the product load.
A. 1044.6 kJ/min B. 1351.6 kJ/min C. 761.5 kJ/min D. 409.9 KJ/min
2. A 10,000 kg fish is to be cooled from 25 C to -10 C in 10 hrs. The freezing temperature of fish is -2 oC and
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latent heat of fusion is 280 KJ/kg. The specific heat above freezing is 3.80 KJ/kg-K and below freezing is 1.8
KJ/kg-K. Find the tons of refrigeration is required.
A. 31.36 B. 34.56 C. 36.34 D. 43.23
3. A 12 tons beef is to be cooled from 25 C to -25 C with freezing temperature at -3 oC in 15 hrs. The c p above
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freezing is 2.8 KJ/kg-K and below freezing is 1.5 KJ/kg-K. The latent heat of fusion is 220 KJ/kg. If
miscellaneous losses is 14%, find the tons of refrigeration needed for the system.
 A. 28.34 B. 16.45 C. 21.65 D. 23.23
4. In an actual refrigeration cycle using R12 as working fluid, the refrigerant flow rate is 0.05 kg/s. Vapor enters
the expansion valve at 1.15 MPa, 40 oC (h = 238.5 kJ/kg) and leaves the evaporator at 175 kPa, –15 oC ( h = 345
kJ/kg). The electric input to motor driving the compressor is measured and found 3.5 kW. Motor efficiency at
this load is 92 percent and mechanical efficiency 82%. Determine the actual coefficient of performance for this
cycle.
A. 1.58 B. 2.02 C. 1.78 D. 1.34
5. Find the enthalpy of air with wet bulb temperature of 25 oC and dry bulb temperature of 32oC using
psychrometric chart.
A. 65.45 KJ/kg B. 76.50 KJ/kg C. 74.29 KJ/kg D. 78.40 KJ/kg
6. Find the enthalpy of air with wet bulb temperature of 25 C and 60% RH using psychrometric chart.
o

A. 74.56 KJ/kg B. 60.34 KJ/kg C. 76.50 KJ/kg D. 77.40 KJ/kg

7. Find the dew point temperature of air with dry bulb temperature of 303 oK and RH of 80% using psychrometric
chart.
A. 26.50oC B. 24.50oC C. 85.25oC D. 32oC
8. Find the humidity ratio of air with enthalpy of 40 KJ/kg and RH of 40%. Using psychrometric chart.
A. 0.0123 B. 0.045 C. 0.00600 D. 0.0068
9. At 30oC, air-vapor mixture has a relative humidity of 75%. Find the humidity ratio if barometric pressure is 100
kpa. At 30oC, Psat = 4.246 kpa
A. 0.123 B. 0.0205 C. 0.054 D. 0.019
10. The humidity ratio of air is 0.05. If barometric pressure is 99 kpa, find the partial pressure of water vapor.
A. 4.23 kpa B. 7.37 kpa C. 6.81 kpa D. 5.23 kpa
11. Air at 32 C and pressure of 101 kpa has a density of 1.10 kg/m3. Find the humidity ratio of air.
o

A. 0.0304 B. 0.6350 C. 0.0635 D. 0.0173

12. What is the enthalpy of the air-vapor mixture at 70% RH and 33 oC when the barometric pressure is 101 kpa?
At 33oC: Psat = 5.628, hg = 2565.3
A. 97.76 KJ/kg B. 74.23 KJ/kg C. 67.34 KJ/kg D. 53.34 KJ/kg
13. Air-vapor mixture has an enthalpy of 73 KJ/kg at 31 C. Find the partial pressure of water vapor. At 31 oC: hg =
o

