Assessing effects of different opening combinations on airflow pattern and air exchange rate of a naturally ventilated dairy building –A CFD approach

Ventilation airflow in buildings is paramount important for creating comfortable environment with acceptable indoor air quality by regulating indoor air parameters, such as air temperature, relative humidity, air speed, and concentrations of chemical species in the air. Airflow inside naturally ventilated dairy (NVD) building is highly variable because of the direct effect of outside weather and large openings. It is difficult to understand airflow characteristics and estimate air exchange rate (AER) precisely with the existing methods. Computational fluid dynamics (CFD) based numerical simulation would be alternative to full scale and scale model experiments for understanding airflow characteristics of an NVD building. The aim of the study was to investigate the effect of different seasonal opening combinations of an NVD building on airflow patterns and AER in and outside of the NVD building using CFD. Typical NVD building located in Northeast Germany was selected for model development and simulation which was designed to accommodate 364 dairy cows. ANSYS 14.5 was used for creating model geometry, meshing and simulation. The standard kinetic energy (k)-dissipation (ε) turbulence model was used for all simulations. In order to improve the quality of CFD calculations, i.e. to make calculations with sufficient accuracy, several important issues (e.g. grid independency and convergence criteria etc) were considered carefully for both the governing equations and the computation. Common seasonal practices in the NVD building were considered as opening combinations for simulation. The opening combinations were namely middle of both sidewalls open (SW), middle and bottom parts of both sidewalls open (SWB), middle and top parts of both sidewalls open (SWT), both sidewalls completely open (SWC), middle and bottom parts of sidewalls and all doors open (SWBD), middle and top parts of sidewalls and all doors open