Momentum Transfer (Set 2) Flashcards
As one of the transport phenomena, the concepts in momentum transfer (also known as fluid mechanics) are crucial for the design, operation, and maintenance of fluid flow equipment such as pipes, pumps/compressors, turbines/expanders, agitators, and metering devices.
1
Q
For the production of very high vacuum, a ____ pump is normally used.
A
diffusion
2
Q
In parallel pipe problems, the
A
head loss is the same through each pipe.
3
Q
Fluid flow through a packed bed is represented by the ____ equation.
A
Ergun’s
4
Q
____ is an example of axial flow impeller.
A
Propeller
5
Q
Froude number is not a factor
A
when there is no vortex formation.
6
Q
If three pipes of different diameters, lengths & friction factors are connected in parallel, then (where, Q = flow rate, V= fluid velocity f = friction factor).
A
Q = Q1 + Q2 + Q3
7
Q
Horsepower requirement for given pump capacity depends upon the
A
all of these
8
Q
Bernoulli’s equation accounts for the
A
different forms of mechanical energy
9
Q
____ pumps are a group of vacuum pumps.
A
Hyter
10
Q
Plunger pumps are used for
A
higher pressure
11
Q
What is the ratio of displacement thickness to nominal thickness for a linear distribution of velocity in the boundary layer on a flat plate ?
A
0.5
12
Q
In turbulent flow, the
A
shear stresses are generally larger than in a similar laminar flow.
13
Q
Momentum correction factor used in fluid flow problems accounts for the
A
non uniform direction of velocities at inlet & outlet sections.
14
Q
Design of the casing of centrifugal pump should be such as to minimise the
A
loss of kinetic head
15
Q
Which of the following is used for pumping crude oil from oil well ?
A
Duplex/triplex reciprocating pump
16
Q
The energy loss in flow through ven-turimeter is less than that through flow nozzle, because in case of a flow nozzle, the
A
sudden expansion of flow in the downstream occurs.
17
Q
____ flow means the flow of incompressible fluid with no shear.
A
Potential
18
Q
The continuity equation
A
relates mass flow rate along a stream tube.
19
Q
The energy loss over a length of pipeline according to Darcy-Weisbach equation for pipe flow is…..the mean velocity of flow.
A
directly proportional to square of
20
Q
Pressure drop in a packed bed for laminar flow is given by the ____ equation.
A
Kozney-Karman
21
Q
The fluid velocity varies as the cube of the cylinderical pipe diameter in case of steady state laminar flow at constant pressure drop for ____ fluid.
A
pseudoplastic
22
Q
Stoke’s law is valid, when NRe, p is less than
A
2
23
Q
Froude number is the ratio of
A
inertial stress to gravitational stress.
24
Q
Normal depth in open channel flow is the depth of flow in the channel
A
corresponding to uniform flow.
25
Which of the following flow measuring devices is an area meter ?
Rotameter
26
With decrease in particle size to be fluidised by a particular fluid, the operating range of fluidisation velocity
does not change
27
Diaphragm valves are used for handling ____ fluids.
corrosive
28
The schedule number of a pipe is an indication of its
wall thickness
29
Minimum porosity for fluidisation is
the porosity of the bed when true fluidisation begins.
30
A centrifugal pump used to pump water is used to pump an oil with specific gravity of 0.8 at the same rate. The power consumption will now
decrease
31
Steady non-uniform flow is exemplified by flow through a/an
expanding tube at constant rate.
32
The maximum depth from which a centrifugal pump can draw water is
34 feet.
33
Hot wire anemometer is used to measure the
velocity of gases.
34
Propeller type centrifugal pumps are most suitable for
high capacity at low heads.
35
The fluid velocity varies as the square of the cylindrical pipe diameter, in case of steady state laminar flow at constant pressure drop, for ____ fluid.
Newtonion
36
Momentum transfer in laminar flow of fluids results due to the
velocity gradient
37
The capillary rise of mercury is maximum in glass tube of dia ____ mm.
0.5
38
Diaphragm pumps are used to transport
slurries
39
For steady ideal fluid flow, the Bernoulli's equation states that the
energy is constant along a stream line, but may vary across stream lines
40
In case of a centrifugal pump, the theoretical head developed is dependent on the ____ the impeller.
a. speed of
b. diameter of
c. fluid velocity leaving
all of these
41
A hydraulic press has a ram of 10 cms in diameter and a plunger of 1 cm in diameter. The force required on the plunger to raise a weight of 10 tons on the ram is ____ kg.
