Counterflow Wort Chiller

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.


  • 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.
  • Six short pieces (about 2″) of 1/2″ copper tube.
  • Two brass male garden-hose to 5/8″ hose-barb adapters. We won’t actually use the hose-barbs, we’re going to solder them on. Make sure that a piece of 1/2″ copper tubing fits fairly snugly inside the hose-barb side of the fitting. Snugly enough that it will be water-tight when soldered.
  • Two hose clamps large enough for the 5/8″ garden hose.
  • Plumbers’ solder. Not tin/lead solder.
  • Acid paste flux.
  • 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.

    End cap schematicCompleted end fitting

    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.

    Homebrew convoluted tubingI 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.


    Cable-pulling lubricantNext 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.

    Chiller endChiller end solder detail

    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.

    Completed wort chillerAnd 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.



    105 responses to “Counterflow Wort Chiller”

    1. Hi Ron,

      This is a really nice looking Counterflow Wort Chiller. It’s surprisingly similar to the one I made (at least as far as the fittings you sweated on go.) That’s a really good idea you had to use the copper wire to increase turbulence. I’m sure you get a great temperature drop with this one.

      I do have a question for you if you don’t mind helping out. I’m also using 3/8″ O.D. copper tube for the wort transfer through the chiller. I’m thinking I’d like to switch from 3/8″ I.D. plastic transfer tubing to 1/2″ tubing, because I’m in the process of adding a spigot to my brew pot that I’m thinking will terminate with a 1/2″ hose barb after the ball valve.

      I’m wondering if you have a suggestion on how best to couple the 1/2″ I.D. tubing with the 3/8″ O.D. copper tubing on my chiller. I was thinking I’d try to find a 1/2″ hose barb to sweat on the chiller “input,” but I’m reconsidering that approach in light of your comments about hose barbs being too difficult to take back apart.

      I don’t know anything about flared fittings–just not part of my plumbing repertoire. Would you be willing to post some pics of your finished input side of your chiller, and maybe what the flare nut ends of your racking hoses look like? I’d really appreciate it!

      Take care, and thanks for the great blog.


    2. First I would like to say thanks for posting this great info. I got some great tips and have improved my own concepts and approach to creating new equipment.

      however, The wire wrapping around the inner coppertubing May work againts your purpose. In dicussion with an aeronautical engineer concerning if this was worth the extas effort and myself being an X-assistant brewmaster of a ten barrel brew system, we decided that a heat transfer system is based on contaact surface. not air tublance or water turblance.

      The more surface area you have the more heat will be transferred.
      The air between the water and the hot copper tubing we felt would act more as a nuetral insulator than a transfer device.

      This is not an attempt to poke holes in your design, I am a commercial photographer and designer, I get excited when solving problems or looking for a good, better, or best solution for a problem. Maybe this will spark a discussion that can improve both our designs.

      Thanks Chris

    3. I like what I see, seems like a solid design for someone who is handy around the shop.

      I was wondering what kind of temp drop you get with this chiller?

    4. Re. Chris’ comment… you may be right, the copper wire may be unnecessary. But I’m not sure what “air” you’re referring to, there should be no air between the cooland and the copper tube.

      Surface area is definitely a major factor on the amount of heat transfer you’ll get. That’s why radiators have fins, after all.

      But flow-rate is a factor too. That’s why radiators have fans in front of them. The idea behind creating the turbulence is just to ensure that there is a decent flow rate at every point on the surface, not just a good average flow-rate (but with dead spots in it). As I wrote above, the turbulence idea isn’t mine… I got it from the “convoluted copper” thing used in commercial high-efficiency chillers.

      Re. Eric’s comment… I get almost 100% heat exchange, I think. The coolant water comes out steaming hot, and the chilled wort comes out really cold. And that’s with a fairly low coolant flow rate.

      Other commenters (in email) have suggested that my 30′ length is excessive. I suspect they’re right. A shorter length would probably give just as good results, and a better wort flow rate (less restriction). I do find my chiller runs a little slow.

