| 摘要 |
When an insulated conductor wire is adjacent to and coextensive with the outside of a steel pipe transporting a fluid and it carries alternating current as one leg of a circuit, with the pipe itself carrying the AC for the return leg, induction and magnetic effects develop which cause the AC flow to concentrate on a band of the surface or "skin" of the pipe close to the wire, thus greatly increasing the resistance of the pipe wall and the heat produced therein. No current is carried in the inner wall of the pipe nor in that part of the outer wall removed from the wire; and there is no current loss to the ground or other surroundings. The insulated conductor wire may be uncovered throughout those portions of its outer surface not directly confronting the pipe by any electrically conductive material which would shield the electromagnetic field generated around the wire in a direction away from the pipe, or it may be covered by a shaped cover of electrical insulation material. However, electrically conductive shielding members may be provided between the wire and the pipe on each side of the wire to trim the effective width of the heating band on the pipe. The conductor wire may comprise a pair of elongated conductors arranged in spaced parallel relation and electrically connected throughout their respective lengths by electrically conductive material having a positive temperature coefficient whereby the current flow and thus the heat generated is automatically regulated in accordance with temperature. Two parallel and adjacent transport pipes may be used, each insulated from the other, and with one taking the place of the conductor wire as the one leg of the circuit. Alternatively, three such pipes may be used, each for one phase of a three phase AC supply, and with electrical connections between the three pipes at their for ends to give a "Y" connection. In such an arrangement, each pipe acts as a conductor wire in cooperation with the other two adjacent pipes.
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