問題一覧
1
Compute the maximum length of the discharge pipe installed on an
outlet of a pressure-relief device in feet for internal pipe diameter of
0.5 inch and rated discharge capacity is 8 lb/min of air. The rated
pressure of relief valve is 10 psig.
A. 0.286 ft B. 0.386 ft C. 0.486 ft D. 0.586 ft
0.286 ft
2
A 1 m x 1.5 m cylindrical tank is full of oil with SG = 0.92. Find the
force acting at the bottom of the tank in dynes.
A. 106.33 x 103 dynes
B. 106.33 x 104 dynes
C. 106.33 x 105 dynes
D. 106.33 x 106 dynes
106.33 x 106 dynes
3
A certain gas at 101.325 kPa and 10°C whose volume is 2.83 m3
capacity. Before admission, the storage vessel contained gas at a
pressure and temperature of 137.8 kPa and 26°C; after admission,
the pressure increased to 1171.8 kPa. What should be the final
temperature of the gas in the vessel in Kelvin?
A. 298.0
B. 319.8
C. 180.0
D. 314.2
314.2
4
Steam at 2 MPa and 250°C in a rigid cylinder is cooled until the
quality is 30%. Find the heat rejected from the cylinder.
@ 2 Mpa and 250°C: υ = 0.11144 m3/kg u = 2679.6 kJ/kg
@ 2 Mpa, (saturated): υf = 0.0011767 m3/kg υg = 0.09963 m3/kg
uf = 906.44kJ/kg ug = 1693.8 kJ/kg
A. -423.23 kJ/kg
B. -926.26 kJ/kg
C. -1265.02 kJ/kg
D. 1082.34 kJ/kg
-1265.02 kJ/kg
5
Water substance at 70 bar and 65°C enters a boiler tube of constant
inside diameter of 35 mm. The water leaves the boiler tube at 50 bar
and 700 K at velocity of 150 m/s. Calculate the inlet volume flow
(liters/s).
From steam tables:
@ 70 bar (7Mpa) and 65°C: υ1 = 0.001017 m3/kg
@ 50 bar (5Mpa) and 700 K (427°C): υ2 = 0.06081 m3/kg
A. 0.821
B. 1.261
C. 0.344
D. 1.609
1.609
6
A diesel engine consumed 945 liters of fuel per day at 35°C. If the fuel
was purchased at 15.6°C and 30°API at P29.00/li. Determine the cost
of fuel to operate the engine per day.
A. P5,677.50
B. P4,677.50
C. P48,088.90
D. P27,127.76
P27,127.76
7
A gaseous fuel mixture has a molal analysis:
H2 = 14% CH4 = 3% CO = 27% O2 = 0.6% CO2 = 4.5%
N2 = 50.9%
Determine the air-fuel ratio for complete combustion on molal basis.
A. 2.130
B. 3.230
C. 1.233
D. 1.130
1.233
8
The following coal has the following ultimate analysis by weight:
C = 70.5% H2 = 4.5% O2 = 6.0% N2 = 1.0% S = 3.0% Ash = 11%
Moisture = 4%
A stocker fired boiler of 195,000 kg/hr steaming capacity uses this
coal as fuel. Calculate volume of air in m3/hr with air at 60°F and 14.7
air pressure if the boiler efficiency is 70% and FE = 1.10.
A. 234,019 m3/hr
B. 215,830 m3/hr
C. 213,830 m3/hr
D. 264,830 m3/hr
234,019 m3/hr
9
In an open feedwater heater for a steam plant, saturated steam at 7
bar is mixed with subcooled liquid at 7 bar and 25°C. Just enough
steam is supplied to ensure that the mixed steam leaving the heater
will be saturated liquid at 7 bar when heater efficiency is 95%.
Calculate the mass flow rate of the subcooled liquid if steam flow rate
is 0.865 kg/s.
Steam properties:
@ 7 bar, saturated vapor: hg = 2763.5 kJ/kg
@ 7 bar and 25°C: hf = 105.5 kJ/kg
@ 7 bar, saturated liquid: hf = 697.22 kJ/kg
A. 2.725 kg/s B. 3.356 kg/s C. 2.869 kg/s D. 3.948 kg/s
2.869 kg/s
10
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 0.75. For cycle
output of 60 MW, what is the mass flow rate of the well water in kg/s?