2556.3 KJ/kg
A. 6.34kpa B. 1.34 kpa C. 4.231 kpa D. 2.61 kpa
14. An ammonia ice plant operates between a condenser temperature of 35 oC and evaporator of –15oC. It
produces 12 metric tons of ice per day from water at 30 C to ice at –5 C. Assuming simple saturation cycle,
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determine the horsepower of the motor if the adiabatic efficiency of the compressor ηc = 0.87 and mechanical
efficiency ηm = 0.96. The specific heat of ice is 2.094 kJ/kg.oC and the latent heat is 335 kJ/kg. From the table for
ammonia the following enthalpies are: condenser entrance = 1703 kJ/kg,
exit = 366.1 kJ/kg; compressor entrance = 1443.9 kJ/kg, exit = 1703 kJ/kg
A. 17.68hp B. 18.61 hp C. 15.5 hp D. 25.2 hp
15. A two stage cascade vapor compression refrigeration system uses ammonia in the low-temperature loop and R-
12 in the high-temperature loop. The ammonia provides 18 tons cooling. If the high-loop temperature requires
10.12 kW compressor power and low-loop 15.93 kW, determine the COP of the system.
A. 2.429 B. 5.22 TR C. 3.314 TR D. 9.1 TR

1. Air in an airconditioner enters at 65% RH with w = 0.025 and leaves at 25 oC dry bulb and 16oC wet bulb. If
mass of air is 10 kg/s, find the refrigeration capacity in tons of refrigeration.
At 65% RH, w = 0.025: h = 85 KJ/kg, v = 0.803 m3/kg
At 25oCdb, 16oCwb: h = 43 KJ/kg;
A. 134.34 TR B. 119.45 TR C. 102.45 TR D. 98.34 TR
2. A 140 kw air conditioner has a has an initial condition of 40 Cdb and 60% RH and leaves at 20 odband 20% RH.
o

Find the volume of air entering the conditioner.

At 40oCdb and 60% RH: h = 112 KJ/kg, w = 0.93m3/kg; At 20oCdb and 20% RH: h = 26 KJ/kg
A. 3.22 m3/s B. 2.62 m3/s C. 1.51 m3/s D. 1.93 m3/s
3. Outside air in an air conditioning unit has a mass of 52 kg at 42 oC is mixed with re-circulated air at 32 kg at
28oC, find the temperature after mixing.
 A. 35.23oC B. 32.23oC C. 36.67oC D. 45.32oC
4. Twenty five kilogram air enters the dryer at 24 Cdb and 35% RH. Fifteen kg of re-circulated air from the dryer
o

has a partial pressure of water vapor of 10 kpa. Find the humidity ratio after mixing.
At 24oCdb, 35% RH: w = 0.0059
A. 0.0325 B. 0.1930 C. 0.0653 D. 0.0292
5. Sixty two kilogram of air with enthalpy of 80 KJ/kg is mixed with another x air until the mixture is 110 kg and
70 KJ/kg enthalpy. Find the enthalpy of x air before mixing.
A. 40.23 KJ/kg B. 57.10 KJ/kg C. 13.75 KJ/kg D. 15.34 KJ/kg
6. Air in a conditioned space has 26 Cdb and 70% RH, find the wet bulb depression.
o

A. 6.00oC B. 15.34oC C. 7.20oC D. 17.80oC

7. A 6 x 5 x 4 m room has a pressure of 101 kpa and temperature of 30oC (Psat = 5 kpa). If percent relative
humidity is 65%, find the mass of vapor (RV = 0.423 KJ/kgoK).
A. 0.345 kg B. 1.23 kg C. 3.04 kg D. 2.19 kg
8. A 75% efficient cooling tower has a water entering at 45 C and wet bulb temperature of air entering at 25 oC.
o

Find the water exit temperature of water.