    5. This is exactly what I was looking for. Thanks for the technical description. I may try a more compact version of this (for space reasons), using a tubing bender to achieve tight coils.

      In reading your responses, I must also disagree with Chris.

      1. What air?

      2. In the event that turbulence is NOT beneficial (which I think it IS), the added wire is still good surface area for heat exchange.

      3. I recall from several college physics classes something called the No Slip Condition, where the molecules at the interface of a liquid or fluid and a solid moving relative to each other (in this case the copper and cooling water) move at the speed of the solid. This is due to the transfer of energy between molecules. Therefore, anything that disrupts this will encourage new (ie. still cold) molecules to contact the copper and take heat.


    6. Ron-

      First off, thanks for the plans. I’m going to make one this weekend.

      But before I do, in retrospect what length would you make this? 25′? 20′?

      I think I’ll skip the “convoluted” step. It was an interesting experiment.

      Thanks again,
      Scott in Milwaukee

    7. Turbulence is very important in heat transfer. However so long as the flow rate of both the wort and water are high enough turbulent flow will be achieved without any convolutions. To figure out if your flow is turbulent find the typical flow rates using a measuring cup (I use a nalgene bottle because it has more gradations) and a stopwatch. Then using the area of the inner and outer pipes you can calculate the reynolds number using the tool on the site
      since the pipe and hose aren’t perfectly smooth and the areas aren’t regular the flow will become turbulent earlier than normal so if the reynolds number for your set up is greater than 1800 or so you should be in good shape. To increase the reynolds number and thus increase your heat transfer increase the height difference across which you are siphoning.

    8. Nice design. I have 2 thoughts about the copper wire which I think was very clever. The first is the wire keeps the hose evenly away from the inter copper tubing. Without it, there could be flat spots were the hose was smushed against the tube reducing contact. That may not be an issue or less of one if the water pressure is great enough. The second is the circular flow of water produces more contact in a given length that flowing staight through.

      I do think the wire acts as a fin which should facilitate some transfer. As far as reduced area on the cooper tube surface, the contact point is very small because of the circular shape of the wire. Only in areas were you soldered would the reduced suface area be of consideration.

      I’m going to make one but I don’t know what length to use. Any others out there make a shorter one and what length did you use?

    9. Ron, I LOVE this! Thank you for the plans and detailed instructions. If I could make one (or two) suggestions – I would clarify the size/type of 2 ” tubes on the T-FITTNG. According to my local ACE store, 2″ RIGID copper is different than 2″ FLEXIBLE copper. I used the 2″ Rigid which gave me a 5/8 Outer Diameter for the T-Fittings. This also allowed me to put a short but flexible “hose extender” on the T-Fitting between the fitting and hose barb – basically giving you some “flex area” to hook up the cold water supply and the drain hose for spent chilling water. If anyone is interested I can email pictures of the finished product. If I had thought it through a little more, this design can also eliminate the need to purchase the hose barb ($4.95 at ACE), if you buy a garden hose with the both brass connections and not just bulk hose.

      I made mine 3 days ago and have use it twice so far. I did not go with the small copper wire for the convoluted design, as I thought it would be more work than worth – I didn’t do it, so I actually have no ground to stand on. I can see how it would be beneficial though.

      As for the shorter length, I found myself buying a 50-foot garden hose, but only 25 feet of flexible copper tubing (this stuff is not cheap). This gave me a 25-foot counter flow chiller and plenty of additional hose to use as a “drain” hose to keep my work area (especially if you brew inside) dry.

      The temperature exchange is phenomenal. Previously, I used an immersion chiller that I built myself out of copper tubing, and it would take 30+ minuets to get the wort chilled down enough just to rack into the carboy… I still had to chill it in a tub of ice to get it cool enough to pitch the yeast. With my new counter flow system, two separate 5-gallon batches of beer cooled from boiling temperature down to 75 – 76 degrees Fahrenheit in the time it takes to siphon 5 gallons of beer. (10 minuets? Maybe less?) I am getting a really good amount of water flow out the “drain” end of the garden hose, it is as if the hose is running freely with the spigot turned to about 3/4 full open. One post stated that the spent chiller water was coming out “hot”? I am only getting luke-warm water coming out of the hose (and remember my finished wort is coming out at 75 degrees), so I am assuming that the heat transfer, and counter flow concept are working very efficiently and effectively.

