Which heat transfer mechanism is driven by the movement of air or liquid around the body?

• A. Conduction
• B. Convection
• C. Radiation
• D. Evaporation

Answer: (B)

Convection is heat transfer driven by the bulk movement of a fluid around the body. When air or water flows over the skin, it carries heat away (or toward the body) with the moving fluid, increasing or decreasing the temperature difference at the skin. This can happen naturally, as warmed fluid becomes less dense and rises, or it can be forced, such as by wind or a fan, which accelerates heat exchange. In contrast, conduction requires direct contact for energy transfer between surfaces, radiation moves energy via photons without a medium, and evaporation cools the body through phase change of moisture. So the mechanism tied to the movement of air or liquid around the body is convection.