Blast freezer to chill wort quickly

[Mathewsbrew]

Hi all, I'm yet to buy or make a wort chiller. But i'm doing small batches of all grain at the moment. with a 15L pot. I don't have a wort chiller and was wondering if putting the whole pot in -40 degree temperatures for 10 mins or so would cause any problems to the beer? As I have a commercial blast freezer at home.

thanks

 

[Mardoo]

Oooo, fun toy. Can you hook up a submersible temp probe to the thermostat? That'd be cool.

Can't think of any problems being created in the wort.

 

[lost at sea]

as long as the wort is sealed some how......but wouldnt it be a waste of power/energy?

 

[Mathewsbrew]

Oooo, fun toy. Can you hook up a submersible temp probe to the thermostat? That'd be cool.

Can't think of any problems being created in the wort.

They are indeed a fun toy. Not sure I'll have to look into that. But sounds cool haha

Sweet I didn't think it would but thought I'd confirm. Thanks for that.

 

[Mathewsbrew]

as long as the wort is sealed some how......but wouldnt it be a waste of power/energy?

It could well be a wast of power/energy but might be alright until I get to my local brew shop for a wort chiller.

 

[Feldon]

as long as the wort is sealed some how......but wouldnt it be a waste of power/energy?

Understand where you're coming from re. sealing it (ie. keeping the wort as sanitary as possible).

But be aware that the wort will contract as it cools. This will reduce the air pressure in the headspace and cause the pot to cave in on itself though the action of the higher external atmospheric pressure. Powerful forces at work here.

To see what I mean, fill an empty PET bottle with hot tap water, seal with the cap and put in the fridge to cool. You'll see what I mean. And don't think the same thing can't happen with metal.

 

[Lionman]

I don't think it would work that well.

The hot wort would very quickly heat the air inside the freezer to sweltering temps.

You could probably work out how fast it can chill the wort by using the power consumption rating of the freezer. This would be for someone better and more up to date with the theory of thermodynamics than myself.

I do no chill and tried cooling the cube in a fridge. Took longer than just putting it outside because the temp in the fridge quickly rose to about 70 degrees. A blast freezer may work better but you will still have a similar problem I think.

It would work a lot better if the evaporator unit of the freezer could be in a more direct contact with the wort so heat transfer didn't have to be via the air in the freezer. Something like one of those phase change chillers for PC's, but with a rod that could be inserted into the wort.

 

[Mathewsbrew]

Understand where you're coming from re. sealing it (ie. keeping the wort as sanitary as possible).

But be aware that the wort will contract as it cools. This will reduce the air pressure in the headspace and cause the pot to cave in on itself though the action of the higher external atmospheric pressure. Powerful forces at work here.

To see what I mean, fill an empty PET bottle with hot tap water, seal with the cap and put in the fridge to cool. You'll see what I mean. And don't think the same thing can't happen with metal.

I was planning on just sitting a pot lid on top not sealed tightly just sitting on top. Would that be ok?

 

[Feldon]

I was planning on just sitting a pot lid on top not sealed tightly just sitting on top. Would that be ok?

As long as air can get sucked inside the pot as it cools to equalise the pressure. Depends on how close the mating surfaces are on the lid and pot rim. If the lid is one of those glass ones with a little hole in it, that should be Ok.

Good luck. Interested to see how the blast freezer goes.

 

[manticle]

I don't think it would work that well.

The hot wort would very quickly heat the air inside the freezer to sweltering temps.

You could probably work out how fast it can chill the wort by using the power consumption rating of the freezer. This would be for someone better and more up to date with the theory of thermodynamics than myself.

I do no chill and tried cooling the cube in a fridge. Took longer than just putting it outside because the temp in the fridge quickly rose to about 70 degrees. A blast freezer may work better but you will still have a similar problem I think.

It would work a lot better if the evaporator unit of the freezer could be in a more direct contact with the wort so heat transfer didn't have to be via the air in the freezer. Something like one of those phase change chillers for PC's, but with a rod that could be inserted into the wort.

