Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
STIRLING COOLING APPARATUS, COOLER, AND REFRIGERATOR
Technical field
The present invention relates to a cooling apparatus, cooler, and refrigerator
employing a Stirling chiller.
Background art
As is well known, conventionally, refrigerants based on CFCs
(chlorofluorocarbons)
and HCFCs (hydrochlorofluorocarbons) have been in wide use as working fluids
in chilling
and air-conditioning systems. However, refrigerants based on CFCs have already
been
totally banned, and the use of refrigerants based on HCFCs is regulated by the
international
treaty for the protection of the ozone layer. On the other hand, newly
developed refrigerants
based on HFCs (hydrofluorocarbons) do not destroy the ozone layer, but are
powerful global
warming substances having global warming coefficients as high as several
hundred to several
thousand times that of carbon dioxide. Thus, these are also targets of
emission regulation.
For this reason, as an alternative technology to the vapor-compression cooling
cycle
which uses a refrigerant mentioned above as a working fluid, research has been
done
extensively on Stirling chillers, which exploits the reverse Stirling cycle to
produce cold.
A conventional Stirling cooling apparatus, disclosed in U. S. Patent No.
5,927,079,
will be described with reference to Fig. 7. Reference numeral 20 represents a
Stirling
chiller; reference numerals 21 and 22 respectively represent a heat releaser
portion and a
radiator of the Stirling chiller 20; reference numeral 23 represents a water
pump for the
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cooling water circulated to cool the heat releaser portion 21; reference
numeral 24 represents
a refrigerant cooler portion for cooling a secondary refrigerant with the cold
obtained from the
Stirling chiller 20; reference numeral 25 represents a refrigerant pipe
through which the
secondary refrigerant is circulated so that the cold is transferred to inside
a cooling chamber
27; and reference numeral 26 represents a refrigerant pump for circulating the
secondary
refrigerant through the refrigerant pipe 25.
In this arrangement, when the Stirling chiller 20, the water pump 23, and the
refrigerant pump 26 are driven, the high-temperature waste heat that is
transmitted to the heat
releaser portion 21 of the Stirling chiller 20 is transferred by the water to
the radiator 22,
where the heat is released to the surrounding space. Simultaneously, the cold
obtained from
the Stirling chiller 20 is transferred, by the secondary refrigerant
circulating through the
refrigerant pipe 25, to inside the cooling chamber 27.
The transfer of the cold produced by the Stirling chiller 20 to the cooling
chamber 27
is achieved by exploiting the sensible heat of the secondary refrigerant, such
as ethanol free
from phase change. Thus, whereas in the refrigerant cooler portion 24 the
secondary
refrigerant is cooled and thus its temperature falls, in the cooling chamber
27 it absorbs heat
and thus its temperature rises. The refrigerant, having its temperature raised
while passing
through the refi-igerant pipe 25, then returns to the refrigerant cooler
portion 24 by the action
of the refrigerant pump 26. This cycle is repeated, and as a result the inside
of the cooling
chamber 27 is cooled to lower and lower temperature.
In this arrangement, however, since the cold is transferred by exploiting the
sensible
heat of the secondary refrigerant, temperature difference arises within the
refrigerant pipe 25,
leading to poor heat transmission efficiency. Moreover, ethanol used as the
secondary
refrigerant has a low flash point (about I2.8 °C) and is highly
volatile, requiring care in its
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handling. Furthermore, the viscosity of ethanol at temperatures from -40 to -
50 °C is as
high as about one hundred times that of water at ordinary temperatures. This
increases the
load on the refrigerant pump 26, and thus reduces the energy ei~iciency of the
Stirling cooling
apparatus.
S
Disclosure of the invention
An object of the present invention is to provide a Stirling cooling apparatus
or cooler
that complies with the regulation of refrigerants based on HCFCs and HFCs and
that oilers
improved cooling efficiency by exploiting latent heat. Another object of the
present
invention is to provide a large-capacity, low-power-consumption refrigerator
that offers good
heat exchange efficiency.
To achieve the above objects, according to one aspect of the present
invention, a
Stirling cooling apparatus is provided with: a Stirling chiller having a high-
temperature
portion whose temperature rises as the Stirling chiller is operated and a low-
temperature
portion whose temperature falls as the Stirling chiller is operated; an
evaporator provided
integrally with or separately from the Stirling chiller; and a refrigerant
circulation circuit for
transferring cold produced by the low-temperature portion to the evaporator by
means of a
refrigerant circulated between the low-temperature portion and the evaporator
by a refrigerant
circulation means. Here, the refrigerant is a natural refrigerant that
liquefies in the low-
temperature portion and vaporizes in the evaporator.
In this configuration, when the Stirling chiller is driven, the cold produced
by the low-
temperature portion is collected as latent heat by the refrigerant circulating
around the
refrigerant circulation circuit. The refrigerant then vaporizes in the
evaporator, absorbing
heat of vaporization and thereby cooling the surrounding air.
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In this case, as the natural refrigerant, carbon dioxide can suitably be used,
which is
inexpensive and harmless to the environment and to humans. However, as
compared with
other refrigerants, carbon dioxide has a low critical point (about 31
°C) and a high critical
pressure (about 74 bar). Thus, the refrigerant circulation means needs to have
sufficiently
high resistance to pressure and hermeticity.
