I wouldn't bother with the added cost and time as a CFC is fairly efficient to begin with. At some point you are limited by the wall thickness of the copper and thermal conductivity.
with a relatively small inner diameter of the copper line, having a rifled or spiraled design, IMHO, just has more places for debris to build up and hide. The constant 360 degree turns creates a natural turbulence with the fluid moving through the turn, which provides plenty of activity to eliminate lament flow. As the fluid travels through the constant turn of the copper tube it will be moving with a swirl-like pattern, so the fluid in contact with the copper wall will quickly be swirled into the center allowing a turbulent flow.
The wire on the inner tube is to separate it from the outside tube, so that surface area is kept open to the cooling water flow. The benefit of the turbulence is very little in this instance, as the tube is already moving through a long radius turn.
Would it be more efficient? Possibly, but I doubt it would be a great improvement compared to the efficiency it already has. I think it would difficult to measure the increase of efficiency for the reasons stated above
Sorry if I misread the question, I have not used a spiraled CFC but I was concentrating on the efficiency claim. My job for the last 20 years is compressed air and gas treatment (manufacturer), quite a few heat exchanger designs! We used to make tube-in-tube here but now we use brazed plate for our cold side heat exchangers.
The Chillzilla is a copper tube-in-tube. I think that style benefits from a twisted tube as it allows a channel for the cooling water to travel around the whole tube. One better would be a multi tube design where the inner tube is divided into multiple smaller tubes, providing more surface area.
The problem with bending copper tube-in-tube is that the inner tube gets pushed against the outer tube while bending, creating a wall so to speak. The twisted design provides openings where the copper tubes meet allowing fluid to travel past. If you are buying one this looks like a fair product.
The DIY-er in me would buy some copper, wire, and vinyl to make a CFC. However the money saved = time and tools needed. Absolutely nothing wrong with buying a pre-made CFC!
I have two of them (Morebeer counter flow convoluted chillers) and they work great. Ground water is warm here in Florida most of the year, so I have two in tandem mounted on a stand. One chiller gets the ground water and the other gets ice water in the cleaned out mash tun and gets pumped into the second chiller. I have tri clamp fittings on them and I do not get any leaks. Hope this helps....
Please check out www.Exchilerator.com we use a co-helical wrap between the shell and the o.d of interior tube for additional mixing and most importantly centering it in the cooling flow. Yes convoluting does increase surface area but like a plate chiller it is very difficult to clean with any confidence
I've owned quite a bit of chillers and bought an Exchilerator about 5 or so years ago. I can say without a doubt it's the best chiller I've ever owned and lives up to all the reviews. I've never used a convoluted chiller though, but can say that my current chiller knocks out my 5 - (very rare 10) gallon batches in minutes and I can run oz's of hops through it, and it cleans easy with no sweat (I just rinse).
The pricing comment above didn't seem right compared to what I paid, even back then . I just priced them out and the same configuration in stainless is $268 vs $264, so a $4 difference (yes in stainless). The copper TC exchilerator version is $219 configured like the coolossus. I would recommend copper all day, my neighbor has a stainless and its just plain slow IMO. I know that some people only want stainless for other reasons, so just my opinion.