This article briefly describes a new piece of apparatus, recently developed at UMIST, which can be used for the determination of ventilation rates in, and air movement rates between, four interconnected cells.
Air movement within enclosures, which may result from a combination of infiltration, mechanical ventilation and convective heat transfer effects, is important for considerations of thermal comfort, ventilation efficiency and energy conservation.
The main air and contaminant flow paths or the spatial distribution of the age of air (or contaminant) in a room are of great interest to estimate the ventilation efficiency performance. A simple measurement method is presented, which consists to inject or more tracer gases at locations of interest and to analyze the concentration at several other locations, carefully chosen for best accuracy. Response functions can be fitted on these measurements, which are the age of the tracers or of the air or the concentration of the tracers in function of the location.
As part of the IEA Research Program Annex 18 "Demand Controlled Ventilating Systems" were tested in a one-family testhouse in relating to energy and ventilating specific aspects. The investigation should show whether demand controlled systems are useful in dwellings or not. Following items were checked: * Infiltration characteristics of the testhouse * Ventilation characteristics of different systems like temperature distribution, air movement, ventilating efficiency, air exchange and air quality.
The predominant route for air movements between the floors of two-storey dwellings is via the stairwell. Such air movements are of significance in the assessment of building performance: for instance, it is possible that moisture could be transferred from ground floor areas to rooms on the first floor, resulting in an increase in condensation risk in such rooms. Several domestic heating schemes have been designed such that heating appliances are provided on the ground floor only; the upper floor relying on convective airflows for heating.
An appropriate way to identify the most efficient ventilation systems and improve their design is to use design codes for ventilation rates. These rates are strongly influenced by spatial and temporal fluctuations in wind pressure on the facade and roof. The influence of the effects of wind on ventilation was studied using a model which includes air compressibility, together with the pressure field measured on a model in a boundary layer wind tunnel. The simulation results obtained are analyzed using a design code.
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