Refrigeration - Evaporator vs. Holding Plate

[newhaul]

Originally Posted by john61ct

Sheer ignorance, 8-)

seawater was a step up from H2O



links to howto, retail supply sources in the US would be appreciated.

I want specific sized tubing to optimize the fit in the target coolboxen.

I suppose if the blue cubes are cheap enough in bulk, could just cut them up and transfer their solution.

john just need rv antifreeze ( food grade)
https://www.google.com/url?sa=t&sour...Tp5egFYCIaTY8x
The specific tube size is up to you to find at your local big box or corner hardware/ plumbing store.
Now I assume this s for an ice box ( tubes to be frozen elsewhere) . I would recommend a 20% antifreeze to water solution . That will give you a -8℃ freeze point. And using food grade means safe if one springs a leak.

Hope this helps you.

[hellosailor]

john-
Sorry, no URLs at hand to give you, but I'm sure every search engine will find dozens of them, and probably YouTube as well. BlueGoo boxes probably will be on sale cheap soon for Memorial Day sales and the start of beach season. Whether they are more effective than a DIY solution I've no idea, but I suspect the BlueGoo is also tailored for the mass market, i.e. to be sure it is fairly safe if it leaks. The polar tubes...PVC is certainly more robust so what you put in it shouldn't be able to leak. I think I'd prefer real copper tubing though, for the heat transfer. Throw some cold galvanize paint over it or a coat of something pretty, will still transfer heat better than heavy wall PVC.

[SV THIRD DAY]

Originally Posted by newhaul

john just need rv antifreeze ( food grade)
https://www.google.com/url?sa=t&sour...Tp5egFYCIaTY8x
The specific tube size is up to you to find at your local big box or corner hardware/ plumbing store.
Now I assume this s for an ice box ( tubes to be frozen elsewhere) . I would recommend a 20% antifreeze to water solution . That will give you a -8℃ freeze point. And using food grade means safe if one springs a leak.

Hope this helps you.

For a Freezer Plate we use 1/3 Glycol and 2/3 Water
For a Refrigerator Plate we use 10% Glycol and 90% Water

Easy as Ice Cream at Anchor in the Tropics.....

[newhaul]

Originally Posted by SV THIRD DAY

For a Freezer Plate we use 1/3 Glycol and 2/3 Water
For a Refrigerator Plate we use 10% Glycol and 90% Water

Easy as Ice Cream at Anchor in the Tropics.....

agreed for a refer or combo refer and freezer
I suggested a 20% due to him using it as ice in a cooler. With that mix it will last longer between freezes. To keep him in cool soda range

[a64pilot]

If your wanting a holding plate to take advantage of the hold over or thermal mass of the thing, then it’s the actual phase change that absorbs a tremendous amount of energy. If your not melting and refreezing daily, then your not using the plates to their max advantage.
Water ice at 32f can absorb a tremendous amount of energy before it melts, and the temp will still be 32f until it’s all melted. Of course it takes a tremendous amount of energy to refreeze it too, yet the temp is still 32 until it’s completely frozen.
So point is you need to tailor the freeze point of the liquid to be right where you want it to be to take advantage of the ability to absorb heat.
If it doesn’t go through a phase change, then you didn’t use it to its max potential.

Most of us, myself included don’t know enough or don’t set our thermostats so that we are taking advantage of a cold plate, most of us have them stay frozen all the time.
I’m looking hard at a stainless lobster, reason is that you can set different temp levels of a fridge based on voltage, when the batteries are being charged, the temp set point can be set lower, then when they are not being charged, the set point is higher, both set points are user adjustable as is the voltage that is considered being charged.
It may be that my compressor may not run at all at night, yet run continuously during the day when the panels are charging.

However I’d not mind some feed back from the manufacturers on if a Stainless Lobster is compatible and if it may somehow harm a system, maybe run it too hard and overheat a compressor or something?

[john61ct]

Thanks for the glycol & golden ratio tips guys!

Originally Posted by hellosailor

I'd prefer real copper tubing though, for the heat transfer. Throw some cold galvanize paint over it or a coat of something pretty, will still transfer heat better than heavy wall PVC.

