koudestraling

Koudestraling is a Dutch term used to describe the emission of thermal radiation by objects at low temperatures, and more generally the radiative heat loss from cold bodies. It is governed by the same physical principles as other forms of thermal radiation, but its relevance is especially noted in cryogenics, space technology and passive cooling applications.

The physical basis rests on Planck's law, which states that every object with a temperature above absolute zero emits electromagnetic radiation with a spectrum determined by that temperature. The total radiated power per unit area follows the Stefan-Boltzmann law, P = εσT^4, where ε is the emissivity and σ is the Stefan-Boltzmann constant. As temperature decreases, the peak of the emitted spectrum shifts toward longer wavelengths, mainly in the infrared and, at very low temperatures, into the far-infrared and microwave regions. Real-world surfaces have emissivities that can differ across wavelengths, influencing the efficiency of koudestraling.

Applications include cryogenic insulation for laboratory equipment, thermal control for spacecraft, and radiative cooling strategies for buildings and electronics. Radiative cooling aims to shed heat by emitting infrared radiation to the cooler surroundings or to the night sky, potentially allowing surfaces to reach temperatures below ambient under favorable conditions. In engineering practice, koudestraling is balanced with conductive and convective heat transfer and depends on factors such as emissivity, surface area, geometry, and the surrounding environment.

See also: radiative cooling, Planck's law, emissivity, Stefan-Boltzmann law.