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Heat Transfer Operations Mcqs

Q:

We can apply LMTD only when?
(i) There is no change in Specific heats
(ii) Overall heat transfer coefficient is constant
(iii) No heat loss
(iv) No pressure drop

A) (ii)(iii)(iv) B) (i)(ii)(iii)
C) (ii)(iii) D) (i)(ii)(iv)
 
Answer & Explanation Answer: B) (i)(ii)(iii)

Explanation: The LMTD has limitations on its applicability which usually are no change in specific heats overall heat transfer coefficient is constant and no heat loss, but it is totally independent on the pressure drop that takes place in the equipment.

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777
Q:

At minimum fluidisation with gas flow, which one of the following is correct?

A) All the particles are in fluidisation with random movement B) The particles at the top of the bed are floating in random movement
C) The particles are stable and not moving D) Half or partial quantity of the solids are in random movement
 
Answer & Explanation Answer: D) Half or partial quantity of the solids are in random movement

Explanation: When fluidisation is reached in gas-solid fluidised bed, the terminal velocity for smaller and lesser density particles is reached earlier which makes them free in the tube. Hence we usually observe fluidisation at the point when half or partial quantity of the solids are in random movement.

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518
Q:

Which of the following statements are incorrect about Baffles in a Shell and Tube HE?

A) Baffles provide mechanical support to the tubes and help them to be in position B) Baffles streamline the motion of the fluid in Shell side and hence decreases the turbulence
C) The most common type of baffle is segmental baffles D) Baffles increase the overall heat transfer coefficient on the shell side
 
Answer & Explanation Answer: B) Baffles streamline the motion of the fluid in Shell side and hence decreases the turbulence

Explanation: One of the important tasks of a baffle is to increase the turbulence on the shell side so that forced convective effect successfully plays its role and increase the overall heat transfer coefficient. It also holds the tubes in their position as well to provide them with mechanical support.

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282
Q:

At fluidisation, the temperature of the bed is _______

A) Constant but non-uniform B) Same for fluid and particles
C) Non uniform D) Increasing from the bottom
 
Answer & Explanation Answer: B) Same for fluid and particles

Explanation: At fluidisation we observe high grade of mixing as the pellets are then behaving as fluids, hence the temperature of the total bed reaches a constant final value.

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242
Q:

In the double pipe setup of the condenser, the refrigerant flows in the ___________

A) Shell B) Annulus
C) Inner Tube D) Jacket
 
Answer & Explanation Answer: B) Annulus

Explanation: The refrigerant having lesser pressure drop is always considered to be kept at the annulus side of the double pipe setup and in the tube side of as Shell-and-tube type setup.

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204
Q:

Shell and tube HE as well as baffle designs are made by strictly following the standards of______

A) TERA B) AESA
C) TEMA D) AISA
 
Answer & Explanation Answer: C) TEMA

Explanation: The design for baffles of a shell and tube heat exchangers are strictly made by following the standards of the Tubular Exchanger Manufacturers Association (TEMA).

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191
Q:

Which one of the following working model is best suited for fluidized bed combustion boilers?

A) Bubbling fluidized beds B) Laminar film fluidised bed
C) Pneumatic conveying regime D) Moving bed (Dense flow)
 
Answer & Explanation Answer: A) Bubbling fluidized beds

Explanation: As the question suggests, fluidized bed combustion boilers commonly use bubbling fluidized beds or turbulent regime to manage the fly ash properly and to have an economic model for long term use.

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161
Q:

In a ___________ heat exchanger, both fluids flow alternatively through the same flow passages, and hence heat transfer is intermittent.

A) Shell and Tube B) Fluidised Bed
C) Storage Type D) Cross Flow Type
 
Answer & Explanation Answer: C) Storage Type

Explanation: In a Storage Type Heat Exchanger, the heat energy from the hot fluid is first stored in the matrix/wall of the heat exchanger. Wherein, cooling of the hot fluid takes place. As the cold fluid passes through this same matrix later, the stored heat energy in the matrix is transferred to the cold fluid. This intermittent flow pattern of hot fluid and cold fluid is an exclusive property of Storage Type HE.

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