Plumbing - solar heated DHW

[Gyn_Paul]

I have acquired a 300 L tank for a solar heating system.

I've taken the inspection panel off the top to try to identify the various 1" and 1 1/4" inlet and outlet pipes.

inside is a coil which appears to be 1", which runs from the top (well as near as is practical after the dome) to about a third of the way down. This has a centre tapping.

There is a direct tapping right at the top, and another right at the bottom (plus a drain tapping underneath, and an anode set into the dome)

Given that the coil is at the top, I deduce it is for drawing heat from the body of tank water rather than for supplying heat to it, therefore the top and bottom must be the pumped flow/return to the panel.

Q1 - Which way does the DHW in the coil flow - top in or top out?

Q2 - What is the coil's centre tapping for? (it seems to have a non-return valve in line with it)

Q3 - peering  into the tank from the top, there is a hollow square-section steel thingy running vertically from top to (I presume) the bottom, surrounding it, a little lower than halfway down, is a sort of bell-shaped structure about the size of a small dinner plate. This is the reason I can't see to determine if the square section steel goes to the bottom or not, or indeed of the bell thing is actually a bell or a ball shape.

What on earth is this for? Some sort of layering device perhaps? It's entirely separate from the anode.

No usable information label remains on the tank exterior, so looking for a manufacturer is out of the question.

 

Anyone with a similar sort of setup able to tell me how their plumber fitted it?