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Heat And Mass Transfer MCQ

Heat And Mass Transfer MCQ Question and Answer

1.The most commonly used method for the design of duct size is the

  • AVelocity reduction method
  • BEqual friction method
  • CStatic regains method
  • DDual or double method
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Correct Answer : (C)

Static regains method

Explanation:

2.Thermal diffusivity is a

  • AFunction of temperature
  • BPhysical property of a substance
  • CDimensionless parameter
  • DAll of these
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Correct Answer : (B)

Physical property of a substance

Explanation:

3.Film coefficient is defined as Inside diameter of tube

  • AEquivalent thickness of film
  • BThermal conductivity Equivalent thickness of film Specific heat × Viscosity
  • CThermal conductivity Molecular diffusivity of momentum Thermal diffusivity
  • DFilm coefficient × Inside diameter Thermal conductivity
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Correct Answer : (B)

Thermal conductivity Equivalent thickness of film Specific heat × Viscosity

Explanation:

4.The amount of radiation mainly depends upon the

  • ANature of the body
  • BTemperature of the body
  • CType of surface of the body
  • DAll of these
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Correct Answer : (D)

All of these

Explanation:

5.The emissive power of a body depends upon its

  • ATemperature
  • BWave length
  • CPhysical nature
  • DAll of the above
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Correct Answer : (D)

All of the above

Explanation:

6.When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by

  • AConduction
  • BConvection
  • CRadiation
  • DConduction and convection
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Correct Answer : (A)

Conduction

Explanation:

7.Sensible heat is the heat required to

  • AChange vapour into liquid
  • BChange liquid into vapour
  • CIncrease the temperature of a liquid of vapour
  • DConvert water into steam and superheat it
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Correct Answer : (C)

Increase the temperature of a liquid of vapour

Explanation:

8.Total heat is the heat required to

  • AChange vapour into liquid
  • BChange liquid into vapour
  • CIncrease the temperature of a liquid or vapour
  • DConvert water into steam and superheat it
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Correct Answer : (D)

Convert water into steam and superheat it

Explanation:

9.A steam pipe is to be insulated by two insulating materials put over each other. For best results

  • ABetter insulation should be put over pipe and better one over it
  • BInferior insulation should be put over pipe and better one over it
  • CBoth may be put in any order
  • DBoth may be put in any order
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Correct Answer : (A)

Better insulation should be put over pipe and better one over it

Explanation:

10.The value of Prandtl number for air is about

  • A0.1
  • B0.3
  • C0.7
  • D1.7
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Correct Answer : (C)

0.7

Explanation:

11.The amount of heat flow through a body by conduction is

  • ADirectly proportional to the surface area of the body
  • BDirectly proportional to the temperature difference on the two faces of the body
  • CDependent upon the material of the body
  • DAll of the above
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Correct Answer : (D)

All of the above

Explanation:

12.The radiation emitted by a black body is known as

  • ABlack radiation
  • BFull radiation
  • CTotal radiation
  • DAll of these
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Correct Answer : (D)

All of these

Explanation:

13.Heat is transferred by all three modes of transfer, viz. conduction, convection and radiation in

  • AElectric heater
  • BSteam condenser
  • CBoiler
  • DRefrigerator condenser coils
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Correct Answer : (C)

Boiler

Explanation:

14.The heat is transferred by conduction, convection and radiation in

  • AMelting of ice
  • BBoiler furnaces
  • CCondensation of steam in condenser
  • DNone of these
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Correct Answer : (B)

Boiler furnaces

Explanation:

15.All radiations in a black body are

  • AReflected
  • BRefracted
  • CTransmitted
  • DAbsorbed
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Correct Answer : (D)

Absorbed

Explanation:

16.Depending on the radiating properties, a body will be black when (Where a = absorptivity, p = reflectivity, X = transmissivity.)

  • AP = 0, x = 0 and a = 1
  • BP= 1, T = 0 and a = 0
  • CP = 0, x = 1 and a = 0
  • DX = 0, a + p = 0
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Correct Answer : (A)

P = 0, x = 0 and a = 1

Explanation:

17.Total emissivity of polished silver compared to black body is

  • ASame
  • BHigher
  • CMore or less same
  • DVery much lower
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Correct Answer : (D)

Very much lower

Explanation:

18.A composite slab has two layers of different materials with thermal conductivities k₁ and k₂. If each layer has the same thickness, then the equivalent thermal conductivity of the slab will be

  • Ak₁ k₂
  • B(k₁ + k₂)
  • C(k₁ + k₂)/ k₁ k₂
  • D2 k₁ k₂/ (k₁ + k₂)
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Correct Answer : (D)

2 k₁ k₂/ (k₁ + k₂)

Explanation:

19.According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

  • APb = pa – pv
  • BPb = pa + pv
  • CPb = pa × pv
  • DPb = pa/pv
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Correct Answer : (B)

Pb = pa + pv

Explanation:

20.Conduction is a process of heat transfer

  • AFrom one particle of the body to another without the actual motion of the particles
  • BFrom one particle of the body to another by the actual motion of the heated particles
  • CFrom a hot body to a cold body, in a straight line, without affecting the intervening medium
  • DNone of the above
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Correct Answer : (A)

From one particle of the body to another without the actual motion of the particles

Explanation: