I built a counterflow wort chiller of the garden-hose variety, like many others out there. I mostly followed the typical pattern. I chose to use 1/2″ copper tubing fittings to make the ends, similar to other designs I’ve seen. The only interesting twist I added was an attempt to better-approximate the efficiency of the “convoluted copper” heat-exchangers like the Chillzilla or Convolutus.
And, as usual, I photographed the construction, thinking that maybe someday I’d make a web-page about it.
Parts:
- 30′ of 3/8″OD copper tubing.
- Garden hose, with an inside-diameter that can form a tight fit on 1/2″ copper tubing. I think mine was 5/8″.
- A long length of 14ga bare copper wire, from the electrical section. Doesn’t need to be one piece. I bought a shorter length of 6ga (TODO: check this) stranded grounding wire, and unwound the individual conductors.
- 1/2″ copper tube fittings, “sweat” type (ie, soldered):
- Two tee fittings.
- Two end caps.
Soldering Copper Tubing
The end fittings are assembled by soldering. Learn how. It’s not that hard, and is a useful skill to have. If you’ve never soldered copper tubing, this is a great way to learn, instead of inside the cabinet under your kitchen sink. Here’s a quick lesson.
You need a propane torch, plumbers’ solder, and acid paste flux. You need an acid brush for applying the paste flux. You need a steel wire-brush or sandpaper, for cleaning the inside and outside surfaces of the pieces to be soldered.
Start by cleaning the mating surfaces with the wire-brush or sandpaper until they are bright and shiny. The idea is to remove surface oxide from the copper. Using the acid brush, apply acid paste to the mating surfaces, the inside of one, and the outside of the other. Push the parts together with a twisting motion. It should go in easily, and with most types of fitting the tubing will hit a stop when it’s been inserted to the correct depth (about 1/2″).
Fire up the propane torch, and adjust to a moderate flame. Apply the flame to one side of the fitting. The acid paste will melt and possibly drip out, so make sure there is nothing important below. The hottest part of the flame is at the tip of the inner cone, try to get that part of the flame right up to the copper. After 10 or 20 seconds (or before, it doesn’t matter), you can apply the solder the opposite side of the joint. The idea is that the copper should melt the solder, not the flame. If the copper can melt the solder, then it’s hot enough to form a proper joint. If the flame melts the solder, the copper may not be hot enough for the metals to alloy together, and you’ll get a “cold” solder joint.
In a proper joint, the solder is “wet” and flows all around. In a cold joint, the solder will be balled up, like water drops on waxed paper.
If the copper is hot enough, the molten solder will be sucked into the joint. Apply solder until the joint seems full, it doesn’t really take very much, just about 1/2″ of solder to do a 1/2″ pipe joint. It takes a bit of practice to get just the right amount of solder. I usually overdo it, and have blobs of excess solder hanging from the bottom of the joint. It still works, it just looks ugly.
End Fittings
Take a copper end cap, and drill a 3/8″ hole in the end.. You want the hole to accomodate the 3/8″OD copper tubing with a snug fit. Solder the three short pieces of tubing (about 3″) into each branch of the tee fitting. Onto one of the straight-through branches of the tee, solder on a drilled end cap. Onto the right-angle branch of the tee, solder the brass 5/8″ garden-hose to hose-barb adapter. The adapter isn’t really made to be soldered like this, but I found one that was a reasonably snug fit on the 1/2″ tubing, good enough that solder could seal it.
It should all look like this. Make two of them.
Inner Tube
The efficiency of counterflow heat exchangers is influenced by two things, the contact area between the hot and cold surfaces, and the ability to maintain a temperature differential between the hot wort and the cooling water. There are conflicting demands at work. Using a smaller diameter for the inner tube will make a more efficient heat-exchanger. The reason is that with a smaller diameter, a larger proportion of the hot wort is in contact with the tubing wall. But efficiency isn’t everything, we also need a decent flow-rate, or you’ll be cooling your wort all night (and that would completely defeat the purpose of a counterflow chiller.) The usual compromise most people go with is 3/8″OD copper tubing for the inner tube. I did the same.
