A Study On Microwave Sterilization Technology In Central Air Conditioning System

The problem of fungal microbial contamination in central air conditioning system is one of the main problems of biological pollution in the building environment.Especially after the outbreak of SARS in 2003,the biological pollution problem of air conditioning system seriously affects people’s health safety.It is of great significance to carry out the basic research of biological pollution control in centralized air conditioning system.The sterilization mechanism,the penetration and the selective heating properties of microwaves determine its wide application prospects in the field of HVAC sterilization.First,through the measurement of biological pollution and DNA high throughput sequencing analysis of a air conditioning unit and a large number of domestic and international survey research reviews,it is determined that the genus and Cladosporium spp.and Penicillium spp.are the dominant fungi in the air conditioning systems.Through microwave sterilization experiment under ideal condition,the sterilization efficiency of microwave for Cladosporium sp.and Penicillium funiculosum was measured by dry weight and colony counting method.The microwave radiation conditions of killing dominant fungi microbes in the air conditioning system in the air conditioning system were determined by 500 W treatment 60 s and 700 W treatment 40 s.The inactivation temperature of fungi in air conditioning system was preliminary determined to be 59℃ under microwave treatment.Second,based on the basic experiment of microwave sterilization,the experiment platform of microwave sterilization in the laboratory scale air conditioning system is set up.The experimental platform takes the humidifier parts of the air conditioning system as the research object and it can determine the different microwave output power,the operating condition of the air conditioning system,the shape of the humidifier and the metal occlusion effect of microwave sterilization.The experimental platform is closely integrated with HVAC features,coupled with several parameters affecting the microwave sterilization,and the control parameters are comprehensive.Third,the temperature distribution,uniformity and sterilization effect of microwave sterilization in the humidifier part of the centralized air conditioning system were studied by the experiment of microwave sterilization in the laboratory scale air conditioning system.The study shows that microwave sterilization can not achieve good sterilization due to the short processing time of the floating air in the air conditioner,so microwave sterilization is mainly aimed at the surface of the components.The microwave sterilization device is most suitable for the non operating condition of the air conditioning system,and in some special cases,it can also be used in the operation of the air conditioning system,because the microwave sterilization has only a minimal effect on the air conditioning system parameters.The microwave sterilization experiment was set up by microwave heating and sterilization experiment.The microwave sterilization method was measured by t sterilization temperature and sterilization rate.The temperature distribution and microwave sterilization experiment of the components after microwave heating were verified.The results showed that the results of microwave heating experiment and microwave sterilization experiment were basically corresponding,a good sterilization effect can be achieved under the power of 900 W after 5 minutes.The optimum sterilization temperature is 59 ℃ with a certain accuracy.It can be used as an effective temperature value for microwave sterilization in engineering field.Microwave sterilization has a wide application prospect in the field of HVAC.Finally,the CST software was used to simulate the microware absorption power of the components.It was verified with the sterilization experiment,and the uniformity of the microwave sterilization was predicted.The sterilization effect of the central part was best and the sterilization effect at the bottom was not good enough.In the application,the agitator and the reflecting plate should be used to promote the microwave reflection and the convection of the hot air,so as to change the temperature distribution in the air handling unit and achieve a more uniform sterilization effect.