Immersion Chiller Efficiency

I’m getting ready to start putting together an immersion chiller for my fermenter (basically using the brewhemoth immersion chiller as a template) and I got to wondering which way the flow is the most efficient.  Either running all the way to the bottom and then up the coil, or down the coil and straight up.  Any thoughts?

none.
people make arguments that there is temperature stratification in the kettle and a little bit of natural circulation can be set up if you cool the top of the wort first and its density increases and drifts to te bottom bringing the warmer wort up to the top with the cooler incoming coolant.  quite honestly if you swish the cooler in the wort or take a spoon and mix it every now and then to break up the boundary layer you will probably do better.

also just build it the same way structurally, you can always switch the flow direction at the hook ups and experiment

It will be more efficient if you put the coolant in at the top, but you wouldn’t even be able to measure the difference.

ETA: I think people are assuming this is for the kettle, rather than the fermenter.

There is an aricle in the new Zymurgy covering chiller performance IIRC.

I have tried it both ways and the difference is negligible but if you occasionally stir the wort as it cools it seems to speed things up a bit, just be sure your spoon or paddle is completely sanitized.

Quite right, the chiller that I’m building is going in a 110g plastic conical fermenter to maintain temp not for rapid cooling.

For what you are doing, I don’t think it will make a noticeable difference either way.

I am doing the same thing.
I use 100ft of 1/2" SS tubing for 350 Gal fermenter.
You have to use SS tubing.
It works quite well.

For your 110 Gal fermenter 50 ft of 1/2" should be enough.
If you have more questions about this let me know.
Good luck.