Mixer design for air handling unit mixing box and investigation of microbial contamination

During the mixing process of fresh air and return air in the mixing chamber of air handling units, thermal stratification occurs and mixing effectiveness decreases. This may cause energy loss and structural damage in air handling units. Therefore, the use of mixer mechanisms is recommended to ensure good mixing of fresh air and return air. In this study, a low-cost static mixer that is applicable to all air conditioning systems was designed and manufactured to increase mixing effectiveness using computational fluid dynamics. Different types of mixers were manufactured and tested experimentally in an air handling unit mixing chamber under laboratory conditions. The mixing effectiveness provided by the mixer was examined with experimental and computational fluid mechanics methods and energy and economic analyzes were made. Due to the Covid-19 epidemic occurring during the thesis study, the change of microbial contamination in air handling units with the fresh air rate was added to the thesis study. Although there is no direct relationship between contamination and mixing effectiveness, both situations are related to the fresh air ratio, and the fresh air ratio has a significant impact on operating costs. While increasing the fresh air rate for air handling units is an effective method to reduce microbial contamination in the air handling unit, another method is the devices that emit ultraviolet light inside the air handling unit. Within the scope of the thesis, the effect of ultraviolet light application on microbial contamination was also examined. It has been demonstrated that microbial contamination in air handling units can be effectively reduced by the application of ultraviolet light accompanying high fresh air flow.