## Heat And Mass Transfer Mcqs Questions MCQs

### Total Questions : 652

Page 1 of 33 pages
Question 1. Unit of thermal diffusivity is
1.     m²/hr
2.     m²/hr °C
3.     kcal/m² hr
4.     kcal/m. hr °C
Explanation :
Question 2. Thermal conductivity of water _________ with rise in temperature.
1.     Remain same
2.     Decreases
3.     Increases
4.     May increase or decrease depending upon temperature
Explanation :
Question 3. The critical radius is the insulation radius at which the resistance to heat flow is
1.     Maximum
2.     Minimum
3.     Zero
4.     None of these
Explanation :
Question 4. The automobile radiator is a heat exchanger of
1.     Parallel flow type
2.     Counter flow type
3.     Cross flow type
4.     Regenerator type
Explanation :
Question 5. The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body
1.     Move actually
2.     Do not move actually
3.     Affect the intervening medium
4.     Does not affect the intervening medium
Explanation :
Question 6. Log mean temperature difference in case of counter flow compared to parallel flow will be
1.     Same
2.     More
3.     Less
4.     Depends on other factors
Explanation :
Question 7. According to stefan's law, the total radiation from a black body per second per unit area is proportional to
1.     Absolute temperature
2.     T2
3.     T5
4.     T
Explanation :
Question 8. Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. it is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. the number of shields should be
1.     One
2.     Two
3.     Three
4.     Four
Explanation :
Question 9. Sensible heat is the heat required to
1.     Change vapour into liquid
2.     Change liquid into vapour
3.     Increase the temperature of a liquid of vapour
4.     Convert water into steam and superheat it
Explanation :
Question 10. The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as
1.     Conduction
2.     Free convection
3.     Forced convection
Explanation :
Question 11. In counter current flow heat exchanger, the logarithmic temperature difference between the fluids is ________ as compared to parallel flow heat exchanger.
1.     Same
2.     Less
3.     Greater
4.     None of these
Explanation :
Question 12. The concept of overall coefficient of heat transfer is used in case of heat transfer by
1.     Conduction
2.     Convection
4.     Conduction and convection
Explanation :
Question 13. In heat transfer, conductance equals conductivity (kcal/hr/sq.m/°c/cm) divided by
1.     Hr (time)
2.     Sq. m (area)
3.     °C (temperature)
4.     K.cal (heat)
Explanation :
Question 14. Unit of thermal diffusivity is
1.     m²/hr
2.     m²/hr °C
3.     kcal/m² hr
4.     kcal/m. hr °C
Explanation :
Question 15. The radiation emitted by a black body is known as
4.     All of these
Explanation :
Question 16. All radiations in a black body are
1.     Reflected
2.     Refracted
3.     Transmitted
4.     Absorbed
Explanation :
Question 17. Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in
1.     Electric heater
2.     Steam condenser
3.     Boiler
4.     Refrigerator condenser coils
Explanation :
Question 18. When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,
1.     α = 1, ρ = 0 and τ = 0
2.     α = 0, ρ = 1 and τ = 0
3.     α = 0, ρ = 0 and τ = 1
4.     α + ρ = 1 and τ = 0
Explanation :
Question 19. Which of the following statement is wrong?
1.     The heat transfer in liquid and gases takes place according to convection
2.     The amount of heat flow through a body is dependent upon the material of the body
3.     The thermal conductivity of solid metals increases with rise in temperature
4.     Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference