Thermal diffusivity of a refractory brick is high, when its ______________ is high?

Related Mcqs:

1. An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture ?

   A. Cork
   B. Saw dust
   C. Sand
   D. Chemically prepared foam

2. Capacity of a refractory brick to withstand-sudden changes in temperature is denoted by the property called_________________?

   A. Spalling resistance
   B. Refractoriness
   C. Refractoriness under load (RUL)
   D. None of these

3. Addition of zircon to silica refractory brick improves its_________________?

   A. Crushing strength
   B. Resistance to slag attack
   C. Both A. and B.
   D. Neither A. nor B.

4. Maximum alumina content in high alumina refractory can be as high as ____________ percent?

   A. 30
   B. 50
   C. 70
   D. 90

5. Thermal conductivity of refractory bricks____________________?

   A. Increases with decrease in porosity
   B. Decreases with decreases in porosity
   C. Is independent of its porosity and is maximum for insulating bricks
   D. Increases with the amount of air entrapped in pores

6. High porosity refractory bricks have________________?

   A. Poor resistance to the penetration of molten slag, metal & flue gases
   B. Poor heat conductivity & low strength
   C. Better thermal spalling resistance
   D. All A., B. and C.

7. Pure aniline is evaporating through a stagnant air film of 1 mm thickness at 300 K and a total pressure of 100 KPa. The vapor pressure of aniline at 300 K is 0.1 KPa. The total molar concentration under these conditions is 40.1 mole/m3. The diffusivity of aniline in air is 0.74 × 10-5m2/s. The numerical value of mass transfer co-efficient is 7.4 × 10-3. Its units are_______________________?

   A. m/s
   B. cm/s
   C. mole/m2.s.Pa
   D. k.mole/m2.s.Pa

8. Refractories used in/for ______________ should have low thermal conductivity?

   A. Coke ovens
   B. Insulation
   C. Regenerators
   D. Muffle furnaces

9. Refractory bricks with lower permeability is produced by using _________________?

   A. Higher firing temperature
   B. Higher moulding pressure
   C. Finer grog size
   D. All A., B. and C.

10. Test piece for determination of RUL of a refractory is heated in a/an__________________?

    A. Oxidising atmosphere
    B. Reducing atmosphere
    C. Electric furnace
    D. Neutral atmosphere