Heat transfer characteristics of subsea long-distance pipeline subject to direct electrical heating

For deep-water pipelines with long tie-back distances, high external pressure, and low ambient temperature, it is a key issue to ensure flow safety by controlling the generation of hydrates and waxes through electric heating technology. In-detail analysis of the heat transfer performance of electric heating pipelines is of great engineering significance for developing the safety of pipeline flow in offshore oil-gas fields. This paper proposed an electrical heating analytical method applicable to long-distance submarine pipelines. Based on the thermal equilibrium theory and the differential equation of heat conduction, a mathematical model of heat-fluid coupling for electric heating pipes is established, involving the theoretical model of the steady-state distribution of the electric heating in the axial and radial directions. Then, the definition of the average temperature of the pipeline is introduced and combined with the two-point Hermite approximation interpolation method, and an improved lumped parameter model of the transient heat transfer of the electric heating pipeline is established. Meanwhile, the finite difference method is applied to solve the ordinary differential equation of the pipeline and the energy equation of the internal fluid. The steady-state calculation result is utilized as the initial value of the transient heat transfer process, and the model is applied to analyze the influence variation on the transient temperature response characteristics of the pipeline under different working conditions, finally determining the prediction formula of the average temperature of the fluid under normal transportation and shutdown conditions.