Abstract:
Moisture control is one of the most common preservation methods used for
enhancing the shelf life of agricultural produce. When processing or storing of fresh
produce, a special attention has to be given in maintaining low temperature of the drying
air. A heat pump based dehumidifier, which comprised of an evaporator, condenser,
compressor, expansion device, a control unit, main frame and a covering chamber, was
designed and fabricated for moisture control of agricultural produce. The air with high
relative humidity coming from the evaporator was passed through the condenser unit and
reheated up to 30 °C. The control unit was designed using Arduino controller to maintain
preferable relative humidity in the storage room with minimum working cycle. Duty cycle of
the system was 20 minutes ‘switch on’ and 5 minutes ‘switch off’ time. The performance of
the heat pump based dehumidifier system was evaluated by studying the temperature and
relative humidity of empty store room and with stored Gotukola (Centella asiatica). The
relative humidity of the empty store room was found to be reduced from 50% to 16% within
6 hours of operation of heat pump dehumidifier. It was also possible to reduce the moisture
content of fresh Gotukola from 88% to 12% within 27 hours. During this period the air
temperature of the storeroom varied from 25°C to 44 °C. The specific moisture extraction
rate of the heat pump dehumidifier system was 0.49 kg/kWh. The designed and developed
heat pump based moisture control system performed satisfactorily and could be effectively
used in moisture control of medicinal plants.
