# Heat Transfer Operations Questions and Answers – Boilers – Kettle Reboiler

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This set of Heat Transfer Operations Multiple Choice Questions & Answers (MCQs) focuses on “Boilers – Kettle Reboiler”.

1. Which one of the following uses a similar type shell and tube heat exchanger with an oversized shell?
a) Flash reboiler
b) Kettle reboiler
c) Vertical Thermosyphon
d) Horizontal Thermosyphon

Explanation: The description of kettle reboiler is that it has an oversized shell with tubes in it carrying the heated fluid.

2. Kettle reboiler is also called a ___________ reboiler.
a) Thermosyphon
b) Submerged bundle
c) Internal
d) Shell and tube

Explanation: The kettle reboiler is necessarily not a shell and tube heat exchanger rather it is an oversized shell with half filled water and the tubes submerged in it.

3. The vaporisation rate in a kettle reboiler can be reached as high as _________ of the feed.
a) 80%
b) 90%
c) 70%
d) 50%

Explanation: The kettle type reboilers are suitable for vacuum operation and high vaporization rate up to about 80% of the feed.

4. Kettle type reboilers have _______ residence time.
a) High
b) Infinity
c) Low
d) Zero

Explanation: The kettle type reboilers are suitable for vacuum operation and high vaporization rate up to about 80% of the feed which in turn requires larger time for evaporation and hence the residence time is greater in kettle type reboilers.

5. Kettle reboiler is suitable for heat sensitive materials as it has low residence time.
a) True
b) False

Explanation: The kettle reboiler is not suitable for heat sensitive materials as it has higher residence time and this prolonged exposure to high temperature is not suitable.

6. In the design of Kettle reboiler given by Kern for isothermal boiling, it is assumed that the degree of sub-cooling and super-heating of the cold fluid is ___________
a) Negligible
b) Infinity
c) 100
d) 10

Explanation: The Kern method of designing reboilers considers only the saturated steam operation regime and not the super/sub-heated steam as it involves the calculation of heat gain and loss of the steam besides its latent heat of vaporisation.

7. The calculation of heat transfer coefficients in kettle type reboilers is similar to that of ______________
a) Double pipe heat exchanger
b) Shell and Tube Heat exchangers
c) Plate type heat exchanger
d) Packed bed HE

Explanation: The kettle reboiler may have an oversized shell, yet the calculations associated with it are the same as shell and tube HE.

8. Kettle reboilers have low heat transfer rate than other types as there is high liquid circulation and hence appropriate for fouling fluids.
a) True
b) False

Explanation: The kettle reboilers often have low heat transfer coefficient than other types as there is negligible liquid convection (less velocity) and hence is not appropriate for fouling/scaling fluids.

9. If the calculated hcal is greater than the maximum heat transfer co-efficient of say arbitrary value of 300 Btu/h.ft2℉ for organics and 1000 Btu/h.ft2℉ for water, then what should we do?
a) Take hcal > 300 Btu/h.ft2℉ for organics and hcal < 1000 Btu/h.ft2 ℉ for water
b) Take hcal= 300 Btu/h.ft2℉ for organics and hcal = 1000 Btu/h.ft2 ℉ for water
c) Take hcal > 300 Btu/h.ft2℉ for organics and hcal > 1000 Btu/h.ft2 ℉ for water
d) Take hcal > 300 Btu/h.ft2℉ for organics and hcal > 1000 Btu/h.ft2 ℉ for water

Explanation: The values obtained should be taken equal to it for the next few iterations, this way the calculations would converge to a particular end value.

10. In a kettle reboiler, the hot fluid is in the ______ and the solution is in the _______
a) Shell, Tube
b) Tube, Shell
c) Bed, Column
d) Column, bed

Explanation: The hot fluid which heats it is obviously kept in the tubes as it is the heating medium and the solution to be heated is kept in the shell.

11. The heat flux in kettle reboilers are _______ the forced convection reboilers.
a) More than
b) Less than
c) Equal to
d) Much less than

Explanation: The kettle type reboilers have lesser heat flux than forced convection ones as there is thorough mixing of the solution and no stagnation of solution.

12. The maximum vapor velocity uv(m/s) at the liquid surface should be less than which of the following value?
a) 0.4$$[\frac{ρ_L-ρ_v}{ρ_v}]^{1/2}$$
b) 0.2$$[\frac{ρ_L-ρ_v}{ρ_v}]^{1/2}$$
c) 0.8$$[\frac{ρ_L-ρ_v}{ρ_v}]^{1/2}$$
d) 0.2$$[\frac{ρ_L-ρ_v}{ρ_v}]^{1/8}$$

Explanation: The maximum vapor velocity uv(m/s) at the liquid surface should be less than the given value
UV < 0.2$$[\frac{ρ_L-ρ_v}{ρ_v}]^{1/2}$$

13. The shell in Kettle reboiler is commonly known as _____________
a) TEMA K-Shell
b) Shell and Tube Heat exchangers
c) TENA L-shell
d) ATEMA M-Shell

Explanation: The shell of a reboiler is commonly named as the TEMA K-shell where TEMA =Tubular Exchanger Manufacturers Association.

14. The kettle reboiler gives the flexibility to be used at _____________ pressure.
a) Low
b) Both low and high
c) High
d) Very High

Explanation: The special design of kettle reboilers of having a shell and tube type arrangement gives it the liberty to be used at both low and high pressure.

15. A reboiler can act as a _________
a) Evaporator only
b) Condenser only
c) Both evaporator and condenser
d) Heat exchanger