Operating Conditions:

During fair days, only solar heat was used. During rainy or cloudy hours of the day and during night,automatically ON-OFF controlled steam heating system was used.

Economic Details:

Cost of materials: iron frame and vinyl sheet 770 $U.S*

(including labour) carrier and rail 580

motor and fan 300

heating fin pipe 200

automatic control apparatus 580 electric cable and steam supplying pipe 400

* $1,00 U.S. = 260 yen Annual Operating Expenditure:

No detailed data. Electric power needed: 1 Kw; steam used: 10-20 Kg/hr. at night.

Estimated Life of the Dryer:

Vinyl panels 3 years, iron frame more than 10 years and motor and heater 7 to 8 years.

Comments on the Dryer:

The author reported that this dryer is not economically feasible in japan because of short sunshine hours and frequent rainy days.

Principal Investigator(s): Terazawa, Shin

Government Forest Experiment Station Shimomeguro 5-37-21 Meguro-ku, Tokyo Japan

Figure 2. Schematic Plan of the Dryer, Front view
Figure 3. Schematic Plan of the Dryer, Side view


us: experimental Heating mode: hybrid

: chamber dryer Air circulation: electric fan-forced ventilation

\ybrid-type dryer uses the sun as a heat source, and uses electricity -er a fan for generating air flow inside the dryer. The economics of ethod are similar to those of air drying, but its main advantage i the drying time is reduced by 50%.


The structure is aligned lengthwise on an north-south axis. Sheets of transparent plastic are fastened to the outer edges of the studs and rafters. The end wall facing north is sheated with plywood and includes a door into the pre-dryer. A second film of transparent plastic is mounted on frames to provide a space of about 10 cm between the two plastic films. Four vents, two being located on the entering air side (east wall) and two on the exhaust air side (west wall) allow for the proper control of air recirculation and humidity in the dryer. Sheets of corrugated aluminum, painted dull black in both sides to absorb solar radiation are nailed to the underside of the studs and rafters. Rectangular openings are cut in the aluminum surfaces of the east and west walls and in the roof, and the metal is bent to form air deflectors. This causes some of the circulated air to pass over the outer as well as the inner face of the heat absorbing metal, and allows a more effective utilization of the sun's heat. An electric fan powered by a 0,5 Kw motor is mounted in a central baffle that extends the entire length of the dryer. The fan actuates the air flow movement inside the dryer. It is controlled by a photo cell and is operated only during daylight hours.

Dimensions: The overall dimensions of the dryer are: 3,86 m long, 2,29 m wide and 2,43 high fan diameter is 60 cm

Figure 3. Comparison of Drying Curves for Air-Dried and Kiln Dried (calculated) Lumber with Those Obtained for Lumber in Charge 1 Dried in the Solar Heated Pre-Dryer.

Materials of Construction;

Drying Chamber:

Transparent cover: 2 laycrti of mylar plastic film

Frames; 5 x 10 cm lumber for walls, and 5 x 15

cm rafters for roof

Insulation: the air gap between the two transparent plastic sheets acts as insulation

Location: Madison, Wisconsin, U.S.A.

Latitude: 43O08'N Longitude: 89┬░20'W Altitude: 261,5 m.

Climatol├│gica1 Data;

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