The refrigerant is circulated around the refrigerant circulation circuit by
the refrigerant
circulation means so as to transfer the cold to the evaporator. Here, if the
refrigerant has not
been cooled sufficiently to a supercooled state by the low-temperature
portion, i.e. if the
temperature of the refrigerant after passing through the condenser is near its
boiling point,
when the refrigerant receives power as the refrigerant circulation means (for
example, a
pump) is driven, part of the refrigerant may vaporize as a result of a local
rise in the
temperature thereof that arises around the power transmission mechanism
(hereinafter, this
phenomenon will be referred to as "cavitations"}
To cope with this, in the present invention, the refrigerant is cooled to a
predetermined
supercooled state by the low-temperature portion. Thus, even if there arises a
partial rise in
the temperature of the refrigerant around the power transmission mechanism of
the refrigerant
circulation means, no part of the refrigerant vaporizes. In this way,
cavitation is prevented.
In the Stirling cooling apparatus according to the present invention, in the
path within
the refrigerant circulation circuit which the refrigerant takes after flowing
out of the low-
temperature portion before flowing into the refrigerant circulation means, a
gas-liquid
separator may be arranged that separates the refrigerant into a gas phase and
a liquid phase
and that permits only the refrigerant in the liquid phase to be supplied to
the refrigerant
circulation means.
In this configuration, the refrigerant that has flown out of the low-
temperature portion
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in the form of a gas-liquid mixture is then separated into two phases, i.e. a
gas phase and a
liquid phase, by the gas-liquid separator so that only the refrigerant in the
liquid phase flows
into the refrigerant circulation means. This helps stabilize the operation of
the refrigerant
circulation means.
S In the Stirling cooling apparatus according to the present invention, the
refrigerant
circulation means may be composed of a gas-liquid separator, which is arranged
in a path
within the refrigerant circulation circuit which the refrigerant takes after
flowing out of the
low-temperature portion before flowing into the refrigerant circulation means
and in a
position higher than the evaporator, and which separates the refrigerant into
a gas phase and a
liquid phase and permits only the refrigerant in the liquid phase to be
supplied to the
refrigerant circulation means. Here, the difference in specific gravity
between the refrigerant
in the liquid phase at the outlet of the gas-liquid separator and the
refrigerant inside the
evaporator is exploited as a power source for circulating the refrigerant.
In this configuration, when the Stirling chiller is driven, the cold produced
by the low-
temperature portion is collected as latent heat by the refrigerant circulating
around the
refrigerant circulation circuit. The refrigerant then vaporizes in the
evaporator, absorbing
heat of vaporization and thereby cooling the surrounding air. In this case,
even without a
circulation pump, the refrigerant circulates around the refrigerant
circulation circuit
spontaneously by exploiting the difference in specific gravity between the
refrigerant in
different phases.
When this Stirling cooling apparatus is incorporated in a refrigerator, the
cold
produced by the low-temperature portion of the Stirling chiller is transferred
by the refrigerant
circulating around the refrigerant circulation circuit so as to efficiently
cool the inside of the
refrigerator chamber.
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According to another aspect of the present invention, in a refrigerator
incorporating a
Stirling chiller, a low-temperature-side evaporator for releasing cold to
inside a refrigerator
chamber is arranged in a position lower than a low-temperature portion of the
Stirling chiller
which produces the cold; a circuit is arranged in such a way that a
refrigerant is circulated
between the low-temperature-side evaporator and the low-temperature portion;
and the
refrigerant liquefies by absorbing the cold in the low-temperature portion,
then flows to the
low-temperature-side evaporator by exploiting the difference in height between
the low
temperature portion and the low-temperature-side evaporator, then vaporizes by
releasing the
cold inside the low-temperature-side evaporator, and then flows in a vaporized
state back to
the low-temperature portion.
According to another aspect of the present invention, in a refrigerator
incorporating a
Stirling chiller, a high-temperature-side condenser for releasing heat to
outside a refrigerator
chamber is arranged in a position higher than a high-temperature portion of
the Stirling chiller
which produces the heat; a circuit is arranged in such a way that a
refrigerant is circulated
between the high-temperature-side condenser and the high-temperature portion;
and the
refrigerant vaporizes by absorbing the heat in the high-temperature portion,
then flows in a
vaporized state to the high-temperature-side condenser, then liquefies by
releasing the heat
inside the high-temperature-side condenser, and then flows back to the high-
temperature
portion by exploiting the difference in height between the high-temperature-
side condenser
and the high-temperature portion.
According to another aspect of the present invention, in a refrigerator
incorporating a
Stirling chiller, a low-temperature-side evaporator for releasing cold to
inside a refrigerator
chamber is arranged in a position lower than a low-temperature portion of the
Stirling chiller
which produces the cold; a circuit is arranged in such a way that a first
refrigerant is circulated
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between the low-temperature-side evaporator and the low-temperature portion;
the first
refrigerant liquefies by absorbing the cold in the low-temperature portion,
then flows to the
low-temperature-side evaporator by exploiting the difference in height between
the low-
temperature portion and the low-temperature-side evaporator, then vaporizes by
releasing the
cold inside the low-temperature-side evaporator, and then flows in a vaporized
state back to
the low-temperature portion; a high-temperature-side condenser for releasing
heat to outside
the refrigerator chamber is arranged in a position higher than a high-
temperature portion of
the Stirling chiller which produces the heat; a circuit is arranged in such a
way that a second
refrigerant is circulated between the high-temperature-side condenser and the
high-
temperature portion; and the second refrigerant vaporizes by absorbing the
heat in the high-
temperature portion, then flows in a vaporized state to the high-temperature-
side condenser,
then liquefies by releasing the heat inside the high-temperature-side
condenser, and then flows
back to the high-temperature portion by exploiting the difference in height
between the high-
temperature-side condenser and the high-temperature portion.