@ 204°C: hf = 870.51 kJ/kg
@ 1.04 MPa: hf = 770.38 kJ/kg hfg = 2009.2 kJ/kg hg = 2779.6 kJ/kg
sg = 6.5729 kJ/kg-K
@ 0.034 MPa: hf = 301.40 kJ/kg hfg = 2328.8 kJ/kg sf = 0.09793 kJ/kg-K sfg =
6.7463 kJ/kg-K
A. 2,933 B. 2,100 C. 1,860 D. 2,444
2,933
11
In a gas unit, air enters the combustion chamber at 550 kPa, 227°C
and 43 m/s. The products of combustion leave the combustor at 511
kPa, 1004°C and 180 m/s. Liquid fuel enters with a heating value of
43,000 kJ/kg. For fuel-air ratio of 0.0229, what is the combustor
efficiency in percent?
A. 70.38% B. 79.38% C. 75.38% D. 82.38%
75.38%
12
A turbine has a mechanical efficiency of 93%, volumetric efficiency of
95% and total efficiency of 82%. If the effective head is 40 m, find the
total head.
A. 48.72 m B. 40.72 m C. 36.22 m D. 34.72 m
36.22 m
13
A single acting compressor has a volumetric efficiency of 89%,
operates at 500 rpm. It takes in air at 100 kPa and 30°C and
discharges it at 600 kPa. The air handled is 8 m3/min measured at
discharged condition. If compression is isentropic, find the effective
mean pressure in kPa.
A. 233.34 B. 973.17 C. 198.34 D. 204.82
233.34
14
A water cooler uses 50 lb/hr of melting ice to cool running water from
80°F to 42°F. Based on the inside coil area, Ui = 110 Btu/hr-ft2-
°F.
Find the gpm of water cooled.
A. 0.10 GPM
B. 0.21 GPM
C. 0.38 GPM
D. 0.45 GPM
0.38 GPM
15
The gain of entropy during isothermal nonflow process of 5 lb of air at
60°F is 0.462 Btu/°R. Find the V1/V2.
A. 3.85
B. 0.259
C. 1.0
D. 0.296
0.259
16
An auditorium seating 1500 people is to be maintained at 80°F dry
bulb and 60°F wet bulb temperature when outdoor air is at 91°F dry
bulb and 75°F wet bulb. Solar heat load is 110,000 Btu/hr and supply
air is at 60°F, determine the amount of supply air.
A. 93,229.17 lb/hr
B. 83,229.17 lb/hr
C. 73,229.17 lb/hr
D. 63,229.17 lb/hr
93,229.17 lb/hr
17
A 35% solution leaves the absorber and 30% solution enters the
absorber. The heat removed from the absorber by cooling water is
547.6 Btu and ammonia is superheated by 10°. Find the pound per
pound of ammonia gas from the evaporating coils.
A. 11 B. 12 C. 13 D. 14
13
18
Predict the pressure of nitrogen gas at T = 200 K and υ = 0.00385 L/g
and b = 0.00141 L/g; a = 0.178 L2-kPa/g2. Use Van der Waals
equation.
A. 15,331 kPa
B. 14,331 kPa
C. 13,331 kPa
D. 12,331 kPa
12,331 kPa
19
A Francis turbine is to be operated at a speed of 600 rpm and with
discharge of 4 m3/s. If r1 = 0.6 m, β = 110°, and the blade height B is
10 cm, what should be the guide vane angle α1 for non-separating
flow condition at the runner entrance?
A. 14.4°
B. 15.4°
C. 16.4°
D. 17.4°
17.4
20
A 300 mm diameter pipe discharges water at a rate of 200 li/s.
Point 1 on the pipe has a pressure of 260 kPa and 3.4 m below point
1 is point 2 with a pressure of 300 kPa. Compute the head loss
between points 1 and 2.
A. 4.29 m B. 2.59 m C. 6.32 m D. 1.87 m
1.87
21
Carbon dioxide flows through a nozzle with speed of 380 m/s. The
entrance condition of nozzle is 250°C and 1200 kPa. Find the
stagnation pressure.
A. 2,136.34 kPa
B. 2,146.34 kPa
C. 2,156.34 kPa
D. 2,166.34 kPa
2,136.34 kPa
22
An insulated rigid tank initially contains 1.5 lb of helium at 80°F and
50 psia. A paddle wheel with power rating of 0.02 hp is operated
within the tank for 30 min. Determine the final temperature.
A. 159.22°F B. 169.22°F C. 179.22°F D. 189.22°F
179.22 F
23
Air passes thru a nozzle with efficiency of 90%. The velocity of air at
the exit is 600 m/s. Find the actual velocity at the exit.
