Overcoat for Boiler ! Jun 11, 2016 9:04:03 GMT
Post by robmort on Jun 11, 2016 9:04:03 GMT
....... Thermos flask which reflects the heat back into the contained liquid. However, the critical point here is that there is a vaccuum between the two walls of the flask and, therefore, no conductance on the far side of the flask wall to lose the heat. The only component is the radiation across the vaccuum to the far wall. This seems to indicate that, of the two, conductance has by far the greatest influence on the transfer of heat.
Although this is only my personal opinion and has no basis in experimental data, I think that since you cannot remove conductance from the equation wrapping boilers in tin foil is a complete waste of time.
Therefore, the best place for the tin foil is the dustbin.
From a scientific point of view, a Thermos flask importantly has silvered walls to the vacuum flask to minimise heat radiation, which is not necessarily less than the conduction would be without the vacuum.
Use of silver foil in one or more layers, with insulation separating them, is clearly the best solution and is used in all the best materials, such as the multilayer foil blanket used in ovens, fridges, buildings, space suits and satellites.
Air is the best common conduction insulator, next to a vacuum; the best conduction insulating blankets use air separated into pockets to minimise convection. (Note fibre-glass is not the best in this respect as the glass itself is too conductive and air pockets are not sealed)
So in the limit, a simple effective solution is to use a single silver foil layer in a gap wide enough to allow an air space to be maintained on one or both sides of the foil by lightly crinkling it to minimise contact with the sides and create distributed air layers, and at the same time minimise any heat convection.