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Old 08-05-2012, 04:13 PM   #21
Docgineer
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Water usage absolutely. Speed to chill nope, that's the myth. I think you knew that though.

For those who don't: the water will match the temperature of the wort on the other side of the copper in short order thanks to the copper's conductance. The limiting factor in cooling rate is the heat capacity of the wort relative to that of plain ol water. Something we just have to deal with.

The technical options for optimizing are really two: agitate the water/wort such that the water/wort on the inside of the flow gets exchanged with the water/wort on the copper wall of the tube (hence convoluted CFC's and whirlpool arms) or, increase your surface area (bigger chillers). Both are still limited by the heat capacity of the water (once you match the temps, nothing's gonna change from that distance on down the chiller) and each has their design trade offs.

The goal of either design is to make sure that all the water (across flow's cross section) at the exit of the chiller is the same temperature as the wort (either in the kettle in the case of immersion or at the outlet in the case of CFC's and plates) Technically, that's as good as it gets. You can of course chill the water but that's not a chiller design issue, that's execution.

"In this house we obey the laws of thermodynamics!"

I would recommend bending up a whirlpool arm if you have a wort pump, it works very nice. I used to run it for the last 15 minutes of the boil to sanitize the lines then turn on the hose at flame out. Presently I am using a convoluted CFC and have a tangential inlet on my kettle to whirlpool cold wort back in and chill the whole volume as fast as possible.

Quote:
Originally Posted by MalFet View Post
I'm not sure what exactly you're saying is a myth here, but certainly slowing down the flow rate can make you more efficient with regards to water usage.

 
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Old 08-05-2012, 04:33 PM   #22
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Indeed.

Phrased slightly differently, there are two potential limiting factors to a heat exchanger system.

The first is the efficiency of heat transfer. In a idealized system, the water leaving the chiller would be the same temperature as the wort. This is relatively easy to measure, and if you're getting a gap of more than a few degrees there are things you can do to improve your system.

However, if you're already outputting water relatively close in temperature to the temperature of your wort, changing your system design won't change anything. The only thing to do in that instance is to either up your rate of water flow or drop your water temperature somehow.

In the OP's case, I suspect he might just be hitting some hard limits imposed by the temperature of his ground water and the rate of water flow he's got. If that's the case, increasing the size of his coil or switching over to a CFC won't actually improve anything. The best thing to do would be to measure the output water to see how much of a difference he's got.

Technical question: anybody able to produce a formula that would describe the volume of water needed in a theoretically perfect system to cool wort from 212 to a given temperature? I tried to figure it out, but my multivariable integration isn't quite what it ought to be.
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Old 08-05-2012, 08:37 PM   #23
Docgineer
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You know, I was just wishing I still had access to ANSYS Fluent so I could model heat exchange through a chiller. Also, I was wishing I still remembered how to use it.

 
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Old 08-05-2012, 09:12 PM   #24
chessking
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Quote:
Originally Posted by MalFet View Post
your options are either ice or refrigeration. I've always had good luck sticking the carboy in my fermentation chamber and pitching the next morning.
This is what I do. Especially with lagers. Get it in the 70 F range with the chiller, then place both carboy and starter in the fermentation chamber and pitch the next day. Pitching warm and the cooling down could make the yeast drop out. This way the wort and starter are simpatico. I know the arguments for pitching ASAP, but 12 to 24 hours is soon enough for a healthy starter. I hear that the "NO Chill" guys sometimes wait weeks before pitching and make great beer.

 
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Old 08-05-2012, 09:58 PM   #25
phoenixs4r
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Quote:
Originally Posted by chessking

This is what I do. Especially with lagers. Get it in the 70 F range with the chiller, then place both carboy and starter in the fermentation chamber and pitch the next day. Pitching warm and the cooling down could make the yeast drop out.
Well warm is a relative term. I stray away from lagers. I don't have any issues with pitching at 75 and letting it cool to whatever I ferment at. Typically 65-70 for safale 05 which is what I usually use.

OT: firs time using whole hops in today's brew. Didn't filter, clogged pump city.

 
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Old 08-05-2012, 10:09 PM   #26
chessking
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Also off topic. Make one of these. 4" to 3" PVC reducer, Gallon paint strainer, SS jubilee clamp, and the belt clip from a 25' Stanley tape measure. Total cost 7 bucks.
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Old 08-05-2012, 10:11 PM   #27
phoenixs4r
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I hate hop spiders, but thanks. I'll probably throw a false bottom in the kettle.

 
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Old 08-07-2012, 01:14 AM   #28
JonnyJumpUp
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Quote:
Originally Posted by MalFet View Post
I'm not sure what exactly you're saying is a myth here, but certainly slowing down the flow rate can make you more efficient with regards to water usage.
I'm saying that the below statement or any variation is a myth:

That to a point slower flow = faster cooling due to increased contact time or whatever.

Doc, had more patience to explain it than me but suffice it to say the above statement goes against the laws of thermodynamics.

PS a student version of chemcad shouldn't be too hard to get your hands on.

 
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Old 08-08-2012, 05:15 AM   #29
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Quote:
Originally Posted by MalFet View Post
Technical question: anybody able to produce a formula that would describe the volume of water needed in a theoretically perfect system to cool wort from 212 to a given temperature? I tried to figure it out, but my multivariable integration isn't quite what it ought to be.
Just determine the specific heat of your wort and you should be good to go.

 
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Old 08-08-2012, 10:53 AM   #30
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Quote:
Originally Posted by TheZer

Just determine the specific heat of your wort and you should be good to go.
How do you figure? Knowing the specific heat isn't enough to model the system. Assume it's the same as water. What's the equation?
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