Chemical Heat Transfer Mcqs - Set 3

1)   Corrosiveness of steam condensate is due to the presence of________________?

a. CO2
b. Dissolved O2
c. Both A. & B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Both A. & B.

Explanation:
No explanation is available for this question!


2)   Solid angle subtended by the finite surface at the radiating element is_________________?

a. Called the view factor
b. Called the angle of vision
c. Proportional to the square of the distance between surfaces
d. Expressed in terms of radians
Answer  Explanation 

ANSWER: Called the angle of vision

Explanation:
No explanation is available for this question!


3)   A sphere of radius ‘R1’ is enclosed in a sphere of radius ‘R2’. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is ________________?

a. 0
b. R2/(R1+R2)
c. 1
d. (R1/R2)2
Answer  Explanation 

ANSWER: R2/(R1+R2)

Explanation:
No explanation is available for this question!


4)   One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to________________?

a. Heat the water from 0°C to 100°C
b. Evaporate the water
c. To superheat the steam
d. Data insufficient, can’t be predicted
Answer  Explanation 

ANSWER: Evaporate the water

Explanation:
No explanation is available for this question!


5)   The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?

a. Re.Gz
b. Nu, Pr
c. Nu, Pr, Re
d. Nu, Gz
Answer  Explanation 

ANSWER: Nu, Gz

Explanation:
No explanation is available for this question!


6)   In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate?

a. Geometric
b. Arithmetic
c. Logarithmic
d. Either A., B. or C.
Answer  Explanation 

ANSWER: Logarithmic

Explanation:
No explanation is available for this question!


7)   The absorptivity of a grey body at a given temperature _____________ with increasing wavelength of radiation?

a. Increases
b. Decreases
c. Remain constant
d. May increase or decrease; depends on the material
Answer  Explanation 

ANSWER: May increase or decrease; depends on the material

Explanation:
No explanation is available for this question!


8)   Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?

a. Long vertical evaporator
b. Horizontal tube evaporator
c. Agitated film evaporator
d. Calandria vertical tube evaporator
Answer  Explanation 

ANSWER: Agitated film evaporator

Explanation:
No explanation is available for this question!


9)   Which of the following has the lowest overall heat transfer co-efficient ?

a. Dowtherm
b. Molten sodium
c. Water
d. Air
Answer  Explanation 

ANSWER: Air

Explanation:
No explanation is available for this question!


10)   Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?

a. Heat transfer co-efficient are high
b. There is no risk of contamination
c. There is no mist formation
d. Cost of equipment is lower
Answer  Explanation 

ANSWER: There is no risk of contamination

Explanation:
No explanation is available for this question!


11)   Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?

a. 0.2
b. 0.4
c. 0.6
d. 0.8
Answer  Explanation 

ANSWER: 0.6

Explanation:
No explanation is available for this question!


12)   The actual temperature drop across the heating surface of an evaporator depends on the_______________?

a. Liquid depth over the heating surface
b. Solution being evaporated
c. Pressure difference between the steam chest and the vapor space above the boiling liquid
d. All A., B. and C.
Answer  Explanation 

ANSWER: All A., B. and C.

Explanation:
No explanation is available for this question!


13)   jH factor for heat transfer depends upon the ____________ number?

a. Biot
b. Nusselt
c. Reynolds
d. Prandtl
Answer  Explanation 

ANSWER: Reynolds

Explanation:
No explanation is available for this question!


14)   A perfect black body is a perfect _____________ of radiation?

a. Absorber
b. Emitter
c. Both A. & B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Both A. & B.

Explanation:
No explanation is available for this question!


15)   The absorptivity of a body is equal to its emissivity _________________?

a. At a particular temperature
b. For circular bodies
c. Under thermal equilibrium
d. None of these
Answer  Explanation 

ANSWER: Under thermal equilibrium

Explanation:
No explanation is available for this question!


16)   The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is__________________?

a. 165.4
b. 167.5
c. 172.5
d. 175
Answer  Explanation 

ANSWER: 165.4

Explanation:
No explanation is available for this question!


17)   If heat transfer rate varies with the time, it is termed as__________________?

a. Forced convection
b. Steady state conduction
c. Monochromatic radiation
d. None of these
Answer  Explanation 

ANSWER: None of these

Explanation:
No explanation is available for this question!


18)   _____________ heat exchanger is used for chilling oil to be dewaxed?

a. U-tube
b. Double pipe
c. Fixed tube
d. Floating head
Answer  Explanation 

ANSWER: Double pipe

Explanation:
No explanation is available for this question!


19)   It is not preferable to use superheated steam in evaporators, because of its very_________________?

a. High temperature
b. High pressure
c. Low film co-efficient
d. None of these
Answer  Explanation 

ANSWER: Low film co-efficient

Explanation:
No explanation is available for this question!


20)   A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of__________________?

a. 2
b. 20.8
c. 20.2
d. 20.5
Answer  Explanation 

ANSWER: 20.8

Explanation:
No explanation is available for this question!


21)   At constant temperature, the thermal conductivities of gases _____________ with rise in pressure?

a. Decrease
b. Increase
c. Remain unchanged
d. May increase or decrease; depends on the pressure
Answer  Explanation 

ANSWER: Decrease

Explanation:
No explanation is available for this question!


22)   When warm and cold liquids are mixed, the heat transfer is mainly by_______________?

a. Conduction
b. Convection
c. Radiation
d. Both A. & C.
Answer  Explanation 

ANSWER: Convection

Explanation:
No explanation is available for this question!


23)   Open pan evaporators are preferred to be used, when the solution to be concentrated is_________________?

a. Scaling
b. Highly viscous
c. Corrosive
d. Salty
Answer  Explanation 

ANSWER: Highly viscous

Explanation:
No explanation is available for this question!


24)   The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to ______________ analogy?

a. Von-Karman
b. Reynolds
c. Colburn
d. Prandtl
Answer  Explanation 

ANSWER: Prandtl

Explanation:
No explanation is available for this question!


25)   The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?

a. Lower tube side pressure drop
b. Lower shell side pressure drop
c. Higher tube side heat transfer co-efficient
d. Higher shell side heat transfer co-efficient
Answer  Explanation 

ANSWER: Higher tube side heat transfer co-efficient

Explanation:
No explanation is available for this question!


26)   Vent pipes are provided in a condenser to ________________?

a. Remove non-condensable gases
b. Purge the condenser
c. Facilitate easy cleaning of tubes
d. None of these
Answer  Explanation 

ANSWER: Remove non-condensable gases

Explanation:
No explanation is available for this question!


27)   LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?

a. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)
b. Outlet temperature of both the hot and cold fluid are same
c. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid
d. None of these
Answer  Explanation 

ANSWER: Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

Explanation:
No explanation is available for this question!


28)   Steam trap is used to_________________?

a. Condense the steam flowing in the pipeline
b. Remove water resulting from partial condensation of steam
c. Stop the supply of steam
d. None of these
Answer  Explanation 

ANSWER: Remove water resulting from partial condensation of steam

Explanation:
No explanation is available for this question!


29)   Planck’s distribution law is valid for _____________ bodies?

a. Black
b. White
c. Coloured
d. All A., B. & C.
Answer  Explanation 

ANSWER: Coloured

Explanation:
No explanation is available for this question!


30)   In a shell and tube heat exchanger, square pitch compared to triangular pitch__________________?

a. Gives a higher shell side pressure drop
b. Gives a lower shell side pressure drop
c. Can pack more surface area into a shell of given diameter
d. None of these
Answer  Explanation 

ANSWER: Gives a higher shell side pressure drop

Explanation:
No explanation is available for this question!