CFD simulations of RTD of a strawberry pulp in a continuous ohmic heater

A pilot ohmic heater is to be tested for the continuous aseptic processing of strawberry pulps and jams. The hydrodynamics and the fluid residence time distribution (RTD) have been experimentally investigated for Newtonian and non-Newtonian fluids (water and an industrial strawberry pulp, respectively), for several inlet flow rates. The results were obtained using Computational Fluid Dynamics (CFD) with a user-defined function (UDF) description of the fluid phase (pulp). For all of the conditions tested the fluid phase is described using the laminar flow model. The results show that the RTD is affected by the inlet flow rate but not so significantly by the process temperature. Some shortcuts and dead zones were detected in the ohmic heater specially for Newtonian fluids. The heater behaves like a piston flow with longitudinal mixing.