In these refrigerators configured as described above, the use of latent heat
obtained
through vaporization and liquefaction of the refrigerant contributes to better
heat transmission
efficiency than when sensible heat is exploited. Thus, cold is efficiently
transferred to inside
the refrigerator chamber, or heat is efficiently released to outside the
refrigerator chamber.
This helps enhance the heat exchange efficiency of refrigerators.
Moreover, the condenser and the evaporator can be formed in the desired sizes.
This
makes it possible to efficiently transfer the heat in the low-temperature and
high-temperature
portions, of which the sizes are limited in consideration of the efficiency of
the reverse
Stirling cycle, to air, which has low thermal conductivity. This helps realize
large-capacity
refrigerators.
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Moreover, the refrigerant is circulated by exploiting the difference in
height, without
the use of external power prepared specially for the circulation of the
refrigerant. This helps
realize low-power-consumption refrigerators.
In the refrigerators according to the present invention, a gas-liquid
separator may be
provided additionally. This helps increase the flow rate of the refrigerant
circulated.
In the refrigerators according to the present invention, as the refrigerant,
carbon
dioxide or water may be used, which is a non-flammable, non-toxic natural
refrigerant. This
helps realize refrigerators friendly to humans and to the global environment.
In the refrigerators according to the present invention, the height of the
refrigerators
may be used effectively to arrange the low-temperature-side and high-
temperature-side heat
exchanger portions. Moreover, the refrigerator chamber may be divided into an
upper
section serving as a refrigerator compartment, a middle section serving as a
vegetables
compartment, and a lower section serving as a freezer compartment. This
contributes to
effective use of the cold air inside the refrigerator chamber.
Brief description of drawings
Fig. 1 is a diagram schematically showing the configuration of the Stirling
cooling
apparatus of a first embodiment of the invention. Fig. 2 is a diagram
schematically showing
the configuration of the Stirling cooling apparatus of a second embodiment of
the invention.
Fig. 3 is a diagram schematically showing the configuration of the Stirling
cooling apparatus
of a third embodiment of the invention. Fig. 4 is a diagram schematically
showing the
configuration of the refrigerator of a fourth embodiment of the invention.
Fig. 5 is a
conceptual diagram of the chiller system of the refrigerator of a fifth
embodiment of the
invention. Fig. 6 is a diagram schematically showing the configuration of the
refrigerator of
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a sixth embodiment of the invention. Fig. '7 is a diagram schematically
showing the
configuration of an example of a conventional Stirling cooling apparatus.
Best mode for carrying out the invention
First, a first embodiment of the present invention will be described with
reference to
the relevant drawing. Fig. 1 is a diagram schematically showing the
configuration of the
Stirling cooling apparatus (hereinafter referred to as the "chiller system"
also) of the first
embodiment. In Fig. 1, reference numeral 1 represents a Stirling chiller;
reference numeral 2
represents a high-temperature portion whose temperature rises as the Stirling
chiller 1 is
operated; reference numeral 3 represents a low-temperature portion that
produces cold as the
Stirling chiller 1 is operated; reference numeral 4 represents a high-
temperature-side heat
exchanger for releasing heat from the high-temperature portion to the
surrounding space.
Moreover, next to the Stirling chiller 1, a cooling chamber 10 is arranged. In
a space .
secured inside a heat-insulation wall so as to communicate with the space
inside the cooing
chamber 10, an evaporator 7 is provided.
Next to the low-temperature portion 3, a condenser 5 is provided. The
condenser 5, a
circulation pump 6, and the evaporator 7 are connected to one another
successively with
refrigerant piping 8 to form a refrigerant circulation circuit. In the figure,
arrows indicate the
direction of the flow of the refrigerant. In this embodiment, as the
refrigerant is used carbon
dioxide, which is a natural refrigerant.
The Stirling chiller 1 has, as a working fluid, helium or nitrogen sealed in a
cylinder,
and has one power piston (not shown) and one displaces (not shown) arranged
parallel to an
axis common to them. When the power piston is driven with a linear motor (not
shown), the
power piston and the displaces reciprocate along the same axis inside the same
cylinder with a
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predetermined phase difference. The Stirling chiller 1 used in this embodiment
is not
limited to a Stirling chiller of the type in which a power piston is driven
with a linear motor as
described above, but may be a Stirling chiller of any other type.
When the linear motor is driven, on the principle described above, waste heat
(hereinafter referred to simply as "heat" also) is transferred to the high-
temperature portion 2
of the Stirling chilIer 1, raising the temperature of the high-temperature
portion 2, and
simultaneously cryogenic cold is produced in the low-temperature portion 3.
Then, in the
high-temperature-side heat exchanger 4 arranged so as to be in contact with
the high-
temperature portion 2, the waste heat is released out of the Stirling chiller
1 by air or water
used as a heat carrier.
Simultaneously, the circulation pump 6 is also driven so that the refrigerant
is
circulated around the refrigerant circulation circuit in the direction
indicated by the arrows.
