Which heat transfer mode is described by the equation Q = hA(T∞ - Tw)?

Which heat transfer mode is described by the equation Q = hA(T∞ - Tw)?

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

Answer: (B)

Convection heat transfer is described by Q = h A (T∞ − Tw) because heat is carried away or toward a surface by a moving fluid, and the rate depends on how effectively the fluid can transport heat (captured by the convective heat transfer coefficient h), the exposed area A, and the driving temperature difference between the fluid far from the surface (T∞) and the surface itself (Tw). If Tw is higher than T∞, heat flows from the surface into the fluid; if Tw is lower, heat flows into the surface from the fluid. This form distinguishes convection from conduction, which involves heat flow through a solid with Q = k A (T1 − T2)/L, and from radiation, which involves T^4 terms and emissivity: Q = ε σ A (T^4 − T_s^4). Evaporation involves latent heat and mass transfer rather than a simple temperature-difference-driven transfer.

Convection heat transfer is described by Q = h A (T∞ − Tw) because heat is carried away or toward a surface by a moving fluid, and the rate depends on how effectively the fluid can transport heat (captured by the convective heat transfer coefficient h), the exposed area A, and the driving temperature difference between the fluid far from the surface (T∞) and the surface itself (Tw). If Tw is higher than T∞, heat flows from the surface into the fluid; if Tw is lower, heat flows into the surface from the fluid. This form distinguishes convection from conduction, which involves heat flow through a solid with Q = k A (T1 − T2)/L, and from radiation, which involves T^4 terms and emissivity: Q = ε σ A (T^4 − T_s^4). Evaporation involves latent heat and mass transfer rather than a simple temperature-difference-driven transfer.