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Figure 5. Plan of the Glass-Roof Dryer, with Gas Heating installation under one Platform.

Plan du Séchoir à Toit-Vitré Montrant l'Installation du Système de Chauffage au Gaz sous l'une des Plateformes.

CASE STUDY ( J

SOLAR FRUIT AND VEGETABLE DRYER (U.S.A.)

Overview:

Status: operational Heating mode: mixed

Type: chanfaer dryer Air circulation: natural convection

This simple chamber type dryer operates in both the direct and indirect mode. It was designed to dry food for domestic needs as well as for a small size restaurant, etc. It was successfully used for drying a wide variety of food products, ranging from fruits and vegetables to herbs and meat.

Figure 1. Section View of the Fruit and Vegetable Dryer

Characteristics:

Air, preheated in a solar air heater located at the base of the dryer, is admitted to the base of the drying enclosure. From there, it rises through the drying racks, dehydrating the product laid on them and is then exhausted with its moisture content by natural convection through openings located at the top, rear wall of the chamber. The drying process is also carried out with the help of direct sun reaching the product through plexiglass sides, front and top panels. The dryer faces south.

Dimensions; The drying box measures 2,45 m wide (8ft.), 1,27 m high (50 inches) and 0,51 m deep (20 inches). The air heater is 0,61 m long (2ft.) and runs all the width of the dryer base. See also the drawing - figure 1.

Figure 2. view of the Installation of the Dryer. The Four Drying Racks are Easily Seen.

Materials of Construction:

Drying Chamber

Transparent cover!

Frames: Insulation: Trays:

3 mm plexiglass plate (glass could be used as well), and translucent fiberglass top wood none used stationary wood frame racks, covered by stretched nylon mesh

Solar Air Heater:

Transparent cover: Absorber:

Insulation: Frames:

none black sheet metal panel, which serves as a chamber plate and cover for the air heater none wood frame with a masonite bottom

Location: El Rito

New Mexico U.S.A.

Latitudej Longitude: 106°12'W Elevation: 2 100 meters

Climatological Data:

Type of climate: semi-arid, sunny Air temperature: early fall days Relative humidity: 30 to 40 percent

In this region, the actual number of sunshine hours is approximately three quarters of the total possible hours of daylight throughout the year.

Practical Operation:

Number of units used in the past: Number of units currently in use:

one one

Periods of Operation:

Field operation: from March 1972 to present. The dryer is used for domestic needs and small restaurant provisioning.

Drying Data:

Materials epricots apples peaches squash mushrooms herbs beef

Quantity dried about 5,5 Kg per load

Pre-Treatment quick blanching, halving and pitting peeling, coring, spiral cutting hand peeling and slicing sliced in strips

Data not reported

Drying time?

The author reported that one day of drying is sufficient under the most favourable conditions; two or three days are necessary if intervals of cloud are frequent. The dried materials were kept in a dry cool place.

Operating Conditions:

Usually sunny weather and normally fairly dry days made the drying process very easy.

Economic Details:

Cost of materials: plexiglass plate, 3 mm thick $16,00

fibre glass roof panel 5,00

black metal sheet 4,00

masonite back-up 4,00

second-hand wood 5,00

labour self-employed spare time

TOTAL MATERIAL COST $34,00

Annual operating expenditures: none

Operating cost of drying per load of Material dried:

1 to 2 hours of domestic labour are required to prepare the materials to be dried and to fill the drying chamber.

Estimated Life of the Dryer: 20 years

Comments on the Dryer:

. simple carpentry skill needed . not expensive

. the main drawback is the lack of interest and initiative of people

Principal Investigator(s); Van Dresser, Peter

El Rito

New Mexico 87530 U.S .A.

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