Since carbon dioxide is used as the refrigerant, the circulation pump 6 is
designed to be
resistant to and hermetic up to a pressure of at least 74 bar. In this
refrigerant circulation
circuit, the refrigerant is condensed by the condenser 5 fitted to the low-
temperature portion 3,
and thereby the cold originating from the low-temperature portion 3 is stored
mainly in the
form of latent heat in the refrigerant.
The refrigerant, having been condensed by the condenser 5 and now in a low-
temperature, liquid state, then flows through the refrigerant piping 8 by the
action of the
circulation pump 6 so as to flow into the evaporator 7. In the evaporator 7,
the refrigerant
vaporizes. As the refrigerant vaporizes, it absorbs heat of vaporization from
the
surroundings, and thereby transfers cold to inside the cooling chamber 10. The
refrigerant,
having vaporized in the evaporator 7 and now in a gaseous state, then flows
through
refrigerant piping 8 back to the condenser 5. As long as the circulation pump
6 is driven,
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this cycle of events is repeated.
Here, if cavitation occurs in the circulation pump 6 in the refrigerant
circulating
around the refrigerant circulation circuit, there arise problems such as air
bubbles corroding
and degrading the circulation pump 6 and the flow rate of the refrigerant
becoming unstable.
Thus, to prevent cavitation, it is essential to set the loading amount and
mass flow rate of the
refrigerant appropriately so that a predetermined supercooled state is
achieved in the
condenser 5. Specifically, the loading amount of the refrigerant is so
determined that, at
operating temperature, the refrigerant in the liquid phase completely fills at
least the total
volume inside that portion of the refrigerant circulation circuit, i.e. mainly
the refrigerant
piping 8, which starts at the point where the refrigerant is completely
liquefied by the
condenser 5, runs through the circulation pump 6, and ends at the entrance of
the evaporator 7.
Moreover, by controlling the mass flow rate of the refrigerant according to
the cooling
capacity of the Stirling chiller 1, it is possible to achieve the desired
supercooled state in the
refrigerant condensed by the condenser 5 at operating temperature. By
maintaining such a
supercooled state, it is possible to prevent cavitation resulting from
vaporization of the
refrigerant in the circulation pump 6 even if pressure loss or heat absorption
occurs in the
refrigerant flowing through that portion of the refrigerant piping 8 leading
from the exit of the
condenser S to the exit of the circulation pump 6, and thereby maintain normal
circulation of
the refrigerant.
Next, a second embodiment of the present invention will be described with
reference
to the relevant drawing. Fig. 2 is a diagram schematically showing the
configuration of the
Stirling cooling apparatus of this embodiment. In Fig. 2, such members as are
common to
the cooling apparatus of the first embodiment shown in Fig. 1 and described
above are
identified with the same reference numerals, and their detailed explanations
will not be
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repeated.
In this embodiment, the refrigerant circulation circuit is formed by
connecting a
condenser 5, a gas-liquid separator 9, a circulation pump 6, and an evaporator
7 to one another
successively with refrigerant piping 8. In the figure, arrows indicate the
direction of the flow
of the refrigerant. In this embodiment, carbon dioxide is used as the
refrigerant. Moreover,
the gas-liquid separator 9 is arranged on the downstream side of the condenser
S in the
refrigerant circulation circuit, and is placed in a position lower than the
condenser 5 and
higher than the circulation pump 6.
In the figure, arrows indicate the direction of the flow of the refrigerant.
In this
embodiment, carbon dioxide is used as the refrigerant. The configuration and
operation of
the Stirling chiller 1 shown in Fig. 2 are the same as in the first embodiment
described above,
and therefore its explanations will not be repeated.
When the linear motor (not shown ) is driven, on the principle described
earlier, waste
heat is transferred to the high-temperature portion 2 of the Stirling chiller
1, raising the
1 S temperature of the high-temperature portion 2, and simultaneously
cryogenic cold is produced
in the low-temperature portion 3. Then, in the high-temperature-side heat
exchanger 4
arranged so as to be in contact with the high-temperature portion 2, the waste
heat is released
out of the Stirling chiller 1 by air or water used as a heat carrier.
Simultaneously, the circulation pump 6 is also driven so that the refrigerant
is
circulated around the refrigerant circulation circuit in the direction
indicated by the arrows.
Since carbon dioxide is used as the refrigerant, the circulation pump 6 is
designed to be
resistant to and hermetic up to a pressure of at least 74 bar. In this
refrigerant circulation
circuit, the refrigerant is condensed by the condenser 5 fitted to the low-
temperature portion 3,
and thereby the cold originating from the low-temperature portion 3 is stored
mainly in the
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form of latent heat in the refrigerant.
The refrigerant, having been condensed by the condenser 5 and now in a low-
temperature, partly gaseous and partly liquid state, then flows into the gas-
liquid separator 9
arranged on the downstream side of the condenser 5. In the gas-liquid
separator 9, the
refrigerant is separated into a gas phase and a liquid phase. The separated
refrigerant in the
liquid phase is then compressed by the circulation pump 6, and then flows
through the
refrigerant piping 8 into the evaporator 7. In the evaporator 7, the
refrigerant vaporizes. As
the refrigerant vaporizes, it absorbs heat of vaporization from the
surroundings, and thereby
transfers cold to inside the cooling chamber 10. The refrigerant, having
vaporized in the
evaporator 7 and now in a gaseous state, then flows through the refrigerant
piping 8 back to
the condenser 5. As long as the circulation pump 6 is driven, this cycle of
events is repeated.
