# Heat and Mass Transfer – Set 01

Are you guys looking for Mechanical Engineering MCQ Questions with Answers PDF Free Download as per Mechanical Engineering new exam pattern? You came to the right page. This may assist you to understand and check your knowledge about the Subjects. Students also can take a free test of the Multiple Choice Questions of Mechanical Engineering. Each question has four options followed by the right answer. These Mechanical Engineering MCQ Questions are selected supported by the newest exam pattern.

## Q1. Unit of thermal conductivity in M.K.S. units is

(A) K cal/kg m² °C
(B) K cal m/hr m² °C
(C) K cal/hr m² °C
(D) K calm/hr °C

Answer:(B) K cal m/hr m² °C

## Q2. Heat transfer in liquid and gases takes place by

(A) Conduction
(B) Convection
(D) Conduction and convection

## Q3. Temperature of steam at around 540°C can be measured by

(A) Thermometer
(B) Thermistor
(C) Thermocouple
(D) None of these

## Q4. Thermal conductivity of glass wool varies from sample to sample because of variation in

(A) Composition
(B) Density
(C) Porosity
(D) All of the above

## Q5. In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

(A) Convection
(C) Conduction
(D) Both convection and conduction

## Q6. In counter flow heat exchangers

(A) Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state
(B) Both the fluids at inlet are in their hottest state
(C) Both the fluids at exit are in their hottest state
(D) One fluid is in hottest state and other in coldest state at inlet

Answer: (B) Both the fluids at inlet are in their hottest state

## Q7. The value of the wavelength for maximum emissive power is given by

(A) Wien’s law
(B) Planck’s law
(C) Stefan’s law
(D) Fourier’s law

## Q8. The thermal diffusivities for solids are generally

(A) Less than those for gases
(B) Less than those for liquids
(C) More than those for liquids and gases
(D) More or less same as for liquids and gases

Answer: (C) More than those for liquids and gases

## Q9. The total radiation from a black body per second per unit area is __ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.

(A) Equal to
(B) Directly proportional to
(C) Inversely proportional to
(D) None of these

## Q10. Upto the critical radius of insulation,

(A) Added insulation will increase heat loss
(B) Added insulation will decrease heat loss
(C) Convective heat loss will be less than conductive heat loss
(D) Heat flux will decrease

(A) 25 mm
(B) 40 mm
(C) 160 mm
(D) 800 mm

## Q12. Thermal diffusivity is a

(A) Function of temperature
(B) Physical property of a substance
(C) Dimensionless parameter
(D) All of these

Answer: (B) Physical property of a substance

## Q13. The heat transfer takes place according to

(A) Zeroth law of thermodynamics
(B) First law of thermodynamics
(C) Second law of thermodynamics
(D) Kirchhoff’s law

Answer: (C) Second law of thermodynamics

## Q14. Thermal diffusivity of a substance is

(A) Directly proportional to the thermal conductivity
(B) Inversely proportional to density of substance
(C) Inversely proportional to specific heat
(D) All of the above

Answer: (D) All of the above

## Q15. According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the

(A) Absolute temperature
(B) Square of the absolute temperature
(C) Cube of the absolute temperature
(D) Fourth power of the absolute temperature

Answer: (D) Fourth power of the absolute temperature

## Q16. The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)

(A) Q = [2πlk (T₁ – T₂)]/2.3 log (r₂/r₁)
(B) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ – T₂)]
(C) Q = [2π (T₁ – T₂)]/2.3 lk log (r₂/r₁)
(D) Q = = 2πlk/2.3 (T₁ – T₂) log (r₂/r₁)

Answer: (A) Q = [2πlk (T₁ – T₂)]/2.3 log (r₂/r₁)

## Q17. The ratio of surface convection resistance to the internal conduction resistance is known as

(A) Grashoff number
(B) Biot number
(C) Stanton number
(D) Prandtl number

## Q18. The heat of sun reaches to us according to

(A) Conduction
(B) Convection
(D) None of these

## Q19. Depending on the radiating properties, body will be transparent when(Where a = absorptivity, p = reflectivity, x = transmissivity)

(A) P = 0, x = 0 and a = 1
(B) P=1, x = 0, and a = 0
(C) P = 0, T= 1, and a = 0
(D) X = 0, a + p = 1

Answer: (C) P = 0, T= 1, and a = 0

## Q20. The insulation ability of an insulator with the presence of moisture would

(A) Increase
(B) Decrease
(C) Remain unaffected
(D) May increase/decrease depending on temperature and thickness of insulation