Mike Jay wrote:Hey Chris, just to make sure we're on the same page... The air exchange piping is a huge "U" that wraps around the freezer but doesn't enter the compartment. So the frozen food doesn't have a path to outside air (per the original freezer wofati concept). The cold air sinks into the "U" to freeze the mass around the wofati freezer and that frozen ground keeps the contents (air and food) frozen.
I agree that stratification can be useful or at least worked with. Keep the stuff that needs to stay frozen down on the floor and things that could handle thawing up higher.
Chris Kott wrote:As to air stratification, I thought that was the point. That's why the "exhaust" (where the warmer air goes) is at the top of the freezer. I would even raise that corner of the ceiling to enhance that effect.
Also, if the intake (where the fresh, cold air comes in) isn't at floor level, but at a level just below the exhaust, the cold air would fall, pushing the warmer up and out the exhaust, much like the diagrams of the 45 degree tube from earlier.
This also allows for some selectivity in terms of storage temperature. It would be possible to store that which must remain rock-solid on the ground. Shelves could store things at progressively higher levels, corresponding to perhaps a 20 degree stratification, which might be desireable, depending on what's being stored.
paul wheaton wrote:
Imagine filling it with water. The mission is to allow water in and hold the water. So the lower side will determine the overall water level - the higher side will have less water and will let some non-water (warm air) in.
Kenneth Elwell wrote:In the single tube at 45*, you have warmer air escaping at the top of the section, and colder air entering at the bottom of the section. This seems like it will act as a counter-flow heat exchanger, no? Diluting the "coolth" coming in with the "warmth" going out.
I imagine that after a few weeks of <32F air entering the wofati, that the interior walls would be freezing to a thickness similar to the "frost line" depth in the surrounding soil. How does the umbrella affect this? If the soil around the wofati is dry, will it be in a "warm bubble", and will it be as efficient in turning to "frost" if there's not water in it? (I understand that water is the enemy of the wood in the wofati structure...but if it was permafrost? maybe not so evil?) Would the membrane be better as a "raincoat" close to the wood, rather than an "umbrella" over the whole site? (maybe allowing more frost to occur?)
I don't think you addressed ...
Mike Jay wrote:Long story short, should we put some insulation under the wofati mass as well?
Kenneth Elwell wrote:Your idea of insulating the floor maybe cuts off a resource?
Let's say floor, roof, and walls all have equal surface area... each 1/3 of total, and the floor is insulated. Now the roof is warming up because of the Summer heat, now it is effectively 50% of the area determining the temperature of the room.
There's a man I know in New Hampshire, who just the day before I saw him this one year, had been cutting ice and stocking the local museum's ice house. He was proud of all they had cut and put up, since they had more to do to replace the ice on the floor (ground?), which had been lost over the past year, owing to the previous Winter being too mild to cut much ice, if at all. Ordinarily the ice on the floor stayed year after year, he said.
Mike Jay wrote:So the goal of the whole freezer wofati is to freeze the dirt around the freezer compartment. That dirt is protected by the layer of insulation that's under the umbrella. I'm just thinking that we should consider extending that insulation layer under the dirt that's under the floor.
Mike Jay wrote:The goal is to have the frigid air circulate through the pipes and freeze all the dirt between the freezer compartment and the insulation. Then you have to hope the insulation keeps it from thawing before November.
paul wheaton wrote:How much elevation difference would be required?
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