DIY Immersion Chiller: The Hydra

In my first blog post , I’ll go into how I constructed my own immersion chiller, which I have nicknamed the Hydra.  It requires no soldering and only basic tools.

The Hydra is different from other chillers in that it uses much thinner copper tubing, only 1/4 inch/ 0.64 cm diameter.  A thinner tube allows a much greater surface area to volume ratio of the coolant fluid, meaning the coolant will pull heat out much more efficiently.  The downside is that the resistance to flow is much higher in a thinner tube, and you simply can’t run as much coolant through.  I got around this my splitting my 50 ft (actually, 48 ft) of copper tubing into 3 separate parallel 16 ft/ 4.88 m sections.

[2014.06.18 UPDATE: This chiller has no relation to the commercial chiller of the same name; I named mine after the three-headed mythical monster.]

The 1/4″ tubing gives a cross-sectional area of 0.049 in²/ 0.316 cm² per tube, or 0.147 in²/ 0.948 cm² in total, which about splits the difference between the two standard tubing sizes used on chillers (0.11 in² for 3/8″ tubing and 0.196 in² for 1/2″ tubing).  So, the total volume of coolant in the pot at any given time is 1.1 gal/ 4.16 L in my chiller verses 0.86 gal/ 3.26 L and 1.52 gal/ 5.75 L for the standards, assuming the others are 50 ft/ 15.2 m chillers.  Most “entry-level” chillers are actually 25 ft/ 7.6 m long which would halve their volumes, meaning the hydra would have far more volume than either 25 ft standard chiller.

The other matter is resistance to flow: it would do no good to have some volume of coolant sitting in the wort indefinitely.  This is only especially important when a pump is being used to source the coolant; the rated gallons per hour is for a no-load condition- hook up some tubing and this rate plummets.  A garden hose should have all the pressure needed for any of the chillers examined.  From wikipedia, the equation for pressure drop through a tube is:

Instead of computing the actual value, which would require information we don’t know, we can simply reduce the equation to , where L and d are the length and diameter of the tube, and then compute the ratio of my chiller to others.  By dividing to compute a ratio, the other terms should cancel, as they are treated as constant.  Another wrinkle is that we must compute the total pressure drop for the three tubes in my chiller.  The basic equation for this is , the same as resistors in parallel in electronics.

Running the numbers, the hydra is most comparable to a 25 ft 3/8″ chiller, being 1.08 times more resistive to flow.  If the 3/8″ chiller is increased to 50 ft, the hydra is about half as resistive, being 0.56 times as resistive to flow as the 50 ft 3/8″ chiller.  The half-inch chiller wins squarely in this category no matter its length- the hydra is 3.41 and 1.71 times more resistive than the 25 ft and 50 ft chillers, respectively.  Note that this does not include any connection lines, only the copper tubing itself.

Construction:

Unfortunately, this was one of my previous projects so I don’t have any “during” photos, so I’ll just have to do the best I can to describe the process.  Also, my apologies to international readers- measurements are easy enough to convert to metric, but I have no idea what sort of plumbing connections and tubing are available to you elsewhere.

The coils are pretty straightforward- use a pipe cutter to cut the pipe into 3 segments, about 16 ft/ 4.88 m each.  I couldn’t get the tube to straighten from the roll perfectly to measure, so instead I measured a 16 ft length of twine and ran it along the tube and cut at the end of the twine.  Each is then coiled around a cylinder of your choosing; you’ll want something about 2/3 the diameter of your brew pot for the best results.  Make sure each end comes up over the top of the pot and swan-necks away a few inches- be careful not to kink the tubing by bending too sharply.  The three coils can then be meshed together, with the inlet end for one being zip-tied to the outlet end for another.  I like to run the cooling water down to the bottom of the pot first, but there are varying schools of thought on this.  It makes it easier to keep the whole coil contraption in the brew kettle for the rest of the process to keep it all together- it can be a bit ungainly.

Next up is the splitter.  There are probably easier, more elegant solutions here- the basic idea is to simply split a garden hose into 3 and attach one to each coil inlet.  My solution starts by cementing all four 1″ slip to 1/2″ threaded adapters into the PVC splitter.  This will allow you to screw in all nylon barb adapters after the cement cures; remember to use some teflon tape on the threading.  Three of these adapters will feed plastic hoses to connect to the inlet side of the coils.  The fourth will attach the system to the coolant source- a garden hose or pump for example.

3-way water splitter for DIY hydra immersion chiller

Finally, use the plastic tubing (I used vinyl- it will get hot enough to get very soft, but it never touches the wort, so no worries about leaching anything) to connect everything.  Run a length from each barb on the splitter to the inlet of each tube; use a pipe clamp to connect at the copper side.  Use a very short length to connect the top barb to an inlet and the splitter will hang directly off of the swan neck of the tube.  I put the hose barb down so it can hang down from the pot.  You will definitely need a pipe clamp on the hose and on the top barb (it supports the weight of the hanging hose, so it needs one, unlike the other barbed connections).  Use the remaining tubing to run an outlet line to each coil, no pipe clamp needed if the tubing is snug enough.  It can be zip tied to the inlet tubing and run back down the same way as the garden hose.  I braided all three exhaust tubes together into one hose to make them look nice.

Hydra: DIY immersion chiller from various angles

The majority of the cost of this chiller was the copper tubing.  If you can find some second hand, just make sure to get any green/black stuff off if present with an acid wash (vinegar or starsan should work), as it can be toxic.  The rest can be found for $20 or less at any hardware store (I got mine from Lowe’s).

Use:

I haven’t had my chiller around for too many batches yet, but here’s how it performed in three 5 gallon batches.  Note that I was very water conscious and the flow rate was kept very low, so chilling could have gone much faster.  Stirring with a sanitized spoon will also help improve heat transfer.

I generally will put the chiller in 10 minutes or so from the end of the boil along with a spoon to sanitize both.  Note that this will usually stop the rolling boil for a few minutes.

warm chill water, low flow rate
212F to 68F (100C to 20C), 85 min

46F chill water, low flow rate
212F to 58F (100C to 14.5C), 60 min

63F chill water, low flow rate
212F to 67F (100C to 19.5C) in 65 min

If you find that your ground water is too hot, you can always construct a pre-chiller coil that runs the ground water through an ice bath (or even just coil your garden hose in a bucket of ice water), or recirculate ice water with a pump after cooling most of the way with ground water.

Complete Parts List:
1: 48 ft 1/4″ copper coil
1: 25 ft 1/4″ inner diameter plastic tubing
4: 1/2″ pipe clamps
1: 4 way PVC splitter, 1″ inner diameter, slip fitting
4: PVC adapter, 1″ slip to 1/2″ threaded (interior diameter)
3: nylon barb, 1/2″ thread to 1/4″ barb
1: nylon barb, 1/2″ thread to 3/8″ barb
zip ties
teflon tape
PVC cement

[2014.03.12 UPDATE: After using this chiller for a while now, one thing I would change is the hose inlet connection.  I think the way I did it is the cheapest way, but disconnecting the hose clamp every time gets a bit tedious.  And, this connection tends to leak or spurt if care is not taken connecting it every time, as my garden hose does not exactly match the diameter of the fitting.  I have taken to wrapping the connection in electrical tape every time for insurance.  At some point, I think I am going to replace this with some sort of quick connect or something.]

– Dennis
Life, Fermented