      I am testing a few concepts on how to clean and sanitize the chiller effectively and I think that “adding” it the cleaning process for all my other equipment is going to be most effective – for example: Siphon the PBW from the boiling pot through the chiller and into the carboy… let soak… wash everything… rinse. Then fill the boiling pot with sanitizing solution (which I normally do not do) to allow you to siphon the sterilizing agent through the chiller and directly into the carboy (or primary fermenter). I like the idea of storing the chiller with some weak sanitizing solution inside, and I think I will go do that now.

      Again, thank you for the great plans!! You have helped me make better beer, faster.


    10. As a purely theoretical discussion point, would scuffing the outside of the copper with, say, 40- or 60-grit sandpaper increase or decrease turbulence?

      Part of me thinks “increase” by means of creating small eddies and obstacles; part of me thinks “decrease” because water could easily “fill the gaps” and flow laminarly (did I make that word up?) over the trapped water…

      Personally I think it’s a theoretical difference and not a practical one, but it’s an interesting discussion point.

    11. Dan wrote :

      I hope your not using lead based solder

      Do they even sell lead-based solder any more? The reason I ask is because last time I went looking for plumbing solder the vast majority of it was varieties of tin or silver-based.

      But that being said, DO make sure the solder you’re using isn’t lead based. The wort, being mildly acidic, will leach the lead right out of it, and into your beer.

    12. In my design, the beer is never in contact with the solder. The beer is inside the tubing, the solder is on the outside surface.

      Anyway, I did use lead-free plumbers’ solder. If it’s good enough for the water pipes in your house, I figure it’s good enough for beer.

      They do still sell lead-based solder, but not in the plumbing section. Mostly for electronics. And for stained-glass work.

    13. Benjamim

      With the great amount of water you are draining, it may be a good idea to add a valve on discharge to slow throughput of water through cooling line. your water will be hotter discharging while using less water thereby saving water and energy. Give it a try you’ll have better results.


    14. When you siphon the wort from your brew pot, how do you get the remaining 30′ of wort from the beer line when the siphon breaks as the brew pot runs dry? Is the force of gravity sufficient to empty a significant portion of the wort from the beer line?

    15. I was careful to wind mine as a single stack of turns. The wort enters at the top, leaves at the bottom. In theory, gravity should drain it all out.

    16. the convolutus says it has about 12′ of tubing, and I saw a similar device that used about the same, but had an outer tube of clear plastic hose. either way, about 12′ of tube seems like a good size…

    17. Hey folks. First off, Great work on the How-to. Love it. We are getting ready to give this a run today, and are anxious to see the results. We will also photograph our work and shoot you a link to the pictures to paste all over your site if you wish. we may also do up an instructable and give you credits for the design. Hears to hoping that all goes well. wish us luck. Nate and Adam

    18. I was wondering if you’ve had any trouble due to the hose not being rated for the temperature of the hot wort. I know most standard garden hoses are only rated to about 110F. I guess since household water lines don’t push the pressure limits of the hose it’s probably not a problem. I was just wondering.

    19. Just wanted to say thanks for the great design. I just finshed it up and will test it out this weekend. I do have to say it is easy enough to build, so well worth saving the money. We are going from ice baths, to this counterflow, so hopefully we can acheive a better cold break. Thanks again!

    20. Hey Guys, the couterflow worked great, however it got clogged. What is the best way to remove the clog, and second how do i best prevent it from happening again

    21. Chris –

      If hot water won’t clear your clog, there are a couple of different ways that you can clean your line.

      First, you need to poke a drainage hole through the line, which can be accomplished by running a length of stiff yet flexible wire through the chiller. I find that a steel guitar string works great here. On one end of this string, attach a small amount of cloth, which will help to increase surface area to push out the gunk in the line. Be firm, but ease the string through gently. You don’t want to scratch the copper line if it can be helped, as this will leave vectors for infection.

