Steady-periodic heat transfer between buried pipelines and environment

The steady-periodic heat transfer between buried offshore pipelines for the transport of fluid hydrocarbons and their environment is investigated. This heat transfer regime occurs for shallow water pipelines, as a consequence of the temperature changes of the seabed during the year. First, the unsteady two dimensional conduction problem is written in a dimensionless form; then, it is transformed into a steady two dimensional problem and solved numerically by means of the finite-element software package COMSOL Multiphysics (© Comsol Inc.). Several values of the burying depth and of the radius of the pipeline, as well as of the thermal properties of the soil are considered. The numerical results are compared with those obtainable by means of an approximate method employed in industrial design. The comparison reveals that the approximate method may yield important errors.