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

1. 25. What is 'effectiveness' (ε) of a heat exchanger?

   • A. The ratio of actual heat transfer rate to the maximum possible heat transfer rate
   • B. The overall heat transfer coefficient
   • C. The LMTD
   • D. The fluid flow rate

2. 26. What is the 'Number of Transfer Units' (NTU) in heat exchanger design?

   • A. A dimensionless parameter indicating the size of the heat exchanger
   • B. The efficiency of the heat exchanger
   • C. The LMTD
   • D. The heat transfer rate

3. 27. What is 'radiation heat transfer'?

   • A. Transfer of energy by electromagnetic waves
   • B. Transfer of energy by direct contact
   • C. Transfer of energy by fluid motion
   • D. Transfer of energy through a vacuum

4. 28. What is the 'view factor' (F_ij) in radiation heat transfer?

   • A. A geometric factor that describes the fraction of radiation leaving surface 'i' that strikes surface 'j'
   • B. The emissivity of a surface
   • C. The temperature of a surface
   • D. The area of a surface

5. 29. What is 'thermal diffusivity' (α)?

   • A. A measure of a material's ability to conduct thermal energy relative to its ability to store thermal energy
   • B. A measure of thermal conductivity
   • C. A measure of specific heat
   • D. A measure of density

6. 30. What is the 'Biot number' (Bi)?

   • A. A dimensionless number that compares the heat transfer resistance within a body to the heat transfer resistance at the surface of the body
   • B. A dimensionless number for fluid flow
   • C. A dimensionless number for mass transfer
   • D. A dimensionless number for radiation

7. 31. What is the 'Nusselt number' (Nu)?

   • A. A dimensionless number representing the ratio of convective to conductive heat transfer across a boundary
   • B. A dimensionless number for fluid flow
   • C. A dimensionless number for mass transfer
   • D. A dimensionless number for radiation

8. 32. What is the 'Prandtl number' (Pr)?

   • A. A dimensionless number that relates momentum diffusivity to thermal diffusivity
   • B. A dimensionless number for mass transfer
   • C. A dimensionless number for fluid flow
   • D. A dimensionless number for heat conduction

9. 33. What is the 'Grashof number' (Gr)?

   • A. A dimensionless number that characterizes natural convection heat transfer
   • B. A dimensionless number for forced convection
   • C. A dimensionless number for conduction
   • D. A dimensionless number for radiation

10. 34. What is the 'critical thickness of insulation'?

    • A. The insulation thickness at which the heat loss from a pipe or sphere is maximized
    • B. The insulation thickness at which heat loss is minimized
    • C. The minimum thickness of insulation required
    • D. The maximum thickness of insulation allowed

11. 35. What is 'transient heat conduction'?

    • A. Heat conduction where the temperature within the body changes with time
    • B. Heat conduction where temperature is constant
    • C. Heat conduction in a steady state
    • D. Heat conduction without any medium

12. 36. What is 'steady-state heat conduction'?

    • A. Heat conduction where the temperature distribution within the body does not change with time
    • B. Heat conduction where temperature changes with time
    • C. Heat conduction in an unsteady state
    • D. Heat conduction with fluid motion