      Once you have punched through the blockage, use hot water to clear out the debris, followed by a strong chlorine solution, followed by lots of hot water to rinse away any trace of the chlorine. Don’t allow the chlorine to sit too long in the pipes, as it will cause copper to corrode if left in contact with it for too long. The chlorine will help to break down the proteins in the trub, which will make the secondary rinse cycle more effective. It will also sanitize the inner pipe.

      To prevent blockage, make sure that you strain any hops in your brew kettle, and use a screen to keep any solid materials from going into the counterflow chiller.

    22. I discoverd this very lovely “hot-to” while searching for “counterflow fitting”.

      I have been considering alternative PEX tubing for a shower waste water heat recovery device to warm the shower’s cold supply side, possibly using radiant heating PEX tubing, probably 3/4″ outer and 1/2″ inner.

      PEX much cheaper (1/3?), for the same size, per foot, than copper these days.
      But comparatively terrible thermal transmission – requiring (substantially) longer length.

      Any comments / suggestions / thoughts from those who have been there / done that, or those who ponder such things? Especially for estimating a length and / or for how to make / find appropriate end fittings?

      Anyone used this new potable plumbing plastic PEX (Polyethelene cross linked) stuff to make beer with?

      Simpler (smarter?) alternative, a plastic barrel for hot / warm shower waste water (drained from the bottom) with the cold water supply coil flowing upwards?

    23. I have been looking for a counter-flow chiller design for a while now. This one is the one I’ll steal. I can see how well it will work. And its inventor is to be congratulated on his well articulated and comprehensive set of instructions.

      The spiral wire feature is brilliant. Whatever it does in respect of turbulence, it keeps the inner and outer tubes out of direct contact with one another along their entire length; and that has to be a big plus. I don’t see how the solder detracts from heat transfer — solder is a good thermal conductor, isn’t it? And obviously none of the solder ever comes in contact with the wort.

      Thanks, Ron.

    24. Nice job Ron! I also made a similar chiller several years ago, but didn’t think to use the wire wrap. I can easily see that the wire would prevent direct contact between the tubing and hose wall, as well as adding some extra heat transfer area. Either of these are sufficeint reasons for using the wrap, but unless you could keep the tubing centered along the entire length of the hose, I don’t feel that the extra turbulence is all that beneficial. The next chiller I build, however, will have the wire wrap.
      A suggestion for anyone planning to build one of these, is to use a common five gallon plastic bucket to coil the hose assembly around the outside, with holes drilled to the inside for the hose barbs. The cold water supply and drain hose both coil neatly inside the bucket, and makes for a compact package. I also made an appropriate height PVC & plywood, collapsible stand, which also stores in the bucket. Thanks, John

    25. @Nekote PEX pipe is VERY cheap compared to alternatives, and can be used in very hot and very cold conditions, is rather rigid yet can flex as much as you want to. The only problem is connecting it. If you use the recommended fittings and attachments, the tool to compress them is ~$200. Hardly makes up the cost.

      Either way, I’m making one of these tonight! Great Design!

    26. PEX would have only a fraction of the thermal conductivity of copper (which is second only to silver in conductivity.) To get enough heat transfer, I think you’d need an insanely long coil. And then you’d end up with alot of restriction and poor flow rate.

      I’d think twice before switching away from copper.

    27. Hi , I don’t know how I got to this Blog and I’m pretty sure that it’s the first one that I’ve ever been on let alone ever even wanted to ask a question about, so here it goes, I was looking for chillers for a indoor ice rink that I want to try to build for my kids , they were involved in a car wreck last year on there way to a training facility and that coach for there team has expressed wanting to go to that same facility again this year. I’m sure my wife and some of the other mothers will strangle him if they find out about it, So that’s why me and some of the other dads decided to try to build this for the team so that there not on the highway in the middle of January. but we don’t have the kind of money that this would cost from what we understand about it so far, and then I somehow found this blog I’m still not sure what it is that you were building but I though I would ask If anyone out there could help provide some valuable info i regards to this project

    28. Not many engineers/scientists here, are there? I only saw Reynolds number mentioned once, and saw a couple people questioning where “air” would come from in turbulent flow.

