Numerical simulation and experimental investigation of the baking process in a hybrid jet impingement and microwave (JIM) oven

Numerical simulation of the baking process in a hybrid JIM oven was carried out. The predictions were compared with experimental data. The research was divided into two parts. First, three-dimensional numerical simulation of flow field and heat transfer in a jet impingement oven with multiple jets was carried out. Distribution of local heat transfer coefficient on a model cookie in the oven cavity was obtained from the predicted flow and temperature fields, and compared with the experimentally measured values. Effects of air temperature and air velocity, location and size of the model cookie on the surface heat transfer coefficient were studied. Numerical predictions showed good agreement with the experimental results. It was found that heat transfer coefficient was a strong function of air velocity while air temperature had no effect on the heat transfer coefficient. The heat transfer coefficient values were not dependent on the location of the model cookie as well as its size.; These results were used in the second part in which the numerical simulation of baking for a model cookie (potato) in jet impingement, microwave and hybrid jet impingement and microwave (JIM) ovens to predict moisture and temperature profiles, moisture loss, and crust formation, was carved out. The mathematical model was based on the formation of a moving evaporation front at crust-crumb interface. Numerical simulation for baking of a potato cylinder was carried out by solving simultaneous heat and mass transfer equations with and without internal heat generation due to microwave energy dissipation based on Lambert's law. Temperature and moisture dependent thermal and dielectric properties were used. For impingement only heating, our model was able to accurately predict the temperature profiles. For JIM heating, temperature profile predicted by the model agreed with experimental results close to the surface of the product. However, temperature profiles close to the center were under predicted. Our model under predicted the moisture loss in both processes. The developed model was used to understand the effect of sequencing of energy modes. Sequencing of energy modes showed that moisture distributions and crust thickness depend on the path followed during the process.