Mechanical Operations

321. The power number for a stirred tank becomes constant at high Reynolds number. In this limit, the variation of power input with impeller rotational speed (N) is proportional to

1. N°
2. N¹
3. N²
4. N³

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322. The process by which fine solids is removed from liquids is termed as

1. Decantation
2. Flocculation
3. Sedimentation
4. Classification

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323. The process opposite to 'dispersion' is termed as the

1. Flocculation
2. Sedimentation
3. Filtration
4. None of these

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324. The ratio of the actual mesh dimension of Taylor series to that of the next smaller screen is

1. 2
2. √2
3. 1.5
4. √3

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325. The ratio of the area of openings in one screen (Taylor series) to that of the openings in the next smaller screen is

1. 1.5
2. 1
3. √2
4. None of these

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326. The reduction ratio for fine grinders is

1. 44109
2. 44105
3. 20-40
4. As high as 100

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327. The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of feed and product respectively).

1. D_f/D_p
2. D_p/D_f
3. D_f - D_p
4. None of these

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328. The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size).

1. c/s
2. s/c
3. s . c
4. 1/s . c

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329. The specific cake resistance for compressible sludges is a function of the pressure drop

1. Over cake
2. Over medium
3. Overall
4. None of these

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330. The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)

1. ∝ ΔP
2. ∝ 1/ ΔP
3. ∝ √ΔP
4. Independent of ΔP

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