Second system extension extension.

[Joeboy]

I've been taking ice packs out of the freezer and sitting them on the bedside table overnight the last couple of nights*, then putting them back to re-freeze in the morning. Don't know how much it helps but anything's worth a try to get a better nights sleep at the moment!

*Don't put your phone next to them as there's quite a puddle of condensation in the morning.

Stig, I used huge tupperware boxes in Spring, not filled all the way to top and with lids on, probably about 3 ltrs per cube and did two of them. It was more for a power off icebox scenario here in Turkey. My point is that they took a LONG time to melt when I turfed them out onto the patio at the end of trip. I defo think the large ice cube and fan has potential in these overheating times.

[openspaceman]

I left the jug in the freezer from 11am-ish to 8pm, by that time it had partially frozen. I set the freezer to -14℃ overnight overnight and by morning the jug was completely frozen.

I wanted the jug to freeze in the daytime and defrost (at least partially) overnight. So that part is a “fail”. Maybe my freezer struggles to achieve super-low temperatures on a very hot day?

If the freezer temperature is accurate then if it all froze at -14C it was not a saturated solution.

The point is you are aiming for the solution to change state at very near the temperature you want to maintain in the freezer, it's the heat getting into the freezer from the outside that causes the temperature to go up and trigger the thermostat but if the heat getting in melts the brine without changing the temperature i.e. the heat of fusion of the ice is being absorbed but the temperature doesn't change.

Now it may just be that as water and ice are not very good conductors and as the difference in temperature is very low, from above and you need delta T for heat to flow from a high temperature (the freezer) to a lower temperature (the ice), then a solid block of ice may not have enough surface area to defrost overnight,

[Stinsy]

I left the jug in the freezer from 11am-ish to 8pm, by that time it had partially frozen. I set the freezer to -14℃ overnight overnight and by morning the jug was completely frozen.

I wanted the jug to freeze in the daytime and defrost (at least partially) overnight. So that part is a “fail”. Maybe my freezer struggles to achieve super-low temperatures on a very hot day?

If the freezer temperature is accurate then if it all froze at -14C it was not a saturated solution.

The point is you are aiming for the solution to change state at very near the temperature you want to maintain in the freezer, it's the heat getting into the freezer from the outside that causes the temperature to go up and trigger the thermostat but if the heat getting in melts the brine without changing the temperature i.e. the heat of fusion of the ice is being absorbed but the temperature doesn't change.

Now it may just be that as water and ice are not very good conductors and as the difference in temperature is very low, from above and you need delta T for heat to flow from a high temperature (the freezer) to a lower temperature (the ice), then a solid block of ice may not have enough surface area to defrost overnight,

Well I put it in the fridge (set to 6℃) last night and is is still only c. 30% defrosted!

[openspaceman]

Well I put it in the fridge (set to 6℃) last night and is is still only c. 30% defrosted!

Then it will be that there is not enough heat exchange surface because a delta T of more than 6C should melt it. Perhaps a shallower metal tray?

I still cannot try this as our freezer is chocka.

[Joeboy]

Well, with no salt to hand I filled a few lidded boxes to a total of 7 ltrs and stuck em in the freezer alongside the 3 types of gin, ice cubes and frozen glasses. Max we see out here is about 4 hours without power, at a push 6. I have a 200ltr water tank on ballcock in the highest part of house that kicks in, multiple usb battery packs and this added coolbox scenario. Keeps it all civilised in the GnT dept along with water for toilets and enough head pressure to run the lower level shower. Beyond that we go to scented candles and the fridge for ice cubes....
I reckon we are good for about 2.5 days.

Are you guys seeing the freezer box photo? Please confirm one way or t'other, thanks.

[Bugtownboy]

All good, Joe - pic of the freezer portion of the fridge, various EtOH bottles.

[Joeboy]

All good, Joe - pic of the freezer portion of the fridge, various EtOH bottles.

Epic! Cheers BTB!

[AE-NMidlands]

looks good... if a bit clean by our standards!
(Like others, our freezers are already full too, mostly summer fruit at this time of year.)

I can't get my head around the point of the brine yet, I see that it stays fluid at a much lower temperature, which might offset the lower SH, also that water-ice has a poor SH and thermal conductivity which count against it too.
I know that NaOH gives out a lot of heat when you dissolve it, also that CaCl gets cold, but I can't find any way that the salt in brine will mop up a lot of heat in a phase-change. https://en.wikipedia.org/wiki/Enthalpy_ ... f_solution shows that salt has a pretty trivial Enthalpy change on solution compared with big +ve and -ve numbers for other compounds. I don't think that latent heat of fusion is relevant here, although I was surprised to see that you can use latent heat of fusion to predict solubility.

I wondered whether it would be worth using water-ice but with heat conductors threaded through: like several upside-down top-hats of copper bar in the water tray so that the low conductivity of ice doesn't handicap it so much...
A

[Stinsy]

Well, with no salt to hand I filled a few lidded boxes to a total of 7 ltrs and stuck em in the freezer alongside the 3 types of gin, ice cubes and frozen glasses. Max we see out here is about 4 hours without power, at a push 6. I have a 200ltr water tank on ballcock in the highest part of house that kicks in, multiple usb battery packs and this added coolbox scenario. Keeps it all civilised in the GnT dept along with water for toilets and enough head pressure to run the lower level shower. Beyond that we go to scented candles and the fridge for ice cubes....
I reckon we are good for about 2.5 days.

Are you guys seeing the freezer box photo? Please confirm one way or t'other, thanks.

Not much food to perish in the every of an outage in there!

[Bugtownboy]

But a warm G&T

Disastrous !