Multiple choice question for engineering
Set 1
1. Radiation heat transfer is characterized by
a) Due to bulk fluid motion, there is transport of energy
b) Thermal energy transfer as vibrational energy in the lattice structure of the material
c) Movement of discrete packets of energy as electromagnetic waves
d) There is circulation of fluid by buoyancy effects
Answer
Answer: c [Reason:] EM waves is characterized by radiant heat transfer.
2. Which is true regarding radiation?
a) Radiation travels only in medium
b) Radiation travels without any medium
c) Radiation travels in medium but sometimes without medium
d) Radiation travels in medium or without medium
Answer
Answer: d [Reason:] It is true that radiation travels in medium or without medium.
3. Radiation exchange occurs in
a) Solid
b) Vacuum
c) Liquid
d) Gas
Answer
Answer: b [Reason:] It occurs more effectively only in vacuum.
4. Energy released by a radiating surface is not continuous but is in the form of successive and separate packets of energy called
a) Photons
b) Protons
c) Electrons
d) Neutrons
Answer
Answer: a [Reason:] The photons are propagated through space as rays.
5. The electromagnetic waves are emitted as a result of
(i) Vibrational movement
(ii) Rotational movement
(iii)Atomic or sub-atomic particles comprising the matter
Identify the correct statement
a) 1 and 2
b) 2 and 3
c) 1 and 3
d) 1, 2 and 3
Answer
Answer: d [Reason:] The emission occurs when the body is excited by an oscillating electrical signal.
6. Thermal radiations occur in the portion of electromagnetic spectrum between the wavelengths
a) 10 -2 to 10 -4 micron
b) 10 -1 to 10 -2 micron
c) 0.1 to 10 2 micron
d) 10 -2 micron onwards
Answer
Answer: c [Reason:] The radiation waves propagates with the speed of light, and their wavelength ranges from 0.1 to 100 micron meter.
7. A perfectly black body
a) Absorbs all the incident radiation
b) Allow all the incident radiation to pass through it
c) Reflects all the incident radiation
d) Has its surface coated with lamp black or graphite
Answer
Answer: a [Reason:] A black body is a perfect emitter and absorber.
8. What is the wavelength band for cosmic rays?
a) Up to 45 * 10 -7 micron meter
b) Up to 23 * 10 -7 micron meter
c) Up to 19 * 10 -7 micron meter
d) Up to 4 * 10 -7 micron meter
Answer
Answer: d [Reason:] This is its maximum wavelength.
9. For a prescribed wavelength a black body radiates how much energy at the temperature of body?
a) Maximum
b) Minimum
c) 20%
d) 50%
Answer
Answer: a [Reason:] A black body neither reflects nor transmits any amount of incident radiations.
10. “Radiation emitted by a black surface is a function of wavelength and temperature but is independent of direction”. Choose the correct answer
a) True
b) False
Answer
Answer: a [Reason:] The black body is a diffused emitter.
Set 2
1. Boiling refers to a change from the
a) Solid to a liquid phase
b) Vapor to a liquid phase
c) Liquid to a solid phase
d) Liquid to a vapor phase
Answer
Answer: d [Reason:] Boiling is a convective heat transfer process that is associated with change in the phase of a fluid.
2. The boiling process has wide-spread applications in
(i) Production of steam in nuclear and steam power plants for generation and for industrial processes and space heating
(ii) Absorption of heat in refrigeration and air-conditioning systems
(iii) Concentration, dehydration and drying of foods and materials
Identify the correct statements
a) 1 and 2
b) 2 and 3
c) 1, 2 and 3
d) 1 and 3
Answer
Answer: c [Reason:] Boiling constitutes the convective heat transfer process that involves a phase change from liquid to vapor state.
3. Maximum heat transfer rate in a modern boiler is about
a) 2 * 10 5 W/m2
b) 3 * 10 5 W/m2
c) 4 * 10 5 W/m2
d) 5 * 10 5 W/m2
Answer
Answer: a [Reason:] Greater importance has recently been given to the boiling heat transfer.
4. Which type of boiling occurs in steam boilers employing natural convection?
a) Forced convection
b) Pool
c) Local
d) Saturated
Answer
Answer: b [Reason:] The liquid above the hot surface is essentially stagnant and the only motion near the surface is because of free convection.
5. In which type of boiling the fluid motion is induced by external means?
a) Pool
b) Local
c) Forced convection
d) Subcooled
Answer
Answer: c [Reason:] The liquid is pumped and forced across the surface in a controlled manner.
6. The temperature of the liquid is below the saturation temperature and boiling takes place only in vicinity of the heated surface. This type of boiling is known as
a) Subcooled
b) Forces
c) Saturated
d) Pool
Answer
Answer: a [Reason:] The vapor bubbles travel a short path and then vanish, apparently they condense in the bulk of the liquid which is at a temperature less than the boiling point.
7. In which type of boiling the temperature of the liquid exceeds the saturation temperature?
a) Forced
b) Saturated
c) Pool
d) Saturated
Answer
Answer: d [Reason:] The vapor bubbles generated at the solid surface are transported through the liquid by buoyancy effects and eventually escape from the surface.
