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GATE 2024 Chemical Engineering, Q27 · Heat Transfer

The correct answers are B. The thickness of the momentum boundary layer is much smaller than that of the thermal boundary layer.; D. The momentum diffusivity is much smaller than the thermal diffusivity..

Question

If the Prandtl number Pr = 0.01, which of the following statements is/are correct?

  • A. The momentum diffusivity is much larger than the thermal diffusivity.
  • B. The thickness of the momentum boundary layer is much smaller than that of the thermal boundary layer.
  • C. The thickness of the momentum boundary layer is much larger than that of the thermal boundary layer.
  • D. The momentum diffusivity is much smaller than the thermal diffusivity.

Official answer: B. The thickness of the momentum boundary layer is much smaller than that of the thermal boundary layer.; D. The momentum diffusivity is much smaller than the thermal diffusivity.

Why

GATE 2024 official key: (B, D). Pr =ν/α=0.01≪1= ν/α = 0.01 \ll 1 means momentum diffusivity νν is much smaller than thermal diffusivity αα (D true, A false), and correspondingly the momentum boundary layer is much thinner than the thermal boundary layer (B true, C false).

Explanation cross-checked for consistency. Final answer matches the official IIT answer key.

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