Report from CF thread

The following is a thread that was at CF but eventually removed. Many interested contacted us for a copy so here it is... (partly completed!)

16-04-2018, 19:27

OzePete

Marine Service Provider

Eutetic Refrigeration for Marine use

There has been a lot said here regards Eutectic marine Refrigeration but mostly opinion and mostly without any basis. This thread is an attempt to explain the eutectic refrigeration system and to present the results of a direct comparison trial conducted between a eutectic stainless steel system and a cyclic aluminium cold plate system used in an identical application.

But first:
1. What is meant by Eutectic refrigeration: Eutectic refrigeration systems use a refrigeration condensing unit much like any other system. The difference is that a eutectic system involves refrigerating a storage tank that contains a solution that freezes solid to a predetermined temperature. (centigrade). The eutectic system benefits from the ‘phase change’ of a stored medium and the enormous energy storage this latent heat application provides

2. To Explain: We all know that a cold drink with ice in it will stay cold and drinkable at a constant temperature while the ice remains, but will warm rapidly once the ice thaws.
The ice is an example of the eutectic principle. The ice absorbs relatively huge amounts of heat from the drink, causing the drink to remain cold, while it thawed from a solid back to a liquid. (Phase changing)
A phase change medium or eutectic solution is stored in the stainless steel eutectic tank or plate within the fridge cabinet and acts like a renewable ice block, freezing solid during the refrigeration run cycle and thawing during off periods, and all the time maintaining a constant fridge cabinet temperature just like the ice did for the cool drink!

3. How does it work: A digital thermostat probe located within the eutectic solution, causes the compressor to run when it senses that the solution has thawed. The compressor runs for a long period to refreeze the solution solid virtually storing thermal energy for cooling in advance. Hold over refrigeration, because once the mass is re-frozen it holds the cabinet at the desired temperature for many hours and often a day or so in cooler climates.

4. So where is the benefit: Phase Change occurs when we freeze a solution solid by removing its heat, or as it thaws into a liquid again while it absorbs heat.
Other products such as a thin aluminium evaporator plate systems can also absorb and dissipate thermal energy (heat) but when a relatively large volume of solution is used as in the eutectic plate and it is allowed to freeze solid on the refrigeration run cycle, then thaw during the off cycle, a massive amount of stored thermal energy is in play.
By comparison with a thin aluminium cold plate, the first and most obvious advantage the eutectic system has is its far greater mass and therefore thermal hold-over storage capacity. (A thin 2mm thick slice of ice will disappear much quicker than a 60mm thick block would)
But this thermal storage advantage pales into insignificance compared to the other unique benefit that the eutectic system phase change phenomenon delivers. This is called ‘Latent heat’. It effectively multiplies the eutectic thermal storage capacity of the medium byup to 80 times (yes eighty times) providing huge hold-over periods where the unit stays off for many hours even days in cooler times.

5. So why use a Eutectic system:
A: Weight. The total weight of an operating eutectic system is less than half the weight of the batteries that would otherwise be required to power up a cyclic cold plate fridge unit to provide the same cooling.
B: Power efficiency. A eutectic system will use much less power to do the same job as a cyclic system. (See test results and reasons why following below).
C: Product temperature pull-down. Warm products added to the cabinet have the benefit of the stored eutectic mass to reduce the temperature of warm product faster, not solely relying on the refrigeration unit’s capacity at the time.
D: Some systems can be set to refreeze the eutectic mass when power is abundant reducing or eliminating battery consumption.
E: Doesn’t require a battery power supply 24 /7. Refreeze can often be when it best suits available power.

6: Refrigeration with NO battery drain. Is it possible?
Because a eutectic system usually only needs one continuous two to three hour run per day, (in average ambient) devices like the Ozefridge ECO2 will cause this run to occur when power is abundant eliminating the need to draw any battery power at all at other times! (Abundant power would be when batteries are fully charged and solaror whatever is being wasted, for example!)

7: What causes a eutectic system to be so efficient?
Firstly, given a cabinet to refrigerate, as in this test, the amount of heat to be removed (measured in watts) is exactly the same regardless of the refrigeration method used. Therefore it gets down to the efficiency of the refrigeration system's operation. .

