PIPE PROBLEMS 1-65

A 15 in. diameter fan operates at 1600 rpm

and develops a head of 6 in. of water and
delivers 120 cfm. What volumetric capacity
for geometrically similar fan that will develop
6 in. of water at 1300 rpm?
a. 147.70 cfm
b. 181.8 cfm
c. 97.5 cmf
d. 79.2 cfm
 A radial-flow pump operating at maximum
efficiency at a specific speed of 2500 is to
deliver 260 gpm against a heat of 129 ft at a
rotative speed of 2100 rpm. Find the required
number of stager (i.e., impellers)
a. 2 stages
b. 3 stages
c. 4 stages
d. 5 stages
 How many identical turbines, operating at
139.0 rpm at 191% efficiency (specific speed =
5.4), are needed to exploit a head of 1200 ft
and a flow of 1660 ft/s.
a. 2 turbines
b. 3 turbines
c. 4 turbines
d. 5 turbines
 How many poles a should a 60-Hz generator
have, if it is connected to a turbine operating
under a design head of 3000ft with a flow of
82 cfs? Assume turbine specific speed and
efficiency 3 and 84 percent respectively.
a. 10-pole
b. 12-pole
c. 14-pole
d. 16-pole
 It is proposed to build a dam in a river where the
flow rate is 10 m3/s and a 32m drop in elevation
can be achieved for flow through a turbine. If
the turbine is 82 percent efficient, what
maximum power that can be achieved? Specific
gravity of river water is 0.998
a. 2570 kW
b. 3133 kW
c. 3820 kW
d. 262 kW
 What type of turbine delivers 25,000 bhp at
500 rpm under a net head of 5350 ft
a. Impulse turbine
b. Francis turbine
c. Kaplan turbine
d. Propeller
 26-Hp pump delivers 475 gpm of gasoline
(γ=42.5 lb/ft3) at 200C with 78% efficiency.
What pressure rise result across the pump?
a. 30.2 psi
b. 32.7 psi
c. 120.3 psi
d. 73.2 psi
 A model pump delivering water at 1800F
(γ=60.6 lb/ft3 ; ρ=7.54 psia) at 900 gpm and 2500
rpm begins to cavitate when the inlet pressure
and velocity are 13 psia and 22 fps. Find the
required NPSH of a prototype which is 4 times
larger and runs at 1100 rpm.
a. 63.5 ft
b. 20.49 ft
c. 6.61 ft
d. 36 ft
 The diameter of the discharge pipe is 8 in and that of
the intake pipe is 10 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
ft3/s of water and the brake horse power is 49.0, find
the efficiency. The intake and the discharge are at
the same elevation.
a. 82.1 %
b. 80.9 %
c. 55.8 %
d. 58.46 %
 A piston positive-displacement pump (PDP)
has 6-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. 13.5 cfm
c. 10 cfm
d. 11.53 cfm
 A centrifugal pump (efficiency 88%) lifts water
through a total height of 40m from reservoir to
discharge. Pumping is through 300 m of 75 mm
diameter pipe at the rate of 20 liters/sec. if pipe
friction factor, f=0.025, what horsepower is
required?
a. 28.4 kW
b. 32.2 kW
c. 25 kW
d. 9 kW
 In order to predict the behavior of a small oil pump,
test are to be made on a model using air, the oil pump
is to be driven by a 1/20-hp motor a t 1800 rpm and ¼-
hp motor is available to drive the air pump at 600
rpm. Using specific gravity of oil at 0.912 and density
of air constant at 0.076 lb/ft3, what size model should
be built?
a. The model should be 2 times as large as the oil pump
b. The model should be 5 times as large as the oil pump
c. The model should be 8 times as large as the oil pump
d. The model should be 10 times as large as the oil pump
 A double-overhung impulse-turbine
installation is to develop 20,000 hp at 275
rpm under a net head of 11,000 ft. determine
the specific speed.
a. 4.34
b. 6.14
c. 203.61
d. 144
 An impulse wheel at best produces 125 hp
under a head of 210 ft. by what percent
should the speed be increased for a 290-ft
head?
a. 82.5 %
b. 17.5 %
c. 72.41 %
d. 71.59 %
 What is the power ratio of a pump and its 1/5
scale model if the ratio of head is 4 to 1?
a. 20
b. 200
c. 12.5
d. 125
 The speed of a centrifugal pump is doubled.
