Case study of design and construction of dehydration for paddy by heat exchanger rectangular two-phase closed thermosyphon(DP-HE/RTPCT)

Abstract

The purpose of this research was to design and produce a dehydration system for paddy using a heat exchanger rectangular two-phase closed thermosyphon (DP-HE/RTPCT), which is a modified version of the rectangular two-phase closed thermosyphon (RTPCT). The working fluids used in this study were R11 and methanol at 50% addition rate of the evaporator volume while evaporator temperatures of DP-HE/RTPCT were set at 60 and 80 °C. The evaporator and condenser of the DP-HE/RTPCT were of equal length, the hot water flow rate into the evaporator was 1.5 L/min whereas the initial moisture content of the paddy was 21.50% of the wet basis. Using methanol as a working fluid at the evaporator temperature of 80 °C reduced the moisture content of the paddy to 14% of the wet basis in 390 min, which yielded the highest DP-HE/RTPCT efficiency of 0.62. This was the shortest time in all cases while the internal heat of the paddy pile peaked at A-depth and decreased at B-depth and C-depth, respectively. Paddy germination rate was 90% in the DP-HE/RTPCT that used R11 as the working fluid, at the evaporator temperature of 60 °C. The design and construction of DP-HE/RTPCT demonstrated a novel application of thermosyphons with a modified cross-sectional area. This study could serve as a foundation for future research on heat exchangers.