English

Kitchen hoods are frequently found in Belgian kitchens. Most of them have as only function intensive ventilation during certain cooking activities. It is expected that kitchen hoods with appropriate performances can also play an important role as devices for guaranteeing basic ventilation. The aims of the research can be summarized as follows: How do occupants evaluate the performance of existing kitchen hoods? What are the sound levels (dB(A)) in various locations in these dwellings due to the kitchen hood?

A commercially available humidity controlled natural ventilation system (Aereco) has been installed in the framework of a CEC demonstration project in 3 apartment buildings in France, the Netherlands and in Belgium. An extensive monitoring campaign in reference apartments and humidity controlled apartments during the 2 previous winters allowed a detailed analysis of various ventilation related parameters. Special attention is given to the evaluation of the humidity control on the performances.

This paper evaluates the suitability of humidity-controlled house ventilation system to determine (i) the effectiveness of relative humidity as a sensing element, and (ii) the operating and performance characteristics of such ventilation strategy. The ventilation system consists of continuously running "mechanical" air extractor units and "passive" air inlet units equipped with humidity sensors. The ventilation system was installed in two single storey houses which were monitored during November 1989 to April 1990.

Seen from the AIVC Technotes 21 and 28, Ventilation Efficiency is still a complex concept. As well for measurements as for simulations. Two more or less separate terms are used: Ventilation Efficiency (-Supply Efficiency) and Ventilation Effectiveness (-Contaminant Removal Effectiveness). In thispaper is shown that the Multizone Ventilation Efficiency has a much wider range than Ventilation Efficiency within one room. In a single room efficiencies can be found for example up to 2 forvery good systems.

We describe the use of constant injection and pulse injection techniques for measurement of airflow in a duct. Tracer-gas measurements were compared with measurements made using a pitot tube and a hot-wire anemometer. Tracer-gas concentration, air velocity and pressure distribution were measured at various distances from the duct wall and inlet. An empirical equation was obtained for the entrance length required to achieve fully-developed turbulent flow and this was compared with measurements made using a pitot tube and hot-wire anemometer.

Knowledge of air movement within a building is often a condition for solving problems with the spread of pollution. The internal airflow paterns are mostly very complex and a survey of the airflow normally demands that measurements are carried out. Measuring equipment for defining air movement within buildings almost always uses the tracer gas technique. We have used two tracer gases and have kept a constant concentration of these in the polluted and the clean zones respectively. Thus enabling us to get a time history of the airflow between the two zanes.

Mechanical devices such as exhaust fans and air handlers interact strongly with natural infiltration. In the past, the effects of mechanical systems have either been treated separately from those of natural infiltration or have been combined using simple models. This paper extends the theory of the interaction of unbalanced mechanical systems with stack-driven infiltration. The effects of leakage distribution and the flow exponent on fan efficiency are discussed. A simple model for combining the two effects is presented and compared with two previously proposed models.

The study recommends adoption of the new higher ventilation rates, but with the use of alternative occupancy densities. To verify compliance with Standard 62-89, the study recommends the method of taking a ratio of temperatures to determine percent outdoor air with a total supply air measurement to determine supplied outside air for each air handler serving the building.

A passive tracer gas technique has been used in an experimental study of the distribution of contaminants in a room with displacement ventilation. Humans are simulated by heated metallic bodies and the tracer concentration in the breathing zone (exposure) is shown to be greatly influenced by both the position of the tracer source and the air convection current around the bodies. It is shown that pollutants emitted close to a body are completely and directly transported to the upper mixed zone and not mixed into the lower zone.

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.