A Numerical Study on Induction-Resistive Electric-Heating Processes of Pipelines

Pumping process fluids through pipelines at subzero temperatures, as a rule, requires the presence of electric-heating systems. An induction-resistive system is widely used for heating long pipelines. It can be considered as a short-circuited coaxial line, the inner conductor of which is a single-core cable, while the outer conductor is a steel pipe that is longitudinally attached to the heated pipeline. The pipeline with an induction-resistive heating system is insulated. To determine the parameters of electric heating, it is necessary at the first stage to determine the heat losses to the environment and, then, having solved the electromagnetic problem, calculate the currents that provide heating of the pipeline. The temperature problem is described by the differential equation of stationary thermal conductivity in a two-dimensional formulation. The solution of this problem in the ANSYS Fluent software package determines the temperature field and heat losses to the environment. As a result of numerical studies, the influence of the pipeline diameter and insulation thickness on the level of heat losses has been determined. The effect of reducing the thickness of the thermal-insulation layer in the area where the induction-resistive heating (IRH) system is located on the growth of heat losses is also investigated. Electromagnetic processes are described by the Poisson differential equation with respect to the vector magnetic potential in a two-dimensional formulation. As a result, by solving this problem in the ANSYS Maxwell software package, the active and reactive resistances of the IRH system are calculated by the finite-element method, which determine the operating current that provides heating of the pipeline. It is established that the location of the cable in the steel pipe of the induction-resistive system does not significantly affect its parameters. Thus, the proposed approach can be used to determine the operational characteristics of the IRH system.