Tracer gas dispersion in ducts - study of a new compact device usiny arrays of sonic micro jets

• Type: Article in International Scientific Journal
• Date: 2004

Authors

A. R. Silva (Author) Other; Clito Afonso (Author) FEUP

Journal

Title: Energy and Buildings

Vol. 36 No. 11

Pages: 1131-1138

ISSN: 0378-7788

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 3 Citations

Scopus - 2 Citations

Other information

Authenticus ID: P-000-7V2

DOI: 10.1016/j.enbuild.2004.04.005

Abstract (EN): One of the most feasible ways to measure duct airflows is by tracer gas techniques, especially for complex situations when the duct lengths are short as well as their access, which makes extremely difficult or impossible other methods to be implemented. One problem associated with the implementation of tracer gas technique when the ducts lengths are short is due to the impossibility of achieving complete mixing of the tracer with airflow and its sampling. In this work, the development of a new device for the injection of tracer gas in ducts is discussed as well as a new tracer-sampling device. The developed injection device has a compact tubular shape, with magnetic fixation to be easy to apply in duct walls. An array of sonic micro jets in counter current direction, with the possibility of angular movement according to its main axle ensures a complete mixing of the tracer in very short distances. The tracer-sampling device, with a very effective integration function, feeds the sampling system for analysis. Both devices were tested in a wind tunnel of approximately 21 m total length. The tests distances between injection and integration device considered were: X/Dh = 22; X/Dh = 4; X/Dh = 2; and X/Dh = 1. For very short distances of X/Dh = 2 and X/Dh = 1, semi-empirical expressions were needed. A good reproducibility of airflow rate values was obtained. These preliminary tests showed that the practical implementation of tracer gas techniques in HVAC systems for measuring airflow rates with a very short mixing distance is possible with the devices developed.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8