External heat transfer coefficient of a partially sunken sealine

The design of sealines involves calculation of their thermal balance with external environment. Usually in engineering practice one-dimensional codes are used to carry out thermal-hydraulic sizing, and they require the value of an external heat transfer coefficient representing all actual heat exchange phenomena, including 2D or 3D configurations. In the following a simplified approach is presented, for defining a surface averaged heat transfer coefficient of a partially sunken sealine. This coefficient is composed by a contribution due to conduction for the sunken pipe section and another term dealing with forced convection for the upper portion. The second effect is found to dominate the external exchange.