JPH04257665A - Supercritical helium circulation device - Google Patents

Abstract

PURPOSE:To perform an effective utilization of cold state of liquid nitrogen during precooling of up to a liquid helium temperature and further to perform the precooling of it in order to consume a large amount of liquid helium at the precooling stage in a system for cooling a superconducting magnet or the like with a supercritical circulation device. CONSTITUTION:A precooling device having liquid nitrogen heat exchangers 11a and 11b for performing a heat exchanging operation with liquid nitrogen and helium gas and having a cryogenic helium blower 4 operated at a liquid nitrogen temperature is assembled in a supercritical circulation device including a supercritical helium pump 5 and a supercritical helium heat exchanger 9. With such an arrangement, the supercritical helium circulation device and a superconducting magnet or the like can be cooled under utilization of cold state of the liquid nitrogen.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical helium circulation system that performs forced cooling using supercritical helium.

0002

2. Description of the Related Art As a combination of a helium refrigeration system and a supercritical helium circulation system, for example, A. C. E
Vol. 27 (P501-508).

[0003] In this known example, the cooling operation of the circulation device is performed from room temperature to liquid helium temperature by utilizing the cold generated by a helium refrigerator or by supplying liquid helium from the outside.

0004

[Problem to be solved by the invention] A superconducting magnet is a typical object to be cooled in a supercritical helium circulation system, but as nuclear fusion technology develops, it will become even larger in the future, so the overall heat capacity will also decrease. growing. In order to cool a magnet with a large heat capacity from room temperature to liquid helium temperature using conventional methods, it is necessary to use a helium refrigerator or a large amount of liquid helium from an external source.

An object of the present invention is to perform precooling at low cost by utilizing the cooling of liquid nitrogen as a means for cooling a supercritical circulation device and a superconducting magnet to the liquid nitrogen temperature level.

[0006]

[Means for solving the problem] In order to achieve the above object, a liquid nitrogen heat exchanger for exchanging heat between liquid nitrogen and helium gas is provided in a supercritical circulation system having a supercritical helium pump and a supercritical helium heat exchanger. It incorporates a pre-cooling device equipped with a low-temperature helium blower that operates at liquid nitrogen temperatures.

More specifically, helium gas is cooled to around the temperature of liquid nitrogen in a liquid nitrogen heat exchanger in a precooling device, is pressurized by a low-temperature helium blower, and then supplied into a supercritical helium loop. After circulating in the critical helium loop, the loop is formed so that it is extracted to the liquid helium line of the supercritical helium heat exchanger and returned to the low-temperature helium blower.

[0008]

[Operation] Helium gas cooled to liquid nitrogen temperature in a liquid nitrogen heat exchanger is pressurized by a low-temperature helium blower.
After being led to the supercritical helium line and cooling the objects to be cooled (superconducting magnets, etc.) and the supercritical helium heat exchanger, it returns to the suction line of the low-temperature helium blower. Through this operation, the object to be cooled and the supercritical circulation device can be precooled to the liquid nitrogen temperature level by cooling the liquid nitrogen.

[0009]

[Embodiment] An embodiment of the present invention will be explained below with reference to FIG.

In FIG. 1, 1 is a helium refrigerator, 2a-g are cryogenic helium transfer tubes, 3a-b are low-temperature nitrogen transfer tubes, and 4 are cryogenic helium transfer tubes.
is a low temperature helium blower, 5 is a supercritical helium pump,
6 is a cryogenic exhaust pump, 7 is a supercritical helium relief valve, 8 is a supercritical helium relief valve.
is a cryogenic helium supply valve, 9 is a supercritical helium heat exchanger, 10 is an object to be cooled (superconducting magnet, etc.), 11a,
b is a liquid nitrogen heat exchanger, 12 is a liquid nitrogen storage tank, 13a~
f is a gate valve, and 14 is a bypass valve.

Next, the operation of this embodiment configured as described above will be explained.