There are two main reasons why the eutectic systems are much more power efficient.

The first relates to the refrigeration systems CoP (Co-efficiency of Performance)
To explain: COP is a factor indicating how much heat is removed relative to electricalenergy consumed. A system with a COP of say 1.13 removes 1.13 watts of heat for each watt of electrical energy consumed. (Similar to miles per gallon, and the bigger the number the greater the efficiency!)
This 1.13 COP would be typical of the cyclic fridge system as its evaporator would mostly run at -23C or colder while refrigerating.
This 1.13 COP rate is very inefficient compared to the eutectic system which would have a much better COP of 1.95. Far more heat removed per watt of battery power consumed!
(The lower the temperature a refrigeration system’s evaporator runs at, the less efficient the system is. Running a system on with a low COP is very false economy)
Secondly, motor start up inefficiencies. All electric motors consume excess energy while providing little benefit during start up. This waste of energy is obviously far less with a eutectic system as it only starts once or twice a day instead of 20 to 60 times as for a cyclic system. This is the greatest cause of inefficiency and would be even worse if compressors didn’t have soft start motor driver modules like those in this test!

8: Power consumption test method and results:
This test was performed with a domestic 150 litre freezer (70mm walls) which had its compressor etc., removed, so basically and empty cabinet.
Two identical Ozefridge condensing units set to operate as air cooled only.
One condensing unit was coupled to a 400mm x 400mm aluminium Cyclic cold plate, the other was couple to an Ozefridge mid range eutectic SS plate 400mm x 330mm overall.
During a two month period each system was operated consecutively to maintain the cabinet at between 2C and 4C controlled via the same digital thermostat. The run period for each system was in 7 to 8 day blocks each consecutively. The ambient temperature which ranged from 10C to 42C maximum was similar for both systems.
Power consumption was recorded and resulted in the cyclic aluminium system using approx twice as much power as the eutectic system to do exactly the same job!
Note: A similar test since in even hotter conditions saw the consumption benefit of the eutectic system reduced, but still quite significant. Also operating as a freezer will also see an efficiency advantage with Eutectic but not nearly as extreme as when operating as a refrigerator like in the test. (The trials were done fairly and the test equipment retained at Ozefridge as is, so if anyone wishes they are welcome to inspect, by appointment.)

9: Other aspects of a Eutectic system:
Eutectic plates are usually 318 grade stainless, not soft aluminium or copper therefore much less likely to be damaged / punctured, easy to clean and don’t grow ‘nasties’ than can taint/ contaminate food.
Negatives:
Initial temperature pull down of a eutectic system is slower than a cyclic system. Expect first run of a DC powered eutectic system to be 3 to 4 hrs.
A eutectic plate takes up more cabinet space than a cyclic plate.
A eutectic system obviously costs more than a cyclic system.

Pictures of the testing.
The first picture is of the 150 litre cabinet used in the test with identical air cooled Ozefridge refrigeration units. One unit refrigerates a cyclic aluminium cold plate and the other a mid size Ozefridge Eutectic cold plate.

(see: second picture of cabinet interior)
A monitoring, data logging station was connected to each system. (See third picture)

The final picture is of a spread sheet colour coded to indicate which system was refrigerating the cabinet and the daily watts consumed.
It can be seen that the cyclic system (green) benefited from ‘hold-over’ of the eutectic plate for its first days consumption for each of its run periods.
Yet even with this advantage the eutectic systems consumption was approx 50% less.
It’ a no-brainer if power consumption is a consideration on board!

Click on picture to enlarge:

Aluminium evaporator 410mmWide x 400 High and 15mm off wall. Eutectic Plate of 400mm Wide x 330 high and 15mm off wall.

< Monitor Views: 284 Size: 232.7 KB ID: 168204" style="margin: 2px" /> <Note: each ‘first day’ for the cyclic periods benefited from holdover of the eutectic.

Conclusion:
This trial was conducted correctly and in average conditions.
At Ozefridge we manufacture both Cyclic and Eutectic systems but recommend eutectic in most cases for reasons that must be obvious.
We welcome visitors to inspect our test system.

