Secagem solar e convencional de amêndoas de jaca.

Abstract

The objective of this work was to study the drying of jack fruit almonds in solar dryers and in stove. Whole almonds with the most external peel, white, that involves them, whole almonds without peel, almonds with peel in half of them, almonds without peel in half of them and grinded almonds were studied. The almonds were dried in stove with circulation of air in temperatures of 40, 50, 60, 70 and 80 °C. The solar drying was accomplished with two dryers, one for drying during the day and the other was based on the accumulation of heat captured through plane solar collectors and the use of the heat for night drying. The solar dryer for use in the day consisted of a square box, in zinc plate covered internally with sheets of isopor painted of black, and covered with plane glass. The solar dryer for night use was set up to heat up water during the day, to store it in a thermal box and to do it circulate in a dressing room of heat during the night to supply heat for a drying box. The drying box was built of zinc plate and covered internally with isopor. The dressing room of heat consisted of a copper tube serpentine with nominal diameter of ¾ inch in its interior. The dryer for night use was composed of two independent circuits of water circulation, provided of taps in order to control the circulation of water between the solar collectors and the thermal reservoir or between the reservoir and the drying camera. During the day, the circuit formed by the solar collectors and the reservoir was opened. In the evening, this circuit was interrupted, while the taps destined to provoke the water circulation in the drying camera circuit were opened. In both circuits, the circulation of water happened through the thermal siphon principle, functioning because of the level of difference of the collectors in relation to the thermal reservoir and of the thermal reservoir in relation to the drying camera. The drying kinetics in stove and in the solar dryers were fitted using Page, Henderson, Henderson & Pabis and Logarithmic models. The drying time in stove varied of 23 at 79 hours. The drying using the solar dryers varied of 32.5 to 36 hours. The drying in the solar dryers had a variable performance, equivalent to drying in the stove in temperatures between 40 and 70 °C depending of the climate conditions. The use of the night dryer resulted in low speed drying, however it always overcame the loss of water of the witness, which had its moisture increased in the night period. The fittings were satisfactory for all the drying, with prominence for Page, Logarithmic and Henderson models.