Page 300 - Instrumentation Reference Book 3E

284 Temperature measurement

Table 14.16 Total emissivity of miscellaneous materials
Total emissivity of unoxidized metals
Material 25 "C I00"C 500 "C I000"C 1500°C ?OOOCC
Aluminum 0.02 0.028 0.060
Bismuth 0.048 0.061
Carbon 0.081 0.081 0.079
Chromium 0.08 -
Cobalt 0.13 0.23 -
Columbium - 0.24
Copper 0.02 - (Liquid 0.15) -
Gold 0.02 0.03 -
Iron 0.05 -
Lead - 0.05
Mercury 0.10 0.12 - - -
Molybdenum - 0.13 0.19 0.24
Nickel 0.045 0.06 0.12 0.19 - -
Platinum 0.037 0.047 0.096 0.152 0.191
Silver 0.02 0.035 -
Tantalum - - 0.21 0.26
Tin 0.043 0.05 - -
Tungsten 0.024 0.032 0.071 0.15 0.23 0.28
Zinc (0.05 at 300°C)
Brass 0.035 0.035 -
Cast Iron 0.21 (Liquid 0.29)
Steel 0.08 (Liquid 0.28)

Total emissivity of miscellaneous materials
Material Temp. ("C) ct Material Temp. ("C) ct
Aluminum (oxidized) 200 0.11 Lead (oxidized) 200 0.63
600 0.19 Monel (oxidized) 200 0.43
Brass (oxidized) 200 0.61 600 0.43
600 0.59 Nickel (oxidized) 200 0.37
Calorized copper 100 0.26 1200 0.85
500 0.26 Silica brick 1000 0.80
Calorized copper (oxidized) 200 0.18 1100 0.85
600 0.19 Steel (oxidized) 25 0.80
Calorized steel (oxidized) 200 0.52 200 0.79
600 0.57 600 0.79
Cast iron (strongly oxidized) 40 0.95 Steel plate (rough) 40 0.94
250 0.95 400 0.97
Cast iron (oxidized) 200 0.64 Wrought iron (dull oxidized) 25 0.94
600 0.78 350 0.94
Copper (oxidized) 200 0.60 20Ni-25Cr-55Fe (oxidized) 200 0.90
1000 0.60 500 0.97
Fire brick 1000 0.75 6ONi-12Cr-28Fe (oxidized) 270 0.89
Gold enamel 100 0.37 560 0.82
100 0.74 100 0.87
Iron (oxidized) 500 0.84 80Ni-20Cr (oxidized) 600 0.87
1200 0.89 1300 0.89
Iron (rusted) 25 0.65
Source: "Temperature its measurement & control" in Science & Indumy, American Institute of Physics. Reinhold Publishing Co. (1941).
A choice of three aperture sizes is available at Furnace temperature by radiation thermometer
the open end. For temperatures up to 1100 "C the Conditions in a furnace which might otherwise
furnace is made of stainless steel, but for higher be considered as perfectly black body conditions
temperatures refractory materials are used. For may be upset by the presence of flame, smoke, or
further details see The Calibration of Them- furnace gases. In these conditions, a total radi-
ometers (HMSO, 1971) and BS 1041: Part 5: 1989. ation thermometer generally indicates a tempera-
Figure 14.51 shows typical black body furnaces. ture between that of the furnace atmosphere and