Eutectic fridges

[alittlebitconcerned]

Ive just stumbled across eutectic fridges and they seem very interesting as on paper it seems to makes a lot of sense to me. One company who produces them is Autofridge. Here's a link...

Autofridge Australia (http://www.autofridge.com.au/)

Does any one have any experience with this type of fridge?
Pros and cons?

[Blknight.aus]

good for long term use, sucky for short term stuff.

they use more power during the initial pull down and smaller ones suck at chilling stuff down when they are off power but for long term use on a managed solar setup (as in only powers up when the panels are producing more than whats needed to charge the batteries) they're the way to go IF you can handle the weight penalty for the storage space they offer.

[cjc_td5]

Yes we have one. We have had ours for about 15 years, it is about a 39l model I think.

The main draw for us at the time was the eutectic function that allows us to run it for only 2-3 hours in morning and again in the afternoon and keep everything cold, even in the Kimberley heat. This allows us to avoid having to go the dual battery route as we can just turn the fridge off when we stop and it will keep cold for many hours.

Our has done the Kimberley three times and 'round Australia once and survived many rough roads.

I remember they were pretty pricey at the time, we bought ours before the cheaper Waecos etc were around on the market.

I believe that they can be sent back to the factory in Botany NSW to be regassed and the eutectic fluid replaced when required. That said, I had ours out today and it performed as expected.

Pros: Doesn't have to be run 24/7 to keep everything cold.

Cons: When the eutectic jacket is frozen, it can be hard to stop some things from freezing in the fridge (think milk with icy bits on your cereal in the morning) . You need to keep these things off the sides of the fridge. That said, you can use this to your advantage by placing meat against the sides of the fridge to keep them coldest.

Chris

[dmdigital]

I have a 70L in the Kamper trailer and would have to concur with the above comments.

When travelling we use the Engel as our daily fridge and the Autofridge as the longer term storage. Very good and reliable unit.

[TonyC]

These people do the guts, with some good "smarts", but you have to build your own "box"
Lots of info on the site, from the point of view of the manufacturer of course

Home (http://ozefridge.com.au/index.html)

They seem to be mainly aimed at yachts but I have read of them fitted to motor homes and the owners happy with the result.

Tony

[vnx205]

Nothing I have read about eutectic fridges makes it clear how they have an advantage over a normal fridge stuffed full of frozen water bottles or something similar.

I understand about the amount of heat required to change the state of a liquid being many times greater than the heat required to raise the temperature. After all that is why ordinary old iceboxes work as well as they do.

The only way I could think of a eutectic fridge being better than just keeping the fridge full would be if the fluid used in the eutectic fridge had a freezing point above 0 degrees Celcius. Is that the case? That would avoid the problem of other things freezing when you didn't want them too.

I'm not claiming they don't work. They obviously do. It is just that none of the many sites I have looked at have explained clearly why they are better than just keeping the fridge stuffed full.

[TonyC]

I understand it has to do with the temperature that the evaporator is running at, the colder it is the less efficient it is, and in a eutectic system it can be relatively high.

have a read of this.
http://autofridge.com.au/files/Autofridge_Technical_Information.pdf

That said it's their sales pitch and I've never studied thermodynamics.

Tony

[vnx205]

My understanding of that article is that the refrigerant in a eutectic fridge evaporates at -10 instead of the usual -25. Does that mean that the lowest temperature that the fridge can achieve is -10? I thought -18 was the optimum for a freezer.

Everything the article said about the latent heat absorbed by the ice as it melts still applies to a fridge full of frozen water bottles.

So unless I have missed something, the main difference seems to be the efficiency achieved by using a refrigerant with a higher evaporating temperature.

[Blknight.aus]

nice but not to be trusted its got some very interesting wordplay but is basically coming down to the same principal as the old kids joke about proving you have 11 fingers

1,2,3,4,5 fingers on one hand
10,9,8,7,6 plus 5 equals 11, every one knows that. Thats not entirely fair a much simpler explanation is "so you're saying my car is more fuel effecient if Im driving it down hill?"

at the end of the day where the eutectic fridges have their advantage is their ability to "store" more cold than a traditional refrigerator and then run their compressor when A, there's more power available and B when the external temperatures are cooler so the heat exchanger is more effecient.

It comes down to how you define better and how you conduct the tests as to which one is better.

as an Example Fozzy, my crappy old 2.25D series III is better than a puma because it goes further per liter of diesel at its GCM than any Puma. In and of itself that statement is entirely true.

What's not immediately obvious is that at GCM a puma tips in at a shade over 7T (8.5ish if you have the HCPU 130 with the 4.5t tow package) fozzy comes in at a paltry 4.6. The far more important fact, that you wouldnt know with out some substantial research is fozzy runs on Vegge oil mainly using diesel to start up in cold weather and the puma cant reliably run vegge oil so once fozzy's started 0l (diesel)/100KM is easily achieved even though the real fuel consumption at full load can be as bad as 50l/100KM

so whats the point here. Better is not a good word to use unless you also include how you're defining better.

Eutectic refrigeration is nothing new its an old idea re-invented think of fozzy as being the eutectic refrigerator and the puma being a good "traditional style" refrigerator. Excluding coolgardi safes once upon a time Eutectic refrigeration was all anybody had because all they had was a well insulated double wall meat safe, a very small space in the middle and a very large surrounding insulated area into which Ice was purchased and placed. zero power consumption at the house but kept meat cold for days at a time.

[123rover50]

The freezer I built in the 6x6 is eutectic.
It has stainless tanks with the refrigerant pipes packed into it and they are surrounded by the eutectic solution which is a mixture of antifreeze and water. This needs a lower temp than 0 C before it freezes so holds the cabinet temp lower for longer. This is the advantage over frozen bottles.

Didiman

[scarry]

They work very well in boats,as the off engine drive refrig compresser only needs running for short periods to freeze the plate,which then keeps the box cold for days.Also some are 240v,these are only run while at the jetty,so the plate will be frozen,ready for a weekend or so away.
They run a simpl refrig. system,no electronics etc to cause grief.

[driftn69]

I've had my Auto Fridge for at least 15yrs, it spent three years rattling between Meekatharra and Wiluna and has also been on some other remote area trips in some hot and dusty conditions, it has also been unused for long periods. It has proven to be efficient and reliable.

However,
1- does not have in built 240volt power reducer. (came as seperate unit, merely an inconvenience)
2- if left to its own devices even on the lowest setting when left switched on it will eventually freeze everything. (Use of an indoor/outdoor thermometer helps prevent frozen and burst frothies, always switch it off overnight)

Would I recommend them as a set and forget fridge option? No

Our caravan came with a Waeco which we now use as our tavelling fridge and we use the Auto Fridge as a freezer in our caravan or for extended camping.

We are reasonably well set up with solar, dual batteries and gen set power so any small differences in power consumption and efficiencies are not a major factor.

My thoughts and experience for what they're worth.