charlesxavier
Mechanical
I'm designing a solar parabolic collector. I need the reflectance of shaining stainless steel value.
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REFLECTANCE OF STAINLESS STEEL 1
- Thread starter charlesxavier
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According to EOI's emissivity page:
polished stainless steel has an emissivity of 0.11, implying a reflectivity of about 89%
TTFN
polished stainless steel has an emissivity of 0.11, implying a reflectivity of about 89%
TTFN
Per the Satellite Thermal Control Handbook published by The Aerospace Corporation, the solar absortance of stainless steel(polished) is 0.42. The infrared emittance is 0.11.
This means that 58% of the SOLAR energy incident on your collector will be reflected!( the previous tip was incorrect)
It is true that the absorptance and emittance are EQUAL, per Kirchhoff's Identity, but this applies only when the material absorbs and emits at the SAME wavelengths.
If you had a heat source radiating at, say, 500C and the collector had a temperature of 400C then absorptance and emittance would be the same. In your case, the sun(your heat source) radiates at 5,555K(uv range). Your collector's temperature will be nowhere nears 5,555K. Therefore, absorptance DOES not equal emittance.
I realize that all this sounds confusing. So, let me recommend the following book: Thermal Radiation Heat Transfer by Siegel and Howell. It is THE BIBLE for aerospace engineers like myself.
Further Recommendation: With a solar absorptance of 0.42, stainless steel is not a great material to use as a collector. You may want to consider alternatives like buffed aluminum, with a reported absorptance of 0.16!!!
IF you want to get real fancy, coatings is the way to go. I would recommend Indium Oxide coatings. They are used in aerospace industry solar reflectors with an absorptance of 0.07!!! This means that 93% is REFLECTED!
Best Regards and Good Luck,
A.C.G
This means that 58% of the SOLAR energy incident on your collector will be reflected!( the previous tip was incorrect)
It is true that the absorptance and emittance are EQUAL, per Kirchhoff's Identity, but this applies only when the material absorbs and emits at the SAME wavelengths.
If you had a heat source radiating at, say, 500C and the collector had a temperature of 400C then absorptance and emittance would be the same. In your case, the sun(your heat source) radiates at 5,555K(uv range). Your collector's temperature will be nowhere nears 5,555K. Therefore, absorptance DOES not equal emittance.
I realize that all this sounds confusing. So, let me recommend the following book: Thermal Radiation Heat Transfer by Siegel and Howell. It is THE BIBLE for aerospace engineers like myself.
Further Recommendation: With a solar absorptance of 0.42, stainless steel is not a great material to use as a collector. You may want to consider alternatives like buffed aluminum, with a reported absorptance of 0.16!!!
IF you want to get real fancy, coatings is the way to go. I would recommend Indium Oxide coatings. They are used in aerospace industry solar reflectors with an absorptance of 0.07!!! This means that 93% is REFLECTED!
Best Regards and Good Luck,
A.C.G
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