100
42
Choose the set of pressure intensities that are equivalent.
4.33 psi, 10 ft. of water, 8.83 inches of Hg.
43
Pick out the wrong statement about a streamline.
It is always parallel to the main direction of the fluid flow.
44
The most serious disadvantage of an orificemeter is that
most of the pressure drop is not recoverable.
45
The discharge through a rectangular weir varies as
H^3/2
46
In case of supersonic flow of a fluid through pipeline, the 'Mach number' is
> 1
47
A centrifugal pump has the following specifications: Power = 4 H.P.; Speed = 800 rpmHead = 8 metresFlow = 1000 litres/minutes.If its speed is halved, the power consumed now will be ____ hp.
0.5
48
Transition length for turbulent flow in smooth pipe is equal to ____ times the pipe diameter.
50
49
Disc compensators are provided in large diameter fuel gas carrying pipelines to
account for contraction/expansion of pipe due to temperature changes of the surroundings.
50
Discharge from a 24 inch pipe of water at 10 ft/sec will be ____ ft3/sec.
125.6
51
Paper pulp is an example of ____ fluid.
bingham plastic
52
The ratio of the depth of flow to the diameter of the channel for maximum discharge in a circular channel in open channel flow is
0.95
53
A conical tank with a bottom opening of cross-sectional area A is filled with water and is mounted on supports as shown in the figure. What is the force F with which plate X must be pushed up to prevent water from leaking ? Assume that the density of air is negligible as compared to the density of water ρL. (1)
ρL . A.Hg
54
A relief valve
is a directional control valve.
55
An isentropic process is the one, in which
pvr = constant, and process is reversible
56
The distribution of shear stress in a stream of fluid in a circular tube is
linear with radius for both laminar & turbulent flow.
57
For motion of spherical particles in a stationary fluid, the drag co-efficient in hindered settling compared to that in free settling is
more
58
Specific speed of a centrifugal pump relates it with another pump having the
dynamic similarity
59
Air vessel fitted to a reciprocating pump
decreases the work done.
60
Deformation drag, which is caused by widespread deformation of fluid around the immersed body
occurs when NRe is very small.
61
In isotropic turbulence, the ____ are equal to each other.
mean square of velocity fluctuations in the three co-ordinate directions
62
Viscosity of water is about ____ times that of air at room temperature.
55
63
Net positive suction head (NPSH) of a centrifugal pump must be
greater than the vapour pressure of the liquid.
64
Actual lift of a pump is always less than the theoretical lift and is limited by the
a. specific gravity & temperature of the liquid.
b. leakage & pressure decreasing at higher elevations.
c. frictional resistance through pipes, fittings & passages.
all of these
65
In case of unsteady fluid flow, conditions & flow pattern change with the passage of time at a position in a flow situation. Which of the following is an example of unsteady flow?
Water flow in the suction and discharge pipe of a reciprocating pump.
66
Nature of fluid flow during the opening of a valve in a pipeline is
unsteady
67
The ____ pressure is measured by a static tube.
static
68
The speed of a sound wave in a gas is analogous to the speed of
an elementary wave in an open channel.
69
Mercury is an ideal barometric fluid mainly due to its
very low vapor pressure.
70
A spherical particle is falling slow in a viscous liquid such that Reynolds number is less than 1. Which statement is correct for this situation ?
Drag, gravitational and buoyancy forces are impportant.
71
A gas
is a supercritical vapor.
72
Pitot tube measures the ____ of a fluid.
point velocity
73
Which of the following is not dimension-less?
Kinematic viscosity
74
In laminar flow through a round tube, the discharge varies
inversely as the viscosity.
75
Which is not a variable head meter ?
Rotameter
76
The pipe wall thickness is minimum for a pipe of given nominal size having schedule number
40
77
Reynolds number for flow of water at room temperature through 2 cm dia pipe at an average velocity of 5 cm/sec is around
1000
78
Centrifugal pumps as compared to reciprocating pumps
can be run with discharge line valve closed for a short interval.
79
What type of motion the fluid element undergoes, when it changes from one position to another position, such that the angle between the two sides change ?
