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a radiant solar food dehydrator that doesn't fight physics - - corrugated polycarbonate

by:Cailong     2019-08-04
a radiant solar food dehydrator that doesn\'t fight physics -  -  corrugated polycarbonate
One day (in 1985)
I need to dry a bunch of green vegetables and the current solar dryer is full (
It can handle only a few).
I have an old window screen and built a corrugated metal roof on our old mobile House.
I climbed up the roof with a ladder, put the screen down first and put the food on it.
I wanted to heat the food while keeping the sun, so I covered it with a piece of black cloth.
Then, to prevent everything from being blown away or disturbed by flies, I covered it with a storm window that was placed on the screen.
Later that afternoon, I thought I would check this experiment.
The Green in the old dryer was still soft, so I climbed the ladder to see what was on the roof.
To my surprise, the roof
The green above is crispy and dry!
It looks like I finally stumbled upon something useful.
Before I was convinced enough of the design, I tried several other foods on the roof in order to build a unit on the ground for easier access.
Through experiments, the main components of this idea are: glass windows (
Glass or greenhouse plastic)
To seal the rain and increase the black surface temperature on the surface of the food (Fabric or metal)
Keep the sun away from food-
A safe screen can hold food and allow moisture to flow outward, corrugated, galvanized, metal roof tilted to accommodate the airflow and towards the sun.
So this is a combination of design factors and also meets what I think is ideal for solar dryers: using passive solar, no moving parts, no need to track sun food that is not exposed to the Sun * spacious enough to accommodate large picking gentle temperatures, fast drying, but not easy to overheat cleaning must definitely work reliably, even at high humidity, also do not need to remove part of the dry food from the dryer overnight in the windy area * stableproof (
All bets are canceled if you have bears in your area! )
* The only exception to the "no sun" rule we know is mushrooms.
Some mushrooms can be dried directly under the Sun (
No glass or plastic shielding UV)
Produce a lot of extra vitamin D in terms of spores. Lentinus (shiitake)
Mushrooms may be 10 times or more as normal and are already high, making them almost a supplement, not a food, and making it possible for mushroom lovers to take excessive amounts of vitamin D!
For more details on mushroom culture, check out Paul stamets's books.
** There are several exceptions depending on where you are and what you are trying to dry.
If there are bears around you, they are hungry (
When are they not? )
You either need some main fence or just put the "bear bait" inside.
If you are drying something very sweet, the ant may climb up the legs of the dryer to find your food.
We suggest applying for ants.
Insect repellent such as orange or mint essential oil to the dryer leg, or make "moat" by cutting"
Close the top of the plastic kettle, trim to fit the neck of each leg, mounted on top
Fill the seam with silicone and fill the water.
Construction of radiation Super dryer: for the whole construction process, you can find a PDF of the details on the following website: according to the basic principles and design standards established by our experiments, we built a 4-by-12 foot, waist-high "shed".
The metal roof on this shed has ripples extending from north to south.
The roof angle is about 12-
Tilt 15 degrees from horizontal and South (
In the northern hemisphere).
This allows warm air to rise, but does not allow food to slide downhill.
The mini "cabin" space below can be used to store firewood or garden accessories. The 4-
The foot width allows the food to arrive from both sides, but is wide enough to reach enough hot air flow.
Legs are 2-by-
2 inch treated wood and stick to the ground about 6-12 inches. Metal fence T-
Columns attached to wooden frames with U-
Bolts are a great choice if you don't like treated wood.
If your dryer is large, additional leg support may be required.
A good "launcher" size is 4 by 4 feet with 4 2-by-2 foot trays.
If you need to increase the capacity, you can make more modules of this size later.
We have 12 dryers. by-
2 feet screens made of diagonal cedar 2by-
2. there is a deck screw in every corner.
The lower inner edge of the frame is cut off so that the screen is recessed a little from the outer edge.
When you lean on the dryer, this eliminates the possibility of wrapping your clothes around the edge of the screen.
The screen is stainless steel, easy to clean although expensive, providing a non-
The toxic surface of food should last a lifetime. A bead of high-temp, food-
Silicone caulking agent (
Any "100% silicone" caulking agent that does not add "anti-mildew" killing agent can be used)
Prevent food particles from sticking between the wood frame and the screen.
A lower cost but controversial screen option is "food-
Screening of grade polypropylene (
Available from Dryit, among other sources. com).
To prevent sagging, you need to provide support under this material.
Since food does not come in direct contact with metal, you can use galvanized metal fence lines or hardware cloth.
My initial experiment used fiberglass window yarn, but then I found out that it was coated with PVC, which was stabilized by several substances, one of which could be lead.
Please do not have direct contact with any material that is not absolutely food safe.
This will include plastic garbage bags/cans, galvanized metal, aluminum screens or cookware.
Although some plastic (
Polypropylene, high density polyethylene, nylon)
Promoted as "food-
Safe ", this may just be a selfserving boast.
We prefer metals in terms of isoestrogen and plastic as we know it now.
Some bloggers with no actual data base question the purity of the Chinese
This means that it may contain some impurities.
From a metallurgical point of view, the 304 or 316 type stainless steel is manufactured in strict formula.
No matter what kind of chemical impurities are found (
Small quantity)
, May react with your food on a metal screen, at least you know they may be necessary as an enzyme
Supporting minerals (Small quantity)
In the human diet
No dietary requirements for plastic!
Cover frame can also be from 2-by-
2 inch diagonal cedar.
The glass we use most is Kalwall brand, 40 mil, fiberglass reinforced polyester.
