I am trying to simulate radiation on galvanized steel shield. Since the operation temperature is much higher that room temperature, want to confirm the emissivity value at higher temperature.
-The emissivity of a given surface is the measure of its ability to emit radiation energy in comparison to a blackbody at the same temperature. The emissivity of a surface at a specified wavelength may vary as temperature changes.
- In general the emissivity of a target is both temperature and wavelength dependent.
-A blackbody has an emissivity of 1, while a perfect reflector or whitebody has an emissivity of 0. Most natural objects are considered "graybodies" as they emit a fraction of their maximum possible blackbody radiation at a given temperature.
-Material - Emissivity : Aluminum (anodized) 0.77, Aluminum (polished) 0.05, Concrete 0.92, Copper (polished) 0.05, Copper (oxidized) 0.65, Glass 0.92, Gypsum 0.08, Ice 0.97 , Sand 0.9, Snow 0.8 , Soil (Dry) 0.92, Soil (Saturated ) 0.95, Stainless Steel 0.59, Water 0.95 .
Yes, according to Holman (Heat Transfer, 5th edition), "The emissivities of variuos substances vary widely with wavelength, temperature, and surface condition" (roughness, cleanliness, etc.). He also recommends "Thermal Radiation Properties Survey," by Gubareff, G.G., Janssen, J.E., and Torborg, R.H., 2nd ed. from Minneapolis Honeywell Regulator Co, 1960.
Please refer the below link which mention the decrease in the emissivity with increase in temperature.
https://engineering.purdue.edu/BTPFL/BTPFL%20Publications/90.pdf
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