Mechanical Operations

91. During agitation of liquids, the

1. Froude number is independent for the curves between power number and Reynolds number in baffled system
2. Power number becomes independent of impellers Reynolds number at high Reynolds number, but is dependent on the geometry of the impeller
3. Froude number is used to account for the effect of surface (e.g., the centre vortex) on the power number
4. All (A), (B) and (C)

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92. During filtration operation, the filtrate encounters the resistance of the

1. Filter medium
2. Cake
3. Channel carrying the slurry to the upstream side of the cake and filtrate away from the filter medium
4. All (A), (B) and (C)

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93. During size reduction by a jaw crusher, the energy consumed decreases with the

1. Decreasing size of product at constant size of feed
2. Decreasing machine capacity
3. Increasing size of feed at constant reduction ratio
4. None of these

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94. During the washing of cake

1. All the resistances are constant
2. Filter medium resistance increases
3. Filter medium resistance decreases
4. Cake resistance decreases

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95. During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration

1. At time zero
2. At the end of filtration
3. When half the filtrate has been obtained
4. At the end of filtration, but decreases with time subsequently

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96. Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively.

1. 200°C and 5 atm
2. 1000°C and 10 atm
3. 500°C and 50 atm
4. 1000°C and 500 atm

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97. Dust laden air can be purified using a

1. Cyclone separator
2. Bag filter
3. Gravity settler
4. Tubular centrifuge

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98. Energy consumed for crushing one ton of material ranges from _________ kWh.

1. 0.01 to 0.1
2. 0.5 to 1.5
3. 2 to 3.5
4. 4 to 5

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99. Energy consumption in a crusher decreases with increase in the

1. Size of the product (at constant feed size)
2. Capacity of the crushing machine
3. Size of feed (at constant reduction ratio)
4. All (A), (B) & (C)

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100. Energy requirement (per unit mass of material crushed/ground) is highest for

1. Jaw crusher
2. Rod mill
3. Ball mill
4. Fluid energy mill

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