Liquid nitrogen is supplied from the liquid nitrogen supply line 3a to the liquid nitrogen storage tank 12, and the evaporated nitrogen gas exits from the exhaust line 3b. The helium gas flowing inside the tube of the liquid nitrogen heat exchanger 11a provided in the liquid nitrogen storage tank 12 is
After being cooled to around the temperature of liquid nitrogen, the pressure is increased by a low-temperature helium blower 4. When the pressure is increased by the low-temperature helium blower 4, the temperature also rises, so the liquid nitrogen is cooled again to near the liquid nitrogen ground temperature by the liquid nitrogen heat exchanger 11b. This cooled helium gas is transferred to the cryogenic helium transfer pipe 2e and the gate valve 1.
3e and is led to the cryogenic helium transfer pipe 2g. The helium gas guided to the transfer pipe 2g passes through the object to be cooled 10,
Cryogenic helium transfer pipe 2f, supercritical helium heat exchanger 9
It then flows to the outside of the tube of the supercritical helium heat exchanger from the supercritical helium relief valve 7 provided at the suction part of the supercritical helium pump 5. Furthermore, this helium gas returns to the liquid nitrogen heat exchanger again via the gate valve 13d. By circulating helium gas through the above-mentioned loop by the low-temperature helium blower 4, the inside of the system can be cooled to around the temperature of liquid nitrogen.

In the above precooling operation, the gate valves 13a to
c, f, bypass valve 14, and cryogenic helium supply valve 8 are kept fully closed. The cooling of the system to the liquid helium temperature is performed as follows.

[0014] When the temperature in the system drops to around liquid nitrogen and the precooling operation is completed, the bypass valve 14 is opened, the low-temperature helium blower 4 is stopped, and the gate valves 13d and 13e are closed. Next, supercritical helium is introduced from the cryogenic helium transfer pipe 2c through the cryogenic helium supply valve 7 to the line of the supercritical helium pump 5. For supercritical helium, supercritical helium heat exchanger 9, cryogenic helium transfer tube 2g, and object to be cooled 10
, flows through the helium transfer pipe 2f to the outside of the supercritical helium heat exchanger 9 from the supercritical helium relief valve 8 so as to maintain it at a predetermined pressure, and further passes through the cryogenic exhaust pump 6.
It is sent to the helium refrigerator 1 through the cryogenic helium transfer pipe 2d. After lowering the temperature of the supercritical helium line by using the sensible heat of supercritical helium, liquid helium is supplied from the cryogenic helium transfer pipes 2a and 2b to the supercritical helium heat exchanger 9 until a predetermined amount is reached. Collect liquid. Furthermore, the gate valve 13c is opened, the supercritical pump 5 is started, the cryogenic helium pump 6 is also started, and the object to be cooled is heated to the liquid helium temperature by utilizing the latent heat of the liquid helium filled in the supercritical helium heat exchanger 9. 10 lines can be cooled.

The gate valves 13a and 13b are appropriately opened during the pre-cooling stage to effectively cool the inside of the supercritical helium loop.

[0016]

[Effects of the Invention] According to the present invention, since the supercritical helium circulation system and the object to be cooled can be cooled using the cooling of liquid nitrogen, the amount of liquid helium consumed in the precooling stage can be reduced, and the cost during precooling operation can be reduced. This has the effect of reducing

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a supercritical helium circulation apparatus showing one embodiment of the present invention.

[Explanation of symbols]

2e... Cryogenic helium transfer tube, 4... Low temperature helium blower, 5... Supercritical helium pump, 9... Supercritical helium heat exchanger, 11a, b... Liquid nitrogen heat exchanger.

Claims (3)

[Claims] Claim 1: A supercritical helium circulation device having a supercritical helium pump, a supercritical helium heat exchanger that exchanges heat between supercritical helium gas and liquid helium, and a liquid that exchanges heat between liquid nitrogen and helium gas. A supercritical helium circulation system characterized by incorporating a precooling device equipped with a nitrogen heat exchanger and a low-temperature helium blower that operates at liquid nitrogen temperature. 2. A supercritical helium loop incorporating the supercritical helium pump is provided with a supercritical helium heat exchanger for cooling circulating helium gas by exchanging heat with liquid helium, and the liquid helium of the heat exchanger A line for extracting helium from the supercritical helium loop is provided to the line, and this line is connected to the suction line of the low temperature helium blower, and the discharge line of the low temperature helium blower is guided into the supercritical helium loop. Item 1. The supercritical helium circulation device according to item 1. Claim 3: Claim 1, wherein the supercritical helium pump, supercritical helium heat exchanger, low temperature helium blower, and low temperature helium blower inlet/outlet heat exchanger are housed in the same vacuum vessel.
The supercritical helium circulation device described.