We always could calculate the power economy that operating a eutectic system with a much higher COP would provide as that is simple indisputable maths, but calculating the loss of efficiency upon compressor start up was not feasible or accurate.
Hence this test which even surprised us.
We expected the eutectic system to use say 30% less power but 40 to 50% was a surprise!
The biggest area of inefficiency is the excessive daily start-ups and when we consider that the test refrigeration units had ‘soft start’ motor driver modules, and therefore more power frugal, how much worse would the cyclic systems consumption be with the old DOL modules!

Cheers OzePete

16-04-2018, 19:47

Eutectic refrigeration for marine use

Thanks Peter for taking the time to test and compare.

Trying to understand why in Tropical conditions, the benefits are less?

Is that because the cold plate system runs longer with not so many startups?

16-04-2018, 20:45

Hi Pelagic,
Yes once the temperature was constantly in the 35C to 45C range the difference in consumption was less. The Cyclic system was using approx 70% more power than the Eutectic while during the test reported the Cyclic system used greater than 100% more power.
We believe the difference was due to two issues and you have mentioned one being that the cyclic system had longer run cycles therefore less inefficient start ups per day. The second issue is that the eutectic plate we used was our mid sized model being 40 x 33 x 6 and should have been the larger 53 x 35 x 6 plate to suit the hotter conditions. The larger eutectic plate would provide slightly better efficiency in both scenarios.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

16-04-2018, 21:52

Re: Eutectic refrigeration for marine use

This is an interesting post and makes me question a descision I just made on my boat.

Our boat is equipped with a "Cold Machine" freezer system (a CU-95 and VD-16). Ever since we have owned her, the CU-95 has been "jumped" for continous operation. The freezer draws 4A all the time and never cycles.

Recently I purchased an electronic control (exactly like the ones in your pictures, STC-8080H). I planned to wire it in and put the system back to cyclic use. However, now I'm wondering if the gains would be worth it.

Right now the freezer is AMAZING. It froze a whole turkey at Christmas, here in the Caribbean. So if wiring in the controller only gains me 10-12Ah over the night, it might not be worth it.

Sorry if this derails the topic.. but maybe you are on to something with the whole cyclic thing.

16-04-2018, 22:11

OzePete

Marine Service Provider

Hi Traveller,
What you have is not a eutectic system nor a cold plate cyclic system, it is a forced air- cross finned evaporator!!
What are the interior dimensions of your cabinet?
OzePete

Pete,
Fantastic post!!!!

A couple of questions:
1) I assume that both systems use Expansion Valves?
2) Have you done the same tests for freezer temps (-20c box temp / -23c evap temp)?

What you have is not a eutectic system nor a cold plate cyclic system, it is a forced air- cross finned evaporator!!
What are the interior dimensions of your cabinet?
OzePete

Yes I have done some reading on our system. It always surprises guests when they open our freezer and see the inside. Most have never seen anything like it.

Like I said it works fantastic. If you put 10 beer in front of the fan they will be drinkable cold in about 8-10 min. However, I wonder how much power I'm wasting because it runs all the time. It was the PO that jumped it to run %100 when the thermostat failed in Cuba and they couldn't get a replacement.

The cabinet is 14(wide) X 24(long) X 23(deep) (all inches). I don't know the R value of the insulation, but the walls are 2.5 inches thick.

Re: Eutectic refrigeration for marine use

I've only just started reading this article, but it looks really good. It would have been very interesting to see a internal temperature graph comparison between the two systems over the 30 days.

Join Date: Sep 2011

Re: Eutectic refrigeration for marine use

It seem you do make a good product, so much so, I want to order one. The problem is your claim against reality of operation and power out comes it seems are too conservative when it comes to boat installations.

Two life long friends who are sail boat owners have installed your system in the Sydney and Pittwater area. They both complained, Unlike your static test, they discovered in real life boat operation your systems are very taxing on available power required to keep them running so they can't use them as required.

