We will assume you have read Parts 1 to 4 of this series, so we won't rehash the aim of this winter stove project in any detail. Briefly though, the design is of a butane/propane stove designed for liquid feed from an inverted canister, and suitable for serious winter use. A key feature of the design is the new type of heat exchanger used to vaporize the liquid fuel when it reaches the stove body. It does not use a 'conventional' metal tube going over the top of the flame: that amount of heat may be needed for a kero stove but it is totally excessive for a butane/propane mix. Instead a metal fin (the 'heat shunt') sticks up into the flame, pulling heat or energy down to the stove body and the fuel inlet. This idea assumes that enough energy can be pulled down. Using conductive aluminum helps.
What this all means is that the heat shunt has to be big enough to pull enough energy down to vaporize the fuel, but not so big that it overheats the stove body. This is a balancing act. Various designs and placements were tested in the lab before the current (quite successful) arrangement was reached. More details can be found in Parts 1 to 4. For this arrangement it was soon found that the cross-section of the fin was what mattered. If it is too thin then quite definitely not enough heat is transported - in fact, thickness rather than width seemed to be critical.
A secondary concern was whether the top end of the fin might get too hot and melt: it is aluminum after all, which melts around 660 - 670 C (depending on the alloy). This is a fair way below the flame temperature of >1000 C, and we have seen melted aluminum pots and aluminum pot fins. Initial testing involved a wet finger down low on the heat shunt: if it didn't sizzle too much then the top end was unlikely to be too hot. Well, fine, but one of the authors (John) thought he could do a bit better than that, first by using an infra-red camera and later on by using some thermocouples.
- Infra-Red Testing
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