This paper is concerned with measurement of airflow in ducts using an active (pumped) sampling system. The system is capable of sampling tracer gases using either tubes packed with adsorbent or sample bags. A perfluorocarbon tracer (PFT) was injected into the ducts using thermostatically-controlled heating blocks. The samples were collected and analysed using a thermal desorber/gas analyser system. Laboratory and field testing of airflow in ducts was carried out. A large office building was studied for measurements of ventilation rate, ventilation efficiency and air quality.
A new model concept has been developed to model the three dimensional energy and mass transfer in an imperfectly mixed fluid. The model permits to predict the dynamic behaviour of the volumetric concentration of heat flow, mass flow and fluid flow. A laboratory test installation has been built to analyse the model capabilities to predict the dynamic behaviour of the air flow pattern within a ventilated space in order to control the energy and mass transfer in the ventilated space.
One of essential problems of the present research related to building analyses is air flows determination. Air flows not only cause energy consumption but also influence air quality parameters, specially in a multizone (and high) buildings. Thepaper presents the main assumptions of the newly developed simulation method. The major departures are addressed which distinguish this alternative method from other multizone models.These include the principles of dividing a dwelling house into zones and the accomplishment of the simulation.
The use of sulphur hexafluoride (SF6), nitrous oxide (N2O) or carbon dioxide (CO2) as tracer-gases have been examined for the measurement of airflow in a two-zone environmental chamber. A series of measurements were carried out to examine airflows through a doorway under natural convection, forced convection and combined natural and forced convection. Results were compared with those predicted using the MULTIC computer program.
The LESO building is a three storey, medium-sized office building on the campus of the Swiss Institute of Technology in Lausanne. In this building component leakages have been carefully determined followed by extensive measurements of the boundary conditions as well as the air flows. This paper first gives some basic concepts of the evaluation and the sensitivity analysis. Then, the measured data are compared with results from simulations performed with the COMIS multizone air flow program.
It has been shown that thermal imaging can give an indication of air flow rates through small cracks. Using a finite difference analysis package it is possible to determine the surface temperature of an air transfer grille when subjected to airflow rates at higher temperatures than the grille surface. This paper will address this technique by presenting the results of the finite difference analysis package for a specific grille.
Multizone models are a common tool for calculating air and contaminant exchange within rooms of a building and between building and outside. Usually a whole room is then modelled by one calculation node with the assumption of homogeneously mixed conditions within this room. In real cases, however, temperature and contaminant concentrations vary in space. The exchange to the neighbouring nodes via the flow paths is then a function of the local values of these variables.
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