All Copper Counterflow Chiller Experiment

>> Tuesday, April 05, 2011

I recently picked up a hopback from B3.  Basically you use a hopback to infuse volatile hop flavor and aroma in you beers. Typically you gravity flow from kettle to hopback, then pump or gravity flow from hopback to a counterflow chiller (CFC) to your fermenter.  By chilling immediately after the hopback you retain those volatile hop flavor and aroma compounds.  So that's the theory but the problem is I didn't have a CFC so the hopback wasn't going to do me much good.

There are lots of commercial CFC's out there but I usually like to go the DIY route; plus some are really expensive.  I like the plate chillers but I worry about break material clogging them up and fowling up future batches.  The HomeBrewNetwork has a nice wiki on a DIY counterflow chiller.  The Cliff's Notes version is you insert 3/8" copper tubing into a 5/8" rubber garden hose, sweat some fittings and bam, you have a very decent CFC.  The only thing I don't like about this is eventually the rubber hose will crack and you'll have to figure out a way to replace it.  This would probably mean you have to cut some tubing out every time you have to fix it.  I stumbled upon a post from PJ on where he'd built an all copper CFC.  I like this option better because you'll never have to deal with a cracked outer tube.

Mine is inspired by PJ's (his site can be found here with great instructions) but the end product is slightly different.  PJ builds his using 25 foot lengths of tubing (actually 50 footers cut in half).  I saw a couple commercial CFC's that used around 12 feet of convoluted tubing, so I decided to try to build a 10 footer and see what would my wife wouldn't approve the budget for anything longer.  I built it a couple weeks ago and just got around to testing it today.

The test was pretty straightforward, I boiled 6 gallons of water and ran it through my CFC and measured the temperature of the water entering and exiting the CFC.  I know this isn't real scientific, but it's fairly practical.  I have ball valves on both my kettle and pump to regulate the flow rates.  The cooling water initial temp was 52.3 F.  I used a couple different flow rates on the cooling water.  I don't have an accurate way to measure how fast the water was flowing, so I'll just call it low and high.  Even on high, the flow rate wasn't terribly high.  Initial Water (Wort) Temperature = 205.3 F.

Round 1 Tests
  1. Gravity feed with ball valves completely open, low chilling water flow - wort output temp = 93.3 F
  2. Gravity feed with ball valve 3/4 open, low chilling water flow - wort output temp = 88.8 F
  3. Gravity feed with ball valve 3/4 open, high chilling water flow - wort output = 84.0
Results will vary, especially when taking varying tap water temperatures into consideration, but as you can see above a 10 foot CFC can provide some pretty decent cooling.  These aren't quite pitching temperatures, but it's below temps where DMS is produced and most importantly should prevent those volatile hops flavors and aromas from being lost.  

That said, I wanted a bit more cooling capacity.  I had some cash burning a hole in my pocket from some hops rhizome sales, so I built a second 10 foot CFC this evening.  The plan is to daisy chain the CFC's so that I essentially end up with one big CFC with dual cooling inlets and outlets.  I don't know if I'd recommend going this route if you're starting from scratch, but since I had already built the first 10 foot CFC I figured this was the best way to ensure it's usefulness.  The price should be close to a 25 foot CFC but you'll have twice as many copper fittings to sweat; not a huge deal and if it is you probably should just buy one off the shelf.  Theoretically mine should provide better cooling than a longer CFC with a single inlet/outlet for the cooling water.  The first circuit will knock the temperature down near 90F.  My prediction is the second circuit should knock it down very close to the temp of the cooling water.

Round 2 Tests - The conditions for round 2 were the same as round 1.  By adjusting the flow rate I was able to get the output temperature down in the low 60's; not bad for a homemade chiller.

The dual circuits make the chiller a bit larger than I would have liked.  If you're starting from scratch I'd go with a 20-25 foot chiller rather than two 10 footers like I've created.  Based on my experience, anything longer than 25 feet would probably be overkill and unnecessary.

Unfortunately, aesthetically speaking, after connecting hoses and such I don't really like the look of my setup much.  It just doesn't have as clean a look as I would like.  One of the aspects that I like about home brewing is it allows for trial and error in various situations and there's always the opportunity to improve processes and techniques.  That said, at some point I may end up going with a plate chiller after all (and cleaning the heck out of it after each batch).  If I do, a 10 foot CFC would make a great pre-chiller.