By what factor does the pump head change?
a. 0.125
b. 0.25
c. 4
d. 8
 A 650 BHP diesel engine uses fuel oil of 280API
gravity, fuel consumption is 0.65 lb/BHP-hr. Cost
of fuel is P 7.95 per liter. For continuous
operation, determine the minimum volume of
cubical day tank in cm3, ambient temperature is
450C.
a. 4,372,890 cm3
b. 5,987,909 cm3
c. 5,291,880 cm3
d. 7,352,789 cm3
 A typical industrial fuel oil, C16H32 with 20%
excess air by weight. Assuming complete
oxidation of the fuel, calculate the actual air-
fuel ratio by weight.
a. 17.56 kgair/kgfuel
b. 15.76 kgair/kgfuel
c. 16.75 kgair/kgfuel
d. 17.65 kgair/kgfuel
 Fuel oil in a day tank for use of an industrial
boiler is tested with hydrometer. The
hydrometer reading indicates a S.G. = 0.924
when the temperature of the oil in the tank is
350C. Calculate the higher heating value of the
fuel.
a. 43,852.13 kJ/kg
b. 53,853.13 kJ/kg
c. 58,352.13 kJ/kg
d. 48,352.13 kJ/kg
 A diesel electric plant supplies energy for Meralco.
During a 24 hr period, the plant consumed at 700
gallons of fuel at 280C and produce 3930 kW-hr.
industrial fuel used is 280API and was purchased
at P 5.50 per liter at 15.60C. What should the cost
of fuel be produce one kW-hr?
a. 1.05
b. 1.10
c. 1.069
d. 1.00
 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 600F (15.60F) and 14.7 psia (101.325 kPa) the coal is burned
with 30% excess air. Boiler efficiency of 70% and factor of
evaporation of 1.10.
a. 212,861.04 m3/hr
b. 221,861.04 m3/hr
c. 218,261.04 m3/hr
d. 281,261.04 m3/hr
 A diesel power plant consumed 1m3 of fuel
with 300API at 270C in 24 hrs. Calculate the
fuel rate in kg/hr.
a. 36.21
b. 26.25
c. 29.34
d. 39.42
 A diesel power plant uses fuel with heating
value of 43,000 kJ/kg. What is the density of
the fuel at 250C?
a. 840 kg/m3
b. 873 kg/m3
c. 970 kg/m3
d. 940 kg/m3
 A water tube boiler has a capacity of 1000 kg/hr of
steam. The factor of evaporation is 1.3, boiler rating
is 200%, boiler efficiency is 65%, heating surface
area is 0.91 m2 per bo. HP, and the heating value of
fuel is 18,400 kCal/kg. the total coal available in the
bunker is 50,000 kg. Determine the no. of hrs to
consume the available fuel.
a. 853.36 hrs
b. 706.57 hrs
c. 979.46 hrs
d. 100.75 hrs
 Two boilers are operating steadily on 91,000 kg of coal
contained in a bunker. One boiler is producing 1591 kg of
steam per hour at 1.2 factor of evaporation and an
efficiency of 65% and another boiler produce 136 kg of
steam per hour at 1.15 factor of evaporation and an
efficiency of 60%. How many hrs will the coal in the
bunker run the boilers If the heating value of coal is 7,590
kCal/kg?
a. 230.80 hrs
b. 280.54 hrs
c. 350.35 hrs
d. 300.54 hrs
 The heating value of fuel supplied in a boiler
is 40,000 kJ/kg. If the factor of evaporation is
1.10 and the actual specific evaporation is 10.
What is the efficiency of the boiler?
a. 62.07 %
b. 53.08 %
c. 78.05 %
d. 54.97 %
What is the rate of evaporation of a water tube
boiler if the factor of evaporation is 1.10
percent rating of 200% and the heating
surface area is 250 m2?
a. 7,817.16 kg/hr
b. 7,898.67 kg/hr
c. 6,789.45 kg/hr
d. 5,768.54 kg/hr
 Steam is admitted to the cylinder of an
engine in such manner the average pressure
is 120 psi. The diameter of the piston is 10 in.
and the length of stroke is 12 in. What is the
Hp of the engine when it is making 300 rpm?
a. 171.4 Hp
b. 175 Hp
c. 173.2 Hp
d. 174 Hp
 Steam enters a turbine stage with an enthalpy
of 3628 kJ/kg at 70 m/s and leaves the same
stage with an enthalpy of 2846 kJ/kg and a
velocity of 124 m/s. Calculate the power if there
are 5 kg/s steam admitted and the turbine
throttle?
a. 4597.45 kW
b. 3976.55 kW
c. 3883.81 kW
d. 1675.42 Kw
 Compute the specific volume of an air-vapor
mixture in cubic meters per kilogram of dry
air when the following conditions prevail: t =
400C, w = 0.015 kg/kg, and Pt = 100 kPa.
a. 0.99 m3/kg
b. 0.89 m3/kg
c. 0.79 m3/kg
d. 0.69 m3/kg
 A coil has an inlet temperature of 700F and
outlet of 800F. if the mean temperature of
the coil is 1300F, find the bypass factor of the
coil.
