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Optimized positioning of exhaust air to improve ventilation effectiveness and energy efficiency with turbulent mixing ventilation

Project details
Project term
December 2018 to May 2021
Funding code
IGF-No: 20440 N
Project management
Gerrid Brockmann

Turbulent mixing ventilation is the most common type of ventilation in buildings. Depending on the type and position of the material loads and the structure of the room air flow, the exhaust air has a considerable influence on the distribution and removal of the contamination, for example from building products or from people in the room.

The flow pattern typical of mixed air systems is characterized by an air movement that is intended to cover the entire room. However, the completely homogeneous dilution of the substance concentrations is an ideal case which cannot be achieved in real ventilation situations. Often the local ventilation efficiency at many places in the room is clearly lower than in the ideal case. The local concentration of contamination increases drastically. In addition, there are often significant flow short-circuits between supply and exhaust air, which reduces the possible ventilation effectiveness and represents an energy loss.

The stagnation areas can be resolved and flow short circuits can be prevented by positioning the exhaust air openings at the ideal place. At the moment, only insufficient models and planning rules exist to take this into account when planning the exhaust air configuration of the air guidance system. Within the research project the influence of position and number of exhaust air openings on the ventilation efficiency of different air duct systems for turbulent mixing ventilation is investigated. Further the load condition, the strength and position of heat sources and contamination sources are considered. For the investigation experimental measurements in a flow laboratory as well as detailed CFD simulations are carried out. Aim of the project are rules and recommendations for the positioning and design of the exhaust air openings. On the basis of this knowledge gain, adapted exhaust air diffusers for more efficient ventilation systems can be developed by the manufacturers.




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