Cryocooler and cryocooler operation method

Patent metadata

Field	Value
Publication number	US-2016178247-A1
Application number	US-201514977208-A
Country	US
Kind code	A1
Filing date	Dec 21, 2015
Priority date	Dec 22, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

In a cryocooler for developing coldness of 4 K or lower by expanding helium, an expander expands high-pressure helium. A compressor compresses low-pressure helium returned from the expander, to generate high-pressure helium, and supplies the high-pressure helium to the expander. When helium temperature in the expander is 2.17 K or lower, the pressure of the low-pressure helium is equal to or higher than pressure given by a curve, in a helium state diagram in which the horizontal axis is temperature and the vertical axis is pressure, along which helium's volumetric thermal expansion coefficient is 0.

First claim

What is claimed is:

1 . A cryocooler for developing coldness of 4 K or lower by expanding helium, the cryocooler comprising:
an expander for expanding high-pressure helium; and a compressor for compressing low-pressure helium, returned from the expander, to generate high-pressure helium, and supplying the high-pressure helium to the expander; wherein when helium temperature in the expander is 2.17 K or lower, the pressure of the low-pressure helium is equal to or higher than pressure given by a curve, in a helium state diagram whose horizontal axis is temperature and vertical axis is pressure, along which helium's volumetric thermal expansion coefficient is 0.

2 . The cryocooler according to claim 1 , wherein the pressure of the low-pressure helium is 15 bar or higher.

3 . The cryocooler according to claim 1 , wherein the pressure of the low-pressure helium is 25 bar or higher.

4 . The cryocooler according to claim 1 , wherein the pressure of the high-pressure helium is lower than or equal to a liquefaction curve for helium in the state diagram.

5 . The cryocooler according to claim 4 , wherein the pressure of the high-pressure helium is 35 bar or lower.

6 . The cryocooler according to claim 1 , wherein letting helium temperature be T K, pressure be P bar, and entropy per unit mass be s J/gK, said curve along which the volumetric thermal expansion coefficient is 0 is a curve expressed by the following Expression 1.

(

∂
T

∂
P

)

S

=
0

Expression



1

7 . The cryocooler according to claim 1 , wherein the helium is helium-4.

8 . The cryocooler according to claim 1 , wherein:
the expander includes a helium expansion chamber and a heat exchanger enclosing the helium expansion chamber; and the cryocooler further includes
a helium tank component coupled to the cryocooler to supply helium to the cryocooler, and
a helium-tank control unit for controlling the helium tank component to start supply of the helium from the helium tank component to the cryocooler based on temperature of the helium expansion chamber and/or of the heat exchanger.

9 . The cryocooler according to claim 8 , wherein:
the cryocooler further comprises a temperature sensor attached to the expander to measure temperature of the helium expansion chamber and/or of the heat exchanger, and is connected with the helium tank control unit to enable communications outputting measured temperature to the helium tank control unit; the helium tank component includes a helium tank, a connection line coupling the helium tank to the cryocooler, and a valve installed in the connection line; and the helium tank control unit includes a temperature comparison unit configured to compare measured temperature with a temperature threshold value, and a valve control unit configured to control the valve according to input from the temperature comparison unit such as to close the valve when the measured temperature is higher than the temperature threshold value, and the valve is opened when the measured temperature is lower than or equal to the temperature threshold value, wherein the temperature threshold value is predetermined from a range of from greater than 2.17 K to less than or equal to 5 K.

10 . The cryocooler according to claim 8 , wherein the helium tank component is connected to a low-pressure side of the compressor.

11 . The cryocooler according to claim 1 , further comprising:
a first cooling unit including a first expander having a helium expansion chamber, a first compressor, and a first helium gas circuit linking the first expander to the first compressor to recover first low-pressure helium from the first expander and supply first high-pressure helium from the first compressor; and a second cooling unit including a second expander having a helium receiving chamber thermally coupled to the helium expansion chamber, a second compressor, and a second helium gas circuit separated from the first helium gas circuit and linking the second expander to the second compressor to recover second low-pressure helium from the second expander and supply second high-pressure helium from the second compressor; wherein the second low pressure is higher than the first low pressure.

12 . A method of operating a cryocooler developing coldness of 4 K or lower by expanding helium in the cryocooler, the cryocooler including an expander for expanding high-pressure helium, and a compressor for compressing low-pressure helium returned from the expander, to generate high-pressure helium, and supplying the high-pressure helium to the expander, comprising:
a step of detecting temperature of helium in the expander; and a step of, when the detected temperature is 2.17 K or lower, setting pressure of the low-pressure helium to pressure given by a curve, in a helium state diagram whose horizontal axis is temperature and vertical axis is pressure, along which helium's volumetric thermal expansion coefficient is 0.

Assignees

• Sumitomo Heavy Industries

Inventors

• De Waele A T A M
• Xu Mingyao
• Bao Qian

Classifications

• F25B9/14 Primary

  characterised by the cycle used, e.g. Stirling cycle · CPC title

• F25B9/12

  using 3He-4He dilution · CPC title

• F25B2309/14

  Compression machines, plants or systems characterised by the cycle used · CPC title

• F25B9/06 Primary

  using expanders (F25B9/10 takes precedence) · CPC title