Dry ice for pre-chilling?

Any one ever tried using dry ice around an immersion chiller to pre cool your water before it goes into a CFC?

Wouldn't dry ice be exponentially expensive compared to the same effective amount of "wet" ice?

TopherM said:

Wouldn't dry ice be exponentially expensive compared to the same effective amount of "wet" ice?

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Well, Yes. But since it is much colder than conventional ice, I was thinking (only thinking at this point) that perhaps it would bring my supply water much cooler than using regular ice and perhaps use less.

My problem is I live in GA and what I am doing is going from my cfc, back into my kettle. I am bringing the whole kettle down to temp before I transfer to the fermentor. This is to remove cold break as much as possible. Even when I now use a pre chiller with ice I still can only get down to around 85 degrees.

i have had success using tap water to get down to about 120 and then re-circulating the cooling water over ice.

If you want the ice bath pre-chiller to be cooler you can add salt to the bath. But, i do not see the need for this. A regular ice bath should easily maintain at near freezing temps until you start dumping hot water in it.

Rather, I would invest in a larger mass of ice bath before buying dry ice. If one doubled the size of the ice bath from a 5 gallon bucket to a 10 gallon tub, one would have twice the thermal mass and would be able to sink more heat into the ice bath per degree of temperature change of the bath. Thus allowing you to cool your wort further.

Of, in other words... use a larger ice bath because water and ice a cheap.

BrewMoreBeers said:

i have had success using tap water to get down to about 120 and then re-circulating the cooling water over ice.

If you want the ice bath pre-chiller to be cooler you can add salt to the bath. But, i do not see the need for this. A regular ice bath should easily maintain at near freezing temps until you start dumping hot water in it.

Rather, I would invest in a larger mass of ice bath before buying dry ice. If one doubled the size of the ice bath from a 5 gallon bucket to a 10 gallon tub, one would have twice the thermal mass and would be able to sink more heat into the ice bath per degree of temperature change of the bath. Thus allowing you to cool your wort further.

Of, in other words... use a larger ice bath because water and ice a cheap.

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Yeah, I was thinking of doing that anyway. For some reason Dry Ice popped into my head and it sounded interesting. How about liquid Nitrogen? I have access to that as well.

Dry ice would freeze the water in your prechiller, possibly ruining the prechiller when the ice expands.

Sardoman said:

Dry ice would freeze the water in your prechiller, possibly ruining the prechiller when the ice expands.

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You think so even at full flow?

One problem with dry ice is a reduced contact on the chiller. That's the great thing about water, or a water ice mixture, is you keep cold liquid in contact with all parts of the chiller. Wouldn't be the case with solid dry ice, and it would just get worse as the dry ice sublimated.

Sardoman brings up freexing the water in your chiller, which certainly could be a possibility depending on your flow rate. With high enough flow rate, you should be able to prevent freezing, but what that rate is, no idea.

Good point. I am imagining the coil getting pretty wrapped up with ice though as the heat exchange takes place.

I am assuming there would be condensation on the chiller which would immediately freeze. Not sure of this but I can picture it.

My addition to my problem also is I am cooling 20 gallons. Looking for a quick drop.

Some things to keep in mind: Just because something is really cold, it doesn't mean that it has a lot of capacity to cool.

[specific] Heat capacity, heat of fusion (energy required to melt/freeze), heat of sublimation (energy required to go from solid to gas for dry ice) and heat of vaporization (liquid to gas for liquid nitrogen) are the factors that affect how much cooling you get.

Water has a high heat capacity, and takes a fair bit of energy to change it's temperature.

What you end up with is a pound of ice provides much greater cooling capacity than a pound of dry ice or pound of liquid nitrogen.

Dry ice is great and used often because it can cool far below freezing, and when used up doesn't leave anything behind...so it's great for food. Liquid nitrogen is used when extremely low temps are required.

Since with beer, neither of those two items are needed, dry ice and liquid nitrogen don't really provide a benefit.

Now that said, if you can get dry ice for nearly free or much less than ice (figure 1/4 to 1/2 the cost per pound) then you may have an advantage in your specific situation.

As for freezing in the prechiller...if it sits stagnant you'd have a risk, but under flow you should be fine. I'd actually still have it in a water bath to get better heat transfer...as the dry ice sublimiates, you'll only have gas next to the coils otherwise with a very low heat transfer rate.

Shockerengr said:

Some things to keep in mind: Just because something is really cold, it doesn't mean that it has a lot of capacity to cool.

[specific] Heat capacity, heat of fusion (energy required to melt/freeze), heat of sublimation (energy required to go from solid to gas for dry ice) and heat of vaporization (liquid to gas for liquid nitrogen) are the factors that affect how much cooling you get.

Water has a high heat capacity, and takes a fair bit of energy to change it's temperature.

What you end up with is a pound of ice provides much greater cooling capacity than a pound of dry ice or pound of liquid nitrogen.

Dry ice is great and used often because it can cool far below freezing, and when used up doesn't leave anything behind...so it's great for food. Liquid nitrogen is used when extremely low temps are required.

Since with beer, neither of those two items are needed, dry ice and liquid nitrogen don't really provide a benefit.

Now that said, if you can get dry ice for nearly free or much less than ice (figure 1/4 to 1/2 the cost per pound) then you may have an advantage in your specific situation.

As for freezing in the prechiller...if it sits stagnant you'd have a risk, but under flow you should be fine. I'd actually still have it in a water bath to get better heat transfer...as the dry ice sublimiates, you'll only have gas next to the coils otherwise with a very low heat transfer rate.

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Makes sense to me. Thanks.

Celticway said:

Makes sense to me. Thanks.

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I do have to make a correction (should have double checked numbers earlier)

it takes water 334kJ/kg to melt, and it takes CO2 572kJ/kg to sublimate.
so from that standpoint, you'll get more cooling from the co2. (which is great for a fridge or cooler)

In practice tho for prechilling water, once co2 sublimates, you get no further cooling (the gas escapes) when ice melts, you have 32F water, that still has a lot of cooling capacity.

Regarding Celticway's point, if you do get ice buildup on the outside of the prechiller, it would provide thermal insulation, so the advantage of using the dry ice would diminish.
A trick that some people use in laboratory environments for cooling biological samples is to use a dry ice, alcohol bath. If you used 100% alcohol, rather than a solution of it in water then you could eliminate any ice buildup on the prechiller surface.

The laws of thermoconductivity dictate that a liquid has more ability to dissipate heat than a solid or a gas. Of all liquids to be considered, pure water is the best. It has many unique molecular properties, one of which is that is has the ability to absorb more energy per mL than any other liquid. The point is stick to cold water, and it doesn't have to be borderline freezing. If you're worried about excessive water usage, recirculate the cold water from a vessel such as a HLT. Even though the water will rise in temp from starting cold temp, it will still have an amazing amount of ability to absorb heat energy.