Computational Fluid Dynamics (CFD) Study on the Influence of Airflow Patterns on Carbon Dioxide Distribution and Emission Rate in a Scaled Livestock Building Li Rong 1), Peter V. Nielsen 1), GuoHong Tong 2) Guoqiang Zhang 3), Peter Ravn 3) 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

Outline Introduction Validation of CFD model Results Conclusion

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

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

Boundary condition Isothermal case Inlet: velocity in m/s, turbulence intensity in 5% and automatic turbulence length scale, CO 2 concentration in 900mg/m 3 Outlet: average pressure in 0Pa Floor: CO 2 concentration in 2000mg/m 3 Other walls: with no CO 2 emission Turbulence model model

Vector and CO 2 concentration distribution (a) Vector and CO 2 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

Definition of non-dimensional CO 2 concentration Non-dimensional CO2 concentration CO2 concentration inside the building Inlet CO2 concentration Outlet CO2 concentration

Definition of non-dimensional CO 2 concentration (a) 45 degree deflector setting model (b) 90 degree deflector setting model Figure 4 comparison of non-dimensional CO 2 concentration between measurements and simulations at y=0.51m, z=0.31m

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 Results

Influence of airflow rate on non-dimensional CO 2 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

(a) 45 degree (b) 90 degree Figure 5 non-dimensional CO 2 distribution along the line with y=0.51m, z=0.31m Figure 6 influence of airflow rate on emission rate

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 Figure 7 models in simulation with an extra outlet 1 － inlet, 2 － outlet 1, 3 － deflector, 4 － the slatted floor, 5 － manure surface, 6 － outlet 2

Boundary conditions Isothermal case Inlet: velocity in m/s, turbulence intensity in 5% and automatic turbulence length scale, CO 2 concentration in 900mg/m 3 Outlet 1: average pressure in 0Pa Outlet 2: 10%, 15%, 20%, 30% of ventilation rate Floor: CO 2 concentration in 2000mg/m 3 Other walls: with no CO 2 emission Turbulence model model

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

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

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

Thank you very much!