Heat Transfer
Thermal transport mechanism involving the movement of gas or liquid within an enclosed sensor housing affects the thermal resistance of internal components. Internal cavity convection occurs when temperature gradients create density differences in the fluid, leading to buoyancy-driven circulation. Movement of heat via this mechanism determines the steady-state temperature of internal electronics.
Thermal Equilibrium
Movement of heat via fluid circulation is often less efficient than conduction through a solid substrate. In small volumes, the fluid may remain stagnant if the Rayleigh number does not exceed a critical threshold. Once circulation begins, the internal cavity convection redistributes energy from hot spots to the cooler walls of the enclosure.
Airflow Boundary
Physical geometry of the cavity determines the pattern and speed of the fluid movement. Narrow gaps or complex internal structures can inhibit the formation of convection cells. Surface roughness and the orientation of the device relative to gravity also play roles in determining the cooling rate.
Boundary layer effects near the walls further restrict the volume available for active internal cavity convection.
Package Design
Engineers model these effects to prevent localized overheating in high-density electronics. Manufacturers use computational fluid dynamics to predict these patterns before physical prototyping begins.
