The temperature of a material is caused by how fast the atoms and molecules inside it are moving. Faster is hotter. Heat moves when the faster moving molecules hit slower molecules and make them move faster. Heat goes from hot to cold places. Air has a very low density and the molecules are far apart so heat passes slowly through air. Good insulation is made from air pockets separated to minimize convective heat transfer.
On the other hand, heat is conducted relatively quickly through dense materials like mud or sand/clay. Minimizing the heat absorbed into the wall (that could have gone into the pot) requires insulation next to the fire. Walls lined with insulation have advantages:
1.) The gases are hotter improving heat transfer.
2.) Hotter temperatures assist more complete combustion.
Using good insulation (as good as the fiberglass insulation in a house) can quickly raise temperatures in a charcoal stove and within minutes the Carbon Monoxide can combust. Achieving thermal efficiencies above 45% (IWA Tier 4) in a high mass wood burning stove may not be possible because the temperature of the gases flowing past the pot will usually be too low. In a stove that starts cold, where energy flows into the stove body and into the pot, water can take a long time to boil.
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Engineers in Technical and Humanitarian Opportunities of Service (ETHOS) is a non-profit organization whose purpose is to facilitate research and the development of appropriate technology by forming collaborative North-South partnerships between universities, research laboratories, engineers, and non-governmental organizations in foreign countries.
By working together, these groups aim to create and then disseminate the best available appropriate technology to families in need.
Since its founding, the ETHOS partnership has grown to include engineering students, faculty, and researchers as well as “on-the-ground” NGOs. Research at Iowa State University, the University of Dayton, Humboldt State University, Colorado State University, and the University of Illinois currently focuses on improving vernacular wood burning cooking stoves, including increasing efficiency and effectiveness while reducing emissions, addressing problems brought forward by the in-field partners.
If you would like to learn more about ETHOS, or register for the upcoming ETHOS 2015 conference, please take a moment to visit the new ETHOS website at http://ethoscon.com
This year’s ETHOS will take place on Friday, January 23rd through Sunday, January 25th.
ethoscon.com has all of the details on hotel, schedule and pricing information.
We hope to see you there!
Aprovecho Research Center
PO Box 1175
Cottage Grove, OR 97424, USA