Eutectic fridges

[BruceS]

Does anyone know and can tell me what these fridges are? They seem to be often referred to on boats and yachts.
Is there any benefit of using one in a rig on the road.
Gee I find it hard having an 'open' forum because if I say caravan, MH or campertrailer etc I'm creating some sort of division.
RIG covers them all I reckon?
RV is too broad......... could be an empty 4X4.

[T1 Terry]

As far as I understand it but I'm sure there are others here that can fill in the bits I missed or stuff up. A eutectic fridge or freezer has a liquid in the walls as part of the insulation/ cooling material. The idea is the fridge is run on mains power till the liquid is frozen, then this only requires enough energy to keep it frozen, everything inside is kept cool because it's surrounded by a block of ice.
There is a mob that took this one step further, they used the energy from the solar panels to run a compressor full time to supercool a liquid to ice and then circulated another liquid through this ice block to act as a refrigerant in the fridge and freezer. The idea is to store the cold energy rather than electrical energy and then convert that to mechanical energy later to drive a compressor. Efficiency between this idea and Li batteries? Buggered if I know, but the electrical energy stored in the batteries can be used for more than just the fridge and the Li batteries are a lot lighter than the liquid storing the cold.

[PandJ R away]

This might help also.

http://www.autofridge.com.au/page/techn ... ation.html.

I also looked at these people when I started the Coaster build and thought about building our own fridge. In the end I purchased a Waeco 2 door as it was simpler choice and its operation was well within or capacities and likely uses. http://www.ozefridge.com.au/

John

[BobnBev]

Eutectic tanks are ok if weight isnt a problem, they hold the head pressure down and have shorter run times and longer off time ( when all is cool)... and will help to save your stuff if there is a down time in power.
Have made a few , they fill them with a salt mix or glycol mix, glycol is the best in a SS tank..
Better a standed fridge in a Van -MH....
Bob....

[Busman]

We have built one for VP using the ozefridge gear, fridge freezer combined, chest type, polyurethane walls and top and bottom. Tanks have Tectaloy radiator coolant in them. Freezer gets down to -20, fridge part whatever you set the thermostat at.
I would expect the larger Danfoss compressor we used to run about 5 hours a day normally, can set it to do its work when plenty power is available.
The whole thing is on slides in one bin, okay for a coach conversion as we have a 240 v 50 ltr bar fridge up top for milk butter and a few coldies but would go for an off the shelf 240 unit and a couple of extra solar panels in something smaller.

William

[Dot]

Any pics of the work you clever lads have done please? sounds interesting even to a female

[Geoff Clifton]

I don't have data but I don't think there is any efficiency of power consumption benefit with a eutectic design in that a standard compressor fridge would use about the same Ah in total as the eutectic uses in one chilling cycle. The absolute advantage is where battery power is too small to run the fridge overnight etc. and the chill cycle can be done while driving (alternator) or when generator can be run or when solar output is good. The stored cold in the eutectic solution can last overnight or days depending on the design volume.

Eutectic appears to be my word for the week. I had only considered it regarding fridges and being a liquid that does not freeze at sub zero, down to say -30*C. Eutectic actually means an alloy whose melt point is lower than any of the separate ingredients. Solder is a good example where the 'eutectic point' is 63% tin : 37% lead although we more commonly use 60:40 for electrical work and 50:50 for plumbing soft solder (no longer used for potable water).

[Dot]

thanks for that Geoff, don't think I shall look any further..

[TigerMK1]

With the current technology of solar, efficent batteries (i use lithium) and commercial fridges, the realities are that a normal domestic high rated fridge will do a great job at half or less the cost.