Refrigeration - Evaporator vs. Holding Plate

[RaymondR]

Originally Posted by Richard Kollmann

I do not know what RaymondR motivation is in building his own system. Thehnautics Cold Blue system is a conventional designed with excellent air cooled performance and eutectic true energy plates, Yes they could build a plate to fit Ray's box but not for the price he will spend on building his own. Many boats require custom built refrigeration.

Conventional refrigeration is what you want unless boat is located close to its manufacturer. Refrigeration techs are not inclined to solve problems on unconventional refrigeration.

I just like learning about and building and repairing things Richard. Probably because I was born into and raised in a society with a very strong pioneering ethos where men were expected to be self sufficient and exhibit a broad range of skills.

In addition I have found that a lot of fridge techs, whilst possibly being skilled at servicing domestic and industrial refrigeration appliances, tend to be less than expert when it comes to the small DC systems we use on boats and consequently my interest is partially necessitated by need in addition to the inclination.

The rebuild I'm undertaking at the moment is on a boat I purchased from a friend who is a refrigeration and aircon professional. When he bought the boat it had an evaporator plate system with the plates installed so that very little refrigerant was retained by the plates and his own subsequent contribution was replacing the thermostat with a generic one which was without the motor speed resister the OEM provided unit came with. Consequent to these factors and the installation being in an enclosure originally built as a very large ice box (I'm 6'7" and about 250 pounds and was able to climb into it and move around to take measurements) the condensing unit ran 50 minutes an hour and pretty well kept the batteries flat all the time.

The rebuild of the box is going very slowly but I figure that by the time I get to the refrigeration component installation part I'll have learned enough about it to get by with it.

[Pelagic]

Originally Posted by RaymondR

Nigel Calder appears to put the temperature point at which the unfrozen slush phenomena dominates in at a fairly low temperature point but does not really address low concentrations of glycol.

I have two Oziefriidge AA480 units to separately maintain Fridge and Freezer.

Wonderful equipment but one design weakness is providing the ability to "dial in" the Eutectic Solution for the all important Phase Change.

Ozefridge recommends a specific brand (TECTALOY) to be used or mixed in two types (Tectaloy+90 and +60) to achieve the desired Phase Change temp
(Freezer -18c° Fridge -5c°)


The problem is that brand is not available in the Philippines, mostly concentrates, so with Oziefridge's help, we calculated a water/concentrate mix from available brand to test.

Found it too strong for phase change at recommended set temperatures, added more water till I saw a bit of freezing at the filler cap and hoped it was freezing all the way down.

Since their is no drain plug at bottom of eutectic plates, I have no ability to drain and try again, so I wish they had just shipped with the correct eutectic solution or put in drain plugs

Maybe, I'm being too fussy, but not knowing if the mix is correct, bugs me

[Networker]

Originally Posted by Exile

Just a layman here interested in hard ice cream and cold beer, and admittedly often cannot follow the more technical posts over the engineering intricacies of modern marine refrigeration. But isn't what you're describing above a product which has long been offered by Technautics/CoolBlue? Or are your comments referencing a system with evaporative plates? If Ray's interest is instead a eutectic/holdover system, then why reinvent the wheel?

Apologies if I lost the flow of the discussion here.

I got lost too. There’s way too much insider talk about the technical details of different refrigerator systems that were confusing to me the layman who just wants some cold food at a good price and energy consumption.

I ended up getting a giant evaporator unit, wrapping it around my freezer, building a spillover system, and the freezer side is 12F (at the bottom), refrigerator is able to cool to my specs between 34-38F at the mid-height of the fridge, and I’m going to have cold food once I cross the Pacific. I use about 5a/hour over a 24 hour period in Miami in summer.

I’m all ears if someone tells me this is too high of an energy consumption, and to get lower, I should go to a holding plate and if I do so, it will go from 5 amps/hour to 2 or 3, but anything else is confusing when talking about Nigel Calder and slush and this and that.

[Richard Kollmann]

Originally Posted by Networker

I got lost too. There’s way too much insider talk about the technical details of different refrigerator systems that were confusing to me the layman who just wants some cold food at a good price and energy consumption.

I ended up getting a giant evaporator unit, wrapping it around my freezer, building a spillover system, and the freezer side is 12F (at the bottom), refrigerator is able to cool to my specs between 34-38F at the mid-height of the fridge, and I’m going to have cold food once I cross the Pacific. I use about 5a/hour over a 24 hour period in Miami in summer.

I’m all ears if someone tells me this is too high of an energy consumption, and to get lower, I should go to a holding plate and if I do so, it will go from 5 amps/hour to 2 or 3, but anything else is confusing when talking about Nigel Calder and slush and this and that.

