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Bed pressure drop in an air fluidised bed of catalyst particles (ρ<sub>p</sub> = 200 kg/m<sup>3</sup>, D<sub>p</sub> = 0.05 cm) of 60 cm bed depth and bed porosity of 0.5 expressed in cm of water (manometer) is
A
90
B
60
C
45
D
30
Correct Answer:
60
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 × 10
3
V
OM
+ 10.94 × 10
6
V
2
OM
(SI units)
If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed?
A
0.2
B
0.5
C
0.7
D
0.8
A student wants to find the absolute pressure of water at a point below the surface of water. He has a barometer and a manometer pressure gauge. The barometer reads 1.3152 bar where as the manometer pressure gauge reads 0.3152 bar. What is the absolute pressure? (Assume that pressure at one end of the manometer is atmospheric.)
A
1 bar
B
1.6304 bar
C
0.3152 bar
D
1.3152 bar
A mercury (specific gravity = 13.6) manometer connected across an orificemeter fitted in a pipe shows a manometer reading of 2 cms. If the manometer liquid is changed to carbon tetrachloride (specific gravity = 1.6), then for the same flow rate of water the new manometer reading will be __________ cms.
A
17
B
42
C
84
D
1.8
A bed consists of particles of density 2000 kg/m
3
. If the height of the bed is 1.5 metres and its porosity 0.6, the pressure drop required to fluidise the bed by air is
A
25.61 kPa
B
11.77 kPa
C
14.86 kPa
D
21.13 kPa
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
A
4.4 KPa
B
2.94 KPa
C
3.7 KPa
D
None of these
A gas (density = 1.5 kg/m
3
, viscosity = 2 × 10
-5
kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5 kg/m
3
and viscosity of 3 × 10
-5
kg/m.s flowing at 3 m/s will be
A
8400 Pa/m
B
12600 Pa/m
C
18900 Pa/m
D
16800 Pa/m
Pressure difference between two points in vessels, pipelines or in two different pipelines can be measured by a differential manometer. The pressure difference measured as the mm of water coloumn in case of mercury-water, differential manometer is equal to (where, H = difference in height of mercury column in mm).
A
H
B
12.6 H
C
13.6 H
D
14.6 H
An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is
A
0.048
B
0.079
C
0.122
D
0.152
A pitot tube is inserted in a ventilation duct with the nose facing the air flow. A vertical U-tube manometer filled with alcohol (specific gravity 0.8) has been used for pressure measurements such that 10.2 mm is read as the total pressure and 8.8 mm as the static pressure. Given the density of air to be 1.2 kg/m
3
, the air velocity at the nose of the pitot tube in m/s is
A
4.27
B
6.53
C
3.29
D
5.67
On a clear night there is radiation from earth’s surface to space. On such a night, the water particles on the plant leaves radiate to the sky whose temperature may be taken as 200 K. The water particles receive heat by convection from the surrounding air, the convection heat transfer coefficient has a value of 30 W/m2 K. If the water should not freeze, make calculations for the air temperature
A
280.474 K
B
345.645 K
C
123.456 K
D
874.387 K