An agitated cylindrical vessel is fitted
with baffles and flat blade impellers. The power number for this system is
given by Np = P/ρn3D5 where P is the power
consumed for the mixing; ρ is the density of the fluid, n is the speed of the
impeller and D is the diameter of the impeller. The diameter of the impeller is
1/3rd the diameter of the tank and the height of liquid level is
equal to the tank diameter. The impeller speed to achieve the desired degree of
mixing is 4 rpm. In a scaled up design, the linear dimensions of the equipment
are to be doubled, holding the power input per unit volume constant. Assuming
the liquid to be Newtonian and Np to be independent of Reynolds
number, what is the impeller speed (in rpm) to achieve the same degree of
mixing in the scaled up vessel?
(A)
0.13
(B)
1.26
(C)
2.52
(D)
3.82
GATE
2016
Answer: (C)
The characteristics curve (Head – Capacity
relationship) of a centrifugal pump is represented by the equation ΔHpump
= 43.8 – 0.19Q, where ΔHpump is the head developed by the pump (in
m) and Q is the flow rate (in m3/h) through the pump. The pump is to
be used for pumping water through a horizontal pipeline. The frictional head
loss ΔHpump (in m) is related to the water flow rate QL
(in m3/h) by the equation 
The flow rate (in m3/h, rounded off to the first decimal place)
of water pumped through the above pipeline, is ___________.
GATE
2016
Answer: 48.91
For a flow
through a smooth pipe, the Fanning friction factor (f) is given by ƒ = mRe-0.2
in the turbulent flow regime, where Re is the Reynolds number and m is a
constant. Water flowing through a section of this pipe with a velocity m/s
results in a frictional pressure drop of 10 kPa. What will be the pressure drop
across this section (in kPa), when the velocity of water is 2 m/s?
(A)
11.5
(B)
20
(C)
34.8
(D)
40
GATE
2016
Answer: (C)
A
vertical cylindrical vessel has a layer of kerosene (of density 800 kg/m3)
over a layer of water (of density 1000 kg/m3). L-shaped glass tubes
are connected to the column 30 cm apart. The interface between the two layers
lies between the two points at which the L-tubes are connected. The levels (in
cm) to which the liquids rise in the respective tubes are shown in the figure
below.
The
distance (x in cm, rounded off to the first decimal place) of the interface
from the point at which the lower L-tube is connected is __________.
GATE
2016
Answer: 10
Two different
liquids are flowing through different pipes of the same diameter. In the first
pipe, the flow is laminar with centerline velocity, Vmax, 1, whereas
in the second pipe, the flow is turbulent. For turbulent flow, the average
velocity is 0.82 times the centerline velocity, Vmax,2. For equal
volumetric flow rates in both the pipes, the ratio Vmax,1/Vmax,2
(up to two decimal places) is _____________.
GATE
2015
Answer: 1.64
For
uniform laminar flow over a flat plate, the thickness of the boundary layer, δ,
at a distance x from the leading edge of the plate follows the relation:
GATE
2015
Answer: (C)
A cylindrical
packed bed of height 1 m is filled with equal sized spherical particles. The
particles are nonporous and have a density of 1500 kg/m3. The void
fraction of the bed is 0.45. The bed is fluidized using air (density 1 kg/m3).
If the acceleration due to gravity is 9.8 m/s2, the pressure drop
(in Pa) across the bed at incipient fluidization (up to one decimal place) is _____________.
GATE
2015
Answer: 8087.85 Pa
For Fanning
friction factor ƒ (for flow in pipes) and drag coefficient CD (for
flow over immersed bodies), which of the following statements are true?
P:
ƒ accounts only for the skin friction
Q:
CD accounts only for the form friction
R:
CD accounts for both skin friction and form friction
S:
Both f ads CD depend on the Reynolds number
T:
For laminar flow through a pipe, ƒ doubles on doubling the volumetric flow
rate.
(A)
R, S, T
(B)
P, Q, S
(C)
P, R, S
(D)
P, Q, S, T
GATE
2015
Answer: (C)
A centrifugal
pump delivers water at the rate of 0.22 m3/s from a reservoir at
ground level to another reservoir at a height H, through a vertical pipe of 0.2
m diameter. Both the reservoirs are open to atmosphere. The power input to the
pump is 90 kW and it operates with an efficiency of 75%.
Data:
Fanning friction factor for pipe flow is ƒ = 0.004. Neglect other head losses.
Take
gravitational acceleration, g = 9.8 m/s2 and density of water is
1000 kg/m3.
The
height H, in meters, to which the water can be delivered (up to one decimal
place) is ________.
GATE
2015
Answer: 26.02 m
A spherical
solid particle of 1 mm diameter is falling with a downward velocity of 1.7 mm/s
through a liquid (viscosity 0.04 Pa.s) at a low Reynolds number (Stokes
regime). The liquid is flowing upward at a velocity of 1 mm/s. All velocities
are with respect to a stationary reference frame. Neglecting the wall effects,
the drag force per unit projected area of the particle, in Pa, (up to two
decimal places) is ______________.
GATE
2015
Answer: 1.296
In case of a
pressure driven laminar flow of a Newtonian fluid of viscosity (µ) through a
horizontal circular pipe, the velocity of the fluid is proportional to
(A)
µ
(B)
µ0.5
(C)
µ-1
(D)
µ-0.5
GATE
2014
Answer: (C)
Slurries
are most conveniently pumped by a
(A) syringe pump
(B) diaphragm pump
(C) vacuum pump
(D) gear pump
GATE
2014
Answer: (B)
Which of the
following statements are correct?
(P) For
a rheopectic fluid, the apparent viscosity increases with time under a constant
applied shear stress.
(Q) For
a pseudoplastic fluid, the apparent viscosity decreases with time under a
constant applied shear stress
(R) For
a Bingham plastic, the apparent viscosity increases exponentially with the
deformation rate
(S) For
a dilatants fluid, the apparent viscosity increases with increasing deformation
rate
(A)
P and Q only
(B)
Q and R only
(C)
R and S only
(D)
P and S only
GATE
2014
Answer: (D)
An
incompressible fluid is flowing through a contraction section of length L and
has a 1-D (x direction) steady state velocity distribution, u = u0(1+2x/L).
If u0 = 2 m/s and L = 3 m, the convective acceleration (in m/s2)
of the fluid at L is _____________.
GATE
2014
Answer: 8
In
a steady incompressible flow, the velocity distribution is given by
where,
V is in m/s and x, y, and z are in m. In order to satisfy the mass
conservation, the value of the constant P (in s-1) is ___________.
GATE
2014
Answer: 8
Match
the following
|
Group I |
Group II |
|
(P)
Turbulence |
(I)
Reciprocating pump |
|
(Q)
NPSH |
(II)
Packed bed |
|
(R)
Ergun equation |
(III)
Fluctuating velocity |
|
(S)
Rotameter |
(IV)
Impeller |
|
(T)
Power number |
(V)
Vena contracta |
(A)
P-III, R-II, T-IV
(B)
Q-V, R-II, T-III
(C)
P-III, R-IV, T-II
(D)
Q-III, S-V, T-IV
GATE
2014
Answer: (A)
In
a steady and incompressible flow of a fluid (density = 1.25 kg m-3),
the difference between stagnation and static pressures at the same location in
the flow is 30 mm of mercury (density = 13600 kg m-3). Considering
gravitational acceleration as 10 m s-2, the fluid speed (in m s-1)
is ___________________.
GATE
2014
Answer: 80
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