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I Has Fridge Compressor But No Skillz

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 15, 2010 5:43 am

I has minibar!

Question is, do I take it apart in order to have onboard compressed air, or would it be best left as-is to have onboard cold beer? hmmm...
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Unread postAuthor: Technician1002 » Mon Nov 15, 2010 6:26 am

Do not open that one. Look up absorption cycle. There is no compressor.
It is full of ammonia. The electrical item is a heater. These use a boiler to separate Ammonia and water. The system is under high pressure.


http://en.wikipedia.org/wiki/Absorption_refrigerator
A single-pressure absorption refrigerator uses three substances: ammonia, hydrogen gas, and water. At standard atmospheric conditions, ammonia is a gas with a boiling point of -33°C, but a single-pressure absorption refrigerator is pressurised to the point where the ammonia is a liquid. The cycle is closed, with all hydrogen, water and ammonia collected and endlessly reused.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 15, 2010 6:39 am

:shock:

Clucking bell, glad I checked before taking a hacksaw to it! I was wondering where the compressor was...

Thanks for the heads up Tech! Cold beer it is then :D
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Unread postAuthor: Technician1002 » Mon Nov 15, 2010 12:25 pm

If you opened it indoors, you would never forget the experience for the rest of your life.

Dilute ammonia water has nothing on saturated ammonia water spraying out of a system at about 400 PSI. A possibility would exist of the strong base of the ammonia causing a very painful death as the moisture in your lungs make ammonia water from the vapor. Sprayed in the eyes can cause blindness.

To add to the hazard, the system is pressurized with Hydrogen.

Blinded, can't breathe, followed by an explosion is no way to enjoy taking one of those apart.

Due to the strong base of the ammonia water and it's reaction to copper, the pipe is steel, not copper.

The item marked Heat Exchanger is the cold part inside. This is where the condensed Ammonia is evaporated to make cold. The ammonia vapor from that is absorbed by the cooled water and the ammonia water runs downhill back to the boiler.

The ammonia does not boil due to low pressure. It evaporates like water below boiling keeps you cold if you put on a wet shirt on a dry day. The water does not boil out of the shirt, but it does evaporate providing cooling.

It took me a very long time to figure out how this works to get cold by adding heat.

I found a diagram of how the plumbing is laid out.
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Unread postAuthor: saefroch » Mon Nov 15, 2010 3:37 pm

Ammonia is NOT a strong base, having a Kb of only 1.79*10^-5.

That doesn't mean it's not hazardous, it's still a powerful base.
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Unread postAuthor: psycix » Mon Nov 15, 2010 5:16 pm

Most small fridges are compressorless.
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Unread postAuthor: Technician1002 » Mon Nov 15, 2010 7:26 pm

Wikipedia lists it as a strong base in water.

Although ammonia is well known as a strong base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the NH2− ion). For example, lithium and ammonia react to give a solution of lithium amide:


In water it is a strong base.

Ammonia is moderately basic, a 1.0 M aqueous solution has a pH of 11.6


It is highly toxic with a 3 rating on the NFPA triangle for health.
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Unread postAuthor: saefroch » Tue Nov 16, 2010 7:51 am

Ammonia is NOT a strong base, any sane chemist knows that only metal hydroxides are strong bases.
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Unread postAuthor: Ragnarok » Tue Nov 16, 2010 9:53 am

Technician1002 wrote:Wikipedia lists it as a strong base in water.

Saefroch is right here.

"Strong base" has a specific meaning in chemistry and should not be mistaken for meaning the same thing as "Powerful base".

Wikipedia, on this one, is mistaken.
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Unread postAuthor: inonickname » Tue Nov 16, 2010 10:11 am

Not to sound like a broken record, but I can assure you it is NOT a strong base. Carbonates and dissolved ammonia are weak bases. Metal hydroxides are strong bases (there are some that are stronger, and not metal hydroxides, such as sodium amide (don't confuse amide with ammonia, there's a difference), and ones composed largely of hydrocarbons).

Copper isn't used because ammonia forms coordination complexes with it and metals such as nickel (amine and hydrazine complexes). It's more a trait of the copper than the ammonia.
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Unread postAuthor: Fnord » Tue Nov 16, 2010 3:42 pm

Do not open that one.


Wow, JSR fail averted!

Of course we know you would have done this outside and with safety glasses, and slowly bled the system rather than ripping away with the hacksaw like an American.

Right? :D
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 16, 2010 11:56 pm

Fnord wrote:Wow, JSR fail averted!


Not *that* much of a close call, I immediately thought there was nothing compressor-like I could see and decided to check here before cutting it up (though more fear of ruining a perfectly good fridge for no reason, as opposed to injuring myself :D)

Of course we know you would have done this outside and with safety glasses, and slowly bled the system rather than ripping away with the hacksaw like an American.


- planning on doing it outside: Image

- ripping away with a hacksaw: Image

As to "safety glasses" and "slow bleeding" (I thought that was something women did?) well, I wouldn't say my attitude is American, but I'm often told I ought to have been born Russian, maybe the East/West divide isn't as bad as once thought :)
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Unread postAuthor: killerbanjo » Tue Mar 06, 2012 1:17 pm

Hi guys i though rather than make i new thread i would use this one. Finnally got the relay housing off and had a look, seems like the top bunch of wires is for the thermosat, right? I have read that you should add a switch on the relay wires, why is that?

The bottom wires must be there AC in as it has an earth wire - So when i wire that to a cable it should work even if i have just left the thermostat wires where they are right?

Sorry for the shitty picture, the compresser is on my lap on an old skateboard deck and i cant be botherd to move and find the camera - too heavy hehe, you get a eee pc webcam pic instead

EDIT: forgot to mention that both the blue and brown wires are connected to the same bits on the relay

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Unread postAuthor: wyz2285 » Tue Mar 06, 2012 2:12 pm

connect the brown wire with he blue one(they are inside the cutted white wire together with the green yarrow one, that´s the ground), with a switch between them, you are good to go.
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Unread postAuthor: killerbanjo » Tue Mar 06, 2012 2:18 pm

Like this? :shock:

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