It is an easy and obvious thing to insulate a pipeline to avoid the decrease in temperature of the oil by keeping the energy supplied by the pumps inside the pipe. The trick is to insulate the pipeline well enough, but not more, so that the return on investment motivates the cost of the insulation. If the petroleum mixture temperature can be kept at a high enough level, the cost of the preheating process can be eliminated and the pump’s energy consumption can be reduced substantially. The reduction of theses costs have to motivate the investment in insulation.

The fluid flow and heat transfer processes in the pipeline can be modeled and simulated accurately using the COMSOL Multiphysics® software. The models can be used to design an insulation that is as inexpensive as possible, yet as efficient as required to keep the oil at the desired temperature.

Designing and Optimizing a Pipeline’s Insulation with COMSOL Multiphysics®

Our Insulation of a Pipeline Section tutorial model features a 150-km pipeline section that has an inlet temperature of 25°C. The oil that enters the pipeline flows at a rate of 2500 m3/h. To set up and solve the energy and flow equations that describe the transport of the fluid within the pipeline, we use the Nonisothermal Pipe Flow interface.

This particular case involves analyzing one pipe wall and one insulation layer, as highlighted in the schematic below. Here, the dark and light gray layers represent a two-layered wall, while light blue represents the film resistances on the inside and outside of the walls. Note that the pipe wall is 2 cm thick in this example.

Schematic of the pipeline cross section, where hint and hext are the film heat transfer coefficients inside and outside of the tube and kins and kwall are the thermal conductivity of the insulation and the wall, respectively.

In the first study, we calculate the temperature along the pipeline for two different cases: one where perfect insulation is assumed and one where the pipeline has no insulation. The plot below shows that the heat resulting from friction forces in the fluid causes its temperature to increase by about 3°C over 150 km. When no insulation is added to the pipeline, the outlet temperature is similar to that of the surroundings.

Plot comparing the fluid temperature when there is perfect insulation on the pipeline (green) and when there is no insulation (blue).