Thermal emittance: Difference between revisions
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'''Thermal emittance''' or '''thermal emissivity''' (<math>\varepsilon</math>) is the ratio of the [[radiant emittance]] of [[heat]] of a specific object or surface to that of a standard [[black body]]. Emissivity and emittivity are both [[dimensionless quantities]] given in the range of 0 to 1, representing the comparative/relative emittance with respect to a blackbody operating in similar conditions, but [[emissivity]] refers to a [[material property]] (of a homogeneous material), while emissivity refers to specific samples or objects.<ref name=":0">{{Cite book|url=https://www.worldcat.org/oclc/905919280|title=Eco-efficient materials for mitigating building cooling needs : design, properties and applications|others=Pacheco-Torgal, F.,, Alchapar, N. L.,|isbn=978-1-78242-401-7|location=Amsterdam [Netherlands]|oclc=905919280}}</ref><ref>{{Cite web|title=The Difference Between Reflectance and Emittance|url=https://www.buildingenclosureonline.com/blogs/14-the-be-blog/post/85546-the-difference-between-reflectance-and-emittance?v=preview|access-date=2020-10-24|website=www.buildingenclosureonline.com|language=en}}</ref> |
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| ⚫ | For building products, thermal emittance measurements are taken for wavelengths in the [[infrared]]. Determining the thermal emittance and [[solar reflectance]] of building materials, especially [[roofing material]]s, can be very useful for reducing heating and cooling [[energy accounting|energy costs]] in buildings. Combined index Solar Reflectance Index (SRI) is often used to determine the overall ability to reflect solar heat and release thermal heat. A roofing surface with high solar reflectance and high thermal emittance will reflect solar heat and release absorbed heat readily. High thermal emittance material radiates thermal heat back into the atmosphere more readily than one with a low thermal emittance. In common construction applications, the thermal emittance of a surface is usually higher than 0.8–0.85.<ref name=":0" /> |
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'''Thermal emittance''' or '''thermal emissivity''' is the ratio of the [[radiant emittance]] of [[heat]] of a specific object or surface to that of a standard [[black body]]. Emissivity and emittivity are both [[dimensionless quantities]] given in the range of 0 to 1, but [[emissivity]] refers to a [[material property]] (of a homogeneous material), while emissivity refers to specific samples or objects. |
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| ⚫ | For building products, thermal emittance measurements are taken for wavelengths in the [[infrared]]. Determining the thermal emittance and [[solar reflectance]] of building materials, especially [[roofing material]]s, can be very useful for reducing heating and cooling [[energy accounting|energy costs]] in buildings. Combined index Solar Reflectance Index (SRI) is often used to determine the overall ability to reflect solar heat and release thermal heat. A roofing surface with high solar reflectance and high thermal emittance will reflect solar heat and release absorbed heat readily. High thermal emittance material radiates thermal heat back into the atmosphere more readily than one with a low thermal emittance. |
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== Referencias == |
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[[Category:Physical quantities]] |
[[Category:Physical quantities]] |
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Revision as of 04:06, 24 October 2020
Thermal emittance or thermal emissivity () is the ratio of the radiant emittance of heat of a specific object or surface to that of a standard black body. Emissivity and emittivity are both dimensionless quantities given in the range of 0 to 1, representing the comparative/relative emittance with respect to a blackbody operating in similar conditions, but emissivity refers to a material property (of a homogeneous material), while emissivity refers to specific samples or objects.[1][2]
For building products, thermal emittance measurements are taken for wavelengths in the infrared. Determining the thermal emittance and solar reflectance of building materials, especially roofing materials, can be very useful for reducing heating and cooling energy costs in buildings. Combined index Solar Reflectance Index (SRI) is often used to determine the overall ability to reflect solar heat and release thermal heat. A roofing surface with high solar reflectance and high thermal emittance will reflect solar heat and release absorbed heat readily. High thermal emittance material radiates thermal heat back into the atmosphere more readily than one with a low thermal emittance. In common construction applications, the thermal emittance of a surface is usually higher than 0.8–0.85.[1]
Referencias
- ^ a b Eco-efficient materials for mitigating building cooling needs : design, properties and applications. Pacheco-Torgal, F.,, Alchapar, N. L.,. Amsterdam [Netherlands]. ISBN 978-1-78242-401-7. OCLC 905919280.
{{cite book}}: CS1 maint: extra punctuation (link) CS1 maint: others (link) - ^ "The Difference Between Reflectance and Emittance". www.buildingenclosureonline.com. Retrieved 2020-10-24.
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