Santamax, what stores the heat inside the bell? Air has virtually no thermal mass. It looks like the material the bell is made of is what captures and stores the heat, so if the bell is light weight, there is not much thermal storage. I can see a bell being useful as a heat-shedding or heat-coupling device though.
My problem is weak floors so I do not want to bring in much heavy masonry. Unfortunately I do not have a masonry wall to connect this to.
Do you have a picture of this fuel tank you have in mind?