English

A comprehensive investigation was made of the dynamic behavior of five low-velocity thermal anemometers with omnidirectional sensors. Both the shape of the dynamic response curves of the instruments and their dynamic response were different. The dynamic response of the anemometers was mainly influenced by the frequency of the velocity fluctuations and only slightly by the mean velocity of the airflow and the amplitude of the velocity fluctuations.

The airflow in buildings involves a combination of many different flow elements. It is, therefore, difficult to find an adequate, all-round turbulence model covering all aspects. Consequently, it is appropriate and economical to choose turbulence models according to the situation that is to be predicted. This paper discusses the use of different turbulence models and their advantages in given situations. As an example, it is shown that a simple zero-equation model can be used for the prediction of special situations as flow with a low level of turbulence.

Knowledge of room air distribution, including its flow and temperature characteristics, is very important to HVAC engineers. This study numerically predicts the air distribution in a room with differentially heated vertical walls. The Rayleigh number in the room is around 2.6-3x 10¹⁰. Time averaged equations of continuity, momentum, and energy are numerically solved by the finite volume method. Three turbulence models, the "standard" k-E model, and two low-Reynolds-number k-E models, are employed to simulate turbulent natural convection in the room.

A three-dimensional, large eddy simulation (LES) model developed for studying the transport of smoke and hot gases during a fire in an enclosure is described. The model uses finite difference techniques to solve the Navier-Stokes equations with an approach emphasizing high spatial resolution and efficient flow-solving techniques. The model uses the Smagorinsky subgrid-scale model. The LES model with Smagorinsky subgrid-scale model was applied to ventilation aiiflow in a three-dimensional room.

The Field and Laboratory Emission Cell (FLEC) is a tool for non-destructive emission testing of materials with even surfaces. Measurement of air velocities inside the cell showed an inhomogenous flow field with a high-velocity area around the inlet axis and an area of comparatively low air velocities perpendicular to the inlet axis. These results suggest that punctual emission sources may lead to different VOC-concentrations depending on the position of the source.