A. 382 m/s B. 540 m/s C. 458 m/s D. 568 m/s
568 m/s
24
A 50 kg block of iron casting at 500 K is thrown into a large lake that
is at a temperature of 285 K. The iron block eventually reaches
thermal equilibrium with the lake water. Assuming average specific
heat of 0.45 kJ/kg-K for the iron, determine the entropy generated
during this process.
A. -12.65 kJ/K B. 16.97 kJ/K C. 4.32 kJ/K D. 6.32 kJ/K
4.32 kJ/K
25
A windmill with a 12 m diameter rotor is to be installed at a location
where the wind is blowing at an average velocity of 10 m/s. Using
standard condition of air (1 atm, 25°C), determine the maximum
power that can be generated by the windmill.
A. 68 kW B. 70 kW C. 72 kW D. 74 kW
70 kW
26
A heat engine receives heat from a source at 1200 K at a rate of 500
kJ/s and rejects the waste heat to a medium at 300 K. The power
output of the engine is 180 kW. Determine the irreversibility rate for
this process.
A. 190 kW B. 195 kW C. 200 kW D. 205 kW
195 kW
27
A rigid tank contains 2 kmol of N2 and 6 kmol of CO2 gases at 300 K
and 115 MPa. Find the tank volume using the ideal gas equation.
A. 7.33 m3 B. 5.33 m3 C. 3.33 m3 D. 1.33 m3
1.33 m3
28
A 5 cm diameter spherical ball whose surface is maintained at a
temperature of 70°C is suspended in the middle of a room at 20°C. If
the convection heat transfer coefficient is 15 W/m2-
°C and the
emissivity of the surface is 0.8, determine the total heat transfer
from the ball.
A. 23.56 watts B. 32.77 watts C. 9.22 watts D. 43.45 watts
32.77 watts
29
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 0.85. The
absorbing surface has an absorptivity of 0.90. The area of the
collector is 5 m2. How much solar energy in watts is absorbed by the
collector?
A. 2500 B. 2880 C. 3510 D. 3060
3060
30
A heat engine receives heat from a source at 1200 K at a rate of 500
kJ/s and rejects the wasted heat to a sink at 300 K. If the power
output of the engine is 200 kW, the second law efficiency of this heat
engine is?
A. 35% B. 40% C. 53% D. 75%
53%
31
A house that was heated by electric resistance heaters consumed
1200 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 2.4, determine how much money the homeowner would
be saved that month. Assume a price of 0.085 $/kWh for electricity.
A. $42.5 B. $59.50 C. $102 D. $97.75
$59.50
32
A twin cylinder ammonia compressor with volume displacement of
14,726 cm3 operates at 300 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 the horsepower required.
A. 60 hp B. 70 hp C. 80 hp D. 90 hp
80 hp
33
A double purpose tank 18 ft wide, 24 ft long and 4 ft depth is filled with
water. What is the weight of water in the tank in long tons?
A. 49 tons B. 48 tons C. 54 tons D. 50 tons
49 tons
34
A small pump serving as model, when tested in laboratory using water
at 3600 rpm, delivered 30 cfs at a head of 125 ft. If the efficiency of
this model pump is 84%, predict the horsepower input to the
prototype pump if it is to develop the same head as model pump and
the model pump has a scale ratio of 1:10. Assume the efficiency of
the prototype pump is 90%.
A. 50.6 hp B. 4730 hp C. 3740 hp D. 60.5 hp
4730 hp
35
A centrifugal pump (efficiency 88%) lifts water through a total height of
40 m from a reservoir to discharge. Pumping is through 300 m of 75
mm diameter pipe at the rate of 20 liter/s. If pipe friction, f = 0.025,
what horsepower is required?
A. 28.4 kW B. 32.2 kW C. 25kW D. 9kW
32.2 kW
36
Compute the specific volume of an air-vapor mixture in cubic meter
per kg of dry air when the following conditions prevail: t = 40°C, w =
0.015 kg/kg, and Pt = 90 kPa.
A. 0.99 m3/kg B. 0.89 m3/kg C. 0.79 m3/kg D. 0.69 m3/kg
0.99 m3/kg
37
Pressure difference of 400 Pa is available to force 20°C air through a
circular sheet-metal duct 450 mm in diameter and 25 m long. At 20°C,
ρ = 1.204 kg/m3 and take friction factor, f =
0.016. Determine the velocity.
A. 27.34 ft/s B. 43.72ft/s C. 89.68 ft/s D. 86.98 ft/s
27.34 ft/s
38
To what height will a barometer column rise if the atmospheric
conditions are 13.9 psia and 68°F and barometer fluid is ethyl
alcohol? Note: @ 68°F; Pv =138.5 lbf/ft3 and specific gravity of 0.79
for ethyl alcohol:
A. 79.37 in B. 37.79 in C. 353.54 in D. 453.53 in
453.53 in
39
What is the pressure 7000 ft below the water surface of the ocean?
