CFD-Guided design and experimental validation of a horizontal ribbon-blade mixer for commercial Leucaena leucocephala-based ruminant feed production

Abstract

Homogeneous mixing of compound animal feed is a prerequisite for nutritional consistency, growth performance, and economic feasibility in commercial ruminant production. Acacia (Leucaena leucocephala) wood chips have emerged as a low-cost, locally available protein-rich roughage in tropical Southeast Asia, but their irregular particle geometry and density mismatch with conventional concentrates pose a persistent processing challenge. This study presents a coupled computational and experimental framework for the design and validation of a 1.5 m³ horizontal ribbon-blade mixer tailored for L. leucocephala-based feed production. Three blade geometries—screw, paddle, and double helical ribbon—were comparatively evaluated using a transient three-dimensional CFD model (Volume-of-Fluid multiphase coupled with a moving reference frame and the k–ε turbulence closure) at shaft speeds of 10, 20, and 50 rpm over a 20 min mixing cycle. The ribbon geometry consistently outperformed the screw and paddle blades, reducing the predicted Coefficient of Variation (CV) from 42.1 % to 11.7 % within 6 min. A full-scale prototype with a centerline ribbon diameter of 1.14 m, pitch of 0.51 m, and a 10 kW motor was subsequently fabricated. Experimental sampling at ten radial–axial locations and one discharge point yielded a minimum CV of 7.01 % and a Lacey mixing index of 0.987 at 10 rpm after 5 min, in close agreement with the CFD prediction (CV = 7.1 %; relative error = 1.3 %). The validated prototype achieved a throughput of 4.5 t h⁻¹ at a specific energy consumption of 0.42 kWh t⁻¹ and a simple payback period of 2.63 years. The combined numerical–experimental–economic evidence demonstrates that CFD-guided geometric selection can deliver a commercially deployable, energy-efficient mixer for heterogeneous lignocellulosic–protein feed mixtures.