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.
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.
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.