Wort Chiller Just Ain't Chillin

[The Judge]

Aaaaaaaaalternatively, get a massive bundled ball of copper wire, leave it in the freezer for a few days before brewing, and then chuck it into the hot wort for a super dooper crash chill :super:

Also watch out for freezer burn.

Sorry OP for being way off topic!!

 

[The Judge]

I was joking.... but i might actually try that.

 

[Ducatiboy stu]

He is an aircon mech. He lost me after the use of ribbed tube...

I just thought ribbed tube tube might be benificial to brewing . Bit like walking into a kitchen shop h

 

[SnakeDoctor]

One question that hasn't been asked, is which direction is the water flowing through the chiller?

If the cooling water is going into the pipe that goes straight to the bottom of the kettle, and exits via the coil, it will take longer to cool down.

So you want the coldest water coiling around the top of the wort, and by the time cooling water has picked up as much heat as it can get, it's exiting the pot as quickly as possible, otherwise the (now hot) water in the chiller sort of works against the cold water going in.

If that makes any sense.

It makes sense, but my testing (and the instructions) indicate that the opposite is the fastest way to chill the wort, you want the cold water going down to the bottom so that heat transfer can take place with the greatest temperature differential.

 

[dago001]

Well I got home from work and read the Zymurgy article as it was hard to read on my phone. You had to read the whole article to get the full story. Its ok to look at the graph and say that this proves the theory. And the graph does prove his theory, BUT, his garden hose turned on flat out puts out 2.5 US gallons per minute. I dont know what your water flow/pressure is like, but mine is approx 3 times that (I'm not checking, I'm going to bed). So by going with the Zymurgy experiment, turning you hose on to between 2 and 2.5 gpm is the most efficient flow rate to cool using an immersion chiller. Somewhere between 7.5 to 9 litres per minute. There in lies the answer. Turn your hose on flat out into a 20 litre bucket for a minute and see how many litres you get. If its only 7.5 to 9 litres per minute, then I would be complaining to the local water authority. As Nev said, ya gotta do the reading.
Cheers
LB

 

[The Judge]

You should clarify that rate is for a specific surface area and concerning efficiency. If you're looking to minimise duration of the cooling process, despite the diminishing returns on flow rate, you would want to have the water flowing at full bore.

 

[Kodos]

It makes sense, but my testing (and the instructions) indicate that the opposite is the fastest way to chill the wort, you want the cold water going down to the bottom so that heat transfer can take place with the greatest temperature differential.

Wouldn't the hottest wort rise to the top, meaning the greatest temperature differential is at the top?

If you were not agitating the wort as you chilled (and it seems to be agreed that you should, I whirlpool with a pump while chilling to achieve this), you would create a layer of cooled wort at the bottom, and the wort at the top would stay warm, reducing convection. Cooling at the top, warmer, layer, would encourage convection currents.

But, I'm not sure I've done proper testing, it's been more anecdotal experience of my own and other brewers. And my copper coil didn't come with instructions

I'll have to go back to reading the article posted above and others.

 

[wereprawn]

Wouldn't the hottest wort rise to the top, meaning the greatest temperature differential is at the top?

If you were not agitating the wort as you chilled (and it seems to be agreed that you should, I whirlpool with a pump while chilling to achieve this), you would create a layer of cooled wort at the bottom, and the wort at the top would stay warm, reducing convection. Cooling at the top, warmer, layer, would encourage convection currents.

But, I'm not sure I've done proper testing, it's been more anecdotal experience of my own and other brewers. And my copper coil didn't come with instructions

I'll have to go back to reading the article posted above and others.

Don't use an immersion chiller but when chilling in sink immediately after the boil the top layers are so hot its bordering on painful and an inch or so at the bottom is cool when changing the water.

 

[Ducatiboy stu]

I remember the first time I used an imersion chiller.....

Needles to say it was the first and only time I stood near the outlet...... They spit hot water everywhere.

 

[Parks]

I remember the first time I used an imersion chiller.....

Needles to say it was the first and only time I stood near the outlet...... They spit hot water everywhere.

