Schmidt number and Lewis number for pure air at atmospheric conditions are respectively__________________?

Related Mcqs:

1. At 750°K and 1 atm, the approximate value of Schmidt number for air is_________________?

   A. 0.01
   B. 0.1
   C. 1
   D. 10

2. At equilibrium the concentration of water in vapour phase (C*) in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is_________________?

   A. 0.0
   B. 0.2
   C. 0.4
   D. 1.0

3. The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around_________________?

   A. 1
   B. 0.24
   C. 3.97
   D. 600

4. The Schmidt number which is defined as, μ/ρ D, is the ratio of the_____________________?

   A. Momentum diffusivity to the mass diffusivity
   B. Thermal diffusivity to the mass diffusivity
   C. Momentum diffusivity to the thermal diffusivity
   D. None of these

5. In physical terms, Schmidt number means _________________?

   A. Thermal diffusivity/mass diffusivity
   B. Thermal diffusivity/momentum diffusivity
   C. Momentum diffusivity/mass diffusivity
   D. Mass diffusivity/thermal diffusivity

6. Schmidt number is given by ___________________?

   A. μ/ρDAB
   B. Re × Pe
   C. Sh × Pe
   D. Re/Pe

7. Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (yin = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone, the number of trays required is/are ?

   A. 4
   B. 8
   C. 9
   D. 10

8. Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is_________________?

   A. Less
   B. More
   C. Same
   D. Unpredictable

9. The binary diffusivity in gases at atmospheric conditions is about ___________________?

   A. 10-9 cm/sec
   B. 10-1 cm2/sec
   C. 10-3 sec/cm
   D. 10-4 cm2/sec2

10. Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of__________________?

    A. Mass diffusivity to momentum diffusivity
    B. Thermal diffusivity to mass diffusivity
    C. Momentum diffusivity to thermal diffusivity
    D. None of these