English

The intention of this paper is not to compare discretization schemes but to show some advantages of a stabilized finite element method for modelling natural ventilation. Based on the finite element theory we present a formulation of boundary conditions that can be used for most ventilation openings in buildings. Stationary as well as transient situations can be considered without modelling of the outdoor space. Mathematical background and implementation details are discussed. Results are presented for ventilation of a living room at typical outdoor conditions.

The effect of the change in object positions (i.e. office furniture) on the air quality in a room was studied using zonal purging flow rates. In relation to the zonal purging flow rate in a room, the transfer probability from the inlet to a certain zone can provide information on the amount of fresh air from the inlet to the zone. In this study, the probability obtained from Markov chain theory was used to analyze the ventilation performance.

The keeping of animals in livestock buildings requires the ventilation of these buildings. On the one hand good climatic conditions for the animals in the livestock building have to be provided, on the other hand the emissions have to be kept at a low level. The airflow through the livestock building plays an important role for both opposing requirements. The targeted control of the climate in the livestock building and for the minimization of emissions calls for knowledge about airflow and emission streams.

Presented in the paper is an efficient and accurate numerical method for simulation of ventilation duct flow. The mathematical method is based on the three-dimensional incompressible RANS equations with isotropic k-w near-wall turbulence closures, written in generalized curvilinear coordinates in strong conservation form. The numerical method presented here is used to calculate the turbulent flow through a bend of rectangular ventilation duct featuring pressure induced secondary motions and rotation effects on turbulence.

In the frame of a Swiss research project, a passive tracer gas technique for the determination of multizone air flow and contaminant transport in buildings was tested, based on previous work in several other countries. First emission characteristics of the three different sources (PMCP, PMCH and o-PDCH) and the adsorption characteristics of the passive samplers (standard Perkin-Elmer AD400 adsorption tubes) were established.

This work is centered on the transient analysis of natural ventilation provided by a single side opening when only indoor-outdoor temperature differences are present (no wind). Using both simplified "engineering" models and a CFD commercial code (2D), different cases have been examined by varying indoor-outdoor temperature difference, window size, and including or not a heating appliance in the room.

In an air-conditioned office building, the ventilation air is normally mixed with the return air from the room in the air-handling unit. Therefore, the value of the air exchange efficiency defined by age of air is usually about 1.0, which is close to the perfect mixing case. If the fresh air and air-conditioning air are supplied separately, it is possible to increase the value of the air exchange efficiency at the breathing zone if the former is supplied directly to the breathing zone. In this paper, the results of the CFD investigations for the ventilation tower system are described.

The Particle Streak Tracking System (PST) is a fast method to measure two- and three-dimensional velocity fields in room air flows with measuring areas up to 5 m2. The two-dimensional method works with a single pulsed white light sheet and one digital camera. For three-dimensional velocity measurements in planes a laser light sheet system using three separate laser sheets with two different wavelengths and two CCD-cameras is employed. To visualise the flow helium filled bubbles are used. A description of the set-up will be given and the data evaluation process will be explained.