Heat and mass transfer MCQs Food science

1. Which type of heat transfer occurs through direct contact between molecules?

a) Radiation
b) Convection
c) Conduction
d) Evaporation
Answer: c) Conduction

2. What is the primary mode of heat transfer in boiling?

a) Conduction
b) Convection
c) Radiation
d) Sublimation
Answer: b) Convection

3. Which process involves the transfer of heat through electromagnetic waves?

a) Conduction
b) Convection
c) Radiation
d) Condensation
Answer: c) Radiation

4. In which type of heat transfer is no medium required?

a) Conduction
b) Convection
c) Radiation
d) Condensation
Answer: c) Radiation

5. Which law governs the rate of heat conduction?

a) Newton’s Law
b) Fourier’s Law
c) Ohm’s Law
d) Pascal’s Law
Answer: b) Fourier’s Law

6. Which equation is used to describe mass transfer by diffusion?

a) Fourier’s Law
b) Fick’s Law
c) Newton’s Law
d) Kirchhoff’s Law
Answer: b) Fick’s Law

7. What is the driving force for heat transfer?

a) Concentration gradient
b) Temperature gradient
c) Pressure gradient
d) Velocity gradient
Answer: b) Temperature gradient

8. In which process does mass transfer occur due to concentration differences?

a) Conduction
b) Convection
c) Diffusion
d) Radiation
Answer: c) Diffusion

9. Which type of heat transfer is involved in the heating of food in an oven?

a) Conduction
b) Convection
c) Radiation
d) Both b and c
Answer: d) Both b and c

10. Which of the following describes the heat transfer in a heat exchanger?

a) Direct contact
b) Indirect contact
c) Radiation
d) Evaporation
Answer: b) Indirect contact

11. What is the primary mechanism of heat transfer in a steam jacketed kettle?

a) Conduction
b) Convection
c) Radiation
d) Conduction and convection
Answer: d) Conduction and convection

12. Which unit operation commonly involves mass transfer through evaporation?

a) Drying
b) Mixing
c) Grinding
d) Extrusion
Answer: a) Drying

13. In which type of mass transfer is there movement of molecules from high concentration to low concentration?

a) Convection
b) Conduction
c) Diffusion
d) Radiation
Answer: c) Diffusion

14. Which heat transfer method is dominant in the cooling of food in a refrigerator?

a) Conduction
b) Convection
c) Radiation
d) Convection and radiation
Answer: b) Convection

15. What is the effect of increasing surface area on the rate of mass transfer?

a) Decreases
b) Increases
c) No effect
d) Depends on the temperature
Answer: b) Increases

16. Which method of heat transfer involves the movement of fluid?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: b) Convection

17. What is the term for the resistance to heat flow in a material?

a) Thermal conductivity
b) Thermal resistance
c) Heat flux
d) Specific heat
Answer: b) Thermal resistance

18. Which dimensionless number is used to describe the relative importance of convective to conductive heat transfer?

a) Reynolds number
b) Nusselt number
c) Prandtl number
d) Grashof number
Answer: b) Nusselt number

19. Which dimensionless number characterizes the flow regime in mass transfer operations?

a) Sherwood number
b) Schmidt number
c) Nusselt number
d) Prandtl number
Answer: a) Sherwood number

20. Which factor does not affect the rate of heat transfer by conduction?

a) Thickness of the material
b) Thermal conductivity
c) Surface area
d) Color of the material
Answer: d) Color of the material

21. Which type of heat transfer occurs in a microwave oven?

a) Conduction
b) Convection
c) Radiation
d) Conduction and convection
Answer: c) Radiation

22. Which property measures the ability of a material to conduct heat?

a) Thermal resistance
b) Thermal conductivity
c) Specific heat
d) Heat flux
Answer: b) Thermal conductivity

23. What is the main mode of heat transfer in the cooking of food in boiling water?

a) Conduction
b) Convection
c) Radiation
d) Evaporation
Answer: b) Convection

24. Which factor does not influence mass transfer by diffusion?

a) Concentration gradient
b) Diffusion coefficient
c) Temperature
d) Pressure
Answer: d) Pressure

