Giant Chiller Liquid Reservoir - What Liquid?

[Yorg]

I bought a 150l chest freezer to contain liquid, which I'll use through my Chiller.
I will pre-chill with tap water, but then switch to the chest freezer, using a pond pump to move the liquid through the chiller.
The night before a brew, I will turn on the freezer on and cool the liquid to around 0C - I reckon the pond pump could probably cope with that.
The aim is to get quickly and easily to lager pitching temps.

Question: What should the liquid be, assuming I have a reliable seperation of the wort and coolant paths? Water, glycol, oil

(I am thinking that thermal mass, given finite volume, would give me the maximum cooling potential.)

??

 

[Sammus]

I'd say glycol or oil, and have the freezer going full biccy, should be able to get it down to -20ish. Now thars some quick chillin for ye!

Or the cheaper way to do it would be to add a bunch of salt to the water...not sure how cold it would go though.

 

[Supra-Jim]

Some kind of glycol mix, this will allow you to cool below 0degC and hence you'll get more bang for your buck. may not be cheapest or greenest option for cooling. Personally i would use the chest freezer for a kegerator (not sure if you keg or bottle though).

How long will the chest freezer take to chill your cooling liquid.


Cheers SJ

 

[samhighley]

Or the cheaper way to do it would be to add a bunch of salt to the water...not sure how cold it would go though.

Not sure how the metal in the freezer would like it either.

Wow, this is going to be one big-arsed chiller!

 

[Adamt]

Water is the number one choice as a heat transfer fluid between 0-100C (atmospheric pressure); its thermal properties (heat capacity, thermal conductivity) are far superior than EG/oils at 0-100C, its of low viscosity making pumping more efficient and it is comparatively inert.

 

[ianh]

A saturated salt solution (23% salt) freezes at -21C. So should still be liquid when the freezer runs -15 to -18C.

Cheap to buy, salt available in bags at pool shops.

Corrosive in contact with some metals.

my 2c

cheers

Ian

 

[Yorg]

Thanks guys, but only Adam seems to have read my question correctly.
I mentioned I don't want to go below 0 degrees. The pump probably wouldn't be able to handle it. Also, I would probably freeze the wort at the outlet of the chiller and halt the system - especially if running it counterflow.
If water has the most thermal mass, then I am thinking of a small addition of glycol to ensure I don't freeze the reservoir at 0C, but not so much as to significantly affect the thermal mass benefit.
So, tough question for a technically savvy person, or perhaps your best guess if you have used glycol:
How much glycol % in water would lower freezing point to about -1or -2C?
Or should I keep it simple, and just cool 100% water to 1 or 2C to achieve essentially the same cooling capacity?

Cheers.

 

[Adamt]

Engineering Toolbox, this site used to be great before they added popups

I still say stick with water...

 

[reVoxAHB]

Engineering Toolbox, this site used to be great before they added popups

OT: Scripts are what control/launch popups. Use NoScript with FireFox and your pop-up woes are finished. Just visited your link using the aforementioned, and was pop-up free. I use NoScript in conjunction with Adblock Plus and a bit of HOSTS management and my net experience is beyonce free

reVox

 

[jayse]

I know your after info on best way to run this system but wouldn't it be much easier to just chill down to tap water temp then leave it in the freezer for several hours/overnite to bring it down to temp. This way you could also run the freezer as a fermentation chamber and serving fridge if you wanted.
Seems much more practical as the freezer can serve a few purposes.
Not knocking your idea at all though as it is a good idea, just pointing out you could have much more options with the freezer. I'am guessing you already have plenty of fermenting space and serving space though.

 

[ianh]

I bought a 150l chest freezer to contain liquid, which I'll use through my Chiller.

Why did you buy a freezer if you are only going to run a solution at around 0C. :huh:

Get maximum cooling effect with the largest temperature differential and providing you stir the wort there should be not problem with freezing.

A salt solution freezes roughly 1C below zero for every 1% salt.

cheers

Ian

 

[Yorg]

Why did you buy a freezer if you are only going to run a solution at around 0C. :huh:

Get maximum cooling effect with the largest temperature differential and providing you stir the wort there should be not problem with freezing.

A salt solution freezes roughly 1C below zero for every 1% salt.

cheers

Ian

Not sure where I went wrong in explaining this.
Zero Celcius because pump probably won't handle lower - as previously mentioned.
No salt necessary because I don't want to go much below zero - see above, and its corrosive.
Freezer because it is going to be quite happy hovering around zero without breaking a sweat, and will get the liquid cooler, quicker overnight - fridges are designed for 4C - likely to last longer.
No stirring, because I don't want to be up all night while its cooling.

 

[ArnieW]

Not sure where I went wrong in explaining this.
Zero Celcius because pump probably won't handle lower - as previously mentioned.
No salt necessary because I don't want to go much below zero - see above, and its corrosive.
Freezer because it is going to be quite happy hovering around zero without breaking a sweat, and will get the liquid cooler, quicker overnight - fridges are designed for 4C - likely to last longer.
No stirring, because I don't want to be up all night while its cooling.

Yorg, I'd go for a good sized mass of water with a small mix of propylene glycol - that means it is not corrosive and food safe. A 30% mix of glycol allows to about -20C or so. You would only need a small amount to stop the water freezing.

