Optimization of Vertical Screw Conveyor for Biomass Sampling: Influence of Pitch Geometry on Energy Dissipation and Material Integrity

Abstract

This study investigates the optimization of vertical screw conveyor design to enhance the efficiency and reliability of automated cassava sampling systems in agro-industrial processing. A comparative analysis was conducted between two screw configurations: Type B (P/D = 0.67) and Type C (P/D = 0.50), with varying screw diameters (0.11-0.20 m) and rotational speeds (56.78, 48.67, and 36.50 rpm for 18-, 21-, and 28-tooth gear sets, respectively) under controlled hydraulic operation (p = 152 bar, Q_oil = 4.875×10⁻⁴ m³/s, P_in = 7,410 W). The results indicate that over 99% of the hydraulic input power is theoretically dissipated as heat, based on the first-law energy balance. The Type B configuration, particularly at a diameter of 0.20 m and maximum rotational speed (56.78 rpm), demonstrated superior performance, achieving the lowest Specific Energy Consumption (SEC) of 23.25 kJ/kg, representing a 25.0% reduction in SEC and a 33.4% gain in useful mechanical work output (P_out : 14.07 vs. 10.55 W) over Type C. Furthermore, the wider pitch of Type B effectively mitigates material compaction and reduces cumulative frictional stress during transport, preserving the physical integrity of cassava chips (bulk density: 496.4 ± 62.4 kg/m³; moisture content: 13.5 ± 0.5% w.b.). The study concludes that the Type B configuration is the optimal design for maximizing flow stability and minimizing energy loss while satisfying quality assurance requirements.