25. Which type of heat transfer is primarily involved in the drying of food using a hot air dryer?

a) Conduction
b) Convection
c) Radiation
d) Conduction and radiation
Answer: b) Convection

26. What is the role of the heat transfer coefficient in convective heat transfer?

a) It measures the thermal conductivity of the fluid
b) It represents the resistance to heat transfer
c) It quantifies the heat transfer rate per unit area per unit temperature difference
d) It is a measure of the fluid velocity
Answer: c) It quantifies the heat transfer rate per unit area per unit temperature difference

27. Which dimensionless number is used to describe the ratio of momentum diffusivity to thermal diffusivity?

a) Reynolds number
b) Nusselt number
c) Prandtl number
d) Grashof number
Answer: c) Prandtl number

28. In which process is mass transfer achieved by the movement of molecules due to a concentration gradient?

a) Convection
b) Conduction
c) Diffusion
d) Radiation
Answer: c) Diffusion

29. Which type of heat exchanger uses countercurrent flow to maximize heat transfer efficiency?

a) Parallel flow heat exchanger
b) Counterflow heat exchanger
c) Crossflow heat exchanger
d) Shell and tube heat exchanger
Answer: b) Counterflow heat exchanger

30. What is the term for the quantity of heat transferred per unit time?

a) Thermal conductivity
b) Heat flux
c) Heat transfer coefficient
d) Thermal resistance
Answer: b) Heat flux

31. Which process involves the transfer of heat by the bulk movement of fluid?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: b) Convection

32. Which law describes the rate of mass transfer by diffusion?

a) Newton’s Law
b) Fourier’s Law
c) Fick’s Law
d) Kirchhoff’s Law
Answer: c) Fick’s Law

33. Which parameter is used to quantify the effectiveness of a heat exchanger?

a) Heat flux
b) Overall heat transfer coefficient
c) Thermal resistance
d) Heat capacity
Answer: b) Overall heat transfer coefficient

34. What is the primary driving force for mass transfer in evaporation?

a) Temperature gradient
b) Pressure gradient
c) Concentration gradient
d) Velocity gradient
Answer: c) Concentration gradient

35. Which method of heat transfer is predominantly used in a pressure cooker?

a) Conduction
b) Convection
c) Radiation
d) Convection and conduction
Answer: d) Convection and conduction

36. What is the primary driving force for heat transfer in a heat exchanger?

a) Temperature gradient
b) Concentration gradient
c) Pressure gradient
d) Velocity gradient
Answer: a) Temperature gradient

37. Which unit operation is primarily concerned with mass transfer through a semi-permeable membrane?

a) Filtration
b) Ultrafiltration
c) Distillation
d) Evaporation
Answer: b) Ultrafiltration

38. Which factor affects the rate of heat transfer in a food drying process?

a) Temperature
b) Airflow rate
c) Relative humidity
d) All of the above
Answer: d) All of the above

39. What type of heat transfer is utilized in an electric stove for cooking food?

a) Conduction
b) Convection
c) Radiation
d) Evaporation
Answer: a) Conduction

40. Which process involves the transfer of heat through the movement of air or liquid?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: b) Convection

41. What is the main driving force for mass transfer during the drying of a food product?

a) Temperature gradient
b) Concentration gradient
c) Pressure gradient
d) Velocity gradient
Answer: b) Concentration gradient

42. Which method of heat transfer is used to maintain the temperature of food in a warming drawer?

a) Conduction
b) Convection
c) Radiation
d) Evaporation
Answer: c) Radiation

43. What effect does increasing the thickness of a material have on heat conduction?

a) Increases heat transfer
b) Decreases heat transfer
c) No effect
d) Depends on the material
Answer: b) Decreases heat transfer

44. Which parameter influences the rate of heat transfer by convection?

a) Fluid velocity
b) Surface area
c) Thermal conductivity
d) Both a and b
Answer: a) Fluid velocity

