Ahem! Electrolux "Gas" Refrigerator

[red_october]

On the subject of oddball gas appliances....

Once upon a time you could get a gas-powered central vacuum. It used the draw from a gas flame to create a vacuum and incinerated everything it vacuumed up.

I'm not sure why ammonia is used in gas cooling appliances; but I know that ammonia-based refrigerant is very effective; it may also be eminently suitable for such applications as there are different types of refrigerants. I also hear that because of environmental issues with alkyl halides, it is comming back for refrigeration because it presents no such risks and ammonia systems actually are statistically surprisingly safe.

 

[fa_f3_20]

Interesting about the gas vacuum. The drawings I've seen of absorption-based refrigeration systems show an ammonia-water solution that is boiled by the burner. This creates an ammonia vapor under pressure. The pressure forces the ammonia through a cooling coil and an expansion valve, where it liquifies. It runs through the evap coil, picks up heat, vaporizes again, and then goes back to the water tank where it is re-absorbed. There's two principles at work here: the vapor cycle of the ammonia, and the going in and out of solution with the water. I'm not quite sure how the latter works; apparently being driven out of solution causes the ammonia to lose heat to the water. Conversely, when it is re-absorbed, it picks up heat from the water. Or some such. Anyway, to make it work, you have to have a refrigerant that is water-soluable, which most fluorocarbon-based refrigerants are not.

I always wondered if it was possible to build a solar air conditioner based on this system. Basically, replace the gas burner with a solar collector. Could it develop enough heat in the collector to make it work and cool an average house?

 

[Cybrvanr]

How exactly does a "frost free" gas refrigerator work exactly? The one in my 1971 camper is marked Frost Free made in Sweden. On the back side, it's basically got Servel markings all over it.

The electric mode on this refrigerator is basically just a heating element wrapped around the gas generator. The fridge doesn't care where it gets it's heat from, just so it's there and in the correct amount! The gas absorption refrigeration is a pretty amazing process...what's even more amazing is that it was invented prior to mechanical refrigeration, which is the common way of doing it today!

There's a little bit more to the process: Check out the "How it works" page on the whole process, which is pretty complex!

http://www.gasrefrigerators.com/howitworks.htm

 

[fa_f3_20]

Frost free gas fridge?

My guess is that it has some valve setup that allows it to run hot water from the burner through the evap coil to defrost.

 

[tolivac]

Ammonia refrigeration systems are favored because they can develop lower temparatures than other systems-the ice cream companies still use Ammonia based systems.However Ammonia IS toxic-like if you can't smell it the damage has been done-some of your olfactory nerves have been burned and destroyed by the gas.In high concentrations ammonia can kill you or severly burn your lungs-causes edema-fluid build up in the lungs.also another thing interesting about ammonia as a refrigerant-you CANNOT use the usual copper pipe like what is used for flourocarbon refrigerents-Ammonia forms EXPLOSIVE nitrides from copper.No joke- after these have formed if you strike them-they EXPLODE!!I tried it years ago as a chemestry experiment.In Ammonia refrgenrent systems iron or steel pipe is used.also ice plants used ammonia in their systems along with a brine solution-the brine worked with the ammonia to produce the ice-water placed into the ice molds-then the molds put into the brine.The ammonia evaporator lines went into the brine-cooling it.Years ago a freind of mine worked in an ice plant with an ammonia based system.He also chilled his soda in the unit on hot summer days.The system had an alarm in case of ammonia leak-shut down compressors and leave!!

 

[dj-gabriele]

Solar powered absortion cooling (not using ammonia)

Tada! I lost the link but it exist, just have a look on google or thatever you like, anyway I found a nice article for you.

The system I've been familiar with has a total power consumtion of only 80W/h for the recirculation pumps and a combined cooling AND heating capacity of up to 40.000W/h (136.000.000btu). It worked on a temperature difference of only 40°C and you only needed a hot side (the solar panels) and a cold side (a pool to be kept "hot" or a pond or else) and it provided (storing it in the molten lithium-bromine salts) heat and cold as needed (also at night then).

http://www.ncsustainableenergy.org/efficiency/DukeSolarHVAC.html

 

[gizmo]

Frost free gas fridge - I doubt it is really Frost Free - more likely auto defrost. I am not clear in mny understanding of exactly how they work, but the basics of it is that the hot part of the cycle, a very small percentage of the hot liquid collects into a dead-end bypass circuit. It takes about 24 hours for the reservoir to fill up, once full it overflows and syphons out into the refrigerator (not freezer) evaporator, suddenly heating up the evaporator and defrosting it into a drip tray underneath. You can see the extra bypass pipe on the back of the fridge. It doesn't work on my fridge though.
i have a refrigeration textbook which explains it, I can put the info here if anyone is interested. Not now, I need to get to sleep.
chris.