Eulerian-Lagrangian Modeling of Multicomponent Spray for Aseptic Treatment of Carton Bottles in the Food Process and Packaging Industry

Abstract

This thesis is a study of the fluid dynamic behaviour of a specific spray nozzle used in the evaporator unit of the Tetra Pak A6 iLine, as well as a sensitivity analysis and methodology development for general evaporating sprays used in industrial applications. The Tetra Pak A6 is a complete sterilisation, filling and packaging machine for the Tetra Evero Aseptic carton bottle. The package is specially designed for ambient white milk. It is developed to be more user friendly than old fashion prism shaped packages due to the easier handling and reclosing feature and more environmental friendly than plastic bottles due to the separable carton body and plastic top. A spray nozzle in the evaporator injects a high-speed liquid mixture of water and hydrogen peroxide that is evaporated, swirled down into the carton bottle and used as aseptic treatment of the inside of the package before the vapor mixture is vented out and the package is filled with beverage. The behaviour of the multicomponent spray was numerically modeled using unsteady RANS and Lagrangian tracking of representative computational parcels of spray droplets. The simulations were performed using STAR-CCM+, a software package for computational fluid dynamic simulations. To break down the complex fluid dynamic problem in the high-speed spray nozzle and be able to isolate and study important physical phenomenon, two different case studies with simplified geometries were performed. The first case study was a parameter and sensitivity analysis of the behaviour of a general evaporating spray in a small cubical domain. The injector is a solid cone injector originating from a single point. Responses such as penetration length, spray width, evaporated mass for the species, diameter- and velocity distributions were studied for varying spray parameters and solver settings. The second case study originates from an experimental and numerical study of wall impingement of diesel spray in an open channel with cross flow [3]. The aim of the study was to investigate the effect of droplet-droplet collisions, wall interaction and fluid film. The conclusions from the case studies were applied to spray simulations of the nozzle and evaporator in the Tetra Pak A6. Comparison with experimental droplet velocities and diameters from laser measurements showed acceptable conformity. The ambition is that the results from the aforementioned studies could be used for sprays in other industrial applications such as diesel or urea spray in the automotive industry since these applications use the same models for simulating spray behaviour.