Actually, besides the enormous cost difference, I'm thinking the minor insulating effect will help keep them in a frozen state a bit longer.

Not being used where food safety is an issue, just keeping drinks & fruit chilled, help fresh veggies last longer, and staging current ingredients from the main box so it only gets opened and rummaged through once a day.

[newhaul]

Originally Posted by john61ct

Thanks for the glycol & golden ratio tips guys!



Actually, besides the enormous cost difference, I'm thinking the minor insulating effect will help keep them in a frozen state a bit longer.

Not being used where food safety is an issue, just keeping drinks & fruit chilled, help fresh veggies last longer, and staging current ingredients from the main box so it only gets opened and rummaged through once a day.

in case you didn't notice fruits and veggies you want to keep cold are food items you don't want to contaminate so use food safe antifreeze ( there is no difference in cost )

[missourisailor]

Originally Posted by a64pilot

If your wanting a holding plate to take advantage of the hold over or thermal mass of the thing, then it’s the actual phase change that absorbs a tremendous amount of energy. If your not melting and refreezing daily, then your not using the plates to their max advantage.

An interesting point that I had not thought of.

Originally Posted by SV THIRD DAY

For a Freezer Plate we use 1/3 Glycol and 2/3 Water
For a Refrigerator Plate we use 10% Glycol and 90% Water

So if we have a box temp of -5F and a holding plate temp of -10F, what ratio of Glycol/water?

[transmitterdan]

Originally Posted by OzePete

Richard, my response following in bold...

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

Pete,

One comment: The correct unit of measure for energy consumed is joules (watt-seconds) or watt-hours not watts or kilowatts. When you label graphs with meaningless units the entire conclusion will be ignored by engineers who know what the units mean.

[john61ct]

Originally Posted by newhaul

in case you didn't notice fruits and veggies you want to keep cold are food items you don't want to contaminate so use food safe antifreeze ( there is no difference in cost )

Sorry just meant wrt temps, not the solution.

[newhaul]

Originally Posted by john61ct

Sorry just meant wrt temps, not the solution.

ok glad to hear that didn't want you getting a Darwin award for this one

[newhaul]

Originally Posted by missourisailor

An interesting point that I had not thought of.




So if we have a box temp of -5F and a holding plate temp of -10F, what ratio of Glycol/water?

for holding plate to freeze at -10℉you would need a solution of approx 35% .

[Richard Kollmann]

There are three things you should know about Glycol used as eutectic solution. When sold as antifreeze it is available in different freeze levels concentrations usually -35 and -50. To be safe I always test a mixed sample in a plastic bottle with thermometer inside before filling a run of plates. Water as a plate solution continues to hold a plate at +32 degrees F until all ice in plate is gone, this is not true when mixed with Glycol solution.
Glycol water mix ice temperature does not remain steady during melting process as temperature slowly rises. True eutectic ice using Brine solutions used in Dole plates are more efficient but only Dole has been able to prevent failures from corrosion.

Glycol can be purchased in food grade and toxic grade meaning to consume three ounces in food can be deadly.
It should also be understood that eutectic solution freeze points below 32 degrees F have short holdover phase change time, this is why even freezer plate solution is generally set to freeze no lower than zero degrees F. The belief that a pound of eutectic solution ice stores more Btu of energy than a pound of water ice is incorrect, because each contain close to 144 Btu of energy per pound of frozen solution.

[missourisailor]

Originally Posted by newhaul

for holding plate to freeze at -10℉you would need a solution of approx 35% .

So just use Rich's "For a Freezer Plate we use 1/3 Glycol and 2/3 Water".

[john61ct]

The tubes are very securely sealed/glued. Plus suspended from the cooler lid above the kept-dry space, pretty sure if one did leak we'd notice.

So Richard, what solution do you think best, assuming the freezer can be held efficiently at well below zero, goal being to get cooling effect as long as possible before swapping.

Starting point being seawater (brine), and no corrosion issue with PVC tubes.