You have to be very careful if you sanitise your plate chiller via recirc of hot wort for 10min too - any water left in the chill sections gets turned to steam and spits out.

 

[Ollieb]

Rightio then.... just spent the last 45 minutes reading everyone's very helpful responses and conflicting opinions along with the attached material. EPIC work team... Thank you all!

I have several different tests and options available to me that is going to make for some fun testing on the weekend for my next brew. I will be sure to update the post with what I find from the experiments to hopefully settle a few differing opinions.

I had no idea that this would generate so much interest/ discussion but it made for some great reading... Thanks to everyone who offered their advice and wisdom. To those who just threw in off the cuff smart ass comments... Good job! I love that shit it always breaks up the seriousness of the discussion.

Cheers to all. :beerbang:

Ollie

 

[dago001]

Plenty to try Ollieb - please report back so we know how you went.

You should clarify that rate is for a specific surface area and concerning efficiency. If you're looking to minimise duration of the cooling process, despite the diminishing returns on flow rate, you would want to have the water flowing at full bore.

^^^ Foundation member of the Flat Earth Society.

 

[Black n Tan]

Well I got home from work and read the Zymurgy article as it was hard to read on my phone. You had to read the whole article to get the full story. Its ok to look at the graph and say that this proves the theory. And the graph does prove his theory, BUT, his garden hose turned on flat out puts out 2.5 US gallons per minute. I dont know what your water flow/pressure is like, but mine is approx 3 times that (I'm not checking, I'm going to bed). So by going with the Zymurgy experiment, turning you hose on to between 2 and 2.5 gpm is the most efficient flow rate to cool using an immersion chiller. Somewhere between 7.5 to 9 litres per minute. There in lies the answer. Turn your hose on flat out into a 20 litre bucket for a minute and see how many litres you get. If its only 7.5 to 9 litres per minute, then I would be complaining to the local water authority. As Nev said, ya gotta do the reading.
Cheers
LB

LB. The point of debate was whether increasing flow rate would increase or decrease the cooling rate. The Zymurgy article clearly demonstrates that the time to chill wort decreases with increasing flow rate ie. higher flow rates cool wort more quickly. The highest flow rate tested was 3G/min (11.4L/min) not 2.5G/min, but what you can see from slope of the lines in graph 1 is that time to chill is continuing to improve even at 3G/min and there is no suggestion that the line has yet begun to plateau. With a lack of a plausible theory to the contrary, I think it is reasonable to assume that in real world situations (above 3G/min) the chill time will continue to decrease as flow rate increases (it may start to plateau, but it won't go in the other direction). So I don't think there is any need to restrict the coolant flow rate to 2.0-2.5G/min as you have suggested. I will continue to turn my tap full on because I have a water tank and know that this will cool my wort the quickest. If you are using mains water, you may wish to use a lower flow rate: it will take longer but you will save water. For example with 1/4" tubing it will take 31 minutes to cool at a flow rate of 1G/min (3.8L/min or 118L total), but it is only 6 minutes quicker to chill at three times the flow rate (11.4L/min or 285L ).

Plenty to try Ollieb - please report back so we know how you went.

^^^ Foundation member of the Flat Earth Society.

Not sure I understand your criticism of Putrino's statement?? Seems pretty reasonable to me.

 

[Burt de Ernie]

Well I got home from work and read the Zymurgy article as it was hard to read on my phone. You had to read the whole article to get the full story. Its ok to look at the graph and say that this proves the theory. And the graph does prove his theory, BUT, his garden hose turned on flat out puts out 2.5 US gallons per minute. I dont know what your water flow/pressure is like, but mine is approx 3 times that (I'm not checking, I'm going to bed). So by going with the Zymurgy experiment, turning you hose on to between 2 and 2.5 gpm is the most efficient flow rate to cool using an immersion chiller. Somewhere between 7.5 to 9 litres per minute. There in lies the answer. Turn your hose on flat out into a 20 litre bucket for a minute and see how many litres you get. If its only 7.5 to 9 litres per minute, then I would be complaining to the local water authority. As Nev said, ya gotta do the reading.
Cheers
LB

I don't get this statement......it sounds like you are saying that you understand the article better than others here and that you refute the findings.

