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.
The use of computers for data acquisition and analysis in air exchange measurements with tracer gases has become state of the art for the researcher. However, for air exchange measurements in the field, reliable operation of the equipment and the proper reporting of the results are still points of concern. Here, the computer can assist the user in the correct handling of the tracer gas equipment, in dealing with unfavourable measurement conditions, and in the production of a readable report.
The performance of ventilation provision in subfloor cavities is relevant to the fields of energy efficiency, condensation risk, and air quality. Thorough programs of site measurements of ventilation rates by means of tracer gas tests are in general protracted and expensive, and it is quite clear that would be highly desirable to be able to predict ventilation rates given details of building design, ventilation provision, and d.egree of exposure.
This paper describes the use of tracer-gas techniques to measure airflow in a rectangular duct and a HVAC system. Experimental procedures are discussed for the application of the constant injection, pulse injection and decay techniques using N2O andSF6 as tracer gases. This paper also describes a new tracer-gas system with variable sampling speed which was used to measure the decay of tracer-gas concentration. A comparison is presented between tracer-gas measurements and those made with a pitot tube and a hot wire anemometer.
In the framework of a CEC-DGXVII demonstration project a hygroregulating natural ventilation system is being evaluated in 52 occupied apartments. Therefore a multi purpose automated tracer gas equipment has been developed enabling the detailed monitoring of air flow rates in 60 rooms continuously. In addition the humidity levels, CO2 levels and air temperatures are measured as well as the outdoor climate. The first measurement campaigns partly used for evaluation of the measurement system are reported and show an impressive amount of data enabling various types of detailed analysis.
This paper describes the activity on Air Infiltration and Ventilation of the research group of "Dipartimento di Energetica" in Politecnico of Turin. The group formed in 1988 and only at the beginning of 1990 it began to work on multizone flow analysis. The aim of the group is to set up an apparatus for air infiltration measurement comparable to those of other countries; up to now only measurements using decay technique were made in laboratory in a scale-model which represents a two-zone system.
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