Radiation heat transfer: The process of converting radiation intercepted by matter to internal thermal energy. Gray surface: A surface for which the spectral absorptivity and the e... Radiation heat transfer: The process of converting radiation intercepted by matter to internal thermal energy. Gray surface: A surface for which the spectral absorptivity and the emissivity are independent of wavelength over the spectral regions of surface irradiation and emission. Radiance: Rate of radiant energy propagation in a particular direction, per unit area normal to the direction, per unit solid angle about the direction, I (W/m2 x sr). Participating medium: Refers to a medium in which radiation absorption is a volumetric process. Thermal radiation: Electromagnetic energy emitted by matter at a finite temperature and concentrated in the spectral region from approximately 0.1 to 100 µm. Absorptivity: Fraction of the incident radiation absorbed by matter. Black body: The ideal emitter and absorber. Modifier referring to ideal behavior. Thermal radiation: The process of radiation production by matter at a finite temperature. Radiosity: Rate of radiant energy emitted by a surface in all directions per unit area of the surface, E (W/m2). Specular surface: Refers to a surface for which the angle of reflected radiation is equal to the angle of incident radiation. View factor: Defined as the fraction of the radiation leaving surface i that is intercepted by surface j. Film condensation: Occurs when a gas flows over a liquid. Boundary layer: It is developed when fluid particles make contact with the surface. Their velocity is reduced significantly relative to their fluid velocity upstream of the plate, and the velocity in most cases is assumed to be zero at the wall. The velocity of the fluid must then increase until it approaches the free stream value. Local heat transfer coefficient: The exact heat transfer coefficient at that specific point of interest. Thermal boundary layer: It is developed if the free stream and surface temperatures differ. Conservation laws: Laws of nature are embodied by the convection transfer equations. Film temperature: An approximation to the temperature of a fluid inside a convection boundary layer. It is calculated as the arithmetic mean of the temperature at the surface of the solid boundary wall and the free stream temperature. Reynolds number: It represents the ratio of the inertia to viscous forces. Prandtl number: It is the ratio of the kinematic viscosity, also referred to as the momentum diffusivity, to the thermal diffusivity. Skin friction coefficient: It is a dimensionless parameter from which the surface frictional drag may be determined. Nusselt number: It is equal to the dimensionless temperature gradient at the surface. It provides a measure of the convection heat transfer occurring at the surface. Internal flow: It is defined by moving fluids surrounded by solid surfaces. For example, water flowing inside a pipe. External flow: It is an unbounded flow that moves over bodies. Grashof number: It is a measure of the ratio of the buoyancy forces to the viscous forces acting on the fluid. Rayleigh number: It is simply the product of the Grashof and Prandtl numbers. Read more