"Experimental and numerical analysis of conjugate heat and mass transfer phenomena in food freezing using hydrofluidisation impingement method"

The research plan of the CoolFood project is proposed in this manner that each activity devoted to the numerical model formulation and validation is accompanied by the experimental activities performed on the designed test rig. Both types of these activities are performed in parallel. Such an approach results in the effective input and validation data transfer. In the first activities, numerical and experimental determination of the refrigerant flow around a single or a group of products in a various set of the operating conditions and geometrical configurations of the test rig is studied. In the next step, the mathematical model developed in the previous activities is completed with heat and mass transfer in the real food product, while in the experiments, the product temperature is monitored at more locations than in the centre only. In the most important last two activities, a horizontal motion of the food products is considered, which makes such a laboratory study closer to the real industrial process.

All the computational tasks to determine the heat and fluid flow in the domain are performed using commercial Ansys Fluent software installed on the computing clusters at the Institute of Thermal Technology of the Silesian University of Technology. Because of the freezing process character, the mathematical model is formulated as a transient one. In the first phase of the project, the refrigerant flow over the product is defined using a single-phase model. Then the obtained results are compared with those obtained from the simultaneously developed two-phase flow model. The liquid refrigerant and atmospheric air are the phases in this model.

In order to validate the temperature and the velocity fields, the experimental results will be recorded by thermocouples within the artificial product and the PIV technique in the surrounding working fluid. The experimental tests will be run for a number of flow conditions, configuration of the perforated plate, distance and shape of the product, the averaged and local values of the heat transfer coefficients on a surface of the considered products will be determined On the basis of the developed model, while the effective freezing times will be obtained from the experimental tests.