
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 |