Networker It sounds like you have an ideal duel refrigeration/freezer unit that could not be replaced with just one eutectic holding plate system. It is also true ether way standard evaporator or eutectic energy plate the same amount of daily energy is required. The product in your rap around freezer will probably taste better after three weeks.

The big question on ether system yours or a single eutectic plate is what size compressor do you have? And where is the energy coming from to operate your unit? There are agreements in this thread that eutectic plates are more energy efficient by 1/ 3 of an amp per hour because compressor cycles more often with your type evaporator.

[Networker]

Richard, the unit I bought came with a BD50 compressor. I designed the spillover based off the tips and articles on your website.

Energy-wise, I have 1200ah lithium, 1800w of solar and a high output alternator.

[Exile]

Originally Posted by Networker

Richard, the unit I bought came with a BD50 compressor. I designed the spillover based off the tips and articles on your website.

Energy-wise, I have 1200ah lithium, 1800w of solar and a high output alternator.

What sort of shape would you say your box insulation is in? I only ask since mine is original, i.e. old, and likely not any longer helping much. I recently lined the inside with 1/4" foil insulation which helped quite a bit, but still probably not great. This comes to mind in the context of this thread, namely whether a poorly insulated box favors eutectic or evaporator plates, or it doesn't matter. If anyone knows or cares to opine . . . .

[Networker]

Originally Posted by Exile

What sort of shape would you say your box insulation is in? I only ask since mine is original, i.e. old, and likely not any longer helping much. I recently lined the inside with 1/4" foil insulation which helped quite a bit, but still probably not great. This comes to mind in the context of this thread, namely whether a poorly insulated box favors eutectic or evaporator plates, or it doesn't matter. If anyone knows or cares to opine . . . .

Visually it looked good, but it was a 20 year old boat, so I was curious how the insulation inside was holding up. I had a FLIR camera for my smartphone to check the leakage and temperature changes.

First I replaced the rubber seal around the doors, which made a difference on the refrigerator side (see before and after). Before that seal, moisture was collecting on the top of the doors, but now seems to be ok. I thought I read a delta T of greater than 10 will create moisture, and this has an ability to check the delta T, and it was only a few degrees different.

inside the freezer, its 13F, the door is 81F (when the AC is on).

[Exile]

Originally Posted by Networker

Visually it looked good, but it was a 20 year old boat, so I was curious how the insulation inside was holding up. I had a FLIR camera for my smartphone to check the leakage and temperature changes.

First I replaced the rubber seal around the doors, which made a difference on the refrigerator side (see before and after). Before that seal, moisture was collecting on the top of the doors, but now seems to be ok. I thought I read a delta T of greater than 10 will create moisture, and this has an ability to check the delta T, and it was only a few degrees different.

inside the freezer, its 13F, the door is 81F (when the AC is on).

Certainly a useful application of the FLIR! Thanks for posting this.

[OzeLouie]

Originally Posted by Pelagic

I have two Oziefriidge AA480 units to separately maintain Fridge and Freezer.

Wonderful equipment but one design weakness is providing the ability to "dial in" the Eutectic Solution for the all important Phase Change.

Ozefridge recommends a specific brand (TECTALOY) to be used or mixed in two types (Tectaloy+90 and +60) to achieve the desired Phase Change temp
(Freezer -18c° Fridge -5c°)


The problem is that brand is not available in the Philippines, mostly concentrates, so with Oziefridge's help, we calculated a water/concentrate mix from available brand to test.

Found it too strong for phase change at recommended set temperatures, added more water till I saw a bit of freezing at the filler cap and hoped it was freezing all the way down.

Since their is no drain plug at bottom of eutectic plates, I have no ability to drain and try again, so I wish they had just shipped with the correct eutectic solution or put in drain plugs

Maybe, I'm being too fussy, but not knowing if the mix is correct, bugs me

Komusta ka Pelagic...
Yes some courier systems / customs don't allow us to send with eutectic solution. It has to be added upon installation albeit mounting much lighter empty eutectic plates has some advantage.
Decades ago the Tectaloy product was among many we tested and proved to be the most consistent and uses 'nucleated water and metal inhibiters.

To test for phase change range....
1: Off the unit and observe eutectic mass until it mostly thaws. Note temp on digital controller.
2: Switch on system (Manual switch) and observe the temperature reduction rate.
3: The rate will be relatively quick until phase change commences then appear to stall (flat line) for a few hours.
4: After phase change is complete, the temperature should again lower more rapidly.
5: The period / temperature range noted as described in 3 above, is your phase change area. Expect this to be over a range of 2-3C for fridge and 3-5C for freezer solutions.

If phase change occurs at a temp too low or not at all (remains a liquid) then replace say 15% of the mix with water, conversely if the phase change occurs too early (remains frozen) then replace say 10% of the mix with pure glycol. May have to repeat to get the best results.

