The drying time between fixed moisture content within diffusion controlled ‘falling rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid) ?

Related Mcqs:

1. The drying time between fixed moisture content within diffusion controlled ‘falling rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid) ?

   A. √T
   B. T
   C. T2
   D. T3

2. A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)) ?

   A. M(Xo – XF)
   B. M(Xo/XF)
   C. M ln(Xo/XF)
   D. MXo ln(Xo/XF)

3. A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids))_____________?

   A. M(Xo – XF)
   B. M(Xo/XF)
   C. M ln(Xo/XF)
   D. MXo ln(Xo/XF)

4. The drying time between fixed moisture contents within the ‘constant rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid) ?

   A. √T
   B. T
   C. T1.5
   D. T3

5. It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%) ?

   A. 15 min
   B. 51 min
   C. 71 min
   D. 94 min

6. Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture ?

   A. Anthracite coal
   B. Rag paper
   C. Bamboo
   D. Inorganic solids

7. Occurrence of ‘case hardening’ during drying of a high moisture solid cake _______________ the drying rate?

   A. Increases
   B. Decreases
   C. Does not affect
   D. Exponentially increases

8. A 25 cm × 25 cm × 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m × 1m × 1cm flat sheet of the same material is to be dried from one side only. Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is ____________________?

   A. 1000
   B. 1500
   C. 2000
   D. 2500

9. A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process ?

   A. Flow rate of inlet air
   B. Relative humidity of outlet air
   C. Humidity of inlet air
   D. Temperature of the solid

10. The falling rate period in the drying of a solid is characterised by__________________?

    A. Increase in rate of drying
    B. Increasing temperatures both on the surface and within the solid
    C. Decreasing temperatures
    D. None of these