5.2 Summary of Simulation Model and Loading


An axisymmetric model is used in the simulation. Only half of the bulkhead is modeled. A swept view of the mesh is shown in Figure 12. The pink material is the insulation applied over the PIP bulkhead. The air gap is shown in yellow, and the hydrocarbon fluid is shown in dark grey. Complete temperature continuity is assumed between the insulation layer and the outer pipeline. Thermal contact is used between the steel of the bulkhead and the air gap and between the inner wall of the carrier pipeline and the hydrocarbon fluid. Only conductive heat transfer is modeled in this simulation; no convection is allowed in either fluid. The thermal conductivity of the hydrocarbon is increased from its actual value in an attempt to offset this assumption. This class of design simulation is well suited for a Fluid Structure Interaction (FSI) simulation, and Technip will likely develop such models in the near future.


The outer surface of the insulation and the exposed outer pipe are assigned the temperature of the surrounding seawater, which is approximately 4 o C. The entire mass of hydrocarbon fluid is given an initial temperature of 43 o C. A steady step heat transfer step is used to calculate the thermal profile under “flowing conditions”. The initial temperature constraint on the hydrocarbon fluidis released and a transient heat transfer step is performed to predict the cooling of the hydrocarbon as heat is lost to the ocean.


5.3 Results


The thermal transients for a series of insulation designs, with increasing thickness, are shown in Figure 13. The temperature profiles are shown for both the inner diameter of the inner pipeline and the centerline of the hydrocarbon fluid. This data allowed the operator to select the most effective and cost efficient insulation material and design for the project’s requirements.


Figure 12. PIP bulkhead mesh (revolved through 180 degrees).


2009 SIMULIA Customer Conference 13


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