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Old 22-04-2011, 08:43   #46
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Re: Fill unused space in freezer?

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Originally Posted by Richard Kollmann View Post
Putting added liquids in freezer to freeze will waste a great deal of energy so fill the empty space with moisture free insulating material.
As others have mentioned, it will take some energy to freeze extra water in the freezer in the first place, but after it's frozen, not, so it is certainly not true that this will "waste a great deal of energy".

I also have a huge separate freezer on my boat which is rarely more than 1/8 full. I don't worry about it -- I just leave it empty. It works fine and doesn't seem to use much power (it's an Isotherm SP job). Putting something to fill up the empty space might reduce convection -- on a front-loader, especially with leaky seals, this could have a noticeable effect. But on a top loader like mine, I wouldn't think it would make much difference.

Having a frozen thermal mass like water jugs in your freezer might reduce cycling of the compressor since the frozen water would store quite a bit of "cold" which would be given back to the food while the compressor is off.

One other reason to fill up empty space in a freezer or fridge (whether with water or with peanuts) might be to reduce the amount of air which is lost when you open the thing and has to be cooled off again. But air has hardly any thermal mass at all and so takes hardly any energy at all to cool down, in the volumes we have in our fridges/freezers.

Therefore -- I simply don't worry about it. Enough other things on board to worry about without this. My refrigeration works excellently as it is.

I was surprised and pleased to find last week that it even works efficiently when the boat is on the hard. The manual says you can use the system with the boat out of the water as long as you keep the through hull open so that air can circulate over the condensor coils (normally cooled by sea water). The boat was on the hard for about 18 hours getting antifouled, and when we launched, the fridge and freezer were still ice cold.
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Old 22-04-2011, 08:57   #47
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Re: Filling Unused Space in Freezer

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Originally Posted by doug86 View Post
"extra heat from frozen water" .... funniest thing I've read all year.
Technically speaking, he's right about it having extra (more) heat. Any mass that is above absolute zero has extra heat. It's the same concept as using a heat pump when it's freezing outside to extract heat, compress it, and release it into another space (home).

Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means.
A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state. The kinetic energy of the ground state cannot be removed. However, in the classical interpretation it is zero and the thermal energy of matter vanishes.
Absolute zero is the null point of any thermodynamic temperature scale. By international agreement, it is defined as 0K on the Kelvin scale and as −273.15C on the Celsius scale.[1][2] This equates to −459.67F on the Fahrenheit scale.[2] Scientists have achieved temperatures very close to absolute zero, where matter exhibits quantum effects such as superconductivity and superfluidity.
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Old 22-04-2011, 09:17   #48
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Re: Filling Unused Space in Freezer

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Originally Posted by svcambria View Post
Better than an empty box, certainly. But better than a box that is fractionally full - say 3/4 full?

Michael
Up to 85 % full, the more full the better, "once it is chilled down". When you open the lid, there is far less air to spill out as well. Another consideration is that if you crowd the cold plate, the temp in the box will be inconsistent, (Colder near the plate).
For this reason I put beers next to the plate, (just short of freezing), and this allows a little air space next to the plate, to help chill the rest of the box. We put the things needing the least refrigeration on the far side.

I had long conversations on the phone with a couple of experts in the field, before starting our all summer refrigeration project. The thickness of foam, (or it's equivalent in Vacuum panel), is not a linear curve. Up to 5" of foam you get big increases in insulation for each inch. We went with the equivalent of 7" except in the lid, which was less important, and therefore, only 5".

Any more insulation than this, and the rate of gain is relatively minor per inch of insulation, compared to the first 5".

NOW... regarding the size of the box, the curve WAS quite linear! Our box, which is 2 cu. ft. in volume, would require about HALF as much cooling (= Ah per day), than if we had made it 4 cu. ft., and the exact same amount of insulation.

So, for high efficiency, make it as small as will serve your needs, insulate to the equivalent of 5" to at best 7" of foam, have a TOTALLY air tight horizontal lid, and forgo having a freezer. It is good to have all foam 100% sealed from the air to keep it dry, and on the outside, a foil IR barrier helps too. Also... putting it in the settee floor was cooler than in the counter top, and we find it easier than clearing the counter to open the lid. (Feet are easy to lift, if the cook tells you to, and you want to get fed!)

These are the things that can get your daily refrigeration Ah consumption to 30 Ah or so, (give or take 10 Ah), depending on weather it's in the tropics in summer, or NC in the fall.

Mark
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Old 22-04-2011, 09:32   #49
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Re: Filling Unused Space in Freezer

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Originally Posted by LakeSuperior View Post
How did you measure the difference in energy and what was difference?
I have a Link 10 monitor that measures the Ah going out at night, and Ah going in in daylight from the solar panels, (which supply 100% of our power, 95% of the time).

To test the Ah consumption of ANY device on the boat, I start with a fully charged battery, shut off all three charging sources, (= NO power in), and shut off EVERY electrical device, (even small phantom loads like the clock on the stereo), EXCEPT the one I want to test! This = no power out, except one. In this case, the refrigerator. Of coarse, I have to open it and use it, to be real.

Now... after 24 hours, I know the Ah consumption of that one device, that day. After 15 years of doing that, 12 years while living aboard, all over the place, then you get a good year long average.

Mark
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Old 22-04-2011, 10:26   #50
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Re: Filling Unused Space in Freezer

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Originally Posted by Mark Johnson View Post
I have a Link 10 monitor that measures the Ah going out at night, and Ah going in in daylight from the solar panels, (which supply 100% of our power, 95% of the time).

To test the Ah consumption of ANY device on the boat, I start with a fully charged battery, shut off all three charging sources, (= NO power in), and shut off EVERY electrical device, (even small phantom loads like the clock on the stereo), EXCEPT the one I want to test! This = no power out, except one. In this case, the refrigerator. Of coarse, I have to open it and use it, to be real.

Now... after 24 hours, I know the Ah consumption of that one device, that day. After 15 years of doing that, 12 years while living aboard, all over the place, then you get a good year long average.

Mark
And what was the power difference you measured for a full freezer versus partially filled freezer?
By the way, neglecting edge effects, the cooling requirements will scale linearly with the internal wall area of the freezer not the volume all other effects being equal. Therefore, a 1.26 x 1.26 x 1.26 = 2 cubic foot freezer, wall area of 7.6 square feet does not use half as much as a 1.6 x 1.6 x 1.6 = 4 cubic foot freezer, area = 9.6 square feet.
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Old 22-04-2011, 12:30   #51
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Re: Filling Unused Space in Freezer

Air in the form of EMPTY SEALED plastic milk jugs...
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Old 22-04-2011, 14:00   #52
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Re: Filling Unused Space in Freezer

WOW! I never thought my inquiry would generate this much response. Refrigeration, or freezers in this case, seem to be an item of importance.

I have decided that I will remove the cold plates from my freezer, cut the liner out so that part of it can be reused and add more insulation. Then I will then reuse part of the liner to reline the box and reinstall the holding plates. Small size freezer and better insulation should decrease my energy needs.

Failing that (running out of time, due to too many projects, before we want to leave) I will fill part of the freezer with foam blocks.

Thanks to all who have responded.
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