LDPE Flows in a Laboratory-Scale Twin-Screw Extruder

With the rising concerns of environmental impacts from fossil fuels new alternative energy technologies, such as hydrogen fuel cell vehicles, are being developed. The development in the hydrogen storage material, ammonia borane (NH₃BH₃), has established the need for an on-board solid material transportation system. By using a laboratory-scale co-rotating twin-screw extruder, this work investigated the transportation of low-density polyethylene (LDPE, a surrogate of ammonia borane) between the hydrogen extraction component and the fuel storage tank. The non-Newtonian gas-solid two-phase flow in the twin-screw extruder was studied experimentally under three operating conditions (assisted, unassisted, and filling) at varied driven power. The twin-screw extruder was assessed with two pairs of rounded thread screws made of aluminum and acrylonitrile butadiene styrene (ABS) plastic, respectively. The aluminum screws were 4 mm larger in diameter than the ABS plastic screws. Under each operating condition, driven powers, torques, and volumetric flow rates were measured. The measured volumetric flow rate by using the ABS plastic screws was 46% greater than that by using the aluminum screws at the same driven power. The aluminum screws also produced larger torque than the ABS plastic screws at the same driven power. The assisted flow condition resulted in an average increase of 3.5% in volumetric flow rate over the unassisted flow condition. The study of the present solid flow may enable the use of ammonia borane as a hydrogen storage material for fuel cell driven vehicles.