Angular deformation
80
In which type of fluid flow, the velocity of flow of fluid changes from point to point in the fluid at any instant ?
Non-uniform
81
The continuity equation in ideal fluid flow states that
net rate of inflow into any small volume must be zero.
82
Bernoulli's equation is not applicable, when the flow is
a. irrotational.
b. incompressible.
c. viscous.
all of these.
83
The equivalent diameter for pressure drop calculation for a duct of square cross-section is given by(where, x = each side of the square duct)
x
84
Centre of pressure of a plane surface of arbitrary shape immersed vertically in a static mass of fluid
is independent of the specific weight of the fluid.
85
Drag co-efficient for flow past immersed body is the ratio of ____ to the product of velocity head and density.
average drag per unit projected area
86
Creeping flow around a sphere is defined, when particle Reynolds number is
< 0.1
87
Open channel liquid flow is most conveniently measured by a
notch
88
Toothpaste is a
dilatent
89
Slurries can be most conveniently pumped by a ____ pump.
centrifugal
90
Volute type of casing is provided in a centrifugal pump to
increase the discharge.
91
Each term of the Bernoulli's equation written in the form, (1) , represents the total energy per unit
mass
92
In a free vortex, the
velocity changes linearly with radial distance.
93
Pick out the wrong statement.
The eddy viscosity is a fluid property.
94
The velocity distribution in direction normal to the direction of flow in plane Poiseuille flow is
parabolic
95
In fluid flow, the stagnation point is defined as a point, where the ____ is zero.
flow velocity
96
A special type of liquid transporting device is the diffuser pump, in which ____ are minimised.
shock losses
97
Which of the following is most prone to pulsating discharge flow ?
Gear pump
98
A streamline is
drawn normal to the velocity vector at every point.
99
Which of the following relationship is valid for the equilibrium position of the float in a rotameter ?(where, Df= Drag force on the float Bf = Buoyant force on the float Wf = Weight of the float)
Df + Bf = Wf
100
Drag is defined as the force exerted by the
fluid on the solid in the direction of flow.
101
The boundary layer is that part of a moving fluid, in which the fluid velocity is
affected by the presence of a solid boundary.
102
The terminal velocity of a solid spherical particle falling through a stationary fluid mass in the Stoke's law range is proportional to the
all of these
103
Which of the following equations as suggested by Colebrook and White gives the increase in roughness of a new surface (ε0) with age/time (t) (where, ε = roughness of the surface after time't'. α = a co-efficient to be experimentally determined)?
ε = ε0 + α.t
104
Nominal size of a pipe is an indication of its ____ diameter.
approximate
105
Fluidised beds are formed, when the
gravity force is less than the fluid friction.
106
A fluid is pumped at the rate of 10 lb/sec to a height of 55 ft. The horse power required is ____ hp.
1
107
Pick out the wrong statement:
The point at which the resultant pressure on an immersed surface acts, is known as the centre of gravity.
108
Medium viscosity lubricating oil can be most ideally pumped by a ____ pump.
vane
109
In a fully turbulent flow (Re > 105) in a pipe of diameter 'd', for a constant pressure gradient, the dependence of volumetric flow rate of an incompressible fluid is
d^2.5
110
Pump used for the transportation of molten sodium in a fast breader reactor is a/an ____ pump.
electromagnetic
111
Small pressure differences in liquids is measured using a/an
inclined tube manometer.
112
With increase in pump speed, its NPSH requirement
increases
113
In the Newton's law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass is ____ the fluid viscosity.
inversely proportional to
114
Gear pump
is a positive displacement pump.
115
Most of the centrifugal pumps used in chemical plants are usually ____ driven.
electric motor
116
Check valve provided in the discharge line of a centrifugal pump serves the purpose of controlling the
back flow of fluid in the event of stoppage of pump.
117
Venturimeters, orificemeters and nozzles are used to measure the fluid discharge from a pipeline. The average fluid velocity in a pipeline can be measured by a/an
hot wire anemometer
118
The time taken for gravity flow of a fixed volume of liquid (as in Redwood viscometer) is directly proportional to its
ratio of absolute viscosity to density.
119
Sewage sludge is ____ type of non-Newtonion fluid.
Bingham plastic
120
Ratio of pressure and inertia force gives ____ number.
Euler
121
Permanent loss in a venturimeter is about ____ percent of the pressure drop in theupstream cone.
