Author Topic: How to cool your wort faster  (Read 2282 times)

Offline bluefoxicy

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How to cool your wort faster
« on: February 16, 2012, 02:51:11 PM »
You all like to use these fancy reverse-flow chillers and immersion heat exchangers and the like to cool your wort; but most of the extract brewers and even some of the all grain brewers tend to just shove the hot pot right into an ice bath in the sink or bath tub.  You want to get it cold fast, right?  Hence the ice, stirring for circulation, the like.

Wanna have some fun?

Get a test tube.  Fill it with straight tap water, put a stopper in the top with a hole and toss in a plastic tube.

Put the test tube into a container of ice water.  What do you get?  ... cold water, right?  Yeah, that's obvious.

Now dump half a cup of salt into the ice bath.  Give it a minute or two, and watch what happens...

Water shoots out of the test tube as it fills with expanding, freezing ice!  Nice trick, right?  How the hell does that happen?

This one's easy:  Adding salt to water creates a saline solution.  The free salt ions (Na+, Cl-) help loosen frozen water from the surface of the ice--in other words, melts it.  But salt water has a lower freezing point than regular water:  the ice is being forcefully melted at a lower temperature.  What will happen is more of the ice gets melted, dropping the temperature of the entire system--if the freezing point is -4C, then the ice bath becomes -4C instead of 0C.

1g of 0C water takes about 80 calories to turn to ice, and vice versa; with salt water that's above its freezing point, it will lose so many calories just to convert the ice into water... instead of converting 1g ice to water at the expense of 80 calories, it converts i.e. 2g ice to water, losing 160 calories--meaning a temperature drop.  Once the temperature reaches the freezing point, it takes as much energy to melt the ice as it does to freeze the salt water--if the salt water cooled more (by melting the ice), it would itself freeze.  This prevents the phase change.  Thus the ice keeps melting until the temperature reaches the freezing point of the saline solution, and then slowly melts to maintain it.

liquid nitrogen on the other hand freezes things it touches.  That's because its boiling point is -192F.  When it boils, it absorbs energy off whatever it touches to phase change to gas from liquid, which is the same direction as solid to liquid.  It'll cool ice to well below freezing because its boiling point is well lower than ice's freezing point.  By contrast, salt water is liquid at the temperature of frozen pure water (i.e. ice is 0C, salt water is liquid at 0C) rather than a gas (it boils above 100C).  Because it's able to melt the ice actively (i.e. by charge interaction with the salt ions, rather than just by temperature), the potential difference causes heat flow into the ice.  In other words, this all makes sense; it's not voodoo magic.

So while you're at rite-aid buying bags and bags of ice for your ice bath, pick up a sack of Epsom salt too.  Dump that in the ice bath and try not to freeze your wort into a solid block.

</uriwaza>

Offline boapiu

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Re: How to cool your wort faster
« Reply #1 on: February 17, 2012, 06:22:03 AM »
as a kid we used to make ice cream when we visited our relatives and a similar technique was employed. i had wondered why they used salt thinking it would melt the ice and that would be wasteful. i think i will give this a try my next brew session.
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Offline beersk

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Re: How to cool your wort faster
« Reply #2 on: February 17, 2012, 08:06:21 AM »
Wow, so you do brew beer?   ;D
Go big AND go home.

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Offline nateo

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Re: How to cool your wort faster
« Reply #3 on: February 17, 2012, 08:49:59 AM »
Wouldn't you get haze issues if you freeze your wort? I suspect you'd get some freezing on around the edges of the pot if you're not careful. But, I also seem to remember Noonan saying you get the best possible cold break if you can chill your wort down to slush.
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Offline erockrph

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Re: How to cool your wort faster
« Reply #4 on: February 17, 2012, 08:56:11 AM »
I've thought about trying this myself. Right now I'm having good results with my current method. I have a dual sink mounted under my countertop, so I place my brew kettle in the larger side and submerge my removable faucet head next to it. I keep the cold water cranked so it circulates around the kettle and spills over into the other basin and drains out there. This keeps a constant flow of ~50-60F water circulating around the kettle.

