Summary

Radiative heat transfer between two or more surfaces can be approximated using the total, normal emissivity. This article provides empirically determined total normal emissivities for a number of materials including metals, metal oxides, common building materials and paints.



Definitions

:Emissivity (dimensionless)
:Absorptivity of a material (dimensionless)
:A property of the normal direction

Introduction

Treatment of radiative emission can be simplified by assuming that the emissivity is spectrally independent i.e. emissivity is constant with respect to wavelength. In this case the simplified emissivity is called the directional emissivity and represents the ‘spectral average’ of emission and hence the common name of this assumption; the grey surface approximation (wavelength of radiation determines colour and the 'average' of all colours is grey).

Although the total emissivity is averaged over all wavelengths it still maintains directional dependence which is a source of complexity in radiative heat transfer calculations. However, as described in the Emissivity article and shown in the figure below, both conductors and non-conductors alike can be reasonably approximated using the emissivity in the normal direction.

In the subsequent sections the typical total, normal emissivities are listed for a range of materials.

Metals and Metallic Oxides

Total, Normal Emissivities of Metals and Metallic Oxides
Material Type Temperature Emissivity Absorptivity
AluminaFlame-sprayed -250.800.28
Aluminum Vacuum-deposited 200.0250.10
Anodized200.840.14
Hard-anodized-250.840.92
Polished200.030.09
Highly polished plate, 98.3% pure 225 - 5750.039 - 0.057-
Commercial sheet1000.09-
Rough polish1000.18-
Rough plate400.055 - 0.07-
Oxidized at 600°C200 - 6000.11 - 0.19-
Heavily oxidized 95 - 5000.20 - 0.31-
Surface roofing380.216-
Foil, As received 200.040.15
Foil, Bright dipped200.0250.10
AntimonyPolished35 - 2600.28 - 0.31-
Beryllium Typical1500.180.77
3700.21-
6000.30-
Anodized 1500.90-
3700.88-
6000.82-
BismuthBright750.34-
BrassPolished40 - 3150.096 - 0.10-
Rolled plate, natural surface 220.06-
Hard rolled plate, polished210.038-
Dull plate50 - 3500.22-
Rubbed with coarse emery220.20-
Oxidized by heating at 600°C 200 - 6000.61 - 0.59-
ChromeBlack plated200.090.87
ChromiumPolished40 - 11000.08 - 0.36-
Copper Electroplated 200.030.47
Carefully polished electrolytic copper800.018-
Polished200.030.18
1150.023-
Commercial, scraped shiny220.072-
Plate, oxidised2250.78-
Plate, heated at 600°C200 - 6000.57-
Cuprous oxide 800 - 11000.66 - 0.54-
Molten copper1075 - 12750.16 - 0.13-
Tarnished200.750.65
GoldPure, highly polished225 - 6250.018 - 0.035-
Inconel XOxidized-250.710.90
IronCast, newly turned220.435-
Cast, turned882 - 9880.60 - 0.70-
Cast, polished2000.21-
Cast, oxidised at 872 K199 - 5990.64 - 0.78-
Cast, strongly oxidised38 - 2490.95-
Electrolytic, highly polished177 - 2270.052 - 0.064-
Electrolytic, smooth oxidised227 - 5270.78 - 0.82-
Freshly emeried200.242-
Ingot, rough499 - 11990.85 - 0.89-
Ingot, rough, oxidised927 - 11170.87 - 0.95-
Molten cast iron1299 - 13990.29-
Molten mild steel 1599 - 17970.28-
Oxide499 - 11990.85 - 0.89-
Oxidised1000.736-
Plate, completely rusted200.685-
Polished427 - 10270.144 - 0.377-
Sheet, smooth899 - 10380.55 - 0.60-
Steel casting, polished771 - 10380.52 - 0.56-
Steel sheet ground938 - 10990.55 - 0.61-
Steel sheet oxidised220.657-
Steel sheet, rough oxide layer240.80-
Steel plate rough38 - 3710.94 - 0.97-
Steel oxidised at 872 K199 - 5990.79-
Wrought iron, highly polished38 - 2490.28-
Wrought, dull oxidised21 - 3600.94-
LeadPure (99.96%), unoxidized125 - 2250.057 - 0.075-
Gray oxidized250.281-
Oxidized at 150°C2000.63-
Oxidized at 200°C2000.03-
MagnesiumPolished35 - 2600.07 - 0.13-
Magnesium oxideTypical275 - 8250.55 - 0.20-
900 - 17050.20-
MercuryTypical0 - 1000.09 - 0.12-
MolybdenumPolished35 - 2600.05 - 0.08-
540 - 13700.10 - 0.18-
27500.29-
Filament727 - 25930.096 - 0.292-
MonelMetal oxidised200 - 6000.41 - 0.46-
NickelElectroplated200.030.22
Electroplated on polished iron and polished230.045-
Electroplated on pickled iron, unpolished200.11-
Polished100 - 3270.072 - 0.087-
Wire187 - 10070.096 - 0.186-
Technically pure, polished227 - 3270.07 - 0.087-
Plate, oxidised by heating to 872 K200 - 6000.37 - 0.48-
Oxide649 - 12540.59 - 0.86-
Oxide, Black plated200.080.92
Nickel AlloysChromonickel52 - 10350.64 - 0.76-
Nickelin, grey oxidised210.262-
KA-28 alloy, rough brown, after heating216 - 4900.44 - 0.36-
KA-28 alloy, after heating at 800 K216 - 5270.62 - 0.73-
NCT 3 alloy, oxidised from service216 - 5270.90 - 0.97-
NCT 6 alloy, oxidised from service271 - 5630.89 - 0.82-
PlatinumPure, polished225 - 6250.054 - 0.104-
Strip927 - 16270.12 - 0.17-
Filament27 - 13270.036 - 0.192-
Wire227 - 13270.073 - 0.182-
SilverPolished, pure227 - 6250.0198 - 0.0324-
Polished37 - 3710.0221 - 0.0312-
Stainless steelTypical polished200.600.37
Typical dull200.210.50
Type 312, heated 300 h at 260°C95 - 4250.27 - 0.32-
Type 301 with Armco black oxide-250.750.89
Type 410, heated to 700°C in air350.130.76
Type 303, sandblasted950.420.68
TantalumFilament1327 - 29990.194 - 0.31-
TinBright tinned iron sheet250.043 - 0.064-
Titanium75A95 - 4250.10 - 0.19-
75A, oxidized 300 h at 450°C35 - 4250.21 - 0.250.80
Anodized-250.730.51
TungstenFilament, aged27 - 33000.032 - 0.35-
Filament33150.39-
ZincPure, polished225 - 3250.045 - 0.053-
Oxidised by heating to 672 K3990.11-
Galvanised sheet1000.21-
Galvanized sheet iron, grey oxidised240.276-
Galvanized sheet iron, fairly bright280.228-


