English | Korean

Emissivity

The emissivity of a material (usually written ε or e) is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. A true black body would have an ε = 1 while any real object would have ε < 1. Emissivity is a dimensionless quantity.

Emissivity table

Metal

Item Smooth Rough corrosion
Aluminum 0.04 0.05 0.11~0.19
Brass 0.03 0.06 ~ 0.2 0.6
Copper 0.02 - 0.57
Gold 0.2 ~ 0.4 - -
Iron 0.13 ~ 0.3 0.25~0.45 0.8~0.95
Lead 0.06~0.08 - 0.63
Nickel 0.04~0.09 - 0.37~0.48
Silver 0.02~0.4 - -
Tin 0.04~0.07 - -
Zinc 0.04~0.05 - 0.11
Yellow calcite 0.23 - 0.23

Nonmetal

Name of article Emissivity
Asbestos 0.93~0.96
Brick 0.75~0.93
Carbon 0.93~0.97
Glass (soft) 0.94
Plaster 0.9
Marble 0.93
Oak 0.9
Paper 0.92~00.94
Lime 0.91
Ceramic 0.92~0.93
Crystal (coarse side) 0.93
Roofing paper 0.91
Rubber 0.86~0.95
Water 0.95~0.96

Paint Emissivity shown in rough figures depends on the surfaces.

Name of article Emissivity
Black lacquer
White lacquer 0.8~0.95
Enamel 0.85~0.91
Oil paint 0.92~0.96
Aluminum paint 0.27~0.67
Varnish 0.89~0.93

Applications

Infrared rays Industry Deterioration diagnosis Electricity, machinery, electronics, buildings and civil engineering
Energy Heat transfer, radiant heat, heat insulation property and test
Non-destructive test Wholesomeness evaluation and structural analysis
Process monitoring Quality control & monitoring
Safety/Environment Fire Fire watch, firefighting & rescue and analysis of source
Gas detection Inspection of contamination and leak
Quarantine Airport inspection
Medicine Body diagnosis Nervous system, musculoskeletal system, blood vascular system and metabolic disorders
Veterinary science -
Security Military Night guard and trace
Night watch Night watch