Neglect compressibility.
A. 512,000 psf
B. 324,500 psf
C. 447,000 psf
D. 213,000 psf
447,000 psf
40
A vapor compression refrigeration system is designed to have a
capacity of 150 tons of refrigeration. It produces chilled water from
22°C to 2°C. Its actual coefficient of performance is 5.86 and 35% of
the power supplied to the compressor is lost in the form of friction
and cylinder cooling losses. Determine the condenser cooling water
required for a temperature rise of 10°C.
A. 14.75 kg/s
B. 15.65 kg/s
C. 18.65 kg/s
D. 13.75 kg/s
14.75 kg/s
41
Which of the following is not a unit of pressure?
A. Pa
B. bars
C. kg/m-s2
D. kg/m2
kg/m-s2
42
Two liters of an ideal gas at a temperature of T1 = 25°C and a
pressure of P1 = 0.101 MPa, are in a 10 cm diameter cylinder with a
piston at one end. The piston is depressed so that the cylinder is
shortened by 10 centimeters. The temperature increases by 2°C.
What is the change in pressure?
A. 0.156 MPa
B. 0.167 MPa
C. 0.251 MPa
D. 0.327 MPa
0.167 MPa
43
A mixing tank mixes two inlet streams containing salt. The salt
concentration in stream 1 is 5% by weight, at stream 2 it is 15% by
weight. Stream 1 flows at 25 kg/s, and stream 2 flows at 10 kg/s.
There is only one exit stream. Find the salt concentration in the exit
stream.
A. 5%
B. 8%
C. 11%
D. 13%
11%
44
A single-stage ammonia compressor is producing 10 tons of
refrigeration and the power consumed is 15 Hp. Suction pressure is
25 psi, condensing pressure is 180 psi. Brine temperature is 20°F off
brine cooler. Determine the actual coefficient of performance.
A. 10.14
B. 11.14
C. 12.14
D. 13.14
13.14
45
Hot gases at 280°C flow on one side of the metal plate 10 mm
thickness and air at 35°C flows on the other side. The heat transfer
coefficient of the gases is 31.5 W/m2-K and that of the air is 32
W/m2-K. Calculate the over-all heat transfer coefficient.
A. 15.82 W/m2-K
B. 16.82 W/m2-K
C. 14.82 W/m2-K
D. 17.82 W/m2-K
15.82 W/m2-K
46
A wall with an area of 10 m2 is made of a 2 cm thickness of white
pine (k = 0.133 W/m-
°C) followed by a 10 cm of brick (k = 0.649 W/m-
°C). The pine is on the inside where the temperature is 30°C while
the outside temperature is 10°C. Assuming equilibrium conditions
exist, what is the temperature at the interface between the two
metals?
A. 15.65 °C
B. 17.64 °C
C. 18.21 °C
D. 19.31 °C
19.31 °C
47
A 650 BHP diesel engine uses fuel oil of 28°API gravity, fuel
consumption is 0.65 lb/BHP-hr. Cost of fuel is P7.95 per liter. For
continuous operation determine the minimum volume of cubical day
tank in cm3, ambient temperature is 45° C.
A. 4,372,890 cm3
B. 5,987,909 cm3
C. 5,291,880 cm3
D. 7,352,789 cm3
5,291,880 cm3
48
A certain coal has the following ultimate analysis:
C = 70.5% H = 4.5% O2 = 6% N2 = 1.0%
S = 3.0% Ash = 11% Moisture = 4%
A stoker fired boiler of 175,000 kg/hr steaming capacity uses this coal
as fuel. Calculate the volume of air in m3/hr with air at 60°F (15.6°F)
and 14.7 psia (101.325 kPa) the coal is burned with 30% excess air.
Boiler efficiency is 70% and factor of evaporation of 1.10.
A. 212,861.04 m3/hr C. 218,261.04 m3/hr
B. 221,861.04 m3/hr D. 281,261.04 m3/hr
212,861.04 m3/hr
49
In a hydroelectric power plant the tailwater elevation is at 500 m.
What is the head water elevation if the net head is 30 m and the head
loss is 5% of the gross head?
A. 785.25 m
B. 582.57 m
C. 528.57 m
D. 758.25 m
528.57 m
50
A two-stage air compressor at 90 kPa and 20°C discharges at 700
kPa. Find the polytropic exponent n if the intercooler intake
temperature is 100°C.
