SOLAR DRYER

SOLAR DRYERDried fruit in different ways. Most of all — air solar method, have, in addition to the obvious advantages (simplicity, accessibility, etc.), the well-known disadvantages.
The proposed option heliodryer free from many inherent in other designs shortcomings. The “greenhouse effect” works in it, as they say, a hundred percent, providing the temperature under the film at 20-25°C above the ambient temperature.
 
The drying process is almost 3 times harder due to the slope of the drying pad and the temperature difference between the air, the conditions for optimum circulation inside the last installation and the positive influence of natural convection. Part of the solar energy is accumulated in the soil (under the “bottom” of the dryer, which is spread out the blackened roll paper), extending the day drying cycle for 5-6 hours. The productivity of the device, despite its apparent “slaveselect”, 0,3—0,5 kg of dried fruit per day per square meter lucioperka surface.
 
Design heliodryer at first glance little different from the traditional “film” greenhouses. In fact, the same box with a vaulted roof made of transparent synthetic on a rigid frame. The material for the manufacture of the boards — any. For example, boards of suitable size. Connected to each other by means of thorns, reinforced metal corners (not shown on the picture), they form strong, oriented lucioperka surface of the sun the skeleton for attaching to it other elements.
Fig. 1. Heliodryer for thermal processing of fruits.
Fig. 1. Heliodryer for thermal processing of fruits:
1 — rod (aluminum tube filled with sand), 2 — transparent cover (plastic film), 3 — Adjuster (rubber bandage), 4 — arc frame (aluminum pipe), 5 — frame (Board 20X200 mm), 6 — front fastening of the arc frame (steel wire), 7 — heat-absorbing coating of the base of the dryer (heavy paper black).
 
To the side walls of a screwed steel rods-stand, which must be mounted on tubular arc of the arch. And as last you can use cut and flattened the pattern to R=750 mm gymnastic hoops: aluminum, diameter 900 mm. To increase durability the ends of the tubular arches, impaled on steel rods-stand, zastepowane (not shown on the picture). In addition, the frame can be additionally bonded on top of the longitudinal tubular element.
 
Very sheer coverage — seamless, synthetic (e.g., polyethylene) roll films. To the base fabric firmly attach the two sides, leaving the North side of the dryer loose site of the main leaf (about 100 mm) — education of the vents. We must also provide something else: welded bend for further strengthening in this rod — cut tube of appropriate diameter (from the straight gymnastic hoops) filled with sand.
 
Fig. 2. Methods of fixing the clear coat heliodryer.
Fig. 2. Methods of fixing the clear coat heliodryer.
 
And — with the help of underwear clothespins:
1 — pin, 2 — metal rod, 3 wrap, 4 — pole (wooden bead cross-section 15X15 mm), 5 — base frame of the dryer.
 
B — using slats and nails:
1 — peg, 2 — rail with cross section of 15X15 mm, 3 — film, 4 — the base frame of the dryer.
 
In using spikes and metal bars:
1 — metal rods, 2 — film, 3 — spike (a nail without a hat), 4 — the base frame of the dryer.
 
Of the existing options for fixing synthetic coating to the frame well proven in practice stajkovic clip, getting wrapped between two metal bars in the edges of the film on clogged every 200 mm nails without hats and detachable connection with… clothespins. The latter can be used for fixing at the desired height rod that provides the specified mode of ventilation during drying.
 
To reduce friction of the film on the arc frame (and thus increase the service life of the clear coat heliodryer), I recommend to wrap these metal elements by a strip of old film. To improve the durability of the coating and serve as rubber bandages, from which is made, the tensioner providing a constant film tension at the sharp gusts of wind.
Fig. 3. A device for welding plastic film.
Fig. 3. A device for welding plastic film:
1 — welding roller (steel washer with knurling on the outer diameter), 2 — axle roller (rivet), 3 — plug (attached to the electric soldering iron instead of the regular stinger).
 
Heliodryer is located on a sloping site, oriented South to maximize the use of radiant solar energy flux. The angle of inclination depends on the latitude of the area and is for the middle band of the country within the limits of 20…30°.
 
Pre-treated (blanching, sulfite) raw material is placed inside the unit on the spread paper (blackened, rolled). About 10-12 kg per square meter. The sun’s rays passing through the transparent synthetic film, are absorbed by the drying products. The mode of operation is largely determined by the width of the vents, regulating the intensity of ventilation.
 
There is a possibility of use as a spring greenhouse for growing early seedlings.
 
S. LARKIN, candidate of agricultural Sciences

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