Effective Eutectic solutions from the food industry

[rgleason]

There are a number of newer eutectic products on the market, and I wonder if these solutions would provide any improvement over our properly mixed polyglycol solutions which freeze up gradually over 2-3 degrees C, starting as an ice slurry and ending at -7c to -8c as ice (for our system)?

[tkeithlu]

Disclaimer - my experience is with eutectic metals, not ice.

No surprises here - a eutectic combination of atoms forms a regular structure as it shifts from liquid to solid, and has a lower freezing/hardening point as a result of that regularity. But, there isn't any liquid out there that releases more energy in hardening that water, so if you are trying to make super ice, it's going to be a eutectic combination of something with water, and you get to be a chemist in finding the best one. Glycol gets you ice at -7C, which means that it will keep your ice cream solid where water ice won't, or won't as long. Your engine doesn't become a solid block until a lower temperature. You can generate sub-zero ice - it's the ice that sticks to your fingers when you touch it.

I'm wandering, but I think that there is a point in here somewhere. A bag of glycol freezer mix, straight from the store, is going to give you darned close to the same performance as others. Have you got a situation so exotic as to require more than the -7C or so?

[rgleason]

This thread is intended to elict suggestions, ideas, and known techniques for effective operation of eutectic systems.

Including controls, compressors, operational timing, etc.

How to plan use of excess power from engine, solar and wind.

[rgleason]

Just asking if there is a better eutectic solution than we are using. The food industry and logistics has studied this and knows more than I know about it.

Yes the change in state is what we are using, and there is no magic solution that increases btu in and out.

However there are some factors to consider, do we want a long gradual period of freezing and thaw, or is it more efficient to have a quicker freeze/ thaw. Can these be different, as fast freeze, slow thaw? The factors involved are complex and the answer is not intuitively clear to me right now.

[jamhass]

There are a lot of considerations involved in selecting a eutectic for holding plates.

As you've already identified, the range of the phase change is important, and needs to be compatible with the parameters of the refrigeration system (R12, R134 ...)

The heat of fusion is also important, as is the volumetric change during phase change.

The slushy state between liquid and solid states allows for the ice to be "slushed" out of the way while freezing, reducing the chance that the holding plate is damaged during freezing.

There are probably many other issues, such as long-term chemical stability, corrosive properties, etc etc.

So, while the question is an interesting one, the parameters are likely many such that a move away from industry practice might require a lot of effort to support, and implementation possibly require more than "simple" changing the eutectic to get better performance.

[rgleason]

Hasn't any company done research or looked into this further?
It does not seem to me that there has been much effort put into being precise about this solution.

[spiv]

Following thread...

[rgleason]

Thanks to @wsmurdock's post with the wayback machine to
.. a study similar to that done by Cruising World in 1995. I recommend taking some time to read that well planned and well executed study as a break from the current muck slinging. https://web.archive.org/web/20061103...d/coldfact.htm


The is an excellent paragraph about eutectic solutions:

Antifreeze vs. True Eutectic Solutions

The true test of any refrigeration system is its ability to maintain correct temperatures for food storage. Forty degrees is considered an ideal refrigerator temperature, but for frozen foods, the colder the better. You will have better results with frozen food storage if the freezer can be maintained at 20 degrees or lower. An installation that allows foods to freeze and thaw, even slightly, will shorten the storage life of foods and is especially hard on fresh foods in the refrigerator. Some manufacturers use an antifreeze solution in their cold plates. This solution does not maintain a constant temperature when frozen. Instead the temperature of the holding plate slowly rises during the holdover period. Manufacturers using antifreeze solutions say that this increase in holding plate temperature should not significantly affect the temperature of the compartment.
A few systems use a eutectic solution valued for its ability to maintain a constant temperature until thawed.



If a true eutectic solution is used, the temperature of the cold plate will remain constant while frozen and will only change when the solution is allowed to thaw. This approach should produce refrigeration temperatures that are more stable.

[Uncle Bob]

Originally Posted by rgleason

Thanks to @wsmurdock's post with the wayback machine to
.. a study similar to that done by Cruising World in 1995. I recommend taking some time to read that well planned and well executed study as a break from the current muck slinging. https://web.archive.org/web/20061103...d/coldfact.htm


The is an excellent paragraph about eutectic solutions:

Hi, I agree with you about the muck slinging in previous threads, Louie was, in my opinion, attempting to use the collective wisdom and knowledge as a sounding board towards possible further development of greater electrical efficiency in reefer systems, until a couple of protagonists started pushing their own agenda's.
The demonstration of the willingness to further develop an existing process/product indicates to me that he would have been the perfect person to take your question further, however I would be surprised if he returns for a further battering.

[rgleason]

"If a true eutectic solution is used, the temperature of the cold plate will remain constant while frozen and will only change when the solution is allowed to thaw. This approach should produce refrigeration temperatures that are more stable."

So I ask if there is such a solution for maintaining 40 degrees for a refridge?
..and what other characteristics would be best?

Uncle Bob, thanks for your words. Louie has already given me some good ideas and I have been in touch with his Dad. I am afraid those ideas won't be shared here...

I think the msmurdock link established that once a refridge is operating they pretty much use the same amount of energy and that a freezer uses 4-5x's the energy. Where eutectic shines is when coupled with solar and engine/alternator when power is plentiful.

[Richard Kollmann]

Originally Posted by rgleason

I think the msmurdock link established that once a refridge is operating they pretty much use the same amount of energy and that a freezer uses 4-5x's the energy. Where eutectic shines is when coupled with solar and engine/alternator when power is plentiful.

rglleason, Your right on it is too bad that back when these system tests were done small 12 volt eutectic systems were not popular. But also popular reliable alternative energy other than on board generators was not available at that time.

[bdgWesternMass]

The ozfridge seems to a good proof of the value of the eutectic plate refrigerator.

Although the express the energy usage in AMP/H per day for a 12V DC system I will express them in the less controversial for of watts per day.

Rounding the Amps up to the nearest whole number of 4 at 12 volts I get 48 watts per day.

Finally our own thread participant Richard Kollmann is quoted defining his process of estimating refrigeration loads.

If one was designing a refrigerator today can they still use your estimating guidelines Richard?

Thanks,

Ben

[Pete7]

Originally Posted by bdgWesternMass

Rounding the Amps up to the nearest whole number of 4 at 12 volts I get 48 watts per day.

Ben, you mean "an hour" surely, which is about what our portable freezer uses.

Pete

[bdgWesternMass]

I don't think so...

I meant to include the ozfridge link so I could be fact checked.
I have no first hand experience. I'm doing design research for marine refrigerators.

Thanks,

Ben

https://www.ozefridge.com/system-estimate


Yes I think you are correct I didn't understand the column on the far right as the cumulative total.

[wsmurdoch]

Glacier Bay used to claim two true eutectics they called TSS+26 and TSS-8. I have never found out what the material was. Jump down to the bottom of page 8 of the attachment.

Bill