Home » Mechanical Engineering » Mechanical Engineering MCQ » Heat And Mass Transfer MCQ

### 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

Static regains method

Explanation:

### 2.Thermal diffusivity is a

• AFunction of temperature
• BPhysical property of a substance
• CDimensionless parameter
• DAll of these

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

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

All of these

Explanation:

### 5.The emissive power of a body depends upon its

• ATemperature
• BWave length
• CPhysical nature
• DAll of the above

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
• DConduction and convection

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

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

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

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

Explanation:

• A0.1
• B0.3
• C0.7
• D1.7

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

All of the above

Explanation:

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

• DAll of these

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

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

Boiler furnaces

Explanation:

• AReflected
• BRefracted
• CTransmitted
• DAbsorbed

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

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

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)

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

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