Questions and answers for exam Preparation

MCQs

Total Questions : 2525 | Page 252 of 253 pages

Question 2511. Pick out the wrong statement ?

The condensing film co-efficient is about 3 times lower for vertical condenser as compared to the equivalent horizontal condenser for identical situat
Film co-efficient for vaporisation decreases as a result of vapor binding
In industrial practice, sub-cooling of condensate is required, when the condensate is a volatile liquid and is to be transferred for storage
Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient, which is higher

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Answer: Option D. -> Overall heat transfer co-efficient in a heat exchanger is controlled by the value of the film coefficient, which is higher
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2512. Pick out the wrong statement ?

With change in temperature, the radiant energy emitted by a black body remains unchanged
Absorptivity of a body approaches unity in case of diffuse reflection
Absorptivity of a perfectly black body is unity
Value of Stefan-Boltzmann constant is 4.876 × 10-8 KCal/m2.hr.°K4

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Answer: Option A. -> With change in temperature, the radiant energy emitted by a black body remains unchanged
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2513. Pick out the wrong statement ?

Economy of a multiple effect evaporator is not influenced by the boiling point elevation
Two identical cubes of iron and copper will have the same heat content under the same conditions of temperature
Double pipe heat exchangers are mostly used in the field of refrigeration
Finned tube heat exchangers are suitable for heating air by steam

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Answer: Option B. -> Two identical cubes of iron and copper will have the same heat content under the same conditions of temperature
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2514. Pick out the correct statement ?

Higher is the temperature of the radiating body, higher is the wavelength of radiation
Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder
The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature
Solid angle subtended by the finite surface at the radiating element is called the angle of incidence

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Answer: Option B. -> Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2515. Choose the correct equation ?

Nu = (Re) (Pr) (Gz)
Nu = (Re) (Pr) (St)
Nu = (Re) (Pr)
Nu = (Pr) (St)

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Answer: Option B. -> Nu = (Re) (Pr) (St)
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2516. Pick out the wrong statement ?

‘Solvates’ are chemical compounds formed by solute with their solvents. When water is the solvent, then it is called a ‘hydrate’
In heat exchanger calculations (Δt) weighted is used in place of Δt, when it involves more than one sequence of heating or cooling i.e., desuperheat
Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted
In case of short tube vertical evaporators, area of central downtake is about 50 to 100% of the total tube cross-sectional area

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Answer: Option C. -> Heat transfer co-efficient during nucleate boiling is not influenced by the agitation imparted
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2517. Pick out the wrong statement?

Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection
The ratio NNu/NRe . Npr is called the Stanton number
The Peclet number is a measure of the ratio of energy transport by convection to that by conduction
The Colburn jH factor for heat transfer is given by Nst Npr

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Answer: Option D. -> The Colburn jH factor for heat transfer is given by Nst Npr
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2518. Pick out the wrong statement?

In process heat exchangers, saturated steam is preferred over the superheated steam
The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1. If the surface temperature is halved, the maximum in
When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, e
A body at 925 K emits an energy of 1.42 x 1011ζW/m2 (ζ is the Stefan-Boltzmann constant) in the wavelength band between 3 μm to 4 μm. The fraction

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Answer: Option B. -> The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1. If the surface temperature is halved, the maximum in
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2519. Pick out the correct equation ?

jH = (St)(Pr)2/3 = f/2
jH = (St)(Pr)1/3 = f/2
jH = (St)2/3(Pr) = f/2
jH = (St)1/3(Pr) = f/2

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Answer: Option A. -> jH = (St)(Pr)2/3 = f/2
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 2520. Pick out the wrong statement?

Bubble size increases with the dynamic viscosity of the liquid in case of nucleate pool boiling
Thermal conductivity of a dry material is more than that of the damp material
Ratio of its capacity to economy equals the steam consumption in kg/hr in an evaporator
Vaporisation of organic substances in evaporator mostly causes foam formation

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Answer: Option B. -> Thermal conductivity of a dry material is more than that of the damp material
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!