Numerical Comparison of Pressure Drop in 90° Bend Layouts in Dilute-Phase Pneumatic Conveying

Abstract Bend configuration influences pressure loss in dilute-phase pneumatic conveying by altering flow direction, particle momentum, and particle-wall interactions. This study compared five 90° bend layouts (horizontal-to-horizontal, H-H; horizontal-to-vertical down, H-V DOWN; vertical-to-horizontal left, V-H LEFT; vertical-to-horizontal right, V-H RIGHT; and horizontal-to-vertical up, H-V UP) using two-way coupled Euler-Lagrange CFD-DPM simulations with the RNG k-ε turbulence model. Every layout was simulated at the same 144 operating conditions, drawn from a grid of three pipe diameters (0.046, 0.071 and 0.120 m), six inlet air velocities (12-28 m/s) and twelve solids mass-flow rates (0.009-0.28 kg/s), giving 720 simulations; combinations at high solids loading and low velocity were not simulated. Pressure drop was evaluated between planes 1D upstream and 10D downstream of the bend. Against published experimental data, the model reproduced single-phase and gas-solid pressure drops with mean absolute relative errors of 3.40% and 4.65% (maximum 5.21%) for the tabulated cases. The overall mean pressure drop was highest for V-H LEFT (185.07 Pa) and lowest for H-V UP (141.31 Pa), a difference of 43.76 Pa (23.7%). Because the layouts share the same conditions, they were compared with a randomised-block ANOVA with operating condition as the block: the layout effect was highly consistent (F(4, 572) = 291.0, p < 0.001), all ten pairwise differences were significant after Holm adjustment, and the ranking V-H LEFT > H-V DOWN > H-H > V-H RIGHT > H-V UP held in 143 of the 144 conditions (one tie). Pipe diameter, air velocity and solids mass-flow rate controlled the magnitude of the pressure drop, while the layout acted as a nearly constant multiplier (about 0.90 to 1.22 times the H-H value), with layout × condition interactions that were detectable but small. Bend orientation is therefore a practical design variable, but the results are simulation-based and the layout mechanisms remain to be confirmed experimentally.