Here, if cavitation occurs in the circulation pump 6 in the refrigerant
circulating
around the refrigerant circulation circuit, there arise problems such as air
bubbles corroding
and degrading the circulation pump 6 and the flow rate of the refrigerant
becoming unstable.
Thus, in this embodiment, to prevent cavitation, special consideration is
given to where to
place the gas-liquid separator 9.
Specifically, the gas-liquid separator 9 is arranged on the downstream side of
the
condenser 5 in the refrigerant circulation circuit, and is placed in a
position lower than the
condenser 5 and higher than the circulation pump 6. This permits that portion
of the
refrigerant piping 8 leading from the liquid surface inside the gas-liquid
separator 9 to the
entrance of the circulation pump 6 to be filled with the refrigerant in the
liquid phase in the
form of an upright column. The pressure of this column of the refrigerant
prevents
cavitation in the circulation pump 6, and thereby ensures normal circulation
of the refrigerator.
Next, a third embodiment of the present invention will be described with
reference to
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the relevant drawing. Fig. 3 is a diagram schematically showing the
configuration of the
Stirling cooling apparatus of this embodiment. In Fig. 3, such members as are
common to
the cooling apparatus of the first embodiment shown in Fig. 1 and described
earlier are
identified with the same reference numerals, and their detailed explanations
will not be
repeated.
In this embodiment, the refrigerant circulation circuit is formed by
connecting a
condenser 5, a gas-liquid separator 9, and an evaporator 7 to one another
successively with
refi-igerant piping 8a and 8b. In the figure, arrows indicate the direction of
the flow of the
refrigerant. In this embodiment, carbon dioxide is used as the refrigerant.
Moreover, the
gas-liquid separator 9 is arranged on the downstream side of the condenser 5
in the refrigerant
circulation circuit, and is placed in a position lower than the condenser 5
and higher than the
evaporator 7.
In the figure, arrows indicate the direction of the flow of the refrigerant.
In this
embodiment, carbon dioxide is used as the refrigerant. The configuration and
operation of
the Stirling chiller 1 shown in Fig. 2 are the same as in the first embodiment
described above,
and therefore its explanations will not be repeated.
When the linear motor (not shown ) is driven, on the principle described
earlier, waste
heat is transferred to the high-temperature portion 2 of the Stirling chiller
l, raising the
temperature of the high-temperature portion 2, and simultaneously cryogenic
cold is produced
in the low-temperature portion 3. Then, in the high-temperature-side heat
exchanger 4
arranged so as to be in contact with the high-temperature portion 2, the waste
heat is released
out of the Stirling chiller 1 by air or water used as a heat carrier.
In this refrigerant circulation circuit, the refrigerant is condensed by the
condenser 5
fitted to the low-temperature portion 3, and thereby the cold originating from
the low-
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temperature portion 3 is stored mainly in the form of latent heat in the
refrigerant. The
refrigerant, having been condensed by the condenser 5 and now in a low-
temperature, partly
gaseous and partly liquid state, then flows into the gas-liquid separator 9
arranged on the
downstream side of the condenser 5. In the gas-liquid separator 9, the
refrigerant is
separated into a gas phase and a liquid phase.
The separated refrigerant in the liquid phase then flows through the
refrigerant piping
8a into the evaporator 7. In the evaporator 7, the refrigerant vaporizes. As
the refrigerant
vaporizes, it absorbs heat of vaporization from the surroundings, and thereby
transfers cold to
inside the cooling chamber 10. The refrigerant, having vaporized in the
evaporator 7 and
now in a gaseous state, then flows through the refrigerant piping 8b back to
the condenser S.
This cycle of events is repeated.
In this configuration, the gas-liquid separator 9 is arranged on the
downstream side of
the condenser 5 in the refrigerant circulation circuit, and is placed in a
position lower than the
condenser 5 and higher than the evaporator 7. As a result, the refrigerant in
the liquid phase
fills the piping 8a leading to the entrance of the evaporator 7, and on the
other hand the
refrigerant in the gas phase flows through the refrigerant piping 8b leading
from the exit of
the evaporator 7 to the condenser 5. Thus, the refrigerant circulates around
the refrigerant
circulation circuit spontaneously by exploiting the difference in specific
density between the
refrigerant in the liquid and gas phases.
In this way, this configuration eliminates the need for a circulation pump 6
for forcibly
circulating the refrigerant around the refrigerant circulation circuit. This
helps reduce the
costs accordingly and realize a energy-saving Stirling cooling apparatus.
Next, a fourth embodiment of the present invention will be described with
reference to
the relevant drawing. Fig. 4 is a sectional view of the refrigerator of this
embodiment. It is
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to be understood that, although a refrigerator incorporating the Stirling
cooling apparatus of
the third embodiment described above is taken up as an example in the
following description,
the configuration of this embodiment applies also to a refrigerator
incorporating a Stirling
cooling apparatus in which the refrigerant is forcibly circulated by the
action of a circulation
pump as in the first and second embodiments.
