heat transfer MCQs – Page 2

Practise focused heat transfer questions with marked answers for exam preparation and subject revision.

heat transfer Mcqs
21. Thermal diffusivity is ____________________?
comments icon0

A. useful in case of heat transfer by radiation

B. a dimensionless parameter

C. a physical property of the material

D. used as mathematical model

E. function of temperature

22. Heat flows from one body to other when they have_________________?
comments icon0

A. different heat contents

B. different temperatures

C. none of the above

D. different specific heat

E. different atomic structure

23. Thermal conductivity of air with rise in temperature__________________?
comments icon0

A. remains constant

B. increases

C. may increase or decrease depending on temperature

D. decreases

E. none of the above

24. Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called__________________?
comments icon0

A. heat-transfer

B. thermal resistance

C. thermal coefficient

D. temperature gradient

E. thermal conductivity
25. Thermal conductivity of non-metallic amorphous solids with decrease in temperature __________________?
comments icon0

A. unpredictable

B. remains constant

C. decreases

D. may increase or decrease depending on temperature

E. increases

26. Thermal conductivity of water at 20C is of the order of_____________________?
comments icon0
A. 0.51

B. 0.42

C. 0.23

D. 0.64

E. 0.1

27. The concept of overall coefficient of heat transfer is used in case of heat transfer by________________?
comments icon0
A. conduction and convection

B. radiation

C. convection and radiation

D. conduction

E. convection

28. In heat transfer, conductance equals conductivity (kcal/hr/sqm/C/cm) divided by ________________?
comments icon0
A. cm (thickness)

B. kcal (heat).

C. C (temperature)

D. sqm (area)

E. hr (time)

29. Which of the following is expected to have highest thermal conductivity_______________?
comments icon0

A. boiling water

B. melting ice

C. steam

D. solid ice

E. water

30. LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is _________________?
comments icon0

A. same

B. lower

C. depends on temperature conditions

D. higher

E. depends on the area of heat exchanger

31. Metals are good conductors of heat because________________?
comments icon0

A. their atoms-are relatively far apart

B. they have high density

C. all of the above

D. their atoms collide frequently

E. they contain free electrons

32. Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in _________________?
comments icon0
A. boiler

B. electric heater

C. steam condenser

D. melting of ice

E. refrigerator condenser coils

33. Which of the following is the case of heat transfer by radiation ___________________?
comments icon0

A. heating of building

B. all of the above

C. blast furnace

D. heat received by a person from fireplace

E. cooling of parts in furnace

34. A steam pipe is to be insulated by two insulating materials put over each other . For best results__________________?
comments icon0
A. better insulation should be put over pipe and better one over it

B. inferior insulation should be put over pipe and better one over it

C. both may be put in any order

D. whether to put inferior OIL over pipe or the better one would depend on steam temperature

E. unpredictable

35. Total heat is the heat required to__________________?
comments icon0
A. convert water into steam and superheat it

B. increase the temperature of a liquid or vapour

C. change liquid into vapour

D. change vapour into liquid

E. convert saturated steam into dry steam

36. According to Prevost theory of heat exchange ___________________?
comments icon0
A. all bodies above absolute zero emit radiation

B. it is impossible to transfer heat from low temperature source to t high temperature source

C. rate of heat transfer depends on thermal conductivity and temperature difference

D. heat transfer by radiation requires no medium

E. heat transfer in most of the cases takes place by combination of conduction, convection and radiation

37. Heat transfer by radiation mainly depends upon___________________?
comments icon0

A. nature of the body

B. none of the above

C. its temperature

D. kind and extent of its surface

E. all of the above
38. Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of____________________?
comments icon0

A. 1:01

B. 1:04

C. 2:01

D. 1 : 2

E. 4:01

39. The time constant of a thermocouple is_______________?
comments icon0

A. determined by the time taken to reach 100C from 0C

B. none of the above

C. the time taken to attain 63.2% of the value of initial temperature difference

D. the time taken to attain 50% of the value of initial temperature difference

E. the time taken to attain the final temperature to be measured

40. Cork is a good insulator because it has___________________?
comments icon0
A. porous body

B. free electrons

C. low density

D. all of the above

E. atoms colliding frequency