Commercial unit is head and shoulders above a fridge.
We have a refrigerated shipping container at work that can drop temp to -18 very quickly and maintain that for a long time even if switched off.

I'm sure op's commercial unit is not a 20ft shipping container but neither is it a domestic fridge.

I'd still look at transferring hot wort to a sealed hdpe no chill cube for mindful ease and peace.

 

[Maheel]

you should run a coil into the Blast F and then pump from pot to chiller back to pot.

that should cool the shizzle out of it

 

[good4whatAlesU]

I was planning on just sitting a pot lid on top not sealed tightly just sitting on top. Would that be ok?

Yes it's fine.

That's exactly what I do with my BigW pot with a glass lid. Make sure you sterilise the lid with some boiling water or sanitiser before you put it on.

I do 12L batches and just cool the wort in the laundry tub with cold water changed out every 15min or so. Gets the job done. Never had one go bad.

 

[klangers]

This is my bread and butter.

Yes it will work, but I doubt 10 minutes will be enough. Give it a go though.

The limiting factor is the heat transfer rate out of the vessel, which is maximised by the blast air flow. Assuming it's a true blast freezer. The capacity of the refrigeration is likely to be sufficient due to this.

Calculating this to an OK accuracy isn't actually that hard, if you're interested.

 

[lost at sea]

when i was a professional fisherman we ran a 'true' blast freezer on the vessel. you dont want to be inside there when that bad boys kicks in thats for sure!

ran at - 60 degs or something like that.

 

[Mathewsbrew]

This is my bread and butter.

Yes it will work, but I doubt 10 minutes will be enough. Give it a go though.

The limiting factor is the heat transfer rate out of the vessel, which is maximised by the blast air flow. Assuming it's a true blast freezer. The capacity of the refrigeration is likely to be sufficient due to this.

Calculating this to an OK accuracy isn't actually that hard, if you're interested.

Yeah I get where you are coming from. With a steel lid on the top would seal of the the air flow and only chill the outside to bring temp down. If I have no lid then a chance of bacteria may get into the beer?

But I am interested in calculating this if you have time to share this info? I have a zannusi blast freezer

 

[Mathewsbrew]

when i was a professional fisherman we ran a 'true' blast freezer on the vessel. you dont want to be inside there when that bad boys kicks in thats for sure!

ran at - 60 degs or something like that.

-60 thats bloody cold mate ahaha. Blast freezers are amazing at bringing things down to frozen in a short period of time.

 

[klangers]

Yeah I get where you are coming from. With a steel lid on the top would seal of the the air flow and only chill the outside to bring temp down. If I have no lid then a chance of bacteria may get into the beer?

But I am interested in calculating this if you have time to share this info? I have a zannusi blast freezer

I can help, to get us started you should find out or measure the below:

• Surface area of your pot, total which will be exposed to air movement (not base. You can probably ignore lid as it will have negligible effect as it contacts air/steam on inside)
• Surface area of your pot which touches wort (the above multiplied by proportion full)
• Material of your pot
• Wall thickness of your pot
• Approximate blast air velocity
• Blast air temperature

If you're not sure that you'll be able to get these metrics, then it's probably not worth attempting to calc it. "Garbage in, garbage out" as they say. If you can get them, then we can crank out a rough heat transfer calc to see how long it'll take to get to x temperature.

 

[lost at sea]

-60 thats bloody cold mate ahaha. Blast freezers are amazing at bringing things down to frozen in a short period of time.

yeah it was around that temp somewhere, few years back now. snap freezing whole tuna at sea lol....

 

[stilvia]

I do no chill and tried cooling the cube in a fridge.

Doesn't that defeat the purpose of no chill haha?

 

[Lionman]

Doesn't that defeat the purpose of no chill haha?

Haha, yep.

It was actually the brew fridge and I thought if I put it in there it would come down to pitch temp ready for the next day.

I was wrong.