One mate has now bought a small 12 volt freezer instead of using the ozeFrig he installed to remedy the problem, his plan is only to use your fridge when he is motoring long distances. The other life friend tells me it takes 80 Ah 24 hours to keep his system running. That is 6.6 Ah per hour.

This is very different to your static test of 12 amp in 24 hours. it seems that the fridge in the photo you presented also had poor instillation as well?

For my part I have a 135 liter eutectic fridge that was run by engine AC compressor. It failed - My plan was to install your system and do away with the engine driven compressor. Now I use the fridge as a storge box for general food dry goods storage. and run a Evakool 45 liter portable fridge freezer instead also only 14 hours a day as it is well insulated fiberglass ice box construction.

I wish it was so, but there is no getting around the law of physics. when you want a cooled beer in the tropics.

Cheers OzePete

Re: Eutectic refrigeration for marine use

The other life friend tells me it takes 80 Ah 24 hours to keep his system running. That is 6.6 Ah per hour.
80Ah a day is 3.3A an hour not 6.6A.

I don't know if your life long friends are using the units as fridges or freezers. But if they are freezers and with standard production boat insulation, 80Ah per day is pretty damn good.

Still not the "...static test of 12 amp in 24 hours", but still well above most.

#11

Re: Eutectic refrigeration for marine use

Haven't eutectic systems been around for awhile? They are common on refrigerated trucks. We have a two truck-plate system in our '82 boat that have two different eutectic freezing point salt solutons, one for refrigeration and one for freezer. The compressors are common supermarket types. We run them for 30-40 minutes once or twice a day. A bag of ice lasts for 1 1/2 weeks. Though they are 120VAC, there's no reason why 12VDC motors couldn't run the compressors.

Other than new electronics, why would I expect to have an improvement with your system?

17-04-2018, 04:31

#12

Re: Eutectic refrigeration for marine use

I could not see any food in the box in the picture!
You MUST have had something in the box to simulate a "standard" food load, otherwise the compressor cycling frequency of the less efficient system would be much higher than normal operation.
I can describe two ways the eutectic system improves efficiency.
1. when a compresssor starts, it does no cooling at first, as it begins to change the pressures in the refrigerant circuit. As time passes, on the order of second or even several minutes, the cooling increases to its full capacity.
During this start-up period, the power used may be lower, but less cooling is done so the efficiency (COP) is very low. By reducing the number of starts per day, a significant power reduction results. This is why refrigerator testing is done with a water load inside the cabinet. Changing the thermostat to a wider dead band can save power by reducing cycling.

What the eutectic system ALSO does is decrease the lift, the pressure difference between the evaporator and the condenser. with the aircooled evaporator, the air right next to the plate is MUCH colder than the eutectic fluid, resulting in a lower refrigerant evaporator pressure. The compressor runs longer to move the same amount of heat.
So I ask again, was there food or water on the box during testing?

17-04-2018, 07:55

#13

Join Date: Nov 2014

Re: Eutectic refrigeration for marine use

Hi All,
I tend to agree there would be an external heat load but without the product load the cold plate unit would seem likely to start/stop more frequently. No "thermal inertia".
I think the stainless case of the eutectic plate is a poor conductor of heat and slows the whole process. Why not aluminium?

The Engine driven compressor (open drive) eutectic was as far as I know introduced to take advantage of the fast "pull down" of the large compressor driven by the engine. In that system it is only necessary to run the compressor once or twice a day for a short time maybe as little as 10 minutes. (In those days there was no 12V compressors, no investors and only car aircon compressors. But they are expensive to build and maintain and regular checking and maintenance is important. I have an open drive eutectic system and if I were to replace it I would go for a cold plate 12V system simply because it will give me the fastest pull down. For day cruising (out for the day) with the family that's all you need. But I love the fast pull down of the current system.

I don't want to be waiting around while a 50W compressor tries to freeze 2L of water. (Before it does anything else). My guess it would take 2 1/4 hrs to get that eutectic plate from 15C to 0C then how long to freeze?

I think that a eutectic 12 V system of less than 100W refrigeration capacity impractical. Unless you can load it with precooled or even refrozen product.
It's a lot of work to go out and prove, in a Lab, any of this.

