So last night I had an epiphany. I'm not very good at describing what's in my head, so ya'll will have to run with it. My idea is to get some 5' or so of 3/4" copper tubing (straight, not to be curved) and filling it with marbles. Now I have not lost my marbles, but hear me out. Assuming you build the cfc around the tube filled with the marbles as normal, I think it will end up with some fairly decent cooling for much less than it would normally cost. My logic is that the marbles (which tend to be 1/2") will more or less force the hot wort to the outer portion of the copper tube, the side that's doing the heat transfer. If you had a long row of these marbles it would, in my theory, cool off wort fairly well. Now the 5' was arbitrary, but 5' surface area equals out to 11.775sq.ft., which is the same as what I currently have (1/4" approx 15' long) Now my current chiller probably has about 5 or so extra feet of tubing that wouldn't be required (I currently get from 212 to 60 with heavy condensation on the "entrance" end of the cold water), so I figure that equals out to 7.85 sq.ft. and 3' of 3/4" would be 7.065. I think I could get away with a 3' chiller.
Now all of this is hypothetical using math only to calculate the surface area of the tubes. Since the marbles increases the volume of wort in contact with the copper, I think this would be the main thing to consider. I really just wanted to hear what you all had to think about my concept. I plan on trying it out soon, since it really shouldn't be too hard to build. And it ought to be relatively cheap, since a 10' piece of tubing is 16 bucks, I plan on using pvc as the jacket so maybe another 5, and then some plumbers putty for sealing, so another 2.
Now all of this is hypothetical using math only to calculate the surface area of the tubes. Since the marbles increases the volume of wort in contact with the copper, I think this would be the main thing to consider. I really just wanted to hear what you all had to think about my concept. I plan on trying it out soon, since it really shouldn't be too hard to build. And it ought to be relatively cheap, since a 10' piece of tubing is 16 bucks, I plan on using pvc as the jacket so maybe another 5, and then some plumbers putty for sealing, so another 2.