Dynamics mode results for the GG5 example simulation

The following figure shows the depressurized drums after the vent valve opens. The drums are depressurized from 6,500 kPa to 850 kPa in 20 minutes. The maximum relief flow is approximately 120,000 kg/h.

The following figure shows the temperature profile in the pipe during the depressurization process.

The fluid enters the pipe at less than ­50°C but then rises again as backpressure builds in the pipe. Note that the fluid is below -­50°C at time 0, before the valve opens. We calculate this temperature from the adiabatic expansion of the fluid through the valve XV5, which is upstream of the pipe. At time 0, there is no flow, but we still get a calculated temperature from the pressure difference. The metal wall is at ambient temperature, as expected.

Each pipe segment gradually cools down. The pipe metal wall and the fluid inside it are initially at ambient temperature. The segment closest to valve XV5 cools down first, as shown by the darkest blue line. The temperature of the last segment (the lightest blue line) slightly increases at first because of the compression of the gas inside the pipe. As we establish flow, the temperature of the metal starts to decrease.

We can see that only the first and second pipe segments cool down to less than -29°C, the temperature at which stainless steel piping may be required. However, all other pipe segments remain above -29°C, meaning that we can make a substantial portion of the pipe (~400 m) by using carbon steel for a significant cost savings.