[sharg54]

I don't know if this is typical, but the 1/4" tubing I have is the same thickness as the 3/8" tubing I use in my chillers.  In any case, the heat transfer you gain from any change in thickness between 1/4" and 3/8" will be wiped out and then some due to the lower coolant flow rate and lower heat transfer coefficient of a 1/4" v. a 3/8" coil.  But do what works for you, of course.

I'm not sure if it's typical or not, it just may be a cheaper brand of tube but I have a piece of 3/8 and 1/2 I used for my manifold and wall thickness is defiantly thinner on the 1/4 inch. I don't see what it would matter if the cooling started from the top or the bottom other than the fact that cooler liquid will sink to the bottom but I don't think the brew pot is big enough for that to happen. I just went that way because everything I looked at the inlet water went to the bottom first so that's how I set it up. It's basically a single coil I just staggered the loops in and out form the bottom up to increase the coverage. The small size was based more on price rather than efficiency but it works very well. 50' of 3/4 or 1/2 was about three times as much as the 1/4 at the time. After getting a fridge for lagering  it kept the wife happy. 

[kramerog]

Two separate coils in parallel are much superior to two coils in series  or to a single coil as you can run a faster flowrate of cooling water.  To maximize natural convection which speeds up chilling and reduces need for mixing do the following: 1. Have water come in at top of coil is better. 2.  The coils should stick out above the top of the wort.  3.  Have more coils at the top than in the bottom.  4. The coils should occupy as much of the kettle as possible (2 overlapping coils that occupy nearly the diameter of the kettle works well).  The above recommendations may not be best for whirlpooling.

[Will's Swill]

3 and 4 are probably true, but...

For number 1, while heat stratification is very real (try touching the top half and bottom half of your kettle while chilling, there's a HUGE difference, with mine anyway), I doubt that the direction of flow will matter at decent flow rates, and Denny has tried it both ways ( ) with no apparent difference.  But if you run your coolant so slow that flow direction does makes a difference, then if you run from the top, you'll actually be doing some heat redistribution, rather than just heat removal.  Imagine a partially chilled kettle, still 100F at the top of the coil and say 70F at the bottom of the coil.  The coolant enters from the top and,, let's say half way down the coil, has reached 80F, say at the same level in the kettle where the wort is 80F.  For the remaining length of the coil, as the coolant continues lower, it will be warmer than the wort and will actually add heat back to the wort until the coolant exits the coil.  If the coolant enters from the bottom, it has the opportunity to cool over the whole length of the coil.

For number 2, I'm just confused.  Coils outside the wort won't do anything useful...

[nofunsally]

I am happy that the post generated discussion. I just went with the simple single coil option.  I the immersion chiller from my previous 5 gallon boil setup that I plan on using as a pre-chiller.

Thanks again,
Mike

[weazletoe]

I don't think there is any advantage to your design.  It's total surface area and water temp that matter IMO.

 Interesting. I've only tried it my way. I guess I was just assuming that heat rises, so the majority of the heat would find it's way to the top of the wort. But, based on what you said, I got to thinking about it. Perhaps because the thick bottoms of the kettle hold so much heat, there is a constant heaating of the wort at the bottom. Then again, I was just making an educated guess based on what I know about air flow. Knowledge is a dangerous thing! 

[Malticulous]

My first one was 20 ft of 1/2 in tubing for my 30 at turkey pot. When I got the 60 qt kettle I made one out of 50 ft of 3/8. The old one fits in the middle and I can use a wye to conect both to cold water. Parallel works better than series. I tried it as a pre-chiller but it's a better ice melter. I need to get a small sump pump and recirculate through it.

[Will's Swill]

Interesting. I've only tried it my way. I guess I was just assuming that heat rises, so the majority of the heat would find it's way to the top of the wort. But, based on what you said, I got to thinking about it. Perhaps because the thick bottoms of the kettle hold so much heat, there is a constant heaating of the wort at the bottom. Then again, I was just making an educated guess based on what I know about air flow. Knowledge is a dangerous thing! 

No, you've got it right.  The top of the wort will be warmer than the bottom as the wort chills.  The kettle itself doesn't hold a lot of heat and can lose that to the surrounding air anyway.

[bluesman]

One of the keys to efficient cooling is uniform heat tranfer throughout the wort. This can be accomplished by gently stirring the wort in the kettle during the chilling process. Or an even better and more versatile chiller, a Whirlpool Immersion Chiller which requires a pump, which not only chills your wort but also reduces the amount of cold break and hops transferred to the fermenter by collecting the trub in the middle of the kettle prior to transfer.