Multiphase flow systems

Mathematical modeling of heat transfer in multiphase flow systems

– Currently started – looking for industrial partners for system design and optimization.

Multiphase flow systems in food industry are widely used such as in aseptic systems where solid and liquid phases are present. The objective in these processes are either pasteurization  or sterilization. There have been various studies reported in the literature for two phase flow systems where the purpose is to determine the residence time distribution or determine the temperature and/or flow profile. The auger systems with a continuous rotating screw used in pasteurization of solid phase flowing with liquid are also widely used in the food industry. Flow of solid-liquid mixtures are complex because particles can interact with each other, and solid particles affect the flow profile and boundaries. Especially, the increase in the solid fraction results in more complex heterogeneous flow. The use of CFD in modelling of multiphase solid-liquid flow in these systems has been limited due to the requirement of the particle tracking. With the increase of computational power,  Eulerian- Lagrangian approaches have become an option for these purposes where the trajectories of particles in the flow might be predicted. However, these methods are reported to be computationally expensive and  valid only for very dilute mixtures, i.e. < ~ 2% v/v.

There have been no studies reported in the food engineering literature regarding modeling of flow dynamics and temperature distribution in the auger systems. The residence time of the solid phase, affected by the rotation speed, distance between the pitches, concentration of the solid phase and the velocity of the liquid phase, is rather important in process design consideration since this directly affects the product quality while ensuring the safety. The objectives of this study are to obtain the flow profile and time-temperature history of solid particles in a auger related cooking system using a commercial CFD software for possible design considerations. For this objective, a lab scale system will be designed, and experiments with spherical particles in hot water will be planned to validate the model.