Which region features the heat flux reaching a local minimum and then increasing again?

Which region features the heat flux reaching a local minimum and then increasing again?

• A. Nucleate Boiling
• B. Transition Boiling
• C. Film Boiling
• D. Convective Boiling

Answer: (C)

In film boiling, a continuous layer of vapor forms between the hot surface and the liquid, acting as a highly effective insulator. This insulating film drives the heat transfer down to a local minimum because the liquid is prevented from making good contact with the surface. As the surface is heated further, the vapor film can become unstable in places and pockets of liquid can rewet the surface or bubbles burst, causing short-lived improvements in contact and a rise in heat transfer. The result is a region where the heat flux first dips to a minimum due to the stable vapor layer and then increases again as instability and rewetting events interrupt the insulation.

In film boiling, a continuous layer of vapor forms between the hot surface and the liquid, acting as a highly effective insulator. This insulating film drives the heat transfer down to a local minimum because the liquid is prevented from making good contact with the surface. As the surface is heated further, the vapor film can become unstable in places and pockets of liquid can rewet the surface or bubbles burst, causing short-lived improvements in contact and a rise in heat transfer. The result is a region where the heat flux first dips to a minimum due to the stable vapor layer and then increases again as instability and rewetting events interrupt the insulation.