A small test room has been built which is five times smaller than the so called Annex-20-room. Different kinds of tracers have been used for visualizing of flow patterns. Velocities, concentrations and mass transfer coefficients have been measured. The measuring instrumentation is based on thermal anemometry (hot wire probes) and a special ammonia-mass transfer method, respectively, in order to estimate the heat flux coefficient at the walls.
Application of hot wirelfilm ariemometry in room air flows presents difficulties because: (1) the effect of natural convection due to the heated wire beconies significant for low air velocity measurements; (2) the angle sensitivity of a hot wire becomes small at low air velocities, which makes it difficult to resolve the direction of each velocity component. This study aimed at quantifying the uncertainty of tlie hot wire anernornetry and examining the angle sensitivity of a hot wire in low air velocity measurements.
Due to the limitations of computer storage and time the flow boundary conditions at an air inlet device have to be specified for numerical simulations of air flow patterns in rooms. With regard to this the present work gives velocity measurements near an industrial air inlet using a Laser-Doppler-Anemometer. From the stochastic velocity data the time-averaged velocity components, standard deviation and turbulent kinetic energy are evaluated.
Within the frame of the IEA Annex 20, laboratory and numerical experiments were conducted in order to study the flow within an isothermal parallepipedic testroom (L x W x H = 4.2 m x 3.6 m x 2.5 m). The air is injected through a complex diffuser (made of 84 nozzles) near the ceiling and is evacuated through a rectangular exit just below the inlet. While other participants to the Annex 20 made measurements on aeraulic testrooms, we used a hydraulic model scaled to the sixth. The parameters were determined according to a Reynolds similitude.
Conventionally used thermal anemometers are able to measure velocity, but cannot determine direction. In the present study, a new kind of thermal anemometer is presented which consists of a 38mm-diameter sphere with 12 NTC resistances on its surface. Each of them is a single Constant Temperature Anemometer which takes measurements of the local heat transfer on the surface depending on the position on the ball.