Other Materials

Total, Normal Emissivities of Common Materials
Material Type Temperature Emissivity Absorptivity
MaterialTypeTemperatureTotal, Normal EmittanceSolar Absorptance
Asbestos Board240.96-
Paper35 - 3700.93 - 0.94-
AsphaltTypical200.900.90
BrickRed, rough210.930.63
Silica, unglazed10020.8-
Silica, glazed, rough12020.85-
Grog, glazed12020.75-
CarbonGraphitized 100 - 3200.76 - 0.75-
Graphitized 320 - 5000.75 - 0.71-
T-carbon127 - 6270.81 - 0.79-
Candle soot 98 - 2710.952-
Graphite, pressed, filed surface 250 - 5100.98-
Lampblack-water-glass coating100 - 1830.957 - 0.952-
Lampblack, thin layer on iron plate210.927-
Lampblack, thick coat200.967-
Lampblack, 0.08 mm or thicker38 - 3710.945-
Filament1038 - 14040.526-
ConcreteTypical200.880.60
EnamelSnow white230.906-
White fused on iron190.897-
GlassSmooth220.937-
Pyrex, lead, and soda 260 - 5400.95 - 0.85-
Gypsum0.5 mm thick on blackened plate200.903-
Human SkinCaucasian200.970.62
MarbleLight grey, polished220.931-
White200.950.46
Oil Layer on polished nickel0.025 mm oil0.27-
0.050 mm oil0.46-
0.125 mm oil0.72-
Thick oil layer0.82-
Oil layer on aluminium foil1 coat of oil1000.561-
2 coats of oil1000.574-
Paint, Lacquer & VarnishAluminium paint1000.27 - 0.67-
Aluminium paint after heating to 600 K149 - 3490.35-
Aluminium lacquer210.39-
Black paint200.970.97
Parson’s optical black -250.950.975
Black shiny lacquer sprayed on iron250.875-
Black shiny shellac on tinned iron sheet210.821-
Black matt shellac77 - 1470.91-
Black lacquer38 - 930.80 - 0.95-
Black matt lacquer38 - 930.96 - 0.98-
Black silicone-25 - 7500.930.94
Black enamel paint 95 - 4250.81 - 0.80-
Black epoxy paint -250.890.95
Oil paints1000.92 - 0.96-
White lacquer38 - 930.80 - 0.95-
White Paint200.930.14
PaperPasted on tinned iron plate190.924-
Pasted on rough iron plate190.929-
Pasted on black lacquered plate190.944-
Roofing210.91-
PlasterLime, rough10 - 880.91-
PorcellainGlazed220.924-
QuartzRough, fused210.932-
Refractory materialsPoor radiators600 - 10000.65 - 0.75-
Good radiators600 - 10000.80 - 0.90-
RubberHard, glossy plate230.945-
Soft, grey, rough250.859-
SerpentinePolished230.900-
SilicaSintered, powdered, fused silica350.840.08
Silicon carbideTypical150 - 6500.83 - 0.96-
SnowTypical00.970.28
WaterTypical0 - 1000.95 - 0.963-
WoodOak, planed210.895-

Further Reading

  1. Chemical Engineering Volume 1, Sixth Edition: Fluid Flow, Heat Transfer and Mass Transfer
  2. Heat Transfer Handbook
  3. Heat Transfer A Practical Approach
  4. Radiative Heat Transfer, Third Edition