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On Finding the Right Sampling Line Height through a Parametric Study of Gas Dispersion in a NVB
Zitatschl├╝ssel Doumbia.2021c
Autor Doumbia, E. Moustapha and Janke, David and Yi, Qianying and Zhang, Guoqiang and Amon, Thomas and Kriegel, Martin and Hempel, Sabrina
Seiten 4560
Jahr 2021
DOI 10.3390/app11104560
Journal Applied Sciences
Jahrgang 11
Nummer 10
Zusammenfassung The tracer gas method is one of the common ways to evaluate the air exchange rate in a naturally ventilated barn. One crucial condition for the accuracy of the method is that both considered gases (pollutant and tracer) are perfectly mixed at the points where the measurements are done. In the present study, by means of computational fluids dynamics (CFD), the mixing ratio NH3/CO2 is evaluated inside a barn in order to assess under which flow conditions the common height recommendation guidelines for sampling points (sampling line and sampling net) of the tracer gas method are most valuable. Our CFD model considered a barn with a rectangular layout and four animal-occupied zones modeled as a porous medium representing pressure drop and heat entry from lying and standing cows. We studied three inflow angles and six combinations of air inlet wind speed and temperatures gradients covering the three types of convection, i.e., natural, mixed, and forced. Our results showed that few cases corresponded to a nearly perfect gas mixing ratio at the currently common recommendation of at least a 3 m measurement height, while the best height in fact lied between 1.5 m and 2.5 m for most cases.
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