[Stoves] Update to the KG4 series of space heating stoves

[Crispin Pemberton-Pigott]

Dear Friends

There is a new version of the KG4 crossdraft gasifier available here<http://www.newdawnengineering.com/website/library/Stoves/Kyrgyzstan/KG%20Model4-Coal/>.

It is a shortened and slightly taller version of the popular KG4 from last winter, with a downdrafting heat exchanger. You will notice the draft tube with a controller at the top leading to the chimney. There is no longer a central divider forcing hot gases down the up again to the chimney. The whole centre is hollow with the chimney pulling from the bottom at one end.

There is as usual, a 'bleeder' that puts heat directly into the chimney so it pulls as soon as the fire is lit. For the first time, a control arm is added to open the bleeder fully so that users can cook in summer without overheating the kitchen. When the control arm is in the 'Closed' position, the hole is not sealed at all. There is a 10 cm2 gap around it to feed heat into the chimney at all times.

The major reason for creating the new dimensions in the combustion chamber case and height is that the refractory bricks which are locally made are no longer going to be 230 x 115 x 65. A new machine has arrived and they are going to be 250 x 120 x 60 from now on. This required some panegyrics to get a pretty-much-identical combustion chamber into a similar stove body.

Drawings include both a steel plate top and a cast iron top for those who can produce it. Although it shows three cast iron rings over the cooking hole, in fact we will use 4 standard ones that are available from a local producer. This is for convenience. We will machine the outer one (Ring 3) on the underside of the outer portion.  That will provide a seal on top of the cooking ring hole perimeter which is raised. This arrangement is the cheapest way to get an air tight seal in a low tech environment. The hopper cover will similarly be machine on the underside, and the top of the hopper lip will be ground using a 9" angle grinder which can cover the whole thing at the same time. The result is a completely flat sealing surface.

Legs and chimney diameter are optional as usual.  The South African version will have a second cooking station but that is not necessary in Kyrgyzstan.

Testing the heat exchanger in Ulaanbaatar in September showed a very small difference between the top and bottom temperature of the side sheets. This was unexpected and will be investigated, we hope, by the CFD people at North West University in Potchefstroom. The difference is only 10-11 degrees C, indicating there is a strong toroidal flow taking place in the heat exchanger.

Regards
Crispin

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