English

This paper reports the results of a study to test two novel procedures to model dynamic thermal conditions of an enclosure within Computational Fluid Dynamics (CFD). The main area of investigation is the performance of the procedures in simulating the varying thermal response of the building fabric, the effects of external thermal load changes and the consequential effect on the air inside the enclosure. The dynamic thermal modelling procedures proposed utilise a transient time-varying grid schedule and Freeze-Flow techniques.

Natural ventilation studies were carried out within the frame of PASCOOL EC Research Project. Research on this topic included experimental and modelling work aiming to fill the existing gaps in our knowledge of indoor air conditions in naturally ventilated buildings. Experiments were carried out in full scale and test cell facilities during the summer period. Single sided and cross ventilation as well as air flow through large internal openings were the basic topics that were studied. Existing models were validated and new ones were developed.

The first part of the paper will show some aspects of experimental research on air distribution in ventilated rooms. The study has been carried out to get an understanding of the air movement and the ventilation effectiveness by means of tracer gas measurements. It has been investigated the velocity and the distribution of the concentration in a two-dimensional isothermal flow issue of a linear supply opening. The second part of the paper will describe a proposed zonal model in 9 zones.

Wind towers (scoops situated on the roofs of buildings to catch the wind) have been in use for centuries in the Middle east and Pakistan, to provide ventilation and cooling with minimal mechanical plant. In Europe, the problem of cooling buildings has generally not been significant, but in recent years there has been a trend towards substantial increases in internal heat gains from IT equipment etc., and overheating in summer has become one of our major concerns.

Tracer gases are commonly used to evaluate the performance of ventilation systems. One way to reduce the time, complexity, and cost of such experiments is to use the carbon dioxide generated by occupants as a tracer gas. In this paper, a method for using the carbon dioxide generated by occupants as a tracer gas for determining the effective supply air flow rate to a zone or the relative air-change effectiveness of a zone is described. The approach is to make use of a model of the accumulation dynamics and a model of the way that occupants generate carbon dioxide.

Many modern buildings in the Nordic countries have mechanical ventilation. Passive stack ventilation is, however, an accepted ventilation system in the Nordic countries according to the current building codes. The building authorities need to be able to supply guidelines on natural ventilation systems in modern buildings, in order to fullfill the requirements on a healthy indoor climate at a reasonable energy cost. Therefore a project was initiated by the Nordic committee on building regulations.