Case Study



Status : operational Type : chamber dryer

Heating mode : Air circulation:

direct natural convection

This simple dryer has been developed in Brazil and tested for the drying of local fruits, it is very simple to build and the performance reported makes it attractive for the needs of a small community.


This small-scale solar dryer is essentially a wooden rectangular box covered by two layers of glass separated by an air gap. The bottom of the dryer is insulated with glass wool sandwiched between an underside plywood sheet and an innerside blackened metallic collector surface. The fruits are spread on the collector surface for drying. The drying chamber is mounted on an upright wood structure and tilted 7° Northward. Only natural convection air circulation is used. The collector heats the inside air which flows over the drying fruits and escapes at the top of the dryer, allowing fresh air to enter au. u»e dryer air inlet.

Dimensions of the dryer: see Figure 2.

Materials of Construction:

Drying Chamber:

Transparent cover: 8 sheets of glass, 3 mm thick

Frames: a plywood sheet, 12 mm thick and 15 m of

70 x 30 mm wooden bars

Insulation: 2 Kg of glass wool

Trays: 2 nr of galvanized iron sheet, 0,8 mm thick.

Fixed trays are used.

Location: campus of Escola de Agronomia at Areia, paraiba, Brazil

Latitude: 6°59'S Longitude: 36°10'W Altitude: 618 m

Climatological Data:

Sunshine hours: Annual rainfall: Relative humidity: Average temperature: Maximum temperature: Minimum temperature:

2 400 per year, 54,8% of the theoretical total 1 470 mm 80% 23°C %

(average) (average)

Practical Operation:

Number of units used in the past: 2 Number of units currently in use: 4

Periods of Operation:

(a) On Experimental Basis:

(b) In Field Operations: May 1973 to present

Drying Data;

Material Number of fruits dried per load

Banana Banana Pineapple Cashew

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