As Fig. 4 shows, in an upper rear portion of the refrigerator 17, a Stirling
chiller 1 is
arranged so as to lay horizontally, with a condenser 5 fitted to the low-
temperature portion 3
(not shown) of the Stirling chiller 1. Moreover, a gas-liquid separator 9 is
provided in a
position lower than the condenser 5. On the other hand, in a lower rear
portion of the
refrigerator 17, an evaporator 7 is arranged. The condenser 5, the gas-liquid
separator 9, and
the evaporator 7 are connected to one another successively with refrigerant
piping 8a and 8b
to form a refrigerant circulation circuit.
The refrigerant in the liquid phase separated by the gas-liquid separator 9,
by falling
spontaneously, flows down through the refrigerant piping 8a, which leads from
the exit of the
gas-liquid separator 9 to the entrance of the evaporator 7, into the
evaporator 7. Thus, the
refrigerant in the liquid phase fills the refrigerant piping 8a. On the other
hand, the
refrigerant in the gas phase vaporized in the evaporator 7 flows up through
the refrigerant
piping 8b, which leads from the exit of the evaporator 7 to the entrance of
the condenser 5.
In this way, the pressure resulting from the difference between the gravity
acting on
the refrigerant in the liquid phase inside the refrigerant piping 8a and the
gravity acting on the
refrigerant in the gas phase inside the refrigerant piping 8b causes the
refrigerant to flow
upward through the refrigerant piping 8a and downward through the refrigerant
piping 8b.
Thus, even without a means, such as a circulation pump, for forcibly
circulating the
refrigerant, the refrigerant can be circulated spontaneously around the
refrigerant circulation
CA 02420028 2003-02-18
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circuit.
The refrigerant condenses by releasing heat through the condenser 5 to the
high-
temperature portion 2 (not shown) of the Stirling chiller 1, and vaporizes by
absorbing heat
from the cold air circulating inside the refrigerator chamber of the
refrigerator 17. The cold
air cooled by the evaporator 7 is then blown into the refrigerator chamber by
a cold air
circulation fan 13 as indicated by arrows, and thereby the space inside the
refrigerator
chamber is cooled. In this way, the cold produced by the Stirling chiller 1 is
transferred to
the refrigerator 17 through the refrigerant circulation circuit formed by the
condenser 5, the
gas-liquid separator 9, and the evaporator 7.
The air outside the refrigerator 17 is introduced into the refrigerator 17
through an air
suction duct 14 and is exhausted out of the refrigerator 17 through an air
exhaust duct 15 by a
fan 12. Meanwhile, by the air passing through the air suction duct 14 and the
air exhaust
duct 1 S, the waste heat transmitted to the high-temperature portion 2 of the
Stirling chiller 1 is
released out of the refrigerator 17 through the high-temperature-side heat
exchanger 4
Part of the moisture contained in the cold air circulating inside the
refrigerator
chamber condenses and forms water droplets on the surface of the evaporator 7.
These
water droplets drain through a drain outlet 16 and collect in a drain pan (not
shown).
Periodically, the drain pan is taken out, and the water collected therein is
disposed of.
Next, a fifth embodiment of the present invention will be described with
reference to
the relevant drawing. Fig. S is a conceptual diagram of the chiller system of
the refrigerator
of this embodiment. In Fig. S, such members as are common to the cooling
apparatus of the
first embodiment shown in Fig. 1 and described earlier are identified with the
same reference
numerals, and their detailed explanations will not be repeated.
This chiller system is composed of a Stirling chiller 1 having a low-
temperature
. CA 02420028 2003-02-18
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portion 3 and a high-temperature portion 2, a tow-temperature-side heat
exchanger portion 30,
and a high-temperature-side heat exchanger portion 31. The low-temperature-
side heat
exchanger portion 30 is a circulation circuit composed of a low-temperature-
side condenser
32 formed by a copper pipe wound around the low-temperature portion 3, a low-
temperature-
S side gas-liquid separator 9 connected to the low-temperature-side condenser
32 by a copper
pipe 33 and arranged in a position lower than the low-temperature portion 3, a
low-
temperature-side evaporator 7 connected to the bottom of the gas-liquid
separator 9 by a
copper pipe 34 and arranged in a still lower position, and a copper pipe 35
connecting
together the evaporator 7 and the low-temperature-side condenser 32. As a
refrigerant,
IO carbon dioxide is sealed in this circuit.
On the other hand, the high-temperature-side heat exchanger portion 31 is a
circulation
circuit composed of a high-temperature-side evaporator 36 formed by a copper
pipe wound
around the high-temperature portion 2, a high-temperature-side condenser 3 8
connected to the
evaporator 36 by a copper pipe 37 and arranged in a position higher than the
high-temperature
15 portion 2, a gas-liquid separator 40 connected to high-temperature side
condenser 38 by a
copper pipe 39 and arranged in a position lower than the high-temperature-side
condenser 38
and higher than the high-temperature portion 2, and a copper pipe 41
connecting together the
bottom of the gas-liquid separator 40 and the evaporator 36. As a refrigerant,
water is sealed
in this circuit. In the figure, arrows indicate the direction of the flow of
the refrigerants.
