The objective of this work was to develop both an accurate ‘reference’ measurement technique to determine ventilation rate through naturally ventilated buildings and a ‘practical’ direct measuring principle for online and continuous field measurements of ventilation rate through naturally ventilated sections. Using tracer-gas decay technique to analyse 444 laboratory experiments in a ventilated room with a ‘reference’ technique for scientific and calibration purposes revealed 35% inaccuracy. Aside the assumption of perfectly mixing, zonal modelling approach has been used for post-processing of tracer-gas data and allowed 14% inaccuracy even at low ventilation rates. To develop a measuring sensor for continuous use in farms with natural ventilation system, two measuring principles have been tested in laboratory conditions: 1) heat dissipation from the heat source at 17 different ventilation rates of a test room in comparison with an accurate ventilation reference measurement. This technique provided 15% inaccuracy as an average of all laboratory experiments. 2) Transit time sonic anemometers were developed for a large scale section by using 16 acoustical lines. They were tested in a chimney with a large diameter (Φ = 0.80 m) and a length of 1.1 m. In total 980 experiments were realised in combination with a reference technique and resulted in 9% inaccuracy even at disturbed flow conditions.status: publishe
