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immersion pre-chiller

Post #1 made 13 years ago
by jrodie
Anyone ever use an immersion pre-chiller? With a standard immersion chiller in the summer time I can just barely get the wort down to 80 degrees after about an hour of chilling. I than pour the wort into the fermenter and let it chill in a fridge for a few more hours to get it down to the mid 60's pitching temp. I started using an immersion pre-chiller to help. It has not been helping very much though. Still can't get the wort below 80 degrees. Normally I let the hose go full open through the immersion chiller. Would it make sense to slow the water flow in order to let the hose water cool in the immersion chiller? Also does anyone know if a pre-chiller works better with pure ice or ice water?

Post #3 made 13 years ago
by housecat
I don't know much about pre chillling.

When you are chilling, there are 2 main points to remember.
1: if the water coming out of the chiller is cool then it is going too fast. This will mean that the heat transfer is inefficient.
2: Whatever the temperature of the cooling water is is pretty much the lowest you will get the wort plus a couple of degrees.

Ice water with some salt in it would wok best for your pre chiller too. This will increase the surface area touching the pre chiller and help cool it down better. You should see a better result if you use a pre chiller and slow down the rate your water flows through it all.

HC
Part of the NoAd brewers

My mum says I'm cool.

Post #4 made 13 years ago
by jrodie
Really..I was told that keeping the water at full blast is best for an immersion chiller (without a pre-chiller) no matter what the temperature of the out water is. The reason being that the immersion chiller works by being a cold object immersed in the wort that can than be pulled out when done. Therefore the colder the outbound water the colder the chiller and the better it must be working.

Post #5 made 13 years ago
by jrodie
thughes...
No chill does sound good to me. The only reason I haven't tried it yet is that it was my understanding that hop additions and other flavorings would need to be adjusted for no-chill, and that as scared me off so far.

Post #6 made 13 years ago
by Squared
Make sure you circulate the wort every so often and you might see a better result. And make sure you know what temp your chill water is so you don`t waste time.

I'm only speaking from experience but I can shave off about 20 mins off chill time simply by agiatating the wort by lifting up the chiller. It makes sense too because the wort around the chiller is really cold but the wort on the outside is hot still. It will only be as good as the amount of surface area your chiller has if you don't move the wort around.

When I`m a few degrees shy of my pitching temp, I`ll leave it alone for 10 mins so I have brilliantly clear wort.

Post #8 made 13 years ago
by PistolPatch
Hi there jr ;)

Agitation definitely makes a difference. Easiest way to do this is to have your sanitised 'potato' masher in the kettle, cover the kettle with the handle sticking out and then give it a little jiggle every now and then. This of course, stirs up the trub as well so let it settle for twenty minutes after the chill has finished.

Pre-Chilling

With pre-chilling the major things are...

1. Don't use the pre-chiller until you have brought the wort temp down as much as possible with the main chiller.

2. Have as much volume as you can around the pre-chiller.

3. Use iced water in the pre-chiller.

The third is extremely important. Putting water that is not iced (say 1 degree above freezing) will not cool the wort anywhere near as much as iced water). The reason is that it takes a tremendous amount of energy to turn ice back into the liquid state. Here's some numbers from Wikipedia
1) To heat one kilogram (about 1 litre) of water from 283.15 K to 303.15 K (10 °C to 30 °C) requires 83.6 kJ.
However, to melt ice and raise the resulting water temperature by 20 K requires extra energy. To heat ice from 273.15 K to water at 293.15 K (0 °C to 20 °C) requires:

(1) 333.55 J/g (heat of fusion of ice) = 333.55 kJ/kg = 333.55 kJ for 1 kg of ice to melt
PLUS
(2) 4.18 J/(g·K) = 4.18 kJ/(kg·K) = 83.6 kJ for 1kg of water to go up 20 K
= 417.15 kJ
Or to restate it in everyday terms, one part ice at 0 °C will cool almost exactly 4 parts water at 20 °C to 0 °C.
In other words, you get about 4 times the chilling power out of icy water compared to chilled water which is a lot!

