Abstract
In order to develop a circulatory dehumidifying drying system in the greenhouse, some fundamental drying characteristics of radish were investigated. The results are summarized as follows:
(1) The time required to reduce the moisture content of the radish from 94.0%w.b. to 9.3%w.b. was observed to be 67 hours and the average drying rate was 1.46%w.b./h. On comparing the experiment in the greenhouse to that of the indoors, the drying time inside the greenhouse was 30 hours shorter, and the drying rate was 1.8 times faster than the indoors.
(2) The average temperature of air in the greenhouse was higher by 11.5°C and 4.0°C in the day and night time respectively, as compared to the average temperature of the open air. The rise of the temperature by solar energy inside the greenhouse could be utilized for radish drying.
(3) The relative humidity of air inside the greenhouse was initially about 100%, but it was reduced finally up to 56%. The relative humidity of dehumidifying drying air was reduced from initial 78% to 30% at the final stage. The average relative humidity of dehumidifying drying air was 18% lower than that of air in the greenhouse.
(4) When the air temperature in the greenhouse was dropped bellow 5°C, the evaporator of heat pump dehumidifier began to be frosted. Therefore, it would be essential to discuss about effective measures inorder to improve the dehumidifying device.
(5) The consumption of electric power was 19kWh (6.9kWh at heat pump dehumidifier and 12.1kWh at fan) per kg of dehydrated radish. It was fixed at 380 yen in terms of the drying cost.
