Apa itu Emisivitas?

Emisivitas adalah ukuran efisiensi di mana permukaan memancarkan energi panas. Ini didefinisikan sebagai fraksi energi yang dipancarkan relatif terhadap yang dipancarkan oleh permukaan hitam termal (benda hitam). Benda hitam adalah bahan yang merupakan penghasil energi panas sempurna dan memiliki nilai emisivitas 1. Bahan dengan nilai emisivitas 0 akan dianggap sebagai cermin termal yang sempurna.

Misalnya, jika suatu objek memiliki potensi untuk memancarkan 100 unit energi tetapi hanya memancarkan 90 unit di dunia nyata, maka objek itu akan memiliki nilai emisivitas 0,90. Di dunia nyata, tidak ada “benda hitam” yang sempurna dan sangat sedikit cermin inframerah sempurna sehingga sebagian besar objek memiliki emisivitas antara 0 dan 1.

Emissivity Table

Material	Emissivity Value
Aluminium: anodised	0.77
Aluminium: polished	0.05
Asbestos: board	0.96
Asbestos: fabric	0.78
Asbestos: paper	0.93
Asbestos: slate	0.96
Brass: highly polished	0.03
Brass: oxidized	0.61
Brick: common	0.81 – 0.86
Brick: common, red	0.93
Brick: facing, red	0.92
Brick: fireclay	0.75
Brick: masonry	0.94
Brick: red	0.90
Carbon: candle soot	0.95
Carbon: graphite, filed surface	0.98
Carbon: purified	0.80
Cement:	0.54
Charcoal: powder	0.96
Chipboard: untreated	0.90
Chromium: polished	0.10
Clay: fired	0.91
Concrete	0.92
Concrete: dry	0.95
Concrete: rough	0.92 – 0.97
Copper: polished	0.05
Copper: oxidized	0.65
Enamel: lacquer	0.90
Fabric: Hessian, green	0.88
Fabric: Hessian, uncoloured	0.87
Fibreglass	0.75
Fibre board: porous, untreated	0.85
Fibre board: hard, untreated	0.85
Filler: white	0.88
Firebrick	0.68
Food & Organic Materials	0.95 – 0.97
Formica	0.94
Galvanized Pipe	0.46
Glass	0.92
Glass: chemical ware (partly transparent)	0.97
Glass: frosted	0.96
Glass: frosted	0.70
Glass: polished plate	0.94
Granite: natural surface	0.96
Graphite: powder	0.97
Gravel	0.28
Gypsum	0.08
Hardwood: across grain	0.82
Hardwood: along grain	0.68 – 0.73
Ice	0.97
Iron: heavily rusted	0.91 – 0.96
Lacquer: bakelite	0.93
Lacquer: dull black	0.97
Lampblack	0.96
Limestone: natural surface	0.96
Mortar	0.87
Mortar: dry	0.94
P.V.C.	0.91 – 0.93
Paint: 3M, black velvet coating 9560 series optical black	@1.00
Paint: aluminium	0.45
Paint, oil: average of 16 colours	0.94
Paint: oil, black, flat	0.94
Paint: oil, black, gloss	0.92
Paint: oil, grey, flat	0.97
Paint: oil, grey, gloss	0.94
Paint: oil, various colours	0.94
Paint: plastic, black	0.95
Paint: plastic, white	0.84
Paper: black	0.90
Paper: black, dull	0.94
Paper: black, shiny	0.90
Paper: cardboard box	0.81
Paper: green	0.85
Paper: red	0.76
Paper: white	0.68
Paper: white bond	0.93
Paper: yellow	0.72
Paper: tar	0.92
Pipes: glazed	0.83
Plaster	0.86 – 0.90
Plaster: rough coat	0.91
Plasterboard: untreated	0.90
Plastic: acrylic, clear	0.94
Plastic: black	0.95
Plastic: white	0.84
Plastic paper: red	0.94
Plastic paper: white	0.84
Plexiglass: Perpex	0.86
Plywood	0.83 – 0.98
Plywood: commercial, smooth finish, dry	0.82
Plywood: untreated	0.83
Polypropylene	0.97
Porcelain: glazed	0.92
Quartz	0.93
Redwood: wrought, untreated	0.83
Redwood: unwrought, untreated	0.84
Rubber	0.95
Rubber: stopper, black	0.97
Sand	0.90
Skin, human	0.95 – 0.98
Snow	0.80
Soil: dry	0.92
Soil: frozen	0.93
Soil: saturated with water	0.95
Stainless Steel	0.59
Stainless Plate	0.34
Steel: galvanized	0.28
Steel: rolled freshly	0.24
Styrofoam: insulation	0.60
Tape: electrical, insulating, black	0.97
Tape: masking	0.92
Tile: floor, asbestos	0.94
Tile: glazed	0.94
Tin: burnished	0.05
Tin: commercial tin-plated sheet iron	0.06
Varnish: flat	0.93
Wallpaper: slight pattern, light grey	0.85
Wallpaper: slight pattern, red	0.90
Water:	0.95
Water: distilled	0.95
Water: ice, smooth	0.96
Water: frost crystals	0.98
Water: snow	0.85
Wood: planed	0.90
Wood: panelling, light finish	0.87
Wood: spruce, polished, dry	0.86