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Home » Engineering » Chemical Engineering » Aptitude Test - 12
1. Why is the negative sign introduced in the equation of Fourier's law of heat conduction? q = – kA (dT / dx)
A. because heat transfer rate is inversely proportional to temperature gradient
B. because value of thermal conductivity k is negative
C. because heat is transferred from higher temperature to lower temperature
D. because heat transfer rate is inversely proportional to temperature gradient
2.The value of thermal conductivity k depends upon
A. the material through which the heat is transferred
B. the intensity of heat energy which is being transferred
C. the area which is parallel to the heat transfer
D. the material through which the heat is transferred
3.The materials which have low thermal conductivity are called as
A. thermal conductors
B. thermal resistors
C. thermal insulators
D. thermal conductors
4.How does the radiation heat transfer occur through perfect vacuum?
A. by light waves
B. by electromagnetic waves
C. both a. and b.
D. by light waves
5.The Stefan-Boltzmann law of thermal radiation is applicable for
A. white body
B. gray body
C. black body
D. white body
6. According to the Stefan-Boltzmann law of thermal radiation for a perfect radiator, the rate of radiant energy per unit area is proportional to
A. the temperature of that radiator
B. the square of the temperature of that radiator
C. the cube of the temperature of that radiator
D. the temperature of that radiator
7. In the equation for the rate radiant heat energy from a perfect radiator q = σ A T4 the constant σ is called as
A. Black body constant
B. Radiation constant
C. Stefan-Boltzmann constant
D. Black body constant
8.What should be the temperature of black body to emit radiant energy which is independent of the conditions in the surroundings?
A. temperature of black body should be less than zero
B. temperature of black body should be more than zero
C. temperature of black body should be equal to zero
D. temperature of black body should be less than zero
9. Consider two black bodies at temperatures T1 and T2 (T1 > T2) having same surface area A, are placed in vacuum. What will be the correct formula for net rate of radiant heat transfer between these su
A. q = σ A (T1 – T2)4
B. q = σ A (T14 – T24)
C. q = σ A (T1 – T2)
D. q = σ A (T1 – T2)4
10.Gray body can emits radiation
A. at higher rate than the black body
B. at lower rate than the black body
C. at equal rate than the black body
D. at higher rate than the black body
11.What is the correct formula for the rate of heat transfer by convection form a surface of area A at temperature T to the surrounding fluid at temperature T0? Where h is convection heat transfer coeff
A. qc = h A (T – T0)4
B. qc = h A (T4 – T04)
C. qc = h A (T – T0)
D. qc = h A (T – T0)4
12.What is the mode of heat transfer from the hot surface to the adjacent layer of fluid which surrounds the surface?
A. conduction mode of heat transfer
B. radiation mode of heat transfer
C. convection mode of heat transfer
D. conduction mode of heat transfer
13.Convective heat transfer coefficient is also known as
A. film convection factor
B. film coefficient
C. film conductance
D. film convection factor
14.Suppose a hot water is placed inside a closed metal vessel of thickness 5 mm. There is atmospheric air outside the vessel at temperature lower than the temperature of hot water. The heat is transferre
A. conduction then convection
B. convection then conduction
C. convection then conduction then convection
D. conduction then convection
15.The current in the electrical system is analogous to
A. the temperature in the heat transfer system
B. the heat flow in the heat transfer system
C. the thermal conductance in the heat transfer system
D. the temperature in the heat transfer system
16.The term in the heat transfer system which is analogous to the electrical resistance is called as
A. thermal resistance
B. conductive resistance
C. potential resistance
D. thermal resistance
17.What will be the simple correct formula for the rate of heat flow (q) through a wall of surface area A and thickness of t ? The two surfaces of the wall are at temperatures T1 and T2 (T1>T2). Consider
A. q = Rh (T1 – T2)
B. q = Rh A (T1 – T2)
C. q = (T1 – T2) / Rh
D. q = Rh (T1 – T2)
18. Consider the heat is transferred through a wall of surface area A and thickness t at the rate of q, what is the thermal resistance of the system ? The thermal conductivity of the wall is k and the he
A. kA
B. 1 / kA
C. kAt
D. kA
19.The potential difference in an electrical system, is analogously considered as
A. a temperature difference in the heat transfer system
B. a current flow in the heat transfer system
C. a resistance in the heat transfer system
D. a temperature difference in the heat transfer system
20. What is the correct formula for the rate of heat transfer (q) through a plane wall of thickness l and surface are A, when temperature difference between two surfaces is ΔT ? The thermal conductivity
A. q = (k A ΔT) / l
B. q = k A l ΔT
C. q = (ΔT) / (k A l)
D. q = (k A ΔT) / l
21. The product of one even and one odd function is
A. even
B. odd
C. prime
D. even
22.Fourier transform of unit impulse at origin is
A. undefined
B. infinity
C. 1
D. undefined
23. How does the gray body differ from the black body
A. all the incident radiation is not absorbed completely by gray body
B. the emissivity of the gray body is less than unity
C. the absorptivity of the gray body is less than unity
D. all the incident radiation is not absorbed completely by gray body
24. How are the real bodies in terms of diffuseness?
A. real bodies are perfectly diffuse
B. real bodies are not perfectly diffuse
C. Both (a) and (b)
D. real bodies are perfectly diffuse
25.For the diffuse surfaces
A. the intensity of emitted radiation is constant and depends upon the direction
B. the intensity of emitted radiation is not constant and depends upon the direction
C. the intensity of emitted radiation is constant and does not depend upon the direction
D. the intensity of emitted radiation is constant and depends upon the direction
26. What is the relation between absorptivity (α), reflectivity (ρ) and transmissivity (τ) for gray body?
A. ρ + α + τ =1
B. α + τ =1
C. ρ + τ =1
D. ρ + α + τ =1
27.What is irradiation (G)?
A. the total radiation incident upon a surface per unit time per unit surface area
B. the total radiation leaving a surface per unit time per unit surface area
C. the net radiation exchanging between two surfaces per unit time per unit surface area
D. the total radiation incident upon a surface per unit time per unit surface area
28.The total radiation leaving a surface per unit time per unit surface area is called as
A. radiosity
B. irradiosity
C. irradiation
D. radiosity
29.Radiosity (J) is the sum of radiation
A. emitted, reflected and absorbed
B. emitted, reflected and transmitted
C. transmitted, reflected and absorbed
D. emitted, reflected and absorbed
30. Radiation shields are used
A. to increase radiant heat transfer
B. to decrease radiant heat transfer
C. to maintain radiant heat transfer constant
D. to increase radiant heat transfer
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