These days with the improvements in solar power the 12v system is much more user friendly.

I appreciate the effort that has gone into the article. Thankyou.

#14

Re: Eutectic refrigeration for marine use

Quote:

Originally Posted by missourisailor

80Ah a day is 3.3A an hour not 6.6A.

I don't know if your life long friends are using the units as fridges or freezers. But if they are freezers and with standard production boat insulation, 80Ah per day is pretty damn good.

Still not the "...static test of 12 amp in 24 hours", but still well above most.

Thanks, I stand corrected,at 3.3 Ah. I'm not so good on night watch!

Never the less, I agree that 80 Ah is a good outcome but than one needs to replace that power which has repercussions. Say if you have a house AGM battery bank like myself of 500 Ah. You will need to recover the used 80 Ah, this it is a significant issue, as battery manufacture recommend that one can't discharged more then say 60% max for say AGM in effect AGM battery's should not be discharged more the 30% if you want to keep the battery manufactures claimed 10 year life and not shorten it to say 3 to 4 years through recycling.

That cold beer you enjoy, is paid for by a power recovery of replacing nearly 1/3rd of your usable battery per day that is not using any other boating equipment to run your boat like nav lights autopilot radar boats computers. This is only if your battery are are relatively new. As most battery can only be recharged up to 85 - 90% capacity. Meaning your battery bank of 500 Ah is really has 450 Ah's at 90% fully topped up. Discharge max should only be say 40% max so in this case what is available is a 180 Ah. - 80Ah for the eutectic 12 volt fridge. You have only 100Ah to run your boat experience shows, that in reality your battery bank has far less available power, depending on your battery age and condition and user abuse.

Your beer is going to cost you big time, in some form of energy generation to replace that fridge power each day through recharging. This is the main issue for most sailors who use their boats more then say weekend or day sailing.

17-04-2018, 13:48

#15

Re: Eutectic refrigeration for marine use

Quote:

Originally Posted by

Hi
Just to clarify, you use a "salt solution" in your eutectic system?

#16

Quote:

Originally Posted by

Hi again
I am not very familiar with your fridge unit except to say that 4.0 A/h is excessive for such a small cabinet.
The suggested Elitech STC 8080 digital controllers are very good but their STC600 model is far better being waterproof.

Your idea is excellent but suggest you place the controller's sensor into the evaporator fins in the last area of the evaporator that thaws. Set the Cut-in to an above freezing temperature and only alter the cut out to suit your temperature requirement. With the controller keeping the unit off until the evaporator fins have all thawed (defrosting on every off cycle) before cutting in again for another cycle, the evaporator coil should remain mostly frost free giving you far better economy.
Good luck with that.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

#17

Re: Eutectic refrigeration for marine use

I have both a cold plate twin drawer Fridge/Freezer for ergonomic convenience and 2 top load eutectic systems for long term cruising provisions (seperate fridge and freezer)

When living onboard all are running... but if ashore, the drawer unit is only used for drinks / lunch and the ocasional breakfast.

Our eutectic system uses antifreeze for phase change (different concentration for fridge and freezer) and is noticeably far more energy efficient and able to reach proper freezing temp, than the drawer cold plate unit (Isotherm)
I think as other suggested, for a day or weekend out or to keep the beer cold, a cold plate system is convenient and fast.

But the eutectic system is what you need for long term use, (especially freezing)

17-04-2018, 14:21

#18

Pete,
Fantastic post!!!!

A couple of questions:
1) I assume that both systems use Expansion Valves? Absolutely not!
2) Have you done the same tests for freezer temps (-20c box temp / -23c evap temp)?

Not yet, each trial takes more than two months and our test room has been busy trialling a new product, but will do when we can.
Also intend to do trials in varying ambient temperatures, with air and watercooled systems, soft star and DOL systems and condenser temp controlled systems.

