Pumping Glycol For Chilling

[Yorg]

After several frustrations getting a wort down to lager pitching temps, not least the cost of ice, I devised a cunning plan and scored a small chest freezer.
Once tap water gets too slow, I'm going to divert to glycol - I'm going to chill a large tub of glycol overnight in the chest freezer, and pump it through my plate chiller, back to the tub.

Should save a lot of water - and my power is 100%green.

Two things.
Would a pond pump cope with subzero temps?
How much glycol at what temp would be needed in the tub to get 20 odd litres down from 25c to about 6C.

Or maybe I should just use glycol from boiling, and avoid water altogether - in which case how much glycol at what temp to get from 100C to 6C

Would the glycol simply be too cold and freeze up the chiller?


Shoud I just make ice?

What do you think?

 

[bonj]

I don't have any concrete answers for you, but from what I've read of threads on this forum, the pond pump seems to be able to cope with the glycol temperatures. In terms of chilling, I can't answer you either, but I will say it's worth a try. Perhaps try it after the water first, and see how you go. To cool from a higher temperature, you're going to need more glycol or a lower glycol temperature. More is probably the easier way to go, but I couldn't tell you how much more, or even how much to start with. You want a large thermal mass so the glycol can cope with the higher temperature better. If you have a freezer dedicated to the task, you should have enough cooling power, it's just a question of how much glycol and the heat transfer efficiency of your chiller.

 

[mika]

Well if you knew the specifc heat capacities of waort and glycol, could work out the cooling capacity of your chest freezer and could work out the efficiency losses in your system, you could come up with an exact answer...and then you'd double it to be sure.
Just taking a wild stab in the dark, you're going to need approximately 1 and 3/4 truckloads of glycol to make it happen. As you return your heated glycol to the freezer (closed system) it's going to transfer heat to the remaining glycol thus reducing the heat removed...see where this is going.
If the two had near similar heat capacities, you're going to end up somewhere between the two where the temp of the glycol matches the temp of the wort.
If you started with maybe 3 times the amount of glycol as wort you want to chill...you might get close.
As a WAG

 

[Sammus]

I've been thinking about designing like a 3 or 4 teir kind of system, so im not constantly warming up the glycol, but so it's drawing from the bottom most teir and returning to the top most in such a way that any overflow is drawn from the bottom into the next teir kind of... i dunno if its advantagous to have teirs, but the design got more complex the more i thought about it, and i eventually gave up

I think at least having it in a nearly-sealed container and somehow gently returning it too the top whilst drawing from the bottom should make the temp transfer more efficient - ie, a higher temp difference than if the glycol was at uniform temperature.

 

[Carbonator]

getting a wort down to lager pitching temps

Please excuse my ignorance, as I am a brew-pack person, but is there a "time-critical" factor here?

Anyway, air flow is relatively environmentally friendly and combined with surface area of your pipes could be the answer.

Something to think about;
From an efficiency point of view, it is well known in physics that heating something is easier and cheaper than cooling something. This is why your wall mounted reverse cycle air conditioners use less electricity to heat-up compared to cool-down your room! Same as your body functions. It's easier to warm-up when cold than to cool-down when hot!

The answer is to find a huge amount of cold stuff that can surround a vastly smaller amount of hot stuff!

Everyone on a tight budget is facing an up-hill battle with this subject, because "cooling costs heaps", unless you live where ice burgs form!

 

[katzke]

Would the glycol simply be too cold and freeze up the chiller?

Shoud I just make ice?

What do you think?

Well I have no first hand experience but have some info for you.

Yes you can freeze up the chiller. At a brew club meeting the talk turned to portable keg cooling. I think they are called jockey boxes where a cooler has a tap put on it and a coil of tubing inside with ice. A guy froze up the coil once. So if that can happen with ice I am sure you can freeze up a plate chiller with what you are thinking.

I think I would ditch the glycol idea and use the free power to make ice. Then make up a cooling coil to put in a bucket of ice water and keep adding ice as needed. If you want to save some water you could pump from the bucket of ice water. This would save with having to change from water to glycol and back in the chiller

Or you could use a cube.

 

[Carbonator]

Then make up a cooling coil to put in a bucket of ice water and keep adding ice as needed.

Ever wondered why your post mix drinks are not that cold at some Hungry Jacks stores? Buckets of ice are what is still used to cool the water. They get the slaves to add ice into a tub with coils in it at the top of the machines. I think some of the slaves sometimes forget to add ice until someone complains about a warm drink and keep in mind if you complain, you are treated like a terrorist these days!