Heat & Mass Transfer Chemical Engineering MCQ - Set 30 - ObjectiveBooks

Heat & Mass Transfer Chemical Engineering MCQ - Set 30

Practice Test: Question Set - 30

1. Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low
    (A) Hardness
    (B) Dissolved solids content
    (C) Suspended solids content
    (D) All (a), (b) and(c)

2. In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate.
    (A) Increases
    (B) Decreases
    (C) Does not affect
    (D) May increase or decrease, depends on the type of baffle

3. __________ paint has the maximum absorption coefficient.
    (A) Black
    (B) Yellow
    (C) White
    (D) Grey

4. The advantage of backward feed multiple effect evaporators over forward feed units is that
    (A) Heat sensitive material can be handled
    (B) There is no additional cost of pumping
    (C) Most concentrated liquid is at highest temperature
    (D) Equal heat transfer co-efficients exist in various effects

5. Baffles are provided in heat exchangers to increase the
    (A) Fouling factor
    (B) Heat transfer area
    (C) Heat transfer co-efficient
    (D) Heat transfer rate

6. Film boiling is usually not desired in commercial equipments, because
    (A) The heat transfer rate is low in view of the large temperature drop
    (B) It is difficult to maintain
    (C) It is not economic
    (D) None of these

7. Pick out the wrong statement.
    (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient
    (B) In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles
    (C) S.I. unit of fouling factor is Watt/m2.°K
    (D) Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

8. A dephlegmator is a
    (A) Total condenser
    (B) Vacuum evaporator
    (C) Partial condenser
    (D) Double pipe heat exchanger

9. Prandtl and Reynold's analogies are identical for Prandtl number value of
    (A) 0
    (B) 0.5
    (C) 1
    (D) 5

10. Reynold's analogy states that (where, St = Stanton number f = friction factor)
    (A) St = f/2
    (B) St = f/4
    (C) St = 4f
    (D) St = f1/2

11. The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti - T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by
    (A) q = [2π k (Ti + T0)/2]/ln (ri/r0)
    (B) q = 2π ri k (Ti - T0)/(r0/ri)
    (C) q = 2π k (Ti - T0)/(r0/ri)
    (D) q = 2π k (Ti - T0)/[(r0 + ri)/2]

12. Heat transfer by natural convection is enhanced in system with
    (A) High viscosity
    (B) High co-efficient of thermal expansion
    (C) Low temperature gradients
    (D) Low density change with temperature

13. If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will
    (A) Increase by 1.8 times
    (B) Decrease by 22
    (C) Increase by 216
    (D) Remain unchanged

14. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical?
    (A) 1
    (B) < 1
    (C) > 1
    (D) None of these

15. A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number.
    (A) Condensation
    (B) Grashoff
    (C) Stanton
    (D) Brinkman

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