Finally...

1. Keep the pre-chiller as close as possible to the main chiller so as the chilled water does not lose its chill.

2. Run the water through slowly. (Running water fast only makes a difference for the first few minutes in a chill - it is not really necessary at all and basically just wastes water once you are down to say maybe mash temps).

:peace:
PP
Last edited by PistolPatch on 21 Jun 2012, 08:40, edited 3 times in total.
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Post #9 made 13 years ago
by BrickBrewHaus
PistolPatch wrote:2. Run the water through slowly. (Running water fast only makes a difference for the first few minutes in a chill - it is not really necessary at all and basically just wastes water once you are down to say maybe mash temps).
+1 I imagine this is a large part of your problem right now.
Last edited by BrickBrewHaus on 21 Jun 2012, 08:57, edited 3 times in total.

Post #10 made 13 years ago
by housecat
jrodie wrote:Really..I was told that keeping the water at full blast is best for an immersion chiller (without a pre-chiller) no matter what the temperature of the out water is. The reason being that the immersion chiller works by being a cold object immersed in the wort that can than be pulled out when done. Therefore the colder the outbound water the colder the chiller and the better it must be working.
Not exactly. Try passing your hand above a candle flame quickly. You won't feel much heat on your hand due to the heat transfer being very minimal. If you want, pass your hand above the same flame slowly and tell me how much more heat you feel. (Don't burn your hand though!)

If the water coming out of the chiller is still cold, the same thing is happening (or the wort has finished chilling).
You want the water to be slow enough for a good heat transfer from the wort. At first, you may need to run the hose fast due to the high amount of heat transferred but as you continue, slowing down the flow will improve chilling speed. It takes a bit of testing adjusting but it works.

And definitely a gentle agitation of the chiller in the wort will help chill it even faster.
Last edited by housecat on 21 Jun 2012, 09:03, edited 3 times in total.
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Post #11 made 13 years ago
by Lylo
Before I started no-chill I had planned to set my IC up so that the garden hose would be coiled inside a garbage can full of water and frozen water bottles.I still think it would work and may give it a try this summer,if I for some reason decide to chill a batch.
AWOL

Post #12 made 13 years ago
by jrodie
I'm not sure the candle flame scenario works in this case. The reason is that the water is not in contact with the wort, the copper coil of the IC is. Therefore the coil is cooling the wort and as long as it is cold it doesn't matter how fast the water is moving through it. I was under the impression that the faster the water was moving, the cooler the IC would be. But if I understand PP correctly you just need to get the IC initially cool with full open hose water, but once it gets to the hose water temp you can slow down the water just to maintain that temperature. Kind of like turning down the propane just enough to maintain a boil?

Post #13 made 13 years ago
by BrickBrewHaus
jrodie wrote:I'm not sure the candle flame scenario works in this case. The reason is that the water is not in contact with the wort, the copper coil of the IC is. Therefore the coil is cooling the wort and as long as it is cold it doesn't matter how fast the water is moving through it.
You're right (I think). But there's a trade-off between cooling more quickly and wasting a metric f*** load of water. The rate of chilling is all about temperature differential between the wort and chiller. By running water through the chiller fast, you're replenishing the warmed water with new, cold water, keeping the water/wort temperature difference as large as possible. This is helpful at first when the water is heating up very fast because the wort is still very hot. Once the wort temp starts to get close to the temp of the water, it doesn't make sense (from a water-economy point of view) to continue to run the water full out. The rate of chilling has slowed significantly because the wort and water are close to the same temperature, meaning the water isn't getting warmed very fast, meaning the water doesn't need to be replenished very quickly, meaning its pointless to turn the water on full blast. So technically, yes, you will chill faster by running the water fast, but its wasting a lot of water.

Now, for the case of running the water slowly through a pre-chiller, you definitely want to run the water slowly. By running it quickly through the pre-chiller you're replenishing the water in the pre-chiller before it has a chance to cool down. Basically you're negating the effects of the pre-chiller by running the water fast.
Last edited by BrickBrewHaus on 22 Jun 2012, 04:14, edited 3 times in total.

