25ft vs 50ft immersion chiller (5 gallon batches)

[wolverinebrewer]

There's an immersion chiller issue that's been bugging me...

After the cool water intake has reached equilibrium with the wort, wouldn't the rest of the length of copper be irrelevant? For example, if I have a 50' chiller with 190F wort and 60F water, if the water reaches 185 at 32', wouldn't the last 18' be worthless? Thoughts?

Yes, but if this was the case, then you would increase the flow so that particular bit of water is at 185* when it exits the end of the copper. Flow is the key whether you have 25' or 50'. If the outlet water is 100* and wort is 150*, you are going too fast and wasting water (less efficient). It is not removing maximum amount of heat so you would slow down the water. This is where a 50' would be better. The longer that the water stays in the wort removing heat, the faster the wort will cool. This allows you to increase the flow. I guess it comes down to how fast is fast enough for you. If your 25' cools in 12 minutes, does it really matter if a 50' cools in 6 minutes? Not really, both will still make great beer and I believe that's the goal of all of us.
I built my own using 20' of 5/8" OD copper. I figured it would be best to have the greatest amount of surface area working given a certain flow rate. I have to run it pretty slow even with my well water thats 50*.

Great discussion.