20 Next, the operation of the low-temperature-side heat exchanger portion 30
will be
described. The cold generated in the low-temperature portion 3 is transmitted
to the low-
temperature-side condenser 32, where most of the refrigerant liquefies. The
refrigerant, now
in a partly liquid and partly gaseous state, then flows through the copper
pipe 33 into the low-
temperature side gas-liquid separator 9 by exploiting the difference in height
between the low-
CA 02420028 2003-02-18
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temperature-side condenser 32 and the low-temperature-side gas-liquid
separator 9. In the
gas-liquid separator 9, the refrigerant in the liquid phase collects. The
refrigerant in the
liquid phase then flows from the bottom of the gas-liquid separator 9 through
the copper pipe
34 into the low-temperature-side evaporator 7. In the low-temperature-side
evaporator 7, the
refrigerant in the liquid phase exchanges the cold it has been carrying with
the heat of the air
inside the refrigerator chamber through the wall surface of the low-
temperature-side
evaporator 7. In this way, as the refrigerant in the liquid phase vaporizes,
it produces cold
air inside the refrigerator chamber.
The refrigerant, now in a vaporized state, flows through the copper pipe 35
into the
low-temperature-side condenser 32 by exploiting the difference in height
between the low-
temperature-side evaporator 7 and the low-temperature-side condenser 32 and
the difference
in pressure resulting from the difference in specific gravity between the
refrigerant in the gas
and liquid phases. By repeating this cycle of events, even without the use of
an external
power for circulating the refrigerant, it is possible to transfer cold to
inside the refrigerator
1 S chamber, and thus it is possible to realize a low-power-consumption
refrigerator.
Here, the use of latent heat obtained through vaporization and liquefaction of
the
refrigerant contributes to better heat transmission efficiency than when
sensible heat is
exploited. This makes it possible to efficiently transmit the cold in the low-
temperature
portion 3 to the low-temperature-side evaporator 7, and thereby enhance the
heat exchange
efficiency of a refrigerator. Moreover, the low-temperature-side condenser 32
and the low-
temperature-side evaporator 7 can be formed in the desired sizes. This makes
it possible to
efficiently transfer the cold in the low-temperature portion 3, of which the
size is limited in
consideration of the efficiency of the reverse Stirling cycle, to the air,
which has low thermal
conductivity, inside the refrigerator chamber. This helps realize a large-
capacity refrigerator.
. CA 02420028 2003-02-18
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Furthermore, as the refrigerant, carbon dioxide is used, which is a non-
flammable, non-toxic
natural refrigerant. This helps realize a refrigerator friendly to humans and
to the global
environment.
Next, the operation of the high-temperature-side heat exchanger portion 31
will be
described. The heat produced in the high-temperature portion 2 is transmitted
to the high
temperature-side evaporator 36, where the refrigerant vaporizes. The
refrigerant, now in a
gaseous state, then flows through the copper pipe 37 into the high-temperature-
side condenser
38 by exploiting the difference in height between the evaporator 36 and the
high-temperature
side condenser 38. In the high-temperature-side condenser 38, the refrigerant
liquefies as it
exchanges the heat it has been carrying with the air outside the refrigerator
chamber through
the wall surface ofthe high-temperature-side condenser 38.
The refrigerant, now in a partly liquid and partly gaseous state, then flows
from the
bottom of the high-temperature-side condenser 38 through the copper pipe 39
into the high-
temperature-side gas-liquid separator 40, where the refrigerant in the liquid
phase collects.
The refrigerant in the liquid phase then flows through the copper pipe 41 into
the evaporator
36 exploiting the difference in height between the high-temperature-side gas-
liquid separator
40 and the evaporator 36. By repeating this cycle of events, even without the
use of an
external power for circulating the refrigerant, it is possible to release heat
out of the
refrigerator chamber, and thus it is possible to realize a low-power-
consumption refrigerator.
Here, the use of latent heat obtained through liquefaction and vaporization of
the
refrigerant contributes to better heat transmission efficiency than when
sensible heat is
exploited. This makes it possible to efficiently transmit the heat in the high-
temperature
portion 2 to the high-temperature-side condenser 38, and thereby enhance the
heat exchange
efficiency of the refrigerator. Moreover, the high-temperature-side evaporator
36 and the
CA 02420028 2003-02-18
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high-temperature-side condenser 38 can be formed in the desired sizes. This
makes it
possible to efficiently transfer the heat in the low-temperature portion 2, of
which the size is
limited in consideration of the efficiency of the reverse Stirling cycle, to
the air, which has
low thermal conductivity, outside the refrigerator chamber. Furthermore, as
the refrigerant,
water is used, which is a non-flammable, non-toxic natural refrigerant. This
helps realize a
refrigerator friendly to humans and to the global environment.
The low-temperature-side gas-liquid separator 9 and the high-temperature-side
gas-
liquid separator 40 are provided for the purpose of increasing the flow rate
of circulation of
the refrigerant, and may be omitted. The flow rate of circulation of the
refrigerant is
determined by optimizing the difference in height between the low-temperature
portion 3 and
the low-temperature-side evaporator 7 and the difference in height between the
high-
temperature portion 2 and the high-temperature-side condenser 38.
The low-temperature-side evaporator 7 and the high-temperature-side condenser
38
are each formed in the shape of a box in their simplest form. However, forming
them, for
example, in the shape of a tube with fins helps increase their surface area
and thereby enhance
heat exchange efficiency.
The low-temperature-side condenser 32 and the high-temperature-side evaporator
36
may be removably kept in contact with, or brazed to, or formed integrally with
the low-
temperature portion 3 and the high-temperature portion 2, respectively.
Alternatively, the
low-temperature portion 3 or the high-temperature portion 2 may be formed in
the shape of a
doughnut having a cavity inside, with the refrigerant passed through the
cavity, so as to serve
simultaneously as a low-temperature-side condenser or a high-temperature-side
condenser,
respectively.
