Development of novel microwave-assisted freeze-drying unit combined with natural working fluid-based refrigeration system for agriculture and marine foods
The experimental data from the reference FD unit will be used to develop and then validate the numerical CFD model of the FD chamber considering the freezing process of the sampled food, heat and mass transfer and fluid flow inside the chamber. For this reason, the three-dimensional chamber geometry and numerical grid will be generated in ICEM CFD software using high-quality structured mesh. Then the commercial ANSYS Fluent software will be used to simulate the fluid flow analysis coupled with heat and mass transfer with the phase-change process in a sample food. The coupling process of fluid flow together with the mentioned phenomena will be developed using C-code program compiled in the Fluent software as the User-Defined Function (UDF). The developed CFD approach will be verified and the mesh sensitivity analysis will be performed to avoid any influence of the numerical grid on the key parameters as the pressure and temperature distribution. Finally, the numerical solver for unsteady-state problems and the solution control will be selected to maintain the best simulation results at reasonable simulation time.Finally, a numerical solution in a transient state and a solution control will be selected to maintain the best simulation results within a reasonable simulation time. The CFD model will be validated on the basis of the results of experimental studies. A validation procedure will be performed for various food samples from agriculture and seafood. The defined accuracy of the CFD model will allow the execution of the procedure of designing the MW block connected with the FD block as part of the next research task.
The heat delivery should be in balance with drying rate of the food product, thus the development of CFD model is essential to control WM-heating unit and maintain good quality of the food product. The microwave radiation heat transfer will be the most important for providing the final design of MW-heated unit. Hence, a developed numerical CFD model coupled with the MW radiation heat transfer within close cooperation with SUT and NTNU will be used to investigate the temperature distribution inside the FD chamber as well as inside the food sample. Moreover, an analysis of the phase-change process in the food sample will be performed. A significant mechanical stresses of the vacuumed MWFD chamber will strongly influence the structure of the drying unit. Hence, the mechanical investigation will be done based on the structural analysis during vacuuming and drying processes. Moreover, the analysis of the drying process will be done within close cooperation between NTNU and SUT based on the results given from the developed CFD model in WP1 coupled with the mechanical analysis.