What do the bubbles do in bulk boiling?

What do the bubbles do in bulk boiling?

• A. Move away from surface and do not collapse
• B. Collapse near the surface
• C. Stay attached to surface
• D. Form a continuous film

Answer: (A)

In bulk boiling, bubbles form at the heated surface but rapidly detach because buoyancy pushes the lighter vapor upward. This causes the bubbles to move away from the wall and rise through the liquid bulk, often coalescing with others as they travel toward the surface. A continuous vapor film over the surface would be film boiling, not bulk boiling, so the typical behavior is discrete bubbles that detach and rise rather than staying attached or forming a film.

In bulk boiling, bubbles form at the heated surface but rapidly detach because buoyancy pushes the lighter vapor upward. This causes the bubbles to move away from the wall and rise through the liquid bulk, often coalescing with others as they travel toward the surface. A continuous vapor film over the surface would be film boiling, not bulk boiling, so the typical behavior is discrete bubbles that detach and rise rather than staying attached or forming a film.