1. Plume rise from free burning fires
Bo Yao
April, 2007

2. Outline
Introduction (previous work on plume rise of industrial emissions)
Approaches: two models
Experiments
Results
Conclusion
Proposed work

3. Introduction Plume rise of industrial emissions
Briggs plume rise equations:
in neutral and unstable conditions
ΔH=1.6Fb1/3(u)-1xf2/3
where Fb=8/π*V(Ts-Ta)/Ts is the buoyancy flux

4. Introduction Briggs plume rise equations: in convective conditions
ΔH=3.0(Fb/u)3/5H*-2/5
where H*=(g/T0)(w’θ’)0 is the buoyancy flux at the surface due to the combined effects of heating and evaporation

5. Introduction
Briggs plume rise equations:
in a stable environment

6. Introduction Semi-empirical equations
Apply to plume rise of industrial sources (stacks) only because they assume the heat is completely released into the plume as the plume is generated by the flare stacks

7. Approach
Mills’ model
Carter’s model

8. Approach Fb=0.037QH assuming Ta=293K L: diameter of the fire
Mill’s model
Briggs plume rise equation:
altered into:
ΔH=[(ΔhB)3+(L/2γ)3]1/3-L/2γ
Fb=0.037QH assuming Ta=293K
L: diameter of the fire
ΔhB=1.6Fb1/3(u)-1xf2/3

9. Approach The Briggs equation becomes:
(1) heat produced is reduced by 30%
(2) L/2γ is inserted in the Briggs equation to take into account the initial diameter of the plume which is considered equal to the extent of the fire. γ = 0.6, entrainment coefficient for buoyant plume rise
Δh=0.47QH1/3(u)-1xf2/3

10. Approach Carter’s model Moore’s formula modified into
Δh=0.512f/u* ΔT0.125[gQX*2(X*+27L)/(CpTa)]0.25
where
X*=XXt(X2+Xt2)-0.5
Xt=XsXn(Xs2+Xn2)-0.5
Xs=120uε-0.5
Xn= Z or if Z>120m
f= Z if Z<120m
f=1 if Z>120m or u-2ε>2.5e-3

11. Approach Carter’s model
suggested the use of Moore formula on the basis of general considerations without the peculiar characteristics of free burning fires.
so the equation is valid for plume rising from any kind of sources.
to compensate for area source, Carter estimates the virtual location of an equivalent point source.

12. Experiments

13. Experiments

14. Comparisons

15. Comparisons

16. Conclusions
The rise of plumes from free burning should not be assessed by means for common industrial emissions.
Good agreement between Mill’s model and experiments has been achieved.
Carter equation has also shown good agreement with maximum differences of about 10%

17. Proposed work More complex models numerical simulation
For larger area fires