a. 0.28
b. 1.20
c. 0.82
d. 0.83
 Compute the pressure drop of 350C al flowing
a mean velocity of 5 m/s in a circular sheet-
metal duct 400mm in diameter and 25m
long. Use a friction factor, f = 0.04, and ρair =
1.3799 kg/m3.
a. 431.22 Pa
b. 221.34 Pa
c. 312.24 Pa
d. 422.31 Pa
 A 1.5 kg of wet stream at a pressure of 5 bar
(h = 640 kJ/kg, h = 2109 kJ/kg) dryness 0.95 is
blown into 70 liters of water of 120C (h = 50.4
kJ/kg). Find the final enthalpy of the mixture.
a. 74.80 kJ/kg
b. 84.80 kJ/kg
c. 94.80 kJ/kg
d. 104.80 kJ/kg
 The absolute pressure at a the bottom of a
vertical column of water is 15.5 psia. What is
the height of this column?
a. 22 in
b. 9.2 in
c. 12 in
d. 9.8 in
 Water temperature rise of 180F in the water
cooled condenser is equivalent in 0C to
a. 7.78 0C
b. 10 0C
c. 263.56 0C
d. -9.44 0C
 An oil storage tank contains oil with specific
gravity of 0.88 and depth of 20 meters. What
is the hydrostatic pressure at the bottom of
the tank in kg/cm2?
a. 1.67
b. 1.76
c. 1.56
d. 1.87
 A vertical column of water will be supported
to what height by standard atmospheric
pressure?
a. 34 ft
b. 36 ft
c. 24 ft
d. 26 ft
 The specific weight of liquid is 60 lb/ft3 what
is the equivalent to kN/m3
a. 9.334
b. 9.249
c. 9.643
d. 9.420
 A cylinder weighs 15 lbf. Its cross sectional
area is 40 square inches. When the cylinder
stands vertically on one end, what pressure
does the cylinder exert on the floor?
a. 14.1 kPa
b. 58.2 kPa
c. 0.258 kPa
d. 0.141 kPa
 What is the absolute pressure exerted on the
surface of a submarine cruising 300 ft below
the free surface of the sea? Assume specific
gravity of sea water is 1.03
a. 133.9 psia
b. 148.6 psia
c. 100.7 psia
d. 103.7 psia
 Air enters a nozzle steadily at 2.21 kg/m3 and
30 m/s. what is the mass flow rate through
the nozzle if the inlet area of the nozzle is 80
cm2
a. 0.35 kg/s
b. 3.5 kg/s
c. 5.3 kg/s
d. 0.53 kg/s
 The work required to accelerate an 800-kg
car from rest to 100 km/hr on a level road:
a. 308.6 kJ
b. 806.3 kJ
c. 608.3 kJ
d. 386 kJ
 Assuming that there are no heat effects and
no friction effects, find the speed of a 3220-
lbm body after it falls 778 ft from rest.
a. 422 ft/sec
b. 424 ft/sec
c. 224 ft/sec
d. 424 ft/sec
 What is the flow rate through a pipe 4 inches
in diameter carrying water at a velocity of
11ft/sec?
a. 430.84 gpm
b. 7.18 gpm
c. 340.28 gpm
d. 39.16 gpm
 The specific weight of a liquid is 58.5 lbf per
cubic foot, what is the specific volume of the
liquid cm3/g?
a. 0.5321 cm3/g
b. 0.6748 cm3/g
c. 0.9504 cm3/g
d. 1.0675 cm3/g
 What is the resulting pressure when one
pound of air at 0.3 psig and 2000F is heated at
constant volume to 8000F?
a. 0.572 psig
b. 28.6 psia
c. 7.857 psia
d. 1.2 psig
 A small pump serving as model, when tested in
laboratory using water at 3600 rpm, delivered 3.0cfs at
a head of 125 ft. if the efficiency of this model pump is
84%. Predict the horse power 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 90%.
a. 50.6 hp
b. 4730 hp
c. 4740 hp
d. 60.5 hp
 Pump at its best efficiency point (BEP) has a
capacity of 10,500 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. 2476
d. 6892
 A pump will be installed below the reservoir water surface
with a required net positive suction head (NPSH R) of 50 ft.
the barometric pressure is 14.3 psia, and the vapor pressure
is 0.5 psia. Assume friction losses in the intake piping are 5
ft. find the maximum allowable elevation of the pump
relative to the water surface intake to avoid cavitation.
 45 ft
 55 ft
 18.2 ft
 23.2 ft
 Answer: D
 Centrifugal pump at best efficiency (BEP).
Assuming the pump characteristic are head,
h = 7m, flow rate, Q = 19 liters/sec, and
rotative speed n = 1170 rpm. Find the specific
speed in SI units.
a. 0.4
b. 0.71
c. 10.41
d. 3.94