Selective radiative cooling with MgO and/or LiF layers

Patent · Fri Sep 14 00:00:00 EDT 1984

OSTI ID:5910375

Berdahl, P H

A selective radiation cooling material which is absorptive only in the 8 to 13 microns wavelength range is accomplished by placing ceramic magnesium oxide and/or polycrystalline lithium fluoride on an infrared-reflective substrate. The reflecting substrate may be a metallic coating, foil or sheet, such as aluminum, which reflects all atmospheric radiation from 0.3 to 8 microns, the magnesium oxide and lithium fluoride being nonabsorptive at those wavelengths. <10% of submicron voids in the material is permissible in which case the MgO and/or LiF layer is diffusely scattering, but still nonabsorbing, in the wavelength range of 0.3 to 8 microns. At wavelengths from 8 to 13 microns, the magnesium oxide and lithium fluoride radiate power through the ''window'' in the atmosphere, and thus remove heat from the reflecting sheet of material and the attached object to be cooled. At wavelengths longer than 13 microns, the magnesium oxide and lithium fluoride reflects the atmospheric radiation back into the atmosphere. This high reflectance is only obtained if the surface is sufficiently smooth: roughness on a scale of 1 micron is permissible but roughness on a scale of 10 microns is not. An infrared-transmitting cover or shield is mounted in spaced relationship to the material to reduce convective heat transfer. If this is utilized in direct sunlight, the infrared transmitting cover or shield should be opaque in the solar spectrum of 0.3 to 3 microns.

• DOE Contract Number: AC03-76SF00098
• Assignee: Dept. of Energy
• Application Number: ON: DE85011595
• OSTI ID: 5910375
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
RADIATIVE COOLING
INFRARED RADIATION
LAYERS
LITHIUM FLUORIDES
MAGNESIUM OXIDES
REFLECTION
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COOLING
ELECTROMAGNETIC RADIATION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
LITHIUM COMPOUNDS
LITHIUM HALIDES
MAGNESIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
420400* - Engineering- Heat Transfer &amp; Fluid Flow