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

1. 181. 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

2. 182. 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

3. 183. 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

4. 184. 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

5. 185. For an opaque surface, what is the relationship between absorptivity, reflectivity, and transmissivity?

   • A. α + ρ + τ = 1
   • B. α + ρ = 1 (since τ = 0)
   • C. α + τ = 1
   • D. ρ + τ = 1

6. 186. What is 'thermal boundary layer'?

   • A. A thin region adjacent to a solid surface in a fluid flow where temperature gradients are significant
   • B. A region of uniform temperature
   • C. A region of stagnant fluid
   • D. A region of high velocity

7. 187. What is 'hydrodynamic boundary layer'?

   • A. A thin region adjacent to a solid surface in a fluid flow where velocity gradients are significant
   • B. A region of uniform velocity
   • C. A region of constant temperature
   • D. A region of high heat transfer

8. 188. What is the relationship between the thermal and hydrodynamic boundary layers?

   • A. The relative thickness depends on the Prandtl number
   • B. They are always of equal thickness
   • C. They are unrelated
   • D. One is always thicker than the other

9. 189. What is the 'critical heat flux' (CHF) in boiling?

   • A. The maximum heat flux that can be achieved in nucleate boiling before film boiling occurs
   • B. The minimum heat flux for boiling
   • C. The heat flux at which boiling stops
   • D. The heat flux for condensation

10. 190. What is 'quenching'?

    • A. Rapid cooling of a material
    • B. Rapid heating of a material
    • C. Slowing down heat transfer
    • D. Insulating a material

11. 191. What is 'regenerator' heat exchanger?

    • A. A heat exchanger where the same flow passages are alternately heated by a hot fluid and then cooled by a cold fluid
    • B. A heat exchanger where fluids flow continuously
    • C. A heat exchanger for boiling
    • D. A heat exchanger for condensation

12. 192. What is the 'overall energy balance' for a heat exchanger at steady state?

    • A. Rate of heat gained by cold fluid = Rate of heat lost by hot fluid
    • B. Rate of heat gained by hot fluid = Rate of heat lost by cold fluid
    • C. Heat input = Heat output + Work done
    • D. Mass input = Mass output