For a turbine agitated and baffled tank, operating at low Reynold’s number (based on impeller diameter), the power number (Np) varies with NRe as_________________?

Related Mcqs:

1. Height of liquid in agitation tank is normally maintained equal to the tank diameter. However, if the tank is too tall and a large liquid hold up is desired, then two or more impellers mounted on the same shaft may be used. The clearance between the tank bottom and the bottom most impeller should be about (where, D = impeller diameter) ?

   A. 0.5 D
   B. D
   C. 1.5 D
   D. 2 D

2. At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied: Po = ρ/ρN3 D5: Power number Re = ρ N D2/μ: Reynold’s number N is the impeller rotational speed, and D is the impeller diameter ?

   A. Po ∝ Re-1.0
   B. Po ∝ Re0.0
   C. Po ∝ Re0.5
   D. Po ∝ Re1.0

3. 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___________________?

   A. N°
   B. N1
   C. N2
   D. N3

4. Highly viscous liquids & pastes are agitated by________________?

   A. Propellers
   B. Turbine agitators
   C. Multiple blade paddles
   D. None of these

5. For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter D. as_________________?

   A. d
   B. √d
   C. d2
   D. 1/d

6. Equivalent diameter of a particle is the diameter of the sphere having the same __________________?

   A. Ratio of surface to volume as the actual volume
   B. Ratio of volume to surface as the particle
   C. Volume as the particle
   D. None of these

7. Sauter mean diameter is the same as the ______________ mean diameter?

   A. Mass
   B. Arithmetic
   C. Volume-surface
   D. Geometric

8. Power consumption during turbulent flow in agitation tank is proportional to the ______________ of the liquid?

   A. Viscosity
   B. Thermal conductivity
   C. Surface tension
   D. Density

9. Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is________________?

   A. > 10
   B. < 10
   C. > 100
   D. < 100

10. Which of the following equations is Rittinger’s crushing law? (Where P = power required by the machine, m = feed rate, k = a constant, D̅ sa & D̅ sb = volume surface mean diameter of feed & product respectively) ?

    A. P/m = K/ √Dp
    B. P/m = K . ln D̅ sa/D̅ sb
    C. P/m = K . (1/ D̅ sb – 1/D̅ sa)
    D. None of these