04-2018, 14:33

#19

OzePete

Marine Service Provider

Quote:

Originally Posted by

I've only just started reading this article, but it looks really good. It would have been very interesting to see a internal temperature graph comparison between the two systems over the 30 days.

thanks, Point taken and future trials we will also use data loggers on the cabinets interior although during this trial each unit was controlled by the same digital cabinet thermostat. It was set to cut in at 4.0C and off at 2.0C At no time was the cabinet temperature outside this range regardless of which system was employed.
We noted that while the cyclic system cycled through out the day, the eutectic system cycled once most days and twice on others, never more. (See chart) This means that the cabinet temperature did not go below or above the set points for that day or half day period. The eutectic phase change was maintaining those cabinet temperatures for up to a day without the unit running!

Cheers, OzePete Ozefridge | 12 Volt Refrigeration Systems

#20

Quote:

Originally Posted by kryga good product, so much so, I want to order one. The problem is your claim against reality of operation and power out comes it seems are too conservative when it comes to boat installations. Please indicate anywhere in the trial process reported that you would dispute

Two life long friends who are sail boat owners have installed your system in the Sydney and Pittwater area. They both complained, Unlike your static test, they discovered in real life boat operation your systems are very taxing on available power required to keep them running so they can't use them as required. This is a very vague statement. How about some actual data like cabinet size, insulation, quality etc etc. AlsoI question why your 'friends' haven't contacted us if they have concerns. We promote service 24 7 and are well known for our endeavours to sort out issues even if they are not our system related!

One mate has now bought a small 12 volt freezer instead of using the ozeFrig he installed to remedy the problem, his plan is only to use your fridge when he is motoring long distances. The other life friend tells me it takes 80 Ah 24 hours to keep his system running. That is 6.6 Ah per hour.
Again, where are the facts regards your 'friends' claims, besides those facts you supplied don't even equate, yet 80A/h could be quite reasonable if its a large freezer and specially if the insulation is wet!

This is very different to your static test of 12 amp in 24 hours. Sir, being nearby you are more than welcome to come check the test equipment used and if you can prove the data quoted as being wrong, I will supply you a system free of charge, but if you can't you pay double.. deal? it seems that the fridge in the photo you presented also had poor instillation as well? It was originally a new domestic freezer and yes the wall thickness was only 70mm but its insulation quality is quite good and likely to match most 100mm thickness marine cabinets, so fairly representative

For my part I have a 135 liter eutectic fridge that was run by engine AC compressor. It failed - My plan was to install your system and do away with the engine driven compressor. Now I use the fridge as a storge box for general food dry goods storage. and run a Evakool 45 liter portable fridge freezer instead also only 14 hours a day as it is well insulated fibeglass ice box construction.

I wish it was so, but there is no getting around the law of physics. when you want a cooled beer in the tropics.

#21

OzePete

Quote:

Originally Posted by

Yes Missouri, you are so right, Without knowing the full story such figures are meaningless and opinions mean zilch! This was why we went to the trouble of conducting an actual trial with data recording so that a meaningful comparison could be made.
I don't know what we would have to do to make the test fairer.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

17-04-2018, 15:29

#22

OzePete

Marine Service Provider

Quote:

Originally Posted by Haven't eutectic systems been around for awhile? They are common on refrigerated trucks. We have a two truck-plate system in our '82 boat that have two different eutectic freezing point salt solutons, one for refrigerationand one for freezer. The compressors are common supermarket types. We run them for 30-40 minutes once or twice a day. A bag of ice lasts for 1 1/2 weeks. Though they are 120VAC, there's no reason why 12VDC motors couldn't run the compressors.

Other than new electronics, why would I expect to have an improvement with your system?

Yes eutectic refrigeration has been around since before Australian James Harrison first patented the vapour compression refrigerator in1855. A block of ice in an insulated box could arguably be called a eutectic fridge!
As you say eutectic refrigeration in the perishable goods transport industry is growing rapidly. Many years ago we engineered eutectic modules for a European supermarket chain. The module would be frozen overnight then slipped into an insulated container to maintain temperature during transport, hence no refrigeration equipment required while mobile.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

17-04-2018, 15:53

#23

Quote:

Originally Posted by could not see any food in the box in the picture!
You MUST have had something in the box to simulate a "standard" food load, otherwise the compressor cycling frequency of the less efficient system would be much higher than normal operation.Hi Red, I have been around this industry for for a long time and fridges are always tested empty.
I can describe two ways the eutectic system improves efficiency.
1. when a compresssor starts, it does no cooling at first, as it begins to change the pressures in the refrigerant circuit. As time passes, on the order of second or even several minutes, the cooling increases to its full capacity.
During this start-up period, the power used may be lower, but less cooling is done so the efficiency (COP) is very low. Isn't that what the report indicates!! By reducing the number of starts per day, a significant power reduction results.Isn't that what the report indicates!!: This is why refrigerator testing is done with a water load inside the cabinet. No they are usually tested empty although temperature sensing is best with the thermostat bulb in a container of water within the centre of the cabinet Changing the thermostat to a wider dead band can save power by reducing cycling.But then the cabinet would not be maintaining recommended temperatures. +4C to +2C is the commonly recognised fridge temperature.

What the eutectic system ALSO does is decrease the lift, the pressure difference between the evaporator and the condenser. What? A eutectic system runs a HIGHER evaporator pressure / temperature than a cyclic plate hence the better COP factor!)with the aircooled evaporator, the air right next to the plate is MUCH colder than the eutectic fluid, resulting in a lower refrigerant evaporator pressure. The compressor runs longer to move the same amount of heat. Exactly, as quoted in my test report! The lower the evaporator temperature, as with a cyclic system, the lower the COP and therefore the longer the compressor runs and the less efficiently it refrigerates
So I ask again, was there food or water on the box during testing? We ate the food and drank the beer!

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

17-04-2018, 16:24

#24

Quote:

Originally Posted by

Hi All,
Hi, agree there would be an external heat load but without the product load the cold plate unit would seem likely to start/stop more frequently. No "thermal inertia".I agree that is correct. The more product stored the longer each run cycle and therefore greater efficiency due to less start ups per day.
I think the stainless case of the eutectic plate is a poor conductor of heat and slows the whole process. Why not aluminium?The use of stainless is common although as you say a poor conductor but this is engineered into the required rate of heat absorption. Aluminium and copper are better heat conductors but very soft and vulnerable to puncturing

The Engine driven compressor (open drive) eutectic was as far as I know introduced to take advantage of the fast "pull down" of the large compressor driven by the engine. In that system it is only necessary to run the compressor once or twice a day for a short time maybe as little as 10 minutes. (In those days there was no 12V compressors, no investors and only car aircon compressors. But they are expensive to build and maintain and regular checking and maintenance is important. I have an open drive eutectic system and if I were to replace it I would go for a cold plate 12V system simply because it will give me the fastest pull down. For day cruising (out for the day) with the family that's all you need. But I love the fast pull down of the current system.

I don't want to be waiting around while a 50W compressor tries to freeze 2L of water. (Before it does anything else). My guess it would take 2 1/4 hrs to get that eutectic plate from 15C to 0C then how long to freeze?Your figures may be right for some of the micro 12VDC eutectic systems, but certainly not the Ozefridge Eutectic. The Ozefridge model AW480 system will typically remove heat at the rate of 271 watts per hour on the start of a cycle through to 172 when near shut down. A refreeze cycle is usually between one and two hour

I think that a eutectic 12 V system of less than 100W refrigeration capacity impractical. Exactly, While the 2cc BD35 powered systems may suit the shoe box sized fridge, the more refrigeration that can be applied in a given time the better. Specially if relying on 'abundant' power when available, to re freeze the eutectic. Unless you can load it with precooled or even refrozen product.
It's a lot of work to go out and prove, in a Lab, any of this.

These days with the improvements in solar power the 12v system is much more user friendly.

I appreciate the effort that has gone into the article. Thankyou.
And thank you Woody, this trialling and reporting process is a work in progress and we appreciate logical input

Cheers

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

17-04-2018, 21:36

#25

Originally Posted by OzePete

Not yet, each trial takes more than two months and our test room has been busy trialling a new product, but will do when we can.
Also intend to do trials in varying ambient temperatures, with air and water cooled systems, soft star and DOL systems and condenser temp controlled systems.