Maintaining a temperature-differential is the whole raison d’etre of the counterflow design. If you had the wort and coolant flowing the same direction, you’d have a very large differential at the input side, but the differential would approach zero partway along the length of the chiller. At that point, the wort is lukewarm, and so is the coolant water, and the transfer of heat will stop. The counterflow approach is better because heat transfer continues along the entire length of the chiller. In fact, with good efficiency, the cooled wort can approach the temperature of the incoming cold water, and the cooling water comes out the other end almost boiling.
The efficiency of counterflow chillers is reduced by laminar flow and the skin effect. When liquid flows in a tube, the flow rate tends to be highest at the centre of the cross-section, but friction makes the flow slower as you move out toward the wall of the tube. The slower flow rate near the walls of the tube reduces the rate of heat-transfer. In addition, laminar flow can result in pockets where the flow-rate approaches zero, effectively eliminating heat transfer entirely in those areas.
The very best counterflow chillers, such as the Chillzilla, overcome laminar flow and skin effect using “convoluted copper” tubing for the inner tube. This is copper tubing with a square cross-section, twisted into a spiral. The result is more turbulence in the flow, breaking up laminar flow, and keeping the temperature of wort and coolant even over the entire cross-section.
I have no access to convoluted tubing, but I tried to approximate the idea by wrapping a spiral of copper wire around the outside of the inner tube, and securing it in place with solder. The wire is on the outer coolant side of the tubing, not the inner wort side, so I’m not worried about the effect on the beer of the solder or acid paste.
I uncoiled the tubing first, and straightened it on my basement floor as best I could. I only soldered in one place every half foot or so. Doing this to 30′ of tubing took quite a long time. Leave the ends of the tubing clear for six inches or so, so there won’t be wire inside the end fittings.
Don’t use too much solder here. It will form hanging blobs on the bottom side of the tube where you won’t see them, and those blobs will make the insertion of the inner tube into the garden hose a nightmare. Trust me on this. While the solder is hot, pluck the tubing like a guitar string to knock off the dangling solder blobs.
Assembly
Next cut the ends off the garden hose, and reduce the length to about 30′. If your hose is long enough, cut pieces on both ends that are long enough that maybe you can make use of it for somthing else, like filling carboys. You want the hose to be shorter than the inner tubing by about the length of both end-fittings, plus a couple inches more to have the inner tubing protruding from the end caps.
Inserting the inner tube into the garden hose is quite tricky. Try to get the inner tube as straight as you can. Try to do the same for the garden hose (good luck with that). To ease the insertion, I used a cable-pulling lubricant, the kind used by electricians to fish cables through walls. It’s basically a soapy water-based gel. Applying it liberally throughout this process will make it much easier. The lubricant is only in the coolant part of the chiller, don’t worry about its effect on your beer. When finished, you should have the inner tube protruding from each end at least a couple inches beyond the end caps.
At this point, slide a couple hose clamps over the garden hose, one at each end. If you forget to do this, you will absolutely hate yourself later.
Now one of the end fittings is installed. Slide it on, letting the inner tubing protrude through the hole drilled in the copper end-cap. The 1/2″ copper tubing at the other end of the fitting should go at least an inch inside the garden hose. Slide the hose-clamp over the tubing and tighten to seal. Now apply solder to seal around where the inner tubing protrudes through the end-cap.
I did not solder the the opposite end-fitting on yet, because the coiling-up operation might cause the inner tube to move relative to the outer hose. So, coiling it up is the next step. I wanted to get mine coiled up as a single orderly stack of turns, thinking that would help all the wort drain out. A random bunch of turns would trap a lot of precious beer in local low spots. I used a carboy as a form to coil it up on. Not easy to do a good job by yourself, get some help. I used a lot of nylon zip ties to hold everything together as I wound it up. Start with the already-soldered end.
When it’s all coiled up, you can install the second end-fitting. First, make sure the hose-clamp is already on there. This end-fitting is installed just the same way as before, but be careful when soldering not to burn the nearby turns of the hose. In fact, it’s probably better to unroll it just a bit while soldering.
And that’s about it.
You have some options on what you do with the wort-in and wort-out fittings. You can just put plastic tubing directly over the copper tubing, and clamp it. Or you could install hose-barbs. They suck though, too hard to take apart again.