8. The phenomenon of stable film boiling is referred to as
a) Nucleate effect
b) Boiling regimes
c) Leiden frost effect
d) Von karma effect
Answer
Answer: c [Reason:] This is the region of stable film boiling.
9. For water evaporating at atmospheric pressure, the burnout occurs at temperature excess slightly above
a) 25 K
b) 55 K
c) 75 K
d) 105 K
Answer
Answer: b [Reason:] The burnout point on the boiling curve represents the point of maximum heat flux at which transition occurs from nucleate to film boiling.
10. The boiling phenomenon is known to occur in how many forms?
a) 1
b) 2
c) 3
d) 4
Answer
Answer: d [Reason:] Pool, forced convection, subcooled and saturated boiling.
Set 3
1. The bubble diameter at the time of detachment from the surface can be worked out from the relation proposed by
a) Stanton
b) Fritz
c) Fourier
d) Nusselt
Answer
Answer: b [Reason:] It is given by Fritz, an American scientist.
2. The nucleate pool boiling is influenced by the following factors
(i) Pressure
(ii) Liquid properties
(iii) Material
Identify the correct statements
a) 1, 2 and 3
b) 2 only
c) 1 and 2
d) 2 and 3
Answer
Answer: a [Reason:] It depends on pressure, material and liquid properties.
3. Consider the following phenomena
(i) Boiling
(ii) Free convection in air
(iii) Forced convection in air
(iv) Conduction in air
Identify the correct sequence (heat transfer coefficient)
a) 3 – 4 – 1 – 2
b) 4 – 1 – 3 – 2
c) 4 – 3 – 2 – 1
d) 4 – 2 – 3 – 1
Answer
Answer: d [Reason:] Heat transfer coefficient is maximum for conduction in air and is least for boiling.
4. The bubble diameter at the time of detachment from the surface can be worked out from the relation proposed by Fritz and is given by
a) C d β [2 σ/g (p t – p v)].
b) C d β [2 σ/g (p t – p v)] 3/2
c) C d β [2 σ/g (p t – p v)] 1/2
d) C d β [2 σ/g (p t – p v)] 5/2
Where, β is the angle of contact
Answer
Answer: c [Reason:] The constant C d has the value 0.0148 for water bubbles.
5. In spite of large heat transfer coefficient in boiling liquids, fins are used advantageously when the entire surface is exposed to
a) Film boiling
b) Transition boiling
c) Nucleate boiling
d) All modes of boiling
Answer
Answer: d [Reason:] Here all modes of boiling i.e. film, transition and nucleate are of great importance.
6. With increase in excess temperature, the heat flux in boiling
a) Increases continuously
b) Decreases and then increases
c) Decreases, then increases and again decreases
d) Increases, then decreases and again increases
Answer
Answer: d [Reason:] It first increases to 50% then decreases not to zero and again increases to its maximum value.
7. The excess temperature range 50 degree Celsius < d t < 200 degree Celsius is indicative of the region of
a) Interface evaporation
b) Nuclear boiling
c) Partial film boiling
d) Stable film boiling
Answer
Answer: c [Reason:] The physical phenomenon of pool boiling is generally divided into four different regions based on the excess temperature.
8. Heat flux increases with temperature excess beyond the Leiden-frost point due to
a) Radiation effect becomes predominant
b) Occurrence of subcooled boiling
c) Vapor space become large
d) Promotion of nucleate boiling
Answer
Answer: a [Reason:] Heat flux increases with temperature excess beyond the Leiden-frost point due to radiation effect becomes predominant.
9. Leiden-frost expansion is related to
a) Condensation of vapor on a cold surface
b) Exchange of heat between two solids
c) Evaporation of a solution
d) Boiling of liquid on a hot surface
Answer
Answer: d [Reason:] It is related to boiling of liquid on a hot surface.
10. Consider the following statements regarding nucleate boiling
(i) The temperature of the surface is greater than the saturation temperature of the liquid
(ii) Bubbles are created by the expansion of entrapped gas oil vapor at small cavities in the surface
(iii) The temperature is greater than that in film boiling
(iv) The heat transfer from the surface to the liquid is greater than that in the film boiling
Which of these statements are correct?
a) 1 and 3
b) 1, 2 and 4
c) 2, 3 and 4
d) 1, 2 and 3
Answer
Answer: b [Reason:] The temperature must be less than that in film boiling.
Set 4
1. If there are n variables in a dimensionally homogeneous equation and if these variables contain m primary dimensions, then the variables can be grouped into how many non-dimensional parameters?
a) m
b) n-m
c) n-2m
d) n
Answer
Answer: b [Reason:] The non-dimensional groups are called pi-terms. If there are n variables in a dimensionally homogenous equation and if these variables contain m primary dimensions, then the variables can be grouped into (n – m) non dimensional parameters.
2. Which of the following is not known as core group?
a) Time
b) Geometric property
c) Fluid property
d) Flow characteristics
Answer
Answer: a [Reason:] These are also known as repeated variables.
