I like the Esbit Titanium Folding Stove as it is clever design and pretty easy to use. As I have designed Esbit stoves before and thought that I would see if I could tweak the design and come up with a more efficient design. Well, I think that I have done this and I also think that this is a great DIY project. The idea is to add a ring to focus the airflow into and out of the Esbit cube (see the picture below):

By doing so, I believe that this has increased the efficiency of the stove. Compared to a control test, I was able to heat up 4 cups of water 15 F hotter when using the ring (n=1). As I said earlier, I think that this is a great DIY project and who share this initial discovery with you. This design is far from optimized and there may be a lot more gains to be made by further tweaking of the concept. Best regards – Jon
If you wish, I made a video of the idea and test:











