Radiation Heat Transfere = emissive powerG = total irradiationJ = total radiosityIn general:Opaque material:a = absorptivityr = reflectivityt = transmissivitye = emissivitya=e

lelEnergyIdeal EmitterSchematicT3> T2> T1

Radiation Heat TransferBlack Bodyabsorptivity = a=1emissivity = e=1ideal emissive power = ebGray Bodyabsorptivity < 1emissivity < 1emissive power

lelEnergySchematic

Radiation Heat TransferThermal EquilibriumView Factor: Fij = fraction of radiation from surface i intercepted by surface j.

Radiation Heat TransferNo net heat flux wallAnalog circuitFind:

Radiation Heat Transfer

Radiation Heat Transfer

Radiation Heat Transfer

Radiation Heat Transfer

Radiation Heat TransferConsider the radiation heat transfer between two infinite parallel plates.Special Case

Radiation Heat TransferConsider the radiation heat transfer between a small object and infinite surroundings.1SSpecial Case