A hydrodynamic comparisons of two different high-pressure homogenizer valve design principles: A step towards increased efficiency

Abstract

Designing more efficient high-pressure homogenizers (HPHs) is important from an industrial perspective (reduce energy cost). Understanding the relationship between valve geometry and breakup is interesting from an emulsification research perspective. Typically, two different design principles are used for commercial HPHs: the traditional outward radial flow design and the newer inward radial flow design. However, little is known about the hydrodynamic difference. This study uses well-validated computational fluid dynamics (CFD) methodology to compare the turbulent stress experienced by a drop travelling though HPH valves (at comparable conditions) between these design and discuss implications on optimal valve design. Regardless of design, the highest stress is observed in the jet downstream of the gap exit. At low to intermediately high homogenizing pressures (<250 MPa), the traditional design gives rise to higher turbulent stress. At extreme pressures (>250 MPa), the inward radial flow design is marginally more efficient. The difference in efficiency between design and operating condition is determined by two opposing forces: The efficiency increases with gap exit velocity (higher in the inward radial flow design) and the efficiency decreases with increasing dissipation volume (smaller for the traditional outward flow design). Implications for improving HPH valve design are discussed.