Computational Fluid Dynamics (CFD) Study on the Influence of Airflow Patterns on Carbon Dioxide Distribution and Emission Rate in a Scaled Livestock Building

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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
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Outline

• Introduction
• Validation of CFD model
• Results
• Conclusion

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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

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Validation of CFD model
(a) Model in experiment 2.2m0.62m2.41m
(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
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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
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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 Z0.31m
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Definition of non-dimensional CO2 concentration
Non-dimensional CO2 concentration
CO2 concentration inside the building
Inlet CO2 concentration
Outlet CO2 concentration
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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 y0.51m, z0.31m
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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

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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

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(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 y0.51m, z0.31m
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Influence of setting an extra outlet below the
slatted floor on emission rate
(a) Left model, outlet 2 located at y0.13m on
the left
(b) Right model, outlet 2 located at y0.13m on
the right
(c) Top left model, outlet 2 located at y0.235m
on the left
(d) Top right model, outlet 2 located at y0.235m
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
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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
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(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
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(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
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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

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Thank you very much!