Temp inversion

[Ted Briggs]

So my glycol is woking much better now. Mayby too well!
After chilling 2 batches to 35f in 12 hours last week, this week it chilled two to 40/39 in 8 hours but it wont go lower. One of the tanks is same one that worked fine last week.
Temp at probe confirmed by sample from perlik. Refrig guy say unit worrking fine. runnig glycol @ 25-27f
So to confirm temp i measured top of batch through the prv and they both are @ 32/31 on top! No signs of ice though on top.
I had tech change glycol to run at 30/33 and set temps to 50. Im thinking ice on the jackets and letting it melt, then tomarrow morning try to chill to 35. Anyone ever seen an inversion like this? The cold beer should drop and form convection currents and mix the beer??
Other thought is pumping out the bottom and in the perlick but I dont know how well this would mix. Cant use the racking port as I dont have racking arms and the port is capped, no valve.
Comments? Guesses?

[Graydon]

Inversion

Ted,

You may want to try connecting a Co2 tank to the bottom out let of your tank and stirring it with co2.

Good luck
Graydon

[Alex T]

Hey,

I've had this happen on 200HL unitanks - I found that if I actually REDUCED the glycol flow that the chilling rate increased - WTF? But yes....

Of course I can never know for sure, but the theory is the glycol was forming a small layer of ice on the inside of the cooling jackets, which meant heat transfer was impeded....

So there you go - try that out........

Cheers,

Alex

[kai]

IIRC water is at its most dense at approximately 4°C, so colder water can float on top of warmer. Obviously beer has different properties, but since its mostly water then before freezing it has to pass through a few degrees where it grows less dense. So, if you can cool a tank of beer faster than convection (and conduction?) temp transfer distribution within the whole tank, then at some point the colder beer will stay on the top. I imagine it would be especially true if your glycol jackets are all situated above the temperature transmitter?

[Ted Briggs]

"water is at its most dense at approximately 4°C, so colder water can float on top of warmer....So, if you can cool a tank of beer faster than convection (and conduction?) temp transfer distribution within the whole tank...true if your glycol jackets are all situated above the temperature transmitter?"

Kai- Good points! Yes, Temp probe is below the jacket. Density explains why it stopped at 40/39f! Im thinking this is what happened, so upping the glycol temp a few degrees should work I hope. (30-33f) Slower cooling, but it will get there. The tanks that worked the week before did take longer to crash.
Thanks for confirming my thought that the natural convection in the tank wasn't working. Allowing them to warm overnight then cool again didn't work though, I guess when this happens mechanical mixing would be necessary.

[Ted Briggs]

UPDATE: I crashed 3 tanks at once and they all cooled nicley to 35f!! Bet theres alot of you that wish they had TOO MUCH cooling power.

[kai]

Oh hooray! Maybe time to expand your capacity to meet the demands of your chiller?