71
Reynold's analogy states that (where, St = Stanton number, f = friction factor)
A)
$${\text{St}} = \frac{{\text{f}}}{2}$$
B)
$${\text{St}} = \frac{{\text{f}}}{4}$$
C)
St = 4f
D)
$${\text{St}} = {{\text{f}}^{\frac{1}{2}}}$$
Answer & Solution
Answer: Option
A
72
Which is the most suitable for the concentration of foamy & frothy liquors?
A)
Agitated film evaporator
B)
Long tube vertical evaporator
C)
Open pan evaporator
D)
None of these
Answer & Solution
Answer: Option
B
73
Pick out the wrong statement.
A)
In process heat exchangers, saturated steam is preferred over the superheated steam
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 the emissive power would occur at a wavelength of 0.5 λ1
C)
When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, exhibits a maximum
D)
A body at 925 K emits an energy of 1.42 × 1011 σW/m2 (σ is the Stefan-Boltzman constant) in the wavelength band between 3 μm to 4 μm. The fraction of this energy in the total energy emitted over the entire wavelength range is equal to emissivity
Answer & Solution
Answer: Option
B
74
Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water.
A)
Boiling point (at the same pressure)
B)
Viscosity
C)
Density
D)
Thermal conductivity
Answer & Solution
Answer: Option
A
75
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is
A)
Thin walled having the value of Ao Ai /< 2
B)
Thick walled
C)
Having the value of Ao /Ai > 2
D)
Both B and C
Answer & Solution
Answer: Option
A
76
In Fourier's law, the proportionality constant is called the
A)
Heat transfer co-efficient
B)
Thermal diffusivity
C)
Thermal conductivity
D)
Stefan-Boltzman constant
Answer & Solution
Answer: Option
C
77
Which area is used in case of heat flow by conduction through a cylinder?
A)
Logarithmic mean area
B)
Arithmetic mean area
C)
Geometric mean area
D)
None of these
Answer & Solution
Answer: Option
A
78
__________ heat exchanger is used for chilling oil to be dewaxed.
A)
U-tube
B)
Double pipe
C)
Fixed tube
D)
Floating head
Answer & Solution
Answer: Option
B
79
For concentrating an aqueous solution of a material like anhydrous Na2 SO4 , whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.
A)
High pressure
B)
Vacuum
C)
Backward feed
D)
None of these
Answer & Solution
Answer: Option
B
80
The purpose of providing a 'catchall' in the vapor line of an evaporator is to
A)
Create vacuum
B)
Regulate the vapor flow
C)
Vent the non-condensible gases
D)
Arrest the entrained liquid
Answer & Solution
Answer: Option
D