10 .
122
Volume of liquid displaced by a floating body is equivalent to its
own weight
123
The ____ is measured by a piezometric opening.
total pressure
124
What is the pipe called which lifts water from a reservoir to a greater height than the initial level in the supply reservoir ?
Siphon
125
Steady uniform flow is represented by flow through a/an
long pipe at constant rate.
126
Pick out the correct statement pertaining to the flow through a converging-diverging tube.
No shock wave develops in the tube when the Mach number at exit is greater than unity.
127
Cavitation can be prevented by
maintaining the suction head sufficiently greater than the vapour pressure.
128
Assuming flow to be laminar, if the diameter of the pipe is halved, then the pressure drop will
increase
129
Steady flow occurs, when the
conditions do not change with time at any point.
130
With increase in the ratio of orifice diameter to pipe diameter, the fraction of the orifice pressure differential that is permanently lost
decreases
131
Which of the following two quantities when same, makes one pipe system equivalent to another pipe system ?
Head & discharge
132
The kinetic energy correction factor for velocity distribution of laminar flow is
1.66
133
Priming of a centrifugal pump is done to
avoid chances of separation inside the impeller.
134
Bed pressure drop in an air fluidised bed of catalyst particles (ρp = 200 kg/m3, Dp = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is
60
135
For pipes that must be broken at intervals for maintenance, the connector used should be a/an
union
136
A fluid is the one, which
cannot remain at rest under the action of shear force.
137
A fluid (1) is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is ____ cm/sec.
7
138
Capillary rise of mercury in a small diameter tube is proportional to (where, d = diameter of the tube, σ = surface tension of mercury)
σ
139
The pressure drop per unit length of pipe incurred by a fluid 'X' flowing through pipe is Δp. If another fluid 'Y' having both the specific gravity & density just double of that of fluid 'X', flows through the same pipe at the same flow rate/average velocity, then the pressure drop in this case will be
2Δp
140
Fluid flow in a/an ____ is an example of pressure flow.
pipe
141
In the laminar boundary layer flow over a flat plate, the ratio (δ/x) varies as :(where, 'δ' is the boundary layer thickness and 'x' is the distance from the leading edge in the direction of flow).
Re^-1/2
142
A rotameter through which air at room temperature and atmospheric pressure is flowing gives a certain reading for a flow rate of 100 cc/sec. If helium (molecular weight 4) is used and rotameter shows the same reading, the flow rate (cc/sec) is
269
143
A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m^3 ) is to be fluidised by water (density 1000 kg/m^3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is
4.4 KPa
144
Select the wrong statement pertaining to flow of an incompressible fluid through a venturimeter.
Venturimeter occupies less space than an orificemeter.
145
Reynolds number for water flow through a tube of I.D. 5 cm is 1500. If a liquid of 5 centipoise viscosity and 0.8 specific gravity flows in the same pipe at the same velocity, then the pressure drop will
increase
146
The bulk modulus of elasticity of a liquid
increases with pressure.
147
Curve III in the above diagram represents a/an
pseudo plastic fluid
148
What is the ratio of total kinetic energy of fluid passing per second to the value obtained on the basis of average velocity (for laminar flow through a circular pipe)?
2
149
The line traced by a single fluid particle as it moves over a period of time is called ____ line.
path
150
A stream tube is that, which has ____ cross-section entirely bounded by stream lines.
any convenient
151
Colebrook equation for friction factor in turbulent flow is given by, (1) . It reduces to Nikuradse equation for a value of (1) equal to
1
152
The unit of velocity head is
ft-lbf/lb
153
Which of the following properties of a fluid is responsible for offering resistance to shear ?
Viscosity.
154
Erosion and pits formation on the impeller of a centrifugal pump may be due to
cavitation.
155
The velocity profile exhibited by laminar flow of Newtonion fluids is such that the velocity distribution w.r.t. radius of the circular pipe is a/an ____ with the apex at the centre line of the pipe.
parabola
156
The excess of the sum of pressure & velocity heads over the vapor pressure of the liquid at the suction is called the
net positive suction head (NPSH).
157
Piezometric head is the sum of the ____ heads.
elevation & pressure
158
Propellers are
axial flow mixers.
159
Which of the following is not an advantage of fluidisation from transfer operation point of view?
Lower fluid pumping power requirement.
