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Why does CONVECTION have HIGHER heat transfer rates than pure conduction for the same temperature difference?
A{'text': 'It does not', 'label': 'A'}
B{'text': 'Bulk fluid motion brings fresh (cooler) fluid to the hot surface, maintaining a large temperature gradient near the wall — effectively replacing slow molecular diffusion with rapid macroscopic transport', 'label': 'B'}
C{'text': 'Conduction is impossible', 'label': 'C'}
D{'text': 'Radiation contributes', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'Bulk fluid motion brings fresh (cooler) fluid to the hot surface, maintaining a large temperature gradient near the wall — effectively replacing slow molecular diffusion with rapid macroscopic transport', 'label': 'B'}
In pure conduction across stagnant fluid, the gradient flattens as time progresses — slowing heat transfer. Convection continuously refreshes fluid at the wall, sustaining the gradient. Forced convection h is 1-2 orders higher than equivalent conduction-only h.
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