ice bath vs. immersion chiller

[mclancy]

Hi,

I'm getting back into brewing now, and thinking about cooling down the wort. I did some numbers to compare the surface area of two common cooling solutions, and was surprised by the results:

Ice bath

Assume a 6-gallon pot with a 13.25" diameter bottom and 12" depth. 5 gallons of wort would mean the wort filled 10" of depth. So if you put the pot in an ice bath, you'd get this much surface area:
pi * radius ^ 2 for the pot bottom = 3.14159 * 6.625 ^ 2 = 125 square inches
pi * diameter * height for the sides of the pot = 3.14159 * 13.25 * 10 = 347 square inches
so a total of 125 + 347 = 472 square inches of cooling surface area

Immersion chiller

Assume a 20 foot (240 inch) long copper coil with a 3/8" (.375") diameter:
pi * diameter * length of coil = 3.14159 * .375 * 240 = 283 square inches of cooling surface area.

So if that's right, then ice bath gets you 472 / 283 = 67% more cooling surface area than an immersion chiller. So as long as you keep the ice bath as cold as the water you would be running through the immersion chiller (which is probably easier, since you can use ice and not just cold water), seems like ice bath would win handily.

This surprised me because ice bath seems to be the "rookie" approach, whereas the more experienced brewers I always thought used immersion chillers (or counterflow chiller).

Any thoughts? Am I thinking about this wrong?

Mike

 

[homebrew57]

I am not an expert but I think immersion chillers work better because of the flow of cold water not contact surface area. The ice bath is still water, it is not wicking the heat away. You have to wait for the giant body of water to absorb all the heat from your kettle and beer. In the immersion chiller the small amount of water in contact with the beer is able to absorb heat quickly and get it away from the beer since it is being forced through and dumped elsewhere.

 

[JustLooking]

Assume a 20 foot (240 inch) long copper coil with a 3/8" (.375") diameter....

Any thoughts? Am I thinking about this wrong?

Most brewers use 50' IC chillers and sometimes use 1/2" diameter.

IC's are most effective if you stir the wort. If you put your kettle in an ice bath, you'd have to stir both the ice bath and the wort for it to be efficient.

 

[Kampenken]

Let me add a few points as well to this.

First, the BK is *likely* a thicker wall than your IC thus more rapid heat transfer from the IC.
Secondly, heat transfer (convection) is enhanced with movement, as noted in the previous posts, and that is key.
Finally, I've done both and the IC is RAPID fire!! Go IC, its cool and quick (and use an ice bath with a small recirculating pump). Brew on!

btw- my IC is 3/8 OD copper pipe. I have 2 coils, one about 10" in dia, the other 4" in dia. I move both, primarily the inner as the outer is close to the BK side walls, and I chill 5.5g from boil to 68 in 15min!

 

[tehnick]

I've done both ice baths and immersion chilling. When I was doing ice baths, I was doing partial mash/extract and topping off with cold water on a 3g boil. The cold water wasn't enough to chill to pitching temps, so I used an ice bath. Took an hour or so to get the needed results.

I've been all grain brewing for about 5 years now and have been using a plain immersion chiller. I generally chill 6.3 gallons of wort to accommodate for trub and fermentor loss. Takes 30 min running the hose. I could probably even save time if I got an aquarium chiller, a pump, and an extra cooler to hold ice to cool it even quicker and have less water waste. I don't want to spend the 600 on the aquarium chiller though lol.

 

[Auger]

I started with ice baths in the sink when doing partial-boil extract batches. I soon built a 25' IC which worked faster. I carried that over when I started doing full-boil AG brewing, which seemed to take forever and required constant stirring of the wort while running water through the chiller. I then added another 25' coil that I use in an ice-bath as a pre-chiller for the cooling water. Finally, I added a recirc pump to the boil kettle, which both cut down the cooling time drastically, and gave me a break from all the blasted stirring. It works well, even with 10gal batches, and I can then pull the chiller and leave the pump running to whirlpool before taking off into the fermenter.

 

[TheCADJockey]

I think, you are over-thinking it. I use an "ice" bath currently in our negative degree weather by mixing in my endless supply of snow as it melts. No matter how much attention I give it in that type of cold, with constant application of ice in the bath.. it still takes minimum 30 minutes unless I plan on topping off with any water.

The last time I used actual ice was horrible, I had run out of ice and had to go to the store to pick some up only making the process longer and more stressful. I'll be picking up an IC before spring.

 

[douglasbarbin]

Hi,

I'm getting back into brewing now, and thinking about cooling down the wort. I did some numbers to compare the surface area of two common cooling solutions, and was surprised by the results:

Ice bath

Assume a 6-gallon pot with a 13.25" diameter bottom and 12" depth. 5 gallons of wort would mean the wort filled 10" of depth. So if you put the pot in an ice bath, you'd get this much surface area:
pi * radius ^ 2 for the pot bottom = 3.14159 * 6.625 ^ 2 = 125 square inches
pi * diameter * height for the sides of the pot = 3.14159 * 13.25 * 10 = 347 square inches
so a total of 125 + 347 = 472 square inches of cooling surface area

Immersion chiller

Assume a 20 foot (240 inch) long copper coil with a 3/8" (.375") diameter:
pi * diameter * length of coil = 3.14159 * .375 * 240 = 283 square inches of cooling surface area.

