Effect of operating and geometric parameters on microwave heating of fluid in continuous mode

The effect of diameter of helical tube and liquid permittivity was investigated on the performance of continuous microwaveheating by coupling electromagnetic equations, heat transfer and laminar flow in COMSOL Multiphysics software. Themodel was implemented numerically using the finite element method and validated with experimental data obtained from akitchen microwave oven. The results for water as handling fluid show that electromagnetic energy and temperaturedistribution are sensitive to tube diameter and input power. As the input power and the loss factor of aqueous phase increase,more electromagnetic energy is converted to heat to reduce the electrical intensity and this lead to more temperaturedifferences and efficiency. Moreover, considering a constant residence time of liquid in MW oven, the optimum diameter ofhelical tube is obtained ۶ and ۴ mm for to the highest energy conversion efficiency and the highest outlet temperature,respectively.

Keywords:

microwave heating , continuous mode , fluid permittivity , tube diameter , thermal field