Water shortage brewing.

[Dutto]

Our water butts 2x200l ran out in early June!

WOW! A home brewer who has time to water his plants! Respect!

SWMBO regards our water butt as an essential bit of garden kit (to religiously water the one Hosta plant that we own) whereas I regard it as a potential breeding ground for mosquitoes.

To prevent the mosquito larva from breathing, I poured in some olive oil that floats on top of the water and doesn't affect the Hosta plant.

It seems to be working as we haven't been bitten ... :thumb:

... yet!

 

[mathorp]

This to expand on Dutto’s post above. If you want to do your own calculations to cool hot wort with water and ice, here is the info you need:

1. Latent heat of fusion/melting of ice (Lm) = 334 joules (J) per gram

2. Specific heat of water (Cwater) varies a little with temperature, but is approx. 4.2 J per gram per °C (J/g°C).

3. Specific heat of ice (Cice) also varies with temperature, but is approx. 2.1 J per gram per °C (J/g°C)

4. Specific heat of wort (Cwort) is slightly lower than water and varies with gravity – say 4.0 J/g°C.

Conversion factors:

· 1 kg water = 1 litre water; or 1 cc = 1 ml = 1 g

· 1 joule = 0.239006 calories

So the energy to melt 1 kg of ice is enough to change 80L of water 1°C or 23L of water 3.5°C.


Example

Dropping 23 litres of 1050 wort from 100°C to 20°C, using an immersion chiller, a 20°C water supply and ice could work as follows:

First stage with water: drop from 100°C to 40°C with the water supply, dumping the returns on your garden, in the bath or down the drain.

Second stage with ice: drop from 40°C to 20°C with a closed loop and an aquarium pump in a container of ice/water (start with just enough water to drown the pump).

In this second stage we have to extract heat from the wort:

Heat = Volume x gravity x Cwort x temp change = 23000 x 1.050 x 4.0 x 20 = 1,932,000 J

The weight of ice to do this is:

Weight = Heat / Lm = 1,932,000 / 334 = 5784 grams, so 6 kgs of ice should do it. With perfect insulation the water in the container would still be cold. However the real world is inefficient and I would have some more ice on standby, at least for cooling the first brew.

 

[Slid]

I don't doubt the arithmetic above, but can't really be bothered to think about it right now, I have only two things to say:

Does the above include the heat required to heat the melted ice, or the heat required to melt it?

It does point out how hard it is to chill to anywhere near 20C using chilling water at 20C. I don't think that tap water temps are quite that high yet, but not sure they are that far off.

 

[mathorp]

I am sorry - that was a bit long winded! The general point was that you can get a lot done with ice. Water cools well when the temperature differential is large, but returns diminish rapidly as the differential shrinks

The answer to your question is that the calculation is for the heat that must be input to turn ice at 0°C to water at 0°C. It is just the heat to melt the ice. The cold water in the container (10 litres at most) is an additional source of cooling, but cannot contribute much

 

[Slid]

OK - latent heat of freezing / melting that was called back in my day of doing O level Physics. I did feel very tired last night - the heat is getting to me! Hence lack of thought.

I suppose, the historical literature supports the idea that pre-cooling by electrically powered machines, brewing in July and August would have been a limiting experience due to inability to get the temps down as well as the oft quoted prevalence of wild yeasts and general bacteria in the ground-level atmosphere.

 

[hucker]

What water shortage? Water has always come out of my tap, despite the moaning from the water board. I just use the hose when nobody's looking, or fill a watering can with a hose behind the shed, then carry that to the plants. 95% of water usage is commercial, banning domestic hosepipes will achieve nothing.

 

[Slid]

What water shortage? Water has always come out of my tap, despite the moaning from the water board. I just use the hose when nobody's looking, or fill a watering can with a hose behind the shed, then carry that to the plants. 95% of water usage is commercial, banning domestic hosepipes will achieve nothing.

The destination of treated water for UU is roughly 52% Household, 21% Commercial, 24.5% Leakage and 2.5% Illegal use. Over two thirds of Household usage is for properties not on a meter as opposed to metered properties.