A. 1.29
B. 1.33
C. 1.4
D. 1.25
1.29
51
Determine the temperature for which a thermometer with degrees
Fahrenheit is numerically twice the reading of the temperature in
degrees Celsius.
A. -24.6
B. 320
C. 160
D. -12.3
160
52
An adiabatic tank containing air is used to power an air turbine during
times of peak power demand. The tank has a volume of 500 m3 and
contains air at 1000 kPa and 500 K. Determine the mass remaining
when the pressure reaches 100 kPa.
A. 273.37 kg
B. 672.73 kg
C. 772.73 kg
D. 227.73 kg
672.73 kg
53
A two-stage, double acting compressor is to deliver 90 lb/min of air
from 14.3 psia to 90°F to a final pressure of 185 psia. The normal
barometer is 29.8 in-Hg and the temperature is 80°F. The pressure
drop in the intercooler is 3 psi and the speed is 210 rpm and pV1.34 =
C during compression and expansion. The clearance is 5% for both
cylinders. Find the volume of free air if the temperature of the cooling
water increased by 18°F.
A. 1282 CFM
B. 1230 CFM
C. 1320 CFM
D. 1822 CFM
1230 CFM
54
Consider 4800 lb of steam per hour flowing through a pipe at 100 psia
pressure. Assume a velocity of 5280 ft/min. What size of pipe is
required? Specific volume of steam at 100 psia v = 4.432 ft3/lb.
A. 3 in
B. 5 in
C. 4 in
D. 6 in
4 in
55
A turbine receives 150 lbm/s of air at 63 psia and 2450°R and
expands it polytropically to 14.7 psia. The exponent n is equal to 1.45
for the process. Determine the power.
A. 52,343.16 BTU/s
B. 52,343.16 kW
C. 53.343.16 HP
D. 53,343.16 ft-lb/s
52,343.16 BTU/s
56
Find the thrust and efficiency of two 2-m diameter propellers through
which flows a total of 600 m3/s of air to 11.3 N/m3. The propellers
are attached to an airplane moving at 250 kph through still air.
Neglect eddy losses.
A. 36,077 N, 73%
B. 77,630 N, 37%
C. 66,033 N, 33%
D. 77,330 N, 77%
36,077 N, 73%
57
The fuel oil has the ff. analysis:
C = 89% N2 = 2% H2 = 8% S = 1%
With 3% excess air, what is the actual amount of air needed to burn
the fuel oil?
A. 13.17 kgair/kgfuel C. 14.47 kgair/kgfuel
B. 13.47 kgair/kgfuel D. 14.17 kgair/kgfuel
14.17 kgair/kgfuel
58
During the working stroke of an engine the heat transferred out of the
system was 150 kJ/kg of working substance. The internal energy also
decreased by 400 kJ/kg of working substance. Determine the work
done.
A. 250 kJ/kg
B. 550 kJ/kg
C. 600 kJ/kg
D. 350 kJ/kg
250 kJ/kg
59
Steam enters a turbine stage with an enthalpy of 3700 kJ/kg and a
velocity of 80 m/s and leaves with an enthalpy of 2864 kJ/kg with a
velocity of 12.8 m/s. If the rate of a steam flow through the turbine is
0.44 kg/s, what is the work done in kW?
A. 365 kW
B. 365.64 kW
C. 366.0 kW
D. 366.50 kW
365.64 kW
60
Consider 1 kg of air at 32°C that expanded by a reversible polytropic
process with n = 1.25 until the pressure is halved. Determine the heat
transfer. Specific heat at constant volume for air is 0.1786 kJ/kg-K.
A. 17.02 kJ heat rejected C. 17.02 kJ heat added
B. 7.05 kJ heat rejected D. 7.05 kJ heat added
17.02 kJ heat added
61
An air compressor takes in 9 kg/min of air at 98 kPa; v1 = 0.125
m3/kg and discharges it at 680 kPa; v2 = 0.03 m3/kg. The increase of
internal energy is 93 kJ/kg and the work done on air is
163 kJ/kg; the change in potential and kinetic energy are neglected.
How much heat is transferred per kg of air?
A. 264.15 kJ/kg
B. 61.85 kJ/kg
C. 288.65 kJ/kg
D. 78.15 kJ/kg
61.85 kJ/kg
62
A Carnot cycle uses nitrogen (k = 1.399) as the working substance.
The heat supplied is 54 kJ and the adiabatic expansion ratio is 10.
Determine the heat rejected.
A. 10 kJ
B. 32.4 kJ
C. 21.6 kJ
D. 54 kJ
21.6 kJ
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