Instructables - Lots of cool ideas.

[Bogwoppit]

I'm not sure the same rules will apply to an immersion chiller as your beer is not being forced into contact through a plate or pipe.

I think if you are using an immersion chiller, then having the cool water coming in at the top will give a more even cooling effect throughout the beer. If it goes in at the bottom, then the beer at the bottom will cool quite quickly and stay at the bottom, the beer at the top will cool less quickly as the cooling water will have warmed up and therefore you will get thermal stratification in the beer.

Putting the cooling water in at the top of the immersion chiller should create a convection current in the beer and therefore lead to a more uniform and probably quicker cooling.

Bw