In a single evaporator system, the steam economy ________________ by creating vacuum in the evaporator?

Related Mcqs:

1. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?

   A. C/E
   B. E/C
   C. CE
   D. 1/CE

2. What is the steam economy in case of a single effect evaporator system ?

   A. 1
   B. > 1
   C. < 1
   D. 0.1

3. Evaporation of 1kg of water from a solution in a single effect evaporator requires about ________________ kg of steam?

   A. 0.4 – 0.6
   B. 1-1.3
   C. 1.8-2
   D. 2 – 2.4

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

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

5. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________?

   A. Lower heat transfer area
   B. Lower steam economy
   C. Higher steam economy
   D. Higher solute concentration in the product

6. For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?

   A. 3
   B. 0.33
   C. 1
   D. 1.33

7. Steam economy in case of a triple effect evaporator will be _________________?

   A. 1
   B. < 1
   C. > 1
   D. Between 0 and 1

8. In a single effect evaporator, the economy is________________?

   A. 1
   B. < 1
   C. > 1
   D. None of these

9. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?

   A. Greater than that for un-insulated steam pipe
   B. Less than that of the un-insulated steam pipe
   C. Equal to that of the un-insulated steam pipe
   D. Less than the steam pipe with 5 cms insulation

10. Vacuum is generally maintained in the vapour space of an evaporator mainly to__________________?

    A. Get economical temperature difference by using moderate pressure steam
    B. Facilitate forward feeding in multiple effect evaporation
    C. Concentrate heat sensitive materials
    D. Achieve very high concentration of the final product