3. What is the dimension of resistance?
a) M L T 2
b) M L T
c) M L T -2
d) M L T -1
Answer
Answer: c [Reason:] Unit of resistance is N. Resistance is the stopping effect exerted by one material thing to another.
4. The resistance R experienced by a partially submerged body depends upon the velocity V, length of the body l, viscosity of the fluid µ, density of the fluid p and gravitational acceleration g. Establish a relation between involving non-dimensional groups
a) R = p V l 2 function [p V l/ µ, V/ (lg) 1/2].
b) R = p l 2 function [p V l/ µ, V/ (lg) 1/2].
c) R = V 2 l 2 function [p V l/ µ, V/ (lg) 1/2].
d) R = p V 2 l function [p V l/ µ, V/ (lg) 1/2].
Answer
Answer: d [Reason:] This can be solved by Buckingham pi theorem.
5. If there are 6 physical quantities and 3 fundamental units, then the number of pi terms are
a) 1
b) 2
c) 3
d) 4
Answer
Answer: c [Reason:] It should be 6-3 = 3.
6. The study of predicting prototype conditions from model observations is known as
a) Similitude
b) Geometrical similarity
c) Prototype
d) Model
Answer
Answer: a [Reason:] It prescribes the relationship between a full scale flow and a flow involving smaller but geometrically similar boundaries.
7. S.I unit of heat is
a) J
b) W
c) J s
d) W/K
Answer
Answer: a [Reason:] Its unit is Joule. Heat is a form of energy that can be transferred between two objects.
8. S.I unit of coefficient of volumetric expansion is
a) Degree
b) Per meter
c) Per second
d) Per degree
Answer
Answer: d [Reason:] Its unit is per degree. Coefficient of volumetric expansion is defined as increase in volume.
9. S.I unit of specific heat is
a) K kg/J
b) kg/K
c) k J/kg K
d) J/K
Answer
Answer: c [Reason:] Its unit is k J/kg K. It is another physical property of matter. All the matter has a temperature associated with it.
10. S.I unit of dynamic viscosity is
a) kg/m
b) kg/m s
c) m/kg
d) m s /kg
Answer
Answer: b [Reason:] Its unit is kg/m s. It is the kinematic viscosity per unit density.
Set 5
1. Some examples of heat exchanger are
(i) Condensers and evaporators in refrigeration units
(ii) Evaporator of an ice plant and milk chiller of a pasteurizing plant
(iii) Automobile radiators and oil coolers of heat engines
Identify the correct answer
a) 1 only
b) 2 and 3
c) 1, 2 and 3
d) 1 and 2
Answer
Answer: c [Reason:] All are the examples of heat exchanger.
2. Heat exchangers are classified into how many categories?
a) 1
b) 2
c) 3
d) 4
Answer
Answer: d [Reason:] Nature of heat exchange process, relative direction of motion of fluid, mechanical design of heat exchange surface and physical state of heat exchanging fluids.
3. Based upon the nature of heat exchange process, the heat exchangers are classified into how many categories
a) 1
b) 2
c) 3
d) 4
Answer
Answer: c [Reason:] Direct contact, regenerators and recuperators.
4. The energy transfer between the hot fluid and cold fluids is brought about by their complete physical mixing in
a) Direct contact heat exchanger
b) Regenerators
c) Recuperators
d) Boilers
Answer
Answer: a [Reason:] In this type of heat exchanger, there is simultaneous transfer of heat and mass.
5. Which type of flow arrangement is this?
a) Counter flow
b) Parallel flow
c) Regenerator
d) Shell and tube
Answer
Answer: b [Reason:] In this type of arrangement, the fluids enter the unit from the same side, flow in the same direction and leave from the same side.
6. Which of the following is not an example of recuperators type heat exchanger?
a) Automobile radiators
b) Condensers
c) Chemical factories
d) Oil heaters for an aero plane
Answer
Answer: c [Reason:] Recuperators are not used in chemical factories.
7. In how many categories heat exchangers are classified on the basis of direction of flow of fluids?
a) 4 categories
b) 3 categories
c) 2 categories
d) 1 categories
Answer
Answer: b [Reason:] Parallel, counter and cross flow.
8. In how many categories heat exchangers are classified on the basis of mechanical design of heat exchanger surface?
a) 2
b) 4
c) 1
d) 3
Answer
Answer: d [Reason:] Concentric tubes, shell and tube and multiple shell.
9. In how many categories heat exchangers are classified on the basis of physical state of heat exchanging fluids?
a) 1
b) 2
c) 3
d) 4
Answer
Answer: b [Reason:] Condenser and evaporator.
10. Many types of heat exchangers have been developed to meet the widely varying applications. Based upon their
(i) Operating principle
(ii) Arrangement of flow path
(iii) Design
Identify the correct statements
a) 1, 2 and 3
b) 1 and 2
c) 2 and 3
d) 1 and 3
Answer
Answer: a [Reason:] Heat exchanger is a process equipment designed for the effective transfer of heat energy between two fluids.