      Reynolds number is important to determine whether or not you even have turbulent flow (I saw this mentioned but it needs to be reiterated).

      Second, the “air” pockets will insulate a slight bit (and yes, there will be air in the tube) -which is bad, but it will be countered and then some by a better heat transfer coefficient from turbulent flow. The “air” is actually from something called cavitation. It comes from low pressure zones in a flowing liquid usually caused by uneven surface geometry. It creates bubbles as a result – it’s why water boils at room temperature in a low enough pressure environment and bubbles rise up behind a boat propeller.

      To Ron-
      Nice work. I did some benchmarking with your design, but haven’t made a final design choice yet. It’s a great start!

    29. I know very little about fluid dynamics (though I do know in a very loose sense what a Reynolds number is). But I’d be really surprised if there was any detectable cavitation going on at the coolant flow rates I use. But sometimes life is surprising.

    30. If you have a Reynolds number high enough to obtain turbulent flow (>2000), and that fluid is shearing over uneven geometry (such as a copper wire wound around the pipe), you’ll get some level cavitation. Like I mentioned above though, it will be minuscule compared to the compensation from a far better heat transfer coefficient. If we want to get real technical, we could acknowledge that it’s very possible to get homogeneous nucleation from rapid heating of the cooling water. All this, like I said, is essentially negligible for wart cooling purposes. I just wanted to clear up a couple posts I saw above.


    31. We, my son and I, are planning on building one today but I still have two questions: will medium duty garden hose (bought from Lowe’s) work satisfactorily and is 25 feet a suitable length to build? The information from the various posts were great. Thanks!

    32. Ron,

      First off, great blog! I’ve been thinking about building a cross flow exchanger for cooling my wort, but had not even thought of using a water hose for the shell! Great idea!

      I am a chemical engineer and, while many of the questions posed here are quite old, maybe I can answer them for the next person that comes by (like me). So here’s a crash course into this cross exchanger:

      First, this system will be in the turbulent flow regime throughout, so there is need to argue whether we need the wire to increase turbulence; we do not.

      However, we DO need the wire to keep the inner tube out-of-contact with the outer hose; otherwise we will only be using a small portion of the heat transfer area and will not get good distrubtion of the cooling medium (water) around the hot inner tube. Commercially built heat exchangers have similar support structures to keep the inner tube in place. The wire will add some additional heat transfer area, but not enough to make much of a difference. The biggest benefit will be holding the two tubes in position, relative to each other. (And I will be using said wire on mine).

      There will not be any cavitation in this system, and the word “air” was introduced by a friend of an aerospac engineer, likely because he or she was relating the question to something they better understood (heat transfer from an aircraft to the air around it). You typically only see cavitation in places where velocities are very high, such as the blades on a centrifigul pump. Cavitating pumps have Reynold’s numbers many orders of magnitude higher than what this system will experience.

      And last, when it comes to “how much copper tube will work”, there is no definitive answer. Whether your exchanger will work or not has to due with 1)the heat flux and 2)the available area. “How long” addresses the available area, but not the heat flux.

      Heat flux will be determined by a) temperature differences (ie driving force), b)fluid velocities, and c)fluid properties. Fluid properties (heat capacity, conductivity, etc.) are already set, as is, for the most part, our driving force (wort is only so hot, and tap water is only so cold). That only leaves fluid velocites or flows.

      What does this mean? It means you can really crank up the water flow and get by with a smaller exchanger (since the water flow is higher, its temperature changes less, which gives you a better driving force across the entire exchanger). Alternatively you can slow down the wort (say with a valve at the end, or by lessening the height from which you are siphoning).

