Development of Multi-Level Hot Air Temperature Dryer Cooperation with Biomass Heat Collection System for Longan Flesh

Abstract

This study investigates the drying of longan flesh through hot air energy derived from a biomass heat collection system. Three heating patterns were developed and selected for study. Next, the drying rate and specific energy consumption were measured and analyzed. The heat from the burner is transferred to the hydraulic oil, and the oil is pumped to the heat exchanger in the drying chamber. The temperature control system in the drying chamber used a temperature controller to stop the operation of the hydraulic oil pump motor. Three patterns of multistep temperature with an airflow velocity of 1.15 m/s were tested. The opening air outdoor system was 10%. Pattern 1 was dried at 80◦C for 3 h, then at 70◦C for 8 h; pattern 2 was dried at 80◦C for 6 h, then at 70◦C for 4 h; and pattern 3 was dried at 80◦C for 5 h, then at 70◦C for 3 h, and at 60◦C for 4 h. 4 kg of longan flesh with an initial moisture content of 330.61 ± 7.03% dry basis was dried to a final moisture content of 17.37 ± 0.254% dry basis. The results showed that the drying rate of pattern 1 was 0.265 ± 0.0009 kg/h, and the specific energy consumption (SEC) was 68.34 ± 3.775 MJ/kg, while the drying rate of pattern 2 was 0.289 ± 0.0010 kg/h, and the SEC was 72.64 ± 5.906 MJ/kg. The drying rate of pattern 3 was 0.244 ± 0.0004 kg/h, and the SEC was 70.03 ± 6.436 MJ/kg. Finally, pattern 1 was the most suitable condition. It was low SEC, and the color quality was a golden color close to market standards.