English

After a short introduction of the "age of air" concept in ventilation, a theorem of conservation for the age of air at the outlet is presented. Restrictions to validity and two applications (to measurements and numerical simulation) are described. A rigorous analytic proof is shown based on field theory.

The contribution of new and used fine bagfilters to indoor air pollution has been determined in a laboratory study by a trained panel as well as by TVOC measurements. The used filters were all taken out of air handling systems which run with full outdoor air supply. The time that a used filter had been situated in the ventilation system until it was taken out and was studied in the laboratory varied from two to ten months. The new filters did not pollute significantly in comparison to the used filters. However, all used filters polluted the air instead of cleaning it.

Pressure distributions around buildings are important factors affecting the air infiltration and ventilation of a building and consequently energy. Existing methods of determining pressure coefficients are costly both in terms of time and resources. This report aims to show the benefits of using a computational fluid dynamics (CFD) program in this field. Work was carried out to predict the pressure distribution around a sheltered building. The CFD program was used to investigate how pressure coeffieicnts vary with building separation and the degree of shelter offered by an upwind building.

This work examines the application of the constant-injection and pulse-injection tracer gas techniques for measurement of airflow in rectangular ducts. Experiments were carried out in ducts with aspect ratios of 1,2, and 4. Tracer gas measurements were generally similar to measurements made using a pitot tube. Relationships for the friction-factor and hydrodynamic entrance length are presented for Reynolds number between 73,300 and 395,000.

The effect of wind on building ventilation is determined by pressure coefficients that depend on many factors such as building geometry, wind direction, mean and turbulent atmospheric boundary layer velocity profiles, and thefactor to be considered here: shelter by upwind obstacles. Pressure coefficients on the exterior of building are defined by normalising the pressure difference between that measured on the surface and a reference pressure by an appropriate stagnation (or velocity) pressure.

The general purpose of heat recovery can be said to be threefold: to reduce energy use; to reduce peak power need; to increase the time constant of the building for heating and ventilation as well as domestic hot water production. In this documant the interest is concentrated on heat recovery in ventilation systems and theirinfluence on power and energy balance for buildings.

This paper discusses some inference problems in measurement programs. The 1991 Swedish energy and indoor climate survey is chosen for the purpose of illustration. The Swedish survey is carried out within the research program "Conservation of Electricity in Existing Buildings" (ELIB), consists of three projects: 1. Technical characteristics of the Swedish housing stock; 2. Indoor climate of the Swedish housing stock; 3. Energy conservation potentials in the Swedish housing stock.

The three common tracer injection strategies all proved reliable in a test chamber under complete mixing conditions. For field studies of air flow patterns in large rooms the step-up method or the pulse method is recommended to escape the initial complete mixing condition of the decay method.

Describes Germany's carbon dioxide reduction programme, which was passed in November 1990. As a step towards the protection of the global atmosphere, the extensive national programme is designed to cut back the carbon dioxide emissions in Germany by 25% by the year 2005. These values are based on the 1987 figures, so that 25% is the equivalent of 300 million tons of CO2. For the construction industry an even higher is to be achieved.

Kitchen hoods play an essential role in the ventilation of kitchens. This paper describes activities carried out at the Belgian Building Research Institute with respect tothe determination of kitchen hood efficiencies. The linkwith European standardization is also described.