Cheers, OzePete

In the "QUOTED" Quote, you said that both systems DID NOT have expansion valves.
I'm assuming that you meant that the thin tube used a capillary system while the holding plate used an expansion valve.

I have asked the very same question many, many times before.
It is the general consciences that if BOTH systems used Expansion valves, the differences between the two would shrink. To the point of both being almost equal.

I was just seeing if your testing was proving or disproving this.

17-04-2018, 22:06

#26

Re: Eutectic refrigeration for marine use

Quote:

Originally Posted by In the "QUOTED" Quote, you said that both systems DID NOT have expansion valves.
I'm assuming that you meant that the thin tube used a capillary system while the holding plate used an expansion valve.
BOTH the cyclic plate and the eutectic plate use a capillary tube NOT TX valve. A capillary system with controlled condensing temperature is a far more reliable system than one with a TX valve. That is provided the system uses a true Filter / Dryer like a 032 or 052 with felt FILTER and not just a spun copper 'pencil' strainer dryer that has NO filter felt at all. !

I have asked the very same question many, many times before.
It is the general consciences that if BOTH systems used Expansion valves, the differences between the two would shrink. Given that more than 99% of the 100 x millions of refrigerators, freezers, air-cons etc. that exist in the world are capillary, surely if using a TEV was so advantages, competition for economy bragging rites would have seen TEV fridges flood the market place. Hasn't happened! To the point of both being almost equal. Absolutely not. Both of the condensing units used in this test have controlled condenser temperature therefore the system performs similarly in any environment. The TX valve is simply a throttling device as is the capillary tube. With controlled condensing the capillary system will out perform the TX system without condenser temperature control as both types are subject to over / under condensing. Please read again the reasons quoted as to why the cyclic system used vastly more power, these factors have nothing to do with being either capillary or TEV throttled.

I was just seeing if your testing was proving or disproving this.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

18-04-2018, 00:12

#27

Registered User

...."that more than 99% of the 100 x millions of refrigerators, freezers, air-cons etc. that exist in the world are capillary, surely if using a TEV was so advantages, competition for economy bragging rites would have seen TEV fridges flood the market place. Hasn't happened!"

I don't know where you are getting the 99% number.
All of the fridges/freezers in my house, the homes A/C unit's, all of my cars/trucks, both the boat's AC and fridge/freezer all use expansion valves.
I will even go on to say that all of my neighbors' same equipment, use expansions valves.

I'm not going to get into a debate about which system is better then the other. Too many test (cap vs TXV) have already been done and the results are out there for the taking.

But what I am going to disagree with is your statement that TXV's are rarely used. Cap's are so prolific because they are "cheap to make". And that is what drives the markets.
Not what is more efficient.
And yes, that includes marine refrigeration.

18-04-2018, 02:20

#28

Marine Service Provider

Capillary tube refrigerant flow control is ideal in most refrigeration units. It is true that mobile refrigeration that is exposed to wide climate temperature changes are less efficient when temperature varies more that plus or minus fifteen degrees from standard day design temperatures. Correct Btu capacity TXVs are most always used with holding plates.

#29

8-04-2018, 11:04

#30

OzePete

Marine Service Provider

Originally Posted by

Pete,
There is something that is bothering me about your graph.
I understand that you did 6 test runs, approx. 10 days each.
And that you alternated the equipment.

What I don't understand is why, with each subsequent test run, on both systems, the average consumed Watts kept rising.
Because this trial was done in a non controlled area. Meaning there was no artificial cooling or heating, just whatever mother nature provided. That is why each system type was employed for approx 10 day periods in sequence so that the trial was fair. We did it this way so that each was subject to a natural environment and as the trials were done in our spring leading into summer, the ambient was generally rising day by day That is why the daily wattage varied as the ambient changed. Normal expectation.

I would think that the results should be some what constant and repeatable. They would be constant if the climate (ambient temperature) was constant but of course it isn't is it!

This would tell me that some "control standard" is changing (i.e. room temp, cond temp...etc).As above

Can you enlighten me on why the average consumed watts is rising? Again, as above!

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

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