45. What is the term for the process where water is removed from a food product through heat and air?

a) Freezing
b) Evaporation
c) Dehydration
d) Boiling
Answer: c) Dehydration

46. Which method of heat transfer is primarily used in a microwave oven to heat food?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: c) Radiation

47. Which dimensionless number is used to characterize heat transfer in a laminar boundary layer?

a) Reynolds number
b) Nusselt number
c) Prandtl number
d) Sherwood number
Answer: b) Nusselt number

48. What is the primary factor that determines the rate of diffusion of gases in food processing?

a) Temperature
b) Pressure
c) Concentration gradient
d) Viscosity
Answer: c) Concentration gradient

49. Which process involves the transfer of heat through a moving fluid in a shell and tube heat exchanger?

a) Conduction
b) Convection
c) Radiation
d) Evaporation
Answer: b) Convection

50. What is the term for the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius?

a) Specific heat
b) Heat capacity
c) Thermal conductivity
d) Heat flux
Answer: a) Specific heat

51. Which unit operation uses the principle of boiling point differences for separating components in a mixture?

a) Filtration
b) Distillation
c) Centrifugation
d) Absorption
Answer: b) Distillation

52. Which heat transfer method is most effective for cooking food in a pressure cooker?

a) Conduction
b) Convection
c) Radiation
d) Convection and conduction
Answer: d) Convection and conduction

53. What is the main factor influencing the rate of heat transfer in a food processor?

a) Temperature difference
b) Material thickness
c) Fluid viscosity
d) Surface area
Answer: a) Temperature difference

54. Which of the following describes the heat transfer rate per unit area per unit temperature difference in a heat exchanger?

a) Heat flux
b) Heat transfer coefficient
c) Thermal resistance
d) Specific heat
Answer: b) Heat transfer coefficient

55. What type of heat transfer is utilized in a radiant oven?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: c) Radiation

56. Which process uses the movement of fluids to transfer heat in a heat exchanger?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: b) Convection

57. What is the primary factor affecting mass transfer during the cooling of food in a freezer?

a) Temperature gradient
b) Concentration gradient
c) Pressure gradient
d) Fluid velocity
Answer: a) Temperature gradient

58. Which property of a material affects its thermal resistance?

a) Thermal conductivity
b) Specific heat
c) Density
d) Viscosity
Answer: a) Thermal conductivity

59. Which process involves the transfer of mass due to thermal gradients in a food product?

a) Convection
b) Diffusion
c) Conduction
d) Evaporation
Answer: b) Diffusion

60. What is the main effect of increasing the airflow rate in a food drying process?

a) Increases heat transfer rate
b) Decreases mass transfer rate
c) No effect
d) Decreases heat transfer rate
Answer: a) Increases heat transfer rate

61. Which factor does not directly impact the rate of heat transfer in conduction?

a) Thermal conductivity
b) Surface area
c) Temperature difference
d) Fluid velocity
Answer: d) Fluid velocity

62. What is the effect of increasing temperature on the rate of heat transfer in convection?

a) Decreases
b) Increases
c) No effect
d) Depends on the fluid properties
Answer: b) Increases

63. Which method of heat transfer is employed in a food dehydrator?

a) Conduction
b) Convection
c) Radiation
d) Diffusion
Answer: b) Convection

64. What is the primary mode of mass transfer during the cooling of a hot beverage?

a) Convection
b) Conduction
c) Radiation
d) Diffusion
Answer: a) Convection

65. Which dimensionless number is used to characterize the relative importance of diffusion and convection in mass transfer?

a) Reynolds number
b) Nusselt number
c) Sherwood number
d) Schmidt number
Answer: d) Schmidt number

66. What is the effect of increasing the surface area on the rate of heat transfer in conduction?

a) No effect
b) Increases the rate of heat transfer
c) Decreases the rate of heat transfer
d) Depends on the material
Answer: b) Increases the rate of heat transfer

67. Which property of a fluid affects the rate of convective heat transfer?

a) Viscosity
b) Thermal conductivity
c) Density
d) Specific heat
Answer: a) Viscosity

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