I use flare-type fittings. I used a flaring tool to flare the ends of the tubing, and then installed flare-flare couplings. I have lots of hoses with flare-nut ends on them. And when the chiller is not in use, I leave it filled with weak iodophor solution, and sealed with flare caps.
Links
From my perspective, the copper wire winding was all about inducing turbulence in the coolant, so that cold coolant is continually brought in contact with the tubing, no dead pockets.
But in your case, unless you take steps, the coolant will be motionless. The coolant in close proximity to the copper tubing will quickly warm up to the hot wort temperature, and then heat transfer will stop. The rate of heat transfer is proportional to the temperature difference. As the coolant temperature outside the tubing approaches the wort temperature inside the tubing, the rate of heat transfer approaches zero.
If the coolant is motionless, then the copper windings will not help induce turbulence. I would suggest that you should get the coolant moving yourself. You could use a pump to circulate the coolant, drawing from the bottom of the bucket, and returning to the top. Since it’s only coolant, not beer, the pump can be any cheapo Home Depot pump, it doesn’t have to be food-grade or magnetically-coupled or anything fancy.
Alternatively, you could put some kind of impeller in the bucket to keep things moving.
I just built one of these yesterday and wanted to add a few comments. I used a 20 ft roll of copper tube, used 14 ga copper wire from scraps from building my workshop, and a 25 ft potable-water hose. Each piece of copper wire was 3-4 feet long and I reversed the wind direction, clockwise to counterclockwise, with each piece to further increase turbulence. I also used drilled out compression fittings to seal where the copper tube exits the chiller. I used lead-free solder since I intend to reclaim the hot outlet water to fill my hot liquor tank for either the next batch (I usually do two in a row) or for cleaning. I plan on testing it in service tomorrow. I will note that my dad and I had a heck of a time getting the hose over the copper – it eventually required using a fish tape and about quart of dish soap. I don’t know how anyone got 30+ feet assembled with the spiral over the tube.
Now for the tech talk. Despite the comments above, I will admit to being a mechanical engineer (witha masters degree and professional egineering license) and a government worker. Scientists always complain about engineer’s assumptions, but without them no practical device gets built. I went through the counter flow heat exchanger calculations using the NTU method (number of transfer units) and found the calculation is quite sensitive to the assumptions (a factor of four or more). The flow inside and outside the tube is borderline turbulent (no wire, smooth concentric tubes assumed), depending on the assumed flowrates. I used 1 gpm on the hot side and 2.5 on the cold. Additionally, the Reynolds number is also considerably effected by the temperature which changes significantly along the tubes and fully turbulent can’t be assumed unless Re > 4000. I can’t calculate the effect of the wire, but in all areas (turbulence, fin, keeping tubes centered) it is in the direction of goodness, though I do think it makes inserting it into the hose more difficult.
I suspect 1 gpm is too high for a gravity system (I have a pump); kettle-to-carboy is not more than a few feet of hieght drop and 20+ feet of 1/4″ ID tubing has a significant frictional effect that cannot be ignored. A decent thumbrule (for cold water) would be about 0.2-0.7 psi pressure loss per foot when flowing at 1 gpm in 1/4 ID line (depending on material and smoothness). Using the low end of the range and 20 ft of tubing would require 4 psi, which would require over 9 feet to get 1 gpm.
Anyway, engineering calculations regarding fluid flow and heat transfer are usually crude and must be validated with empirical data.
Also, regarding Mike’s question above: Yes it will work, however. . .
You will hve to melt almost a pound of ice for each pound of wort (about 8 lbs per gallon) to keep the ice bath at 32F. You might be able to use a little less if you let the water bath (melted ice) increase in temperature at the end. Tube length could be almost any length you want depending on how fast the flow is (faster flow, longer tube) and how much you stir the ice bath. A CFC will use 2-3 times more water, but no electricity is wasted freezing the ice.
I’d considered putting a small “immersion” chiller (in a bucket full of ice) in line with my CFC water inlet to drop the temperature to improve cooling. However, that adds complexity to my setp and the same cooling effect could be achieved by reducing the flowrate of the wort (my inlet water never gets above 60F).
