Temporal and spatial representation of temperature and moisture in drying chamber and its impact on vertical vacuum dehumidifying rice seed dryer performance

Abstract

Population growth is resulting in a daily increase in rice consumption demand. To grow paddy for this expanding population, quality seeds are necessary. The study was conducted to evaluate the performance and estimate the drying cost of the vertical vacuum dehumidifying dryer. The studied dryer consists of four main parts: drying chamber, heating and cooling chamber, compressor and blower. The paddy (BRRI dhan 80) sample sizes were 100, 125 and 150 kg as treatment per batch. In three treatments, the drying chamber temperature was varied from 21.1 to 57.0 °C. Paddy was dried from initial moisture content 21.8 to 10.6%, 21.1 to 12.0% and 20.7 to 11.9% in three treatments within the drying time of 6.0, 6.5 and 7.0 hrs respectively. During the drying process, the relative humidity was differed from 60 to 35%. The rate of drying was found 2.08, 2.12 and 2.01 kghr −1 respectively for 100, 125 and 150 kg per batch. The capacities of the dryer were found 16.66, 19.23 and 21.43 kghr −1 for three treatments respectively. The drying efficiency was found 68.85% (for 100 kg batch), 69.85% (for 125 kg batch) and 66.20% (for 150 kg batch). The drying cost of paddy (Tk./kg) was found 0.71, 0.56 and 0.47 for three treatments respectively. • The performance of the vertical vacuum dehumidifying rice seed dryer was assessed in terms of drying rate, drying capacity, drying efficiency, and drying cost. • The temperatures of different points in the drying chamber were obtained in the range of 44.2–57.0 °C. • The paddy moisture content was reduced to the final moisture content of 10.6–12.0%. • The Vertical Vacuum Dehumidifying dryer meets the requirements of Bangladesh's small-scale farmers in terms of drying efficiency, drying capacity, and drying cost.