# Flame Arrester Example

FluidFlow allows users to model Non-Standard pipe or duct fittings using the "User Defined Generic" node which is available from the "General Resistances" tab on the component palette. This node tends to be more accurate than the Kv node as when using this node we need to define the manufacturer's curve relationship for the fitting. The Kv node by comparison, only requires a single point on the curve. FluidFlow then scales up or down accordingly based on the actual system flow rate. This section will demonstrate how to develop the full curve relationship for a flame arrester using the User Defined Generic node and model the pressure loss relationship in a network. Details of the flame arrester pressure loss are set out in Figure 1. Figure 1: Flame Arrester Model DN 150 / 6". The first step is to define a number of coordinates from the relevant curve (Flame Arrester Model DN 150 / 6") into a table in MS Excel. From this table, create a graph plot of the curve (Insert | Scatter | Scatter with only markers). Right mouse-click on the coordinates and select Add Trendline. A new dialog will appear titled Format Trendline. Click through each of the trendline/curve-fit options taking care to select the curve which best reflects the coordinate positions. Place a check mark in the option for Display the Equation on the chart. Finally, select OK. It is important that the user gives careful consideration to selecting the appropriate curve fit in Excel, in this case, the Power Law curve fit has been selected. Figure 2 provides details of this data entry. Figure 2: Excel Graph Plot for Flame Arrester Model DN 150 / 6". The variables derived from the excel equation are those which may now be defined in FluidFlow (see Figure 3). Note, ensure the flow and pressure loss units are set to m3/h and mbar as per the manufacturer's curve data. Figure 3: Data Entry for User Defined Generic Node. Now the User Defined node has been fully defined, we can build a few sample models using different flow rates to test the accuracy. Figure 4 provides details of the test models. We can see that the calculated friction loss values compare well with those set out in the manufacturer's datasheet illustrated in Figure 1. Figure 4: Test Models using different design flow rates. If any of the above is unclear or you require any further information, please contact us at: support@fluidflowinfo.com.