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Thread: Whirlpool operation

  1. #1
    Join Date
    Nov 2003
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    Whirlpool operation

    Seeking an explanation as to how a combined kettle/whirlpool actually works - I have not been able to find an explanation yet and I have never seen one.

    My guess is that there is a draw nozzle on one side of the vessel connected to a pump which returns the wort through another nozzle, thereby imparting rotational momentum on the wort still in the kettle. The bulk wort slowly begins to rotate, and the trub collects in the middle. Then, when happy that all of the trub is in the middle, you disconnect the return hose on the discharge of the pump to your plate HEX and transfer the wort to the fermenters.

    How is this for a guess?

    Any hints regarding nozzle design, location, other issues?

    Thanks.

  2. #2
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    Jun 2003
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    You got it in one try!

    The systems I've used usually have the drain on the brew kettle located over on the side (where the bottom meets the side). That will be hard-piped to the wort pump, and from there will either go to a manifold (where you can choose to send it to either the whirlpool jet or to the wort chiller and on to the fermenters), or you'll have a hose you can connect to either the whirlpool or chiller.

    The whirlpool jet (there's a German name that escapes me right now...vorlauf?) is a fitting with a valve that goes into the side of the kettle somewhat below the level of the wort, and turns to one side so that the wort will come out parallel to the side. You control the speed of the whirlpool by regulating the flow back into the kettle with that valve. You'll want a nice, steady, slowish flow, about the speed of a man walking.

    Cheers, Tim

  3. #3
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    Feb 2004
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    You control the speed of the whirlpool by regulating the flow back into the kettle with that valve.

    A variable speed pump and using a paddle might be better solutions.

    Choking the inlet will increse particle shearing.


    Basic Stokes law Vg=d^2 (S-S1)g / 18m

    Where:

    Vg is settling velocity

    d^2 is the particle diameter squared

    S-S1 is density difference of the particle and the liquid
    m is viscosity if the liquid

    g is the gravitational constant


    With this equation you can see the importance of maintaining the trub particle size. We cannot change the viscosity of the liquid without changing the OG of the beer. We also cannot change gravity in a whirlpool. Changing the gravitational constant could be accomplished in a centrifuge.

    In a kettle, trub particle may be 5-10mm in size. After shearing in the transfer pump, they are usually 30-80 microns in size.


    Limit whirlpool pump time (2-6 rpm is ideal wort rotation speed in a whirlpool). Any more is not going to help.

    The inlet speed should not exceed 3.5 meter per second to reduce trub particle break up. 2 meters per second is a good limit if you are going through 90 degree pipe bends.

    Also, the higher up on the side of the vessel, the better the rotation. To high may limit you ability to do small batches.

  4. #4
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    You're almost certainly right about that, but in my experience with six different brewing systems in American micro and brew pubs (5bbl - 50bbl), the pumps are on/off and the flow is regulated by valve.

    Totally a "for what it's worth" note!

    Cheers, Tim

  5. #5
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    Eugene OR
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    Flow should ALWAYS be throttled on the outlet side of the pump. Never on the inlet, or cavitation will result.

    --
    Mike Bennett
    Head Brew Dude, Southside Speakeasy, Salem OR
    Recognized BJCP Beer Judge
    [1958, 287.1] Apparent Rennerian
    mjb<at>efn.org

    ....Give a man a beer, he'll waste an hour.
    Teach a man to brew and he'll waste a lifetime....

  6. #6
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    I had one experience where we had to throttle both inlet and outlet due to poor design (the pump was way bigger than spec). To prevent cavitation, we throttled the outlet way down, and then throttled the inlet until things calmed down.

    Cheers, Tim

  7. #7
    Join Date
    Feb 2004
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    Most system builders don't understand the finer points of the brewing process. I have seen many bad designs.

    On a small system (<30 bbl) a good whirlpool can be achieved with a few strokes of a mash paddle. Or at least limit pump time. The less trub breakup translates to better shelf life of the product.

  8. #8
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    Oct 2002
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    Ft. Madison, IA, USA
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    whirlpool

    Save yourself a great deal of trouble and headache.

    Whirlpool/ Kettles are inefficient. As someone has said, you would almost be better off on a 10 - 20 hl system to create the effect with a paddle. Many of the german made systems are mash/kettle and lauter/whirlpool for this very reason. Lots of cleaning during the brew day, but there is some evidence that a sieve (such as the false bottom) increases efficiency.