As a side note, I had been using an immersion chiller which worked pretty well, but decided to go with a CFC to save the 25-45 minutes of chill time (10-12 gal) since chilling and racking will now be simultanious. With the IC, I found a great improvement by doing a few things: 1) make sure the coils are at the top of the wort level, 2) mist/spray water on the outside of the kettle, and 3) stir the wort occasionally using the immersion coils. I intend to continue to spray down the kettle when I use my CFC.
Scott
I finally used mine yesterday. It worked great. I could get a little over 1 gpm flow through the 20 ft chiller, about 7 feet of hose, and my tube areator. I could throttle my 50 psi water flow down and still maintain the wort outlet between 65-75F with 59F inlet water temp. I have to refine my technique to reuse the hot outlet water to refill my hot liquor tank (HLT). I tried on my second batch, but I had the wort throttle down to about 0.5 gpm and the water flow pretty high – that put about 80F water in my HLT. I had to throttle the wort flow because the high flow makes my areating tube go crazy and my bucket was overflowing with foam by 2.5-3 gallons.
Thanks for the awesome plans, I’m shortly about to build my own. This topic brings to mind the similar principles in water cooling a PC when over-clocking. I’m thinking of applying some of these principles into my design, ie a radiater/fan, reservoir and pump, albeit on a slightly larger scale. Water turbulance appears to be a key factor in good pc water cooling sytems and I see no reason why turbulence in this application wouldn’t be the same.
Thought i’d better explain my reasonings better, I’m thinking of applying some of these principles into my design, ie a radiater/fan, reservoir and pump, albeit on a slightly larger scale, In Australia we have water restrictions so the above would cool and recycle the water (or so my thoughts go)
Does it matter which way the cooling water enters. Going to build one today and try it out this weekend. Just not sure if the cold water should go into the end where the wort comes out or where it goes in?
Oh, it matters. The key concept in a counterflow chiller is counterflow… meaning the flows are in opposite directions.
The rate of heat transfer from the wort to the coolant is proportional to the temperature difference between them. If the there is no temperature difference between coolant and wort, then there will be no heat transfer.
Suppose that the wort and coolant are flowing in the same direction. There will be a great deal of heat transfer at first because the wort would be very hot and the coolant very cool. But after traveling along together for a short while, they would reach an equilibrium, wort and coolant at the same temperature… the average temperature. No matter how long the chiller was, you’d never get the wort any cooler, or the coolant any hotter. They would emerge together at the far end both luke-warm.
Conversely, suppose they’re flowing in opposite directions. In that case, the coolant near the end of its travel is encountering incoming wort at very high temperature. And the wort at the end of its travel is encountering incoming coolant at very low temperature. So, even at the ends of the chiller, there is still going to be some heat transfer going on. As the length of the chiller approaches infinity, the heat exchange asymptotically approaches 100%. At infinity, the wort temperature out exactly equals the coolant temperature in, and vice versa.
In practice, you can get very close to 100% heat exchange with a practical chiller length. I get wort coming out that is cold, and coolant coming out steaming hot. I get one hell of a cold-break too. My chiller is, I think, rather longer than it needs to be, which costs me in flow-rate. It takes a fairly long time to drain my kettle into the fermenter.
But it does need to be counterflow, or the whole thing is shot.
Wow, three year old blog and still getting attention. Very nice.
Love the design, and wondering if anyone followed Luke A’s design change of using a 1/4″ inner tube? If it’s sufficient, it should be a lot easier to get through the garden hose!
I haven’t seen 1/4″ soft copper in my neck of the woods, but yes it would be easier. Using a similar design, the only difficult part was the Cu tube insertion, more specifically the last 5 feet of it. Turns out the not so smooth Cu end was peeling a thin layer off the inside of the garden hose. Great arm workout, that was. However, the finished piece was very functional, cooling 5 gal 95 deg C wort to 18 deg C in about 15 minutes, using 10 deg C input coolant (didn’t measure flow rate).
Starting one of these without a pump or ball valve on one’s kettle is tricky. I ended up priming the sanitized chiller with hot water, clipping closed the outlet to the fermenter and then putting my copper racking cane attached to the chiller into the wort. Unclip at the fermenter gave enough suction to start what turned out to be an efficient siphon. Sucking on the outlet hose just ain’t enough!
@piper – The ‘coolant’ is cold water which runs from a tap, through the garden house. It isn’t motionless, so I’m not sure I understand what you mean?