HEAT AND MASS TRANSFER MCQ

 

SECTION-3

 
Q61. ‘The total emissive power for any body at a given temperature is equal to its absorptivity multiplied by the total emissive power of a perfect black body at the same temperature’— this statement is known as

(a) Wien’s law 
(b) Planck’s law 
(c) Kirchhoff’s law 
(d) Stefan Boltzman law. 

Ans:(c) Kirchhoff’s law
 

 

Q62. The ratio of total emissive power of a body to the total emissive power of a black body is called

(a) absorptivity 
(b) reflectivity 
(c) transmissivity 
(d) emissivity. 

Ans:(d) emissivity.
 

 

Q63. If the ratio of emission of a body to that of a black body at a given temperature is constant for all wavelengths, the body is called

(a) black body 
(b) grey body 
(c) white body 
(d) opaque body.

Ans:(b) grey body
 

 

Q64. The heat transfer, from one particle of a fluid to another by the actual motion (which is caused by the difference in density due to temperature) of the particle known as

(a) forced convection 
(b) free convection 
(c) artificial convection 
(d) none of the above.

Ans:(b) free convection
 

 

Q65.The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be,  the interface temperature at the end of the 2nd layer would be

(a) 700°C 
(b) 680°C 
(c) 500°C 
(d) 360°C. 

Ans:(d) 360°C.
 

 

Q66. The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be, the temperature at the outer surface of the wall would be

(a) 700°C 
(b) 680°C 
(c) 40°C 
(d) 360°C. 

Ans:(c) 40°C
 

Q67. Choose the correct statement

(a) The film heat transfer co-efficient is property of the fluid. 
(b) The thermal conductivity is not a property of material. 
(c) A body which is black in colour is called black body. 
(d) A body which reflects all radiations is called white body.

Ans:(d) A body which reflects all radiations is called white body.
 

 
Q68. The vapour compression refrigerators are based on the principle that fluids absorb heat while changing from a

(a) vapour phase to liquid phase and give up heat in changing from a liquid phase to vapour phase 
(b) liquid phase to vapour phase and give up heat in changing from a vapour phase to liquid phase 
(c) vapour phase to liquid phase only 
(d) none of the above.

Ans: (b) liquid phase to vapour phase and give up heat in changing from a vapour phase to liquid phase
 

 

Q69. The difference between vapour compression and vapour absorption refrigeration cycle is that

(a) absorption cycle requires more work input 
(b) absorption cycle requires less work input 
(c) vapour compression cycle requires a pump 
(d) none of the above.

Ans:(b) absorption cycle requires less work input
 

 

Q70. The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be

(a) 700°C 
(b) 680°C 
(c) 500°C 
(d) 360°C.

Ans:(c) 500°C
 

 

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Read More Sections of Heat Transfer and Mass Transfer

Each section contains maximum 80 Questions. To practice more questions visit other sections.
 

Heat and Mass Transfer, RAC  MCQ – Section-1

 
Heat and Mass Transfer, RAC  MCQ – Section-2

 
Heat and Mass Transfer, RAC  MCQ – Section-3

 

Heat and Mass Transfer, RAC  MCQ – Section-4

 


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