5 ms·
How about this theory. The hot water causes the freezer to run its compressor sooner. The system is nonlinear due to intentional hysteresis in thermostats, and
by sgtnoodle 4y ago
How about this theory. The hot water causes the freezer to run its compressor sooner. The system is nonlinear due to intentional hysteresis in thermostats, and the excess energy stored in the hot water is trivial compared to the capability of the heat pump.
Introducing hot water into a freezer rapidly raises the ambient temperature of the freezer. This causes the thermostat to click on, and the heat pump therefore runs until the ambient air drops down below the thermostat's shut off point. A lot of heat is removed very early on, and the ambient freezer temp is at its lowest going into the liquid to solid phase change.
With the cold water, the ambient air of the freezer doesn't rise nearly as much. The thermostat does n't click on until a long while later, once enough heat leaks out of the freezer. The ambient air is warmer going into the phase change.
It doesn't work if you put the two cups in the same freezer, but at least it could explain some anecdotes.
- incanus77 4y agoI observed the phenomenon growing up when I filled buckets of hot and cold water and left them outside in freezing temperatures.
- cowtools 4y agoI think it might have something to do with the convection current of the hot water. Perhaps the higher initial velocity allows the ice crystals to nucleate faster?
- Jensson 4y agoHot water melts snow, and the ground is much colder than the snow which isolates heat. So in your case the simple explanation is just that, the hot buckets melted the snow/ice and therefore stopped being isolated against the cold ground so froze faster.
- ascar 4y agoThe assumption being they were placed on snow, which I would argue is an unlikely assumption to hold up. We have much more days with freezing temperatures than days with snow lying around and even then with lots of snow there are enough places that don't have any (like a balcony).
- incanus77 4y agoThey were set on concrete.
- sgtnoodle 4y agoSome more ideas. Cold water holds more dissolved air in it than hot water, and the hot water heater would have recently rendered most of those gases out. That dissolved air could negatively impact the thermal conductivity of the water. Near boiling water is about 4% less dense than near freezing water. If you filled the buckets right to the top, there would be less water in the hot bucket.
- stdbrouw 4y ago> the excess energy stored in the hot water is trivial compared to the capability of the heat pump I don't know if I'd call it trivial, bringing 1 kg of water from 85C to 0C involves about 100W for a duration of one hour whereas a typical freezer removes heat at, what, 200W or 300W?
- danieljacksonno 4y agoBut a 100ml beaker would only require 10W
- chmod775 4y ago>bringing 1 kg of water from 85C to 0C involves about 100W That looks like the amount of energy needed to heat that water. But cooling things doesn't work the same way. Instead you want to extract that energy/move it somewhere else. The efficiency of some approaches, unlike when heating something, can hugely depend on ambient temperature. It's possible you'll be able to extract more useful energy cooling something than you'll have to expend!
- deleted 4y ago[deleted]
- b112 4y agoHow about this theory. The hot water causes the freezer to run its compressor sooner. This may happen but, in a normal freezer, the action of the compressor is meaningless. My feezer is 70% full, with probably 30kg of stuff in it. This stuff is mostly at -22C (I have a thermometer), and so, this mass is what cools new things added to the freezer, fast. (Why -22C instead of -18C? Salt water fish is in there, and I also want a little headroom.)
- titzer 4y agoUnless the new things are physically touching the other mass, then my guess is that the primary cooling effect is due to 1.) convection through the air in the freezer, followed by the 2.) conduction through the surface the new things are sitting on, followed by the 3.) IR radiation of the new thing. The existing thermal mass in the freezer interacts with the new thing via 1 (indirectly) and 3 (by absorption), but I suspect that the compressor cooling the air is a bigger effect.
- b112 4y agoAll documentation I've read, and personal experience, says otherwise. For example, most manuals urge one to not have an empty freezer. That cold mass is one reason why. When I was a kid, we had a fridge from the 50s in a cottage. When I started drinking, we'd put 5 cases of beer (24*5) in glass bottles in there, and 2 hours, yes hours later they'd be at 1C. Now, modern fridges/freezers literally do not have that degree of cooling power. This is on purpose, for it is more efficient to power a small compressor all the time, than a massive compressor for 10 minutes. You may want to argue this point, and that's fine, but I am merely providing info both from the manuals of modern freezers and fridges, which I have read, and from online when looking at why they are so bloody slow to cool things. My LG fridge manual actually says not to put warm meat in my freezer, unless the thing has loads of frozen stuff in it. Otherwise the meat could go bad before freezing. Oh, another wonder of modern fridges. If you buy one and put it outside, or in an unheated garage, the freezer becomes useless. This is because many fridges have no thermometer in the freezer part, and only get a reading when the compressor comes on, to cool the fridge. As the fridge is always cool when it is 3C outside, or cooler, the freezer never keeps stuff frozen.
- comboy 4y agoI love that theory. I would assume they use big enough freezer or with enough ice inside for that not to matter, but that would be a hilarious solution.