If you are interested I have 20 litres here and I'm happy to part with small amounts. I'm in Oakleigh.

cheers

 

[jendres]

Yorg,

Water has a good latent heat of fusion. This means if you have a big ice block, and a bit of water at 0C then you need extra energy to melt the ice before you start heating up the water.

I don't know how much wort you are looking to chill but wikipedia gives a little calculation to guide you.

To heat one kilogram (about 1 liter) of water from 10 C to 30 C requires 20 kcal.
However, to melt ice and raise the resulting water temperature 20 C requires extra energy. To heat ice from 0 C to water at 20 C requires:

(1) 80 cal/g (heat of fusion of ice) = 80 kcal for 1 kg
PLUS
(2) 1 cal/(gC) = 20 kcal for 1 kg to go up 20 C
= 100 kcal

So you can see from this that melting ice is like having water much colder (around 80C) than it actually is.

Also from the Engineering toolbox page it says

Note! The specific heat capacity of ethylene glycol based water solutions are less than the specific heat capacity of clean water. For a heat transfer system with ethylene glycol the circulated volume must be increased compared to a system with clean water.

So you might find that using an ice slurry will work better than using glycol. It definitely will if you don't want to go below 0C (you probably should however).

 

[jendres]

This is a helpful tool and shows you just how much ice or water you need to get to the right pitching temp.

http://www.onlineconversion.com/mixing_water.htm

Just remember that the heat exchanger isn't going to be as effective as just mixing water especially when the difference between the wort and the coolant are nearly the same so you will need to compensate for that.

 

[bigholty]

How do you keep the water in the chest freezer? Mine has a drain hole in the bottom, and I wouldn't trust the joins inside it to be watertight against 150kg of H2O either. (Just curious!)

 

[Thirsty Boy]

Water should do the trick nicely - you said "at the outlet of the chiller" so I assume a plate or CFC chiller??

Anyway - we chill at work with 3 water and I think that is because that temp gives the best balance between energy required to chill, rate of chilling and common sense. Does the job and no need for glycol, brine etc - those things are used for other refrigeration purposes... but its just plain old 3 water for the wort cooling heat exchangers.

 

[seravitae]

To get down to -22C you need a 40% propylene glycol/water solution.
specific heat capacity of water is 4.1855J per kelvin per gram for water
specific heat capacity of ethylene gylcol is 2.41g per kelvin per gram

as a 40% solution, this has a liquid specific heat capacity of 3.474J per kelvin per gram.

density of water ~=1g/ml
density of ethylene glycol = ~1.1g/ml

as a 40% mixture, the density is ~1.04g/ml

150000ml * 1.04g/ml = 156,000grams.

one may consider the freezer water to be "useless" at say, 30 deg celcius.
so from -22C to 30C, thats 52C gap.

3.474J * 156,000grams * 52C = 28181088 Joules that can be absorbed.

For reference, a 30 liter batch of beer at 75 celcius, to cool to 25 Celcius (max pitching temperature?) thats 50C, or 6278250 joules.
According to theory unless i've messed up somewhere (its very late) that should equate to you being able to cool almost 5 batches of 30L of wort from 75C to 25C using that system.


Now, here's the fun part: (at least for me):


Water has a specific heat capacity of 4.1855J/g/K however, its enthalpy of fusion is 333.55J/g. Basically, when ice melts, it requires 333.55J per gram to melt to liquid, which is nearly 80 times the energy required to raise the same amount of LIQUID water from 0C to 1C!!
This is why ice stays cold a long time, but cold water heats up fast..


To cool down 5 batches of 30L wort from 75C to 25C needs 6278250 Joules, so if you consider ONLY the heat of enthalpy of ice->water transition, (333.55J per gram), 6278250J/333.55J/g --> 18853 grams of ICE needed to melt to cool down 5 batches.

Now since water hydrogen bonds it has an astonishingly high enthalpy of fusion. Ethylene glycol does not, so it doesnt even compare.

In aroundabout way of saying, melting ~19kgs of ice from 0C to 1C is roughly equivilant to 'warming up' 150L of -22C 40% glycol to 30C.

My advice would be not to bother with glycol at all, set the freezer to actually freeze.


peace

 

[Yorg]

To respond to a couple of posts:
One of the things I'm trying to do with this, is to have a reservoir of liquid that I can use for cooling, and which can be left there between brews. I want to save some water, and also don't want to be removing a large volume of water ( once ice has melted) to put into ice trays to put back to then make ice. PITA.
So this means a reservoir of liquid. The advice about which liquid to use has been great.
I did a brew today using this, and it got 50C down to 14C pretty quickly, and was still quite cold at the end though I didn't think to measure it. (Started at 5C.)

I have managed to get all the water into it by silicone sealing the seems. The drain hole for mine is at the bottom front, and when closed doesn't leak.

A tip for anyone wanting to do this: To prevent mould, you need something in the water. For me, it was a 5 litre batch of 94% ethanol I'd distilled. It smells like a giant bath of vodka - which I consider an unintentional benefit.

 

[seravitae]

unless i misread something, using the chest freezer, if you account for the increase in volume going from liquid water to ice, you can just freeze the water right in the chest freezer, no ice-tray rubbish..



also, ethanol only has a sterilizing effect at concentrations about 70%. What you have done is not prevent, but retard growth. Eventually, you'll get growth in there - ethanol resistant strains which might cause problems elsewhere in your brewery.

I would suggest using distilled or reverse-osmosis water instead, as the bugs cannot grow without nutrients very easily, it is more effective than adding ethanol.