A. 32o CB. 30oC C. 34.34oC D. 23.44oC
9. Water enters the cooling tower at 55 oC and leaves at 30oC while the heat rejected to air is 120 KW. Find the
capacity of the pump needed to pump the water.
A. 1.15 li/s B. 3.22 li/s C. 2.34 li/s D. 4.23 li/s
10. Air enters the tower at the rate of 60 kg/s. The entrance enthalpy is 86 KJ/kg and exit enthalpy of 53 KJ/kg.
Find the temperature range of the tower if mass flow rate of water is 30 kg/s.
A. 14.34oC B. 16.34oC C. 10.23oC D. 15.76oC
11. A 100 BHP diesel engine has a brake thermal efficiency of 30% and jacket water loss of 34%. The engine is to
be cooled by means of a cooling tower having a range of 27 oC. Find the mass of water leaving the tower.
A. 5,238.45 kg/hr B. 2692.35 kg/hr C. 7038.45 kg/hr D. 6108.62 kg/hr
12. A 120 tons refrigeration system with COP of 5 has a condenser which is to be cooled by means of a cooling
tower. Air enters the tower at 25 oCdb and 50% RH and leaves at 35 oCdb and 80% RH. Find the volume of air
needed m3/hr. At 25oC and 50% RH: h = 50 KJ/kg, v = 0.86 m3/kg At 350C db and 80% RH: h = 108
A. 7.51 m3/s B. 2.34 m3/s C. 4.98 m3/s D. 3.16 m3/s

13. The evaporative condenser of an ammonia refrigeration plant has a water flow rate of 100 kg/s and enters a
natural draft cooling tower at 43oC. The water is cooled to 30 oC by air entering at 27oCdb 24oC wet bulb. The
air leaves the tower as 90% RH and 32oC db. Calculate the percent of make-up water needed the tower.
At 27oCdb and 24oCwb: h = 72.5 KJ/kg, w = 0.0178
At 90% RH and 32oCdb: h = 102 KJ/kg, w = 0.0275
A. 2.34% B. 1.79% C. 3.12% D. 2.84%
14. A cooling tower cools water from 39 C to 24 C at the rate of 25 kg/s. Air enters the tower at 18 oC at the rate of
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35 kg/s. Find the temperature of air leaving the tower.

A. 50.71oC B. 62.86oC C. 45.23oC D. 34.45oC
15. An airconditioning system has a sensible heat load of 120 kw and latent heat load of 25 kw. Find the sensible
heat factor.
A. 64.45% B. 73.45% C. 56.34% D. 82.76%
16. Find the dew point temperature of air whose humidity ratio is 0.0150 kg water/kg dry air.
A. 22.50oC B. 23.50oC C. 20.30oC D. 25.5oC
17. The moisture removed from a material is 200 lb/hr and change of humidity ratio in dryer is 0.015. Determine
the fan capacity if specific volume of air entering is 38 ft3/lb.
A. 400,000 ft3/hr B. 450,000 ft3/hr C. 506,667 ft3/hr D. 550,000 ft3/hr
18. A dryer has a 17% moisture wet feed and 3% moisture of dried product. Find the moisture removed for every 5
kg of solids in the final product.
A. 0.187 kg B. 0.395 kg C. 0.234 kg D. 0.84 kg
19. An auditorium is supplied with 35 m /s of air at 14oC db. The total heat load is 320 kw and has a sensible heat
3

factor of 0.82. Find the temperature inside the auditorium using air at standard pressure.
A. 16oC B. 18oC C. 20oC D. 24oC
20. An air conditioned theater is to be maintained at 80 oF dry bulb temperature and 50% RH(h = 31.35 Btu/lb). The
calculated total sensible heat load in the theater is 500,000 Btu/hr, and the latent heat load is 150,000 Btu/hr.
The air mixture at 84oFdb and 72oFwbtemperature(h = 35.82 Btu/lb) is cooled to 63 oF dry bulb and 59oF wet
bulb temperature (h = 25.78 Btu/lb)by chilled water cooling coils and delivered as supply air to the theater.
Calculate the tons of refrigeration required.
A. 83 B. 130 C. 127 D. 122
21. Bypass factor of coil is 0.8 for one row. What is the bypass factor if there are 8 coils in a row?
A. 0.029 B. 0.70 C. 0.80 D. 0.49
22. A coil has an inlet temperature of 50 F and outlet of 85 F. If the mean temperature of coil is 100 oF, find the
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bypass factor of the coil.

