SPATIAL DISTRIBUTION OF AIR FLOW AND CO2 CONCENTRATION IN A NATURALLY VENTILATED DAIRY BUILDING

Abstract

Air flow measurements as well as concentration measurements within a naturally ventilated dairy barn (NVD) were carried out during one summer season of 2012. Air flow measurements were performed using ultrasonic anemometers (UA), either as short duration (20 min duration) measurements with a higher spatial distribution (using up to 9 UAs at the same time) or as long period (roughly 2 weeks) measurements with a lower spatial resolution (3 to 5 UAs). Measurements were conducted at two heights, at 1.5 m within the animal occupied zone (AOZ) and at 2.6 m height above the AOZ for understanding the distribution of airflow within the building. The three wind components (u, v and w) were measured either as lateral profile or evenly distributed at the ground area of the building. The results showed that wind speeds measured at the height 2.6 m were generally smaller than wind speeds measured at the height 1.5 m. The analysis of the lateral profile showed that only the first third of the wind facing side seem to benefit from the approaching wind. The long term measurements (duration 2 weeks) showed a high variability in the data and a correlation analysis showed lower CO2 concentrations for higher wind speeds. However, the linear correlation was weak (p= -0.7), which implies that the relationship cannot be described simply by a linear correlation.