Ideal Ventilation Conditions in Lecture Halls

Applied fluid dynamics in the laboratory environment at MCI

Last week, our third-semester students in Smart Building Technologies swapped the lecture hall for the laboratory – although the former still played an important role. The familiar lecture hall environment became the subject of investigation. Lecturer Manuel Berger dedicated one day per small group to the implementation of fluid dynamics concepts in the laboratory and IT environment for investigating and measuring the flow conditions in the lecture hall.

The students were able to study the flow of liquid particles in the air in lecture hall 4A-024 at the MCI Campus Technology & Life Sciences and perform simulations to improve ventilation. Measuring, controlling, and regulating in smart buildings—based on the ideal ventilation conditions for their teaching environment, this was a very tangible example from everyday student life.

Guided by Manuel Berger, the students used LDA (laser Doppler anemometry) to non-invasively determine the speed of the fluid particles in the air with stationary boundary conditions in a 1:100 scale lecture hall model using laser optics. A robot and a RobotStudio plugin developed by MCI graduates Johannes Sieberer (graduate of the MCI master's programs in Medical & Sports Technologies and Industrial Engineering & Management) and MCI employee Thomas Hausberger (Department of Mechatronics) were used for local positioning, which made this investigation possible in the first place.

In the laboratory environment, students evaluated the turbulent flow – the fluid, the liquid in the air, is an unstable variable and therefore subject to constant changes over time. The evaluation of the turbulent flow is partly automated by the non-invasive LDA software – the droplet velocity in the air is measured at individual points and used to determine how good the ventilation in the room is (velocity distribution of the droplets in the air).

Finally, the simulation evaluation took place in the computer room: The Ansys Fluent software illustrates the different levels of the room – for this purpose, the students evaluated individual measuring points at different heights. Depending on the position on the z-axis (height of the room), a differentiated picture of the flow rate in the room can be visualized. The velocity is used as an indicator of the volume flow at individual points in the measured room.

The results of the laboratory exercise show that flow simulations based on the finite volume method correspond very well with the LDA measurements. In addition, the room was simulated in its original size. The Reynolds similarity theory was confirmed by the simulation, so that investigations on a scale of 1:100 are permissible. In the laboratory environment, the students were able to measure the real conditions and simulate suggestions for improvement using the model without affecting the measurement results by their presence in the real lecture hall.