      I plan to build one of these over the holidays, and what I plan to add is a ball valve to the wort outlet. This way I can leave my kettle where it is and control the wort flow with the valve (once it is siphoned and ready to flow). If the wort is coming out too hot, I will throttle down on the valve a bit to slow it down (thus giving it more time to cross exchange with the incoming water). If the water is coming out too cool, I can back of the faucet.

      If you’re exchanger is too long, the wort will still come out at 80F, which is the real objective. The water leaving can range anywhere from 200F to 68F, depending on how much you manage to get to flow through your system.

      So what’s left? I’m building mine of 1/4″ copper tube inside a 5/8″ hose. I figured with a 3ft height difference from the pot to the floor, I would get 2.2gpm flowing through the 1/4″ tube. I neglected friction here, so the pot could empty in anywhere from 2 to 5 minutes.

      I then calculated what I expect my water flowrate to be, considering that my water pressure is 40psig, dropping down to 0psig (to the atmosphere). I came out with around 2gpm of water flowing through the annulus.

      With these flows, and my given tube diameter and hose diameter, I came out with 11ft of tubing required. Slap on around a 50% margin, and you’ve got 15-20ft of tubing to get it done.

      BTW, soft copper tubing comes in convenient 20ft rolls.

      So I hope that this answers additional questions…Ron, you did a great job on the write-up (if you’re even still around). Thanks.

      Oh, I see one more question that needs answering. The type of water hose shouldn’t matter. Sitting in the sun, your hose is going to get every bit as hot as it will get in this application.

    33. Of course I’m still around. Still adding new material too.

      Thanks for the great information you added there. I’ll have to look up some of the math you referred to there, like the expected flow rate given the tubing size, viscosity, and pressure difference. That’s probably something I should have thought about before I built mine with 30ft of 3/8″ tubing.

    34. Piper,

      Sorry, I didn’t realize that was your handle. I was looking for something involving “ron”. =)

      Draining the pot by gravity is the classic “Torricelli Problem”. That is if you neglect friction in the hose (hey, we’re just getting close, right?).

      You use the continuity equation and Bernouli’s equation to derive what is called the “Toricelli Equation”. That is:


      V=liquid velocity leaving the tube
      g=accel. of gravity (32.2 ft/s2)
      h=height (ft)
      with D2=diameter of the hose and D1 being the diameter of the pot. (Beta is dimensionless, so it doesn’t matter whether you use inches or feet here for the diameters).

      so a 1/4″ line and a 15″ pot, 3ft height gives a velocity of 14 ft/s.

      Flow = V * A, V=14 ft/s, A= Pi * (0.25/12/2)^2=0.000341 ft^2

      Flow = 0.005 ft^3/s or 2.25 gal/min

      Of course, to get the true time required you have to integrate (h is changing as the pot empties) but this is close enough for gov’t work.

    35. Interesting. That equation surprises me in two ways. I would have thought that the viscosity of the fluid would appear somewhere. Surely a pot of honey will drain slower than a pot of water. Viscosity seems to me to be a separate thing from friction in the hose, but maybe I’m wrong about that.

      Second, I wouldn’t have thought that the diameter of the pot would be a factor. It doesn’t affect the pressure at the drain port, only the height of the liquid column affects that.

      The “beta^4” term where the diameter of the pot appears works out to be very, very small, so dividing by “1-beta^4″ can probably be ignored for engineering purposes, which makes the resulting equation closer to what I would have expected. Still, I don’t really grok how the pot diameter could ever have appeared in the first place.

      Actually, thinking about it more, I think the pot diameter appears because apparently your height includes both the liquid depth in the pot, plus the vertical drop of the 1/4” tube, which means effectively that the pot is being treated mathematically as just a really wide section of tube. I think you could probably derive the flow rate differently, by starting with just the pressure at the drain port (which is independent of the diameter of the pot), and somehow calculating flow rate from that.

    36. I just discovered Poiseuille’s Law, which seems to capture what I was expecting:

      FlowRate = (PressureDrop x pi x r^4) / (Length x DynamicViscosity x 8 )

      Water has a dynamic viscosity of 9*10^-4 Pa*s at room temperature.