 

[hucker]

I don't know what a "UU" is. But I disagree, I read it's 95% commercial. But if your stats are correct, it looks rather like the water boards are throwing a lot of it away (a quarter loss!!), their problem, not mine. I pay them to supply me with water, if they can't do that, they aren't doing their job properly.

 

[TheQuokka]

I run my water from immersion chiller or still into a galvanised 44 gallon drum, then either re-use it with a pump or use the excess to water my chillies and hops. In summer I tend to use ground water for the immersion chiller as it is cooler - but the need for watering plants is greater, so it all works out.

 

[bobukbrewer]

fill the sink with ice and salt mix, put wort in a 14 litre stainless steel vessel, immerse in salt bath and stir wort well constantly 95 t0 25 deg c in 10 minutes,,,,,,

 

[Clint]

Water butts...I've just hacked my way through last year's echium stems planted in large pots between the greenhouse and my brew shed...to reach the water butt...which I assumed was empty as it always leaked. It was full...so we used lots of it to water the pots....now it leaks ...

 

[MyQul]

fill the sink with ice and salt mix, put wort in a 14 litre stainless steel vessel, immerse in salt bath and stir wort well constantly 95 t0 25 deg c in 10 minutes,,,,,,

What does the salt do?

 

[Slid]

Salt will lower the freezing point of water, but in the context of chilling beer, I don't see that this actually helps as adding salt to ice does not extract more heat from the hot object, from a thermodynamic standpoint.

 

[MyQul]

Salt will lower the freezing point of water, but in the context of chilling beer, I don't see that this actually helps as adding salt to ice does not extract more heat from the hot object, from a thermodynamic standpoint.

I didnt think addding salt to water would extract heat faster. I dont have a science background so didnt know whether my 'knowledge' was correct or not

 

[Dutto]

Salt will lower the freezing point of water, but in the context of chilling beer, I don't see that this actually helps as adding salt to ice does not extract more heat from the hot object, from a thermodynamic standpoint.

But it will speed up the heat exchange by increasing the temperature differential.

Adding salt kids the ice that it should be a liquid and it drops the temperature to suit so although "no heat is lost or gained" the slight increase in temperature difference will speed up the chilling process ...

... but by only a small amount.

 

[GerritT]

I didnt think addding salt to water would extract heat faster. I dont have a science background so didnt know whether my 'knowledge' was correct or not

Adiabatic expansion. Salt forces itself between the water, expands, and that lowers the temp. And that was all that I could remember from school But think of spray deodorants: it's ambient temperature but as soon as it leaves the vessel, it expands and pulling the expansion energy from the surroundings.

 

[Slid]

Ah, that's an interesting thought, so you might need more ice to chill it down, but it may well get you there faster.

From the beers I chilled in the sink (10-12L), I recall that 2 or 3 changes of water were usually needed - that would be in winter most likely. I never used ice very much due to lack of freezer space. Adding ice plus salt would be a bit of a luxury in terms of freezer space, but I can see it working. time-wise.

The other thing I recall about heat transfer is that you want to stir both liquids, the wort in the pot and the cooling water in the sink, using different spoons, as the wort has to be as sterile as possible.

 

[GerritT]

The destination of treated water for UU is roughly 52% Household, 21% Commercial, 24.5% Leakage and 2.5% Illegal use. Over two thirds of Household usage is for properties not on a meter as opposed to metered properties.

So... there is no shortage. Just spillage.

 

[MyQul]

Adiabatic expansion. Salt forces itself between the water, expands, and that lowers the temp. And that was all that I could remember from school But think of spray deodorants: it's ambient temperature but as soon as it leaves the vessel, it expands and pulling the expansion energy from the surroundings.

So, If I spray my kettle with deodorant it'll cool it down faster ? :tinhat:

 

[GerritT]

So, If I spray my kettle with deodorant it'll cool it down faster ? :tinhat:

Yes! Yes it does!

... but by only a small amount.