Using Computational Fluid Dynamics to Evaluate the Impact of Convection Currents of Liquid Food for Simulating High Pressure Processing

Temperature, velocity and pressure profiles during the early stages of high pressure compression of liquid food (water), within a three dimensional cylinder basket are simulated in this work. The computations domain was performed for a cylinder with a diameter of 38 mm and height of 290 mm, which are the same dimensions as those of the high pressure unit FOOD-LAB model S-FL-850-9-W used for measurements. Direct processing of water at pressure level of 500 MPa and a pressure holding time of 970 s is simulated. Pressure is assumed to rise from atmospheric pressure to the treatment pressure linearly by enforced mass flow. The governing equations for continuity, momentum and energy conservation are solved using a commercial Computational Fluid Dynamics (CFD) package (PHOENICS), version 3.5, which is based on a finite volume method of solution. The objective of this research was to study the impact of convection currents. The simulation for the liquid food shows for the first time, the effect of forced and free convection flow, on the temperature distribution in the liquid at the early stages of compression. This is due to the difference between the velocity of the pumping fluid as it enters the cylinder inlet hole (10-2 to 10-3) m/s and the velocity in the treatment chamber (10-8-10-9) m/s. Validation of the computed temperature at the different height at the axis of the cylinder are in a good agreement with those measured experimentally.