      If I divide your 3′ height into 1′ for the pot and 2′ for the tube, and convert to metric units (because all the viscosity figures I can find are in metric), I get a pot depth of 0.0305m, and tube length of 0.061m. 1/4″ diameter converts to 0.3175×10^-2m radius.

      The pressure at the drain port with a 30.5cm water column would be 2981 Pa. The pressure drops to 0 at the other end of the tube. (Actually it drops to atmospheric pressure, but I’ll assume atmospheric pressure is equal at the top and bottom, so it cancels out.)

      That works out to a flow rate of 0.0022 m^3/s, or 34.8 gal/m. That seems kinda high. I’m not sure where it went wrong.

      Your method doesn’t account for viscosity. My method doesn’t account for gravity accelerating the fluid down the tube. Clearly if the tube hangs down it should drain a bit faster than if it lies horizontally. If the tube went upwards from the drain port, the water wouldn’t flow at all, but my calculations don’t seem to account for that. It must enter into the PressureDrop term somehow. Neither of us is integrating over the dropping liquid level in the pot. But it’s interesting that we get such radically different answers. I wonder why?

      I’m tempted to run an experiment and measure the actual result.

    37. piper,

      Bernoulli’s equation (and the Toricelli equation which is derived from it) both assume inviscid flow. We make this assumption when we throw out frictional losses.

      The pot diameter comes into play because the Toricelli equation is derived from 1) Bernoulli’s equation and 2)the continuity equation. The continuity equation is a form of accounting for mass; V1*A1*Rho=V2*A2*Rho. Do a google search for Toricelli and you’ll come up with a better derivation than I can give in this reply (but the deriviation is quite simple).

      But we’re getting way to technical; I tried to simplify the system by assuming the entire thing was one big pot with a hole punched in the bottom; the height of the fluid is the difference between the height of the liquid and the chiller discharge.

    38. Piper

      Ye old counter-flow chiller. Nicely done. I used a similar design, with some changes, some years back when I created my chiller for ten gallon batches (about 11.25 gallons at boil end, accounting for future wasteage, to arrive at a ten gallon keg). Some parameters I had to keep in mind: all my tubing is 1/2″ ID (roughly twice the cross-section of 3/8″ tubing, same wait but twice the delivery), and my faucet water temp varies from 53 to 78 degrees. The 53 degree stuff works lickety split, but the 78 degree stuff means the chiller has to be very efficient. I used 50′ of 1/2″ OD copper. Copper tubing exits the fittings through epoxied compression fittings. Vinyl tubing hose clamps simply to copper tube. I used 70′ of 3/4″ rubber garden hose (very heat tolerant), cutting off 7.5′ off each end and using these two lengths to connect to faucet and sink drain. The remaining long length then was the outer coolant jacket. Mating the hose and copper tubing was an elaborate frontyard + backyard affair with ends secured to fences, KY lubricant, and wound around a single larger (6 gal) size ‘5 gal bucket’ (actually, it was several buckets nested inside each other for rigidity for the winding process). The super long size requires a pump, a March 809 magnetic impeller with polysulfone head, on the wort input side. This is not a self-priming pump, so I ‘charge’ the whole 1/2″ tubing run with faucet then drop ends into 5 gal bucket of whatever for cleaning/sani. Wort outlet is ball-valved. In addition, I made two tubing thermometers for measuring the coolant ‘in’ temp and wort ‘out’ temp. One is 1′ of 1/2″ OD copper with a strip thermometer taped longitudinally to it and surrounded by insulating foam (except where the strip thermometer is, so you can read it). This goes in-line on the wort ‘out’ side, before the valve. The other tubing thermometer is similar but with 3/4″ rigid copper and soldered fittings to mate with garden hose fittings. This goes in-line on the coolant ‘in’ side. Subsequent addition was 20′ of coiled copper inside the 6 gal bucket. With an ice-water bath in the bucket and the counter-flow’s output routed to the 20′ copper section and then out to fermenter, I have achieved 40 degree wort output on 10 gal batch with 78 degree coolant, in good time. Typically, I only chill to about 68 to 72 degrees for ale production. So, in the winter, I use counter-flow only, and, in the summer, counter-flow + ice chiller. Two bags of ice do the job nicely when it’s 100 degree days. Works like a dream, it’s never clogged (I only use hop pellets), and it looks very impressive sitting in the kitchen on it’s own cart.