160
Upto what value of 'Mach number', a fluid may be considered as incompressible ?
0.3
161
The head developed by a centrifugal pump is largely determined by the
angle of the vanes and the speed of the tip of the impeller.
162
Pick out the wrong statement:
Friction losses in pipe fittings are generally expressed in terms of velocity heads.
163
Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a
pitot tube
164
Potential flow is the flow of
incompressible fluids with no shear.
165
The value of critical Reynolds number for pipe flow is
1300
166
Mach number is important in a fluid flow problem, when the inertia and ____ forces predominate.
elastic
167
Fanning friction factor is equal to(where, fB = Blassius friction factor).
fB/4
168
In case of coutte flow, the fluid flow is between two large flat parallel plates with
top plate moving and the bottom plate fixed.
169
In a stabilised soap bubble, pressure inside it compared to external pressure is
more
170
The component of acceleration resulting due to unsteady nature of flow is called ____ acceleration.
local
171
Power required for mixing Newtonion fluids is a function of the
a. speed of impeller, diameter of impeller & viscosity.
b. density & viscosity of fluid only.
c. density of fluid, viscosity of fluid & impeller dia only.
none of these.
172
Multistage compressors are used in industry, because they
resemble closely to isothermal compression.
173
The hydrodynamic and thermal boundary layers will merge, when
Prandtl number is one.
174
Differential manometer measures the
pressure difference between two points.
175
For a stable equilibrium of a submerged body (where, G and B are centres of gravity & buoyancy respectively).
B is above G
176
With increase in the ratio of orifice diameter to pipe diameter in case of an orificemeter, the overall pressure loss
remains constant
177
The vent valve provided in a liquid handling centrifugal pump is
all (a), and (b) and (c).
178
The discharge through a semi-circular weir varies as (where, H = Head of liquid.)
H^2
179
The Mach number for hypersonic flow of compressible fluid is
> 4
180
Boundary layer thickness in turbulent flow over a flat plate increases as(where, d = distance from the leading edge.)
d^4/5
181
The valve used for very remote and accurate control of fluid is a ____ valve.
needle
182
f = 16/NRe, is valid for
none of these
183
A mixed flow centrifugal pump
employs such an impeller, through which the flow is a combination of radial & axial flow.
184
In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure ____ the vapor pressure of the liquid at the suction temperature.
higher than
185
A rectangular surface 3' x 4', has the lower 3 edge horizontal and 6' below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is(where, y = specific weight of water)
48y
186
A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun's equation for the above fluid-particle system (in SI units) is given below : Δ P/L = 375 x 10^3 VOM + 10.94 x 10^6 V^2OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is
16 mm/s
187
One dimensional flow implies
a flow which does not account for changes in transverse direction.
188
In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where, Vavg = average fluid velocity)
1.2 Vavg
189
Centrifugal compressors compared to reciprocating compressors
all of these
190
For laminar flow of Newtonion fluids through a circular pipe, for a given pressure drop and length & diameter of pipe, the velocity of fluid is proportional to(where, μ = fluid viscosity )
1/μ
191
Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles) no change in the
bed height
192
Stoke's law is valid, when the particle Reynolds number is
< 1
193
Which of the following is not a dimension-less parameter ?
Kinematic viscosity
194
In which of the following cases, it is possible for flow to occur from low pressure to high pressure ?
Flow through a converging section.
195
The blades of a centrifugal impeller are said to be curved forward, if the ____ of the motion of impeller blades.
outlet tip of a blade is towards the direction
196
For the same terminal conditions and fitting size, the least friction loss is incurred in a/an
union
197
A floating/submerged body is always stable, if its centre of gravity
lies below its centre of buoyancy.
198
Critical velocity in a pipe flow
increases as pipe diameter increases.
199
A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump
all of these
200
In an incompressible flow of fluid, the fluid
density does not change with pressure & temperature.
201
The ratio of maximum to average velocity in case of streamline flow between parallel plates is
1.5
202
A weir is used to measure the large water discharge rate from a river or from an open channel. A weir is not of ____ shape.
circular
203
Pressure co-efficient is the ratio of pressure forces to ____ forces.
inertial
204
Which of the following conditions must be satisfied for lift force to be developed ?
Circulation around the body is essentially required.
205
The Reynolds number for an ideal fluid flow is
∞
