EMP mentioned "promote swrling" and that popped a question in my mind : the Swiss volcano stove has a ribbed wall ( otherwise straight up, not conical) so what is the purpose of those ribs in the wall ?? Strength of the wall ?? Swiriling ??

Also, have you compared the caldera conical design with the volcano straight up design ??

mmmm ... I think there are many variables to compare , like the ribbed /vs/ straight walls, the diameter of the pot ..etc. In the volcano stove , the cooking pot has a larger ratio of surface area to volume, but in the caldera, you have a larger area at the bottom of the pot, where most of the heat is.