An electromagnetic simulation study of the distribution of the power absorbed in evaporative humidifier elements

To resolve the uneven microwave heating of an evaporative humidifier element, the distribution of the electric field in the humidifier cavity and the power absorbed in the humidifier element were investigated using a microwave simulation. The dielectric constant and loss tangent from changes in the water content of the humidifier element were measured using a rectangular waveguide method and calculated using microwave simulation to perform the electric field calculations. Then the penetration depth of microwaves in the element was identified for different water densities. The results demonstrated that the microwave could penetrate a 100-mm-thick element with a water density of 0.054 g/cm3. The simulation results indicated that the average power density lost across the cross-section of the element (thickness) was attenuated from the front face to the rear face with increasing water density. The depth profile of the power absorbed in the element agrees with the experimental results. However, the vertical profile of the power absorbed into the element did not match with heating patterns. An air fluid analysis should be undertaken in future simulations to predict the temperature change of the evaporative humidifier element.