A. 0.4 B. 2 C. 1.667 D. 0.3
23. Find the sensible heat factor of an airconditioning unit having a sensible heat load of 60 kw and latent heat load
of 20 kw.
A. 70% B. 80% C. 75% D. 85%
24. An air conditioned theater is to be maintained at 80 F dry bulb temperature and 50% RH(h = 31.35 Btu/lb). The
o

calculated total sensible heat load in the theater is 620,000 Btu/hr, and the latent heat load is 210,000
Btu/hr. The air mixture at 84oF db and 72oF wbtemperature(h = 35.82 Btu/lb) is cooled to 63 oF dry bulb and
59oF wet bulb temperature (h = 25.78 Btu/lb)by chilled water cooling coils and delivered as supply air to the
theater. Calculate the tons of refrigeration required.
A. 125 B. 130 C. 127 D. 122
25. Wet material, containing 200% moisture (dry basis) is to be dried at the rate of 1.6 kg/s in a continuous dryer to
give a product containing 10% moisture (dry basis) . Find the moisture removed, kg/hr.
A. 3543.75 kg/hr B. 3513.75 kg/hr C. 3563.75 kg/hr D. 3648.00 kg/hr
26. Copra enters a dryer containing 75% moisture and leaves at 6% moisture. Find the moisture removed on each
pound of solid in final product.
A. 6.258lb B. 1.258 lb C. 4.258 lb D. 2.936 lb
27. An auditorium seating 1600 people is to be maintained at 80 oF dry bulb and 65oF wet bulb temperature when
outdoor air is at 91oF dry bulb and 75oF wet bulb. Solar heat load is 120,000 Btu/hr and supply air is at 60 oF,
determine the amount of supply air. (Use sensible heat load of 225 Btu/hr per person)
A. 100,000.00lb/hr B. 83,229.17 lb/hr C. 73,229.17 lb/hr D. 63,229.17 lb/hr
28. A classroom that normally contains 40 people is to be air-conditioned with window air-conditioning units of 5
KW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of about 360 KJ/hr. There are
10 light bulbs in the room, each with a rating of 100 watts. The rate of heat transfer to the classroom through
the walls and the windows is estimated to be 15,000 KJ/hr. If the room air is to be maintained at a constant
temperature of 21oC, determine the number of window air-conditioning units required.
A. 1 unit B. 2 units C. 3 units D. 4 units
29. Compute the specific volume of an air-vapor mixture in cubic meters pre kilogram of dry air when the
following conditions prevail : t = 45C, w = 0.015 kg/kg, and Pt = 100 kPa.
A. 0.99 m3/kg B. 0.93 m3/kg C. 0.79 m3/kg D. 0.69 m3/kg
30. A coil has an inlet temperature of 70 F and outlet of 80F. If the mean temperature of the coil is 120F, find the
bypass factor of the coil.
A. 0.28 B. 0.80 C. 0.82 D. 0.83
31. Compute the pressure drop of 35 C air flowing with a mean velocity of 7 m/s in a circular sheet-metal duct 450
mm in diameter and 25 m long. Use a friction factor, f = 0.04, and air = 1.3799 kg/m3.
A. 43.22 Pa B. 21.34 Pa C. 75.12 Pa D. 52.31 Pa
32. A pressure difference of 500 Pa is available to force 20 C air through a circular sheet-metal duct 450 mm in
diameter and 30 m long. At 20C,  = 1.204 kg/m3 and take friction factor, f = 0.016. Determine the velocity.
A. 27.34ft/s B. 43.72 ft/s C. 91.54 ft/s D. 86.98 ft/s
33. An air-conditioning system is used to maintain a house at 65 F when the temperature outside is 85oF. The house
o

is gaining heat through the walls and windows at a rate of 1250 Btu/min, and the heat generation rate within
the house from people, lights, and appliances amounts to 350 Btu/min. Determine the minimum power input
required for this air-conditioning system.
A. 10.06hp B. 1.36 hp C. 1.44 hp D. 7.94 hp