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Re: AW: [EnergyPlus_Support] IR Hemispherical Emissivity

If the glass (or any other opaque or transparent object for that matter) is at a different temperature than any of the surroundings that it "looks at", there will be a radiational heat exchange governed by the emmisivity and absorptivity (not solar absorption of the thickness of the glass) of the glass.  Typical emmisivity value is for glass is 0.84 unless there is a special coating (low-e glazing), but the coatings are seldon applied to exposed surfaces of the glass.  Even if you intend to defy the laws of nature and have glass that does not absorb solar energy, there will still be an energy exchange based on temperatures and possible conductance from the glass to the surroundings.  Please note that simple thermal heat transfer coeficients for surfaces published in ASHRAE are always a combination of conductance, convection and radient heat exchange.

>>> alexander.beisteiner@xxxxxxxxxxxxxxxxxx 10/22/02 02:32 AM >>>

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