Konveksiin

Konveksiin refers to heat transfer by the bulk motion of a fluid, a process known as convection. It occurs when a fluid’s temperature differs from its surroundings, creating density differences that drive motion. Convection can be natural, driven by buoyancy forces such as warm air rising in a room or mantle convection in the Earth, or forced, where external devices like fans, pumps, or stirrers move the fluid to enhance heat transfer.

The mechanism involves a convective boundary layer near solid surfaces, with efficiency described by the convective heat transfer coefficient h and the Nusselt number Nu, which compares convective to conductive heat transfer. Governing equations include the Navier–Stokes equations for momentum and the energy equation; exact solutions are rare, so modeling relies on numerical simulation or empirical correlations. Dimensionless numbers used to analyze convection include the Rayleigh number Ra, Grashof number Gr, Prandtl number Pr, and Reynolds number Re.

Applications span multiple fields, from heating, ventilation, and air conditioning (HVAC) and electronic device cooling to industrial heat exchangers, cooking, meteorology, and oceanography. In design practice, engineers select natural, forced, or mixed convection and use correlations or computational fluid dynamics to estimate heat transfer rates. Convection often occurs alongside conduction and radiation, with its behavior depending on geometry, flow regime, and fluid properties.