[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 53
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А вы полагаете, что холодильник даёт больше тепловой энергии, чем потребляет электрической энергии из сети?
Пример: Ставим холодильник в помещение. Мощность компрессора - 170 Вт, работает 30 минут в час, образно говоря,
вот в час и выдаёт 85 Вт тепла в среднем.
No. I later clarified what I meant. It's just that your post was ahead of the clarification.
But only a freshly plugged-in refrigerator will generate more heat than it consumes electricity. When the temperature in it stabilises, the "thermal efficiency" will again be =100%.
Well, at some point, the debt will have to be repaid - when the door is opened, for example. Or a shutdown.
Yes, I agree, but we are talking about a long process. I was unfortunately in a hurry and didn't phrase the question in great detail straight away.
But, you are thinking in the right direction.
No. I later clarified what I meant. It's just that your post preceded the clarification.
I'll delete it then.
Да, согласен, но мы говорим о том, что это длительный процесс. Я к сожалению поспешил и сразу не сформулировал вопрос очень подробно.
Но, вы мыслите в правильном направлении.
An air conditioner, then. But only it will be an outdoor heater. ;)
Yes, you're right. People usually think that salt melts snow, but it turns out it cools it down. Saltpetre is also one of those substances, and so are, for example, photographic film developer fixative (sodium thiosulphate) and many other substances. Most of them are very water soluble indeed.
Salt does not cool the snow. The physics (not to be confused with chemistry) of the process is this. Snow consumes melting energy (like any solid phase of matter when melting). If there is no source of that energy, there will be no melting (fusion). If there is not a drop of water when combining snow and salt, nothing will happen. This is possible, for example, at -50C. If the temperature is close to 0C and there is at least a drop of water, a salt solution will form in this drop. This solution has a lower freezing point (crystallization), so it can give off heat energy by cooling down, but not freezing. Which it does. The energy it gives off is consumed by neighbouring snow, which, thanks to this energy, melts. The amount of brine increases. And so on.
So it is not the salt that melts the snow, but the brine which, as it cools, gives off heat.
I don't remember whether dissolving table salt in water is an exothermic reaction or an endothermic reaction. However, if, in this dissolution, some heat is released, it also goes into melting the snow.
.
A heater which consumes 1kW and gives out 1.5kW is known to everyone here. But I figured that no one should say it aloud, or the intrigue would disappear. Well, in that case, I won't either. I only want to say that refrigerator, though according to its parameters doesn't pass, but it certainly is such a device.
An air conditioner, then. But only it will be an outdoor heater. ;)
Yes. It really is an air conditioner. Congratulations. Mischek was first, you're second, Yurixx is third.
Why for the street? Nowadays, air conditioners are also made reversible. In summer these air conditioners cool the room and remove
and in winter they heat it, consuming much less energy than they give out. The rest of the energy is taken from
street air. In Canada, such systems have long been made on a "large scale" in the form of energy units, while we are still lagging behind.
Yurixx, I mostly agree with you.Salt is a solid substance. So is snow. The reaction will go if there is even a little bit of liquid. You won't believe it, but that amount is there for snow at all times, even at -50g C.
But, you wrote that it is a solution, it can give off heat energy by cooling down. This is where you are not quite right. By cooling, it does not give energy, it takes it from the outside environment. It would give it back if it were heating. The internal energy of the solution is greater, so it has no choice but to cool down to take energy from the external environment.
Да. Это действительно кондиционер. Поздравляю. Первым догадался Mischek, вы - второй.
Почему для улицы? Сейчас кондиционеры делаются также реверсивными. Летом такие кондёры охлаждают помещение и удаляют из него
влагу, а зимой - отапливают его, при чём потребляя при этом намного меньше энергии, чем выделяя. Остальная энергия берётся из
воздуха улицы. В Канаде уже давно такие системы изготавливаются в "больших масштабах" в виде энергоблоков, а мы пока отстали.
I didn't know. Well, hooray for that!
Yeah. But I seem to have killed the suspense. Pardon me.
It's a fun topic. It made me laugh when I read it. Especially the one about the ton of flies. :)
Air conditioning connoisseurs = fridge connoisseurs?
Practical question, at what ambient temperature do modern refrigerators stop freezing?
I didn't know. Well, hooray for that!
Yeah. But I seem to have killed the intrigue. Pardon me.
That's a fun topic. It made me laugh when I read it. Especially the one about the ton of flies. :)
It's not that intriguing. I didn't realize my questions were so complicated. Well, I won't do it again, I like puzzles myself, especially technical ones.