The software automatically calculates wind area for a flare tip as follows:
The area is stated as an effective area per unit length. For example, if we calculate an area of 3 ft^2/ft or 3 ft that means that the flare tip has an effective width of 3 ft over it's length. If a flare tip is 10 ft long then the total wind area will be 3 ft^2/ft*10 ft = 30 ft^2.
Cf_riser - Shape factor of Riser which is automatically determined based upon wind standard selected
Cf_pipe - Shape factor for small diameter pipe which is automatically determined based upon wind standard selected
Single Point Flare Tip:
OD = Flare Tip OD, specified by user
L = Flare tip length, specified by user
N = Number of Pilots
UtilityOD = Utility Pipe OD of 1.315 inch [33.4 mm] [This value is hard coded and can't be altered]
The assumption is that there are two utility lines per pilot and that they are each 1 inch nominal diameter
Wind Area = Cf_riser*OD + N*Cf_pipe*2*UtlityOD
For example:
Cf_Riser = 0.7
OD = 36 inch [914 mm]
NumPilots = 3
CfPipe = 1.2
L = 10 ft [3.048 m]
Imperial Units: Wind Area = 0.7*(36/12) + 3*1.2*2*(1.315/12) = 2.889 ft in or 2.889 ft^2/ft
Total Wind Area = 2.889*10 = 28.89 ft^2
Metric Units: Wind Area = 0.7 * 0.914 + 3*1.2*2*0.0334 =0.881 m or 0.881 m^2/m
Total Wind Area = 0.881*3.048 = 2.685 m^2
Multi-Point Flare Tip:
TipOD - The OD at the base of the flare tip, specified by user
Lb = The length of the larger diameter barrel at the base of the tip, specified by user
Darm = Outer Diameter of Multi-Point arms, specified by user
Narm = Quantity of Multi-point arms, specified by user
Wind Area Total = Cf_riser*OD*Lb + Cf_pipe*N*2*UtilityOD*L+Cf_pipe*Darm*Narm*(L-Lb)
Wind Area = Wind Area Total / L
For example,
Cf_Riser = 0.7
OD = 36 inch [914 mm]
NumPilots = 3
CfPipe = 1.2
L = 10 ft [3.048 m]
Lb = 4 ft [1.219 m]
Darm = 4.5 in [ 114.3 mm]
Narm = 8
Imperial Units: Wind Area Total = 0.7*3*4 + 1.2*3*2*(1.315/12)*10 + 1.2*(4.5/12)*8*(10-4) = 33.945 ft^2
Wind Area = 33.945 / 10 = 3.3945 ft^2/ft
Metric Units: Wind Area Total = 0.7*0.914*1.219 + 1.2*3*2*0.0334*3.048 = 1.2*0.114*8*(3.048-1.219) = 3.154 m^2
Wind Area = 3.154 / 3.048 = 1.035 m^2/m