The chiller system described above, provided with a low-temperature-side heat
CA 02420028 2003-02-18
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exchanger portion 30 or a high-temperature-side heat exchanger portion 31, is
a highly
versatile chiller system that finds wide application in many industrial
fields, such as food
distribution, environment testing, medicine, biotechnology, and semiconductor
manufacture,
as well as in home-use appliances and the like.
Next, a sixth embodiment of the present invention will be described with
reference to
the relevant drawing. Fig. 6 is a diagram schematically showing the
configuration of the
refrigerator of this embodiment. It is to be noted that, in the following
description, a
refrigerator incorporating the Stirling cooling apparatus of the fifth
embodiment described
above is taken up as an example.
In a back central portion of the refrigerator 42, the Stirling chiller 1 is
arranged; in a
back lower portion of the refrigerator 42, the low-temperature-side heat
exchanger portion 30
is arranged; and, in the back upper portion of the refrigerator 42, the high-
temperature-side
heat exchanger portion 31 is arranged. The low-temperature-side evaporator 7
is arranged
inside a cold air duct 43 inside the refrigerator chamber of the refrigerator
42, and the high-
temperature-side condenser 38 is arranged inside an air exhaust duct 15 inside
the refrigerator
chamber of the refrigerator 42. The refrigerator chamber of the refrigerator
42 is divided
into an upper section serving as a refrigerator compartment 44, a central
section serving as a
vegetables compartment 45, and a lower section serving as a freezer
compartment 46. The
cold air duct 43 communicates with the refrigerator compartment 44, the
vegetables
compartment 45, and the freezer compartment 46. The refrigerator compartment
44 and the
vegetables compartment 45 communicate with each other.
When the Stirling chiller 1 is started, as described earlier, the heat
produced in the
high-temperature portion 2 is released through the high-temperature-side
condenser 38 to the
air surrounding it. Simultaneously, a fan 12 discharges the warm air inside
the air exhaust
CA 02420028 2003-02-18
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duct 1 S out of the refrigerator chamber of the refrigerator 42 and takes in
the air outside
refrigerator chamber of the refrigerator 42 to prompt heat exchange. The fan
12 may be
omitted; in that case, the air inside the air exhaust duct 15 and the air
outside the refrigerator
chamber of the refrigerator 42 are circulated by natural convection.
On the other hand, as described earlier, the cold produced in the low-
temperature
portion 3 is transferred through the low-temperature-side evaporator 7 to the
air inside the
cold air duct 43. Simultaneously, a cold air circulation fan 13 passes the
cold air inside the
cold air duct 43 into the freezer compartment 46, and passes part of the cold
air into the
refrigerator compartment 44. The cold air passed into the refrigerator
compartment 44 then
flows into the vegetables compartment 45, and then flows through the cold air
duct 43 back to
near the evaporator 7.
When the low-temperature-side evaporator 7 is defrosted, drained water is
discharged
out of the refrigerator chamber of the refrigerator 42 through a drain outlet
provided in a
bottom portion of the refrigerator 42.
In this way, by incorporating the chiller system of the fifth embodiment in a
large,
horizontal-type refrigerator, it is possible to effectively exploit the height
of the refrigerator in
the arrangement of the low-temperature-side heat exchanger portion 30 and the
high-
temperature-side heat exchanger portion 31. Moreover, by arranging the freezer
compartment 46 nearest to the low-temperature-side evaporator 7 and arranging
the
vegetables compartment 45 under the refrigerator compartment 44, it is
possible to effectively
use the cold air inside the refrigerator chamber of the refi-igerator 42.
Industrial applicability
As described above, according to the present invention, the use of latent heat
obtained
CA 02420028 2003-02-18
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through vaporization and liquefaction of the refrigerant contributes to better
heat transmission
efficiency than when sensible heat is exploited. Thus, cold is efficiently
transferred to inside
the refrigerator or cooler chamber, or heat is efficiently released to outside
the refrigerator or
cooler chamber. This helps enhance the heat exchange efficiency of
refrigerators.
Moreover, the condenser and the evaporator can be formed in the desired sizes.
This makes
it possible to efficiently transfer the heat in the low-temperature and high-
temperature
portions, of which the sizes are limited in consideration of the efficiency of
the reverse
Stirling cycle, to air, which has low thermal conductivity. This helps realize
large-capacity
refrigerators. Moreover, the refrigerant is circulated by exploiting the
difference in height,
without the use of external power prepared specially for the circulation of
the refrigerant.
This helps realize low-power-consumption refrigerators. Moreover, the
provision of the gas-
liquid separator ensures stable circulation of the refrigerant without the use
of a means for
forcibly circulating the refrigerant. This helps reduce costs and save energy.
Moreover, the
use of carbon dioxide or water, which is a non-flammable, non-toxic natural
refrigerant, as the
refrigerant helps realize refrigerators friendly to humans and to the global
environment.
Moreover, by dividing the refrigerator chamber into an upper section serving
as a refrigerator
compartment, a middle section serving as a vegetables compartment, and a lower
section
serving as a freezer compartment, it is possible to effectively use the cold
air inside the
refrigerator chamber. Moreover, the incorporation of the Stirling cooling
apparatus helps
realize coolers that produce far lower noise, that have far simpler
configurations, and that save
far more space than conventional vapor-compression-type coolers employing a
compressor.
