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) ?

Related Mcqs:

1. 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

2. About 2-3 hp, power per gallon of a thin liquid provides vigorous agitation in an agitator. ‘Power number’ in agitation is given by __________________?

   A. P. gc/n3. D2. ρ
   B. P. gc. ρ/μ2
   C. n3. D3. ρ/P. gc
   D. P. gc/n2. D2. ρ

3. 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

4. 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_________________?

   A. Np ∝ NRe
   B. Np ∝ √NRe
   C. Np → constant
   D. Np ∝ 1/NRe

5. 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

6. 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

7. During agitation of liquids, the_________________?

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

8. During agitation of liquids, power consumption during laminar flow is not proportional to the ________________?

   A. Density of the liquid
   B. Viscosity of the liquid
   C. Cube of impeller diameters
   D. Square of rotational speed

9. Which of the following is not accomplished by agitation of liquids in agitators ?

   A. Dispersing gas in liquid
   B. Blending of immiscible liquids
   C. Dispersing immiscible liquid in form of emulsion
   D. Suspending solid particles

10. Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is ________________ ?

    A. 0.5
    B. 1
    C. √2
    D. √3