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ISOTHERMAL
DRYER

FOR FRUITS AND PLANTS

Drying fruits and plants through solar radiation.

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PROJECT ISOTHERMAL DRYER

IN SHORT

The drying of plants and fruits is an important technology for the preservation, distribution and marketing of locally grown products. It is attractive to use solar radiation and the ambient air as elements for such drying, because the radiant energy is free of charge. The same holds true for the air as a heat carrier and desiccant.

 
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The sun only shines during the day. At night conventional solar dryers often recondense water vapor in the air, which re-humidifies the goods to be dried.
The drying temperature should be about 40 °C for most of the plants in order to retain vitamins and other valuable ingredients.

CHALLENGES

IN DRYING FRUIT, VEGETABLES 

AND MEDICAL PLANTS

THE CONCEPT

OF THE ISOTHERMAL DRYER

The Isothermal Dryer works day and night, keeps the temperature at the desired level and collects the water that is desorbed from the goods during the drying process.

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HOW TO

A STEP BY STEP DISCRIPTION

The isothermal dryer works in a closed process. 
 

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During the day, the air is moved by the heat of solar radiation and thus melts a phase changing material (PCM) that determines the desired drying temperature (isothermal process).The air flows in this isothermal process around the goods to be dried.

The water, desorbed from the goods in the form of steam, is recondensed by a cooler, which is an integrated part of the dryer.

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The now dried air flows back into the cycle and is again warmed up by the sun – this process is repeated continuously.

At night the PCM material solidifies and thus it is releasing isothermically the heat gained from the sun during the day.

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Functioning demonstration units of the Isothermal Dryers can be found at the TTT-Center in Portugal.