Maybe I'll stop the water and add salt and ice to the sink once the wort hits ~90-100F to push it down the last few degrees more quickly.
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Re: How to cool your wort faster
« Reply #5 on: February 17, 2012, 09:51:20 AM »
I like turtles.
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Offline beersk

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Re: How to cool your wort faster
« Reply #6 on: February 17, 2012, 11:38:51 AM »
I like turtles.
You would! lulz

EDIT: The new format of the forum puts the page back at the top after you post...not liking that.
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Offline dbeechum

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Re: How to cool your wort faster
« Reply #7 on: February 17, 2012, 12:08:27 PM »
EDIT: The new format of the forum puts the page back at the top after you post...not liking that.

This is why I run the forum reverse sorted with newer messages at the top
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Offline tschmidlin

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Re: How to cool your wort faster
« Reply #8 on: February 17, 2012, 12:16:10 PM »
EDIT: The new format of the forum puts the page back at the top after you post...not liking that.

This is why I run the forum reverse sorted with newer messages at the top
So you're suggesting we should all conform to your way of doing things? :)
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Re: How to cool your wort faster
« Reply #9 on: February 17, 2012, 12:46:48 PM »
EDIT: The new format of the forum puts the page back at the top after you post...not liking that.

This is why I run the forum reverse sorted with newer messages at the top
So you're suggesting we should all conform to your way of doing things? :)

You're just figuring that out?   :D
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Re: How to cool your wort faster
« Reply #10 on: February 17, 2012, 12:47:22 PM »
I like turtles.
You would! lulz

EDIT: The new format of the forum puts the page back at the top after you post...not liking that.

Not for me...it takes me right back to what I just posted.
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Offline beersk

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Re: How to cool your wort faster
« Reply #11 on: February 17, 2012, 01:02:22 PM »
EDIT: The new format of the forum puts the page back at the top after you post...not liking that.

This is why I run the forum reverse sorted with newer messages at the top
Ah, I get it.  Did that. 
Go big AND go home.

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Offline punatic

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Re: How to cool your wort faster
« Reply #12 on: February 17, 2012, 08:20:22 PM »
BFI - may I suggest that you research:
heat capacity of water
latent heat of fusion
latent heat of vaporization
freezing point depression
boiling point elevation
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Offline kgs

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Re: How to cool your wort faster
« Reply #13 on: February 18, 2012, 07:36:59 AM »


So while you're at rite-aid buying bags and bags of ice for your ice bath, pick up a sack of Epsom salt too.  Dump that in the ice bath and try not to freeze your wort into a solid block.


I stopped at "Epsom salt." I'm trying to figure out why this is recommended and may have an answer. When I use an ice bath, it's usually on a deck, and I dump the water into the backyard 30 feet below and/or keep some of it for watering my deck roses.

Epsom salt = happy deck roses & happy random backyard plants (mostly elderly shrubs--hard to explain typical backyards in hilly residential SF, but most people don't actually USE them)

Salt water = sudden and ignominious desertification of all growing matter

I don't know enough about, well, anything to fully understand how Epsom salts are and are not similar to salt. (I do know I like beer and homebrewing, and I also know roses love Epsom salts.)

Am I right?

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Offline punatic

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Re: How to cool your wort faster
« Reply #14 on: February 18, 2012, 09:08:38 AM »
Epsom salt is magnesium sulfate (heptahydrate).  As with most.things, it is best in moderation.  I'm sure your roses would find too much epsom salt offensive.

"Salt" is sodium chloride - offensive to most plants, except those adapted to living near the ocean.

I use magnesium chloride for making ice cream (and my coconut shell based activated carbon).  MgCl2 gets the icebath cooler in my icecream machine.  It comes in 60# bags from Morton for salting icey roads (a big problem here   ;) ). MgCl2 is less expensive than epsom salt, and is less offensive to the plants than sodium chloride.

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