Effect of inlet chamber design and operation conditions on laminar drop deformation in a production-scale high-pressure homogenizer—A hydrodynamic investigation

Abstract

Due to their wide utilization and low thermodynamic efficiency, there is a large interest in designing more efficient high-pressure homogenizer valves. Drop breakup in these devices is by turbulent interaction downstream of the gap exit. However, recent investigations in scaled systems suggest that the drops can be ‘primed’ for breakup by elongation upstream of the gap entrance. This study uses hydrodynamic modelling to investigate (1) if this effect is expected in production-scale valves and (2) if it can be enhanced by simple design modifications. Results confirm the high velocity gradients formed upstream of the gap (and proposes a model for estimating them based on design and operating conditions). However, regardless of which of the three deformation/relaxation models that is applied, no sizable drop deformation is predicted at the gap exit under standard conditions (e.g., in dairy processing, the single largest application). The drops are too small to deform substantially. Under extreme conditions (higher pressures, flowrates and inlet angles, and shorter gaps), a lightly deformed drop exits the gap. However, when taking into account the constraints set by applications, energy cost and valve manufacturing, no sizable deformation is possible to achieve by simple design modifications to the inlet chamber.