To resolve uneven microwave heating on the evaporative humidifier element, we investigate the distribution of electric field in the humidifier cavity and power absorbed in the humidifier element using microwave simulation. The dielectric constant and loss tangent by 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 in the water densities. The results demonstrated that the microwave can be penetrated into the 100 mm of the thick element with a water density of 0.054 g/cm3. The simulation results shown that the average of power loss density across the cross section of the element (thickness) was attenuated from the front face to the rear face when increased the water density. The distribution for the thickness of power absorbed in the element agrees with the experimental results. However, absorbed power into the element for vertical profile of the element did not match with heating patterns. To predict temperature change on the evaporative humidifier element, an air fluid analysis in the simulation should be undertaken.