      1) I doubt the soldered wire makes much difference. However, I’m not willing to disect my setup and splice one in to verify this assertion.

      2) Engineers, god love ’em. Sometimes I ride roller coasters just to show how much I believe in them. But you gotta keep an eye on ’em. They like to simplify until they reach something tractable, i.e. something you can then run through a calculator and get an answer. Being from the physics department, I know that your calculations only match the real world when your givens reflect them. Take this given for example: wort is infinitely viscous (did I say that right?) and flows through frictionless tubing. This makes the math easy but defies experience. I’ll eat my shorts if that guy gets 2.25 gpm through 20′ of 1/4″ tubing plus all the vinyl tubing to get to fermenter with actual wort flowing through, solids precipitating and all. Not without putting the boil vessel on the roof, at least. And the first time he has to wait hours to cool that monster 1.100 wort, viscosity will, indeed, play a role. Engineers should wear a number on their forehead that indicates what percentage of that which comes out of their calculator actually pans out ‘real world’, givens and all. My brother’s an engineer, BTW, so I say all this out of love.

      Good brewing

    39. I’m at a loss about your concern over using lead based solder? If the wort only goes in and comes out thru the 3/8in tube and the solder is only applied to the 1/2 in tubing where is the issue?? The wort never touches the solder.

    40. Yeah, you’re right about that. The way I built mine, lead solder wouldn’t hurt. But I guess it doesn’t hurt to encourage people to be safe rather than sorry.

    41. I have noticed that many brewers are not very technically oriented, luckily, I am. I have made brewing aids for myself, including an “active” low cost mash tun made from an electric turkey fryer, and equipped it with a digital temperature controller, amongst other things.

      Concerning the wort cooler, I have the following advice.

      I have a lot of experience with hydraulic oil coolers, and the same principles apply here. Firstly, high water and wort velocity is a key factor. You get maximum efficiency and reduction of fouling. If you look at a commercial engine air / oil cooler, it will have a closely pitched copper ribbon spring inside of the the cooling tubes, along with fins on the outside. Turbulence is definitely desireable in this case. Shell type water / oil coolers of the 4 pass type are the most effective, again from the high cooling medium velocity. By the way, some of the expensive counterflow coolers from brew supply shops are way overpriced. I have found the identical units from industrial supplies for far less. Educate youselves about coolers on the internet. Try these links and read up on the theory.

      Concerning soldering issues, I would recommend soldering any joints with pure silver solder, available from any welding supply company. For the flux, buy some borax and make a smooth, thick paste with some water. Apply the flux to the joints, then gently heat the joints to dry the flux slightly. Heat the joint and watch the flux. It will melt and become clear, and afterwards it will take on a mottled appearance. This is the time to apply the solder, if it balls and doesn’t flow, heat a bit more. Do not overheat the joint. If you see brown smoke, it’s overheated. If so, cool the joint, re-flux it and try again. once you have a good joint, the flux will either need to be chipped off, or immerse the part in boiling water for a few minutes to remove it. If this is too much to cope with, take you parts to a jewellry repair shop, and have them do it. When you cooler is finished, fill and flush it out with a peroxide based cleaner such as Aseptox.

      Happy brewing,


    42. One thing I found as I did my wort cooler today the hose ends are actually 3/4 inch barbs, they will press right on the 1/2in tubing. If you want to use a pump Harbor Freight has a tiny 12 volt bilge pump for $39. It has a stainless steel housing, I don’t know what the inside is made of. I bought mine yesterday on sale for $32. Its self primping and will pump about 4 gals per minute. It only has a short cord but so you either need a battery handy or some other power supply. My son uses a power supply out of an old computer for his and has been using it for some time with good success.

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