|
|
Post by satamax on Feb 25, 2014 12:11:07 GMT -8
Hi everybody. After mintcake's thread What kills Ytong? I checked the R values of the stuff. www.ytong.fr/fr/docs/Fiche_Multipor_ITI_02-2012_OK.pdfAnd that made me wonder what R value we need around the core and heat riser of batch and J tubes? I remember Peter saying 1 inch of perlite 2 of vermiculite or rockwool. So, what's the R value of all this, so we can compare? |
|
|
|
Post by 2tranceform on Feb 25, 2014 13:06:11 GMT -8
R Values of building materials (rockwool, vermiculite, etc) If I calculated correctly from Satamax's document, it is .6 r-value per inch. This document Document shows 1.25 r-value per inch for AAC. It appears that it depends on the AAC product being used. 
|
|
|
|
Post by satamax on Feb 25, 2014 19:20:59 GMT -8
So two inches should do the same trick as 1 inch of perlite. Tho, here they're more common in 4 inches. And it's easier to work with. It's funny, theR values given by your first document seems weird. But i know i have seen R values on us sites which seemed proper dementia. Like R40! I don't even know if this is atainable. House wise, R13 in the roof and R10 in the walls is considered pasive here. Definately that site is missleading for me. R value of 4 inch of fiberglass from Knauf (the best type they have) is R3.15 over here.
But after all that, we can say minimum for a rocket is R2.7 or thereabouts. (american R value)
Shit, it's getting complicated!
|
|
|
|
Post by Donkey on Feb 25, 2014 21:00:21 GMT -8
American system is different. We us the "R", but it means something different.
|
|
|
|
Post by satamax on Feb 25, 2014 22:04:48 GMT -8
American system is different. We us the "R", but it means something different. So, wouldn't we be better off using SI units? Like the "U" W/(m².K) |
|
|
|
Post by mintcake on Feb 26, 2014 1:50:31 GMT -8
American system is different. We us the "R", but it means something different. So, wouldn't we be better off using SI units? Like the "U" W/(m².K) Yes, I'm all in favour of SI! But U is for the entire structure including guessing something for convection/radiation. Lambda (w/mK) is the one for the bulk material.According to somewhere I found on google, Perlite has a lambda of 0.05, and vermiculite 0.07. Divide thickness by lambda and you get r, add up your different 'r's and press 1/x on your calculator to get U. L (lambda) for YTONG is 0.11 W/mK at normal house temperatures, "normal refractory brick" is 1.4, my local supplier's 1430C insulating firebrick (0.8 x density of water) is 0.33. According to somewhere I found on google, Perlite has a lambda of 0.05, and vermiculite 0.07. Thus 5cm of perlite (0.05m, ~2inches) gives an r of 1 m2K/W, add some air boundary effect on the cold side (r=0.044 is suggested for movement at about 3m/s) and the U of the wall is 1/1.044 =.99 W/K/m2 This all means that: in terms of (steady state) insulation, 5cm (2in) perlite = 7cm vermiculite = 11cm YTONG = 33cm insulating firebrick = 1.4m of normal refractory brick. (Hate to think how much wood you have to burn to get that up to temperature!) I suggest, therefore that we use lambda, and the "equivalent to 2 inches of perlite standard". Oh, and that we don't try to "insulate" our risers with firebrick! David |
|
