Modeling of fluid dynamics and water vapor transport in microwave ovens

Abstract

This work was aimed to study the water vapor transport inside microwave ovens (MWO), both experimentally and through mathematical modeling and simulation. The evaporated water from foods must be purged from the oven to prevent its accumulation. When vapor reaches the oven cold walls, it may condense and produces drops, which continue to grow until they eventually fall. This can cause damage to the containers due to the rapid heating of the water on them. In this work, the airflow circulating inside an MWO was experimentally determined. Afterwards, a 3D model of the MWO geometry was built and the air inlet and outlet sections were approximated with rectangles. Given the low measured airflow a laminar model was sufficient to simulate the airflow inside the oven. Various airflow simulations were performed inside the oven. After that, heating experiments with water in a glass were carried out (power: 10, 20 and 30%); the humidity and temperature of the outlet air and the water temperature on the glass during the process were measured. Subsequently, the geometry of the glass with water and the magnetron and waveguide were incorporated into the model, in such a way that includes the energy and mass balance. The electromagnetic field in the oven and the fluid dynamics in air were solved in steady state, and then the velocity field was used to solve the energy and mass balance in transient state in the air. The accuracy of humidity and temperature predictions were acceptable compared to the experimental values.