Plume rise from free burning fires

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
• ?H1.6Fb1/3(u)-1xf2/3
• where Fb8/pV(Ts-Ta)/Ts is the
  buoyancy flux

4
Introduction

• Briggs plume rise equations
• in convective conditions
• ?H3.0(Fb/u)3/5H-2/5
• where H(g/T0)(w?)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
• Carters model

8
Approach

• Mills model
• Briggs plume rise equation
• altered into
• ?H(?hB)3(L/2?)31/3-L/2?
• Fb0.037QH assuming Ta293K
• L diameter of the fire

?hB1.6Fb1/3(u)-1xf2/3
9
Approach

• The Briggs equation becomes
• (1) heat produced is reduced by 30
• (2) L/2? 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. ? 0.6, entrainment coefficient for
  buoyant plume rise

?h0.47QH1/3(u)-1xf2/3
10
Approach

• Carters model
• Moores formula modified into
• ?h0.512f/u ?T0.125gQX2(X27L)/(CpTa)
  0.25
• where
• XXXt(X2Xt2)-0.5
• XtXsXn(Xs2Xn2)-0.5
• Xs120ue-0.5
• Xn192019.2Z or 4224 if Zgt120m
• f0.160.007Z if Zlt120m
• f1 if Zgt120m or u-2egt2.5e-3

11
Approach

• Carters 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 Mills 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