In the hail, it supports much better than the glass, and the weight is much smaller.
My neighbor made a dryer but used the acrylic glass window.
Acrylic was originally cheaper, but due to the formation of many cracks, it needs to be replaced after three years of use.
New dryers made by friends and neighbors use the transparent corrugated fiberglass greenhouse glass windows provided locally.
It is much cheaper than Kalwall and looks durable at the same time.
Our favorite glass, the one we currently use, is a corrugated polycarbonate.
This is the most durable, with the least amount of yellow over time and continuous exposure to the sun, it is still the most brittle.
The final passage can be sealed using a silicone filler or a foam strip sold for this purpose, or it can be kept open.
The dryer works fine in either case, although the sealing end may make the black collector sheet cleaner.
We have received some technical questions about the physical properties of glass windows, whether necessary or functional.
When the sun shines through the light
The transparent material changes a bit.
Most text mentions that the light will "slow down" when passing through air, water, clear glass windows, etc ".
In reality, the light will not slow down even if it looks like this.
Light always travels at "light speed" relative to the observer, but when it passes through a transparent medium other than a full vacuum, its frequency moves down ("Red class ").
It is said that on the other side of the glass window, the light recovered the frequency, but there was no energy conversion efficiency of 100%, and some downward shifts still existed.
This makes the UV light lighterUV)
More infrared light (heat)
Invisible Light
Therefore, the glass windows not only prevent the wind from taking the heat away from the black absorption sheet through convection (wind)
In fact, it also helps to create more heat for the absorber to radiate down to the food.
If you think you can dry your food in the sun or just with a plastic/glass cover, guess again!
Some solar dryers are actually designed to generate heat by sunlight (
Fodor design in Mother Earth News publication).
UV-plastic/glass cutting
B radiation, but not ultraviolet
So a layer of black metal or cloth is a necessary condition to maintain the highest possible level of nutrition.
We now use a thin layer of aluminum sheet with "barbecue black" paint on both sides, nailed to the lower side of the cover frame, not the black cloth used in the original experiment.
The top is black to absorb the heat of the Sun, the bottom is black
Radiate heat to food.
Steel plate can be used (
28 table or lighter-
No galvanized, so the paint will stick better)
Or use "printer board" but it is easy to find aluminum "flashing" in 2"foot widths.
The black metal radiator is more convenient to use than the black fabric, not messy, and may be cheaper in the long run.
One way to improve collector efficiency is to use "selective surface" or "black chrome" paint on the top floor of the metal plate.
These paints absorb sunlight like normal black paint, but have a smaller emission at a lower wavelength.
That means they re-
Once the metal gets hot, it releases less heat into space.
When the typical temperature on the metal is 15f, this means that the efficiency is increased by 35%.
But it costs a lot more and you can only use it at the top.
If you use it on both sides, it will reduce the amount of heat that radiates to the food.
If you are at high altitude or low latitude, additional efficiency will result in higher temperatures, which is more likely to burn your food.
The lid frame is attached to the T-dryer base
The belt has hinges on both north and south sides.
These are loose.
Pin hinge so you can open the dryer from both sides by pulling the pin and lifting the lid on the opposite side.
A curved steel rod can be inserted into the hinge to support the lid to open.
Fix the right angle bracket to the south edge of the roof below each screen (
Where the hinge is placed)
To prevent the food tray from sliding down the downhill side.
All Cedar is coated with homemade sealant: Melt 1 pound of paraffin, remove from the heat, and vigorously stir 3 quarts of flax seed oil and 1 cup of gum pine.
It looks like crystal honey when it's cold.
Apply freely with a brush.
This is also great for windowsill or exterior that wants to be waterproof.
Recalculation in subsequent years when required.
Legs and underneath
If you use the treated wood option, no other sealant is required for the frame.
ACQ treatment of wood is the latest option and is said to be more eco-friendly.
As a convenient working space, improve and alternate use of shelves or tables for easy storage in winter 1-
Inch square aluminum frame for collector, not wood adjustable slope for holding seasonal sun angle change, or for high latitude area, reflective white/silver walls on the back of the dryer can increase the Sun gain the higher latitude of the Brown collector the green, red or blue paint on the metal plate to avoid excessive
Heat the food when the dryer is used near the equator or at a higher altitude, or use an open dryer
Weave a shading cloth or window yarn on the collector to reduce heat input
Solar area, giving you the option to remove it on cloudy or partially cloudy days, allowing the temperature to recover on both sides of closed or blocked things to prevent excessive cross cooling
The wind collectors who flow under the food screen can also play the role of catching a cold.
Frame covers can be replaced if Black heating materials are removable, or other cheaper screen materials can be separated, as long as they are safe for direct contact with food.
Remember, you can do that.
You can replace what we use with what you have.
You can use recycled materials.
You can use the most accessible building materials in your area.
You can even use your parked car as a food dryer.
Just set the screen, cover it with a black cloth, park the largest window on the equator, put the screen on the path of the sun, let the window open a little bit and let the moisture drain.
It's better for a car than driving it, but since you're already doing it, why not do both? Long-
To answer some questions about the storage of dry food, we store all dry and canned food in a cool, dark room (our pantry).
Plastic is not a reliable barrier to prevent moisture, and dry vegetables must remain completely dry (
Not so picky fruit
They can still store well with some flexibility).
We used the old blue.
Half green quart
The gallons found in the sale of the dump, and the old ones
Rubber rings and zinccoated covers.
This helps keep the light out even if the jar is not in the storage room.
Light and Heat are not conducive to the nutritional value of the contents, so any way to reduce them can improve storage time.
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