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
Related Mcqs:
- Refractoriness under load (RUL) is the most important property for the refractory bricks_________________?
A. At the hearth bottom of the furnace on which stock is placed
B. Used for furnace insulation
C. Used in the roof of the furnace
D. None of these - High thermal conductivity of a refractory material is not important, when it is to be used in the______________________?
A. Coke oven regenerators
B. Muffle furnace
C. Blast furnace
D. Recuperators - Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of ______________ percent respectively?
A. 80 and 20
B. 20 and 80
C. 50 and 50
D. 60 and 40 - Sillimanite (Al2O3.SiO2) refractory, which is a neutral refractory, is not used in________________?
A. Pottery furnace
B. Glass melting furnace
C. Crucibles
D. Gas retorts - Thermal diffusivity of a refractory brick is high, when its ____________ is high?
A. Density
B. Specific heat
C. Thermal conductivity
D. None of these - Spalling of a refractory means its____________________?
A. Softening
B. Fracture due to uneven expansion at high temperature
C. Resistance to compressive loads
D. Resistance to chemical action of gases and molten fluxes - Refractory castables are used for__________________?
A. Producing monolithic linings
B. Patch work
C. Minimising the number of joints in the structure
D. All A., B. and C. - Fusion point of an acidic refractory material is________________?
A. Increased by the addition of basic oxides
B. Reduced by the addition of basic oxides
C. Not affected by the addition of basic oxides
D. Always more than 2500°C - To resist spalling tendency, a refractory should have________________?
A. Greater diffusivity
B. Low specific heat
C. Low thermal co-efficient of expansion
D. All A., B. and C. - Which is required in an insulating refractory ?
A. High thermal conductivity
B. Low porosity
C. Both A. and B.
D. Neither A. nor B.
