Chilling - pre chill water or post chill wort

Discussion in 'General Brewing Techniques' started by pirateagenda, 4/12/17.

 

  1. pirateagenda

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    Posted 4/12/17
    I've rigged up a counterflow chiller which gets wort down to about 5C above groundwater in 1 pass.

    Now my tap water is about 25 at the moment so this means i'm only getting it to about 30C. I have a stainless coil (about 12m left) from an immersion chiller that I hacked up and am planning to use it in a bucket of ice water.

    Would it be more effective if i ran the 30C wort through it after it exits the counterflow chiller, or run the tap water through it before it goes into the CFC to give the CFC better cooling capacity?

    I do minimum 40L batches and it takes a while in the fridge to go from 30 to 18 to pitch.
     
  2. eldertaco

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    Posted 4/12/17
    I'm no expert but I would have thought you'd be best off using the icebucket + immersion chiller to bring down your tapwater temperature before the CFC.
     
  3. mtb

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    Posted 4/12/17
    Ice it after it hits 30C - otherwise you're wasting its potential.
    On another note, have you considered just pitching warm? Not 30C.. but 25 ought to be safe. I've never noticed any ill effects of doing so myself, as long as I brought temp down over the following 6 - 9hrs
     
  4. pirateagenda

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    Posted 4/12/17
    yeah I have pitched warm @ around 23-24C for ales and haven't had any issues i'm aware of. still a lot of waiting for 40L to cool that 6-7C in the fridge.

    Would want to get it even lower for a lager though which means a heaps longer wait (probably overnight) from the 30C
     
  5. Matplat

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    Posted 4/12/17
    I use an immersion chiller, tap water gets me to 30deg in a reasonable time frame at the moment. After that I have a spare 25L FV full of water/ice which I then run through the chiller and I hit pitching temp.

    You could do the same if you plumb the chiller back into the kettle with tap water chilling until you reach 30, then a second pass into the FV using iced water to cool the chiller. This does away with using the second coil, and your cooling water is in direct contact with the ice rather than on the other side of a stainless wall, so you should get colder cooling water and quicker chilling.
     
  6. MHB

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    Posted 4/12/17
    Two stage cooling is more efficient than trying to get the temperature down in one pass.
    If you use the tap/ground water to get the wort down to 30oC then use the ice to cool to pitching temperatures you will use less ice (= Energy ($)).
    In two stages you are cooling from say 90-30oC (60oC) in the first stage and for an ale cooled to say 20 from 30-20oC (10oC) in the second stage, it's a lot easier to peel 10oC off than it is to take of 70oc that would be the case with any single step configuration.

    The main components (well variables) of wort chilling are -
    Temperature difference (gradient)
    Thermal conductivity of the chiller (copper is good SS sux but has other advantages)
    Wall thickness (thinner is better)
    Flow rate (slower is better than going too fast)
    Mark
     
  7. Garfield

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    Posted 5/12/17
    How long? You could pitch at 30 while it's working it's way down to 18. Yeast much prefers to grow warm but for flavour sake we don't let it. If it's down to 18 in a few hours I doubt you'll notice any concerning flavours
     
  8. pirateagenda

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    Posted 5/12/17
    30 to 18 is usually overnight a bit too long to be comfortable with pitching high. If i brew in the morning i can usually pitch around 23 by the evening.

    It would be nice to be able to do an afternoon brew and pitch straight away without any worries.
     
  9. pcqypcqy

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    Posted 6/12/17
    It depends on what you do with the water when it exits the chiller.

    If you are just dumping it, then I would use the coil to do a prechill on your incoming tap water the ice. You can knock several degrees of it and get your wort coming out at pitch temperatures.

    If you are recirculating that water in the bucket, then I agree with the others that doing this in one go would use your ice up quickly for little benefit.

    Edit: also depends on what you do with your wort as it exits the chiller - are you cycling back into the kettle or just dumping into fermenter?
     
    Last edited: 6/12/17
  10. Lyrebird_Cycles

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    Posted 6/12/17
    Have you measured the exit water temperature and volume from the counterflow chiller? If so we can use them to calculate the chiller effectiveness and answer your question.

    Without that data we are just guessing, hence the disparate responses.
     
    Last edited: 6/12/17
  11. pirateagenda

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    Posted 6/12/17
    the chiller is 6m of 12mm copper, water enters at the end and halfway along, so it's effectively 2 x 3m chillers. I dump the water.

    haven't measure the exiting water.
     
  12. pcqypcqy

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    Posted 7/12/17
    If you are dumping the water, I would use the extra coil to prechill your tap water with ice prior to putting it into your counterflow chiller.

    That way you're only using the ice to chill tap water from 20/25 down to whatever, so you're not likely to melt all of your ice during the chill. You could probably get away with a bucket with a few ice bricks / frozen bottles in it for the prechill.

    If your coil gives you wort 5 degrees warmer than your incoming chill water, then you can dial in your prechill accordingly to give you your pitching temp in one pass.
     
  13. Adrianc5

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    Posted 7/12/17
    I've tried pre-chilling tap water with a copper coil about 1.5m long in an ice-bath before, and found it didn't have much effect unless I agitated the chiller coil in the ice-bath constantly. If the pre-chill coil sat still the temp drop of the water through the ice-bath was minimal. Any other experience with this type of setup?
     
  14. pirateagenda

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    Posted 7/12/17
    To be honest i don't think 1.5m is long enough for you to get much change. I've got about 12m left I think so it should lower the water a bit i'd imagine.
     
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  15. Andy_27

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    Posted 7/12/17
    I cant really agree with all of this. SS might not conduct as well as copper, but it definitely doesnt suck. And regarding flow rates, Ive tested my SS immersion chiller at low flow and quite fast. The higher flow cooled the wort to 30 in about 15 minutes. The slow flow was a good 15 minutes longer. I hook the other end of the chiller up to the sprinkler and get a good spray to determine the best flow rate.

    It also helps big time to stir or recirc the wort while chilling. Otherwise the hot stuff rises and sits and the top of the kettle and doesnt really come down in temp.
     
  16. Lyrebird_Cycles

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    Posted 7/12/17
    SS sucks as a heat transfer medium but in this application it is unlikely to be the rate limiting step.

    It will be clobbered by flow velocity: if the flow is below the Reynold's number you'll get poor heat transfer as the flow laminae act as insulators. If the flow is above the Reynold's number you'll get much better transfer but you'll use a lot more water.
     
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  17. malt junkie

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    Posted 7/12/17
    Hmmm some more light night reading.
     
  18. Adrianc5

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    Posted 7/12/17
    +1 on the recirc wort to really decrease chilling time. Since I added a pump and do a recirc whirlpool while chilling it's reduced chill time by about 1/2 (30 minutes or so now with tap water for the first 20 and then pond pump in an ice bath for the last 10 or so).
     
  19. pcqypcqy

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    Posted 7/12/17
    I think there's a sweet spot in flow rate to get the best out of your chiller. The biggest thing is maintaining the differential between wort and chilling water. If there is still differential there, you want to control the flow of water to extract the most heat out of the wort as it passes through. However, if it gets too hot by the end, you'll be losing efficiency. So there's a balance there between efficiency of the coil and the amount of water you need to use. If water isn't an issue (using tank water or reusing it somehow), then I'd just prechill it a bit and go for it.

    When i was using my immersion chiller, I was throttling the flow with a tap to ensure the output was always very warm. As the temperature of the wort dropped, I slowed the flow rate to ensure I was extracting as much heat as I could for a given volume of water.
     
  20. pcqypcqy

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    Posted 7/12/17
    Just need to induce/maintain critical flow and we'll be set!
     

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