I hope this helps... Louie

[OzeLouie]

Originally Posted by Richard Kollmann

What happens in a eutectic plate when warm is it only takes one Btu per pond to lower the liquid solution one degree in temperature. Once solution reaches its adjusted freeze point Popsicle texture ice begins forming on the evaporator coil inside plate. This coil frost continues to expand and the thicker it becomes it acts as an insulator of a heat, unless coming in contact without better heat conductor like plates surface metal or metal frame or cooling fins. The slush first begins at the bottom of plate although when liquid solution in plate is below the freezing point of water plate's exterior surface will develop frost nearest to refrigerant evaporator coil. True eutectic plates require structurally sound plates and with a small energy sours compressor the energy transference inside plate requires a special design application. Of the large number of plates I manufactured only a few were efficient enough for 12 volt compressors and those that were had evaporator coils spot welded to exterior plate's surface.

Richard, surely this is a misquote!! Evaporator coils should NEVER be spot welded to the plate's surface. Hopefully you meant soft soldered to or better still, adhered to with non acetic silastic.
If using 50/50 soft solder (with Ezeweld 801 flux) to solder copper evap tubing to stainless steel case, the soldering should only be on the apex of the 180 degree bends, not on straight runs, and best applied using a tiny /soft flame.
BTW it is essential to study and comprehend the difference between 'specific heat (or sensible) and 'latent heat!
Sorry, but without that basic knowledge it is near impossible to understand eutectic refrigeration.

[Richard Kollmann]

Louie there are ways to trance fer heat energy contact of dissimilar metals by spot welding, think about it. Why don't you post a picture of the inside of your plate before you bolt the leak resistant cover on it? The efficiency of a good eutectic plate depends on creating latent heat in ice while using sensible heat at the same time to efficiently lower box temperature.

What plate would a boater rather have when using a small 12 volt compressor one that on start up for the day cools box while freezing eutectic energy ice or one that takes several hours to freeze eutectic solution and slowly cool box?

[newhaul]

Originally Posted by Richard Kollmann

Louie there are ways to trance fer heat energy contact of dissimilar metals by spot welding, think about it. Why don't you post a picture of the inside of your plate before you bolt the leak resistant cover on it? The efficiency of a good eutectic plate depends on creating latent heat in ice while using sensible heat at the same time to efficiently lower box temperature.

What plate would a boater rather have when using a small 12 volt compressor one that on start up for the day cools box while freezing eutectic energy ice or one that takes several hours to freeze eutectic solution and slowly cool box?

Are you sure you actually understand the finer points of using eutectic plate systems vs evaporator systems? Once the system is running and the box and plate are initially pulled down and frozen your attempt at deflection is at best showing your lack of knowledge and at worst out and out intentionally incorrect . I'm not sure which.

[RaymondR]

Originally Posted by Networker

Energy-wise, I have 1200ah lithium, 1800w of solar and a high output alternator.

With that much electrical power generation and storage you should not have to worry about power saving overnight.

The primary reason for using the eutectic systems is to limit the wear and tear on the house batteries and minimize the refrigeration cost by consuming the electricity required to power the refrigerator at the time it is being generated by the solar panels.

[Richard Kollmann]

Originally Posted by newhaul

Are you sure you actually understand the finer points of using eutectic plate systems vs evaporator systems? Once the system is running and the box and plate are initially pulled down and frozen your attempt at deflection is at best showing your lack of knowledge and at worst out and out intentionally incorrect . I'm not sure which.

Yes I am sure having spent thirty years in the eutectic plate business and many systems sold used my methods to record their systems performance a few were in my 12/24 volt book. You are correct eutectic plates on a live aboard boat do not have to be completely frozen every morning. A point to remember is the plates mentioned on this thread are not true eutectic solutions so if your are looking to maintain a narrow box temperature the plate must be cycled several times. Temperature drift is not always a problem on beer coolers though.

You should know by now that it is important to question any and all posts here by searching the web for answers to engineering and supporting info. I enjoy being questioned as long as it is maturely presented with no agenda, I will do my best to reply honestly. I look to boaters like you to be the arbitrator when you see opposing what are claimed to be facts.

[RaymondR]

I'm fairly certain Ozylou's employer Ozyfridge would have tested the eutectic solutions they use to see whether the concentrations they specify have any significant freeze temperature range problems, they seem to be fairly thorough sort of people with an inclination to support their theoretical musings with empirical methods.

They also appear to be fairly innovative with the way they designed their dual water/air cooled condensers and their method of avoiding over-condensing and controlling the balance of refrigerent volume between condenser and evaporator whilst using the simple capillary tube flow control device and minimizing cooling fan power consumption.