1498. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

Total heat transfer area of all the effects is -less than that in a single effect evaporator system
Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect
Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system
Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system
✅ The correct answer is option B.

1500. In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred

Through a metallic wall
By direct contact of hot flue gas with air
By heating an intermediate material (like chequor bricks) and then heating the air from this hot material
None of these
✅ The correct answer is option C.