# Biochemical Engineering - Agitation and Aeration

### Exercise :: Agitation and Aeration - Section 1

31.

Power number is ratio of

 A. imposed forced to intertial force B. bouyant force to inertial force C. gravitation force to inertial force D. imposed force to gravitational force

Explanation:

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32.

The volume of liquid (VL) in a cylindrical reactor can be calculated from the liquid height (HL) and tank diameter (Dt) using the following equation

 A. VL = 4/3 x π x HL x Dt3/8 B. VL= HL x π x Dt2/4 C. VL= HL x π x Dt2 D. VL = 4 x π x Dt2

Explanation:

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33.

The average fractional gas hold up (H) can be given as (where Zf and Zl are the level of aerated and clear liquid respectively)

 A. H = (Zf-Zl)/Zf B. H = Zf/Zl C. H = Zf/ZfZl D. H =(Zf+Zl)/Zf

Explanation:

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34.

Which of the following(s) is/are non-mechanically agitated reactors?

 A. Stirrer tank reactor B. Bubble column C. Air lift reactor D. Both (b) and (c)

Explanation:

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35.

Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions?

 A. Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor B. Crystals and precipitates are thoroughly broken down, so as to ensure easy separation of the solids from the mother liquor C. Both (a) and (b) D. Axial flow impellers provide low shear, energy efficient mixing conditions