A study on the effectiveness of microwave heating for disinfection of humidifier elements

In this study, microwave irradiation was tested as a possible means to disinfect evaporative humidifiers in air-conditioning systems. A mock-up of a humidifier was prepared to identify the applicability of the microwave irradiation system. To characterize the heating properties of this system under optimum operating conditions, the temperature distribution of the humidifier element was measured as a function of various parameters. Variables included the use of ventilation and water spraying during microwave irradiation, the level of radiation output power and whether the element was dry or wet. The results showed that microwave irradiation can heat the evaporative humidifier element about 60°C at 1200 W for exposure times greater than 3 min under nonoperating conditions (without air blower and water spraying). However, the temperature distribution of the element was nonuniform, regardless of whether the conditions were dry or wet. The effectiveness of microwave heating is limited due to nonuniform distribution of temperature. To achieve a uniform surface temperature on the element, further studies are necessary.