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

Related Mcqs:

1. 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

2. 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

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. 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

5. 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.

6. 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

7. A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distance R from the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is ___________________?

   A. ½w2 . R2 . ρL
   B. ½w2 . δ2 . ρL
   C. ½w2 . δρL (2R + δ)
   D. ½w2 . R . ρL(R + 2δ)

8. For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid ?

   A. Kozeny-Carman equation
   B. Leva’s equation
   C. Blake-Plummer equation
   D. None of these

9. Pick out the wrong statement pertaining to the turbine agitator ?

   A. Recommended peripheral speed for the turbine agitator is 200-250 metres/minute
   B. Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow
   C. Generally, the diameter of the agitator is kept between l/3rd to l/6th of the tank diameter while
   the blade length is l/4th of agitator diameter (with central disc, it is l/8th of the agitator
   diameter)
   D. Turbine agitator should be located at a height not less than one agitator diameter length from
   the bottom. If the depth of liquid in the tank is more than twice the agitator diameter, two
   agitators should be used

10. Helical screw agitator is used for________________?

    A. Mixing highly viscous pastes
    B. Blending immiscible liquids
    C. Mixing liquids at very high temperature (> 250 °C)
    D. None of these