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Influence of Airflow Patterns on CO2 Distribution in Livestock Building: CFD Study

This computational fluid dynamics study assesses the impact of ventilation system variations on CO2 distribution and emission rates in a scaled livestock building. Conclusion underscores the importance of airflow patterns.

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Influence of Airflow Patterns on CO2 Distribution in Livestock Building: CFD Study

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  1. Computational Fluid Dynamics (CFD) Study on the Influence of Airflow Patterns on Carbon Dioxide Distribution and Emission Rate in a Scaled Livestock Building Li Rong1), Peter V. Nielsen1), GuoHong Tong2) Guoqiang Zhang3), Peter Ravn3) 1)Department of Civil Engineering, Aalborg University 2) Shenyang Agricultural University , China 3) Department of Agricultural Engineering, Research Centre Bygholm, University of Aarhus 24/06/2008

  2. Outline • Introduction • Validation of CFD model • Results • Conclusion

  3. Introduction • Concentration distribution inside the livestock building relating to: ventilation system heat condition manure condition etc. • Objective of this paper is to investigate the influence of the ventilation system on concentration distribution

  4. Validation of CFD model (a) Model in experiment 2.2m*0.62m*2.41m (b)45 degree deflector setting model (c) 90 degree deflector setting model 1－inlet, 2－outlet, 3－deflector, 4－slatted floor, ‘﹡’－measurement points Figure 1 models in experiment and simulations

  5. Boundary condition • Isothermal case • Inlet: velocity in 0.2196m/s, turbulence intensity in 5% and automatic turbulence length scale, CO2 concentration in 900mg/m3 • Outlet: average pressure in 0Pa • Floor: CO2 concentration in 2000mg/m3 • Other walls: with no CO2 emission Turbulence model model

  6. Vector and CO2 concentration distribution (a) Vector and CO2 distribution in 45 degree setting model (b) Vector and CO2 distribution in 90 degree setting model Figure 2 vector and CO2 concentration distribution at Z=0.31m

  7. Definition of non-dimensional CO2 concentration Non-dimensional CO2 concentration CO2 concentration inside the building Inlet CO2 concentration Outlet CO2 concentration

  8. Definition of non-dimensional CO2 concentration (b) 90 degree deflector setting model (a) 45 degree deflector setting model Figure 4 comparison of non-dimensional CO2 concentration between measurements and simulations at y=0.51m, z=0.31m

  9. Results • Influence of airflow rate on non-dimensional CO2 concentration • Influence of airflow rate on emission rate • Influence of an extra outlet setting below the slatted floor on emission rate

  10. Influence of airflow rate on non-dimensional CO2 concentration distribution and emission rate Boundary conditions • Airflow rate including 100, 150, 200m3/h • Isothermal cases • Floor: with CO2 concentration in 2000mg/m3 • Other walls: with no CO2 emission • Deflector: 45 degree, 90 degree

  11. (a) 45 degree Figure 6 influence of airflow rate on emission rate (b) 90 degree Figure 5 non-dimensional CO2 distribution along the line with y=0.51m, z=0.31m

  12. Influence of setting an extra outlet below the slatted floor on emission rate (a) Left model, outlet 2 located at y=0.13m on the left (b) Right model, outlet 2 located at y=0.13m on the right (c) Top left model, outlet 2 located at y=0.235m on the left (d) Top right model, outlet 2 located at y=0.235m on the right side 1－inlet, 2－outlet 1, 3－deflector, 4－the slatted floor, 5－manure surface, 6－outlet 2 Figure 7 models in simulation with an extra outlet

  13. Boundary conditions • Isothermal case • Inlet: velocity in 0.2196m/s, turbulence intensity in 5% and automatic turbulence length scale, CO2 concentration in 900mg/m3 • Outlet 1: average pressure in 0Pa • Outlet 2: 10%, 15%, 20%, 30% of ventilation rate • Floor: CO2 concentration in 2000mg/m3 • Other walls: with no CO2 emission Turbulence model model

  14. (b) Emission rate from outlet 1 (a) Total emission rate from outlet 1 and outlet 2 Figure 8 Influence of setting an extra outlet below the slatted floor on emission rate in 45 degree deflector setting models

  15. (b) Emission rate from outlet 1 (a) Total emission rate from outlet 1 and outlet 2 Figure 9 Influence of setting an extra outlet below the slatted floor on emission rate in 90 degree deflector setting models

  16. Conclusion • K-e model is an appropriate model to predict concentration distribution in this case • Airflow patterns have an important effect on concentration distribution and the emission rate increases with increasing the airflow rate as expected • Setting an extra outlet below the slatted floor can decrease the emission rate if the contaminants can be cleaned completely from this outlet and the emission rate will decrease when the percent of the ventilation rate from the outlet below the slatted floor increases in these cases

  17. Thank you very much!

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