Mathematical modeling of continuous flow microwave heating of liquids (effects of dielectric properties and design parameters)

A detailed numerical model is presented to study heat transfer in liquids as they flow continuously in a circular duct that is subjected to microwave heating. Three types of food liquids are investigated: apple sauce, skim milk, and tomato sauce. The transient Maxwell's equations are solved by the finite difference time domain (FDTD) method to describe the electromagnetic field in the microwave cavity and the waveguide. The temperature field inside the applicator duct is determined by the solution of the momentum, energy, and Maxwell's equations. Simulations aid in understanding the effects of dielectric properties of the fluid, the applicator diameter and its location, as well as the geometry of the microwave cavity on the heating process. Numerical results show that the heating pattern strongly depends on the dielectric properties of the fluid in the duct and the geometry of the microwave heating system.