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Heat of freezing ?
02-19-2015, 09:48 AM (This post was last modified: 02-19-2015 09:49 AM by Wieslaw.)
Post: #1
Heat of freezing ?
I got a very nice pictures, which really surprised me.


   


The roof of the block is warmer in the wrong place! More cold it is on the edge and at the chimney, where we usually see warmer places.
The roof is covered with roofing sheet, painted. Entire attic are inhabited, than isolated.
Meteo archive says that there was 90% RH, DP (-1) C, the sky was clear (but its temperature changes in elevation!), almost no wind.
My suspicion is that the moisture from the atmosphere freezes on the colder parts of the roof and forms rime - clotting produces heat which we see.


Do You agree ? Or am I wrong ?
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02-19-2015, 11:03 AM
Post: #2
RE: Heat of freezing ?
Could you attach the original IR jpg image so we could analyze please?

Thanks
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02-19-2015, 11:27 AM (This post was last modified: 02-19-2015 11:37 AM by Wieslaw.)
Post: #3
RE: Heat of freezing ?
(02-19-2015 11:03 AM)Gary Orlove Wrote:  Could you attach the original IR jpg image so we could analyze please?

Thanks
Garry, it is from T600 camera - too big, ca' 1,3MB .. is any procedure to extract only IR from it ? Or - may be csv helps... this one I can export and attach here in zip.

Thanks for interest
Wieslaw


Attached File(s)
.zip  roof.zip (Size: 408.93 KB / Downloads: 6)
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02-26-2015, 05:47 AM
Post: #4
RE: Heat of freezing ?
After Gary (ITC) valuable consultation, I can proudly say that the Flir "Tools +" amazing "local parameters" feature - finaly helped me understand strange anomalies in the IR picture.
   
What we can see the "colder", actually is warmer (-3C) than what we see as "warmer" (actually -5C). And it is mainly because of varying emissivity : roofing sheet (polyester coating, e = 0.6) and Frost (e = 0.97) , at Tref=-50C.
What I thought : the frost settles directly from water vapor (desublimation) giving off heat, which for some time (temporarily !) even more increases the temperature as seen in IR. (but it is only for transit time - then picture stabilises on what we see here).


Thank You Gary, for invaluable help !

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