Numerical study of heat transfer from an offshore buried pipeline under steady-periodic thermal boundary conditions

The steady-periodic heat transfer between offshore buried pipelines for the transport of hydrocarbons and their environment is investigated. This heat transfer regime occurs for shallow water buried 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 ((C) 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 important discrepancies with respect to this approximate method may occur. (C) 2007 Elsevier Ltd. All rights reserved.