Emmisivity in Passive Thermal Management
By David Alster
All devices generate waste heat as a by-product of their operation. This heat needs to be dissipated in order to avoid the generation of undesirable high temperatures and damage to the devices.
The waste heat can be dissipated from a device by one of several mechanisms
Conduction to a housing or any other larger heat-sink
Conduction to a cooling heat-transfer liquid and from there to a heat transfer unit operating thru convection or radiation
Natural or forced convection to the atmosphere As thermal infra-red radiation
The two conduction options can only serve as interim measures because they cannot store ever increasing amounts of heat and it must eventually be dissipated by convection or radiation.
When the device to be cooled or the heat-sink is located where there is no possibility of convection because there is no atmosphere – such as in a vacuum enclosure or on a satellite in space – the only available mechanism is thermal infra-red radiation.
The amount of heat which can be radiated from a surface is a direct function of the surface temperature and of the emissivity of the radiating surface.
It is in the context of the management of this passive thermal process that the extremely high emissivity of Acktar Black Coatings play a decisive roll.
In space applications radiation is especially effective because radiation is to a zero Kelvin background.