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Salt as mass

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I am new to this and did a search to try to find an answer but didn't see one.

I am wondering if Salt could be used as the main mass in a Rocket Mass heater, surrounded by cob?

I had read a long time ago that salt was the best mineral at retaining and storing heat.

Just throwing this out there because I'm curious.
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Location: New Zealand
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I'm guessing that the fact it attracts moisture would be the killer for this idea
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Location: West Texas - near Big Bend National Park
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Thought I would toss this out for you to look at.  There are lots of pages on specific heat of liquids and solids so this should just be a starter.  Specific heat is expressed as (BTU/lb per degree F)
-OR- (kJ/kg K).  The higher the specific heat of a substance, the more effective that substance is at storing/holding heat.

webpage on specific heat of materials

Keep in mind the specific heat of water is very high compared to most building materials.  When one looks at a traditional cast iron woodstove the specific heat of cast iron is .46 kJ/kg K.  Many high end woodstove manufacturers will add soapstone into their stoves.  Soapstone has a specific heat of .88 kJ/kg K which is twice a good as cast iron alone.  What is interesting is that coal has a specific heat of 1.32 kJ/kg K.  Water has a specific heat of 4.185 kJ/kg K.

I would think that using coal rather than salt would hold more heat, but if one can figure out how to use water it is even better.  The trick with water is it must stay below the boiling point, or it will change phases and go to vapor.  If that phase change occurs in a closed system you could have a steam explosion.

Hope this helps your thinking.


Tom Riker
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I just bought the rocket mass heater book and am going crazy with all this.

I will stick to what the book says. Thanks for the replies.

I am in the process of building a dome home and I think a rocket mass heater would be a great addition.
permaculture is giving a gift to your future self. After reading this tiny ad:
Rocket Mass Heater Plans: Annex 6
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