Temperature control of paddy bulk storage with aeration–thermosyphon heat pipe

A technology of an aeration–thermosyphon heat pipe is developed for controlling paddy temperature in a paddy bulk silo. A prototype of paddy bulk storage of 1000 kg has a set of copper tubes with steel fins embedded in the paddy bed. The total heat transfer area of the tubes with fins is 16 m2. The tubes act as the evaporator of a thermosyphon heat pipe and absorb heat resulting from the paddy respiration. The thermosyphon has a total condenser area of 12.2 m2 that is exposed to ambient air. At the bottom of the silo, ambient air is fed upward through the paddy bed for the aeration. The initial moisture content of the paddy is around 12.8% wet basis.A mathematical model to predict the paddy bed temperature in the silo with the hybrid aeration–thermosyphon is developed, and the results agree very well with the experimental data. The operating period of its blower could be found from the simulation. The blower is on when the paddy bed temperature, Tb, is over or equal to 28 °C and the difference temperature between the bed and the ambient, Td, is over or equal to 1 °C. The appropriate evaporator area should be over 8 m2. At the area of 8 m2, the operation time of the blower is 8–9% of the annual period compared with 30–40% for normal aeration alone. The monthly paddy bed temperature could be maintained between 24 and 27 °C under the climate of Chiang Mai, Thailand.