Step 4

Once the two-phase relieving capacity is known then we will use DIERS methodology to determine the maximum fluid flux (Gmax), using the direct integration of the VdP integral for the relief nozzle, based on an article by Larry Simpson, "Estimating two-phase flow in Safety Devices", which then sets the basis for the design of the relief orifice size using the equation,  A = W/(Gmax), where "A", is the required orifice size, "W", is the two-phase relief rate, and "Gmax" is the maximum fluid flux that occurs at sonic (choke) conditions or at the pipe exit.

This method will also be employed to determine the sizing of the inlet and outlet piping based on the Simpson article, " Navigating the two-phase Maze"  We can then compare the two-phase relief orifice size with the existing single-phase orifice and piping size to determine if the existing relief device size and piping is adequate for both single and two-phase venting. 

Step 4-A

Enter the System, and Operating Data just as was done for the single-phase fire case.