Effective emissivity

A real body at temperature T does not emit with the black body emissive power $\sigma\cdot{T^4}$ but rather with some fraction $\epsilon$.

The total emittances for a variety of surfaces is given in the following table which is an extract from the slides Radiative heat transfer for the course Heat transfer by John Richard Thome (EPFL, 2008).

Symbol

$\epsilon_{rad}$

Related

$K_t$

Effective emissivity object surface

Choices

Material	Type / treatment	temperature °C	temperature °F	nom	min	max	median
Aluminium	Polished, 98% pure	200-600	392-1112		0.04	0.06	0.05
Aluminium	Commercial sheet	90	194	0.09
Aluminium	Heavily oxidized	90-540	194-1004	0.3	0.2	0.33	0.265
Brass	Highly polished	260	500	0.04
Brass	Dull plate	40-260	104-500	0.22
Brass	Oxidized	40-260	104-500		0.46	0.56	0.51
Copper	Highly polished electrolyte	90	194	0.02
Copper	Slightly polished to dull	40	104		0.12	0.15	0.135
Copper	Black oxidized	40	104	0.04
Steel	Polished	40-260	104-500		0.07	0.1	0.085
Stainless steel	after repeated heating	230-900	446-1652		0.5	0.7	0.6
Paint	Black gloss	40	104	0.9
Paint	White paint	40	104		0.89	0.97	0.93
Paint	Lacquer	40	104		0.8	0.95	0.875
Paint	Various oil paints	40	104		0.92	0.96	0.94
Paint	Red lead	90	194	0.93