Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
Correct answer: D. Prandtl & Grashoff
- A. Grashoff
- B. Reynolds
- C. Both 'a' & 'b'
- D. Prandtl & Grashoff
Explanation
Natural-convection transition is governed by the Rayleigh number, Ra = Gr·Pr, so both the Grashof and Prandtl numbers are involved. Option d expresses this product, although the question would be clearer if it named the Rayleigh number.
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