I am appealing to the vast knowledge database here in order to figure out this problem. I have noticed that many of the commercial CFCs (even the non convoluted one) are 1/2" on the inside and 7/8" on the outside. It seems that when people build their CFCs they always go 3/8" inside and 5/8" outside. I get the idea of reducing to 3/8" for the inside tube in order to increase surface area and reduce the size of the center flow, but wouldn't using 7/8" for the outside make more sense?
I am not an engineer or a welder and this is going to be one of my first projects and I want to do it right. My thought is that 7/8" copper for the exterior would allow more cold water and allot more heat to be exchanged. If you consider that most CFCs have the initial water coming out steaming hot isn't there a call to maybe allot for more water flow?
Also, has anyone seen square copper tube? I have looked with the thought of trying to build a convoluted CFC, but can't find any.