Obviously the "lower flow is more efficient" argument was born on not fully understanding the science behind what had been written.

 

[pk.sax]

What he is saying is that too little information is dangerous.

That's what I 'think' he means.

 

[Feldon]

Its not that hard. Theory and science are all very well. But you have know how to apply it.

When cooling your wort with an immersion coil you want the exit cooling water to be as hot as possible. This means that the water is extracting the heat in the wort to the maximum potential of your cooling system (ie. whatever type of coil you use; whatever mains water pressure you have; whether or you jiggle the coil or not, etc, etc, etc).

So put a thermometer in the outflow water (good idea to plumb a short-stick dial thermometer with a T-piece at the exit end of your coil). Increase the input water flow until the temp just starts to drop. This is the point at which the water flow is so high that the cooling water does not have enough time in the coil to heat up by absorbing as much heat as it can from the wort. Back off the water flow a tad.

But the situation does not remain the same.

Heat transfer from wort to water is not a constant. The greater the temp difference between the wort and the cooling water the greater is the rate of heat transfer between the two. So the maximum potential heat transfer occurs at the start of cooling process when the wort is just off the boil.

As the wort cools the temp difference between the wort and the water is reduced, so the rate of heat transfer diminishes. This means you have to give the water more time in the coil to account for the poorer rate of heat transfer. So you have to progressively back off the water flow as the wort cools to give the water more time to absord the wort's heat. If you don't you are needlessly wasting water.

Towards the end, when you're getting down towards pitching temp, the rate of heat transfer is appalling compared to the beginning. It will take the most time, but the least water, to knock off the last few degrees. If you have another coil to put in an ice bath (ie. a pre-chiller) this is the time to use it. You will increase the temperature difference between the water (which is now icy cold) and the now not-so-hot wort and thus increase the rate of heat transfer between the two. (Note that at the start of the cooling process its pretty pointless using a pre-chiller because the temperature differential is large anyway - you will get max use out of the ice in your pre-chiller bucket by using it towards the end of the wort cooling process).

Hope this dispels the idea that you can just pick one water flow rate for the whole process to run at best efficiency. Nature disagrees.

Re. the copper is better than stainless myth - in a practical sense, in a homebrew immersion coil situation, there is not really any difference between using either of the two metals. Both are more than adequate conductors of heat - the weak point in the chain of events is the relatively poor abilty of both wort and water to transfer heat to and from the metal. You can't do anything about this. You could make a coil out of gold (better conductor than copper)and it would not make much difference to the cooling of the wort.

 

[dago001]

I'll make some justification. I do this stuff everyday as part of my job. I work in an industry that relies heavily on heat exchangers for cooling water, oil and blast furnaces. I speak not only from practical experience but also from the knowledge gained from research into flow rates to achieve efficient cooling. Even cooling a 700 degree shaft in a furnace has a limit to how much water flow is required. Too much water flow will result in less cooling (heat exchange) resulting in downtime and thousands of dollars in expenses. We monitor our flows to maintain the correct flow for efficient heat transfer. I've been doing this stuff for 25 years. A geeky 30 minute test in a beer magazine proves only half of the theory behind the what is really happening. But anyway, open your taps fully, I couldn't give a **** anymore.
Cheers
LB

 

[Parks]

LB - are you literally saying it will take longer if the flow rate is too fast or are you talking about heat transfer efficiency?

I believe people in this thread are confusing the two separate issues and would like to know exactly what you mean.

 

[Goose]

Too much water flow will result in less cooling (heat exchange) resulting in downtime and thousands of dollars in expenses.

Sorry mate I do not agree with the first part of this statement. More water flow will result in more heat exchange, but the result is just less temperature difference in the water in vs out. I do not disagree however, with the expense part. Of course you will use more water in the process which costs more.

Any other Chemical Engineers out there ?

 

[dago001]

It will take longer if the flow rate is too fast. What I said in my first post. They are both relative. Heat transfer efficiency is effected by flow rate. Feldons post sums it up nicely.