Post #15 made 13 years ago
by kartoffel
I want to try to clarify wort chiller flow in a very very simple way since I see so many different ideas. This about it this way. If the water that is coming out is cold then the whole 20+ feet of your chiller is cold inside of your hot wort IE like an ice cube that doesn't melt. If the water coming out is any warmer or hot then not all of your IC is cold and not all of it is even chilling the wort. You want the water coming out to be at least as cold as you want your wort to end up. If the water going is only 80F then you can't get your wort under 80F and you should lower the flow of water going in so that it's at its lowest flow while still being 80 or a bit above so that your whole wort chiller and all 20+ feet of copper you paid for is doing its job. You start to lower the flow once the out temperature stabilizes so you don't waist as much water. It's more complicated than that, but you deffinitley want your whole IC to be cooling or you might as well get a 5 foot one.

Post #16 made 13 years ago
by thughes
One question: The wort needs to be cooled because it contains heat energy. In order to dissipate that heat energy it needs to be transfered to either the air, the kettle walls (which then transfer it to the air), or the chiller (which then transfers it to the water running through the chiller) correct? So, if the water coming out of the chiller is warm, that would seem to indicate that the wort is transferring it's heat energy to the water in the chiller and the water is carrying that heat energy away. If the water coming out of the chiller is cold that would seem to indicate that heat transfer is not taking place (or rather is very inefficient).

What part of physics, fluid dynamics, and thermal dynamics do I not understand? :scratch:

--Todd


"Dammit Jim, I'm a brewer....not a physicist"
WWBBD?
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Post #17 made 13 years ago
by BrickBrewHaus
todd, think of it this way...You're right about heat being a form of energy. I think the part you're missing here is that temperature is more of a term that measures heat per volume (at least in this case). By running water more quickly through the chiller, you're simply diluting/replacing the warmed water faster, making it feel colder. By running water more slowly, the warmed water isn't being diluted/replaced as fast, making it feel warm. But really you're pulling roughly the same amount of energy from the hot wort**.

I guess an analogy to heating water in a pot can be made. Say you have two pots side-by-side on two identical burners. In Pot A you fill with 1L of water and let it sit. In Pot B you fill with 1L of water for 1 minute, then replace that water 1 min later with a fresh 1L of water. Pot B's water after 2min will feel colder, but the same amount of heat is being transferred from the burner to the water in the pots.

Hopefully that makes sense...

**actually more for fast flowing water since the temp differential is higher

Post #19 made 13 years ago
by kartoffel
The second law of thermodynamics says heat always moves from high temperature to a lower temperature. So ice cubes pull out the heat from water making it colder and the ice cubes lose their thermal mass. If the water coming out of your IC is hot you don't have enough thermal mass to use all of your IC efficiently. Yes you're getting good transfer but the copper is always transerfing at the same speed based on the difference between the two temperatures inside and outside. It would be coppers transfer of heat coefficient and would be based on the two temperatures on either side. Now if the water coming out of your IC is somewhat cold then your whole IC is cold and all of it has surface area in the hot wort to transfer heat and hot flows to the cold chiller taking out heat. If the water is too fast you have more thermal mass (cooling potential) than the copper can easily transfer to the wort. This is why you would want to lower the flow to just the point at which the water coming out is maybe a few degrees hotter than going in so you can know for sure you have optimal thermal mass(cooling potential). If the water passing through heats up at all you have room for more thermal mass(cooling potential) once it stops heating up you're at an optimal flux in heat transfer through the copper any more thermal mass or flow is waisted and not being heated up.

Of course everything is more complex than it needs to be so if you want
http://en.wikipedia.org/wiki/Heat_excha ... _exchanger
http://en.wikipedia.org/wiki/Newton%27s_law_of_cooling

Post #22 made 13 years ago
by joshua
Good Day, Not going into Thermodynamics,
But if you can pour two cups of HOT water.
Add Ice to one cup right off, wait 1/2 hour, check the temperature of each cup.
Then, Add Ice to the second cup. wait 1/2 hour, and check the temperature again.

