Heat and Mass Transfer Interview Questions and Answers PDF

Heat and Mass Transfer Interview Questions and Answers PDF

1. Pick up the wrong case. Heat flowing from one side to other depends directly on
(a) face area
(b) time
(c) thickness
(d) temperature difference
(e) thermal conductivity.

Answer:C
2. Metals are good conductors of heat because
(a) their atoms collide frequently
(b) their atoms-are relatively far apart
(c) they contain free electrons
(d) they have high density
(e) all of the above.

Answer:A
3. The time constant of a thermocouple is
(a) the time is taken to attain the final temperature to be measured
(b) the time is taken to attain 50% of the value of initial temperature difference
(c) the time is taken to attain 63.2% of the value of initial temperature difference
(d) determined by the time taken to reach 100°C from 0°C
(e) none of the above.

Answer:C
4. Thermal conductivity of air with rising in temperature
(a) increases
(b) decreases
(c) remains constant
(d) may increase or decrease depending on temperature
(e) none of the above.

Answer:A
5. Heat flows from one body to other when they have
(a) different heat contents
(b) different specific heat
(c) different atomic structure
(d) different temperatures
(e) none of the above.

Answer:D
6. The concept of overall coefficient of heat transfer is used in heat transfer problems of
(a) conduction
(b) convection
(c) radiation
(d) all the three combined
(e) conduction and comte_ction.

Answer:E
7. In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by
(a) hr (time)
(b) sqm (area)
(c) °C (temperature)
(d) cm (thickness)
(e) kcal (heat).

Answer:D
8. Which of the following is a case of steady-state heat transfer
(a) I.C. engine
(b) air preheaters
(c) heating of building in winter
(d) all of the above
(e) none of the above.

Answer:E
9. Total heat is the heat required for
(a) change vapour into liquid
(b) change liquid into vapour
(c) increase the temperature of a liquid or vapour
(d) convert water into steam and superheat it
(e) convert saturated steam into dry steam.

Answer:D
10. Cork is a good insulator because it has
(a) free electrons
(b) atoms colliding frequency
(c) low density
(d) porous body
(e) all of the above.

Answer:D
11. Thermal conductivity of water in general with rising in temperature
(a) increases
(b) decreases
(c) remains constant
(d) may increase or decrease depending on temperature
(e) none of the above.

Answer:D
12. Thermal conductivity of water at 20°C is of the order of
(a) 0.1
(b) 0.23
(c) 0.42
(d) 0.51
(e) 0.64.

Answer:D
13. Temperature of steam at around 540°C can be measured by
(a) thermometer
(b) radiation pyrometer
(c) thermistor
(d) thermocouple
(e) thermopile.

Answer:D
14. Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of
(a) 0.002
(b) 0.02
(c) 0.01
(d) 0.1
(e) 0.5.

Answer:B
15. The amount of heat flow through a body by conduction is
(a) directly proportional to the surface area of the body
(b) directly proportional to the temperature difference between the two faces of the body
(c) dependent upon the material of the body
(d) inversely proportional to the thickness of the body
(e) all of the above.

Answer:E
16. Which of the following has the least value of conductivity
(a) glass
(b) water
(c) plastic
(d) rubber
(e) air.

Answer:E
17. Which of the following is expected to have highest thermal conductivity
(a) steam
(b) solid ice
(c) melting ice
(d) water
(e) boiling water.

Answer:B
18. Heat transfer by radiation mainly depends upon
(a) its temperature
(b) nature of the body
(c) kind and extent of its surface
(d) all of the above
(e) none of the above.

Answer:D
19. Thermal diffusivity is
(a) a dimensionless parameter
(b) a function of temperature
(c) used as the mathematical model
(d) a physical property of the material
(e) useful in case of heat transfer by radiation.

Answer:D
20. Unit of thermal conductivity in M.K.S. units is
(a) kcal/kg m2 °C
(b) kcal-m/hr m2 °C
(c) kcal/hr m2 °C
(d) kcal-m/hr °C
(e) kcal-m/m2 °C.

Answer:B
21. Unit of thermal conductivity in S.I. units is
(a) J/m2 sec
(b) J/m °K sec
(c) W/m °K
(d) (a) and (c) above
(e) (b) and (c) above.

Answer:E
22. Thermal conductivity of solid metals with rising in temperature normally
(a) increases
(b) decreases
(c) remains constant
(d) may increase or decrease depending on temperature
(e) unpredictable.

Answer:B
23. Thermal conductivity of non-metallic amorphous solids with decrease in temperature
(a) increases
(b) decreases
(c) remains constant
(d) may increase or decrease depending on temperature
(e) unpredictable.

Answer:B
24. Heat transfer takes place as per –
(a) zeroth law of thermodynamics
(b) first law of thermodynamics
(c) the second law of the thermodynamics
(d) Kirchoff’s law (e) Stefan’s law.

Answer:C
25. By the actual speed of the heated particles, heat is transmitted from one particle of the body to the other, it is referred to as heat transfer by
(a) conduction
(b) convection
(c) radiation
(d) conduction and convection
(e) convection and radiation.

Answer:A

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