Initial Setup

1. Start the Flaresim program through the Windows Start button in the usual way.

2. We are going to build our first model through the Setup Wizard. For a new installation of Flaresim this will open automatically, ready to build a new model. If this does not appear then you should select the File - Preferences menu option and select the “Use Setup Wizard for New Cases”

check box on the Files & Options tab. Then select File -

°

New File Icon

New or the New File icon on the tool bar to create a new case with the Setup Wizard.

3. In the opening view of the Setup Wizard, set the unit set to Default Field as shown. Then click the Next button to move to the Fluid definition tab.

4. In the Fluid tab of the Setup Wizard, enter the following data items, using the tab key or the mouse to move from field to field.

Temperature = 300 F Mole Weight = 46.1 LHV = 21500 btu/lb Cp/Cv = 1.1

Figure 2-1, Setup Wizard Opening View

°

Note that some of these values (e.g Temperature or Cp/Cv) are originally displayed in purple colour denoting a default value. When you enter a value the colour changes to blue denoting a user specified value.

The full list of colours used by Flaresim to display values

is:-Purple for a fixed default value Red for calculated default values Blue for a user specified value

Grey for a fixed, unchangeable input value Black for a calculated result

The remaining values for Ref Pressure, LEL and Saturation can be left at their default values. The finished view is shown below

Figure 2-2, Setup Wizard Fluid Tab

LEL is used only by the Brzustowski flare radiation method.

Note that Flaresim requires the lower heating value for a fluid within its calculations. We are assuming that the value we have been given is the lower, net heating value rather than the higher, gross heating value.

Advice on the usage of each input value and the allowable input range is displayed in the advice panel as you move through the input fields.

When the entries are complete click the Next button.

5. In the Tip tab, select the radio button to set the tip type to a Pipe Tip. In the table including the selection of F Factor method, select the check box to select the Generic Pipe method.

The F Factor, i.e. the fraction of heat radiated by the flame, is a critical design parameter for flare system design. The Generic Pipe correlation has been developed to predict F Factors across a range of exit velocities and fluid molecular weights and is generally recommended for initial calcula-tions. For final designs, we would always recommend con-sulting a flare system vendor for advice on the appropriate F Factor for a specific fluid and specific flare tip.

6. Still in the Tip tab, enter the Fluid Mass Flow Rate as 100,000 lb/hr. After this entry has been completed, the Tip Diameter field is updated to show the tip diameter required for the default Mach number of 0.45. In our case we know the tip diameter is 18 in so we update the calculated value to 18 in. The Mach number will be updated to 0.199 to

indicate the velocity for the new diameter.

When complete the view should be as shown in Figure 2-3.

Click the Next button to move to the next tab.

7. In the next tab, the Environment tab, enter the wind speed.

Since the value we have been given is 20 mph, we first click the entry displaying ft/s and select mph in the drop down menu before entering the value. If we wish to see the value in ft/s, click again in the units entry and select ft/s to display the converted value of 29.33 ft/s.

The remaining items can be left at their default values namely Wind Direction as 0 (i.e. North), Temperature 59

F, Humidity 10% and the User Transmissivity 1.0, with the Transmissivity Method set to “User specified”. Note this default transmissivity method with a specified transmissiv-ity value of 1.0 is the most conservative option.

The final input is to remove the tick from the check box labelled “Include Solar Radiation” which means that the

Figure 2-3, Setup Wizard Tip Tab

The humidity value is only °

used when calculating the transmissivity.

specified solar radiation value will NOT be added to the cal-culated value of flare radiation.

Including solar radiation leads to a more conservative design. API 521 states that its inclusion should be consid-ered on a case by case basis. Solar radiation can have a sig-nificant impact on the flare design when low radiation values are considered. Since we are considering a low design radiation for the Helideck, in this case we will exclude solar radiation for this example.

The completed view is shown as Figure 2-4. Click the Next button to continue.

Figure 2-4, Setup Wizard Environment Tab

8. In the Stack tab, select the radio button to set the Vertical Orientation to 60 degrees from horizontal. Then set the Stack Horizontal Orientation angle to 0 (i.e. North). The Stack Length will be left unspecified to let Flaresim calculate it.

Click the Next button to continue

9. In the Receptors tab, click on the default receptor point

“RP_1” and rename it to “Stack Base”. Set its Distance Downwind from Stack to 0 ft and confirm that the Allowable Radiation for the point is 1500 btu/hr/ft2.

Click the Add button to create an additional receptor point for the radiation at the Helideck. Change the default name

“RP_2” to “Helideck” and enter the location as Northing -150ft, Easting 0ft, Elevation 30ft. and the radiation limit as

Figure 2-5, Setup Wizard Receptors Tab

600 btu/hr/ft². The completed form is shown as Figure 2-5 above. Click the Next button to continue.

10. In the Calculations tab, set Calculation Method check box to Mixed and the Flame Elements to 25.

As discussed in the Methods chapter, the Mixed method is a compromise designed to give the best accuracy for calculat-ing radiation both close to and further away from the flame.

As such it is a good default method. 25 flame elements is usually sufficient to calculate the flame shape with a reason-able degree of accuracy.

The completed view is shown as Figure 2-6. We have com-pleted the Setup Wizard so click the Finish button.

11. When the Finish button is clicked, the Setup Wizard takes the data we have supplied and uses it to create the Flaresim

Figure 2-6, Setup Wizard Calculations Tab

objects that we need for our initial model. The Case Navigator view will be displayed to list all of these objects as shown in Figure 2-7. Note that the icon is shown against each object indicating it is ready to calculate and that the icon is shown against the key object branches to indicate that the model has the minimum information needed to run calculations.

At this point you can open each object’s view by double clicking on them in the Case Navigator to see how the Setup Wizard has initialised the values.

12. This is a suitable point to save the data we have entered so far. Click the button in the tool bar at the top of the Case Navigator or main tool bar. Since we have not yet saved the file, a File Save Dialog window will appear to allow us to specify the location and name of the file. Use the name

“Ex1 - Offshore - Ready To Run”.

Figure 2-7, Case Summary