[Stoves] the 150 gasifier in operation in Vietnam

[Crispin Pemberton-Pigott]

Dear Friends

 

There are two approaches of the screen-above-the-flame that I have seen and they work the same way: providing a bluff body (though perforated) to create a tertiary combustion zone above the flame.

 

This one is the vertical cylinder approach:

 



(Photo credit: Kerona brand heaters, from Korea)

 

and the other is the type Paul is using. Jeplin Industries in Port Elizabeth, South Africa sells one of the horizontal type (also a dome). It is a heater with a cooking station immediately above the wire dome.

 

A variation on the theme is the FSP stove which was in the intermediate stage of development using a wire mesh. A perforated plate was also tried to good effect. 

 



(Photo: FSP Stove 2006. It is a ‘gravity stove’ like the REDI, i.e. low pressure, < 2m)

 

In the end the bluff body is a pressed metal part that accomplishes the same overall effect without the wires (which have durability problems). Use thin nichrome wire if you can. It is available in sheets. Some use an expanded steel mesh with very small holes.

 

Acting as a bluff body (constriction or interrupter of flow) the CO burns out very well. Jeplin’s heater with a wire dome has extremely low CO and burns kerosene.  The noticeable effect to a user is that the dome turns non-radiating hot gas energy into infrared radiant energy. When you are in a room you want to heat, it is not as pleasant for the user to have the hot gases rise to the top of the room and the cold remain on the floor. If you use a radiant heater, the heat is directed outward near the floor giving the impression it ‘gives more heat’ because you feel warmer, even though the total energy in the same.

 

This is an important design consideration for space heating stoves in a Yurt (Ger) because if you live in the bottom 3 feet of the space and the stove only heats the top 6 feet, you are always cold, even though the stove puts out enough energy to heat the whole room. Thus, space heating stoves have to have a radiant body (or part of it) near the floor level.

 

Regards

Crispin

 

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