So if that's right, then ice bath gets you 472 / 283 = 67% more cooling surface area than an immersion chiller. So as long as you keep the ice bath as cold as the water you would be running through the immersion chiller (which is probably easier, since you can use ice and not just cold water), seems like ice bath would win handily.

This surprised me because ice bath seems to be the "rookie" approach, whereas the more experienced brewers I always thought used immersion chillers (or counterflow chiller).

Any thoughts? Am I thinking about this wrong?

Mike

Yes, you are thinking about it wrong. With the ice bath, the bottom of the kettle is exposed to a negligible amount of water (unless your kettle floats when full...mine doesn't). So you really can't count those 125 square inches because there isn't much heat exchange going on. What's important here is the volume of cool water in (indirect) contact with your wort.

Also, you would be amazed at how quickly a kettle full of boiling wort heats up your ice bath. Within a few minutes, your "ice bath" is well over a hundred degrees unless you drain it and refill. Since the wort chiller has a constant supply of running water, it doesn't have this problem.

 

[Tinpanharry]

I do both an icebath and IC. I recently picked up a 50 ft 3/8 copper immersion chiller. I was previously doing an icebath in a laundry sink in the basement.

Now with the sink partially plugged, I run cold water through the IC. But the IC hookup to my faucet is kind of loose. So I now use the IC (full blast cold- that is important!) and it also fills the sink for an ice bath. I am careful to not let the water that is leaking into the laundry tub get into the wort I am stirring.

I also tend it to make sure the rate of cold water going in to the laundry tub is enough to fill but not overfill the laundry tub. It sounds hoakey but work great. Takes about 15 minutes for 5 gallons to go from boiling to about 65.

 

[MaxStout]

I think the amount of time it takes speaks for itself. I once cooled a 5 gallon batch of wort from boiling to <70 using an ice bath in a big plastic tub. After refilling the tub with ice a couple times, I was able to get to my target temp in about 2 hours. After that one brew I built an IC from 50' of 3/8" copper tubing. With good cold tap water the same job takes about 12 minutes.

I'll pick the method that only requires 1/10 the amount of time.

 

[Sailingeric]

I brewed 2.5 gallons on the stove and would ice bath it. I did not time it but did take a long time to cool down so I could pour it and not burn myself and when I topped off the bucket to 5 gallons I still had to wait a few hours to cool to pitching temp. I did my second batch in 7.5 gallon pot doing full boil and used a 25 foot IC and was down to pitching temp about 20-25 minutes, about enough time to clean up and put my equipment away.

 

[wilserbrewer]

I have culled using both IC and ice baths. An ice bath works tremendously well if you have enough ice! I had access to a commercial ice machine, and would put about 60-80 lbs of ice in 1/2 a 55 gallon drum with just enough water to float the ice, put the kettle in that type of ice bath and bam, it cools pretty darn quick!

 

[RJS]

It all depends on batch size. Ice bath is not possible with a bigger system.

 

[mclancy]

All great comments, thank you. I did the ice bath method last night and got 5.5 gallons down to pitching temp in 20 minutes, so really fast (for me). However, I had pretty optimal conditions; based largely on the advice above, I did the following:

1) Used a deep double sink, and would do the bath on one side, then when the water warmed up I'd switch sinks
2) Put a tuna can at the bottom of each sink to raise the pot and let water circulate on the bottom of the pot
3) Gently stirred the wort to keep it moving and keep new hot wort against the side of the pot also kept the bath water moving around a good bit
4) Had the critical benefit of lots of snow on the ground outside (free ice) and really cold wintertime tap water
5) Totally cheated by adding a half gallon of nearly-freezing spring water right at the end (the last 10-20 degrees were slow going), I wanted to get up to 6 gallons anyway

So it worked well, but I was working the whole 20 minutes and like I said I had pretty much optimal conditions. Not a good option for me for summer brewing, in which case it would probably take me an hour or two, and cost $$$ for ice.

Thanks for the advice.

 

[BadWolfBrewing]

Unfortunately, heat transfer is considerably more complicated than surface area.

In an IC,the waters flowing pretty fast, so this is forced convection. An ice bath, even with some swirling, it more based on natural convection. The difference is that there will be a thin layer of warm water around the kettle. It takes a surprising amount of agitation to break this layer up faster than it forms.

In an IC, the cooling occurs closer to the center of mass, which speeds things up too.

The conduction differences are probably not significant, given the thin wall.

I'm not saying an ice bath can't be effective, just that looking only at surface area is very misleading.

I do research on the modeling and simulation of dynamical systems for a living. I keep meaning to write up an article on heat transfer, but it is a very complicated subject. Probably the most challenging that I encountered in 10 years of college for mechanical engineering. Aside from pointing out trends and basic concepts, I'm not sure it would do a lot of good. Aside with getting people arguing that flowing more slowly through a HERMS coil increases heat transfer...