JPS6120305A - Power lead for ultra low temperature - Google Patents

Abstract

PURPOSE:To increase cooling effect and to drastically reduce the infiltrated quantity of external heat by making the external cylinder covering a conductor alternately project or recess along the direction of length in the cross section along radial direction. CONSTITUTION:The external cylinder 12 covering a conductor 11 is made to alternately have a recession 13 and a projection 14 in the cross section of radial direction and the heat transfer route from one end of the other end is extended without increasing the dimension of the length and the surface area of the external cylinder is increased. This can reduce the infiltrated quantity of external heat and the rise of temperature due to generation of heat in the conductor is also restrained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power lead (current lead) used to supply current from a normal temperature part to an electrical device such as a superconducting magnet placed at an extremely low temperature. .

[Prior art]

As conventionally known cryogenic power leads, there are those shown in FIGS. 2 to 4. The power lead in Figure 2 is
A finned tube conductor 1 is covered with an outer cylinder 2, and in the case shown in FIG. 3, an aggregate of mesh conductors 1 is covered with an outer cylinder 2. In addition, the lead shown in Fig. 4 has an outer cylinder 2 covering a spirally wound thin plate conductor 1. In this way, each lead covers the conductor with an outer cylinder and is placed inside this outer cylinder at a low temperature. The conductor is cooled by flowing evaporated gas from a refrigerant such as liquid helium for equipment cooling from the connection end to the equipment.

[Problem that the invention seeks to solve]

Although sufficient consideration has been given to the cooling of the conductor in the power lead as mentioned above, the cooling performance of the outer cylinder 2, which is generally made of stainless steel, and the measures against heat intrusion from the normal temperature part through this are not sufficient. That is, a straight pipe with a smooth surface is used for the outer cylinder 2, but this pipe has a short heat transfer path from one end to the other and has a small surface area, so heat exchange with the cooling gas is difficult. The exchangeability is also poor, and therefore, external heat enters the cryogenic equipment side through this outer cylinder, accelerating the evaporation of the refrigerant liquid for cooling one equipment, and also having an adverse effect on the equipment.

[Failure to solve the problem]

In order to eliminate the above-mentioned problems, the present invention, as shown in FIG. Extends the heat transfer path from one end to the other without increasing the directional dimension.

Moreover, the surface area of the outer cylinder is increased. According to this, it is possible to reduce the amount of intrusion of external heat, and also suppress the temperature rise due to heat generation of the conductor.

That is, the amount of heat Q flowing from one end of the outer cylinder 12 to the other end is.

Q”” ” (TI T2 ) / L However, K - Thermal conductivity of the outer cylinder A - Cross-sectional area of tr T 1.T2 = Temperature at both ends of tt L = Expressed by the length formula of The value of L is much longer than before due to the unevenness, and the surface area of the outer cylinder is greatly increased, which increases the cooling effect of the evaporative refrigerant gas flowing along the inner and outer surfaces, thereby reducing external heat. The amount of penetration becomes smaller.

In addition, if the cooling effect of the outer cylinder increases, the cooling effect of the conductor 11 surrounded by it will also improve, and the electrical resistance of the conductor will decrease, so the amount of heat expressed by 12R will decrease and the temperature rise of the conductor will also be small. Become.

The outer cylinder 12 is formed of a bellows tube in which the concave portion 13 and the convex portion 14 are independent in the length direction, but it may also be made of a corrugated tube in which both the concave and convex portions are continuous in a spiral shape. Further, as the material, a material with low thermal conductivity, such as stainless steel or brass, is used. Among them, the former, bellows pipes and corrugated pipes, are economically advantageous because they are available on the market at low prices.

The conductor 11 is preferably a single mesh wire or a set of mesh wires, but a spiral thin plate conductor as shown in FIG. 4 does not pose any practical problems because the cooling gas flows into the outer cylinder through the gaps between the plate layers. .

However, a tube conductor can also be used if a large number of through holes are provided in the middle, since gas will flow into the outer cylinder through the holes.

Note that it is desirable to provide conductor support portions 15.15 at both ends of the outer cylinder 12. The symbol 1b in the figure is the normal temperature side terminal, 17
18 is a low-temperature side terminal portion, and 18 is an insulating flange that is integrated with the outer cylinder by bonding or otherwise, in order to fix the outer cylinder to the top flange of a cryogenic refrigerant container (cryostat).

〔effect〕

As explained above, the power lead of the present invention is as follows.

The outer cylinder has been made uneven to lengthen the heat transfer path from one end to the other, and at the same time, the surface area of the outer cylinder has been increased to enhance the cooling effect. The amount of heat intrusion is greatly reduced.

Furthermore, since the conductor is also cooled to a lower temperature due to the improved cooling effect of the outer cylinder, the temperature rise due to heat generation in the conductor is also suppressed.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view showing one embodiment of the power lead of the present invention, and FIGS. 2 to 4 are views showing conventional power leads. DESCRIPTION OF SYMBOLS 11... Conductor, 12... Outer cylinder, 13... Recessed part, 1
4...Convex part, 15.15...Conductor support part, 16...
・Normal temperature side terminal, 17... Low temperature side terminal part, 18... Insulating 7 lunge Patent author: Sumitomo Electric Industries, Ltd. Agent: Kama 1) Bun 2 No. 1
Figure 1b Figure 2 Figure 3 Figure 4 Figure 1''

Claims (1)

[Claims] In a power lead, a conductor that supplies current to electrical equipment placed at extremely low temperatures is covered with an outer cylinder, and a cooling gas is allowed to flow inside the outer cylinder to cool the conductor. A cryogenic power lead characterized by having a shape in which unevenness is alternately present in the length direction when viewed in cross section.