On 29/05/2021 17:15, Ken chetin wrote:
The domes at the end of a cylinder is for strength to withstand pressure
and retain shape against side was distortion, ie sheer forces. Just look
at petrol carrying and such tankers. It is the mathematics involved
telling you to use a concave or convex dome on such vessels - not any
dome but what the one structural analysis dictates.

Well, structural analysis will give you the minimum copper solution. In
DHW cylinders it is usual to have convex at the bottom, so it will stand
upright on a flat floor while convex at the top is probably cheaper to
make, as well as making it easy to have a take-off point at the warmest
place, and avoiding a trapped air bubble.