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#1 Posted : Tuesday, September 15, 2009 2:14:17 AM
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Okay,really interesting,have'nt done this stuff since h.s. so bear with me here goes:Got my pocket reference here for practically everything on the panet and the r value for stone(pretty much what you can base granite on)is .8 which is the resistance to heat conductivity,the "k" value is heat transmittance of a material and is 12.5 or the reciprocal of the r value.This is based on 1" of material.The thermal conductivity of water is far far greater,actually almost opposite that of stone or 4.86 kJ/CM.Go to Wikipedia and look up specific heat tables for your substances.

Pat Miketinac
#2 Posted : Tuesday, September 15, 2009 10:17:00 PM
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There is a kind of high manganese brick made for heat storage and release that is used in "Russian" style fireplaces that have a long path for the smoke. It was used in MOM's first earth shelter at Eco-Village. Type "My Mother's House" in the search box at the top of this page to find the article.

#3 Posted : Thursday, September 17, 2009 3:32:21 AM
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Ignoring the effects of phase-change materials like wax or special rocks... The thermal mass for most materials is within a .8 to 4 range.



So for water you have 4.1813  (J/(kg·K)) (joule per kilogram-kelvin)

and lets say stone is .8 (J/(kg·K)) (joule per kilogram-kelvin)

That means you get 5.2 (4.18/ 0.8 ) times more thermal mass from the same weight of water than stone. However stone weighs more for a set volume...

>  If I have about 830 lbs of water how many lbs of granite will it take to equal the thermal capacity.

A: 830 pounds of water * 5.2 = 4316 pounds of stone



John Stiles
#4 Posted : Thursday, October 15, 2009 4:48:33 PM
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Hi, It's getting cold here now, frost most nights in upstate NY. Below are my calculations etc. in regards to my project. Thanks again. I'm now asking quest ions about my new stove (see energy).Currently, I haven't added any mass. I'm going to price short steel and include metal and maybe a water garden in my experiment for thermal mass. My cement floor and chimney area are warming nicely and I'm going to celotex the outside of my cabin, I think (see building).then, John 


This one rambles, I've been working on it. First off, thank you to all who have an interest and to those who responded, this forum is still my favorite.    I had figured to equal my target of 200 gal of water with 5 ton of stone. A bit heavy but I wanted an even number of units. Most pallets of stone weigh about 3000lbs so I’ll get 3 pallets. I might add iron to help conduct the heat into the dry stacked wall.    How much water, stone (granite) or cast iron for equal thermal mass?  Please forgive my using different tables from the urls; so some of the math won’t be perfect but this will cross reference the answer.    Using specific heat of: water @4190; stone@790; iron@540.    Specific heat ratio is: water/stone/iron/ is 1 to 5.3 to 7.8.    100 gals/water = 835lbs; stone = 4424.5lbs; iron = 6513lbs.   1 cu. ft. of water = 62lbs; stone = 165lbs; iron = 450lbs. 100gal/water = 7.5gal. = 13.4 cu ft    Density ratio: 1 to 2.7 to 7.3        Very roughly, stone is 1/3 the size of water and holds 1/5th the heat and iron is 1/7th the size of water but holds 1/8th the heat.   1. Dividing density by specific heat when density of: water is 1000; stone is 2400 and iron is 7200 we get 1000 to 452.8 to 923 Does this show anything?    Here are some urls if ur interested. http://www.engineeringto...c-heat-solids-d_154.html


http://www.cpci.ca/downl...y%20Conservation%203.pdf http://www.engineeringto...heat-storage-d_1217.html

http://www.ces.purdue.edu/extmedia/ae/ae-89.html http://hypertextbook.com...s/thermal/heat-sensible/




wall stone is $200 to $600 pallet; short cast iron is (unknown) and water is free but needs to be contained.   To be continued sometime 10/15/09

John Stiles
#5 Posted : Thursday, October 15, 2009 4:48:33 PM
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Posts: 134,494

I'm about to get some thermal mass for my new stove area. My wife and I want stone instead of water. I've tried to do the math but haven't really figured out what the difference in thermal capacity measured in either volume or weight between granite and water.

or:  If I have 100 gal of water how much stone does it take to equal the thermal capacity. This could also be stated as: If I have about 830 lbs of water how many lbs of granite will it take to equal the thermal capacity.

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