    If you can get a single side tank that is ideally 2x diameter:height of the volume you need with a flat sloped bottom. A slight cone will work also. If you can flow wort in through the bottom until you cover the tangetial flow inlet. At that point whirlpool action can start using a pump with a power inverter. This allows you to dial in pump speed and rotation within the whirlpool.

    On systems with a kettle/whirlpool we would pump for 10 minutes after a 10 min post boil rest. Another 10 minute rest would follow before knockout. With a separate whirlpool, knockout occured at end of boil. We would pump rotation for 15 minutes at 3 rpm. After this we would rest depending on the hop load of the brew. One tower system I worked on had a knockout time of 2 minutes (gravity and correctly sized lines).

  9. #9
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    Oct 2002
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    Originally posted by MoreBeer
    Most system builders don't understand the finer points of the brewing process. I have seen many bad designs.

    On a small system (<30 bbl) a good whirlpool can be achieved with a few strokes of a mash paddle. Or at least limit pump time. The less trub breakup translates to better shelf life of the product.
    LOL...Yea, but those cool vortex equations sure give you somthing to think about while your paddling!

  10. #10
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    Nov 2003
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    Thanks for all your excellent answers and comments.

    Does anyone ever add anything to the wort prior to whirlpooling to promote agglomeration of the trub particles?

    Also, does anyone use a low-shear pump (i.e. not centrifugal!) for the wort circulation exercise?

    And, is anyone concerned about introducing infections to the wort by use of a paddle? Is it preferable to use a pump to keep the outside air away from the wort?

  11. #11
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    Does anyone ever add anything to the wort prior to whirlpooling to promote agglomeration of the trub particles?

    Irish moss is commonly used.


    Also, does anyone use a low-shear pump (i.e. not centrifugal!) for the wort circulation exercise?

    Centrifugal pumps can be used without a problem if they are sized properly. Variable speed controls will allow the pump to be slowed to achieve good results. Centrifugal pumps are also cheaper than most other solutions (unless gravity is used to transfer to a whirlpool).

    And, is anyone concerned about introducing infections to the wort by use of a paddle? Is it preferable to use a pump to keep the outside air away from the wort?

    The wort is just below boiling at this point, infection is unlikely. As for air, stir ...don't splash.


    MoreBeer

  12. #12
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    A couple of points not really mentioned so far.

    Irish Moss (Carageenan) - needs to be optimised in the same way that auxillary and white finings are. The use of carageenan will help final beer clarity enourmously.

    The whirlpool depth to diameter ratio is not really that critical, certainly not as much as some people would have you believe, but better to err on the shallow side rather than deep side for best results. Bottom slope - only a couple of degrees - just enough to allow wort runoff, but not trub runoff.

    They are not really very suitable if using whole hops. They can be used, but you tend to have a looser debris cone, and lose more wort. It is possible to overload a whirlpool, especially with high gravity, highly hopped beers. Try to ensure a clear rind of stainless whirlpool bottom around the cone, or else you will draw into the wort run to FV. You can start drawing off early if you have a runoff point part way up the vessel wall, but this is probably only a suitable option for big breweries - certainly the cleaning can be quite awkward, and may outweigh the benefits.

    Since many breweries aerate the hot wort, not cold wort, a little splashing may not be too much of a problem, but certainly vigorous aeration should be avoided to prevent colour pickup and flavour changes.

    Cheers
    dick

  13. #13
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    Nov 2003
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    Great answers and info.

    Last question (I hope!):

    In clarifying wort, do you typically work out your brewery's optimal whirlpool rotational velocity and subsequent clarification/trub deposition on a 'light' wort first (i.e. one you can see through!) and then apply the same regime to dark worts? Or do different worts behave differently and so is there some other way of confirming trub separation for all worts besides having to take a look into the kettle?

  14. #14
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    Oct 2002
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    Ft. Madison, IA, USA
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    whirlpool

    It is easiest to see when your trub pile begins to build and is nearly fininshed on lighter worts, but remember that you will have evaporation going on and that means you may not be able to see too well without a high powered light (ie too many clouds in the kettle/ whirlpool).

    As for finding out how effective your whirlpool is, aside from the trub pile, its compactness and size, another measure of its effectiveness is an inline densitometer. If you can afford one of these, we really shouldn't be talking about kettle/ whirlpool combos, should we?

    Kidding aside, the sight glass you have after your wort aerator should give you a good idea both of how well your whirlpool action was and if you begin to draw out trub at any point during wort transfer.

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