You should find the first cup melts the Ice quickly and drops the temperature only a few degrees.
Both cups will cool over time and only be a few degees different after 1/2 hour.

After adding Ice to the second cup, it will cool much more than the first cup did.

The Thermodynamics idea is....."Really hot stuff" cools quickly to the normal temperatures. Ice can then, cool it much lower after that time.

The moral to this story is use the IC with tap water to lower tempertures, than go with Ice.

Or forget all this *%^$, and try "NO-Chill"
Honest Officer, I swear to Drunk, I am Not God.
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Post #23 made 13 years ago
by thughes
joshua wrote:.....forget all this *%^$, and try "NO-Chill"
Finally, something that I understand!!


(I believe that's what I said back in post #2 :whistle: )
Last edited by thughes on 23 Jun 2012, 09:30, edited 3 times in total.
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Post #24 made 11 years ago
by jrodie
Over the past 4 or 5 brews I have found that using the wort pre-chiller as a second wort chiller works much better. I keep the two chillers attached in-line and just put what was the pre-chiller directly in the wort with my old wort chiller. The extra surface area seems to help much more than pre-chilling the water.

Post #25 made 11 years ago
by PistolPatch
jrodie, nice to see you report back. Good stuff ;).

I especially want to say extra thanks to you because without you bumping the thread, I would have missed housecat's post #10. I must have missed it when he first posted but that is like the best analogy ever!!! I'm surprised no one commented on it :think:. I think that and a lot of other things have been missed in this thread. Many things on this site are too easy to read too quickly.

Read this slowly...

(Like many posts on this site, an hour or more has been spent writing it. Spending ten minutes reading it slowly and well instead of skimming will reward everyone. If you do read it slowly and carefully, please post back in this thread so as we know if that hour or more was well spent, wasted or could be improved ;)).

1. If your tap water is cooler than your required pitching temp then throw as many chillers as you have into the wort. That will be best. (Bit clumsy to manage though I would imagine. Better off with one well-designed chiller than two.) But remember, no matter what you do, your wort will never get below your tap water temperature.

2. If you have two chillers and your tap water is hotter than your required pitching temperature, then you need to have one (chiller A) in the wort and one (chiller B) out of it and then.

Wait until chiller A has done as much as it can. For example, if your tap water is 28 C (82.4 F) as it often is here, then you would wait until your wort cooled to say 29 or 30 C. Once it reached that then, you need to do the following...

Immerse your chiller B (the pre-chiller) in a tub of iced water (not ice alone). Keep the flow slow. Run it fast and the exact same as housecat's analogy will occur but in the opposite way. You need to allow time for the chilly water to 'steal' the heat from the wort.

And btw, it takes a lot of energy (ice) to cool say 6 gallons (about 23 L) from 28 C to 18 C. From 18 C to 9 C takes heaps more again. Here's some numbers...

If your wort was at 28 C and you dumped 2.3 kg of ice into the wort, then the wort would be 18 C. If your wort was at 28 C and you dumped 4.9 kg of ice into the wort, then the wort would be 9 C. See here.

But, you can't dump the ice straight in your wort. It needs a medium which is iced water so the above numbers need to be increased depending on your tap water temperature and how much water it takes to create the bath and depending on how small your ice is.

It's at this point we want to get to some practicalities...

1. You can't chill below your tap water temp unless you employ a pe-chiller in an ice-bath.

2. The pre-chiller in an ice bath should not be employed until your wort reaches temps very close to your tap water temp.

3. You need the pre-chiller to be in an ice bath.

4. Your ice needs to be in small cubes not blocks.

5. If your tap water temperature is high, you will need a lot of ice cubes.

6. Make a lot of ice cubes, a lot more than you think you will need.

7. Make an initial ice bath and add your ice cubes slowly as and when your ice bath turns into just iced water.

Yep, that's it :peace:.
PP
Last edited by PistolPatch on 11 Apr 2014, 19:09, edited 3 times in total.
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