Oil consumption has been steadily increasing around the world; consequently, the petroleum industries have been endeavoring to keep up with the demand through exploration in deeper ocean environments. At current seafloor depths, pipeline insulation is essential to prevent pipeline blockage resulting from the solidification of paraffin waxes that exist as in the crude oil. To maintain crude oil temperatures above the paraffin solidification point, new and better insulation techniques are essential to minimize pipeline heat loss and maintain crude oil temperatures. The main objective of this project was to determine whether or not the thermal resistance of a new insulation concept involving interstitial screen-wire insulation would translate directly into comparable values for a prototype fabricated pipe segment. In other words, whether the reduction in heat transfer observed for small laboratory samples was realistic for application to a pipeline configuration.
This phase of the project involved both an analytical modeling study and a series of experimental verification tests. The analytical model for the interstitial insulation contained both conforming and nonconforming interfaces within the wire screen contacts in the interstitial space between the coaxial pipes. The experimental study of this novel insulation technology consisted of a prototype coaxial pipe fabricated with two layers of low conductivity wire-screen (stainless steel) as the interstitial insulation material. Both the inner and outer surface temperatures of the coaxial pipes were measured in order to evaluate the effective thermal conductivity and thermal diffusivity of the insulation concept. The predicted results from the model compared favorably with the experimental results, confirming both the trends and magnitudes of the experimental data.
With the experimental results for thermal conductivity and thermal diffusivity from the prototype pipe segment, this study has confirmed the feasibility and performance of the insulation concept and demonstrated the thermal competitiveness of the interstitially insulated coaxial pipe technology.