Heat Transfer (Chemical Perspective) – Multiple Choice Questions (MCQs)

1. 37. What is the 'thermal resistance' concept in heat transfer?

   • A. The opposition a material offers to the flow of heat
   • B. The rate of heat flow
   • C. The temperature difference
   • D. The area for heat transfer

2. 38. What is 'thermal contact resistance'?

   • A. Resistance to heat transfer at the interface between two solid surfaces due to imperfect contact
   • B. Resistance within a single material
   • C. Resistance due to fluid flow
   • D. Resistance due to radiation

3. 39. What is the 'log mean area' used for in heat conduction through thick-walled cylinders?

   • A. To calculate the effective heat transfer area
   • B. To calculate the volume of the cylinder
   • C. To calculate the density of the material
   • D. To calculate the mass of the cylinder

4. 40. What is 'counter-current flow' in a heat exchanger?

   • A. The hot and cold fluids flow in opposite directions
   • B. The hot and cold fluids flow in the same direction
   • C. The fluids flow perpendicular to each other
   • D. One fluid is stagnant

5. 41. What is 'parallel-current flow' (or co-current flow) in a heat exchanger?

   • A. The hot and cold fluids flow in opposite directions
   • B. The hot and cold fluids flow in the same direction
   • C. The fluids flow perpendicular to each other
   • D. One fluid is stagnant

6. 42. What is 'cross-flow' in a heat exchanger?

   • A. The hot and cold fluids flow perpendicular to each other
   • B. The hot and cold fluids flow in the same direction
   • C. The hot and cold fluids flow in opposite directions
   • D. One fluid is stagnant

7. 43. What is 'heat flux' (q'')?

   • A. The rate of heat transfer per unit area
   • B. The total rate of heat transfer
   • C. The temperature difference
   • D. The heat transfer coefficient

8. 44. What is the unit of heat flux (q'') in SI units?

   • A. W/(m·K)
   • B. J/(kg·K)
   • C. W/(m²·K)
   • D. W/m²

9. 45. What is 'thermal radiation'?

   • A. Energy emitted by matter as a result of changes in the electronic configurations of atoms or molecules
   • B. Energy transferred by molecular collisions
   • C. Energy transferred by fluid motion
   • D. Energy transferred by direct contact

10. 46. What is 'absorptivity' (α) in radiation?

    • A. The fraction of incident radiation that is absorbed by a surface
    • B. The fraction of incident radiation that is reflected
    • C. The fraction of incident radiation that is transmitted
    • D. The ability to emit radiation

11. 47. What is 'reflectivity' (ρ) in radiation?

    • A. The fraction of incident radiation that is absorbed
    • B. The fraction of incident radiation that is reflected by a surface
    • C. The fraction of incident radiation that is transmitted
    • D. The ability to emit radiation

12. 48. What is 'transmissivity' (τ) in radiation?

    • A. The fraction of incident radiation that is absorbed
    • B. The fraction of incident radiation that is reflected
    • C. The fraction of incident radiation that is transmitted through a medium
    • D. The ability to emit radiation