Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Reexamination Certificate
2001-11-27
2002-11-26
Doerrler, William C. (Department: 3744)
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
Reexamination Certificate
active
06484515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pulse tube refrigerator, and more particularly, to a pulse tube refrigerator, which is capable of increasing the available area of a cold heat exchanger and of reducing the size of a refrigerator.
2. Description of the Background Art
In general, a cryogenic refrigerator is a refrigerator of low oscillation and high reliability, which is used for refrigerating small electronic parts or a superconductor. A stirling refrigerator, a Giford-Mcmahon (GM) refrigerator, and a Joule-Thomson refrigerator are widely known.
However, the reliability of such refrigerators deteriorates when the refrigerators are driven at high speed. Also, additional lubricating means must be included for the abrasion of the portions that undergo friction during the driving of the refrigerators. Therefore, a cryogenic refrigerator, whose reliability is maintained during the high speed driving and which needs not be repaired for a long time because additional lubrication is not necessary, has been recently required. One of such cryogenic refrigerators is a pulse tube refrigerator.
FIG. 1
is a schematic sectional view showing an example of a conventional pulse tube refrigerator. As shown in
FIG. 1
, the conventional pulse tube refrigerator includes a driving unit
10
for generating the reciprocal movement of a working gas and a refrigerating unit
20
having a cold head due to the thermodynamic cycle of the working gas that is sucked up into/discharged from the driving unit
10
and is in a reciprocal movement in a plumbing line.
The driving unit
10
includes a closed case
11
having an inner space that shields a middle housing
11
b
and a lower housing
11
c
, an upper housing
11
a
, which is tightly coupled to the upper peripheral edge of the closed case
11
and in the middle of which a cylinder
10
a
is formed, a piston
14
, which is located in the closed case
11
, whose upper surface is tightly-coupled to the bottom of the upper housing
11
a
, to the inside of which an elastic supporter
15
is fastened, and which is inserted into the cylinder
10
a
, the middle housing
11
b
, in which a driving motor
12
including a driving axis
13
connected to the piston
14
is fixedly loaded, the lower housing
11
c
, which is located in the closed case
11
, whose upper surface is tightly coupled to the lower surface of the middle housing, and to the inside of which an elastic supporter
16
is fastened, and a cover
11
d
, whose upper surface is tightly coupled to the bottom of the lower housing
11
c.
The refrigerating unit
20
includes an aftercooler
21
, which is tightly coupled to the upper housing
11
a
of the driving unit
10
and is connected to the cylinder
10
a
, a regenerator
22
connected to the other end of the aftercooler
21
, a cold heat exchanger
23
A connected to the other end of the regenerator
22
, a pulse tube
23
connected to the other end of the cold heat exchanger
23
A (that is, the inlet of the pulse tube), a hot heat exchanger
23
B connected to the other end of the pulse tube
23
(that is, the outlet of the pulse tube), an inertance tube
24
connected to the other end of the hot heat exchanger
23
B, a reservoir
25
connected to the other end of the inertance tube
24
, and a sealed cell
26
, which holds the regenerator
22
and the pulse tube
23
, whose lower surface is tightly coupled to the upper surface of the aftercooler
21
, in the middle portion of whose upper surface a through hole corresponding to the outer circumference of the pulse tube
23
is formed, and the middle portion of whose upper surface is tightly coupled to the outer circumference of the pulse tube
23
.
The aftercooler
21
is formed of a metal and performs a function of a heat exchanger for removing the heat generated in the working gas when the driving unit
10
compresses the working gas.
The regenerator
22
is a kind of a heat exchanger for providing a means for letting the maximum amount of potential work (cooling power) reach a low temperature region with the working gas not having much heat. The regenerator
22
does not simply provide heat to a system or remove heat from the system.
The regenerator
22
absorbs heat from the working gas in a part of a pressure cycle and returns the absorbed heat to the pressure cycle in another part.
The cold heat exchanger
23
A absorbs heat from a member to be cooled and forms the cold head.
The pulse tube
23
moves heat from the cold heat exchanger
23
A to the hot heat exchanger
23
B when a suitable phase relationship is established between a pressure pulse and the mass flow of the working gas in the pulse tube
23
.
The hot heat exchanger
23
B removes the heat that passed through the pulse tube
23
from the cold heat exchanger
23
A.
The inertance tube
24
and the reservoir
25
provide a phase shift so that heat flow can be maximized under an appropriate design.
The conventional pulse tube refrigerator operates as follows.
When power is applied to the driving motor
12
, the driving axis
13
is in a linear reciprocal movement together with the elastic supporters
15
and
16
. The piston
14
integrally combined with the driving axis
13
is in the linear reciprocal movement in the cylinder
10
a
and sucks up/discharges the working gas of the refrigerating unit
20
, to thus form the cold head in the cold heat exchanger
23
A.
That is, the working gas compressed in the cylinder
10
a
and pushed out of the cylinder
10
a
when the piston
14
compresses the working gas is refrigerated to an appropriate temperature through the aftercooler
21
and is flown to the regenerator
22
. The working gas that passed through the regenerator
22
is flown to the cold heat exchanger
23
A of the pulse tube
23
and pushes the working gas filled in the pulse tube
23
toward the hot heat exchanger
23
B. The working gas emits heat, while passing through the hot heat exchanger
23
B, and is flown to the reservoir
25
through the inertance tube
24
.
At this time, because the mass flow of the working gas that flows through the inertance tube
24
is relatively smaller than the mass flow of the working gas flown to the pulse tube
23
, the inside of the pulse tube
23
forms thermal equilibrium at a high pressure.
When the working gas flown to the pulse tube
23
during the suction of the working gas by the piston
14
is returned to the cylinder
10
a
, while passing through the regenerator
22
, the mass flow of the working gas returned to the pulse tube
23
through the inertance tube
24
is relatively smaller than the mass flow of the working gas returned from the pulse tube
23
. Therefore, the working gas in the pulse tube
23
adiabatic expands. In general, the working gas rapidly adiabatic expands in the cold heat exchanger
23
A. Therefore, the cold head is formed in the cold heat exchanger
23
A.
Therefore, the inside of the pulse tube
23
forms the thermal equilibrium at a low pressure. The working gas continuously moves from the reservoir
25
to the pulse tube
23
through the inertance tube
24
and increases the pressure of the working gas in the pulse tube
23
, to thus recover the initial temperature. Such a series of processes are repeated.
However, in the refrigerating unit of the conventional pulse tube refrigerator, the area of the cold heat exchanger
23
A, to which a member to be actually refrigerated is attached, is narrow. Therefore, there is a limitation in refrigerating a large amount of members.
That is, the regenerator
22
is combined with one side of the cold heat exchanger
23
A and the pulse tube is combined with the other side of the cold heat exchanger
23
A. Therefore, the available area, to which the members to be refrigerated can be attached, is restricted to the outer circumference of the cold heat exchanger
23
A.
As shown in
FIG. 1
, the entire length of the refrigerator increases because the regenerator
22
, the pulse tube
23
, the inertance tube
24
, and the reservoir
25
are installed in a line. Therefore, a
Hwang Dong Kon
Kim Seon Young
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