JPH02152111A - Superconducting cable - Google Patents

Abstract

PURPOSE:To increase a cooling effect for a superconducting wire and an allowable electric current flow by applying the predetermined thickness of a covering material having lower thermal conductivity than the superconducting wire to the external surface thereof. CONSTITUTION:The external surface of a superconducting wire 1 is applied with covering 2. The superconducting wire 1 having the covering 2 is passed through a pipe 3 wherein a liquid coolant is flowing. In the cable so constituted, liquid helium or liquid nitrogen as a coolant is made to flow through the pipe 5 and the superconducting wire 1 is cooled with nuclear boiling via the covering 2. In this case, PTEE, for example, can be used as the material of the covering 2, and the thickness of the covering 2 in this case is made 40 to 60mum. According to the aforesaid construction, cooling speed with nuclear boiling effect can be raised.

Description

[Detailed description of the invention] [Industrial application field 1 The present invention relates to superconducting cables.

[Prior Art 1] Currently, various superconducting materials are being developed, but those that can still be put to practical use are limited to those that exhibit superconductivity only at extremely low temperatures.

Therefore, when mounting a superconducting wire, the superconducting wire itself is cooled with a low-temperature coolant such as liquid helium or liquid nitrogen, thereby maintaining superconductivity.

[Problem to be solved by the invention] Conventionally, superconducting wires are cooled by nucleate boiling by bringing a refrigerant into direct contact with them, but now there is a need for a technology that more effectively enhances the cooling effect and increases the allowable current. It has become.

[Means for Solving the Problems] The present invention provides that in nucleate boiling cooling using a refrigerant, if a coating layer of a low thermal conductivity material is provided with an appropriate thickness on the surface of an object to be cooled, the cooling rate increases. This was done based on the paradoxical finding that a superconducting wire is inserted as an object to be cooled into a pipe through which a liquid refrigerant that cools the object by nucleate boiling cooling effect, and the outer surface of the superconducting wire is The superconducting wire is characterized by being coated with a material having lower thermal conductivity than the superconducting wire to a predetermined thickness.

[Example 1 The present invention will be explained in detail below.

FIG. 1 shows the configuration of a superconducting cable according to an embodiment.

In the figure, reference numeral 1 denotes a superconducting wire, the outer surface of which is covered with an extremely thin coating 2 made of a material with low thermal conductivity.

The superconducting wire 1 provided with the coating 2 is inserted into a pipe 3 through which liquid refrigerant flows. In this cable, liquid helium or liquid nitrogen is made to flow as a refrigerant in the vibrator 3, and the superconducting wire 1 is cooled through the coating 2 by nucleate boiling.

In this case, as the material of the coating 2, for example, PTFE (tetrafluoroethylene resin) can be used. In that case, the thickness of the coating 2 is set to 40 μm to 60 μm. This improves the cooling rate due to nucleate boiling.

In addition, by providing minute irregularities on the outer surface of the coating 2 by solvent treatment, etc., the irregularities can act as existing bubble nuclei, thereby activating nucleate boiling and further increasing the cooling effect on the superconducting wire 1. It is possible to increase the amount of

In addition, other materials for the coating 2 include E-PTFE (
(Stretched tetrafluoroethylene resin) can also be used. In this case, coating can be achieved by winding a 60 μm thick E-PTFE tape. When E-PTFE is used, as shown in FIG. 2, the material itself has minute irregularities, which act as existing bubble nuclei to activate nucleate boiling and enhance the cooling effect.

Further, as another material for the coating 2, PFA
(Perfluoroalkoxy?jf N ) can also be used. In the case of this material, 45 μa by extrusion
It can be coated with a thickness of about 1 to 60 μm. When this material is coated, the cooling effect can be further promoted by forming minute irregularities on the outer surface through surface treatment.

[Effect of the Invention 1] According to the present invention, the outer surface of the superconducting wire is intentionally coated with a material having a lower thermal conductivity than the outer surface of the superconducting wire, thereby achieving an increased cooling effect on the superconducting wire. Therefore, it has become possible to obtain a superconducting cable with a large allowable current.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of the superconducting cable of the present invention, Figure 2
The figure is a partially enlarged view of an example of the same cable. 1...Superconducting wire, 2...Coating, 3.
...Vibro Figure 1

Claims (1)

[Claims] A superconducting wire is inserted as an object to be cooled into a pipe through which a liquid refrigerant that cools an object to be cooled by nucleate boiling cooling action is passed, and the outer surface of this superconducting wire is coated with a material having a lower thermal conductivity than that of the superconducting wire. A superconducting cable characterized by being formed by applying the same to a predetermined thickness.