The work index in
Bond’s law for crushing of solids has the following dimensions
(A) No
units (dimension less)
(B) KWh/Ton
(C) KW/Ton
(D) KWm1/2/Ton
GATE
1998
Answer: (B)
At low Reynolds
numbers, the power (P) required for operating a fluid in a stirred tank becomes
independent of internal forces. In this limit, indicate which of the following
relation is satisfied.
(A) Po
α Re-1
(B) Po
α Re0
(C) Po α Re0.5
(D) Po
α Re1
GATE
1998
Answer: (A)
For crushing of
solids, the Rittenger’s law states that the work required for crushing is
proportional to
(A)
The new surface created
(B)
The size reduction ratio
(C)
The change in volume due to crushing
(D)
None of these
GATE
1997
Answer: (A)
A suspension of
glass beads ethylene glycol has a hindered settling velocity of 1.7 mm/s while
terminal settling velocity of the single glass bead in the ethylene glycol is
17 mm/s. If the Richardson – Zaki hindered settling index is 4.5, the volume
fraction of solids in the suspension is
(A) 0.1
(B) 0.4
(C) 0.6
(D) 0.8
GATE 1997
Answer: (B)
The spherecity
of a cylinder of 1 cm diameter and length 3 cm is
(A)
0.9
(B)
0.78
(C)
0.6
(D)
0.5
GATE
1996
Answer: (B)
Stoke’s
equation is valid in the Reynolds number range
(A) 0.01
to 0.1
(B) 0.1
to 2
(C) 2
to 10
(D) 10
to 100
GATE
1996
Answer: (A)
A binary mixture
of 100 µm size having densities of 2 g/cm3 and 4 g/cm3 is
to be classified by elutriation technique using water. Estimate the range of
velocities that can do the job and recommend a suitable value.
(A)
5.50×10-3 and 16.50×10-3
m/s
(B)
6.50×10-3 and 17.50×10-3
m/s
(C)
18.0×10-3 and 21.0×10-3
m/s
(D)
22.0×10-3 and 24.0×10-3
m/s
GATE 1995
Answer: (A)
A fluid energy
mill is used for
(A) Cutting
(B) Grinding
(C) Ultra
grinding
(D) Crushing
GATE 1995
Answer: (C)
A suspension of
uniform particles in water at a concentration of 500 Kg of solids per cubic
meter of slurry is settling in a tank. Density of the particles is 2500 Kg/m3
and terminal velocity of a single particle is 20 cm/s. What will be the
settling velocity of suspension? Richardson – Zaki index is 4.6.
(A) 20
cm/s
(B) 14.3
cm/s
(C) 7.16
cm/s
(D) 3.58
cm/s
GATE
1995
Answer: (C)
A
small model reactor is to be built for scale up studies of the behavior of a
proposed large industrial stirred tank reactor having 100 times capacity. The
bigger unit of 2 m diameter will have a liquid depth of 2 m. This will be
fitted with a four bladed Rushtom Turbine of 0.6 m diameter. Estimate the
dimensions of the smaller unit
(A)
0.06 m
(B)
0.08 m
(C)
0.095 m
(D)
0.10 m
GATE 1995
Answer: (A)
For separating
particles of different densities, the differential settling method uses a
liquid sorting medium of density
(A) Intermediate
between those of the light and heavy ones
(B) Less
than that of either one
(C) Greater
than that of either one
(D) Of
any arbitrary value
GATE
1993
Answer: (B)
At very low rpm
(Re less than 5), the power required for agitation is proportional to
(A) D
(B) D2
(C) D3
(D) D5
GATE 1993
Answer: (C)
Particle A of
diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10
poise under stokes law. A particle B with diameter of 20 microns settling in
the same oil will have a settling velocity
(A)
Same as that of A
(B)
One fourth as that of A
(C)
Twice that of A
(D)
Four times as that of A
GATE
1992
Answer: (D)
For a turbine-
agitated and baffled tank, operating at low Reynolds number (based on impeller
diameter) the power number P0 varies with Re as
(A) Po
α Re
(B) Po
α Re0.5
(C) Po
= constant
(D) Po
α (1/Re)
GATE
1992
Answer: (D)
Energy
requirement (per unit mass of material crushed /ground) is highest for
(A) Jaw
crusher
(B) Rod
mill
(C) Ball
mill
(D) Fluid
energy mill
GATE
1991
Answer: (D)
In power
correlations for agitated vessels the effect of Froude number appears
(A) For
baffled vessels when Reynolds number is less than 300
(B) For
un-baffled vessels when Reynolds number greater than 300
(C) When
there is no vortex formation
(D) When
the Reynolds number is less than 300
GATE 1990
Answer: (B)
A mixture of
coal and sand particles having sizes smaller than 1×10-4 m in diameter is to be
separated by screening and subsequent elutriation with water. Recommend a
screen aperture such that the oversize from the screen can be separated
completely into sand and coal particles by elutriation. Assume stoke’s law is
applicable. Ρsand =2650 kg/m3, ρcoal = 1350
kg/m3, ρwater = 1000 kg/m3, µwater
= 1×10-3 kg/m.s
(A)
4.6×10-5 m
(B)
5.6×10-5 m
(C)
6.6×10-5 m
(D)
6.9×10-5 m
GATE
1990
Answer: (A)
In a gyratory
crusher, the size reduction os primarily is effected by
(A)
Compression
(B)
Impact
(C)
Attrition
(D)
Cutting action
GATE
1990
Answer: (A)
A
leaf filter filtering a slurry gave a total of 8 m3 filtrate is 30
min. Filtrate was continued till 11.3 m3 of filtrate was collected.
Estimate washing time in minutes, if 11.3 m3 of wash water are used.
The resistance of the cloth can be neglected a constant pressure is used
throughout.
(A)
120 min
(B)
150 min
(C)
170 min
(D)
190 min
GATE
1989
Answer: (A)
A pair of rolls
is to take a feed equivalent to spheres of 3 cm in diameter and crush them to
spheres having 1 cm diameter. If the angle of nip is 16⁰,
what would be the diameter of rolls?
(A)
47 cm
(B) 48
cm
(C) 50 cm
(D) 52 cm
GATE
1988
Answer: (B)
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