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You can use ether as a refrigerant, but a bad side effect is that any leaks will tend to allow oxygen into the system, which will make for a extremely explosive reaction.
I'm not certain, but I think the big issue is that with ether you have a relatively low pressure in the system- so there's not much mass of ether so it can't carry much heat.
Also I'm pretty sure you need to consider the latent heat of evaporation and other parameters.It's complicated.
Ok,So, what I've described will work.
I didn't mean to imply that the system would work with no energy added. Obviously, even the vapor pressure will be higher on the warm side than on the cold side, so the vacuum pump still needs power. I guess that does also mean more pressure on the warm return side to recover some of that added energy. But, at least some energy would need to be expended, especially if the goal is to remove either warmth or cold from the system. Otherwise the system would tend towards iso-thermal and stop.We've already discussed that one could make ice by putting water into a vacuum chamber... this is more or less using the same concept.
I missed the bit about making ice with a vacuum. If the idea is to lower the pressure above the water to make it freeze, that does not make sense to me. The freezing temperature of water does not increase as pressure decreases.
"How did the discussion get to ice?"Because some git posted a video of what happens when you connect a vacuum pump to a container of water.[...]Have a look at this.http://www.youtube.com/watch?v=8oCjj8iDB9IOnce the water freezes the vapour pressure drops even further. It's a good way of getting the clothes cold, but not so good at getting them dry.
Quote from: Geezer on 21/12/2011 22:06:34The freezing temperature of water does not increase as pressure decreases.What's your second guess?At best, it depends on what temperature / pressure you start at.
The freezing temperature of water does not increase as pressure decreases.
Although, the actual difference in freezing point of water between pressures of 101KPA (1ATM) and .6KPA is only 0.01 °C
I was looking at this vapor pressure chart in Wikipedia. Sorry it only has a few substances, but the idea is the same. http://en.wikipedia.org/wiki/Vapor_pressureLooking at, say the difference in vapor pressure between -10°C (below freezing), and +20°C (room temperature).If you choose, something like Propane (BP is -42°C), one goes from a vapor pressure from about 2.5 ATM to about 8.5 ATM, or a difference of about 6 ATM.However, if one chooses a refrigerant like Diethyl-Ether, one goes from about 0.15 ATM up to about 0.6 ATM. So...Theoretically, running the diethyl-ether in a vacuum, rather that under pressure, one should be able to force the phase change with an absolute difference of only about 0.5 ATM.It would seem as if one should be able to design the diethyl-ether refrigerant to use less energy. Although, I know that a vacuum pump in air, seems to have to work quite a bit to achieve a low pressure.